Adaptation and maladaptation of the heart in diabetes: Part II: potential mechanisms

Cardiac PET-CT for monitoring medical and interventional therapy in patients with CAD: PET alone versus hybrid PET-CT?

This review focuses on optimal use of PET and PET-CT in monitoring medical and interventional therapy in patients with CAD. PET provides quantitative measurement of absolute myocardial blood flow and thus permits comprehensive physiological assessment of the coronary circulation. Hybrid PET-CT, in particular CCTA, adds anatomical information to maximal MBF measurement and so facilitates distinction of triple vessel focal epicardial disease from coronary microvascular disease or diffuse coronary atherosclerosis without focal stenoses. Hybrid PET-CT also may be of value in determining appropriateness and feasibility of percutaneous interventional therapy for chronic total coronary occlusion. PET alone, however, is the preferred modality to address functional status of the coronary circulation and response over time, if required, to medical or interventional therapy. CT at a minimum provides attenuation correction. More detailed CCTA should be added only when a well-defined need for anatomical information is required to answer the clinical question posed.

Role of O-GlcNAcylation in nutritional sensing, insulin resistance and in mediating the benefits of exercise

The purpose of this review is to highlight the role of O-linked β-N-acetylglucosamine (O-GlcNAc) protein modification in metabolic disease states and to summarize current knowledge of how exercise affects this important post-translational signalling pathway. O-GlcNAc modification is an intracellular tool capable of integrating energy supply with demand. The accumulation of excess energy associated with obesity and insulin resistance is mediated, in part, by the hexosamine biosynthetic pathway (HBP), which results in the O-GlcNAcylation of a myriad of proteins, thereby affecting their respective function, stability, and localization. Insulin resistance is related to the excessive O-GlcNAcylation of key metabolic proteins causing a chronic blunting of insulin signalling pathways and precipitating the accompanying pathologies, such as heart and kidney disease. Lifestyle modifications such as diet and exercise also modify the pathway. Exercise is a front-line and cost-effective therapeutic approach for insulin resistance, and recent work shows that the intervention can alter O-GlcNAc gene expression, signalling, and protein modification. However, there is currently no consensus on the effect of frequency, intensity, type, and duration of exercise on O-GlcNAc modification, the HBP, and its related enzymes. On one end of the spectrum, mild, prolonged swim training reduces O-GlcNAcylation, while on the other end, higher intensity treadmill running increases cardiac protein O-GlcNAc modification. Clearly, a balance between acute and chronic stress of exercise is needed to reap the benefits of the intervention on O-GlcNAc signalling.

Heart failure in the diabetic population - pathophysiology, diagnosis and management

Evidence from clinical trials repeatedly confirms the association of diabetes with heart failure, independent of hypertension, atherosclerosis, coronary artery disease and valvular heart disease. However, the importance of coexistence of diabetes and heart failure is not universally recognized, despite the fact that it may significantly contribute to morbidity and mortality of the diabetic population. It seems that prevention of heart failure, early diagnosis, and appropriate management could improve the outcome. Unfortunately, the etiology of heart failure in diabetic patients is still to be elucidated. It is multifactorial in nature and several cellular, molecular and metabolic factors are implicated. Additionally, there are still no definite guidelines on either the diagnosis and treatment of heart failure in diabetic patients or on the therapy of diabetes in subjects with heart failure. This review focuses on the pathophysiology, diagnosis, and prevention of heart failure in the diabetic population as well as management of both comorbidities.

Prognostic Value of Normal Perfusion but Impaired Left Ventricular Function in the Diabetic Heart on Quantitative Gated Myocardial Perfusion SPECT

PURPOSE

This study aimed at identifying the predictive parameters on quantitative gated myocardial perfusion single-photon emission computed tomography (QG-SPECT) in diabetic patients with normal perfusion but impaired function.

METHODS

Among the 533 consecutive diabetic patients, 379 patients with normal perfusion on rest Tl-201/dipyridamole-stress Tc-99m sestamibi Gated SPECT were enrolled. Patients were grouped into those with normal post-stress left ventricular function (Group I) and those with impaired function (EF <50 or impaired regional wall motion, Group II). We investigated cardiac events and cause of death by chart review and telephone interview. Survival analysis and Cox proportional hazard model analysis were performed.

RESULTS

Between the Group I and II, cardiac events as well as chest pain symptoms, smoking, diabetic complications were significantly different (P < 0.05). On survival analysis, event free survival rate in Group II was significantly lower than in Group I (P = 0.016). In univariate Cox proportional hazard analysis on overall cardiac event, Group (II over I), diabetic nephropathy, summed motion score (SMS), summed systolic thickening score (STS), numbers of abnormal segmental wall motion and systolic thickening predicted more cardiac events (P < 0.05). Multivariate analysis showed that STS was the only independent predictor cardiac event.

CONCLUSION

The functional parameter, especially summed systolic thickening score on QG-SPECT had prognostic values, despite normal perfusion, in predicting cardiac events in diabetic patients, and QG-SPECT provides clinically useful risk stratification in diabetic patients with normal perfusion.

LT175 is a novel PPARα/γ ligand with potent insulin-sensitizing effects and reduced adipogenic properties

Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors regulating lipid and glucose metabolism. Ongoing drug discovery programs aim to develop dual PPARα/γ agonists devoid of the side effects of the marketed antidiabetic agents thiazolidinediones and the dual agonists glitazars. Recently, we described a new dual PPARα/γ ligand, LT175, with a partial agonist profile against PPARγ and interacting with a newly identified region of the PPARγ-ligand binding domain (1). Here we show that LT175 differentially activated PPARγ target genes involved in fatty acid esterification and storage in 3T3-L1-derived adipocytes. This resulted in a less severe lipid accumulation compared with that triggered by rosiglitazone, suggesting that LT175 may have a lower adipogenic activity. Consistent with this hypothesis, in vivo administration of LT175 to mice fed a high-fat diet decreased body weight, adipocyte size, and white adipose tissue mass, as assessed by magnetic resonance imaging. Furthermore, LT175 significantly reduced plasma glucose, insulin, non-esterified fatty acids, triglycerides, and cholesterol and increased circulating adiponectin and fibroblast growth factor 21 levels. Oral glucose and insulin tolerance tests showed that the compound improves glucose homeostasis and insulin sensitivity. Moreover, we demonstrate that the peculiar interaction of LT175 with PPARγ affected the recruitment of the coregulators cyclic-AMP response element-binding protein-binding protein and nuclear corepressor 1 (NCoR1), fundamentals for the PPARγ-mediated adipogenic program. In conclusion, our results describe a new PPAR ligand, modulating lipid and glucose metabolism with reduced adipogenic activity, that may be used as a model for a series of novel molecules with an improved pharmacological profile for the treatment of dyslipidemia and type 2 diabetes.

