Enhancing Supplemental Effects of Acute Natural Antioxidant Derived from Yeast Fermentation and Vitamin C on Sports Performance in Triathlon Athletes: A Randomized, Double-Blinded, Placebo-Controlled, Crossover Trial.

This study investigated the acute effects of natural antioxidants, derived from yeast fermentation containing glutathione and dietary vitamin C supplementation, on metabolic function, skeletal muscle oxygenation, cardiac function, and antioxidant function during submaximal exercise in middle-aged triathlon athletes. Twelve participants (aged 49.42 ± 5.9 years) completed 90 min submaximal cycling trials corresponding to 70% maximal oxygen uptake with either vitamin C and glutathione (VitC+Glu), vitamin C (VitC), glutathione (Glu) supplementation, or placebo. Metabolic function (minute ventilation, oxygen uptake, carbon dioxide output [VCO2], respiratory exchange ratio [RER], oxygen pulse [O2pulse], carbohydrate oxidation, fat oxidation, and energy expenditure), skeletal muscle oxygenation (oxidized hemoglobin and myoglobin in skeletal muscle tissue, total hemoglobin and myoglobin in skeletal muscle tissue [tHb]), cardiac function (heart rate [HR], stroke volume [SV], cardiac output, end-diastolic volume, end-systolic volume, and ejection fraction), and antioxidant function parameters (blood lactate, superoxide dismutase, catalase, glutathione peroxidases, glutathione [GSH], diacron reactive oxygen metabolite [dROM], and biological antioxidant potential [BAP]) were measured during submaximal exercise and recovery. VCO2, RER, HR, blood lactate after exercise, and dROM were significantly lower, and O2pulse, tHb, and BAP were significantly higher for VitC+Glu than for the other trials (p < 0.05). In conclusion, combined vitamin C and glutathione supplementation was more effective in improving metabolic function, skeletal oxygenation, cardiac function, and antioxidant function during prolonged submaximal exercise in middle-aged triathletes.

Effect of dietary leucine supplementation on skeletal muscle fiber type transformation in weaning piglets.

To investigate the effects of dietary leucine supplementation on muscle fiber type transformation in weaning piglets, 54 21-day-old male DLY (Duroc × Landrace × Yorkshire) weaned piglets were randomly divided into control, 0.25% and 0.5% leucine groups. The experiment lasted for 42 d. The results showed that dietary supplementation of 0.25% leucine significantly increased the protein expressions of slow MyHC, myoglobin and Troponin I-SS and the mRNA expressions of MyHC I, MyHC IIa, Tnni1, Tnnc1, Tnnt1 and myoglobin, while decreased the protein level of fast MyHC and the mRNA level of MyHC IIb in longissimus dorsi (LD) muscle. Furthermore, 0.25% leucine significantly increased succinic dehydrogenase (SDH) activity and decreased lactate dehydrogenase (LDH) activity. In addition, our data found that 0.25% leucine significantly increased serum adiponectin (AdipoQ) concentration, and the protein levels of AdipoQ, adiponectin receptor 1 (AdipoR1), phosphorylated AMP-activated protein kinase (p-AMPK) and PPAR-γ coactivator-1α (PGC-1α) and the mRNA levels of AdipoQ, AdipoR1 and AMPKα2. Together, our findings indicate that leucine promotes porcine skeletal muscle fiber type transformation from fast-twitch to slow-twitch, and the effect may be mediated by AdipoQ-AMPK-PGC-1α signaling pathway.

Effect of alfalfa (Medicago sativa L.) saponins on meat color and myoglobin reduction status in the longissimus thoracis muscle of growing lambs.

The effect of alfalfa saponins (AS) supplementation on the meat quality especially the color for growing lamb was investigated. Fifty Hu male lambs with body weights (BW, 19.21 ± 0.45 kg) were divided into five groups and supplemented AS with 0, 500, 1,000, 2,000, and 4,000 mg/kg of dietary dry matter intake. After 90 days, all lambs were slaughtered. The longissimus thoracis muscle in lamb displayed significant changes in the content of intramuscular fat, especially n-3 polyunsaturated fatty acids, and drip loss within AS treatment (p < .05) between control and treatments groups. Redness (a*) significantly improved in both 0-day and 7-day storage with the AS supplementation coupled with the percentage of met-myoglobin reduction (p < .05). The redness (a*) change may result from improved met-myoglobin reducing activity, antioxidant enzymes, lactate dehydrogenase, and succinate dehydrogenase (p < .05) by AS supplementation in muscle. These enzymes may help to protect mitochondria function and reduce met-myoglobin, which bring a bright and red meat color.

