Peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC1alpha) is a metabolic regulator of intestinal epithelial cell fate. Proc Natl Acad Sci U S A. 2011;108:6603-6608. [PMID: 21467224 DOI: 10.1073/pnas.1016354108]

Pleiotropic Regulation of PGC-1α in Tumor Initiation and Progression

Significance: Mitochondria are recognized as a central metabolic hub with bioenergetic, biosynthetic, and signaling functions that tightly control key cellular processes. As a crucial component of mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) is involved in regulating various metabolic pathways, including energy metabolism and reactive oxygen species homeostasis. Recent Advances: Recent studies have highlighted the significant role of PGC-1α in tumorigenesis, cancer progression, and treatment resistance. However, PGC-1α exhibits pleiotropic effects in different cancer types, necessitating a more comprehensive and thorough understanding. Critical Issues:In this review, we discuss the structure and regulatory mechanisms of PGC-1α, analyze its cellular and metabolic functions, explore its impact on tumorigenesis, and propose potential strategies for targeting PGC-1α. Future Directions: The targeted adjustment of PGC-1α based on the metabolic preferences of different cancer types could offer a hopeful therapeutic approach for both preventing and treating tumors.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

Molecular targets associated with ulcerative colitis and the benefits of atractylenolides-based therapy

Ulcerative colitis (UC) is a chronic inflammatory disease of the intestines that can significantly impact quality of life and lead to various complications. Currently, 5-aminosalicylic acid derivatives, corticosteroids, immunosuppressants, and biologics are the major treatment strategies for UC, but their limitations have raised concerns. Atractylenolides (ATs), sesquiterpene metabolites found in Atractylodes macrocephala Koidz., have shown promising effects in treating UC by exerting immune barrier modulation, alleviating oxidative stress, gut microbiota regulation, improving mitochondrial dysfunction and repairing the intestinal barrier. Furthermore, ATs have been shown to possess remarkable anti-fibrosis, anti-thrombus, anti-angiogenesis and anti-cancer. These findings suggest that ATs hold important potential in treating UC and its complications. Therefore, this review systematically summarizes the efficacy and potential mechanisms of ATs in treating UC and its complications, providing the latest insights for further research and clinical applications.

Clostridium butyricum upregulates GPR109A/AMPK/PGC-1α and ameliorates acute pancreatitis-associated intestinal barrier injury in mice

Acute pancreatitis frequently causes intestinal barrier damage, which aggravates pancreatitis. Although Clostridium butyricum exerts anti-inflammatory and protective effects on the intestinal barrier during acute pancreatitis, the underlying mechanism is unclear. The G protein-coupled receptors 109 A (GPR109A) and adenosine monophosphate-activated protein kinase (AMPK)/ peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) signaling pathways can potentially influence the integrity of the intestinal barrier. Our study generated acute pancreatitis mouse models via intraperitoneal injection of cerulein and lipopolysaccharides. After intervention with Clostridium butyricum, the model mice showed reduced small intestinal and colonic intestinal barrier damage, dysbiosis amelioration, and increased GPR109A/AMPK/PGC-1α expression. In conclusion, Clostridium butyricum could improve pancreatic and intestinal inflammation and pancreatic injury, and relieve acute pancreatitis-induced intestinal barrier damage in the small intestine and colon, which may be associated with GPR109A/AMPK/PGC-1α.

Dietary purple potato supplement attenuates DSS-induced colitis in mice: impact on mitochondrial function

Inflammatory bowel disease (IBD) is a condition characterized by disrupted intestinal barrier function, abnormal immune response, and mucosal structure loss. This study evaluated the beneficial role of purple potato (PP) supplementation against IBD symptoms using a murine model of dextran sulfate sodium (DSS)-induced colitis, and further explored the underlying mechanisms. Six-week-old C57BL/6J male mice were randomized into two groups and fed a standard rodent diet with or without 10% PP powder for 7 weeks. At the 5th week of dietary supplements, mice in each group were further divided into two subgroups and were either induced with or without 2.5% DSS induction for 7 days, followed by 7 days of recovery. Data showed that PP supplementation ameliorated the disease activity index in DSS-treated mice and reversed the colonic structure loss, mucosal damage, macrophage infiltration, and pro-inflammatory cytokine secretion induced by DSS in the colonic tissue. PP supplementation also restored the levels of tight junction proteins and caudal type homeobox 2 in DSS-treated mice. Furthermore, dietary PP enhanced peroxisome proliferator-activated receptor-γ coactivator-1α signaling pathway, mitochondrial biogenesis, mitochondrial proteostasis, and protein-folding capacity. In summary, dietary PP ameliorated DSS-induced colitis and improved gut structures and barrier function, which was associated with improved mitochondrial function. These results support further investigation of PP as a potential dietary intervention for IBD.

α-Ketoglutarate for Preventing and Managing Intestinal Epithelial Dysfunction

The epithelium lining the intestinal tract serves a multifaceted role. It plays a crucial role in nutrient absorption and immune regulation and also acts as a protective barrier, separating underlying tissues from the gut lumen content. Disruptions in the delicate balance of the gut epithelium trigger inflammatory responses, aggravate conditions such as inflammatory bowel disease, and potentially lead to more severe complications such as colorectal cancer. Maintaining intestinal epithelial homeostasis is vital for overall health, and there is growing interest in identifying nutraceuticals that can strengthen the intestinal epithelium. α-Ketoglutarate, a metabolite of the tricarboxylic acid cycle, displays a variety of bioactive effects, including functioning as an antioxidant, a necessary cofactor for epigenetic modification, and exerting anti-inflammatory effects. This article presents a comprehensive overview of studies investigating the potential of α-ketoglutarate supplementation in preventing dysfunction of the intestinal epithelium.

Transcriptional regulation of metabolism in the intestinal epithelium

Epithelial metabolism in the intestine is increasingly known to be important for stem cell maintenance and activity while also affecting weight gain and diseases. This review compiles studies from recent years which describe major transcription factors controlling metabolic activity across the intestinal epithelium as well as transcriptional and epigenetic networks controlling the factors themselves. Recent studies show that transcriptional regulators serve as the link between signals from the microbiota and diet and epithelial metabolism. Studies have advanced this paradigm to identify druggable targets to block weight gain or disease progression in mice. As such, there is great potential that a better understanding of these regulatory networks will improve our knowledge of intestinal physiology and promote discoveries to benefit human health.

A genomic perspective of the aging human and mouse lung with a focus on immune response and cellular senescence

BACKGROUND

The aging lung is a complex process and influenced by various stressors, especially airborne pathogens and xenobiotics. Additionally, a lifetime exposure to antigens results in structural and functional changes of the lung; yet an understanding of the cell type specific responses remains elusive. To gain insight into age-related changes in lung function and inflammaging, we evaluated 89 mouse and 414 individual human lung genomic data sets with a focus on genes mechanistically linked to extracellular matrix (ECM), cellular senescence, immune response and pulmonary surfactant, and we interrogated single cell RNAseq data to fingerprint cell type specific changes.

