Genotype/phenotype relationships in HNF-4alpha/MODY1: haploinsufficiency is associated with reduced apolipoprotein (AII), apolipoprotein (CIII), lipoprotein(a), and triglyceride levels.

Hepatocyte nuclear factor (HNF)-4alpha is a transcription factor that plays an important role in regulation of gene expression in pancreatic beta-cells and in the liver. Heterozygous mutations in the HNF-4alpha gene are responsible for maturity-onset diabetes of the young 1 (MODY1), which is characterized by pancreatic beta-cell-deficient insulin secretion. HNF-4alpha is a major transcriptional regulator of many genes expressed in the liver. However, no liver defect has been identified in individuals with HNF-4alpha mutations. In this study, we have identified HNF-4alpha target genes that are mainly expressed in the liver, including alpha1-antitrypsin, alpha1-antichymotrypsin, alpha-fetal protein, ceruloplasmin, IGF binding protein 1, transferrin, apolipoprotein(AI) [apo(AI)], apo(AII), apo(B), and apo(CIII). Serum levels of these proteins and Lp(a) and triglycerides were measured in 24 members of the HNF-4alpha/MODY1 RW pedigree (Q268X mutation), including 12 diabetic patients with HNF-4alpha mutations (D-HNF4+/-), 6 nondiabetic subjects with HNF-4alpha mutations (N-HNF4+/-), 6 normal relatives (N-HNF4+/+), 6 unrelated normal matched control subjects (N-HNF4+/+), and 12 matched diabetic (non-MODY1-5) patients (D-HNF4+/+). Serum levels of apo(AII), apo(CIII), lipoprotein(a) [Lp(a)], and triglyceride were significantly reduced in HNF4+/- subjects (26.9, 19.8, 12.1, and 72.1 mg/dl, respectively) compared with HNF4+/+ subjects (37.4, 26.5, 45.2, and 124.2 mg/dl, respectively) (P = 0.00001, P = 0.01, P = 0.00006, and P = 0.000003, respectively). This reduction was not found when apo(AII), apo(CIII), Lp(a), and triglyceride levels were compared in D-HNF4+/- versus N-HNF4+/- or in D-HNF4+/+ versus N-HNF4+/+ subjects, which indicates that HNF-4alpha haploinsufficiency rather than hyperglycemia is the primary cause of decreased serum protein and triglyceride concentrations. Furthermore, we determined that genetic or environmental modifiers other than HNF-4alpha do not appear to contribute to the observed decrease of HNF-4alpha-regulated serum proteins. This study demonstrates that a heterozygous HNF-4alpha mutation leads to an HNF-4alpha-dependent hepatocyte secretory defect of liver-specific proteins.

Reduced pancreatic polypeptide response to hypoglycemia and amylin response to arginine in subjects with a mutation in the HNF-4alpha/MODY1 gene.

Subjects with the Q268X mutation in the hepatocyte nuclear factor (HNF)-4alpha gene (RW pedigree/maturity-onset diabetes of the young [MODY]-1) have diminished insulin and glucagon secretory responses to arginine. To determine if pancreatic polypeptide (PP) secretion is likewise involved, we studied PP responses to insulin-induced hypoglycemia in 17 RW pedigree members: 6 nondiabetic mutation-negative [ND(-)], 4 nondiabetic mutation-positive [ND(+)], and 7 diabetic mutation-positive [D(+)]. Subjects received 0.08 U/kg body wt human regular insulin as an intravenous bolus to produce moderate self-limited hypoglycemia. PP areas under the curve (PP-AUCs) were compared among groups. With hypoglycemia, the PP-AUC was lower in the D(+) group (14,907 +/- 6,444 pg/ml, P = 0.03) and the ND(+) group (14,622 +/- 6,015 pg/ml, P = 0.04) compared with the ND(-) group (21,120 +/- 4,158 pg/ml). In addition, to determine if the beta-cell secretory defect in response to arginine involves amylin in addition to insulin secretion, we analyzed samples from 17 previously studied RW pedigree subjects. We compared the AUCs during arginine infusions for the 3 groups both at euglycemia and hyperglycemia as well as their C-peptide-to-amylin ratios. The D(+) and ND(+) groups had decreased amylin AUCs during both arginine infusions compared with the ND(-) group, but had similar C-peptide-to-amylin ratios. These results suggest that the HNF-4alpha mutation in the RW/MODY1 pedigree confers a generalized defect in islet cell function involving PP cells in addition to beta- and alpha-cells, and beta-cell impairment involving proportional deficits in insulin and amylin secretion.

