Therapeutic response to medium-chain triglycerides and omega-3 fatty acids in a patient with the familial chylomicronemia syndrome

Severe hypertriglyceridemia: Existing and emerging therapies

Severe hypertriglyceridemia (sHTG), defined as a triglyceride (TG) concentration ≥ 500 mg/dL (≥ 5.7 mmol/L) is an important risk factor for acute pancreatitis. Although lifestyle, some medications, and certain conditions such as diabetes may lead to HTG, sHTG results from a combination of major and minor genetic defects in proteins that regulate TG lipolysis. Familial chylomicronemia syndrome (FCS) is a rare disorder caused by complete loss of function in lipoprotein lipase (LPL) or LPL activating proteins due to two homozygous recessive traits or compound heterozygous traits. Multifactorial chylomicronemia syndrome (MCS) and sHTG are due to the accumulation of rare heterozygous variants and polygenic defects that predispose individuals to sHTG phenotypes. Until recently, treatment of sHTG focused on lifestyle interventions, control of secondary factors, and nonselective pharmacotherapies that had modest TG-lowering efficacy and no corresponding reductions in atherosclerotic cardiovascular disease events. Genetic discoveries have allowed for the development of novel pathway-specific therapeutics targeting LPL modulating proteins. New targets directed towards inhibition of apolipoprotein C-III (apoC-III), angiopoietin-like protein 3 (ANGPTL3), angiopoietin-like protein 4 (ANGPTL4), and fibroblast growth factor-21 (FGF21) offer far more efficacy in treating the various phenotypes of sHTG and opportunities to reduce the risk of acute pancreatitis and atherosclerotic cardiovascular disease events.

Feeding of fish oil and medium-chain triglycerides to canines impacts circulating structural and energetic lipids, endocannabinoids, and non-lipid metabolite profiles

Introduction

The effect of medium-chain fatty acid-containing triglycerides (MCT), long-chain polyunsaturated fatty acid-containing triglycerides from fish oil (FO), and their combination (FO+MCT) on the serum metabolome of dogs (Canis familiaris) was evaluated.

Methods

Dogs (N = 64) were randomized to either a control food, one with 7% MCT, one with FO (0.18% eicosapentaenoate and 1.3% docosahexaenoate), or one with FO+MCT for 28 days following a 14-day washout period on the control food. Serum metabolites were analyzed via chromatography followed by mass spectrometry.

Results

Additive effects of serum metabolites were observed for a number of metabolite classes, including fatty acids, phospholipids, acylated amines including endocannabinoids, alpha-oxidized fatty acids, and methyl donors. Some effects of the addition of FO+MCT were different when the oils were combined compared with when each oil was fed separately, namely for acylcarnitines, omega-oxidized dicarboxylic acids, and amino acids. Several potentially beneficial effects on health were observed, including decreased circulating triglycerides and total cholesterol with the addition of FO (with or without MCT) and decreases in N-acyl taurines with the addition of MCT, FO, or FO+MCT.

Discussion

Overall, the results of this study provide a phenotypic characterization of the serum lipidomic response to dietary supplementation of long-chain n3-polyunsaturated and medium-chain saturated fats in canines.

Nutritional Treatment of Hypertriglyceridemia in Childhood: From Healthy-Heart Counselling to Life-Saving Diet

Hypertriglyceridemia is a lipid disorder with a varying prevalence; it is very common if we consider triglyceride plasma values slightly above the threshold, whereas it is extremely rare if only severely elevated triglyceride levels are considered. In most cases, severe forms of hypertriglyceridemia are caused by genetic mutations in the genes that regulate triglyceride metabolism, thus leading to extreme triglyceride plasma values and acute pancreatitis risk. Secondary forms of hypertriglyceridemia are usually less severe and are mainly associated with weight excess, but they can also be linked to liver, kidney, endocrinologic, or autoimmune diseases or to some class of drugs. Nutritional intervention is the milestone treatment for patients with hypertriglyceridemia and it has to be modulated on the underlying cause and on triglyceride plasma levels. In pediatric patients, nutritional intervention must be tailored according to specific age-related energy, growth and neurodevelopment requests. Nutritional intervention is extremely strict in case of severe hypertriglyceridemia, whereas it is similar to good healthy nutritional habits counselling for mild forms, mainly related to wrong habits and lifestyles, and to secondary causes. The aim of this narrative review is to define different nutritional intervention for various forms of hypertriglyceridemia in children and adolescents.

Safety and efficacy of therapies for chylomicronemia

INTRODUCTION

Primary chylomicronemia is characterized by pathological accumulation of chylomicrons in the plasma causing severe hypertriglyceridemia, typically >10 mmol/L (>875 mg/dL). Patients with the ultra-rare familial chylomicronemia syndrome (FCS) subtype completely lack lipolytic capacity and respond minimally to traditional triglyceride-lowering therapies. The mainstay of treatment is a low-fat diet, which is difficult to follow and compromises quality of life. New therapies are being developed primarily to prevent episodes of life-threatening acute pancreatitis.

AREAS COVERED

Antagonists of apolipoprotein (apo) C-III, such as the antisense oligonucleotide (ASO) volanesorsen, significantly reduce triglyceride levels in chylomicronemia. However, approval of and access to volanesorsen are restricted since a substantial proportion of treated FCS patients developed thrombocytopenia. Newer apo C-III antagonists, namely, the ASO olezarsen (formerly AKCEA-APOCIII-LRx) and short interfering RNA (siRNA) ARO-APOC3, appear to show efficacy with less risk of thrombocytopenia. Potential utility of antagonists of angiopoietin-like protein 3 (ANGPTL3) such as evinacumab and the siRNA ARO-ANG3 in subtypes of chylomicronemia remains to be defined.

EXPERT OPINION

Emerging pharmacologic therapies for chylomicronemia show promise, particularly apo C-III antagonists. However, these treatments are still investigational. Further study of their efficacy and safety in patients with both rare FCS and more common multifactorial chylomicronemia is needed.