Structure, functional properties and iron bioavailability of Pneumatophorus japonicus myoglobin and its glycosylation products.

Developing safe and efficient iron supplements is significant for the alleviation of iron-deficient anemia (IDA). Myoglobin (Mb) is a heme-protein rich in bioavailable iron. Pneumatophorus japonicus (P. japonicus), one important economic fish in China, contain a high Mb level in its dark meat normally discarded during processing. The present study aimed to determine the structure, physicochemical properties, and iron bioavailability of Mb extracted from P. japonicus. Meanwhile, the effects of glycosylation, a commonly applied chemical modification of proteins, on these parameters were evaluated. Using Box-Behnken design, the optimal conditions for Mb-chitosan glycosylation were obtained: 45.07 °C, pH 6.10 and Mb/chitosan mass ratio of 6.29. The structure and functional properties of the glycosylated Mb (Mb-gly) were investigated. Compared with the original Mb, Mb-gly obtained a more ordered secondary structure. The surface hydrophobicity of Mb-gly was found to be decreased together with the observations of elevated water solubility. Moreover, glycosylation enhanced the Mb antioxidant capacity, and improved its stability in enzymatic digestion system. Regarding to the iron bioavailability, the cellular uptake of Mb­iron was significantly higher than FeSO4, and further elevated by glycosylation. These results provided a basis for the development of Mb-based iron supplements, promoting the utilization of fish-processing industries wastes.

The Effect of Fermented Porcine Placental Extract on Fatigue-Related Parameters in Healthy Adults: A Double-Blind, Randomized, Placebo-Controlled Trial.

BACKGROUND: Fatigue is one of the major health conditions induced by excessive stress or abnormal immune function or defective antioxidant systems. Placental extract has been reported to have various effects such as immune modulation and cellular regeneration. Fermented porcine placenta (FPP) is a safe nontoxic material, which is highly valuable as a functional food. The aim of this study was to investigate the anti-fatigue effects of FPP supplementation compared with a placebo product. METHODS: In this double-blind, parallel, randomized, and placebo-controlled trial 84 healthy males and females, aged between 30 and 60 years were randomized to 320 mg of FPP once daily or placebo. The main outcome measures included efficacy of fatigue-inducing treadmill exercise on physical fatigue and fatigue-related parameters based on the questionnaire administered. RESULTS: The IL-1ß mRNA expression and fatigue severity scale were changed significantly after 8 weeks of treatment with fermented porcine placenta compared with placebo (p < 0.05). Cortisol levels were significantly improved in participants younger than 45 years following treatment with FPP compared with placebo. Furthermore, the lactate and myoglobin levels were improved significantly in participants with BMI ≥ 23 kg/m2 (p = 0.045 and p = 0.011, respectively) following treatment with FPP versus placebo. CONCLUSIONS: Our study showed that FPP supplementation significantly ameliorated fatigue-related parameters and subjective symptoms in healthy adults. Therefore, our results indicate that FPP supplementation induced anti-fatigue effect by regulating the inflammatory response.

Phytoplankton Supplementation Lowers Muscle Damage and Sustains Performance across Repeated Exercise Bouts in Humans and Improves Antioxidant Capacity in a Mechanistic Animal.