The heart in obesity-hypertension

There is growing recognition that obesity is reaching epidemic proportions throughout the world. In adults, obesity is associated with increased cardiovascular morbidity and mortality. A series of endocrine, metabolic and hemodynamic mechanisms have been responsible for the development of obesity-hypertension. These mechanisms include: a suppressed biologic activity and availability of natriuretic peptide, increased sympathetic adrenergic activity, release of angiotensin ll from adipocytes and activation of the renin-angiotensin-aldosterone system, leptin resistance, chronic hyperleptinemia and hyperinsulinemia. The systemic hemodynamic profile of obesity includes high intravascular volume, increased cardiac output and inappropriately normal peripheral resistance. The cardiovascular adaptations to these changes include changes in vascular responsiveness and concentric-eccentric left ventricular hypertrophy, and may be responsible for increased risk of congestive heart failure, arrhythmia and sudden death.

Comparison of statin alone versus bezafibrate and statin combination in patients with diabetes mellitus and acute coronary syndrome

Acute coronary syndromes (ACS) in patients with diabetes mellitus (DM) are associated with a high risk for major adverse cardiovascular events (MACEs) despite statin treatment. The impact of combined bezafibrate and statin therapy in patients with DM and ACS has not been specifically investigated. The aim of this study was to evaluate the association of combined therapy with 30-day MACEs in patients with DM participating in the nationwide Acute Coronary Syndrome Israeli Surveys (ACSIS). The study population comprised 3,063 patients with DM from the ACSIS 2000, 2002, 2004, 2006, 2008, and 2010 enrollment waves who were alive at discharge and received statins. Of these, 225 (7.3%) received on discharge combined bezafibrate and statin therapy, and 2,838 (92.7%) were treated with statins alone. MACEs were defined as a composite measure of death, recurrent myocardial infarction, recurrent ischemia, stent thrombosis, ischemic stroke, and urgent revascularization. The development of 30-day MACEs was recorded in 8% patients receiving combination therapy and 14.2% of those receiving statins alone (p = 0.01). Crude 1-year mortality and 30-day rehospitalization rates were also significantly lower in patients receiving combination therapy: 4.0% versus 8.1% (p = 0.03) and 13.3% versus 21.6% (p = 0.003), respectively. Multivariate analysis identified combined therapy as an independent predictor of reduced risk for 30-day MACEs, with an odds ratio of 0.56 (95% confidence interval 0.34 to 0.92), corresponding to a 44% relative risk reduction. In conclusion, a significantly lower risk for 30-day MACEs was observed in statin-treated patients with DM who also received bezafibrate after ACS. Signals regarding improvement of 30-day rehospitalization and 1-year mortality rates emerged as well.

Structural and Metabolic Effects of Obesity on the Myocardium and the Aorta

Obesity per se is a recognized risk factor for cardiovascular disease exerting independent adverse effects on the cardiovascular system. Despite this well documented link, the mechanisms by which obesity modulates cardiovascular risk are not well understood. Obesity is linked to a wide variety of cardiac changes, from subclinical diastolic dysfunction to end stage systolic heart failure. In addition, obesity causes changes in cardiac metabolism that make ATP production and utilization less efficient producing functional consequences that are linked to the increased rate of heart failure in this population. This review focuses on the cardiovascular structural and metabolic remodelling that occurs in obesity with and without co-morbidities and the potential links to increased mortality in this population. © 2014 S. Karger GmbH, Freiburg.

GPR120 agonism as a countermeasure against metabolic diseases

Obesity, type 2 diabetes mellitus and cardiovascular disease are at epidemic proportions in developed nations globally, representing major causes of ill-health and premature death. The search for drug targets to counter the growing prevalence of metabolic diseases has uncovered G-protein-coupled receptor 120 (GPR120). GPR120 agonism has been shown to improve inflammation and metabolic health on a systemic level via regulation of adiposity, gastrointestinal peptide secretion, taste preference and glucose homeostasis. Therefore, GPR120 agonists present as a novel therapeutic option that could be exploited for the treatment of impaired metabolic health. This review summarizes the current knowledge of GPR120 functionality and the potential applications of GPR120-specific agonists for the treatment of disease states such as obesity, type 2 diabetes mellitus and cardiovascular disease.

Recent advances in metabolic imaging

Abnormalities in myocardial substrate metabolism play a central role in the manifestations of most forms of cardiac disease such as ischemic heart disease, heart failure, hypertensive heart disease, and the cardiomyopathy due to either obesity or diabetes mellitus. Their importance is exemplified by both the development of numerous imaging tools designed to detect the specific metabolic perturbations or signatures related to these different diseases, and the vigorous efforts in drug discovery/development targeting various aspects of myocardial metabolism. Since the prior review in 2005, we have gained new insights into how perturbations in myocardial metabolism contribute to various forms of cardiac disease. For example, the application of advanced molecular biologic techniques and the development of elegant genetic models have highlighted the pleiotropic actions of cellular metabolism on energy transfer, signal transduction, cardiac growth, gene expression, and viability. In parallel, there have been significant advances in instrumentation, radiopharmaceutical design, and small animal imaging, which now permit a near completion of the translational pathway linking in-vitro measurements of metabolism with the human condition. In this review, most of the key advances in metabolic imaging will be described, their contribution to cardiovascular research highlighted, and potential new clinical applications proposed.

