Brown adipose tissue metabolism in women is dependent on ovarian status

Abstract

In rodents, loss of estradiol (E₂) reduces brown adipose tissue (BAT) metabolic activity. Whether E₂ impacts BAT activity in women is not known. BAT oxidative metabolism was measured in premenopausal (n = 27; 35 ± 9 yr; body mass index = 26.0 ± 5.3 kg/m²) and postmenopausal (n = 25; 51 ± 8 yr; body mass index = 28.0 ± 5.0 kg/m²) women at room temperature and during acute cold exposure using [¹¹C]acetate with positron emission tomography coupled with computed tomograph. BAT glucose uptake was also measured during acute cold exposure using 2-deoxy-2-[¹⁸F]fluoro-d-glucose. To isolate the effects of ovarian hormones from biological aging, measurements were repeated in a subset of premenopausal women (n = 8; 40 ± 4 yr; BMI = 28.0 ± 7.2 kg/m²) after 6 mo of gonadotropin-releasing hormone agonist therapy to suppress ovarian hormones. At room temperature, there was no difference in BAT oxidative metabolism between premenopausal (0.56 ± 0.31 min^-1) and postmenopausal women (0.63 ± 0.28 min^-1). During cold exposure, BAT oxidative metabolism (1.28 ± 0.85 vs. 0.91 ± 0.63 min^-1, P = 0.03) and net BAT glucose uptake (84.4 ± 82.5 vs. 29.7 ± 31.4 nmol·g^-1·min^-1, P < 0.01) were higher in premenopausal than postmenopausal women. In premenopausal women who underwent gonadotropin-releasing hormone agonist, cold-stimulated BAT oxidative metabolism was reduced to a similar level (from 1.36 ± 0.66 min^-1 to 0.91 ± 0.41 min^-1) to that observed in postmenopausal women (0.91 ± 0.63 min^-1). These results provide the first evidence in humans that reproductive hormones are associated with BAT oxidative metabolism and suggest that BAT may be a target to attenuate age-related reduction in energy expenditure and maintain metabolic health in postmenopausal women.NEW & NOTEWORTHY In rodents, loss of estrogen reduces brown adipose tissue (BAT) activity. Whether this is true in humans is not known. We found that BAT oxidative metabolism and glucose uptake were lower in postmenopausal compared to premenopausal women. In premenopausal women who underwent ovarian suppression to reduce circulating estrogen, BAT oxidative metabolism was reduced to postmenopausal levels. Thus the loss of ovarian function in women leads to a reduction in BAT metabolic activity independent of age.

Keywords: cold-induced thermogenesis; energy metabolism; estradiol; human; positron emission tomography.

Graphical abstract

Figure 1.

Thermoregulatory responses in premenopausal and postmenopausal women. A: change in skin temperature during acute cold exposure. B: change in core temperature during acute cold exposure. C: shivering intensity during acute cold exposure based on the average shivering intensity of 8 different muscles. D: area under the curve for shivering activity during acute cold exposure. E: shivering intensity in individual muscles during acute cold exposure. *P < 0.05, premenopausal vs. postmenopausal. F: energy expenditure at room temperature (RT) and during acute cold exposure. **P < 0.05, RT vs. cold. SCM, sternocleidomastoid; MVC, maximum voluntary contraction.

Figure 2.

Brown adipose tissue (BAT) metabolism in premenopausal and postmenopausal women at room temperature (RT) and during acute cold exposure. A: time activity curves of [¹¹C]acetate activity in premenopausal women at room temperature and during acute cold exposure. SUV_mean, mean standard uptake values. B: time activity curves of [¹¹C]acetate activity in postmenopausal women at room temperature and during acute cold exposure. C: [¹¹C]acetate uptake rate in BAT. *P < 0.05, premenopausal vs. postmenopausal; **P < 0.05, RT vs. cold. D: BAT oxidative metabolism. *P < 0.05, premenopausal vs. postmenopausal; **P < 0.05, RT vs. cold. E: BAT tissue radiodensity. *P < 0.05, premenopausal vs. postmenopausal; **P < 0.05, RT vs. cold. F: fractional glucose uptake in BAT, muscles, and subcutaneous white adipose tissue (scWAT). *P < 0.05, premenopausal vs. postmenopausal. G: net glucose uptake in BAT, muscles, and scWAT. *P < 0.05, premenopausal vs. postmenopausal.

Figure 3.

Thermoregulatory responses in premenopausal before and after ovarian suppression [gonadotropin-releasing hormone agonist (GnRH_AG)]. A: change in skin temperature during acute cold exposure. B: change in core temperature during acute cold exposure. C: shivering intensity during acute cold exposure based on the average shivering intensity of 8 different muscles. D: area under the curve for shivering activity during acute cold exposure. E: shivering intensity during acute cold exposure in individual muscles. F: energy expenditure at room temperature (RT) and during acute cold exposure. SCM, sternocleidomastoid; MVC, maximum voluntary contraction.

Figure 4.

Brown adipose tissue (BAT) metabolism in premenopausal before and after ovarian suppression [gonadotropin-releasing hormone agonist (GnRH_AG)]. A: time activity curves of [¹¹C]acetate activity at baseline room temperature (RT) and during acute cold exposure. SUV_mean, mean standard uptake values. B: time activity curves of [¹¹C]acetate activity after GnRH_AG at room temperature and during acute cold exposure. C: [¹¹C]acetate uptake rate in BAT. D: BAT oxidative metabolism. Inset: individual changes in BAT oxidative metabolism during cold exposure before and after GnRH_AG. E: BAT tissue radiodensity. F: fractional glucose uptake in BAT, muscles, and subcutaneous white adipose tissue (scWAT). Inset: individual changes in fractional BAT glucose uptake during cold exposure before and after GnRH_AG. G: net glucose uptake in BAT, muscles, and scWAT. Inset: individual changes in net BAT glucose uptake during cold exposure before and after GnRH_AG.