Associations of GPCR autoantibodies with clinical, histological, metabolic and hemodynamic features in non-ischemic heart failure patients

Background

Roughly one third of cases of chronic heart failure (HF) are caused by genetic predisposition, metabolic stress and cardiac inflammation. Animal studies suggest that heart-reactive autoantibodies, most notably those directed against G-protein-coupled receptors (GPCR), could also play a pathogenetic role in the disease. However, so far, a causal link between humoral GPCR-autoimmunity and human non-ischemic heart failure other than Chagas' cardiomyopathy remains unclear.

Purpose

Here, we investigated possible associations of GPCR autoantibodies with inflammatory, hemodynamic, metabolic and functional parameters in patients with chronic non-ischemic HF unrelated to Chagas' disease.

Methods

We prospectively included 95 patients with newly diagnosed non-ischemic heart failure of unknown origin. Basic cardiac characterization comprised transthoracic echocardiography, cardiac magnetic resonance imaging, coronary angiography and right heart catheterization with endomyocardial biopsy. Mitochondrial oxidative phosphorylation capacity and coupling was measured using high-resolution respirometry in permeabilized myocardial fibers. A panel of candidate GPCR-autoantibodies was determined by validated and certified immune-assays in peripheral venous blood of the HF-patients and 60 matched healthy individuals. Results were normalized to total IgG.

Results

Among 10 candidate GPCR-autoantibodies determined, only autoantibodies for α1-adrenergic receptor (α1AR), β1-adrenergic receptor (β1AR), muscarinic receptor M5 (M5AR), angiotensin II receptor type 1 (AT1R) and type 2 (AT2R) exhibited HF-associated alterations:

Autoantibodies against β1AR, M5R and AT2R were increased. Autoantibodies against α1AR and AT1R were decreased (Figure). These alterations were significant (p<0.01), but not, or only weakly, correlated with markers of cardiac inflammation, cardiac damage, hemodynamics, endomyocardial histology or left ventricular inflammation judged by T2-mapping.

However, in HF-patients, increased AT2R autoantibodies were associated with improved myocardial mitochondrial coupling (r=−0.27, p=0.021), and decreased AT2R autoantibodies were associated with insulin resistance (r=−0.24 p=0.027).

Conclusion(s)

Some previously postulated alterations of GPCR autoantibodies were confirmed in thoroughly characterized HF-patients. However, association of these alterations with cardiac function was not traceable, which argues against a specific pathogenic role. Our data are compatible with multifaceted interactions of GPCR-autoantibodies with the myocardium and potentially with glucose metabolism, possibly indicating a disease-modifying or compensatory role.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Research comission of the Heinrich-Heine University Duesseldorf

Absolute treatment effects for the primary outcome and all-cause mortality in the cardiovascular outcome trials in type 2 diabetes: a meta-analysis of individual patient data

Background and purpose

Treatment effects from the large cardiovascular outcome trials (CVOTs) in diabetes are almost exclusively communicated as hazard ratios, although reporting guidelines recommend to report treatment effects also on an absolute scale, e.g. as numbers needed to treat (NNT). We aimed to analyze NNT in CVOTs of novel oral antidiabetic drugs comparing dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, or sodium-glucose cotransporter-2 (SGLT2) inhibitors to placebo.

Methods and results

We extracted individual time-to-event information for the primary outcome and all-cause mortality from 19 CVOTs that compared DPP-4 inhibitors, GLP-1 receptor agonists, or SGLT2 inhibitors to placebo. We estimated Weibull models for each trial and outcome and derived monthly NNTs. NNTs were summarized across all trials and within drug-classes by random effects meta-analysis methods. Treatment effects in the CVOTs appear smaller if they are reported as NNTs: Overall, 60 (95%-CI: 40–124) patients have to be treated for 29 months (the median follow-up time across all trials) to avoid a single event of the primary outcome, and 101 (95%-CI: 69–191) patients have to be treated for 39 months to avoid a single death.

Conclusion

We found that the respective treatment effects of novel oral antidiabetic drugs look less impressive when communicated on an absolute scale, as numbers needed to treat. For a valid overall picture of the benefit of these drugs, trial authors should thus also report treatment effects on an absolute scale.

Funding Acknowledgement

Type of funding sources: None.

Development of CMR-derived aortic stiffness parameters in patients with metabolic comorbidities after ST-segment elevation myocardial infarction

Background

Aortic stiffness has demonstrated an independent prediction of adverse cardiovascular events after ST-segment elevation myocardial infarction (STEMI) [1]. The general impact of the comorbidities diabetes mellitus (DM), chronic kidney disease (CKD), anemia on aortic stiffness is well known [2,3]. Therefore, the present study aimed to investigate the influence of metabolic comorbidities on cardiovascular magnetic resonance (CMR)-derived aortic parameters early and 6 months after STEMI.

Methods

From the prospective STEMI pathway, 161 patients (mean age: 63.7 years; 75% male) with initial CMR 5 days after STEMI were included. 105 patients pursued in a 6-month follow-up CMR. Aortic stiffness was assessed using different parameters: 1) pulse wave velocity (PWV) from velocity-encoded phase-contrast images, 2) aortic distensibility, and 3) radial strain from the ascending aorta obtained from cine images. DM was diagnosed when either pre-existing, HbA1c ≥6.5% at index hospitalization or 2-hour OGCT ≥200 mg/dl. CKD was present when glomeruli filtration rate (GFR) was less than 60 ml/min/m2, Anemia was defined according to WHO classifications.

