Разрешите преставиться

Профессор биоэтики Иезекииль Эмануэль объясняет, почему он хочет умереть в 75 лет, несмотря на то что медицина достигла больших успехов в продлении жизни.

© 2014 The Atlantic Media Co., as first published in The Atlantic Magazine All rights reserved. Distributed by Tribune Content Agency, LLC.
Иллюстрации Студия 3D mode.

http://esquire.ru/ezekiel-emanuel

Семьдесят пять лет. Именно в этом возрасте я хотел бы покинуть наш бренный мир. Эта мысль страшно раздражает мою дочь, злит моих братьев, а друзья из-за нее считают меня настоящим психом. Они думают, что на самом-то деле я этого совсем не желаю, что я не обдумал все, как следует: ведь жизнь постоянно открывает перед нами так много нового и интересного. Чтобы разубедить меня, они то и дело подкидывают мне примеры бесчисленных знакомых, которым уже стукнуло 75 и которые тем не менее чувствуют себя прекрасно. Они уверены, что по мере приближения к избранной дате я непременно буду сдвигать планку, желая дожить до 80, затем — до 85, а может быть, и до 90.

Но я уверен в своем выборе. Да, смерть — это огромная потеря. Она лишает нас массы впечатлений, достижений, возможностей, она подводит черту под всем, что мы любим. Но есть и еще одна неоспоримая истина, которую многие не желают признавать: слишком долгая жизнь — это тоже потеря. Когда мне исполнится 75, за моими плечами будет целиком прожитая жизнь. Я смогу с удовлетворением сказать, что любил и был любим. Мои дети успеют вырасти, и их жизнь будет в самом расцвете. Я успею увидеть, как родятся и войдут в мир мои внуки. Работая над своими замыслами, я сумею внести в них свой вклад, а насколько значимым он окажется — тут уж как получится. Моя смерть в 75 лет не станет трагедией. Кроме того, я собираюсь устроить свою поминальную службу еще до того, как умру. Я не хочу слышать на ней плач и стенания. Надеюсь, там соберется приятная компания, которая будет тепло вспоминать забавные истории, подтрунивать над моей неловкостью и искренне радоваться тому, какую отличную жизнь я прожил. После моей смерти мои наследники тоже, если захотят, могут заказать поминальные службы — меня это уже не будет волновать.

Давайте-ка я сформулирую свое желание более четко. Я не прошу у судьбы дополнительного времени в придачу к тому, что мне отведено, и не собираюсь по собственной воле прерывать свою жизнь. Сегодня, насколько об этом осведомлены мы с моим лечащим врачом, я нахожусь в отличной форме. У меня нет хронических болезней. Недавно вместе с двумя своими племянниками я взобрался на вершину Килиманджаро. Так что я не пытаюсь выторговать у бога 75 лет жизни, в то время как меня пожирает смертельный недуг. Кроме того, я не планирую, проснувшись прекрасным утром через 18 лет, закончить жизнь посредством эвтаназии или иной формы самоубийства с помощью врачей.

Моя позиция касается лишь того, сколько именно я хотел бы прожить и какого рода медицинскую помощь я готов получать после того, как мне исполнится 75. Сегодня американцы помешаны на физических занятиях, упражнениях для ума, потреблении разнообразных соков и протеиновых коктейлей, витаминов и добавок в отчаянном стремлении обмануть смерть, как можно дольше задержаться на бренной земле. Это стремление стало столь массовым, что на его основе образовался целый пласт культуры, адептов которого я называю «американскими бессмертными». Лично мне это стремление чуждо. Я считаю, что маниакальное стремление жить как можно дольше — ошибка, способная породить самые деструктивные последствия. 75 — отличный возраст, чтобы поставить точку, и причин тому множество.

Начнем, пожалуй, с демографии. Мы живем дольше, но в старости качество нашей жизни невысоко. С середины XIX века средняя продолжительность жизни американцев растет. Для родившихся в 1900 году она составляла 47 лет, в 1930-м — 59,7, в 1960-м — уже 69,7, а для тех, кто родился в 1990-м, она достигла 75,4 года. Те, кто появляется на свет в эти дни, могут рассчитывать дожить примерно до 79 лет. Американские бессмертные отчаянно хотят верить в «сокращение заболеваемости». Эта теория, выдвинутая в 1980 году Джеймсом Ф. Фрайсом, ныне почетным профессором медицины Стэнфордского университета, утверждает: в 1980-90-х наша жизнь станет не только более долгой, но и значительно более здоровой. Люди будут позже сталкиваться с ограничениями, накладываемыми на них болезнями, да и общее число таких случаев будет уменьшаться. Но действительно ли с увеличением продолжительности жизни мы обретаем больше здоровья? Можно ли сказать, что 70 — это новые 50?

Не совсем. Действительно, пожилые люди, в сравнении со своими сверстниками, жившими полвека назад, более здоровы и мобильны. Но в последние десятилетия, похоже, увеличение продолжительности жизни сопровождается не сокращением, а, напротив, ростом числа болезней. Возьмем для примера результаты, полученные Эйлин Кримминс, научным сотрудником университета Южной Калифорнии, и ее коллегами при анализе материалов общенационального исследования состояния здоровья. Между 1998-м и 2006 годом ограничения мобильности у пожилых прогрессировали: так, в 1998 году примерно 28% американских мужчин в возрасте 80 лет и старше страдали от тех или иных форм нарушений двигательных функций, а к 2006 году эта цифра достигла уже 42%. У женщин результат оказался еще более тревожным: те или иные формы ограниченности физических возможностей были обнаружены более чем у половины испытуемых. Эти данные подтвердило недавнее общемировое исследование «ожидаемой продолжительности здоровой жизни», проведенное учеными Гарвардской школы общественного здравоохранения: их выводы тоже свидетельствуют о том, что уровень заболеваемости не только не сокращается, но и постоянно возрастает.

Что они имеют в виду? Это хорошо видно на примере моего отца. Лет десять назад, незадолго до 77-летия, его начали мучить боли в животе. Как любой порядочный врач, он долго отказывался признать, что это хоть сколько-нибудь серьезно. Но прошло три недели, а улучшения не наступало. Тогда он, наконец, поддался на уговоры близких и отправился к врачу. Как выяснилось, он перенес на ногах сердечный приступ, из-за которого ему пришлось сделать катетеризацию сердца, а впоследствии — и аортокоронарное шунтирование. С тех пор он так и не стал собой прежним. Когда-то бывший истинным воплощением гиперактивного представителя семьи Эмануэль, он стал медленнее ходить, говорить, понимать и отпускать шутки. Сегодня он в состоянии плавать, читать газеты и подтрунивать над детьми по телефону, и он по-прежнему живет в собственном доме вместе с моей мамой. Но его жизнь похожа на стоячее болото. Сердечный приступ не убил его, однако сегодня уже никто не станет утверждать, что он живет насыщенной жизнью. Обсуждая со мной эту тему, он вздохнул: «Я стал чудовищно медлителен. Это факт. Я уже не совершаю обходы в госпитале, не преподаю». Несмотря на это, впрочем, он заявил, что вполне счастлив.

Как формулирует Кримминс, за последние 50 лет медицина достигла куда больших успехов в деле продления жизни, нежели в борьбе со старением. Как ясно видно на примере моего отца, тем самым она растянула процесс умирания. Проблема покажется еще более серьезной, если коснуться самой ужасной из возможных перспектив — перспективы столкнуться со старческим слабоумием или другими приобретаемыми с возрастом психическими проблемами. Сегодня примерно пять миллионов американцев в возрасте от 65 и старше страдают болезнью Альцгеймера, а среди тех, кому уже стукнуло 85, недуг поразил каждого третьего. При этом если в ближайшие десятилетия эта ситуация изменится, то только к худшему: по мнению ученых, число пожилых американцев, страдающих болезнью Альцгеймера, к 2050 году вырастет примерно на 300%, по сравнению с сегодняшним днем.

Но ведь остается еще огромное множество пожилых людей, избежавших физической и умственной немощи. Если мы попадем в число этих счастливчиков, зачем останавливаться на 75? Почему не попытаться прожить как можно дольше?

