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Adiponectin, C1Q and collagen domain containing

PDB rendering based on 1c28.
Available structures
1c28, 1c3h
Identifiers
Symbols ADIPOQ; ACDC; ACRP30; APM-1; APM1; GBP28; adiponectin
External IDs OMIM605441 MGI106675 HomoloGene3525 GeneCards: ADIPOQ Gene
RNA expression pattern
PBB GE ADIPOQ 207175 at tn.png
More reference expression data
Orthologs
Species Human Mouse
Entrez 9370 11450
Ensembl ENSG00000181092 ENSMUSG00000022878
UniProt Q15848 Q6GTX4
RefSeq (mRNA) NM_004797 NM_009605
RefSeq (protein) NP_004788 NP_033735
Location (UCSC) Chr 3:
188.04 - 188.06 Mb
Chr 16:
23.06 - 23.07 Mb
PubMed search [1] [2]

Adiponectin (also referred to as GBP-28, apM1, AdipoQ and Acrp30) is a protein which in humans is encoded by the ADIPOQ gene.[1]

Contents

Structure

Adiponectin is a 244-amino-acid-long polypeptide. There are four distinct regions of adiponectin. The first is a short signal sequence that targets the hormone for secretion outside the cell; next is a short region that varies between species; the third is a 65-amino acid region with similarity to collagenous proteins; the last is a globular domain. Overall this gene shows similarity to the complement 1Q factors. However, when the 3-dimensional structure of the globular region was determined, a striking similarity to TNFα was observed, despite unrelated protein sequences.[2]

Function

Adiponectin is a protein hormone that modulates a number of metabolic processes, including glucose regulation and fatty acid catabolism.[3] Adiponectin is exclusively secreted from adipose tissue into the bloodstream and is very abundant in plasma relative to many hormones. Levels of the hormone are inversely correlated with body fat percentage in adults,[4] while the association in infants and young children is less clear. The hormone plays a role in the suppression of the metabolic derangements that may result in type 2 diabetes,[4] obesity, atherosclerosis,[3] non-alcoholic fatty liver disease (NAFLD) and an independent risk factor for metabolic syndrome.[5]

Adiponectin is secreted into the bloodsteam where it accounts for approximately 0.01% of all plasma protein at around 5-10 μg/mL. Plasma concentrations reveal a sexual dimorphism, with females having higher levels than males. Levels of adiponectin are reduced in diabetics compared to non-diabetics. Weight reduction significantly increases circulating levels.[6]

Adiponectin automatically self-associates into larger structures. Initially, three adiponectin molecules bind together to form a homotrimer. The trimers continue to self-associate and form hexamers or dodecamers. Like the plasma concentration, the relative levels of the higher-order structures are sexually dimorphic, where females have increased proportions of the high-molecular weight forms. Questions remain about what the physiologically active forms of the protein are and how they carry out their action.

Adiponectin exerts some of its weight reduction effects via the brain. This is similar to the action of leptin,[7] but the two hormones perform complementary actions, and can have additive effects.

Receptors

Adiponectin binds to a number of receptors. So far, two receptors have been identified, with homology to G protein-coupled receptors and one receptor similar to the cadherin family:[8][9]

  • adiponectin receptor 1 – ADIPOR1
  • adiponectin receptor 2 – ADIPOR2
  • T-cadherin - T-Cad

These have distinct tissue specificities within the body and have different affinities to the various forms of adiponectin. The receptors affect the downstream target AMP kinase, an important cellular metabolic rate control point. Expression of the receptors are correlated with insulin levels, as well as reduced in mouse models of diabetes, particularly in skeletal muscle and adipose tissue.[10][11]

Discovery

Adiponectin was first characterised in mice as a transcript overexpressed in preadipocytes[12] (precursors of fat cells) differentiating into adipocytes.[13][12]

The human homologue was identified as the most abundant transcript in adipose tissue. Contrary to expectations, despite being produced in adipose tissue, adiponectin was found to be decreased in obesity.[7][3][4] This downregulation has not been fully explained. The gene was localised to chromosome 3p27, a region highlighted as affecting genetic susceptibility to type 2 diabetes and obesity. Supplementation by differing forms of adiponectin were able to improve insulin control, blood glucose and triglyceride levels in mouse models.

The gene was investigated for variants that predispose to type 2 diabetes.[12][14][15][7][16][17] Several single nucleotide polymorphisms in the coding region and surrounding sequence were identified from several different populations, with varying prevalences, degrees of association and strength of effect on type 2 diabetes. Berberine, an herbal folk medicine, has been shown to increase adiponectin expression[18] which partly explains its beneficial effects on metabolic disturbances.

Metabolic effects

Adiponectin affects:

Hypoadiponectinemia

It is an independent risk factor for developing:

Pharmaceutical therapy

Because adiponectin is a novel hormone, no therapy has yet been developed with adiponectin and it may be some years before clinical trials commence. One obvious pharmaceutical treatment would be the administration of adiponectin; in mouse models such administration has shown positive effects.[3] Problems to be overcome prior to human administration include establishing what the biologically active molecule is, what role post-translational modifications have upon the function and associated difficulties in generating biologically active molecules on a large scale. However, this remains a promising area of research for clinical therapy in diseases such as obesity, type 2 diabetes and fatty liver disease.[16]

