Showing papers by "Jan F. C. Glatz published in 2016"

Assessing Cardiac Metabolism

Abstract: 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.

Novel Biomarkers to Improve the Prediction of Cardiovascular Event Risk in Type 2 Diabetes Mellitus

Abstract: Background We evaluated the ability of 23 novel biomarkers representing several pathophysiological pathways to improve the prediction of cardiovascular event (CVE) risk in patients with type 2 diabetes mellitus beyond traditional risk factors. Methods and Results We used data from 1002 patients with type 2 diabetes mellitus from the Second Manifestations of ARTertial disease (SMART) study and 288 patients from the European Prospective Investigation into Cancer and Nutrition‐NL (EPIC‐NL). The associations of 23 biomarkers (adiponectin, C‐reactive protein, epidermal‐type fatty acid binding protein, heart‐type fatty acid binding protein, basic fibroblast growth factor, soluble FMS‐like tyrosine kinase‐1, soluble intercellular adhesion molecule‐1 and ‐3, matrix metalloproteinase [MMP]‐1, MMP‐3, MMP‐9, N‐terminal prohormone of B‐type natriuretic peptide, osteopontin, osteonectin, osteocalcin, placental growth factor, serum amyloid A, E‐selectin, P‐selectin, tissue inhibitor of MMP‐1, thrombomodulin, soluble vascular cell adhesion molecule‐1, and vascular endothelial growth factor) with CVE risk were evaluated by using Cox proportional hazards analysis adjusting for traditional risk factors. The incremental predictive performance was assessed with use of the c‐statistic and net reclassification index (NRI; continuous and based on 10‐year risk strata 0–10%, 10–20%, 20–30%, >30%). A multimarker model was constructed comprising those biomarkers that improved predictive performance in both cohorts. N‐terminal prohormone of B‐type natriuretic peptide, osteopontin, and MMP‐3 were the only biomarkers significantly associated with an increased risk of CVE and improved predictive performance in both cohorts. In SMART, the combination of these biomarkers increased the c‐statistic with 0.03 (95% CI 0.01–0.05), and the continuous NRI was 0.37 (95% CI 0.21–0.52). In EPIC‐NL, the multimarker model increased the c‐statistic with 0.03 (95% CI 0.00–0.03), and the continuous NRI was 0.44 (95% CI 0.23–0.66). Based on risk strata, the NRI was 0.12 (95% CI 0.03–0.21) in SMART and 0.07 (95% CI −0.04–0.17) in EPIC‐NL. Conclusions Of the 23 evaluated biomarkers from different pathophysiological pathways, N‐terminal prohormone of B‐type natriuretic peptide, osteopontin, MMP‐3, and their combination improved CVE risk prediction in 2 separate cohorts of patients with type 2 diabetes mellitus beyond traditional risk factors. However, the number of patients reclassified to a different risk stratum was limited.

Molecular mechanism of lipid-induced cardiac insulin resistance and contractile dysfunction

Abstract: Long-chain fatty acids are the main cardiac substrates from which ATP is generated continually to serve the high energy demand and sustain the normal function of the heart. Under healthy conditions, fatty acid β-oxidation produces 50-70% of the energy demands with the remainder largely accounted for by glucose. Chronically increased dietary lipid supply often leads to excess lipid accumulation in the heart, which is linked to a variety of maladaptive phenomena, such as insulin resistance, cardiac hypertrophy and contractile dysfunction. CD36, the predominant cardiac fatty acid transporter, has a key role in setting the heart on a road to contractile dysfunction upon the onset of chronic lipid oversupply by translocating to the cell surface and opening the cellular 'doors' for fatty acids. The sequence of events after the CD36-mediated myocellular lipid accumulation is less understood, but in general it has been accepted that the excessively imported lipids cause insulin resistance, which in turn leads to contractile dysfunction. There are several gaps of knowledge in this proposed order of events which this review aims to discuss. First, the molecular mechanisms underlying lipid-induced insulin resistance are not yet completely disclosed. Specifically, several mediators have been proposed, such as diacylglycerols, ceramides, peroxisome proliferator-activated receptors (PPAR), inflammatory kinases and reactive oxygen species (ROS), but their relative contributions to the onset of insulin resistance and their putatively synergistic actions are topics of controversy. Second, there are also pieces of evidence that lipids can induce contractile dysfunction independently of insulin resistance. Perhaps, a more integrative view is needed, in which several lipid-induced pathways operate synergistically or in parallel to induce contractile dysfunction. Unraveling of these processes is expected to be important in designing effective therapeutic strategies to protect the lipid-overloaded heart.

