Reduced Nogo expression inhibits diet-induced metabolic disorders by regulating ChREBP and insulin activity

IRX3 promotes adipose tissue browning and inhibits fibrosis in obesity-resistant mice

Obesity is one of the threats to human health and survival. High fat diet (HFD)-induced obesity leads to adipose tissue fibrosis and a series of metabolic diseases. There are some people still thin under HFD, a phenomenon known as the "obesity resistance (OR) phenotype". It was found that Iroquois homeobox 3 (IRX3) is considered as a regulator in obesity, but the regulatory mechanism between OR and IRX3 is still unclear. In this study, we investigated OR on a HFD and the role of the IRX3 gene. Using mice, we observed that OR mice had lower body weights, reduced liver lipid synthesis, and increased white adipose tissue (WAT) lipolysis compared to obesity-prone (OP) mice. Additionally, OR mice exhibited spontaneous WAT browning and less fibrosis, correlating with higher Irx3 expression. Utilizing 3T3-L1 differentiated adipocytes, our study demonstrated that overexpression of Irx3 promoted thermogenesis-related gene expression and reduced adipocyte fibrosis. Therefore, Irx3 promotes WAT browning and inhibits fibrosis in OR mice. These results provide insight into the differences between obesity and OR, new perspectives on obesity treatment, and guidance for lessening adipose tissue fibrosis.

Nogo-B inhibition facilitates cholesterol metabolism to reduce hypercholesterolemia

The strategy of lowering cholesterol levels by promoting cholesterol excretion is still lacking, and few molecular targets act on multiple cholesterol metabolic processes. In this study, we find that Nogo-B deficiency/inhibition simultaneously promotes hepatic uptake of cholesterol and cholesterol excretion. Nogo-B deficiency decreases cholesterol levels by activating ATP-binding cassette transporters (ABCs), apolipoprotein E (ApoE), and low-density lipoprotein receptor (LDLR) expression. We discover that Nogo-B interacts with liver X receptor α (LXRα), and Nogo-B deficiency inhibits ubiquitination degradation of LXRα, thereby enhancing its function on cholesterol excretion. Decreased cellular cholesterol levels further activate SREBP2 and LDLR expression, thereby promoting hepatic uptake of cholesterol. Nogo-B inhibition decreases atherosclerotic plaques and cholesterol levels in mice, and Nogo-B levels are correlated to cholesterol levels in human plasma. In this study, Nogo-B deficiency/inhibition not only promotes hepatic uptake of blood cholesterol but also facilitates cholesterol excretion. This study reports a strategy to lower cholesterol levels by inhibiting Nogo-B expression to promote hepatic cholesterol uptake and cholesterol excretion.

Protective effects of Nogo-B deficiency in NAFLD mice and its multiomics analysis of gut microbiology and metabolism

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a prevalent chronic liver ailment that can lead to serious conditions such as cirrhosis and hepatocellular carcinoma. Hepatic Nogo-B regulates glucose and lipid metabolism, and its inhibition has been shown to be protective against metabolic syndrome. Increasing evidence suggests that imbalances in the gut microbiota (GM) and lipid metabolism disorders are significant contributors to NAFLD progression. Nevertheless, it is not yet known whether Nogo-B can affect NAFLD by influencing the gut microbiota and metabolites. Hence, the aim of the present study was to characterize this process and explore its possible underlying mechanisms.

METHODS

A NAFLD model was constructed by administering a high-fat diet (HFD) to Nogo-B-/- and WT mice from the same litter, and body weight was measured weekly in each group. The glucose tolerance test (GTT) and insulin tolerance test (ITT) were performed to assess blood glucose levels. At the end of the 12-week period, samples of serum, liver, and intestinal contents were collected and used for serum biochemical marker and inflammatory factor detection; pathology evaluation; and gut microbiome and metabolomics analysis. Spearman's correlation analysis was performed to determine possible correlations between differential gut microbiota and differential serum metabolites between groups.

RESULTS

Nogo-B deficiency attenuated the effects of the HFD, including weight gain, liver weight gain, impaired glucose tolerance, hepatic steatosis, elevated serum lipid biochemicals levels, and liver function. Nogo-B deficiency suppressed M1 polarization and promoted M2 polarization, thus inhibiting inflammatory responses. Furthermore, Nogo-B-/--HFD-fed mice presented increased gut microbiota richness and diversity, decreased Firmicutes/Bacteroidota (F/B) ratios, and altered serum metabolites compared with those of WT-HFD-fed mice. During analysis, several differential gut microbiota, including Lachnoclostridium, Harryflintia, Odoribacter, UCG-009, and unclassified_f_Butyricoccaceae, were screened between groups. These microbiota were found to be positively correlated with upregulated purine metabolism and bile acid metabolites in Nogo-B deficiency, while they were negatively correlated with downregulated corticosterone and tricarboxylic acid cyclic metabolites in Nogo-B deficiency.

CONCLUSION

Nogo-B deficiency delayed NAFLD progression, as demonstrated by reduced hepatocellular lipid accumulation, attenuated inflammation and liver injury, and ameliorated gut microbiota dysbiosis and metabolic disorders. Importantly, Odoribacter was strongly positively correlated with ALB and taurodeoxycholic acid, suggesting that it played a considerable role in the influence of Nogo-B on the progression of NAFLD, a specific feature of NAFLD in Nogo-B-/- mice. The regulation of bile acid metabolism by the gut microbiota may be a potential target for Nogo-B deficiency to ameliorate NAFLD.