The purpose of this study was to investigate the impact of antioxidant-rich marine phytoplankton supplementation (Oceanix, OCX) on performance and muscle damage following a cross-training event in endurance-trained subjects. Additionally, an animal model was carried out to assess the effects of varying dosages of OCX, with exercise, on intramuscular antioxidant capacity. METHODS: In the human trial, endurance-trained subjects (average running distance = 29.5 ± 2.6 miles × week-1) were randomly divided into placebo (PLA) and OCX (25 mg) conditions for 14 days. The subjects were pre-tested on a one-mile uphill run, maximal isometric strength, countermovement jump (CMJ) and squat jump (SJ) power, and for muscle damage (creatine kinase (CK)). On Day 12, the subjects underwent a strenuous cross-training event. Measures were reassessed on Day 13 and 14 (24 h and 48 h Post event). In the animal model, Wistar rats were divided into four groups (n = 7): (i) Control (no exercise and placebo (CON)), (ii) Exercise (E), (iii) Exercise + OCX 1 (Oceanix, 2.55 mg/day, (iv) Exercise + OCX 2 (5.1 mg/day). The rats performed treadmill exercise five days a week for 6 weeks. Intramuscular antioxidant capacity (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px)) and muscle damage (CK and myoglobin (MYOB) were collected. The data were analyzed using repeated measures ANOVA and t-test for select variables. The alpha value was set at p < 0.05. RESULTS: For the human trial, SJ power lowered in PLA relative to OCX at 24 h Post (-15%, p < 0.05). Decrements in isometric strength from Pre to 48 h Post were greater in the PLA group (-12%, p < 0.05) than in the OCX. Serum CK levels were greater in the PLA compared to the OCX (+14%, p < 0.05). For the animal trial, the intramuscular antioxidant capacity was increased in a general dose-dependent manner (E + Oc2 > E + Oc1 > E > CON). Additionally, CK and MYOB were lower in supplemented compared to E alone. CONCLUSIONS: Phytoplankton supplementation (Oceanix) sustains performance and lowers muscle damage across repeated exercise bouts. The ingredient appears to operate through an elevating oxidative capacity in skeletal muscle.

Interactions of indole alkaloids with myoglobin: A mass spectrometry based spectrometric and computational method.

RATIONALE: Interactions of drug molecules and proteins play important roles in physiological and pathological processes in vivo. It is of significance to establish a reliable strategy for studying protein-drug ligand interactions and would be helpful for the design and screening of new drugs in pharmacological research. METHODS: The interactions between four indole alkaloids (IAs) extracted from Ophiorrhiza japonica (O. japonica) and myoglobin (Mb) protein were investigated using a multi-spectrometric and computational method of native electrospray ionization mass spectrometry (native ESI-MS), hydrogen/deuterium exchange mass spectrometry (HDX-MS), circular dichroism (CD) and molecular docking (MD). RESULTS: The IA-bound Mb complexes were analyzed using native ESI-MS, with the obtained protein-to-ligand stoichiometry at 1:1, 1:2 and 1:3. Binding constants were measured according to the interpretation of MS spectra. MD complemented MS measurements, probing the binding sites and modes of the four IAs to Mb. Analyses involving CD and HDX-MS demonstrated that exposure to IAs could affect the conformation of Mb by decreasing the α-helix content and made Mb more susceptible to HDX at the backbone. CONCLUSIONS: A new MS-based integrated analysis method has been developed to successfully study the interactions of Mb and IAs extracted from O. japonica. The experimental and calculation results have good consistency, revealing all of the four IA molecules could bind to Mb to form 1:1, 1:2 and 1:3 Mb-IA complexes. The order of binding ability of these IAs to Mb was ophiorrhine B > compound C > ophiorrhine A > compound D. CD and HDX-MS results indicated that binding with IAs destabilizes Mb. HDX-MS analysis suggests that Mb becomes more susceptible to HDX, indicating that binding with IAs destabilizes the structure of Mb. In addition, the interaction with IAs affected the overall structure of Mb, ascribed to the decrease of α-helix content and less folding of the backbone.

Antioxidant efficiency and mechanisms of green tea, rosemary or maté extracts in porcine Longissimus dorsi subjected to iron-induced oxidative stress.

