Project description:Many metabolism-related genes undergo alternative splicing to generate circular RNAs although their functions remain poorly understood. Here we report that circPRKAA1, a circRNA derived from the α1 subunit of AMPK, fulfils a fundamental role in maintaining lipid homeostasis. CircPRKAA1 expression facilitates fatty acid synthesis and promotes lipid storage through two coordinated functions. First, circPRKAA1 promotes a tetrameric complex between the Ku80/Ku70 heterodimer and the mature form of sterol regulatory element-binding protein-1 (mSREBP1) to enhance the stability of mSREBP1. Secondly, circPRKAA1 selectively binds to the promoters of the ACC1, ACLY, SCD1 and FASN genes to recruit mSREBP1, upregulating their transcription and increasing fatty acid synthesis to promote cancer growth. Moreover, circPRKAA1 biogenesis is negatively regulated by AMPK activity with lower AMPK activation in hepatocellular carcinoma tissues frequently associated with elevated circPRKAA1 expression. Together, this work identifies circPRKAA1 as an integral element of AMPK-regulated reprogramming of lipid metabolism in cancer cells.
Project description:Glucocorticoids play central roles in the regulation of energy metabolism by shifting it toward catabolism, while AMPK is the master regulator of energy homeostasis, sensing energy depletion and stimulating pathways of increasing fuel uptake and saving on peripheral supplies. We showed here that AMPK regulates glucocorticoid actions on carbohydrate metabolism by targeting the glucocorticoid receptor (GR) and modifying transcription of glucocorticoid-responsive genes in a tissue- and promoter-specific fashion. Activation of AMPK in rats reversed glucocorticoid-induced hepatic steatosis and suppressed glucocorticoid-mediated stimulation of glucose metabolism. Transcriptomic analysis in the liver suggested marked overlaps between the AMPK and glucocorticoid signaling pathways directed mostly from AMPK to glucocorticoid actions. AMPK accomplishes this by phosphorylating serine 211 of the human GR indirectly through phosphorylation and consequent activation of p38 MAPK and by altering attraction of transcriptional coregulators to DNA-bound GR. In human peripheral mononuclear cells, AMPK mRNA expression positively correlated with that of glucocorticoid-responsive GILZ, which correlated also positively with the body mass index of subjects. These results indicate that the AMPK-mediated energy control system modulates glucocorticoid action at target tissues. Since increased action of glucocorticoids is associated with development of metabolic disorders, activation of AMPK could be a promising target for developing pharmacologic interventions to these pathologies. We tested the hypothesis by treateing rats with the synthetic glucocorticoid dexamethasone and the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR).
Project description:Identification and validation of the pathways and functions regulated by the orphan nuclear receptor, ROR alpha1, in skeletal muscle The retinoic acid receptor-related orphan receptor (ROR) alpha has been demonstrated to regulate lipid metabolism. We were interested in the physiologically relevant roles, and pathways regulated by RORalpha1 action in skeletal muscle. This major mass organ accounts for ~40% of the total body mass, and significant levels of lipid catabolism, glucose disposal and energy expenditure. We utilized the strategy of targeted muscle specific expression of a truncated (dominant negative) RORalphaâDE in transgenic mice, to investigate RORalpha1 signalling (and function) in this peripheral tissue. Expression profiling and pathway analysis indicated that RORalpha regulated genes involved in: (i) lipid and carbohydrate metabolism, cardiovascular and metabolic disease; and (ii) the LXR nuclear receptor signaling pathway and, (iii) the Akt and AMPK signaling cascades. This analysis was extensively validated by rigorous qPCR analysis using TaqMan Low Density Arrays, coupled to rigorous statistical analysis (with Empirical Bayes, and Benjamini-Hochberg). Moreover, westerns and metabolic profiling were utilized to validate the genes, proteins and pathways (lipogenic, Akt, AMPK and fatty acid oxidation) involved in the regulation of metabolism by RORalph1. The identified genes and pathways were in concordance with the demonstration of hyperglycemia, glucose intolerance, attenuated insulin stimulated phosphorylation of Akt, and impaired glucose uptake in the transgenic heterozygous Tg-RORalphaâDE animals. In conclusion, we propose that RORalpha1 is involved in regulating the Akt2-AMPK signalling pathways in the context of lipid homeostasis in skeletal muscle. Total RNA was compared from quadriceps femoris of both transgenic and wild type mice. Transgenic mice contained a truncated version of human RORalpha1 (RORalpha1delDE) where the entire E region and part of the hinge/D region have been removed. This transgene is driven by a skeletal muscle specific human skeletal alpha-actin (HSA) promoter.
