Oxidised palm oil and sucrose induced hyperglycemia in normal rats: effects of Sclerocarya birrea stem barks aqueous extract

Abstract

Background: Consumption of foods rich in carbohydrates and fats, result in an increase in obesity and consequently type 2 diabetes. The present study was carried out to evaluate the effects of oxidised palm oil and sucrose (SOPO +S) on some metabolic parameters and to investigate the effects of aqueous extract from barks of Sclerocarrya birrea on SOPO + S induced damages.

Methods: During 16 weeks, animals received every day a supplement of oxidised palm oil (10 %) and 10 % sucrose as drinking water). Control rat received standard diet and drinking water without sucrose. At the end of this period, animal presenting intolerance in glucose test and insensitivity to insulin were continuously feed with hypercaloric diet along with the administration of the plant extract (150 or 300 mg/kg) or glibenclamide (10 mg/kg) during three weeks. OGTT was performed; insulin sensitivity was assessed by performing insulin tolerance test and determining insulin sensitivity index (Kitt). Several parameters were evaluated including body weight, abdominal fat mass, blood glucose levels, blood pressure, serum lipid profile, and serum transaminases (ALT and AST). Oxidative parameters were measured by MDA levels, nitrites levels, SOD levels, reduced glutathione content and by enzyme activities of SOD and catalase.

Results: Animal receiving a supplement of oxidised palm oil and sucrose showed hyperglycaemia, glucose intolerance, insulin resistance and a significant increase in body weight and abdominal fat mass compared to normal rats. In addition, there was a significant increase of SOD in aorta and heart, nitrites in liver and kidney, malondialdehyde (MDA) in heart, liver and kidney. It was also observed a significant reduction in the activities of the SOD and catalase in liver, kidney and reduced glutathione levels in heart. Concomitant treatment of plant extract with SOPO + S brought glycaemia and blood pressure towards normal value, restored glucose tolerance and insulin sensitivity. The plant extract prevent the increase or decrease in the activity of the enzyme depending to the organ, reduced MDA and nitrites levels.

Conclusion: These results highlighted the hyperglycaemic and oxidant character of SOPO + S diet and confirm the hypoglycaemic, and antioxidant action of sclerocarya birrea aqueous extract in diabetes.

Fig. 1

Effects of a supplement of oxidised palm oil (10 %) and sucrose (10 %) on body weight. Each point represents mean ± SEM, n = 5. *p < 0.05 vs. standard diet

Fig. 2

Oral glucose tolerance test in animals receiving hypercaloric diet (SOPO + S). Each point represents mean ± SEM, n = 5. ***p < 0.001 vs. standard diet; ^a p < 0.05; ^c p < 0.001 vs. initial value

Fig. 3

Effect of SOPO+S diet on insulin sensitivity test (a) and insulin index (b) Each point represents mean ± SEM, n = 5. ***p < 0.001 vs. standard diet; ^a p < 0.05; ^c p < 0.001 vs. initial value. SOPO + S = supplement in oxidised palm oil and sucrose

Fig. 4

Effects of a concomitant administration of S. birrea extract and a supplement of oxidised palm oil and sucrose (SOPO + S) on body weight (a) and abdominal fat mass (b). Each point or bar represents mean ± SEM, n = 5. *p < 0.05 , **p < 0.01 ***p < 0.001 vs. SOPO + S; ^a p < 0.05; ^c p < 0.001 vs. Standard diet. SOPO + S = supplement in oxidised palm oil and sucrose

Fig. 5

Effects of sclerocarya birrea aqueous extract on glucose test tolerance (a), insulin sensitivity test (b) and insulin sensitivity index (c) in rat receiving SOPO + S diet. Each point or bar represents mean ± SEM. n = 5 *p < 0.05 , **p < 0.01 ***p < 0.001 vs. SOPO + S; ^a p < 0.05; ^c p < 0.001 vs. standard diet and ^$ p < 0.05 ^$$$ p < 0.001 vs. initial value. SOPO + sucrose = supplement in oxidised palm oil and sucrose

Fig. 6

Effects of concomitant administration of Sclerocarya birrea and SOPO + sucrose on MDA (a), SOD (b), Nitrites (c), catalase (d) and redued glutathione (e). Each bar represents mean ± SEM. n = 5 *p < 0.05 , **p < 0.01 vs. SOPO + S;. ^$ p < 0.05 ^$$ p < 0.01 vs. standard diet. SOPO + sucrose = supplement in oxidised palm oil and sucrose