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Biomedical subjects

P Froguel

Publications and source records attributed to P Froguel.

At least 73 records · Page 4Linked to original sources
PubMed2000

Genetic and clinical characterisation of maturity-onset diabetes of the young in Spanish families.

OBJECTIVE: To investigate the frequencies of the major maturity-onset diabetes of the young (MODY) subtypes in a panel of Spanish families and to assess phenotypic differences in patients with the different subtypes of MODY. METHODS: Forty-eight subjects from twenty families with clinical diagnosis of MODY were studied. They underwent a standardised clinical examination and a 75-g oral glucose tolerance test (OGTT) was performed. Estimations of insulin sensitivity (%S) and insulin secretion capacity (%B) were calculated by the computer-solved homeostasis model assessment (HOMA). Mutations in the coding regions of hepatocyte nuclear factor (HNF)-4alpha/MODY1, glucokinase (GCK/MODY2) and HNF-1alpha/MODY3 genes were investigated by single strand comformation polymorphism and sequencing analysis. RESULTS: Mutations in the GCK and HNF-1alpha genes were observed in 5 (25%) and 7 (35%) families respectively. Novel mutations included R385X, M238fsdelT, V226fsdelTinsAA and S418-7del11 in the GCK gene, and S121fsdelC, V133M, R159Q and V259D in the HNF-1alpha gene. No MODY1 families were found. Subjects which were neither MODY2 nor MODY3 (MODY-X) had a higher fasting glucose than subjects in the other groups. Insulin secretion capacity was similar in the three groups and the insulin sensitivity was decreased in MODY-X subjects. Glucose levels were significantly higher and insulin levels significantly lower, throughout the OGTT, in MODY3 compared with MODY2 subjects. CONCLUSIONS: Mutations in the GCK/MODY2 and HNF-1alpha/MODY3 genes account for the majority of cases in a panel of Spanish MODY families, with MODY3 being the most frequent subtype. The relative frequencies and the clinical characteristics of these MODY subtypes are in agreement with data previously reported in other European populations. MODY-X patients seem to present a heterogeneous clinical profile.

Adult↗
PubMed2000

Genetic variation in the hepatocyte nuclear factor-3beta gene (HNF3B) does not contribute to maturity-onset diabetes of the young in French Caucasians.

Mutations in genes encoding hepatocyte nuclear factor (HNF) are responsible for three of the five subtypes of maturity-onset diabetes of the young (MODY). This observation and molecular studies indicate that the HNF network is required for normal function of pancreatic beta-cells. This suggests that transcription factors involved in this complex network are candidates for genetic defects in MODY. Because the HNF-3beta gene is implicated in this network, we screened it for mutations in 21 probands of French ancestry with clinical diagnosis of MODY and early-onset type 2 diabetes. All of the five known MODY genes, HNF-4alpha, glucokinase, HNF-1alpha, HNF-1beta, and IPF1, were previously excluded as being the cause of diabetes in these families. By direct sequencing, we identified two transitions, an A-to-G at position -213 and a C-to-T at position -63 in the promoter and exon 1, respectively, of the HNF-3beta gene. A G-to-C transversion at position +32 in the intron 1 and three transitions, C-to-T at position 291, A-to-G at position 837, and G-to-A at position 1188 in the exon 3, resulting in noncoding mutations Ala97Ala, Gly279Gly, and Gln396Gln, respectively, were also identified. The allele frequencies were not significantly different between a control group and MODY probands. Familial segregation studies and linkage analysis showed that genetic variation in the HNF-3beta gene is unlikely to be the cause of early-onset type 2 diabetes in these Caucasian families.

Adult↗
PubMed2000

Soluble leptin receptor in serum of subjects with complete resistance to leptin: relation to fat mass.

