Oral glutamine supplementation attenuates inflammation and oxidative stress-mediated skeletal muscle protein content degradation in immobilized rats: Role of 70 kDa heat shock protein

Effects of essential amino acid (EAA) and glutamine supplementation on skeletal muscle wasting in acute, subacute, and postacute conditions

Under optimal physiological conditions, muscle mass maintenance is ensured by dietary protein, which balances the amino acid loss during the post-absorption period and preserves the body's protein homeostasis. Conversely, in critical clinical conditions (acute, subacute or postacute), particularly those related to hypomobility or immobility, combined with malnutrition, and local/systemic inflammation, the loss of muscle mass and strength can be quantitatively significant. A decline of more than 1% in muscle mass and of more than 3% in muscle strength has been registered in subjects with aged 20-37 yr after just five days of bed rest, similarly to those observed during one year of age-related decline in individuals over the age of 50. Loss of muscle mass and strength can have a dramatic effect on subjects' functional capacities, on their systemic metabolic control and on the amino acid reserve function, all of which are fundamental for the maintenance of other organs' and tissues' cell processes. References available indicate that the average 1%-2% reduction per day of muscle mass in patients in the intensive care unit (ICU) could represent an independent predictor of hospital mortality and physical disability in the five years following hospitalization. After just a few days or weeks of administration, supplementation with EAAs and glutamine has shown significant effects in maintaining muscle size and strength, which are typically negatively affected by some acute/subacute or postacute critical conditions (muscle recovery after surgery, oncology patients, ICU treatments), especially in the elderly or in those with pre-existing degenerative diseases. In this review, we focused on the theoretical bases and the most relevant clinical studies of EAA and glutamine supplementation as a single compound, with the aim of clarifying whether their combined use in a blend (EAAs-glutamine) could be potentially synergistic to prevent disease-related muscle wasting and its impact on the duration and quality of patients' clinical course.

Tolerability of glutamine supplementation in older adults: a double-blind placebo-controlled randomized clinical trial

In this double-blind placebo-controlled randomized investigation, we assessed the tolerability of glutamine in older adults recruited from three daycare centers. The relevance of studying glutamine supplementation in elderly patients lies in its potential to provide a well-tolerated intervention. Glutamine, a crucial amino acid, plays a vital role in various physiological processes, including immune function and protein synthesis. Understanding its impact on older adults is essential, given the potential implications for their health and well-being. Participants received a daily dose of 12.4 g of oral effervescent glutamine (EGln group) or maltodextrin (placebo group) for 60 days. Fifteen patients from each group completed the study. The mean ages were 77.0±9.1 and 79.0±6.9 years for the EGln and placebo groups, respectively. We evaluated body mass index, aminogram, hemogram, plasma levels of glucose, prealbumin, albumin, urea, creatinine, uric acid, C-reactive protein, vitamin D, calcium, sodium, potassium, and the plasma activities of aspartate aminotransferase and alanine aminotransferase. Notably, we quantified a broad array of inflammatory markers and growth factors providing a holistic understanding of the potential effects of glutamine supplementation. The results demonstrated that oral glutamine did not induce significant changes in any evaluated parameters, and no adverse effects were reported. This finding suggested that the dosage of glutamine used in this study was well-tolerated and safe. This information contributes to the broader understanding of glutamine supplementation, emphasizing its safety and supporting its potential as a viable intervention for maintaining health in aging individuals.

Oral glutamine supplementation relieves muscle loss in immobilized rats, altering p38MAPK and FOXO3a signaling pathways

BACKGROUND

Skeletal muscle synthesizes, stores, and releases body L-glutamine (GLN). Muscle atrophy due to disabling diseases triggers the activation of proteolytic and pro-apoptotic cell signaling, thus impairing the body's capacity to manage GLN content. This situation has a poor therapeutic prognosis.

OBJECTIVE

Evaluating if oral GLN supplementation can attenuate muscle wasting mediated by elevated plasma cortisol and activation of caspase-3, p38MAPK, and FOXO3a signaling pathways in soleus and gastrocnemius muscles of rats submitted to 14-day bilateral hindlimbs immobilization.