The therapeutic potential of GPR43: a novel role in modulating metabolic health

GPR43 is a receptor for short-chain fatty acids. Preliminary data suggest a putative role for GPR43 in regulating systemic health via processes including inflammation, carcinogenesis, gastrointestinal function, and adipogenesis. GPR43 is involved in secretion of gastrointestinal peptides, which regulate appetite and gastrointestinal motility. This suggests GPR43 may have a role in weight control. Moreover, GPR43 regulates plasma lipid profile and inflammatory processes, which further indicates that GPR43 could have the ability to modulate the etiology and pathogenesis of metabolic diseases such as obesity, type 2 diabetes mellitus, and cardiovascular disease. This review summarizes the current evidence regarding the ability of GPR43 to mediate both systemic and tissue specific functions and how GPR43 may be modulated in the treatment of metabolic disease.

Insulin resistance protects the heart from fuel overload in dysregulated metabolic states

Reversing impaired insulin sensitivity has been suggested as treatment for heart failure. However, recent clinical evidence suggests the opposite. Here we present a line of reasoning in support of the hypothesis that insulin resistance protects the heart from the consequences of fuel overload in the dysregulated metabolic state of obesity and diabetes. We discuss pathways of myocardial fuel toxicity, as well as several layers of defense against fuel overload. Our reassessment of the literature suggests that in the heart, insulin-sensitizing agents result in an elimination of some of the defenses, leading to cytotoxic damage. In contrast, a normalization of fuel supply should either prevent or reverse the process. Taken together, we offer a new perspective on insulin resistance of the heart.

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.

Metabolic syndrome and right ventricle: an updated review

The cluster of metabolic and hemodynamic abnormalities which characterize the metabolic syndrome (MS) is responsible for subclinical cardiac and extra-cardiac damage such as left ventricular hypertrophy, diastolic dysfunction, carotid atherosclerosis and microalbuminuria. The development of different non-invasive imaging methods enabled a detail investigation of right ventricular structure and function, and revealed that right ventricular remodeling followed changes in the left ventricular structure and function in patients with arterial hypertension, diabetes or obesity. Previous investigations also reported that the coexistence of two components of the MS induced more significant cardiac remodeling than the presence of only one MS risk-factor. The relationship between different components of the MS (increased blood pressure, abdominal obesity, increased fasting glucose level and dyslipidemia) and right ventricular remodeling could be explained by several hemodynamic and non-hemodynamic mechanisms. However, the association between right ventricular remodeling and the MS has not been sufficiently investigated so far. The aim of this article was to review recent articles focusing on the association between metabolic syndrome components and the metabolic syndrome itself with impairments in right ventricular structure and function assessed by different imaging techniques.

Acetyl-l-carnitine and oxfenicine on cardiac pumping mechanics in streptozotocin-induced diabetes in male Wistar rats

INTRODUCTION

In the treatment of patients with diabetes, one objective is an improvement of cardiac metabolism to alleviate the left ventricular (LV) function. For this study, we compared the effects of acetyl-l-carnitine (one of the carnitine derivatives) and of oxfenicine (a carnitine palmitoyltransferase-1 inhibitor) on cardiac pumping mechanics in streptozotocin-induced diabetes in male Wistar rats, with a particular focus on the pressure-flow-volume relationship.

METHODS

Diabetes was induced by a single tail vein injection of 55 mg kg(-1) streptozotocin. The diabetic animals were treated on a daily basis with either acetyl-L-carnitine (1 g L(-1) in drinking water) or oxfenicine (150 mg kg(-1) by oral gavage) for 8 wk. They were also compared with untreated age-matched diabetic controls. LV pressure and ascending aortic flow signals were recorded to calculate the maximal systolic elastance (E max) and the theoretical maximum flow (Q max). Physically, E max reflects the contractility of the myocardium as an intact heart, whereas Q max has an inverse relationship with the LV internal resistance.

RESULTS

When comparing the diabetic rats with their age-matched controls, the cardiodynamic condition was characterized by a decline in E max associated with the unaltered Q max. Acetyl-l-carnitine (but not oxfenicine) had reduced cardiac levels of malondialdehyde in these insulin-deficient animals. However, treating with acetyl-l-carnitine or oxfenicine resulted in an increase in E max, which suggests that these 2 drugs may protect the contractile status from deteriorating in the diabetic heart. By contrast, Q max showed a significant fall after administration of oxfenicine, but not with acetyl-L-carnitine. The decrease in Q max corresponded to an increase in total vascular resistance when treated with oxfenicine.

CONCLUSIONS

Acetyl-l-carnitine, but not oxfencine, optimizes the integrative nature of cardiac pumping mechanics by preventing the diabetes-induced deterioration in myocardial intrinsic contractility associated with unaltered LV internal resistance.

Myocardial substrate metabolism in obesity

Obesity is linked to a wide variety of cardiac changes, from subclinical diastolic dysfunction to end-stage systolic heart failure. Obesity causes changes in cardiac metabolism, which make ATP production and utilization less efficient, producing functional consequences that are linked to the increased rate of heart failure in this population. As a result of the increases in circulating fatty acids and insulin resistance that accompanies excess fat storage, several of the proteins and genes that are responsible for fatty acid uptake and metabolism are upregulated, and the metabolic machinery responsible for glucose utilization and oxidation are inhibited. The resultant increase in fatty acid metabolism, and the inherent alterations in the proteins of the electron transport chain used to create the gradient needed to drive mitochondrial ATP production, results in a decrease in efficiency of cardiac work and a relative increase in oxygen usage. These changes in cardiac mitochondrial metabolism are potential therapeutic targets for the treatment and prevention of obesity-related heart failure.

Clues from bariatric surgery: reversing insulin resistance to heal the heart

Obesity is a state of metabolic dysregulation of the whole organism and a major contributing factor to the epidemic of insulin resistant diabetes. The nonpharmacologic treatment of obesity with bariatric surgery results in a dramatic and almost instantaneous reversal of insulin resistance. The present review collectively addresses the evidence for this phenomenon in the literature and discusses potential metabolic and neurohumoral mechanisms. We propose that nutrient restriction lowers the cell's defense mechanisms for nutrient overload in insulin responsive organs.

