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1.
GLP-1 and insulin regulation of skeletal and cardiac muscle microvascular perfusion in type 2 diabetes.
Love, KM, Liu, J, Regensteiner, JG, Reusch, JEB, Liu, Z
Journal of diabetes. 2020;(7):488-498
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Abstract
Muscle microvasculature critically regulates skeletal and cardiac muscle health and function. It provides endothelial surface area for substrate exchange between the plasma compartment and the muscle interstitium. Insulin fine-tunes muscle microvascular perfusion to regulate its own action in muscle and oxygen and nutrient supplies to muscle. Specifically, insulin increases muscle microvascular perfusion, which results in increased delivery of insulin to the capillaries that bathe the muscle cells and then facilitate its own transendothelial transport to reach the muscle interstitium. In type 2 diabetes, muscle microvascular responses to insulin are blunted and there is capillary rarefaction. Both loss of capillary density and decreased insulin-mediated capillary recruitment contribute to a decreased endothelial surface area available for substrate exchange. Vasculature expresses abundant glucagon-like peptide 1 (GLP-1) receptors. GLP-1, in addition to its well-characterized glycemic actions, improves endothelial function, increases muscle microvascular perfusion, and stimulates angiogenesis. Importantly, these actions are preserved in the insulin resistant states. Thus, treatment of insulin resistant patients with GLP-1 receptor agonists may improve skeletal and cardiac muscle microvascular perfusion and increase muscle capillarization, leading to improved delivery of oxygen, nutrients, and hormones such as insulin to the myocytes. These actions of GLP-1 impact skeletal and cardiac muscle function and systems biology such as functional exercise capacity. Preclinical studies and clinical trials involving the use of GLP-1 receptor agonists have shown salutary cardiovascular effects and improved cardiovascular outcomes in type 2 diabetes mellitus. Future studies should further examine the different roles of GLP-1 in cardiac as well as skeletal muscle function.
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Seven-day overfeeding enhances adipose tissue dietary fatty acid storage and decreases myocardial and skeletal muscle dietary fatty acid partitioning in healthy subjects.
Noll, C, Montastier, É, Amrani, M, Kunach, M, Frisch, F, Fortin, M, Bouffard, L, Dubreuil, S, Phoenix, S, Cunnane, SC, et al
American journal of physiology. Endocrinology and metabolism. 2020;(2):E286-E296
Abstract
Increased myocardial partitioning of dietary fatty acids (DFA) and decreased left ventricular (LV) function is associated with insulin resistance in prediabetes. We hypothesized that enhanced myocardial DFA partitioning and reduced LV function might be induced concomitantly with reduced insulin sensitivity upon a 7-day hypercaloric (+50% in caloric intake), high-saturated fat (~11%energy), and simple carbohydrates (~54%energy) diet (HIGHCAL) versus an isocaloric diet (ISOCAL) with a moderate amount of saturated fat (~8%energy) and carbohydrates (~50%energy). Thirteen healthy subjects (7 men/6 women) underwent HIGHCAL versus ISOCAL in a randomized crossover design, with organ-specific DFA partitioning and LV function measured using the oral 14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid and [11C]acetate positron emission tomography methods at the end of both interventions. HIGHCAL induced a decrease in insulin sensitivity indexes with no significant change in body composition. HIGHCAL led to increased subcutaneous abdominal (+4.2 ± 1.6%, P < 0.04) and thigh (+2.4 ± 1.2%, P < 0.08) adipose tissue storage and reduced cardiac (-0.31 ± 0.11 mean standard uptake value [(SUV), P < 0.03] and skeletal muscle (-0.17 ± 0.08 SUV, P < 0.05) DFA partitioning without change in LV function. We conclude that early increase in adipose tissue DFA storage protects the heart and skeletal muscles from potential deleterious effects of DFA.
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Noninvasive Imaging Estimation of Myocardial Iron Repletion Following Administration of Intravenous Iron: The Myocardial-IRON Trial.
