Extremely low levels of low-density lipoprotein potentially suggestive of familial hypobetalipoproteinemia: A separate phenotype of NAFLD?

J-shaped association between apolipoprotein B and CV outcomes in statin-treated patients with chronic coronary syndrome

INTRODUCTION AND OBJECTIVES

The association between apolipoprotein B (apoB) and residual cardiovascular (CV) risk in patients with chronic coronary syndrome (CCS) remains unclear. We aimed to investigate the association between apoB levels and CV outcomes in statin-treated CCS patients.

METHODS

We enrolled 8641 statin-treated CCS patients at Fuwai Hospital. The patients were divided into 5 groups based on to apoB quintiles (Q1 to Q5). The primary endpoint was 3-year CV events, including CV death, nonfatal myocardial infarction, and nonfatal stroke.

RESULTS

During a median follow-up of 3.17 years, there were 232 (2.7%) CV events. After multivariable adjustment, a restricted cubic spline illustrated a J-shaped relationship between apoB levels and 3-year CV events, with the risk remaining flat until apoB levels exceeded 0.73g/L, after which the risk increased (nonlinear P <.05). Kaplan-Meier curves showed the lowest CV event rate in the Q3 group (0.68-0.78g/L). Compared with the Q3 group, multivariable Cox regression models revealed that both low (Q1, ≤0.57g/L) and high (Q5, >0.93g/L) apoB levels were associated with an increased risk of major adverse cardiac events (all P <.05). Notably, patients with low apoB levels (Q1) had the highest risk of CV death (HR, 2.44; 95%CI, 1.17-5.08).

CONCLUSIONS

Our analysis indicates that both low and high levels of apoB are associated with elevated CV risk, with the risk being particularly pronounced at higher levels (> 0.73g/L).

J-shaped association between apolipoprotein B and CV outcomes in statin-treated patients with chronic coronary syndrome

INTRODUCTION AND OBJECTIVES

The association between apolipoprotein B (apoB) and residual cardiovascular (CV) risk in patients with chronic coronary syndrome (CCS) remains unclear. We aimed to investigate the association between apoB levels and CV outcomes in statin-treated CCS patients.

METHODS

We enrolled 8641 statin-treated CCS patients at Fuwai Hospital. The patients were divided into 5 groups based on to apoB quintiles (Q1 to Q5). The primary endpoint was 3-year CV events, including CV death, nonfatal myocardial infarction, and nonfatal stroke.

RESULTS

During a median follow-up of 3.17 years, there were 232 (2.7%) CV events. After multivariable adjustment, a restricted cubic spline illustrated a J-shaped relationship between apoB levels and 3-year CV events, with the risk remaining flat until apoB levels exceeded 0.73g/L, after which the risk increased (nonlinear P <.05). Kaplan-Meier curves showed the lowest CV event rate in the Q3 group (0.68-0.78g/L). Compared with the Q3 group, multivariable Cox regression models revealed that both low (Q1, ≤0.57g/L) and high (Q5, >0.93g/L) apoB levels were associated with an increased risk of major adverse cardiac events (all P <.05). Notably, patients with low apoB levels (Q1) had the highest risk of CV death (HR, 2.44; 95%CI, 1.17-5.08).

CONCLUSIONS

Our analysis indicates that both low and high levels of apoB are associated with elevated CV risk, with the risk being particularly pronounced at higher levels (> 0.73g/L).

Hypolipidemia due to Familial Hypobetalipoproteinemia in Adolescents

Background/Objective

Individuals with heterozygous familial hypobetalipoproteinemia (h-FHBL) due to loss-of-function mutation in the apolipoprotein B gene are typically asymptomatic with mild liver dysfunction, which is often detected incidentally. About 5% to 10% of those with h-FHBL develop steatohepatitis which occasionally progress to cirrhosis especially in the presence of alcohol use, excess calorie consumption, or liver injury. We report 3 patients with hypobetalipoproteinemia, 2 with confirmed h-FHBL, and 1 with suspected h-FHBL.