Intestinal Nogo-B reduces GLP1 levels by binding to proglucagon on the endoplasmic reticulum to inhibit PCSK1 cleavage

Glucagon-like peptide 1 (GLP1), which is mainly processed and cleaved from proglucagon in enteroendocrine cells (EECs) of the intestinal tract, acts on the GLP1 receptor in pancreatic cells to stimulate insulin secretion and to inhibit glucagon secretion. However, GLP1 processing is not fully understood. Here, we show that reticulon 4B (Nogo-B), an endoplasmic reticulum (ER)-resident protein, interacts with the major proglucagon fragment of proglucagon to retain proglucagon on the ER, thereby inhibiting PCSK1-mediated cleavage of proglucagon in the Golgi. Intestinal Nogo-B knockout in male type 2 diabetes mellitus (T2DM) mice increases GLP1 and insulin levels and decreases glucagon levels, thereby alleviating pancreatic injury and insulin resistance. Finally, we identify aberrantly elevated Nogo-B expression and inhibited proglucagon cleavage in EECs from diabetic patients. Our study reveals the subcellular regulatory processes involving Nogo-B during GLP1 production and suggests intestinal Nogo-B as a potential therapeutic target for T2DM.

Inhibition of Nogo-B reduces the progression of pancreatic cancer by regulation NF-κB/GLUT1 and SREBP1 pathways

Pancreatic cancer (PC) is a lethal disease and associated with metabolism dysregulation. Nogo-B is related to multiple metabolic related diseases and types of cancers. However, the role of Nogo-B in PC remains unknown. In vitro, we showed that cell viability and migration was largely reduced in Nogo-B knockout or knockdown cells, while enhanced by Nogo-B overexpression. Consistently, orthotopic tumor and metastasis was reduced in global Nogo knockout mice. Furthermore, we indicated that glucose enhanced cell proliferation was associated to the elevation expression of Nogo-B and nuclear factor κB (NF-κB). While, NF-κB, glucose transporter type 1 (GLUT1) and sterol regulatory element-binding protein 1 (SREBP1) expression was reduced in Nogo-B deficiency cells. In addition, we showed that GLUT1 and SREBP1 was downstream target of NF-κB. Therefore, we demonstrated that Nogo deficiency inhibited PC progression is regulated by the NF-κB/GLUT1 and SREBP1 pathways, and suggested that Nogo-B may be a target for PC therapy.

Effect of High-Sucrose Diet on the Occurrence and Progression of Diabetic Retinopathy and Dietary Modification Strategies

As the most serious of the many worse new pathological changes caused by diabetes, there are many risk factors for the occurrence and development of diabetic retinopathy (DR). They mainly include hyperglycemia, hypertension, hyperlipidemia and so on. Among them, hyperglycemia is the most critical cause, and plays a vital role in the pathological changes of DR. High-sucrose diets (HSDs) lead to elevated blood glucose levels in vivo, which, through oxidative stress, inflammation, the production of advanced glycation end products (AGEs) and vascular endothelial growth factor (VEGF), cause plenty of pathological damages to the retina and ultimately bring about loss of vision. The existing therapies for DR primarily target the terminal stage of the disease, when irreversible visual impairment has appeared. Therefore, early prevention is particularly critical. The early prevention of DR-related vision loss requires adjustments to dietary habits, mainly by reducing sugar intake. This article primarily discusses the risk factors, pathophysiological processes and molecular mechanisms associated with the development of DR caused by HSDs. It aims to raise awareness of the crucial role of diet in the occurrence and progression of DR, promote timely changes in dietary habits, prevent vision loss and improve the quality of life. The aim is to make people aware of the importance of diet in the occurrence and progression of DR. According to the dietary modification strategies that we give, patients can change their poor eating habits in a timely manner to avoid theoretically avoidable retinopathy and obtain an excellent prognosis.

Liver ChREBP deficiency inhibits fructose-induced insulin resistance in pregnant mice and female offspring

High fructose intake during pregnancy increases insulin resistance (IR) and gestational diabetes mellitus (GDM) risk. IR during pregnancy primarily results from elevated hormone levels. We aim to determine the role of liver carbohydrate response element binding protein (ChREBP) in insulin sensitivity and lipid metabolism in pregnant mice and their offspring. Pregnant C57BL/6J wild-type mice and hepatocyte-specific ChREBP-deficient mice were fed with a high-fructose diet (HFrD) or normal chow diet (NC) pre-delivery. We found that the combination of HFrD with pregnancy excessively activates hepatic ChREBP, stimulating progesterone synthesis by increasing MTTP expression, which exacerbates IR. Increased progesterone levels upregulated hepatic ChREBP via the progesterone-PPARγ axis. Placental progesterone activated the progesterone-ChREBP loop in female offspring, contributing to IR and lipid accumulation. In normal dietary conditions, hepatic ChREBP modestly affected progesterone production and influenced IR during pregnancy. Our findings reveal the role of hepatic ChREBP in regulating insulin sensitivity and lipid homeostasis in both pregnant mice consuming an HFrD and female offspring, and suggest it as a potential target for managing gestational metabolic disorders, including GDM.

