Insulin resistance: metabolic mechanisms and consequences in the heart

Evolution of myocardial steatosis in high cardiovascular risk T2DM patients treated by GLP1 receptor agonists: LICAS study

BACKGROUND

We hypothesized that the reduction of intramyocardial fat content may be involved in the cardioprotective effect of glucagon-like peptide-1 receptor agonists (GLP1-RA) in patients with type 2 diabetes (T2D). Therefore, we aimed to evaluate the change in intramyocardial triglyceride content in T2D patients treated with GLP1-RA.

METHODS

This monocentric proof-of-concept cohort study included patients with unbalanced T2D prior to the introduction of GLP1-RA. Patients underwent cardiac magnetic resonance imaging (MRI) coupled with nuclear magnetic resonance (NMR) spectroscopy at baseline and six months after the introduction (M6) of a GLP1-RA to assess changes in intramyocardial triglyceride levels and morphological, functional, and cardiac tissue parameters. The relative delta (Δr) between baseline and M6 was calculated and analyzed by Student test or sign test.

RESULTS

Twenty-six patients (mean age = 62.2 ± 6.7 years, median HbA1c = 9.1 %) fulfilled inclusion criteria and had both NMR measures. Compared with baseline, relative intramyocardial triglyceride levels significantly decreased after six months of treatment (mean Δr = -26 % [95 %CI:-39; -13]p = 0.003), as well as glycated hemoglobin (HbA1c) (median Δr = -26 % [IQR:25], p < 0.0001), body mass index (BMI) (mean Δr = -6% [-9; -4], p < 0.0001) and left ventricular mass (mean Δr = -6 [-12; -1] p = 0.02). The relative evolution of intramyocardial triglyceride content was not correlated with the relative evolution of HbA1c (r = 0.10) and BMI (r = -0.02).

CONCLUSIONS

We demonstrate a significant reduction in intramyocardial triglyceride content in patients with T2D after six months of treatment with GLP1-RA. The lack of correlation with reductions in HbA1c and BMI suggests a specific effect of GLP1-RA on myocardial steatosis, which might contribute to their previously demonstrated cardiovascular benefits.

Role of glycogen in cardiac metabolic stress

Metabolic stress in the myocardium arises from a diverse array of acute and chronic pathophysiological contexts. Glycogen mishandling is a key feature of metabolic stress, while maladaptation in energy-stress situations confers functional deficits. Cardiac glycogen serves as a pivotal reserve for myocardial energy, which is classically described as an energy source and contributes to glucose homeostasis during hypoxia or ischemia. Despite extensive research activity, how glycogen metabolism affects cardiovascular disease remains unclear. In this review, we focus on its regulation across myocardial energy metabolism in response to stress, and its role in metabolism, immunity, and autophagy. We further summarize the cardiovascular-related drugs regulating glycogen metabolism. In this way, we provide current knowledge for the understanding of glycogen metabolism in the myocardium.

Evaluating sex-specific responses to western diet across the lifespan: impact on cardiac function and transcriptomic signatures in C57BL/6J mice at 530 and 640/750 days of age

BACKGROUND

Long-term consumption of Western Diet (WD) is a well-established risk factor for the development of cardiovascular disease (CVD); however, there is a paucity of studies on the long-term effects of WD on the pathophysiology of CVD and sex-specific responses.

METHODS

Our study aimed to investigate the sex-specific pathophysiological changes in left ventricular (LV) function using transthoracic echocardiography (ECHO) and LV tissue transcriptomics in WD-fed C57BL/6 J mice for 125 days, starting at the age of 300 through 425 days.

RESULTS

In female mice, consumption of the WD diet showed long-term effects on LV structure and possible development of HFpEF-like phenotype with compensatory cardiac structural changes later in life. In male mice, ECHO revealed the development of an HFrEF-like phenotype later in life without detectable structural alterations. The transcriptomic profile revealed a sex-associated dichotomy in LV structure and function. Specifically, at 530-day, WD-fed male mice exhibited differentially expressed genes (DEGs), which were overrepresented in pathways associated with endocrine function, signal transduction, and cardiomyopathies. At 750 days, WD-fed male mice exhibited dysregulation of several genes involved in various lipid, glucagon, and glutathione metabolic pathways. At 530 days, WD-fed female mice exhibited the most distinctive set of DEGs with an abundance of genes related to circadian rhythms. At 640 days, altered DEGs in WD-fed female mice were associated with cardiac energy metabolism and remodeling.

CONCLUSIONS

Our study demonstrated distinct sex-specific and age-associated differences in cardiac structure, function, and transcriptome signature between WD-fed male and female mice.

The role of the triglyceride-glucose index as a biomarker of cardio-metabolic syndromes

BACKGROUND

The Triglyceride-glucose (TyG) index represents a simple, cost-effective, and valid proxy for insulin resistance. This surrogate marker has also been proposed as a predictor of metabolic and cardiovascular disease (CVD). In this descriptive review, we aimed to assess the utility of the TyG index as a predictive biomarker of cardiometabolic diseases.

METHODS

A search was conducted in PubMed, and Web of Science to identify cross-sectional and more importantly prospective studies examining the use of the TyG index as a predictive biomarker. The following terms were utilized in addition to the TyG index: "insulin resistance", "metabolic syndrome", "diabetes"; "cardiovascular diseases".

RESULTS

This descriptive review included thirty prospective studies in addition to cross-sectional studies. Following adjustment for confounding variables, an elevated TyG index was associated with a significantly increased risk for the development of Metabolic Syndrome (MetS), Type 2 Diabetes, hypertension, and CVD. Also in limited studies, the TyG index was associated with endothelial dysfunction, increased oxidative stress and a pro-inflammatory phenotype.

CONCLUSION

Overall, our findings support the use of the TyG index as a valid biomarker to assess the risk of developing MetS, T2DM, as well as atherosclerotic cardiovascular disease.

Central Actions of Leptin Induce an Atrophic Pattern and Improves Heart Function in Lean Normoleptinemic Rats via PPARβ/δ Activation

Leptin, acting centrally or peripherally, has complex effects on cardiac remodeling and heart function. We previously reported that central leptin exerts an anti-hypertrophic effect in the heart via cardiac PPARβ/δ activation. Here, we assessed the impact of central leptin administration and PPARβ/δ inhibition on cardiac function. Various cardiac properties, including QRS duration, R wave amplitude, heart rate (HR), ejection fraction (EF), end-diastolic left ventricular mass (EDLVM), end-diastolic volume (EDV), and cardiac output (CO) were analyzed. Central leptin infusion increased cardiac PPARβ/δ protein content and decreased HR, QRS duration, and R wave amplitude. These changes induced by central leptin suggested a decrease in the ventricular wall growth, which was confirmed by MRI. In fact, the EDLVM was reduced by central leptin while increased in rats co-treated with leptin and GSK0660, a selective antagonist of PPARβ/δ activity. In summary, central leptin plays a dual role in cardiac health, potentially leading to ventricular atrophy and improving heart function when PPARβ/δ signaling is intact. The protective effects of leptin are lost by PPARβ/δ inhibition, underscoring the importance of this pathway. These findings highlight the therapeutic potential of targeting leptin and PPARβ/δ pathways to combat cardiac alterations and heart failure, particularly in the context of obesity.

Adiposity in mares induces insulin dysregulation and mitochondrial dysfunction which can be mitigated by nutritional intervention

Obesity is a complex disease associated with augmented risk of metabolic disorder development and cellular dysfunction in various species. The goal of the present study was to investigate the impacts of obesity on the metabolic health of old mares as well as test the ability of diet supplementation with either a complex blend of nutrients designed to improve equine metabolism and gastrointestinal health or L-carnitine alone to mitigate negative effects of obesity. Mares (n = 19, 17.9 ± 3.7 years) were placed into one of three group: normal-weight (NW, n = 6), obese (OB, n = 7) or obese fed a complex diet supplement for 12 weeks (OBD, n = 6). After 12 weeks and completion of sample collections, OB mares received L-carnitine alone for an additional 6 weeks. Obesity in mares was significantly associated with insulin dysregulation, reduced muscle mitochondrial function, and decreased skeletal muscle oxidative capacity with greater ROS production when compared to NW. Obese mares fed the complex diet supplement had better insulin sensivity, greater cell lipid metabolism, and higher muscle oxidative capacity with reduced ROS production than OB. L-carnitine supplementation alone did not significantly alter insulin signaling, but improved lipid metabolism and muscle oxidative capacity with reduced ROS. In conclusion, obesity is associated with insulin dysregulation and altered skeletal muscle metabolism in older mares. However, dietary interventions are an effective strategy to improve metabolic status and skeletal muscle mitochondrial function in older mares.

Characterizing the polygenic overlap and shared loci between rheumatoid arthritis and cardiovascular diseases

BACKGROUND

Despite substantial research revealing that patients with rheumatoid arthritis (RA) have excessive morbidity and mortality of cardiovascular disease (CVD), the mechanism underlying this association has not been fully known. This study aims to systematically investigate the phenotypic and genetic correlation between RA and CVD.

METHODS

Based on UK Biobank, we conducted two cohort studies to evaluate the phenotypic relationships between RA and CVD, including atrial fibrillation (AF), coronary artery disease (CAD), heart failure (HF), and stroke. Next, we used linkage disequilibrium score regression, Local Analysis of [co]Variant Association, and bivariate causal mixture model (MiXeR) methods to examine the genetic correlation and polygenic overlap between RA and CVD, using genome-wide association summary statistics. Furthermore, we explored specific shared genetic loci by conjunctional false discovery rate analysis and association analysis based on subsets.

