Intraoperative ultrasound imaging in the surgical treatment of congenital hyperinsulinism: prospective, blinded study.

BACKGROUND: In congenital hyperinsulinism (CHI), preoperative prediction of the histological subtype (focal, diffuse, or atypical) relies on genetics and 6-[18F]fluoro-l-3,4-dihydroxyphenylalanine (18F-DOPA) PET-CT. The scan also guides the localization of a potential focal lesion along with perioperative frozen sections. Intraoperative decision-making is still challenging. This study aimed to describe the characteristics and potential clinical impact of intraoperative ultrasound imaging (IOUS) during CHI surgery. METHODS: This was a prospective, observational study undertaken at an expert centre over a 2-year interval. IOUS was performed blinded to preoperative diagnostic test results (genetics and 18F-DOPA PET-CT), followed by unblinding and continued IOUS during pancreatic resection. Characteristics and clinical impact were assessed using predefined criteria. RESULTS: Eighteen consecutive, surgically treated patients with CHI, with a median age of 5.5 months, were included (focal 12, diffuse 3, atypical 3). Focal lesions presented as predominantly hypoechoic, oval lesions with demarcated or blurred margins. Patients with diffuse and atypical disease had varying echogenicity featuring stranding and non-shadowing hyperechoic foci in three of six, whereas these characteristics were absent from those with focal lesions. The blinded IOUS-based subclassification was correct in 17 of 18 patients; one diffuse lesion was misclassified as focal. IOUS had an impact on the surgical approach in most patients with focal lesions (9 of 12), and in those with diffuse (2 of 3) and atypical (2 of 3) disease when the resection site was close to the bile or pancreatic duct. CONCLUSION: Uniform IOUS characteristics made all focal lesions identifiable. IOUS had a clinical impact in 13 of 18 patients by being a useful real-time supplementary modality in terms of localizing focal lesions, reducing the need for frozen sections, and preserving healthy tissue and delicate structures.

Disease pattern in Danish patients with Peutz-Jeghers syndrome.

PURPOSE: In this paper, we aimed to collect genetic and medical information on all Danish patients with Peutz-Jeghers syndrome (PJS), in order to contribute to the knowledge of phenotype and genotype. Peutz-Jeghers syndrome is a hereditary syndrome characterized by multiple hamartomatous polyps in the GI tract, mucocutaneous pigmentations, and an increased risk of cancer in the GI tract and at extraintestinal sites. Over 90 % of patients harbour a pathogenic mutation in STK11. METHODS: Based on the Danish Pathology Data Bank, the Danish National Patient Register, as well as information from relevant departments at Danish hospitals, we identified patients and collected clinical and genetic information. RESULTS: We identified 43 patients of which 14 were deceased. The prevalence was estimated to be ∼1 in 195,000 individuals. The median age at first symptom was 27.5 with invagination of the small bowel as the most frequent presenting symptom. We noted 18 occurrences of cancer at various anatomical sites, including a case of thyroid cancer and penile cancer. Eight of the deceased patients had died of cancer. Eighteen different mutations in STK11 had been detected in 28 patients. CONCLUSION: This is the first comprehensive study of patients with Peutz-Jeghers syndrome in the Danish population identified from nationwide registers and databases. We have demonstrated that the expressivity of Peutz-Jeghers syndrome varies greatly among the patients, even within the same families, underlining the great phenotypic spectrum. Patients with PJS should be offered surveillance from childhood in order to prevent morbidity and reduce mortality.

JP-HHT phenotype in Danish patients with SMAD4 mutations.

Patients with germline mutations in SMAD4 can present symptoms of both juvenile polyposis syndrome (JPS) and hereditary hemorrhagic telangiectasia (HHT): the JP-HHT syndrome. The complete phenotypic picture of this syndrome is only just emerging. We describe the clinical characteristics of 14 patients with SMAD4-mutations. The study was a retrospective, register-based study. SMAD4 mutations carriers were identified through the Danish HHT-registry, the genetic laboratories - and the genetic departments in Denmark. The medical files from relevant departments were reviewed and symptoms of HHT, JPS, aortopathy and family history were noted. We detected 14 patients with SMAD4 mutations. All patients had polyps removed and 11 of 14 fulfilled the diagnostic criteria for JPS. Eight patients were screened for HHT-symptoms and seven of these fulfilled the Curaçao criteria. One patient had aortic root dilation. Our findings support that SMAD4 mutations carriers have symptoms of both HHT and JPS and that the frequency of PAVM and gastric involvement with polyps is higher than in patients with HHT or JPS not caused by a SMAD4 mutation. Out of eight patients screened for aortopathy, one had aortic root dilatation, highlighting the need for additional screening for aortopathy.