Results

Of the 161 patients, 46 presented with anemia at admission, 79 with anemia at day 5, 26 with CKD and 57 with DM. Initial anemia resulted in a significantly lower distensibility (p=0.003) and aortic strain (p=0.02). A correlation between initial haemoglobin levels and distensibility (r=0.253; p=0.002) was found. CKD Patients showed a lower distensibility (p=0.012). There were correlations between GFR and PWV (r=−0.298; p<0.001), distensibility (r=0.370; p<0.001), and radial strain (r=−0.388; p<0.001). After 6 month this significant correlation remained. The DM group showed higher PWV values (p=0.02) and a lower radial strain (p=0.003). PWV showed a correlation with the 2-hour OGCT value (r=0.249; p=0.011) while the radial strain correlated with HbA1c (r=0.216; p=0.007). After multivariable analyses, diabetes remained the only significant predictor to show higher PWV (p=0.004) and poorer radial strain values (p=0.0045) while initial anemia remained the only significant predictor of lower distensibility (p=0.0033). Aortic stiffness parameters did not show any changes after 6 months in all groups. Only NTproBNP 5 days after STEMI correlated significantly with 6-months PWV (r=0.247; p=0.02), radial strain (r=0.36; p=0.001), distensibility (r=−0.226; p=0.018).

Conclusion

Anemia, DM and CKD show a detrimental impact on values of aortic stiffness early after STEMI. Diabetes remains the only significant predictor of higher PWV and poorer radial strain values after multivariable analysis while initial anemia remains significant predictor of lower distensibility. After 6 months none of the groups showed improvement in aortic stiffness parameters.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Sonderforschungsbereich 1116

Chronic insulin resistance deteriorates cardiac mitochondrial quality control in a mouse model of SEC-NAFLD-IR

Background

Insulin resistance and nonalcoholic fatty liver disease (NAFLD) both relate to cardiovascular mortality. Using a mouse model of chronic lipid overload and secondary-NAFLD-induced insulin resistance (SEC-NAFLD-IR), we recently deciphered that SEC-NAFLD-IR already at young age provoked myocardial lipotoxicity with reduced mitochondrial efficiency and increased vulnerability to cardiac ischemia. However, long-term consequences of SEC-NAFLD-IR remain elusive.

Purpose

Here we aimed to elucidate the impact of long-term SEC-NAFLD-IR on multiple mitochondrial quality control (mQC) mechanisms in the heart and its consequences for cardiac function.

Methods

We studied 36 SEC-NAFLD-IR mice (72-week-old). For mechanistic experiments, we applied palmitate-induced insulin resistant murine HL-1 cells. Cardiac mitochondrial dynamics were measured via quantification of mitochondrial morphology and expression of mitochondrial fusion and fission factors (Opa1, Drp1, Fis1, Mfn 1 & 2). Mitophagy level was evaluated via immunofluorescence and protein expression of key mitophagy-related genes (Parkin, NIX, LC3). Mitochondrial biogenesis and mass were examined via quantitation of PGC-1α expression, mtDNA and citrate synthase activity.

Results

72-week-old SEC-NAFLD-IR mice exhibited 21% (p=0.001) and 32% (p<0.001) higher body weight and heart weight compared with controls. Along with elevated oxidative stress, hepatic lipid accumulation and inflammation, 6h-fasted SEC-NAFLD-IR mice were characterized by increased plasma glucose, insulin and cholesterol. SEC-NAFLD-IR mice displayed a cardiac phenotype with 21% higher left ventricular mass (normalized to body weight, p<0.001) and 6% lower ejection fraction compared to controls (73.5% SEM 0.90 vs 69.4% SEM 1.65, p=0.04). We found several advantageous mQC mechanisms suppressed in aged SEC-NAFLD-IR mice including long form OPA1-mediated mitochondrial fusion, Parkin- and NIX-mediated mitophagy. Likewise, mitochondrial biogenesis was suppressed in the aged insulin-resistant heart, which was connected to a 65% downregulation of PGC-1α1 expression (p=0.01). Interestingly, downregulation of cardiac PGC-1α1 in aged SEC-NAFLD-IR mice coincided with upregulation of PARIS, indicating the crucial participation of the Parkin/PARIS pathway in mQC of the insulin-resistant heart. In addition, induction of insulin resistance in murine HL-1 cardiomyocytes also led to increased mitochondrial fragmentation and decreased PGC-1α1 expression.

Conclusion

This study demonstrated that regulation of mitochondrial network and turnover is hampered by SEC-NAFLD-IR in the hearts of aged mice, which may contribute to hypertrophy and cardiac dysfunction in insulin resistance.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Collaborative Research Centre 1116 (German Research Foundation)

Impaired Cardioprotection by HDL in CAD and Diabetes in Ischemia/Reperfusion Injury: role of S1P and SR-BI

Background

HDL dysfunction rather than HDL-cholesterol concentration is involved in the pathogenesis of coronary artery disease (CAD) and type-2 diabetes (T2DM). While causes and consequences of HDL dysfunction are manifold, reduced concentrations of HDL-sphingosine-1-phsophate (S1P) are partially responsible for impaired vasodilation and suppression of inflammation by CAD-HDL. Administration of healthy human HDL prior to coronary ischemia/reperfusion (I/R) in mice reduced infarct size (IS) due to HDL-S1P. The role of major HDL receptor SR-BI is unexplored in this context.

Purpose

In this study, we, a) investigated the cardioprotective properties of healthy versus CAD-HDL and T2DM-HDL in a murine model of acute myocardial infarction (AMI), b) tested the effect of S1P loading of CAD-HDL in cardioprotection, and c) detected the relevant HDL receptor of this cardioprotection.