RESULTS

Compared with the general population, RA patients showed a higher incidence of CVD (hazard ratio [HR] = 1.21, 95% confidence interval [CI]: 1.15-1.28). We observed positive genetic correlations of RA with AF and stroke, and a mixture of negative and positive local genetic correlations underlying the global genetic correlation for CAD and HF, with 13 ~ 33% of shared genetic variants for these trait pairs. We further identified 23 pleiotropic loci associated with RA and at least one CVD, including one novel locus (rs7098414, TSPAN14, 10q23.1). Genes mapped to these shared loci were enriched in immune and inflammatory-related pathways, and modifiable risk factors, such as high diastolic blood pressure.

CONCLUSIONS

This study revealed the shared genetic architecture of RA and CVD, which may facilitate drug target identification and improved clinical management.

From Beats to Metabolism: the Heart at the Core of Interorgan Metabolic Cross Talk

The heart, once considered a mere blood pump, is now recognized as a multifunctional metabolic and endocrine organ. Its function is tightly regulated by various metabolic processes, at the same time it serves as an endocrine organ, secreting bioactive molecules that impact systemic metabolism. In recent years, research has shed light on the intricate interplay between the heart and other metabolic organs, such as adipose tissue, liver, and skeletal muscle. The metabolic flexibility of the heart and its ability to switch between different energy substrates play a crucial role in maintaining cardiac function and overall metabolic homeostasis. Gaining a comprehensive understanding of how metabolic disorders disrupt cardiac metabolism is crucial, as it plays a pivotal role in the development and progression of cardiac diseases. The emerging understanding of the heart as a metabolic and endocrine organ highlights its essential contribution to whole body metabolic regulation and offers new insights into the pathogenesis of metabolic diseases, such as obesity, diabetes, and cardiovascular disorders. In this review, we provide an in-depth exploration of the heart's metabolic and endocrine functions, emphasizing its role in systemic metabolism and the interplay between the heart and other metabolic organs. Furthermore, emerging evidence suggests a correlation between heart disease and other conditions such as aging and cancer, indicating that the metabolic dysfunction observed in these conditions may share common underlying mechanisms. By unraveling the complex mechanisms underlying cardiac metabolism, we aim to contribute to the development of novel therapeutic strategies for metabolic diseases and improve overall cardiovascular health.

Transplantation of committed pre-adipocytes from brown adipose tissue improves whole-body glucose homeostasis

Obesity and its co-morbidities including type 2 diabetes are increasing at epidemic rates in the U.S. and worldwide. Brown adipose tissue (BAT) is a potential therapeutic to combat obesity and type 2 diabetes. Increasing BAT mass by transplantation improves metabolic health in rodents, but its clinical translation remains a challenge. Here, we investigated if transplantation of 2-4 million differentiated brown pre-adipocytes from mouse BAT stromal fraction (SVF) or human pluripotent stem cells (hPSCs) could improve metabolic health. Transplantation of differentiated brown pre-adipocytes, termed "committed pre-adipocytes" from BAT SVF from mice or derived from hPSCs improves glucose homeostasis and insulin sensitivity in recipient mice under conditions of diet-induced obesity, and this improvement is mediated through the collaborative actions of the liver transcriptome, tissue AKT signaling, and FGF21. These data demonstrate that transplantation of a small number of brown adipocytes has significant long-term translational and therapeutic potential to improve glucose metabolism.

Prognosis of a malignant phenotype of obesity defined by a cardiac biomarker in hypertension: the Japan Morning Surge-Home Blood Pressure study

Obesity with increased high-sensitive cardiac troponin T (hs-cTnT) has been reported to be more likely to progress cardiovascular disease (CVD) events, which suggests that hs-cTnT may identify a "malignant" phenotype of obesity. We classified 3513 hypertensive patients from the Japan Morning Surge-Home Blood Pressure (J-HOP) study into groups based on body mass index (BMI) (normal weight: <25 kg/m2, overweight: 25-29.9 kg/m2, obesity: ≥30 kg/m2) and elevations in biomarker levels (hs-cTnT ≥3 ng/mL: 51.3%, 54.9%, 53.3%, and N-terminal pro-brain natriuretic peptide [NT-ProBNP] ≥55 pg/mL: 51.1%, 40.7%, 36.0% in each BMI category). We evaluated the independent and combined associations of BMI and each hs-cTnT/NT-proBNP or both with CVD events (fatal and nonfatal coronary artery disease, stroke, and hospitalized heart failure). During the mean 6.4 ± 3.9-year follow-up, 232 CVD events occurred. Obesity with elevated hs-cTnT was associated with a risk of CVD events compared to normal weight without elevated hs-cTnT (hazard ratio 3.22, 95% confidence interval: 1.83-5.68). A similar pattern of results was also observed across the status of obesity and elevated NT-proBNP. There was a significant interaction between hs-cTnT and CVD events according to the obesity status (p = 0.039), while this association was marginal in NT-proBNP (p = 0.060). The magnitude of the mediation of hs-cTnT for the association between obesity and CVD risk was 41.2%, and that for NT-proBNP was 8.1%. In this Japanese hypertensive population, the elevation of hs-cTnT identified obese patients at particularly high risk for developing CVD events, suggesting that hs-cTnT may identify a 'malignant' phenotype of obesity.

The Role of Pro-Opiomelanocortin Derivatives in the Development of Type 2 Diabetes-Associated Myocardial Infarction: Possible Links with Prediabetes

Myocardial infarction is a major contributor to CVD-related mortality. T2DM is a risk factor for MI. Stress activates the HPA axis, SNS, and endogenous OPS. These POMC derivatives increase the blood glucose and cardiovascular response by inhibiting the PI3K/AkT insulin signaling pathway and increasing cardiac contraction. Opioids regulate the effect of the HPA axis and SNS and they are cardioprotective. The chronic activation of the stress response may lead to insulin resistance, cardiac dysfunction, and MI. Stress and T2DM, therefore, increase the risk of MI. T2DM is preceded by prediabetes. Studies have shown that prediabetes is associated with an increased risk of MI because of inflammation, hyperlipidemia, endothelial dysfunction, and hypertension. The HPA axis is reported to be dysregulated in prediabetes. However, the SNS and the OPS have not been explored during prediabetes. The effect of prediabetes on POMC derivatives has yet to be fully explored and understood. The impact of stress and prediabetes on the cardiovascular response needs to be investigated. This study sought to review the potential impact of prediabetes on the POMC derivatives and pathways that could lead to MI.

Endothelial Dysfunction in Obesity and Therapeutic Targets

Parallel to the increasing prevalence of obesity in the world, the mortality from cardiovascular disease has also increased. Low-grade chronic inflammation in obesity disrupts vascular homeostasis, and the dysregulation of adipocyte-derived endocrine and paracrine effects contributes to endothelial dysfunction. Besides the adipose tissue inflammation, decreased nitric oxide (NO)-bioavailability, insulin resistance (IR), and oxidized low-density lipoproteins (oxLDLs) are the main factors contributing to endothelial dysfunction in obesity and the development of cardiorenal metabolic syndrome. While normal healthy perivascular adipose tissue (PVAT) ensures the dilation of blood vessels, obesity-associated PVAT leads to a change in the profile of the released adipo-cytokines, resulting in a decreased vasorelaxing effect. Higher stiffness parameter β, increased oxidative stress, upregulation of pro-inflammatory cytokines, and nicotinamide adenine dinucleotide phosphate (NADP) oxidase in PVAT turn the macrophages into pro-atherogenic phenotypes by oxLDL-induced adipocyte-derived exosome-macrophage crosstalk and contribute to the endothelial dysfunction. In clinical practice, carotid ultrasound, higher leptin levels correlate with irisin over-secretion by human visceral and subcutaneous adipose tissues, and remnant cholesterol (RC) levels predict atherosclerotic disease in obesity. As a novel therapeutic strategy for cardiovascular protection, liraglutide improves vascular dysfunction by modulating a cyclic adenosine monophosphate (cAMP)-independent protein kinase A (PKA)-AMP-activated protein kinase (AMPK) pathway in PVAT in obese individuals. Because the renin-angiotensin-aldosterone system (RAAS) activity, hyperinsulinemia, and the resultant IR play key roles in the progression of cardiovascular disease in obesity, RAAS-targeted therapies contribute to improving endothelial dysfunction. By contrast, arginase reciprocally inhibits NO formation and promotes oxidative stress. Thus, targeting arginase activity as a key mediator in endothelial dysfunction has therapeutic potential in obesity-related vascular comorbidities. Obesity-related endothelial dysfunction plays a pivotal role in the progression of type 2 diabetes (T2D). The peroxisome proliferator-activated receptor gamma (PPARγ) agonist, rosiglitazone (thiazolidinedione), is a popular drug for treating diabetes; however, it leads to increased cardiovascular risk. Selective sodium-glucose co-transporter-2 (SGLT-2) inhibitor empagliflozin (EMPA) significantly improves endothelial dysfunction and mortality occurring through redox-dependent mechanisms. Although endothelial dysfunction and oxidative stress are alleviated by either metformin or EMPA, currently used drugs to treat obesity-related diabetes neither possess the same anti-inflammatory potential nor simultaneously target endothelial cell dysfunction and obesity equally. While therapeutic interventions with glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide or bariatric surgery reverse regenerative cell exhaustion, support vascular repair mechanisms, and improve cardiometabolic risk in individuals with T2D and obesity, the GLP-1 analog exendin-4 attenuates endothelial endoplasmic reticulum stress.

The Influence of Anthropometrics on Cardiac Mechanics in Healthy Women With Opposite Obesity Phenotypes (Android vs Gynoid)

BACKGROUND

The possible influence exerted by mechanical factors and/or compressive phenomena on myocardial strain parameters in healthy individuals with opposite obesity phenotypes (android vs gynoid) has never been previously investigated. Accordingly, we aimed at evaluating the relationship between anthropometrics, such as the waist-to-hip ratio (WHR), modified Haller index (MHI, the ratio of chest transverse diameter over the distance between sternum and spine), and epicardial adipose tissue (EAT), and left ventricular (LV)-global longitudinal strain (GLS), in healthy women with opposite obesity phenotypes (android vs gynoid).

