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K Clément

Publications and source records attributed to K Clément.

35 records · Page 2Linked to original sources
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↗
PubMed1998

A mutation in the human leptin receptor gene causes obesity and pituitary dysfunction.

The adipocyte-specific hormone leptin, the product of the obese (ob) gene, regulates adipose-tissue mass through hypothalamic effects on satiety and energy expenditure. Leptin acts through the leptin receptor, a single-transmembrane-domain receptor of the cytokine-receptor family. In rodents, homozygous mutations in genes encoding leptin or the leptin receptor cause early-onset morbid obesity, hyperphagia and reduced energy expenditure. These rodents also show hypercortisolaemia, alterations in glucose homeostasis, dyslipidaemia, and infertility due to hypogonadotropic hypogonadisms. In humans, leptin deficiency due to a mutation in the leptin gene is associated with early-onset obesity. Here we describe a homozygous mutation in the human leptin receptor gene that results in a truncated leptin receptor lacking both the transmembrane and the intracellular domains. In addition to their early-onset morbid obesity, patients homozygous for this mutation have no pubertal development and their secretion of growth hormone and thyrotropin is reduced. These results indicate that leptin is an important physiological regulator of several endocrine functions in humans.

Adult↗
PubMed1998

Leptin receptor gene in a large cohort of massively obese subjects: no indication of the fa/fa rat mutation. Detection of an intronic variant with no association with obesity.

The massive obesity caused in rodents by the disruption of the leptin-receptor signal through genetic defects at the level of either leptin (OB) or leptin receptor (OB-R) has raised the question of the relevance of these genes to morbid obesity in humans. In this study, we screened a large population of massively obese subjects for the presence of a leptin receptor mutation homologous to that of fa/fa rats, a single base substitution changing glutamine 269, a highly conserved glutamine found at position 270 in the human sequence. After polymerase chain reaction (PCR) amplification of a DNA region encompassing the end of exon 5, intron 5, and the beginning of exon 6, we performed restriction fragment length polymorphism analysis. Within the limitations of this approach where only mutations introducing restriction sites (5 of 8 possibilities) could be assessed, no evidence of mutation at the codon gln 270 was found in 343 massively obese subjects. However, a new OB-R gene variant in intron 5 was revealed by MaeII digestion of the PCR products. MaeII/hOB-R genotyping revealed no difference in the distribution of the genotypes between obese subjects and a group of 79 unrelated nonobese control subjects. In addition, no significant association between various obesity-related metabolic phenotypes and the presence of MaeII/hOB-R alleles was found. Thus, our results did not support a significant role for the MaeII/hOB-R gene variant in the development of the obese phenotype in the population we studied.

Adult↗
PubMed1997

Genetic studies of neuropeptide Y and neuropeptide Y receptors Y1 and Y5 regions in morbid obesity.

Synthesis and release of neuropeptide Y (NPY) are both regulated by leptin binding to its hypothalamic receptor mediating some of the effects of leptin on food intake. Moreover, NPY administration is a powerful stimulant of feeding behaviour. Thus, we investigated the potential implication of NPY, NPY-Y1 and -Y5 subtype receptors [rNPY-Y1/-Y5] in the development of human obesity. Two complementary genetic approaches were used: 1) linkage analyses between obesity and polymorphic markers located nearby NPY and rNPY-Y1/-Y5 genes (respectively on chromosomes 7p15.1 and 4q[31.3-32]) in 93 French Caucasian morbidly obese families; 2) single strand conformation polymorphism (SSCP) scanning of the coding region of the NPY and rNPY-Y1 genes performed in 50 unrelated obese patients ascertained on the basis of a body mass index of 27 kg/m2 or more and a family history of obesity. No evidence of linkage between morbid obesity or obesity-related quantitative traits and NPY and rNPY-Y1/ Y5 regions was found in this population. Moreover, SSCP scanning revealed no mutation in the coding region of NPY and rNPY-Y1 genes among obese subjects. These results suggest that NPY and NPY-Y1/ Y5 receptors are unlikely to be implicated in the development of human morbid obesity, at least in the French Caucasian population.

Alleles↗
PubMed1997

Association of poorly controlled diabetes with low serum leptin in morbid obesity.

