Acute hyperinsulinemia increases the contraction of retinal arterioles induced by elevated blood pressure.

Diabetic retinopathy is accompanied by disturbances in retinal blood flow, which is assumed to be related to the diabetic metabolic dysregulation. It has previously been shown that normoinsulinemic hyperglycemia has no effect on the diameter of retinal arterioles at rest and during an increase in the arterial blood pressure induced by isometric exercise. However, the influence of hyperinsulinemia on this response has not been studied in detail. In seven normal persons, the diameter response of retinal arterioles to an increased blood pressure induced by isometric exercise, to stimulation with flickering light, and to the combination of these stimuli was studied during euglycemic normoinsulinemia (protocol N) on one examination day, and euglycemic hyperinsulinemia (protocol H) on another examination day. Isometric exercise induced significant contraction of retinal arterioles at all examinations, but during a repeated examination the diameter response was significantly reduced in the test persons following the N protocol and increased in the persons following the H protocol. Flicker stimulation induced a significant dilatation of retinal arterioles at all examinations, and the response was significantly higher during a repeated examination, irrespective of the insulin level. Repeated exposure to isometric exercise reduces contraction, whereas repeated exposure to flickering light increases dilatation of retinal arterioles in vivo. Hyperinsulinemia increases contraction of retinal arterioles induced by isometric exercise.

Increased action of pulsatile compared to non-pulsatile insulin delivery during a meal-like glucose exposure simulated by computerized infusion in healthy humans.

It has previously been demonstrated that pulsatile insulin has a greater hypoglycemic effect than non-pulsatile insulin during euglycemic conditions. The aim of the present study was to examine the effect of pulsatile versus non-pulsatile insulin delivery during a meal-like iv-glucose challenge. Ten healthy young subjects were examined on two occasions. A pancreatic-pituitary clamp was maintained with somatostatin infusion and replacement of glucagon and growth hormone at baseline levels. During the first three hours on both study days, insulin was infused in a pulsatile manner. Hereafter glucose and insulin were infused by computer-controlled pumps for four hours in a pattern mimicking the postprandial glucose and insulin profiles. At one study day, insulin infusion was done in a continuous manner, while at the other study day this profile was done in a pulsatile pattern. The hypoglycemic effect of insulin was measured as the integrated area under the curve of glucose during the four-hour infusion period. The mean insulin concentration measured as the integrated area under the curve was identical (P > .9). The hypoglycemic effect of insulin was significantly augmented by 13% during pulsatile delivery as compared to continuous delivery (P = .015). Likewise was the maximal glucose concentration significantly lower at the day of the pulsatile profile (9.9 ± 1.0 vs. 11.4 ± 2.3 mmol/l, P = .036). Pulsatile insulin release plays an important role in the postprandial glucose homeostasis. The disturbed insulin pulsatility in type 2 diabetes mellitus may contribute to the postprandial hyperglycemia.

Microarray expression analysis in delayed cardioprotection: the effect of exercise, AICAR, or metformin and the possible role of AMP-activated protein kinase (AMPK).

AMP-activated protein kinase (AMPK) is an enzyme which may be involved in cardioprotective mechanisms in the ischemic heart. Exercise, AICAR, and metformin, all known activators of AMPK, induce delayed cardioprotection which protects the heart against ischemia-reperfusion injury. The objective was to determine the effect of exercise, AICAR, and metformin on gene expression profile and to demonstrate possible interactions in different genes and functions. Rats were divided into either an exercise, AICAR, metformin, or control group. 3, 12, and 24 h after either a single bout of exercise training, a single injection of AICAR or a single dose of metformin, hearts were removed and gene expression profiles were analyzed in tissue from the left ventricle using Affymetrix gene chip probe arrays. Ingenuity Pathway Analysis (IPA) tool was used to analyze the regulated genes for relevant functions and diseases. Each gene chip identified up to 30,000 different probesets of which Ingenuity identified approximately up to 12,000 genes. A total of 147, 304, and 114 different genes in the left ventricle whose expressions were altered >2.0-fold were identified in the exercise, AICAR, and metformin group, respectively. Seventy eight different genes were overlapping the exercise and AICAR group at 24 h. Ingenuity identified six overlapping genes between the exercise, AICAR, and metformin groups including NR4A3, TNFRSF12A, HBB, PENK, PAP, and MAP4K4. IPA software revealed an overabundance of focus molecules in all three intervention groups involving functions related to cell death, cellular growth and proliferation, gene expression and cancer. Exercise, AICAR, and metformin regulate several genes in the rat myocardium with the majority of overlapping genes observed in the exercise and AICAR group. Changes in gene programming mainly involved inflammatory and opioid systems recognized as cardioprotective pathways. Some of these genes may represent possible candidate genes involved in the molecular mechanisms of AMPK-induced delayed PC.