Núñez, J, Miñana, G, Cardells, I, Palau, P, Llàcer, P, Fácila, L, Almenar, L, López-Lereu, MP, Monmeneu, JV, Amiguet, M, et al
Journal of the American Heart Association. 2020;(4):e014254
Abstract
Background Intravenous ferric carboxymaltose (FCM) improves symptoms, functional capacity, and quality of life in heart failure and iron deficiency. The mechanisms underlying these effects are not fully understood. The aim of this study was to examine changes in myocardial iron content after FCM administration in patients with heart failure and iron deficiency using cardiac magnetic resonance. Methods and Results Fifty-three stable heart failure and iron deficiency patients were randomly assigned 1:1 to receive intravenous FCM or placebo in a multicenter, double-blind study. T2* and T1 mapping cardiac magnetic resonance sequences, noninvasive surrogates of intramyocardial iron, were evaluated before and 7 and 30 days after randomization using linear mixed regression analysis. Results are presented as least-square means with 95% CI. The primary end point was the change in T2* and T1 mapping at 7 and 30 days. Median age was 73 (65-78) years, with N-terminal pro-B-type natriuretic peptide, ferritin, and transferrin saturation medians of 1690 pg/mL (1010-2828), 63 ng/mL (22-114), and 15.7% (11.0-19.2), respectively. Baseline T2* and T1 mapping values did not significantly differ across treatment arms. On day 7, both T2* and T1 mapping (ms) were significantly lower in the FCM arm (36.6 [34.6-38.7] versus 40 [38-42.1], P=0.025; 1061 [1051-1072] versus 1085 [1074-1095], P=0.001, respectively). A similar reduction was found at 30 days for T2* (36.3 [34.1-38.5] versus 41.1 [38.9-43.4], P=0.003), but not for T1 mapping (1075 [1065-1085] versus 1079 [1069-1089], P=0.577). Conclusions In patients with heart failure and iron deficiency, FCM administration was associated with changes in the T2* and T1 mapping cardiac magnetic resonance sequences, indicative of myocardial iron repletion. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT03398681.
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4.
Hierarchical modeling of force generation in cardiac muscle.
Kimmig, F, Caruel, M
Biomechanics and modeling in mechanobiology. 2020;(6):2567-2601
Abstract
Performing physiologically relevant simulations of the beating heart in clinical context requires to develop detailed models of the microscale force generation process. These models, however, may reveal difficult to implement in practice due to their high computational costs and complex calibration. We propose a hierarchy of three interconnected muscle contraction models-from the more refined to the more simplified-that are rigorously and systematically related to each other, offering a way to select, for a specific application, the model that yields a good trade-off between physiological fidelity, computational cost and calibration complexity. The three model families are compared to the same set of experimental data to systematically assess what physiological indicators can be reproduced or not and how these indicators constrain the model parameters. Finally, we discuss the applicability of these models for heart simulation.
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Myocardial Injury After Balloon Predilatation Versus Direct Transcatheter Aortic Valve Replacement: Insights From the DIRECTAVI Trial.
Akodad, M, Roubille, F, Marin, G, Lattuca, B, Macia, JC, Delseny, D, Gandet, T, Robert, P, Schmutz, L, Piot, C, et al
Journal of the American Heart Association. 2020;(24):e018405
Abstract
Background Myocardial injury is associated with higher mortality after transcatheter aortic valve replacement (TAVR) and might be increased by prior balloon aortic valvuloplasty (BAV). We aimed to evaluate the impact of prior BAV versus direct prosthesis implantation on myocardial injury occurring after (TAVR) with balloon-expandable prostheses. Methods and Results The DIRECTAVI (Direct Transcatheter Aortic Valve Implantation) trial, an open-label randomized study, demonstrated noninferiority of TAVR without BAV (direct TAVR group) compared with systematic BAV (BAV group) with the Edwards SAPIEN 3 valve. High-sensitivity troponin was assessed before and the day after the procedure. Incidence of myocardial injury after the procedure (high-sensitivity troponin elevation >15× the upper reference limit [14 ng/L]) was the main end point. Impact of myocardial injury on 1-month adverse events (all-cause mortality, stroke, major bleeding, major vascular complications, transfusion, acute kidney injury, heart failure, pacemaker implantation, and aortic regurgitation) was evaluated. Preprocedure and postprocedure high-sensitivity troponin levels were available in 211 patients. The mean age of patients was 83 years (78-87 years), with 129 men (61.1%). Mean postprocedure high-sensitivity troponin was 124.9±81.4 ng/L in the direct TAVR group versus 170.4±127.7 ng/L in the BAV group (P=0.007). Myocardial injury occurred in 42 patients (19.9%), including 13 patients (12.2%) in the direct TAVR group and 29 (27.9%) in the BAV group (P=0.004). BAV increased by 2.8-fold (95% CI, 1.4-5.8) myocardial injury probability. Myocardial injury was associated with 1-month adverse events (P=0.03). Conclusions BAV increased the incidence and magnitude of myocardial injury after TAVR with new-generation balloon-expandable valves. Myocardial injury was associated with 1-month adverse events. These results argue in favor of direct SAPIEN 3 valve implantation. Registration URL: https://www.Clinicaltrials.gov; Unique identifier: NCT02729519.
