Clinical practice. Hypertriglyceridemia

Lipid management in human immunodeficiency virus

The development and use of antiretroviral medications to treat patients infected with human immunodeficiency virus (HIV) has dramatically changed the course of this disease from one that was fatal to a chronic and more manageable condition. Recommendations and guidelines for the general population are presented in this review with suggestions as to how they may be applied to this patient population. Issues for which there is little or no information available are noted to highlight the many gaps in our knowledge regarding diagnosis and management of dyslipidemia for patients living with HIV.

The Liver Clock Controls Cholesterol Homeostasis through Trib1 Protein-mediated Regulation of PCSK9/Low Density Lipoprotein Receptor (LDLR) Axis

Disruption of the body clock has been recognized as a risk factor for cardiovascular disease. How the circadian pacemaker interacts with the genetic factors associated with plasma lipid traits remains poorly understood. Recent genome-wide association studies have identified an expanding list of genetic variants that influence plasma cholesterol and triglyceride levels. Here we analyzed circadian regulation of lipid-associated candidate genes in the liver and identified two distinct groups exhibiting rhythmic and non-rhythmic patterns of expression during light-dark cycles. Liver-specific inactivation of Bmal1 led to elevated plasma LDL/VLDL cholesterol levels as a consequence of the disruption of the PCSK9/LDL receptor regulatory axis. Ablation of the liver clock perturbed diurnal regulation of lipid-associated genes in the liver and markedly reduced the expression of the non-rhythmically expressed gene Trib1. Adenovirus-mediated rescue of Trib1 expression lowered plasma PCSK9 levels, increased LDL receptor protein expression, and restored plasma cholesterol homeostasis in mice lacking a functional liver clock. These results illustrate an unexpected mechanism through which the biological clock regulates cholesterol homeostasis through its regulation of non-rhythmic genes in the liver.

High-Fat Diet Alters Serum Fatty Acid Profiles in Obesity Prone Rats: Implications for In Vitro Studies

High-fat diets (HFD) are commonly used in rodents to induce obesity, increase serum fatty acids and induce lipotoxicity in various organs. In vitro studies commonly utilize individual free fatty acids (FFA) to study lipid exposure in an effort to model what is occurring in vivo; however, these approaches are not physiological as tissues are exposed to multiple fatty acids in vivo. Here we characterize circulating lipids in obesity-prone rats fed an HFD in both fasted and fed states with the goal of developing physiologically relevant fatty acid mixtures for subsequent in vitro studies. Rats were fed an HFD (60% kcal fat) or a control diet (10% kcal fat) for 3 weeks; liver tissue and both portal and systemic blood were collected. Fatty acid profiles and absolute concentrations of triglycerides (TAG) and FFA in the serum and TAG, diacylglycerol (DAG) and phospholipids in the liver were measured. Surprisingly, both systemic and portal serum TAG were ~40% lower in HFD-fed compared to controls. Overall, compared to the control diet, HFD feeding consistently induced an increase in the proportion of circulating polyunsaturated fatty acids (PUFA) with a concomitant decline in monounsaturated fatty acids (MUFA) and saturated fatty acids (SFA) in both serum TAG and FFA. The elevations of PUFA were mostly attributed to increases in n-6 PUFA, linoleic acid and arachidonic acid. In conclusion, fatty acid mixtures enriched with linoleic and arachidonic acid in addition to SFA and MUFA should be utilized for in vitro studies attempting to model lipid exposures that occur during in vivo HFD conditions.

A hepatic amino acid/mTOR/S6K-dependent signalling pathway modulates systemic lipid metabolism via neuronal signals

Metabolism is coordinated among tissues and organs via neuronal signals. Levels of circulating amino acids (AAs), which are elevated in obesity, activate the intracellular target of rapamycin complex-1 (mTORC1)/S6kinase (S6K) pathway in the liver. Here we demonstrate that hepatic AA/mTORC1/S6K signalling modulates systemic lipid metabolism via a mechanism involving neuronal inter-tissue communication. Hepatic expression of an AA transporter, SNAT2, activates the mTORC1/S6K pathway, and markedly elevates serum triglycerides (TGs), while downregulating adipose lipoprotein lipase (LPL). Hepatic Rheb or active-S6K expression have similar metabolic effects, whereas hepatic expression of dominant-negative-S6K inhibits TG elevation in SNAT2 mice. Denervation, pharmacological deafferentation and β-blocker administration suppress obesity-related hypertriglyceridemia with adipose LPL upregulation, suggesting that signals are transduced between liver and adipose tissue via a neuronal pathway consisting of afferent vagal and efferent sympathetic nerves. Thus, the neuronal mechanism uncovered here serves to coordinate amino acid and lipid levels and contributes to the development of obesity-related hypertriglyceridemia.

Primary hypertriglyceridemia in children and adolescents

Primary disorders of lipid metabolism causing hypertriglyceridemia (HyperTG) result from genetic defects in triglyceride synthesis and metabolism. With the exception of lipoprotein lipase deficiency, these primary HyperTG disorders usually present in adulthood. However, some are unmasked earlier by precipitating factors, such as obesity and insulin resistance, and can be diagnosed in adolescence. Physical findings may be present and can include eruptive, palmer, or tuberoeruptive xanthomas. Triglyceride levels are very high to severe and can occur in the absence or the presence of other lipid abnormalities. Each of the causes of HyperTG is associated with an increased risk to develop recurrent pancreatitis and some may increase the risk of premature cardiovascular disease. Adoption of a healthy lifestyle that includes a low-fat diet, optimizing body weight, smoking avoidance/cessation, and daily physical activity is the first line of therapy. Pharmacologic therapies are available and can be beneficial in select disorders. Here, we review the causes of primary HyperTG in children and adolescents, discuss their clinical presentation and associated complications including the risk of pancreatitis and premature cardiovascular disease, and conclude with management and novel therapies currently in development. The goal of this article is to provide a useful resource for clinicians who may encounter primary HyperTG in the pediatric population.