METHODS

Forty healthy women with obesity (body mass index (BMI) ≥30 Kg/m2) and WHR ≥0.85 ("android group") (52.5±13.2 yrs), 40 age- and BMI-matched healthy women with obesityand WHR <0.78 ("gynoid group") (49.8±13.4 yrs) and 40 age-matched healthy women without obesity (BMI <30 Kg/m2) (controls) (50.3±12.5 yrs) were retrospectively analyzed. All women underwent transthoracic echocardiography implemented with echocardiographic strain analysis of all cardiac chambers. Correlation between LV-GLS and anthropometrics (WHR, MHI, and EAT) was assessed in both groups of obese women. Age, WHR, homeostasis model assessment for insulin resistance (HOMA-IR), and left ventricular mass index (LVMi) were included in the logistic regression analysis performed for evaluating the independent predictors of reduced LV-GLS magnitude (less negative than -20%) in women with android obesity.

RESULTS

Compared to the other groups of women, those with android obesity were found with significantly greater LVMi, higher LV filling pressures, and lower biventricular and biatrial deformation indices. A strong inverse correlation between LV-GLS and all anthropometrics (WHR, MHI, and EAT) was demonstrated in both groups of women with obesity. Univariate logistic regression analysis revealed that WHR (OR 1.58, 95%CI 1.22-2.03, p<0.001) and LVMi (OR 1.09, 95%CI 1.02-1.16, p=0.006) were independently correlated with LV-GLS impairment in women with android obesity. On multivariate logistic regression analysis, the WHR maintained a statistically significant association with the above-mentioned outcome (OR 1.68, 95%CI 1.14-2.48, p=0.009). Receiver operating characteristic (ROC) curve analysis showed that a WHR value ≥1.01 had 93% sensitivity and 100% specificity for detecting LV-GLS impairment in women with android obesity (AUC=0.98; 95%CI 0.96-1.00).

CONCLUSIONS

Anthropometrics may strongly influence cardiac mechanics in healthy women with obesity. The WHR is associated with reduced LV-GLS magnitude in healthy women with android obesity, independent of age, glycometabolic status, and LV size.

Role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in diabetic complications

Cardiovascular disease (CVD) complications have remained a major cause of death among patients with diabetes. Hence, there is a need for effective therapeutics against diabetes-induced CVD complications. Since its discovery, proprotein convertase subtilisin/kexin type 9 (PCSK9) has been reported to be involved in the pathology of various CVDs, with studies showing a positive association between plasma levels of PCSK9, hyperglycemia, and dyslipidemia. PCSK9 regulates lipid homeostasis by interacting with low-density lipoprotein receptors (LDLRs) present in hepatocytes and subsequently induces LDLR degradation via receptor-mediated endocytosis, thereby reducing LDL uptake from circulation. In addition, PCSK9 also induces pro-inflammatory cytokine expression and apoptotic cell death in diabetic-CVD. Furthermore, therapies designed to inhibit PCSK9 effectively reduces diabetic dyslipidemia with clinical studies reporting reduced cardiovascular events in patients with diabetes and no significant adverse effect on glycemic controls. In this review, we discuss the role of PCSK9 in the pathogenesis of diabetes-induced CVD and the potential mechanisms by which PCSK9 inhibition reduces cardiovascular events in diabetic patients.

Relation between the Epicardial Fat Thickness and the Cardiac Conduction System in Children and Adolescents with Diabetes

INTRODUCTION

Atherosclerosis in patients with type 1 diabetes starts early in childhood with subclinical abnormalities. The epicardial fat thickness (EFT) is a novel method for detecting these early changes. Furthermore, electrocardiographic markers may be altered in patients with diabetes owing to early cardiovascular changes. This study aimed to determine the relationship between EFT and electrocardiographic markers in children with type 1 diabetes mellitus.

METHODS

Children with type 1 diabetes who were followed up at the Alexandria University Children's Hospital Diabetes Clinic were enrolled in this study. The study recruited three groups of participants, including 20 patients with a diabetes duration of less than 5 years, 20 patients with a diabetes duration of 5 years or more, and 20 healthy controls. All participants were evaluated with emphasis on anthropometric measurements, fasting blood glucose levels, and lipid profile. HbA1c levels were measured in the cohort with diabetes. All participants underwent electrocardiography for measurement of P-wave dispersion, corrected QT interval and its dispersion, and Tp-e measurement. Echocardiography was performed to measure the EFT.

RESULTS

Among all participants, EFT was significantly higher in children with a diabetes duration of ≥5 years (p = 0.009). Furthermore, P-wave dispersion was significantly prolonged in children with diabetes compared to that in nondiabetics (p = 0.041). There was a statistically significant correlation between EFT and P-wave dispersion in patients with diabetes aged ≥5 years (p = 0.021).

CONCLUSIONS

Measurement of EFT by echocardiography is a novel and easy way to predict early cardiovascular changes in children with diabetes, including conduction system disorders.

The role of fibrinolysis in the development of prediabetes-associated coronary heart disease: a focus on the plasminogen activator inhibitor -1 and its potential use as a predictive marker in diet-induced prediabetes

Introduction

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of cardiovascular diseases (CVD). However, the onset of T2DM is preceded by prediabetes, which is associated with sedentary lifestyles and consumption of high-calorie diets. Studies have shown that impaired glucose homeostasis creates an environment for developing T2DM-related complications. Using a high-fat-high-carbohydrate diet-induced prediabetes animal model, this study sought to assess the risk factors of coronary heart disease (CHD) in diet-induced prediabetes and identify biomarkers that can be used for early detection of prediabetes-associated CHD.

Methods

Male Sprague Dawley rats were randomly grouped into two groups and were kept on different diets for 20 weeks (n = 6 in each group). One group was fed standard rat chow to serve as a non-prediabetes (NPD) control, while the other group consumed a high-fat-high-carbohydrate diet to induce prediabetes (PD). Post induction, the homeostasis model assessment- insulin resistance (HOMA-IR) and glycated haemoglobin (HbA1c) was used to test for insulin resistance. Body weight, mean arterial pressure (MAP), resting heart rate (HR), inflammatory cytokines (C-reactive protein (CRP), tumor necrosis factor (TNF-α), interleukin-6 (IL-6)), lipids (total cholesterol (TC), triglyceride (TG), lipoproteins (HDL, LDL, VLDL)), endothelial function (endothelial nitric oxide (eNOS), endothelin -1 (ET-1)), fibrinolysis (plasminogen activator inhibitor-1 (PAI-1)) were all measured to assess the risk of CHD. All data were expressed as means ± S.E.M. Statistical comparisons were performed with Graph Pad. Instat Software using Student's two-sided t-test. The Pearson correlation coefficient and linear regression were calculated to assess the association. The value of p < 0.05 was considered statistically significant.

Results

There was significant insulin resistance accompanied by significantly increased HbA1c and body weight in PD compared to NPD. Simultaneously, there was a significant increase in inflammatory cytokines in PD compared to NPD. This was accompanied by significantly increased TG and VLDL and endothelial dysfunction in PD. The association between HOMA-IR and PAI-1 was insignificantly positive in NPD, whereas a significantly strong positive association was observed in PD.

Conclusion

There is a positive correlation between insulin resistance and PAI-1 during prediabetes; therefore, suggesting that prediabetes increases the risk of developing vascular thrombosis. The current therefore study warrants further investigation on PAI-1 and other markers of fibrinolysis for the early detection of thrombosis and risk of CHD in prediabetes.

Crosstalk between autophagy and insulin resistance: evidence from different tissues

Insulin is a critical hormone that promotes energy storage in various tissues, as well as anabolic functions. Insulin resistance significantly reduces these responses, resulting in pathological conditions, such as obesity and type 2 diabetes mellitus (T2DM). The management of insulin resistance requires better knowledge of its pathophysiological mechanisms to prevent secondary complications, such as cardiovascular diseases (CVDs). Recent evidence regarding the etiological mechanisms behind insulin resistance emphasizes the role of energy imbalance and neurohormonal dysregulation, both of which are closely regulated by autophagy. Autophagy is a conserved process that maintains homeostasis in cells. Accordingly, autophagy abnormalities have been linked to a variety of metabolic disorders, including insulin resistance, T2DM, obesity, and CVDs. Thus, there may be a link between autophagy and insulin resistance. Therefore, the interaction between autophagy and insulin function will be examined in this review, particularly in insulin-responsive tissues, such as adipose tissue, liver, and skeletal muscle.

Characterisation of the Paternal Influence on Intergenerational Offspring Cardiac and Brain Lipid Homeostasis in Mice

There is growing evidence that poor paternal diet at the time of conception increase the risk of offspring developing a range of non-communicable metabolic diseases, such as obesity, diabetes and cardiovascular disease, in adulthood. We hypothesise that a paternal low protein-high carbohydrate diet perturbs offspring tissue lipid abundance through both sperm and seminal plasma-mediated mechanisms. To test our hypothesis, we fed male C57BL/6 mice either a control normal protein diet (NPD; 18% protein) or an isocaloric low protein diet (LPD; 9% protein) for a minimum of 8 weeks. We generated offspring through artificial insemination, in combination with vasectomised male mating. Using this approach, we derived offspring from either NPD or LPD sperm but in the presence of NPD or LPD seminal plasma. Using high resolution mass-spectrometry, we found that offspring derived from either LPD sperm or seminal fluid displayed perturbed cardiac and brain lipid abundance from just three weeks of age, typically associated with the altered abundance of tissue triglycerides. We also observed the differential sex-specific patterns of lipids between the control and experimental offspring's hearts and brains. These observations indicate that poor paternal diet at the time of conception affects offspring cardiac and brain lipid profiles in an age-, sex- and generation-specific manner.

