Decreased Clearance of Low-Density Lipoprotein Cholesterol is Causally Associate With Increased Mortality of Septic Shock

Objective: To determine whether low-density lipoprotein cholesterol (LDL-C) levels, set by the balance of clearance and production, causally contribute to septic shock 28-day mortality. Design: We measured LDL-C levels and genotypes in patients with septic shock. Using Genotyping and Genome-Wide Association Study summary statistics from over 150,000 Japanese participants, we genetically predicted pre-infection LDL-C levels. Two-sample Mendelian randomization was used to assess the causal relationship between predicted pre-infection LDL-C levels and 28-day mortality. We analyzed PCSK9 and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) genotypes to determine if LDL-C clearance or production was the underlying mechanism. Setting: Multicenter ICUs in Japan. Patients: Genotyped septic shock patients ( n = 614). Interventions: None. Measurements and Main Results: Predicted pre-infection LDL-C levels were much higher than directly measured LDL-C levels at the onset of septic shock (141 mg/dL vs. 40 mg/dL, p < 0.001). Two-sample Mendelian randomization revealed that high predicted pre-infection LDL-C levels were causally associated with increased septic shock 28-day mortality (hazard ratio, 2.78; p = 0.039). PCSK9 genetic variants that increase LDL-C clearance via the LDL receptor (genetically proxied PCSK9 inhibitor treatment) were associated with decreased mortality ( p = 0.003) while HMGCR genetic variants that decrease LDL-C production (genetically proxied statin treatment) were not associated with decreased septic shock mortality (indeed the opposite effect was observed, p = 0.039). The two main genetic variants driving the association between high predicted pre-infection LDL-C levels and increased mortality were in apolipoprotein genes ( ApoB100 -rs13306206 and ApoE -rs7412), apolipoproteins involved in LDL-C binding to the LDL receptor. Conclusions: Low LDL-C clearance explains the causal association between high genetically predicted pre-infection LDL-C levels and increased septic shock mortality. PCSK9 , ApoB , and ApoE variants were identified as causal, all related to the LDL receptor or its interaction with LDL-C. Enhancing LDL receptor-mediated clearance of pathogen lipid toxins may improve septic shock outcomes.