Black mulberry extract inhibits hepatic adipogenesis through AMPK/mTOR signaling pathway in T2DM mice

ETHNOPHARMACOLOGICAL RELEVANCE

Black mulberry (Morus nigra L.) is an ancient dual-use plant resource for medicine and food. It is widely used in Uyghur folklore for hypoglycemic treatment and is a folkloric plant medicine with regional characteristics. However, the mechanism of Morus nigra L. treatment in diabetes mellitus has not been fully understood, especially from the perspective of hepatic lipid accumulation is less reported.

OBJECTIVE OF THIS STUDY

This study was to explore the potential of Morus nigra L. fruit ethyl acetate extract (MNF-EA) to reduce blood sugar levels by preventing the production of hepatic lipogenesis and to provide more evidence for the use of MNF-EA as an adjuvant therapy for type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

In this study, the chemical composition of MNF-EA was first analyzed and characterized using UPLC-Q-TOF-MS technique. A series of in vitro studies were performed with HepG2-IR cells and oleic acid (OA)-induced HepG2 cells, including MTT assay, glucose uptake assay, oil red O staining and Western blot analysis. The STZ-HFD co-induced T2DM mice were employed for in vivo research, including physical indices, biochemical analysis, histopathological examination, and Western blot analysis.

RESULTS

The 19 compounds in MNF-EA were identified by UPLC-Q-TOF-MS technique. Insulin resistance (IR) and lipid droplet accumulation in HepG2 cells were greatly improved by MNF-EA treatment, which had no appreciable side effects at the dosage used. In T2DM mice, MNF-EA decreased fasting blood glucose (FBG), saved body weight, and significantly improved oral glucose tolerance (OGTT) and IR status. In addition, MNF-EA treatment also improved lipid metabolism disorders and liver function in T2DM mice. Histopathological sections showed that MNF-EA treatment reduced hepatic steatosis. Mechanistic studies suggest that MNF-EA acted through the AMPK/mTOR pathway.

CONCLUSIONS

These results suggest that MNF-EA has great potential to reverse the metabolic abnormalities associated with T2DM by regulating the AMPK/mTOR signaling pathway. Therefore, we believe that MNF is a promising medicinal and food-homologous agent to improve T2DM.

Berberine protects mice against type 2 diabetes by promoting PPARγ-FGF21-GLUT2-regulated insulin sensitivity and glucose/lipid homeostasis

Type 2 diabetes (T2D) is a chronic, burdensome disease that is characterized by disordered insulin sensitivity and disturbed glucose/lipid homeostasis. Berberine (BBR) has multiple therapeutic actions on T2D, including regulation of glucose and lipid metabolism, improvement of insulin sensitivity and energy expenditure. Recently, the function of BBR on fibroblast growth factor 21 (FGF21) has been identified. However, if BBR ameliorates T2D through FGF21, the underlying mechanisms remain unknown. Herein, we used T2D wild type (WT) and FGF21 global knockout (FKO) mice [mouse T2D model: established by high-fat diet (HFD) feeding plus streptozotocin (STZ) injection], and hepatocyte-specific peroxisome proliferator activated receptor γ (PPARγ) deficient (PPARγHepKO) mice, and cultured human liver carcinoma cells line, HepG2 cells, to characterize the role of BBR in glucose/lipid metabolism and insulin sensitivity. We found that BBR activated FGF21 expression by up-regulating PPARγ expression at the cellular level. Meanwhile, BBR ameliorated glucosamine hydrochloride (Glcn)-induced insulin resistance and increased glucose transporter 2 (GLUT2) expression in a PPARγ/FGF21-dependent manner. In T2D mice, BBR up-regulated the expression of PPARγ, FGF21 and GLUT2 in the liver, and GLUT2 in the pancreas. BBR also reversed T2D-induced insulin resistance, liver lipid accumulation, and damage in liver and pancreas. However, FGF21 deficiency diminished these effects of BBR on diabetic mice. Altogether, our study demonstrates that the therapeutic effects of BBR on T2D were partly accomplished by activating PPARγ-FGF21-GLUT2 signaling pathway. The discovery of this new pathway provides a deeper understanding of the mechanism of BBR for T2D treatment.

Olfactomedin 4 deletion exacerbates nonalcoholic fatty liver disease through P62-dependent mitophagy in mice

BACKGROUND & AIMS

Olfactomedin 4 (OLFM4) is a glycoprotein that is related to obesity and insulin resistance. This study aims to investigate the role and mechanisms of OLFM4 in nonalcoholic fatty liver disease (NAFLD).

APPROACH & RESULTS

OLFM4 expression levels were significantly increased in liver samples from NAFLD patients and in cellular and mouse models of NAFLD. Cell lines deficient in or overexpressing OLFM4 and Olfm4-/- mice were established to study its role in NAFLD. OLFM4 deficiency significantly aggravated diet-induced hepatic steatosis and inflammation, while re-expression of OLFM4 ameliorated diet-induced hepatic steatosis and inflammation in mice. Mechanistically, OLFM4 deficiency disrupted mitochondrial structure and decreased mitophagy in hepatocytes, thereby aggravating hepatic lipogenesis, inflammation, and insulin resistance. Moreover, OLFM4 directly interacted with P62, and OLFM4 deficiency decreased mitophagy in both cellular and mouse models of NAFLD through a P62-dependent mechanism. We also show that blocking the P62-ZZ-domain using XRK3F2 prevented diet-induced NAFLD in Olfm4-/- mice.

CONCLUSION

OLFM4 is significantly upregulated in NAFLD, and OLFM4 deletion exacerbates NAFLD through P62-dependent mitophagy.

