Myosin-based regulation of twitch and tetanic contractions in mammalian skeletal muscle

Time-resolved X-ray diffraction of isolated fast-twitch muscles of mice was used to show how structural changes in the myosin-containing thick filaments contribute to the regulation of muscle contraction, extending the previous focus on regulation by the actin-containing thin filaments. This study shows that muscle activation involves the following sequence of structural changes: thin filament activation, disruption of the helical array of myosin motors characteristic of resting muscle, release of myosin motor domains from the folded conformation on the filament backbone, and actin attachment. Physiological force generation in the 'twitch' response of skeletal muscle to single action potential stimulation is limited by incomplete activation of the thick filament and the rapid inactivation of both filaments. Muscle relaxation after repetitive stimulation is accompanied by a complete recovery of the folded motor conformation on the filament backbone but by incomplete reformation of the helical array, revealing a structural basis for post-tetanic potentiation in isolated muscles.

Evaluation of RNA quality and functional transcriptome of beef longissimus thoracis over time post-mortem

Evaluating RNA quality and transcriptomic profile of beef muscle over time post-mortem may provide insight into RNA degradation and underlying biological and functional mechanisms that accompany biochemical changes occurring post-mortem during transformation of muscle to meat. RNA was extracted from longissimus thoracis (LT) sampled from British Continental crossbred heifer carcasses (n = 7) stored at 4°C in an abattoir drip cooler at 5 time points post-mortem, i.e., 45 min (0 h), 6 h, 24 h, 48 h, and 72 h. Following RNA-Sequencing, processed reads were aligned to the ARS-UCD1.2 bovine genome assembly. Subsequent differential expression (DE) analysis identified from 51 to 1434 upregulated and 27 to 2256 downregulated DE genes at individual time points compared to time 0 h, showing a trend for increasing counts of both upregulated and downregulated genes over time. Gene ontology and biological pathway term enrichment analyses on sets of DE genes revealed several processes and their timelines of activation/deactivation that accompanied or were involved with muscle transformation to meat. Although the quality of RNA in refrigerated LT remained high for several days post-mortem, the expression levels of several known biomarker genes for meat quality began to change from 24 h onwards. Therefore, to ensure accuracy of predictions on meat quality traits based on the expression levels of those biomarker genes in refrigerated beef muscle tissue, it is crucial that those expression measurements be made on RNA sampled within 24 h post-mortem. The present study also highlighted the need for more research on the roles of mitochondrial genes and non-coding genes in orchestrating muscle tissue processes after death, and how pre-mortem immune status might influence post-mortem meat quality.

Assessment of the ANDE 6C Rapid DNA system and investigative biochip for the processing of calcified and muscle tissue

The ANDE 6C Rapid DNA system could offer a potential alternative for the processing of calcified and soft tissue samples, often encountered in mass disaster scenarios. While originally designed for single source buccal swabs, interest in the performance of these instruments when using other types of single source samples continues to grow. To enhance the recovery of otherwise lesser quality samples, the manufacturer developed the investigative biochip, an alternative to the NDIS approved Arrestee biochip for reference sample buccal swabs. This study explores the viability of using the ANDE 6C system and the investigative biochip to process soft and calcified tissue, and uses conventional sample processing to contrast the results. Though the success rate obtained using the instrument's expert system was lower than expected - 0% muscle, 11% ribs, and 50% teeth -, the ANDE 6C offers an advantage over conventional calcified tissue processing in terms of turn-around time and processing complexity. If robust analysis parameters can be established to allow the evaluation of the generated data by a qualified analyst on a third party software platform, the use of the ANDE 6C and investigative biochip could be a suitable alternative for currently employed procedures. However, as is the case with conventional DNA typing, the quantity, age, type of biological material and quality of the exemplars could all play a role in the success of the ANDE 6C typing process. In addition, it appears as if the calcified tissue pre-processing protocol that provides the better opportunity for the ANDE 6C success is not appropriate to be carried out in the field or by non-trained personnel as special equipment as well as a certain level of exe expertise and technique is necessary. Nevertheless, disaster victim and unidentified human remain samples could be processed in a laboratory setting using the Rapid DNA ANDE 6C platform provided sufficient material is available to conduct a second, 'rescue' sample processing if necessary.

Control of rat muscle nitrate levels after perturbation of steady state dietary nitrate intake

The roles of nitrate and nitrite ions as nitric oxide (NO) sources in mammals, complementing NOS enzymes, have recently been the focus of much research. We previously reported that rat skeletal muscle serves as a nitrate reservoir, with the amount of stored nitrate being highly dependent on dietary nitrate availability, as well as its synthesis by NOS1 enzymes and its subsequent utilization. We showed that at conditions of increased NO need, this nitrate reservoir is used in situ to generate nitrite and NO, at least in part via the nitrate reductase activity of xanthine oxidoreductase (XOR). We now further investigate the dynamics of nitrate/nitrite fluxes in rat skeletal muscle after first increasing nitrate levels in drinking water and then returning to the original intake level. Nitrate/nitrite levels were analyzed in liver, blood and several skeletal muscle samples, and expression of proteins involved in nitrate metabolism and transport were also measured. Increased nitrate supply elevated nitrate and nitrite levels in all measured tissues. Surprisingly, after high nitrate diet termination, levels of both ions in liver and all muscle samples first declined to lower levels than the original baseline. During the course of the overall experiment there was a gradual increase of XOR expression in muscle tissue, which likely led to enhanced nitrate to nitrite reduction. We also noted differences in basal levels of nitrate in the different types of muscles. These findings suggest complex control of muscle nitrate levels, perhaps with multiple processes to preserve its intracellular levels.

