The intravenous insulin tolerance test is an accurate method for screening a general population for insulin resistance and related abnormalities

Randomized, double-blind, placebo-controlled trial to evaluate the effect of Helicobacter pylori eradication on glucose homeostasis in type 2 diabetic patients

BACKGROUND AND AIMS

Literature data suggest an association between Helicobacter pylori infection and glucose homeostasis. However, a causative link between them has not been demonstrated yet. The aim of this study is to investigate the effect of H. pylori eradication on glucose homeostasis in patients with type 2 diabetes.

METHODS AND RESULTS

A randomized, double-blind, placebo-controlled trial was conducted to investigate the effect of H. pylori eradication on glucose homeostasis in 154 patients with type 2 diabetes and who tested positive for H. pylori infection (mean age (SD), 63.1 (8.1) years). Subjects were assigned to H. pylori eradication treatment or placebo. Metabolic and inflammatory parameters were measured in all subjects at baseline and 4 weeks after the treatment. H. pylori eradication led to an improvement in glucose homeostasis, measured by HOMA-IR (p < 0.001) and KITT (0 = 0.041), due to the decrease in fasting insulin levels (p = 0.004). The results also showed that lower levels of inflammatory parameters were present after eradication.

CONCLUSION

To our knowledge this is the first randomized, double blind, controlled study where the effect of H. pylori eradication on glucose homeostasis in subjects with type 2 diabetes has been investigated. Our findings demonstrate that H. pylori eradication improves glucose homeostasis in patients with type 2 diabetes through a decrease in pro-inflammatory factors.

TRIAL REGISTRATION NUMBER

ACTRN12609000255280 (https://www.anzctr.org.au/).

Limbic dysregulation is associated with lowered heart rate variability and increased trait anxiety in healthy adults

OBJECTIVES

We tested whether dynamic interaction between limbic regions supports a control systems model of excitatory and inhibitory components of a negative feedback loop, and whether dysregulation of those dynamics might correlate with trait differences in anxiety and their cardiac characteristics among healthy adults.

EXPERIMENTAL DESIGN

Sixty-five subjects received fMRI scans while passively viewing angry, fearful, happy, and neutral facial stimuli. Subjects also completed a trait anxiety inventory, and were monitored using ambulatory wake ECG. The ECG data were analyzed for heart rate variability, a measure of autonomic regulation. The fMRI data were analyzed with respect to six limbic regions (bilateral amygdala, bilateral hippocampus, Brodmann Areas 9, 45) using limbic time-series cross-correlations, maximum BOLD amplitude, and BOLD amplitude at each point in the time-series.

PRINCIPAL OBSERVATIONS

Diminished coupling between limbic time-series in response to the neutral, fearful, and happy faces was associated with greater trait anxiety, greater sympathetic activation, and lowered heart rate variability. Individuals with greater levels of trait anxiety showed delayed activation of Brodmann Area 45 in response to the fearful and happy faces, and lowered Brodmann Area 45 activation with prolonged left amygdala activation in response to the neutral faces.

CONCLUSIONS

The dynamics support limbic regulation as a control system, in which dysregulation, as assessed by diminished coupling between limbic time-series, is associated with increased trait anxiety and excitatory autonomic outputs. Trait-anxious individuals showed delayed inhibitory activation in response to overt-affect stimuli and diminished inhibitory activation with delayed extinction of excitatory activation in response to ambiguous-affect stimuli.

Are plasma VEGF and its soluble receptor sFlt-1 atherogenic risk factors? Cross-sectional data from the SAPHIR study

AIMS

Vascular endothelial growth factor (VEGF) is a potent hypoxia-regulated angiogenic factor. Its soluble receptor soluble (s)Flt-1 binds VEGF with high affinity inhibiting the angiogenic function of VEGF. The role of circulating VEGF in atherosclerosis is unclear.

