SREBP-1c as a molecular bridge between lipogenesis and cell cycle progression of clear cell renal carcinoma

Cystathionine gamma-lyase deficiency exaggerates diethylnitrosamine-induced liver damage in mice

Cystathionine gamma-lyase (CSE) is a key enzyme in reverse transsulfuration pathway and contributes to the majority of H2S generation in liver tissues via cysteine metabolism. Dysfunction of the CSE/H2S system is linked to both chronic and acute liver damage. This study investigated the regulatory role of CSE deficiency on diethylnitrosamine (DEN)-induced liver damage in mice. A single injection of DEN was administered into 4-week-old male CSE knockout (CSE-KO) mice and wild-type (WT) littermates, and the mice were sacrificed at 28 weeks of age. Compared to age-matched WT mice, CSE-KO mice spontaneously developed steatosis with increased oxidative stress and higher expressions of inflammation and fibrosis-related genes at 28-weeks of age. Following DEN injection, CSE-KO mice experienced more severe liver damage in comparison with the WT group as reflected by elevated levels of lipid accumulation, increased activities of alanine aminotransferase and aspartate aminotransferase, higher oxidative stress and fibrosis development, and increased expressions of inflammation and fibrosis-related genes. No visible tumors were observed in both types of mice with DEN treatment. In addition, the expression levels of the three H2S-generating proteins (CSE, cystathionine beta-synthase, and 3-mercaptopyruvate sulfurtransferase) and the H2S production rate in liver tissues were unaffected by DEN. Taken together, our study demonstrates that CSE provides a significant hepatoprotective effect and deficiency of CSE exaggerates DEN-induced liver damage in mice. Based on these findings, it can be suggested that targeting the CSE/H2S signaling pathway could be a potential therapeutic target for the treatment of liver diseases.

MED15 is upregulated by HIF-2α and promotes proliferation and metastasis in clear cell renal cell carcinoma via activation of SREBP-dependent fatty acid synthesis

Emerging evidence has highlighted that dysregulation of lipid metabolism in clear cell renal cell carcinoma (ccRCC) is associated with tumor development and progression. HIF-2α plays an oncogenic role in ccRCC and is involved in abnormal lipid accumulation. However, the underlying mechanisms between these two phenomena remain unknown. Here, MED15 was demonstrated to be a dominant factor for HIF-2α-dependent lipid accumulation and tumor progression. HIF-2α promoted MED15 transcriptional activation by directly binding the MED15 promoter region, and MED15 overexpression significantly alleviated the lipid deposition inhibition and malignant tumor behavior phenotypes induced by HIF-2α knockdown. MED15 was upregulated in ccRCC and predicted poor prognosis. MED15 promoted lipid deposition and tumor progression in ccRCC. Mechanistic investigations demonstrated that MED15 acts as SREBP coactivator directly interacting with SREBPs to promote SREBP-dependent lipid biosynthesis enzyme expression, and promotes SREBP1 and SREBP2 activation through the PLK1/AKT axis. Overall, we describe a molecular regulatory network that links MED15 to lipid metabolism induced by the SREBP pathway and the classic HIF-2α pathway in ccRCC. Efforts to target MED15 or inhibit MED15 binding to SREBPs as a novel therapeutic strategy for ccRCC may be warranted.

Visfatin-induced upregulation of lipogenesis via EGFR/AKT/GSK3β pathway promotes breast cancer cell growth

Breast cancer (BC) incidence and associated mortality have increased in tandem with the growth in obesity among the females worldwide. An adipokine, visfatin, has been shown to potentially impact glucose, lipid, and protein metabolism, and promote cancer growth however, the mechanism underlying the effect of visfatin on lipid metabolism dysregulation contributing to BC cell survival, proliferation, and metastasis has not been elucidated. Herein, we have investigated the role of visfatin on the induction of Sterol regulatory element binding protein (SREBP-1) and its upstream and downstream mediators in MCF-7 breast cancer cells. The survival and proliferation was investigated using MTT and Trypan blue assays, cytosolic lipid accumulation was observed using Nile red staining, mRNA and protein expressions were examined using RT-qPCR and western blotting, respectively, and cell cycle analysis was performed using fluorescence-activated cell sorting. Our results indicate that visfatin increased the survival and proliferation of MCF-7 cells in a time- and dose-dependent manner and augmented lipid buildup via activation of SREBP-1 and its associated downstream lipid synthesizing enzymes, at both mRNA and protein levels in MCF-7 cells. Inhibiting SREBP-1 using fatostatin or silencing with siRNA abrogated excessive lipid deposition by suppressing the expression of genes related to lipid synthesis pathway. Further, in-silico study showed high affinity binding of visfatin with epidermal growth factor receptor (EGFR), which was confirmed in an in-vitro study where visfatin increased the phosphorylation of EGFR at tyrosine residue and activated its downstream proteins via phosphorylation of AKT and GSK3β in MCF-7 cells. Inhibition of GSK3β by phosphorylation led to increased activity of SREBP-1 and associated downstream proteins. In summary, SREBP-1 may be a critical player in visfatin-induced lipid synthesis and accumulation in BC cells via activation of EGFR/AKT/GSK3β pathway leading to increased cell survival and proliferation of BC cells.

