Diabetes mellitus and coronary heart disease

Cardiac function and quality of life improvement with fasudil hydrochloride in patients with diabetes post-PCI: a randomized controlled trial

OBJECTIVE

We assessed the efficacy of fasudil hydrochloride, a Rho-kinase inhibitor, as adjunct therapy for enhancing cardiac function, managing blood sugar, and improving quality of life in patients with diabetes who have coronary heart disease (CHD) and who underwent percutaneous coronary intervention (PCI).

METHODS

We conducted a randomized controlled trial including 100 patients with diabetes and CHD who underwent PCI. Participants were randomly assigned to an experimental group receiving fasudil hydrochloride plus standard therapy or a control group receiving standard therapy alone. Treatment outcomes were evaluated over 3 months, focusing on cardiac function, blood sugar levels, and quality of life across physical, social, activities of daily living, and psychological domains.

RESULTS

The experimental group showed significant improvement in cardiac function and blood sugar control, compared with the control group. Additionally, quality of life scores were markedly higher for the experimental group in all evaluated domains.

CONCLUSIONS

Fasudil hydrochloride effectively targets endothelial dysfunction and atherosclerosis, contributing to better cardiac performance and metabolic regulation. These effects translate into improved post-PCI quality of life for patients with diabetes and CHD. As an adjunct to standard PCI therapy, fasudil hydrochloride treatment offers a promising strategy for enhancing clinical outcomes in this high-risk patient population.

Exogenous thyroxine increases cardiac GLUT4 translocation in insulin resistant OLETF rats

During insulin resistance, the heart undergoes a metabolic shift in which fatty acids (FA) account for roughly about 99% of the ATP production. This metabolic shift is indicative of impaired glucose metabolism. A shift in FA metabolism with impaired glucose tolerance can increase reactive oxygen species (ROS), lipotoxicity, and mitochondrial dysfunction, ultimately leading to cardiomyopathy. Thyroid hormones (TH) may improve the glucose intolerance by increasing glucose reabsorption and metabolism in peripheral tissues, but little is known on its effects on cardiac tissue during insulin resistance. In the present study, insulin resistant Otsuka Long Evans Tokushima Fatty (OLETF) rats were used to assess the effects of exogenous thyroxine (T4) on glucose metabolism in cardiac tissue. Rats were assigned to four groups: (1) lean, Long Evans Tokushima Otsuka (LETO; n=6), (2) LETO + T4 (8 μg/100 g BM/d × 5 wks; n = 7), (3) untreated OLETF (n = 6), and (4) OLETF + T4 (8 μg/100 g BM/d × 5 wks; n = 7). T4 increased GLUT4 gene expression by 85% in OLETF and increased GLUT4 protein translocation to the membrane by 294%. Additionally, T4 increased p-AS160 by 285%, phosphofructokinase-1 (PFK-1) mRNA, the rate limiting step in glycolysis, by 98% and hexokinase II by 64% in OLETF. T4 decreased both CPT2 mRNA and protein expression in OLETF. The results suggest that exogenous T4 has the potential to increase glucose uptake and metabolism while simultaneously reducing fatty acid transport in the heart of insulin resistant rats. Thus, L-thyroxine may have therapeutic value to help correct the impaired substrate metabolism associated with diabetic cardiomyopathy.

Cardiodiabetology: Newer Pharmacologic Strategies for Reducing Cardiovascular Disease Risks

Globally, nearly 500 million adults currently have diabetes, which is expected to increase to approximately 700 million by 2040. Cardiovascular diseases (CVD), including coronary heart disease, stroke, heart failure, and peripheral arterial disease, are the principal causes of death in persons with diabetes. Key to the prevention of CVD is optimization of associated risk factors. However, few persons with diabetes are at recommended targets for key CVD risk factors including LDL-cholesterol, blood pressure, HbA1c, nonsmoking status, and body mass index. While lifestyle management forms the basis for the prevention and control of these risk factors, newer and existing pharmacologic approaches are available to optimize the potential for CVD risk reduction, particularly for the management of lipids, blood pressure and blood glucose. For higher risk patients, antiplatelet therapy is recommended. Medication for blood pressure, statins, and most recently, icosapent ethyl, have evidence for reducing CVD events in persons with diabetes. Newer medications for diabetes, including SGLT2 inhibitors and GLP-1 receptor agonists also reduce CVD and SGLT2 inhibitors in particular also reduce progression of kidney disease and reduce heart failure hospitalizations. Most importantly, a multidisciplinary team is required to address the polypharmaceutical options to best reduce CVD risks persons with diabetes.

Senescence and Type 2 Diabetic Cardiomyopathy: How Young Can You Die of Old Age?

Inflammation is well understood to be a physiological process of ageing however it also underlies many chronic diseases, including conditions without an obvious pathogenic inflammatory element. Recent findings have unequivocally identified type 2 diabetes (T2D) as a chronic inflammatory disease characterized by inflammation and immune senescence. Immunosenescence is a hallmark of the prolonged low-grade systemic inflammation, in particular associated with metabolic syndrome and can be a cause as well as a consequence of T2D. Diabetes is a risk factor for cardiovascular mortality and remodelling and with particular changes to myocardial structure, function, metabolism and energetics collectively resulting in diabetic cardiomyopathy. Both cardiomyocytes and immune cells undergo metabolic remodelling in T2D and as a result become trapped in a vicious cycle of lost metabolic flexibility, thus losing their key adaptive mechanisms to dynamic changes in O₂ and nutrient availability. Immunosenescence driven by metabolic stress may be both the cause and key contributing factor to cardiac dysfunction in diabetic cardiomyopathy by inducing metabolic perturbations that can lead to impaired energetics, a strong predictor of cardiac mortality. Here we review our current understanding of the cross-talk between inflammaging and cardiomyocytes in T2D cardiomyopathy. We discuss potential mechanisms of metabolic convergence between cell types which, we hypothesize, might tip the balance between resolution of the inflammation versus adverse cardiac metabolic remodelling in T2D cardiomyopathy. A better understanding of the multiple biological paradigms leading to T2D cardiomyopathy including the immunosenescence associated with inflammaging will provide a powerful target for successful therapeutic interventions.

