Protection against High-Fat-Diet-Induced Obesity in MDM2C305F Mice Due to Reduced p53 Activity and Enhanced Energy Expenditure

High-Fat Diet and Altered Radiation Response

High-fat diets (HFDs) have become increasingly prevalent in modern societies, driving rising rates of obesity and metabolic syndrome. Concurrently, radiation exposure from medical treatments and environmental sources poses health risks shaped by both biological and environmental factors. This review explores the intersection between HFDs and radiation sensitivity/susceptibility, focusing on how diet-induced metabolic alterations influence the body's response to radiation. Evidence from preclinical and clinical studies indicates that HFDs significantly alter metabolism, leading to increased oxidative stress and immune system dysregulation. These metabolic changes can exacerbate radiation-induced oxidative stress, inflammation, and DNA damage, potentially increasing radiation sensitivity in normal tissues. Conversely, obesity and HFD-induced metabolic disruptions may activate cellular pathways involved in DNA repair, cell survival, and inflammatory responses, fostering tumor resistance and modifying the tumor microenvironment, which may impair the efficacy of radiation therapy in cancer treatment. Understanding the interplay between diet and radiation exposure is critical for optimizing public health guidelines and improving therapeutic outcomes. These findings underscore the need for further research into dietary interventions that may mitigate radiation-associated risks.

NRH, a potent NAD+ enhancer, improves glucose homeostasis and lipid metabolism in diet-induced obese mice through an active adenosine kinase pathway

AIMS

NAD+ deficiency underlies obesity-induced metabolic disturbances. This study evaluated dihydronicotinamide riboside (NRH), a potent NAD+ enhancer, in lean and obese mice and explored whether NRH operates through a unique mechanism involving adenosine kinase (ADK), an enzyme critical for NRH-driven NAD+ synthesis.

METHODS

Pharmacokinetic and pharmacodynamic analyses were performed following a single 250 mg/kg intraperitoneal injection of NRH in healthy mice. In long-term studies, lean and high-fat diet-induced obese mice were treated with 250 mg/kg NRH thrice weekly for 7 weeks. Blood NAD+ levels, body composition, energy expenditure, and glucose and lipid metabolism were monitored. To test ADK's role, the ADK inhibitor ABT702 was co-administered with NRH in obese mice.

RESULTS

NRH entered tissues unassisted and was rapidly metabolized for NAD+ biosynthesis, while ADK inhibition blocked its phosphorylation, leading to NRH accumulation in all examined tissues and possible release back into circulation. The 7-week NRH administration was well-tolerated in both lean and obese mice. In obese mice, NRH improved glucose homeostasis by boosting insulin secretion, enhancing muscle insulin signaling, and reducing hepatic gluconeogenesis. It also lowered fat mass, decreased serum lipids, and improved white adipose function. These benefits were linked to elevated tissue NAD+ levels, enhanced Sirtuin activities, and increased mitochondrial antioxidant defenses. ADK inhibition abolished these effects, confirming that NRH's direct entry into tissues and subsequent phosphorylation is essential for its full benefits.

CONCLUSION

This study establishes NRH as a promising therapeutic agent for obesity-induced metabolic dysfunction, correcting glucose intolerance and hyperlipidemia through ADK-dependent NAD+ enhancement.

Feedback regulation of retinaldehyde reductase DHRS3, a critical determinant of retinoic acid homeostasis

Retinoic acid is crucial for vertebrate embryogenesis, influencing anterior-posterior patterning and organogenesis through its interaction with nuclear hormone receptors comprising heterodimers of retinoic acid receptors (RARα, β, or γ) and retinoid X receptors (RXRα, β, or γ). Tissue retinoic acid levels are tightly regulated since both its excess and deficiency are deleterious. Dehydrogenase/reductase 3 (DHRS3) plays a critical role in this regulation by converting retinaldehyde to retinol, preventing excessive retinoic acid formation. Mutations in DHRS3 can result in embryonic lethality and congenital defects. This study shows that mouse Dhrs3 expression is responsive to vitamin A status and is directly regulated by the RAR/RXR complex through cis-regulatory elements. This highlights a negative feedback mechanism that ensures retinoic acid homeostasis.

Differential chromatin accessibility and Gene Expression Associated with Backfat Deposition in pigs

BACKGROUND

Backfat serves as a vital fat reservoir in pigs, and its excessive accumulation will adversely impact pig growth performance, farming efficiency, and pork quality. The aim of this research is to integrate assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and RNA sequencing (RNA-seq) to explore the molecular mechanisms underlying porcine backfat deposition.

RESULTS

ATAC-seq analysis identified 568 genes originating from 698 regions exhibiting differential accessibility, which were significantly enriched in pathways pertinent to adipocyte differentiation and lipid metabolism. Besides, a total of 283 transcription factors (TFs) were identified by motif analysis. RNA-seq analysis revealed 978 differentially expressed genes (DEGs), which were enriched in pathways related to energy metabolism, cell cycle and signal transduction. The integration of ATAC-seq and RNA-seq data indicates that DEG expression levels are associated with chromatin accessibility. This comprehensive study highlights the involvement of critical pathways, including the Wnt signaling pathway, Jak-STAT signaling pathway, and fatty acid degradation, in the regulation of backfat deposition. Through rigorous analysis, we identified several candidate genes (LEP, CTBP2, EHHADH, OSMR, TCF7L2, BCL2, FGF1, UCP2, CCND1, TIMP1, and VDR) as potentially significant contributors to backfat deposition. Additionally, we constructed TF-TF and TF-target gene regulatory networks and identified a series of potential TFs related to backfat deposition (FOS, STAT3, SMAD3, and ESR1).

CONCLUSIONS

This study represents the first application of ATAC-seq and RNA-seq, affording a novel perspective into the mechanisms underlying backfat deposition and providing invaluable resources for the enhancement of pig breeding programs.

miR-10167-3p targets TCF7L1 to inhibit bovine adipocyte differentiation and promote bovine adipocyte proliferation

MicroRNAs (miRNAs) are widely involved in various lipogenic processes, including adipocyte proliferation and differentiation, lipid droplet formation, and adipocyte-specific gene activation. The present study aimed to investigate the gene expression profiles of bovine preadipocytes under high miR-10167-3p expression using the RNA-seq technique and to verify the functions of its downstream target genes on the proliferation and differentiation of bovine preadipocytes. First, RNA-seq identified 573 differentially expressed genes (DEGs), of which 243 were downregulated and 330 were upregulated. Then, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that 15.19% of the DEGs were enriched in pathways related to lipid metabolism. Meanwhile, dual-luciferase reporter gene assay verified the target-binding relationship between miR-10167-3p and TCF7L1. The function of TCF7L1 was assessed using several experiments in adipocytes with high TCF7L1 expression and RNA interference. The mRNA and protein expression of proliferation, differentiation, and apoptosis marker genes were detected using qPCR and western blot, respectively; lipid droplet synthesis was detected using oil red O, Nile red, and bodipy staining; adipocyte proliferation was detected by EdU; and apoptosis was detected using flow cytometry. The results revealed that TCF7L1 overexpression inhibited bovine preadipocyte differentiation and apoptosis and promoted their proliferation, with opposite results obtained with its RNA interference. These results may provide a reference for the subsequent investigation of the molecular mechanism of bovine fat deposition.

Comparative mathematical modeling reveals the differential effects of high-fat diet and ketogenic diet on the PI3K-Akt signaling pathway in heart

BACKGROUND

Obesity is a global health concern associated with increased risk of diseases like cardiovascular conditions including ischemic heart disease, a leading cause of mortality. The ketogenic diet (KD) has potential therapeutic applications in managing obesity and related disorders. However, the intricate effects of KD on diverse physiological conditions remain incompletely understood. The PI3K-Akt signaling pathway is critical for heart health, and its dysregulation implicates numerous cardiac diseases.

METHODS

We developed comprehensive mathematical models of the PI3K-Akt signaling pathway under high-fat diet (HFD) and KD conditions to elucidate their differential impacts and quantify apoptosis. Simulations and sensitivity analysis were performed.