Увы, даже если нас не поразит старческая деменция, наши умственные способности в старости угасают. Наука давно доказала существование негативных возрастных изменений в мозге человека: скорость мышления падает, долговременная и краткосрочная память ухудшаются, снижается способность к решению любых задач. Известно примечательное высказывание Эйнштейна: «Тому, кто не внес значительного вклада в науку к 30 годам, уже не суждено сделать это». Он, конечно, был слишком радикален в своих воззрениях. И неправ. Декан Кис Симонтон из Калифорнийского университета в Дэвисе на базе целого ряда исследований построил график, демонстрирующий среднестатистическое соотношение возраста и творческих способностей. Из него видно, что наши креативные возможности быстро растут на старте карьеры, достигают пика примерно через 20 лет, где-то в районе 40-45, и затем начинают медленно приходить в упадок. В зависимости от вашей специальности этот график видоизменяется, но незначительно. Сегодня средний возраст, в котором делают свое главное открытие физики — лауреаты Нобелевской премии, — 48 лет. Теоретики в области химии и физики добиваются значимых результатов несколько раньше, нежели исследователи-практики. Поэты достигают пика раньше, чем прозаики. Исследование, проведенное Симонтоном среди композиторов-классиков, показало: типичный представитель этой профессии пишет первое значительное произведение в 26 лет, в 40 он достигает наибольшей творческой зрелости и плодовитости, а затем снижает обороты, и в 52 пишет последнее свое значительное музыкальное произведение.

Эта схема соотношения возраста и творческих сил — чисто статистическая, она — продукт закона больших чисел. Разумеется, у каждого индивидуума отмечаются те или иные отклонения от мейнстрима. Разумеется, есть люди, чей талант расцветает поздно. Но статистических выкладок это не изменит. По определению исключениями суждено стать лишь немногим. Чаще всего мы смиряемся со своей физической и умственной ограниченностью. Незаметно, шаг за шагом, мы меняем свою жизнь. Мы сами не замечаем, как уходят наши стремления, как идей становится все меньше. Мы по-прежнему довольны жизнью, но ее картина стремительно сужается. Обычный американский бессмертный, когда-то бывший заметной фигурой в профессиональном сообществе, активно участвовавший в общественной жизни, теперь с радостью предается любимым хобби: наблюдает за птицами, катается на велосипеде, лепит из глины и так далее, и тому подобное. И, наконец, когда ходьба становится слишком трудным делом, а пальцы, скрюченные артритом, теряют подвижность, жизнь его сводится к тому, чтобы, сидя дома, читать или слушать книги или разгадывать кроссворды. А потом...

Впрочем, возможно, я слишком резок в своих суждениях. Жизнь не ограничивается юношескими стремлениями к успехам в карьере и творчестве. В конце концов, есть еще и наши потомки: дети, внуки, правнуки. Но и тут, увы, у чрезмерно долгой жизни имеются темные стороны, которые мы зачастую отказываемся признавать. Не буду касаться той тяжелой нагрузки — и финансовой, и физической, — которая легла на многих, если не на всех представителей так называемого «срединного поколения»: взрослых людей, вынужденных разрываться между заботой о малолетних детях и пожилых родителях. Но с эмоциональной точки зрения наша долгая жизнь также становится тяжким бременем для потомков.

Ни один ребенок — конечно, если не говорить о случаях семейного насилия — не хочет смерти своим родителям. В любом возрасте это станет для него тяжелейшей потерей. Эту зияющую пропасть ничем невозможно заполнить. Но при этом дети в той или иной степени всегда живут в родительской тени. Неважно, идет ли речь о родителях, которые держатся отчужденно и не особо интересуются жизнью чад, или о тех, кто глубоко любит своего ребенка, — так или иначе они нагружают детей собственными ожиданиями, судят их поступки, навязывают свое мнение, вмешиваются в происходящее. Одним словом, весьма решительно демонстрируют свое присутствие в жизни уже выросших детей. Иногда это радует. Иногда — страшно раздражает. В ряде случаев — разрушает жизнь. Но этого присутствия никак не избежать, пока родители живы. И хотя дети не смогут полностью избавиться от этого бремени даже после смерти родителей, все же после этого события они куда меньше мучаются от необходимости соответствовать родительским ожиданиям.

Пока живы родители, взрослый ребенок не имеет возможности стать главным в роде. Если родители живут до 95, детям приходится сохранять свое подчиненное положение до собственной пенсии. Для жизни по своим правилам у них остается не так уж много времени, причем все оно приходится на старость. Если же родители проживут до 75, у детей будет достаточно времени для того, чтобы насладиться близостью с ними, но останется немало и для собственной жизни.

Но есть кое-что важнее, чем родительский авторитет, — воспоминания. Какими мы хотим остаться в памяти детей и внуков? Мы хотим, чтобы они запомнили нас в расцвете сил. Активными, энергичными, заинтересованными, оживленными, проницательными, полными энтузиазма, веселыми, душевными, любящими. А не согбенными, вялыми, забывчивыми, вечно твердящими одно и то же и переспрашивающими: «Что она сказала?» Мы хотим остаться в их памяти самостоятельными людьми, а не тяжким бременем.

Семьдесят пять лет. Именно столько я хочу прожить. Но если я не собираюсь прибегать к эвтаназии или суициду, не становится ли от этого моя философия безответственной болтовней? Может быть, мне просто не хватает мужества поступить в соответствии с моими принципами? Нет. Когда мне исполнится 75, я полностью изменю отношение к заботе о своем здоровье. Я не буду активно приближать смерть. Но я не собираюсь прилагать усилия к тому, чтобы продлить жизнь. Я руководствуюсь тем, что написал на рубеже XIX и XX веков Уильям Ослер в своей классической книге «Принципы и практические рекомендации в области медицины». «Пневмонию можно с полным правом назвать подругой стариков, — утверждает он. — Смерть от этой болезни приходит неожиданно, быстро и чаще всего безболезненно, избавляя стареющего человека от „холодных объятий угасания“, приносящих столько страданий ему и его близким».

После 75 мне потребуются серьезные причины для того, чтобы зайти к врачу, не говоря уже о том, чтобы пройти то или иное обследование или лечение — пусть оно будет совершенно рутинным и абсолютно безболезненным. Я откажусь от регулярных профилактических обследований, скрининга и иных вмешательств. Я откажусь от колоноскопии и иных исследований, нацеленных на раннюю диагностику рака, причем еще до наступления 75-летия. Если бы у меня диагностировали рак сегодня, когда мне 57, я, возможно, соглашусь на лечение, если только прогноз не будет однозначно неблагоприятным. Но в 65 я пройду колоноскопию в последний раз. Точно так же я откажусь от тестирования на кардиостресс. Никаких водителей ритма, никакой замены сердечных клапанов или кардиошунтирования. Что насчет более рутинных вещей? Прививки от гриппа — долой. Большой вопрос — антибиотики для лечения пневмонии, кожных заболеваний или инфекций мочевых путей. Антибиотики стоят дешево и легко справляются с инфекционными заболеваниями. От них трудно отказаться. Но, как напоминает нам Ослер, в отличие от мучительного распада, который несут нам хронические болезни, смерть от этих инфекций приходит быстро и сравнительно безболезненно. А стало быть — никаких антибиотиков. Само собой, я подпишу отказ от реанимации, а также полный набор предварительных медицинских распоряжений — об отказе от ИВЛ, диализа, любых хирургических вмешательств и других лечебных мероприятий. Ничего, кроме паллиативной помощи, даже если я буду оставаться в сознании, но при этом не в здравом уме. Все эти указания я надлежащим образом зафиксировал и подписал.

Многим людям, особенно сочувствующим идеям американских бессмертных, моя позиция покажется неприемлемой, даже отталкивающей. Они вспомнят миллион исключений — как будто их существование доказывает ложность моей теории. Подобно моим друзьям, они решат, что я рисуюсь или просто сошел с ума. Сопротивление моей позиции вполне естественно. В конце концов, стремление прожить как можно дольше заложено в нас эволюцией: мы запрограммированы бороться за жизнь. Но лично для меня рубеж настанет в 2038 году. Мои дочери и друзья будут по-прежнему убеждать меня, что я неправ, и что я могу жить с не меньшей продуктивностью гораздо дольше. И я оставляю за собой право изменить свою точку зрения и энергично начать отстаивать идею как можно более долгой жизни. В конце концов, это будет означать, что и после 75 во мне еще остались кое-какие способности.

