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Biomedical subjects

G Velho

Publications and source records attributed to G Velho.

At least 19 recordsLinked to original sources
PubMed2005

Vitamin D endocrine system and the genetic susceptibility to diabetes, obesity and vascular disease. A review of evidence.

The Vitamin D endocrine system regulates multiple aspects of calcium metabolism and cellular differentiation and replication in the immune system, endocrine pancreas, liver, skeletal muscles and adipocytes. It plays an important role in glucose homeostasis, notably, in the mechanism of insulin release. Actions of vitamin D are mediated by the binding of 1, 25-(OH)2D3 to a specific cytosolic/nuclear vitamin D receptor (VDR), a member of the steroid/thyroid hormone receptor superfamily. Several frequent polymorphisms are found in the VDR gene and were reported to be associated with a variety of physiological and pathological phenotypes in many populations. In this paper, we will review the evidences suggesting associations of allelic variations in the VDR gene and phenotypes related to body weight, glucose homeostasis, diabetes and its vascular complications.

Diabetes Mellitus↗
PubMed2005

The Ala45Thr polymorphism of NEUROD1 is associated with type 1 diabetes in Brazilian women.

BACKGROUND: NEUROD1 encodes a transcription factor expressed in the endocrine pancreas, and involved in beta-cell development, function and mechanisms of apoptosis. In this study, we investigated the association of a frequent polymorphism in exon 2 of NEUROD1 (G > A; Ala45Thr) with Type 1 diabetes in Brazilian subjects. METHODS: A population/association study comprising 246 unrelated Type 1 diabetic and 275 nondiabetic white Brazilian subjects. The Ala45Thr variant was genotyped by a PCR-RFLP method. RESULTS: The frequency of the Thr allele was significantly higher in patients with Type 1 diabetes than in controls (42.3% vs 35.3%, P=0.02). Stratification by gender showed that homozygosity for the Thr allele was associated with Type 1 diabetes in women with odds ratio of 3.66 (95% C.I. 1.43-10.11, P=0.009) as compared to homozygosity for the Ala allele. This effect was not observed in men. CONCLUSIONS: We found a gender-specific association of the Ala45Thr variant of NEUROD1 with Type 1 diabetes in Brazilian women. Our results suggest that gender as well as ethnicity might modulate the association of NEUROD1 with Type 1 diabetes.

Alanine↗
PubMed2005

Cutaneous manifestations of familial amyloidotic polyneuropathy.

Familial amyloidotic polyneuropathy is an autosomal dominant amyloidosis, characterized by the systemic deposition of amyloid with a particular involvement of the peripheral nerves. The disease generally manifests as a severe sensory, motor and autonomic neuropathy. Cardiomyopathy, nephropathy, vitreous opacities and carpal tunnel syndrome may occur in a variable association with the neuropathy. Trophic dermatological lesions are frequent in the more advanced stages of the disease. We examined the skin of 142 patients. The cutaneous manifestations more frequently observed were: xerosis (81.6%), seborrheic dermatitis (21.8%), traumatic and burn lesions (19.7%), acne (18.3%), neurotrophic ulcers (14%) and onychomycosis (10.5%). Among the hepatic transplanted patients (31%), seborrheic dermatitis and acne were the most frequent diagnoses.

Adult↗
PubMed2004

The Gly482Ser polymorphism in the peroxisome proliferator-activated receptor-gamma coactivator-1 gene is associated with hypertension in type 2 diabetic men.

