PLASMA ADRENAL, GONADAL, AND CONJUGATED STEROIDS BEFORE AND AFTER LONG-TERM OVERFEEDING IN IDENTICAL-TWINS

An analysis of the data collected in the Quebec Overfeeding Study of i dentical twins was undertaken to determine any evidence of a genotype effect on plasma levels of adrenal and gonadal steroids arising from l ong term positive energy balance. Plasma levels of sex hormone-binding globulin (SHBG), testosterone, dihydrotestosterone (DHT), dehydroepia ndrosterone sulfate (DHEA-S), androsterone glucuronide, androstane-3 a lpha,17 beta-diol grucuronide (3 alpha-DIOL-G), and cortisol were meas ured in 12 pairs of young, sedentary, male monozygotic twins before an d after 100 days of overfeeding. The dietary energy excess of 4.2 MJ/d ay (1000 Cal), 6 days a week, resulted in a total positive energy bala nce of 358 MJ (84,000 Cal). Overfeeding induced significant changes (P < 0.0001) in body weight and other measures of body composition. With in-twin pair resemblance was observed at baseline in all steroids, exc ept cortisol [intraclass correlation range: DHEA-S, 0.50 (P < 0.05); D HT, 0.77 (P < 0.001)] and was lost with overfeeding, except for DHT an d SHBG (P < 0.05). SHBG levels fell and Scr-DIOL-G rose with the gain in body fatness. The change in testosterone was a significant correlat e of the change in upper body fat (r = -0.48; P < 0.05). The change in 3 alpha-DIOL-G correlated positively with increases in all measures o f central adiposity (r = 0.52; P < 0.01). A decrease in DHEA-S occurre d with a higher, but not with a lower, gain in abdominal visceral fat (P < 0.05). Thus, analysis of adrenal and gonadal steroids and of conj ugated metabolites before and after overfeeding in monozygous twins su pports the idea that there is a genotype effect on steroid circulating steroid levels and that these blood levels are correlated with the pa ttern of body fat distribution. Moreover, the baseline within-twin pai rs similarity in steroid levels was attenuated by prolonged positive e nergy balance and body fat gain.