Among biomarkers of neutrophil activity, matrix metalloproteinases 8 independently predicts remission of metabolic syndrome

BACKGROUND AND AIMS

Inflammation due to the excess of nutrient intake plays an important role in the pathophysiology of metabolic syndrome (MetS). Here, the potential influence of neutrophils and their degranulation markers on MetS improvement upon dietary and behavioral counselling, has been investigated. Specifically, we aimed at investigating their role as potential predictors of metabolic syndrome improvements.

METHODS AND RESULTS

patients with MetS (n = 127) received behavioral and dietary recommendations before follow-up at 6 months. Serum levels of matrix metalloproteinases (MMP)8, MMP9, myeloperoxidase (MPO), tissue inhibitor of MMP (TIMP)-1, TIMP-2, TIMP-3 and resistin were tested at baseline. In the whole cohort, baseline levels of proinflammatory MMP8, MMP9 and MPO increased together with the number of MetS criteria. Seventy-three (57%) patients experienced a reduction in MetS-defining criteria at follow-up. With respect to those with no improvement, such individuals showed lower weight and waist circumference at enrolment, less frequent smoking habits, higher levels of triglycerides and lower circulating MMP8. At logistic regression analysis, baseline MMP8 showed negative predictive ability (odds ratio (OR) 0.979 [0.961-0.997]; p = 0.025) against MetS improvement. Such findings hold true even when included in the backward stepwise logistic regression model confirming MMP8 as an independent predictor (OR 0.970 [0.949-0.993]; p = 0.009). Receiver operating characteristic (ROC) curve confirmed the predictive ability of MMP8 combined in a model including baseline MetS criteria and waist circumference. Bootstrap resampling analysis internally validated our findings.

CONCLUSION

Improvement of MetS is independently associated with baseline low MMP-8 levels, suggesting a pivotal role for inflammation in metabolic alteration.

Cardiovascular protection by SGLT2 inhibitors - Do anti-inflammatory mechanisms play a role?

BACKGROUND

Metabolic syndrome and related metabolic disturbances represent a state of low-grade inflammation, which accelerates insulin resistance, type 2 diabetes (T2D) and cardiovascular disease (CVD) progression. Among antidiabetic medications, sodium glucose co-transporter (SGLT) 2 inhibitors are the only agents which showed remarkable reductions in heart failure (HF) hospitalizations and major cardiovascular endpoints (MACE) as well as renal endpoints regardless of diabetes status in large randomized clinical outcome trials (RCTs). Although the exact mechanisms underlying these benefits are yet to be established, growing evidence suggests that modulating inflammation by SGLT2 inhibitors may play a key role.

SCOPE OF REVIEW

In this manuscript, we summarize the current knowledge on anti-inflammatory effects of SGLT2 inhibitors as one of the mechanisms potentially mediating their cardiovascular (CV) benefits. We introduce the different metabolic and systemic actions mediated by these agents which could mitigate inflammation, and further present the signalling pathways potentially responsible for their proposed direct anti-inflammatory effects. We also discuss controversies surrounding some of these mechanisms.

MAJOR CONCLUSIONS

SGLT2 inhibitors are promising anti-inflammatory agents by acting either indirectly via improving metabolism and reducing stress conditions or via direct modulation of inflammatory signalling pathways. These effects were achieved, to a great extent, in a glucose-independent manner which established their clinical use in HF patients with and without diabetes.

Identification of Myocardial Insulin Resistance by Using Liver Tests: A Simple Approach for Clinical Practice

BACKGROUND

We report that myocardial insulin resistance (mIR) occurs in around 60% of patients with type 2 diabetes (T2D) and was associated with higher cardiovascular risk in comparison with patients with insulin-sensitive myocardium (mIS). These two phenotypes (mIR vs. mIS) can only be assessed using time-consuming and expensive methods. The aim of the present study is to search a simple and reliable surrogate to identify both phenotypes.

METHODS

Forty-seven patients with T2D underwent myocardial [18F]FDG PET/CT at baseline and after a hyperinsulinemic-euglycemic clamp (HEC) to determine mIR were prospectively recruited. Biochemical assessments were performed before and after the HEC. Baseline hepatic steatosis index and index of hepatic fibrosis (FIB-4) were calculated. Furthermore, liver stiffness measurement was performed using transient elastography.

RESULTS

The best model to predict the presence of mIR was the combination of transaminases, protein levels, FIB-4 score and HOMA (AUC = 0.95; sensibility: 0.81; specificity: 0.95). We observed significantly higher levels of fibrosis in patients with mIR than in those with mIS (p = 0.034). In addition, we found that patients with mIR presented a reduced glucose uptake by the liver in comparison with patients with mIS.

CONCLUSIONS

The combination of HOMA, protein, transaminases and FIB-4 is a simple and reliable tool for identifying mIR in patients with T2D. This information will be useful to improve the stratification of cardiovascular risk in T2D.

Insulin signaling in the heart is impaired by growth hormone: a direct and early event

Growth hormone (GH) exerts major actions in cardiac growth and metabolism. Considering the important role of insulin in the heart and the well-established anti-insulin effects of GH, cardiac insulin resistance may play a role in the cardiopathology observed in acromegalic patients. As conditions of prolonged exposure to GH are associated with a concomitant increase of circulating GH, IGF1 and insulin levels, to dissect the direct effects of GH, in this study, we evaluated the activation of insulin signaling in the heart using four different models: (i) transgenic mice overexpressing GH, with chronically elevated GH, IGF1 and insulin circulating levels; (ii) liver IGF1-deficient mice, with chronically elevated GH and insulin but decreased IGF1 circulating levels; (iii) mice treated with GH for a short period of time; (iv) primary culture of rat cardiomyocytes incubated with GH. Despite the differences in the development of cardiomegaly and in the metabolic alterations among the three experimental mouse models analyzed, exposure to GH was consistently associated with a decreased response to acute insulin stimulation in the heart at the receptor level and through the PI3K/AKT pathway. Moreover, a blunted response to insulin stimulation of this signaling pathway was also observed in cultured cardiomyocytes of neonatal rats incubated with GH. Therefore, the key novel finding of this work is that impairment of insulin signaling in the heart is a direct and early event observed as a consequence of exposure to GH, which may play a major role in the development of cardiac pathology.

Nonalcoholic fatty liver disease and health outcomes: An umbrella review of systematic reviews and meta-analyses

Purpose:

A large number of systemic reviews and meta-analyses have explored the relationship between nonalcoholic fatty liver disease (NAFLD) and multiple health outcomes. The aim of this study is to conduct an umbrella review to assess the strength and evidence for the association between NAFLD and health outcomes.

Methods:

We systematically identified the present meta-analyses of observational studies reporting an association between NAFLD and health outcomes. For each meta-analysis, we assessed the quality with AMSTAR2 and graded the epidemiologic evidence.

Results:

Fifty-four articles comprising 111 unique meta-analyses were included in this study. Eighty-five unique outcomes showed significant associations ( P ← 0.05), whereas 26 unique outcomes showed insignificant associations, and we cannot assess the epidemiologic evidence. For 85 significant health outcomes, four outcomes (carotid intima-media thickness (C-IMT), peak A velocity, left ventricle end-diastolic diameter, incident chronic kidney disease (CKD) in adult patients) was graded as high quality of evidence, 23 outcomes were graded as the moderate quality of evidence, and the remaining 58 outcomes were graded as weak quality of evidence. Fourty-seven (87.03%) studies showed critically low methodological quality.

Conclusion:

In this umbrella review, only four statistically significant health outcomes showed high epidemiologic evidence. NAFLD seems to relate to an increased risk of C-IMT, peak A velocity, left ventricle end-diastolic diameter, and incident CKD in adult patients.

Association between aspartate aminotransferase-to-alanine aminotransferase ratio and insulin resistance among US adults

OBJECTIVE

To determine whether a low aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio (AST/ALT ratio) is associated with insulin resistance among those without liver dysfunction.

METHODS

In this cross-sectional study of the National Health and Nutrition Examination Survey (NHANES) 2011-2016, we included 2747 (1434 male and 1313 nonpregnant female) adults ≥20 years without evidence of liver dysfunction (ALT<30 in male and <19 in female, negative viral serologies, no excess alcohol consumption, no elevated transferrin saturation, AST/ALT <2). Serum AST/ALT ratio was categorized into sex-specific quartiles (female: <1.12, 1.12-1.29, 1.29-1.47, ≥1.47 and male: <0.93, 0.93-1.09, 1.09-1.26, ≥1.26). The primary outcome was insulin resistance, as determined by Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) index score ≥3. Covariate-adjusted odds ratios (ORs) were estimated. Study analysis completed from 13 March 2020 to 21 April 2021.

RESULTS

Among the 2747 individuals, 33% had insulin resistance. Those in the lowest quartile (Q1) of AST/ALT had 75% higher adjusted odds of insulin resistance compared to the highest quartile (Q4) [aOR (95% confidence interval (CI), 1.75 (1.20-2.57)]. This association was more pronounced in those with elevated BMI [Q1 vs. Q4; BMI ≥ 25: 2.29 (1.58-3.33), BMI < 25: 0.66 (0.26-1.69); NAFLD per Fatty Liver Index ≥ 60: 2.04 (1.21-3.44), No NAFLD: 1.68 (0.94-3.01)].

CONCLUSION

Lower AST/ALT ratio is associated with increased insulin resistance among those with healthy-range ALT, especially in those with BMI greater than or equal to 25 kg/m2.

