Lipid-Lowering and Antioxidant Activity of RF13 Peptide From Vacuolar Protein Sorting-Associated Protein 26B (VPS26B) by Modulating Lipid Metabolism and Oxidative Stress in HFD Induced Obesity in Zebrafish Larvae

Obesity is one of the major contributing factors responsible for the onset of various metabolic syndrome. In obesity-related metabolic syndrome, increased oxidative stress in accumulated fat is a key pathogenic mechanism. The aim of this study is to investigate the lipid-lowering and antioxidant effects of RF13 peptide derived from vacuolar protein sorting associated protein 26B (VPS26B) in high fat diet (HFD) induced zebrafish larvae. Based on the arrangement, composition, and bioinformatics analysis of the VPS26B protein sequence, we predicted and synthesized a short peptide, 1RRGKGGRRVTMSF13 (RF13). In vitro analysis (DPPH, ABTS and nitric oxide assay) of RF13 on showed its potential antioxidant properties and radical scavenging capacity. Rat skeletal muscle cells (L6) and human erythrocyte cells are used for the evaluation of RF13 cytotoxicity at differing concentrations showed no cytotoxic effect. Zebrafish larvae feeding HFD, on day 4 post fertilization (dpf) to 6 dpf, there was an increase in production of reactive oxygen species (ROS) and lipid accumulation, which showed decreased expression of antioxidative enzymes such as glutathione S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx). However, RF13 treatment has significantly reduced the total cholesterol and triglycerides levels, enhanced antioxidant enzyme levels, and decreased lipid peroxidation. In addition, RF13 treatment has significantly decreased lipid accumulation, intracellular ROS and apoptosis in zebrafish larvae as compared to the HFD group. Furthermore, RF13 significantly downregulated the lipid metabolizing genes such as CCAAT/enhancer-binding protein-α (C/EBP-α), sterol regulatory element-binding protein 1 (SREBP1) and fatty acid synthase (FAS), while they upregulated the antioxidant-related genes. These results suggests that RF13 peptides can be used as functional foods and natural drugs to enhance the antioxidant ability and also to alleviate lipid accumulation by regulating lipid metabolism.