New Therapies for Primary Hyperlipidemia

Primary hyperlipidemias include a heterogeneous set of monogenic and polygenic conditions characterized by a strong family aggregation, severe forms of hypercholesterolemia and/or hypertriglyceridemia, appearance early on life, and a high risk of cardiovascular events and/or recurrent pancreatitis. In real life, a small proportion of the primary hyperlipidemia cases is recognized and treated properly. Our goal is to present an update of current and upcoming therapies for patients with primary hyperlipidemia. Recently, new lipid-lowering medications have obtained authorization from the U.S. Food and Drug Administration and the European Medicines Agency. These drugs target metabolic pathways, including (adenosine 5'-triphosphates)-citrate lyase (bempedoic acid), proprotein convertase subtilisin/kexin 9 (inclisiran), apolipoprotein CIII (volanesorsen), and angiopoietin-like 3 (volanesorsen), that have additive effects with the actions of the currently available therapies (i.e., statins, ezetimibe or fibrates). We discuss the potential clinical indications for the novel medications. To conclude, the addition of these new medications to the therapeutic options for primary hyperlipidemia patients may increase the likelihood of achieving the treatment targets. Also, it could be a safer alternative for patients with side effects for the currently available drugs.

Causes, clinical findings and therapeutic options in chylomicronemia syndrome, a special form of hypertriglyceridemia

The prevalence of hypertriglyceridemia has been increasing worldwide. Attention is drawn to the fact that the frequency of a special hypertriglyceridemia entity, named chylomicronemia syndrome, is variable among its different forms. The monogenic form, termed familial chylomicronemia syndrome, is rare, occuring in 1 in every 1 million persons. On the other hand, the prevalence of the polygenic form of chylomicronemia syndrome is around 1:600. On the basis of the genetical alterations, other factors, such as obesity, alcohol consumption, uncontrolled diabetes mellitus and certain drugs may significantly contribute to the development of the multifactorial form. In this review, we aimed to highlight the recent findings about the clinical and laboratory features, differential diagnosis, as well as the epidemiology of the monogenic and polygenic forms of chylomicronemias. Regarding the therapy, differentiation between the two types of the chylomicronemia syndrome is essential, as well. Thus, proper treatment options of chylomicronemia and hypertriglyceridemia will be also summarized, emphasizing the newest therapeutic approaches, as novel agents may offer solution for the effective treatment of these conditions.

Comparison of plasmapheresis with medical apheresis in terms of efficacy and cost in the acute treatment of hypertriglyceridemia in children with lipoprotein lipase deficiency

OBJECTIVES

We aimed to compare plasmapheresis and medical apheresis as lipid-lowering therapies in children with familial lipoprotein lipase (LPL) deficiency.

METHODS

The data of 13 patients who were followed up after a diagnosis of LPL deficiency were retrospectively analyzed. Plasma triglyceride, cholesterol, amylase, and lipase values and complications were recorded before and after each patient underwent plasmapheresis or medical apheresis.

RESULTS

The mean follow-up period of the patients was 99.64 ± 52.92 months in the medical apheresis group and 118 ± 16.97 months in the plasmapheresis group. While the mean triglyceride level before plasmapheresis was 1,875.38 ± 547.46 mg/dL, it was 617 ± 228.28 mg/dL after plasmapheresis. While the mean triglyceride level before medical apheresis was 1,756.86 ± 749.27 mg/dL, it was found to be 623.03 ± 51.36 mg/dL after medical apheresis. Triglyceride levels were decreased by 59.62% with medical apheresis and 65.57% with plasmapheresis. The cost of treatment for medical apheresis was found to be lower compared to plasmapheresis 296.93 ± 29.94 Turkish lira (USD 43.34 ± 4.01) vs. 3,845.42 ± 156.17 Turkish lira (USD 561.37 ± 20.93; p<0.001).

CONCLUSIONS

Although there is no standardized strategy for the acute treatment of hypertriglyceridemia due to LPL deficiency, medical apheresis is a safe and effective treatment with a low risk of side effects. Unlike plasmapheresis, medical apheresis can be performed in any center, which is another important advantage of the procedure.

Volanesorsen in the Treatment of Familial Chylomicronemia Syndrome or Hypertriglyceridaemia: Design, Development and Place in Therapy

Severe hypertriglyceridaemia is associated with pancreatitis and chronic pancreatitis-induced diabetes. Familial chylomicronaemia syndrome (FCS) is a rare autosomal recessive disorder of lipid metabolism characterised by high levels of triglycerides (TGs) due to failure of chylomicron clearance. It causes repeated episodes of severe abdominal pain, fatigue and attacks of acute pancreatitis. There are few current options for its long-term management. The only universal long-term therapy is restriction of total dietary fat intake to <10-15% of daily calories (15 to 20g per day). Many patients have been treated with fibrates and statins with a variable response, but many remain susceptible to pancreatitis. Other genetic syndromes associated with hypertriglyceridaemia include familial partial lipodystrophy (FPLD). Targeting apolipoprotein C3 (apoC3) offers the ability to increase clearance of chylomicrons and other triglyceride-rich lipoproteins. Volanesorsen is an antisense oligonucleotide (ASO) inhibitor of apoC3, which reduces TG levels by 70–80% which has been shown also to reduce rates of pancreatitis and improve well-being in FCS and reduce TGs and improve insulin resistance in FPLD. It is now undergoing licensing and payer reviews. Further developments of antisense technology including small interfering RNA therapy to apoC3 as well as other approaches to modulating triglycerides are in development for this rare disorder.

