The association between diabetes mellitus and reduction in myocardial glucose uptake: a population-based 18F-FDG PET/CT study

Systemic Deletion of ARRDC4 Improves Cardiac Reserve and Exercise Capacity in Diabetes

BACKGROUND

Exercise intolerance is an independent predictor of poor prognosis in diabetes. The underlying mechanism of the association between hyperglycemia and exercise intolerance remains undefined. We recently demonstrated that the interaction between ARRDC4 (arrestin domain-containing protein 4) and GLUT1 (glucose transporter 1) regulates cardiac metabolism.

METHODS

To determine whether this mechanism broadly impacts diabetic complications, we investigated the role of ARRDC4 in the pathogenesis of diabetic cardiac/skeletal myopathy using cellular and animal models.

RESULTS

High glucose promoted translocation of MondoA into the nucleus, which upregulated Arrdc4 transcriptional expression, increased lysosomal GLUT1 trafficking, and blocked glucose transport in cardiomyocytes, forming a feedback mechanism. This role of ARRDC4 was confirmed in human muscular cells from type 2 diabetic patients. Prolonged hyperglycemia upregulated myocardial Arrdc4 expression in multiple types of mouse models of diabetes. We analyzed hyperglycemia-induced cardiac and skeletal muscle abnormalities in insulin-deficient mice. Hyperglycemia increased advanced glycation end-products and elicited oxidative and endoplasmic reticulum stress leading to apoptosis in the heart and peripheral muscle. Deletion of Arrdc4 augmented tissue glucose transport and mitochondrial respiration, protecting the heart and muscle from tissue damage. Stress hemodynamic analysis and treadmill exhaustion test uncovered that Arrdc4-knockout mice had greater cardiac inotropic/chronotropic reserve with higher exercise endurance than wild-type animals under diabetes. While multiple organs were involved in the mechanism, cardiac-specific overexpression using an adenoassociated virus suggests that high levels of myocardial ARRDC4 have the potential to contribute to exercise intolerance by interfering with cardiac metabolism through its interaction with GLUT1 in diabetes. Importantly, the ARRDC4 mutation mouse line exhibited greater exercise tolerance, showing the potential therapeutic impact on diabetic cardiomyopathy by disrupting the interaction between ARRDC4 and GLUT1.

CONCLUSIONS

ARRDC4 regulates hyperglycemia-induced toxicities toward cardiac and skeletal muscle, revealing a new molecular framework that connects hyperglycemia to cardiac/skeletal myopathy to exercise intolerance.

Sex-specific differences in myocardial glucose metabolic rate in non-diabetic, pre-diabetic and type 2 diabetic subjects

BACKGROUND

Evidence has shown that women with type 2 diabetes (T2DM) have a higher excess risk for cardiovascular disease (CVD) than men with T2DM. Subjects with either T2DM or prediabetes exhibit myocardial insulin resistance, but it is still unsettled whether sex-related differences in myocardial insulin resistance occur in diabetic and prediabetic subjects.

METHODS

We aimed to evaluate sex-related differences in myocardial glucose metabolic rate (MRGlu), assessed using dynamic PET with 18F-FDG combined with euglycemic-hyperinsulinemic clamp, in subjects with normal glucose tolerance (NGT; n = 20), prediabetes (n = 11), and T2DM (n = 26).

RESULTS

Women with prediabetes or T2DM exhibited greater relative differences in myocardial MRGlu than men with prediabetes or T2DM when compared with their NGT counterparts. As compared with women with NGT, those with prediabetes exhibited an age-adjusted 35% lower myocardial MRGlu value (P = 0.04) and women with T2DM a 74% lower value (P = 0.006), respectively. Conversely, as compared with men with NGT, men with T2DM exhibited a 40% lower myocardial MRGlu value (P = 0.004), while no significant difference was observed between men with NGT and prediabetes. The statistical test for interaction between sex and glucose tolerance on myocardial MRGlu (P < 0.0001) was significant suggesting a sex-specific association.

CONCLUSIONS

Our data suggest that deterioration of glucose homeostasis in women is associated with a greater impairment in myocardial glucose metabolism as compared with men. The sex-specific myocardial insulin resistance could be an important factor responsible for the greater effect of T2DM on the excess risk of cardiovascular disease in women than in men.

Point-of-care β-hydroxybutyrate measurement predicts adequate glucose metabolism suppression in cardiac FDG-PET/CT

AIMS

The aims of our study were to evaluate whether point-of-care β-hydroxybutyrate (BHB) measurement can be used to identify patients with adequate cardiac glucose metabolism suppression for cardiac [18F]-fluoro-2-deoxy- d-glucose-positron emission tomography with computerized tomography (FDG-PET/CT) and to develop a pretest probability calculator of myocardial suppression using other metabolic factors attainable before imaging.

