Serum lipid responses to weight loss differ between overweight adults with familial hypercholesterolemia and those with familial combined hyperlipidemia

Clinical Aspects of Genetic and Non-Genetic Cardiovascular Risk Factors in Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is the most common monogenic metabolic disorder characterized by considerably elevated low-density lipoprotein cholesterol (LDL-C) levels leading to enhanced atherogenesis, early cardiovascular disease (CVD), and premature death. However, the wide phenotypic heterogeneity in FH makes the cardiovascular risk prediction challenging in clinical practice to determine optimal therapeutic strategy. Beyond the lifetime LDL-C vascular accumulation, other genetic and non-genetic risk factors might exacerbate CVD development. Besides the most frequent variants of three genes (LDL-R, APOB, and PCSK9) in some proband variants of other genes implicated in lipid metabolism and atherogenesis are responsible for FH phenotype. Furthermore, non-genetic factors, including traditional cardiovascular risk factors, metabolic and endocrine disorders might also worsen risk profile. Although some were extensively studied previously, others, such as common endocrine disorders including thyroid disorders or polycystic ovary syndrome are not widely evaluated in FH. In this review, we summarize the most important genetic and non-genetic factors that might affect the risk prediction and therapeutic strategy in FH through the eyes of clinicians focusing on disorders that might not be in the center of FH research. The review highlights the complexity of FH care and the need of an interdisciplinary attitude to find the best therapeutic approach in FH patients.

Association of dietary patterns and components with atherosclerosis risk biomarkers in familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia (FH) is a relatively common genetic disorder associated with elevated atherosclerotic risk. Dietary interventions can modulate processes associated with cardiovascular risk and potentiate the impact of pharmacological lipid-lowering therapies. This review evaluates recent findings of dietary patterns and their components on risk biomarkers in people with FH.

RECENT FINDINGS

Diets lower in saturated fatty acids (SFA) may reduce low-density lipoprotein-cholesterol (LDL-C); however, their effects seem to be modest. A Mediterranean style diet apparently exerts more robust effects on plasma LDL-C, apolipoprotein B and C reactive protein concentrations than one restricted in SFA. Supplementation of plant sterols and stanols reduces LDL-C especially in children with FH. Caloric restricted diets may reduce weight and improve triglyceride levels in individuals with FH and excess body weight.

SUMMARY

Despite the strong impact of genetic variants, dietary patterns mostly low in SFA and especially the Mediterranean diet may influence risk biomarkers in FH. However, most available studies are limited by cross-sectional design, small number of study subjects and short-term follow-ups. Robust interventional studies are necessary to test the impact of dietary patterns in people with FH.

Familial combined hyperlipidemia is a polygenic trait

PURPOSE OF REVIEW

: Familial combined hyperlipidemia (FCH), defined by concurrently elevated plasma triglyceride (TG) and low-density lipoprotein (LDL) cholesterol, has long been investigated to characterize its genetic basis. Despite almost half a century of searching, a single gene cause for the phenotype has not yet been identified.

RECENT FINDINGS

: Recent studies using next-generation genetic analytic methods confirm that FCH has a polygenic basis, with a clear large contribution from the accumulation of small-to-moderate effect common single nucleotide polymorphisms (SNPs) throughout the genome that is associated with raising TG, and probably also those raising LDL cholesterol. On the other hand, rare monogenic variants, such as those causing familial hypercholesterolemia, play a negligible role, if any. Genetic profiling suggests that patients with FCH and hypertriglyceridemia share a strong polygenic basis and show a similar profile of multiple TG-raising common SNPs.

SUMMARY

: Recent progress in genomics has shown that most if not all of the genetic susceptibility to FCH is polygenic in nature. Future research should include larger cohort studies, with wider ancestral diversity, ancestry-specific polygenic scores, and investigation of epigenetic and lifestyle factors to help further elucidate the causative agents at play in cases where the genetic etiology remains to be defined.

Efficacy of therapeutic lifestyle changes on lipid profiles assessed by NMR in children with familial and non-familial hypercholesterolemia

BACKGROUND AND AIMS

The first line of therapy in children with hypercholesterolaemia is therapeutic lifestyle changes (TLSC). The efficacy of lifestyle intervention in children with familial hypercholesterolaemia (FH), where LDL-C levels are genetically driven, deserves a focused study.

AIMS

To evaluate the impact of a lifestyle education program, focused on food patterns and physical activity, on lipid profiles assessed by nuclear magnetic resonance (NMR) in children with FH vs. non-FH.