Leptin resistance and obesity have been related to mutations of the leptin receptor gene in rodents and, recently, in a consanguineous family. The latter mutation results in a receptor lacking transmembrane and intracellular domains. Homozygous and heterozygous individuals with this mutation had serum leptin levels higher than expected, given their BMIs: 600, 670, and 526 ng/ml and 145, 362, 294, 240, and 212 ng/ml, respectively. Their serum leptin was fractionated by gel filtration: >80% was present as a high-molecular size complex vs. 7.5% in the nonmutated sister. Western blot analysis showed a band at 146 kDa reacting specifically with an antibody directed against the leptin receptor ectodomain. In 10 obese control subjects, as in the mutated patients, free leptin levels correlated with BMI (r = 0.70, P = 0.0011) and reflected fat mass, regardless of leptin receptor functioning. In the patients, bound leptin levels correlated with BMI (r = 0.99, P = 0.0002) and were related to the number of mutated alleles. These data demonstrate that the truncated receptor is secreted into blood and binds the majority of serum leptin, markedly increasing bound and total leptin. Free serum leptin was similarly correlated with BMI in the mutated and nonmutated obese individuals, providing evidence that the relationship between BMI and circulating free leptin is preserved in this family. This finding suggests that the leptin receptor itself may not be specifically involved in the control of leptin secretion, and it supports the concept of relative resistance to leptin in common obesity.

Adipose Tissue↗
PubMed2000

Promoter polymorphism T(-107)C of the paraoxonase PON1 gene is a risk factor for coronary heart disease in type 2 diabetic patients.

The serum enzyme paraoxonase (PON) protects LDLs from oxidative stress. We recently identified promoter polymorphisms of the PON gene that strongly affect gene expression and serum levels of the enzyme. The present study tested the hypothesis that promoter polymorphism T(-107)C could be a risk factor for vascular disease in type 2 diabetic patients by virtue of its ability to modulate serum concentrations of the antioxidant enzyme. The low-expressor genotype (TT) was associated with significantly lower serum PON concentrations, and it was over-represented in type 2 diabetic patients with coronary heart disease (CHD) (TT vs. TC+CC: odds ratio [OR] 1.64 [95% CI 1.03-2.61], P < 0.05). The association of the low-expressor genotype with an increased risk of disease was independent of other risk factors, including the coding region Q191R polymorphism (OR 2.12 [95% CI 1.19-3.70], P = 0.01). However, an interaction of the promoter polymorphism with the Q191R polymorphism, which was previously identified as an independent risk factor, was observed. The low-expressor promoter allele (-107T) associated with the high-risk 191R allele showed a lower-than-expected level of risk (OR 2.21 vs. the expected 4.76). The data are consistent with the hypothesis that low expression of the antioxidant enzyme PON increases the risk of CHD. Moreover, the promoter polymorphism appears to have a modulating effect on risk that is associated with the coding region polymorphism Q191R. This study indicates a strong genetic component to the antioxidant capacity of HDLs.

Aryldialkylphosphatase↗
PubMed2000

Mutation screening of the PPARalpha gene in type 2 diabetes associated with coronary heart disease.

The peroxisome proliferator-activated receptor alpha (PPARalpha) is a ligand-activated transcription factor belonging to the nuclear hormone receptor superfamily. PPARalpha plays a key role in lipid and glucose metabolism, inflammatory response and energy homeostasis. The aim of our study was to screen the PPARalpha gene for mutations, and to test the genetic contribution of PPARalpha in diabetes and its vascular complications. The first two non coding exons and the coding region of the PPARalpha gene were screened by single strand conformation polymorphism (SSCP) and sequencing in 74 unrelated Type 2 diabetic patients with history of coronary heart disease (CHD) (18 Caucasian and 56 Indian subjects). A total of 7 nucleotide variants were detected: two single amino acid substitutions, a silent mutation, four intron base changes. Association studies were undertaken in two populations of Type 2 diabetic patients from Pondichery and from France, to test the distribution of allelic frequencies for L162V (exon 5) and A268V (exon 7) polymorphisms. No association was found between these PPARalpha variants and diabetes or CHD. However, in the Caucasian diabetic male population with CHD, the Val162 allele carriers showed higher concentrations of total cholesterol and Apo B when compared to non-carriers (p =0.01 and p =0.005, respectively). A trend toward elevated concentrations of total cholesterol and Apo B was also observed in the Caucasian diabetic male patients without CHD carrying Val162 allele. In conclusion, it is likely that PPARalpha gene does not have a major role in diabetes and CHD in our populations, although we can not exclude a minor contribution of the PPARalpha gene to the risk of CHD associated with Type 2 diabetes through a modulation of atherogenic plasma lipids.

