Adipose Tissue and Metabolic Alterations: Regional Differences in Fat Cell Size and Number Matter, but Differently: a Cross-sectional Study

Objective: White adipose tissue can expand by increasing the size and/or number of fat cells. Although increased sc and visceral fat cell size associates with an adverse metabolic profile, the relationship with fat cell number in either depot is unknown. We hypothesized that adipocyte number and size displayed different relationships with clinically relevant metabolic variables.

Methods: This was a cross-sectional study of 204 patients scheduled for gastric bypass surgery. Fat cell size and number were determined in visceral and abdominal sc adipose tissue and related to insulin sensitivity (by hyperinsulinemic euglycemic clamp), fasting plasma levels of insulin, triglycerides and high-density lipoprotein (HDL) cholesterol.

Results: Visceral and sc fat cell volumes were positively correlated with insulin and triglyceride levels and negatively with insulin sensitivity and HDL-cholesterol (P = .0020 or better). In contrast, although visceral fat cell number did not associate with any metabolic parameter, sc adipocyte number displayed a positive association with insulin sensitivity and HDL-cholesterol and a negative relationship with insulin and triglyceride levels (P = .0014 or better). All results were independent of body fat mass.

Conclusions: Variations in fat cell size and number correlate differently with metabolic parameters in obesity. Increased fat cell size in visceral and sc depots associates with a pernicious metabolic profile, whereas increased sc, but not visceral, fat cell number correlates with a more beneficial phenotype. Whether determination of sc fat cell number, in addition to adipocyte size, may have a predictive value for the risk of type 2 diabetes needs to be demonstrated in prospective or mechanistic studies.