Up-regulation of amino acid transporter SLC6A19 activity and surface protein abundance by PKB/Akt and PIKfyve

Background: The amino acid transporter B0AT1 (SLC6A19) accomplishes concentrative cellular uptake of neutral amino acids. SLC6A19 is stimulated by serum- & glucocorticoid-inducible kinase (SGK) isoforms. SGKs are related to PKB/Akt isoforms, which also stimulate several amino acid transporters. PKB/Akt modulates glucose transport in part by phosphorylating and thus activating phosphatidylinositol-3-phosphate-5-kinase (PIKfyve), which fosters carrier protein insertion into the cell membrane. The present study explored whether PKB/Akt and/or PIKfyve stimulate SLC6A19. Methods: SLC6A19 was expressed in Xenopus oocytes with or without wild-type PKB/Akt or inactive T308A/S473APKB/Akt without or with additional expression of wild-type PIKfyve or PKB/Akt-resistant S318APIKfyve. Electrogenic amino acid transport was determined by dual electrode voltage clamping. Results: In SLC6A19-expressing oocytes but not in water-injected oocytes, the addition of the neutral amino acid L-leucine (2 mM) to the bath generated a current (Ile), which was significantly increased following coexpression of PKB/Akt, but not by coexpression of T308A/S473APKB/Akt. The effect of PKB/Akt was augmented by additional coexpression of PIKfyve but not of S318APIKfyve. Coexpression of PKB/Akt enhanced the maximal transport rate without significantly modifying the affinity of the carrier. The decline of Ile following inhibition of carrier insertion by brefeldin A (5 µM) was similar in the absence and presence of PKB/Akt indicating that PKB/Akt stimulated carrier insertion into rather than inhibiting carrier retrieval from the cell membrane. Conclusion: PKB/Akt up-regulates SLC6A19 activity, which may foster amino acid uptake into PKB/Akt-expressing epithelial and tumor cells

Protective Effects of Hydro-alcoholic Extract of Apium Graveolens on Carbon Tetrachloride Induced Hepatotoxicity in Sprague-Dawley male Rats

Background & Objective: Apium graveolens has antioxidant property because of its flavonoid compounds. In the present study, we investigated the hepatoprotective effects of hydroalcoholic extract of Apium graveolens in Sprague Dawley male rats treated with carbon tetrachloride (CCl4).Materials & Methods: In this study, 48 rats (weighted 180-200 gram) were divided into six groups each having eight rats. The six groups were control, sham, CCl4, and three experimental groups. The experimental groups (4-6) received 1ml/kg CCl4 twice a week and olive oil with the ratio of 1:1 by intraperitoneal injection for 40 days. In addition, they received 2 cc hydroalcoholic extract of Apium graveolens by daily gavage with the concentrations of 200, 400, and 600 mg/kg/cc, respectively. The sham group received only olive oil with the mentioned ratio and the other group received CCl4 and olive oil. At the end, Alkaline Phosphatase (ALP), Aspartate amino Transferase (AST), Alanine amino Transferase (ALT), and the serum concentrations of albumin, total and direct bilirubin were measured and analyzed by using statistical ANOVA Test. Results: Injection of CCl4 increased the serum levels of liver enzymes and total and direct bilirubin but it decreased the concentration of serum albumin. On the other hand, hydroalcoholic extract of Apium graveolens decreased the liver enzymes and increased albumin level (p<0.001). Conclusion: The results of this study reveals that the consumption of hydro-alcoholic extract of Apium graveolens maintain the integrity of the liver and protects it against damage