Dynamics of adipose tissue macrophage populations after gastric bypass surgery

ObjectiveThis case-control study aimed to analyze the dynamics of macrophage infiltration in subcutaneous adipose tissue following bariatric surgery or conservative treatment of obesity and to clarify whether these features predict the weight loss outcome after the surgery. MethodsSubcutaneous tissue samples taken before and 12 months after laparoscopic Roux-en-Y gastric bypass surgery (n = 39) or conservative (n = 43) treatment for obesity were analyzed. Fat cell size was determined, and with CD68 immunohistochemistry, crown-like structures (CLS) were counted and single macrophages were quantitated. ResultsA major decline in CLS density from 4.1 (SD 3.5) to 1.1 (SD 0.8) per 1000 fat cells (p < 0.000) was found, regardless of the degree of weight loss after the surgery. Surgery had no effect on the fraction of infiltrating single-cell macrophages in subcutaneous adipose tissue. The abundance of these macrophage populations before the intervention did not predict the degree of postsurgery weight loss or suboptimal response to the surgery. ConclusionsThe effect of gastric bypass on adipose tissue inflammatory status associates closely with CLS density even in subjects with suboptimal weight loss. The study suggests that factors related to bypass surgery other than weight loss modify the inflammatory response in adipose tissue.

Automated summary

This case-control study analyzed the macrophage infiltration in subcutaneous adipose tissue after bariatric surgery or conservative treatment of obesity, and investigated whether these features could predict weight loss outcome. The study found a significant decline in crown-like structures (CLS) density after surgery, regardless of weight loss. However, surgery had no effect on the infiltration of single-cell macrophages, and the abundance of these macrophage populations before surgery did not predict weight loss or response to surgery.