Glycohypoxia: a hypothesis linking chronic hyperglycemia to functional hypoxia and diabetic complications in type 2 diabetes

Given that chronic hyperglycemia in type 2 diabetes induces functional cellular hypoxia by constraining the release of oxygen from hemoglobin, a hypothesis of glycohypoxia was proposed. This hypothesis positions glucose as a novel regulator of respiratory dynamics beyond its metabolic functions. This narrative review aims to unravel the molecular framework of glycohypoxia, reinterpret diabetic complications from a hypoxia-centric perspective, highlight underrecognized hypoxic interconnections, and advocate for innovative hypoxia-targeted therapeutic strategies to transform diabetes management. The glycohypoxia hypothesis illuminates type 2 diabetes as a disorder of impaired oxygen delivery. According to this hypothesis, non-enzymatic glycation of hemoglobin may yield glycated hemoglobin via covalent binding to β-chain N-terminal valine, potentially locking hemoglobin in a high-affinity state, shifting the oxyhemoglobin dissociation curve leftward (the partial pressure of oxygen at which hemoglobin is 50% saturated, P50≍23 mmHg vs. 26.8 mmHg), and restricting oxygen unloading, possibly undermining Bohr and Haldane effects. Hyperglycemia may exacerbate this process by driving osmotic stress through glucose transporter-mediated influx, aquaporin-1/3 activation, and sodium-potassium adenosine triphosphatase engagement, resulting in cellular swelling. The polyol pathway, catalyzed by aldose reductase, may convert glucose into sorbitol. This process depletes nicotinamide adenine dinucleotide phosphate and generates reactive oxygen species via nicotinamide adenine dinucleotide phosphate oxidase, thereby impairing glycocalyx integrity and mitochondrial function. Insulin resistance may further compromise glucose transporter type 4 translocation, perpetuating hyperglycemia and limiting adenosine triphosphate synthesis. Overall, these cascades may activate hypoxia-inducible factor-1α, elevate vascular endothelial growth factor and transforming growth factor-β, and promote fibrosis and angiogenesis, contributing to complications, such as retinopathy, neuropathy, nephropathy, cardiomyopathy, and potentially cancer, via Warburg-like metabolic shifts. Therefore, anti-glycation agents (e.g., aminoguanidine), polyol inhibitors (e.g., epalrestat), glucose transporter type 4 agonists (e.g., fisetin), and 2,3-bisphosphoglycerate enhancers can restore oxygen unloading function, improve hyperglycemia, and treat diabetes.