Impact of sex on the heart's metabolic and functional responses to diabetic therapies

Human cardiac metabolism

The heart is the most metabolically active organ in the human body, and cardiac metabolism has been studied for decades. However, the bulk of studies have focused on animal models. The objective of this review is to summarize specifically what is known about cardiac metabolism in humans. Techniques available to study human cardiac metabolism are first discussed, followed by a review of human cardiac metabolism in health and in heart failure. Mechanistic insights, where available, are reviewed, and the evidence for the contribution of metabolic insufficiency to heart failure, as well as past and current attempts at metabolism-based therapies, is also discussed.

High-Intensity Interval Versus Moderate-Intensity Continuous Exercise Training on Glycemic Control, Beta Cell Function, and Aerobic Fitness in Women with Type 2 Diabetes

Objective: This study aimed to compare the effects of High-Intensity Interval Training (HIIT) and Moderate-Intensity Continuous Training (MICT) on glycemic control, beta-cell function, and aerobic fitness in women with Type 2 Diabetes Mellitus (T2DM). Methods: Thirty-six women with T2DM were assigned equally to HIIT, MICT, and control (CON) groups. Participants in the exercise cohorts underwent a 12-week training regimen (three sessions per week), while the CON group maintained an inactive lifestyle. Glycaemia variables, beta-cell function, maximal oxygen uptake (VO2max), lipid profiles, and body composition were assessed at baseline and post-intervention. Results: Both HIIT and MICT interventions led to significant improvements in glucose, insulin, HbA1c, and insulin resistance index. Moreover, visceral adiposity index (VAI), lipid accumulation product (LAP), total cholesterol (TC), and low-density lipoprotein (LDL) levels significantly decreased in the HIIT and MICT groups after 12 weeks. Triglyceride (TG) levels decreased only after MICT, while high-density lipoprotein (HDL) levels increased after both interventions. Maximal oxygen uptake (VO2max), body mass, body mass index (BMI), and waist circumference (WC) significantly improved in all exercise groups. Notably, the HIIT group showed greater reductions in body mass compared to MICT. Nevertheless, beta-cell function remained unaltered after these two exercise regimens. Conclusion: Both HIIT and MICT interventions effectively managed T2DM in women, regardless of exercise intensity. The HIIT regimen can be considered for time-efficient lifestyle interventions in people with T2DM.

Reduced in utero substrate supply decreases mitochondrial abundance and alters the expression of metabolic signalling molecules in the fetal sheep heart

Babies born with fetal growth restriction (FGR) are at higher risk of developing cardiometabolic diseases across the life course. The reduction in substrate supply to the developing fetus that causes FGR not only alters cardiac growth and structure but may have deleterious effects on metabolism and function. Using a sheep model of placental restriction to induce FGR, we investigated key cardiac metabolic and functional markers that may be altered in FGR. We also employed phase-contrast magnetic resonance imaging MRI to assess left ventricular cardiac output (LVCO) as a measure of cardiac function. We hypothesized that signalling molecules involved in cardiac fatty acid utilisation and contractility would be impaired by FGR and that this would have a negative impact on LVCO in the late gestation fetus. Key glucose (GLUT4 protein) and fatty acid (FATP, CD36 gene expression) substrate transporters were significantly reduced in the hearts of FGR fetuses. We also found reduced mitochondrial numbers as well as abundance of electron transport chain complexes (complexes II and IV). These data suggest that FGR diminishes metabolic and mitochondrial capacity in the fetal heart; however, alterations were not correlated with fetal LVCO. Overall, these data show that FGR alters fetal cardiac metabolism in late gestation. If sustained ex utero, this altered metabolic profile may contribute to poor cardiac outcomes in FGR-born individuals after birth. KEY POINTS: Around the time of birth, substrate utilisation in the fetal heart switches from carbohydrates to fatty acids. However, the effect of fetal growth restriction (FGR) on this switch, and thus the ability of the fetal heart to effectively metabolise fatty acids, is not fully understood. Using a sheep model of early onset FGR, we observed significant downregulation in mRNA expression of fatty acid receptors CD36 and FABP in the fetal heart. FGR fetuses also had significantly lower cardiac mitochondrial abundance than controls. There was a reduction in abundance of complexes II and IV within the electron transport chain of the FGR fetal heart, suggesting altered ATP production. This indicates reduced fatty acid metabolism and mitochondrial function in the heart of the FGR fetus, which may have detrimental long-term implications and contribute to increased risk of cardiovascular disease later in life.

Current challenges in the treatment of cardiac fibrosis: Recent insights into the sex-specific differences of glucose-lowering therapies on the diabetic heart: IUPHAR Review 33

A significant cardiac complication of diabetes is cardiomyopathy, a form of ventricular dysfunction that develops independently of coronary artery disease, hypertension and valvular diseases, which may subsequently lead to heart failure. Several structural features underlie the development of diabetic cardiomyopathy and eventual diabetes-induced heart failure. Pathological cardiac fibrosis (interstitial and perivascular), in addition to capillary rarefaction and myocardial apoptosis, are particularly noteworthy. Sex differences in the incidence, development and presentation of diabetes, heart failure and interstitial myocardial fibrosis have been identified. Nevertheless, therapeutics specifically targeting diabetes-associated cardiac fibrosis remain lacking and treatment approaches remain the same regardless of patient sex or the co-morbidities that patients may present. This review addresses the observed anti-fibrotic effects of newer glucose-lowering therapies and traditional cardiovascular disease treatments, in the diabetic myocardium (from both preclinical and clinical contexts). Furthermore, any known sex differences in these treatment effects are also explored. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Loss of endothelial glucocorticoid receptor accelerates organ fibrosis in db/db mice

Endothelial cells play a key role in maintaining homeostasis and are deranged in many disease processes, including fibrotic conditions. Absence of the endothelial glucocorticoid receptor (GR) has been shown to accelerate diabetic kidney fibrosis in part through upregulation of Wnt signaling. The db/db mouse model is a model of spontaneous type 2 diabetes that has been noted to develop fibrosis in multiple organs over time, including the kidneys. This study aimed to determine the effect of loss of endothelial GR on organ fibrosis in the db/db model. db/db mice lacking endothelial GR showed more severe fibrosis in multiple organs compared with endothelial GR-replete db/db mice. Organ fibrosis could be substantially improved either through administration of a Wnt inhibitor or metformin. IL-6 is a key cytokine driving the fibrosis phenotype and is mechanistically linked to Wnt signaling. The db/db model is an important tool to study the mechanisms of fibrosis and its phenotype in the absence of endothelial GR highlights the synergistic effects of Wnt signaling and inflammation in the pathogenesis or organ fibrosis.NEW & NOTEWORTHY The major finding of this work is that endothelial glucocorticoid receptor-mediated upregulation of Wnt signaling and concurrent hyperinflammation work synergistically to exacerbate organ fibrosis in a genetic mouse model of diabetes. This study adds to our understanding of diabetic renal fibrosis and has important implications for the use of metformin in this condition.

Glycemic control and its association with sleep quality and duration among type 2 diabetic patients

Background

Poor glycemic control is the current most important tragedy in type 2 diabetic patients. Sleep has a major modulatory effect on endocrine and metabolic function. Sleep disturbance is associated with increased circulating cortisol levels, sympathetic activity, and epinephrine secretion. These physiological conditions are directly or indirectly associated with glucose metabolism in our body cells. In Ethiopia, sleep pattern association with glycemic control level is not studied yet.

Objectives

To assess glycemic control and its association with sleep quality, sleep duration and napping among patients with type 2 diabetes mellitus in Felege Hiwot Comprehensive Referral and Specialized Hospital Northwest Ethiopia.

Method

An institutional-based cross-sectional study was conducted among 407 type 2 diabetes mellitus patients from July 1, 2020, to April 28, 2021, using a systematic random sampling technique. We drew 5 mL of blood from each patient before breakfast to determine their fasting blood sugar level. The Pittsburg Sleep Quality Index was used to assess patients' sleep quality, and the presence or absence of Obstructive Sleep Apnea was determined using the STOP-BANG questionnaire. Data were analysed using STATA version 14.1.variables with a P-value of <0.05 were considered statistically significant.

