Abnormal cardiac and skeletal muscle energy metabolism in patients with type 2 diabetes

Quantitative Assessment of Peripheral Oxidative Metabolism With a New Dynamic 1H MRI Technique: A Pilot Study in People With and Without Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is linked to impaired mitochondrial function. Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is a gadolinium-contrast-free 1H method to assess mitochondrial function by measuring low-concentration metabolites. A CEST MRI-based technique may serve as a non-invasive proxy for assessing mitochondrial health.

HYPOTHESIS

A 1H CEST MRI technique may detect significant differences in in vivo skeletal muscle phosphocreatine (SMPCr) kinetics between healthy volunteers and T2DM patients undergoing standardized isometric exercise.

STUDY TYPE

Cross-sectional study.

SUBJECTS

Seven subjects without T2DM (T2DM-) and seven age, sex, and BMI-matched subjects with T2DM (T2DM+).

FIELD STRENGTH/SEQUENCE

Single-shot rapid acquisition with refocusing echoes (RARE) and single-shot gradient-echo sequences, 3 T.

ASSESSMENT

Subjects underwent a rest-exercise-recovery imaging protocol to dynamically acquire SMPCr maps in calf musculature. Medial gastrocnemius (MG) and soleus SMPCr concentrations were plotted over time, and SMPCr recovery time, τ , was determined. Mitochondrial function index was calculated as the ratio of resting SMPCr to τ . Participants underwent a second exercise protocol for imaging of skeletal muscle blood flow (SMBF), and its association with SMPCr was assessed.

STATISTICAL TESTS

Unpaired t-tests and Pearson correlation coefficient. A P value <0.05 was considered statistically significant.

RESULTS

SMPCr concentrations in MG and soleus displayed expected declines during exercise and returns to baseline during recovery. τ was significantly longer in the T2DM+ cohort (MG 83.5 ± 25.8 vs. 54.0 ± 21.1, soleus 90.5 ± 18.9 vs. 51.2 ± 14.5). The mitochondrial function index in the soleus was significantly lower in the T2DM+ cohort (0.33 ± 0.08 vs. 0.66 ± 0.19). SMBF was moderately correlated with the SMPCr in T2DM-; this correlation was not significant in T2DM+ (r = -0.23, P = 0.269).

CONCLUSION

The CEST MRI method is feasible for quantifying SMPCr in peripheral muscle tissue. T2DM+ individuals had significantly lower oxidative capacities than T2DM- individuals. In T2DM, skeletal muscle metabolism appeared to be decoupled from perfusion.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

Reciprocal Regulation of Cardiac β-Oxidation and Pyruvate Dehydrogenase by Insulin

The heart alters the rate and relative oxidation of fatty acids and glucose based on availability and energetic demand. Insulin plays a crucial role in this process diminishing fatty acid and increasing glucose oxidation when glucose availability increases. Loss of insulin sensitivity and metabolic flexibility can result in cardiovascular disease. It is therefore important to identify mechanisms by which insulin regulates substrate utilization in the heart. Mitochondrial pyruvate dehydrogenase (PDH) is the key regulatory site for the oxidation of glucose for ATP production. Nevertheless, the impact of insulin on PDH activity has not been fully delineated, particularly in the heart. We sought in vivo evidence that insulin stimulates cardiac PDH and that this process is driven by inhibition of fatty acid oxidation. Mice injected with insulin exhibited dephosphorylation and activation of cardiac PDH. This was accompanied by an increase in the content of malonyl-CoA, an inhibitor of carnitine palmitoyltransferase 1 (CPT1) and, thus, mitochondrial import of fatty acids. Administration of the CPT1 inhibitor oxfenicine was sufficient to activate PDH. Malonyl-CoA is produced by acetyl-CoA carboxylase (ACC). Pharmacologic inhibition or knockout of cardiac ACC diminished insulin-dependent production of malonyl-CoA and activation of PDH. Finally, circulating insulin and cardiac glucose utilization exhibit daily rhythms reflective of nutritional status. We demonstrate that time of day-dependent changes in PDH activity are mediated, in part, by ACC-dependent production of malonyl-CoA. Thus, by inhibiting fatty acid oxidation, insulin reciprocally activates PDH. These studies identify potential molecular targets to promote cardiac glucose oxidation and treat heart disease.

Association between Obesity and Atrial Function in Patients with Non-Valvular Atrial Fibrillation: An Echocardiographic Study

Background: Obesity is a public health problem which prevalence has increased worldwide and is associated with different degrees of hemodynamic alterations and structural cardiac changes. The aim of the study is to investigate the impact of body mass index (BMI) on left atrial function using standard and advanced echocardiography in a population of patients with non-valvular atrial fibrillation (AF). Methods: 395 adult patients suffering from non-valvular AF, divided into three tertiles based on BMI value, carry out a cardiological examination with standard and advanced echocardiography. Results: Peak atrial longitudinal strain (PALS), a measure of left atrial function, is lower in the tertile with highest BMI (14.3 ± 8.2%) compared to both the first (19 ± 11.5%) and the second tertile (17.7 ± 10.6%) in a statistically significant manner (p < 0.002). Furthermore, BMI is significantly associated independent with the PALS by multilinear regression analysis, even after correction of the data for CHA2DS2-VASc score, left ventricular mass index, left ventricular ejection fraction, E/E' ratio and systolic pulmonary arterial pressure (coefficient standardized β = -0.127, p < 0.02; Cumulative R2 = 0.41, SEE = 0.8%, p < 0.0001). Conclusions: BMI could be considered an additional factor in assessing cardiovascular risk in patients with non-valvular atrial fibrillation, in addition to the well-known CHA2DS2-VASc score.

Pathophysiology and Advances in the Therapy of Cardiomyopathy in Patients with Diabetes Mellitus

Diabetes mellitus (DM) is known as the first non-communicable global epidemic. It is estimated that 537 million people have DM, but the condition has been properly diagnosed in less than half of these patients. Despite numerous preventive measures, the number of DM cases is steadily increasing. The state of chronic hyperglycaemia in the body leads to numerous complications, including diabetic cardiomyopathy (DCM). A number of pathophysiological mechanisms are behind the development and progression of cardiomyopathy, including increased oxidative stress, chronic inflammation, increased synthesis of advanced glycation products and overexpression of the biosynthetic pathway of certain compounds, such as hexosamine. There is extensive research on the treatment of DCM, and there are a number of therapies that can stop the development of this complication. Among the compounds used to treat DCM are antiglycaemic drugs, hypoglycaemic drugs and drugs used to treat myocardial failure. An important element in combating DCM that should be kept in mind is a healthy lifestyle-a well-balanced diet and physical activity. There is also a group of compounds-including coenzyme Q10, antioxidants and modulators of signalling pathways and inflammatory processes, among others-that are being researched continuously, and their introduction into routine therapies is likely to result in greater control and more effective treatment of DM in the future. This paper summarises the latest recommendations for lifestyle and pharmacological treatment of cardiomyopathy in patients with DM.

Redefining Diabetic Cardiomyopathy: Perturbations in Substrate Metabolism at the Heart of Its Pathology

Cardiovascular disease represents the leading cause of death in people with diabetes, most notably from macrovascular diseases such as myocardial infarction or heart failure. Diabetes also increases the risk of a specific form of cardiomyopathy, referred to as diabetic cardiomyopathy (DbCM), originally defined as ventricular dysfunction in the absence of underlying coronary artery disease and/or hypertension. Herein, we provide an overview on the key mediators of DbCM, with an emphasis on the role for perturbations in cardiac substrate metabolism. We discuss key mechanisms regulating metabolic dysfunction in DbCM, with additional focus on the role of metabolites as signaling molecules within the diabetic heart. Furthermore, we discuss the preclinical approaches to target these perturbations to alleviate DbCM. With several advancements in our understanding, we propose the following as a new definition for, or approach to classify, DbCM: "diastolic dysfunction in the presence of altered myocardial metabolism in a person with diabetes but absence of other known causes of cardiomyopathy and/or hypertension." However, we recognize that no definition can fully explain the complexity of why some individuals with DbCM exhibit diastolic dysfunction, whereas others develop systolic dysfunction. Due to DbCM sharing pathological features with heart failure with preserved ejection fraction (HFpEF), the latter of which is more prevalent in the population with diabetes, it is imperative to determine whether effective management of DbCM decreases HFpEF prevalence.

ARTICLE HIGHLIGHTS

3D ultra-short echo time 31P-MRSI with rosette k-space pattern: Feasibility and comparison with conventional weighted CSI

Phosphorus-31 magnetic resonance spectroscopic imaging (31P-MRSI) provides valuable non-invasive in vivo information on tissue metabolism but is burdened by poor sensitivity and prolonged scan duration. Ultra-short echo time (UTE) acquisitions minimize signal loss when probing signals with relatively short spin-spin relaxation time (T2), while also preventing first-order dephasing. Here, a three-dimensional (3D) UTE sequence with a rosette k-space trajectory is applied to 31P-MRSI at 3T. Conventional chemical shift imaging (CSI) employs highly regular Cartesian k-space sampling, susceptible to substantial artifacts when accelerated via undersampling. In contrast, this novel sequence's "petal-like" pattern offers incoherent sampling more suitable for compressed sensing (CS). These results showcase the competitive performance of UTE rosette 31P-MRSI against conventional weighted CSI with simulation, phantom, and in vivo leg muscle comparisons.