RESULTS

Simulations demonstrate that KD can reduce the activation of key molecules like Erk and Trp53 to mitigate apoptosis compared to HFD. Findings align with experimental data, highlighting the potential cardiac benefits of KD. Sensitivity analysis identifies regulators like Trp53 and Bcl2l1 that critically influence apoptosis under HFD.

CONCLUSIONS

Mathematical modeling provides quantitative insights into the contrasting effects of HFD and KD on cardiac PI3K-Akt signaling and apoptosis. Findings have implications for precision nutrition and developing novel therapeutic strategies to address obesity-related cardiovascular diseases.

Endothelial c-Myc knockout disrupts metabolic homeostasis and triggers the development of obesity

Introduction: Obesity is a major risk factor associated with multiple pathological conditions including diabetes and cardiovascular disease. Endothelial dysfunction is an early predictor of obesity. However, little is known regarding how early endothelial changes trigger obesity. In the present work we report a novel endothelial-mediated mechanism essential for regulation of metabolic homeostasis, driven by c-Myc. Methods: We used conditional knockout (EC-Myc KO) and overexpression (EC-Myc OE) mouse models to investigate the endothelial-specific role of c-Myc in metabolic homeostasis during aging and high-fat diet exposure. Body weight and metabolic parameters were collected over time and tissue samples collected at endpoint for biochemical, pathology and RNA-sequencing analysis. Animals exposed to high-fat diet were also evaluated for cardiac dysfunction. Results: In the present study we demonstrate that EC-Myc KO triggers endothelial dysfunction, which precedes progressive increase in body weight during aging, under normal dietary conditions. At endpoint, EC-Myc KO animals showed significant increase in white adipose tissue mass relative to control littermates, which was associated with sex-specific changes in whole body metabolism and increase in systemic leptin. Overexpression of endothelial c-Myc attenuated diet-induced obesity and visceral fat accumulation and prevented the development of glucose intolerance and cardiac dysfunction. Transcriptome analysis of skeletal muscle suggests that the protective effects promoted by endothelial c-Myc overexpression are associated with the expression of genes known to increase weight loss, energy expenditure and glucose tolerance. Conclusion: Our results show a novel important role for endothelial c-Myc in regulating metabolic homeostasis and suggests its potential targeting in preventing obesity and associated complications such as diabetes type-2 and cardiovascular dysfunction.

Dulaglutide reduces oxidative DNA damage and hypermethylation in the somatic cells of mice fed a high-energy diet by restoring redox balance, inflammatory responses, and DNA repair gene expressions

Obesity is an established risk factor for numerous malignancies, although it remains uncertain whether the disease itself or weight-loss drugs are responsible for a greater predisposition to cancer. The objective of the current study was to determine the impact of dulaglutide on genetic and epigenetic DNA damage caused by obesity, which is a crucial factor in the development of cancer. Mice were administered a low-fat or high-fat diet for 12 weeks, followed by a 5-week treatment with dulaglutide. Following that, modifications of the DNA bases were examined using the comet assay. To clarify the underlying molecular mechanisms, oxidized and methylated DNA bases, changes in the redox status, levels of inflammatory cytokines, and the expression levels of some DNA repair genes were evaluated. Animals fed a high-fat diet exhibited increased body weights, elevated DNA damage, oxidation of DNA bases, and DNA hypermethylation. In addition, obese mice showed altered inflammatory responses, redox imbalances, and repair gene expressions. The findings demonstrated that dulaglutide does not exhibit genotoxicity in the investigated conditions. Following dulaglutide administration, animals fed a high-fat diet demonstrated low DNA damage, less oxidation and methylation of DNA bases, restored redox balance, and improved inflammatory responses. In addition, dulaglutide treatment restored the upregulated DNMT1, Ogg1, and p53 gene expression. Overall, dulaglutide effectively maintains DNA integrity in obese animals. It reduces oxidative DNA damage and hypermethylation by restoring redox balance, modulating inflammatory responses, and recovering altered gene expressions. These findings demonstrate dulaglutide's expediency in treating obesity and its associated complications.

Identification of potential obese-specific biomarkers and pathways associated with abdominal subcutaneous fat deposition in pig using a comprehensive bioinformatics strategy

Abdominal subcutaneous fat deposition (ASFD) is not only related to meat quality in the pig industry but also to human health in medicine. It is of great value to elucidate the potential molecular mechanisms of ASFD. The present study aims to identify obese-specific biomarkers and key pathways correlated with ASFD in pigs. The ASF-related mRNA expression dataset GSE136754 was retrieved from the Gene Expression Omnibus (GEO) database and systematically analyzed using a comprehensive bioinformatics method. A total of 565 differentially expressed genes (DEGs) were identified between three obese and three lean pigs, and these DEGs were mainly involved in the p53 signaling pathway, MAPK signaling pathway and fatty acid metabolism. A protein-protein interaction (PPI) network, consisting of 540 nodes and 1,065 edges, was constructed, and the top ten genes with the highest degree scores-ABL1, HDAC1, CDC42, HDAC2, MRPS5, MRPS10, MDM2, JUP, RPL7L1 and UQCRFS1-were identified as hub genes in the whole PPI network. Especially HDAC1, MDM2, MRPS10 and RPL7L1 were identified as potential robust obese-specific biomarkers due to their significant differences in single gene expression levels and high ROC area; this was further verified by quantitative real-time PCR (qRT-PCR) on abdominal subcutaneous fat samples from obese-type (Saba) and lean-type (Large White) pigs. Additionally, a mRNA-miRNA-lncRNA ceRNA network consisting of four potential biomarkers, 15 miRNAs and 51 lncRNAs was established, and two targeted lncRNAs with more connections, XIST and NEAT1, were identified as potentially important regulatory factors. The findings of this study may provide novel insights into the molecular mechanism involved in ASFD.

Maternal undernutrition results in transcript changes in male offspring that may promote resistance to high fat diet induced weight gain

Maternal nutrition during embryonic development and lactation influences multiple aspects of offspring health. Using mice, this study investigates the effects of maternal caloric restriction (CR) during mid-gestation and lactation on offspring neonatal development and on adult metabolic function when challenged by a high fat diet (HFD). The CR maternal model produced male and female offspring that were significantly smaller, in terms of weight and length, and females had delayed puberty. Adult offspring born to CR dams had a sexually dimorphic response to the high fat diet. Compared to offspring of maternal control dams, adult female, but not male, CR offspring gained more weight in response to high fat diet at 10 weeks. In adipose tissue of male HFD offspring, maternal undernutrition resulted in blunted expression of genes associated with weight gain and increased expression of genes that protect against weight gain. Regardless of maternal nutrition status, HFD male offspring showed increased expression of genes associated with progression toward nonalcoholic fatty liver disease (NAFLD). Furthermore, we observed significant, sexually dimorphic differences in serum TSH. These data reveal tissue- and sex-specific changes in gene and hormone regulation following mild maternal undernutrition, which may offer protection against diet induced weight gain in adult male offspring.

Hepatic Huwe1 loss protects mice from non-alcoholic fatty liver disease through lipid metabolic rewiring

Non-alcoholic fatty liver disease (NAFLD) is the most pervasive liver pathology worldwide. Here, we demonstrate that the ubiquitin E3 ligase Huwe1 is vital in NAFLD pathogenesis. Using mass spectrometry and RNA sequencing, we reveal that liver-specific deletion of Huwe1 (Huwe1LKO) in 1-year-old mice (approximately middle age in humans) elicits extensive lipid metabolic reprogramming that involves downregulation of de novo lipogenesis and fatty acid uptake, upregulation of fatty acid β-oxidation, and increased oxidative phosphorylation. ChEA transcription factor prediction analysis inferred these changes result from attenuated PPARɑ, LXR, and RXR activity in Huwe1LKO livers. Consequently, Huwe1LKO mice fed chow diet exhibited significantly reduced hepatic steatosis and superior glucose tolerance compared to wild-type mice. Huwe1LKO also conferred protection from high-fat diet-induced hepatic steatosis by 6-months of age, with increasingly robust differences observed as mice reached middle age. Together, we present evidence that Huwe1 plays a critical role in the development of age- and diet-induced NAFLD.