Methods

HDL were isolated from plasma of healthy volunteers, CAD, and T2DM patients by density ultra-centrifugation and injected (43 mg HDL protein/KG) in the tail vein of C57Bl/6J mice 5 minutes prior to 30 minutes of ischemia. Cardiac function was assessed after 24 hours of reperfusion by echocardiography. IS was analyzed by TTC staining and S1P concentration measured by LC-MS/MS, respectively.

Results

Administration of human healthy HDL reduced IS by 23% and increased ejection fraction (EF) by 22% 24 hours after I/R (IS: Control 43.8±6.9% [n=17] vs. healthy HDL 32.9±3.6% [n=9]; EF: Control 34.5±5.7% vs. healthy HDL 41.9±4.1%). In contrast, CAD-HDL in the same dosage had no protective effect (IS: 40.1±5.7% [n=12]; EF: 31.9±8.4%). As HDL-S1P concentrations were 33% lower in CAD-HDL compared to healthy HDL, we tested whether S1P-loading may correct CAD-HDL's defective cardioprotection. Indeed, S1P-loading (38 μg S1P/kg in 43 mg HDL protein/KG) completely restored CAD-HDL cardioprotection to levels achieved by healthy HDL. S1P-loading of healthy HDL had no additional benefit. Administration of T2DM-HDL prior to I/R led to 28% larger IS and 22% worse EF compared to healthy HDL (IS: healthy HDL 33.0±4.3% [n=6] vs. T2DM-HDL 42.4±8.9% [n=13]; EF: healthy HDL 38.5±5.8% [n=6] vs. T2DM-HDL 33.1±.4.0%). Compared to healthy HDL, T2DM-HDL exhibited a 19% decrease in S1P content. We thus tested whether the major HDL receptor SR-BI is involved in HDL-S1P mediated cardioprotection using global SR-BI deficient mice (Scarb1−/−). Remarkably, cardioprotection by HDL administration was completely absent in Scarb1−/− mice but intact in wild type controls. (IS Scarb1++: Vehicle 38.6±8.3% [n=12] vs. HDL 29.9±8.5% [n=11], Scarb1−/−: Vehicle 31.4±5.6% [n=12] vs. HDL 31.1±6.9% [n=17])

Conclusion

We have identified: (a) impaired cardioprotection after I/R as new characteristic of HDL dysfunction in CAD and T2DM; (b) low HDL-S1P as its cause and the possibility of its therapeutic correction by S1P loading, and (c) SR-BI as the HDL receptor responsible for HDL-S1P-mediated cardioprotection.

Funding Acknowledgement

Type of funding sources: None.

Prediabetes relates to impaired mitochondrial function in human ventricular myocardium

Background/Introduction

With the growing prevalence of prediabetes in developed countries, complications of this predecessor of diabetes mellitus type 2 become increasingly important for medical research and practice. Prediabetes is defined as impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) and may also incorporate elevated hemoglobin A1. While overt type 2 diabetes is a well-established risk factor and can even be the cause of cardiac failure, this is not yet proven for prediabetes. Mitochondrial impairment is a key pathomechanism in heart failure, but it remains uncertain, whether prediabetes impairs myocardial energy metabolism in humans just as type 2 diabetes does.

Purpose

We aimed to scrutinize the impact of prediabetes on myocardial mitochondrial metabolism and cardiac function.

Methods

We included 50 heart transplant recipients with normal glucose tolerance (GT, n=25), prediabetes (n=8, 3 IFG and 5 IGT) or type 2 diabetes mellitus (T2DM, n=17), who had received a healthy donor heart from a non-diabetic donor. In this cohort, the impact of the recipients' metabolism should be displayed in the donor heart after transplantation. We performed oral glucose tolerance tests to assess the diabetes status, and cardiac magnetic resonance imaging to assess cardiac systolic and diastolic function, circulating biomarkers of oxidative stress in serum samples (thiobarbituric acid reactive substances (TBARS) and redox potential), as well as global T2 relaxation times as a marker of myocardial inflammation. In transcatheter endomyocardial biopsies, we assessed myocardial mitochondrial oxidative capacity using high-resolution respirometry and myocardial mRNA expression of nuclear factor kappa B p105 subunit (NFKB1).

Results

GT and IFG/IGT patients exhibited comparable demographic and clinical characteristics, whereas T2DM had higher BMI, glycemia, triglycerides and creatine kinase (all p<0.05). None of systolic (p=0.99), diastolic cardiac function (p=0.81), myocardial NFKB1 expression (p=0.74), circulating oxidative stress markers (p=0.94 and 0.95) or cardiac T2 relaxation times (p=0.99) were altered in IFG/IGT compared to GT, but diastolic strainrate was impaired (p=0.03) and circulating oxidative stress (TBARS: p=0.03, redox potential: p=0.04) were higher in T2DM than in GT. However, myocardial mitochondrial function stood out to be already impaired in IFG/IGT to a similar extend as in T2DM. This particularly applied to substrates of mitochondrial complex I (GT vs. IFG/IGT vs. T2DM: 126±7 vs. 89±12 vs. 93±6 pmol s–1 mg–1. p=0.02) and II (188±13 vs. 123±17 vs. 138±11 pmol s–1 mg–1. p=0.02). Intrinsic uncoupling was not altered in IFG/IGT but tended to be higher in T2DM (leak control ratio: 0.49±0.02 vs. 0.46±0.06 vs. 0.57±0.04 [arbirary units]).

