Inactivation of the winged helix transcription factor HNF3alpha affects glucose homeostasis and islet glucagon gene expression in vivo. (1/2319)

Mice homozygous for a null mutation in the winged helix transcription factor HNF3alpha showed severe postnatal growth retardation followed by death between P2 and P12. Homozygous mutant mice were hypoglycemic despite unchanged expression of HNF3 target genes involved in hepatic gluconeogenesis. Whereas insulin and corticosteroid levels were altered as expected, plasma glucagon was reduced markedly in the mutant animals despite the hypoglycemia that should be expected to increase glucagon levels. This correlated with a 70% reduction in pancreatic proglucagon gene expression. We also showed that HNF3alpha could bind to and transactivate the proglucagon gene promoter. These observations invoke a central role for HNF3alpha in the regulatory control of islet genes essential for glucose homeostasis in vivo.  (+info)

Hypoglycemia and torpor in Siberian hamsters. (2/2319)

We tested whether reduced blood glucose concentrations are necessary and sufficient for initiation of torpor in Siberian hamsters. During spontaneous torpor bouts, body temperature (Tb) decreases from the euthermic value of 37 to <31 degrees C. Among hamsters that displayed torpor during maintenance in a short-day length (10 h light/day) at an air temperature of 15 degrees C, blood glucose concentrations decreased significantly by 28% as Tb fell from 37 to <31 degrees C and increased during rewarming so that by the time Tb first was >36 degrees C, glucose concentrations had returned to the value preceding torpor. Hamsters did not display torpor when maintained in a long-day length (16 h light/day) and injected with a range of insulin doses (1-50 U/kg body mass), some of which resulted in sustained, pronounced hypoglycemia. We conclude that changes in blood glucose concentrations may be a consequence rather than a cause of the torpid state and question whether induction of torpor by 2-deoxy-D-glucose is due to its general glucoprivic actions.  (+info)

Time-dependent and tissue-specific effects of circulating glucose on fetal ovine glucose transporters. (3/2319)

To determine the cellular adaptations to fetal hyperglycemia and hypoglycemia, we examined the time-dependent effects on basal (GLUT-1 and GLUT-3) and insulin-responsive (GLUT-4) glucose transporter proteins by quantitative Western blot analysis in fetal ovine insulin-insensitive (brain and liver) and insulin-sensitive (myocardium, skeletal muscle, and adipose) tissues. Maternal glucose infusions causing fetal hyperglycemia resulted in a transient 30% increase in brain GLUT-1 but not GLUT-3 levels and a decline in liver and adipose GLUT-1 and myocardial and skeletal muscle GLUT-1 and GLUT-4 levels compared with gestational age-matched controls. Maternal insulin infusions leading to fetal hypoglycemia caused a decline in brain GLUT-3, an increase in brain GLUT-1, and a subsequent decline in liver GLUT-1, with no significant change in insulin-sensitive myocardium, skeletal muscle, and adipose tissue GLUT-1 or GLUT-4 concentrations, compared with gestational age-matched sham controls. We conclude that fetal glucose transporters are subject to a time-dependent and tissue- and isoform-specific differential regulation in response to altered circulating glucose and/or insulin concentrations. These cellular adaptations in GLUT-1 (and GLUT-3) are geared toward protecting the conceptus from perturbations in substrate availability, and the adaptations in GLUT-4 are geared toward development of fetal insulin resistance.  (+info)

Molecular heterogeneity in very-long-chain acyl-CoA dehydrogenase deficiency causing pediatric cardiomyopathy and sudden death. (4/2319)

