Subcutaneous adipocyte size but not adiposity was associated with inflammation, ER stress, and insulin resistance markers

Background: The fat storage capability of the adipose tissue prevents ectopic lipid deposition, which is one of the risk factors for metabolic abnormalities in obesity. This capability depends on the adipogenic gene expression and blood supply provision for tissue expansion through angiogenesis. Here, we studied hyperplasia/hypertrophy of subcutaneous white adipose tissue (scWAT) concerning adipogenic gene expression, angiogenic status, and metabolic parameters in non-obese, Class I, and Class II+III obese subjects. Methods: The scWAT samples were collected from 80 subjects. The anthropometric parameters, adipose tissue cell size, serum biochemistry, ER stress induced XBP1 splicing, PPARγ2, SFRP1, WNT10B, and VEGFA gene expression levels were studied. In addition, the CD31 level was investigated by Western blotting. Results: The obese subjects had greater waist circumferences and higher serum TG, TC, insulin, and HOMA-IR than the non-obese group. The Class I obese group showed the largest adipocyte size, increased TNFα, insulin, HOMA-IR, and sXBP-1, WNT10B, and VEGFAexpression. In contrast, the expression of SFRP1 was not significantly different between all studied groups. The Class II+III obesity group showed high PPARγ2 expression and CD31 levels. Class I obesity, with hypertrophic scWAT adipocytes and limited capability of adipose tissue expansion, showed inflammation, insulin resistance, and ER stress. Conclusion: The results suggest that the capability of adipogenesis with inadequate angiogenesis is related to metabolic status, inflammation, and ER function. Therefore, therapeutic strategies to simultaneously promote angiogenesis and adipogenesis can effectively prevent obesity complications.