METHODS AND RESULTS

We recruited 193 patients with any clinical indication for whole body [18F]-FDG-PET/CT. BHB level was measured with a point-of-care device. Maximal myocardial standardized uptake value using lean body mass (SULmax) was measured from eight circular regions of interest with 1 cm circumference and background from left ventricular blood pool. Correlations SULmax and point-of-care measured BHB were analysed. The ability of BHB test to predict adequate suppression was evaluated with receiver operating characteristic analysis. Liver and spleen attenuation in computed tomography were measured to assess the presence of fatty liver. BHB level correlated with myocardial uptake and, using a cut-off value of 0.35 mmol/L to predict adequate myocardial suppression, we reached specificity of 90% and sensitivity of 56%. Other variables to predict adequate suppression were diabetes, obesity, ketogenic diet and fatty liver. Using information attainable before imaging, we created a pretest probability calculator of inadequate myocardial glucose metabolism suppression. The area under the curve for BHB test alone was 0.802 and was 0.857 for the pretest calculator (p = 0.319).

CONCLUSIONS

BHB level measured with a point-of-care device is useful in predicting adequate myocardial glucose metabolism suppression. More detailed assessment of other factors potentially contributing to cardiac metabolism is needed.

Imaging diabetic cardiomyopathy in a type 1 diabetic rat model using 18F-FEPPA PET

OBJECTIVE

Diabetic patients often experience chronic inflammation and fibrosis in their cardiac tissues, highlighting the pressing need for the development of sensitive diagnostic methods for longitudinal assessment of diabetic cardiomyopathy. This study aims to evaluate the significance of an inflammatory marker known as translocator protein (TSPO) in a positron emission tomography (PET) protocol for longitudinally monitoring cardiac dysfunction in a diabetic animal model. Additionally, we compared the commonly used radiotracer, 18F-fluoro-2-deoxy-d-glucose (18F-FDG).

METHODS

Fourteen 7-week-old female Sprague-Dawley rats were used in this study. Longitudinal PET experiments were conducted using 18F-N-2-(2-fluoroethoxy)benzyl)-N-(4-phenoxypyridin-3-yl)acetamide (18F-FEPPA) (n = 3), the TSPO radiotracer, and 18F-FDG (n = 3), both before and after the onset of diabetes. Histological and immunohistochemical staining assays were also conducted in both the control (n = 4) and diabetes (n = 4) groups.

RESULTS

Results indicated a significant increase in cardiac tissue uptake of 18F-FEPPA after the onset of diabetes (P < 0.05), aligning with elevated TSPO levels observed in diabetic animals according to histological data. Conversely, the uptake of 18F-FDG in cardiac tissue significantly decreased after the onset of diabetes (P < 0.05).

CONCLUSION

These findings suggest that 18F-FEPPA can function as a sensitive probe for detecting chronic inflammation and fibrosis in the cardiac tissues of diabetic animals.

High dietary intake of unsaturated fatty acids is associated with improved insulin resistance - a cross-sectional study based on the NHANES database

BACKGROUND

A moderate intake of unsaturated fatty acids (UFA) is associated positively with improved insulin resistance. The aim of this study was to investigate the relationship between the dietary intake of unsaturated fatty acids/total fats (UFA/TF) and insulin resistance.

METHODS

15,560 participants were selected from the National Health and Nutrition Examination Survey (NHANES) database enrolled between March 2017 and 2020, and excluded those under 20 years of age, pregnant, or with missing data for key research items. Finally, 7,630 participants were included in the study. R software was used for data analysis that included: (1) general descriptive statistics; (2) comparison of differences in baseline information of three UFA/TF groups, namely low, medium, and high ratios; (3) calculation of the correlation between the UFA/TF ratio and markers of insulin resistance: triglyceride-glucose index (TyG) and homeostatic model assessment for insulin resistance (HOMA-IR); (4) stratification of the study subjects into two groups, with or without insulin resistance, using a cut-off value of HOMA-IR ≥ 2, followed by logistic regression analysis to examine the relationship between UFA/TF and insulin resistance status in the two groups; and (5) further stratification of the subjects according to age, gender, body mass index (BMI), race, total energy intake, total protein, total carbohydrate, total sugars, total dietary fiber, total fat, alcohol consumption, diabetes, hypercholesterolemia to analyze the impact of UFA/TF on insulin resistance status in different subgroups.

RESULTS

(1) A high UFA/TF level was associated with a low TyG index and HOMA-IR [β (vs. TyG index) = -0.559, 95% CI: (-0.821~-0.297), P < 0.001; β (vs. HOMA-IR) = -0.742, 95% CI: (-1.083~-0.402), P < 0.001]. This negative relationship became more pronounced when UFA/TF exceeded 57.9% (i.e., the higher group). (2) Logistic regression analysis showed that a higher UFA/TF level was associated with a lower risk of developing insulin resistance [Q3 vs. Q1: 0.838 (95%CI: 0.709 ~ 0.991); P for trend = 0.038]. After adjusting for covariates such as gender, age, and BMI, this protective effect remained significant (P value < 0.05). (3) Analysis also showed that increased UFA/TF intake reduced the risk of developing insulin resistance (OR = 0.266, 95% CI: (0.075 ~ 0.946), P = 0.041). Subgroup analysis showed that although elevated UFA/TF intake showed no statistically significant difference in its effect in most subgroups, the large study population in this study provides valuable insights on potential changes. Increased UFA/TF intake may confer relatively greater benefits within specific subgroups, particularly among the elderly [Q3 age group, OR = 0.114, 95%CI: (0.012 ~ 1.078), P = 0.058], females [OR = 0.234, 95%CI: (0.041 ~ 1.333), P = 0.102], those with a BMI ≤ 25 kg/m²[OR = 0.191, 95%CI: (0.016 ~ 2.344), P = 0.196], and individuals without hypercholesterolemia [OR = 0.207, 95%CI: (0.042 ~ 1.013), P = 0.0519]. The impact of high UFA/TF levels within subgroups based on the presence or absence of coronary heart disease and stroke displayed contrasting trends. In those without coronary heart disease, there was a significant protective effect against insulin resistance [OR = 0.254, 95% CI: (0.07 ~ 0.929), P = 0.0384], while in the stroke subgroup, a significantly protective effect against insulin resistance was observed [OR = 0.002, 95%CI: (0 ~ 0.695), P = 0.0376].

