Elucidation of osteoporosis prevention mechanism by citrus limonoid

Dr Yoshifumi Kimira is part of a research team that is investigating how citrus fruits could potentially alleviate various types of bone disease. He is based in the Department of Clinical Dietetics and Human Nutrition in the Faculty of Pharmaceutical Sciences at Josai University, Japan. He is working alongside fellow Josai University researchers, as well as collaborators from Liberty House, a food processing company, and from Moroyama town, Saitama. These collaborations were necessary, as Kimira explains: 'I'm not a specialist in food processing, so collaborating with companies specialising in food processing was very important.' The team's project is entitled 'Citrus limonoid nomilin inhibits osteoclastogenesis in vitro by suppression of NFATc1 and MAPK signalling pathways'. Liminoids are phytochemicals found in citrus fruit, 53 of which have been identified, including the limonoids nomilin and nomilinic acid. These have been studied in anti-cancer research and now Kimira and his team are studying the potential effects of nomalin on osteoclastogenesis, which is the development of osteoclasts – a type of bone cell that breaks down bone tissue – from blood cells. Despite nomalin having been reported to have many biological activities in animal systems, its mechanism on bone metabolism is unclear. Kimira and his team are trying to fill the gaps in the research on nomilin and how it affects osteoclasts. 'Although the effect of nomilin on the gene expression of osteoclasts and the effect on intracellular signalling can be seen, we have not been able to examine how nomilin exerts influence on cells from outside the cell,' Kimira explains. 'Since nomilin has been reported to be a ligand for TGR5, which is a bile acid receptor expressed in the intestinal tract, if it can be confirmed that TGR5 is expressed in osteoclasts, I believe the effect of nomilin can be extracellularly considered.Impact is published under a CC-BY Creative Commons licence