The Effect of In Vitro-digestion on Mammalian Milks’ Insulin and IGF-1

Abstract

Abstract Objectives This study investigated the impact of in vitro-digestion and spray-dry processing on insulin concentration and insulin growth factor-1 (IGF-1) in milk from several species. Diabetes is a growing health problem in the U.S. and worldwide, predicted to affect 642 million people by 2040. To date, insulin therapy is considered to be the best treatment due to its low side effects. However, insulin treatment in type-2 diabetes can lead to insulin resistance. Natural alternatives are used to treat diabetes in many regions of the world, and mechanisms of action need investigating. Literature shows that daily camel milk consumption led to a decrease in insulin dose in patients with type 1 diabetes and can improve glucose control in type-2 diabetes. The presence of bioactive insulin has been hypothesized as a mechanism for this effect. Methods Human Insulin and Bovine IGF-1 immunoactivity were measured in milk from Human, Bovine, Goat, and Camel and spray dried milk from goat and camel by ELISA (RayBioTech) with microplate reader. Raw and pasteurized samples subjected to in vitro digestion were also measured. Results Raw goat and camel milk showed insulin immunoreactivity with approximately 31, and 20 µIU/mL, respectively. Spray-dried goat and camel milk from different animals showed insulin immunoreactivity of approximately 26, and 20 µIU/mL, respectively. Insulin immunoactivity in bovine and human milk was 16 and 20 µIU/mL. In vitro digestion did not decrease insulin levels in either goat or camel milk, but significantly reduced human and bovine milk insulin immunoactivity. Bovine IGF1 did not cross react with this anti-human insulin antibody. IGF-1 immunoactivity was present in goat milk at very low concentration but not detected in other samples. Conclusions Goat and camel milk (fresh and spray dried) had high insulin concentrations. There was no impact of in vitro-digestion and spray dried processing on insulin levels. IGF-1 was only present in raw goat milk. IGF-1 was not detected in camel milk samples suggesting that the antidiabetic effects of camel milk is due to its insulin concentration and the ability of the insulin to survive gastric and intestinal digestion, as well as pasteurization. Funding Sources NIFA; NCSU.