METHODS

Animals were randomly distributed into six groups: non-immobilized rats (Control), control orally supplemented with GLN (1 g kg-1) in solution with L-alanine (ALA: 0.61 g kg-1; GLN+ALA), control orally supplemented with dipeptide L-alanyl-L-glutamine (DIP; 1.49 g kg-1), hindlimbs immobilized rats (IMOB), IMOB orally GLN+ALA supplemented (GLN+ALA-IMOB), and IMOB orally DIP supplemented (DIP-IMOB). Plasma and muscle GLN concentration, plasma cortisol level, muscle caspase-3 activity, muscle p38MAPK and FOXO3a protein content (total and phosphorylated forms), and muscle cross-sectional area (CSA) were measured.

RESULTS

Compared to controls, IMOB rats presented: a) increased plasma cortisol levels; b) decreased plasma and muscle GLN concentration; c) increased muscle caspase-3 activity; d) increased total and phosphorylated p38MAPK protein content; e) increased FOXO3a and decreased phosphorylated FOXO3a protein content; f) reduced muscle weight and CSA befitting to atrophy. Oral supplementation with GLN+ALA and DIP was able to significantly attenuate these effects.

CONCLUSIONS

These findings attest that oral GLN supplementation in GLN+ALA solution or DIP forms attenuates rats' skeletal muscle mass wasting caused by disuse-mediated muscle atrophy.

Glutamine alleviates Lipopolysaccharide-induced corneal epithelial inflammation and oxidative stress in dogs

Pseudomonas aeruginosa is a common pathogenic bacteria in canine ophthalmology. Lipopolysaccharide (LPS), a component in the cell wall of gram-negative bacteria, is released following bacterial lysis and causes pathology and inflammation of the cornea. Antibiotics are used to treat bacterial keratitis, and the reuse of antibiotics can easily cause bacterial resistance. Research has shown that glutamine (GLN) has anti-inflammatory and antioxidant biological functions. Herein, we explored the effects and underlying mechanisms of GLN and established an LPS-induced cornea inflammation model. Treatment groups comprised: control check (CK), LPS, LPS + GLN, and Sham groups. Topical GLN treatment alleviated corneal opacity, reduced corneal injury, and accelerated corneal wound healing. Furthermore, GLN treatment altered the uniform distribution of corneal epithelial cells and transformed the healing approach of these cells in the corneal wound from crawling to filling. The expression of Toll-like receptor 4 (TLR4), IL-6, TNF-α, and p-p65 and the activity of myeloperoxidase and superoxide dismutase decreased while the content of malondialdehyde increased in the LPS + GLN group compared with those in the LPS group. Thus, our study suggests that LPS-induced inflammation and oxidative stress may be suppressed via the TLR4/NF-κB signaling pathway by GLN and that GLN could be used as an adjunct therapy to reduce antibiotic use.

Glutamine inhibits inflammation, oxidative stress, and apoptosis and ameliorates hyperoxic lung injury

Glutamine (Gln) is the most widely acting and abundant amino acid in the body and has anti-inflammatory properties, regulates body metabolism, and improves immune function. However, the mechanism of Gln's effect on hyperoxic lung injury in neonatal rats is unclear. Therefore, this work focused on examining Gln's function in lung injury of newborn rats mediated by hyperoxia and the underlying mechanism. We examined body mass and ratio of wet-to-dry lung tissue weights of neonatal rats. Hematoxylin and eosin (HE) staining was performed to examine histopathological alterations of lung tissues. In addition, enzyme-linked immunoassay (ELISA) was conducted to measure pro-inflammatory cytokine levels within bronchoalveolar lavage fluid (BALF). Apoptosis of lung tissues was observed using TUNEL assay. Western blotting was performed for detecting endoplasmic reticulum stress (ERS)-associated protein levels. The results showed that Gln promoted body weight gain, significantly reduced pathological damage and oxidative stress in lung tissue, and improved lung function in neonatal rats. Gln reduced pro-inflammatory cytokine release as well as inflammatory cell production in BALF and inhibited apoptosis in lung tissue cells. Furthermore, we found that Gln could downregulate ERS-associated protein levels (GRP78, Caspase-12, CHOP) and inhibit c-Jun N-terminal kinase (JNK) and inositol-requiring enzyme 1 alpha (IRE1α) phosphorylation. These results in an animal model of bronchopulmonary dysplasia (BPD) suggest that Gln may have a therapeutic effect on BPD by reducing lung inflammation, oxidative stress, and apoptosis and improving lung function; its mechanism of action may be related to the inhibition of the IRE1α/JNK pathway.