Delayed ß-cell response and glucose intolerance in young women with Turner syndrome.

BACKGROUND: To investigate glucose homeostasis in detail in Turner syndrome (TS), where impaired glucose tolerance (IGT) and type 2 diabetes are frequent. METHODS: Cross sectional study of women with Turner syndrome (TS)(n = 13) and age and body mass index matched controls (C) (n = 13), evaluated by glucose tolerance (oral and intravenous glucose tolerance test (OGTT and IVGTT)), insulin sensitivity (hyperinsulinemic, euglycemic clamp), beta-cell function (hyperglycaemic clamp, arginine and GLP-1 stimulation) and insulin pulsatility. RESULTS: Fasting glucose and insulin levels were similar. Higher glucose responses was seen in TS during OGTT and IVGTT, persisting after correction for body weight or muscle mass, while insulin responses were similar in TS and C, despite the higher glucose level in TS, leading to an insufficient increase in insulin response during dynamic testing. Insulin sensitivity was comparable in the two groups (TS vs. control: 8.6 ± 1.8 vs. 8.9 ± 1.8 mg/kg*30 min; p = 0.6), and the insulin responses to dynamic ß-cell function tests were similar. Insulin secretion patterns examined by deconvolution analysis, approximate entropy, spectral analysis and autocorrelation analysis were similar. In addition we found low IGF-I, higher levels of cortisol and norepinephrine and an increased waist-hip ratio in TS. CONCLUSIONS: Young normal weight TS women show significant glucose intolerance in spite of normal insulin secretion during hyperglycaemic clamping and normal insulin sensitivity. We recommend regularly testing for diabetes in TS. TRIAL REGISTRATION: Registered with http://clinicaltrials.com, ID nr: NCT00419107.

Basal and insulin mediated VLDL-triglyceride kinetics in type 2 diabetic men.

OBJECTIVE: Increased very-low-density lipoprotein triglycerides (VLDL-TG) concentration is a central feature of diabetic dyslipidemia. The objective was to compare basal and insulin mediated VLDL-TG kinetics, oxidation, and adipose tissue storage in type 2 diabetic and healthy (nondiabetic) men. RESEARCH DESIGN AND METHODS: Eleven type 2 diabetic and 11 healthy men, matched for BMI and age, were included. Ex vivo-labeled VLDL-TG tracers, blood and breath samples, fat biopsies, indirect calorimetry, and body composition measures were applied to determine VLDL-TG kinetics, VLDL-TG fatty acids (FA) oxidation, and storage in regional adipose tissue before and during a hyperinsulinemic euglycaemic clamp. RESULTS: VLDL-TG secretion was significantly greater in diabetic compared with healthy men (basal: 86.9 [31.0] vs. 61.9 [30.0] µmol/min, P = 0.03; clamp: 60.0 [26.2] vs. 34.2 [17.9] µmol · min⁻¹, P = 0.01). The insulin mediated suppression of VLDL-TG secretion was significant in both groups. VLDL-TG clearance was lower in diabetic men (basal: 84.6 [32.7] vs. 115.4 [44.3] ml · min⁻¹, P = 0.08; clamp: 76.3 [30.6] vs. 119.0 [50.2] ml · min⁻¹, P = 0.03). During hyperinsulinemia fractional VLDL-TG FA oxidation was comparable, but in percentage of energy expenditure (EE), significantly higher in diabetic men. Basal VLDL-TG storage was similar, but significantly greater in abdominal compared with leg fat. CONCLUSIONS: Increased VLDL-TG in type 2 diabetic men is caused by greater VLDL-TG secretion and less so by lower VLDL-TG clearance. The ability of hyperinsulinemia to suppress VLDL-TG secretion appears preserved. During hyperinsulinemia VLDL-TG FA oxidation is significantly increased in proportion of EE in type 2 diabetic men. Greater basal abdominal VLDL-TG storage may help explain the accumulation of upper-body fat in insulin-resistant individuals.

