Plasma kinetics of a cholesterol-rich emulsion in subjects with or without coronary artery disease

A cholesterol-rich emulsion (LDE) that resembles the LDL lipidic structure is taken-up by LDL receptors after intravenous injection by means of apolipoprotein E it acquires in the circulation and can be used to probe LDL metabolism. In this study, LDE was labeled with [14C]cholesteryl oleate and [3H]cholesterol and injected into 19 patients with coronary artery disease (CAD) and into 14 subjects without CAD to verify whether the kinetic behavior of the radioactive lipids is different in CAD. Blood was sampled over 24 h for radioactivity measurement after lipid extraction and separation by thin-layer chromatography. Fractional clearance rate (FCR, in h-1) of [14C]cholesteryl ester was not different in CAD and nonCAD expressed as median (25%; 75%): 0.08 (0.062; 0.134) h-1 versus 0.06 (0.04; 0.083) h-1, P = 0.167. However, [3H]cholesterol FCR was greater in CAD than in nonCAD (mean +/- SEM): 0.163 +/- 0.016 h-1 versus 0.077 +/- 0.014 h-1, P < 0.001. Esterification of the LDE [3H]cholesterol was also greater in CAD subjects than nonCAD at 10 h and 24 h after emulsion injection (P = 0.029 and 0.024 respectively). In conclusion, both removal from the plasma and esterification of the LDE-cholesterol were increased in CAD. These findings may contribute for unraveling pro-atherogenic mechanisms and the establishment of novel CAD markers.     

5'-AMP-activated protein kinase activity and subunit expression in exercise-trained human skeletal muscle.

5'-AMP-activated protein kinase (AMPK) has been proposed to be a pivotal factor in cellular responses to both acute exercise and exercise training. To investigate whether protein levels and gene expression of catalytic (alpha(1), alpha(2)) and regulatory (beta(1), beta(2), gamma(1), gamma(2), gamma(3)) AMPK subunits and exercise-induced AMPK activity are influenced by exercise training status, muscle biopsies were obtained from seven endurance exercise-trained and seven sedentary young healthy men. The alpha(1)- and alpha(2)-AMPK mRNA contents in trained subjects were both 117 +/- 2% of that in sedentary subjects (not significant), whereas mRNA for gamma(3) was 61 +/- 1% of that in sedentary subjects (not significant). The level of alpha(1)-AMPK protein in trained subjects was 185 +/- 34% of that in sedentary subjects (P < 0.05), whereas the levels of the remaining subunits (alpha(2), beta(1), beta(2), gamma(1), gamma(2), gamma(3)) were similar in trained and sedentary subjects. At the end of 20 min of cycle exercise at 80% of peak O(2) uptake, the increase in phosphorylation of alpha-AMPK (Thr(172)) was blunted in the trained group (138 +/- 38% above rest) compared with the sedentary group (353 +/- 63% above rest) (P < 0.05). Acetyl CoA-carboxylase beta-phosphorylation (Ser(221)), which is a marker for in vivo AMPK activity, was increased by exercise in both groups but to a lower level in trained subjects (32 +/- 5 arbitrary units) than in sedentary controls (45 +/- 1 arbitrary units) (P < 0.01). In conclusion, trained human skeletal muscle has increased alpha(1)-AMPK protein levels and blunted AMPK activation during exercise.     

Exercise training increases membrane bound form of tumor necrosis factor-alpha receptors with decreases in the secretion of soluble forms of receptors in rat adipocytes

