Selective overexpression of Toll-like receptor-4 in skeletal muscle impairs metabolic adaptation to high-fat feeding.

Toll-like receptor-4 (TLR-4) is elevated in skeletal muscle of obese humans, and data from our laboratory have shown that activation of TLR-4 in skeletal muscle via LPS results in decreased fatty acid oxidation (FAO). The purpose of this study was to determine whether overexpression of TLR-4 in skeletal muscle alters mitochondrial function and whole body metabolism in the context of a chow and high-fat diet. C57BL/6J mice (males, 6-8 mo of age) with skeletal muscle-specific overexpression of the TLR-4 (mTLR-4) gene were created and used for this study. Isolated mitochondria and whole muscle homogenates from rodent skeletal muscle (gastrocnemius and quadriceps) were investigated. TLR-4 overexpression resulted in a significant reduction in FAO in muscle homogenates; however, mitochondrial respiration and reactive oxygen species (ROS) production did not appear to be affected on a standard chow diet. To determine the role of TLR-4 overexpression in skeletal muscle in response to high-fat feeding, mTLR-4 mice and WT control mice were fed low- and high-fat diets for 16 wk. The high-fat diet significantly decreased FAO in mTLR-4 mice, which was observed in concert with elevated body weight and fat, greater glucose intolerance, and increase in production of ROS and cellular oxidative damage compared with WT littermates. These findings suggest that TLR-4 plays an important role in the metabolic response in skeletal muscle to high-fat feeding.

Ovarian tumor-initiating cells display a flexible metabolism.

An altered metabolism during ovarian cancer progression allows for increased macromolecular synthesis and unrestrained growth. However, the metabolic phenotype of cancer stem or tumor-initiating cells, small tumor cell populations that are able to recapitulate the original tumor, has not been well characterized. In the present study, we compared the metabolic phenotype of the stem cell enriched cell variant, MOSE-LFFLv (TIC), derived from mouse ovarian surface epithelial (MOSE) cells, to their parental (MOSE-L) and benign precursor (MOSE-E) cells. TICs exhibit a decrease in glucose and fatty acid oxidation with a concomitant increase in lactate secretion. In contrast to MOSE-L cells, TICs can increase their rate of glycolysis to overcome the inhibition of ATP synthase by oligomycin and can increase their oxygen consumption rate to maintain proton motive force when uncoupled, similar to the benign MOSE-E cells. TICs have an increased survival rate under limiting conditions as well as an increased survival rate when treated with AICAR, but exhibit a higher sensitivity to metformin than MOSE-E and MOSE-L cells. Together, our data show that TICs have a distinct metabolic profile that may render them flexible to adapt to the specific conditions of their microenvironment. By better understanding their metabolic phenotype and external environmental conditions that support their survival, treatment interventions can be designed to extend current therapy regimens to eradicate TICs.

Metabolic changes during ovarian cancer progression as targets for sphingosine treatment.

Tumor cells often exhibit an altered metabolic phenotype. However, it is unclear as to when this switch takes place in ovarian cancer, and the potential for these changes to serve as therapeutic targets in clinical prevention and intervention trials. We used our recently developed and characterized mouse ovarian surface epithelial (MOSE) cancer progression model to study metabolic changes in distinct disease stages. As ovarian cancer progresses, complete oxidation of glucose and fatty acids were significantly decreased, concurrent with increases in lactate excretion and (3)H-deoxyglucose uptake by the late-stage cancer cells, shifting the cells towards a more glycolytic phenotype. These changes were accompanied by decreases in TCA flux but an increase in citrate synthase activity, providing substrates for de novo fatty acid and cholesterol synthesis. Also, uncoupled maximal respiration rates in mitochondria decreased as cancer progressed. Treatment of the MOSE cells with 1.5 µM sphingosine, a bioactive sphingolipid metabolite, decreased citrate synthase activity, increased TCA flux, decreased cholesterol synthesis and glycolysis. Together, our data confirm metabolic changes during ovarian cancer progression, indicate a stage specificity of these changes, and suggest that multiple events in cellular metabolism are targeted by exogenous sphingosine which may be critical for future prevention trials.