A High Activity Level Is Required for Augmented Muscle Capillarization in Older Women

PURPOSE

This study aimed to evaluate the influence of lifelong regular physical activity on skeletal muscle capillarization in women.

METHODS

Postmenopausal women, 61±4 yr old, were divided according to self-reported physical activity level over the past 20 yrs: sedentary (SED; n = 14), moderately active (MOD; n = 12), and very active (VERY; n = 15). Leg blood flow (LBF) was determined by ultrasound Doppler, and blood samples were drawn from the femoral artery and vein for calculation of leg oxygen uptake (LVO2) at rest and during one-legged knee extensor exercise. A skeletal muscle biopsy was obtained from the vastus lateralis and analyzed for capillarization and vascular endothelial growth factor (VEGF) and mitochondrial OXPHOS proteins. Platelets were isolated from venous blood and analyzed for VEGF content and effect on endothelial cell proliferation.

RESULTS

The exercise-induced rise in LBF and LVO2 was faster (P = 0.008) in VERY compared with SED and MOD. Steady-state LBF and LVO2 were lower (P < 0.04) in MOD and VERY compared with SED. Capillary-fiber ratio and capillary density were greater (P < 0.03) in VERY (1.65 ± 0.48 and 409.3 ± 57.5) compared with MOD (1.30 ± 0.19 and 365.0 ± 40.2) and SED (1.30 ± 0.30 and 356.2 ± 66.3). Skeletal muscle VEGF and OXPHOS complexes I, II, and V were ~1.6-fold and ~1.25-fold (P < 0.01) higher, respectively, in VERY compared with SED. Platelets from all groups induced an approximately nine-fold (P < 0.001) increase in endothelial cell proliferation.

CONCLUSION

A very active lifestyle is associated with superior skeletal muscle exercise hemodynamics and greater potential for oxygen extraction concurrent with a higher skeletal muscle capillarization and mitochondrial capacity.

Hyperreflexia and enhanced ripple oscillations in the taurine-deficient mice

In this study, we examined neuronal excitability and skeletal muscle physiology and histology in homozygous knockout mice lacking cysteine sulfonic acid decarboxylase (CSAD-KO). Neuronal excitability was measured by intracerebral recording from the prefrontal cortex. Skeletal muscle response was measured through stretch reflex in the ankle muscles. Specifically, we measured the muscle tension, amplitude of electromyogram and velocity of muscle response. Stretch reflex responses were evoked using a specialized stretching device designed for mice. The triceps surae muscle was stretched at various speeds ranging from 18 to 18,000° s^-1. A transducer recorded the muscle resistance at each velocity and the corresponding EMG. We also measured the same parameter in anesthetized mice. We found that at each velocity, the CSAD-KO mice generated more tension and exhibited higher EMG responses. To evaluate if the enhanced response was due to neuronal excitability or changes in the passive properties of muscles, we anesthetize mice to eliminate the central component of the reflex. Under these conditions, CSAD-KO mice still exhibited an enhanced stretch reflex response, indicating ultrastructural alterations in muscle histology. Consistent with this, we found that sarcomeres from CSAD-KO muscles were shorter and thinner when compared to control sarcomeres. Neuronal excitability was further investigated using intracerebral recordings of brain waves from the prefrontal cortex. We found that extracellular field potentials in CSAD-KO mice were characterized by reduced amplitude of low-frequency brain waves (delta, theta, alpha, beta and gamma) and increased in the high low-frequency brain waves (slow and fast ripples). Increased slow and fast ripple rates serve as a biomarker of epileptogenic brain. We have previously shown that taurine interacts with GABA_A receptors and induces biochemical changes in the GABAergic system. We suggest that taurine deficiency leads to alterations in the GABAergic system that contribute to the enhanced stretch reflex in CSAD-KO mice through biochemical mechanisms that involve alterations not only at the spinal level but also at the cortical level.

Performance of different portable and hand-held near-infrared spectrometers for predicting beef composition and quality characteristics in the abattoir without meat sampling

The availability of portable and handheld NIR instruments on the market opens up new possibilities in meat analysis. However, there is lack of research comparing different NIR instruments for evaluating beef characteristics from spectra obtained directly on the meat surface. Our aim, therefore, was to build and test calibration and prediction models for predicting beef characteristics, and to compare the performances of three NIR instruments differing in size and characteristics: a transportable visible-NIR spectrometer (Vis-NIRS), a portable (NIRS), and a hand-held Micro-NIRS. Spectra were collected from 178 beef samples (Longissimus thoracis muscle) from the meat surface in the abattoir. The spectra were subjected to different mathematical pretreatments then partial least square regressions. The results showed that all instruments predicted dry matter, protein and lipids with R²_VAL 0.23 to 0.70; pH and cooking loss R²_VAL 0.19 to 0.25; and color R²_VAL 0.35 to 0.77. Overall, the prediction performances of the three instruments were similar, although Micro-NIRS performed better in some respects.

