Smilax china Polyphenols Stimulate Browning via [Formula: see text]3-Adrenergic Receptor/AMP-Activated Protein Kinase [Formula: see text] Signaling Pathway in 3T3-L1 Adipocytes

The aim of this study is to investigate the molecular mechanism of Smilax china L. polyphenols (SCLPs) in enhancing lipid metabolism and stimulating browning to reduce lipid accumulation in 3T3-L1 adipocytes. SCLP treatment obviously decreased lipid content in a dose-dependent manner (10-40 μg/mL) in adipocytes. SCLP treatment cooperated with noradrenalin to increase lipolysis. SCLPs reduced the gene expressions of C/EBP[Formula: see text] and Ap2 and enhanced the expressions of ACO, CPT, pHSL/HSL, ATGL, and PKA in adipocytes. Furthermore, SCLPs increased mRNA and protein expressions of brown adipocyte-specific factors (UCP-1, PRDM16, PGC-1α, and PPARγ) and mRNA expressions of beige adipocyte-specific markers (CD137, Tbx1, and Tmem26) in 3T3-L1 adipocytes, as well as mitochondrial biogenesis genes (Nrf1 and Tfam). In addition, according to the immunofluorescence staining, the mitochondria number was increased by SCLP. Moreover, β3-AR or AMPK agonist synergistic SCLPs enhanced the expressions of UCP-1, PRDM16, and PGC-1α. While β3-AR or AMPK antagonist significantly decreased the expressions of these brown adipocyte-specific factors, SCLP treatment inhibited the effect of antagonist to improve the expression of UCP-1, PRDM16, and PGC-1α. These results indicated that SCLPs may regulate lipid metabolism and stimulate browning via the β3-AR/AMPKα signaling pathway. Thus, SCLPs likely have potential therapeutic effects on obesity.

DNA Damage in AML-12 Hepatocytes and 3T3-L1 Adipocytes Treated with Clopidogrel

BACKGROUND

Clopidogrel has been commonly prescribed as a selective P2Y12 receptor antagonist to reduce heart attack and stroke risk. Nearly 10 % of absorbed clopidogrel is metabolized by cytochrome P450 (CYP) enzymes in the liver to active forms and 90 % to inactive clopidogrel carboxylate by esterases.

OBJECTIVE

Since different forms of clopidogrel have cytotoxic potential, our aim was to determinate the effect of clopidogrel (7.5, 40 and 75µM) over DNA damage in adipocyte and hepatocytes. Material Methods: In the present study DNA damage was investigated by Comet analysis using 3T3-L1 adipocytes and Alpha Mouse 12 (AML-12) hepatocytes.

RESULTS

DNA fragmentation was found to be increased as a response to 7.5 µM, 40 µM and 75 µM clopidogrel treatment compared to non-treated control groups in AML-12 hepatocytes (p<0.01, p<0.001, p<0.01 respectively) and 3T3-L1 adipocytes (p<0.001, p<0.001 and p<0.001 respectively). DNA damage levels as a response to clopidogrel treatment was found to be higher in 3T3-L1 adipocytes than AML-12 hepatocytes. Also, DNA damage levels in adipocytes and hepatocytes were found to increase dose dependently for 7.5 and 40 μM clopidogrel whereas decreased as a response to 75 μM.

CONCLUSION

According to our results, clopidogrel results in more DNA damage in adipocytes than in hepatocytes. The molecular mechanism of clopidogrel genotoxicity need to be further investigated especially in adipose tissue.

EFFECTS OF EXENDIN-4 ON ENDOPLASMIC RETICULUM STRESS-MEDIATED INSULIN RESISTANCE IN 3T3-L1 ADIPOCYTES

Objective

Endoplasmic reticulum stress (ERS) is suspected as an important factor in the initiation of insulin resistance.

Aim

To explore the effects of exendin-4 (Ex-4) on the endoplasmic reticulum stress (ERS)-mediated insulin resistance in 3T3-L1 adipocytes. In our study, 3T3-L1 adipocytes were pre-treated with ERS inhibitors tauroursodeoxycholic acid (TUDCA), Ex-4 and an ERS inducer tunicamycin (TM) then induced insulin resistance. Glucose consumption of the adipocytes was measured. Western blots determined the protein levels of ERS markers and insulin signaling pathway.

