Transcription Factor MITF Inhibits the Transcription of CPT1B to Regulate Fatty Acid β-Oxidation and Thus Affects Stemness in Lung Adenocarcinoma Cells

INTRODUCTION

Cancer stem cells (CSCs) play critical roles in lung adenocarcinoma (LUAD) progression, and fatty acid oxidation is key for CSC growth and survival. Therefore, investigating the molecular mechanisms regulating fatty acid β-oxidation in LUAD is important for its treatment.

METHODS

Bioinformatics analysis assessed CPT1B and MITF expression and their correlation in LUAD tissues, as well as the pathways enriched by CPT1B. qRT-PCR assessed expression of CPT1B and MITF, while CCK-8 and sphere-forming assays were used to measure cell viability and stemness, respectively. Dual staining detected lipid accumulation, while kits were used to measure fatty acid β-oxidation and glycerol content. qRT-PCR was used to assay expression of lipid oxidation genes. Western blot was used to examine expression of stem cell-related markers. Dual-luciferase assay and ChIP assay were used to verify the binding relationship between MITF and CPT1B.

RESULTS

CPT1B was found to be highly expressed in LUAD and enriched in linoleic acid metabolism pathway and α-linolenic acid metabolism pathway. Functional experiments showed that CPT1B could promote stemness in LUAD cells by regulating fatty acid β-oxidation. Additionally, CPT1B was found to be regulated by the upstream transcription factor MITF, which was lowly expressed in LUAD and could downregulate CPT1B expression. Rescue experiments revealed that CPT1B/MITF axis could affect stemness in LUAD cells by regulating fatty acid β-oxidation.

CONCLUSION

Transcription factor MITF inhibited transcription of CPT1B to regulate fatty acid β-oxidation, thereby suppressing stemness in LUAD cells. MITF and CPT1B may become new targets for LUAD.

NPRA promotes fatty acid metabolism and proliferation of gastric cancer cells by binding to PPARα

Among cancers, gastric cancer (GC) ranks third globally in morbidity and mortality, particularly in East Asia. Natriuretic peptide receptor A (NPRA), a receptor for guanylate cyclase, plays important roles in regulating water and sodium balance. Recent studies have suggested that NPRA is involved in tumorigenesis, but its role in GC development remains unclear. Herein, we showed that the expression level of NPRA was positively correlated with gastric tumor size and clinical stage. Patients with high NPRA expression had a lower five-year survival rate than those with low expression, and NPRA was identified as an independent predictor of GC prognosis. NPRA knockdown suppressed GC cell proliferation, migration and invasion. NPRA overexpression enhanced cell malignant behavior. Immunohistochemistry of collected tumor samples showed that tumors with high NPRA expression had higher peroxisome proliferator-activated receptor α (PPARα) levels. In vivo and in vitro studies showed that NPRA promotes fatty acid oxidation and tumor cell metastasis. Co-IP showed that NPRA binds to PPARα and prevents PPARα degradation. PPARα upregulation under NPRA protection activates arnitine palmitoyl transferase 1B (CPT1B) to promote fatty acid oxidation. In this study, new mechanisms by which NPRA promotes the development of GC and new regulatory mechanisms of PPARα were identified.

Increasing maternal age associates with lower placental CPT1B mRNA expression and acylcarnitines, particularly in overweight women

Older pregnant women have increased risks of complications including gestational diabetes and stillbirth. Carnitine palmitoyl transferase (CPT) expression declines with age in several tissues and is linked with poorer metabolic health. Mitochondrial CPTs catalyze acylcarnitine synthesis, which facilitates fatty acid oxidization as fuel. We hypothesized that the placenta, containing maternally-inherited mitochondria, shows an age-related CPT decline that lowers placental acylcarnitine synthesis, increasing vulnerability to pregnancy complications. We assessed CPT1A, CPT1B, CPT1C and CPT2 mRNA expression by qPCR in 77 placentas and quantified 10 medium and long-chain acylcarnitines by LC-MS/MS in a subset of 50 placentas. Older maternal age associated with lower expression of placental CPT1B, but not CPT1A, CPT1C or CPT2. CPT1B expression positively associated with eight acylcarnitines and CPT1C with three acylcarnitines, CPT1A negatively associated with nine acylcarnitines, while CPT2 did not associate with any acylcarnitine. Older maternal age associated with reductions in five acylcarnitines, only in those with BMI≥ 25 kg/m2, and not after adjusting for CPT1B expression. Our findings suggest that CPT1B is the main transferase for placental long-chain acylcarnitine synthesis, and age-related CPT1B decline may underlie decreased placental metabolic flexibility, potentially contributing to pregnancy complications in older women, particularly if they are overweight.

