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PubMed1995

Effect of oral digoxin, topical ouabain and salbutamol on transepithelial nasal potential difference in patients with cystic fibrosis.

1. Airway epithelium in cystic fibrosis is characterized by a defect in chloride secretion across the apical membrane and an increase in sodium absorption. The increased rate of sodium absorption can be inhibited in vitro by ouabain, a Na(+)-K(+)-ATPase inhibitor, and in cystic fibrosis patients the number and activity of nasal epithelial Na(+)-K(+)-ATPase pumps is increased. 2. We have performed a series of studies to determine whether drugs which modify airway epithelial Na(+)-K(+)-ATPase activity in vitro can modify nasal potential in cystic fibrosis patients in vivo. As transepithelial nasal potential difference measurements were used to study the effect of drug modulation of airway epithelial ion transport in vivo, the repeatability of the technique was first evaluated. In order to assess the effectiveness of the technique used for measuring nasal potential difference, a pilot study was carried out using topical amiloride, a drug which has previously been shown to inhibit airway epithelium sodium transport in vivo. We then studied the effects of ouabain and digoxin, two inhibitors of Na(+)-K(+)-ATPase, on nasal potential difference. 3. In study 1, nasal potential difference measurements were repeated on non-consecutive days in 20 patients with cystic fibrosis and 20 healthy individuals. Healthy subjects had a mean (SEM) potential difference value of -19.5 (0.9) mV with a 95% range for a single estimate of 75-133%. In patients with cystic fibrosis, the mean (SEM) potential difference was -40.4, (2.1) mV, with a 95% range for a single estimate of 74-136%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2003

Ileal adenocarcinoma in a mild phenotype of abetalipoproteinemia.

Abetalipoproteinemia (ABL) is a rare autosomal recessive disorder that is characterized by defective assembly and secretion of plasma apolipoprotein (apo) B-containing lipoproteins. This disorder results from mutations in the MTP gene encoding the microsomal triglyceride transfer protein. We report a 58-year-old male homozygote for a missense mutation, S590I, in MTP. The patient had a lifelong history of fat malabsorption, but was only diagnosed with ABL at age 52, based upon such classic features as absence of apo B-containing lipoproteins, acanthocytosis, atypical retinitis pigmentosa and markedly depressed serum beta-carotene concentration. However, his presentation was notable not only by survival to the sixth decade of life without specific treatment, but also by the absence of neurological involvement and by normal serum vitamin E concentration. He subsequently developed adenocarcinoma of the ileum, which required ileal resection. Therefore, this missense mutation appears to be associated with a late-presenting and relatively mild ABL phenotype that lacks some classical features, particularly neuropathy, but appears to be associated with other atypical features, specifically small intestinal cancer.

Abetalipoproteinemia↗

PubMed1998

Polycystic ovaries and associated metabolic abnormalities in Indian subcontinent Asian women.

