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

Cardiac Remodeling and Ventricular Pacing: From Genes to Mechanics

Cardiac remodeling and ventricular pacing represent intertwined phenomena with profound implications for cardiovascular health and therapeutic interventions. This review explores the intricate relationship between cardiac remodeling and ventricular pacing, spanning from the molecular underpinnings to biomechanical alterations. Beginning with an examination of genetic predispositions and cellular signaling pathways, we delve into the mechanisms driving myocardial structural changes and electrical remodeling in response to pacing stimuli. Insights into the dynamic interplay between pacing strategies and adaptive or maladaptive remodeling processes are synthesized, shedding light on the clinical implications for patients with various cardiovascular pathologies. By bridging the gap between basic science discoveries and clinical translation, this review aims to provide a comprehensive understanding of cardiac remodeling in the context of ventricular pacing, paving the way for future advancements in cardiovascular care.

Influence of trimetazidine on myocardial injury in mice with diabetic cardiomyopathy

INTRODUCTION

The prevalence of diabetes mellitus is increasing year by year globally, and diabetic cardiomyopathy (DCM), as the most common complication of type 2 diabetes mellitus, seriously affects the prognosis of patients. Trimetazidine (TMZ), as a drug affecting myocardial energy metabolism, mainly reduces the oxidation rate of β-oxidation by inhibiting 3-ketoacyl-CoA thiolase (3-KAT), a key enzyme in β-oxidation of free fatty acid (FFA), so that the energy metabolism substrate of cardiomyocytes preferentially selects glucose rather than fatty acids, increases the content of intracellular adenosine triphosphate (ATP), enhances the contractile function of cardiomyocytes, and improves the state of cellular ischemia and hypoxia. Previous studies have shown that TMZ is closely related to the activation and induction of apoptosis of the MAPK pathway and AMPK pathway, and plays a role in the treatment of diabetic cardiomyopathy, but the specific mechanism is still unclear.

OBJECTIVE

This study aims to investigate the impact of TMZ on myocardial damage in mice exhibiting diabetic cardiomyopathy (DCM), and to furnish a laboratory foundation for the clinical treatment of diabetic cardiomyopathy.

METHOD

Male db/db mice (6 weeks old, n = 21) and male wild-type (wt) (6 weeks old, n = 20) mice were selected for the study. The wt mice were randomly assigned to the wt group (n = 10) and wt + TMZ group (n = 10), while the remaining db/db mice were randomly allocated to the db/db group (n = 11) and db/db + TMZ group (n = 10). Following 8 weeks of feeding, the wt + TMZ group and db/db + TMZ group received TMZ via gavage, whereas the remaining groups were administered physiological saline. Periodic measurements of blood glucose, blood lipids, and myocardial enzymes were conducted in mice, with samples obtained after the 12th week for subsequent biochemical analysis, myocardial pathology assessment, immunohistochemistry, western blot analysis, and TUNEL staining (TdT-mediated dUTP Nick-End Labeling).

RESULT

GLU, TC, TG, LDL-C, and CK-MB levels were significantly higher in db/db mice compared to wt mice (GLU: M ± SD wt 5.94 ± 0.37, db/db 17.63 ± 0.89, p < 0.05, ES = 0.991; TC: M ± SD wt 3.01 ± 0.32, db/db 6.97 ± 0.36, p < 0.05, ES = 0.972; TG: M ± SD wt 0.58 ± 0.2, db/db 1.75 ± 0.14, p < 0.05, ES = 0.920; LDL-C: M ± SD wt 1.59 ± 0.12, db/db 3.87 ± 0.14, p < 0.05, ES = 0.989; CK-MB: M ± SD wt 0.12 ± 0.01, db/db 0.31 ± 0.04, p < 0.05, ES = 0.928). HDL-C levels were significantly lower in db/db mice (M ± SD wt 1.89 ± 0.08, db/db 0.64 ± 0.09, p < 0.05, ES = 0.963). Histopathological analysis confirmed myocardial damage in db/db mice. Treatment with TMZ reduced GLU, TC, TG, LDL-C, and CK-MB levels (p < 0.05, ES > 0.9) and increased HDL-C levels compared to untreated db/db mice. Additionally, TMZ treatment significantly decreased myocardial cell apoptosis (p < 0.05, ES = 0.980). These results demonstrate the efficacy of TMZ in reversing myocardial injury in DCM mice.

CONCLUSION

TMZ can mitigate myocardial damage in db/db mice by downregulating the expression of caspase-12, a protein associated with the endoplasmic reticulum stress (ERS) cell apoptosis pathway, consequently diminishing cell apoptosis. This underscores the protective efficacy of TMZ against myocardial damage in mice afflicted with DCM.

Construction and validation of a predictive model for major adverse cardiovascular events in the long term after percutaneous coronary intervention in patients with acute ST-segment elevation myocardial infarction

PURPOSE

Construction of a prediction model to predict the risk of major adverse cardiovascular events (MACE) in the long term after percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI).

METHOD

Retrospective analysis of STEMI patients treated with PCI from April 2018 to April 2021 in Fuyang People's Hospital. Lasso regression was used to screen the risk factors for the first occurrence of MACE in patients, and multifactorial logistic regression analysis was used to construct a prediction model. The efficacy was evaluated by area under the ROC curve (AUC), Hosmer-Lemeshow deviance test, calibration curve, clinical decision curve (DCA) and clinical impact curve (CIC).

RESULTS

Logistic regression results showed that hypertension, diabetes mellitus, left main plus three branches lesion, estimated glomerular filtration rate and medication adherence were influential factors in the occurrence of distant MACE after PCI in STEMI patients (P < 0.05). The AUC was 0.849 in the modeling group and 0.724 in the validation group; the calibration curve had a good fit to the standard curve, and the result of the Hosmer-Lemeshow test of deviance was x2 = 7.742 (P = 0. 459); the DCA and the CIC indicated that the predictive model could provide a better net clinical benefit for STEMI patients.

CONCLUSION

A prediction model constructed from a total of five predictor variables, namely hypertension, diabetes, left main + three branches lesions, eGFR and medication adherence, can be used to assess the long-term prognosis after PCI in STEMI patients and help in early risk stratification of patients.

Adipsin inhibits Irak2 mitochondrial translocation and improves fatty acid β-oxidation to alleviate diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) causes the myocardium to rely on fatty acid β-oxidation for energy. The accumulation of intracellular lipids and fatty acids in the myocardium usually results in lipotoxicity, which impairs myocardial function. Adipsin may play an important protective role in the pathogenesis of DCM. The aim of this study is to investigate the regulatory effect of Adipsin on DCM lipotoxicity and its molecular mechanism.

METHODS

A high-fat diet (HFD)-induced type 2 diabetes mellitus model was constructed in mice with adipose tissue-specific overexpression of Adipsin (Adipsin-Tg). Liquid chromatography-tandem mass spectrometry (LC-MS/MS), glutathione-S-transferase (GST) pull-down technique, Co-immunoprecipitation (Co-IP) and immunofluorescence colocalization analyses were used to investigate the molecules which can directly interact with Adipsin. The immunocolloidal gold method was also used to detect the interaction between Adipsin and its downstream modulator.

RESULTS

The expression of Adipsin was significantly downregulated in the HFD-induced DCM model (P < 0.05). Adipose tissue-specific overexpression of Adipsin significantly improved cardiac function and alleviated cardiac remodeling in DCM (P < 0.05). Adipsin overexpression also alleviated mitochondrial oxidative phosphorylation function in diabetic stress (P < 0.05). LC-MS/MS analysis, GST pull-down technique and Co-IP studies revealed that interleukin-1 receptor-associated kinase-like 2 (Irak2) was a downstream regulator of Adipsin. Immunofluorescence analysis also revealed that Adipsin was co-localized with Irak2 in cardiomyocytes. Immunocolloidal gold electron microscopy and Western blotting analysis indicated that Adipsin inhibited the mitochondrial translocation of Irak2 in DCM, thus dampening the interaction between Irak2 and prohibitin (Phb)-optic atrophy protein 1 (Opa1) on mitochondria and improving the structural integrity and function of mitochondria (P < 0.05). Interestingly, in the presence of Irak2 knockdown, Adipsin overexpression did not further alleviate myocardial mitochondrial destruction and cardiac dysfunction, suggesting a downstream role of Irak2 in Adipsin-induced responses (P < 0.05). Consistent with these findings, overexpression of Adipsin after Irak2 knockdown did not further reduce the accumulation of lipids and their metabolites in the cardiac myocardium, nor did it enhance the oxidation capacity of cardiomyocytes expose to palmitate (PA) (P < 0.05). These results indicated that Irak2 may be a downstream regulator of Adipsin.

