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Karlsson HK, Tuulari JJ, Tuominen L, Hirvonen J, Honka H, Parkkola R, Helin S, Salminen P, Nuutila P, Nummenmaa L. Weight loss after bariatric surgery normalizes brain opioid receptors in morbid obesity. Mol Psychiatry 2016; 21:1057-62. [PMID: 26460230 DOI: 10.1038/mp.2015.153] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/05/2015] [Accepted: 08/10/2015] [Indexed: 12/13/2022]
Abstract
Positron emission tomography (PET) studies suggest opioidergic system dysfunction in morbid obesity, while evidence for the role of the dopaminergic system is less consistent. Whether opioid dysfunction represents a state or trait in obesity remains unresolved, but could be assessed in obese subjects undergoing weight loss. Here we measured brain μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) availability in 16 morbidly obese women twice-before and 6 months after bariatric surgery-using PET with [(11)C]carfentanil and [(11)C]raclopride. Data were compared with those from 14 lean control subjects. Receptor-binding potentials (BPND) were compared between the groups and between the pre- and postoperative scans among the obese subjects. Brain MOR availability was initially lower among obese subjects, but weight loss (mean=26.1 kg, s.d.=7.6 kg) reversed this and resulted in ~23% higher MOR availability in the postoperative versus preoperative scan. Changes were observed in areas implicated in reward processing, including ventral striatum, insula, amygdala and thalamus (P's<0.005). Weight loss did not influence D2R availability in any brain region. Taken together, the endogenous opioid system plays an important role in the pathophysiology of human obesity. Because bariatric surgery and concomitant weight loss recover downregulated MOR availability, lowered MOR availability is associated with an obese phenotype and may mediate excessive energy uptake. Our results highlight that understanding the opioidergic contribution to overeating is critical for developing new treatments for obesity.
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Affiliation(s)
- H K Karlsson
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - J J Tuulari
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - L Tuominen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.,Department of Psychiatry, University of Turku and Turku University Hospital, Turku, Finland
| | - J Hirvonen
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.,Medical Imaging Centre of Southwest Finland, Turku, Finland.,Department of Radiology, University of Turku and Turku University Hospital, Turku, Finland
| | - H Honka
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - R Parkkola
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.,Department of Radiology, University of Turku and Turku University Hospital, Turku, Finland
| | - S Helin
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - P Salminen
- Department of Digestive Surgery, University of Turku and Turku University Hospital, Turku, Finland
| | - P Nuutila
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.,Department of Endocrinology, Turku University Hospital, Turku, Finland
| | - L Nummenmaa
- Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland.,Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, Espoo, Finland.,Department of Psychology, University of Turku, Turku, Finland
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Laurila JMM, Xhaard H, Ruuskanen JO, Rantanen MJM, Karlsson HK, Johnson MS, Scheinin M. The second extracellular loop of alpha2A-adrenoceptors contributes to the binding of yohimbine analogues. Br J Pharmacol 2007; 151:1293-304. [PMID: 17558432 PMCID: PMC2189838 DOI: 10.1038/sj.bjp.0707330] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Rodent alpha(2A)-adrenoceptors bind the classical alpha(2)-antagonists yohimbine and rauwolscine with lower affinity than the human alpha(2A)-adrenoceptor. A serine-cysteine difference in the fifth transmembrane helix (TM; position 5.43) partially explains this, but all determinants of the interspecies binding selectivity are not known. Molecular models of alpha(2A)-adrenoceptors suggest that the second extracellular loop (XL2) folds above the binding cavity and may participate in antagonist binding. EXPERIMENTAL APPROACH Amino acids facing the binding cavity were identified using molecular models: side chains of residues 5.43 in TM5 and xl2.49 and xl2.51 in XL2 differ between the mouse and human receptors. Reciprocal mutations were made in mouse and human alpha(2A)-adrenoceptors at positions 5.43, xl2.49 and xl2.51, and tested with a set of thirteen chemically diverse ligands in competition binding assays. KEY RESULTS Reciprocal effects on the binding of yohimbine and rauwolscine in human and mouse alpha(2A)-adrenoceptors were observed for mutations at 5.43, xl2.49 and xl2.51. The binding profile of RS-79948-197 was reversed only by the XL2 substitutions. CONCLUSIONS AND IMPLICATIONS Positions 5.43, xl2.49 and xl2.51 are major determinants of the species preference for yohimbine and rauwolscine of the human versus mouse alpha(2A)-adrenoceptors. Residues at positions xl2.49 and xl2.51 determine the binding preference of RS-79948-197 for the human alpha(2A)-adrenoceptor. Thus, XL2 is involved in determining the species preferences of alpha(2A)-adrenoceptors of human and mouse for some antagonists.
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Affiliation(s)
- J M M Laurila
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Itäinen Pitkäkatu 4B, FL-20520 Turku, Finland.
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