CPT1B, a metabolic molecule, is also an independent risk factor in CN-AML

BACKGROUND

Fatty acid oxidation has been considered as an important energy source for tumorigenesis and development. Several studies have investigated the role of CPT1A, a kind of fatty acid oxidation rate-limiting enzyme, in AML. However, prognostic value and regulatory network of another subtype, CPT1B in AML remains elusive. This study aims to clarify the independent prognostic role of CPT1B in CN-AML based on clinical data and molecular level data (mRNA, miRNA and lncRNA).

OBJECTIVE

The aim of this study is to investigate the prognostic value of CPT1B in AML patients.

METHODS

First, we analyzed the CPT1B expression in AML cohort via the online database "GEPIA". Subsequently, miRNA-mRNA and ceRNA networks were constructed to help predict the role of CPT1B in AML. Several molecules which showed the prognostic value and metabolic function of CPT1B were identified. Finally, the expression of CPT1B in our own cohort of 324 CN-AML patients was analyzed to clarify the results.

RESULTS

It was found that CPT1B was markedly higher in AML patients compared to normal people and this upregulation was associated with the poor clinical outcome. Several molecules revealed the possible regulatory mechanism of CPT1B in AML.

CONCLUSION

CPT1B is a potential prognostic factor and a therapeutic target for AML treatment.

Identification of fatty acid metabolism-based molecular subtypes and prognostic signature to predict immune landscape and guide clinical drug treatment in renal clear cell carcinoma

Three subtypes of samples were generated based on genes involved in fatty acid metabolism in The Cancer Genome Atlas (TCGA)-RCC patients using a non-negative matrix factorization (NMF) algorithm. 32 co-expressed modules were identified using WCGNA. We constructed a four-gene signature in our training set using least absolute shrinkage selection operator regression analysis and verified it in our testing and overall sets. A relevant study analysis in clinical trials was conducted, which showed the model had good stability and potential application value for predicting outcomes. We analyzed the immune microenvironment using MCPcounter, CIBERSORT, quanTIseq, TIMER and ESTIMATE algorithms, and the result indicated risk was positively related to T cells, B-lineage, and fibroblasts and negatively correlated with monocytic lineage, myeloid dendritic cells, neutrophils, and endothelial cells, and CPT1B was positively related to T cells, CD8 + T cells, Cytotoxic lymphocytes and NK cells, and negatively correlated with myeloid dendritic cells, fibroblasts, endothelial cells. Tumor mutation burden was positively related to risk score and the expression of CPT1B using the R packages corrplot, circlize. Through the R package pRRophetic, drug sensitivity tests showed that the low-risk score group would benefit more from sunitinib and less from pazopanib, sorafenib, temsirolimus, gemcitabine and doxorubicin than the high-risk score group. We performed the relevant basic assay validation for CPT1B, and the proliferation ability of RCC cells was inhibited after the knockdown of protein expression of CPT1B. In conclusion, we established a four-gene model that can predict outcomes of RCC with potential applications in diagnosis and treatment.

The effect of CPT1B gene on lipid metabolism and its polymorphism analysis in Chinese Simmental cattle

Carnitine palmitoyltransferase 1B (CPT1B) is a candidate gene that regulates livestock animal lipid metabolism and encodes the rate-limiting enzyme in fatty acid β-oxidation. To explore the effect of this gene on lipid metabolism in cattle, this study examined CPT1B gene polymorphism in Chinese Simmental cattle and the effect of CPT1B on lipid metabolism. The results showed that the triglyceride content increased significantly with increasing CPT1B gene expression in bovine fetal fibroblasts (BFFs) (p < 0.05), while CPT1B knockout led to decreased CPT1B expression and a downward trend in triglyceride levels. Correlation analysis showed a significant association between the g.119896238 G > C locus and Chinese Simmental cattle backfat thickness (p < 0.05). Backfat thickness was significantly greater in individuals with the GC genotype (0.93 ± 0.67 cm) than in those with the CC genotype (0.84 ± 0.60 cm). The g.119889302 T > C locus was significantly correlated with arachidonic acid content in Chinese Simmental cattle (p < 0.05). The arachidonic acid content in the longissimus muscle was significantly higher in CC genotype beef cattle (0.054 g/100 g) than in those with the other two genotypes (0.046 g/100 g, 0.049 g/100 g). These molecular markers can be effectively used for marker-assisted selection in cattle breeding.

miR-27a Regulates Sheep Adipocyte Differentiation by Targeting CPT1B Gene

Simple Summary

The content of intramuscular fat (IMF) is the main determinant of the nutritional and economic value of sheep meat. Therefore, lipid synthesis in sheep longissimus lumborum (LL) has become an important research focus. MicroRNA-27a (miR-27a) has been shown to play a crucial role in the proliferation and differentiation of adipocyte progenitor cells. In this study, we revealed that miR-27a significantly inhibited the formation of lipid droplets by targeting CPT1B to inhibit genes involved in lipid synthesis including PPAR γ, SCD, LPL, and FABP4. Here, we constructed a miR-27a-CPT1B regulatory network map, which revealed the interaction between miR-27a and CPT1B in lipid synthesis in ovine preadipocytes.