Resequencing of 200 human exomes identifies an excess of low-frequency non-synonymous coding variants.

Targeted capture combined with massively parallel exome sequencing is a promising approach to identify genetic variants implicated in human traits. We report exome sequencing of 200 individuals from Denmark with targeted capture of 18,654 coding genes and sequence coverage of each individual exome at an average depth of 12-fold. On average, about 95% of the target regions were covered by at least one read. We identified 121,870 SNPs in the sample population, including 53,081 coding SNPs (cSNPs). Using a statistical method for SNP calling and an estimation of allelic frequencies based on our population data, we derived the allele frequency spectrum of cSNPs with a minor allele frequency greater than 0.02. We identified a 1.8-fold excess of deleterious, non-syonomyous cSNPs over synonymous cSNPs in the low-frequency range (minor allele frequencies between 2% and 5%). This excess was more pronounced for X-linked SNPs, suggesting that deleterious substitutions are primarily recessive.

Suppression of circulating free fatty acids with acipimox in chronic heart failure patients changes whole body metabolism but does not affect cardiac function.

Circulating free fatty acids (FFAs) may worsen heart failure (HF) due to myocardial lipotoxicity and impaired energy generation. We studied cardiac and whole body effects of 28 days of suppression of circulating FFAs with acipimox in patients with chronic HF. In a randomized double-blind crossover design, 24 HF patients with ischemic heart disease [left ventricular ejection fraction: 26 ± 2%; New York Heart Association classes II (n = 13) and III (n = 5)] received 28 days of acipimox treatment (250 mg, 4 times/day) and placebo. Left ventricular ejection fraction, diastolic function, tissue-Doppler regional myocardial function, exercise capacity, noninvasive cardiac index, NH(2)-terminal pro-brain natriuretic peptide (NT-pro-BNP), and whole body metabolic parameters were measured. Eighteen patients were included for analysis. FFAs were reduced by 27% in the acipimox-treated group [acipimox vs. placebo (day 28-day 0): -0.10 ± 0.03 vs. +0.01 ± 0.03 mmol/l, P < 0.01]. Glucose and insulin levels did not change. Acipimox tended to increase glucose and decrease lipid utilization rates at the whole body level and significantly changed the effect of insulin on substrate utilization. The hyperinsulinemic euglycemic clamp M value did not differ. Global and regional myocardial function did not differ. Exercise capacity, cardiac index, systemic vascular resistance, and NT-pro-BNP were not affected by treatment. In conclusion, acipimox caused minor changes in whole body metabolism and decreased the FFA supply, but a long-term reduction in circulating FFAs with acipimox did not change systolic or diastolic cardiac function or exercise capacity in patients with HF.

Exercise and fasting activate growth hormone-dependent myocellular signal transducer and activator of transcription-5b phosphorylation and insulin-like growth factor-I messenger ribonucleic acid expression in humans.

CONTEXT: GH secretion is increased by stress, such as fasting and exercise. OBJECTIVE: Our study was designed to test the hypothesis that fasting and exercise increase GH levels, GH-dependent signal transducer and activator of transcription (STAT)-5b phosphorylation, and IGF-I mRNA levels in human skeletal muscle. DESIGN AND PARTICIPANTS: Eight healthy men (25.5 +/- 4.3 yr) were studied for 6 h (a 4 h basal and a 2 h clamp period) in the basal state and after 72 h fasting and a 1-h ergometer cycling at 65% maximal oxygen uptake. Muscle biopsies were taken at t = 30 and 270 min. SETTING: The study was conducted at a university clinical research unit. RESULTS: During exercise, GH concentrations rapidly increased to greater than 10 ng/ml (P < 0.001). Thirty minutes after exercise, we observed a 4-fold increase in signal transducer and activator of transcription (STAT)-5 phosphorylation (P < 0.001) followed by an increase in IGF-I mRNA after 270 min (P = 0.026). During fasting, more sporadic GH bursts occurred, leading to an overall 3-fold increase in GH area under the curve(t=0-270) (P < 0.001). Similarly, STAT5 patterns were less consistent, with a tendency toward increased phosphorylation (P = 0.067, area under the curve(t=0-270)), whereas IGF-I mRNAs were persistently increased (P < 0.01). CONCLUSIONS: Our data show that myocellular GH signaling is stimulated after exercise and fasting in terms of increased STAT5 phosphorylation and/or IGF-I gene expression. This suggests that exercise with brief, well-defined GH peaks leads to distinct STAT5 phosphorylation and subsequent IGF-I gene expression, whereas fasting induces more sporadic GH bursts and less distinct but more persistent activation of the GH signal.

