Increased myocardial uptake of dietary fatty acids linked to cardiac dysfunction in glucose-intolerant humans

Tracers and Imaging of Fatty Acid and Energy Metabolism of Human Adipose Tissues

White adipose tissue and brown adipose tissue (WAT and BAT) regulate fatty acid metabolism and control lipid fluxes to other organs. Dysfunction of these key metabolic processes contributes to organ insulin resistance and inflammation leading to chronic diseases such as type 2 diabetes, metabolic dysfunction-associated steatohepatitis, and cardiovascular diseases. Metabolic tracers combined with molecular imaging methods are powerful tools for the investigation of these pathogenic mechanisms. Herein, I review some of the positron emission tomography and magnetic resonance imaging methods combined with stable isotopic metabolic tracers to investigate fatty acid and energy metabolism, focusing on human WAT and BAT metabolism. I will discuss the complementary strengths offered by these methods for human investigations and current gaps in the field.

NT-proBNP and cardiovascular event risk in individuals with prediabetes undergoing cardiovascular evaluation

AIMS

Cardiovascular risk assessment beyond traditional risk factors in subjects with prediabetes is not well-established. Here, we evaluated the utility of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in predicting incident adverse cardiovascular outcomes in prediabetic subjects.

METHODS

NT-proBNP was analyzed in 3,235 stable subjects with prediabetes undergoing cardiovascular risk evaluation and followed for both 3-year major adverse cardiac events (MACE; death, myocardial infarction, stroke), and 5-year all-cause mortality.

RESULTS

Using Cox proportional hazard models, we found that plasma NT-proBNP was associated with incident (3-year) MACE risk (Q4 vs Q1, HR 6.04 [95%CI 4.17-8.76], P < 0.001) and 5-year mortality risk (HR 8.64 [95%CI 5.78-12.9], P < 0.001). These associations remained significant after adjustments for traditional cardiovascular risk factors, multiple indices of glycemic control, cardiovascular disease (CVD), left ventricular ejection fraction (LVEF), and medication (e.g. diuretic) use (adjusted HR for 3-year MACE 2.65 [95% CI 1.16-6.05], P < 0.05; and adjusted HR for 5-year mortality 3.45 [95% CI 1.42-8.39], P < 0.01). NT-proBNP significantly improved the clinical prognostic value (C-statistic, NRI, IDI) for both 3-year MACE and 5-year death when added to models.

CONCLUSIONS

NT-proBNP independently predicts increased long-term MACE and mortality risks in prediabetic subjects, and may help identify those for whom more aggressive global preventive efforts are indicated.

Cardiorenal ketone metabolism: a positron emission tomography study in healthy humans

Ketones are alternative energy substrates for the heart and kidney but no studies have investigated their metabolism simultaneously in both organs in humans. The present double tracer positron emission tomography (PET) study evaluated the organ distribution and basal kinetic rates of the radiolabeled ketone, 11C-acetoacetate (11C-AcAc), in the heart and kidney compared to 11C-acetate (11C-Ac), which is a well-validated metabolic radiotracer. Both tracers were highly metabolized by the left ventricle and the renal cortex. In the heart, kinetic rates were similar for both tracers. But in the renal cortex, uptake of 11C-Ac was higher compared to 11C-AcAc, while the reverse was observed for the clearance. Interestingly, infusion of 11C-AcAc led to a significantly delayed release of radioactivity in the renal medulla and pelvis, a phenomenon not observed with 11C-Ac. This suggests an equilibrium of 11C-AcAc with the other ketone, 11C-D-beta-hydroxybutyrate, and a different clearance profile. Overall, this suggests that in the kidney, the absorption and metabolism of 11C-AcAc is different compared to 11C-Ac. This dual tracer PET protocol provides the opportunity to explore the relative importance of ketone metabolism in cardiac and renal diseases, and to improve our mechanistic understanding of new metabolic interventions targeting these two organs.

Epicardial Adipose Tissue Assessed by Computed Tomography and Echocardiography Are Associated With Adverse Cardiovascular Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

Epicardial adipose tissue (EAT) has garnered attention as a prognostic and risk stratification factor for cardiovascular disease. This study, via meta-analyses, evaluates the associations between EAT and cardiovascular outcomes stratified across imaging modalities, ethnic groups, and study protocols.

METHODS

Medline and Embase databases were searched without date restriction on May 2022 for articles that examined EAT and cardiovascular outcomes. The inclusion criteria were (1) studies measuring EAT of adult patients at baseline and (2) reporting follow-up data on study outcomes of interest. The primary study outcome was major adverse cardiovascular events. Secondary study outcomes included cardiac death, myocardial infarction, coronary revascularization, and atrial fibrillation.

RESULTS

Twenty-nine articles published between 2012 and 2022, comprising 19 709 patients, were included in our analysis. Increased EAT thickness and volume were associated with higher risks of cardiac death (odds ratio, 2.53 [95% CI, 1.17-5.44]; P=0.020; n=4), myocardial infarction (odds ratio, 2.63 [95% CI, 1.39-4.96]; P=0.003; n=5), coronary revascularization (odds ratio, 2.99 [95% CI, 1.64-5.44]; P<0.001; n=5), and atrial fibrillation (adjusted odds ratio, 4.04 [95% CI, 3.06-5.32]; P<0.001; n=3). For 1 unit increment in the continuous measure of EAT, computed tomography volumetric quantification (adjusted hazard ratio, 1.74 [95% CI, 1.42-2.13]; P<0.001) and echocardiographic thickness quantification (adjusted hazard ratio, 1.20 [95% CI, 1.09-1.32]; P<0.001) conferred an increased risk of major adverse cardiovascular events.

CONCLUSIONS

The utility of EAT as an imaging biomarker for predicting and prognosticating cardiovascular disease is promising, with increased EAT thickness and volume being identified as independent predictors of major adverse cardiovascular events.

REGISTRATION

URL: https://www.crd.york.ac.uk/prospero; Unique identifier: CRD42022338075.

Impacts of a high-fat diet on the metabolic profile and the phenotype of atrial myocardium in mice

AIMS

Obesity, diabetes, and metabolic syndromes are risk factors of atrial fibrillation (AF). We tested the hypothesis that metabolic disorders have a direct impact on the atria favouring the formation of the substrate of AF.

METHODS AND RESULTS

Untargeted metabolomic and lipidomic analysis was used to investigate the consequences of a prolonged high-fat diet (HFD) on mouse atria. Atrial properties were characterized by measuring mitochondria respiration in saponin-permeabilized trabeculae, by recording action potential (AP) with glass microelectrodes in trabeculae and ionic currents in myocytes using the perforated configuration of patch clamp technique and by several immuno-histological and biochemical approaches. After 16 weeks of HFD, obesogenic mice showed a vulnerability to AF. The atrial myocardium acquired an adipogenic and inflammatory phenotypes. Metabolomic and lipidomic analysis revealed a profound transformation of atrial energy metabolism with a predominance of long-chain lipid accumulation and beta-oxidation activation in the obese mice. Mitochondria respiration showed an increased use of palmitoyl-CoA as energy substrate. APs were short duration and sensitive to the K-ATP-dependent channel inhibitor, whereas K-ATP current was enhanced in isolated atrial myocytes of obese mouse.

CONCLUSION

HFD transforms energy metabolism, causes fat accumulation, and induces electrical remodelling of the atrial myocardium of mice that become vulnerable to AF.

Pharmacotherapy of type 2 diabetes: An update and future directions

Type 2 diabetes (T2D) is a widely prevalent disease with substantial economic and social impact for which multiple conventional and novel pharmacotherapies are currently available; however, the landscape of T2D treatment is constantly changing as new therapies emerge and the understanding of currently available agents deepens. This review aims to provide an updated summary of the pharmacotherapeutic approach to T2D. Each class of agents is presented by mechanism of action, details of administration, side effect profile, cost, and use in certain populations including heart failure, non-alcoholic fatty liver disease, obesity, chronic kidney disease, and older individuals. We also review targets of novel therapeutic T2D agent development. Finally, we outline an up-to-date treatment approach that starts with identification of an individualized goal for glycemic control then selection, initiation, and further intensification of a personalized therapeutic plan for T2D.

