Subcutaneous and visceral adipose tissue: structural and functional differences Ibrahim M.M. Obes. Rev., 2009, Jul 28; 11: P. 11–18 It is known that the cardiovascular risk associated with obesity and excess body weight is mainly related to the distribution pattern of fat in the body, not the total amount. Individuals with upper (abdominal, android, central) obesity have a higher risk compared to those with lower (gluteal-femoral, gynoid, peripheral) obesity. Visceral fat, present around internal organs, mesentery, and omentum, differs from subcutaneous fat in adipocyte type, endocrine function, lipolytic activity, insulin sensitivity, and other hormones. Subcutaneous fat accounts for about 80% of total body fat. Abdominal fat is composed of two main depots: subcutaneous and intra-abdominal. Visceral fat accounts for up to 10-20% of total body fat in men and 5-8% in women. With age, visceral fat mass increases in both sexes. Unlike subcutaneous fat, venous blood draining from visceral fat directly enters the liver via the portal system. This leads to the direct entry of large amounts of free fatty acids (FFAs) and adipokines synthesized in visceral fat into the liver. Adipokines, in turn, activate hepatic immune mechanisms leading to the formation of pro-inflammatory mediators such as C-reactive protein (CRP) and others. Large amounts of FFAs entering the liver from visceral fat cause hepatic insulin resistance. Visceral adipose tissue contains a large number of large adipocytes, unlike subcutaneous fat, which is mainly composed of small fat cells. Small young adipocytes actively absorb FFAs from the bloodstream during postprandial periods and accumulate triglycerides, but lose this ability as they grow. In contrast, large adipocytes are insulin-resistant, have high lipolytic activity, and are not sensitive to insulin's anti-lipolytic effect. Visceral adipose tissue is more vascularized, perfused, and innervated compared to subcutaneous fat. Regional differences in receptor density, affinity, and post-receptor signal transduction are characteristic of adipose tissue. Visceral fat has a higher density of glucocorticoid and androgen receptors, while subcutaneous fat has higher affinity of estrogen receptors for their substrates. Visceral adipocytes have higher density and sensitivity of β3-adrenergic receptors, providing greater sensitivity to lipolytic effects of catecholamines and less sensitivity to α2-adrenergic suppression of lipolysis compared to subcutaneous fat cells. Thus, visceral adipocytes are more metabolically active and have higher lipolytic activity compared to subcutaneous onesSubcutaneous and visceral adipose tissue: structural and functional differences Ibrahim M.M. Obes. Rev., 2009, Jul 28; 11: P. 11–18 It is known that the cardiovascular risk associated with obesity and excess body weight is mainly related to the distribution pattern of fat in the body, not the total amount. Individuals with upper (abdominal, android, central) obesity have a higher risk compared to those with lower (gluteal-femoral, gynoid, peripheral) obesity. Visceral fat, present around internal organs, mesentery, and omentum, differs from subcutaneous fat in adipocyte type, endocrine function, lipolytic activity, insulin sensitivity, and other hormones. Subcutaneous fat accounts for about 80% of total body fat. Abdominal fat is composed of two main depots: subcutaneous and intra-abdominal. Visceral fat accounts for up to 10-20% of total body fat in men and 5-8% in women. With age, visceral fat mass increases in both sexes. Unlike subcutaneous fat, venous blood draining from visceral fat directly enters the liver via the portal system. This leads to the direct entry of large amounts of free fatty acids (FFAs) and adipokines synthesized in visceral fat into the liver. Adipokines, in turn, activate hepatic immune mechanisms leading to the formation of pro-inflammatory mediators such as C-reactive protein (CRP) and others. Large amounts of FFAs entering the liver from visceral fat cause hepatic insulin resistance. Visceral adipose tissue contains a large number of large adipocytes, unlike subcutaneous fat, which is mainly composed of small fat cells. Small young adipocytes actively absorb FFAs from the bloodstream during postprandial periods and accumulate triglycerides, but lose this ability as they grow. In contrast, large adipocytes are insulin-resistant, have high lipolytic activity, and are not sensitive to insulin's anti-lipolytic effect. Visceral adipose tissue is more vascularized, perfused, and innervated compared to subcutaneous fat. Regional differences in receptor density, affinity, and post-receptor signal transduction are characteristic of adipose tissue. Visceral fat has a higher density of glucocorticoid and androgen receptors, while subcutaneous fat has higher affinity of estrogen receptors for their substrates. Visceral adipocytes have higher density and sensitivity of β3-adrenergic receptors, providing greater sensitivity to lipolytic effects of catecholamines and less sensitivity to α2-adrenergic suppression of lipolysis compared to subcutaneous fat cells. Thus, visceral adipocytes are more metabolically active and have higher lipolytic activity compared to subcutaneous ones