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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pathogenesis of type 2 diabetes is complex, with two distinct mechanisms: insulin resistance (decrease of insulin action on peripheral tissues) and insulin deficiency (impaired insulin secretion by pancreatic beta-cells). These abnormalities are due to genetic and environmental factors. Type 2 diabetes is a heterogeneous disease: besides the common form with obesity, monogenic forms (such as MODY) exist. Knowledge of these forms has permit a better understanding of the genetic factors involved in diabetes, and of their relationship with insulin resistance. In this review, we discuss the main data available on genetics of type 2 diabetes, as well as the various research approaches. Today, the genetic determinism of functional abnormalities of pancreatic beta-cell is no longer discussed. However, it is also clearly established that acquired metabolic factors may contribute to pancreatic beta-cell failure. Hyperglycaemia, even moderate, induces a reduced insulin biosynthesis potential (glucotoxicity), and the increased free fatty acid flux accelerates pancreatic beta-cell apoptosis (lipotoxicity). The role of these metabolic abnormalities in the development of type 2 diabetes is briefly described.
Diabetes Metab 2002 Dec
PMID:[Physiological basis of insulin secretion abnormalities]. 1270 60

We review the progress in testing the thrifty phenotype hypothesis. Many human epidemiological studies both by ourselves and others have confirmed and extended the original observations on which the hypothesis was based. We are not aware of any contradictory findings and we emphasise the strength of the association between birth weight and the subsequent development of the metabolic syndrome. We have worked extensively experimentally to test the hypothesis in a rat model in which pregnant and/or lactating dams are fed a diet moderately restricted in proteins. The range of programming effects that we have discovered in this example of fetal and early postnatal growth restriction is listed and includes changes in hormone receptors, signalling molecules and regulatory enzymes. We have shown the model to develop diabetes, the metabolic syndrome and signs of premature renal failure. We summarise these and other similarities between the phenotype of this model and human Type 2 diabetes and the metabolic syndrome. The number of insults during early development which can lead to a similar outcome is discussed and the suggestion is made that the early life response to stress is limited in its flexibility with outcomes including ageing and decreased longevity. Our preliminary results indicate that some MODY genes could suggest pathways whereby the changes occur and that epigenetic changes during development are involved. We conclude that the way is now clear to discover early human markers of programming by early life growth restriction and to use these to devise strategies for the prevention of Type 2 diabetes.
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PMID:For debate: Fetal and early postnatal growth restriction lead to diabetes, the metabolic syndrome and renal failure. 1523 71

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.
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PMID:[MODY in clinical practice. When and why to consider it?]. 1291 54

In Hong Kong, the prevalence of diabetes is estimated to be 2% in the young population. In the diabetic population, 30% of patients have diagnosis before the age of 40 years. Besides, 30% of young diabetic patients have varying degrees of albuminuria. Mutations in the gene encoding the hepatocyte nuclear factor (HNF)-1beta are associated with a subtype of maturity-onset diabetes of the young (MODY 5) characterized by urogenital abnormalities. We examined 74 unrelated Chinese subjects with young-onset diabetes complicated by nephropathy for variants in this gene. The HNF-1beta gene was screened by direct sequencing and the functional properties of wild-type and mutant proteins were analyzed by transactivation analysis.A novel variant in exon 3 (E260D) was found in one patient. Extended family analysis revealed four other siblings carrying this variant. One subject had diabetes and another had impaired glucose tolerance. Another sibling had microalbuminuria but normal glucose tolerance. Transfection studies showed insignificant differences in transactivation ability between wild-type and mutated HNF-1beta. A silent polymorphism Q378Q was identified in another unrelated subject. These results suggest genetic variants in HNF-1beta are not a common cause of young-onset diabetes or diabetic nephropathy in Chinese, but may modify disease manifestation and progression. Other potential candidate genes should be looked for to account for the high prevalence of young-onset diabetes and nephropathy in this population.
J Diabetes Complications
PMID:Genetic variants of hepatocyte nuclear factor-1beta in Chinese young-onset diabetic patients with nephropathy. 1458 83