RESULTS

We identified 117 and 68 mouse and human genes linked to ECM remodeling which accounted for 46% and 27%, respectively of all ECM coding genes. Furthermore, we identified 73 and 31 mouse and human genes linked to cellular senescence, and the majority code for the senescence associated secretory phenotype. These cytokines, chemokines and growth factors are primarily secreted by macrophages and fibroblasts. Single-cell RNAseq data confirmed age-related induced expression of marker genes of macrophages, neutrophil, eosinophil, dendritic, NK-, CD4+, CD8+-T and B cells in the lung of aged mice. This included the highly significant regulation of 20 genes coding for the CD3-T-cell receptor complex. Conversely, for the human lung we primarily observed macrophage and CD4+ and CD8+ marker genes as changed with age. Additionally, we noted an age-related induced expression of marker genes for mouse basal, ciliated, club and goblet cells, while for the human lung, fibroblasts and myofibroblasts marker genes increased with age. Therefore, we infer a change in cellular activity of these cell types with age. Furthermore, we identified predominantly repressed expression of surfactant coding genes, especially the surfactant transporter Abca3, thus highlighting remodeling of surfactant lipids with implications for the production of inflammatory lipids and immune response.

CONCLUSION

We report the genomic landscape of the aging lung and provide a rationale for its growing stiffness and age-related inflammation. By comparing the mouse and human pulmonary genome, we identified important differences between the two species and highlight the complex interplay of inflammaging, senescence and the link to ECM remodeling in healthy but aged individuals.

Intestinal Pgc1α ablation protects from liver steatosis and fibrosis

Background & Aims

The gut-liver axis modulates the progression of metabolic dysfunction-associated steatotic liver disease (MASLD), a spectrum of conditions characterised by hepatic steatosis and a progressive increase of inflammation and fibrosis, culminating in metabolic dysfunction-associated steatohepatitis. Peroxisome proliferator-activated receptor-gamma coactivator 1α (Pgc1α) is a transcriptional co-regulator of mitochondrial activity and lipid metabolism. Here, the intestinal-specific role of Pgc1α was analysed in liver steatosis and fibrosis.

Methods

We used a mouse model in which Pgc1α was selectively deleted from the intestinal epithelium. We fed these mice and their wild-type littermates a Western diet to recapitulate the major features of liver steatosis (after 2 months of diet) and metabolic dysfunction-associated steatohepatitis (after 4 months of diet). The chow diet was administered as a control diet.

Results

In humans and mice, low expression of intestinal Pgc1α is inversely associated with liver steatosis, inflammation, and fibrosis. Intestinal disruption of Pgc1α impairs the transcription of a wide number of genes, including the cholesterol transporter Niemann-Pick C1-like 1 (Npc1l1), thus limiting the uptake of cholesterol from the gut. This results in a lower cholesterol accretion in the liver and a decreased production of new fatty acids, which protect the liver from lipotoxic lipid species accumulation, inflammation, and related fibrotic processes.

Conclusions

In humans and mice, intestinal Pgc1α induction during Western diet may be another culprit driving hepatic steatosis and fibrosis. Here, we show that enterocyte-specific Pgc1α ablation protects the liver from steatosis and fibrosis by reducing intestinal cholesterol absorption, with subsequent decrease of cholesterol and de novo fatty acid accumulation in the liver.

Impact and implications

Liver diseases result from several insults, including signals from the gut. Although the incidence of liver diseases is continuously increasing worldwide, effective drug therapy is still lacking. Here, we showed that the modulation of an intestinal coactivator regulates the liver response to a Western diet, by limiting the uptake of dietary cholesterol. This results in a lower accumulation of hepatic lipids together with decreased inflammation and fibrosis, thus limiting the progression of liver steatosis and fibrosis towards severe end-stage diseases.

Rebalancing of mitochondrial homeostasis through an NAD+-SIRT1 pathway preserves intestinal barrier function in severe malnutrition

BACKGROUND

The intestine of children with severe malnutrition (SM) shows structural and functional changes that are linked to increased infection and mortality. SM dysregulates the tryptophan-kynurenine pathway, which may impact processes such as SIRT1- and mTORC1-mediated autophagy and mitochondrial homeostasis. Using a mouse and organoid model of SM, we studied the repercussions of these dysregulations on malnutrition enteropathy and the protective capacity of maintaining autophagy activity and mitochondrial health.

METHODS

SM was induced through feeding male weanling C57BL/6 mice a low protein diet (LPD) for 14-days. Mice were either treated with the NAD+-precursor, nicotinamide; an mTORC1-inhibitor, rapamycin; a SIRT1-activator, resveratrol; or SIRT1-inhibitor, EX-527. Malnutrition enteropathy was induced in enteric organoids through amino-acid deprivation. Features of and pathways to malnutrition enteropathy were examined, including paracellular permeability, nutrient absorption, and autophagic, mitochondrial, and reactive-oxygen-species (ROS) abnormalities.

FINDINGS

LPD-feeding and ensuing low-tryptophan availability led to villus atrophy, nutrient malabsorption, and intestinal barrier dysfunction. In LPD-fed mice, nicotinamide-supplementation was linked to SIRT1-mediated activation of mitophagy, which reduced damaged mitochondria, and improved intestinal barrier function. Inhibition of mTORC1 reduced intestinal barrier dysfunction and nutrient malabsorption. Findings were validated and extended using an organoid model, demonstrating that resolution of mitochondrial ROS resolved barrier dysfunction.

INTERPRETATION

Malnutrition enteropathy arises from a dysregulation of the SIRT1 and mTORC1 pathways, leading to disrupted autophagy, mitochondrial homeostasis, and ROS. Whether nicotinamide-supplementation in children with SM could ameliorate malnutrition enteropathy should be explored in clinical trials.

FUNDING

This work was supported by the Bill and Melinda Gates Foundation, the Sickkids Research Institute, the Canadian Institutes of Health Research, and the University Medical Center Groningen.