Conclusion

Our findings point towards mitochondrial impairment as a predecessor of overt heart failure in prediabetes and may represent an early footprint of prediabetic cardiomyopathy.

Funding Acknowledgement

Type of funding sources: None.

Absolute treatment effects of novel oral antidiabetic drugs on cardiovascular mortality and hospitalization for heart failure: a meta-analysis of digitalized individual patient outcomes

Background and purpose

Absolute treatment effects of novel oral antidiabetic drugs for cardiovascular outcomes have thus far not been comprehensively evaluated. We thus aimed to perform a meta-analysis of digitalized individual patient data.

Methods and results

Individual patient outcomes from Cardiovascular Outcome Trials (CVOTs) evaluating dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists and sodium glucose transporter 2 (SGLT2) inhibitors against placebo with time-to-event information for cardiovascular mortality (CM) and/or hospitalization for heart failure (HHF) endpoints were digitalized from Kaplan-Meier plots; Weibull regression models with random-effects meta-analysis were used to estimate numbers-needed-to-treat (NNT) and Meta-NNT with 95% confidence intervals (CI). Sixteen CVOTs reported time-to-event information (14 in primary diabetes, two in primary heart failure populations). Thirteen studies including 96,860 patients were meta-analyzed for CM: at the median follow-up of 30 months, Meta-NNTs were 178 (64 to ∞ to −223) for DPP-4 inhibitors, 261 (158 to 745) for GLP-1 receptor agonists and 118 (68 to 435) for SGLT2 inhibitors. Ten studies including 96,128 patients were meta-analyzed for HHF: at the median follow-up of 29 months, estimated Meta-NNTs were −644 (229 to ∞ to −134) for DPP-4 inhibitors, 441 (184 to ∞ to −1100) for GLP-1 receptor agonists and 126 (91 to 208) for SGLT2 inhibitors. SGLT2 inhibitors were especially effective for HHF in primary heart failure populations (Meta-NNT 25 (19 to 39)) vs. primary diabetes populations (Meta-NNT 233 (167 to 385)) at 16 months of follow-up.

Conclusion

We found modest treatment benefits of GLP-1 receptor agonists and SGLT2 inhibitors for CM and HHF in primary T2DM populations. In primary heart failure populations, however, SGLT2 inhibitor benefits were substantial and comparable to established heart failure medication.

Funding Acknowledgement

Type of funding sources: None.

Regional analysis of inflammation and contractile function in reperfused acute myocardial infarction by in vivo 19F cardiovascular magnetic resonance in pigs

Inflammatory cell infiltration is central to healing after acute myocardial infarction (AMI). The relation of regional inflammation to edema, infarct size (IS), microvascular obstruction (MVO), intramyocardial hemorrhage (IMH), and regional and global LV function is not clear. Here we noninvasively characterized regional inflammation and contractile function in reperfused AMI in pigs using fluorine (¹⁹F) cardiovascular magnetic resonance (CMR). Adult anesthetized pigs underwent left anterior descending coronary artery instrumentation with either 90 min occlusion (n = 17) or without occlusion (sham, n = 5). After 3 days, in surviving animals a perfluorooctyl bromide nanoemulsion was infused intravenously to label monocytes/macrophages. At day 6, in vivo ¹H-CMR was performed with cine, T2 and T2* weighted imaging, T2 and T1 mapping, perfusion and late gadolinium enhancement followed by ¹⁹F-CMR. Pigs were sacrificed for subsequent ex vivo scans and histology. Edema extent was 35 ± 8% and IS was 22 ± 6% of LV mass. Six of ten surviving AMI animals displayed both MVO and IMH (3.3 ± 1.6% and 1.9 ± 0.8% of LV mass). The ¹⁹F signal, reflecting the presence and density of monocytes/macrophages, was consistently smaller than edema volume or IS and not apparent in remote areas. The ¹⁹F signal-to-noise ratio (SNR) > 8 in the infarct border zone was associated with impaired remote systolic wall thickening. A whole heart value of ¹⁹F integral (¹⁹F SNR × milliliter) > 200 was related to initial LV remodeling independently of edema, IS, MVO, and IMH. Thus, ¹⁹F-CMR quantitatively characterizes regional inflammation after AMI and its relation to edema, IS, MVO, IMH and regional and global LV function and remodeling.

Time dependent deterioration of mitochondrial oxidative capacity in heart transplantat recipients with type 2 diabetes mellitus

Background

Diabetic cardiomyopathy is defined as Heart failure in patients with Type 2 Diabetes (T2DM) in absence of traditional risk factors.

Following HTX, a substantial number of recipients develop insulin resistance or T2DM, associated with cardiac allograft vasculopathy and with increased mortality.

Recently we have shown that endomyocardial biopsies of heart transplant (HTX) recipients with T2DM express reduced mitochondrial respiration.

Purpose

The current study analyses time depended impact of T2DM on myocardial mitochondrial respiration of a priorly non-diabetic heart.

We hypothesized that myocardial mitochondrial oxidative phosphorylation capacity declines in patients with T2DM compared to glucose tolerant heart transplant recipients and that reduced mitochondrial respiration leads to impairment of cardiac function.

Methods

We included 101 HTX recipients who underwent routine endomyocardial biopsy. Patients with T1DM or a Donor with DM were excluded. Patients were classified according to criteria of the American Diabetes Association as non-diabetic (n=23), prediabetic (n=38) or T2DM (n=40), by either Fasting Plasma Glucose, 2h Plasma Glucose, HbA1c or intake of antidiabetic medication. We performed ex vivo high resolution respirometry on permeabilized fibres to assess myocardial mitochondrial respiration. Left ventricular ejection fraction (LV-EF) was assessed by cardiac-MRI or Echocardiography.