Project description:Esophageal squamous cell carcinoma (ESCC) is characterized as a metabolic disorder characterized by lipid metabolic reprogramming. To investigate the regional characteristics of ESCC patients in Xinjiang Province, China, and lipid metabolism, in this study, we described the characteristics of the serum lipid composition in Kazakh ESCC patients by performing an integrated analysis of the transcriptome and lipidomic data. Serum samples from 30 Kazakh ESCC patients and 30 healthy individuals were subjected to targeted lipid metabolomics analysis via UPLC‒MS/MS, while 3 tumor samples and matched adjacent normal tissues from 30 ESCC patients were subjected to transcriptome analysis. Compared with those in the healthy group, we observed obvious changes in the serum lipid subclass content, chain length and unsaturation in the ESCC patients. Integrated lipidomic and transcriptomic analyses revealed that unsaturated fatty acid biosynthesis, fatty acid metabolism, lipid degradation, cholesterol metabolism and the AMPK signaling pathway were enriched in tumor tissues. In addition, RT–qPCR results demonstrated that genes closely related to these pathways were differentially expressed between the ESCC group and the healthy control group. Considering the key role of AMPK in lipid metabolism, we conducted a targeted lipid metabolomics analysis on AMPK-knockdown esophageal cancer cells by UPLC‒MS/MS. These findings suggested that AMPK might be correlated with lipid metabolism in Kazakh ESCC patients, identifying potential therapeutic targets of AMPK and other lipid metabolism-related markers against the progression of ESCC.
Project description:Background: The AMP-activated protein kinase (AMPK) is an intracellular fuel sensor for lipid and glucose metabolism. In addition to the short-term regulation of metabolic enzymes by phosphorylation, AMPK may also exert long-term effects on the transcription of downstream genes through the regulation of transcription factors and coactivators. In this study, RNA interference (RNAi) was conducted to investigate the effects of knockdown of TcAMPKα on lipid and carbohydrate metabolism in the red flour beetle, Tribolium castaneum, and the transcriptome profiles of dsTcAMPKα-injected and dsEGFP-injected beetles under normal conditions were compared by RNA-sequencing. Results: RNAi-mediated suppression of TcAMPKα increased whole-body triglyceride (TG) level and the ratio between glucose and trehalose, as was confirmed by in vivo treatment with the AMPK-activating compound, 5-Aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR). A total of 1184 differentially expressed genes (DEGs) were identified between dsTcAMPKα-injected and dsEGFP-injected beetles. These include genes involved in lipid and carbohydrate metabolism as well as insulin/insulin-like growth factor signaling (IIS). Real-time quantitative polymerase chain reaction analysis confirmed the differential expression of selected genes. Interestingly, metabolism-related transcription factors such as sterol regulatory element-binding protein 1 (SREBP1) and carbohydrate response element-binding protein (ChREBP) were also significantly upregulated in dsTcAMPKα-injected beetles. Conclusions: AMPK plays a critical role in the regulation of beetle metabolism. The findings of DEGs involved in lipid and carbohydrate metabolism provide valuable insight into the role of AMPK signaling in the transcriptional regulation of insect metabolism.
