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The GLP-1 analogue exenatide improves hepatic and muscle insulin sensitivity in diabetic rats: tracer studies in the basal state and during hyperinsulinemic-euglycemic clamp.

Wu H, Sui C, Xu H, Xia F, Zhai H, Zhang H, Weng P, Han B, Du S, Lu Y - J Diabetes Res (2014)

Bottom Line: During hyperinsulinemic-euglycemic clamp, glucose uptake into gastrocnemius muscles was measured with 2-deoxy-D-(14)C-glucose.During the clamp, Ra of glucose was also reduced, whereas the rate of disappearance of glucose increased and there was increased glucose uptake into muscle (P < 0.01) during the clamp.In addition to its known effects on insulin secretion, administration of the GLP-1 analogue, exenatide, is associated with increased inhibition of gluconeogenesis and improved glucose uptake into muscle in diabetic rats, implying improved hepatic and peripheral insulin sensitivity.

View Article: PubMed Central - PubMed

Affiliation: Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People's Hospital Affiliated Shanghai Jiaotong University School of Medicine, Shanghai 200011, China.

ABSTRACT

Objective: Glucagon-like peptide-1 (GLP-1) analogues (e.g., exenatide) increase insulin secretion in diabetes but less is known about their effects on glucose production or insulin-stimulated glucose uptake in peripheral tissues.

Methods: Four groups of Sprague-Dawley rats were studied: nondiabetic (control, C); nondiabetic + exenatide (C + E); diabetic (D); diabetic + exenatide (D + E) with diabetes induced by streptozotocin and high fat diet. Infusion of 3-(3)H-glucose and U-(13)C-glycerol was used to measure basal rates of appearance (Ra) of glucose and glycerol and gluconeogenesis from glycerol (GNG). During hyperinsulinemic-euglycemic clamp, glucose uptake into gastrocnemius muscles was measured with 2-deoxy-D-(14)C-glucose.

Results: In the diabetic rats, exenatide reduced the basal Ra of glucose (P < 0.01) and glycerol (P < 0.01) and GNG (P < 0.001). During the clamp, Ra of glucose was also reduced, whereas the rate of disappearance of glucose increased and there was increased glucose uptake into muscle (P < 0.01) during the clamp. In the nondiabetic rats, exenatide had no effect.

Conclusion: In addition to its known effects on insulin secretion, administration of the GLP-1 analogue, exenatide, is associated with increased inhibition of gluconeogenesis and improved glucose uptake into muscle in diabetic rats, implying improved hepatic and peripheral insulin sensitivity.

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Tracer perfusion platform in the rat. Catheters were inserted into the tail artery and vein. This procedure used small incisions and enabled the rats to be kept conscious and relaxed throughout the experiment. It was constantly infused through the i.v. infusion line driven by a Harvard mini-infusion pump (Harvard Apparatus, Holliston, MA, USA) for 75 min (basal period). The infusion rates were 0.5 μCi/kg/min (3-3H-glucose) and 0.84 μmol/kg/min (U-13C-glycerol). Blood was sampled prior to infusion of tracer and at 65, 70, and 75 min. Subsequently, while the 3-3H-glucose infusion continued, a primed and continuous infusion of recombinant human insulin 5 mIu/kg/min was initiated for another 90 min. The plasma glucose concentration was kept constant at the basal level by monitoring the plasma glucose every 10 minutes and empirically adjusting the infusion rate of a 50% glucose solution. Twenty minutes before the end of the chase period, 1 μCi of 2-deoxy-D-14C-glucose was injected through the i.v. infusion line to enable measurement of tissue glucose uptake. During the final 10 minutes, 3 more blood samples were collected at 5-minute intervals.
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fig1: Tracer perfusion platform in the rat. Catheters were inserted into the tail artery and vein. This procedure used small incisions and enabled the rats to be kept conscious and relaxed throughout the experiment. It was constantly infused through the i.v. infusion line driven by a Harvard mini-infusion pump (Harvard Apparatus, Holliston, MA, USA) for 75 min (basal period). The infusion rates were 0.5 μCi/kg/min (3-3H-glucose) and 0.84 μmol/kg/min (U-13C-glycerol). Blood was sampled prior to infusion of tracer and at 65, 70, and 75 min. Subsequently, while the 3-3H-glucose infusion continued, a primed and continuous infusion of recombinant human insulin 5 mIu/kg/min was initiated for another 90 min. The plasma glucose concentration was kept constant at the basal level by monitoring the plasma glucose every 10 minutes and empirically adjusting the infusion rate of a 50% glucose solution. Twenty minutes before the end of the chase period, 1 μCi of 2-deoxy-D-14C-glucose was injected through the i.v. infusion line to enable measurement of tissue glucose uptake. During the final 10 minutes, 3 more blood samples were collected at 5-minute intervals.