Results

Groups were of comparable age (p=0.06), sex (p=0.25) and time since HTX (p=0.91). Mean time since HTX was 29 months. Current rejection episodes (p=0.37) or corticoid pulse therapy (p=0.46) did not significantly differ between groups.

Linear regression in T2DM patients revealed an inverse relationship between time since HTX and mitochondrial respiration at state III conditions supported by the substrates octanoyl-carnitine and ADP (R2=0.16, F(1,38)=6.97, p=0.01). Regression analyses for non-DM group and Prediabetes group revealed no significant relationship between time since HTX and mitochondrial function (non-DM: R2=0.04, F(1,21)=0.9, p=0.35; Prediabetes: R2=0.01, F(1,36)=0.27, p=0.61). Exclusion of patients with cellular allograft rejection (ISHLT ≥1) or of patients with recent corticoid pulse therapy did not alter these results.

Linear correlation revealed a significant relationship (r=0.33, p=0.04) between declining mitochondrial state III respiration and left ventricular ejection fraction (n=39), suggesting associated functional consequences.

Conclusions

Our results suggest a T2DM associated decline of mitochondrial oxidative capacity in HTX recipients. Reduced mitochondrial respiration is associated to lower LV-EF. Targeting mitochondrial respiration might be a promising novel therapeutic approach to address T2DM associated mortality.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Research Counsil

Ventricular endomyocardial mitochondrial impairment and inflammation accompany diastolic dysfunction in the type 2 diabetic human heart

 

Type 2 Diabetes Mellitus (T2DM) is a major risk factor for chronic heart failure, even independent of coronary artery disease. Various underlying mechanisms worsening ventricular function in T2DM have been postulated based on data from animal studies, including mitochondrial abnormalities, alterations of Nuclear factor kappa-B (NfκB) expression, increased oxidative stress and inflammation and cardiac fibrosis and diastolic impairment. However, evidence in humans for these mechanisms is currently lacking. Especially early T2DM-related alterations and the impact of T2DM in the absence of coronary artery disease remain unclear.

We hypothesize that T2DM (I) leads to distinct changes in diastolic cardiac function, (II) impairs mitochondrial function of the ventricular myocardium, and (III) increases ventricular myocardial NfκB expression.

Heart transplant recipients with T2DM (“T2DM”, n=17) and without (“Non-DM”, n=32) T2DM (as determined by oral glucose tolerance tests) were included, if they had received their heart from a donor without Diabetes Mellitus. Thus, diabetes-exposure of the transplanted hearts exactly corresponded to the time since transplantation. Magnetic resonance imaging was performed to assess left ventricular ejection fraction, global longitudinal strain (GLS), diastolic strain, and T2 relaxation times, a marker of myocardial edema. We assessed NfκB p105 subunit (NfκB1) mRNA expression using real-time PCR and myocardial mitochondrial respiration using high-resolution respirometry in ventricular endomyocardial biopsies.

All participants had normal left ventricular ejection fraction (LVEF) without angiographic signs of coronary artery disease post transplantation (average 2.9±2.4 years). Age, sex distribution and LVEF were comparable between T2DM and Non-DM participants (p=0.50, 0.40 and 0.36, respectively). While GLS was not different (p=0.34), T2DM exhibited lower diastolic strain (1.0±0.4 vs. 1.4±0.4s-1, p<0.01) and higher T2 relaxation times (67±3 vs. 64±3ms, p<0.05) than Non-DM, indicating impaired diastolic function and increased myocardial edema. In T2DM, myocardial mitochondrial respiration with fatty acids and glycolytic substrates was 22–27% lower and mitochondrial uncoupling was 19% higher, whereas ORP and TBARS were 17% and 34% higher than in Non-DM (all p<0.05). Myocardial oxidative capacity related negatively to fasting blood glucose (r=−0.35; p<0.01), and positively to insulin sensitivity (r=0.49; p<0.05) across all participants. Myocardial NfκB mRNA expression was 60% higher in T2DM (0.45 [0.29; 0.71] vs. 0.28 [0.21; 0.44] AU, p<0.05) and correlated inversely with complex I respiration (r=−0.33; p<0.05).

Exposure to T2DM diminishes mitochondrial function in ventricular myocardium, which relates to hyperglycemia, insulin resistance, oxidative stress, inflammation, and ventricular diastolic dysfunction and edema. These changes appear within short-term overt diabetes and might precede T2DM-related heart failure.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): This work was supported by funding from the German Research Council (SFB1116) and a grant provided by the research commission of the Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany.

Aetiology-dependent impairment of mitochondrial function in the failing human heart

Background

Alterations of mitochondrial function have been identified to play a role in Heart Failure (HF) pathophysiology. Oxidative phosphorylation (OXPHOS) capacity of the myocardium was shown to be reduced in the failing heart. Ineffective mitochondrial function promotes formation of reactive oxygen species (ROS) that may affect remodelling in ischemia. Thus far, human mitochondrial function comparing dilated cardiomyopathy (DCM) and ischemic cardiomyopathy (ICM) resembling the main aetiologies of heart failure with reduced ejection fraction (HFrEF) has not been investigated.

