Researchers investigating pancreatic islets in mice compared normal mice pancreatic tissue during development to that of knockout mice. They found that a normal mouse pancreas includes a population of ghrelin-producing cells. Before further investigation took place, it was thought that Nkx2.2 and Pax4 genes promote cell differentiation of β-cells, but in their absence they instead form ε-cells. This was later confirmed by the findings that in the absence of both Nkx2.2 and Pax4 genes, β-cells fail to form and are replaced by ε-cells. Overall, the findings were that there is a population of ghrelin-producing ε-cells in the mouse pancreas, and that knockout of insulin-producing β-cells leads to an enormous amount of ε-cells. The cells are round or oval in shape and usually in the perimeter of the islets, sometimes with cytoplasmic extensions. ε-cells have also been proposed to be from a similar cell lineage to both α-cells and β-cells, but have been found to be more closely related to α-cells. ε-cells have been found in pancreas of Xenopus frogs, cat fish, and zebrafish among other animals. This suggests that this islet cell is evolutionarily conserved. A separate study used In situ hybridization for ghrelin mRNA and similarly concluded that there is a separate, previously unrecognised, islet cell population that are the ε-cells. Researchers are hopeful that their novel knowledge on ghrelin-producing ε-cells will aid in therapeutic treatment to block formation of ε-cells, which could potentially block a cellular cascade that could aid in treatment of Type II Diabetes. These islet cells are also being studied in pancreatic cancer, where it is hoped that they can act as markers to previously silent tumors.
Humans are the only species known to keep ghrelin-producing ε-cells in the pancreas into adulthood. As a result, there are difficulties to study this cell type in adults since it can only be observed in the human pancreas. During the weeks 15-26 of the fetus during development, ε-cells compose about 10% of the islet cells, but following birth, their composition decreases to only 1% of adult islet cells. Estimates of the average number of ε-cells per islet in adults vary in number with differing results. One study found that there are about 3 to 5 ε-cells present in each islet of the adult pancreas, which includes a total of about 1,000 islets. Another study observed an average of 12±1.2 ε-cells per islet. In adult pancreas samples, they are observed to be round or oval shaped and remain localized on the mantle of the islets in different amounts, both in clusters and or single cells. In mice, ε-cells are present in the pancreatic islets and stomach during development, but are found strictly in the stomach after birth. In both humans and mice, results have varied on whether or not ghrelin is co-localized with other hormones in stages of adulthood or development. Because of the scarcity of ε-cells in an adult pancreas, it is predicted that they do not continue to produce large amounts of ghrelin that circulates throughout the body. The human adult pancreas has an ε-cell composition of about 0.13 grams. Sex and age do not affect the average number of ε-cells in islets. However, an inverse relationship between BMI and number of ε-cells is noted: as body weight increases, ε-cells decrease in number. Loss of these cells due to increase in BMI leads to an increase in insulin secretion, and increased risk of apoptosis and inflammation in pancreatic islets. Cell membrane receptors in adult ε-cells include short-chained fatty acid receptor FFAR3, G protein–coupled bile acid receptor 1 (GPCR), interferon-α and interferon-β receptor subunit 1, interferon-γ receptor 2, a receptor known for its regulation of immunoglobulin G uptake, plasminogen receptor, and a CD320 receptor. The variety of receptors allow hormones, nutrients, lipids, and cytokine ligands to bind. The primary cellular metabolic pathway factor present in ε-cells are members that compose the fatty acid metabolism pathway, ACSL1. ACSL1 is an enzyme involved in the first step of fatty acid oxidation, and this pathway functions in this islet cell specifically to modify ghrelin acyl modification. Transcription factors that are necessary ε-cell maturation and preservation are numbered to a total of 366. The functions of each individual transcription factor have not yet been studied.
