九州大学-研究者情報 [溝上顕子 (准教授) 歯学研究院歯学部門]

骨を用いたメタボリックシンドローム予防効果を有する食品素材の開発
2013.08～2014.03, 代表者：松田　美穂, 九州大学, 九州大学（日本）
骨の細胞が作るオステオカルシン(OC)はインスリン分泌を促し、全身の代謝を活性化するとことで注目されている。また、消化管ホルモンの1つであるインクレチンは新しい作用機序をもつ糖尿病治療薬として近年注目を集めている。OCは、インクレチンの一種であるグルカゴン様ペプチド-1（GLP-1）の分泌を促し、相互に関連して糖代謝に働きかけることが明らかになった。通常、骨に多く存在するGla型OC(GlaOC)を注射しても代謝活性化に無効であるが、経口投与すると効果が現れる。本研究課題では、入手が容易でGlaOCを豊富に含む骨基質成分を食品素材として実用化し、メタボリックシンドロームの予防への応用を目指す。.

研究業績

主要原著論文

全てを見る→

1.	Kayo Mori, Akiko Mizokami, Tomomi Sano, Satoru Mukai, Fumitaka Hiura, Yasunori Ayukawa, Kiyoshi Koyano, Takashi Kanematsu, Eijiro Jim, RANKL elevation activates NIK/NF-κB pathway, inducing obesity in ovariectomized mice, Journal of Endocrinology, https://doi.org/10.1530/JOE-21-0424, 2022.04, Menopausal women are susceptible to visceral obesity, which increases the risk of metabolic disorders. However, the mechanisms of menopause-induced visceral fat accumulation are not fully understood. Circulating levels of receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL) are elevated in an animal model of menopause. RANKL, a multifunctional cytokine, activates the NF-κB pathway, which serves as a pivotal mediator of inflammatory responses. Here, we investigated whether RANKL-induced non-canonical NF-κB pathway activation induces inflammation and lipid accumulation in adipose tissues. RANKL induced Tnfa expression via the non-canonical NF-κB pathway in bone marrow cells. We therefore analyzed aly/aly mice, in which the non-canonical NF-κB pathway is not activated, owing to an inactive form of NF-κB-inducing kinase. A postmenopausal obesity model was generated by ovariectomy and subsequent high-fat and high-sucrose diet feeding. In aly/aly mice with postmenopausal obesity, serum RANKL levels were elevated, and hepatic lipid accumulation and adipocyte hypertrophy were suppressed, resulting in reduced macrophage infiltration and inflammatory cytokine mRNA expression in visceral adipose tissue. Furthermore, aly/aly mice showed protection from glucose intolerance and insulin resistance, which were observed in ovariectomized wild-type obese mice. These findings indicate that non-canonical NF-κB pathway activation via serum RANKL elevation contributes to postmenopausal obesity..
2.	Satoru Mukai, Akiko Mizokami, Takahito Otani, Tomomi Sano, Miho Matsuda, Sakura Chishaki, Jing Gao, Tomoyo Kawakubo-Yasukochi, Ronghao Tang, Takashi Kanematsu, Hiroshi Takeuchi, Eijiro Jimi, Masato Hirata, Adipocyte-specific GPRC6A ablation promotes diet-induced obesity by inhibiting lipolysis, Journal of Biological Chemistry, 10.1016/j.jbc.2021.100274, 296, 2021.01, The G protein-coupled receptor GPRC6A regulates various physiological processes in response to its interaction with multiple ligands, such as extracellular basic amino acids, divalent cations, testosterone, and the uncarboxylated form of osteocalcin (GluOC). Global ablation of GPRC6A increases the susceptibility of mice to diet-induced obesity and related metabolic disorders. However, given that GPRC6A is expressed in many tissues and responds to a variety of hormonal and nutritional signals, the cellular and molecular mechanisms underlying the development of metabolic disorders in conventional knockout mice have remained unclear. On the basis of our previous observation that long-term oral administration of GluOC markedly reduced adipocyte size and improved glucose tolerance in WT mice, we examined whether GPRC6A signaling in adipose tissue might be responsible for prevention of metabolic disorders. We thus generated adipocyte-specific GPRC6A knockout mice, and we found that these animals manifested increased adipose tissue weight, adipocyte hypertrophy, and adipose tissue inflammation when fed a high-fat and high-sucrose diet compared with control mice. These effects were associated with reduced lipolytic activity because of downregulation of lipolytic enzymes such as adipose triglyceride lipase and hormone-sensitive lipase in adipose tissue of the conditional knockout mice. Given that, among GPR6CA ligands tested, GluOC and ornithine increased the expression of adipose triglyceride lipase in cultured 3T3-L1 adipocytes in a manner dependent on GPRC6A, our results suggest that the constitutive activation of GPRC6A signaling in adipocytes by GluOC or ornithine plays a key role in adipose lipid handling and the prevention of obesity and related metabolic disorders..