AIMS/HYPOTHESIS: Peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) acts as a cofactor for several nuclear hormone receptors in many tissues and organs implicated in blood pressure regulation. Here, we assessed the association between the Gly482Ser variant of PPARGC1 and the arterial hypertension frequently found in subjects with type 2 diabetes. METHODS: We studied a group of 479 men and 253 women with type 2 diabetes. Arterial hypertension was present in 70% of the men and in 73% of the women. Genotypes were examined by PCR restriction fragment length polymorphism. A logistic regression analysis was performed to assess the covariables associated with arterial hypertension. RESULTS: There was an association between Ser allele homozygosis and arterial hypertension in type 2 diabetic men (odds ratio of 2.52 vs Gly allele homozygosis; 95% CI: 1.32-5.00; p=0.0064), but not in women. The prevalence of arterial hypertension in type 2 diabetic men was 77% vs 73% vs 67% for Ser-Ser, Gly-Ser and Gly-Gly carriers respectively (p=0.021). Age, BMI, the use of insulin, and triglyceride and creatinine levels were also independently associated with arterial hypertension in this cohort. CONCLUSIONS/INTERPRETATION: We have observed a sex-specific association between the PPARGC-1 gene Gly482Ser polymorphism and arterial hypertension in type 2 diabetic men. Further studies are needed to investigate the genetic, biochemical and pathophysiological basis of this allelic association.

Amino Acid Substitution↗
PubMed2003

[MODY in clinical practice. When and why to consider it?].

It is important to consider in clinical practice the diagnosis of MODY and to characterise the MODY sub-type. Indeed, evolution, clinical consequences and treatment of these forms of diabetes will be different according to the genetic origin of MODY. The main characteristics and consequences in clinical practice of these genetic abnormalities are briefly described, with a particular emphasis on the two most frequent sub-types, MODY-2 and MODY-3, caused by mutations of the enzyme glucokinase and of the transcription factor hepatocyte nuclear factor-1 alpha (HNF-1a) respectively.

Adult↗
PubMed2002

Sulfonylurea receptor -1 (SUR1): genetic and metabolic evidences for a role in the susceptibility to type 2 diabetes mellitus.

The pancreatic B-cell ATP-sensitive potassium channel (K(ATP)) is composed of two distinct subunits, an inwardly rectifying ion channel forming the pore (Kir6.2), and a regulatory subunit, namely the sulfonylurea receptor-1 (SUR1), which binds this widely used class of insulin-secreting drugs. Mutations in the genes encoding Kir6.2 and SUR1 may result in familial persistent hyperinsulinemic hypoglycaemia of infancy, demonstrating their role in the regulation of insulin secretion. Studies in various populations with different ethnic background provided evidence that various alleles of single nucleotide polymorphisms (SNPs) in the SUR1 gene, and to a less extent in the Kir6.2 gene, confer a significantly increased risk for the development of type 2 diabetes mellitus (T2DM). Allelic variations of these SNPs were shown to modulate insulin secretion and insulin sensitivity in vivo, thus providing a pathophysiological background to explain their contribution to the genetic susceptibility to T2DM. The aim of this review is to summarise and discuss the significant results of recent literature on the implication of K(ATP), and particularly of SUR1, in the genetic and pathopysiological mechanisms of T2DM.

ATP-Binding Cassette Transporters↗
PubMed2002

Allelic variation in exon 18 of the sulfonylurea receptor 1 (SUR1) gene, insulin secretion and insulin sensitivity in nondiabetic relatives of type 2 diabetic subjects.

BACKGROUND: We have previously observed associations of the T-allele of the exon 18 variant (ACC --> ACT; Thr759Thr) of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus (T2DM). Here we assess beta-cell function and insulin sensitivity in carriers of different genotypes at this locus. METHODS: Pre-hepatic insulin secretion rates (ISR) derived by deconvolution of circulating C-peptide levels, and glucose clearance were assessed during graded infusions of intravenous glucose in CC-homozygous (n=6) and CT-heterozygous (n=6) nondiabetic relatives of CT-heterozygous type 2 diabetic subjects. RESULTS: Average ISR over the duration of the study, adjusted for sex, age, BMI and prevailing glucose levels, were lower in CT-heterozygous subjects as compared with CC-homozygous subjects (3.91 +/- 0.40 vs. 4.84 +/- 0.28 pmol/kg x min(-1); p=0.048). The correlation curves relating ISR to glucose levels were significantly different in the two groups (analyses of covariance p=0.029). Glucose clearance was similar in both groups. CONCLUSIONS: Insulin secretion rates, but not insulin sensitivity, assessed during graded infusion of glucose were mildly decreased in nondiabetic relatives of type 2 diabetic subjects, who carry the at risk T-allele of exon 18 variant of the SUR1 gene. These results suggest that the at-risk allele might have a small effect on pancreatic B-cell function and contribute to the development of T2DM in these families.

