Activation of RyR2 by class I kinase inhibitors.

BACKGROUND AND PURPOSE: Kinase inhibitors are a common treatment for cancer. Class I kinase inhibitors that target the ATP-binding pocket are particularly prevalent. Many of these compounds are cardiotoxic and can cause arrhythmias. Spontaneous release of Ca2+ via cardiac ryanodine receptors (RyR2), through a process termed store overload-induced Ca2+ release (SOICR), is a common mechanism underlying arrhythmia. We explored whether class I kinase inhibitors could modify the activity of RyR2 and trigger SOICR to determine if this contributes to the cardiotoxic nature of these compounds. EXPERIMENTAL APPROACH: The impact of class I and II kinase inhibitors on SOICR was studied in HEK293 cells and ventricular myocytes using single-cell Ca2+ imaging. A specific effect on RyR2 was confirmed using single channel recordings. Ventricular myocytes were also used to determine if drug-induced changes in SOICR could be reversed using anti-SOICR agents. KEY RESULTS: Class I kinase inhibitors increased the propensity of SOICR. Single channel recording showed that this was due to a specific effect on RyR2. Class II kinase inhibitors decreased the activity of RyR2 at the single channel level but had little effect on SOICR. The promotion of SOICR mediated by class I kinase inhibitors could be reversed using the anti-SOICR agent VK-II-86. CONCLUSIONS AND IMPLICATIONS: Part of the cardiotoxicity of class I kinase inhibitors can be assigned to their effect on RyR2 and increase in SOICR. Compounds with anti-SOICR activity may represent an improved treatment option for patients.

Sympathetic hyper-excitation in obesity and pulmonary hypertension: physiological relevance to the 'obesity paradox'.

BACKGROUND: Within the lung, sympathetic nerve activity (SNA) has an important role in facilitating pulmonary vasodilation. As SNA is elevated in obesity, we aimed to assess the impact of sympathetic hyper-excitation on pulmonary vascular homeostasis in obesity, and its potential role in ameliorating the severity of pulmonary hypertension (PH); the well-documented 'obesity paradox' phenomenon. METHODS: Zucker obese and lean rats were exposed to normoxia or chronic hypoxia (CH-10% O2) for 2 weeks. Subsequently, pulmonary SNA (pSNA) was recorded (electrophysiology), or the pulmonary microcirculation was visualized using Synchrotron microangiography. Acute hypoxic pulmonary vasoconstriction (HPV) was assessed before and after blockade of ß1-adrenergic receptors (ARs) (atenolol, 3 mg kg(-1)) and ß1+ß2-adrenergic (propranolol, 2 mg kg(-1)). RESULTS: pSNA of normoxic obese rats was higher than lean counterparts (2.4 and 0.5 µV s, respectively). SNA was enhanced following the development of PH in lean rats, but more so in obese rats (1.7 and 6.8 µV s, respectively). The magnitude of HPV was similar for all groups (for example, ~20% constriction of the 200-300 µm vessels). Although ß-blockade did not modify HPV in lean rats, it significantly augmented the HPV in normoxic obese rats (ß1 and ß2 blockade), and more so in obese rats with PH (ß2-blockade alone). Western blots showed, while the expression of pulmonary ß1-ARs was similar for all rats, the expression of ß2-ARs was downregulated in obesity and PH. CONCLUSIONS: This study suggests that sympathetic hyper-excitation in obesity may have an important role in constraining the severity of PH and, thus, contribute in part to the 'obesity paradox' in PH.

Influence of adiposity on tonic sympathetic support of resting metabolism in healthy adults.