3.	Mizokami A., Mukai S., Gao J., Kawakubo-Yasukochi T., Otani T., Takeuchi H., Jimi E., Hirata M., GLP-1 signaling is required for improvement of glucose tolerance by osteocalcin, Journal of Endocrinology, 10.1530/JOE-19-0288, 2020.01.
4.	Akiko Mizokami, Da Guang Wang, Mitsuru Tanaka, Jing Gao, Hiroshi Takeuchi, Toshiro Matsui, Masato Hirata, An extract from pork bones containing osteocalcin improves glucose metabolism in mice by oral administration, Bioscience, Biotechnology and Biochemistry, 10.1080/09168451.2016.1214530, 80, 11, 2176-2183, 2016.11, [URL], Osteocalcin (OC) is a bone-derived hormone that regulates energy metabolism. OC exists in two forms, carboxylated (GlaOC) and uncaboxylated (GluOC), but only the latter appears to have an endocrine function. In this study, we prepared an extract containing both Gla- and GluOC from boiled pork bone using 0.2 M carbonate buffer at pH 9.5, and tested whether the extract had beneficial effects on improving metabolic parameters in obese mice. The extract equivalent of 1.2 μg of GluOC/mouse was orally administrated to C57BL/6 female mice fed a high-fat, high-sucrose diet. Daily oral administration of the extract for four weeks decreased blood glucose levels and promoted glucose tolerance as well as insulin sensitivity. Our study shows for the first time that boiled pork bones are a source material for osteocalcin in the large-scale production of supplements designed to improve glucose metabolism..
5.	Yu Yasutake, Akiko Mizokami, Tomoyo Kawakubo-Yasukochi, Sakura Chishaki, Ichiro Takahashi, Hiroshi Takeuchi, Masato Hirata, Long-term oral administration of osteocalcin induces insulin resistance in male mice fed a high-fat, high-sucrose diet, American Journal of Physiology - Endocrinology and Metabolism, 10.1152/ajpendo.00334.2015, 310, 8, E662-E675, 2016.04, [URL], Uncarboxylated osteocalcin (GluOC), a bone-derived hormone, regulates energy metabolism by stimulating insulin secretion, pancreatic β-cell proliferation, and adiponectin expression in adipocytes. Previously, we showed that long-term intermittent or daily oral administration of GluOC reduced the fasting blood glucose level, improved glucose tolerance, and increased the fasting serum insulin concentration as well as pancreatic β-cell area in female mice fed a normal or high-fat, high-sucrose diet. We have now performed similar experiments with male mice and found that such GluOC administration induced glucose intolerance, insulin resistance, and adipocyte hypertrophy in those fed a high-fat, high-sucrose diet. In addition, GluOC increased the circulating concentration of testosterone and reduced that of adiponectin in such mice. These phenotypes were not observed in male mice fed a high-fat, high-sucrose diet after orchidectomy, but they were apparent in orchidectomized male mice or intact female mice that were fed such a diet and subjected to continuous testosterone supplementation. Our results thus reveal a sex difference in the effects of GluOC on glucose homeostasis. Given that oral administration of GluOC has been considered a potentially safe and convenient option for the treatment or prevention of metabolic disorders, this sex difference will need to be taken into account in further investigations..
6.	Akiko Mizokami, Yu Yasutake, Sen Higashi, Tomoyo Kawakubo-Yasukochi, Sakura Chishaki, Ichiro Takahashi, Hiroshi Takeuchi, Masato Hirata, Oral administration of osteocalcin improves glucose utilization by stimulating glucagon-like peptide-1 secretion, Bone, 10.1016/j.bone.2014.09.006, 69, 68-79, 2014.09, [URL], Uncarboxylated osteocalcin (GluOC), a bone-derived hormone, regulates energy metabolism by stimulating insulin secretion and pancreatic β-cell proliferation. We previously showed that the effect of GluOC on insulin secretion is mediated largely by glucagon-like peptide-1 (GLP-1) secreted from the intestine in response to GluOC exposure. We have now examined the effect of oral administration of GluOC on glucose utilization as well as the fate of such administered GluOC in mice. Long-term intermittent or daily oral administration of GluOC reduced the fasting blood glucose level and improved glucose tolerance in mice without affecting insulin sensitivity. It also increased the fasting serum insulin concentration as well as the β-cell area in the pancreas. A small proportion of orally administered GluOC