"The Pancreas | Boundless Anatomy and Physiology". courses.lumenlearning.com. Retrieved 2019-02-19. https://courses.lumenlearning.com/boundless-ap/chapter/the-pancreas/
Lodish, Harvey F. (2016-04-01). Molecular cell biology. Macmillan Learning. ISBN 9781464183393. OCLC 1003278428. 9781464183393
Sussel, Lori; Sosa-Pineda, Beatriz; Elghazi, Lynda; Pugh-Bernard, Aimee E.; Prado, Catherine L. (2004-03-02). "Ghrelin cells replace insulin-producing β cells in two mouse models of pancreas development". Proceedings of the National Academy of Sciences. 101 (9): 2924–2929. Bibcode:2004PNAS..101.2924P. doi:10.1073/pnas.0308604100. ISSN 0027-8424. PMC 365721. PMID 14970313. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC365721
Wierup, Nils; Sundler, Frank; Heller, R Scott (2013-09-18). "The islet ghrelin cell". Journal of Molecular Endocrinology. 52 (1): R35 – R49. doi:10.1530/jme-13-0122. ISSN 0952-5041. PMID 24049065. https://doi.org/10.1530%2Fjme-13-0122
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Raghay, Kawtar; Gallego, Rosalia; Scoazec, Jean-Yves; Garcia-Caballero, Tomas; Morel, Gérard (2013-04-13). "Different ghrelin localisation in adult human and rat endocrine pancreas". Cell and Tissue Research. 352 (3): 487–494. doi:10.1007/s00441-013-1593-y. ISSN 0302-766X. PMID 23584608. S2CID 18128870. /wiki/Doi_(identifier)
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Wierup, Nils; Sundler, Frank; Heller, R Scott (2013-09-18). "The islet ghrelin cell". Journal of Molecular Endocrinology. 52 (1): R35 – R49. doi:10.1530/jme-13-0122. ISSN 0952-5041. PMID 24049065. https://doi.org/10.1530%2Fjme-13-0122
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Xin, Yurong; Gromada, Jesper; Murphy, Andrew J.; Adler, Christina; Ni, Min; Ding, Yueming; Wei, Yi; Gray, Sarah M.; Niu, JingJing (2018-12-01). "Gene Signature of the Human Pancreatic ε Cell". Endocrinology. 159 (12): 4023–4032. doi:10.1210/en.2018-00833. PMC 6963699. PMID 30380031. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963699
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Xin, Yurong; Gromada, Jesper; Murphy, Andrew J.; Adler, Christina; Ni, Min; Ding, Yueming; Wei, Yi; Gray, Sarah M.; Niu, JingJing (2018-12-01). "Gene Signature of the Human Pancreatic ε Cell". Endocrinology. 159 (12): 4023–4032. doi:10.1210/en.2018-00833. PMC 6963699. PMID 30380031. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963699
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Xin, Yurong; Gromada, Jesper; Murphy, Andrew J.; Adler, Christina; Ni, Min; Ding, Yueming; Wei, Yi; Gray, Sarah M.; Niu, JingJing (2018-12-01). "Gene Signature of the Human Pancreatic ε Cell". Endocrinology. 159 (12): 4023–4032. doi:10.1210/en.2018-00833. PMC 6963699. PMID 30380031. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963699
"Epsilon Cells, Ghrelin Cells Development in the Islets of Langerhans - LifeMap Discovery". discovery.lifemapsc.com. Retrieved 2019-02-25. https://discovery.lifemapsc.com/in-vivo-development/pancreas/islets-of-langerhans/epsilon-cells-ghrelin-cells
Wierup, Nils; Sundler, Frank; Heller, R Scott (2013-09-18). "The islet ghrelin cell". Journal of Molecular Endocrinology. 52 (1): R35 – R49. doi:10.1530/jme-13-0122. ISSN 0952-5041. PMID 24049065. https://doi.org/10.1530%2Fjme-13-0122
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Xin, Yurong; Gromada, Jesper; Murphy, Andrew J.; Adler, Christina; Ni, Min; Ding, Yueming; Wei, Yi; Gray, Sarah M.; Niu, JingJing (2018-12-01). "Gene Signature of the Human Pancreatic ε Cell". Endocrinology. 159 (12): 4023–4032. doi:10.1210/en.2018-00833. PMC 6963699. PMID 30380031. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963699
Andralojc, K. M; Mercalli, A; Nowak, K. W; Albarello, L; Calcagno, R; Luzi, L; Bonifacio, E; Doglioni, C; Piemonti, L (2008). "Ghrelin-producing epsilon cells in the developing and adult human pancreas". Diabetologia. 52 (3): 486–93. doi:10.1007/s00125-008-1238-y. PMID 19096824. https://doi.org/10.1007%2Fs00125-008-1238-y
Xin, Yurong; Gromada, Jesper; Murphy, Andrew J.; Adler, Christina; Ni, Min; Ding, Yueming; Wei, Yi; Gray, Sarah M.; Niu, JingJing (2018-12-01). "Gene Signature of the Human Pancreatic ε Cell". Endocrinology. 159 (12): 4023–4032. doi:10.1210/en.2018-00833. PMC 6963699. PMID 30380031. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6963699