Carnitine o-octanoyltransferase is a p53 target that promotes oxidative metabolism and cell survival following nutrient starvation

Whereas it is known that p53 broadly regulates cell metabolism, the specific activities that mediate this regulation remain partially understood. Here, we identified carnitine o-octanoyltransferase (CROT) as a p53 transactivation target that is upregulated by cellular stresses in a p53-dependent manner. CROT is a peroxisomal enzyme catalyzing very long-chain fatty acids conversion to medium chain fatty acids that can be absorbed by mitochondria during β-oxidation. p53 induces CROT transcription through binding to consensus response elements in the 5'-UTR of CROT mRNA. Overexpression of WT but not enzymatically inactive mutant CROT promotes mitochondrial oxidative respiration, while downregulation of CROT inhibits mitochondrial oxidative respiration. Nutrient depletion induces p53-dependent CROT expression that facilitates cell growth and survival; in contrast, cells deficient in CROT have blunted cell growth and reduced survival during nutrient depletion. Together, these data are consistent with a model where p53-regulated CROT expression allows cells to be more efficiently utilizing stored very long-chain fatty acids to survive nutrient depletion stresses.

Sting and p53 DNA repair pathways are compromised in Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia. A common finding in AD is DNA damage. Double-strand DNA breaks (DSBs) are particularly hazardous to neurons because their post-mitotic state forces neurons to rely on error-prone and potentially mutagenic mechanisms to repair DNA breaks. However, it remains unclear whether DNA damage results from increased DNA damage or failure of DNA repair. Oligomerization of the tumor suppressor protein p53 is an essential part of DSB repair, and p53 phosphorylated on S15 is an indicator of DNA damage. We report that the monomer:dimer ratio of phosphorylated (S15) p53 is increased by 2.86-fold in temporal lobes of AD patients compared to age-matched controls, indicating that p53 oligomerization is compromised in AD. In vitro oxidation of p53 with 100 nM H2O2 produced a similar shift in the monomer:dimer ratio. A COMET test showed a higher level of DNA degradation in AD consistent with double-strand DNA damage or inhibition of repair. Protein carbonylation was also elevated (190% of control), indicating elevated oxidative stress in AD patients. Levels of the DNA repair support protein 14-3-3σ, γ-H2AX, a phosphorylated histone marking double strand DNA breaks, and phosphorylated ataxia telangiectasia mutated (ATM) protein were all increased. cGAS-STING-interferon signaling was impaired in AD and was accompanied by a depletion of STING protein from Golgi and a failure to elevate interferon despite the presence of DSBs. The results suggest that oxidation of p53 by ROS could inhibit the DDR and decrease its ability to orchestrate DSB repair by altering the oligomerization state of p53. The failure of immune-stimulated DNA repair may contribute to cell loss in AD and suggests new therapeutic targets for AD.

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.

A MDM2 inhibitor MX69 inhibits adipocytes adipogenesis and differentiation

Adipose tissue, a key regulator of systemic energy homeostasis, can synthesize and store triglycerides to meet long-term energy demands. In response to nutrient overload, adipose tissue expands by hypertrophy or hyperplasia. As an oncogene, MDM2 has exerted diverse biological activities including human development, tissue regeneration, and inflammation, in addition to major oncogenic activities. Recently, some studies indicated that MDM2 plays an important role in adipose tissue function. However, the role of MX69, a MDM2 inhibitor, in adipose tissue function has not been fully elucidated. Here, we administered MX69 intraperitoneally to high-fat diet-induced obesity (DIO) wild type C57BL/6 mice and found that MX69 could promote the body weight and white adipose tissue weight of DIO mice. Moreover, MX69 had no effects on glucose tolerance and insulin sensitivity in DIO mice. And MX69 treatment decreased the size of adipocytes and fat deposition in adipose tissue and inhibited 3T3-L1 preadipocytes differentiation. Mechanistically, MX69 inhibited the protein levels of MDM2 and the mRNA levels of genes related to adipogenesis and differentiation. In summary, our results indicated that MDM2 has a crucial and complex role in regulating adipose tissue function.

Coordinated metabolic transitions and gene expression by NAD+ during adipogenesis

Adipocytes are the main cell type in adipose tissue, which is a critical regulator of metabolism, highly specialized in storing energy as fat. Adipocytes differentiate from multipotent mesenchymal stromal cells (hMSCs) through adipogenesis, a tightly controlled differentiation process involving close interplay between metabolic transitions and sequential programs of gene expression. However, the specific gears driving this interplay remain largely obscure. Additionally, the metabolite nicotinamide adenine dinucleotide (NAD+) is becoming increasingly recognized as a regulator of lipid metabolism, and a promising therapeutic target for dyslipidemia and obesity. Here, we explored how NAD+ bioavailability controls adipogenic differentiation from hMSC. We found a previously unappreciated repressive role for NAD+ on adipocyte commitment, while a functional NAD+-dependent deacetylase SIRT1 appeared crucial for terminal differentiation of pre-adipocytes. Repressing NAD+ biosynthesis during adipogenesis promoted the adipogenic transcriptional program, while two-photon microscopy and extracellular flux analyses suggest that SIRT1 activity mostly relies on the metabolic switch. Interestingly, SIRT1 controls subcellular compartmentalization of redox metabolism during adipogenesis.

Copy Number Variations Contribute to Intramuscular Fat Content Differences by Affecting the Expression of PELP1 Alternative Splices in Pigs

Simple Summary

Copy number variation (CNV) is a type of variant that may influence meat quality of, for example intramuscular fat (IMF). In this study, a genome-wide association study (GWAS) was then performed between CNVs and IMF in a pig F2 resource population. A total of 19 CNVRs were found to be significantly associated with IMF. RNA-seq and qPCR validation results indicated that CNV150, which is located on the 3′UTR end of the proline, as well as glutamate and the leucine rich protein 1 (PELP1) gene may affect the expression of PELP1 alternative splices. We infer that the CNVR may influence IMF content by regulating the alternative splicing of the PELP1 gene and ultimately affects the structure of the PELP1 protein. These findings suggest a novel mechanistic approach for meat quality improvement in animals and the potential treatment of insulin resistance in human beings.

Abstract

Intramuscular fat (IMF) is a key meat quality trait. Research on the genetic mechanisms of IMF decomposition is valuable for both pork quality improvement and the treatment of obesity and type 2 diabetes. Copy number variations (CNVs) are a type of variant that may influence meat quality. In this study, a total of 1185 CNV regions (CNVRs) including 393 duplicated CNVRs, 432 deleted CNVRs, and 361 CNVRs with both duplicated and deleted status were identified in a pig F2 resource population using next-generation sequencing data. A genome-wide association study (GWAS) was then performed between CNVs and IMF, and a total of 19 CNVRs were found to be significantly associated with IMF. QTL colocation analysis indicated that 3 of the 19 CNVRs overlapped with known QTLs. RNA-seq and qPCR validation results indicated that CNV150, which is located on the 3′UTR end of the proline, as well as glutamate and the leucine rich protein 1 (PELP1) gene may affect the expression of PELP1 alternative splices. Sequence alignment and Alphafold2 structure prediction results indicated that the two alternative splices of PELP1 have a 23 AA sequence variation and a helix-fold structure variation. This region is located in the region of interaction between PELP1 and other proteins which have been reported to be significantly associated with fat deposition or insulin resistance. We infer that the CNVR may influence IMF content by regulating the alternative splicing of the PELP1 gene and ultimately affects the structure of the PELP1 protein. In conclusion, we found some CNVRs, especially CNV150, located in PELP1 that affect IMF. These findings suggest a novel mechanistic approach for meat quality improvement in animals and the potential treatment of insulin resistance in human beings.