CONCLUSION

A high dietary intake of UFA relative to total fat consumption could be a protective factor against the risk of developing insulin resistance.

Cardiac Insulin Resistance in Subjects With Metabolic Syndrome Traits and Early Subclinical Atherosclerosis

OBJECTIVE

Experimental evidence suggests that metabolic syndrome (MetS) is associated with changes in cardiac metabolism. Whether this association occurs in humans is unknown.

RESEARCH DESIGN AND METHODS

821 asymptomatic individuals from the Progression of Early Subclinical Atherosclerosis (PESA) study (50.6 [46.9-53.6] years, 83.7% male) underwent two whole-body 18F-fluorodeoxyglucose positron emission tomography-magnetic resonance (18F-FDG PET-MR) 4.8 ± 0.6 years apart. Presence of myocardial 18F-FDG uptake was evaluated qualitatively and quantitatively. No myocardial uptake was grade 0, while positive uptake was classified in grades 1-3 according to target-to-background ratio tertiles.

RESULTS

One hundred fifty-six participants (19.0%) showed no myocardial 18F-FDG uptake, and this was significantly associated with higher prevalence of MetS (29.0% vs. 13.9%, P < 0.001), hypertension (29.0% vs. 18.0%, P = 0.002), and diabetes (11.0% vs. 3.2%, P < 0.001), and with higher insulin resistance index (HOMA-IR, 1.64% vs. 1.23%, P < 0.001). Absence of myocardial uptake was associated with higher prevalence of early atherosclerosis (i.e., arterial 18F-FDG uptake, P = 0.004). On follow-up, the associations between myocardial 18F-FDG uptake and risk factors were replicated, and MetS was more frequent in the group without myocardial uptake. The increase in HOMA-IR was associated with a progressive decrease in myocardial uptake (P < 0.001). In 82% of subjects, the categorization according to presence/absence of myocardial 18F-FDG uptake did not change between baseline and follow-up. MetS regression on follow-up was associated with a significant (P < 0.001) increase in myocardial uptake.

CONCLUSIONS

Apparently healthy individuals without cardiac 18F-FDG uptake have higher HOMA-IR and higher prevalence of MetS traits, cardiovascular risk factors, and early atherosclerosis. An improvement in cardiometabolic profile is associated with the recovery of myocardial 18F-FDG uptake at follow-up.

Impaired insulin-stimulated myocardial glucose metabolic rate is associated with reduced estimated myocardial energetic efficiency in subjects with different degrees of glucose tolerance

BACKGROUND

Alterations in myocardial mechano-energetic efficiency (MEEi), which represents the capability of the left ventricles to convert the chemical energy obtained by oxidative metabolism into mechanical work, have been associated with cardiovascular disease. Although whole-body insulin resistance has been related to impaired myocardial MEEi, it is unknown the relationship between cardiac insulin resistance and MEEi. Aim of this study was to evaluate the relationship between insulin-stimulated myocardial glucose metabolic rate (MrGlu) and myocardial MEEi in subjects having different degrees of glucose tolerance.

METHODS

We evaluated insulin-stimulated myocardial MrGlu using cardiac dynamic positron emission tomography (PET) with 18F-Fluorodeoxyglucose (18F-FDG) combined with euglycemic-hyperinsulinemic clamp, and myocardial MEEi in 57 individuals without history of coronary heart disease having different degrees of glucose tolerance. The subjects were stratified into tertiles according to their myocardial MrGlu values.

RESULTS

After adjusting for age, gender and BMI, subjects in I tertile showed a decrease in myocardial MEEi (0.31 ± 0.05 vs 0.42 ± 0.14 ml/s*g, P = 0.02), and an increase in myocardial oxygen consumption (MVO2) (10,153 ± 1375 vs 7816 ± 1229 mmHg*bpm, P < 0.0001) as compared with subjects in III tertile. Univariate correlations showed that insulin-stimulated myocardial MrGlu was positively correlated with MEEi and whole-body glucose disposal, and negatively correlated with waist circumference, fasting plasma glucose, HbA1c and MVO2. In a multivariate regression analysis running a model including several CV risk factors, the only variable that remained significantly associated with MEEi was myocardial MrGlu (β 0.346; P = 0.01).

CONCLUSIONS

These data suggest that an impairment in insulin-stimulated myocardial glucose metabolism is an independent contributor of depressed myocardial MEEi in subjects without history of CHD.