Red cell distribution width is correlated with extensive coronary artery disease in patients with diabetes mellitus

Introduction:

Previous studies have predicted an independent relationship between red cell distribution width (RDW) and the risk of death and cardiovascular events in patients with coronary artery disease (CAD). The aim of this study was to investigate the relationship between RDW and extensiveness of CAD in patients with diabetes mellitus (DM).

Methods:

Two hundred and thirty-three diabetic patients who underwent coronary angiographies at our centre in 2010 were included in the study. All of the angiograms were re-evaluated and Gensini scores were calculated. Triple-vessel disease wasdiagnosed in the presence of stenosis > 50% in all three coronary artery systems.

Result:

RDW was significantly higher in diabetic CAD patients (p < 0.001). Patients with CAD who had a RDW value above the cut-off point also had higher Gensini scores, higher percentages of obstructive CAD and triple-vessel disease (p ≤ 0.001 for all). According to the cut-off values calculated using ROC analysis, RDW > 13.25% had a high diagnostic accuracy for predicting CAD. RDW was also positively correlated with Gensini score, obstructive CAD and triple-vessel disease (r < 0.468 and p < 0.001 for all).

Conclusion:

RDW values were found to be increased in the diabetic CAD population. Higher RDW values were related to more extensive and complex coronary lesions in patients with DM.

Atherogenic dyslipidaemia in type 2 diabetes and metabolic syndrome: current and future treatment options

Dyslipidaemia is a major risk factor for atherosclerotic coronary heart disease, which in turn is the commonest cause of mortality in type 2 diabetes. This highlights the importance of appropriate management of diabetic dyslipidaemia. Management is typically multifactorial and includes dietary recommendations, routine physical exercise, aggressive control of other lifestyle risk factors, and for many patients drug intervention. Future drug treatments will increasingly target not only mechanisms that might improve glucose and LDL cholesterol blood levels, but also improve other facets of diabetic dyslipidaemia, atherogenesis and vascular risk.

Evaluation of Silent Myocardial Ischemia with Single-Photon Emission Computed Tomography/Computed Tomography in Asymptomatic Subjects with Diabetes and Pre-Diabetes

Objective:

The aim of this study was to disclose the prevalence of myocardial ischemia, as detected by adenosine stress myocardial perfusion imaging (MPI) with hybrid single-photon emission computed tomography/computed tomography (SPECT/CT), in asymptomatic diabetic and pre-diabetic patients and to find out whether ischemia predicted the occurrence of adverse cardiac/cerebrovascular events (ACCE) at follow-up.

Methods:

Forty-three diabetic and thirty-five pre-diabetic asymptomatic patients without any history of coronary artery disease, underwent MPI and were followed-up for a 12.8±2.2 (8-19) months for the occurrence of ACCE. Baseline variables that would predict the presence of ischemia and the value of ischemia on MPI for predicting the occurrence of ACCE at follow-up were evaluated by logistic regression analysis.

Results:

Ischemia was detected in ten (23.3%) of the diabetic and in four (11.4%) of the pre-diabetic patients. The presence of diabetes was the only independent predictor of myocardial ischemia [odds ratio (OR): 12.31, 95% confidence interval (CI): 1.83-82.66; p<0.01]. During 12.8±2.2 (8-19) months of follow-up, ACCE was observed in five out of 78 (6.4%) patients. Patients with ischemia were significantly more likely to have ACCE during follow-up as compared to those with normal MPI scans (event rates: 21.4% vs. 3.1%, OR: 8.455 95% CI: 1.264-56.562, p=0.038).

Conclusion:

Myocardial ischemia as detected by adenosine stress SPECT/CT in a population of asymptomatic patients with diabetes mellitus or pre-diabetes appeared to predict the occurrence of ACCE at follow-up.

Transcriptomic alterations in the heart of non-obese type 2 diabetic Goto-Kakizaki rats

Background

There is a spectacular rise in the global prevalence of type 2 diabetes mellitus (T2DM) due to the worldwide obesity epidemic. However, a significant proportion of T2DM patients are non-obese and they also have an increased risk of cardiovascular diseases. As the Goto-Kakizaki (GK) rat is a well-known model of non-obese T2DM, the goal of this study was to investigate the effect of non-obese T2DM on cardiac alterations of the transcriptome in GK rats.

Methods

Fasting blood glucose, serum insulin and cholesterol levels were measured at 7, 11, and 15 weeks of age in male GK and control rats. Oral glucose tolerance test and pancreatic insulin level measurements were performed at 11 weeks of age. At week 15, total RNA was isolated from the myocardium and assayed by rat oligonucleotide microarray for 41,012 genes, and then expression of selected genes was confirmed by qRT-PCR. Gene ontology and protein–protein network analyses were performed to demonstrate potentially characteristic gene alterations and key genes in non-obese T2DM.

Results

Fasting blood glucose, serum insulin and cholesterol levels were significantly increased, glucose tolerance and insulin sensitivity were significantly impaired in GK rats as compared to controls. In hearts of GK rats, 204 genes showed significant up-regulation and 303 genes showed down-regulation as compared to controls according to microarray analysis. Genes with significantly altered expression in the heart due to non-obese T2DM includes functional clusters of metabolism (e.g. Cyp2e1, Akr1b10), signal transduction (e.g. Dpp4, Stat3), receptors and ion channels (e.g. Sln, Chrng), membrane and structural proteins (e.g. Tnni1, Mylk2, Col8a1, Adam33), cell growth and differentiation (e.g. Gpc3, Jund), immune response (e.g. C3, C4a), and others (e.g. Lrp8, Msln, Klkc1, Epn3). Gene ontology analysis revealed several significantly enriched functional inter-relationships between genes influenced by non-obese T2DM. Protein–protein interaction analysis demonstrated that Stat is a potential key gene influenced by non-obese T2DM.

Conclusions

Non-obese T2DM alters cardiac gene expression profile. The altered genes may be involved in the development of cardiac pathologies and could be potential therapeutic targets in non-obese T2DM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0424-3) contains supplementary material, which is available to authorized users.

Long-term maintenance of efficacy of dapagliflozin in patients with type 2 diabetes mellitus and cardiovascular disease

AIM

To evaluate the long-term efficacy, safety and tolerability of dapagliflozin versus placebo added to usual care in patients with type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD).

