There is increasing concern that most current published research findings are false. The probability that a research claim is true may depend on study power and bias, the number of other studies on the same question, and, importantly, the ratio of true to no relationships among the relationships probed in each scientific field. In this framework, a research finding is less likely to be true when the studies conducted in a field are smaller; when effect sizes are smaller; when there is a greater number and lesser preselection of tested relationships; where there is greater flexibility in designs, definitions, outcomes, and analytical modes; when there is greater financial and other interest and prejudice; and when more teams are involved in a scientific field in chase of statistical significance. Simulations show that for most study designs and settings, it is more likely for a research claim to be false than true. Moreover, for many current scientific fields, claimed research findings may often be simply accurate measures of the prevailing bias. In this essay, I discuss the implications of these problems for the conduct and interpretation of research.

Why most published research findings are false

Heart failure is a major cause of death and disability. Impairments in blood circulation that accompany heart failure can be traced, in part, to alterations in the activity of the sarcoplasmic reticulum Ca2+ pump that are induced by its interactions with phospholamban, a reversible inhibitor. If phospholamban becomes superinhibitory or chronically inhibitory, contractility is diminished, inducing dilated cardiomyopathy in mice and humans. In mice, phospholamban seems to encumber an otherwise healthy heart, but humans with a phospholamban-null genotype develop early-onset dilated cardiomyopathy.

Phospholamban: a crucial regulator of cardiac contractility

Understanding precisely how the heart can recognize and respond to many different extracellular signalling molecules, such as neurotransmitters, hormones and growth factors, will aid the identification of new therapeutic targets through which cardiovascular diseases can be combated. In recent years, we have learned more about the complex interactions that occur between the receptors and the signalling pathways of the heart and its environment. Most of these discoveries have focused on the most common type of cardiac receptor - the seven-transmembrane-spanning receptor or G-protein-coupled receptor.

Seven-transmembrane-spanning receptors and heart function

Recent studies call into question the necessity of hypertrophic growth of the heart as a "compensatory" response to hemodynamic stress. These findings, coupled with recent progress in dissecting the molecular bases of hypertrophy, raise the prospect of suppressing hypertrophy without provoking circulatory insufficiency. In this article, we focus on signaling pathways that hold promise as potential targets for therapeutic intervention. We also summarize observations from animal models and clinical trials that suggest benefit from an antihypertrophic strategy.

Hypertrophy of the heart: a new therapeutic target?

It is now recognized that contracting skeletal muscle may synthesize and release interleukin-6 (IL-6) into the interstitium as well as into the systemic circulation in response to a bout of exercise. Although several sources of IL-6 have been demonstrated, contracting muscles contributes to most of the IL-6 present in the circulation in response to exercise. The magnitude of the exercise-induced IL-6 response is dependent on intensity and especially duration of the exercise, while the mode of exercise has little effect. Several mechanisms may link muscle contractions to IL-6 synthesis: Changes in calcium homeostasis, impaired glucose availability, and increased formation of reactive oxygen species (ROS) are all capable of activating transcription factors known to regulate IL-6 synthesis. Via its effects on liver, adipose tissue, hypothalamic-pituitary-adrenal (HPA) axis and leukocytes, IL-6 may modulate the immunological and metabolic response to exercise. However, prolonged exercise involving a significant muscle mass in the contractile activity is necessary in order to produce a marked systemic IL-6 response. Furthermore, exercise training may reduce basal IL-6 production as well as the magnitude of the acute exercise IL-6 response by counteracting several potential stimuli of IL-6. Accordingly, a decreased plasma IL-6 concentration at rest as well as in response to exercise appears to characterize normal training adaptation.

Interleukin-6 in acute exercise and training: what is the biological relevance?