METHODS AND RESULTS

In 909 healthy subjects (511 male, 398 female) from the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) we determined fasting plasma VEGF and sFlt-1 concentration, cardiovascular risk factors and carotid atherosclerosis. VEGF levels were lower and sFlt-1 levels higher in men than in women. VEGF and sFlt-1 showed a positive correlation. In the entire population VEGF correlated positively with age, BMI, insulin resistance, white blood cell and platelet count, C-reactive protein (CRP) and carotid intima media thickness (IMT). After adjustment for age, VEGF showed a weak positive correlation with BMI, liver enzymes, CRP and platelet count in males. In females VEGF correlated negatively with LDL-cholesterol and positively with insulin resistance and platelet count. After adjustment for age, no significant correlation with carotid atherosclerosis could be detected.

CONCLUSION

Plasma VEGF and sFlt-1 are only weakly correlated with cardiovascular risk factors, suggesting that circulating VEGF levels do have only a minor impact on the development of atherosclerosis.

Effect of obesity and insulin sensitivity on adiponectin isoform distribution

BACKGROUND

Adiponectin is an insulin-sensitizing, antiatherogenic and anti-inflammatory adipocytokine that circulates in three isoforms: a trimer [low-molecular weight (LMW)], a hexamer (trimer-dimer) of medium molecular weight (MMW) and a multimeric high molecular weight (HMW) isoform. Evidence is accumulating that HMW adiponectin is the active isoform of the adipocytokine. We investigated the impact of adipose tissue and insulin sensitivity on adiponectin isoform distribution.

MATERIALS AND METHODS

One hundred and eighty-seven normolipidaemic, non-diabetic lean or obese subjects with or without insulin resistance participating in the Salzburg Atherosclerosis Prevention program in subjects at High Individual Risk (SAPHIR) were included in the study. Insulin sensitivity was determined by the short insulin tolerance test and the homeostasis model assessment (HOMA) index. Serum adiponectin isoform distribution was determined by an enzyme immunoassay.

RESULTS

Total adiponectin as well as HMW/total adiponectin ratio was significantly increased in female subjects. Circulating total adiponectin levels were lowest in obese patients due to reduced concentrations of HMW adiponectin. As determined by stepwise regression analysis, besides age and high density lipoprotein (HDL) cholesterol, visceral fat area and waist-to-hip ratio predicted concentrations of HMW adiponectin, while insulin sensitivity had no influence on either total adiponectin or its isoforms.

CONCLUSIONS

Our results underline that determination of adiponectin isoforms are more useful than measurement of total adiponectin in clinical settings. Our data suggest that adiponectin concentrations are strongly associated with visceral fat area but not with insulin sensitivity. Thus, we hypothesize that insulin resistance is a consequence rather than the cause of hypoadiponectinaemia in obese subjects.

Comparison of short insulin tolerance test with HOMA Method for assessment of insulin sensitivity in Asian Indians in north India

BACKGROUND

Cost-effective method to assess insulin resistance is needed for Asian Indians.

METHODS

We compared HOMA with SITT methods in 40 subjects.

RESULTS

Values obtained from both methods did not show any correlation.

CONCLUSIONS

Both methods should be evaluated against hyperinsulinemic clamp to determine suitability in Asian Indians.

Platelet nitric oxide production and IR: relation with obesity and hypertriglyceridemia

BACKGROUND AND AIM

Three NOS isoforms are responsible for nitric oxide production in various tissues. Endothelial constitutive NOS is expressed in vascular endothelium and in platelets, contributing to vascular tone regulation and platelet aggregation. The aim of the present work was to examine eNOS polymorphism, to find a correlation with platelet NO production and degree of insulin resistance (IR) in non-diabetic subjects and in patients affected by type 2 diabetes.

METHODS AND RESULTS

Seventy-one non-diabetic subjects and 37 patients affected by Type 2 diabetes were recruited. The subjects were subdivided into 3 groups as cut-off for the definition of an insulin resistant state: IR non-diabetic subjects, insulin sensitive subjects, and insulin-resistant patients affected by Type 2 diabetes. Plasma glyco-metabolic parameters, platelet nitric oxide production, endothelial nitric oxide synthase (eNOS) gene polymorphism were measured in all subjects enrolled. Significant differences between groups were found in BMI, fasting glycaemia, fructosamine and HbA(1c), triglycerides and HDL cholesterol levels. Evaluating all the subjects, platelet NO production was significantly related with BMI, waist circumference, and triglycerides concentrations, thus suggesting an association between increased platelet NO production, obesity and hypertriglyceridemia, independent of the degree of insulin-resistance.