BACKGROUND: Genetic defects are being increasingly recognized in the etiology of primary cardiomyopathy (CM). Very-long-chain acyl-CoA dehydrogenase (VLCAD) catalyzes the first step in the beta-oxidation spiral of fatty acid metabolism, the crucial pathway for cardiac energy production. METHODS AND RESULTS: We studied 37 patients with CM, nonketotic hypoglycemia and hepatic dysfunction, skeletal myopathy, or sudden death in infancy with hepatic steatosis, features suggestive of fatty acid oxidation disorders. Single-stranded conformational variance was used to screen genomic DNA. DNA sequencing and mutational analysis revealed 21 different mutations on the VLCAD gene in 18 patients. Of the mutations, 80% were associated with CM. Severe CM in infancy was recognized in most patients (67%) at presentation. Hepatic dysfunction was common (33%). RNA blot analysis and VLCAD enzyme assays showed a severe reduction in VLCAD mRNA in patients with frame-shift or splice-site mutations and absent or severe reduction in enzyme activity in all. CONCLUSIONS: Infantile CM is the most common clinical phenotype of VLCAD deficiency. Mutations in the human VLCAD gene are heterogeneous. Although mortality at presentation is high, both the metabolic disorder and cardiomyopathy are reversible.  (+info)

Chronic hypoglycemia and diabetes impair counterregulation induced by localized 2-deoxy-glucose perfusion of the ventromedial hypothalamus in rats. (5/2319)

Previous studies have demonstrated that the ventromedial hypothalamus (VMH) plays a critical role in sensing and responding to systemic hypoglycemia. To evaluate the mechanisms of defective counterregulation caused by iatrogenic hypoglycemia and diabetes per se, we delivered 2-deoxy-glucose (2-DG) via microdialysis into the VMH to produce localized cellular glucopenia in the absence of systemic hypoglycemia. Three groups of awake chronically catheterized rats were studied: 1) nondiabetic (with a mean daily glucose [MDG] of 6.9 mmol/l) BB control rats (n = 5); 2) chronically hypoglycemic nondiabetic (3-4 weeks, with an MDG of 2.7 mmol/l) BB rats (n = 5); and 3) moderately hyperglycemic insulin-treated diabetic (with an MDG of 12.4 mmol/l) BB rats (n = 8). In hypoglycemic rats, both glucagon and catecholamine responses to VMH glucopenia were markedly (77-93%) suppressed. In diabetic rats, VMH 2-DG perfusion was totally ineffective in stimulating glucagon release. The epinephrine response, but not the norepinephrine response, was also diminished by 38% in the diabetic group. We conclude that impaired counterregulation after chronic hypoglycemia may result from alterations of the VMH or its efferent pathways. In diabetes, the capacity of VMH glucopenia to activate the sympathoadrenal system is only modestly diminished; however, the communication between the VMH and the alpha-cell is totally interrupted.  (+info)

The neuroendocrine protein 7B2 is required for peptide hormone processing in vivo and provides a novel mechanism for pituitary Cushing's disease. (6/2319)

The neuroendocrine protein 7B2 has been implicated in activation of prohormone convertase 2 (PC2), an important neuroendocrine precursor processing endoprotease. To test this hypothesis, we created a null mutation in 7B2 employing a novel transposon-facilitated technique and compared the phenotypes of 7B2 and PC2 nulls. 7B2 null mice have no demonstrable PC2 activity, are deficient in processing islet hormones, and display hypoglycemia, hyperproinsulinemia, and hypoglucagonemia. In contrast to the PC2 null phenotype, these mice show markedly elevated circulating ACTH and corticosterone levels, with adrenocortical expansion. They die before 9 weeks of severe Cushing's syndrome arising from pituitary intermediate lobe ACTH hypersecretion. We conclude that 7B2 is indeed required for activation of PC2 in vivo but has additional important functions in regulating pituitary hormone secretion.  (+info)

Biopsychobehavioral model of risk of severe hypoglycemia. Self-management behaviors. (7/2319)