reached the small intestine and remained there for at least 24. h. GluOC also entered the general circulation, and the serum GLP-1 concentration was increased in association with the presence of GluOC in the intestine and systemic circulation. The putative GluOC receptor, GPRC6A was detected in intestinal cells, and was colocalized with GLP-1 in some of these cells. Our results suggest that orally administered GluOC improved glucose handling likely by acting from both the intestinal lumen and the general circulation, with this effect being mediated in part by stimulation of GLP-1 secretion. Oral administration of GluOC warrants further study as a safe and convenient option for the treatment or prevention of metabolic disorders..
7.	Akiko Mizokami, Yu Yasutake, Jing Gao, Miho Matsuda, Ichiro Takahashi, Hiroshi Takeuchi, Masato Hirata, Osteocalcin Induces Release of Glucagon-Like Peptide-1 and Thereby Stimulates Insulin Secretion in Mice, PLoS One, 10.1371/journal.pone.0057375, 8, 2, 2013.02, [URL], The uncarboxylated form (ucOC), but not the γ-carboxylated form (GlaOC), of the bone-derived protein osteocalcin stimulates insulin secretion and regulates energy metabolism in insulin target tissues. Glucagon-like peptide-1 (GLP-1) is an insulin secretagogue that is released from the gut in response to food intake. We have now found that Gprc6a, a putative ucOC receptor, is expressed in epithelial cells of the mouse small intestine as well as in STC-1 enteroendocrine cells. Secretion of GLP-1 by STC-1 cells was stimulated by ucOC but not by GlaOC. The serum GLP-1 concentration in mice was increased by intraperitoneal or oral administration of ucOC, whereas GlaOC was effective in this regard only after oral application. Serum insulin levels were also increased by ucOC, and this effect was potentiated by an inhibitor of dipeptidyl peptidase IV and blocked by a GLP-1 receptor antagonist. Intravenous injection of ucOC in mice increased the serum GLP-1 concentration, and also increased the serum level of insulin. Our results suggest that ucOC acts via Gprc6a to induce GLP-1 release from the gut, and that the stimulatory effect of ucOC on insulin secretion is largely mediated by GLP-1..
8.	Akiko Mizokami, Takashi Kanematsu, Hitoshi Ishibashi, Taku Yamaguchi, Isei Tanida, Kei Takenaka, Keiichi Nakayama, Kiyoko Fukami, Tadaomi Takenawa, Eiki Kominami, Stephen J. Moss, Tsuneyuki Yamamoto, Junichi Nabekura, Masato Hirata, Phosholipase C-related inactive protein is involved in trafficking of γ2 subunit-containing GABA_A receptors to the cell surface, Journal of Neuroscience, 10.1523/JNEUROSCI.3155-06.2007, 27, 7, 1692-1701, 2007.02, [URL], The subunit composition of GABA_A receptors is known to be associated with distinct physiological and pharmacological properties. Previous studies that used phospholipase C-related inactive protein type 1 knock-out (PRIP-1 KO) mice revealed that PRIP-1 is involved in the assembly and/or the trafficking of γ2 subunit-containing GABA_A receptors. There are two PRIP genes in mammals; thus the roles of PRIP-1 might be compensated partly by those of PRIP-2 in PRIP-1 KO mice. Here we used PRIP-1 and PRIP-2 double knock-out (PRIP-DKO) mice and examined the roles for PRIP in regulating the trafficking of GABA_A receptors. Consistent with previous results, sensitivity to diazepam was reduced in electrophysiological and behavioral analyses of PRIP-DKO mice, suggesting an alteration of γ2 subunit-containing GABA_A receptors. The surface numbers of diazepam binding sites (α/γ2 subunits) assessed by [³H]flumazenil binding were reduced in the PRIP-DKO mice as compared with those of wild-type mice, whereas the cell surface GABA binding sites (α/β subunits, assessed by [³H]muscimol binding) were increased in PRIP-DKO mice. The association between GABA_A receptors and GABA_A receptor-associated protein (GABARAP) was reduced significantly in PRIP-DKO neurons. Disruption of the direct interaction between PRIP and GABA_A receptor β subunits via the use of a peptide corresponding to the PRIP-1 binding site reduced the cell surface expression of γ2 subunit-containing GABA_A receptors in cultured cell lines and neurons. These results suggest that PRIP is implicated in the trafficking of γ2 subunit-containing GABA_A receptors to the cell surface, probably by acting as a bridging molecule between GABARAP and the receptors..

