Browsing by Author "Boutagy, Nabil E."
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- Early Skeletal Muscle Adaptations to Short-Term High-Fat Diet in Humans Before Changes in Insulin SensitivityAnderson, 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.
- Overfeeding and Substrate Availability, But Not Age or BMI, Alter Human Satellite Cell FunctionFausnacht, Dane W.; McMillan, Ryan P.; Boutagy, Nabil E.; Lupi, Ryan A.; Harvey, Mordecai M.; Davy, Brenda M.; Davy, Kevin P.; Rhoads, Robert P.; Hulver, Matthew W. (MDPI, 2020-07-24)Satellite cells (SC) aid skeletal muscle growth and regeneration. SC-mediated skeletal muscle repair can both be influenced by and exacerbate several diseases linked to a fatty diet, obesity, and aging. The purpose of this study was to evaluate the effects of different lifestyle factors on SC function, including body mass index (BMI), age, and high-fat overfeeding. For this study, SCs were isolated from the vastus lateralis of sedentary young (18–30 years) and sedentary older (60–80 years) men with varying BMIs (18–32 kg/m2), as well as young sedentary men before and after four weeks of overfeeding (OVF) (55% fat/ + 1000 kcal, n = 4). The isolated SCs were then treated in vitro with a control (5 mM glucose, 10% fetal bovine serum (FBS)) or a high substrate growth media (HSM) (10% FBS, 25 mM glucose, and 400 μM 2:1 oleate–palmitate). Cells were assessed on their ability to proliferate, differentiate, and fuel substrate oxidation after differentiation. The effect of HSM was measured as the percentage difference between SCs exposed to HSM compared to control media. In vitro SC function was not affected by donor age. OVF reduced SC proliferation rates (–19% p < 0.05) but did not influence differentiation. Cellular proliferation in response to HSM was correlated to the donor’s body mass index (BMI) (r2 = 0.6121, p < 0.01). When exposed to HSM, SCs from normal weight (BMI 18–25 kg/m2) participants exhibited reduced proliferation and fusion rates with increased fatty-acid oxidation (p < 0.05), while SCs from participants with higher BMIs (BMI 25–32 kg/m2) demonstrated enhanced proliferation in HSM. HSM reduced proliferation and fusion (p < 0.05) in SCs isolated from subjects before OVF, whereas HSM exposure accelerated proliferation and fusion in SCs collected following OVF. These results indicated that diet has a greater influence on SC function than age and BMI. Though age and BMI do not influence in vitro SC function when grown in controlled conditions, both factors influenced the response of SCs to substrate challenges, indicating age and BMI may mediate responses to diet.
- Probiotic Supplementation, The Gut Microbiota, and Cardiovascular HealthBoutagy, Nabil E. (Virginia Tech, 2014-08-26)Cardiovascular disease (CVD) is the leading cause of death in the United States. Recently, the gut microbiota has been implicated in the pathophysiology and progression of CVD. Experimental evidence suggests that high fat feeding alters the functional composition of the gut microbiota (dysbiosis); leading to increased translocation of the pro-inflammatory, endotoxin, and increased production of the pro-atherogenic, trimethylamine-N-oxide (TMAO). Together, these changes are hypothesized to accelerate CVD progression. Conversely, administration of gut microbiota modulating agents, such as antibiotics and probiotics, attenuate high fat feeding induced CVD in rodent models. In humans, the capacity to produce TMAO following L-carnitine or phosphatidylcholine challenges is abolished after receiving broad spectrum antibiotics for a period of one week. However, whether gut modulation over a longer period of time decreases fasting serum endotoxin, fasting plasma TMAO, and CVD risk in response to high fat feeding has been unexplored in humans. To address these issues we conducted a randomized, placebo controlled, parallel group designed, controlled feeding study in healthy, non-obese males receiving the multi-strain probiotic, VSL #3 (or placebo), while a consuming a high fat diet for 4-weeks. First, we tested the hypothesis that VSL #3 would attenuate the rise in serum endotoxin and consequent arterial stiffening following high fat feeding in healthy, non-obese males. Second, we tested the hypothesis that VSL #3 would attenuate the rise in plasma TMAO concentrations following high fat feeding in healthy, non-obese males. In contrast to our first hypotheses, serum endotoxin concentrations and arterial stiffness did not change in response to high fat feeding or with VSL#3 treatment. Interestingly, VSL #3 significantly attenuated the increase in body mass (+ 1.4±0.4 vs. +2.3±0.3 kg; P < 0.05) and fat mass (+0.7±0.1 vs. + 1.4±0.3 kg; P < 0.05) following high fat feeding compared to the placebo. In contrast to our second hypothesis, probiotic supplementation did not attenuate the rise in plasma TMAO following high fat feeding. Future studies are necessary to elucidate the mechanisms responsible for the prevention of body mass and fat mass gain with VSL#3 supplementation following high fat feeding. In addition, studies are needed to determine whether higher doses of VSL #3, other single or multispecies probiotics, prebiotics, or synbiotics attenuate the production of the proatherogenic, TMAO.
