ANGPTL3 Deficiency and Risk of Hepatic Steatosis

Abstract

Background: ANGPTL3 (angiopoietin-like 3) is a therapeutic target for reducing plasma levels of triglycerides and low-density lipoprotein cholesterol. A recent trial with vupanorsen, an antisense oligonucleotide targeting hepatic production of ANGPTL3, reported a dose-dependent increase in hepatic fat. It is unclear whether this adverse effect is due to an on-target effect of inhibiting hepatic ANGPTL3.

Methods: We recruited participants with ANGPTL3 deficiency related to ANGPTL3 loss-of-function (LoF) mutations, along with wild-type (WT) participants from 2 previously characterized cohorts located in Campodimele, Italy, and St. Louis, MO. Magnetic resonance spectroscopy and magnetic resonance proton density fat fraction were performed to measure hepatic fat fraction and the distribution of extrahepatic fat. To estimate the causal relationship between ANGPTL3 and hepatic fat, we generated a genetic instrument of plasma ANGPTL3 levels as a surrogate for hepatic protein synthesis and performed Mendelian randomization analyses with hepatic fat in the UK Biobank study.

Results: We recruited participants with complete (n=6) or partial (n=32) ANGPTL3 deficiency related to ANGPTL3 LoF mutations, as well as WT participants (n=92) without LoF mutations. Participants with ANGPTL3 deficiency exhibited significantly lower total cholesterol (complete deficiency, 78.5 mg/dL; partial deficiency, 172 mg/dL; WT, 188 mg/dL; P<0.05 for both deficiency groups compared with WT), along with plasma triglycerides (complete deficiency, 26 mg/dL; partial deficiency, 79 mg/dL; WT, 88 mg/dL; P<0.05 for both deficiency groups compared with WT) without any significant difference in hepatic fat (complete deficiency, 9.8%; partial deficiency, 10.1%; WT, 9.9%; P>0.05 for both deficiency groups compared with WT) or severity of hepatic steatosis as assessed by magnetic resonance imaging. In addition, ANGPTL3 deficiency did not alter the distribution of extrahepatic fat. Results from Mendelian randomization analyses in 36 703 participants from the UK Biobank demonstrated that genetically determined ANGPTL3 plasma protein levels were causally associated with low-density lipoprotein cholesterol (P=1.7×10^-17) and triglycerides (P=3.2×10^-18) but not with hepatic fat (P=0.22).

Conclusions: ANGPTL3 deficiency related to LoF mutations in ANGPTL3, as well as genetically determined reduction of plasma ANGPTL3 levels, is not associated with hepatic steatosis. Therapeutic approaches to inhibit ANGPTL3 production in hepatocytes are not necessarily expected to result in the increased risk for hepatic steatosis that was observed with vupanorsen.

Keywords: angiopoietin-like protein 3; fatty acids, nonesterified; fatty liver; lipids; magnetic resonance spectroscopy; triglycerides.

Figure 1.. ANGPTL3 deficiency and quantity of hepatic fat.

Hepatic fat fraction as estimated by MR-S (A) and MR-PDFF (B) is shown according to degree of ANGPTL3 deficiency. Boxes and error bars represent mean and SEM, respectively. P>0.05 between genotype groups by Kruskal-Wallis test. ANGPTL3: angiopoietin-like 3 protein; LoF: loss of function; MR-S: magnetic resonance spectroscopy; MR-PDFF: magnetic resonance proton density fat fraction.

Figure 2.. ANGPTL3 deficiency and severity of hepatic steatosis.

Hepatic steatosis severity as estimated by MR-S (A) and MR-PDFF (B) is shown according to degree of ANGPTL3 deficiency. Severity of hepatic steatosis was calculated as reported in the methods. ANGPTL3: angiopoietin-like 3 protein; LoF: loss of function; MR-S: magnetic resonance spectroscopy; MR-PDFF: magnetic resonance proton density fat fraction.

Figure 3.. ANGPTL3 deficiency and extrahepatic fat distribution.

Distribution of extrahepatic fat in (A) visceral adipose tissue, (B) subcutaneous adipose tissue, (C) skeletal intramuscular adipose tissue, and (D) skeletal subcutaneous adipose tissue is shown according to degree of ANGPTL3 deficiency. Boxes and error bars represent means and SEM, respectively. P>0.05 between genotype groups by Kruskal-Wallis test. ANGPTL3: angiopoietin-like 3 protein; LoF: loss of function.

Figure 4.. Mendelian Randomization of genetically determined plasma ANGPTL3 with plasma lipids and hepatic fat in the UK Biobank study.

(A) Estimated effect (with 95% confidence intervals) of each variant included in the Mendelian Randomization analysis on ANGPTL3 levels for (A) plasma triglycerides (P=3.2x10⁻¹⁸), (B) plasma LDL cholesterol (P=1.7x10⁻¹⁷), and (C) hepatic fat (P=0.22). Red lines indicate the causal effect estimates.