Nr2e1 ablation impairs liver glucolipid metabolism and induces inflammation, high-fat diets amplify the damage

Increased nuclear receptor subfamily 2, group E, member 1 (NR2E1) concentrations of PBMCs are associated with chronic inflammation in overweight/obesity

Background

Chronic inflammation plays a crucial role in the pathogenesis of overweight/obesity. Nuclear receptor subfamily 2, group E, member 1 (NR2E1) is one of the nuclear receptor family proteins that play crucial roles in regulating numerous life processes. In this study, we attempted to detect NR2E1 levels in peripheral blood mononuclear cells (PBMCs) of overweight/obese people and preliminarily elucidate the regulatory role of NR2E1 in obesity-related chronic inflammation.

Methods

We conducted a cross-sectional analysis of the clinical and biochemical data from 62 overweight/obese people and 70 control subjects. PBMCs of the participants were collected for detection of NR2E1 levels. PBMCs isolated from the control subjects were treated with different concentrations of palmitic acid (PA). We also transfected p-EGFP-N1-NR2E1 plasmids into PBMCs and treated them with PA, then detected TNF-α and IL-6 concentrations in the supernatant of PBMCs.

Results

The NR2E1 mRNA and protein levels in overweight/obese people were both significantly higher than those in normal-BMI people (p < 0.01). NR2E1 mRNA levels in PBMCs of overweight/obese people were positively related with TC, FFA, IL-6, TNF-α (r = 0.387, 0.440, 0.610, 0.530, p < 0.01) and LDL-c (r = 0.290, p < 0.05). A similar correlation was also found between NR2E1 protein levels and these parameters. The expression of NR2E1 in PBMCs from the control subjects increased apparently with the treatment of PA in a concentration-depend manner in vitro. Overexpression of NR2E1 in PBMCs decreased TNF-α and IL-6 expression induced by PA (p < 0.01).

Conclusion

NR2E1 levels are increased in overweight/obese people and have a positive relationship with TC, FFA, LDL-C, TNF-α and IL-6. Overexpression of NR2E1 could alleviate PA-induced chronic inflammation. NR2E1 may be a potential target for regulating chronic inflammation in obesity.

Lack of Nr2e1 expression in hepatocytes impaired cell survival and aggravated palmitate-induced oxidative stress

PURPOSE

Nuclear receptor subfamily 2 group E member 1 (Nr2e1) has been regarded as an essential regulator in neural stem cells. However, its function is still not clear in hepatocytes. This study aimed to clarify the effects of Nr2e1-deficiency in hepatocytes in lipotoxic conditions.

MATERIALS/METHODS

Nr2e1-knockdown AML12 ​cells were generated by lentiviral vector transfection. The influences of Nr2e1-deficiency on hepatocyte survival were determined by cell cycle progression and cell apoptosis rate using flow cytometry. Real-time quantitative PCR and Western blot were used to examine the genes and protein expression related to apoptosis, lipid metabolism, and oxidative stress. Meanwhile, RNA sequencing was adopted in liver samples from Nr2e1-knockout (Nr2e1-KO) mice.

RESULTS

Nr2e1 expression was observed with a significant decrease in AML12 ​cells after palmitic acid-stimulation. Knockdown of Nr2e1 in AML12 ​cells resulted in increased sensitivity to lipotoxicity, evidenced by a partial G0/G1 cell-cycle arrest and higher rates of cell apoptosis. Moreover, Nr2e1-knockdown AML12 ​cells presented increased gene expressions relative to lipid synthesis but decreased levels of β-oxidation related genes. Lack of Nr2e1 augmented palmitate-induced oxidative stress in hepatocytes. In vivo, differential genes in Nr2e1-KO mice liver were enriched in pathways associated with liver regeneration and cell proliferation.

CONCLUSIONS

This study indicated that hepatocytes lacking Nr2e1 were more susceptible to lipotoxic-mediated damage. Nr2e1 may serve as a potential target for the development of novel therapies for lipotoxicity-induced liver injury.

Protective effect of Xixin-Ganjiang herb pair for warming the lungs to dissolve phlegm in chronic obstructive pulmonary disease rats based on integrated network pharmacology and metabolomics

