Effect of hind limb muscle unloading on liver metabolism of rats.

In response to decreased use, skeletal muscle undergoes an adaptive reductive remodeling. There is a shift in fiber types from slow twitch to fast twitch fiber types. Associated with muscle unloading is an increased reliance on carbohydrate metabolism for energy. The hind limb suspended (HLS) rat model was used as the experimental model to determine whether skeletal muscle unloading had any impact on the liver. We used a combination of actual enzyme assays and microarray mRNA expression to address this question. The GenMAPP program was used to identify altered metabolic pathways. We found that the major changes in the liver with HLS were increases in the expression of genes involved in the generation of energy fuels for export, specifically gluconeogenesis and lipogenesis. The expression of mRNA was increased (P<0.05) for three of the four enzymes involved in the regulation of gluconeogenesis pathway (pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G-6-Pase). Actual assay of enzymatic activity, in micromol . min(-1) . mg protein(-1) showed G-6-Pase (0.14+0.01 vs 0.17+0.01 P<0.05), fructose 1,6, bisphophosphatase (0.048+0.002 vs 0.054+0.002, P<0.07), and PEPCK (0.031+0.002 vs 0.038+0.012 (P<0.05) to be increased. We conclude that 1) atrophied muscle is not the only tissue to be affected by HLS, as there is also a response by the liver; and 2) the major changes in liver substrate metabolism induced by HLS appear to be limited to glucose and triglyceride production. The increase in glycolytic capacity in disused muscle is paralleled by an increase in glucogenic capacity by the liver.

Association between gene expression profile and tumor invasion in oral squamous cell carcinoma.

There are limited studies attempting to correlate the expression changes in oral squamous cell carcinoma with clinically relevant variables. We determined the gene expression profile of 16 tumor and 4 normal tissues from 16 patients by means of Affymetrix Hu133A GeneChips. The hybridized RNA was isolated from cells obtained with laser capture microdissection, then was amplified and labeled using T7 polymerase-based in vitro transcription. The expression of 53 genes was found to differ significantly (33 upregulated, 20 downregulated) in normal versus tumor tissues under two independent statistical methods. The expression changes in four selected genes (LGALS1, MMP1, LAGY, and KRT4) were confirmed with reverse transcriptase polymerase chain reaction. Two-dimensional hierarchical clustering of the 53 genes resulted in the samples clustering according to the extent of tumor infiltration: normal epithelial tissue, tumors less than or equal to 4 cm in dimension, and tumors more than 4 cm in dimension (P = 0.0014). The same pattern of clustering was also observed for the 20 downregulated genes. We did not observe any associations with lymph node metastasis (P = 0.097).