Metabolic Stress-Induced Activation of AMPK and Inhibition of Constitutive Phosphoproteins Controlling Smooth Muscle Contraction: Evidence for Smooth Muscle Fatigue?

Molecular and biochemical investigations of the anti-fatigue effects of tea polyphenols and fruit extracts of Lycium ruthenicum Murr. on mice with exercise-induced fatigue

Background: The molecular mechanisms regulating the therapeutic effects of plant-based ingredients on the exercise-induced fatigue (EIF) remain unclear. The therapeutic effects of both tea polyphenols (TP) and fruit extracts of Lycium ruthenicum (LR) on mouse model of EIF were investigated. Methods: The variations in the fatigue-related biochemical factors, i.e., lactate dehydrogenase (LDH), superoxide dismutase (SOD), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-2 (IL-2), and interleukin-6 (IL-6), in mouse models of EIF treated with TP and LR were determined. The microRNAs involved in the therapeutic effects of TP and LR on the treatment of mice with EIF were identified using the next-generation sequencing technology. Results: Our results revealed that both TP and LR showed evident anti-inflammatory effect and reduced oxidative stress. In comparison with the control groups, the contents of LDH, TNF-α, IL-6, IL-1β, and IL-2 were significantly decreased and the contents of SOD were significantly increased in the experimental groups treated with either TP or LR. A total of 23 microRNAs (21 upregulated and 2 downregulated) identified for the first time by the high-throughput RNA sequencing were involved in the molecular response to EIF in mice treated with TP and LR. The regulatory functions of these microRNAs in the pathogenesis of EIF in mice were further explored based on Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses with a total of over 20,000-30,000 target genes annotated and 44 metabolic pathways enriched in the experimental groups based on GO and KEGG databases, respectively. Conclusion: Our study revealed the therapeutic effects of TP and LR and identified the microRNAs involved in the molecular mechanisms regulating the EIF in mice, providing strong experimental evidence to support further agricultural development of LR as well as the investigations and applications of TP and LR in the treatment of EIF in humans, including the professional athletes.

Comprehensive evaluation of military training-induced fatigue among soldiers in China: A Delphi consensus study

Objective

Military training-induced fatigue (MIF) often results into non-combat attrition. However, standard evaluation of MIF is unavailable. This study aimed to provide credible suggestions about MIF-evaluation.

Methods

A 3-round Delphi study was performed. The authority of the experts was assessed by the authority coefficient (Aa). In round 1, categories of indicators were collected via anonymous survey of experts, then potential indicators were selected via literature search. In round 2, experts should evaluate the clinical implication, practical value, and importance of each potential indicators, or recommend new indicators based on feedback of round 1. Indicators with recommendation proportions ≥ 70% and new recommended indicators would be included in round 3 to be rated on a 5-point Likert scale. "Consensus in" was achieved when coefficient of concordance (Kendall's W) of a round was between 0.2 and 0.5 and the coefficient of variation (CV) of each aspect for an indicator was < 0.5. If round 3 could not achieve "consensus in," more rounds would be conducted iteratively based on round 3. Indicators included in the recommendation set were ultimately classified into grade I (highly recommended) or grade II (recommended) according to the mean score and CV of the aspects.

Results

Twenty-three experts participated with credible authority coefficient (mean Aa = 0.733). "Consensus in" was achieved in round 3 (Kendall's W = 0.435, p < 0.001; all CV < 0.5). Round 1 recommended 10 categories with 73 indicators identified from 2,971 articles. After 3-round consultation, consensus was reached on 28 indicators focusing on the cardiovascular system (n = 4), oxygen transport system (n = 5), energy metabolism/metabolite level (n = 6), muscle/tissue damage level (n = 3), neurological function (n = 2), neuropsychological/psychological function (n = 3), endocrine function (n = 3), and exercise capacity (n = 2). Among these, 11 indicators were recommended as grade I: basic heart rate, heart-rate recovery time, heart rate variability, hemoglobin, blood lactic acid, urine protein, creatine kinase, reaction time, Borg Rating of Perceived Exertion Scale, testosterone/cortisol, and vertical jump height.

Conclusion

This study developed a reliable foundation for the comprehensive evaluation of MIF among soldiers.

Orosomucoid: a promising biomarker for the assessment of exercise-induced fatigue triggered by basic combat training

Background

Orosomucoid (ORM) is a positive acute phase protein verified to be upregulated in various forms of exercise-induced fatigued (EIF) rodents. However, its association with EIF among human beings remained unknown. This study aimed to explore the association between serum ORM and EIF triggered by military basic combat training (BCT).