Xixin-Ganjiang herb pair (XGHP) is a classic combination for warming the lungs to dissolve phlegm and is often used to treat a variety of chronic lung diseases; it can treat the syndrome of cold phlegm obstruction of lungs. First, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to examine the composition of XGHP, and network pharmacology was used to predict its potential core targets and signaling pathways in the current study. Second, a rat model of chronic obstructive pulmonary disease (COPD) was established for assessing the anti-COPD activity of XGHP, and metabolomics was used to explore the biomarkers and metabolic pathways. Finally, the sample was validated using molecular docking and Western blotting. The integration of metabolomics and network pharmacology results identified 11 targets, 3 biomarkers, 3 pathways, and 2 metabolic pathways. Western blotting showed that XGHP effectively regulated the expression of core proteins via multiple signaling pathways (downregulation of toll-like receptor 4 [TLR4] and upregulation of serine/threonine-protein kinase 1 [p-AKT1] and nitric oxide synthase 3 [NOS3]). Molecular docking results showed that the 10 potentially active components of XGHP have good affinity with tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase 9 (MMP-9), TLR4, p-AKT1, and NOS3. Our findings suggest that XGHP may regulate glucolipid metabolism, improve energy supply, and inhibit inflammatory responses (TNF-α, IL-6, and MMP-9) via the PI3K-Akt signaling pathway and HIF-1 signaling pathway in the management of COPD.

The roles of nuclear receptors in cholesterol metabolism and reverse cholesterol transport in nonalcoholic fatty liver disease

As the most prevalent chronic liver disease globally, NAFLD encompasses a pathological process that ranges from simple steatosis to NASH, fibrosis, cirrhosis, and HCC, closely associated with numerous extrahepatic diseases. While the initial etiology was believed to be hepatocyte injury caused by lipid toxicity from accumulated triglycerides, recent studies suggest that an imbalance of cholesterol homeostasis is of greater significance. The role of nuclear receptors in regulating liver cholesterol homeostasis has been demonstrated to be crucial. This review summarizes the roles and regulatory mechanisms of nuclear receptors in the 3 main aspects of cholesterol production, excretion, and storage in the liver, as well as their cross talk in reverse cholesterol transport. It is hoped that this review will offer new insights and theoretical foundations for the study of the pathogenesis and progression of NAFLD and provide new research directions for extrahepatic diseases associated with NAFLD.

Time-of-day defines NAD+ efficacy to treat diet-induced metabolic disease by synchronizing the hepatic clock in mice

The circadian clock is an endogenous time-tracking system that anticipates daily environmental changes. Misalignment of the clock can cause obesity, which is accompanied by reduced levels of the clock-controlled, rhythmic metabolite NAD⁺. Increasing NAD⁺ is becoming a therapy for metabolic dysfunction; however, the impact of daily NAD⁺ fluctuations remains unknown. Here, we demonstrate that time-of-day determines the efficacy of NAD⁺ treatment for diet-induced metabolic disease in mice. Increasing NAD⁺ prior to the active phase in obese male mice ameliorated metabolic markers including body weight, glucose and insulin tolerance, hepatic inflammation and nutrient sensing pathways. However, raising NAD⁺ immediately before the rest phase selectively compromised these responses. Remarkably, timed NAD⁺ adjusted circadian oscillations of the liver clock until completely inverting its oscillatory phase when increased just before the rest period, resulting in misaligned molecular and behavioral rhythms in male and female mice. Our findings unveil the time-of-day dependence of NAD⁺-based therapies and support a chronobiology-based approach.

Inonotus hispidus Protects against Hyperlipidemia by Inhibiting Oxidative Stress and Inflammation through Nrf2/NF-κB Signaling in High Fat Diet Fed Mice

Obesity is frequently associated with dysregulated lipid metabolism and lipotoxicity. Inonotus hispidus (Bull.: Fr.) P. Karst (IH) is an edible and medicinal parasitic mushroom. In this study, after a systematic analysis of its nutritional ingredients, the regulatory effects of IH on lipid metabolism were investigated in mice fed a high-fat diet (HFD). In HFD-fed mice, IH reversed the pathological state of the liver and the three types of fat and significantly decreased the levels of low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglycerides (TG), and leptin (LEP) and increased the level of high-density liptein cholesterol (HDL-C) in serum. Meanwhile, IH ameliorated liver damage by reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST), interleukin (IL)-1β, IL-6, tumor necrosis factor-alpha (TNF-α), and plasminogen activator inhibitor-1 (PAI-1) levels in the liver and serum. Compared with HFD-fed mice, IH significantly modulated the gut microbiota, changed the relative abundances of microflora at different taxonomic levels, and regulated lipid levels. The results showed that 30 differential lipids were found. Results from Western blotting confirmed that IH regulated the nuclear factor erythroid-2 related factor 2 (Nrf2)/nuclear factor-kappa B (NF-κB) signaling pathway and oxidative stress. This study aimed to provide experimental evidence for the applicability of IH in obesity treatment.