It’s Getting Complicated—A Fresh Look at p53-MDM2-ARF Triangle in Tumorigenesis and Cancer Therapy

Anti-tumorigenic mechanisms mediated by the tumor suppressor p53, upon oncogenic stresses, are our bodies’ greatest weapons to battle against cancer onset and development. Consequently, factors that possess significant p53-regulating activities have been subjects of serious interest from the cancer research community. Among them, MDM2 and ARF are considered the most influential p53 regulators due to their abilities to inhibit and activate p53 functions, respectively. MDM2 inhibits p53 by promoting ubiquitination and proteasome-mediated degradation of p53, while ARF activates p53 by physically interacting with MDM2 to block its access to p53. This conventional understanding of p53-MDM2-ARF functional triangle have guided the direction of p53 research, as well as the development of p53-based therapeutic strategies for the last 30 years. Our increasing knowledge of this triangle during this time, especially through identification of p53-independent functions of MDM2 and ARF, have uncovered many under-appreciated molecular mechanisms connecting these three proteins. Through recognizing both antagonizing and synergizing relationships among them, our consideration for harnessing these relationships to develop effective cancer therapies needs an update accordingly. In this review, we will re-visit the conventional wisdom regarding p53-MDM2-ARF tumor-regulating mechanisms, highlight impactful studies contributing to the modern look of their relationships, and summarize ongoing efforts to target this pathway for effective cancer treatments. A refreshed appreciation of p53-MDM2-ARF network can bring innovative approaches to develop new generations of genetically-informed and clinically-effective cancer therapies.

Tubule-specific deletion of LincRNA-p21ameliorates lipotoxic kidney injury

Lipotoxicity has been implicated in the pathogenesis of obesity-related kidney damage and propagates chronic kidney injury like diabetic kidney disease; however, the underlying mechanisms have not yet been fully elucidated. To date, reduction of lipid acquisition and enhancement of lipid metabolism are the major, albeit non-specific, approaches to improve lipotoxic kidney damage. In the kidneys of high-fat diet (HFD)-fed mice and tubule cells cultured with palmitic acid (PA), we observed a dramatic upregulation of the long intergenic non-coding RNA-p21 (LincRNA-p21) through a p53-dependent mechanism. Kidney tubule cell-specific deletion of LincRNA-p21 attenuated oxidative stress, inflammation, apoptosis, and endoplasmic reticulum stress, leading to reduction of histological and functional kidney injury despite persistent obesity and hyperlipidemia. Mechanistically, HFD- or PA-initiated lipotoxicity suppressed the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR)/murine double minute 2 homolog (MDM2) signaling cascade to activate p53 and enhance the transcriptional activity of LincRNA-p21. Collectively, our findings suggest that the p53/LincRNA-p21 axis is the downstream effector in lipotoxic kidney injury and that targeting this axis particularly in the kidney tubule could be a novel therapeutic strategy.

Identification of MDM2, YTHDF2 and DDX21 as potential biomarkers and targets for treatment of type 2 diabetes

Type 2 diabetes (T2D) is a multifactorial and polygenetic disease, although its exact etiology remains poorly understood. The objective of this study was to identify key biomarkers and potential molecular mechanisms in the development of T2D. Human RNA-Seq datasets across different tissues (GSE18732, GSE41762, and GSE78721) were collected from the Gene Expression Omnibus (GEO) database and differentially expressed genes (DEGs) between T2D and controls were identified using differential analysis. A total of 90 overlapping DEGs were identified, among which YTHDF2, DDX21, and MDM2 were considered as key genes due to their central positions in the PPI network and the same regulatory pattern in T2D. Logistic regression analysis showed that low expression of the key genes increased the risk of T2D. Enrichment analysis revealed that the key genes are involved in various important biological functions and signaling pathways including Notch, Fork head box O (FOXO), and phosphoinositide 3-kinase (PI3K)-Akt. RT-qPCR and Western blot analysis showed that all three key genes were down-regulated in pancreatic islets of both prediabetic and diabetic mouse models. Finally, the insulin-sensitizer, pioglitazone was used to treat db/db mice and immunofluorescence analysis showed that the expression of all three key genes was significantly down-regulated in db/db islets, an effect that was overcome by pioglitazone treatment. Together, these results suggest that the identified key genes could be involved in the development of T2D and serve as potential biomarkers and therapeutic targets for this disease.

Blood Immune Cell Composition Associated with Obesity and Drug Repositioning Revealed by Epigenetic and Transcriptomic Conjoint Analysis

This research was designed to analyze the composition of immune cells in obesity and identify novel and potent drugs for obesity management by epigenetic and transcriptomic conjoint analysis. DNA methylation data set (GSE166611) and mRNA expression microarray (GSE18897) were obtained from the Gene Expression Omnibus database. A total of 72 objects (35 obese samples and 37 controls) were included in the study. Immune cell composition analysis, drug repositioning, and gene set enrichment analysis (GSEA) were performed using CIBERSORT, connectivity map (CMap), and GSEA tools. Besides, we performed a single-cell RNA-seq of the immune cells from whole blood samples obtained from one obese patient and one healthy control. mRNA levels of drug target genes were analyzed by qPCR assay in blood samples from six patients and six healthy controls. Immune cell composition analysis found that CD8 + T cells and NK cells were significantly lower in the obese group. 11 drugs/compounds are considered to possess obesity-control potential, such as atorvastatin. Moreover, the expression of drug targets (STAT3, MCL1, PMAIP1, SOD2, FOX O 3, FOS, FKBP5) in obese patients were higher than those in controls. In conclusion, immune cells are potential therapeutic targets for obesity. Our results also contribute to accelerate research on drug development of obesity.

Biomonitoring and Digital Data Technology as an Opportunity for Enhancing Animal Study Translation

The failure of animal studies to translate to effective clinical therapeutics has driven efforts to identify underlying cause and develop solutions that improve the reproducibility and translatability of preclinical research. Common issues revolve around study design, analysis, and reporting as well as standardization between preclinical and clinical endpoints. To address these needs, recent advancements in digital technology, including biomonitoring of digital biomarkers, development of software systems and database technologies, as well as application of artificial intelligence to preclinical datasets can be used to increase the translational relevance of preclinical animal research. In this review, we will describe how a number of innovative digital technologies are being applied to overcome recurring challenges in study design, execution, and data sharing as well as improving scientific outcome measures. Examples of how these technologies are applied to specific therapeutic areas are provided. Digital technologies can enhance the quality of preclinical research and encourage scientific collaboration, thus accelerating the development of novel therapeutics.

Heritable genetic variants in key cancer genes link cancer risk with anthropometric traits

BACKGROUND

Height and other anthropometric measures are consistently found to associate with differential cancer risk. However, both genetic and mechanistic insights into these epidemiological associations are notably lacking. Conversely, inherited genetic variants in tumour suppressors and oncogenes increase cancer risk, but little is known about their influence on anthropometric traits.

METHODS

By integrating inherited and somatic cancer genetic data from the Genome-Wide Association Study Catalog, expression Quantitative Trait Loci databases and the Cancer Gene Census, we identify SNPs that associate with different cancer types and differential gene expression in at least one tissue type, and explore the potential pleiotropic associations of these SNPs with anthropometric traits through SNP-wise association in a cohort of 500,000 individuals.

RESULTS

We identify three regulatory SNPs for three important cancer genes, FANCA, MAP3K1 and TP53 that associate with both anthropometric traits and cancer risk. Of particular interest, we identify a previously unrecognised strong association between the rs78378222[C] SNP in the 3' untranslated region (3'-UTR) of TP53 and both increased risk for developing non-melanomatous skin cancer (OR=1.36 (95% 1.31 to 1.41), adjusted p=7.62E-63), brain malignancy (OR=3.12 (2.22 to 4.37), adjusted p=1.43E-12) and increased standing height (adjusted p=2.18E-24, beta=0.073±0.007), lean body mass (adjusted p=8.34E-37, beta=0.073±0.005) and basal metabolic rate (adjusted p=1.13E-31, beta=0.076±0.006), thus offering a novel genetic link between these anthropometric traits and cancer risk.

CONCLUSION

Our results clearly demonstrate that heritable variants in key cancer genes can associate with both differential cancer risk and anthropometric traits in the general population, thereby lending support for a genetic basis for linking these human phenotypes.

