INS and type 2 diabetes mellitus: β-cell failure in T2D may be caused by prolonged metabolic stress exerted by e.g., free fatty acids (FFA) such as palmitate, and by the persistent increased demand for insulin production due to peripheral insulin resistance ultimately leading to β-cell failure (Prentki and Nolan, 2006; Oh et al., 2018; Wysham and Shubrook, 2020).