We examined the effects of exercise training (treadmill running over 9 weeks) on the ability of isolated adipocytes to secrete tumor necrosis factor-alpha (TNF-alpha) and type 1 soluble TNF receptor (sTNFR1) in vitro in Wistar rats. We also examined the effects of exercise training on the expression of membrane bound forms of type 1 TNF receptor (mTNFR1) in adipocyte crude membranes of the same rat subjects. Exercise training significantly increased the secretions of TNF-alpha from isolated adipocytes. Treatment with a cyclooxygenase inhibitor, either indomethacin (100 microM) or eicosatetraynoic acid (100 microM), significantly blocked the release of TNF-alpha from adipocytes in both exercise-trained rat group and sedentary control rat group, suggesting that some cyclooxygenase metabolite(s) acts as a ligand in TNF-alpha synthesis. Decreased amounts of TNF-alpha were found to be significantly greater in both exercise-trained rat group than in sedentary control rat group after incubation with inhibitors. Thus, the inhibitory effect of both indomethacin and eicosatetraynoic acid was significantly greater in adipocytes from exercise-trained rats. Both plasma sTNFR1 levels and adipocytes-derived sTNFR1 were found to be significantly less in the exercise-trained rat group. Western blot analysis revealed that exercise training remarkably increased the expressions of mTNFR1 in adipocyte crude membrane. Thus, exercise training enhanced the ability of isolated adipocytes to secrete TNF-alpha with reduced secretion of sTNFR1, and provoked the greater expressions of mTNFR1 in adipocyte crude membrane. These alterations may induce enhanced the autocrine effects of TNF-alpha within adipocytes in exercise-trained rats.     

Exercise training changes autonomic cardiovascular balance in mice.

Experiments were performed to investigate the influence of exercise training on cardiovascular function in mice. Heart rate, arterial pressure, baroreflex sensitivity, and autonomic control of heart rate were measured in conscious, unrestrained male C57/6J sedentary (n = 8) and trained mice (n = 8). The exercise training protocol used a treadmill (1 h/day; 5 days/wk for 4 wk). Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses induced by sodium nitroprusside and phenylephrine, respectively. Autonomic control of heart rate and intrinsic heart rate were determined by use of methylatropine and propranolol. Resting bradycardia was observed in trained mice compared with sedentary animals [485 +/- 9 vs. 612 +/- 5 beats/min (bpm)], whereas mean arterial pressure was not different between the groups (106 +/- 2 vs. 108 +/- 3 mmHg). Baroreflex-mediated tachycardia was significantly enhanced in the trained group (6.97 +/- 0.97 vs. 1.6 +/- 0.21 bpm/mmHg, trained vs. sedentary), whereas baroreflex-mediated bradycardia was not altered by training. The tachycardia induced by methylatropine was significantly increased in trained animals (139 +/- 12 vs. 40 +/- 9 bpm, trained vs. sedentary), whereas the propranolol effect was significantly reduced in the trained group (49 +/- 11 vs. 97 +/- 11 bpm, trained vs. sedentary). Intrinsic heart rate was similar between groups. In conclusion, dynamic exercise training in mice induced a resting bradycardia and an improvement in baroreflex-mediated tachycardia. These changes are likely related to an increased vagal and decreased sympathetic tone, similar to the exercise response observed in humans.     

Influence of exercise training on maternal and fetal morphological characteristics in the rat

Evidence in both humans and animals has shown that exercise before or during pregnancy may effect fetal outcome. The purpose of this investigation was to examine the effects of an exercise program on fetal development in the rat. Prior to impregnation one group of animals was exercise-trained on a Quinton shock-stimulus rodent treadmill. The exercised group was trained to run 5 days/wk, for 2.0 h/day at 31 m/min up an 8 degree incline for 8 wk before mating. Following mating the training intensity was reduced to 27 m/min up a 5 degree incline, and the exercise period decreased to 1 h/day. On day 19 of gestation, 24 h postexercise for the trained mothers, the animals were killed in the fed state and the maternal and fetal characteristics were measured. The sedentary controls gained significantly (P less than 0.05) more body weight during pregnancy. This can be attributed to three factors: higher number of fetuses, 14.83 +/- 0.04 vs. 12.2 +/- 0.85 for the trained; larger litter weights, 44.25 +/- 4.97 vs. 26.17 +/- 1.82 g/dam for the trained; and slightly larger lipid stores. In addition to having fewer pups the trained mothers had a greater number of fetal resorptions; 0.9/dam as opposed to 0.17/dam for the sedentary control. Analysis of fetal body composition showed no difference in total body water, protein, or fat between the pups of sedentary and trained dams. The results of this study indicate that exercise training prior to and during pregnancy influences fetal development in the rat.     

