Characteristics of patients with familial Mediterranean fever in Denmark: a retrospective nationwide register-based cohort study.

Objectives: To investigate epidemiology, demography, and genetic and clinical characteristics of patients with familial Mediterranean fever (FMF) in Denmark. Method: In this population-based, cross-sectional cohort study, we identified FMF patients from discharge diagnoses using ICD-10 codes in the Danish National Patient Register, and linked data from the Danish Civil Registration System and laboratory databases for results of MEFV gene variant screening. Results: We identified 495 FMF patients (prevalence 1:11 680) with a median age of 29 years and a female ratio of 51%. The median age at diagnosis of FMF was 13 (IQR 7-22) years, with an estimated median diagnostic delay of 3 (IQR 0.7-6.9) years. The predominant ethnicities were Turkish (41.8%), Lebanese (15.8%), Syrian (6.5%), South-West Asian (7.9%), and South-East Asian (3.0%). The MEFV genotype distribution was 18.7% homozygous, 21.2% compound heterozygous, 32.0% heterozygous, 11.0% with complex alleles or unresolved zygosity, and 17.1% with no detected variants. M694V was the most prevalent variant in the overall cohort (32.5%). Homozygous or compound heterozygous MEFV exon 10 variants were associated with younger age at diagnosis (p < 0.001) and reduced number of hospital contacts before diagnosis (p = 0.008). The Charlson Comorbidity Index was ≥ 2 in 8.1% of patients. The prevalence of amyloidosis was 1.0%. Conclusions: FMF in Denmark is rare and patients are mainly of Eastern Mediterranean ethnicity. Diagnostic delay was long but patients with exon 10 MEFV variants were diagnosed at a younger age. Prolonged diagnostic delay is probably caused by lack of FMF awareness in the Danish healthcare system.

A novel Phe75fsdelT mutation in the hepatocyte nuclear factor-4alpha gene in a Danish pedigree with maturity-onset diabetes of the young.

Mutations in 5 different genes [the hepatocyte nuclear factor (HNF)-4alpha), glucokinase, HNF-1alpha, insulin promoter factor-1, and HNF-1beta genes] have been shown to cause maturity onset diabetes of the young (MODY). About 50% of all known MODY in Danish Caucasian MODY probands can be explained by mutations in the HNF-1alpha gene (MODY3). To estimate the prevalence of MODY caused by mutations in the HNF-4alpha gene (MODY1), we screened 10 non-MODY3 probands for mutations in the minimal promoter and the 12 exons of the HNF-4alpha gene. One of the probands had a novel frameshift mutation (Phe75fsdelT) in exon 2 of the HNF-4alpha gene, resulting in a premature termination of translation after 117 amino acids of the messenger RNA encoded by that allele. The mutation cosegregated with diabetes in the pedigree and was not detected in 84 unrelated Danish Caucasian healthy glucose-tolerant control subjects or in 84 type 2 diabetic patients. At the time of examination, 4 of 6 mutation carriers were treated with insulin and 2 with oral hypoglycemic medication. Two mutation carriers had late-diabetic complications. Even though the HNF-4alpha protein is known to be important in the regulation of genes involved in lipid metabolism, carriers of the mutation did not differ from age and sex-matched control subjects, in regard to levels of fasting serum total cholesterol, serum high-density lipoprotein-cholesterol, and serum triglyceride. In conclusion, by screening 10 non-MODY3 probands for mutations in the HNF-4alpha gene, we identified 1 diabetes-associated frameshift mutation (Phe75fsdelT), suggesting that defects in HNF-4alpha are a rare cause of MODY in Denmark.

Partial and whole gene deletion mutations of the GCK and HNF1A genes in maturity-onset diabetes of the young.

AIMS/HYPOTHESIS: Heterozygous mutations of glucokinase (GCK) and hepatocyte nuclear factor-1 alpha (HNF1A; also known as hepatic transcription factor 1 [TCF1]) genes are the most common cause of MODY. Genomic deletions of the HNF1B (also known as TCF2) gene have recently been shown to account for one third of mutations causing renal cysts and diabetes syndrome. We investigated the prevalence of partial and whole gene deletions in UK patients meeting clinical criteria for GCK or HNF-1alpha/-4alpha MODY and in whom no mutation had been identified by sequence analysis. METHODS: A multiplex ligation-dependent probe amplification (MLPA) assay was developed using synthetic oligonucleotide probes for 30 exons of the GCK, HNF1A and HNF4A genes. RESULTS: Partial or whole gene deletions were identified in 1/29 (3.5%) probands using the GCK MLPA assay and 4/60 (6.7%) of probands using the HNF1A/-4A MLPA assay. Four different deletions were detected: GCK exon 2, HNF1A exon 1, HNF1A exons 2 to 10 and HNF1A exons 1 to 10. An additional Danish pedigree with evidence of linkage to HNF1A had a deletion of exons 2 to 10. Testing other family members confirmed co-segregation of the deletion mutations with diabetes in the pedigrees. CONCLUSIONS/INTERPRETATION: Large deletions encompassing whole exons can cause GCK or HNF-1alpha MODY and will not be detected by sequencing. Gene dosage assays, such as MLPA, are a useful adjunct to sequence analysis when a diagnosis of MODY is strongly suspected.