Insulin sensitivity and body composition in cirrhosis: changes after TIPS.

Insertion of a transjugular intrahepatic porto-systemic shunt (TIPS) increases body cell mass (BCM) in patients with liver cirrhosis. The responsible mechanism is unidentified, but may involve changes in insulin sensitivity and glucose metabolism. Eleven patients with liver cirrhosis were examined before and 6 mo after a TIPS procedure with bioimpedance analyses, 2-h oral glucose tolerance tests, and two-step hyperinsulinemic euglycemic clamp with tracer-determined endogenous glucose production. After TIPS, BCM increased by 4.8 kg [confidence interval (CI): 2.7-7.3]. Fasting (f)-insulin increased from 123 +/- 81 to 193 +/- 124 pmol/l (P = 0.03), whereas f-glucose was unchanged (6.0 +/- 0.8 vs. 6.2 +/- 1.0 mmol/l). Glucose and insulin oral glucose tolerance test area under the curve increased by 14% (CI: 7-22%) and 53% (CI: 14-90%), respectively, P < 0.05. The C-peptide-to-insulin ratio decreased by 21% (CI: 8-35%, P = 0.01). Insulin sensitivity based on glucose infusion rate (4.69 +/- 1.82 vs. 4.85 +/- 2.37 mg.kg(-1).min(-1)) and glucose tracer-based rate of disappearance were unchanged (5.01 +/- 1.61 vs. 4.97 +/- 2.13 mg.kg(-1).min(-1)). Despite a further increase in peripheral hyperinsulinemia, f-endogenous glucose production did not change between study days (2.01 +/- 0.42 vs. 2.42 +/- 0.58 mg.kg(-1).min(-1)) and was suppressed equally by insulin (1.1 +/- 0.1 vs. 1.0 +/- 0.1 mg.kg(-1).min(-1)). Insulin clearance, growth hormone, cortisol, and glucagon levels were unchanged. BCM improvement did not correlate with the measured variables. After TIPS, BCM rose, despite enhanced hyperinsulinemia and aggravated glucose intolerance, but unchanged peripheral and hepatic insulin sensitivity. This apparent discrepancy may be ascribed to shunt-related decreased insulin exposure to the liver cells. However, the anabolic effect of TIPS seems not to be related to improvements in insulin sensitivity and remains mechanistically unexplained.

Pioglitazone use in combination with insulin in the prospective pioglitazone clinical trial in macrovascular events study (PROactive19).