OBJECTIVES: Leptin may be involved in the regulation of body weight, food intake, and energy expenditure. In view of a possible link between leptin concentrations and diabetes that has been suggested in obese rodents, we investigated the potential relationship between serum leptin concentrations and hyperglycaemia in French patients with morbid obesity. SUBJECTS: Fasting leptin concentrations were measured in 241 morbidly obese patients with various degrees of glucose tolerance in a cross-sectional study. RESULTS: Fasting serum leptin concentrations did not differ between normoglycaemia (NG, 61.5 +/- 24.0 ng/ml) and glucose intolerant morbidly obese subjects (IGT, 56.5 +/- 18.5 ng/ml) and were slightly lower in those with controlled diabetes (55.1 +/- 30.3 ng/ml, P = 0.06 when compared to NG subjects). In contrast, leptin concentrations were 30% lower in patients with poorly controlled diabetes (43.0 +/- 22.2 ng/ml, P = 0.001 vs NG subjects). Leptin concentrations were negatively correlated with fasting glucose in all groups combined (p = -0.24, P = 0.0001) and particularly in NIDDM subjects (p = 0.31, P = 0.0054). Although leptin concentrations were higher in women than in men, similar significant correlation with fasting glucose was found when females were analyzed separately. A positive correlation was found with BMI (p = 0.25, P = 0.0001) in all groups. Multivariate analysis revealed that fasting glucose was independently associated with serum leptin concentrations (F = 12.5, P = 0.0005). Sex, age, BMI, waist/hip ratio, fasting glucose and insulin, total cholesterol and triglycerides, tested in the model, explained 42% of the leptin variability in this population. CONCLUSIONS: Poorly controlled diabetes was accompanied by a significant reduction of serum leptin concentrations in morbidly obese subjects. We suggest that a relative leptin deficiency (lower than expected for the BMI) associated with insulin deficiency in this population might contribute to a vicious cycle maintaining (or even worsening) obesity itself and/or its metabolic complications.

Adult↗
PubMed1997

Genetic studies of the sulfonylurea receptor gene locus in NIDDM and in morbid obesity among French Caucasians.

The sulfonylurea receptor (SUR) is a key component in glucose-stimulated insulin secretion. Obesity and NIDDM are frequently associated and share some metabolic abnormalities, suggesting that they might also share some susceptibility genes. Thus, the SUR encoding gene is a plausible candidate for a primary pancreatic beta-cell defect and thus for hyperglycemia and weight gain. Through association and linkage studies, we have investigated the potential role of the SUR gene in families with NIDDM and in two independent sets of morbidly obese families. The exon 22 T-allele at codon 761 was more common in patients with NIDDM (7.7%) and morbid obesity (7.8%) than in control subjects (1.8%, P = 0.030 and P = 0.023, respectively). This variant was associated with morbid obesity (odds ratio 3.71, P = 0.017) and NIDDM (odds ratio 2.20, P = 0.04; association dependent on BMI). Although the frequencies for intron 24 variant were similar in all groups, morbidly obese patients homozygous for the c-allele had a more deleterious form of obesity. Sib-pair linkage studies with NIDDM in French Caucasian families gave no evidence for linkage to the SUR locus. However, in one set of the obese families, we found an indication for linkage with a SUR-linked microsatellite marker (D11S419, P = 0.0032). We conclude that in Caucasians, the SUR locus may contribute to the genetic susceptibility to NIDDM and obesity.

ATP-Binding Cassette Transporters↗
PubMed1996

Assessment of insulin sensitivity in glucokinase-deficient subjects.

The chronic hyperglycaemia of glucokinase-deficient diabetes results from a glucose-sensing defect in pancreatic beta cells and abnormal hepatic glucose phosphorylation. We have evaluated the contribution of insulin resistance to this form of chronic hyperglycaemia. Insulin sensitivity, assessed by the homeostasis model assessment (HOMA) method in 35 kindreds with glucokinase mutations, was found to be significantly decreased in 125 glucokinase-deficient subjects as compared to 141 unaffected first-degree relatives. Logistic regression analysis showed that in glucokinase-deficient subjects a decrease in insulin sensitivity was associated with deterioration of the glucose tolerance status. A euglycaemic hyperinsulinaemic clamp was performed in 14 glucokinase-deficient subjects and 12 unrelated control subjects. In six patients and six control subjects the clamp was coupled to dideutero-glucose infusion to measure glucose turnover. Average glucose infusion rates (GIR) at 1 and 5 mU.kg body weight.min-1 insulin infusion rates were significantly lower in (the glucokinase-deficient) patients than in control subjects. Although heterogeneous results were observed, in 8 out of the 14 patients GIRs throughout the experiment were lower than 1 SD below the mean of the control subjects. Hepatic glucose production at 1 mU.kg body weight-1.min-1 insulin-infusion rate was significantly higher in patients than in control subjects. In conclusion, insulin resistance correlates with the deterioration of glucose tolerance and contributes to the hyperglycaemia of glucokinase-deficient diabetes. Taken together, our results are most consistent with insulin resistance being considered secondary to the chronic hyperglycaemia and/or hypoinsulinaemia of glucokinase-deficiency. Insulin resistance might also result from interactions between the unbalanced glucose metabolism and susceptibility gene(s) to low insulin sensitivity likely to be present in this population.

