Lactate dehydrogenase B deficiency-dependent hyperlactatemia coordinates with necroptosis to worsen septic liver and kidney injuries

Hyperlactatemia is intimately correlated with severity and poor prognosis of patients with sepsis. However, little experimental evidence on this process is known. We report here that lactate dehydrogenase B (LDHB), the glycolytic enzyme that catalyzes conversion of lactate to pyruvate, is transcriptionally downregulated in blood samples of hyperlactatemic patients, while mice receiving lactate injection have reduced LDHB activity in liver and kidney. LDHB knockout (Ldhb^-/-) mice with hyperlactatemia are vulnerable to lethality, hypotension and vascular leakage. The hyperlactatemic Ldhb^-/- mice develop severe liver and kidney injuries accompanied by increased hepatic and renal SLC16A1 abundance but unaltered morphology. Pharmacological targeting of SLC16A1 with AZD3965 in Ldhb^-/- mice rescues the hyperlactatemia-induced lethality, liver and kidney injuries. Loss of LDHB renders hyperlactatemia, lethality, vascular leakage, liver and kidney injuries in response to abdominal sepsis. AZD3965 treatment partially abrogates liver and kidney injuries of septic Ldhb^-/- mice without affecting necrosis. Blockade of necroptosis significantly protects Ldhb^-/- mice against septic liver and kidney injuries, enabling a compensation towards the therapeutic efficacy of AZD3965. Our study together unearth the coordination of hyperlactatemia and necroptosis in septic liver and kidney injuries in the context of LDHB deficiency, and support further investigation of combined targeting SLC16A1 and necroptosis for clinical treatment of sepsis with low LDHB activity.