The myosin II coiled-coil domain atomic structure in its native environment

The atomic structure of the complete myosin tail within thick filaments isolated from Lethocerus indicus flight muscle is described and compared to crystal structures of recombinant, human cardiac myosin tail segments. Overall, the agreement is good with three exceptions: the proximal S2, in which the filament has heads attached but the crystal structure doesn't, and skip regions 2 and 4. At the head-tail junction, the tail α-helices are asymmetrically structured encompassing well-defined unfolding of 12 residues for one myosin tail, ∼4 residues of the other, and different degrees of α-helix unwinding for both tail α-helices, thereby providing an atomic resolution description of coiled-coil "uncoiling" at the head-tail junction. Asymmetry is observed in the nonhelical C termini; one C-terminal segment is intercalated between ribbons of myosin tails, the other apparently terminating at Skip 4 of another myosin tail. Between skip residues, crystal and filament structures agree well. Skips 1 and 3 also agree well and show the expected α-helix unwinding and coiled-coil untwisting in response to skip residue insertion. Skips 2 and 4 are different. Skip 2 is accommodated in an unusual manner through an increase in α-helix radius and corresponding reduction in rise/residue. Skip 4 remains helical in one chain, with the other chain unfolded, apparently influenced by the acidic myosin C terminus. The atomic model may shed some light on thick filament mechanosensing and is a step in understanding the complex roles that thick filaments of all species undergo during muscle contraction.

The protein and fat quality of thigh muscles from Polish goose varieties

This study aimed to evaluate the nutritional value of thigh meat from 4 Polish geese varieties. Protein, fat, and cholesterol content, as well as amino acid and fatty acid profiles, were determined. Based on the percentage of amino acid in protein and fatty acids in meat lipids, the health lipid indices were calculated. The experimental material covered thigh muscles from 17-week-old Kartuska (Ka), Suwalska (Su), Lubelska (Lu), and Kielecka (Ki) geese reared in a semi-intensive system. Muscle protein content did not differ significantly between varieties. The protein content of the Ka, Su, Lu, and Ki goose meat was deemed high-value as it contained all the essential amino acids in the proportions consistent with standard protein values. The muscles of all the researched geese varieties were characterized by a high level of Lys, which indicates that this meat is a good source of it (AASLys 240-280%). Current findings showed that polyunsaturated fatty acids (PUFA)/saturated fatty acids (SFA) and PUFA n-6/n-3 ratios in Ka, Su, Lu, and Ki muscles were found to be within the optimum values for human diets. No significant differences were observed in monounsaturated fatty acids, PUFA, and unsaturated fatty acids (UFA) between the analyzed muscles. The meat of Ka and Su contained significantly more lipids than Lu and Ki. A more beneficial amino acid profile was found in Ka meat due to a higher content of PUFA n-3 and the best n-6/n-3 ratio in comparison with other varieties. The muscles of the Ka variety also contained the least cholesterol. However, the Ki goose muscles stood out among other varieties with the least percentage of SFA, the highest share of docosahexaenoic acid (C 22:6 n-3), as well as the most beneficial value of the following indices: UFA/SFA, hypocholesterolemic fatty acid/hypercholesterolemic fatty acid ratio, and nutritive value index. The thigh muscles of Ka, Su, Lu, and Ki were characterized by an atherogenicity index that met the levels of recommended values (<1) in the diet of a human being, while the thrombogenicity index was slightly higher than the recommended value (<0.5).

Dietary oleuropein extract supplementation and its combination with α-tocopheryl acetate and selenium modifies the free fatty acid profile of pork and improves its stability

BACKGROUND

Olive-derived antioxidants have been shown to affect the oxidative status of meat and have also been associated with greater consumption of glucose, which might affect glycogen stores and muscle characteristics. This study evaluated the effect of oleuropein extract supplementation (OLE) versus vitamin E + Se (VE), and their combination (VEOLE), in pig diets, on pH, drip loss, the proportion of free fatty acids, and meat stability, and their prediction by blood oxidative status markers.

RESULTS

The drip loss of muscle was lower in antioxidant-supplemented groups when compared with controls. α-Tocopherol concentration and total fatty acids profile were not affected by dietary oleuropein supplementation. However, OLE and VEOLE had lower free n-3 polyunsaturated fatty acid (PUFA) levels when compared with VE and tended to have higher free monounsaturated fatty acid (MUFA) levels. Furthermore, the VEOLE group had lower free n-6 PUFA levels when compared with controls or VE, whereas the OLE group had intermediated values. Muscle samples from pigs subjected to the antioxidant-mixed supplementation (VEOLE) had lower malondialdehyde concentration when compared with the others. The VE and OLE groups showed intermediate malondialdehyde values. Chilled meat stability was highly correlated with antioxidant status in vivo.

