The impact of persistent milk consumption in the pathogenesis of type 2 diabetes mellitus

Abstract

Background: Milk and sugar are excessively consumed in a Western diet. There is increasing epidemiological evidence that the intake of unfermented pasteurized cow's milk is associated with an increased risk of type 2 diabetes mellitus (T2D). It is the intention of this review to provide translational biochemical evidence for milk's diabetogenic mode of action. Milk proteins provide the highest amounts of branched-chain amino acids (BCAAs) and thus contribute to total BCAA intake, which enhances BCAA plasma levels associated with increased risk of T2D. The consumption of pasteurized milk raises plasma levels of miRNA-29b, which is a diabetogenic miRNA promoting insulin resistance (IR). miRNA29b inhibits the activity of branched-chain αketa acid dehydrogenase, the rate limiting enzyme of BCAA catabolism, which is impaired in patients with IR and T2D. Milk consumption stimulates mTORC1 activity and increases insulin synthesis. β-cell mTORC1 is overactivated in T2D patients resulting in impaired autophagy which enhances endoplasmic reticulum (ER) stress associated with a greater risk of early β-cell apoptosis, the pathogenic hallmark of T2D. Chronic insulinotropic action of milk-derived BCAAs, IR-promoting mTORC1 overactivity, and miRNA-29b signaling combined with excessive glucose-mediated insulin secretion overburden β-cell insulin homeostasis. Epidemiological and translational evidence identifies continued milk intake as a promoter of T2D, the most common metabolic disease of Western civilization.