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6.
Impact of Nutrition on Cardiovascular Function.
Bianchi, VE
Current problems in cardiology. 2020;(1):100391
Abstract
The metabolic sources of energy for myocardial contractility include mainly free fatty acids (FFA) for 95%, and in lesser amounts for 5% from glucose and minimal contributions from other substrates such lactate, ketones, and amino acids. However, myocardial efficiency is influenced by metabolic condition, overload, and ischemia. During cardiac stress, cardiomyocytes increase glucose oxidation and reduce FFA oxidation. In patients with ischemic coronary disease and heart failure, the low oxygen availability limits myocardial reliance on FFA and glucose utilization must increase. Although glucose uptake is fundamental to cardiomyocyte function, an excessive intracellular glucose level is detrimental. Insulin plays a fundamental role in maintaining myocardial efficiency and in reducing glycemia and inflammation; this is particularly evident in obese and type-2 diabetic patients. An excess of F availability increase fat deposition within cardiomyocytes and reduces glucose oxidation. In patients with high body mass index, a restricted diet or starvation have positive effects on cardiac metabolism and function while, in patients with low body mass index, restrictive diets, or starvation have a deleterious effect. Thus, weight loss in obese patients has positive impacts on ventricular mass and function, whereas, in underweight heart failure patients, such weight reduction adds to the risk of heart damage, predisposing to cachexia. Nutrition plays an essential role in the evolution of cardiovascular disease and should be taken into account. An energy-restricted diet improves myocardial efficiency but can represent a potential risk of heart damage, particularly in patients affected by cardiovascular disease. Micronutrient integration has a marginal effect on cardiovascular efficiency.
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Markers of Myocardial Stress, Myocardial Injury, and Subclinical Inflammation and the Risk of Sudden Death.
Everett, BM, Moorthy, MV, Tikkanen, JT, Cook, NR, Albert, CM
Circulation. 2020;(12):1148-1158
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Abstract
BACKGROUND The majority of sudden cardiac deaths (SCDs) occur in low-risk populations often as the first manifestation of cardiovascular disease (CVD). Biomarkers are screening tools that may identify subclinical cardiovascular disease and those at elevated risk for SCD. We aimed to determine whether the total to high-density lipoprotein cholesterol ratio, high-sensitivity cardiac troponin I, NT-proBNP (N-terminal pro-B-type natriuretic peptide), or high-sensitivity C-reactive protein individually or in combination could identify individuals at higher SCD risk in large, free-living populations with and without cardiovascular disease. METHODS We performed a nested case-control study within 6 prospective cohort studies using 565 SCD cases matched to 1090 controls (1:2) by age, sex, ethnicity, smoking status, and presence of cardiovascular disease. RESULTS The median study follow-up time until SCD was 11.3 years. When examined as quartiles or continuous variables in conditional logistic regression models, each of the biomarkers was significantly and independently associated with SCD risk after mutually controlling for cardiac risk factors and other biomarkers. The mutually adjusted odds ratios for the top compared with the bottom quartile were 1.90 (95% CI, 1.30-2.76) for total to high-density lipoprotein cholesterol ratio, 2.59 (95% CI, 1.76-3.83) for high-sensitivity cardiac troponin I, 1.65 (95% CI, 1.12-2.44) for NT-proBNP, and 1.65 (95% CI, 1.13-2.41) for high-sensitivity C-reactive protein. A biomarker score that awarded 1 point when the concentration of any of those 4 biomarkers was in the top quartile (score range, 0-4) was strongly associated with SCD, with an adjusted odds ratio of 1.56 (95% CI, 1.37-1.77) per 1-unit increase in the score. CONCLUSIONS Widely available measures of lipids, subclinical myocardial injury, myocardial strain, and vascular inflammation show significant independent associations with SCD risk in apparently low-risk populations. In combination, these measures may have utility to identify individuals at risk for SCD.