6-Methyl flavone inhibits Nogo-B expression and improves high fructose diet-induced liver injury in mice

Excessive fructose consumption increases hepatic de novo lipogenesis, resulting in cellular stress, inflammation and liver injury. Nogo-B is a resident protein of the endoplasmic reticulum that regulates its structure and function. Hepatic Nogo-B is a key protein in glycolipid metabolism, and inhibition of Nogo-B has protective effects against metabolic syndrome, thus small molecules that inhibit Nogo-B have therapeutic benefits for glycolipid metabolism disorders. In this study we tested 14 flavones/isoflavones in hepatocytes using dual luciferase reporter system based on the Nogo-B transcriptional response system, and found that 6-methyl flavone (6-MF) exerted the strongest inhibition on Nogo-B expression in hepatocytes with an IC50 value of 15.85 μM. Administration of 6-MF (50 mg· kg-1 ·d-1, i.g. for 3 weeks) significantly improved insulin resistance along with ameliorated liver injury and hypertriglyceridemia in high fructose diet-fed mice. In HepG2 cells cultured in a media containing an FA-fructose mixture, 6-MF (15 μM) significantly inhibited lipid synthesis, oxidative stress and inflammatory responses. Furthermore, we revealed that 6-MF inhibited Nogo-B/ChREBP-mediated fatty acid synthesis and reduced lipid accumulation in hepatocytes by restoring cellular autophagy and promoting fatty acid oxidation via the AMPKα-mTOR pathway. Thus, 6-MF may serve as a potential Nogo-B inhibitor to treat metabolic syndrome caused by glycolipid metabolism dysregulation.

The effect of hormones insulin and glucagon on ubiquitin modifications elucidated by proteomics in liver cells

AIMS

Insulin action is intertwined with changing levels of glucose and counter-regulatory hormone glucagon. While insulin lowers blood sugar level, glucagon raises it by promoting the breakdown of the stored glycogen in liver and releases glucose into the bloodstream. The hormones insulin and glucagon are key in the pathogenesis of type 2 diabetes (T2D). Insulin resistance is a primary predisposing factor for diabetes. Phosphorylation of insulin signaling molecules is altered in the insulin-resistant state. However, ubiquitin (Ub) modifications in insulin-resistant state are relatively understudied. To dissect the underlying mechanisms, we performed a proteomics study on hepatoma cells to study the regulation of ubiquitination by insulin and glucagon.

MATERIALS AND METHODS

We performed western blotting, immunoprecipitations, and affinity pull down using tandem Ub binding entities (TUBE) reagents on hepatoma cells treated with insulin or glucagon. Next, we performed MS/MS analysis on Ub-linkage specific affinity pull down samples. Gene ontology analysis and protein-protein interaction network analysis was performed using DAVID GO and STRING db, respectively.

KEY FINDINGS

The ubiquitination pattern of total Ub, K48-linked Ub, and K63-linked Ub was altered with the treatment of hormones insulin and glucagon. Ubiquitination in immunoprecipitated samples showed enrichment with total Ub and K48-linked Ub but not with K63-linked Ub. Ubiquitination by treatment with hormones mainly enriched key signaling pathways MAPK, Akt, oxidative stress etc. SIGNIFICANCE: Our study identified key altered proteins and signal transduction pathways which aids in understanding the mechanisms of hormonal action on ubiquitination and identify new therapeutic targets for T2D.

Plasma proteomic signatures of a direct measure of insulin sensitivity in two population cohorts

AIMS/HYPOTHESIS

The euglycaemic-hyperinsulinaemic clamp (EIC) is the reference standard for the measurement of whole-body insulin sensitivity but is laborious and expensive to perform. We aimed to assess the incremental value of high-throughput plasma proteomic profiling in developing signatures correlating with the M value derived from the EIC.

METHODS

We measured 828 proteins in the fasting plasma of 966 participants from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study and 745 participants from the Uppsala Longitudinal Study of Adult Men (ULSAM) using a high-throughput proximity extension assay. We used the least absolute shrinkage and selection operator (LASSO) approach using clinical variables and protein measures as features. Models were tested within and across cohorts. Our primary model performance metric was the proportion of the M value variance explained (R2).

RESULTS

A standard LASSO model incorporating 53 proteins in addition to routinely available clinical variables increased the M value R2 from 0.237 (95% CI 0.178, 0.303) to 0.456 (0.372, 0.536) in RISC. A similar pattern was observed in ULSAM, in which the M value R2 increased from 0.443 (0.360, 0.530) to 0.632 (0.569, 0.698) with the addition of 61 proteins. Models trained in one cohort and tested in the other also demonstrated significant improvements in R2 despite differences in baseline cohort characteristics and clamp methodology (RISC to ULSAM: 0.491 [0.433, 0.539] for 51 proteins; ULSAM to RISC: 0.369 [0.331, 0.416] for 67 proteins). A randomised LASSO and stability selection algorithm selected only two proteins per cohort (three unique proteins), which improved R2 but to a lesser degree than in standard LASSO models: 0.352 (0.266, 0.439) in RISC and 0.495 (0.404, 0.585) in ULSAM. Reductions in improvements of R2 with randomised LASSO and stability selection were less marked in cross-cohort analyses (RISC to ULSAM R2 0.444 [0.391, 0.497]; ULSAM to RISC R2 0.348 [0.300, 0.396]). Models of proteins alone were as effective as models that included both clinical variables and proteins using either standard or randomised LASSO. The single most consistently selected protein across all analyses and models was IGF-binding protein 2.

