The effect of mosapride (5HT-4 receptor agonist) on insulin sensitivity in subjects with impaired glucose tolerance

Abstract

[한글]

Mosapride는 소화관 운동장애 시에 소화관 운동 촉진제로 널리 사용되어 지고 있는 약제이다. 최근 mosapride를 일본인 제 2형 당뇨병 환자에게 투여하였을 때 공복혈당이 감소하고 인슐린 저항성이 개선되었다는 보고가 있다. 본 연구는 내당능 장애환자로 제 2형 당뇨병의 위험도가 큰 당뇨병 전단계 환자에서 5HT-4 수용체 효현제인 mosapride를 투여하였을 때 내당능 장애 환자의 공복 혈당과 인슐린 저항성 개선 여부를 알아보고 mosapride가 인슐린 저항성을 개선시키는 기전을 알아보고자 하였다.Mosapride 투여군 20명, 위약군 10명을 선정하여 mosapride 5mg을 하루 3차례 경구 투여하기를 2주 동안 하였다. 이 때 약물 투여 전과 투여 2주 후 신체계측 및 생화학적 검사를 시행하고 정상혈당 클램프 검사(euglycemic hyperinsulinemic clamp test)를 시행하였다.또한, 일차 배양한 인간 골격근 세포에서 SDS-PAGE와 Immunoblotting 방법을 사용하여 인슐린과 mosapride를 처치 하였을 때 포도당수송체-4의 발현의 차이를 관찰하였다. 인슐린 신호 전달 체계에서 어떤 부위가 5HT-4 수용체 신호와 연관 되는지를 알아보기 위하여 인슐린수용체 기질-1의 인산화가 mosapride로 처치 하였을 때 증가하는 지를 관찰하였다.약물 투여 전 두 군간의 나이, 성별, 체 질량 지수, 혈압, 총 콜레스테롤, 중성지방, HDL 콜레스테롤, LDL 콜레스테롤의 차이는 없었다. 2주간 약물 투여 후 투여 군에서 투여전과 비교하여 공복혈당 (115.2 ± 21.3 vs. 107.11± 15.3 mg/dL, P<0.05), 공복 인슐린 (5.30 ± 3.0 vs. 4.81 ± 2.8 μIU/mL, P<0.05)이 의미있게 감소하였으며, 정상 혈당 클램프 검사에서 얻은 인슐린 감수성의 지표인 glucose disposal rate의 상승(5.47 ± 1.72 에서 7.06 ± 2.13 mg.kg-1.min-1, P<0.05)이 관찰되어 인슐린 저항성이 개선 되었음을 알 수 있었다.Mosaprede를 처치한 골격근세포에서 인슐린으로 자극하였을 때 포도당수송체-4의 세포막으로의 전위(translocation)가 증가됨을 관찰할 수 있었는데 이것을 mosapride의 인슐린 저항성 개선 기전으로 유추 할 수 있겠다. 인슐린 신호 전달 체계에서 어떤 부위가 5HT-4 수용체 신호와 연관 되는지를 알아보기 위하여 인슐린수용체 기질-1의 인산화가 mosapride 로 처치 하였을 때 증가하는 지를SDS-PAGE와 immunmonoblotting 방법을 이용하여 관찰하였으나 인슐린만 처치 한 골격근 세포와 비교하였을 때 오히려 감소 되는 것으로 나타났다.본 연구에서 내당능 장애 환자에서 mosapride를 경구로 투여하였을 때 공복혈당이 의미있게 감소하였고 이 때 C-peptide 의 증가가 동반되지 않은 것으로 보아, 췌장의 베타 세포를 자극하지 않은 상태에서 당 대사를 개선 시켰음을 알 수 있다. 췌장에서 인슐린 분비의 증가 없이 인슐린 저항성의 개선을 통해 당 대사를 호전 시켰음을 알 수 있고 인슐린 저항성의 개선은 정상 혈당 클램프 검사를 통해 확인 할 수 있었다. Mosapride의 인슐린 저항성 개선 기전은 아직 밝혀진 바가 없는데, 기존의 문헌을 통해 인간의 골격근에 5HT-4 수용체가 존재한다는 것이 알려져 있다. 본 연구에서도 인간 골격근에 mosapride를 처치 하였을 때 인슐린으로 자극한 경우 포도당수송체-4가 세포막으로 이동이 증가함을 확인 할 수 있었다. 그러나, 인슐린수용체 기질-1의 인산화는 오히려 인슐린만 처치 한 경우보다 감소하여 mosapride 의 포도당수송체-4가 세포막으로 전위를 증가시키는 기전이 세포내 인슐린 신호 전달체계의 초기 신호 단계와는 무관할 것으로 생각 할 수 있겠다. 인슐린 신호전달의 마지막 단계인 수송체-4의 전위를 유도하는데 중요한 역할을 하는 PI3-kinase 의 활성화 여부, 이 후 단계로 알려져 있는 AKt/atypical protein kinase C (ζ/λ)의 자극 여부 등 가능한 기전에 관한 연구가 mosapride의 인슐린 저항성 개선 기전을 밝히는데 더 필요하겠다.

