Biomedical subjects

Tom R Thomas

Publications and source records attributed to Tom R Thomas.

13 recordsLinked to original sources

PubMed2006

Weight-bearing, aerobic exercise increases markers of bone formation during short-term weight loss in overweight and obese men and women.

We investigated the impact of weight-bearing, aerobic exercise- and diet-induced weight loss on markers of bone turnover during a larger study of changes in metabolic fitness during short-term weight reduction using a repeated-measures, within-subject experimental design. Subjects (N = 19) underwent 6 weeks of energy restriction (reduced by approximately 3140 kJ/d) and aerobic exercise ( approximately 1675 kJ/d, walking or jogging at 60% maximum oxygen consumption) to induce a 5% reduction in body weight. Bone turnover markers and hormones were measured in serum collected at baseline and after 6 weeks of weight loss. Despite a 5% reduction in body weight at week 6, markers of bone formation, osteocalcin, and bone alkaline phosphatase, were significantly increased, and resorption markers, C-terminal cross-links of type I collagen and soluble receptor activator of nuclear factor kappaB ligand, were unchanged after 6 weeks of energy restriction and exercise. The concentration of leptin was significantly reduced after weight loss, but insulin-like growth factor I (IGF-I) and cortisol levels were unaffected. In conclusion, weight-bearing, aerobic exercise training may favorably affect the balance between bone resorption and formation during weight loss.

Adolescent↗

PubMed2006

Short-term lifestyle modification alters circulating biomarkers of endothelial health in sedentary, overweight adults.

Obesity and inactivity are associated with endothelial dysfunction that may contribute to the development of atherosclerosis. We examined the effects of a short-term lifestyle intervention on circulating biomarkers of endothelial health. Nineteen overweight or obese (mean body mass index (BMI): 28.9 +/- 0.7 kg/m2) men and women underwent 6 weeks of body mass reduction induced by moderate energy restriction (approximately 750 kcal/d; 1 kcal = 4.184 kJ) and aerobic training (approximately 400 kcal/d). Fasting serum samples were collected at baseline and after reduction in body mass (week 6) to assess concentrations of nitrotyrosine (NT), secretory phospholipase A2 (sPLA2), and soluble intracellular adhesion molecule-1 (sICAM-1). Body mass was significantly reduced from 81.3 +/- 2.8 to 77.3 +/- 2.6 kg (p < 0.05). Circulating concentrations of NT and sICAM-1 were significantly reduced with treatment (approximately 25% and approximately 10%, respectively), whereas sPLA2 levels were significantly elevated (approximately 45%). Elevations in sPLA2 were negatively correlated with changes in NT (r = -0.58, p = 0.047); reductions in NT did not correlate significantly with reductions in sICAM-1. It appears that circulating markers of endothelial health are susceptible to short-term exercise interventions with modest reduction in body mass, and such a lifestyle modification may improve endothelial health by reducing protein nitration products and cellular adhesion.

Adolescent↗

PubMed2006

Lipoprotein subfraction changes after continuous or intermittent exercise training.

PURPOSE: This study compared total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) and their respective subfractions after completing 4 wk of either intermittent (INT-EX) or continuous (CON-EX) aerobic exercise training (TRAIN). METHODS: Untrained males (N = 7) and females (N = 11) completed 4 wk of TRAIN of supervised treadmill jogging occurring 5 d.wk(-1) for 30 min per session at 60% VO2max (75% HRmax). CON-EX was a single 30-min bout. INT-EX consisted of three 10-min bouts separated by 20 min of seated rest. Pre- and post-TRAIN fasting plasma samples were collected after subjects had followed 48 h of activity restriction and a 24-h repeated diet including a 12-h dietary fast. Postprandial lipemia was measured for 8 h following a standardized high-fat meal. RESULTS: Fasting triglycerides and very LDL-C were not affected by TRAIN, and TRAIN did not change postprandial area under the curve or peak in either group. With groups combined, TRAIN significantly decreased TC, total LDL-C, and the TC:HDL ratio, and increased HDL-C subfraction 2 and LDL mean particle size. Total intermediate-density lipoprotein cholesterol remained unchanged at post-TRAIN, and was not different between groups. CONCLUSIONS: To prevent dyslipidemia, our findings suggest that persons who are normolipidemic can improve the lipoprotein profile equally with CON-EX and INT-EX by lowered TC through the sum of changes in LDL-C subfractions, increased mean LDL particle size, and increased HDL-C subfraction 2 concentration.