Diminished insulin and glucagon secretory responses to arginine in nondiabetic subjects with a mutation in the hepatocyte nuclear factor-4alpha/MODY1 gene.

Nondiabetic subjects with the Q268X mutation in the hepatocyte nuclear factor (HNF)-4alpha/MODY1 gene have impaired glucose-induced insulin secretion. To ascertain the effects of the nonglucose secretagogue arginine on insulin and glucagon secretion in these subjects, we studied 18 members of the RW pedigree: 7 nondiabetic mutation negative (ND[-]), 7 nondiabetic mutation positive (ND[+]), and 4 diabetic mutation positive (D[+]). We gave arginine as a 5-g bolus, followed by a 25-min infusion at basal glucose concentrations, and after glucose infusion to clamp plasma glucose at approximately 200 mg/dl. The acute insulin response (AIR), the 10-60 min insulin area under the curve (AUC), and the insulin secretion rate (ISR) were compared, as were the acute glucagon response (AGR) and glucagon AUC. The ND[+] and D[+] groups had decreased insulin AUC and ISR and decreased glucose potentiation of AIR, insulin AUC, and ISR to arginine administration when compared with the ND[-] group. At basal glucose concentrations, glucagon AUC was greatest for the ND[-] group, intermediate for the ND[+] group, and lowest for the D[+] group. During the hyperglycemic clamp, there was decreased suppression of glucagon AUC for both ND[+] and D[+] groups compared with the ND[-] group. The decreased ISR to arginine in the ND[+] group compared with the ND[-] group, magnified by glucose potentiation, indicated that HNF-4alpha affects the signaling pathway for arginine-induced insulin secretion. The decrease in glucagon AUC and decreased suppression of glucagon AUC with hyperglycemia suggest that mutations in HNF-4alpha may lead to alpha-cell as well as beta-cell secretory defects or a reduction in pancreatic islet mass.

Mutations in the hepatocyte nuclear factor-1alpha gene in maturity-onset diabetes of the young (MODY3)

The disease non-insulin-dependent (type 2) diabetes mellitus (NIDDM) is characterized by abnormally high blood glucose resulting from a relative deficiency of insulin. It affects about 2% of the world's population and treatment of diabetes and its complications are an increasing health-care burden. Genetic factors are important in the aetiology of NIDDM, and linkage studies are starting to localize some of the genes that influence the development of this disorder. Maturity-onset diabetes of the young (MODY), a single-gene disorder responsible for 2-5% of NIDDM, is characterized by autosomal dominant inheritance and an age of onset of 25 years or younger. MODY genes have been localized to chromosomes 7, 12 and 20 (refs 5, 7, 8) and clinical studies indicate that mutations in these genes are associated with abnormal patterns of glucose-stimulated insulin secretion. The gene on chromosome 7 (MODY2) encodes the glycolytic enzyme glucokinases which plays a key role in generating the metabolic signal for insulin secretion and in integrating hepatic glucose uptake. Here we show that subjects with the MODY3-form of NIDDM have mutations in the gene encoding hepatocyte nuclear factor-1alpha (HNF-1alpha, which is encoded by the gene TCF1). HNF-1alpha is a transcription factor that helps in the tissue-specific regulation of the expression of several liver genes and also functions as a weak transactivator of the rat insulin-I gene.