OBJECTIVE: In this post hoc analysis, we examined insulin requirements and regimens, glycemic control, cardiovascular outcomes, and safety in the patients treated with insulin at baseline in the Prospective Pioglitazone Clinical Trial in Macrovascular Events study. DESIGN: The Prospective Pioglitazone Clinical Trial in Macrovascular Events study was a double-blind, placebo-controlled outcome study (mean follow-up 34.5 months) in 5238 high-risk patients with type 2 diabetes randomized to pioglitazone (force titrated to 45 mg) or placebo. One third of the total population (pioglitazone 864; placebo 896) were receiving insulin at baseline. RESULTS: A rapid and sustained decrease in insulin dose was observed with pioglitazone vs. a progressive increase with placebo. By study end, the mean insulin dose was lower with pioglitazone (42 vs. 55 U/d with placebo; P < 0.0001). The insulin regimen (number on insulin, need for multiple injections, and reduction in oral agents) had been simplified vs. placebo; nevertheless, a greater glycosylated hemoglobin reduction was observed with pioglitazone (-0.93%) vs. placebo (-0.45%; P < 0.0001). At the final visit, insulin had been discontinued in 9% of pioglitazone vs. 2% of placebo patients (P < 0.0001). More insulin-resistant patients (defined as poorly controlled type 2 diabetes despite high doses of insulin) in the pioglitazone plus insulin group showed the greatest glycosylated hemoglobin decline. There were nonsignificant reductions with pioglitazone relative to placebo in the cardiovascular primary (hazard ratio 0.86; 95% confidence interval 0.71, 1.04; P = 0.1198) and main secondary (hazard ratio 0.85; 95% confidence interval 0.67, 1.08; P = 0.1831) end points in insulin-treated patients. The rates of overall heart failure, edema, and hypoglycemia were higher with pioglitazone [13.5 vs 10.5% (P = 0.0489); 30.8 vs. 18.2% (P < 0.0001); and 42.1 vs 29.0% (P < 0.0001), respectively], but there were no significant differences in serious events. CONCLUSIONS: Pioglitazone use in combination with insulin resulted in a sustained improved glycemic control and allowed the treatment regimens to be simplified and the insulin doses reduced.

Effect of nateglinide on the incidence of diabetes and cardiovascular events.

BACKGROUND: The ability of short-acting insulin secretagogues to reduce the risk of diabetes or cardiovascular events in people with impaired glucose tolerance is unknown. METHODS: In a double-blind, randomized clinical trial, we assigned 9306 participants with impaired glucose tolerance and either cardiovascular disease or cardiovascular risk factors to receive nateglinide (up to 60 mg three times daily) or placebo, in a 2-by-2 factorial design with valsartan or placebo, in addition to participation in a lifestyle modification program. We followed the participants for a median of 5.0 years for incident diabetes (and a median of 6.5 years for vital status). We evaluated the effect of nateglinide on the occurrence of three coprimary outcomes: the development of diabetes; a core cardiovascular outcome that was a composite of death from cardiovascular causes, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure; and an extended cardiovascular outcome that was a composite of the individual components of the core composite cardiovascular outcome, hospitalization for unstable angina, or arterial revascularization. RESULTS: After adjustment for multiple testing, nateglinide, as compared with placebo, did not significantly reduce the cumulative incidence of diabetes (36% and 34%, respectively; hazard ratio, 1.07; 95% confidence interval [CI], 1.00 to 1.15; P=0.05), the core composite cardiovascular outcome (7.9% and 8.3%, respectively; hazard ratio, 0.94, 95% CI, 0.82 to 1.09; P=0.43), or the extended composite cardiovascular outcome (14.2% and 15.2%, respectively; hazard ratio, 0.93, 95% CI, 0.83 to 1.03; P=0.16). Nateglinide did, however, increase the risk of hypoglycemia. CONCLUSIONS: Among persons with impaired glucose tolerance and established cardiovascular disease or cardiovascular risk factors, assignment to nateglinide for 5 years did not reduce the incidence of diabetes or the coprimary composite cardiovascular outcomes. (ClinicalTrials.gov number, NCT00097786.)

Effect of valsartan on the incidence of diabetes and cardiovascular events.

BACKGROUND: It is not known whether drugs that block the renin-angiotensin system reduce the risk of diabetes and cardiovascular events in patients with impaired glucose tolerance. METHODS: In this double-blind, randomized clinical trial with a 2-by-2 factorial design, we assigned 9306 patients with impaired glucose tolerance and established cardiovascular disease or cardiovascular risk factors to receive valsartan (up to 160 mg daily) or placebo (and nateglinide or placebo) in addition to lifestyle modification. We then followed the patients for a median of 5.0 years for the development of diabetes (6.5 years for vital status). We studied the effects of valsartan on the occurrence of three coprimary outcomes: the development of diabetes; an extended composite outcome of death from cardiovascular causes, nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, arterial revascularization, or hospitalization for unstable angina; and a core composite outcome that excluded unstable angina and revascularization. RESULTS: The cumulative incidence of diabetes was 33.1% in the valsartan group, as compared with 36.8% in the placebo group (hazard ratio in the valsartan group, 0.86; 95% confidence interval [CI], 0.80 to 0.92; P<0.001). Valsartan, as compared with placebo, did not significantly reduce the incidence of either the extended cardiovascular outcome (14.5% vs. 14.8%; hazard ratio, 0.96; 95% CI, 0.86 to 1.07; P=0.43) or the core cardiovascular outcome (8.1% vs. 8.1%; hazard ratio, 0.99; 95% CI, 0.86 to 1.14; P=0.85). CONCLUSIONS: Among patients with impaired glucose tolerance and cardiovascular disease or risk factors, the use of valsartan for 5 years, along with lifestyle modification, led to a relative reduction of 14% in the incidence of diabetes but did not reduce the rate of cardiovascular events. (ClinicalTrials.gov number, NCT00097786.)