BACKGROUND: beta-Adrenergic receptor sympathetic nervous system (beta-AR SNS) support of resting metabolic rate (RMR) is attenuated with older age, female sex, and a sedentary lifestyle. Total and abdominal adiposity and/or body fat pattern modulate some SNS-mediated physiological functions. OBJECTIVE: To determine if total and abdominal adiposity and/or body fat distribution are independently related to SNS support of RMR. DESIGN: Cross-sectional comparison of beta-AR SNS support of RMR. SUBJECTS: A total of 54 healthy male and female subjects aged 18-75 y. MEASUREMENTS: RMR (ventilated hood, indirect calorimetry) before (baseline) and during complete beta-AR blockade; body composition by dual energy X-ray absorptiometry. RESULTS: Forward stepwise multiple regression analysis using sex, exercise status, age group, %body fat, total adiposity, abdominal adiposity, and the ratio of abdominal adiposity to hip adiposity as variables revealed sex to be the strongest predictor, explaining 21% of the variability in beta-AR SNS support of RMR (P=0.0006). Age group explained an additional 4% and exercise status a further 4% (both P=0.10). %Body fat, total adiposity, abdominal adiposity, and the ratio of abdominal adiposity to hip adiposity did not enter the equation. CONCLUSION: Total and abdominal adiposity and body fat pattern are not independent physiological determinants of beta-AR SNS support of RMR among healthy men and women. Moreover, further support is provided for our previous finding of attenuated beta-AR SNS support of RMR with age, female sex, and sedentary lifestyle.

Altered autonomic support of arterial blood pressure with age in healthy men.

BACKGROUND: Primary aging is associated with changes in the autonomic nervous system (ANS), but the functional significance of these changes for systemic circulatory control of arterial blood pressure (BP) is unknown. We tested the hypothesis that ANS support of BP is altered in healthy older humans. METHODS AND RESULTS: A total of 23 young (aged 24+/-1 years; systolic/diastolic BP, 126+/-2/66+/-1 mm Hg) and 16 older (aged 65+/-1 years; systolic/diastolic BP, 125+/-3/62+/-2 mm Hg) healthy men were studied before and during ganglionic blockade (intravenous trimethaphan). The reduction in mean BP (radial artery catheter) with trimethaphan was almost twice as great in the older men (-33+/-2 versus -19+/-2 mm Hg; -40% versus -22% of baseline; P<0.01) due to a lack of increase in heart rate (3+/-2 versus 25+/-2 bpm; P<0.001) and cardiac output (-0.42+/-0.19 versus 1.01+/-0.26 L/min; P<0.001); the decreases in systemic vascular resistance were not different. The absence of tachycardia in the older men was associated with reduced baseline heart rate variability (HRV, P<0.05); the change in heart rate with trimethaphan correlated with the standard deviation of the R-R intervals (HRV(SD R-R interval); r=0.57, P<0.001). Among individual subjects (pooled groups), the reductions in mean BP with trimethaphan were most strongly related to measures of sympathetic activity (r=0.58 to 0.67, P<0.005), change in mean BP with intravenous phenylephrine (r=0.57, P<0.001), and HRV(SD R-R interval) (r=-0.40, P<0.01). CONCLUSIONS: ANS support of BP is altered with age in healthy men due to less cardiac vagal inhibition of heart rate and cardiac output. Basal sympathetic activity and alpha-adrenergic vascular sensitivity are also key physiological correlates of ANS support of BP in healthy men.

Tonic sympathetic support of metabolic rate is attenuated with age, sedentary lifestyle, and female sex in healthy adults.

