Beneficial effect of troglitazone, an insulin-sensitizing antidiabetic agent, on coronary circulation in patients with non-insulin-dependent diabetes mellitus

Impact of pemafibrate on lipid profile and insulin resistance in hypertriglyceridemic patients with coronary artery disease and metabolic syndrome

This study examined the effects of pemafibrate, a selective peroxisome proliferator-activated receptor α agonist, on the serum biochemical parameters of male patients with coronary artery disease and metabolic syndrome (MetS). This was a post hoc analysis of a randomized, crossover study that treated hypertriglyceridemia with pemafibrate or bezafibrate for 24 weeks, followed by a crossover of another 24 weeks. Of the 60 patients enrolled in the study, 55 were male. Forty-one of 55 male patients were found to have MetS. In this sub-analysis, male patients with MetS (MetS group, n = 41) and those without MetS (non-MetS group, n = 14) were compared. The primary endpoint was a change in fasting serum triglyceride (TG) levels during pemafibrate therapy, and the secondary endpoints were changes in insulin resistance-related markers and liver function parameters. Serum TG levels significantly decreased (MetS group, from 266.6 to 148.0 mg/dL, p < 0.001; non-MetS group, from 203.9 to 97.6 mg/dL, p < 0.001); however, a percent change (%Change) was not significantly different between the groups (- 44.1% vs. - 51.6%, p = 0.084). Serum insulin levels and homeostasis model assessment of insulin resistance significantly decreased in the MetS group but not in the non-MetS group. %Change in liver enzyme levels was markedly decreased in the MetS group compared with that in the non-MetS group (alanine aminotransferase, - 25.1% vs. - 11.3%, p = 0.027; gamma-glutamyl transferase, - 45.8% vs. - 36.2%, p = 0.020). In conclusion, pemafibrate can effectively decrease TG levels in patients with MetS, and it may be a more efficient drug for improving insulin resistance and liver function in such patients.

Urinary albumin excretion within the normal range predicts the development of diabetes in Korean men

AIMS

Urine albumin creatinine ratio (UACR) is a reliable index of urinary albumin excretion. Elevated UACR is known to be associated with increased risk for diabetes complications. However there is only limited information about the predictability of UACR within normal range for diabetes. Therefore, this study was designed to investigate the association between UACR within the normal range and the development of diabetes.

METHODS

The 1410 non-diabetic Korean men with UACR within the normal range were identified in 2005 and followed-up until 2010. All subjects were classified into four categories according to their baseline level of UACR, from the lowest to the highest quartile. Cox proportional hazards analysis was used to evaluate the independent hazard ratios (HRs) for diabetes according to the UACR levels of their quartile group.

RESULTS

During follow-up, diabetes developed in 114 out of 1410 subjects (8.1%), and incidence of diabetes increased in proportion to the level of UACR (quartile 1; 4.5%, quartile 2; 7.9%, quartile 3: 8.8%, quartile 4: 11.1%, p = 0.002). The subjects with incident diabetes had a higher UACR than those without incident diabetes (6.6 ± 5.5 μg/mg v 5.3 ± 4.2 μg/mg, p=0.013). When quartile 1 was considered as the reference, HRs (95% confidential interval) for diabetes was higher in quartile 2 (1.04; 0.45-2.38), quartile 3 (1.09; 0.47-2.52) and quartile 4 (2.16; 1.02-4.57), even after adjusting for other potential confounders.

CONCLUSIONS

Elevated UACR, even within the normal range, could predict the future development of diabetes.

Therapeutic angiogenesis in diabetes and hypercholesterolemia: influence of oxidative stress

Despite significant improvements in the medical, percutaneous, and surgical management, numerous patients are first seen with non-revascularizable coronary artery disease (CAD). The growth of new blood vessels to improve myocardial perfusion (i.e., therapeutic angiogenesis) is an attractive treatment option for these patients. However, the successes of angiogenic therapy, observed in preclinical studies, have not been realized in clinical trials. Increasing evidence suggests that this discrepancy between animal and human studies may be due to the nature of the substrate, or the molecular and cellular environment within which the angiogenic agent acts. Antiangiogenic influences, including endothelial dysfunction, hypercholesterolemia, and diabetes, are present in virtually all patients with advanced CAD. Recent studies have better characterized the abnormalities associated with these disease states, providing novel targets for intervention. These substrate-modifying interventions can potentially enhance the response to protein-, gene-, or cell-based angiogenic therapy. In this review, we discuss key aspects of the angiogenic process and the pathophysiologic and molecular mechanisms that contribute to an impaired angiogenic response in the setting of endothelial dysfunction, hypercholesterolemia, and diabetes, with a focus on the role of oxidative stress. Last, we briefly explore substrate modifying agents that have been evaluated in preclinical and clinical studies to improve the angiogenic response.