Methods

The degree of EIF were measured by Borg’s Rating of Perceived Exertion Scale (Borg-RPE-Scale®) as RPE score after BCT. Fifty-three male recruits were classified into three groups according to the RPE score: (1) group 1 (slight fatigue group): RPE score after BCT < 13; (2) group 2 (moderate fatigue group): RPE score after BCT = 13 or 14; (3) group 3 (severe fatigue group): RPE score after BCT > 14. The levels of blood ORM, lactate (LAC), cortisol and C-reactive protein (CRP) were determined before and after BCT. The diagnostic value of ORM was evaluated by receiver operating characteristic (ROC) curve analysis and logistic regression.

Results

After BCT, the level of LAC, CRP, and cortisol increased among all groups, but the changes had no significant between-group difference (all p > 0.05). The level of ORM had a specific significant increase in group 3 (p = 0.039), and the changes of ORM (ΔORM) had significant difference among groups (p = 0.033). ROC curve analysis showed that the estimated area under ROC curve for ΔORM was 0.724 (p = 0.009) with the recommended optimal cut-off value as 0.2565 mg/mL. Logistic analysis showed that recruits with ΔORM ≥ 0.2565 mg/mL had higher odds for suffering from severe EIF, 5.625 times (95% CI 1.542–20.523, p = 0.009) as large as those with ΔORM < 0.2565 mg/mL.

Conclusion

ORM might be a promising biomarker of severe EIF triggered by BCT among male recruits. Its potential optimal cut-off value regarding ΔORM was recommended to be 0.2565 mg/mL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-022-00490-6.

Insight Into Rho Kinase Isoforms in Obesity and Energy Homeostasis

Obesity and associated complications increasingly jeopardize global health and contribute to the rapidly rising prevalence of type 2 diabetes mellitus and obesity-related diseases. Developing novel methods for the prevention and treatment of excess body adipose tissue expansion can make a significant contribution to public health. Rho kinase is a Rho-associated coiled-coil-containing protein kinase (Rho kinase or ROCK). The ROCK family including ROCK1 and ROCK2 has recently emerged as a potential therapeutic target for the treatment of metabolic disorders. Up-regulated ROCK activity has been involved in the pathogenesis of all aspects of metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in both white and beige adipogenesis. Studies using ROCK pan-inhibitors in animal models of obesity, diabetes, and associated complications have demonstrated beneficial outcomes. Studies via genetically modified animal models further established isoform-specific roles of ROCK in the pathogenesis of metabolic disorders including obesity. However, most reported studies have been focused on ROCK1 activity during the past decade. Due to the progress in developing ROCK2-selective inhibitors in recent years, a growing body of evidence indicates more attention should be devoted towards understanding ROCK2 isoform function in metabolism. Hence, studying individual ROCK isoforms to reveal their specific roles and principal mechanisms in white and beige adipogenesis, insulin sensitivity, energy balancing regulation, and obesity development will facilitate significant breakthroughs for systemic treatment with isoform-selective inhibitors. In this review, we give an overview of ROCK functions in the pathogenesis of obesity and insulin resistance with a particular focus on the current understanding of ROCK isoform signaling in white and beige adipogenesis, obesity and thermogenesis in adipose tissue and other major metabolic organs involved in energy homeostasis regulation.

Amelioration of perivascular adipose inflammation reverses vascular dysfunction in a model of nonobese prediabetic metabolic challenge: potential role of antidiabetic drugs