Docosahexaenoate-enriched fish oil and medium chain triglycerides shape the feline plasma lipidome and synergistically decrease circulating gut microbiome-derived putrefactive postbiotics

The purpose of this study was to examine the influence of medium-chain fatty acid-containing triglycerides (MCT), long-chain polyunsaturated fatty acid-containing triglycerides, and their combination on the plasma metabolome of cats (Felis catus), including circulating microbiome-derived postbiotics. After a 14-day lead-in on the control food, cats were randomized to one of four foods (control, with 6.9% MCT, with fish oil [FO; 0.14% eicosapentaenoate, 1.0% docosahexaenoate], or with FO+MCT; n = 16 per group) for 28 days. Analysis of plasma metabolites showed that the addition of FO and MCT led to synergistic effects not seen with either alone across a number of lipid classes, including fatty acids, acylcarnitines, and acylated amines including endocannabinoids. Notably, the FO+MCT group had an increase in ketone body production relative to baseline and beyond that seen with MCT alone. N-acyl taurines, the accumulation of which has been implicated in the onset of type 2 diabetes, were significantly decreased in the FO+MCT group. Significant decreases in the gut microbiome-derived postbiotic classes of indoles/indolic sulfates and phenols/phenolic sulfates were observed only the FO+MCT group. Overall, the combination of MCT and FO led to number of changes in plasma metabolites that were not observed with either oil alone, particularly in postbiotics.

Pharmacological treatment options for severe hypertriglyceridemia and familial chylomicronemia syndrome

INTRODUCTION

A spectrum of disorders, ranging from rare severe cases of homozygous null lipoprotein lipase deficiency (LPLD)-familial chylomicronemia syndrome (FCS) to heterozygous missense LPLD or polygenic causes, result in hypertriglyceridemia and pancreatitis. The effects of mutations are exacerbated by environmental factors such as diet, pregnancy, and insulin resistance. Areas covered: In this review, authors discuss chronic treatment of FCS by ultra-low fat diets allied with the use of fibrates, omega-3 fatty acids, niacin, statins, and insulin-sensitizing therapies depending on the extent of residual lipoprotein lipase (LPL) activity; novel therapies in development target triglyceride (TG)-rich lipoprotein particle clearance. Previously, a gene therapy approach to LPL-alipogene tiparvovec showed that direct targeting of LPL function reduced pancreatitis events. An antisense oligonucleotide to apolipoprotein-C3, volanesorsen has been shown to decrease TGs by 70-80% and possibly to reduce rates of pancreatitis admissions. Studies are underway to validate its long-term efficacy and safety. Other approaches investigating the role of LPL modulating proteins such as angiopoietin-like petide-3 (ANGPTL3) are under consideration. Expert opinion: Current therapeutic options are not sufficient for management of many cases of FCS. The availability of antisense anti-apoC3 therapies and, in the future, ANGPTL3 therapies may remedy this.

Characterizing familial chylomicronemia syndrome: Baseline data of the APPROACH study

BACKGROUND

Familial chylomicronemia syndrome (FCS) is a rare metabolic disorder caused by mutations in lipoprotein lipase (LPL) or genes required for LPL functionality and is characterized by hyperchylomicronemia that results in recurrent episodes of acute pancreatitis. Owing to the rarity of FCS, there are few case series describing the phenotypic variability in FCS patients in detail.

OBJECTIVE

To provide baseline characteristics in the largest study population to date of patients with FCS.

METHODS

We analyzed baseline demographic and clinical characteristics of adult FCS patients in the phase 3 APPROACH study of volanesorsen sodium (antisense inhibitor of apolipoprotein C-III).

RESULTS

Sixty-six patients were included in the analysis. Mean (SD) age was 46 (13) years; and mean body mass index was 24.9 (5.7) kg/m². We identified causal mutations in 79% (52) of patients, with LPL mutations accounting for 62% (41) of cases. Median age at diagnosis was 24 years, 54% were females, and 81% were Caucasian. All patients followed a low-fat diet, 43% received fibrates, 27% fish oils, and 21% statins. Median fasting triglyceride levels (P25, P75) were 1985 (1179, 3047 mg/dL). Overall, 76% of patients reported ≥1 lifetime episode of acute pancreatitis; 23 patients reported a total of 53 pancreatitis events in the 5 years before enrollment.

CONCLUSIONS

Our data emphasize the severe hypertriglyceridemia characteristic of FCS patients despite restrictive low-fat diets and frequent use of existing hypolipemic therapies. Acute pancreatitis and recurrent acute pancreatitis are frequent complications of FCS. Diagnosis at an older age suggests likely underdiagnosis and underappreciation of this rare disorder.

Nutritional management of hyperapoB

Plasma apoB is a more accurate marker of the risk of CVD and type 2 diabetes (T2D) than LDL-cholesterol; however, nutritional reviews targeting apoB are scarce. Here we reviewed eighty-seven nutritional studies and present conclusions in order of strength of evidence. Plasma apoB was reduced in all studies that induced weight loss of 6–12 % using hypoenergetic diets (seven studies; 5440–7110 kJ/d; 1300–1700 kcal/d; 34–50 % carbohydrates; 27–39 % fat; 18–24 % protein). When macronutrients were compared in isoenergetic diets (eleven studies including eight randomised controlled trials (RCT); n 1189), the diets that reduced plasma apoB were composed of 26–51 % carbohydrates, 26–46 % fat, 11–32 % protein, 10–27 % MUFA, 5–14 % PUFA and 7–13 % SFA. Replacement of carbohydrate by MUFA, not SFA, decreased plasma apoB. Moreover, dietary enriching with n-3 fatty acids (FA) (from fish: 1·1–1·7 g/d or supplementation: 3·2–3·4 g/d EPA/DHA or 4 g/d EPA), psyllium (about 8–20 g/d), phytosterols (about 2–4 g/d) or nuts (30–75 g/d) also decreased plasma apoB, mostly in hyperlipidaemic subjects. While high intake of trans-FA (4·3–9·1 %) increased plasma apoB, it is unlikely that these amounts represent usual consumption. Inconsistent data existed on the effect of soya proteins (25–30 g/d), while the positive association of alcohol consumption with low plasma apoB was reported in cross-sectional studies only. Five isoenergetic studies using Mediterranean diets (including two RCT; 823 subjects) reported a decrease of plasma apoB, while weaker evidence existed for Dietary Approaches to Stop Hypertension (DASH), vegetarian, Nordic and Palaeolithic diets. We recommend using a Mediterranean dietary pattern, which also encompasses the dietary components reported to reduce plasma apoB, to target hyperapoB and reduce the risks of CVD and T2D.