Genetic variation of macronutrient tolerance in Drosophila melanogaster

Carbohydrates, proteins and lipids are essential nutrients to all animals; however, closely related species, populations, and individuals can display dramatic variation in diet. Here we explore the variation in macronutrient tolerance in Drosophila melanogaster using the Drosophila genetic reference panel, a collection of ~200 strains derived from a single natural population. Our study demonstrates that D. melanogaster, often considered a "dietary generalist", displays marked genetic variation in survival on different diets, notably on high-sugar diet. Our genetic analysis and functional validation identify several regulators of macronutrient tolerance, including CG10960/GLUT8, Pkn and Eip75B. We also demonstrate a role for the JNK pathway in sugar tolerance and de novo lipogenesis. Finally, we report a role for tailless, a conserved orphan nuclear hormone receptor, in regulating sugar metabolism via insulin-like peptide secretion and sugar-responsive CCHamide-2 expression. Our study provides support for the use of nutrigenomics in the development of personalized nutrition.

TLX, an Orphan Nuclear Receptor With Emerging Roles in Physiology and Disease

TLX (NR2E1), an orphan member of the nuclear receptor superfamily, is a transcription factor that has been described to be generally repressive in nature. It has been implicated in several aspects of physiology and disease. TLX is best known for its ability to regulate the proliferation of neural stem cells and retinal progenitor cells. Dysregulation, overexpression, or loss of TLX expression has been characterized in numerous studies focused on a diverse range of pathological conditions, including abnormal brain development, psychiatric disorders, retinopathies, metabolic disease, and malignant neoplasm. Despite the lack of an identified endogenous ligand, several studies have described putative synthetic and natural TLX ligands, suggesting that this receptor may serve as a therapeutic target. Therefore, this article aims to briefly review what is known about TLX structure and function in normal physiology, and provide an overview of TLX in regard to pathological conditions. Particular emphasis is placed on TLX and cancer, and the potential utility of this receptor as a therapeutic target.

Nr2e1 deficiency aggravates insulin resistance and chronic inflammation of visceral adipose tissues in a diet-induced obese mice model

AIMS

To investigate the nuclear receptor subfamily 2 group E member 1 (Nr2e1) expression in adipose tissues of obese mice and assess the role of Nr2e1 in insulin resistance and chronic inflammation of the adipose tissues.

MAIN METHODS

An obese model was established in Nr2e1 knockout (KO) mice and their wild type (WT) littermates through a long-term high-fat diet (HFD) feeding regime. The epididymal fat weight, body weight, and daily food intake were recorded. The blood lipid profile, blood inflammatory factors, and the levels of fasting blood glucose (FBG) and fasting insulin were determined. We estimated insulin resistance by the homeostasis model assessment (HOMA). The expression of inflammatory factors and F4/80 was examined by polymerase chain reaction (PCR) and western blotting to assess adipose tissues inflammation. We also determined the molecules of insulin signaling and the nuclear factor kappa B (NF-κB) pathway by western blotting.

KEY FINDINGS

The Nr2e1 expression was upregulated in WT obese mice when compared with that in control mice. Despite a lower body weight and epididymal fat mass in Nr2e1^-/- mice, these rats showed increased inflammatory cytokines secretion, more pronounced hyperlipidemia, and impaired insulin sensitivity after HFD treatment. Further investigation revealed that Nr2e1 deletion affected the expression of insulin signaling and NF-κB pathway-related molecules in visceral adipose tissues.

SIGNIFICANCE

Nr2e1 may act as a potential target to improve insulin sensitivity and inflammation in obesity and related complications.

Comparison of the Effects of a Bean-Based and a White Rice-Based Breakfast Diet on Postprandial Glucose and Insulin Levels in Chinese Patients with Type 2 Diabetes

BACKGROUND This study compared the effects of a bean-based and a white rice-based breakfast diet on postprandial glucose and insulin levels in Chinese patients with type 2 diabetes mellitus (T2DM). MATERIAL AND METHODS We recruited 63 patients with T2DM. The patients participated in the randomized 2×2 crossover trial. The bean-based diet group and white rice control group were matched for 50 g of available carbohydrate at breakfast. The patients followed the diets for 3 days. Vein blood samples were collected at 0, 30, 60, 120, and 180 min after eating. Data were analyzed using a repeated-measures analysis of variance. The results are expressed as the mean±standard error of mean (SEM) or as the median with interquartile range values. RESULTS Compared with the white rice control, postprandial glucose was significantly lower with the bean-based diet treatments at 60 min (P=0.004), 120 min (P=0.000), and 180 min (P=0.000). The insulin levels of the bean-based diet group were significantly higher at 60 min (P=0.013). The C-peptide levels of the bean-based diet group were significantly higher at 30 min (P=0.042) and 60 min (P=0.005) postprandial. The glucose area under the curve (AUC) showed a similar trend (P=0.000). There were no statistically significant differences in the AUC of insulin and C-peptide, except C-peptide AUC at 0 to 60 min (P=0.027). CONCLUSIONS Compared with a white rice-based breakfast, a bean-based diet significantly reduced postprandial glucose levels and promoted insulin secretion. These results support a dietary approach to reduce postprandial hyperglycemia.