Discovery of molecular pathways mediating 1,25-dihydroxyvitamin D3 protection against cytokine-induced inflammation and damage of human and male mouse islets of Langerhans.

Protection against insulitis and diabetes by active vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), in nonobese diabetic mice has until now mainly been attributed to its immunomodulatory effects, but also protective effects of this hormone on inflammation-induced ß-cell death have been reported. The aim of this study was to clarify the molecular mechanisms by which 1,25(OH)2D3 contributes to ß-cell protection against cytokine-induced ß-cell dysfunction and death. Human and mouse islets were exposed to IL-1ß and interferon-γ in the presence or absence of 1,25(OH)2D3. Effects on insulin secretion and ß-cell survival were analyzed by glucose-stimulated insulin release and electron microscopy or Hoechst/propidium iodide staining, respectively. Gene expression profiles were assessed by Affymetrix microarrays. Nuclear factor-κB activity was tested, whereas effects on secreted chemokines/cytokines were confirmed by ELISA and migration studies. Cytokine exposure caused a significant increase in ß-cell apoptosis, which was almost completely prevented by 1,25(OH)2D3. In addition, 1,25(OH)2D3 restored insulin secretion from cytokine-exposed islets. Microarray analysis of murine islets revealed that the expression of approximately 4000 genes was affected by cytokines after 6 and 24 hours (n = 4; >1.3-fold; P < .02), of which nearly 250 genes were modified by 1,25(OH)2D3. These genes belong to functional groups involved in immune response, chemotaxis, cell death, and pancreatic ß-cell function/phenotype. In conclusion, these findings demonstrate a direct protective effect of 1,25(OH)2D3 against inflammation-induced ß-cell dysfunction and death in human and murine islets, with, in particular, alterations in chemokine production by the islets. These effects may contribute to the beneficial effects of 1,25(OH)2D3 against the induction of autoimmune diabetes.

National mutation study among Danish patients with hereditary haemorrhagic telangiectasia.

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominantly inherited vascular disease characterized by the presence of mucocutaneous telangiectasia and visceral arteriovenous malformations (AVM). The clinical diagnosis of HHT is based on the Curaçao criteria. About 85% of HHT patients carry mutations in the ENG, ACVRL1 or SMAD4 genes. Here, we report on the genetic heterogeneity in the Danish national HHT population and address the prevalence of pulmonary arteriovenous malformations (PAVM). Probands of 107 apparently unrelated families received genetic testing, including sequencing and multiplex ligation-dependent probe amplification (MLPA) analyses of ENG, ACVRL1 and SMAD4. These 107 families included 320 patients confirmed to have HHT either clinically or genetically. In 89% of the probands (n=95), a mutation was identified. We detected 64 unique mutations of which 27 (41%) were novel. Large deletions were identified in ENG and ACVRL1. The prevalence of PAVM was 52.3% in patients with an ENG mutation and 12.9% in the ACVRL1 mutation carriers. We diagnosed 80% of the patients clinically, fulfilling the Curaçao criteria, and those remaining were diagnosed by genetic testing. It is discussed when to assign pathogenicity to missense and splice site mutations. The adding of an extra criterion to the Curaçao criteria is suggested.

Unraveling the effects of 1,25OH2D3 on global gene expression in pancreatic islets.