CONCLUSIONS

Adipsin improves fatty acid β-oxidation and alleviates mitochondrial injury in DCM. The mechanism is related to Irak2 interaction and inhibition of Irak2 mitochondrial translocation.

The neurometabolic axis: A novel therapeutic target in heart failure

Abnormal cardiac metabolism or cardiac metabolic remodeling is reported before the onset of heart failure with reduced ejection fraction (HFrEF) and is known to trigger and maintain the mechanical dysfunction and electrical, and structural abnormalities of the ventricle. A dysregulated cardiac autonomic tone characterized by sympathetic overdrive with blunted parasympathetic activation is another pathophysiological hallmark of HF. Emerging evidence suggests a link between autonomic nervous system activity and cardiac metabolism. Chronic β-adrenergic activation promotes maladaptive metabolic remodeling whereas cholinergic activation attenuates the metabolic aberrations through favorable modulation of key metabolic regulatory molecules. Restoration of sympathovagal balance by neuromodulation strategies is emerging as a novel nonpharmacological treatment strategy in HF. The current review attempts to evaluate the 'neuro-metabolic axis' in HFrEF and whether neuromodulation can mitigate the adverse metabolic remodeling in HFrEF.

DNA Damage and Nuclear Morphological Changes in Cardiac Hypertrophy Are Mediated by SNRK Through Actin Depolymerization

BACKGROUND

Proper nuclear organization is critical for cardiomyocyte function, because global structural remodeling of nuclear morphology and chromatin structure underpins the development and progression of cardiovascular disease. Previous reports have implicated a role for DNA damage in cardiac hypertrophy; however, the mechanism for this process is not well delineated. AMPK (AMP-activated protein kinase) family of proteins regulates metabolism and DNA damage response (DDR). Here, we examine whether a member of this family, SNRK (SNF1-related kinase), which plays a role in cardiac metabolism, is also involved in hypertrophic remodeling through changes in DDR and structural properties of the nucleus.

METHODS

We subjected cardiac-specific Snrk-/- mice to transaortic banding to assess the effect on cardiac function and DDR. In parallel, we modulated SNRK in vitro and assessed its effects on DDR and nuclear parameters. We also used phosphoproteomics to identify novel proteins that are phosphorylated by SNRK. Last, coimmunoprecipitation was used to verify Destrin (DSTN) as the binding partner of SNRK that modulates its effects on the nucleus and DDR.

RESULTS

Cardiac-specific Snrk-/- mice display worse cardiac function and cardiac hypertrophy in response to transaortic banding, and an increase in DDR marker pH2AX (phospho-histone 2AX) in their hearts. In addition, in vitro Snrk knockdown results in increased DNA damage and chromatin compaction, along with alterations in nuclear flatness and 3-dimensional volume. Phosphoproteomic studies identified a novel SNRK target, DSTN, a member of F-actin depolymerizing factor proteins that directly bind to and depolymerize F-actin. SNRK binds to DSTN, and DSTN downregulation reverses excess DNA damage and changes in nuclear parameters, in addition to cellular hypertrophy, with SNRK knockdown. We also demonstrate that SNRK knockdown promotes excessive actin depolymerization, measured by the increased ratio of G-actin to F-actin. Last, jasplakinolide, a pharmacological stabilizer of F-actin, rescues the increased DNA damage and aberrant nuclear morphology in SNRK-downregulated cells.

CONCLUSIONS

These results indicate that SNRK is a key player in cardiac hypertrophy and DNA damage through its interaction with DSTN. This interaction fine-tunes actin polymerization to reduce DDR and maintain proper cardiomyocyte nuclear shape and morphology.

Subclinical right ventricular dysfunction in patients with asymptomatic type 2 diabetes mellitus: A cross-sectional study

BACKGROUND

Diabetic cardiomyopathy, which involves both the right and left ventricles, progresses from a preclinical stage to overt heart failure. Detection of this entity at a preclinical stage could be crucial in intervening to halt its progression to overt heart failure. There is a paucity of literature on subclinical RV dysfunction in diabetic patients, and it is even rarer in the Indian literature. Our study intended to study this clinical entity through an echocardiographic assessment of asymptomatic patients.

OBJECTIVES

This was a cross-sectional observational analytic study, comparing subclinical RV dysfunction in diabetic and non-diabetic subjects by using echocardiography as a primary objective, while the secondary objective of the study was to find out the correlation between RV dysfunction and the duration of diabetes mellitus and HbA1C levels.

METHODS

Conventional echocardiography with tissue Doppler imaging (TDI) was used to measure nine different echocardiographic parameters in the diabetic and non-diabetic groups. All probable causes of RV dysfunction were excluded before enrolling the patients in the study. Unpaired t-test was used to compare the parameters between the two groups, and multivariate regression analysis was done taking into consideration age, duration of diabetes, and HbA1C levels as the independent variables, and echocardiographic parameters as the dependent variables.

RESULTS

Out of the nine different echocardiographic parameters, Tricuspid annular plane systolic excursion (TAPSE), RV end diastolic diameter (RVEDD), Tricuspid peak late diastolic velocity (A), E/A ratio, RV basal segment peak myocardial systolic velocity (Sm), RV basal segment peak early diastolic velocity (Em), RV basal segment peak late diastolic velocity (Am), and E/Em ratio showed statistically significant differences between the two groups. These results show the presence of subclinical RV dysfunction in diabetic patients. TAPSE and E/A ratio showed a significant correlation with the duration of diabetes, while Em showed a significant correlation with HbA1C.

CONCLUSION

Diabetes mellitus is associated with subclinical systolic as well as diastolic RV dysfunction. In addition to helping identify people at high risk, the early recognition of RV dysfunction gives us a window of opportunity to take action and slow down the disease's course. This study emphasizes that the early identification of RV diastolic as well as systolic dysfunction in asymptomatic Type 2 diabetic patients can be a helpful tool in halting the progression of disease from subclinical to frank clinical cases, thereby preventing the morbidity and mortality associated with heart failure. Hence, it adds value to the pre-existing literature.

DNA damage and nuclear morphological changes in cardiac hypertrophy are mediated by SNRK through actin depolymerization

BACKGROUND

Proper nuclear organization is critical for cardiomyocyte (CM) function, as global structural remodeling of nuclear morphology and chromatin structure underpins the development and progression of cardiovascular disease. Previous reports have implicated a role for DNA damage in cardiac hypertrophy, however, the mechanism for this process is not well delineated. AMPK family of proteins regulate metabolism and DNA damage response (DDR). Here, we examine whether a member of this family, SNF1-related kinase (SNRK), which plays a role in cardiac metabolism, is also involved in hypertrophic remodeling through changes in DDR and structural properties of the nucleus.

METHODS

We subjected cardiac specific (cs)- Snrk -/- mice to trans-aortic banding (TAC) to assess the effect on cardiac function and DDR. In parallel, we modulated SNRK in vitro and assessed its effects on DDR and nuclear parameters. We also used phospho-proteomics to identify novel proteins that are phosphorylated by SNRK. Finally, co-immunoprecipitation (co-IP) was used to verify Destrin (DSTN) as the binding partner of SNRK that modulates its effects on the nucleus and DDR.

RESULTS

cs- Snrk -/- mice display worse cardiac function and cardiac hypertrophy in response to TAC, and an increase in DDR marker pH2AX in their hearts. Additionally, in vitro Snrk knockdown results in increased DNA damage and chromatin compaction, along with alterations in nuclear flatness and 3D volume. Phospho-proteomic studies identified a novel SNRK target, DSTN, a member of F-actin depolymerizing factor (ADF) proteins that directly binds to and depolymerize F-actin. SNRK binds to DSTN, and DSTN downregulation reverses excess DNA damage and changes in nuclear parameters, in addition to cellular hypertrophy, with SNRK knockdown. We also demonstrate that SNRK knockdown promotes excessive actin depolymerization, measured by the increased ratio of globular (G-) actin to F-actin. Finally, Jasplakinolide, a pharmacological stabilizer of F-actin, rescues the increased DNA damage and aberrant nuclear morphology in SNRK downregulated cells.

CONCLUSIONS

These results indicate that SNRK is a key player in cardiac hypertrophy and DNA damage through its interaction with DSTN. This interaction fine-tunes actin polymerization to reduce DDR and maintain proper CM nuclear shape and morphology.

Clinical Perspective

What is new? Animal hearts subjected to pressure overload display increased SNF1-related kinase (SNRK) protein expression levels and cardiomyocyte specific SNRK deletion leads to aggravated myocardial hypertrophy and heart failure.We have found that downregulation of SNRK impairs DSTN-mediated actin polymerization, leading to maladaptive changes in nuclear morphology, higher DNA damage response (DDR) and increased hypertrophy. What are the clinical implications? Our results suggest that disruption of DDR through genetic loss of SNRK results in an exaggerated pressure overload-induced cardiomyocyte hypertrophy.Targeting DDR, actin polymerization or SNRK/DSTN interaction represent promising therapeutic targets in pressure overload cardiac hypertrophy.

