Magnesium upregulates insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide-induced type-2 diabetic rats
The effects of magnesium supplementation on glucose tolerance, insulin sensitivity, oxidative stress, concentration of insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide induced type-2 diabetic (T2D) rats.
JAN 1, 2018
Written by Morakinyo AO, Samuel TA, Adekunbi DA
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We investigated the effects of magnesium supplementation on glucose tolerance, insulin sensitivity, oxidative stress as well as the concentration of insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide induced type-2 diabetic (T2D) rats. Rats were divided into four groups designated as: 1) control (CTR); 2) diabetic untreated (DU); 3) diabetic treated with 1 mg of Mg/kg diet (Mg1-D); and 4) diabetic treated with 2 mg of Mg/kg diet (Mg2-D). T2D was induced with a single intraperitoneal (i.p.) injection of freshly prepared streptozotocin (55 mg/kg) aft er an initial i.p. injection of nicotinamide (120 mg/kg). Glucose tolerance, insulin sensitivity, lipid profile, malondialdehyde (MAD) and glutathione content, insulin receptors (INSR) and glucose transporter-4 (GLUT4), fasting insulin and glucose levels were measured, and insulin resistance index was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR). Magnesium supplementation improved glucose tolerance and lowered blood glucose levels almost to the normal range. We also recorded a noticeable increase in insulin sensitivity in Mg-D groups when compared with DU rats. Lipid perturbations associated T2D were significantly attenuated by magnesium supplementation. Fasting glucose level was comparable to control values in the Mg-D groups while the HOMA-IR index was significantly lower compared with the DU rats. Magnesium reduced MDA but increased glutathione concentrations compared with DU group. Moreover, INSR and GLUT4 levels were elevated following magnesium supplementation in T2D rats. These findings demonstrate that magnesium may mediate effective metabolic control by stimulating the antioxidant defense, and increased levels of INSR and GLUT4 in diabetic rats.
In conclusion, these data support a role for magnesium in glucose and lipid metabolism as well as insulin resistance in rat model of type 2 diabetes, which may be associated with the beneficial effect of magnesium in antioxidant defense as well as induction of increased insulin receptors and glucose transporter-4 proteins in the skeletal muscle. These findings provide a mechanistic basis for the use of magnesium supplements in the maintenance of glucose homeostasis in type 2 diabetes condition.