Effect of omega-3 fatty acid supplementation on arterial elasticity in patients with familial hypercholesterolaemia on statin therapy.

BACKGROUND AND AIMS: Increased arterial stiffness is closely linked with raised blood pressure that contributes substantially to enhanced risk of coronary heart disease in high risk individuals with familial hypercholesterolaemia (FH). Omega-3 fatty acid (ω3-FA) supplementation has been demonstrated to lower blood pressure in subjects with a high cardiovascular disease risk. Whether ω3-FA supplementation improves arterial stiffness in FH subjects, on background statin therapy, has yet to be investigated. METHOD AND RESULTS: We carried out an 8-week randomized, crossover intervention trial to test the effect of 4 g/d ω3-FA supplementation (46% eicosapentaenoic acid and 38% docosahexaenoic acid) on arterial elasticity in 20 adults with FH on optimal cholesterol-lowering therapy. Large and small artery elasticity were measured by pulse contour analysis of the radial artery. ω3-FA supplementation significantly (P < 0.05 in all) increased large artery elasticity (+9%) and reduced systolic blood pressure (-6%) and diastolic blood pressure (-6%), plasma triglycerides (-20%), apoB concentration (-8%). In contrast, ω3-FAs had no significant effect on small artery elasticity. The change in large artery elasticity was not significantly associated with changes in systolic blood pressure or plasma triglyceride concentration. CONCLUSIONS: ω3-FA supplementation improves large arterial elasticity and arterial blood pressure independent of statin therapy in adults with FH. CLINICAL TRIAL REGISTRATION: https://www.clinicaltrials.com/NCT01577056.

Quantification and genotyping of lipoprotein lipase in patients with diabetic lipaemia.

AIMS: To determine if diabetic lipaemia is caused by loss of function mutations in the lipoprotein lipase gene, LPL. METHODS: We conducted a case-control study over 2 years in two tertiary care hospitals in South Australia. Six patients with a history of diabetic lipaemia and 12 control subjects, with previous diabetic ketoacidosis and peak triglyceride concentrations < 2.4 mmol/l were included. Participants were well at the time of study investigations. RESULTS: Only one patient with lipaemia had a loss of function mutation in LPL and no functional mutations in APOC2 or GPIHBP1 were identified. The mean lipoprotein lipase concentration was lower in patients with diabetic lipaemia than in control subjects (306 vs. 484 µg/l, P = 0.04). The mean fasting C-peptide concentration was higher in patients with diabetic lipaemia than in control subjects (771 vs. 50 pmol/l; P = 0.001). CONCLUSIONS: Lipoprotein lipase deficiency in patients with a history of diabetic lipaemia was predominantly quantitative, rather than secondary to mutations in LPL, APOC2 or GPIHBP1. The majority of patients with severe hypertriglyceridaemia in diabetic ketoacidosis may have ketosis-prone Type 2, rather than Type 1, diabetes.

Familial lipoprotein lipase deficiency caused by known (G188E) and novel (W394X) LPL gene mutations.

Lipoprotein lipase (LPL) is the key enzyme in the catabolism of triglyceride-rich lipoproteins in the circulation. Familial LPL deficiency is characterized by hypertriglyceridaemia and absence of LPL activity. We report a case of LPL deficiency in a 43-year-old woman, who initially presented in childhood with chylomicronaemia syndrome. At that time, her plasma triglyceride concentration was approximately 30 mmol/L and post-heparin lipolytic activity was very low. In addition to having the known missense mutation LPL G188E, the patient was also found to have a novel nonsense mutation in exon 8, namely LPL W394X. The novel substitution in exon 8 (c.1262G > A) predicts a truncated protein product of 393 amino acids that lacks the carboxylterminal 12% of the mature LPL. Trp(394) is part of a cluster of exposed tryptophan residues in the carboxyl-terminal domain of LPL important for binding lipid substrate. Of 11 members from her three-generation family, three were heterozygotes for G188E (mean plasma triglyceride, 3.5 +/- 2.0 mmol/L), whereas six were heterozygotes for W394X (triglyceride, 4.3 +/- 1.8 mmol/L). In summary, we describe a case of familial LPL deficiency caused by compound heterozygosity for known (G188E) and novel (W394X) LPL gene mutations.

Novel mutations in abetalipoproteinaemia and homozygous familial hypobetalipoproteinaemia.

