Protective Effect of Unacylated Ghrelin on Compression-Induced Skeletal Muscle Injury Mediated by SIRT1-Signaling

Unacylated ghrelin attenuates acute liver injury and hyperlipidemia via its anti-inflammatory and anti-oxidative activities

Objectives

Liver injury and hyperlipidemia are major issues that have drawn more and more attention in recent years. The present study aimed to investigate the effects of unacylated ghrelin (UAG) on acute liver injury and hyperlipidemia in mice.

Materials and Methods

UAG was injected intraperitoneally once a day for three days. Three hours after the last administration, acute liver injury was induced by intraperitoneal injection of carbon tetrachloride (CCl4), and acute hyperlipidemia was induced by intraperitoneal injection of poloxamer 407, respectively. Twenty-four hours later, samples were collected for serum biochemistry analysis, histopathological examination, and Western blotting.

Results

In acute liver injury mice, UAG significantly decreased liver index, serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), reduced malondialdehyde (MDA) concentration and increased superoxide dismutase(SOD) in liver tissue. NF-kappa B (NF-κB) protein expression in the liver was down-regulated. In acute hyperlipidemia mice, UAG significantly decreased serum total cholesterol (TC), triglyceride (TG), ALT, and AST, as well as hepatic TG levels. Meanwhile, hepatic MDA decreased and SOD increased significantly. Moreover, UAG improved the pathological damage in the liver induced by CCl4 and poloxamer 407, respectively.

Conclusion

Intraperitoneal injection of UAG exhibited hepatoprotective and lipid-lowering effects on acute liver injury and hyperlipidemia, which is attributed to its anti-inflammatory and anti-oxidant activities.

Emerging Relevance of Ghrelin in Programmed Cell Death and Its Application in Diseases

Ghrelin, comprising 28 amino acids, was initially discovered as a hormone that promotes growth hormones. The original focus was on the effects of ghrelin on controlling hunger and satiation. As the research further develops, the research scope of ghrelin has expanded to a wide range of systems and diseases. Nevertheless, the specific mechanisms remain incompletely understood. In recent years, substantial studies have demonstrated that ghrelin has anti-inflammatory, antioxidant, antiapoptotic, and other effects, which could affect the signaling pathways of various kinds of programmed cell death (PCD) in treating diseases. However, the regulatory mechanisms underlying the function of ghrelin in different kinds of PCD have not been thoroughly illuminated. This review describes the relationship between ghrelin and four kinds of PCD (apoptosis, necroptosis, autophagy, and pyroptosis) and then introduces the clinical applications based on the different features of ghrelin.

Molecular and cellular mechanisms underlying the hepatoprotective role of ghrelin against NAFLD progression

The underlying mechanisms for the development and progression of nonalcoholic fatty liver disease (NAFLD) are complex and multifactorial. Within the last years, experimental and clinical evidences support the role of ghrelin in the development of NAFLD. Ghrelin is a gut hormone that plays a major role in the short-term regulation of appetite and long-term regulation of adiposity. The liver constitutes a target for ghrelin, where this gut-derived peptide triggers intracellular pathways regulating lipid metabolism, inflammation, and fibrosis. Interestingly, circulating ghrelin levels are altered in patients with metabolic diseases, such as obesity, type 2 diabetes, and metabolic syndrome, which, in turn, are well-known risk factors for the pathogenesis of NAFLD. This review summarizes the molecular and cellular mechanisms involved in the hepatoprotective action of ghrelin, including the reduction of hepatocyte lipotoxicity via autophagy and fatty acid β-oxidation, mitochondrial dysfunction, endoplasmic reticulum stress and programmed cell death, the reversibility of the proinflammatory phenotype in Kupffer cells, and the inactivation of hepatic stellate cells. Together, the metabolic and inflammatory pathways regulated by ghrelin in the liver support its potential as a therapeutic target to prevent NAFLD in patients with metabolic disorders.

The potential role of ferroptosis in the physiopathology of deep tissue injuries

Deep tissue injuries (DTIs) are a serious type of pressure injuries that mainly occur at the bony prominences and can develop rapidly, making prevention and treatment more difficult. Although consistent research efforts have been made over the years, the cellular and molecular mechanisms contributing to the development of DTIs remain unclear. More recently, ferroptosis, a novel regulatory cell death (RCD) type, has been identified that is morphological, biochemical and genetic criteria distinct from apoptosis, autophagy and other known cell death pathways. Ferroptosis is characterized by iron overload, iron-dependent lipid peroxidation and shrunken mitochondria. We also note that some of the pathological features of DTI are known to be key features of the ferroptosis pathway. Numerous studies have confirmed that ferroptosis may be involved in chronic wounds, including DTIs. Here, we elaborate on the basic pathological features of ferroptosis. We also present the evidence that ferroptosis is involved in the pathology of DTIs and highlight a future perspective on this emerging field, desiring to provide more possibilities for the prevention and treatment of DTIs.