The onset of vascular impairment precedes that of diagnostic hyperglycemia in diabetic patients suggesting a vascular insult early in the course of metabolic dysfunction without a well-defined mechanism. Mounting evidence implicates adipose inflammation in the pathogenesis of insulin resistance and diabetes. It is not certain whether amelioration of adipose inflammation is sufficient to preclude vascular dysfunction in early stages of metabolic disease. Recent findings suggest that antidiabetic drugs, metformin, and pioglitazone, improve vascular function in prediabetic patients, without an indication if this protective effect is mediated by reduction of adipose inflammation. Here, we used a prediabetic rat model with delayed development of hyperglycemia to study the effect of metformin or pioglitazone on adipose inflammation and vascular function. At the end of the metabolic challenge, these rats were neither obese, hypertensive, nor hyperglycemic. However, they showed increased pressor responses to phenylephrine and augmented aortic and mesenteric contraction. Vascular tissues from prediabetic rats showed increased Rho-associated kinase activity causing enhanced calcium sensitization. An elevated level of reactive oxygen species was seen in aortic tissues together with increased Transforming growth factor β1 and Interleukin-1β expression. Although, no signs of systemic inflammation were detected, perivascular adipose inflammation was observed. Adipocyte hypertrophy, increased macrophage infiltration, and elevated Transforming growth factor β1 and Interleukin-1β mRNA levels were seen. Two-week treatment with metformin or pioglitazone or switching to normal chow ameliorated adipose inflammation and vascular dysfunction. Localized perivascular adipose inflammation is sufficient to trigger vascular dysfunction early in the course of diabetes. Interfering with this inflammatory process reverses this early abnormality.

Potential vascular mechanisms in an ex vivo functional pig bladder model

AIMS

Chronic ischemia is a recognized factor in the pathophysiology of underactive bladder (UAB). Although relative ischemia (ie, low blood flow) is known to occur during filling, little is known regarding the pathophysiology that leads to UAB. Therefore, we developed an ex vivo functional porcine model to investigate the role of transient ischemia and whether autoregulation, a mechanism that maintains tissue oxygenation in certain vital organs, also exists in the bladder.

METHODS

Using bladders from slaughtered pigs, we prepared an isolated perfused model where we studied the effects of bladder perfusion flow rate on perfusion pressure and tissue oxygenation during the filling phase. Bladders were perfused at an initial flow rate of 20 mL/min and then clamped in a sequentially decreasing stepwise manner down to no flow and back to the initial flow rate.

RESULTS

We found a linear relationship between flow rate and perfusion pressure until the flow rate decreased below 5 mL/min at which point the vascular resistance decreased; however, tissue pO₂ remained stable after an initial decline.

CONCLUSIONS

These findings suggest that there may be an intrinsic autoregulatory mechanism in the bladder that allows it to undergo cyclic episodes of relative ischemia during its normal function. Factors that overcome this mechanism such as complete or chronic ischemia may be critical in the progression to detrusor underactivity and thereby highlight the importance of intervention during the early phases of this disease process.

The AMP-Dependent Protein Kinase (AMPK) Activator A-769662 Causes Arterial Relaxation by Reducing Cytosolic Free Calcium Independently of an Increase in AMPK Phosphorylation

Although recent studies reveal that activation of the metabolic and Ca²⁺ sensor AMPK strongly inhibits smooth muscle contraction, there is a paucity of information about the potential linkage between pharmacological AMPK activation and vascular smooth muscle (VSM) contraction regulation. Our aim was to test the general hypothesis that the allosteric AMPK activator A-769662 causes VSM relaxation via inhibition of contractile protein activation, and to specifically determine which activation mechanism(s) is(are) affected. The ability of A-769662 to cause endothelium-independent relaxation of contractions induced by several contractile stimuli was examined in large and small musculocutaneous and visceral rabbit arteries. For comparison, the structurally dissimilar AMPK activators MET, SIM, and BBR were assessed. A-769662 displayed artery- and agonist-dependent differential inhibitory activities that depended on artery size and location. A-769662 did not increase AMPK-pT172 levels, but did increase phosphorylation of the downstream AMPK substrate, acetyl-CoA carboxylase (ACC). A-769662 did not inhibit basal phosphorylation levels of several contractile protein regulatory proteins, and did not alter the activation state of rhoA. A-769662 did not inhibit Ca²⁺- and GTPγS-induced contractions in β-escin-permeabilized muscle, suggesting that A-769662 must act by inhibiting Ca²⁺ signaling. In intact artery, A-769662 immediately reduced basal intracellular free calcium ([Ca²⁺]_i), inhibited a stimulus-induced increase in [Ca²⁺]_i, and inhibited a cyclopiazonic acid (CPA)-induced contraction. MET increased AMPK-pT172, and caused neither inhibition of contraction nor inhibition of [Ca²⁺]_i. Together, these data support the hypothesis that the differential inhibition of stimulus-induced arterial contractions by A-769662 was due to selective inhibition of a Ca²⁺ mobilization pathway, possibly involving CPA-dependent Ca²⁺ entry via an AMPK-independent pathway. That MET activated AMPK without causing arterial relaxation suggests that AMPK activation does not necessarily cause VSM relaxation.