Vitamin D3 restores altered cholinergic and insulin receptor expression in the cerebral cortex and muscarinic M3 receptor expression in pancreatic islets of streptozotocin induced diabetic rats

The Journal of Nutritional Biochemistry
doi:10.1016/j.jnutbio.2010.03.010
Peeyush T. Kumara, Sherin Antonya, Mohan S. Nandhua, Jayanarayanan Sadanandana, George Naijila and Chiramadathikudiyil S. PauloseCorresponding Author Contact Information, a, E-mail The Corresponding Author, E-mail The Corresponding Author, E-mail The Corresponding Author

a Molecular Neurobiology and Cell Biology Unit, Centre for Neuroscience, Cochin University of Science and Technology, Cochin, Kerala 682 022, India
Received 11 November 2009; revised 6 March 2010; accepted 12 March 2010. Available online 23 July 2010.

Nutritional therapy is a challenging but necessary dimension in the management of diabetes and neurodegenerative changes associated with it. The study evaluates the effect of vitamin D3 in preventing the altered function of cholinergic, insulin receptors and GLUT3 in the cerebral cortex of diabetic rats. Muscarinic M3 acetylcholine receptors in pancreas control insulin secretion. Vitamin D3 treatment in M3 receptor regulation in the pancreatic islets was also studied. Radioreceptor binding assays and gene expression was done in the cerebral cortex of male Wistar rats. Immunocytochemistry of muscarinic M3 receptor was studied in the pancreatic islets using specific antibodies. Y-maze was used to evaluate the exploratory and spatial memory. Diabetes induced a decrease in muscarinic M1, insulin and vitamin D receptor expression and an increase in muscarinic M3, ?7 nicotinic acetylcholine receptor, acetylcholine esterase and GLUT3 expression.

Vitamin D3 and insulin treatment reversed diabetes-induced alterations to near control. Diabetic rats showed a decreased Y-maze performance while vitamin D3 supplementation improved the behavioural deficit. In conclusion, vitamin D3 shows a potential therapeutic effect in normalizing diabetes-induced alterations in cholinergic, insulin and vitamin D receptor and maintains a normal glucose transport and utilisation in the cortex. In addition vitamin D3 modulated muscarinic M3 receptors activity in pancreas and plays a pivotal role in controlling insulin secretion.

Hence our findings proved, vitamin D3 supplementation as a potential nutritional therapy in ameliorating diabetes mediated cortical dysfunctions and suggest an interaction between vitamin D3 and muscarinic M3 receptors in regulating insulin secretion from pancreas.
Article Outline
1. Introduction
2. Materials and methods
2.1. Estimation of blood glucose
2.2. Y-maze test
2.3. Total muscarinic, muscarinic M1 and M3 receptor binding studies in the cerebral cortex
2.4. Receptor data analysis
2.5. Analysis of gene expression by real-time polymerase chain reaction
2.6. Muscarinic M3 receptor expression studies in the pancreas of control and experimental rats using confocal microscope
2.7. Statistics
3. Results
3.1. Y-maze performance of control and experimental groups of rats
3.2. Total muscarinic receptor analysis
3.2.1. Scatchard analysis of 3H QNB binding against atropine in the cerebral cortex of control, diabetic, diabetic+insulin- and diabetic+vitamin D3-treated diabetic rats
3.3. Muscarinic M1 receptor analysis
3.3.1. Scatchard analysis of 3HQNB binding against pirenzepine in the cerebral cortex of control, diabetic, diabetic+insulin- and diabetic+vitamin D3-treated diabetic rats
3.4. Muscarinic M3 receptor analysis
3.4.1. Scatchard analysis of 3H DAMP binding against 4-DAMP mustard in the cerebral cortex of control, diabetic, diabetic+insulin and diabetic+vitamin D3 diabetic rats
3.5. Real time-PCR analysis of muscarinic M1 receptor
3.6. Real time-PCR analysis of muscarinic M3 receptor
3.7. Real-time-PCR analysis of ?7 nicotinic acetylcholine receptor
3.8. Real-time PCR analysis of acetylcholine esterase
3.9. Real-time PCR analysis of choline acetyl esterase
3.10. Real-time PCR analysis of insulin receptor
3.11. Real time-PCR analysis of GLUT3 receptor
3.12. Real-time PCR analysis of VDR receptor
3.13. Immunocytochemistry of muscarinic M3 receptor antibody staining in control and experimental groups of rats

4. Discussion
References