Browsing by Author "Frisard, Madlyn I."

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    Aging, resistance training, and diabetes prevention
    Flack, Kyle D.; Davy, Kevin P.; Hulver, Matthew W.; Winett, Richard A.; Frisard, Madlyn I.; Davy, Brenda M. (2010-12-15)
    With the aging of the baby-boom generation and increases in life expectancy, the American population is growing older. Aging is associated with adverse changes in glucose tolerance and increased risk of diabetes; the increasing prevalence of diabetes among older adults suggests a clear need for effective diabetes prevention approaches for this population. The purpose of paper is to review what is known about changes in glucose tolerance with advancing age and the potential utility of resistance training (RT) as an intervention to prevent diabetes among middle-aged and older adults. Age-related factors contributing to glucose intolerance, which may be improved with RT, include improvements in insulin signaling defects, reductions in tumor necrosis factor-α, increases in adiponectin and insulin-like growth factor-1 concentrations, and reductions in total and abdominal visceral fat. Current RT recommendations and future areas for investigation are presented.
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    AMP-activated protein kinase and muscle metabolism
    Scheffler, Tracy L. (Virginia Tech, 2012-07-11)
    AMP-activated protein kinase (AMPK) is a major regulator of skeletal muscle metabolism with relevance to agriculture and human health. During the conversion of muscle to meat, the rate and extent of postmortem metabolism and pH decline largely determine pork quality development. Pigs with the AMPKγ3 R200Q mutation generate pork with low ultimate pH (pHu); this is attributed to high glycogen content, and greater "potential" to produce lactate and H+. We hypothesized that decreasing muscle phosphocreatine and creatine would decrease ATP buffering capacity, resulting in earlier termination of glycolysis and pH decline. Dietary supplementation with the creatine analogue, β-GPA, decreased muscle total creatine but negatively affected performance. Another experiment was conducted using control or β-GPA diet and wild type and AMPKγ3R200Q pigs in a 2Ã 2 factorial design. The loss of muscle total creatine was important in maintenance of ATP levels in AMPKγ3R200Q muscle early postmortem. Moreover, elevated glycogen did not affect pHu, supporting that energetic modifications induced by feed restriction and β-GPA supplementation influence extent of pH decline. Next, we utilized a line of pigs selected for differences in pHu. Another AMPKγ3 mutation (V199I), which is associated with higher pHu and lower glycolytic potential, was prevalent. The 199II genotype increased pHu in castrated males only. The wild type VV genotype increased glycolytic potential, but neither glycolytic potential nor lactate predicted pHu. In humans, AMPK activation is at least partly responsible for the beneficial effects of exercise on glucose transport and increased oxidative capacity in skeletal muscle. An inverse relationship exists between skeletal muscle fiber cross-sectional area and oxidative capacity, which suggests muscle fibers hypertrophy at the expense of oxidative capacity. Therefore, we utilized pigs possessing mutations associated with increased oxidative capacity (AMP-activated protein kinase, AMPKγ3R200Q) or fiber hypertrophy (ryanodine receptor 1, RyR1R615C) to determine if these events occur in parallel. RyR1R615C increased muscle fiber size; AMPKγ3R200Q increased oxidative capacity, evidenced by enhanced enzyme activity, mitochondrial function, and expression of mitochondrial proteins. Thus, pigs with both AMPKγ3R200Q and RyR1R615C possess increased fiber size and oxidative capacity, suggesting hypertrophy and oxidative capacity can occur simultaneously in skeletal muscle.
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    Angiotensin II receptor blockade and insulin sensitivity in overweight and obese adults with elevated blood pressure
    Marinik, Elaina (Virginia Tech, 2012-02-07)
    Currently, it is reported that ~65% and 34% of the U.S. population is overweight and obese, respectively. Obesity is a major risk factor for cardiovascular disease. Overweight and obese individuals are also at an increased risk of developing hypertension. Whole-body insulin sensitivity is reduced in obesity, resulting in insulin resistance and increased risk of type 2 diabetes. One possible mechanism contributing to insulin resistance in obesity hypertension is renin-angiotensin system (RAS) overactivation. The RAS exhibits vasocontricting and sodium-retaining properties, yet in vivo and in vitro animal experiments suggest impairment of whole-body insulin sensitivity with increased angiotensin II (Ang II) exposure. Furthermore, evidence from clinical studies indicates Ang II receptor blockers (ARBs) may reduce the incidence of new-onset diabetes compared to other antihypertensive agents in at-risk hypertensive patients. However, it is unclear if whole-body insulin sensitivity is improved with Ang II receptor blockade in humans. Thus, we tested the hypothesis that 8-week Ang II receptor blockade with olmesartan would improve whole-body insulin sensitivity in overweight and obese individuals with elevated blood pressure (BP). Olmesartan was selected for the present study because it is devoid of partial PPARγ agonist activity. To test our hypothesis, intravenous glucose tolerance tests were performed to measure insulin sensitivity before and after control and ARB treatment in a randomized crossover manner. Because skeletal muscle tissue accounts for ~75-90% of insulin-stimulated glucose uptake, a secondary exploratory aim was to examine skeletal muscle inflammatory and collagen response in relation to insulin sensitivity during ARB treatment. No baseline differences were observed between treatments (P>0.05). Both systolic (-11.7 mmHg; P=0.008) and diastolic (-12.1 mmHg; P=0.000) BP were reduced with ARB treatment. Insulin sensitivity was not different between treatments (P>0.05). No correlates of insulin sensitivity were identified. In addition, skeletal muscle inflammatory and collagen gene expression did not change from pre- to post-ARB treatment (P>0.05). Our findings suggest that short-term RAS blockade in overweight and obese adults with elevated BP does not improve whole-body insulin sensitivity, despite a significant BP reduction. Further studies are needed to clarify the role of individual RAS blockers on insulin sensitivity during RAS inhibition in obesity hypertension.