INTRODUCTION: Vitamin D deficiency has been linked to type 1 and 2 diabetes, whereas supplementation may prevent both diseases. However, the extent of the effects of vitamin D or its metabolites directly on pancreatic islets is still largely unknown. The aim of the present study was to investigate how active vitamin D, 1,25(OH)2D3, affects beta cells directly by establishing its effects on global gene expression in healthy murine islets. MATERIALS AND METHODS: Pancreatic islets were isolated from 2 to 3 week old C57BL/6 mice and cultured in vitro with 1,25(OH)2D3 or vehicle for 6 and 24h. Total RNA was extracted from the islets and the effects on global gene expression were analyzed using Affymetrix microarrays. RESULTS AND DISCUSSION: Exposure to 1,25(OH)2D3 compared to vehicle resulted in 306 and 151 differentially expressed genes after 6 and 24h, respectively (n=4, >1.3-fold, p<0.02). Of these 220 were up-regulated, whereas 86 displayed a decreased expression after 6h. Furthermore, expression levels were increased for 124 and decreased for 27 genes following 24h of exposure. Formation of intercellular junctions, cytoskeletal organization, and intracellular trafficking as well as lipid metabolism and ion transport were among the most affected gene classes. Effects on several genes already identified as being part of vitamin D signaling in other cell types were observed along with genes known to affect insulin release, although with our assay we were not able to detect any effects of 1,25(OH)2D3 on glucose-stimulated insulin release from healthy pancreatic islets. CONCLUSION: The effects of 1,25(OH)2D3 on the expression of cytoskeletal and intracellular trafficking genes along with genes involved in ion transport may influence insulin exocytosis. However, an effect of 1,25(OH)2D3 on insulin release could not be detected for healthy islets in contrast to islets subjected to pathological conditions such as cytokine exposure and vitamin D deficiency as suggested by other studies. Thus, in addition to previously identified tolerogenic effects on the immune system, 1,25(OH)2D3 may affect basic functions of pancreatic beta cells, with the potential to render them more resistant to the detrimental conditions encountered during type 1 and 2 diabetes. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

The spectrum of ABCC8 mutations in Norwegian patients with congenital hyperinsulinism of infancy.

Potassium channels in the plasma membrane of the pancreatic beta cells are critical in maintaining glucose homeostasis by responding to ATP and coupling metabolic changes to insulin secretion. These channels consist of subunits denoted the sulfonylurea receptor SUR1 and the inwardly rectifying ion channel KIR6.2, which are encoded by the genes ABCC8 and KCNJ11, respectively. Activating mutations in the subunit genes can result in monogenic diabetes, whereas inactivating mutations are the most common cause of congenital hyperinsulinism of infancy (CHI). Twenty-six Norwegian probands with CHI were analyzed for alterations in ABCC8 and KCNJ11. Fifteen probands (58%) had mutations in the ABCC8 gene. Nine patients were homozygous or compound heterozygous for the mutations, indicating diffuse pancreatic disease. In five patients, heterozygous and paternally inherited mutations were found, suggesting focal disease. One patient had a de novo mutation likely to cause a milder, dominant form of CHI. Altogether, 16 different ABCC8 mutations (including the novel alterations W231R, C267X, IVS6-3C>G, I462V, Q917X and T1531A) were identified. The mutations IVS10+1G>T, R1493W and V21D occurred in five, three and two families, respectively. KCNJ11 mutations were not found in any patients. Based on our mutation screening, we estimate the minimum birth prevalence of ABCC8-CHI in Norway to 1:70,000 during the past decade. Our results considerably extend the knowledge of the molecular genetics behind CHI in Scandinavia.

Transcriptional profiling of myotubes from patients with type 2 diabetes: no evidence for a primary defect in oxidative phosphorylation genes.

AIMS/HYPOTHESIS: Microarray-based studies of skeletal muscle from patients with type 2 diabetes and high-risk individuals have demonstrated that insulin resistance and reduced mitochondrial biogenesis co-exist early in the pathogenesis of type 2 diabetes independently of hyperglycaemia and obesity. It is unknown whether reduced mitochondrial biogenesis or other transcriptional alterations co-exist with impaired insulin responsiveness in primary human muscle cells from patients with type 2 diabetes. METHODS: Using cDNA microarray technology and global pathway analysis with the Gene Map Annotator and Pathway Profiler (GenMapp 2.1) and Gene Set Enrichment Analysis (GSEA 2.0.1), we examined transcript levels in myotubes established from obese patients with type 2 diabetes and matched obese healthy participants, who had been extensively metabolically characterised both in vivo and in vitro. We have previously reported reduced basal lipid oxidation and impaired insulin-stimulated glycogen synthesis and glucose oxidation in these diabetic myotubes. RESULTS: No single gene was differently expressed after correction for multiple testing, and no biological pathway was differently expressed using either method of global pathway analysis. In particular, we found no evidence for differential expression of genes involved in mitochondrial oxidative metabolism. Consistently, there was no difference in mRNA levels of genes known to mediate the transcriptional control of mitochondrial biogenesis (PPARGC1A and NRF1) or in mitochondrial mass between diabetic and control myotubes. CONCLUSIONS/INTERPRETATION: These results support the hypothesis that impaired mitochondrial biogenesis is not a primary defect in the sequence of events leading to insulin resistance and type 2 diabetes.