Results

Glycemic control was found to be poor in 54.05% of the study participants. Female sex, poor sleep quality, and short and long sleep durations were all significantly associated with impaired glycemic control. Being female increased the odds of poor glycemic control by 2.7 times (AOR = 2.7, 95% CI: 1.23, 6.15) compared to males. T2DM patients who had poor sleep quality had 3.3 times (AOR = 3.3, 95% CI (1.16, 9.37) higher odds of poor glycemic control compared to patients who had good sleep quality. The odds of having poor glycemic control among T2DM patients who were at low risk of OSA and intermediate risk of OSA were decreased by 96% (AOR = 0.03, 95% CI: 0.01, 0.12) and 86% (AOR = 0.14, 95% CI: 0.05, 0.43) compared to T2DM patients who were at high risk of OSA, respectively. T2DM patients who had short sleep duration (<6 hours) were 8.3 times (AOR = 8.3, 95% CI: 2.66-25.85) higher chances of poor glycemic control compared to patients who had average sleep duration. T2DM patients who had long sleep duration (>8 hours) increased the odds of poor glycemic control by 2.6 times (AOR = 2.6, 95% CI (1.12-6.04) compared to those who had average sleep duration. The chances of having poor glycemic control among T2DM patients who did not take the balanced diet recommended by their physician were increased by 3.8 times (AOR = 3.8 95% CI: 1.05-13.77).

Conclusion

The prevalence of poor glycemic control in T2DM patients was high. Poor sleep quality, both short and long sleep duration, and an intermediate or low risk of obstructive sleep apnea were statistically associated with poor glycemic control. Hence, good sleep quality and appropriate sleep duration are recommended to maintain glycemic control levels in the normal range.

Loss of endothelial glucocorticoid receptor accelerates organ fibrosis in db/db mice

Endothelial cells play a key role in maintaining homeostasis and are deranged in many disease processes, including fibrotic conditions. Absence of the endothelial glucocorticoid receptor (GR) has been shown to accelerate diabetic kidney fibrosis in part through up regulation of Wnt signaling. The db/db mouse model is a model of spontaneous type 2 diabetes that has been noted to develop fibrosis in multiple organs over time, including the kidneys. This study aimed to determine the effect of loss of endothelial GR on organ fibrosis in the db/db model. Db/Db mice lacking endothelial GR showed more severe fibrosis in multiple organs compared to endothelial GR-replete db/db mice. Organ fibrosis could be substantially improved either through administration of a Wnt inhibitor or metformin. IL-6 is a key cytokine driving the fibrosis phenotype and is mechanistically linked to Wnt signaling. The db/db model is an important tool to study mechanisms of fibrosis and its phenotype in the absence of endothelial GR highlights the synergistic effects of Wnt signaling and inflammation in the pathogenesis or organ fibrosis.

Impact of telemedicine on glycemic control in type 2 diabetes mellitus during the COVID-19 lockdown period

BACKGROUND

The lockdown at the start of coronavirus disease 2019 (COVID-19) pandemic in Saudi Arabia (March 2020 to June 2020) shifted routine in-person care for patients with type 2 diabetes mellitus (T2DM) to telemedicine. The aim of this study was to investigate the impact telemedicine had during this period on glycemic control (HbA1c) in patients with T2DM.

METHODS

4,266 patients with T2DM were screened from five Ministry of National Guard Health Affairs hospitals in the Kingdom of Saudi Arabia. Age, gender, body mass index (BMI), HbA1c (before and after the COVID-19 lockdown), duration of T2DM, comorbidities and antidiabetic medications data were obtained. Mean and standard deviation of differences in HbA1c were calculated to assess the impact of telemedicine intervention. Correlations between clinically significant variances (when change in the level is ≥0.5%) in HbA1c with demographics and clinical characteristic data were determined using chi square test.

RESULTS

Most of the participants were Saudis (97.7%) with 59.7% female and 56.4% ≥60 years of age. Obesity was 63.8%, dyslipidemia 91%, and hypertension 70%. Mean HbA1c of all patients slightly rose from 8.52% ± 1.5% before lockdown to 8.68% ± 1.6% after lockdown. There were n=1,064 patients (24.9%) whose HbA1c decreased by ≥0.5%, n =1,574 patients whose HbA1c increased by ≥0.5% (36.9%), and n =1,628 patients whose HbA1c changed by <0.5% in either direction (38.2%). More males had significant improvements in glycemia compared to females (28.1% vs 22.8%, p<0.0001), as were individuals below the age of 60 years (28.1% vs 22.5%, p<0.0001). Hypertensive individuals were less likely than non-hypertensive to have glycemic improvement (23.7% vs 27.9%, p=0.015). More patients on sulfonylureas had improvements in HbA1c (42.3% vs 37.9%, p=0.032), whereas patients on insulin had higher HbA1c (62.7% vs 56.2%, p=0.001). HbA1c changes were independent of BMI, duration of disease, hyperlipidemia, heart and kidney diseases.

CONCLUSION

Telemedicine was helpful in delivering care to T2DM patients during COVID-19 lockdown, with 63.1% of patients maintaining HbA1c and improving glycemia. More males than females showed improvements. However, the HbA1c levels in this cohort of patients pre- and post-lockdown were unsatisfactorily high, and may be due to in part lifestyle, age, education, and hypertension.

Concentration-dependent effects of dichloroacetate in type 2 diabetic hearts assessed by hyperpolarized [1-13 C]-pyruvate magnetic resonance imaging

Personalized medicine or individualized therapy promises a paradigm shift in healthcare. This is particularly true in complex and multifactorial diseases such as diabetes and the multitude of related pathophysiological complications. Diabetic cardiomyopathy represents an emerging condition that could be effectively treated if better diagnostic and, in particular, better therapeutic monitoring tools were available. In this study, we investigate the ability to differentiate low and high doses of metabolically targeted therapy in an obese type 2 diabetic rat model. Low-dose dichloroacetate (DCA) treatment was associated with increased lactate production, while no or little change was seen in bicarbonate production. High-dose DCA treatment was associated with a significant metabolic switch towards increased bicarbonate production. These findings support further studies using hyperpolarized [1-¹³ C]-pyruvate magnetic resonance imaging to differentiate treatment effects and thus allow for personalized titration of therapeutics.

Metformin in nucleus accumbens core reduces cue-induced cocaine seeking in male and female rats

This study investigated the potential therapeutic effects of the FDA‐approved drug metformin on cue‐induced reinstatement of cocaine seeking. Metformin (dimethyl‐biguanide) is a first‐line treatment for type II diabetes that, among other mechanisms, is involved in the activation of adenosine monophosphate activated protein kinase (AMPK). Cocaine self‐administration and extinction is associated with decreased levels of phosphorylated AMPK within the nucleus accumbens core (NAcore). Previously, it was shown that increasing AMPK activity in the NAcore decreased cue‐induced reinstatement of cocaine seeking. Decreasing AMPK activity produced the opposite effect. The goal of the present study was to determine if metformin in the NAcore reduces cue‐induced cocaine seeking in adult male and female Sprague Dawley rats. Rats were trained to self‐administer cocaine followed by extinction prior to cue‐induced reinstatement trials. Metformin microinjected in the NAcore attenuated cue‐induced reinstatement in male and female rats. Importantly, metformin's effects on cocaine seeking were not due to a general depression of spontaneous locomotor activity. In female rats, metformin's effects did generalize to a reduction in cue‐induced reinstatement of sucrose seeking. These data support a potential role for metformin as a pharmacotherapy for cocaine use disorder but warrant caution given the potential for metformin's effects to generalize to a natural reward in female rats.

