Adiponectin protects the rats liver against chronic intermittent hypoxia induced injury through AMP-activated protein kinase pathway

Protective activity of hirsutidin in high-fat intake and streptozotocin-induced diabetic rats: In silico and in vivo study

Background

Type 2 diabetes mellitus (T2DM) is defined by a wide variety of metabolic abnormalities, persistent hyperglycemia, and a slew of other complications. Catharanthus roseus L. (apocyanaceae), remarkably notable as Vinca Rosea, appears to be the source of the active component hirsutidin, which is reported in various diseases.

Objective

The study intended to appraise the antidiabetic capability of hirsutidin in a high-fat diet (HFD) and streptozotocin (STZ) induced diabetes in experimental rats.

Materials and methods

An experimental rodent T2DM model was elicited by consuming an HFD regimen with STZ 50 mg/kg, i.p. dose formulated in a 0.1 M cold citrate buffer (pH 4.5). The test drug hirsutidin (10 and 20 mg/kg) and the standard drug glimeclamide (5 mg/kg) were administered daily for six weeks. The efficacy of hirsutidin was observed on several diabetes parameters. The average body weight and an array of biochemical markers were determined, including blood glucose, insulin, dyslipidemia (lipid profile), total protein (TP), liver injury [aspartate aminotransferase (AST), alanine aminotransferase (ALT)], inflammation [IL-6, IL-1β, tumor necrosis factor-α (TNF-α)], oxidative stress [malondialdehyde (MDA)] and antioxidant status [catalase (CAT), glutathione (GSH), and superoxide dismutase (SOD)]. In addition, the concentrations of leptin, adiponectin, and resistin were also assessed. Also, molecular docking studies were undertaken to investigate critical targets associated with diabetes, including TNF-α, insulin, adiponectin, and leptin.

Results

Diabetes induction with HFD/STZ resulted in hyperglycemia (significantly reduced blood glucose and increased insulin level), dyslipidemia (significantly reduced TC, TG and increased HDL), total protein (significantly reduced), oxidative stress and antioxidant status (significantly reduced MDA and increased CAT, SOD and GSH levels), inflammation (significantly decreased IL-6, IL-1β, TNF-α), liver damage (significantly reduced AST, ALT), and specific hormones such as adiponectin, leptin significantly improved and resistin significantly reduced as evidenced by biochemical data in this study. Intermolecular interactions of ligands and docking score, hirsutidin proteins TNF-α (2AZ5), Insulin (4IBM), Adiponectin (6KS1), Leptin (7Z3Q) with binding energy of -6.708, -7.674, -7.2 and -7.547 Kcal/mol.

Conclusion

Hirsutidin may have an evidential hypoglycemic outcome and may exhibit potent antidiabetic activity in HFD/STZ-induced T2DM in rats. Treatment with hirsutidin significantly improved glycemic control, lipid metabolism, oxidative stress, inflammation, and liver function. Additionally, it normalized dysregulated levels of adiponectin, leptin, and resistin. Molecular docking confirmed its strong binding affinity to key diabetic targets.

Blockade of the mitochondrial DNA release ameliorates hepatic ischemia-reperfusion injury through avoiding the activation of cGAS-Sting pathway

BACKGROUND

Liver surgery during the perioperative period often leads to a significant complication known as hepatic ischemia-reperfusion (I/R) injury. Hepatic I/R injury is linked to the innate immune response. The cGAS-STING pathway triggers the activation of innate immune through the detection of DNA within cells. Nevertheless, the precise mechanism and significance of the cGAS-STING pathway in hepatic I/R injury are yet to be investigated.

METHODS

Mouse model of hepatic I/R injury was used in the C57BL/6 WT mice and the STING knockout (STING-KO) mice. In addition, purified primary hepatocytes were used to construct oxygen-glucose deprivation reperfusion (OGD-Rep) treatment models.

RESULTS

Our research revealed a notable increase in mRNA and protein levels of cGAS and STING in liver during I/R injury. Interestingly, the lack of STING exhibited a safeguarding impact on hepatic I/R injury by suppressing the elevation of liver enzymes, liver cell death, and inflammation. Furthermore, pharmacological cGAS and STING inhibition recapitulated these phenomena. Macrophages play a crucial role in the activation of the cGAS-STING pathway during hepatic I/R injury. The cGAS-STING pathway experiences a significant decrease in activity and hepatic I/R injury is greatly diminished following the elimination of macrophages. Significantly, we demonstrate that the activation of the cGAS-STING pathway is primarily caused by the liberation of mitochondrial DNA (mtDNA) rather than nuclear DNA (nDNA). Moreover, the safeguarding of the liver against I/R injury is also attributed to the hindrance of mtDNA release through the utilization of inhibitors targeting mPTP and VDAC oligomerization.