Ketogenic diet modulates cardiac metabolic dysregulation in streptozocin-induced diabetic rats

The ketogenic diet (KD) might improve cardiac function in diabetic cardiomyopathy, but the mechanisms remain unclear. This study investigated the effects of KD on myocardial fatty acid (FA), glucose, and ketone metabolism in diabetic cardiomyopathy. Echocardiograms, biochemistry, and micro-positron emission tomography were performed to evaluate cardiac function and glucose uptake in control rats and streptozotocin-induced diabetes mellitus (DM) rats with normal diet (ND) or KD for 6 weeks. Histopathology, adenosine triphosphate measurement, and Western blot were performed in the ventricular myocytes to analyze fibrosis, FA, ketone body, and glucose utilization. The ND-fed DM rats exhibited impaired left ventricular systolic function and increased chamber dilatation, whereas control and KD-fed DM rats did not. The KD reduced myocardial fibrosis and apoptosis in the DM rats. Myocardial glucose uptake in the micro-positron emission tomography was similar between ND-fed DM rats and KD-fed DM rats and was substantially lower than the control rats. Compared with the control rats,  ND-fed DM rats had increased phosphorylation of acetyl CoA carboxylase and higher expressions of CD-36, carnitine palmitoyltransferase-1β, tumor necrosis factor-α, interleukin-1β, interleukin6, PERK, and e-IF2α as well as more myocardial fibrosis and apoptosis (assessed by Bcl-2, BAX, and caspase-3 expression); these increases were attenuated in the KD-fed DM rats. Moreover, ND-fed DM rats had significantly lower myocardial adenosine triphosphate, BHB, and OXCT1 levels than the control and KD-fed DM rats. The KD may improve the condition of diabetic cardiomyopathy by suppressing FA metabolism, increasing ketone utilization, and decreasing endoplasmic reticulum stress and inflammation.

Energy substrate metabolism and oxidative stress in metabolic cardiomyopathy

Metabolic cardiomyopathy is an emerging cause of heart failure in patients with obesity, insulin resistance, and diabetes. It is characterized by impaired myocardial metabolic flexibility, intramyocardial triglyceride accumulation, and lipotoxic damage in association with structural and functional alterations of the heart, unrelated to hypertension, coronary artery disease, and other cardiovascular diseases. Oxidative stress plays an important role in the development and progression of metabolic cardiomyopathy. Mitochondria are the most significant sources of reactive oxygen species (ROS) in cardiomyocytes. Disturbances in myocardial substrate metabolism induce mitochondrial adaptation and dysfunction, manifested as a mismatch between mitochondrial fatty acid oxidation and the electron transport chain (ETC) activity, which facilitates ROS production within the ETC components. In addition, non-ETC sources of mitochondrial ROS, such as β-oxidation of fatty acids, may also produce a considerable quantity of ROS in metabolic cardiomyopathy. Augmented ROS production in cardiomyocytes can induce a variety of effects, including the programming of myocardial energy substrate metabolism, modulation of metabolic inflammation, redox modification of ion channels and transporters, and cardiomyocyte apoptosis, ultimately leading to the structural and functional alterations of the heart. Based on the above mechanistic views, the present review summarizes the current understanding of the mechanisms underlying metabolic cardiomyopathy, focusing on the role of oxidative stress.

Metabolic Syndrome Is Associated With Impaired Insulin-Stimulated Myocardial Glucose Metabolic Rate in Individuals With Type 2 Diabetes: A Cardiac Dynamic 18F-FDG-PET Study

Metabolic syndrome is a condition characterized by a clustering of metabolic abnormalities associated with an increased risk of type 2 diabetes and cardiovascular disease. An impaired insulin-stimulated myocardial glucose metabolism has been shown to be a risk factor for the development of cardiovascular disease in patients with type 2 diabetes. Whether cardiac insulin resistance occurs in subjects with metabolic syndrome remains uncertain. To investigate this issue, we evaluated myocardial glucose metabolic rate using cardiac dynamic 18F-FDG-PET combined with euglycemic-hyperinsulinemic clamp in three groups: a group of normal glucose tolerant individuals without metabolic syndrome (n = 10), a group of individuals with type 2 diabetes and metabolic syndrome (n = 19), and a group of subjects with type 2 diabetes without metabolic syndrome (n = 6). After adjusting for age and gender, individuals with type 2 diabetes and metabolic syndrome exhibited a significant reduction in insulin-stimulated myocardial glucose metabolic rate (10.5 ± 9.04 μmol/min/100 g) as compared with both control subjects (32.9 ± 9.7 μmol/min/100 g; P &lt; 0.0001) and subjects with type 2 diabetes without metabolic syndrome (25.15 ± 4.92 μmol/min/100 g; P = 0.01). Conversely, as compared with control subjects (13.01 ± 8.53 mg/min x Kg FFM), both diabetic individuals with metabolic syndrome (3.06 ± 1.7 mg/min × Kg FFM, P = 0.008) and those without metabolic syndrome (2.91 ± 1.54 mg/min × Kg FFM, P = 0.01) exhibited a significant reduction in whole-body insulin-stimulated glucose disposal, while no difference was observed between the 2 groups of subjects with type 2 diabetes with or without metabolic syndrome. Univariate correlations showed that myocardial glucose metabolism was positively correlated with insulin-stimulated glucose disposal (r = 0.488, P = 0.003), and negatively correlated with the presence of metabolic syndrome (r = −0.743, P &lt; 0.0001) and with its individual components. In conclusion, our data suggest that an impaired myocardial glucose metabolism may represent an early cardio-metabolic defect in individuals with the coexistence of type 2 diabetes and metabolic syndrome, regardless of whole-body insulin resistance.