Impact of rosiglitazone and glyburide on nitrosative stress and myocardial blood flow regulation in type 2 diabetes mellitus

Cardiovascular disease, the leading cause of death in patients with type 2 diabetes mellitus (T2DM), is usually preceded by endothelial dysfunction and altered myocardial blood flow (MBF) regulation. Hyperglycemia, oxidative-nitrosative stress, systemic inflammation, and insulin resistance are implicated in the pathogenesis of abnormal MBF regulation, myocardial ischemia, and apoptosis. However, the impact of oral antihyperglycemic therapy on myocardial perfusion is controversial. Our objective was to explore the effect of rosiglitazone and glyburide on nitrosative stress and MBF regulation in subjects with T2DM. [(13)N]ammonia positron emission tomography and cold pressor testing were used in 27 diabetic subjects (mean age, 49 +/- 11 years; glycohemoglobin, 7% +/- 1.5%) randomized to either rosiglitazone 8 mg/d or glyburide 10 mg/d for 6 months. Isotope dilution gas chromatography-mass spectrometry was used to quantify plasma 3-nitrotyrosine, a stable marker of reactive nitrogen species. At 6 months, there were no significant differences between groups in the mean glycohemoglobin, blood pressure, or plasma lipids. Rosiglitazone significantly reduced plasma nitrotyrosine, high-sensitivity C-reactive protein, and von Willebrand antigen (P < .03 for all) and significantly increased plasma adiponectin (P < .05). No significant changes in these parameters were observed with glyburide. Treatment with glyburide, but not rosiglitazone, resulted in a significant deterioration in both resting and stress MBF. Rosiglitazone, but not glyburide, ameliorated markers of nitrosative stress and inflammation in subjects with T2DM without impairing myocardial perfusion.

Functional, cellular, and molecular characterization of the angiogenic response to chronic myocardial ischemia in diabetes

BACKGROUND

Ischemic heart disease is the most common cause of mortality in diabetic patients. Although therapeutic angiogenesis is an attractive option for these patients, they appear to have reduced collateral formation in response to myocardial ischemia. The aims of this study were to establish a large animal model of diabetes and chronic myocardial ischemia, evaluate the effects of diabetes on the angiogenic response, and elucidate the molecular pathways involved.

METHODS AND RESULTS

Diabetes was induced in male Yucatan miniswine using a pancreatic beta-cell specific toxin, alloxan (150 mg/kg; n=8). Age-matched swine served as controls (n=8). Eight weeks after induction, chronic ischemia was induced by ameroid constrictor placement around the circumflex coronary artery. Myocardial perfusion and function were assessed at 3 and 7 weeks after ameroid placement using isotope-labeled microspheres. Endothelial cell density and myocardial expression of angiogenic mediators was evaluated. Diabetic animals exhibited significant endothelial dysfunction. Collateral dependent perfusion and LV function were significantly impaired in diabetic animals. Diabetic animals also demonstrated reduced endothelial cell density (173+/-14 versus 234+/-23 cells/hpf, P=0.03). Expression of VEGF, Ang-1, and Tie-2 was reduced, whereas antiangiogenic proteins, angiostatin (4.4+/-0.9-fold increase, P<0.001), and endostatin (2.9+/-0.4-fold increase, P=0.03) were significantly elevated in the diabetic myocardium.

CONCLUSIONS

Diabetes results in a profound impairment in the myocardial angiogenic response to chronic ischemia. Pro- and antiangiogenic mediators identified in this study offer novel targets for the modulation of the angiogenic response in diabetes.

A comparative evaluation of Tl-201 and Tc-99m sestamibi myocardial perfusion spect imaging in diabetic patients

AIM

Myocardial perfusion scintigraphy (MPS) is an effective tool for early diagnosis of coronary artery disease (CAD) in type II diabetes mellitus (DM). The purpose of this study was to review the comparative findings of Tc-99m MIBI and Tl-201 MPS in defining normal and abnormal myocardial segments, type and extent of the perfusion defects with reference to coronary angiography findings in diabetic patients.

METHODS

Thirty patients with type II DM who had abnormal Tc-99m MIBI MPS findings and underwent coronary angiography were included this study (20 male, 10 female; mean age was 64 +/- 11 years). Those patients were also investigated with Tl-201 MPS thereafter. All scintigraphic images were evaluated semiquantitatively using a 20-segments myocardial model. The perfusion of myocardial segments, reversibility and severity of defects based on defect score were compared using the MIBI and Tl-201 images in relation to coronary angiography. Diffuse slow-washout of Tl-201 was also noted.