Is increased myocardial triglyceride content associated with early changes in left ventricular function? A 1H-MRS and MRI strain study

Background

Type 2 diabetes (T2D) and obesity induce left ventricular (LV) dysfunction. The underlying pathophysiological mechanisms remain unclear, but myocardial triglyceride content (MTGC) could be involved.

Objectives

This study aimed to determine which clinical and biological factors are associated with increased MTGC and to establish whether MTGC is associated with early changes in LV function.

Methods

A retrospective study was conducted using five previous prospective cohorts, leading to 338 subjects studied, including 208 well-phenotyped healthy volunteers and 130 subjects living with T2D and/or obesity. All the subjects underwent proton magnetic resonance spectroscopy and feature tracking cardiac magnetic resonance imaging to measure myocardial strain.

Results

MTGC content increased with age, body mass index (BMI), waist circumference, T2D, obesity, hypertension, and dyslipidemia, but the only independent correlate found in multivariate analysis was BMI (p=0.01; R²=0.20). MTGC was correlated to LV diastolic dysfunction, notably with the global peak early diastolic circumferential strain rate (r=-0.17, p=0.003), the global peak late diastolic circumferential strain rate (r=0.40, p<0.0001) and global peak late diastolic longitudinal strain rate (r=0.24, p<0.0001). MTGC was also correlated to systolic dysfunction via end-systolic volume index (r=-0.34, p<0.0001) and stroke volume index (r=-0.31, p<0.0001), but not with longitudinal strain (r=0.009, p=0.88). Interestingly, the associations between MTGC and strain measures did not persist in multivariate analysis. Furthermore, MTGC was independently associated with LV end-systolic volume index (p=0.01, R²=0.29), LV end-diastolic volume index (p=0.04, R²=0.46), and LV mass (p=0.002, R²=0.58).

Conclusions

Predicting MTGC remains a challenge in routine clinical practice, as only BMI independently correlates with increased MTGC. MTGC may play a role in LV dysfunction but does not appear to be involved in the development of subclinical strain abnormalities.

The effects of G protein-coupled receptor 30 (GPR30) on cardiac glucose metabolism in diabetic ovariectomized female rats

BACKGROUND

Diabetic cardiometabolic disorders are characterized by significant changes in cardiac metabolism and are increased in postmenopausal women, which emphasize the role of 17β-estradiol (E2). Despite this, there are few safe and effective pharmacological treatments for these disorders. The role of G protein-coupled estrogen receptor (GPR30), which mediates the non-genomic effects of E2, is mostly unexplored.

METHODS

In this study, we used ovariectomy (menopausal model) and type 2 diabetic (T2D) rats' models to evaluate the preclinical action of G-1 (GPR30 agonist) against cardiometabolic disorders. T2D was induced by a high-fat diet and a low dose of streptozotocin. G-1 was administrated for six weeks after the establishment of T2D.

RESULTS

We found that G-1 counteracts the effects of T2D and ovariectomy by increasing the body weight, reducing fasting blood sugar, heart weight, and heart weight to body weight ratio. Also, both ovariectomy and T2D led to decreases in the cardiac protein levels of hexokinase 2 (HK2) and GLUT4, while G-1-treated female rats reversed these changes and only increased HK2 protein level. In addition, T2D and ovariectomy increased glucose and glycogen content in the heart, but G-1 treatment significantly reduced them.

CONCLUSIONS

In conclusion, our work demonstrates that G-1 as a selective GPR30 agonist is a viable therapeutic approach against T2D and cardiometabolic diseases in multiple preclinical female models.

Association of continuous positive airway pressure therapy on cardiac hypertrophy in patients with sleep apnea comorbid with type 2 diabetes mellitus

Previous reports indicated the therapeutic effect of chronic continuous positive airway pressure (CPAP) therapy on cardiac hypertrophy due to sleep apnea syndrome. However, little is known for cases involving diabetic complications. This retrospective observational study examined the effects of CPAP therapy on left ventricular hypertrophy (LVH) in patients with obstructive sleep apnea syndrome (OSAS) and type 2 diabetes mellitus (T2DM). For all cases, the observation period was 3 years from the time when the patient was introduced to CPAP therapy. Overall, 123 patients were divided into a good CPAP group (CPAP ≥4 h/day, n = 63) and non-adherence group (CPAP <4 h/day, n = 60). The mean CPAP usage times were 5.58 ± 1.23 and 1.03 ± 1.17 h/day in the good CPAP and non-adherence groups, respectively. Regression tendencies of the thickness of the left ventricular posterior (-0.30 ± 1.19 mm) and interventricular septal walls (-0.48 ± 1.22 mm) were observed in the good CPAP group. Hypertrophic tendencies of the left ventricular posterior wall (+0.59 ± 1.44 mm) and interventricular septal wall thickness (+0.59 ± 1.43) were observed in the non-adherence group. Left ventricular posterior wall thickness (coefficient: -0.254, p = 0.0376) and interventricular septal wall thickness (coefficient: -0.426, p = 0.0006) were more likely to be greater in the non-adherence group than in the good CPAP group. Patients in the non-adherence group with an apnea hypopnea index ≥30 had increased left ventricular posterior wall thickness (coefficient: -0.263, p = 0.0673) and interventricular septal wall thickness (coefficient: -0.450, p = 0.0011). In conclusion, appropriate CPAP therapy is an effective treatment for LVH in patients with T2DM and OSAS, especially for severe cases.

Circadian rhythms in cardiac metabolic flexibility

Numerous aspects of cardiovascular physiology (e.g., heart rate, blood pressure) and pathology (e.g., myocardial infarction and sudden cardiac death) exhibit time-of-day-dependency. In association with day-night differences in energetic demand and substrate availability, the healthy heart displays remarkable metabolic flexibility through temporal partitioning of the metabolic fate of common substrates (glucose, lipid, amino acids). The purpose of this review is to highlight the contribution that circadian clocks provide toward 24-hr fluctuations in cardiac metabolism and to discuss whether attenuation and/or augmentation of these metabolic rhythms through adjustment of nutrient intake timing impacts cardiovascular disease development.

Comprehensive assessment of biventricular myocardial function by two-dimensional speckle tracking echocardiography in infants of gestational diabetic mothers

AIMS

No previous research provided a complete biventricular and multidirectional left ventricular (LV) functional assessment by two-dimensional (2D) speckle tracking echocardiography (STE) in infants of gestational diabetic mothers (IGDM) METHODS: A total of 30 consecutive IGDM and 30 infants of healthy mothers were examined between March 2021 and July 2021. Both groups of infants underwent evaluation by neonatologist and 2D transthoracic echocardiography (TTE) implemented with 2D-STE quantification of LV-global longitudinal strain (GLS), LV-global circumferential strain (GCS), LV-global radial strain (GRS) and right ventricular (RV)-GLS, within 3 days of life and at 40 days after birth. Predictors of persistent subclinical myocardial dysfunction, defined as a LVGLS less negative than -20% at 40-day follow-up, in IGDM population, were determined.

RESULTS

At 2.2 ± 1.3 days after birth, LV-GLS (- 17.2 ± 1.9 vs. - 23.9 ± 3.8%), LV-GCS (- 17.9 ± 2.7 vs. - 27.3 ± 3.4%), LV-GRS (25.6 ± 3.4 vs. 35.8 ± 3.6%) and RV-GLS (- 17.6 ± 3.6 vs. - 22.6 ± 3.8%) were significantly impaired in IGDM than controls (all p < 0.001). At 36.8 ± 5.2 days of life, LV-GLS was still impaired (less negative than -20%) in 26.6% of IGDM. Maternal third trimester body mass index (BMI) (OR 1.89, 95%CI 1.05-3.39) and third trimester glycosylated hemoglobin (HbA1C) (OR 1.59, 95%CI 1.08-2.19) were independently associated with persistent LV-GLS impairment in IGDM. Maternal BMI ≥ 30 Kg/m2 and HbA1C ≥ 38 mmol/mol showed the maximum of sensitivity and specificity for predicting persistent subclinical myocardial dysfunction in IGDM at 40 days of life.

CONCLUSIONS

IGDM have diffuse pattern of myocardial dysfunction during perinatal period. This dysfunction may be persistent up to 40 days of life in infants of GDM women with obesity and uncontrolled diabetes.

SIRPα Mediates IGF1 Receptor in Cardiomyopathy Induced by Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is characterized by increased myocardial mass despite near-normal blood pressure, suggesting the presence of a separate trigger. A potential driver is SIRPα (signal regulatory protein alpha)-a mediator impairing insulin signaling. The objective of this study is to assess the role of circulating SIRPα in CKD-induced adverse cardiac remodeling.