OBJECTIVES: To determine the prevalence of polycystic ovaries (PCO) in Asian women living in England who are of Indian subcontinent origin or ancestry and to investigate the relationship between the presence of PCO and/or non-insulin dependent diabetes mellitus (NIDDM) and insulin sensitivity and other metabolic parameters. DESIGN: A random sample of Indian subcontinent Asian women was obtained from the lists of local General Practitioners and a translating service. These women were invited to attend for a medical history questionnaire, examination, venous blood sample for hormonal assessment and transvaginal ovarian ultrasonography. Groups of women without PCO or NIDDM, with NIDDM but not PCO, with PCO but not NIDDM and with both NIDDM and PCO were drawn at random from this population and from Indian subcontinent Asian women attending the Diabetes Unit. They underwent further studies, including measurement of insulin sensitivity using a short intravenous insulin tolerance test. SUBJECTS: 212 Indian subcontinent Asian women aged 18-40 took part in the initial study. Insulin sensitivity was measured in 13 women without PCO or NIDDM, 13 women with NIDDM but not PCO, 15 women with PCO but not NIDDM and 12 women with both NIDDM and PCO. MEASUREMENTS: The main outcome measures were prevalence of polycystic ovaries, clinical features of hyperandrogenism, fertility, blood pressure, serum gonadotrophins, testosterone and sex hormone binding globulin, fasting blood lipids, glucose and insulin, and insulin sensitivity. RESULTS: The prevalence of PCO in Indian subcontinent Asian women was 52% (110/212). There were significant associations between PCO and menstrual irregularity; infertility; the Ferriman and Gallwey score for body hair distribution; the presence of acanthosis nigricans and the fasting blood glucose concentration. There were no differences between women with PCO and those with normal ovarian morphology with respect to systolic and diastolic blood pressure, fasting total, HDL and LDL cholesterol and triglyceride concentrations. The subgroup of women without PCO or NIDDM had the highest insulin sensitivity (189.1 +/- 46.4 mumol glucose/l/min, mean +/- SD) and the women with both PCO and NIDDM had the lowest insulin sensitivity (80.5 +/- 30.9 mumol glucose/l/min). There was no significant difference in insulin sensitivity between those with PCO but not NIDDM (125.0 +/- 59.5 mumol glucose/l/min) and those with NIDDM but not PCO (120.8 + 38.0 mumol glucose/l/min). The effects of NIDDM and PCO on insulin sensitivity were independent; the effect of PCO on insulin sensitivity was -60 mumol glucose/l/min (95% confidence interval -100 to -21, P = 0.004) and the effect of NIDDM was -68 mumol glucose/l/min (95% confidence interval -105 to -31, P < 0.001). There were no significant relationships between insulin sensitivity and fasting plasma insulin, systolic or diastolic blood pressure, fasting serum cholesterol or triglyceride. CONCLUSIONS: The prevalence of polycystic ovaries in Indian subcontinent Asian women is very high and it has significant clinical associations. Polycystic ovaries and non-insulin dependent diabetes mellitus are associated with similar degrees of reduced insulin sensitivity in this population. Their effects are independent suggesting that these changes in insulin sensitivity involve different mechanisms. Polycystic ovaries unlike non-insulin dependent diabetes mellitus, are not associated with a defect in the secretion of insulin.

Adolescent↗

PubMed2000

Biliary lipid composition in patients with cholesterol and pigment gallstones and gallstone-free subjects: deoxycholic acid does not contribute to formation of cholesterol gallstones.

BACKGROUND: Four main disturbances have been attributed to cholesterol gallstone disease: hypersecretion of cholesterol from the liver with cholesterol supersaturation in bile; disturbed motility with defective absorption and secretion by the gallbladder; increased crystallisation of cholesterol in the gallbladder bile; and slow intestinal transit with increased amount of deoxycholic acid in the bile acid pool. We aimed to evaluate the biliary lipid composition in a large series of gallstone patients, with emphasis on the amount of deoxycholic acid and with respect to number of stones, compared to gallstone free subjects. MATERIALS AND METHODS: Bile was sampled during operations through puncture of the gallbladder from 145 cholesterol gallstone patients, 23 patients with pigment stones and 87 gallstone free patients undergoing cholecystectomy. Biliary lipid composition, cholesterol saturation, bile acid composition, nucleation time and cholesterol crystals were analysed. RESULTS: The patients with cholesterol gallstones showed higher molar percentage of cholesterol, lower total biliary lipid concentration, higher cholesterol saturation, shorter nucleation time and higher proportion of crystals in bile than the other groups. The nucleation time was significantly shorter in multiple cholesterol gallstone patients, but this was not due to higher cholesterol saturation. Male cholesterol gallstone patients showed higher cholesterol levels, lower total biliary lipid concentration, and higher cholesterol saturation in bile than female patients. There was no difference in biliary content of deoxycholic acid, but significantly lower content of cholic acid in gallstone patients compared to gallstone free patients. CONCLUSIONS: We conclude that deoxycholic acid does not contribute to gallstone formation in cholesterol gallstone patients. The short nucleation time in patients with multiple cholesterol stones is not due to higher cholesterol saturation.

Adolescent↗

PubMedDate not supplied

[MODY, a model of genotype/phenotype interactions in type 2 diabetes].

