INS and obesity due to melanocortin 4 receptor deficiency: RA, the active form of vitamin A, plays a key role in regulating insulin secretion and supporting pancreatic β‐cell function: it promotes β‐cell proliferation and survival by modulating gene expression, thereby sustaining normal insulin secretion; furthermore, vitamin A is involved in regulating glucose and lipid metabolism, which is essential for preventing insulin resistance, a key pathological factor in type 2 diabetes, often associated with obesity and chronic inflammation (Said et al. 2021; Trasino and Gudas 2015).