Suppression of SREBP-1 Expression by Simvastatin Decreases Visfatin-Induced Chemoresistance to Sunitinib in Human Renal Carcinoma 786-O Cells

The resistance of renal cell carcinoma (RCC) to sunitinib impedes the success of chemotherapy in cancer treatment. Although several sunitinib resistance mechanisms have been proposed, little is known concerning the impact of obesity and adipokines in RCC cells. The upregulation of sterol-regulatory element-binding protein-1 (SREBP-1) has been reported to modulate the progression of tumor cells. The present study investigated the effect of visfatin on sunitinib-induced cytotoxicity in RCC cells through SREBP-1 expression. We found that visfatin-induced Akt and p70S6K activation increased SREBP-1 expression in 786-O cells. The visfatin-induced SREBP-1 mRNA and protein levels were attenuated through the inactivation of Akt and p70S6K by pharmacological inhibitors. In addition, the SREBP-1 knockdown using siRNA enhanced the cytotoxic effects of sunitinib. Our results also revealed the roles of simvastatin in attenuating the effects of visfatin on 786-O cells by inhibiting the production of reactive oxygen species. In particular, simvastatin co-treatment increased the cell cytotoxicity of sunitinib in visfatin-treated 786-O cells, which were associated with down-regulation of SREBP-1 expression. Our results suggest an important role of SREBP-1 in visfatin-induced drug resistance of RCC cells to sunitinib. The cytotoxic mechanism of simvastatin on RCC cells may provide a new strategy to improve therapeutic outcomes for the RCC treatment.

A novel lipid metabolism-related lncRNA signature predictive of clinical prognosis in cervical cancer

Background: Cervical cancer (CC) is a serious threat to women populations worldwide. Lipid metabolism is believed to have modulating functions in cancer. Long non-coding RNAs (lncRNAs) are potential biomarkers for the different tumor prognosis. Our work aims at investigating the prognostic value of lipid metabolism-related lncRNAs in CC.

Methods: LncRNA expression profiling was conducted in 291 patients from The Cancer Genome Atlas (TCGA). Patient samples were randomly assigned to the training or testing set in a 3:2 ratio. A novel lipid metabolism-related five-lncRNA signature with prognostic value for CC was built through the univariate Cox regression, least absolute contraction and selection operator (LASSO) regression and multivariate Cox regression analyses, and was further evaluated by the Kaplan-Meier methods. Relevant analyses were also applied to identify the independent clinicopathological factors. GO and KEGG analyses were conducted to investigate the biological functions and molecular pathways. Immune infiltration analysis was included to probe the relationship between lncRNA signature and cancer cell microenvironment.

Results: The novel lipid metabolism-related five-lncRNA signature was confirmed to be predictive of overall survival (OS) in CC patients. Risk score, cancer stage, pregnancy, and BMI were validated as independent factors with prognostic value. GO and KEGG indicated that lipid metabolism participated in several tumor associated functions and pathways. Moreover, our results suggested that the five-lncRNA expression has potential link with tumor immune microenvironment.

Conclusion: In conclusion, we built an innovative prognostic risk signature based upon lipid metabolism-related lncRNAs. The five-lncRNA signature may be beneficial to provide novel potential therapeutic targets and improve personalized treatment strategies for CC patients in future clinical treatments.

