Sex steroids deficiency impairs glucose transporter 4 expression and its translocation through defective Akt phosphorylation in target tissues of adult male rat.
There is a substantial body of evidence suggesting that altered level of sex steroids in male is associated with insulin resistance and type 2 diabetes mellitus. However, the mechanism of this effect is not apparent. Our recent study indicated that testosterone deprivation decreases insulin receptor expression and glucose oxidation in insulin target tissues. The present study was designed to assess the impact of deficiency of testosterone and estradiol on Akt phosphorylation, glucose transporter expression, and glucose uptake in skeletal muscle, adipose tissue, and liver of adult male rat. Adult male albino rats of Wistar strain were orchidectomized and supplemented with testosterone (100 microg/100 g body weight per day), estradiol (5 microg/100 g body weight per day), and their combination (100 microg testosterone plus 5 microg estradiol per 100 g body weight per day) for 15 days from the 11th day postorchidectomy. On the day after the last treatment, animals were perfused; and blood was collected for the assay of plasma glucose, serum insulin, testosterone, and estradiol. Gastrocnemius muscle, adipose tissue, and liver were dissected out and used for the assay of various parameters such as Akt phosphorylation, glucose transporter (GLUT) 2 and 4 expression, glucose uptake, and glycogenic and glycogenolytic enzymes activity. Castration elevated the blood glucose level, which was accompanied by inhibitory effect on serum insulin, Akt phosphorylation, GLUT4 expression and its plasma membrane population, glucose uptake, glycogen and glycogen synthase activity, and stimulatory effect on GLUT2 expression and glycogen phosphorylase activity in tissues studied. After testosterone and its combination with estradiol supplementation to castrated rats, a normal pattern of all these parameters was restored. Estradiol administration to castrated rats increased the Akt phosphorylation without altering other parameters studied. It is concluded from the present study that sex steroids deficiency-induced defective glucose uptake in skeletal muscle and adipose tissue is mediated through defective Akt phosphorylation and GLUT4 expression in plasma membrane.
Muthusamy
Thirupathi
T
Department of Endocrinology, Dr ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Chennai 600 113, Tamil Nadu, India.
Murugesan
Palaniappan
P
Balasubramanian
Karundevi
K
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D051273:Glucose Transporter Type 2 / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis* / Q000378:metabolism; D024981:Glycogen Phosphorylase / Q000378:metabolism; D012739:Gonadal Steroid Hormones / Q000172:deficiency*; D008099:Liver / Q000378:metabolism; D008112:Liver Glycogen / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D051058:Oncogene Protein v-akt / Q000378:metabolism*; D009919:Orchiectomy; D010766:Phosphorylation; D021381:Protein Transport; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013739:Testosterone / Q000494:pharmacology
D001786:Blood Glucose; D051273:Glucose Transporter Type 2; D051275:Glucose Transporter Type 4; D012739:Gonadal Steroid Hormones; D008112:Liver Glycogen; C495683:Slc2a2 protein, rat; C495694:Slc2a4 protein, rat; D013739:Testosterone; D004958:Estradiol; D024981:Glycogen Phosphorylase; D051058:Oncogene Protein v-akt; D005947:Glucose