METHODS

Data were pooled from two phase III studies (NCT01031680 and NCT01042977) in high-risk patients (N = 1887) with T2DM and CVD treated with dapagliflozin (10 mg/day) or placebo. Patients completing the double-blind treatment studies (24 weeks) entered one or two sequential double-blind, long-term (LT) extensions of 28 (LT1; n = 1649) and 52 (LT2; n = 568) weeks.

RESULTS

Baseline and CVD characteristics were similar in the two groups. Patients entering LT1 and LT2 on dapagliflozin maintained a greater mean reduction in glycated haemoglobin (HbA1c) versus placebo at 52 weeks [LT1, -0.58% (95% confidence interval -0.68, -0.49)] and 104 weeks [LT2, -0.35% (95% confidence interval -0.59, -0.12)]. Mean body weight and systolic blood pressure (SBP) reductions versus placebo were maintained in patients entering LT1 (52 weeks; -2.23 kg and -3.25 mmHg, respectively) and LT2 (104 weeks; -3.16 kg and -2.03 mmHg, respectively). Patients on dapagliflozin had a better three-item composite endpoint of clinical benefit (glycaemia, weight and SBP) compared with placebo at week 24 (LT1, 10.1% vs. 1.1%) and week 104 (LT2, 6.7% vs. 1.4%). Genital and urinary tract infections were more frequent with dapagliflozin than with placebo. Events of hypoglycaemia, renal impairment/failure and volume depletion were similar between groups.

CONCLUSIONS

The long-term efficacy of dapagliflozin to maintain reductions in HbA1c, SBP and body weight over 2 years, together with its tolerability profile, make dapagliflozin an appropriate option in high-risk patients with T2DM and CVD.

Sexual dimorphism in myocardial acylcarnitine and triglyceride metabolism

Background

Cardiovascular disease is the leading cause of death among diabetic patients. Importantly, recent data highlight the apparent sexual dimorphism in the pathogenesis of cardiovascular disease in diabetics with respect to both frequency- and age-related risk factors. The disposition to cardiovascular disease among diabetic patients has been attributed, at least in part, to excess lipid supply to the heart culminating in lipotoxicity of the heart and downstream derangements. A confounding factor in obese animal models of diabetes is that increased peripheral lipid availability to the heart can induce cardio-metabolic remodeling independent of the underlying pathophysiology of diabetes, thus masking the diabetic phenotype. To that end, we hypothesized that the use of non-obese diabetic (NOD) animal models will reveal metabolic signatures of diabetes in a sex-specific manner.

Methods

To test this hypothesis, male and female NOD Goto-Kakizaki (GK) rats were used to assess the expression profile of 84 genes involved in lipid metabolism. In parallel, targeted lipidomics analysis was performed to characterize sex differences in homeostasis of non-esterified fatty acids (NEFA), acylcarnitines (AC), and triglycerides (TG).

Results

Our analysis revealed significant sex differences in the expression of a broad range of genes involved in transport, activation, and utilization of lipids. Furthermore, NOD male rats exhibited enhanced oxidative metabolism and accumulation of TG, whereas female NOD rats exhibited reduced TG content coupled with accumulation of AC species. Multi-dimensional statistical analysis identified saturated AC16:0, AC18:0, and AC20:0 as dominant metabolites in mediating sex differences in AC metabolism. Confocal microscopy of rat cardiomyocytes exposed to AC14:0, AC16:0, and AC18:0 confirmed induction of ROS with AC18:0 being more potent followed by AC14:0.

Conclusion

Overall, we demonstrate sex differences in myocardial AC and TG metabolism with implications for therapy and diagnosis of diabetic cardiovascular disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-016-0077-7) contains supplementary material, which is available to authorized users.

Sulforaphane prevents the development of cardiomyopathy in type 2 diabetic mice probably by reversing oxidative stress-induced inhibition of LKB1/AMPK pathway

Type 2 diabetes mellitus (T2DM)-induced cardiomyopathy is associated with cardiac oxidative stress, inflammation, and remodeling. Sulforaphane (SFN), an isothiocyanate naturally presenting in widely consumed vegetables, particularly broccoli, plays an important role in cardiac protection from diabetes. We investigated the effect of SFN on T2DM-induced cardiac lipid accumulation and subsequent cardiomyopathy. Male C57BL/6J mice were fed a high-fat diet for 3months to induce insulin resistance, followed by a treatment with 100mg/kg body-weight streptozotocin to induce hyperglycemia; we referred to it as the T2DM mouse model. Other age-matched mice were fed a normal diet as control. T2DM and control mice were treated with or without 4-month SFN at 0.5mg/kg daily five days a week. At the study's end, cardiac function was assessed. SFN treatment significantly attenuated cardiac remodeling and dysfunction induced by T2DM. SFN treatment also significantly inhibited cardiac lipid accumulation, measured by Oil Red O staining, and improved cardiac inflammation oxidative stress and fibrosis, shown by down-regulating diabetes-induced PAI-1, TNF-α, CTGF, TGF-β, 3-NT, and 4-HNE expression. Elevated 4-HNE resulted in the increase of 4-HNE-LKB1 adducts that should inhibit LKB1 and subsequent AMPK activity. SFN upregulated the expression of Nrf2 and its downstream genes, NQO1 and HO-1, decreased 4-HNE-LKB1 adducts and then reversed diabetes-induced inhibition of LKB1/AMPK and its downstream targets, including sirtuin 1, PGC-1α, phosphorylated acetyl-CoA carboxylase, carnitine palmitoyl transferase-1, ULK1, and light chain-3 II. These results suggest that SFN treatment to T2DM mice may attenuate the cardiac oxidative stress-induced inhibition of LKB1/AMPK signaling pathway, thereby preventing T2DM-induced lipotoxicity and cardiomyopathy.

Ca(2+) mishandling and cardiac dysfunction in obesity and insulin resistance: role of oxidative stress

Obesity and insulin resistance (IR) are strongly connected to the development of subclinical cardiac dysfunction and eventually can lead to heart failure, which is the main cause of morbidity and death in patients having these metabolic diseases. It has been considered that excessive fat tissue may play a critical role in producing systemic IR and enhancing reactive oxygen species (ROS) generation. This oxidative stress (OS) may elicit or exacerbate IR. On the other hand, evidence suggests that some of the cellular mechanisms involved in the pathophysiology of obesity and IR-related cardiomyopathy are excessive myocardial ROS production and abnormal Ca(2+) homeostasis. In addition, emerging evidence suggests that augmented ROS production may contribute to Ca(2+) mishandling by affecting the redox state of key proteins implicated in this process. In this review, we focus on the role of Ca(2+) mishandling in the development of cardiac dysfunction in obesity and IR and address the evidence suggesting that OS might also contribute to cardiac dysfunction by affecting Ca(2+) handling.