ATP-Binding Cassette Transporters↗
PubMed2001

Variations in the vitamin D-binding protein (Gc locus) and risk of type 2 diabetes mellitus in French Caucasians.

Electrophoretic variants of the vitamin D-binding protein (DBP) have been reported to be associated with type 2 diabetes mellitus (DM) or with prediabetic phenotypes in several non-Caucasian populations. Two frequent missense polymorphisms at codons 416 (Asp --> Glu) and 420 (Thr --> Lys) are the genetic basis for the 3 common electrophoretic variants of DBP (Gc1F, Gc1S, and Gc2) and the resulting circulating phenotypes (Gc1F/Gc1F, Gc1F/Gc1S, Gc1S/Gc1S, Gc1F/Gc2, Gc1S/Gc2, and Gc2/Gc2). In this study, we investigated the association of these polymorphisms with type 2 DM in French Caucasian subjects. Variations at codons 416 and 420 were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Allele frequencies at both codons did not differ in type 2 DM patients and in control subjects (Asp416: 42.4% v 46.2%, respectively, P =.33; Lys420: 25.5% v 29.0%, respectively, P =.31). Distribution of genotypes at both codons, of the haplotypes defined by the 2 codons, and of the DBP phenotypes defined by the haplotypes were also similar in diabetic and control subjects. In conclusion, our study suggests that genetic variants of the DBP gene are not associated with the susceptibility to type 2 DM in French Caucasians.

Adult↗
PubMed2001

Glucose-induced insulin hypersecretion in lipid-infused healthy subjects is associated with a decrease in plasma norepinephrine concentration and urinary excretion.

We investigated the effect of a 48 h triglyceride infusion on the subsequent insulin secretion in response to glucose in healthy men. We measured the variations in plasma concentration and urinary excretion of catecholamines as an indirect estimation of sympathetic tone. For 48 h, 20 volunteers received a triglyceride/heparin or a saline solution, separated by a 1-month interval. At time 48 h, insulin secretion in response to glucose was investigated by a single iv glucose injection (0.5 g/kg(-1)) followed by an hyperglycemic clamp (10 mg.kg(-1).min(-1), during 50 min). The triglyceride infusion resulted in a 3-fold elevation in plasma free fatty acids and an increase in insulin and C-peptide plasma concentrations (1.5- and 2.5-fold, respectively, P < 0.05), compared with saline. At time 48 h of lipid infusion, plasma norepinephrine (NE) concentration and urinary excretion levels were lowered compared with saline (plasma NE: 0.65 +/- 0.08 vs. 0.42 +/- 0.06 ng/ml, P < 0.05; urinary excretion: 800 +/- 70 vs. 620 +/- 25 nmol/24 h, P < 0.05). In response to glucose loading, insulin and C-peptide plasma concentrations were higher in lipid compared with saline infusion (plasma insulin: 600 +/- 98 vs. 310 +/- 45 pM, P < 0.05; plasma C-peptide 3.5 +/- 0.2 vs. 1.7 +/- 0.2 nM, P < 0.05). In conclusion, in healthy subjects, a 48-h lipid infusion induces basal hyperinsulinemia and exaggerated insulin secretion in response to glucose which may be partly related to a decrease in sympathetic tone.

Adult↗
PubMed2001

Genetic determinants of type 2 diabetes.

Hyperglycemia of type 2 diabetes mellitus (T2DM) results from a complex interplay of genetic and environmental factors that influence a number of intermediate traits (e.g., beta-cell mass, insulin secretion, insulin action, fat distribution, obesity). The primary biochemical events leading to diabetes are still unknown in most cases. Although several monogenic forms of diabetes have been identified, T2DM seems to be a polygenic disorder in the majority of cases. T2DM is probably also multigenic, meaning that many different combinations of gene defects may exist among diabetic patients. Significant results were obtained in the identification of the genetic determinants of monogenic forms of diabetes with young age of onset. However, despite the evidence for a strong genetic background, little of the genetic risk factors for the more-common forms of polygenic T2DM are known to date. The goal of this chapter is to summarize and discuss the significant results of recent literature on the genetics of both the monogenic and polygenic forms of T2DM.

