Microalbuminuria, cardiovascular autonomic dysfunction, and insulin resistance in patients with type 2 diabetes mellitus

FGR-associated placental insufficiency and capillary angiogenesis involves disruptions in human placental miRNAs and mRNAs

Fetal growth restriction (FGR) is one of the most common pregnancy complications culminating in adverse fetal outcome, including preterm birth, neonatal mortality and stillbirth. Compromised placental development and function, especially disruption in angiogenesis and inadequate nutrient supply are contributing factors. Fetal sex also influences placental function. Knowledge of gene expression changes and epigenetic factors contributing to placental dysfunction in FGR pregnancies will help identify biomarkers and help target interventions. This study tested the hypothesis that FGR pregnancies are associated with disruptions in miRNA - an epigenetic factor and mRNAs involving key mediators of angiogenesis and microvessel development. Changes in expression of key genes/proteins involved in placental dysfunction by RT-PCR and immunohistochemistry and miRNA changes by RNA sequencing were undertaken with term placenta from 12 control and 20 FGR pregnancies. Findings showed changes in expression of genes involved in steroidogenesis, steroid action, IGF family members, inflammatory cytokines and angiogenic factors in FGR pregnancies. In addition, upregulation of MIR451A and downregulation of MIR543 in placentas from FGR group with female newborns and upregulation of MIR520G in placentas from FGR group with male newborns were also noted. MIR451A and MIR543 have been implicated in angiogenesis. Consistent with gene changes, CD34, the microvessel angiogenesis marker, also showed reduced staining only in female FGR group. These findings provide evidence that epigentically regulated gene expression changes in angiogenesis and capillary development influence placental impairment in FGR pregnancies. Our preliminary observations also support for these changes to be driven in a sex-specific manner.

Insulin Resistance is Associated with Clinical Manifestations of Diabetic Kidney Disease (Glomerular Hyperfiltration, Albuminuria, and Kidney Function Decline)

Clinical features of diabetic kidney disease include glomerular hyperfiltration, albuminuria, and kidney function decline towards End-Stage Kidney Disease (ESKD). There are presently neither specific markers of kidney involvement in patients with diabetes nor strong predictors of rapid progression to ESKD. Serum-creatinine-based equations used to estimate glomerular filtration rate are notoriously unreliable in patients with diabetes. Early kidney function decline, reduced glomerular filtration rate, and proteinuria contribute to identifying diabetic patients at higher risk for rapid kidney function decline. Unlike proteinuria, the elevation of urinary albumin excretion in the range of microalbuminuria is frequently transient in patients with diabetes and does not always predict progression towards ESKD. Although the rate of progression of kidney function decline is usually accelerated in the presence of proteinuria, histological lesions of diabetes and ESKD may occur with normal urinary albumin excretion. No substantial reduction in the rate of ESKD associated with diabetes has been observed during the last decades despite intensified glycemic control and reno-protective strategies, indicating that existing therapies do not target underlying pathogenic mechanisms of kidney function decline. Very long-term effects of sodium-glucose transporters- 2 inhibitors and glucagon-like peptide-1 analogs remain to be defined. In patients with diabetes, glucagon secretion is typically elevated and induces insulin resistance. Insulin resistance is consistently and strongly associated with clinical manifestations of diabetic kidney disease, suggesting that reduced insulin sensitivity participates in the pathogenesis of the disease and may represent a therapeutic objective. Amelioration of insulin sensitivity in patients with diabetes is associated with cardioprotective and kidney-protective effects.

Gender-specific and age-specific associations of the homoeostasis model assessment for IR (HOMA-IR) with albuminuria and renal function impairment: a retrospective cross-sectional study in Southeast China

OBJECTIVES

The study aimed to investigate the association of insulin resistance (IR), which was estimated by the homoeostasis model assessment for IR (HOMA-IR), with albuminuria and renal function impairment in a general Chinese population.

DESIGN

A retrospective cross-sectional study.

SETTING AND PARTICIPANTS

A total of 13 742 adults (age: ≥18 years) who underwent a health check-up at a hospital in Southeast China during 2013-2014 were enrolled. 216 subjects were excluded due to lack of enough fasting time, be pregnant, have chronic diseases influencing metabolic functions or have glomerulonephritis, renal cancer, kidney transplant. Eventually, 7552 men and 5974 women were included for the present analysis.

PRIMARY OUTCOME MEASURES

The association of HOMA-IR with albuminuria and renal function impairment were analysed. The HOMA-IR cut-off value for detecting albuminuria and renal function impairment were determined.

RESULTS

An increase in the HOMA-IR quartile was significantly associated with the prevalence of albuminuria and renal function impairment in all men and women aged >45 years. The multivariable logistic regression analyses revealed a significant association of the HOMA-IR with albuminuria and renal function impairment in subjects aged >45 years of the fourth quartiles compared with those of the first quartile after adjusting for potential confounders (albuminuria: men OR, 2.39; 95% CI 1.51 to 3.79, p<0.001; women OR, 2.40; 95% CI 1.44 to 4.01; p=0.001; renal function impairment: men OR, 2.30; 95% CI 1.50 to 3.51; p<0.001; women OR, 2.20; 95% CI 1.35 to 3.58; p=0.002). The optimal cut-off value of HOMA-IR for detecting albuminuria and renal function impairment was 2.69 in men aged ≤45 years, 1.60 in men aged >45 years and 1.86 in women aged >45 years.

