Melatonin ameliorates hepatic fibrosis via the melatonin receptor 2-mediated upregulation of BMAL1 and anti-oxidative enzymes.

Hepatic fibrosis, when left untreated, causes serious health problems that progress to cirrhosis and, in some cases, liver cancer. Activation of hepatic stellate cells may be a key characteristic in the development of hepatic fibrosis. Melatonin, a pineal hormone, exerts anti-fibrotic effects; however, the exact mechanisms remain unclear. In this study, the beneficial effects of melatonin against hepatic fibrosis and the underlying mechanisms were investigated using the human hepatic stellate cell line, LX-2, and in vivo murine animal models. The results showed that melatonin suppressed the expression of transforming growth factor (TGF)-ß1-induced fibrosis markers and production of reactive oxygen species in LX-2 cells. Either 4-phenyl-2-propionamidotetralin, a melatonin receptor 2 selective antagonist, or melatonin receptor 2 small interfering RNA abolished the suppressive effects of melatonin, suggesting the involvement of melatonin receptor 2 in melatonin-induced anti-fibrotic and anti-oxidative actions. Melatonin increased the expression of the brain and muscle aryl hydrocarbon receptor nuclear translocator-like 1 (BMAL1), a positive circadian clock gene. BMAL1 knockdown reduced the anti-fibrotic and anti-oxidative effects of melatonin, demonstrating the protective effects of melatonin against TGF-ß1-induced hepatic stellate cell activation by exhibiting melatonin receptor 2-BMAL1-anti-oxidative effects. In high-fat diet-induced and carbon tetrachloride-induced hepatic fibrosis models, oral melatonin administration decreased the expression of hepatic fibrosis markers and increased the expression of messenger RNA and levels of proteins of BMAL1 and melatonin receptor 2. Thus, melatonin exerted protective effects against hepatic fibrosis through melatonin receptor 2 activation, followed by an upregulation of the BMAL1-anti-oxidative enzyme pathways.

Anti-obesity effects of Lactiplantibacillus plantarum SKO-001 in high-fat diet-induced obese mice.

PURPOSE: Previous reports showed that some probiotics provide beneficial effects on various diseases including metabolic disorders. This study aimed to investigate the anti-obesity effects of Lactiplantibacillus (L.) plantarum SKO-001 (SKO-001), a probiotic strain newly isolated from Angelica gigas. METHODS: C57BL/6J mice were fed with high-fat diet (HFD, 60% fat) for four weeks, and then different doses of SKO-001 (n = 10 each group) were orally given for 12 weeks. Following treatment, body weight, fat weight, serum parameters and adipose and liver tissues were analyzed. RESULTS: SKO-001 (2 × 1010 CFU/day, per os) reduced body weight gain after 10th week of administration, accompanied by a reduction in body fat mass of mice. In the SKO-001-fed group, increased serum adiponectin, decreased leptin, insulin, total cholesterol, low-density lipoprotein cholesterol, free fatty acids, and triglyceride levels were observed. Hematoxylin and eosin staining of various fat depots showed that increased adipocyte size caused by HFD intake was markedly reduced and correlated with reduced mRNA levels of lipogenesis genes, including sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor gamma, and CCAAT/enhancer binding protein alpha, and increased uncoupling protein 1 levels. Similarly, SKO-001 reduced lipid accumulation, decreased the mRNA levels of lipogenic genes, and reduced α-smooth muscle actin and collagen type 1 alpha 1 levels in the liver. CONCLUSIONS: SKO-001 ameliorates obesity and related metabolic abnormalities in adipose and liver tissues, possibly via the regulation of lipid metabolism. Based on the results of the present study, SKO-001 may be applicable as an anti-obesity therapeutic or functional food.

Tranilast protects pancreatic ß-cells from palmitic acid-induced lipotoxicity via FoxO-1 inhibition.

