Bone and body composition response to testosterone therapy vary according to polymorphisms in the CYP19A1 gene

PURPOSE

To evaluate the influence of single nucleotide polymorphisms (SNPs) of CYP19A1 on the response and susceptibility to side effects from testosterone therapy. This is a prospective, single-arm study of men with low-morning serum testosterone (<10.68 nmol/l) administered testosterone cypionate 200 mg intramuscularly every 2 weeks for 18 months.

METHODS

We measured areal bone mineral density (aBMD) and body composition by dual energy X-ray absorptiometry, tibial volumetric BMD and geometry by peripheral quantitative computer tomography, bone turnover markers by enzyme-linked immunosorbent assay, testosterone, and estradiol by liquid-chromatography/mass-spectroscopy, genotyping by microarray, CYP19A1 expression by quantitative polymerase chain reaction, hematocrit and prostate-specific antigen (PSA).

RESULTS

We enrolled 105 men (40-74-years-old). SNPs rs1062033 and rs700518 were associated with significant differences in outcomes at 18 months. The GG genotype in rs1062033 had significant increase in whole body aBMD, but had significant decrease in tibial bone size compared to the CG and CC genotypes. Body composition analysis showed that the CC genotype of rs1062033, and the AA genotype of rs700518, had significant increase in total lean and appendicular lean mass compared to CG and GG, and AG and GG, respectively. The GG genotype of rs700518 had significant increase in PSA (GG = 105.8 ± 23.3% vs. AG + AA = 53.4 ± 11.3%, p = 0.046) while hematocrit changes were comparable among genotypes. CYP19A1 expression was highest in GG genotype in both SNPs.

CONCLUSIONS

For the first time, we demonstrated that CYP19A1 SNPs influence response to testosterone therapy in hypogonadal men, highlighting the importance of genetic profiling in therapeutics even for common clinical conditions.

High aromatase activity in hypogonadal men is associated with higher spine bone mineral density, increased truncal fat and reduced lean mass

OBJECTIVE

Because the aromatase enzyme catalyzes the conversion of testosterone to estradiol (E2), the activity of this enzyme could be important in the musculoskeletal health of men with low testosterone. The objective of the present study is to determine the influence of aromatase activity on the bone mineral density (BMD) and body composition of patients with hypogonadism.

DESIGN

Cross-sectional study.

METHODS

The baseline data of 90 patients between 40 and 74 years old who participated in a genetic study of response to testosterone therapy in men with low testosterone (i.e., <300 ng/dl) were analyzed. BMD and body composition were measured by dual-energy X-ray absorptiometry. Serum testosterone was measured by automated immunoassay, E2 was measured by ultrasensitive enzyme immunoassay, and sex hormone-binding globulin was measured by enzyme immunoassay.

RESULTS

Men in the highest tertile of E2 to testosterone ratio (E2:T) had the highest spine BMD (P ≤ 0.037), highest truncal fat (P=0.046), and lowest truncal lean body mass (P=0.045). A similar pattern was observed in the upper extremities; that is, fat mass significantly increased (P=0.047), whereas lean mass significantly decreased (P=0.034) with increasing E2:T tertiles.

CONCLUSION

The present findings suggest that in men with hypogonadism, aromatase activity could be an important determinant of musculoskeletal health. Men with high aromatase activity are able to maintain a higher BMD despite low circulating testosterone, but they have lower lean and higher truncal fat mass as compared to those with lower aromatase activity.

Testosterone and Adipokines are Determinants of Physical Performance, Strength, and Aerobic Fitness in Frail, Obese, Older Adults

In this study, we evaluated the independent and combined effects of baseline circulating gonadal, anabolic hormones and adipokines on physical function in 107 frail, obese (BMI ≥ 30 kg/m(2)), and older (≥65 yr) subjects. Our results showed significant positive correlations between circulating testosterone and insulin growth factor-1 (IGF-1) with knee flexion, knee extension, one-repetition maximum (1-RM), and peak oxygen consumption (VO2 peak), while no correlation was observed with estradiol. Among the adipokines, high sensitivity C-reactive protein (Hs-CRP) and leptin negatively correlated with the modified physical performance testing (PPT), knee flexion, knee extension, 1-RM, and VO2 peak. Interleukin-6 ( Il-6) negatively correlated with knee flexion and VO2 peak and soluble tumor necrosis factors receptor-1 (sTNFr1) correlated with PPT, 1-RM, and VO2 peak. Adiponectin correlated negatively with 1-RM. Multiple regression analysis revealed that, for PPT, sTNFr1 was the only independent predictor. Independent predictors included adiponectin, leptin, and testosterone for knee flexion; leptin and testosterone for knee extension; adiponectin, leptin, and testosterone for 1-RM; and IGF-1, IL-6, leptin, and testosterone for VO2 peak. In conclusion, in frail obese older adults, circulating levels of testosterone, adiponectin, and leptin appear to be important predictors of physical strength and fitness, while inflammation appears to be a major determinant of physical frailty.