Maximal vascular leg conductance in trained and untrained men

Lower leg blood flow and vascular conductance were studied and related to maximal oxygen uptake in 15 sedentary men (28.5 +/- 1.2 yr, mean +/- SE) and 11 endurance-trained men (30.5 +/- 2.0 yr). Blood flows were obtained at rest and during reactive hyperemia produced by ischemic exercise to fatigue. Vascular conductance was computed from blood flow measured by venous occlusion plethysmography, and mean arterial blood pressure was determined by auscultation of the brachial artery. Resting blood flow and mean arterial pressure were similar in both groups (combined mean, 3.0 ml X min-1 X 100 ml-1 and 88.2 mmHg). After ischemic exercise, blood flows were 29- and 19-fold higher (P less than 0.001) than rest in trained (83.3 +/- 3.8 ml X min-1 X 100 ml-1) and sedentary subjects (61.5 +/- 2.3 ml X min-1 X 100 ml-1), respectively. Blood pressure and heart rate were only slightly elevated in both groups. Maximal vascular conductance was significantly higher (P less than 0.001) in the trained compared with the sedentary subjects. The correlation coefficients for maximal oxygen uptake vs. vascular conductance were 0.81 (trained) and 0.45 (sedentary). These data suggest that physical training increases the capacity for vasodilation in active limbs and also enables the trained individual to utilize a larger fraction of maximal vascular conductance than the sedentary subject.     

Extracellular cyclic AMP and adenosine appearance in adipose tissue of Sus scrofa: effects of exercise

Cyclic AMP (cAMP) appears extracellularly in a variety of tissues including brain, liver, and kidney; whether it appears in adipose tissue and responds to physiological perturbation is unknown. The purpose of this study was to examine adipose tissue extracellular cAMP appearance and metabolism in situ and in vitro in physiologically challenged animals. Littermate swine were either sedentary or exercise trained on a treadmill for 3 months and subjected to acute exercise on experiment day. In situ, microdialysis probes in subcutaneous back fat were perfused before, during, and after animals performed 20 mins of acute exercise, and dialysate was analyzed for cAMP and adenosine. In vitro, isolated adipocytes were hormonally stimulated to provoke cAMP synthesis and efflux, and plasma membrane phosphodiesterase and 5'-nucleotidase activities were measured. Extracellular cAMP and adenosine levels in adipose tissue of sedentary swine averaged 5.2 +/- 1.7 and 863 +/- 278 nM, respectively. Exercise training tended to increase extracellular cAMP (11.3 +/- 1.7 nM) and reduce extracellular adenosine (438 +/- 303 nM), although neither change was statistically significant. Acute exercise caused a significant 3-fold and 16-fold increase in extracellular cAMP and adenosine, respectively, compared to rest. These changes occurred despite a 2- to 3-fold increase in adipose tissue blood flow during acute exercise. In vitro, cAMP efflux from exercise-trained swine was 42% greater than that from adipocytes of sedentary swine, yet adipocyte plasma membranes from exercise-trained and sedentary swine did not differ in maximal phosphodiesterase and 5'-nucleotidase activities. We conclude that cAMP appears extracellularly in swine adipose tissue and that the levels of extracellular cAMP and adenosine in intact swine adipose tissue are influenced by both acute and chronic exercise. The subsequent impact of the changes in these biochemicals on local cellular metabolism and growth remains to be determined.     

Exercise effects on chromium excretion of trained and untrained men consuming a constant diet

Chromium excretion of eight trained and five sedentary men was determined on rest days and after exercise to exhaustion at 90% of maximum O2 consumption (VO2max) to determine if degree of physical fitness affects urinary Cr losses. Subjects were fed a constant daily diet containing approximately 9 micrograms Cr/1,000 kcal. VO2max of the trained runners was in the good or above range based on their age and that of the sedentary subjects was average or below. While consuming the control diet, basal urinary Cr excretion of subjects who exercise regularly was significantly lower than that of the sedentary control subjects, 0.09 +/- 0.01 and 0.21 +/- 0.03 microgram/day (mean +/- SE), respectively. When subjects consumed self-chosen diets, basal urinary Cr excretion of the trained subjects was also significantly lower than that of the untrained subjects. Daily urinary Cr excretion of trained subjects was significantly higher on the day of a single exercise bout at 90% VO2max compared with nonexercise days, 0.12 +/- 0.02 and 0.09 +/- 0.01 microgram/day, respectively. Urinary Cr excretion of sedentary subjects was not altered after controlled exercise. These data demonstrate that basal urinary Cr excretion and excretion in response to exercise are related to VO2max and therefore degree of physical fitness.     

