Insulin Secretion and Action in the Hyperthyroid Rat

Varnum, B.A.; Mb, Davidson; Venkatesan, Natarajan

doi:10.1055/s-2007-1013553

Cited by 8 publications

(2 citation statements)

References 25 publications

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“…Rats treated with T 4 for 5 days and then examined by use of IVGTT had lower serum insulin concentrations and significantly higher MCR-I values. 29 An increase in MCR-I has also been detected in hyperthyroid humans, and this variable has been positively correlated with serum free T 4 concentrations. 27 Increased insulin binding and a greater density of insulin receptors have been detected in adipocytes harvested from rats treated with T 4 .…”

Section: Discussionmentioning

confidence: 95%

Effects of oral administration of levothyroxine sodium on concentrations of plasma lipids, concentration and composition of very-low-density lipoproteins, and glucose dynamics in healthy adult mares

Frank¹,

Sommardahl²,

Eiler³

et al. 2005

ajvr

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Section: Discussionmentioning

confidence: 95%

Effects of oral administration of levothyroxine sodium on concentrations of plasma lipids, concentration and composition of very-low-density lipoproteins, and glucose dynamics in healthy adult mares

Frank¹,

Sommardahl²,

Eiler³

et al. 2005

ajvr

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“…After a 12-h fasting period rats were anaesthetized with an i.p: injection of sodium pentothal (75 mg/kg body weight). An intravenous glucose tolerance test (IVGTr) was performed as described by Varnum et al [19], with minor modifications. After tracheotomy, a catheter was placed into the right common carotid artery and a basal blood sample was taken.…”

Section: Materials Porcine Monocomponent Insulin (Novo Researchmentioning

confidence: 99%

Impaired tyrosine-kinase activity of muscle insulin receptors from hypomagnesaemic rats

Su�rez¹,

Pulido

Casla

et al. 1995

Diabetologia

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SummaryThe 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/1, p < 0.001), 2) higher basal serum glucose (6.8 +__ 0.2 vs 5.5 + 0.2 mmol/1, 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 x 10 -l~ mol/1 (3.0 + 0.9 vs 5.4 + 0.6, p < 0.05) and 5 x 10 -9 tool/1 (6.3 + 0.5 vs 8.0 + 0.5, p < 0.05), 3) normal glucose uptake at a maximal insulin concentration of i x 10 .7 mol/1, and 4) 50 % reduction in the insulin sensitivity (ED50:1.3 +_ 0.3 vs 0.55 + 0.1 mol/1, 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 fi-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.

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Impaired tyrosine-kinase activity of muscle insulin receptors from hypomagnesaemic rats

Suárez¹,

et al. 1995

View full text Add to dashboard Cite

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 +/- 0.02 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 x 10(-10) mol/l (3.0 +/- 0.9 vs 5.4 +/- 0.6, p < 0.05) and 5 x 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 x 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 beta-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.

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Insulin Secretion and Action in the Hyperthyroid Rat

Cited by 8 publications

References 25 publications

Effects of oral administration of levothyroxine sodium on concentrations of plasma lipids, concentration and composition of very-low-density lipoproteins, and glucose dynamics in healthy adult mares

Effects of oral administration of levothyroxine sodium on concentrations of plasma lipids, concentration and composition of very-low-density lipoproteins, and glucose dynamics in healthy adult mares

Impaired tyrosine-kinase activity of muscle insulin receptors from hypomagnesaemic rats

Impaired tyrosine-kinase activity of muscle insulin receptors from hypomagnesaemic rats

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