Michael L. Mestek

Aerobic exercise and postprandial lipemia in men with the metabolic syndrome.

INTRODUCTION It is currently unclear as to how exercise prescription variables influence attenuations of postprandial lipemia (PPL) in men with the metabolic syndrome (MetS) after exercise. Therefore, the purposes of this investigation were to compare the effects of low- and moderate-intensity exercise and accumulated versus continuous exercise on PPL in males with MetS. METHODS Fourteen males with MetS (waist circumference (WC) = 110.2 +/- 10.9 cm; triglycerides (TG) = 217 +/- 84 mg dL(-1); fasting blood glucose = 105 +/- 7 mg dL(-1); high-density lipoprotein cholesterol (HDL-C) = 44 +/- 7 mg dL(-1); systolic blood pressure (SBP) = 120 +/- 12 mm Hg; diastolic blood pressure (DBP) = 76 +/- 10 mm Hg) completed a control condition consisting of a high-fat meal and blood sampling at 2 h intervals for 6 h. Next, participants completed the following exercise conditions: 1) continuous moderate-intensity (MOD-1), 2) continuous low-intensity (LOW-1), and 3) two accumulated moderate-intensity sessions (MOD-2). The test meal and blood sampling were repeated 12-14 h after exercise. Area under the curve (AUC) scores and temporal postprandial responses were analyzed using repeated-measures ANOVA for TG and insulin. RESULTS The TG AUC decreased by 27% after LOW-1. TG concentrations were also reduced by 22% and 21% at 4 h postmeal after LOW-1 and MOD-1, yet TG parameters were no different from the control condition after MOD-2 (P < 0.05 for all). CONCLUSION These findings indicate that 500 kcal of continuous aerobic exercise before a meal attenuates PPL in men with MetS. This outcome can be achieved through low- or moderate-intensity exercise performed in a single session. Accumulating moderate-intensity exercise does not appear to effectively modulate PPL in men with MetS.

The Relationship Between Pedometer-Determined and Self-Reported Physical Activity and Body Composition Variables in College-Aged Men and Women

Pedometer-determined physical activity (PA) is inversely related to body composition in middle-aged adults; however, researchers have not established such a relationship in college students. Objective and Participants: In this study, the authors attempted to characterize PA and examine its relationship with body composition in undergraduate college students (N = 88). Methods: The authors measured the BC of 44 women (M age = 21 ± 1 year, M body mass index [BMI] = 23.9 ± 4 kg/m2) and 44 men (M age = 22 ± 1 year, BMI = 26.9 ± 0.9 kg/m2); participants also wore a pedometer for 7 days and completed a PA questionnaire. Results: Men averaged significantly more steps/day (10,027 ± 3,535) than did women (8,610 ± 2,252). For women only, the authors observed significant correlations between steps/day and body composition variables. Men reported engaging in vigorous PA significantly more often than did women. Conclusions: These findings indicate that men engage in PA more often but that PA is related to body composition only in women. In addition, there is better agreement between pedometer-measured and self-reported PA in college-aged men than women.

Paraoxonase responses to exercise and niacin therapy in men with metabolic syndrome

Abstract Our purpose was to characterize changes in paraoxonase 1 (PON1) activity and concentration after single aerobic exercise sessions conducted before and after 6 weeks of niacin therapy in men with metabolic syndrome (MetS). Twelve men with MetS expended 500 kcal by walking at 65% of VO2max before and after a 6-week regimen of niacin. Niacin doses were titrated by 500 mg/week from 500 to 1500 mg/day and maintained at 1500 mg/day for the last 4 weeks. Fasting blood samples were collected before and 24 hours after each exercise session and analyzed for PON1 activity, PON1 concentration, myeloperoxidase (MPO), apolipoprotein A1, oxidized low-density lipoprotein (oLDL), lipoprotein particle sizes and concentrations. PON1 activity, PON1 concentration, MPO, and oLDL were unaltered following the independent effects of exercise and niacin (P > 0.05 for all). High-density lipoprotein particle size decreased by 3% (P = 0.040) and concentrations of small very low-density lipoprotein increased (P = 0.016) following exercise. PON1 activity increased 6.1% (P = 0.037) and PON1 concentrations increased 11.3% (P = 0.015) with the combination of exercise and niacin. Exercise and niacin works synergistically to increase PON1 activity and concentration with little or no changes in lipoproteins or markers of lipid oxidation.