High Dose Caffeine + Non-Alcoholic Fatty Liver Disease = 355% Increased Very Low Density Lipoprotein (VLDL)

 http://suppversity.blogspot.de/2012/05/high-dose-caffeine-non-alcoholic-fatty.html

Image 1: Already in "pill form" - Coffee beans

Caffeine, the world's #1 drug certainly is a remarkable substance. It does not only have myriads of well-established physiological effects, already, but it seems that - if you wanted to - you could identify another one everyday. It is thus not really surprising that a recently published study by Abd El-Ghany, M.A., Rasha, M. Nagib and Hagar, M. El-Saiyed from the Mansoura University in Egypt casts yet another, in this case, however, pretty scary light on the lifeblood of the average Starbucks junkie (El-Ghany. 2012).

Caffeine prevents weight gain - whohooo! Or not?

The scientists set out to investigate the differential effects the oral administration of 10mg/day of pure caffeine, or dose-equivalents from coffee, (black) tea, cacao and Nescafe (note: this is my understanding of the somewhat sloppy English translation of the methods) would have on the lipid levels of rats who had been pretreated with a lard-based high fat diet and CCl4 for three months. This treatment had elucidated the expected inflammatory response and fatty acid deposition in the livers of the animals that were then randomly assigned to either one of the 5 treatment or a non-treated control group.

Figure 1: Weight gain (relative to initial weight) and food intake in non-treated, caffeine, cacao, Nescafe, coffee, or black tea treated rodent model of NAFLD (data adapted from El-Ghany. 2012)

And when you peak at the study outcome in figure 1 I would bet that your first reaction is: "Hey, cool! I must ramp up my caffeine intake even more, then!" We are in fact so conditioned to believe that weight loss, or the absence of weight gain is a "good thing" that I made the same stupid mistake, when I first looked at the (in the study) tabular data of the El-Ghany study. Then, I began to wonder: "How come that coffee and cacoa, of which I have repeatedly read that they help with weight loss, did increase the weight gain to levels that were higher than those in the non-treated control group." Finally, it dawned on me: What we are dealing with, here, is not weight loss or ameliorated weight gain, what we are seeing in all the groups is more of a special form of "failure to thrive"! After all, the non-CCL4 treated 'real' control group (data not shown in figure 1) did gain 45% of their initial body weight and thus still 15% more than the coffee group, of which I was mislead to believe that they "performed" worst.

High dose caffeine is for NAFLD sufferers not!

Looking at the rest of the data it became increasingly clear, the whopping dose of 10mg of caffeine per rodent per day, a dose, by the way, which happens to translates into a human equivalent dose of 10mg/kg (i.e. 800mg for an 80kg adult), did a pretty decent job in liberating fatty acids from the adipose tissue. So "decent", in fact, that the already compromised weight gain in those sick creatures was further attenuated.

Figure 2. Lipid levels in the treatment groups expressed relative to non-treated NAFLD rodents (left); selected liver slices (right; based on El-Ghany. 2012)

But it gets even worse, the sudden influx of fatty acids from the adipose tissue was so overwhelming that the already damaged livers of the NAFLD rodents started to spill out copious amounts of very low density lipoprotein (VLDL) - those nasty little cholesterol molecules of which researchers believe that they are the cause of cardiovascular disease. And despite the fact that we do not have any tissue images of the heart, the congested vein in the liver slice from one of the caffeine guzzling rodents appears to confirm the causal relationship of VLDL and clogging of the blood vessels; an effect, by the way, which could neither be countered by the -71% reduction in triglyceride levels, nor the -44% reduction in total lipids (compared to non-treated NAFLD control). 

Figure 3: Total cholesterol (CHO) and LDLc to HDL-c ratios in the non-treated, as well as the treated groups expressed relative to non-NAFLD control (data calculated based on El-Ghany. 2012)

In a 1985 letter to the editor of the Journal of the American Medical Association (Jama) William and Simpson explain the sudden occurrence of enormous amounts of VDLD in response to the lipolytic (=fat liberating) effects of caffeine as follows:

Upon liberation from the adipocyte, fatty acids are transported to the liver, where they are reesterified and the resultant triglycerides packaged for release in very-low-density lipoprotein (VLDL), which also contains apolipoprotein B.

If we assume that this hypothesis is correct, coffee, cacao and even Nescafe must obviously contain substances which help the liver to cope with the additional influx of fatty acids, as the animals in the respective groups do not only have significantly lower VLDL levels than the poor critters in the caffeine group, but also exhibit the most beneficial total cholesterol-to-HDL and LDL-to-HDL ratios (cf. figure 3) of all groups.

Say no to stims, energy drinks and coke and chose natural caffeine sources

In view of the ameliorative effects all the caffeine containing preparations had on the pathological features of NAFLD (cf. figure 2, right), and based on the results from previous studies and the assumption that the VLDL increase in the tea group was similarly well-handled in the rest of the body as it was in the liver, which did not present any of the congested veins that were so characteristic of the livers of the animals in the caffeine only group, the take home message of this study is one every SuppVersity student should be familiar with, by now: Nature knows best!

Image 2: I don't have to tell you that the study at hand suggests that those sugary caffeine bombs people call "energy drink" could give many of their livers their quietus.

Note: If you live in Dallas County, it does take no more than three attempts to identify a neighbor, friend, someone from your family or simply a pedestrian being in the early stages of NAFLD. And given the fact that the 33.6% NAFD rate in Dallas County was measure in 2005 already (Szczepaniak. 2005), it is almost certain that your neighbors' liver, which may still have been comparably healthy in 2005 has caught meanwhile. The results of this study could thus have greater implications on public health than you may initially have thought and it clearly suggest that the use of high dose "fat burners" and / or pre-workout supplements, as well the regular consumption of caffeine and sugar laden "energy drinks" or even coke is absolutely contra-indicated; and that not just in the obese, but also in the insulin resistant normal weight, whose liver is often similarly clogged with fat as the one of his 200lbs heavier comrade in crime.

If the caffeine is ingested in the absence of its natural adjuvants bad things happen. If they remain where they belong, however, the same whopping dose of caffeine that makes things worse could actually turn into a decent "liver fat burner".

While Coffee, tea and cacao drinkers can thus breathe a sigh of relieve, the average stim junkie who is already squirreling caffeine laden, geranium (DMAA) intoxicated pre-workout supplements and fat burners for the days after the DMAA ban, should better watch his liver health. Otherwise it may well be that he or she will end as a "case study" in the library of the FDA - filed under "death by fulminant liver failure induced by geranium + caffeine containing pre-workout supplement" - btw. isn't it strange that the FEDs don't have such a case study for one of the commercially available energy drinks, or even plain Coke, already?

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4203840/

Biol Sport. Dec 2014; 31(4): 251–259. 

Published online Sep 12, 2014. doi:  10.5604/20831862.1120931

PMCID: PMC4203840

GENE DOPING IN SPORT – PERSPECTIVES AND RISKS

E Brzeziańska,1 D Domańska,1 and  A Jegier2

Author information ► Article notes ► Copyright and License information ►

Go to:

Abstract

In the past few years considerable progress regarding the knowledge of the human genome map has been achieved. As a result, attempts to use gene therapy in patients’ management are more and more often undertaken. The aim of gene therapy is to replace defective genes in vivo and/or to promote the long-term endogenous synthesis of deficient protein. In vitro studies improve the production of human recombinant proteins, such as insulin (INS), growth hormone (GH), insulin-like growth factor-1 (IGF-1) and erythropoietin (EPO), which could have therapeutic application. Unfortunately, genetic methods developed for therapeutic purposes are increasingly being used in competitive sports. Some new substances (e.g., antibodies against myostatin or myostatin blockers) might be used in gene doping in athletes. The use of these substances may cause an increase of body weight and muscle mass and a significant improvement of muscle strength. Although it is proven that uncontrolled manipulation of genetic material and/or the introduction of recombinant proteins may be associated with health risks, athletes are increasingly turning to banned gene doping. At the same time, anti-doping research is undertaken in many laboratories around the world to try to develop and refine ever newer techniques for gene doping detection in sport. Thanks to the World Anti-Doping Agency (WADA) and other sports organizations there is a hope for real protection of athletes from adverse health effects of gene doping, which at the same time gives a chance to sustain the idea of fair play in sport.