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    Angiotensin II suppresses autophagy and disrupts ultrastructural morphology and function of mitochondria in mouse skeletal muscle
    Silva, Kleiton Augusto Santos; Ghiarone, Thaysa; Grant, DeAna; White, Tommi; Frisard, Madlyn I.; Chandrasekar, Bysani; Delafontaine, Patrice; Yoshida, Tadashi; Schreiber, Kathy; Sukhanov, Sergiy (2019-06-01)
    Angiotensin II (ANG II)-induced skeletal muscle wasting is characterized by activation of the ubiquitin-proteasome system. However, the potential involvement of proteolytic system macroautophagy/autophagy in this wasting process remains elusive. Autophagy is precisely regulated to maintain cell survival and homeostasis; thus its dysregulation (i.e., overactivation or persistent suppression) could lead to detrimental outcomes in skeletal muscle. Here we show that infusion of ANG II for 7 days in male FVB mice suppressed autophagy in skeletal muscle. ANG II blunted microtubule-associated protein 1 light chain 3B (LC3B)-I-to-LC3B-II conversion (an autophagosome marker), increased p62/SQSTM1 (an autophagy cargo receptor) protein expression, and decreased the number of autophagic vacuoles. ANG II inhibited UNC-51-like kinase 1 via inhibition of 5=-AMP-activated kinase and activation of mechanistic target of rapamycin complex 1, leading to reduced phosphorylation of beclin-1Ser14 and Autophagy-related protein 14Ser29, suggesting that ANG II impairs autophagosome formation in skeletal muscle. In line with ANG II-mediated suppression of autophagy, ANG II promoted accumulation of abnormal/damaged mitochondria, characterized by swelling and disorganized cristae and matrix dissolution, with associated increase in PTEN-induced kinase 1 protein expression. ANG II also reduced mitochondrial respiration, indicative of mitochondrial dysfunction. Together, these results demonstrate that ANG II reduces autophagic activity and disrupts mitochondrial ultrastructure and function, likely contributing to skeletal muscle wasting. Therefore, strategies that activate autophagy in skeletal muscle have the potential to prevent or blunt ANG II-induced skeletal muscle wasting in chronic diseases. NEW & NOTEWORTHY Our study identified a novel mechanism whereby angiotensin II (ANG II) impairs mitochondrial energy metabolism in skeletal muscle. ANG II suppressed autophagosome formation by inhibiting the UNC-51-like kinase 1(ULK1)-beclin-1 axis, resulting in accumulation of abnormal/damaged and dysfunctional mitochondria and reduced mitochondrial respiratory capacity. Therapeutic strategies that activate the ULK1-beclin-1 axis have the potential to delay or reverse skeletal muscle wasting in chronic diseases characterized by increased systemic ANG II levels.
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    Arterial Destiffening with Weight Loss in Overweight and Obese Middle-Aged and Older Adults
    Dengo Flores, Ana Laura (Virginia Tech, 2010-06-15)
    Cardiovascular diseases (CVD) are the leading cause of mortality in the United States. Aging is the major risk factor for CVD development, which is independently predicted by arterial stiffness (AS). Arterial stiffening is closely related to age-related arterial structural/functional changes and obesity. Therefore, obese middle-aged and older adults are considered a high CVD risk population. In light of the current obesity epidemic and the projected growth of the older population, there is an overwhelming need to determine if weight loss (WL) may reduce AS (CVD risk) in this population. Thus, we hypothesized that WL via a hypocaloric diet-alone would reduce AS in overweight and obese middle-aged and older adults. To test our hypothesis, baseline assessment of anthropometrics, blood pressure and AS was conducted, and subjects were randomized to a 12-week WL intervention or a control group. Arterial stiffness was measured using applanation tonometry to estimate carotid-femoral artery pulse wave velocity (C-F PWV), and with high-resolution ultrasonography of the carotid artery (β-SI). There were no baseline differences between groups in our variables of interest. Consistent with our hypothesis, both measures of AS were significantly reduced (C-F PWV= -16% and β-SI= -12%, P<0.05) with WL (-8%, P<0.05). Weight loss also resulted in significantly decreased blood pressure, total body and abdominal fat. No such changes were observed in the control group. Pooled correlation analysis suggests that the magnitude of change in C-F PWV was not associated with changes in systolic, diastolic or mean blood pressure. We further hypothesized that reductions in AS, if observed, would be associated with the magnitude of reduction in total body or abdominal adiposity. Concordant with our hypothesis, the reductions in C-F PWV were significantly associated with total and abdominal fat. However, linear regression analysis indicate that neither total body nor abdominal body fat were capable of independently predicting reductions in C-F PWV. Our findings suggest that moderate WL in overweight and obese middle-aged and older adults is an efficacious treatment strategy for reducing AS. Further studies are needed to determine if the improvements in arterial compliance would be sustained with long-term WL maintenance.