Reductions in serum levels of LDL cholesterol, apolipoprotein B, triglycerides and lipoprotein(a) in hypercholesterolaemic patients treated with the liver-selective thyroid hormone receptor agonist eprotirome

BACKGROUND

Liver-selective thyromimetic agents could provide a new approach for treating dyslipidaemia.

METHODS

We performed a multicentre, randomized, placebo-controlled, double-blind study to evaluate the efficacy and safety of eprotirome, a liver-selective thyroid hormone receptor agonist, in 98 patients with primary hypercholesterolaemia. After previous drug wash-out and dietary run-in, patients received 100 or 200 μg day(-1) eprotirome or placebo for 12 weeks. The primary end-point was change in serum LDL cholesterol; secondary end-points included changes in other lipid parameters and safety measures.

RESULTS

Eprotirome treatment at 100 and 200 μg daily reduced serum LDL cholesterol levels by 23 ± 5% and 31 ± 4%, respectively, compared with 2 ± 6% for placebo (P < 0.0001). Similar reductions were seen in non-HDL cholesterol and apolipoprotein (apo) B, whereas serum levels of HDL cholesterol and apo A-I were unchanged. There were also considerable reductions in serum triglycerides and lipoprotein(a), in particular in patients with elevated levels at baseline. There was no evidence of adverse effects on heart or bone and no changes in serum thyrotropin or triiodothyronine, although the thyroxine level decreased. Low-grade increases in liver enzymes were evident in most patients.

CONCLUSION

In hypercholesterolaemic patients, the liver-selective thyromimetic eprotirome decreased serum levels of atherogenic lipoproteins without signs of extra-hepatic side effects. Selective stimulation of hepatic thyroid hormone receptors may be an attractive way to modulate lipid metabolism in hyperlipidaemia.

Lipid abnormalities in kidney disease and management strategies

Patients with kidney diseases continue to experience significant cardiovascular disease (CVD) morbidity and mortality. Although there are many important risk factors playing a role in the pathogenesis of CVD in chronic kidney disease (CKD) patients, dyslipidemia (elevated triglycerides, elevated oxidized low-density lipoprotein and low/dysfunctional low high-density) represents one of the modifiable risk factors. Renal failure patients have unique lipid abnormalities which not only have complex role in pathogenesis of CVD but also cause relative resistance to usual interventions. Most of the randomized trials have been in hemodialysis population and data from CKD non-dialysis, peritoneal dialysis and renal transplant populations is extremely limited. Compared to general population, evidence of mortality benefit of lipid lowering medications in CKD population is scarce. Future research should be directed towards establishing long term benefits and side effects of lipid lowering medications, through randomized trials, in CKD population.

Hypertriglyceridemia in the genomic era: a new paradigm

Hypertriglyceridemia (HTG) is a highly prevalent condition that is associated with increased cardiovascular disease risk. HTG may arise as a result of defective metabolism of triglyceride-rich lipoproteins and their remnants, ie, impaired clearance, or increased production, or both. Current categorization of HTG segregates primary and secondary cases, implying genetic and nongenetic causes for each category. Many common and rare variants of the genes encoding factors involved in these pathways have been identified. Although monogenic forms of HTG do occur, most cases are polygenic and often coexist with nongenetic conditions. Cumulative, multiple genetic variants can increase the risks for HTG, whereas environmental and lifestyle factors can force expression of a dyslipidemic phenotype in a genetically susceptible person. HTG states are therefore best viewed as a complex phenotype resulting from the interaction of cumulated multiple susceptibility genes and environmental stressors. In view of the heterogeneity of the HTG states, the absence of a unifying metabolic or genetic abnormality, overlap with the metabolic syndrome and other features of insulin resistance, and evidence in some patients that accumulation of numerous small-effect genetic variants determines whether an individual is susceptible to HTG only or to HTG plus elevated low-density lipoprotein cholesterol, we propose that the diagnosis of primary HTG and further delineation of familial combined hyperlipidemia from familial HTG is neither feasible nor clinically relevant at the present time. The hope is that with greater understanding of genetic and environmental causes and their interaction, therapy can be intelligently targeted in the future.

Hypertriglyceridemia: a too long unfairly neglected major cardiovascular risk factor

The existence of an independent association between elevated triglyceride (TG) levels, cardiovascular (CV) risk and mortality has been largely controversial. The main difficulty in isolating the effect of hypertriglyceridemia on CV risk is the fact that elevated triglyceride levels are commonly associated with concomitant changes in high density lipoprotein (HDL), low density lipoprotein (LDL) and other lipoproteins. As a result of this problem and in disregard of the real biological role of TG, its significance as a plausible therapeutic target was unfoundedly underestimated for many years. However, taking epidemiological data together, both moderate and severe hypertriglyceridaemia are associated with a substantially increased long term total mortality and CV risk. Plasma TG levels partially reflect the concentration of the triglyceride-carrying lipoproteins (TRL): very low density lipoprotein (VLDL), chylomicrons and their remnants. Furthermore, hypertriglyceridemia commonly leads to reduction in HDL and increase in atherogenic small dense LDL levels. TG may also stimulate atherogenesis by mechanisms, such excessive free fatty acids (FFA) release, production of proinflammatory cytokines, fibrinogen, coagulation factors and impairment of fibrinolysis. Genetic studies strongly support hypertriglyceridemia and high concentrations of TRL as causal risk factors for CV disease. The most common forms of hypertriglyceridemia are related to overweight and sedentary life style, which in turn lead to insulin resistance, metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM). Intensive lifestyle therapy is the main initial treatment of hypertriglyceridemia. Statins are a cornerstone of the modern lipids-modifying therapy. If the primary goal is to lower TG levels, fibrates (bezafibrate and fenofibrate for monotherapy, and in combination with statin; gemfibrozil only for monotherapy) could be the preferable drugs. Also ezetimibe has mild positive effects in lowering TG. Initial experience with en ezetimibe/fibrates combination seems promising. The recently released IMPROVE-IT Trial is the first to prove that adding a non-statin drug (ezetimibe) to a statin lowers the risk of future CV events. In conclusion, the classical clinical paradigm of lipids-modifying treatment should be changed and high TG should be recognized as an important target for therapy in their own right. Hypertriglyceridemia should be treated.