An oncogenic JMJD6-DGAT1 axis tunes the epigenetic regulation of lipid droplet formation in clear cell renal cell carcinoma

Characterized by intracellular lipid droplet accumulation, clear cell renal cell carcinoma (ccRCC) is resistant to cytotoxic chemotherapy and is a lethal disease. Through an unbiased siRNA screen of 2-oxoglutarate (2-OG)-dependent enzymes, which play a critical role in tumorigenesis, we identified Jumonji domain-containing 6 (JMJD6) as an essential gene for ccRCC tumor development. The downregulation of JMJD6 abolished ccRCC colony formation in vitro and inhibited orthotopic tumor growth in vivo. Integrated ChIP-seq and RNA-seq analyses uncovered diacylglycerol O-acyltransferase 1 (DGAT1) as a critical JMJD6 effector. Mechanistically, JMJD6 interacted with RBM39 and co-occupied DGAT1 gene promoter with H3K4me3 to induce DGAT1 expression. JMJD6 silencing reduced DGAT1, leading to decreased lipid droplet formation and tumorigenesis. The pharmacological inhibition (or depletion) of DGAT1 inhibited lipid droplet formation in vitro and ccRCC tumorigenesis in vivo. Thus, the JMJD6-DGAT1 axis represents a potential new therapeutic target for ccRCC.

Zhenqing recipe relieves diabetic nephropathy through the SIK1/SREBP-1c axis in type 2 diabetic rats

BACKGROUND

Salt-inducible kinase 1 (SIK1) plays an important role in lipid metabolism, which inhibits lipid synthesis by directly phosphorylating multiple serine residue sites of sterol regulatory element-binding protein 1c (SREBP-1c). This study examined potential therapeutic effect of a Chinese herbal medicine Zhenqing Recipe (ZQR) and metformin on diabetic nephropathy and investigated whether the SIK1/SREBP-1c axis is involved.

METHODS

The rat model of type 2 diabetes was developed by high-sucrose plus high fat diet for one month combined with low-dose Streptozocin intraperitoneal injection for three days, after which the presence of hyperglycemia and hyperlipidemia was examined to validate the model. The diabetic rats were then randomly allocated to diabetic groups treated by either ZQR or metformin, and normal rats receiving normal diet were included as a control group. Metabolic parameters, renal function, and renal triglyceride were examined and compared between groups.

RESULTS

After a treatment of 12 weeks, ZQR and metformin significantly reduced serum glucose and triglyceride, inhibited diabetic nephropathy and improved renal function. The mRNA level of SIK1 was significantly lower in the diabetic rats than that in the control group, while the expression of SREBP-1c had an opposite pattern. However, after receiving ZQR or metformin treatment, the SIK1 level in diabetic rats increased and the SREBP-1c level was downregulated. Consistent results were observed at the protein level.

CONCLUSION

The data suggested that similar to metformin, ZQR could alleviate diabetic nephropathy through SIK1/SREBP-1c axis.

SREBP1 site 1 protease inhibitor PF-429242 suppresses renal cell carcinoma cell growth

Renal cell carcinoma (RCC) cells have increased lipogenesis and cholesterol synthesis. Sterol regulatory element-binding protein-1 (SREBP1) is cleaved by site 1 protease (S1P) to release the transcriptionally active amino-terminal domain. PF-429242 is a potent and competitive S1P inhibitor. We here tested its activity in RCC cells. In established and primary human RCC cells, PF-429242 potently inhibited cell proliferation, migration, and invasion. The S1P inhibitor provoked apoptosis activation in RCC cells. Furthermore, shRNA-mediated S1P silencing or CRISPR/Cas9-induced S1P knockout led to RCC cell growth inhibition and apoptosis activation. Conversely, ectopic overexpression of SREBP1 or S1P augmented RCC cell proliferation and migration. Daily i.v. injection of a single dose of PF-429242 robustly inhibited RCC xenograft growth in severe combined immunodeficiency mice. Additionally, intratumoral injection of S1P shRNA lentivirus inhibited RCC xenograft growth in mice. SREBP1, S1P, and its target gene low density lipoprotein receptor (LDLR) were significantly elevated in human RCC tissues. These results suggest that targeting S1P by PF-429242 inhibited RCC cell growth in vitro and in vivo.

