Pharmacological effects of salidroside on central nervous system diseases.

Salidroside (SAL) is a phenylpropanoid glycoside monomer extracted from Rhodiola at high altitudes. It has been proven to have protective effects on myocardial injury, liver cancer, renal fibrosis, and other organ diseases, as well as play neuroprotective roles in central nervous system (CNS) diseases. Specifically, SAL can inhibit a series of pathological reactions in CNS diseases and improve neurological dysfunction. This review elucidated the pharmacological effects of SAL on inflammation, oxidative stress, apoptosis, autophagy, and neuronal regeneration. Furthermore, how SAL affects various signaling pathways to regulate pathological processes in CNS diseases is also assessed. However, the relationship between various pathways and the mechanisms in different pathological stages remains unclear. Additionally, the appropriate dosage and side effects of SAL on the clinical outcomes of CNS diseases have not been fully determined due to the limited number of clinical studies on SAL. Therefore, the regulatory mechanisms and clinical applications of SAL still need to be further demonstrated. This review tracked and summarized studies from the past eight years reported in databases, including PubMed, ScienceDirect, and Google Scholar, filtered using the keywords "salidroside" and/or paired with "diseases" and "CNS diseases".

Antioxidant and Immunomodulatory Activities of Essential Oil Isolated from Anti-Upper Respiratory Tract Infection Formulation and Their Chemical Analysis.

This study evaluates the in vitro antioxidant and immunomodulation activities of essential oils isolated from an anti-upper respiratory tract infection (URTI) formulation with a view to their therapeutic potential. The chemical components of the essential oil were analysed by gas chromatography-mass spectrometry (GC-MS). The antioxidative activity of the oils was investigated with regard to their ability to scavenge DPPH●, ABTS●+, and hydroxyl free radical (•OH). Their immunostimulatory activities were determined using murine macrophage cells. The main components of the oil with pharmacological and biological activities include 1,8-eucalyptol (42.9%), patchouli alcohol (19.9%), trans-erinolide (9.2%), and guaiacol (5%). The oils displayed high DPPH, ABTS, and hydroxyl radical scavenging activities and anti-inflammatory activities by reducing tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production. The results indicate that essential oils have the potential to be used in products for anti-URTI treatment.

Effect of Sirtuin-1 and Wnt/ß-Catenin Signaling Pathway in Rat Model of Spinal Cord Injury.

Sirtuin-1 (SIRT1) has anti-inflammatory and antioxidant effects and has been reported to be involved in spinal cord injury (SCI). Wnt/ß-catenin signal has been shown to play a critical role in the pathogenesis of chronic diseases, and it participated in the recovery of nerve function after SCI. However, the specific link between them in SCI is unclear. In addition, targeting posttraumatic astrocyte apoptosis is crucial for improving neural degeneration and locomotor function. Therefore, in this article, we studied the relationship of ß-catenin and SIRT1 using in the SCI rat model and primary astrocyte treated with hydrogen peroxide (H2O2) or lithium chloride (LiCl). Results showed that after SCI, SCI area and motor function recover over time, and ß-catenin is gradually increased to the seventh day and then in turn decreases until 4 weeks, positively correlated with cell apoptosis. The expression of SIRT1 and downstream FOXO4 gradually increased, and ß-catenin is negatively correlated with SIRT1 expression. Moreover, treatment with H2O2 in primary cultured astrocyte significantly increased ß-catenin and Caspase-3 expression, while decreased SIRT1 and Forkhead box O- (FOXO-) 4. The immunofluorescence results are consistent with this. Administration of LiCl further aggravates the above results. These findings suggest that SIRT1 is negatively correlated with ß-catenin in SCI, which promotes the apoptosis of motor neuron cells, which may be related to the participation of FOXO4.

Effects of Sirtuin 1 on microglia in spinal cord injury: involvement of Wnt/ß-catenin signaling pathway.