Large-scale studies of the Leu72Met polymorphism of the ghrelin gene in relation to the metabolic syndrome and associated quantitative traits.

AIM: Recently, low-frequency polymorphisms in the coding region of the ghrelin gene were suggested to be involved in the aetiology of obesity and to modulate glucose-induced insulin secretion in different ethnic study groups. The objective of the present large study was to investigate whether the Leu72Met polymorphism of the ghrelin gene associates with features of the metabolic syndrome (MS) in the Danish population. METHODS: The variant was examined, using PCR-RFLP, in the DanMONICA cohort, a population-based sample of 2413 subjects. The metabolic syndrome was defined using the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII) criteria. RESULTS: The allelic frequency of the Met72 allele was 8.6%[6.3-10.9%] in the MS group and 7.8%[7.0-8.6%] among subjects classified as not having the MS (NS). Similarly, there were no significant differences across the three groups of genotypes with respect to any of the examined variables, including BMI, waist circumference, fasting serum lipids, plasma glucose, serum insulin and HOMA estimates of insulin resistance and insulin secretion. CONCLUSION: In conclusion, the Leu72Met polymorphism of the ghrelin gene is not associated with the metabolic syndrome or related quantitative traits in the Danish population.

Genetic variability of the SUR1 promoter in relation to beta-cell function and Type II diabetes mellitus.

AIMS/HYPOTHESIS: We aimed to examine the promoter of SUR1 for genetic variation and to determine if variants were associated with Type II (non-insulin-dependent) diabetes mellitus or measures of beta-cell function. METHODS: We examined 465 bp upstream of the ATG site in 46 Type II diabetic patients and 15 glucose tolerant control subjects by SSCP-heteroduplex analysis. RESULTS: We identified an a --> t substitution 437 bp upstream of the ATG site. The allelic frequency was similar in 455 unrelated Type II diabetic patients and in 203 glucose tolerant control subjects matched for age (0.036, [95 % CI 0.019-0.053] vs 0.034 [95 % CI 0.009-0.059]; p = 0.92). Among the glucose tolerant subjects there were no differences between non-carriers (n = 189) and carriers (n = 14) of the variant in fasting values or 30 min values of plasma glucose and serum insulin during an oral glucose tolerance test. In a study of 233 glucose tolerant offspring of and spouses to Danish Caucasian Type II diabetic patients, non-carriers (n = 193) and carriers (n = 37) of the -437 a/t polymorphism did not differ in glucose or tolbutamide stimulated insulin response during an intravenous glucose tolerance test with intravenous tolbutamide injection [AUCs-insulin (0-8) min, 2290 +/- 1660 vs 2308 +/- 1935 pmol/l x min and AUCs-insulin(20-30 min), 3113 +/- 2033 vs. 3393 +/- 2830 pmol/l x min, respectively]. CONCLUSION/INTERPRETATION: We have identified a novel a/t polymorphism of the SUR1 gene promoter which is not associated with Type II diabetes mellitus or measures of beta-cell function. Previous reported non-functional variants of SUR1 associated with Type II diabetes mellitus still need to be accounted for.

Discovery of amino acid variants in the human glucose-dependent insulinotropic polypeptide (GIP) receptor: the impact on the pancreatic beta cell responses and functional expression studies in Chinese hamster fibroblast cells.

