Mechanisms related to the anti-diabetic properties of mango (Mangifera indica L.) juice by-product Sarahí Rodríguez-González a , Itzel Mireya Gutiérrez-Ruíz a , Iza F. Pérez-Ramírez a , Ofelia Mora b , Minerva Ramos-Gomez a , Rosalía Reynoso-Camacho a,⇑ a Research and Graduate Studies in the Department of Food Science (PROPAC), School of Chemistry, Universidad Autónoma de Querétaro, Cerro de las Campanas S/N, Col. Centro, Querétaro, Querétaro 76010, Mexico b Laboratory of Rumiology and Nutritional Metabolism (RuMeN), FES-C, Universidad Nacional Autónoma de México, Querétaro 76230, Mexico article info Article history: Received 15 February 2017 Received in revised form 22 June 2017 Accepted 25 July 2017 Keywords: Mango by product Dietary fiber Antioxidants Diabetic rats Renal dysfunction Adipocyte cells Insulin cascade abstract This study aimed to determine the nutraceutical composition of mango by-product (BP) and to evaluate the mechanisms related to its antidiabetic properties. Mango BP reduced (p < 0.05) serum glucose in streptozotocin-induced diabetic rats, which was not associated with a decreased glucose intestinal absorption or to the protection of Langerhans islets. Mango BP showed insulin mimetic effects in 3T3-L1 adipocyte cells, increasing Glut4, Irs1 and Pi3k expression. Mango BP reduced (p < 0.05) serum triacylglycerides in diabetic rats, which was associated to a decreased lipid intestinal absorption, and ameliorated diabetic nephropathy due to its renal antioxidant activity. The anti-diabetic effect of mango BP was associated to its high content of soluble fiber, as well as several polyphenols and carotenoids, like ellagic acid, gallic acid, quercetin, epicatechin gallate, and b-carotene. Therefore, these results suggest that mango BP could be used as a functional supplement for diabetes treatment. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Diabetes is characterized by elevated blood glucose, which is partly due to oxidative damage in pancreatic b-cells, leading to apoptosis, thus decreasing insulin secretion (Rochette, Zeller, Cottin, & Vergely, 2014). Insulin stimulates glucose uptake into peripheral tissues by inducing the translocation of glucose trans- porter 4 (GLUT4) through the regulation of insulin receptor tyro- sine kinase (IRS1) and phosphatidylinositol 3 kinase (PI3K). Insulin signaling is affected during insulin resistance, and increas- ing glucose blood (Govers, 2014). The resulting hyperglycemia pro- motes oxidative stress, which is related to the development and progression of renal dysfunction, a common complication during of diabetes (Wada, Sun, & Kanwar, 2011). Diabetes can be ameliorated with the consumption of diets rich in dietary fiber (DF) and antioxidants like polyphenols and carote- noids, since these compounds reduce blood glucose and oxidative stress (Coney et al., 2005; Latha & Daisy, 2011; Lattimer & Haub, 2010). These bioactive compounds can be found in fruit by-products (BP) obtained from processing industries, which represent 35–65% of total production (Larrauri, Rupérez, Borroto, & Saura-Calixto, 1996). Fruit BP are commonly discarded, thus rep- resenting an interesting source of DF and antioxidant compounds with nutraceutical potential. Mango (Mangifera indica L.) is mainly used to elaborate for nec- tar and juices, and the resulting BP is mostly composed of peel, seeds, and pulp remnants (Dorta, Lobo, & Gonzalez, 2012). Mango by-product shows a high content of soluble DF (SDF) (Amaya-Cruz et al., 2015), which decreases carbohydrates and lipid absorption due to its high water retention capacity and gelling power (Lattimer & Haub, 2010). Moreover, mango by-product has a high antioxidant capacity due to its high content of mangiferin, gallic acid, epicatechin, ferulic acid, a-tocopherol, and b-carotene, as well as condensed and hydrolysable tannins (Amaya-Cruz et al., 2015). Several studies have reported the beneficial effect of mango on diabetes-related complications. For instance, the supplementation with 5 and 10% (w/v) of mango peel exerted hypoglycemic, hypolipidemic, and renoprotective effects in diabetic rats, which were related only to its antioxidant capacity (Gondi, Basha, Bhaskar, Salimath, & Prasada Rao, 2015). Furthermore, Parmar and Kar (2008) reported that a methanolic extract of mango peel improved serum glucose, insulin, and lipids in rats fed with an atherogenic diet. These authors suggested that the beneficial effects of mango may be related to the protection of b-cell death; http://dx.doi.org/10.1016/j.jff.2017.07.058 1756-4646/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: C.U., Cerro de las Campanas S/N, Querétaro, Querétaro 76010, Mexico. E-mail address: rrcamachomx@yahoo.com.mx (R. Reynoso-Camacho). Journal of Functional Foods 37 (2017) 190–199 Contents lists available at ScienceDirect Journal of Functional Foods journal homepage: www.elsevier.com/locate/jff