Case Report

Three asymptomatic adolescents presented with low lipid levels detected on screening laboratory studies. Patient 1, a 13 6/12-year-old male and patient 2, a 15 9/12-year-old female, were siblings. Patient 3 was a 12 6/12-year-old female. All had total cholesterol ranging from 61 to 87 mg/dL, low-density lipoprotein cholesterol 10 to 28 mg/dL, and triglycerides 19 to 36 mg/dL. Aspartate transaminase and alanine transaminase levels were normal in patients 1 and 3 and were elevated in patient 2. Liver ultrasounds of patients 2 and 3 showed hepatic steatosis. Molecular testing identified pathogenic variant of apolipoprotein B gene in patients 1 and 2, c.133C>T(p.Arg.45Ter) confirming the diagnosis of h-FHBL.

Discussion

More studies are needed in children with h-FHBL and other forms of hypobetalipoproteinemia to improve awareness of these disorders and to develop guidelines for monitoring and risk reduction in affected patients.

Conclusion

Health care providers should be aware that persistent hypolipidemia may indicate h-FHBL, which can be a risk factor for liver dysfunction. Youth with h-FHBL should be counseled about lifestyle modifications and screened for the development of metabolic dysfunction-associated steatotic liver disease.

Food Network Analysis in Non-Obese Patients with or without Steatosis

BACKGROUND

Steatosis is the most common liver disease worldwide and the leading cause of liver-associated morbidity and mortality. The aim of this study was to explore the differences in blood parameters and dietary habits in non-obese patients with and without steatosis.

METHODS

The present study included 987 participants with BMI < 30, assessed in the fourth recall of the MICOL study. Patients were divided by steatosis grade, and a validated food frequency questionnaire (FFQ) with 28 food groups was administered.

RESULTS

The prevalence of non-obese participants with steatosis was 42.86%. Overall, the results indicated many statistically significant blood parameters and dietary habits. Analysis of dietary habits revealed that non-obese people with or without steatosis had similar dietary habits, although higher daily amounts of red meat, processed meat, ready meals, and alcohol were recorded in participants with liver disease (p < 0.05).

CONCLUSIONS

Many differences were found in non-obese people with and without steatosis, but in light of a network analysis, the two groups demonstrated similar dietary habits, proving that pathophysiological, genetic, and hormonal patterns are probably the basis of their liver status, regardless of weight. Future genetic analyses will be performed to analyze the expression of genes involved in the development of steatosis in our cohort.

Comparison between obese and non-obese nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver conditions that are characterized by excess accumulation of fat in the liver, and is diagnosed after exclusion of significant alcohol intake and other causes of chronic liver disease. In the majority of cases, NAFLD is associated with overnutrition and obesity, although it may be also found in lean or non-obese individuals. It has been estimated that 19.2% of NAFLD patients are lean and 40.8% are non-obese. The proportion of patients with more severe liver disease and the incidence of all-cause mortality, liver-related mortality, and cardiovascular mortality among non-obese and obese NAFLD patients varies across studies and may be confounded by selection bias, underestimation of alcohol intake, and unaccounted weight changes over time. Genetic factors may have a greater effect towards the development of NAFLD in lean or non-obese individuals, but the effect may be less pronounced in the presence of strong environmental factors, such as poor dietary choices and a sedentary lifestyle, as body mass index increases in the obese state. Overall, non-invasive tests, such as the Fibrosis-4 index, NAFLD fibrosis score, and liver stiffness measurement, perform better in lean or non-obese patients compared to obese patients. Lifestyle intervention works in non-obese patients, and less amount of weight loss may be required to achieve similar results compared to obese patients. Pharmacological therapy in non-obese NAFLD patients may require special consideration and a different approach compared to obese patients.

Recent advances in lean NAFLD

As the predominant type of chronic liver disease, the growing prevalence of nonalcoholic fatty liver disease (NAFLD) has become a concern worldwide. Although obesity plays the most pivotal role in NAFLD, approximately 10-20% of individuals with NAFLD who are not overweight or obese (BMI < 25 kg/m2, or BMI < 23 kg/m2 in Asians) have "lean NAFLD." Lean individuals with NAFLD have a lower prevalence of diabetes, hypertension, hypertriglyceridemia, central obesity, and metabolic syndrome than nonlean individuals with NAFLD, but higher fibrosis scores and rates of cardiovascular morbidity and all-cause mortality in advanced stages. The pathophysiological mechanisms of lean NAFLD remain poorly understood. Studies have shown that lean NAFLD is more correlated with factors such as environmental, genetic susceptibility, and epigenetic regulation. This review will examine the way in which the research progress and characteristic of lean NAFLD, and explore the function of epigenetic modification to provide the basis for the clinical treatment and diagnosis of lean NAFLD.