Ketone body metabolism and cardiovascular disease

Ketone bodies are metabolized through evolutionarily conserved pathways that support bioenergetic homeostasis, particularly in brain, heart, and skeletal muscle when carbohydrates are in short supply. The metabolism of ketone bodies interfaces with the tricarboxylic acid cycle, β-oxidation of fatty acids, de novo lipogenesis, sterol biosynthesis, glucose metabolism, the mitochondrial electron transport chain, hormonal signaling, intracellular signal transduction pathways, and the microbiome. Here we review the mechanisms through which ketone bodies are metabolized and how their signals are transmitted. We focus on the roles this metabolic pathway may play in cardiovascular disease states, the bioenergetic benefits of myocardial ketone body oxidation, and prospective interactions among ketone body metabolism, obesity, metabolic syndrome, and atherosclerosis. Ketone body metabolism is noninvasively quantifiable in humans and is responsive to nutritional interventions. Therefore, further investigation of this pathway in disease models and in humans may ultimately yield tailored diagnostic strategies and therapies for specific pathological states.

FXR activation improves myocardial fatty acid metabolism in a rodent model of obesity-driven cardiotoxicity

BACKGROUND AND AIMS

Obesity-driven lipotoxicity is a risk factors for cardiovascular disease. The Farnesoid X Receptor (FXR) is a bile acids sensor and member of the nuclear receptor superfamily. Activation of FXR lowers plasma triacylglycerols and glucose levels through a mechanism that involves both the repression of key regulatory genes in the liver and the modulation of insulin sensitivity in peripheral tissues. In the present study we have investigated whether administering obese (fa/fa) Zucker rats, a genetic model of obesity associated with dyslipidemia and insulin resistance, with an FXR ligand protects against lipid-induced cardiomyopathy.

METHODS AND RESULTS

FXR is expressed in neonatal cardiomyocytes and the treatment with FXR agonists, chenodeoxycholic acid (CDCA), and GW4064, increased the mRNA expression of FXR and its canonical target gene, the small heterodimer partner (SHP), as well as proliferator-activated receptor alpha PPARα, acyl-CoA oxidase (AOX) and pyruvate dehydrogenase kinase (PDK-4). Feeding obese fa/fa rats with CDCA, 12 weeks, reduced hyperinsulinemia and hyperlipidaemia. The histological-pathological analysis of hearts demonstrated that treatment with the FXR ligand reduced lipid heart content decreased the rate of apoptosis, fibrosis scores and restored heart insulin signalling. Chronic CDCA administration, in the heart, induced PPARα and PPARα-regulated genes involved in β-oxidation.

CONCLUSION

FXR agonism exerts beneficial effects in a genetic model of lipid-induced cardiomyopathy. The striking benefit of this therapy on cardiac function in this model warrants an effort to determine whether a counterpart of this activity translates in human settings.

Effect of acute hyperglycemia on left ventricular contractile function in diabetic patients with and without heart failure: two randomized cross-over studies

BACKGROUND

It is unknown whether changes in circulating glucose levels due to short-term insulin discontinuation affect left ventricular contractile function in type 2 diabetic patients with (T2D-HF) and without (T2D-nonHF) heart failure.

MATERIALS AND METHODS

In two randomized cross-over-designed trials, 18 insulin-treated type 2 diabetic patients with (Ejection Fraction (EF) 36 ± 6%, n = 10) (trial 2) and without systolic heart failure (EF 60 ± 3%, n = 8) (trial 1) were subjected to hyper- and normoglycemia for 9-12 hours on two different occasions. Advanced echocardiography, bicycle exercise tests and 6-minute hall walk distance were applied.

RESULTS

Plasma glucose levels differed between study arms (6.5 ± 0.8 mM vs 14.1 ± 2.6 mM (T2D-HF), 5.8 ± 0.4 mM vs 9.9 ± 2.1 mM (T2D-nonHF), p<0.001). Hyperglycemia was associated with an increase in several parameters: maximal global systolic tissue velocity (Vmax) (p<0.001), maximal mitral annulus velocity (S'max) (p<0.001), strain rate (p = 0.02) and strain (p = 0.05). Indices of increased myocardial systolic contractile function were significant in both T2D-HF (Vmax: 14%, p = 0.02; S'max: 10%, p = 0.04), T2D-nonHF (Vmax: 12%, p<0.01; S'max: 9%, p<0.001) and in post exercise S'max (7%, p = 0.049) during hyperglycemia as opposed to normoglycemia. LVEF did not differ between normo- and hyperglycemia (p = 0.17), and neither did peak exercise capacity nor catecholamine levels. Type 2 diabetic heart failure patients' 6-minute hall walk distance improved by 7% (p = 0.02) during hyperglycemia as compared with normoglycemia.

CONCLUSIONS

Short-term hyperglycemia by insulin discontinuation is associated with an increase in myocardial systolic contractile function in type 2 diabetic patients with and without heart failure and with a slightly prolonged walking distance in type 2 diabetic heart failure patients. (Clinicaltrials.gov identifier NCT00653510).

Obesity-related alterations in cardiac lipid profile and nondipping blood pressure pattern during transition to diastolic dysfunction in male db/db mice

Obesity and a nondipping circadian blood pressure (BP) pattern are associated with diastolic dysfunction. Ectopic lipid accumulation is increasingly recognized as an important metabolic abnormality contributing to diastolic dysfunction. However, little is known about the contribution of different lipids and the composition of lipid analytes to diastolic dysfunction. We have performed functional and structural studies and analyzed cardiac lipid profile at two time points during progression to diastolic dysfunction in a genetic model of obesity. Serial cardiac magnetic resonance imaging and telemetric measures of BP between 12 and 15 wk of age in obese male db/db mice indicated a nondipping circadian BP pattern and normal diastolic function at 12 wk that progressed to a deteriorating nondipping pattern and onset of diastolic dysfunction at 15 wk of age. Lipidomic analysis demonstrated elevated fatty acids and ceramides in db/db at 12 wk, but their levels were decreased at 15 wk, and this was accompanied by persistent mitochondrial ultrastructural abnormalities in concert with evidence of increased fatty acid oxidation and enhanced production of reactive oxygen species. Triacylglyceride and diacylglyceride levels were elevated at both 12 and 15 wk, but their composition changed to consist of more saturated and less unsaturated fatty acyl at 15 wk. An increase in the lipid droplets was apparent at both time points, and this was associated with increases in phosphatidycholine. In conclusion, a distinct pattern of myocardial lipid remodeling, accompanied by oxidative stress, is associated with the onset of diastolic dysfunction in obese, insulin-resistant db/db mice.