CONCLUSIONS

The results of our study suggest that the release of mtDNA plays a significant role in causing damage to liver by activating the cGAS-STING pathway during I/R injury. Furthermore, inhibiting the release of mtDNA can provide effective protection against hepatic I/R injury.

Chronic intermittent hypoxia aggravated diabetic cardiomyopathy through LKB1/AMPK/Nrf2 signaling pathway

Chronic intermittent hypoxia (CIH) may play an important role in the development of diabetic cardiomyopathy (DCM). However, the exact mechanism of CIH-induced myocardial injury in DCM remains unclear. In vivo, the db/db mice exposed to CIH were established, and in vitro, the H9C2 cells were exposed to high glucose (HG) combined with intermittent hypoxia (IH). The body weight (BW), fasting blood glucose (FBG) and food intake were measured every two weeks. The glycolipid metabolism was assessed with the oral glucose tolerance test (OGTT) and insulin resistance (IR). Cardiac function was detected by echocardiography. Cardiac pathology was detected by HE staining, Masson staining, and transmission electron microscopy. The level of reactive oxygen species (ROS) in myocardial tissue was detected by dihydroethidium (DHE). The apoptosis was detected by TUNEL staining. The cell viability, ROS, and the mitochondrial membrane potential were detected by the cell counting kit-8 (CCK-8) assay and related kits. Western blotting was used to analyze the liver kinase B1/AMP-activated protein kinase/ nuclear factor-erythroid 2-related factor 2 (LKB1/AMPK/Nrf2) signaling pathway. CIH exposure accelerated glycolipid metabolism disorders and cardiac injury, and increased the level of cardiac oxidative stress and the number of positive apoptotic cells in db/db mice. IH and HG decreased the cell viability and the level of mitochondrial membrane potential, and increased ROS expression in H9C2 cells. These findings indicate that CIH exposure promotes glycolipid metabolism disorders and myocardial apoptosis, aggravating myocardial injury via the LKB1/AMPK/Nrf2 pathway in vitro and in vivo.

Globular adiponectin protects hepatocytes against intermittent hypoxia-induced injury via Pink1/Parkin-mediated mitophagy induction

PURPOSE

This study sought to determine the effect of Pink1/Parkin-mediated mitophagy on liver cells exposed to intermittent hypoxia (IH) and the roles of globular adiponectin (gAPN).

METHODS

The hepatocyte model of IH was established. Cell apoptosis was assessed using flow cytometry. Mitochondrial membrane potential (MMP) level was determined using JC-1, and mitophagy was assessed using a confocal laser. Mitochondrial injury associated protein levels of bax and bcl-2, and protein levels of Pink1 and Parkin were evaluated via western blotting. We downregulated Parkin expression by transfecting the cells with Parkin siRNA.

RESULTS

Pink1 and Parkin protein levels, mitophagy, and cell apoptosis rate were high, while the MMP level and protein level ratio of bcl-2/bax were low in IH-treated hepatocyte. gAPN upregulated Pink1 and Parkin protein levels, MMP level, protein level ratio of bcl-2/bax, and mitophagy while it reduced the rate of cell apoptosis in IH-treated hepatocytes. Inhibiting Parkin expression significantly reduced mitophagy and increased mitochondrial injury and the rate of hepatocyte apoptosis under IH or IH with gAPN.

CONCLUSION

gAPN alleviated IH-induced mitochondrial injury and hepatocyte apoptosis by upregulating Pink1/Parkin-mediated mitophagy.

d-Pinitol protects against endoplasmic reticulum stress and apoptosis in hepatic ischemia-reperfusion injury via modulation of AFT4-CHOP/GRP78 and caspase-3 signaling pathways