CONCLUSIONS

Our study revealed that HOMA-IR was significantly associated with albuminuria and renal function impairment in individuals aged >45 years.

A cohort study of incident microalbuminuria in relation to HOMA-IR in Korean men

BACKGROUND

Despite the previous studies showing the relationship between microalbuminuria and insulin resistance, longitudinal effect of insulin resistance on development of microalbuminuria is not clearly identified in non-diabetic population.

METHODS

One thousand six hundred three non-diabetic Korean men without microalbuminuria in 2005 had been followed up for the development of microalbuminuria until 2010. Microalbuminuria was evaluated by urine-albumin creatinine ration, and insulin resistance was evaluated by homeostasis model assessment of insulin resistance (HOMA-IR). Cox proportional hazards model was used to estimate the risk for microalbuminuria according to the tertile of HOMA-IR.

RESULTS

During 5465.8 person-y of average follow-up, microalbuminuria developed in 76 (4.7%) participants. Incidence of microalbuminuria increased in proportion to the level of HOMA-IR (tertile 1: 3.0%, tertile 2: 4.1%, tertile 3: 7.1%, P<0.001). When the 1st tertile of HOMA-IR was set as reference, hazard ratios and 95% confidence interval were 1.15 (0.56-2.35) and 2.07 (1.05-4.09) for those in the 2nd and 3rd tertiles of HOMA-IR, even after adjusting multiple covariates, respectively (P for linear trend=0.054).

CONCLUSIONS

Increased insulin resistance was a predictor of microalbuminuria in Korean men.

Plasma norepinephrine is an independent predictor of adverse cerebral and cardiovascular events in type 2 diabetic patients without structural heart disease

BACKGROUND

Resting plasma norepinephrine (NE) level was reportedly related to high mortality in patients with heart failure. The current study investigated whether resting NE could predict long-term major adverse cerebral and cardiovascular events (MACCEs) in Japanese type 2 diabetic patients without heart disease.

METHODS AND SUBJECTS

We evaluated resting NE in 95 patients with type 2 diabetes who did not have severe complications. Based on the ROC curves, high NE was defined as ≥333pg/ml. Accurate follow-up information during a mean of 3.6±1.9 years was obtained in 27 high NE patients (13 female, mean age 64±12 years) and 68 low NE patients (29 female, 60±12 years).

ESSENTIAL RESULTS

The Kaplan-Meier curves revealed that MACCE-free ratio was significantly lower in the high NE patients than in the low NE patients (log-rank 10.3, p=0.0013). Cox proportional hazards regression analysis revealed that female gender (hazard ratio 7.75), low baroreflex sensitivity (hazard ratio 6.66), and high NE (hazard ratio 5.40) were independently associated with the incidence of MACCE.

PRINCIPAL CONCLUSIONS

Our results suggest that resting NE is comparably useful to identify the high-risk patients for MACCE to baroreflex sensitivity in type 2 diabetic patients. The results also suggest that pathogenic sympathetic activation leading to MACCE may be identified by the assessment of resting NE, more easily and less expensively compared to cardiac iodine 123 metaiodobenzylguanidine scintigraphy in this population.

Presence of macroalbuminuria predicts severe hypoglycemia in patients with type 2 diabetes: a 10-year follow-up study

OBJECTIVE

We investigated the factors that might influence the development of severe hypoglycemia in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

From January 2000 to December 2002, patients with type 2 diabetes aged 25-75 years without chronic kidney disease (estimated glomerular filtration rate ≥60 mL/min/1.73 m(2)) were consecutively recruited (n = 1,217) and followed-up in January 2011 and May 2012. Severe hypoglycemia (SH) was defined as an event requiring the assistance of another person to actively administer glucose, hospitalization, or medical care in an emergency department. We used Cox proportional hazard regression analysis to test the association between SH episodes and potential explanatory variables.

RESULTS

After a median 10.4 years of follow-up, 111 (12.6%) patients experienced 140 episodes of SH, and the incidence was 1.55 per 100 patient-years. Mean age and duration of diabetes were 55.3 ± 9.8 and 9.8 ± 6.5 years, respectively. The incidence of SH events was higher in older patients (P < 0.001), in those with a longer duration of diabetes (P < 0.001), in those who used insulin (P < 0.001) and sulfonylurea (P = 0.003), and in those who had macroalbuminuria (P < 0.001) at baseline. Cox hazard regression analysis revealed that SH was associated with longer duration of diabetes and the presence of macroalbuminuria (normoalbuminuria versus macroalbuminuria: hazard ratio, 2.52; 95% CI 1.31-4.84; P = 0.006).

CONCLUSIONS

The development of SH was independently associated with duration of diabetes and presence of macroalbuminuria, even with normal renal function in patients with type 2 diabetes.