CONCLUSION

The administration of 96 mg oleuropein kg^-1 feed produced similar meat quality characteristics as the use of 100 mg kg^-1 α-tocopheryl acetate +0.26 mg kg^-1 sodium selenite and it would be an interesting alternative in Mediterranean countries. The VEOLE group was the most effective for reducing lipid oxidation and for the production of polyunsaturated free fatty acids in meat, which would result in lower rancidity formation and better aroma development in products. © 2020 Society of Chemical Industry.

Muscle Typology of World-Class Cyclists across Various Disciplines and Events

PURPOSE

Classic track-and-field studies demonstrated that elite endurance athletes exhibit a slow muscle typology, whereas elite sprint athletes have a predominant fast muscle typology. In elite cycling, conclusive data on muscle typology are scarce, which may be due to the invasive nature of muscle biopsies. The noninvasive estimation of muscle typology through the measurement of muscle carnosine enabled to explore the muscle typology of 80 world-class cyclists of different disciplines.

METHODS

The muscle carnosine content of 80 cyclists (4 bicycle motor cross racing [BMX], 33 track, 8 cyclo-cross, 24 road, and 11 mountain bike) was measured in the soleus and gastrocnemius by proton magnetic resonance spectroscopy and expressed as a z-score relative to a reference population. Track cyclists were divided into track sprint and endurance cyclists based on their Union Cycliste Internationale (UCI) ranking. Moreover, road cyclists were further characterized based on the percentage of UCI points earned during either single and multistage races.

RESULTS

BMX cyclists (carnosine aggregate z-score of 1.33) are characterized by a faster muscle typology than track, cyclo-cross, road, and mountain bike cyclists (carnosine aggregate z-score of -0.08, -0.76, -0.96, and -1.02, respectively; P < 0.05). Track cyclists also possess a faster muscle typology compared with mountain bikers (P = 0.033) and road cyclists (P = 0.005). Moreover, track sprinters show a significant faster muscle typology (carnosine aggregate z-score of 0.87) compared with track endurance cyclists (carnosine aggregate z-score of -0.44) (P < 0.001). In road cyclists, the higher the carnosine aggregate z-score, the higher the percentage of UCI points gained during single-stage races (r = 0.517, P = 0.010).

CONCLUSIONS

Prominent differences in the noninvasively determined muscle typology exist between elite cyclists of various disciplines, which opens opportunities for application in talent orientation and transfer.

Effect of chickpea (Cicer arietinum L.) protein isolate on the heat-induced gelation properties of pork myofibrillar protein

BACKGROUND

Heat-induced composite gels were prepared with 30 mg mL^-1 pork myofibrillar protein (MP) and chickpea protein isolate (CPI) (0, 3, 6, 9, 12, and 15 g kg^-1 ) in 0.6 mol L^-1 NaCl, at pH 7.0. The gel strength, water-holding capacity, rheological properties, and microstructure of MP-CPI composite gels were investigated.

RESULTS

Chickpea protein isolate improved (P < 0.05) gel strength and water-holding capacity of the MP composite gels. The rheological properties of MP-CPI composite gels were improved significantly by the addition of CPI. Meanwhile, the effects of CPI on the storage modulus of composite gels were positively correlated with the increased addition of CPI. Furthermore, according to low-field nuclear magnetic resonance (LF-NMR) results, the addition of CPI reduced the relaxation time of the composite gels and the relaxation peak area of free water, indicating that CPI could improve the water-holding capacity of MP-CPI composite gels. The microstructure of MP-CPI composite gels presented smaller and more uniform pores, which means that more water could be retained.

CONCLUSION

The addition of chickpea protein isolate improved the gel strength, water-holding capacity, rheological properties, and microstructure of MP gels, indicating that CPI could be a potential protein additive to improve the microstructure, texture, and functional quality of meat products. © 2020 Society of Chemical Industry.

Effect of pelvic suspension and post-mortem ageing on the quality of three muscles from Holstein Friesian bulls and steers

BACKGROUND

The use of bulls rather than steers from the dairy herd offers a more profitable and environmentally friendly option; however, the beef eating quality from bulls is an issue of concern. This study assessed the effect of two tenderization techniques - pelvic suspension and ageing - on three different muscles of Holstein Friesian males from two different production systems.

RESULTS

The results indicate that a production system based on steers slaughtered at 24 months (S24) produced beef with better eating quality than from bulls slaughtered at 19 months (B19) when tenderization techniques were not applied. Instrumental texture of longissimus thoracis and gluteus medius muscles was improved with ageing and/or pelvic suspension, with both tenderization techniques exerting greater impact on B19 meat. No differences were found in semitendinosus muscle due to suspension method, whereas ageing for longer than 14 days decreased its instrumental tenderness. Sensory results indicate that, after 14 days of ageing, panellists still preferred meat from S24, and they could differentiate between pelvic and traditional suspension.

CONCLUSION

Tenderization methodologies should be optimized for each production system and muscle; however, both panel and instrumental texture results indicate that eating quality of beef from either production systems is acceptable after 14 days of ageing, or even earlier if the suspension method is applied. © 2020 Society of Chemical Industry.