Dyslipidemia and associated cardiovascular risk factors in HIV-positive and HIV-negative patients visiting ambulatory clinics: A hospital-based study

Background

Dyslipidemia is a well-known risk factor for cardiovascular disease (CVD), accounting for more than half of all instances of coronary artery disease globally (CAD).

Purpose

The purpose of this study was to determine lipid-related cardiovascular risks in HIV-positive and HIV-negative individuals by evaluating lipid profiles, ratios, and other related parameters.

Methods

A hospital-based study was carried out from January 2019 to February 2021 in both HIV + and HIV- ambulatory patients.

Results

High TG (p = .003), high TC (p = .025), and low HDL (p < .001) were all associated with a two-fold increased risk of CVD in people aged 45 and up. Due to higher TG (p < .001) and lower HDL (p < .001), males were found to have a higher risk of atherogenic dyslipidemia. A twofold increase in the likelihood of higher TG levels has been associated with smoking (p = .032) and alcohol intake (p = .022). A twofold increase in a high TC/HDL ratio and an elevated TG/HDL ratio was observed with an increase in waist-to-height ratio (p = .030) and a high level of FBS (126 mg/dl) and/or validated diabetes (p = .017), respectively. In HIV + participants, central obesity (p < .001), diabetes (p < .001), and high blood pressure (p < .001) were all less common than in HIV- participants.

Conclusions

Dyslipidemia is linked to advanced age, male gender, diabetes, smoking, alcohol consumption, and increased waist circumference, all of which could lead to an increased risk of CVD, according to the study. The study also revealed that the risks are less common in HIV + people than in HIV-negative ambulatory patients.

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.

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.

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.

Concurrent diabetes and heart failure: interplay and novel therapeutic approaches

Diabetes mellitus increases the risk of developing heart failure, and the co-existence of both diseases worsens cardiovascular outcomes, hospitalization and the progression of heart failure. Despite current advancements on therapeutic strategies to manage hyperglycemia, the likelihood of developing diabetes-induced heart failure is still significant, especially with the accelerating global prevalence of diabetes and an ageing population. This raises the likelihood of other contributing mechanisms beyond hyperglycemia in predisposing diabetic patients to cardiovascular disease risk. There has been considerable interest in understanding the alterations in cardiac structure and function in the diabetic patients, collectively termed as "diabetic cardiomyopathy". However, the factors that contribute to the development of diabetic cardiomyopathies is not fully understood. This review summarizes the main characteristics of diabetic cardiomyopathies, and the basic mechanisms that contribute to its occurrence. This includes perturbations in insulin resistance, fuel preference, reactive oxygen species generation, inflammation, cell death pathways, neurohormonal mechanisms, advanced glycated end-products accumulation, lipotoxicity, glucotoxicity, and posttranslational modifications in the heart of the diabetic. This review also discusses the impact of antihyperglycemic therapies on the development of heart failure, as well as how current heart failure therapies influence glycemic control in diabetic patients. We also highlight the current knowledge gaps in understanding how diabetes induces heart failure.

Effect of fasting duration on myocardial fluorodeoxyglucose uptake in diabetic and nondiabetic patients

OBJECTIVE

To detect cardiac hypermetabolic lesions using fluorodeoxyglucose (FDG) with PET/computed tomography (PET/CT), the efficiency of long fasting and temperature condition for lowering physiological myocardial FDG uptake is controversial and may be confounded by other factors. We thus aimed to investigate the impact of fasting duration and ambient temperature on myocardial uptake in diabetic and nondiabetic patients.

METHODS

FDG PET/CT scans (n = 666) were reviewed and the myocardial uptake was visually graded on a four-point scale and quantified using standardized uptake value (SUV). The associations between myocardial uptake and fasting duration, diabetes status, ambient temperature parameters, age, gender, and BMI were evaluated.

RESULTS

Intraobserver [κ = 0.94; intraclass correlation coefficient (ICC) = 0.99] and interobserver (κ = 0.91; ICC = 0.99) reliabilities of both visual and SUV measurements were all excellent. Fasting duration and diabetes status were found to be significantly associated with myocardial FDG uptake, but the ambient temperature parameters and other factor were not. Patients with intense (Grade 4) myocardial uptake had a shorter fasting duration (P = 0.011). The SUVmax of myocardium was significantly higher in nondiabetic than diabetic patients (P < 0.001). Fasting duration ≥ 12 h in diabetic and ≥16 h in nondiabetic patients was associated with low prevalence of Grade 4 uptake (4.2%, P = 0.016; 2.3%, P = 0.028).