References

  1. ^ Maeda K, Okubo K, Shimomura I, Funahashi T, Matsuzawa Y, Matsubara K (April 1996). "cDNA cloning and expression of a novel adipose specific collagen-like factor, apM1 (AdiPose Most abundant Gene transcript 1)". Biochem. Biophys. Res. Commun. 221 (2): 286–9. doi:10.1006/bbrc.1996.0587. PMID 8619847.  
  2. ^ Shapiro L, Scherer PE (March 1998). "The crystal structure of a complement-1q family protein suggests an evolutionary link to tumor necrosis factor". Curr. Biol. 8 (6): 335–8. doi:10.1016/S0960-9822(98)70133-2. PMID 9512423.  
  3. ^ a b c d e Díez JJ, Iglesias P (March 2003). "The role of the novel adipocyte-derived hormone adiponectin in human disease". Eur. J. Endocrinol. 148 (3): 293–300. doi:10.1530/eje.0.1480293. PMID 12611609.  
  4. ^ a b c Ukkola O, Santaniemi M (November 2002). "Adiponectin: a link between excess adiposity and associated comorbidities?". J. Mol. Med. 80 (11): 696–702. doi:10.1007/s00109-002-0378-7. PMID 12436346.  
  5. ^ a b Renaldi O, Pramono B, Sinorita H, Purnomo LB, Asdie RH, Asdie AH (January 2009). "Hypoadiponectinemia: a risk factor for metabolic syndrome". Acta Med Indones 41 (1): 20–4. doi:10.1267/science.040579197 (inactive 2009-03-05). PMID 19258676.  
  6. ^ Coppola A, Marfella R, Coppola L, Tagliamonte E, Fontana D, Liguori E, Cirillo T, Cafiero M, Natale S, Astarita C (March 2008). "Effect of weight loss on coronary circulation and adiponectin levels in obese women". Int. J. Cardiol.. doi:10.1016/j.ijcard.2007.12.087. PMID 18378021.  
  7. ^ a b c d e f g Nedvídková J, Smitka K, Kopský V, Hainer V (2005). "Adiponectin, an adipocyte-derived protein". Physiol Res 54 (2): 133–40. PMID 15544426. http://www.biomed.cas.cz/physiolres/pdf/54/54_133.pdf.  
  8. ^ Yamauchi T, Kamon J, Ito Y, Tsuchida A, Yokomizo T, Kita S, Sugiyama T, Miyagishi M, Hara K, Tsunoda M, Murakami K, Ohteki T, Uchida S, Takekawa S, Waki H, Tsuno NH, Shibata Y, Terauchi Y, Froguel P, Tobe K, Koyasu S, Taira K, Kitamura T, Shimizu T, Nagai R, Kadowaki T (June 2003). "Cloning of adiponectin receptors that mediate antidiabetic metabolic effects". Nature 423 (6941): 762–9. doi:10.1038/nature01705. PMID 12802337.  
  9. ^ Hug C, Wang J, Ahmad NS, Bogan JS, TSao TS, Lodish HF (2004). Proc Natl Acad Sci U S A 101 (28): 10308–13. PMID : doi = 10.1073/pnas.0403382101 15210937 : doi = 10.1073/pnas.0403382101.  
  10. ^ Fang X, Sweeney G (November 2006). "Mechanisms regulating energy metabolism by adiponectin in obesity and diabetes". Biochem. Soc. Trans. 34 (Pt 5): 798–801. doi:10.1042/BST0340798. PMID 17052201.  
  11. ^ Bonnard C, Durand A, Vidal H, Rieusset J (February 2008). "Changes in adiponectin, its receptors and AMPK activity in tissues of diet-induced diabetic mice". Diabetes Metab. 34 (1): 52–61. doi:10.1016/j.diabet.2007.09.006. PMID 18222103.  
  12. ^ a b c d Lara-Castro C, Fu Y, Chung BH, Garvey WT (June 2007). "Adiponectin and the metabolic syndrome: mechanisms mediating risk for metabolic and cardiovascular disease". Curr. Opin. Lipidol. 18 (3): 263–70. doi:10.1097/MOL.0b013e32814a645f. PMID 17495599.  
  13. ^ Matsuzawa Y, Funahashi T, Kihara S, Shimomura I (January 2004). "Adiponectin and metabolic syndrome". Arterioscler. Thromb. Vasc. Biol. 24 (1): 29–33. doi:10.1161/01.ATV.0000099786.99623.EF. PMID 14551151.  
  14. ^ a b Hara K, Yamauchi T, Kadowaki T (April 2005). "Adiponectin: an adipokine linking adipocytes and type 2 diabetes in humans". Curr. Diab. Rep. 5 (2): 136–40. doi:10.1007/s11892-005-0041-0. PMID 15794918.  
  15. ^ a b c d Vasseur F, Leprêtre F, Lacquemant C, Froguel P (April 2003). "The genetics of adiponectin". Curr. Diab. Rep. 3 (2): 151–8. doi:10.1007/s11892-003-0039-4. PMID 12728641.  
  16. ^ a b c Hug C, Lodish HF (April 2005). "The role of the adipocyte hormone adiponectin in cardiovascular disease". Curr Opin Pharmacol 5 (2): 129–34. doi:10.1016/j.coph.2005.01.001. PMID 15780820.  
  17. ^ a b Vasseur F, Meyre D, Froguel P (2006). "Adiponectin, type 2 diabetes and the metabolic syndrome: lessons from human genetic studies". Expert Rev Mol Med 8 (27): 1–12. doi:10.1017/S1462399406000147. PMID 17112391.  
  18. ^ Choi BH, Kim YH, Ahn IS, Ha JH, Byun JM, Do MS. (June 2009) "The inhibition of inflammatory molecule expression on 3T3-L1 adipocytes by berberine is not mediated by leptin signaling." Nutr Res Pract. 3(2):84-88. doi: 10.4162/nrp.2009.3.2.84.
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