Cardiovascular disease (CVD) and pulmonary disease are strongly correlated, but the molecular basis of this connection is not known. Altered lipid metabolism is a known determinant of CVD, and alveolar type 2 cells (T2C) sustain a highly active lipid metabolism to maintain surfactant homeostasis. Surfactant is mainly composed of phospholipids. The low-density lipoprotein receptor related protein 1 (LRP1) was described as a chylomicron remnant receptor, but it can participate in many cell processes. Mutations in (LRP1) correlate with decreased lung function in chronic obstructive pulmonary disease patients, but the role of LRP1 in the lung is unknown. We hypothesize that lipid metabolism and LRP1 in T2C link pulmonary and cardiovascular disease and have generated in vitro and in vivo models to study the role of LRP1 in lipid and lipoprotein metabolism.LRP1 shRNA-stably transfected human T2C were generated. They showed intracellular triglyceride and decreased phospholipid intracellularly and in the secreted surfactant. This was associated with lower mRNA expression of lipid metabolic enzymes. We have also generated a tamoxifen-inducible T2C-specific LRP1 knockout mouse (SPC-LRP1-/-). SPC-LRP1-/- mice had higher body weight and adiposity than WT mice. SPC-LRP1-/- mice also showed a twofold increase in fasting plasma TG levels and larger liver cytoplasmic lipid droplets. We hypothesize that that LRP1 in T2C partakes in systemic lipoprotein metabolism. We will determine the impact of T2C-specific LRP1 knockout on lipid and lipoprotein metabolism in vivo. We will test tissue TG and liver lipoprotein secretion in WT and in SPC-LRP1-/- mice. The origin of hepatic TG will be determined by pathway and lipidomic analysis in collaboration with Dr Area (Lipidomics Core, Columbia University). We will also analyze hepatic mitochondrial fatty acid oxidation and adipose morphology and lipid metabolism. We will determine the role of LRP1 in T2C lipid metabolism regulation too. TG uptake will be measured in T2C from WT and SPC-LRP1-/- mice. We will analyze intracellular T2C lipid metabolism by assessing anabolic and catabolic pathways. Lipogenesis, fatty acid oxidation and lipophagy will be measured. Surfactant secretion to the alveoli will also be measured and common and alternative pathways of phospholipid synthesis will also be assessed.The experiments in this proposal will help understand the relationship between cardiovascular and pulmonary disease.
|Effective start/end date||07/01/2017 → 06/30/2019|