Adolescent↗
PubMed1996

Clinical phenotypes, insulin secretion, and insulin sensitivity in kindreds with maternally inherited diabetes and deafness due to mitochondrial tRNALeu(UUR) gene mutation.

An A-to-G transition in the mitochondrial tRNALeu(UUR) gene at base pair 3243 has been shown to be associated with the maternally transmitted clinical phenotype of NIDDM and sensorineural hearing loss in white and Japanese pedigrees. We have detected this mutation in 25 of 50 tested members of five white French pedigrees. Affected (mutation-positive) family members presented variable clinical features, ranging from normal glucose tolerance (NGT) to insulin-requiring diabetes. The present report describes the clinical phenotypes of affected members and detailed evaluations of insulin secretion and insulin sensitivity in seven mutation-positive individuals who have a range of glucose tolerance from normal (n = 3) to impaired (n = 1) to NIDDM (n = 3). Insulin secretion was evaluated during two experimental protocols: the first involved the measurement of insulin secretory responses during intravenous glucose tolerance test, hyperglycemic clamp, and intravenous injection of arginine. The second consisted of the administration of graded and oscillatory infusions of glucose and studies to define C-peptide kinetics. This protocol was aimed at assessing two sensitive measures of beta-cell dysfunction: the priming effect of glucose on the glucose-insulin secretion rate (ISR) dose-response curve and the ability of oscillatory glucose infusion to entrain insulin secretory oscillations. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp. Evaluation of insulin secretion demonstrated a large degree of between- and within-subject variability. However, all subjects, including those with NGT, demonstrated abnormal insulin secretion on at least one of the tests. In the four subjects with normal or impaired glucose tolerance, glucose failed to prime the ISR response, entrainment of ultradian insulin secretory oscillations was abnormal, or both defects were present. The response to arginine was always preserved, including in subjects with NIDDM. Insulin resistance was observed only in the subjects with overt diabetes. In conclusion, the pathophysiological mechanisms responsible for the development of NIDDM and insulin-requiring diabetes in this syndrome are complex and might include defects in insulin production, glucose toxicity, and insulin resistance. However, our data suggest that a defect of glucose-regulated insulin secretion is an early possible primary abnormality in carriers of the mutation. This defect might result from the progressive reduction of oxidative phosphorylation and implicate the glucose-sensing mechanism of beta-cells.

Adenine↗
PubMed1996

Candidate gene approach of familial morbid obesity: linkage analysis of the glucocorticoid receptor gene.

BACKGROUND: Morbid obesity is a multifactorial disease, with a strong but almost unknown genetic component. Familial linkage studies using the candidate gene approach have been shown to be powerful tools for identifying susceptibility genes for inherited diseases. AIM OF THE STUDY: We have investigated the role of the Glucocorticoid Receptor gene (GRL) in morbid obesity. SUBJECTS: Eighty obese families were recruited through a multimedia campaign (42 families, sample 1) or from the department of nutrition of the Hotel Dieu hospital in Paris (38 families, sample 2). METHODS: A multipoint linkage analysis with markers on chromosome 5q placed the GRL gene between D5S658 and D5S436 at genetic distances of 3.5 and 5 centimorgans, respectively. Using this map, we have chosen seven polymorphic microsatellite markers located in the vicinity of the GRL gene locus for sib pair linkage analysis. In addition to the obesity status, different quantitative phenotypes associated with obesity and insulin resistance were used for analysis. RESULTS: In sample 1, the results show a tendency towards linkage between three markers (one bc/1 intragenic RFLP and two microsatellite markers) in the GRL region and obesity characterised by a BMI > 27. However, using this phenotype, we failed to replicate the results in the second set of families. When using a more precise phenotype (the individual coefficient of variation of the BMI compared to a sex and age matched French reference population (pop) defined as the Zscore (indBMI-popBMI/SD of popBMI), a tendency for linkage was found for one marker in sample 2 as well as in the whole sample. No linkage was found when using quantitative traits associated with obesity. CONCLUSION: The GRL locus does not appear to be a major locus for obesity, but we cannot exclude that this gene or gene located nearby may have some minor effects on the obese phenotype or may be involved in some subtypes of obesity. Larger cohorts of families are probably necessary to improve the power of such linkage analysis in this heterogeneous disease.