主要総説, 論評, 解説, 書評, 報告書等

全てを見る→

Akiko Mizokami, Tomoyo Kawakubo-Yasukochi, Masato Hirata, Osteocalcin and its endocrine functions, Biochemical Pharmacology, 10.1016/j.bcp.2017.02.001, 2017.05, [URL], Bone has traditionally been regarded as a static structural organ that supports movement of the body and protects the internal organs. However, evidence has been accumulated in the past decade showing that bone also functions as an endocrine organ that regulates systemic glucose and energy metabolism. Osteocalcin, an osteoblast-specific secreted protein, acts as a hormone by stimulating insulin production and increasing energy expenditure and insulin sensitivity in target organs. Animal studies have shown that an increase in the circulating concentration of osteocalcin, including via exogenous application of the protein, prevents obesity and glucose intolerance. Moreover, a number of epidemiological analyses support the role of osteocalcin in the regulation of glucose and energy homeostasis in humans. Therefore, it has been suggested that osteocalcin could be a feasible preventive or therapeutic agent for metabolic disorders. In this review, we summarize the current knowledge regarding the endocrine functions of osteocalcin and its various modes of action..

Akiko Mizokami, Tomoyo Kawakubo-Yasuchochi, Hiroshi Takeuchi, Masato Hirata, Organ network for preventing metabolic syndromes with a reference to the roles of osteocalcin, Folia Pharmacologica Japonica, 10.1254/fpj.145.201, 2015.01, [URL].

主要学会発表等

全てを見る→

1.	溝上顕子, ＠大谷崇仁, 兼松隆, 自見英治郎, 平田雅人, 脂肪細胞表面受容体GPRC6Aによる脂質代謝制御, 第63回歯科基礎医学会, 2021.10.
2.	溝上顕子, 安武　雄, 竹内　弘, 高靖, 平田雅人, Osteocalcin induces release of glucagon-like peptide-1 and improves metabolic state in mice, The 8th Japan-Korea Conference on Cellular Signaling for Young Scientists, 2013.11.

学会活動

所属学会名

日本性差医学・医療学会

日本薬理学会

日本生化学会

歯科基礎医学会

学協会役員等への就任

2013.11～2013.11, The 8th Japan-Korea conference on cellular signaling for young scientists, 運営委員.

学会大会・会議・シンポジウム等における役割

2022.10.29～2022.10.30, KOB (Kyudai Oral Biosciences)・OBT・DDR 合同国際シンポジウム, オーガナイザー.

2021.11.27～2021.11.28, KOB (Kyudai Oral Biosciences)・OBT 合同国際シンポジウム.

2021.10.09～2021.10.11, 第63回歯科基礎医学会学術大会, 歯科基礎アカデミーシンポジウム　オーガナイザー.

2021.02.06～2021.02.06, Kyudai Oral Bioscience & OBT Research Center Joint International Symposium 2021.

2020.02.08～2020.02.09, Kyudai Oral Bioscience & OBT Research Center Joint International Symposium 2019.

2019.03.01～2019.03.01, Kyudai Oral Bioscience & OBT Research Center Joint International Symposium 2020.

2013.11.07～2013.11.08, The 8th Japan-Korea Conference on Cellular Signaling for Young Scientists.

学術論文等の審査

年度	外国語雑誌査読論文数	合計
2022年度	5	5
2021年度	6	6
2020年度	3	3
2019年度	2	2

受賞

ソロプチミスト日本財団女性研究者賞　クラブ賞, 国際ソロプチミスト福岡-第2クラブ, 2020.10.

第３２回学会奨励賞, 歯科基礎医学会, 2020.09.