Robust dual-angle T 1 $$ {T}_1 $$ measurement in magnetization transfer spectroscopy by time-optimal control

Magnetization transfer spectroscopy relies heavily on the robust determination ofT 1 $$ {T}_1 $$ relaxation times of nuclei participating in metabolic exchange. Challenges arise due to the use of surface RF coils for transmission (highB 1 + $$ {B}_1^{+} $$ variation) and the broad resonance band of most X nuclei. These challenges are particularly pronounced when fastT 1 $$ {T}_1 $$ mapping methods, such as the dual-angle method, are employed. Consequently, in this work, we develop resonance offset andB 1 + $$ {B}_1^{+} $$ robust excitation RF pulses for 31P magnetization transfer spectroscopy at 7T through ensemble-based time-optimal control. In our approach, we introduce a cost functional for designing robust pulses, incorporating the full Bloch equations as constraints, which are solved using symmetric operator splitting techniques. The optimal control design of the RF pulses developed demonstrates improved accuracy, desired phase properties, and reduced RF power when applied to dual-angleT 1 $$ {T}_1 $$ mapping, thereby improving the precision of exchange-rate measurements, as demonstrated in a preclinical in vivo study quantifying brain creatine kinase activity.

Underlying mechanisms and cardioprotective effects of SGLT2i and GLP-1Ra: insights from cardiovascular magnetic resonance

Originally designed as anti-hyperglycemic drugs, Glucagon-Like Peptide-1 receptor agonists (GLP-1Ra) and Sodium-glucose cotransporter-2 inhibitors (SGLT2i) have demonstrated protective cardiovascular effects, with significant impact on cardiovascular morbidity and mortality. Despite several mechanisms have been proposed, the exact pathophysiology behind these effects is not yet fully understood. Cardiovascular imaging is key for the evaluation of diabetic patients, with an established role from the identification of early subclinical changes to long-term follow up and prognostic assessment. Among the different imaging modalities, CMR may have a key-role being the gold standard for volumes and function assessment and having the unique ability to provide tissue characterization. Novel techniques are also implementing the possibility to evaluate cardiac metabolism through CMR and thereby further increasing the potential role of the modality in this context. Aim of this paper is to provide a comprehensive review of changes in CMR parameters and novel CMR techniques applied in both pre-clinical and clinical studies evaluating the effects of SGLT2i and GLP-1Ra, and their potential role in better understanding the underlying CV mechanisms of these drugs.

A double-tuned 1 H/31 P coil for rabbit heart metabolism detection at 3 T

Magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS) employing proton nuclear resonance has emerged as a pivotal modality in clinical diagnostics and fundamental research. Nonetheless, the scope of MRI/MRS extends beyond protons, encompassing nonproton nuclei that offer enhanced metabolic insights. A notable example is phosphorus-31 (31 P) MRS, which provides valuable information on energy metabolites within the skeletal muscle and cardiac tissues of individuals affected by diabetes. This study introduces a novel double-tuned coil tailored for 1 H and 31 P frequencies, specifically designed for investigating cardiac metabolism in rabbits. The proposed coil design incorporates a butterfly-like coil for 31 P transmission, a four-channel array for 31 P reception, and an eight-channel array for 1 H reception, all strategically arranged on a body-conformal elliptic cylinder. To assess the performance of the double-tuned coil, a comprehensive evaluation encompassing simulations and experimental investigations was conducted. The simulation results demonstrated that the proposed 31 P transmit design achieved acceptable homogeneity and exhibited comparable transmit efficiency on par with a band-pass birdcage coil. In vivo experiments further substantiated the coil's efficacy, revealing that the rabbit with experimentally induced diabetes exhibited a lower phosphocreatine/adenosine triphosphate ratio compared with its normal counterpart. These findings emphasize the potential of the proposed coil design as a promising tool for investigating the therapeutic effects of novel diabetes drugs within the context of animal experimentation. Its capability to provide detailed metabolic information establishes it as an indispensable asset within this realm of research.

The role of empagliflozin-induced metabolic changes for cardiac function in patients with type 2 diabetes. A randomized cross-over magnetic resonance imaging study with insulin as comparator

BACKGROUND

Metabolic effects of empagliflozin treatment include lowered glucose and insulin concentrations, elevated free fatty acids and ketone bodies and have been suggested to contribute to the cardiovascular benefits of empagliflozin treatment, possibly through an improved cardiac function. We aimed to evaluate the influence of these metabolic changes on cardiac function in patients with T2D.

METHODS

In a randomized cross-over design, the SGLT2 inhibitor empagliflozin (E) was compared with insulin (I) treatment titrated to the same level of glycemic control in 17 patients with type 2 diabetes, BMI of > 28 kg/m2, C-peptide > 500 pM. Treatments lasted 5 weeks and were preceded by 3-week washouts (WO). At the end of treatments and washouts, cardiac diastolic function was determined with magnetic resonance imaging from left ventricle early peak-filling rate and left atrial passive emptying fraction (primary and key secondary endpoints); systolic function from left ventricle ejection fraction (secondary endpoint). Coupling between cardiac function and fatty acid concentrations, was studied on a separate day with a second scan after reduction of plasma fatty acids with acipimox. Data are Mean ± standard error. Between treatment difference (ΔT: E-I) and treatments effects (ΔE: E-WO or ΔI: I -WO) were evaluated using Students' t-test or Wilcoxon signed rank test as appropriate.

RESULTS

Glucose concentrations were similar, fatty acids, ketone bodies and lipid oxidation increased while insulin concentrations decreased on empagliflozin compared with insulin treatment. Cardiac diastolic and systolic function were unchanged by either treatment. Acipimox decreased fatty acids with 35% at all visits, and this led to reduced cardiac diastolic (ΔT: -51 ± 22 ml/s (p < 0.05); ΔE: -33 ± 26 ml/s (ns); ΔI: 37 ± 26 (ns, p < 0.05 vs ΔE)) and systolic function (ΔT: -3 ± 1% (p < 0.05); ΔE: -3 ± 1% (p < 0.05): ΔI: 1 ± 2 (ns, ns vs ΔE)) under chronotropic stress during empagliflozin compared to insulin treatment.

CONCLUSIONS

Despite significant metabolic differences, cardiac function did not differ on empagliflozin compared with insulin treatment. Impaired cardiac function during acipimox treatment, could suggest greater cardiac reliance on lipid metabolism for proper function during empagliflozin treatment in patients with type 2 diabetes.

TRIAL REGISTRATION

EudraCT 2017-002101-35, August 2017.

Targeting mitochondrial quality control for diabetic cardiomyopathy: Therapeutic potential of hypoglycemic drugs

Diabetic cardiomyopathy is a chronic cardiovascular complication caused by diabetes that is characterized by changes in myocardial structure and function, ultimately leading to heart failure and even death. Mitochondria serve as the provider of energy to cardiomyocytes, and mitochondrial dysfunction plays a central role in the development of diabetic cardiomyopathy. In response to a series of pathological changes caused by mitochondrial dysfunction, the mitochondrial quality control system is activated. The mitochondrial quality control system (including mitochondrial biogenesis, fusion and fission, and mitophagy) is core to maintaining the normal structure of mitochondria and performing their normal physiological functions. However, mitochondrial quality control is abnormal in diabetic cardiomyopathy, resulting in insufficient mitochondrial fusion and excessive fission within the cardiomyocyte, and fragmented mitochondria are not phagocytosed in a timely manner, accumulating within the cardiomyocyte resulting in cardiomyocyte injury. Currently, there is no specific therapy or prevention for diabetic cardiomyopathy, and glycemic control remains the mainstay. In this review, we first elucidate the pathogenesis of diabetic cardiomyopathy and explore the link between pathological mitochondrial quality control and the development of diabetic cardiomyopathy. Then, we summarize how clinically used hypoglycemic agents (including sodium-glucose cotransport protein 2 inhibitions, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, thiazolidinediones, metformin, and α-glucosidase inhibitors) exert cardioprotective effects to treat and prevent diabetic cardiomyopathy by targeting the mitochondrial quality control system. In addition, the mechanisms of complementary alternative therapies, such as active ingredients of traditional Chinese medicine, exercise, and lifestyle, targeting mitochondrial quality control for the treatment of diabetic cardiomyopathy are also added, which lays the foundation for the excavation of new diabetic cardioprotective drugs.

