Xenin

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Coatomer subunit alpha
Identifiers
SymbolCOPA
RefSeqNP_001091868
UniProtP53621
Other data
LocusChr. 1 q23.2

Xenin is a peptide hormone secreted from the chromogranin A-positive enteroendocrine cells called the in the mucous membrane of the duodenum and stomach of the upper gut.[1][2] The peptide has been found in humans, dogs, pigs, rats, and rabbits.

In humans, xenin circulates in the blood plasma.[3] There is a relationship between peaks of xenin concentration in the plasma and the third phase of the Migrating Motor Complex. For example, infusion of synthetic xenin in fasting volunteers will cause phase III activity. After a meal (the 'postprandial state'), infusion of xenin increases both frequency and the percentage of aborally propagated contractions. In higher concentrations xenin stimulates exocrine pancreatic secretion and inhibits the gastrin-stimulated secretion of acid in dogs. Xenin is also produced in neuroendocrine tumors of the duodenal mucosa.

In vitro, xenin interacts with the neurotensin receptor 1.

Structure and sequence[]

Xenin is a 25-amino acid polypeptide. The amino acid sequence of xenin is identical to the N-terminal end of cytoplasmic coatomer subunit alpha,[4] from which xenin can be cleaved by aspartic proteases. Xenin is structurally related to the amphibian peptide and to the neuropeptide neurotensin.

Surpassed by insulin, xenin reflects the second highest degree of homology traced along the evolutionary tree among the regulatory peptides, indicating its prominent structural conservatism.[5]

Proxenin[]

Proxenin is the precursor to xenin. It is a 35-amino acid polypeptide. Like xenin, its amino acid sequence exactly matches the N-terminus of coatomer subunit alpha.[4]

As a drug target[]

Xenin promotes beta-cell survival and xenin has been evaluated in animal models of obesity and diabetes where it has demonstrated an antidiabetic potential.[6] In humans, co-administration of xenin-25 and gastric inhibitory polypeptide (GIP) reduces postprandial glycemia by delaying gastric emptying.[7]

Effects[]

Overnight worker––who had lower insulin sensitivity and increased adiposity from disrupted hemostasis––exhibited a slow postprandial increase in their anorexigenic xenin level, while a suppression in their orexigenic ghrelin level.[1]

Xenin promotes insulin release by gastric inhibitory polypetide to regulate glucose homeostasis.[2] Its increase of insulin secretion is indirect and would not produce any effects by itself.[8] Xenin's effect on insulin increase is not observed in type 2 diabetes patients when using a dosage of 4 pmol ⋅kg−1⋅min−1.[9]

However, a separate study conducted utilizing higher dosages of xenin infusion underlines its effective reduction of postprandial glucose level, even in humans with type 2 diabetes.[10] After activating neurotensin receptor-1, xenin leads to an increase in the cytosolic calcium concentration and acetylcholine release of some myenteric neurons.[8]

References[]

  1. ^ a b Schiavo-Cardozo D, Lima MM, Pareja JC, Geloneze B (December 2013). "Appetite-regulating hormones from the upper gut: disrupted control of xenin and ghrelin in night workers". Clinical Endocrinology. 79 (6): 807–11. doi:10.1111/cen.12114. PMID 23199168. S2CID 24887534.
  2. ^ a b Mazella J, Béraud-Dufour S, Devader C, Massa F, Coppola T (2012). "Neurotensin and its receptors in the control of glucose homeostasis". Frontiers in Endocrinology. 3: 143. doi:10.3389/fendo.2012.00143. PMC 3515879. PMID 23230428.
  3. ^ Feurle GE, Hamscher G, Kusiek R, Meyer HE, Metzger JW (November 1992). "Identification of xenin, a xenopsin-related peptide, in the human gastric mucosa and its effect on exocrine pancreatic secretion". The Journal of Biological Chemistry. 267 (31): 22305–9. doi:10.1016/S0021-9258(18)41670-5. PMID 1429581.
  4. ^ a b UniProtKB/Swiss-Prot entry P53621 COPA_HUMAN
  5. ^ Maryanovich AT, Kormilets DY, Polyanovsky AD (April 2018). "Xenin: the oldest after insulin?". Molecular Biology Reports. 45 (2): 143–150. doi:10.1007/s11033-018-4147-2. PMID 29340900. S2CID 3836004.
  6. ^ Craig SL, Gault VA, Irwin N (September 2018). "Emerging therapeutic potential for xenin and related peptides in obesity and diabetes". Diabetes/Metabolism Research and Reviews. 34 (6): e3006. doi:10.1002/dmrr.3006. PMID 29633491. S2CID 4756921.
  7. ^ Hussain MA, Akalestou E, Song WJ (April 2016). "Inter-organ communication and regulation of beta cell function". Diabetologia. 59 (4): 659–67. doi:10.1007/s00125-015-3862-7. PMC 4801104. PMID 26791990.
  8. ^ a b Zhang S, Hyrc K, Wang S, Wice BM (December 2012). "Xenin-25 increases cytosolic free calcium levels and acetylcholine release from a subset of myenteric neurons". American Journal of Physiology. Gastrointestinal and Liver Physiology. 303 (12): G1347-55. doi:10.1152/ajpgi.00116.2012. PMC 3532549. PMID 23086920.
  9. ^ Wice BM, Reeds DN, Tran HD, Crimmins DL, Patterson BW, Dunai J, et al. (July 2012). "Xenin-25 amplifies GIP-mediated insulin secretion in humans with normal and impaired glucose tolerance but not type 2 diabetes". Diabetes. 61 (7): 1793–800. doi:10.2337/db11-1451. PMC 3379667. PMID 22522617.
  10. ^ Chowdhury S, Reeds DN, Crimmins DL, Patterson BW, Laciny E, Wang S, et al. (February 2014). "Xenin-25 delays gastric emptying and reduces postprandial glucose levels in humans with and without type 2 diabetes". American Journal of Physiology. Gastrointestinal and Liver Physiology. 306 (4): G301-9. doi:10.1152/ajpgi.00383.2013. PMC 3920124. PMID 24356886.

Further reading[]

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