Mentions: All rats were fasted overnight (12–14 hours) and studied the following morning. After local anesthesia with lidocaine, catheters were inserted into the lateral tail vein for infusion of tracers and in the tail artery for blood sampling as described previously [9]. Throughout the experiments, animals were conscious and relaxed; they groomed normally and drank water periodically or sat calmly, indicating that stress resulting from the procedures was minimal (Figure 1). 3-3H-Glucose (PerkinElmer, Waltham, MA, USA) and U-13C-glycerol (Cambridge Isotope, Andover, MA, USA) were constantly infused through the i.v. infusion line driven by a Harvard mini-infusion pump (Harvard Apparatus, Holliston, MA, USA) for 75 min (basal period). The infusion rates were 0.5 μCi/kg/min (3-3H-glucose) and 0.84 μmol/kg/min (U-13C-glycerol). Blood was sampledprior to infusion of tracer and at 65, 70, and 75 min. Subsequently, while the 3-3H-glucose infusion continued, a primed and continuous infusion of recombinant human insulin (5 mIu/kg/min, Novolin R, Novo Nordisk, Denmark) was initiated for another 90 min (chase period). The plasma glucose concentration was kept constant at the basal level by monitoring the plasma glucose every 10 minutes and empirically adjusting the infusion rate of a 50% glucose solution. Twenty minutes before the end of the chase period, 1 μCi of 2-deoxy-D-14C-glucose (PerkinElmer) was injected through the i.v. infusion line to enable measurement of tissue glucose uptake. During the final 10 minutes, 3 more blood samples were collected at 5-minute intervals. A flow chart of the study design is shown in Figure 2. The rats were euthanized by heart opening under anesthesia with pentobarbital (50 mg/kg) to reduce the blood content of the tissues. A biopsy was promptly taken from gastrocnemius muscle, cut into small pieces and immersed in liquid nitrogen, and stored at −80°C. Plasma samples were prepared on ice, centrifuged at 4°C, separated, and stored at −80°C until assayed.


The GLP-1 analogue exenatide improves hepatic and muscle insulin sensitivity in diabetic rats: tracer studies in the basal state and during hyperinsulinemic-euglycemic clamp.

Wu H, Sui C, Xu H, Xia F, Zhai H, Zhang H, Weng P, Han B, Du S, Lu Y - J Diabetes Res (2014)

Tracer perfusion platform in the rat. Catheters were inserted into the tail artery and vein. This procedure used small incisions and enabled the rats to be kept conscious and relaxed throughout the experiment. It was constantly infused through the i.v. infusion line driven by a Harvard mini-infusion pump (Harvard Apparatus, Holliston, MA, USA) for 75 min (basal period). The infusion rates were 0.5 μCi/kg/min (3-3H-glucose) and 0.84 μmol/kg/min (U-13C-glycerol). Blood was sampled prior to infusion of tracer and at 65, 70, and 75 min. Subsequently, while the 3-3H-glucose infusion continued, a primed and continuous infusion of recombinant human insulin 5 mIu/kg/min was initiated for another 90 min. The plasma glucose concentration was kept constant at the basal level by monitoring the plasma glucose every 10 minutes and empirically adjusting the infusion rate of a 50% glucose solution. Twenty minutes before the end of the chase period, 1 μCi of 2-deoxy-D-14C-glucose was injected through the i.v. infusion line to enable measurement of tissue glucose uptake. During the final 10 minutes, 3 more blood samples were collected at 5-minute intervals.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4279913&req=5

