Jeong-Heon Cha

Gallic acid improves glucose tolerance and triglyceride concentration in diet-induced obesity mice

Abstract Gallic acid, a phenolic phytochemical, has been shown to exert a variety of effects, including anti-oxidative, anti- carcinogenic, anti-allergic, and anti-inflammatory effects. In this study, we attempted to determine whether gallic acid affects metabolic syndrome such as obesity and diabetes. Diet-induced obesity mice were treated intraperitoneally once per day with gallic acid (10 mg/kg/day). After 2 weeks of treatment, the mice were sacrificed to collect the blood for metabolic parameter assessments, and the adipose tissues and liver to weigh and analyze. The triglyceride concentrations were significantly improved in the gallic acid group relative to those measured in the control group. And most importantly, the blood glucose concentrations in the gallic acid group were significantly improved. In the epididymal white adipose tissue of the gallic acid group, adipocyte size was reduced, PPARγ expression was induced, and the Akt signaling pathway was activated. Our results demonstrate that gallic acid improves glucose tolerance and lipid metabolism in the obesity mice, thereby showing evidence of anti-hyperglycemic activity. The findings of an upregulation of PPARγ expression and Akt activation also contribute to our current understanding of the mechanisms underlying the effects of gallic acid on glucose metabolism.

Effect of the interaction between periodontitis and type 1 diabetes mellitus on alveolar bone, mandibular condyle and tibia.

Abstract Objective. This study examined the effect of the interaction between periodontitis and type 1 diabetes mellitus on alveolar bone, mandibular condyle and tibia in animal models. Materials and methods. Rats were divided into normal, periodontitis, diabetic and diabetic with periodontitis groups. After injection of streptozotocin to induce diabetes, periodontitis was induced by ligation of both lower-side first molars for 30 days. Alveolar bone loss and trabecular bone volume fraction (BVF) of the mandibular condyle and tibia were estimated via hematoxylin and eosin staining and micro-computed tomography, respectively. Osteoclastogenesis of bone marrow cells isolated from tibia and femur was assayed using tartrate-resistant acid phosphatase staining. Results. The cemento-enamel junction to the alveolar bone crest distance and ratio of periodontal ligament area in the diabetic with periodontitis group were significantly increased compared to those of the periodontitis group. Mandibular condyle BVF did not differ among groups. The BVF of tibia in the diabetic and diabetic with periodontitis groups was lower than that of the normal and periodontitis groups. Osteoclastogenesis of bone marrow cells in the diabetic groups was higher than that in the non-diabetic groups. However, the BVF of tibia and osteoclastogenesis in the diabetic with periodontitis group were not significantly different than those in the diabetic group. Conclusions. Type 1 diabetes mellitus aggravates alveolar bone loss induced by periodontitis, but periodontitis does not alter the mandibular condyle and tibia bone loss induced by diabetes. Alveolar bone, mandibular condyle and tibia may have different responses to bone loss stimuli in the diabetic environment.

Helicobacter pylori-Induced HB-EGF Upregulates Gastrin Expression via the EGF Receptor, C-Raf, Mek1, and Erk2 in the MAPK Pathway

Helicobacter pylori is associated with hypergastrinemia, which has been linked to the development of gastric diseases. Although the molecular mechanism is not fully understood, H. pylori is known to modulate the Erk pathway for induction of gastrin expression. Herein we found that an epidermal growth factor (EGF) receptor kinase inhibitor significantly blocked H. pylori-induced gastrin promoter activity, suggesting involvement of EGF receptor ligands. Indeed, H. pylori induced mRNA expression of EGF family members such as amphiregulin, EGF, heparin-binding EGF-like growth factor (HB-EGF), and transforming growth factor-α. Of these, specific siRNA targeting of HB-EGF significantly blocked H. pylori-induced gastrin expression. Moreover, H. pylori induced HB-EGF ectodomain shedding, which we found to be a critical process for H. pylori-induced gastrin expression. Thus, we demonstrate a novel role for human mature HB-EGF in stimulating gastrin promoter activity during H. pylori infection. Further investigation using specific siRNAs targeting each isoform of Raf, Mek, and Erk elucidated that the mechanism underlying H. pylori-induced gastrin expression can be delineated as the sequential activation of HB-EGF, the EGF receptor, C-Raf, Mek1, and the Erk2 molecules in the MAPK pathway. Surprisingly, whereas Erk2 acts as a potent activator of gastrin expression, siRNA knockdown of Erk1 induced gastrin promoter activity, suggesting that Erk1 typically acts as a repressor of gastrin expression. Elucidation of the mechanism of gastrin modulation by HB-EGF-mediated EGF receptor transactivation should facilitate the development of therapeutic strategies against H. pylori-related hypergastrinemia and consequently gastric disease development, including gastric cancers.

Crystal structure of CagL from Helicobacter pylori K74 strain.

Helicobacter pylori (Hp) CagL is a component of the type IV secretion system (T4SS) and interacts with integrin in host cells through its flexible RGD domain to translocate CagA. Differences in CagL amino acid polymorphisms between Western and East-Asian Hps are correlated with clinical outcome. CagL of East-Asian clinical Hp isolate K74 (CagL(K74)) contains multiple residue variations upstream of RGD motif and has different integrin binding affinities compared to those of CagL from Western Hp 26695. Here, we report the crystal structure of CagL(K74). The structure displayed a six-helix bundle including two short α-helices, and the RGD motif was found in the long rigid α2 helix flanked by the conserved protease-sensitive and RGD-helper sequences, as observed in CagL(26695). However, two additional salt bridges were found between the helices compared with the CagL(26695) structure, suggesting that the putative flexible region harboring the RGD motif may be more stable in this CagL variant.