Protective effects of Acyl-coA thioesterase 1 on diabetic heart via PPARα/PGC1α signaling

Background

Using fatty acids (FAs) exclusively for ATP generation was reported to contribute to the development of diabetic cardiomyopathy. We studied the role of substrate metabolism related genes in the heart of the diabetes to find out a novel therapeutic target for diabetic cardiomyopathy.

Methods and Results

By microarray analysis of metabolic gene expression, acyl-CoA thioesterase 1 (acot1) was clearly upregulated in the myocardia of db/db mice, compared with normal control C57BL/Ks. Therefore, gain-of-function and loss-of-function approaches were employed in db/db mice to investigate the functions of ACOT1 in oxidative stress, mitochondrial dysfunction and heart function. We found that in the hearts of db/db mice which overexpressed ACOT1, H₂O₂ and malondialdehyde (MDA) were reduced, the activities of ATPases in mitochondria associated with mitochondrial function were promoted, the expression of uncoupling protein 3 (UCP3) contributing to oxygen wastage for noncontractile purposes was decreased, and cardiac dysfunction was attenuated, as determined by both hemodynamic and echocardiographic detections. Consistently, ACOT1 deficiency had opposite effects, which accelerated the cardiac damage induced by diabetes. Notably, by real-time PCR, we found that overexpression of ACOT1 in diabetic heart repressed the peroxisome proliferator-activated receptor alpha/PPARγ coactivator 1α (PPARα/PGC1α) signaling, as shown by decreased expression of PGC1α and the downstream genes involved in FAs use.

Conclusion

Our results demonstrated that ACOT1 played a crucial protective role in diabetic heart via PPARα/PGC1α signaling.

Similar patterns of myocardial metabolism and perfusion in patients with type 2 diabetes and heart disease of ischaemic and non-ischaemic origin

AIMS/HYPOTHESIS

Type 2 diabetes and insulin resistance are often associated with the co-occurrence of coronary atherosclerosis and cardiac dysfunction. The aim of this study was to define the independent relationships between left ventricular dysfunction or ischaemia and patterns of myocardial perfusion and metabolism in type 2 diabetes.

METHODS

Twenty-four type 2 diabetic patients--12 with coronary artery disease (CAD) and preserved left ventricular function and 12 with non-ischaemic heart failure (HF)--were enrolled in a cross-sectional study. Positron emission tomography (PET) was used to assess myocardial blood flow (MBF) at rest, after pharmacological stress and under euglycaemic hyperinsulinaemia. Insulin-mediated myocardial glucose disposal was determined with 2-deoxy-2-[(18)F]fluoroglucose PET.

RESULTS

There was no difference in myocardial glucose uptake (MGU) between the healthy myocardium of CAD patients and the dysfunctional myocardium of HF patients. MGU was strongly influenced by levels of systemic insulin resistance in both groups (CAD, r = 0.85, p = 0.005; HF, r = 0.77, p = 0.01). In HF patients, there was an inverse association between MGU and the coronary flow reserve (r = -0.434, p = 0.0115). A similar relationship was observed in non-ischaemic segments of CAD patients. Hyperinsulinaemia increased MBF to a similar extent in the non-ischaemic myocardial of CAD and HF patients.

CONCLUSIONS/INTERPRETATION

In type 2 diabetes, similar metabolic and perfusion patterns can be detected in the non-ischaemic regions of CAD patients with normal cardiac function and in the dysfunctional non-ischaemic myocardium of HF patients. This suggests that insulin resistance, rather than diagnosis of ischaemia or left ventricular dysfunction, affects the metabolism and perfusion features of patients with type 2 diabetes.

Emerging role of epigenetics and miRNA in diabetic cardiomyopathy

The prevalence of heart failure independent of coronary artery disease and hypertension is increasing rapidly in diabetic patients. Thus, this pathophysiology has been recognized as a distinct clinical entity termed "diabetic cardiomyopathy." Several studies support the notion that diabetes is a threatening insult for the myocardium resulting in functional, cellular, and structural changes manifesting as a cardiac myopathy. Recent data suggested that epigenetics including DNA and histone modifications as well as microRNAs play an important role in the development of cardiac diseases. The role of epigenetics in diabetes is largely recognized; however, its role in diabetes-associated cardiomyopathy remains elusive. Thus, molecular, cellular, and functional modulations in the diabetic cardiomyopathy will be investigated in this review. Moreover, particular attention will be drawn on the epigenetic mechanisms that may play an important role in the pathophysiology of diabetic cardiomyopathy.

Sphingolipids, lipotoxic cardiomyopathy, and cardiac failure

In the setting of obesity and type 2 diabetes mellitus, the ectopic disposition of lipids may be a cause of heart failure. Clinical studies have clearly shown a correlation between the accumulation of triglycerides and heart dysfunction. In this process, it is likely that there are also changes in the contents of sphingolipids. Sphingolipids are important structural and signaling molecules. One specific sphingolipid, ceramide, may cause cardiac dysfunction, whereas another, sphingosine 1-phosphate, is cardioprotective. In this review, the authors focus on the role of sphingolipids in the development and prevention of cardiac failure.

A new insight of mechanisms, diagnosis and treatment of diabetic cardiomyopathy

Diabetes mellitus is one of the most common chronic diseases across the world. Cardiovascular complication is the major morbidity and mortality among the diabetic patients. Diabetic cardiomyopathy, a new entity independent of coronary artery disease or hypertension, has been increasingly recognized by clinicians and epidemiologists. Cardiac dysfunction is the major characteristic of diabetic cardiomyopathy. For a better understanding of diabetic cardiomyopathy and necessary treatment strategy, several pathological mechanisms such as impaired calcium handling and increased oxidative stress, have been proposed through clinical and experimental observations. In this review, we will discuss the development of cardiac dysfunction, the mechanisms underlying diabetic cardiomyopathy, diagnostic methods, and treatment options.

Diabetic cardiovascular disease: getting to the heart of the matter

Diabetes is a major risk factor for heart disease, and heart disease is responsible for substantial morbidity and mortality among people living with diabetes. The diabetic metabolic milieu predisposes to aggressive obstructive coronary artery disease that causes heart attacks, heart failure, and death. Furthermore, diabetes can be associated with heart failure, independent of underlying coronary artery disease, hypertension, or valve abnormalities. The pathogenesis of the vascular and myocardial complications of diabetes is, as yet, incompletely understood. Although a number of medical and surgical approaches can improve outcomes in diabetic patients with cardiovascular disease, much remains to be learned in order to optimize approaches to these critical complications.