Plant extracts from rosemary (RE), green tea (GTE), and maté (ME) were compared for the protection against iron-induced oxidation in porcine homogenates at total phenolic concentrations from 25 to 250 ppm. Lipid oxidation as indicated by TBARS was in all cases sufficiently suppressed, especially for RE. Hydrophobic RE retarded overall oxidation in the homogenates with an inverted dose-dependent response. Optimum delay of oxygen consumption was found at the lowest concentration applied, similar to protection against thiols and formation of protein radicals as measured by ESR, whereas the high concentration increased oxygen consumption and caused additionally thiol loss possibly due to thiol-quinone interactions, generating protein-phenol complexes. Hydrophilic ME or GTE increased the initial oxygen consumption rate as an indication of prooxidant activities at elevated concentrations. However, they were found to protect myoglobin and protein at those high concentrations with GTE being more efficient, possibly due to better chelation effect.

Defect and Additional Active Sites on the Basal Plane of Manganese-Doped Molybdenum Diselenide for Effective Enzyme Immobilization: In Vitro and in Vivo Real-Time Analyses of Hydrogen Peroxide Sensing.

The defect engineering makes the new concepts and designs to further enhance the electrocatalytic activity of layered structures. In this work, we demonstrated the synthesis of Mn-doped MoSe2 and reported the resultant defective sites. Subsequently, the MnMoSe2 was developed as a new type of electrocatalyst for electrochemical biosensors. The formation of defect/distortion and effective immobilization of myoglobin (Mb) were evidently confirmed by using the transmission electron microscopy and UV-vis spectroscopy analyses, respectively. The result of electrochemical impedance spectroscopy analysis reveals that the Mn doping not only helps  to enzyme immobilization but also enhances the electronic conductivity of layered material.  Owing to the multiple signal amplification strategies, the proposed Mb-immobilized MnMoSe2 (Mb@MnMoSe2) exhibited an ultralow detection limit (0.004 µM) and a higher sensitivity (222.78 µA µM-1 cm-2) of H2O2. In real-sample analysis, the Mb@MnMoSe2 showed a feasible recovery range of H2O2 detection in human serum (95.6-102.1%), urine (101.2-102.3%), and rain water (100.7-102.1%) samples. On the other hand, an in vivo study using HaCaT (7.1 × 105/mL) and RAW 264.7 (1 × 106/mL) living cells showed the feasible current responses of 0.096 and 0.085 µA, respectively. Finally, the Mn doping gives a new opportunity to fabricate a promising electrocatalyst for H2O2 biosensing.

Oxidative stability of beef from steers finished exclusively with concentrate, supplemented, or on legume-grass pasture.

The objective of this study was to evaluate the effects of three finishing systems based on concentrate and legume-grass pasture on beef. Steers were finished for 91 days with an exclusively whole corn grain-based (GRAIN) diet, grazed on legume-grass pasture plus 1.4% of body weight of whole corn grain supplementation (SUPP), or grazed on legume-grass pasture (PAST) only. Lipid and myoglobin oxidation, pH, objective color, and α-tocopherol concentrations were evaluated on M. longissimus thoracis steaks. Dietary treatments did not affect pH and minimally affected protein carbonylation. Steaks from steers fed GRAIN were less red, showed higher lipid oxidation during retail display, and higher metmyoglobin formation from day 7 to 13 when compared to PAST. Levels of α-tocopherol were higher in steaks from steers fed diets containing legume and grass. Inclusion of roughage in finishing diets is essential to maintain retail color and prevent lipid and myoglobin oxidation.

Effect of dietary nitrate supplementation on conduit artery blood flow, muscle oxygenation, and metabolic rate during handgrip exercise.