In vivo multi-tissue efficacy of peroxisome proliferator-activated receptor-γ therapy on glucose and fatty acid metabolism in obese type 2 diabetic rats

OBJECTIVE

To identify the disturbances in glucose and lipid metabolism observed in type 2 diabetes mellitus, we examined the interaction and contribution of multiple tissues (liver, heart, muscle, and brown adipose tissue) and monitored the effects of the Peroxisome Proliferator-Activated Receptor-γ (PPARγ) agonist rosiglitazone (RGZ) on metabolism in these tissues.

DESIGN AND METHODS

Rates of [(18) F]fluorodeoxyglucose ([(18) F]FDG) and [(11) C]Palmitate uptake and utilization in the Zucker diabetic fatty (ZDF) rat were quantified using noninvasive positron emission tomography imaging and quantitative modeling in comparison to lean Zucker rats. Furthermore, we studied two separate groups of RGZ-treated and untreated ZDF rats.

RESULTS

Glucose uptake is impaired in ZDF brown fat, muscle, and heart tissues compared to leans, while RGZ treatment increased glucose uptake compared to untreated ZDF rats. Fatty acid (FA) uptake decreased, but FA flux increased in brown fat and skeletal muscle of ZDF rats. RGZ treatment increased uptake of FA in brown fat but decreased uptake and utilization in liver, muscle, and heart.

CONCLUSION

Our data indicate tissue-specific mechanisms for glucose and FA disposal as well as differential action of insulin-sensitizing drugs to normalize substrate handling and highlight the role that preclinical imaging may play in screening drugs for obesity and diabetes.

Genomic and metabolic disposition of non-obese type 2 diabetic rats to increased myocardial fatty acid metabolism

Lipotoxicity of the heart has been implicated as a leading cause of morbidity in Type 2 Diabetes Mellitus (T2DM). While numerous reports have demonstrated increased myocardial fatty acid (FA) utilization in obese T2DM animal models, this diabetic phenotype has yet to be demonstrated in non-obese animal models of T2DM. Therefore, the present study investigates functional, metabolic, and genomic differences in myocardial FA metabolism in non-obese type 2 diabetic rats. The study utilized Goto-Kakizaki (GK) rats at the age of 24 weeks. Each rat was imaged with small animal positron emission tomography (PET) to estimate myocardial blood flow (MBF) and myocardial FA metabolism. Echocardiograms (ECHOs) were performed to assess cardiac function. Levels of triglycerides (TG) and non-esterified fatty acids (NEFA) were measured in both plasma and cardiac tissues. Finally, expression profiles for 168 genes that have been implicated in diabetes and FA metabolism were measured using quantitative PCR (qPCR) arrays. GK rats exhibited increased NEFA and TG in both plasma and cardiac tissue. Quantitative PET imaging suggests that GK rats have increased FA metabolism. ECHO data indicates that GK rats have a significant increase in left ventricle mass index (LVMI) and decrease in peak early diastolic mitral annular velocity (E’) compared to Wistar rats, suggesting structural remodeling and impaired diastolic function. Of the 84 genes in each the diabetes and FA metabolism arrays, 17 genes in the diabetes array and 41 genes in the FA metabolism array were significantly up-regulated in GK rats. Our data suggest that GK rats’ exhibit increased genomic disposition to FA and TG metabolism independent of obesity.

APPL1 transgenic mice are protected from high-fat diet-induced cardiac dysfunction

APPL1 (adaptor protein containing PH domain, PTB domain, and leucine zipper motif 1) has been established as an important mediator of insulin and adiponectin signaling. Here, we investigated the influence of transgenic (Tg) APPL1 overexpression in mice on high-fat diet (HFD)-induced cardiomyopathy in mice. Wild-type (WT) mice fed an HFD for 16 wk showed cardiac dysfunction, determined by echocardiography, with decreased ejection fraction, decreased fractional shortening, and increased end diastolic volume. HFD-fed APPL1 Tg mice were significantly protected from this dysfunction. Speckle tracking echocardiography to accurately assess cardiac tissue deformation strain and wall motion also indicated dysfunction in WT mice and a similar improvement in Tg vs. WT mice on HFD. APPL1 Tg mice had less HFD-induced increase in circulating nonesteridied fatty acid levels and myocardial lipid accumulation. Lipidomic analysis using LC-MS-MS showed HFD significantly increased myocardial contents of distinct ceramide, sphingomyelin, and diacylglycerol (DAG) species, of which increases in C16:0 and C18:0 ceramides plus C16:0 and C18:1 DAGs were attenuated in Tg mice. A glucose tolerance test indicated less peripheral insulin resistance in response to HFD in Tg mice, which was also apparent by measuring cardiac Akt phosphorylation and cardiomyocyte glucose uptake. In summary, APPL1 Tg mice exhibit improved peripheral metabolism, reduced cardiac lipotoxicity, and improved insulin sensitivity. These cellular effects contribute to protection from HFD-induced cardiomyopathy.

Activation of type 2 cannabinoid receptors (CB2R) promotes fatty acid oxidation through the SIRT1/PGC-1α pathway

Abnormal fatty acid oxidation has been associated with obesity and type 2 diabetes. At the transcriptional level, peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) has been reported to strongly increase the ability of hormone nuclear receptors PPARα and ERRα to drive transcription of fatty acid oxidation enzymes. In this study, we report that a specific agonist of the type 2 cannabinoid receptor (CB2R) can lead to fatty acid oxidation through the PGC-1α pathway. We have found that CB2R is expressed in differentiated C2C12 myotubes, and that use of the specific agonist trans-caryophyllene (TC) stimulates sirtuin 1 (SIRT1) deacetylase activity by increasing the phosphorylation of cAMP response element-binding protein (CREB), thus leading to increased levels of PGC-1α deacetylation. This use of TC treatment increases the expression of genes linked to the fatty acid oxidation pathway in a SIRT1/PGC-1α-dependent mechanism and also drastically accelerates the rate of complete fatty acid oxidation in C2C12 myotubes, neither of which occur when CB2R mRNA is knocked down using siRNA. These results reveal that activation of CB2R by a selective agonist promotes lipid oxidation through a signaling/transcriptional pathway. Our findings imply that pharmacological manipulation of CB2R may provide therapeutic possibilities to treat metabolic diseases associated with lipid dysregulation.

