Effect of yam (Dioscorea cayenensis) and dasheen (Colocassia esculenta) extracts on the kidney of streptozotocin-induced diabetic rats.

Streptozotocin-induced diabetic wistar rats were maintained for 4 weeks on a supplement of extracts of yam (Dioscorea cayenensis) or dasheen (Colocassia esculenta). The activities of malic enzyme, NADP+ isocitrate dehydrogenase, Glucose 6-P-dehydrogenase and the transaminases were determined to assess any degree of metabolic alteration caused by diabetic nephropathy. Diabetic rats fed normal diet and those fed yam extract, dasheen extract and commercial linamarin respectively lost weight significantly compared to healthy controls. The diabetic rats fed dasheen extract, maintained near normoglycaemic values compared to diabetic rats on normal diet (P < 0.05). Malic enzyme activity was significantly reduced (P < 0.05) in diabetic rats on the normal diet compared to normal healthy controls. Feeding of yam or dasheen extract raised the activity of this enzyme towards normal. Feeding of dasheen extract or commercial linamarin significantly lowered (P < 0.05) the activity of NADP+ isocitrate dehydrogenase below that of healthy controls. Glucose 6-P-dehydrogenase activity was significantly increased (P < 0.05) in diabetic rats compared to healthy controls. Alanine transaminase in the kidney of diabetic rats fed yam extract was significantly higher than healthy controls (P < 0.05). These results demonstrate an overall aggravation of the diabetic nephropathy by yam and dasheen extracts in the diet. In the Caribbean region where these foods are dietary staples, there may be a correlation with the reported high prevalence of diabetes mellitus and the development of renal disease.

Blood lipids and lipid metabolism in the liver of streptozotocin-induced diabetes rats fed organic extracts of yam (d.cayenensis, cv. round leaf yellow yam) and dasheen (c. esculenta)

Yams and dasheen are widely produced in the caribbean where they grow readily. They are important sources of carbohydrates and vitamins. They were basically traditional foods of the people of Africa and the Caribbean until the introduction of `western diets'. It has been insinuated that this shift has led to the increase in cardiovascular diseases and diabetes. This study aims at examining the effects of organic extracts of yams and dasheen on diabetic rats in the light of the fact that they have been shown to contain linamarin in low quantities. Linamarin, a cyanoglucoside, is suspected to be involved in the aggravation of diabetes mellitus. A study was conducted on the lipid metabolism of the streptozotocin-induced diabetic rats fed supplements of organic extracts of yam and dasheen for four weeks. The levels of blood glucose and lipids were determined. Lipid metabolism and transaminase activities in the liver were assessed. The diabetic rats and the groups fed extracts of yam, dasheen and linamarin supplements lost weight significantly despite the non-significantly difference in their food intake. Liver weights were significantly (p<0.05> reduced in these groups compared to the healthy control rats fed a similar diet without the appropriate supplements (p<0.05>. The groups fed yam and dasheen extracts had significantly lower liver weights when compared to the diabetic group fed regular rat diet (p<0.05), and the diabetic group fed normal rat diet plus commercial linamarin additive (p<0.05). Rats fed dasheen organic extract supplement had significantly lower blood glucose levels (13.18 ñ 3.53 mmol/l) compared to the diabetic group fed normal rat diet (19.50 ñ 5.16 mmol/l) at p<0.05. Rats fed dasheen organic extract supplement had significantly lower blood triglyceride levels (2.29 ñ 0.16 mmol/l) with respect to the normal; 9.85 ñ 0.57 mmol; p<0.05, while yam extract (9.57 ñ 0.55 mmol/l) and linamarin (10.63 ñ 0.46 mmol/l) fed groups did not show significant changes in blood triglyceride levels. Blood total cholesterol level was reduced from 9.71 ñ 0.23 mmol/l in the diabetic state to 6.14 ñ 0.05 mmol/l and 6.66 ñ 0.65 mmol/l by feeding supplements of yam and dasheen extracts, respectively. The diabetic condition did not significantly affect the integrity of the liver as measured by alanine and asparate transaminase activities in this short term study.(AU)