Detection of Locked Nucleic Acid Gapmers from Mouse Muscle Samples Using ELISA

Antisense oligonucleotide (ASO)-mediated therapy is promising for the treatment of a variety of genetic disorders, such as Duchenne muscular dystrophy. As more ASOs advance in therapeutic development and enter clinical trials, it becomes necessary to have a means of quantifying their amounts in biological samples post-treatment. This information will be valuable for evaluating the safety and pharmacokinetic profiles of ASOs, and in deciding how the efficacy of these drugs can be improved. Gapmers are a class of ASOs characterized by having a central DNA portion that is surrounded by chemically modified nucleotides on both ends. While relatively simple and accessible methods to quantify other ASOs such as phosphorodiamidate morpholino oligomers (PMOs) using enzyme-linked immunosorbent assay (ELISA)-based techniques are available and have been used for in vivo studies, no such method is available for gapmers to our knowledge. Here, we describe a sensitive ELISA protocol that can be used to quantify the levels of locked nucleic acid (LNA) gapmers in mouse muscle tissue.

Differences in oxidative susceptibilities between glycerophosphocholine and glycerophosphoethanolamine in dried scallop (Argopecten irradians) adductor muscle during storage: an oxidation kinetic assessment

BACKGROUND

Phospholipids, the main lipid component in marine shellfish, mainly comprise glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE). GPC and GPE in marine shellfish, especially scallop, carry n-3 long-chain polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), although different types of glycerophospholipids (GP) have different health benefits on human health. Moreover, different GP subclasses such as GPC and GPE have different oxidative susceptibilities in complex food systems. The present study compared the oxidative susceptibilities of GPC and GPE in dried scallop during storage by high-performance liquid chromatography-tandem mass spectrometry and kinetic models, and also investigated the effects of natural phenolic antioxidant on their susceptibilities.

RESULTS

The results showed that GPC and GPE molecular species (carrying EPA or DHA) contents in samples continuously reduced during storage at two different temperatures. The first-order kinetic model better reflected the changes of GPC and GPE molecular species (carrying EPA or DHA) in samples than the zero-order kinetic model during storage. According to the oxidation rate (k) obtained from first-order kinetic models, GPE possessed a greater oxidation rate than GPC during storage. Moreover, the results showed that antioxidants of bamboo leaves (AOB, polar polyphenolic antioxidants) significantly decreased the oxidation rates of GPC and GPE molecular species (carrying EPA or DHA) in samples during storage, and GPC could be more effectively protected by AOB compared to GPE.

CONCLUSION

The present study provides a practical method for accurately evaluating the oxidative susceptibility of different phospholipid classes in complex food systems. © 2020 Society of Chemical Industry.

C-terminal troponin-I residues trap tropomyosin in the muscle thin filament blocked-state

Tropomyosin and troponin regulate muscle contraction by participating in a macromolecular scale steric-mechanism to control myosin-crossbridge - actin interactions and consequently contraction. At low-Ca²⁺, the C-terminal 30% of troponin subunit-I (TnI) is proposed to trap tropomyosin in a position on thin filaments that sterically interferes with myosin-binding, thus causing muscle relaxation. In contrast, at high-Ca²⁺, inhibition is released after the C-terminal domains dissociate from F-actin-tropomyosin as its component switch-peptide domain binds to the N-lobe of troponin-C (TnC). Recent, paradigm-shifting, cryo-EM reconstructions by the Namba group have revealed density attributed to TnI along cardiac muscle thin filaments at both low- and high-Ca²⁺ concentration. Modeling the reconstructions showed expected high-Ca²⁺ hydrophobic interactions of the TnI switch-peptide and TnC. However, under low-Ca²⁺ conditions, sparse interactions of TnI and tropomyosin, and in particular juxtaposition of non-polar switch-peptide residues and charged tropomyosin amino acids in the published model seem difficult to reconcile with an expected steric-blocking conformation. This anomaly is likely due to inaccurate fitting of tropomyosin into the cryo-EM volume. In the current study, the low-Ca²⁺ cryo-EM volume was fitted with a more accurate tropomyosin model and representation of cardiac TnI. Our results show that at low-Ca²⁺ a cluster of hydrophobic residues at the TnI switch-peptide and adjacent H₄ helix (Ala149, Ala151, Met 154, Leu159, Gly160, Ala161, Ala163, Leu167, Leu169, Ala171, Leu173) draw-in tropomyosin surface residues (Ile143, Ile146, Ala151, Ile154), presumably attracting the entire tropomyosin cable to its myosin-blocking position on actin. The modeling confirms that neighboring TnI "inhibitory domain" residues (Arg145, Arg148) bind to thin filaments at actin residue Asp25, as previously suggested. ClusPro docking of TnI residues 137-184 to actin-tropomyosin, including the TnI inhibitory-domain, switch-peptide and Helix H₄, verified the modeled configuration. Our residue-to-residue contact-mapping of the TnI-tropomyosin association lends itself to experimental validation and functional localization of disease-bearing mutations.

Effects of Intermittent Fasting or Calorie Restriction on Markers of Lipid Metabolism in Human Skeletal Muscle

CONTEXT

Impaired lipid metabolism is linked with obesity-associated insulin resistance, which may be reversed by caloric restriction (CR).

