Myoglobin, an intracellular haemoprotein expressed in the heart and oxidative skeletal myofibres of vertebrates, binds molecular oxygen and may facilitate oxygen transport from erythrocytes to mitochondria, thereby maintaining cellular respiration during periods of high physiological demand. Here we show, however, that mice without myoglobin, generated by gene-knockout technology, are fertile and exhibit normal exercise capacity and a normal ventilatory response to low oxygen levels (hypoxia). Heart and soleus muscles from these animals are depigmented, but function normally in standard assays of muscle performance in vitro across a range of work conditions and oxygen availability. These data show that myoglobin is not required to meet the metabolic requirements of pregnancy or exercise in a terrestrial mammal, and raise new questions about oxygen transport and metabolic regulation in working muscles.

Coronary artery calcium (CAC), a measure of subclinical coronary heart disease (CHD), may be useful in identifying asymptomatic persons at risk of CHD events. The current study included 10,746 adults who were 22-96 years of age, were free of known CHD, and had their CAC quantified by electron-beam tomography at baseline as part of a preventive medical examination at the Cooper Clinic (Dallas, Texas) during 1995-2000. During a mean follow-up of 3.5 years, 81 hard events (CHD death, nonfatal myocardial infarction) and 287 total events (hard events plus coronary revascularization) occurred. Age-adjusted rates (per 1,000 person-years) of hard events were computed according to four CAC categories: no detectable CAC and incremental sex-specific thirds of detectable CAC; these rates were, respectively, 0.4, 1.5, 4.8, and 8.7 (trend p<0.0001) for men and 0.7, 2.3, 3.1, and 6.3 (trend p=0.02) for women. CAC levels also were positively associated with rates of total CHD events for women and men (trend p<0.0001 each). The association between CAC and CHD events remained significant after adjustment for CHD risk factors. CAC was associated with CHD events in persons with no baseline CHD risk factors and in younger (aged <40 years) and older (aged >65 years) study participants. These findings show that CAC is associated with an increased risk of CHD events in asymptomatic women and men.

Importance Cardiorespiratory fitness (CRF) as assessed by formalized incremental exercise testing is a strong independent predictor of numerous chronic diseases but has received little attention as a predictor of incident cancer or survival following a diagnosis of cancer. Objective To assess the association between midlife CRF and incident cancer and survival following a cancer diagnosis. Design Prospective, observational cohort study. Setting Preventive medicine clinic Participants and Exposures The prospective, observational cohort study included 13,949 community-dwelling men who had a baseline fitness examination. All men completed a comprehensive medical examination, a cardiovascular risk factor assessment, and incremental treadmill exercise test to evaluate CRF. We utilized age-sex specific distribution of treadmill duration from the overall CCLS population to define fitness groups as low (lowest 20%), moderate (middle 40%), and high (upper 40%) fit groups. The adjusted multivariable model included: age, exam year, body mass index, smoking, total cholesterol, systolic blood pressure, diabetes, fasting glucose. Main Outcome Measures (1) Incident prostate, lung, and colorectal cancer, and (2) all-cause mortality and cause-specific mortality among men who developed cancer are Medicare age (on or after age 65 years). Results Compared to low CRF, the adjusted hazard ratio (HR) for incident lung, colorectal, and prostate cancer among men with high CRF was 0.45 (95% CI: 0.29-0.68), 0.56 (95% CI: 0.36-0.87), 1.22 (95% CI: 1.02-1.46), respectively. Among those diagnosed with cancer at Medicare age (65 years), high CRF in mid-life was associated with an adjusted 36% (HR 0.64, 95% CI: 0.45-0.93) risk reduction in all cancer related deaths and a 69% reduction in cardiovascular disease mortality following a cancer diagnosis (HR 0.31, 95% CI: 0.15-0.62) compared to low fit men in mid-life. Conclusions and Relevance There is a strong inverse relationship between midlife CRF and incident lung and colorectal cancer but not prostate cancer. High mid-life CRF is also protective against the risk of cause-specific mortality in those diagnosed with cancer at Medicare age.

