Hiroyuki Sato1, Naoto Kubota2,3,4,5, Tetsuya Kubota1,6,7,8, Iseki Takamoto1, Kaito Iwayama9, Kumpei Tokuyama9, Masao Moroi8, Kaoru Sugi8, Keizo Nakaya10, Moritaka Goto10, Takahito Jomori10, Takashi Kadowaki11. 1. Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. 2. Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. nkubota-tky@umin.ac.jp. 3. Department of Clinical Nutrition Therapy, University of Tokyo, Tokyo, Japan. nkubota-tky@umin.ac.jp. 4. Clinical Nutrition Program, National Institute of Health and Nutrition, Tokyo, Japan. nkubota-tky@umin.ac.jp. 5. Laboratory for Metabolic Homeostasis, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan. nkubota-tky@umin.ac.jp. 6. Clinical Nutrition Program, National Institute of Health and Nutrition, Tokyo, Japan. 7. Laboratory for Metabolic Homeostasis, RIKEN Center for Integrative Medical Sciences, Kanagawa, Japan. 8. Division of Cardiovascular Medicine, Toho University Ohashi Medical Center, Tokyo, Japan. 9. Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan. 10. Mie Research Laboratories, Sanwa Kagaku Kenkyusho Co. Ltd, Mie, Japan. 11. Department of Diabetes and Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. kadowaki-3im@h.u-tokyo.ac.jp.
Abstract
AIMS/HYPOTHESIS: Recently, incretin-related agents have been reported to attenuate insulin resistance in animal models, although the underlying mechanisms remain unclear. In this study, we investigated whether anagliptin, the dipeptidyl peptidase 4 (DPP-4) inhibitor, attenuates skeletal muscle insulin resistance through endothelial nitric oxide synthase (eNOS) activation in the endothelial cells. We used endothelium-specific Irs2-knockout (ETIrs2KO) mice, which show skeletal muscle insulin resistance resulting from a reduction of insulin-induced skeletal muscle capillary recruitment as a consequence of impaired eNOS activation. METHODS: In vivo, 8-week-old male ETIrs2KO mice were fed regular chow with or without 0.3% (wt/wt) DPP-4 inhibitor for 8 weeks to assess capillary recruitment and glucose uptake by the skeletal muscle. In vitro, human coronary arterial endothelial cells (HCAECs) were used to explore the effect of glucagon-like peptide 1 (GLP-1) on eNOS activity. RESULTS: Treatment with anagliptin ameliorated the impaired insulin-induced increase in capillary blood volume, interstitial insulin concentration and skeletal muscle glucose uptake in ETIrs2KO mice. This improvement in insulin-induced glucose uptake was almost completely abrogated by the GLP-1 receptor (GLP-1R) antagonist exendin-(9-39). Moreover, the increase in capillary blood volume with anagliptin treatment was also completely inhibited by the NOS inhibitor. GLP-1 augmented eNOS phosphorylation in HCAECs, with the effect completely disappearing after exposure to the protein kinase A (PKA) inhibitor H89. These data suggest that anagliptin treatment enhances insulin-induced capillary recruitment and interstitial insulin concentrations, resulting in improved skeletal muscle glucose uptake by directly acting on the endothelial cells via NO- and GLP-1-dependent mechanisms in vivo. CONCLUSIONS/ INTERPRETATION: Anagliptin may be a promising agent to ameliorate skeletal muscle insulin resistance in obese patients with type 2 diabetes.
AIMS/HYPOTHESIS: Recently, incretin-related agents have been reported to attenuate insulin resistance in animal models, although the underlying mechanisms remain unclear. In this study, we investigated whether anagliptin, the dipeptidyl peptidase 4 (DPP-4) inhibitor, attenuates skeletal muscle insulin resistance through endothelial nitric oxide synthase (eNOS) activation in the endothelial cells. We used endothelium-specific Irs2-knockout (ETIrs2KO) mice, which show skeletal muscle insulin resistance resulting from a reduction of insulin-induced skeletal muscle capillary recruitment as a consequence of impaired eNOS activation. METHODS: In vivo, 8-week-old male ETIrs2KO mice were fed regular chow with or without 0.3% (wt/wt) DPP-4 inhibitor for 8 weeks to assess capillary recruitment and glucose uptake by the skeletal muscle. In vitro, human coronary arterial endothelial cells (HCAECs) were used to explore the effect of glucagon-like peptide 1 (GLP-1) on eNOS activity. RESULTS: Treatment with anagliptin ameliorated the impaired insulin-induced increase in capillary blood volume, interstitial insulin concentration and skeletal muscle glucose uptake in ETIrs2KO mice. This improvement in insulin-induced glucose uptake was almost completely abrogated by the GLP-1 receptor (GLP-1R) antagonist exendin-(9-39). Moreover, the increase in capillary blood volume with anagliptin treatment was also completely inhibited by the NOS inhibitor. GLP-1 augmented eNOS phosphorylation in HCAECs, with the effect completely disappearing after exposure to the protein kinase A (PKA) inhibitor H89. These data suggest that anagliptin treatment enhances insulin-induced capillary recruitment and interstitial insulin concentrations, resulting in improved skeletal muscle glucose uptake by directly acting on the endothelial cells via NO- and GLP-1-dependent mechanisms in vivo. CONCLUSIONS/ INTERPRETATION:Anagliptin may be a promising agent to ameliorate skeletal muscle insulin resistance in obesepatients with type 2 diabetes.