Open Access Kent State (OAKS)

PROBLEM: To date, no studies have evaluated sex-specific differences in response to an acute bout of resistance exercise (RE) on vascular function. Therefore, we sought to determine the sex-specific responses of pulse wave reflection and aortic arterial stiffness after an acute bout of RE. METHODS: Aortic hemodynamics, pulse wave reflection, and aortic arterial stiffness were assessed at rest and 10 minutes after 3 sets of 10 repetitions at 75% 1-repetition maximum on the squat, bench press, and deadlift in resistance-trained men (n=14) and women (n=12). A mixed ANOVA was used to analyze the effects of sex (men, women) across condition (acute resistance exercise, control) and time (rest, recovery). RESULTS: The sexes had similar values at rest and after the acute RE. There was no effect of the RE on brachial or aortic blood pressures. There were significant condition x time interactions for the augmentation index (AIx: rest: 12.1±7.9%; recovery:19.9±10.5%, p=0.003), AIx at 75bpm (rest: 5.3±7.9%; recovery: 24.5±14.3%, p=0.0001), augmentation pressure (rest: 4.9±2.8mmHg; recovery: 8.3±6.0mmHg, p=0.004), and aortic arterial stiffness (rest: 5.3±0.6ms; recovery: 5.9±0.7ms, p=0.02) with significant increases after the acute RE. There was also a significant condition x time for the time of the reflected wave (rest: 150±7ms; recovery: 147±9ms, p=0.02) and the subendocardial variability ratio (rest: 147±17%; recovery: 83±24%, p=0.0001) such that they were reduced after the acute RE. CONCLUSIONS: These data suggest that an acute bout of RE increases pulse wave reflection and aortic arterial stiffness similarly between the sexes without significantly altering aortic hemodynamics.

Oxidative stress has been shown to be an early predictor and key pathological feature of neurodegenerative diseases including Alzheimer’s disease (AD). Previous work in our laboratory has demonstrated that administration of the peptide hormone amylin can reduce levels of oxidative stress in a transgenic mouse model of AD (APP/PS1) as well as Neuroscreen-1 cultures (neuronal cell model). Although it is apparent that amylin has antioxidant activity, its mechanism of action remains unclear. Because mitochondria are the main producers of reactive oxygen species (ROS) that account for oxidative stress in a cell, they have been a target of our investigation. Specifically, we determined whether amylin treatment regulates mitochondrial dynamics-associated proteins and mobility deficits in the APP/PS1 AD mouse model. Our data show that amylin treatment regulates mitochondrial dynamics-associated proteins as well as proteins associated with mitochondrial biogenesis. Taken together, our data suggest that some of the effects of amylin on oxidative stress regulation may stem from improving mitochondrial function.

Abstract

The reduced metabolic cost of isolated eccentric contractions compared to concentric contractions is well established. However, the net impact of this difference across an entire session of resistance exercise has yet to be determined. Thus, the purpose of this investigation was to determine the extent to which metabolic and cardiovascular stress varied between training sessions comprised only of eccentric, concentric or traditional resistance exercises. Twelve subjects completed a traditional (TRAD), concentric (CON), and eccentric (ECC) full-body resistance workout comprised of 6 upper and lower body exercises. Resistance was set at 65% of their 1 repetition max and mechanical work was matched across conditions. Oxygen consumption (VO₂), respiratory exchange ratio (RER), heart rate (HR), mean arterial pressure (MAP), and blood lactate were recorded throughout the exercise sessions. Both the TRAD (9.26±1.83ml/kg/min) and CON (10.03±1.63ml/kg/min) conditions resulted in greater VO₂ values when compared to the ECC (6.67±1.25ml/kg/min) condition. HR and MAP values were 46% and 4% greater in CON compared to that of ECC conditions. Furthermore, RER during CON (1.00±0.03) and TRAD (1.03±0.04) were greater than during ECC (0.88±0.09). Blood lactate was also greater in CON (8.9±1.7mM) and TRAD (9.0±3.0mM) compared to ECC (2.5±1.9mM) (p

Luteinizing hormone (LH) plays an important role in learning and memory as well as Alzheimer’s Disease (AD). Previously, our laboratory has demonstrated that there is an inverse relationship between blood and brain levels of LH and that when levels are normalized post-ovariectomy, both cognition and spine density losses are reversed. Because these differences appear to depend on the reproductive status of the mouse, we determined whether normal cyclic fluctuations in LH during the estrous cycle correlate with neuronal markers of neuroplasticity that are associated with cognition. To address this, we measured serum LH levels using sandwich RIA ELISAs and determined changes in synaptophysin and spinophilin in cognition-associated brain regions. As expected, preliminary data suggests that LH levels fluctuate during the estrous cycle and may correlate with synaptic markers associated with cognitive function. Given that others have found that cognition function fluctuates during the estrous cycle, our data demonstrates that these fluctuations may be at least, in part, dependent on changes in serum and brain LH.

Obesity is a leading health problem in the United States, despite the abundance of weight-loss programs available. There is an increasing interest in weight-loss methods that use time-restricted feeding, including intermittent fasting, where days of limited food access are alternated with days of normal food intake. To determine the benefits of intermittent fasting to obesity, we employed a rat model of inherent leanness and obesity, with the lean rats being more physically active (high-capacity runners) than the obesity-prone (low-capacity runners). Our hypothesis stated that intermittent fasting would induce loss of fat and lean mass in both rat types with the obesity-prone rats losing more body weight. Body weight and composition were measured before intermittent fasting in lean and obesity-prone male rats (n=8/group). Rats were allowed free access to food on fed days, alternating with fasting days (no calories consumed). Rats were weighed daily and the body composition was analyzed weekly using magnetic resonance spectroscopy (EchoMRI). All rats lost weight over eight weeks of intermittent fasting. Obesity-prone rats lost significantly more fat mass and body weight compared to the lean rats, whereas loss of lean mass differed by only a few grams. Results were similar in female rats but contrasted with previous findings when weight loss was induced using 50% calorie restriction. Compared to standard calorie restriction, intermittent fasting decreased the loss of lean mass while enhancing the loss of fat mass. Intermittent fasting was thus found to be successful in inducing weight loss in obese rats.