Role of Mcpip1 in obesity-induced hepatic steatosis as determined by myeloid and liver-specific conditional knockouts

Monocyte chemoattractant protein-induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through cleavage of transcripts coding for proinflammatory cytokines and by inhibition of NFκB activity. Moreover, it was demonstrated that MCPIP1 regulates lipid metabolism both in adipose tissue and in hepatocytes. In this study, we investigated the effects of tissue-specific Mcpip1 deletion on the regulation of hepatic metabolism and development of nonalcoholic fatty liver disease (NAFLD). We used control Mcpip1^fl/fl mice and animals with deletion of Mcpip1 in myeloid leukocytes (Mcpip1^fl/fl LysM^Cre ) and in hepatocytes (Mcpip1^fl/fl Alb^Cre ), which were fed chow or a high-fat diet (HFD) for 12 weeks. Mcpip1^fl/fl LysM^Cre mice fed a chow diet were characterized by a significantly reduced hepatic expression of genes regulating lipid and glucose metabolism, which subsequently resulted in low plasma glucose level and dyslipidemia. These animals also displayed systemic inflammation, demonstrated by increased concentrations of cytokines in the plasma and high Tnfa, Il6, IL1b mRNA levels in the liver and brown adipose tissue (BAT). Proinflammatory leukocyte infiltration into BAT, together with low expression of Ucp1 and Ppargc1a, resulted in hypothermia of 22-week-old Mcpip1^fl/fl LysM^Cre mice. On the other hand, there were no significant changes in phenotype in Mcpip1^fl/fl Alb^Cre mice. Although we detected a reduced hepatic expression of genes regulating glucose metabolism and β-oxidation in these mice, they remained asymptomatic. Upon feeding with a HFD, Mcpip1^fl/fl LysM^Cre mice did not develop obesity, glucose intolerance, nor hepatic steatosis, but were characterized by low plasma glucose level and dyslipidemia, along with proinflammatory phenotype. Mcpip1^fl/fl Alb^Cre animals, following a HFD, became hypercholesterolemic, but accumulated lipids in the liver at the same level as Mcpip1^fl/fl mice, and no changes in the level of soluble factors tested in the plasma were detected. We have demonstrated that Mcpip1 protein plays an important role in the liver homeostasis. Depletion of Mcpip1 in myeloid leukocytes, followed by systemic inflammation, has a more pronounced effect on controlling liver metabolism and homeostasis than the depletion of Mcpip1 in hepatocytes.

Chitosan from Crabs (Scylla serrata) Represses Hyperlipidemia-Induced Hepato-Renal Dysfunctions in Rats: Modulation of CD43 and p53 Expression

Hepato-renal dysfunctions associated with hyperlipidemia necessitates a continuous search for natural remedies. This study thus evaluated the effect of dietary chitosan on diet-induced hyperlipidemia in rats. A total of 30 male Wistar rats (90 ± 10) g were randomly allotted into six (6) groups (n = 5): Normal diet, High-fat diet (HFD), and Normal diet + 5% chitosan. The three other groups received HFD, supplemented with 1%, 3%, and 5% of chitosan. The feeding lasted for 6 weeks, after which the rats were sacrificed. The liver and kidneys were harvested for analyses. Hepatic alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) activity, and renal biomarkers (ALT, AST, urea, and creatinine) were assayed spectrophotometrically. Additionally, expression of hepatic and renal CD43 and p53 was estimated immunohistochemically. The HFD group had elevated bodyweight compared to normal which was reversed in the chitosan-supplemented groups. Hyperlipidemia caused a significant (p < 0.05) decrease in the hepatic (AST, ALT, and ALP) and renal (AST and ALT) activities, while renal urea and creatinine increased. Furthermore, the HFD group showed an elevated level of hepatic and renal CD43 while p53 expression decreased. However, groups supplemented with chitosan showed improved hepatic and renal biomarkers, as well as corrected the aberrations in the expressions of p53 and CD43. Conclusively, dietary chitosan inclusion in the diet (between 3% and 5%) could effectively improve kidney and liver functionality via abatement of inflammatory responses.

Lisofylline mitigates cardiac inflammation in a mouse model of obesity through improving insulin secretion and activating cardiac AMPK signaling pathway

Obesity has emerged as a leading cause of death in the last few decades, mainly due to associated cardiovascular diseases. Obesity, inflammation, and insulin resistance are strongly interlinked. Lisofylline (LSF), an anti-inflammatory agent, demonstrated protection against type 1 diabetes, as well as reduced obesity-induced insulin resistance and adipose tissue inflammation. However, its role in mitigating cardiac inflammation associated with obesity is not well studied. Mice were divided into 4 groups; the first group was fed regular chow diet, the second was fed regular chow diet and treated with LSF, the third was fed high fat diet (HFD), and the fourth was fed HFD and treated with LSF. Cardiac inflammation was interrogated via expression levels of TNF α, interleukins 6 and 10, phosphorylated STAT4 and lipoxygenases 12 and 12/15. Apoptosis and expression of the survival gene, AMPK, were also evaluated. We observed that LSF alleviated obesity-induced cardiac injury indirectly by improving both pancreatic β-cell function and insulin sensitivity, as well as, directly via upregulation of cardiac AMPK expression and downregulation of cardiac inflammation and apoptosis. LSF may represent an effective therapy targeting obesity-induced metabolic and cardiovascular complications.

The Intricate Role of p53 in Adipocyte Differentiation and Function

For more than three decades, numerous studies have demonstrated the function of p53 in cell cycle, cellular senescence, autophagy, apoptosis, and metabolism. Among diverse functions, the essential role of p53 is to maintain cellular homeostatic response to stress by regulating proliferation and apoptosis. Recently, adipocytes have been studied with increasing intensity owing to the increased prevalence of metabolic diseases posing a serious public health concern and because metabolic dysfunction can directly induce tumorigenesis. The prevalence of metabolic diseases has steadily increased worldwide, and a growing interest in these diseases has led to the focus on the role of p53 in metabolism and adipocyte differentiation with or without metabolic stress. However, our collective understanding of the direct role of p53 in adipocyte differentiation and function remains insufficient. Therefore, this review focuses on the newly discovered roles of p53 in adipocyte differentiation and function.

Faecal virome transplantation decreases symptoms of type 2 diabetes and obesity in a murine model

OBJECTIVE

Development of obesity and type 2 diabetes (T2D) are associated with gut microbiota (GM) changes. The gut viral community is predominated by bacteriophages (phages), which are viruses that attack bacteria in a host-specific manner. The antagonistic behaviour of phages has the potential to alter the GM. As a proof-of-concept, we demonstrate the efficacy of faecal virome transplantation (FVT) from lean donors for shifting the phenotype of obese mice into closer resemblance of lean mice.

DESIGN

The FVT consisted of viromes with distinct profiles extracted from the caecal content of mice from different vendors that were fed a low-fat (LF) diet for 14 weeks. Male C57BL/6NTac mice were divided into five groups: LF (as diet control), high-fat (HF) diet, HF+ampicillin (Amp), HF+Amp+FVT and HF+FVT. At weeks 6 and 7 of the study, the HF+FVT and HF+Amp+FVT mice were treated with FVT by oral gavage. The Amp groups were treated with Amp 24 hours prior to first FVT treatment.

RESULTS

Six weeks after first FVT, the HF+FVT mice showed a significant decrease in weight gain compared with the HF group. Further, glucose tolerance was comparable between the LF and HF+FVT mice, while the other HF groups all had impaired glucose tolerance. These observations were supported by significant shifts in GM composition, blood plasma metabolome and expression levels of genes associated with obesity and T2D development.

CONCLUSIONS

Transfer of caecal viral communities from mice with a lean phenotype into mice with an obese phenotype led to reduced weight gain and normalised blood glucose parameters relative to lean mice. We hypothesise that this effect is mediated via FVT-induced GM changes.

Life and Death Decision-Making by p53 and Implications for Cancer Immunotherapy

The tumor-suppressor protein p53 is mutated in approximately half of all cancers, whereas the p53 signaling network is perturbed in almost all cancers. In response to different stress stimuli, p53 selectively activates genes to elicit a cell survival or cell death response. How p53 makes the decision between life and death remains a fascinating question and an exciting field of research. Understanding how this decision is made has major implications for improving cancer treatments, particularly in recently evolved immune checkpoint inhibition therapy. We highlight progress and challenges in understanding the mechanisms governing the p53 life and death decision-making process, and discuss how this decision is relevant to immune system regulation. Finally, we discuss how knowledge of the p53 pro-survival and pro-death decision node can be applied to optimize immune checkpoint inhibitor therapy for cancer treatment.