Non-insulinoma persistent hyperinsulinaemic hypoglycaemia caused by an activating glucokinase mutation: hypoglycaemia unawareness and attacks.

OBJECTIVE: Adult-onset non-insulinoma persistent hyperinsulinaemic hypoglycaemia (NI-PHH) and the variant NI-pancreatogenous hypoglycaemia syndrome (NIPHS) are genetically unexplained diseases, without reports of hypoglycaemia unawareness or familial inheritance. DESIGN AND PATIENTS: In a prospective 8-year follow-up, a boy (i) with NI-PHH since age 14 years, his mother (ii), the mother's brother (iii) and his daughter (iv) were studied. RESULTS: Patient (i) was characterized by especially postprandial hypoglycaemia down to 1.6 mmol/l and pronounced variability in diazoxide need with obesity; (ii) had asymptomatic blood glucose down to 2.9 mmol/l, but a severe hypoglycaemic postprandial attack after a slimming diet; (iii) had moderate hypoglycaemic symptoms since childhood and need of frequent eating; and (iv) was asymptomatic until a hypoglycaemic accident in the age of 24. After a slimming diet, symptomatic fasting, but especially postprandial hypoglycaemia occurred (blood glucose 1.9 mmol/l after 19 h fasting; 1.6 mmol/l 3.5 h after OGTT). By CT-scan/endoscopic ultrasound in three of the individuals, insulinoma could not be detected. In all four individuals, an activating glucokinase (GCK) mutation A456V was found. No mutations were found in the ABCC8 or KCNJ11 genes. The patients responded to treatment with diazoxide or octreotide long acting release. CONCLUSION: This is the first report to highlight a genetic cause to adult-onset NI-PHH/NIPHS. The activating GCK mutation was dominantly inherited, but only after year-long follow-up and investigations, other family members were diagnosed symptomatic. Hypoglycaemia unawareness seems to be a prominent feature, but hypoglycaemic attacks occur after slimming, especially postprandially. PHH-GCK was medical responsive.

Molecular genetic analysis of 1053 Danish individuals with clinical signs of familial hypercholesterolemia.

The lipid disorder familial hypercholesterolemia (FH) predisposes to cardiovascular disease. With a prevalence of approximately one in 500 in the general Caucasian population, FH is one of the most frequent single-gene disorders. As the mutational spectra vary between populations, it is crucial to identify the mutations in a given population in order to implement a molecular genetic screening strategy. A total of 1053 referred individuals with clinical signs of FH were investigated, and mutations were identified in 425 individuals. Fifty-four different mutations were identified, of which 13 are novel. The five most frequent mutations accounted for 56.3% of all disease-causing mutations. The majority of the remaining mutations were of a private nature only encountered in single families. In this study, a reliable molecular genetic screening protocol was established, and the relevance of performing presymptomatic genetic analysis as part of a preventive strategy was documented. We have acquired knowledge of the mutational spectra in the Danish population and thus will be able to trace mutations in their relatives through our index cases.

Clinical symptoms according to genotype amongst patients with hereditary haemorrhagic telangiectasia.

BACKGROUND: Hereditary haemorrhagic telangiectasia (HHT) is a dominantly inherited disease, characterized by a wide variety of clinical manifestations, including epistaxis, gastrointestinal (GI) bleeding, pulmonary arteriovenous malformations (PAVMs) and neurological symptoms. HHT is a genetically heterogeneous disorder involving at least two loci; HHT 1 mapping to chromosome 9 q 34.1 (ENG) and HHT 2 mapping to chromosome 12 q 31 (ALK-1). OBJECTIVE: To evaluate and describe the diversity of clinical manifestations in a Danish population of HHT patients with known HHT 1 or HHT 2 subtype. DESIGN: Prospective clinical examination with genetic evaluation and follow-up. SETTING: Investigation centre was Odense University Hospital. All HHT patients in the County of Fyn were included. METHODS: HHT family members were invited to a clinical examination including registration of HHT manifestations, screening for PAVM and neurological evaluation. Blood tests were performed for analysis of disease-causing mutation, and clinical manifestations in the HHT subtypes were compared. The survival of the patients was studied in the follow-up period. RESULTS: Included in the study were 73 HHT patients representing 18 families. In 14 of the families we identified a disease-causing mutation. Thirty-nine patients (from 10 families) had HHT1 and 16 HHT patients from four families had HHT2. CONCLUSION: Amongst patients with HHT1 genotype the prevalence of PAVM was higher than amongst HHT patients with HHT2 genotype. HHT1 patients had experienced more severe GI bleeding than HHT2 patients. There was no significant difference in severity of epistaxis or age at debut. Finally the mortality over a 90-month observation period was not significantly increased.

