Abdominal visceral fat accumulation is associated with the results of (123)I-metaiodobenzylguanidine myocardial scintigraphy in type 2 diabetic patients

Visceral Fat Accumulation Is Associated with Asthma in Patients with Type 2 Diabetes

OBJECTIVE

The number of patients with type 2 diabetes has increased in Japan, and type 2 diabetes has attracted attention as a risk factor for asthma. However, the risk factors for the development of asthma in patients with type 2 diabetes have not been determined. This study was performed to clarify whether visceral fat accumulation (VFA) and insulin resistance are risk factors for the development of asthma in patients with type 2 diabetes.

MATERIALS AND METHODS

A cross-sectional study was conducted. The study group comprised 15 patients with type 2 diabetes with asthma, and the control group comprised 145 patients with type 2 diabetes without asthma. Their fat distribution was evaluated by measuring the VFA by abdominal computed tomography at the umbilical level. Their glucose status was assessed by measuring the fasting plasma glucose (FPG) concentration, fasting immunoreactive insulin concentration, homeostasis model assessment (HOMA) index, and hemoglobin A1c concentration.

RESULTS

Among patients with type 2 diabetes, VFA was significantly greater in patients with asthma than those without asthma (P < 0.0001). The FPG concentration, fasting immunoreactive insulin concentration, and HOMA index were higher in patients with asthma than those without asthma (P < 0.05, P < 0.0001, and P < 0.0001, respectively). Multiple logistic regression analysis showed that VFA and the HOMA index were significantly associated with asthma in patients with type 2 diabetes (odds ratio, 1.78; 95% confidence interval, 1.31-3.89; P = 0.0115 and odds ratio, 3.65; 95% confidence interval, 1.37-7.85; P = 0.0078, respectively).

CONCLUSIONS

Our data suggest that VFA and insulin resistance are associated with the development of asthma in patients with type 2 diabetes.

Norepinephrine transporter expression is inversely associated with glycaemic indices: a pilot study in metabolically diverse persons with overweight and obesity

Objective

The objective of this study was to examine the cross‐sectional relationship between the expression of norepinephrine transporter (NET), the protein responsible for neuronal uptake‐1, and indices of glycaemia and hyperinsulinaemia, in overweight and obese individuals.

Methods

Thirteen non‐medicated, non‐smoking subjects, aged 58 ± 1 years (mean ± standard error of the mean), body mass index (BMI) 31.4 ± 1.0 kg m⁻², with wide‐ranging plasma glucose and haemoglobin A1c (HbA1c, range 5.1% to 6.5%) participated. They underwent forearm vein biopsy to access sympathetic nerves for the quantification of NET by Western blot, oral glucose tolerance test (OGTT), euglycaemic hyperinsulinaemic clamp, echocardiography and assessments of whole‐body norepinephrine kinetics and muscle sympathetic nerve activity.

Results

Norepinephrine transporter expression was inversely associated with fasting plasma glucose (r = −0.62, P = 0.02), glucose area under the curve during OGTT (AUC_0–120, r = −0.65, P = 0.02) and HbA1c (r = −0.67, P = 0.01), and positively associated with steady‐state glucose utilization during euglycaemic clamp (r = 0.58, P = 0.04). Moreover, NET expression was inversely related to left ventricular posterior wall dimensions (r = −0.64, P = 0.02) and heart rate (r = −0.55, P = 0.05). Indices of hyperinsulinaemia were not associated with NET expression. In stepwise linear regression analysis adjusted for age, body mass index and blood pressure, HbA1c was an independent inverse predictor of NET expression, explaining 45% of its variance.

Conclusions

Hyperglycaemia is associated with reduced peripheral NET expression. Further studies are required to identify the direction of causality.

A randomized controlled trial of the effects of pioglitazone treatment on sympathetic nervous system activity and cardiovascular function in obese subjects with metabolic syndrome

CONTEXT

Insulin resistance and sympathetic nervous system overactivity are closely associated and contribute to cardiovascular risk.

