Impaired Chylomicron Secretion Results in Reduced Body Fat and Increased Intestinal Fatty Acid Oxidation by Activation of Autophagy

Abstract Intestinal absorption of dietary lipid is essential for systemic lipid homeostasis; however, elevated postprandial plasma lipid levels are associated with obesity and increased risk for atherosclerotic cardiovascular disease. In humans and rodents, biological sex impacts dietary triglyceride absorption and males tend to have higher postprandial triglyceride levels compared to females, but the physiological basis for this is not well understood. Here, we show that the gene DENND5B is associated with body composition in humans and mice and that genetic deletion of Dennd5b in mice prevents postprandial plasma triglyceride elevations in both sexes. Our findings establish a role for this protein in intestinal chylomicron secretion and reveal a biological sex-biased differential impact of its deletion on body composition, dietary fatty acid uptake, and intestinal metabolism. Mechanistically, our findings implicate autophagy and mitochondrial beta oxidation in coping with enterocyte lipid accumulation due to impaired chylomicron secretion. This work extends the emerging concept that the intestinal epithelium may play a prominent role in oxidation of diet-derived fatty acids and suggests that this process may contribute to biological sex-based differences in postprandial lipemia and body composition. Highlights The DENND5B gene is required for dietary triglyceride absorption and is associated with metabolic phenotypes in humans and mice. Disruption of chylomicron secretion differentially affects body composition, dietary lipid absorption, and intestinal metabolic activity in male and female mice. In mice, genetic disruption of Dennd5b results in lower body fat in both sexes, and increased lean mass only in males. Metabolic phenotypes in Dennd5b-deficient mice are driven by reduced absorption of dietary lipid characterized by enterocyte lipid retention and increased fecal lipid excretion. Impaired chylomicron secretion in Dennd5b−/− mice induces autophagy-mediated disposal of cellular triglyceride and increased fatty acid oxidation in intestinal tissue. Competing Interest Statement The authors have declared no competing interest. Footnotes Minor edits to the main text and addition of one panel to Figure 6.