Purpose

We hypothesised that

1. ROS production is elevated in left ventricular myocardial tissue specimens of ICM patients compared to DCM.

2. Mitochondrial OXPHOS capacity is higher in left ventricular myocardial tissue specimens of DCM compared to ICM patients.

Methods

Myocardial tissue was obtained from the left ventricular apex from 63 patients (38 ICM, 25 DCM) with advanced HFrEF requiring implantation of a Left Ventricular Assist Device (LVAD). We performed high-resolution respirometry (HRR, OROBOROS Oxygraph-2k) in saponine-permeabilised myocardial fibres and measured ROS production fluoroscopically via the Amplex Red method. Statistical analysis was conducted using GraphPad Prism 7 and IBM SPSS v26.0.

Results

Groups were of comparable age (61.5±1.2 vs. 59.3±2.4 years, p=n.s.), sex (87% vs 85% male, p=n.s.), diabetic status (32% vs 38.4% type 2 diabetes mellitus, p=n.s.), and body mass index (28.1±0.8 vs. 26.3±1.1 kg/m2, p=n.s.). We detected reduced myocardial mitochondrial OXPHOS capacity in ICM under state 3 conditions by about 15% (68.7±34.0 vs. 80.9±30.5 pmol/(s*mg), p<0.05), after addition of Glutamate by 25% (78.9±38.7 vs. 104.8±41.2 pmol/(s*mg), p<0.01) as well as after Succinate (115.5±65.5 vs. 155±62.0 pmol/(s*mg), p<0.01), uncoupling agent FCCP (114.1±56.8 vs. 150.5±47.3 pmol/(s*mg), p<0.01), and by about 40% after addition of Complex I inhibitor Rotenone (55.5±25.9 vs. 96.9±28.0 pmol/(s*mg), p<0.001). We detected no difference in ROS production between ICM and DCM (0.6±0.05 vs. 0.76±0.08 pmol/(s*ml), p=n.s.).

Conclusion

This is the first human study deciphering distinct alterations in mitochondrial function (OXPHOS capacity) in ventricular myocardium of HFrEF patients. Future studies may address how distinct metabolic patterns at the time of implantation may relate to long-term outcome of HFrEF in terms of remodelling and recovery.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): DFG (German Research Foundation)

Evaluation of lipoprotein-associated phospholipase A2 as a marker for renal microvasculopathy in adolescents with Type 1 diabetes

AIM

To assess the relevance of lipoprotein-associated phospholipase A2 activity as a diagnostic and prognostic marker for renal microvascular diseases.

METHODS

We analysed lipoprotein-associated phospholipase A2 activity and lysophosphatidylcholine levels (as a surrogate marker of oxidative stress) in 165 adolescents (aged 17.0 ± 2.3 years) with a history of Type 1 diabetes greater than 10 years. Clinical data were obtained from the German/Austrian nationwide Diabetes-Patients Follow-up (DPV) registry at blood collection and on average 2.4 ± 1.3 years later at follow-up. Relationships between lipoprotein-associated phospholipase A2 activity and clinical, demographic and laboratory variables, lysophosphatidylcholine levels and presence of albuminuria were evaluated by multivariable linear and logistic regression.

RESULTS

Lipoprotein-associated phospholipase A2 activity was higher in male than female adolescents (P = 0.002). Albuminuria was present in 14% (22/158) of participants at baseline, and 5% (4/86) of participants without albuminuria at baseline developed albuminuria until follow-up. Lipoprotein-associated phospholipase A2 activity was associated neither with present nor with incident albuminuria. Lysophosphatidylcholine did not correlate with lipoprotein-associated phospholipase A2 activity. Cross-sectional bivariate correlation as well as multivariable linear regression analysis revealed a negative correlation of lipoprotein-associated phospholipase A2 activity with HbA_1c and HDL-cholesterol.

CONCLUSIONS

Lipoprotein-associated phospholipase activity was not associated with surrogate markers for oxidative stress and early diabetic nephropathy. The association of decreased lipoprotein-associated phospholipase A2 activity with poor glucose control might limit its function as a predictor of micro- and macrovascular diseases in Type 1 diabetes.

Distinct trajectories of HbA1c in newly diagnosed Type 2 diabetes from the DPV registry using a longitudinal group-based modelling approach

AIM

To identify groups of heterogeneous HbA_1c trajectories over time in newly diagnosed Type 2 diabetes.

METHODS

The study comprised 6355 adults with newly diagnosed Type 2 diabetes (55% men, median age 62 years, baseline BMI 31 kg/m² ) from the Diabetes Patienten Verlaufsdokumentation (DPV) prospective multicentre diabetes registry (Germany, Austria). Individuals were assessed during the first 5 years after diabetes diagnosis if they had ≥ 3 aggregated HbA_1c measurements during follow-up. Latent class growth modelling was used to determine distinct subgroups that followed similar longitudinal HbA_1c patterns (SAS: Proc Traj). Multinomial logistic regression models were used to investigate which variables were associated with the respective HbA_1c trajectory groups.

RESULTS

Four distinct longitudinal HbA_1c trajectory (glycaemic control) groups were found. The largest group (56% of participants) maintained stable good glycaemic control (HbA_1c 42-45 mmol/mol). Twenty-six percent maintained stable moderate glycaemic control (HbA_1c 57-62 mmol/mol). A third group (12%) initially showed severe hyperglycaemia (HbA_1c 97 mmol/mol) but reached good glycaemic control within 1 year. The smallest group (6%) showed stable poor glycaemic control (HbA_1c 79-88 mmol/mol). Younger age at diabetes diagnosis, male sex, and higher BMI were associated with the stable moderate or poor glycaemic control groups. Insulin therapy was strongly associated with the highly improved glycaemic control group.

