Publications by Colleges and Departments (MSU - Bozeman)
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Item Carbohydrates for physical activity: A strategy to avoid undesirable health consequences(2012-03) Miles, MaryIntake of carbohydrates above the dietary guidelines to support performance of physical activity is common but may be unnecessary and counterproductive. Sports nutrition guidelines have not been designed to incorporate characteristics that may make high carbohydrate consumption a source of metabolic stress that may increase oxidative stress, inflammation, and lipogenesis. This metabolic stress is linked to the physiology underlying the development of insulin resistance, type 2 diabetes mellitus, and cardiovascular diseases. This review describes research-based evidence to aid in bridging the gap between dietary guidelines for overall health and those to support physical activity. Characteristics that increase the likelihood of metabolic stress resulting from carbohydrate intake include overweight and obesity, central/visceral adiposity, older age, sedentary lifestyle, and caloric state. Carbohydrate-based foods that provide the most health benefits are whole grains, beans and legumes, fruits, and vegetables. Carbohydrate-based foods that most readily elicit metabolic stress are those with added sugars and refined grains or that have a high glycemic index. A checklist that incorporates both the number of these characteristics and prevailing guidelines for nutrition and physical activity is presented. This may be useful in determining whether additional carbohydrates are needed to support the physical activity level of the individual.Item Low-dose creatine supplementation enhances fatigue resistance in the absence of weight gain(Elsevier, 2011-04) Miles, Mary; Rawson, E.S.; Stech, M.J.; Frederickson, Sara J.Objective: We examined the effects of 6 wk of low-dose creatine supplementation on body composition, muscle function, and body creatine retention. Methods: Twenty healthy men and women (21 ± 2 y old) were randomized to receive creatine (0.03 g • kg -1 • d-1; n=10, 4 women) for 6 wk in a double-blind placebo-controlled fashion. Participants were tested on two occasions before supplementation to establish a reliable baseline, and then were retested after supplementation. Testing included body composition, maximal strength (three-repetition maximal concentric knee extension at 180 degrees/s), muscle fatigue (five sets of 30 concentric knee extensions at 180 degrees/s), and plasma creatine concentration. Results: There were no significant differences in body mass, fat-free mass, fat mass, body fat percentage, total body water, or maximal strength in either group from before to after supple-mentation (all P > 0.05). After supplementation, plasma creatine increased significantly in the creatine group (+182%, P = 0.03), with no difference in the placebo group. Compared with baseline values, creatine-supplemented volunteers were more resistant to fatigue during sets 2 (7%), 3 (9%), 4 (9%), and 5 (11%) (all P < 0.05). In placebo-supplemented participants, there was no improvement in fatigue resistance during sets 2 (0%), 3 (1%), 4 (0%), and 5 (1%) (all P > 0.05). Conclusion: Ingesting a low dose (2.3 g/d) of creatine for 6 wk significantly increased plasma creatine concentration and enhanced resistance to fatigue during repeated bouts of high-intensity contractions.Item Creatine supplementation does not reduce muscle damage or enhance recovery from resistance exercise(2007-11) Rawson, E.S.; Conti, M.P.; Miles, MaryPrevious studies have shown that creatine supplementation reduces muscle damage and inflammation following running but not following high-force, eccentric exercise. Although the mechanical strain placed on muscle fibers during high-force, eccentric exercise may be too overwhelming for creatine to exert any protective effect, creatine supplementation may protect skeletal muscle stressed by a resistance training challenge that is more hypoxic in nature. The purpose of this study was to examine the effects of short-term creatine supplementation on markers of muscle damage (i.e., strength, range of motion, muscle soreness, muscle serum protein activity, C-reactive protein) to determine whether creatine supplementation offers protective effects on skeletal muscle following a hypoxic resistance exercise test. Twenty-two healthy, weight-trained men (19–27 years) ingested either creatine or a placebo for 10 days. Following 5 days of supplementation, subjects performed a squat exercise protocol (5 sets of 15–20 repetitions at 50% of 1 repetition maximum [1RM]). Assessments of creatine kinase (CK) and lactate dehydrogenase activity, high-sensitivity C-reactive protein, maximal strength, range of motion (ROM), and muscle soreness (SOR) with movement and palpation were conducted