Maturity onset diabetes of the young (MODY) is a subtype of familial diabetes mellitus characterised by early onset, autosomal dominant inheritance and primary defects of insulin secretion. Mutations in six known genes (the enzyme glucokinase and five transcription factors expressed in pancreatic beta-cells) cause most of the MODY cases. This genetic heterogeneity is associated with metabolic and clinical heterogeneity making MODY an interesting model of genotype/phenotype interaction in diabetes.

DNA-Binding Proteins↗

PubMed2003

Dietary habits and their relations to insulin resistance and postprandial lipemia in nonalcoholic steatohepatitis.

The relations of dietary habits to insulin sensitivity and postprandial triglyceride metabolism were evaluated in 25 patients with nonalcoholic steatohepatitis (NASH) and 25 age-, body mass index (BMI)-, and gender-matched healthy controls. After a 7-day alimentary record, they underwent a standard oral glucose tolerance test (OGTT), and the insulin sensitivity index (ISI) was calculated from the OGTT; an oral fat load test was also performed in 15 patients and 15 controls. The dietary intake of NASH patients was richer in saturated fat (13.7% +/- 3.1% vs. 10.0% +/- 2.1% total kcal, respectively, P =.0001) and in cholesterol (506 +/- 108 vs. 405 +/- 111 mg/d, respectively, P =.002) and was poorer in polyunsaturated fat (10.0% +/- 3.5% vs. 14.5% +/- 4.0% total fat, respectively, P =.0001), fiber (12.9 +/- 4.1 vs. 23.2 +/- 7.8 g/d, respectively, P =.000), and antioxidant vitamins C (84.3 +/- 43.1 vs. 144.2 +/- 63.1 mg/d, respectively, P =.0001) and E (5.4 +/- 1.9 vs. 8.7 +/- 2.9 mg/d, respectively, P =.0001). The ISI was significantly lower in NASH patients than in controls. Postprandial total and very low density lipoproteins triglyceride at +4 hours and +6 hours, triglyceride area under the curve, and incremental triglyceride area under the curve were higher in NASH compared with controls. Saturated fat intake correlated with ISI, with the different features of the metabolic syndrome, and with the postprandial rise of triglyceride. Postprandial apolipoprotein (Apo) B48 and ApoB100 responses in NASH were flat and strikingly dissociated from the triglyceride response, suggesting a defect in ApoB secretion. In conclusion, dietary habits may promote steatohepatitis directly by modulating hepatic triglyceride accumulation and antioxidant activity as well as indirectly by affecting insulin sensitivity and postprandial triglyceride metabolism. Our findings provide further rationale for more specific alimentary interventions, particularly in nonobese, nondiabetic normolipidemic NASH patients.

Adult↗

PubMed2002

Insulin resistance in patients with the mitochondrial tRNA(Leu(UUR)) gene mutation at position 3243.

UNLABELLED: The point mutation at position 3243 of the tRNA Leu(UUR) of the mitochondrial DNA is associated with mitochondrial encephalomyopathy, lactic acidosis and strokes (MELAS) as well as with mitochondrial diabetes and deafness (MIDD). A defect in insulin secretion has been found in most of these patients. However, there have been controversial findings to which extent insulin resistance contributes to pathogenesis. The aim of the present investigation was to study the insulin sensitivity index (SI), insulin secretion (AIR(Glucose)) and glucose effectiveness (Sg) in patients with the 3243-mutation. MATERIAL AND METHODS: 7 patients of a large pedigree (some of the members who were not investigated had MELAS) and 3 siblings of another family in whom the 3243-mutation had been detected, as well as 23 non-related, healthy control subjects underwent a modified intravenous glucose tolerance test (Bergman's minimal model). In addition, a screening of islet cell antibodies (ICA) was performed. RESULTS: All patients except for one with known diabetes mellitus revealed normal glucose tolerance. There was no difference between patients and controls for SI, AIR(Glucose) or Sg. However, when looking at the individual results, there were 4 closely related members of the large family with very poor insulin sensitivity. The other 2 patients of this pedigree were more distantly related and extremely insulin sensitive. The siblings of the other family revealed normal or even a very good insulin sensitivity. In one patient, ICA were detected. CONCLUSIONS: The 3243-mutation does not seem to be causative for insulin resistance in our patients. Whether nuclear genes are involved and indirectly influence the expression of the 3243-mutation or, more likely, directly lead to impaired insulin sensitivity in some of our patients cannot be answered by our data. It remains open whether there is a difference in the pathogenesis of diabetes between patients with MIDD and those with MELAS.