Hepatic Steatosis in Infancy: The Beginning of Pediatric Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease is clinically silent and the age of its onset is unknown. Fatty liver can occur as early as in utero in the context of an unfavorable maternal metabolic environment. Our objective was to determine the prevalence of hepatic steatosis in a cohort of previously healthy infants less than 3 months of age.

Methods

Retrospective study of all abdominal computed tomography (CT) scans performed from 2009 to 2019 for the investigation of trauma. Two independent reviewers applied published criteria to determine the presence of hepatic steatosis. Descriptive statistics were used. The groups with and without steatosis were compared using Wilcoxon-Mann Whitney or Fisher exact test.

Results

Of 119 CT scans available in infants younger than 3 months of age, 65 were performed in previously healthy infants for the investigation of trauma. The included population was predominantly male, non-Hispanic, with a median age of 60 days (interquartile range, 34-73 d). Depending on the criteria used, 23% or 26% of infants had evidence of fatty liver. The prevalence of maternal obesity and/or diabetes was 11% (of the 65 pregnancies) but there was no significant difference in maternal risk factors between infants with and without evidence of steatosis.

Conclusions

Findings suggest CT evidence of hepatic steatosis in up to a quarter of otherwise healthy infants ≤3 months of age. This may represent early manifestation of pediatric nonalcoholic fatty liver disease. The natural history and pathophysiology of this condition need to be studied to determine optimal detection, prevention and early intervention strategies.

Can Baseline Characteristics be Used to Predict Liver Disease Outcomes in Pediatric Nonalcoholic Fatty Liver Disease?

OBJECTIVE

Longitudinal studies on childhood predictors of nonalcoholic fatty liver disease (NAFLD) progression are lacking. The objective of this study was to determine whether baseline clinical or laboratory measures predict liver disease outcomes in a pediatric NAFLD cohort.

METHODS

A retrospective study of patients with presumed NAFLD was conducted using baseline and follow-up clinical and laboratory measures. Disease outcomes were defined using the mean serum alanine aminotransferase (ALT) levels from 24 to 36 months after the first visit. Logistic regression assessed the relationship between ALT progression/regression and predictor variables. Multivariable regression determined the best model for predicting the ALT outcome. Markov process modeling explored the likelihood for a patient to transition between ALT states.

RESULTS

Of a total of 816 patients identified, 144 had sufficient data. Regression was seen in 26%, whereas 30% progressed. No baseline clinical or laboratory measurements had a significant effect on disease outcomes. Markov modeling demonstrated that subjects were more likely to either remain in their baseline ALT group or worsen rather than improve.

CONCLUSIONS

Routinely obtained baseline clinical or laboratory measures cannot help risk-stratify youth with presumed NAFLD in terms of long-term outcomes. Close clinical, radiographic, and histologic evaluation of patients is warranted to determine those at risk of progression.

Phenotypic Differences Between Polygenic and Monogenic Hypobetalipoproteinemia

OBJECTIVE

Primary hypobetalipoproteinemia is characterized by LDL-C (low-density lipoprotein cholesterol) concentrations below the fifth percentile. Primary hypobetalipoproteinemia mostly results from heterozygous mutations in the APOB (apolipoprotein B) and PCSK9 genes, and a polygenic origin is hypothesized in the remaining cases. Hypobetalipoproteinemia patients present an increased risk of nonalcoholic fatty liver disease and steatohepatitis. Here, we compared hepatic alterations between monogenic, polygenic, and primary hypobetalipoproteinemia of unknown cause. Approach and Results: Targeted next-generation sequencing was performed in a cohort of 111 patients with hypobetalipoproteinemia to assess monogenic and polygenic origins using an LDL-C-dedicated polygenic risk score. Forty patients (36%) had monogenic hypobetalipoproteinemia, 38 (34%) had polygenic hypobetalipoproteinemia, and 33 subjects (30%) had hypobetalipoproteinemia from an unknown cause. Patients with monogenic hypobetalipoproteinemia had lower LDL-C and apolipoprotein B plasma levels compared with those with polygenic hypobetalipoproteinemia. Liver function was assessed by hepatic ultrasonography and liver enzymes levels. Fifty-nine percent of patients with primary hypobetalipoproteinemia presented with liver steatosis, whereas 21% had increased alanine aminotransferase suggestive of liver injury. Monogenic hypobetalipoproteinemia was also associated with an increased prevalence of liver steatosis (81% versus 29%, P<0.001) and liver injury (47% versus 0%) compared with polygenic hypobetalipoproteinemia.