OBJECTIVE

In a secondary analysis of a randomized controlled trial, we compared the effects of intermittent fasting (IF) and CR on markers of lipid metabolism in muscle.

DESIGN

Seventy-six women (body mass index, 25-40 kg/m2) were randomly assigned to 1 of 3 diets for 8 weeks and provided foods at 70% (CR70 and IF70) or 100% (IF100) of energy requirements. IF groups ate breakfast prior to a 24-hour fast on 3 nonconsecutive days per week. On nonfasting days, IF70 ate at 100% and IF100 ate at 145% of energy requirements to achieve the prescribed target. Weight, body composition, insulin sensitivity by clamp, nonesterified fatty acids (NEFAs), β-hydroxybutyrate (BHB), and markers of lipid metabolism and oxidative stress in muscle by quantitative polymerase chain reaction were measured at baseline and week 8 following a 12-hour overnight fast (all groups) and 24-hour fast (IF groups).

RESULTS

IF70 resulted in greater weight and fat loss and reduced NEFAs vs CR70 and IF100 after an overnight fast. IF70 and IF100 induced a greater reduction only in mRNA levels of antioxidant enzymes glutathione peroxidase 1 (GPX1), superoxide dismutase 1, soluble (SOD1), and SOD2 vs CR70. Fasting for 24 hours increased NEFAs and BHB in IF groups, but impaired insulin sensitivity and increased PLIN5 mRNA levels.

CONCLUSIONS

In comparison to CR, IF did not increase markers of lipid metabolism in muscle, but reduced expression of antioxidant enzymes. However, fasting-induced insulin resistance was detected, alongside increased PLIN5 expression, potentially reflecting transient lipid storage.

Estimation of the stability of skeletal muscle myoglobin of chilled pork treated with brine activated by low-frequency high-intensity ultrasound

We studied the effect of ultrasonic activation of brine (3%) during salting on the degree of stability of colour parameters of pork with normal (NOR) and abnormal course of autolysis in the CIE Lab colour space. The mechanism of stabilisation of the colour of meat is attributed to donor-acceptor bonds of metmyoglobin (MetMb). The accumulation of excessive number of free electrons in the medium are capable of activating MetMb. This reduces the activity of meat, when the native participants of the metmyoglobin reductase system and their own antioxidant systems of meat are depleted. Based on the additive calculation of deviations (increase / decrease) by the coordinates L*, a*, b* in the CIE Lab system, and the total colour difference (ΔE) in control and experimental samples, recommendations were developed. To optimize the colour characteristics of all types of meat, both on the surface and in the thickness of the meat, the preliminary activation of a 3% brine in a low-frequency submersible ultrasonic unit is recommended. Moreover, preliminary cavitation activation of a 3% is more preferable to stabilise the colour of PSE - meat (pale, soft, exudative (watery),) brine in a flow-through installation.

Sex Differences in Insulin Sensitivity are Related to Muscle Tissue Acylcarnitine But Not Subcellular Lipid Distribution

OBJECTIVE

Sex differences in insulin sensitivity are present throughout the life-span, with men having a higher prevalence of insulin resistance and diabetes compared with women. Differences in lean mass, fat mass, and fat distribution-particularly ectopic fat-have all been postulated to contribute to the sexual dimorphism in diabetes risk. Emerging data suggest ectopic lipid composition and subcellular localization are most relevant; however, it is not known whether they explain sex differences in obesity-induced insulin resistance.

METHODS

To address this gap, this study evaluated insulin sensitivity and subcellular localization of intramuscular triacylglycerol, diacylglycerol, and sphingolipids as well as muscle acylcarnitines and serum lipidomics in people with obesity.

RESULTS

Insulin sensitivity was significantly lower in men (P < 0.05); however, no sex differences were found in localization of intramuscular triacylglycerol, diacylglycerol, or sphingolipids in skeletal muscle. In contrast, men had higher total muscle acylcarnitine (P < 0.05) and long-chain muscle acylcarnitine (P < 0.05), which were related to lower insulin sensitivity (r = -0.42, P < 0.05). Men also displayed higher serum ceramide (P = 0.05) and lysophosphatidylcholine (P < 0.01).

CONCLUSIONS

These data reveal novel sex-specific associations between lipid species involved in the coupling of mitochondrial fatty acid transport, β-oxidation, and tricarboxylic acid cycle flux that may provide therapeutic targets to improve insulin sensitivity.

Potential of Creatine in Glucose Management and Diabetes

Creatine is one of the most popular supplements worldwide, and it is frequently used by both athletic and non-athletic populations to improve power, strength, muscle mass and performance. A growing body of evidence has been identified potential therapeutic effects of creatine in a wide variety of clinical conditions, such as cancer, muscle dystrophy and neurodegenerative disorders. Evidence has suggested that creatine supplementation alone, and mainly in combination with exercise training, may improve glucose metabolism in health individuals and insulin-resistant individuals, such as in those with type 2 diabetes mellitus. Creatine itself may stimulate insulin secretion in vitro, improve muscle glycogen stores and ameliorate hyperglycemia in animals. In addition, exercise induces numerous metabolic benefits, including increases in insulin-independent muscle glucose uptake and insulin sensitivity. It has been speculated that creatine supplementation combined with exercise training could result in additional improvements in glucose metabolism when compared with each intervention separately. The possible mechanism underlying the effects of combined exercise and creatine supplementation is an enhanced glucose transport into muscle cell by type 4 glucose transporter (GLUT-4) translocation to sarcolemma. Although preliminary findings from small-scale trials involving patients with type 2 diabetes mellitus are promising, the efficacy of creatine for improving glycemic control is yet to be confirmed. In this review, we aim to explore the possible therapeutic role of creatine supplementation on glucose management and as a potential anti-diabetic intervention, summarizing the current knowledge and highlighting the research gaps.

