Effect of Exercise Training on Lipoprotein Subclass Particle Concentrations and Sizes in Older Women: Results from a Randomized Controlled Trial.

BACKGROUND: Evidence suggests that lipoprotein subclass particles are critical markers of cardiovascular disease (CVD) risk. Older women have increased CVD risk related to age. The purpose of this study was to determine whether low and moderate doses of exercise influence lipoprotein subclasses. METHODS: Women (60-75 years) were randomized into groups for 16 weeks of moderate-intensity exercise training at a low or moderate dose (33.6 and 58.8 kJ/kg body weight weekly, respectively). Lipoprotein subclasses were determined by nuclear magnetic resonance spectroscopy before and after the training. RESULTS: The average weekly exercise duration was 109 and 164 min, for low- and moderate-dose groups, respectively. In the low-dose group, high-density lipoprotein particle (HDL-P) concentration decreased (Δ = -1.9 ± 3.1 µmol/L, mean ± SD, p = 0.002) and mean HDL-P size increased (Δ = 0.1 ± 0.3 nm, p = 0.028). In the moderate-dose group, mean HDL-P size (Δ = 0.1 ± 0.2 nm; p = 0.024) and low-density lipoprotein particle size increased (Δ = 0.4 ± 3.9 nm; p = 0.007). Baseline body mass index, peak oxygen consumption and age were associated with changes in a few lipoprotein subclasses. CONCLUSIONS: In this sample of inactive older women, moderate-intensity exercise training at a dose equivalent to or even lower than the minimally recommended level by public health agencies induced changes in lipoprotein subclasses in line with reduced CVD risk. However, higher doses are encouraged for greater health benefits.

Lactate dehydrogenase regulation in aged skeletal muscle: Regulation by anabolic steroids and functional overload.

Aging alters the skeletal muscle response to overload-induced growth. The onset of functional overload is characterized by increased myoblast proliferation and an altered muscle metabolic profile. The onset of functional overload is associated with increased energy demands that are met through the interconversion of lactate and pyruvate via the activity of lactate dehydrogenase (LDH). Testosterone targets many of the processes activated at the onset of functional overload. However, the effect of aging on this metabolic plasticity at the onset of functional overload and how anabolic steroid administration modulates this response is not well understood. The purpose of this study was to determine if aging would alter overload-induced LDH activity and expression at the onset of functional overload and whether anabolic steroid administration would modulate this response. Five-month and 25-month male Fischer 344xF1 BRN were given nandrolone decanoate (ND) or sham injections for 14days and then the plantaris was functionally overloaded (OV) for 3days by synergist ablation. Aging reduced muscle LDH-A & LDH-B activity 70% (p<0.05). Aging also reduced LDH-A mRNA abundance, however there was no age effect on LDH-B mRNA abundance. In 5-month muscle, both ND and OV decreased LDH-A and LDH-B activity. However, there was no synergistic or additive effect. In 5-month muscle, ND and OV decreased LDH-A mRNA expression with no change in LDH-B expression. In 25-month muscle, ND and OV increased LDH-A and LDH-B activity. LDH-A mRNA expression was not altered by ND or OV in aged muscle. However, there was a main effect of OV to decrease LDH-B mRNA expression. There was also an age-induced LDH isoform shift. ND and OV treatment increased the "fast" LDH isoforms in aged muscle, whereas ND and OV increased the "slow" isoforms in young muscle. Our study provides evidence that aging alters aspects of skeletal muscle metabolic plasticity normally induced by overload and anabolic steroid administration.

Musculoskeletal changes in mice from 20-50 cGy of simulated galactic cosmic rays.

