Roselle (Hibiscus sabdariffa) calyce ethanolic extract decreases insulin resistance in high carbohydrate diet fed cats

Abstract

The objective of this study was to determine whether roselle calyce extract can modulate insulin resistance in cats fed high carbohydrate diets. Fifteen non-obese, mixed-breed, adult and clinically healthy cats were used in this study. Following consumption of a commercially available control diet for 2 weeks, venous blood was collected to determine a baseline of blood glucose. Then the cats were randomly separated into 5 groups of 3 cats each.  Group 1 received the control diet throughout the experiment. Groups 2-5 received high carbohydrate diets (HC) for 2 weeks to induce insulin resistance. After that, group 2 continued to receive a HC diet for further 5 weeks while groups 3 and 4 received a HC diet with roselle extract at doses of 0.1 or 1g/kg BW/day. Group 5 cats received acarbose at a level of 25 mg/cat orally once daily. An intravenous glucose tolerance test (IVGTT) was performed after the 4^th week of treatments in all groups and fasting blood was collected to measure insulin, glucose, triglycerides, cholesterol, and BUN. The fasting glucose and insulin values were used to apply the Homeostasis model assessment for insulin resistance (HOMA-IR). Then in the 5^th week, blood samples were collected over 24 hours at 0 min, 30 min, 1, 2, 3, 4, 6, 8, 11, 14, 18 and 24 hour for monitoring glucose for a 24 hour period. The IVGTT showed the area under the plasma glucose time curve (AUC) of the HC diet control group was significantly higher than that of cats receiving a normal control diet (p < 0.05). Interestingly, the AUC glucose levels of the HC diet group treated with roselle extract at both doses (180.6 ± 25.8 and 178.5 ± 10.9 min.mg/dL) were significantly lower than that of the HC control group (270.1 ± 19.1 min.mg/dL). For 24 hour glucose, the AUC glucose of the HC group was significantly (p < 0.05) higher than that of normal control diet group. However, treatment with both doses of roselle extract did not affect the 24 hour AUC glucose levels of HC fed cats. Additionally, the HC diet control group had a significantly higher HOMA-IR score than the normal control diet group. This high HOMA-IR returned to normal levels in the group that received roselle extract.  These results indicate that roselle extract can reduce blood glucose by reducing insulin resistance in HC fed cats. Roselle calyce extract might therefore be used as alternative medicine for treating type-2 diabetic cats.