Total Postprandial Hepatic Nonesterified and Dietary Fatty Acid Uptake Is Increased and Insufficiently Curbed by Adipose Tissue Fatty Acid Trapping in Prediabetes With Overweight

Excessive lean tissue uptake of fatty acids (FAs) is important in the development of insulin resistance and may be caused by impaired dietary FA (DFA) storage and/or increased nonesterified FA (NEFA) flux from adipose tissue intracellular lipolysis. Cardiac and hepatic total postprandial FA uptake of NEFA+DFA has, however, never been reported in prediabetes with overweight. In this study, 20 individuals with impaired glucose tolerance (IGT) and 19 participants with normal glucose tolerance (NGT) and normal fasting glucose underwent postprandial studies with whole-body positron emission tomography/computed tomography (PET/CT) with oral [18F]fluoro-thia-heptadecanoic acid and dynamic PET/CT with intravenous [11C]palmitate. Hepatic (97 [range 36-215] mmol/6 h vs. 68 [23-132] mmol/6 h, P = 0.03) but not cardiac (11 [range 4-24] mmol/6 h vs. 8 [3-20] mmol/6 h, P = 0.09) uptake of most sources of postprandial FA (NEFA + DFA uptake) integrated over 6 h was higher in IGT versus NGT. DFA accounted for lower fractions of total cardiac (21% [5-47] vs. 25% [9-39], P = 0.08) and hepatic (19% [6-52] vs. 28% [14-50], P = 0.04) uptake in IGT versus NGT. Increased adipose tissue DFA trapping predicted lower hepatic DFA uptake and was associated with higher total cardiac FA uptake. Hence, enhanced adipose tissue DFA trapping in the face of increased postprandial NEFA flux is insufficient to fully curb increased postprandial lean organ FA uptake in prediabetes with overweight (ClinicalTrials.gov; NCT02808182).

The Role of Mitochondria in Metabolic Syndrome–Associated Cardiomyopathy

With the rapid development of society, the incidence of metabolic syndrome (MS) is increasing rapidly. Evidence indicated that patients diagnosed with MS usually suffered from cardiomyopathy, called metabolic syndrome–associated cardiomyopathy (MSC). The clinical characteristics of MSC included cardiac hypertrophy and diastolic dysfunction, followed by heart failure. Despite many studies on this topic, the detailed mechanisms are not clear yet. As the center of cellular metabolism, mitochondria are crucial for maintaining heart function, while mitochondria dysfunction plays a vital role through mechanisms such as mitochondrial energy deprivation, calcium disorder, and ROS (reactive oxygen species) imbalance during the development of MSC. Accordingly, in this review, we will summarize the characteristics of MSC and especially focus on the mechanisms related to mitochondria. In addition, we will update new therapeutic strategies in this field.

Phenotype of higher post-load insulin response as a predictor of all-cause mortality and cardiovascular mortality in the Chinese non-diabetic population

AIM

This study aimed to assess whether a higher insulin response increased the long-term risk of mortality in a non-diabetic population.

METHODS

A total of 446 people with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT) who participated in the Da Qing Diabetes Study, were stratified into quartiles subgroups according to their baseline insulin area under the curve (AUC) during oral glucose tolerance test, defined as Q1, Q2, Q3 and Q4. The participants were followed from 1986 to 2016 to assess the risk of death in association with the magnitude of post-load insulin response.

RESULTS

Over 30 years, the rates of all cause death were 9.94, 14.81, 15.02, and 17.58 per 1000 person-years across the four groups respectively. The rate for cardiovascular disease (CVD) death was 5.14, 6.50, 6.80 and 10.47 per 1000 person-years. Compared with Q1, the risk of all-cause death was significantly higher in participants in Q4 (HR = 2.14, 95% CI 1.34-3.42), Q3 (HR = 1.94, 95% CI 1.20-3.14), and Q2 group (HR = 1.70, 95% CI 1.06-2.74). In the Fine-Gray model with non-CVD death as competing risk, the increased insulin AUC were also significantly associated with the CVD death (Q4 vs Q1, HR = 2.04, 95% CI 1.10-3.79). In the fractional polynomial regression analysis, a nonlinear association between insulin AUC and all-cause and CVD death was demonstrated. In addition, insulin AUC was associated with a progressively higher risk of all-cause death and CVD death (fractional power 3, P < 0.001).

CONCLUSION

A higher post-load insulin response was significantly associated with a long-term increased risk of all-cause and CVD deaths in the Chinese non-diabetic population. It suggests that people featured by this phenotype is a potential important target for further intervention.

Fat Cell Size: Measurement Methods, Pathophysiological Origins, and Relationships With Metabolic Dysregulations

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex.

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.

Management of Obesity in Cardiovascular Practice: JACC Focus Seminar

Obesity contributes to reduced life expectancy because of its link with type 2 diabetes and cardiovascular disease. Yet, targeting this poorly diagnosed, ill-defined, and underaddressed modifiable risk factor remains a challenge. In this review, we emphasize that the tendency among health care professionals to amalgam all forms of obesity altogether as a single entity may contribute to such difficulties and discrepancies. Obesity is a heterogeneous condition both in terms of causes and health consequences. Attention should be given to 2 prevalent subgroups of individuals: 1) patients who are overweight or moderately obese with excess visceral adipose tissue; and 2) patients with severe obesity, the latter group having distinct additional health issues related to their large body fat mass. The challenge of tackling high-cardiovascular-risk forms of obesity through a combination of personalized clinical approaches and population-based solutions is compounded by the current obesogenic environment and economy.

Insulin signaling in the heart

Insulin receptors are highly expressed in the heart and vasculature. Insulin signaling regulates cardiac growth, survival, substrate uptake, utilization, and mitochondrial metabolism. Insulin signaling modulates the cardiac responses to physiological and pathological stressors. Altered insulin signaling in the heart may contribute to the pathophysiology of ventricular remodeling and heart failure progression. Myocardial insulin signaling adapts rapidly to changes in the systemic metabolic milieu. What may initially represent an adaptation to protect the heart from carbotoxicity may contribute to amplifying the risk of heart failure in obesity and diabetes. This review article presents the multiple roles of insulin signaling in cardiac physiology and pathology and discusses the potential therapeutic consequences of modulating myocardial insulin signaling.

Obesity and Heart Failure with Preserved Ejection Fraction

Obese heart failure with preserved ejection fraction (HFpEF) is a distinct HFpEF phenotype. Sodium retention, high circulating neurohormone levels, alterations in energy substrate metabolism, group 3 pulmonary hypertension, pericardial restraint, and systemic inflammation are central pathophysiologic mechanisms. Confirming the diagnosis may be challenging and high suspicion is required. Reduction of visceral adipose tissue, via caloric restriction and/or bariatric surgery, may improve outcomes in obese HFpEF patients. Furthermore, mineralocorticoid receptor inhibition, neprilysin inhibition, and sodium-glucose cotransporter 2 inhibition can ameliorate the effects of adiposity on the cardiovascular system, allowing for promising new treatment targets for the obese HFpEF phenotype.