CONCLUSIONS/INTERPRETATION

A plasma proteomic signature identified using a standard LASSO approach improves the cross-sectional estimation of the M value over routine clinical variables. However, a small subset of these proteins identified using a stability selection algorithm affords much of this improvement, especially when considering cross-cohort analyses. Our approach provides opportunities to improve the identification of insulin-resistant individuals at risk of insulin resistance-related adverse health consequences.

Nogo-B inhibition restricts ulcerative colitis via inhibiting p68/miR-155 signaling pathway

BACKGROUND & AIMS

Ulcerative colitis (UC) is a main type of inflammatory bowel diseases which spreads globally during the westernization of lifestyle over the past few decades. However, the cause of UC is still not fully understood. We aimed to disclose the role of Nogo-B in the development of UC.

METHODS

Nogo-deficiency (Nogo^-/-) and wild-type male mice were treated with dextran sodium sulfate (DSS) to conduct a UC model, followed by determination of colon and serum inflammatory cytokines level. RAW264.7, THP1 and NCM460 cells were used to determine macrophage inflammation as well as proliferation and migration of NCM460 cells under Nogo-B or miR-155 intervention.

RESULTS

Nogo deficiency significantly reduced DSS-induced weight loss, colon length and weight reduction, and inflammatory cells accumulation in the intestinal villus, while increased the expression of tight junctions (TJs) proteins (Zonula occludens-1, Occludin) and adherent junctions (AJs) proteins (E-cadherin, α-catenin), implying that Nogo deficiency attenuated DSS-induced UC. Mechanistically, Nogo-B deficiency reduced TNFα, IL-1β and IL-6 levels in the colon, serum, RAW264.7 cells and THP1-derived macrophages. Furthermore, we identified that Nogo-B inhibition can reduce the maturation of miR-155, which is essential for Nogo-B-affected inflammatory cytokines expression. Interestingly, we determined that Nogo-B and p68 can interact with each other to promote the expression and activation of Nogo-B and p68, thus facilitating miR-155 maturation to induce macrophage inflammation. Blocking p68 inhibited Nogo-B, miR-155, TNFα, IL-1β and IL-6 expression. Moreover, the culture medium collected from Nogo-B overexpressed macrophages can inhibit enterocytes NCM460 cells proliferation and migration.

CONCLUSION

We disclose that Nogo deficiency reduced DSS-induced UC via inhibiting p68-miR-155-activated inflammation. Our results indicate that Nogo-B inhibition serves as a new potential therapeutic candidate for the prevention and treatment of UC.

Nogo-B deficiency suppresses white adipogenesis by regulating β-catenin signaling

AIMS

Obesity is a global epidemic around the world. Reticulon-4B (Nogo-B) is an endoplasmic reticulum-resident protein. Our previous work demonstrated that Nogo-B deficiency inhibited obesity and decreased the size of white adipocytes. However, the underlying molecular mechanism of Nogo-B in white adipogenesis remains poorly understood. This study aims to explore the effect of Nogo-B in white adipogenesis, as well as its underlying molecular mechanisms.

MAIN METHODS AND FINDINGS

The study adopted mouse embryonic fibroblasts (MEFs) and 3T3-L1 preadipocytes to induce white adipogenesis and investigate the effect of Nogo-B on adipogenesis using qRT-PCR, Western blotting, immunofluorescence, lipid quantification, and Oil Red O staining. During white adipogenesis, Nogo-B expression was increased accompanied by upregulation of adipogenic markers. In contrast, Nogo-B deficiency inhibited white adipocyte markers expression and lipid accumulation. Furthermore, the mechanism study showed that Nogo-B deficiency decreased the destruction complex [AXIN1-APC-glycogen synthase kinase 3β (GSK3β)] levels through activating protein kinase B 2 (AKT2), resulting in β-catenin translocating into the nucleus and inhibiting the expression of adipogenic markers. Moreover, Nogo-B deficiency promoted the expression of brown/beige adipocytes markers while improving mitochondrial thermogenesis by activating β-catenin pathway. In addition, Nogo-B deficiency reduced the levels of inflammatory molecules during white adipogenic differentiation.

SIGNIFICANCE

This study revealed that Nogo-B deficiency inhibited white adipogenesis through AKT2/GSK3β/β-catenin pathway. Meanwhile, Nogo-B deficiency increased the expression of brown/beige adipocyte markers and promoted mitochondrial thermogenesis. In addition, Nogo-B deficiency reduced inflammatory cytokine levels caused by adipogenesis. Collectively, blocking Nogo-B expression may be a potential strategy to suppress white adipogenesis.