Adolescent↗

PubMed2004

Effect of n-3 fatty acids on free tryptophan and exercise fatigue.

Free tryptophan (Trp), which is augmented by liberated free fatty acids (FFA) from adipose tissue, can induce mental fatigue via serotonin during exercise. Since an attenuation in FFA has been observed with omega-3 fatty acid (n-3fa) use, our purpose was to examine the effect of n-3fa supplementation on free Trp availability and exercise fatigue. Ten recreationally trained men ( n=5) and women ( n=5), with maximal oxygen consumption (VO(2max))of 51.6 (3.0) and 44.3 (1.4) ml kg(-1) min(-1), respectively, were studied on two occasions following an overnight fast, before and after n-3fa supplementation (4 g day(-1) for 4 weeks). The exercise trials consisted of a 75-min treadmill run at 60% VO(2max) followed immediately by a high-intensity incremental bout to fatigue. Measurements included exercise monitors, plasma volume (PV), triglycerides (TG), FFA, glycerol, lactate, and glucose. Free Trp and branched-chain amino acids (BCAA) were measured and correlated with time to fatigue; all blood variables were corrected for PV. Free Trp, lactate, glucose, FFA, and glycerol were not significantly different between trials, but TG ( P<0.001) and the free Trp/BCAA ratio were significantly lower after n-3fa use [1.76 (0.18)x10(-2) microg ml(-1)] versus before supplementation [2.17 (0.22), P=0.033]. There was a non-significant increase in time to fatigue after supplementation [10.2 (0.3) min] versus before n-3fa use [9.7 (0.2), P=0.068], and a tendency for higher BCAA levels after supplementation, P=0.068. However, neither free Trp nor the free Trp/BCAA ratio significantly predicted time to fatigue. In conclusion, n-3fa supplementation did not diminish free Trp concentrations or significantly improve endurance performance during a maximal bout of exercise.

Adult↗

PubMed2004

Lipoproteins during the estrous cycle in swine.

The purpose of this study was to examine lipoprotein values at high versus low 17beta-estradiol (E2) concentrations in Yucatan miniature swine. Estrous cycles were measured by heat checking the female on a daily basis using a boar. All swine were fed a 1,050-g low-fat, standard chow diet (8% kcal from fat) once per day. Fasted (24 hours) blood samples were collected during low (early luteal, day 5) and high (late follicular, day 18) E2 concentrations to determine differences in concentrations of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL-C), high-density lipoprotein cholesterol (HDL-C), and subfractions. Concentrations of E2 differed significantly from day 5 (3.5 +/- 0.7 pg/mL) to day 18 (14.2 +/- 1.8 pg/mL) of the estrous cycle. Except for HDL(3)-C, all lipoprotein parameters examined were significantly elevated during high E2 versus low E2. TC/HDL-C and LDL-C/HDL-C ratios were significantly lower during the high E2 phase. These results suggest that lipoprotein concentrations fluctuate during the estrous cycle of swine, with high E2 concentrations associated with elevated lipoprotein concentrations.

Animals↗

PubMed2004

Effects of omega-3 fatty acid supplementation and exercise on low-density lipoprotein and high-density lipoprotein subfractions.

