HMGCS2 desuccinylation modulates acetoacetate to drive tubule-macrophage inflammatory crosstalk in diabetic kidney disease.

Mitochondrial dysfunction in renal tubular epithelial cells (TECs) is a hallmark of diabetic kidney disease (DKD), accompanied by macrophage infiltration, yet how metabolic perturbations in TECs-macrophage driven inflammation remains unclear. Here, we identify 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), the rate-limiting enzyme of ketogenesis, as a critical mediator linking tubular mitochondrial stress to macrophage M1 polarization in DKD. In mice subjected to DKD, conditional knockout HMGCS2 in TECs decreases mitochondrial fission of TECs, M1 macrophage infiltration and tubular inflammatory injury. Combining LC-MS/MS and ketone flux detection reveals that desuccinylated HMGCS2 produced more acetoacetate (AcAc) than beta-hydroxybutyrate (β-HB) in TECs of DKD. Mechanistically, Signal Transducer and Activator of Transcription 3 (STAT3) promotes Hmgcs2 transcription and sirtuin 5 (SIRT5) activates HMGCS2 through lysine desuccinylation at K367, which promotes AcAc overload shuttling from TECs to macrophages. AcAc acts as a signaling metabolite to activate the MIF/ERK pathway, driving M1 polarization and amplifying a pro-inflammatory feedback loop of tubular injury. In addition, AAV9-mediated Hmgcs2 silencing therapy improves tubular inflammatory injury and attenuates DKD progression. Taken together, this study unveils a tubule-macrophage metabolic crosstalk axis mediated by HMGCS2-driven AcAc accumulation, which couples mitochondrial stress to immune response in DKD.