Wogonin suppresses osteopontin expression in adipocytes by activating PPARα

Abstract

Aim: Wogonin (5,7-dihydroxy-8-methoxyflavone), a major bioactive compound of the flavonoid family, is commonly extracted from the traditional Chinese medicine Scutellaria baicalensis and possesses antioxidant and anti-inflammatory activities and is assumed to have anti-diabetes function. Indeed, a current study has shown that it can possibly treat metabolic disorders such as those found in db/db mice. However, the underlying molecular mechanism remains largely unclear. The aim of this study was to investigate the impact of wogonin on osteopontin (OPN) expression in adipose tissue from type 1 diabetic mice and in 3T3-L1 adipocytes. Methods: Type 1 diabetes was induced by streptozotocin (STZ) injection. 3T3-L1 preadipocytes were converted to 3T3-L1 adipocytes through treatment with insulin, dexamethasone, and 3-isobutyl-1-methylxanthine (IBMX). Western blot analysis and RT-PCR were performed to detect protein expression and mRNA levels, respectively. Results: Wogonin treatment suppressed the increase in serum OPN levels and reduced OPN expression in adipose tissue from STZinduced type 1 diabetic mice. Administration of wogonin enhanced PPARα expression and activity. Silencing of PPARα diminished the inhibitory effects of wogonin on OPN expression in 3T3-L1 adipocytes. Furthermore, the levels of c-Fos and phosphorylated c-Jun were reduced in wogonin-treated adipose tissue and 3T3-L1 adipocytes. In addition, wogonin treatment dramatically mitigated p38 MAPK phosphorylation. Pharmacological inhibition of p38 MAPK by its specific inhibitor SB203580 increased PPARα activity and decreased OPN expression. Conclusion: Our results suggest that wogonin downregulated OPN expression in adipocytes through the inhibition of p38 MAPK and the sequential activation of the PPARα pathway. Given the adverse effects of high OPN levels on metabolism, our results provide evidence for the potential administration of wogonin as a treatment for diabetes.

APPL1-Mediating Leptin Signaling Contributes to Proliferation and Migration of Cancer Cells

“…The levels of APPL1 were determined by western blot using specific anti-APPL1 antibody. Phosphoprotein bands were scan by fluorescence at 532 nm [23, 24]. …”

Wogonin enhances intracellular adiponectin levels and suppresses adiponectin secretion in 3T3-L1 adipocytes

“…Wogonin has been proved to improve hyperglycemia in db/db and STZ-induced diabetic mice [27,28]. Our findings suggest that the beneficial metabolic effects of wogonin may be independent on adiponectin levels whereas attributes to its anti-inflammatory and anti-oxidative abilities.…”

“…The cells were washed with modified Eagle's medium without phenol red and and anti-inflammatory activities and has been explored for the prevention and treatment of several diseases including cancer, liver and lung injuries, neurodegenerative diseases, and inflammatory diseases [23][24][25]. Currently, wogonin was found to inhibit high glucose-induced vascular inflammation in vitro and in vivo [26], mitigate hyperglycemia in db/db mice and STZ-induced diabetic mice [27,28], and ameliorate dyslipidemia in db/db mice [27], indicating a beneficial effect on diabetes and diabetes-related diseases. Interestingly, wogonin-treated db/db mice displays higher adiponectin levels in white adipose tissues as compared with control mice [27], suggesting that wogonin may regulate adiponectin generation.…”

“…3T3-L1 differentiation was performed as our previously described [28,29]. In To quantify different molecular weight fractions of adiponectin, the cell lysates were subjected to 2-15% SDS-PAGE under non-reducing and non-heat-denaturing conditions.…”

“…Western blot was performed as our previously described protocol [6,7,28,29]. Briefly, 3T3-L1 adipocytes were lysed in lysis buffer containing 50 mmol/L HEPES, pH 7.6, 150 mmol/L NaCl, 1% Triton X-100, 10 mmol/L NaF, 20 mmol/L sodium pyrophosphate, 20 mmol/L β-glycerol phosphate, 1 mmol/L sodium orthovanadate, 10 μg/mL leupeptin, 10 μg/mL aprotinin, and 1 mmol/L phenylmethanesulfonyl fluoride.…”