Nonlinear relationship between aspartate aminotransferase to alanine aminotransferase ratio and the risk of prediabetes: A retrospective study based on chinese adults

OBJECTIVE

Recent evidence has revealed that the aspartate aminotransferase to alanine aminotransferase ratio (AST/ALT ratio) may be closely associated with metabolic syndrome and insulin resistance. However, it is unclear whether the AST/ALT ratio correlates with prediabetes risk. The aim of our study was to examine the association between AST/ALT ratios and the risk of prediabetes among a large cohort of Chinese subjects.

METHODS

This retrospective cohort study recruited 75204 Chinese adults with normoglycemia at baseline who underwent physical examinations at the Rich Healthcare Group from 2010 to 2016. The AST/ALT ratio at baseline was the target independent variable, and the risk of developing prediabetes during follow-up was the dependent variable. Cox proportional-hazards regression was used to evaluate the independent association between the AST/ALT ratio and prediabetes. This study identified nonlinear relationships by applying a generalized additive model (GAM) and smooth curve fitting. In order to assess the robustness of this study, we performed a series of sensitivity analyses. Moreover, we performed a subgroup analysis to evaluate the consistency of the association in different subgroups. Data from this study have been updated on the DATADRYAD website.

RESULTS

The AST/ALT ratio was negatively and independently related to the prediabetes risk among Chinese adults (HR: 0.76, 95% CI: 0.75-0.84, P&lt;0.0001) after adjusting demographic and biochemical covariates. Furthermore, a nonlinear relationship between the AST/ALT ratio and the risk of developing prediabetes was found at an inflection point of 1.50 for the AST/ALT ratio. When the AST/ALT ratio was to the left of the inflection point (AST/ALT ratio ≤ 1.50), the AST/ALT ratio was negatively related to the prediabetes risk (HR:0.70, 95%CI: 0.65-0.76, P&lt;0.0001). In contrast, the relationship tended to be saturated when the AST/ALT ratio was more than 1.50 (HR: 1.01, 95%CI: 0.89-1.15, P=0.8976). Our findings remained robust across a range of sensitivity analyses. Subgroup analysis revealed that other variables did not alter the relationship between the AST/ALT ratio and prediabetes risk.

CONCLUSION

This study revealed that AST/ALT ratio was negatively and independently associated with prediabetes risk among Chinese participants. The relationship between the AST/ALT ratio and prediabetes risk was nonlinear, and AST/ALT ratio ≤ 1.50 was strongly inversely correlated with prediabetes risk.

[Molecular mechanisms of adaptive and therapeutic effects of physical activity in patients with cardiovascular diseases]

Physical activity is one of the main components of the rehabilitation of patients with cardiovascular disease (CVD). As shown by practice and the results of evidence-based studies, the beneficial effects of physical activity on disease outcomes in a number of cardiac nosologies are comparable to drug treatment. This gives the doctor another tool to influence the unfavorable epidemiological situation in developed countries with the spread of diseases of the cardiovascular system and CVD mortality. Reliable positive results of cardiorehabilitation (CR) were obtained using various methods. The goal of CR is to restore the optimal physiological, psychological and professional status, reduce the risk of CVD and mortality. In most current CVD guidelines worldwide, cardiac rehabilitation is a Class I recommendation. The molecular mechanisms described in the review, initiated by physical activity, underlie the multifactorial effect of the latter on the function of the cardiovascular system and the course of cardiac diseases. Physical exercise is an important component of the therapeutic management of patients with CVD, which is supported by the results of a meta-analysis of 63 studies associated with various forms of aerobic exercise of varying intensity (from 50 to 95% VO₂) for 1 to 47 months, which showed that CR based on physical exercise improves cardiorespiratory endurance. Knowledge of the molecular basis of the influence of physical activity makes it possible to use biochemical markers to assess the effectiveness of rehabilitation programs.

Elevated circulating high-sensitivity cardiac troponin t and cardiac remodeling in obesity

BACKGROUND

It is well established that body mass index (BMI) and troponins are independently associated. However, whether the obesity could cause myocardial injury independent of coronary heart disease (CHD) remains unclear. This study focuses on the relationship between BMI and troponins, and whether this relationship is being attenuated when CHD is accounted for.

METHODS

In populations without acute ischemic events, 383 patients with coronary artery stenosis less than 75% were included, that is, people who have not yet reached the indications for coronary intervention, and of them 70 patients being obese according to BMI ≥ 28 kg/m². Continuous variables were represented as mean ± SD or median(inter quartile range[IQR]). Chi-square test was adopted for categorical data. Correlations between variables were evaluated by Spearman analysis, multiple regression or logistic regression.

RESULTS

The circulating hs-cTnT level was higher in the obese group [8(6,11) ng/L vs. 6(4,9) ng/L; p < 0.001). In subgroup analysis based on the presence or absence of coronary heart disease(CHD), the adjusted β(95%CI) for circulating hs-cTnT exhibited a proportional relationship with BMI when the non-obesity were defined as the reference[β; 2.22(95%CI, 0.73 to 3.71) in non-CHD, 5.58(95%CI, 0.70 to 10.46) in CHD, p < 0.05]. Additionally, the degree of coronary stenosis has shown a positive correlation with circulating hs-cTnT (rho = 0.1162; p < 0.05).

CONCLUSION

When CHD is taken into account, obesity is independently associated to the elevation of circulating hs-cTnT, a biomarker of myocardial injury, potentially indicating the impact of obesity on non-ischemic subclinical myocardial injury.

Lipid Droplet-Associated Proteins in Cardiomyopathy

BACKGROUND

The heart requires a high rate of fatty-acid oxidation (FAO) to meet its energy needs. Neutral lipids are the main source of energy for the heart and are stored in lipid droplets (LDs), which are cytosolic organelles that primarily serve to store neutral lipids and regulate cellular lipid metabolism. LD-associated proteins (LDAPs) are proteins either located on the surface of the LDs or reside in the cytosol and contribute to lipid metabolism. Therefore, abnormal cardiac lipid accumulation or FAO can alter the redox state of the heart, resulting in cardiomyopathy, a group of diseases that negatively affect the myocardial function, thereby leading to heart failure and even cardiac death.

SUMMARY

LDs, along with LDAPs, are pivotal for modulating heart lipid homeostasis. The proper cardiac development and the maintenance of its normal function depend largely on lipid homeostasis regulated by LDs and LDAPs. Overexpression or deletion of specific LDAPs can trigger myocardial dysfunction and may contribute to the development of cardiomyopathy. Extensive connections and interactions may also exist between LDAPs. Key Message: In this review, the various mechanisms involved in LDAP-mediated regulation of lipid metabolism, the association between cardiac development and lipid metabolism, as well as the role of LDAPs in cardiomyopathy progression are discussed.

Cardiac-specific VEGFB overexpression reduces lipoprotein lipase activity and improves insulin action in rat heart

Cardiac muscle uses multiple sources of energy including glucose and fatty acid (FA). The heart cannot synthesize FA and relies on obtaining it from other sources, with lipoprotein lipase (LPL) breakdown of lipoproteins suggested to be a key source of FA for cardiac use. Recent work has indicated that cardiac vascular endothelial growth factor B (VEGFB) overexpression expands the coronary vasculature and facilitates metabolic reprogramming that favors glucose utilization. We wanted to explore whether this influence of VEGFB on cardiac metabolism involves regulation of LPL activity with consequent effects on lipotoxicity and insulin signaling. The transcriptomes of rats with and without cardiomyocyte-specific overexpression of human VEGFB were compared by using RNA sequencing. Isolated perfused hearts or cardiomyocytes incubated with heparin were used to enable measurement of LPL activity. Untargeted metabolomic analysis was performed for quantification of cardiac lipid metabolites. Cardiac insulin sensitivity was evaluated using fast-acting insulin. Isolated heart and cardiomyocytes were used to determine transgene-encoded VEGFB isoform secretion patterns and mitochondrial oxidative capacity using high-resolution respirometry and extracellular flux analysis. In vitro, transgenic cardiomyocytes incubated overnight and thus exposed to abundantly secreted VEGFB isoforms, in the absence of any in vivo confounding regulators of cardiac metabolism, demonstrated higher basal oxygen consumption. In the whole heart, VEGFB overexpression induced an angiogenic response that was accompanied by limited cardiac LPL activity through multiple mechanisms. This was associated with a lowered accumulation of lipid intermediates, diacylglycerols and lysophosphatidylcholine, that are known to influence insulin action. In response to exogenous insulin, transgenic hearts demonstrated increased insulin sensitivity. In conclusion, the interrogation of VEGFB function on cardiac metabolism uncovered an intriguing and previously unappreciated effect to lower LPL activity and prevent lipid metabolite accumulation to improve insulin action. VEGFB could be a potential cardioprotective therapy to treat metabolic disorders, for example, diabetes.NEW & NOTEWORTHY In hearts overexpressing vascular endothelial growth factor B (VEGFB), besides its known angiogenic response, multiple regulatory mechanisms lowered coronary LPL. This was accompanied by limited cardiac lipid metabolite accumulation with an augmentation of cardiac insulin action. Our data for the first time links VEGFB to coronary LPL in regulation of cardiac metabolism. VEGFB may be cardioprotective in metabolic disorders like diabetes.

Nonlinear Relationship Between AST-to-ALT Ratio and the Incidence of Type 2 Diabetes Mellitus: A Follow-Up Study

Background

The aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio has been demonstrated to be associated with insulin resistance and metabolic syndrome. However, few studies have directly explored the association between the AST/ALT ratio and the incidence of type 2 diabetes mellitus (T2DM). As such, the present study aimed to investigate the relationship between the AST/ALT ratio and incident T2DM during follow-up in a population-based cohort.

Methods

This retrospective cohort analysis included 15,464 Japanese males and females without DM at baseline between 2004 and 2015. The association between AST/ALT ratio and T2DM was retrospectively examined using the Cox proportional hazard model after adjusting for multiple potential confounders.

