Arginine-rich coconut kernel diet influences nitric oxide synthase activity in alloxandiabetic rats.

Background: Coconut kernel protein (CKP) has been reported to contain significant amounts of L-arginine. Its potential effect on glucose homeostasis, possibly through the nitric oxide synthase (NO) pathway, was therefore investigated in alloxan-induced diabetic rats. Diabetes was induced by a single intraperitoneal dose of alloxan (150 mg kg⁻¹ body weight). Experimental rats were grouped as follows: Group I, normal control; Group II, diabetic control; Group III, diabetic + CKP; Group IV, diabetic + L-arginine; Group V, diabetic + L-arginine + L-N(G)-Nitroarginine methyl ester (L-NAME). Purified CKP isolated from dried coconut kernel and L-arginine was administered to rats along with a semi-synthetic diet for 45 days. L-NAME (0.5 mg kg⁻¹ body weight) was given to Group V animals. After the experimental period, serum glucose, insulin, activities of liver nitric oxide synthase and arginase, liver glycogen levels and histopathology of the pancreas were evaluated.

Results: Serum glucose, insulin and antioxidant enzyme activities and liver glycogen levels were found to be restored to basal levels in CKP-fed rats. Decreased arginase and increased nitric oxide synthase (NOS) activities were found in CKP- and arginine-fed rats. L-NAME treatment showed a partial effect on these parameters. Histopathology revealed that CKP and L-arginine feeding reduced the diabetes-related pancreatic damage in treated rats compared to the diabetic control.

Conclusion: The results observed in this study indicate that the potential antidiabetic activity of CKP may be through an arginine-NO pathway leading to pancreatic beta cell regeneration.