[영문]Mosapride, a widely used prokinetic agent for the patients with non-ulcer dyspepsia, diabetic gastroparesis, or reflux esophagitis, enhances gastric emptying by the mechanism of the agonist action at serotonin 5-HT 4 (5-hydroxytryptamine) receptors and facilitation of cholinergic excitatory neurotransmission. Previous clinical study showed that mosapride is effective in decreasing plasma glucose concentrations without stimulating insulin secretion in type II diabetic patients. We investigated the effect of mosapride on blood glucose and insulin concentration in subjects with impaired glucose tolerance. To evaluate the mechanism of mosapride, we used human skeletal muscle cells in primary culture and in these cultured myotubes, we assessed insulin-induced GLUT-4 (glucose transporter 4) translocation and tyrosine phosphorylation of IRS-1 (insulin receptor substrate-1). Thirty subjects with impaired glucose tolerance were randomly assigned to receive either mosapride (5mg orally three times a day, n=20) or a placebo (n=10) for 2 weeks. Changes in blood glucose and insulin concentrations were determined basally as well as after mosapride treatment. Insulin sensitivity was evaluated during euglycemic hyperinsulinemic clamp test. After 2 weeks treatment of mosapride in subjects with IGT follow-up glucose disposal rates were higher than initial values, and were significantly increased to those of control (mosapride 5.47 ± 1.72 vs 7.06 ± 2.13 p=0.004, placebo 5.42 ± 1.85 vs 5.23 ± 1.53 mg.kg-1.min-1). Fasting plasma glucose and insulin levels were decreased. But other metabolic parameters such as blood pressure, total cholesterol, triglyceride and HDL-cholesterol were not improved. In primary cultured human skeletal muscle cell, GLUT-4 expression and tyrosine phosphorylation of IRS-1 is measured using SDS-PAGE and immunoblotting method. Mosapride increased contents of GLUT4 in the plasma membrane that occurs as result of the increased recruitment of glucose transporters from an intracellular pool to the cell surface. Treatment of human skeletal muscle cell with insulin resulted in tyrosine phosphorylation of IRS-1. In contrast, mosapride did not increase tyrosine phosphorylation of IRS-1. The present results indicate that 5 HT-4 receptor agonist is effective in decreasing plasma blood glucose concentration without stimulating insulin secretion in IGT subjects and its mechanism is potentially stimulation of GLUT4 translocation in skeletal muscle.Mosapride, a widely used prokinetic agent for the patients with non-ulcer dyspepsia, diabetic gastroparesis, or reflux esophagitis, enhances gastric emptying by the mechanism of the agonist action at serotonin 5-HT 4 (5-hydroxytryptamine) receptors and facilitation of cholinergic excitatory neurotransmission. Previous clinical study showed that mosapride is effective in decreasing plasma glucose concentrations without stimulating insulin secretion in type II diabetic patients. We investigated the effect of mosapride on blood glucose and insulin concentration in subjects with impaired glucose tolerance. To evaluate the mechanism of mosapride, we used human skeletal muscle cells in primary culture and in these cultured myotubes, we assessed insulin-induced GLUT-4 (glucose transporter 4) translocation and tyrosine phosphorylation of IRS-1 (insulin receptor substrate-1). Thirty subjects with impaired glucose tolerance were randomly assigned to receive either mosapride (5mg orally three times a day, n=20) or a placebo (n=10) for 2 weeks. Changes in blood glucose and insulin concentrations were determined basally as well as after mosapride treatment. Insulin sensitivity was evaluated during euglycemic hyperinsulinemic clamp