Endothelial dysfunction is associated with reduced myocardial mechano-energetic efficiency in drug-naïve hypertensive individuals

Impaired myocardial mechano-energetics efficiency (MEE) was shown to predict incident heart failure, but pathophysiological mechanisms linking impaired MEE with heart failure have not been elucidated. Endothelial dysfunction is a plausible candidate because it has been associated with heart failure. This study aims to investigate the association between MEE and endothelium-dependent vasodilation, among drug-naïve hypertensive individuals. 198 Drug-naïve hypertensive individuals participating in the CATAnzaro MEtabolic RIsk factors (CATAMERI) study were included. All participants underwent to an oral glucose tolerance test and to an echocardiogram for myocardial LVM-normalized mechano-energetic efficiency (MEEi) measurement. Endothelial-dependent and endothelial-independent vasodilatation were measured by strain-gauge plethysmography during intra-arterial infusion of acetylcholine and sodium nitroprusside, respectively. A multivariate linear regression analysis was conducted to investigate the independent association between maximal endothelial-dependent vasodilation and MEEi. Maximal ACh-stimulated forearm blood flow (FBF) was associated to decreased myocardial MEEi (β = 0.205, p = 0.002) independently of well-established cardiovascular risk factors including age, sex, BMI, waist circumference, smoking status, total and HDL cholesterol, triglycerides, hsCRP, glucose tolerance status, and HOMA-IR index of insulin resistance. Conversely, no association was observed between SNP-stimulated vasodilation and MEEi. Endothelium-mediated vasodilation may contribute to reduce myocardial MEEi independently of several potential confounders. Because diminished myocardial MEE has been previously associated with incident heart failure, a non-invasive assessment of myocardial MEEi may improve the identification of individuals at higher cardiovascular risk who may benefit from the initiation of pharmacological treatments ameliorating the endothelial dysfunction.

Dual roles of myocardial mitochondrial AKT on diabetic cardiomyopathy and whole body metabolism

BACKGROUND

The PI3K/AKT pathway transduces the majority of the metabolic actions of insulin. In addition to cytosolic targets, insulin-stimulated phospho-AKT also translocates to mitochondria in the myocardium. Mouse models of diabetes exhibit impaired mitochondrial AKT signaling but the implications of this on cardiac structure and function is unknown. We hypothesized that loss of mitochondrial AKT signaling is a critical step in cardiomyopathy and reduces cardiac oxidative phosphorylation.

METHODS

To focus our investigation on the pathophysiological consequences of this mitochondrial signaling pathway, we generated transgenic mouse models of cardiac-specific, mitochondria-targeting, dominant negative AKT1 (CAMDAKT) and constitutively active AKT1 expression (CAMCAKT). Myocardial structure and function were examined using echocardiography, histology, and biochemical assays. We further investigated the underlying effects of mitochondrial AKT1 on mitochondrial structure and function, its interaction with ATP synthase, and explored in vivo metabolism beyond the heart.

RESULTS

Upon induction of dominant negative mitochondrial AKT1, CAMDAKT mice developed cardiac fibrosis accompanied by left ventricular hypertrophy and dysfunction. Cardiac mitochondrial oxidative phosphorylation efficiency and ATP content were reduced, mitochondrial cristae structure was lost, and ATP synthase structure was compromised. Conversely, CAMCAKT mice were protected against development of diabetic cardiomyopathy when challenged with a high calorie diet. Activation of mitochondrial AKT1 protected cardiac function and increased fatty acid uptake in myocardium. In addition, total energy expenditure was increased in CAMCAKT mice, accompanied by reduced adiposity and reduced development of fatty liver.

CONCLUSION

CAMDAKT mice modeled the effects of impaired mitochondrial signaling which occurs in the diabetic myocardium. Disruption of this pathway is a key step in the development of cardiomyopathy. Activation of mitochondrial AKT1 in CAMCAKT had a protective role against diabetic cardiomyopathy as well as improved metabolism beyond the heart.

Metabolic Syndrome and C-reactive Protein are Associated With a Reduced Myocardial Mechano-energetic Efficiency

CONTEXT

Metabolic syndrome and elevated high-sensitivity C-reactive protein (hsCRP) levels are associated with risk of cardiovascular diseases. A reduced myocardial mechano-energetic efficiency (MEE) has been found to be an independent predictor of cardiovascular disease.

OBJECTIVE

To evaluate the association between metabolic syndrome and hsCRP levels with impaired MEE.

METHODS

Myocardial MEE was assessed by a validated echocardiography-derived measure in 1975 nondiabetic and prediabetic individuals subdivided into 2 groups according to the presence of metabolic syndrome.

RESULTS

Individuals with metabolic syndrome exhibited increased stroke work and myocardial oxygen consumption estimated by rate pressure product, and a reduced MEE per gram of left ventricular mass (MEEi) compared with subjects without metabolic syndrome, after adjusting for age and sex. Myocardial MEEi progressively decreased in parallel with the increase in the number of metabolic syndrome components. In a multivariable regression analysis, both metabolic syndrome and hsCRP contributed to reduced myocardial MEEi independently of sex, total cholesterol, high-density lipoprotein, triglycerides, fasting, and 2-hour postload glucose levels. When the study population was divided into 4 groups by the presence or absence of metabolic syndrome and by hsCRP levels above and below 3 mg/L, hsCRP levels ≥3 mg/L were associated with reduced myocardial MEEi both in subjects with metabolic syndrome and in those without the syndrome.

CONCLUSION

Nondiabetic and prediabetic individuals with metabolic syndrome exhibit increased stroke work and myocardial oxygen consumption, and an impaired MEEi, an established predictor of adverse cardiovascular events, and elevated hsCRP levels in combination with metabolic syndrome aggravate the myocardial MEEi impairment.

Gene-diet interaction analysis using novel weighted food scores discovers the adipocytokine signaling pathway associated with the development of type 2 diabetes

Introduction

The influence of dietary patterns measured using Recommended Food Score (RFS) with foods with high amounts of antioxidant nutrients for Type 2 diabetes (T2D) was analyzed. Our analysis aims to find associations between dietary patterns and T2D and conduct a gene-diet interaction analysis related to T2D.

Methods

Data analyzed in the current study were obtained from the Korean Genome and Epidemiology Study Cohort. The dietary patterns of 46 food items were assessed using a validated food frequency questionnaire. To maximize the predictive power of the RFS, we propose two weighted food scores, namely HisCoM-RFS calculated using the novel Hierarchical Structural Component model (HisCoM) and PLSDA-RFS calculated using Partial Least Squares-Discriminant Analysis (PLS-DA) method.

Results

Both RFS (OR: 1.11; 95% CI: 1.03- 1.20; P = 0.009) and PLSDA-RFS (OR: 1.10; 95% CI: 1.02-1.19, P = 0.011) were positively associated with T2D. Mapping of SNPs (P < 0.05) from the interaction analysis between SNPs and the food scores to genes and pathways yielded some 12 genes (CACNA2D3, RELN, DOCK2, SLIT3, CTNNA2, etc.) and pathways associated with T2D. The strongest association was observed with the adipocytokine signalling pathway, highlighting 32 genes (STAT3, MAPK10, MAPK8, IRS1, AKT1-3, ADIPOR2, etc.) most likely associated with T2D. Finally, the group of the subjects in low, intermediate and high using both the food scores and a polygenic risk score found an association between diet quality groups with issues at high genetic risk of T2D.

Conclusion

A dietary pattern of poor amounts of antioxidant nutrients is associated with the risk of T2D, and diet affects pathway mechanisms involved in developing T2D.

Skeletal Muscle Bioenergetics in Critical Limb Ischemia and Diabetes

INTRODUCTION

Mitochondrial dysfunction is implicated in the metabolic myopathy accompanying peripheral artery disease (PAD) and critical limb ischemia (CLI). Type-2 diabetes mellitus (T2DM) is a major risk factor for PAD development and progression to CLI and may also independently be related to mitochondrial dysfunction. We set out to determine the effect of T2DM in the relationship between CLI and muscle mitochondrial respiratory capacity and coupling control.

METHODS

We studied CLI patients undergoing revascularization procedures or amputation, and non-CLI patients with or without T2DM of similar age. Mitochondrial respiratory capacity and function were determined in lower limb permeabilized myofibers by high-resolution respirometry.

RESULTS

Fourteen CLI patients (65 ± 10y) were stratified into CLI patients with (n = 8) or without (n = 6) T2DM and were compared to non-CLI patients with (n = 18; 69 ± 5y) or without (n = 19; 71 ± 6y) T2DM. Presence of CLI but not T2DM had a marked impact on all mitochondrial respiratory states in skeletal muscle, adjusted for the effects of sex. Leak respiration (State 2, P < 0.025 and State 4o, P < 0.01), phosphorylating respiration (P < 0.001), and maximal respiration in the uncoupled state (P < 0.001), were all suppressed in CLI patients, independent of T2DM. T2DM had no significant effect on mitochondrial respiratory capacity and function in adults without CLI.