METHODS

SIRPα expression was evaluated in mouse models and patients with CKD. Specifically, mutant, muscle-specific, or cardiac muscle-specific SIRPα KO (knockout) mice were examined after subtotal nephrectomy. Cardiac function was assessed by echocardiography. Metabolic responses were confirmed in cultured muscle cells or cardiomyocytes.

RESULTS

We demonstrate that SIRPα regulates myocardial insulin/IGF1R (insulin growth factor-1 receptor) signaling in CKD. First, in the serum of both mice and patients, SIRPα was robustly secreted in response to CKD. Second, cardiac muscle upregulation of SIRPα was associated with impaired insulin/IGF1R signaling, myocardial dysfunction, and fibrosis. However, both global and cardiac muscle-specific SIRPα KO mice displayed improved cardiac function when compared with control mice with CKD. Third, both muscle-specific or cardiac muscle-specific SIRPα KO mice did not significantly activate fetal genes and maintained insulin/IGF1R signaling with suppressed fibrosis despite the presence of CKD. Importantly, SIRPα directly interacted with IGF1R. Next, rSIRPα (recombinant SIRPα) protein was introduced into muscle-specific SIRPα KO mice reestablishing the insulin/IGF1R signaling activity. Additionally, overexpression of SIRPα in myoblasts and cardiomyocytes impaired pAKT (phosphorylation of AKT) and insulin/IGF1R signaling. Furthermore, myotubes and cardiomyocytes, but not adipocytes treated with high glucose or cardiomyocytes treated with uremic toxins, stimulated secretion of SIRPα in culture media, suggesting these cells are the origin of circulating SIRPα in CKD. Both intracellular and extracellular SIRPα exert biologically synergistic effects impairing intracellular myocardial insulin/IGF1R signaling.

CONCLUSIONS

Myokine SIRPα expression impairs insulin/IGF1R functions in cardiac muscle, affecting cardiometabolic signaling pathways. Circulating SIRPα constitutes an important readout of insulin resistance in CKD-induced cardiomyopathy.

Strategies for Imaging Metabolic Remodeling of the Heart in Obesity and Heart Failure

PURPOSE OF REVIEW

Define early myocardial metabolic changes among patients with obesity and heart failure, and to describe noninvasive methods and their applications for imaging cardiac metabolic remodeling.

RECENT FINDINGS

Metabolic remodeling precedes, triggers, and sustains functional and structural remodeling in the stressed heart. Alterations in cardiac metabolism can be assessed by using a variety of molecular probes. The glucose tracer analog, 18F-FDG, and the labeled tracer 11C-palmitate are still the most commonly used tracers to assess glucose and fatty acid metabolism, respectively. The development of new tracer analogs and imaging agents, including those targeting the peroxisome proliferator-activated receptor (PPAR), provides new opportunities for imaging metabolic activities at a molecular level. While the use of cardiac magnetic resonance spectroscopy in the clinical setting is limited to the assessment of intramyocardial and epicardial fat, new technical improvements are likely to increase its usage in the setting of heart failure. Noninvasive imaging methods are an effective tool for the serial assessment of alterations in cardiac metabolism, either during disease progression, or in response to treatment.

Functions and origins of cardiac fat

Triglyceride droplets can be stored within cardiac adipocytes (CAs) and cardiomyocytes in the heart. Cardiac adipocytes reside in three distinct regions: pericardial, epicardial, and intramyocardial adipose tissues. In healthy individuals, cardiac adipose tissues modulate cardiovascular functions and energy partitioning, which are, thus, protective. However, ectopic deposition of cardiac adipose tissues turns them into adverse lipotoxic, prothrombotic, and pro-inflammatory tissues with local and systemic contribution to the development of cardiovascular disorders. Accumulation of triglyceride droplets in cardiomyocytes may lead to lipotoxic injury of cardiomyocytes and contribute to the development of cardiac hypertrophy and dysfunction. Here, we summarize the roles of CAs and myocardial triglyceride droplets under physiological and pathological conditions and review the cellular sources of CAs in heart development and diseases. Understanding the functions and cellular origins of cardiac fat will provide clues for future studies on pathophysiological processes and treatment of cardiovascular diseases.

Glycemic Control and the Heart: The Tale of Diabetic Cardiomyopathy Continues

Cardiovascular diseases are the leading cause of death in people with diabetes. Diabetic cardiomyopathy (DC) is an important complication of diabetes and represents a distinct subtype of heart failure that occurs in absence of cardiovascular diseases. Chronic hyperglycemia and hyperinsulinemia along with insulin resistance and inflammatory milieu are the main mechanisms involved in the pathophysiology of DC. Changes in lifestyle favoring healthy dietary patterns and physical activity, combined with more innovative anti-diabetes therapies, are the current treatment strategies to safeguard the cardiovascular system. This review aims at providing an updated comprehensive overview of clinical, pathogenetic, and molecular aspects of DC, with a focus on the effects of anti-hyperglycemic drugs on the prevention of pump dysfunction and consequently on cardiovascular health in type 2 diabetes.

Empagliflozin Treatment Is Associated With Improvements in Cardiac Energetics and Function and Reductions in Myocardial Cellular Volume in Patients With Type 2 Diabetes

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk of major adverse cardiovascular (CV) events and hospitalization for heart failure (HF) in patients with type 2 diabetes (T2D). Using CV MRI (CMR) and 31P-MRS in a longitudinal cohort study, we aimed to investigate the effects of the selective SGLT2 inhibitor empagliflozin on myocardial energetics and cellular volume, function, and perfusion. Eighteen patients with T2D underwent CMR and 31P-MRS scans before and after 12 weeks' empagliflozin treatment. Plasma N-terminal prohormone B-type natriuretic peptide (NT-proBNP) levels were measured. Ten volunteers with normal glycemic control underwent an identical scan protocol at a single visit. Empagliflozin treatment was associated with significant improvements in phosphocreatine-to-ATP ratio (1.52 to 1.76, P = 0.009). This was accompanied by a 7% absolute increase in the mean left ventricular ejection fraction (P = 0.001), 3% absolute increase in the mean global longitudinal strain (P = 0.01), 8 mL/m2 absolute reduction in the mean myocardial cell volume (P = 0.04), and 61% relative reduction in the mean NT-proBNP (P = 0.05) from baseline measurements. No significant change in myocardial blood flow or diastolic strain was detected. Empagliflozin thus ameliorates the "cardiac energy-deficient" state, regresses adverse myocardial cellular remodeling, and improves cardiac function, offering therapeutic opportunities to prevent or modulate HF in T2D.

Disturbed Glucose Metabolism and Left Ventricular Geometry in the General Population

Background: This study sought to investigate the prevalence and clinical outcome of left ventricular (LV) geometry in prediabetes and type 2 diabetes mellitus (T2DM) and the impact of glucose metabolism on the incidence of left ventricular hypertrophy (LVH). Methods: 15,010 subjects (35–74 years) of the population-based Gutenberg Health Study were categorized into euglycemia, prediabetes, and T2DM according to clinical and metabolic (HbA1c) information. Clinical outcome was assessed via structured follow-up. Results: The study comprised 12,121 individuals with euglycemia (81.6%), 1415 with prediabetes (9.5%), and 1316 with T2DM (8.9%). Prevalence of LVH increased from euglycemia (10.2%) over prediabetes (17.8%) to T2DM (23.8%). Prediabetes and T2DM were associated with increased LV mass index (prediabetes: β1.3 (95% CI 0.78–1.81), p < 0.0001; T2DM: β2.37 (95% CI 1.81; 2.92), p < 0.0001) independent of age, sex, and cardiovascular risk factors (CVRF). The frequency of LVH was related to the presence of T2DM (prevalence ratio (PR)T2DM 1.2 (95% CI 1.06–1.35), p = 0.0038). T2DM was related to mortality independent of age, sex, and CVRF regardless of LVH (hazard ratio (HR)T2DM-LVH 2.67 (95% CI 1.94–3.66), p < 0.0001; HRT2DM-noLVH 1.59 (95% CI 1.29–1.96), p < 0.0001), prediabetes was only associated with outcome in individuals with LVH independent of age and sex (HRprediabetes-LVH 1.51 (95% CI 1.01–2.25), p = 0.045). Neither T2DM nor prediabetes were predictors of incident LVH after adjustment for clinical covariates. Conclusions: Prediabetes and T2DM promote alterations of cardiac geometry. T2DM and particularly the coprevalence of T2DM with LVH substantially reduce life expectancy. These findings highlight the need for new therapeutic and screening approaches to prevent and detect cardiometabolic diseases at an early stage.