Alterations of calcium channels and cell excitability in intracardiac ganglion neurons from type 2 diabetic rats

Clinical study has demonstrated that patients with type 2 diabetes with attenuated arterial baroreflex have higher mortality rate compared with those without arterial baroreflex dysfunction. As a final pathway for the neural control of the cardiac function, functional changes of intracardiac ganglion (ICG) neurons might be involved in the attenuated arterial baroreflex in the type 2 diabetes mellitus (T2DM). Therefore, we measured the ICG neuron excitability and Ca(2+) channels in the sham and T2DM rats. T2DM was induced by a combination of both high-fat diet and low-dose streptozotocin (STZ, 30 mg/kg ip) injection. After 12-14 wk of the above treatment, the T2DM rats presented hyperglycemia, hyperlipidemia, and insulin resistance but no hyperinsulinemia, which closely mimicked the clinical features of the patients with T2DM. Data from immunofluorescence staining showed that L, N, P/Q, and R types of Ca(2+) channels were expressed in the ICG neurons, but only protein expression of N-type Ca(2+) channels was decreased in the ICG neurons from T2DM rats. Using whole cell patch-clamp technique, we found that T2DM significantly reduced the Ca(2+) currents and cell excitability in the ICG neurons. ω-Conotoxin GVIA (a specific N-type Ca(2+) channel blocker, 1 μM) lowered the Ca(2+) currents and cell excitability toward the same level in sham and T2DM rats. These results indicate that the decreased N-type Ca(2+) channels contribute to the suppressed ICG neuron excitability in T2DM rats. From this study, we think high-fat diet/STZ injection-induced T2DM might be an appropriate animal model to test the cellular and molecular mechanisms of cardiovascular autonomic dysfunction.

Smoking cessation predicts amelioration of microalbuminuria in newly diagnosed type 2 diabetes mellitus: a 1-year prospective study

The objective of the study was to assess the effect of smoking cessation on microalbuminuria in subjects with newly diagnosed type 2 diabetes mellitus (DM). From 500 smokers newly diagnosed with type 2 DM and microalbuminuria, only 193 (96 men/97 women; age, 56.4 ± 7.8 years) agreed to participate and were educated on smoking cessation, diet, and exercise. Pharmacological interventions were not different among the studied groups. All subjects were contacted by phone monthly with emphasis on smoking cessation. Anthropometric, biochemical parameters and urine specimens were obtained at baseline and at 12-month follow-up. Microalbuminuria was defined as an albumin to creatinine ratio of 30 to 299.9 μg/mg creatinine. Ankle brachial pressure index was determined by ultrasound. A total of 120 (62.2%) subjects quit smoking. Prevalence of microalbuminuria was reduced at 1 year to 72.6% in the subjects who quit smoking and to 22.5% in those who continued smoking (P = .015). Multivariate logistic regression analysis demonstrated that independently associated with the reduction in albumin to creatinine ratio (84.8 vs 28.7 μg/mg creatinine) were amelioration of glycemic control (P < .001), blood pressure (P = .02), dyslipidemia (P = .02), and insulin resistance (P = .05). Smoking cessation also reduced the prevalence of peripheral vascular disease (P = .03) and neuropathy (P = .04). From the pharmacological and lifestyle interventions, smoking cessation had the highest and an independent contribution to the reduction of microalbuminuria (P < .001). Smoking cessation in newly diagnosed type 2 DM patients is associated with amelioration of metabolic parameters, blood pressure, and the reduction of microalbuminuria. Stricter counseling about the importance of quitting smoking upon type 2 DM diagnosis is necessary to protect against the development of diabetic nephropathy and vascular complications.

Gender difference in baroreflex sensitivity to predict cardiac and cerebrovascular events in type 2 diabetic patients

BACKGROUND

Cardiovascular autonomic neuropathy is a major complication in patients with diabetes mellitus (DM), and baroreflex sensitivity (BRS) reportedly can predict cardiovascular prognosis in type 2 DM patients. The hypothesis that cardiovascular events are associated with gender differences in BRS was tested in the present study.

METHODS AND RESULTS

From 1998, we have evaluated BRS by phenylephrine methods in 185 consecutive type 2 DM patients. The long-term prognostic value of BRS was compared between 91 female (5812 years) and 94 male patients (5811 years). There was no significant difference in age or severity and duration of DM between the 2 groups. When compared to male, the BRS value in female patients was significantly lower (9.266.0 vs. 5.975.0 ms/mmHg, P < 0.0001). During a mean of 62.7 months of follow-up, 16 female patients developed cardiovascular events (17.6%) including stroke, acute myocardial infarction, angina pectoris requiring percutaneous coronary intervention or coronary artery bypass grafting and congestive heart failure requiring admission, while only 4 male patients developed events (4.3%, P < 0.005). In females, the Kaplan-Meier curves revealed that those with depressed BRS (< 6 ms/mmHg) had a higher incidence of cardiovascular events than those with preserved BRS (P < 0.05), but this relationship was not observed in male patients.

CONCLUSIONS

Although the reason why females had a more depressed BRS remains unclear, our findings demonstrated that a depressed BRS value can accurately predict cardiovascular events, especially in female patients with type 2 DM.

Association between insulin resistance and development of microalbuminuria in type 2 diabetes: a prospective cohort study

OBJECTIVE

An association between insulin resistance and microalbuminuria in type 2 diabetes has often been found in cross-sectional studies. We aimed to reassess this relationship in a prospective Taiwanese cohort of type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS

We enrolled 738 normoalbuminuric type 2 diabetic subjects, aged 56.6 ± 9.0 years, between 2003 and 2005 and followed them through the end of 2009. Average follow-up time was 5.2 ± 0.8 years. We used urine albumin-to-creatinine ratio to define microalbuminuria and the homeostasis model assessment of insulin resistance (HOMA-IR) to assess insulin resistance. The incidence rate ratio and Cox proportional hazards model were used to evaluate the association between HOMA-IR and development of microalbuminuria.