IMPORTANCE Few data are available to guide clinical recommendations for individuals with high levels of physical activity in the presence of clinically significant coronary artery calcification (CAC). OBJECTIVE To assess the association among high levels of physical activity, prevalent CAC, and subsequent mortality risk. DESIGN, SETTING, AND PARTICIPANTS The Cooper Center Longitudinal Study is a prospective observational study of patients from the Cooper Clinic, a preventive medicine facility. The present study included participants seen from January 13, 1998, through December 30, 2013, with mortality follow-up through December 31, 2014. A total of 21 758 generally healthy men without prevalent cardiovascular disease (CVD) were included if they reported their physical activity level and underwent CAC scanning. Data were analyzed from September 26, 2017, through May 2, 2018. EXPOSURES Self-reported physical activity was categorized into at least 3000 (n = 1561), 1500 to 2999 (n = 3750), and less than 1500 (n = 16 447) metabolic equivalent of task (MET)-minutes/week (min/wk). The CAC scores were categorized into at least 100 (n = 5314) and less than 100 (n = 16 444) Agatston units (AU). MAIN OUTCOMES AND MEASURES All-cause and CVD mortality collected from the National Death Index Plus. RESULTS Among the 21 758 male participants, baseline mean (SD) age was 51.7 (8.4) years. Men with at least 3000 MET-min/wk were more likely to have prevalent CAC of at least 100 AU (relative risk, 1.11; 95% CI, 1.03-1.20) compared with those accumulating less physical activity. In the group with physical activity of at least 3000 MET-min/wk and CAC of at least 100 AU, mean (SD) CAC level was 807 (1120) AU. After a mean (SD) follow-up of 10.4 (4.3) years, 759 all-cause and 180 CVD deaths occurred, including 40 all-cause and 10 CVD deaths among those with physical activity of at least 3000 MET-min/wk. Men with CAC of less than 100 AU and physical activity of at least 3000 MET-min/wk were about half as likely to die compared with men with less than 1500 MET-min/wk (hazard ratio [HR], 0.52; 95% CI, 0.29-0.91). In the group with CAC of at least 100 AU, men with at least 3000 MET-min/wk did not have a significant increase in all-cause mortality (HR, 0.77; 95% CI, 0.52-1.15) when compared with men with physical activity of less than 1500 MET-min/wk. In the least active men, those with CAC of at least 100 AU were twice as likely to die of CVD compared with those with CAC of less than 100 AU (HR, 1.93; 95% CI, 1.34-2.78). CONCLUSIONS AND RELEVANCE This study suggests there is evidence that high levels of physical activity (Ն3000 MET-min/wk) are associated with prevalent CAC but are not associated with increased all-cause or CVD mortality after a decade of follow-up, even in the presence of clinically significant CAC levels.

Heat shock proteins are proposed to limit injury resulting from diverse environmental stresses, but direct metabolic evidence for such a cytoprotective function in vertebrates has been largely limited to studies of cultured cells. We generated lines of transgenic mice to express human 70-kDa heat shock protein constitutively in the myocardium. Hearts isolated from these animals demonstrated enhanced recovery of high energy phosphate stores and correction of metabolic acidosis following brief periods of global ischemia sufficient to induce sustained abnormalities of these variables in hearts from nontransgenic littermates. These data demonstrate a direct cardioprotective effect of 70-kDa heat shock protein to enhance postischemic recovery of the intact heart.Previous studies have demonstrated a cytoprotective function for heat shock proteins during thermal stress or energy deprivation in cultured cells (1-6). Expression of endogenous 70-kDa heat shock protein (hsp7o) is induced by ischemia in intact hearts (6, 7), and this response correlates with a reduced susceptibility to ischemic injury (8-11). Preconditioning stimuli that induce hsp70, however, also invoke other responses that may mitigate myocardial dysfunction resulting from ischemia (12)(13)(14). The proposition that stress proteins exert direct cardioprotective effects remained conjectural until the development of transgenic mouse models, which provide an opportunity for rigorous tests of this hypothesis by examination of relationships between heat shock protein expression and various descriptors of ischemic injury. The goal of this work was to assess the effects of forced constitutive expression of hsp70 on recovery of high-energy phosphate metabolism (assessed by 31P NMR spectroscopy) following periods of global ischemia in isolated perfused mouse hearts. assay. RNA was extracted from myocardial tissue samples by standard methods, and cDNA was synthesized with reverse transcriptase by using an oligo(dT) primer. Primer pairs were specific either for murine glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (loading control) or human hsp7o cDNA and generated amplification products of 400 or 496 bp, respectively. RNA isolated from heat shocked human HeLa cells served as a positive control. The identity of the PCR product generated from the transgenic hearts when using human hsp7o primer pairs was confirmed by cleavage with Cla I, the restriction site for which is absent from the murine hsp70 sequence, to produce a 453-bp fragment. Proteins extracted from whole hearts were separated by isoelectric focusing and SDS/PAGE, and two-dimensional immunoblot assays (17) were conducted by using an exquisitely sensitive rabbit antihuman inducible hsp7o antibody. MATERIALS AND METHODSLangendorff Perfusion. The care and treatment of all animals in this study were in accord with the recommendations of the National Institutes of Health and the U. S. Department of Health and Human Services. The protocol was approved by the Institutional Review Board for Animal Rese...