Hepatic ischemia-reperfusion injury (IRI) is a major unavoidable clinical problem often accompanying various liver surgery and transplantation. d-Pinitol, a cyclic polyol, exhibits hepatoprotective efficacy. The objective of this study is to determine the possible mechanism of action of pinitol against endoplasmic reticulum (ER) stress regulation-mediated hepatic IRI and compare its effects with thymoquinone (TQ) in experimental rats. Male Sprague Dawley rats were pre-treated orally with either vehicle (DMSO) or d-Pinitol (5, 10, and 20 mg/kg) or TQ (30 mg/kg) for 21 days and subjected to 60 min of partial hepatic ischemia followed by 24 h of reperfusion. Pre-treatment with pinitol (10 and 20 mg/kg) effectively (P < 0.05) protected against IRI-induced hepatic damage reflected by attenuation of elevated oxidative stress and pro-inflammatory cytokines. Additionally, western blot and ELISA analyses suggested that pinitol significantly (P < 0.05) down-regulated expression of endoplasmic reticulum stress apoptotic markers, namely glucose-regulated protein (GRP)-78, CCAAT/enhancer-binding protein homologous protein (CHOP), activating transcription factor (AFT)-4 and -6α, X-box binding protein-1, and caspase-3, 9, and 12. Additionally, pinitol pre-treatment effectively (P < 0.05) improved mitochondrial function and phosphorylation of Extracellular signal-regulated kinase (ERK)-1/2 and p38. Pinitol markedly (P < 0.05) protected hepatic apoptosis determined by flow cytometry. Further, pinitol provided effective (P < 0.05) protection against hepatic histological and ultrastructural aberrations induced by IRI. TQ showed more pronounced protective effect against attenuation of IRI-induced hepatic injury as compared to d-Pinitol. Pinitol offered protection against endoplasmic reticulum stress-mediated phosphorylation of ERK1/2 and p38, thereby inhibiting AFT4-CHOP/GRP78 signaling response and caspase-3 induced hepatocellular apoptosis during hepatic ischemia-reperfusion insults. Thus, Pinitol can be considered as a viable option for the management of hepatic IRI.

Adiponectin involved in portal flow hepatic extraction of 13C-methacetin in obesity and non-alcoholic fatty liver

Obesity and non-alcoholic fatty liver disease (NAFLD) are high prevalence, inter-related conditions at increased risk for advanced liver diseases and related mortality. Adiponectin and leptin have divergent roles in the pathogenesis of fat accumulation and NAFLD. However, the relationships between body and liver fat accumulation, early modification of liver function and unbalanced adipokine levels are still scarcely explored. We studied by (13C)-methacetin breath test ((13C)-MBT) 67 adults stratified according to body mass index, and to presence/absence of ultrasonographic nonalcoholic fatty liver disease (uNAFLD). uNAFLD was detected in 20%, 73% and 96% of normal weight, overweight and obese subjects, respectively. The delta over baseline after 15 min (DOB₁₅), a marker of hepatic extraction efficiency from portal blood flow, was lower in obese than in normal weight subjects, and in subjects with-, as compared to those without uNAFLD. The cumulative percent dose recovery after 30 min (cPDR₃₀), a marker of liver microsomal function, was lower in uNAFLD patients. DOB₁₅ was positively correlated with adiponectin levels in obese and in uNAFLD patients. uNAFLD patients also showed a positive correlation between cPDR₃₀ values and adiponectin. Our data indicate the existence of early alterations of liver function in obese and in patients with uNAFLD. These dysfunctions are linked to altered leptin/adiponectin balance and can be identified noninvasively by (13C)-MBT.

Calycosin Alleviates Injury in Airway Epithelial Cells Caused by PM 2.5 Exposure via Activation of AMPK Signalling

Methods

Phospho-AMP-activated protein kinase (p-AMPK) and AMP-activated protein kinase (AMPK) were detected by western blot. Immunofluorescence staining was used to validate changes in the levels of nuclear factor kappa B (NF-кB) p65 nuclear translocation. Mice were administered intraperitoneally with calycosin one hour before anaesthesia and endotracheal instillation of PM 2.5. The extent of lung injury was evaluated in the H&E-stained lung sections. Apoptotic cells were detected by TUNEL staining.

Results

Administration of calycosin was increased in PM 2.5-treated B2B cells in a dose-dependent manner in vitro. Fluorescence signals from anti-NF-кB p65 were increased in nuclei of cells pretreated with calycosin. The level of p-AMPK was increased by calycosin in vitro and in vivo. After pretreatment with compound C, the inhibitory effects of calycosin on cytotoxicity, levels of inflammatory cytokines and p-AMPK, and levels of NF-кB p65 nuclear translocation were not significantly decreased in vitro or in vivo.

