Unlocking Clenbuterol’s Anabolic Potential

Title:Role of IGF-I and IGFBPs in the changes of mass and phenotype induced in rat soleus muscle by clenbuterol.Researchers: Bonaventure L. Awede, Jean-Paul Thissen, and Jean LebacqSource: American Journal of Physiology Endocrinology & Metabolism, 2002 282: E31-E37 Research Summary Administration of clenbuterol to three-month-old female Wistar rats resulted in a 10 and 13 percent increase of soleus muscle mass after three and nine days, respectively, reaching 16 percent after four weeks. When associated with triiodothyronine (T3), clenbuterol induced a dramatic slow-to-fast fiber-type change. In parallel, clenbuterol administration induced in soleus muscle a fivefold increase in IGF-I mRNA levels associated with an eightfold increase in IGF-binding protein (IGFBP)-4 and a fivefold increase of IGFBP-5 mRNA levels on day three. This increased IGF-I gene expression was associated with an increase in muscle IGF-I content, already detected on day one and persisting until day five without an increase in serum IGF-I concentrations. These data show that muscle hypertrophy induced by clenbuterol is associated with a local increase in muscle IGF-I content.

Discussion

Clenbuterol induces both hypertrophy and a slow-to-fast fiber-type change in skeletal muscle, but the mechanisms are still unknown. Let me acknowledge that this was a study done on mice, not men. Its value lies in its ability to shed light on how clenbuterol works to build muscle. The researchers theorized that IGF-1 might play a role in clenbuterol-induced muscle hypertrophy. From their results, we see that IGF-1 certainly is playing a role here.The anabolic effect of clenbuterol was most clearly demonstrated early on during treatment. Intramuscular IGF-1 levels were raised dramatically with clenbuterol treatment and are believed to be a major reason for this anabolic effect. However, many of the changes in mRNA levels were back to baseline by nine days into the experiment. This indicates that although there were some very mild anabolic effects after the first week and a half, clenbuterol should be considered a short-term anabolic. The anabolic effect of clenbuterol was increased with T3 administration. T3 also significantly increased the conversion of slow twitch fibers into fast twitch fibers. This is significant because fast twitch fibers have a greater potential for hypertrophy.Clenbuterol also increased the production of IGF-1 binding proteins. These binding proteins regulate the activity of IGF-1. Some binding proteins increase its activity and some decrease it. Clenbuterol increased both IGF1BP-4 and 5. The net result is increased IGF-1 activity within the cell, but decreased IGF-1 activity on satellite cells. This means that unlike physically loading a muscle, clenbuterol will only increase protein sythesis, it will not enhance the addition of a more nuclei-like testosterone. Thus, the ultimate potential for growth is limited if relying on Clenbuterol alone. Does Testosterone Shorten Life Span?Title: Exposure to anabolic-androgenic steroids shortens life span of male mice.Researchers: Franklin H Bronson, Curt M MatherneSource: Medicine & Science in Sports & Exercise 29(5): 615-619, 1997

Research Summary

Adult male laboratory mice were exposed for six months to a combination of four anabolic-androgenic steroids of the kinds, and at the relative levels, to which human athletes and bodybuilders expose themselves. The four included testosterone, two 17-alkylated steroids, and an ester, and they were given at doses that totaled either five or 20 times normal androgenic maintenance levels for mice. By the time the survivors were 20 months old (one year after termination of steroid exposure), 52 percent of the mice given the high dose of steroids had died compared with 35 percent of the mice given the low dose and only 12 percent of the control mice that were given no exogenous hormones. Autopsy of the steroid-treated mice typically revealed tumors in the liver or kidney, other kinds of damage to these two organs, broadly invasive lymphosarcomas, or heart damage, and usually more than one of these conditions. Discussion

OK, a few issues need to be discussed. First, lets talk about what was given, and then discuss how much and for how long.

The researchers used testosterone, methyltestosterone, test-cypionate, and norethandrolone. Testosterone, the hormone/drug that all other anabolic steroids are based on, is not really toxic, even in doses used in this study (five to 20 times maintenance). Methyltestosterone, on the other hand, is. Methyltest is one of the oldest and most toxic of all steroids. Unfortunately, it isn’t very anabolic; it doesn’t stimulate protein synthesis to any great degree. It’s very androgenic and produces noticeable side effects even at low doses. Expect plenty of bloat, gyno, acne and aggression. Methyltest’s only legitimate use might be to increase aggression before training. Testosterone cypionate is an injectable ester of testosterone. It’s less toxic than methyltest, but still causes the usual side effects. Because of testosterone’s propensity to convert to estrogen, gyno and bloat are probably the primary side effects seen with testcyp. Testosterone also converts to dihydrotestosterone (DHT), which will aggravate male pattern balding and acne. These side effects are dose-dependant. Real testcyp is rare. Finally, norethandrolone (Nilevar) can be thought of as a tweaked version of nandrolone. It’s an oral steroid, making it toxic on the liver. Although it’s similar to nandrolone, it doesn’t seem to have the same properties. It’s a weaker anabolic and stronger androgenic compound than nandrolone. It also appears to increase progestagenic activity, making gyno a problem. Doses were adjusted so each drug was 25 percent of the total amount given. Now, to address the doses used. Five to 20 times maintenance is equivalent to about 500 to 2,000 milligrams per week. It was given in the form of an implant that slowly releases the hormones over many weeks or months. They used this dose because they felt it was similar to what bodybuilders use, which is pretty close, with the exception of a few guys who use quite a bit more.The duration of the study was intentionally long to try to mimic the long-term use of bodybuilders. It turns out that the length of time these mice were “on” was considerably longer than most bodybuilders would be. Mice generally live for about three years. They were exposed to the drugs for six months, or about a fifth of their entire lives. Most bodybuilders aren’t on steroids that long, so the results should be interpreted with this in mind.The primary cause of death of the mice exposed to either five or 20 times maintenance doses was cancer. This occurred most often in the liver and kidney. Interestingly, kidney damage is not widely seen in bodybuilders. Liver damage, however, is much more common, attributable mostly to the two oral drugs used, methyltest and norethandrolone.So, do steroids cause premature death? This study clearly demonstrated that cancer causes premature death. Do steroids cause cancer? They can. Do they cause cancer in most users? Not according to medical reports. All in all, anybody who considers using high doses of steroids known to be toxic should do so only after educating themselves about the health consequences.

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