Keywords: gene doping, methods of gene doping, methods of proteomic profiling, sport, WADA

Go to:

Introduction

With the development of science, athletes enjoy the more modern methods and pharmacological agents supporting their physical fitness, muscle strength and improving athletic skills.

Doping, although banned by the International Olympic Committee (IOC) and the World Anti-Doping Agency (WADA), has been used since the early 1920s, in the form of, among others, anabolic steroids, erythropoietin, amphetamine and modafinil. Now, with the completion of the Human Genome Project (HUGO Project) and the development of gene therapy in medicine, there has been dynamic progress of research on gene doping and gene delivery technologies to improve athletic performance in various sports.

According to the published data, gene doping is associated with the introduction into the body of the transgene and/or recombinant protein in order to bring it to expression or to modulate the expression of an existing gene to achieve the further advantage of an athlete's physiological performance [1–7]. According to the list of prohibited substances published by WADA in 2008, gene doping has been defined as: “nontherapeutic use of cells, genes, genetic elements, or modulation of gene expression, having the capacity to enhance athletic performance” [8].

In 2013 WADA clarified the type of manipulation of genetic material prohibited in sport as the transfer of nucleic acids or their analogues into cells and the use of genetically modified cells [9].

Go to:

Methods of gene delivery

Genetic material can be introduced into a cell either in vivo or ex vivo. The in vivo strategy is direct gene delivery into the human body, i.e., into main blood vessels or the target tissue/organ. In indirect DNA transfer strategy, i.e., ex vivo gene delivery, cells are collected from the body of the patient, and then, after genetic modification, breeding and selection, are reintroduced into the patient's body.

In gene therapy and, similarly, in gene doping the genetic material is delivered into cells and tissues using various carriers that can be viral or non-viral [10]. Using viral vectors (attenuated retroviruses, adenoviruses or lentiviruses) a transgene is released in target cells and is expressed using cell replication machinery. Some of these viruses, such as retroviruses, integrate their genetic material with chromosomes of a human cell. Other viruses, such as adenoviruses, introduce the transgene into the cell nucleus without chromosomal integration [11].

Viral vectors are efficient gene delivery carriers and they offer several advantages: large packaging capacity, cell-specific tropism, and/or long-term expression [12]. In some cases, however, irreversible side effects, such as unexpected endogenous virus recombination, may occur. It leads to the rapid transformation of normal cells in vitro as well as initiating tumours in vivo via amplification of the host proto-oncogene sequences in the viral genome [10–13]. Additionally, viral vectors can be recognized by the host immune system, resulting in an increased immune response. This effect reduces the effectiveness of the transfection efficiency by reducing the efficiency of the subsequent transgene delivery. The most important biological properties of the viral vectors used in gene therapy, including the treatment of sports injuries, are shown in Table 1.

TABLE 1

BIOLOGICAL PROPERTIES OF VIRAL VECTORS USED FOR GENE DELIVERY INTO CELLS IN THE TREATMENT OF VARIOUS DISEASES AND/OR SPORTS INJURIES [9, 14–16].

Non-viral gene delivery techniques are less effective methods of introducing genetic material into human cells, though characterized by low cytotoxicity. These include physical methods, such as electroporation, “gene gun” [17] and chemical carriers using cationic liposomes, or biodegradable polymers (polyethylenimines; PEIs) [18]. Non-viral gene delivery systems may cause an increased immune response [19–20].

Physical methods of gene delivery allow DNA transfer into the cell cytoplasm or nucleus, through local and reversible damage of the cell membrane. The most common physical technique is electroporation, based on the application of a high voltage electrical pulse to the cells, leading to the formation of hydrophilic pores in the cell membrane, of several nanometres in diameter [15]. Electroporation is a very effective method, and one of its strengths is the protection of cells against the introduction of undesirable substances during the transgene delivery. Nowadays, electroporation is the most frequently used method to introduce DNA into skin cells or liver cells.

Biochemical methods involve the use of chemical carriers, which form complexes with nucleic acids to neutralize their negative charge. Such complexes are introduced into the cell by phagocytosis, and less frequently by fusion with the cell membrane. Some of the chemical carriers facilitate the release of nucleic acid into the cytoplasm from the endosome, and protect it from cellular nucleases [15].

The main difficulty in the application of gene transfer in gene doping is to achieve a long-lasting effect, as well as monitoring the changes induced in the genome. A long-lasting effect can be achieved by multiple (repeated) gene doping applications or by the integration of a transgene into the chromosome. However, it should be emphasized that the integration of gene transfer vectors is associated with a risk of undesirable side effects, including insertional mutagenesis. Integration of the transgene at the wrong site may lead to the development of cancerous cells [21].

Go to:

Is gene doping already a reality?

Research on gene doping, which has been carried out mainly in animal models, but also more and more often as gene therapy in humans, has brought many successes. It was reported that injection of a plasmid with a vascular endothelial growth factor (VEGFA) gene into the muscle of patients with chronic critical limb ischaemia led to improved distal flow [22]. Injection of the peroxisome proliferator-activated receptor-delta/beta (Ppard/β) gene into mouse zygotes improved the endurance and running capacity of mice on a treadmill, and simultaneously resulted in resistance to obesity, even in the absence of exercise and with a high-fat diet [23]. In rats, the introduction of the insulin-like growth factor-1 (Igf1) gene in a recombinant viral vector led to an increase in muscle mass and strength and to increase in endurance [24]. Transfer of the phosphoenolpyruvate carboxykinase (Pck1) gene resulted in increased activity of the transgenic mice, increased strength and speed during a race, and additionally, the mice were characterized by lower mass and fat content as compared to control mice [25].

In other studies on animals, gene therapy was used to increase the production of growth hormone (GH). By intramuscular injection of a plasmid containing the somatoliberin (Ghrh) gene, under the control of a muscle-specific gene promoter, increased concentrations of GH and IGF-1, and improvement of anabolic and haematological parameters were achieved. Moreover, the obtained results persisted for over one year [26].

The results of such studies are a major cause for concern over the direct threat of the spread of gene doping in competitive sports.

Another problem – which is a priority for sport organizations – is the difficulty in detecting gene doping. So far, the attempts to standardize the ideal test that could be used to detect gene doping have failed [5–6]. It should be emphasized, however, that several intensive studies on a number of promising strategies are being carried out (e.g., detection of a transgenic protein or vector that is the carrier of the genetic material in the site of intramuscular or tissue injection, monitoring the immune response after the use of a viral vector, or gene expression profiling) [5–6, 27]. Lack of tests to detect gene doping is associated with the fact that the protein produced by the foreign gene or genetically manipulated cells will be structurally and functionally very similar to the endogenous proteins. Most transgenic proteins, especially those that enhance muscle strength, are produced locally in the injected muscle and may be undetectable in blood or urine. The only reliable method would require a muscle biopsy, but such an approach is virtually impossible to use in sport. Furthermore, gene expression can be modulated as desired using the appropriate pharmacotherapy. At present, according to the opinion of the United States Anti-Doping Agency (USADA), it is not possible to detect gene doping with current technology.

Gene doping makes it possible to create a “super athlete”, but at the cost of breaking the rules of sporting ethics and undermining the principles of fair play in sport. It is also associated with a high risk of danger to the health of athletes.

Go to:

Gene doping and its side effects

The main candidates for gene doping are: EPO, IGF1, VEGFA, GH, hypoxia-inducible factors (HIFs), PPARD, PCK1, myostatins (MSTN), and some of their recombinant protein products (rEPO, rhGH) [2, 5, 6]. Data suggest that IGF1, GH, MSTN and rhGH may play a major role in strength sports while EPO, VEGFA, HIF-1, PPARD, PCK1 and rEPO are essential in endurance sports. Of course, the full list is much longer.

Functional protein products of those genes are related to specific increase of endurance, physical strength, redistribution of fat or increase of muscle mass. Some of them control the distribution of oxygen to the tissues, or regulate the growth and/or regeneration of muscle tissue. In addition, gene doping takes into account the genes encoding the peptides that relieve pain (e.g., endorphins and enkephalins) – they can be used as prohibited analgesics [28].