Age of Onset↗
PubMed2001

Vitamin D receptor gene polymorphisms are associated with obesity in type 2 diabetic subjects with early age of onset.

OBJECTIVE: Allelic variations in the vitamin D receptor (VDR) gene were reported to modulate insulin secretion in response to glucose. VDR was investigated as a candidate gene for type 2 diabetes mellitus (T2DM). METHOD: Four single nucleotide polymorphisms (SNPs) in intron 8 (BsmI, Tru9I, ApaI) and exon 9 (TaqI) of the VDR gene were examined in 309 unrelated French subjects with T2DM and 143 controls. RESULTS: The distribution of alleles and genotypes of the four SNPs was similar in patients and controls. However, in patients whose age at diagnosis of diabetes was < or =45 years, homozygous subjects for the T-allele of the TaqI SNP had a higher body mass index (BMI) (31.7+/-6.7 kg/m2, P=0.0058) and an increased prevalence of obesity (81%, P=0.005) with respect to heterozygous subjects (27.9+/-5.0 kg/m2; 46%) or homozygous subjects for the t-allele (27.7+/-5.0 kg/m2; 52%). Similar results were observed for homozygous subjects for the b-allele of the BsmI SNP. Logistic regression analysis demonstrated that TT homozygosity was independently associated with obesity in these subjects (odds ratio, 4.64; 95% confidence interval (CI), 1.64-14.76; P=0.0056). CONCLUSION: VDR is not a major gene for T2DM in French Caucasians. However, polymorphisms in the VDR gene are associated with the susceptibility to obesity in subjects with early-onset T2DM. The pathophysiological mechanisms of these associations remain unexplained, but they could be related to a direct effect of vitamin D in adypocyte differentiation and metabolism, or to an indirect effect by modulation of insulin secretion.

Age of Onset↗
PubMed2001

beta-cell genes and diabetes: quantitative and qualitative differences in the pathophysiology of hepatic nuclear factor-1alpha and glucokinase mutations.

Mutations in the beta-cell genes encoding the glycolytic enzyme glucokinase (GCK) and the transcription factor hepatocyte nuclear factor (HNF)-1alpha are the most common causes of maturity-onset diabetes of the young (MODY). Studying patients with mutations in these genes gives insights into the functions of these two critical beta-cell genes in humans. We studied 178 U.K. and French MODY family members, including 45 GCK mutation carriers and 40 HNF-1alpha mutation carriers. Homeostasis model assessment of fasting insulin and glucose showed reduced beta-cell function in both GCK (48% controls, P<0.0001) and HNF-1alpha (42% controls, P<0.0001). Insulin sensitivity was similar to that of control subjects in the GCK subjects (93% controls, P = 0.78) but increased in the HNF-1alpha subjects (134.5% controls, P = 0.005). The GCK patients showed a similar phenotype between and within families with mild lifelong fasting hyperglycemia (fasting plasma glucose [FPG] 5.5-9.2 mmol/l, interquartile [IQ] range 6.6-7.4), which declined slightly with age (0.017 mmol/l per year) and rarely required pharmacological treatment (17% oral hypoglycemic agents, 4% insulin). HNF-1alpha patients showed far greater variation in fasting glucose both between and within families (FPG 4.1-18.5 mmol/l, IQ range 5.45-10.4), with a marked deterioration with age (0.06 mmol/l per year), and 59% of patients required treatment with tablets or insulin. Proinsulin-to-insulin ratios are increased in HNF-1alpha subjects (29.5%) but not in GCK (18.5%) subjects. In an oral glucose tolerance test, the 0- to 120-min glucose increment was small in GCK patients (2.4+/-1.8 mmol/l) but large in HNF-1alpha patients (8.5+/-3.0 mmol/l, P< 0.0001). This comparison shows that the clear clinical differences in these two genetic subgroups of diabetes reflect the quantitative and qualitative differences in beta-cell dysfunction. The defect in GCK is a stable defect of glucose sensing, whereas the HNF-1alpha mutation causes a progressive defect that alters beta-cell insulin secretion directly rather than the sensing of glucose.