Sprint Interval Training on Stationary Air Bike Elicits Cardiorespiratory Adaptations While Being Time-Efficient

ABSTRACT

Moghaddam, M, Cervantes, M, Cheshier, B, and Jacobson, BH. Sprint interval training on stationary air bike elicits cardiorespiratory adaptations while being time-efficient. J Strength Cond Res 37(9): 1795-1801, 2023-Sprint interval training (SIT) refers to a set of brief intermittent exercises that are performed at maximal intensity. This study compared the effects of 2 SIT protocols (e.g., 10-5-SIT and 20-10-SIT) vs. moderate-intensity continuous training (MICT) on cardiovascular adaptations, using stationary air bikes. Thirty-two recreationally active individuals were randomly assigned to the 3 performance groups, such as 10-5-SIT (n = 11), 20-10-SIT (n = 10), and MICT (n = 11), to train 3 days per week for 4 weeks. Moderate-intensity continuous training included 30 minutes of cycling at 75% of maximal heart rate reserve, whereas the SIT protocols consisted of 3 sets of 8 intervals at all-out intensity. The 10-5-SIT and 20-10-SIT were performed with 10-second work:5-second rest and 20-second work:10-second rest, with 2.5- and 5-minute recovery periods between sets, respectively. A ramp protocol was used before and after the intervention via cycle ergometer to assess aerobic performance. Time to exhaustion (TTE), absolute V̇o2max (A-V̇o2max), relative V̇o2max (R-V̇o2max), and metabolic equivalents (METs) were measured and analyzed with 2-way mixed factorial analyses of variance (ANOVAs). In addition, total work (TW) during 12 sessions were recorded and analyzed with 1-way ANOVA. Significant (p < 0.05) differences were found for TW (10-5-SIT: 907.3 ± 332.0, 20-10-SIT: 1230.0 ± 188.1, and MICT: 2263.0 ± 896.9 calories) between groups. A significant main effect of time was observed for 10-5-SIT, 20-10-SIT, and MICT (p < 0.05) in TTE (increased by 7.3, 8.7, and 8.2%), A-V̇o2max (increased by 13.0, 11.8, and 13.6%), R-V̇o2max (increased by 12.6, 12.1, and 14.8%), and METs (increased by 12.7, 12.3, and 14.9%), respectively. Despite less volume and duration, both SIT protocols induced cardiorespiratory adaptations similar to MICT. These findings suggest that performing SIT on a stationary air bike is valuable because of time-efficiency and cardiorespiratory adaptations.

The Mitochondrial ATP Synthase/IF1 Axis in Cancer Progression: Targets for Therapeutic Intervention

Cancer poses a significant global health problem with profound personal and economic implications on National Health Care Systems. The reprograming of metabolism is a major trait of the cancer phenotype with a clear potential for developing effective therapeutic strategies to combat the disease. Herein, we summarize the relevant role that the mitochondrial ATP synthase and its physiological inhibitor, ATPase Inhibitory Factor 1 (IF1), play in metabolic reprogramming to an enhanced glycolytic phenotype. We stress that the interplay in the ATP synthase/IF1 axis has additional functional roles in signaling mitohormetic programs, pro-oncogenic or anti-metastatic phenotypes depending on the cell type. Moreover, the same axis also participates in cell death resistance of cancer cells by restrained mitochondrial permeability transition pore opening. We emphasize the relevance of the different post-transcriptional mechanisms that regulate the specific expression and activity of ATP synthase/IF1, to stimulate further investigations in the field because of their potential as future targets to treat cancer. In addition, we review recent findings stressing that mitochondria metabolism is the primary altered target in lung adenocarcinomas and that the ATP synthase/IF1 axis of OXPHOS is included in the most significant signature of metastatic disease. Finally, we stress that targeting mitochondrial OXPHOS in pre-clinical mouse models affords a most effective therapeutic strategy in cancer treatment.

PGC-1α Is a Master Regulator of Mitochondrial Lifecycle and ROS Stress Response

Mitochondria play a major role in ROS production and defense during their life cycle. The transcriptional activator PGC-1α is a key player in the homeostasis of energy metabolism and is therefore closely linked to mitochondrial function. PGC-1α responds to environmental and intracellular conditions and is regulated by SIRT1/3, TFAM, and AMPK, which are also important regulators of mitochondrial biogenesis and function. In this review, we highlight the functions and regulatory mechanisms of PGC-1α within this framework, with a focus on its involvement in the mitochondrial lifecycle and ROS metabolism. As an example, we show the role of PGC-1α in ROS scavenging under inflammatory conditions. Interestingly, PGC-1α and the stress response factor NF-κB, which regulates the immune response, are reciprocally regulated. During inflammation, NF-κB reduces PGC-1α expression and activity. Low PGC-1α activity leads to the downregulation of antioxidant target genes resulting in oxidative stress. Additionally, low PGC-1α levels and concomitant oxidative stress promote NF-κB activity, which exacerbates the inflammatory response.

Mitochondrial remodeling in colorectal cancer initiation, progression, metastasis, and therapy: A review

Colorectal cancer (CRC) is a major health concern with multifactorial pathophysiology representing intense therapeutic challenges. It is well known that deregulation of spatiotemporally-controlled signaling pathways and their metabolic reprogramming effects play a pivotal role in the development and progression of CRC. As such, the mitochondrial role in CRC initiation gained a lot of attention recently, as it is considered the powerhouse that regulates the bioenergetics in CRC. In addition, the crosstalk between microRNAs (miRNAs) and mitochondrial dysfunction has become a newfangled passion for deciphering CRC molecular mechanisms. This review sheds light on the relationship between different signaling pathways involved in metabolic reprogramming and their therapeutic targets, alterations in mitochondrial DNA content, mitochondrial biogenesis, and mitophagy, and the role of polymorphisms in mitochondrial genes as well as miRNAs regulating mitochondrial proteins in CRC initiation, progression, metastasis, and resistance to various therapies.

Microsomal Prostaglandin E Synthase-1 and -2: Emerging Targets in Non-Alcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) affects a substantial proportion of the general population and is even more prevalent in obese and diabetic patients. NAFLD, and particularly the more advanced manifestation of the disease, nonalcoholic steatohepatitis (NASH), increases the risk for both liver-related and cardiovascular morbidity. The pathogenesis of NAFLD is complex and multifactorial, with many molecular pathways implicated. Emerging data suggest that microsomal prostaglandin E synthase-1 and -2 might participate in the development and progression of NAFLD. It also appears that targeting these enzymes might represent a novel therapeutic approach for NAFLD. In the present review, we discuss the association between microsomal prostaglandin E synthase-1 and -2 and NAFLD.

Gut bacteria-derived 3-phenylpropionylglycine mitigates adipocyte differentiation of 3T3-L1 cells by inhibiting adiponectin-PPAR pathway

BACKGROUND

Gut microbiota provide numerous types of metabolites that humans cannot produce and have a huge influence on the host metabolism. Accordingly, gut bacteria-derived metabolites can be employed as a resource to develop anti-obesity and metabolism-modulating drugs.

OBJECTIVE

This study aimed to examine the anti-adipogenic effect of 3-phenylpropionylglycine (PPG), which is a glycine conjugate of bacteria-derived 3-phenylpropionic acid (PPA).

METHODS

The effect of PPG on preadipocyte-to-adipocyte differentiation was evaluated in 3T3-L1 differentiation models and the degree of the differentiation was estimated by Oil red O staining. The molecular mechanisms of the PPG effect were investigated with transcriptome analyses using RNA-sequencing and quantitative real-time PCR.

RESULTS

PPG suppressed lipid droplet accumulation during the adipogenic differentiation of 3T3-L1 cells, which is attributed to down-regulation of lipogenic genes such as acetyl CoA carboxylase 1 (Acc1) and fatty acid synthase (Fasn). However, other chemicals with chemical structures similar to PPG, including cinnamoylglycine and hippuric acid, had little effect on the lipid accumulation of 3T3-L1 cells. In transcriptomic analysis, PPG suppressed the expression of adipogenesis and metabolism-related gene sets, which is highly associated with downregulation of the peroxisome proliferator-activated receptor (PPAR) signaling pathway. Protein-protein association network analysis suggested adiponectin as a hub gene in the network of genes that were differentially expressed genes in response to PPG treatment.