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    Body Project Implementation in Virginia Tech Athletics: Effect on Body Image Satisfaction and Thin Idealization
    Labiaga, Janelle S. C. (Virginia Tech, 2020-05-21)
    Eating disorders and disordered eating have a prevalence of 6% to 45% in collegiate female athletes (Knapp, Aerni, & Anderson, 2014). Thin idealization and body image dissatisfaction are risk factors for the development of disordered eating and eating disorders. Dissonance-based prevention programs have been shown to be effective in reducing thin idealization and body image dissatisfaction, as well as lessening risk of developing disordered eating and eating disorders. Currently, Virginia Tech Athletics does not utilize a group-based eating disorder prevention program for its female athletes. The purpose of this pilot project was to administer the Body Project, a dissonance-based prevention program aimed at reducing thin idealization and body image dissatisfaction, to female swimmers at Virginia Tech and evaluate the program’s effect on thin idealization and body image dissatisfaction. Thin idealization and body image dissatisfaction were evaluated via the Body Parts Satisfaction Survey-Revised (BPSS-R) and the Ideal Body Stereotype Survey-Revised (IBSS-R), respectively, before and after completion of the Body Project. Ten female swimmers, without current eating disorders, volunteered to participate, and nine swimmers (19.44 ± 1.42 years old; 5 freshmen, 2 juniors, and 2 seniors) completed the full project. Sixty-seven percent of participants (6 out of 9) experienced a reduction in their subscription to thin-ideal internalization (IBSS-R 2.96 ± 0.92 pre, 1.85 ± 0.88 post, p<0.05), while 78% of participants (7 out of 9) experienced an increase in body satisfaction (BPSS-R 4.42 ± 1.35 pre, 5.08 ± 0.90 post, p<0.05, p< 0.05). The findings of this pilot project suggest that the Body Project is an effective tool to influence subscription to thin-ideal internalization and body satisfaction in female college athletes. Continued effort to refine and implement the Body Project as group-based eating disorder prevention program for female college athletes is needed.
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    Cellular Reprogramming in Skeletal Muscle after Repeated Exposures to Endotoxin
    Denko, Laura Michelle (Virginia Tech, 2012-06-21)
    Obesity-related metabolic derangements have been linked to toll-like receptor 4 (TLR4), an innate immune system receptor, due to its role in proinflammatory pathways. Lipopolysaccharide (LPS), a gram-negative bacteria cell wall component, is the ligand for TLR4, and has been shown to be elevated in states of metabolic disease. Heightened levels of circulating endotoxin is termed metabolic endotoxemia and has been linked to systemic inflammation which is associated with obesity, type 2 diabetes mellitus (T2DM), and cardiovascular disease (CVD). Immune cells exhibit a protective ability to develop endotoxin tolerance. The objective of this study was to determine if endotoxin tolerance exists in skeletal muscle cells, and if a condition that mimics a state of over nutrition, such as elevated levels of fatty acids, affect this tolerance. To this end, L6 skeletal muscle cells were treated with low (50 pg/mL)- and high (500 ng/mL)-doses of LPS, with and without the presence of free fatty acids (FFAs). Tolerance was assessed by measuring: 1) changes in mRNA expression of interleukin-6 (IL-6) and monocyte chemoattractant-1 (MCP-1) as markers of a pro-inflammatory response; and 2) mRNA levels of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC1-°) and mitochondrial oxidative capacity via an XF24 Flux Analyzer (Seahorse Bioscience) as measures of the metabolic response. Tolerance to LPS was observed in response to low- and high-doses with MCP-1 mRNA transcription but not IL-6. Changes in PGC1-° and mitochondrial OCR exhibited a tolerant effect in response to the high dose of LPS but not the low dose. The addition of free fatty acids to LPS treatments did not prevent the tolerant effects under any conditions. In conclusion, LPS tolerance exists in skeletal muscle cells but appears to differ depending on pro-inflammatory target and LPS concentration. Additionally, fatty acids, in the current model, have no effect on LPS tolerance.