Conclusions

Calycosin effectively decreased the release of inflammatory cytokines and alleviated injury caused by PM 2.5. These effects were mediated through activation of AMPK to suppress NF-κB signalling.

Data on Adiponectin from 2010 to 2020: Therapeutic Target and Prognostic Factor for Liver Diseases?

The review describes the role of adiponectin in liver diseases in the presence and absence of surgery reported in the literature in the last ten years. The most updated therapeutic strategies based on the regulation of adiponectin including pharmacological and surgical interventions and adiponectin knockout rodents, as well as some of the scientific controversies in this field, are described. Whether adiponectin could be a potential therapeutic target for the treatment of liver diseases and patients submitted to hepatic resection or liver transplantation are discussed. Furthermore, preclinical and clinical data on the mechanism of action of adiponectin in different liver diseases (nonalcoholic fatty disease, alcoholic liver disease, nonalcoholic steatohepatitis, liver cirrhosis and hepatocellular carcinoma) in the absence or presence of surgery are evaluated in order to establish potential targets that might be useful for the treatment of liver disease as well as in the practice of liver surgery associated with the hepatic resections of tumors and liver transplantation.

Adiponectin ameliorates lung injury induced by intermittent hypoxia through inhibition of ROS-associated pulmonary cell apoptosis

PURPOSE

Obstructive sleep apnea hypopnea syndrome has been reported to be associated with pulmonary hypertension (PH). Adiponectin (Ad) has many protective roles in the human body, including its function as an anti-inflammatory and an anti-oxidant, as well as its role in preventing insulin resistance and atherosclerosis. This study aimed to investigate the molecular mechanism of chronic intermittent hypoxia (CIH)-induced pulmonary injury and the protective role of Ad in experimental rats.

METHODS

Thirty male Sprague-Dawley rats were randomly divided into three groups with 10 rats in each group: normal control (NC) group, CIH group, and CIH + Ad group. Rats in the NC group were kept breathing room air for 12 weeks. Rats in the CIH group were intermittently exposed to a hypoxic environment for 8 h/day for 12 weeks. Rats in the CIH + Ad group received 10 μg Ad twice weekly via intravenous injection. After 12 weeks of CIH exposure, we detected the pulmonary function, pulmonary artery pressure, lung histology, pulmonary cell apoptosis, pulmonary artery endothelial cell apoptosis, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) level. We also analyzed expression proteins involved in the mitochondria-, endoplasmic reticulum (ER) stress-, and Fas receptor-associated pulmonary apoptosis pathways, as well as the SIRT3/SOD2 pathway.

RESULTS

CIH exposure for 12 weeks did not lead to abnormal pulmonary function, PH, or pulmonary artery endothelial cell apoptosis. However, we observed a significant increase in the rate of pulmonary cell apoptosis, the expression of proteins involved in mitochondria-, ER stress-, and Fas receptor-associated pulmonary apoptosis pathways, and the generation of ROS in the CIH group compared with the NC group. In contrast, the MMP and protein expressions of SIRT3/SOD2 pathway were significantly decreased in the CIH group compared with the NC group. Ad supplementation in the CIH + Ad group partially improved these changes induced by CIH.

CONCLUSION

Even though CIH did not cause abnormal pulmonary function or PH, early lung injury was detected at the molecular level in rats exposed to CIH. Treatment with Ad ameliorated the pulmonary injury by activating the SIRT3/SOD2 pathway, reducing ROS generation, and inhibiting ROS-associated lung cell apoptosis.

The role of ferroptosis in chronic intermittent hypoxia-induced liver injury in rats

PURPOSE

Obstructive sleep apnea (OSA) has been related to an increased risk of liver injury. Ferroptosis is a form of programmed cell death implicated in multiple physiological and pathological processes. This study aimed to explore the role of ferroptosis in chronic intermittent hypoxia (CIH)-induced liver injury as well as to uncover the underlying mechanisms using a CIH rat model.

METHODS

Fourteen male Sprague-Dawley rats were randomly allocated to either the normal control (NC) (n = 7) or the CIH group (n = 7). Rats were exposed to intermittent hypoxia for 8 weeks in CIH group. Liver function, histological changes, and markers of oxidative stress were evaluated. The protein levels of hypoxia-inducible factor-1α, nuclear factor E2-related factor 2 (Nrf2), Acyl-CoA synthetase long-chain family member 4 (ACSL4), and glutathione peroxidase 4 (GPX4) in liver were examined by Western blot analysis.