Emerging Roles for the INK4a/ARF (CDKN2A) Locus in Adipose Tissue: Implications for Obesity and Type 2 Diabetes

Besides its role as a cell cycle and proliferation regulator, the INK4a/ARF (CDKN2A) locus and its associated pathways are thought to play additional functions in the control of energy homeostasis. Genome-wide association studies in humans and rodents have revealed that single nucleotide polymorphisms in this locus are risk factors for obesity and related metabolic diseases including cardiovascular complications and type-2 diabetes (T2D). Recent studies showed that both p16^INK4a-CDK4-E2F1/pRB and p19^ARF-P53 (p14^ARF in humans) related pathways regulate adipose tissue (AT) physiology and adipocyte functions such as lipid storage, inflammation, oxidative activity, and cellular plasticity (browning). Targeting these metabolic pathways in AT emerged as a new putative therapy to alleviate the effects of obesity and prevent T2D. This review aims to provide an overview of the literature linking the INK4a/ARF locus with AT functions, focusing on its mechanisms of action in the regulation of energy homeostasis.

RBM10, a New Regulator of p53

The tumor suppressor p53 acts as a transcription factor that regulates the expression of a number of genes responsible for DNA repair, cell cycle arrest, metabolism, cell migration, angiogenesis, ferroptosis, senescence, and apoptosis. It is the most commonly silenced or mutated gene in cancer, as approximately 50% of all types of human cancers harbor TP53 mutations. Activation of p53 is detrimental to normal cells, thus it is tightly regulated via multiple mechanisms. One of the recently identified regulators of p53 is RNA-binding motif protein 10 (RBM10). RBM10 is an RNA-binding protein frequently deleted or mutated in cancer cells. Its loss of function results in various deformities, such as cleft palate and malformation of the heart, and diseases such as lung adenocarcinoma. In addition, RBM10 mutations are frequently observed in lung adenocarcinomas, colorectal carcinomas, and pancreatic ductal adenocarcinomas. RBM10 plays a regulatory role in alternative splicing. Several recent studies not only linked this splicing regulation of RBM10 to cancer development, but also bridged RBM10's anticancer function to the p53 pathway. This review will focus on the current progress in our understanding of RBM10 regulation of p53, and its role in p53-dependent cancer prevention.

Bacteriophage-mediated manipulation of the gut microbiome – promises and presents limitations

Gut microbiome (GM) composition and function are linked to human health and disease, and routes for manipulating the GM have become an area of intense research. Due to its high treatment efficacy, the use of fecal microbiota transplantation (FMT) is generally accepted as a promising experimental treatment for patients suffering from GM imbalances (dysbiosis), e.g. caused by recurrent Clostridioides difficile infections (rCDI). Mounting evidence suggests that bacteriophages (phages) play a key role in successful FMT treatment by restoring the dysbiotic bacterial GM. As a refinement to FMT, removing the bacterial component of donor feces by sterile filtration, also referred to as fecal virome transplantation (FVT), decreases the risk of invasive infections caused by bacteria. However, eukaryotic viruses and prophage-encoded virulence factors remain a safety issue. Recent in vivo studies show how cascading effects are initiated when phage communities are transferred to the gut by e.g. FVT, which leads to changes in the GM composition, host metabolome, and improve host health such as alleviating symptoms of obesity and type-2-diabetes (T2D). In this review, we discuss the promises and limitations of FVT along with the perspectives of using FVT to treat various diseases associated with GM dysbiosis.

P53/PANK1/miR-107 signalling pathway spans the gap between metabolic reprogramming and insulin resistance induced by high-fat diet

High-fat diet (HFD) leads to obesity, type II diabetes mellitus (T2DM) and increases the coincidence of cardiovascular diseases and cancer. Insulin resistance (IR) is considered as the 'common soil' of those diseases. Furthermore, people on HFD showed restrained glycolysis and enhanced fatty acid oxidation, which is the so-called metabolic reprogramming. However, the relationship between metabolic reprogramming and IR induced by HFD is still unclear. Here, we demonstrate that PANK1 and miR-107 were up-regulated in the liver tissue of mice on HFD for 16 weeks and involved in metabolic reprogramming induced by palmitate acid (PA) incubation. Importantly, miR-107 within an intron of PANK1 gene facilitated IR by targeting caveolin-1 in AML12 cells upon PA incubation. Moreover, we identify that HFD enhanced P53 expression, and activation of P53 with nutlin-3a induced PANK1 and miR-107 expression simultaneously in transcriptional level, leading to metabolic reprogramming and IR, respectively. Consistently, inhibition of P53 with pifithrin-α hydrobromide ameliorated PA-induced metabolic reprogramming and IR. Thus, our results revealing a new mechanism by which P53 regulate metabolism. In addition, the results distinguished the different roles of PANK1 and its intron miR-107 in metabolic regulation, which will provide more accurate intervention targets for the treatment of metabolic diseases.

Maize extract rich in ferulic acid and anthocyanins prevents high-fat-induced obesity in mice by modulating SIRT1, AMPK and IL-6 associated metabolic and inflammatory pathways

The aim was to compare the antiobesity efficacy of different concentrations of a phenolic-rich water extract from purple maize pericarp (PPE) in a murine model of obesity for 12 weeks. Forty C57BL/6 mice (n=10/group) were randomized: standard diet (SD), high-fat diet (HFD), HFD+200 mg PPE/kg (200 PPE) and HFD+500 mg PPE/kg (500 PPE). PPE contained mainly ferulic acid, anthocyanins and other phenolics (total phenolics: 448.5 μg/mg dry weight, DW). Body weight (-27.9%), blood glucose (-26.5%) and blood triglycerides (-22.1%) were most attenuated (P<.05) in 500 PPE group compared to HFD group. Also, 500 PPE group had reduced (P<.05) plasma levels of TNF-α, MCP-1, resistin and leptin compared to HFD group. Fatty liver disease scores were highest for HFD (8.4), followed by 200 PPE (6.1), 500 PPE (2.7) and SD (0.4) groups. Relative adipose tissue was lower (P<.05) in 200 PPE (7.6%), 500 PPE (8.0%) and SD (0.8%) compared to HFD (12.1%) group. In 500 PPE group, compared to HFD group, important genes were modulated related to adipogenesis (Mmp3, fold-change [FC]=7.4), inflammation (Nfkb1, FC=-1.8) and glucose metabolism (Slc2a4, FC=23.6) in adipose tissue. In liver, 500 PPE group showed modulation of genes related to gluconeogenesis (Pck1, FC=-2.9), lipogenesis (Fasn, FC=-2.4) and β-oxidation (Cpt1b, FC=3.1). Maize rich in ferulic acid and anthocyanins prevented obesity through the modulation of TLR and AMPK signaling pathways reducing adipogenesis and adipose inflammation, and promoting energy expenditure.

Targeting MDM2 for novel molecular therapy: Beyond oncology

The murine double minute 2 (MDM2) oncogene exerts major oncogenic activities in human cancers; it is not only the best-documented negative regulator of the p53 tumor suppressor, but also exerts p53-independent activities. There is an increasing interest in developing MDM2-based targeted therapies. Several classes of MDM2 inhibitors have been evaluated in preclinical models, with a few entering clinical trials, mainly for cancer therapy. However, noncarcinogenic roles for MDM2 have also been identified, demonstrating that MDM2 is involved in many chronic diseases and conditions such as inflammation and autoimmune diseases, dementia and neurodegenerative diseases, heart failure and cardiovascular diseases, nephropathy, diabetes, obesity, and sterility. MDM2 inhibitors have been shown to have promising therapeutic efficacy for treating inflammation and other nonmalignant diseases in preclinical evaluations. Therefore, targeting MDM2 may represent a promising approach for treating and preventing these nonmalignant diseases. In addition, a better understanding of how MDM2 works in nonmalignant diseases may provide new biomarkers for their diagnosis, prognostic prediction, and monitoring of therapeutic outcome. In this review article, we pay special attention to the recent findings related to the roles of MDM2 in the pathogenesis of several nonmalignant diseases, the therapeutic potential of its downregulation or inhibition, and its use as a biomarker.