E2F1 promotes proliferation and metastasis of clear cell renal cell carcinoma via activation of SREBP1-dependent fatty acid biosynthesis

Enhanced synthesis or uptake of lipids contributes to rapid cancer cell proliferation and tumor progression. In recent years, cell cycle regulators have been shown to be involved in the control of lipid synthesis, in addition to their classical function of controlling the cell cycle. Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancer and is characterized by lipid-rich cytoplasmic deposition. However, the relationship between altered lipid metabolism and tumor progression in ccRCC is poorly understood. Here, we demonstrated that E2F transcription factor 1 (E2F1), in addition to its key role in regulating the cell cycle, induces extensive lipid accumulation and elevated levels of lipogenic enzymes in ccRCC cells by upregulating sterol regulatory element-binding protein 1 (SREBP1). E2F1 knockdown or SREBP1 suppression attenuated fatty acid (FA) de novo synthesis, cell proliferation and epithelial-mesenchymal transition (EMT) in ccRCC cells. Furthermore, overexpression of E2F1 promoted lipid storage, tumor growth and metastasis in a mouse xenograft model, whereas E2F1 downregulation or SREBP1 inhibition reversed these effects. In ccRCC patients, high levels of E2F1 and SREBP1 were associated with increased lipid accumulation and correlated with poor prognosis. Our results demonstrate that E2F1 can increase proliferation and metastasis through SREBP1-induced aberrant lipid metabolism, which is a novel critical signaling mechanism driving human ccRCC progression.

The Role of the Unfolded Protein Response on Renal Lipogenesis in C57BL/6 Mice

Renal injury observed in several pathologies has been associated with lipid accumulation in the kidney. While it has been suggested that the accumulation of renal lipids depends on free fatty acids released from adipose tissue, it is not known whether in situ renal lipogenesis due to endoplasmic reticulum (ER) stress contributes to kidney injury. The aim of the present study was to elucidate the role of pharmacological ER stress in renal structure and function and its effect on renal lipid metabolism of C57BL/6 mice. ER stress increased serum creatinine and induced kidney structural abnormalities. Tunicamycin-administered mice developed hyperinsulinemia, augmented lipolysis and increased circulating leptin and adiponectin. Renal unfolded protein response (UPR) gene expression markers, the lipogenic transcription factor SREBP1 and the phosphorylation of eIF2α increased 8 h after tunicamycin administration. At 24 h, an increase in BiP protein content was accompanied by a reduction in p-eIF2α and increased SREBP-1 and FASn protein content, in addition to a significant increase in triglyceride content and a reduction in AMPK. Thus, ER stress induces in situ lipid synthesis, leading to renal lipid accumulation and functional alterations. Future pharmacological and/or dietary strategies must target renal ER stress to prevent kidney damage and the progression of metabolic diseases.

A novel metformin derivative showed improvement of lipid metabolism in obese rats with type 2 diabetes

In this study, we investigated the lipid metabolism regulatory activity of a novel metformin derivative (MD568) and its potential mechanism of action in obese rats with type 2 diabetes mellitus (T2 DM). Previous gene chip analysis of 3T3-L1 cells have shown that MD568 regulates the transcription of genes involved in the peroxisome proliferator-activated receptor (PPAR) signalling pathway, fatty acid metabolism, and glycerolipid metabolism. In this study, obese T2 DM rats were treated with MD568 (200 mg/kg) for 8 weeks. Results showed that MD568 significantly reduced the body weight gain, plasma glucose, insulin, total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels. MD568 treatment also improved the insulin resistance of obese T2 DM model rats. In particular, in white adipose tissue, MD568 inhibited the excessive volume increment of adipose cells by down-regulating the protein levels of CCAAT/enhancer-binding protein-α (C/EBP-α) and PPAR-γ, as well as the transcription of their target lipid metabolism-related genes. In the liver, MD568 inhibited hepatic fatty lesions and interfered with hepatic gluconeogenesis by regulating the expression of lipid metabolism-related genes and glycogen-related kinases. In conclusion, our results suggest that the newly synthesized MD568 affects the maintenance of lipid homeostasis in obese type 2 diabetic rats.

The genetic basis of high-carbohydrate and high-monosodium glutamate diet related to the increase of likelihood of type 2 diabetes mellitus: a review

Diabetes is one of the most common metabolic diseases. Aside from the genetic factor, previous studies stated that other factors such as environment, lifestyle, and paternal-maternal condition play critical roles in diabetes through DNA methylation in specific areas of the genome. One of diabetic cases is caused by insulin resistance and changing the homeostasis of blood glucose control so glucose concentration stood beyond normal rate (hyperglycemia). High fat diet has been frequently studied and linked to triggering diabetes. However, most Asians consume rice (or food with high carbohydrate) and food with monosodium glutamate (MSG). This habit could lead to pathophysiology of type 2 diabetes mellitus (T2D). Previous studies showed that high-carbohydrate or high-MSG diet could change gene expression or modify protein activity in body metabolism. This imbalanced metabolism can lead to pleiotropic effects of diabetes mellitus. In this study, the authors have attempted to relate various changes in genes expression or protein activity to the high-carbohydrate and high-MSG-induced diabetes. The authors have also tried to relate several genes that contribute to pathophysiology of T2D and proposed several ideas of genes as markers and target for curing people with T2D. These are done by investigating altered activities of various genes that cause or are caused by diabetes. These genes are selected based on their roles in pathophysiology of T2D.