Amino Acid Substitution↗
PubMed2000

[Genomic approach to obesity: understanding a complex syndrome].

Obesity is a multifactoral condition. Environmental risk factors related to sedentary lifestyle and unlimited access to food apply constant pressure in subjects with a genetic make-up predisposing to gaining weight. Recent genetic studies have demonstrated a continuum among the different forms of human obesity: certain cases, mainly very severe forms beginning in childhood, are monogenic conditions transmitted by recessive inheritance, the environment simply playing a permissive role. Other more frequent mutations, such as mutation of the melanocortin receptor 4 gene, have variable expression, but inactivity is sufficient to lead to early eating disorders. The common forms of obesity are however polygenic. The extreme pressure of the modern environment over-runs the capacity of homeostatic adaptation in individuals genetically predisposed to obesity, leading to an energy imbalance favoring energy storage in the form of fat; Certain candidate genes such as decoupling proteins, adrenergic beta-3 receptor, or regions regulating the leptin gene play a minor role in the development or aggravation of obesity. Recently, "whole genome" screening in families of obese subjects has localized major obesity genes on chromosomes 2, 5, 10, 11 and 20. Their identification using techniques of positional cloning and functional genomics will help better understand the molecules determining obesity and define targets for future therapy.

Chromosome Mapping↗
PubMed2000

[Genetics of type II diabetes].

Type 2 diabetes is a multifactorial disease composed of subtypes strongly associated with environmental factors at one end of the spectrum and highly genetic forms at the other hand. The former forms have been largely elucidated in the last years by the identification of the 5 genes responsible for the autosomal dominant MODY subtype: glucokinase, and 4 transcription factors which play a key role in the development of the endocrine pancreas or in the expression of glucose metabolism genes. Apart from the monogenic forms of type 2 diabetes little is known about the nature of the genetic factors involved. Minor contributors include insulin, sulfamide receptor and some others. Genome scans of diabetic families have revealed susceptibility loci on chromosome 1q, 2p, 2q (where the gene calpain 10 was recently cloned), 3q, 12q and 20. The identification of diabetes susceptibility gene is the first step to define targets of new drugs against diabetes.

Adolescent↗
PubMed1999

Anatomy of a homeoprotein revealed by the analysis of human MODY3 mutations.

Hepatocyte nuclear factor 1alpha (HNF1alpha) is an atypical dimeric homeodomain-containing protein that is expressed in liver, intestine, stomach, kidney, and pancreas. Mutations in the HNF1alpha gene are associated with an autosomal dominant form of non-insulin-dependent diabetes mellitus called maturity-onset diabetes of the young (MODY3). More than 80 different mutations have been identified so far, many of which involve highly conserved amino acid residues among vertebrate HNF1alpha. In the present work, we investigated the molecular mechanisms by which MODY3 mutations could affect HNF1alpha function. For this purpose, we analyzed the properties of 10 mutants resulting in amino acid substitutions or protein truncation. Some mutants have a reduced protein stability, whereas others are either defective in the DNA binding or impaired in their intrinsic trans-activation potential. Three mutants, characterized by a complete loss of trans-activation, behave as dominant negatives when transfected with the wild-type protein. These data define a clear causative relationship between MODY3 mutations and functional defects in HNF1alpha trans-activation. In addition, our analysis sheds new light on the structure of a homeoprotein playing a key role in pancreatic beta cell function.

Amino Acid Substitution↗
PubMed1999

No evidence of linkage or diabetes-associated mutations in the transcription factors BETA2/NEUROD1 and PAX4 in Type II diabetes in France.

