Apelin

Source: Wikipedia, the free encyclopedia.
APLN
Identifiers
Gene ontology
Molecular function
Cellular component
Biological process
Sources:Amigo / QuickGO
Ensembl
UniProt
RefSeq (mRNA)

NM_017413

NM_013912

RefSeq (protein)

NP_059109

NP_038940

Location (UCSC)Chr X: 129.65 – 129.65 MbChr X: 47.11 – 47.12 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Apelin (also known as APLN) is a peptide that in humans is encoded by the APLN gene.

G-protein-coupled APJ receptor[6][7][8][9][10] that is expressed at the surface of some cell types.[11] It is widely expressed in various organs such as the heart, lung, kidney, liver, adipose tissue, gastrointestinal tract, brain, adrenal glands, endothelium, and human plasma
.

Discovery

Apelin is a peptide hormone that was identified in 1998 by Masahiko Fujino and his colleagues at Gunma University and Takeda Pharmaceutical Company.[5] In 2013, a second peptide hormone named Elabela was found by Bruno Reversade to also act as an endogenous ligand to the APLNR.

Biosynthesis

The apelin gene encodes a pre-proprotein of 77 amino acids,[5] with a signal peptide in the N-terminal region. After translocation into the endoplasmic reticulum and cleavage of the signal peptide, the proprotein of 55 amino acids may generate several active fragments: a 36 amino acid peptide corresponding to the sequence 42-77 (apelin 36), a 17 amino acid peptide corresponding to the sequence 61-77 (apelin 17) and a 13 amino acid peptide corresponding to the sequence 65-77 (apelin 13). This latter fragment may also undergo a pyroglutamylation at the level of its N-terminal glutamine residue. However the presence and/or the concentrations of those peptides in human plasma has been questioned.[12] Recently, 46 different apelin peptides ranging from apelin 55 (proapelin) to apelin 12 have been identified in bovine colostrum, including C-ter truncated isoforms.[13]

Physiological functions

The sites of receptor expression are linked to the different functions played by apelin in the organism.

Vascular

Vascular expression of the

Genetic knockout of the apelin gene is associated with a delay in the development of the retinal vasculature.[22]

Cardiac

The apelin receptor is expressed early during the

cardiomyocytes, the contractile cells of the heart.[23][24] Its expression is also detected in the cardiomyocytes of the adult where apelin behaves as one of the most potent stimulator of cardiac contractility.[7][25][26] Aged apelin knockout mice develop progressive impairment of cardiac contractility.[27] Apelin acts as a mediator of the cardiovascular control, including for blood pressure and blood flow. It is one of the most potent stimulators of cardiac contractility yet identified, and plays a role in cardiac tissue remodeling. Apelin levels are increased in left ventricles of patients with chronic heart failure and also in patients with chronic liver disease.[28]

Exercise

The plasma concentration of apelin is shown to increase during exercise.[29] Paradoxically, exogenous apelin in healthy volunteers reduced VO2 peak (peak oxygen consumption) in an endurance test.[30]

Brain

Apelin receptor is also expressed in the neurons of brain areas involved in regulating water and food intake.[6][31][32] Apelin injection increases water intake[6] and apelin decreases the hypothalamic secretion of the antidiuretic hormone vasopressin.[33] This diuretic effect of apelin in association with its hypotensive effect participates in the homeostatic regulation of body fluid. Apelin is also detected in brain areas which control appetite, but its effects on food intake are very contradictory.[34][35][36]

Adipose tissue

Apelin is expressed and secreted by adipocytes, and its production is increased during adipocyte differentiation and is stimulated by insulin.[37] Most obese people have elevated levels of insulin, which may therefore be the reason why obese people have been reported to also have elevated levels of apelin.[37]

Digestive

Apelin receptor is expressed in several cell types of the

colon epithelial cells.[41]
In stomach, activation of receptors on enterochromaffine-like cells by apelin secreted by

Bone

Receptor expression is also observed at the surface of osteoblasts, the cell progenitors involved in bone formation.[44]

Muscle aging

Muscle apelin expression decreases with age in rodents and humans.

cellular proliferation and differentiation of these cells into mature muscle cells that participate in muscle regeneration. Finally, muscle apelin could be used as a biomarker of physical exercise success in aged individuals since its production is correlated to the benefit of a chronic physical exercise in aged individuals.[45]

In late 2022, the

critical illness myopathy (the broad weakening of the muscles during extended bed rest). Each of these conditions are associated with poor functional recovery and substantially increased risk of death after illness.[46]

References

  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000171388 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000037010 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^
    PMID 9792798
    .
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  11. on 2011-07-22. Retrieved 2009-09-02.
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  32. ^ De Mota et al., 2000
  33. S2CID 39313631
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  40. ^ Sorhede Winzell et al., 2005
  41. PMID 19660504
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  46. ^
    BusinessWire
    . 5 December 2022. Retrieved 14 January 2023.
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Further reading

External links

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