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Biomedical subjects

R A Hegele

Publications and source records attributed to R A Hegele.

At least 19 recordsLinked to original sources
PubMed2006

Analysis of a missense variant of the human N-formyl peptide receptor that is associated with agonist-independent beta-arrestin association and indices of inflammation.

Formyl-Met-Leu-Phe (fMLP) is a potent chemoattractant molecule released from both bacteria and damaged mitochondria that activates fMLP receptors (FPR) leading to neutrophil chemotaxis, degranulation and superoxide production. A common missense single nucleotide polymorphism in the human FPR1 gene at nucleotide c.32C>T results in the amino-acid substitution, p.I11T, in the FPR1 extracellular amino-terminus. The minor (c.32T) allele frequencies were 0.25, 0.27, 0.25, 0.15 and 0.14 in healthy Caucasian, African, East Indian, Chinese and Native Canadian individuals, respectively. In subjects homozygous for the p.T11 allele, we find elevated serum concentrations of C-reactive protein, increased absolute counts of blood leukocytes and neutrophils, and erythrocyte sedimentation rates. When expressed in HEK 293 and RBL-2H3 cells a substantial proportion of FPR1 p.I11T variant is retained intracellularly and agonist-independent internalization of the FPR1 p.I11T variant, but not the wild-type FPR1, is constitutively associated with beta-arrestin2-GFP in vesicles. Moreover, basal N-acetyl-D-glucosaminidase release is increased in primary neutrophils isolated from subjects either heterozygous or homozygous for the FPR1 p.T11 allele. Taken together, the data suggest an increased receptor activity and phenotypic expression of increased inflammatory indices in subjects with the p.T11 allele.

Arrestins↗
PubMed2006

Clinical and genetic associations with hypertriglyceridemic waist in a Canadian aboriginal population.

OBJECTIVES: To determine the prevalence of 'hypertriglyceridemic waist' (HTGW) in Oji-Cree, to examine its interaction with hepatic nuclear factor-1alpha (HNF1A) in association with type 2 diabetes, and to characterize its putative genetic determinants. METHOD: The presence or absence of HTGW was determined in 522 Oji-Cree subjects (223 males, 299 females), >or=18 years of age, in whom physical measurements and fasting plasma analyte concentrations were gathered, and a 75-g oral glucose tolerance test was administered, as part of a cross-sectional study. Subjects were genotyped for HNF1A codon 319, angiotensinogen (AGT) codons 174 and 235, G-protein beta3-subunit (GNB3) nucleotide 825, fatty acid-binding protein (FABP2) codon 54, nucleotides -455 and -482 of the apolipoprotein (apo) C-III (APOC3) promoter, and a 5-bp insertion/deletion polymorphism within the 3'-untranslated region of protein phosphatase 1 regulatory subunit 3 (PPP1R3). RESULTS: The unadjusted prevalence of HTGW in Oji-Cree adults was 20.5%, with more males affected than females (27.8 vs 15.1%, P=0.0004). Logistic regression analysis, adjusted for age and gender, showed type 2 diabetes was associated with both HNF1A G319S (odds ratio (OR) 4.85, 95% CI 2.45, 9.58) and HTGW (OR 4.96, 95% CI 2.49, 9.88). When the HNF1A mutation and HTGW were present in combination, the OR for type 2 diabetes was markedly increased (OR 43.2, 95% CI 12.4, 150). In women only, both GNB3 825C>T and FABP2 A54T genotypes were significantly associated with HTGW (OR 2.02, 95% CI 1.01, 4.05 and OR 1.95, 95% CI 1.01, 3.74, respectively). CONCLUSIONS: HTGW is prevalent in Oji-Cree, especially in men. The ORs for type 2 diabetes were similar ( approximately 5-fold) for subjects with either the presence of HTGW or the private HNF1A G319S mutation. These two independent risk factors acted synergistically to confer an even greater increased risk of type 2 diabetes.

Abdominal Fat↗
PubMed2005

Lessons from human mutations in PPARgamma.

Familial partial lipodystrophy (FPLD) is characterized by adipose tissue repartitioning with multiple metabolic disturbances, including insulin resistance and dyslipidemia. Classical FPLD results from mutations in LMNA encoding nuclear lamin A/C (FPLD2), but recently some families with partial lipodystrophy and normal LMNA sequence were found to have germline mutations in PPARgamma (FPLD3). For instance, all four affected subjects in a three-generation Canadian FPLD3 kindred ascertained based upon a clinical diagnosis of partial lipodystrophy were heterozygous for the PPARgamma F388L mutation, which altered a highly conserved residue within helix 8 of the predicted ligand-binding pocket of PPARgamma. The mutation was absent from normal subjects, and functional studies showed that the mutant receptor had significantly decreased basal transcriptional activity and impaired stimulation by rosiglitazone, with no evidence of a dominant-negative mechanism. Other reported FPLD3 patients with mutant PPARgamma were ascertained either directly based on a clinical diagnosis of lipodystrophy (R425C mutation), or based on insulin resistance with subsequent demonstration of lipodystrophy (V290M and P467L mutations). Compared to subjects with mutant LMNA, lipodystrophic subjects with mutant PPARgamma had less severe adipose involvement, together with more severe clinical and biochemical manifestations of insulin resistance, and more variable response to treatment with thiazolidinediones. Thus, rare natural mutations affecting PPARgamma ligand binding and/or transactivation functions cause partial lipodystrophy, with associated components that resemble the metabolic syndrome.