Because posttraumatic inflammation contributes to the progression of neuron degeneration, attenuating inflammation is important for reducing neural degeneration. Sirtuin 1 (SIRT1) has been shown to play a critical role in the chronic diseases, such as neurodegenerative diseases and aging. However, the role that SIRT1 plays in regulating neuroinflammation in spinal cord injuries (SCIs) remains unclear. In this study, we investigate the effect of SIRT1 on the SCI model and on lipopolysaccharide (LPS)-treated primary microglia using a pharmacological intervention (SRT1720, an agonist of SIRT1). Results showed that SIRT1 levels gradually decreased in spinal cord until the fourth week after SCI, while the level of 8-hydroxy-2'-deoxyguanosine increased. SIRT1 was negatively correlated with the expression of ß-catenin following SCI. The administration of SRT1720 significantly improved number of neurons and the Basso, Beattie, and Bresnahan score after SCI. The number of ionizing calcium-binding adaptor molecule 1 (Iba1)-positive microglia, levels of ß-catenin and NF-kB p65, and proinflammatory cytokines [tumor necrosis factor alpha and interleukin (IL) 12] decreased significantly after SRT1720 treatment, while IL-10 increased after SCI. Furthermore, both SIRT1 and SRT1720 significantly inhibited ß-catenin gene and protein expression; ß-catenin transcriptional activity also decreased in a dose-dependent manner following SIRT1 treatment of LPS-treated microglia. These findings suggest that SIRT1 may have a neuroprotective effect by suppressing microglial activation via downregulation of the Wnt/ß-catenin signal following SCI.

Neuroprotection by nicotinamide mononucleotide adenylyltransferase 1 with involvement of autophagy in an aged rat model of transient cerebral ischemia and reperfusion.

Recent researches suggest that autophagic degradation declines with age, and this leads to an accumulation of damage that contributes to age-related cellular dysfunction. Nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) shows therapeutic potential for cerebral ischemia in young-adult animals. This study investigated the role of NMNAT1 in focal cerebral ischemia in aged rats with a focus on neuronal autophagy. Focal cerebral ischemia was induced in aged rats by middle cerebral artery occlusion (MCAO). NMNAT1 levels in the peri-infarct penumbra increased at 12 and 24 h after ischemia in aged rats. Knockdown of NMNAT1 significantly increased infarct volume, whereas overexpression of NMNAT1 reduced ischemia-induced cerebral injuries in aged rats with acute ischemic stroke. Meanwhile, lentiviral overexpression of NMNAT1 increased autophagy, reduced the phosphorylation of mammalian target of rapamycin (mTOR), and enhanced the sirtuin 1 (SIRT1) protein level. In cultured cortical neurons, SIRT1 regulated the mTOR-mediated autophagy upon oxygen-glucose deprivation (OGD) stress and the effect of NMNAT1 on autophagy was blocked in cultured SIRT1-knockout neurons. Furthermore, autophagy inhibitor 3-methyladenine (3-MA) partly abolished the neuroprotection induced by NMNAT1 overexpression. The results suggest NMNAT1 protects against acute ischemic stroke in aged rats by inducing autophagy via regulating the SIRT1/mTOR pathway.

Cytoprotective Effect of Taurine against Hydrogen Peroxide-Induced Oxidative Stress in UMR-106 Cells through the Wnt/ß-Catenin Signaling Pathway.

Osteoporosis development is closely associated with oxidative stress and reactive oxygen species (ROS). Taurine has potential antioxidant effects, but its role in osteoblasts is not clearly understood. The aim of this study was to determine the protective effects and mechanisms of actions of taurine on hydrogen peroxide (H2O2)-induced oxidative stress in osteoblast cells. UMR-106 cells were treated with taurine prior to H2O2 exposure. After treatment, cell viability, apoptosis, intracellular ROS production, malondialdehyde content, and alkaline phosphate (ALP) activity were measured. We also investigated the protein levels of ß-catenin, ERK, CHOP and NF-E2-related factor 2 (Nrf2) along with the mRNA levels of Nrf2 downstream antioxidants. The results showed that pretreatment of taurine could reverse the inhibition of cell viability and suppress the induced apoptosis in a dose-dependent manner: taurine significantly reduced H2O2-induced oxidative damage and expression of CHOP, while it induced protein expression of Nrf2 and ß-catenin and activated ERK phosphorylation. DKK1, a Wnt/ß-catenin signaling inhibitor, significantly suppressed the taurine-induced Nrf2 signaling pathway and increased CHOP. Activation of ERK signaling mediated by taurine in the presence of H2O2 was significantly inhibited by DKK1. These data demonstrated that taurine protects osteoblast cells against oxidative damage via Wnt/ß-catenin-mediated activation of the ERK signaling pathway.

