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Heterozygous coding mutations in the INS gene that encodes preproinsulin were recently shown to be an important cause of permanent neonatal diabetes. These dominantly acting mutations prevent normal folding of proinsulin, which leads to beta-cell death through endoplasmic reticulum stress and apoptosis. We now report 10 different recessive INS mutations in 15 probands with neonatal diabetes. Functional studies showed that recessive mutations resulted in diabetes because of decreased insulin biosynthesis through distinct mechanisms, including gene deletion, lack of the translation initiation signal, and altered mRNA stability because of the disruption of a polyadenylation signal. A subset of recessive mutations caused abnormal INS transcription, including the deletion of the C1 and E1 cis regulatory elements, or three different single base-pair substitutions in a CC dinucleotide sequence located between E1 and A1 elements. In keeping with an earlier and more severe beta-cell defect, patients with recessive INS mutations had a lower birth weight (-3.2 SD score vs. -2.0 SD score) and were diagnosed earlier (median 1 week vs. 10 weeks) compared to those with dominant INS mutations. Mutations in the insulin gene can therefore result in neonatal diabetes as a result of two contrasting pathogenic mechanisms. Moreover, the recessively inherited mutations provide a genetic demonstration of the essential role of multiple sequence elements that regulate the biosynthesis of insulin in man.

Objective: Mutations in the ABCC8 gene encoding the SUR1 subunits of the beta-cell K-ATP channel cause neonatal diabetes (ND) mellitus. We aimed to determine the contribution of ABCC8 gene to ND in Poland, to describe the clinical phenotype associated with its mutations and to examine potential modifying factors., Patients: The Nationwide Registry of ND in Poland includes patients diagnosed before 6 months of age. In total 16 Kir6.2 negative patients with ND, 14 permanent and 2 relapsed transient, were examined., Measurements: ABCC8 gene mutations were detected by direct sequencing. Mutation carriers' characteristics included clinical data and biochemical parameters. In addition, we performed the hyperinsulinaemic euglycaemic clamp and tested for islet-specific antibodies in diabetic subjects., Results: We identified two probands with permanent ND (one heterozygous F132V mutation carrier and one compound heterozygote with N23H and R826W mutations) and two others with relapsed transient ND (heterozygotes for R826W and V86A substitutions, respectively). One subject, a heterozygous relative with the R826W mutation, had adult onset diabetes. There were striking differences in the clinical picture of the mutation carriers as the carrier of two mutations, N23H and R826W, was controlled on diet alone with HbA(1c) of 7.3%, whereas the F132V mutation carrier was on 0.66 IU/kg/day of insulin with HbA(1c) of 11.7%. The C-peptide level varied from 0.1 ng/ml (F132V) to 0.75 ng/ml (V86A). We also observed a variable insulin resistance, from moderate (M = 5.5 and 5.6 mg/kg/min, respectively, in the two R826W mutation carriers) to severe (M = 2.6 mg/kg/min in the F132V mutation carrier). We were able to transfer two patients off insulin to sulphonylurea (SU) and to reduce insulin dose in one other patient. Interestingly, there was no response to SU in the most insulin resistant F132V mutation carrier despite high dose of glibenclamide. All examined auto-antibodies were present in one of the subjects, the V86A mutation carrier, although this did not seem to influence the clinical picture, as we were able to transfer this girl off insulin., Conclusion: Mutations in SUR1 are the cause of about 15% of Kir6.2 negative permanent ND in Poland. The clinical phenotype of SUR1 diabetic mutation carriers is heterogeneous and it appears to be modified by variable sensitivity to insulin.

