Abstract
BACKGROUND: Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have clinical, pathological and genetic overlapping. Lipid pathways are implicated in ALS. This study examined the effect of blood lipid levels on ALS, FTD risk, and survival in ALS. METHODS: A systematic review and meta-analysis of high and low-density lipoprotein cholesterol (HDL-c and LDL-c), total cholesterol, triglycerides, apolipoproteins B and A1 levels with ALS was performed. Two-sample Mendelian randomisation (MR) analysis sought the causal effects of these exposures on ALS, FTD, and survival in ALS. The effect of lipid-lowering drugs was also examined using genetic proxies for targets of lipid-lowering medications. RESULTS: Three cohort studies met the inclusion criteria for meta-analysis. Meta-analysis indicated an association between higher LDL-c (HR(per mmol/L) = 1.07, 95%CI:1.02-1.12; I2 =18%) and lower HDL-c (HR(per mmol/L) = 0.83, 95%CI:0.74-0.94; I2 =0%) with an increased risk of ALS. MR suggested causal effects of higher LDL-c (OR(IVW) = 1.085, 95%:CI 1.008-1.168, p(FDR) = 0.0406), total cholesterol (OR(IVW) = 1.081, 95%:CI 1.013-1.154, p(FDR) = 0.0458) and apolipoprotein B (OR(IVW) = 1.104, 95%:CI 1.041-1.171, p(FDR) = 0.0061) increasing ALS risk, and higher apolipoprotein B level increasing FTD risk (OR(IVW) = 1.424, 95%CI 1.072-1.829, p(FDR) = 0.0382). Reducing LDL-c through APOB inhibition was associated with lower ALS (OR(IVW) = 0.84, 95%CI 0.759-0.929, p(FDR) = 0.00275) and FTD risk (OR(IVW) = 0.581, 95%CI 0.387-0.874, p(FDR) = 0.0362). CONCLUSION: These data support the influence of LDL-c and total cholesterol on ALS risk and apolipoprotein B on the risk of ALS and FTD. Potential APOB inhibition might decrease the risk of sporadic ALS and FTD. Further work in monogenic forms of ALS and FTD is necessary to determine whether blood lipids influence penetrance and phenotype.