Suspected acute coronary syndrome in the emergency room: Limited added value of heart type fatty acid binding protein point of care or ELISA tests: The FAME-ER (Fatty Acid binding protein in Myocardial infarction Evaluation in the Emergency Room) study.

Abstract: Background:Timely recognition of acute coronary syndrome remains a challenge as many biomarkers, including troponin, remain negative in the first hours following the onset of chest pain. We assessed the diagnostic accuracy of heart-type fatty acid binding protein (H-FABP), a cardiac biomarker with potential value immediately post symptom onset.Methods and results:Prospective monocentre diagnostic accuracy study of H-FABP bedside point of care (CardioDetect®) and ELISA tests in acute coronary syndrome suspected patients presenting within 24 hours of symptom onset to the emergency department, in addition to clinical findings, electrocardiography and the currently recommended biomarker high sensitivity troponin-T (hs-cTnT). The final diagnosis of acute coronary syndrome was adjudicated by two independent cardiologists, blinded to H-FABP results. Acute coronary syndrome was diagnosed in 149 (32.9%) of 453 unselected patients with suspected acute coronary syndrome (56% men, mean age 62.6 years). Negative predi...

The interaction between AMPKβ2 and the PP1-targeting subunit R6 is dynamically regulated by intracellular glycogen content

Abstract: AMP-activated protein kinase (AMPK) is a metabolic stress-sensing kinase. We previously showed that glucose deprivation induces autophosphorylation of AMPKβ at threonine-148 (Thr-148), which prevents the binding of AMPK to glycogen. Furthermore, in MIN6 cells, AMPKβ1 binds to R6 (PPP1R3D), a glycogen-targeting subunit of protein phosphatase 1 (PP1), thereby regulating the glucose-induced inactivation of AMPK. Here, we further investigated the interaction of R6 with AMPKβ and the possible dependency on Thr-148 phosphorylation status. Yeast two-hybrid analyses and co-immunoprecipitation of the overexpressed proteins in HEK293T cells revealed that both AMPKβ1 and β2 wild-type (WT) isoforms bind to R6. The AMPKβ/R6 interaction was stronger with the muscle-specific β2-WT and required association with the substrate-binding motif of R6. When HEK293T cells or C2C12 myotubes were cultured in high-glucose medium, AMPKβ2-WT and R6 weakly interacted. In contrast, glycogen depletion significantly enhanced this protein interaction. Mutation of AMPKβ2 Thr-148 prevented the interaction with R6 irrespective of the intracellular glycogen content. Treatment with the AMPK activator oligomycin enhanced AMPKβ2/R6 interaction in conjunction with increased Thr-148 phosphorylation in cells grown in low glucose medium. These data are in accordance with R6 binding directly to AMPKβ2 when both proteins detach from the diminishing glycogen particle, which is simultaneous to increased AMPKβ2 Thr-148 autophosphorylation. Such model points to a possible control of AMPK by PP1-R6 upon glycogen depletion in muscle.

Basics in Metabolically Relevant Biochemistry

Abstract: The two main compounds involved in cardiac energy metabolism are glucose and long-chain fatty acids. Depending on the condition, the heart may also use lactate, ketone bodies, and amino acids as substrates for the production of metabolic energy. This chapter covers the biochemical characteristics of each of these substrates, glycogen, and triacylglycerol, which serve as intracellular storage depots for glucose and fatty acids, respectively. In addition, the molecular mechanisms involved in the cellular uptake of these substrates are described. Finally, the principles of enzyme activities and their regulation and rate-limiting steps in metabolic pathways are explained. Together, this chapter describes the basic biochemistry knowledge that is required for understanding the aspects of cardiac metabolism outlined in subsequent chapters.