Chylomicronaemia--current diagnosis and future therapies

This Review discusses new developments in understanding the basis of chylomicronaemia--a challenging metabolic disorder for which there is an unmet clinical need. Chylomicronaemia presents in two distinct primary forms. The first form is very rare monogenic early-onset chylomicronaemia, which presents in childhood or adolescence and is often caused by homozygous mutations in the gene encoding lipoprotein lipase (LPL), its cofactors apolipoprotein C-II or apolipoprotein A-V, the LPL chaperone lipase maturation factor 1 or glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1. The second form, polygenic late-onset chylomicronaemia, which is caused by an accumulation of several genetic variants, can be exacerbated by secondary factors, such as poor diet, obesity, alcohol intake and uncontrolled type 1 or type 2 diabetes mellitus, and is more common than early-onset chylomicronaemia. Both forms of chylomicronaemia are associated with an increased risk of life-threatening pancreatitis; the polygenic form might also be associated with an increased risk of cardiovascular disease. Treatment of chylomicronaemia focuses on restriction of dietary fat and control of secondary factors, as available pharmacological therapies are only minimally effective. Emerging therapies that might prove more effective than existing agents include LPL gene therapy, inhibition of microsomal triglyceride transfer protein and diacylglycerol O-acyltransferase 1, and interference with the production and secretion of apoC-III and angiopoietin-like protein 3.

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.

Severe/Extreme Hypertriglyceridemia and LDL Apheretic Treatment: Review of the Literature, Original Findings

Hypertriglyceridemia (HTG) is a feature of numerous metabolic disorders including dyslipidemias, metabolic syndrome, and diabetes mellitus type 2 and can increase the risk of premature coronary artery disease. HTG may also be due to genetic factors (called primary HTG) and particularly the severe/extreme HTG (SEHTG), which is a usually rare genetic disorder. Even rarer are secondary cases of SEHTG caused by autoimmune disease. This review considers the causes of SEHTG, and their management including treatment with low density lipoprotein apheresis and analyzes the original findings.

Dietary medium-chain triglyceride supplementation has no effect on apolipoprotein B-48 and apolipoprotein B-100 kinetics in insulin-resistant men

BACKGROUND

Medium-chain triglyceride (MCT) supplements are used by clinicians to treat patients with severe hypertriglyceridemia who are at risk of pancreatitis. However, the potential mechanisms underlying the effects of MCT on triglyceride-rich lipoprotein (TRL) metabolism have not yet been thoroughly examined in humans.

OBJECTIVE

This double-blind randomized crossover study compared the impact of 4 wk of supplementation with 20 g MCT oil/d or 20 g corn oil/d on the kinetics of apolipoprotein (apo) B-48-containing TRLs and apo B-100-containing very-low-density lipoprotein (VLDL), as well as on the expression of key intestinal genes involved in lipid metabolism in 28 obese, insulin-resistant men.

DESIGN

The in vivo kinetics of TRL apo B-48 and VLDL apo B-100 were assessed by using a primed-constant infusion of l-[5,5,5-d3]leucine for 12 h in the fed state. Real-time polymerase chain reaction quantification was performed on duodenal biopsy samples taken at the end of each phase of supplementation.

RESULTS

Compared with corn oil, MCT supplements had no significant effect on plasma lipoprotein profile or TRL apo B-48 and VLDL apo B-100 kinetics. Positive correlations were observed between the intestinal expression of several key genes involved in lipoprotein metabolism in a subgroup of participants (n = 16) after MCT supplementation. However, there was no difference between MCT and the corn oil control supplement in the intestinal messenger RNA expression levels of these key genes.

CONCLUSION

These data indicate that short-term supplementation with MCT has a neutral effect on TRL apo B-48 and VLDL apo B-100 kinetics and on the intestinal expression of genes involved in lipid and fatty acid metabolism in men with insulin resistance. This trial was registered at www.clinicaltrials.gov as NCT01806142.

Diagnosis and management of familial dyslipoproteinemias

The three major pathways of lipoprotein metabolism provide a superb paradigm to delineate systematically the familial dyslipoproteinemias. Such understanding leads to improved diagnosis and treatment of patients. In the exogenous (intestinal) pathway, defects in LPL, apoC-II, APOA-V, and GPIHBP1 disrupt the catabolism of chylomicrons and hepatic uptake of their remnants, producing very high TG. In the endogenous (hepatic) pathway, six disorders affect the activity of the LDLR and markedly increase LDL. These include FH, FDB, ARH, PCSK9 gain-of-function mutations, sitosterolemia and loss of 7 alpha hydroxylase. Hepatic overproduction of VLDL occurs in FCHL, hyperapoB, LDL subclass pattern B, FDH and syndrome X, often due to insulin resistance and resulting in high TG, elevated small LDL particles and low HDL-C. Defects in APOB-100 and loss-of-function mutations in PCSK9 are associated with low LDL-C, decreased CVD and longevity. An absence of MTP leads to marked reduction in chylomicrons and VLDL, causing abetalipoproteinemia. In the reverse cholesterol pathway, deletions or nonsense mutations in apoA-I or ABCA1 transporter disrupt the formation of the nascent HDL particle. Mutations in LCAT disrupt esterification of cholesterol in nascent HDL by LCAT and apoA-1, and formation of spherical HDL. Mutations in either CETP or SR-B1 and familial high HDL lead to increased large HDL particles, the effect of which on CVD is not resolved. The major goal is to prevent or ameliorate the major complications of many familial dyslipoproteinemias, namely, premature CVD or pancreatitis. Dietary and drug treatment specific for each inherited disorder is reviewed.