RESULTS

CIH treatment caused significant increase of serum alanine aminotransferase, aspartate aminotransferase, and malondialdehyde (MDA). Liver MDA was significantly higher in CIH group than that in NC group. Histology showed that CIH treatment induced discernible swelled, disordered hepatocytes, necrosis, and infiltrated inflammatory cells. CIH treatment significantly reduced the expression of GPX4, while markedly up-regulated expression of ACSL4, indicating elevation in hepatic ferroptosis. In addition, the protein expression of Nrf2 in CIH group was significantly lower than that in NC group.

CONCLUSIONS

Ferroptosis played a crucial role in CIH-induced liver injury. The hepatic ferroptosis in CIH rat model might be mediated by the dysregulation of Nrf2. This highlights a potential therapeutic target for the treatment of OSA-related liver injury.

Adiponectin and PPAR: a setup for intricate crosstalk between obesity and non-alcoholic fatty liver disease

Adiponectin, a soluble adipocytokine, plays an important role in the functioning of adipose tissue and in the regulation of inflammation, particularly hepatic inflammation. The adiponectin subsequently imparts a crucial role in metabolic and hepato-inflammatory diseases. The most recent evidences indicate that lipotoxicity-induced inflammation in the liver is associated with obesity-derived alterations and remolding in adipose tissue that culminates in most prevalent liver pathology named as non-alcoholic fatty liver disease (NAFLD). A comprehensive crosstalk of adiponectin and its cognate receptors, specifically adiponectin receptor-2 in the liver mediates ameliorative effects in obesity-induced NAFLD by interaction with hepatic peroxisome proliferator-activated receptors (PPARs). Recent studies highlight the implication of molecular mediators mainly involved in the pathogenesis of obesity and obesity-driven NAFLD, however, the plausible mechanisms remain elusive. The present review aimed at collating the data regarding mechanistic approaches of adiponectin and adiponectin-activated PPARs as well as PPAR-induced adiponectin levels in attenuation of hepatic lipoinflammation. Understanding the rapidly occurring adiponectin-mediated pathophysiological outcomes might be of importance in the development of new therapies that can potentially resolve obesity and obesity-associated NAFLD.

Hepatic ischemia-reperfusion injury in liver transplant setting: mechanisms and protective strategies

Hepatic ischemia-reperfusion injury is a major cause of liver transplant failure, and is of increasing significance due to increased use of expanded criteria livers for transplantation. This review summarizes the mechanisms and protective strategies for hepatic ischemia-reperfusion injury in the context of liver transplantation. Pharmacological therapies, the use of pre-and post-conditioning and machine perfusion are discussed as protective strategies. The use of machine perfusion offers significant potential in the reconditioning of liver grafts and the prevention of hepatic ischemia-reperfusion injury, and is an exciting and active area of research, which needs more study clinically.

AICAR-Induced AMPK Activation Inhibits the Noncanonical NF-κB Pathway to Attenuate Liver Injury and Fibrosis in BDL Rats

BACKGROUND

To evaluate the AMP-activated protein kinase- (AMPK-) mediated signaling and NF-κB-related inflammatory pathways that contribute to cholestatic diseases in the bile duct ligation (BDL) rat model of chronic cholestasis and verify the protective role of 5-Aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR) against hepatic injury and fibrosis triggered by cholestasis-related inflammation.

METHODS

Animals were randomly divided into three groups: sham-operated group, BDL group, and BDL+ AICAR group. Cholestatic liver injury was induced by common BDL. Two weeks later, rats in BDL+AICAR group started receiving AICAR treatment. Hepatic pathology was examined by haematoxylin and eosin (H&E) and sirius red staining and hydroxyproline assay was performed in evaluating the severity of hepatic cirrhosis. Real-time PCR and Western blot were performed for RNA gene expression of RNA and protein levels, respectively.

RESULTS

The BDL group showed liver injury as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, and inflammation. The mRNA expression of canonical NF-κB inflammatory cytokines such as TNF-α, IL-1β, TGF-β, and the protein of noncanonical NF-κB, P100, and P52 was upregulated in the livers of BDL rats. The BDL rats with the administration of AICAR could induce AMPK activation inhibiting the noncanonical NF-κB pathway to attenuate liver injury and fibrosis in BDL rats.