Erythropoietin (EPO)

The EPO gene encodes a glycoprotein hormone that increases the number of red blood cells and the amount of oxygen in the blood, thereby increasing the oxygen supply to the muscles [29, 43]. The expected effect of the physiological expression of the EPO gene would be increased endurance. For gene doping, an additional copy of the EPO gene may be introduced into the athlete's body using a viral vector, thus leading to the overexpression of EPO, increased production of red blood cells in the liver and kidneys, and to increased oxygen binding capacity of the blood. Physiologically dangerous side effects of doping with EPO transfer are primarily an increase in haematocrit, which may enhance the likelihood of stroke, myocardial infarction, thrombosis and an increase in total peripheral vascular resistance [29].

In 2002, the British pharmaceutical company Oxford BioMedica developed Repoxygen as a potential drug for the treatment of anaemia associated with chemotherapy used in kidney cancer. The drug is administered intramuscularly, and consists of a viral vector transferring the modified human EPO gene under the control of genes encoding proteins of oxygen homeostasis (e.g., HIF-1, HIF-2). EPO transgene is expressed in response to low levels of oxygen, and is turned off when the oxygen concentration reaches the correct value. In 2006, Repoxygen attracted the attention of the world of sports, when in Germany it began to be administered to young female runners to maintain constant expression of EPO in muscle cells. Repoxygen is prohibited under the World Anti-Doping Code 2009 Prohibited List.

Recombinant EPO (rEPO) is widely used to treat anaemia caused by chronic renal disease. Erythropoietin was the first recombinant haematopoietic growth factor produced and available commercially as a recombinant protein drug [30]. Several types of rEPO are now commercially available, including: epoetin alpha (Eprex, Janssen-Cilag), epoetin beta (Neorecormon, Roche), and darbepoetin alfa (Nespo, Dompe`) [30, 31]. It is estimated that doping with rEPO is used by 3–7% of the best athletes of endurance sports [32]. The Sydney 2000 Olympics marked the beginning of the use of effective methods to detect injected rEPO.

Insulin-like growth factor 1 (IGF1) and growth hormone (GH)

Potentially, gene doping using IGF1 gene transfer could provide the desired, stable and high levels of IGF1 protein. This method would be relatively safe, because the effect of its actions would be limited to the target muscles. It has been shown that overexpression of IGF1 and its protein product combined with increased resistance training induced greater muscle hypertrophy [24]. Additionally, studies have shown that IGF1 gene transfer enabled the regeneration of skeletal muscle following injury and was more efficient than systemic administration of its protein product [33]. IGF1 expression is associated with increased muscle size and weight, thereby increasing muscle strength [2]. However, IGF1 delivery may lead to profound hypoglycaemia, similar to the administration of insulin. Moreover, IGF1 expression is also associated with cell cycle progression and apoptosis inhibition, by interacting with signalling pathways, such as IGF-1/ PI3K/Akt/AP-1 or IGF-1/Shc/Ras/MAPK, that are activated during carcinogenesis (e.g., in colon, breast or prostate cancer) [34–36].

IGF1 protein, also known as somatomedin C, belongs to the group of polypeptide hormones, which are essential for proper development of the fetus. In the mature organism it is involved in the regeneration of tissues, especially connective tissue, and also exhibits insulin-like activity, e.g., inducing hypoglycaemia [37]. IGF1 mediates some anabolic processes of growth hormone. One of the main functions of GH – mediated also by IGF1 – is the stimulation of body growth and body weight. GH also affects carbohydrate metabolism (stimulation of glycogenolysis and increased glucose release from the liver), fat metabolism (increased lipolysis and decreased lipogenesis) and protein metabolism (increased protein synthesis) [38]. There are only a few published reports confirming the enhancing effects of GH on muscle strength and cardiovascular and respiratory functions in trained healthy individuals [39–40]. On the other hand, evidence of the health risks associated with the use of GH (e.g., insulin resistance, impaired glucose tolerance and limited efficiency of the cardiovascular and respiratory systems) is accumulating. GH overexpression is associated with intracranial hypertension, headache, peripheral oedema, carpal tunnel syndrome, joint and muscle pain, or cardiomegaly in trained persons [41]. However, there is anecdotal evidence that recombinant GH (rGH) is commonly abused by athletes.

Hypoxia-inducible factor-1 (HIF-1)

The HIF-1 gene encodes proteins involved in the process of hypoxia, angiogenesis and erythropoiesis activation or regulation of glucose metabolism. Doping associated with stimulation of HIF-1 expression under normal conditions of oxygen supply, e.g., using chemical agents or gene transfer into cells, may improve athletic endurance. On the other hand, it affects mitochondrial oxygen metabolism, while also stimulating genes associated with metabolic adaptation of cells (e.g., GLUT1, GLUT3, GPI, ENO1), angiogenesis, apoptosis, or carcino carcinogenesis (e.g., VEGFA, IGF-1, IGF-2, TGFβ, Ang1, MMP, ADM) [42]. These molecular changes in the cells may result in myocardial infarction, stroke or cancer. HIF-1 regulates oxygen homeostasis, thus facilitating the cell's adaptation to low oxygen conditions. HIF-1 also affects erythropoiesis, iron metabolism, pH regulation, apoptosis, cell proliferation and intracellular interactions. Hypoxia itself regulates the expression of genes involved, among others, in cell energy metabolism, glucose transport and angiogenesis [42]. Thus, gene therapy using the HIF-1 gene or protein may result in physiological changes at many levels in the body. Research is being conducted with the use of HIF-1 in the treatment of cardiovascular diseases. Based on the animal studies and early clinical trials in humans, it is believed that HIF-1 administered as gene therapy effectively induces neovascularization in ischaemic tissues [43–45].

Peroxisome proliferator-activated receptor (PPAR)

The family of PPARs consists of the following genes: PPARA (α), PPARD (δ), and PPARG (γ). PPAR-αinfluences carbohydrate-lipid metabolism, thus regulating homeostasis and body mass [46]. Experiments have shown that the activation of PPARD reduces weight gain, increases skeletal muscle metabolic rate and endurance, and improves insulin sensitivity. It was further found that the increase in PPARD expression suppresses atherogenic inflammation [47]. The results of some studies suggest that polymorphisms in exon 4 (+15 C/T) and exon 7 (+65 A/G) of the PPARD gene correlate with changes in the capacity of the cardiovascular system and the concentration of lipids and glucose in healthy subjects in response to regular exercise [48, 49]. Nuclear hormone receptor protein is associated with de novo formation of skeletal muscle fibres of type I (slow-twitch fibres) and their transformation from type II fibres (fast-twitch fibres), which determine the athlete's endurance and speed. In addition, PPARD also plays an important role in the differentiation and maturation of adipocytes. It controls the body's energy balance. Thus, this protein plays an important role in the control of body weight [50]. So far, no studies have been conducted on gene doping with PPARD in humans or in animal models.

Peroxisome proliferator-activated receptor D (PPARD) agonist (GW1516; GW501516)

Animal studies showed that administration of GW1516 for a period of five weeks to mice subjected to training increased the exercise tolerance by 60-70%, as compared to mice in the control group. It is recognized that GW1516 improves the exercise capacity of trained animals [51]. However, there are no published data on the ergogenic effects of GW1516 in healthy and trained people. GW1516 is an experimental drug that has been used in the treatment of obesity, metabolic syndrome, and type 2 diabetes in some clinical trials [52]. This molecule is included in the WADA prohibition list and there are reports that some athletes have already been caught using such doping.

Adenosine monophosphate analogue (AMP)-(AICAR)

It is an analogue of adenosine monophosphate (AMP), the activator of AMP-dependent kinase (AMPK). Studies have shown that activated AMPK enzyme may reduce the level of anabolic processes, including synthesis of fatty acids and proteins, and increase the level of catabolic pathways such as glycolysis and fatty acid oxidation [53]. It has been proven that after 4 weeks of AICAR administration to mice subjected to training their speed and strength increased by 20-40%. It is believed that the ergogenic effect is achieved by the mutual interaction between AICAR and training, and their effect on the activation of many genes, determining the exertion efficiency [51, 54]. So far, however, there have not been published any data on AICAR ergogenic effects in healthy and trained people. AICAR is also an experimental drug and is included in the WADA prohibition list. The method to detect this molecules in humans by anti-doping laboratories was described by Narkar et al. [51].

Myostatin (MSTN)

The protein product of the MSTN gene belongs to the transforming growth factor β (TGF-β) superfamily, and is considered as a negative regulator of muscle growth and biogenesis [55].