CONCLUSION

Fasting for long enough durations but not ambient temperature was associated with decreased physiological myocardial FDG uptake. A fasting duration of more than 12 h for diabetic, 16 h for nondiabetic patients is a simple and valuable recommendation.

SGLT2 Inhibition Does Not Affect Myocardial Fatty Acid Oxidation or Uptake, but Reduces Myocardial Glucose Uptake and Blood Flow in Individuals With Type 2 Diabetes: A Randomized Double-Blind, Placebo-Controlled Crossover Trial

Sodium-glucose cotransporter 2 (SGLT2) inhibition reduces cardiovascular morbidity and mortality in individuals with type 2 diabetes. Beneficial effects have been attributed to increased ketogenesis, reduced cardiac fatty acid oxidation, and diminished cardiac oxygen consumption. We therefore studied whether SGLT2 inhibition altered cardiac oxidative substrate consumption, efficiency, and perfusion. Thirteen individuals with type 2 diabetes were studied after 4 weeks' treatment with empagliflozin and placebo in a randomized, double-blind, placebo-controlled crossover study. Myocardial palmitate and glucose uptake were measured with ¹¹C-palmitate and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT). Oxygen consumption and myocardial external efficiency (MEE) were measured with ¹¹C-acetate PET/CT. Resting and adenosine stress myocardial blood flow (MBF) and myocardial flow reserve (MFR) were measured using ¹⁵O-H₂O PET/CT. Empagliflozin did not affect myocardial free fatty acids (FFAs) uptake but reduced myocardial glucose uptake by 57% (P < 0.001). Empagliflozin did not change myocardial oxygen consumption or MEE. Empagliflozin reduced resting MBF by 13% (P < 0.01), but did not significantly affect stress MBF or MFR. In conclusion, SGLT2 inhibition did not affect myocardial FFA uptake, but channeled myocardial substrate utilization from glucose toward other sources and reduced resting MBF. However, the observed metabolic and hemodynamic changes were modest and most likely contribute only partially to the cardioprotective effect of SGLT2 inhibition.

Associations of physiologic myocardial 18F-FDG uptake with fasting duration, HbA1c, and regular exercise

OBJECTIVE

The variability of physiologic ¹⁸F-FDG uptake in the myocardium has hampered the accurate evaluation of cardiac glucose metabolism. We investigated the effects of multiple factors, including fasting duration and physical activity, on the physiologic uptake of ¹⁸F-FDG by the myocardium in healthy participants.

METHODS

A total of 446 participants (predominantly male, 91%) in a health screening program were included in this retrospective study. For the visual analysis of myocardial ¹⁸F-FDG uptake, the participants were categorized into three groups according to qualitative visual scales (QVS). For the quantitative analysis, the maximum SUV of the left ventricular myocardium was measured.

RESULTS

Significant differences were observed in fasting duration (p < 0.001), SUV_max (p < 0.001), aspartate aminotransferase (AST) (p < 0.001), alanine aminotransferase (ALT) (p < 0.001), gamma-glutamyl transpeptidase (γ-GTP) (p = 0.001), and uric acid (p = 0.015) among the QVS groups. Participants who regularly exercised with vigorous activity (p = 0.032) and HbA1c > 6% (p = 0.005) showed significant association with myocardial FDG uptake in the Chi-squared test. The median value of fasting duration decreased significantly as the QVS of the myocardium increased. Twenty-nine of the 31 participants (93.5%) who fasted for 21.5 h or more showed a suppressed FDG uptake (mean SUV_max = 2.1). In multivariate logistic regression analysis, fasting duration (OR = 0.74, 95% CI 0.69-0.80, p < 0.001), HbA1c > 6% (OR = 0.29, 95% CI: 0.12 - 0.66, p = 0.004), uric acid (OR = 0.82, 95% CI 0.68-1.00, p = 0.049) and regular exercise with vigorous activity (OR = 1.75, 95% CI 1.13-2.70, p = 0.012) were significant factors for physiologic myocardial FDG uptake.

CONCLUSIONS

Reduced physiologic ¹⁸F-FDG uptake of the myocardium was associated with longer fasting duration, higher level of HbA1c, and less frequency of regular exercise with vigorous activity. For the preparation of cardiac ¹⁸F-FDG PET, inclusion of longer fasting duration (more than 18 h) might be necessary for the adequate suppression of physiologic ¹⁸F-FDG myocardial uptake.

Optimizing the Use of iPSC-CMs for Cardiac Regeneration in Animal Models

Simple Summary

In 2006, the first induced pluripotent stem cells were generated by reprogramming skin cells. Induced pluripotent stem cells undergo fast cell division, can differentiate into many different cell types, can be patient-specific, and do not raise ethical issues. Thus, they offer great promise as in vitro disease models, drug toxicity testing platforms, and for autologous tissue regeneration. Heart failure is one of the major causes of death worldwide. It occurs when the heart cannot meet the body’s metabolic demands. Induced pluripotent stem cells can be differentiated into cardiac myocytes, can form patches resembling native cardiac tissue, and can engraft to the damaged heart. However, despite correct host/graft coupling, most animal studies demonstrate an arrhythmogenicity of the engrafted tissue and variable survival. This is partially because of the heterogeneity and immaturity of the cells. New evidence suggests that by modulating induced pluripotent stem cells-cardiac myocytes (iPSC-CM) metabolism by switching substrates and changing metabolic pathways, you can decrease iPSC-CM heterogeneity and arrhythmogenicity. Novel culture methods and tissue engineering along with animal models of heart failure are needed to fully unlock the potential of cardiac myocytes derived from induced pluripotent stem cells for cardiac regeneration.

