Evaluation of Immunomodulatory Properties of Fish-Protein Hydrolysate from Skipjack Tuna by-products (Katsuwonus pelamis, Linnaeus 1758) in Streptozotocin-Nicotinamide-Induced Diabetic Rats

Fish protein hydrolysate (FPH) is an alternative to managing fish by-products. Protein hydrolysis by proteolytic enzymes breaks down the protein into bioactive peptides (BP). Bioactive has a high-protein content and various beneficial health properties, including antioxidants, immunoregulatory, antibacterial, anti-inflammatory, and other activities. The current study aimed to investigate the anti-diabetic and immunomodulatory activities of FPH from skipjack tuna by-products. Male Sprague Dawley rats (n = 25) were equally divided into five groups: healthy group, diabetic mellitus (DM) group, DM + Imunos 0.8 g/ kg BW (drug control group), DM + 0.8 g/kg BW (FPH 1), DM + 1.6 g/kg BW FPH (FPH 2). Diabetic rats were induced by being fed with a high-fat diet (HFD) for 3 months, followed by nicotinamide (NA; 120 mg/kg BW)-streptozotocin (STZ) injection (60 mg/kg BW). The initial and final body weights before and after treatment were measured. The leukocyte and lymphocyte levels were measured using a hematology analyzer. The pro-inflammatory cytokine tumor necrosis factor α (TNFα) level was measured using enzyme-linked immunosorbent assay (ELISA). The result showed that the blood glucose levels after treatment using FPH significantly decreased compared with DM rats. Leukocyte and lymphocyte numbers also decreased significantly after treatment using FPH 1 than in DM rats. The pro-inflammatory cytokine TNFα in the FPH rat groups improved significantly compared with DM rats. These study results suggested that FPH from skipjack tuna by-product administration can be used as anti-diabetic and immunomodulatory candidates.