Increased postprandial nonesterified fatty acid efflux from adipose tissue in prediabetes is offset by enhanced dietary fatty acid adipose trapping

The mechanism of increased postprandial nonesterified fatty acid (NEFA) appearance in the circulation in impaired glucose tolerance (IGT) is due to increased adipose tissue lipolysis but could also be contributed to by reduced adipose tissue (AT) dietary fatty acid (DFA) trapping and increased "spillover" into the circulation. Thirty-one subjects with IGT (14 women, 17 men) and 29 with normal glucose tolerance (NGT, 15 women, 14 men) underwent a meal test with oral and intravenous palmitate tracers and the oral [¹⁸F]-fluoro-thia-heptadecanoic acid positron emission tomography method. Postprandial palmitate appearance (Ra_palmitate) was higher in IGT versus NGT (P < 0.001), driven exclusively by Ra_palmitate from obesity-associated increase in intracellular lipolysis (P = 0.01), as Ra_palmitate from DFA spillover was not different between the groups (P = 0.19) and visceral AT DFA trapping was even higher in IGT versus NGT (P = 0.02). Plasma glycerol appearance was lower in IGT (P = 0.01), driven down by insulin resistance and increased insulin secretion. Thus, we found higher AT DFA trapping, limiting spillover to lean organs and in part offsetting the increase in Ra_palmitate from intracellular lipolysis. Whether similar findings occur in frank diabetes, a condition also characterized by insulin resistance but relative insulin deficiency, requires further investigation (Clinicaltrials.gov: NCT04088344, NCT02808182).NEW & NOTEWORTHY We found higher adipose tissue dietary fatty acid trapping, limiting spillover to lean organs, that in part offsets the increase in appearance rate of palmitate from intracellular lipolysis in prediabetes. These results point to the adaptive nature of adipose tissue trapping and dietary fatty acid spillover as a protective mechanism against excess obesity-related palmitate appearance rate from intracellular adipose tissue lipolysis.

Therapeutic Manipulation of Myocardial Metabolism: JACC State-of-the-Art Review

The mechanisms responsible for the positive and unexpected cardiovascular effects of sodium-glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonists in patients with type 2 diabetes remain to be defined. It is likely that some of the beneficial cardiac effects of these antidiabetic drugs are mediated, in part, by altered myocardial metabolism. Common cardiometabolic disorders, including the metabolic (insulin resistance) syndrome and type 2 diabetes, are associated with altered substrate utilization and energy transduction by the myocardium, predisposing to the development of heart disease. Thus, the failing heart is characterized by a substrate shift toward glycolysis and ketone oxidation in an attempt to meet the high energetic demand of the constantly contracting heart. This review examines the metabolic pathways and clinical implications of myocardial substrate utilization in the normal heart and in cardiometabolic disorders, and discusses mechanisms by which antidiabetic drugs and metabolic interventions improve cardiac function in the failing heart.

100th anniversary of the discovery of insulin perspective: insulin and adipose tissue fatty acid metabolism

Insulin inhibits systemic nonesterified fatty acid (NEFA) flux to a greater degree than glucose or any other metabolite. This remarkable effect is mainly due to insulin-mediated inhibition of intracellular triglyceride (TG) lipolysis in adipose tissues and is essential to prevent diabetic ketoacidosis, but also to limit the potential lipotoxic effects of NEFA in lean tissues that contribute to the development of diabetes complications. Insulin also regulates adipose tissue fatty acid esterification, glycerol and TG synthesis, lipogenesis, and possibly oxidation, contributing to the trapping of dietary fatty acids in the postprandial state. Excess NEFA flux at a given insulin level has been used to define in vivo adipose tissue insulin resistance. Adipose tissue insulin resistance defined in this fashion has been associated with several dysmetabolic features and complications of diabetes, but the mechanistic significance of this concept is not fully understood. This review focusses on the in vivo regulation of adipose tissue fatty acid metabolism by insulin and the mechanistic significance of the current definition of adipose tissue insulin resistance. One hundred years after the discovery of insulin and despite decades of investigations, much is still to be understood about the multifaceted in vivo actions of this hormone on adipose tissue fatty acid metabolism.

Activation of the cardiac non-neuronal cholinergic system prevents the development of diabetes-associated cardiovascular complications

BACKGROUND

Acetylcholine (ACh) plays a crucial role in the function of the heart. Recent evidence suggests that cardiomyocytes possess a non-neuronal cholinergic system (NNCS) that comprises of choline acetyltransferase (ChAT), choline transporter 1 (CHT1), vesicular acetylcholine transporter (VAChT), acetylcholinesterase (AChE) and type-2 muscarinic ACh receptors (M2AChR) to synthesize, release, degrade ACh as well as for ACh to transduce a signal. NNCS is linked to cardiac cell survival, angiogenesis and glucose metabolism. Impairment of these functions are hallmarks of diabetic heart disease (DHD). The role of the NNCS in DHD is unknown. The aim of this study was to examine the effect of diabetes on cardiac NNCS and determine if activation of cardiac NNCS is beneficial to the diabetic heart.

METHODS

Ventricular samples from type-2 diabetic humans and db/db mice were used to measure the expression pattern of NNCS components (ChAT, CHT1, VAChT, AChE and M2AChR) and glucose transporter-4 (GLUT-4) by western blot analysis. To determine the function of the cardiac NNCS in the diabetic heart, a db/db mouse model with cardiac-specific overexpression of ChAT gene was generated (db/db-ChAT-tg). Animals were followed up serially and samples collected at different time points for molecular and histological analysis of cardiac NNCS components and prosurvival and proangiogenic signaling pathways.

RESULTS

Immunoblot analysis revealed alterations in the components of cardiac NNCS and GLUT-4 in the type-2 diabetic human and db/db mouse hearts. Interestingly, the dysregulation of cardiac NNCS was followed by the downregulation of GLUT-4 in the db/db mouse heart. Db/db-ChAT-tg mice exhibited preserved cardiac and vascular function in comparison to db/db mice. The improved function was associated with increased cardiac ACh and glucose content, sustained angiogenesis and reduced fibrosis. These beneficial effects were associated with upregulation of the PI3K/Akt/HIF1α signaling pathway, and increased expression of its downstream targets-GLUT-4 and VEGF-A.

CONCLUSION

We provide the first evidence for dysregulation of the cardiac NNCS in DHD. Increased cardiac ACh is beneficial and a potential new therapeutic strategy to prevent or delay the development of DHD.

Liver fat storage pathways: methodologies and dietary effects

PURPOSE OF REVIEW

Nonalcoholic fatty liver is the result of an imbalance between lipid storage [from meal, de novo lipogenesis (DNL) and fatty acid (FA) uptake] and disposal (oxidation and VLDL output). Knowledge on the contribution of each of these pathways to liver fat content in humans is essential to develop tailored strategies to prevent and treat nonalcoholic fatty liver. Here, we review the techniques available to study the different storage pathways and review dietary modulation of these pathways.

RECENT FINDINGS

The type of carbohydrate and fat could be of importance in modulating DNL, as complex carbohydrates and omega-3 FAs have been shown to reduce DNL. No effects were found on the other pathways, however studies investigating this are scarce.

SUMMARY

Techniques used to assess storage pathways are predominantly stable isotope techniques, which require specific expertise and are costly. Validated biomarkers are often lacking. These methodological limitations also translate into a limited number of studies investigating to what extent storage pathways can be modulated by diet. Further research is needed to elucidate in more detail the impact that fat and carbohydrate type can have on liver fat storage pathways and content.

21st Century Advances in Multimodality Imaging of Obesity for Care of the Cardiovascular Patient

Although obesity is typically defined by body mass index criteria, this does not differentiate true body fatness, as this includes both body fat and muscle. Therefore, other fat depots may better define cardiometabolic and cardiovascular disease (CVD) risk imposed by obesity. Data from translational, epidemiological, and clinical studies over the past 3 decades have clearly demonstrated that accumulation of adiposity in the abdominal viscera and within tissue depots lacking physiological adipose tissue storage capacity (termed "ectopic fat") is strongly associated with the development of a clinical syndrome characterized by atherogenic dyslipidemia, hyperinsulinemia/glucose intolerance/type 2 diabetes mellitus, hypertension, atherosclerosis, and abnormal cardiac remodeling and heart failure. This state-of-the-art paper discusses the impact of various body fat depots on cardiometabolic parameters and CVD risk. Specifically, it reviews novel and emerging imaging techniques to evaluate adiposity and the risk of cardiometabolic diseases and CVD.