Diagnosis and treatment of severe hypertriglyceridemia

Severe hypertriglyceridemia is associated with acute pancreatitis and can be a manifestation of lipoprotein lipase (LPL) deficiency. It is associated with a spectrum of disorders, ranging from heterozygous LPL deficiency allied with environmental factors to rare severe cases of homozygous LPL deficiency. The genes associated with reduced LPL activity include LPL, its cofactor apoC-2, a controlling protein apoA-5 and the LPL receptor GPI-HBP1. The effects of mutations are exacerbated by environmental factors such as diet, pregnancy and insulin resistance. Treatment of clinical LPL deficiency is by ultra-low-fat diet along with the use of fibrates, omega-3 fatty acids, niacin, statins and insulin-sensitizing therapies, depending on the extent of residual LPL activity. Novel therapies that target lipoprotein particle assembly through the antisense oligonucleotides or by interference with triglyceride-loading microsomal transport protein inhibitors offer new potential options for treating hypertriglyceridemia.

Management of severe hypertriglyceridemia in the hospital: a review

For hospitalists, hypertriglyceridemia (HTG) is more than cardiovascular risk. Severe HTG occurs when serum triglycerides rise above 1000 mg/dL, and it carries a risk of abdominal pain and pancreatitis. The etiology of severe HTG is usually a combination of genetic and secondary factors. A detailed history with attention to family history, medications, and alcohol consumption can often lead to the cause. Physical examination findings may stretch across multiple organ systems. Patients with severe HTG should be admitted to the hospital for aggressive medical therapy if they develop symptoms such as abdominal pain or pancreatitis. Asymptomatic patients with severe HTG who have significant short-term risk for developing symptoms require urgent consultation that may lead to a brief hospitalization to address exacerbating factors. Treatment of severe HTG includes a combination of pharmacologic agents and a restriction on dietary triglyceride intake. If oral medications fail to adequately lower triglyceride levels, intravenous insulin and in rare cases therapeutic plasma exchange may be required. To prevent recurrent severe HTG, the patient should be counseled about adherence to long-term medications and lifestyle changes.

Primeiro relato de uma criança Brasileira portadora da mutação G188E do gene da lipoproteína lipase

OBJETIVO: Relatar o caso de uma criança com hipertrigliceridemia grave por mutações do gene da lipoproteína lipase. DESCRIÇÃO DE CASO: Menino de três anos que apresentou, com um mês de idade, soro lipêmico. Seu perfil lipídico indicou hipertrigliceridemia grave, com concentrações de triglicerídeos plasmáticos iguais a 25000mg/dL. Foi detectada a mutação G188E no éxon 5 da lipoproteína lipase em homozigose na criança e em heterozigose nos pais. COMENTÁRIOS: A deficiência da lipoproteína lípase é uma doença de herança autossômica recessiva e esses pacientes evoluem com hipertrigliceridemia grave.

Diagnosis and treatment of apolipoprotein B dyslipoproteinemias

Conventionally, atherogenic dyslipidemias have been defined by elevated levels of triglyceride and/or LDL cholesterol. However, cholesterol and triglycerides are not metabolically and physically independent entities. Rather, they are constituents of the atherogenic apolipoprotein B (apoB) particles, which differ in their origin and their metabolic function. Moreover, the risk of vascular disease is not related to the plasma concentration of cholesterol or triglyceride per se, but to the number, composition and size of the apoB particles, within which the cholesterol and triglycerides are contained. After all, the entire apoB particle--rather than individual cholesterol or triglyceride molecules--enters and is trapped within the arterial wall, and this particle initiates and sustains the process that results in atherosclerosis. Accordingly, we suggest a change of name and focus from dyslipidemias to dyslipoproteinemias. Virtually all the atherogenic apoB dyslipoproteinemias can be specifically identified on the basis of plasma levels of cholesterol, triglyceride and apoB. Not only does this enable an accurate diagnosis in the individual, but the major familial dyslipoproteinemias can be identified as well. Here, we review the diagnostic algorithm for apoB dyslipoproteinemias and provide, for the first time, a treatment plan on the basis of a reduction of atherogenic lipoprotein particles rather than plasma lipids.

Mutation of conserved cysteines in the Ly6 domain of GPIHBP1 in familial chylomicronemia

We investigated a family from northern Sweden in which three of four siblings have congenital chylomicronemia. LPL activity and mass in pre- and postheparin plasma were low, and LPL release into plasma after heparin injection was delayed. LPL activity and mass in adipose tissue biopsies appeared normal. [(35)S]Methionine incorporation studies on adipose tissue showed that newly synthesized LPL was normal in size and normally glycosylated. Breast milk from the affected female subjects contained normal to elevated LPL mass and activity levels. The milk had a lower than normal milk lipid content, and the fatty acid composition was compatible with the milk lipids being derived from de novo lipogenesis, rather than from the plasma lipoproteins. Given the delayed release of LPL into the plasma after heparin, we suspected that the chylomicronemia might be caused by mutations in GPIHBP1. Indeed, all three affected siblings were compound heterozygotes for missense mutations involving highly conserved cysteines in the Ly6 domain of GPIHBP1 (C65S and C68G). The mutant GPIHBP1 proteins reached the surface of transfected Chinese hamster ovary cells but were defective in their ability to bind LPL (as judged by both cell-based and cell-free LPL binding assays). Thus, the conserved cysteines in the Ly6 domain are crucial for GPIHBP1 function.

Novel LPL mutations associated with lipoprotein lipase deficiency: two case reports and a literature review

Lipoprotein lipase (LPL) is a key enzyme involved with hydrolysis and removal of triglycerides from plasma. LPL deficiency is a rare condition with an estimated prevalence of 1 in 106. It is characterized biochemically by elevated triglycerides and lowered HDL in the plasma and clinically by a constellation of signs and symptoms during childhood including failure to thrive, lipemia retinalis, eruptive xanthomas, hepatosplenomegaly, and acute pancreatitis. Nearly 100 mutations in the LPL gene have been associated with LPL deficiency. Here we report 2 unrelated pedigrees with LPL deficiency from 2 novel disease-causing LPL mutations: a Gly159Glu missense mutation in exon 5 and a 4-bp ACGG deletion at the 3' boundary of exon 2. We present molecular findings of these 2 cases and review the biochemical, clinical, and genetic features of LPL deficiency.