METHODS

Phase 1 was a cross-sectional study of baseline characteristics, and phase 2 was a prospective TLSC intervention study. In total, the study included 238 children (4 to 18 years old; 47% girls) attending the lipid unit of our hospital due to high cholesterol levels. Eighty-five were diagnosed with FH (72% genetic positive), and 153 were diagnosed with non-Familial hypercholesterolaemia. A quantitative food frequency questionnaire (FFQ) including 137 items was used. Physical activity (PA) was assessed by the Minnesota questionnaire. The lipid profile was assessed using the 2D-1H-NMR (Liposcale test). A total of 127 children (81 in the FH group) participated in the prospective phase and were re-assessed after 1 year of the TLSC intervention, consisting of education on lifestyle changes delivered by a specialized nutritionist.

RESULTS

The FH and non-FH groups were similar in anthropometry and clinical data, except that those in the FH were slightly younger than those in the non-FH group. Both the FH and non-FH groups showed a similar diet composition characterized by a high absolute calorie intake and a high percentage of fat, mainly saturated fat. The PA was below the recommended level in both groups. After one year of TLSC, the percentage of total and saturated fats was reduced, and the amount of fiber increased significantly in both groups. The percentage of protein increased slightly. The number of children engaged in at least 1 hour/day of PA increased by 56% in the FH group and by 53% in the non-FH group, and both these increases were significant. The total and small-LDL particle numbers were reduced in both groups, although the absolute change was greater in the FH group than in the non-FH group.

CONCLUSIONS

Educational strategies to implement TLSC in children lead to empowerment, increased adherence, and overall metabolic improvement in children with high blood cholesterol, including those with FH.

Special Commentary: Is diet management helpful in familial hypercholesterolemia?

PURPOSE OF REVIEW

Familial hypercholesterolemia is a genetic condition where low-density lipoprotein (LDL) receptor defects cause severe elevations of LDL cholesterol. As significant LDL-lowering effects are needed, medication is considered the cornerstone of therapy, and dietary therapy has received less emphasis. This review will re-visit older studies of diet intervention and new insights from genetic and mechanistic studies to determine the value of diet management for familial hypercholesterolemia patients.

RECENT FINDINGS

Saturated fat reduction improves cardiovascular outcomes, particularly in those with genetic predisposition to risk. Secular trends in saturated fat intake may have improved familial hypercholesterolemia outcomes. Dietary mechanisms of LDL cholesterol-lowering complement pharmacologic approaches.

SUMMARY

Diet treatment adds incremental health benefit to pharmacologic treatment in familial hypercholesterolemia.

Non-Cholesterol Sterol Concentrations as Biomarkers for Cholesterol Absorption and Synthesis in Different Metabolic Disorders: A Systematic Review

Non-cholesterol sterols are validated biomarkers for intestinal cholesterol absorption and endogenous cholesterol synthesis. However, their use in metabolic disturbances has not been systematically explored. Therefore, we conducted a systematic review to provide an overview of non-cholesterol sterols as markers for cholesterol metabolism in different metabolic disorders. Potentially relevant studies were retrieved by a systematic search of three databases in July 2018 and ninety-four human studies were included. Cholesterol-standardized levels of campesterol, sitosterol and cholestanol were collected to reflect cholesterol absorption and those of lathosterol and desmosterol to reflect cholesterol synthesis. Their use as biomarkers was examined in the following metabolic disorders: overweight/obesity (n = 16), diabetes mellitus (n = 15), metabolic syndrome (n = 5), hyperlipidemia (n = 11), cardiovascular disease (n = 17), and diseases related to intestine (n = 16), liver (n = 22) or kidney (n = 2). In general, markers for cholesterol absorption and synthesis displayed reciprocal patterns, showing that cholesterol metabolism is tightly regulated by the interplay of intestinal absorption and endogenous synthesis. Distinctive patterns for cholesterol absorption or cholesterol synthesis could be identified, suggesting that metabolic disorders can be classified as 'cholesterol absorbers or cholesterol synthesizers'. Future studies should be performed to confirm or refute these findings and to examine whether this information can be used for targeted (dietary) interventions.

Dyslipidemias in clinical practice

Most dyslipidemic conditions have been linked to an increased risk of cardiovascular disease. Over the past few years major advances have been made regarding the genetic and metabolic basis of dyslipidemias. Detailed characterization of the genetic basis of familial lipid disorders and knowledge concerning the effects of environmental factors on the expression of dyslipidemias have increased substantially, contributing to a better diagnosis in individual patients. In addition to these developments, therapeutic options to lower cholesterol levels in clinical practice have expanded even further in patients with familial hypercholesterolemia and in subjects with cardiovascular disease. Finally, promising upcoming therapeutic lipid lowering strategies will be reviewed. All these advances will be discussed in relation to current clinical practice with special focus on common lipid disorders including familial dyslipidemias.

