Acarbose modulates microglial Pkm2 acetylation to reshape immunometabolism and preserve retinal neurons after ischemia-reperfusion

Retinal ischemia-reperfusion (IR) elicits microglia-driven neuroinflammation and mitochondrial failure that led to retinal ganglion cell (RGCs) loss, yet effective disease-modifying therapies remain limited. Acarbose (ACA), an α-glucosidase inhibitor widely used for diabetes, has recently been recognized for its dual regulatory potential on immune metabolism and aging-associated neurodegeneration. Here, we demonstrate that intravitreal ACA administration attenuates retinal inflammation and improves RGCs survival following IR injury. Single-cell RNA Sequencing revealed extensive inflammatory activation and metabolic reprogramming across the retina, characterized by enhanced nicotinamide adenine dinucleotide (NAD) catabolism, particularly in microglia. ACA treatment was associated with reversal of these alterations, replenished NAD levels, and restored mitochondrial integrity. Integrative proteomic and biochemical analyses identified Pyruvate Kinase, muscle-type 2 (Pkm2) as a candidate regulatory node affected by ACA. Intravitreal delivery of siPkm2 partially protected against IR injury, and co-administration with ACA produced an additive trend in neuroprotection. Mechanistically, ACA upregulated Sirtuin 1 (SIRT1) and reduced Pkm2 acetylation at lysine 270 (K270), which was linked to pro-inflammatory microglial activation. Structure-based virtual screening further identified HY-113082, a small molecule targeting Pkm2-K270, which synergized with ACA to suppress inflammation and enhance retinal protection. Moreover, Pkm2^fl/flCx3cr1-Cre mice conferred partial resistance to IR injury, but blunted the additional benefit of HY-113082 when combined with ACA, consistent with on-target engagement. Our findings support that ACA exerts retinal protection through the Sirt1-Pkm2-NAD axis, suggesting a metabolic checkpoint that integrates immune and mitochondrial regulation. This study provides mechanistic insight into ACA's dual immunometabolic and neuroprotective actions, holding promise for therapeutic insights into neuroinflammation.