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Folate and vitamin B12 imbalance induces endoplasmic reticulum stress and cholesterol biosynthesis gene expression in human adipocytes

ABSTRACT: Rationale: Low B12 has been shown to play an important role in the prediction of metabolic risk, but its significance and mechanism in the development of adiposity and adipose tissue dysfunction is largely unknown. Objective: To investigate the role of B12 and folic acid in the development of adipocyte dysfunction. Methods and Results: Microarray analysis of human adipocytes (CHUB-S7 cell line) cultured and differentiated in customised media with varying concentrations of B12 and folic acid led to the identification of two important pathways: cholesterol synthesis and unfolded protein response (UPR). Adipocytes cultured in media with low B12 (150 pmol/L) or no B12 had increased intracellular total cholesterol, higher secreted homocysteine levels, induced UPR and reduced glucose uptake capacity compared to adipocytes cultured in normal media with higher B12. The folate concentrations had either no or little effect on the measured functions. Further analysis of these adipocytes for overall DNA methylation showed that the promoter regions of sterol regulatory element-binding transcription factor 1 (SREBF1) and low density lipoprotein receptor (LDLR) were hypomethylated in the low and no B12 conditions. The SREB proteins (SREBP1 and 2) and mRNA expressions (SREBF1 and LDLR) were also increased in the same conditions. Conclusion: The data suggest that low B12 can lead to adipocyte dysfunction by inducing excess cholesterol biosynthesis, homocysteine production and induction of UPR and overall adipocyte dysfunction. Both of these pathways and adipocyte dysfunction play a significant role in the development of cardiovascular diseases.

ORGANISM(S): Homo sapiens

PROVIDER: GSE43166 | GEO | 2012/12/30

SECONDARY ACCESSION(S): PRJNA184810

REPOSITORIES: GEO

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Project description:Recents studies in mice and humans demonstrated the relevance of H2S-synthesising enzymes (such as CTH, CBS and MPST) in adipose tissue physiology and preadipocyte differentiation into adipocytes. Here, we aimed to investigate the combined role of CTH, CBS and MPST in the preservation of adipocyte protein persulfidation and adipogenesis. Joint CTH, CBS and MPST gene knockdown was achieved treating fully human adipocytes with siRNAs against these transcripts (siRNA_MIX). Adipocyte protein persulfidation was analyzed by a mass spectrometry label-free quantitative approach coupled with a dimedone-switch method for protein labeling and purification. The proteomic analysis quantified 216 proteins with statistically different persulfidation levels in KD cells compared to control adipocytes. In fully differentiated adipocytes, CBS and MPST mRNA and protein levels were abundant, whereas CTH expression was very low. Of note, siRNA_MIX administration resulted in a significant decrease in CBS and MPST expression, without impacting on CTH. Dual CBS and MPST gene knockdown resulted in decreased expression of relevant genes for adipocyte biology, including adipogenesis, mitochondrial biogenesis and lipogenesis, but increased proinflammatory- and senescence-related genes, in parallel to a significant disruption in adipocyte protein persulfidation pattern. While among less persulfidated proteins, we identified several relevant proteins for adipocyte adipogenesis and function, among the most persulfidated, key mediators of adipocyte inflammation and dysfunction, but also some proteins that might have a positive role of adipogenesis were found. In conclusion, current study indicates that joint knockdown of CBS and MPST (but not CTH) in adipocytes impairs adipogenesis and promotes inflammation, possibly by disrupting the pattern of protein persulfidation in these cells, and suggesting that these enzymes were required for the functional maintenance of adipocytes.

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Folate and vitamin B12 imbalance induces endoplasmic reticulum stress and cholesterol biosynthesis gene expression in human adipocytes

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