Impact of obesity on day-night differences in cardiac metabolism

An intrinsic property of the heart is an ability to rapidly and coordinately adjust flux through metabolic pathways in response to physiologic stimuli (termed metabolic flexibility). Cardiac metabolism also fluctuates across the 24‐hours day, in association with diurnal sleep‐wake and fasting‐feeding cycles. Although loss of metabolic flexibility has been proposed to play a causal role in the pathogenesis of cardiac disease, it is currently unknown whether day‐night variations in cardiac metabolism are altered during disease states. Here, we tested the hypothesis that diet‐induced obesity disrupts cardiac “diurnal metabolic flexibility”, which is normalized by time‐of‐day‐restricted feeding. Chronic high fat feeding (20‐wk)‐induced obesity in mice, abolished diurnal rhythms in whole body metabolic flexibility, and increased markers of adverse cardiac remodeling (hypertrophy, fibrosis, and steatosis). RNAseq analysis revealed that 24‐hours rhythms in the cardiac transcriptome were dramatically altered during obesity; only 22% of rhythmic transcripts in control hearts were unaffected by obesity. However, day‐night differences in cardiac substrate oxidation were essentially identical in control and high fat fed mice. In contrast, day‐night differences in both cardiac triglyceride synthesis and lipidome were abolished during obesity. Next, a subset of obese mice (induced by 18‐wks ad libitum high fat feeding) were allowed access to the high fat diet only during the 12‐hours dark (active) phase, for a 2‐wk period. Dark phase restricted feeding partially restored whole body metabolic flexibility, as well as day‐night differences in cardiac triglyceride synthesis and lipidome. Moreover, this intervention partially reversed adverse cardiac remodeling in obese mice. Collectively, these studies reveal diurnal metabolic inflexibility of the heart during obesity specifically for nonoxidative lipid metabolism (but not for substrate oxidation), and that restricting food intake to the active period partially reverses obesity‐induced cardiac lipid metabolism abnormalities and adverse remodeling of the heart.

Electron Microscopy Revealed Massive Lipid Droplets in Cardiomyocytes in a Patient with Cardiogenic Shock Following a Fulminant Type 1 Diabetes Mellitus

A 52-year-old man with consciousness disorder following a 2-day history of general fatigue, diarrhea, vomiting and excessive thirst was admitted to our hospital. Severe hyperglycemia (1,739 mg/dL) with a slightly elevated HbA1c level (6.9%), ketonuria and low C-peptide level (0.07 ng/mL) confirmed the diagnosis of fulminant type 1 diabetes mellitus (FT1DM). Following sudden unexplained cardiogenic shock shortly after the initiation of insulin therapy with no evidence of myocardial ischemia assessed by coronary angiography, the patient was supported with percutaneous venoarterial extracorporeal membrane oxygenation. Electron microscopic analysis of the myocardium revealed massive lipid droplets without the infiltration of inflammatory cells. His left ventricular function began to recover during the following days and returned to a normal level on day 14. Currently, the impact of FT1DM on intramyocardial lipid deposition is poorly understood. However, this case suggests that even short-term exposure to high concentrations of glucose can be responsible for lipotoxicity followed by severe cardiac dysfunction.

A Role of Glucose Overload in Diabetic Cardiomyopathy in Nonhuman Primates

Type 2 diabetes (T2D) plays a major role in the development of heart failure. Patients with T2D have an increased risk to develop HF than healthy subjects, and they always have very poor outcomes and survival rates. However, the underlying mechanisms for this are still unclear. To help develop new therapeutic interventions, well-characterized animal models for preclinical and translational investigations in T2D and HF are urgently needed. Although studies in rodents are more often used, the research findings in rodents have often failed to be translated into humans due to the significant metabolic differences between rodents and humans. Nonhuman primates (NHPs) serve as valuable translational models between basic studies in rodent models and clinical studies in humans. NHPs can recapitulate the natural progress of these diseases in humans and study the underlying mechanism due to their genetic similarity and comparable spontaneous T2D rates to humans. In this review, we discuss the importance of using NHPs models in understanding diabetic cardiomyopathy (DCM) in humans with aspects of correlations between hyperglycemia and cardiac dysfunction progression, glucose overload, and altered glucose metabolism promoting cardiac oxidative stress and mitochondria dysfunction, glucose, and its effect on cardiac resynchronization therapy with defibrillator (CRT-d), the currently available diabetic NHPs models and the limitations involved in the use of NHP models.

Thyroid Hormone Signalling Alteration in Diabetic Nephropathy and Cardiomyopathy: a "Switch" to the Foetal Gene Programme

PURPOSE OF THE REVIEW

In this study, we will analyse how diabetes induces the reactivation of organs' developmental programmes and growth, discuss how thyroid hormone (TH) signalling orchestrates these processes, and suggest novel strategies for exploiting TH-mediated reparative and regenerative properties.

RECENT FINDINGS

Diabetes is a global pandemic that poses an enormous threat to human health. The kidney and the heart are among the organs that are the most severely damaged by diabetes over time. They undergo profound metabolic, structural, and functional changes that may be due (at least partially) to a recapitulation of their early developmental programmes. There is growing evidence to suggest that this foetal reprogramming is controlled by the TH/TH receptor alpha 1 (TRα1) axis. We introduce the hypothesis that in diabetes-and probably in other diseases-TH signalling acts in an antagonistic manner: it recapitulates a foetal profile that is necessary to coordinate metabolic and structural adaptations to sustain energy preservation and growth, but in the long term the persistent changes in these pathways are detrimental.

Metabolic Risk Factors and Left Ventricular Diastolic Function in Middle-Aged Chinese Living in the Tibetan Plateau

Background

Data regarding the metabolic risk factors clustering on the risk of left ventricular diastolic dysfunction (LVDD) are lacking among people living at high altitude and under hypoxic conditions. In this study, we explored the association between metabolic risk factor clustering and LVDD among the Tibetan population of China.

Methods and Results

We conducted a cross‐sectional survey in a representative sample of 1963 Tibetans in 2014 to 2016. Grading LVDD was based on recommendations for the evaluation of LV diastolic function by echocardiography (2009). The prevalence of LVDD among 1963 participants (mean age: 51.51 years, 41.11% male) was 34.39%. Odds ratios (95% CI) of LVDD for the 1, 2, and 3 to 5 risk factors clustering were 1.45 (0.96–2.17), 2.68 (1.8–3.98), and 2.9 (1.9–4.43), respectively (P for trend <0.001). The association between metabolic risk factors clustering and LVDD was much more pronounced in the middle‐aged group than in the elderly (P for interaction=0.0170). High altitude was one of the major independent risk factors for LVDD; however, habitation altitude had no significant effect on the association between metabolic risk factors and LVDD (P for interaction=0.1022). The multivariable dominance analysis indicated that abdominal obesity, hypertension, and elevated blood glucose were the significant contributors to LVDD.

Conclusions

There was a significant positive association between the metabolic risk factor clustering number and LVDD among a population living at high altitude, especially in middle‐aged adults. However, habitation altitude itself has no significant effect on the association between metabolic risk factors and LVDD.

Alterations in plasma triglycerides and ceramides: links with cardiac function in humans with type 2 diabetes

Cardiac dysfunction in T2D is associated with excessive FA uptake, oxidation, and generation of toxic lipid species by the heart. It is not known whether decreasing lipid delivery to the heart can effect improvement in cardiac function in humans with T2D. Thus, our objective was to test the hypothesis that lowering lipid delivery to the heart would result in evidence of decreased "lipotoxicity," improved cardiac function, and salutary effects on plasma biomarkers of cardiovascular risk. Thus, we performed a double-blind randomized placebo-controlled parallel design study of the effects of 12 weeks of fenofibrate-induced lipid lowering on cardiac function, inflammation, and oxidation biomarkers, and on the ratio of two plasma ceramides, Cer d18:1 (4E) (1OH, 3OH)/24:0 and Cer d18:1 (4E) (1OH, 3OH)/16:0 (i.e., "C24:0/C16:0"), which is associated with decreased risk of cardiac dysfunction and heart failure. Fenofibrate lowered plasma TG and cholesterol but did not improve heart systolic or diastolic function. Fenofibrate treatment lowered the plasma C24:0/C16:0 ceramide ratio and minimally altered oxidative stress markers but did not alter measures of inflammation. Overall, plasma TG lowering correlated with improvement of cardiac relaxation (diastolic function) as measured by tissue Doppler-derived parameter e'. Moreover, lowering the plasma C24:0/C16:0 ceramide ratio was correlated with worse diastolic function. These findings indicate that fenofibrate treatment per se is not sufficient to effect changes in cardiac function; however, decreases in plasma TG may be linked to improved diastolic function. In contrast, decreases in plasma C24:0/C16:0 are linked with worsening cardiac function.