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    Characterization of an in vitro exercise model and the effects of a metabolic endotoxemia on skeletal muscle adaptation to electric pulse stimulation
    Harvey, Mordecai Micah (Virginia Tech, 2017-06-20)
    The prevalence of obesity and type II diabetes is increasing. Although exercise is widely accepted for prevention and treatment, evidence of resistance to exercise in patients with these diseases is also mounting. Muscle contraction during exercise stimulate cellular responses important for adaptation. These responses include the release of myokines and the subsequent increase in substrate metabolism. This study aimed to define a culture model for simulating exercise in human primary skeletal muscle cells. We hypothesized that chronic electric pulse stimulation (EPS) of human myotubes in vitro would emulate cellular and molecular responses to exercise observed in vivo. To define this model, we applied EPS to human myotubes for varied lengths of time and measured interleukin-6 (Il-6), peroxisome proliferator-activated receptor gamma coactivator 1- (PGC1-), superoxide dismutase 2 (SOD2), substrate metabolism, metabolic enzyme activity, heat stress markers, and pH. To recreate the inflammatory milieu observed in metabolic disease states we treated the myotubes with a low dose of 20 EU lipopolysaccharide (LPS). Following the 24-hour stimulation we observed significant increases in transcription of Il-6, PGC1-, and SOD2. Basal glucose and fatty acid oxidation were also markedly increased in the cells after EPS. Cells treated with LPS elicited a blunted transcriptional, metabolic, and enzymatic response to EPS. These findings suggest that EPS is a viable model for simulating the effects of exercise. Our observations also indicate that an inflammatory environment could play a role in interfering with the adaptations to exercise.
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    Characterization of Metabolic Differences in Benign, Slow Developing and Tumor Initiating Ovarian Cancers
    Anderson, Angela S. (Virginia Tech, 2013-05-14)
    Ovarian cancer is known as the "silent killer," due to its late diagnosis and frequent recurrence after initial treatment.  Finding a new way to diagnose and treat ovarian cancer in conjunction with current therapies is paramount.  By capitalizing on metabolic changes that occur during cancer progression, interventions can be developed.  The Nobel laureate Otto Warburg is credited with discovering an altered metabolic state within cancer cells known as the Warburg effect.  In the Warburg effect, cancer cells participate in an increased rate of aerobic glycolysis with an excess secretion of lactate, allowing for carbon flux into biosynthetic pathways.  Exactly which metabolic pathways are altered in ovarian cancer and at which stage in the progression of ovarian cancer they are occurring was unknown.  Therefore using the recently established mouse ovarian surface epithelial (MOSE) progression model, we were able to measure metabolic changes in varying states of disease and levels of aggressiveness.  As cells progressed from a benign early stage (MOSE-E), through a transitional intermediate stage (MOSE-I), to an aggressive late stage (MOSE-L), the MOSE cells became more glycolytic and lipogenic, establishing the MOSE model as a valuable model for studying ovarian cancer metabolism.  Treating the MOSE cells with the naturally occurring chemotherapeutic agent sphingosine decreased p-AKT  protein levels in the cell, decreased the glycolytic rate and decreased de novo cholesterol synthesis.  Cancer stem cells are known to be resistant to chemotherapy treatments and targeting their metabolism may be promising for combinatorial treatments.  Therefore, the metabolism of highly aggressive tumor-initiating cells (TIC), harvested from ascites of C57Bl/6 mice injected with MOSE-L cells were characterized.  Although the basal metabolism of the TICs was similar to the MOSE-L cells, TICs were more resistant to cell death as a consequence of external stresses and substrate depletion.  The TICs could also up-regulate oxygen consumption rate (OCR) when uncoupled and increase glycolysis when ATP Synthase was inhibited, highlighting their resiliency.  Taken together, we have identified targets for treatment strategies that could suppress the growth of primary tumors and may be effective against TICs, thereby suppressing tumor recurrence and possibly prolonging the life of women with ovarian cancer.
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    Control of mitochondrial metabolism and systemic energy homeostasis by microRNAs 378 and 378*
    Carrer, Michele; Liu, Ning; Grueter, Chad E.; Williams, Andrew H.; Frisard, Madlyn I.; Hulver, Matthew W.; Bassel-Duby, Rhonda; Olson, Eric N. (NAS, 2012-09-18)
    Obesity and metabolic syndrome are associated with mitochondrial dysfunction and deranged regulation of metabolic genes. Peroxisome proliferator-activated receptor γ coactivator 1β (PGC-1β) is a transcriptional coactivator that regulates metabolism and mitochondrial biogenesis through stimulation of nuclear hormone receptors and other transcription factors. We report that the PGC-1β gene encodes two microRNAs (miRNAs), miR-378 and miR-378*, which counterbalance the metabolic actions of PGC-1β. Mice genetically lacking miR-378 and miR-378* are resistant to high-fat diet-induced obesity and exhibit enhanced mitochondrial fatty acid metabolism and elevated oxidative capacity of insulin-target tissues. Among the many targets of these miRNAs, carnitineO-acetyltransferase, a mitochondrial enzyme involved in fatty acid metabolism, and MED13, a component of the Mediator complex that controls nuclear hormone receptor activity, are repressed by miR-378 and miR-378*, respectively, and are elevated in the livers of miR-378/378* KO mice. Consistent with these targets as contributors to the metabolic actions of miR-378 and miR-378*, previous studies have implicated carnitine O-acetyltransferase and MED13 in metabolic syndrome and obesity. Our findings identify miR-378 and miR-378* as integral components of a regulatory circuit that functions under conditions of metabolic stress to control systemic energy homeostasis and the overall oxidative capacity of insulin target tissues. Thus, these miRNAs provide potential targets for pharmacologic intervention in obesity and metabolic syndrome.