Hyperinsulinemic hypoglycemia in Beckwith-Wiedemann syndrome due to defects in the function of pancreatic beta-cell adenosine triphosphate-sensitive potassium channels.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth syndrome that is clinically and genetically heterogeneous. Hyperinsulinemic hypoglycemia occurs in about 50% of children with BWS and, in the majority of infants, it resolves spontaneously. However, in a small group of patients the hypoglycemia can be persistent and may require pancreatectomy. The mechanism of persistent hyperinsulinemic hypoglycemia in this group of patients is unclear. PATIENTS AND METHODS: Using patch-clamp techniques on pancreatic tissue obtained at the time of surgery, we investigated the electrophysiological properties of ATP-sensitive K(+) (K(ATP)) channels in pancreatic beta-cells in a patient with BWS and severe medically-unresponsive hyperinsulinemic hypoglycemia. RESULTS: Persistent hyperinsulinism was found to be caused by abnormalities in K(ATP) channels of the pancreatic beta-cell. Immunofluorescence studies using a SUR1 antibody revealed perinuclear pattern of staining in the BWS cells, suggesting a trafficking defect of the SUR1 protein. No mutations were found in the genes ABCC8 and KCNJ11 encoding for the two subunits, SUR1 and KIR6.2, respectively, of the K(ATP) channel. Genetic analysis of this patients BWS showed evidence of mosaic paternal isodisomy. CONCLUSIONS: In this novel case of BWS with mosaic paternal uniparental disomy for 11p15, persistent hyperinsulinism was due to abnormalities in K(ATP) channels of the pancreatic beta-cell. The mechanism/s by which mosaic paternal uniparental disomy for 11p15 causes a trafficking defect in the SUR1 protein of the K(ATP) channel remains to be elucidated.

Significantly higher adrenocorticotropin-stimulated cortisol and 17-hydroxyprogesterone levels in 337 consecutive, premenopausal, caucasian, hirsute patients compared with healthy controls.

OBJECTIVE: To investigate whether elevated ACTH-stimulated 17-hydroxyprogesterone (17OHP) levels are caused by CYP21 genetic defects or by a general adrenal hyperresponsiveness in hirsute patients. METHODS: A total of 337 hirsute patients were evaluated by Ferriman-Gallwey score, serum testosterone, ACTH-stimulated 17OHP, and cortisol during the follicular phase. A cutoff value of 16 nmol/liter for maximum ACTH-stimulated 17OHP (M17OHP) responses was defined as the upper limit of the 95% confidence interval (CI) for the 97.5 percentile in 42 female controls. All patients were offered total screening of the CYP21 gene, and 252 healthy, premenopausal women with regular menses underwent genetic screening. RESULTS: Patients were divided into idiopathic hirsutism (IH) (n = 180) and polycystic ovary syndrome (PCOS) (n = 157) groups. M17OHP levels were significantly higher in IH [geometric mean value (nmol/liter +/- 2 sd) 12.2 (4.6-32.3)] and PCOS [11.9 (5.3-27.2)] compared with controls [8.5 (5.1-14.2)] (P < 0.001). A similar percentage of IH and PCOS patients had elevated M17OHP (20.5 vs. 20.8%, not significant), and these also had significantly higher 30-min cortisol levels compared with controls (P < 0.05). The prevalence of CYP21 mutations in patients was 8.6% compared with 6.3% in controls (P = 0.38). Ten of 19 carriers had M17OHP levels below the cutoff limit. CONCLUSION: The significantly higher ACTH-stimulated levels of cortisol and 17OHP in hirsute patients indicated adrenal hyperresponsiveness in IH and PCOS. CYP21-carrier status could not explain the observed high prevalence of abnormal ACTH-stimulated 17OHP levels in the hirsute population.