The goal of this study was to characterize the genetic contribution to both forced and voluntary exercise performance and to determine whether performance in these two paradigms is controlled by similar genetic influences. There were marked strain differences in treadmill exercise performance, with Swiss Webster (SW) and FVB/NJ mice showing elevated performance and C57BL/6J animals showing decreased performance compared with all other strains. There was no apparent relationship between treadmill performance and voluntary wheel performance, with the exception of SW mice, which demonstrated high performances on both the treadmill and the voluntary wheel. Numerous properties were measured to attempt to understand the basis for these differences in exercise performance. DBA/1J and SW mice exhibited significantly greater cardiac contractility than all other analyzed strains. Conversely, BALB/cByJ mice exhibited significantly reduced cardiac contractility compared with all other strains. Expression of molecular indicators of hypertrophy (atrial natriuretic factor and beta-myosin heavy chain) was significantly elevated in DBA/2J myocardium compared with all other analyzed strains.

https://www.physiology.org/doi/pdf/10.1152/japplphysiol.01045.2001

Genetic variability in forced and voluntary endurance exercise performance in seven inbred mouse strains

The medical treatment of chronic heart failure has undergone a dramatic transition in the past decade. Short-term approaches for altering hemodynamics have given way to long-term, reparative strategies, including β-adrenergic receptor (βAR) blockade. This was once viewed as counterintuitive, because acute administration causes myocardial depression. Cardiac myocytes from failing hearts show changes in βAR signaling and excitation-contraction coupling that can impair cardiac contractility, but the role of these abnormalities in the progression of heart failure is controversial. We therefore tested the impact of different manipulations that increase contractility on the progression of cardiac dysfunction in a mouse model of hypertrophic cardiomyopathy. High-level overexpression of the β2AR caused rapidly progressive cardiac failure in this model. In contrast, phospholamban ablation prevented systolic dysfunction and exercise intolerance, but not hypertrophy, in hypertrophic cardiomyopathy mice. Cardiac expression of a peptide inhibitor of the βAR kinase 1 not only prevented systolic dysfunction and exercise intolerance but also decreased cardiac remodeling and hypertrophic gene expression. These three manipulations of cardiac contractility had distinct effects on disease progression, suggesting that selective modulation of particular aspects of βAR signaling or excitation-contraction coupling can provide therapeutic benefit.

/pdf/alterations-in-cardiac-adrenergic-signaling-and-calcium-5exu6umwwq.pdf

Alterations in cardiac adrenergic signaling and calcium cycling differentially affect the progression of cardiomyopathy.

Context Conflicts of interest (COIs) may influence medical literature. However, it is unclear whether medical journals have consistent policies for defining and soliciting COI disclosures. Objective To determine the prevalence of author COI policies, requirements for signed disclosure statements, and variability in COI definitions among medical journals. Design A cross-sectional survey of Instructions for Authors and manuscript submission documents, including authorship responsibility forms, for high-impact medical journals across 35 subject categories available from March through October 2008. Main Outcome Measure Presence of language referring to COI disclosure in the Instructions for Authors or manuscript submission documents. Results Of 256 journals, 89% had author COI policies. Fifty-four percent required authors to sign a disclosure statement, and 77% provided definitions of COI. Most definitions were limited to direct financial relationships; a minority of journals requested disclosure of other potential conflicts such as personal relationships (42%), paid expert testimony (42%), relationships with other organizations (26%), or travel grants (12%). The prevalence of policies varied by subject category: all internal medicine, respiratory medicine, and toxicology journals studied had comprehensive COI definitions, with 19 of these 24 journals requiring signed disclosure attestations. In contrast, 6 of 19 geriatrics, radiology, and rehabilitation journals requested author COI disclosure. Most journals that officially endorsed International Committee of Medical Journal Editors guidelines had COI policies (68/69), compared with 84% of journals not endorsing the guidelines (158/187). Conclusions In 2008, most medical journals with relatively high impact factors had author COI policies available for public review. Among journals, there was substantial variation in policies for solicitation of author COIs and in definitions of COI.

https://jamanetwork.com/journals/jama/articlepdf/184918/jbr90004_2230_2234.pdf

Kalev Freeman

Papers

Genetic variability in forced and voluntary endurance exercise performance in seven inbred mouse strains

Alterations in cardiac adrenergic signaling and calcium cycling differentially affect the progression of cardiomyopathy.

Requirements and Definitions in Conflict of Interest Policies of Medical Journals

Genetic variability in forced and voluntary endurance exercise performance in seven inbred mouse strains

Clinical Decisionmaking: Opening the Black Box of Cognitive Reasoning