Abstract 19498: Scavenger Receptor BI (SR-BI) Deficiency Uncouples Obesity From Glucose Intolerance in Mice

Abstract

Introduction: Scavenger receptor BI (SR-BI) is a multi-purpose player in cholesterol metabolism. Interestingly, several studies in humans have suggested that a significant relationship exists between the presence of common variants in the SR-BI gene and a higher body mass index. We therefore evaluated the contribution of SR-BI to high fat diet-induced obesity in mice. Methods and Results: Male SR-BI knockout (SR-BI KO; N=10) and wild-type (WT; N=9) mice were fed a diet containing 45% energy as fat for 12 weeks. SR-BI KO mice exhibited a worsened metabolic plasma profile as compared to WT controls with higher fasting levels of free cholesterol (+111%; P<0.001), cholesterol esters (+84%; P<0.001), triglycerides (+40%; P<0.01), and glucose (+20%; P<0.01). Daily food intake was similar in the two types of mice; 4.5±0.3 g for SR-BI KO vs 4.1±0.3 g for WT. Importantly, the relative increase in body weight over time was significantly greater in SR-BI KO mice (+51%) as compared to WT controls (+33%; two-way ANOVA P<0.001 for genotype). The exacerbated increase in body weight could be attributed to a higher white adipose tissue mass (correlation coefficient R=0.87; P<0.001). High fat diet-fed WT mice were glucose intolerant, but remained resistant to atherosclerosis. In contrast, atherosclerotic lesions could be readily detected in the aortic root of SR-BI KO mice (6.9±1.5 x 10 3 μm 2 ; P<0.001), while their glucose tolerance was remarkably higher compared to that of controls (oral glucose tolerance test AUC 484±68 mM.min for SR-BI KO vs 875±130 mM.min for WT; P<0.05). SR-BI deficiency thus uncouples obesity from glucose intolerance in mice. Conclusions: Our studies for the first time show that a proper SR-BI function inhibits the development of obesity in mice. Furthermore, these data imply that SR-BI may serve as therapeutic target to overcome the glucose intolerance normally associated with the presence of (morbid) obesity.