Rubrofusarin-6-β-gentiobioside inhibits lipid accumulation and weight gain by regulating AMPK/mTOR signaling

BACKGROUND

Although rubrofusarin-6-β-gentiobioside (RFG), which is a component of Cassiae tora seed, could likely regulate hyperlipidemia, its anti-obesity effect and related mechanism have not been elucidated.

PURPOSE

The aim of this study was to examine whether RFG can ameliorate obesity and the mechanism of lipid accumulation regulated by RFG.

STUDY DESIGN

In in vitro experiments, we confirmed the anti-adipogenic effect of RFG using 3T3-L1 cells and human adipose mesenchymal stem cells (hAMSCs). To confirm the anti-obesity effect, High-Fat Diet (HFD)-induced obese mice were selected as a model.

METHODS

We investigated anti-adipogenic effects of RFG using MTS assay, Oil Red O Staining, real-time RT-PCR, western blot analysis, and immunofluorescence staining. The anti-obesity effect of RFG was confirmed in HFD-induced mice model using hematoxylin and eosin staining and serum analysis.

RESULTS

RFG inhibited lipid accumulation in 3T3-L1 cells and hAMSCs by reducing expression of mammalian targets of rapamycin (mTOR), peroxisome proliferator-activated receptor (PPAR)γ, and CCAAT-enhancer binding protein (C/EBP)α. RFG phosphorylated AMP-activated protein kinase (AMPK) in a liver kinase B (LKB) 1-independent manner. Moreover, the anti-adipogenic effect of RFG was blocked by AMPK inhibitor. These results suggest that RFG inhibits lipid accumulation via AMPK signaling. Furthermore, RFG reduced the body weight, size of epididymal white adipose tissue (eWAT), and fatty liver in the mice. RFG also suppressed levels of adipogenic factors PPARγ, C/EBPα, FAS, LPL, and aP2) by activating AMPK in the eWAT and liver.

CONCLUSION

RFG can ameliorate obesity, and thus, could be used as a therapeutic agent for treating obesity.

GLUT12 and adipose tissue: Expression, regulation and its relation with obesity in mice

AIM

The facilitative glucose transporter GLUT12 was isolated from the breast cancer cell line MCF-7 by its homology with GLUT4. GLUT12 is expressed in insulin-sensitive tissues such as adipose tissue. The aim of this work was to investigate GLUT12 expression and hormonal regulation in 3T3-L1 adipocytes and in adipose tissue of lean and diet-induced obese mice.

METHODS

Uptake studies were performed using radio-labelled sugars; α-methyl-d-glucose (αMG) was used as specific substrate of GLUT12. Expression and localization of GLUT12 in adipocytes were investigated by western blot and immunohistochemical methods.

RESULTS

GLUT12 is expressed in the peri-nuclear region of mouse adipocytes. Insulin, by AKT activation, and TNF-α, by AMPK activation, increase αMG uptake by inducing GLUT12 translocation to the membrane. In contrast, leptin and adiponectin decrease GLUT12 activity through its internalization. Under hypoxia conditions GLUT12 expression is upregulated. The response of GLUT12 to TNF-α, leptin, adiponectin and hypoxia is the opposite to that of GLUT4. In diet-induced obese mice and obese subjects, GLUT12 protein is decreased. Intraperitoneal injection of insulin increases AKT phosphorylation and GLUT12 expression, but this effect is lost in obese animals.

CONCLUSION

We hypothesize that GLUT12 would contribute to modulate sugar absorption in physiological and pathophysiological situations such as obesity.

Transcriptional Response of White Adipose Tissue to Withdrawal of Vitamin B3

SCOPE

Distinct markers for mild vitamin B3 deficiency are lacking. To identify these, the molecular responses of white adipose tissue (WAT) to vitamin B3 withdrawal are examined.

METHODS AND RESULTS

A dietary intervention is performed in male C57BL/6JRccHsd mice, in which a diet without nicotinamide riboside (NR) is compared to a diet with NR at the recommended vitamin B3 level. Both diets contain low but adequate level of tryptophan. Metabolic flexibility and systemic glucose tolerance are analyzed and global transcriptomics, qRT-PCR, and histology of epididymal WAT (eWAT) are performed. A decreased insulin sensitivity and a shift from carbohydrate to fatty acid oxidation in response to vitamin B3 withdrawal are observed. This is consistent with molecular changes in eWAT, including an activated MEK/ERK signaling, a lowering of glucose utilization markers, and an increase in makers of fatty acid catabolism, possibly related to the consistent lower expression of mitochondrial electron transport complexes. The synthesis pathway of tetrahydropteridine (BH4), an essential cofactor for neurotransmitter synthesis, is transcriptionally activated. Genes marking these processes are technically validated.

CONCLUSION

The downregulation of Anp32a, Tnk2 and the upregulation of Mapk1, Map2k1, Qdpr, Mthfs, and Mthfsl are proposed as a WAT transcriptional signature marker for mild vitamin B3 deficiency.

Implications of altered NAD metabolism in metabolic disorders

Nicotinamide adenine dinucleotide (NAD) is an important coenzyme that participates in various energy metabolism pathways, including glycolysis, β-oxidation, and oxidative phosphorylation. Besides, it is a required cofactor for post-translational modifications such as ADP-ribosylation and deacetylation by poly (ADP-ribose) polymerases (PARPs) and sirtuins, respectively. Thus, NAD regulates energy metabolism, DNA damage repair, gene expression, and stress response through these enzymes. Numerous studies have shown that NAD levels decrease with aging and under disturbed nutrient conditions, such as obesity. Additionally, a decline in NAD levels is closely related to the development of various metabolic disorders, including diabetes and fatty liver disease. In addition, many studies have revealed that administration of NAD precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), efficiently increase NAD levels in various tissues and prevent such metabolic diseases. These NAD precursors are contained in natural foods, such as cow milk, vegetables, and meats. Therefore, altered NAD metabolism can be a practical target for nutritional intervention. Recently, several human clinical trials using NAD precursors have been conducted to investigate the safety, pharmacokinetics, and efficacy against metabolic disorders such as glucose intolerance. In this review, we summarize current knowledge on the implications of NAD metabolism in metabolic diseases and discuss the outcomes of recent human clinical trials.

The long and the short of it: the MDM4 tail so far

The mouse double minute 4 (MDM4) is emerging from the shadow of its more famous relative MDM2 and is starting to steal the limelight, largely due to its therapeutic possibilities. MDM4 is a vital regulator of the tumor suppressor p53. It restricts p53 transcriptional activity and also, at least in development, facilitates MDM2's E3 ligase activity toward p53. These functions of MDM4 are critical for normal cell function and a proper response to stress. Their importance for proper cell maintenance and proliferation identifies them as a risk for deregulation associated with the uncontrolled growth of cancer. MDM4 tails are vital for its function, where its N-terminus transactivation domain engages p53 and its C-terminus RING domain binds to MDM2. In this review, we highlight recently identified cellular functions of MDM4 and survey emerging therapies directed to correcting its dysregulation in disease.

p53 Functions in Adipose Tissue Metabolism and Homeostasis

As a tumor suppressor and the most frequently mutated gene in cancer, p53 is among the best-described molecules in medical research. As cancer is in most cases an age-related disease, it seems paradoxical that p53 is so strongly conserved from early multicellular organisms to humans. A function not directly related to tumor suppression, such as the regulation of metabolism in nontransformed cells, could explain this selective pressure. While this role of p53 in cellular metabolism is gradually emerging, it is imperative to dissect the tissue- and cell-specific actions of p53 and its downstream signaling pathways. In this review, we focus on studies reporting p53’s impact on adipocyte development, function, and maintenance, as well as the causes and consequences of altered p53 levels in white and brown adipose tissue (AT) with respect to systemic energy homeostasis. While whole body p53 knockout mice gain less weight and fat mass under a high-fat diet owing to increased energy expenditure, modifying p53 expression specifically in adipocytes yields more refined insights: (1) p53 is a negative regulator of in vitro adipogenesis; (2) p53 levels in white AT are increased in diet-induced and genetic obesity mouse models and in obese humans; (3) functionally, elevated p53 in white AT increases senescence and chronic inflammation, aggravating systemic insulin resistance; (4) p53 is not required for normal development of brown AT; and (5) when p53 is activated in brown AT in mice fed a high-fat diet, it increases brown AT temperature and brown AT marker gene expression, thereby contributing to reduced fat mass accumulation. In addition, p53 is increasingly being recognized as crucial player in nutrient sensing pathways. Hence, despite existence of contradictory findings and a varying density of evidence, several functions of p53 in adipocytes and ATs have been emerging, positioning p53 as an essential regulatory hub in ATs. Future studies need to make use of more sophisticated in vivo model systems and should identify an AT-specific set of p53 target genes and downstream pathways upon different (nutrient) challenges to identify novel therapeutic targets to curb metabolic diseases.