CONCLUSION

PPG inhibits preadipocyte-to-adipocyte differentiation by suppressing the adiponectin-PPAR pathway. These data provide a potential candidate from bacteria-derived metabolites with anti-adipogenic effects.

Resveratrol-Mediated Regulation of Mitochondria Biogenesis-associated Pathways in Neurodegenerative Diseases: Molecular Insights and Potential Therapeutic Applications

Neurodegenerative disorders include different neurological conditions that affect nerve cells, causing the progressive loss of their functions and ultimately leading to loss of mobility, coordination, and mental functioning. The molecular mechanisms underpinning neurodegenerative disease pathogenesis are still unclear. Nonetheless, there is experimental evidence to demonstrate that the perturbation of mitochondrial function and dynamics play an essential role. In this context, mitochondrial biogenesis, the growth, and division of preexisting mitochondria, by controlling mitochondria number, plays a vital role in maintaining proper mitochondrial mass and function, thus ensuring efficient synaptic activity and brain function. Mitochondrial biogenesis is tightly associated with the control of cell division and variations in energy demand in response to extracellular stimuli; therefore, it may represent a promising therapeutic target for developing new curative approaches to prevent or counteract neurodegenerative disorders. Accordingly, several inducers of mitochondrial biogenesis have been proposed as pharmacological targets for treating diverse central nervous system conditions. The naturally occurring polyphenol resveratrol has been shown to promote mitochondrial biogenesis in various tissues, including the nervous tissue, and an ever-growing number of studies highlight its neurotherapeutic potential. Besides preventing cognitive impairment and neurodegeneration through its antioxidant and anti-inflammatory properties, resveratrol has been shown to be able to enhance mitochondria biogenesis by acting on its main effectors, including PGC-1α, SIRT1, AMPK, ERRs, TERT, TFAM, NRF-1 and NRF-2. This review aims to present and discuss the current findings concerning the impact of resveratrol on the machinery and main effectors modulating mitochondrial biogenesis in the context of neurodegenerative diseases.

The Warburg effect and mitochondrial oxidative phosphorylation: Friends or foes?

Cancer cells display an altered energy metabolism, which was proposed to be the root of cancer. This early discovery was done by O. Warburg who conducted one of the first studies of tumor cell energy metabolism. Taking advantage of cancer cells that exhibited various growth rates, he showed that cancer cells display a decreased respiration and an increased glycolysis proportional to the increase in their growth rate, suggesting that they mainly depend on fermentative metabolism for ATP generation. Warburg's results and hypothesis generated controversies that are persistent to this day. It is thus of great importance to understand the mechanisms by which cancer cells can reversibly regulate the two pathways of their energy metabolism as well as the functioning of this metabolism in cell proliferation. In this review, we discuss of the origin of the decrease in cell respiratory rate, whether the Warburg effect is mandatory for an increased cell proliferation rate, the consequences of this effect on two major players of cell energy metabolism that are ATP and NADH, and the role of the microenvironment in the regulation of cellular respiration and metabolism both in cancer cell and in yeast.

Association between PPARγ, PPARGC1A, and PPARGC1B genetic variants and susceptibility of gastric cancer in an Eastern Chinese population

PURPOSE

Previous studies showed that peroxisome proliferator-activated receptor gamma (PPARγ) and PPARγ coactivator1 family (PPARGC1A and PPARGC1B) gene single nucleotide variants (SNVs)were strongly associated with cancer susceptibility. The purpose of this study was to investigate the association of PPARγ, PPARGC1A, and PPARGC1B variants with the risk of gastric cancer (GC).

PATIENTS AND METHODS

We performed a case-control study of 490 GC cases and 1,476 healthy controls from eastern China. PPARγ rs1801282 C > G, rs3856806 C > T, PPARGC1A rs2970847 C > T, rs8192678 C > T and PPARGC1B rs7732671 G > C, rs17572019 G > A SNVs were selected to investigate the association between these SNVs and GC susceptibility. Genotypes of the SNVs were assessed by multiplex fluorescent PCR using a custom-by-design 48-Plex SNPscan^tm Kit.

RESULTS

The PPARγ rs1801282 SNV was associated with a decreased risk for GC (GC vs. CC: odds ratio (OR) = 0.62, 95% confidence interval (95%CI) = 0.42-0.93, adjusted P = 0.019; GC + GG vs. GG: OR = 0.63 95%CI = 0.42-0.93, adjusted P = 0.019; respectively). In addition, stratified analysis revealed that the PPARγ rs1801282 SNV was correlated with the risk of GC in subgroups of age ≥ 61, no smoking, and no alcohol consuming. We also confirmed that the PPARγ rs3856806 C > T SNV promoted the risk of GC in women. The PPARGC1A rs8192678 TT genotype decreased the susceptibility of GC in men. The PPARGC1A rs2970847 C > T SNV decreased the susceptibility of GC in the subgroup of BMI ≥ 24 kg/m². The PPARGC1B rs7732671 G > C and rs17572019 G > A SNVs promoted the risk of GC in the subgroup of BMI ≥ 24 kg/m².

CONCLUSION

This study indicates that the PPARγ, PPARGC1A, and PPARGC1B SNVs may be associated with the susceptibility of GC in eastern Chinese population. Future studies with larger populations, detailed H. pylori infection status for subgroup analysis, and functional study are needed to further clarify the relationship between these SNVs and GC risk.

PGC-1α Regulates Cell Proliferation, Migration, and Invasion by Modulating Leucyl-tRNA Synthetase 1 Expression in Human Colorectal Cancer Cells

Although mounting evidence has demonstrated that peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) can promote tumorigenesis, its role in cancer remains controversial. To find potential target molecules of PGC-1α, GeneFishing^TM DEG (differentially expressed genes) screening was performed using stable HEK293 cell lines expressing PGC-1α (PGC-1α-HEK293). As results, leucyl-tRNA synthetase 1 (LARS1) was upregulated. Western blot analysis showed that LARS1 was increased in PGC-1α overexpressed SW480 cells but decreased in PGC-1α shRNA knockdown SW620 cells. Several studies have suggested that LARS1 can be a potential target of anticancer agents. However, the molecular network of PGC-1α and LARS1 in human colorectal cancer cells remains unclear. LARS1 overexpression enhanced cell proliferation, migration, and invasion, whereas LARS1 knockdown reduced them. We also observed that expression levels of cyclin D1, c-Myc, and vimentin were regulated by LARS1 expression. We aimed to investigate whether effects of PGC-1α on cell proliferation and invasion were mediated by LARS1. Our results showed that PGC-1α might modulate cell proliferation and invasion by regulating LARS1 expression. These results suggest that LARS1 inhibitors might be used as anticancer agents in PGC-1α-overexpressing colorectal cancer. Further studies are needed in the future to clarify the detailed molecular mechanism by which PGC-1α regulates LARS1 expression.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Maternal exercise improves epithelial development of fetal intestine by enhancing apelin signaling and oxidative metabolism