CONCLUSIONS

Skeletal muscle mitochondrial respiratory capacity was blunted by ∼35% in patients with CLI. T2DM was not associated with muscle oxidative capacity and did not moderate the relationship between muscle mitochondrial respiratory capacity and CLI.

Hidden chronic metabolic acidosis of diabetes type 2 (CMAD): Clues, causes and consequences

Interpretation of existing data revealed that chronic metabolic acidosis is a pathognomic feature for type 2 diabetes (T2D), which is described here as "chronic metabolic acidosis of T2D (CMAD)" for the first time. The biochemical clues for the CMAD are summarised in the following; low blood bicarbonate (high anionic gap), low pH of interstitial fluid and urine, and response to acid neutralization, while the causes of extra protons are worked out to be; mitochondrial dysfunction, systemic inflammation, gut microbiota (GM), and diabetic lung. Although, the intracellular pH is largely preserved by the buffer system and ion transporters, a persistent systemic mild acidosis leaves molecular signature in cellular metabolism in diabetics. Reciprocally, there are evidences that CMAD contributes to the initiation and progression of T2D by; reducing insulin production, triggering insulin resistance directly or via altered GM, and inclined oxidative stress. The details about the above clues, causes and consequences of CMAD are obtained by searching literature spanning between 1955 and 2022. Finally, the molecular bases of CMAD are discussed in details by interpretation of an up-to-date data and aid of well constructed diagrams, with a conclusion unravelling that CMAD is a major player in T2D pathophysiology. To this end, the CMAD disclosure offers several therapeutic potentials for prevention, delay or attenuation of T2D and its complications.

Non-neuronal cholinergic system delays cardiac remodelling in type 1 diabetes

Aims

Type 1 diabetes mellitus (T1DM) is associated with increased risk of cardiovascular disease (CVD) and mortality. The underlying mechanisms for T1DM-induced heart disease still remains unclear. In this study, we aimed to investigate the effects of cardiac non-neuronal cholinergic system (cNNCS) activation on T1DM-induced cardiac remodelling.

Methods

T1DM was induced in C57Bl6 mice using low-dose streptozotocin. Western blot analysis was used to measure the expression of cNNCS components at different time points (4, 8, 12, and 16 weeks after T1DM induction). To assess the potential benefits of cNNCS activation, T1DM was induced in mice with cardiomyocyte-specific overexpression of choline acetyltransferase (ChAT), the enzyme required for acetylcholine (Ac) synthesis. We evaluated the effects of ChAT overexpression on cNNCS components, vascular and cardiac remodelling, and cardiac function.

Key findings

Western blot analysis revealed dysregulation of cNNCS components in hearts of T1DM mice. Intracardiac ACh levels were also reduced in T1DM. Activation of ChAT significantly increased intracardiac ACh levels and prevented diabetes-induced dysregulation of cNNCS components. This was associated with preserved microvessel density, reduced apoptosis and fibrosis, and improved cardiac function.

Significance

Our study suggests that cNNCS dysregulation may contribute to T1DM-induced cardiac remodelling, and that increasing ACh levels may be a potential therapeutic strategy to prevent or delay T1DM-induced heart disease.

From Obesity-Induced Low-Grade Inflammation to Lipotoxicity and Mitochondrial Dysfunction: Altered Multi-Crosstalk between Adipose Tissue and Metabolically Active Organs

Obesity is a major risk factor for several metabolic diseases, including type 2 diabetes, hyperlipidemia, cardiovascular diseases, and brain disorders. Growing evidence suggests the importance of inter-organ metabolic communication for the progression of obesity and the subsequent onset of related disorders. This review provides a broad overview of the pathophysiological processes that from adipose tissue dysfunction leading to altered multi-tissue crosstalk relevant to regulating energy homeostasis and the etiology of obesity. First, a comprehensive description of the role of adipose tissue was reported. Then, attention was turned toward the unhealthy expansion of adipose tissue, low-grade inflammatory state, metabolic inflexibility, and mitochondrial dysfunction as root causes of systemic metabolic alterations. In addition, a short spot was devoted to iron deficiency in obese conditions and the role of the hepcidin-ferroportin relationship in the management of this issue. Finally, different classes of bioactive food components were described with a perspective to enhance their potential preventive and therapeutic use against obesity-related diseases.

PCr/ATP ratios and mitochondrial function in the heart. A comparative study in humans

Cardiac energy status, measured as phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio with 31P-Magnetic Resonance Spectroscopy (31P-MRS) in vivo, is a prognostic factor in heart failure and is lowered in cardiometabolic disease. It has been suggested that, as oxidative phosphorylation is the major contributor to ATP synthesis, PCr/ATP ratio might be a reflection of cardiac mitochondrial function. The objective of the study was to investigate whether PCr/ATP ratios can be used as in vivo marker for cardiac mitochondrial function. We enrolled thirty-eight patients scheduled for open-heart surgery in this study. Cardiac 31P-MRS was performed before surgery. Tissue from the right atrial appendage was obtained during surgery for high-resolution respirometry for the assessment of mitochondrial function. There was no correlation between the PCr/ATP ratio and ADP-stimulated respiration rates (octanoylcarnitine R² < 0.005, p = 0.74; pyruvate R² < 0.025, p = 0.41) nor with maximally uncoupled respiration (octanoylcarnitine R² = 0.005, p = 0.71; pyruvate R² = 0.040, p = 0.26). PCr/ATP ratio did correlate with indexed LV end systolic mass. As no direct correlation between cardiac energy status (PCr/ATP) and mitochondrial function in the heart was found, the study suggests that mitochondrial function might not the only determinant of cardiac energy status. Interpretation should be done in the right context in cardiac metabolic studies.

Functional and Metabolic Imaging in Heart Failure with Preserved Ejection Fraction: Promises, Challenges, and Clinical Utility

Heart failure with preserved ejection fraction (HFpEF) is recognised as an increasingly prevalent, morbid and burdensome condition with a poor outlook. Recent advances in both the understanding of HFpEF and the technological ability to image cardiac function and metabolism in humans have simultaneously shone a light on the molecular basis of this complex condition of diastolic dysfunction, and the inflammatory and metabolic changes that are associated with it, typically in the context of a complex patient. This review both makes the case for an integrated assessment of the condition, and highlights that metabolic alteration may be a measurable outcome for novel targeted forms of medical therapy. It furthermore highlights how recent technological advancements and advanced medical imaging techniques have enabled the characterisation of the metabolism and function of HFpEF within patients, at rest and during exercise.

Phosphorus-Containing Polymers as Sensitive Biocompatible Probes for 31P Magnetic Resonance

The visualization of organs and tissues using ³¹P magnetic resonance (MR) imaging represents an immense challenge. This is largely due to the lack of sensitive biocompatible probes required to deliver a high-intensity MR signal that can be distinguished from the natural biological background. Synthetic water-soluble phosphorus-containing polymers appear to be suitable materials for this purpose due to their adjustable chain architecture, low toxicity, and favorable pharmacokinetics. In this work, we carried out a controlled synthesis, and compared the MR properties, of several probes consisting of highly hydrophilic phosphopolymers differing in composition, structure, and molecular weight. Based on our phantom experiments, all probes with a molecular weight of ~3-400 kg·mol^-1, including linear polymers based on poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(ethyl ethylenephosphate) (PEEP), and poly[bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)]phosphazene (PMEEEP) as well as star-shaped copolymers composed of PMPC arms grafted onto poly(amidoamine) dendrimer (PAMAM-g-PMPC) or cyclotriphosphazene-derived cores (CTP-g-PMPC), were readily detected using a 4.7 T MR scanner. The highest signal-to-noise ratio was achieved by the linear polymers PMPC (210) and PMEEEP (62) followed by the star polymers CTP-g-PMPC (56) and PAMAM-g-PMPC (44). The ³¹P T₁ and T₂ relaxation times for these phosphopolymers were also favorable, ranging between 1078 and 2368 and 30 and 171 ms, respectively. We contend that select phosphopolymers are suitable for use as sensitive ³¹P MR probes for biomedical applications.

Cardiac 31P MR spectroscopy: development of the past five decades and future vision-will it be of diagnostic use in clinics?

In the past five decades, the use of the magnetic resonance (MR) technique for cardiovascular diseases has engendered much attention and raised the opportunity that the technique could be useful for clinical applications. MR has two arrows in its quiver: One is magnetic resonance imaging (MRI), and the other is magnetic resonance spectroscopy (MRS). Non-invasively, highly advanced MRI provides unique and profound information about the anatomical changes of the heart. Excellently developed MRS provides irreplaceable and insightful evidence of the real-time biochemistry of cardiac metabolism of underpinning diseases. Compared to MRI, which has already been successfully applied in routine clinical practice, MRS still has a long way to travel to be incorporated into routine diagnostics. Considering the exceptional potential of ³¹P MRS to measure the real-time metabolic changes of energetic molecules qualitatively and quantitatively, how far its powerful technique should be waited before a successful transition from "bench-to-bedside" is enticing. The present review highlights the seminal studies on the chronological development of cardiac ³¹P MRS in the past five decades and the future vision and challenges to incorporating it for routine diagnostics of cardiovascular disease.