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin promotes inflammation in mouse testes: The critical role of Klotho in Sertoli cells.

Increasing evidence shows that 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD) enhances inflammation, and inflammation has a significant negative impact on fertility. Therefore, the aim of this study was to investigate the effects of TCDD on testis inflammation. Pregnant mice and primary Sertoli cells were treated with TCDD, and male offspring and Sertoli cells were treated with lipopolysaccharides(LPS). We then measured testis apoptotic cells, proinflammatory cytokines, and observed the Klotho/PDLIM2/p65 pathway. In vivo results revealed that TCDD further enhanced LPS-increased testis apoptotic cells and concentrations of testicular proinflammatory cytokines (IL1ß, IL18, and IL12) (p < 0.05). An in vitro investigation showed the levels of proinflammatory cytokines were increased in TCDD + LPS-treated cells compared with LPS-treated cells (p < 0.05). Compared with the LPS-treated cells, expression of Klotho and PDLIM2 was significantly decreased in TCDD + LPS-treated cells (p < 0.05), while expression of p65 and NLRP3 were significantly increased in the cotreatment cells (p < 0.05). However, the addition of Klotho to the TCDD + LPS-cotreated cells significantly increased PDLIM2 and decreased p65 activation and NLRP3 (p < 0.05). Meanwhile, mRNA levels and the secretion of proinflammatory cytokines were both suppressed by exogenous Klotho (p < 0.05). Administration of Klotho decreased TCDD + LPS-induced cytokines and apoptosis in mice (p < 0.05). Taken together, TCDD may increase testicular inflammation by affecting the secretion of proinflammatory cytokines in Sertoli cells via the Klotho/PDLIM2/p65 pathway, which influences the testicular microenvironment and induces germ cell apoptosis.

The Neuroprotective Effects of Muscle-Derived Stem Cells via Brain-Derived Neurotrophic Factor in Spinal Cord Injury Model.

Muscle-derived stem cells (MDSCs) possess multipotent differentiation and self-renewal capacities; however, the effects and mechanism in neuron injury remain unclear. The aim of this study was to investigate the effects of MDSCs on neuron secondary injury, oxidative stress-induced apoptosis. An in vivo study showed the Basso, Beattie, and Bresnahan (BBB) score and number of neurons significantly increased after MDSCs' transplantation in spinal cord injury (SCI) rats. An in vitro study demonstrated that MDSCs attenuated neuron apoptosis, and the expression of antioxidants was upregulated as well as the ratio of Bcl-2 and Bax in the MNT (MDSCs cocultured with injured neurons) group compared with the NT (injured neurons) group. Both LC3II/LC3I and ß-catenin were enhanced in the MNT group, while XAV939 (a ß-catenin inhibitor) decreased the expression of nuclear erythroid-related factor 2 (Nrf2) and LC3II/LC3I. Moreover, MDSCs became NSE- (neuron-specific enolase-) positive neuron-like cells with brain-derived neurotrophic factor (BDNF) treatment. The correlation analysis indicated that there was a significant relation between the level of BDNF and neuron injury. These findings suggest that MDSCs may protect the spinal cord from injury by inhibiting apoptosis and replacing injured neurons, and the increased BDNF and ß-catenin could contribute to MDSCs' effects.