On a mission to Mars, astronauts will be exposed to a complex mix of radiation from galactic cosmic rays. We have demonstrated a loss of bone mass from exposure to types of radiation relevant to space flight at doses of 1 and 2 Gy. The effects of space radiation on skeletal muscle, however, have not been investigated. To evaluate the effect of simulated galactic cosmic radiation on muscle fiber area and bone volume, we examined mice from a study in which brains were exposed to collimated iron-ion radiation. The collimator transmitted a complex mix of charged secondary particles to bone and muscle tissue that represented a low-fidelity simulation of the space radiation environment. Measured radiation doses of uncollimated secondary particles were 0.47 Gy at the proximal humerus, 0.24-0.31 Gy at the midbelly of the triceps brachii, and 0.18 Gy at the proximal tibia. Compared to nonirradiated controls, the proximal humerus of irradiated mice had a lower trabecular bone volume fraction, lower trabecular thickness, greater cortical porosity, and lower polar moment of inertia. The tibia showed no differences in any bone parameter. The triceps brachii of irradiated mice had fewer small-diameter fibers and more fibers containing central nuclei. These results demonstrate a negative effect on the skeletal muscle and bone systems of simulated galactic cosmic rays at a dose and LET range relevant to a Mars exploration mission. The presence of evidence of muscle remodeling highlights the need for further study.

Modulation of overload-induced inflammation by aging and anabolic steroid administration.

Aging can alter the skeletal muscle growth response induced by overload. The initiation of overload induces muscle extracellular matrix expansion, increased cellularity, and inflammatory gene expression, which are all related to processes important for myofiber growth. These remodeling processes are also biological targets of testosterone. It is not certain how aging affects the inflammatory response to functional overload and whether anabolic steroid administration can alter this response. The effect of anabolic steroid administration on inflammatory processes during functional overload is not known. The purpose of this study was to determine if age altered the skeletal muscle inflammatory response at the onset of functional overload and whether anabolic steroid administration would modulate this response in young or older animals. Five-month and 25 month F344 x BRN rats were given nandrolone decanoate (ND) (6 mg/kg bw/wk) or sham injections for 3 weeks, and then the soleus muscle was overloaded (OV) for 3 days by synergist ablation. ND alone induced a 230% increase in ED1(+) cells in 5 month muscle. Three days of OV had no effect on ED1(+) cell number at either age. OV combined with ND induced a 90% increase in ED2(+) cells in 5 month muscle, while there was no effect of either treatment alone at this age. In 25 month muscle, OV induced a 40% increase in ED2(+) cells. Regardless of age, OV induced muscle TNF-alpha mRNA expression (300%) and IL-6 mRNA expression (900%). ND attenuated OV-induced IL-6 mRNA but not TNF-alpha expression in both age groups. The overload induction of IL-1beta mRNA was 3-fold greater in 25 month muscle (1400%), compared to 5 month muscle (400%). ND administration ablated the overload IL-1beta mRNA induction in 25 month muscle. Anabolic steroid administration can suppress inflammatory cytokine gene expression at the onset of overload and this effect is age dependent.

Nandrolone decanoate modulates cell cycle regulation in functionally overloaded rat soleus muscle.

Functionally overloading rat soleus muscle by synergist ablation induces a rapid increase in mass. Muscle remodeling during the first week of overload is critical for the overload-induced growth. Anabolic steroid modulation of this overload-induced remodeling response is not well understood. The purpose of this study was to determine whether pretreatment with nandrolone decanoate, a clinically administered anabolic steroid, alters muscle morphology and gene expression related to muscle growth during the initiation of functional overload in the rat soleus muscle. Adult (5 mo) male Fisher 344 x Brown Norway rats were randomly assigned to control (Sham), 3-day functional overload (OV), nandrolone decanoate administration (ND), or 3-day functional overload with nandrolone decanoate administration (OV+ND) treatment groups. Morphologically, OV increased the percentage of small (361%) and large (150%) fibers and expanded the ECM 50%. ND administration decreased the 3-day OV induction of small fibers 51% and nuclei associated with the ECM 20%. ND administration also attenuated the induction of cell cycle regulator p21 (64%) and myogenin (37%) mRNAs after 3 days of overload. These data demonstrate that nandrolone decanoate pretreatment can alter morphological and cell cycle regulator expression related to muscle growth at the onset of functional overload.

Lactate dehydrogenase expression at the onset of altered loading in rat soleus muscle.

