The Role of Dennd5b in Intestinal Lipid Absorption and Metabolism

Project Title The role of Dennd5b in intestinal lipid absorption and metabolism Abstract Postprandial plasma triacylglyceride levels are independently associated with risk of cardiovascular disease. The intestine plays a dynamic role in the regulation of dietary triacylglyceride absorption by packaging and secreting lipids in chylomicron particles. The intracellular steps of chylomicron biogenesis and transport have been fairly well described, however, there is a significant knowledge gap in the mechanism for the final steps of chylomicron secretion by enterocytes, specifically post-golgi transport and secretion. We recently identified a protein that plays a critical role in this pathway, DENND5B. Our newly generated Dennd5b-/- mouse demonstrates an essential role for this gene in golgi to plasma membrane transport of chylomicron secretory vesicles. Dennd5b-deficient mice are resistant to diet-induced: obesity, changes in plasma lipids, and atherosclerosis. In humans, exome sequencing studies reveal that a common DENND5B variant is correlated with body mass index. These studies establish an important role for DENND5B in post-golgi chylomicron secretion and a subsequent influence on body composition and peripheral lipoprotein metabolism. The overall objective of this project is to gain fundamental knowledge about the process of dietary lipid absorption by the intestine and to apply this knowledge to identify novel targets for treatment of obesity and cardiovascular disease. This objective aligns well with the NIH mission to seek fundamental knowledge about living systems and to apply this knowledge to enhance health. While Dennd5b is expressed in the intestinal epithelium, it is also expressed at relatively high levels in liver and brain. Because our preliminary studies were performed in whole-body Dennd5b-/- mice, our recent NIH R01 submission proposed to develop a novel tissue-specific Dennd5b-/- mouse to better understand the mechanistic role of Dennd5b in the small intestine. Although we have recently generated a Dennd5b-floxed mouse strain, reviewer comments strongly criticized the proposal for not having the tissue-specific strain in hand. The objective of this Pilot proposal is to generate additional preliminary data in response to reviewer comments for our R01 resubmission. Aim 1 will develop an intestine- specific Dennd5b-/- mouse strain and measure dietary fat absorption to determine if their phenotype is consistent with whole-body knockout mice. Aim 2 will determine the impact of Dennd5b-/- on intestinal metabolic pathways by performing RNA sequencing analysis of intestinal tissue from tissue-specific knockout mice. Successful completion of these Aims will directly address reviewer concerns by generating and validating this strain and performing an initial characterization of the effects of intestinal Dennd5b knockout on metabolic pathways. Having this model and additional data on metabolic consequences of Dennd5b knockout with significantly strengthen our application for NIH funding.