Obesity in pregnancy is currently the leading cause of gestational complications for the mother and fetus worldwide. Maternal obesity (MO), common in western societies, impedes development of intestinal epithelium in the fetuses, which causes disorders in the nutrient absorption and intestine-related immune responses in offspring. Here, using a mouse model of maternal exercise (ME), we found that exercise during pregnancy protects the impairment of fetal intestinal morphometrical formation and epithelial development due to MO. MO decreased villus length and epithelial proliferation markers in E18.5 fetal small intestine, which was increased due to ME. The expression of the epithelial differentiation markers, Lyz1, Muc2, and Tff3, in fetal small intestine was decreased due to MO, but protected by ME. Consistently, the biomarkers related to mitochondrial biogenesis and oxidative metabolism were downregulated in MO fetal small intestine but recovered by ME. Apelin injection to dams partially mirrored the beneficial effects of ME. ME and apelin injection activated AMPK, the downstream target of apelin receptor signaling, which might mediate the improvement of fetal epithelial development and oxidative metabolism. These findings suggest that ME, a highly accessible intervention, is effective in improving fetal intestinal epithelium of obese dams. Apelin-AMPK-mitochondrial biogenesis axis provides amenable therapeutic targets to facilitate fetal intestinal development of obese mothers.

Mitochondrial function in intestinal epithelium homeostasis and modulation in diet-induced obesity

Background

Systemic low-grade inflammation observed in diet-induced obesity has been associated with dysbiosis and disturbance of intestinal homeostasis. This latter relies on an efficient epithelial barrier and coordinated intestinal epithelial cell (IEC) renewal that are supported by their mitochondrial function. However, IEC mitochondrial function might be impaired by high fat diet (HFD) consumption, notably through gut-derived metabolite production and fatty acids, that may act as metabolic perturbators of IEC.

Scope of review

This review presents the current general knowledge on mitochondria, before focusing on IEC mitochondrial function and its role in the control of intestinal homeostasis, and featuring the known effects of nutrients and metabolites, originating from the diet or gut bacterial metabolism, on IEC mitochondrial function. It then summarizes the impact of HFD on mitochondrial function in IEC of both small intestine and colon and discusses the possible link between mitochondrial dysfunction and altered intestinal homeostasis in diet-induced obesity.

Major conclusions

HFD consumption provokes a metabolic shift toward fatty acid β-oxidation in the small intestine epithelial cells and impairs colonocyte mitochondrial function, possibly through downstream consequences of excessive fatty acid β-oxidation and/or the presence of deleterious metabolites produced by the gut microbiota. Decreased levels of ATP and concomitant O₂ leaks into the intestinal lumen could explain the alterations of intestinal epithelium dynamics, barrier disruption and dysbiosis that contribute to the loss of epithelial homeostasis in diet-induced obesity. However, the effect of HFD on IEC mitochondrial function in the small intestine remains unknown and the precise mechanisms by which HFD induces mitochondrial dysfunction in the colon have not been elucidated so far.

Epithelial SMYD5 Exaggerates IBD by Down-regulating Mitochondrial Functions via Post-Translational Control of PGC-1α Stability

BACKGROUND & AIMS

The expression and role of methyltransferase SET and MYND domain-containing protein 5 (SMYD5) in inflammatory bowel disease (IBD) is completely unknown. Here, we investigated the role and underlying mechanism of epithelial SMYD5 in IBD pathogenesis and progression.

METHODS

The expression levels of SMYD5 and the mitochondrial transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) were examined by Western blot, immunofluorescence staining, and immunohistochemistry in intestinal epithelial cells (IECs) and in colon tissues from human IBD patients and colitic mice. Mice with Smyd5 conditional knockout in IECs and littermate controls were subjected to dextran sulfate sodium-induced colitis and the disease severity was assessed. SMYD5-regulated mitochondrial biogenesis was examined by quantitative reverse-transcription polymerase chain reaction and transmission electron microscopy, and the mitochondrial oxygen consumption rate was measured in a Seahorse Analyzer system (Agilent, Santa Clara, CA). SMYD5 and PGC-1α interaction was determined by co-immunoprecipitation assay. PGC-1α degradation and turnover (half-life) were analyzed by cycloheximide chase assay. SMYD5-mediated PGC-1α methylation was assessed via in vitro methylation assay followed by mass spectrometry for identification of methylated lysine residues.

RESULTS

Up-regulated SMYD5 and down-regulated PGC-1α were observed in intestinal epithelia from IBD patients and colitic mice. Smyd5 depletion in IECs protected mice from dextran sulfate sodium-induced colitis. SMYD5 was critically involved in regulating mitochondrial biology such as mitochondrial biogenesis, respiration, and apoptosis. Mechanistically, SMYD5 regulates mitochondrial functions in a PGC-1α-dependent manner. Furthermore, SMYD5 mediates lysine methylation of PGC-1α and subsequently facilitates its ubiquitination and degradation.

CONCLUSIONS

SMYD5 attenuates mitochondrial functions in IECs and promotes IBD progression by enhancing PGC-1α degradation in a methylation-dependent manner. Strategies to decrease SMYD5 expression and/or increase PGC-1α expression in IECs might be a promising therapeutic approach to treat IBD patients.

Identification of a Novel Immune Landscape Signature for Predicting Prognosis and Response of Colon Cancer to Immunotherapy

Purpose

To construct an immune-related gene prognostic index (IRGPI) for colon cancer and elucidate the molecular and immune characteristics as well as the benefit of immune checkpoint inhibitor (ICI) therapy in IRGPI-defined groups of colon cancer.

Experimental Design

Transcriptional and clinical data of colon cancer samples were obtained from The Cancer Genome Atlas (TCGA) (n = 521). Immune-related genes were obtained from ImmPort and InnateDB databases. 21 immune-related hub genes were identified byweighted gene co-expression network analysis (WGCNA). the Cox regression method was used to construct IRGPI and validated with Gene Expression Omnibus (GEO) dataset (n = 584). Finally, the molecular and immune profiles in the groups defined by IRGPI and the benefit of ICI treatment were analyzed.

Results

8 genes were identified to construct IRGPI. IRGPI-low group had a better overall survival (OS) than IRGPI-high group. And this was well validated in the GEO cohort. Overall results showed that those with low IRGPI scores were enriched in antitumor metabolism, and collated with high infiltration of resting memory CD4 T cells and less aggressive phenotypes, benefiting more from ICI treatment. Conversely, high IRGPI scores were associated with cell adhesion molecules (CAMs) and chemokine signaling pathways, high infiltration of macrophage M1, suppressed immunity, more aggressive colon cancer phenotypes, as well as reduced therapeutic benefit from ICI treatment.