Contralateral needling at unblocked collaterals for hemiplegia following acute ischemic stroke

Hemiplegia caused by stroke indicates dysfunction of the network between the brain and limbs, namely collateral shock in the brain. Contralateral needling is the insertion of needles into acupoints on the relative healthy side of the body to treat diseases such as apoplexy. However, there is little well-designed and controlled clinical evidence for this practice. This study investigated whether contralateral needling could treat hemiplegia after acute ischemic stroke in 106 randomly selected patients with acute ischemic stroke. These patients were randomly assigned to three groups: 45 in the contralateral needling group, receiving acupuncture on the unaffected limbs; 45 in the tional acupuncture group, receiving acupuncture on the hemiplegic limbs; and 16 in the control group, receiving routine treatments without acupuncture. Acupuncture at acupoints Chize (LU5) in the upper limb and Jianliao (TE14) in the lower limb was performed for 45 minutes daily for 30 consecutive days. The therapeutic effective rate, Neurological Deficit Score, Modified Barthel Index and Fugl-Meyer Assessment were evaluated. The therapeutic effective rate of contralateral needling was higher than that of conventional acupuncture (46.67% vs. 31.11%, P < 0.05). The neurological deficit score of contralateral needling was significantly decreased compared with conventional acupuncture (P < 0.01). The Modified Barthel Index and Fugl-Meyer Assessment score of contralateral needling increased more significantly than those of conventional acupuncture (both P < 0.01). The present findings suggest that contralateral needling unblocks collaterals and might be more effective than conventional acupuncture in the treatment of hemiplegia following acute ischemic stroke.

Familial chylomicronemia syndrome and response to medium-chain triglyceride therapy in an infant with novel mutations in GPIHBP1

BACKGROUND

Severe hypertriglyceridemia predisposes to attacks of acute pancreatitis, a serious condition complicated by multiorgan failure, pancreatic necrosis, and mortality rates up to 20% in adults and 6.5% in children.

OVERVIEW

We describe an infant who suffered from an episode of acute pancreatitis from severe hypertriglyceridemia. Two major challenges complicate the case: identifying the etiology of severe hypertriglyceridemia and finding an efficacious treatment. A thorough history, physical examination, and laboratory workup failed to identify a clear etiology, prompting a genetic workup that identified compound heterozygous mutations in the glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) gene. This patient's hypertriglyceridemia responded to an infant formula rich in medium chain triglycerides (MCTs), and she remained free of pancreatitis 6 months later.

CONCLUSIONS

This case highlights the need to pursue a genetic evaluation in the absence of secondary causes of severe hypertriglyceridemia in infants. Patients with mutations in GPIHBP1 fail to respond to currently available lipid-lowering agents so dietary management-specifically, an extremely low-fat diet and supplementation with MCT-remains the cornerstone of therapy. Treatment in infants should focus on dietary measures rather than pharmacologic agents.

Common genetic variants contribute to primary hypertriglyceridemia without differences between familial combined hyperlipidemia and isolated hypertriglyceridemia

BACKGROUND

The majority of hypertriglyceridemias are diagnosed as familial combined hyperlipidemia (FCHL) and primary isolated hypertriglyceridemias. The contribution of common genetic variants in primary hypertriglyceridemias and the genetic difference between FCHL and isolated hypertriglyceridemias have not been thoroughly examined.

METHODS AND RESULTS

This study involved 580 patients with hypertriglyceridemias and 403 controls. Of the 37 single nucleotide polymorphisms examined, 12 located in 10 genes showed allelic and genotype frequency differences between hypertriglyceridemias and controls. The minor alleles of APOE, APOA5, GALNTN2, and GCKR variants were positively correlated with plasma triglycerides, whereas minor alleles of ADIPOR2, ANGPTL3, LPL, and TRIB1 polymorphisms were inversely associated. Body mass index, glucose, sex, rs328 and rs7007797 in LPL, rs662799 and rs3135506 in APOA5, and rs1260326 in GCKR explained 36% of the variability in plasma triglycerides, 7.3% of which was attributable to the genetic variables. LPL, GCKR, and APOA5 polymorphisms fit dominant, recessive, and additive inheritance models, respectively. Variants more frequently identified in isolated hypertriglyceridemias were rs7412 in APOE and rs1800795 in IL6; rs2808607 in CYP7A1 and rs3812316 and rs17145738 in MLXIPL were more frequent in FCHL. The other 32 single nucleotide polymorphisms presented similar frequencies between isolated hypertriglyceridemias and FCHL.

CONCLUSIONS

Common genetic variants found in LPL, APOA5, and GCKR are associated with triglycerides levels in patients with primary hypertriglyceridemias. FCHL and isolated hypertriglyceridemias are probably trace to an accumulation of genetic variants predisposing to familial and sporadic hypertriglyceridemias or to hypertriglyceridemias and hypercholesterolemia in case of FCHL.

Risk prediction with triglycerides in patients with stable coronary disease on statin treatment

BACKGROUND

The aim of the prospective Homburg Cream and Sugar study was to analyze the role of fasting and postprandial serum triglycerides (TG) as risk modifiers in patients with coronary artery disease (CAD).