Endurance training increased HDL cholesteryl ester metabolism in rats

We studied the effects of endurance training on the metabolism of high-density lipoprotein (HDL, 1.063 less than density less than 1.15 kg/l) cholesteryl ester and proteins in rats fed a cholesterol-rich (1%) semipurified diet. The HDL were labeled with 131I in the apoproteins and with cholesteryl-[1-14C]oleate in the esters. The HDL were intravenously administered to endurance-trained (n = 10) and cage-sedentary (n = 10) rats. Blood samples were taken over the next 36 h while the rats were conscious and feeding. The trained rats had higher plasma HDL cholesterol (0.72 vs. 0.28 mM) and HDL apoprotein (461 vs. 267 mg/l) concentrations than the sedentary rats. The production or disposal rate of HDL cholesteryl ester was higher in the trained rats (1.36 mumol/h) than in the sedentary rats (0.72 mumol/h), whereas the production or disposal rate of HDL apoproteins was similar in the trained (0.64 mg/h) and sedentary (0.60 mg/h) rats. The residence time of the HDL cholesteryl esters (4.72 +/- 0.22 vs. 3.37 +/- 0.21 h) and HDL apoprotein (7.65 +/- 0.36 vs. 4.55 +/- 0.28 h) was longer for the trained than for the sedentary rats. These data indicate that endurance training resulted in a significant change in the metabolism of HDL cholesteryl esters and apoproteins as well as an increase in their concentrations.     

Synthetic nanoemulsion resembling a protein-free model of 7-ketocholesterol containing low density lipoprotein: In vitro and in vivo studies

7-ketocholesterol (7-KC) differs from cholesterol by a functional ketone group at C7. It is an oxygenated cholesterol derivative (oxysterol), commonly present in oxidized low-density lipoprotein (LDL). Oxysterols are generated and participate in several physiologic and pathophysiologic processes. For instance, the cytotoxic effects of oxidized LDL have been widely attributed to bioactive compounds like oxysterols. The toxicity is in part due to 7-KC. Here we aimed to demonstrate the possibility of incorporating 7-KC into the synthetic nanoemulsion LDE, which resembles LDL in composition and behavior. This would provide a suitable artificial particle resembling LDL to study 7-KC metabolism. We were able to incorporate 7-KC in several amounts into LDE. The incorporation was evaluated and confirmed by several methods, including gel filtration chromatography, using radiolabeled lipids. The incorporation did not change the main lipid composition characteristics of the new nanoparticle. Particle sizes were also evaluated and did not differ from LDE. In vivo studies were performed by injecting the nanoemulsion into mice. The plasma kinetics and the targeted organs were the same as described for LDE. Therefore, 7-KC-LDE maintains composition, size and some functional characteristics of LDE and could be used in experiments dealing with 7-ketocholesterol metabolism in lipoproteins.     

Regular exercise enhances insulin activation of IRS-1-associated PI3-kinase in human skeletal muscle.

