MON-LB016 Sex and Sex Steroid Effects on Brown Adipose Tissue Temperature in Healthy Humans

Abstract

Retrospective studies indicate that women have more brown adipose tissue (BAT) than men. Furthermore, animal studies show that sex steroids modulate BAT activity, wherein estrogen increases BAT function. We aimed to characterize BAT thermogenesis using infrared thermography (IRT) in healthy men (n=14; age 23.07 ± 0.7 years, BMI 23.22 ± 0.7 kg/m2) and in women during 2 stages of the menstrual cycle (luteal, n=9; age 25.22 ± 1.7 years, BMI 21.56 ± 0.4 kg/m2 and follicular, n=11; age 24.64 ± 1.2 years, BMI 22.12 ± 0.9 kg/m2). We measured cutaneous temperature in the supraclavicular (BAT positive) and the manubrium (BAT negative) regions, at baseline and in response to dietary and cold stimuli. Temperature recordings were at 1 min intervals, at an ambient temperature of 18.5-20°C. To activate cold-induced thermogenesis, one hand was immersed into water at 15°C for 5 min. Post-prandial thermogenesis was stimulated by the consumption of a liquid meal (Ensure, 10 kcal/ kg body weight). In fasted participants, baseline BAT temperature was higher (P<0.05) in women during the luteal phase than in either women during the follicular phase or men. Innate variation in baseline temperature was correlated (P<0.001) with serum progesterone concentrations, without being associated with estrogen or testosterone concentrations. The temperature response to cold exposure was biphasic, with an initial increase during cold exposure and a secondary increase approximately 20 min later; the latter phase has been referred to as adaptive thermogenesis. Women had greater (P<0.05) adaptive thermogenic responses to cold and dietary stimuli and this effect was greater (P<0.05) during the luteal phase of the menstrual cycle. During cold-exposure, the increase in BAT temperature was lower (P<0.05) in females during the follicular phase than during the luteal phase. Post-cold and post-prandial adaptive thermogenesis was greater in women than men, irrespective of the stage of menstrual cycle. Regression analyses showed that the degree of adaptive thermogenesis was positively correlated with serum estrogen concentrations (cold; P<0.05, meal; P=0.07), but negatively associated with serum testosterone concentrations (cold; P=0.07, meal; P<0.05). In summary, women typically display greater thermogenic responses than men, with an influence of the stage of menstrual cycle in women. Furthermore, we highlight that innate variation in BAT temperature and thermogenic responses to cold and diet are associated with fluctuations in the circulating levels of estrogen, progesterone and testosterone. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.