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- Gabrielsson, Britt, 1957, et al.
(författare)
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Molecular characterization of a local sulfonylurea system in human adipose tissue.
- 2004
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Ingår i: Molecular and cellular biochemistry. - 0300-8177 .- 1573-4919. ; 258:1-2, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- ATP-sensitive potassium (KATP) channels are present in many cell types and link cellular metabolism to the membrane potential. These channels are heterooctamers composed of two subunits. The sulfonylurea receptor (SUR) subunits are targets for drugs that are inhibitors or openers of the KATP channels, while the inwardly rectifying K+ (Kir) subunits form the ion channel. Two different SUR genes (SUR1 and SUR2) and two different Kir6.x genes (Kir6.1 and Kir6.2) have been identified. In addition, isoforms of SUR2, SUR2A and SUR2B, have been described. We have previously performed expression profiling on pooled human adipose tissue and found high expression of SUR2. Others have reported expression of SUR1 in human adipocytes. The aim of this study was to characterize the expression of the sulfonylurea receptor complex components in human adipose tissue. RT-PCR analysis, verified by restriction enzyme digestions and DNA sequencing, showed that SUR2B, Kir6.1 and alpha-endosulfine, but not SUR1, SUR2A or Kir6.2, are expressed in human adipose tissue. Real-time RT-PCR showed that SUR2B was expressed at higher levels in subcutaneous compared with omental adipose tissue in paired biopsies obtained from seven obese men (p < 0.05). Analysis of tissue distribution showed that SUR2B expression in adipose tissue was lower than that in muscle, similar to that in heart and liver, while the expression in pancreas was lower. The effect of caloric restriction was tested in obese men (n = 10) treated with very low calorie diet for 16 weeks, followed by a gradual reintroduction of ordinary food for 2 weeks. Biopsies were taken at week 0, 8 and 18. There was no consistent effect of weight reduction on SUR2B or Kir6.1 expression. We conclude that the necessary components for a local sulfonylurea system are expressed in human adipose tissue and that the sulfonylurea receptor complex in this tissue is composed of SUR2B and Kir6.1. The expression of SUR2B was higher in subcutaneous compared with omental adipose tissue and was not affected by weight loss.
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| 2. |
- N'Guessan, Benoit, et al.
(författare)
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Evaluation of quantitative and qualitative aspects of mitochondrial function in human skeletal and cardiac muscles
- 2004
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Ingår i: Molecular and Cellular Biochemistry. - Dordrecht, Netherlands : Kluwer Academic Publishers. - 0300-8177 .- 1573-4919. ; 256-257:1-2, s. 267-80
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Forskningsöversikt (refereegranskat)abstract
- Techniques and protocols of assessment of mitochondrial properties are of physiological and physiopathological important significance. A precise knowledge of the advantages and limitations of the different protocols used to investigate the mitochondrial function, is therefore necessary. This report presents examples of how the skinned (or permeabilized) fibers technique could be applied for the polarographic determination of the actual quantitative and qualitative aspects of mitochondrial function in human muscle samples. We described and compared the main available respiration protocols in order to sort out which protocol seems more appropriate for the characterization of mitochondrial properties according to the questions under consideration: quantitative determination of oxidative capacities of a given muscle, characterization of the pattern of control of mitochondrial respiration, or assessment of a mitochondrial defect at the level of the respiratory chain complexes. We showed that while protocol A, using only two levels of the phosphate acceptor adenosine diphosphate (ADP) concentration and the adjunction of creatine, could be used for the determination of quantitative changes in very small amount of muscle samples, the ADP sensitivity of mitochondrial respiration was underestimated by this protocol in muscles with high oxidative capacities. The actual apparent Km for ADP and the role of functional activation of miCK in ATP production and energy transfer in oxidative muscles, are well-assessed by protocol B (in the absence of creatine) together with protocol C (in the presence of creatine) that use increasing concentrations of ADP ranging from 2.5-2000 microM. Protocol D is well-adapted to investigate the potential changes at different levels of the respiratory chain, by the use of specific substrates and inhibitors. As can be seen from the present data and the current review of previous reports in the literature, a standardization of the respiration protocols is needed for useful comparisons between studies.
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