CONCLUSION

The modified platelet NO synthesis does not seem to be due to eNOS Glu298Asp polymorphism, while it can be hypothesized that it is caused by an iNOS induction, present in obesity, hypertriglyceridemia and in type 2 diabetes.

Comparison of different definitions of the metabolic syndrome

BACKGROUND

The International Diabetes Federation (IDF) published a new definition of the metabolic syndrome (MetS). For this definition we compared frequency, concordance, clinical and laboratory stigmata and carotid atherosclerosis with those of the established definitions by the National Cholesterol Education Program (NCEP) and World Health Organization (WHO).

MATERIALS AND METHODS

A total of 1518 subjects (943 men, 575 women) from the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR), free of clinical atherosclerosis, were included in this study. To estimate insulin sensitivity two methods, i.e. homeostasis model assessment of insulin resistance (HOMA-IR) and the short insulin tolerance test, were employed. Carotid intima media thickness (IMT) and plaque extent were quantified for all subjects using high-resolution ultrasound.

RESULTS

Prevalence of the MetS was 18.7% for men and 16.2% for women for the WHO definition, 18.9% and 17.0%, respectively, for the NCEP definition, and 25.8% and 19.5%, respectively, for the IDF definition. Concordance was lower between the definitions of WHO and IDF (< 50%) than between NCEP and IDF (> 67%). Compared to subjects identified by NCEP definition, subjects identified in excess by IDF (3.1-11.7%) showed less insulin resistance and lower IMT and plaque extent indistinguishable from MetS-free subjects.

CONCLUSIONS

Our data suggest that the IDF definition includes subjects as MetS sufferers above these detected by NCEP or WHO, who exhibit considerably less insulin resistance and carotid atherosclerosis blurring the distinction between health and disease.

Insulin resistance and body composition in Turner syndrome: Effect of sequential change in the route of estrogen administration

The aim of the present study was to examine the impact of sequential change in the route of estrogen administration on body composition and insulin resistance in patients with Turner syndrome (TS) using cyclical hormone replacement therapy (HRT) with conjugated equine estrogens (CEE) plus medroxyprogesterone acetate (MPA). We carried out a self-controlled study of nine non-obese patients with TS, with an average age of 23 +/- 4.9 years. Body mass index (BMI), waist-to-hip ratio (WHR), fasting glycemia, insulin tolerance (glucose disappearance constant during an insulin tolerance test, kITT) and body composition (dual-energy X-ray absorptiometry) were studied after 1 year's use of CEE plus MPA and repeated after 1 year's use of 17beta-estradiol gel with the same schedule of MPA administration. We did not observe any difference between the oral and percutaneous HRT with regard to BMI, WHR and insulin tolerance (kITT: 4.9 +/- 1.5 vs. 5.3 +/- 1.5%/min, p = 0.8). During administration of the 17beta-estradiol gel a tendency to increased total lean mass (p = 0.054) was observed. We conclude that sequential change in the route of estrogen administration in TS patients using cyclical HRT with CEE and MPA does not affect insulin resistance, although use of percutaneous 17beta-estradiol gel seems to exert favorable changes in body composition.

Asymptomatic Helicobacter pylori infection increases asymmetric dimethylarginine levels in healthy subjects

BACKGROUND

Chronic infections have been demonstrated to be early factors of atherosclerosis and cardiovascular diseases, and their relevance increases when they are caused by agents with extremely broad spectrum of disease outcome such as Helicobacter pylori. The consequent endothelial impairment leads to a reduced bioavailability of nitric oxide. Increasing evidences have pointed out that the endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine, defined as a risk factor for cardiovascular disease, may increase in infections and plays an important role impairing the vascular functions of the endothelium. Starting from these findings, we aim to investigate whether H. pylori may affect asymmetric dimethylarginine levels.

MATERIALS AND METHODS

The study was carried out on a group of 186 subjects (age 46.2 +/- 14.9 years). We evaluated asymmetric dimethylarginine, symmetric dimethylarginine, L-arginine, presence of H. pylori by 13C-urea breath test, and the main parameters of glyco and lipo metabolic balance.