Effect of Glutamine on the Growth Performance, Oxidative Stress, and Nrf2/p38 MAPK Expression in the Livers of Heat-Stressed Broilers

The purpose of this work was to study the effects of glutamine (Gln) on the growth performance, oxidative stress, Nrf2, and p38 MAPK pathway in the livers of heat-stressed broilers. In total, 300 broilers were divided into five groups, including a normal temperature (NT, without dietary Gln) group and four cyclic high temperature groups (HT, GHT1, GHT2, and GHT3) fed with 0%, 0.5%, 1.0%, and 1.5% Gln, respectively. High temperature conditions increased (p < 0.05) liver malonaldehyde (MDA) concentration, but decreased (p < 0.05), body weight gain (BWG), feed intake (FI), liver superoxide dismutase (SOD), total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), and glutathione (GSH) levels in broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were lower (p < 0.05) in the NT group than that in the HT group. However, dietary 1.5% Gln decreased (p < 0.05) liver MDA concentration, but increased (p < 0.05) BWG, FI, liver SOD, T-AOC, GSH-Px, GST, and GSH levels in heat-stressed broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were higher (p < 0.05) in the GHT3 group than that in the HT group. In summary, Gln improved oxidative damage through the activation of Nrf2 and p38 MAPK expression in the livers of heat-stressed broilers.

U0126 and BAY11-7082 Inhibit the Progression of Endometriosis in a Rat Model by Suppressing the MEK/ERK/NF-κB Pathway

Endometriosis is an aggressive disease. It is the main cause of chronic pelvic pain, dysmenorrhea, and infertility, affecting the well-being of women. This study aimed to explore the role of U0126 and BAY11-7082 in endometriosis (EMs) treatment in rats by targeting the MEK/ERK/NF-κB pathway. The EMs model was generated and the rats were divided into model, dimethyl sulfoxide, U0126, BAY11-708, and control groups (Sham operation group). After 4 weeks of treatment, the rats were sacrificed. Compared with model group, U0126 and BAY11-7082 treatment significantly inhibited ectopic lesion growth, glandular hyperplasia, and interstitial inflammation. Compared to control group, PCNA and MMP9 levels were significantly increased in the eutopic and ectopic endometrial tissues of model group; the levels of MEK/ERK/NF-κB pathway proteins also increased significantly. Compared with model group, MEK, ERK, and NF-κB levels decreased significantly after U0126 treatment and NF-κB protein expression decreased significantly after BAY11-7082 treatment, with no significant difference in MEK and ERK levels. The proliferation and invasion activities of eutopic and ectopic endometrial cells also significantly decreased after U0126 and BAY11-7082 treatment. In summary, our results showed that U0126 and BAY11-7082 inhibited ectopic lesion growth, glandular hyperplasia, and interstitial inflammatory response in EMs rats by inhibiting the MEK/ERK/NF-κB signaling pathway.

Acute heat stress-indued apoptosis in mouse skeletal muscle is not associated with alteration of glutamine homeostasis

We previously demonstrated that exposing mice to heat causes functional and ultrastructural mitochondrial alterations and apoptosis in skeletal muscle. Emerging evidence indicates that glutamine (Gln) deprivation may increase cell susceptibility to apoptosis whereas Gln supplementation may protect cells against heat stress. In this study, we investigated the effect of short-term Gln treatment on heat-induced changes in mouse skeletal muscle. Male mice received vehicle, low-dose Gln (100 mg/kg/d) or high-dose Gln (300 mg/kg/d) through daily gavage for 10 days before a heat exposure test. During heat exposure, mice displayed a hyperthermic response and no significant differences in peak core body temperature were noted across the three groups. Neither heat exposure nor pretreatment with low-dose or high-dose Gln significantly affected Gln concentrations in plasma and gastrocnemius muscles. Heat-exposed mice had significantly higher caspase 3/7 levels in gastrocnemius muscle compared to unexposed controls. Heat exposure significantly increased ROS production and mitochondrial fragmentation and decreased mitochondrial membrane potential in flexor digitorum brevis muscle. These changes were not affected by low- or high-dose Gln pretreatment. Together, acute heat stress did not disrupt Gln homeostasis in mouse skeletal muscle and Gln supplementation did not protect mouse skeletal muscle against heat-induced injury. The results of this study do not support a role of Gln in heat-induced skeletal muscle apoptosis.