Adult↗
PubMed1996

Additive effect of A-->G (-3826) variant of the uncoupling protein gene and the Trp64Arg mutation of the beta 3-adrenergic receptor gene on weight gain in morbid obesity.

OBJECTIVE: Obesity results from an imbalance between caloric intake and energy expenditure, which is partly genetically determined. We have investigated, using a PCR-RFLP assay, the effects on weight gain of two genetic variants of the uncoupling proteins and the beta 3-adrenoceptor, two major expressed proteins of the brown adipose tissue (BAT) involved in thermo-genesis. SUBJECTS: 238 morbidly obese and 91 non obese Caucasian subjects. RESULTS: A high prevalence (27%) in French Caucasians of the A-->G change variation located in the 5' flanking domain of the UCP gene was observed with no significant difference between morbidly obese patients and non obese subjects, suggesting that UCP gene is not a major gene for obesity. However, in the population of morbidly obese subjects, the presence of the A-->G allelic variant of the UCP gene showed to be an associated factor of high weight gain during adult life (odd-ratio: 1.4, P = 0.02). Such an association was previously described for the Trp64Arg mutation of the beta 3-AR gene. Furthermore, an additive effect of these two gene variants on weight gain was observed (Odd-Ratio: 4.95, trend test: P = 0.05). The attributable risks for UCP gene and beta 3-AR gene variants were respectively: 25% and 9%. CONCLUSION: These data support the hypothesis of a possible link between energy balance, BAT and weight gain in human.

Adipose Tissue, Brown↗
PubMed1995

Genetic variation in the beta 3-adrenergic receptor and an increased capacity to gain weight in patients with morbid obesity.

BACKGROUND: The beta 3-adrenergic receptor, located mainly in adipose tissue, is involved in the regulation of lipolysis and thermogenesis. The potential relevance of this receptor to obesity in humans led us to screen obese French patients for a recently identified mutation in the gene for the receptor. METHODS: We used the polymerase chain reaction to amplify a region of the gene for the beta 3-adrenergic receptor encoding amino acid residues 27 to 110 in genomic DNA extracted from leukocytes from 185 patients with morbid obesity (body-mass index [the weight in kilograms divided by the square of the height in meters], > 40) and 94 normal subjects. A mutation resulting in the replacement of tryptophan by arginine at position 64 (Trp64Arg) was detected by an analysis of restriction-fragment-length polymorphisms with the use of the endonuclease BstNl, which discriminates between the normal and mutant sequences. RESULTS: The frequency of the Trp64Arg allele was similar in the morbidly obese patients and the normal subjects (0.08 and 0.10, respectively). However, the patients with morbid obesity who were heterozygous for the Trp64Arg mutation had an increased capacity to gain weight; the mean weight in the 14 heterozygous patients was 140 kg, as compared with 126 kg in the 171 patients without the mutation (P = 0.03). There were no homozygotes in this sample. The cumulative 25-year change in weight (from the age of 20 years) was 67 kg in the Trp64Arg heterozygotes, as compared with 51 kg in those without the mutation. The maximal weight differential (the maximal lifetime weight minus the weight at 20 years of age) in the Trp64Arg heterozygotes was 74 kg, as compared with 59 kg in the patients without the mutation (P = 0.02). CONCLUSIONS: People with the Trp64Arg mutation of the gene for the beta 3-adrenergic receptor may have an increased capacity to gain weight.

Adult↗
PubMed1994

Insulin secretory abnormalities in subjects with hyperglycemia due to glucokinase mutations.