AIMS/HYPOTHESIS: The identification of mutations in hepatocyte nuclear factors-1alpha, -4alpha, -1beta and insulin promoter factor-1 in maturity onset diabetes of the young (MODY) has highlighted the role that transcription factors may have in the development of diabetes. This result has focused molecular genetic studies of diabetes on other transcription factors expressed in the pancreatic beta cell. The basic helix-loop-helix transcription factor BETA2/NEUROD1 (gene symbol, NEUROD1) and the paired box homeodomain transcription factor PAX4 (PAX4) have an important role in islet and beta-cell development. We have examined the contribution of these transcription factors to the development of MODY and late-onset Type II (non-insulin-dependent) diabetes mellitus. METHODS: Linkage studies have been done in MODY families reported to have no mutations in the five known MODY genes and in affected sibling pairs from families with late-onset Type II diabetes. Mutation screening of the coding regions of both genes was also realised by SSCP followed by sequencing in MODY patients and in probands with late-onset Type II diabetes. RESULTS: There was no evidence of linkage with the markers for NEUROD1 and PAX4 either with MODY or late-onset Type II diabetes. Mutation screening showed single nucleotide polymorphisms, several of which resulted in amino acid substitutions: NEUROD1, Ala45Thr; PAX4, Pro321His and Pro334Ala. These amino acid sequence variants were not associated with Type II diabetes. CONCLUSION/INTERPRETATION: Our results indicate that NEUROD1 and PAX4 are not a common cause of either MODY or late-onset Type II diabetes in the French Caucasian population.

Basic Helix-Loop-Helix Proteins↗
PubMed1999

Prevalence of macular pattern dystrophy in maternally inherited diabetes and deafness. GEDIAM Group.

OBJECTIVE: To evaluate the prevalence of macular pattern dystrophy (MPD) in maternally inherited diabetes and deafness (MIDD), a new subtype of diabetes mellitus that cosegregates with a mutation of mitochondrial DNA (i.e., the substitution of guanine for adenine at position 3243 of leucine transfer RNA) and to report the clinical characteristics of MPD. DESIGN: Prospective cohort study. PARTICIPANTS: Forty-six patients from 29 families with an adenine-to-guanine mutation of mitochondrial DNA were recruited from a French collaborative multicenter study. Thirty-five patients had MIDD, 8 were asymptomatic children of MIDD patients, and 3 had MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes). The 33 MIDD patients with diabetes were matched for diabetes duration and gender with 33 patients with "common" type-2 diabetes to compare the prevalence of diabetic retinopathy (DR) in both series. METHODS: All patients had a full ophthalmologic examination and fundus photographs. MAIN OUTCOME MEASURES: The presence and severity of MPD and DR were assessed in each patient. RESULTS: Thirty MIDD patients (85.7%) of 35 exhibited bilateral MPD characterized by linear pigmentation surrounding the macula and optic disc. In 24 of these 30 patients, visual acuity was 20/25 or more in both eyes. The prevalence of DR was 6% in MIDD patients with diabetes versus 15% for patients with common type-2 diabetes (a difference that was not significant, P = 0.23). The fundus of each of the eight asymptomatic children was normal. MPD was present in one of the three cases of MELAS. CONCLUSION: The prevalence of MPD in MIDD is high. Its detection may be helpful for the diagnosis of this new subtype of diabetes, for which specific treatments may be proposed.

Adult↗
PubMed1999

Molecular Genetics of Maturity-onset Diabetes of the Young.

Maturity-onset diabetes of the young (MODY) is a genetically and clinically heterogeneous subtype of Type 2 diabetes characterized by early onset, autosomal dominant inheritance and primary defects in insulin secretion. To date, five proteins have been identified whose genetic absence or impairment causes MODY, the enzyme glucokinase (GCK/MODY2) and four transcription factors: hepatocyte nuclear factor 4alpha (HNF-4alpha/MODY1), HNF-1alpha/MODY3, insulin promoter factor 1 (IPF-1/MODY4) and HNF-1beta/MODY5. Additional MODY genes remain to be identified.

Journal Article↗
PubMed1999

Free fatty acids and insulin levels--relationship to leptin levels and body composition in various patient groups from South Africa.