Insulin action in skeletal muscle is enhanced by regular exercise. Whether insulin signaling in human skeletal muscle is affected by habitual exercise is not well understood. Phosphatidylinositol 3-kinase (PI3-kinase) activation is an important step in the insulin-signaling pathway and appears to regulate glucose metabolism via GLUT-4 translocation in skeletal muscle. To examine the effects of regular exercise on PI3-kinase activation, 2-h hyperinsulinemic (40 mU. m(-2). min(-1))-euglycemic (5.0 mM) clamps were performed on eight healthy exercise-trained [24 +/- 1 yr, 71.8 +/- 2.0 kg, maximal O(2) uptake (VO(2 max)) of 56.1 +/- 2.5 ml. kg(-1). min(-1)] and eight healthy sedentary men and women (24 +/- 1 yr, 64.7 +/- 4.4 kg, VO(2 max) of 44.4 +/- 2.7 ml. kg(-1). min(-1)). A [6, 6-(2)H]glucose tracer was used to measure hepatic glucose output. A muscle biopsy was obtained from the vastus lateralis muscle at basal and at 2 h of hyperinsulinemia to measure insulin receptor substrate-1(IRS-1)-associated PI3-kinase activation. Insulin concentrations during hyperinsulinemia were similar for both groups (293 +/- 22 and 311 +/- 22 pM for trained and sedentary, respectively). Insulin-mediated glucose disposal rates (GDR) were greater (P < 0.05) in the exercise-trained compared with the sedentary control group (9.22 +/- 0.95 vs. 6.36 +/- 0.57 mg. kg fat-free mass(-1). min(-1)). Insulin-stimulated PI3-kinase activation was also greater (P < 0.004) in the trained compared with the sedentary group (3.8 +/- 0.5- vs. 1.8 +/- 0.2-fold increase from basal). Endurance capacity (VO(2 max)) was positively correlated with PI3-kinase activation (r = 0.53, P < 0.04). There was no correlation between PI3-kinase and muscle morphology. However, increases in GDR were positively related to PI3-kinase activation (r = 0.60, P < 0.02). We conclude that regular exercise leads to greater insulin-stimulated IRS-1-associated PI3-kinase activation in human skeletal muscle, thus facilitating enhanced insulin-mediated glucose uptake.     

Effects of exercise training on contractile function in myocardial trabeculae after ischemia-reperfusion.

Potential protective effects of aerobic exercise training on the myocardium, before an ischemic event, are not completely understood. The purpose of the study was to investigate the effects of exercise training on contractile function after ischemia-reperfusion (Langendorff preparation with 15-min global ischemia/30-min reperfusion). Trabeculae were isolated from the left ventricles of both sedentary control and 10- to 12-wk treadmill exercise-trained rats. The maximal normalized isometric force (force/cross-sectional area; Po/CSA) and shortening velocity (Vo) in isolated, skinned ventricular trabeculae were measured using the slack test. Ischemia-reperfusion induced significant contractile dysfunction in hearts from both sedentary and trained animals; left ventricular developed pressure (LVDP) and maximal rates of pressure development and relaxation (+/-dP/dtmax) decreased, whereas end-diastolic pressure (EDP) increased. However, this dysfunction (as expressed as percent change from the last 5 min before ischemia) was attenuated in trained myocardium [LVDP: sedentary -60.8 +/- 6.4% (32.0 +/- 5.5 mmHg) vs. trained -15.6 +/- 8.6% (64.9 +/- 6.6 mmHg); +dP/dtmax: sedentary -54.1 +/- 4.7% (1,058.7 +/- 124.2 mmHg/s) vs. trained -16.7 +/- 8.4% (1,931.9 +/- 188.3 mmHg/s); -dP/dtmax: sedentary -44.4 +/- 2.5% (-829.3 +/- 52.0 mmHg/s) vs. trained -17.9 +/- 7.2% (-1,341.3 +/- 142.8 mmHg/s); EDP: sedentary 539.5 +/- 147.6%; (41.3 +/- 6.0 mmHg) vs. trained 71.6 +/- 30.6%; 11.4 +/- 1.2 mmHg]. There was an average 26% increase in Po/CSA in trained trabeculae compared with sedentary controls, and this increase was not affected by ischemia-reperfusion. Ischemia-reperfusion reduced Vo by 39% in both control and trained trabeculae. The relative amount of the beta-isoform of myosin heavy chain (MHC-beta) was twofold greater in trained trabeculae as well as in the ventricular free walls. Despite a possible increase in the economy in the trained heart, presumed from a greater amount of MHC-beta, ischemia-reperfusion reduced Vo, to a similar extent in both control and trained animals. Nevertheless, the trained myocardium appears to have a greater maximum force-generating ability that may, at least partially, compensate for reduced contractile function induced by a brief period of ischemia.     

Endurance exercise training increases insulin responsiveness in isolated adipocytes through IRS/PI3-kinase/Akt pathway.

