Joseph R. Libonati

Decreased scholastic achievement in overweight middle school students.

The purpose of this study was to investigate whether overweight students achieved a lower relative degree of scholastic achievement compared to nonoverweight students. Subjects consisted of 6th and 7th grade students enrolled in a large public middle school in a suburb of Philadelphia, Pennsylvania. We compared grade point averages (GPAs), nationally standardized reading scores, school detentions, school suspensions, school attendance, tardiness to school, physical fitness test scores, and participation on school athletic teams among nonoverweight, at risk for overweight, and overweight students. Overweight students achieved lower grades (P < 0.001) and lower physical fitness scores (P < 0.0001) than their nonoverweight peers. Overweight students demonstrated a 0.4 letter grade lower GPA (on a 4.00 scale) and 11% lower national percentile reading scores than their nonoverweight peers. The overweight students also demonstrated significantly more detentions, worsened school attendance, more tardiness to school, and less participation on school athletic teams than their nonoverweight peers. Our study suggests that body mass is an important indicator of scholastic achievement, attendance, behavior, and physical fitness among middle school students, reiterating the need for healthy lifestyle intervention and prevention measures.

Reduced ischemia and reperfusion injury following exercise training

We examined the effects of two exercise training modalities, i.e., low-intensity endurance and sprint running, on in vitro, isovolumic myocardial performance following ischemia and reperfusion. Rats ran on a treadmill 5 d.wk-1 for 6 wk at the following levels: endurance; 20 m.min-1, 0% grade, 60 min.d-1 and sprint; five 1-min runs at 75 m.min-1, 15% grade interspersed with 1-min active recovery runs at 20 m.min-1, 15% grade. Both endurance and sprint training significantly improved exercise tolerance relative to control (P < 0.05) on two graded exercise tests. Buffer perfused hearts of control (N = 18), endurance (N = 20), and sprint (N = 13) trained animals underwent no-flow ischemia (20 min) and reperfusion (30 min) in a Langendorff mode. During reperfusion, left ventricular developed pressure and its first derivative were 20% higher in sprint (P < 0.05) than either endurance or control hearts. Left ventricular end-diastolic pressure was lowest in sprint during reperfusion (sprint, 10 +/- 1 mm Hg vs endurance, 14 +/- 2 mm Hg; and control, 14 +/- 2 mm Hg, at 30 min reperfusion). Hearts were then used for biochemical studies or dissociated into single cells for measurement of contraction, cell calcium, and action potential duration. Single cell contractions were greatest in sprint despite similar calcium transients in all groups. Ischemia/reperfusion caused action potential prolongation in control but not trained myocytes. Hearts from sprint had the greatest glyceraldehyde-3-phosphate dehydrogenase activity (P < 0.05) and a tendency towards increased superoxide dismutase activity. These results suggest that sprinting increases myocardial resistance to ischemia/reperfusion. This protection may be secondary to increased myofilament calcium sensitivity and/or myocardial expression of glyceraldehyde-3-phosphate dehydrogenase.

Regulated Overexpression of the A1-Adenosine Receptor in Mice Results in Adverse but Reversible Changes in Cardiac Morphology and Function

Background— Both the A1- and A3-adenosine receptors (ARs) have been implicated in mediating the cardioprotective effects of adenosine. Paradoxically, overexpression of both A1-AR and A3-AR is associated with changes in the cardiac phenotype. To evaluate the temporal relationship between AR signaling and cardiac remodeling, we studied the effects of controlled overexpression of the A1-AR using a cardiac-specific and tetracycline-transactivating factor–regulated promoter. Methods and Results— Constitutive A1-AR overexpression caused the development of cardiac dilatation and death within 6 to 12 weeks. These mice developed diminished ventricular function and decreased heart rate. In contrast, when A1-AR expression was delayed until 3 weeks of age, mice remained phenotypically normal at 6 weeks, and >90% of the mice survived at 30 weeks. However, late induction of A1-AR still caused mild cardiomyopathy at older ages (20 weeks) and accelerated cardiac hypertrophy and the development of dilatation after pressure overload. These changes were accompanied by gene expression changes associated with cardiomyopathy and fibrosis and by decreased Akt phosphorylation. Discontinuation of A1-AR induction mitigated cardiac dysfunction and significantly improved survival rate. Conclusions— These data suggest that robust constitutive myocardial A1-AR overexpression induces a dilated cardiomyopathy, whereas delaying A1-AR expression until adulthood ameliorated but did not eliminate the development of cardiac pathology. Thus, the inducible A1-AR transgenic mouse model provides novel insights into the role of adenosine signaling in heart failure and illustrates the potentially deleterious consequences of selective versus nonselective activation of adenosine-signaling pathways in the heart.