Klotho ameliorates cyclosporine A-induced nephropathy via PDLIM2/NF-kB p65 signaling pathway.

Klotho, an antiaging protein, can extend the lifespan and modulate cellular responses to inflammation and oxidative stress which can ameliorate chronic kidney diseases (CKD). To investigate the molecular mechanism of Klotho on inflammation in cyclosporine A (CsA) induced nephropathy, the mice were transfected with adenovirus mediated Klotho gene and treated with cyclosporine A (CsA; 30 mg/kg/day) for 4 weeks. Also, primary human renal proximal tubule epithelial cells (RPTECs) were treated with soluble Klotho protein and LPS. The results showed that Ad-klotho significantly reduced serum creatinine (Scr) and blood urea nitrogen (BUN) caused by CsA, and significantly increased creatinine clearance. Tubule interstitial fibrosis score (TIF), renal 8-OHdG excretion, macrophage infiltration and MCP-1 were decreased after Ad-klotho gene transfer. In addition, the overexpression of Klotho led to increase in the expression of PDLIM2, decreased in the amount of NF-kB p65, and inhibited the production of inflammatory cytokines (TNFα, IL-6, IL-12) and iNOS. Accordingly, in vitro results showed, Klotho enhanced PDLIM2 expression and reduced NF-kB p65 expression, while PDLIM2 siRNA could block the inhibitory effects of Klotho on expression of NF-kB p65. Secretion of inflammatory cytokines was also inhibited by Klotho treatment, and PDLIM2 siRNA hindered regulatory effects of Klotho on the cytokines. Real-time PCR and Luciferase assay showed that Klotho markedly increased expression of PDLIM2 mRNA and PDLIM2 reporter activity in a dose-dependent manner. These findings suggest that Klotho can modulate inflammation via PDLIM2/NF-kB p65 pathway in CsA-induced nephropathy.

MP Resulting in Autophagic Cell Death of Microglia through Zinc Changes against Spinal Cord Injury.

Methylprednisolone pulse therapy (MPPT), as a public recognized therapy of spinal cord injury (SCI), is doubted recently, and the exact mechanism of MP on SCI is unclear. This study sought to investigate the exact effect of MP on SCI. We examined the effect of MP in a model of SCI in vivo and an LPS induced model in vitro. We found that administration of MP produced an increase in the Basso, Beattie, and Bresnahan scores and motor neurons counts of injured rats. Besides the number of activated microglia was apparently reduced by MP in vivo, and Beclin-1 dependent autophagic cell death of microglia was induced by MP in LPS induced model. At the same time, MP increases cellular zinc concentration and level of ZIP8, and TPEN could revert effect of MP on autophagic cell death of microglia. Finally, we have found that MP could inhibit NF-κß in LPS induced model. These results show that the MP could result in autophagic cell death of microglia, which mainly depends on increasing cellular labile zinc, and may be associated with inhibition of NF-κß, and that MP can produce neuroprotective effect in SCI.

Simvastatin inhibits neural cell apoptosis and promotes locomotor recovery via activation of Wnt/ß-catenin signaling pathway after spinal cord injury.