Dietary nitrate supplementation has positive effects on mitochondrial and muscle contractile efficiency during large muscle mass exercise in humans and on skeletal muscle blood flow (Q̇) in rats. However, concurrent measurement of these effects has not been performed in humans. Therefore, we assessed the influence of nitrate supplementation on Q̇ and muscle oxygenation characteristics during moderate- (40 %peak) and severe-intensity(85% peak) handgrip exercise in a randomized, double-blind, crossover design. Nine healthy men (age: 25 ± 2 yr) completed four constant-power exercise tests (2/intensity) randomly assigned to condition [nitrate-rich (nitrate) or nitrate-poor (placebo) beetroot supplementation] and intensity (40 or 85% peak). Resting mean arterial pressure was lower after nitrate compared with placebo (84 ± 4 vs. 89 ± 4 mmHg, P < 0.01). All subjects were able to sustain 10 min of exercise at 40% peak in both conditions. Nitrate had no effect on exercise tolerance during 85% peak (nitrate: 358 ± 29; placebo: 341 ± 34 s; P = 0.3). Brachial artery Q̇ was not different after nitrate at rest or any time during exercise. Deoxygenated [hemoglobin + myoglobin] was not different for 40% peak ( P > 0.05) but was elevated throughout 85% peak ( P < 0.05) after nitrate. The metabolic cost (V̇o2) was not different at the end of exercise; however, the V̇o2 primary amplitude at the onset of exercise was elevated after nitrate for the 85% peak work rate (96 ± 20 vs. 72 ± 12 ml/min, P < 0.05) and had a faster response. These findings suggest that an acute dose of nitrate reduces resting blood pressure and speeds V̇o2 kinetics in young adults but does not augment Q̇ or reduce steady-state V̇o2 during small muscle mass handgrip exercise. NEW & NOTEWORTHY We show that acute dietary nitrate supplementation via beetroot juice increases the amplitude and speed of local muscle V̇o2 on kinetics parameters during severe- but not moderate-intensity handgrip exercise. These changes were found in the absence of an increased blood flow response, suggesting that the increased V̇o2 was attained via improvements in fractional O2 extraction and/or spatial distribution of blood flow within the exercising muscle.

Cardiac myoglobin participates in the metabolic pathway of selenium in rats.

As an essential micronutrient, selenium deficiency is a leading cause of cardiovascular diseases. The heart is continuously beating to deliver blood to the entire body, and this requires a high amount of energy. An adult heart normally obtains 50-70% of its adenosine 5'-triphosphate from fatty acid ß-oxidation. An increase in fatty acid oxidation activity induces the generation of larger amounts of by-products (reactive oxygen species, ROS) from mitochondrial oxidative phosphorylation. Selenium-dependent glutathione peroxidases play a critical role in the removal of these ROS, especially organic hydroperoxides, from the heart. The definitive transport and/or detailed metabolic pathways from the selenium-source compounds to the selenoproteins in the heart still remain unclear. We explored the selenium-binding proteins in a rat cardiac cell lysate using its reactive metabolic intermediate, selenotrisulfide (STS), and MALDI TOF-mass spectrometry. Several proteins with a free cysteine (Cys) thiol were found to be reactive with STS through a thiol-exchange reaction. The most distinctive Cys-containing protein in the cardiac cell lysate was identified as myoglobin (Mb) from a rat protein database search and tryptic fragmentation experiments. When separately examined in selenium adequate rats, selenium-binding to the cardiac Mb was verified using selenium-specific fluorometry. Cardiac Mb is thought to participate in the selenium metabolic pathway in the heart.

Danhong Injection Protects Against Hypertension-Induced Renal Injury Via Down-Regulation of Myoglobin Expression in Spontaneously Hypertensive Rats.

BACKGROUND/AIMS: High blood pressure is a major risk factor for chronic kidney disease. Currently, single-target anti-hypertensive drugs are not designed for high blood pressure-related organ damages. Danhong injection (DHI), made from the aqueous extracts of Radix Salviae miltiorrhizae and Flos Carthamus tinctorius, has various pharmacological effects, including BP lowering in SHR, mediated by the reduction of vascular remodeling and the up-regulation of Kallikrein-kinin system published recently by our team, yet if it renders renal protection remains unknown. The current study demonstrated a protective role of DHI in renal injury caused by hypertension and identified its molecular targets in the kidney of spontaneously hypertensive rats (SHR). METHODS: Adult SHR and age/gender-matched normotensive Wistar-Kyoto (WKY) rats were treated with DHI, Losartan, or saline for 4 weeks. Serum levels of Creatinine (CRE), Micro-albumin (mAlb), Beta2-microglobulin (ß2-MG), and Uric acid (UA) were detected using ELISA kits. Renal pathology was examined by hematoxylin and Eosin (H&E) stains. Microarray analysis was performed on kidney tissues, and gene expression changes were validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analyses. RESULTS: Renal histopathological scores showed that SHR exhibited serious kidney injury compared to normotensive WKY rats. The intervention with DHI potently suppressed the renal injury biomarker (KIM-1) and kidney lesions compared to the untreated hypertensive subjects. Microarray analysis revealed that among the 124 genes that were differentially expressed by DHI treatment in SHR kidney, down-regulation of renal myoglobin (Mb) gene was the most prominent and was subsequently confirmed by qRT-PCR and Western blot analysis. CONCLUSION: Hypertension-induced renal injury in SHR may be alleviated by DHI in part by local suppression of Kidney injury molecule-1 and down-regulation of Myoglobin. However, if this effect is independent of the known anti-hypertensive action of DHI in blood vessel remains to be determined.