Efficacy of repeated phlebotomies in hypertriglyceridemia and iron overload: A prospective, randomized, controlled trial

BACKGROUND

High ferritin concentration is associated with hypertriglyceridemia, although it is not elucidated if iron overload has a causal role.

OBJECTIVE

To evaluate the efficacy of repeated phlebotomies in patients with iron overload and hypertriglyceridemia.

METHODS

Twelve weeks, 1:1 randomized, parallel-groups trial conducted at a University Hospital Lipid Clinic, including 86 subjects aged 18-70 years with serum ferritin >300 ng/mL in men or >200 ng/mL in women and triglycerides >200 mg/dL. Participants underwent: (1) three phlebotomies (every 3 weeks) and lipid-lowering dietary counseling or (2) lipid-lowering dietary counseling. The main outcome measured was the mean difference in percent change in triglyceride concentration between groups after the intervention. The mean differences in percent change of other clinical and biochemical variables (including cytokines and proinflammatory markers) after the intervention were also evaluated.

RESULTS

Subjects who received phlebotomies showed a significant improvement in iron metabolism. The mean percent change in triglycerides between groups was -4.68 [-20.8, 11.4]%, P = .721. Retinol-binding protein 4 decreased by 9.98 ± 21.7% after phlebotomies, with a mean percent change between groups of -14.2 [-25.8, -2.73]%, P = .017, and correlated to gamma glutamyl transferase, alanine aminotransferase and aspartate aminotransferase change. Subjects with a large reduction in hepcidin showed a large improvement in liver enzymes and proinflammatory markers.

CONCLUSIONS

A lipid-lowering diet plus a substantial reduction in iron deposits with repeated phlebotomies in subjects with hyperferritinemia and hypertriglyceridemia did not reduce triglyceride concentration in comparison with a lipid-lowering diet. Iron depletion for lipid management in these patients is not supported.

Does lifestyle contribute to disease severity in patients with inherited lipid disorders?

PURPOSE OF REVIEW

Patients with familial hypercholesterolemia, familial combined hyperlipidemia and hyperlipoprotein(a) are at high cardiovascular risk. Increasing evidence suggest that lifestyle-related risk factors such as physical inactivity, and poor diet quality could influence cardiovascular risk in these patients. Our objective is to review the evidence that supports the role of lifestyle-related factors in the prediction of cardiovascular risk in patients with inherited lipid disorders.

RECENT FINDINGS

Recent studies have shown that smoking, a poor diet quality, physical inactivity, fitness levels, abdominal obesity, insulin resistance, and type 2 diabetes were associated with the presence of atherosclerosis and long-term cardiovascular outcomes in patients with familial hypercholesterolemia. Recent evidence also suggest that managing other cardiovascular risk factors such as cholesterol levels, obesity, glycemic control, blood pressure, smoking, physical inactivity, and diet quality could reduce long-term cardiovascular risk associated with hyperlipoprotein(a). Whether targeting these risk factors could ultimately decrease cardiovascular risk in these patients remains unknown.

SUMMARY

Although reducing the number of atherogenic apolipoprotein-B containing particle with lipid-lowering therapy represents the cornerstone of treatment of patients with inherited lipid disorders, lifestyle-related risk factors such as physical inactivity and poor diet quality need to be targeted for the optimal management of these high-risk patients.

Association of blood glucose and lipid levels with complete blood count indices to establish a regression model

Hyperglycemia and hyperlipidemia, which are usually diagnosed by analysis of blood glucose (GLU) and lipid levels, are two of the most common diseases in modern society. The purpose of the current study was to investigate the potential association between blood GLU and lipid levels with complete blood count (CBC) indices in overweight and healthy individuals and establish a regression model. There were 456 healthy and 421 overweight participants in the study. Data were collected on triglyceride (TG), total cholesterol (CHO), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), blood GLU and CBC. The distribution characteristics and differences between healthy and overweight subjects were analyzed. Subsequently, the associations between TG, CHO, HDL, LDL and GLU with CBC were analyzed using correlation analysis and multiple linear regression (MLR). Significant differences were identified between the healthy and overweight individuals in TG, CHO, HDL, LDL, GLU and in the majority of the CBC indices. The correlation analysis indicated that there were strong correlations between TG, LDL, HDL, CHO and GLU with CBC indices in the healthy and overweight subjects. The MLR demonstrated that the regression models of TG, LDL, HDL and CHO, but no GLU, were statistically significant in the two groups (P<0.001). The HDL regression model exhibited the best regression parameters; the multiple correlation coefficients (R) were 0.351 and 0.308 in the healthy and overweight subjects, respectively. In the overweight and healthy subjects, there were strong correlations between TG, LDL, HDL and CHO with CBC indices, with HDL being the most relevant to the CBC indices. The CBC demonstrated statistical significance in the diagnosis of hyperlipidemia.