Statins exhibit neuroprotective effects after spinal cord injury (SCI). However, the molecular mechanism underlying these effects remains unknown. This study demonstrates that the hydroxymethylglutaryl coenzyme A reductase inhibitor simvastatin (Simv) exhibits neuroprotective effects on neuronal apoptosis and supports functional recovery in a rat SCI model by activating the Wnt/ß-catenin signaling pathway. In specific, Simv administration after SCI significantly up-regulated the expression of low density lipoprotein receptor-related protein 6 phosphorylation and ß-catenin protein, increased the mRNA expression of lymphoid enhancer factor-1 and T-cell factor-1, and suppressed the expression of ß-catenin phosphorylation in the spinal cord neurons. Simv enhanced motor neuronal survival in the spinal cord anterior horn and decreased the lesion of spinal cord tissues after SCI. Simv administration after SCI also evidently reduced the expression levels of Bax, active caspase-3, and active caspase-9 in the spinal cord neurons and the proportion of transferase UTP nick end labeling (TUNEL)-positive neuron cells, but increased the expression level of Bcl-2 in the spinal cord neurons. However, the anti-apoptotic effects of Simv were reduced in cultured spinal cord nerve cells when the Wnt/ß-catenin signaling pathway was suppressed in the lipopolysaccharide-induced model. Furthermore, the Basso, Beattie, and Bresnahan scores indicated that Simv treatment significantly improved the locomotor functions of rats after SCI. This study is the first to report that Simv exerts neuroprotective effects by reducing neuronal apoptosis, and promoting functional and pathological recovery after SCI by activating the Wnt/ß-catenin signaling pathway. We verified the neuroprotective properties associated with simvastatin following spinal cord injury (SCI). Simvastatin reduced neuronal apoptosis, improved the functional and pathological recovery via activating Wnt/ß-catenin signal pathway, however, the anti-apoptosis effects of simvastatin were reversed following suppressing Wnt/ß-catenin signaling pathway in primary spinal cord neurons. The significant findings may provide clinical therapeutic value of simvastatin for treating SCI.

Neuroprotective Effect of Simvastatin via Inducing the Autophagy on Spinal Cord Injury in the Rat Model.

Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, is invariably used to treat cardiovascular diseases. Simvastatin has been recently demonstrated to have a neuroprotective effect in nervous system diseases. The present study aimed to further verify the neuroprotection and molecular mechanism of simvastatin on rats after spinal cord injury (SCI). The expression of Beclin-1 and LC3-B was evidently enhanced at postoperation days 3 and 5, respectively. However, the reduction of the mTOR protein and ribosomal protein S6 kinase p70 subtype (p70S6K) phosphorylation level occurred at the same time after SCI. Simvastatin significantly increased the expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). Meanwhile, immunofluorescence results indicated that the expression of chondroitin sulfate proteoglycan (CSPG) and caspase-3 protein was obviously reduced by simvastatin. Furthermore, Nissl staining and Basso, Beattie, and Bresnahan (BBB) scores showed that the quantity and function of motor neurons were visibly preserved by simvastatin after SCI. The findings of this study showed that simvastatin induced autophagy by inhibiting the mTOR signaling pathway and contributed to neuroprotection after SCI.

VEGF inhibits the inflammation in spinal cord injury through activation of autophagy.

Vascular endothelial growth factor (VEGF) is a secreted mitogen associated with angiogenesis and re-vascularization of spinal cord injury (SCI). VEGF has long been thought to be a potent neurotrophic factor for the survival of spinal cord neuron. However, the neuroprotective mechanism of VEGF is still unclear. The aim of this study was to investigate the effect of VEGF on spinal cord injury and its mechanisms. Young male Wistar rats were subjected to SCI and then VEGF165 were injected directly into the lesion epicenter 24 h post injury. We detected Basso, Beattie and Bresnahan (BBB) scores and numbers of motor neuron via Nissl staining. The expressions of autophagy related protein Beclin1 and LC3B were determined by Western blot and RT-PCR. We also detected the contents of inflammation factors interleukin-1ß (IL-1ß), tumor necrosis factor alpha (TNF-α) and interleukin-10(IL-10) in LPS (Lipopolysaccharide) treated spinal neuron-glia co-culture by ELISA. We found that VEGF165 administration increased the BBB score and reduced the loss of motor neuron of rats induced by SCI. VEGF decreased the protein expressions of IL-1ß, TNF-α and IL-10 and up-regulated the expressions of Beclin1 and LC3B of rats. In the in vitro study, VEGF165 decreased the levels of IL-1ß, IL-10 and TNF-a in the medium of LPS treated spinal neuron-glia co-culture, which was partially blocked by 3-MA, the inhibitor of autophagy. In addition, VEGF165 up-regulate the expressions of Beclin1 and LC3B in co-culture cells. The results suggested that VEGF165 attenuated the spinal cord injury by inhibiting the inflammation and increasing the autophagy function.