Tranilast, an anti-allergic drug used in the treatment of bronchial asthma, was identified as an inhibitor of the transcription factor Forkhead box O-1 (FoxO-1) by high throughput chemical library screening in the present study. Based on FoxO-1's role in apoptotic cell death and differentiation, we examined the effect of tranilast on palmitic acid (PA)-induced cell damage in INS-1 cells. Tranilast substantially inhibited lipoapoptosis and restored glucose-stimulated insulin secretion under high PA exposure. Moreover, PA-mediated downregulation of PDX-1, MafA, and insulin expression was attenuated by tranilast. PA-induced oxidative and ER stress were also reduced in the presence of tranilast. These protective effects were accompanied by increased phosphorylation and decreased nuclear translocation of FoxO-1. Conversely, the effects of tranilast were diminished when treated in transfected cells with FoxO-1 phosphorylation mutant (S256A), suggesting that the tranilast-mediated effects are associated with inactivation of FoxO-1. Examination of the in vivo effects of tranilast using wild type and diabetic db/db mice showed improved glucose tolerance along with FoxO-1 inactivation in the pancreas of the tranilast-treated groups. Thus, we report here that tranilast has protective effects against PA-induced lipotoxic stress in INS-1 cells, at least partly, via FoxO-1 inactivation, which results in improved glucose tolerance in vivo.

Sodium salicylate induces browning of white adipocytes via M2 macrophage polarization by HO-1 upregulation.

Browning, a white to brown-like (beige) adipocyte conversion, offers a promising therapeutic strategy for the treatment of human obesity. In the present study, the effects of sodium salicylate, a nonsteroidal anti-inflammatory drug, on adipocyte browning were investigated. We found sodium salicylate altered the macrophage phenotype to M2 in RAW264.7 cells, mediated by up-regulation of heme oxygenase-1 (HO-1), and sodium salicylate-treated conditioned medium from macrophages (Sal-M2 CM) induced browning of fully differentiated 3T3-L1 adipocytes. Conversely, the conditioned medium obtained from macrophages when treated with sodium salicylate in the presence of either ZnPP (a HO-1 inhibitor) or HO-1 siRNA did not induce browning. In association with macrophage HO-1 induction by sodium salicylate, iron production also increased, and deferoxamine (an iron chelator) blunted the browning effects of Sal-M2 CM, suggesting that iron may play a role in the Sal-M2 CM-induced browning. The in vivo browning effects of sodium salicylate were confirmed in ob/ob mice, whereas in vivo macrophage depletion by clodronate as well as HO-1 blockade by either ZnPP or adeno-associated virus carrying HO-1 shRNA (AAV-HO-1 shRNA) attenuated the browning effects of sodium salicylate. These results reveal sodium salicylate induces browning in vitro and in vivo by up-regulating HO-1 thus promoting M2 polarization.

Adapalene induces adipose browning through the RARß-p38 MAPK-ATF2 pathway.

Adipose browning has recently been reported to be a novel therapeutic strategy for obesity. Because the retinoic acid receptor (RAR) is a potential target involved in browning, adapalene (AD), an anti-acne agent with RAR agonism, was examined in detail for its effects on adipose browning and the underlying mechanisms in vitro and in vivo. AD upregulated the expression of adipose browning-related markers in a concentration-dependent manner, promoted mitochondrial biogenesis, increased oxygen consumption rates, and lowered lipid droplet sizes in differentiated 3T3/L1 white adipocytes. Among the three retinoic acid receptors (RARα, RARß, and RARγ), knockdown of the gene encoding RARß mitigated AD-induced adipose browning. Similarly, LE135 (a selective RARß antagonist) attenuated AD action, suggesting that AD promotes adipose browning through RARß. Sequential phosphorylation of p38 mitogen-activated protein kinase (MAPK) and activating transcription factor 2 (ATF2) was critical for AD-induced adipose browning, based on the observations that either SB203580 (a p38 MAPK inhibitor) or ATF2 siRNA reduced the effects of AD. In vivo browning effects of AD were confirmed in C57BL/6J mice and high-fat diet-induced obese (DIO) mice after oral administration of AD either acutely or chronically. This study identifies new actions of AD as an adipose browning agent and demonstrates that RARß activation followed by increased phosphorylation of p38 MAPK and ATF2 appears to be a key mechanism of AD action.

Novel FoxO1 inhibitor, JY-2, ameliorates palmitic acid-induced lipotoxicity and gluconeogenesis in a murine model.