Abetalipoproteinaemia (ABL) and homozygous familial hypobetalipoproteinaemia (FHBL) are rare inherited disorders associated with low or undetectable levels of apolipoprotein B (apoB)-containing lipoproteins. Patients present with the symptoms and sequelae of fat malabsorption, including fat-soluble vitamin deficiencies. We describe two novel mutations: one an APOB gene mutation causing FHBL and the other a microsomal triglyceride transfer protein (MTP) gene mutation causing ABL. Two siblings of consanguineous parents were homozygous for an apoB mutation 4339delT causing an apoB-30.9 truncation. In another family, a boy born to consanguineous parents was homozygous for a 319 bp in-frame deletion of MTP exon 15 (c.2076-39_2303 + 52del319). All three children presented with malabsorption and liver dysfunction and had similar very low serum lipid, apoB, and fat-soluble vitamin levels. The FHBL parents had low serum lipid and apoB profiles distinguishing the disorder from the normal levels in ABL parents. Future patients presenting with FHBL or ABL should be genotyped to provide further insight into the varying clinical severity related to molecular heterogenicity in these two conditions.

A neuropsychological profile of off-diet adults with phenylketonuria.

The metabolic disorder phenylketonuria (PKU) is treated early by a low-phenylalanine diet. While this prevents global cognitive impairment, some patients still experience cognitive and neurophysiological abnormalities. Neuropsychological testing of early treated, currently off-diet, PKU patients attending an adult PKU clinic showed a reduction in the Perceptual Organization Index (POI), Processing Speed Index (PSI) from the Wechsler Adult Intelligence Scale Third Edition (WAIS-III), and Part A of the Trail Making Test for the PKU group relative to controls. Taken together, these results supported a profile of reduced information-processing speed.

Meta-analysis of neuropsychological symptoms of adolescents and adults with PKU.

Phenylketonuria (PKU; OMIM 261600) is an autosomal recessive inborn error of phenylanaline metabolism. PKU is characterized by deficient or defective phenylalanine hydroxylase activity and persistantly increased levels of the essential amino acid phenylalanine in the circulation. The present article examines current understanding of the etiology of PKU, along with a meta-analysis examining neuropsychological and intellectual presentations in continuously treated adolescents and adults. Patients with PKU differed significantly from controls on Full-Scale IQ, processing speed, attention, inhibition, and motor control. Future research utilizing an integrative approach and detailed analysis of specific cognitive domains will assist both the scientist and clinician, and ultimately the patient.

Violent behavior associated with hypocholesterolemia due to a novel APOB gene mutation.

A 26-year-old male, the index patient, presented with persecutory delusions and suicidal behavior. He had 10 paternal male relatives in two prior generations. Five of them died by violent suicide and one, of the five, also committed a double homicide. The index patient was found to be hypocholesterolemic due to being heterozygous for a novel mutation of apolipoprotein B (apoB-29.4). His mother and paternal grandmother were normocholesterolemic, whereas a surviving paternal uncle was hypocholesterolemic and heterozygous for the apoB-29.4 mutation. This indicated that the index patient's father and paternal grandfather, both of which died by violent suicide, were obligate heterozygotes for the apoB-29.4 mutation and that the index patient inherited the mutation from his paternal grandfather. The odds ratio for the association between hypocholesterolemia and violent behavior in this family, where cholesterol status was known, was 16.9 (95% confidence interval 1.1-239.3). Therefore, our results support an inheritable relationship between violent behavior and hypocholesterolemia.

Event-related potentials elicited during a visual Go-Nogo task in adults with phenylketonuria.

OBJECTIVE: The aim of the present study was to examine the nature of previously reported deficits in sustained attention and response inhibition in adults with the developmental disorder, phenylketonuria (PKU). METHODS: This study used event-related potentials (ERPs) to examine the performance of PKU adults (n=9) and a matched control group (n=9) on a visual Go-Nogo task. RESULTS: Comparison of behavioural measures between the PKU and control groups failed to reach statistical significance, yet analysis of the ERPs showed statistically significant amplitude reductions in the P1 and N1 components elicited following presentation of stimuli, and a reduction in the amplitude of the N2 component elicited following presentation of Nogo stimuli. CONCLUSIONS: These results suggest that adults with PKU, despite being continuously treated from birth, manifest subtle impairments in distinct aspects of information processing including early sensory processing of visually presented information, as well as impairments in inhibitory functions. SIGNIFICANCE: The results contribute to an understanding of the neurophysiological mechanisms that are implicated in PKU and highlight the sensitivity of ERP techniques for the identification of the loci of information processing deficits in clinical groups.

