Genome sequencing and gene-based therapies appear poised to advance the management of rare lipoprotein disorders and associated dyslipidaemias. However, in practice, underdiagnosis and undertreatment of these disorders are common, in large part due to interindividual variability in the genetic causes and phenotypic presentation of these conditions. To address these challenges, the European Atherosclerosis Society formed a task force to provide practical clinical guidance focusing on patients with extreme concentrations (either low or high) of plasma low-density lipoprotein cholesterol, triglycerides, or high-density lipoprotein cholesterol. The task force also recognises the scarcity of quality information regarding the prevalence and outcomes of these conditions. Collaborative registries are needed to improve health policy for the care of patients with rare dyslipidaemias.

Authors: Robert A Hegele, Jan Borén, Henry N Ginsberg, Marcello Arca, Maurizio Averna, Christoph J Binder et al.

Severe hypertriglyceridemia is an endocrine emergency and is associated with acute pancreatitis and hyperviscosity syndrome. We describe an infant with lipoprotein lipase deficiency with severe hypertriglyceridemia who presented with acute pancreatitis. She was managed acutely with fasting and intravenous insulin infusion, followed by low-fat diet with no pharmacological agent. Subsequent follow-up until the age of 5 years showed satisfactory lipid profile and she has normal growth and development.

Authors: Sarah W Y Poon, Karen K Y Leung and Joanna Y L Tung

Familial chylomicronaemia syndrome (FCS) is a rare, inherited disorder characterised by impaired clearance of triglyceride (TG)-rich lipoproteins from plasma, leading to severe hypertriglyceridaemia (HTG) and a markedly increased risk of acute pancreatitis. It is due to the lack of lipoprotein lipase (LPL) function, resulting from recessive loss of function mutations in the genes coding LPL or its modulators. A large overlap in the phenotype between FCS and multifactorial chylomicronaemia syndrome (MCS) contributes to the inconsistency in how patients are diagnosed and managed worldwide, whereas the incidence of acute hypertriglyceridaemic pancreatitis is more frequent in FCS. A panel of European experts provided guidance on the diagnostic strategy surrounding FCS and proposed an algorithm-based diagnosis tool for identification of these patients, which can be readily translated into practice. Features included in this FCS score comprise: severe elevation of plasma TGs (fasting TG levels >10 mmol/L [885 mg/dL] on multiple occasions), refractory to standard TG-lowering therapies, a young age at onset, the lack of secondary factors (except for pregnancy and oral oestrogens) and a history of episodes of acute pancreatitis. Considering 53 FCS patients from three cohorts and 52 MCS patients from three cohorts, the overall sensitivity of the FCS score (≥10) was 88% (95% confidence interval [CI]: 0.76, 0.97) with an overall specificity of 85% (95% CI: 0.75, 0.94). Receiver operating characteristic curve area was 0.91. Pragmatic clinical scoring, by standardising diagnosis, may help differentiate FCS from MCS, may alleviate the need for systematic genotyping in patients with severe HTG and may help identify high-priority candidates for genotyping.

Authors: Philippe Moulina  Robert Dufourb  Maurizio AvernaMarcello ArcaAngelo B. CefalùDavide Notoc  Laura D’ErasmoAlessia Di CostanzoChristophe MarçaisLuis Antonio Alvarez-Sala Walthere  Maciej Banachf  Jan Boréng  Robert Crambh  Ioanna Gouni-Bertholdi  Elizabeth HughesColin JohnsonXavier Pintól  Željko Reinerm   Jeanine Roeters van LennepHandrean SoranClaudia Stefanuttip  Erik Stroesq  Eric Bruckertr

The DNA sequences were determined for the lipoprotein lipase (LPL) gene from five unrelated Japanese patients with familial LPL deficiency. The results demonstrated that all five patients are homozygotes for distinct point mutations dispersed throughout the LPL gene. Patient 1 has a G-to-A transition at the first nucleotide of intron 2, which abolishes normal splicing. Patient 2 has a nonsense mutation in exon 3 (Tyr61—-Stop) and patient 3 in exon 8 (Trp382—-Stop). The latter mutation emphasizes the importance of the carboxy-terminal portion of the enzyme in the expression of LPL activity. Missense mutations were identified in patient 4 (Asp204—-Glu) and patient 5 (Arg243—-His) in the strictly conserved amino acids. Expression study of both mutant genes in COS-1 cells produced inactive enzymes, establishing the functional significance of the two mis-sense mutations. In these patients, postheparin plasma LPL mass was either virtually absent (patients 1 and 2) or significantly decreased (patients 3-5). To detect these mutations more easily, we developed a rapid diagnostic test for each mutation. We also determined the DNA haplotypes for patients and confirmed the occurrence of multiple mutations on the chromosomes with an identical haplotype. These results demonstrate that familial LPL deficiency is a heterogeneous genetic disease caused by a wide variety of gene mutations.

Authors: T Gotoda, N Yamada, M Kawamura, K Kozaki, N Mori, S Ishibashi, H Shimano, F Takaku, Y Yazaki and Y Furuichi

There has been great interest over the past two decades in developing gene therapies (GTs) to treat a variety of diseases; however, translating research findings into clinical treatments have proved to be a challenge. A major milestone in the development of GT has been achieved with the approval of alipogene tiparvovec (Glybera(®)) in Europe for the treatment of familial lipoprotein lipase deficiency. At this important stage with the evolution of GT into the clinic, this review will examine the safety aspects GT with adeno-associated virus (AAV) vectors. The topics that will be covered include acute reactions, immunological reactions to the AAV capsid and expressed transgene, viral biodistribution and shedding, DNA integration and carcinogenicity. These safety aspects of GT will be discussed with a focus on alipogene tiparvovec, in addition to other AAV vector GT products currently in clinical development.