Both functional overload and hindlimb disuse induce significant energy-dependent remodeling of skeletal muscle. Lactate dehydrogenase (LDH), an important enzyme involved in anaerobic glycolysis, catalyzes the interconversion of lactate and pyruvate critical for meeting rapid high-energy demands. The purpose of this study was to determine rat soleus LDH-A and -B isoform expression, mRNA abundance, and enzymatic activity at the onset of increased or decreased loading in the rat soleus muscle. The soleus muscles from male Sprague-Dawley rats were functionally overloaded for up to 3 days by a modified synergist ablation or subjected to disuse by hindlimb suspension for 3 days. LDH mRNA concentration was determined by Northern blotting, LDH protein isoenzyme composition was determined by zymogram analysis, and LDH enzymatic activity was determined spectrophotometrically. LDH-A mRNA abundance increased by 372%, and LDH-B mRNA abundance decreased by 43 and 31% after 24 h and 3 days of functional overload, respectively, compared with that in control rats. LDH protein expression demonstrated a shift by decreasing LDH-B isoforms and increasing LDH-A isoforms. LDH-B activity decreased 80% after 3 days of functional overload. Additionally, LDH-A activity increased by 234% following 3 days of hindlimb suspension. However, neither LDH-A or LDH-B mRNA abundance was affected following 3 days of hindlimb suspension. In summary, the onset of altered loading induced a differential expression of LDH-A and -B in the rat soleus muscle, favoring rapid energy production. Long-term altered loading is associated with myofiber conversion; however, the rapid changes in LDH at the onset of altered loading may be involved in other physiological processes.

RhoA induction by functional overload and nandrolone decanoate administration in rat skeletal muscle.

The regulation of skeletal muscle regeneration and growth in response to functional overload is a coordinated interaction of mechanical and endocrine signaling pathways. This study's purpose was to determine if RhoA expression and activity in rat plantaris muscle was induced by functional overload with or without anabolic steroid administration. Male Sprague Dawley (125 g) rats were subjected to bilateral ablation of the gastrocnemius muscle for 3 and 21 days and treated with nandrolone decanoate (ND, 6 mg/kg b.w.) or sesame seed oil injections. Western blot analysis revealed that RhoA protein expression was induced 2.1-fold by overload and 1.9-fold by ND at 3 days. RhoA protein remained elevated by overload after 21 days (3.8-fold). In addition, RhoA protein expression in C2C12 myotubes was induced after 18 h of 1% (1.8-fold) or 2% (2.2-fold) chronic radial stretch. Competitive RT PCR revealed that RhoA mRNA concentration increased 1.9-fold with ND, 2.9-fold with overload, and 11.8-fold with overload and ND administration when compared to sham at 3 days, indicating pre-translational control of RhoA by ND and a synergism between ND and overload to up-regulate RhoA mRNA. The ratio of RhoA protein associated with the muscle membrane fraction, an indicator of RhoA activity, increased 3.7-fold after 3 days of overload compared to controls. Although ND with overload (3.8-fold) produced a larger induction of RhoA protein than overload alone, the ratio of RhoA protein associated with the membrane fraction was not altered by ND treatment at 3 days. In conclusion, RhoA is an integrator of both mechanical and growth factor signaling whose expression and activity are increased by the combination of anabolic steroid and functional overload treatments in rat plantaris muscle.

Regulation of androgen receptor expression at the onset of functional overload in rat plantaris muscle.