The combination of Alisma and Atractylodes ameliorates cerebral ischaemia/reperfusion injury by negatively regulating astrocyte-derived exosomal miR-200a-3p/141-3p by targeting SIRT1

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Alisma and Atractylodes (AA), a classical traditional Chinese herbal decoction, may protect against cerebral ischaemia/reperfusion injury (CIRI). However, the underlying mechanism has not been characterized. Intriguingly, exosomal microRNAs (miRNAs) have been recognized as vital factors in the pharmacology of Chinese herbal decoctions.

AIM OF THE STUDY

The aim of the present study was to assess whether the neuroprotective effect of AA was dependent on the efficient transfer of miRNAs via exosomes in the brain.

MATERIALS AND METHODS

Bilateral common carotid artery ligation (BCAL) was used to induce transient global cerebral ischaemia/reperfusion (GCI/R) in C57BL/6 mice treated with/without AA. Neurological deficits were assessed with the modified neurological severity score (mNSS) and Morris water maze (MWM) test. Western blot (WB) analysis was used to detect the expression of sirtuin 1 (SIRT1) in the cerebral cortex. The inflammatory state was quantitatively evaluated by measuring the expression of phospho-Nuclear factor kappa B (p-NF-κB), Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) using WB analysis and glial fibrillary acidic protein (GFAP) immunohistochemical staining. The protein expression of zonula occluden-1 (ZO-1), occludin, caudin-5 and CD31 was examined by immunohistochemical staining to determine blood‒brain barrier (BBB) permeability. Exosomes were extracted from the brain interstitial space by ultracentrifugation and identified by transmission electron microscopy (TEM), WB analysis and nanoparticle tracking analysis (NTA). The origin of exosomes was clarified by measuring the specific mRNAs within exosomes via Real Time Quantitative PCR (RT‒qPCR). Differential miRNAs in exosomes were identified using microarray screening and were validated by RT‒qPCR. Exosomes were labelled with fluorescent dye (PKH26) and incubated with bEnd.3 cells, the supernatant was collected, IL-1β/TNF-α expression was measured using enzyme-linked immunosorbent assay (ELISA), total RNA was extracted, and miR-200a-3p/141-3p expression was examined by RT‒qPCR. In addition, the levels of miR-200a-3p/141-3p in oxygen glucose deprivation/reoxygenation (OGD/R)-induced bEnd.3 cells were quantified. The direct interaction between miR-200a-3p/141-3p and the SIRT1 3' untranslated region (3'UTR) was measured by determining SIRT1 expression in bEnd.3 cells transfected with the miR-200a-3p/141-3p mimic/inhibitor.

RESULTS

Severe neurological deficits and memory loss caused by GCI/R in mice was markedly ameliorated by AA treatment, particularly in the AA medium-dose group. Moreover, AA-treated GCI/R-induced mice showed significant increases in SIRT1, ZO-1, occludin, caudin-5, and CD31 expression levels and decreases in p-NF-κB, IL-1β, TNF-α, and GFAP expression levels compared with those in untreated GCI/R-induced mice. Furthermore, we found that miR-200a-3p/141-3p was enriched in astrocyte-derived exosomes from GCI/R-induced mice and could be inhibited by treatment with a medium dose of AA. The exosomes mediated the transfer of miR-200a-3p/141-3p into bEnd.3 cells, promoted IL-1β and TNF-α release and downregulated the expression of SIRT1. No significant changes in the levels of miR-200a-3p/141-3p were observed in OGD/R-induced bEnd.3 cells. The miR-200a-3p/141-3p mimic/inhibitor decreased/increased SIRT1 expression in bEnd.3 cells, respectively.

CONCLUSION

Our findings demonstrated that AA attenuated inflammation-mediated CIRI by inhibiting astrocyte-derived exosomal miR-200a-3p/141-3p by targeting the SIRT1 gene, which provided further evidence and identified a novel regulatory mechanism for the neuroprotective effects of AA.

