Muscle Glycogen Depletion Following 75-km of Cycling Is Not Linked to Increased Muscle IL-6, IL-8, and MCP-1 mRNA Expression and Protein Content

The cytokine response to heavy exertion varies widely for unknown reasons, and this study evaluated the relative importance of glycogen depletion, muscle damage, and stress hormone changes on blood and muscle cytokine measures. Cyclists (N=20) participated in a 75-km cycling time trial (168±26.0 min), with blood and vastus lateralis muscle samples collected before and after. Muscle glycogen decreased 77.2±17.4%, muscle IL-6, IL-8, and MCP-1 mRNA increased 18.5±2.8-, 45.3±7.8-, and 8.25±1.75-fold, and muscle IL-6, IL-8, and MCP-1 protein increased 70.5±14.1%, 347±68.1%, and 148±21.3%, respectively (all, P<0.001). Serum myoglobin and cortisol increased 32.1±3.3 to 242±48.3 mg/mL, and 295±27.6 to 784±63.5 nmol/L, respectively (both P<0.001). Plasma IL-6, IL-8, and MCP-1 increased 0.42±0.07 to 18.5±3.8, 4.07±0.37 to 17.0±1.8, and 96.5±3.7 to 240±21.6 pg/mL, respectively (all P<0.001). Increases in muscle IL-6, IL-8, and MCP-1 mRNA were unrelated to any of the outcome measures. Muscle glycogen depletion was related to change in plasma IL-6 (r=0.462, P=0.040), with change in myoglobin related to plasma IL-8 (r=0.582, P=0.007) and plasma MCP-1 (r=0.457, P=0.043), and muscle MCP-1 protein (r=0.588, P=0.017); cortisol was related to plasma IL-8 (r=0.613, P=0.004), muscle IL-8 protein (r=0.681, P=0.004), and plasma MCP-1 (r=0.442, P=0.050). In summary, this study showed that muscle IL-6, IL-8, and MCP-1 mRNA expression after 75-km cycling was unrelated to glycogen depletion and muscle damage, with change in muscle glycogen related to plasma IL-6, and changes in serum myoglobin and cortisol related to the chemotactic cytokines IL-8 and MCP-1

The biological basis for toughness in beef

The aim of this thesis was to elucidate role of small heat shock proteins (sHSPs) in the development of tenderness in beef. Data in this thesis were predominantly obtained from bull M. longissimus dorsi aged at -1.5°C for up to 28 days post mortem. High (pH ≥ 6.2) and low (≤ 5.79) ultimate pH (pHu) at were acceptably tender within 1 and 7 days post mortem, respectively. Tenderness in these pHu groups is attributed to the extensive degradation of titin, nebulin, filamin and desmin by endogenous proteases. Rapid μ-calpain autolysis in high pHu meat was concurrent with the faster degradation of titin, nebulin and filamin in this pHu group. Conversely, faster degradation of desmin was concomitant with increasing cathepsin B activity in low pHu meat. It is hypothesised that meat tenderness is pHu compartmentalised by the variable degradation rates of myofibrillar proteins, which are in turn regulated by μ-calpain and cathepsin B activities. Intermediate pHu (5.8 ≤ pHu ≤ 6.19) meat attained acceptable tenderness at 28 days post mortem. However, due to the high variance of shear force in this group, some intermediate pHu meat will be unacceptably tough even after ageing. With up to 19% of bull beef attaining intermediate pHu, understanding the mechanisms for the inconsistent tenderness in this group is advantageous to the meat industry. Myofibrillar protein degradation was less extensive in intermediate pHu meat, partly owing to the sub-optimal activities of μ-calpain and cathepsin B in this group. Exogenous αβ-crystallin reduced the extent of desmin and titin degradation induced by μ-calpain in vitro. Furthermore, αβ-crystallin inhibited μ-calpain activity, possibly by acting an alternative substrate for the enzyme. In post mortem muscle, the increasing association of αβ-crystallin to muscle myofibrils was concomitant with the declining levels of HSP20, HSP27 and αβ-crystallin in muscle sarcoplasm as pH declined. This suggests the translocation of sHSPs from the sarcoplasm to the myofibrils and optimal binding of sHSP to the myofibrils in intermediate pHu meat. It is hypothesised that the high chaperoning potential and μ-calpain inhibition of sHSP combined with the low proteolytic activity in intermediate pHu meat results in the less extensive degradation of myofibrillar proteins leading to meat toughness as observed in intermediate pHu meat

Rapid on-line Glycogen measurement and prediction of ultimate pH in slaughter beef