Female↗

PubMed2004

Therapeutic effects of PKC activators in Alzheimer's disease transgenic mice.

Alzheimer's disease (AD) characteristically presents with early memory loss. Regulation of K(+) channels, calcium homeostasis, and protein kinase C (PKC) activation are molecular events that have been implicated during associative memory which are also altered or defective in AD. PKC is also involved in the processing of the amyloid precursor protein (APP), a central element in AD pathophysiology. In previous studies, we demonstrated that benzolactam (BL), a novel PKC activator, reversed K(+) channels defects and enhanced secretion of APP alpha in AD cells. In this study we present data showing that another PKC activator, bryostatin 1, at subnanomolar concentrations dramatically enhances the secretion of the alpha-secretase product sAPP alpha in fibroblasts from AD patients. We also show that BL significantly increased the amount of sAPP alpha and reduced A beta 40 in the brains of APP[V717I] transgenic mice. In a more recently developed AD double-transgenic mouse, bryostatin was effective in reducing both brain A beta 40 and A beta 42. In addition, bryostatin ameliorated the rate of premature death and improved behavioral outcomes. Collectively, these data corroborate PKC and its activation as a potentially important means of ameliorating AD pathophysiology and perhaps cognitive impairment, thus offering a promising target for drug development. Because bryostatin 1 is devoid of tumor-promoting activity and is undergoing numerous clinical studies for cancer treatment in humans, it might be readily tested in patients as a potential therapeutic agent for Alzheimer's disease.

Alzheimer Disease↗

PubMed1991

DS28-6, a temperature-sensitive mutant of Chinese hamster ovary cells, expresses key phenotypic changes associated with brefeldin A treatment.

The temperature-sensitive Chinese hamster ovary (CHO) cell mutant DS28-6 has been previously shown to be pleiotropically defective in protein secretion. We have examined the mutant cells to determine the intracellular site of the block in secretion. By transmission electron microscopy a time-dependent disassembly of the Golgi apparatus was found under nonpermissive temperature, which resulted in the loss of the cisternal stack. Complete reorganization of the Golgi apparatus occurred after shift to permissive temperature. Under nonpermissive temperature, a microtubule- and energy-dependent redistribution of Golgi mannosidase II and galactosyltransferase into a pattern characteristic of the endoplasmic reticulum (ER) was observed. Inhibition of protein synthesis by cycloheximide had no influence on Golgi mannosidase II redistribution. Evidence for Golgi apparatus-associated processing of oligosaccharides in the ER was obtained by lectin-gold cytochemistry revealing the presence of the galactose (beta 1----4)N-acetylglucosamine sequence and sialic acid residues. Furthermore, 7-nitrobenz-2-oxa-1,3-diazol-4-yl-tagged ceramide, a lipidic trans-Golgi apparatus marker in CHO cells, exhibited an energy-dependent redistribution into the ER. These effects were fully reversible upon shift to permissive temperature. Thus, mutant DS28-6 cells exhibit key features of the brefeldin A phenotype, which suggests that the observed brefeldin A effects result from interference with a normally occurring cellular process.

Animals↗

PubMed2001

Post-transcriptional stimulation of the assembly and secretion of triglyceride-rich apolipoprotein B lipoproteins in a mouse with selective deficiency of brown adipose tissue, obesity, and insulin resistance.