RESULTS

We found incidences of microalbuminuria of 64.8, 83.5, 93.3, and 99.0 per 1,000 person-years for the lowest to highest quartiles of HOMA-IR. Compared with those in the lowest quartile of HOMA-IR, the incidence rate ratios for those in the 2nd, 3rd, and highest quartiles were 1.28 (95% CI 0.88-1.87), 1.44 (0.99-2.08), and 1.52 (1.06-2.20), respectively (trend test: P < 0.001). By comparison with those in the lowest quartile, the adjusted hazard ratios were 1.37 (0.93-2.02), 1.66 (1.12-2.47), and 1.76 (1.20-2.59) for those in the 2nd, 3rd, and highest HOMA-IR quartiles, respectively.

CONCLUSIONS

According to the dose-response effects of HOMA-IR shown in this prospective study, we conclude that insulin resistance could significantly predict development of microalbuminuria in type 2 diabetic patients.

Baroreflex sensitivity predicts cardiovascular events in patients with type 2 diabetes mellitus without structural heart disease

BACKGROUND

Cardiovascular autonomic neuropathy is a major complication in patients with diabetes mellitus (DM). However, the relationship between cardiovascular autonomic neuropathy and the incidence of cardiovascular events has been poorly investigated in type 2 DM. The present study aimed to assess the long-term cardiovascular predictive value of baroreflex sensitivity (BRS) in Japanese patients with type 2 DM without structural heart disease.

METHODS AND RESULTS

BRS was evaluated using the phenylephrine method in 210 patients with type 2 DM who did not have structural heart disease or other severe complications. BRS was considered depressed if <6 ms/mmHg. Accurate follow-up information for 3-10 years (mean 4.7 years) was obtained in 184 patients (90 females, 94 males; mean age 58+/-12 years). The initial onset of a major adverse cardiovascular event (MACE) was investigated. During follow-up, 19 patients presented with a MACE (4 cardiovascular deaths, 3 nonfatal myocardial infarctions, 4 coronary revascularizations, 5 strokes, 2 congestive heart failures). Cox proportional hazards regression analysis revealed that depressed BRS was independently associated with the incidence of MACE (hazard ratio 1.93, 95% confidence interval 1.09-3.82, P=0.0236).

CONCLUSIONS

Depressed BRS at baseline has long-term cardiovascular predictive value in Japanese patients with type 2 DM without structural heart disease.

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.

Insulin resistance is an independent correlate of increased urine albumin excretion: a cross-sectional study in Iranian Type 2 diabetic patients

AIMS

To assess the association of insulin resistance with increased urinary albumin excretion (UAE) in a cohort of Iranian Type 2 diabetic patients.

METHODS

Three hundred and sixty-one men and 472 women with Type 2 diabetes were enrolled from three different outpatient clinics (Tehran, Iran) during the period 2005-2008. Patients with obstructive uropathy, severe heart failure, liver disease, cancer, autoimmune disease and macroalbuminuria were not included. Microalbuminuria (MA; defined as UAE >or= 30 mg/day) was found in 242 (29.1%) patients; 591 (70.9%) subjects had normoalbuminuria (UAE < 30 mg/day). Insulin resistance was assessed using homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

HOMA-IR index values were higher in subjects with MA than those with normoalbuminuria (P < 0.00001). Adjusted values (for age, sex and duration of diabetes) of UAE and HOMA-IR were 11.81 +/- 7.51 (mg/day) and 3.30 +/- 2.21 in normoalbuminuric and 75.36 +/- 55.57 (mg/day) and 4.98 +/- 3.22 in the MA group, respectively (P < 0.00001 for all). Multiple regression analysis showed that UAE was predicted by HOMA-IR, independently of age, duration of diagnosed diabetes, triglycerides, waist circumference, metabolic control, blood pressure and related treatments (P < 0.00001). When patients were categorized into quartiles of HOMA-IR, those of the fourth quartile (i.e. the most insulin resistant) were at a higher risk of increased UAE than other quartiles [odds ratio (OR) 3.7 (95% confidence intervals 2.7-6.2)].

CONCLUSIONS

In Iranian Type 2 diabetic patients, albuminuria was strongly associated with insulin resistance. HOMA-IR is an independent predictor of UAE.

Postchallenge plasma glucose and glycemic spikes are associated with pulse pressure in patients with impaired glucose tolerance and essential hypertension

Elevated pulse pressure (PP) is associated with an increased risk of cardiovascular events. We examined whether PP is associated with post-challenge hyperglycemia in Japanese patients with essential hypertension and impaired glucose tolerance (IGT). In a total of 70 untreated essential hypertensive patients (age: 57+/-4 years, mean+/-SD; males=35, females=35), 24-h ambulatory blood pressure (ABP) monitoring, 75 g oral glucose tolerance testing (OGTT), metabolic analysis and echocardiography were performed. Patients were categorized into a high PP group (PP>or=60 mmHg, n=33) or a normal PP group (PP<60 mmHg, n=37). In all patients, 24-h systolic ABP, daytime systolic ABP, nighttime systolic ABP, and nighttime heart rate were significantly higher in the high PP group. Additionally, fasting immunoreactive insulin (F-IRI), homeostasis model assessment (HOMA) index, left ventricular mass index (LVMI) were also elevated in the high PP group. Finally, the high PP group exhibited impaired insulin secretion, increased post-challenge glucose concentrations and greater glucose spikes (PGS) during 75 g OGTT. Of the parameters measured, 24-h PP correlated positively with age, triglyceride, uric acid, F-IRI, HOMA index, 1-h postload glucose and insulin, 2-h postload glucose and insulin, PGS60, PGS120, PGSmax, LVMI, and deceleration time but correlated negatively with HDL-cholesterol and E/A ratio. Multiple regression analysis revealed that PP level was independently predicted by age, LVMI, and PGS120. Our results show that age, LVMI, and PGS120 are significantly associated with high PP in Japanese patients with IGT and essential hypertension.