- Resistance exercise training and in vitro skeletal muscle oxidative capacity in older adultsFlack, Kyle D.; Davy, Brenda M.; DeBerardinis, Martin; Boutagy, Nabil E.; McMillan, Ryan P.; Hulver, Matthew W.; Frisard, Madlyn I.; Anderson, Angela S.; Savla, Jyoti S.; Davy, Kevin P. (2016-07)Whether resistance exercise training (RET) improves skeletal muscle substrate oxidative capacity and reduces mitochondrial production of reactive oxygen species in older adults remains unclear. To address this, 19 older males (≥60 years) were randomized to a RET (n = 11) or to a waitlist control group (n = 8) that remained sedentary for 12 weeks. RET was comprised of three upper body and four lower body movements on resistance machines. One set of 8-12 repetitions to failure of each movement was performed on three nonconsecutive days/week. Improvements in chest press and leg press strength were assessed using a three-repetition maximum (3 RM). Body composition was assessed via dual energy X-ray absorptiometry. Muscle biopsies were obtained from the vastus lateralis muscle at baseline and at both 3 weeks and 12 weeks. Palmitate and pyruvate oxidation rates were measured from the (14)CO2 produced from [1-(14)C] palmitic acid and [U-(14)C] pyruvate, respectively, during incubation of muscle homogenates. PGC-1α, TFAM, and PPARδ levels were quantified using qRT-PCR Citrate synthase (CS) and β-HAD activities were determined spectrophotometrically. Mitochondrial production of reactive oxygen species (ROS) were assessed using the Amplex Red Hydrogen Peroxide/Peroxidase assay. There were no significant changes in body weight or body composition following the intervention. Chest press and leg press strength (3RM) increased ~34% (both P < 0.01) with RET There were no significant changes in pyruvate or fatty acid oxidation or in the expression of target genes with the intervention. There was a modest increase (P < 0.05) in βHAD activity with RET at 12 weeks but the change in CS enzyme activity was not significant. In addition, there were no significant changes in ROS production in either group following RET Taken together, the findings of this study suggest that 12 weeks of low volume RET does not increase skeletal muscle oxidative capacity or reduce ROS production in older adults.
- Serum endotoxin, gut permeability and skeletal muscle metabolic adaptations following a short term high fat diet in humansBowser, Suzanne M.; McMillan, Ryan P.; Boutagy, Nabil E.; Tarpey, Michael D.; Smithson, Andrew T.; Osterberg, Kristin L.; Neilson, Andrew P.; Davy, Brenda M.; Davy, Kevin P.; Hulver, Matthew W. (2019-11-27)Background: Our previous work demonstrated that a short-term high fat diet (HFD) increased fasting serum endotoxin, altered postprandial excursions of serum endotoxin, and led to metabolic and transcriptional responses in skeletal muscle in young, healthy male humans. Purpose: The purpose of the present study was to determine if a short-term high fat diet: 1) increases intestinal permeability and, in turn, fasting endotoxin concentrations and 2) decreases postprandial skeletal muscle fat oxidation. Methods: Thirteen normal weight young adult males (BMI 23.1 +/- 0.8 kg/m(2), age 22.2 +/- 0.4 years) were fed a control diet (55% carbohydrate, 30% fat, 9% of which was saturated, 15% protein) for two weeks, followed by 5 days of an isocaloric HFD (30% carbohydrate, 55% fat, 25% of which was saturated, 15% protein, isocaloric to the control diet). Intestinal permeability (via four sugar probe test) was assessed in the fasting state. Both before and after the HFD, a high fat meal challenge (HFM, 820 kcal, 25% carbohydrate, 63% fat, 26% of which was saturated, and 12% protein) was administered. After an overnight fast, blood samples were collected before and every hour for 4 h after the HFM to assess endotoxin, and other serum blood measures. Muscle biopsies were obtained from the vastus lateralis before and 4 h after the HFM in order to assess substrate oxidation (glucose, fatty acid and pyruvate) using radiolabeled techniques. Insulin sensitivity was assessed via intravenous glucose tolerance test. Intestinal permeability, blood samples and muscle biopsies were assessed in the same manner before and following the HFD. Main findings: Intestinal permeability was not affected by HFD (p > 0.05), but fasting endotoxin increased two fold following the HFD (p = 0.04). Glucose oxidation and fatty acid oxidation in skeletal muscle homogenates significantly increased after the HFM before the HFD (+97%, and +106% respectively) but declined after the HFM following 5 days of the HFD (-24% and +16% respectively). Fatty acid suppressibility of pyruvate oxidation increased significantly after the HFM (+32%) but this physiological effect was abolished following 5 days of the HFD (+7%). Insulin sensitivity did not change following the HFD. Conclusion: These findings demonstrate that in healthy young men, consuming an isocaloric HFD for 5 days increases fasting endotoxin, independent of changes in gut permeability. These changes in endotoxin are accompanied by a broad effect on skeletal muscle substrate metabolism including increases in postprandial fat oxidation. Importantly, the latter occurs independent of changes in body weight and whole-body insulin sensitivity.