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    Delay Discounting, Reinforcing Value of Food, and Components of Metabolic Health
    Bellows, Abby Gail (Virginia Tech, 2018-07-02)
    Background: According to the Centers for Disease Control and Prevention (CDC), over one-third of US adults are obese. In order to assess causes of and treatments for obesity, researchers have evaluated a number of processes underlying health-related behaviors, one of which is delay discounting. Delay discounting is a cognitive process that describes the phenomenon by which individuals discount the value of a future reward compared to the value of an immediate reward. Researchers have associated delay discounting with drug addiction, alcoholism, and cigarette smoking. More recently, delay discounting has been studied with regards to health-related behaviors, such as body weight management, food intake, glucose control, and physical activity. While a number of studies have concluded that obese individuals tend to be greater discounters, the relationship between delay discounting and various health-related behaviors beyond smoking and drug use remains unclear. The purpose of this study is to evaluate the relationship between delay discounting and diet quality, glucose tolerance, physical activity, and fasting vs. non-fasting conditions. Methods: Sixty-five males (n=20) and females (n=45) were recruited for the present study. Participants completed two lab sessions: one under non-fasting conditions, and one under fasting conditions which involved measurements of body mass and composition, blood pressure, blood glucose, blood lipids, and health-related questionnaires. Delay discounting and food purchase tasks were completed at both visits. Participants were asked to complete a four-day food intake record and wear a physical activity monitor for four days. Results: Lower rates of discounting were found in those who consumed more total vegetables, and lower food reinforcement was observed in those who spent less time sedentary and more time physically active, had greater dietary Restraint, and had a lower resting heart rate. There were no significant differences between discounting rates and food reinforcement across fasting and non-fasting conditions.
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    Do Probiotics Protect Against the Deleterious Effects of a High-Fat Diet?
    Fundaro, Gabrielle F. (Virginia Tech, 2014-06-27)
    High-fat diets and obesity have been linked to unfavorable changes in gut bacteria and increased leakage of bacterially-derived lipopolysaccharide (endotoxin) from the intestinal tract into circulation, which is associated with low-grade inflammation, metabolic dysregulation and degradation of tight-junction proteins between intestinal cells. Probiotic supplementation is the practice of ingesting live strains of bacteria that are proposed to have a beneficial effect on the host by enriching the intestine with healthy bacteria. The purpose of this project was to determine if probiotic supplementation would prevent increased inflammatory tone, decreased oxidative capacity, and decreased tight-junction protein expression associated with high-fat feeding and elevated endogenous endotoxin. Male C57BL/6J mice were fed either a control (CD, 10% fat) or high-fat (HFD, 60% fat) diet for 4 weeks while receiving a daily oral gavage of water (C-VSL#3, HF-VSL#3) or probiotics (C+VSL#3, HF+VSL#3) equivalent to 1.2 billion live cultures. Changes in body weight, body composition, respiratory exchange ratio, energy expenditure, and glucose and insulin tolerance were measured in live mice. Markers of metabolic function were measured in whole muscle homgenates and mitochondria isolated from red and white skeletal muscle. Plasma endotoxin was measured in blood collected from fasted mice at the time of euthanization. The large and small intestines were collected and mRNA levels of tight-junction proteins and markers of nutrient sensing were measured. To determine a possible protective effect against endogenous LPS, a second cohort of mice were given an intraperitoneal injection of 0.1µg/kg LPS or saline to induce endotoxemia after four weeks of the aforementioned feeding protocol. Markers of metabolic function and inflammation were measured in mitochondria, skeletal muscle and liver. VSL#3 supplementation improved glucose homeostasis and markers of inflammation while enhancing nutrient sensing in the gut.
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    Early Skeletal Muscle Adaptations to Short-Term High-Fat Diet in Humans Before Changes in Insulin Sensitivity
    Anderson, Angela S.; Haynie, Kimberly R.; McMillan, Ryan P.; Osterberg, Kristin L.; Boutagy, Nabil E.; Frisard, Madlyn I.; Davy, Brenda M.; Davy, Kevin P.; Hulver, Matthew W. (Wiley-Blackwell, 2015-04-01)
    Objective—The purpose of this investigation was to understand the metabolic adaptations to a short-term (5 days), isocaloric, high fat diet (HFD) in healthy, young males. Methods—Two studies were undertaken with 12 subjects. Study 1 investigated the effect of the HFD on skeletal muscle substrate metabolism and insulin sensitivity. Study 2 assessed the metabolic and transcriptional response in skeletal muscle to the transition from a fasted-to-fed state using a high fat meal challenge prior to and following 5 days of HFD. Results—Study 1 showed no effect of a HFD on skeletal muscle metabolism or insulin sensitivity in fasting samples. Study 2 showed that a HFD elicits significant increases in fasting serum endotoxin, and disrupts the normal postprandial excursions of serum endotoxin, and metabolic and transcriptional responses in skeletal muscle. These effects following 5 days of HFD were accompanied by an altered fasting and postprandial response in the ratio of phosphorylated to total p38 protein. These changes all occurred in the absence of alterations in insulin sensitivity. Conclusions—Our findings provide evidence for early biological adaptations to high fat feeding that proceed and possibly lead to insulin resistance.