METHODS AND RESULTS

A sequential oral triglyceride and glucose tolerance test was developed to obtain standardized measurements of postprandial TG kinetics and glucose in 514 consecutive patients with stable CAD confirmed by angiography (95% were treated with a statin). Fasting and postprandial TG predicted the primary outcome measure of cardiovascular death and hospitalizations after 48 months follow-up (fasting TG >150 vs. <106 mg/dl: Hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.31-2.45, p = 0.0001; area under the curve >1120 vs. <750 mg/dl/5 hr: HR 1.78, 95% CI 1.29-2.45, p = 0.0003). Parameters of the postprandial TG increase did not improve risk prediction compared to fasting TG. The number of cardiovascular deaths and myocardial infarctions was higher in the upper tertile of fasting TG (HR 1.79, 95%-CI 1.04-3.09, p = 0.03). Risk prediction by TG was independent of traditional risk factors, medication, glucose metabolism, LDL- and HDL-cholesterol. Total cholesterol, LDL- and HDL-cholesterol concentrations were not associated with the primary outcome.

CONCLUSIONS

Fasting serum triglycerides >150 mg/dl independently predict cardiovascular events in patients with coronary artery disease on guideline-recommended medication. Assessment of postprandial TG does not improve risk prediction compared to fasting TG in these patients.

Olanzapine-induced triglyceride and aminotransferase elevations without weight gain or hyperglycemia normalized after switching to aripiprazole

Olanzapine induced a marked elevation in triglyceride and cholesterol levels and in liver transaminase enzymes after 12 weeks of treatment in a patient with schizophrenia. These changes were not seen in an earlier 10-week course of treatment with risperidone, and improved substantially 1 week after the patient stopped olanzapine and began treatment with aripiprazole. The patient did not exhibit weight gain or hyperglycemia with any of the medications. This case and a review of the literature suggest that olanzapine may have unique properties that affect hepatic enzyme pathways, independent of any effects on weight and glucose, that may lead to hyperlipidemia and transaminitis in some patients.

Genetic and environmental determinants of the susceptibility of Amerindian derived populations for having hypertriglyceridemia

Here, we discuss potential explanations for the higher prevalence of hypertriglyceridemia in populations with an Amerindian background. Although environmental factors are the triggers, the search for the ethnic related factors that explain the increased susceptibility of the Amerindians is a promising area for research. The study of the genetics of hypertriglyceridemia in Hispanic populations faces several challenges. Ethnicity could be a major confounding variable to prove genetic associations. Despite that, the study of hypertriglyceridemia in Hispanics has resulted in significant contributions. Two GWAS reports have exclusively included Mexican mestizos. Fifty percent of the associations reported in Caucasians could be generalized to the Mexicans, but in many cases the Mexican lead SNP was different than that reported in Europeans. Both reports included new associations with apo B or triglycerides concentrations. The frequency of susceptibility alleles in Mexicans is higher than that found in Europeans for several of the genes with the greatest effect on triglycerides levels. An example is the SNP rs964184 in APOA5. The same trend was observed for ANGPTL3 and TIMD4 variants. In summary, we postulate that the study of the genetic determinants of hypertriglyceridemia in Amerindian populations which have major changes in their lifestyle, may prove to be a great resource to identify new genes and pathways associated with hypertriglyceridemia.

Treatment options for hypertriglyceridemia: from risk reduction to pancreatitis

While there has been considerable focus on the role and treatment of LDL cholesterol levels, a definitive role of triglycerides in the management of cardiovascular disease has been uncertain. Notably, with increasing triglyceride levels, there is a parallel increase in cholesterol levels carried by triglyceride-rich lipoproteins, which has prompted interest in the use of non-HDL cholesterol levels as a tool guiding interventions. Recent studies have provided evidence for an independent role of triglyceride levels as a cardiovascular risk factor, and recently, an Endocrine Society guideline was published for treatment of hypertriglyceridemia. In contrast to the relative uncertainty regarding triglycerides and cardiovascular disease, a role of very high triglyceride levels as a risk factor for pancreatitis has been well known. The present paper summarizes the underlying evidence for a risk role for triglyceride levels in cardiovascular disease and pancreatitis, current treatment recommendations and areas of future research.

Impact of admission triglyceride for early outcome in diabetic patients with stable coronary artery disease

Background

The role of triglyceride (TG) in predicting the outcomes in diabetic patients with coronary artery disease (CAD) has not been well investigated.

Methods

A total of 329 cases with stable angina pectoris (SAP) were prospectively enrolled and followed up for an average of 12 months. They were classified into the two groups according to the cut-off values of predicting early outcome of fasting TG level (low group <1.2 mmol/L, n = 103; High group ≥1.2 mmol/L, n = 226). The relationship between the TG levels and early outcomes were evaluated.

Results

High TG group showed severer lipid profile and elevated inflammatory markers. During an average of 12-month follow-up, 47 out of 329 patients suffered from pre-specified outcomes. Area under the receivers operating characteristic curve suggested that TG, similar to serum Hemoglobin A1C (HbA1C), was a significant predictor of early outcome for diabetic patients with SAP (P = 0.002). In Cox regression models, after adjusted age, gender, body mass index, other lipid parameters, fasting blood glucose, high sensitivity C-reactive protein, neutrophil count and HbA1C, TG remained as an independent predictor of adverse prognosis.

Conclusions

High level of fasting TG (≥1.2 mmol/L) was an independent predictor for early outcome of diabetic patients with SAP as like as HBA1c and number of affected coronary arteries in the era of revascularization and statin therapeutics.

Lymphocyte-suppressing action of simvastatin in patients with isolated hypertriglyceridemia

BACKGROUND

No previous study examined whether statins affect lymphocyte cytokine release in patients with isolated hypertriglyceridemia.

METHODS

The study included 46 patients with elevated triglyceride levels and peripheral artery stenosis, randomly assigned to receive simvastatin or placebo. Plasma lipids, glucose homeostasis markers, plasma C-reactive protein and lymphocyte cytokine release were measured at baseline and at the end of the treatment.

RESULTS

Ninety-day simvastatin treatment reduced lymphocyte release of TNF-α, interleukin-2 and interferon-γ, which was accompanied by a decrease in plasma C-reactive protein.

CONCLUSION

The obtained results suggest that statins produce lymphocyte-suppressing and systemic anti-inflammatory effects in patients with isolated hypertriglyceridemia.