A mouse model of insulin resistance and its associated dyslipidemia was generated by crossing mice expressing human apolipoprotein B (apoB) with mice lacking only brown adipose tissue (BATless). On a high fat diet, male apoB/BATless mice became obese, hypercholesterolemic, hypertriglyceridemic, and hyperinsulinemic compared with control apoB mice. Fast performance liquid chromatography revealed increased triglyceride concentrations in intermediate density lipoprotein/low density lipoprotein (LDL) and reduced high density lipoprotein cholesterol concentrations. Inhibition of lipolysis by the drug, tetrahydrolipostatin, demonstrated that very low density lipoprotein-sized particles were initially secreted. Metabolic studies employing Triton WR-1339 and either [(3)H]glycerol or [(3)H]palmitate showed that the hypertriglyceridemia in apoB/BATless mice was due to the increased synthesis and secretion of triglyceride. Furthermore, lipoprotein lipase and hepatic lipase activities were not defective. ApoB was also secreted at increased rates in the apoB/BATless mice. Similar levels of apoB mRNA in apoB and apoB/BATless mice indicated that apoB secretion was regulated post-transcriptionally. LDL receptor mRNA was increased in the apoB/BATless mice, indicating that the observed increase in apoB-lipoprotein secretion was not due to their decreased reuptake. Finally, mRNA levels of the large subunit of microsomal triglyceride transfer protein, a required component for very low density protein assembly, were not different between apoB and apoB/BATless mice. This rodent model should prove useful in exploring mechanisms underlying the regulation of apoB secretion in the context of insulin resistance.

Adipose Tissue, Brown↗

PubMed2005

Helicobacter pylori encoding the pathogenicity island activates matrix metalloproteinase 1 in gastric epithelial cells via JNK and ERK.

Helicobacter pylori colonizes the human gastric epithelium and induces an inflammatory response that is a trigger for gastric carcinogenesis. Matrix metalloproteinases (MMPs) have recently been shown to be up-regulated in gastric epithelial cells infected with H. pylori and might contribute to the pathogenesis of peptic ulcer. The aim of this study was to extend the knowledge about the effect of H. pylori infection on MMP-1 expression by gastric epithelial cells, the kinetics of induction, the pathogenetic properties of the bacterium, and the intracellular signaling pathways required for MMP-1 up-regulation. Expression of MMP-1 was induced more than 10-fold by co-culture of AGS+cells with H. pylori strains carrying the pathogenicity island (PAI). H. pylori strains with mutations in the PAI and a defective type IV secretion system had no effect on MMP-1. Double immunofluorescence revealed strong MMP-1 staining in epithelial cells of gastric biopsies at sites of bacterial attachment. In vitro, MMP-1 is up-regulated by interleukin-1beta and tumor necrosis factor-alpha, but these regulatory mechanisms are not operating in H. pylori infection as shown by inhibitory antibodies. Specific inhibitors of JNK kinase and ERK1/2 kinase were found to suppress the H. pylori-induced MMP-1 expression and activity. AGS cells treated with antisense MMP-1 showed a significantly reduced potential to degrade reconstituted basement membrane. Our results suggest that in gastric epithelial cells, H. pylori up-regulates MMP-1 in a type IV secretion system-dependent manner via JNK and ERK1/2. Induction of MMP-1 is further implicated in complex processes induced by H. pylori, resulting in tissue degradation and remodeling of the gastric mucosa.

Epithelium↗

PubMed2003

The GAP activity of Msb3p and Msb4p for the Rab GTPase Sec4p is required for efficient exocytosis and actin organization.

Polarized growth in Saccharomyces cerevisiae is thought to occur by the transport of post-Golgi vesicles along actin cables to the daughter cell, and the subsequent fusion of the vesicles with the plasma membrane. Previously, we have shown that Msb3p and Msb4p genetically interact with Cdc42p and display a GTPase-activating protein (GAP) activity toward a number of Rab GTPases in vitro. We show here that Msb3p and Msb4p regulate exocytosis by functioning as GAPs for Sec4p in vivo. Cells lacking the GAP activity of Msb3p and Msb4p displayed secretory defects, including the accumulation of vesicles of 80-100 nm in diameter. Interestingly, the GAP activity of Msb3p and Msb4p was also required for efficient polarization of the actin patches and for the suppression of the actin-organization defects in cdc42 mutants. Using a strain defective in polarized secretion and actin-patch organization, we showed that a change in actin-patch organization could be a consequence of the fusion of mistargeted vesicles with the plasma membrane.