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    The Effect of a Probiotic Supplement on Insulin Sensitivity and Skeletal Muscle Substrate Oxidation during High Fat Feeding
    Osterberg, Kristin (Virginia Tech, 2014-08-28)
    Background: Modifying the gut microbiota through the administration of probiotics during high fat feeding has been shown to attenuate weight gain and body fat accretion while improving insulin sensitivity in animal models. Objective: Our objective was to determine the effects of the probiotic VSL#3 on body weightand composition, skeletal muscle substrate oxidation, and insulin sensitivity and during 4 weeks of high-fat, hypercaloric feeding. We hypothesized that the probiotic would attenuate the body weight and fat gain and adverse changes in insulin sensitivity and substrate oxidation following high fat, hypercaloric feeding in young, non-obese males. Methods: Twenty non-obese males (18-30 y) volunteered to participate in the present study. Following a 2-week eucaloric control diet, subjects underwent a dual x-ray absorptiometry (DXA) to determine body composition, an intravenous glucose tolerance test (IVGTT) to determine insulin sensitivity, a skeletal muscle biopsy for measurement of substrate oxidation. Serum endotoxin was also measured. Subsequently, subjects were randomized to receive either VSL#3 (2 satchets) or placebo during 4 weeks of consuming a high fat (55% fat), hypercaloric diet (+1,000 kcal/day). Macronutrient composition of the high fat diet was 55% fat, 30% carbohydrate, and 15% protein. Results: There were no differences between the groups in subject characteristics or in the dependent variables at baseline. Body weight and fat mass increased less (P<0.045) following the high fat diet with VSL#3 compared to placebo. Insulin sensitivity (and other IVGTT variables) and both glucose and fat oxidation did not change significantly with time or VSL#3 treatment. Serum endotoxin concentration was not different between groups following the high-fat diet. Conclusions: VSL#3, a multi-strain probiotic, attenuated body weight and fat gain following a 4-week high fat, hypercaloric diet compared with a placebo. There were no differences between the VSL and control in circulating endotoxin, insulin sensitivity (and other IVGTT variables) or in skeletal muscle substrate oxidation.
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    The effect of hypoxia and 3D culture conditions on heterogeneous ovarian cancer spheroids
    Liu, Lu (Virginia Tech, 2017-01-10)
    Epithelial ovarian cancer (EOC) is the leading cause of death from gynecological malignancy due to the insufficient accurate screening programs for the early detection of EOC. To improve the accuracy of the early detection, there is a need to deeply understand the mechanism of EOC progression and the interaction between cancer cells with their unique microenvironment. Therefore, this work investigated the metabolic shift in the mouse model for progressive ovarian cancer, and evaluated the effects of hypoxic environment, spheroid formation as well as stromal vascular fractions (SVF) on the metabolic shift, proliferation rate, drug resistance and protein markers in functional categories. The results demonstrated an increasingly glycolytic nature of MOSE cells as they progress from a tumorigenic (MOSE-L) to a highly aggressive phenotype (MOSE-FFL), and also showed changes in metabolism during ovarian cancer spheroid formation with SVF under different oxygen levels. More specifically, the hypoxic environment enhanced glycolytic shift by upregulating the glucose uptake and lactate secretion, and the spheroid formation affected the cellular metabolism by increasing the lactate secretion to acidify local environments, modulating the expression of cell adhesion molecules to enhance cell motility and spheroids disaggregation, and up-regulating invasiveness markers and stemness makers to promote ovarian cancer aggressive potential. Hypoxia and spheroid formation decreased ovarian cancer cells growth but increased the chemoresistance, which leads to the promotion of aggressiveness and metastasis potential of ovarian cancer. SVF co-cultured spheroids further increased the glycolytic shift of the heterogeneous of ovarian cancer spheroids, induced the aggressive phenotype by elevating the corresponding protein markers. Decreasing the glycolytic shift and suppression of the proteins/pathways may be used to inhibit aggressiveness or metastatic potential of ovarian cancer heterogeneous of ovarian cancer spheroids, induced the aggressive phenotype by elevating the corresponding protein markers. Decreasing the glycolytic shift and suppression of the proteins/pathways may be used to inhibit aggressiveness or metastatic potential of ovarian cancer.
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    Effect of Nebivolol and Lifestyle Modification on Large Artery Stiffness in Middle-Aged and Older Hypertensive Adults
    Werner, Timothy Jason (Virginia Tech, 2013-07-24)
    For more than half a century cardiovascular disease has been the leading cause of death in the United States.  Aging, hypertension, and obesity are major risk factors for cardiovascular disease and clearly associated with arterial stiffness.  Arterial stiffness generates higher afterloads and diminishes coronary perfusion thereby causing ventricular hypertrophy and ischemia.  Importantly, arterial stiffness is an independent predictor of cardiovascular disease risk and all-cause mortality.   Current strategies such as inhibition of angiotensin II or angiotensin converting enzyme, reduction of smooth muscle tone, blood volume, or inflammatory mediators, and improving glucose homeostasis are effective destiffening options.  Nebivolol, a third generation beta-blocker, has unique vasodilatory characteristics and may be particularly efficacious as a destiffening agent.  Only a few studies have addressed this issue while relying on indirect, blood pressure-dependent stiffness indices precluding clear understanding of study outcomes.  There remains a need to determine the potential utility of nebivolol therapy as an arterial destiffening strategy.   Thus, we hypothesized that the combination of nebivolol and lifestyle modification would reduce central arterial stiffness in middle-aged and older hypertensive adults more than either intervention alone.  To test this hypothesis, we randomized 45 hypertensive adults to receive lifestyle modification, nebivolol, or combination for 12 weeks.  β-stiffness index, pulse wave analysis, and arterial compliance were measured at baseline and following the intervention.  No baseline differences in variables of  interest were observed between groups.  In contrast to our hypothesis, lifestyle modification, nebivolol, and combination groups had similar (P>0.05) reductions in beta-stiffness index (-1.87±0.83; -2.03±0.60; and -2.51±0.90 U), respectively, while carotid-femoral pulse wave velocity declined only in the nebivolol and combination groups.   Our findings suggest combination of nebivolol and lifestyle modification reduces arterial stiffness to a similar degree as either intervention alone in middle-aged and older hypertensive adults.  Further studies are needed to determine if the changes in arterial stiffness continue to occur or remain clinically significant over longer durations.