We recently demonstrated in young adult humans that the sympathetic nervous system contributes to the control of resting metabolic rate via tonic beta-adrenergic receptor stimulation. In the present follow-up study we determined the respective effects of age, habitual exercise status, and sex on this regulatory mechanism. Resting metabolic rate (ventilated hood, indirect calorimetry) was determined in 55 healthy sedentary or endurance exercise-trained adults, aged 18-35 or 60-75 yr (29 men and 26 women), before (baseline) and during the infusion of either a nonselective beta-adrenergic receptor antagonist (propranolol) or saline (control). Relative to baseline values, during beta-adrenergic receptor antagonism resting metabolic rate adjusted for fat-free mass was reduced to a lesser extent in older (mean +/- SE, -130 +/- 46 kJ/d) compared with young (-297 +/- 46) adults, sedentary (-151 +/- 50) compared with endurance exercise-trained (-268 +/- 46) adults, and women (-105 +/- 33) compared with men (-318 +/- 50; all P < 0.01). Reductions in resting metabolic rate during beta-adrenergic receptor antagonism were positively related to higher baseline resting metabolic rate and plasma catecholamine concentrations and negatively related to adiposity (all P < 0.05). Resting metabolic rate was unchanged in response to saline control in all groups. These results provide experimental support for the hypothesis that aging, sedentary living, and female sex are associated with attenuated sympathetic nervous system support of resting metabolic rate in healthy adult humans.

Age-related decline in RMR in physically active men: relation to exercise volume and energy intake.

We tested the hypothesis that resting metabolic rate (RMR) declines with age in physically active men (endurance exercise > or =3 times/wk) and that this decline is related to weekly exercise volume (h/wk) and/or daily energy intake. Accordingly, we studied 137 healthy adult men who had been weight stable for > or =6 mo: 32 young [26 +/- 1 (SE) yr] and 34 older (62 +/- 1 yr) sedentary males (internal controls); and 39 young (27 +/- 1 yr) and 32 older (63 +/- 2 yr) physically active males (regular endurance exercise). RMR was measured by indirect calorimetry (ventilated hood system) after an overnight fast and approximately 24 h after exercise. Because RMR is related to fat-free mass (FFM; r = 0.76, P < 0.001, current study), FFM was covaried to adjust RMR (RMR(adj)). RMR(adj) was lower with age in both the sedentary (72.0 +/- 2.0 vs. 64.0 +/- 1.3 kcal/h, P < 0.01) and the physically active (76.6 +/- 1.1 vs. 67.9 +/- 1.2 kcal/h, P < 0.01) males. In the physically active men, RMR(adj) was related to both exercise volume (no. of h/wk, regardless of intensity; r = 0.56, P < 0.001) and estimated energy intake (r = 0.58, P < 0.001). Consistent with these relations, RMR(adj) was not significantly different in subgroups of young and older physically active men matched either for exercise volume (h/wk; n = 11 each) or estimated energy intake (kcal/day; n = 6 each). These results indicate that 1) RMR, per unit FFM, declines with age in highly physically active men; and 2) this decline is related to age-associated reductions in exercise volume and energy intake and does not occur in men who maintain exercise volume and/or energy intake at a level similar to that of young physically active men.

The aging cardiovascular system: changes in autonomic function at rest and in response to exercise.

Tonic vagal modulation of cardiac period (R-R interval) decreases with advancing age, but is greater in middle-aged and older adults who habitually perform aerobic exercise compared with their sedentary peers. Cardiovagal baroreflex sensitivity also declines markedly with age in sedentary adults but only 50% as much in regularly exercising adults. In previously sedentary middle-aged and older adults, a 3-month program of moderate aerobic exercise increases cardiovagal baroreflex sensitivity by 25%. Tonic (basal) sympathetic nervous system (SNS) activity increases with advancing age in both sedentary and habitually exercising adults. Despite this, SNS beta-adrenergic support of energy metabolism (resting metabolic rate--RMR) declines with age in sedentary individuals. However, SNS beta-adrenergic support of RMR is maintained with age in endurance exercise-trained adults and therefore is much greater in middle-aged and older individuals who exercise regularly compared with their sedentary peers. Thus, regular aerobic (endurance) exercise modulates selective age-associated impairments in autonomic nervous system-physiological function.

Relation of leptin and insulin to adiposity-associated elevations in sympathetic activity with age in humans.