Shear Stress and Metabolic Disorders-Two Sides of the Same Plaque

Significance: Shear stress and metabolic disorder are the two sides of the same atherosclerotic coin. Atherosclerotic lesions are prone to develop at branches and curvatures of arteries, which are exposed to oscillatory and low shear stress exerted by blood flow. Meanwhile, metabolic disorders are pivotal contributors to the formation and advancement of atherosclerotic plaques. Recent Advances: Accumulated evidence has provided insight into the impact and mechanisms of biomechanical forces and metabolic disorder on atherogenesis, in association with mechanotransduction, epigenetic regulation, and so on. Moreover, recent studies have shed light on the cross talk between the two drivers of atherosclerosis. Critical Issues: There are extensive cross talk and interactions between shear stress and metabolic disorder during the pathogenesis of atherosclerosis. The communications may amplify the proatherogenic effects through increasing oxidative stress and inflammation. Nonetheless, the precise mechanisms underlying such interactions remain to be fully elucidated as the cross talk network is considerably complex. Future Directions: A better understanding of the cross talk network may confer benefits for a more comprehensive clinical management of atherosclerosis. Critical mediators of the cross talk may serve as promising therapeutic targets for atherosclerotic vascular diseases, as they can inhibit effects from both sides of the plaque. Hence, further in-depth investigations with advanced omics approaches are required to develop novel and effective therapeutic strategies against atherosclerosis. Antioxid. Redox Signal. 37, 820-841.

Alanyl-Glutamine Protects Mice against Methionine- and Choline-Deficient-Diet-Induced Steatohepatitis and Fibrosis by Modulating Oxidative Stress and Inflammation

Nonalcoholic steatohepatitis (NASH) is a common chronic liver disease with increasing prevalence rates over years and is associated with hepatic lipid accumulation, liver injury, oxidative stress, hepatic inflammation, and liver fibrosis and lack of approved pharmacological therapy. Alanyl-glutamine (Ala-Gln) is a recognized gut-trophic nutrient that has multiple pharmacological effects in the prevention of inflammation- and oxidative-stress-associated diseases. Nevertheless, whether Ala-Gln has a protective effect on NASH still lacks evidence. The aim of this study is to explore the influence of Ala-Gln on NASH and its underlying mechanisms. Here, C57BL/6 mice were fed a methionine- and choline-deficient (MCD) diet to establish the model of NASH, and Ala-Gln at doses of 500 and 1500 mg/kg were intraperitoneally administered to mice along with a MCD diet. The results showed that Ala-Gln treatment significantly attenuated MCD-induced hepatic pathological changes, lowered NAFLD activity score, and reduced plasma alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase (LDH) levels. Ala-Gln dramatically alleviated lipid accumulation in liver through modulating the expression levels of fatty acid translocase (FAT/CD36) and farnesoid X receptor (FXR). In addition, Ala-Gln exerted an anti-oxidant effect by elevating the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX). Moreover, Ala-Gln exhibited an anti-inflammatory effect via decreasing the accumulation of activated macrophages and suppressing the production of proinflammatory mediators. Notably, Ala-Gln suppressed the development of liver fibrosis in MCD-diet-fed mice, which may be due to the inhibition of hepatic stellate cells activation. In conclusion, these findings revealed that Ala-Gln prevents the progression of NASH through the modulation of oxidative stress and inflammation and provided the proof that Ala-Gln might be an effective pharmacological agent to treat NASH.

Overexpression of Heat Shock Protein 70 Ameliorates Meat Quality of Broilers Subjected to Pre-Slaughter Transport at High Ambient Temperatures by Improving Energy Status of Pectoralis Major Muscle and Antioxidant Capacity