Nicotinamide Mononucleotide Adenylyltransferase 1 Protects Neural Cells Against Ischemic Injury in Primary Cultured Neuronal Cells and Mouse Brain with Ischemic Stroke Through AMP-Activated Protein Kinase Activation.

Nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) is a nicotinamide adenine dinucleotide biosynthetic enzyme. It has been shown to be neuroprotective against neonatal excitotoxicity-induced brain injury, but its role in ischemic stroke is unclear. In this study, the role of NMNAT1 in oxygen-glucose deprivation (OGD)-induced primary cultured neuronal cell injury and mouse middle cerebral artery occlusion-induced cerebral ischemic injury and its regulation on AMP-activated protein kinase (AMPK) activation were evaluated. The results showed that NMNAT1 overexpression reduced cell death and apoptosis both in vitro and in vivo. Conversely, NMNAT1 knockdown exacerbated cell death and apoptosis. Furthermore, NMNAT1 overexpression regulated neuron survival via AMPK activation, as NMNAT1 overexpression enhanced AMPK activity in OGD-treated cortical neurons, and AMPK inhibitor blocked LV-NMNAT1-induced neuroprotection in OGD-treated cortical neurons. In addition, NMNAT1 overexpression could reduce brain infarction size and improve behavioral outcomes in mice with ischemic stroke. These results suggested that up-regulation of NMNAT1 could induce neuroprotection against ischemic injury through AMPK activation and indicated that NMNAT1 is a potential therapeutic target for stroke.

Protective effects of aerobic swimming training on high-fat diet induced nonalcoholic fatty liver disease: regulation of lipid metabolism via PANDER-AKT pathway.

This study aimed to investigate the mechanism by which aerobic swimming training prevents high-fat-diet-induced nonalcoholic fatty liver disease (NAFLD). Forty-two male C57BL/6 mice were randomized into normal-diet sedentary (ND; n = 8), ND exercised (n = 8), high-fat diet sedentary (HFD; n = 13), and HFD exercised groups (n = 13). After 2 weeks of training adaptation, the mice were subjected to an aerobic swimming protocol (60 min/day) 5 days/week for 10 weeks. The HFD group exhibited significantly higher mRNA levels of fatty acid transport-, lipogenesis-, and ß-oxidation-associated gene expressions than the ND group. PANDER and FOXO1 expressions increased, whereas AKT expression decreased in the HFD group. The aerobic swimming program with the HFD reversed the effects of the HFD on the expressions of thrombospondin-1 receptor, liver fatty acid-binding protein, long-chain fatty-acid elongase-6, Fas cell surface death receptor, and stearoyl-coenzyme A desaturase-1, as well as PANDER, FOXO1, and AKT. In the HFD exercised group, PPARα and AOX expressions were much higher. Our findings suggest that aerobic swimming training can prevent NAFLD via the regulation of fatty acid transport-, lipogenesis-, and ß-oxidation-associated genes. In addition, the benefits from aerobic swimming training were achieved partly through the PANDER-AKT-FOXO1 pathway.

Wnt signaling regulates hepatic metabolism.

The contribution of the Wnt pathway has been extensively characterized in embryogenesis, differentiation, and stem cell biology but not in mammalian metabolism. Here, using in vivo gain- and loss-of-function models, we demonstrate an important role for Wnt signaling in hepatic metabolism. In particular, ß-catenin, the downstream mediator of canonical Wnt signaling, altered serum glucose concentrations and regulated hepatic glucose production. ß-Catenin also modulated hepatic insulin signaling. Furthermore, ß-catenin interacted with the transcription factor FoxO1 in livers from mice under starved conditions. The interaction of FoxO1 with ß-catenin regulated the transcriptional activation of the genes encoding glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), the two rate-limiting enzymes in hepatic gluconeogenesis. Moreover, starvation induced the hepatic expression of mRNAs encoding different Wnt isoforms. In addition, nutrient deprivation appeared to favor the association of ß-catenin with FoxO family members, rather than with members of the T cell factor of transcriptional activators. Notably, in a model of diet-induced obesity, hepatic deletion of ß-catenin improved overall metabolic homeostasis. These observations implicate Wnt signaling in the modulation of hepatic metabolism and raise the possibility that Wnt signaling may play a similar role in the metabolic regulation of other tissues.

