Gene Expression Profile In Skeletal Muscle Of Type 2 Diabetic Rats

Objectives: To explore gene expression profile in skeletal muscle between type 2 diabetic rats and normal rats using cDNA microarray. Methods: (1) The rats were assigned to normal rats and type 2 diabetic rats developed by intraperitoneal injection low dose streptozotocin(STZ) plus high fat diet. (2) Skeletal muscle biopsy specimens from two groups were assayed by electron microscopy. (3) Total RNA was isolated from skeletal muscle tissue and converted to cDNA by reverse transcription.The probes were prepared by labeling normal tissue mRNA and tissue mRNA of diabetic rats with Cy3-dUTP and Cy5-dUTP separately. (4) The mixed probes were hybridized to cDNA microarray(including 4096 genes).The microarray was scanned for the fluorescent signals. (5) Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) validation was performed on several differential expression of genes.Results: (1) The body mass and serum triglyceride fast blood glucose and insulin of the diabetes group were significantly increased and insulin seasitivity index was decreased. (2) Using electron microscopy, intramyocellula lipid deposition and mitochondria swelling were found in type 2 diabetic rats. (3) Of the 4096 genes on the array, 257 genes were identified with statistically changs in the level of expression, including 36 expressed sequence tags(ESTs), 157 genes were up-regulated and 100 genes were down-regulated. Genes of inhibiting glycolysis, accelerating glycogenolysis and gluconeogenesis were up-regulated in type 2 diabetic rats. (4) Genes of lipoprotein lipase and the enzymes related to fatty acid (-oxidation were also up-regulated in type 2 diabetic rats. (5) Genes of mitochondrial electron transport chain and energy metabolism were down-regulated. (6) Genes related to insulin signaling pathway altered in type 2 diabetic rats. (7) Genes of anti-oxidation stress were down -regulated. (8) Using RT-PCR approach, lipoprotein lipase and thiolase were up-regulated in type 2 diabetic rats.Conclusions: (1) This novel rat model simulates human type 2 diabetes in obesity, hyperglycemia, hypertriglyceridemia and insulin resistance. It may provide a particular advantage for investigating type 2 diabetes and diabetic complications. (2) The accumulation of lipid in skeletal muscle and increasing of fatty acid (-oxidation in type 2 diabetic rats could inhibit glucose oxidation and mitochondrial energy metabolism.It may play an important role in the pathogenesis of insulin resistance in skeletal muscle.