pre-exercise and during a 5-day follow up. Following the exercise test, maximal strength and ROM decreased, whereas SOR and CK increased. Creatine and placebo-supplemented subjects experienced significant decreases in maximal strength (creatine: 13.4 kg, placebo: 17.5 kg) and ROM (creatine: 2.4°, placebo: 3.0°) immediately postexercise, with no difference be-tween groups. Following the exercise test, there were significant increases in SOR with movement and palpation (p < 0.05 at 24, 48, and 72 hours postexercise), and CK activity (p < 0.05 at 24 and 48 hours postexercise), with no differences between groups at any time. These data suggest that oral creatine supplementation does not reduce skeletal muscle damage or enhance recovery following a hypoxic resistance exercise challenge.Item Apolipoprotein A1 genotype affects the change in high density lipoprotein cholesterol subfractions with exercise training.(2006-03) Ruaño, G.; Seip, R.L.; Windemuth, Andreas; Zöllner, S.; Tsongalis, Gregory J.; Otvos, J.; Ordovas, J.M.; Bilbie, C.; Miles, Mary; Zoeller, Robert F.; Visich, Paul S.; Gordon, P.M.; Angelopoulos, T.J.; Pescatello, Linda S.; Moyna, Niall M.; Thompson, P.D.High density lipoprotein cholesterol (HDL-C) is a primary risk factor for cardiovascular disease. Apolipoprotein A-1 (apoA1) is the major HDL-associated apolipoprotein. The −75 G/A single nucleotide polymorphism (SNP) in the apolipoprotein A1 gene (APOA1) promoter has been reported to be associated with HDL-C concentrations as well as HDL-C response to dietary changes in polyunsaturated fat intake. We examined the effect of this APOA1 SNP on exercise-induced changes in HDL subfraction distribution. From a cohort of healthy normolipidemic adults who volunteered for 6 months of supervised aerobic exercise, 75 subjects were genotyped for the −75 G/A SNP. Of these, 53 subjects were G homozygotes (G/G) and 22 were A carriers (A/G and A/A). HDL subfractions were measured by nuclear magnetic resonance (NMR) spectroscopy by adding categories HDL-C 1 + 2 for the small subfraction, and HDL-C 3 + 4 + 5 for the large. The change in total HDL-C after exercise was 0.8 ± 7.2 mg/dL (+1.7%), and was not statistically significant. HDL subfraction amounts also did not significantly change with exercise training in the total cohort or in G homozygotes or A carriers. The amount of the large HDL subfraction increased in the G homozygotes and decreased in the A carriers (mean ± S.E.M., 1.8 ± 6.6 mg/dL versus −6.1 ± 2.3 mg/dL, p < 0.0005). In contrast, the amount of the small HDL subfraction decreased in G homozygotes and increased in A carriers (−1.3 ± 6.6 mg/dL versus 4.7 ± 1.2 mg/dL, p < 0.005). These results show that genetic variation at the APOA1 gene promoter is associated with HDL subfraction redistribution resulting from exercise training.Item Basal, diurnal, and acute inflammation in normal versus overweight men.(Lippincott Williams & Wilkins, 2012-12) Miles, Mary; Keller, J.M.; Kordick, L.K.; Kidd, J.R.Increased inflammation is present in obese compared with normal weight individuals, but inflammation characteristics of nonobese, overweight individuals are less clear. Purpose: The objective of this study was to determine whether basal, circadian, and posteccentric exercise inflammation levels differ between normal and overweight men. Methods: Men (18–35 yr old) classified as normal weight (body mass index ≤2 5 kg·m-2, n = 20) and overweight (body mass index = 25–30 kg·m-2 conditions in random order. Maximal voluntary effort and eccentric actions (3 X 15) using the elbow flexor muscles of one arm were performed, and blood was collected preexercise and 4, 8, 12, and 24 h postexercise at 7:00 a.m., 12:00 p.m., 4:00 p.m., 8:00 p.m., and 7:00 a.m. Blood was collected on a time-matched schedule without exercise for CON. Soluble tumor necrosis factor receptor-1, interleukin-6, C-reactive protein (CRP), and cortisol responses (EX value j time-matched CON value) were measured. Results: Basal CRP was higher in the overweight compared with normal weight group (mean ± SD, 0.542 ± 0.578 vs 1.395 ± 1.041 mg·L-1). Soluble tumor necrosis factor receptor-1 increased (P < 0.05) 8 h postexercise in both groups, and the response was greater 12 and 24 h postexercise in the overweight compared with normal weight groups. Interleukin-6 increased (P < 0.05) 8 h postexercise, with a trend (P = 0.09) to be greater in the overweight group. CRP and cortisol responses were not detected. Conclusions: The low-grade inflammation state in overweight compared with normal weight men includes both higher basal CRP concentrations and enhanced acute inflammation, but not in changes to the circadian patterns of cortisol and inflammation variables.Item Apolipoprotein E genotype and changes in serum lipids and maximal oxygen uptake with exercise training(W.B. Saunders Co, 2004) Thompson, P.D.; Tsongalis, Gregory