O-GlcNAcylation of SPOP promotes carcinogenesis in hepatocellular carcinoma

Aberrantly elevated O-GlcNAcylation level is commonly observed in human cancer patients, and has been proposed as a potential therapeutic target. Speckle-type POZ protein (SPOP), an important substrate adaptor of cullin3-RING ubiquitin ligase, plays a key role in the initiation and development of various cancers. However, the regulatory mechanisms governing SPOP and its function during hepatocellular carcinoma (HCC) progression remain unclear. Here, we show that, in HCC, SPOP is highly O-GlcNAcylated by O-GlcNAc transferase (OGT) at Ser96. In normal liver cells, the SPOP protein mainly localizes in the cytoplasm and mediates the ubiquitination of the oncoprotein neurite outgrowth inhibitor-B (Nogo-B) (also known as reticulon 4 B) by recognizing its N-terminal SPOP-binding consensus (SBC) motifs. However, O-GlcNAcylation of SPOP at Ser96 increases the nuclear positioning of SPOP in hepatoma cells, alleviating the ubiquitination of the Nogo-B protein, thereby promoting HCC progression in vitro and in vivo. In addition, ablation of O-GlcNAcylation by an S96A mutation increased the cytoplasmic localization of SPOP, thereby inhibiting the Nogo-B/c-FLIP cascade and HCC progression. Our findings reveal a novel post-translational modification of SPOP and identify a novel SPOP substrate, Nogo-B, in HCC. Intervention with the hyper O-GlcNAcylation of SPOP may provide a novel strategy for HCC treatment.

Exploration of Succinimide Derivative as a Multi-Target, Anti-Diabetic Agent: In Vitro and In Vivo Approaches

Diabetes mellitus (DM) is counted among one of the leading challenges in the recent era, and it is a life-threatening disorder. Compound 4-hydroxy 3-methoxy phenylacetone (compound 1) was previously isolated from Polygonum aviculare. This compound was reacted with N-benzylmaleimide to synthesize the targeted compound 3. The purpose of this research is to exhibit our developed compound 3's ability to concurrently inhibit many targets that are responsible for hyperglycemia. Compound 3 was capable of inhibiting α-amylase, α-glucosidase, and protein tyrosine phosphatase 1 B. Even so, outstanding in vitro inhibition was shown by the compound against dipeptidyl peptidase-4 (DPP-4) with an IC₅₀ value of 0.07 µM. Additionally, by using DPPH in the antioxidant activity, it exhibited good antioxidant potential. Similarly, in the in vivo activity, the experimental mice proved to be safe by treatment with compound 3. After 21 days of examination, the compound 3 activity pattern was found to be effective in experimental mice. Compound 3 decreased the excess peak of total triglycerides, total cholesterol, AST, ALT, ALP, LDL, BUN, and creatinine in the STZ-induced diabetic mice. Likewise, the histopathology of the kidneys, liver, and pancreas of the treated animals was also evaluated. Overall, the succinimde moiety, such as compound 3, can affect several targets simultaneously, and, finally, we were successful in synthesizing a multi-targeted preclinical therapy.

Endoplasmic Reticulum Architecture and Inter-Organelle Communication in Metabolic Health and Disease

The endoplasmic reticulum (ER) is a key organelle involved in the regulation of lipid and glucose metabolism, proteostasis, Ca²⁺ signaling, and detoxification. The structural organization of the ER is very dynamic and complex, with distinct subdomains such as the nuclear envelope and the peripheral ER organized into ER sheets and tubules. ER also forms physical contact sites with all other cellular organelles and with the plasma membrane. Both form and function of the ER are highly adaptive, with a potent capacity to respond to transient changes in environmental cues such as nutritional fluctuations. However, under obesity-induced chronic stress, the ER fails to adapt, leading to ER dysfunction and the development of metabolic pathologies such as insulin resistance and fatty liver disease. Here, we discuss how the remodeling of ER structure and contact sites with other organelles results in diversification of metabolic function and how perturbations to this structural flexibility by chronic overnutrition contribute to ER dysfunction and metabolic pathologies in obesity.

Compound Danshen Dripping Pill inhibits hypercholesterolemia/atherosclerosis-induced heart failure in ApoE and LDLR dual deficient mice via multiple mechanisms

Heart failure is the leading cause of death worldwide. Compound Danshen Dripping Pill (CDDP) or CDDP combined with simvastatin has been widely used to treat patients with myocardial infarction and other cardiovascular diseases in China. However, the effect of CDDP on hypercholesterolemia/atherosclerosis-induced heart failure is unknown. We constructed a new model of heart failure induced by hypercholesterolemia/atherosclerosis in apolipoprotein E (ApoE) and LDL receptor (LDLR) dual deficient (ApoE^-/-LDLR^-/-) mice and investigated the effect of CDDP or CDDP plus a low dose of simvastatin on the heart failure. CDDP or CDDP plus a low dose of simvastatin inhibited heart injury by multiple actions including anti-myocardial dysfunction and anti-fibrosis. Mechanistically, both Wnt and lysine-specific demethylase 4A (KDM4A) pathways were significantly activated in mice with heart injury. Conversely, CDDP or CDDP plus a low dose of simvastatin inhibited Wnt pathway by markedly up-regulating expression of Wnt inhibitors. While the anti-inflammation and anti-oxidative stress by CDDP were achieved by inhibiting KDM4A expression and activity. In addition, CDDP attenuated simvastatin-induced myolysis in skeletal muscle. Taken together, our study suggests that CDDP or CDDP plus a low dose of simvastatin can be an effective therapy to reduce hypercholesterolemia/atherosclerosis-induced heart failure.

MEK1/2 inhibitors induce class I alcohol dehydrogenase (ADH1) expression by regulating farnesoid X receptor in hepatic cell lines and C57BL/6J mouse

BACKGROUND

Alcohol is mainly catabolized by class I alcohol dehydrogenase (ADH1) in liver. ADH deficiency can aggravate ethanol-induced tissue injury. Extracellular signal-regulated kinases 1/2 (ERK1/2) is involved in alcohol metabolism. However, the relationship between ERK1/2 and ADH1 remains unclear.