Development and validation of a high-performance liquid chromatography–electrospray mass spectrometry method for the simultaneous determination of 23 eicosanoids

Inflammation is implicated in the pathogenesis of a number of diseases, including cardiovascular disease. Current research is focused on developing assays to search for biomarkers for inflammation. Eicosanoids are the oxidative metabolites of arachidonic acid (eicosatetraenoic acid, AA), a long chain polyunsaturated fatty acid common in Western diets. AA can be oxidized by one of three pathways to form prostaglandins (PGs), leukotrienes (LTs), or a number of hydroxyl and epoxy compounds. These eicosanoids have a variety of physiological functions, including regulating inflammation. We have developed a method utilizing LC-MS to separate and quantitate 23 different eicosanoids from all the three oxidative pathways. The eicosanoids were separated using a gradient elution of acetonitrile with 0.1% formic acid (v/v) and water with 0.1% formic acid (v/v) at a flow rate of 1 mL/min with a Symmetry C18 column (250 mm x 4.6 mm). Deuterated eicosanoids were used as internal standards for quantitation. Mass spectrometric detection was carried out using an Agilent 1100-series LC-MSD with an electrospray ionization interface. Electrospray ionisation (ESI) mass spectra were acquired using negative ionization and selective ion monitoring. The method was validated and shown to be sensitive (LOQ at pg levels for most compounds), accurate (recovery values 75-120%) and precise (R.S.D.<20 for all compounds) with a linear range over several orders of magnitude. The method was applied to rat kidney tissue and shown to be indicative of the eicosanoid levels within a specific organ. The analysis of eicosanoids can provide insight into the inflammatory mechanisms associated with cardiovascular disease.

Left ventricular remodeling with exercise in hypertension

We investigated how exercise training superimposed on chronic hypertension impacted left ventricular remodeling. Cardiomyocyte hypertrophy, apoptosis, and proliferation in hearts from female spontaneously hypertensive rats (SHRs) were examined. Four-month-old SHR animals were placed into a sedentary group (SHR-SED; n = 18) or a treadmill running group (SHR-TRD, 20 m/min, 1 h/day, 5 days/wk, 12 wk; n = 18). Age-matched, sedentary Wistar Kyoto (WKY) rats were controls (n = 18). Heart weight was greater in SHR-TRD vs. both WKY (P < 0.01) and SHR-SED (P < 0.05). Morphometric-derived left ventricular anterior, posterior, and septal wall thickness were increased in SHR-SED relative to WKY and augmented in SHR-TRD. Cardiomyocyte surface area, length, and width were increased in SHR-SED relative to WKY and further increased in SHR-TRD. Calcineurin abundance was increased in SHR-SED vs. WKY (P < 0.001) and attenuated in SHR-TRD relative to SHR-SED (P < 0.05). Protein abundance and mRNA of Akt was not different among groups. The rate of apoptosis was increased in SHR-SED relative to WKY and mitigated in SHR-TRD. The abundance of Ki-67(+) cells across groups was not statistically different across groups. The abundance of cardiac progenitor cells (c-Kit(+) cells) was increased in SHR-TRD relative to WKY. These data suggest that exercise training superimposed on hypertension augmented cardiomyocyte hypertrophy, despite attenuating calcineurin abundance. Exercise training also mitigated apoptosis in hypertension and showed a tendency to enhance the abundance of cardiac progenitor cells, resulting in a more favorable cardiomyocyte number in the exercise-trained hypertensive heart.