2019 International Congress on Obesity and Metabolic Syndrome & Asia-Oceania Conference on Obesity Travel Grant, Scientific Committee of the Korean Society for the Study of Obesity (KSSO), 2019.08.

岩垂育英会賞, 一般財団法人岩垂育英会, 2015.03.

研究資金

科学研究費補助金の採択状況(文部科学省、日本学術振興会)

2022年度～2024年度, 基盤研究(C), 代表, 性差から解き明かす新たな認知症制御機構.

2021年度～2023年度, 基盤研究(C), 分担, 抗腫瘍免疫を賦活化する新しい制癌シグナル分子の機能解明研究.

2020年度～2023年度, 基盤研究(B), 分担, エピゲノムによる生活習慣病の世代間継承と内在性オステオカルシンによる回避.

2018年度～2021年度, 基盤研究(C), 代表, オステオカルシンによるサルコペニア肥満回避機構の解明.

2017年度～2019年度, 基盤研究(A), 分担, 骨・腸・代謝戦艦による糖脂質代謝異常の予防戦略.

2016年度～2017年度, 若手研究(B), 代表, オステオカルシンによる膵α細胞のグルカゴンからGLP-1への変換機構の解明.

2014年度～2015年度, 若手研究(B), 代表, オステオカルシンの内分泌作用に関する研究.

2012年度～2016年度, 基盤研究(S), 分担, 骨・腸・代謝連関シグナルの解明と性差の明確化.

日本学術振興会への採択状況(科学研究費補助金以外)

2010年度～2013年度, 特別研究員, 代表, GABAシグナリング調節分子による摂食調節機構の解明.

競争的資金(受託研究を含む)の採択状況

2013年度～2013年度, 公益財団法人　武田科学振興財団　2013年度　医学系研究奨励, 代表, オステオカルシンのホルモン作用の解明
─インクレチンおよびインスリン分泌への関わり─
.

2013年度～2013年度, 一般財団法人　島原科学振興会　研究助成金, 代表, 骨・腸・代謝連関におけるオステオカルシンの役割解明研究 .

2013年度～2013年度, 研究成果展開事業研究成果最適展開支援プログラムA-STEP フィージビリティスタディステージ　探索タイプ, 分担, 骨を用いたメタボリックシンドローム予防効果を有する食品素材の開発.

2014年度～2015年度, A-STEP 探索タイプ, 代表, 骨基質タンパク質を用いたメタボリックシンドローム改善薬の開発.

共同研究、受託研究(競争的資金を除く)の受入状況

2014.12～2015.12, 代表, JST 第２回研究成果展開事業研究成果最適展開支援プログラム（A-STEP）探索タイプ
骨基質タンパク質を用いたメタボリックシンドローム改善薬の開発.

2013.12～2014.12, 分担, JST 第１回研究成果展開事業研究成果最適展開支援プログラム（A-STEP）探索タイプ
骨を用いたメタボリックシンドローム予防効果を有する食品素材の開発.

寄附金の受入状況

2018年度, ロッテ財団　第５回奨励研究助成
脂肪細胞表面受容体を介した栄養センシングと脂肪蓄積の分子機構解明.

2017年度, 一般財団法人　貝原守一医学振興財団　研究助成金
オステオカルシン・インクレチンのリレーによるメタボリックシンドロームの回避.

2013年度, 一般財団法人　島原科学振興会　研究助成金
骨・腸・代謝連関におけるオステオカルシンの役割解明研究.

2012年度, 公益財団法人　武田科学振興財団　医学系研究奨励
オステオカルシンのホルモン作用の解明　-インクレチン及びインスリン分泌への関わり.

2012年度, 公益財団法人　上原記念生命科学財団　研究奨励金
オステオカルシンのホルモン作用とDDS.

学内資金・基金等への採択状況

2019年度～2019年度, QRプログラム（わかばチャレンジ）, 代表, 脂肪細胞表面受容体GPRC6Aを介した脂質代謝調節機構　-肥満の形成における性差の解明-.

九大関連コンテンツ

pure2017年10月2日から、「九州大学研究者情報」を補完するデータベースとして、Elsevier社の「Pure」による研究業績の公開を開始しました。

QIR　九州大学学術情報リポジトリシステム情報科学研究院

歯学部・歯学研究院


	※ 研究者情報全体を検索する場合は右端の「すべて」を選択して下さい。