Metformin and high-sensitivity cardiac troponin I and T trajectories in type 2 diabetes patients: a post-hoc analysis of a randomized controlled trial

BACKGROUND

Metformin has favorable effects on cardiovascular outcomes in both newly onset and advanced type 2 diabetes, as previously reported findings from the UK Prospective Diabetes Study and the HOME trial have demonstrated. Patients with type 2 diabetes present with chronically elevated circulating cardiac troponin levels, an established predictor of cardiovascular endpoints and prognostic marker of subclinical myocardial injury. It is unknown whether metformin affects cardiac troponin levels. The study aimed to evaluate cardiac troponin I and T trajectories in patients with diabetes treated either with metformin or placebo.

METHODS

This study is a post-hoc analysis of a randomized controlled trial (HOME trial) that included 390 patients with advanced type 2 diabetes randomized to 850 mg metformin or placebo up to three times daily concomitant to continued insulin treatment. Cardiac troponin I and T concentrations were measured at baseline and after 4, 17, 30, 43 and 52 months. We evaluated cardiac troponin trajectories by linear mixed-effects modeling, correcting for age, sex, smoking status and history of cardiovascular disease.

RESULTS

This study enrolled 390 subjects, of which 196 received metformin and 194 received placebo. In the treatment and placebo groups, mean age was 64 and 59 years; with 50% and 58% of subjects of the female sex, respectively. Despite the previously reported reduction of macrovascular disease risk in this cohort by metformin, linear mixed-effects regression modelling did not reveal evidence for an effect on cardiac troponin I and cardiac troponin T levels [- 8.4% (- 18.6, 3.2), p = 0.150, and - 4.6% (- 12, 3.2), p = 0.242, respectively]. A statistically significant time-treatment interaction was found for troponin T [- 1.6% (- 2.9, - 0.2), p = 0.021] but not troponin I concentrations [- 1.5% (- 4.2, 1.2), p = 0.263].

CONCLUSIONS

In this post-hoc analysis of a 4.3-year randomized controlled trial, metformin did not exert a clinically relevant effect on cardiac troponin I and cardiac troponin T levels when compared to placebo. Cardioprotective effects of the drug observed in clinical studies are not reflected by a reduction in these biomarkers of subclinical myocardial injury. Trial registration ClinicalTrials.gov identifier NCT00375388.

Gender differences in new hypoglycemic drug effects on renal outcomes: a systematic review

INTRODUCTION

Lifetime diabetes risk is greater in women than in men. Women with diabetes mellitus (DM) have a greater prevalence of diabetic kidney disease (DKD) risk factors. The diagnosis of DM is often delayed in women, with poorer outcomes and with expected therapeutic goals missed.

AREA COVERED

A systematic literature review following PRISMA guidelines was conducted in the PubMed gateway of the MEDLINE database and Clinicaltrials.gov. The purpose of our research was to establish the sex differences on renal outcomes in users of the new hypoglycemic drugs: sodium-glucose transport protein 2 inhibitors (SGLT-2i), dipeptidyl peptidase-IV Inhibitors (DPP-IVi) and glucagon-like peptide-1 inhibitors (GLP-1i).

EXPERT OPINION

New hypoglycemic drugs represent promising tools in the treatment and prevention of severe complications of diabetes, cardiovascular diseases and chronic kidney disease. Even if renal outcomes are investigated in both randomized controlled trials and cardiovascular outcome trials, gender-based analysis is not always performed. This may lead to relevant information for risk-benefit evaluation and therapeutic choices being missed, with gender-based equality in outcomes lacking. Our systematic review demonstrated that the gap among sexes in DKD can be partially filled using new hypoglycemic drugs. Sexual dimorphism analysis could represent a keystone for the development of adequate gender-specific therapies.

Metformin: Sex/Gender Differences in Its Uses and Effects—Narrative Review

Metformin (MTF) occupies a major and fundamental position in the therapeutic management of type 2 diabetes mellitus (T2DM). Gender differences in some effects and actions of MTF have been reported. Women are usually prescribed lower MTF doses compared to men and report more gastrointestinal side effects. The incidence of cardiovascular events in women on MTF has been found to be lower to that of men on MTF. Despite some promising results with MTF regarding pregnancy rates in women with PCOS, the management of gestational diabetes, cancer prevention or adjunctive cancer treatment and COVID-19, most robust meta-analyses have yet to confirm such beneficial effects.

Self-care and type 2 diabetes mellitus (T2DM): a literature review in sex-related differences

T2DM is a multifactorial disease, and it is considered a worldwide challenge for its increasing prevalence and its negative impact on patients' wellbeing. Even if it is known that self-care is a key factor in reaching optimal outcomes, and males and females implement different self-care behaviors, sex-related differences in self-care of patients with T2DM have been poorly investigated. Especially, an overall view of the available evidence has not yet been done. Accordingly, this review aims to summarize, critically review, and interpret the available evidence related to the sex-related differences in self-care behaviors of patients with T2DM. An extensive literature review was performed with a narrative synthesis following the PRISMA statement and flowchart through four databases: PubMed, CINAHL, Scopus, and Embase. From the 5776 identified records by the queries, only 29 articles were included, having a high-quality evaluation. Both females and males with T2DM must improve their self-care: more males reported performing better behaviors aimed at maintaining health and clinical stability (i.e., self-care maintenance) than females, but mainly in relation to physical activity. On the other hand, more females reported performing adequate behaviors aimed at monitoring their signs and symptoms (i.e., self-care monitoring) but with worse glycemic control and diabetic complications (i.e., self-care management). This review firstly provides an overall view of different self-care behaviors implemented by males and females with T2DM, showing that self-care management should be improved in both sexes. Health education must include the problems related to the diabetic pathology and the patient's own characteristics, such as sex.

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.

Fetal Cardiac Lipid Sensing Triggers an Early and Sex-related Metabolic Energy Switch in Intrauterine Growth Restriction

CONTEXT

Intrauterine growth restriction (IUGR) is an immediate outcome of an adverse womb environment, exposing newborns to developing cardiometabolic disorders later in life.

OBJECTIVE

This study investigates the cardiac metabolic consequences and underlying mechanism of energy expenditure in developing fetuses under conditions of IUGR.

METHODS

Using an animal model of IUGR characterized by uteroplacental vascular insufficiency, mitochondrial function, gene profiling, lipidomic analysis, and transcriptional assay were determined in fetal cardiac tissue and cardiomyocytes.

RESULTS

IUGR fetuses exhibited an upregulation of key genes associated with fatty acid breakdown and β-oxidation (Acadvl, Acadl, Acaa2), and mitochondrial carnitine shuttle (Cpt1a, Cpt2), instigating a metabolic gene reprogramming in the heart. Induction of Ech1, Acox1, Acox3, Acsl1, and Pex11a indicated a coordinated interplay with peroxisomal β-oxidation and biogenesis mainly observed in females, suggesting sexual dimorphism in peroxisomal activation. Concurring with the sex-related changes, mitochondrial respiration rates were stronger in IUGR female fetal cardiomyocytes, accounting for enhanced adenosine 5'-triphosphate production. Mitochondrial biogenesis was induced in fetal hearts with elevated expression of Ppargc1a transcript specifically in IUGR females. Lipidomic analysis identified the accumulation of arachidonic, eicosapentaenoic, and docosapentaenoic polyunsaturated long-chain fatty acids (LCFAs) in IUGR fetal hearts, which leads to nuclear receptor peroxisome proliferator-activated receptor α (PPARα) transcriptional activation in cardiomyocytes. Also, the enrichment of H3K27ac chromatin marks to PPARα-responsive metabolic genes in IUGR fetal hearts outlines an epigenetic control in the early metabolic energy switch.

CONCLUSION

This study describes a premature and sex-related remodeling of cardiac metabolism in response to an unfavorable intrauterine environment, with specific LCFAs that may serve as predictive effectors leading to IUGR.

