Effect of feeding 0.5% curcumin diet or 1% cholesterol diet was examined in albino rats rendered diabetic with streptozotocin injection. Diabetic rats maintained ...
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Molecular and Cellular Biochemistry 152: 13-21, 1995. I1J1995 Kluwer Academic Publishers. Printed in the Netherlands.
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Influence of dietary curcumin and cholesterol on the progression of experimentally induced diabetes in albino rat "'I
P. Suresh Babu and K. Srinivasan Department of Biochemistry Received 27 February
and Nutrition, Central Food Technological Research Institute, Mysore
1995; accepted
- 570
013, India
19 May 1995
Abstract
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Effect of feeding 0.5% curcumin diet or 1% cholesterol diet was examined in albino rats rendered diabetic with streptozotocin injection. Diabetic rats maintained on curcumin diet for 8 weeks excreted comparatively less amounts of albumin, urea, creatinine and inorganic phosphorus. Urinary excretion of the electrolytes sodium and potassium were also significantly lowered under curcumin treatment. Dietary curcumin also partially reversed the abnormalities in plasma albumin, urea, creatinine and inorganicphosphorus in diabeticanimals. On the other hand, glucose excretion or the fasting sugar level was unaffectedby dietary curcumin and so also the body weights were not improved to any significantextent. Diabetic rats fed curcumin diet had a lowered relative liver weight at the end of the study compared to other diabetic rat groups. Diabetic rats fed a curcumin diet also showed lowered lipid peroxidation in plasma and urine when compared to other diabetic groups. The extent of lipid peroxidation on the other hand, was still higher in cholesterol fed diabetic groups compared to diabetic rats fed with control diet. Thus, the study reveals that curcumin feeding improves the metabolic status in diabetic condition, despite no effect on hyperglycemic status or the body weights. The mechanism by which curcumin improves this situation is probably by virtue of its hypocholesterolemic influence, antioxidant nature and free radical scavenging property. (Mol Cell Biochem 152: 13-21, 1995) Key words: curcumin, diabetes, hyperglycemia, lipid peroxidation, urinary metabolites
Introduction
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to the normal belief that HCD favours glomerulosclerosis. However, Traianedes et al have contradicted this by evidencing that high cholesterol diet worsens the metabolic control in streptozotocin treated rats by increasing hepatic glucose production [6]. Spices form an important class of food adjuncts and are known to exhibit a wide variety of physiological and pharmacological properties besides enhancing taste and flavour of foods [7]. Inclusion of spices like fenugreek and garlic in the diet appear to have beneficial effects in improving the diabetic status [8, 9]. Curcumin, the active component of the most commonly used yellow colouring spice turmeric (Curcuma longa) [10], is known to be hypocholesterolemic in induced hypercholesterolemic rats [II, 12]. Curcumin is a good antioxidant and inhibits lipid peroxidation in rat liver
Diabetes mellitus is characterised by several complications that affect many organs of the body and these complications playa detrimental role in the final outcome of the disease. A growing body of evidence suggests that reactive oxygen radicals playa crucial role in the pathogenesis of diabetes along with hyperglycemia, hyperlipidemia and hypertension. It is well known that nutritional factors can modulate the progression of diabetes mellitus. Studies in humans and rodents have demonstrated that low fat diets high in fibre and complex carbohydrates [1, 2] or protein [3, 4] lead to improved metabolic control in insulin dependent diabetes. Reyes et al have recently reported that high cholesterol diet (HCD) improves the diabetic renal tubular abnormalities [5] which is contrary
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Address for offPrints: K. Srinivasan,
Biochemistry
and Nutrition,
Central
Food
Technological
Research
Institute,
Mysore-570013,
India
14 microsomes [13]. It is a good scavenger of reactive oxygen species and lowers the formation of compounds such as prostaglandins and leukotrienes [14--16]. In view of the above, detailed investigations were carried in our Laboratory to examine if this hypocholesterolemic food additive offers any beneficial hypolipidernic effect in diabetic condition and consequently influence the severity of secondary complications. In the present article, our observations on the influence of curcumin on the progression of streptozotocin induced diabetes is presented. Influence of cholesterol enriched diet in diabetic animals was also examined in a parallel study along with the hypolipidernic spice principle, curcumin.
terol and 0.125% bile salts replacing the same amount of starch from the control diet. Diet was given in clean serving cups every afternoon and used cups were removed to prevent contamination with urine and feces. At weekly intervals, 24 h urine samples were collected for the determination of urinary metabolites. After collection of the urine samples for the last time, i.e., after 8 weeks of experimental diets, rats were sacrificed by exsanguination from the hearts under light ether anaesthesia. The blood plasma was separated by centrifugation and stored at -20°C until further analysis. ..
Analytical methods
Materials and methods Chemicals Streptozotocin, glucose oxidase, o-dianisidine and horse raddish peroxidase were obtained from Sigma Chemical Company, USA. Curcumin (over 99.5% pure) was procured from Mis Flavours and Essences Pvt.Ltd., Mysore. Cholesterol was from E.Merck Co., Germany, and all other chemicals used here were of analytical grade.
Study design
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Fig. 1. Liver weights of diabetic rats maintained on curcumin and cholesterol diets. [Values are mean :t S.E.M. of 12 animals per group] Groups: 1-4, Normal rats; 5-8, Diabetic rats Diets: I and 5: Control; 2 and 6: 0.5% Curcumin; 3 and 7: I% cholesterol 4 and 8: RCD + 0.5% Curcumin 'Significant compared to Group 1; """-'h'h *- ...1.", '.