Exercise training improves systolic function in hypertensive myocardium

The general purpose of this study was to test the effect of exercise training on the left ventricular (LV) pressure-volume relationship (LV/PV) and apoptotic signaling markers in normotensive and hypertensive hearts. Four-month-old female normotensive Wistar-Kyoto rats (WKY; n = 37) and spontaneously hypertensive rats (SHR; n = 38) were assigned to a sedentary (WKY-SED, n = 21; SHR-SED, n = 19) or treadmill-trained (WKY-TRD, n = 16; SHR-TRD, n = 19) group (∼60% Vo(2 peak), 60 min/day, 5 days/wk, 12 wk). Ex vivo LV/PV were established in isovolumic Langendorff-perfused hearts, and LV levels of Akt, phosphorylated Akt (Akt(Pi)), Bad, phosphorylated Bad (Bad(Pi)) c-IAP, x-IAP, calcineurin, and caspases 3, 8, and 9 were measured. Heart-to-body weight ratio was increased in SHR vs. WKY (P < 0.05), concomitant with increased calcineurin mRNA (P < 0.05). There was a rightward shift in the LV/PV (P < 0.05) and a reduction in systolic elastance (E(s)) in SHR vs. WKY. Exercise training corrected E(s) in SHR (P < 0.05) but had no effect on the LV/PV in WKY. Caspase 3 was increased in SHR-SED relative to WKY-SED, while Bad(Pi,) c-IAP, and x-IAP were significantly lower in SHR relative to WKY (P < 0.05). Exercise training increased Bad(Pi) in both WKY and SHR but did not alter caspase 9 activity in either group. While caspase 3 activity was increased with training in WKY (P < 0.05), it was unchanged with training in SHR. We conclude that moderate levels of regular aerobic exercise attenuate systolic dysfunction early in the compensatory phase of hypertrophy, and that a differential phenotypical response to moderate-intensity exercise exists between WKY and SHR.

Concomitant Low Dose Doxorubicin Treatment and Exercise

Cardiotoxicity is a side effect for cancer patients treated with doxorubicin (DOX). We tested the hypothesis that low-intensity aerobic exercise concomitant with DOX treatment would offset DOX-induced cardiotoxicity while also improving the therapeutic efficacy of DOX on tumor progression. B16F10 melanoma cells (3 × 10(5)) were injected subcutaneously into the scruff of 6- to 8-wk-old male C57BL/6 mice (n = 48). A 4 mg/kg cumulative dose of DOX was administered over 2 wk, and exercise (EX) consisted of treadmill walking (10 m/min, 45 min/day, 5 days/wk, 2 wk). Four experimental groups were tested: 1) sedentary (SED) + vehicle, 2) SED + DOX, 3) EX + vehicle, and 4) EX + DOX. Tumor volume was attenuated in DOX and lowest in EX + DOX. DOX-treated animals had less gain in body weight, reduced heart weights (HW), smaller HW-to-body weight ratios, and shorter tibial lengths by the end of the protocol; and exercise did not reverse the cardiotoxic effects of DOX. Despite decreased left ventricular (LV) mass with DOX, cardiomyocyte cross-sectional area, β-myosin heavy chain gene expression, and whole heart systolic (fractional shortening) and diastolic (E/A ratio) function were similar among groups. DOX also resulted in increased LV fibrosis with lower LV end diastolic volume and stroke volume. Myocardial protein kinase B activity was increased with both DOX and EX treatments, and tuberous sclerosis 2 (TSC2) abundance was reduced with EX. Downstream phosphorylation of TSC2 and mammalian target of rapamycin were similar across groups. We conclude that exercise increases the efficacy of DOX in inhibiting tumor growth without mitigating subclinical DOX-induced cardiotoxicity in a murine model of melanoma.

Exercise and diastolic function after myocardial infarction.