Cardiovascular and metabolic effects of 48-h glucagon-like peptide-1 infusion in compensated chronic patients with heart failure.

The incretin hormone glucagon-like peptide-1 (GLP-1) and its analogs are currently emerging as antidiabetic medications. GLP-1 improves left ventricular ejection fraction (LVEF) in dogs with heart failure (HF) and in patients with acute myocardial infarction. We studied metabolic and cardiovascular effects of 48-h GLP-1 infusions in patients with congestive HF. In a randomized, double-blind crossover design, 20 patients without diabetes and with HF with ischemic heart disease, EF of 30 +/- 2%, New York Heart Association II and III (n = 14 and 6) received 48-h GLP-1 (0.7 pmol.kg(-1).min(-1)) and placebo infusion. At 0 and 48 h, LVEF, diastolic function, tissue Doppler regional myocardial function, exercise testing, noninvasive cardiac output, and brain natriuretic peptide (BNP) were measured. Blood pressure, heart rate, and metabolic parameters were recorded. Fifteen patients completed the protocol. GLP-1 increased insulin (90 +/- 17 pmol/l vs. 69 +/- 12 pmol/l; P = 0.025) and lowered glucose levels (5.2 +/- 0.1 mmol/l vs. 5.6 +/- 0.1 mmol/l; P < 0.01). Heart rate (67 +/- 2 beats/min vs. 65 +/- 2 beats/min; P = 0.016) and diastolic blood pressure (71 +/- 2 mmHg vs. 68 +/- 2 mmHg; P = 0.008) increased during GLP-1 treatment. Cardiac index (1.5 +/- 0.1 l.min(-1).m(-2) vs. 1.7 +/- 0.2 l.min(-1).m(-2); P = 0.54) and LVEF (30 +/- 2% vs. 30 +/- 2%; P = 0.93), tissue Doppler indexes, body weight, and BNP remained unchanged. Hypoglycemic events related to GLP-1 treatment were observed in eight patients. GLP-1 infusion increased circulating insulin levels and reduced plasma glucose concentration but had no major cardiovascular effects in patients without diabetes but with compensated HF. The impact of minor increases in heart rate and diastolic blood pressure during GLP-1 infusion requires further studies. Hypoglycemia was frequent and calls for caution in patients without diabetes but with HF.

Treatment with an SSRI antidepressant restores hippocampo-hypothalamic corticosteroid feedback and reverses insulin resistance in low-birth-weight rats.

Low birth weight (LBW) is associated with type 2 diabetes and depression, which may be related to prenatal stress and insulin resistance as a result of chronic hypothalamic-pituitary-adrenal (HPA) axis hyperactivity. We examined whether treatment with a selective serotonin reuptake inhibitor [escitalopram (ESC)] could downregulate HPA axis activity and restore insulin sensitivity in LBW rats. After 4-5 wk of treatment, ESC-exposed LBW (SSRI-LBW) and saline-treated control and LBW rats (Cx and LBW) underwent an oral glucose tolerance test or a hyperinsulinemic euglycemic clamp to assess whole body insulin sensitivity. Hepatic phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression and red skeletal muscle PKB Ser(473) phosphorylation were used to assess tissue-specific insulin sensitivity. mRNA expression of the hypothalamic mineralocorticoid receptor was fivefold upregulated in LBW (P < 0.05 vs. Cx), accompanied by increased corticosterone release during restraint stress and total 24-h urinary excretion (P < 0.05 vs. Cx), whole body insulin resistance (P < 0.001 vs. Cx), and impaired insulin suppression of hepatic PEPCK mRNA expression (P < 0.05 vs. Cx). Additionally, there was a tendency for reduced red muscle PKB Ser(473) phosphorylation. The ESC treatment normalized corticosterone secretion (P < 0.05 vs. LBW), whole body insulin sensitivity (P < 0.01) as well as postprandial suppression of hepatic mRNA PEPCK expression (P < 0.05), and red muscle PKB Ser(473) phosphorylation (P < 0.01 vs. LBW). We conclude that these data suggest that the insulin resistance and chronic HPA axis hyperactivity in LBW rats can be reversed by treatment with an ESC, which downregulates HPA axis activity, lowers glucocorticoid exposure, and restores insulin sensitivity in LBW rats.