Mutations in endoglin and in activin receptor-like kinase 1 among Danish patients with hereditary haemorrhagic telangiectasia.

Hereditary haemorrhagic telangiectasia (HHT) is a rare disorder with one per 6000-10,000 affected individuals in the general Caucasian population. HHT is genetically heterogeneous, involving at least two loci HHT1 mapping to chromosome 9q34.1 and HHT2 mapping to chromosome 12q31. The loci have been identified as endoglin (ENG) and activin receptor-like kinase 1 (ALK1). In order to gain knowledge of the genotype distribution and prevalence in the Danish population and to establish a reproducible and sensitive molecular genetic test method, we developed a denaturating gradient gel electrophoresis protocol for mutation scanning of the two loci. Twenty-five Danish HHT families were tested. A total of eight new as well as seven previously reported mutations were identified. A founder mutation was characterized present in seven families and possibly introduced around 350 years ago. In one individual, a presumed spontaneous mutation was characterized. The method developed proved to be very sensitive for mutation detection in both ENG and ALK1. Genetic screening in HHT families facilitates an early treatment strategy for silent HHT manifestations in first degree relatives.

New mutations in the lipoprotein lipase gene in a young boy with chylomicronaemia syndrome and in his family.

UNLABELLED: The case is reported of a 4-y-old boy with chylomicronaemia syndrome, under treatment with a low-fat diet and medium-chain triglycerides. The clinical and biochemical characteristics of the patient and 11 members of his family were studied. Lipoprotein profile, lipoprotein lipase (LPL) mass and activity were evaluated. Nucleotide substitutions in LPL promoter and exons were screened. The proband presented with severe hypertriglyceridaemia (triglycerides = 13.25 mmol l(-1)) and non-detectable LPL activity and mass. The boy was a compound heterozygote for four molecular defects in the LPL gene, two of which have not been reported before (CGT764 CTT/Arg170 --> Leu; GGA1482 --> GGT/Gly409 --> Gly). Among the family members, the proband was the only one who carried two genetic variants that modify LPL amino acid composition. CONCLUSION: The association of different alterations in the LPL gene could be a key factor in causing the severe phenotype observed. Moreover, treatment with a low-fat diet and medium-chain triglycerides failed to normalize the patient's hypertriglyceridaemia.

Effect of insulin on protein phosphatase 2A expression in muscle in type 2 diabetes.

BACKGROUND: Protein phosphatase 2A (PP2A) acts on a number of enzymes involved in the insulin regulation of glucose uptake and glycogen synthesis. This study was carried out to investigate the effect of insulin on PP2A expression in skeletal muscles of type 2 diabetic and control subjects. MATERIAL AND METHODS: Ten type 2 diabetic and 10 matched, control subjects were studied using the euglycaemic-hyperinsulinaemic clamp technique combined with indirect calorimetry. Immunoreactive protein levels of the catalytic alpha subunit of PP2A (PP2A-C alpha) were measured in biopsies from the vastus lateralis muscle obtained in the basal and insulin-stimulated state. RESULTS: In type 2 diabetic subjects insulin-mediated glucose disposal, glucose oxidation and nonoxidative glucose metabolism were reduced, whereas lipid oxidation was increased (all P < 0.05). Insulin down-regulated PP2A-C alpha expression in skeletal muscle of the control subjects (P < 0.05) but not in the type 2 diabetic subjects. In the control subjects, the insulin-mediated decrease in PP2A-C alpha correlated with the insulin-mediated increase in glucose disposal, glucose oxidation, nonoxidative glucose metabolism (all P < 0.05) and decrease in lipid oxidation (P < 0.01). In the type 2 diabetic subjects these relationships were absent. CONCLUSIONS: Down-regulation of PP2A-C alpha expression by insulin in skeletal muscle seems to be associated with a normal insulin action on glucose storage, glucose and lipid oxidation. Impaired down-regulation of PP2A-C alpha expression by insulin may be a marker for insulin resistance and contribute to the pathogenesis of type 2 diabetes.

[Congenital hyperinsulinism]. / Kongenit hyperinsulinisme.