Attenuation of Glucose-Induced Myoglobin Glycation and the Formation of Advanced Glycation End Products (AGEs) by (R)-α-Lipoic Acid In Vitro.

High-carbohydrate containing diets have become a precursor to glucose-mediated protein glycation which has been linked to an increase in diabetic and cardiovascular complications. The aim of the present study was to evaluate the protective effect of (R)-α-lipoic acid (ALA) against glucose-induced myoglobin glycation and the formation of advanced glycation end products (AGEs) in vitro. METHODS: The effect of ALA on myoglobin glycation was determined via the formation of AGEs fluorescence intensity, iron released from the heme moiety of myoglobin and the level of fructosamine. The extent of glycation-induced myoglobin oxidation was measured via the levels of protein carbonyl and thiol. RESULTS: The results showed that the co-incubation of ALA (1, 2 and 4 mM) with myoglobin (1 mg/mL) and glucose (1 M) significantly decreased the levels of fructosamine, which is directly associated with the decrease in the formation of AGEs. Furthermore, ALA significantly reduced the release of free iron from myoglobin which is attributed to the protection of myoglobin from glucose-induced glycation. The results also demonstrated a significant protective effect of ALA on myoglobin from oxidative damage, as seen from the decreased protein carbonyls and increased protein thiols. CONCLUSION: The anti-glycation properties of ALA suggest that ALA supplementation may be beneficial in the prevention of AGEs-mediated diabetic and cardiovascular complications.

(R)-α-Lipoic acid inhibits fructose-induced myoglobin fructation and the formation of advanced glycation end products (AGEs) in vitro.

BACKGROUND: Fructose-mediated protein glycation (fructation) has been linked to an increase in diabetic and cardiovascular complications due to over consumption of high-fructose containing diets in recent times. The objective of the present study is to evaluate the protective effect of (R)-α-lipoic acid (ALA) against fructose-induced myoglobin fructation and the formation of advanced glycation end products (AGEs) in vitro. METHODS: The anti-glycation activity of ALA was determined using the formation of AGEs fluorescence intensity, iron released from the heme moiety of myoglobin and the level of fructosamine. The fructation-induced myoglobin oxidation was examined using the level of protein carbonyl content and thiol group estimation. RESULTS: The results showed that co-incubation of myoglobin (1 mg/mL), fructose (1 M) and ALA (1, 2 and 4 mM) significantly inhibited the formation of AGEs during the 30 day study period. ALA markedly decreased the levels of fructosamine, which is directly associated with the reduction of AGEs formation. Furthermore, ALA significantly reduced free iron release from myoglobin which is attributed to the protection of myoglobin from fructose-induced glycation. The results also demonstrated a significant protective effect of ALA on myoglobin oxidative damages, as seen from decreased protein carbonyl content and increased protein thiols. CONCLUSION: These findings provide new insights into the anti-glycation properties of ALA and emphasize that ALA supplementation is beneficial in the prevention of AGEs-mediated diabetic and cardiovascular complications.

Effects of dietary coated cysteamine hydrochloride on pork color in finishing pigs.