OBJECTIVE: To determine whether plasma leptin and insulin concentrations are related to adiposity-associated elevations in muscle sympathetic nerve activity (MSNA) with age in healthy adult humans. DESIGN: Cross-sectional investigation of young and older adult men. SUBJECTS: Thirty healthy adult men, 16 young (25+/-1 y, mean+/-s.e.) and 14 older (61+/-1 y). MEASUREMENTS/RESULTS: The older men had higher (P<0.05) levels of body mass, BMI, total fat mass and truncal fat mass (dual energy X-ray absorptiometry) than the young men. MSNA burst frequency (microneurography) was approximately 75% higher in the older men (P<0.001). Plasma leptin concentrations were approximately 150% higher (P<0.01), whereas plasma insulin concentrations were approximately 70% higher (P<0.05) in the older subjects. MSNA was related to both total (r=0.51, P<0.01) and truncal (r=0.56, P<0.01) fat mass. Plasma leptin concentrations were related to total and truncal fat mass (both r=0.83, P<0.001), and to MSNA (r=0.49, P<0.01). Plasma insulin concentrations were related to MSNA (r=0.38, P<0.05). We used partial correlation analyses to assess whether leptin and/or insulin are potential contributors to the relation between body fat and MSNA. Adjusting for the effects of plasma leptin, but not insulin, concentrations eliminated the significant relations between MSNA and total and truncal fat mass. CONCLUSION: Our results: (1) demonstrate a positive relation between MSNA and plasma leptin concentrations in young and older healthy men; and (2) support the concept that circulating leptin concentrations may act as a humoral signal contributing to adiposity-associated elevations in MSNA with age in adult humans.

Identification of an IFN-gamma responsive region in an intron of the invariant chain gene.

The mechanism by which IFN-gamma up-regulates invariant chain mRNA in antigen-presenting cells has been under intensive investigation. This study shows that in murine monocytic cells the transcriptional up-regulation mediated by the invariant chain (Ii) upstream enhancer only accounts for part of the induction of Ii mRNA by IFN-gamma. We have identified an intronic region in the murine Ii gene that contributes to the transcriptional up-regulation by IFN-gamma. The region has S (H), X/X2 and Y boxes similar to those in MHC class II promoters and the Ii upstream enhancer. Mutations at the putative S, X and Y boxes have abolished the ability of the region to mediate Ii up-regulation by IFN-gamma. Consistent with the functions of these boxes, our findings reveal that the up-regulation of Ii transcription by IFN-gamma mediated by the intronic region is dependent on the induction of class II transactivator by IFN-gamma.

Age-associated arterial wall thickening is related to elevations in sympathetic activity in healthy humans.

Arterial wall hypertrophy occurs with age in humans and is a strong predictor of cardiovascular disease risk. The responsible mechanism is unknown, but data from studies in experimental animals suggest that elevated sympathetic-adrenergic tone may be involved. To test this hypothesis in humans we studied 11 young (29 +/- 1 yr; means +/- SE) and 13 older (63 +/- 1) healthy normotensive men under supine resting conditions. Muscle sympathetic nerve activity (MSNA) burst frequency (peroneal microneurography) was 70% higher in the older men (39 +/- 1 vs. 23 +/- 2 bursts/min; P < 0.001). Femoral artery intima media thickness (IMT; B-mode ultrasound) and the femoral IMT-to-lumen diameter ratio (IMT/lumen) were approximately 75% greater in the older men (both P < 0.001). Femoral IMT (r = 0. 82) and the femoral IMT/lumen (r = 0.85) were strongly and positively related to MSNA (both P < 0.001). The significant age group differences in femoral IMT and the IMT/lumen were abolished when the influence of MSNA was removed. In contrast, the relationship between MSNA and femoral wall thickness remained significant after removing the influence of age. We conclude that 1) primary aging is associated with femoral artery hypertrophy in humans and 2) this is strongly related to elevations in sympathetic nerve activity to the vasculature. These results support the hypothesis that tonic elevations in sympathetic nerve activity may be an important mechanism in the arterial remodeling that occurs with human aging.