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    The Effects of a 5-Day High-Fat Diet on Skeletal Muscle O-GlcNAcylation
    Nealon, Lily Irene (Virginia Tech, 2016-07-06)
    Continual intake of high-fat foods, coupled with limited physical activity, can lead to metabolic inflexibility. Eventually, this may lead to significant health issues such as obesity, insulin resistance, cardiovascular disease, and other chronic diseases. Metabolic flexibility of human skeletal muscles is influenced by changes to mitochondrial, nuclear, and cytosolic proteins, in part as a result of posttranslational modifications (PTMs). O-linked B-D-N-acetylglucosamine, known as O-GlcNAc, has recently been identified as an important posttranslational modification that responds to nutrient sensing and cellular stress. Unlike other PTMs, O-GlcNAc has only two cycling enzymes. Because of its novelty, little research has been performed on the role of O-GlcNAc in human skeletal muscle and metabolic flexibility. The purpose of the current study was to establish the effects of a 5-day high-fat diet on skeletal muscle O-GlcNAcylation. In the proposed study, 13 non-obese, sedentary, college-aged males consumed a controlled diet for two weeks followed by a high-fat diet composed of 55% fat, 30% carbohydrate, and 15% protein. Muscle biopsies were taken from the vastus lateralis both fasted and four hours after a high-fat meal, following both the control diet and the high-fat diet. Western blot analysis was used to assess global O-GlcNAc and protein concentrations of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) in whole-homogenates and isolated mitochondria from skeletal muscle. Results were analyzed using independent, two-tailed t-tests and 2-way ANOVA analysis with repeated measures and Bonferroni corrections; a p-value was set to α less than or equal to 0.05. It was found that O-GlcNAc and OGT levels remained stable, although fasting levels of OGA significantly decreased after the 5-day high-fat diet. It is possible that healthy individuals are capable of maintaining normal levels of O-GlcNAc and its cycling enzymes, but there is still more to learn about O-GlcNAc and its role in metabolic flexibility.
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    The Effects of Acute Consumption and Chronic Supplementation of Cocoa on Overweight and Obese Adults at Risk of Developing Diabetes
    Strat, Karen M. (Virginia Tech, 2016-09-07)
    The prevalence of obesity and diabetes is increasing in the United States and abroad and strategies are needed to prevent the progression from an at-risk state to the clinically diagnosed diseases. Flavanols in cocoa powder have been shown to reduce blood glucose concentrations, improve insulin sensitivity, and decrease gut permeability in animals and humans, but it is unknown if this occurs in adults with prediabetes. Therefore, we first hypothesized that an acute dose of cocoa would reduce postprandial glucose and enhance insulin and incretin hormone responses to a mixed meal challenge compared to a placebo. Second, we hypothesized that 15 g cocoa/day for 4-weeks would reduce gut permeability, attenuate endotoxin response to a high fat meal, improve insulin sensitivity, and improve measures of skeletal muscle substrate flexibility in a randomized, double blinded, placebo controlled parallel group design. To test the first hypothesis, 30 overweight or obese volunteers who were at-risk for diabetes completed two meal challenges using a randomized crossover design. Blood samples were collected hourly for 4 hours and were analyzed for glucose, insulin, C-peptide, glucagon-like peptide 1 (GLP-1), and gastric inhibitory peptide (GIP). Cocoa did not influence these measures. However, participants with the lowest fasting blood glucose concentrations were more likely to respond to the cocoa as hypothesized. To test our second hypothesis, 15 overweight or obese adults at risk for developing diabetes consumed either the cocoa or placebo treatments along with a controlled diet for one month. Overall, cocoa did not seem to influence insulin sensitivity, gut permeability, or endotoxin levels, although cocoa may influence skeletal muscle substrate metabolism. In conclusion, the data for both studies suggests that cocoa did not exert substantial effects on the evaluated outcomes. However, the experiments did provide valuable information about incretin hormone levels in adults with impaired glucose tolerance. More research is needed to understand how cocoa can affect glucose homeostasis for overweight or obese adults.