Bariatric Surgery Rapidly Decreases Cardiac Dietary Fatty Acid Partitioning and Hepatic Insulin Resistance Through Increased Intra-abdominal Adipose Tissue Storage and Reduced Spillover in Type 2 Diabetes

Reduced storage of dietary fatty acids (DFAs) in abdominal adipose tissues with enhanced cardiac partitioning has been shown in subjects with type 2 diabetes (T2D) and prediabetes. We measured DFA metabolism and organ partitioning using positron emission tomography with oral and intravenous long-chain fatty acid and glucose tracers during a standard liquid meal in 12 obese subjects with T2D before and 8-12 days after bariatric surgery (sleeve gastrectomy or sleeve gastrectomy and biliopancreatic diversion with duodenal switch). Bariatric surgery reduced cardiac DFA uptake from a median (standard uptake value [SUV]) 1.75 (interquartile range 1.39-2.57) before to 1.09 (1.04-1.53) after surgery (P = 0.01) and systemic DFA spillover from 56.7 mmol before to 24.7 mmol over 6 h after meal intake after surgery (P = 0.01), with a significant increase in intra-abdominal adipose tissue DFA uptake from 0.15 (0.04-0.31] before to 0.49 (0.20-0.59) SUV after surgery (P = 0.008). Hepatic insulin resistance was significantly reduced in close association with increased DFA storage in intra-abdominal adipose tissues (r = -0.79, P = 0.05) and reduced DFA spillover (r = 0.76, P = 0.01). We conclude that bariatric surgery in subjects with T2D rapidly reduces cardiac DFA partitioning and hepatic insulin resistance at least in part through increased intra-abdominal DFA storage and reduced spillover.

Strategies of Unloading the Failing Heart from Metabolic Stress

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

Seven-day overfeeding enhances adipose tissue dietary fatty acid storage and decreases myocardial and skeletal muscle dietary fatty acid partitioning in healthy subjects

Increased myocardial partitioning of dietary fatty acids (DFA) and decreased left ventricular (LV) function is associated with insulin resistance in prediabetes. We hypothesized that enhanced myocardial DFA partitioning and reduced LV function might be induced concomitantly with reduced insulin sensitivity upon a 7-day hypercaloric (+50% in caloric intake), high-saturated fat (~11%energy), and simple carbohydrates (~54%energy) diet (HIGHCAL) versus an isocaloric diet (ISOCAL) with a moderate amount of saturated fat (~8%energy) and carbohydrates (~50%energy). Thirteen healthy subjects (7 men/6 women) underwent HIGHCAL versus ISOCAL in a randomized crossover design, with organ-specific DFA partitioning and LV function measured using the oral 14(R,S)-[¹⁸F]fluoro-6-thia-heptadecanoic acid and [¹¹C]acetate positron emission tomography methods at the end of both interventions. HIGHCAL induced a decrease in insulin sensitivity indexes with no significant change in body composition. HIGHCAL led to increased subcutaneous abdominal (+4.2 ± 1.6%, P < 0.04) and thigh (+2.4 ± 1.2%, P < 0.08) adipose tissue storage and reduced cardiac (-0.31 ± 0.11 mean standard uptake value [(SUV), P < 0.03] and skeletal muscle (-0.17 ± 0.08 SUV, P < 0.05) DFA partitioning without change in LV function. We conclude that early increase in adipose tissue DFA storage protects the heart and skeletal muscles from potential deleterious effects of DFA.

Clinical significance of quantitative assessment of glucose utilization in patients with ischemic cardiomyopathy

BACKGROUND

The aim of this study was to prospectively quantify the rate of myocardial glucose uptake (MRGlu) in myocardium with different perfusion-metabolism patterns and determine its prognostic value in patients with ischemic cardiomyopathy.

METHODS AND RESULTS

79 patients with ischemic cardiomyopathy were prospectively enrolled for dynamic cardiac FDG PET, and then followed for at least 6 months. Perfusion-metabolism patterns were determined based on visual score analysis of 201Tl SPECT and FDG PET. MRGlu was analyzed using the Patlak kinetic model. The primary end-point was cardiovascular mortality. Significantly higher MRGlu was observed in viable compared with non-viable areas. Negative correlations were found between MRGlu in transmural match and a history of hyperlipidemia, statin usage, and triglyceride levels. Diabetic patients receiving dipeptidyl peptidase-4 inhibitors (DPP4i) had a significantly lower MRGlu in transmural match, mismatch, and reverse mismatch. Patients with MRGlu in transmural match ≥ 23.40 or reverse mismatch ≥ 36.90 had a worse outcome.

CONCLUSIONS

Myocardial glucose utilization was influenced by substrates and medications, including statins and DPP4i. MRGlu could discriminate between viable and non-viable myocardium, and MRGlu in transmural match and reverse mismatch may be prognostic predictors of cardiovascular death in patients with ischemic cardiomyopathy.

Mechanisms and Evidence for Heart Failure Benefits from SGLT2 Inhibitors

PURPOSE OF REVIEW

To review the clinical trial data and underlying mechanistic principles in support of the robust cardiovascular (CV) benefits, in particular, heart failure (HF) outcomes association with sodium-glucose co-transporter-2 (SGLT2) inhibitors.

RECENT FINDINGS

Several large CV outcome trials in patients with type 2 diabetes mellitus (T2DM) and with either established atherosclerotic CV disease (ASCVD) or at high risk for ASCVD reveal that SGLT2 inhibitors cause reductions in CV and HF endpoints. The reduction in ASCVD appears to be confined to those with established ASCVD on the order of ≈ 14%, as does the mortality benefit-all-cause and CV-related. However, hospitalization for HF are reduced by ≈ 33% and occur regardless of baseline patient characteristics. The unprecedented HF outcomes are theorized to occur via several possible mechanisms and include optimization of conventional ASCVD risk factors, improvement in hemodynamics, prevention of cardiac and renal remodeling, inhibition of hormone dysregulation, use of more efficient metabolic substrates, ion channel inhibition, anti-inflammatory effects, and anti-oxidant effects. Recent evidence has unveiled the irrefutable data that SGLT2 inhibitors reduce CV events in patients with T2DM, with a profound effect on reductions in hospitalization for HF. Though several mechanisms conveying this benefit are suggested, most are based in limited data requiring further validation. Nonetheless, the arrival of SGLT2 inhibitors has ushered in a new era of CV risk reductions therapies.

Molecular Imaging of the Heart

Multimodality cardiovascular imaging is routinely used to assess cardiac function, structure, and physiological parameters to facilitate the diagnosis, characterization, and phenotyping of numerous cardiovascular diseases (CVD), as well as allows for risk stratification and guidance in medical therapy decision-making. Although useful, these imaging strategies are unable to assess the underlying cellular and molecular processes that modulate pathophysiological changes. Over the last decade, there have been great advancements in imaging instrumentation and technology that have been paralleled by breakthroughs in probe development and image analysis. These advancements have been merged with discoveries in cellular/molecular cardiovascular biology to burgeon the field of cardiovascular molecular imaging. Cardiovascular molecular imaging aims to noninvasively detect and characterize underlying disease processes to facilitate early diagnosis, improve prognostication, and guide targeted therapy across the continuum of CVD. The most-widely used approaches for preclinical and clinical molecular imaging include radiotracers that allow for high-sensitivity in vivo detection and quantification of molecular processes with single photon emission computed tomography and positron emission tomography. This review will describe multimodality molecular imaging instrumentation along with established and novel molecular imaging targets and probes. We will highlight how molecular imaging has provided valuable insights in determining the underlying fundamental biology of a wide variety of CVDs, including: myocardial infarction, cardiac arrhythmias, and nonischemic and ischemic heart failure with reduced and preserved ejection fraction. In addition, the potential of molecular imaging to assist in the characterization and risk stratification of systemic diseases, such as amyloidosis and sarcoidosis will be discussed. © 2019 American Physiological Society. Compr Physiol 9:477-533, 2019.