Progression of cardiovascular autonomic dysfunction in patients with type 2 diabetes: a 7-year follow-up study

OBJECTIVE

We investigated whether cardiovascular autonomic dysfunction was associated with glycemic control status over time in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

From 1999 to 2000, cardiovascular autonomic nerve function testing (AFT) was performed on patients with type 2 diabetes (n = 1,021) and was followed-up in 2006 and February 2008. Tests for cardiovascular autonomic functions measured heart rate variability parameters (expiration-to-inspiration [E/I] ratio, responses to the Valsalva maneuver, and standing). AFT scores were determined from the results of the each test as follows: 0 for normal and 1 for abnormal. We began with those who had a score of 0 and assessed the changes in total score along with biannual A1C levels.

RESULTS

At follow-up, the development of cardiovascular autonomic dysfunction was 34.5% (E/I ratio 21.9%, Valsalva maneuver 77.8%, and posture 58.9%; n = 783). The development of cardiovascular autonomic dysfunction was higher in older patients (P < 0.001); in those with longer duration of diabetes (P < 0.001); of hypertension (P = 0.005), and of diabetic retinopathy (P < 0.001); and in those who had higher levels of microalbuminuria (P = 0.002). Logistic regression analysis revealed that the development of cardiovascular autonomic dysfunction was strongly associated with the mean A1C level during the follow-up period (mean A1C >9.0% vs. <or=7.0%, odds ratio 2.984, 95% CI 1.177-7.561; P = 0.021).

CONCLUSIONS

The development of cardiovascular autonomic dysfunction was independently associated with microvascular complications and glycemic control status during this 7.5-year follow-up in patients with type 2 diabetes.

Pioglitazone shift circadian rhythm of blood pressure from non-dipper to dipper type in type 2 diabetes mellitus

BACKGROUND

Insulin resistance significantly correlated with a non-dipper type of essential hypertension. Thiazolidinediones (TZD), oral hypoglycaemic agents that act as insulin sensitizers, have been demonstrated in multiple in vivo and in vitro studies to possess antihypertensive properties. This study examined the efficacy of TZD therapy with pioglitazone at transforming the circadian rhythms of blood pressure from a non-dipper to a dipper type.

MATERIALS

We examined 31 patients with type 2 diabetes mellitus during both a baseline period and a period of treatment with pioglitazone. Patients received 15 mg day(-1) pioglitazone for four weeks and 30 mg day(-1) for 12 weeks. Twenty-four hour ambulatory blood pressure monitoring (ABPM) and laboratory data (blood tests for cardiovascular risk factors) were obtained at the beginning and end of the study.

RESULTS

In non-dippers (n = 16), but not dippers (n = 15), we observed a significant interaction between pioglitazone therapy and nocturnal falls in systolic and diastolic blood pressure. This examination indicated that the magnitude of the nocturnal blood pressure fall was affected by pioglitazone therapy. In non-dippers, but not dippers, a significant correlation was observed between the percent decrease in nocturnal BP and the homeostasis model assessment (HOMA) index (r = 0.774, P = 0.0007).

CONCLUSIONS

The present study demonstrated that pioglitazone can restore the nocturnal BP declines in parallel to reductions in the HOMA index, suggesting that insulin resistance may play an important role in the genesis of circadian BP rhythms. TZD-based treatment may thus have the additional therapeutic advantage of reducing the risk of cardiovascular complications by transforming the circadian rhythm of BP.

Hypoadiponectinemia in type 2 diabetes mellitus in men is associated with sympathetic overactivity as evaluated by cardiac 123I-metaiodobenzylguanidine scintigraphy

Hypoadiponectinemia is associated with insulin resistance. However, there is very limited information about the relationship between plasma adiponectin and cardiac autonomic nervous function. We tested the hypothesis that hypoadiponectinemia is associated with cardiac sympathetic overactivity in patients with type 2 diabetes mellitus. Thirty-three male type 2 diabetic patients not on insulin treatment were classified into a hypoadiponectinemia group (plasma adiponectin concentration, <4.0 microg/mL; age, 58.6 +/- 8.6 years [mean +/- SD]; n = 14) and an age-matched normoadiponectinemia group (serum adiponectin concentration, >/=4.0 microg/mL; age, 58.2 +/- 8.1 years; n = 19). In each patient, baroreflex sensitivity, heart rate variability, plasma norepinephrine concentration, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphic findings were assessed. Compared with the normoadiponectinemia group, the hypoadiponectinemia group had a higher body mass index (P < .01), higher plasma concentrations of glucose and insulin (P < .05 and P < .01, respectively), higher homeostasis model assessment of insulin resistance (HOMA-IR) values (P < .005), higher plasma triglyceride levels (P < .05), and lower plasma high-density lipoprotein cholesterol levels (P < .05). In the hypoadiponectinemia group, the autonomic function measurements included a lower baroreflex sensitivity (P< .05) and a lower delayed myocardial uptake of (123)I-MIBG (P < .01) with a higher washout rate (P < .05). Multiple regression analysis revealed that the plasma adiponectin level was independently associated with HOMA-IR (F = 9.916) and the percent washout rate of (123)I-MIBG (F = 5.985). Our results suggest that in middle-aged men with type 2 diabetes mellitus, hypoadiponectinemia is associated with cardiac sympathetic overactivity as determined by (123)I-MIBG scintigraphy.