Self-perceptions of critical thinking skills in university students are associated with BMI and exercise.

Objective: To assess the role of body mass index (BMI) and exercise levels in self-perception of critical thinking skills. Participants: Three hundred forty-seven students from an upper-division nutrition class over two consecutive years. Methods: A pre/post survey with a 15-week intervention assessed perceived critical thinking skills in a blended classroom. Results: Students gained in perceived critical thinking skills in six areas over the semester. A higher BMI was associated with decreased perception of one's ability to think logically, along with increased perception that memorization was the key to success. Those that exercised reported that they had strong critical thinking skills compared to those that exercised less frequently. Conclusions: A blended classroom approach was effective in increasing multiple areas of perceptions of critical thinking. However, some perceptions of critical thinking are viewed differently for those of different BMIs and exercise frequency. Consequently, designing interventions specifically targeting those with higher BMIs, could work to erase these inequities.

The Impact of a 1-Year COVID-19 Extension on Undergraduate Dentistry in Dundee: Final Year Students' Perspectives of Their Training in Oral Surgery.

BACKGROUND: The detrimental impact of the COVID-19 pandemic on dental education prompted the Scottish Government to fund an additional year to the dental course to ensure that the students had the necessary clinical experience. The aim of the study was to better understand the final year student perceptions of this extension on their oral surgery experience at the University of Dundee. METHODS: This mixed methods study consisted of an anonymous online questionnaire and a focus group. RESULTS: Forty-one students (69.3%) completed the questionnaire and ten students participated in the focus group. Thirty-six (88.8%) students agreed that the oral surgery teaching provided sufficient knowledge to undertake independent practice. All of the students felt confident to carry out an extraction, and the majority of them (n = 40, 95%) felt confident to remove a retained root, however, their confidence with surgery was lower. CONCLUSION: The extension gave the students sufficient experience in oral surgery to gain confidence in clinical skills and an appropriate level of knowledge in preparation for the next phase of their career. Most of the students agreed that the extension was necessary and beneficial. This cohort graduated with more oral surgery experience than any of the students did in the previous 4 years from Dundee and with experience that was comparable with the students at other schools in the pre-COVID-19 era.

An Educational Evaluation of Thiel Cadavers as a Model for Teaching Suturing Skills to Dental Students during the COVID-19 Pandemic.

Suturing is an essential skill in dentistry and not one easily acquired. The COVID-19 pandemic prompted a change to the use of Thiel cadavers and online resources with the aim of improving skill acquisition using the best model available. This study investigated the utility of the Thiel cadaver for teaching suturing skills and the potential impact of the lockdown. Fifty-seven year 4 students attended a teaching session. Student views on this teaching were explored via a questionnaire survey and qualitative data collected from a focus group. Data were analysed using an inductive approach. The response rate was 53% (30 students) for the questionnaire with 9 students participating in the focus group. Independent feedback was provided by two members of the teaching staff. Online video resources were very well received by the students with 97% agreeing that it was useful preparation. Ninety percent (90%) thought that the cadaveric model was suitable for this teaching and realistic. Positive emergent themes from the focus group centred on the use of the cadaveric model and the positive and relaxed teaching and learning environment. Staff perceived this model as superior to previously used models. There were no reported negative pandemic impacts and the cadaver model was well received.

Increased body weight affects academic performance in university students.

For K-12 students, obesity has been linked to student educational achievements. The study objective was to determine whether academic performance in university students is correlated with BMI. Students from two consecutive academic years (Jan-May 2013 and Jan-May 2014) were given an optional class survey in May, as extra credit. Of the 452 students that completed the survey, 204 females and 75 males (N = 279; 73% female and 27% male) consented to participate in the study. The number of correct answers to problem-solving questions (PSQs) and the overall final grade for the class were compared to the calculated BMI using linear regression with a Pearson's R correlation and unpaired t-tests. BMI was significantly negatively correlated with student's final grades (P = 0.001 Pearson's r = - 0.190) and PSQs were positively correlated with final grades (P < 0.001; Pearson's r = 0.357). Our findings show a correlation between healthy body weight and improved academic performance. Further, the data suggest that future research in the area of body weight, diet, and exercise and any correlations of these with academic performance in college students are warranted.

