ANGPTL3 Deficiency and Risk of Hepatic Steatosis.

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.

Clinical Implications of Monogenic Versus Polygenic Hypercholesterolemia: Long-Term Response to Treatment, Coronary Atherosclerosis Burden, and Cardiovascular Events.

Background Familial hypercholesterolemia (FH) may arise from deleterious monogenic variants in FH-causing genes as well as from a polygenic cause. We evaluated the relationships between monogenic FH and polygenic hypercholesterolemia in influencing the long-term response to therapy and the risk of atherosclerosis. Methods and Results A cohort of 370 patients with clinically diagnosed FH were screened for monogenic mutations and a low-density lipoprotein-rising genetic risk score >0.69 to identify polygenic cause. Medical records were reviewed to estimate the response to lipid-lowering therapies and the occurrence of major atherosclerotic cardiovascular events during a median follow-up of 31.0 months. A subgroup of patients (n=119) also underwent coronary computed tomographic angiography for the evaluation of coronary artery calcium score and severity of coronary stenosis as compared with 135 controls. Two hundred nine (56.5%) patients with hypercholesterolemia were classified as monogenic (FH/M+), 89 (24.1%) as polygenic, and 72 (19.5%) genetically undefined (FH/M-). The response to lipid-lowering therapy was poorest in monogenic, whereas it was comparable in patients with polygenic hypercholesterolemia and genetically undetermined. Mean coronary artery calcium score and the prevalence of coronary artery calcium >100 units were significantly higher in FH/M+ as compared with both FH/M- and controls. Finally, after adjustments for confounders, we observed a 5-fold higher risk of incident major atherosclerotic cardiovascular events in FH/M+ (hazard ratio, 4.8; 95% CI, 1.06-21.36; Padj=0.041). Conclusions Monogenic cause of FH is associated with lower response to conventional cholesterol-lowering therapies as well as with increased burden of coronary atherosclerosis and risk of atherosclerotic-related events. Genetic testing for hypercholesterolemia is helpful in providing important prognostic information.

Contribution of mutations in low density lipoprotein receptor (LDLR) and lipoprotein lipase (LPL) genes to familial combined hyperlipidemia (FCHL): a reappraisal by using a resequencing approach.

BACKGROUND: Defective low-density lipoprotein receptor (LDLR) and lipoprotein lipase (LPL) alleles have been implicated in familial combined hyperlipidemia (FCHL). However, their contribution might have been influenced by diagnostic criteria. This study was aimed to reassess the frequency of rare and common variants in LDLR and LPL in FCHL individuals classified with stringent criteria. METHODS: LDLR and LPL were resequenced in 208 FHCL and 171 controls. Variants were classified as loss- (LOF) or gain-of-function (GOF) based upon in silico prediction, familial segregation and available functional data. RESULTS: Eight LOF variants were detected in LDLR, 6 of which were missense and 2 were predicted to disrupt normal splicing; all were present at heterozygous state. They were found in 10 FCHL but not in controls, thus indicating that 4.8% of FCHL individuals should be reclassified as FH. LDL-C (positive) and BMI (negative) were the strongest predictors of LDLR mutations with LDL-C 181 mg/dl being the best threshold for diagnosing the presence of dysfunctional LDLR alleles. The cumulative prevalence of definite LPL defective alleles (1 rare and 2 common heterozygous missense variants) was comparable between FCHL and controls (10.1% vs. 10.5%). Conversely, the LPL GOF variant p.Ser474* showed a lower frequency in FCHL than in controls (13.5% vs. 24.0%, p = 0.008). Overall, LOF LPL variants did not show a TG-modulating effect. CONCLUSIONS: Our findings indicate that, in well characterized FCHL individuals, variants in LDLR and LPL provide a small contribution to this dyslipidemia, thus limiting the need for such genetic testing.

Clinical characteristics and plasma lipids in subjects with familial combined hypolipidemia: a pooled analysis.

Angiopoietin-like 3 (ANGPTL3) regulates lipoprotein metabolism by modulating extracellular lipases. Loss-of function mutations in ANGPTL3 gene cause familial combined hypolipidemia (FHBL2). The mode of inheritance and hepatic and vascular consequences of FHBL2 have not been fully elucidated. To get further insights on these aspects, we reevaluated the clinical and the biochemical characteristics of all reported cases of FHBL2. One hundred fifteen FHBL2 individuals carrying 13 different mutations in the ANGPTL3 gene (14 homozygotes, 8 compound heterozygotes, and 93 heterozygotes) and 402 controls were considered. Carriers of two mutant alleles had undetectable plasma levels of ANGPTL3 protein, whereas heterozygotes showed a reduction ranging from 34% to 88%, according to genotype. Compared with controls, homozygotes as well as heterozygotes showed a significant reduction of all plasma lipoproteins, while no difference in lipoprotein(a) [Lp(a)] levels was detected between groups. The prevalence of fatty liver was not different in FHBL2 subjects compared with controls. Notably, diabetes mellitus and cardiovascular disease were absent among homozygotes. FHBL2 trait is inherited in a codominant manner, and the lipid-lowering effect of two ANGPTL3 mutant alleles was more than four times larger than that of one mutant allele. No changes in Lp(a) were detected in FHBL2. Furthermore, our analysis confirmed that FHBL2 is not associated with adverse clinical sequelae. The possibility that FHBL2 confers lower risk of diabetes and cardiovascular disease warrants more detailed investigation.