RESULTS

A total of 600 myocardial segments were comparatively analyzed. Diagnostic concordance between both tracers in defining normal and abnormal perfusion on a segmental basis was 88% (kappa = 0.71). The percentage of normal, reversible and non-reversible segments in the Tc-99m MIBI and Tl-201 study were 67-61%, 11-20% and 22-19% respectively. While the number of irreversible defects were similar for both tracers, more number of reversible defects were identified by Tl-201 MPS than Tc-99m MIBI (65 vs. 123, p = 0.001). No significant difference between the defect scores of both tracers was found.

CONCLUSION

MPS using both tracers offered agreement in defining or excluding perfusion abnormalities in a major part of the data. However, Tl-201 MPS yielded better detection rate of myocardial ischemia than Tc-99m MIBI MPS in diabetic patients.

The vascular endothelium in diabetes: a practical target for drug treatment?

Vascular disease remains a major cause of morbidity and mortality in diabetes mellitus, in spite of recent improvements in outcome, some of which may be modulated by improved endothelial function. Therapeutic strategies aimed directly at preventing, or minimising the extent of, these sequelae are required as an adjunct to treatments directed at normalising the metabolic milieu. The microvasculature, and the endothelium in particular, are early contributors to vascular dysfunction, thus raising the question as to how best to specifically target the endothelium. However, the expansive nature of the microvasculature, the varying demands that tissues have in terms of blood flow, and the heterogeneity that exists amongst cell types in different sites raises potential problems as to the practicality of such an approach. Further-more, temporal and genetic factors in the genesis of diabetic microvascular dysfunction may impact on therapeutic strategies. It is suggested that a systematic approach is required to understand the heterogeneity of the microvasculature, with particular emphasis on relating differences in gene and protein expression with functional properties. Such an approach may then provide the necessary information to allow exploitation of endothelial cell heterogeneity for unique targeted interventions, as well as providing the necessary rationale for pharmacological interventions (both prophylactic and corrective) aimed at the endothelium as a whole.

Peroxisome proliferator-activated receptor γ polymorphisms affect systemic inflammation and survival in end-stage renal disease patients starting renal replacement therapy

BACKGROUND

Inflammation may contribute to the markedly increased cardiovascular morbidity and mortality in end-stage renal disease (ESRD). However, the prevalence of inflammation varies in different ESRD populations. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is an important nuclear signaling protein that may regulate inflammatory response, and recent studies have revealed genetic polymorphisms that have significant effect on PPAR-gamma signaling. The aim of this study was to clarify whether the PPAR-gamma 161C/T and PPAR-gamma2 Pro12Ala single-nucleotide polymorphisms (SNPs) influence the inter-individual variance of inflammation and mortality in ESRD patients.

METHODS

The present prospective study included 229 incident Caucasian ESRD patients (62% males) just prior to starting renal replacement therapy and 207 healthy controls (62% males). Blood samples were taken for measuring systemic inflammatory (CRP, TNF-alpha, IL-6) and nutritional (S-albumin) parameters. The presence of diabetes mellitus, malnutrition (subjective global assessment (SGA)) and cardiovascular disease (CVD) were also assessed. Genotyping of the two PPAR-gamma SNPs was performed using Pyrosequencing. During follow-up (1621+/-63 days), both all-cause and CVD-mortality were investigated.

RESULTS

ESRD patients had a higher prevalence of both the PPAR-gamma 161 CC and PPAR-gamma2 Pro12Pro genotypes than the general population (p<0.01). Whereas the Pro12Pro genotype was associated with higher median serum levels of both hs-CRP (p<0.05) and TNF-alpha (p<0.01) the 161CC genotype was associated with a significantly higher (6.6 mg/L versus 3.3 mg/L; p<0.01) median hs-CRP level. Following adjustment for age, gender, SGA and CVD a significantly higher mortality rate was observed in patients with the Pro12Pro genotype.

CONCLUSION

This study demonstrates significant differences in PPAR-gamma genotype distribution between ESRD patients and healthy controls. Furthermore, as the PPAR-gamma2 Pro12Pro genotype was associated with both higher levels of biomarkers of inflammation as well as shorter survival, genetic polymorphisms seem to play a role in determining systemic inflammatory status and outcome in this patient group.