Endurance exercise training promotes important metabolic adaptations, and the adipose tissue is particularly affected. The aim of this study was to investigate how endurance exercise training modulates some aspects of insulin action in isolated adipocytes and in intact adipose tissue. Male Wistar rats were submitted to daily treadmill running (1 h/day) for 7 wk. Sedentary age-matched rats were used as controls. Final body weight, body weight gain, and epididymal fat pad weight did not show any statistical differences between groups. Adipocytes from trained rats were smaller than those from sedentary rats (205 +/- 16.8 vs. 286 +/- 26.4 pl; P < 0.05). Trained rats showed decreased plasma glucose (4.9 +/- 0.13 vs. 5.3 +/- 0.07 mM; P < 0.05) and insulin levels (0.24 +/- 0.012 vs. 0.41 +/- 0.049 mM; P < 0.05) and increased insulin-stimulated glucose uptake (23.1 +/- 3.1 vs. 12.1 +/- 2.9 pmol/cm(2); P < 0.05) compared with sedentary rats. The number of insulin receptors and the insulin-induced tyrosine phosphorylation of insulin receptor-beta subunit did not change between groups. Insulin-induced tyrosine phosphorylation insulin receptor substrates (IRS)-1 and -2 increased significantly (1.57- and 2.38-fold, respectively) in trained rats. Insulin-induced IRS-1/phosphatidylinositol 3 (PI3)-kinase (but not IRS-2/PI3-kinase) association and serine Akt phosphorylation also increased (2.06- and 3.15-fold, respectively) after training. The protein content of insulin receptor-beta subunit, IRS-1 and -2, did not differ between groups. Taken together, these data support the hypothesis that the increased adipocyte responsiveness to insulin observed after endurance exercise training is modulated by IRS/PI3-kinase/Akt pathway.     

Exercise-induced increase in the capacity of rat skeletal muscle to oxidize ketones.

During and after strenuous prolonged exercise, sedentary individuals develop high blood levels of acetoacetate and beta-hydroxybutyrate whereas exercise-trained animals and human subjects do not. We have investigated the possibility that exercise training can increase the capacity of skeletal muscle to oxidize ketones. In this study we measured rates of D-beta[3-14-C]-hydroxybutyrate and [3-14-C]acetoacetate oxidation, and the levels of activity of the enzymes involved in the oxidation of ketones in homogenates of gastrocnemius muscles of exercise-trained and of untrained male rats. The trained animals had markedly lower blood ketone levels immediately and 60 min after a 90 min long bout of exercise than did the sedentary animals. The rates of D-beta-[13-14C]hydroxybutryate and [3-14-C]acetoacetate oxidation were twice as high in homogenates of muscles from the trained as compared to the sedentary rats. The increases in levels of activity in gastrocnemius muscle in response to the exercise program were: beta-hydroxybutyrate dehydrogenase threefold; 3-ketoacid CoA-transferase twofold; and acetoacetyl-CoA thiolase 55%. This exercise-induced increase in the capacity of skeletal muscle to oxidize ketones could play a role in preventing development of ketosis in the physically trained animal during and following prolonged strenuous exercise.     

Cholesteryl ester transfer protein expression attenuates atherosclerosis in ovariectomized mice

Reduced estrogen levels result in loss of protection from coronary heart disease in postmenopausal women. Enhanced and diminished atherosclerosis have been associated with plasma levels of cholesteryl ester transfer protein (CETP); however, little is known about the role of CETP-ovarian hormone interactions in atherogenesis. We assessed the severity of diet-induced atherosclerosis in ovariectomized (OV) CETP transgenic mice crossbred with LDL receptor knockout mice. Compared with OV CETP expressing ((+)), OV CETP non-expressing ((-)) mice had higher plasma levels of total, VLDL-, LDL-, and HDL-cholesterol, as well as higher antibodies titers against oxidized LDL. The mean aortic lesion area was 2-fold larger in OV CETP(-) than in OV CETP(+) mice (147 +/- 90 vs. 73 +/- 42 x 10(3) micro m(2), respectively). Estrogen therapy in OV mice blunted the CETP dependent differences in plasma lipoproteins, oxLDL antibodies, and atherosclerosis severity. Macrophages from OV CETP(+) mice took up less labeled cholesteryl ether (CEt) from acetyl-LDL than macrophages from OV CETP(-) mice. Estrogen replacement induced a further reduction in CEt uptake and an elevation in HDL mediated cholesterol efflux from pre-loaded OV CETP(+) as compared with OV CETP(-) macrophages. These findings support the proposed anti-atherogenic role of CETP in specific metabolic settings.     