The purpose of this study was to examine the effect of combining exercise with omega-3 fatty acids (n-3fa) supplementation on lipoprotein subfractions and associated enzymes. Subjects were 10 recreationally active males, aged 25 +/- 1.5 years (mean +/- SE), who supplemented n-3fa (60% eicosapentaenoic acid [EPA] and 40% docosahexaenoic [DHA]) at 4 g/d for 4 weeks. Before and after supplementation, subjects completed a 60-minute session of treadmill exercise at 60% Vo(2)max. Following a 24-hour diet and activity control period, blood was collected immediately before and after the exercise session to assess lipid variables: high-density lipoprotein cholesterol (HDL-C) and subfractions, low-density lipoprotein cholesterol (LDL-C) and subfractions and particle size, lecithin:cholesterol acyltransferase (LCAT) activity, and cholesterol ester transfer protein (CETP) activity. Supplementation with n-3fa alone increased total HDL-C and HDL(2)-C, while exercise alone increased total HDL-C, HDL(3)-C, and total LDL-C. LDL subfractions, particle size, and LCAT and CETP activities were not affected by supplementation. Combination treatment resulted in an additive effect for HDL(3)-C only and also increased LDL(1)-C versus baseline. LCAT and CETP activities were not affected by treatments. These results suggest that n-3fa supplementation or an exercise session each affect total HDL-C and subfractions but not LDL-C or subfractions. In addition, the combination of n-3fa and exercise may have additional effects on total HDL-C and LDL-C subfractions as compared to either treatment alone in active young men.

Adult↗

PubMed2004

Effect of exercise on postprandial lipemia following a higher calorie meal in Yucatan miniature swine.

Exercise has been shown to attenuate the postprandial lipemic (PPL) response to a modest kcal high-fat meal in numerous human studies, but has not been fully examined in swine. In addition, the effects of exercise on a high-fat meal of larger magnitude have not been examined in humans or in swine. Thus, the purpose of this study was to examine the PPL response to a single, high-fat/cholesterol (HFC) meal (approximately 3,000 kcal, 1,300 kcal from fat) and determine if exercise attenuates the PPL response. Sedentary, female Yucatan miniature swine (n = 10) completed 3 PPL trials: (1) pre diet (PRE); (2) post HFC diet (POST); and (3) post HFC diet plus exercise (EX, 45 minutes at 75% heart rate maximum). Blood samples were collected before (0 hour) and at 2, 4, 6, and 8 hours after the single HFC meal for PPL analysis. Postheparin lipoprotein lipase (LPL) activity was assessed at 8 hours. While fasting LPL activity was significantly increased with the HFC diet, the PPL response to the HFC meal did not differ depending on diet. Furthermore, the PPL response was not significantly altered with a single session of exercise, perhaps because of the severity of the HFC meal, the sedentary nature of the swine, or because LPL activity was not elevated after exercise. These findings suggest that administration of a HFC meal of this magnitude (approximately 3,000 kcal, 1,300 kcal from fat) will promote significant elevations in postprandial triglyceride (TG) concentrations, overwhelm the adaptive response to a HFC diet (elevated LPL activity), and attenuate the beneficial effects of a single exercise session on this system.

Animals↗

PubMed2004

Exercise plus n-3 fatty acids: additive effect on postprandial lipemia.

The purpose of this study was to examine changes in postprandial lipemia (PPL) in recreationally active males following aerobic exercise, omega-3 fatty acids (n-3FA) supplementation, and the combination of the two. PPL following a high-fat meal was measured in 10 recreationally active males (25 +/-1.5 years) under each of the following conditions: no exercise and no n-3 FA supplementation (control); exercise and no n-3FA supplementation (exercise); n-3FA supplementation and no exercise (n-3FA); and exercise and n-3 FA supplementation (combined). Blood was collected before the high-fat meal and at 2, 4, 6, and 8 hours after the meal to assess the PPL response. Supplementation consisted of 4.0 g of n-3FA per day for 5 weeks. Triglyceride (TG) peak response, the total area under the TG curve (TG-AUCT), and the incremental area under the TG curve (TG-AUCI) were used to define the PPL response. TG peak response was significantly reduced 38% by n-3FA supplementation and 50% by the combination of exercise and n-3FA supplementation. N-3FAs significantly reduced the TG-AUCT by 27% and by 42% when combined with exercise. When compared with the exercise trial, the TG-AUCT during the combined trial was significantly lower. Exercise, n-3FAs, and the combination significantly reduced the TG-AUCI by 40%, 42%, and 58%, respectively. These results suggest that the combination of exercise and n-3FA supplementation reduce PPL to a greater degree in recreationally active males when compared with the individual treatments.

Adult↗

PubMed2004

Effects of acute 60 and 80% VO2max bouts of aerobic exercise on state anxiety of women of different age groups across time.