test. After 2 weeks treatment of mosapride in subjects with IGT follow-up glucose disposal rates were higher than initial values, and were significantly increased to those of control (mosapride 5.47 ± 1.72 vs 7.06 ± 2.13 p=0.004, placebo 5.42 ± 1.85 vs 5.23 ± 1.53 mg.kg-1.min-1). Fasting plasma glucose and insulin levels were decreased. But other metabolic parameters such as blood pressure, total cholesterol, triglyceride and HDL-cholesterol were not improved. In primary cultured human skeletal muscle cell, GLUT-4 expression and tyrosine phosphorylation of IRS-1 is measured using SDS-PAGE and immunoblotting method. Mosapride increased contents of GLUT4 in the plasma membrane that occurs as result of the increased recruitment of glucose transporters from an intracellular pool to the cell surface. Treatment of human skeletal muscle cell with insulin resulted in tyrosine phosphorylation of IRS-1. In contrast, mosapride did not increase tyrosine phosphorylation of IRS-1. The present results indicate that 5 HT-4 receptor agonist is effective in decreasing plasma blood glucose concentration without stimulating insulin secretion in IGT subjects and its mechanism is potentially stimulation of GLUT4 translocation in skeletal muscle.Mosapride, a widely used prokinetic agent for the patients with non-ulcer dyspepsia, diabetic gastroparesis, or reflux esophagitis, enhances gastric emptying by the mechanism of the agonist action at serotonin 5-HT 4 (5-hydroxytryptamine) receptors and facilitation of cholinergic excitatory neurotransmission. Previous clinical study showed that mosapride is effective in decreasing plasma glucose concentrations without stimulating insulin secretion in type II diabetic patients. We investigated the effect of mosapride on blood glucose and insulin concentration in subjects with impaired glucose tolerance. To evaluate the mechanism of mosapride, we used human skeletal muscle cells in primary culture and in these cultured myotubes, we assessed insulin-induced GLUT-4 (glucose transporter 4) translocation and tyrosine phosphorylation of IRS-1 (insulin receptor substrate-1). Thirty subjects with impaired glucose tolerance were randomly assigned to receive either mosapride (5mg orally three times a day, n=20) or a placebo (n=10) for 2 weeks. Changes in blood glucose and insulin concentrations were determined basally as well as after mosapride treatment. Insulin sensitivity was evaluated during euglycemic hyperinsulinemic clamp test. After 2 weeks treatment of mosapride in subjects with IGT follow-up glucose disposal rates were higher than initial values, and were significantly increased to those of control (mosapride 5.47 ± 1.72 vs 7.06 ± 2.13 p=0.004, placebo 5.42 ± 1.85 vs 5.23 ± 1.53 mg.kg-1.min-1). Fasting plasma glucose and insulin levels were decreased. But other metabolic parameters such as blood pressure, total cholesterol, triglyceride and HDL-cholesterol were not improved. In primary cultured human skeletal muscle cell, GLUT-4 expression and tyrosine phosphorylation of IRS-1 is measured using SDS-PAGE and immunoblotting method. Mosapride increased contents of GLUT4 in the plasma membrane that occurs as result of the increased recruitment of glucose transporters from an intracellular pool to the cell surface. Treatment of human skeletal muscle cell with insulin resulted in tyrosine phosphorylation of IRS-1. In contrast, mosapride did not increase tyrosine phosphorylation of IRS-1. The present results indicate that 5 HT-4 receptor agonist is effective in decreasing plasma blood glucose concentration without stimulating insulin secretion in IGT subjects and its mechanism is potentially stimulation of GLUT4 translocation in skeletal muscle.