Forkhead transcription factor forkhead box O1 (FoxO1) plays an important role in glucose and lipid metabolism, contributing to the pathogenesis of metabolic disorders. This study aimed to discover a novel FoxO1 inhibitor as a potential new anti-diabetic drug candidate, and describes the biological effects of JY-2, 5-(2,4-dichlorophenyl)-3-(pyridin-2-yl)-1,2,4-oxadiazole in vitro and in vivo. JY-2 inhibited FoxO1 transcriptional activity in a concentration-dependent manner, with an IC50 value of 22 µM. The inhibitory effects of JY-2 on FoxO3a and FoxO4 appeared to be weaker than that on FoxO1. Consistent with its inhibitory effect on FoxO1, JY-2 reduced the palmitic acid (PA)-stimulated mRNA expression of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), two key enzymes involved in gluconeogenesis in HepG2 cells. In association with the reduced expression of lipid metabolism genes, triglyceride accumulation was also reduced by JY-2, as determined by Oil Red O staining. In addition, JY-2 restored PA-impaired glucose-stimulated insulin secretion (GSIS), in conjunction with an increased mRNA expression of PDX1, MafA, and insulin in INS-1 cells. The in vivo efficacy of JY-2 was examined using C57BL/6J, db/db, and high fat-diet induced obese and diabetic (DIO) mice models, and showed that JY-2 improved glucose tolerance, in parallel with a reduced mRNA expression of gluconeogenic genes. Pharmacokinetic analysis revealed that JY-2 exhibited excellent oral bioavailability (98%), with little adverse effects. These results demonstrated that the novel FoxO1 inhibitor, JY-2, may exert beneficial anti-diabetic effects and that it warrants further investigation as a novel anti-diabetic drug candidate.

Discovery of a novel fibroblast activation protein (FAP) inhibitor, BR103354, with anti-diabetic and anti-steatotic effects.

Fibroblast growth factor (FGF) 21 is a class of hepatokines that plays a protective role against obesity, insulin resistance, and liver damage. Despite this, protective effects of FGF21 in human appear to be minimal, possibly due to its proteolytic cleavage by the fibroblast activation protein (FAP). Here, we presented a novel FAP inhibitor, BR103354, and described its pharmacological activities as a potential therapeutic agent for the treatment of metabolic disorders. BR103354 inhibited FAP with an IC50 value of 14 nM, showing high selectivity against dipeptidyl peptidase (DPP)-related enzymes and prolyl oligopeptidase (PREP). In differentiated 3T3/L1 adipocytes, the addition of FAP diminished hFGF21-induced Glut1 and phosphorylated levels of ERK, which were restored by BR103354. BR103354 exhibited good pharmacokinetic properties as evidenced by oral bioavailability of 48.4% and minimal hERG inhibition. Single co-administration of BR103354 with hFGF21 reduced nonfasting blood glucose concentrations, in association with increased intact form of hFGF21 in ob/ob mice. Additionally, chronic treatment of BR103354 for 4 weeks reduced nonfasting blood glucose concentrations with improved glucose tolerance and with reduced triglyceride (TG) content in liver of ob/ob mice. Consistently, BR103354 improved hepatic steatosis and fibrosis in a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced non-alcoholic steatohepatitis (NASH) mouse model. FAP inhibitory effects of BR103354 were confirmed in normal cynomolgus monkeys. Together, BR103354 acts as an effective FAP inhibitor in vitro and in vivo, thereby demonstrating its potential application as an anti-diabetic and anti-NASH agent.

Angiotensin AT1 receptor antagonism by losartan stimulates adipocyte browning via induction of apelin.

Adipocyte browning appears to be a potential therapeutic strategy to combat obesity and related metabolic disorders. Recent studies have shown that apelin, an adipokine, stimulates adipocyte browning and has negative cross-talk with angiotensin II receptor type 1 (AT1 receptor) signaling. Here, we report that losartan, a selective AT1 receptor antagonist, induces browning, as evidenced by an increase in browning marker expression, mitochondrial biogenesis, and oxygen consumption in murine adipocytes. In parallel, losartan up-regulated apelin expression, concomitant with increased phosphorylation of protein kinase B and AMP-activated protein kinase. However, the siRNA-mediated knockdown of apelin expression attenuated losartan-induced browning. Angiotensin II cotreatment also inhibited losartan-induced browning, suggesting that AT1 receptor antagonism-induced activation of apelin signaling may be responsible for adipocyte browning induced by losartan. The in vivo browning effects of losartan were confirmed using both C57BL/6J and ob/ob mice. Furthermore, in vivo apelin knockdown by adeno-associated virus carrying-apelin shRNA significantly inhibited losartan-induced adipocyte browning. In summary, these data suggested that AT1 receptor antagonism by losartan promotes the browning of white adipocytes via the induction of apelin expression. Therefore, apelin modulation may be an effective strategy for the treatment of obesity and its related metabolic disorders.