Treatment of hypertension in patients with diabetes mellitus

Antihypertensive treatment in diabetes mellitus, especially in diabetics known to have cardiac autonomic neuropathy, may have to consider the status of the autonomic nervous system. In diabetic subjects with cardiac autonomic neuropathy, vagal activity during the night is often reduced. The reduction results in relative or absolute sympathetic activation, which could increase cardiovascular risk. Pathophysiological and clinical data suggests that antihypertensive treatment should reduce rather than induce sympathetic activity in this setting. Beta blocking agents, ACE inhibitors, calcium antagonists of verapamil or diltiazem type and selective imidazoline receptor agonists reduce sympathetic activity and, therefore, may have a beneficial effect in diabetic patients with disturbed sympathovagal balance.

Smoking is associated with urinary albumin excretion: an evaluation of premenopausal patients with type 2 diabetes mellitus

Cigarette smoking and an increase in urinary albumin excretion are associated with high mortality in patients with type 2 diabetes mellitus. We tested the hypothesis that the presence of a smoking habit correlates with increased urinary albumin excretion in premenopausal Japanese women with type 2 diabetes mellitus. The study consisted of 20 premenopausal Japanese patients with type 2 diabetes mellitus in the current-smokers group (age, 45 +/- 4 years, mean +/- SD). The control group consisted of 35 age-matched never-smoker patients (age, 45 +/- 5 years). Serum triglyceride levels were higher and high-density lipoprotein cholesterol levels were lower in the current-smokers group than in the never-smokers group (P < .05 and P < .01, respectively). Furthermore, fasting plasma insulin concentrations and the homeostasis model assessment index were higher in the current-smokers group than in the never-smokers group (P < .005 and P < .001, respectively). Urinary albumin excretion also was higher in the current-smokers group than in the never-smokers group (P < .0001). Multivariate logistic analysis revealed that urinary albumin excretion is independently associated with current smoking in Japanese premenopausal with type 2 diabetes mellitus (odds ratio, 1.79; 95% confidence interval, 1.08-3.87; P < .01). The results of this study show that current smoking is associated with an increased level of urinary albumin excretion, suggesting that smoking was a risk factor in the development of increased urinary albumin excretion in these patients.

Homocysteine levels are associated with the results of 123I-metaiodobenzylguanidine myocardial scintigraphy in type 2 diabetic patients

PURPOSE

Elevated total plasma homocysteine (tHcy) levels and cardiovascular autonomic dysfunction are associated with a high mortality in type 2 diabetic patients. We tested the hypothesis that hyperhomocysteinemia is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients not receiving insulin treatment.

METHODS

The study group consisted of 17 type 2 diabetic patients with high tHcy levels (>15 mmol/l, age 58+/-5 years, high tHcy group). The control group consisted of 23 age-matched type 2 diabetic patients with normal tHcy levels (<or=15 mmol/l, age 58+/-9 years, normal tHcy group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations, and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy.

RESULTS

Early and delayed (123)I-MIBG myocardial uptake values were lower (p<0.005 and p<0.01, respectively) and the percent washout rate of (123)I-MIBG was higher (p<0.001) in the high tHcy group than in the normal tHcy group. The fasting plasma insulin concentrations (p<0.0001) and the homeostasis model assessment (HOMA) index values (p<0.0001) were higher in the high tHcy group than in the normal tHcy group. Multiple regression analysis revealed that the level of tHcy was independently predicted by the HOMA index values and the myocardial uptake of (123)I-MIBG at the delayed phase.

CONCLUSION

Our results demonstrate that high levels of tHcy are associated with depressed cardiovascular autonomic function and insulin resistance in patients with type 2 diabetes mellitus.

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

BACKGROUND

Smoking and cardiovascular autonomic dysfunction are associated with high mortality in type 2 diabetic patients. This study tested the hypothesis that smoking is associated with insulin resistance/hyperinsulinaemia and cardiovascular autonomic dysfunction in type 2 diabetic patients who are not treated with insulin.

MATERIALS AND METHODS

The study patients were 22 current smokers with type 2 diabetes mellitus (age: 57 +/- 5 years, mean +/- SD) and 30 age-matched never-smoked patients with type 2 diabetes mellitus (control group, 57 +/- 8 years). The quality of blood glucose was assessed by fasting plasma glucose (FPG), fasting immunoreactive insulin (F-IRI), homeostasis model assessment (HOMA) index and haemoglobin A1c (HbA1c). The severity of smoking status was expressed by the Brinkman index, which is calculated as number of cigarettes per day multiplied by years of smoking. Cardiovascular autonomic function was assessed by baroreflex sensitivity (BRS), heart-rate variability, plasma norepinephrine concentration and cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphic findings.