Mechanisms underlying altered neuromuscular function in people with DPN

Diabetes alters numerous physiological functions and can lead to disastrous consequences in the long term. Neuromuscular function is particularly affected and is impacted early, offering an opportunity to detect the onset of diabetes-related dysfunctions and follow the advancement of the disease. The role of physical training for counteracting the deleterious effects of diabetes is well accepted but at the same time, it appears difficult to reliably assess the effects of exercise on functional capacity in patients with diabetic peripheral neuropathy (DPN). In this paper, we will review the specific characteristics of various neuromuscular dysfunctions associated with diabetes according to the DPN presence or not, and their changes over time. We present several propositions regarding the onset of neuromuscular alterations in people with diabetes compared to people with DPN. It appears that motor unit loss and neuromuscular transmission impairment are among the main mechanisms explaining the considerable degradation of neuromuscular function in the transition from a diabetic to neuropathic state. Rate of force development and contractile properties could start to decrease with the onset of preferential type II fiber atrophy, commonly reported in people with DPN. Finally, M_max amplitude could decrease with neuromuscular fatigue only in people with DPN, reflecting the fatigue-related neuromuscular transmission impairment reported in people with DPN. In this review, we show that the different neuromuscular parameters are altered at different stages of diabetes, according to the presence of DPN or not. The precise evaluation of these parameters might participate in adapting the physical training prescription.

Morphological and Mechanical Properties of Lower-Limb Muscles in Type 2 Diabetes: New Potential Imaging Indicators for Monitoring the Progress of DPN

The aim of this study was to explore changes in morphological and mechanical properties of lower-limb skeletal muscles in patients with diabetes with and without diabetic peripheral neuropathy (DPN) and seek to find a potential image indicator for monitoring the progress of DPN in patients with type 2 diabetes mellitus (T2DM). A total of 203 patients with T2DM, with and without DPN, were included in this study. Ultrasonography and ultrasound shear wave imaging (USWI) of the abductor hallux (AbH), tibialis anterior (TA), and peroneal longus (PER) muscles were performed for each subject, and the shear wave velocity (SWV) and cross-sectional area (CSA) of each AbH, TA, and PER were measured. The clinical factors influencing AbH_CSA and AbH_SWV were analyzed, and the risk factors for DPN complications were investigated. AbH_CSA and AbH_SWV in the T2DM group with DPN decreased significantly (P < 0.05), but no significant differences were found in the SWV and CSA of the TA and PER between the two groups. Toronto Clinical Scoring System (CSS) score and glycosylated hemoglobin (HbA1c) were independent predictors of AbH_CSA and AbH_SWV. As AbH_SWV and AbH_CSA decreased, Toronto CSS score and HbA1c increased and incidence of DPN increased significantly. In conclusion, the AbH muscle of T2DM patients with DPN became smaller and softer, while its morphological and mechanical properties were associated with the clinical indicators related to the progression of DPN. Thus, they could be potential imaging indicators for monitoring the progress of DPN in T2DM patients.

Coexistent Diabetes Is Associated With the Presence of Adverse Phenotypic Features in Patients With Hypertrophic Cardiomyopathy

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is associated with worsened clinical outcomes in hypertrophic cardiomyopathy (HCM) patients. We sought to investigate whether HCM patients with T2DM comorbidity exhibit adverse cardiac alterations in myocardial energetics, function, perfusion, or tissue characteristics.

RESEARCH DESIGN AND METHODS

A total of 55 participants with concomitant HCM and T2DM (HCM-DM) (n = 20) or isolated HCM (n = 20) and healthy volunteers (HV) (n = 15) underwent 31P-MRS and cardiovascular MRI. The HCM groups were matched for HCM phenotype.

RESULTS

Mean ± SD European Society of Cardiology sudden cardiac death risk scores were comparable between the HCM groups (HCM 2.2 ± 1.5%, HCM-DM 1.9 ± 1.2%; P = not significant), and sarcomeric mutations were equally common. HCM-DM patients had the highest median NT-proBNP levels (HV 42 ng/L [interquartile range 35-66], HCM 298 ng/L [157-837], HCM-DM 726 ng/L [213-8,695]; P < 0.0001). Left ventricular (LV) ejection fraction, mass, and wall thickness were similar between the HCM groups. HCM-DM patients displayed a greater degree of fibrosis burden with higher scar percentage and lower global longitudinal strain compared with HCM patients. PCr/ATP (the relative concentrations of phosphocreatine and ATP) was significantly lower in the HCM-DM group than in both HCM and HV (HV 2.17 ± 0.49, HCM 1.93 ± 0.38, HCM-DM 1.54 ± 0.27; P = 0.002). In a similar pattern, stress myocardial blood flow was significantly lower in the HCM-DM group than in both HCM and HV (HV 2.06 ± 0.42 mL/min/g, HCM 1.74 ± 0.44 mL/min/g, HCM-DM 1.39 ± 0.42 mL/min/g; P = 0.002).

CONCLUSIONS

We show for the first time that HCM-DM patients display greater reductions in myocardial energetics, perfusion, and contractile function and higher myocardial scar burden and serum NT-proBNP levels compared with patients with isolated HCM despite similar LV mass and wall thickness and presence of sarcomeric mutations. These adverse phenotypic features may be important components of the adverse clinical manifestation attributable to a combined presence of HCM and T2DM.

Increased cardiac Pi/PCr in the diabetic heart observed using phosphorus magnetic resonance spectroscopy at 7T

Phosphorus magnetic resonance spectroscopy (³¹P-MRS) has previously demonstrated decreased energy reserves in the form of phosphocreatine to adenosine-tri-phosphate ratio (PCr/ATP) in the hearts of patients with type 2 diabetes (T2DM). Recent ³¹P-MRS techniques using 7T systems, e.g. long mixing time stimulated echo acquisition mode (STEAM), allow deeper insight into cardiac metabolism through assessment of inorganic phosphate (Pi) content and myocardial pH, which play pivotal roles in energy production in the heart. Therefore, we aimed to further explore the cardiac metabolic phenotype in T2DM using STEAM at 7T. Seventeen patients with T2DM and twenty-three healthy controls were recruited and their cardiac PCr/ATP, Pi/PCr and pH were assessed at 7T. Diastolic function of all patients with T2DM was assessed using echocardiography to investigate the relationship between diastolic dysfunction and cardiac metabolism. Mirroring the decreased PCr/ATP (1.70±0.31 vs. 2.07±0.39; p<0.01), the cardiac Pi/PCr was increased (0.13±0.07 vs. 0.10±0.03; p = 0.02) in T2DM patients in comparison to healthy controls. Myocardial pH was not significantly different between the groups (7.14±0.12 vs. 7.10±0.12; p = 0.31). There was a negative correlation between PCr/ATP and diastolic function (R² = 0.33; p = 0.02) in T2DM. No correlation was observed between diastolic function and Pi/PCr and (R² = 0.16; p = 0.21). In addition, we did not observe any correlation between cardiac PCr/ATP and Pi/PCr (p = 0.19). Using STEAM ³¹P-MRS at 7T we have for the first time explored Pi/PCr in the diabetic human heart and found it increased when compared to healthy controls. The lack of correlation between measured PCr/ATP and Pi/PCr suggests that independent mechanisms might contribute to these perturbations.

Diabetes, GDF-15 and incident heart failure: the atherosclerosis risk in communities study

AIMS/HYPOTHESIS

Elevated circulating growth differentiation factor-15 (GDF-15), a marker of cellular stress, is associated with both heart failure (HF) and diabetes. However, it is unclear to what extent GDF-15 is associated with HF among individuals with and without diabetes.

METHODS

We evaluated 10,570 participants free of HF at Visit 3 (1993-1995) of the Atherosclerosis Risk in Communities study. We used Cox regression to evaluate the joint associations of GDF-15 and diabetes with incident HF. Models were adjusted for traditional cardiovascular risk factors.

RESULTS

Among a total of 10,570 individuals (mean age of 60.0 years, 54% women, 27% black adults), elevated GDF-15 (≥75th percentile) was more common in people with diabetes compared with those without diabetes (32.8% vs 23.6%, p<0.0001). During 23 years of follow-up, there were 2429 incident HF events. GDF-15 (in quartiles) was independently associated with HF among those with and without diabetes, with a stronger association among individuals with diabetes (p-for-diabetes-GDF-15 interaction = 0.034): HR for highest vs lowest GDF-15 quartile (reference): 1.64 (95% CI 1.41, 1.91) among those without diabetes and 1.72 (95% CI 1.32, 2.23) among those with diabetes. Individuals with diabetes and elevated GDF-15 had the highest risk of incident HF (HR 2.46; 95% CI 1.99, 3.03). After accounting for HF risk factors, GDF-15 provided additional prognostic information among participants with diabetes (ΔC statistic for model with vs model without GDF-15: +0.008, p = 0.001) and among those without diabetes (+0.006, p<0.0001).

