The protective roles of GLP-1R signaling in diabetic nephropathy: possible mechanism and therapeutic potential.

Abstract

Glucagon-like peptide-1 (GLP-1) is a gut incretin hormone that has an antioxidative protective effect on various tissues. Here, we determined whether GLP-1 has a role in the pathogenesis of diabetic nephropathy using nephropathy-resistant C57BL/6-Akita and nephropathy-prone KK/Ta-Akita mice. By in situ hybridization, we found the GLP-1 receptor (GLP-1R) expressed in glomerular capillary and vascular walls, but not in tubuli, in the mouse kidney. Next, we generated C57BL/6-Akita Glp1r knockout mice. These mice exhibited higher urinary albumin levels and more advanced mesangial expansion than wild-type C57BL/6-Akita mice, despite comparable levels of hyperglycemia. Increased glomerular superoxide, upregulated renal NAD(P)H oxidase, and reduced renal cAMP and protein kinase A (PKA) activity were noted in the Glp1r knockout C57BL/6-Akita mice. Treatment with the GLP-1R agonist liraglutide suppressed the progression of nephropathy in KK/Ta-Akita mice, as demonstrated by reduced albuminuria and mesangial expansion, decreased levels of glomerular superoxide and renal NAD(P)H oxidase, and elevated renal cAMP and PKA activity. These effects were abolished by an adenylate cyclase inhibitor SQ22536 and a selective PKA inhibitor H-89. Thus, GLP-1 has a crucial role in protection against increased renal oxidative stress under chronic hyperglycemia, by inhibition of NAD(P)H oxidase, a major source of superoxide, and by cAMP-PKA pathway activation.

• Authors: Hiroki Fujita, Tsukasa Morii, Hiromi Fujishima, Takehiro Sato, Tatsunori Shimizu, Mihoko Hosoba, Katsushi Tsukiyama, Takuma Narita, Takamune Takahashi, Daniel J Drucker, Yutaka Seino, Yuichiro Yamada
• Journal: Kidney international (Kidney Int) Vol. 85 Issue 3 Pg. 579-89 (Mar 2014) ISSN: 1523-1755 [Electronic] United States
• PMID: 24152968 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Glp1r protein, mouse
• Glucagon-Like Peptide-1 Receptor
• Receptors, Glucagon
• Nitric Oxide
• Liraglutide
• Glucagon-Like Peptide 1
• Cyclic AMP
• NADPH Oxidases
• Cyclic AMP-Dependent Protein Kinases

Topics

• Animals
• Cyclic AMP (analysis)
• Cyclic AMP-Dependent Protein Kinases (metabolism)
• Diabetic Nephropathies (drug therapy, etiology, metabolism)
• Glucagon-Like Peptide 1 (analogs & derivatives, therapeutic use)
• Glucagon-Like Peptide-1 Receptor
• Kidney Glomerulus (immunology, pathology)
• Liraglutide
• Male
• Mice, Inbred C57BL
• NADPH Oxidases (antagonists & inhibitors)
• Nitric Oxide (analysis)
• Oxidative Stress
• Receptors, Glucagon (agonists, physiology)
• Signal Transduction (physiology)