Lack of age-associated elevations in 24-h systolic and pulse pressures in women who exercise regularly.

We tested the hypothesis that the elevations in 24-h arterial systolic (SBP) and pulse (PP) pressures with age in sedentary adult females are absent or smaller in women who exercise regularly. Four groups of healthy normotensive women were studied: premenopausal (n = 12; 29 +/- 1 yr, mean +/- SE) and postmenopausal (n = 20; 62 +/- 1) sedentary, and premenopausal (n = 14; 30 +/- 1) and postmenopausal (n = 12; 58 +/- 1) endurance-exercise trained (distance runners). In the sedentary group, 24-h SBP and PP (Spacelabs ambulatory monitor 90207) were approximately 10 mmHg higher (P < 0.05) in the postmenopausal women than in the premenopausal controls; this was because of higher daytime and nighttime SBP and PP levels in the postmenopausal women. In contrast, 24-h, daytime and nighttime SBP and PP were not different with age in the endurance-trained women. SBP variability and SBP load (% of all recordings > 140 mmHg) generally were greater with age in the sedentary women (e.g., SBP load = 14 +/- 4 vs. 3 +/- 1%, P < 0.05) but not in the endurance-trained women. In the pooled population, 24-h SBP and PP were related to waist-to-hip ratio (measure of abdominal adiposity) (r = 0.48 and 0.49, respectively, P < 0.001) and carotid augmentation index (measure of arterial stiffness) (r = 0.43 and 0.53, P < 0.005). In the sedentary women, accounting for the influence of either of these factors eliminated the significant age-associated differences in 24-h SBP and PP (P > 0.3). Our results suggest that the elevations in 24-h SBP and PP with age in sedentary adult females may not occur in women who regularly perform endurance exercise. This appears to be related to the absence of age-associated increases in abdominal adiposity and arterial stiffness in the exercising women.

Limb blood flow and vascular conductance are reduced with age in healthy humans: relation to elevations in sympathetic nerve activity and declines in oxygen demand.

BACKGROUND: We tested the hypothesis that basal (resting) limb blood flow and vascular conductance are reduced with age in adult humans and that these changes are related to elevations in sympathetic vasoconstrictor nerve activity and reductions in limb oxygen demand. METHODS AND RESULTS: Sixteen young (28+/-1 years; mean+/-SEM) and 15 older (63+/-1 years) healthy normotensive adult men were studied. Diastolic blood pressure and body fat were higher (P<0.005) in the older men, but there were no other age-related differences in subject characteristics. Femoral artery blood flow (Doppler ultrasound) was 26% lower in the older men (P<0.005), despite similar levels of cardiac output (systemic arterial blood flow) in the 2 groups. Femoral artery vascular conductance was 32% lower and femoral vascular resistance was 45% higher in the older men (P<0. 005). Muscle sympathetic nerve activity (peroneal microneurography) was 74% higher in the older men (P<0.001) and correlated with femoral artery blood flow (r=-0.55, P<0.005), vascular conductance (r=-0.65, P<0.001), and vascular resistance (r=0.61, P<0.001). The age-related differences in femoral hemodynamics were no longer significant after correction for the influence of muscle sympathetic nerve activity. There were no significant age-group differences in leg tissue mass (by dual-energy x-ray absorptiometry), but estimated leg oxygen consumption was 15% lower in the older men (P<0.001). Femoral artery blood flow was directly related to estimated leg oxygen consumption (r=0.78, P<0.001). The age-group differences in femoral artery blood flow were no longer significant after correction for estimated leg oxygen consumption by ANCOVA. CONCLUSIONS: (1) Basal whole-leg arterial blood flow and vascular conductance are reduced with age in healthy adult men; (2) these changes are associated with elevations in sympathetic vasoconstrictor nerve activity; and (3) the lower whole-limb blood flow is related to a lower oxygen demand that is independent of tissue mass.