CONCLUSIONS/INTERPRETATION

In a community-based sample of US adults, GDF-15 provided complementary prognostic information on the HF risk, especially among individuals with diabetes.

Trichloroethylene modifies energy metabolites in the amniotic fluid of Wistar rats

Exposure to trichloroethylene (TCE), an industrial solvent, is associated with several adverse pregnancy outcomes in humans and decreased fetal weight in rats. However, effects of TCE on energy metabolites in amniotic fluid, which have associations with pregnancy outcomes, has not been published previously. In the current exploratory study, timed-pregnant Wistar rats were exposed to 480 mg TCE/kg/day via vanilla wafer or to vehicle (wafer) alone from gestational day (GD) 6-16. Amniotic fluid collected on GD 16 was analyzed for metabolites important in energy metabolism using short chain fatty acid and tricarboxylic acid plus platforms (N = 4 samples/sex/treatment). TCE decreased concentrations of the following metabolites in amniotic fluid for both fetal sexes: 6-phosphogluconate, guanosine diphosphate, adenosine diphosphate, adenosine triphosphate, and flavin adenine dinucleotide. TCE decreased fructose 1,6-bisphosphate and guanosine triphosphate concentrations in amniotic fluid of male but not female fetuses. Moreover, TCE decreased uridine diphosphate-D-glucuronate concentrations, and increased arginine and phosphocreatine concentrations, in amniotic fluid of female fetuses only. No metabolites were increased in amniotic fluid of male fetuses. Pathway analysis suggested that TCE altered folate biosynthesis and pentose phosphate pathway in both sexes. Using metabolite ratios to investigate changes within specific pathways, some ratio alterations, including those in arginine metabolism and phenylalanine metabolism, were detected in females only. Ratio analysis also suggested enzymes, including gluconokinase, as potential TCE targets. Together, results from this exploratory study suggest that TCE differentially modified energy metabolites in amniotic fluid based on sex. These findings may inform future studies of TCE reproductive toxicity.

In vivo Human MR Spectroscopy Using a Clinical Scanner: Development, Applications, and Future Prospects

MR spectroscopy (MRS) is a unique and useful method for noninvasively evaluating biochemical metabolism in human organs and tissues, but its clinical dissemination has been slow and often limited to specialized institutions or hospitals with experts in MRS technology. The number of 3-T clinical MR scanners is now increasing, representing a major opportunity to promote the use of clinical MRS. In this review, we summarize the theoretical background and basic knowledge required to understand the results obtained with MRS and introduce the general consensus on the clinical utility of proton MRS in routine clinical practice. In addition, we present updates to the consensus guidelines on proton MRS published by the members of a working committee of the Japan Society of Magnetic Resonance in Medicine in 2013. Recent research into multinuclear MRS equipped in clinical MR scanners is explained with an eye toward future development. This article seeks to provide an overview of the current status of clinical MRS and to promote the understanding of when it can be useful. In the coming years, MRS-mediated biochemical evaluation is expected to become available for even routine clinical practice.

Dipeptidyl peptidase-4 is associated with myogenesis in patients with adolescent idiopathic scoliosis possibly via mediation of insulin sensitivity

Background

Abnormal metabolic features have been previously described in adolescent idiopathic scoliosis (AIS) patients. As an important regulator involved in energy metabolism, DPP-4 activity was reported to be remarkably decreased in osteoblasts of AIS patients. To date, there was still a lack of knowledge concerning the role of DPP-4 in the myogenesis of AIS.

Methods

Circulation DPP-4 level was assessed in the serum of 80 AIS girls and 50 healthy controls by ELISA. Myoblasts were purified from muscle specimens of AIS patients and LDH controls, and then treated with metabolic effectors including glucose and insulin. CCK-8 assay was used to assess the cell viability and myotube fusion index was calculated to evaluate myogenesis ability. Gene expressions of downstream signals of DPP-4 were evaluated by RT-qPCR and Western blot respectively.

Results

AIS girls had remarkably down-expressed DPP-4 in both serum level (0.76 fold) and tissue (0.68 fold) level. Treatment with metabolic effectors led to significantly increased DPP-4 expression in the control cells, while there was no increase of DPP-4 in AIS cells. CCK-8 assay showed that the proliferation rate of control cells was significantly increased after being treated. Remarkably higher fusion index was also observed in the treated control cells. By contrast, the fusion index and cell proliferation rate were comparable between the treated and the untreated AIS cells.

Conclusions

Our study suggested a potential role of DPP-4 in abnormal metabolic condition of AIS patients. Compared with control cells, AIS myoblasts presented obviously impaired sensitivity to the treatment of glucose and insulin. Aberrant DPP-4 expression could lead to impaired insulin sensitivity in myoblasts and further influence the cell viability during myogenesis. The molecular mechanism connecting DPP-4 and insulin-related signaling in AIS is worthy of further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-02978-w.

Evaluation of Acute Supplementation With the Ketone Ester (R)-3-Hydroxybutyl-(R)-3-Hydroxybutyrate (deltaG) in Healthy Volunteers by Cardiac and Skeletal Muscle 31P Magnetic Resonance Spectroscopy

In this acute intervention study, we investigated the potential benefit of ketone supplementation in humans by studying cardiac phosphocreatine to adenosine-triphosphate ratios (PCr/ATP) and skeletal muscle PCr recovery using phosphorus magnetic resonance spectroscopy (³¹P-MRS) before and after ingestion of a ketone ester drink. We recruited 28 healthy individuals: 12 aged 23–70 years for cardiac ³¹P-MRS, and 16 aged 60–75 years for skeletal muscle ³¹P-MRS. Baseline and post-intervention resting cardiac and dynamic skeletal muscle ³¹P-MRS scans were performed in one visit, where 25 g of the ketone monoester, deltaG^®, was administered after the baseline scan. Administration was timed so that post-intervention ³¹P-MRS would take place 30 min after deltaG^® ingestion. The deltaG^® ketone drink was well-tolerated by all participants. In participants who provided blood samples, post-intervention blood glucose, lactate and non-esterified fatty acid concentrations decreased significantly (−28.8%, p ≪ 0.001; −28.2%, p = 0.02; and −49.1%, p ≪ 0.001, respectively), while levels of the ketone body D-beta-hydroxybutyrate significantly increased from mean (standard deviation) 0.7 (0.3) to 4.0 (1.1) mmol/L after 30 min (p ≪ 0.001). There were no significant changes in cardiac PCr/ATP or skeletal muscle metabolic parameters between baseline and post-intervention. Acute ketone supplementation caused mild ketosis in blood, with drops in glucose, lactate, and free fatty acids; however, such changes were not associated with changes in ³¹P-MRS measures in the heart or in skeletal muscle. Future work may focus on the effect of longer-term ketone supplementation on tissue energetics in groups with compromised mitochondrial function.

Role of Creatine Supplementation in Conditions Involving Mitochondrial Dysfunction: A Narrative Review

Creatine monohydrate (CrM) is one of the most widely used nutritional supplements among active individuals and athletes to improve high-intensity exercise performance and training adaptations. However, research suggests that CrM supplementation may also serve as a therapeutic tool in the management of some chronic and traumatic diseases. Creatine supplementation has been reported to improve high-energy phosphate availability as well as have antioxidative, neuroprotective, anti-lactatic, and calcium-homoeostatic effects. These characteristics may have a direct impact on mitochondrion's survival and health particularly during stressful conditions such as ischemia and injury. This narrative review discusses current scientific evidence for use or supplemental CrM as a therapeutic agent during conditions associated with mitochondrial dysfunction. Based on this analysis, it appears that CrM supplementation may have a role in improving cellular bioenergetics in several mitochondrial dysfunction-related diseases, ischemic conditions, and injury pathology and thereby could provide therapeutic benefit in the management of these conditions. However, larger clinical trials are needed to explore these potential therapeutic applications before definitive conclusions can be drawn.

Multimodality imaging approach to left ventricular dysfunction in diabetes: an expert consensus document from the European Association of Cardiovascular Imaging

Heart failure (HF) is among the most important and frequent complications of diabetes mellitus (DM). The detection of subclinical dysfunction is a marker of HF risk and presents a potential target for reducing incident HF in DM. Left ventricular (LV) dysfunction secondary to DM is heterogeneous, with phenotypes including predominantly systolic, predominantly diastolic, and mixed dysfunction. Indeed, the pathogenesis of HF in this setting is heterogeneous. Effective management of this problem will require detailed phenotyping of the contributions of fibrosis, microcirculatory disturbance, abnormal metabolism, and sympathetic innervation, among other mechanisms. For this reason, an imaging strategy for the detection of HF risk needs to not only detect subclinical LV dysfunction (LVD) but also characterize its pathogenesis. At present, it is possible to identify individuals with DM at increased risk HF, and there is evidence that cardioprotection may be of benefit. However, there is insufficient justification for HF screening, because we need stronger evidence of the links between the detection of LVD, treatment, and improved outcome. This review discusses the options for screening for LVD, the potential means of identifying the underlying mechanisms, and the pathways to treatment.