Results

After follow-up, 373 (2.41%) patients developed T2DM. A nonlinear relationship between the AST/ALT ratio and T2DM was observed after adjusting for potential confounders. The risk for developing T2DM decreased with AST/ALT ratio up to a threshold of 0.93 (adjusted hazard ratio [HR] 0.14 [95% confidence interval (CI) = 0.02-0.90; P = 0.0385]). An AST/ALT ratio >0.93 was not associated with the risk for developing T2DM (adjusted HR = 0.67, 95% CI = 0.17-2.65; P = 0.5718).

Conclusion

The AST/ALT ratio was associated with a lower incidence of T2DM in a nonlinear pattern. The threshold AST/ALT ratio for developing T2DM was 0.93. AST/ALT levels were inversely correlated with the occurrence of T2DM when AST/ALT ratio ≤0.93.

Changes in Cardiac Metabolism in Prediabetes

In type 2 diabetes mellitus (T2DM), there is an increased prevalence of cardiovascular disease (CVD), even when corrected for atherosclerosis and other CVD risk factors. Diastolic dysfunction is one of the early changes in cardiac function that precedes the onset of cardiac failure, and it occurs already in the prediabetic state. It is clear that these changes are closely linked to alterations in cardiac metabolism; however, the exact etiology is unknown. In this narrative review, we provide an overview of the early cardiac changes in fatty acid and glucose metabolism in prediabetes and its consequences on cardiac function. A better understanding of the relationship between metabolism, mitochondrial function, and cardiac function will lead to insights into the etiology of the declined cardiac function in prediabetes.

Concordance between Triglyceride Glucose Index and Admission Insulin Resistance Index in Non-diabetic Subjects of Acute Coronary Syndrome

BACKGROUND: Acute coronary syndrome (ACS) is the leading cause of death in the world and is closely related to insulin resistance (IR). The examination of the triglyceride glucose (TyG) Index and admission IR index (AIRI) can be an alternative examination to assess IR. AIM: The aim of the study was to analyze the concordance between the TyG index and AIRI in assessing IR in nondiabetic subjects of ACS. METHODS: This study was a cross-sectional study using secondary data from ACS patient medical records in Wahidin Sudirohusodo Hospital Makassar from September 2020 until April 2021. An examination of RBG, TyG, and fasting insulin was performed. The statistical test results were considered significant if the p < 0.05. RESULTS: This study included 67 subjects, of which 54 were male and 13 were female, there were 24 people aged <50 years, 43 people aged 50 years old, with a mean of 55.15 ± 12.71 years, a diagnosis of ST-elevation myocardial infarction (STEMI) 25 people, non STEMI 34 people and unstable angina pectoris 8 people, p < 0.05. The receiver operating characteristic curve showed that the cut-off value of the TyG index in predicting AIRI was 3141, with a sensitivity of 88.98% and specificity of 59.09%. The OR value revealed that subjects with a TyG index of >9.06 indicated an 11-time greater risk for IR than subjects with a TyG index ≤9.06. CONCLUSIONS: There was a significant concordance between the TyG index and the AIRI in non-diabetic acute coronary syndrome patient.

Interactions of hypertension, obesity, left ventricular hypertrophy, and heart failure

PURPOSE OF REVIEW

Hypertension (HTN) and obesity are major risk factors for cardiac remodeling and dysfunction, leading to left ventricular hypertrophy (LVH) and heart failure (HF). In this review, we discuss the complex mechanisms and effects of HTN and obesity, and their treatments in LVH, ventricular function, and HF.

RECENT FINDINGS

Obesity and HTN impact the heart through overlapping neurohormonal pathways. However, the relationship between obesity and cardiomyopathy is more complex, and additional metabolic and hemodynamic pathways seem to contribute to cardiac dysfunction in these patients. Weight loss and blood pressure (BP) control help to prevent and reverse at least some of the damage caused by obesity and HTN even beyond what would be expected from solely the hemodynamic changes.

SUMMARY

Obesity and HTN cause maladaptive changes in the heart that can lead to LVH and HF. Weight loss and BP control help to, at least partially, reverse some of these changes and improve clinical outcomes in patients with HF.

Ameliorative Effects of Oral Glucosamine on Insulin Resistance and Pancreatic Tissue Damage in Experimental Wistar rats on a High-fat Diet

Hyperlipidemia due to a high-fat diet (HFD) is a risk factor for inducing insulin resistance (IR) and adverse effects on pancreatic β-cells in obesity and type 2 diabetes mellitus. This relationship may be due to activation of the hexosaminebiosynthesis pathway. Administration of exogenous glucosamine (GlcN) can increase the end product of this pathway (uridine-5'-diphosphate-N-acetyl-glucosamine), which can mediate IR and protein glycosylation. The objective of this study was to evaluate the effects of oral GlcN and HFD on IR and pancreatic histologic damage in a 22 wk study of 4 groups of male Wistar rats: control group with normal chow diet, HFD group (24%. g/g lard), GlcN group (500 mg/kg^-1 per day of glucosamine hydrochloride in drinking water) and HFD plus oral GlcN. Metabolic variables related to IR that were measured included triglycerides (TG), free fatty acids (FFAs) and malondialdehyde (MDA). Histopathologic evaluation of the pancreas was also performed. The results showed IR in the HFD group, which had increased pancreatic nuclear pyknosis and vacuolization, with fatty infiltration and structural alteration of the islets of Langerhans. TG, FFAs and MDA were higher in serum and pancreatic tissue as compared with the control group. The GlcN group did not develop IR and had only mild nuclear pyknosis with no significant change in the pancreatic content of TG, FFAs and MDA. However, the combined administration of GlcN and HFD attenuated IR and improved TG, FFAs and MDA levels in serum and pancreatic tissue and the pancreatic histopathologic changes, with no significant differences as compared with the control group. These findings suggest that the oral GlcN at a dose of 500 mg/kg^-1 is protective against IR and the pancreatic histologic damage caused by HFD.

Therapeutic potential of targeting oxidative stress in diabetic cardiomyopathy

Even in the absence of coronary artery disease and hypertension, diabetes mellitus (DM) may increase the risk for heart failure development. This risk evolves from functional and structural alterations induced by diabetes in the heart, a cardiac entity termed diabetic cardiomyopathy (DbCM). Oxidative stress, defined as the imbalance of reactive oxygen species (ROS) has been increasingly proposed to contribute to the development of DbCM. There are several sources of ROS production including the mitochondria, NAD(P)H oxidase, xanthine oxidase, and uncoupled nitric oxide synthase. Overproduction of ROS in DbCM is thought to be counterbalanced by elevated antioxidant defense enzymes such as catalase and superoxide dismutase. Excess ROS in the cardiomyocyte results in further ROS production, mitochondrial DNA damage, lipid peroxidation, post-translational modifications of proteins and ultimately cell death and cardiac dysfunction. Furthermore, ROS modulates transcription factors responsible for expression of antioxidant enzymes. Lastly, evidence exists that several pharmacological agents may convey cardiovascular benefit by antioxidant mechanisms. As such, increasing our understanding of the pathways that lead to increased ROS production and impaired antioxidant defense may enable the development of therapeutic strategies against the progression of DbCM. Herein, we review the current knowledge about causes and consequences of ROS in DbCM, as well as the therapeutic potential and strategies of targeting oxidative stress in the diabetic heart.

Targeting Adrenergic Receptors in Metabolic Therapies for Heart Failure

The heart has a reduced capacity to generate sufficient energy when failing, resulting in an energy-starved condition with diminished functions. Studies have identified numerous changes in metabolic pathways in the failing heart that result in reduced oxidation of both glucose and fatty acid substrates, defects in mitochondrial functions and oxidative phosphorylation, and inefficient substrate utilization for the ATP that is produced. Recent early-phase clinical studies indicate that inhibitors of fatty acid oxidation and antioxidants that target the mitochondria may improve heart function during failure by increasing compensatory glucose oxidation. Adrenergic receptors (α1 and β) are a key sympathetic nervous system regulator that controls cardiac function. β-AR blockers are an established treatment for heart failure and α1A-AR agonists have potential therapeutic benefit. Besides regulating inotropy and chronotropy, α1- and β-adrenergic receptors also regulate metabolic functions in the heart that underlie many cardiac benefits. This review will highlight recent studies that describe how adrenergic receptor-mediated metabolic pathways may be able to restore cardiac energetics to non-failing levels that may offer promising therapeutic strategies.

Obesity cardiomyopathy: evidence, mechanisms, and therapeutic implications

The prevalence of heart failure is on the rise and imposes a major health threat, in part, due to the rapidly increased prevalence of overweight and obesity. To this point, epidemiological, clinical, and experimental evidence supports the existence of a unique disease entity termed “obesity cardiomyopathy,” which develops independent of hypertension, coronary heart disease, and other heart diseases. Our contemporary review evaluates the evidence for this pathological condition, examines putative responsible mechanisms, and discusses therapeutic options for this disorder. Clinical findings have consolidated the presence of left ventricular dysfunction in obesity. Experimental investigations have uncovered pathophysiological changes in myocardial structure and function in genetically predisposed and diet-induced obesity. Indeed, contemporary evidence consolidates a wide array of cellular and molecular mechanisms underlying the etiology of obesity cardiomyopathy including adipose tissue dysfunction, systemic inflammation, metabolic disturbances (insulin resistance, abnormal glucose transport, spillover of free fatty acids, lipotoxicity, and amino acid derangement), altered intracellular especially mitochondrial Ca²⁺ homeostasis, oxidative stress, autophagy/mitophagy defect, myocardial fibrosis, dampened coronary flow reserve, coronary microvascular disease (microangiopathy), and endothelial impairment. Given the important role of obesity in the increased risk of heart failure, especially that with preserved systolic function and the recent rises in COVID-19-associated cardiovascular mortality, this review should provide compelling evidence for the presence of obesity cardiomyopathy, independent of various comorbid conditions, underlying mechanisms, and offer new insights into potential therapeutic approaches (pharmacological and lifestyle modification) for the clinical management of obesity cardiomyopathy.

