ISSN:
1432-0428
Keywords:
Key words Magnesium
;
insulin receptors
;
tyrosine kinase
;
skeletal muscle
;
insulin secretion
;
glucose disposal
;
GLUT 4.
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effect of magnesium deficiency on glucose disposal, glucose-stimulated insulin secretion and insulin action on skeletal muscle was investigated in rats which were fed a low magnesium-containing diet for 4 days. Control rats were fed a standard diet. Compared to the control rats, the rats fed with low magnesium diet presented: 1) lower serum magnesium levels (0.45 ± 0.02 vs 0.78 ± 0.01 mmol/l, p 〈 0.001), 2) higher basal serum glucose (6.8 ± 0.2 vs 5.5 ± 0.2 mmol/l, p 〈 0.05) and similar basal serum insulin, 3) 40 % reduction (p 〈 0.001) in the glucose disappearance rate after its i. v. administration, and 4) 45 % reduction (p 〈 0.05) in the glucose-stimulated insulin secretion. The insulin action upon the glucose uptake by skeletal muscle was determined by means of hindquarter perfusions. Compared with control rats, magnesium-deficient rats presented: 1) normal basal glucose uptake, 2) lower stimulatory effect on the glucose uptake by insulin at the concentrations of 5 × 10−10 mol/l (3.0 ± 0.9 vs 5.4 ± 0.6, p 〈 0.05) and 5 × 10−9 mol/l (6.3 ± 0.5 vs 8.0 ± 0.5, p 〈 0.05), 3) normal glucose uptake at a maximal insulin concentration of 1 × 10−7 mol/l, and 4) 50 % reduction in the insulin sensitivity (ED50: 1.3 ± 0.3 vs 0.55 ± 0.1 mol/l, p 〈 0.05). In partially purified insulin receptors prepared from gastrocnemius muscle, 125I-insulin binding was similar in both groups of rats. However, the autophosphorylation of the β -subunit of the insulin receptor was significantly reduced by 50 % in magnesium-deficient rats and the tyrosine kinase activity of insulin receptors toward the exogenous substrate Poly Glu4: Tyr 1 was also reduced (p 〈 0.05) by hypomagnesaemia. The abundance of the insulin-sensitive glucose transporter protein (muscle/fat GLUT4), measured by Western blot analysis using polyclonal antisera, was similar in muscles of control and hypomagnesaemic rats. These findings indicate that hypomagnesaemia has a deleterious effect on glucose metabolism due to an impairment of both insulin secretion and action. The insulin resistance observed in skeletal muscle of magnesium-deficient rats may be attributed, at least in part, to a defective tyrosine kinase activity of insulin receptors. [Diabetologia (1995) 38: 1262–1270]
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00401757
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