OBJECTIVE: To identify self-management antecedents of low blood glucose (BG) (< 3.9 mmol/l) that might be easily recognized, treated, or avoided altogether. RESEARCH DESIGN AND METHODS: Ninety-three adults with type 1 diabetes (age, 35.8 +/- 8 years [mean +/- SD]; duration of diabetes, 17.0 +/- 11 years; daily insulin dose, 0.58 +/- 0.18 U/kg; and HbAlc, 8.6 +/- 1.8%) were recruited to participate in the study. Of the 93 subjects, 42 had a history of severe hypoglycemia (SH), defined as two or more hypoglycemic episodes in the preceding 12 months, and 51 subjects had no history of SH (No-SH) in the same time period. Before each of 70 BG measurements obtained over a 3-week period, subjects used a handheld computer to record whether their most recent insulin, food, and exercise was more than, less than, or the same as usual. Associations among self-management behaviors preceding BG readings < 3.9 mmol/l versus those preceding BG readings of 5.6-7.8 mmol/l were determined using chi 2 tests, analyses of variance, and logistic regression analyses. RESULTS: Analysis of 6,425 self-management/self-monitoring of BG events revealed that the usual amounts of insulin, food, and exercise preceded the events 58.3% of the time. No significant differences were observed for changes in insulin before readings of BG < 3.9 mmol/l versus 7.8 < BG > 5.6 mmol/l, but significantly less food (P < 0.01) was eaten and more exercise (P < 0.001) was performed before the low BG measurement. No interactions between SH and No-SH groups and management behaviors were observed. However, each of the three management variables entered significantly in a logistic model that predicted 61% of all readings of BG < 3.9 mmol/l. CONCLUSIONS: Subjects with a history of SH did not report managing their diabetes differently from those with no such history. Specifically, when low BG occurred, the preceding management behaviors, although predictive of low BG, were not different in SH and No-SH subjects. Overall, self-management behaviors did not distinguish SH from No-SH subjects. Thus, even though it might be beneficial for all patients to review their food and exercise management decisions to reduce their frequency of low BG, an educational intervention whose content stresses insulin, food, and exercise would be unlikely by itself to be sufficient to reduce the frequency of SH.  (+info)

Effectiveness of human ultralente versus NPH insulin in providing basal insulin replacement for an insulin lispro multiple daily injection regimen. A double-blind randomized prospective trial. The Canadian Lispro Study Group. (8/2319)

OBJECTIVE: To compare human ultralente (UL) insulin with human NPH insulin as basal insulin replacement in patients who use insulin lispro before meals. RESEARCH DESIGN AND METHODS: There were 178 patients with type 1 diabetes who were randomized to receive either human NPH or UL insulin once daily at bedtime in a 1-year double-blind clinical study. Eight-point blood glucose profiles were collected once monthly in the first 4 months, then every 2 months for the remainder of the study. Patients were also asked to perform premeal blood glucose measurements every day throughout the study. If before-supper blood glucose levels consistently exceeded 8 mmol/l despite optimal postprandial control with the lunch dose of insulin lispro, a second dose of basal insulin before breakfast was administered. RESULTS: For the group as a whole, insulin doses before meals and basal insulin doses were similar at baseline. At study's end, meal doses remained the same (30 +/- 1 U/day for UL., 29 +/- 1 U/day for NPH), while basal requirements were somewhat higher for the UL group than the NPH group: 30 +/- 1 U/day vs. 26 +/- 1 U/day, respectively (P < 0.05). The rates of severe hypoglycemia were similar for patients on NPH (0.05 +/- 0.03 per patient every 30 days) and for UL (0.07 +/- 0.04 per patient every 30 days) insulin. There was no significant difference for glycemic control between the NPH and UL groups overall (HbAlc at the end of the study: 7.6 +/- 0.1 vs. 7.7 +/- 0.1%, respectively), and by study's end a similar number of patients in the NPH and the UL groups needed to be switched to twice daily basal insulin (21 and 24%, respectively). Patients requiring twice-daily injections of basal insulin had a longer duration of diabetes (17.8 +/- 1.5 vs. 14.0 +/- 0.8 years, P < 0.05) and a highest baseline HbAlc (8.6 +/- 0.1 vs. 8.0 +/- 0.1%, P < 0.002) and were significantly older (38 +/- 2 vs. 34 +/- 1 years, P < 0.007). Patients who were switched to twice-daily NPH insulin had lower HbAlc levels at study's end compared with those switched to twice-daily UL insulin (7.7 +/- 0.2 vs. 8.2 +/- 0.3%), but this difference was not statistically significant. Distribution of hypoglycemia across the day was also similar in both groups. CONCLUSIONS: UL or NPH insulin, when used as the basal insulin for multiple injection regimens, results in similar glycemic control in patients using insulin lispro before meals. However, in patients who require a second injection of basal insulin, NPH insulin appears to provide lower prebreakfast and prelunch glucose levels compared with UL insulin.  (+info)