OBJECTIVE

The objective of the study was to test the hypotheses that pharmacological improvement in insulin sensitivity would (1) attenuate sympathetic neural drive and (2) enhance neuronal norepinephrine uptake.

PARTICIPANTS AND METHODS

A randomized, double-blind trial was conducted in 42 obese, unmedicated individuals with metabolic syndrome (mean age 56 ± 1 y, body mass index 34 ± 0.6 kg/m(2)) who received 12 weeks of pioglitazone (PIO; 15 mg for 6 wk, then 30 mg daily) or matched placebo. Clinical measurements included whole-body norepinephrine kinetics [spillover rate, plasma clearance, and the steady state ratio of tritiated 3,4-dihydroxyphenylglycol to tritiated norepinephrine ([(3)H]-DHPG to [(3)H]-NE) as an index of neuronal uptake-1], muscle sympathetic nerve activity, spontaneous baroreflex sensitivity, euglycemic hyperinsulinemic clamp, oral glucose tolerance test, ambulatory blood pressure, and Doppler echocardiography.

RESULTS

PIO treatment increased glucose uptake by 35% and was accompanied by significant reductions in diastolic blood pressure and improved left ventricular diastolic and endothelial function. Resting muscle sympathetic nerve activity burst frequency decreased by -6 ± 3 burst/min compared with baseline (P = .03), but the magnitude of change was not different from placebo (P = .89). Norepinephrine spillover and clearance rates and baroreflex sensitivity were unchanged. Post hoc subgroup analyses revealed an 83% increase in [(3)H]-DHPG to [(3)H]-NE ratio in hyperinsulinemic (P = .04) but not normoinsulinemic subjects (time × group interaction, P = .045). Change in [(3)H]-DHPG to [(3)H]-NE ratio correlated with improvements in diastolic blood pressure (r = -0.67, P = .002), the ratio of early (E) to late (A) peak transmitral diastolic inflow velocity (r = 0.62, P = .008), E wave deceleration time (r = -0.48, P = .05), and Δinsulin area under the curve0-120 during the oral glucose tolerance test (r = -0.42, P = .08).

CONCLUSIONS

Compared with placebo, PIO does not affect resting sympathetic drive or norepinephrine disposition in obese subjects with metabolic syndrome. Treatment induced changes in the [(3)H]-DHPG to [(3)H]-NE ratio related to reduction in hyperinsulinemia and improvements in diastolic function.

The effects of dietary weight loss on indices of norepinephrine turnover: modulatory influence of hyperinsulinemia

OBJECTIVES

This study was conducted to examine (1) the effects of dietary weight loss on indices of norepinephrine (NE) turnover and (2) whether baseline hyperinsulinemia modulates sympathetic neural adaptations.

METHODS

Obese individuals aged 56 ± 1 year, BMI 32.5 ± 0.4 kg/m(2) , with metabolic syndrome, underwent a 12-week hypocaloric diet (HCD, n = 39) or no treatment (n = 26). Neurochemical measurements comprised arterial dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylglycol (DHPG), and NE concentrations, the steady-state ratio of [3H]-DHPG to [3H]-NE, as an index of neuronal uptake, and calculated whole-body plasma NE clearance and spillover rates.

RESULTS

Body weight decreased by -7.4 ± 0.5% in HCD group (P < 0.001) and was accompanied by reductions in DOPA, NE, and DHPG averaging -14 ± 5% (P = 0.001), -23 ± 4% (P <0.001), and -5 ± 4% (P = 0.03), respectively. NE spillover rate decreased by -88 ± 39 ng/min (P = 0.01), whereas neuronal uptake and NE plasma clearance were unchanged. Despite similar weight loss, hyperinsulinemic subjects exhibited greater reductions in NE and NE spillover rate, compared to normoinsulinemic subjects (group by time interaction P < 0.05).