Cardiac energetics alteration in a chronic hypoxia rat model: A non-invasive in vivo31P magnetic resonance spectroscopy study

BACKGROUND

Energetics alteration plays a crucial role in the myocardial injury process in chronic hypoxia diseases (CHD). 31P magnetic resonance spectroscopy (MRS) can investigate alterations in cardiac energetics in vivo.

OBJECTIVE

To characterize the potential value of 31P MRS in evaluating cardiac energetics alteration of chronic hypoxic rats (CHRs).

METHODS

Twenty-four CHRs were induced by SU5416 combined with hypoxia and divided into four groups according to the modeling time of one, two, three and five weeks, respectively. Control group also contains six rats. 31P MRS was performed weekly and the ratio of concentrations of phosphocreatine (PCr) to adenosine triphosphate (ATP) (PCr/ATP) was obtained. In addition, the cardiac structure index and systolic function parameters, including the right ventricular ejection fraction (RVEF), right ventricular end-diastolic volume index (RVEDVi), right ventricular end-systolic volume index (RVESVi), and the left ventricular function parameters, were measured.

RESULTS

Decreased resting cardiac PCr/ATP ratio in CHRs was observed at the first week, compared to the control group (2.90±0.35 vs. 3.31±0.45, p = 0.045), while the RVEF, RVEDVi, and RVESVi decreased at the second week (p < 0.05). The PCr/ATP ratio displayed a significant correlation with RVEF (r = 0.605, p = 0.001), RVEDVi, and RVESVi (r = -0.661, r = -0.703; p < 0.001).

CONCLUSIONS

31P MRS can easily detect the cardiac energetics alteration in a CHR model before the onset of ventricular dysfunction. The decreased PCr/ATP ratio likely reveales myocardial injury and cardiac dysfunction.

Diabetic cardiomyopathy: Clinical phenotype and practice

Diabetic cardiomyopathy (DCM) is a pathophysiological condition of cardiac structure and function changes in diabetic patients without coronary artery disease, hypertension, and other types of heart diseases. DCM is not uncommon in people with diabetes, which increases the risk of heart failure. However, the treatment is scarce, and the prognosis is poor. Since 1972, one clinical study after another on DCM has been conducted. However, the complex phenotype of DCM still has not been fully revealed. This dilemma hinders the pace of understanding the essence of DCM and makes it difficult to carry out penetrating clinical or basic research. This review summarizes the literature on DCM over the last 40 years and discusses the overall perspective of DCM, phase of progression, potential clinical indicators, diagnostic and screening criteria, and related randomized controlled trials to understand DCM better.

Heart failure in diabetes

Heart failure and cardiovascular disorders represent the leading cause of death in diabetic patients. Here we present a systematic review of the main mechanisms underlying the development of diabetic cardiomyopathy. We also provide an excursus on the relative contribution of cardiomyocytes, fibroblasts, endothelial and smooth muscle cells to the pathophysiology of heart failure in diabetes. After having described the preclinical tools currently available to dissect the mechanisms of this complex disease, we conclude with a section on the most recent updates of the literature on clinical management.

Energetic Basis for Exercise-Induced Pulmonary Congestion in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Transient pulmonary congestion during exercise is emerging as an important determinant of reduced exercise capacity in heart failure with preserved ejection fraction (HFpEF). We sought to determine whether an abnormal cardiac energetic state underpins this process.

METHODS

We recruited patients across the spectrum of diastolic dysfunction and HFpEF (controls, n=11; type 2 diabetes, n=9; HFpEF, n=14; and severe diastolic dysfunction attributable to cardiac amyloidosis, n=9). Cardiac energetics were measured using phosphorus spectroscopy to define the myocardial phosphocreatine to ATP ratio. Cardiac function was assessed by cardiovascular magnetic resonance cine imaging and echocardiography and lung water using magnetic resonance proton density mapping. Studies were performed at rest and during submaximal exercise using a magnetic resonance imaging ergometer.

RESULTS

Paralleling the stepwise decline in diastolic function across the groups (E/e' ratio; P<0.001) was an increase in NT-proBNP (N-terminal pro-brain natriuretic peptide; P<0.001) and a reduction in phosphocreatine/ATP ratio (control, 2.15 [2.09, 2.29]; type 2 diabetes, 1.71 [1.61, 1.91]; HFpEF, 1.66 [1.44, 1.89]; cardiac amyloidosis, 1.30 [1.16, 1.53]; P<0.001). During 20-W exercise, lower left ventricular diastolic filling rates (r=0.58; P<0.001), lower left ventricular diastolic reserve (r=0.55; P<0.001), left atrial dilatation (r=-0.52; P<0.001), lower right ventricular contractile reserve (right ventricular ejection fraction change, r=0.57; P<0.001), and right atrial dilation (r=-0.71; P<0.001) were all linked to lower phosphocreatine/ATP ratio. Along with these changes, pulmonary proton density mapping revealed transient pulmonary congestion in patients with HFpEF (+4.4% [0.5, 6.4]; P=0.002) and cardiac amyloidosis (+6.4% [3.3, 10.0]; P=0.004), which was not seen in healthy controls (-0.1% [-1.9, 2.1]; P=0.89) or type 2 diabetes without HFpEF (+0.8% [-1.7, 1.9]; P=0.82). The development of exercise-induced pulmonary congestion was associated with lower phosphocreatine/ATP ratio (r=-0.43; P=0.004).

CONCLUSIONS

A gradient of myocardial energetic deficit exists across the spectrum of HFpEF. Even at low workload, this energetic deficit is related to markedly abnormal exercise responses in all 4 cardiac chambers, which is associated with detectable pulmonary congestion. The findings support an energetic basis for transient pulmonary congestion in HFpEF.

The Contribution of Cardiac Fatty Acid Oxidation to Diabetic Cardiomyopathy Severity

Diabetes is a major risk factor for the development of cardiovascular disease via contributing and/or triggering significant cellular signaling and metabolic and structural alterations at the level of the heart and the whole body. The main cause of mortality and morbidity in diabetic patients is cardiovascular disease including diabetic cardiomyopathy. Therefore, understanding how diabetes increases the incidence of diabetic cardiomyopathy and how it mediates the major perturbations in cell signaling and energy metabolism should help in the development of therapeutics to prevent these perturbations. One of the significant metabolic alterations in diabetes is a marked increase in cardiac fatty acid oxidation rates and the domination of fatty acids as the major energy source in the heart. This increased reliance of the heart on fatty acids in the diabetic has a negative impact on cardiac function and structure through a number of mechanisms. It also has a detrimental effect on cardiac efficiency and worsens the energy status in diabetes, mainly through inhibiting cardiac glucose oxidation. Furthermore, accelerated cardiac fatty acid oxidation rates in diabetes also make the heart more vulnerable to ischemic injury. In this review, we discuss how cardiac energy metabolism is altered in diabetic cardiomyopathy and the impact of cardiac insulin resistance on the contribution of glucose and fatty acid to overall cardiac ATP production and cardiac efficiency. Furthermore, how diabetes influences the susceptibility of the myocardium to ischemia/reperfusion injury and the role of the changes in glucose and fatty acid oxidation in mediating these effects are also discussed.

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.

Myocardial inflammation and energetics by cardiac MRI: a review of emerging techniques

The role of inflammation in cardiovascular pathophysiology has gained a lot of research interest in recent years. Cardiovascular Magnetic Resonance has been a powerful tool in the non-invasive assessment of inflammation in several conditions. More recently, Ultrasmall superparamagnetic particles of iron oxide have been successfully used to evaluate macrophage activity and subsequently inflammation on a cellular level. Current evidence from research studies provides encouraging data and confirms that this evolving method can potentially have a huge impact on clinical practice as it can be used in the diagnosis and management of very common conditions such as coronary artery disease, ischaemic and non-ischaemic cardiomyopathy, myocarditis and atherosclerosis. Another important emerging concept is that of myocardial energetics. With the use of phosphorus magnetic resonance spectroscopy, myocardial energetic compromise has been proved to be an important feature in the pathophysiological process of several conditions including diabetic cardiomyopathy, inherited cardiomyopathies, valvular heart disease and cardiac transplant rejection. This unique tool is therefore being utilized to assess metabolic alterations in a wide range of cardiovascular diseases. This review systematically examines these state-of-the-art methods in detail and provides an insight into the mechanisms of action and the clinical implications of their use.

Lipotoxicity: a driver of heart failure with preserved ejection fraction?