Myocardial adipose triglyceride lipase overexpression protects diabetic mice from the development of lipotoxic cardiomyopathy

Although diabetic cardiomyopathy is associated with enhanced intramyocardial triacylglycerol (TAG) levels, the role of TAG catabolizing enzymes in this process is unclear. Because the TAG hydrolase, adipose triglyceride lipase (ATGL), regulates baseline cardiac metabolism and function, we examined whether alterations in cardiomyocyte ATGL impact cardiac function during uncontrolled type 1 diabetes. In genetic (Akita) and pharmacological (streptozotocin) murine models of type 1 diabetes, cardiac ATGL protein expression and TAG content were significantly increased. To determine whether increased ATGL expression during diabetes is detrimental or beneficial to cardiac function, we studied streptozotocin-diabetic mice with heterozygous ATGL deficiency and cardiomyocyte-specific ATGL overexpression. After diabetes, streptozotocin-diabetic mice with heterozygous ATGL deficiency displayed increased TAG accumulation, lipotoxicity, and diastolic dysfunction comparable to wild-type mice. In contrast, myosin heavy chain promoter (MHC)-ATGL mice were resistant to diabetes-induced increases in intramyocardial TAG levels, lipotoxicity, and cardiac dysfunction. Moreover, hearts from diabetic MHC-ATGL mice exhibited decreased reliance on palmitate oxidation and blunted peroxisome proliferator--activated receptor-α activation. Collectively, this study shows that after diabetes, increased cardiac ATGL expression is an adaptive, albeit insufficient, response to compensate for the accumulation of myocardial TAG, and that overexpression of ATGL is sufficient to ameliorate diabetes-induced cardiomyopathy.

Green tea polyphenols improve cardiac muscle mRNA and protein levels of signal pathways related to insulin and lipid metabolism and inflammation in insulin-resistant rats

Epidemiological studies indicate that the consumption of green tea polyphenols (GTP) may reduce the risk of coronary artery disease. To explore the underlying mechanisms of action at the molecular level, we examined the effects of GTP on the cardiac mRNA and protein levels of genes involved in insulin and lipid metabolism and inflammation. In rats fed a high-fructose diet, supplementation with GTP (200 mg/kg BW daily dissolved in distilled water) for 6 wk, reduced systemic blood glucose, plasma insulin, retinol-binding protein 4, soluble CD36, cholesterol, triglycerides, free fatty acids and LDL-C levels, as well as the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and IL-6. GTP did not affect food intake, bodyweight and heart weight. In the myocardium, GTP also increased the insulin receptor (Ir), insulin receptor substrate 1 and 2 (Irs1 and Irs2), phosphoinositide-3-kinase (Pi3k), v-akt murine thymoma viral oncogene homolog 1 (Akt1), glucose transporter 1 and 4 (Glut1 and Glut4) and glycogen synthase 1 (Gys1) expression but inhibited phosphatase and tensin homolog deleted on chromosome ten (Pten) expression and decreased glycogen synthase kinase 3beta (Gsk3beta) mRNA expression. The sterol regulatory element-binding protein-1c (Srebp1c) mRNA, microsomal triglyceride transfer protein (Mttp) mRNA and protein, Cd36 mRNA and cluster of differentiation 36 protein levels were decreased and peroxisome proliferator-activated receptor (Ppar)gamma mRNA levels were increased. GTP also decreased the inflammatory factors: Tnf, Il1b and Il6 mRNA levels, and enhanced the anti-inflammatory protein, zinc-finger protein, protein and mRNA expression. In summary, consumption of GTP ameliorated the detrimental effects of high-fructose diet on insulin signaling, lipid metabolism and inflammation in the cardiac muscle of rats.

Regulation of MAP kinase-directed mitogenic and protein kinase B-mediated signaling by cannabinoid receptor type 1 in skeletal muscle cells

OBJECTIVE

The endogenous cannabinoid (or endocannabinoid) system (ECS) is part of a central neuromodulatory system thought to play a key role in the regulation of feeding behavior and energy balance. However, increasing evidence suggests that modulation of the ECS may also act to regulate peripheral mechanisms involved in these processes, including lipogenesis in adipose tissue and liver, insulin release from pancreatic beta-cells, and glucose uptake into skeletal muscle. It was recently shown that cannabinoid receptor type 1 (CB1) and type 2 (CB2), both key components of the ECS, are expressed in human and rodent skeletal muscle. However, their role in modulating insulin sensitivity in this metabolically active tissue has yet to be determined. Our aim was to establish the role, if any, of these receptors in modulating insulin sensitivity in skeletal muscle cells.

RESEARCH DESIGN AND METHODS

Cultured skeletal muscle cells were exposed to CB1 and/or CB2 pharmacological agonists/antagonists/inverse agonists, and the resulting effects on insulin-regulated phosphatidylinositol 3 kinase (PI 3-kinase)-protein kinase B (PKB) and extracellular signal-related kinases 1/2 (ERK1/2)-directed signaling were determined.

RESULTS

Here, we report that modulating the activity of the ECS in skeletal muscle regulates both insulin-dependent mitogen-activated protein (MAP) kinase (ERK1/2) and the canonical PI 3-kinase/PKB signaling pathways. We show that pharmacological activation or inhibition of CB1 receptor activity exerts a differential effect with regard to MAP kinase- and PKB-directed signaling.

CONCLUSIONS

Our study provides evidence that signaling via cannabinoid receptors can significantly modulate mitogenic and metabolic signaling in skeletal muscle with important implications for muscle growth and differentiation as well as the regulation of glucose and lipid metabolism.