Conclusions

IRGPI is a promising biomarker to differentiate the prognostic and molecular profile of colon cancer, as well as the therapeutic benefits of ICI treatment.

Ndufs4 knockout mouse models of Leigh syndrome: pathophysiology and intervention

Mitochondria are small cellular constituents that generate cellular energy (ATP) by oxidative phosphorylation (OXPHOS). Dysfunction of these organelles is linked to a heterogeneous group of multisystemic disorders, including diabetes, cancer, ageing-related pathologies and rare mitochondrial diseases. With respect to the latter, mutations in subunit-encoding genes and assembly factors of the first OXPHOS complex (complex I) induce isolated complex I deficiency and Leigh syndrome. This syndrome is an early-onset, often fatal, encephalopathy with a variable clinical presentation and poor prognosis due to the lack of effective intervention strategies. Mutations in the nuclear DNA-encoded NDUFS4 gene, encoding the NADH:ubiquinone oxidoreductase subunit S4 (NDUFS4) of complex I, induce 'mitochondrial complex I deficiency, nuclear type 1' (MC1DN1) and Leigh syndrome in paediatric patients. A variety of (tissue-specific) Ndufs4 knockout mouse models were developed to study the Leigh syndrome pathomechanism and intervention testing. Here, we review and discuss the role of complex I and NDUFS4 mutations in human mitochondrial disease, and review how the analysis of Ndufs4 knockout mouse models has generated new insights into the MC1ND1/Leigh syndrome pathomechanism and its therapeutic targeting.

Deoxynivalenol triggers porcine intestinal tight junction disorder through hijacking SLC5A1 and PGC1α-mediated mitochondrial function

Deoxynivalenol (DON) is a mycotoxin frequently occurring in human and animal food worldwide, which raises increasing public health concerns. Growing evidence suggests that mitochondria is a pivotal molecular target for DON. However, the contribution of mitochondrial dysfunction to the pathogenesis of DON-induced gut epithelial barrier disruption remains poorly understood. In an animal experiment, piglets exposed to 2.89 mg DON/kg feed for 4 weeks showed altered metabolomic profiling in the serum and compromised transcriptome in the jejunum. DON exposure also impaired mitochondrial structure in the jejunal mucosa, corresponding with dysfunction of the tight junctions. In IPEC-J2 cells, metabolomic and transcriptomic analyses revealed that DON exposure perturbed biological processes occurring in the mitochondria and disordered the expression of genes involved in mitochondrial energy metabolism. Fuel utilization from glucose was affected by DON exposure, as were mitochondrial morphological dynamics leading to increased fragmentation. A marked loss of Na⁺/glucose cotransporter (SLC5A1) and peroxisome proliferator activated receptor-γ co-activator 1α (PGC1α) was observed in DON-treated cells. Taken together, our data highlight the critical role of impaired mitochondrial energy metabolism and mitochondrial biogenesis in abnormal intestinal tight junction upon DON exposure, and provide a potential mitochondrial target for intestinal mucosal restoration following DON exposure.

Modulating gut dysbiosis and mitochondrial dysfunction in oxazolone-induced ulcerative colitis: the restorative effects of β-glucan and/or celastrol

Objectives

Microbiome–Mitochondria interaction is gaining a significant attention; thus, studying its mechanism emerges as a must to provide restorative lines in managing diseases. The aim is to study the mechanistic effects of β-Glucan and/or Celastrol in oxazolone-induced ulcerative colitis (UC).

Methods

75 Wistar rats were allocated into 5 equal groups. Group I: control group. Group II: UC group, Group III: β-Glucan-treated UC group, Group IV: Celastrol-treated UC group & Group V: mutual treatment group. All groups were subjected to the detection of free fatty acid receptor 2 (FFAR-2) and peroxisome proliferator-activated receptor gamma co-activator1α (PGC-1α) mRNA gene expressions. Citrate synthase (CS) activity, mitochondrial membrane potential (MMP), ATP concentration, reactive oxygen species (ROS) were detected. Trimethylamine N-oxide (TMAO) concentration was measured.

Results

After treatment we monitored significant upregulation of FFAR-2 and PGC-1α mRNA expression. Likewise, ATP level and CS activity were significantly increased. On the contrary, there was a significant lessening in ROS and TMAO levels with improvement of MMP.

Conclusion

Mutual use of β- Glucan and Celastrol had a greater effect than each alone against UC, which is considered a novel finding highlighting the ameliorative effects of this combined treatment in modulating Microbiome/Mitochondria axis, thus launching promising avenues for UC.

O-GlcNAcylation regulation of cellular signaling in cancer

O-GlcNAcylation is a post-translational modification occurring on serine/threonine residues of nuclear and cytoplasmic proteins, mediated by the enzymes OGT and OGA which catalyze the addition or removal of the UDP-GlcNAc moieties, respectively. Structural changes brought by this modification lead to alternations of protein stability, protein-protein interactions, and phosphorylation. Importantly, O-GlcNAcylation is a nutrient sensor by coupling nutrient sensing with cellular signaling. Elevated levels of OGT and O-GlcNAc have been reported in a variety of cancers and has been linked to regulation of multiple cancer signaling pathways. In this review, we discuss the most recent findings on the role of O-GlcNAcylation as a metabolic sensor in signaling pathways and immune response in cancer.

Enterocyte superoxide dismutase 2 deletion drives obesity

Compelling evidence support an involvement of oxidative stress and intestinal inflammation as early events in the predisposition and development of obesity and its related comorbidities. Here, we show that deficiency of the major mitochondrial antioxidant enzyme superoxide dismutase 2 (SOD2) in the gastrointestinal tract drives spontaneous obesity. Intestinal epithelium-specific Sod2 ablation in mice induced adiposity and inflammation via phospholipase A2 (PLA2) activation and increased release of omega-6 polyunsaturated fatty acid arachidonic acid. Remarkably, this obese phenotype was rescued when fed an essential fatty acid-deficient diet, which abrogates de novo biosynthesis of arachidonic acid. Data from clinical samples revealed that the negative correlation between intestinal Sod2 mRNA levels and obesity features appears to be conserved between mice and humans. Collectively, our findings suggest a role of intestinal Sod2 levels, PLA2 activity, and arachidonic acid in obesity presenting new potential targets of therapeutic interest in the context of this metabolic disorder.