Vagus Nerve Stimulation Attenuates Acute Skeletal Muscle Injury Induced by Hepatic Ischemia/Reperfusion Injury in Rats

Vagus nerve stimulation (VNS) has a protective effect on distal organ injury after ischemia/reperfusion (I/R) injury. We aimed to investigate the protective efficacy of VNS on hepatic I/R injury-induced acute skeletal muscle injury and explore its underlying mechanisms. To test this hypothesis, male Sprague-Dawley rats were randomly divided into three groups: sham group (sham operation, n = 6); I/R group (hepatic I/R with sham VNS, n = 6); and VNS group (hepatic I/R with VNS, n = 6). A hepatic I/R injury model was prepared by inducing hepatic ischemia for 1 h (70%) followed by hepatic reperfusion for 6 h. VNS was performed during the entire hepatic I/R process. Tissue and blood samples were collected at the end of the experiment for biochemical assays, molecular biological preparations, and histological examination. Our results showed that throughout the hepatic I/R process, VNS significantly reduced inflammation, oxidative stress, and apoptosis, while significantly increasing the protein levels of silent information regulator 1 (SIRT1) and decreasing the levels of acetylated forkhead box O1 and Ac-p53, in the skeletal muscle. These data suggest that VNS can alleviate hepatic I/R injury-induced acute skeletal muscle injury by suppressing inflammation, oxidative stress, and apoptosis, potentially via the SIRT1 pathway.

Potential Mechanism Underlying Exercise Upregulated Circulating Blood Exosome miR-215-5p to Prevent Necroptosis of Neuronal Cells and a Model for Early Diagnosis of Alzheimer's Disease

Exercise is crucial for preventing Alzheimer's disease (AD), although the exact underlying mechanism remains unclear. The construction of an accurate AD risk prediction model is beneficial as it can provide a theoretical basis for preventive exercise prescription. In recent years, necroptosis has been confirmed as an important manifestation of AD, and exercise is known to inhibit necroptosis of neuronal cells. In this study, we extracted 67 necroptosis-related genes and 32 necroptosis-related lncRNAs and screened for key predictive AD risk genes through a random forest analysis. Based on the neural network Prediction model, we constructed a new logistic regression-based AD risk prediction model in order to provide a visual basis for the formulation of exercise prescription. The prediction model had an area under the curve (AUC) value of 0.979, indicative of strong predictive power and a robust clinical application prospect. In the exercise group, the expression of exosomal miR-215-5p was found to be upregulated; miR-215-5p could potentially inhibit the expressions of IDH1, BCL2L11, and SIRT1. The single-cell SCENIC assay was used to identify key transcriptional regulators in skeletal muscle. Among them, CEBPB and GATA6 were identified as putative transcriptional regulators of miR-215. After "skeletal muscle removal of load," the expressions of CEBPB and GATA6 increased substantially, which in turn led to the elevation of miR-215 expression, thereby suggesting a putative mechanism for negative feedback regulation of exosomal homeostasis.

Low temperature exerts protective effects by inhibiting mitochondria-mediated apoptosis pathway following pressure injury to rat muscle

OBJECTIVE

We aimed to determine the effect of different low-temperature range interventions at different time-points in a rat model of pressure injury (PI) produced by Ischemia/Reperfusion (I/R) injury.

METHODS

Sprague-Dawley rats were randomly assigned to blank control, injury control, and temperature intervention groups. Rats in the injury control and temperature intervention groups (involving exposure to different temperature range at different time-points) were subjected to three cycles of I/R injury with 2-h ischemia and 0.5-h reperfusion to induce PI.

RESULTS

The muscle tissues exhibited degenerative changes after compression. Low temperature intervention of 16-18°C in the ischemia period resulted in the lowest degree of tissue damage and significantly decreased levels of Bcl-2-associated X protein (Bax), caspase-9, and caspase-3. Moreover, it resulted in the highest expression level of B-cell lymphoma 2 (Bcl-2) and lowest expression levels of Bax, caspase-9, and caspase-3 in muscle tissues among all intervention groups.

CONCLUSION

Low-temperature intervention at 16-18°C during the ischemia period showed optimal effects on the expressions of apoptotic factors during the development of PI with I/R-induced tissue damage.

Importance of plasma ghrelin levels with special reference to nutritional metabolism and energy expenditure in pediatric patients with severe motor and intellectual disabilities

BACKGROUND & AIMS

Nutritional metabolism is complex in pediatric patients with severe motor and intellectual disability (SMID), and therefore, appropriate estimation of the energy requirements is difficult. Focusing on ghrelin's role in energy metabolism regulation, we investigated plasma ghrelin levels in pediatric SMID patients and analyzed its nutritional significance as a regulatory marker of energy reserve.

METHODS

Fasting plasma total, acyl, and des-acyl ghrelin levels in 40 patients with SMID, including cerebral palsy (CP) (n = 20) and muscular disease (MD) (n = 8), and healthy controls (n = 13) were investigated. The correlations of plasma ghrelin levels with anthropometry, blood nutritional markers, energy intake, and resting energy expenditure (REE) measured with indirect calorimetry were analyzed. A p value < 0.05 was considered significant.