BACKGROUND: Coated cysteamine hydrochloride (CC) was applied as a feed additive in animal production. The influence and the mechanisms of CC used as a feed additive in promoting meat quality in finishing pigs were investigated. RESULTS: Dietary CC supplementation increased (P < 0.05) the a* and H* values and reduced (P < 0.05) the L* value in the longissimus dorsi muscles at 48 h postmortem (P < 0.05). The deoxymyoglobin content was enhanced (P < 0.05) and the metmyoglobin and malondialdehyde contents were reduced (P < 0.05) in pigs fed the dietary CC. Pigs fed a dietary CC of 0.035 g kg-1 had a lower cooking loss (P < 0.05) and a higher a* (24 h) value in the longissimus dorsi muscles than pigs on control treatment. The messenger RNA expression of superoxide dismutase 1 was upregulated (P < 0.05) in the longissimus dorsi. CONCLUSION: Dietary supplementation with CC could improve antioxidant status and delay meat discoloration by improving glutathione levels and antioxidase activity after longer chill storage (for 48 h after slaughter). Dietary supplementation with CC at 0.035 g kg-1 may promote the stability of pork color by reducing oxidation. © 2017 Society of Chemical Industry.

Cardiac performance is limited by oxygen delivery to the mitochondria in the crystalloid-perfused working heart.

The left ventricular working, crystalloid-perfused heart is used extensively to evaluate basic cardiac function, pathophysiology, and pharmacology. Crystalloid-perfused hearts may be limited by oxygen delivery, as adding oxygen carriers increases myoglobin oxygenation and improves myocardial function. However, whether decreased myoglobin oxygen saturation impacts oxidative phosphorylation (OxPhos) is unresolved, since myoglobin has a much lower affinity for oxygen than cytochrome c oxidase (COX). In the present study, a laboratory-based synthesis of an affordable perfluorocarbon (PFC) emulsion was developed to increase perfusate oxygen carrying capacity without impeding optical absorbance assessments. In left ventricular working hearts, along with conventional measurements of cardiac function and metabolic rate, myoglobin oxygenation and cytochrome redox state were monitored using a novel transmural illumination approach. Hearts were perfused with Krebs-Henseleit (KH) or KH supplemented with PFC, increasing perfusate oxygen carrying capacity by 3.6-fold. In KH-perfused hearts, myoglobin was deoxygenated, consistent with cytoplasmic hypoxia, and the mitochondrial cytochromes, including COX, exhibited a high reduction state, consistent with OxPhos hypoxia. PFC perfusate increased aortic output from 76 ± 6 to 142 ± 4 ml/min and increased oxygen consumption while also increasing myoglobin oxygenation and oxidizing the mitochondrial cytochromes. These results are consistent with limited delivery of oxygen to OxPhos resulting in an adapted lower cardiac performance with KH. Consistent with this, PFCs increased myocardial oxygenation, and cardiac work was higher over a wider range of perfusate Po2. In summary, heart mitochondria are limited by oxygen delivery with KH; supplementation of KH with PFC reverses mitochondrial hypoxia and improves cardiac performance, creating a more physiological tissue oxygen delivery. NEW & NOTEWORTHY Optical absorbance spectroscopy of intrinsic chromophores reveals that the commonly used crystalloid-perfused working heart is oxygen limited for oxidative phosphorylation and associated cardiac work. Oxygen-carrying perfluorocarbons increase myocardial oxygen delivery and improve cardiac function, providing a more physiological mitochondrial redox state and emphasizing cardiac work is modulated by myocardial oxygen delivery.

The effect of dietary nitrate supplementation on the spatial heterogeneity of quadriceps deoxygenation during heavy-intensity cycling.