Skeletal muscle androgen receptor (AR) expression at the onset of functional overload (OV) has not been well described. It is also not known if overload and/or anabolic steroid differentially regulate AR expression. The purpose of this study was to examine AR gene expression at the onset of functional OV in rat plantaris muscle with and without nandrolone decanoate (ND) administration. The functional significance of AR protein induction was examined using skeletal alpha-actin promoter activity in transiently transfected CV-1 fibroblast cells. Male Sprague-Dawley rats ( approximately 125 g) were functionally overloaded for 1, 3, 7, or 21 days. A subset of animals was given an ND (6 mg/kg) injection at day 0 and then overloaded for 3 days. Control animals underwent sham surgeries. AR protein concentration increased 106 and 279% after 7 and 21 days of OV, respectively. AR mRNA increased 430% after 7 days of OV. AR protein expression in C2C12 murine myotubes subjected to 1% chronic radial stretch for 18 h was elevated 101% compared with control. ND treatment increased AR protein concentration 1,300% compared with controls, and there was no additional effect when ND and OV were combined. ND with 3 days of OV treatment increased AR mRNA expression 50% compared with control. AR overexpression in transiently transfected CV-1 fibroblast cells increased -424 bp skeletal alpha-actin promoter activity 80 to 1,800% in a dose-dependent fashion. Co-overexpression of either serum response factor (SRF) or active RhoA with AR overexpression induced a synergistic 36- and 28-fold induction of skeletal alpha-actin promoter. Cotransfection of AR, SRF, and active RhoA induced 180-fold increase in skeletal alpha-actin promoter activity. In conclusion, AR protein expression is increased after 7 days of functional OV, and this induction is regulated pretranslationally. AR induction in conjunction with SRF and RhoA signaling may be an important regulator of gene expression during overload-induced muscle growth.

Smooth muscle gamma-actin promoter regulation by RhoA and serum response factor signaling.

Smooth muscle gamma-actin (SMGA) is both an early marker of smooth muscle cell differentiation, which demonstrates an expression pattern restricted to smooth muscle and the post meiotic spermatocyte. Serum response factor (SRF) DNA-binding is an important regulator of muscle differentiation, including SMGA expression during smooth muscle cell differentiation. RhoA, a low molecular weight GTPase protein, can regulate cardiac, skeletal, and smooth muscle differentiation through SRF-dependent mechanisms. This study's purpose was to examine RhoA expression during smooth muscle cell development, and determine if the SMGA promoter activity is sensitive to RhoA-mediated signaling through SRF. Additionally, the study identified the promoter regulation modifying SMGA expression by RhoA signaling. Western blot analysis of embryonic chick gizzard whole protein extracts during 5 to 14 days of development demonstrated a large induction of RhoA (10-fold) and beta1 integrin expression at day 8, which corresponds to the time SMGA expression and differentiation are occurring. Transient transfections in CV-1 fibroblast cells demonstrated that co-overexpression of SRF and RhoA could induce a 40-fold induction of -176 bp SMGA promoter activity. Mutational analysis demonstrated that serum response element (SRE)-1, but not SRE2, was necessary for RhoA/SRF activation of the SMGA promoter. Deletion analysis revealed that although SRE1 was necessary for SMGA promoter activation by RhoA and SRF, it was not sufficient, implicating a possible obligatory role of additional promoter sequences in the response. Overexpression of a mutated SRF protein that was unable to bind DNA demonstrated that the 40-fold RhoA/SRF activation was largely dependent on SRF binding to the SMGA promoter. Thus, as the SMGA promoter appears to be a target of RhoA-mediated transcriptional regulation, the uncovering of these signaling mechanisms effecting SMGA promoter activity should provide a regulatory paradigm that can then be examined during the regulation of other smooth muscle genes.

Ambulatory activity and simple cardiorespiratory parameters at rest and submaximal exercise.

The purpose of this study was to explore the relationship between objectively determined ambulatory activity and simple cardiorespiratory parameters (heart rate and blood pressure at rest and during submaximal exercise) in individuals who were stratified for self-reported participation (yes/any vs. no/none) in vigorous physical activity (PA). Ninety-eight subjects (African Americans: 7 M, 16 F; Caucasians: 33 M, 42 F; mean age 46.4 +/- 15.4 yrs; mean BMI 26.7 +/- 4.8) wore a pedometer for 21 consecutive days and completed a 10-min submaximal treadmill graded exercise test with HR (beats/min) and BP (mmHg) measured while walking at 4.8 km/hr and a 10% grade. Subjects averaged 7,618 +/- 3.045 steps/day. There were no differences in steps/day by self-reported vigorous PA strata. There was an inverse relationship (r = -0.35, p = 0.03) between steps/day and resting HR in subjects who reported no vigorous PA. There was an inverse relationship (r = -0.22, p = 0.04) between steps/day and submaximal HR in all subjects. When stratified for self-reported vigorous PA, the inverse relationship between steps/day and submaximal HR was stronger for those reporting no vigorous PA (r = -0.39, p = 0.01) vs. those reporting any vigorous PA (r = -0.28, p = 0.05). There was no relationship between steps/day and BP at rest or during exercise in this normotensive sample.

