Dietary supplementation with liophilised strawberry improves insulin sensitivity and redox status in mouse model of diet induced obesity

Abstract

Healthy dietary habits with abundant fruit consumption may reduce prevalence and positively affect development and progression of various chronic diseases including obesity and insulin-resistance related diseases. Strawberry (Fragaria × ananassa Duch.) represent a valuable source of vitamins, minerals, fatty acids, dietary fiber, and various bioactive polyphenolic compounds such as anthocyanins and flavonoids which are known for their antioxidant and anti-inflammatory activities. In this study we evaluated the effect of newly introduced strawberry cultivar „Aprika” supplemented in the form of lyophilized powder, on obesity-related metabolic alterations in high-fat-diet fed mice. We hypothesized that chronic (8 weeks) supplementation of lyophilized strawberries in the amount comparable to two servings per day in humans, would ameliorate insulin resistance associated with obesity in C57BL/6 mice. Furthermore, we hypothesized that strawberry meal consumed at 7PM i.e. before active feeding period of mice (which corresponds to early breakfast in humans) would induce more pronounced beneficial effects compared to meal consumed at 7AM i.e. at the end of the active feeding period (which corresponds to late dinner in humans). High fat diet induced hyperglycaemia, hyperinsulinaemia, insulin resistance and obesity; and disturbed hepatic insulin signaling. Lyophilized strawberries, only when consumed before feeding period, reduced body weight gain and improved insulin sensitivity induced by high-fat diet (evidenced by lower area under the curve after an intraperitoneal GTT, reduced serum insulin levels and an insulin resistance index (IR-HOMA). Strawberry meals consumed after active feeding period had no such effect. However, strawberries, regardless of the time of consumption, restored protein level of Insulin receptor substrate 1 (IRS1) in the liver and increased hepatic antioxidant enzymes level. In conclusion, strawberries improve insulin sensitivity and raise hepatic antioxidant capacity in mouse model of diet induced obesity. Nevertheless, more beneficial effects were achieved when strawberries were consumed before active feeding period, as an early breakfas