Inhibition of serine palmitoyl transferase I reduces cardiac ceramide levels and increases glycolysis rates following diet-induced insulin resistance

OBJECTIVE

Diet-induced obesity (DIO) leads to an accumulation of intra-myocardial lipid metabolites implicated in causing cardiac insulin resistance and contractile dysfunction. One such metabolite is ceramide, and our aim was to determine the effects of inhibiting de novo ceramide synthesis on cardiac function and insulin stimulated glucose utilization in mice subjected to DIO.

MATERIALS AND METHODS

C57BL/6 mice were fed a low fat diet or subjected to DIO for 12 weeks, and then treated for 4 weeks with either vehicle control or the serine palmitoyl transferase I (SPT I) inhibitor, myriocin. In vivo cardiac function was assessed via ultrasound echocardiography, while glucose metabolism was assessed in isolated working hearts.

RESULTS

DIO was not associated with an accumulation of intra-myocardial ceramide, but rather, an accumulation of intra-myocardial DAG (2.63±0.41 vs. 4.80±0.97 nmol/g dry weight). Nonetheless, treatment of DIO mice with myriocin decreased intra-myocardial ceramide levels (50.3±7.7 vs. 26.9±2.7 nmol/g dry weight) and prevented the DIO-associated increase in intra-myocardial DAG levels. Interestingly, although DIO impaired myocardial glycolysis rates (7789±1267 vs. 2671±326 nmol/min/g dry weight), hearts from myriocin treated DIO mice exhibited an increase in glycolysis rates.

CONCLUSIONS

Our data reveal that although intra-myocardial ceramide does not accumulate following DIO, inhibition of de novo ceramide synthesis nonetheless reduces intra-myocardial ceramide levels and prevents the accumulation of intra-myocardial DAG. These effects improved the DIO-associated impairment of cardiac glycolysis rates, suggesting that SPT I inhibition increases cardiac glucose utilization.

Na+/Ca2+ exchanger-1 protects against systolic failure in the Akitains2 model of diabetic cardiomyopathy via a CXCR4/NF-κB pathway

Diabetic cardiomyopathy is characterized, in part, by calcium handling imbalances associated with ventricular dysfunction. The cardiac Na(+)/Ca(2+) exchanger 1 (NCX1) has been implicated as a compensatory mechanism in response to reduced contractility in the heart; however, its role in diabetic cardiomyopathy remains unknown. We aimed to fully characterize the Akita(ins2) murine model of type 1 diabetes through assessing cardiac function and NCX1 regulation. The CXCL12/CXCR4 chemokine axis is well described in its cardioprotective effects via progenitor cell recruitment postacute myocardial infarction; however, it also functions in regulating calcium dependent processes in the cardiac myocyte. We therefore investigated the potential impact of CXCR4 in diabetic cardiomyopathy. Cardiac performance in the Akita(ins2) mouse was monitored using echocardiography and in vivo pressure-volume analysis. The Akita(ins2) mouse is protected against ventricular systolic failure evident at both 5 and 12 mo of age. However, the preserved contractility was associated with a decreased sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a)/phospholamban ratio and increased NCX1 content. Direct myocardial injection of adenovirus encoding anti-sense NCX1 significantly decreased NCX1 expression and induced systolic failure in the Akita(ins2) mouse. CXCL12 and CXCR4 were both upregulated in the Akita(ins2) heart, along with an increase in IκB-α and NF-κB p65 phosphorylation. We demonstrated that CXCR4 activation upregulates NCX1 expression through a NF-κB-dependent signaling pathway in the cardiac myocyte. In conclusion, the Akita(ins2) type 1 diabetic model is protected against systolic failure due to increased NCX1 expression. In addition, our studies reveal a novel role of CXCR4 in the diabetic heart by regulating NCX1 expression via a NF-κB-dependent mechanism.

p53-induced adipose tissue inflammation is critically involved in the development of insulin resistance in heart failure

Several clinical studies have shown that insulin resistance is prevalent among patients with heart failure, but the underlying mechanisms have not been fully elucidated. Here, we report a mechanism of insulin resistance associated with heart failure that involves upregulation of p53 in adipose tissue. We found that pressure overload markedly upregulated p53 expression in adipose tissue along with an increase of adipose tissue inflammation. Chronic pressure overload accelerated lipolysis in adipose tissue. In the presence of pressure overload, inhibition of lipolysis by sympathetic denervation significantly downregulated adipose p53 expression and inflammation, thereby improving insulin resistance. Likewise, disruption of p53 activation in adipose tissue attenuated inflammation and improved insulin resistance but also ameliorated cardiac dysfunction induced by chronic pressure overload. These results indicate that chronic pressure overload upregulates adipose tissue p53 by promoting lipolysis via the sympathetic nervous system, leading to an inflammatory response of adipose tissue and insulin resistance.

Diabetes in mice with monogenic obesity: the db/db mouse and its use in the study of cardiac consequences

The leptin receptor deficient db/db mouse has served as a rodent model for obesity and type 2 diabetes for more than 40 years. Diabetic features in db/db mice follow an age-dependent progression, with early insulin resistance followed by an insulin secretory defect resulting in profound hyperglycemia. Diabetic db/db mice have been utilized to assess the cardiac consequences of diabetes, specifically evidence for a distinct diabetic cardiomyopathy. The db/db model is characterized by a contractile function deficit in the heart which becomes manifest 8-10 weeks after birth. Metabolic changes include an increased reliance on fatty acids and a decreased reliance on glucose as a fuel source for oxidative metabolism within the heart. As a mouse model for type 2 diabetes, both drug treatment and transgenic manipulation have proven beneficial towards improving metabolism and contractile function. The db/db mouse model has provided a useful resource to understand and treat the type 2 diabetic condition.