In an animal model, it has been proven that suppression of the gene leads to reduced muscle growth restriction, and thus to increased muscle mass and strength [56]. Studies have demonstrated that the introduction of small interfering RNA (siRNA) into the body may negatively regulate MSTN [57]. It has been shown that suppression of the myostatin gene or protein triggers non-physiological – in terms of the number and size of cells – development of the muscle tissue. In some pathological conditions, the increase of muscle mass in a short period of time can promote hypertonic cardiomyopathy, subsequently resulting in a heart attack. The excessive growth of muscle mass also leads to overloading of the musculoskeletal system, increasing the susceptibility to bone and tendon injuries.

Phosphoenolpyruvate carboxykinase (PCK1, PEPCK-C)

It is a key enzyme regulating gluconeogenesis. This enzyme is considered crucial in glucose homeostasis and is involved in the Krebs cycle [46]. Studies in mice have shown that its expression is associated with increased muscle endurance in animals [25].

So far, there are no published literature data confirming the occurrence of side effects associated with transfer of the PCK1 gene or protein used as doping.

Gene transfer as a method of strengthening the desired physical and physiological characteristics or improving the natural athlete phenotype is an attractive way to achieve success in sport for many athletes [17]. For this reason, intensive investigations on the potential use of gene doping in many sports are nowadays increasing in number.

Table 2 shows the genes that could be potential targets for doping in sport and indicates the potential risk to the athlete's health in case of a possible application of this type of doping.

TABLE 2

POTENTIAL GENES THAT CAN BE USED IN DOPING, TARGET TISSUES/SYSTEMS AND POTENTIAL RISK TO THE ATHLETE'S HEALTH [29–65].

Go to:

Methods of gene doping detection

Nowadays, the detection of gene doping is a priority for many sports organizations, because of the proven effects of its use in experimental animals and the progress achieved in over 1000 clinical trials of gene therapy in humans [3–4].

Scientists supported by the WADA are looking for effective methods and tests for the detection of gene doping used currently in sport. The first developed and officially approved test to detect gene doping is a test for the presence of GW1516. It is known that GW1516 affects muscle strength and endurance, and also increases the cell's ability to burn fat [9, 52, 66].

However, there are still problems associated with the development of a credible and effective test to detect gene doping. This type of problem includes a plurality of protein isoforms encoded by a single gene and the similarity of genetically modified proteins to their endogenous counterparts. In addition, most transgenic proteins – especially those that enhance muscle strength – are synthesized locally in the muscle into which they are injected. Therefore they may be undetectable in the blood and urine. It appears that the only reliable method of their detection would require muscle biopsy, but this approach is practically impossible to use in sport.

The search for methods of gene doping detection in sport is based on the identification of both the carriers, such as a vectors, as well as the detection of the introduced genes (QPCR, real-time PCR) or their protein products (protein profiling method: mass spectrometry, phosphoproteomics, glycoproteomics, SELDI-TOF method).

Detection of viral vectors and monitoring of the host immune response

Detection of the carrier used in gene doping, usually a vector (used to transduce the gene), is possible in the site of intramuscular injection or tissues within weeks, and often months, after the application of doping. However, the collection of samples for testing would require information about the exact site of injection, and finally muscle biopsy. However, both approaches are inapplicable in a sport setting [67]. An additional difficulty in detecting delivery vectors in body fluids is the need for sampling in a relatively short time after doping administration. This requires regular testing of athletes out of competition. Another problem is the collection of samples, their storage and further analysis. These steps should be conducted according to the standardized, validated protocols, including snap freezing of samples in liquid nitrogen.

It seems that the evaluation of the host immune response to the viral vector is also an effective approach, but it requires refinement. There is a possibility that the tested athlete could have been infected by the virus via non-doping routes (such as viral infection or reactivation of latent viral infection by a pathogen similar to the used viral vector). Therefore the test confirming the presence of antibodies against the virus in the blood will not constitute irrefutable evidence of the use of doping. It is also possible to produce genetically engineered viral vectors which are less immunogenic, thereby minimizing a host immune response [5, 67]. Systematic and periodic testing of athletes – in order to detect the antibodies against viral vectors – would be required to monitor the level of anti-viral antibodies, which could potentially be used as a method for the detection of gene doping.

Methods of gene and proteomic profiling

Profiling methods are based on the monitoring of the secondary changes which arise as a result of gene doping. Transgene expression will lead to alterations in expression of other genes and their protein products.

Gene expression profiling assesses the expression profile of endogenous genes that may be modified following the expression of the introduced gene [5, 27, 67]. For this purpose DNA microarrays – which simultaneously compare mRNA expression patterns of thousands of genes – are used. In this method mRNA is isolated from cells of the athlete who used doping and cells from normal individuals from a control group. Then, mRNA is transcribed into cDNA, which is radioactively or fluorescently labelled. The principle of the method is based on the complementary binding of synthesized cDNA with oligonucleotides (probes) immobilized on glass or silicon plates (chips). Next, a laser is used to scan the chip to visualize the fluorescent signal given by the cDNA bound to the complementary probes. Changes in fluorescent signal intensity reflect increase/decrease of expression of the studied genes [68–69].

Based on this method, there is a possibility to develop microarray chips for expression analysis of the panel of genes that can be used in gene doping. Development of such chips gives the potential of expression analysis of genes used in doping as well as genes regulated by the transgene. For example, the development of a microarray chip for the EPO gene makes it possible to monitor the modified expression of about 100 EPO-dependent genes [27]. Expression analysis of these genes – in relation to the reference gene – might be an indirect method of doping detection.

Another strategy is proteomic profiling. This technique is based on the detection of minor structural differences between the recombinant proteins – which result from the expression of transgenes – and their endogenous counterparts. Investigation of global alterations in protein biomarkers upon doping can be done using the SELDI-TOF (surface enhanced laser desorption/ionization time-of-flight mass spectrometry) method, which combines chromatography and mass spectrometry for protein profiling [21, 70]. This technique is particularly applicable to indirect identification of GH, which is used in doping, by detecting the presence of the alpha chain of haemoglobin in blood serum [71].

Another method of protein expression profiling is searching for transgenic proteins based, among others, on differences in their glycosylation or differences in the evoked host immune response. Such research has already been applied in the case of the EPO protein [72].

Both gene and proteomic profiling require extensive research, in order to establish the reference ranges for the general population and individual athletes. Specific reference ranges should be established with regard to gender, population and sport.

Summary

Progress of research on gene therapy and clinical trials in this area significantly increased the possibilities of gene doping in sport. Simultaneously, the prospect carried by this new method of doping – the creation of a “super athlete” and lucrative professional sports – further complicates the situation.

It is believed that new methods, including ex vivo gene transfer to allogeneic stem cells, would considerably accelerate the possibility of the practical application of gene doping in sports. It should be noted, however, that these manipulations involve a lot of risks. The transmission of foreign genes into the genome can cause numerous – as yet unrecognized – interactions between genes and the internal and environmental modulators.

In contrast to gene therapy, which is carried out under strictly controlled conditions, gene doping can be performed without the use of security and protective measures. Vectors for gene transfer produced in uncontrolled laboratory conditions can be contaminated e.g., by chemical and/or biological agents, thereby endangering the health and life of athletes.

However, despite the documented and unpredictable risks associated with gene doping, some athletes ignore safety issues.

An additional problem is still not completed work on the standardization of reliable tests to detect gene doping. The scientific and medical communities should support the activities of the World Anti-Doping Agency (WADA) in developing new methods of gene doping detection and updating the lists of banned agents. In addition to educational programmes for athletes, and development of tests for gene doping detection, an individual method of gene doping control should be introduced, in which each athlete would be the self-reference baseline. In the case of such an approach it would be necessary to collect in an individual athlete database the results of his/her tests (biochemical and haematological), and possibly the expression profile of genes that can be potentially used for gene doping, to monitor it over time. UCI (Union Cycliste Internationale), WADA and IAAF (International Association of Athletics Federations) have already introduced a project known as the Athlete Passport to gather individual athlete testing data (WADA 2009–2013). In the future, such a personalized method of doping control may be the main method of combating this complex problem. In summary, to prevent the development of gene doping, international sports organizations should conduct numerous educational campaigns among athletes, pointing to the risks and ethical problems associated with its use.