The purpose of this investigation was to study the effects of an acute bout of aerobic exercise on state anxiety of women while controlling for iron status (hemoglobin and serum ferritin). Participants were 24 active women, ages 18-20 years (n = 12) and 35-45 years (n = 12). In addition to a nonexercise control condition, participants completed one exercise bout at 60% maximal oxygen uptake (VO2max) and one at 80% VO2max. Each exercise session consisted of a 33-min bout in which participants exercised at their target intensities for a 20-min segment. Immediately before each exercise trial, participants were given the Spielberger State Anxiety Inventory (SAI). The SAI was again administered immediately following the exercise session and at 30, 60, and 90 min postexercise. Data were analyzed using an Age x Intensity x Time (2 x 3 x 5) repeated measures analysis of covariance (ANCOVA) with iron status serving as the covariate. The ANCOVA on state anxiety yielded significant effects for time (p < .0001, eta2(p) = .48), the Intensity x Time interaction (p = .0006, eta2(p) = .19), and the Intensity x Age interaction (p = .04, eta2(p) = .15). All three exercise conditions (including control) showed a decline in state anxiety across time, but the 80% VO2max condition showed a sharper decline. Intensity of exercise conditions did not differ in state anxiety at baseline or immediately after exercise, but a difference favoring the 80% VO2max condition over the control condition emerged at 30 min postexercise. After controlling for iron status, older women who exercised at 80% VO2max exhibited lower SAI scores compared to the control condition.

Adolescent↗

PubMed2004

Single sessions of intermittent and continuous exercise and postprandial lipemia.

PURPOSE: This study compared the effects of continuous (CON-EX) and intermittent (INT-EX) exercise on postprandial lipemia (PPL). METHODS: Subjects were 18 inactive males (N = 7) and females (N = 11), aged 25 +/- 1.8 yr (mean +/- SE), VO2max 38.4 +/- 1.5 (mL x kg(-1)x min(-1)), and BMI 23.2 +/- 0.8 (kg x m(-2)). After 48-h activity and 24-h dietary control periods, subjects consumed a high-fat meal (HFM) containing 1.5 g fat (88% of calories), 0.05 g protein, and 0.4 g carbohydrate per kilogram body weight for three trials: no exercise (NOEX), CON-EX, and INT-EX. Both exercise trials consisted of 30 min of treadmill running at 60% VO2max. INT-EX was conducted in a single session of three bouts, each lasting 10 min and separated by a 20-min rest period. Blood was collected before the HFM (0 h) and at 2, 4, 6, and 8 h post-HFM. Exercise trials were completed 12 h before the HFM. Trials were separated by 7-10 d and were performed in random order. RESULTS: Plasma analysis indicated TG incremental area under the curve (AUCI) and TG incremental peak (PeakI) were significantly lower in INT-EX compared with NOEX, but CON-EX was not different from INT-EX or NOEX. Compared with females, males had significantly higher AUCI and PeakI in both exercise trials, but genders were not different in the NOEX trial. No difference was discovered among trials in high density lipoprotein (HDL)Total-C, HDL2-C, and HDL3-C, or fasting total cholesterol (TC) or fasting TC:HDL ratio. Females had higher fasting HDLTotal-C, HDL2-C, and HDL3-C compared with males. No gender or trial difference was found for fasting TC or TC:HDL ratio. CONCLUSIONS: Our data suggest that a single bout of INT-EX is more effective than CON-EX for lowering PPL as compared with NOEX in inactive, normolipidemic individuals.

Adult↗

PubMed2003

C-reactive protein correlates with macrophage accumulation in coronary arteries of hypercholesterolemic pigs.

