Insulin resistance involvement in prevalence of familial dysbetalipoproteinemia in ε2ε2 subjects by Bayesian network modeling

Clinical and biochemical features of atherogenic hyperlipidemias with different genetic basis: A comprehensive comparative study

Patients with genetically-based hyperlipidemias exhibit a wide phenotypic variability. Investigation of clinical and biochemical features is important for identifying genetically-based hyperlipidemias, determining disease prognosis, and initiating timely treatment. We analyzed genetic data from 3374 samples and compared clinical data, lipid levels (low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, triglycerides, and lipoprotein (a)), frequency, age at onset of coronary heart disease (CHD), and the severity of carotid and femoral atherosclerosis (plaque number, maximum stenosis, total stenosis, maximum plaque height, and plaque score) among patients with familial hypercholesterolemia (FH), familial dysbetalipoproteinemia (FD), polygenic hypercholesterolemia (HCL), severe HCL, and those without lipid disorders (n = 324). FH patients exhibited the highest LDL-C (median 8.03 mmol/L, p < 0.001). FD patients had elevated triglyceride levels (median 4.10 mmol/L), lower LDL-C (median 3.57 mmol/L), and high-density lipoprotein cholesterol (median 1.03 mmol/L) compared to FH, polygenic HCL, and severe HCL, p < 0.05. FH and FD patients had similar early onset of CHD, with a median age of 44 and 40 years and comparable frequencies of 29.5% and 31.0%, respectively. They were more likely to develop CHD than subjects without lipid disorders (p = 0.042 and p < 0.001, respectively). Additionally, FH patients had higher a carotid plaque number, total carotid stenosis, and carotid plaque score. This study presents the first simultaneous comparison of clinical and biochemical features among FD, FH, polygenic, and severe HCL, along with the first comprehensive evaluation of carotid and femoral atherosclerosis ultrasound parameters in FD patients. The results highlight distinct phenotypic features unique to each hyperlipidemia analyzed and underscore FH and FD as the most atherogenic hyperlipidemias.

Spectrum and Prevalence of Rare APOE Variants and Their Association with Familial Dysbetalipoproteinemia

Familial dysbetalipoproteinemia (FD) is a highly atherogenic, prevalent genetically based lipid disorder. About 10% of FD patients have rare APOE variants associated with autosomal dominant FD. However, there are insufficient data on the relationship between rare APOE variants and FD. Genetic data from 4720 subjects were used to identify rare APOE variants and investigate their pathogenicity for autosomal dominant FD. We observed 24 variants in 86 unrelated probands. Most variants were unique (66.7%). Five identified APOE variants (p.Glu63ArgfsTer15, p.Gly145AlafsTer97, p.Lys164SerfsTer87, p.Arg154Cys, and p.Glu230Lys) are causal for autosomal dominant FD. One of them (p.Lys164SerfsTer87) was described for the first time. When we compared clinical data, it was found that carriers of pathogenic or likely pathogenic APOE variants had significantly higher triglyceride levels (median 5.01 mmol/L) than carriers of benign or likely benign variants (median 1.70 mmol/L, p = 0.034) and variants of uncertain significance (median 1.38 mmol/L, p = 0.036). For the first time, we estimated the expected prevalence of causal variants for autosomal dominant FD in the population sample: 0.27% (one in 619). Investigating the spectrum of APOE variants may advance our understanding of the genetic basis of FD and underscore the importance of APOE gene sequencing in patients with lipid metabolism disorders.

Applicability of Diagnostic Criteria and High Prevalence of Familial Dysbetalipoproteinemia in Russia: A Pilot Study

Familial dysbetalipoproteinemia (FD) is a highly atherogenic genetically based lipid disorder with an underestimated actual prevalence. In recent years, several biochemical algorithms have been developed to diagnose FD using available laboratory tests. The practical applicability of FD diagnostic criteria and the prevalence of FD in Russia have not been previously assessed. We demonstrated that the diagnostic algorithms of FD, including the diagnostic apoB levels, require correction, taking into account the distribution of apoB levels in the population. At the same time, a triglycerides cutoff ≥ 1.5 mmol/L may be a useful tool in identifying subjects with FD. In this study, a high prevalence of FD was detected: 0.67% (one in 150) based on the ε2ε2 haplotype and triglycerides levels ≥ 1.5 mmol/L. We also analyzed the presence and pathogenicity of APOE variants associated with autosomal dominant FD in a large research sample.