Go to:

REFERENCES

1. Unal M, Ozer Unal D. Gene doping in sports. Sports Med. 2004;34:357–62.  [PubMed]

2. DeFrancesco L. The faking of champions. Nat Biotechnol. 2004;22:1069–71.  [PubMed]

3. Azzazy HM, Mansour MM, Christenson RH. Doping in the recombinant era: strategies and counterstrategies. Clin Biochem. 2005;38:959–65.  [PubMed]

4. Haisma HJ, de Hon O. Gene doping. Int J Sports Med. 2006;27:257–66.  [PubMed]

5. Azzazy HM, Mansour MM. Rogue athletes and recombinant DNA technology: challenges for doping control. Analyst. 2007;132:951–57.  [PubMed]

6. Baoutina A, Alexander IE, Rasko JE, Emslie KR. Potential use of gene transfer in athletic performance enhancement. Mol Ther. 2007;15:1751–66.  [PubMed]

7. Pokrywka A, Kaliszewski P, Majorczyk E, Zembroń-Łacny A. Genes in sport and doping. Biol Sport. 2013;30:155–161. [PMC free article]  [PubMed]

8. WADA 2008. The World Anti–Doping Code: The 2008 Prohibited List international Standard; 2008. 

9. WADA 2013. The World Anti–Doping Code: The 2013 Prohibited List international Standard; 2013. 

10. Lundstrom K, Boulikas T. Viral and non–viral vectors in gene therapy: technology development and clinical trials. Technol Cancer Res Treat. 2003;2:471–86.  [PubMed]

11. Inesi G, Lewis D, Sumbilla C, Nandi A, Strock C, Huff KW, Rogers TB, Johns DC, Kessler PD, Ordahl CP. Cell–specific promoter in adenovirus vector for transgenic expression of SERCA1 ATPase in cardiac myocytes. Am J Physiol. 1998;274:645–53.  [PubMed]

12. Jager L, Ehrhardt A. Emerging adenoviral vectors for stable correction of genetic disorders. Curr Gene Ther. 2007;74:272–83.  [PubMed]

13. Kung HJ, Liu J.L.  Retroviral oncogenesis. Philadelphia: Lippineott–Raven Publishers; 1997. pp. 235–266.

14. Crystal R. Transfer of genes to humans: early lessons and obstacles to success. Science. 1995;270:404–10.  [PubMed]

15. Hackett C, Geurts A, Hackett P. Predicting preferential DNA vector insertion sites: implications for functional genomics and gene therapy. Genome Biol. 2007;8:S12. [PMC free article]  [PubMed]

16. Lentz T, Gray S, Samulski J. Viral vectors for gene delivery to the central nervous system. Neurobiol Dis. 2012;48:179–188. [PMC free article]  [PubMed]

17. Fallahi A, Ravasi A, Farhud D. Genetic doping and health damages. Iran J Public Health. 2011;40:1–14. [PMC free article]  [PubMed]

18. Lemkine GF, Demeneix BA. Polyethylenimines for in vivo gene delivery. Curr Opin Mol Ther. 2001;3:178–82.  [PubMed]

19. Yew NS, Zhao H, Wu IH, Song A, Tousignant JD, Przybylska M, Cheng SH. Reduced inflammatory response to plasmid DNA vectors by elimination and inhibition of immunostimulatory CpG motifs. Mol Ther. 2000;1:255–26.  [PubMed]

20. Liu F, Conwell CC, Yuan X, Shollenberger LM, Huang L. Novel nonviral vectors target cellular signaling pathways: regulated gene expression and reduced toxicity. J Pharmacol Exp Ther. 2007;321:777–83.  [PubMed]

21. Kaiser J. Gene therapy. Seeking the cause of induced leukemias in X–SCID trial. Science. 2003;24:5495–606.  [PubMed]

22. Shyu KG, Chang H, Wang BW, Kuan P. Intramuscular vascular endothelial growth factor gene therapy in patients with chronic critical leg ischemia. Am J Med. 2003;1:85–92.  [PubMed]

23. Wang YX, Zhang CL, Yu RT. Regulation of muscle fiber type and running endurance by PPARdelta. PLoS Biol. 2004;2:294. [PMC free article]  [PubMed]

24. Lee S, Barton ER, Sweeney HL, Farrar RP. Viral expression of insulin–like growth factor–I enhances muscle hypertrophy in resistance–trained rats. J Appl Physiol. 2004;96:1097–104.  [PubMed]

25. Hakimi P, Yang J, Casadesus G, Massillon D, Tolentino-Silva F, Nye CK, Cabrera ME, Hagen DR, Utter CB, Baghdy Y, Johnson DH, Wilson DL, Kirwan JP, Kalhan SC, Hanson RW. Overexpression of the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) in skeletal muscle repatterns energy metabolism in the mouse. J Biol Chem. 2007;9:32844–55.  [PubMed]

26. Khan AS, Brown PA, Draghia–Akli R. Plasmid–based growth hormone–releasing hormone supplementation and its applications. Curr Opin Mol Ther. 2005;7:306–16.  [PubMed]

27. Diamanti–Kandarakis E, Konstantinopoulos PA, Papailiou J, Kandarakis SA, Andreopoulos A, Sykiotis GP. Erythropoietin abuse and erythropoietin gene doping: detection strategies in the genomic era. Sports Med. 2005;35:831–40.  [PubMed]

28. Machelska H, Schroff M, Oswald D, Binder W, Sitte N, Mousa SA, Rittner HL, Brack A, Labuz D, Busch M, Wittig B, Schäfer M, Stein C. Peripheral non-viral MIDGE vector-driven delivery of beta-endorphin in inflammatory pain. Mol Pain. 2009;14(5):72. [PMC free article]  [PubMed]

29. Bergestrom J. New aspects of erythropoietin treatment. J Int Med. 1993;233:1–18.

30. Caldini A, Moneti G, Fanelli A, Bruschettini A, Mercurio S, Pieraccini G, Cini E, Ognibene A, Luceri F, Messeri G. Epoetin alpha, epoetin beta and darbepoetin alfa:two–dimensional gel electrophoresis isoforms characterization and mass spectrometry analysis. Proteomics. 2003;3:937–41.  [PubMed]

31. Pascual JA, Belalcazar V, de Bolos C, Gutiérrez R, Llop E, Segura J. Recombinant erythropoietin and analogues: a challenge for doping control. Ther Drug Monit. 2004;26:175–79.  [PubMed]

32. Wilber RL. Detection of DNA– recombinant human epoetin–alfa as a pharmacological ergogenic aid. Sports Med. 2002;32:125–42.  [PubMed]

33. Schertzer JD, Lynch GS. Comparative evaluation of IGF–I gene transfer and IGF–I protein administration for enhancing skeletal muscle regeneration after injury. Gene Ther. 2006;13:1657–64.[PubMed]

34. Tentori L, Graziani G. Doping with growth hormone/IGF–1, anabolic steroids or erythropoietin: is there a cancer risk? Pharmacol Res. 2007;55:359–69.  [PubMed]

35. Ma J, Sawai H, Matsuo Y, Yasuda A, Ochi N, Takahashi H, Wakasugi T, Funahashi H, Sato M, Takeyama M. IGF-1 and PTEN regulate the proliferation and invasiveness of colon cancer cells through opposite effects on PI3K/Akt signaling. Arch Med Sci. 2009;5:195–206.