Expression and regulation of osteoprotegerin in adipose tissue.

PURPOSE: Osteoprotegerin (OPG), a potent inhibitor of osteoclastic bone resorption, has a variety of biological functions that include anti-inflammatory effects. Adipocytes and osteoblasts share a common origin, and the formation of new blood vessels often precedes adipogenesis in developing adipose tissue microvasculature. We examined whether OPG is secreted from adipocytes, therefore contributing to the prevention of neovascularization and protecting the vessels from intimal inflammation and medial calcification. MATERIALS AND METHODS: The mRNA expression of OPG and receptor activator of NF-kappaB ligand (RANKL) was measured in differentiated 3T3L1 adipocytes and adipose tissues. RESULTS: OPG mRNA expression increased with the differentiation of 3T3L1 adipocytes, while RANKL expression was not significantly altered. OPG mRNA was expressed at higher levels in white adipose tissue than in brown adipose tissue and was most abundant in the epididymal portion. In differentiated 3T3L1 adipocytes, Rosiglitazone and insulin reduced the OPG/RANKL expression ratio in a dose- and time- dependent manner. In contrast, tumor necrosis factor-alpha (TNF-alpha) increased the expression of both OPG and RANKL in a time-dependent manner. The OPG/RANKL ratio was at a maximum two hours after TNF-alpha treatment and then returned to control levels. Furthermore, OPG was abundantly secreted into the media after transfection of OPG cDNA with Phi C31 integrase into 3T3L1 cells. CONCLUSION: Our results indicate that OPG mRNA is expressed and regulated in the adipose tissue. Considering the role of OPG in obesity-associated inflammatory changes in adipose tissue and vessels, we speculate that OPG may have both a protective function against inflammation and anti-angiogenic effects on adipose tissue.

Peripheral effect of alpha-melanocyte-stimulating hormone on fatty acid oxidation in skeletal muscle.

To study the peripheral effects of melanocortin on fuel homeostasis in skeletal muscle, we assessed palmitate oxidation and AMP kinase activity in alpha-melanocyte-stimulating hormone (alpha-MSH)-treated muscle cells. After alpha-MSH treatment, carnitine palmitoyltransferase-1 and fatty acid oxidation (FAO) increased in a dose-dependent manner. A strong melanocortin agonist, NDP-MSH, also stimulated FAO in primary culture muscle cells and C2C12 cells. However, [Glu6]alpha-MSH-ND, which has ample MC4R and MC3R agonistic activity, stimulated FAO only at high concentrations (10(-5) M). JKC-363, a selective MC4R antagonist, did not suppress alpha-MSH-induced FAO. Meanwhile, SHU9119, which has both antagonistic activity on MC3R and MC4R and agonistic activity on both MC1R and MC5R, increased the effect of alpha-MSH on FAO in both C2C12 and primary muscle cells. Small interference RNA against MC5R suppressed the alpha-MSH-induced FAO effectively. cAMP analogues mimicked the effect of alpha-MSH on FAO, and the effects of both alpha-MSH and cAMP analogue-mediated FAO were antagonized by a protein kinase A inhibitor (H89) and a cAMP antagonist ((Rp)-cAMP). Acetyl-CoA carboxylase activity was suppressed by alpha-MSH and cAMP analogues by phosphorylation through AMP-activated protein kinase activation in C2C12 cells. Taken together, these results suggest that alpha-MSH increases FAO in skeletal muscle, in which MC5R may play a major role. Furthermore, these results suggest that alpha-MSH-induced FAO involves cAMP-protein kinase A-mediated AMP-activated protein kinase activation.