Evaluation of the relationship between hyperinsulinaemia and myocardial ischaemia/reperfusion injury in a rat model of depression.

Major depression is associated with medical co-morbidity, such as ischaemic heart disease and diabetes, but the underlying pathophysiological mechanisms remain unclear. The FSL (Flinders Sensitive Line) rat is a genetic animal model of depression exhibiting features similar to those of depressed individuals. The aim of the present study was to compare the myocardial responsiveness to I/R (ischaemia/reperfusion) injury and the effects of IPC (ischaemic preconditioning) in hearts from FSL rats using SD (Sprague-Dawley) rats as controls and to characterize differences in glucose metabolism and insulin sensitivity between FSL and SD rats. Hearts were perfused in a Langendorff model and were subjected or not to IPC before 40 min of global ischaemia, followed by 120 min of reperfusion. Myocardial infarct size was found to be significantly larger in the FSL rats than in the SD rats following I/R injury (62.4+/-4.2 compared with 46.9+/-2.9%; P<0.05). IPC reduced the infarct size (P<0.01) and improved haemodynamic function (P<0.01) in both FSL and SD rats. No significant difference was found in blood glucose levels between the two groups measured after 12 h of fasting, but fasting plasma insulin (70.1+/-8.9 compared with 40.9+/-4.7 pmol/l; P<0.05) and the HOMA (homoeostatic model assessment) index (P<0.01) were significantly higher in FSL rats compared with SD rats. In conclusion, FSL rats had larger infarct sizes following I/R injury and were found to be hyperinsulinaemic compared with SD rats, but appeared to have a maintained cardioprotective mechanism against I/R injury, as IPC reduced infarct size in these rats. This animal model may be useful in future studies when examining the mechanisms that contribute to the cardiovascular complications associated with depression.

5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside increases myocardial glucose uptake during reperfusion and induces late pre-conditioning: potential role of AMP-activated protein kinase.

Late pre-conditioning protects against myocardial ischaemic-reperfusion injury. AMP-activated protein kinase (AMPK) is activated by exercise and 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). Early pre-conditioning involves AMPK activation and increased myocardial glucose uptake. The aim of the present study was to determine whether AICAR activates myocardial AMPK and induces late pre-conditioning and whether myocardial glucose uptake during reperfusion was modulated. Twenty-four hours after AICAR treatment or exercise, Wistar rats were subjected to ischaemia and reperfusion in a Langendorff model and compared to control rats. AMPK activity increased immediately 2.5-fold in AICAR-treated animals (P < 0.01) and twofold in exercised animals (P < 0.05). AICAR and exercise reduced infarct size by 60% and 50% (both P < 0.01), respectively, and increased myocardial glucose uptake during reperfusion (AICAR; 45%, P < 0.05, exercise; 40%, P < 0.05). In conclusion, AICAR induces late pre-conditioning and increases myocardial glucose uptake during reperfusion in rat hearts. AICAR and exercise activate AMPK, suggesting a role of AMPK in the signalling mechanisms behind late pre-conditioning.

SLC30A3 responds to glucose- and zinc variations in beta-cells and is critical for insulin production and in vivo glucose-metabolism during beta-cell stress.