Activating mutations in the KCNJ11 gene encoding the ATP-sensitive potassium-channel subunit of Kir6.2 result in the phenotype of permanent neonatal diabetes (PNDM). Patients with PNDM can be successfully transferred from insulin to sulphonylurea. It is not clear, however, whether the type of diet may play a role in the metabolic control in PNDM patients. This report describes two cases of patients with PNDM due to the R201H mutation coming from the Polish Nationwide Registry of PNDM treated with the same sulphonylurea (glipizide GITS). In one of them, diet was practically free (Pol1), the other one (Pol2) avoided high glycemic-index products. Both mutation carriers were submitted to a 72 h continuous glucose monitoring system (CGMS) (Medtronic, CA). Before the CGMS record, families were encouraged not to alter their usual pattern of food intake during recording periods and to use food diaries. The postprandial glycemia in Poll reached the maximal level of 9.5 mmo/l, 5 episodes of glycemia above 8.0 mmol/l lasting overall for about 6 hours followed the ingestion of high-glycemic-index (>70) meals. Patient Pol2 did not use high-glycaemic-index-products and his postprandial blood glucose did not exceed 7.0 mmol/l. Following the CGMS record, an additional diet-oriented educational session with patient Poll and his parents was performed, Poll declared to avoid the intake of high-glycemic-index products. He remained on the same dose of Glipizide GITS. Results of home blood glucose monitoring performed 2 months later showed normoglycemia. We conclude that to achieve normoglycemia, patients with PNDM who are on sulphonylurea should refrain from eating high glycemic-index products.

Familial LCAT deficiency (FLD) is a rare genetic disorder associated with corneal opacities, anaemia and proteinuria with renal failure. Here we report detailed analyses on plasma lipids, lipoproteins, and the molecular defect in two siblings from a Polish family presenting classical symptoms of FLD and their family members with newly discovered Val309Met mutation in exon 6 of LCAT gene. Both patients displayed low total (2.19 and 2.94 mmol/l) and HDL-cholesterol concentrations (0.52 and 0.48 mmol/l), low percentage of cholesteryl esters (CE) (11.1 and 12%), and decreased apo AI and apo AII serum levels. Low LDL-cholesterol, apo B and Lp(a) levels, and increased oleate/linoleate ratios in CE could be of importance in the development of atherosclerosis in these patients with low HDL-cholesterol. LCAT activity was 10% of normal, alpha-LCAT activity was 0, and LCAT concentration was undetectable by immunoassay. Plasma CETP activity was at lower limits of normal. PCR and sequence analysis of DNA from the proband and affected brother revealed a novel G-->A mutation in exon 6 of LCAT gene, which resulted in an amino acid substitution of valine for methionine (Val309Met). The proband and affected brother were both homozygous carriers, while the mother, siblings and children of patients were heterozygous carriers of a newly discovered mutation. This is the first LCAT mutation described in the Slavic population.

Objective: To determine the distribution of the age at onset of diabetes (maturity-onset diabetes of the young-3 [MODY3]) and to identify determinants of the onset of diabetes in carriers of HNF-1alpha mutations., Research Design and Methods: Extended families (n = 104) with type 2 diabetes inherited in a dominant pattern were recruited and screened for diabetes-causing mutations in HNF-1alpha., Results: HNF-1alpha mutations cosegregated with diabetes in only 13 families, all with a mean age at onset <35 years. Insulin secretion was diminished or absent in mutation carriers (n = 101), and diabetes developed in 65% by age 25 years and in 100% by age 50 years. If the mutation was inherited from the mother, diabetes onset was very young in those exposed to diabetes in utero; 57 +/- 8% were affected by age 15 years as compared with 0.0% in those not exposed (P < 7 x 10(-6)). By age 25 years, the difference was reduced (85 +/- 6 and 55 +/- 12%, respectively; P = 0.02). If the mutation was inherited from the father, diabetes developed in 52 +/- 8% by age 25 years. Age at diagnosis was shown to be highly heritable (h(2) = 0.47, P = 0.003). When parent of origin was included in the analyses, the magnitude of genetic contribution increased markedly (h(2) = 0.91)., Conclusions: Mutations in HNF-1alpha accounts for diabetes in a small proportion of families with a dominant pattern of inheritance. Age at onset of diabetes in MODY3 families varied widely and was influenced by familial factors (including modifying genes) and parent of origin (whether a mutation carrier was exposed to diabetes in utero).

