This review will focus on sex differences in human white adipose tissues.ĭeterminants of sex differences in body fat and fat distributionįor the same body mass index (BMI), women typically present with ~10% higher body fat compared to men. The regulation of brown adipose tissue mass and function in determining susceptibility to obesity in men and women is currently an active and important area of investigation, but little is known. Of interest with regard to sex differences in metabolism, limited data indicate that women tend to have higher quantities of brown fat, but the significance of this observation is not clear, as women do not have higher energy expenditure (adjusted for lean mass). The exact role of this specialized tissue in the regulation of energy balance in humans remains to be determined (, and reviewed in ). Indeed brown fat mass and activity are induced by cold stress. Whereas the function of white adipose tissues is to store excess energy, the function of brown fat is to produce heat. It has been recently recognized that humans, even in adulthood, possess islands of brown adipose tissue, mainly in the supraclavicular/dorsal cervical area. Adipose tissues in the retroperitoneal compartment (~7% of total ) do not drain into the portal vein and are therefore not considered ‘visceral’. VATs drain their blood into the portal vein and account for 6-20% of total body fat, with higher values in males than females. Intra-abdominal depots include visceral adipose tissues (VAT, omental and mesenteric), which are associated with digestive organs. These subcutaneous adipose tissues have distinct morphological and metabolic profiles and exhibit sex-specific differences in size and function that we will review in detail. Subcutaneous white adipose tissue (SAT) depots, just under the skin, store ~80-90% of total body fat, mainly in the abdominal (around the waist), subscapular (on the upper back), gluteal and femoral (thigh) areas.
Because excellent reviews of sex differences in the regulation of food intake and body weight have been recently published, in this review, we focus on physiologic and genetic determinants of sex differences in fat distribution.Ĭinti convincingly argues that body fat is stored in the adipose organ which consists of definable fat depots. Furthermore, and especially important for understanding the pathogenesis of obesity and its metabolic complications, interactions of sex differences in gene expression with environmental variables such as diet composition and exercise/activity on fatness and fat distribution remain largely unexplored. Inflammatory and developmental genes, some of which are modulated by sex steroid hormones, are prominent among depot- and sex-specific genes. Microarray analyses show that adipose mass and depot differences in adipose tissue gene expression in mice are regulated by sexually dimorphic gene networks. Although sex differences in fat distribution and correlations to metabolic health are well established in the clinical and epidemiological literatures, the biological underpinnings of these associations remain poorly understood. This ‘female’ fat distribution, independent of total body fat, confers protection against metabolic diseases, such as type 2 diabetes and atherosclerosis. Women, compared to men, have higher percent body fat and deposit it in a different pattern, with relatively more adipose tissue in the hips and thighs. We provide a brief overview of the relationship of fat distribution to metabolic health in men and women, and then focus on mechanisms underlying sex differences in adipose tissue biology. Gluteal-femoral adipose tissues of women may simply provide a safe lipid reservoir for excess energy, or they may directly regulate systemic metabolism via release of metabolic products or adipokines. Available evidence points to possible intrinsic, cell autonomous differences in preadipocytes and adipocytes, as well as modulatory roles for sex steroids, the microenvironment within each adipose tissue, and developmental factors.
To understand the mechanisms regulating adiposity and adipose tissue distribution in men and women, significant research attention has focused on comparing adipocyte morphological and metabolic properties, as well as the capacity of preadipocytes derived from different depots for proliferation and differentiation. Women have more body fat than men, but in contrast to the deleterious metabolic consequences of the central obesity typical of men, the pear-shaped body fat distribution of many women is associated with lower cardiometabolic risk.
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