Abstract

MiRNAs are vital regulators and play a major role in cell differentiation, biological development, and disease occurrence. In recent years, many studies have found that miRNAs are involved in the proliferation and differentiation of adipocytes. The objective of this study was to evaluate the effect of miR-27a and its target gene CPT1B on ovine preadipocytes differentiation in Small-tailed Han sheep (Ovis aries). Down-regulation of miR-27a significantly promoted the production of lipid droplets, while overexpression of miR-27a led to a reduction in lipid droplet production. In addition, inhibition of miR-27a led to a significant increase in the expression of genes involved in lipid synthesis, including PPAR γ, SCD, LPL, and FABP4. Target Scan software predicted that CPT1B is a new potential target gene of miR-27a. Further experiments revealed that CPT1B gene expression and protein levels were negatively correlated with miR-27a expression. Overexpression of miR-27a led to a significant decrease in CPT1B mRNA levels and inhibited the accumulation of lipid droplets and vice versa. Moreover, overexpression of CPT1B promoted the synthesis of lipid droplets in ovine preadipocytes. Furthermore, luciferase reporter assays confirmed CPT1B to be a miR-27a direct target gene. This study confirmed that miR-27a increases the expression of genes related to lipid synthesis in ovine preadipocytes by targeting CPT1B, thereby promoting the synthesis of lipid droplets. The results of this study can be used to be exploited in devising novel approaches for improving the IMF content of sheep.

Emergent Coordination of the CHKB and CPT1B Genes in Eutherian Mammals: Implications for the Origin of Brown Adipose Tissue

Mitochondrial fatty acid oxidation (FAO) contributes to the proton motive force that drives ATP synthesis in many mammalian tissues. In eutherian (placental) mammals, brown adipose tissue (BAT) can also dissipate this proton gradient through uncoupling protein 1 (UCP1) to generate heat, but the evolutionary events underlying the emergence of BAT are unknown. An essential step in FAO is the transport of cytoplasmic long chain acyl-coenzyme A (acyl-CoA) into the mitochondrial matrix, which requires the action of carnitine palmitoyltransferase 1B (CPT1B) in striated muscle and BAT. In eutherians, the CPT1B gene is closely linked to the choline kinase beta (CHKB) gene, which is transcribed from the same DNA strand and terminates just upstream of CPT1B. CHKB is a rate-limiting enzyme in the synthesis of phosphatidylcholine (PC), a predominant mitochondrial membrane phospholipid, suggesting that the coordinated expression of CHKB and CPT1B may cooperatively enhance mitochondrial FAO. The present findings show that transcription of the eutherian CHKB and CPT1B genes is linked within a unitary epigenetic domain targeted to the CHKB gene, and that that this regulatory linkage appears to have resulted from an intergenic deletion in eutherians that significantly altered the distribution of CHKB and CPT1B expression. Informed by the timing of this event relative to the emergence of BAT, the phylogeny of CHKB-CPT1B synteny, and the insufficiency of UCP1 to account for eutherian BAT, these data support a mechanism for the emergence of BAT based on the acquisition of a novel capacity for adipocyte FAO in a background of extant UCP1.

Gan-Jiang-Ling-Zhu decoction alleviates hepatic steatosis in rats by the miR-138-5p/CPT1B axis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a commonly-encountered chronic liver disease which lacks verified pharmacological interventions. Gan-Jiang-Ling-Zhu decoction (GJLZ) is a classic formula utilized in clinical practice. In this study, we aimed to evaluate the therapeutic effect of GJLZ in NAFLD and explore the possible underlying mechanisms.