METHODS AND RESULTS

To inhibit ERK1/2, HepG2 and BNL cells were treated with mitogen-activated protein kinases 1/2 (MEK1/2) inhibitors (U0126 and PD98059), and C57BL/6J mice were fed U0126. After treatment, the protein and mRNA expression of ADH1 were determined by Western blot and quantitative real time-PCR. The activity of ADH1 promoter was detected using luciferase assay. The results showed MEK1/2 inhibitors significantly increased ADH1 protein expression by inducing its transcription activity. Then we demonstrated a farnesoid X receptor (FXR) response element (FXRE) in ADH1 promoter by ChIP assay. To test whether FXR mediates the induction of MEK1/2 inhibitors on ADH1, HepG2 cells were transfected with FXR siRNA or ADH1 promoters with FXRE mutation. We found both FXR siRNA and FXRE mutation in ADH1 promoter abolished MEK1/2 inhibitors-induced ADH1 expression, indicating the activation of MEK1/2 inhibitors on ADH1 depends on FXR.

CONCLUSIONS

Our findings revealed inhibition of ERK1/2 can significantly increase ADH1 expression, indicating MEK1/2 inhibitors may possess potential application in alcohol-related diseases.

Inhibition of high-fat diet-induced obesity via reduction of ER-resident protein Nogo occurs through multiple mechanisms

Obesity is a risk factor for insulin resistance, type 2 diabetes, and cardiovascular diseases. Reticulon-4 (Nogo) is an endoplasmic reticulum–resident protein with unclear functions in obesity. Herein, we investigated the effect of Nogo on obesity and associated metabolic disorders. Human serum samples were collected to explore the relationship between circulating Nogo-B and body mass index value. Nogo-deficient and WT littermate control mice were fed normal chow or high-fat diet (HFD) for 14 weeks, and HFD-induced obese C57BL/6J mice were injected scrambled or Nogo siRNA for 2 weeks. We found that in human and mouse serum, Nogo-B was positively correlated to body mass index/bodyweight and lipid profiles. Reduced Nogo (by genetic deletion or siRNA transfection) protected mice against HFD-induced obesity and related metabolic disorders. We demonstrate that Nogo deficiency reversed HFD-induced whitening of brown adipose tissue, thereby increasing thermogenesis. It also ameliorated lipid accumulation in tissues by activating the adiponectin–adiponectin receptor 1–AMP-activated kinase α signaling axis. Finally, Nogo deficiency potently reduced HFD-induced serum proinflammatory cytokines and infiltration of macrophages into metabolic organs, which is related to enhanced NF-κB p65 degradation via the lysosome pathway. Collectively, our study suggests that reduced levels of Nogo protect mice against HFD-induced obesity by increasing thermogenesis and energy metabolism while inhibiting NF-κB-mediated inflammation. Our results indicate that inhibition of Nogo may be a potential strategy for obesity treatment.

The role of FGF21 in the pathogenesis of cardiovascular disease

ABSTRACT

The morbidity and mortality of cardiovascular diseases (CVDs) are increasing worldwide and seriously threaten human life and health. Fibroblast growth factor 21 (FGF21), a metabolic regulator, regulates glucose and lipid metabolism and may exert beneficial effects on the cardiovascular system. In recent years, FGF21 has been found to act directly on the cardiovascular system and may be used as an early biomarker of CVDs. The present review highlights the recent progress in understanding the relationship between FGF21 and CVDs including coronary heart disease, myocardial ischemia, cardiomyopathy, and heart failure and also explores the related mechanism of the cardioprotective effect of FGF21. FGF21 plays an important role in the prediction, treatment, and improvement of prognosis in CVDs. This cardioprotective effect of FGF21 may be achieved by preventing endothelial dysfunction and lipid accumulating, inhibiting cardiomyocyte apoptosis and regulating the associated oxidative stress, inflammation and autophagy. In conclusion, FGF21 is a promising target for the treatment of CVDs, however, its clinical application requires further clarification of the precise role of FGF21 in CVDs.

Targeting mitochondria-inflammation circle by renal denervation reduces atheroprone endothelial phenotypes and atherosclerosis

OBJECTIVE

The disruption of mitochondrial redox homeostasis in endothelial cells (ECs) can cause chronic inflammation, a substantial contributor to the development of atherosclerosis. Chronic sympathetic hyperactivity can enhance oxidative stress to induce endothelial dysfunction. We determined if renal denervation (RDN), the strategy reducing sympathetic tone, can protect ECs by ameliorating mitochondrial reactive oxygen species (ROS)-induced inflammation to reduce atherosclerosis.

METHODS AND RESULTS

ApoE deficient (ApoE^-/-) mice were conducted RDN or sham operation before 20-week high-fat diet feeding. Atherosclerosis, EC phenotype and mitochondrial morphology were determined. In vitro, human arterial ECs were treated with norepinephrine to determine the mechanisms for RDN-inhibited endothelial inflammation. RDN reduced atherosclerosis, EC mitochondrial oxidative stress and inflammation. Mechanistically, the chronic sympathetic hyperactivity increased circulating norepinephrine and mitochondrial monoamine oxidase A (MAO-A) activity. MAO-A activation-impaired mitochondrial homeostasis resulted in ROS accumulation and NF-κB activation, thereby enhancing expression of atherogenic and proinflammatory molecules in ECs. It also suppressed mitochondrial function regulator PGC-1α, with involvement of NF-κB and oxidative stress. Inactivation of MAO-A by RDN disrupted the positive-feedback regulation between mitochondrial dysfunction and inflammation, thereby inhibiting EC atheroprone phenotypic alterations and atherosclerosis.