Gene-gene interaction between CETP and APOE polymorphisms confers higher risk for hypertriglyceridemia in oldest-old Chinese women

The knowledge of dyslipidemia and its genetic contributors in oldest-old subjects is limited; in addition, the majority of oldest-old subjects are females. Evidence has accumulated that multiple genetic factors play important roles in determining susceptibility to dyslipidemia and extended life span. Cholesterol ester transfer protein (CETP) and apolipoprotein E (APOE) are two plausible candidate genes for human longevity owing to their functionally related modulation of circulating lipid homeostasis; however, few studies have considered their interplay. In this study, we analyzed the distribution of CETP*V (rs5882) and APOE*4 (rs429358 and rs7412) in 372 oldest-old Chinese women (aged 80-109) and 340 controls (aged 20-58). In addition to replicating the association of longevity, our main goal was to evaluate the contribution of CETP*V, APOE*4 and CETP*APOE interaction to the risk of dyslipidemia. Only APOE*4 conferred a risk against longevity and was associated with high-cholesterol (hTC) and mixed dyslipidemia for oldest-old females. Moreover, CETP*V was found to be associated with hypertriglyceridemia (hTG) independently from APOE*4, age, BMI, alcohol drinking, TC, TG, HDL-c, and LDL-c. The stratification test, multivariable-adjusted logistic regression, and nonparametric MDR analysis all suggested a significant CETP*APOE interaction associated with hTG. The unadjusted odds for hTG were more than 4-fold in subjects with CETP*V and APOE*4 than those without either (OR=4.36, P<0.001). These results provide evidence of strong independent associations between hTG and CETP*V in oldest-old Chinese females, and APOE*4, as an independently non-significant variant, might interact with CETP*V resulting in an increased risk for hTG.

Genotype-phenotype relationships in patients with type I hyperlipoproteinemia

CONTEXT

Type I hyperlipoproteinemia (T1HLP) is a rare, autosomal recessive disorder characterized by extreme hypertriglyceridemia that fails to respond to lipid-lowering agents, predisposing to frequent attacks of acute pancreatitis. Mutations in lipoprotein lipase (LPL), apolipoprotein CII (APOC2), lipase maturation factor 1 (LMF1), glycosyl-phosphatidylinositol anchored high-density lipoprotein-binding protein 1 (GPIHBP1), and apolipoprotein AV (APOA5) cause T1HLP, but we lack data on phenotypic variations among the different genetic subtypes.

OBJECTIVE

To study genotype-phenotype relationships among subtypes of T1HLP patients.

DESIGN/INTERVENTION

Genetic screening for mutations in LPL, APOC2, GPIHBP1, LMF1, and APOA5.

SETTING

Tertiary referral center.

PATIENTS

Ten patients (7 female, 3 male) with chylomicronemia, serum triglyceride levels about 2000 mg/dL, and no secondary causes of hypertriglyceridemia.

MAIN OUTCOME MEASURES

Genotyping and phenotypic features.

RESULTS

Four patients harbored homozygous or compound heterozygous mutations in LPL, 3 had homozygous mutations in GPIHBP1, and 1 had a heterozygous APOA5 mutation. We failed to fully identify the genetic etiology in 2 cases: 1 had a heterozygous LPL mutation only and another did not have any mutations. We identified 2 interesting phenotypic features: the patient with heterozygous APOA5 mutation normalized triglyceride levels with weight loss and fish oil therapy, and all 7 female patients were anemic.

CONCLUSIONS

Our data suggest the possibility of novel loci for T1HLP. We observed that heterozygous APOA5 mutation can cause T1HLP but such patients may unexpectedly respond to therapy, and females with T1HLP suffer from anemia. Further studies of larger cohorts may elucidate more phenotype-genotypes relationships among T1HLP subtypes.

Determining triglyceride reductions needed for clinical impact in severe hypertriglyceridemia

BACKGROUND

Patients with severe hypertriglyceridemia have an increased risk of cardiovascular disease and pancreatitis. Target triglyceride levels associated with clinical benefit for patients with severe hypertriglyceridemia are not currently known. This study evaluates the association between lower follow-up triglyceride levels and incidence of clinical events for patients with severe hypertriglyceridemia.

METHODS

By using claims data from 2 large US healthcare databases, we conducted a retrospective cohort study and identified 41,210 adults with severe hypertriglyceridemia (triglycerides ≥ 500 mg/dL) between June 2001 and September 2010. The date of the first severe hypertriglyceridemia laboratory result was the index date. Patients were categorized into 1 of 5 triglyceride ranges (<200 mg/dL, 200-299 mg/dL, 300-399 mg/dL, 400-499 mg/dL, and ≥ 500 mg/dL) based on a follow-up triglyceride level assessed 6 to 24 weeks after initial triglyceride levels were measured. Adjusted Cox regression models were developed to evaluate the impact of follow-up triglyceride levels on rates of pancreatitis episodes and cardiovascular events.

RESULTS

The mean age of patients was 50 years, 72% were male, and the mean follow-up was 825 days. Patients with severe hypertriglyceridemia with follow-up triglyceride levels <200 mg/dL experienced a lower rate of pancreatitis episodes (adjusted incidence rate ratio, 0.45; 95% confidence interval, 0.34-0.60) and cardiovascular events (adjusted incidence rate ratio, 0.71; 95% confidence interval, 0.64-0.78) with some clinical benefit in adults with severe hypertriglyceridemia with follow-up triglyceride levels 200 to 299 mg/dL and 300 to 399 mg/dL (P < .001 for trend).

CONCLUSIONS

We observed the greatest impact on clinical events among patients with severe hypertriglyceridemia with the lowest follow-up triglyceride levels.

Icosapent ethyl for treatment of elevated triglyceride levels

OBJECTIVES

To review the pharmacology, pharmacokinetics, clinical trial data, adverse effects, and formulary considerations of icosapent ethyl for the treatment of high triglyceride (TG) levels.