Calcineurin and vacuolar-type H+-ATPase modulate macrophage effector functions.

While effector molecules produced by activated macrophages (including nitric oxide, tumor necrosis factor alpha, interleukin 1, etc.) help to eliminate pathogens, high levels of these molecules can be deleterious to the host itself. Despite their importance, the mechanisms modulating macrophage effector functions are poorly understood. This work introduces two key negative regulators that control the levels and duration of macrophage cytokine production. Vacuolar-type H+-ATPase (V-ATPase) and calcineurin (Cn) constitutively act in normal macrophages to suppress expression of inflammatory cytokines in the absence of specific activation and to inhibit macrophage cytokine responses induced by bacterial lipopolysaccharide (V-ATPase), interferon gamma (V-ATPase and Cn), and calcium (Ca2+) flux (Cn). Cn and V-ATPase modulate effector gene expression at the mRNA level by inhibiting transcription factor NF-kappaB. This negative regulation by Cn is opposite to its crucial positive role in T cells, where it activates NFAT transcription factor(s) leading to expression of interleukin 2, tumor necrosis factor alpha, and other cytokine genes. The negative effects of V-ATPase and Cn on NF-kappaB-dependent gene expression are not limited to the macrophage lineage, as similar effects have been seen with a murine fibroblast cell line and with primary astrocytes.

Influence of gender on the sympathetic neural adjustments to alterations in systemic oxygen levels in humans.

The purpose of this investigation was to determine whether gender influences the muscle sympathetic nerve activity (MSA) and systemic cardiovascular adjustments to alterations in systemic oxygen levels. To accomplish this, we performed direct (intraneural) measurements of muscle sympathetic nerve activity in 11 male and seven female young healthy adults during room air breathing, moderate isocapnic hypoxaemia and hyperoxaemia. During hypoxaemia, arterial oxygen saturation declined similarly in men and women. The magnitudes of the peak increases in MSA and stimulus-response 'gain' were not different between groups. However, the women had a shorter latency of response (P < 0.05). Women also demonstrated a greater increase in heart rate and a modest elevation in diastolic blood pressure, whereas the ventilatory responses were identical in the two groups. During normoxic recovery, MSA returned to baseline more quickly in women than in men (P < 0.05). During hyperoxaemia, muscle sympathetic nerve activity decreased only in the men (P < 0.05). Heart rate decreased slightly (P < 0.05) in both men and women, whereas blood pressure and minute ventilation were unchanged from normoxic control levels. Our findings fail to support an effect of gender on the peak muscle sympathetic nerve activity response to moderate isocapnic hypoxaemia in healthy young adult humans, although women demonstrate a shorter latency for sympathoexcitation and recovery under these conditions. In response to hyperoxaemia, women fail to demonstrate the sympathoinhibition consistently observed in men, possibly because of the low resting levels of MSA characteristic of young adult women. Thus, gender appears to contribute to the interindividual variability in sympathetic and cardiovascular responses to alterations in systemic oxygen levels.

Elevated heart rate variability in physically active young and older adult women.