Resistance exercise training and in vitro skeletal muscle oxidative capacity in older adults.

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 ß-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 ßHAD 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.

Low levels of lipopolysaccharide modulate mitochondrial oxygen consumption in skeletal muscle.

OBJECTIVE: We have previously demonstrated that activation of toll-like receptor 4 (TLR4) in skeletal muscle results in an increased reliance on glucose as an energy source and a concomitant decrease in fatty acid oxidation under basal conditions. Herein, we examined the effects of lipopolysaccharide (LPS), the primary ligand for TLR4, on mitochondrial oxygen consumption in skeletal muscle cell culture and mitochondria isolated from rodent skeletal muscle. MATERIALS/METHODS: Skeletal muscle cell cultures were exposed to LPS and oxygen consumption was assessed using a Seahorse Bioscience extracellular flux analyzer. Mice were also exposed to LPS and oxygen consumption was assessed in mitochondria isolated from skeletal muscle. RESULTS: Acute LPS exposure resulted in significant reductions in Carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP)-stimulated maximal respiration (state 3u) and increased oligomycin induced state 4 (state 4O) respiration in C2C12 and human primary myotubes. These findings were observed in conjunction with increased mRNA of uncoupling protein 3 (UCP3), superoxide dismutase 2 (SOD2), and pyruvate dehydrogenase activity. The LPS-mediated changes in substrate oxidation and maximal mitochondrial respiration were prevented in the presence of the antioxidants N-acetylcysteine and catalase, suggesting a potential role of reactive oxygen species in mediating these effects. Mitochondria isolated from red gastrocnemius and quadriceps femoris muscle from mice injected with LPS also demonstrated reduced respiratory control ratio (RCR), and ADP- and FCCP-stimulated respiration. CONCLUSION: LPS exposure in skeletal muscle alters mitochondrial oxygen consumption and substrate preference, which is absent when antioxidants are present.

Early skeletal muscle adaptations to short-term high-fat diet in humans before changes in insulin sensitivity.

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 responses in skeletal muscle to the transition from a fasted to fed state using a high-fat meal challenge before and after 5 days of the 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, as well as metabolic and transcriptional responses in skeletal muscle. These effects after 5 days of the 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.

Angiotensin II receptor blockade and skeletal muscle metabolism in overweight and obese adults with elevated blood pressure.

OBJECTIVES: Whether angiotensin II receptor blockade improves skeletal muscle fatty acid oxidation in overweight and obese humans is unknown. The purpose of the study was to test the hypothesis that the angiotensin II receptor blocker, olmesartan, would increase fatty acid oxidation and the activity of enzymes associated with oxidative metabolism in skeletal muscle of overweight and obese humans. METHODS: A total of 12 individuals (6 men and 6 women) aged 18-75 and with a body mass index ⩾25 kg/m2 were assigned to olmesartan or placebo for 8 weeks in a crossover fashion. Fatty acid oxidation was measured before and after each intervention by counting the (14)CO2 produced from [1-(14)C] palmitic acid in skeletal muscle homogenates. RESULTS: Fatty acid oxidation was not significantly different between treatment periods at baseline and post intervention. In addition, the enzyme activities of citrate synthase and ß-hydroxyacyl-coenzyme A dehydrogenase in skeletal muscle homogenates did not differ between treatment periods at baseline or post intervention. CONCLUSIONS: Treatment with olmesartan for 8 weeks does not improve fatty acid oxidation or the activity of enzymes associated with oxidative metabolism in skeletal muscle from overweight and obese individuals. Taken together, our results indicate that improvements in skeletal muscle metabolism are not among the additional benefits of olmesartan that extend beyond blood pressure reduction.