Author Correction: Telmisartan induces browning of fully differentiated white adipocytes via M2 macrophage polarization.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Clomiphene promotes browning of white adipocytes via casein kinase-2 inhibition.

Browning of white adipocytes is considered as a new strategy for the treatment of obesity and its related metabolic diseases. Based on the recent finding that casein kinase-2 (CK2) acts as a negative regulator of browning, new CK2 inhibitors were investigated as potential browning agents. This led to the identification of clomiphene as a candidate. Clomiphene was found to inhibit CK2 activity with an IC50 of 2.39 µM. Accordingly, clomiphene increased mRNA and protein expression of browning markers, including uncoupling protein-1 (UCP1) in 3T3-L1 white adipocytes and in murine primary adipocytes. In agreement with the increased expression of browning markers, reduced lipid droplets, increased oxygen consumption rates, and mitochondrial biogenesis were detected after clomiphene treatment. Furthermore, phosphorylation of histone deacetylase (HDAC) 1 and 2, downstream mediators of CK2 actions, was decreased by clomiphene. On the other hand, CK2 overexpression diminished clomiphene-induced mitochondrial biogenesis as well as expression of browning markers, suggesting that clomiphene-induced browning is related to its inhibition of CK2. In vivo administration of clomiphene increased the mRNA expression of browning markers in various adipose tissues, accompanied by reduced fat weights and body weights in mice. In summary, these data suggested that clomiphene induced the browning of white adipocytes via CK2 inhibition, which may implicate it as a new anti-obesity drug.

Telmisartan induces browning of fully differentiated white adipocytes via M2 macrophage polarization.

Telmisartan is a well-known anti-hypertensive drug acting as an angiotensin 2 receptor blocker (ARB), but it also possesses partial PPARγ agonistic activity and induces insulin sensitivity. In the present study, we investigated the effects of telmisartan on macrophage polarization in association with its browning capacity, because PPARγ plays a key role in M2 polarization and in the browning of white adipocytes. Telmisartan induced M2 marker expression in murine macrophages concentration dependently, which was confirmed by flow cytometry. Both PPARγ and PPARδ activations appear to be responsible for telmisartan-induced M2 polarization. Telmisartan-treated conditioned medium (Tel-CM) of RAW264.7 cells and of bone marrow derived macrophages (BMDM) induced the expressions of browning markers in fully differentiated white adipocytes with reduced lipid droplets, and increased oxygen consumption rate and mitochondrial biogenesis. Levels of catecholamines (CA) released into the conditioned medium as well as intracellular tyrosine hydroxylase (TH) mRNAs were found to be increased by telmisartan, and browning effects of Tel-CM were lessened by ß3 receptor antagonist (L-748,337), suggesting CA secreted into CM play a role in Tel-CM-induced adipocyte browning. Acute administration of telmisartan (2 weeks, p.o.) to C57BL/6J mice increased the expressions of browning markers and M2 markers in white adipose tissues, whereas macrophage depletion by clodronate liposome pretreatment attenuated the telmisartan-induced expressions of browning markers. Together, telmisartan was observed to induce the browning of fully differentiated white adipocytes, at least in part, via PPAR activation-mediated M2 polarization.

Foenumoside B isolated from Lysimachia foenum-graecum extract suppresses LPS-induced inflammatory response via NF-κB/AP-1 inactivation in murine macrophages and in endotoxin-induced shock model.

Foenumoside B (FSB), a bioactive component isolated from the Lysimachia foenum-graecum extract (LFE), has been shown to possess anti-inflammatory effects, but the underlying molecular mechanisms involved have not been elucidated. Accordingly, the authors investigated the mechanisms responsible for the anti-inflammatory effects of FSB in murine macrophages activated by LPS. FSB suppressed the LPS-induced expressions of iNOS and COX-2 at protein and mRNA levels and consequently decreased NO and PGE2 production in RAW264.7 and primary macrophages. FSB also reduced the LPS-induced inductions of TNF-α, IL-6 and IL-1ß at protein and mRNA levels. Studies of the molecular mechanisms involved in the anti-inflammatory effects of FSB showed that it inhibited the transcriptional activities of NF-κB and AP-1, and the nuclear translocation of NF-κB via inhibition of the phosphorylations of AKT, p38 and STAT3. In a sepsis model, pretreatment with FSB inhibited the LPS-stimulated mRNA and protein levels of proinflammatory mediators, such as, iNOS, COX-2, TNF-α, IL-6 and IL-1ß in plasma and liver. Importantly, FSB increased the survival rate of mice in the LPS-induced sepsis model. Taken together, these results show that the anti-inflammatory effects of FSB against LPS-induced inflammatory conditions are associated with inhibitions of the phosphorylations of AKT, p38 and STAT3 followed by the transcriptional suppressions of NF-κB and AP-1, and thus, reduced expressions of pro-inflammatory genes.

