Fu-Ming Shen

Metformin promotes irisin release from murine skeletal muscle independently of AMP‐activated protein kinase activation

Irisin, a novel myocyte‐secreted hormone mediating beneficial effects of exercise on metabolism, is supposed to be an ideal therapeutic target for metabolic disorders such as obesity and diabetes. Here, we investigated the potential effects of metformin and glibenclamide, two antidiabetic medicines, on irisin release in mouse.

Exercise-stimulated FGF23 promotes exercise performance via controlling the excess reactive oxygen species production and enhancing mitochondrial function in skeletal muscle

OBJECTIVEnPhysical exercise induces many adaptive changes in skeletal muscle and the whole body and improves metabolic characteristics. Fibroblast growth-factor 23 (FGF23) is a unique member of the FGF family that acts as a hormone regulating phosphate metabolism, calcitriol concentration, and kidney functions. The role of FGF23 in exercise and skeletal muscle is largely unknown yet.nnnMATERIALS AND METHODSnC57BL/6J mice were exercised on a motor treadmill. Mice serum FGF23 levels; FGF23 mRNA expression in various organs including the liver, heart, skeletal muscle tissue, and thyroid; and FGF23 receptor Klotho mRNA expression were examined using enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and immunoblotting, respectively, after a single bout of acute exercise (60min), exhaustive exercise, and chronic prolonged exercise (60min every day for one week). C57BL/6J mice were injected with recombinant FGF23 (100mg/kg, twice per day, i.p.) or vehicle control (saline) for 3days, and then the exercise performance, reactive oxygen species (ROS), H2O2 production, and mitochondrial functional biomarkers in muscle (gene expression of sirtuin 1, PPAR-δ, PGC-1α and mitochondrial transcription factor A [TFAM], and citrate synthase activity) were assayed.nnnRESULTSnThree forms of exercise, acute exercise, exhaustive exercise, and chronic exercise, increased serum FGF23 levels. However, only chronic exercise upregulated FGF23 mRNA and protein expression in skeletal muscle. FGF23 mRNA expression in the heart, liver, and thyroid was not affected. FGF23 protein was mainly located in the cytoplasm in skeletal muscle tissue and the localization of FGF23 was not altered by exercise. Exogenous FGF23 treatment significantly extended the time to exhaustion and reduced the exercise-induced ROS and H2O2 production. FGF23 treatment increased the mRNA level of PPAR-δ and citrate synthase activity, but did not influence the mRNA expression of sirtuin 1, PGC-1α, and TFAM in skeletal muscle.nnnCONCLUSIONnThese results demonstrate that exercise-stimulated FGF23 promotes exercise performance via controlling the excess ROS production and enhancing mitochondrial function in skeletal muscle, which reveals an entirely novel role of FGF23 in skeletal muscle.

High-salt diet enhances hippocampal oxidative stress and cognitive impairment in mice

Previous evidence suggests that a high-salt (HS) diet may increase oxidative stress and contribute to the development of hypertension that is already present. Oxidative stress is thought to play a critical role in the development of neurodegenerative diseases. Lower dietary sodium intake putatively contributes to a lower rate of cognitive impairment; however, the specific effects of HS diet on cognitive function remain poorly understood. In this work, C57BL/6J mice were administered a normal-salt (NS) diet (0.4% NaCl) or a HS diet (7.0% NaCl) for 12 weeks, and cognitive ability and oxidative stress in the brain were measured. It was found that the HS diet significantly impaired retention of spatial memory. Additionally, superoxide anion production in the hippocampus was significantly increased in the HS diet mice compared with that in the NS mice. Interestingly, the antioxidant defense capacities for HS diet mice were markedly reduced in the hippocampus, but not in the cerebral cortex, compared with the NS mice. Taken together, these data demonstrate that HS diet directly impairs retention of spatial memory, which may be related to the increased oxidative stress observed in the hippocampus.

Glibenclamide attenuates myocardial injury by lipopolysaccharides in streptozotocin-induced diabetic mice