Pancreatic beta-cell function was studied in six subjects with mutations in the enzyme glucokinase (GCK) who were found to have elevated fasting and postprandial glucose levels in comparison to six normoglycemic controls. Insulin secretion rates (ISRs) were estimated by deconvolution of peripheral C-peptide values using a two-compartment model and individual C-peptide kinetics obtained after bolus intravenous injections of biosynthetic human C-peptide. First-phase insulin secretory responses to intravenous glucose and insulin secretion rates over a 24-h period on a weight maintenance diet were not different in subjects with GCK mutations and controls. However, the dose-response curve relating glucose and ISR obtained during graded intravenous glucose infusions was shifted to the right in the subjects with GCK mutations and average ISRs over a glucose range between 5 and 9 mM were 61% lower than those in controls. In the controls, the beta cell was most sensitive to an increase in glucose at concentrations between 5.5 and 6.0 mM, whereas in the patients with GCK mutations the point of maximal responsiveness was increased to between 6.5 and 7.5 mM. Even mutations that resulted in mild impairment of in vitro enzyme activity were associated with a > 50% reduction in ISR. The responsiveness of the beta cell to glucose was increased by 45% in the subjects with mutations after a 42-h intravenous glucose infusion at a rate of 4-6 mg/kg per min. During oscillatory glucose infusion with a period of 144 min, profiles from the subjects with mutations revealed reduced spectral power at 144 min for glucose and ISR compared with controls, indicating decreased ability to entrain the beta cell with exogenous glucose. In conclusion, subjects with mutations in GCK demonstrate decreased responsiveness of the beta cell to glucose manifest by a shift in the glucose ISR dose-response curve to the right and reduced ability to entrain the ultradian oscillations of insulin secretion with exogenous glucose. These results support a key role for the enzyme GCK in determining the in vivo glucose/ISR dose-response relationships and define the alterations in beta-cell responsiveness that occur in subjects with GCK mutations.

Adolescent↗
PubMed1994

[Brief antiseptic application of iodine in neonatal intensive care units: effects on thyroid function].

BACKGROUND: Transient thyroid dysfunction with its adverse effects of diminished levels of thyroid hormone on mental development has been reported in neonates whose skin has been cleaned with iodine-containing substances. We report the results of thyroid screening in iodine-exposed neonates and controls. POPULATION AND METHODS: Thirty seven neonates admitted to an intensive care unit from 1990 to 1992 and whose medical condition required umbilical catheterization were included in the study. There were 21 neonates (six term and 15 preterm) for whom the area around the umbilicus was cleansed with iodine antiseptic and 16 controls (four term and 12 preterm) for whom the antiseptic used did not contain iodine. Levels of serum free T3 and T4, and TSH were determined by 7 days after catheterization as did urinary iodine and creatinine concentrations. RESULTS: Iodine-exposed neonates had significant high levels of TSH (P < 0.01) and low free T3 (P < 0.05); levels of free T4 were lower than in controls but not significantly. Urinary iodine excretion was significantly increased. The increase in TSH disappeared between 15 and 30 days after iodine application. CONCLUSION: Application of iodine antiseptics may cause transient thyroid dysfunction in neonates leading to propose the use of non iodinated substances with similar antibacterial efficacy.

Anti-Infective Agents, Local↗
PubMed1992

Close linkage of glucokinase locus on chromosome 7p to early-onset non-insulin-dependent diabetes mellitus.

Non-insulin-dependent diabetes mellitus (NIDDM) is a major health problem, affecting 5% of the world population. Genetic factors are important in NIDDM, but the mechanisms leading to glucose intolerance are unknown. Genetic linkage has been investigated in multigeneration families to localize, and ultimately identify, the gene(s) predisposing to NIDDM. Here we report linkage between the glucokinase locus on chromosome 7p and diabetes in 16 French families with maturity-onset diabetes of the young, a form of NIDDM characterized by monogenic autosomal dominant transmission and early age of onset. Statistical evidence of genetic heterogeneity was significant, with an estimated 45-95% of the 16 families showing linkage to glucokinase. Because glucokinase is a key enzyme of blood glucose homeostasis, these results are evidence that a gene involved in glucose metabolism could be implicated in the pathogenesis of NIDDM.

Adenosine Deaminase↗
PubMed1991

[Thyroid cancer revealed by a suppressive hot nodule].

We report the case of a 62-year old woman in euthyroidism who presented with a thyroid cancer located within a hot nodule. The nodule was partially extinctive, and the triiodothyronine test showed incomplete suppression. Fine needle cytology showed no malignant cells. Systematic lobectomy was performed, and the diagnosis of cancer was made at pathology. This rare situation does not mean that all non-toxic hot nodules must be removed, but if surgery is decided an extemporaneous histological examination is mandatory. Besides, such cases provide an additional argument in favour of surgery or treatment of toxic adenomas.

Female↗