Abstract

Type 2 diabetes mellitus is a progressive metabolic disorder in which pancreatic beta cell dysfunction plays a central 
and early role in disease initiation and progression. Long before the onset of overt hyperglycemia, beta cells were 
exposed to a hostile metabolic environment characterized by nutrient excess, oxidative stress, and low-grade 
inflammation, leading to impaired insulin secretion and loss of functional beta cell mass. This review aimed to 
critically examine the molecular and biochemical mechanisms underlying beta cell dysfunction in the early stages of 
Type 2 diabetes, with a particular focus on metabolic stress pathways. A narrative synthesis of experimental, 
translational, and clinical studies was employed to integrate current evidence on beta cell biology and metabolic 
stress responses. Available data indicated that chronic glucotoxicity and lipotoxicity disrupt beta cell metabolism, 
induce oxidative and endoplasmic reticulum stress, impair mitochondrial function, and activate inflammatory 
signaling pathways that compromise insulin biosynthesis and secretion. These interconnected stress mechanisms 
ultimately promoted beta cell dedifferentiation, apoptosis, and failure to adapt to increasing insulin demand. Early 
beta cell dysfunction represented a critical pathogenic event in Type 2 diabetes and an underexploited therapeutic 
target. Interventions aimed at alleviating metabolic stress and preserving beta-cell integrity may offer substantial 
benefits in delaying or preventing disease progression.