5-LO inhibition ameliorates palmitic acid-induced ER stress, oxidative stress and insulin resistance via AMPK activation in murine myotubes.

Leukotriene B4 (LTB4) production via the 5-lipoxygenase (5-LO) pathway contributes to the development of insulin resistance in adipose and hepatic tissues, but the role of LTB4 in skeletal muscle is relatively unknown. Here, the authors investigated the role of LTB4 in C2C12 myotubes in palmitic acid (PA)-induced ER stress, inflammation and insulin resistance. PA (750 µM) evoked lipotoxicity (ER stress, oxidative stress, inflammation and insulin resistance) in association with LTB4 production. 5-LO inhibition reduced all the lipotoxic effects induced by PA. On the other hand, PA did not induce cysteinyl leukotrienes (CysLTs), which themselves had no effect on ER stress and inflammation. The beneficial effects of 5-LO suppression from PA-induced lipotoxicity were related with AMPK activation. In ob/ob mice, once daily oral administration of zileuton (50, 100 mg/kg) for 5 weeks improved insulin resistance, increased AMPK phosphorylation, and reduced LTB4 and ER stress marker expression in skeletal muscle. These results show that 5-LO inhibition by either zileuton or 5-LO siRNA protects C2C12 myotubes from PA-induced lipotoxicity, at least partly via AMPK activation, and suggest that the in vivo insulin-sensitizing effects of zileuton are in part attributable to its direct action on skeletal muscle via LTB4 downregulation followed by AMPK activation.

Baicalein protects rat insulinoma INS-1 cells from palmitate-induced lipotoxicity by inducing HO-1.

OBJECTIVE: ß-Cell dysfunction plays a central role in the pathogenesis of type 2 diabetes (T2D), and the identification of novel approaches to improve ß-cell function is essential to treat this disease. Baicalein, a flavonoid originally isolated from the root of Scutellaria Baicalensis, has been shown to have beneficial effects on ß-cell function. Here, the authors investigated the molecular mechanism responsible for the protective effects of baicalein against palmitate (PA)-induced impaired ß-cell function, and placed focus on the role of heme oxygenase (HO)-1. METHODS: Rat pancreatic ß-cell line INS-1 cells or mouse pancreatic islets were cultured with PA (500 µM) to induce lipotoxicity in the presence or absence of baicalein (50 µM), and the expressions of the ER stress markers, ATF-3, CHOP and GRP78 were detected by Western blotting and/or qPCR. The involvement of HO-1 was evaluated by HO-1 siRNA transfection and using the HO-1 inhibitor ZnPP. RESULTS: Baicalein reduced PA-induced ER stress and inflammation and enhanced insulin secretion, and these effects were associated with the induction of HO-1. Furthermore, these protective effects were attenuated by ZnPP and by HO-1 siRNA. Pretreatment of PD98059 (an ERK inhibitor) significantly inhibited the protective effects of baicalein and blocked HO-1 induction. On the other hand, CO production by RuCO (a CO donor) ameliorated PA-induced ER stress, suggesting that CO production followed by HO-1 induction may contribute to the protective effects of baicalein against PA-induced ß-cell dysfunction. CONCLUSION: Baicalein protects pancreatic ß-cells from PA-induced ER stress and inflammation via an ERK-HO-1 dependent pathway. The authors suggest HO-1 induction in pancreatic ß-cells appears to be a promising therapeutic strategy for T2D.

Activating transcription factor-3 induction is involved in the anti-inflammatory action of berberine in RAW264.7 murine macrophages.