Molecular Mechanisms Responsible for Diastolic Dysfunction in Diabetes Mellitus Patients

In diabetic patients, cardiomyopathy is an important cause of heart failure, but its pathophysiology has not been completely understood thus far. Myocardial hypertrophy and diastolic dysfunction have been considered the hallmarks of diabetic cardiomyopathy (DCM), while systolic function is affected in the latter stages of the disease. In this article we propose the potential pathophysiological mechanisms responsible for myocardial hypertrophy and increased myocardial stiffness leading to diastolic dysfunction in this specific entity. According to our model, increased myocardial stiffness results from both cellular and extracellular matrix stiffness as well as cell–matrix interactions. Increased intrinsic cardiomyocyte stiffness is probably the most important contributor to myocardial stiffness. It results from the impairment in cardiomyocyte cytoskeleton. Several other mechanisms, specifically affected by diabetes, seem to also be significantly involved in myocardial stiffening, i.e., impairment in the myocardial nitric oxide (NO) pathway, coronary microvascular dysfunction, increased inflammation and oxidative stress, and myocardial sodium glucose cotransporter-2 (SGLT-2)-mediated effects. Better understanding of the complex pathophysiology of DCM suggests the possible value of drugs targeting the listed mechanisms. Antidiabetic drugs, NO-stimulating agents, anti-inflammatory agents, and SGLT-2 inhibitors are emerging as potential treatment options for DCM.

Emerging Technologies to Image Tissue Metabolism

Due to the implication of altered metabolism in a large spectrum of tissue function and disease, assessment of metabolic processes becomes essential in managing health. In this regard, imaging can play a critical role in allowing observation of biochemical and physiological processes. Nuclear imaging methods, in particular positron emission tomography, have been widely employed for imaging metabolism but are mainly limited by the use of ionizing radiation and the sensing of only one parameter at each scanning session. Observations in healthy individuals or longitudinal studies of disease could markedly benefit from non-ionizing, multi-parameter imaging methods. We therefore focus this review on progress with the non-ionizing radiation methods of MRI, hyperpolarized magnetic resonance and magnetic resonance spectroscopy, chemical exchange saturation transfer, and emerging optoacoustic (photoacoustic) imaging. We also briefly discuss the role of nuclear and optical imaging methods for research and clinical protocols.

Direct cardiovascular impact of SGLT2 inhibitors: mechanisms and effects

Diabetes is a global epidemic and a leading cause of death with more than 422 million patients worldwide out of whom around 392 million alone suffer from type 2 diabetes (T2D). Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are novel and effective drugs in managing glycemia of T2D patients. These inhibitors gained recent clinical and basic research attention due to their clinically observed cardiovascular protective effects. Although interest in the study of various SGLT isoforms and the effect of their inhibition on cardiovascular function extends over the past 20 years, an explanation of the effects observed clinically based on available experimental data is not forthcoming. The remarkable reduction in cardiovascular (CV) mortality (38%), major CV events (14%), hospitalization for heart failure (35%), and death from any cause (32%) observed over a period of 2.6 years in patients with T2D and high CV risk in the EMPA-REG OUTCOME trial involving the SGLT2 inhibitor empagliflozin (Empa) have raised the possibility that potential novel, more specific mechanisms of SGLT2 inhibition synergize with the known modest systemic improvements, such as glycemic, body weight, diuresis, and blood pressure control. Multiple studies investigated the direct impact of SGLT2i on the cardiovascular system with limited findings and the pathophysiological role of SGLTs in the heart. The direct impact of SGLT2i on cardiac homeostasis remains controversial, especially that SGLT1 isoform is the only form expressed in the capillaries and myocardium of human and rodent hearts. The direct impact of SGLT2i on the cardiovascular system along with potential lines of future research is summarized in this review.

Interscapular brown adipose tissue denervation does not promote the oxidative activity of inguinal white adipose tissue in male mice

Brown adipose tissue (BAT) thermogenesis is a key controller of energy metabolism. In response to cold or other adrenergic stimuli, brown adipocytes increase their substrate uptake and oxidative activity while uncoupling ATP synthesis from the mitochondrial respiratory chain activity. Brown adipocytes are found in classic depots such as in the interscapular BAT (iBAT). They can also develop in white adipose tissue (WAT), such as in the inguinal WAT (iWAT), where their presence has been associated with metabolic improvements. We previously reported that the induction of oxidative metabolism in iWAT is low compared with that of iBAT, even after sustained adrenergic stimulation. One explanation to this apparent lack of thermogenic ability of iWAT is the presence of an active iBAT, which may prevent the full activation of iWAT. In this study, we evaluated whether iBAT denervation-induced browning of white fat enhanced the thermogenic activity of iWAT following cold acclimation, under beta-3 adrenergic stimulation (CL 316,243). Following a bilateral denervation of iBAT, we assessed energy balance, evaluated the oxidative activity of iBAT and iWAT using ¹¹C-acetate, and quantified the dynamic glucose uptake of those tissues using 2-deoxy-2-[¹⁸F]- fluoro-d-glucose. Our results indicate that despite portraying marked browning and mildly enhanced glucose uptake, iWAT of cold-adapted mice does not exhibit significant oxidative activity following beta-3 adrenergic stimulation in the absence of a functional iBAT. The present results suggest that iWAT is not readily recruitable as a thermogenic organ even when functional iBAT is lacking.

Oral ethinylestradiol-levonorgestrel attenuates cardiac glycogen and triglyceride accumulation in high fructose female rats by suppressing pyruvate dehydrogenase kinase-4

Fructose (FRU) intake has increased dramatically in recent decades with a corresponding increased incidence of insulin resistance (IR), particularly in young adults. The use of oral ethinylestradiol-levonorgestrel (EEL) formulation is also common among young women worldwide. The present study aimed at determining the effect of EEL on high fructose-induced cardiac triglyceride (TG) and glycogen accumulation. The study also investigated the possible involvement of pyruvate dehydrogenase kinase-4 (PDK-4) in EEL and/or high fructose metabolic effects on the heart. Ten-week-old female Wistar rats were allotted into four groups. The control, EEL, FRU, and EEL + FRU rats received distilled water (vehicle, p.o.), 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel (p.o.), 10% fructose (w/v), and 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel and 10% fructose, respectively, daily for 8 weeks. Data showed that EEL or high fructose caused IR' impaired glucose tolerance' hyperlipidemia' increased plasma lactate, lactate dehydrogenase, PDK-4, uric acid, xanthine oxidase (XO), adenosine deaminase (ADA), malondialdehyde (MDA), cardiac uric acid, TG, TG/HDL- cholesterol, glycogen synthesis, MDA, and visceral fat content and reduced glutathione. High fructose also resulted in impaired pancreatic β-cell function, hyperglycemia, and increased cardiac PDK-4, lactate synthesis, and mass. Nonetheless, these alterations were ameliorated in EEL plus high fructose rats. This study demonstrates that high fructose-induced myocardial TG and glycogen accumulation is attributable to increased PDK-4. Besides, EEL could be a useful pharmacological utility for protection against cardiac dysmetabolism by inhibiting PDK-4.

Searching for novel PET radiotracers: imaging cardiac perfusion, metabolism and inflammation

Advances in medical imaging technology have led to an increased demand for radiopharmaceuticals for early and accurate diagnosis of cardiac function and diseased states. Myocardial perfusion, metabolism, and hypoxia positron emission tomography (PET) imaging radiotracers for detection of cardiac disease lack specificity for targeting inflammation that can be an early indicator of cardiac disease. Inflammation can occur at all stages of cardiac disease and currently, 18F-fluorodeoxyglucose (FDG), a glucose analog, is the standard for detecting myocardial inflammation. 18F-FDG has many ideal characteristics of a radiotracer but lacks the ability to differentiate between glucose uptake in normal cardiomyocytes and inflammatory cells. Developing a PET radiotracer that differentiates not only between inflammatory cells and normal cardiomyocytes, but between types of immune cells involved in inflammation would be ideal. This article reviews current PET radiotracers used in cardiac imaging, their limitations, and potential radiotracer candidates for imaging cardiac inflammation in early stages of development of acute and chronic cardiac diseases. The select radiotracers reviewed have been tested in animals and/or show potential to be developed as a radiotracer for the detection of cardiac inflammation by targeting the enzymatic activities or subpopulations of macrophages that are recruited to an injured or infected site.