fig1: Tracer perfusion platform in the rat. Catheters were inserted into the tail artery and vein. This procedure used small incisions and enabled the rats to be kept conscious and relaxed throughout the experiment. It was constantly infused through the i.v. infusion line driven by a Harvard mini-infusion pump (Harvard Apparatus, Holliston, MA, USA) for 75 min (basal period). The infusion rates were 0.5 μCi/kg/min (3-3H-glucose) and 0.84 μmol/kg/min (U-13C-glycerol). Blood was sampled prior to infusion of tracer and at 65, 70, and 75 min. Subsequently, while the 3-3H-glucose infusion continued, a primed and continuous infusion of recombinant human insulin 5 mIu/kg/min was initiated for another 90 min. The plasma glucose concentration was kept constant at the basal level by monitoring the plasma glucose every 10 minutes and empirically adjusting the infusion rate of a 50% glucose solution. Twenty minutes before the end of the chase period, 1 μCi of 2-deoxy-D-14C-glucose was injected through the i.v. infusion line to enable measurement of tissue glucose uptake. During the final 10 minutes, 3 more blood samples were collected at 5-minute intervals.
Mentions: All rats were fasted overnight (12–14 hours) and studied the following morning. After local anesthesia with lidocaine, catheters were inserted into the lateral tail vein for infusion of tracers and in the tail artery for blood sampling as described previously [9]. Throughout the experiments, animals were conscious and relaxed; they groomed normally and drank water periodically or sat calmly, indicating that stress resulting from the procedures was minimal (Figure 1). 3-3H-Glucose (PerkinElmer, Waltham, MA, USA) and U-13C-glycerol (Cambridge Isotope, Andover, MA, USA) were constantly infused through the i.v. infusion line driven by a Harvard mini-infusion pump (Harvard Apparatus, Holliston, MA, USA) for 75 min (basal period). The infusion rates were 0.5 μCi/kg/min (3-3H-glucose) and 0.84 μmol/kg/min (U-13C-glycerol). Blood was sampledprior to infusion of tracer and at 65, 70, and 75 min. Subsequently, while the 3-3H-glucose infusion continued, a primed and continuous infusion of recombinant human insulin (5 mIu/kg/min, Novolin R, Novo Nordisk, Denmark) was initiated for another 90 min (chase period). The plasma glucose concentration was kept constant at the basal level by monitoring the plasma glucose every 10 minutes and empirically adjusting the infusion rate of a 50% glucose solution. Twenty minutes before the end of the chase period, 1 μCi of 2-deoxy-D-14C-glucose (PerkinElmer) was injected through the i.v. infusion line to enable measurement of tissue glucose uptake. During the final 10 minutes, 3 more blood samples were collected at 5-minute intervals. A flow chart of the study design is shown in Figure 2. The rats were euthanized by heart opening under anesthesia with pentobarbital (50 mg/kg) to reduce the blood content of the tissues. A biopsy was promptly taken from gastrocnemius muscle, cut into small pieces and immersed in liquid nitrogen, and stored at −80°C. Plasma samples were prepared on ice, centrifuged at 4°C, separated, and stored at −80°C until assayed.

Bottom Line: During hyperinsulinemic-euglycemic clamp, glucose uptake into gastrocnemius muscles was measured with 2-deoxy-D-(14)C-glucose.During the clamp, Ra of glucose was also reduced, whereas the rate of disappearance of glucose increased and there was increased glucose uptake into muscle (P < 0.01) during the clamp.In addition to its known effects on insulin secretion, administration of the GLP-1 analogue, exenatide, is associated with increased inhibition of gluconeogenesis and improved glucose uptake into muscle in diabetic rats, implying improved hepatic and peripheral insulin sensitivity.

View Article: PubMed Central - PubMed

Affiliation: Institute and Department of Endocrinology and Metabolism, Shanghai Ninth People's Hospital Affiliated Shanghai Jiaotong University School of Medicine, Shanghai 200011, China.

ABSTRACT

Objective: Glucagon-like peptide-1 (GLP-1) analogues (e.g., exenatide) increase insulin secretion in diabetes but less is known about their effects on glucose production or insulin-stimulated glucose uptake in peripheral tissues.

Methods: Four groups of Sprague-Dawley rats were studied: nondiabetic (control, C); nondiabetic + exenatide (C + E); diabetic (D); diabetic + exenatide (D + E) with diabetes induced by streptozotocin and high fat diet. Infusion of 3-(3)H-glucose and U-(13)C-glycerol was used to measure basal rates of appearance (Ra) of glucose and glycerol and gluconeogenesis from glycerol (GNG). During hyperinsulinemic-euglycemic clamp, glucose uptake into gastrocnemius muscles was measured with 2-deoxy-D-(14)C-glucose.

Results: In the diabetic rats, exenatide reduced the basal Ra of glucose (P < 0.01) and glycerol (P < 0.01) and GNG (P < 0.001). During the clamp, Ra of glucose was also reduced, whereas the rate of disappearance of glucose increased and there was increased glucose uptake into muscle (P < 0.01) during the clamp. In the nondiabetic rats, exenatide had no effect.

Conclusion: In addition to its known effects on insulin secretion, administration of the GLP-1 analogue, exenatide, is associated with increased inhibition of gluconeogenesis and improved glucose uptake into muscle in diabetic rats, implying improved hepatic and peripheral insulin sensitivity.

Show MeSH
Related in: MedlinePlus