Decreased heat shock response upon adipose differentiation of 3T3-L1 cells

Gene expression profiling in developing pig adipose tissue: non-secreted regulatory proteins

The expression of many genes encoding secreted and non-secreted factors have been studied in human and rodent adipose tissue with cDNA microarrays, but few such studies in adipose tissue from growing pigs have been reported. Total RNA was collected at slaughter from outer subcutaneous adipose tissue (OSQ) and middle subcutaneous adipose tissue (MSQ) samples from gilts at 90, 150 and 210 days (n = 5/age). Dye-labeled cDNA probes were hybridized to custom microarrays (70-mer oligonucleotides) representing about 600 pig genes involved in growth and reproduction. Gene expression intensity ratios changed little with age for 100 transcription factors, nuclear receptors, enzymes and other regulatory proteins in OSQ and MSQ from pigs between 90 and 210 days of age. However, the relative expression of 13 genes distinguished OSQ and MSQ depots in growing pigs. The expression of several genes were influenced by age including an increase in CCND3, HSF1 and PTGR1 expression in MSQ and a decrease in UCP2 and REA (prohibitin-2) expression in OSQ. These studies demonstrate for the first time the expression of several key regulatory genes in pig adipose tissue. Simple linear regression analysis showed that leptin gene expression was associated with expression of some of these regulatory genes. Negative associations between expression of some regulatory factors and leptin gene expression indicated that local leptin may decrease or antagonize adipogenesis.

Heat stimulation reduces early adipogenesis in 3T3-L1 preadipocytes

In this study, we used 3T3-L1 preadipocytes as a model to investigate the effects of heat stimulation on adipogenesis, which is a key process in the development of obesity. Heat stimulation at 43 degrees C for 60 min significantly reduced lipid accumulation, as measured by Oil Red-O assay. In the early phase of adipogenesis, heat stimulation almost completely blocked the increase of CCAAT/enhancer binding protein delta (C/EBPdelta) gene expression and delayed the onset of the increase of C/EBPbeta gene expression. The expression of proliferator-activated receptor gamma (PPARgamma), which is regulated by these factors, was also reduced. In the later phase of adipogenesis, the induction of adipocyte-specific genes, such as C/EBPalpha, adipocyte protein 2 (aP2), lipoprotein lipase (LPL), adiponectin, and glucose transporter 4 (Glut4), which are regulated by PPARgamma, was reduced. However, adipogenesis was not significantly reduced if heat stimulation was carried out after the early phase of adipogenesis. These results suggest that heat stimulation reduces adipogenesis by decreasing the expression of adipogenesis-related transcriptional factors during early adipogenesis.

Identification and characterization of cvHsp. A novel human small stress protein selectively expressed in cardiovascular and insulin-sensitive tissues

Starting with computational tools that search for tissue-selective expression of assembled expressed sequenced tags, we have identified by focusing on heart libraries a novel small stress protein of 170 amino acids that we named cvHsp. cvHsp was found as being computationally selectively and highly (0.3% of the total RNA) expressed in human heart. The cvHsp gene mapped to 1p36.23-p34.3 between markers D1S434 and D1S507. The expression of cvHsp was analyzed with RNA dot, Northern blots, or reverse transcription-polymerase chain reaction: expression was high in heart, medium in skeletal muscle, and low in aorta or adipose tissues. In the heart of rat models of cardiac pathologies, cvHsp mRNA expression was either unchanged (spontaneous hypertension), up-regulated (right ventricular hypertrophy induced by monocrotaline treatment), or down-regulated (left ventricular hypertrophy following aortic banding). In obese Zucker rats, cvHsp mRNA was increased in skeletal muscle, brown, and white adipose tissues but remained unchanged in the heart. Western blot analysis using antipeptide polyclonal antibodies revealed two specific bands at 23 and 25 kDa for cvHsp in human heart. cvHsp interacted in both yeast two-hybrid and immunoprecipitation experiments with alpha-filamin or actin-binding protein 280. Within cvHsp, amino acid residues 56-119 were shown to be important for its specific interaction with the C-terminal tail of alpha-filamin.

Molecular events involved in transcriptional activation of heat shock genes become progressively refractory to heat stimulation during aging of human diploid fibroblasts

We examined the induction, by heat shock, of heat shock transcription factor (HSTF) DNA-binding and hsp 70 gene promoter activities during aging of the IMR-90 human diploid fibroblasts. Cells with population doubling level (PDL) ranging from 15-48 were heat shocked at temperatures of 39, 42, and 45 degrees C for various time periods; the binding of HSTF to its consensus DNA was determined by gel retardation assay and the promoter activity of the human hsp 70 gene was analyzed by transient expression of reporter gene activity. We observed that the induction of HSE-binding activity was inversely related to the PDL of the cells used. Importantly, as cells progress through their life span, a higher temperature and a longer period of heat shock were needed to evoke an optimal increase in HSE-binding activity. A substantial and rapid (within 30 min) increase in HSE-binding activity was observed when PDL 20 cells were heat shocked at 39, 42, or 45 degrees C. However, PDL 35 cells did not respond to 39 degrees C, and PDL 48 cells responded slowly to heat shock at 45 degrees C, but not 39 or 42 degrees C. Experiments on the heat induced increase in hsp 70 promoter driven reporter gene expression provided similar information on the age-dependent decrease in transcriptional activation of hsps. These results were further corroborated by quantitation of the abundance of mRNA of hsp 70. Analysis of the cAMP induced expression of the rat somatostatin promoter driven CAT gene provided evidence that the decrease in transcriptional activation of hsps in aging diploid cells was not a reflection of a generalized dysfunction of signal transduction. We conclude that functional changes in the heat shock response occur before cells lose their capacity to replicate, and we suggest that these changes are likely to have a central role in the expression of the aging phenotype.