RESULTS

Increased levels of asymmetric dimethylarginine were found in H. pylori-positive subjects with respect to H. pylori-negative subjects (0.46 x/ / 1.13 versus 0.42 x/ / 1.23 mol/l, p < .001, respectively). No differences were detected in L-arginine levels between the two groups. Multiple regression analysis performed in H. pylori-positive subjects and H. pylori-negative subjects showed profound differences in the variables related to asymmetric dimethylarginine (R2 = 66.9%, p < .01 versus 34.3%, p < .01, respectively) and symmetric dimethylarginine (R2 = 39.2%, p < .01 versus 20.6%, p = .09, respectively) levels.

CONCLUSIONS

Our data clearly demonstrate that H. pylori infection increases asymmetric dimethylarginine levels. Moreover, this infection causes a profound metabolic modification that alters the role of the known determinants of asymmetric dimethylarginine levels. We conclude that H. pylori infection must be taken into account as a cause of increased asymmetric dimethylarginine levels and that the eradication of H. pylori may therefore lead to a decrease in asymmetric dimethylarginine levels, which is a further reason for the reduction of the risk for cardiovascular disease in this large portion of population.

Effect of atorvastatin on non-cholesterol sterols in patients with type 2 diabetes mellitus and cardiovascular disease

An increased risk of cardiovascular morbidity and mortality in diabetes mellitus type 2 has been associated with disturbances of lipid homeostasis. Recently, decreased intestinal absorption of cholesterol and increased liver cholesterol production have been reported. To investigate the influence of cholesterol lowering therapy using statin on cholesterol turnover in diabetes mellitus type 2, the levels of non-cholesterol based sterols were studied. One hundred and thirty five patients with type 2 diabetes and non-diabetic controls with cardiovascular diseases were studied. Both groups were divided into two subgroups: treated with atorvastatin and without statin therapy. The diabetics showed significantly higher levels of lathosterol (6.97micromol l(-1) versus 5.11micromol l(-1), p = 0.012) and lower levels of sitosterol (5.03micromol l(-1) versus 8.98micromol l(-1), p < 0.001) and campesterol (6.35micromol l(-1) versus 9.80micromol l(-1), p < 0.001). Non-diabetics showed no significant differences in non-cholesterol based sterols in relation to atorvastatin therapy. A significantly lower level of lathosterol as well as a decrease in lathosterol/cholesterol ratio in the statin treated groups was found in diabetics (4.11micromol l(-1) versus 7.83micromol l(-1), p < 0.001). The results based on ANOVA analysis show that the effect of atorvastatin on the lathosterol level is more pronounced in diabetics. Regression analysis showed the relationship between increased triglycerides levels and the increase in cholesterol synthesis. The calculated regression model for loglathosterol in diabetics has the following form: log(lathosterol) = 2.76 - 0.52.statin + 0.22.cholesterol (ANOVA, p < 0.001, R(2) = 34%, p = 0.005 for statin, p < 0.001 for cholesterol). We conclude that in spite the total cholesterol level in diabetics type 2 is not increased, its endogenous synthesis is enhanced. Our results show that the diabetics type 2 with increased serum lathosterol and expressed metabolic syndrome (mild increase of triglycerides) might represent a suitable group for intensive treatment with statins.

Sibutramine enhances insulin sensitivity ameliorating metabolic parameters in a double-blind, randomized, placebo-controlled trial

AIM

To assess the effect of sibutramine-assisted weight reduction program on insulin sensitivity and metabolic parameters in obese normal glucose tolerant individuals over a period of 24 weeks.

RESEARCH DESIGN AND METHODS

A double-blind, placebo-controlled, parallel, prospective clinical trial was carried out at our medical centre. Forty female normal glucose tolerant patients, body mass index: 34.3 +/- 2.9 kg/m2 and age: 41.1 +/- 9.9 (range: 19-58 years), were randomized to placebo or sibutramine, 10 mg once daily.