In vivo metabolic phenotyping of myocardial substrate metabolism in rodents: differential efficacy of metformin and rosiglitazone monotherapy

BACKGROUND

Cardiovascular disease is the leading cause of death among diabetic patients, with alteration in myocardial substrate metabolism being a likely contributor. We aimed to assess noninvasively the efficacy of metformin and rosiglitazone monotherapy in normalizing myocardial substrate metabolism in an animal model of type 2 diabetes mellitus.

METHODS AND RESULTS

The study used 18 male ZDF rats (fa/fa) with 6 rats in each group: an untreated group; a group treated with metformin (16.6 mg/kg/d), and a group treated with rosiglitazone (4 mg/kg). Each rat was scanned at age 14 weeks (baseline) and subsequently at 19 weeks with small-animal positron emission tomography to estimate myocardial glucose utilization (MGU) and myocardial utilization (MFAU), oxidation (MFAO), and esterification (MFAE). Treatment lasted for 5 weeks after baseline imaging. At week 19, rats were euthanized and hearts were extracted for expression analysis of select genes encoding for GLUT transporters and fatty acid transport and oxidation genes. In addition, echocardiography measurements were obtained at weeks 13 and 18 to characterize cardiac function. Metformin had no significant effect on either MGU or MFAU and MFAO. In contrast, rosiglitazone tended to enhance MGU and significantly reduced MFAU and MFAO. Rosiglitazone-induced increase in glucose uptake correlated significantly with increased expression of GLUT4, whereas diminished MFAO correlated significantly with decreased expression of FATP-1 and MCAD. Finally, changes in fractional shortening as a measure of cardiac function were unchanged throughout the study.

CONCLUSIONS

Treatment with rosiglitazone enhanced glucose utilization and diminished MFAO, thus reversing the metabolic phenotype of the diabetic heart.

[Heart failure in diabetes]

Interactions of glucose metabolism and chronic heart failure have been confirmed by many epidemiologic studies. The association of HbA1c with an increasing risk of heart failure clearly underlines the connection between both diseases. Coronary artery disease (CAD), hypertension and diabetic cardiomyopathy are long-term complications of diabetes mellitus, resulting in diabetic heart failure. Dysfunction of many regulation systems leads to specific diabetic cardiomyopathy, which has been firstly described by Rubler. A reduction in the cardiac expression of the Na-Ca exchanger pump and SERCA2a protein results in an imbalance in cardiac calcium handling. The overactive renin angiotensin aldosteron system (RAAS) also contributes to the impairment of myocardial function. Hyperlipidaemia, hpyerinsulinaemia and hyperglycaemia directly trigger diabetic cardiomyopathy. Generally chronic heart failure is a clinical diagnosis verified by blood tests like NT-proBNP and cardiac ultrasound. Recommendations on treatment of diabetic heart failure are based on subgroup analysis of the large heart failure trials.

The Influence of Diabetes Mellitus in Patients Undergoing Coronary Artery Bypass Graft Surgery: A Prospective Cohort Study

This study was conducted to prospectively assess if there are any outcome differences between patients undergoing coronary artery bypass graft surgery with and without diabetes. This is an 11-year, prospective, hospitalization cohort study. Data were collected on 225 variables. A total of 8935 patients were available for our analysis (6023 nondiabetics, 319 diet-controlled diabetics, 1636 diabetics on oral medications, 957 insulin-controlled diabetics). Compared with nondiabetics, diet-treated diabetics possessed four significant comorbidities, diabetics treated with oral medications possessed 12 significant comorbidities, and insulin-treated diabetics possessed 13 significant comorbidities ( P < 0.05). There was no significant difference between diet-treated diabetics and nondiabetics for all outcomes. Diabetics treated with oral medications possessed a longer length of stay [relative risk (RR), 1.09; CI, 1.08–1.10], longer intensive care unit length of stay (RR, 1.56; CI, 1.12–2.00), and more intraoperative complications (RR, 1.42; CI, 1.12–1.66). Insulin-treated diabetics possessed more neurological complications (RR, 2.39; CI, 1.52–3.77), wound complications (RR, 2.42; CI, 1.19–4.95), and renal complications (RR, 2.43; CI, 1.70–3.49), longer length of stay (RR, 1.20; CI, 1.14–1.27), and longer intensive care unit length of stay (RR, 1.33; CI, 1.16–1.48). In diabetics undergoing coronary artery bypass graft surgery, as their diabetes progresses from diet treated with oral medications to insulin-dependent, this is associated with more comorbidities at surgical presentation and more morbidity after surgery.

Time course of alterations in myocardial glucose utilization in the Zucker diabetic fatty rat with correlation to gene expression of glucose transporters: a small-animal PET investigation

Diabetic cardiomyopathy is associated with abnormalities in glucose metabolism. We evaluated myocardial glucose metabolism in a rodent model of type 2 diabetes, namely the Zucker diabetic fatty (ZDF) rat, and validated PET measurements of glucose uptake against gene and protein expression of glucose transporters (GLUTs).

METHODS

Six lean and ZDF rats underwent small-animal PET at the age of 14 wk and at the age of 19 wk. The imaging protocol consisted of a 60-min dynamic acquisition with 18F-FDG (18.5-29.6 MBq). Dynamic images were reconstructed using filtered backprojection with a 2.5 zoom on the heart and 40 frames per imaging session. PET measurements of myocardial glucose uptake (MGUp) rate and utilization were determined with an input function derived by the hybrid image-blood-sampling algorithm on recovery-corrected anterolateral myocardial regions of interest. After the PET session at week 19 (W19), hearts were extracted for gene and protein expression analysis of GLUT-1 and GLUT-4. The dependence of MGUp on gene expression of GLUT-1 and GLUT-4 was characterized by multiple-regression analysis.

RESULTS

MGUp in ZDF rats at both week 14 (W14) and W19 (P < 0.006) was significantly lower than MGUp in lean littermate control rats. Moreover, lean rats at W19 displayed significantly higher MGUp than they did at W14 (P = 0.007). Consistent with a diminished MGUp result, gene expression of GLUT-4 was significantly (P = 0.004) lower in ZDF rats. Finally, MGUp significantly (P = 0.0003) correlated with gene expression of GLUT-4.

CONCLUSION

Using small-animal PET, we confirmed alterations in myocardial glucose utilization and validated PET measurement of MGUp against gene and protein expression of GLUTs in the diabetic heart of an animal model of type 2 diabetes.