Redox modulation of insulin signaling and endothelial function

Reactive oxygen and nitrogen species (ROS and RNS) recently emerged as critical signaling molecules in cardiovascular research. Several studies over the past decade have shown that physiological effects of vasoactive factors are mediated by these reactive species and, conversely, that altered redox mechanisms are implicated in the occurrence of metabolic and cardiovascular diseases. Oxidant stress occurs when ROS and/or RNS production exceeds the cell natural antioxidant systems, and pathological events ensue. Cardiovascular risk factors are associated with an imbalance of the redox equilibrium toward oxidative stress, leading to endothelial activation and proinflammatory processes implicated in atherogenesis and metabolic disorders. Recent studies indicate that insulin and insulin-sensitizing drugs activate antiinflammatory pathways that may limit oxidant stress in insulin target tissues. The main goal of this brief review is to discuss recent progress in the field of cellular redox signaling as it pertains to insulin modulation of vascular endothelial function in cardiovascular diseases.

Peroxisome proliferator-activated receptor gamma: the more the merrier?

The consequence of activating the nuclear hormone receptor, peroxisome proliferator-activated receptor gamma (PPARgamma), which coordinates adipocyte differentiation, validates the concept, 'you are what you eat'. Excessive caloric intake leads to fat formation if the energy from these nutrients is not expended. However, this evolutionary adaptation to store energy in fat, which can be released under the form of fatty acids, potent PPARgamma agonists, has become a disadvantage in today's affluent society as it results in numerous metabolic imbalances, collectively known as the metabolic syndrome. With the surge of human and genetic studies on PPARgamma function, the limitations to the benefits of PPARgamma signalling have been realized. It is now evident that the most effective strategy for resetting the balance of this thrifty gene is through its modulation rather than full activation, with the goal to improve glucose homeostasis while preventing adipogenesis. Finally, as more PPARgamma targeted pathways are revealed such as bone homeostasis, atherosclerosis and longevity, it is most certain that the PPARgamma thrifty gene hypothesis will evolve to incorporate these.

Peroxisome proliferator-activated receptor-gamma: too much of a good thing causes harm

The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) helps to translate 'what you eat' into 'what you are' because it allows dietary fatty acids (PPARgamma ligands) to modulate gene transcription. Treatments for diabetes include PPARgamma activators, as they sensitize the body to insulin. Our understanding of PPARgamma function has recently been enhanced by a flurry of human and mouse genetic studies, and the characterization of new PPARgamma ligands. This insight has led us to propose that modulating PPARgamma activity, rather than activating it, might be the most effective strategy for treating metabolic disorders, as this will improve glucose homeostasis while preventing adipogenesis.

Diabetic cardiomyopathy: evidence, mechanisms, and therapeutic implications

The presence of a diabetic cardiomyopathy, independent of hypertension and coronary artery disease, is still controversial. This systematic review seeks to evaluate the evidence for the existence of this condition, to clarify the possible mechanisms responsible, and to consider possible therapeutic implications. The existence of a diabetic cardiomyopathy is supported by epidemiological findings showing the association of diabetes with heart failure; clinical studies confirming the association of diabetes with left ventricular dysfunction independent of hypertension, coronary artery disease, and other heart disease; and experimental evidence of myocardial structural and functional changes. The most important mechanisms of diabetic cardiomyopathy are metabolic disturbances (depletion of glucose transporter 4, increased free fatty acids, carnitine deficiency, changes in calcium homeostasis), myocardial fibrosis (association with increases in angiotensin II, IGF-I, and inflammatory cytokines), small vessel disease (microangiopathy, impaired coronary flow reserve, and endothelial dysfunction), cardiac autonomic neuropathy (denervation and alterations in myocardial catecholamine levels), and insulin resistance (hyperinsulinemia and reduced insulin sensitivity). This review presents evidence that diabetes is associated with a cardiomyopathy, independent of comorbid conditions, and that metabolic disturbances, myocardial fibrosis, small vessel disease, cardiac autonomic neuropathy, and insulin resistance may all contribute to the development of diabetic heart disease.

Peroxisome proliferator-activated receptors: are they involved in atherosclerosis progression?

Peroxisome proliferator-activated receptors (PPAR) are nuclear receptors present in several organs and cell types. They are subdivided into PPAR alpha, PPAR gamma and PPAR delta (or beta). PPAR alpha and gamma are the two main categories of these receptors, which are both characterized by their ability to influence lipid metabolism, glucose homeostasis, cell proliferation, differentiation and apoptosis, as well as the inflammatory response, by transcriptional activation of target genes. PPAR alpha are activated by fatty acids, eicosanoids and fibrates, while PPAR gamma activators include arachidonic acid metabolites, oxidized low density lipoprotein and thiazolidinediones. Atherosclerosis is now considered a chronic inflammatory condition. Thus, PPAR activation appears a promising approach to favorably affect atherosclerosis development through both metabolic and anti-inflammatory effects. However, the clinical data in favor of an anti-atherosclerotic action of PPAR agonists are still scanty, and some experimental data would even indicate possible pro-atherogenic effects, or a lack of effect in the female sex. New controlled clinical studies will provide the information necessary to understand the true significance and usefulness of PPAR alpha, gamma and delta activators in the control of atherosclerotic disease.