This study investigated the influence of dietary inorganic nitrate (NO3-) supplementation on pulmonary O2 uptake (V˙O2) and muscle deoxyhemoglobin/myoglobin (i.e. deoxy [Hb + Mb]) kinetics during submaximal cycling exercise. In a randomized, placebo-controlled, cross-over study, eight healthy and physically active male subjects completed two step cycle tests at a work rate equivalent to 50% of the difference between the gas exchange threshold and peak V˙O2 over separate 4-day supplementation periods with NO3--rich (BR; providing 8.4 mmol NO3-∙day-1) and NO3--depleted (placebo; PLA) beetroot juice. Pulmonary V˙O2 was measured breath-by-breath and time-resolved near-infrared spectroscopy was utilized to quantify absolute deoxy [Hb + Mb] and total [Hb + Mb] within the rectus femoris, vastus lateralis, and vastus medialis There were no significant differences (P > 0.05) in the primary deoxy [Hb + Mb] mean response time or amplitude between the PLA and BR trials at each muscle site. BR significantly increased the mean (three-site) end-exercise deoxy [Hb + Mb] (PLA: 91 ± 9 vs. BR: 95 ± 12 µmol/L, P < 0.05), with a tendency to increase the mean (three-site) area under the curve for total [Hb + Mb] responses (PLA: 3650 ± 1188 vs. BR: 4467 ± 1315 µmol/L sec-1, P = 0.08). The V˙O2 slow component reduction after BR supplementation (PLA: 0.27 ± 0.07 vs. BR: 0.23 ± 0.08 L min-1, P = 0.07) correlated inversely with the mean increases in deoxy [Hb + Mb] and total [Hb + Mb] across the three muscle regions (r2 = 0.62 and 0.66, P < 0.05). Dietary NO3- supplementation increased O2 diffusive conductance across locomotor muscles in association with improved V˙O2 dynamics during heavy-intensity cycling transitions.

The physiological response to cold-water immersion following a mixed martial arts training session.

Combative sport is one of the most physically intense forms of exercise, yet the effect of recovery interventions has been largely unexplored. We investigated the effect of cold-water immersion on structural, inflammatory, and physiological stress biomarkers following a mixed martial arts (MMA) contest preparation training session in comparison with passive recovery. Semiprofessional MMA competitors (n = 15) were randomly assigned to a cold-water immersion (15 min at 10 °C) or passive recovery protocol (ambient air) completed immediately following a contest preparation training session. Markers of muscle damage (urinary myoglobin), inflammation/oxidative stress (urinary neopterin + total neopterin (neopterin + 7,8-dihydroneopterin)), and hypothalamic-pituitary axis (HPA) activation (saliva cortisol) were determined before, immediately after, and 1, 2, and 24 h postsession. Ratings of perceived soreness and fatigue, counter movement jump, and gastrointestinal temperature were also measured. Concentrations of all biomarkers increased significantly (p < 0.05) postsession. Cold water immersion attenuated increases in urinary neopterin (p < 0.05, d = 0.58), total neopterin (p < 0.05, d = 0.89), and saliva cortisol after 2 h (p < 0.05, d = 0.68) and urinary neopterin again at 24 h (p < 0.01, d = 0.57) in comparison with passive recovery. Perceived soreness, fatigue, and gastrointestinal temperatures were also lower for the cold-water immersion group at several time points postsession whilst counter movement jump did not differ. Combative sport athletes who are subjected to impact-induced stress may benefit from immediate cold-water immersion as a simple recovery intervention that reduces delayed onset muscle soreness as well as macrophage and HPA activation whilst not impairing functional performance.

Fast-to-slow shift of muscle fiber-type composition by dietary apple polyphenols in rats: Impact of the low-dose supplementation.

Our previous studies demonstrated that an 8-week intake of 5% (w/w) apple polyphenol (APP) in the diet improves muscle endurance of young-adult rats. In order to identify a lower limit of the dietary contribution of APP to the effect, the experiments were designed for lower-dose supplementation (8-week feeding of 0.5% APP in AIN-93G diet) to 12-week-old male Sprague-Dawley rats. Results clearly showed that the 0.5% APP diet significantly up-regulates slower myosin-heavy-chain (MyHC) isoform ratios (IIx and IIa relative to total MyHC) and myoglobin expression in lower hind-limb muscles examined (P < 0.05). There was a trend to increased fatigue resistance detected from measurements of relative isometric plantar-flexion force torque generated by a stimulus train delivered to the tibial nerve (F(98, 1372) = 1.246, P = 0.0574). Importantly, there was no significant difference in the animal body-phenotypes or locomotor activity shown as total moving distance in light and dark periods. Therefore, the present study encourages the notion that even low APP-intake may increase the proportions of fatigue-resistant myofibers, and has promise as a strategy for modifying performance in human sports and improving function in age-related muscle atrophy.