BACKGROUND: Ion transporters of the Slc30A- (ZnT-) family regulate zinc fluxes into sub-cellular compartments. beta-cells depend on zinc for both insulin crystallization and regulation of cell mass. METHODOLOGY/PRINCIPAL FINDINGS: This study examined: the effect of glucose and zinc chelation on ZnT gene and protein levels and apoptosis in beta-cells and pancreatic islets, the effects of ZnT-3 knock-down on insulin secretion in a beta-cell line and ZnT-3 knock-out on glucose metabolism in mice during streptozotocin-induced beta-cell stress. In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression. Zinc chelation by DEDTC lowered INS-1E insulin content and insulin expression. Furthermore, zinc depletion increased ZnT-3- and decreased ZnT-8 gene expression whereas the amount of ZnT-3 protein in the cells was decreased. Zinc depletion and high glucose induced apoptosis and necrosis in INS-1E cells. The most responsive zinc transporter, ZnT-3, was investigated further; by immunohistochemistry and western blotting ZnT-3 was demonstrated in INS-1E cells. 44% knock-down of ZnT-3 by siRNA transfection in INS-1E cells decreased insulin expression and secretion. Streptozotocin-treated mice had higher glucose levels after ZnT-3 knock-out, particularly in overt diabetic animals. CONCLUSION/SIGNIFICANCE: Zinc transporting proteins in beta-cells respond to variations in glucose and zinc levels. ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels. Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment.

Sulfonylureas and prognosis after myocardial infarction in patients with diabetes: a population-based follow-up study.

BACKGROUND: The cardiovascular safety, including risk of myocardial infarction (MI), of individual sulfonylureas (SUs) may differ. It remains uncertain whether treatment with individual SUs influences prognosis following MI. METHODS: We conducted a nationwide population-based follow-up study among all Danish patients hospitalized with first-time MI from 1996 to 2004. From the national health databases, we identified 3930 MI patients who used SUs at the time of admission. We computed mortality rates and rates of MI and heart failure readmission according to type of SU and used Cox's proportional hazards regression analysis to compute hazard ratios (HRs) as estimates of relative risk controlling for differences in prognostic covariates. RESULTS: The 30-day and 1-year mortality after MI among SU users was 22.0% and 35.3%, respectively. We found no substantial differences in 30-day and 1-year mortality among users of different SUs. Use of gliclazide in monotherapy showed a trend towards lower mortality; adjusted HR of 1-year mortality 0.70 (95% CI: 0.48-1.00). Users of the different SUs appeared to have similar risks of new MI and heart failure following MI. CONCLUSIONS: The prognosis after MI was not substantially influenced by the choice of SU.

High prevalence of impaired glucose homeostasis and myopathy in asymptomatic and oligosymptomatic 3243A>G mitochondrial DNA mutation-positive subjects.

INTRODUCTION: The point mutation of 3243A>G mtDNA is the most frequent cause of mitochondrial diabetes, often presenting as the syndrome maternally inherited diabetes and deafness (MIDD). The mutation may also cause myopathy, ataxia, strokes, ophthalmoplegia, epilepsy, and cardiomyopathy in various combinations. Consequently, it is difficult to predict the "phenotypic risk profile" of 3243A>G mutation-positive subjects. The 3243A>G mutation coexists in cells with wild-type mtDNA, a phenomenon called heteroplasmy. The marked variability in mutation loads in different tissues is the main explanation for the different phenotypes associated with this mutation. AIM: The aim of the study was to screen asymptomatic and oligosymptomatic 3243A>G mtDNA carriers for diabetes and myopathy. METHODS: The study is a case-control study. Nineteen adult 3243A>G carriers presumed to be normoglycemic and matched healthy controls were subjected to an oral glucose tolerance test. Twenty-six adult 3243A>G carriers with unknown myopathy status and 17 healthy controls had a maximal cycle test and a muscle biopsy performed. The mutation loads were quantified in blood and muscle biopsies and correlated to the clinical manifestations of the mutation. RESULTS: In the presumed normoglycemic 3243A>G-positive subjects, one subject had overt diabetes, and 10 subjects had impaired glucose tolerance. Sixteen of the 26 subjects with unknown oxidative capacity fulfilled criteria for myopathy. The mutation load in blood and muscle correlated with the age for diagnosis of impaired glucose homeostasis and hearing impairment (rho = -0.71 to -0.78; P < 0.0001). CONCLUSION: The findings suggest that 3243A>G mutation carriers should be screened for diabetes and myopathy.