The number of glomeruli and pyruvate metabolism is not strongly coupled in the healthy rat kidney

PURPOSE

The number of glomeruli is different in men and women, as they also present different prevalence and progression of chronic kidney disease. A recent study has demonstrated a potential difference in renal metabolism between sexes, and a potential explanation could be the differences in glomeruli number. This study investigates the potential correlation between glomerular number and pyruvate metabolism in healthy kidneys.

METHODS

This study is an experimental study with rats (N = 12). We used cationized-ferritin MRI to visualize and count glomeruli and hyperpolarized [1-¹³ C]pyruvate to map the metabolism. Dynamic contrast-enhanced MRI was used to analyze kidney hemodynamics using gadolinium tracer.

RESULTS

Data showed no or subtle correlation between the number of glomeruli and the pyruvate metabolism. Minor differences were observed in the number of glomeruli (female = 24,509 vs. male = 26 350; p = .16), renal plasma flow (female = 606.6 vs. male= 455.7 ml/min/100 g; p = .18), and volume of distribution (female = 87.44 vs. male = 76.61 ml/100 ml; p = .54) between sexes. Mean transit time was significantly prolonged in males compared with females (female = 8.868 s vs. male = 10.63 s; p = .04).

CONCLUSION

No strong statistically significant correlation between the number of glomeruli and the pyruvate metabolism was found in healthy rat kidneys.

Sex Differences in Kidney Function and Metabolism Assessed Using Hyperpolarized [1-13C]Pyruvate Interleaved Spectroscopy and Nonspecific Imaging

Metabolic sex differences have recently been shown to be particularly important in tailoring treatment strategies. Sex has a major effect on fat turnover rates and plasma lipid delivery in the body. Differences in kidney structure and transporters between male and female animals have been found. Here we investigated sex-specific renal pyruvate metabolic flux and whole-kidney functional status in age-matched healthy Wistar rats. Blood oxygenation level–dependent and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) were used to assess functional status. Hyperpolarized [1-¹³C]pyruvate was used to assess the metabolic differences between male and female rats. Female rats had a 41% ± 3% and 41% ± 5% lower absolute body and kidney weight, respectively, than age-matched male rats. No difference was seen between age-matched male and female rats in the kidney-to-body weight ratio. A 56% ± 11% lower lactate production per mL/100 mL/min was found in female rats than in age-matched male rats measured by hyperpolarized magnetic resonance and DCE MRI. Female rats had a 33% ± 11% higher glomerular filtration rate than age-matched male rats measured by DCE MRI. A similar renal oxygen tension (T2*) was found between age-matched male and female rats as shown by blood oxygenation level–dependent MRI. The results were largely independent of the pyruvate volume and the difference in body weight. This study shows an existing metabolic difference between kidneys in age-matched male and female rats, which indicates that sex differences need to be considered when performing animal experiments.

Sex-specific differences in left ventricular mass and myocardial energetic efficiency in non-diabetic, pre-diabetic and newly diagnosed type 2 diabetic subjects

Background

Women with type 2 diabetes (T2DM) have a higher excess risk for cardiovascular disease (CVD) than their male counterparts. However, whether the risk for CVD is higher in prediabetic women than men is still debated. We aimed to determine whether sex-related differences exist in left ventricular mass index (LVMI), and myocardial mechano-energetic efficiency (MEEi) in with normal glucose tolerant (NGT), pre-diabetic and newly diagnosed type 2 diabetic subjects.

Methods

Sex-related differences in LVMI and myocardial MEEi, assessed by validated echocardiography-derived measures, were examined among 1562 adults with NGT, prediabetes, and newly diagnosed T2DM, defined according to fasting glucose, 2-h post-load glucose, or HbA1c.

Results

Worsening of glucose tolerance in both men and women was associated with an increase in age-adjusted LVMI and myocardial MEEi. Women with newly diagnosed T2DM exhibited greater relative differences in LVMI and myocardial MEEi than diabetic men when compared with their NGT counterparts. Prediabetic women exhibited greater relative differences in myocardial MEEi, but not in LVMI, than prediabetic men when compared with their NGT counterparts. The statistical test for interaction between sex and glucose tolerance on both LVMI (P < 0.0001), and myocardial MEEi (P < 0.0001) was significant suggesting a sex-specific association.

Conclusions

Left ventricle is subject to maladaptive changes with worsening of glucose tolerance, especially in women with newly diagnosed T2DM. The sex-specific increase in LVM and decrease in MEEi, both being predictors of CVD, may have a role in explaining the stronger impact of T2DM on the excess risk of CVD in women than in men.

Metabolic and Molecular Imaging of the Diabetic Cardiomyopathy

The term diabetic cardiomyopathy is defined as the presence of abnormalities in myocardial structure and function that occur in the absence of, or in addition to, well-established cardiovascular risk factors. A key contributor to this abnormal structural-functional relation is the complex interplay of myocardial metabolic remodeling, defined as the loss the flexibility in myocardial substrate metabolism and its downstream detrimental effects, such as mitochondrial dysfunction, inflammation, and fibrosis. In parallel with the growth in understanding of these biological underpinnings has been developmental advances in imaging tools such as positron emission tomography and magnetic resonance imaging and spectroscopy that permit the detection and in many cases quantification, of the processes that typifies the myocardial metabolic remodeling in diabetic cardiomyopathy. The imaging readouts can be obtained in both preclinical models of diabetes mellitus and patients with diabetes mellitus facilitating the bi-directional movement of information between bench and bedside. Moreover, imaging biomarkers provided by these tools are now being used to enhance discovery and development of therapies designed to reduce the myocardial effects of diabetes mellitus through metabolic modulation. In this review, the use of these imaging tools in the patient with diabetes mellitus from a mechanistic, therapeutic effect, and clinical management perspective will be discussed.

Delayed metabolic dysfunction in myocardium following exertional heat stroke in mice

KEY POINTS

Exposure to exertional heat stroke (EHS) is associated with increased risk of long-term cardiovascular disorders in humans. We demonstrate that in female mice, severe EHS results in metabolic changes in the myocardium, emerging only after 9-14 days. This was not observed in males that were symptom-limited at much lower exercise levels and heat loads compared to females. At 14 days of recovery in females, there were marked elevations in myocardial free fatty acids, ceramides and diacylglycerols, consistent with development of underlying cardiac abnormalities. Glycolysis shifted towards the pentose phosphate and glycerol-3-phosphate dehydrogenase pathways. There was evidence for oxidative stress, tissue injury and microscopic interstitial inflammation. The tricarboxylic acid cycle and nucleic acid metabolism pathways were also negatively affected. We conclude that exposure to EHS in female mice has the capacity to cause delayed metabolic disorders in the heart that could influence long-term health.

ABSTRACT

Exposure to exertional heat stroke (EHS) is associated with a higher risk of long-term cardiovascular disease in humans. Whether this is a cause-and-effect relationship remains unknown. We studied the potential of EHS to contribute to the development of a 'silent' form of cardiovascular disease using a preclinical mouse model of EHS. Plasma and ventricular myocardial samples were collected over 14 days of recovery. Male and female C57bl/6J mice underwent forced wheel running for 1.5-3 h in a 37.5°C/40% relative humidity until symptom limitation, characterized by CNS dysfunction. They reached peak core temperatures of 42.2 ± 0.3°C. Females ran ∼40% longer, reaching ∼51% greater heat load. Myocardial and plasma samples (n = 8 per group) were obtained between 30 min and 14 days of recovery, analysed using metabolomics/lipidomics platforms and compared to exercise controls. The immediate recovery period revealed an acute energy substrate crisis from which both sexes recovered within 24 h. However, at 9-14 days, the myocardium of female mice developed marked elevations in free fatty acids, ceramides and diacylglycerols. Glycolytic and tricarboxylic acid cycle metabolites revealed bottlenecks in substrate flow, with build-up of intermediate metabolites consistent with oxidative stress and damage. Males exhibited only late stage reductions in acylcarnitines and elevations in acetylcarnitine. Histopathology at 14 days showed interstitial inflammation in the female hearts only. The results demonstrate that the myocardium of female mice is vulnerable to a slowly emerging metabolic disorder following EHS that may harbinger long-term cardiovascular complications. Lack of similar findings in males may reflect their lower heat exposure.