Analysis of volatile compounds and flavor fingerprint in Jingyuan lamb of different ages using gas chromatography-ion mobility spectrometry (GC-IMS)

In this study, gas chromatography coupled to an ion mobility spectrometry (GC-IMS) was used for analyzing some volatile components and flavor fingerprint in samples from Jingyuan lambs of different ages (2, 6, and 12 months). The data obtained from ion mobility were processed using laboratory analysis view processing software for fingerprint recognition, and the principal component analysis (PCA) was performed. GC-IMS provided information on the characteristics and strength of 66 volatile flavor compounds (monomers and dimers). The differences in flavoring substances between lambs of different ages were observed. The compounds with higher intensity peaks in the lamb meat samples were alcohols (1-octen-3-ol, ethanol, (E)-2-hexen-1-ol, 1-pentanol, and 2-propanol), ketones (2-pentanone, 2-heptanone, 3-hydroxy-2-butanone, 2-hexanone, 2-butanone, 2-propanone, and 4-methyl-2-pentanone), aldehydes (n-nonanal, octanal, heptanal, 3-methylbutanal, hexanal, pentanal, 2-methylbutanal, (E)-2-octenal, (E)-2-nonenal, methional, and phenylacetaldehyde), esters (methyl benzoate), furan (2-pentylfuran), and thiazole (trimethylthiazole). The results showed that the flavor fingerprint in samples from Jingyuan lambs of different ages (2, 6, and 12 months) can be established by GC-IMS and PCA based on the identified volatile compounds. This method might be used for the rapid and comprehensive analysis of volatile components in lamb meat.

Changes in the growth, ileal digestibility, intestinal histology, behavior, fatty acid composition of the breast muscles, and blood biochemical parameters of broiler chickens by dietary inclusion of safflower oil and vitamin C

BACKGROUND

The effects of safflower oil and vitamin C (Vit. C) inclusion in broiler chicken diets on the growth performance, apparent ileal digestibility coefficient "AID%" of amino acids, intestinal histology, behavior, carcass traits, fatty acid composition of the breast muscle, antioxidant and immune status for a 35-day feeding period were evaluated. A total of 300 three-day-old Ross chicks (58.25 g ± 0.19) were randomly allotted in a 2 × 3 factorial design consisting of two levels of vitamin C (0 and 400 mg/kg diet) and three levels of safflower oil (0, 5, and 10 g/kg diet).

RESULTS

An increase in the final body weight, total body weight gain, total feed intake, and the relative growth rate (P <  0.05) were reported by safflower oil and vitamin C inclusion. Dietary supplementation of safflower oil and vitamin C had a positive effect (P <  0.05) on the ingestive, resting, and feather preening behavior. Vitamin C supplementation increased (P <  0.05) the AID% of lysine, threonine, tryptophan, arginine, and valine. Safflower inclusion (10 g/kg) increased (P <  0.05) the AID% of methionine and isoleucine. Safflower oil inclusion increased (P <  0.05) the levels of stearic acid, linoleic acid, saturated fatty acids, and omega-3 fatty acids (ω-3) in the breast muscle. In contrast, the supplementation of only 10 g of safflower oil/kg diet increased (P = 0.01) the omega-3/omega-6 (ω-3/ω-6) fatty acids ratio. Vit. C supplementation increased (P <  0.05) the CAT serum levels, SOD, and GSH enzymes. Dietary supplementation of safflower oil and vitamin C improved the intestinal histology. They increased the villous height and width, crypt depth, villous height/crypt depth ratio, mucosal thickness, goblet cell count, and intra-epithelium lymphocytic lick cell infiltrations. The serum levels of IgA and complement C3 were increased (P <  0.01) by Vit. C supplementation and prominent in the 400 vit. C +  10 safflower Oil group.

CONCLUSION

A dietary combination of safflower oil and vitamin C resulted in improved growth rate, amino acids AID%, intestinal histology, welfare, immune and antioxidant status of birds, and obtaining ω-3 and linoleic acid-enriched breast muscles. The best inclusion level was 400 vit. C +  10 safflower Oil.