36. Lu Y, Zi X, Zhao Y, Pollak M. Overexpression of ErbB2 receptor inhibits IGF-I-induced Shc-MAPK signaling pathway in breast cancer cells. Biochem Biophys Res Commun. 2004;313:709–15.  [PubMed]

37. Boyne MS, Thame M, Bennett F, Osmond C, Miell JP, Forrester TE. The relationship among circulating insulin– like growth factor (IGF)–I, IGF–binding proteins–1 and –2, and birth anthropometry: a prospective study. J Clin Endocrinol Metab. 2003;88:1687–1691.  [PubMed]

38. Petersenn S, Schulte HM. Structure and function of the growth–hormone– releasing hormone receptor. Vitam Horm. 2000;59:35–69.  [PubMed]

39. Kniess A, Ziegler E, Thieme D, Müller RK. Intra-individual variation of GH-dependent markers in athletes: comparison of population based and individual thresholds for detection of GH abuse in sports. J Pharm Biomed Anal. 2013;84:201–8.  [PubMed]

40. Cox HD, Rampton J, Eichner D. Quantification of insulin-like growth factor-1 in dried blood spots for detection of growth hormone abuse in sport. Anal Bioanal Chem. 2013;405:1949–58.  [PubMed]

41. Harridge SD, Velloso CP. IGF–I and GH: potential use in gene doping. Growth Horm IGF Res. 2009;19:378–82.  [PubMed]

42. Schofield CJ, Ratcliffe PJ. Oxygen sensing by HIF hydroxylases. Nat Rev Mol Cell Biol. 2004;5:343–354.  [PubMed]

43. Lippi G, Guidi GC. Gene manipulation and improvement of athletic performances: new strategies in blood doping. Br J Sports Med. 2004;38:641. [PMC free article]  [PubMed]

44. Döring F, Onur S, Fischer A, Boulay MR, Pérusse L, Rankinen T, Rauramaa R, Wolfarth B, Bouchard C. A common haplotype and the Pro582Ser polymorphism of the hypoxia–inducible factor–1alpha (HIF1A) gene in elite endurance athletes. J Appl Physiol. 2010;108:1497–500.  [PubMed]

45. Marx J. How Cells Endure Low Oxygen. Cell Biology. 2004;5:1454–56.  [PubMed]

46. Chakravarthy MV, Pan Z, Zhu Y, Tordjman K, Schneider JG, Coleman T, Turk J, Semenkovich CF. New hepatic fat activates PPARalpha to maintain glucose, lipid, and cholesterol homeostasis. Cell Metab. 2005;1:309–22.  [PubMed]

47. Reilly SM, Lee CH. PPAR delta as a therapeutic target in metabolic disease. FEBS Lett. 2008;582:26–31. [PMC free article]  [PubMed]

48. Hautala AJ, Leon AS, Skinner JS, Rao DC, Bouchard C, Rankinen T. Peroxisome proliferator–activated receptor–delta polymorphisms are associated with physical performance and plasma lipids: the HERITAGE Family Study. Am J Physiol Heart Circ Physiol. 2007;292:2498–505.  [PubMed]

49. Lee CH, Olson P, Hevener A, Mehl I, Chong LW, Olefsky JM, Gonzalez FJ, Ham J, Kang H, Peters JM, Evans RM. PPARδ regulates glucose metabolism and insulin sensitivity. Proc Natl Acad Sci. 2006;103:3444–9. [PMC free article]  [PubMed]

50. Grimaldi PA. Regulatory role of peroxisome proliferator–activated receptor delta (PPAR delta) in muscle metabolism. A new target for metabolic syndrome treatment? Biochimie. 2005;87:5–8.  [PubMed]

51. Narkar VA, Downes M, Yu RT, Embler E, Wang YX, Banayo E, Mihaylova MM, Nelson MC, Zou Y, Juguilon H, Kang H, Shaw RJ, Evans RM. AMPK and PPARd agonists are exercise mimetics. Cell. 2008;134:405–415. [PMC free article]  [PubMed]

52. Thevis M, Beuck S, Thomas A, Kortner B, Kohler M, Rodchenkov G, Schänzer W. Doping control analysis of emerging drugs in human plasma – identification of GW501516, S–107, JTV–519, and S–40503. Rapid Commun Mass Spectrom. 2009;23:1139–1146.  [PubMed]

53. Winder WW, Hardie DG. AMP–activated protein kinase, a metabolic master switch: possible roles in type 2 diabetes. Am J Physiol. 1999;277:E1–E10.  [PubMed]

54. Rantzau C, Christopher M, Alford FP. Contrasting effects of exercise, AICAR, and increased fatty acid supply on in vivo and skeletal muscle glucose metabolism. J Appl Physiol. 2008;104:363–370.  [PubMed]

55. Carnac G, Ricaud S, Vernus B, Bonnieu A. Myostatin: biology and clinical relevance. Mini Rev Med Chem. 2006;6:765–70.  [PubMed]

56. Whittemore LA, Song K, Li X, Aghajanian J, Davies M, Girgenrath S, Hill JJ, Jalenak M, Kelley P, Knight A, Maylor R, O'Hara D, Pearson A, Quazi A, Ryerson S, Tan XY, Tomkinson KN, Veldman GM, Widom A, Wright JF, Wudyka S, Zhao L, Wolfman NM. Inhibition of myostatin in adult mice increases skeletal muscle mass and strength. Biochem Biophys Res Commun. 2003;24:965–71.  [PubMed]

57. Furalyov VA, Kravchenko IV, Khotchenkov VP, Popov VO. SiRNAs targeting mouse myostatin. Biochemistry. 2008;7:342–45.  [PubMed]

58. Paynea J, Montgomery H. Angiotensinconverting enzyme and human physical performance. Equine and Comp Exerc Physiol. 2004;1:255–60.

59. Thompson J, Raitt J, Hutchings L, Drenos F, Bjargo E, Loset A, Grocott M, Montgomery H, Caudwell Xtreme Everest Research Group Angiotensin–Converting Enzyme Genotype and Successful Ascent to Extreme High Altitude. High Alt Med Biol. 2007;28:278–85.  [PubMed]

60. Gayagay G, Yu B, Hambly B, Boston T, Hahn A, Celermajer DS, Trent RJ. Elite endurance athletes and the ACE I allele–the role of genes in athletic performance. Hum Genet. 1998;103:48–50.  [PubMed]

61. Woods D, Hickman M, Jamshidi Y, Brull D, Vassiliou V, Jones A, Humphries S, Montgomery H. Elite swimmers and the Dallele of the ACE I/D polymorphism. Hum Genet. 2001;108:230–32.  [PubMed]

62. Hernandez D, de la Rosa A, Barragan A, Barrios Y, Salido E, Torres A, Martín B, Laynez I, Duque A, De Vera A, Lorenzo V, González A. The ACE/DD genotype is associated with the extent of exercise– induced left ventricular growth in endurance athletes. J Am Coll Cardiol. 2003;42:527–32.  [PubMed]

63. Drozdovska S, Dosenko V, Ahmetov I, Ilyin V. The association of gene polymorphisms with athlete status in Ukrainians. Biol Sport. 2013;30:163–167. [PMC free article]  [PubMed]

64. Ahmetov I, Donnikov A, Trofimov DY. ACTN3 genotype is associated with testosterone levels of athletes. Biol Sport. 2014;31:105–108. [PMC free article]  [PubMed]

65. Busquets S, Figueras M, Almendro V, López-Soriano FJ, Argilés JM. Interleukin– 15 increases glucose uptake in skeletal muscle. An antidiabetogenic effect of the cytokine. Biochim Biophys Acta. 2006;1760:1613–17.  [PubMed]

66. Thomas A, Beuck S, Eichoff JC, Guddat S, Krug O, Kamber M, Schänzer W, Thevis M. Quantification of urinary AICAR concentrations as a matter of doping control. Anal Bioanal Chem. 2010;396:2899–2908.[PubMed]

67. Baoutina A, Alexander IE, Rasko J, Emslie KR. Developing strategies for detection of gene doping. J Gene Med. 2008;10:3–20.  [PubMed]

68. Joos L, Eryuksel E, Brutsche MH. Functional genomics and gene microarrays – the use in research and clinical medicine. Swiss Med Wkly. 2003;133:31–38.  [PubMed]

69. Chaudhuri J.D. Genes arrayed out for you: the amazing world of microarrays. Med Sci Monit. 2005;11:RA52–RA62.  [PubMed]

70. Issaq HJ, Veenstra TD, Conrads TP, Felschow D. The SELDI-TOF MS approach to proteomics: protein profiling and biomarker identification. Biochem Biophys Res Commun. 2002;292:587–592.  [PubMed]

71. Chung L, Clifford D, Buckley M, Baxter RC. Novel biomarkers of human growth hormone actionfrom serum proteomic profiling using protein chip mass spectrometry. J Clin Endocrinol Metab. 2006;91:671–677.  [PubMed]

72. Lasne F, Martin L, de Ceaurriz J, Larcher T, Moullier P, Chenuaud P. Genetic doping with erythropoietin cDNA in primate muscle is detectable. Mol Ther. 2004;10:409–410.  [PubMed]