Adult↗
PubMed2000

Maternal diabetes alters birth weight in glucokinase-deficient (MODY2) kindred but has no influence on adult weight, height, insulin secretion or insulin sensitivity.

AIMS/HYPOTHESIS: Altered fetal insulin secretion caused by fetal or maternal glucokinase mutations influence birth weight. Here, we attempt to answer two additional questions: firstly, whether this variation in birth weight (from low birth weight to macrosomia) has an effect on adult height or weight. Secondly, whether maternal hyperglycaemia during fetal life has an effect on metabolic phenotypes of the adult offspring. METHODS: We studied 447 family members from 37 MODY2 kindred, divided into four groups according to the presence or absence of a glucokinase mutation in the subject (S+ or S-, respectively) and his/her mother (M+ or M-). Birth weight data were obtained from a questionnaire sent to the mothers. RESULTS: Birth weight was reduced in the presence of a fetal mutation (M-S+) and increased in the presence of a maternal mutation (M+ S-). These effects are additive as similar birth weights were observed in M+ S+ and M-S- offspring. Adult height, weight or body mass index (weight/height2) were, however, similar in the four groups of subjects. Non-diabetic adult offspring, regardless of the glycaemic status of the mothers (M+ S- or M-S-), had similar insulin secretion, insulin sensitivity, blood pressures and lipid profiles. These variables as well as the severity of hyperglycaemia were similar in adult M+ S+ and M-S+ MODY2 subjects. CONCLUSION/INTERPRETATION: Maternal environment and fetal genotypes could alter growth in utero by changing fetal insulin secretion but these effects do not result in a persistent programming in latter life.

Adolescent↗
PubMed2000

Association of a variant in exon 31 of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus in French Caucasians.

The sulfonylurea receptor (SUR1) of the pancreatic beta-cell ATP-sensitive potassium channel plays a key role in glucose-induced insulin secretion. The A-allele of a single nucleotide polymorphism (SNP) in exon 31 of the SUR1 gene (AGG-->AGA; Arg1273Arg) has previously been shown to be associated with hyperinsulinemia in nondiabetic Mexican-American subjects. Here, we have investigated the association of this SNP with type 2 diabetes mellitus (T2DM) in French Caucasian subjects. We have observed an increased frequency of the A allele (37.1% vs 27.6%, P=0.0048; odds ratio 1.54), of the AA genotype (15.7% vs 9.8%; P=0.025), and of the combined AA/AG genotypes (58.5% vs 45.5%, P=0.0098; odds ratio 1.69) in patients compared with controls. This association is stronger in the subgroup of patients with age of diagnosis of diabetes equal to or less than 45 years: A allele 43.2% (P=0.0003 compared with controls; odds ratio 1.99), AA genotype 21.4% (P=0.0032), and combined AA/AG genotypes 65.1% (P=0.0022; odds ratio 2.23). Unexpectedly, the G allele is strongly associated with arterial hypertension in obese diabetic subjects (GG vs AA odds ratio 19.97). In conclusion, we have observed an association of an SNP in exon 31 of the SUR1 gene with T2DM. These data reinforce the hypothesis that insulin secretion defects in T2DM might be at least partially related to allelic variations in the SUR1 gene.

ATP-Binding Cassette Transporters↗
PubMed2000

Identification of a novel Tru9 I polymorphism in the human vitamin D receptor gene.

We found a novel Tru9 I restriction polymorphism in intron 8 of the vitamin D receptor (VDR) gene in healthy French Caucasians. It corresponds to a substitution of A for G at nucleotide +443 bp from the end of exon 8. The allelic frequency of G and A in 151 unrelated subjects was 0.894 and 0.106, respectively. This polymorphism is located in the reverse primer binding site of primers that have been frequently used in the literature to genotype a BsmI restriction polymorphism. The presence of the Tru9I A allele may result in allele drop-out when the BsmI restriction fragment length polymorphism (RFLP) is genotyped with the original set of primers. This novel Tru9I polymorphism may be useful for analysis of the VDR gene.

Chromosomes, Human, Pair 12↗