The two incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), are insulinotropic factors released from the small intestine to the blood stream in response to oral glucose ingestion. The insulinotropic effect of GLP-1 is maintained in patients with Type II (non-insulin-dependent) diabetes mellitus, whereas, for unknown reasons, the effect of GIP is diminished or lacking. We defined the exon-intron boundaries of the human GIP receptor, made a mutational analysis of the gene and identified two amino acid substitutions, A207 V and E354Q. In an association study of 227 Caucasian Type II diabetic patients and 224 matched glucose tolerant control subjects, the allelic frequency of the A207 V polymorphism was 1.1% in Type II diabetic patients and 0.7% in control subjects (p = 0.48), whereas the allelic frequency of the codon 354 polymorphism was 24.9% in Type II diabetic patients versus 23.2% in control subjects. Interestingly, the glucose tolerant subjects (6% of the population) who were homozygous for the codon 354 variant had on average a 14% decrease in fasting serum C-peptide concentration (p = 0.01) and an 11% decrease in the same variable 30 min after an oral glucose load (p = 0.03) compared with subjects with the wild-type receptor. Investigation of the function of the two GIP receptor variants in Chinese hamster fibroblasts showed, however, that the GIP-induced cAMP formation and the binding of GIP to cells expressing the variant receptors were not different from the findings in cells expressing the wildtype GIP receptor. In conclusion, amino acid variants in the GIP receptor are not associated with random Type II diabetes in patients of Danish Caucasian origin or with altered GIP binding and GIP-induced cAMP production when stably transfected in Chinese hamster fibroblasts. The finding of an association between homozygosity for the codon 354 variant and reduced fasting and post oral glucose tolerance test (OGTT) serum C-peptide concentrations, however, calls for further investigations and could suggest that GIP even in the fasting state regulates the beta-cell secretory response.

Studies of variability in the islet amyloid polypeptide gene in relation to Type 2 diabetes.

AIMS: To explore whether the coding region of the islet amyloid polypeptide (IAPP) gene contains genetic variants associated with Type 2 diabetes and whether a previously reported association of the promoter variant -132g-->a with Type 2 diabetes could be reproduced in Danish Caucasians. METHODS: The coding region was analyzed using single strand conformation polymorphism (SSCP) and heteroduplex analysis in 192 Type 2 diabetic patients. Restriction fragment length polymorphism (RFLP) was employed to screen for the promoter variant in 414 Type 2 diabetic patients and 182 glucose-tolerant control subjects. RESULTS: The SSCP analysis identified an IVS+75a-->g variant in two patients. The frequency of heterozygous carriers of the promoter variant in the case-control study was 4.1% (17/414) and 7.1% (13/182), respectively. Odds ratio of the prevalence of Type 2 diabetes in carriers compared with non-carriers was estimated to be 0.47 (95% confidence interval 0.19, 1.15). CONCLUSION: Neither variability in the coding region of the IAPP gene nor the -132g-->a promoter variant was associated with Type 2 diabetes among the studied Danish Caucasians.

Search for variants of the gene-promoter and the potential phosphotyrosine encoding sequence of the insulin receptor substrate-2 gene: evaluation of their relation with alterations in insulin secretion and insulin sensitivity.

AIMS/HYPOTHESIS: The aim of this study was to screen part of the putative promoter sequence in addition to 14 potential phosphotyrosine residues of human IRS-2 for genetic variability which might cause changes in protein expression or function. Furthermore, the potential impact on insulin secretion and sensitivity of a previously identified IRS-2 variant (Gly1057Asp) was analysed. METHODS: The screenings were carried out by the SSCP-heteroduplex technique on DNA from Type II (non-insulin-dependent) diabetic patients. The impact of the Gly1057Asp variant was analysed in four glucose-tolerant Scandinavian study groups. RESULTS: The results showed no nucleotide substitutions in the promoter sequence, however, a novel heterozygous amino acid variant was identified (Leu647Val). In an association study, the new variant was found in 3 of 413 diabetic patients and in none of 280 glucose tolerant subjects. The variant did not affect the binding of IRS-2 to the insulin receptor or p85alpha of phosphatidylinositol 3-kinase when measured in the yeast two-hybrid system. Examination of the common Gly1057Asp variant in 363 young healthy subjects and in 228 glucose tolerant offspring of one diabetic parent showed no differences in insulin secretion or insulin sensitivity after an intravenous glucose tolerance test. Glucose tolerant middle-aged subjects homozygous for the polymorphism (n = 31), however, had on average a 25 % decrease in fasting serum insulin concentrations (p = 0.009) and 28 % (p = 0.01) and 34 % (p = 0.003) reductions in serum insulin concentrations at 30 and 60 min, respectively, during an OGTT compared with wildtype carriers (n = 107). In a cohort of 639 elderly Swedish men the amino acid variant did not have any detectable impact on insulin secretion after an OGTT. CONCLUSION/INTERPRETATION: No genetic variability was found in the IRS-2 promoter. A rare IRS-2 variant at codon 647 has been identified in Type II diabetic patients. The prevalent codon 1057 polymorphism had no consistent effect on insulin secretion or insulin sensitivity. [Diabetologia (1999) 42: 1244-1249]