SIK2 enhances synthesis of fatty acid and cholesterol in ovarian cancer cells and tumor growth through PI3K/Akt signaling pathway

Salt-inducible kinase 2 (SIK2) has been established as a regulator of diverse biological processes including cell metabolism. A recent study has reported that SIK2 is required for adipocyte-induced ovarian cancer (OC) survival through facilitating fatty acid oxidation. However, whether SIK2 also plays a role in the lipid synthesis in OC cells remains elusive. Here, we showed that SIK2 significantly promoted the lipid synthesis in OC cells. On the one hand, SIK2 enhanced fatty acid synthesis through upregulating the expression of sterol regulatory element binding protein 1c (SREBP1c) and thus the transcription of major lipogenic enzyme FASN. On the other hand, SIK2 promoted cholesterol synthesis through upregulating the expression of sterol regulatory element binding protein 2 (SREBP2) and thus the transcription of major cholesterol synthesis enzymes HMGCR. Moreover, PI3K/Akt signaling pathway was found to be involved in the upregulation of SREBP1c and SREBP2 in OC cells. Moreover, in vitro and in vivo assays indicated that the SIK2-regulated fatty acid and cholesterol synthesis played a critical role in the growth of OC cells. Our findings demonstrate that SIK2 is a critical regulator of lipid synthesis in OC cells and thus promotes OC growth, which provides a strong line of evidence for this molecule to be used as a therapeutic target in the treatment of this malignancy.

Overexpression of PPT2 Represses the Clear Cell Renal Cell Carcinoma Progression by Reducing Epithelial-to-mesenchymal Transition

Clear cell renal cell carcinoma (ccRCC) is one of the most common malignant tumors of the urinary system and has a poor response to radiotherapy and chemotherapy. To date, it is urgent to find effective biomarkers for the prevention and treatment of ccRCC. The occurrence and development of ccRCC is closely related to metabolic disturbances. Palmitoyl protein thioesterase 2 (PPT2) is a lysosomal thioesterase which is highly associated with metabolism, and it has never been studied in ccRCC. In this study, we first revealed PPT2 is significantly downregulated in ccRCC, and its expression level is highly correlated with clinicopathological parameters of ccRCC patients. Our ROC curve analyses evaluated the potential of PPT2 as a novel diagnostic marker and prognostic factor. Functional experiment results showed overexpression of PPT2 represses the proliferation, migration and invasion of ccRCC cells in vitro. Mechanistic investigations demonstrated that overexpression of PPT2 represses the ccRCC progression by reducing epithelial-to-mesenchymal transition (EMT). In conclusion, PPT2 is downregulated in ccRCC. Decreased PPT2 expression may be considered as a novel diagnostic marker and prognostic factor and serve as a therapeutic target for ccRCC.

Acute Effects of Transdermal Administration of Jojoba Oil on Lipid Metabolism in Mice

Background and objectives: Aroma therapy is a complementary therapy using essential oils diluted with carrier oils. Jojoba oils have been widely used as carrier oils. However, limited information is available regarding their effects on blood biochemical parameters. This study aimed to investigate the effect of transdermal administration of jojoba oil on blood biochemical parameters in mice. Materials and Methods: Eight-week-old male hairless mice were randomly divided into naïve control and treatment groups. In the treatment group, mice were topically administered 4 μL of jojoba oil, per gram of body weight, on the dorsa 30 min before euthanasia. Thereafter, serum biochemical parameters were assayed, and gene expression was analyzed in various tissues via a real-time polymerase chain reaction. Results: Serum non-esterified fatty acid (NEFA) levels increased significantly 30 min after topical application of jojoba oil (p < 0.05). Atgl was significantly upregulated in the liver (p < 0.05), and Atgl upregulation in the liver was positively correlated with serum NEFA levels (r = 0.592, p < 0.05). Furthermore, a trend of decreasing fatty acid trafficking-related gene (FABPpm, FATP-1, FATP-3, and FATP-4) expression in the skin after topical application of jojoba oil (p = 0.067, 0.074, 0.076, and 0.082, respectively) was observed. Conclusions: Serum NEFA levels were elevated 30 min after transdermal administration of jojoba oil. The mechanisms of elevated serum NEFA levels might be related to both enhanced lipolysis in the liver and reduced fatty acid trafficking in the skin.