Actins↗

PubMed1998

Mutations in the human lambda5/14.1 gene result in B cell deficiency and agammaglobulinemia.

B cell precursors transiently express a pre-B cell receptor complex consisting of a rearranged mu heavy chain, a surrogate light chain composed of lambda5/14.1 and VpreB, and the immunoglobulin (Ig)-associated signal transducing chains, Igalpha and Igbeta. Mutations in the mu heavy chain are associated with a complete failure of B cell development in both humans and mice, whereas mutations in murine lambda5 result in a leaky phenotype with detectable humoral responses. In evaluating patients with agammaglobulinemia and markedly reduced numbers of B cells, we identified a boy with mutations on both alleles of the gene for lambda5/14.1. The maternal allele carried a premature stop codon in the first exon of lambda5/14.1 and the paternal allele demonstrated three basepair substitutions in a 33-basepair sequence in exon 3. The three substitutions correspond to the sequence in the lambda5/14. 1 pseudogene 16.1 and result in an amino acid substitution at an invariant proline. When expressed in COS cells, the allele carrying the pseudogene sequence resulted in defective folding and secretion of mutant lambda5/14.1. These findings indicate that expression of the functional lambda5/14.1 is critical for B cell development in the human.

Agammaglobulinemia↗

PubMed2006

Incretin mimetics and dipeptidyl peptidase-IV inhibitors: a review of emerging therapies for type 2 diabetes.

Type 2 diabetes is thought to develop as a result of progressive beta-cell dysfunction in the setting of insulin resistance, leading to increased risks of microvascular and macrovascular complications. Type 2 diabetes is currently treated with diet and exercise, followed by oral drug therapy, and finally exogenous insulin. While this approach is known to improve glycemic control, none of the currently available therapies significantly improve beta-cell function. In addition, this approach does not address defects in hormonal secretion thought to play key roles in the pathophysiology of type 2 diabetes. Type 2 diabetes is characterized by excess glucagon secretion and insufficient secretion of the hormone amylin from the pancreatic beta-cell. In addition, individuals with type 2 diabetes demonstrate insufficient secretion of the incretin hormone glucagon-like peptide-1 (GLP-1). Novel therapies that leverage the so-called "incretin effect" of GLP-1 (including the incretin mimetics and dipeptidyl peptidase-IV (DPP-IV) inhibitors) are being actively developed for the management of type 2 diabetes. Incretin mimetics are either derivatives of GLP-1, modified to resist proteolysis, or are novel peptides that share glucoregulatory functions with GLP-1 and are naturally resistant to proteolysis. DPP-IV inhibitors enhance the concentration of endogenous GLP-1 by limiting proteolysis of native GLP-1. With the approval of exenatide- the first "incretin mimetic"-treatment of type 2 diabetes will no doubt be changed. An understanding of the effects of these compounds will be needed to enhance the clinical approach to diabetes treatment.

Diabetes Mellitus, Type 2↗

PubMed2005

Intrauterine diagnosis and management of fetal goitrous hypothyroidism: a report of an Iranian family with three consecutive pregnancies complicated by fetal goiter.

The diagnosis and treatment of hypothyroidism during the fetal period may decrease perinatal morbidity and are believed to be important to optimize growth and intellectual development. Herewith a case report of fetal goitrous hypothyroidism is presented in a euthyroid mother, detected at 34 weeks' gestation by ultrasonography, and treated with intra-amniotic levothyroxine injections. The mother had two previous consecutive pregnancies (13 and 8 years ago), also complicated by the occurrence of fetal goiter, resulting in tracheal compression, asphyxia, and early neonatal death in the first and in an emergency cesarean section delivery, because of fetal malpresentation, in the second neonate affected by congenital hypothyroidism (CH). The present male newborn, although born without observable goiter, had a large thyroid on ultrasonography and an early rise of his peripheral venous blood thyrotropin confirmed the diagnosis of CH. Low serum thyroglobulin in the proband and his older brother and parental consanguinity was mostly compatible with a thyroglobulin defective synthesis and secretion as the cause of CH and fetal goiter. Despite apparently sufficient dose of intraamniotic levothyroxine injections repeated weekly from 34-37 weeks' gestation (i.e., four injections of 500 microg levothyroxine), neonatal bone age on the second day of life showed delayed skeletal maturation.