Sex-related differences in self-care behaviors of adults with type 2 diabetes mellitus

PURPOSE

To describe sex-related differences in self-care; to identify determinants of self-care according to sex, and to investigate how sex interacts with the effect of clinical and socio-demographic variables on self-care in adults with Type 2 Diabetes Mellitus (T2DM).

METHODS

Cross-sectional multicentre study with a consecutive sampling recruitment strategy, enrolling 540 adults with T2DM at six outpatient diabetes services. Clinical and socio-demographic variables were collected by medical records. Self-care maintenance, monitoring, management, and confidence were measured by the self-care of diabetes inventory.

RESULTS

Females reported higher disease prevention behaviors (P < 0.001), health-promoting behaviors (P < 0.001), body listening (P < 0.001), and symptom recognition (P = 0.010), but lower health-promoting exercise behaviors (P < 0.001). Determinants of self-care were different in male and female patients, where the role of task-specific self-care confidence predicted self-care monitoring (RR = 0.98; P < 0.001) and management (RR = 0.99; P < 0.001) among males, while persistence self-care confidence predicted self-care maintenance (RR = 0.97; P = 0.016) and management (RR = 0.99; P = 0.009) among females.

CONCLUSIONS

Males and females differently perform self-care. Self-care confidence plays a different role predicting self-care behaviors in males and females. Future research should longitudinally describe self-care and its determinants in males and females with T2DM. Sex-specific self-care confidence interventions should be developed to improve self-care in male and female patients with T2DM.

Metformin and cognition from the perspectives of sex, age, and disease

Metformin is the safest and the most widely prescribed first-line therapy for managing hyperglycemia due to different underlying causes, primarily type 2 diabetes mellitus. In addition to its euglycemic properties, metformin has stimulated a wave of clinical trials to investigate benefits on aging-related diseases and longevity. Such an impact on the lifespan extension would undoubtedly expand the therapeutic utility of metformin regardless of glycemic status. However, there is a scarcity of studies evaluating whether metformin has differential cognitive effects across age, sex, glycemic status, metformin dose, and duration of metformin treatment and associated pathological conditions. By scrutinizing the available literature on animal and human studies for metformin and brain function, we expect to shed light on the potential impact of metformin on cognition across age, sex, and pathological conditions. This review aims to provide readers with a broader insight of (a) how metformin differentially affects cognition and (b) why there is a need for more translational and clinical studies examining multifactorial interactions. The outcomes of such comprehensive studies will streamline precision medicine practices, avoiding "fit for all" approach, and optimizing metformin use for longevity benefit irrespective of hyperglycemia.

Androgen-Regulated Cardiac Metabolism in Aging Men

The prevalence of cardiovascular mortality is higher in men than in age-matched premenopausal women. Gender differences are linked to circulating sex-related steroid hormone levels and their cardio-specific actions, which are critical factors involved in the prevalence and features of age-associated cardiovascular disease. In women, estrogens have been described as cardioprotective agents, while in men, testosterone is the main sex steroid hormone. The effects of testosterone as a metabolic regulator and cardioprotective agent in aging men are poorly understood. With advancing age, testosterone levels gradually decrease in men, an effect associated with increasing fat mass, decrease in lean body mass, dyslipidemia, insulin resistance and adjustment in energy substrate metabolism. Aging is associated with a decline in metabolism, characterized by modifications in cardiac function, excitation-contraction coupling, and lower efficacy to generate energy. Testosterone deficiency -as found in elderly men- rapidly becomes an epidemic condition, associated with prominent cardiometabolic disorders. Therefore, it is highly probable that senior men showing low testosterone levels will display symptoms of androgen deficiency, presenting an unfavorable metabolic profile and increased cardiovascular risk. Moreover, recent reports establish that testosterone replacement improves cardiomyocyte bioenergetics, increases glucose metabolism and reduces insulin resistance in elderly men. Thus, testosterone-related metabolic signaling and gene expression may constitute relevant therapeutic target for preventing, or treating, age- and gender-related cardiometabolic diseases in men. Here, we will discuss the impact of current evidence showing how cardiac metabolism is regulated by androgen levels in aging men.

Measuring the data gap: inclusion of sex and gender reporting in diabetes research

Background

Important sex and gender differences have been found in research on diabetes complications and treatment. Reporting on whether and how sex and gender impact research findings is crucial for developing tailored diabetes care strategies. To analyze the extent to which this information is available in current diabetes research, we examined original investigations on diabetes for the integration of sex and gender in study reporting.

Methods

We examined original investigations on diabetes published between January 1 and December 31, 2015, in the top five general medicine journals and top five diabetes-specific journals (by 2015 impact factor). Data were extracted on sex and gender integration across seven article sections: title, abstract, introduction, methods, results, discussion, and limitations.

Results

We identified 155 original investigations on diabetes, including 115 randomized controlled trials (RCTs) and 40 observational studies. Sex and gender were rarely incorporated in article titles, abstracts and introductions. Most methods sections did not describe plans for sex/gender analyses; 47 (30.3%) articles described plans to control for sex/gender in the analysis and 12 (7.7%) described plans to stratify results by sex/gender. While most articles (151, 97.4%) reported the sex/gender of study participants, only 10 (6.5%) of all articles reported all study outcomes separately by sex/gender. Discussion of sex-related issues was incorporated into 21 (13.5%) original investigations; however, just 1 (0.6%) discussed gender-related issues. Comparison by journal type (general medicine vs. diabetes specific) yielded only minor differences from the overall integration results. In contrast, RCTs performed more poorly on multiple sex/gender assessment metrics compared to observational studies.

Conclusions

Sex and gender are poorly integrated in current diabetes original investigations, suggesting that substantial improvements in sex and gender data reporting are needed to inform the evidence to support sex- and gender-specific diabetes care.

Sex differences and correlates of poor glycaemic control in type 2 diabetes: a cross-sectional study in Brazil and Venezuela

OBJECTIVE

Examine whether glycaemic control varies according to sex and whether the latter plays a role in modifying factors associated with inadequate glycaemic control in patients with type 2 diabetes (T2D) in Brazil and Venezuela.

DESIGN, SETTING AND PARTICIPANTS

This was a cross-sectional, nationwide survey conducted in Brazil and Venezuela from February 2006 to June 2007 to obtain information about glycaemic control and its determinants in patients with diabetes mellitus attending outpatient clinics.

MAIN OUTCOME MEASURES

Haemoglobin A1c (HbA1c) level was measured by liquid chromatography, and patients with HbA1c ≥7.0% (53 mmol/mol) were considered to have inadequate glycaemic control. The association of selected variables with glycaemic control was analysed by multivariate linear regression, using HbA1c as the dependent variable.

RESULTS

A total of 9418 patients with T2D were enrolled in Brazil (n=5692) and in Venezuela (n=3726). They included 6214 (66%) women and 3204 (34%) men. On average, HbA1c levels in women were 0.13 (95% CI 0.03 to 0.24; p=0.015) higher than in men, after adjusting for age, marital status, education, race, country, body mass index, duration of disease, complications, type of healthcare, adherence to diet, adherence to treatment and previous measurement of HbA1c. Sex modified the effect of some factors associated with glycaemic control in patients with T2D in our study, but had no noteworthy effect in others.

CONCLUSIONS

Women with T2D had worse glycaemic control than men. Possible causes for poorer glycaemic control in women compared with men include differences in glucose homeostasis, treatment response and psychological factors. In addition, sex modified factors associated with glycaemic control, suggesting the need to develop specific treatment guidelines for men and women.

Metformin does not affect postabsorptive hepatic free fatty acid uptake, oxidation or resecretion in humans: A 3-month placebo-controlled clinical trial in patients with type 2 diabetes and healthy controls

AIMS

To explore whether the pre-clinical findings that metformin improves lipid metabolism, possibly through modulation of intrahepatic partitioning of fatty acids towards oxidation and away from re-esterification and resecretion as triglycerides (TGs), can be translated to a human setting.