OBJECTIVE: To investigate the relationship between leptin concentrations, various metabolic indices and body composition in six different groups. DESIGN AND MEASUREMENTS: Anthropometric measurements, fasting plasma glucose, serum insulin, C-peptide, FFA and leptin levels were performed. In the obese and diabetic subjects, body composition was analysed with bio-impedance equipment and as a 5 level CT scan. SUBJECTS: Five lipoatrophic diabetes mellitus (LDM) patients, five normal subjects (N), nine white and nine black obese women (WW, BW), and nine white and nine black diabetic women (DWW, DBW) were investigated after an overnight fast. RESULTS: In both ethnic groups there was a positive correlation between leptin and BMI (black group: r=0.8; P<0.0001, white group: r=0.7, P<0.002) and leptin and SC fat mass (black group: r=0.6; P<0.005, white group: r=0.6; P<0.004). CONCLUSIONS: Across the groups, there were positive linear correlations between leptin concentrations, BMI, SC fat mass and FFA levels. Leptin and FFA concentrations are higher and insulin levels lower in both groups of black women compared to the two groups of white women, despite a similar BMI and body fat mass. In the DBW the large increase in visceral fat mass may be indicative of a more complex relationship between compensatory insulin resistance, elevated FFA levels and leptin secretion.

Adult↗
PubMed1999

Defective mutations in the insulin promoter factor-1 (IPF-1) gene in late-onset type 2 diabetes mellitus.

Type 2 diabetes mellitus is a common disabling disease with onset in middle-aged individuals, caused by an imbalance between insulin production and action. Genetic studies point to major genetic components, but, with the exception of maturity-onset diabetes of the young (MODY), specific diabetes susceptibility genes remain to be identified. Recent studies showed that a dominant negative mutation in the insulin promoter factor-1 (IPF-1), a pancreatic beta-cell specific transcription factor, causes pancreatic agenesis and MODY. Thus, we investigated 192 French, non-MODY type 2 diabetic families for mutations in IPF-1. We identified 3 novel IPF-1 mutations, including 2 substitutions (Q59L and D76N) and an in-frame proline insertion (InsCCG243). Functional transactivation assays of these IPF-1 mutant isoforms in a beta-pancreatic tumor cell line transfected with a transcriptional reporter and IPF-1 expression plasmids demonstrate a significant inhibition of basal insulin promoter activity (stronger with the InsCCG243 mutant). We find that the InsCCG243 mutation is linked, in 2 families, to an autosomal dominant-like late-onset form of type 2 diabetes, in which insulin secretion becomes progressively impaired. The lower penetrance D76N and Q59L mutations were more prevalent and were associated with a relative risk of 12.6 for diabetes and with decreased glucose-stimulated insulin-secretion in nondiabetic subjects. We propose that IPF-1 mutations can cause MODY or apparently monogenic late-onset diabetes and that they represent a significant risk factor for type 2 diabetes in humans.

Blood Glucose↗
PubMed1999

Insulin secretion and insulin sensitivity in diabetic and non-diabetic subjects with hepatic nuclear factor-1alpha (maturity-onset diabetes of the young-3) mutations.

OBJECTIVE: To evaluate insulin secretion and sensitivity in affected (diabetes mellitus or impaired glucose tolerance; n=7) and in unaffected (normal glucose tolerance; n=3) carriers of hepatocyte nuclear factor-1alpha (maturity-onset diabetes of the young-3 (MODY3)) gene mutations. METHODS: Insulin secretion was assessed by an i.v. glucose tolerance test (IVGTT), hyperglycemic clamp and arginine test, and insulin sensitivity by an euglycemic hyperinsulinemic clamp. Results were compared with those of diabetic MODY2 (glucokinase-deficient) and control subjects. RESULTS: The amount of insulin secreted during an IVGTT was decreased in affected MODY3 subjects (46+/-24 (s.d.) pmol/kg body weight (BW)) as compared with values in MODY2 (120+/-49pmol/kg BW) and control (173+/-37pmol/kg BW; P=0.0004) subjects. The amount of insulin secreted during a 10mmol/l glucose clamp was decreased in affected MODY3 subjects (171+/-78pmol/kg BW) and MODY2 subjects (302+/-104pmol/kg BW) as compared with control subjects (770+/-199pmol/kg BW; P=0.0001). Insulin secretion in response to arginine was decreased in affected MODY3 subjects. Milder and heterogeneous defects were observed in the unaffected MODY3 subjects; the amount of insulin secreted during the hyperglycemic clamp was 40-79% of that of controls. The response to arginine was abnormally delayed. Insulin sensitivity was decreased in diabetic but not in non-diabetic MODY3 subjects. CONCLUSIONS: Beta-cell dysfunction in response to glucose and arginine is observed in affected and unaffected MODY3 subjects. The MODY3 and MODY2 subtypes present different insulin secretion profiles. Secondary insulin resistance might contribute to the chronic hyperglycemia of MODY3 patients and modulate their glucose tolerance.

