Temporal profiling of the transcriptional basis for the development of corticosteroid-induced insulin resistance in rat muscle

Abstract

Elevated systemic levels of glucocorticoids are causally related to peripheral insulin resistance. The pharmacological use of synthetic glucocorticoids (corticosteroids) often results in insulin resistance/type II diabetes. Skeletal muscle is responsible for close to 80% of the insulininduced systemic disposal of glucose and is a major target for glucocorticoid-induced insulin resistance. We used Affymetrix gene chips to profile the dynamic changes in mRNA expression in rat skeletal muscle in response to a single bolus dose of the synthetic glucocorticoid methylprednisolone. Temporal expression profiles (analyzed on individual chips) were obtained from tissues of 48 drugtreated animals encompassing 16 time points over 72 h following drug administration along with four vehicletreated controls. Data mining identified 653 regulated probe sets out of 8799 present on the chip. Of these 653 probe sets we identified 29, which represented 22 gene transcripts, that were associated with the development of insulin resistance. These 29 probe sets were regulated in three fundamental temporal patterns. 16 probe sets coding for 12 different genes had a profile of enhanced expression. 10 probe sets coding for eight different genes showed decreased expression and three probe sets coding for two genes showed biphasic temporal signatures. These transcripts were grouped into four general functional categories: signal transduction, transcription regulation, carbohydrate/fat metabolism, and regulation of blood flow to the muscle. The results demonstrate the polygenic nature of transcriptional changes associated with insulin resistance that can provide a temporal scaffolding for translational and post-translational data as they become available.

Glucocorticoids, metabolism and metabolic diseases

“…Almon et al obtained gene expression profiles from skeletal muscle of rats treated with Dex and identified changes in 22 genes associated with the development of insulin resistance [246]. Although functional validation of transcriptional changes remains to be determined, such approaches will be helpful in order to achieve a more global picture of the molecular mechanisms of GC action in muscle.…”

Assessing the Dynamics of Nuclear Glucocorticoid-Receptor Complex: Adding Flexibility to Gene Expression Modeling

“…The details of our microarray studies are published (17,18). Briefly, total RNA from rat liver was extracted using Trizol reagent according to manufacturer's protocols.…”

“…The mRNA time profiles for hepatic TAT, CEBP-β, ornithine decarboxylase (ODC), argininosuccinate synthetase (ASS), aldehyde dehydrogenase (ADH), low density lipoprotein receptor (LDL-R), carbonic anhydrase (CA) and glutaminase mRNA from our microarray study (17,18) from the high-dose group (50 mg/kg single dose) of MPL treated animals are examples of rapid and slow responding genes. Equation (12) was used to describe the increase in transcription of TAT, CEBP-β, ODC and ASS mRNA.…”

“…In these earlier studies, we were technically limited to studying relatively few target genes at a time, such as the up-regulation of hepatic TAT mRNA and activity, hepatic phosphoenol-pyruvate carboxykinase (PEPCK) mRNA and activity (15), glutamine synthetase (GS) mRNA and activity in the muscle (16), and down-regulation of GR mRNA. However, in microarray experiments (17,18), where the effects of CS treatment were simultaneously examined for several thousands of genes, we encountered classes of rapidly up-or down-regulated genes which could not be described by our previous model. The nuclear drug-receptor complex (DR(N) in Fig.…”

Mathematical Modeling of Corticosteroid Pharmacogenomics in Rat Muscle following Acute and Chronic Methylprednisolone Dosing

“…8 In addition, many transcription factors are also regulated by CS. 9 It is likely that, besides the direct effects by CS itself, the alterations of these transcription factors elicit further and more extensive regulatory effects on gene transcription and modify the pharmacological actions of the drugs. This evidence suggests that CS elicit diverse functions through various connected pathways.…”