Adult↗

PubMed1997

Identification of nine novel mutations in the hepatocyte nuclear factor 1 alpha gene associated with maturity-onset diabetes of the young (MODY3).

Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous subtype of non-insulin-dependent diabetes mellitus (NIDDM) characterised by early onset, autosomal dominant inheritance and a primary defect in insulin secretion. Recent studies have shown that mutations in the two functionally related transcription factors, hepatocyte nuclear factor 4 alpha (HNF-4alpha) and hepatocyte nuclear factor 1 alpha (HNF-1alpha) are associated with the MODY1 and MODY3 forms of diabetes respectively, whereas mutations in the enzyme glucokinase are the cause of the MODY2 form. We have examined 10 unrelated Caucasian families in which MODY/NIDDM co-segregated with markers for MODY3 for mutations in the HNF-1alpha gene (TCF1). Ten different mutations were observed in these families, all of which co-segregated with diabetes. There were no obvious relationships between the nature of the mutations observed (i.e. frameshift, nonsense, or missense) or their location in the gene with clinical features of diabetes (age at onset, severity) in these families. The mechanisms by which mutations in the HNF-1alpha gene cause diabetes mellitus are unclear but might include abnormal pancreatic islet development during foetal life thereby limiting their later function, as well as impaired transcriptional regulation of genes that play a key role in normal pancreatic beta cell function.

DNA-Binding Proteins↗

PubMed1999

Adenoviral gene therapy of the Tay-Sachs disease in hexosaminidase A-deficient knock-out mice.

The severe neurodegenerative disorder, Tays-Sachs disease, is caused by a beta-hexosaminidase alpha-subunit deficiency which prevents the formation of lysosomal heterodimeric alpha-beta enzyme, hexosaminidase A (HexA). No treatment is available for this fatal disease; however, gene therapy could represent a therapeutic approach. We previously have constructed and characterized, in vitro, adenoviral and retroviral vectors coding for alpha- and beta-subunits of the human beta-hexosaminidases. Here, we have determined the in vivo strategy which leads to the highest HexA activity in the maximum number of tissues in hexA -deficient knock-out mice. We demonstrated that intravenous co-administration of adenoviral vectors coding for both alpha- and beta-subunits, resulting in preferential liver transduction, was essential to obtain the most successful results. Only the supply of both subunits allowed for HexA overexpression leading to massive secretion of the enzyme in serum, and full or partial enzymatic activity restoration in all peripheral tissues tested. The enzymatic correction was likely to be due to direct cellular transduction by adenoviral vectors and/or uptake of secreted HexA by different organs. These results confirmed that the liver was the preferential target organ to deliver a large amount of secreted proteins. In addition, the need to overexpress both subunits of heterodimeric proteins in order to obtain a high level of secretion in animals defective in only one subunit is emphasized. The endogenous non-defective subunit is otherwise limiting.

Adenoviridae↗

PubMed2004

The challenge of type 1 diabetes mellitus.

Diabetes mellitus is a heterogeneous group of diseases characterized by high blood glucose levels due to defects in insulin secretion, insulin action, or both. With the number of cases expected to increase rapidly in the years to come, diabetes is a growing health challenge worldwide. Of the approximately 16 million diabetics in the United States, about 1.5 million suffer from type 1 diabetes. In this catabolic disorder afflicting predominantly young individuals, blood insulin is almost completely absent, leading to hyperglycemia and alterations in lipid metabolism. Type 1 diabetes is thought to be induced by a toxic or infectious insult that occurs in genetically predisposed individuals. With recent advances in the understanding of the involved immunology and cellular and molecular mechanisms, researchers strive to battle the disease with new preventive and corrective strategies.

Diabetes Complications↗