Analysis of regulatory mechanisms of an insulin-inducible SHARP-2 gene by (S)-Equol.
Small compounds that activate the insulin-dependent signaling pathway have potential therapeutic applications in controlling type 2 diabetes mellitus. The rat enhancer of split- and hairy-related protein-2 (SHARP-2) is an insulin-inducible transcription factor that decreases expression of the phosphoenolpyruvate carboxykinase gene, a gluconeogenic enzyme gene. In this study, we screened for soybean isoflavones that can induce the rat SHARP-2 gene expression and analyzed their mechanism(s). Genistein and (S)-Equol, a metabolite of daidzein, induced rat SHARP-2 gene expression in H4IIE rat hepatoma cells. The (S)-Equol induction was mediated by both the phosphoinositide 3-kinase- and protein kinase C (PKC)-pathways. When a dominant negative form of atypical PKC lambda (aPKCλ) was expressed, the induction of SHARP-2 mRNA level by (S)-Equol was inhibited. In addition, Western blot analyses showed that (S)-Equol rapidly activated both aPKCλ and classical PKC alpha. Furthermore, the (S)-Equol induction was inhibited by treatment with a RNA polymerase inhibitor or a protein synthesis inhibitor. Finally, a reporter gene assay revealed that the transcriptional stimulation by (S)-Equol was mediated by nucleotide sequences located between -4687 and -4133 of the rat SHARP-2 gene. Thus, we conclude that (S)-Equol is an useful dietary supplement to control type 2 diabetes mellitus.
Department of Health and Nutritional Science, Faculty of Human Health Science, Matsumoto University, 2095-1 Niimura, Matsumoto, Nagano 390-1295, Japan.
Ayumi
A
Haneishi
Katsuhiro
K
Takagi
Kosuke
K
Asano
Taichi
T
Yamamoto
Takashi
T
Tanaka
Soichiro
S
Nakamura
Tamio
T
Noguchi
Kazuya
K
Yamada
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D060754:Equol / Q000378:metabolism / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D018398:Homeodomain Proteins / Q000235:genetics*; D007328:Insulin / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D007529:Isoflavones / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013025:Glycine max / Q000737:chemistry; D014158:Transcription, Genetic / Q000187:drug effects; D000099293:Protein Kinase C-lambda
D051792:Basic Helix-Loop-Helix Proteins; D060754:Equol; D018398:Homeodomain Proteins; D007328:Insulin; D007527:Isoenzymes; D007529:Isoflavones; D011493:Protein Kinase C; D012333:RNA, Messenger; D000099293:Protein Kinase C-lambda; C491538:Bhlhe40 protein, rat; C004742:daidzein