RESULTS

SMID patients had significantly higher acyl ghrelin, and lower body mass index (BMI), z-scores of body weight (BW), body height and BMI, and albumin than controls. CP patients had significantly higher total and acyl ghrelin, z-score of the mid-upper arm circumference (MUAC), retinol-binding protein, transthyretin, creatinine, and glucose than MD patients. Total and acyl ghrelin in CP patients and des-acyl ghrelin in MD patients had significant negative correlations with MUAC and upper arm fat area. In CP patients, total and acyl ghrelin had significant positive correlations with REE/BW (kcal/kg), and total ghrelin was predictive of REE/BW (r² = 0.625, p < 0.0001).

CONCLUSIONS

An increase in acyl ghrelin observed in SMID patients possibly indicates energy reserve deficiency. In CP patients, total and acyl ghrelin inversely reflected total body fat mass, resulting in strongly positive correlations with REE/BW. The measurement of plasma ghrelin may be useful to assess nutritional metabolism and energy reserve in pediatric SMID patients, such as CP and MD patients.

Regulatory effects of ghrelin on endoplasmic reticulum stress, oxidative stress, and autophagy: Therapeutic potential

Ghrelin is a regulatory peptide that is the endogenous ligand of the growth hormone secretagogue 1a (GHS-R1a) which belongs to the G protein-coupled receptor family. Ghrelin and GHS-R1a are widely expressed in the central and peripheral tissues and play therapeutic potential roles in the cytoprotection of many internal organs. Endoplasmic reticulum stress (ERS), oxidative stress, and autophagy dysfunction, which are involved in various diseases. In recent years, accumulating evidence has suggested that ghrelin exerts protective effects by regulating ERS, oxidative stress, and autophagy in diverse diseases. This review article summarizes information about the roles of the ghrelin system on ERS, oxidative stress, and autophagy in multiple diseases. It is suggested that ghrelin positively affects the treatment of diseases and may be considered as a therapeutic drug in many illnesses.

Biochemical mechanism and biological effects of the inhibition of silent information regulator 1 (SIRT1) by EX-527 (SEN0014196 or selisistat)

The human sirtuin silent information regulator 1 (SIRT1) is a NAD⁺-dependent deacetylase enzyme. It deacetylates many protein substrates, including histones and transcription factors, thereby controlling many physiological and pathological processes. Several synthetic inhibitors and activators of SIRT1 have been developed, and some therapeutic applications have been explored. The indole EX-527 and its derivatives are among the most potent and selective SIRT1 inhibitors. EX-527 has been often used as a pharmacological tool to explore the effect of SIRT1 inhibition in various cell types. Its therapeutic potential has, therefore, been evaluated in animal models for several pathologies, including cancer. It has also been tested in phase II clinical trial for the treatment of Huntington’s disease (HD). In this review, we will provide an overview of the literature on EX-527, including its mechanism of inhibition and biological studies.

Protective effects of ex-527 on cerebral ischemia-reperfusion injury through necroptosis signaling pathway attenuation

Necroptosis, a novel type of programmed cell death, is involved in ischemia-reperfusion-induced brain injury. Sirtuin 1 (Sirt1), as a well-known member of histone deacetylase class III, plays pivotal roles in inflammation, metabolism, and neuron loss in cerebral ischemia. We explored the relationship between Sirt1 and the necroptosis signaling pathway and its downstream events by administration of ex-527, as a selective and potent inhibitor of Sirt1, and necrostatin-1 (nec-1), as a necroptosis inhibitor, in an animal model of focal cerebral ischemia. Our data showed different patterns of sirt1 and necroptosis critical regulators, including receptor-interacting protein kinase 3 and mixed lineage kinase domain-like protein gene expressions in the prefrontal cortex and the hippocampus after ischemia-reperfusion. We found that ex-527 microinjection reduces the infarction volume of ischemic brains and improves the survival rate, but not stroke-associated neurological deficits. Additionally, treatment with ex-527 effectively abolished the elevation of the critical regulators of necroptosis, whereas necroptosis inhibition through nec-1 microinjection did not influence Sirt1 expression levels. Our data also demonstrated that the ex-527 relieves ischemia-induced perturbation of necroptosis-associated metabolic enzymes activity in downstream. This study provides a new approach to the possible neuroprotective potential of ex-527 orchestrated by necroptosis pathway inhibition to alleviate ischemia-reperfusion brain injury.