A growing body of evidence supports the hypothesis that C-reactive protein (CRP) is a marker of inflammation in coronary artery disease. The purpose of the present study was to test the hypothesis that CRP correlates with macrophage accumulation during the initial stages of coronary vascular disease. Adult male pigs were fed a normal chow (NF) or a high-fat high-cholesterol (HF) diet for 20 wk. After 20 wk, blood was collected for analyses of interleukin-6 (IL-6), CRP, and lipids. After blood collection, the pigs were euthanized and the right coronary arteries (RCA) were harvested and fixed in neutral buffered formalin. Paraffin-embedded sections of RCA were stained immunohistochemically for CRP, scavenger receptor A (SRA), and monocyte chemoattractant protein-1 (MCP-1). All cholesterol fractions were elevated in the HF vs. the NF group (P < 0.05). There was little or no positive staining for CRP, SRA, or MCP-1 in the RCA of NF pigs, but there was extensive staining in lipidladen macrophage foam cells in the HF pigs. Double staining revealed colocalization of CRP with SRA and CRP with MCP-1 in foam cells. Serum IL-6 was below the assay detection limit in all pigs. Serum CRP correlated directly with plasma total cholesterol (R = 0.727, P = 0.041) and accumulation of SRA-positive macrophages (R = 0.938, P < 0.001) in RCA of HF pigs. We conclude that serum CRP correlates with macrophage accumulation and coronary artery disease in hypercholesterolemic pigs.

Animals↗

PubMed2002

Exercise training does not reduce hyperlipidemia in pigs fed a high-fat diet.

The pig is often used as a model for studying lipoprotein metabolism as it relates to human atherosclerosis, but few studies have examined the complete lipoprotein profile and related enzymes in swine ingesting an atherogenic diet. We examined whether exercise training would moderate the effects of an atherogenic diet on lipoproteins and lipoprotein lipase (LPL) activity in miniature swine. Male (n = 30) and female (n = 32) swine were initially divided into 2 dietary groups: one consumed low-fat (8%) pig chow, and one consumed pig chow supplemented with 2% cholesterol, 17.1% coconut oil, 2.3% corn oil, and.7% sodium cholate (46% kcal from fat). Following 30 days on the diets, pigs from each diet group were further divided into sedentary and exercise trained subgroups, each cell with 6 to 8 pigs. Training occurred 5 days per week on a treadmill in which the intensity and duration were progressively increased during the 16- to 20-week training period to 75 minutes of aerobic running per session. A 4-way analysis of variance (ANOVA) with repeated measures on time indicated that at the conclusion of the study the atherogenic diet caused significantly (P <.05) increased cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and subfractions, low-density lipoprotein cholesterol (LDL-C) and subfractions, and LPL activity in both genders. For cholesterol, TG, HDL-C, HDL(2)-C, LDL-C, LDL(1&2)-C, and hepatic lipase, the female response to the diet was exaggerated compared to the male response. Exercise training produced no group differences or interactions on any lipoprotein variable. These results suggest that an atherogenic diet has a greater impact on the lipoproteins of female miniature swine than males. Furthermore, under the conditions of this study, exercise training does not moderate the effects of an atherogenic diet on lipoproteins.

Animals↗

PubMed2002

Changes in LPLa and reverse cholesterol transport variables during 24-h postexercise period.

We investigated the time course of exercise-induced lipoprotein lipase activity (LPLa) and reverse cholesterol transport (RCT) during the 24-h postexercise period. Subjects were 10 sedentary normolipidemic males [NTG; fasting triglyceride (TG) = 89.1 +/- 8.6 mg/dl] and 6 hyperlipidemic males (HTG; fasting TG = 296.8 +/- 64.0 mg/dl). Each subject performed a control trial (no exercise) and 4 exercise trials. In the exercise trials, a subject jogged on a treadmill at 60% of his maximal O(2) consumption for 1 h. Pre- and postheparin blood samples were taken before exercise (baseline) and at 4, 8, 12, and 24 h after exercise. There was no group difference in LPLa (P > 0.05) over the time points. When the LPLa data from the two groups were combined, LPLa at 24 h after exercise was higher than baseline or at 4, 8, 12 h after exercise (P < 0.05). Plasma TG and lecithin-cholesterol acyltransferase activity (LCATa) were higher in HTG than in NTG, and the total high-density lipoprotein-cholesterol (HDL(tot)-Chol) was lower in HTG than in NTG (P < 0.05). HDL(2)-Chol, LCATa, and cholesterol ester transfer protein activity did not differ during the 24-h postexercise period (P > 0.05). These results suggest that LPLa is still increasing 24 h after an acute aerobic exercise and that the magnitude of the increase in exercise-induced LPLa in HTG was similar to that in NTG. Furthermore, in the sedentary population with or without HTG, the variables related to RCT do not change during the 24-h period after exercise.

Adult↗