Does chronic glycation increase mitochondrial reactive oxygen species and reduce metabolic flexibility?

Chronic glycation, driven by the accumulation of advanced glycation end products (AGEs) and reactive dicarbonyls like methylglyoxal, plays a critical role in cellular aging and metabolic decline.

Mechanisms of mitochondrial oxidative stress

• Direct electron transport chain damage: Reactive dicarbonyls directly glycate key mitochondrial proteins, specifically targeting complexes I and III of the electron transport chain (ETC). This structural modification destabilizes normal electron flow, resulting in increased electron leakage and elevated superoxide generation.
• Indirect signaling cascades: AGEs bind to their receptor (RAGE), which activates cytosolic NADPH oxidase (NOX). The resulting cytosolic oxidative stress triggers mitochondrial permeability transition (mPT) pore opening, compounding complex I deficiency and establishing a damaging feed-forward loop of reactive oxygen species (ROS) production.

Impairment of metabolic flexibility

• Disrupted fuel switching: The loss of mitochondrial redox balance and respiratory capacity restricts the cell's ability to transition dynamically between lipid and carbohydrate oxidation.
• Insulin resistance mediation: AGE-RAGE signaling disrupts downstream insulin pathways, driving insulin resistance. Because metabolic flexibility is clinically quantified by the change in respiratory exchange ratio ($\Delta$RER) under insulin stimulation, this resistance blunts the $\Delta$RER. This forces skeletal muscle and other tissues to continue oxidizing fatty acids even in the fed state.

Bottom line

• Chronic glycation directly impairs mitochondrial complexes I and III while promoting insulin resistance via the AGE-RAGE axis, collectively undermining the body's capacity to dynamically switch between glucose and fat oxidation.