In the last five years, our knowledge about the heterogenous syndrome of congenital hyperinsulinism (HI) has expanded explosively. HI may be familiar or sporadic, mild or severe, transitory or persistent, and histologically focal or diffuse. At least 63 disease-causing mutations have been found in the genes for the beta cell's ATP-dependent potassium channel, whose elements are the sulphonylurea receptor, SUR1, and Kir6.2. Other mutations cause enhancement of the glucose-stimulated ATP production in the beta cell. The resulting non-functional, or closed, potassium channel causes hypersecretion of insulin. Genetic screening has succeeded in detecting mutations in less than 50% of HI-patients. Genotype-phenotype relations, diagnosis and treatment are reviewed.

Mutations in the ALK-1 gene and the phenotype of hereditary hemorrhagic telangiectasia in two large Danish families.

Mutations in the ENG gene on chromosome 9 (HHT 1) and in the ALK-1 gene on chromosome 12 (HHT 2) have been reported as causes of hereditary hemorrhagic telangiectasia (HHT). HHT 1 has been correlated with a higher prevalence of pulmonary arteriovenous malformations than HHT 2. Other distinct phenotype-genotype correlations have not been described. The prevalence of HHT in the county of Fyn, Denmark, was 15.6 per 100,000 on January 1, 1995. All living patients and their first-degree relatives were invited to attend a detailed clinical examination and blood was drawn for mutation analysis. In two families mutations were identified in exon 8 of the ALK-1 gene. In family 6 we found a T1193A mutation. In this family a high prevalence of PAVM and severe GI bleeding was documented, while in family 8 with a C1120T mutation no individuals with PAVM were identified and only one patient had a history of severe GI bleeding. No mutations in the endoglin locus were found in either family.

Predominance of a 6 bp deletion in exon 2 of the LDL receptor gene in Africans with familial hypercholesterolaemia.

In South Africa, the high prevalence of familial hypercholesterolaemia (FH) among Afrikaners, Jews, and Indians as a result of founder genes is in striking contrast to its reported virtual absence in the black population in general. In this study, the molecular basis of primary hypercholesterolaemia was studied in 16 Africans diagnosed with FH. DNA analysis using three screening methods resulted in the identification of seven different mutations in the coding region of the low density lipoprotein (LDLR) gene in 10 of the patients analysed. These included a 6 bp deletion (GCGATG) accounting for 28% of defective alleles, and six point mutations (D151H, R232W, R385Q, E387K, P678L, and R793Q) detected in single families. The Sotho patient with missense mutation R232W was also heterozygous for a de novo splicing defect 313+1G-->A. Several silent mutations/polymorphisms were detected in the LDLR and apolipoprotein B genes, including a base change (g-->t) at nucleotide position -175 in the FP2 LDLR regulatory element. This promoter variant was detected at a significantly higher (p<0.05) frequency in FH patients compared to controls and occurred in cis with mutation E387K in one family. Analysis of four intragenic LDLR gene polymorphisms showed that the same chromosomal background was identified at this locus in the four FH patients with the 6 bp deletion. Detection of the 6 bp deletion in Xhosa, Pedi, and Tswana FH patients suggests that it is an ancient mutation predating tribal separation approximately 3000 years ago.

Genetic diversity and population structure of 20 North European cattle breeds.

Blood samples were collected from 743 animals from 15 indigenous, 2 old imported, and 3 commercial North European cattle breeds. The samples were analyzed for 11 erythrocyte antigen systems, 8 proteins, and 10 microsatellites, and used to assess inter- and intrabreed genetic variation and genetic population structures. The microsatellites BoLA-DRBP1 and CSSM66 were nonneutral markers according to the Ewens-Watterson test, suggesting some kind of selection imposed on these loci. North European cattle breeds displayed generally similar levels of multilocus heterozygosity and allelic diversity. However, allelic diversity has been reduced in several breeds, which was explained by limited effective population sizes over the course of man-directed breed development and demographic bottlenecks of indigenous breeds. A tree showing genetic relationships between breeds was constructed from a matrix of random drift-based genetic distance estimates. The breeds were classified on the basis of the tree topology into four major breed groups, defined as Northern indigenous breeds, Southern breeds, Ayrshire and Friesian breeds, and Jersey. Grouping of Nordic breeds was supported by documented breed history and geographical divisions of native breeding regions of indigenous cattle. Divergence estimates between Icelandic cattle and indigenous breeds suggested a separation time of more than 1,000 years between Icelandic cattle and Norwegian native breeds, a finding consistent with historical evidence.