Proteome changes in the myocardium of experimental chronic diabetes and hypertension: role of PPARα in the associated hypertrophy

Diabetes with or without the presence of hypertension damages the heart. However, there is currently a lack of information about these associated pathologies and the alteration of linked proteins. For these reasons, we were interested in the potential synergistic interaction of diabetes and hypertension in the heart, focusing on the proteome characterization of the pathological phenotypes and the associated hypertrophic response. We treated normotensive and spontaneously hypertensive (SHR) rats with either streptozotocin or vehicle. After 22weeks, type-I diabetic (DM1), SHR, SHR/DM1 and control left-ventricles were studied using proteomic approaches. Proteomics revealed that long-term DM1, SHR and SHR/DM1 rats exhibited 24, 53 and 53 altered proteins in the myocardia, respectively. DM1 myocardium showed over-expression of apoptotic and cytoskeleton proteins, and down-regulation of anti-apoptotic and mitochondrial metabolic enzymes. In both SHR and SHR/DM1 these changes were exacerbated and free fatty-acid (FFA) ß-oxidation enzymes were additionally decreased. Furthermore, SHR/DM1 hearts exhibited a misbalance of specific pro-hypertrophic, anti-apoptotic and mitochondrial ATP-carrier factors, which could cause additional damage. Differential proteins were validated and then clustered into different biological pathways using bioinformatics. These studies suggested the implication of FFA-nuclear receptors and hypertrophic factors in these pathologies. Although key ß-oxidation enzymes were not stimulated in DM1 and hypertensive hearts, peroxisome proliferator-activated receptors-α (PPARα) were potentially activated for other responses. In this regard, PPARα stimulation reduced hypertrophy and pro-hypertrophic factors such as annexin-V in high-glucose and angiotensin-II induced cardiomyocytes. Thus, activation of PPARα could reflect a compensatory response to the metabolic-shifted, apoptotic and hypertrophic status of the hypertensive-diabetic cardiomyopathy.

Diet-induced obesity up-regulates the abundance of GPR43 and GPR120 in a tissue specific manner

BACKGROUND/AIMS

GPR43 and GPR120 have recently been deorphanised as receptors for fatty acids. Fatty acids mediate a variety of metabolic processes in the body, however, the effect these receptors have on metabolism is not fully understood. Here, we characterise the effect of diet-induced obesity on the expression of GPR43 and GPR120 in tissues important in maintaining metabolic health.

METHODS

Six-week old male Sprague Dawley rats were fed either a high fat diet (HFD; 22% fat) or control diet (5% fat; n = 8-9/group) for 12 weeks. Rats were euthanized and the heart, liver, soleus and extensor digitorum longus (EDL) skeletal muscles were excised. GPR43 and GPR120 receptor abundance was quantified by 'real-time' PCR.

RESULTS

GPR43 mRNA abundance was significantly up-regulated by a HFD in liver and soleus and EDL skeletal muscles compared to control (p ≤ 0.05). Whilst a HFD significantly up-regulated GPR120 gene transcripts in cardiac tissue and EDL skeletal muscle when compare to control (p ≤ 0.05).

CONCLUSION

We have shown for the first time that up-regulation of GPR43 and GPR120 in response to a HFD, is tissue specific. This suggests these receptors have different roles in mediating metabolic function in a number of tissues in the human body.

Increased basal coronary blood flow as a cause of reduced coronary flow reserve in diabetic patients

A reduced coronary flow reserve (CFR) has been demonstrated in diabetes, but the underlying mechanisms are unknown. We assessed thermodilution-derived CFR after 5-min intravenous adenosine infusion through a pressure-temperature sensor-tipped wire in 30 coronary arteries without significant lumen reduction in 30 patients: 13 with and 17 without a history of diabetes. We determined CFR as the ratio of basal and hyperemic mean transit times (Tmn); fractional flow reserve (FFR) as the ratio of distal and proximal pressures at maximal hyperemia to exclude local macrovascular disease; and an index of microvascular resistance (IMR) as the distal coronary pressure at maximal hyperemia divided by the inverse of the hyperemic Tmn. We also assessed insulin resistance by the homeostasis model assessment (HOMA) index. FFR was normal in all investigated arteries. CFR was significantly lower in diabetic vs. nondiabetic patients [median (interquartile range): 2.2 (1.4–3.2) vs. 4.1 (2.7–4.4); P = 0.02]. Basal Tmn was lower in diabetic vs. nondiabetic subjects [median (interquartile range): 0.53 (0.25–0.71) vs. 0.64 (0.50–1.17); P = 0.04], while hyperemic Tmn and IMR were similar. We found significant correlations at linear regression analysis between logCFR and the HOMA index ( r2 = 0.35; P = 0.0005) and between basal Tmn and the HOMA index ( r2 = 0.44; P < 0.0001). In conclusion, compared with nondiabetic subjects, CFR is lower in patients with diabetes and epicardial coronary arteries free of severe stenosis, because of increased basal coronary flow, while hyperemic coronary flow is similar. Basal coronary flow relates to insulin resistance, suggesting a key role of cellular metabolism in the regulation of coronary blood flow.

Concomitant renal insufficiency and diabetes mellitus as prognostic factors for acute myocardial infarction

Background

Diabetes mellitus and renal dysfunction are prognostic factors after acute myocardial infarction (AMI). However, few studies have assessed the effects of renal insufficiency in association with diabetes in the context of AMI. Here, we investigated the clinical outcomes according to the concomitance of renal dysfunction and diabetes mellitus in patients with AMI.

Methods

From November 2005 to August 2008, 9905 patients (63 ± 13 years; 70% men) with AMI were enrolled in a nationwide prospective Korea Acute Myocardial Infarction Registry (KAMIR) and were categorized into 4 groups: Group I (n = 5700) had neither diabetes nor renal insufficiency (glomerular filtration rate [GFR] ≥ 60 ml/min/1.73 m²), Group II (n = 1730) had diabetes but no renal insufficiency, Group III (n = 1431) had no diabetes but renal insufficiency, and Group IV (n = 1044) had both diabetes and renal insufficiency. The primary endpoints were major adverse cardiac events (MACE), including a composite of all cause-of-death, myocardial infarction, target lesion revascularization, and coronary artery bypass graft after 1-year clinical follow-up.

