Pathophysiology and Pathogenesis of Visceral Fat Obesity

Abstract

Based on the analysis of fat distribution by computed tomography (CT) scans, the classification scheme for obesity should include visceral fat obesity in which fat accumulationis predominant in the intra-abdominalcavity. Obese subjectsivith visceral fat accumulation more frequently demonstrateimpairment of glucose andlipid metabolism than those withsubcutaneous fat accumulation. Wehaveshownthatvisceralfat obesity is present in almost90% ofobesepatientswithischemicheart disease. Even in non-obese subj ects, visceral fat accumulation is correlatedwith glucose intolerance, hyperlipidemia and hypertension. Forty percent of non-obese subjects with coronary artery disease (CAD) had increased visceral fat. In non-obese subjects, visceral fat area assessed by abdominal CT at the level of the umbilicus correlates with metabolic risk factors, whereas in obese subjects the visceralfat area to subcutaneous fat area ratio provides a more significant correlation.From clinical and basic investigations, aging, sex hormones, excess intake of sucrose and lackof physical exercise have been suggested to be determinants for visceral fat accumulation. Since intra-abdominal fat (mesenteric andomentum fat) has beenshown to havehigh activities of bothlipogenesis and lipolysis,its accumulation can induce high levels offree fatty acids, a product of lipolysis, in portal circulation which go into the liver. Excess free fatty acids may cause the enhancement of lipid synthesis and gluconeogenesis as well as insulin resistance, resulting in hyperlipidemia, glucose intolerance and hypertension and finally atherosclerosis.

Intermuscular and intramuscular adipose tissues: Bad vs. good adipose tissues

“…[10][11][12][13][14] Indeed, it appears that the preponderance of evidence states that SQF adiposity supplies a measure of protection against metabolic dysregulation, whereas VAT is considered a source of dysregulation (especially insulin resistance). 2,[15][16][17][18][19][20][21][22][23] However, this message is further muddied by new reports that demonstrate that truncal SQF adipose tissue may actually aid in the metabolic changes that occur with obesity as this depot supplies a greater percentage of adipose tissue compared with the VAT and that the protective effects of SQ fat is limited more to the gluteal femoral SQ depot (or the so-called "pear-shape"). 11,15,[24][25][26][27][28] The protective action of gluteal femoral SQF seems to be further limited to the femoral subcutaneous region and not necessarily with the gluteal region in black South African women further confounding the issue with ethnicity differences.…”

Subcutaneous abdominal adipose tissue is associated with an index of insulin sensitivity/resistance

“…The subcutaneous abdominal fat area of female was 124.7C/¡46.13 (mean §SD) cm 2 and that of male was 77.53C/¡37.53 cm 2 . In this study, we considered that upper limit of standard value for the female subcutaneous abdominal fat area was 217 cm 2 (meanC2SD) and upper limit of standard value for male subcutaneous abdominal fat area was 153 cm 2 (meanC2SD).…”

“…We compared HOMA-IR between subjects whose visceral abdominal fat area was above 100 cm 2 but that the subcutaneous abdominal fat area was above the mean C 2SD (20 subjects, 7 male and 13 female) with subjects whose visceral abdominal fat area was above 100 cm 2 and also subcutaneous abdominal fat area was below the mean C 2SD (15 subjects, 6 male and 9 female). As shown in Table 1, the HOMA-IR of the former subjects group was 3.37 § 2.07 and that of the latter subjects group was 8.17 § 6.22 (p D 0.0486).…”

“…Visceral and subcutaneous abdominal fat area was determined by CT (CT) using L4-L5 level method as previously reported by Matsuzawa et al 2 Plasma glucose and insulin levels following an overnight fast and the homeostatic model assessment of insulin resistance (HOMA-IR) was used to estimate peripheral insulin sensitivity. Total cholesterol, leptin, and TNF-a were determined by LSI Medience Corporation.…”

“…[1][2][3][4] On the other hand, it was reported that the Health, Aging, and Body Composition Study reported that large subcutaneous thigh fat was independently associated with more favorable glucose (in men) and lipid profile (in both genders). 5 Similarly, Porter et al reported that subcutaneous abdominal fat plays a protective role on atherosclerosis and triglyceride unlike visceral abdominal fat.…”