Heart failure with preserved ejection fraction (HFpEF) is a growing public health concern, with rising incidence alongside high morbidity and mortality. However, the pathophysiology of HFpEF is not yet fully understood. The association between HFpEF and the metabolic syndrome (MetS) suggests that dysregulated lipid metabolism could drive diastolic dysfunction and subsequent HFpEF. Herein we summarise recent advances regarding the pathogenesis of HFpEF in the context of MetS, with a focus on impaired lipid handling, myocardial lipid accumulation and subsequent lipotoxicity.

Vanillin modulates activities linked to dysmetabolism in psoas muscle of diabetic rats

Skeletal muscles are important in glucose metabolism and are affected in type 2 diabetes (T2D) and its complications. This study investigated the effect of vanillin on redox imbalance, cholinergic and purinergic dysfunction, and glucose-lipid dysmetabolism in muscles of rats with T2D. Male albino rats (Sprague-Dawley strain) were fed 10% fructose ad libitum for 2 weeks before intraperitoneally injecting them with 40 mg/kg streptozotocin to induce T2D. Low (150 mg/kg bodyweight (BW)) and high (300 mg/kg BW) doses of vanillin were orally administered to diabetic rats. Untreated diabetic rats and normal rats made up the diabetic control (DC) and normal control (NC) groups, respectively. The standard antidiabetic drug was metformin. The rats were humanely put to sleep after 5 weeks of treatment and their psoas muscles were harvested. There was suppression in the levels of glutathione, activities of SOD, catalase, ENTPDase, 5'Nucleotidase and glycogen levels on T2D induction. This was accompanied by concomitantly elevated levels of malondialdehyde, serum creatine kinase-MB, nitric oxide, acetylcholinesterase, ATPase, amylase, lipase, glucose-6-phosphatase (G6Pase), fructose-1,6-biphophastase (FBPase) and glycogen phosphorylase activities. T2D induction further resulted in the inactivation of fatty acid biosynthesis, glycerolipid metabolism, fatty acid elongation in mitochondria and fatty acid metabolism pathways. There were close to normal and significant reversals in these activities and levels, with concomitant reactivation of the deactivated pathways following treatment with vanillin, which compared favorably with the standard drug (metformin). Vanillin also significantly increased muscle glucose uptake ex vivo. The results suggest the therapeutic effect of vanillin against muscle dysmetabolism in T2D as portrayed by its ability to mitigate redox imbalance, inflammation, cholinergic and purinergic dysfunctions, while modulating glucose-lipid metabolic switch and maintaining muscle histology.

Roles of MicroRNAs in Glucose and Lipid Metabolism in the Heart

MicroRNAs (miRNAs) are small non-coding RNAs that participate in heart development and pathological processes mainly by silencing gene expression. Overwhelming evidence has suggested that miRNAs were involved in various cardiovascular pathological processes, including arrhythmias, ischemia-reperfusion injuries, dysregulation of angiogenesis, mitochondrial abnormalities, fibrosis, and maladaptive remodeling. Various miRNAs could regulate myocardial contractility, vascular proliferation, and mitochondrial function. Meanwhile, it was reported that miRNAs could manipulate nutrition metabolism, especially glucose and lipid metabolism, by regulating insulin signaling pathways, energy substrate transport/metabolism. Recently, increasing studies suggested that the abnormal glucose and lipid metabolism were closely associated with a broad spectrum of cardiovascular diseases (CVDs). Therefore, maintaining glucose and lipid metabolism homeostasis in the heart might be beneficial to CVD patients. In this review, we summarized the present knowledge of the functions of miRNAs in regulating cardiac glucose and lipid metabolism, as well as highlighted the miRNA-based therapies targeting cardiac glucose and lipid metabolism.

Depressed myocardial mechano-energetic efficiency in subjects with dysglycemia

AIMS

Evidence indicate that 1 h post-load glucose levels (1hPG) ≥ 155 mg/dl identify amongst subjects with normal glucose tolerance (NGT) a new category of prediabetes (NGT 1 h-high). A compromised myocardial mechano-energetic efficiency (MEE) is associated with type 2 diabetes and predicts adverse cardiovascular outcomes. Herein, we explored the association between prediabetes conditions such as NGT 1 h-high, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) and a decreased MEE.

METHODS

MEE was assessed by an echocardiography-derived measure in 1467 non-diabetic individuals subdivided according to their glucose tolerance: NGT and 1-hPG < 155 mg/dl (NGT 1 h-low, n = 617), NGT 1 h-high (n = 210), isolated IFG (n = 237), and IGT (n = 403).

RESULTS

Subjects with NGT 1 h-high, isolated IFG, and IGT displayed a higher myocardial oxygen consumption, and a decreased MEE in comparison to NGT 1 h-low group. MEE was inversely related to male sex, age, body mass index, total cholesterol, triglycerides, fasting and post-load glucose and insulin, C reactive protein, and positively correlated with insulin sensitivity estimated by the Matsuda index. In a stepwise multivariate linear regression model including several cardio-metabolic risk factors, 1hPG was the major predictor of MEE.

CONCLUSIONS

Subjects with NGT 1 h-high, isolated IFG, and IGT have a raised myocardial oxygen consumption and a reduced MEE.

Molecular basis of ventricular arrhythmogenicity in a Pgc-1α deficient murine model

Mitochondrial dysfunction underlying metabolic disorders such as obesity and diabetes mellitus is strongly associated with cardiac arrhythmias. Murine Pgc-1α-/- hearts replicate disrupted mitochondrial function and model the associated pro-arrhythmic electrophysiological abnormalities. Quantitative PCR, western blotting and histological analysis were used to investigate the molecular basis of the electrophysiological changes associated with mitochondrial dysfunction. qPCR analysis implicated downregulation of genes related to Na+-K+ ATPase activity (Atp1b1), surface Ca2+ entry (Cacna1c), action potential repolarisation (Kcnn1), autonomic function (Adra1d, Adcy4, Pde4d, Prkar2a), and morphological properties (Myh6, Tbx3) in murine Pgc-1α-/- ventricles. Western blotting revealed reduced NaV1.5 but normal Cx43 expression. Histological analysis revealed increased tissue fibrosis in the Pgc-1α-/- ventricles. These present findings identify altered transcription amongst a strategically selected set of genes established as encoding proteins involved in cardiac electrophysiological activation and therefore potentially involved in alterations in ventricular activation and Ca2+ homeostasis in arrhythmic substrate associated with Pgc-1α deficiency. They complement and complete previous studies examining such expression characteristics in the atria and ventricles of Pgc-1 deficient murine hearts.

Biliary diversion increases resting energy expenditure leading to decreased blood glucose level in mice with type 2 diabetes

AIMS/INTRODUCTION

Type 2 diabetes mellitus is a group of metabolism abnormalities in carbohydrates and energy. Our aim was to investigate resting energy expenditure (REE) and blood glucose changes after biliary diversion in mice with diabetes.

MATERIALS AND METHODS

Male mice with diabetes were randomly divided into biliary diversion and sham groups. REE was detected by indirect calorimetry, the levels of fasting blood glucose, total bile acids and triiodothyronine were analyzed. After mice were killed, the weight amount of brown adipose tissue (BAT) and gastrocnemius was measured, and the expression level of G protein-coupled bile acid receptor and type 2 iodothyronine deiodinase in BAT and gastrocnemius were examined.

RESULTS

The two groups of mice were pair-fed, the bodyweights (P < 0.001) and the fasting blood glucose level (P < 0.001) in the biliary diversion group significantly decreased 24 weeks after surgery. The intraperitoneal glucose tolerance test (P = 0.035) and oral glucose tolerance test (P = 0.027) showed improvement in glucose tolerance after surgery. The REE level significantly increased 24 weeks after surgery (P = 0.005), the levels of total bile acids (P = 0.014) and triiodothyronine (P < 0.001) increased at the 24th postoperative week. The weight ratio of BAT (P = 0.038) and gastrocnemius (P = 0.026) in the biliary diversion group were higher than that in the sham group. The expression of G protein-coupled bile acid receptor in BAT (P < 0.001) and gastrocnemius (P = 0.003) were upregulated after surgery, and the type 2 iodothyronine deiodinase expression also increased in BAT (P = 0.015) and gastrocnemius (P = 0.015).

CONCLUSIONS

The REE level increased and the glucose metabolism improved in mice with diabetes after biliary diversion.

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.

Run for your life: can exercise be used to effectively target GLUT4 in diabetic cardiac disease?

The global incidence, associated mortality rates and economic burden of diabetes are now such that it is considered one of the most pressing worldwide public health challenges. Considerable research is now devoted to better understanding the mechanisms underlying the onset and progression of this disease, with an ultimate aim of improving the array of available preventive and therapeutic interventions. One area of particular unmet clinical need is the significantly elevated rate of cardiomyopathy in diabetic patients, which in part contributes to cardiovascular disease being the primary cause of premature death in this population. This review will first consider the role of metabolism and more specifically the insulin sensitive glucose transporter GLUT4 in diabetic cardiac disease, before addressing how we may use exercise to intervene in order to beneficially impact key functional clinical outcomes.