Abnormal Myocardial Dietary Fatty Acid Metabolism and Diabetic Cardiomyopathy

Patients with diabetes are at very high risk of hospitalization and death from heart failure. Increased prevalence of coronary heart disease, hypertension, autonomic neuropathy, and kidney failure all play a role in this increased risk. However, cardiac metabolic abnormalities are now recognized to play a role in this increased risk. Increased reliance on fatty acids to produce energy might predispose the diabetic heart to oxidative stress and ischemic damage. Intramyocellular accumulation of toxic lipid metabolites leads to a number of cellular abnormalities that might also contribute to cardiac remodelling and cardiac dysfunction. However, fatty acid availability from circulation and from intracellular lipid droplets to fuel the heart is critical to maintain its function. Fatty acids delivery to the heart is very complex and includes plasma nonesterified fatty acid flux as well as triglyceride-rich lipoprotein-mediated transport. Although many studies have shown a cross-sectional association between enhanced fatty acid delivery to the heart and reduction in left ventricular function in subjects with prediabetes and diabetes, these mechanisms change very rapidly during type 2 diabetes treatment. The present review focuses on the role of fatty acids in cardiac function, with particular emphasis on the possible role of early abnormalities of dietary fatty acid metabolism in the development of diabetic cardiomyopathy.

Chronic O-GlcNAcylation and Diabetic Cardiomyopathy: The Bitterness of Glucose

Type 2 diabetes (T2D) is a major risk factor for heart failure. Diabetic cardiomyopathy (DC) is characterized by diastolic dysfunction and left ventricular hypertrophy. Epidemiological data suggest that hyperglycaemia contributes to the development of DC. Several cellular pathways have been implicated in the deleterious effects of high glucose concentrations in the heart: oxidative stress, accumulation of advanced glycation end products (AGE), and chronic hexosamine biosynthetic pathway (HBP) activation. In the present review, we focus on the effect of chronic activation of the HBP on diabetic heart function. The HBP supplies N-acetylglucosamine moiety (O-GlcNAc) that is O-linked by O-GlcNAc transferase (OGT) to proteins on serine or threonine residues. This post-translational protein modification modulates the activity of the targeted proteins. In the heart, acute activation of the HBP in response to ischaemia-reperfusion injury appears to be protective. Conversely, chronic activation of the HBP in the diabetic heart affects Ca²⁺ handling, contractile properties, and mitochondrial function and promotes stress signaling, such as left ventricular hypertrophy and endoplasmic reticulum stress. Many studies have shown that O-GlcNAc impairs the function of key protein targets involved in these pathways, such as phospholamban, calmodulin kinase II, troponin I, and FOXO1. The data show that excessive O-GlcNAcylation is a major trigger of the glucotoxic events that affect heart function under chronic hyperglycaemia. Supporting this finding, pharmacological or genetic inhibition of the HBP in the diabetic heart improves heart function. In addition, the SGLT2 inhibitor dapagliflozin, a glucose lowering agent, has recently been shown to lower cardiac HBP in a lipodystophic T2D mice model and to concomitantly improve the diastolic dysfunction of these mice. Therefore, targeting cardiac-excessive O-GlcNAcylation or specific target proteins represents a potential therapeutic option to treat glucotoxicity in the diabetic heart.

Plasma Palmitoyl-Carnitine (AC16:0) Is a Marker of Increased Postprandial Nonesterified Incomplete Fatty Acid Oxidation Rate in Adults With Type 2 Diabetes

OBJECTIVES

Enhanced mitochondrial fatty acid utilization is known to increase radical oxidative stress and induce insulin resistance. An increased level of plasma acylcarnitine (AC) has been proposed to indicate mitochondrial energy substrate overload, a possible mechanism leading to insulin resistance. The aim of our study was to determine fasting and postprandial plasma acetyl-carnitine (AC2:0), palmitoyl-carnitine (AC16:0), oleoyl-carnitine (AC18:1) and linoleoyl-carnitine (AC18:2) levels and their relationships with plasma nonesterified fatty acid appearance and oxidation rates and insulin sensitivity in participants with type 2 diabetes and normoglycemic offspring of 2 parents with type 2 diabetes (FH+) compared to healthy participants without family histories of type 2 diabetes (FH-).

METHODS

All participants underwent 3 metabolic protocols: 1) a euglycemic hyperinsulinemic clamp at fasting; 2) a 6-hour steady-state oral standard liquid meal and 3) an identical 6-hour steady-state meal intake study with a euglycemic hyperinsulinemic clamp. AC levels were measured by liquid chromatography with tandem mass spectrometry, and fatty acid oxidation (FAO) rates were measured by stable isotopic tracer techniques with indirect respiratory calorimetry.

RESULTS

During the insulin clamp at fasting, AC16:0 was significantly higher in the group with type 2 diabetes vs. FH- (p<0.05). In the postprandial state, AC2:0, AC16:0 and AC18:1 decreased significantly, but this reduction was blunted in type 2 diabetes, even during normalization of postprandial glucose levels during the insulin clamp. Fasting AC16:0 correlated with FAO (ρ=+0.604; p=0.0002); triacylglycerol (ρ=+0.427; p<0.02) and waist circumference (ρ=+0.416; p=0.02).

CONCLUSIONS

Spillover of AC occurs in type 2 diabetes but is not fully established in FH+. AC16:0 can be a useful biomarker of excessive FAO.

Postprandial VLDL-TG metabolism in type 2 diabetes

BACKGROUND

Type 2 diabetes is associated with excess postprandial lipemia due to accumulation of chylomicrons and VLDL particles. This is a risk factor for development of cardiovascular disease. However, whether the excess lipemia is associated with an impaired suppression of VLDL-TG secretion and/or reduced clearance into adipose tissue is unknown.

OBJECTIVE

We measured the postprandial VLDL-TG secretion, clearance and adipose tissue storage to test the hypothesis that impaired postprandial suppression of VLDL-TG secretion, combined with impaired VLDL-TG storage in adipose tissue, is associated with excess postprandial lipemia.

DESIGN

We studied 11 men with type 2 diabetes and 10 weight-matched non-diabetic men using ex-vivo labeled VLDL-TG tracers during an oral high-fat mixed-meal tolerance test to measure postprandial VLDL-TG secretion, clearance and storage. In addition, adipose tissue biopsies were analyzed for LPL activity and cellular storage factors.

RESULTS

Men with type 2 diabetes had greater postprandial VLDL-TG concentration compared to non-diabetic men. However, postprandial VLDL-TG secretion rate was similar in the two groups with equal suppression of VLDL-TG secretion rate (≈50%) and clearance rate. In addition, postprandial VLDL-TG storage was similar in the two groups in both upper body and lower body subcutaneous adipose tissue.

CONCLUSIONS

Despite greater postprandial VLDL-TG concentration, men with type 2 diabetes have similar postprandial suppression of VLDL-TG secretion and a similar ability to store VLDL-TG in adipose tissue compared to non-diabetic men. This may indicate that abnormalities in postprandial VLDL-TG metabolism are a consequence of obesity/insulin resistance more than a result of type 2 diabetes per se.

The impact of obesity in the cardiac lipidome and its consequences in the cardiac damage observed in obese rats

AIMS

To explore the impact of obesity on the cardiac lipid profile in rats with diet-induced obesity, as well as to evaluate whether or not the specific changes in lipid species are associated with cardiac fibrosis.

METHODS

Male Wistar rats were fed either a high-fat diet (HFD, 35% fat) or standard diet (3.5% fat) for 6 weeks. Cardiac lipids were analyzed using by liquid chromatography-tandem mass spectrometry.