Mutations in the hepatocyte nuclear factor-4alpha gene in maturity-onset diabetes of the young (MODY1)

The disease maturity-onset diabetes of the young (MODY) is a genetically heterogeneous monogenic form of non-insulin-dependent (type 2) diabetes mellitus (NIDDM), characterized by early onset, usually before 25 years of age and often in adolescence or childhood, and by autosomal dominant inheritance. It has been estimated that 2-5% of patients with NIDDM may have this form of diabetes mellitus. Clinical studies have shown that prediabetic MODY subjects have normal insulin sensitivity but suffer from a defect in glucose-stimulated insulin secretion, suggesting that pancreatic beta-cell dysfunction rather than insulin resistance is the primary defect in this disorder. Linkage studies have localized the genes that are mutated in MODY on human chromosomes 20 (MODY1), 7 (MODY2) and 12 (MODY3), with MODY2 and MODY3 being allelic with the genes encoding glucokinase, a key regulator of insulin secretion, and hepatocyte nuclear factor-1alpha (HNF-1alpha), a transcription factor involved in tissue-specific regulation of liver genes but also expressed in pancreatic islets, insulinoma cells and other tissues. Here we show that MODY1 is the gene encoding HNF-4alpha (gene symbol, TCF14), a member of the steroid/thyroid hormone receptor superfamily and an upstream regulator of HNF-1alpha expression.

Altered insulin secretory responses to glucose in diabetic and nondiabetic subjects with mutations in the diabetes susceptibility gene MODY3 on chromosome 12.

One form of maturity-onset diabetes of the young (MODY) results from mutations in a gene, designated MODY3, located on chromosome 12 in band q24. The present study was undertaken to define the interactions between glucose and insulin secretion rate (ISR) in subjects with mutations in MODY3. Of the 13 MODY3 subjects, six subjects with normal fasting glucose and glycosylated hemoglobin and seven overtly diabetic subjects were studied as were six nondiabetic control subjects. Each subject received graded intravenous glucose infusions on two occasions separated by a 42-h continuous intravenous glucose infusion designed to prime the beta-cell to secrete more insulin in response to glucose. ISRs were derived by deconvolution of peripheral C-peptide levels. Basal glucose levels were higher and insulin levels were lower in MODY3 subjects with diabetes compared with nondiabetic subjects or with normal healthy control subjects. In response to the graded glucose infusion, ISRs were significantly lower in the diabetic subjects over a broad range of glucose concentrations. ISRs in the nondiabetic MODY3 subjects were not significantly different from those of the control subjects at plasma glucose levels <8 mmol/l. As glucose rose above this level, however, the increase in insulin secretion in these subjects was significantly reduced. Administration of glucose by intravenous infusion for 42 h resulted in a significant increase in the amount of insulin secreted over the 5-9 mmol/l glucose concentration range in the control subjects and nondiabetic MODY3 subjects (by 38 and 35%, respectively), but no significant change was observed in the diabetic MODY3 subjects. In conclusion, in nondiabetic MODY3 subjects insulin secretion demonstrates a diminished ability to respond when blood glucose exceeds 8 mmol/l. The priming effect of glucose on insulin secretion is preserved. Thus, beta-cell dysfunction is present before the onset of overt hyperglycemia in this form of MODY. The defect in insulin secretion in the nondiabetic MODY3 subjects differs from that reported previously in nondiabetic MODY1 or mildly diabetic MODY2 subjects.

Maturity onset diabetes of the young (MODY).

MODY is a sub-type of NIDDM. It is characterized by an early age of onset and autosomal dominant mode of inheritance. These features, and the availability of large multigenerational pedigrees, make MODY useful for genetic studies of diabetes. In the large 5-generational RW pedigree, MODY is tightly linked to genetic markers on chromosome 20q. Affected subjects in this family show abnormalities of carbohydrate metabolism, varying from impaired glucose tolerance (IGT) to severe diabetes. Approximately 30% of diabetic subjects become insulin-requiring, and vascular complications occur. MODY is also linked to the glucokinase gene on chromosome 7p and many different mutations associated with MODY have been identified in this gene. MODY, due to mutations in the glucokinase gene, is a relatively mild form of diabetes with mild fasting hyperglycaemia and IGT in the majority. Clinical investigative studies indicate that the genetic or primary defect in MODY is characterized by deranged and deficient insulin secretion and not by insulin resistance. There are quantitative and qualitative differences in insulin secretory defects which differentiate subjects with MODY due to mutation in the gene on chromosome 20q from those with glucokinase mutations. These differences correlate with the severity of diabetes between these two genetic forms of MODY.

A yeast artificial chromosome-based map of the region of chromosome 20 containing the diabetes-susceptibility gene, MODY1, and a myeloid leukemia related gene.