Long-term LVEF trajectories in patients with type 2 diabetes and heart failure: diabetic cardiomyopathy may underlie functional decline

Background

Left ventricular ejection fraction (LVEF) trajectories and functional recovery with current heart failure (HF) management is increasingly recognized. Type 2 diabetes mellitus (T2D) leads to a worse prognosis in HF patients. However, it is unknown whether T2D interferes with LVEF trajectories. The aim of this study was to prospectively assess very long-term (up to 15 years) LVEF trajectories in patients with and without T2D and underlying HF.

Methods

Ambulatory patients admitted to a multidisciplinary HF clinic were prospectively evaluated by scheduled two-dimensional echocardiography at baseline, 1 year, and then every 2 years afterwards, up to 15 years. Statistical analyses of LVEF change with time were performed using the linear mixed effects (LME) models, and locally weighted error sum of squares (Loess) curves were plotted.

Results

Of the 1921 patients, 461 diabetic and 699 non-diabetic patients with LVEF < 50% were included in the study. The mean number of echocardiography measurements performed in diabetic patients was 3.3 ± 1.6. Early LVEF recovery was similar in diabetic and non-diabetic patients, but Loess curves showed a more pronounced inverted U shape in diabetics with a more pronounced decline after 9 years. LME analysis showed a statistical interaction between T2D and LVEF trajectory over time (p = 0.009), which was statistically significant in patients with ischemic etiologies (p < 0.001). Other variables that showed an interaction between LVEF trajectories and T2D were male sex (p = 0.04) and HF duration (p = 0.008).

Conclusions

LVEF trajectories in T2D patients with depressed systolic function showed a pronounced inverted U shape with a marked decline after 9 years. Diabetic cardiomyopathy may underlie the functional decline observed.

Strategies of Unloading the Failing Heart from Metabolic Stress

We propose a unifying perspective of heart failure in patients with type 2 diabetes mellitus. The reasoning is as follows: cellular responses to fuel overload include dysregulated insulin signaling, impaired mitochondrial respiration, reactive oxygen species formation, and the accumulation of certain metabolites, collectively termed glucolipotoxicity. As a consequence, cardiac function is impaired, with intracellular calcium cycling and diastolic dysfunction as an early manifestation. In this setting, increasing glucose uptake by insulin or insulin sensitizing agents only worsens the disrupted fuel homeostasis of the heart. Conversely, restricting fuel supply by means of caloric restriction, surgical intervention, or certain pharmacologic agents will improve cardiac function by restoring metabolic homeostasis. The concept is borne out by clinical interventions, all of which unload the heart from metabolic stress.

Cardiac ketone body metabolism

The ketone bodies, d-β-hydroxybutyrate and acetoacetate, are soluble 4-carbon compounds derived principally from fatty acids, that can be metabolised by many oxidative tissues, including heart, in carbohydrate-depleted conditions as glucose-sparing energy substrates. They also have important signalling functions, acting through G-protein coupled receptors and histone deacetylases to regulate metabolism and gene expression including that associated with anti-oxidant activity. Their concentration, and hence availability, increases in diabetes mellitus and heart failure. Whilst known to be substrates for ATP production, especially in starvation, their role(s) in the heart, and in heart disease, is uncertain. Recent evidence, reviewed here, indicates that increased ketone body metabolism is a feature of heart failure, and is accompanied by other changes in substrate selection. Whether the change in myocardial ketone body metabolism is adaptive or maladaptive is unknown, but it offers the possibility of using exogenous ketones to treat the failing heart.

Positioning Metabolism as a Central Player in the Diabetic Heart

In type 2 diabetes (T2D), the leading cause of death is cardiovascular complications. One mechanism contributing to cardiac pathogenesis is alterations in metabolism, with the diabetic heart exhibiting increased fatty acid oxidation and reduced glucose utilisation. The processes classically thought to underlie this metabolic shift include the Randle cycle and changes to gene expression. More recently, alternative mechanisms have been proposed, most notably, changes in post-translational modification of mitochondrial proteins in the heart. This increased understanding of how metabolism is altered in the diabetic heart has highlighted new therapeutic targets, with an aim to improve cardiac function in T2D. This review focuses on metabolism in the healthy heart and how this is modified in T2D, providing evidence for the mechanisms underlying this shift. There will be emphasis on the current treatments for the heart in diabetes, alongside efforts for metabocentric pharmacological therapies.

Involvement of Heparanase in Endothelial Cell-Cardiomyocyte Crosstalk

Traditionally, the management of diabetes has focused mainly on controlling high blood glucose levels. Unfortunately, despite valiant efforts to normalize this blood glucose, poor medication management predisposes these patients to heart failure. Following diabetes, how the heart utilizes different sources of fuel for energy is key to the development of heart failure. The diabetic heart switches from using both glucose and fats, to predominately using fats as an energy resource for maintaining its activities. This transformation to using fats as an exclusive source of energy is helpful in the initial stages of the disease and is tightly controlled. However, over the progression of diabetes, there is a loss of this controlled supply and use of fats, which ultimately has terrible consequences since the uncontrolled use of fats produces toxic by-products which weaken heart function and cause heart disease. Heparanase is a key player that directs how much fats are provided to the heart and does so in association with several partners like LPL and VEGFs. Together, they regulate the amount of fats supplied, and their subsequent breakdown to provide energy. Following diabetes, there is a disruption in this network resulting in fat oversupply and cell death. Understanding how the heparanase-LPL-VEGFs "ensemble" cooperates, and its dysfunction in the diabetic heart would be useful in restoring metabolic equilibrium and limiting diabetes-related cardiac damage.

The Role of Diabetes Mellitus in Diseases of the Gallbladder and Biliary Tract

BACKGROUND

The increasing prevalence of diabetes mellitus worldwide continues to pose a heavy burden. Though its gastrointestinal impact is appropriately recognized, the lesser known associations may be overlooked.

OBJECTIVE

We aim to review the negative implications of diabetes on the gallbladder and the biliary tract.

METHODS

A MEDLINE® database search of literature was conducted with emphasis on the previous five years, combining keywords such as "diabetes," "gallbladder," and "biliary".

RESULTS

The association of diabetes to the formation of gallstones, gallbladder cancer, and cancer of the biliary tract are discussed along with diagnosis and treatment.

CONCLUSION

Though we uncover the role of diabetic neuropathy in gallbladder and biliary complications, the specific individual diabetic risk factors behind these developments is unclear. Also, in addition to diabetes control and surgical gallbladder management, the treatment approach also requires further focus.

Mechanisms of Protective Effects of SGLT2 Inhibitors in Cardiovascular Disease and Renal Dysfunction

Type 2 diabetes mellitus is one of the most common forms of the disease worldwide. Hyperglycemia and insulin resistance play key roles in type 2 diabetes mellitus. Renal glucose reabsorption is an essential feature in glycaemic control. Kidneys filter 160 g of glucose daily in healthy subjects under euglycaemic conditions. The expanding epidemic of diabetes leads to a prevalence of diabetes-related cardiovascular disorders, in particular, heart failure and renal dysfunction. Cellular glucose uptake is a fundamental process for homeostasis, growth, and metabolism. In humans, three families of glucose transporters have been identified, including the glucose facilitators GLUTs, the sodium-glucose cotransporter SGLTs, and the recently identified SWEETs. Structures of the major isoforms of all three families were studied. Sodium-glucose cotransporter (SGLT2) provides most of the capacity for renal glucose reabsorption in the early proximal tubule. A number of cardiovascular outcome trials in patients with type 2 diabetes have been studied with SGLT2 inhibitors reducing cardiovascular morbidity and mortality. The current review article summarises these aspects and discusses possible mechanisms with SGLT2 inhibitors in protecting heart failure and renal dysfunction in diabetic patients. Through glucosuria, SGLT2 inhibitors reduce body weight and body fat, and shift substrate utilisation from carbohydrates to lipids and, possibly, ketone bodies. These pleiotropic effects of SGLT2 inhibitors are likely to have contributed to the results of the EMPA-REG OUTCOME trial in which the SGLT2 inhibitor, empagliflozin, slowed down the progression of chronic kidney disease and reduced major adverse cardiovascular events in high-risk individuals with type 2 diabetes. This review discusses the role of SGLT2 in the physiology and pathophysiology of renal glucose reabsorption and outlines the unexpected logic of inhibiting SGLT2 in the diabetic kidney.