The induction of heat shock protein 70 (HSP70) potentially mediates meat-quality development under stress conditions. To investigate the effects and mechanism of HSP70 on the meat quality of the pectoralis major (PM) muscles of broilers exposed to pre-slaughter transport, a total of 168 broilers were intraperitoneally injected with L-glutamine (Gln) or saline. Twenty-four hours later, broilers were subjected to transport or held under normal living conditions. The results indicated that acute Gln supplementation significantly increased HSP70 expression in the PM of transported broilers (p < 0.05). The overexpression of HSP70 significantly alleviated the decreases in muscle pH and water-holding capacity and improved the shrinking of muscle fibers induced by transport (p < 0.05). HSP70 induction increased ATP content, decreased the activities of glycolytic enzymes, and lowered the phosphorylation level of AMP-activated protein kinase in transported broilers (p < 0.05). In addition, the overexpression of HSP70 greatly increased total superoxide dismutase and the total antioxidant capability and decreased the levels of reactive oxygen species, malonaldehyde, and carbonyls in the PM of transported broilers (p < 0.05). Overall, this work indicated that HSP70 could effectively improve the meat quality of transported broilers by improving the energy status, inhibiting glycolytic influx, and restoring redox homeostasis.

Alanyl-Glutamine Protects against Lipopolysaccharide-Induced Liver Injury in Mice via Alleviating Oxidative Stress, Inhibiting Inflammation, and Regulating Autophagy

Acute liver injury is a worldwide problem with a high rate of morbidity and mortality, and effective pharmacological therapies are still urgently needed. Alanyl-glutamine (Ala-Gln), a dipeptide formed from L-alanine and L-glutamine, is known as a protective compound that is involved in various tissue injuries, but there are limited reports regarding the effects of Ala-Gln in acute liver injury. This present study aimed to investigate the protective effects of Ala-Gln in lipopolysaccharide (LPS)-induced acute liver injury in mice, with a focus on inflammatory responses and oxidative stress. The acute liver injury induced using LPS (50 μg/kg) and D-galactosamine (D-Gal) (400 mg/kg) stimulation in mice was significantly attenuated after Ala-Gln treatment (500 and 1500 mg/kg), as evidenced by reduced plasma alanine transaminase (ALT) (p < 0.01, p < 0.001), aspartate transaminase (AST) (p < 0.05, p < 0.001), and lactate dehydrogenase (LDH) (p < 0.01, p < 0.001) levels, and accompanied by improved histopathological changes. In addition, LPS/D-Gal-induced hepatic apoptosis was also alleviated by Ala-Gln administration, as shown by a greatly decreased ratio of TUNEL-positive hepatocytes, from approximately 10% to 2%, and markedly reduced protein levels of cleaved caspase-3 (p < 0.05, p < 0.001) in liver. Moreover, we found that LPS/D-Gal-triggered oxidative stress was suppressed after Ala-Gln treatment, the effect of which might be dependent on the elevation of SOD and GPX activities, and on GSH levels in liver. Interestingly, we observed that Ala-Gln clearly inhibited LPS/D-Gal exposure-induced macrophage accumulation and the production of proinflammatory factors in the liver. Furthermore, Ala-Gln greatly regulated autophagy in the liver in LPS/D-Gal-treated mice. Using RAW264.7 cells, we confirmed the anti-inflammatory role of Ala-Gln-targeting macrophages.

Linoleic Acid Attenuates Denervation-Induced Skeletal Muscle Atrophy in Mice through Regulation of Reactive Oxygen Species-Dependent Signaling

Muscle atrophy is a major muscle disease, the symptoms of which include decreased muscle volume leading to insufficient muscular support during exercise. One cause of muscle atrophy is the induction of oxidative stress by reactive oxygen species (ROS). This study aimed to identify the antioxidant mechanism of linoleic acid (LA) in muscle atrophy caused by oxidative stress. H₂O₂ has been used to induce oxidative stress in myoblasts in vitro. C2C12 myoblasts treated with H₂O₂ exhibited decreased viability and increased ROS synthesis. However, with LA treatment, the cells tended to recover from oxidative effects similar to those of the control groups. At the molecular level, the expression of superoxide dismutase 1 (SOD1), Bax, heat shock protein 70 (HSP70), and phosphorylated forkhead box protein O1 was increased by oxidative stress, causing apoptosis. LA treatment suppressed these changes. In addition, the expression of MuRF1 and Atrogin-1/MAFbx mRNA increased under oxidative stress but not in the LA-treated group. Sciatic denervation of C57BL/6 mice manifested as atrophy of the skeletal muscle in micro-computed tomography (micro-CT). The protein expression levels of SOD1, HSP70, and MuRF1 did not differ between the atrophied muscle tissues and C2C12 myoblasts under oxidative stress. With LA treatment, muscle atrophy recovered and protein expression was restored to levels similar to those in the control. Therefore, this study suggests that LA may be a candidate substance for preventing muscle atrophy.