Background Primary prevention of Alzheimer disease and other types of dementia (all-cause dementia) is an important public health goal. Evidence to date is insufficient to recommend any lifestyle change to prevent or delay the onset of dementia. Objective To assess the association between objectively measured midlife cardiorespiratory fitness (“fitness”) levels and development of all-cause dementia in advanced age. Design Prospective, observational cohort study. Setting Preventive medicine clinic. Patients 19 458 community-dwelling, nonelderly adults who had a baseline fitness examination. Measurements Fitness levels, assessed using the modified Balke treadmill protocol between 1971 and 2009, and incident all-cause dementia using Medicare Parts A and B claims data from 1999 to 2009. Results 1659 cases of incident all-cause dementia occurred during 125 700 person-years of Medicare follow-up (median follow-up, 25 years [interquartile range, 19 to 30 years]). After multivariable adjustment, participants in the highest quintile of fitness level had lower hazard of all-cause dementia than those in the lowest quintile (hazard ratio, 0.64 [95% CI, 0.54 to 0.77]). Higher fitness levels were associated with lower hazard of all-cause dementia with previous stroke (hazard ratio, 0.74 [CI, 0.53 to 1.04]) or without previous stroke (hazard ratio, 0.74 [CI, 0.61 to 0.90]). Limitations Dementia diagnoses were based on Medicare claims, and participants generally were non-Hispanic white, healthy, and well-educated and had access to preventive health care. This study evaluated fitness levels, so a specific exercise prescription cannot be generated from results and the findings may not be causal. Conclusion Higher midlife fitness levels seem to be associated with lower hazards of developing all-cause dementia later in life. The magnitude and direction of the association were similar with or without previous stroke, suggesting that higher fitness levels earlier in life may lower risk for dementia later in life, independent of cerebrovascular disease.

Background: The associations of low-density lipoprotein cholesterol (LDL-C) with cardiovascular disease (CVD) and coronary heart disease mortality in an exclusively low estimated 10-year risk group are not well delineated. We sought to determine the long-term associations of various LDL-C and non–high-density lipoprotein cholesterol (HDL-C) thresholds and CVD and coronary heart disease mortality in a large, low 10-year risk cohort. Methods: The study sample included participants of the CCLS (Cooper Center Longitudinal Study) without a history of CVD or diabetes mellitus and defined as low risk (<7.5%) for 10-year atherosclerotic CVD events at baseline based on Pooled Cohort Risk Assessment Equations. The associations of fasting LDL-C and non–HDL-C with CVD mortality were tested with Cox proportional hazards models. Results: In 36 375 participants (72% men, median age 42) followed for a median of 26.8 years, 1086 CVD and 598 coronary heart disease deaths occurred. Compared with LDL-C <100 mg/dL, LDL-C categories 100 to 129 mg/dL, 130 to 159 mg/dL, 160 to 189.9 mg/dL, and ≥190 mg/dL were associated with a significantly higher risk of CVD death, with hazard ratios of 1.4 (95% CI, 1.1–1.7), 1.3 (95% CI, 1.1–1.6), 1.9 (95% CI, 1.5–2.4), and 1.7 (95% CI, 1.3–2.3), and mean reductions in years free of CVD death of 1.8, 1.1, 4.3, and 3.9, respectively. After adjustment for atherosclerotic CVD risk factors, LDL-C categories 160 to 189 mg/dL and ≥190 mg/dL remained independently associated with CVD mortality, with hazard ratios of 1.7 (95% CI, 1.4–2.2) and 1.5 (95% CI, 1.2–2.1), respectively. In multivariable-adjusted models using non–HDL-C <130 mg/dL as the reference, non–HDL-C 160 to 189 mg/dL, 190 to 219 mg/dL, and ≥220 mg/dL were significantly associated with CVD death, with hazard ratios of 1.3 (95% CI, 1.1–1.6), 1.8 (95% CI, 1.4–2.2), and 1.5 (95% CI, 1.2–2.0), respectively. Restricting the cohort to those with 10-year risk <5% did not diminish the associations of LDL-C and non–HDL-C with CVD mortality. Conclusions: In a low 10-year risk cohort with long-term follow-up, LDL-C and non–HDL-C ≥160 mg/dL were independently associated with a 50% to 80% increased relative risk of CVD mortality. These findings may have implications for future cholesterol treatment paradigms.

Abstract-Mice lacking myoglobin survive to adulthood and meet the circulatory demands of exercise and pregnancy without cardiac decompensation. In the present study, we show that many myoglobin-deficient embryos die in utero at midgestation with signs of cardiac failure. Fetal mice that survive to gestational day 12.5, however, suffer no subsequent excess mortality. Survival in the absence of myoglobin is associated with increased vascularity and the induction of genes encoding the hypoxia-inducible transcription factors 1␣ and 2, stress proteins such as heat shock protein 27, and vascular endothelial growth factor. These adaptations are evident in late fetal life, persist into adulthood, and are sufficient to maintain normal myocardial oxygen consumption during stressed conditions. These data reveal that myoglobin is necessary to support cardiac function during development, but adaptive responses evoked in some animals can fully compensate for the defect in cellular oxygen transport resulting from the loss of myoglobin.