CONCLUSIONS

The interplay between MAO-A-induced mitochondrial oxidative stress and inflammation in ECs is a key driver in atherogenesis, and it can be reduced by RDN.

Live Combined B. subtilis and E. faecium Alleviate Liver Inflammation, Improve Intestinal Barrier Function, and Modulate Gut Microbiota in Mice with Non-Alcoholic Fatty Liver Disease

Background

Non-alcoholic fatty liver disease (NAFLD) is a chronic, progressive liver disease with an increasing incidence rate. This study investigated the protective effects of live combined Bacillus subtilis and Enterococcus faecium (LCBE) on NAFLD, and its possible mechanisms.

Material/Methods

Five-week-old C57BL/6 mice were randomly divided into 3 groups: chow, HFD, and HFD+LCBE groups. The levels of serum biochemical markers, glucose tolerance, insulin, the inflammatory cytokines IL-1β, IL-6, and TNF-α, LPS, and histological staining were measured using commercial kits. qPCR was used to examine the mRNA expression levels of inflammatory cytokines in the liver. Western blotting was used to determine the protein levels of TLR4, NF-κB p65, PPAR-α, and CPT-1 in the liver, and occludin and Claudin1 in the intestine. The intestinal flora of the mice was analyzed by high-throughput sequencing of the V3–V4 region of 16S rDNA.

Results

LCBE significantly lowered the body weight, liver/body weight ratio, and serum glucose level, and increased the serum insulin level in NAFLD mice. In addition, LCBE treatment improved the liver function and lipid profile, decreased the levels of LPS and inflammatory cytokines, and downregulated the expression of TLR4 and NF-κB p65. Moreover, LCBE enhanced the intestinal barrier function by increasing the expression of occludin and Claudin1. Furthermore, LCBE modulated the composition of the gut microbiota by reducing the Firmicutes to Bacteroidetes ratio, and the proportion of inflammation-related and LPS-producing bacteria, thus re-arranging the structure of the gut microbiota.

Conclusions

LCBE protects against NAFLD by alleviating inflammation, restoring the intestinal barrier, and modulating gut microbiota composition.

NGBR is required to ameliorate type 2 diabetes in mice by enhancing insulin sensitivity

The reduction of insulin resistance or improvement of insulin sensitivity is the most effective treatment for type 2 diabetes (T2D). We previously reported that Nogo-B receptor (NGBR), encoded by the NUS1 gene, is required for attenuating hepatic lipogenesis by blocking nuclear translocation of liver X receptor alpha, suggesting its important role in regulating hepatic lipid metabolism. Herein, we demonstrate that NGBR expression was decreased in the liver of obesity-associated T2D patients and db/db mice. NGBR knockout in mouse hepatocytes resulted in increased blood glucose, insulin resistance, and beta-cell loss. High-fat diet (HFD)/streptozotocin (STZ)-treated mice presented the T2D phenotype by showing increased nonesterified fatty acid (NEFA) and triglyceride (TG) in the liver and plasma and increased insulin resistance and beta-cell loss. AAV-mediated NGBR overexpression in the liver reduced NEFA and TG in the liver and circulation and improved liver functions. Consequently, HFD/STZ-treated mice with hepatic NGBR overexpression had increased insulin sensitivity and reduced beta-cell loss. Mechanistically, NGBR overexpression restored insulin signaling of AMPKα1-dependent phosphorylation of AKT and GSK3β. NGBR overexpression also reduced expression of endoplasmic reticulum stress-associated genes in the liver and skeletal muscle to improve insulin sensitivity. Together, our results reveal that NGBR is required to ameliorate T2D in mice, providing new insight into the role of hepatic NGBR in insulin sensitivity and T2D treatment.

Analysis of N6-Methyladenosine Methylation Modification in Fructose-Induced Non-Alcoholic Fatty Liver Disease

Improvements in living standards have led to non-alcoholic fatty liver disease (NAFLD), one of the most common chronic liver diseases worldwide. Recent studies have shown that N6-methyladenosine (m6A), a type of RNA modification, is strongly associated with many important biological processes. However, the relationship between m6A methylation modifications and NAFLD remains poorly understood. In the present study, through methylated RNA immunoprecipitation sequencing and RNA transcriptome sequencing in high fructose diet-induced NAFLD mice, we found that hypermethylation-encoding genes were mainly enriched in lipid metabolism processes. We identified 266 overlapping and differentially expressed genes (DEGs) that changed at both the mRNA expression level and m6A modification level. Among them, 193 genes displayed increased expression and m6A modification, indicating that m6A RNA modifications tend to be positively correlated with NAFLD. We further compared the high fructose diet-induced NAFLD mouse model with leptin receptor-deficient mice and found that DEGs enriched in the lipid metabolism pathway were up-regulated in both groups. In contrast, DEGs associated with the immune inflammatory response were up-regulated in the high fructose diet group, but down-regulated in leptin receptor-deficient mice. Taken together, our results demonstrate that m6A methylation modifications may play an important role in the development of NAFLD.