Sex-differential expression of metabolism-related genes in response to a high-fat diet

objective: The aim of this work was to determine the sex-associated differences in the expression of genes related to lipid metabolism and fuel partitioning in response to a high-fat ( HF) diet in rats, and whether this is linked to the higher tendency of males to suffer from metabolic disorders. Methods and Procedures: Male and female Wistar rats were fed for 6 months on a normal-fat ( NF) or an HF diet. Body weight, fat depot weight, lipid concentration in liver, blood metabolites, and the expression of genes involved in fuel metabolism and partitioning in the liver, white adipose tissue ( WAT), and skeletal muscle were measured. Results: Female rats fed on an HF diet gained more weight and had a greater increase in the adiposity index than male rats, while the circulating insulin levels remained unaltered; these animals also showed an increased expression of genes related to the energy influx in WAT and with fat utilization in skeletal muscle. Male but not female rats showed increased hepatic peroxisome proliferator-activated receptor-alpha ( PPAR-alpha) and CPT1L mRNA expression, suggesting enhanced lipid handling and oxidation by this organ, and have a higher triacylglycerol content in liver. Male rats under the HF diet also displayed higher blood insulin levels. Discussion: These results show sex-dependent differences in lipid handling and partitioning between tissues in response to an HF diet, with females showing a higher capacity for storing fat in adipose tissue and for oxidizing fatty acids in muscle. These adaptations can help to explain the lower tendency of females to suffer from obesity-linked disorders under the conditions of an HF diet.