Intestinal-derived FGF15 preserves muscle and bone mass following sleeve gastrectomy

Abstract

Bariatric surgeries such as the Vertical Sleeve Gastrectomy (VSG) are invasive, but provide the most effective long-term metabolic improvements in obese and Type 2 diabetic patients. These powerful effects of manipulating the gastrointestinal tract point to an important role of gastrointestinal signals in regulating both energy balance and metabolism. To that end, we have used mouse models of VSG to identify key gut signals that mediate these beneficial effects. Preliminary data from our rodent model of VSG led us to hypothesize a potential role for the hormone Fibroblast-Growth Factor15/19 (mouse/human ortholog) which pharmacologically can regulate many aspects of energy homeostasis and glucose handling. FGF15 is expressed in ileal enterocytes of the small intestine and is released postprandially. Like many other gut hormones, postprandial plasma levels in humans and ileal FGF15 expression in mice increase after VSG. We generated intestinal-specific FGF15 knock out (VilCreERT2;Fgf15 f/f ) mice and controls, which were maintained on 60% high-fat diet. Interestingly, ablation of intestinal FGF15 in adult mice results in little change to body weight or glucose regulation when challenged with a high-fat diet. Unlike what we had predicted, intestinal-specific FGF15 knock out mice lost more weight after VSG and this was a result of increased lean tissue loss compared to control mice. Further, the loss of bone mineral density observed after VSG in control mice was increased in intestinal-specific FGF15 knock out mice. Finally the effect of VSG to reduce hepatic cholesterol was also absent in intestinal-specific FGF15 knock out mice. These data point to an important role for intestinal FGF15 to protect the organism from deleterious effects of rapid weight loss that occurs after VSG.