Regional Differences in Adipose Tissue Metabolism in Women

Abstract

Studies comparing adipose tissue metabolism in central versus peripheral fat depots have generated equivocal data. We examined whether regional differences in abdominal subcutaneous and omental adipose tissue metabolism in women exist and whether they persist across the spectrum of body fatness and abdominal adiposity values. We measured adipocyte size; lipoprotein lipase (LPL) activity; and basal, isoproterenol-, forskolin-, and dibutyryl cAMPstimulated lipolysis in adipose tissue or mature adipocytes isolated from the omental and subcutaneous fat depots in a sample of 55 healthy women undergoing elective gynecological surgery. Measures of body fat mass and body fat distribution were also obtained by dual-energy X-ray absorptiometry and computed tomography. Subcutaneous adipocytes were significantly larger than omental adipocytes (P < 0.0001). LPL activity expressed as a function of cell number was significantly higher in subcutaneous versus omental adipose tissue (P < 0.0001). Basal, isoproterenol-stimulated, dibutyryl cAMP-stimulated (10 ؊3 mol/l) and forskolin-stimulated (10 ؊5 mol/l) lipolysis (expressed as a function of cell number) were all significantly higher in subcutaneous versus omental adipocytes (P < 0.05 to P < 0.0001). However, the response of omental adipocytes to lipolytic stimuli tested (fold increase over basal level) was significantly greater in magnitude compared with subcutaneous adipocytes (P < 0.01). These differences were relatively constant across total body fat mass and visceral adipose tissue area tertiles. In conclusion, compared with adipocytes from the omental fat compartment, subcutaneous adipocytes are larger, have higher LPL activity, and are more lipolytic on an absolute basis, which may reflect a higher fat storage capacity in this depot in women. In contrast, omental adipocytes display greater relative responsiveness to both adrenergic receptor-and postreceptor-acting agents compared with subcutaneous adipocytes. Overall and visceral obesity have only minor effects on regional differences in adipose tissue metabolism.

Hypertrophy and hyperplasia of abdominal adipose tissues in women

“…We also observed marked regional differences in adipose tissue metabolism in fat cells from these two depots, and these differences were relatively constant across the spectrum of adiposity values. 3 In men, omental and subcutaneous fat cells appear to reach similar sizes at relatively low body fatness values. Consequently, regional differences in fat cell metabolism are less apparent.…”

Markers of macrophage infiltration and measures of lipolysis in human abdominal adipose tissues

“…Adipocyte weight and cell number in the suspensions were calculated using lipid weight, average cell volume, and the density of triolein. Lipolysis data were previously published in a different study on regional differences in lipolytic responsiveness (20). On the basis of the demonstration that adipocyte size appears to be a critical determinant of regional differences in lipolysis, we expressed lipolytic responsiveness as fold over basal.…”

“…Glycerol release was assessed as described (20). Lipid weight of the cell suspension was measured using Dole's extraction.…”

“…Fresh tissue samples were digested with collagenase type I in KrebsRinger-Henseleit buffer for 45 min at 37 C according to a modified version of the Rodbell method (19), as described (20). Average adipocyte diameter was used in analyses.…”

Sagittal abdominal diameter is more predictive of cardiovascular risk than abdominal fat compartments in severe obesity

“…1,2 It has been proposed that cardiovascular risk factors are related to the proportions of several abdominal adipose subcompartments, rather than abdominal fat 'per se'. [3][4][5][6] By computed tomography (CT), these are distinguished as total subcutaneous (tSAT) and visceral adipose tissue (VAT). Within the former, a superficial subcompartment (sSAT) can be distinguished from the deep subcompartment (dSAT).…”