Protein Kinase G Activation Reverses Oxidative Stress and Restores Osteoblast Function and Bone Formation in Male Mice With Type 1 Diabetes

• Published in: Diabetes (New York, N.Y.) Vol. 67; no. 4; pp. 607 - 623
• Main Authors: Kalyanaraman, Hema, Schwaerzer, Gerburg, Ramdani, Ghania, Castillo, Francine, Scott, Brian T, Dillmann, Wolfgang, Sah, Robert L, Casteel, Darren E, Pilz, Renate B
• Format: Journal Article
• Language: English
• Published: United States American Diabetes Association 01.04.2018
• Subjects: Acetylglucosamine - metabolism; AKT protein; Animals; Antioxidants; Benzoates - pharmacology; Bone growth; Bone loss; Bones; Cancellous bone; Cell Proliferation; Cell Survival; Cortical bone; Cyclic GMP; Cyclic GMP - metabolism; Cyclic GMP-Dependent Protein Kinases - drug effects; Cyclic GMP-Dependent Protein Kinases - metabolism; Diabetes; Diabetes mellitus; Diabetes mellitus (insulin dependent); Diabetes Mellitus, Experimental - metabolism; Diabetes Mellitus, Type 1 - metabolism; Feedback, Physiological; Fractures; Glucose - pharmacology; Glucose monitoring; Guanosine; Guanylate cyclase; Guanylate Cyclase - metabolism; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Hyperglycemia; Insulin; Insulin - pharmacology; Kinases; Male; Mice; N-Acetylglucosamine; NAD(P)H oxidase; NADPH Oxidase 4 - drug effects; NADPH Oxidase 4 - metabolism; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase Type III - drug effects; Nitric Oxide Synthase Type III - metabolism; Nitric-oxide synthase; Osteoblastogenesis; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteogenesis; Osteogenesis - drug effects; Oxidative stress; Oxidative Stress - drug effects; Protein kinase; Proto-Oncogene Proteins c-akt - metabolism; Rodents; Signal Transduction; Survival; Transcription
• ISSN: 0012-1797; 1939-327X
• DOI: 10.2337/db17-0965

Bone loss and fractures are underrecognized complications of type 1 diabetes and are primarily due to impaired bone formation by osteoblasts. The mechanisms leading to osteoblast dysfunction in diabetes are incompletely understood, but insulin deficiency, poor glycemic control, and hyperglycemia-induced oxidative stress likely contribute. Here we show that insulin promotes osteoblast proliferation and survival via the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) signal transduction pathway and that PKG stimulation of Akt provides a positive feedback loop. In osteoblasts exposed to high glucose, NO/cGMP/PKG signaling was reduced due in part to the addition of -linked -acetylglucosamine to NO synthase-3, oxidative inhibition of guanylate cyclase activity, and suppression of PKG transcription. Cinaciguat-an NO-independent activator of oxidized guanylate cyclase-increased cGMP synthesis under diabetic conditions and restored proliferation, differentiation, and survival of osteoblasts. Cinaciguat increased trabecular and cortical bone in mice with type 1 diabetes by improving bone formation and osteocyte survival. In bones from diabetic mice and in osteoblasts exposed to high glucose, cinaciguat reduced oxidative stress via PKG-dependent induction of antioxidant genes and downregulation of excess NADPH oxidase-4-dependent H O production. These results suggest that cGMP-elevating agents could be used as an adjunct treatment for diabetes-associated osteoporosis.