BackgroundSepsis is a common disease that continues to increase in incidence in the world. Diseases, such as diabetes mellitus, may make the situation worse. Diabetic patients are at increased risk for common infections. This study was designed to investigate the role of glibenclamide on myocardial injury by lipopolysaccharides (LPS) in streptozotocin induced diabetic mice (STZ-mice).MethodsLPS was used to induce endotoxemia in STZ-mice. Heart rate and mean arterial pressure were measured by MPA-HBBS. Serum epinephrine level was measured by enzyme-linked immunosorbent assays (ELISA). Myocardial injury was examined by light and transmission electron microscope and TUNEL staining. Macrophage infiltration was measured by immunohistochemistry. Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) levels in myocardial tissue and serum in STZ-mice, and in conditional medium of primary cultured peritoneal macrophages were determined by ELISA. Nalp3 and Caspase-1 protein levels were measured by Western blotting analysis.ResultsSTZ administration decreased body weight and increased blood glucose in C57BL/6 mice. LPS injection caused decreases of heart rate and mean arterial pressure, and elevated serum epinephrine level in C57BL/6 mice. Compared with control mice without STZ treatment, LPS induced more severe myocardial injury and macrophage infiltration in STZ-mice, which was attenuated by pretreatment of glibenclamide. LPS stimulation enhanced the levels of IL-1β and TNF-α in both cardiac tissue and serum. Glibenclamide pretreatment significantly inhibited the serum levels of pro-inflammatory cytokines. Either high glucose or LPS increased the levels of IL-1β and TNF-α in the conditional medium of peritoneal macrophages. Glibenclamide treatment suppressed the increase of IL-1β level induced by high glucose and LPS. Furthermore, Nalp3 and Caspase-1 levels were markedly increased by high glucose plus LPS, and both proteins were significantly inhibited by glibenclamide treatment.ConclusionsWe conclude that glibenclamide could attenuate myocardial injury induced by LPS challenge in STZ-mice, which was possibly related to inhibiting inflammation through Nalp3 inflammasomes.

Simvastatin attenuates radiation-induced tissue damage in mice

The aim of this study was to investigate the protective effect of simvastatin against radiation-induced tissue injury in mice. Mice were radiated with 4 Gy or 8 Gy after 20 mg/kg/d simvastatin treatment over 2 weeks. Morphological changes were observed in the jejunum and bone marrow, and apoptotic cells were determined in both tissues. Peripheral blood cells were counted, and the superoxide dismutase (SOD) activity and the malondialdehyde (MDA) level in tissues of both thymus and spleen were measured. Compared with the radiation-only group, 20 mg/kg/d simvastatin administration significantly increased the mean villi height and decreased apoptotic cells in jejunum tissue, and stimulated regeneration and reduced apoptotic cells in bone marrow. Peripheral blood cell analysis revealed that simvastatin treatment induced a larger number of red blood cells and increased the hemoglobin level present after 4 Gy of radiation. Interestingly, it was also found that the number of peripheral endothelial progenitor cells was markedly increased following simvastatin administration. Antioxidant determination for tissues displayed that simvastatin therapy increased the SOD activity after both 4 and 8 Gy of radiation, but only decreased the MDA level after 4 Gy. Simvastatin ameliorated radiation-induced tissue damage in mice. The radioprotective effect of simvastatin was possibly related to inhibition of apoptosis and improvement of oxygen-carrying and antioxidant activities.

α7 Nicotinic Acetylcholine Receptor Relieves Angiotensin II–Induced Senescence in Vascular Smooth Muscle Cells by Raising Nicotinamide Adenine Dinucleotide–Dependent SIRT1 Activity

Objective—&agr;7 nicotinic acetylcholine receptor (&agr;7nAChR) is a subtype of nAChR and has been reported to be involved in hypertension end-organ damage. In this study, we tested the role of &agr;7nAChR in angiotensin II (Ang II)–induced senescence of vascular smooth muscle cells (VSMCs). Approach and Results—Expression of &agr;7nAChR was not influenced by Ang II. Ang II induced remarkable senescent phenotypes in rodent and human VSMCs, including increased senescence-associated &bgr;-galactosidase activity, phosphorylation of H2A.XSer139, phosphorylation of Chk1Ser317, reduced replication, and downregulation of proliferating cell nuclear antigen. Activation of &agr;7nAChR with a selective agonist PNU-282987 blocked Ang II–induced senescence in cultured VSMCs. Moreover, PNU-282987 treatment attenuated the Ang II infusion–induced VSMC senescence in wild-type but not in &agr;7nAChR−/− mice. PNU-282987 reduced the Ang II–enhanced reactive oxygen species, lipid peroxidation, and the expression of NADPH oxidase 1, NADPH oxidase 4, and p22phox in cultured VSMCs isolated from wild-type but not in &agr;7nAChR−/− mice. Furthermore, PNU-282987 diminished Ang II–induced prosenescence signaling pathways, including p53, acetyl-p53, p21, and p16INK4a. Finally, although &agr;7nAChR activation by PNU-282987 did not affect the Ang II–induced downregulation of sirtuin 1 (SIRT1), it significantly increased intracellular NAD+ levels, and thereby enhanced SIRT1 activity in an AMP-dependent protein kinase–independent manner. Depletion of SIRT1 by knockdown or SIRT1 inhibitor EX527 abrogated the antisenescence effect of &agr;7nAChR against Ang II. Conclusions—Our results demonstrate that activation of &agr;7nAChR alleviates Ang II–induced VSMC senescence through promoting NAD+–SIRT1 pathway, suggesting that &agr;7nAChR may be a potential therapeutic target for the treatment of Ang II–associated vascular aging disorders.