J.; Seip, R.L.; Bilbie, C.; Miles, Mary; Zoeller, Robert F.; Visich, Paul S.; Gordon, P.M.; Angelopoulos, T.J.; Pescatello, Linda S.; Bausserman, L.; Moyna, Niall M.Physical activity improves lipid levels by altering triglyceride (TG) metabolism. Apolipoprotein E (Apo E) facilitates TG clearance by mediating lipoprotein binding to hepatic receptors, but Apo E also has less defined roles in skeletal muscle and nervous tissue. This study examined if variants in Apo E genotype affect the lipid and physiologic response to exercise training. Seven centers genetically screened 566 individuals to recruit 120 subjects into 6 gender-specific cohorts equal for the most common Apo E genotypes: E2/3, E3/3, and E3/4. Anthropometics, exercise capacity (Vo2max), serum lipids, and post heparin (PH) plasma lipase activities were measured before and after 6 months of supervised exercise training. Difference in the response (Δ) to training among the Apo E genotypes was the primary outcome variable. Differences in pretraining serum lipids among the Apo E genotypes mimicked those observed in population studies: TGs were slightly higher in E2/3 subjects, whereas low-density lipoprotein (LDL)-cholesterol (C) was lower (P = not significant [NS] ). TGs decreased 11% with training for the entire cohort (P < .0001) and 7%, 12%, and 14% for the Apo E 2/3, 3/3 and 3/4 groups, respectively (P = NS for Δ). LDL-C did not change in the entire cohort, but decreased slightly in the 2/3 and 3/3 subjects and increased 4% in the 3/4 group (P = NS for Δ). High-density lipoprotein (HDL)-C increased 2% for the entire cohort (P = .06) due to a 6% increase in the 3/3 group (P = .07 for Δ). Total cholesterol (TC)/HDL and LDL/HDL decreased with training in the 2/3 and 3/3 groups, but increased in the 3/4 subjects and these responses differed among the genotypes (P < .05 for Δ). Vo2max increased 9% to 10% for the entire cohort, but only 5% in the 3/3 subjects versus 13% in the 2/3 and 3/4 groups and these differences were significantly different among the genotypes (P < .01 for Δ). This is the first prospective study to demonstrate that the serum lipid response to exercise training differs by Apo E genotype in a pattern consistent with known metabolic differences among the variants. Surprisingly, Apo E genotype also affected the increase in aerobic capacity produced by exercise training possibly via undefined effects on nerve and skeletal muscle function.Item Enhanced inflammation with high carbohydrate intake during recovery from eccentric exercise(Springer, 2010-08) Miles, Mary; Depner, Chris M.; Kirwan, Rochelle D.; Frederickson, Sara J.Inflammation associated with adipose tissue is modulated by macronutrient availability. For example, glucose increases inflammation in obese but not lean individuals. Little is known about how macronutrient intake influences inflammation associated with muscle. The aim of this study was to determine the impact of macronutrient intake differences during recovery from eccentric exercise on the inflammatory response. The study was a cross-over design in which young men and women (n = 12) completed high and low carbohydrate (CHO) conditions. Both conditions consisted of six sets of ten maximal high-force eccentric contractions of the elbow flexors and extensors followed by a controlled diet for the first 8 h post-exercise. Glucose, insulin, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and C-reactive protein were measured from blood samples pre-exercise, 1.5, 4, 8, and 24 h post-exercise. Perceived muscle soreness, strength loss, and serum CK activity were measured through 120 h post-exercise. Perceived soreness was elevated (P < 0.001) at all time points post-exercise in both conditions and was higher (P < 0.05) in the high compared to the low CHO condition. IL-1β increased (P = 0.05) 24 h post-exercise in the high compared to the low CHO condition. There was a trend (P = 0.06) for IL-6 to be elevated in the high compared to the low CHO condition. We conclude that inflammation induced by high-force eccentric exercise in skeletal muscle is greater when a high CHO compared to a low CHO diet is consumed during recovery.Item Influence of macronutrient intake and anthropometric characteristics on plasma insulin after eccentric exercise(W.B. Saunders Co, 2010-10) Miles, Mary; Frederickson, Sara J.; Depner, Chris M.; Kirwan, Rochelle D.To increase understanding of the interaction between macronutrients and insulin resistance (IR), this study sought to determine the influence of macronutrient intake and anthropometric differences on IR and inflammation responses to eccentric resistance exercise. Men and women (n = 12, 19-36 years old) participated in a crossover study and completed 6 sets of 10 unilateral maximal eccentric contractions of the elbow flexors and extensors followed by controlled