Glutamine supplementation improves contractile function of regenerating soleus muscles from rats

This study evaluated the effects of glutamine supplementation immediately after freezing injury on morphological and contractile function of regenerating soleus muscles from rats. Young male Wistar rats were subjected to cryolesion of soleus muscles, and immediately after received a daily supplementation of glutamine (1 g/kg/day). The muscles were evaluated on post-injury days 3 and 10. Glutamine-supplemented injured muscles had a lower number of CD11b positive immune cells and higher mRNA levels of IL-4 compared to those from the cryolesioned muscles analyzed on post-injury day 3. The mRNA and protein expression levels of the myogenic transcription factor MyoD were also higher in glutamine-supplemented injured muscles than in injured muscles examined on post-cryolesion day 3. In addition, glutamine-supplemented injured muscles had a higher size of their regenerating myofibers, attenuated decline in maximum tetanic strength and improved fatigue resistance compared to those from injured muscles evaluated on post-cryolesion day 10. No effect was observed in uninjured muscles supplemented with glutamine. Our results suggest that glutamine supplementation improves the resolution of inflammation, as well as the size and functional recovery of regenerating myofibers from soleus muscles by accelerating the up-regulation of IL-4 and MyoD expression. Future non-pharmacological rehabilitation studies are warranted to investigate the effect of glutamine supplementation on the outcome of injured skeletal muscles.

HSP70 as a biomarker of the thin threshold between benefit and injury due to physical exercise when exposed to air pollution

Physical exercise has acute and chronic effects on inflammatory balance, metabolic regulation, and redox status. Exercise-induced adaptations are mediated by enhanced 70-kDa heat shock protein (HSP70) levels and an improved heat shock response (HSR). Therefore, exercise could be useful against disease conditions [obesity, diabetes mellitus (DM), and exposure to atmospheric pollutants] marked by an impaired HSR. However, exercise performed by obese or diabetic subjects under pollution conditions might also be dangerous at certain intensities. Intensity correlates with an increase in HSP70 levels during physical exercise until a critical point at which the effort becomes harmful and impairs the HSR. Establishing a unique biomarker able to indicate the exercise intensity on metabolism and cellular fatigue is essential to ensure adequate and safe exercise recommendations for individuals with obesity or DM who require exercise to improve their metabolic status and live in polluted regions. In this review, we examined the available evidence supporting our hypothesis that HSP70 could serve as a biomarker for determining the optimal exercise intensity for subjects with obesity or diabetes when exposed to air pollution and establishing the fine threshold between anti-inflammatory and pro-inflammatory exercise effects.

Nutrients with anabolic/anticatabolic, antioxidant, and anti-inflammatory properties: Targeting the biological mechanisms of aging to support musculoskeletal health

Old age is associated with declines in bone density and muscle mass and function, which predisposes to mobility disability, falls, and fractures. Poor nutritional status, a risk factor for several age-related pathologies, becomes prevalent in old age and contributes to the structural and functional changes of the musculoskeletal system that increases the risk of osteoporosis, sarcopenia, osteosarcopenia, and physical frailty. The biological mechanisms underpinning these pathologies often overlap and include loss of proteostasis, impaired redox functioning, and chronic low-grade inflammation. Thus, provision of nutrients with anabolic/anticatabolic, antioxidant, and anti-inflammatory properties may be an effective strategy to offset these age-related pathologies. We searched PUBMED for pre-clinical and clinical work examining the effects of nutrients with a combined effect on muscle and bone. This review summarizes recent evidence on the mechanisms of action and potential clinical use of nutrients that concomitantly improve muscle and bone health in older persons.

Effects of aerobic and resistance exercise training associated with carnosine precursor supplementation on maximal strength and V̇O2max in rats with heart failure

BACKGROUND

Combined exercise training (CET) has been associated with positive responses in the clinical status of patients with heart failure (HF). Other nonpharmacological tools, such as amino acid supplementation, may further enhance its adaptation. The aim was to test whether CET associated with supplementing carnosine precursors could present better responses in the functional capacity and biochemical variables of rats with HF.