RESULTS

Baroreflex sensitivity was lower in the current smokers group than in the never-smoked group (P < 0.05). Early and delayed (123)I-MIBG myocardial uptake values were lower (P < 0.05, and P < 0.01, respectively) and the percentage washout-rate of (123)I-MIBG was higher (P < 0.0001) in the current smokers group than in the never-smoked group. Fasting immunoreactive insulin (F-IRI) concentration (P < 0.0001) and the homeostasis model assessment (HOMA) index (P < 0.0001) were higher in the current smokers group than the never-smoked group. Multiple logistic regression analysis revealed that smoking was independently predicted by F-IRI and the percentage washout-rate of (123)I-MIBG.

CONCLUSIONS

The results of the study suggested that smoking was associated with cardiovascular autonomic dysfunction and hyperinsulinaemia and that F-IRI and the percentage washout-rate of (123)I-MIBG were independent predictors of smoking in these Japanese patients with type 2 diabetes mellitus.

Insulin resistance and microalbuminuria: a cross-sectional, case-control study of 158 patients with type 2 diabetes and different degrees of urinary albumin excretion

Microalbuminuria is a risk factor for renal and cardiovascular disease. A role for insulin resistance in the pathogenesis of microalbuminuria has been suggested but is still unproven. In this case-control, cross-sectional study, we compared glucose disposal rate (GDR), measured by hyperinsulinemic-euglycemic clamp, in 50 pairs of matched type 2 diabetic patients with micro- or normoalbuminuria (main study) and in 29 matched pairs of diabetic patients with macro- or microalbuminuria (substudy). In the main study, GDR was approximately 25% lower in micro- than in normoalbuminuric patients (5.20 +/- 1.91 vs. 6.86 +/- 2.88 mg . kg(-1) . min(-1), P < 0.05) and was independently associated with microalbuminuria (P = 0.002), with each 1 mg . kg(-1) . min(-1) decrease predicting approximately 40% increased prevalence (odds ratio 1.37 [95% CI 1.14-1.70]). Microalbuminuria was threefold more frequent in patients with GDR < or =7.50 +/- 2.56 mg . kg(-1) . min(-1) than in those with higher GDR (60% vs. 20%, P < 0.005). In the substudy, GDR in macro- and microalbuminuric patients was comparable (5.52 +/- 2.56 vs. 5.16 +/- 1.61 mg . kg(-1) . min(-1)) and independent of macroalbuminuria. GDR was significantly correlated with urinary albumin excretion rate in the main study (P = 0.004) but not in the substudy (P = 0.60). In type 2 diabetes, more severe insulin resistance is independently associated with microalbuminuria. Longitudinal studies are needed to clarify the role of insulin resistance in the pathogenesis of microalbuminuria and related complications.

Impairment of Presynaptic ??2-Adrenoceptor-Regulated Norepinephrine Overflow in Failing Hearts from Zucker Diabetic Fatty Rats

The aim of this study was to assess whether cardiac norepinephrine overflow is affected in Type 2 diabetes mellitus. Homozygous (fa/fa) Zucker diabetic fatty (ZDF) rats were used as a model of Type 2 diabetes; heterozygous (fa/+) ZDF rats served as non-diabetic controls. Cardiac performance was determined in isolated working hearts; release of endogenous norepinephrine was induced by electrical field stimulation in Langendorff-perfused hearts. At a mean age of 30 weeks, left ventricular contraction, relaxation, and developed pressure were reduced by 20% to 35% in ZDF-fa/fa rats compared with ZDF-fa/+ rats. Stepwise increase of stimulation frequency gradually increased norepinephrine overflow in isolated hearts from both rat strains. Compared to ZDF-fa/+ rats, cardiac norepinephrine overflow was suppressed by 25% to 45% in ZDF-fa/fa rats. During presynaptic alpha2-adrenoceptor blockade with rauwolscine, increase of norepinephrine overflow was significantly higher in ZDF-fa/fa rats than in ZDF-fa/+ rats whereas alpha2-adrenoceptor activation with UK 14,304 suppressed norepinephrine overflow solely in ZDF-fa/+ rats. Myocardial tissue content of norepinephrine did not differ markedly between the two groups. In conclusion, cardiac norepinephrine overflow is inhibited in failing hearts from ZDF-fa/fa rats. This inhibition may result from a hyperactive status of presynaptic alpha2-adrenoceptors.

Microalbuminuria in patients with previous myocardial infarction

Microalbuminuria (MA) is a cardiovascular risk factor. The aim of this study was to examine the relationship between MA and the intima-media complex of the carotid and brachial artery, endothelial function, glucose metabolism, haemostatic variables and cardiac hypertrophy in patients with coronary heart disease. A total of 123 patients, aged 31-80 years, with a history of previous myocardial infarction and without known diabetes mellitus were examined with B-mode ultrasound of common carotid and brachial arteries, flow-mediated dilatation of the brachial artery and echocardiography. A standard oral glucose tolerance test with 75 g of glucose was performed. MA was defined as excretion of 20-200 microg albumin/min. MA was present in 11% of patients. Patients with MA had significantly higher level of 2-h plasma glucose, a lower displacement of the atrioventricular plane, a thicker septum wall and a higher prevalence of impaired glucose tolerance test compared with patients with normoalbuminuria (P<0.05). Urinary albumin excretion (UAE) was significantly and positively associated with calculated intima-media area (cIMa) in both brachial and common carotid arteries as well as with age and interventricular septum thickness. In conclusion, UAE was significantly and positively associated with cIMa in both the common carotid and the brachial arteries as well as with left ventricular septum thickness and glucose intolerance in patients with a history of previous myocardial infarction without known diabetes mellitus.