Adult↗
PubMed2005

Compound heterozygosity for two non-synonymous polymorphisms in NPC1L1 in a non-responder to ezetimibe.

Ezetimibe reduces plasma low-density lipoprotein (LDL) cholesterol by blocking sterol absorption in enterocytes. The NPC1L1 gene product was recently identified as the molecular target for ezetimibe, although functional details are incomplete. We used the non-response phenotype of plasma LDL cholesterol to ezetimibe treatment to ascertain individuals who might have variant NPC1L1. We found that one non-responder to ezetimibe was a compound heterozygote for two rare non-synonymous polymorphisms in NPC1L1 that were absent in normal control subjects. We also characterized other NPC1L1 polymorphisms. While there are many explanations for non-response to medications, our data suggest a possible relationship between NPC1L1 variation and ezetimibe response and further indicate that a non-response phenotype might ascertain subjects with genomic DNA variants that could help define metabolic pathways.

Adult↗
PubMed2005

Synergism between mutant HNF1A and the metabolic syndrome in Oji-Cree Type 2 diabetes.

AIMS: To determine the prevalence of the metabolic syndrome in the Sandy Lake Oji-Cree and to examine its interaction with HNF1A in association with impaired glucose tolerance and Type 2 diabetes. METHODS: Using data collected from the Sandy Lake Health and Diabetes Project (1993-1995), the presence or absence of the metabolic syndrome was determined in 515 Oji-Cree subjects, > or = 18 years of age. In the original study, fasting plasma analytes were measured, a 75-g oral glucose tolerance test was administered, and subjects were genotyped for HNF1A G319S. RESULTS: The unadjusted prevalence of the metabolic syndrome in the Oji-Cree adults was 29.9%. The adjusted odds ratio (OR) and 95% confidence interval for Type 2 diabetes among subjects who carried the HNF1A G319S mutation and had the modified metabolic syndrome (excluding hyperglycaemia) was 20.3 (6.94, 59.6). Adjusted ORs for Type 2 diabetes for subjects with either the HNF1A G319S mutation alone or the modified metabolic syndrome alone were 5.56 (2.85, 10.9) and 4.84 (2.53, 9.27), respectively. The risk of having impaired glucose tolerance was not influenced by the presence of either factor. CONCLUSIONS: The risk of Type 2 diabetes was similar (approximately five-fold increased) for subjects with either the presence of the modified metabolic syndrome or the private HNF1A G319S mutation. Interestingly, when present in combination, the two independent risk factors appeared to act synergistically to confer an even greater increased risk of Type 2 diabetes.

Adult↗
PubMed2005

An imaging study of body composition including lipodeposition pattern in a patient of familial partial lipodystrophy (Dunnigan type).

Familial Partial Lipodystrophy, Dunnigan type (FPLD), is characterised by loss of subcutaneous fat from the limbs and an excessive accumulation of fat on the neck, shoulder girdle and face. Affected individuals have insulin resistance, dyslipidaemia and early cardiovascular events. Body composition (BC) with details of adipose tissue distribution were studied by Dual-Energy X-ray Absorptiometry (DEXA) and Magnetic Resonance Imaging (MRI) ina heterozygote for the FPLD mutation LMNA R482W, and in an age, sex and body mass index (BMI) matched normal control. DEXA revealed a marked decrease in total as well as regional fat percentage in the patient compared to a normal control. Marked reductions in subcutaneous fat in the extremities with substantial lipodeposition in the nape of the neck were confirmed with. MRI. The importance of increased perinephric, retroperitoneal and intermuscular fat in the thighs found in this patient, needs to be explored vis-à-vis the pathogenesis of insulin resistance found in FPLD.

Absorptiometry, Photon↗
PubMed2004

Single nucleotide polymorphism in CTH associated with variation in plasma homocysteine concentration.

