Whole sorghum flour improves glucose tolerance, insulin resistance and preserved pancreatic islets function in obesity diet-induced rats

Highlights

• First data about effects of sorghum flour fractions on oxidative stress and obesity.

• Sorghum flour fractions improved liver CAT, GRd and GPx activities.

• Sorghum flours fractions reduced liver fat.

• Sorghum flour fractions decreased plasma lipid peroxidation.

• Whole sorghum flour improved glucose tolerance and insulin resistance.

Abstract

The effects of sorghum flour fractions (whole and decorticated flours and bran) were evaluated for oxidative stress and obesity parameters in diet-induced obese rats. Compared to high fat-fructose groups, sorghum flour fractions reduced liver fat and whole sorghum flour decreased fasting glucose, improved glucose tolerance, insulin resistance and reduced insulin secretion. Sorghum showed a slight improvement in antioxidant status. Animals fed with sorghum flour fractions improved liver CAT, GRd and GPx activities and decreased plasma lipid peroxidation. Additionally, whole sorghum flour can be used as a strategy to ameliorate glucose/insulin homeostasis by increasing insulin sensitivity, leading to pancreatic islet function preservation in a prediabetic condition.

Introduction

Obesity is a worldwide public health problem. In 2014, more than 1.9 billion adults were overweight and over 600 million were obese (WHO, 2015). As a multifactorial development disease, the excess of food intake, in mainly high-fat and high-fructose diets, has been related to an increase in the prevalence of obesity (Deer et al., 2015, Samuel, 2011). Excessive caloric intake has been also suggested to increase oxidative stress in different tissues and depletion of antioxidant enzymes and reduced glutathione levels (Marineli et al., 2015, Noeman et al., 2011). Weight gain and oxidative stress are major risk factors for the development of insulin resistance, glucose intolerance, type 2 diabetes mellitus, atherosclerosis, chronic low-grade inflammatory state and non-alcoholic fatty liver disease (Deer et al., 2015, Wang et al., 2014).

Diet modification is a crucial strategy for intervention against obesity and associated diseases. Increasing whole grain intake has been considered an important role as a dietary strategy for reducing the development risks of those diseases. Beneficial effects of whole grain are associated to phenolic compound contents as well as dietary fiber (Poquette et al., 2014, Wang et al., 2014). Sorghum grain composes this background with specific phenolic compound groups such as luteolinidin and apigeninidin, condensed tannin as well as dietary fibers, such as resistant starch and β-glucan (Dunn et al., 2015, Moraes et al., 2015, Shen et al., 2015). Recent studies have demonstrated that these compounds display a regulator key role in glucose homeostasis and insulin secretion, as well as cholesterol-lowering effects, reducing adiposity, improving antioxidant status and decreasing oxidative and low-grade inflammation biomarkers (Khan et al., 2015, Kim et al., 2015, Moraes et al., 2012, Poquette et al., 2014, Shen et al., 2015).

Sorghum studies have focused on the use of whole flour, phenolic extract and decorticated flour (Kim and Park, 2012, Moraes et al., 2012, Shen et al., 2015). Nevertheless, sorghum abrasive processes produce decorticated grains and bran, which have different approximate compositions, phenolic compounds and dietary fiber content (Awika et al., 2005, Moraes et al., 2015). Additionally, our previous study demonstrated that sorghum bran contains higher amounts of phenolic compounds, antioxidant capacity, dietary fiber and has a lower estimated glycemic index in comparison to decorticated sorghum flour (Moraes et al., 2015). It may suggest that different metabolic outcomes may be achieved with sorghum flour fraction intake. Thus, we hypothesized that diets containing sorghum flour fractions with different phenolic and dietary fiber features could reduce obesity and associated disease risk factors in rats fed with a high fat-fructose diet. Therefore, this study aimed to evaluate the effects of whole sorghum flour (WSF), decorticated sorghum flour (DSF) and sorghum bran (SB) on oxidative stress and obesity parameters in diet-induced obese rats.