Liver Fatty Acid Binding Protein Gene-Ablated Female Mice Exhibit Increased Age-Dependent Obesity

摘要

Previous work done in our laboratory suggested a role for liver fatty acid binding protein (L-FABP) in obesity that develops in aging female L-FABP gene-ablated (−/−) mice. To examine this possibility in more detail, cohorts of wild-type (+/+) and L-FABP (−/−) female mice were fed a standard low-fat nonpurified rodent diet for up to 18 mo. Various obesity-related parameters were examined including body weight and fat and lean tissue mass. Obesity in (−/−) mice was associated with increased expression of nuclear receptors that induce peroxisome proliferator-activated receptor α (PPARα) (e.g., hepatocyte nuclear factor 1α, genotype effectα and of PPARα-regulated proteins involved in uptake of free (lipoprotein lipase and fatty acid transport protein, genotype and/or age effect) and esterified (scavenger receptor class B type 1, genotype effect) long chain fatty acids (LCFAs). Hepatic total lipid and neutral lipid levels were not affected by age or genotype, consistent with absence of gross and histologic steatosis. There was increased mRNA expression of liver proteins involved in LCFA oxidation [mitochondrial 3-oxoacyl-CoA thiolase (genotype effect) and butyryl-CoA dehydrogenase (genotype and/or age effect)], increased expression of LCFA esterification enzymes [glycerol-3-phosphate acyltransferase (age × genotype effect) and acyl-CoA:cholesterol acyltransferase-2 (genotype and/or age effect)], and increased expression of proteins involved in intracellular transfer and secretion of esterified LCFA [liver microsomal triacylglycerol transfer protein (genotype effect), serum apolipoprotein B (genotype or age effect), and liver apolipoprotein B (age and age × genotype effect)]. The data support a working model in which obesity development in these mice results from shifts toward reduced energy expenditure and/or more efficient energy uptake in the gut.