MATERIALS AND METHODS

We performed a 3-month randomized, placebo-controlled, parallel-group clinical trial in patients with type 2 diabetes (T2D; n = 24) and healthy controls (n = 12). Patients with T2D received either placebo (placebo group) or 1000 mg metformin twice daily (metformin group), while healthy subjects were all treated with metformin (control group). Hepatic fatty acid metabolism was measured by [¹¹ C]palmitate positron-emission tomography, hepatic TG secretion and peripheral oxidation by ex vivo labelled [1-¹⁴ C]VLDL-TG and VLDL particle size by TG/apolipoprotein B ratio. Body composition was assessed by dual-energy X-ray and whole-body lipid oxidation by indirect calorimetry.

RESULTS

Metformin treatment for 3 months produced the anticipated decrease in fasting plasma glucose (FPG) in the metformin group (FPG 7.9 ± 1.8 mM [study day 1] vs 6.4 ± 1.1 mM [study day 2]), whereas patients in the placebo group and healthy controls had similar FPG levels before and after the trial (mixed model group vs time interaction; P = .003); however, contrary to our hypothesis, metformin treatment did not affect hepatic lipid metabolism or peripheral oxidation.

CONCLUSION

The observed beneficial effects on lipid metabolism during metformin treatment in humans appear to be secondary to long-term alterations in body composition or glucose homeostasis.

High-intensity interval training versus continuous training on physiological and metabolic variables in prediabetes and type 2 diabetes: A meta-analysis

AIMS

To compare the effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on functional capacity and cardiometabolic markers in individuals prediabetes and type 2 diabetes (T2D).

METHODS

The search was performed in PubMed (MEDLINE), EMBASE, PEDro, CENTRAL, Scopus, LILACS database, and Clinical Trials from the inception to July 2017, included randomized clinical trials that compared the use of HIIT and MICT in prediabetes and T2D adults. The risk of bias was defined by Cochrane Handbook and quality of evidence by GRADE.

RESULTS

From 818 relevant records, seven studies were included in systematic review (64 prediabetes and 120 T2D patients) and five with T2D were meta-analyzed. HIIT promoted significantly increased of 3.02 mL/kg/min (CI95% 1.42-4.61) of VO₂max, measured for functional capacity, compared to MICT. No differences were found between two modalities of exercises considering the outcomes HbA1c, systolic and diastolic blood pressure, total cholesterol, HDL and LDL cholesterol, triglycerides, BMI, and waist-to-hip ratio. Most of the studies presented unclear risk of bias, and low and very low quality of evidence.

CONCLUSION

HIIT induces cardiometabolic adaptations similar to those of MICT in prediabetes and T2D, and provides greater benefits to functional capacity in patients with T2D.

PROSPERO

CRD42016047151.

Identifying the Critical Gaps in Research on Sex Differences in Metabolism Across the Life Span

The National Institutes of Health (NIH) Office of Research in Women's Health now functions under a mandate calling for the systematic inclusion of both female and male cells, animals, and human subjects in all types of research, so that sex as a biological variable is understood in health and disease. Sex-specific data can improve disease prevention, diagnosis, and treatment as well as reduce inequities. Inclusion of women in research studies has modestly improved over the last 20 years, yet preclinical research is still primarily done using male animal models and male-derived cells, with the result that many conclusions are made based on incomplete and sex-biased data. There are important, yet poorly studied, sex differences in cardiometabolic disease. To begin to address these sex differences, the Center for Women's Health Research at the University of Colorado held its inaugural National Conference, "Sex Differences Across the Lifespan: A Focus on Metabolism," in September 2016 (cwhr@ucdenver.edu). Research to address the important goal of understanding key sex differences in cardiometabolic disease across the life span is lacking. The goal of this article is to discuss the current state of research addressing sex differences in cardiometabolic health across the life span, to outline critical research gaps that must be addressed in response to NIH mandates, and, importantly, to develop strategies to address sex as a biological variable to understand disease mechanisms as well as develop diagnostic and therapeutic modalities.

Sex Differences in Cardiac Mitochondria in the New Zealand Obese Mouse

Background: Obesity is a risk factor for diseases including type 2 diabetes mellitus (T2DM) and cardiovascular disorders. Diabetes itself contributes to cardiac damage. Thus, studying cardiovascular events and establishing therapeutic intervention in the period of type T2DM onset and manifestation are of highest importance. Mitochondrial dysfunction is one of the pathophysiological mechanisms leading to impaired cardiac function. Methods: An adequate animal model for studying pathophysiology of T2DM is the New Zealand Obese (NZO) mouse. These mice were maintained on a high-fat diet (HFD) without carbohydrates for 13 weeks followed by 4 week HFD with carbohydrates. NZO mice developed severe obesity and only male mice developed manifest T2DM. We determined cardiac phenotypes and mitochondrial function as well as cardiomyocyte signaling in this model. Results: The development of an obese phenotype and T2DM in male mice was accompanied by an impaired systolic function as judged by echocardiography and MyH6/7 expression. Moreover, the mitochondrial function only in male NZO hearts was significantly reduced and ERK1/2 and AMPK protein levels were altered. Conclusions: This is the first report demonstrating that the cardiac phenotype in male diabetic NZO mice is associated with impaired cardiac energy function and signaling events.

Molecular mechanisms of cardiac pathology in diabetes - Experimental insights

Diabetic cardiomyopathy is a distinct pathology independent of co-morbidities such as coronary artery disease and hypertension. Diminished glucose uptake due to impaired insulin signaling and decreased expression of glucose transporters is associated with a shift towards increased reliance on fatty acid oxidation and reduced cardiac efficiency in diabetic hearts. The cardiac metabolic profile in diabetes is influenced by disturbances in circulating glucose, insulin and fatty acids, and alterations in cardiomyocyte signaling. In this review, we focus on recent preclinical advances in understanding the molecular mechanisms of diabetic cardiomyopathy. Genetic manipulation of cardiomyocyte insulin signaling intermediates has demonstrated that partial cardiac functional rescue can be achieved by upregulation of the insulin signaling pathway in diabetic hearts. Inconsistent findings have been reported relating to the role of cardiac AMPK and β-adrenergic signaling in diabetes, and systemic administration of agents targeting these pathways appear to elicit some cardiac benefit, but whether these effects are related to direct cardiac actions is uncertain. Overload of cardiomyocyte fuel storage is evident in the diabetic heart, with accumulation of glycogen and lipid droplets. Cardiac metabolic dysregulation in diabetes has been linked with oxidative stress and autophagy disturbance, which may lead to cell death induction, fibrotic 'backfill' and cardiac dysfunction. This review examines the weight of evidence relating to the molecular mechanisms of diabetic cardiomyopathy, with a particular focus on metabolic and signaling pathways. Areas of uncertainty in the field are highlighted and important knowledge gaps for further investigation are identified. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Immediate reduction of serum citrulline but no change of steroid profile after initiation of metformin in individuals with type 2 diabetes

Metformin is the most important first-line treatment for type 2 diabetes mellitus (T2DM) but its exact mode of action remains unknown. In this study, we used targeted metabolomics to gain new insights into the metabolic effects of metformin in humans with T2DM. We also examined changes in the serum steroid hormone profile. We quantified 167 serum metabolites and 19 steroid hormones using liquid chromatography-tandem mass spectrometry at three time points in individuals with previously untreated T2DM: before the start of metformin therapy (time point A), after the first dose (B) and after short-term therapy for 4-6 weeks (C). For metabolite analysis, we split the study cohort into a discovery and a replication study of 88 and 45 subjects, respectively. The statistical analysis was done using linear mixed-effects models. Among the metabolites quantified, citrulline showed the most pronounced changes. Compared to its baseline serum concentration, citrulline was reduced by 17% after the first dose of metformin (p=1.34E-07) and by 24% after short-term therapy (p=2.84E-08) in the discovery study. These results were confirmed in the replication study. The only other metabolite significantly changed after correction for multiple testing was PC ae C36:4 between baseline and 4-6 weeks. The serum steroid hormone profile showed no significant changes after metformin intake. In summary, we observed an immediate and sustained reduction of serum citrulline by metformin in humans. This may be relevant for some of the wanted or unwanted effects of the drug.