Comparison of body water turnover in endurance runners and age-matched sedentary men

This study compared the body water turnover in endurance athletes and age-matched sedentary men. Eight competitive endurance athletes (20.8+/-1.9 yr) and age-matched eight sedentary men (21.6+/-2.5 yr) participated in this study. Total body water and body water turnover were measured using the deuterium (D(2)O) dilution technique. Urine samples were obtained every day for 10 days after oral administration of D(2)O. The day-by-day concentrations were used to calculate the biological half-life of D(2)O and body water turnover. Maximal oxygen uptake (VO(2max)) and oxygen uptake corresponding to ventilatory threshold (VO(2VT)) as an index of aerobic capacity were determined during a graded exercise test. Both VO(2max) and VO(2VT) were higher in the exercise group than in the sedentary group (P<0.05). The biological half-life of D(2)O was significantly shorter in the exercise group than in the sedentary group (5.89+/-0.81 days vs. 7.52+/-0.77 days, P<0.05), and the percentage of the body water turnover was significantly higher in the exercise group than in the sedentary group (11.99+/-1.96% vs. 9.39+/-1.21%, P<0.05). The body water turnover was correlated with VO(2max) and VO(2VT), respectively (P<0.05). Based on these findings, this study speculates that a level of physical activity may induce a body water turnover higher in the healthy state, since the better trained subjects have a higher body water turnover.     

Acute sympathetic vasoconstriction at rest and during dynamic exercise in cyclists and sedentary humans.

The impact of exercise training on sympathetic activation is not well understood, especially across untrained and trained limbs in athletes. Therefore, in eight sedentary subjects (maximal oxygen consumption = 40 +/- 2 ml x kg(-1) x min(-1)) and eight competitive cyclists (maximal oxygen consumption = 64 +/- 2 ml x kg(-1) x min(-1)), we evaluated heart rate, blood pressure, blood flow, vascular conductance, and vascular resistance in the leg and arm during acute sympathetic stimulation [cold pressor test (CPT)]. The CPT was also performed during dynamic leg (knee extensor) or arm (handgrip) exercise at 50% of maximal work rate (WRmax) with measurements in the exercising limb. At rest, the CPT decreased vascular conductance similarly in the leg and arm of sedentary subjects (-33 +/- 8% leg, -38 +/- 6% arm) and cyclists (-34 +/- 4% leg, -31 +/- 9% arm), and during exercise CPT-induced vasoconstriction was blunted (i.e., sympatholysis) in both the leg and arm of both groups. However, the magnitude of sympatholysis was significantly different between the arm and leg of the sedentary group (-47 +/- 11% arm, -25 +/- 8% leg), and it was less in the arm of cyclists (-28 +/- 11%) than sedentary controls. Taken together, these data provide evidence that sympathetically mediated vasoconstriction is expressed equally and globally at rest in both sedentary and trained individuals, with a differential pattern of vasoconstriction during acute exercise according to limb and exercise training status.     

Lecithin:cholesterol acyltransferase deficiency increases atherosclerosis in the low density lipoprotein receptor and apolipoprotein E knockout mice.

The purpose of the present study was to test the hypothesis that lecithin:cholesterol acyltransferase (LCAT) deficiency would accelerate atherosclerosis development in low density lipoprotein (LDL) receptor (LDLr-/-) and apoE (apoE-/-) knockout mice. After 16 weeks of atherogenic diet (0.1% cholesterol, 10% calories from palm oil) consumption, LDLr-/- LCAT-/- double knockout mice, compared with LDLr-/- mice, had similar plasma concentrations of free (FC), esterified (EC), and apoB lipoprotein cholesterol, increased plasma concentrations of phospholipid and triglyceride, decreased HDL cholesterol, and 2-fold more aortic FC (142 +/- 28 versus 61 +/- 20 mg/g protein) and EC (102 +/- 27 versus 61+/- 27 mg/g). ApoE-/- LCAT-/- mice fed the atherogenic diet, compared with apoE-/- mice, had higher concentrations of plasma FC, EC, apoB lipoprotein cholesterol, and phospholipid, and significantly more aortic FC (149 +/- 62 versus 109 +/- 33 mg/g) and EC (101 +/- 23 versus 69 +/- 20 mg/g) than did the apoE-/- mice. LCAT deficiency resulted in a 12-fold increase in the ratio of saturated + monounsaturated to polyunsaturated cholesteryl esters in apoB lipoproteins in LDLr-/- mice and a 3-fold increase in the apoE-/- mice compared with their counterparts with active LCAT. We conclude that LCAT deficiency in LDLr-/- and apoE-/- mice fed an atherogenic diet resulted in increased aortic cholesterol deposition, likely due to a reduction in plasma HDL, an increased saturation of cholesteryl esters in apoB lipoproteins and, in the apoE-/- background, an increased plasma concentration of apoB lipoproteins.     

