Study of fatty acids regulated genes in 3T3-L1 preadipocytes during adipogenesi

Obesity and obesity-related type 2 diabetes are known as serious health issues in the United States and worldwide. Environmental factors, including diets, may play an important role in the development of these diseases. Adipose and muscle tissue are significantly affected in individuals with obesity and obesity-related type 2 diabetes. It has been observed previously in the laboratory that high concentrations of the saturated fatty acid (palmitic acid) differentially affect muscle cells and adipocytes. Palmitic acid damages muscle cells and induces muscle cell death while causing more lipid accumulation in adipocytes. The polyunsaturated fatty acid linoleic acid also causes more lipid accumulation in adipocytes but does not damage muscle cells. Based on the cellular level analysis, it was hypothesized that saturated and polyunsaturated fatty acids differentially regulate genes during differentiation of preadipocytes. The planned research was based on mimicking hyperlipidemia conditions observed in obesity/type 2 diabetes individuals by incubating mouse 3T3-L1 preadipocytes in media containing fatty acids. The 3T3-L1 cells analyzed by Oil Red-O staining, cell counting, Propidium Iodide and Hoechst 33342 staining confirmed the effects of fatty acids to adipocytes at cellular level. None of the fatty acids damaged or induced cell death of adipocytes. And both, palmitic acid and linoleic acid induced more lipid accumulation in differentiated 3T3-L1 adipocytes. The focus of this research was to study the regulation of the candidate genes in adipocytes picked by DNA microarrays. Real-Time PCR was used to validate the candidate genes regulated by palmitic and linoleic acids from a previous DNA microarray screening, and Western Blot analysis was used to further confirm the results. Palmitic and linoleic acids differentially regulate the candidate genes. CHOP, a protein associated with apoptosis and growth arrest, its mRNA levels were upregulated by the saturated fatty acid while not regulated by the polyunsaturated fatty acid. GADD34, another protein associated to apoptosis, however its mRNA levels were upregulated by both palmitic and linoleic acid. Fignl2, a protein associated with cellular activities like cell growth, its mRNA levels were induced by linoleic acid. It may indicate that polyunsaturated fatty acid is favorable to cell growth. GRP78, a key regulator protein of endoplasmic reticulum stress, showed a gradual upregulation at both mRNA and protein levels by palmitic acid.