METHODS

Twenty-four rats were randomly divided into three groups: normal group, fed with chow diet for 8 weeks; model group, fed with high fat diet for 8 weeks; and GJLZ group, initially fed HFD for 4 weeks, and then administered the GJLZ decoction for 4 weeks by oral gavage while continuously feeding HFD. Rats were sacrificed after the intervention, and liver tissues and blood samples were harvested. Liver steatosis was detected by HE and Oil Red O staining. Body weight and liver index were analyzed. Liver triglyceride (TG), total cholesterol (TC), and low-density lipoprotein (LDL), serum almandine aminotransferase (ALT), aspartate aminotransferase (AST), and nonesterified fatty acid (NEFA) were assayed using commercial kits. Differentially expressed genes were identified by RNA-sequencing and verified using real-time PCR (RT-PCR) and western blotting. Whole miRNAs were detected by RNA-sequence analysis, and mRNA-targeted miRNAs were verified by RT-PCR. The miRNA-mRNA regulation pattern was confirmed using the dual-luciferase reporter assay.

RESULTS

Treatment with GJLZ significantly improved hepatic steatosis and inflammation, reduced liver index and liver TG content, and also significantly reduced serum ALT and AST levels. Based on the results of RNA-sequence analysis, five differentially expressed genes (DEGs) in the peroxisome proliferator-activated receptor (PPAR) signaling pathway were recognized. RT-PCR confirmed that carnitine palmitoyltransferase 1b (CPT1B) expression was significantly regulated by GJLZ treatment. GJLZ decoction intervention also increased significantly hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha (HADHA) expression. Next, miRNA profiling and screening were performed based on CPT1B alteration. Rno-miR-138-5p likely responded to GJLZ intervention, and rno-miR-138-5p inhibitor increased CPT1B expression while rno-miR-138-5p mimic reduced CPT1B expression. When CPT1B mutated, miR-138-5p mimic and inhibitor could not regulate the luciferase activity of CPT1B.

CONCLUSIONS

GJLZ is an effective formula for NAFLD management, and its possible mechanism of action involves the regulation of CPT1B expression via rno-miR-138-5p.

Polymorphisms in CPT1B and CPT2 have no significant effect on plasma carnitine levels in Japanese cancer patients

Treatment of cancer patients undergoing chemotherapy with L-carnitine (LC) supplementation is becoming increasingly popular in the clinic. The present study aimed to examine the possible effects of polymorphisms in CPT1B and CPT2 (CPT1B G320D, S427C, c.282-18 C>T, and p.E531K, and CPT2 V368I) on the plasma concentration of carnitine in humans. The subjects were the 218 participants of the Iga Cohort Study. Differences in plasma-free carnitine levels by genotype were examined. Genotyping was conducted by polymerase chain reaction with confronting two-pair primers (PCR-CTPP). The plasma carnitine levels were significantly higher in males (P<0.001; Student’s t-test), and there was no significant difference in plasma carnitine levels between the age groups (P=0.202; ANOVA). One-way ANOVA revealed the plasma levels of carnitine were neither significantly different by CPT1B G320D, S427C, c.282-18 C>T, or p.E531K, nor by CPT2 V368I genotypes (P=0.133, P=0.538, P=0.636, P=0.509, and P=0.398, respectively). When analysis of covariance (ANCOVA) adjusted for age and sex was applied, the plasma levels of carnitine were not statistically significantly different according to these genotypes (P=0.299, P=0.715, P=0.980, P=0.851, and P=0.674, respectively). The present study did not identify any statistically significant differences in plasma carnitine levels between subjects with different CPT1 and CPT2 genotypes, suggesting that there may be no need to tailor treatments to patients’ genotypes when determining the dose/amount of LC to be administered to cancer patients undergoing palliative care.

Regulation of energy metabolism by long-chain fatty acids

In mammals, excess energy is stored primarily as triglycerides, which are mobilized when energy demands arise. This review mainly focuses on the role of long chain fatty acids (LCFAs) in regulating energy metabolism as ligands of peroxisome proliferator-activated receptors (PPARs). PPAR-alpha expressed primarily in liver is essential for metabolic adaptation to starvation by inducing genes for beta-oxidation and ketogenesis and by downregulating energy expenditure through fibroblast growth factor 21. PPAR-delta is highly expressed in skeletal muscle and induces genes for LCFA oxidation during fasting and endurance exercise. PPAR-delta also regulates glucose metabolism and mitochondrial biogenesis by inducing FOXO1 and PGC1-alpha. Genes targeted by PPAR-gamma in adipocytes suggest that PPAR-gamma senses incoming non-esterified LCFAs and induces the pathways to store LCFAs as triglycerides. Adiponectin, another important target of PPAR-gamma may act as a spacer between adipocytes to maintain their metabolic activity and insulin sensitivity. Another topic of this review is effects of skin LCFAs on energy metabolism. Specific LCFAs are required for the synthesis of skin lipids, which are essential for water barrier and thermal insulation functions of the skin. Disturbance of skin lipid metabolism often causes apparent resistance to developing obesity at the expense of normal skin function.