Pet Imaging and its Application in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death worldwide and represent a great challenge for modern research and medicine. Despite advances in preventing and treating CVD over the decades, there remains an urgent need to develop sensitive and safe methods for early detection and personalized treatment. With refinements of molecular imaging technologies such as positron emission tomography (PET), noninvasive imaging of CVDs is experiencing impressive progress in both preclinical and clinical settings. In this review, we summarize advances in cardiovascular PET imaging, highlight the latest development of CVD imaging probes, and illustrate the potential for individualized therapy based on metabolic phenotype.

Sprint interval training decreases left-ventricular glucose uptake compared to moderate-intensity continuous training in subjects with type 2 diabetes or prediabetes

Type 2 diabetes mellitus (T2DM) is associated with reduced myocardial glucose uptake (GU) and increased free fatty acid uptake (FFAU). Sprint interval training (SIT) improves physical exercise capacity and metabolic biomarkers, but effects of SIT on cardiac function and energy substrate metabolism in diabetic subjects are unknown. We tested the hypothesis that SIT is more effective than moderate-intensity continuous training (MICT) on adaptations in left and right ventricle (LV and RV) glucose and fatty acid metabolism in diabetic subjects. Twenty-six untrained men and women with T2DM or prediabetes were randomized into two-week-long SIT (n = 13) and MICT (n = 13) interventions. Insulin-stimulated myocardial GU and fasted state FFAU were measured by positron emission tomography and changes in LV and RV structure and function by cardiac magnetic resonance. In contrast to our hypothesis, SIT significantly decreased GU compared to MICT in LV. FFAU of both ventricles remained unchanged by training. RV end-diastolic volume (EDV) and RV mass increased only after MICT, whereas LV EDV, LV mass, and RV and LV end-systolic volumes increased similarly after both training modes. As SIT decreases myocardial insulin-stimulated GU compared to MICT which may already be reduced in T2DM, SIT may be metabolically less beneficial than MICT for a diabetic heart.

A Systems Biology Approach to Investigating Sex Differences in Cardiac Hypertrophy

BACKGROUND

Heart failure preceded by hypertrophy is a leading cause of death, and sex differences in hypertrophy are well known, although the basis for these sex differences is poorly understood.

METHODS AND RESULTS

This study used a systems biology approach to investigate mechanisms underlying sex differences in cardiac hypertrophy. Male and female mice were treated for 2 and 3 weeks with angiotensin II to induce hypertrophy. Sex differences in cardiac hypertrophy were apparent after 3 weeks of treatment. RNA sequencing was performed on hearts, and sex differences in mRNA expression at baseline and following hypertrophy were observed, as well as within-sex differences between baseline and hypertrophy. Sex differences in mRNA were substantial at baseline and reduced somewhat with hypertrophy, as the mRNA differences induced by hypertrophy tended to overwhelm the sex differences. We performed an integrative analysis to identify mRNA networks that were differentially regulated in the 2 sexes by hypertrophy and obtained a network centered on PPARα (peroxisome proliferator-activated receptor α). Mouse experiments further showed that acute inhibition of PPARα blocked sex differences in the development of hypertrophy.

CONCLUSIONS

The data in this study suggest that PPARα is involved in the sex-dimorphic regulation of cardiac hypertrophy.

Metformin effects on the heart and the cardiovascular system: A review of experimental and clinical data

BACKGROUND

Metformin, the eldest and most widely used glucose lowering drug, is likely to be effective also on cardiac and vascular disease prevention. Nonetheless, uncertainty still exists with regard to its effects on the cardiovascular system as a whole and specifically on the myocardium, both at the organ and cellular levels.

METHODS

We reviewed the available data on the cardiac and vascular effects of metformin, encompassing both in vitro, either tissue or isolated organ, and in vivo studies in experimental animals and humans, as well as the evidence generated by major clinical trials.

RESULTS

At the cellular level metformin's produces both AMP-activated kinase (AMPK) dependent and independent effects. At the systemic level, possibly also through other pathways, this drug improves endothelial function, protects from oxidative stress and inflammation, and from the negative effects of angiotensin II. On the myocardium it attenuates ischemia-reperfusion injury and prevents adverse remodeling induced by humoral and hemodynamic factors. The effects on myocardial cell metabolism and contractile function being not evident at rest or in more advanced stages of cardiac dysfunction, could be relevant during transient ischemia, during an acute increase in workload and in the early stages of diabetic/hypertensive cardiomyopathy as confirmed by few small clinical trials and some observational studies. The overall evidence emerging from both clinical trials and real world registry is in favor of a protective effect of metformin with respect to both coronary events and progression to heart failure.

CONCLUSIONS

Given this potential, its efficacy and its safety (and also its low cost) metformin remains the central pillar of the therapy of diabetes.

Two-year follow-up of 4 months metformin treatment vs. placebo in ST-elevation myocardial infarction: data from the GIPS-III RCT

Objectives

Preclinical and clinical studies suggested cardioprotective effects of metformin treatment. In the GIPS-III trial, 4 months of metformin treatment did not improve left ventricular ejection fraction in patients presenting with ST-elevation myocardial infarction (STEMI). Here, we report the 2-year follow-up results.

Methods

Between January 2011 and May 2013, 379 STEMI patients without diabetes undergoing primary percutaneous coronary intervention were randomized to a 4-month treatment with metformin (500 mg twice daily) (N = 191) or placebo (N = 188) in the University Medical Center Groningen. Two-year follow-up data was collected to determine its effect on predefined secondary endpoints: the incidence of major adverse cardiac events (MACE), its individual components, all-cause mortality, and new-onset diabetes.

Results

For all 379 patients all-cause mortality data were available. For seven patients (2%) follow-up data on MACE was limited, ranging from 129 to 577 days. All others completed the 2-year follow-up visit. Incidence of MACE was 11 (5.8%) in metformin and 6 (3.2%) in placebo treated patients [hazard ratio (HR) 1.84, confidence interval (CI) 0.68–4.97, P = 0.22]. Three patients died in the metformin group and one in the placebo treatment group. Individual components of MACE were also comparable between both groups. New-onset diabetes mellitus was 34 (17.8%) in metformin and 32 (17.0%) in placebo treated patients (odds ratio 1.15, CI 0.66–1.98, P = 0.84). After multivariable adjustment the incidence of MACE was comparable between the treatment groups (HR 1.02, CI 0.10–10.78, P = 0.99).

Conclusions

Four months metformin treatment initiated at the time of hospitalization in STEMI patients without diabetes did not exert beneficial long-term effects.

Trial registration

clinicaltrials.gov Identifier: NCT01217307.

Electronic supplementary material

The online version of this article (doi:10.1007/s00392-017-1140-z) contains supplementary material, which is available to authorized users.

Autophagy modulation: a potential therapeutic approach in cardiac hypertrophy

Autophagy is an evolutionarily conserved process used by the cell to degrade cytoplasmic contents for quality control, survival for temporal energy crisis, and catabolism and recycling. Rapidly increasing evidence has revealed an important pathogenic role of altered activity of the autophagosome-lysosome pathway (ALP) in cardiac hypertrophy and heart failure. Although an early study suggested that cardiac autophagy is increased and that this increase is maladaptive to the heart subject to pressure overload, more recent reports have overwhelmingly supported that myocardial ALP insufficiency results from chronic pressure overload and contributes to maladaptive cardiac remodeling and heart failure. This review examines multiple lines of preclinical evidence derived from recent studies regarding the role of autophagic dysfunction in pressure-overloaded hearts, attempts to reconcile the discrepancies, and proposes that resuming or improving ALP flux through coordinated enhancement of both the formation and the removal of autophagosomes would benefit the treatment of cardiac hypertrophy and heart failure resulting from chronic pressure overload.