Four novel mutations in APOB causing heterozygous and homozygous familial hypobetalipoproteinemia.

Familial hypobetalipoproteinemia (FHBL) is a rare codominant disorder of lipoprotein metabolism characterized by low levels of low-density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B. Heterozygotes for FHBL have less-than-half normal LDL-cholesterol and apoB concentrations, whereas homozygotes have extremely low or undetectable LDL-cholesterol and apoB levels. These reductions in LDL-cholesterol and apoB have been suggested to provide FHBL subjects with resistance to atherosclerosis. FHBL can be caused by mutations in the APOB gene on chromosome 2. We present four novel mutations and one previously described mutation in APOB causing FHBL in five families. Immunoblotting and DNA sequencing were used to characterize the novel mutation apoB-40.3 (c.5564_5565insC) and the previously reported mutation apoB-80.5 (c.11040T>G). The apoB-6.9 (c.1018_1025del) and apoB-25.8 (c.3600T>A) mutations were identified by DNA sequence analysis, as variants shorter than apoB-31 are not detectable in plasma. A fifth mutation, the splice variant c.82+1G>A, was identified by sequencing and was found in a homozygous subject. In approximately 50% of the FHBL subjects, plasma alanine aminotransferase concentrations were mildly increased, suggestive of fatty liver. All affected FHBL subjects had low to low-normal serum vitamin E concentrations, highlighting the important and recognized relationship between lipid and vitamin E concentrations.

Critical assessment of the outcome of infrainguinal vein bypass.

OBJECTIVE: To perform a more critical assessment of infrainguinal vein bypass. SUMMARY BACKGROUND DATA: Graft patency may give an unrealistic impression of the outcome of bypass surgery. METHODS: During a 6-year period, 236 patients undergoing primary vein grafts were entered into the study. An ideal outcome required the patient to have survived 12 months with a patent graft on duplex scanning, no perioperative complication, and no further related open or endovascular surgery or admission. RESULTS: At 12 months, the secondary graft patency rate was 82%; however, only 22% of patients had an ideal outcome. At 1 year, 44 (19%) patients died, 93 (39%) required further ipsilateral and 39 (17%) contralateral intervention, and a total of 108 (46%) were readmitted. An ideal outcome was more likely in patients receiving calcium channel blockers, principally because of improved primary patency, and less likely in those with cardiac failure requiring furosemide, principally because of worse survival in these patients. CONCLUSIONS: Few patients achieve an ideal result after infrainguinal vein bypass. Outcome may be improved by the use of calcium channel blockers. Careful consideration is required before performing revascularization in patients with cardiac failure.

Clinical and biochemical features, molecular diagnosis and long-term management of a case of cerebrotendinous xanthomatosis.

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive sterol storage disease characterised clinically by juvenile bilateral cataracts, progressive neurological dysfunction, and formation of tendon xanthomata. We describe the clinical and biochemical features, molecular diagnosis and long-term management of the first reported Australasian case of CTX. Molecular analysis confirmed the diagnosis of CTX and demonstrated that the patient was homozygous for a G-->A transition in the splice donor site of intron 4 of the sterol 27-hydroxylase gene. Serum cholestanol concentrations were decreased with the HMG-CoA reductase inhibitor simvastatin alone and greater reductions were achieved after the addition of the bile acid chenodeoxycholic acid; suggesting a synergistic effect of this combination. Despite serum cholestanol concentrations remaining within the low-normal range, there has been no significant improvement in mental and physical abilities or in EEG abnormalities with 5 years of treatment. Metabolism of radiolabeled 7-ketocholesterol to aqueous soluble products was absent in CTX-derived macrophages. Consistent with this finding, plasma 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, and 7-ketocholesterol concentrations were increased in the CTX subject compared with controls.

Common and rare ABCA1 variants affecting plasma HDL cholesterol.