Understanding host-microbiota interactions in the commercial piglet around weaning

Weaning is a critical period in the life of pigs with repercussions on their health and welfare and on the economy of the swine industry. This study aimed to assess the effect of the commercial early weaning on gut microbiota, intestinal gene expression and serum metabolomic response via an integrated-omic approach combining 16S rRNA gene sequencing, the OpenArray gene expression technology and ¹H-NMR spectroscopy. Fourteen piglets from different litters were sampled for blood, jejunum tissue and caecal content two days before (− 2d), and three days after (+ 3d) weaning. A clearly differential ordination of caecal microbiota was observed. Higher abundances of Roseburia, Ruminococcus, Coprococcus, Dorea and Lachnospira genera in weaned piglets compared to prior to weaning showed the quick microbial changes of the piglets’ gut microbiota. Downregulation of OCLN, CLDN4, MUC2, MUC13, SLC15A1 and SLC13A1 genes, also evidenced the negative impact of weaning on gut barrier and digestive functions. Metabolomic approach pinpointed significant decreases in choline, LDL, triglycerides, fatty acids, alanine and isoleucine and increases in 3-hydroxybutyrate after weaning. Moreover, the correlation between microbiota and metabolome datasets revealed the existence of metabolic clusters interrelated to different bacterial clusters. Our results demonstrate the impact of weaning stress on the piglet and give insights regarding the associations between gut microbiota and the animal gene activity and metabolic response.

Ndufs4 knockout mouse models of Leigh syndrome: pathophysiology and intervention

Mitochondria are small cellular constituents that generate cellular energy (ATP) by oxidative phosphorylation (OXPHOS). Dysfunction of these organelles is linked to a heterogeneous group of multisystemic disorders, including diabetes, cancer, ageing-related pathologies and rare mitochondrial diseases. With respect to the latter, mutations in subunit-encoding genes and assembly factors of the first OXPHOS complex (complex I) induce isolated complex I deficiency and Leigh syndrome. This syndrome is an early-onset, often fatal, encephalopathy with a variable clinical presentation and poor prognosis due to the lack of effective intervention strategies. Mutations in the nuclear DNA-encoded NDUFS4 gene, encoding the NADH:ubiquinone oxidoreductase subunit S4 (NDUFS4) of complex I, induce ‘mitochondrial complex I deficiency, nuclear type 1’ (MC1DN1) and Leigh syndrome in paediatric patients. A variety of (tissue-specific) Ndufs4 knockout mouse models were developed to study the Leigh syndrome pathomechanism and intervention testing.

Here, we review and discuss the role of complex I and NDUFS4 mutations in human mitochondrial disease, and review how the analysis of Ndufs4 knockout mouse models has generated new insights into the MC1ND1/Leigh syndrome pathomechanism and its therapeutic targeting.

Mitochondria and Inflammatory Bowel Diseases: Toward a Stratified Therapeutic Intervention

Mitochondria serve numerous critical cellular functions, rapidly responding to extracellular stimuli and cellular demands while dynamically communicating with other organelles. Mitochondrial function in the gastrointestinal epithelium plays a critical role in maintaining intestinal health. Emerging studies implicate the involvement of mitochondrial dysfunction in inflammatory bowel disease (IBD). This review presents mitochondrial metabolism, function, and quality control that converge in intestinal epithelial stemness, differentiation programs, barrier integrity, and innate immunity to influence intestinal inflammation. Intestinal and disease characteristics that set the stage for mitochondrial dysfunction being a key factor in IBD, and in turn, pathogenic mitochondrial mechanisms influencing and potentiating the development of IBD, are discussed. These findings establish the basis for potential mitochondrial-targeted interventions for IBD therapy. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dual Role of Phenyl Amides from Hempseed on BACE 1, PPARγ, and PGC-1α in N2a-APP Cells

In Alzheimer's disease (AD) the accumulation of amyloid β (Aβ) plaques in the brain leads to neuroinflammation, neuronal cell dysfunction, and progressive memory loss. Therefore, blocking the formation of Aβ plaques has emerged as one of the most promising strategies to develop AD treatments. Hempseed is widely used as a food, and recently its compounds have shown beneficial effects on neuroinflammation. The objective of this study was to investigate whether a fraction rich in phenyl amide compounds, N-trans-caffeoyltyramine (CAFT) and N-trans-coumaroyltyramine (CUMT), can affect gene expression: β-site amyloid-precursor-protein-cleaving enzyme 1 (BACE 1), peroxisome proliferator-activated receptor gamma (PPAR γ), and PPARγ-coactivator-1α (PGC-1α) in N2a-APP cells. The mRNA levels were measured using RT-qPCR. The ethyl acetate fraction and CAFT were found to reduce BACE1 gene expression and are promissory PPARγ and PGC-1α natural agonists. The results show that hempseed compounds can inhibit the expression of BACE 1, which is involved in the accumulation of Aβ plaques and positively affect transcription factors involved in complex and diverse biological functions.

PGC-1α promotes mitochondrial respiration and biogenesis during the differentiation of hiPSCs into cardiomyocytes

Although it is widely accepted that human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are readily available, robustly reproducible, and physiologically appropriate human cells for clinical applications and research in the cardiovascular field, hiPSC-CMs cultured in vitro retain an immature metabolic phenotype that limits their application, and little is known about the underlying molecular mechanism controlling mitochondrial metabolic maturation during human induced pluripotent stem cells (hiPSCs ) differentiation into cardiomyocytes. In this study, we found that peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) played an important role in inducing mitochondrial biogenesis and establishing oxidative phosphorylation (OXPHOS) during the cardiac differentiation of hiPSCs. Knocking down PGC-1α by siRNA impaired mitochondrial respiration, while upregulating PGC-1α by ZLN005 promoted mitochondrial biosynthesis and function by regulating the expression of downstream genes involved in mitochondrial dynamics and oxidative metabolism in hiPSC-CMs. Furthermore, we found that estrogen-related receptor α (ERRα) was required for the induction of PGC-1α stimulatory effects in hiPSC-CMs. These findings provide key insights into the molecular control of mitochondrial metabolism during cardiac differentiation and may be used to generate more metabolically mature cardiomyocytes for application.

Allostatic hypermetabolic response in PGC1α/β heterozygote mouse despite mitochondrial defects

Aging, obesity, and insulin resistance are associated with low levels of PGC1α and PGC1β coactivators and defective mitochondrial function. We studied mice deficient for PGC1α and PGC1β [double heterozygous (DH)] to investigate their combined pathogenic contribution. Contrary to our hypothesis, DH mice were leaner, had increased energy dissipation, a pro-thermogenic profile in BAT and WAT, and improved carbohydrate metabolism compared to wild types. WAT showed upregulation of mitochondriogenesis/oxphos machinery upon allelic compensation of PGC1α4 from the remaining allele. However, DH mice had decreased mitochondrial OXPHOS and biogenesis transcriptomes in mitochondria-rich organs. Despite being metabolically healthy, mitochondrial defects in DH mice impaired muscle fiber remodeling and caused qualitative changes in the hepatic lipidome. Our data evidence first the existence of organ-specific compensatory allostatic mechanisms are robust enough to drive an unexpected phenotype. Second, optimization of adipose tissue bioenergetics is sufficient to maintain a healthy metabolic phenotype despite a broad severe mitochondrial dysfunction in other relevant metabolic organs. Third, the decrease in PGC1s in adipose tissue of obese and diabetic patients is in contrast with the robustness of the compensatory upregulation in the adipose of the DH mice.