CONCLUSION

The BDL model of hepatic cholestatic injury resulting in activation of Kupffer cells and recruitment of immune cells might initiate an inflammatory response through activation of the NF-κB pathway. The AMPK activator AICAR significantly alleviated BDL-induced inflammation in rats by mainly inhibiting the noncanonical NF-κB pathway and thus protecting against hepatic injury and fibrosis triggered by BDL.

Melatonin prevents chronic intermittent hypoxia-induced injury by inducing sirtuin 1-mediated autophagy in steatotic liver of mice

BACKGROUND

Hepatic steatosis that occasionally results in nonalcoholic steatohepatitis (NASH) is related to obstructive sleep apnea (OSA). Many studies have shown that autophagy exerts protective effects on liver damage caused by various diseases and melatonin exhibits hepatoprotective properties. However, the mechanisms of liver injury induced by chronic intermittent hypoxia (CIH) and the effect of melatonin on the regulation of liver injury remain unclear.

PURPOSE

This study was aimed to evaluate the role of CIH in steatohepatitis progression and the regulatory function of melatonin on fatty liver sensitivity to CIH injury, mainly focusing on autophagy signaling.

METHODS

A high-fat diet (FD)-induced obesity mouse model was subjected to intermittent hypoxia/normoxia events for approximately 8 h per day using an autophagy agonist, rapamycin, or an inhibitor, 3-methyladenine (3-MA), and SRT1720, a sirtuin 1 (SIRT1) activator, or sirtinol, a SIRT1 inhibitor, with or without melatonin for a total of six successive weeks, followed by assessment of expression of autophagy-related genes and activity of serum aminotransferase as well as histological evaluation of tissue morphology.

RESULTS

Neither FD nor CIH alone causes significant liver injury; however, the combination yielded higher serum aminotransferase activities and more severe histological changes, accompanied by a decrease in autophagy activity. Melatonin markedly inhibited FD/CIH-stimulated liver injury by enhancing autophagy. In contrast, SIRT1 inhibition resulted in a decrease in the expression of melatonin-induced autophagy-related genes as well as diminished its protective effects on FD/CIH-induced liver injury.

CONCLUSION

These results suggest that melatonin could ameliorate FD/CIH-induced hepatocellular damage by activating SIRT1-mediated autophagy signaling.

Adiponectin regulates thermal nociception in a mouse model of neuropathic pain

BACKGROUND

Adiponectin, a cytokine secreted by adipocytes, plays an important role in regulating glucose and lipid metabolism. However, the role of adiponectin in pain conditions is largely unknown. This study aimed to identify the role and mechanism of adiponectin in nociceptive sensitivity under physiological and pathological states utilising adiponectin knockout (KO) mice.

METHODS

Wild type (WT) and adiponectin KO mice were subjected to partial sciatic nerve ligation (pSNL) or sham operation. Pain-like behavioural tests, including thermal allodynia, hyperalgesia, and mechanical allodynia, were performed before and after pSNL from Day 3-21. Dorsal root ganglions (DRGs), lumbar spinal segments at L3-5, and somatosensory cortex were collected for protein measurement via western blotting and immunofluorescence staining.

RESULTS

Compared with WT mice, KO mice had significantly lower (40-50%) paw withdrawal latency to innocuous and noxious stimuli before and after pSNL. In DRG neurones from KO mice, where adiponectin receptor (AdipoR) 2 is located, phosphorylated p38 mitogen-activated protein kinase (p-p38 MAPK) and heat-sensitive transient receptor potential cation channel subfamily V member 1 (TRPV1) were significantly higher (by two- to three-fold) than from WT mice. In spinal microglia and somatosensory cortical neurones, where AdipoR1 is mainly located, p-p38 MAPK and TRPV1 were also higher (by two- to three-fold) in KO compared with WT mice, and altered signalling of these molecules was exacerbated (1.2- to 1.3-fold) by pSNL.

CONCLUSIONS

Our results show that adiponectin regulates thermal nociceptive sensitivity by inhibiting activation of DRG neurones, spinal microglia, and somatosensory cortical neurones in physiological and neuropathic pain states. This study has relevance for patients with adiponectin disorders, such as obesity and diabetes.