Wheat germ-derived peptide ADWGGPLPH abolishes high glucose-induced oxidative stress via modulation of the PKCζ/AMPK/NOX4 pathway

This study explores the antioxidative effect of a specific wheat germ-derived peptide on high glucose-induced oxidative stress in vascular smooth muscle cells (VSMCs) and the underlying mechanisms. The peptide ADWGGPLPH was identified by LC-MS/MS. The effects of this peptide on the production of ROS and the expression of oxidative stress signaling proteins in VSMCs were determined. STZ-induced mice were utilized to confirm the anti-oxidative and anti-diabetic cardiovascular disease effects of this peptide in vivo. The results showed that ADWGGPLPH significantly prevented high glucose-induced cell proliferation, decreased intracellular ROS generation, stimulated AMPK activity, inhibited the PKCζ, AKT and Erk1/2 phosphorylation, and suppressed NOX4 protein expression. In addition, ADWGGPLPH enhanced the antioxidant abilities and attenuated inflammatory cytokine generation in STZ-induced diabetic mice. Therefore, ADWGGPLPH prevents high glucose-induced oxidative stress in VSMCs by modulating the PKCζ/AMPK/NOX4 pathway.

Measuring Hypertension Progression With Transition Probabilities: Estimates From the WHO SAGE Longitudinal Study

This paper assessed the transition probabilities between the stages of hypertension severity and the length of time an individual might spend at a particular disease state using the new American College of Cardiology/American Heart Association hypertension blood pressure guidelines. Data for this study were drawn from the Ghana WHO SAGE longitudinal study, with an analytical sample of 1884 across two waves. Using a multistate Markov model, we estimated a seven-year transition probability between normal/elevated blood pressure (systolic ≤ 129 mm Hg & diastolic <80 mm Hg), stage 1 (systolic 130-139 mm Hg & diastolic 80-89 mm Hg), and stage 2 (systolic ≥140mm Hg & diastolic≥90 mm Hg) hypertension and adjusted for the individual effects of anthropometric, lifestyle, and socio-demographic factors. At baseline, 22.5% had stage 1 hypertension and 52.2% had stage 2 hypertension. The estimated seven-year transition probability for the general population was 19.0% (95% CI: 16.4, 21.8) from normal/elevated blood pressure to stage 1 hypertension, 31.6% (95% CI: 27.6, 35.4%) from stage 1 hypertension to stage 2 hypertension, and 48.5% (45.6, 52.1%) for remaining at stage 2. Other factors such as being overweight, obese, female, aged 60+ years, urban residence, low education and high income were associated with an increased probability of remaining at stage 2 hypertension. However, consumption of recommended servings of fruits and vegetables per day was associated with a delay in the onset of stage 1 hypertension and a recovery to normal/elevated blood pressure. This is the first study to show estimated transition probabilities between the stages of hypertension severity across the lifespan in sub-Saharan Africa. The results are important for understanding progression through hypertension severity and can be used in simulating cost-effective models to evaluate policies and the burden of future healthcare.

Energy Metabolites as Biomarkers in Ischemic and Dilated Cardiomyopathy

With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10⁻⁶). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets.

Fatty liver index and left ventricular mass: prospective associations from two independent cohorts

OBJECTIVES

Heart disease is the most common cause of death in patients with nonalcoholic fatty liver disease (NAFLD). Emerging data have shown that NAFLD may affect subclinical myocardial remodeling, mainly left ventricular hypertrophy; however, evidence from the prospective studies is still lacking.

METHODS

Prospective analyses were performed to investigate the association of fatty liver index (FLI) with left ventricular mass (LVM) among 1962 participants from the Bogalusa Heart Study (BHS, 1995-2010) and 1547 participants from the Cardiovascular Risk in Young Finns Study (YFS, 2001-2011) free of cardiovascular diseases (CVD) at baseline. LVM was assessed by two-dimensional guided M-mode echocardiography and indexed (LVMI) to body height (m2.7). Multivariable regression models were applied after adjustment for traditional CVD risk factors.

RESULTS

In both cohorts, we observed significant and positive associations between FLI and LVM (BHS: β=0.59, P < 0.001; YFS: β=0.41, P < 0.001) and LVMI (BHS: β=0.14, P < 0.001; YFS: β=0.09, P < 0.001). In addition, we found that the relationship between FLI and LVMI was stronger in women than men (BHS: P-interaction = 0.01; YFS: P-interaction < 0.01); and the relationship between FLI and LVM/LVMI was stronger in black than white individuals (LVM: P-interaction = 0.02; LVMI: P-interaction = 0.04). Moreover, we found that the associations of FLI with LVM and LVMI were attenuated by high physical activity, especially in BHS (P-interaction = 0.02).

CONCLUSION

Our findings from two independent prospective cohorts indicate that FLI is positively associated with LVM/LVMI, independent of traditional cardiovascular risk factors. Such relationships are more pronounced among women and black individuals and are attenuated by high physical activity.

Association between insulin resistance and left ventricular hypertrophy in asymptomatic, Black, sub-Saharan African, hypertensive patients: a case-control study

Background

Conflicting information exists regarding the association between insulin resistance (IR) and left ventricular hypertrophy (LVH). We described the associations between obesity, fasting insulinemia, homeostasis model assessment of insulin resistance (HOMA-IR), and LVH in Black patients with essential hypertension.

Methods

A case–control study was conducted at the Centre Médical de Kinshasa (CMK), the Democratic Republic of the Congo, between January and December 2019. Cases and controls were hypertensive patients with and without LVH, respectively. The relationships between obesity indices, physical inactivity, glucose metabolism and lipid disorder parameters, and LVH were assessed using linear and logistic regression analyses in simple and univariate exploratory analyses, respectively. When differences were observed between LVH and independent variables, the effects of potential confounders were studied through the use of multiple linear regression and in conditional logistic regression in multivariate analyses. The coefficients of determination (R²), adjusted odds ratios (aORs), and their 95% confidence intervals (95% CIs) were calculated to determine associations between LVH and the independent variables.

Results

Eighty-eight LVH cases (52 men) were compared against 132 controls (81 men). Variation in left ventricular mass (LVM) could be predicted by the following variables: age (19%), duration of hypertension (31.3%), body mass index (BMI, 44.4%), waist circumference (WC, 42.5%), glycemia (20%), insulinemia (44.8%), and HOMA-IR (43.7%). Hypertension duration, BMI, insulinemia, and HOMA-IR explained 68.3% of LVM variability in the multiple linear regression analysis. In the logistic regression model, obesity increased the risk of LVH by threefold [aOR 2.8; 95% CI (1.06–7.4); p = 0.038], and IR increased the risk of LVH by eightfold [aOR 8.4; 95 (3.7–15.7); p < 0.001].

Conclusion

Obesity and IR appear to be the primary predictors of LVH in Black sub-Saharan African hypertensive patients. The comprehensive management of cardiovascular risk factors should be emphasized, with particular attention paid to obesity and IR. A prospective population-based study of Black sub-Saharan individuals that includes the use of serial imaging remains essential to better understand subclinical LV deterioration over time and to confirm the role played by IR in Black sub-Saharan individuals with hypertension.

A High Incidence of Metabolic Syndrome Traits in Mexicans Points at Obesity-Related Metabolic Dysfunction

INTRODUCTION

Metabolic Syndrome (MS) is a construct relating to a series of metabolic dysfunctions attributable to insulin resistance and obesity. Here, we estimate the incidence of MS according to their individual components using a Mexican open-population cohort.

METHODS

We evaluated data of 6144 Mexicans amongst whom 3340 did not have MS either by IDF or ATP-III definitions using data from an open-population cohort. We estimated the incidence of MS and each of its traits after a median follow-up of 2.24 (IQR 2.05-2.58) years and evaluated risk factors for MS incidence and each of its traits. We also explored individuals without any MS trait to evaluate trait and MS incidence after follow-up.

RESULTS

We observed a high incidence of MS-IDF (115.11 cases per 1000 person-years, 95% CI 107.76-122.47), followed by MS-ATP-III (75.77 cases per 1000 person-years, 95% CI). The MS traits with the highest incidence were low HDL-C and abdominal obesity, which was consistent for subjects without MS and those without any MS trait. When assessing predictors of MS incidence, obesity, insulin resistance, and increased apolipoprotein B levels predicted MS incidence. Weight loss >5% of body weight and physical activity were the main protective factors. Obesity was a main determinant for incident MS traits in our population, with weight loss being also a protective factor for most MS traits.

CONCLUSION

We observed a high incidence of MS in apparently healthy Mexican adults. Low HDL-C and abdominal obesity were the most frequent incident MS traits, with obesity being the main determinant of its incidence.

The Effect of Dapagliflozin Treatment on Epicardial Adipose Tissue Volume and P-Wave Indices: An Ad-hoc Analysis of The Previous Randomized Clinical Trial

AIM

Epicardial adipose tissue (EAT) may be associated with arrhythmogenesis. P-wave indices such as P-wave dispersion and P-wave variation indicated a slowed conduction velocity within the atria. This study investigated the effect of dapagliflozin on EAT volume and P-wave indices.

METHODS

In the present ad hoc analysis, 35 patients with type 2 diabetes mellitus and coronary artery disease were classified into dapagliflozin group (n=18) and conventional treatment group (n=17). At baseline, EAT volume, HbA1c and plasma level of tumor necrotic factor-α (TNF-α) levels, echocardiography, and 12-lead electrocardiogram (ECG) were performed. EAT volume was measured using computed tomography. Using 12-lead ECG, P-wave indices were measured.