Plasma total homocysteine (tHcy) concentration, an independent risk factor of atherosclerosis, has numerous genetic and environmental determinants. While the thermolabile polymorphism in MTHFR encoding methylenetetrahydrofolate reductase is the best-studied genetic factor associated with variation in plasma tHCy, other candidate genes are being evaluated. Recently, we discovered that cystathioninuria was caused by mutations in the CTH gene encoding cystathionine gamma-lyase, an enzyme that converts cystathionine to cysteine in the trans-sulfuration pathway. We also identified a common single nucleotide polymorphism (SNP), namely c.1364G>T (S403I) in exon 12 of CTH. In the current analysis, we studied the association of genotypes of this SNP with plasma tHcy concentrations in 496 Caucasian subjects. CTH 1364T/T homozygotes had significantly higher mean plasma tHcy concentration than subjects with other genotypes, and the effect sizes of CTH and MTHFR genotypes were similar. The findings suggest that common variation in CTH may be a determinant of plasma tHcy concentrations.

Amino Acid Substitution↗
PubMed2004

Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare genetic disorder that causes premature, rapid aging shortly after birth. Recently, de novo point mutations in the Lmna gene have been found in individuals with HGPS. Lmna encodes lamin A and C, the A-type lamins, which are an important structural component of the nuclear envelope. The most common HGPS mutation is located at codon 608 (G608G). This mutation creates a cryptic splice site within exon 11, which deletes a proteolytic cleavage site within the expressed mutant lamin A. Incomplete processing of prelamin A results in nuclear lamina abnormalities that can be observed in immunofluorescent studies of HGPS cells. Mouse models, such as Lmna knockout, Zmpste24 knockout, and Lmna L530P knockin will help the study of progeria. Lmna mutations have also recently been found in patients with atypical forms of progeria. The discovery of the HGPS mutations brings the total number of diseases caused by mutant Lmna to nine, underscoring the astonishing spectrum of laminopathies. Future research into HGPS could also provide important clues about the general process of aging and aging-related diseases.

Aging↗
PubMed2003

Activation of peroxisome proliferator-activated receptor gamma and retinoid X receptor results in net depletion of cellular cholesteryl esters in macrophages exposed to oxidized lipoproteins.

OBJECTIVE: Peroxisome proliferator-activated receptor gamma (PPARgamma), a ligand-activated transcription factor, has pleiotropic effects, including regulation of macrophage differentiation and lipid homeostasis. The PPARgamma ligands, thiazolidinediones (TZDs), attenuate atherosclerosis in mice by uncertain mechanisms. The objective of this study was to determine whether activation of PPARgamma or its obligate heterodimer, retinoid X receptor (RXR), modulates macrophage foam cell formation induced by oxidized (ox) lipoproteins. METHODS AND RESULTS: Incubation of THP-1 macrophages with oxHTG-VLDL, oxREM, or oxLDL increased cellular cholesteryl ester over 6-fold. Preincubation with the TZD, ciglitazone, the RXR-specific ligand, 9-cis retinoic acid (9cRA) or the combination reduced CE mass accumulation by up to 65%. Ciglitazone and 9cRA increased CD36 mRNA (up to 4-fold); however, uptake of [125I]oxLDL was only modestly enhanced (up to 1.8-fold) becaues of a concomitant PPARgamma:RXR-induced decrease in SRAI/II activity (up to 40%). This suggested that PPARgamma:RXR activation inhibited cholesteryl ester accumulation by enhancing cholesterol efflux. Ciglitazone and 9cRA were found to increase the expression of ATP-binding cassette proteins A1 and G1, resulting in enhanced cholesterol efflux to lipoprotein-deficient serum, apoAI and HDL3. CONCLUSIONS: PPARgamma and/or RXR activation inhibit foam cell formation through enhanced cholesterol efflux despite increased oxLDL uptake. These observations explain the reduced atherosclerosis in TZD-treated mice and may extend the therapeutic implications of these ligands.

ATP Binding Cassette Transporter 1↗
PubMed2003

Relation of waist circumference and glycemic status to C-reactive protein in the Sandy Lake Oji-Cree.

OBJECTIVE: To determine the prevalence of elevated C-reactive protein (CRP) in the Sandy Lake Oji-Cree, an aboriginal community residing in the Sioux Lookout zone of Northwestern Ontario, Canada, and to determine the associations of obesity and diabetes with CRP in a community with a very high prevalence of type II diabetes. DESIGN: We surveyed 512 community members aged 18 y and older to determine the prevalence and the determinants of elevated CRP in Sandy Lake. MEASUREMENTS: Clinical variables, indices of obesity and serum concentrations of CRP, insulin, serum amyloid A (SAA) and interleukin-6 (IL-6). RESULTS: The prevalence of CRP >or=3.8 mg/l was significantly higher in women than in men (51% vs. 32%, P<0.0001). Regression analysis determined that body mass index and IL-6 were independent determinants of CRP concentration in women and waist circumference and IL-6 were independent determinants of CRP concentration in men. Diabetes was associated with elevated CRP in both sexes, but was only a moderate strong determinant in CRP concentration in multivariate regression analysis. CONCLUSIONS: The prevalence of elevated CRP in this aboriginal community is remarkably high. These data further demonstrate that the association between CRP and specific indices of obesity and metabolism vary according to gender and glycemic status.

