Hyung-Bok Jeong

Petalonia improves glucose homeostasis in streptozotocin-induced diabetic mice

The anti-diabetic potential of Petalonia binghamiae extract (PBE) was evaluated in vivo. Dietary administration of PBE to streptozotocin (STZ)-induced diabetic mice significantly lowered blood glucose levels and improved glucose tolerance. The mode of action by which PBE attenuated diabetes was investigated in vitro using 3T3-L1 cells. PBE treatment stimulated 3T3-L1 adipocyte differentiation as evidenced by increased triglyceride accumulation. At the molecular level, peroxisome proliferator-activated receptor gamma (PPARgamma) and terminal marker protein aP2, as well as the mRNA of GLUT4 were up-regulated by PBE. In mature adipocytes, PBE significantly stimulated the uptake of glucose and the expression of insulin receptor substrate-1 (IRS-1). Furthermore, PBE increased PPARgamma luciferase reporter gene activity in COS-1 cells. Taken together, these results suggest that the in vivo anti-diabetic effect of PBE is mediated by both insulin-like and insulin-sensitizing actions in adipocytes.

Molecular characterization and transcriptional analysis of non-mammalian type Toll like receptor (TLR21) from rock bream (Oplegnathus fasciatus).

Toll-like receptors (TLRs) are a large family of pattern recognition receptors, which are involved in triggering host immune responses against various pathogens by detecting their evolutionarily conserved pathogen associated molecular patterns (PAMPs). TLR21 is a non-mammalian type TLR, which recognizes unmethylated CpG DNA, and is considered as a functional homolog of mammalian TLR9. In this study, we attempted to identify and characterize a novel TLR21 counterpart from rock bream (Oplegnathus fasciatus) designated as RbTLR21, at molecular level. The complete coding sequence of RbTLR21 was 2919bp in length, which encodes a polypeptide of 973 amino acids with a predicted molecular mass of 112kDa and a theoretical isoelectric point of 8.6. The structure of the deduced RbTLR21 protein is similar to that of the members of typical TLR family, and includes the ectodomain, which consists of 16 leucine rich repeats (LRRs), a transmembrane domain, and a cytoplasmic Toll/interleukin-1 receptor (TIR) domain. According to the pairwise sequence analysis data, RbTLR21 was homologous to that of the orange-spotted grouper (Epinephelus coioides) with 76.9% amino acid identity. Furthermore, our phylogenetic analysis revealed that RbTLR21 is closely related to E. coioides TLR21. The RbTLR21 was ubiquitously expressed in all the tissues tested, but the highest expression was found in spleen. Additionally, upon stimulation with Streptococcus iniae, rock bream iridovirus (RBIV), and Edwardsiella tarda, RbTLR21 mRNA was significantly up-regulated in spleen tissues. Collectively, our findings suggest that RbTLR21 is indeed an ortholog of the TLR21 family and may be important in mounting host immune responses against pathogenic infections.

Masculinization in juvenile longtooth grouper, Epinephelus bruneus, with aromatase inhibitor: changes in GtH subunit mRNA expression and steroids hormone levels

Abstract We investigated the effects of fadrozol, an aromatase inhibitor (AI), and 17α-methyltestosterone (MT) on the induction of sex change in juvenile longtooth grouper Epinephelus bruneus, via histological observation of gonads. Changes in the mRNA expression of GtH subunits (FSH-β and LH-β) in the pituitary, and estradiol-17β (E2) and 11-ketotestosterone (11-KT) levels in the blood were also surveyed after AI and MT treatment. Juvenile longtooth groupers (113±17 g body weight; 16.2±1.2 cm body length) received intramuscular injections of AI at 3 (3-AI) and 5 (5-AI) mg/kg BW doses and MT at a 5 mg/kg BW (5-MT) dose. At week 7 post-injection, 3-AI and 5-MT oocytes were degenerated, and gonads of the 5-AI group initiated spermatogenesis. At week 21 post-injection, 3-AI- and 5-MT-treated gonads contained spermatogonia and spermatocytes, while 5-AI treatment induced advanced stages of spermatogenesis. The serum E2 level showed no significant differences throughout the experimental period, whereas that of 11-KT was significantly elevated in the 5-AI group at weeks 7 and 21 post-injection. A significant increase in the expression of FSH-β mRNA was evident in the 5-AI group at week 21 post-injection. In contrast, LH-β mRNA expression did not significantly differ among groups during the experimental period. These results imply that sex change has two stages in the longtooth grouper. In the first stage, oocytes are degenerated by the stimulation by 11-KT, and in the second stage spermatogenesis occurs, owing to the co-effects of 11-KT and FSH-β.

Molecular cloning of GnRH1 gene and GTH cDNAs of the protogynous longtooth grouper, Epinephelus bruneus

In teleosts, gonadotropin-releasing hormone (GnRH) and gonadotropin hormone (GTH) play important roles in regulating gonadal development and maturation. In Southeast Asia, the longtooth grouper, Epinephelus bruneus, is a commercially important aquaculture fish. In this study, we cloned and characterized the longtooth grouper GnRH1 gene and cDNAs of three gonadotropin subunits (GTHα, FSHβ, LHβ). The GnRH1 gene of longtooth grouper was 4, 032 bp long, and contained four exons, 61, 151, 99, and 423 bp long. GTHα, FSHβ, and LHβ cDNAs were 509, 576, and 579 bp, respectively. Phylogenetic and Southern hybridization analyses revealed that the longtooth grouper GTH subunits were evolutionarily close to those of groupers and are one-copy genes. RT-PCR analyses showed that GTH subunit mRNAs were expressed at a higher level in the pituitary glands of immature fish than in those of mature fish, suggesting a role in gonadal maturation.