Results

Primary endpoints occurred in 1804 (18.2%) patients. There were significant differences in composite MACE among the 4 groups (Group I, 12.5%; Group II, 15.7%; Group III, 30.5%; Group IV, 36.5%; p < 0.001). In a Cox proportional hazards model, after adjusting for multiple covariates, the 1-year mortality increased stepwise from Group III to IV as compared with Group I (hazard ratio [HR], 1.96; 95% confidence interval [CI], 1.34-2.86; p = 0.001; and HR, 2.42; 95% CI, 1.62-3.62; p < 0.001, respectively). However, Kaplan-Meier analysis showed no significant difference in probability of death at 1 year between Group III and IV (p = 0.288).

Conclusions

Renal insufficiency, especially in association with diabetes, is associated with the occurrence of composite MACE and indicates poor prognosis in patients with AMI. Categorization of patients with diabetes and/or renal insufficiency provides valuable information for early-risk stratification of AMI patients.

Diabetes and the risk of heart failure

Prevalence of diabetes and heart failure are increasing exponentially worldwide. Diabetes is well-known to increase the risk of heart failure independent of other traditional risk factors and ischemia. Current evidence indicates the presence of several biochemical and molecular changes associated with diabetes that lead to diastolic dysfunction or American Heart Association stage B heart failure. Some, if not all, changes may also predate the development of frank diabetes. In this review, the authors present some of the epidemiologic evidence and a brief description of major mechanistic pathways that favor the development of heart failure in prediabetic and diabetic states.

Lipoprotein lipase mediated fatty acid delivery and its impact in diabetic cardiomyopathy

Although cardiovascular disease is the leading cause of diabetes-related death, its etiology is still not understood. The immediate change that occurs in the diabetic heart is altered energy metabolism where in the presence of impaired glucose uptake, glycolysis, and pyruvate oxidation, the heart switches to exclusively using fatty acids (FA) for energy supply. It does this by rapidly amplifying its lipoprotein lipase (LPL-a key enzyme, which hydrolyzes circulating lipoprotein-triglyceride to release FA) activity at the coronary lumen. An abnormally high capillary LPL could provide excess fats to the heart, leading to a number of metabolic, morphological, and mechanical changes, and eventually to cardiac disease. Unlike the initial response, chronic severe diabetes "turns off" LPL, this is also detrimental to cardiac function. In this review, we describe a number of post-translational mechanisms that influence LPL vesicle formation, actin cytoskeleton rearrangement, and transfer of LPL from cardiomyocytes to the vascular lumen to hydrolyze lipoprotein-triglyceride following diabetes. Appreciating the mechanism of how the heart regulates its LPL following diabetes should allow the identification of novel targets for therapeutic intervention, to prevent heart failure. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.

Longitudinal analysis of arterial blood pressure and heart rate response to acute behavioral stress in rats with type 1 diabetes mellitus and in age-matched controls

We recorded via telemetry the arterial blood pressure (BP) and heart rate (HR) response to classical conditioning following the spontaneous onset of autoimmune diabetes in BBDP/Wor rats vs. age-matched, diabetes-resistant control (BBDR/Wor) rats. Our purpose was to evaluate the autonomic regulatory responses to an acute stress in a diabetic state of up to 12 months duration. The stress was a 15-s pulsed tone (CS+) followed by a 0.5-s tail shock. The initial, transient increase in BP (i.e., the "first component," or C(1)), known to be derived from an orienting response and produced by a sympathetic increase in peripheral resistance, was similar in diabetic and control rats through ∼9 months of diabetes; it was smaller in diabetic rats 10 months after diabetes onset. Weakening of the C(1) BP increase in rats that were diabetic for >10 months is consistent with the effects of sympathetic neuropathy. A longer-latency, smaller, but sustained "second component" (C(2)) conditional increase in BP, that is acquired as a rat learns the association between CS+ and the shock, and which results from an increase in cardiac output, was smaller in the diabetic vs. control rats starting from the first month of diabetes. A concomitant HR slowing was also smaller in diabetic rats. The difference in the C(2) BP increase, as observed already during the first month of diabetes, is probably secondary to the effects of hyperglycemia upon myocardial metabolism and contractile function, but it may also result from effects on cognition. The small HR slowing concomitant with the C(2) pressor event is probably secondary to differences in baroreflex activation or function, though parasympathetic dysfunction may contribute later in the duration of diabetes. The nearly immediate deficit after disease onset in the C(2) response indicates that diabetes alters BP and HR responses to external challenges prior to the development of structural changes in the vasculature or autonomic nerves.

Potentiation of abnormalities in myocardial metabolism with the development of diabetes in women with obesity and insulin resistance

BACKGROUND

Because studies in animal models of type-2 diabetes mellitus (DM) show that excessive myocardial fatty acid (FA) metabolism (at the expense of glucose metabolism) cause cardiac dysfunction, we hypothesized that women with DM would have more FA and less glucose myocardial metabolism than normal or even obese (OB) women.

RESEARCH DESIGN AND METHODS

Women who were lean volunteers (NV) (N = 14; age 35 ± 17 years, body mass index 23 ± 1 kg/m(2)), OB (N = 28;31 ± 6 years, BMI 39 ± 7 kg/m2), and DM (n = 22; 54 ± 11 years, BMI 38 ± 5 kg/m2) were studied. Cardiac positron emission tomography was performed for the determination of myocardial blood flow, oxygen consumption, FA and glucose metabolism. Cardiac work was measured by echocardiography and efficiency by the ratio of work to myocardial oxygen consumption.

RESULTS

Fractional glucose uptake was comparable between NV and OB but lower in DM (P < .05 versus NV). Myocardial FA utilization and oxidation were both higher in DM compared with NV and OB (P < .0001). Myocardial FA utilization and oxidation had positive correlations with HOMA (R = 0.35, P = .005 and R = 0.40, P = .001, respectively) whereas fractional glucose uptake exhibited an inverse correlation (R = -.31, P = .01). Cardiac work and efficiency were similar among the three groups.

CONCLUSIONS

In women, the presence of OB and DM compared with OB alone is associated with a greater reliance on myocardial FA metabolism at the expense of glucose metabolism. These perturbations in myocardial metabolism are not associated in a decline left ventricular efficiency or function suggesting that the metabolic perturbations may precede an eventual decline left ventricular function as is seen in animal models of DM.