title: Identification of cysteinylated transthyretin, a predictive biomarker of treatment response to partially hydrolyzed guar gum in type 2 diabetes rats, by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry.
abstract: Recent evidence has indicated that total fiber intake is inversely related to type 2 diabetes risk. The present study aimed to investigate the effects of chronic administration of partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber, on the occurrence of diabetes and its complications, fatty liver and nephropathy. We also identified predictive serum biomarkers of treatment response to PHGG by mass spectroscopy-based proteomic analysis using Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a good model of human non-insulin-dependent diabetes mellitus. In this study, at 5 weeks of age, OLETF rats and control strain Long-Evans Tokushima Otsuka (LETO) rats were fed a control diet or a high-fiber diet (5% PHGG) for 57 weeks. Body weight, food intake, oral glucose tolerance test, plasma insulin levels, and urine glucose and protein levels were regularly measured. Oral glucose tolerance tests (OGTT) and storage of serum in a deep freezer were conducted at the beginning of the experiment and every 4 weeks after overnight fasting during the experiments. PHGG treatment affected neither meal patterns nor the body weight of OLETF and LETO rats. Repeated measure analysis of variance revealed significant differences in fasting plasma glucose and plasma glucose at 2 h after OGTT between control OLETF (OLETF-C) rats and OLETF rats treated with PHGG (OLETF-F). The glucose response determined by the area under the curve of OGTT was significantly greater in OLETF-C rats than that in OLETF-F rats at 25 weeks of age. HOMA-IR, an index of insulin resistance, increased at 25 weeks of age in OLETF-C rats, while this increase was significantly inhibited in OLETF-F rats. At 62 weeks of age, PHGG treatment significantly improved hepatic steatosis as well as renal mesangial matrix accumulation in OLETF rats. To identify the risk marker for diabetes mellitus by SELDI-TOF MS, we collected sera from 21-week-old individuals. Among the 12 specific peaks that were risk marker candidates for diabetes mellitus, the m/z 13,720 peak was identified as that of cysteinylated transthyretin by sequencing of four tryptic peptides using tandem mass spectrometry and peak distribution around the m/z 13,720 peak in the SELDI-TOF spectra. In conclusion, we found that chronic treatment with PHGG improved insulin resistance, delayed the onset of diabetes, and inhibited the development of diabetic complications, as well as identified cysteinylated transthyretin as a predictive biomarker of treatment response to PHGG in OLETF rats.
authors.affiliation: Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Naito
authors.affiliation: Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto 610-0321, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ichikawa
authors.affiliation: Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Satomi
authors.initials: S
authors.lastname: Akagiri
authors.affiliation: Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Uchiyama
authors.affiliation: Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Takagi
authors.affiliation: Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Handa
authors.affiliation: Nutrition Division, Taiyo Kagaku Co., Ltd., 1-3 Takaramachi, Yokkaichi, Mie 510-0844, Japan.
authors.forename: Zenta
authors.initials: Z
authors.lastname: Yasukawa
authors.affiliation: Nutrition Division, Taiyo Kagaku Co., Ltd., 1-3 Takaramachi, Yokkaichi, Mie 510-0844, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Tokunaga
authors.affiliation: Nutrition Division, Taiyo Kagaku Co., Ltd., 1-3 Takaramachi, Yokkaichi, Mie 510-0844, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ishihara
authors.affiliation: Nutrition Division, Taiyo Kagaku Co., Ltd., 1-3 Takaramachi, Yokkaichi, Mie 510-0844, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Okubo
authors.affiliation: Biomarker Science Co., Ltd., 103-5 Tanaka-Monzencho, Sakyo-ku, Kyoto 540-0029, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Mukai
authors.affiliation: Biomarker Science Co., Ltd., 103-5 Tanaka-Monzencho, Sakyo-ku, Kyoto 540-0029, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ohki
authors.affiliation: Biomarker Science Co., Ltd., 103-5 Tanaka-Monzencho, Sakyo-ku, Kyoto 540-0029, Japan.
authors.forename: Kagehiro
authors.initials: K
authors.lastname: Uchida
authors.affiliation: Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Yoshikawa
keywords: biomarker; cysteinylation; diabetes mellitus; dietary fiber; transthyretin