Mechanisms of diabetic dyslipidemia: relevance for atherogenesis.

Diabetic dyslipidemia is due to a multiple array of metabolic abnormalities determining a typical phenotype characterized by increased plasma triglycerides, reduced HDL and a preponderance of small, dense LDL. This dyslipidemia, defined as atherogenic dyslipidemia, is thought to be highly responsible for the increased cardiovascular risk in diabetes mellitus. Several lines of evidence indicate that the increased liver production of VLDL is the main underlying defect in atherogenic dyslipidemia. This review will recapitulate the pathophysiological aspects of diabetic dyslipidemia with special focus on the molecular mechanism causing increased liver production of VLDL in diabetic patients. The consequences of atherogenic dyslipidemia on mechanisms of atherogenesis will be also reviewed.

Mutations in the ANGPTL3 gene and familial combined hypolipidemia: a clinical and biochemical characterization.

CONTEXT: Familial combined hypolipidemia causes a global reduction of plasma lipoproteins. Its clinical correlates and metabolic implications have not been well defined. OBJECTIVE: The objective of the study was to investigate the genetic, clinical, and metabolic characteristics of a cohort of subjects with familial combined hypolipidemia. DESIGN: The design of the study included candidate gene screening and the comparison of the clinical and metabolic characteristics between carrier and noncarrier individuals. SETTING: The study was conducted in a general community. SUBJECTS: Participants in the study included individuals belonging to nine families with familial combined hypolipidemia identified in a small town (Campodimele) as well as from other 352 subjects living in the same community. MAIN OUTCOMES MEASURES: Serum concentrations of lipoproteins, Angiopoietin-like 3 (Angptl3) proteins, and noncholesterol sterols were measured. RESULTS: The ANGPTL3 S17X mutation was found in all probands, 20 affected family members, and 32 individuals of the community. Two additional frame shift mutations, FsE96del and FsS122, were also identified in two hypocholesterolemic individuals. Homozygotes for the ANGPTL3 S17X mutation had no circulating Angptl3 and a marked reduction of all plasma lipids (P < 0.001). Heterozygotes had 42% reduction in Angptl3 level compared with noncarriers (P < 0.0001) but a significant reduction of only total cholesterol and high-density lipoprotein cholesterol. No differences were observed in the plasma noncholesterol sterols between carriers and noncarriers. No association between familial combined hypolipidemia and the risk of hepatic or cardiovascular diseases were detected. CONCLUSIONS: Familial combined hypolipidemia segregates as a recessive trait so that apolipoprotein B- and apolipoprotein A-I-containing lipoproteins are comprehensively affected only by the total deficiency of Angptl3. Familial combined hypolipidemia does not perturb whole-body cholesterol homeostasis and is not associated with adverse clinical sequelae.

Treating statin-intolerant patients.

Statins are effective in reducing cardiovascular events and are safe for almost all patients. Nevertheless, intolerance to statins is frequently faced in clinical practice. This is mostly due to muscular symptoms (myalgia with or without increase of plasma creatinine kinase) and/or elevation of hepatic aminotransferases, which overall constitutes approximately two-thirds of reported adverse events during statin therapy. These side effects raise concerns in patients as well as in doctors and are likely to reduce patients' adherence and, as a consequence, the cardiovascular benefit. Therefore, it is mandatory that clinicians improve their knowledge on the clinical aspects of muscular and hepatic side effects of statin therapy as well as their ability to manage patients with statin intolerance. Besides briefly examining the clinical aspects and the mechanisms that are proposed to be responsible for the most common statin-associated side effects, the main purpose of this article is to review the available approaches to manage statin-intolerant patients. The first step is to determine whether the adverse events are indeed related to statin therapy. If so, lowering the dosage or changing statin, alternate dosing options, or the use of nonstatin compounds may be practical strategies. The cholesterol-lowering potency as well as the usefulness of these different approaches in treating statin-intolerant patients will be examined based on currently available data. However, the cardiovascular benefit of these strategies has not been well established, so their use has to be guided by a careful clinical assessment of each patient.

The relationship between metabolic syndrome, its components, and the whole-body atherosclerotic disease burden as measured by computed tomography angiography.