The rapid determination of glycogen on indicator muscle immediately after slaughter is advantageous as it permits the prediction of a muscle’s ultimate pH (pHu) and allows the identification of high pHu meat carcasses by extrapolation. This thesis examines the development of two rapid glycogen determination methods. The first aim of this thesis was to find a new glucometer to replace the Bayer ESPRIT™ (Bayer) glucometer currently used in the Rapid pH (RpH) method. Roche’s Accuchek® Advantage II (Accuchek) and Abbott’s Medisense Optium™ (Medisense) glucometers were compared. Accuchek measurements exhibited a positive linear relationship in glucose standards made with water, RpH buffer and glucose spiked meat/buffer slurries ranging from 0 to 500 mg dL-1 (r2 = 0.999, 0.998 and 0.995 respectively). Medisense also exhibited a strong positive relationship for glucose standards made with water and RpH buffer; however, a non-linear trend in spiked meat slurries was observed. The second aim of this thesis was to explore the calibration of the KES K201 (KES Analysis Inc., NY, USA) near-infrared (NIR) diode array spectrometer to measure glycogen and pH at approximately 45 minutes after slaughter (pH45), and to predict pHu in pre-rigor M. longissimus dorsi (LD) from beef. This first required finding a reference method to calibrate against the NIR instrument. The RpH, Iodine and Bergmeyer methods were compared. Analysis of glycogen in replicate samples of three beef LD muscles at timepoints post-mortem (1, 4, 9 and 20 hours) was conducted. No significant difference in glycogen concentration was found between an enzymatic and an iodine based colorimetric method at each timepoint; however, the Iodine method was more consistent than the Bergmeyer method at all timepoints. Glucose measurements from the RpH method were consistent; however the pattern of glycogen decline at increasing timepoints post-mortem did not correspond with existing published studies. NIR spectra (538 to 1677 nm) of LD muscles from steers (n = 47), cows (n = 28) and bulls (n = 20) routinely slaughtered in a commercial abattoir were collected on-line approximately 45 minutes after slaughter. Poor results were obtained for Partial Least Squares (PLS) models generated from the mean reflectance spectra of each animal to measure glycogen and pH45, and predict pHu (r2 = 0.23, 0.37 and 0.20 respectively). A high mean square error of prediction (MSEP) for glycogen was also obtained (7.75). Validation of qualitative models generated with Generalised Partial Least Squares regression (GPLS) found that the optimum model was able to correctly categorise only 42% of high pHu samples with the remaining portion being wrongly classified as normal pHu meat. When the effect of gender was removed, only 21% of high pHu carcasses were correctly categorised. Exploratory analysis of the absorbance spectra of the LD muscles showed that a group composed predominantly of steers had a significantly lower pH45 than other existing groups. Further work is recommended for NIR to be successfully utilised on-line to measure glycogen or predict pHu in pre-rigor carcasses

New Zealand Bitter Hops Extract Reduces Hunger During a 24 h Water Only Fast

Intermittent fasting improves metabolic and cardiac health. However, increased hunger towards the end of the fasting period may affect compliance and limit its application. Our aim was to determine the effect of anorexigenic agent co-therapy on subjective ratings of appetite during the 16&ndash;24 h period of a day-long water-only intermittent fast. Thirty adult men were recruited and required to fast for 24 h from 18:00 h to 18:00 h on the same day of the week for three subsequent weeks. Treatments of either a placebo or one of two doses (high dose; HD: 250 mg or low dose; LD: 100 mg) of a bitter hops-based appetite suppressant (Amarasate&reg;) were given twice per day at 16 and 20 h into the fast. From 18&ndash;24 h of the 24 h fast, both the HD and LD treatment groups exhibited a statistically significant (p &lt; 0.05) &gt; 10% reduction in hunger. Additionally, the expected lunchtime increase in hunger that was present in the placebo group (12:00 h) was absent in both the HD and LD groups. These data suggest that appetite suppressant co-therapy may be useful in reducing hunger during intermittent fasting, and show that bitter compounds may regulate appetite independently of meal timing

Timed consumption of a New Zealand blackcurrant juice support positive affective responses during a self-motivated moderate walking exercise in healthy sedentary adults

Background Affective responses experienced during exercise are a significant determinant on exercise adherence. We have previously demonstrated that consumption of New Zealand (NZ) blackcurrants preserves cognition by attenuating the feeling of fatigue. This positive affective response correlated with the ability of blackcurrant polyphenols to support monoamine neurotransmission via inhibition of monoamine oxidase-B (MAO-B) activity. Here we explore how the consumption of a NZ blackcurrant juice (BJ) influenced affective responses and potential ergogenic action on the motivation to adhere to a low impact walking exercise. Methods In a parallel randomized controlled study (Trial registration #: ACTRN12617000319370p, registered 28th February 2017, http://www.anzctr.org.au/), 40 healthy sedentary male and female participants drank a BJ or matched placebo (PLA) (n = 20 per group), 1 h prior to a self-motivated treadmill walk, where heart rate and affective responses (exertion [ES] or feeling / mood [FS]) scores) were recorded at 3 or 5 min intervals. Blood glucose, lactate, malondialdehyde (MDA) and platelet MAO-B activity were measured pre- and post-exercise and comparisons were conducted using with Student’s t-tests. Subjective data were analysed using 2-way ANOVA with appropriate post hoc tests. Results Consuming a BJ 1 h prior to exercise caused a 90% decline in platelet MAO-B activity. The exercise had no significant (p > 0.05) effect on blood lactate, glucose or plasma MDA levels. Assessment of affective responses over the first 60 mins (adjusting for participant drop-out) revealed a time-dependent ES increase in both groups, with ES reported by participants in the BJ group consistently lower than those in the PLA group (p  10 km compared to only 10% for the PLA group (p = 0.28), statistical significance was not achieved. Conclusion Our findings demonstrate that drinking a polyphenolic-rich NZ blackcurrant juice 1 h prior to exercise supports positive affective responses during a self-motivated exercise