Surf4 deficiency reduces intestinal lipid absorption and secretion and decreases metabolism in mice

Background Postprandial dyslipidemia is a causative risk factor for cardiovascular disease. The majority of absorbed dietary lipids are packaged into chylomicron and then delivered to circulation. Previous studies showed that Surfeit4 (Surf4) mediates very low-density lipoprotein secretion from hepatocytes. Silencing hepatic Surf4 markedly reduces the development of atherosclerosis in different mouse models of atherosclerosis without causing hepatic steatosis. However, the role of Surf4 in chylomicron secretion is unknown. Methods We developed inducible intestinal-specific Surf4 knockdown mice ( Surf4 IKO ) using Vil 1Cre-ER T2 and Surf4 flox mice. Metabolic cages were used to monitor mouse metabolism. Enzymatic kits were employed to measure serum and tissue lipid levels. The expression of target genes was detected by qRT-PCR and Western Blot. Transmission electron microscopy and radiolabeled oleic acid were used to assess the structure of enterocytes and intestinal lipid absorption and secretion, respectively. Proteomics was performed to determine changes in protein expression in serum and jejunum. Results Surf4 IKO mice, especially male Surf4 IKO mice, displayed significant body weight loss, increased mortality, and reduced metabolism. Surf4 IKO mice exhibited lipid accumulation in enterocytes and impaired fat absorption and secretion. Lipid droplets and small lipid vacuoles were accumulated in the cytosol and the endoplasmic reticulum lumen of the enterocytes of Surf4 IKO mice, respectively. Surf4 colocalized with apoB and co-immunoprecipitated with apoB48 in differentiated Caco-2 cells. Intestinal Surf4 deficiency also significantly reduced serum triglyceride, cholesterol and free fatty acid levels in mice. Proteomics data revealed that diverse pathways were altered in Surf4 IKO mice. In addition, Surf4 IKO mice had mild liver damage, decreased liver size and weight, and reduced hepatic triglyceride levels. Conclusion Our findings demonstrate that intestinal Surf4 plays an essential role in lipid absorption and chylomicron secretion and suggest that the therapeutic use of Surf4 inhibition requires highly cell/tissue-specific targeting. Highlights Intestinal Surf4 deficiency reduces chylomicron secretion. Lack of intestinal Surf4 reduces absorption of dietary lipids. Silencing intestinal Surf4 reduces serum lipid levels. Intestinal Surf4 deficiency leads to lipid accumulation in intestinal villi. Intestinal Surf4 is essential for dietary lipid absorption and secretion.