S(G), S(I), and EGP of exercise-trained middle-aged men estimated by a two-compartment labeled minimal model

To examine the effects of physical training on glucose effectiveness (S(G)), insulin sensitivity (S(I)), and endogenous glucose production (EGP) in middle-aged men, stable-labeled frequently sampled intravenous glucose tolerance tests (FSIGTT) were performed on 11 exercise-trained middle-aged men and 12 age-matched sedentary men. The time course of EGP during the FSIGTT was estimated by nonparametric stochastic deconvolution. Glucose uptake-specific indexes of glucose effectiveness (S(2*)(G) x 10(2): 0.81 +/- 0.08 vs. 0.60 +/- 0.05 dl. min(-1). kg(-1), P < 0.05) and insulin sensitivity [S(2*)(I) x 10(4): 24.59 +/- 2.98 vs. 11.89 +/- 2.36 dl. min(-1). (microU/ml)(-1). kg(-1), P < 0.01], which were analyzed using the two-compartment minimal model, were significantly greater in the trained group than in the sedentary group. Plasma clearance rate (PCR) of glucose was consistently greater in the trained men than in sedentary men throughout FSIGTT. Compared with sedentary controls, EGP of trained middle-aged men was higher before glucose load. The EGP of the two groups was similarly suppressed by approximately 70% within 10 min, followed by an additional suppression after insulin infusion. EGP returned to basal level at approximately 60 min in the trained men and at 100 min in the controls, followed by its overshoot, which was significantly greater in the trained men than in the controls. In addition, basal EGP was positively correlated with S(2*)(G) . The higher basal EGP and greater EGP overshoot in trained middle-aged men appear to compensate for the increased insulin-independent (S(2*)(G)) and -dependent (S(2*)(I)) glucose uptake to maintain glucose homeostasis.     

Insulin-like growth factor I receptor signaling is required for exercise-induced cardiac hypertrophy

The receptors for IGF-I (IGF-IR) and insulin (IR) have been implicated in physiological cardiac growth, but it is unknown whether IGF-IR or IR signaling are critically required. We generated mice with cardiomyocyte-specific knockout of IGF-IR (CIGF1RKO) and compared them with cardiomyocyte-specific insulin receptor knockout (CIRKO) mice in response to 5 wk exercise swim training. Cardiac development was normal in CIGF1RKO mice, but the hypertrophic response to exercise was prevented. In contrast, despite reduced baseline heart size, the hypertrophic response of CIRKO hearts to exercise was preserved. Exercise increased IGF-IR content in control and CIRKO hearts. Akt phosphorylation increased in exercise-trained control and CIRKO hearts and, surprisingly, in CIGF1RKO hearts as well. In exercise-trained control and CIRKO mice, expression of peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) and glycogen content were both increased but were unchanged in trained CIGF1RKO mice. Activation of AMP-activated protein kinase (AMPK) and its downstream target eukaryotic elongation factor-2 was increased in exercise-trained CIGF1RKO but not in CIRKO or control hearts. In cultured neonatal rat cardiomyocytes, activation of AMPK with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) prevented IGF-I/insulin-induced cardiomyocyte hypertrophy. These studies identify an essential role for IGF-IR in mediating physiological cardiomyocyte hypertrophy. IGF-IR deficiency promotes energetic stress in response to exercise, thereby activating AMPK, which leads to phosphorylation of eukaryotic elongation factor-2. These signaling events antagonize Akt signaling, which although necessary for mediating physiological cardiac hypertrophy, is insufficient to promote cardiac hypertrophy in the absence of myocardial IGF-I signaling.