Berberine is an isoquinoline alkaloid found in Rhizoma coptidis, and elicits anti-inflammatory effects through diverse mechanisms. Based on previous reports that activating transcription factor-3 (ATF-3) acts as a negative regulator of LPS signaling, the authors investigated the possible involvement of ATF-3 in the anti-inflammatory effects of berberine. It was found berberine concentration-dependently induced the expressions of ATF-3 at the mRNA and protein levels and concomitantly suppressed the LPS-induced productions of proinflammatory cytokines (TNF-α, IL-6, and IL-1ß). In addition, ATF-3 knockdown abolished the inhibitory effects of berberine on LPS-induced proinflammatory cytokine production, and prevented the berberine-induced suppression of MAPK phosphorylation, but had little effect on AMPK phosphorylation. On the other hand, the effects of berberine, that is, ATF-3 induction, proinflammatory cytokine inhibition, and MAPK inactivation, were prevented by AMPK knockdown, suggesting ATF-3 induction occurs downstream of AMPK activation. The in vivo administration of berberine to mice with LPS-induced endotoxemia increased ATF-3 expression and AMPK phosphorylation in spleen and lung tissues, and concomitantly reduced the plasma and tissue levels of proinflammatory cytokines. These results suggest berberine has an anti-inflammatory effect on macrophages and that this effect is attributable, at least in part, to pathways involving AMPK activation and ATF-3 induction.

Suppression of Adipocyte Differentiation by Foenumoside B from Lysimachia foenum-graecum Is Mediated by PPARγ Antagonism.

Lysimachia foenum-graecum extract (LFE) and its active component foenumoside B (FSB) have been shown to inhibit adipocyte differentiation, but their mechanisms were poorly defined. Here, we investigated the molecular mechanisms responsible for their anti-adipogenic effects. Both LFE and FSB inhibited the differentiation of 3T3-L1 preadipocytes induced by peroxisome proliferator-activated receptor-γ (PPARγ) agonists, accompanied by reductions in the expressions of the lipogenic genes aP2, CD36, and FAS. Moreover, LFE and FSB inhibited PPARγ transactivation activity with IC50s of 22.5 µg/ml and 7.63 µg/ml, respectively, and showed selectivity against PPARα and PPARδ. Rosiglitazone-induced interaction between PPARγ ligand binding domain (LBD) and coactivator SRC-1 was blocked by LFE or FSB, whereas reduced NCoR-1 binding to PPARγ by rosiglitazone was reversed in the presence of LFE or FSB. In vivo administration of LFE into either ob/ob mice or KKAy mice reduced body weights, and levels of PPARγ and C/EBPα in fat tissues. Furthermore, insulin resistance was ameliorated by LFE treatment, with reduced adipose tissue inflammation and hepatic steatosis. Thus, LFE and FSB were found to act as PPARγ antagonists that improve insulin sensitivity and metabolic profiles. We propose that LFE and its active component FSB offer a new therapeutic strategy for metabolic disorders including obesity and insulin resistance.

Bortezomib attenuates palmitic acid-induced ER stress, inflammation and insulin resistance in myotubes via AMPK dependent mechanism.

Bortezomib is an anti-cancer agent that induces ER stress by inhibiting proteasomal degradation. However, the effects of bortezomib appear to be dependent on its concentration and cellular context. Since ER stress is closely related to type 2 diabetes, the authors examined the effects of bortezomib on palmitic acid (PA)-induced ER stress in C2C12 murine myotubes. At low concentrations (<20nM), bortezomib protected myotubes from PA (750µM)-induced ER stress and inflammation. Either tunicamycin or thapsigargin-induced ER stress was also reduced by bortezomib. In addition, reduced glucose uptake and Akt phosphorylation induced by PA were prevented by co-treating bortezomib (10nM) both in the presence or absence of insulin. These protective effects of bortezomib were found to be associated with reduced JNK phosphorylation. Furthermore, bortezomib-induced AMPK phosphorylation, and the protective effects of bortezomib were diminished by AMPK knockdown, suggesting that AMPK activation underlies the effects of bortezomib. The in vivo administration of bortezomib at nontoxic levels (at 50 or 200µg/kg, i.p.) twice weekly for 5weeks to ob/ob mice improved insulin resistance, increased AMPK phosphorylation, reduced ER stress marker levels, and JNK inhibition in skeletal muscle. The study shows that bortezomib reduces ER stress, inflammation, and insulin resistance in vitro and in vivo, and suggests that bortezomib has novel applications for the treatment of metabolic disorders.

