Purpose Skeletal muscle is a major insulin responsive tissue, but it is not readily available in humans as an intact single cell preparation. T lymphocytes (T cells) are easily obtainable from blood, but in "resting " state are devoid of insulin receptors (IR). Upon activation, they develop de novo IR, become insulin sensitive, and metabolize glucose in a dose-dependent response to insulin. The degree to which the transcriptomes and proteomes differ in diabetic and nondiabetic muscle and T cells is not known.
Method T cells were separated into CD4 and CD8 with the use of specific antibodies by negative isolation. We analyzed the genes expressed (transcriptome) and proteins translated (proteome) in activated T cells and muscle of four newly diagnosed type 2 diabetes and compared them to their four matched controls. None of the subjects were on any medications. The genes expressed were determined using Affymetrix human U133 Plus 2.0 microarray chips and data analyzed using GCOS and GeneSifter software. Proteins translated were analyzed using the Cyphergen SELDI-TOF mass spectrometry system.
Result Gene expression of CD4 and CD8 activated T cells and muscles from normal subjects were compared to those diabetic subjects. In these cells up-regulation of the insulin receptor, insulin degrading enzyme (IDE), Akt, IRS-1, and IRS-2 genes was at least twofold less in diabetic than in control subjects, whereas there was greater than twofold up-regulation of plasma cell glyco protein-1(PC-1) in the diabetic compared to normal subjects. Transcriptomes of enzymes involved in the glycolytic pathway were also decreased twofold or greater in the diabetic tissues. The proteome profile of the normal vs diabetic subjects showed differences in protein concentrations. The proteins corresponding to the molecular weight of the above-translated transcriptomes were decreased in concentration in the diabetic tissues by twofold or greater compared to normal subjects. Changes in the proteome and transcriptome in muscle and activated T cells of diabetic tissues were comparable but reflected changes in the tissue specific-isoforms of the enzymes (ie, T cells or muscle).
Conclusion We conclude that activated CD4 and CD8 T cells express insulin signaling and glucose metabolism genes and gene products, analogous to muscle cells. Furthermore, muscle and activated T cells in diabetics exhibit less than half the expression of genes and gene products in these pathways, relative to nondiabetic controls.
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