Abstract

Heart failure (HF) is a common disease in which the heart cannot meet the metabolic demands of the body. It mostly occurs in individuals 65 years or older. Cardiac transplantation is the best option for patients with advanced HF. High numbers of patient-specific cardiac myocytes (CMs) can be generated from induced pluripotent stem cells (iPSCs) and can possibly be used to treat HF. While some studies found iPSC-CMS can couple efficiently to the damaged heart and restore cardiac contractility, almost all found iPSC-CM transplantation is arrhythmogenic, thus hampering the use of iPSC-CMs for cardiac regeneration. Studies show that iPSC-CM cultures are highly heterogeneous containing atrial-, ventricular- and nodal-like CMs. Furthermore, they have an immature phenotype, resembling more fetal than adult CMs. There is an urgent need to overcome these issues. To this end, a novel and interesting avenue to increase CM maturation consists of modulating their metabolism. Combined with careful engineering and animal models of HF, iPSC-CMs can be assessed for their potential for cardiac regeneration and a cure for HF.

Hepatic steatosis is associated with abnormal hepatic enzymes, visceral adiposity, altered myocardial glucose uptake measured by 18F-FDG PET/CT

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a multisystem disease that affects the liver and a variety of extra-hepatic organ systems. This study aimed to investigate the relationship between hepatic steatosis and glucose metabolism in liver and extra-hepatic tissues and organs.

METHODS

The whole body 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) images of 191 asymptomatic tumor screening patients were retrospectively analyzed. Patients with the ratio of spleen/liver CT densities > 1.1 were defined to have NAFLD, and their clinical symptoms, laboratory markers, FDG uptake in a variety of tissues and organs including heart, mediastinal blood pool, liver, spleen, pancreas, and skeletal muscle, as well as abdominal adipose tissue volumes including visceral adipose tissue (VAT) volume and subcutaneous adipose tissue (SAT) volume were compared with those of the non-NAFLD patients and used to analyze the independent correlation factors of NAFLD.

RESULTS

Among the 191 patients, 33 (17.3%) were NAFLD, and 158 (82.7%) were non-NAFLD. There was no significant correlation between the mean standardized uptake value (SUVmean) and CT density of liver as well as the ratio of spleen/liver CT densities. Hepatic steatosis, but not FDG intake, was more significant in NAFLD patients with abnormal liver function than those with normal liver function. Compared with the non-NAFLD patients, NAFLD patients had significantly reduced myocardial glucose metabolism, but significantly increased mediastinal blood pool, spleen SUVmean and abdominal adipose tissue volumes (including VAT and SAT volumes) (P < 0.05). Multivariate regression analysis showed that elevated serum ALT, increased abdominal VAT volume, and decreased myocardial FDG uptake were independent correlation factors for NAFLD. Further studies showed that hepatic steatosis and myocardial FDG uptake were mildly linearly correlated (r = 0.366 with hepatic CT density and - 0.236 with the ratio of spleen/liver CT densities, P < 0.05).

CONCLUSIONS

NAFLD is a systemic disease that can lead to the change of glucose metabolism in some extra-hepatic tissues and organs, especially the myocardium.

Pet tracers for vulnerable plaque imaging

Most of the acute ischemic events, such as acute coronary syndromes and stroke, are attributed to vulnerable plaques. These lesions have common histological and pathophysiological features, including inflammatory cell infiltration, neo-angiogenesis, remodelling, haemorrhage predisposition, thin fibrous cap, large lipid core, and micro-calcifications. Early detection of the presence of a plaque prone to rupture could be life-saving for the patient; however, vulnerable plaques usually cause non-haemodynamically significant stenosis, and anatomical imaging techniques often underestimate, or may not even detect, these lesions. Although ultrasound techniques are currently considered as the "first-line" examinations for the diagnostic investigation and treatment monitoring in patients with atherosclerotic plaques, positron emission tomography (PET) imaging could open new horizons in the assessment of atherosclerosis, given its ability to visualize metabolic processes and provide molecular-functional evidence regarding vulnerable plaques. Moreover, modern hybrid imaging techniques, combining PET with computed tomography or magnetic resonance imaging, can evaluate simultaneously both functional and morphological parameters of the atherosclerotic plaques, and are expected to significantly expand their clinical role in the future. This review summarizes current research on the PET imaging of the vulnerable atherosclerotic plaques, outlining current and potential applications in the clinical setting.

