Multiple factors promote insulin resistance. In this study, we evaluated the 
mRNA levels of presenilins-associated rhomboid-like protein (PARL) and 
mitochondrial content and enzyme activity from skeletal muscle isolated from 
insulin-resistant rats. Rats fed a high-fat diet for 35 days developed moderate 
insulin resistance, which was determined by an increase in plasma glucose and 
insulin concentrations following an oral glucose tolerance test. The PARL mRNA 
level was lower in the insulin-resistant rats than in control animals, and is 
associated with low mitochondrial content and reduced mitochondrial enzyme 
activity in the skeletal muscle from the insulin-resistant rats. The results 
suggest that high-fat-diet-induced insulin resistance is associated with 
mitochondrial dysfunction in skeletal muscle, and may be the result of the 
decreased expression of the PARL gene, which encodes the protein with functional 
significance in mitochondria.