RESULTS

Seventeen patients from sibutramine group and 14 placebo had completed the study protocol. Significant weight change was seen in sibutramine (p < 0.01) (-5.6 kg or -6.1% vs. +0.9 kg or +1.1% in placebo). Insulin sensitivity enhanced in sibutramine group (Kitt: from 4.03 +/- 1.97 to 5.09 +/- 2.48%/min; p < 0.05). Homeostasis model assessment-IR (HOMA-IR) decreased from 7.8 +/- 6.9 to 5.6 +/- 4.5 (p < 0.05). HOMA-beta also decreased from 508 +/- 381 to 374 +/- 256 (p < 0.05). No changes were observed in the placebo control group regarding insulin sensitivity or secretion. Concomitant reductions were observed in the sibutramine group in lipid parameters (triglycerides and high-density lipoprotein-cholesterol), uric acid and gamma-glutamyl transferase (p < 0.05).

CONCLUSIONS

Sibutramine has demonstrated efficacy in reducing weight in non-diabetic women along with amelioration in insulin sensitivity and additional improvement in metabolic parameters.

A pilot study of long-term effects of a novel obesity treatment: omentectomy in connection with adjustable gastric banding

AIM

To determine whether visceral fat reduction in connection with bariatric surgery could improve weight loss and metabolic profile of obese subjects.

PATIENTS AND METHODS

In a one-center, randomized and controlled pilot trial we assigned 50 subjects with severe obesity (body mass index >35 kg/m(2)) to either adjustable gastric banding (AGB) alone (11 men and 14 women), or AGB plus surgical removal of the total greater omentum (11 men and 14 women). The patients were followed at regular intervals for 2 y and examined at 0 and 24 months with respect to body composition and metabolic profile.

RESULTS

No significant differences between control and omentectomized patients were observed at baseline. The removed greater omentum constituted 0.8+/-0.4% (mean+/-s.d.) of total body fat. At 2 y follow-up there was an expected decrease in body weight and an improvement in metabolic profile in both groups. Although omentectomized subjects tended to lose more weight than control subjects the difference was not statistically significant and changes in waist-to-hip ratio and saggital diameter did not differ between groups. However, the improvements in oral glucose tolerance, insulin sensitivity and fasting plasma glucose and insulin were 2-3 times greater in omentectomized as compared to control subjects (P from 0.009 to 0.04), which was statistically independent of the loss in body mass index. No differences in blood lipids between the groups were recorded. No adverse effects related to omentectomy were observed.

CONCLUSIONS

Omentectomy, when performed together with AGB, has significant positive and long-term effects on the glucose and insulin metabolic profiles in obese subjects.

The insulin tolerance test in morbidly obese patients undergoing bariatric surgery

OBJECTIVE

To assess the effect of massive weight loss in relation to insulin resistance and its correlation to changes in glycemic homeostasis and lipid profile in severely obese patients.

RESEARCH METHODS AND PROCEDURES

A prospective clinical intervention study was carried out with 31 morbidly obese women (body mass index: 54.2 +/- 8.8 kg/m(2)) divided into three groups according to their glucose tolerance test: 14 normal, 8 impaired glucose tolerance, and 9 type 2 diabetes. All subjects underwent an insulin tolerance test with intravenous bolus of 0.1 U insulin/kg body weight before silastic ring vertical gastroplasty Roux-en-Y gastric bypass surgery, and again at 2, 4, 6, and 12 months postoperatively. Fasting plasma glucose, hemoglobin A1c, and lipid profile were also evaluated.

RESULTS

A reduction of 68 +/- 15% in initial excess body weight was evident within 1 year. Along with weight loss, the following statistically significant changes were found: an increase in the insulin-sensitivity index (Kitt) and a decrease in fasting plasma glucose and hemoglobin A1c, most notably in the type 2 diabetes group. An overall improvement in lipid profile was observed in all three groups.

DISCUSSION

Bariatric surgery was an effective therapeutic approach for these obese patients because it reduced both weight and insulin resistance, along with improving metabolic parameters. Significant correlations were found between insulin resistance and metabolic improvements. Weight loss after bariatric surgery induced an improvement in metabolic fitness, related to the reduction in insulin resistance over a range of glucose tolerance statuses from normal to diabetic.