Background: The influences of genetic and environmental factors form a clinical picture of type 2 diabetes mellitus. Genetic studies of type 2 diabetes mellitus become increasingly important. The knowledge of the molecular background of type 2 diabetes has been growing rapidly over recent years. One of the forms of the disease defined on the molecular level is maternally inherited type 2 diabetes mellitus. This diabetes, which is frequently accompanied by hearing impairment of deafness (maternally inherited diabetes with deafness-MIDD), was linked with sequence differences in mitochondrial DNA. The most frequent cause of MIDD is A3243G substitution in a mitochondrial tRNA(Leu) gene. While this mutation was identified in different races in several populations, it is still important and valuable to evaluate its prevalence in various ethnic groups. The aim of the project was to determine the prevalence of A3243G substitution in a mitochondrial tRNA(Leu) gene among Polish diabetic subjects., Material and Methods: In total 129 individuals, with type 2 diabetes and 12 with gestational diabetes were selected for this study. Two techniques based on restriction fragment length polymorphism (RFLP) method were used to screen for A3243G mutation. In the first approach, non-radioactive PCR reactions of mitochondrial DNA region of interest were performed using DNA of the study participants. This was followed by Apa I restriction enzyme digestion of the PCR product. Subsequently an electrophoretic separation was done on 2% agarose gel with ethidium bromide staining. In the second, more sensitive, modification of RFLP, [alpha 32P]dCTP was used for internal primer labeling and the electrophoresis was done on acrylamide gel. A positive sample was used to control the quality of the genotyping., Results: In both approaches none of the samples, except for the positive control, showed the evidence of the G variant., Conclusions: In summary, the A3243G mutation in mitochondrial tRNA(Leu) gene is not a frequent cause of diabetes in the Polish population. Further screening of enlarging study group is necessary to fully determine the prevalence of this mutation in our population. This, together with the search for other mitochondrial mutations, should allow to fully determine the prevalence of MIDD and its specific molecular background in the Polish population.

Aims Exocrine pancreatic insufficiency has been described in Type 1 and Type 2 diabetes. The hepatocyte nuclear factor (HNF)-1α gene associated with maturity-onset diabetes of the young (MODY3) is expressed in several organs, including the exocrine pancreas. The aim of this study was to determine the prevalence of exocrine pancreas dysfunction in HNF-1α MODY patients. Methods Thirty-one diabetic HNF-1α MODY patients (mean age 37.2 ± 14.6 years) and 35 healthy control subjects (39.1 ± 13.9 years) participated. In addition, 25 Type 1 diabetic (T1DM) subjects were also examined (mean age 30.6 ± 10.1 years). Exocrine pancreas function was assessed by measurement of stool elastase 1 (E1) activity. All diabetic patients and control subjects completed a gastrointestinal (GI) symptoms questionnaire. Results In all but two individuals, stool E1 levels were normal (> 200 µg/g). The only case of severely impaired pancreas exocrine function (E1 = 47.5 µg/g) was observed in the MODY3 group. The mean stool E1 elastase level in the HNF-1α MODY group was significantly lower than in the control subjects (401.0 ± 118.4  vs. 482.7 ± 151.1 µg/g, P = 0.001). Similarly, E1 levels in T1DM were lower than in control subjects (344.8 ± 132.1 µg/g, P = 0.001); one patient with a moderate enzyme decrease was identified in this group. In addition, more frequent GI complaints were reported by HNF-1α MODY patients when compared with control subjects and also with T1DM patients. Conclusion Pancreatic exocrine insufficiency is not common in HNF-1α MODY diabetic patients, although their stool E1 levels are lower than in healthy control subjects. [ABSTRACT FROM AUTHOR]