Comparison of pedometer and accelerometer measures of free-living physical activity.

PURPOSE: The purpose of this investigation was 1) to evaluate agreement between dual-mode CSA accelerometer outputs and Yamax pedometer outputs assessed concurrently under free-living conditions; 2) to determine the relationship between pedometer-steps per day and CSA-time spent in inactivity and in light-, moderate-, and vigorous-intensity activities; and 3) to identify a value of pedometer-steps per day that corresponds with a minimum of 30 CSA-min x d(-1) of moderate ambulatory activity. METHODS: Data were analyzed from 52 participants (27 men, 25 women; mean age = 38.2 +/- 12.0 yr; mean BMI = 26.4 +/- 4.5 kg x m(-2)) who were enrolled in the International Physical Activity Questionnaire study and wore both motion sensors during waking hours for 7 consecutive days. RESULTS: Participants averaged 415.0+/-159.5 CSA-counts x min(-1) x d(-1), 357,601 +/- 138,425 CSA-counts x d(-1), 11,483 +/- 3,856 CSA-steps x d(-1), and 9,638 +/- 4,030 pedometer-steps x d(-1). There was a strong relationship between all CSA outputs and pedometer outputs (r = 0.74-0.86). The mean difference in steps detected between instruments was 1845+/-2116 steps x d(-1) (CSA > pedometer; t = 6.29, P < 0.0001). There were distinct differences (effect sizes >0.80) in mean CSA-time (min x d(-1)) in moderate and vigorous activity with increasing pedometer-determined activity quartiles; no differences were noted for inactivity or light activity. Approximately 33 CSA-min x d(-1) of moderate activity corresponded with 8000 pedometer-steps x d(-1). CONCLUSION: Differences in mean steps per day detected may be due to differences in set instrument sensitivity thresholds and/or attachment. Additional studies with different populations are needed to confirm a recommended number of steps per day associated with the duration and intensity of public health recommendations for ambulatory activity.

Sources of variance in daily physical activity levels as measured by an accelerometer.

PURPOSE: To examine sources of variance in objective measures of physical activity in a group of healthy adults (N = 92) participating in a physical activity measurement study. METHODS: Physical activity was assessed for up to 21 consecutive days using the Computer Science Applications (CSA) accelerometer. Day-of-the-week effects were evaluated for activity counts (ct.min(-1).d(-1), ct.d(-1)) and time (min.d(-1)) spent in inactivity (0-499 ct), moderate-1 (500-1951 ct), and moderate-2-vigorous activity (> or =1952 ct). Random effects models were employed to estimate variance components for subject, day of the week, and residual error from which the number of days of assessment required to achieve 80% reliability were estimated. RESULTS: Physical inactivity was lower on weekend days, and Saturday was the least inactive day of the week for both men and women. Inter-individual variation, or differences between subjects, was proportionally the largest source of variance (55-60% of total) in accelerometer counts and time spent in moderate to vigorous activity. Differences within subjects (intra-individual variation) accounted for 30-45% of the overall variance, and day-of-the-week effects accounted for 1-8%. For activity counts, and time spent in moderate to vigorous activity, at least 3-4 d of monitoring were required to achieve 80% reliability. Reliable measures of physical inactivity required at least 7 d of monitoring. CONCLUSION: These findings provide insight for understanding the behavioral variability in the activity patterns of adults and suggest that reliable measures of activity behaviors require at least 7 d of monitoring.