• Keith R Walley, John H Boyd, HyeJin Julia Kong, and James A Russell.
• All authors: Centre for Heart Lung Innovation, University of British Columbia, Vancouver, BC, Canada.
• Crit. Care Med. 2019 Mar 1; 47 (3): 463-466.

ObjectivesLow low-density lipoprotein levels are associated with increased mortality in sepsis. Whether low low-density lipoprotein levels contribute causally to adverse sepsis outcome is unknown.DesignRetrospective analysis of two sepsis patient cohorts using a Mendelian Randomization strategy.SettingSepsis patients enrolled into clinical research cohorts at tertiary care teaching hospitals.PatientsThe first cohort included 200 sepsis patients enrolled in an observational study in a hospital Emergency Department. The second cohort included genotyped patients enrolled in the Vasopressin and Septic Shock Trial.InterventionsRetrospective analysis of these patient datasets. In 632 patients enrolled in Vasopressin and Septic Shock Trial, Proprotein Convertase Subtilisin/Kexin type 9, and 3-Hydroxy-3-Methylglutaryl-CoA Reductase single nucleotide polymorphisms known to be associated with low-density lipoprotein levels were genotyped, and a genetic score related to low-density lipoprotein levels was calculated.Measurements And Main ResultsIn the first cohort, we replicated the finding that low low-density lipoprotein levels are associated with increased 28-day mortality. In genotyped patients in the Vasopressin and Septic Shock Trial trial, we found that the 3-Hydroxy-3-Methylglutaryl-CoA Reductase genetic score, known to be directly related to low low-density lipoprotein levels, was not associated with increased mortality. Surprisingly the Proprotein Convertase Subtilisin/Kexin type 9 genetic score, known to be directly related to low low-density lipoprotein levels, was associated with decreased (not increased) mortality.ConclusionsBoth 3-Hydroxy-3-Methylglutaryl-CoA Reductase and Proprotein Convertase Subtilisin/Kexin type 9 genetic scores should have been associated with increased mortality if low low-density lipoprotein levels contributed causally to sepsis mortality. But this was not the case, and the opposite was observed for the Proprotein Convertase Subtilisin/Kexin type 9 genetic score. This suggests that low-density lipoprotein levels, per se, do not contribute causally to adverse sepsis outcomes. The Proprotein Convertase Subtilisin/Kexin type 9 genetic score finding raises the possibility that increased low-density lipoprotein clearance (the effect of these Proprotein Convertase Subtilisin/Kexin type 9 genotypes) may contribute to improved sepsis outcomes.

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