CONCLUSIONS

Four subgroups with distinct HbA_1c trajectories were determined in newly diagnosed Type 2 diabetes using a group-based modelling approach. Approximately one-third of people with newly diagnosed Type 2 diabetes need either better medication adherence or earlier intensification of glucose-lowering therapy.

P3476High-resolution respirometry reveals enhanced myocardial mitochondrial ketone oxidation after fasting and ventricular unloading

Background

Impairment of myocardial mitochondrial function is regarded as an established pathomechanism in heart failure. Enhanced oxidation of ketone bodies may potentially exert protective effects on myocardial function. High-resolution respirometry (HRR) resembles a gold-standard methodology to determine myocardial mitochondrial metabolism and oxidative function but has not been validated for ketone substrates yet.

Purpose

We hypothesized that (1) quantification of ketone body oxidative capacity (OC) in myocardium utilizing ex-vivo HRR is feasible and that (2) ketone-associated OC is elevated after fasting and under conditions of chronic mechanical ventricular unloading.

Methods

We established new HRR (Oxygraph-2k) protocols, measuring oxygen flux generated by oxidation of the ketone substrates beta-hydroxybutyrate (HBA) and acetoacetate (ACA). Ketone protocols were then applied to twelve C57BL/6 mice' (of which six were fasted for 16h) left ventricular and right liver lobe tissue, as well as to eleven terminal heart failure patients' left ventricular tissue, harvested at heart transplantation. Heart transplant recipients were subdivided into patients with left ventricular assist device prior to transplantation (LVAD group, n=6) or no unloading prior to transplantation (HTX group, n=5).

Results

In non-fasted rodent hearts, HBA yielded an OC of 25±4 pmol/(s*mg tissue) above basal respiration, when applied as sole substrate (21±11 pmol/(s*mg) in liver). ACA alone did not induce oxygen flux, but ACA+succinate yielded 229% higher oxygen flux than succinate alone in state III (146±32 vs 44±12 pmol/(s*mg); p=0.0003). When titrated after succinate, ACA increased OC by 93±25 pmol/(s*mg) (p=0.0003). In 16h-fasted rodent hearts, HBA-supported OC was 27% higher (41±3 vs 52±9 pmol/(s*mg); p=0.04), while OC with ACA+succinate was unchanged (p=0.60). In rodent liver, no oxygen flux was induced by ACA, reflecting absence of 3-oxoacid CoA-transferase. However, HBA-supported OC was 118% higher in fasted liver (37±13 vs 57±13 pmol/(s*mg); p=0.03). In humans, left ventricular unloading was not associated with altered myocardial OC for fatty acids and glycolytic substrates (standard protocol, p=0.13), but HBA-supported OC was 39% higher in the LVAD group compared to the HTX group (54±12 vs 39±9 pmol/(s*mg), p=0.04).

Conclusion

Quantification of ketone body OC with HRR is feasible in permeabilized myocardial fibers. Applying this novel method revealed increased HBA-supported myocardial mitochondrial respiration after fasting and chronic left ventricular unloading. These data support a concept of enhanced ketone oxidation following ventricular unloading in myocardial mitochondria. Our findings facilitate new studies on myocardial ketone turnover and the interaction of mitochondrial ketone metabolism with cardiac performance.

Acknowledgement/Funding

CRC 1116, Research commission of the University Hospital Düsseldorf

Meal-derived glucagon responses are related to lower hepatic phosphate concentrations in obesity and type 2 diabetes

AIM

Type 2 diabetes (T2D) alters glucagon, glucagon-like peptide (GLP)-1, glucose-dependent insulinotropic polypeptide (GIP) and hepatic energy metabolism, yet the possible relationships remain unclear.

METHODS

In this observational study, lean insulin-sensitive control subjects (BMI: 23.2±1.5kg/m²), age-matched insulin-resistant obese subjects (BMI: 34.3±1.7kg/m²) and similarly obese elderly T2D patients (BMI: 32.0±2.4kg/m²) underwent mixed-meal tolerance tests (MMTTs), and assessment of hepatic γATP, inorganic phosphate (P_i) and lipids using ³¹P/¹H magnetic resonance spectroscopy. Meal-induced secretion of glucagon and incretins was calculated from incremental areas under the concentration-time curves (iAUCs). Peripheral and adipose tissue insulin sensitivity were assessed from time courses of circulating glucose, insulin and free fatty acids.

RESULTS

MMTT-derived peripheral insulin sensitivity was lowest in T2D patients (P<0.001), while glucagon concentrations were comparable across all three groups. At 260min, GLP-1 was lower in T2D patients than in controls, whereas GIP was lowest in obese individuals. Fasting glucagon concentrations correlated positively with fasting (r=0.60) and postprandial hepatocellular lipid levels (160min: r=0.51, 240min: r=0.59), and negatively with adipose tissue insulin sensitivity (r=-0.73). Higher meal-induced glucagon release (iAUC_0-260min) correlated with lower fasting (r=-0.62) and postprandial P_i levels (160min: r=-0.43, 240min: r=-0.42; all P<0.05). Higher meal-induced release of GIP (iAUC_0-260min) correlated positively with fasting (r=0.54) and postprandial serum triglyceride concentrations (iAUC_0-260min, r=0.54; all P<0.01).

CONCLUSION

Correlations between fasting glucagon and hepatic lipids and between meal-induced glucagon and hepatic P_i suggest a role for glucagon in hepatic energy metabolism.