Adiposity and the development of dyslipidemia in APOE ε2 homozygous subjects: A longitudinal analysis in two population-based cohorts

BACKGROUND AND AIMS

Familial dysbetalipoproteinemia (FD), characterized by remnant lipoprotein accumulation and premature cardiovascular disease, occurs in homozygous carriers of the APOE ε2 allele, but genetic predisposition alone does not suffice for the clinical phenotype. Cross-sectional studies suggest that a second metabolic hit - notably adiposity or insulin resistance - is required, but the association between these risk factors and development of FD has not been studied prospectively.

METHODS

For this study, we evaluated 18,987 subjects from two large prospective Dutch population-based cohorts (PREVEND and Rotterdam Study) of whom 118 were homozygous APOE ε2 carriers. Of these, 69 subjects were available for prospective analyses. Dyslipidemia - likely to be FD - was defined as fasting triglyceride (TG) levels >3 mmol/L in untreated subjects or use of lipid lowering medication. The effect of weight, body mass index (BMI), waist circumference, type 2 diabetes mellitus and non-TG metabolic syndrome on development of dyslipidemia was investigated.

RESULTS

Eleven of the 69 ε2ε2 subjects (16%) developed dyslipidemia - likely FD - during follow-up. Age-, sex- and cohort-adjusted risk factors for the development of FD were BMI (OR 1.19; 95%CI 1.04-1.39), waist circumference (OR 1.26 95%CI 1.01-1.61) and presence of non-TG metabolic syndrome (OR 4.39; 95%CI 1.04-18.4) at baseline. Change in adiposity during follow-up was not associated with development of dyslipidemia.

CONCLUSIONS

Adiposity increases the risk of developing an FD-like lipid phenotype in homozygous APOE ε2 subjects. These results stress the importance of healthy body weight in subjects at risk of developing FD.

Insulin resistance in children with familial hyperlipidemia

Background The aim of the study was to investigate whether there is insulin resistance in children with familial hyperlipidemia (FHL) and to determine the factors affecting insulin resistance. Methods Hyperlipidemic children aged between 4 and 18 years and followed up with an FHL diagnosis were included in the study. The children of adults followed up with an FHL diagnosis were also recruited after the screening period. The scanned children were divided into two groups as hyperlipidemic and normolipidemic. A total of 77 patients of whom 52 were hyperlipidemic and 25 were normolipidemic were assessed in the study. Insulin resistance was evaluated (homeostatic model assessment of insulin resistance [HOMA-IR]) by performing the oral glucose tolerance test (OGTT). Results Of the patients, 36 were male and 41 were female; the average age was 11.6±3.9 years, and the body mass index (BMI) was established to be 20.3±4.4. In hyperlipidemic and normolipidemic patients, the following were determined: fasting insulin: 10.6 (±0.89) μU/mL, 4.9 (±0.45) μU/mL (p=0.000); 2-h insulin: 28.7 (±12.7) μU/mL, 18.9 (±10.5) μU/mL (p=0.000); and HOMA-IR: 1.9 (±0.17), 0.86 (±0.7) (p=0.000). No relationship was identified between lipid profiles and insulin resistance. Nevertheless, there was a positive correlation between insulin resistance and apolipoprotein B (Apo B) levels (0.52), and a negative correlation was determined in carnitine levels (-0.64). Conclusions Insulin resistance was established to be higher in children with FHL compared to normolipidemic children. Insulin resistance was not related to lipid phenotypes, but to Apo B levels and carnitine levels. Insulin resistance should be a routine method of evaluation in the follow-up of children with FHL.