We have generated a physical map of human chromosome bands 20q11.2-20q13.1, a region containing a gene involved in the development of one form of early-onset, non-insulin-dependent diabetes mellitus, MODY1, as well as a putative myeloid tumor suppressor gene. The yeast artificial chromosome contig consists of 71 clones onto which 71 markers, including 20 genes, 5 expressed sequence tags, 32 simple tandem repeat DNA polymorphisms, and 14 sequence-tagged sites have been ordered. This region spans about 18 Mb, which represents about 40% of the physical length of 20q. Using this physical map, we have refined the location of MODY1 to a 13-centimorgan interval (approximately equal to 7 Mb) between D20S169 and D20S176. The myeloid tumor suppressor gene was localized to an 18-centimorgan interval (approximately equal to 13 Mb) between RPN2 and D20S17. This physical map will facilitate the isolation of MODY1 and the myeloid tumor suppressor gene.

Localization of MODY3 to a 5-cM region of human chromosome 12.

Maturity-onset diabetes of the young (MODY) is a heterogeneous disorder that appears to be characterized by a primary defect in insulin secretion. Mutations in an unknown locus (MODY1) on chromosome 20 and the glucokinase gene (MODY2) on chromosome 7 can cause this form of non-insulin-dependent diabetes. Recent genetic studies have identified a third locus on chromosome 12 (MODY3) that is linked to MODY in a group of French families. We have identified three families from Denmark, Germany, and the U.S. (Michigan) showing evidence of linkage with MODY3 and a family from Japan showing suggestive evidence. Analysis of key recombinants in these families localized MODY3 to a 5-cM interval between the markers D12S86 and D12S807/D12S820.

Fructose-1,6-bisphosphatase: genetic and physical mapping to human chromosome 9q22.3 and evaluation in non-insulin-dependent diabetes mellitus.

PCR primers specific to the human liver fructose-1,6-bisphosphatase (FBP) gene were designed and used to isolate a cosmid clone. Physical mapping of the FBP cosmid by FISH, and genetic mapping of an associated GA repeat polymorphism (PIC = 0.35), located the liver FBP gene to chromosome 9q22.3 with no recombination between FBP and the index markers D9S196 (Zmax = 13.2), D9S280 (Zmax = 11.7), D9S287 (Zmax = 15.6), and D9S176 (Zmax = 14.4). Amplification using FBP exon-specific primers with a YAC contig from this region of chromosome 9 further refined the placement of FBP genomic sequences to an approximately 1.7-cM region flanked by D9S280 and D9S287, near the gene for Fanconi anemia group C. Precise localization of the FBP gene enabled evaluation of FBP as a candidate gene for maturity-onset diabetes of the young (MODY) and non-insulin-dependent diabetes (NIDDM) in both Caucasian and African-American families, using the highly informative markers D9S287 and D9S176. Although FBP is a rate-limiting enzyme in gluconeogenesis, using both parametric and nonparametric analysis there was no evidence for linkage of FBP to diabetes in these families.

Altered insulin secretory responses to glucose in subjects with a mutation in the MODY1 gene on chromosome 20.

This study was undertaken to test the hypothesis that the diabetes susceptibility gene on chromosome 20q12 responsible for maturity-onset diabetes of the young (MODY) in a large kindred, the RW family, results in characteristic alterations in the dose-response relationships between plasma glucose concentration and insulin secretion rate (ISR) that differentiate this form of MODY from MODY in subjects with glucokinase mutations. Ten marker-positive subjects and six matched nondiabetic marker-negative subjects from the RW family received graded intravenous glucose infusions on two occasions separated by a 42-h continuous intravenous glucose infusion designed to prime the beta-cell to secrete more insulin in response to glucose. ISR was derived by deconvolution of peripheral C-peptide levels. Basal glucose and insulin levels were similar in marker-negative and marker-positive groups (5.3 +/- 0.2 vs. 5.0 +/- 0.2 mmol/l, P > 0.2, and 86.1 +/- 3.9 vs. 63.7 +/- 12.1 pmol/l, P > 0.1, respectively). However, the marker-positive subjects had defective insulin secretory responses to an increase in plasma glucose concentrations. Thus, as the glucose concentration was raised above 7 mmol/l, the slope of the curve relating glucose and ISR was significantly blunted in the marker-positive subjects (13 +/- 4 vs. 68 +/- 8 pmol.min-1.mmol-1 x 1, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal insulin secretion, not insulin resistance, is the genetic or primary defect of MODY in the RW pedigree.