Multiclass, Multiresidue Method for the Quantification and Confirmation of 112 Veterinary Drugs in Game Meat (Bison, Deer, Elk, and Rabbit) by Rapid Polarity Switching Liquid Chromatography-Tandem Mass Spectrometry

An analytical program for multiclass, multiresidue residue analysis to qualitatively and quantitatively determine veterinary drug compounds in game meats by LC-MS/MS has been developed and validated. The method was validated for the analysis of muscle from bison, deer, elk, and rabbit to test for 112 veterinary drug residues from the following drug classes: β-agonists, anthelmintics, anti-inflammatory drugs, corticosteroids, fluoroquinolones, β-lactams, macrolides, nitroimidazoles, phenicols, polypeptides, sulfonamides, tetracyclines, thyreostats, and tranquilizers. Muscle was extracted using a simple and quick procedure based on a solvent extraction with 80% ACN/water and sample cleanup with dispersive solid-phase extraction. The compounds of interest were separated using a Waters HSS T3 column and detected by tandem mass spectrometry with rapid polarity switching to detect both negatively and positively charged ions in a single run. Recoveries were calculated using extracted matrix-matched calibration curves for each type of matrix. The average accuracy of fortified compounds ranged from 95.6 to 101% at the target quantitative validation level in the four matrices. The method was also validated as a qualitative screening method where all sample responses were compared with a single extracted matrix-matched calibrant at the target testing level (5 or 25 ng/g). Samples demonstrating a presumptive positive above the threshold value were re-extracted and analyzed with a five-point matrix-matching extracted calibration curve. Since the beginning of this survey program, 360 samples have been analyzed for veterinary drug residues in game meats. Antibiotic or tranquilizer residues have been identified in deer (chlortetracycline, haloperidol, and tulathromycin) and rabbit (sulfadiazine).

High-Throughput Mega-Method for the Analysis of Pesticides, Veterinary Drugs, and Environmental Contaminants by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry and Robotic Mini-Solid-Phase Extraction Cleanup + Low-Pressure Gas Chromatography-Tandem Mass Spectrometry, Part 1: Beef

In this work, a new mega-method of sample preparation called "QuEChERSER" (more than QuEChERS) is being presented for the first time. Fast, efficient, and cost-effective analysis of chemical contaminants in meat is useful for international trade, domestic monitoring, risk assessment, and other purposes. The goal of this study was to develop and validate a simple high-throughput mega-method for residual analysis of 161 pesticides, 63 veterinary drugs, 24 metabolites, and 14 legacy environmental contaminants (polychlorinated biphenyls) in bovine muscle for implementation in routine laboratory analyses. Sample preparation of 2 g test portions entailed QuEChERS-based extraction with 10 mL of 4:1 (v/v) acetonitrile/water, and then 204 μL was taken, diluted, and ultracentrifuged prior to analysis of veterinary drugs and pesticides by ultra-high-performance liquid chromatography-tandem mass spectrometry. The remaining extract was salted out with 4:1 (w/w) anhydrous MgSO₄/NaCl, and 1 mL was transferred to an autosampler vial for automated mini-cartridge solid-phase extraction (Instrument Top Sample Preparation) cleanup with immediate injection using fast low-pressure gas chromatography-tandem mass spectrometry analysis. The automated cleanup and both instruments were all operated in parallel in 13-15 min cycle times per sample. Method validation according to United States Department of Agriculture requirements demonstrated that 221 (85%) of the 259 analytes gave average recovery between 70 and 120% and interday relative standard deviation of ≤25%. Analysis of a certified reference material for veterinary drugs in freeze-dried bovine muscle was also very accurate, further demonstrating that the QuEChERSER mega-method can be implemented to save time, labor, and resources compared to current practices to use multiple methods to cover the same analytical scope.

High-Throughput Mega-Method for the Analysis of Pesticides, Veterinary Drugs, and Environmental Contaminants by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry and Robotic Mini-Solid-Phase Extraction Cleanup + Low-Pressure Gas Chromatography-Tandem Mass Spectrometry, Part 2: Catfish

The goal of this study was to develop and validate a new method for simultaneous determination of 106 veterinary drugs and 227 pesticides and their metabolites plus 16 polychlorinated biphenyls (PCBs) at and below their regulatory levels established for catfish muscle in the European Union and U.S.A. To do this, two different QuEChERS-based methods for veterinary drugs and pesticides and PCBs were modified and merged into a single mega-method dubbed "QuEChERSER" (more than QuEChERS), which is presented here for the first time. The mega-method was validated in catfish at four different spiking levels with 10 replicates per level. Sample extraction of 2 g test portions was made with 10 mL of 4:1 (v/v) acetonitrile/water, and then an aliquot was taken for ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis of 106 veterinary drugs and 125 pesticides, including metabolites. The remaining extract after salting out was subjected to automated mini-solid-phase extraction cleanup (Instrument Top Sample Preparation) for immediate injection in low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS). The cleanup was conducted in parallel with the 10 min LPGC-MS/MS analysis for 167 PCBs, pesticides, and metabolites, which was conducted in parallel with the 10 min UHPLC-MS/MS analysis for 231 analytes to increase sample throughput (49 analytes were included in both techniques). In MS/MS, three ion transitions were monitored for nearly all targeted analytes to provide unambiguous identification as well as quantification. Satisfactory recoveries (70-120%) and relative standard deviations of ≤20% were achieved for 98 (92%) of the veterinary drugs and their metabolites and for 222 (91%) of pesticides, metabolites, and PCBs, demonstrating that the developed method is applicable for the analysis of these contaminants in fish as part of regulatory monitoring programs and other purposes.