Takashi Sakai

Division of Molecular Pathophysiology

Research Summary

We aim to reveal pathways to lead diseases associated with stresses induced by nutrition intake.

In order to approach the goal, we developed several materials including Nucling gene deficiency (Knockout) mice and cells. Nucling is a proapoptotic protein that regulates the Apaf-1-procaspase-9 apoptosome and nuclear factor-kappa B (NF-κB) signaling pathways. We have found that the metabolic homeostasis or redox balance may be impaired in Nucling-KO mice.

1. Development of novel carcinogenicity prediction system applying Nucling gene deficient mice
we observed spontaneous fatty change development in liver with or without HCC in aged Nucling gene deficient(=knockout, KO) mice. We also found significantly high levels of serum cholesterol in Nucling-KO mice. In addition, we demonstrated that DEN treatment induced steatohepatitis at early stages followed by the development of HCC at late stages more efficiently in Nucling-KO mice than in wild-type mice.

2. Elucidation of the onset of inflammatory diseases including NAFLD, HCC and diabetes mellitus.
We focus on the possibility of steatohepatitis as a preliminary step of tumor initiation, since we observed spontaneous fatty change development in liver with or without HCC in aged Nucling-KO mice. Nonalcoholic fatty liver disease (NAFLD) is defined by liver fat content>5–10% by weight in the absence of excess alcohol consumption or any other liver disease. In spite of the presence of many indirect associations, a clear-cut link between NAFLD and abnormal β-cell function in type II diabetes (T2DM) is yet to be reported. One of the most important points to prove what is considered a likely causative relationship between NAFLD and T2DM is to elucidate the transcriptional regulation of insulin. In general NAFLD shows insulin tolerance and hyperinsulinemia. Hyperinsulinemia is likely to be the consequence rather than a cause of NAFLD, though its mechanism is still unknown. On the other hand, whether hyperinsulinemia is cause or consequence in T2DM is a vital and controversial issue. In addition, late stage of T2DM tend to show hypoinsulinemia, which mechanism is not clarified.

Selected Papers
1) Nucling, a novel apoptosis-associated protein, controls mammary gland involution by regulating NF-κB and STAT3. Dang HV, Sakai T, Pham TA, Tran DH, Yorita K, Shishido Y, Fukui K. J Biol Chem., 290: 24626-24635, 2015.
2) Identification of DNA-binding proteins that interact with the 5'-flanking region of the human d-amino acid oxidase gene by pull-down assay coupled with two-dimensional gel electrophoresis and mass spectrometry. Tran DH, Shishido Y, Chung SP, Trinh HT, Yorita K, Sakai T, Fukui K. J Pharm Biomed Anal., 2015 Feb 23. pii: S0731-7085(15)00127-2.
3) Identification of two promoters for human D-amino acid oxidase gene: implication for the differential promoter regulation mediated by PAX5/PAX2. Tran DH, Shishido Y, Chung SP, Trinh HT, Yorita K, Sakai T, Fukui K. J Biochem., 157(5):377-387, 2015.
4) Nucling, a novel protein associated with NF-κB, regulates endotoxin-induced apoptosis in vivo. Kim SM, Sakai T, Dang HV, Tran NH, Ono K, Ishimura K, Fukui K. J Biochem. 153(1):93-101, 2013.
5) D-Amino acid oxidase-induced oxidative stress, 3-bromopyruvate and citrate inhibit angiogenesis, exhibiting potent anticancer effects. Sakai T, Fukui Ket al. J. Bioenerg. Biomembr. 44 (5): 513-523, 2012.
6) D-amino acid oxidase gene therapy sensitizes glioma cells to the antiglycolytic effect of 3-bromopyruvate. Sakai T, Fukui K et al. Cancer gene ther 19(1):1-18, 2012.
7) 3-Bromopyruvate antagonizes effects of lactate and pyruvate, synergizes with citrate and exerts novel anti-glioma effects. Sakai T, Fukui K. J Bioenerg Biomembr 44(1): 61-79, 2012.
8) The role of kupffer cells in carbon tetrachloride intoxication in mice. Sakai T, Fukui K et all. Biol Pharm Bull. 35(6):980-983, 2012.
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