Maturity-onset diabetes of the young (MODY) is a form of non-insulin-dependent diabetes mellitus (NIDDM) associated with autosomal-dominant inheritance. In the RW pedigree, MODY is associated with polymorphic DNA markers on chromosome 20q. To determine the early abnormalities of insulin action and insulin secretion in MODY, we studied nondiabetic members of the RW pedigree with and without the gene marker. Six nondiabetic marker-negative and 5 nondiabetic marker-positive members of the RW pedigree were studied, as were 4 diabetic marker-positive family members. Unrelated, young, healthy subjects served as comparison groups. Insulin action and insulin secretion were assessed with a frequently sampled intravenous glucose tolerance test. Insulin secretion was further assessed during constant glucose infusion by deconvolution of plasma C-peptide and by pulse analysis. The nondiabetic marker-positive group had normal sensitivity to insulin and unimpaired acute insulin response to intravenous glucose (AIRglu). However, the nondiabetic marker-positive group had decreased mean plasma C-peptide concentration and reduced absolute amplitude of insulin secretory oscillations during prolonged glucose infusion. These responses to prolonged glucose infusion were similar to those observed in the diabetic group. No alterations of insulin secretion were observed in the nondiabetic marker-negative family members. Deranged and deficient insulin secretion, and not insulin resistance, appears to be the genetic or primary abnormality that characterizes nondiabetic individuals who are predisposed to MODY in the RW pedigree.(ABSTRACT TRUNCATED AT 250 WORDS)

Maturity-onset diabetes of the young.

Maturity-onset diabetes of the young (MODY) is a subtype of noninsulin dependent diabetes mellitus (NIDDM). It is characterized by an early age of onset and autosomal dominant mode of inheritance. These features and the availability of large multigenerational pedigrees make MODY useful for genetic studies of diabetes. In the large, 5-generational RW pedigree, MODY is tightly linked to genetic markers on chromosome 20q. Affected subjects in this family show abnormalities of carbohydrate metabolism varying from impaired glucose tolerance (IGT) to severe diabetes. Approximately 30% of diabetic subjects become insulin requiring and vascular complications occur. MODY is also linked to the glucokinase gene on chromosome 7p and many different mutations associated with MODY have been identified in this gene. MODY due to mutations in the glucokinase gene is a relatively mild form of diabetes with mild fasting hyperglycemia and IGT in the majority. IT is rarely insulin requiring and rarely has vascular complications. Clinical studies indicate that the genetic or primary defect in MODY is characterized by deranged and deficient insulin secretion and not by insulin resistance and that there are quantitative and qualitative differences in insulin secretory defects which differentiate subjects with MODY due to glucokinase mutations from those with mutations in the gene on chromosome 20q. These differences correlate with the severity of diabetes between these two genetic forms of MODY.

Administration of sulfonylureas can increase glucose-induced insulin secretion for decades in patients with maturity-onset diabetes of the young.

OBJECTIVE: To ascertain whether the effect of sulfonylureas on glucose-mediated insulin release persists for years to decades in patients with maturity-onset diabetes of the young. RESEARCH DESIGN AND METHODS: The effect of sulfonylurea treatment on glucose-induced insulin secretion was ascertained prospectively for up to 33 yr in 12 diabetic patients of the maturity-onset diabetes of the young RW pedigree, who are genetically homogeneous because they share DNA markers on chromosome 20q. In 7 of these patients, paired glucose tolerance tests, given while the patients were on and off sulfonylureas, were performed after 7-31 yr. RESULTS: Glucose-induced insulin secretion showed an average increase of 68% in diabetic patients who remained responsive to chlorpropamide after having been on and off the drug for decades. In most patients, however, glucose-induced insulin secretion declines over time (1-4%/yr). Some patients become unresponsive to sulfonylureas after 3-25 yr and then have very small or no increases in glucose-induced insulin secretion and require treatment with insulin to normalize fasting hyperglycemia. CONCLUSIONS: Increase in glucose-induced insulin secretion remains the most important mechanism of the action of sulfonylureas during long-term administration.