Hypertriglyceridemia: impact and treatment

The treatment of elevated levels of low-density lipoprotein cholesterol is standard medical practice supported by conclusive outcome data. Less definitive information exists for hypertriglyceridemia. Only in the setting of severe hyperchylomicronemia is the benefit of triglyceride lowering clear: it is a means to reduce the risk of pancreatitis. The relationship of triglycerides and cardiovascular disease is still unclear. Moreover, the cardiovascular benefits of reducing triglycerides and of using triglyceride-lowering medications remain unproved. Nonetheless it has become almost standard to reduce the levels of triglyceride-rich lipoproteins that are a major component of plasma non-high-density lipoprotein cholesterol.

Approaches to dyslipidemia treatment in children and adolescents

Atherosclerosis represents a disease that begins in childhood, and alterations in lipid concentration play a fundamental role in the development of this condition. Children and adolescents with high cholesterol levels are more likely than their peers in the general population to present with dyslipidemia in adulthood. Precocious identification of dyslipidemias associated with premature cardiovascular disease is crucial during childhood to delay or prevent the atherosclerotic process. The National Cholesterol Education Program has established guidelines for the diagnosis and treatment of dyslipidemia during pediatric age. It has been suggested that a heart-healthy diet should begin at 2 years of age, and no adverse effects on psychological aspects, growth, pubertal development and nutritional status in children and adolescents limiting total and saturated fat intake have been demonstrated. Pharmacotherapy should be considered in children aged 10 years or older when low-density lipoprotein cholesterol concentrations remain very high despite dietary therapy, especially when multiple risk factors are present. The lipid-lowering drugs recommended for childhood and adolescence are resins and statins. The increasing use of statins is dependent on their effectiveness and safety. Ezetimibe, a selective cholesterol absorption inhibitor, may provide a similar cholesterol-lowering effect as that reached with statin treatment. This review provides an update on recent advances in the therapy of dyslipidemia, especially hypercholesterolemia, during pediatric age and adolescence.

Clinical and laboratory assessment of cardiovascular risk in children: Guidelines for screening, evaluation, and treatment

The early lesions of atherosclerosis begin in childhood and are related to antecedent cardiovascular disease (CVD) risk factors. Environmental and genetic factors (eg, diet, obesity, exercise, and certain inherited dyslipidemias) influence progression of such lesions. Identification of youth at risk for atherosclerosis includes an integrated assessment of these predisposing factors. Treatment starts with a diet low in total and saturated fat and cholesterol, use of water-soluble fiber, plant stanols and plant sterols, weight control, and exercise. Drug therapy, for example, with inhibitors of hydroxymethylglutaryl-CoA reductase, bile acid sequestrants, and cholesterol absorption inhibitors, can be considered in those with a positive family history of premature CVD and low-density lipoprotein cholesterol >160 mg/dL after dietary and hygienic measures. Candidates for drug therapy often include those with familial hypercholesterolemia, familial combined hyperlipidemia, the metabolic syndrome, polycystic ovarian syndrome, type 1 diabetes, and the nephrotic syndrome. Such dietary and drug therapy appears safe and efficacious. Early identification and treatment of youth with CVD risk factors and dyslipidemia are likely to retard the atherosclerotic process. Optimal detection and treatment of high-risk children either from the general population or from families with premature CVD will require a comprehensive universal screening and evaluation program.

Treatment of dyslipidemia in children and adolescents

The early lesions of atherosclerosis begin in childhood, and are related to antecedent cardiovascular disease risk factors. Environmental and genetic factors such as diet, obesity, exercise, and certain inherited dyslipidemias influence the progression of such lesions. The identification of youth at risk for atherosclerosis includes an integrated assessment of these predisposing factors. Treatment starts with a diet low in total and saturated fat and cholesterol, the use of water-soluble fiber and plant sterols, weight control, and exercise. Drug therapy, for example, with inhibitors of hydroxymethylglutaryl CoA reductase, bile acid sequestrants, and cholesterol absorption inhibitors, can be considered in those with a positive family history of premature coronary artery disease and a low-density lipoprotein cholesterol above 160 mg/dL, after dietary and hygienic measures. Candidates for drug therapy often include those with familial hypercholesterolemia, familial combined hyperlipidemia, the metabolic syndrome, polycystic ovarian syndrome, type I diabetes, and the nephrotic syndrome. We review the safety and efficacy of dietary and drug therapy, and propose an updated diagnostic and therapeutic algorithm that includes the metabolic syndrome. The early identification and treatment of youth with dyslipidemias is likely to retard the atherosclerotic process.

Drug treatment of combined hyperlipidemia

Combined hyperlipidemia is increasing in frequency and is the most common lipid disorder associated with obesity, insulin resistance and diabetes mellitus. It is associated with other features of the metabolic syndrome including hypertension, hyperuricemia, hyperinsulinemia and highly atherogenic subfractions of lipoprotein remnant particles including small dense low density lipoprotein-cholesterol. This review examines the mechanisms by which combined hyperlipidemia arises and the various drugs including fibric acid derivatives, hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, and nicotinic acid which can be used either as monotherapy or in combination to manage it and to improve prognosis from atherosclerotic disease in diabetes mellitus, insulin resistant states and primary combined hyperlipidemia. The therapeutic approach to combined hyperlipidemia involves determination of whether the cause is hepatocyte damage or metabolic derangements. Combined hyperlipidemia due to hepatocyte damage should be treated by attention to the primary cause. In the case of metabolic dysfunction because of imbalance in glucose and fat metabolism, therapy of diabetes mellitus and obesity should be optimised prior to commencement of lipid lowering drugs. Both fibric acid derivatives and HMG-CoA reductase inhibitors can be used in the treatment of combined hyperlipidemia with fibric acid derivatives having greater effects on triglycerides and HMG-CoA reductase inhibitors on LDL-C though both have effects on the other cardiovascular risk factors. There is some evidence of benefit with both interventions in mild combined hyperlipidemias and large scale trials are underway. Fibric acid derivatives and HMG-CoA reductase inhibitor therapy can be combined with care, provided that gemfibrozil is avoided, fibric acid derivatives are given in the mornings and shorter half -life HMG-CoA reductase inhibitors are used at night. Combined hyperlipidemia emergencies occur with predominant hypertriglyceridemia in pregnancy or as a cause of pancreatitis. Therapy in the former should aim to reduce chylomicron production by a low fat diet and intervention to suppress VLDL-C secretion using omega-3 fatty acids. In the latter case, fluid therapy alone and medium chain plasma triglyceride infusions usually reduce levels satisfactorily though apheresis may be required. Blood glucose levels also need aggressive management in these conditions. Combined hyperlipidemia is likely to become an increasing problem with the increase in the prevalence of obesity and diabetes mellitus and needs aggressive management to reduce cardiovascular risk.