Sex Differences in Metabolic Cardiomyopathy

In contrast to ischemic cardiomyopathies which are more common in men, women are over-represented in diabetic cardiomyopathies. Diabetes is a risk factor for cardiovascular disease; however, there is a sexual dimorphism in this risk factor: heart disease is five times more common in diabetic women but only two-times more common in diabetic men. Heart failure with preserved ejection fraction, which is associated with metabolic syndrome, is also more prevalent in women. This review will examine potential mechanisms for the sex differences in metabolic cardiomyopathies. Sex differences in metabolism, calcium handling, nitric oxide, and structural proteins will be evaluated. Nitric oxide synthase and PPARα exhibit sex differences and have also been proposed to mediate the development of hypertrophy and heart failure. We focused on a role for these signalling pathways in regulating sex differences in metabolic cardiomyopathies.

Reduced up-regulation of the nitric oxide pathway and impaired endothelial and smooth muscle functions in the female type 2 diabetic goto-kakizaki rat heart

Background

Type 2 diabetes is associated with greater relative risk of cardiovascular diseases in women than in men, which is not well understood. Consequently, we have investigated if male and female displayed differences in cardiac function, energy metabolism, and endothelial function which could contribute to increased cardiovascular complications in type 2 diabetic female.

Methods

Male and female Control and type 2 diabetic Goto-Kakizaki (GK) isolated rat hearts were perfused during 28 min with a physiological buffer before freeze-clamping for biochemical assays. High energy phosphate compounds and intracellular pH were followed using ³¹P magnetic resonance spectroscopy with simultaneous measurement of contractile function. Nitric oxide (NO) pathway and endothelium-dependent and independent vasodilatations were measured as indexes of endothelial function. Results were analyzed via two-way ANOVA, p < 0.05 was considered as statistically significant.

Results

Myocardial function was impaired in male and female diabetic versus Control groups (p < 0.05) without modification of energy metabolism. Coronary flow was decreased in both diabetic versus Control groups but to a higher extent in female GK versus male GK rat hearts (p < 0.05). NO production was up-regulated in diabetic groups but to a less extent in female GK rat hearts (p < 0.05). Endothelium-dependent and independent vasodilatations were impaired in female GK rat compared with male GK (p < 0.05) and female Control (p < 0.05) rat hearts.

Conclusions

We reported here an endothelial damage characterized by a reduced up-regulation of the NO pathway and impaired endothelial and smooth muscle functions, and coronary flow rates in the female GK rat hearts while energy metabolism was normal. Whether these results are related to the higher risk of cardiovascular complications among type 2 diabetic female needs to be further elicited in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0157-z) contains supplementary material, which is available to authorized users.

Sex and Gender Differences in Risk, Pathophysiology and Complications of Type 2 Diabetes Mellitus

The steep rise of type 2 diabetes mellitus (T2DM) and associated complications go along with mounting evidence of clinically important sex and gender differences. T2DM is more frequently diagnosed at lower age and body mass index in men; however, the most prominent risk factor, which is obesity, is more common in women. Generally, large sex-ratio differences across countries are observed. Diversities in biology, culture, lifestyle, environment, and socioeconomic status impact differences between males and females in predisposition, development, and clinical presentation. Genetic effects and epigenetic mechanisms, nutritional factors and sedentary lifestyle affect risk and complications differently in both sexes. Furthermore, sex hormones have a great impact on energy metabolism, body composition, vascular function, and inflammatory responses. Thus, endocrine imbalances relate to unfavorable cardiometabolic traits, observable in women with androgen excess or men with hypogonadism. Both biological and psychosocial factors are responsible for sex and gender differences in diabetes risk and outcome. Overall, psychosocial stress appears to have greater impact on women rather than on men. In addition, women have greater increases of cardiovascular risk, myocardial infarction, and stroke mortality than men, compared with nondiabetic subjects. However, when dialysis therapy is initiated, mortality is comparable in both males and females. Diabetes appears to attenuate the protective effect of the female sex in the development of cardiac diseases and nephropathy. Endocrine and behavioral factors are involved in gender inequalities and affect the outcome. More research regarding sex-dimorphic pathophysiological mechanisms of T2DM and its complications could contribute to more personalized diabetes care in the future and would thus promote more awareness in terms of sex- and gender-specific risk factors.

Sexual dimorphism in myocardial acylcarnitine and triglyceride metabolism

Background

Cardiovascular disease is the leading cause of death among diabetic patients. Importantly, recent data highlight the apparent sexual dimorphism in the pathogenesis of cardiovascular disease in diabetics with respect to both frequency- and age-related risk factors. The disposition to cardiovascular disease among diabetic patients has been attributed, at least in part, to excess lipid supply to the heart culminating in lipotoxicity of the heart and downstream derangements. A confounding factor in obese animal models of diabetes is that increased peripheral lipid availability to the heart can induce cardio-metabolic remodeling independent of the underlying pathophysiology of diabetes, thus masking the diabetic phenotype. To that end, we hypothesized that the use of non-obese diabetic (NOD) animal models will reveal metabolic signatures of diabetes in a sex-specific manner.

Methods

To test this hypothesis, male and female NOD Goto-Kakizaki (GK) rats were used to assess the expression profile of 84 genes involved in lipid metabolism. In parallel, targeted lipidomics analysis was performed to characterize sex differences in homeostasis of non-esterified fatty acids (NEFA), acylcarnitines (AC), and triglycerides (TG).

Results

Our analysis revealed significant sex differences in the expression of a broad range of genes involved in transport, activation, and utilization of lipids. Furthermore, NOD male rats exhibited enhanced oxidative metabolism and accumulation of TG, whereas female NOD rats exhibited reduced TG content coupled with accumulation of AC species. Multi-dimensional statistical analysis identified saturated AC16:0, AC18:0, and AC20:0 as dominant metabolites in mediating sex differences in AC metabolism. Confocal microscopy of rat cardiomyocytes exposed to AC14:0, AC16:0, and AC18:0 confirmed induction of ROS with AC18:0 being more potent followed by AC14:0.

Conclusion

Overall, we demonstrate sex differences in myocardial AC and TG metabolism with implications for therapy and diagnosis of diabetic cardiovascular disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13293-016-0077-7) contains supplementary material, which is available to authorized users.

Assessing Cardiac Metabolism: A Scientific Statement From the American Heart Association

In a complex system of interrelated reactions, the heart converts chemical energy to mechanical energy. Energy transfer is achieved through coordinated activation of enzymes, ion channels, and contractile elements, as well as structural and membrane proteins. The heart's needs for energy are difficult to overestimate. At a time when the cardiovascular research community is discovering a plethora of new molecular methods to assess cardiac metabolism, the methods remain scattered in the literature. The present statement on "Assessing Cardiac Metabolism" seeks to provide a collective and curated resource on methods and models used to investigate established and emerging aspects of cardiac metabolism. Some of those methods are refinements of classic biochemical tools, whereas most others are recent additions from the powerful tools of molecular biology. The aim of this statement is to be useful to many and to do justice to a dynamic field of great complexity.

Imaging of myocardial fatty acid oxidation

Myocardial fuel selection is a key feature of the health and function of the heart, with clear links between myocardial function and fuel selection and important impacts of fuel selection on ischemia tolerance. Radiopharmaceuticals provide uniquely valuable tools for in vivo, non-invasive assessment of these aspects of cardiac function and metabolism. Here we review the landscape of imaging probes developed to provide non-invasive assessment of myocardial fatty acid oxidation (MFAO). Also, we review the state of current knowledge that myocardial fatty acid imaging has helped establish of static and dynamic fuel selection that characterizes cardiac and cardiometabolic disease and the interplay between fuel selection and various aspects of cardiac function. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.