Several lines of evidence suggest that the aetio-pathogenesis of the common form of type 2 diabetes mellitus and its intrinsically related features of impaired insulin secretion and decreased insulin sensitivity (insulin resistance) includes a strong genetic component. At present, however, little is known about the nature of this genetic component although familial clustering of the disease has been described for decades. Major break-throughs in the genetic sciences of type 2 diabetes have been identifications of insulin receptor gene mutations in syndromes of severe insulin resistance and mutations in pancreatic beta-cell genes in the monogenic sub-group of type 2 diabetes: maturity-onset-diabetes-of-the-young, MODY. Pathophysiological models of insulin resistance in skeletal muscles and impaired glucose-induced insulin secretion in the beta-cells have formed a basis for selecting candidate genes with potential influence on the development of type 2 diabetes ("diabetogenes"). This process of selecting and analyzing genes for mutations that potentially associate with either type 2 diabetes mellitus, insulin resistance or impaired insulin secretion is often described as the "candidate gene approach". The studies reported in this thesis are excerpts from an extensive strategy of genetically dissecting (mutation analysis) in: 1) patients with the common form of late-onset type 2 diabetes mellitus the pathways that transduce the insulin signals from the plasma membrane to the activation of glycogen synthesis in skeletal muscle, and in 2) patients with either late-onset type diabetes or MODY the pathways involved in normal beta-cell development and beta-cell function (insulin secretion). Twelve of the genes that encode proteins in the insulin-signalling pathway from the insulin receptor through the phosphatidylinositide-regulated kinases down to the complex of phosphatases that regulate glycogen synthesis in skeletal muscle were analyzed. We could not confirm that a Val985Met variant in the insulin receptor is associated with type 2 diabetes or that the Met326Val of the p85 alpha regulatory subunit of the phosphoinositide-3 kinase is associated with insulin resistance. We found no coding mutations (missense) in the insulin signalling protein kinases but we confirmed that the 5 bp deletion (PP1ARE) in the 3'-end of the PPP1R3 gene that encodes the glycogen-associated regulatory subunit of protein phosphatase-1 (PP1G) is associated with insulin resistance estimated as insulin mediated glucose uptake. In contrast to protein kinases in skeletal muscles the genes encoding beta-cell transcription factors (IPF-1, NeuroD1/BETA2, and Neurogenin 3) are polymorphic but we could not confirm that the Asp76Asn of IPF-1 is a susceptibility gene for late-onset type 2 diabetes. On the other hand we confirmed that the Ala45Thr variant in NeuroD1/BETA2 may represent a susceptibility gene for type 1 diabetes but none of these genes revealed any MODY-specific mutations. Also the gene encoding the ATP-regulatable potassium channels of the beta-cell (Kir6.2) is polymorphic but none of these polymorphisms associated with changes in glucose-induced insulin secretion. Reviewed in context of the existing data our studies support the candidate gene approach as a feasible method for directly either identifying or excluding any gene as a diabetes-susceptibility gene ("diabetogene").
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PMID:Candidate genes and late-onset type 2 diabetes mellitus. Susceptibility genes or common polymorphisms? 1469 50

Mutations in the hepatocyte nuclear factor-1-alpha gene cause maturity onset diabetes of the young 3 (MODY 3). Here we describe a new family affected by this disorder carrying the so far unknown mutation Pro224Ser in exon 3. First we identified a 17-year-old patient. OGTT demonstrated that insulin secretion was severely impaired: basal insulin was 3.7 uU/ml and 60 min after an oral glucose load plasma insulin peaked only threefold to 10.7 uU/ml. In addition, this patient carries the homozygous polymorphism Ile27Leu (exon1) in the hepatocyte nuclear factor-1-alpha gene that was shown to be associated with insulin resistance. So far, we have no evidence for insulin resistance in this individual patient. Additionally, two other family members carry the hepatocyte nuclear factor-1-alpha mutation Pro224Ser and the homozygous polymorphism Ile27Leu. A similar case with these two mutations in the HNF-1-alpha gene has not been described before. This data will allow to discover more patients with MODY 3.
Exp Clin Endocrinol Diabetes 2004 Feb
PMID:A new mutation in the hepatocyte nuclear factor-1-alpha gene (P224S) in a newly discovered German family with maturity-onset diabetes of the young 3 (MODY 3). Family members carry additionally the homozygous I27L amino acid polymorphism in the HNF1 alpha gene. 1503 72

Type 2 diabetes is a complex disease that arises from physiological disruptions of the body's sensitivity to insulin and ability to metabolize glucose. Multipoint linkage analyses for insulin sensitivity phenotypes were conducted in 1,280 Mexican Americans from 41 families who participated in the San Antonio Family Heart Study. A significant linkage signal (logarithm of odds [LOD] = 2.98) affecting corrected insulin response to glucose was detected on chromosome 13q between D13787 and D13S252, in the region where the MODY-4 gene has previously been mapped. Another signal on chromosome 13 was observed at D13S285 (LOD = 1.86), where the insulin receptor substrate 2 gene resides. Significant linkage (LOD = 3.09) for insulin response to glucose was found on chromosome 8 between D8S1130 and D8S1106, near the lipoprotein lipase and macrophage scavenger receptor genes. Multipoint analysis of abdominal skinfold with an LOD of 2.68 showed signals in the same region. There was also suggestive evidence for linkage of quantitative insulin sensitivity check index and fasting glucose to a previously reported location at D9S301 (LOD = 2.19). These results indicate that chromosomal locations on 8p and 13q might harbor genes that affect a variety of insulin- and glucose-related phenotypes that contribute to the observed variations in these important risk factors for diabetes in Mexican Americans.
Diabetes 2004 May
PMID:Genome-wide scans reveal quantitative trait Loci on 8p and 13q related to insulin action and glucose metabolism: the San Antonio Family Heart Study. 1511 8