1. Low heart rate variability is associated with an increased risk of cardiac sudden death, coronary heart disease and all-cause mortality. We have previously shown that physically active postmenopausal women demonstrate higher levels of heart rate variability and cardiac baroreflex sensitivity compared to their sedentary peers. The purpose of the present prospective study was to test the hypothesis that heart rate variability and cardiac baroreflex sensitivity would be reduced with age in sedentary but not physically active women. To accomplish this, we measured heart rate variability (both time and frequency domain) and spontaneous cardiac baroreflex sensitivity (SBRS, sequence method) in the sitting posture in 23 sedentary women [11 premenopausal and 12 postmenopausal (age, 28 +/- 1 and 61 +/- 2 years; VO2max, 35.3 +/- 1.4 and 21.7 +/- 1.5 ml.min-1.kg-1 respectively] and in 22 physically active women [12 premenopausal and 10 postmenopausal (age, 31 +/- 1 and 59 +/- 2 years; VO2max, 52.5 +/- 1.4 and 39.7 +/- 1.8 ml.min-1.kg-1)]. 2. The S.D. of the R-R interval (time domain) was reduced (P < 0.05) with age in both sedentary (52 +/- 6 versus 33 +/- 4 ms) and physically active women (72 +/- 8 versus 49 +/- 9 ms). The high-frequency power (3740 +/- 1527 versus 915 +/- 188 and 9516 +/- 2849 versus 2803 +/- 1083 ms2/Hz), total power of heart rate variability and SBRS (11 +/- 2 versus 7 +/- 2 and 19 +/- 3 versus 13 +/- 2 ms/mmHg) also demonstrated similar age-related reductions in sedentary and physically active women, respectively (all P < 0.05). The S.D. of the R-R interval, high-frequency and total power of heart rate variability, and SBRS were higher (all P < 0.05) in the physically active compared with the sedentary women at any age. There was no significant influence of age or physical activity status on the low-frequency power of heart rate variability. In addition, no significant differences in any of the time or frequency domain measures of heart rate variability or SBRS were observed in users compared with non-users of hormone replacement therapy. 3. The results of the present study suggest that heart rate variability and cardiac baroreflex sensitivity decline similarly with age in healthy sedentary and physically active women. However, physically active women demonstrate higher levels of heart rate variability and cardiac baroreflex sensitivity compared with their sedentary peers, regardless of age.

Hemodynamic sequelae of age-related increases in arterial stiffness in healthy women.

Stiffening of central arteries is believed to contribute to the increase in the incidence of cardiovascular disease with age, presumably through its adverse influence on arterial blood pressure. We found that (1) the physiologic link between age-related increases in arterial stiffness and blood pressure appears to be elevated systemic vascular resistance, and (2) increased arterial stiffness and systemic vascular resistance with age were inversely related to blood volume, stroke volume, and cardiac output.

Smaller differences in total and regional adiposity with age in women who regularly perform endurance exercise.

Our aim was to determine if women who regularly perform endurance exercise demonstrate age-related elevations in body mass and adiposity. Ninety-five healthy females were studied: premenopausal (n = 28; mean +/- SE age 30 +/- 1 yr) and postmenopausal (n = 31; 56 +/- 1 yr) endurance-trained runners and premenopausal (n = 17; 29 +/- 1 yr) and postmenopausal (n = 19; 61 +/- 1 yr) sedentary controls. In the runners, body mass did not differ across age, but percent fat and fat mass were higher (P < 0.05) in the postmenopausal women. The age-related difference in total body fat, however, was only approximately 50% as great (P < 0.01) as that observed in the sedentary controls due in part to smaller age-related differences in central (truncal) fat. The higher fat mass in the postmenopausal runners was modestly (inversely) related to both exercise volume (r = -0.44, P < 0.01) and maximal oxygen consumption (r = -0.41, P < 0.01). The present findings provide experimental support for the hypothesis that women who regularly engage in vigorous endurance exercise may not gain body weight, undergo only a modest increase in total body fat, and do not demonstrate a significant elevation in central adiposity with age.

Influence of body fatness on the coronary risk profile of physically active postmenopausal women.