Decreased expression of hepatic cytochrome P450 1A2 (CYP1A2) in a chronic intermittent hypoxia mouse model

Background

Hepatic cytochrome P450 (CYP) isoforms, CYP1A2, is one of important enzymes for many drugs metabolism. Studies have confirmed that sustained hypoxia can influence the expression of hepatic CYP, including CYP1A2. The impact of chronic intermittent hypoxia (CIH), a marked characteristic of sleep apnea, on CYP1A2 remains unclear. The aim of the present study was to evaluate the effect of CIH on the expression of hepatic CYP1A2 in a mouse model with sleep apnea.

Methods

Twenty four old male (6-8 weeks) C57BL/6J mice (n=12 in each group) were randomly assigned to either normoxia group or CIH group. Mice in CIH group underwent 12 weeks intermittent hypoxia exposure. The different gene expression of hepatic CYP1A2 between two groups was analyzed by quantity real-time polymerase chain reaction. The protein levels of hepatic CYP1A2 in each group were observed by using western blotting and immunohistochemistry.

Results

After 12 weeks of exposure to intermittent hypoxia, the expression of hepatic CYP1A2, at the mRNA and protein levels was decreased more significantly in the CIH group than the normoxia group (P<0.01).

Conclusions

CIH contributes to inhibiting the expression of hepatic CYP1A2. This implies that the dosage of drugs metabolized by CYP1A2, should be adjusted in patients with sleep apnea.

The emerging role of AMP-activated protein kinase in cholestatic liver diseases

AMP-activated protein kinase (AMPK), recognized as an energy sensor with three heterotrimeric subunits (α, β and γ), not only maintains basal intracellular adenosine triphosphate levels but also regulates energy-intensive pathological responses, such as neurodegenerative and metabolic diseases, through multiple signaling pathways. Recent studies open a new direction for AMPK research and demonstrate that AMPK is a critical player in the pathogenesis of cholestatic liver injury and plays paradoxical roles in the regulation of different pathological processes, including the disruption of bile acid homeostasis and the regulation of hepatic polarity, inflammation and fibrosis. In the present review, we summarize recent findings that implicate AMPK-mediated signaling pathways in the pathogenesis of cholestatic liver injury. These findings provide novel insight regarding the potential use of AMPK as a therapeutic target for the treatment of cholestatic liver injury.

Hypoxia in 3T3-L1 adipocytes suppresses adiponectin expression via the PERK and IRE1 unfolded protein response

Adiponectin, an adipocytokine produced by adipocytes, functions as an anti-inflammatory and anti-apoptotic substance, while also enhancing insulin sensitivity. Patients or model animals with obesity or diabetes typically present attenuated expression of adiponectin. Moreover, obesity and diabetes are often accompanied with hypoxia in adipose tissue, which may result in endoplasmic reticulum (ER) stress as well as low expression of adiponectin. The purpose of this study was to investigate the specific role of the unfolded protein response (UPR) involved in the low expression of adiponectin induced by hypoxia. Subjecting 3T3-L1 adipocytes to hypoxia significantly reduced adiponectin expression and activated the PERK and IRE1 signaling pathways in a time-dependent manner. The ATF6 signaling pathway showed no obvious changes with hypoxia treatment under a similar time course. Moreover, the down-regulated expression of adiponectin induced by hypoxia was relieved once the PERK and IRE1 signaling pathways were suppressed by the inhibitors GSK2656157 and 4μ8C, respectively. Overall, these data demonstrate that hypoxia can suppress adiponectin expression and activate the PERK and IRE1 signaling pathways in differentiated adipocytes, and this two pathways are involved in the suppression of adiponectin expression induced by hypoxia.

Regulation of longevity by FGF21: Interaction between energy metabolism and stress responses

Fibroblast growth factor 21 (FGF21) is a hormone-like member of FGF family which controls metabolic multiorgan crosstalk enhancing energy expenditure through glucose and lipid metabolism. In addition, FGF21 acts as a stress hormone induced by endoplasmic reticulum stress and dysfunctions of mitochondria and autophagy in several tissues. FGF21 also controls stress responses and metabolism by modulating the functions of somatotropic axis and hypothalamic-pituitary-adrenal (HPA) pathway. FGF21 is a potent longevity factor coordinating interactions between energy metabolism and stress responses. Recent studies have revealed that FGF21 treatment can alleviate many age-related metabolic disorders, e.g. atherosclerosis, obesity, type 2 diabetes, and some cardiovascular diseases. In addition, transgenic mice overexpressing FGF21 have an extended lifespan. However, chronic metabolic and stress-related disorders involving inflammatory responses can provoke FGF21 resistance and thus disturb healthy aging process. First, we will describe the role of FGF21 in interorgan energy metabolism and explain how its functions as a stress hormone can improve healthspan. Next, we will examine both the induction of FGF21 expression via the integrated stress response and the molecular mechanism through which FGF21 enhances healthy aging. Finally, we postulate that FGF21 resistance, similarly to insulin resistance, jeopardizes human healthspan and accelerates the aging process.

