We are doing research in the field of endocrinology and metabolism with special interest in the molecular mechanissms of energy metabolism by hormones and nutrients.

Ghrelin is a stomach-derived hormone with potent appetite- and growth hormnone-stimulating activities.We are doing research to dissect the molecular mechanisms involved in the regulation of ghrelin prodoction and secretion by using originally-developed ghrelin-secreting cell lines. One of our goals is to develop ghrelin-regulating drugs to treat diseases such as cachexia, somatopause, or sarcopenia.

Previous our works

The regulation of ghrelin secretion
Previously, we developed a ghrelin-secreting cell line, MGN3-1 cels, from a ghrelinoma originated from a ghrelin-promoter SV40-Tag transgenic mouse. MGN3-1 cells produces subbstantial amount of ghrelin with phisiological processing and acyl-modification. We found that ghrelin secretion is regulated by autonomic nerves, peptide hormones (oxytocin and somatostatin), nutrients (lactate, tryptophan, and lipids), and cytokines (PGE2 and IL-1β) (Koyama, Iwakura et al. Endocrinology 2016, Bando, Iwakura et al. Mol Cell Endo 2017).

Origin of octanoic acids for acyl-modification of ghrelin
We found that ghrelin-producing cells have a higher ability to incoroporate long-chain fatty acids, with relatively slow progression of β-oxidation of medium chain fatty acids. We think that octanoic acids are effectively provided for the acyl-modification by these characteritcs of the ghrelin-producing cells (Bando et al. FEBS Lett. 2016).

GPR142 is a G-protein coupled receptor, whose most potent ligand is tryptophan.GPR142 expression are observed in enteroendocrine cells and pancreatic islet cells, where the receptor senses tryptophan to regulate the secretion of hormones. We have found that GPR142 and CaSR have different role in the stimulation of insluin secretion by tryptophan in between obese and lean animals（Ueda et al. PLos One 2018).