Results

TM treatment reduced insulin-stimulated glucose consumption by 19.7% in 3T3-L1 adipocytes. This repression was blunted by 24h pre-treatment with TUDCA or Ex-4. Ex-4 augmented insulin-stimulated glucose consumption in adipocytes by 14.9%. Western blotting showed that TM treatment significantly increased the ER stress markers including p-IRE, p-JNK, p-PERK, p-eIF2a and ATF6 expression, whereas 24h pre-treatment of adipocytes with TUDCA or Ex-4 alleviated the ER stress. Ex-4 alleviates ERS-induced insulin resistance by upregulating the expression of phosphorylated Akt.

Conclusion

ERs mediates insulin resistance in 3T3-L1 adipocytes, and exendin-4 significantly improves this insulin resistance.

Increasing cAMP levels of preadipocytes by cyanidin-3-glucoside treatment induces the formation of beige phenotypes in 3T3-L1 adipocytes

Obesity is a serious health problem and a major risk factor for the onset of several diseases such as heart disease, diabetes, stroke and cancer. The conversion of white adipocytes to brown-like adipocytes, also called beige or brite adipocytes, by pharmacological and dietary compounds has gained attention as an effective treatment for obesity. Cyanidin-3-glucoside (Cy3G), a polyphenolic compound contained in black soybean, blueberry and grape, has several antiobesity effects. However, there are no reports on the role of Cy3G in the induction of differentiation of preadipocytes to beige adipocytes and corresponding phenotypes. Here, the formation of beige adipocyte phenotypes following treatment with Cy3G was evaluated using 3T3-L1 adipocytes. Cy3G induced phenotypic changes to white adipocytes, such as increased multilocular lipid droplets and mitochondrial content. Additionally, the expression of mitochondrial genes (TFAM, SOD2, UCP-1 and UCP-2), UCP-1 protein and beige adipocyte markers (CITED1 and TBX1) in 3T3-L1 adipocytes was increased by Cy3G. Furthermore, Cy3G promoted preadipocyte differentiation by up-regulating of C/EBPβ through the elevation of the intracellular cAMP levels. These results indicated that Cy3G elevates the intracellular cAMP levels, which induces beige adipocyte phenotypes. This is the first report on the effect of Cy3G on induction of differentiation of preadipocytes into beige adipocyte phenotypes.

Identification of differentially expressed proteins by treatment with PUGNAc in 3T3-L1 adipocytes through analysis of ATP-binding proteome

O-GlcNAc (2-acetamino-2-deoxy-β-D-glucopyranose), an important modification for cellular processes, is catalyzed by O-GlcNAc transferase and O-GlcNAcase. O-(2-acetamido-2-deoxy-D-glucopyranosylidene) amino-N-phenylcarbamate (PUGNAc) is a nonselective inhibitor of O-GlcNAcase, which increases the level of protein O-GlcNAcylation and is known to induce insulin-resistance in adipose cells due to uncharacterized targets of this inhibitor. In this study, using ATP affinity chromatography, we applied a targeted proteomic approach for identification of proteins induced by treatment with PUGNAc. For optimization of proteomic methods using ATP affinity chromatography, comparison of two cell lines (3T3-L1 adipocytes and C2C12 myotubes) and two different digestion steps was performed using four different structures of immobilized ATP-bound resins. Using this approach, based on DNA sequence homologies, we found that the identified proteins covered almost half of ATP-binding protein families classified by PROSITE. The optimized ATP affinity chromatography approach was applied for identification of proteins that were differentially expressed in 3T3-L1 adipocytes following treatment with PUGNAc. For label-free quantitation, a gel-assisted method was used for digestion of the eluted proteins, and analysis was performed using two different MS modes, data-independent (671 proteins identified) and data-dependent (533 proteins identified) analyses. Among identified proteins, 261 proteins belong to nucleotide-binding proteins and we focused on some nucleotide-binding proteins, ubiquitin-activation enzyme 1 (E1), Hsp70, vasolin-containing protein (Vcp), and Hsp90, involved in ubiquitin-proteasome degradation and insulin signaling pathways. In addition, we found that treatment with PUGNAc resulted in increased ubiquitination of proteins in a time-dependent manner, and a decrease in both the amount of Akt and the level of phosphorylation of Akt, a key component in insulin signaling, through downregulation of Hsp90. In this study, based on a targeted proteomic approach using ATP affinity chromatography, we found four proteins related to ubiquitination and insulin signaling pathways that were induced by treatment with PUGNAc. This result would provide insight into understanding functions of PUGNAc in 3T3-L1 cells.