DATA SOURCES

A literature search with keywords Vascepa, icosapent ethyl, AMR101, and eicosapentaenoic acid of articles up to July 2013, along with the package insert for Vascepa and current guidelines for hypertriglyceridemia.

STUDY SELECTION/DATA EXTRACTION

Two phase-III, placebo-controlled, randomized, double-blind, 12-week clinical trials were included in this review: the MARINE trial and ANCHOR study. The MARINE trial consisted of mainly overweight Caucasian men with fasting TG ≥500 and ≤2000 mg/dL taking 4 g/day icosapent ethyl, 2 g/day, or placebo. The ANCHOR study consisted of mainly overweight Caucasians with type-2 diabetes mellitus on statin therapy, with fasting TG ≥200 and <500 mg/dL taking 4 g/day icosapent ethyl, 2 g/day, or placebo.

DATA SYNTHESIS

The MARINE trial showed a placebo-corrected median decrease in TG of 33.1% for patients receiving 4 g/day icosapent ethyl, with no significant change in low-density lipoprotein cholesterol (LDL-C) levels. TG was reduced by 19.7% in those taking 2 g/day. The ANCHOR study showed a placebo-corrected decrease in TG of 21.5% with a 6.3% decrease in LDL-C for patients taking 4 g/day icosapent ethyl as add-on to statin therapy. TG was reduced by 10.1% in those taking 2 g/day. The main adverse effect observed was joint pain (2.3%).

CONCLUSIONS

Icosapent ethyl is effective in reducing TG levels without increasing LDL-C, and has efficacy similar to other TG-lowering therapies with fewer adverse effects or interactions.

Small-dense LDL cholesterol/large-buoyant LDL cholesterol ratio as an excellent marker for indicating lipodystrophy in HIV-infected patients

OBJECTIVES

To examine whether the lipid parameters are predicting factors for human immunodeficiency virus (HIV)-associated lipodystrophy.

METHODS

Whole-body fat compositions of HIV-positive patients receiving stavudine-containing antiretroviral regimens (n = 79) were determined. Lipodystrophy was defined as a ratio of trunk fat mass/lower limb fat mass greater than 2.28. Blood samples were analyzed for total cholesterol (TC), triglycerides, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), small-dense LDL-C (sdLDL-C), apoAI, apoB, lipoprotein(a), and CD4 cell counts. Large-buoyant LDL-C (lbLDL-C) was calculated (LDL-C minus sdLDL-C).

RESULTS

Twenty-six patients were classified as having lipodystrophy. The mean values of triglycerides, HDL-C, sdLDL-C, apoB, TC/HDL-C, apolipoprotein (apo) B/apoAI, and sdLDL-C/lbLDL-C showed significant differences between patients with and without lipodystrophy (P < .02). Using logistic regression analysis, sdLDL-C/lbLDL-C was identified as a significant predictor of lipodystrophy (P < .001). At a ratio of 0.554, the odds ratio was 17.8 with a likelihood ratio of 5.5.

CONCLUSIONS

The sdLDL-C/lbLDL-C ratio is an excellent marker for indicating lipodystrophy in HIV-infected patients.

Dyslipidemia in obesity: mechanisms and potential targets

Obesity has become a major worldwide health problem. In every single country in the world, the incidence of obesity is rising continuously and therefore, the associated morbidity, mortality and both medical and economical costs are expected to increase as well. The majority of these complications are related to co-morbid conditions that include coronary artery disease, hypertension, type 2 diabetes mellitus, respiratory disorders and dyslipidemia. Obesity increases cardiovascular risk through risk factors such as increased fasting plasma triglycerides, high LDL cholesterol, low HDL cholesterol, elevated blood glucose and insulin levels and high blood pressure. Novel lipid dependent, metabolic risk factors associated to obesity are the presence of the small dense LDL phenotype, postprandial hyperlipidemia with accumulation of atherogenic remnants and hepatic overproduction of apoB containing lipoproteins. All these lipid abnormalities are typical features of the metabolic syndrome and may be associated to a pro-inflammatory gradient which in part may originate in the adipose tissue itself and directly affect the endothelium. An important link between obesity, the metabolic syndrome and dyslipidemia, seems to be the development of insulin resistance in peripheral tissues leading to an enhanced hepatic flux of fatty acids from dietary sources, intravascular lipolysis and from adipose tissue resistant to the antilipolytic effects of insulin. The current review will focus on these aspects of lipid metabolism in obesity and potential interventions to treat the obesity related dyslipidemia.

Monocyte-suppressing effects of simvastatin in patients with isolated hypertriglyceridemia

BACKGROUND

No previous study investigated statin action on monocyte cytokine release and systemic inflammation in patients with isolated hypertriglyceridemia.

METHODS

Our study included 43 subjects with isolated hypertriglyceridemia and peripheral artery stenosis randomly allocated to one of two groups, treated for 12 weeks with either simvastatin (40 mg twice daily) or placebo. Plasma lipids, glucose homeostasis markers, plasma C-reactive protein and monocyte cytokine release were determined on the day of allocation and at the end of the treatment period.

RESULTS

Simvastatin, but not placebo, reduced monocyte release of tumor necrosis factor-α, interleukin-6, interleukin-1β and monocyte chemoattractant protein-1, as well decreased plasma levels of C-reactive protein.

CONCLUSIONS

Our study shows that simvastatin reduces monocyte secretory function and has systemic anti-inflammatory properties in patients with isolated hypertriglyceridemia.

Epanova® and hypertriglyceridemia: pharmacological mechanisms and clinical efficacy

While LDL-cholesterol lowering has become the cornerstone of cardiovascular risk reduction strategies, considerable interest in additional targeting of hypertriglyceridemia continues. While ω-3 fatty acids are commonly used in clinical practice for triglyceride lowering, no large-scale clinical trial evaluating their impact on clinical events has been performed. As a result, there remains a lack of consensus with regards to their optimal clinical use. Epanova® (Omthera Pharmaceuticals Inc., NJ, USA) is a novel ω-3 free fatty acid formulation, developed to maximize eicosapentenoic acid and docosahexenoic acid bioavailability with low-fat diets, suggesting a potential therapeutic advantage compared with ω-3-acid ethyl esters in the treatment of patients with hypertriglyceridemia. Additional human studies are needed to define more clearly the cellular and molecular basis for the triglyceride-lowering effects of Epanova and this drug’s favorable cardiovascular effects, particularly in patients with hypertriglyceridemia.