Project description:Energy homeostasis plays a key role in retarding aging, and mitochondria are responsible for energy production.AMPK plays a central role in maintaining energy homeostasis and mitochondrial homeostasis, and commands autophagy, a clearing and recycling process to maintain cellular homeostasis. However, the effect of AMPK activators on kidney aging has not been fully elucidated. We testified the effects of O304, a novel direct AMPK activator, in naturally aging mice model and D-galactose (D-gal)-treated renal tubular cell culture. We identified that O304 perfectly protects against cellular senescence and aged-related fibrosis in kidneys. Also, O304 restored energy metabolism, promoted autophagy, and preserved mitochondrial homeostasis. Transcriptomic sequencing also proved that O304 induced fatty acid metabolism, mitochondrial biogenesis and ATP process, and downregulated cell aging, DNA damage response and collagen organization. All these results suggest that O304 has a strong potential to retard aged kidney injury through regulating AMPK-induced multiple pathways.
Project description:Background and aims: Metabolic diseases, including diabetes, obesity, and dyslipidemia, are significant public health concerns worldwide. The insulin-like growth factor 2 (IGF2) gene have been implicated in various physiological processes, but its specific role in lipid metabolism remains unclear. We aim to elucidate the role of IGF2 in regulating lipid metabolism in adipose tissues and its association with metabolic syndrome (MetS). Methods: The research employed a multidisciplinary approach to investigate the role of IGF2 in lipid metabolism. We investigated the correlation between genetic variations within the IGF2 gene and metabolic parameters. We conduct a cross-sectional human study to evaluate relationships between varying IGF2 serum concentrations and the incidence of MetS. Additionally, manipulation of IGF2 expression levels in mouse and cell models via overexpression and knockdown to assess impacts on lipid metabolism in adipose tissue, specifically lipid accumulation, insulin resistance, and the balance between lipogenesis and lipolysis. Furthermore, the study employs metabolomics techniques to scrutinize the broader metabolic profiles in adipose tissues in response to IGF2 modulation. Results: Multiple SNP loci in the IGF2 gene were significantly associated with BMI, HbA1c, and diabetes. Insufficient or excessive expression of IGF2 was identified as a risk factor for hyperlipidemia, low HDL-c, and central obesity in MetS. We observed that IGF2 was mainly concentrated in adipose tissues and adipocytes. Enhanced IGF2 expression stimulated adipogenesis and lipid accumulation, whereas IGF2 knockdown hindered lipolysis, exacerbating ectopic lipid accumulation and insulin resistance. There is a substantial enlargement of pancreatic tissue and heightened insulin generation in mice deficient in IGF2. Activation of the PI3K/Akt pathway through IGF1R in IGF2 excess or INSR in conditions of IGF2 scarcity, along with inhibition of AMPK, implies a common downstream process that favors lipid accumulation and metabolic reprogramming in adipocytes. Conclusions: Our study demonstrated that upregulation of IGF2 enhanced adipogenesis and lipogenesis, while knockdown of IGF2 inhibited lipolysis, which resulting in accelerating lipid accumulation through PI3K/Akt-AMPK pathway.
Project description:Glucocorticoids play central roles in the regulation of energy metabolism by shifting it toward catabolism, while AMPK is the master regulator of energy homeostasis, sensing energy depletion and stimulating pathways of increasing fuel uptake and saving on peripheral supplies. We showed here that AMPK regulates glucocorticoid actions on carbohydrate metabolism by targeting the glucocorticoid receptor (GR) and modifying transcription of glucocorticoid-responsive genes in a tissue- and promoter-specific fashion. Activation of AMPK in rats reversed glucocorticoid-induced hepatic steatosis and suppressed glucocorticoid-mediated stimulation of glucose metabolism. Transcriptomic analysis in the liver suggested marked overlaps between the AMPK and glucocorticoid signaling pathways directed mostly from AMPK to glucocorticoid actions. AMPK accomplishes this by phosphorylating serine 211 of the human GR indirectly through phosphorylation and consequent activation of p38 MAPK and by altering attraction of transcriptional coregulators to DNA-bound GR. In human peripheral mononuclear cells, AMPK mRNA expression positively correlated with that of glucocorticoid-responsive GILZ, which correlated also positively with the body mass index of subjects. These results indicate that the AMPK-mediated energy control system modulates glucocorticoid action at target tissues. Since increased action of glucocorticoids is associated with development of metabolic disorders, activation of AMPK could be a promising target for developing pharmacologic interventions to these pathologies.