- Skeletal muscle autophagy and mitophagy in endurance-trained runners before and after a high-fat mealTarpey, Michael D.; Davy, Kevin P.; McMillan, Ryan P.; Bowser, Suzanne M.; Halliday, Tanya M.; Boutagy, Nabil E.; Davy, Brenda M.; Frisard, Madlyn I.; Hulver, Matthew W. (Elsevier, 2017-10-24)Objective: We tested the hypothesis that skeletal muscle of endurance-trained male runners would exhibit elevated autophagy and mitophagy markers, which would be associated with greater metabolic flexibility following a high-fat meal (HFM). Methods: Muscle biopsies were collected to determine differences in autophagy and mitophagy protein markers and metabolic flexibility under fasting conditions and 4 h following a HFM between endurance-trained male runners (n =10) and sedentary, non-obese controls (n = 9). Results: Maximal oxygen consumption (ml・kg・min⁻¹) was approximately 50% higher (p < 0.05) in endurance-trained runners compared with sedentary controls (65.8 ±2.3 and 43.1 ±3.4, respectively). Autophagy markers were similar between groups. Mitophagy and mitochondrial dynamics protein markers were significantly higher in skeletal muscle of endurance-trained runners compared with sedentary controls in the fasted state, although unaffected by the HFM. Skeletal muscle metabolic flexibility was similar between groups when fasted (p > 0.05), but increased in response to the HFM in endurance-trained athletes only (p < 0.005). Key mitophagy markers, phospho-Pink1Thr257 and phospho- ParkinS⁶⁵(r = 0.64, p < 0.005), and phospo-ParkinSer⁶⁵ and phospho-Drp1Ser⁶¹⁶ (r = 0.70, p < 0.05) were correlated only within the endurance-trained group. Autophagy and mitophagy markers were not correlated with metabolic flexibility. Conclusion: In summary, mitophagy may be enhanced in endurance-trained runners based on elevated markers of mitophagy and mitochondrial dynamics. The HFM did not alter autophagy or mitophagy in either group. The absence of a relationship between mitophagy markers and metabolic flexibility suggests that mitophagy is not a key determinant of metabolic flexibility in a healthy population, but further investigation is warranted.
- Using Isolated Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High throughput Microplate Respiratory MeasurementsBoutagy, Nabil E.; Rogers, George W.; Pyne, Emily S.; Ali, Mostafa M.; Hulver, Matthew W.; Frisard, Madlyn I. (Journal of Visualized Experiments, 2015-10-01)Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of mitochondrial function in this tissue has become more prevalent. Although many technologies and assays exist that measure mitochondrial respiratory pathways in a variety of cells, tissue and species, there is currently a void in the literature in regards to the compilation of these assays using isolated mitochondria from mouse skeletal muscle for use in microplate based technologies. Importantly, the use of microplate based respirometric assays is growing among mitochondrial biologists as it allows for high throughput measurements using minimal quantities of isolated mitochondria. Therefore, a collection of microplate based respirometric assays were developed that are able to assess mechanistic changes/adaptations in oxygen consumption in a commonly used animal model. The methods presented herein provide step-bystep instructions to perform these assays with an optimal amount of mitochondrial protein and reagents, and high precision as evidenced by the minimal variance across the dynamic range of each assay.