Insulin-resistant cardiomyopathy clinical evidence, mechanisms, and treatment options

Increasing evidence points to insulin resistance as a primary etiologic factor in the development of nonischemic heart failure (HF). The myocardium normally responds to injury by altering substrate metabolism to increase energy efficiency. Insulin resistance prevents this adaptive response and can lead to further injury by contributing to lipotoxicity, sympathetic up-regulation, inflammation, oxidative stress, and fibrosis. Animal models have repeatedly demonstrated the existence of an insulin-resistant cardiomyopathy, one that is characterized by inefficient energy metabolism and is reversible by improving energy use. Clinical studies in humans strongly support the link between insulin resistance and nonischemic HF. Insulin resistance is highly prevalent in the nonischemic HF population, predates the development of HF, independently defines a worse prognosis, and predicts response to antiadrenergic therapy. Potential options for treatment include metabolic-modulating agents and antidiabetic drugs. This article reviews the basic science evidence, animal experiments, and human clinical data supporting the existence of an "insulin-resistant cardiomyopathy" and proposes specific potential therapeutic approaches.

Acute diabetes moderates trafficking of cardiac lipoprotein lipase through p38 mitogen-activated protein kinase-dependent actin cytoskeleton organization

OBJECTIVE

Heart disease is a leading cause of death in diabetes and could occur because of excessive use of fatty acid for energy generation. Our objective was to determine the mechanisms by which AMP-activated protein kinase (AMPK) augments cardiac lipoprotein lipase (LPL), the enzyme that provides the heart with the majority of its fatty acid.

RESEARCH DESIGN AND METHODS

We used diazoxide in rats to induce hyperglycemia or used 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and thrombin to directly stimulate AMPK and p38 mitogen-activated protein kinase (MAPK), respectively, in cardiomyocytes.

RESULTS

There was a substantial increase in LPL at the coronary lumen following 4 h of diazoxide. In these diabetic animals, phosphorylation of AMPK, p38 MAPK, and heat shock protein (Hsp)25 produced actin cytoskeleton rearrangement to facilitate LPL translocation to the myocyte surface and, eventually, the vascular lumen. AICAR activated AMPK, p38 MAPK, and Hsp25 in a pattern similar to that seen with diabetes. AICAR also appreciably enhanced LPL, an effect reduced by preincubation with the p38 MAPK inhibitor SB202190 or by cytochalasin D, which inhibits actin polymerization. Thrombin activated p38 MAPK in the absence of AMPK phosphorylation. Comparable with diabetes, activation of p38 MAPK and, subsequently, Hsp25 phosphorylation and F-actin polymerization corresponded with an enhanced LPL activity. SB202190 and silencing of p38 MAPK also prevented these effects induced by thrombin and AICAR, respectively.

CONCLUSIONS

We propose that AMPK recruitment of LPL to the cardiomyocyte surface (which embraces p38 MAPK activation and actin cytoskeleton polymerization) represents an immediate compensatory response by the heart to guarantee fatty acid supply when glucose utilization is compromised.

Impairment of cardiac insulin signaling and myocardial contractile performance in high-cholesterol/fructose-fed rats

Although insulin resistance is recognized as a potent and prevalent risk factor for coronary heart disease, less is known as to whether insulin resistance causes an altered cardiac phenotype independent of coronary atherosclerosis. In this study, we investigated the relationship between insulin resistance and cardiac contractile dysfunctions by generating a new insulin resistance animal model with rats on high cholesterol-fructose diet. Male Sprague-Dawley rats were given high cholesterol-fructose (HCF) diet for 15 wk; the rats developed insulin resistance syndrome characterized by elevated blood pressure, hyperlipidemia, hyperinsulinemia, impaired glucose tolerance, and insulin resistance. The results show that HCF induced insulin resistance not only in metabolic-response tissues (i.e., liver and muscle) but also in the heart as well. Insulin-stimulated cardiac glucose uptake was significantly reduced after 15 wk of HCF feeding, and cardiac insulin resistance was associated with blunted Akt-mediated insulin signaling along with glucose transporter GLUT4 translocation. Basal fatty acid transporter FATP1 levels were increased in HCF rat hearts. The cardiac performance of the HCF rats exhibited a marked reduction in cardiac output, ejection fraction, stroke volume, and end-diastolic volume. It also showed decreases in left ventricular end-systolic elasticity, whereas the effective arterial elasticity was increased. In addition, the relaxation time constant of left ventricular pressure was prolonged in the HCF group. Overall, these results indicate that insulin resistance reduction of cardiac glucose uptake is associated with defects in insulin signaling. The cardiac metabolic alterations that impair contractile functions may lead to the development of cardiomyopathy.

Alterations in energy metabolism in cardiomyopathies

Despite the fact that the heart requires huge amounts of energy to sustain contractile function, it has limited energy reserves and must therefore continually produce large amounts of adenosine triphosphate (ATP) to sustain function. Fatty acids are the primary energy substrate of the adult heart, with more than 60% of the energy normally obtained from the oxidation of fatty acids, the remainder coming from the metabolism of carbohydrates. Alterations in both the rates of ATP production and the type of energy substrate used by the heart can have consequences on contractile function, as well as on its ability to respond to energetic stresses. Switches in myocardial substrate utilization and energy production rates have been shown to occur in various cardiomyopathies, as well as in any subsequent heart failure. Heart failure is characterized by an inefficient pumping of the heart, which fails to meet the energy requirements of the body. A number of cardiomyopathies can lead to heart failure. This paper will review the alterations in energy metabolism that occur in a number cardiomyopathies, including ischemic and diabetic cardiomyopathies, as well as hypertrophic cardiomyopathies resulting from mutations in enzymes involved in energy metabolism, such as 5' adenosine monophosphate-activated protein kinase (AMPK).