Inverse association of insulin antibody levels with insulin sensitivity in adults with Type 1 diabetes

AIMS

Insulin resistance may contribute to the pathogenesis of autoimmune-mediated diabetes. Antibodies against β-cell-associated molecules, comprising islet cell antigen (ICA), glutamic acid decarboxylase (GAD) and insulin, characterize the autoimmune process. Because the link between insulin resistance and autoimmunity might be relevant for disease progression and treatment, we hypothesized that insulin resistance associates positively with β-cell-directed antibodies in newly diagnosed Type 1 diabetes.

METHODS

Within the German Diabetes Study, an observational study including adults with newly diagnosed diabetes, 142 adults [84 men, 58 women; age 33.1 (26.4, 41.9) years; diabetes duration 6.3 (4.2, 9.1) months] positive for at least one antibody against ICA, GAD or insulin underwent hyperinsulinaemic-euglycaemic clamp tests to assess insulin sensitivity (M-value) in a cross-sectional setting.

RESULTS

Insulin-directed antibodies were inversely correlated with M-values (β = -0.039). Albeit not strong, the association persisted after adjustment for age, sex and BMI, and even after further adjustment for confounders reflecting exposure to exogenous insulin and residual β-cell secretory capacity. Correlation network-based analyses revealed a complex interaction between levels of fasting insulin and of insulin antibodies with respect to their relationship with the M-value. GAD- or ICA-directed antibodies did not correlate with insulin sensitivity.

CONCLUSIONS

In adults with recent-onset Type 1 diabetes expressing at least one β-cell-directed antibody, insulin sensitivity is inversely related to insulin antibody titres, but not to other autoantibodies. Our finding may allow for the identification of insulin resistance in adults with high levels of insulin antibodies.

Prediabetes is associated with microalbuminuria, reduced kidney function and chronic kidney disease in the general population: The KORA (Cooperative Health Research in the Augsburg Region) F4-Study

BACKGROUND AND AIMS

We investigated the associations of serum fasting (FG) and 2-h postload (2HG) glucose from an oral glucose tolerance test (OGTT), glycated hemoglobin (HbA1c), fasting insulin and the homeostasis model assessment-insulin resistance index (HOMA-IR) with urinary albumin-to-creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR).

METHODS AND RESULTS

We performed cross-sectional analyses of 2713 subjects (1429 women; 52.7%) without known type 2 diabetes, aged 31-82 years, from the KORA (Cooperative Health Research in the Augsburg Region) F4-Study. FG, 2HG, HbA1c, fasting insulin, HOMA-IR and glucose tolerance categories were analyzed for association with ACR and eGFR in multivariable adjusted linear and median regression models, and with isolated microalbuminuria (i-MA), isolated reduced kidney function (i-RKF) and chronic kidney disease (CKD, defined as MA and/or RKF) in multivariable adjusted logistic regression models. Among the 2713 study participants, 28% revealed prediabetes (isolated impaired fasting glucose [i-IFG], isolated glucose tolerance [i-IGT] or both by American Diabetes Association definition), 4.2% had unknown type 2 diabetes, 6.5% had i-MA, 3.1% i-RKF and 10.9% CKD. In multivariable adjusted analysis, all continuous variables (FG, 2HG, HbA1c, fasting insulin and HOMA-IR) were associated with i-MA, i-RKF and CKD. The odds ratios (ORs) for i-MA and CKD were 1.54 (95% confidence interval: 1.02-2.33) and 1.58 (1.10-2.25) for individuals with i-IFG. Moreover, the OR for i-RKF was 2.57 (1.31-5.06) for individuals with IFG + IGT.

CONCLUSION

Our findings suggest that prediabetes might have harmful effects on the kidney.

Absence of the kinase S6k1 mimics the effect of chronic endurance exercise on glucose tolerance and muscle oxidative stress

Objective

Ribosomal protein S6 Kinase-1 (S6K1) has been linked to resistance exercise-mediated improvements in glycemia. We hypothesized that S6K1 may also play a role in regulating glycemic control in response to endurance exercise training.

Methods

S6k1-knockout (S6K1KO) and WT mice on a 60 cal% high-fat diet were trained for 4 weeks on treadmills, metabolically phenotyped, and compared to sedentary controls.

Results

WT mice showed improved glucose tolerance after training. In contrast, S6K1KO mice displayed equally high glucose tolerance already in the sedentary state with no further improvement after training. Similarly, training decreased mitochondrial ROS production in skeletal muscle of WT mice, whereas ROS levels were already low in the sedentary S6K1KO mice with no further decrease after training. Nevertheless, trained S6K1KO mice displayed an increased running capacity compared to trained WT mice, as well as substantially reduced triglyceride contents in liver and skeletal muscle. The improvements in glucose handling and running endurance in S6K1KO mice were associated with markedly increased ketogenesis and a higher respiratory exchange ratio.

Conclusions

In high-fat fed mice, loss of S6K1 mimics endurance exercise training by reducing mitochondrial ROS production and upregulating oxidative utilization of ketone bodies. Pharmacological targeting of S6K1 may improve the outcome of exercise-based interventions in obesity and diabetes.

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Absence of S6k1 upregulates oxidative substrate utilization under HFD consumption.

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S6k1 knockout mice show enhanced running performance and improved glycemia already in the sedentary state.

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Aerobic endurance exercise training of S6k1 knockout mice further improves running performance but not glycemia.

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Metabolic improvements are associated with lower rates of TCA-linked mitochondrial H₂O₂ production and increased ketogenesis.