OBJECTIVE: Quantify the whole-body atherosclerotic disease in asymptomatic subjects with and without metabolic syndrome (MetS) and to assess the contribution of the syndrome and its components to the atherosclerotic burden. METHODS: Sixty-five subjects with and 51 without ATPIII-defined MetS underwent a 64-slice computed tomography angiography (CTA). Plaques causing >0% stenosis in coronary or extra-coronary arteries were classified as positive. RESULTS: The prevalence of plaques in coronary, carotid and peripheral arteries as well as their severity did not differ between groups. Conversely, it was seen an almost 3-fold increased likelihood (OR=2.70; 95% CI 1.30-5.57; P<0.001) of atherosclerosis in any district across categories of MetS components (0-1 vs. 2-3 vs. 4-5). Hypertriglyceridemia (P<0.05) and high blood glucose (P<0.05) were independent predictors of the atherosclerotic burden. CONCLUSIONS: Atherosclerotic burden as revealed by 64-TCA appears to be more strongly associated with the number of MetS-related factors than to the clinical diagnosis of MetS itself.

Usefulness of atherogenic dyslipidemia for predicting cardiovascular risk in patients with angiographically defined coronary artery disease.

The identification of factors contributing to residual cardiovascular risk is important to improve the management of patients with established coronary artery disease (CAD). This study was conducted to assess the predictive value of atherogenic dyslipidemia (defined as high triglycerides and low high-density lipoprotein [HDL] cholesterol) for long-term outcomes in patients with CAD. In 284 patients (238 men, 46 women; mean age at baseline 59.2 +/- 8.9 years) with coronary stenosis (>50% in > or =1 vessel), the presence of atherogenic dyslipidemia was prospectively associated with the incidence of major adverse cardiovascular events (MACEs) during a median follow-up of 7.8 years. MACEs were defined as cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, the recurrence of angina, and revascularization procedures. MACEs were observed in 111 (39.1%) patients with CAD. MACEs occurred more frequently in patients with atherogenic dyslipidemia (50.9%) than in those with isolated low HDL cholesterol or high triglycerides (33.0%) or with normal HDL cholesterol and triglyceride concentrations (29.2%) (p <0.01 for trend). Kaplan-Meier survival analysis showed a decrease in event-free survival in patients with compared with those without atherogenic dyslipidemia (log-rank p = 0.006). Patients with atherogenic dyslipidemia presented with increased plasma concentrations of remnants, denser low-density lipoprotein, more atherogenic HDL particles, and insulin-resistant status. After adjustment for potential confounding variables, the magnitude of increased risk associated with atherogenic dyslipidemia was 1.58 (95% confidence interval 1.12 to 2.21, p = 0.008). In conclusion, these data provide evidence that atherogenic dyslipidemia is an independent predictor of cardiovascular risk in patients with CAD, even stronger than isolated high triglycerides or low HDL cholesterol.

Comparison of atorvastatin versus fenofibrate in reaching lipid targets and influencing biomarkers of endothelial damage in patients with familial combined hyperlipidemia.

Statins and fibrates have different effects on lipid abnormalities of familial combined hyperlipidemia (FCHL); thus, the selection of the first-line drug is troublesome. We evaluated to what extent monotherapy with a potent statin is more effective than fibrate in reaching the recommended lipid targets in FCHL. Fifty-six patients were randomized to receive optimal dosage of atorvastatin (n = 27) or 200 mg/d micronized fenofibrate (n = 29) for 24 weeks. To reach the optimal dosage, atorvastatin was up-titrated at each follow-up visit if low-density lipoprotein (LDL) cholesterol >130 mg/dL (>100 mg/dL in patients with coronary or cerebrovascular disease). The effects of fenofibrate and atorvastatin on lipoprotein fractions as well as on plasma levels of endothelin-1 (ET-1) and adrenomedullin (AM) were also evaluated. At end of trial, a greater proportion of patients on atorvastatin (average dosage, 20.8 mg/d) reached lipid targets in comparison with those on fenofibrate (64% vs 32.1%, P = .02). Atorvastatin was significantly more effective in reducing total cholesterol, LDL cholesterol, apolipoprotein B, and non-high-density lipoprotein (HDL) cholesterol. Conversely, triglycerides decreased and HDL increased more during fenofibrate. Nevertheless, atorvastatin produced a marked reduction in very low-density lipoprotein and very low-density lipoprotein remnants. Atorvastatin lowered all LDL subtypes, although fenofibrate appeared to be more effective on denser LDL. Compared with 43 normolipemic controls, FCHL patients presented increased baseline plasma levels of ET-1 (P = .007) but not of AM. Fenofibrate, but not atorvastatin, significantly lowered ET-1 levels by 16.7% (P < .05). Neither drug significantly affected plasma concentrations of AM. In summary, although fenofibrate showed superiority in raising HDL and reducing ET-1, atorvastatin was more effective in reaching lipid targets in FCHL so that it can be proposed as the first-line option in the management of this atherogenic hyperlipidemia.