The Function of Lipin in the Wing Development of Drosophila melanogaster

Lipin is evolutionarily conserved from yeast to mammals. Although its roles in lipid metabolism in adipocyte tissue, skeletal muscle, and the liver, and as a transcriptional co-activator are known, its functions during development are still under investigation. In this study, we analyzed the role of Drosophila lipin (dLipin) in development. Specifically, we showed that the tissue-selective knockdown of dLipin in the wing pouch led to an atrophied wing. Elevated DNA damage was observed in the wing imaginal disc of dLipin-knockdown flies. dLipin dysfunction induced accumulation of cells in S phase and significantly reduced the number of mitotic cells, indicating DNA damage-induced activation of the G2/M checkpoint. Reduced expression of cyclin B, which is critical for the G2 to M transition, was observed in the margin of the wing imaginal disc of dLipin-knockdown flies. The knockdown of dLipin led to increased apoptotic cell death in the wing imaginal disc. Thus, our results suggest that dLipin is involved in DNA replication during normal cell cycle progression in wing development of Drosophila melanogaster.

PLIN3 is up-regulated and correlates with poor prognosis in clear cell renal cell carcinoma

BACKGROUND

PLIN3, one of the members of the perilipin family, has been reported to be involved in the formation and accumulation of lipid droplets. However, the expression levels and diagnostic and prognostic value of PLIN3 in renal cell carcinoma (RCC) remain unclear.

METHODS

Bioinformatic analysis was used to assess the levels of PLIN3 and the correlation between PLIN3 levels and clinicopathological parameters in renal cancer. The expression levels of PLIN3 were determined in human RCC tissues and cell lines by western blot, immunofluorescence and immunohistochemistry assays. Receiver operating characteristic curves and Kaplan-Meier curves were used to analyze the diagnostic and prognostic significance of PLIN3 in RCC.

RESULTS

The expression level of PLIN3 was elevated in RCC tissues and cell lines, which was consistent with the analysis of the TCGA and Oncomine cancer database. The receiver operating characteristic curve indicated that high PLIN3 expression can distinguish cancer tissues from normal kidney tissues (area under the curve = 0.7270, P<0.0001). Kaplan-Meier curves revealed that elevated PLIN3 predicted poor disease-free survival and overall survival.

CONCLUSIONS

PLIN3 is highly expressed in kidney cancer, and high expression of PLIN3 can serve as a useful diagnostic and prognostic biomarker. PLIN3 functional inhibition can be used as a new clinical treatment option.

Heat shock protein 70 promotes lipogenesis in HepG2 cells

Background

The increasing prevalence of non-alcoholic fatty liver disease (NAFLD) has followed the international rise in obesity rates. Multiple mechanisms are involved in NAFLD, including endoplasmic reticulum stress and oxidative stress. Heat shock protein 70 (HSP70), which is abundant in most organisms, is sensitive to stress. However, the role of HSP70 in NAFLD has not been investigated. Here, we investigated the possible role of HSP70 in lipid synthesis.

Methods

C57BL/6 mice were fed a high-fat diet, and HepG2 cells were treated with 0.5 mM palmitic acid (PA). HSP70 expression was detected by qPCR, Western blot and immunohistochemistry. Total cholesterol (TC) and triglyceride (TG) levels were detected by enzyme-linked immunosorbent assay (ELISA). After Hsp70 overexpression and knockdown, TC and TG levels and FAS, SCD, and ACC expression were detected.

Results

HSP70 expression was significantly increased in the livers of obese mice. In vitro, HSP70 expression was markedly induced by PA in HepG2 cells. Notably, HSP70 overexpression in HepG2 cells enhanced TC and TG synthesis, in parallel with the upregulation of lipogenic genes, including FAS, SCD and ACC. By contrast, HSP70 knockdown decreased the levels of cellular lipids and the expression of FAS, SCD, and ACC in HepG2 cells. Together, our results suggest that HSP70 may promote lipogenesis in HepG2 cells.

Conclusions

Heat shock protein 70 promotes lipogenesis in HepG2 cells.