CONCLUSIONS

Weight loss is associated with down-regulation of sympathetic nervous activity but no overall alteration in disposition indices. Hyperinsulinemic subjects derive a greater sympathoinhibitory benefit during weight loss.

Cardiac autonomic neuropathy in patients with diabetes and no symptoms of coronary artery disease: comparison of 123I-metaiodobenzylguanidine myocardial scintigraphy and heart rate variability

Purpose

The purpose of this study was to evaluate the prevalence of cardiac autonomic neuropathy (CAN) in a cohort of patients with type 2 diabetes, truly asymptomatic for coronary artery disease (CAD), using heart rate variability (HRV) and ¹²³I-metaiodobenzylguanidine (¹²³I-mIBG) myocardial scintigraphy.

Methods

The study group comprised 88 patients with type 2 diabetes prospectively recruited from an outpatient diabetes clinic. In all patients myocardial perfusion scintigraphy, CAN by HRV and ¹²³I-mIBG myocardial scintigraphy were performed. Two or more abnormal tests were defined as CAN-positive (ECG-based CAN) and one or fewer as CAN-negative. CAN assessed by ¹²³I-mIBG scintigraphy was defined as abnormal if the heart-to-mediastinum ratio was <1.8, the washout rate was >25%, or the total defect score was >13.

Results

The prevalence of CAN in patients asymptomatic for CAD with type 2 diabetes and normal myocardial perfusion assessed by HRV and ¹²³I-mIBG scintigraphy was respectively, 27% and 58%. Furthermore, in almost half of patients with normal HRV, ¹²³I-mIBG scintigraphy showed CAN.

Conclusion

The current study revealed a high prevalence of CAN in patients with type 2 diabetes. Secondly, disagreement between HRV and ¹²³I-mIBG scintigraphy for the assessment of CAN was observed.

White matter lesions are associated with the results of 123I-metaiodobenzylguanidine myocardial scintigraphy in type 2 diabetes mellitus patients

White matter lesions (WMLs) and cardiovascular autonomic dysfunction are associated with high mortality in type 2 diabetes mellitus patients. This preliminary study was therefore designed to test the hypothesis that WML is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetes mellitus patients without insulin treatment. Based on brain magnetic resonance imaging findings, 55 type 2 diabetes mellitus patients were divided into 2 groups: a WML-positive group (59 +/- 5 years [mean +/- SD], n = 21) and a WML-negative group (58 +/- 6 years, n = 34). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy. Baroreflex sensitivity was lower in the WML-positive group than in the WML-negative group (P < .01). Early and delayed (123)I-MIBG myocardial uptake values were lower (P < .005 and P < .001, respectively) and the percentage washout rate (WR) of (123)I-MIBG was higher (P < .0001) in the WML-positive group than in the WML-negative group. The fasting plasma glucose (P < .005) and insulin concentrations (P < .0001) and the homeostasis model assessment (HOMA) index values (P < .0001) were higher in the WML-positive group than in the WML-negative group. Multiple logistic regression analysis revealed that HOMA index and percentage WR of (123)I-MIBG were associated with WML patients. Our results suggested that WML was associated with depressed cardiovascular autonomic function and insulin resistance and that HOMA index and the percentage WR of (123)I-MIBG were independent associations for WML in Japanese patients with type 2 diabetes mellitus.

Diabetic retinopathy is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients

Diabetic retinopathy (DR) and cardiovascular autonomic dysfunction are associated with high mortality in type 2 diabetic patients. This preliminary study was therefore designed to test the hypothesis that DR is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients without insulin treatment. Seventy persons were diagnosed to have type 2 diabetes in the examination from June 2004 to May 2006. The study group consisted of 29 type 2 diabetic patients with DR (age: 58+/-6 years, mean+/-s.d.) and 41 type 2 diabetic patients with no DR (NDR) (n=41, 58+/-5 years). Cardiovascular autonomic function was assessed by baroreflex sensitivity (BRS), heart rate variability, plasma norepinephrine concentration and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphic findings. DR patients had lower BRS, early and delayed (123)I-MIBG myocardial uptake values and higher percent washout rate (WR) of (123)I-MIBG than the NDR patients. With respect to metabolic findings, DR patients had higher fasting plasma insulin concentration (P<0.0001) and higher homeostasis model assessment (HOMA) index (P<0.00001) than the NDR patients. Multiple logistic regression analysis revealed that the presence of DR was independently predicted by HOMA index and the percent WR of (123)I-MIBG (P<0.01 and P<0.05, respectively). Our results suggest that DR is associated with depressed cardiovascular autonomic function and insulin resistance and that HOMA index and the percent WR of (123)I-MIBG are independently associated with DR in Japanese patients with type 2 diabetes mellitus.

Hepatocyte growth factor levels are associated with the results of 123I-metaiodobenzylguanidine myocardial scintigraphy in patients with type 2 diabetes mellitus

Elevated hepatocyte growth factor (HGF) levels and cardiovascular autonomic dysfunction are associated with a high mortality rate in patients with type 2 diabetes mellitus. We tested the hypothesis that elevated HGF is associated with insulin resistance and cardiovascular autonomic dysfunction in patients with type 2 diabetes mellitus not receiving insulin treatment. The study group consisted of 21 type 2 diabetes mellitus patients with high HGF levels (>0.26 ng/mL, 58 +/- 5 years old, high-HGF group). The control group consisted of 25 type 2 diabetes mellitus patients with normal HGF levels (<or=0.26 ng/mL, 58 +/- 9 years old, normal-HGF group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy. Early and delayed (123)I-MIBG myocardial uptake values were lower (P < .005 and P < .01, respectively) and the percentage of washout rate of (123)I-MIBG was higher (P < .001) in the high-HGF group than in the normal-HGF group. The fasting plasma insulin concentrations (P < .0001) and the homeostasis model assessment index values (P < .0001) were higher in the high-HGF group than in the normal-HGF group. Multiple regression analysis revealed that the level of HGF was independently predicted by the homeostasis model assessment index values and the myocardial uptake of (123)I-MIBG at the delayed phase. Our results demonstrate that high levels of HGF are associated with depressed cardiovascular autonomic function and insulin resistance in patients with type 2 diabetes mellitus.

Role of interleukin-6 levels in cardiovascular autonomic dysfunction in type 2 diabetic patients

PURPOSE

Increased serum interleukin-6 (IL-6) levels are associated with an increased risk of cardiovascular disease, and cardiovascular autonomic dysfunction is associated with high mortality in type 2 diabetic patients. However, the relationship between IL-6 levels and cardiovascular autonomic dysfunction has not been fully elucidated. The aim of this study was to determine whether serum IL-6 levels are associated with cardiovascular autonomic dysfunction in type 2 diabetic patients.

METHODS

Eighty type 2 diabetic patients who did not have organic heart disease were categorized into a high IL-6 group (>2.5 pg/ml, n = 40, age 59 +/- 12 years) or a non-high IL-6 group (<2.5 pg/ml, n = 40, 61 +/- 12 years). Cardiac autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations and (123)I-metaiodobenzylguanidine (MIBG) scintigraphy.

RESULTS

The body mass index values (BMI), fasting insulin levels and homeostasis model assessment index values were higher in the high IL-6 group than in the non-high IL-6 group (p < 0.01). Early and delayed (123)I-MIBG myocardial uptake values were lower (p < 0.01), and the percent washout rate of (123)I-MIBG was higher (p < 0.05) in the high IL-6 group than in the non-high IL-6 group. Furthermore, multiple regression analysis revealed that the IL-6 level was independently predicted by the BMI and the myocardial uptake of (123)I-MIBG during the delayed phase.

CONCLUSIONS

The results indicate that elevated IL-6 levels are associated with depressed cardiovascular autonomic function and obesity in type 2 diabetic patients.