Diabetic cardiomyopathy: Pathophysiology, theories and evidence to date

The prevalence of type 2 diabetes (T2D) has increased worldwide and doubled over the last two decades. It features among the top 10 causes of mortality and morbidity in the world. Cardiovascular disease is the leading cause of complications in diabetes and within this, heart failure has been shown to be the leading cause of emergency admissions in the United Kingdom. There are many hypotheses and well-evidenced mechanisms by which diabetic cardiomyopathy as an entity develops. This review aims to give an overview of these mechanisms, with particular emphasis on metabolic inflexibility. T2D is associated with inefficient substrate utilisation, an inability to increase glucose metabolism and dependence on fatty acid oxidation within the diabetic heart resulting in mitochondrial uncoupling, glucotoxicity, lipotoxicity and initially subclinical cardiac dysfunction and finally in overt heart failure. The review also gives a concise update on developments within clinical imaging, specifically cardiac magnetic resonance studies to characterise and phenotype early cardiac dysfunction in T2D. A better understanding of the pathophysiology involved provides a platform for targeted therapy in diabetes to prevent the development of early heart failure with preserved ejection fraction.

The Potential Role of Undercarboxylated Osteocalcin Upregulation in Microvascular Insufficiency in a Rat Model of Diabetic Cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) is accompanied by microvascular complications that lead to myocardial dysfunction and heart failure. Most conventional therapies cannot ameliorate the microvascular insufficiency in DCM. In this study, we tested the hypothesis that undercarboxylated osteocalcin (ucOC) may be a new adjuvant therapy against the progression of DCM and its underlying microvascular pathology.

MATERIALS AND METHODS

Diabetes was induced in Wistar rats with a high-fat diet combined with streptozotocin injections, and ucOC was upregulated after warfarin administration in the treated group. After 8 weeks, cardiac functions were assessed using a Langendorff apparatus. Cardiac tissue samples were also extracted to assess the ucOC receptor and vascular endothelial growth factor (VEGF) for histopathological studies.

RESULTS

Both the systolic and the diastolic dysfunction observed in the DCM group were significantly improved after the increase in ucOC blood levels. Significant improvement in VEGF and CD31 expression after warfarin injection was associated with increased capillary density, neovascularization, and decreased myocardial fibrosis together with the reestablishment of myocardial structural and ultrastructural patterns.

CONCLUSION

Undercarboxylated osteocalcin may have a promising effect in improving microvascular insufficiency and myocardial dysfunction in DCM.

Carbonic anhydrase II/sodium-proton exchanger 1 metabolon complex in cardiomyopathy of ob-/- type 2 diabetic mice

Heart failure is the leading cause of death among diabetic people. Cellular and molecular entities leading to diabetic cardiomyopathy are, however, poorly understood. Coupling of cardiac carbonic anhydrase II (CAII) and Na⁺/H⁺ exchanger 1 (NHE1) to form a transport metabolon was analyzed in obese type 2 diabetic mice (ob^-/-) and control heterozygous littermates (ob^+/-). Echocardiography showed elevated systolic interventricular septum thickness and systolic posterior wall thickness in ob^-/- mice at 9 and 16 weeks. ob^-/- mice showed increased left ventricular (LV) weight/tibia length ratio and increased cardiomyocyte cross sectional area as compared to controls, indicating cardiac hypertrophy. Immunoblot analysis showed increased CAII expression in LV samples of ob^-/-vs. ob^+/- mice, and augmented Ser⁷⁰³ phosphorylation on NHE1 in ob^-/- hearts. Reciprocal co-immunoprecipitation analysis showed strong association of CAII and NHE1 in LV samples of ob^-/- mice. NHE1-dependent rate of intracellular pH (pH_i) normalization after transient acid loading of isolated cardiomyocytes was higher in ob^-/- mice vs. ob^+/-. NHE transport activity was also augmented in cultured H9C2 rat cardiomyoblasts treated with high glucose/high palmitate, and it was normalized after CA inhibition. We conclude that the NHE1/CAII metabolon complex is exacerbated in diabetic cardiomyopathy of ob^-/- mice, which may lead to perturbation of pH_i and [Na⁺] and [Ca²⁺] handling in these diseased hearts.

Cardiomyopathy Associated with Diabetes: The Central Role of the Cardiomyocyte

The term diabetic cardiomyopathy (DCM) labels an abnormal cardiac structure and performance due to intrinsic heart muscle malfunction, independently of other vascular co-morbidity. DCM, accounting for 50%–80% of deaths in diabetic patients, represents a worldwide problem for human health and related economics. Optimal glycemic control is not sufficient to prevent DCM, which derives from heart remodeling and geometrical changes, with both consequences of critical events initially occurring at the cardiomyocyte level. Cardiac cells, under hyperglycemia, very early undergo metabolic abnormalities and contribute to T helper (Th)-driven inflammatory perturbation, behaving as immunoactive units capable of releasing critical biomediators, such as cytokines and chemokines. This paper aims to focus onto the role of cardiomyocytes, no longer considered as “passive” targets but as “active” units participating in the inflammatory dialogue between local and systemic counterparts underlying DCM development and maintenance. Some of the main biomolecular/metabolic/inflammatory processes triggered within cardiac cells by high glucose are overviewed; particular attention is addressed to early inflammatory cytokines and chemokines, representing potential therapeutic targets for a prompt early intervention when no signs or symptoms of DCM are manifesting yet. DCM clinical management still represents a challenge and further translational investigations, including studies at female/male cell level, are warranted.

Effects of Exercise to Improve Cardiovascular Health

Obesity is a complex disease that affects whole body metabolism and is associated with an increased risk of cardiovascular disease (CVD) and Type 2 diabetes (T2D). Physical exercise results in numerous health benefits and is an important tool to combat obesity and its co-morbidities, including cardiovascular disease. Exercise prevents both the onset and development of cardiovascular disease and is an important therapeutic tool to improve outcomes for patients with cardiovascular disease. Some benefits of exercise include enhanced mitochondrial function, restoration and improvement of vasculature, and the release of myokines from skeletal muscle that preserve or augment cardiovascular function. In this review we will discuss the mechanisms through which exercise promotes cardiovascular health.

Possibility of a New Therapeutic Strategy for Left Ventricular Dysfunction in Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) substantially increases the risk of cardiovascular events, including heart failure (HF), due to complications such as hypertension, obesity and dyslipidemia based on metabolic syndrome, which plays the central pathological role in HF. A reason is that T2DM causes left ventricular (LV) diastolic dysfunction beginning in the early phase of the disease, which in turn increases the risk of development of HF independently of the control of blood glucose levels, blood pressure or the presence of coronary artery diseases. Intracellular metabolic disorders and increased oxidative stress due to hyperglycemia, increased insulin resistance and chronic inflammation are pathogenic mechanisms involved in the LV diastolic dysfunction caused by T2DM. These mechanisms lead to structural changes in the heart such as LV hypertrophy and interstitial fibrosis, resulting in HF. The prevalence of HF with preserved ejection fraction (HFpEF), the major pathology of LV diastolic dysfunction, has been increasing recently, and a high incidence of HFpEF in patients with T2DM was reported. An effective therapy has not been established for HFpEF because multiple comorbidities such as advanced age, hypertension, obesity, dyslipidemia, chronic kidney disease and atrial fibrillation as well as diabetes are involved in its pathology. In the present review, we review the involvement of associated conditions such as hypertension, obesity and advanced age from the aspect of the T2DM and LV diastolic dysfunction and discuss the possibility of the development of a new therapeutic strategy for LV diastolic dysfunction and HFpEF.

Metabolic Effects of Metformin in the Failing Heart

Accumulating evidence shows that metformin is an insulin-sensitizing antidiabetic drug widely used in the treatment of type 2 diabetes mellitus (T2DM), which can exert favorable effects on cardiovascular risk and may be safely used in patients with heart failure (HF), and even able to reduce the incidence of HF and to reduce HF mortality. In failing hearts, metformin improves myocardial energy metabolic status through the activation of AMP (adenosine monophosphate)-activated protein kinase (AMPK) and the regulation of lipid and glucose metabolism. By increasing nitric oxide (NO) bioavailability, limiting interstitial fibrosis, reducing the deposition of advanced glycation end-products (AGEs), and inhibiting myocardial cell apoptosis metformin reduces cardiac remodeling and hypertrophy, and thereby preserves left ventricular systolic and diastolic functions. While a lot of preclinical and clinical studies showed the cardiovascular safety of metformin therapy in diabetic patients and HF, to confirm observed benefits, the specific large-scale trials configured for HF development in diabetic patients as a primary endpoints are necessary.