METHODS

Twenty-one male Wistar rats were subjected to myocardial infarction and allocated to three groups: sedentary (SED, n = 7), CET supplemented with placebo (CETP, n = 7), and CET with HF supplemented with β-alanine and L-histidine (CETS, n = 7). The trained animals were submitted to a strength protocol three times per week. Aerobic training was conducted twice per week. The supplemented group received β-alanine and L-histidine orally (250 mg/kg per day).

RESULTS

Maximum oxygen uptake, running distance, time to exhaustion and maximum strength were higher in the CET-P group than that in the SED group and even higher in the CET-S group than that in the CET-P group (P < 0.01). CET-S showed lower oxidative stress and inflammation markers and higher heat shock protein 72 kDa content and mRNA expression for calcium transporters in the skeletal muscle compared to SED.

CONCLUSION

CET together with β-alanine and L-histidine supplementation in rats with HF can elicit adaptations in both maximum oxygen uptake, running distance, time to exhaustion, maximum strength, oxidative stress, inflammation and mRNA expression. Carnosine may influence beneficial adjustments in the cell stress response in the skeletal muscle and upregulate the mRNA expression of calcium transporters.

L-Glutamine Supplementation Enhances Strength and Power of Knee Muscles and Improves Glycemia Control and Plasma Redox Balance in Exercising Elderly Women

We investigated the effects of oral L-glutamine (Gln) supplementation, associated or not with physical exercises, in control of glycemia, oxidative stress, and strength/power of knee muscles in elderly women. Physically active (n = 21) and sedentary (n = 23) elderly women aged 60 to 80 years were enrolled in the study. Plasma levels of D-fructosamine, insulin, reduced (GSH) and oxidized (GSSG) glutathione, iron, uric acid, and thiobarbituric acid-reactive substances (TBARs) (lipoperoxidation product), as well as knee extensor/flexor muscle torque peak and average power (isokinetic test), were assessed pre- and post-supplementation with Gln or placebo (30 days). Higher plasma D-fructosamine, insulin, and iron levels, and lower strength/power of knee muscles were found pre-supplementation in the NPE group than in the PE group. Post-supplementation, Gln subgroups showed higher levels of GSH, GSSG, and torque peak, besides lower D-fructosamine than pre-supplementation values. Higher muscle average power and plasma uric acid levels were reported in the PE + Gln group, whereas lower insulin levels were found in the NPE + Gln than pre-supplementation values. TBARs levels were diminished post-supplementation in all groups. Gln supplementation, mainly when associated with physical exercises, improves strength and power of knee muscles and glycemia control, besides boosting plasma antioxidant capacity of elderly women.

Measurement of muscle quantity/quality has additional predictive value for postoperative complications and long-term survival after gastrectomy for gastric cancer in patients with probable sarcopenia as defined by the new EWGSOP2 consensus: Analysis from a large-scale prospective study

OBJECTIVES

We investigated whether measurement of muscle quantity/quality has additional predictive value for postoperative complications and long-term survival after gastrectomy for gastric cancer in patients with probable sarcopenia, as defined by the new European Working Group on Sarcopenia in Older People 2 consensus.

METHODS

We conducted a prospective study of patients who underwent a radical gastrectomy for gastric cancer between August 2014 and June 2019. Muscle strength was measured using a handgrip dynamometer. Computed tomography images at the third lumbar vertebra level were used to assess muscle quantity and quality by the measuring cross-sectional muscle area and mean muscle attenuation, respectively. Probable sarcopenia was defined by low muscle strength. Sarcopenia was diagnosed by additional low muscle quantity or quality. Clinical outcomes were obtained by prospective data collection and follow up.

RESULTS

Probable sarcopenia was identified in 419 patients, including 285 patients with sarcopenia. Patients with sarcopenia had a higher incidence of postoperative complications, higher costs, longer length of postoperative hospital stay, and worse overall survival (OS) and disease-free survival (DFS) compared with patients with low muscle strength only. The multivariate logistic analysis showed that sarcopenia and hypoproteinemia were independent risk factors for postoperative complications in patients with probable sarcopenia. Moreover, multivariate Cox analyses showed that sarcopenia remained an independent risk factor for OS and DFS in patients with probable sarcopenia.

CONCLUSIONS

The measurement of muscle quantity/quality has additional predictive value for postoperative complications, OS, and DFS after gastrectomy for gastric cancer in patients with probable sarcopenia.