diet conditions for the first 8 hours postexercise of carbohydrate/fat/protein proportions of either 75%/15%/10% (CHO) or 6%/70%/24% (FAT/PRO). Fasting glucose, insulin, homeostatic model assessment (HOMA) variables, and interleukin (IL)-1β were measured preexercise and 23 hours postexercise (additional measures of glucose and insulin 1 hour after meals consumed 0.5, 3, and 7 hours postexercise). Insulin increased more (P < .01) in the CHO compared with the FAT/PRO condition at 1.5, 4, and 8 hours postexercise. Insulin, HOMA-IR, and HOMA-β-cell function increased 23 hours postexercise in both conditions, whereas IL-1β increased 23 hours postexercise only in the CHO condition. Magnitude of change (Δ) for these variables associated positively with body mass index (BMI) and waist to hip ratio (WHR) in the CHO and inversely in the FAT/PRO condition; that is, r = 0.53 (P = .10) and r = −0.82 (P < .01) for BMI vs Δ insulin in CHO and FAT/PRO conditions, respectively. The Δ IL-1β associated with BMI (r = 0.62, P < .05) and WHR (r = 0.84, P < .01) in the CHO condition. The CHO enhanced IR and inflammation as BMI and WHR increased, whereas fat and protein enhanced IR as BMI and WHR decreased. Thus, BMI and WHR may need to be taken into account in the development of nutritional strategies to prevent IR.Item Apolipoprotein E genotype and sex influence C-reactive protein levels regardless of exercise training status(W.B. Saunders Co, 2008) Miles, Mary; Lowndes, J.; Sivo, S.; Seip, R.L.; Angelopoulos, T.J.C-reactive protein (CRP) is a marker for systemic inflammation and increased cardiovascular disease risk. Regular exercise may decrease CRP. Apolipoprotein E (apo E) has 3 common genotype variants—E2/3, 3/3, and 3/4—that modulate lipid metabolism and may have other metabolic physiologic roles, including some evidence that the genotype affects CRP levels. We assessed fasting serum CRP in 117 (male = 51, female = 66) healthy adults who volunteered for a 6-month aerobic exercise program. Both pre- and posttraining measurements were available in 71 (male = 31, female = 40) subjects. At baseline and follow-up, the numbers of subjects in the 3 groups were approximately equal: 2/3, n = 33 and 20; 3/3, n = 41 and 26; and 3/4, n = 43 and 25. At baseline, CRP levels differed by apo E genotype: means ± SD were 2.84 ± 2.18, 2.59 ± 2.34, and 1.90 ± 2.13 mg/L for E2/3, 3/3, and 3/4 subjects, respectively (3/4 vs 2/3, P b .05). In women, CRP was higher than that in men (3.14 ± 2.49 vs 2.12 ± 2.13 mg/L, P b .006). Exercise failed to affect CRP in the entire cohort (2.68 ± 2.38 vs 2.52 ± 2.48 mg/L) or in any apo E genotype group, and the apo E genotype effect observed at baseline persisted after training. In a largely white study cohort, CRP is higher in apo E3/3 than in 3/4 subjects and in women compared with men, but remains unchanged by 6 months of standard aerobic exercise training of the volume and higher intensity promoted by national organizations to reduce cardiovascular disease risk. How apo E genotype affects CRP is not known.Item Cytokine production by stimulated mononuclear cells did not change with aging in apparently healthy, well-nourished women(Elsevier, 2001) Ahluwalia, N.; Mastro, A.M.; Ball, R.; Miles, Mary; Rajendra, R.; Handte, G.Aging is often associated with a dysregulation of the immune system. We examined mitogen-stimulated production of interleukin (IL)-2 and proinflammatory cytokines, IL-1β and IL-6, in apparently healthy and generally well-nourished old versus young women. Subjects were screened for health using the SENIEUR protocol and a panel of laboratory tests for inflammation, as well as for the adequacy of nutritional status using criteria related to undernutrition, and protein, iron, vitamin B12, and folate status. Young (n=26, age: 20–40 years) and old (n=44, age: 62–88 years) cohorts did not differ on the number of circulating monocytes, granulocytes, B (CD19+) cells, and T (CD3+, CD4+, and CD8+) cells. No differences (P>0.10) were seen between the two age groups in IL-2, IL-1β and IL-6 levels in whole blood cultures at 48 h after stimulation with PHA (5 mg/l). Furthermore, no age-related differences were noted in the absolute amounts (pg) of IL-1β and IL-6 after normalizing for circulating monocytes, B cells, or T cells (P>0.10). Similarly, no age-related decline in absolute amount of IL-2 (pg) after normalizing for circulating T cells was noted (P>0.10). Thus, contrary to most previous reports, our results do not support an increase in the production of proinflammatory cytokines IL-1β and IL-6, and a reduced production of IL-2 with aging when health and nutritional status are maintained. These findings support our previous results of no change in monocyte function and few alterations in acquired immune response in a carefully selected group of healthy and well-nourished elderly women.