Sex hormones and macronutrient metabolism

Abstract

The biological differences between males and females are determined by a different set of genes and by a different reactivity to environmental stimuli, including the diet, in general. These differences are further emphasized and driven by the exposure to a different hormone flux throughout the life. These differences have not been taken into appropriate consideration by the scientific community. Nutritional sciences are not immune from this "bias" and when nutritional needs are concerned, females are considered only when pregnant, lactating or when their hormonal profile is returning back to "normal," i.e., to the male-like profile. The authors highlight some of the most evident differences in aspects of biology that are associated with nutrition. This review presents and describes available data addressing differences and similarities of the "reference man" vs. the "reference woman" in term of metabolic activity and nutritional needs. According to this assumption, available evidences of sex-associated differences of specific biochemical pathways involved in substrate metabolism are reported and discussed. The modulation by sexual hormones affecting glucose, amino acid and protein metabolism and the metabolization of nutritional fats and the distribution of fat depots, is considered targeting a tentative starting up background for a gender concerned nutritional science.

Keywords: Gender; amino acids; fat; polymorphism.

Figure 1. Simplified scheme illustrating some of major differences in fat metabolism associated to gender (see text for more details). Left panel: In males, the relative abundance of circulating android hormone is associated with central body fat depots, usually characterized by small size mature adipocytes expressing high levels of ERβ and high levels of Aromatase. In this setting, adipocytes secrete lower levels of adiponectin and leptin which in turn modulate endocrine system and metabolic rate. Central body fat distribution is usually also characterized by more reactive autonomic nervous system (epinephrine, norepinephrine, and pancreatic polypeptide), cardiovascular (systolic and mean arterial pressure), and specific metabolic (carbohydrate oxidation) changes. Right panel: in women, high levels of circulating Estradiol are associated to lower body fat deposition which is in general characterized by larger size mature adipocytes expressing lower levels of ERβ and higher levels of Aromatase, in comparison to males. Adiponectin and leptin secretion are upregulated. In lower body adipose tissue, lipolysis is less sensitive (or responsive) to β-adrenergic stimulation than subcutaneous adipose tissue in the upper body. Women usually show an increased lipolytic response to exercise in the presence of a lower affinity of adrenergic receptors. SHPB = Steroid hormone binding protein. Alb = Albumin. T = Testosterone. E2 = Estradiol.