Synthesis of α-Ketoglutaramic acid

α-Ketoglutaramic acid (KGM, α-ketoglutaramate), also known as 2-oxoglutaramic acid (OGM, 2-oxoglutaramate), is a substrate of ω-amidase, also known as Nitrilase 2 (NIT2), and is essential for studying the canonical role of ω-amidase, as well as its role in multiple diseases. Until now, KGM used for biological studies has been prepared most often by the enzymatic oxidation of l-glutamine using snake venom l-amino acid oxidase, which provides KGM as an aqueous solution, containing by-products including 5-oxoproline and α-ketoglutarate. The enzymatic method for KGM preparation, therefore, cannot provide pure product or an accurate percent yield evaluation. Here, we report a synthetic method for the preparation of this important substrate, KGM, in 3 steps, from l-2-hydroxyglutaramic acid, in pure form, in 53% overall yield.

Distinct expression and localization patterns of HSP70 in developmental reproductive organs of rams

Heat shock protein 70 (HSP70) has been widely reported to play a vital role in maintaining intracellular homeostasis, mainly through cellular protection and immune regulation. The expression and function of HSP70 can vary depending upon species and age. To explore the expression signatures and regulatory functions of HSP70 in the reproductive organs of male sheep, we evaluated the expression and distribution patterns of HSP70 in the testes and epididymides (caput, corpus, and cauda) of Tibetan sheep at three developmental stages (i.e., 3 months, 1 year and 3 years after birth) by qRT-PCR, Western blot and immunofluorescence. HSP70 was found to be expressed in testes, caput, corpus, and cauda epididymides throughout the developmental stages but is mainly expressed postpuberty (1 year and 3 years old). Immunofluorescence results revealed that in the testes, a positive reaction for HSP70 protein was mainly seen in round spermatids and luminal sperms from the groups aged 1 year and 3 years. In caput epididymides, the positive signals for HSP70 protein was notably observed in sperm and principal cells of the epididymal epithelium from the groups aged 1 year and 3 years, and positive signals in the epididymal interstitium were found in all three age groups. In corpus and cauda epididymides, HSP70 protein was present in the epididymal epithelium and interstitium, and the positive signals gradually increased with age. In conclusion, these findings suggest that Tibetan sheep HSP70 may play a crucial role in further development and maturation of postmeiotic germ cells and participate in regulation of intraepididymal homeostasis maintenance in Tibetan sheep.

Muscle Disuse Atrophy Caused by Discord of Intracellular Signaling

Significance: Regular contractile activity plays a critical role in maintaining skeletal muscle morphological integrity and physiological function. If the muscle is forced to stop contraction, such as during limb immobilization (IM), the IGF/Akt/mTOR signaling pathway that normally stimulates protein synthesis and inhibits proteolysis will be suppressed, whereas the FoxO-controlled catabolic pathways such as ubiquitin-proteolysis and autophagy/mitophagy will be activated and dominate, resulting in muscle fiber atrophy. Recent Advances: Mitochondria occupy a central position in the regulation of both protein synthesis and degradation through several redox-sensitive pathways, including peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), mitochondrial fusion and fission proteins, mitophagy, and sirtuins. Prolonged IM downregulates PGC-1α due to AMPK (5'-AMP-activated protein kinase) and FoxO activation, thus decreasing mitochondrial biogenesis and causing oxidative damage. Decrease of mitochondrial inner membrane potential and increase of mitochondrial fission can trigger cascades of mitophagy leading to loss of mitochondrial homeostasis (mitostasis), inflammation, and apoptosis. The phenotypic outcomes of these disorders are compromised muscle function and fiber atrophy. Critical Issues: Given the molecular mechanism of the pathogenesis, it is imperative that the integrity of intracellular signaling be restored to prevent the deterioration. So far, overexpression of PGC-1α via transgene and in vivo DNA transfection has been found to be effective in ameliorating mitostasis and reduces IM-induced muscle atrophy. Nutritional supplementation of select amino acids and phytochemicals also provides mechanistic and practical insights into the prevention of muscle disuse atrophy. Future Directions: In light of the importance of mitochondria in regulating the various critical signaling pathways, future work should focus on exploring new epigenetic strategies to restore mitostasis and redox balance.