RESULTS

At baseline, EAT volumes in the dapagliflozin and conventional treatment groups were 113±20 and 110±27 cm3, respectively. Not only HbA1c and plasma level of TNF-α but also echocardiography findings including left atrial dimension and P-wave indices were comparable between the two groups. After 6 months, plasma level of TNF-α as well as EAT volume significantly decreased in the dapagliflozin group only. P-wave dispersion and P-wave variation significantly decreased in the dapagliflozin group only (-9.2±8.7 vs. 5.9±19.9 ms, p=0.01; -3.5±3.5 vs. 1.7±5.9 ms, p=0.01). The change in P-wave dispersion correlated with changes in EAT volume and plasma level of TNF-α. In multivariate analysis, the change in EAT volume was an independent determinant of the change in P-wave dispersion.

CONCLUSION

Dapagliflozin reduced plasma level of TNF-α, EAT volume, and P-wave indices, such as P-wave dispersion. The changes in P-wave indices were especially associated with changes in EAT volume.The number and date of registration: UMIN000035660, 24/Jan/2019.

Sodium-Glucose Cotransporter Type 2 (SGLT-2) Inhibitors and Ketogenesis: the Good and the Bad

PURPOSE OF REVIEW

The micro/macrovascular complications of diabetes cause considerable morbidity and premature mortality. The SGLT2 inhibitors are the first diabetes medications with significant benefits on microvascular disease (nephropathy) and macrovascular cardiovascular disease. In this review, we evaluate one of the potential mechanisms for these cardiorenal benefits-the production of ketones, their benefits, and risks.

RECENT FINDINGS

In recent cardiovascular outcome trials (CVOTs), the SGLT2 inhibitors demonstrated significant cardiorenal benefits and they are now approved to reduce CV events/death, heart failure hospitalization, and progression to end-stage renal disease. Glucosuria induced by the SGLT2 inhibitors leads to increased ketone production. Ketones are an efficient fuel source and can improve myocardial and renal function. Further, the ketone body beta-hydroxybutyrate exhibits anti-inflammatory/anti-oxidative actions, which favorably impact myocardial and renal remodeling/fibrosis. Uncontrolled ketogenesis leads to ketoacidosis, especially during conditions of acute illness and excessive insulin dose reductions. The SGLT2 inhibitors have demonstrated significant cardiorenal benefits in large CVOTs. Studies are in progress to elucidate whether SGLT2 inhibitor-induced low-grade hyperketonemia contributes to these benefits.

Effects of High-Fat Diet Induced Obesity and Fructooligosaccharide Supplementation on Cardiac Protein Expression

The mechanism by which high fat-diet induced obesity affects cardiac protein expression is unclear, and the extent to which this is modulated by prebiotic treatment is not known. These outcomes were assessed in rats initially fed a high-fat diet, then the top 40% weight gain group were randomly allocated to control (CON), high-fat (HF) and HF supplemented with fructooligosaccharide (32 g; HF-FOS) treatments for 12 weeks (n = 10/group). At sacrifice, left ventricles were either frozen or preserved in formalin. Serum was stored for glucose and insulin measurements. Protein spectra was obtained using an Orbitrap analyzer, processed with Sequest and fold changes assessed with Scaffold Q +. Treatment effects for body weights, glucose and insulin were assessed using one-way ANOVA, and the differential protein expression was assessed by a Mann-Whitney U test. The Database for Annotation, Visualization and Integrated Discovery and the Kyoto Encyclopedia of Genes and Genomes identified pathways containing overrepresented proteins. Hematoxylin and eosin sections were graded for hypertrophy and also quantified; differences were identified using Chi-square analyses and Mann-Whitney U tests. HF diet fed rats were significantly (p < 0.05) heavier than CON, and 23 proteins involved in mitochondrial function and lipid metabolism were differentially expressed between HF and CON. Between HF-FOS and HF, 117 proteins involved in contractility, lipid and carbohydrate metabolism were differentially expressed. HF cardiomyocytes were significantly (p < 0.05) more hypertrophic than CON. We conclude that high-fat feeding and FOS are associated with subcellular deviations in cardiac metabolism and contractility, which may influence myocardial function and alter the risk of cardiovascular disease.

Cumulative soft drink consumption is associated with insulin resistance in Mexican adults

BACKGROUND

Insulin resistance (IR) is an important risk factor for type 2 diabetes (T2D) and other cardiometabolic diseases. Recent studies suggest that soft drink consumption could increase IR. However, inconsistent findings have been observed.

OBJECTIVE

The aim was to estimate the association between the cumulative consumption of soft drinks and IR by means of the HOMA-IR in Mexican adults.

METHODS

We analyzed the association between cumulative consumption of soft drinks and HOMA-IR change after 7 y of follow-up in participants (n = 1073) of the Health Workers Cohort Study. Soft drink consumption was estimated by food-frequency questionnaires. Insulin was measured by chemiluminescence, and fasting glucose was measured with the enzymatic colorimetric method. HOMA-IR was computed as fasting insulin (mIU/L) × fasting glucose (mmol/L)/22.5. To assess the relation between cumulative soft drink consumption and HOMA-IR change, we performed robust linear regression models. Additionally, we used fixed-effects models to estimate the association between changes in soft drink consumption and change in HOMA-IR.

RESULTS

At baseline, the average age was 44 y. Mean cumulative soft drink consumption was 0.42 servings/d. Median HOMA-IR increased from 1.5 at baseline to 2.0 at follow-up. Soft drink consumption was positively associated with HOMA-IR change. In the multiple linear regression analysis, for each increase in the consumption of 2 (355 mL) soft drinks/d, the average change between baseline and follow-up HOMA-IR showed an increase of 1.11 units (95% CI: 0.74, 1.48).

CONCLUSIONS

Our data support the hypothesis that, in Mexican adults, a higher soft drink consumption is associated with an increase in HOMA-IR, despite known risk factors. These findings support the need for reinforcing policies to reduce soft drink consumption in our population.

Tsg101 Is Involved in the Sorting and Re-Distribution of Glucose Transporter-4 to the Sarcolemma Membrane of Cardiac Myocytes

Cardiac cells can adapt to pathological stress-induced energy crisis by shifting from fatty acid oxidation to glycolysis. However, the use of glucose-insulin-potassium (GIK) solution in patients undergoing cardiac surgery does not alleviate ischemia/reperfusion (I/R)-induced energy shortage. This indicates that insulin-mediated translocation of glucose transporter-4 (Glut-4) is impaired in ischemic hearts. Indeed, cardiac myocytes contain two intracellular populations of Glut-4: an insulin-dependent non-endosomal pool (also referred to as Glut-4 storage vesicles, GSVs) and an insulin-independent endosomal pool. Tumor susceptibility gene 101 (Tsg101) has been implicated in the endosomal recycling of membrane proteins. In this study, we aimed to examine whether Tsg101 regulated the sorting and re-distribution of Glut-4 to the sarcolemma membrane of cardiomyocytes under basal and ischemic conditions, using gain- and loss-of-function approaches. Forced overexpression of Tsg101 in mouse hearts and isolated cardiomyocytes could promote Glut-4 re-distribution to the sarcolemma, leading to enhanced glucose entry and adenosine triphosphate (ATP) generation in I/R hearts which in turn, attenuation of I/R-induced cardiac dysfunction. Conversely, knockdown of Tsg101 in cardiac myocytes exhibited opposite effects. Mechanistically, we identified that Tsg101 could interact and co-localize with Glut-4 in the sarcolemma membrane of cardiomyocytes. Our findings define Tsg101 as a novel regulator of cardiac Glut-4 trafficking, which may provide a new therapeutic strategy for the treatment of ischemic heart disease.

The combination of insulin resistance and visceral adipose tissue estimation improves the performance of metabolic syndrome as a predictor of type 2 diabetes

AIMS

To assess the performance of metabolic syndrome as a predictor of type 2 diabetes in a model that also includes both a measure of insulin resistance and a metabolic score for visceral fat, and to propose a novel metabolic syndrome definition.

METHODS

In a prospective Metabolic Syndrome Cohort (n=6143), we evaluated improvements in type 2 diabetes risk prediction using International Diabetes Federation-defined and Adult Treatment Panel III-defined metabolic syndrome, after inclusion in the model of updated homeostatic model assessment of insulin resistance and a metabolic score for visceral fat. We also developed a modified metabolic syndrome construct, 'MS-METS', which used the metabolic score for visceral fat instead of waist circumference to evaluate improved predictive performance for risk of developing type 2 diabetes.

RESULTS

Participants who had metabolic syndrome as defined by both the Adult Treatment Panel III and the International Diabetes Federation criteria had a higher risk of type 2 diabetes compared to participants who did not meet these criteria. Addition of updated homeostatic model assessment of insulin resistance and metabolic score for visceral fat to both metabolic syndrome definitions increased predictive performance for type 2 diabetes risk. Homeostatic model assessment of insulin resistance was the only additional predictor of type 2 diabetes in participants without metabolic syndrome. Conversely, in participants with metabolic syndrome, the use of the metabolic score for visceral fat was the stronger added predictor for type 2 diabetes. When evaluating participants using the MS-METS definition we observed the largest improvement in predictive ability for type 2 diabetes risk and a significant reduction in risk overestimation compared to evaluation using metabolic syndrome defined according to the International Diabetes Federation and Adult Treatment Panel III criteria alone.

CONCLUSION

Inclusion of updated homeostatic model assessment of insulin resistance and metabolic score for visceral fat increases performance of metabolic syndrome in prediction of type 2 diabetes. Assessment of insulin resistance could be more useful than conventional metabolic syndrome and assessment of visceral adipose tissue could be more useful in people with metabolic syndrome. Metabolic syndrome as defined using our modified MS-METS construct improved the accuracy of type 2 diabetes prediction.