The protective effects of human milk-derived peptides on the pancreatic islet biology

Several epidemiological studies support the protective role of breast-feeding in reducing the risk for type 1 diabetes. Human breast milk is the perfect nutrition for infants and contains many complex proteins, lipids and carbohydrates. In this study, we examined the physiological effects of human milk-derived opioid peptides, beta casomorphins (BCM), and compared them with bovine milk-derived opioid peptides on pancreatic hormone regulation and β-cell regeneration. Exposure of wild-type zebrafish embryos to 50 µg/mL of human BCM -5 and -7 from 3 days post fertilisation until 6 days post fertilisation resulted in an increased insulin domain of expression while exposure to bovine BCM -5 and -7 significantly reduced the insulin domain of expression as analysed by whole-mount in-situ hybridisation. These changes may be accounted for by reduced insulin expression or β-cell number and were mitigated by the µ-opioid receptor antagonist, naloxone. The effect of BCM on β-cell regeneration was assessed following ablation of β-cells in Tg (ins: CFP-NTR) zebrafish from 3 days post fertilisation to 4 days post fertilisation, followed by exposure of bovine and human BCM -5 and -7 (50 µg/mL) from 4 days post fertilisation until 7 days post fertilisation. The regenerative capacity of β-cells was not impeded following exposure to human BCM -5 and -7, whereas the capacity of β-cells to regenerate following bovine BCM -5 and -7 exposure was reduced. Our data suggests that human BCM -5 and -7 may promote β-cell development and enable the regeneration of β-cells, while the bovine milk derived peptides, BCM -5 and -7 play an opposite role. These data may provide some biological explanation for the protective effect of breastfeeding on the development of Type 1 Diabetes.