Women undergoing repeated bariatric surgery due to recurrent weight gain exhibit an inflammatory molecular and functional signature of subcutaneous adipose tissue

Background: Repeated metabolic-bariatric surgery (MBS, r-BS) represents 10-25% of all MBS procedures and is commonly performed for recurrent weight gain after initial weight loss. How weight loss followed by regain reshapes adipose tissue biology remains unclear. We hypothesized that women undergoing r-BS exhibit a distinct adipose tissue signature compared with those undergoing primary bariatric surgery (p-BS). Methods: We analyzed subcutaneous and visceral adipose tissues (SAT, VAT, respectively) from women undergoing either p-BS, or r-BS with documented >15% weight loss after prior MBS. Tissues were assessed histologically, molecularly, and functionally (activation of human microglia cells (HMC3) by SAT secretome). Results: Consistent with other cohorts, women undergoing r-BS (n=21) trended to be older (47.2 vs. 40.5 y, p=0.06) than those undergoing p-BS (n=35), with a lower BMI (42.3 vs. 45.6 kg/m2, respectively, p=0.103), and a trend for improved cardiometabolic risk parameters such as fasting insulin, CRP and HDL-c. Adipose tissue histological features (adipocyte size, fibrosis, macrophage and crown-like structure abundance) were similar, while adipose mast cells were slightly (though insignificantly) more prevalent in r-BS. A single-nucleus RNA-seq-based deconvolution algorithm applied to bulk RNA-seq confirmed the absence of a major shift in adipose tissue cell-type composition. Yet, it uncovered a unique SAT transcriptome, with activation of inflammatory pathways in r-BS. Consistently, SAT explants from r-BS secreted higher protein concentrations of NFkB-regulated cytokines IL6 and IL8. Biological impact of the more inflammatory secretome was demonstrated by its increased ability to activate human microglia cells. Conclusions: Prior BS with significant weight loss-regain in women is associated with an inflammatory SAT transcriptome and secretome, possibly reflecting altered adipose-brain endocrine communication.