Supplementing obese Zucker rats with niacin induces the transition of glycolytic to oxidative skeletal muscle fibers

In the present study, we tested the hypothesis that niacin increases the oxidative capacity of muscle by increasing the oxidative type I muscle fiber content. Twenty-four obese Zucker rats were assigned to 2 groups of 12 rats that were fed either a control diet (O group) or a diet supplemented with 750 mg/kg diet niacin (O+N group) for 4 wk. In addition, one group of lean rats (L group) was included in the experiment and fed the control diet for 4 wk. Plasma and liver concentrations of TG were markedly greater in obese groups than in the L group but markedly lower in the O+N group than in the O group (P < 0.05). Rats of the O+N group had a higher percentage of oxidative type I fibers and higher mRNA levels of genes encoding regulators of muscle fiber composition (Ppard, Ppargc1a, Ppargc1b), angiogenic factors (Vegfa, Vegfb), and genes involved in fatty acid utilization (Cpt1b, Slc25a20, Slc22a4, Slc22a5, Slc27a1) and oxidative phosphorylation (Cox4i1, Cox6a2) and a higher activity of the mitochondrial oxidative enzyme succinate dehydrogenase in muscle than rats of the O and L groups (P < 0.05). These niacin-induced changes in muscle metabolic phenotype are indicative of an increased capacity of muscle for oxidative utilization of fatty acids and are likely mediated by the upregulation of Ppard, Ppargc1a, and Ppargc1b, which are key regulators of muscle fiber composition, mitochondrial biogenesis, angiogenesis, and genes involved in fatty acid catabolism and oxidative phosphorylation. The increased utilization of fatty acids by muscle might contribute to the strong TG-lowering effect of niacin treatment.

Lipid management in the prevention of stroke: a meta-analysis of fibrates for stroke prevention

Background

Fibrates has been extensively used to improve plasma lipid levels and prevent adverse cardiovascular outcomes. However, the effect of fibrates on stroke is unclear at the present time. We therefore carried out a comprehensive systematic review and meta-analysis to evaluate the effects of fibrates on stroke.

Methods

We systematically searched Medline, Embase, the Cochrane Central Register of Controlled Trials, reference lists of articles, and proceedings of major meetings to identify studies for our analysis. We included randomized placebo controlled trials which reported the effects of fibrates on stroke. Relative risk (RR) was used to measure the effect of fibrates on the risk of stroke under random effect model. The analysis was further stratified by factors that could affect the treatment effects.

Results

Overall, fibrate therapy was not associated with a significant reduction on the risk of stroke (RR, 1.02, 95% CI, 0.90 to 1.16, P = 0.78). In the subgroup analyses, we observed that gemfibrozil therapy showed a beneficial effect on stroke (RR, 0.72, 95% CI, 0.53 to 0.98, P = 0.04). Similarly, fibrate therapy comparing to placebo had no effect on the incidence of fatal stroke. Subgroup analysis suggested that fibrate therapy showed an effect on fatal stroke when the Jadad score more than 3 (RR, 0.41, 95% CI, 0.17 to 1.00, P = 0.049). Furthermore, a sensitivity analysis indicated that fibrate therapy may play a role in fatal stroke (RR, 0.49, 95% CI, 0.26 to 0.93, P = 0.03) for patients with previous diabetes, cardiovascular disease or stroke.

Conclusions

Our study indicated that fibrate therapy might play an important role in reducing the risk of fatal stroke in patients with previous diabetes, cardiovascular disease or stroke. However, it did not have an effect on the incidence of stroke.

Medical resource use and costs associated with chylomicronemia

BACKGROUND

The prevalence of severe hypertriglyceridemia (TG > 1000 mg/dl) is estimated at 150-400 per 100,000 individuals in North America. Severe hypertriglyceridemia in the fasting state is associated with increased acute pancreatitis risk and is a sign of chylomicronemia which reflects the accumulation in the bloodstream of chylomicrons, the large lipoprotein particles produced in the gut after a meal.

OBJECTIVE

To assess medical resource use and costs associated with chylomicronemia.

METHODS

Patients with chylomicronemia of different causes (≥2 diagnoses with ICD-9 code 272.3) were identified from a large US claims database (years 2000 to 2009) and matched 1:1 to controls free of chylomicronemia based on age, gender, demographics, comorbidities, and use of lipid lowering drugs. During a 1-year study period, medical resource use and costs associated with chylomicronemia or acute pancreatitis were compared between matched cases and controls.

RESULTS

Among 6472 matched pairs, annual per-patient medical costs, calculated independently of the occurrence of acute pancreatitis, were significantly greater by $808 for chylomicronemia cases vs controls ($8029 vs $7220, p < 0.01), half of which was attributable to chylomicronemia-related services (p < 0.01). Chylomicronemia cases with a history of acute pancreatitis (n = 46) had greater rates of inpatient visits (p < 0.05) and greater average costs for subsequent acute pancreatitis or abdominal pain (p < 0.01) as well as greater total medical costs ($33,587 vs $4402, p < 0.01) vs matched controls. The average episode of acute pancreatitis (n = 104 episodes) generated medical costs of $31,820, almost entirely due to inpatient stays.

LIMITATIONS

Triglyceride levels were not available to characterize disease severity.

CONCLUSIONS

Patients with chylomicronemia, and especially those with a history of acute pancreatitis, incurred significantly greater total medical costs compared with individuals without chylomicronemia but with an otherwise comparable health profile.