PURPOSE The purpose of this study was to determine the effects of exercise training on LV geometry and LV diastolic function in a rat model of MI. METHODS One month after MI induced by ligation of the left anterior descending artery (N = 45) or sham operation (N = 26), rats were randomized to either a sedentary or exercise group. Exercise consisted of treadmill running at 24 m.min-1, 1 h.d-1, 5 d.wk-1, for 3 wk. Passive LV pressure volume relationships were established with an isolated, red-cell-perfused Langendorff preparation. Infarct size was determined histologically and categorized as small (<30% of LV) or large (> or =30% of LV). RESULTS LV end-diastolic pressure-volume relationships were shifted rightward with increasing infarct size (P < 0.05). Exercise training further shifted the LV end-diastolic pressure-volume relationships rightward in sham, small MI and large MI (P < 0.05). Peak LV developed pressure was comparable in sedentary and exercised-trained hearts in sham, small MI, and large MI. LV diameter and septal wall thickness were greatest in large MI (P < 0.05). Exercise-trained hearts showed a tendency for a greater LV diameter and septal wall thickness in sham, small MI, and large MI. Scar thinning was most notable in large MI (P < 0.05). CONCLUSION Moderate-intensity treadmill running induces myocardial remodeling and a rightward shift in the LV end-diastolic pressure-volume relationship after MI, an adaptation similar to what is observed with exercise training in sham hearts without MI.

Exercise training improves left ventricular isovolumic relaxation.

PURPOSE Left ventricular (LV) diastolic function is an important determinant of aerobic fitness. The purpose of this paper was to investigate the relationship between aerobic fitness and the rate and extent of isovolumic LV relaxation. METHODS Two series of experiments were performed utilizing both human and animal models. In the first series of experiments, the relationship between LV diastolic time intervals and exercise capacity was assessed in two groups of collegiate men (N = 18) with variable peak run times (Bruce protocol). In the second series of experiments, the extent of LV relaxation was examined in sedentary and exercise-trained rats (treadmill running), using an isolated, isovolumic heart preparation. Subsequent morphological assessment was also performed in rats. RESULTS At rest, men with greater peak treadmill time had a shorter resting LV isovolumic relaxation time (R-R interval adjusted 1000 ms) (long duration runners, 84+/-5 ms vs short duration runners, 105+/-7 ms, P < 0.05) despite a similar LV diastolic interval. Peak treadmill time was inversely correlated to LV isovolumic relaxation time (R-R interval adjusted 1000 ms) (r = -0.55; P < 0.02). In animal studies (N = 26), the LV pressure-volume relationship was shifted rightward in exercise-trained rats (P = 0.003). Exercise-trained rats had an increased LV inner diameter (sedentary, 5.1+/-0.35 mm vs exercise-trained, 6.1+/-0.28 mm, P < 0.05) and a thicker interventricular septum (sedentary, 1.52+/-0.06 mm vs exercise-trained, 1.72+/-0.09 mm, P < 0.05). CONCLUSION This study suggests that both the rate and extent of LV isovolumic relaxation is enhanced with exercise training. Further study is required to understand the interrelationship between exercise and diastolic function.

The effects of exercise on cardiovascular outcomes before, during, and after treatment for breast cancer

Asymptomatic cardiotoxicity following breast cancer treatment is a significant issue for many patients, as these patients typically face an increased risk of cardiovascular disease (CVD). Exercise has well established benefits to improve and maintain cardiovascular function across patients with and without CVD. However, there is a dearth of information on the effects of exercise on cardiovascular outcomes in breast cancer patients. While pre-clinical studies support the use of exercise in mitigating cardiotoxicity, only one human study has specifically investigated cardiac function following an exercise intervention during chemotherapy treatment. No significant differences were observed between groups, which highlights the unidentified role of exercise in altering the risk of cardiotoxicity in breast cancer patients. Issues such as establishing the optimal timing, type, and intensity of an exercise program before, during, or after oncologic treatment for breast cancer are unclear. CVD risk and incidence increase in breast cancer survivors post therapy, and CVD is the number one killer of women in the United States. Thus, there is an increasing need to define the efficacy of exercise as a non-pharmacologic intervention in this growing population.