Mutations in ABCA1, a member of the ATP-binding cassette family, have been shown to underlie Tangier disease (TD) and familial hypoalphalipoproteinemia (FHA), which are genetic disorders that are characterized by depressed concentrations of plasma high density lipoprotein (HDL) cholesterol. An important question is whether common variants within the coding sequence of ABCA1 can affect plasma HDL cholesterol in the general population. To address this issue, we developed a screening strategy to find common ABCA1 variants. This strategy involved long-range amplification of genomic DNA by using coding sequences only, followed by deep sequencing into the introns. This method helped us to characterize a new set of amplification primers, which permitted amplification of virtually all of the coding sequence of ABCA1 and its intron-exon boundaries with a single DNA amplification program. With these new sequencing primers, we found 3 novel ABCA1 mutations: a frameshift mutation (4570insA, A1484S-->X1492), a missense mutation (A986D) in a TD family, and a missense mutation (R170C) in aboriginal subjects with FHA. We also used these sequencing primers to characterize 4 novel common amino acid variants in ABCA1, in addition to 5 novel common silent variants. We tested for association of the ABCA1 I/M823 variant with plasma HDL cholesterol in Canadian Inuit and found that M823/M823 homozygotes had significantly higher plasma HDL cholesterol compared with subjects with the other genotypes. The results provide proof of principle of the effectiveness of this approach to identify both rare and common ABCA1 genomic variants and also suggest that common amino acid variation in ABCA1 is a determinant of plasma HDL cholesterol in the general population.

Sterol 27-hydroxylase acts on 7-ketocholesterol in human atherosclerotic lesions and macrophages in culture.

27-Hydroxycholesterol (27OH) is the major oxysterol in human atherosclerotic lesions, followed by 7-ketocholesterol (7K). Whereas 7K probably originates nonenzymically, 27OH arises by the action of sterol 27-hydroxylase, a cytochrome P450 enzyme expressed at particularly high levels in the macrophage and proposed to represent an important pathway by which macrophages eliminate excess cholesterol. We hypothesized and here show that 27-hydroxylated 7-ketocholesterol (270H-7K) is present in human lesions, probably generated by the action of sterol 27-hydroxylase on 7K. Moreover, [(3)H]27OH-7K was produced by human monocyte-derived macrophages (HMDMs) supplied with [(3)H]7K but not in HMDMs from a patient with cerebrotendinous xanthomatosis (CTX) shown to have a splice-junction mutation of sterol 27-hydroxylase. Whereas [(3)H]27OH-7K was predominantly secreted into the medium, [(3)H]-27OH formed from [(3)H]-cholesterol was mostly cell-associated. The majority of supplied [(3)H]7K was metabolized beyond 27OH-7K to aqueous-soluble products (apparently bile acids derived from the sterol 27-hydroxylase pathway). Metabolism to aqueous-soluble products was ablated by a sterol 27-hydroxylase inhibitor and absent in CTX cells. Sterol 27-hydroxylase therefore appears to represent an important pathway by which macrophages eliminate not only cholesterol but also oxysterols such as 7K. The fact that 7K (and cholesterol) still accumulates in lesions and foam cells indicates that this pathway may be perturbed in atherosclerosis and affords a new opportunity for the development of therapeutic strategies to regress atherosclerotic lesions.

Acyl coenzyme A: cholesterol acyltransferase inhibition and hepatic apolipoprotein B secretion.

Acyl coenzyme A: cholesterol acyltransferase (ACAT) is postulated to play a role in hepatic and intestinal lipoprotein secretion. There is accumulating evidence, both in vitro and in vivo, that cholesterol and/or cholesteryl ester availability can regulate hepatic VLDL secretion. How ACAT inhibition regulates the assembly and secretion of apolipoprotein (apo) B containing lipoproteins within the hepatocyte has not been clearly established. ApoB kinetic studies performed in animals indicate that reduction in VLDL apoB secretion is an important mechanism whereby ACAT inhibitors decrease the plasma concentrations of these lipoproteins. However, in cultured hepatocytes, the effect of ACAT inhibition on apoB secretion has been inconsistent. Recent evidence has suggested the existence of more than one ACAT enzyme in mammals, which has culminated in the recent cloning of ACAT2. ACAT1 and ACAT2 respond differently to ACAT inhibitors of differing structures and classes. ACAT2 is present in the liver and intestine, the sites of apoB containing lipoprotein secretion and may represent the enzyme responsible for generating cholesteryl esters destined for lipoprotein assembly and secretion.