Role of changes in cardiac metabolism in development of diabetic cardiomyopathy

In patients with diabetes, an increased risk of symptomatic heart failure usually develops in the presence of hypertension or ischemic heart disease. However, a predisposition to heart failure might also reflect the effects of underlying abnormalities in diastolic function that can occur in asymptomatic patients with diabetes alone (termed diabetic cardiomyopathy). Evidence of cardiomyopathy has also been demonstrated in animal models of both Type 1 (streptozotocin-induced diabetes) and Type 2 diabetes (Zucker diabetic fatty rats and ob/ob or db/db mice). During insulin resistance or diabetes, the heart rapidly modifies its energy metabolism, resulting in augmented fatty acid and decreased glucose consumption. Accumulating evidence suggests that this alteration of cardiac metabolism plays an important role in the development of cardiomyopathy. Hence, a better understanding of this dysregulation in cardiac substrate utilization during insulin resistance and diabetes could provide information as to potential targets for the treatment of cardiomyopathy. This review is focused on evaluating the acute and chronic regulation and dysregulation of cardiac metabolism in normal and insulin-resistant/diabetic hearts and how these changes could contribute toward the development of cardiomyopathy.

The Influence of Type 2 Diabetes Mellitus in Patients Undergoing Coronary Artery Bypass Graft Surgery

OBJECTIVE

To prospectively assess whether there are any outcome differences between patients with and without type 2 diabetes mellitus undergoing coronary artery bypass graft (CABG) surgery.

STUDY DESIGN

This was an 8-year, prospective hospitalization cohort study. Data were collected on 225 variables concurrently with hospital admission. The main outcome was total operative mortality. In addition, we evaluated 12 morbidity outcomes. To minimize confounding, we controlled for 16 other variables.

RESULTS

A total of 6,711 patients were available for our analysis (diabetic patients, 2,178; and nondiabetic patients, 4,533). The diabetic patients were significantly more likely to be women, to have more left ventricular hypertrophy, to have a history of cerebrovascular disease, hypertension, and COPD, to have a greater body surface area, to have higher creatinine levels, to be African-American, to have undergone more elective procedures, to have a shorter pump time, and to have less of a history of tobacco use compared to nondiabetic patients (p < 0.05). Multiple regression analysis found no significant difference between the two groups for all 12 morbidity outcomes of interest. Diabetic patients experienced significantly more mortality than nondiabetic patients (relative risk, 1.67; 95% confidence interval, 1.20 to 2.30; p < 0.004).

CONCLUSION

Patients with type 2 diabetes who are undergoing CABG surgery experience significantly more total operative mortality compared to nondiabetic patients, even after controlling for multiple variables. There was no difference between the groups for 12 morbidity outcomes.

Preventing cardiovascular disease in diabetes and glucose intolerance: evidence and implications for care

With the increased attention being given to cardiovascular risk factor reduction, the opportunity exists to substantially decrease the largest cause of mortality in diabetic patients. The concept that type 2 diabetes and CVD are linked via a common etiologic pathway (metabolic syndrome) has substantial ramifications for the care of individual patients. Many of the metabolic abnormalities that contribute to both glycemic disorders and CVD are interrelated. For example, hyperinsulinemia and insulin resistance coupled with abdominal obesity further worsens HTN and hyperlipidemia. Likewise, the procoagulant state and endothelial dysfunction increase with worsening glycemic control. Specific interventions include tobacco cessation, a food management and physical activity plan, choice of antidiabetic agent (such as metformin), and use of ACE inhibitors for hypertension and microalbuminuria (Table 5). Programs to enhance cardiovascular risk factor reduction as part of the comprehensive evaluation and management of diabetic patients have been described [95,99]. One community-based program provided free screening to diabetic patients with randomization to either annotated result reports provided to the patient and their physician or results provided by a project nurse (either face-to-face or over the phone). Greater improvements in mean glycohemoglobin, cholesterol, and blood pressure were noted with verbal presentation of results [99]. Recent data from the Centers for Disease Control and Prevention Diabetes Cost-effectiveness Group support the idea that interventions to decrease CVD in diabetics are economically beneficial. Intensive management of hypertension, glycemic control, and hyperlipidemia each improved health outcomes. Hypertension control reduced costs. Although intensive treatment of glucose and hyperlipidemia increased costs, the increase was comparable to that of other frequently used health care interventions [100]. Further directions include further exploration of the implications and management of metabolic syndrome as it relates to CVD prevention. Interventions such as exercise, which can impact on all outcomes, require special attention. Efforts by physicians, health systems, and society are necessary to increase physical activity for individuals of all ages. It makes clinical sense that the recommendations for prevention of CVD in diabetics described in this article may also benefit patients with prediabetes (fasting glucose 110-125 mg/dl), but this remains to be definitively shown.

Characteristics and lipid distribution of a large, high-risk, hypertensive population: the lipid-lowering component of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT)

The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) consisted of 42,418 participants randomized to one of four antihypertensive treatment groups: chlorthalidone, amlodipine, lisinopril, or doxazosin. A subset of these participants with fasting low-density lipoprotein cholesterol levels 100-189 mg/dL were randomized into a lipid-lowering component: 5170 to receive pravastatin (40 mg daily) and 5185 to receive usual care. This report describes the characteristics and lipid distribution of these participants. There were no important differences between the randomized treatment groups. Women had higher total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol than men. There was a similar finding for black participants compared with whites, except blacks had lower triglycerides. Diabetics had lower high-density lipoprotein cholesterol and higher triglycerides than nondiabetics, and patients with body mass index <25 kg/m(2) had higher high-density lipoprotein cholesterol but lower low-density lipoprotein cholesterol and triglycerides than patients with higher body mass index. The success of the randomization of this large, diverse population and the differences in the lipid distributions among its subgroups will allow further understanding of optimal lipid-lowering treatment.

Population stratification and spurious allelic association

Great efforts and expense have been expended in attempts to detect genetic polymorphisms contributing to susceptibility to complex human disease. Concomitantly, technology for detection and scoring of single nucleotide polymorphisms (SNPs) has undergone rapid development, extensive catalogues of SNPs across the genome have been constructed, and SNPs have been increasingly used as a means for investigation of the genetic causes of complex human diseases. For many diseases, population-based studies of unrelated individuals--in which case-control and cohort studies serve as standard designs for genetic association analysis--can be the most practical and powerful approach. However, extensive debate has arisen about optimum study design, and considerable concern has been expressed that these approaches are prone to population stratification, which can lead to biased or spurious results. Over the past decade, a great shift has been noted, away from case-control and cohort studies, towards family-based association designs. These designs have fewer problems with population stratification but have greater genotyping and sampling requirements, and data can be difficult or impossible to gather. We discuss past evidence for population stratification on genotype-phenotype association studies, review methods to detect and account for it, and present suggestions for future study design and analysis.