Effect of Raw and Cooked Ginger (Zingiber officinale Roscoe) Extracts on Insulin Sensitivity in Normal and High-fat Diet-induced Diabetic Rats

Abstract

Few studies have determined the effect of different ginger extracts on insulin sensitivity, very few have explored the effect of raw extract of this spice on this parameter while the effect of cooked ginger extract (the form in which the spice is commonly consumed) is yet to be ascertained. This experimental study was therefore designed to determine the effect of raw and cooked ginger extracts on insulin sensitivity in normal and high-fat diet-induced diabetic rats. Ginger rhizomes were washed, peeled, wet-milled and sieved without adding water to obtain the raw extract. The raw extract was boiled for 1 hour to obtain the cooked extract. Seventy male albino rats of weight range 120-160g were divided into seven groups (n=10) and designated thus: ND2C-non-diabetic control; ND2R-non-diabetic rats given raw ginger extract (2ml/kg body weight); ND2Co- non-diabetic rats given cooked (boiled) ginger extracts; D2C-diabetic control; D2R- diabetic rats given raw ginger extract; D2Co- diabetic rats given cooked ginger extract; and D2D-diabetic rats given metformin (anti-diabetic drug)-200mg/kg body weight. Diabetes was induced in the diabetic groups by feeding the animals with high-fat diet (HFD) for 12 weeks to mimic Type 2 diabetes. Ginger extracts and the drug were administered as a daily oral dose for 4 weeks after diabetes induction. Insulin sensitivity (Insulin Tolerance Test) was determined before and after diabetes induction and at the end of the 4 weeks extracts administration using standard analytical method. Mean data were analyzed using ANOVA at p ≤ 0.05. Baseline Insulin Sensitivity (IS-%/min) in all the groups ranged from 2.2 to 2.4. After 12 weeks feeding, the IS in the three groups fed normal diet ranged from 1.9 to 2.1 while in the four groups fed HFD Insulin Sensitivity ranged from 0.1 to 0.3. Four weeks administration of raw and cooked ginger extracts did not significantly alter IS in normal rats while in diabetic rats raw, cooked ginger extracts and metformin significantly increased IS (%/min) to 2.1, 1.2 and 1.7 respectively relative to control which was 0.1. Insulin Sensitivity was maintained within the normal level in normal rats that were given raw and cooked ginger extracts while the raw extract was more effective than the cooked extract in increasing insulin sensitivity to normal level in diabetic rats. Both raw and cooked ginger extracts improved insulin sensitivity in high-fat diet-induced diabetic rats but the raw extract was more effective, hence, ginger in both forms may be applicable in the management of Type 2 diabetes. Human trial is hereby recommended.