CONCLUSIONS

This study highlights the importance of genetic diagnosis in the clinical care of primary hypobetalipoproteinemia patients. It shows for the first time that a polygenic origin of hypobetalipoproteinemia is associated with a lower risk of liver steatosis and liver injury versus monogenic hypobetalipoproteinemia. Thus, polygenic risk score is a useful tool to establish a more personalized follow-up of primary hypobetalipoproteinemia patients.

Angiopoietin-like protein 3, an emerging cardiometabolic therapy target with systemic and cell-autonomous functions

Angiopoietin like protein 3 (ANGPTL3) is best known for its function as an inhibitor of lipoprotein and endothelial lipases. Due to the capacity of genetic or pharmacologic ANGPTL3 suppression to markedly reduce circulating lipoproteins, and the documented cardioprotection upon such suppression, ANGPTL3 has become an emerging therapy target for which both antibody and antisense oligonucleotide (ASO) therapeutics are being clinically tested. While the antibody is relatively selective for circulating ANGPTL3, the ASO also depletes the intra-hepatocellular protein, and there is emerging evidence for cell-autonomous functions of ANGPTL3 in the liver. These include regulation of hepatocyte glucose and fatty acid uptake, insulin sensitivity, LDL/VLDL remnant uptake, VLDL assembly/secretion, polyunsaturated fatty acid (PUFA) and PUFA-derived lipid mediator content, and gene expression. In this review we elaborate on (i) why ANGPTL3 is considered one of the most promising new cardiometabolic therapy targets, and (ii) the present evidences for its intra-hepatocellular or cell-autonomous functions.

A Novel Variant in APOB Gene Causes Extremely Low LDL-C Without Known Adverse Effects

A novel frameshift variant was identified in APOB that segregates in a dominant manner with low levels of low-density lipoprotein cholesterol. Affected family members show no apparent clinical complications. There is no consensus regarding clinical management, and the long-term consequences of low levels of low-density lipoprotein cholesterol remain unknown. (Level of Difficulty: Advanced.).

Hypobetalipoproteinemia and abetalipoproteinemia: liver disease and cardiovascular disease

PURPOSE OF REVIEW

Several mutations in the apolipoprotein (apo) B, proprotein convertase subtilisin kexin 9 (PCSK9) and microsomal triglyceride transfer protein genes result in low or absent levels of apoB and LDL cholesterol (LDL-C) in plasma which cause familial hypobetalipoproteinemia (FHBL) and abetalipoproteinemia (ABL). Mutations in the angiopoietin-like protein 3 ANGPTL3 gene cause familial combined hypolipidemia (FHBL2). Clinical manifestations range from none-to-severe, debilitating and life-threatening disorders. This review summarizes recent genetic, metabolic and clinical findings and management strategies.

RECENT FINDINGS

Fatty liver, cirrhosis and hepatocellular carcinoma have been reported in FHBL and ABL probably due to decreased triglyceride export from the liver. Loss of function mutations in PCSK-9 and ANGPTL3 cause FHBL but not hepatic steatosis. In 12 case-control studies with 57 973 individuals, an apoB truncation was associated with a 72% reduction in coronary heart disease (odds ratio, 0.28; 95% confidence interval, 0.12-0.64; P = 0.002). PCSK9 inhibitors lowered risk of cardiovascular events in large, randomized trials without apparent adverse sequelae.

SUMMARY

Mutations causing low LDL-C and apoB have provided insight into lipid metabolism, disease associations and the basis for drug development to lower LDL-C in disorders causing high levels of cholesterol. Early diagnosis and treatment is necessary to prevent adverse sequelae from FHBL and ABL.