Adolescent↗
PubMed1999

A sib-pair analysis study of 15 candidate genes in French families with morbid obesity: indication for linkage with islet 1 locus on chromosome 5q.

As part of an ongoing search for susceptibility genes in obese families, we performed linkage analyses in 101 French families between qualitative and quantitative traits related to morbid obesity and polymorphisms located in or near 15 candidate genes whose products are involved in body weight regulation. These included cholecystokinin A and B receptors (CCK-AR and CCK-BR), glucagon-like peptide 1 receptor (GLP-1R), the LIM/homeodomain islet-1 gene (Isl-1), the caudal-type homeodomain 3 (CDX-3), the uncoupling protein 1 (UCP-1), the beta3-adrenoceptor (beta3-AR), the fatty acid-binding protein 2 (FABP-2), the hormone-sensitive lipase (HSL), the lipoprotein lipase (LPL), the apoprotein-C2 (apo-C2), the insulin receptor substrate-1 (IRS-1), the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), tumor necrosis factor-alpha (TNF-alpha), and the liver carnitine palmitoyltransferase-1 (CPT-1). Phenotypes related to obesity such as BMI, adult life body weight gain, fasting leptin, insulin, fasting glycerol, and free fatty acids were used for nonparametric sib-pair analyses. A weak indication for linkage was obtained between the Isl-1 locus and obesity status defined by a z score over one SD of BMI (n = 226 sib pairs, pi = 0.54 +/- 0.02, P = 0.03). Moreover, a suggestive indication for linkage was found between the Isl-1 locus and BMI and leptin values (P = 0.001 and 0.0003, respectively) and leptin adjusted for BMI (P = 0.0001). Multipoint analyses for leptin trait with Isl-1 and two flanking markers (D5S418 and D5S407) showed that the logarithm of odds (LOD) score is 1.73, coinciding with the Isl-1 locus. Although marginally positive indications for linkage in subgroups of families were found with IRS-1, CPT-1, and HSL loci, our data suggested that these genes are not major contributors to obesity. Whether an obesity susceptibility gene (Isl-1 itself or another nearby gene) lies on chromosome 5q should be determined by further analyses.

Body Mass Index↗
PubMed1999

[What have we learned thanks to genetics in type II diabetes and its complications?].

Genetic and environmental factors contribute to the development of type 2 diabetes. However, type 2 diabetes appears to be an heterogeneous syndrome composed of sub-types strongly associated with environmental factors at one end of the spectrum, and highly genetic forms at the other end. Therefore, a first approach has been to differentiate the potential monogenic forms of diabetes, as a paradigm for genetic studies, such as maturity onset diabetes of the young (MODY) which is characterized by an early age of onset and autosomal dominant inheritance. Recent studies have shown mutations in four transcription factors, members of the hepatocyte nuclear factor family. Furthermore, some data suggest that non-MODY monofactorial forms of late-onset NIDDM, due to islet transcription factors defects exist. The positional cloning of type 2 diabetes susceptibility genes is in progress, and will help to understand the molecular basis of diabetes, first step to identify targets of new drugs that will provide a better care to diabetic patients.

Adolescent↗