Glycine N-methyltransferase deficiency in female mice impairs insulin signaling and promotes gluconeogenesis by modulating the PI3K/Akt pathway in the liver

Yi Jen Liao, Tzong Shyuan Lee, Yuh Ching Twu, Shih Ming Hsu, Ching Ping Yang, Chung Kwe Wang, Yu Chih Liang, Yi-Ming Chen

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Background: Glycine N-methyltransferase (GNMT) is abundantly expressed in the normal liver but is down-regulated in liver cancer tissues. GNMT knockout (Gnmt-/-) mice can spontaneously develop chronic hepatitis, fatty liver, and liver cancer. We previously demonstrated that hepatic GNMT is decreased in high-fat-diet-induced type 2 diabetes mellitus, but its contribution to metabolic syndrome is unclear. Here we show that GNMT modulates key aspects of metabolic syndrome in mice. Methods: Eleven-week-old Gnmt-/- and wild-type (WT) mice with a C57BL/6 genetic background were used in this study. The metabolic defects of GNMT deficiency were measured by glucose and insulin tolerance tests, lipid homeostasis, gluconeogenesis, and insulin signaling. Results: Gnmt-/- mice, especially females, exhibited glucose intolerance and insulin resistance. However, their body fat and lean mass, food and water intakes, and energy expenditure did not differ from those of WT mice. In addition, glucose-stimulated insulin secretion and insulin-stimulated glucagon secretion were normal in the serum and pancreatic islets of Gnmt-/- mice. Importantly, we found that GNMT deficiency increased lipogenesis and triglycerides in the liver. The elevated triglycerides disrupted the ability of insulin to induce Akt and S6 ribosomal protein phosphorylation, and then triggered insulin resistance and gluconeogenesis in female Gnmt-/- mice. Conclusions: Our data indicate that hepatic GNMT regulates lipid and glucose homeostasis, and provide insight into the development of insulin resistance through modulating the PI3K/Akt pathway.

Original languageEnglish
Pages (from-to)1-9
Number of pages9
JournalJournal of Biomedical Science
Volume23
Issue number1
DOIs
Publication statusPublished - Oct 4 2016

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Glycine N-Methyltransferase
Gluconeogenesis
Phosphatidylinositol 3-Kinases
Liver
Insulin
Insulin Resistance
Liver Neoplasms
Glucose
Triglycerides
Homeostasis
Ribosomal Protein S6
Lipids
Lipogenesis
Glucose Intolerance
Fats
High Fat Diet
Fatty Liver
Chronic Hepatitis
Glucose Tolerance Test
Glucagon

Keywords

  • Glycine N-methyltransferase
  • Insulin signaling
  • Liver
  • PI3K/Akt pathway
  • Triglycerides

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Pharmacology (medical)

Cite this

Glycine N-methyltransferase deficiency in female mice impairs insulin signaling and promotes gluconeogenesis by modulating the PI3K/Akt pathway in the liver. / Liao, Yi Jen; Lee, Tzong Shyuan; Twu, Yuh Ching; Hsu, Shih Ming; Yang, Ching Ping; Wang, Chung Kwe; Liang, Yu Chih; Chen, Yi-Ming.

In: Journal of Biomedical Science, Vol. 23, No. 1, 04.10.2016, p. 1-9.

Research output: Contribution to journalArticle

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AU - Liao, Yi Jen

AU - Lee, Tzong Shyuan

AU - Twu, Yuh Ching

AU - Hsu, Shih Ming

AU - Yang, Ching Ping

AU - Wang, Chung Kwe

AU - Liang, Yu Chih

AU - Chen, Yi-Ming

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N2 - Background: Glycine N-methyltransferase (GNMT) is abundantly expressed in the normal liver but is down-regulated in liver cancer tissues. GNMT knockout (Gnmt-/-) mice can spontaneously develop chronic hepatitis, fatty liver, and liver cancer. We previously demonstrated that hepatic GNMT is decreased in high-fat-diet-induced type 2 diabetes mellitus, but its contribution to metabolic syndrome is unclear. Here we show that GNMT modulates key aspects of metabolic syndrome in mice. Methods: Eleven-week-old Gnmt-/- and wild-type (WT) mice with a C57BL/6 genetic background were used in this study. The metabolic defects of GNMT deficiency were measured by glucose and insulin tolerance tests, lipid homeostasis, gluconeogenesis, and insulin signaling. Results: Gnmt-/- mice, especially females, exhibited glucose intolerance and insulin resistance. However, their body fat and lean mass, food and water intakes, and energy expenditure did not differ from those of WT mice. In addition, glucose-stimulated insulin secretion and insulin-stimulated glucagon secretion were normal in the serum and pancreatic islets of Gnmt-/- mice. Importantly, we found that GNMT deficiency increased lipogenesis and triglycerides in the liver. The elevated triglycerides disrupted the ability of insulin to induce Akt and S6 ribosomal protein phosphorylation, and then triggered insulin resistance and gluconeogenesis in female Gnmt-/- mice. Conclusions: Our data indicate that hepatic GNMT regulates lipid and glucose homeostasis, and provide insight into the development of insulin resistance through modulating the PI3K/Akt pathway.

AB - Background: Glycine N-methyltransferase (GNMT) is abundantly expressed in the normal liver but is down-regulated in liver cancer tissues. GNMT knockout (Gnmt-/-) mice can spontaneously develop chronic hepatitis, fatty liver, and liver cancer. We previously demonstrated that hepatic GNMT is decreased in high-fat-diet-induced type 2 diabetes mellitus, but its contribution to metabolic syndrome is unclear. Here we show that GNMT modulates key aspects of metabolic syndrome in mice. Methods: Eleven-week-old Gnmt-/- and wild-type (WT) mice with a C57BL/6 genetic background were used in this study. The metabolic defects of GNMT deficiency were measured by glucose and insulin tolerance tests, lipid homeostasis, gluconeogenesis, and insulin signaling. Results: Gnmt-/- mice, especially females, exhibited glucose intolerance and insulin resistance. However, their body fat and lean mass, food and water intakes, and energy expenditure did not differ from those of WT mice. In addition, glucose-stimulated insulin secretion and insulin-stimulated glucagon secretion were normal in the serum and pancreatic islets of Gnmt-/- mice. Importantly, we found that GNMT deficiency increased lipogenesis and triglycerides in the liver. The elevated triglycerides disrupted the ability of insulin to induce Akt and S6 ribosomal protein phosphorylation, and then triggered insulin resistance and gluconeogenesis in female Gnmt-/- mice. Conclusions: Our data indicate that hepatic GNMT regulates lipid and glucose homeostasis, and provide insight into the development of insulin resistance through modulating the PI3K/Akt pathway.

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