Adiponectin Is Involved in Connective Tissue Growth Factor-Induced Proliferation, Migration and Overproduction of the Extracellular Matrix in Keloid Fibroblasts

Adiponectin, an adipocyte-derived hormone, exerts pleiotropic biological effects on metabolism, inflammation, vascular homeostasis, apoptosis and immunity. Recently, adiponectin has been suggested to attenuate the progression of human dermal fibrosis. Connective tissue growth factor (CTGF) is induced in keloids and is thought to be participated in the formation of keloid fibrosis. However, the roles played by adiponectin in keloids remain unclear. In this study, we explored the effects of adiponectin on CTGF-induced cell proliferation, migration and the deposition of extracellular matrix (ECM) and their associated intracellular signalling pathways in keloid fibroblasts (KFs). We also explored possible mechanisms of keloid pathogenesis. Primary fibroblast cultures were established from foreskin biopsies and skin biopsies from patients with keloids. The expression of adiponectin and adiponectin receptors (adipoRs) was evaluated by reverse transcription-PCR (RT-PCR), quantitative real-time RT-PCR, immunofluorescence staining, and immunohistochemical analysis. Next, KFs and normal dermal fibroblasts (NFs) were treated with CTGF in the presence or absence of adiponectin. A cell counting kit-8 (CCK-8) and the Transwell assay were used to examine cell proliferation and migration. The level of the collagen I, fibronectin (FN) and α-smooth muscle actin (α-SMA) mRNAs and proteins were determined by quantitative real-time RT-PCR and western blotting. The effects of RNA interference (RNAi) targeting the adipoR genes were detected. Phosphorylation of adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK), mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase-protein kinase (PI3K-Akt) were examined by western blotting to further investigate the signalling pathways. Furthermore, inhibitors of signal transduction pathways were investigated. The expression levels of adiponectin and adipoRs were significantly decreased in keloids compared with those in normal skin tissue. Adiponectin suppressed the CTGF-induced KFs, but not NFs, proliferation, migration and ECM production. Moreover, adiponectin inhibited the phosphorylation of AMPK, p38 and extracellular-regulated kinase (ERK), but not that of Jun N-terminal kinase (JNK) or Akt, in CTGF-treated KFs. The activity of adiponectin-mediated signalling pathways was attenuated by small interfering RNAs (siRNAs) targeting adipoR1 (but not siRNAs targeting adipoR2, T-cadherin or calreticulin), AMPK (Compound C), p38 (SB203580) inhibitors, and mitogen-activated protein kinase kinase (MEK) inhibitor (PD98059). Based on our results, adiponectin suppresses CTGF-induced KFs proliferation, migration and ECM overproduction. One of the underlying mechanisms is the activation of the adipoR1, AMPK, p38, and ERK signalling pathways. Therefore, adiponectin may play an important role in the progression of keloids, suggesting a potential novel target for keloid treatment.

Protective benefits of AMP-activated protein kinase in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is a major cause of hepatic failure and death after liver trauma, haemorrhagic shock, resection surgery and liver transplantation. AMP-activated protein kinase (AMPK) is an energy sensitive kinase that plays crucial roles in the regulation of metabolic homeostasis. In HIRI, ischemia induces the decline of ATP and the increased ratio of AMP/ATP, which promotes the phosphorylation and activation of AMPK. Three AMPK kinases, liver kinase B1 (LKB1), Ca²⁺/calmodulin-depedent protein kinase kinase β (CaMKKβ) and TGF-β-activated kinase-1 (TAK1), are main upstream kinases for the phosphorylation of AMPK. In addition to the changed AMP/ATP ratio, the activated CaMKKβ by increased intracelluar Ca²⁺ and the overproduction of reactive oxygen species (ROS) are also involved in the activation of AMPK during HIRI. The activated AMPK might provide protective benefits in HIRI via prevention of energy decline, inhibition of inflammatory response, suppression of hepatocyte apoptosis and attenuation of oxidative stress. Thus, AMPK might become a novel target for the pharmacological intervention of HIRI.