Relationship Between Changes in Myocardial F-18 Fluorodeoxyglucose Uptake and Radiation Dose After Adjuvant Three-Dimensional Conformal Radiotherapy in Patients with Breast Cancer

This study aimed to assess the relationship between radiation dose and changes in the irradiated myocardial F-18 fluorodeoxyglucose (FDG) uptake after radiotherapy (RT) in breast cancer patients. The data of 55 patients with left and 48 patients with right breast cancer who underwent curative surgical resection and adjuvant three-dimensional conformal RT and staging (PET1), post-adjuvant chemotherapy (PET2), post-RT (PET3), and surveillance (PET4) FDG positron emission tomography/computed tomography (PET/CT) were retrospectively reviewed. The median interval between PET1 and curative surgical resection, between the end of adjuvant chemotherapy and PET2, between the end of RT and PET3, and between the end of RT and PET4 were five days, 13 days, 132 days, and 353 days, respectively. The myocardial-to-blood pool uptake ratio was measured in all patients. For patients with left breast cancer, the 30 Gy- (30 Gy) and 47.5 Gy-irradiated myocardium-to-low-irradiated myocardium (47.5 Gy) FDG uptake ratios were additionally measured. There were no differences in the myocardial-to-blood pool uptake ratios between left and right breast cancer on all PET scans. For left breast cancer, higher 30 Gy and 47.5 Gy uptake ratios were observed on PET3 than on PET1 and PET2. Both uptake ratios decreased on PET4 compared to PET3, but, were still higher compared to PET1. On PET3 and PET4, the 47.5 Gy were higher than the 30 Gy uptake ratios, while there were no differences between them on PET1 and PET2. Although the whole myocardium FDG uptake showed no significant change, the irradiated myocardium FDG uptake significantly increased after RT and was related to radiation dose to the myocardium in breast cancer patients. These results might be an imaging evidence that supports the increased risk of heart disease after RT in patients with left breast cancer.

Clinical significance of quantitative assessment of right ventricular glucose metabolism in patients with heart failure with reduced ejection fraction

PURPOSE

Dynamic ¹⁸F-fluorodeoxyglucose (FDG) PET can be used to quantitatively assess the rate of myocardial glucose uptake (MRGlu). The aim of this study was to evaluate the clinical significance and prognostic value of right ventricular (RV) MRGlu in patients with coronary artery disease and heart failure with reduced ejection fraction.

METHODS

Patients with left ventricular ejection fraction (LVEF) ≤ 40% were consecutively enrolled for FDG PET between November 2012 and May 2017. Global LV and RV MRGlu (μmol/min/100 g) were analyzed. Outcome events were independently assessed using electronic medical records to determine hospitalization for revascularization, new-onset ischemic events, heart failure, cardiovascular, and all-cause death. Differences between LV and RV MRGlu and associations with clinical characteristics and echocardiographic data were evaluated. Associations among FDG PET findings and outcomes were analyzed using Kaplan-Meier survival analysis.

RESULTS

Seventy-five patients (mean age 62.2 ± 12.7 years, male 85.3%, LVEF 19.3 ± 8.6%) were included for analysis. The mean glucose utilization ratio of RV-to-LV (RV/LV MRGlu) was 89.5 ± 264.9% (r = 0.77, p < 0.001). Positive correlations between RV MRGlu and maximal tricuspid regurgitation peak gradient (r = 0.28, p = 0.033) and peak tricuspid regurgitation jet velocity (r = 0.29, p = 0.021) were noted. LVEF was positively correlated with LV MRGlu (r = 0.27, p = 0.018), but negatively correlated with end-diastolic volume (r = - 0.37, p = 0.001), end-systolic volume (r = - 0.54, p < 0.001), and RV/LV MRGlu (r = - 0.40, p < 0.001). However, RV MRGlu was not well correlated with LVEF. Forty-three patients received revascularization procedures after FDG PET, and 13 patients died in a mean follow-up period of 496 ± 453 days (1-1788 days), including nine cardiovascular deaths. Higher RV and LV MRGlu values, LVEF ≤ 16% and LV end-diastolic volume ≥ 209 ml of gated-PET were associated with poor overall survival and cardiac outcomes.

CONCLUSIONS

In patients with coronary artery disease and ischemic cardiomyopathy, RV glucose utilization was positively correlated with RV pressure overload, but not LVEF. Global LV and RV MRGlu, LVEF, and LV end-diastolic volume showed significant prognostic value.

Non-Invasive Imaging in Diabetic Cardiomyopathy

There is increasing recognition of a specific diabetic cardiomyopathy beyond ischemic cardiomyopathy, which leads to structural and functional myocardial abnormalities. The aim of this review is to summarize the recent literature on diagnostic findings and prognostic significance of non-invasive imaging including echocardiography, nuclear imaging, computed tomography and cardiovascular magnetic resonance in diabetic cardiomyopathy.

Review of cardiovascular imaging in the Journal of Nuclear Cardiology 2018. Part 1 of 2: Positron emission tomography, computed tomography, and magnetic resonance

In this review, we summarize key articles that have been published in the Journal of Nuclear Cardiology in 2018 pertaining to nuclear cardiology with advanced multi-modality and hybrid imaging including positron emission tomography, cardiac-computed tomography, and magnetic resonance. In an upcoming review, we will summarize key articles that relate to the progress made in the field of single-photon emission computed tomography. We hope that these sister reviews will be useful to the reader to navigate the literature in our field.