Acute hepatic response to diet modification and exercise-induced endotoxemia during a laboratory-based duathlon.

The purpose of the study was to compare the acute hepatic response to diet modification and exercise-induced endotoxemia, and to determine if associations exist between liver damage markers, body core temperature, and IL-6 responses to a laboratory-based duathlon. Eleven moderately-trained healthy males followed a low-carbohydrate (CHO) and a high CHO diet to change their glycogen stores two-days before completing a duathlon. Blood samples were obtained at rest, immediately after and 1and 2-h following the duathlon for determination of endotoxin-lipopolysaccharide binding protein (LPS-LBP) complex, IL-6, and liver integrity markers AST, ALT, and AST/ALT ratio. Hydration status and body core temperature were assessed at rest, during, and after the duathlon. Athletes were more dehydrated and had higher AST/ALT ratios in the lowcompared to the high-CHO diet trial regardless of the measurement time (p<0.05). IL-6 increased from resting to immediately after, 1and 2-h following duathlon regardless of the diet (p<0.05). A higher LPS-LBP complex concentration was observed from rest to immediately after the duathlon. No significant correlations were found between LPS-LBP complex levels and body core temperature. In conclusion, athletes on a low-CHO diet showed higher hepatic structural damage and finished more dehydrated compared to athletes on a high-CHO diet. Body core temperature and LPS-LBP complex levels were unrelated beyond the increase in body core temperature explained by exercise. No significant associations were found between body core temperature, IL-6 and LPS-LBP complex concentrations.

Postprandial lipemia: what is the impact of exercise outside of the laboratory?

N onfasting triglyceride concentrations are now recognized as a risk factor for both cardiovascular diseases and all-cause mortality (7). Even a single session of aerobic exercise can favorably improve several aspects of postprandial metabolism in study cohorts ranging from young and healthy adults to those with overt disease. Indeed, it has long been established that moderate-intensity aerobic exercise performed 1–18 h before a meal results in reductions in triglyceride concentrations in the postprandial state (6,8). With such a wealth of evidence already in place, it seems well justified to conclude that previous aerobic exercise is an effective intervention for improving triglyceride metabolism in the hours after meal consumption. Case closed—or is it? Recent evidence has suggested that aerobic exercise may not have an effect on postprandial lipid metabolism in the absence of an exercise-induced caloric deficit (2,4). Therefore, the true effect of exercise needs to be considered in the context of nutritional considerations, such as compensatory caloric consumption, which are frequently overlooked by many investigators (1). Furthermore, this opens a debate as to whether or not the aforementioned results from carefully controlled laboratory experiments accurately reflect the effect of exercise on postprandial lipemia in free-living conditions. In this issue of Medicine & Science in Sports & Exercise, Farah et al. (3) provide insight into this very question by assessing the influence of exercise on postprandial lipemia after ad libitum feeding in overweight men. Several methodological aspects of this study were intended to mimic a real-life setting. First, the single session of aerobic exercise was performed at an intensity of 50% of maximal aerobic power until 33.5 kJIkg of body mass was expended. Thus, the protocol was consistent with current public health recommendations for the cohort being studied (5). Second, in contrast to previous study designs, the authors took the unique approach of providing ad libitum buffet meals, where participants were allowed to self-select the type and quantity of food. Despite unrestricted access to food, participants did not significantly increase caloric consumption the day after the exercise session. In fact, the caloric deficit that resulted from this exercise and ad libitum feeding protocol was similar to that produced as a result of more regimented laboratory protocols. Interestingly, the authors also reported that previous aerobic exercise attenuated the postprandial triglyceride response to a degree comparable to that documented with other protocols. This highlights the importance of exercise-induced negative energy balance as a key variable in mediating the effect of aerobic exercise on postprandial lipemia. Further creative research, such as that conducted by Farah et al., is warranted to clarify this issue. From a public health perspective, these are the most compelling results to date because they strongly indicate that the ability of aerobic exercise to attenuate postprandial lipemia does in fact extend beyond the laboratory and into everyday life.