Octanoate oxidation measured by 13C-NMR spectroscopy in rat skeletal muscle, heart, and liver

Contribution of octanoate to the oxidative metabolism of the major sites of fatty acid oxidation (heart, liver, and resting and contracting skeletal muscle) was assessed in the intact rat with 13C-NMR spectroscopy. Under inhalation anesthesia, [2,4,6,8-13C4]octanoate was infused into the jugular vein and the sciatic nerve of one limb was stimulated for 1 h. Octanoate was a principal contributor to the acetyl-CoA pool in all tissues examined, with highest oxidation occurring in heart and soleus muscle followed by predominantly red portion of gastrocnemius muscle (RG), liver, and then white portion of gastrocnemius muscle (WG). Fractional contribution of 13C-labeled octanoate to the acetyl-CoA pool (Fc2) was 0.563 +/- 0.066 for heart and 0.367 +/- 0.054 for liver. Significant differences were observed between each of the muscle types during both rest and contraction. In muscle, Fc2 was highest in soleus (0.565 +/- 0.089 rested, 0.564 +/- 0.096 contracted), followed by RG (0.470 +/- 0.092 rested, 0.438 +/- 0.072 contracted), and lowest in WG (0.340 +/- 0.081 rested, 0.272 +/- 0.065 contracted). Our findings demonstrate that the fractional contribution of octanoate to oxidative metabolism correlates with oxidative capacity of the tissue and that octanoate metabolism increases in contracted muscle in proportion to the overall increase in oxidative rate.

Energy contribution of octanoate to intact rat brain metabolism measured by 13C nuclear magnetic resonance spectroscopy

Glucose is the dominant oxidative fuel for brain, but studies have indicated that fatty acids are used by brain as well. We postulated that fatty acid oxidation in brain could contribute significantly to overall energy usage and account for non-glucose-derived energy production. [2,4,6,8-13C4]octanoate oxidation in intact rats was determined by nuclear magnetic resonance spectroscopy. We found that oxidation of 13C-octanoate in brain is avid and contributes approximately 20% to total brain oxidative energy production. Labeling patterns of glutamate and glutamine were distinct, and analysis of these metabolites indicated compartmentalized oxidation of octanoate in brain. Examination of liver and blood spectra revealed that label from 13C-octanoate was incorporated into glucose and ketones, which enabled calculation of its overall energy contribution to brain metabolism: glucose (predominantly unlabeled) and 13C-labeled octanoate can account for the entire oxidative metabolism of brain. Additionally, flux through anaplerotic pathways relative to tricarboxylic acid cycle flux (Y) was calculated to be 0.08 +/- 0.039 in brain, indicating that anaplerotic flux is significant and should be considered when assessing brain metabolism. Y was associated with the glutamine synthesis compartment, consistent with the view that anaplerotic flux occurs primarily in astrocytes.

Long-term follow-up of patients with acute hypertriglyceridemia-induced pancreatitis

BACKGROUND

An acute and potentially life-threatening complication of hypertriglyceridemia (HTG) is acute pancreatitis (AP). Hypertriglyceridemia, usually severe, may be primary in origin or secondary to alcohol abuse, diabetes mellitus, pregnancy, and use of drugs.

STUDY

The efficacy of treatment to prevent relapses in 17 patients with AP attributed to HTG was investigated in the current prospective study. The mean follow-up period of patients was 42 months. Hypertriglyceridemia-induced AP comprised 6.9% of all patients with AP (n = 246) hospitalized in our clinic during the study (6 years).

RESULTS

Causative conditions of HTG-induced AP were familial HTG in eight patients, HTG caused by uncontrolled diabetes mellitus in five, HTG aggravated by drugs in two (one by tamoxifen and one by fluvastatin), familial hyperchylomicronemia (HCM) in one, and lipemia of pregnancy in one. During the acute phase of pancreatitis, patients underwent standard treatment. Thereafter, HTG was efficiently controlled with high dosages of fibrates or a fibrate plus acipimox, except for the patient with HCM, who was on a specific diet (the only source of fat was a special oil consisting of medium chain triglyceride) and taking a high dosage of acipimox. One of the patients died during the acute phase of pancreatitis with acute respiratory distress syndrome. During follow-up, maintenance treatment was successful and only one patient relapsed, because he discontinued diet and drug treatment.

CONCLUSION

Appropriate diet and drug treatment, including dose titration, of severe HTG is very effective in preventing relapses of HTG-induced AP.

Serum triglycerides, the liver and the pancreas

Massive hypertriglyceridaemia associated with fatty liver and abdominal pain or frank pancreatitis (the chylomicronaemia syndrome) is uncommon, but clinically important and under-recognized. It may arise as a result of severe genetic defects in lipolysis or, more commonly, from a moderate primary hypertriglyceridaemia that is exacerbated by a secondary cause. The latter include several drugs, among which the protease inhibitors, used for the treatment of human immunodeficiency virus infection, are increasingly apparent. In the acute situation plasma exchange, fat-free parenteral nutrition and acute insulin treatment, even in nondiabetic persons, may be valuable. A potentially major advance in prophylaxis is the use of high-dose antioxidant therapy, which has been shown to reduce attacks of pancreatitis even in the absence of a reduction in serum triglycerides. Asymptomatic patients with abnormal liver function tests are common in the lipid clinic, and can be a difficult group in which to make management decisions. Among those who are not taking excessive amounts of alcohol, many will have nonalcoholic steatohepatitis. The care of these patients is discussed, but there remains considerable uncertainty regarding their optimum management and prognosis.

