Friday, April 29, 2011

Exogenous Leptin Works! At Least in Already "Normal" Weight Exercise Junkies - 19% Body Fat Reduction in 10 Weeks on Metreleptin

In view of the promising results from early rodent studies it came as a surprise that leptin, a "16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism" (Wikipedia), turned out to be ineffective in obese patients, even if it was administered at very high doses. A recent Harvard study (Brinkoetter. 2011) published in the American Journal of Physiology - Endocrinology & Metabolism on April, 19th, does yet show that leptin does very well working its magic, if a patient's leptin receptors have not been desensitized by years of overeating.
Figure 1: Leptin induced reduction in body fat percentage (reminder: notice the difference between a 19% reduction in the total amount of body fat and a 19% reduction in body fat percentage) in amenorrheic women with hypoleptinemia after 10w and 19m, respectively (data adapted from Brinkoetter. 2011)

Investigating both short- (group 1: 10 weeks) as well as long-term effects (group 2: 9 months) of physiologic doses of exogenous recombinant methionyl human leptin, Metreleptin (group 1: 0.08 mg/kg per day; group 2: 0.08 mg/kg for 3 months, then 0.12 mg/kg per day for 6 months), on 2 groups of lean, strenuously-exercising amenorrheic women with hypoleptinemia (age: 25 ± 6 yrs, %-body fat: 22 ± 4 %) the researchers found that
Metreleptin significantly reduced total body fat by an average of 18.6% after 10 weeks (P<0.001) in the single-arm trial, and by 19.5% after 9 months (placebo-subtracted; P for interaction = 0.025; P for metreleptin = 0.004) in the placebo-controlled trial. There were no significant changes in lean body mass (P≥0.33), or in serum concentrations of myostatin (P≥0.35), follistatin (P≥0.30) and activin A (P≥0.20), whether in the 10-week trial or the 9-month trial.
While these results [body fat was reliably measured by dual energy X-ray absorptiometry (DXA), btw] won't help lazy couch potatoes, I bet they will turn out to be very "inspiring" for figure competitors, bodybuilders and other athletes who plateau in their efforts "to make weight". As it was the case for the female subjects in this study, leptin injections may effectively jumpstart their starved and over-trained metabolisms while shifting energy provision from valuable muscle to unwanted fat tissue. In view of these benefits, it would be downright audacious to ask for an additional decrease in myostatin (accompanied by an increase in muscle mass), don't you think so? Anyways, I guess we will soon see the black market prices for respective products rise to new heights.