Authors: Salmon F, Grosios K and Petry H

The present review summarizes the clinical development of adeno-associated viral vector (AAV)1-lipoprotein lipase (LPL)S447X gene therapy (alipogene tiparvovec) for lipoprotein lipase deficiency. Lipoprotein lipase deficiency is a rare inherited disease characterized by severe hypertriglyceridaemia, chylomicronaemia and risk of recurrent pancreatitis or other complications. AAV1-LPLS447X gene therapy is based on the rationale that by adding episomal copies of functional LPL genes into muscle cells lacking active LPL, metabolic function could be improved or restored.

Authors: Daniel Gaudet, Julie Méthot and John Kastelein

Lipoprotein lipase (LPL) deficiency is a monogenetic disorder that underlies persistently elevated triglyceride (TG) levels and consequently predisposes patients to potentially life-threatening pancreatitis.

Authors: Erik S. Stroes, Melchior C. Nierman, Janneke J. Meulenberg, Remco Franssen, Jaap Twisk, C. Pieter Henny, Mario M. Maas, Aeilko H. Zwinderman, Colin Ross, Eleonora Aronica, Katherine A. High, Marcel M. Levi, Michael R. Hayden, John J. Kastelein, and Jan Albert Kuivenhoven

Clinical characteristics.

Familial lipoprotein lipase (LPL) deficiency usually presents in childhood and is characterized by very severe hypertriglyceridemia with episodes of abdominal pain, recurrent acute pancreatitis, eruptive cutaneous xanthomata, and hepatosplenomegaly. Clearance of chylomicrons from the plasma is impaired, causing triglycerides to accumulate in plasma and the plasma to have a milky (lactescent or lipemic) appearance. Symptoms usually resolve with restriction of total dietary fat to ≤20 g/day.

Authors: John R Burnett, MB ChB, MD, PhD, FRCPA, Amanda J Hooper, PhD, and Robert A Hegele, MD, FRCPC, FACP.

Raised plasma triglycerides (TGs) and nonesterified fatty acid (NEFA) concentrations are thought to play a role in the pathogenesis of insulin-resistant diabetes. We report on two sisters with extreme hypertriglyceridemia and overt diabetes, in whom surgical normalization of TGs cured the diabetes. In all of the family members (parents, two affected sisters, ages 18 and 15 years, and an 11-year-old unaffected sister), we measured oral glucose tolerance, insulin sensitivity (by the euglycemic-hyperinsulinemic clamp technique), substrate oxidation (indirect calorimetry), endogenous glucose production (by the [6,6-2H2]glucose technique), and postheparin plasma lipoprotein lipase (LPL) activity. In addition, GC-clamped polymerase chain reaction-amplified DNA from the promoter region and the 10 coding LPL gene exons were screened for nucleotide substitution. Two silent mutations were found in the father’s exon 4 (Glu118 Glu) and in the mother’s exon 8 (Thr361 Thr), while a nonsense mutation (Ser447 Ter) was detected in the mother’s exon 9. Mutations in exons 4 and 8 were inherited by the two affected girls. At 1-2 years after the appearance of hyperchylomicronemia, both sisters developed hyperglycemia with severe insulin resistance. Because medical therapy (including high-dose insulin) failed to reduce plasma TGs or control glycemia, lipid malabsorption was surgically induced by a modified biliopancreatic diversion. Within 3 weeks of surgery, plasma TGs and NEFA and cholesterol levels were drastically lowered. Concurrently, fasting plasma glucose levels fell from 17 to 5 mmol/l (with no therapy), while insulin-stimulated glucose uptake, oxidation, and storage were all markedly improved. Throughout the observation period, plasma TG levels were closely correlated with both plasma glucose and insulin concentrations, as measured during the oral glucose tolerance test. These cases provide evidence that insulin-resistant diabetes can be caused by extremely high levels of TGs.

Authors: G Mingrone, F L Henriksen, A V Greco, L N Krogh, E Capristo, A Gastaldelli, M Castagneto, E Ferrannini,  G Gasbarrini and H Beck-Nielsen

To describe the characteristics of lipoprotein lipase (LPL)-deficient patients seen in infancy and to evaluate the safety and efficacy of severe fat restriction. LPL deficiency was demonstrated in 16 infants who presented with irritability (n = 7), lower intestinal bleeding (n = 2), pallor, anemia, or splenomegaly (n = 5), and a family history or fortuitous discovery (n = 2). All plasma samples were lactescent at presentation. Chylomicronemia responded rapidly to dietary fat restriction, and it was possible to maintain satisfactory metabolic control for a prolonged period of time. Only 1 adolescent girl had an episode of pancreatitis associated with the use of oral contraceptives. No persistent adverse effects on growth were seen. We obtained abnormal values for serum ironalkaline phosphatase, and total calcium.

Authors: Juan Carlos Feoli-Fonseca MD, Emile Lévy PhD, Muriel Godard RD, Marie Lambert MD