Adipocyte triglyceride turnover is independently associated with atherogenic dyslipidemia

BACKGROUND

Inappropriate storage of fatty acids as triglycerides in adipocytes and their removal from adipocytes through lipolysis and subsequent oxidation may cause the atherogenic dyslipidemia phenotype of elevated apolipoprotein B levels and subsequent hypertriglyceridemia. We tested whether turnover of triglycerides in fat cells was related to dyslipidemia.

METHODS AND RESULTS

The age of triglycerides (reflecting removal) and triglyceride storage in adipocytes was determined under free living conditions by measuring incorporation of atmospheric (14)C into these lipids within the adipocytes in 47 women and 26 men with a large interindividual variability in body mass index. Because limited (14)C data were available, triglyceride age was also determined in 97 men and 233 women by using an algorithm based on adipocyte lipolysis, body fat content, waist-to-hip ratio, and insulin sensitivity. This cohort consisted of nonobese subjects since obesity per se is related to all components in the algorithm. Triglyceride turnover (age and storage) was compared with plasma levels of apolipoproteins and lipids. Plasma levels of apolipoprotein B and triglycerides were positively related to triglyceride age in adipocytes, when measured directly using radiocarbon analyses (r=0.45 to 0.47; P<0.0001). This effect was independent of subject age, waist circumference measures, and insulin sensitivity (partial r=0.29 to 0.45; P from 0.03 to <0.0001). Triglyceride storage showed no independent correlation (partial r=0.02 to 0.11; P=0.42 to 0.91). Algorithm-based values for adipocyte removal of triglycerides were positively associated with plasma triglycerides and apolipoprotein B (r=0.44 to 0.45; P<0.0001) and (also positively) with the inflammation status of adipose tissue (r=0.39 to 0.47; P<0.05). These correlations were statistically independent of subject age and observed in men and women as well as in lean and overweight subjects when subgroups were examined separately.

CONCLUSIONS

Decreased removal of adipocyte triglycerides (as indicated by a high triglyceride age in fat cells) is independently associated with circulating apolipoprotein B and triglycerides. This suggests a hitherto unknown role of triglyceride turnover in adipocytes for the development and/or maintenance of atherogenic dyslipidemia.

Treatment with ginger ameliorates fructose-induced Fatty liver and hypertriglyceridemia in rats: modulation of the hepatic carbohydrate response element-binding protein-mediated pathway

Ginger has been demonstrated to improve lipid derangements. However, its underlying triglyceride-lowering mechanisms remain unclear. Fructose overconsumption is associated with increase in hepatic de novo lipogenesis, thereby resulting in lipid derangements. Here we found that coadministration of the alcoholic extract of ginger (50 mg/kg/day, oral gavage, once daily) over 5 weeks reversed liquid fructose-induced increase in plasma triglyceride and glucose concentrations and hepatic triglyceride content in rats. Plasma nonesterified fatty acid concentration was also decreased. Attenuation of the increased vacuolization and Oil Red O staining area was evident on histological examination of liver in ginger-treated rats. However, ginger treatment did not affect chow intake and body weight. Further, ginger treatment suppressed fructose-stimulated overexpression of carbohydrate response element-binding protein (ChREBP) at the mRNA and protein levels in the liver. Consequently, hepatic expression of the ChREBP-targeted lipogenic genes responsible for fatty acid biosynthesis was also downregulated. In contrast, expression of neither peroxisome proliferator-activated receptor- (PPAR-) alpha and its downstream genes, nor PPAR-gamma and sterol regulatory element-binding protein 1c was altered. Thus the present findings suggest that in rats, amelioration of fructose-induced fatty liver and hypertriglyceridemia by ginger treatment involves modulation of the hepatic ChREBP-mediated pathway.

Alipogene tiparvovec: gene therapy for lipoprotein lipase deficiency

Homozygous lipoprotein lipase (LPL) deficiency is an ultra-orphan disease associated with increased rates of pancreatitis. Current treatments based on acute plasmapheresis allied with ultra-low fat diets are inadequate as responses to fibrates or other triglyceride-lowering therapies tend to be poor. Alipogene tiparvovec is an adeno-associated virus type I (AAV1) gene therapy using a hyper-functional LPL serine(447)-stop (S447X) insert administered intramuscularly under general anaesthetic with allied immunosuppression. Treatment results in histological muscle expression of LPL allied with a transient 40% reduction in triglycerides and improvements in postprandial chylomicron triglyceride content. Alipogene tiparvovec is the first possibly curative treatment for LPL deficiency.

Hypertriglyceridemic waist, cytokines and hyperglycaemia in Chinese

BACKGROUND

Abdominal obesity and hypertriglyceridemia confer high risk for cardiometabolic disease. Few studies have investigated the associations of hypertriglyceridemic waist with cytokines and hyperglycaemia in Chinese.

METHODS

Anthropometric indexes, fasting plasma concentrations of glucose, glycohemoglobin, insulin, lipid profile, inflammatory factors and adipokines were measured among 3289 Chinese men and women 50-70 years of age.

RESULTS

An increment of every 2 cm of waist circumference was associated with increased levels of high-sensitive C-reactive protein (hsCRP), interleukin 6 and RBP 4 by 0·033 mg/L, 0·018 ng/L and 0·556 mg/L and reduced levels of adiponectin by 0·269 mg/L (all P<0·05), respectively, with controlling for potential confounders. For triglycerides, each an increment of 20 mg/dL was associated with increased levels of hsCRP, RBP4, and decreased levels of adiponectin by 0·021 mg/L, 0·655 mg/L, and 0·371 mg/L (all P<0·05), respectively. Individuals with hypertriglyceridemic waist had increased risks of having hyperglycaemia (OR: 1·48; 95% CI: 1·09, 2·00) and diabetes mellitus (OR: 2·12; 95% CI: 1·47, 3·04) compared with those with neither of the phenotypes.

CONCLUSIONS

Hypertriglyceridemic waist is associated with a worse profile of inflammatory factors and adipokines as well as with an increased risk of having hyperglycaemia among Chinese.