HERZ Carsten

Brown Adipose Tissue and Bariatric Surgery

Obesity is a major cause of cardio-metabolic morbidity and mortality in the Western world. Bariatric surgery has proven to be the most effective therapeutic approach to normalize weight and subsequently reduce obesity-associated risk. So far, it has however not been entirely elucidated how bariatric procedures exert these beneficial effects which cannot be solely explained by the procedures' restrictive and malabsorptive components. In the last years, brown adipose tissue (BAT) has emerged as a potential player in human energy metabolism. Studies have shown that the presence of BAT is associated with a more favorable metabolic profile and that bariatric procedures increase the presence and activity of BAT in humans. Following bariatric surgery, circulating levels of B-type natriuretic peptide (BNP) increase by more than two-fold. BNP as wells as atrial natriuretic peptide (ANP), on the other hand, induce a thermogenic program in adipocytes and thereby increase the volume and the activity of BAT. Additionally, changes in post-prandial incretin response and bile acid metabolism as well as changes in gut microbial composition have previously been hypothesized to contribute the success of metabolic surgery. There is literature in other settings that these changes are linked to increased BAT activity as well. So far there no studies examining the physiological mechanisms underlying the increase in BAT activity following bariatric surgery. Based on these observations, we hypothesize that:

• the increase in BAT activity is associated with the loss of fat mass following surgery
• the increases in circulating natriuretic peptides (ANP and BNP) levels are associated with the increase in BAT activity following surgery
• the increases in circulating post-prandial bile acid levels are associated with the increase in BAT activity following surgery
• the increases in circulating glucagon-like peptide 1 (GLP-1) levels are associated with the increase in BAT activity following surgery
• the increase in BAT activity is linked to distinct changes in the gut microbiome following surgery
• the increase in BAT activity is associated with the improvement in insulin sensitivity following surgery
• there is a difference between one-anastomosis gastric bypass (OAGB) and sleeve gastrectomy (SG) in post-operative BAT activation

Methods and Skills:

Indirect calorimetry; body composition analysis; clinical studies