Myocyte [Na+]i Dysregulation in Heart Failure and Diabetic Cardiomyopathy

By controlling the function of various sarcolemmal and mitochondrial ion transporters, intracellular Na⁺ concentration ([Na⁺]_i) regulates Ca²⁺ cycling, electrical activity, the matching of energy supply and demand, and oxidative stress in cardiac myocytes. Thus, maintenance of myocyte Na⁺ homeostasis is vital for preserving the electrical and contractile activity of the heart. [Na⁺]_i is set by the balance between the passive Na⁺ entry through numerous pathways and the pumping of Na⁺ out of the cell by the Na⁺/K⁺-ATPase. This equilibrium is perturbed in heart failure, resulting in higher [Na⁺]_i. More recent studies have revealed that [Na⁺]_i is also increased in myocytes from diabetic hearts. Elevated [Na⁺]_i causes oxidative stress and augments the sarcoplasmic reticulum Ca²⁺ leak, thus amplifying the risk for arrhythmias and promoting heart dysfunction. This mini-review compares and contrasts the alterations in Na⁺ extrusion and/or Na⁺ uptake that underlie the [Na⁺]_i increase in heart failure and diabetes, with a particular emphasis on the emerging role of Na⁺ - glucose cotransporters in the diabetic heart.

Streptozotocin-induced type II diabetic rat administered with nonobesogenic high-fat diet is highly susceptible to myocardial ischemia-reperfusion injury: An insight into the function of mitochondria

RATIONALE

Our recent study suggested that ischemia-reperfusion (I/R) induced oxidative stress was minimal in the rat heart during initial stage of diabetes and the one that progressed to diabetic cardiomyopathy (DCM), despite having higher infarct and low cardiac performance. Mitochondrial dysfunction is an important mediator for adverse outcome in rat heart affected with diabetes, which is also a potential contributor for the cardiac reperfusion injury.

OBJECTIVE

The current study aims to evaluate the susceptibility of diabetes heart with or without myopathy to I/R injury and its influence on cardiac mitochondrial function.

METHODS AND RESULTS

Male Wistar rats (3 weeks old) were fed with high-fat diet for 8 weeks followed by diabetes mellitus (DM) induction via streptozotocin (35 mg/kg body weight) and maintained for further 4 weeks. The animal displayed cardiomyopathy characteristics like hypertrophy, fibrosis, and insulin resistance-termed diabetic cardiomyopathy (DCM). To study the specific effect of DCM on I/R, we included diabetic rats without cardiomyopathy. Induction of I/R in different groups suggested higher vulnerability to injury in DCM rat hearts than DM and normal (measured via hemodynamics, triphenyltetrazolium chloride stain, and apoptotic markers). Mitochondrial function at the subpopulation level was evaluated with respect to adenosine triphosphate (ATP) concentration, membrane potential, swelling behavior, and oxidative stress, wherein the results confirmed I/R-induced mitochondrial dysfunction. Unlike normal heart, DM, and DCM heart challenged to I/R exhibited altered ATP producing capacity among subsarcolemmal and interfibrillar mitochondria.

CONCLUSION

The above results suggest that mitochondrial changes associated with diabetes and cardiomyopathy significantly contribute to the adverse outcome of I/R injury.

Chronic heart failure in patients with nonalcoholic fatty liver disease: prevalence, clinical features, and relevance

Objective This study was performed to assess the prevalence of nonalcoholic fatty liver (NAFL) in patients with symptomatic congestive heart failure (CHF) and compare the clinical features with those of patients without NAFL. Methods In total, 102 patients with CHF were divided into NAFL and non-NAFL groups according to their hepatic ultrasonography findings. All patients underwent transthoracic echocardiography and cardiac magnetic resonance examination. Follow-up was performed for major cardiovascular events (MACE) and readmission due to heart failure at 1, 3, 6, and 12 months after the index hospitalization. Results NAFL was detected in 37 of 102 patients (36.27%). Compared with the non-NAFL group, patients with NAFL were younger, had a higher body mass index and left ventricular (LV) mass index, and had more severe fibrosis. MACE and readmission occurred in 15 patients in the NAFL group and 29 patients in the non-NAFL group, without a significant difference. Linear regression analysis revealed that after adjusting for confounders, NAFL was independently associated with the LV fibrosis size and the ratio of the LV fibrosis size to the LV mass index. Conclusions NAFL is present in more than one-third of patients with CHF and is associated with the severity of LV fibrosis.

[At the heart of diabetic cardiomyopathy: Bscl2 knockout mice to investigate glucotoxicity]

Type 2 diabetes mellitus (T2DM) is a well-recognized independent risk factor for heart failure (HF). T2DM is associated with altered cardiac energy metabolism, leading to ectopic lipid accumulation and glucose overload. However, the relative contribution of these two parameters remains unclear. In order to get new insight into the mechanism involved in diabetic cardiomyopathy, the cardiac phenotype of a unique T2DM mice model has been performed: the seipin knockout mice (SKO). Cardiac phenotyping revealed a diastolic dysfunction associated with hyperglycemia in these mice with a chronic activation of the hexosamine biosynthetic pathway (HBP), suggesting a glucose overload. An inhibitor of the renal sodium/glucose cotransporter 2 (SGLT2), dapagliflozin, successfully prevented the development of cardiomyopathy in SKO mice. This is particularly relevant, given that SGLT2i treatment reduces cardiovascular event in T2DM patients. Therefore, glucose lowering appears an important therapeutic target to prevent cardiac dysfunction associated with T2DM.

Diabetes-related cardiomyopathy: The sweet story of glucose overload from epidemiology to cellular pathways

Type 2 diabetes (T2D) is a major risk factor for heart failure (HF). Although the number of cases of myocardial infarction in the T2D population has been reduced by 25% over the last 10 years, the incidence of HF is continuously increasing, making it the most worrying diabetes complication. This strongly reinforces the urgent need for innovative therapeutic interventions to prevent cardiac dysfunction in T2D patients. To this end, epidemiological, imaging and animal studies have aimed to highlight the mechanisms involved in the development of diabetic cardiomyopathy. Epidemiological observations clearly show that hyperglycaemia correlates with severity of cardiac dysfunction and mortality in T2D patients. Both animal and cellular studies have demonstrated that, in the context of diabetes, the heart loses its ability to utilize glucose, therefore leading to glucose overload in cardiomyocytes that, in turn, promotes oxidative stress, accumulation of advanced glycation end-products (AGEs) and chronic activation of the hexosamine pathway. These have all been found to activate apoptosis and to alter heart contractility, calcium signalling and mitochondrial function. Although, in the past, tight glycaemic control has failed to improve cardiac function in T2D patients, recent clinical trials have reported cardiovascular benefit with hypoglycaemic antidiabetic drugs of the SGLT2-inhibitor family. This review, based on clinical evidence from mechanistic studies as well as several large clinical trials, covers 15 years of research, and strongly supports the idea that hyperglycaemia and glucose overload play a central role in the pathophysiology of diabetic cardiomyopathy.

SGLT2 Inhibitors and Cardiovascular Outcomes: Current Perspectives and Future Potentials

PURPOSE OF REVIEW

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have been shown to exert benefit on cardiac outcomes. In this review, we provide updates on available clinical data, studies on potential mechanisms for the CV effects, as well as discuss potential clinical implications of these new findings.

RECENT FINDINGS

Since the publications of the EMPA-REG and CANVAS trials, large multi-national cohort studies have further shown the cardioprotective effects of SGLT2i. Moreover, new studies examining SGLT2i action on sodium-hydrogen exchanger proteins in both the heart and the kidney, on myocardial energetics and impact on inflammation and atherosclerosis continue to shed light on the multitude of pleotropic effects of these agents. Though more data is needed to substantiate the safety and efficacy, SGLT2i should be considered as a valuable therapy to help reduce CV risk in patients with diabetes. Ultimately, SGLT2i may have utility in preventing progression to diabetes or providing CV protection in patients who do not have diabetes.

The Impact of Type 2 Diabetes Mellitus on Long-Term Prognosis in Patients of Different Ages with Myocardial Infarction

The objective of the study was to assess the impact of DM2 at baseline on long-term mortality after acute myocardial infarction (MI) among different age groups. The data were taken from: "Register of Acute Myocardial Infarction." A total of 862 patients were followed for five years after acute myocardial infarction. The primary endpoint was death from any cause. The patients were categorized into 2 groups based on their ages: group 1-comprised patients older than working age (n = 358) and group 2-comprised employable patients (n = 504). A total of 208 patients were diagnosed with both cardiovascular disease and DM2. Elderly patients with DM2 had worse prognosis and increased five-year mortality compared with patients of the same age group without DM2. Statistically significant differences in long-term outcomes were found in adult patients (p = 0.004) only in group with longer duration of diabetes, unlike the group with DM2 onset. In conclusion, Type 2 DM increased 5-year mortality rate of elderly patients with myocardial infarction. However, younger patients with both myocardial infarction and DM2 had more complications in the early post-MI period compared with patients of the same age group without DM2 but did not show any statistically significant differences in the long-term outcome.