Adolescent↗
PubMed2003

Ileal adenocarcinoma in a mild phenotype of abetalipoproteinemia.

Abetalipoproteinemia (ABL) is a rare autosomal recessive disorder that is characterized by defective assembly and secretion of plasma apolipoprotein (apo) B-containing lipoproteins. This disorder results from mutations in the MTP gene encoding the microsomal triglyceride transfer protein. We report a 58-year-old male homozygote for a missense mutation, S590I, in MTP. The patient had a lifelong history of fat malabsorption, but was only diagnosed with ABL at age 52, based upon such classic features as absence of apo B-containing lipoproteins, acanthocytosis, atypical retinitis pigmentosa and markedly depressed serum beta-carotene concentration. However, his presentation was notable not only by survival to the sixth decade of life without specific treatment, but also by the absence of neurological involvement and by normal serum vitamin E concentration. He subsequently developed adenocarcinoma of the ileum, which required ileal resection. Therefore, this missense mutation appears to be associated with a late-presenting and relatively mild ABL phenotype that lacks some classical features, particularly neuropathy, but appears to be associated with other atypical features, specifically small intestinal cancer.

Abetalipoproteinemia↗
PubMed2002

Acanthocytosis in a patient with homozygous familial hypobetalipoproteinemia due to a novel APOB splice site mutation.

We report on acanthocytosis in a 31-year-old woman with homozygous familial hypobetalipoproteinemia due to a mutation affecting the splicing of the APOB gene encoding apolipoprotein B. Treatment with fat-soluble vitamins was associated with arrest of the usually progressive neurological complications of this condition. However, the acanthocytosis - literally 'thorny' erythrocytes that result from abnormal membrane fluidity - persists despite treatment.

Acanthocytes↗
PubMed2002

Cardiomyopathy in congenital complete lipodystrophy.

Molecular genetic studies have pointed to a relationship between congenital lipodystrophy syndromes and some cardiac disorders. For instance, mutations in LMNA cause either lipodystrophy or cardiomyopathy, indicating that different mutations in the same gene can produce these clinical syndromes. The present authors describe a 10-year-old female with Berardinelli-Seip congenital complete lipodystrophy (MIM 606158) caused by homozygosity for a frameshift mutation in BSCL2. In addition to the typical attributes of complete lipodystrophy, this subject had hypertrophic cardiomyopathy diagnosed in the first year of her life; its progress has been followed with non-invasive imaging. The mechanism underlying the hypertrophic cardiomyopathy in complete lipodystrophy is unclear. It may result from a direct effect of the mutant gene or it might be secondary to the effects of hyperinsulinemia on cardiac development. The variability of the associated cardiomyopathy in patients with complete generalized lipodystrophy may be caused by differential effects of mutations in the same gene or of mutations in different genes which underlie the lipodystrophy phenotype.

Cardiomyopathies↗
PubMed2001

Premature atherosclerosis associated with monogenic insulin resistance.

BACKGROUND: The common insulin resistance syndrome, with obesity, dyslipidemia, hyperglycemia, and hypertension, is associated with increased risk of atherosclerosis. Early atherosclerosis in rare monogenic forms of insulin resistance, however, has not been extensively documented. Cardiovascular end points were thus evaluated in subjects with Dunnigan-type familial partial lipodystrophy (FPLD) due to mutations at LMNA codon 482. METHODS AND RESULTS: FPLD subjects >/=35 years old were stratified by genotype for either the LMNA R482Q or R482W mutation. Twenty-three subjects were heterozygous mutation carriers, and 17 were R482/R482 homozygous family control subjects. All LMNA mutation carriers had FPLD with insulin resistance. In addition, LMNA mutation carriers had significantly more type 2 diabetes, hypertension, and dyslipidemia than normal family control subjects. Eight LMNA mutation carriers had coronary heart disease (CHD), compared with 1 normal control subject (OR 5.9, 95% CI 1.2 to 30.2). Six LMNA mutation carriers had CHD end points before age 55 years, and 4 of these, all women, had been hospitalized for CABG surgery between the ages of 35 and 54 years. CONCLUSIONS: Rare LMNA mutations that underlie FPLD with insulin resistance and hyperinsulinemia are also associated with early CHD, notably in women. This suggests that abnormalities of the nuclear envelope can result in a phenotype that recapitulates most of the important attributes of the common insulin resistance syndrome, including accelerated cardiovascular disease. FPLD thus appears to be an appropriate human monogenic model for the common insulin resistance syndrome.

Age Distribution↗