RESULTS

HFD rats showed cardiac fibrosis and enhanced levels of cardiac superoxide anion (O₂), HOMA index, adiposity, and plasma leptin, as well as a reduction in those of cardiac glucose transporter (GLUT 4), compared with control animals. Cardiac lipid profile analysis showed a significant increase in triglycerides, especially those enriched with palmitic, stearic, and arachidonic acid. An increase in levels of diacylglycerol (DAG) was also observed. No changes in cardiac levels of diacyl phosphatidylcholine, or even a reduction in total levels of diacyl phosphatidylethanolamine, diacyl phosphatidylinositol, and sphingomyelins (SM) was observed in HFD, as compared with control animals. After adjustment for other variables (oxidative stress, HOMA, cardiac hypertrophy), total levels of DAG were independent predictors of cardiac fibrosis while the levels of total SM were independent predictors of the cardiac levels of GLUT 4.

CONCLUSIONS

These data suggest that obesity has a significant impact on cardiac lipid composition, although it does not modulate the different species in a similar manner. Nonetheless, these changes are likely to participate in the cardiac damage in the context of obesity, since total DAG levels can facilitate the development of cardiac fibrosis, and SM levels predict GLUT4 levels.

Cardiac effects of SGLT2 inhibitors: the sodium hypothesis

The effects of intense glycaemic control on macrovascular complications in patients with type 2 diabetes are incompletely resolved, and many glucose-lowering medications negatively affect cardiovascular outcomes. Recently, the EMPA-REG OUTCOME trial revealed that empagliflozin, an inhibitor of the sodium-glucose cotransporter 2 (SGLT2), substantially reduced the risk of hospitalization for heart failure, death from cardiovascular causes, and all-cause mortality in patients with type 2 diabetes mellitus at high cardiovascular risk. Although several mechanisms may explain this benefit, plasma volume contraction and a metabolic switch favouring cardiac ketone bodies oxidation have recently been proposed as the major drivers. Recent experimental work has prompted a novel and intriguing hypothesis, according to which empagliflozin may reduce intracellular sodium (Na+) load observed in failing cardiac myocytes by inhibiting the sarcolemmal Na+/H+ exchanger. Since elevated intracellular Na+ hampers mitochondrial Ca2+ handling and thereby, deteriorates energy supply and demand matching and the mitochondrial antioxidative defence systems, empagliflozin may positively affect cardiac function by restoring mitochondrial function, and redox state in the failing heart. Here, we review the current evidence for such a third mechanistic hypothesis, which may foster heart failure and diabetes research into a new direction which harbours several potential targets for therapeutic intervention.

HNF1α defect influences post-prandial lipid regulation

Purpose

Hepatocyte nuclear factor 1 alpha (HNF1α) defects cause Mature Onset Diabetes of the Young type 3 (MODY3), characterized by defects in beta-cell insulin secretion. However, HNF1α is involved in many other metabolic pathways with relevance for monogenic or polygenic type 2 diabetes. We aimed to investigate gut hormones, lipids, and insulin regulation in response to a meal test in HNF1α defect carriers (MODY3) compared to non-diabetic subjects (controls) and type 2 diabetes (T2D).

Methods

We administered a standardized liquid meal to each participant. Over 6 hours, we measured post-meal responses of insulin regulation (blood glucose, c-peptide, insulin), gut hormones (ghrelin, glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1) and lipids (non-esterified fatty acids [NEFA] and triglycerides).

Results

We found that MODY3 participants had lower insulin secretion indices than controls and T2D participants, showing the expected β-cell defect. MODY3 had similar glycated hemoglobin levels (HbA1c median [IQR]: 6.5 [5.6–7.6]%) compared to T2D (median: 6.6 [6.2–6.9]%; P<0.05). MODY3 had greater insulin sensitivity (Matsuda index: 71.9 [29.6; 125.5]) than T2D (3.2 [4.0; 6.0]; P<0.05). MODY3 experienced a larger decrease in the ratio of NEFA to insulin (NEFA 30–0 / insulin 30–0: -39 [-78; -30] x10⁴) in the early post-prandial period (0–30 minutes) compared to controls and to T2D (-2.0 [-0.6; -6.4] x10⁴; P<0.05). MODY3 had lower fasting (0.66 [0.46; 1.2] mM) and post-meal triglycerides levels compared to T2D (fasting: 2.3 [1.7; 2.7] mM; P<0.05). We did not detect significant post-meal differences in ghrelin and incretins between MODY3 and other groups.

Conclusion

In response to a standard meal test, MODY3 showed greater early post-prandial NEFA diminution in response to relatively low early insulin secretion, and they maintained very low post-prandial triglycerides levels.

Molecular imaging of postprandial metabolism

Disordered postprandial metabolism of energy substrates is one of the main defining features of prediabetes and contributes to the development of several chronic diseases associated with obesity, such as type 2 diabetes and cardiovascular diseases. Postprandial energy metabolism has been studied using classical isotopic tracer approaches that are limited by poor access to splanchnic metabolism and highly dynamic and complex exchanges of energy substrates involving multiple organs and systems. Advances in noninvasive molecular imaging modalities, such as PET and MRI/magnetic resonance spectroscopy (MRS), have recently allowed important advances in our understanding of postprandial energy metabolism in humans. The present review describes some of these recent advances, with particular focus on glucose and fatty acid metabolism in the postprandial state, and discusses current gaps in knowledge and new perspectives of application of PET and MRI/MRS for the investigation and treatment of human metabolic diseases.

Liver fat: a relevant target for dietary intervention? Summary of a Unilever workshop

Currently it is estimated that about 1 billion people globally have non-alcoholic fatty liver disease (NAFLD), a condition in which liver fat exceeds 5 % of liver weight in the absence of significant alcohol intake. Due to the central role of the liver in metabolism, the prevalence of NAFLD is increasing in parallel with the prevalence of obesity, insulin resistance and other risk factors of metabolic diseases. However, the contribution of liver fat to the risk of type 2 diabetes mellitus and CVD, relative to other ectopic fat depots and to other risk markers, is unclear. Various studies have suggested that the accumulation of liver fat can be reduced or prevented via dietary changes. However, the amount of liver fat reduction that would be physiologically relevant, and the timeframes and dose-effect relationships for achieving this through different diet-based approaches, are unclear. Also, it is still uncertain whether the changes in liver fat per se or the associated metabolic changes are relevant. Furthermore, the methods available to measure liver fat, or even individual fatty acids, differ in sensitivity and reliability. The present report summarises key messages of presentations from different experts and related discussions from a workshop intended to capture current views and research gaps relating to the points above.

The Sodium-Glucose Cotransporter 2 Inhibitor Dapagliflozin Prevents Cardiomyopathy in a Diabetic Lipodystrophic Mouse Model

Type 2 diabetes mellitus (T2DM) is a well-recognized independent risk factor for heart failure. T2DM is associated with altered cardiac energy metabolism, leading to ectopic lipid accumulation and glucose overload, the exact contribution of these two parameters remaining unclear. To provide new insight into the mechanism driving the development of diabetic cardiomyopathy, we studied a unique model of T2DM: lipodystrophic Bscl2^-/- (seipin knockout [SKO]) mice. Echocardiography and cardiac magnetic resonance imaging revealed hypertrophic cardiomyopathy with left ventricular dysfunction in SKO mice, and these two abnormalities were strongly correlated with hyperglycemia. Surprisingly, neither intramyocardial lipid accumulation nor lipotoxic hallmarks were detected in SKO mice. [¹⁸F]Fludeoxyglucose positron emission tomography showed increased myocardial glucose uptake. Consistently, the O-GlcNAcylated protein levels were markedly increased in an SKO heart, suggesting a glucose overload. To test this hypothesis, we treated SKO mice with the hypoglycemic sodium-glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin and the insulin sensitizer pioglitazone. Both treatments reduced the O-GlcNAcylated protein levels in SKO mice, and dapagliflozin successfully prevented the development of hypertrophic cardiomyopathy. Our data demonstrate that glucotoxicity by itself can trigger cardiac dysfunction and that a glucose-lowering agent can correct it. This result will contribute to better understanding of the potential cardiovascular benefits of SGLT2 inhibitors.