We have shown previously that endurance-trained postmenopausal runners demonstrate more favorable coronary heart disease (CHD) risk factors compared with age-matched sedentary women. However, the runners exhibited higher levels of physical activity and lower levels of body fatness, both of which can influence CHD risk factors. To gain insight into the influence of body fatness per se, we studied 38 postmenopausal healthy women: 10 swimmers, 10 runners, and nine obese and nine leaner sedentary subjects matched for age, hormone replacement use, and years postmenopause. Swimmers and runners were further matched for exercise training volume (4.5+/-0.2 v 4.6+/-0.6 h/wk) and relative competitive performance (79%+/-5% v 77+/-3% of age-adjusted world record). Maximal oxygen consumption (VO2max) on the treadmill was lower (P < .01) in swimmers versus runners. Body mass (65.0+/-2.0 v 59.0+/-1.3 kg), percent body fat (29%+/-2% v 23%+/-2%), and waist circumference (79+/-3 v 71+/-1 cm) were greater (P < .01) in swimmers than in runners. There were no significant differences in total caloric intake or dietary composition between swimmers and runners. Insulin sensitivity (via Bergman's minimal model) and fasting plasma concentrations of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), glucose, and plasminogen activator inhibitor-1 (PAI-1) activity were not different between the groups. However, plasma high-density lipoprotein cholesterol (HDL-C), HDL2-C, HDL-C/TC, insulin, fibrinogen, fibrin D-dimer, PAI antigen, tissue plasminogen activator (t-PA) activity, and t-PA antigen levels all were less favorable (P < .05) in swimmers versus runners. Daytime, nighttime, and 24-hour systolic blood pressure (SBP) was 6 to 10 mm Hg higher in swimmers compared with runners, but resting blood pressure, 24-hour blood pressure load, and blood pressure variability were not significantly different. Stepwise regression showed that measures of body fatness were the primary independent determinants of most of the metabolic CHD risk factors. When analysis of covariance (ANCOVA) was performed with body fatness as a covariate, differences in CHD risk factors between swimmers and runners were abolished (P=.18 to .90). We conclude that among endurance-trained postmenopausal women matched for training volume and competitive eliteness, higher total and abdominal body fatness is, in general, associated with a less favorable metabolic CHD risk profile. Thus, high levels of habitual aerobic exercise do not appear to negate the deleterious effects of adiposity on the coronary risk profile of healthy middle-aged and older women.

Role of central circulatory factors in the fat-free mass-maximal aerobic capacity relation across age.

Fat-free mass (FFM) (primarily skeletal muscle mass) is related to maximal aerobic capacity among healthy humans across the adult age range. The basis for this physiological association is assumed to be a direct relation between skeletal muscle mass and its capacity to consume oxygen. We tested the alternative hypothesis that FFM exerts its influence on maximal aerobic capacity in part via an association with central circulatory function. To do so, we analyzed data from 103 healthy sedentary adults aged 18-75 yr. FFM was strongly and positively related to maximal oxygen consumption (r = 0.80, P < 0. 001). FFM was also strongly and positively related to supine resting levels of blood volume (r = 0.79, P < 0.001) and stroke volume (r = 0.75, P < 0.001). Statistically controlling for the collective influences of blood volume and stroke volume abolished the tight relation between FFM and maximal oxygen consumption (r = 0.12, not significant). These results indicate that 1) FFM may be an important physiological determinant of blood volume and stroke volume among healthy sedentary adult humans of varying age; and 2) this relation between FFM and central circulatory function appears to represent the primary physiological basis for the strong association between FFM and maximal aerobic capacity in this population. Our findings suggest that sarcopenia (loss of skeletal muscle mass with aging) may contribute to the age-related decline in maximal aerobic capacity primarily via reductions in blood volume and stroke volume rather than a direct effect on the oxygen-consuming potential of muscle per se.

The invariant chain gene intronic enhancer shows homology to class II promoter elements.

Coordinate expression of MHC class II proteins and the class II-associated invariant chain (Ii) is important for proper MHC class II functioning in Ag processing and presentation. The coordinate regulation of these genes results, in part, from the sharing of transcriptional regulatory regions between MHC class II and Ii genes; the Ii has previously been shown to have an upstream enhancer closely related to the essential class II promoter elements. We report here the characterization of a second enhancer in the Ii gene, located within the first intron. This intronic enhancer is contained within a 155-bp region, enhances transcription from the Ii minimal promoter, and also contains elements that are homologous to class II promoter elements X1, X2, and Y boxes.