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    Effects of an active halftime rewarm-up, with carbohydrate supplementation, on player's blood glucose and second half performance during a collegiate soccer match
    O'Brien, Patrick C. (Virginia Tech, 2017-09-27)
    BACKGROUND: The half-time (HT) period of a soccer match is viewed as a period for recovery. Completely inactive and passive HT has implications on metabolic responses and subsequent performance during the initial phases of the second half. PURPOSE: Determine the effects of an active rewarm-up, compared to a passive period, at halftime on various measures of performance during the first 15-minutes of the second half using global positioning system (GPS) units. Identify the effects of the active versus passive HT period, with CHO beverage supplementation, on blood parameters. METHODS: Crossover design study, twenty collegiate male soccer players participated in two 90-minute soccer matches with passive rest (CON) or a moderate-intensity rewarm-up (RWU) during HT with CHO supplementation. Subjects received five fingerstick blood samples throughout the match (BG) and four subjects had serum insulin/BG taken three times during the match. RESULTS: RWU had significantly (p<0.05) higher measures for total distance, average speed, speed exertion, accelerations, HMP distance, decelerations, and EE during TI-4 half when compared to CON. No subjects experienced hypoglycemia. However, CON did have a significant drop in BG after HT and the lowest mean BG taken at 60-minutes. Tendency for CON and RWU to have HT insulin levels that were elevated and reduced, respectively. CONCLUSION: A passive HT period is not optimal, given its causal role in temporary physical performance deficits in the second half of soccer matches. The results provide a strong rationale for collegiate soccer players and teams to incorporate the 8-minute RWU into the HT regime to optimize second half performance.
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    The Effects of Carbohydrate and Quercetin on Team Sport Athletic Performance and Exercise-Induced Inflammation and Oxidative Stress
    Abbey, Elizabeth Lea (Virginia Tech, 2009-03-31)
    Over 270 million people play soccer worldwide, and its popularity grows every day. In team sport exercise, fatigue may result from numerous factors including limited fuel, depleted energy stores and production of compounds that promote an inflammatory response. While inflammation is an essential mechanism for repairing damaged muscle tissue with exercise, prolonged inflammation leads to increased production of reactive oxygen species that can damage cell membranes, muscle, and signaling proteins. To prevent this response and improve performance, athletes are increasingly looking to nutritional interventions. Carbohydrate and antioxidant supplementation have both shown evidence of producing an ergogenic effect and attenuating inflammation and oxidative stress with prolonged endurance exercise. Less is known about how these interventions may influence intermittent, high-intensity exercise characteristic of soccer. In particular, this exercise presents a unique challenge in that opportunities for nutrient intake are limited to pre-game and half-time. In our first study, we had 10 male collegiate soccer players perform a 90-min. soccer-simulation test, that we developed, which was followed by a progressive shuttle run (PSR) test to exhaustion. They consumed a honey-sweetened beverage (H), a sports drink (S), or a placebo (P) before and half-way through the protocol. Both H and S provided 1.0 g·kg⁻¹ carbohydrate and ~17.6 mL·kg⁻¹ total volume for each trial. Overall, the test resulted in increased fatigue and production of inflammatory markers and antioxidant capacity. There was no significant difference between treatments for any performance measure. Mean times for a high intensity run and rating of perceived exertion increased with time, and there was an overall decrease in PSR time compared to baseline (-22.9%). There was a rise in glucose (15.6%), IL-6 (548%), IL-1ra, IL-10 (514%) and ORAC (15%) post-test but no change in cortisol. Insulin was significantly lower by 1 h-post. IL-1ra levels increased post-test for H (25.8%), S (65.5%), and P (63.9%), but the change for H was less than the other treatments. No treatment effects for the other blood measures were observed. The lack of an ergogenic effect of carbohydrate on soccer performance calls into question the benefit of supplementation at a frequency typical of a regulation soccer match in highly trained athletes with adequate energy stores. Since acute carbohydrate ingestion in the first study did not attenuate some markers of inflammation (e.g. IL-6), we chose to focus on an alternative theory for the rise in inflammatory markers with strenuous exercise in our second study. One aspect of soccer, repeated sprinting, results in increased ROS production partially through the activation of the enzyme xanthine oxidase (XO). Quercetin, a flavonol in plants that has shown some ergogenic effects with endurance exercise, inhibits XO in vitro. The effect of quercetin on team sport exercise had not been studied. We gave recreationally active males a commercial sports drink (S) or S + 500 mg of quercetin (Q) 2x/d for 1 wk prior to a repeated sprint test (RST). Sprint times increased (5.9%) for both treatments as did plasma XO activity (47%), IL-6 (77%), and uric acid (25%) from pre-test to post-test. Q supplementation did not attenuate plasma XO activity or IL-6 and actually increased one calculated index of fatigue, percent fatigue decrement (5.1%- Q and 3.8%- P). These findings add to the growing body of literature that quercetin supplementation does not attenuate exercise-induced inflammation and oxidative stress in vivo. Collectively, this research has practical implications for sports drink companies who are exploring the use of flavonoid compounds in product formulation. Specifically, they should reconsider adding quercetin to their beverages if they are marketing to team sport athletes. Also, soccer players should be made aware that, at ingestion frequencies typical of a soccer match, they may not expect a significant performance benefit from acute carbohydrate supplementation.