Control of metabolism by p53 - Cancer and beyond

p53 is an important tumour suppressor gene, with loss of p53 contributing to the development of most human cancers. However, the activation of p53 in response to stress signals underpins a role for p53 in diverse aspects of health and disease. Activities of p53 that regulate metabolism can play a role in maintaining homeostasis and protecting cells from damage - so preventing disease development. By contrast, either loss or over-activation of p53 can contribute to numerous metabolic pathologies, including aging, obesity and diabetes.

Usp25m protease regulates ubiquitin-like processing of TUG proteins to control GLUT4 glucose transporter translocation in adipocytes

Insulin stimulates the exocytic translocation of specialized vesicles in adipocytes, which inserts GLUT4 glucose transporters into the plasma membrane to enhance glucose uptake. Previous results support a model in which TUG (Tether containing a UBX domain for GLUT4) proteins trap these GLUT4 storage vesicles at the Golgi matrix and in which insulin triggers endoproteolytic cleavage of TUG to translocate GLUT4. Here, we identify the muscle splice form of Usp25 (Usp25m) as a protease required for insulin-stimulated TUG cleavage and GLUT4 translocation in adipocytes. Usp25m is expressed in adipocytes, binds TUG and GLUT4, dissociates from TUG-bound vesicles after insulin addition, and colocalizes with TUG and insulin-responsive cargoes in unstimulated cells. Previous results show that TUG proteolysis generates the ubiquitin-like protein, TUGUL (for TUGubiquitin-like). We now show that TUGUL modifies the kinesin motor protein, KIF5B, and that TUG proteolysis is required to load GLUT4 onto these motors. Insulin stimulates TUG proteolytic processing independently of phosphatidylinositol 3-kinase. In nonadipocytes, TUG cleavage can be reconstituted by transfection of Usp25m, but not the related Usp25a isoform, together with other proteins present on GLUT4 vesicles. In rodents with diet-induced insulin resistance, TUG proteolysis and Usp25m protein abundance are reduced in adipose tissue. These effects occur soon after dietary manipulation, prior to the attenuation of insulin signaling to Akt. Together with previous data, these results support a model whereby insulin acts through Usp25m to mediate TUG cleavage, which liberates GLUT4 storage vesicles from the Golgi matrix and activates their microtubule-based movement to the plasma membrane. This TUG proteolytic pathway for insulin action is independent of Akt and is impaired by nutritional excess.

Inhibition of Mdmx (Mdm4) in vivo induces anti-obesity effects

Although cell-cycle arrest, senescence and apoptosis remain as major canonical activities of p53 in tumor suppression, the emerging role of p53 in metabolism has been a topic of great interest. Nevertheless, it is not completely understood how p53-mediated metabolic activities are regulated in vivo and whether this part of the activities has an independent role beyond tumor suppression. Mdmx (also called Mdm4), like Mdm2, acts as a major suppressor of p53 but the embryonic lethality of mdmx-null mice creates difficulties to evaluate its physiological significance in metabolism. Here, we report that the embryonic lethality caused by the deficiency of mdmx, in contrast to the case for mdm2, is fully rescued in the background of p53^3KR/3KR, an acetylation-defective mutant unable to induce cell-cycle arrest, senescence and apoptosis. p53^3KR/3KR/mdmx^-/- mice are healthy but skinny without obvious developmental defects. p53^3KR/3KR/mdmx^-/- mice are resistant to fat accumulation in adipose tissues upon high fat diet. Notably, the levels of p53 protein are only slightly increased and can be further induced upon DNA damage in p53^3KR/3KR/mdmx^-/- mice, suggesting that Mdmx is only partially required for p53 degradation in vivo. Further analyses indicate that the anti-obesity phenotypes in p53^3KR/3KR/mdmx^-/- mice are caused by activation of lipid oxidation and thermogenic programs in adipose tissues. These results demonstrate the specific effects of the p53/Mdmx axis in lipid metabolism and adipose tissue remodeling and reveal a surprising role of Mdmx inhibition in anti-obesity effects beyond, commonly expected, tumor suppression. Thus, our study has significant implications regarding Mdmx inhibitors in the treatment of obesity related diseases.

The p53/Adipose-Tissue/Cancer Nexus

Obesity and the resultant metabolic complications have been associated with an increased risk of cancer. In addition to the systemic metabolic disturbances in obesity that are associated with cancer initiation and progression, the presence of adipose tissue in the tumor microenvironment (TME) contributes significantly to malignancy through direct cell-cell interaction or paracrine signaling. This chronic inflammatory state can be maintained by p53-associated mechanisms. Increased p53 levels that are observed in obesity exacerbate the release of inflammatory cytokines that fuel cancer initiation and progression. Dysregulated adipose tissue signaling from the TME can reprogram tumor cell metabolism. The links between p53, cellular metabolism and adipose tissue dysfunction and how they relate to cancer, will be presented in this review.

Lifestyle alters GUT-bacteria function: Linking immune response and host

Microbiota in human is a "mixture society" of different species (i.e. bacteria, viruses, funguses) populations with a different way of relationship classification to Human. Human GUT serves as the host of the majority of different bacterial populations (GUT flora, more than 500 species), which are with us ("from the beginning") in an innate manner known as the commensal (no harm to each other) and symbiotic (mutual benefit) relationship. A homeostatic balance of host-bacteria relationship is very important and vital for a normal health process. However, this beneficial relationship and delicate homeostatic state can be disrupted by the imbalance of microbiome-composition of gut microbiota, expressing a pathogenic state. A strict homeostatic balance of microbiome-composition strongly depends on several factors; 1- lifestyle, 2- geography, 3- ethnicities, 4- "mom" as prime of the type of bacterial colonization in infant and 5- the disease. With such diversity in individuals combined with huge number of different bacterial species and their interactions, it is wise to perform an in-depth systems biology (e.g. genomics, proteomics, glycomics, and etcetera) analysis of personalized microbiome. Only in this way, we are able to generate a map of complete GUT microbiota and, in turn, to determine its interaction with host and intra-interaction with pathogenic bacteria. A specific microbiome analysis provides us the knowledge to decipher the nature of interactions between the GUT microbiota and the host and its response to the invading bacteria in a pathogenic state. The GUT-bacteria composition is independent of geography and ethnicity but lifestyle well affects GUT-bacteria composition and function. Microbiome knowledge obtained by systems biology also helps us to change the behavior of GUT microbiota in response to the pathogenic microbes as protection. Functional microbiome changes in response to environmental factors will be discussed in this review.

Nutrient availability dictates the regulation of metabolism by the ribosomal protein-MDM2-p53 pathway

Nutrient availability alters ribosomal biogenesis, causing ribosomal proteins to act as secondary messengers of nutrient response by binding to MDM2 and activating p53. Recent work suggests that the ribosomal protein (RP)-MDM2-p53 pathway responds to the deficiency or overabundance of nutrients through seemingly contradictory mechanisms; however, both of these responses promote organism survival.