Serglycin Is Involved in Adipose Tissue Inflammation in Obesity.

Chronic local inflammation of adipose tissue is an important feature of obesity. Serglycin is a proteoglycan highly expressed by various immune cell types known to infiltrate adipose tissue under obese conditions. To investigate if serglycin expression has an impact on diet-induced adipose tissue inflammation, we subjected and mice (C57BL/6J genetic background) to an 8-wk high-fat and high-sucrose diet. The total body weight was the same in and mice after diet treatment. Expression of white adipose tissue genes linked to inflammatory pathways were lower in mice. We also noted reduced total macrophage abundance, a reduced proportion of proinflammatory M1 macrophages, and reduced formation of crown-like structures in adipose tissue of compared with mice. Further, mice had more medium-sized adipocytes and fewer large adipocytes. Differentiation of preadipocytes into adipocytes (3T3-L1) was accompanied by reduced mRNA expression. In line with this, analysis of single-cell RNA sequencing data from mouse and human adipose tissue supports that mRNA is predominantly expressed by various immune cells, with low expression in adipocytes. mRNA expression was higher in obese compared with lean humans and mice, accompanied by an increased expression of immune cell gene markers. and inflammatory marker mRNA expression was reduced upon substantial weight loss in patients after bariatric surgery. Taken together, this study introduces a role for serglycin in the regulation of obesity-induced adipose inflammation.