Maturity-onset diabetes of the young is an autosomal dominant form of non-insulin dependent diabetes mellitus and is caused by mutations in at least six different genes. In the most common forms, i.e. MODY2 and MODY3, the glucokinase (GCK) and the hepatocyte nuclear factor (HNF)-1alpha gene is affected, respectively. We have screened the GCK gene and HNF-1alpha gene by direct sequencing in three German families with early onset type-2-diabetes, possibly MODY. Next to known polymorphisms we have identified two novel intronic insertions in GCK and a novel non-sense mutation in exon 9 (C364 X). The latter mutation has an autosomal dominant inheritance pattern. Accordingly, this novel mutation segregates with diabetes phenotype in this family.
Exp Clin Endocrinol Diabetes 2004 Jun
PMID:A novel nonsense mutation in GCK exon 9 co-segregates with diabetes phenotype. 1521 46

Glucokinase (GK) is a glycolytic key enzyme that functions as a glucose sensor in the pancreatic beta-cell, where it governs glucose-stimulated insulin secretion (GSIS). Heterozygous inactivating mutations in the glucokinase gene (GCK) cause a mild form of diabetes (maturity-onset diabetes of the young [MODY]2), and activating mutations have been associated with a mild form of familial hyperinsulinemic hypoglycemia. We describe the first case of severe persistent hyperinsulinemic hypoglycemia due to a "de novo" mutation in GCK (Y214C). A baby girl presented with hypoglycemic seizures since the first postnatal day as well as with inappropriate hyperinsulinemia. Severe hypoglycemia persisted even after treatment with diazoxide and subtotal pancreatectomy, leading to irreversible brain damage. Pancreatic histology revealed abnormally large and hyperfunctional islets. The mutation is located in the putative allosteric activator domain of the protein. Functional studies of purified recombinant glutathionyl S-transferase fusion protein of GK-Y214C showed a sixfold increase in its affinity for glucose, a lowered cooperativity, and increased kcat. The relative activity index of GK-Y214C was 130, and the threshold for GSIS predicted by mathematical modeling was 0.8 mmol/l, compared with 5 mmol/l in the wild-type enzyme. In conclusion, we have identified a de novo GCK activating mutation that causes hyperinsulinemic hypoglycemia of exceptional severity. These findings demonstrate that the range of the clinical phenotype caused by GCK mutations varies from complete insulin deficiency to extreme hyperinsulinemia.
Diabetes 2004 Aug
PMID:Severe persistent hyperinsulinemic hypoglycemia due to a de novo glucokinase mutation. 1527 2

HNF-4alpha (hepatocyte nuclear factor-4alpha) is required for tissue-specific expression of many of the hepatic, pancreatic, enteric and renal traits. Heterozygous HNF-4alpha mutants are inflicted by MODY-1 (maturity onset diabetes of the young type-1). HNF-4alpha expression is reported here to be negatively autoregulated by HNF-4alpha1 and to be activated by dominant-negative HNF-4alpha1. Deletion and chromatin immunoprecipitation analysis indicated that negative autoregulation by HNF-4alpha1 was mediated by its association with the TATA-less HNF-4alpha core promoter enriched in Sp1, but lacking DR-1 response elements. Also, negative autoregulation by HNF-4alpha1 was independent of its transactivation function, being similarly exerted by transcriptional-defective MODY-1 missense mutants of HNF-4alpha1, or under conditions of suppressing or enhancing HNF-4alpha activity by small heterodimer partner or by inhibiting histone deacetylase respectively. Negative autoregulation by HNF-4alpha1 was abrogated by overexpressed Sp1. Transcriptional suppression by HNF-4alpha1 independently of its transactivation function may extend the scope of its transcriptional activity to interference with docking of the pre-transcriptional initiation complex to TATA-less promoters.
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PMID:Negative autoregulation of HNF-4alpha gene expression by HNF-4alpha1. 1565 81


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