Early Metabolic Improvement After Bariatric Surgery: The First Steps Toward Remission of Type 2 Diabetes

The introduction of bariatric surgery into clinical practice in the 1980s was followed by a relatively long watch-and-wait period before the very rapid accumulation of scientific literature, over the past decade, concerning its clinical effectiveness and safety and its mechanisms of action in the treatment of obesity. These surgical procedures now emerge as the most effective therapeutic modality to induce long-term remission of type 2 diabetes. Recent research has shed light on the potential mechanisms leading to the profound improvement of glucose homeostasis following most bariatric surgery procedures. These mechanisms can be classified as weight loss dependent and independent, both playing sequential and then synergistic antidiabetes roles. Many groups, including our own, have contributed to our understanding of the relative roles of these mechanisms at differing time periods following these procedures. Here we summarize what we currently know about the mechanisms underlying the very rapid, weight loss-independent improvement in glucose homeostasis after bariatric surgery. Beyond its impact in the field of bariatric surgery, this new knowledge about the very rapid in vivo "reverse engineering" of type 2 diabetes actually provides unique insights into the intricate and complex mechanisms linking nutrition and obesity with the development of this disease.

Dietary fatty acid metabolism in prediabetes

PURPOSE OF REVIEW

Experimental evidences are strong for a role of long-chain saturated fatty acids in the development of insulin resistance and type 2 diabetes. Ectopic accretion of triglycerides in lean organs is a characteristic of prediabetes and type 2 diabetes and has been linked to end-organ complications. The contribution of disordered dietary fatty acid (DFA) metabolism to lean organ overexposure and lipotoxicity is still unclear, however. DFA metabolism is very complex and very difficult to study in vivo in humans.

RECENT FINDINGS

We have recently developed a novel imaging method using PET with oral administration of 14-R,S-F-fluoro-6-thia-heptadecanoic acid (FTHA) to quantify organ-specific DFA partitioning. Our studies thus far confirmed impaired storage of DFA per volume of fat mass in abdominal adipose tissues of individuals with prediabetes. They also highlighted the increased channeling of DFA toward the heart, associated with subclinical reduction in cardiac systolic and diastolic function in individuals with prediabetes.

SUMMARY

In the present review, we summarize previous work on DFA metabolism in healthy and prediabetic states and discuss these in the light of our novel findings using PET imaging of DFA metabolism. We herein provide an integrated view of abnormal organ-specific DFA partitioning in prediabetes in humans.

Dietary fatty acid metabolism of brown adipose tissue in cold-acclimated men

In rodents, brown adipose tissue (BAT) plays an important role in producing heat to defend against the cold and can metabolize large amounts of dietary fatty acids (DFA). The role of BAT in DFA metabolism in humans is unknown. Here we show that mild cold stimulation (18 °C) results in a significantly greater fractional DFA extraction by BAT relative to skeletal muscle and white adipose tissue in non-cold-acclimated men given a standard liquid meal containing the long-chain fatty acid PET tracer, 14(R,S)-[¹⁸F]-fluoro-6-thia-heptadecanoic acid (¹⁸FTHA). However, the net contribution of BAT to systemic DFA clearance is comparatively small. Despite a 4-week cold acclimation increasing BAT oxidative metabolism 2.6-fold, BAT DFA uptake does not increase further. These findings show that cold-stimulated BAT can contribute to the clearance of DFA from circulation but its contribution is not as significant as the heart, liver, skeletal muscles or white adipose tissues.

Brown adipose tissue (BAT) takes up and burns fatty acids for thermogenesis in mice. Here the authors use PET to show that, in humans, cold stimulation increases BAT dietary fatty acid uptake from plasma and oxidative metabolism, although, unlike mice, human BAT takes up less fatty acids than other metabolic tissues.

Maternal-engineered nanomaterial exposure disrupts progeny cardiac function and bioenergetics

Nanomaterial production is expanding as new industrial and consumer applications are introduced. Nevertheless, the impacts of exposure to these compounds are not fully realized. The present study was designed to determine whether gestational nano-sized titanium dioxide exposure impacts cardiac and metabolic function of developing progeny. Pregnant Sprague-Dawley rats were exposed to nano-aerosols (~10 mg/m³, 130- to 150-nm count median aerodynamic diameter) for 7-8 nonconsecutive days, beginning at gestational day 5-6 Physiological and bioenergetic effects on heart function and cardiomyocytes across three time points, fetal (gestational day 20), neonatal (4-10 days), and young adult (6-12 wk), were evaluated. Functional analysis utilizing echocardiography, speckle-tracking based strain, and cardiomyocyte contractility, coupled with mitochondrial energetics, revealed effects of nano-exposure. Maternal exposed progeny demonstrated a decrease in E- and A-wave velocities, with a 15% higher E-to-A ratio than controls. Myocytes isolated from exposed animals exhibited ~30% decrease in total contractility, departure velocity, and area of contraction. Bioenergetic analysis revealed a significant increase in proton leak across all ages, accompanied by decreases in metabolic function, including basal respiration, maximal respiration, and spare capacity. Finally, electron transport chain complex I and IV activities were negatively impacted in the exposed group, which may be linked to a metabolic shift. Molecular data suggest that an increase in fatty acid metabolism, uncoupling, and cellular stress proteins may be associated with functional deficits of the heart. In conclusion, gestational nano-exposure significantly impairs the functional capabilities of the heart through cardiomyocyte impairment, which is associated with mitochondrial dysfunction.NEW & NOTEWORTHY Cardiac function is evaluated, for the first time, in progeny following maternal nanomaterial inhalation. The findings indicate that exposure to nano-sized titanium dioxide (nano-TiO₂) during gestation negatively impacts cardiac function and mitochondrial respiration and bioenergetics. We conclude that maternal nano-TiO₂ inhalation contributes to adverse cardiovascular health effects, lasting into adulthood.

A Randomized Comparison of Reservoir-Based Polymer-Free Amphilimus-Eluting Stents Versus Everolimus-Eluting Stents With Durable Polymer in Patients With Diabetes Mellitus: The RESERVOIR Clinical Trial

OBJECTIVES

The aim of this study was to compare the efficacy of amphilimus-eluting stents (AES) with that of everolimus-eluting stents (EES) in patients with diabetes mellitus (DM).

BACKGROUND

The AES is a polymer-free drug-eluting stent that elutes sirolimus formulated with an amphiphilic carrier from laser-dug wells. This technology could be associated with a high efficacy in patients with DM.

METHODS

This was a multicenter, randomized, noninferiority trial. Patients with DM medically treated with oral glucose-lowering agents or insulin and de novo coronary lesions were randomized in a 1:1 fashion to AES or EES. The primary endpoint was the neointimal (NI) volume obstruction assessed by optical coherence tomography at 9-month follow-up.

RESULTS

A total of 116 lesions in 112 patients were randomized. Overall, 40% were insulin-treated patients, with a median HbA1c of 7.3% (interquartile range: 6.7% to 8.0%). The primary endpoint, NI volume obstruction, was 11.97 ± 5.94% for AES versus 16.11 ± 18.18% for EES, meeting the noninferiority criteria (p = 0.0003). Pre-specified subgroup analyses showed a significant interaction between stent type and glycemic control (p = 0.02), with a significant reduction in NI hyperplasia in the AES group in patients with the higher HbA1c (p = 0.03). By quantitative coronary angiography, in-stent late loss was 0.14 ± 0.24 for AES versus 0.24 ± 0.57 mm for EES (p = 0.27), with a larger minimal lumen diameter at follow-up for AES (p = 0.02), mainly driven by 2 cases of occlusive restenosis in the EES group.

CONCLUSIONS

AES are noninferior to EES for the coronary revascularization of patients with DM. These results suggest a high efficacy of the AES and may support the potential benefit of this stent in patients with DM. (A Randomized Comparison of Reservoir-Based Polymer-Free Amphilimus-Eluting Stents Versus Everolimus-Eluting Stents With Durable Polymer in Patients With Diabetes Mellitus [RESERVOIR]; NCT01710748).