Impact of diabetes mellitus on angiographically silent coronary atherosclerosis

Constrictive remodeling occurs in significant atherosclerotic lesions of the diabetic patient, but the impact of diabetes mellitus (DM) on the angiographically normal coronary artery is still unclear. Morphometric analysis using intravascular ultrasound (IVUS) prior to intervention evaluated 54 sites in 33 DM patients and 106 in 62 non-diabetic patients. Vessel area (VA) and lumen area (LA) were measured at angiographically normal sites in the vessel. Plaque area (PA) was calculated as VA - LA. Percentage plaque area (%PA) was calculated as PA VA. Even in the angiographically normal site, mild coronary atherosclerosis was detected by IVUS in both groups. In the patients with DM, VA and LA were significantly smaller than in the non-diabetic patient (15.5 vs 17.8 mm(2), p<0.01; and 10.1 vs 12.2 mm(2), p<0.01 respectively), whereas % PA was similar (34.5 vs 31.6%). At angiographically normal sites where mild coronary atherosclerosis is detected by IVUS, the coronary artery of diabetic patients is smaller than that of the non-diabetic. These results suggest impaired compensatory enlargement or some other constrictive mechanism has already occurred in the early stages of coronary atherosclerosis in patients with DM.

Optimum Hypoglycemic Therapy can Improve Coronary Flow Velocity Reserve in Diabetic Patients-Demonstration by Transthoracic Doppler Echocardiography-

The purpose of this study was to determine whether the elimination or the alleviation of hyperglycemia would improve coronary flow velocity reserve (CFVR) using transthoracic Doppler echocardiography (TTDE). CFVR was measured by TTDE in the left anterior descending coronary artery in 49 poorly controlled diabetic patients before and after antidiabetic treatment and 15 well controlled diabetic patients also underwent the same measurements. The fasting blood glucose level in the poorly controlled patients reduced from 270 +/-106 mg/dl to 116+/-39 mg/dl at 20+/-15 days after the intensive treatment. Although baseline coronary flow velocity (CFV) did not change between the 2 measurements (19.9+/-6.9 cm/s vs 19.0+/-5.4 cm/s, p=NS), the hyperemic CFV increased significantly after the treatment (47.3+/-13.4 cm/s vs 55.4+/-13.2 cm/s, p<0.001). Thus, the CFVR improved significantly after the treatment (2.47+/-0.55 vs 2.98+/-0.56, p<0.001). Although there was minimal improvement in the control group (2.37+/-0.38 vs 2.50+/-0.37, p<0.05), the improvement in CFVR was significantly greater in the poorly controlled patients with intensive treatment (0.51+/-0.33 vs 0.12+/-0.19, p<0.001) than that in the control group. These results suggest that optimal hypoglycemic therapy is important to improve the CFVR in poorly controlled diabetic patients.

Combination therapy of exercise and angiotensin-converting enzyme inhibitor markedly improves insulin sensitivities in hypertensive patients with insulin resistance

The contraction of muscle enhances the release of bradykinin (BK) and improves glucose uptake by the muscle. Angiotensin-converting enzyme inhibitor (ACEI) slows the breakdown of BK, thus the effect of BK is augmented in the presence of ACEI. The present study investigated whether the combination of exercise (increased production of BK) and ACEI (delay in breakdown of BK) might further improve insulin sensitivity in hypertensive patients with insulin resistance (HOMA-R>1.8). Patients were assigned either to increased walking distance (Walking group) or taking 2 mg temocapril, an ACEI, daily (ACEI group) for 8 weeks. Then both interventions were given to all patients for 8 weeks (ACEI+Walking group). Blood concentrations of triglycerides were slightly lower in the ACEI+Walking group than at baseline, although there were no significant differences in total cholesterol or high density lipoprotein-cholesterol among the 2 groups. Blood glucose was not significantly different with each treatment, but blood concentrations of insulin and HOMA-R were significantly lower in the Walking and ACEI groups compared with the Control group. The combination of walking and ACEI further lowered blood concentrations of insulin and HOMA-R, which suggests that this treatment is beneficial for hypertensive patients with insulin resistance.