Vagus Nerve Attenuates Hepatocyte Apoptosis upon Ischemia–reperfusion via α7 Nicotinic Acetylcholine Receptor on Kupffer Cells in Mice

Background:Hepatic ischemia–reperfusion (HIR) injury is a complication of liver surgery. As much as 50% of hepatocytes undergo apoptosis within the first 24u2009h of reperfusion. The neurotransmitters of the vagus nerve can activate &agr;7 nicotinic acetylcholine receptor (&agr;7nAChR) on macrophages. The function of Kupffer cells (KCs) determines HIR injury. We hypothesize that the vagus nerve could attenuate HIR-induced hepatocyte apoptosis by activating &agr;7nAChR on KCs. Methods:Hepatic vagotomized C57BL/6J mice, KC-eliminated C57BL/6J mice, and &agr;7nAChR−/− mice were used for HIR. Primary KCs and hepatocytes were subjected to hypoxia/reoxygenation (HR). Liver injury, hepatocyte apoptosis, reactive oxygen species (ROS) production, and soluble CD163 were measured. Results:Hepatic vagotomy and &agr;7nAChR−/− caused higher levels of alanine transaminase and liver caspase-3 and -8 activity by HIR. Activating &agr;7nAChR attenuated these changes in wild-type but not in the &agr;7nAChR−/− mice. Furthermore, activating &agr;7nAChR diminished hepatic injury and reduced liver apoptosis by HIR in vagotomized mice. In vitro, activating &agr;7nAChR reduced apoptosis of hepatocytes cocultured with KCs that suffered HR. Similar to the effects by catalase, activating &agr;7nAChR on KCs reduced ROS and H2O2 by HR. The supernatant from KCs, with &agr;7nAChR activated or catalase treated, prevented hepatocyte apoptosis by HR. Finally, KC elimination reduced HIR-induced H2O2 production in mice. Activating &agr;7nAChR significantly attenuated soluble CD163 both in mice by HIR (serum: 240u2009±u200934 vs. 446u2009±u200972; mean ± SD; n = 8; P < 0.01) and in KCs by HR (supernatant: 4.23u2009±u20090.06 vs. 5.60u2009±u20090.18; n = 3; P < 0.01). Conclusions:The vagus nerve could minimize HIR-induced liver apoptosis through activating &agr;7nAChR on KCs possibly by preventing their excessive ROS production.

Activation of Alpha 7 Nicotinic Acetylcholine Receptor Protects Mice from Radiation-Induced Intestinal Injury and Mortality

Radiation-induced gastrointestinal syndrome occurs when the body is exposed to a high dose of radiation. Currently, safe and effective radioprotectants are not available. Apoptosis was reported to play a primary role in radiation-induced injury. Recent evidence suggests that stimulation of α7 nicotinic acetylcholine receptor (α7nAChR) prevents cell death by inhibition of apoptosis. In this study, we demonstrated that a single dose of PNU282987 (100 μg/kg, i.p.), a selective α7nAChR agonist, protected mice from intestinal injury and significantly improved survival when administered prior to lethal 8 Gy total body irradiation. In vitro, PNU282987 protected against 8 Gy radiation-induced cell death in human umbilical venous endothelial cells by inhibiting apoptosis. We conclude that activation of α7nAChR may provide a new therapeutic pathway for the treatment of radiation-induced damage and mortality.

Targeting α7 nicotinic acetylcholine receptor to combat inflammation in cardio-cerebral-vascular diseases.

BACKGROUNDnCardio-cerebral-vascular diseases, including myocardial infarction, atherosclerosis, hypertension, and stroke etc, are the major reasons for morbidity and mortality all over the world. Recent studies showed that inflammation exerts an important impact on the pathogenesis and development of cardio-cerebral-vascular diseases. The cholinergic anti-inflammatory pathway, mainly modulated through α7 nicotinic acetylcholine receptor (α7nAChR), has attracted much attention.nnnOBJECTIVEnThe purpose of this review was to discuss the role of α7nAChR during the pathological processes in myocardial infarction, atherosclerosis, hypertension and stroke.nnnRESULTSnMost of the existing literatures involved in studying on myocardial infarction, atherosclerosis, hypertension and stroke showed that activation of α7nAChR might be a potential strategy for the prevention and treatment of these diseases.nnnCONCLUSIONnTargeting α7nAChR to combat inflammation might be a novel therapy in cardiocerebral- vascular diseases.