Progress in the care of common inherited atherogenic disorders of apolipoprotein B metabolism

Familial hypercholesterolaemia, familial combined hyperlipidaemia (FCH) and elevated lipoprotein(a) are common, inherited disorders of apolipoprotein B metabolism that markedly accelerate the onset of atherosclerotic cardiovascular disease (ASCVD). These disorders are frequently encountered in clinical lipidology and need to be accurately identified and treated in both index patients and their family members, to prevent the development of premature ASCVD. The optimal screening strategies depend on the patterns of heritability for each condition. Established therapies are widely used along with lifestyle interventions to regulate levels of circulating lipoproteins. New therapeutic strategies are becoming available, and could supplement traditional approaches in the most severe cases, but their long-term cost-effectiveness and safety have yet to be confirmed. We review contemporary developments in the understanding, detection and care of these highly atherogenic disorders of apolipoprotein B metabolism.

Lipids in liver transplant recipients

Hyperlipidemia is very common after liver transplantation and can be observed in up to 71% of patients. The etiology of lipid disorders in these patients is multifactorial, with different lipid profiles observed depending on the immunosuppressive agents administered and the presence of additional risk factors, such as obesity, diabetes mellitus and nutrition. Due to recent improvements in survival of liver transplant recipients, the prevention of cardiovascular events has become more important, especially as approximately 64% of liver transplant recipients present with an increased risk of cardiovascular events. Management of dyslipidemia and of other modifiable cardiovascular risk factors, such as hypertension, diabetes and smoking, has therefore become essential in these patients. Treatment of hyperlipidemia after liver transplantation consists of life style modification, modifying the dose or type of immunosuppressive agents and use of lipid lowering agents. At the start of administration of lipid lowering medications, it is important to monitor drug-drug interactions, especially between lipid lowering agents and immunosuppressive drugs. Furthermore, as combinations of various lipid lowering drugs can lead to severe side effects, such as myopathies and rhabdomyolysis, these combinations should therefore be avoided. To our knowledge, there are no current guidelines targeting the management of lipid metabolism disorders in liver transplant recipients. This paper therefore recommends an approach of managing lipid abnormalities occurring after liver transplantation.

Rare genetic variants with large effect on triglycerides in subjects with a clinical diagnosis of familial vs nonfamilial hypertriglyceridemia

BACKGROUND

Most primary severe hypertriglyceridemias (HTGs) are diagnosed in adults, but their molecular foundations have not been completely elucidated.

OBJECTIVE

We aimed to identify rare dysfunctional mutations in genes encoding regulators of lipoprotein lipase (LPL) function in patients with familial and non-familial primary HTG.

METHODS

We sequenced promoters, exons, and exon-intron boundaries of LPL, APOA5, LMF1, and GPIHBP1 in 118 patients with severe primary HTG (triglycerides >500 mg/dL) and 53 normolipidemic controls. Variant functionality was analyzed using predictive software and functional assays for mutations in regulatory regions.

RESULTS

We identified 29 rare variants, 10 of which had not been previously described: c.(-16A>G), c.(1018+2G>A), and p.(His80Arg) in LPL; p.(Arg143Alafs*57) in APOA5; p.(Val140Ile), p.(Leu235Ile), p.(Lys520*), and p.(Leu552Arg) in LMF1; and c.(-83G>A) and c.(-192A>G) in GPIHBP1. The c.(1018+2G>A) variant led to deletion of exon 6 in LPL cDNA, whereas the c.(-16A>G) analysis showed differences in the affinity for nuclear proteins. Overall, 20 (17.0%) of the patients carried at least one allele with a rare pathogenic variant in LPL, APOA5, LMF1, or GPIHBP1. The presence of a rare pathogenic variant was not associated with lipid values, family history of HTG, clinical diagnosis, or previous pancreatitis.

CONCLUSIONS

Less than one in five subjects with triglycerides >500 mg/dL and no major secondary cause for HTG may carry a rare pathogenic mutation in LPL, APOA5, LMF1, or GPIHBP1. The presence of a rare pathogenic variant is not associated with a differential phenotype.