Proteinuria is a prognostic marker for cardiovascular mortality: NIPPON DATA 80, 1980-1999

BACKGROUND: Proteinuria has been considered to be a prognostic marker for persons with diabetes mellitus, but only a limited number of studies about the relationship between proteinuria and mortality among general population has been available.

METHODS: The subjects were 10,897 individuals who participated in the National Cardiovascular Survey conducted in 1980 and who were aged 30 years or older living in 300 districts that had been randomly selected throughout Japan. The vital records were confirmed in 1999 and 7,203 subjects (3,180 males and 4,023 females) without a history of hypertension, stroke, heart disease, renal disease, or diabetes mellitus at the start of the study were investigated.

RESULTS: There were 126,825 person-years of follow-up. During the observed period of time, 371 died of cardiovascular causes, including 171 stroke deaths and 74 coronary deaths. The risk of proteinuria for cardiovascular mortality was greater than unity for those with a normal serum creatinine level, after adjusting for age and other cardiovascular disease risk factors.

CONCLUSIONS: When contrasted with other cardiovascular disease risk factors, urinary protein is an independent risk factor for cardiovascular death among the Japanese population.

Carbohydrate metabolism in uraemia

PURPOSE OF REVIEW

Most uraemic patients are insulin resistant. This review focuses on the occurrence, mechanisms and consequences of this insulin resistance. Hypoglycaemia is also possible in a minority of uraemic patients; its causes are discussed at the end of the review.

RECENT FINDINGS

Insulin resistance is detectable when the glomerular filtration rate is below 50 ml/min per 1.73 m in non-diabetic uraemic individuals. Uraemia can alter insulin sensitivity even in diabetic patients; familial insulin resistance may favour the occurrence of diabetic nephropathy. Although reduced glucose non-oxidative disposal is the most evident defect of carbohydrate metabolism, abnormal glucose oxidation, endogenous glucose production and insulin secretion are also contributors. The accumulation of nitrogenous compounds is the most important mechanism of a specific state of insulin resistance in uraemia. Their identification is progressing, particularly in the field of carbamoylated amino acids. The consequences of chronic renal failure such as anaemia, metabolic acidosis and secondary hyperparathyroidism also indirectly play a role.

SUMMARY

The treatment of uraemia by renal replacement therapies or low-protein diets improves insulin sensitivity. However, patients still have a high cardiovascular risk. The identification of the accumulating molecular species that specifically alter insulin sensitivity is therefore of great interest. The favourable effect of non-specific insulin sensitizers such as glitazone may also help to reduce this risk.

Type 2 diabetes mellitus: a cardiovascular perspective

Diabetes mellitus is a disease, which is at the epitome of cardiovascular risk factors causing considerable morbidity and mortality. In addition to microvascular complications, there is two- to six-fold increased risk of macrovascular diseases, such as coronary artery disease, peripheral artery disease and stroke. While the mortality from coronary artery disease in patients without diabetes has declined over the past 20 years, the mortality in men with type 2 diabetes mellitus has not changed. Furthermore, the prevalence of diabetes in the UK has increased by 30% since 1991 and the same among the world population in 2010 is expected to be twice in 1990. This dramatic increase has serious implications from a cardiovascular perspective and thus the aggressive management of blood pressure, dyslipidaemia and blood glucose in diabetes is of vital importance. The aim of this review is to evaluate the current evidence and to discuss the implications of type 2 diabetes and its relevance to clinical practice in cardiology. We address this broad subject in discussing (i) the pathophysiology of cardiovascular disease in the setting of type 2 diabetes and (ii) the prevalence of cardiovascular risk, complications and prognostic implications in type 2 diabetes, with a discussion of current therapeutic interventions for the prevention or delay of these consequences where relevant.

High-sensitivity C-reactive protein is associated with insulin resistance and cardiovascular autonomic dysfunction in type 2 diabetic patients

We tested the hypothesis that elevated levels of plasma high-sensitivity C-reactive protein (HSCRP) are associated with insulin resistance/hyperinsulinemia and cardiovascular autonomic dysfunction in type 2 diabetic patients without insulin treatment. The study group consisted of 17 type 2 diabetic patients with high HSCRP (0.3-1.0 mg/dL; age, 59+/-8 years, mean+/-SD; high HSCRP group). The control group consisted of 18 age-matched type 2 diabetic patients with low HSCRP (<0.3 mg/dL; 59+/-7 years; low HSCRP group). Cardiovascular autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentration, and cardiac metaiodobenzylguanidine (MIBG) labeled with iodine 123 scintigraphic findings. Baroreflex sensitivity was lower in the high HSCRP group than in the low HSCRP group (P<.05). Early and delayed 123I-MIBG myocardial uptake values were lower (P<.05 and P<.005, respectively) and the percent washout rate of 123I-MIBG was higher (P<.01) in the high HSCRP group than in the low HSCRP group. Fasting plasma insulin concentration (P<.01) and the homeostasis model assessment index (P<.01) were higher in the high HSCRP group than in the low HSCRP group. Multiple regression analysis revealed that the level of HSCRP was independently predicted by fasting plasma insulin concentration and myocardial uptake of 123I-MIBG at a delayed phase. Our results suggest that high levels of HSCRP are associated with depressed cardiovascular autonomic function and hyperinsulinemia and that fasting plasma insulin concentration and myocardial uptake of 123I-MIBG at a delayed phase are independent predictors of HSCRP level in our Japanese patients with type 2 diabetes mellitus.