Involvement of Prolyl Hydroxylase Domain Protein in the Rosiglitazone-Induced Suppression of Osteoblast Differentiation.

Rosiglitazone is a well-known anti-diabetic drug that increases insulin sensitivity via peroxisome proliferator-activated receptor γ (PPARγ) activation, but unfortunately it causes bone loss in animals and humans. A previous study showed that prolyl hydroxylase domain protein (PHD) plays a role in rosiglitazone-induced adipocyte differentiation. Based on the inverse relationship between adipocyte and osteoblast differentiation, we investigated whether PHD is involved in the effects of rosiglitazone on osteoblast differentiation. Rosiglitazone inhibited osteoblast differentiation in a concentration-dependent manner, and in parallel induced three PHD isoforms (PHD1, 2, and 3). PHD inhibitors and knockdown of each isoform prevented the inhibitory effects of rosiglitazone on osteoblast differentiation and increased the expression of Runx2, a transcription factor essential for osteoblastogenesis. MG-132, a proteasomal inhibitor also prevented the rosiglitazone-induced degradation of Runx2. Furthermore, both increased PHD isoform expressions and reduced osteoblast differentiation by rosiglitazone were prevented by PPARγ antagonists, indicating these effects were mediated via PPARγ activation. In vivo oral administration of rosiglitazone to female ICR mice for 8 weeks reduced bone mineral densities and plasma alkaline phosphatase (ALP) activity, and increased PHD expression in femoral primary bone marrow cells and the ubiquitination of Runx2. Together, this suggests that the rosiglitazone-induced suppression of osteoblast differentiation is at least partly induced via PPARγ-mediated PHD induction and subsequent promotion of the ubiquitination and degradation of Runx2.

Determination of a novel phosphodiesterase4 inhibitor, 3-[1-(3cyclopropylmethoxy-4-difluoromethoxybenzyl)-1H-pyrazol-3-yl]-benzoic acid (PDE-423) in rat plasma using liquid chromatography-tandem mass spectrometry.

A method for determining a novel phosphodiesterase-4 inhibitor, 3-[1-(3cyclopropylmethoxy-4-difluoromethoxybenzyl)-1H-pyrazol-3-yl]-benzoic acid (PDE-423), in rat plasma was developed and validated using liquid chromatography-tandem mass spectrometry for further pharmacokinetic study for development as a novel anti-asthmatic drug. PDE-423 in the concentration range of 0.02-10 µg/mL was linear with a correlation coefficient of >0.99, and the mean intra- and inter-assay precisions of the assay were 7.50 and 3.86%, respectively. The validated method was used successfully for a pharmacokinetic study of PDE-423 in rats.

Metformin suppresses lipopolysaccharide (LPS)-induced inflammatory response in murine macrophages via activating transcription factor-3 (ATF-3) induction.

Metformin, a well known antidiabetic agent that improves peripheral insulin sensitivity, also elicits anti-inflammatory actions, but its mechanism is unclear. Here, we investigated the mechanism responsible for the anti-inflammatory effect of metformin action in lipopolysaccharide (LPS)-stimulated murine macrophages. Metformin inhibited LPS-induced production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in a concentration-dependent manner and in parallel induction of activating transcription factor-3 (ATF-3), a transcription factor and member of the cAMP-responsive element-binding protein family. ATF-3 knockdown abolished the inhibitory effects of metformin on LPS-induced proinflammatory cytokine production accompanied with reversal of metformin-induced suppression of mitogen-activated protein kinase (MAPK) phosphorylation. Conversely, AMP-activated protein kinase (AMPK) phosphorylation and NF-κB suppression by metformin were unaffected by ATF-3 knockdown. ChIP-PCR analysis revealed that LPS-induced NF-κB enrichments on the promoters of IL-6 and TNF-α were replaced by ATF-3 upon metformin treatment. AMPK knockdown blunted all the effects of metformin (ATF-3 induction, proinflammatory cytokine inhibition, and MAPK inactivation), suggesting that AMPK activation by metformin is required for and precedes ATF-3 induction. Oral administration of metformin to either mice with LPS-induced endotoxemia or ob/ob mice lowered the plasma and tissue levels of TNF-α and IL-6 and increased ATF-3 expression in spleen and lungs. These results suggest that metformin exhibits anti-inflammatory action in macrophages at least in part via pathways involving AMPK activation and ATF-3 induction.