Esterification of free fatty acids in adipocytes: a comparison between octanoate and oleate

Medium-chain triacylglycerols (MCT) are present in milk, coconut oil and other foods, and are used therapeutically in special diets for certain disorders of lipid and glucose utilization. Recently, it has become apparent that MCT are not only oxidized in the liver, but are also present in lymph and fat tissue, particularly after chronic treatment. To evaluate the influence of MCT on metabolism in fat cells, we compared incorporation of octanoate and oleate into cellular triacylglycerols of 3T3-L1 adipocytes as well as their effects on preadipocyte differentiation. We found that less octanoate than oleate was stored and that more octanoate than oleate was oxidized. Octanoate was esterified to a greater extent at the sn-1,3 position of glyceryl carbons than at the sn-2 position, whereas the opposite was true for oleate. Glycerol release from fat cells pre-treated with octanoate was also greater than from cells pre-treated with oleate, presumably related to the preferential release of octanoate from the sn-1,3 position. Octanoate was not incorporated into lipids in undifferentiated cells and did not induce differentiation in these cells, whereas oleate was readily stored and actually induced differentiation. Incorporation of octanoate into lipids increased as cells differentiated, but reached a maximum of about 10% of the total stored fatty acids. If these effects in vitro also occur in vivo, substitution of octanoate for oleate or other long-chain fatty acids could have the beneficial effect of diminishing fat-cell number and lipid content.

Dietary medium-chain triacylglycerol prevents the postprandial rise of plasma triacylglycerols but induces hypercholesterolemia in primary hypertriglyceridemic subjects

BACKGROUND

Previous studies showed divergent results concerning the influence of medium-chain triacylglycerol (MCT) on lipoprotein metabolism.

OBJECTIVE

The objective of this study was to compare the effects of MCT and corn oil on plasma lipids in primary hypertriglyceridemic patients.

DESIGN

Ten subjects ate different proportions of corn oil and MCT for 12 wk. The subjects first ate a low-fat diet for 2 wk and during the next 4 wk, corn oil was added as the sole source of fat. Thereafter, for 2-wk periods, the subjects were sequentially fed corn oil and MCT mixed in the following proportions: 3:1, 1:1, and 0:1. Fasting plasma total cholesterol, triacylglycerol, and HDL-cholesterol concentrations were measured at the end of each period. At the end of the 100%-corn oil and of the 100%-MCT periods, subjects were fed a test meal containing the respective oil (40 g fat/m(2) body surface area) and total cholesterol and triacylglycerols were measured at 2-h intervals over 8 h; fasting lipoprotein composition was also measured.

RESULTS

Compared with corn oil, MCT was associated with a higher mean (+/-SD) fasting total cholesterol concentration (6.39 +/- 1.14 compared with 5.51 +/- 0.98 mmol/L, respectively; P < 0. 05); non-HDL-cholesterol concentrations were also higher with MCT (5. 36 +/- 1.11 mmol/L) than with corn oil (4.51 +/- 0.92 mmol/L; P < 0. 005). In response to the liquid test meal, plasma total cholesterol did not change with either diet but triacylglycerols increased with the 100%-corn oil diet.

CONCLUSIONS

MCT prevents the risk of pancreatitis due to postprandial hypertriglyceridemia but has the inconvenience of raising total cholesterol concentrations in primary hypertriglyceridemic subjects.

Role of protein kinase C in the translational regulation of lipoprotein lipase in adipocytes

The hypertriglyceridemia of diabetes is accompanied by decreased lipoprotein lipase (LPL) activity in adipocytes. Although the mechanism for decreased LPL is not known, elevated glucose is known to increase diacylglycerol, which activates protein kinase C (PKC). To determine whether PKC is involved in the regulation of LPL, we studied the effect of 12-O-tetradecanoyl phorbol 13-acetate (TPA) on adipocytes. LPL activity was inhibited when TPA was added to cultures of 3T3-F442A and rat primary adipocytes. The inhibitory effect of TPA on LPL activity was observed after 6 h of treatment, and was observed at a concentration of 6 nM. 100 nM TPA yielded maximal (80%) inhibition of LPL. No stimulation of LPL occurred after short term addition of TPA to cultures. To determine whether TPA treatment of adipocytes decreased LPL synthesis, cells were labeled with [35S]methionine and LPL protein was immunoprecipitated. LPL synthetic rate decreased after 6 h of TPA treatment. Western blot analysis of cell lysates indicated a decrease in LPL mass after TPA treatment. Despite this decrease in LPL synthesis, there was no change in LPL mRNA in the TPA-treated cells. Long term treatment of cells with TPA is known to down-regulate PKC. To assess the involvement of the different PKC isoforms, Western blotting was performed. TPA treatment of 3T3-F442A adipocytes decreased PKC alpha, beta, delta, and epsilon isoforms, whereas PKC lambda, theta, zeta, micro, iota, and gamma remained unchanged or decreased minimally. To directly assess the effect of PKC inhibition, PKC inhibitors (calphostin C and staurosporine) were added to cultures. The PKC inhibitors inhibited LPL activity rapidly (within 60 min). Thus, activation of PKC did not increase LPL, but inhibition of PKC resulted in decreased LPL synthesis by inhibition of translation, indicating a constitutive role of PKC in LPL gene expression.

The familial chylomicronemia syndrome

The chylomicronemia syndrome is a disorder characterized by severe hypertriglyceridemia and fasting chylomicronemia. Genetic causes of the syndrome are rare and include deficiency of lipoprotein lipase (LPL), apolipoprotein C-II, and familial inhibitor of LPL. Patients with familial forms of hypertriglyceridemia in combination with secondary acquired disorders account for most individuals presenting with chylomicronemia. The clinical manifestations--lipid and other biochemical abnormalities--as well as treatment options for chylomicronemic patients are discussed.