Scavenger receptor BI (SR-BI) has been suggested to modulate adipocyte function. To uncover the potential relevance of SR-BI for the development of obesity and associated metabolic complications, we compared the metabolic phenotype of wild-type and SR-BI deficient mice fed an obesogenic diet enriched in fat. Both male and female SR-BI knockout mice gained significantly more weight as compared to their wild-type counterparts in response to 12 weeks high fat diet feeding (1.5-fold; P < .01 for genotype). Plasma free cholesterol levels were ~2-fold higher (P < .001) in SR-BI knockout mice of both genders, whilst plasma cholesteryl ester and triglyceride concentrations were only significantly elevated in males. Strikingly, the exacerbated obesity in SR-BI knockout mice was paralleled by a better glucose handling. In contrast, only SR-BI knockout mice developed atherosclerotic lesions in the aortic root, with a higher predisposition in females. Biochemical and histological studies in male mice revealed that SR-BI deficiency was associated with a reduced hepatic steatosis degree as evident from the 29% lower (P < .05) liver triglyceride levels. Relative mRNA expression levels of the glucose uptake transporter GLUT4 were increased (+47%; P < .05), whilst expression levels of the metabolic PPARgamma target genes CD36, HSL, ADIPOQ and ATGL were reduced 39%-58% (P < .01) in the context of unchanged PPARgamma expression levels in SR-BI knockout gonadal white adipose tissue. In conclusion, we have shown that SR-BI deficiency is associated with a decrease in adipocyte PPARgamma activity and a concomitant uncoupling of obesity development from hepatic steatosis and glucose intolerance development in high fat diet-fed mice.
Keywords: PPARgamma; adipocyte; glucose intolerance; hepatic steatosis; obesity; scavenger receptor BI.
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