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Pooled summary of native T1 value and extracellular volume with MOLLI variant sequences in normal subjects and patients with cardiovascular disease.
Vo, HQ, Marwick, TH, Negishi, K
The international journal of cardiovascular imaging. 2020;(2):325-336
Abstract
T1 mapping by cardiac magnetic resonance (CMR) allows detection of abnormal myocardium. A number of myocardial abnormalities affects the signal captured in T1 mapping. We performed a systematic review and meta-analysis of native T1 and extracellular volume (ECV) in subjects with and without cardiac disease (1) to determine the normal ranges of T1 values and ECV by sequences as well as parameters influencing them, and (2) to summarize the differences in T1 values and ECV of the diseases relative to the normal ranges. Three databases (EMBASE, SCOPUS, and MEDLINE) were systematically searched for native T1 time and ECV. Only human studies with a sample size of ≥ 20 subjects were included. A random effect model was used to pool data. The 69 selected articles included 1954 healthy subjects and 3186 with disease. T1 of normal healthy was different among MOLLI variants: in 1.5T sequences, ShMOLLI had the shortest (944 ms [95% confidence interval 925, 963]), followed by MOLLI 3(3)3(3)5 flip-angle 50°, 967 [959, 975] and flip-angle 35°, 969 [951, 988]. 3T had longer T1 than 1.5T by approximately 100-200 ms. ECV of the normal healthy was consistent among the studies (ranging from 25 to 27%), irrespective of subjects' factors, sequences, vendors, and contrast type. Many diseases demonstrated longer native T1 than normal subjects, but T1 was shorter in Fabry disease and iron overload. In contrast, all disease states showed either normal or increased ECV. Diagnostic accuracy of native T1 time was minimally affected by the difference in the sequences. ECV is less influenced by methodology than T1 time among normal subjects. Different myocardial diseases are associated with shorter or longer T1 times, whereas ECV is consistently increased independent of the underlying pathophysiology.
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Reduction in Global Myocardial Glucose Metabolism in Subjects With 1-Hour Postload Hyperglycemia and Impaired Glucose Tolerance.
Succurro, E, Pedace, E, Andreozzi, F, Papa, A, Vizza, P, Fiorentino, TV, Perticone, F, Veltri, P, Cascini, GL, Sesti, G
Diabetes care. 2020;(3):669-676
Abstract
OBJECTIVE Impaired insulin-stimulated myocardial glucose uptake has occurred in patients with type 2 diabetes with or without coronary artery disease. Whether cardiac insulin resistance is present remains uncertain in subjects at risk for type 2 diabetes, such as individuals with impaired glucose tolerance (IGT) or those with normal glucose tolerance (NGT) and 1-h postload glucose ≥155 mg/dL during an oral glucose tolerance test (NGT 1-h high). This issue was examined in this study. RESEARCH DESIGN AND METHODS The myocardial metabolic rate of glucose (MRGlu) was measured by using dynamic 18F-fluorodeoxyglucose positron emission tomography combined with a euglycemic-hyperinsulinemic clamp in 30 volunteers without coronary artery disease. Three groups were studied: 1) those with 1-h postload glucose <155 mg/dL (NGT 1-h low) (n = 10), 2) those with NGT 1-h high (n = 10), 3) and those with IGT (n = 10). RESULTS After adjusting for age, sex, and BMI, both subjects with NGT 1-h high (23.7 ± 6.4 mmol/min/100 mg; P = 0.024) and those with IGT (16.4 ± 6.0 mmol/min/100 mg; P < 0.0001) exhibited a significant reduction in global myocardial MRGlu; this value was 32.8 ± 9.7 mmol/min/100 mg in subjects with NGT 1-h low. Univariate correlations showed that MRGlu was positively correlated with insulin-stimulated whole-body glucose disposal (r = 0.441; P = 0.019) and negatively correlated with 1-h (r = -0.422; P = 0.025) and 2-h (r = -0.374; P = 0.05) postload glucose levels, but not with fasting glucose. CONCLUSIONS This study shows that myocardial insulin resistance is an early defect that is already detectable in individuals with dysglycemic conditions associated with an increased risk of type 2 diabetes, such as IGT and NGT 1-h high.
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Ketogenesis in arrhythmogenic cardiomyopathy.
Huynh, K
Nature reviews. Cardiology. 2020;(5):266