Aromatase inhibitors, specifically Letrozole, have been part of the bodybuilding pre-contest pharmacopia since their commercial release. We know that lowering estrogen can decrease subcutaneous water levels, leading to that dry, grainy look that wins contests. But now there’s reason to think that the inhibition of aromatase can do more on a precontest diet than just helping with water. In healthy men, it appears that aromatase inhibition (at least in the short term) can improve insulin sensitivity and aid glucose metabolism.
The drug used in the following studies was Letrozole, although a 2008 study performed at the University of Siena showed that another aromatase inhibitor Exemestane (Anastrozole) given to women for two years (without any change in diet or training), lowered their body fat and increased their fat free mass.
Eur. J. Endocrinol 2009 Mar;160(3):397-402. Epub 2008 Dec 2.
Short-term aromatase inhibition: effects on glucose metabolism and serum leptin levels in young and elderly men.
Lapauw B, T’Sjoen G, Mahmoud A, Kaufman JM, Ruige JB.
Department of Endocrinology, Ghent University Hospital, Ghent, Belgium. firstname.lastname@example.org
To assess and compare the effects of short-term aromatase inhibition on glucose metabolism, lipid profile, and adipocytokine levels in young and elderly men.
DESIGN AND METHODS:
Ten elderly and nine young healthy men were randomized to receive letrozole 2.5 mg daily or placebo for 28 days in a crossover design.
Both in young and elderly men, active treatment significantly increased serum testosterone (+128 and +99%, respectively) and decreased estradiol levels (-41 and -62%, respectively). Fasting glucose and insulin levels decreased in young men after active intervention (-7 and -37%, respectively) compared with placebo. Leptin levels fell markedly in both age groups (-24 and -25%, respectively), while adiponectin levels were not affected by the intervention. Lipid profile was slightly impaired in both groups, with increasing low density lipoprotein-cholesterol levels (+14%) in the younger age group and 10% lower levels of APOA1 in the elderly. A decline in IGF1 levels (-15%) was observed in the younger age group. No changes in weight or body mass index were observed in either young or old men.
Short-term aromatase inhibition appears to affect glucose metabolism in young men, and lipid metabolism, including leptin secretion, in young and elderly men. Furthermore, the short period of exposure suggests that these changes might be mediated by direct effects of sex steroids rather than by changes in body composition.
Diabetes Care 2010 Aug;33(8):1831-3. Epub 2010 May 18.
Sex steroids affect triglyceride handling, glucose-dependent insulinotropic polypeptide, and insulin sensitivity: a 1-week randomized clinical trial in healthy young men.
Lapauw B, Ouwens M, ‘t Hart LM, Wuyts B, Holst JJ, T’Sjoen G, Kaufman JM, Ruige JB.
Department of Endocrinology, Ghent University Hospital, Ghent, Belgium.
To evaluate metabolic effects of sex steroids in nonfasting and fasting conditions, independent from changes in body composition.
RESEARCH DESIGN AND METHODS:
A randomized clinical trial was performed to create contrasting sex steroid levels in healthy young men: by letrozole (aromatase inhibitor) to lower estradiol (E(2)) and increase testosterone (group T, n = 10) versus letrozole plus E(2) patches to lower T and raise E(2) (group E, n = 10). Mixed meals and hyperinsulinemic-euglycemic clamps were performed before and after a 1-week treatment period.
Following intervention, the postprandial triglyceride response displayed a diverging response with a decline in group T and an increase in group E; the postprandial glucose-dependent insulinotropic polypeptide (GIP) response increased in group T. Insulin sensitivity increased in group T but remained unaltered in group E.
In healthy young men, short-term changes in sex steroids affect postprandial triglyceride and GIP response and insulin sensitivity.