Estrogen-related receptor alpha (ERRα) is a key regulator of intestinal homeostasis and protects against colitis

The estrogen-related receptor alpha (ERRα) is a primary regulator of mitochondrial energy metabolism, function and dynamics, and has been implicated in autophagy and immune regulation. ERRα is abundantly expressed in the intestine and in cells of the immune system. However, its role in inflammatory bowel disease (IBD) remains unknown. Here, we report a protective role of ERRα in the intestine. We found that mice deficient in ERRα were susceptible to experimental colitis, exhibiting increased colon inflammation and tissue damage. This phenotype was mediated by impaired compensatory proliferation of intestinal epithelial cells (IEC) following injury, enhanced IEC apoptosis and necrosis and reduced mucus-producing goblet cell counts. Longitudinal analysis of the microbiota demonstrated that loss of ERRα lead to a reduction in microbiome α-diversity and depletion of healthy gut bacterial constituents. Mechanistically, ERRα mediated its protective effects by acting within the radio-resistant compartment of the intestine. It promoted disease tolerance through transcriptional control of key genes involved in intestinal tissue homeostasis and repair. These findings provide new insights on the role of ERRα in the gut and extends our current knowledge of nuclear receptors implicated in IBD.

Molecular characterization of colorectal cancer: A five-gene prognostic signature based on RNA-binding proteins

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide. RNA-binding proteins (RBPs) regulate essential biological processes and play essential roles in a variety of cancers. The present study screened differentially expressed RBPs, analyzed their function and constructed a prognostic model to predict the overall survival of patients with CRC.

METHODS

We downloaded CRC RNA-sequencing data from the Cancer Genome Atlas (TCGA) portal and screened differentially expressed RBPs. Then, functional analyses of these genes were performed, and a risk model was established by multivariate Cox regression.

RESULTS

We obtained 132 differentially expressed RBPs, including 66 upregulated and 66 downregulated RBPs. Functional analysis revealed that these genes were significantly enriched in RNA processing, modification and binding, ribosome biogenesis, post-transcriptional regulation, ribonuclease and nuclease activity. Additionally, some RBPs were significantly related to interferon (IFN)-alpha and IFN-beta biosynthetic processes and the Toll-like receptor signaling pathway. A prognostic model was constructed and included insulin like growth factor 2 messenger ribonucleic acid binding protein 3 (IGF2BP3), poly (A) binding protein cytoplasmic 1 like (PABPC1L), peroxisome proliferator activated receptor gamma coactivator 1 alpha (PPARGC1A), peptidyl- transfer ribonucleic acid hydrolase 1 homolog (PTRH1) and tudor domain containing 7 (TDRD7). The model is an independent risk factor for clinicopathological characteristics.

CONCLUSION

Our study provided novel insights into the pathogenesis of CRC and constructed a prognostic gene model, which may be helpful for determining the prognosis of CRC.

PPARγ: The Central Mucus Barrier Coordinator in Ulcerative Colitis

Ulcerative colitis (UC) is an idiopathic, long-term inflammatory disorder of the colon, characterized by a continuous remitting and relapsing course. The intestinal mucus barrier is the first line at the interface between the host and microbiota and acts to protect intestinal epithelial cells from invasion. Data from patients and animal studies have shown that an impaired mucus barrier is closely related to the severity of UC. Depletion of the mucus barrier is not just the strongest but is also the only independent risk factor predicting relapse in patients with UC. Peroxisome proliferator-activated receptor gamma (PPARγ), a nuclear transcription regulator, is involved in the regulation of inflammatory cytokine expression. It is also known to promote mucus secretion under pathological conditions to expel pathogenic bacteria or toxins. More important, PPARγ has been shown to affect host-microbiota interactions by modulating the energy metabolism of colonocytes and the oxygen availability of the intestinal microbiome. It is well known that gut microbiota homeostasis is essential for butyrate generation by the commensal bacteria to supply energy resources for colonocytes. Therefore, it can be speculated that PPARγ, as a central coordinator of the mucus barrier, may be a promising target for the development of effective agents to combat UC.

A Balanced Act: The Effects of GH-GHR-IGF1 Axis on Mitochondrial Function

Mitochondrial function is multifaceted in response to cellular energy homeostasis and metabolism, with the generation of adenosine triphosphate (ATP) through the oxidative phosphorylation (OXPHOS) being one of their main functions. Selective elimination of mitochondria by mitophagy, in conjunction with mitochondrial biogenesis, regulates mitochondrial function that is required to meet metabolic demand or stress response. Growth hormone (GH) binds to the GH receptor (GHR) and induces the JAK2/STAT5 pathway to activate the synthesis of insulin-like growth factor 1 (IGF1). The GH–GHR–IGF1 axis has been recognized to play significant roles in somatic growth, including cell proliferation, differentiation, division, and survival. In this review, we describe recent discoveries providing evidence for the contribution of the GH–GHR–IGF1 axis on mitochondrial biogenesis, mitophagy (or autophagy), and mitochondrial function under multiple physiological conditions. This may further improve our understanding of the effects of the GH–GHR–IGF1 axis on mitochondrial function, which may be controlled by the delicate balance between mitochondrial biogenesis and mitophagy. Specifically, we also highlight the challenges that remain in this field.

The Role of Organelles in Intestinal Function, Physiology, and Disease

The intestine maintains homeostasis by coordinating internal biological processes to adjust to fluctuating external conditions. The intestinal epithelium is continuously renewed and comprises multiple cell types, including absorptive cells, secretory cells, and resident stem cells. An important feature of this organ is its ability to coordinate many processes including cell proliferation, differentiation, regeneration, damage/stress response, immune activity, feeding behavior, and age-related changes by using conserved signaling pathways. However, the subcellular spatial organization of these signaling events and the organelles involved has only recently been studied in detail. Here we discuss how organelles of intestinal cells serve to initiate, mediate, and terminate signals, that are vital for homeostasis.

The PGC1α/NRF1-MPC1 axis suppresses tumor progression and enhances the sensitivity to sorafenib/doxorubicin treatment in hepatocellular carcinoma

Targeting energy metabolism holds the potential to effectively treat a variety of malignant diseases, and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) is a key regulator of energy metabolism. However, PGC1α's role in cancer, especially in hepatocellular carcinoma (HCC) remains largely unknown. In the present study, we reported that PGC1α was significantly downregulated in HCC cell lines and specimens. Moreover, reduced expression of PGC1α in tumor cells was correlated with poor prognosis. PGC1α overexpression substantially inhibited cell proliferation and induced apoptosis in vitro and in vivo. On the contrary, the knockdown of PGC1α produced the opposite effect. The mechanism was at least partially due to the upregulation of mitochondrial pyruvate carrier 1 (MPC1) caused by PGC1α, which promoted mitochondrial biogenesis by binding to nuclear respiratory factor 1 (NRF1). Consequently, the production of cellular reactive oxygen species (ROS) caused by mitochondrial oxidation was elevated above a critical threshold for survival. Furthermore, we found that PGC1α could enhance the antitumor activity of sorafenib and doxorubicin in HCC through ROS accumulation-mediated cell death. These results indicate that PGC1α/NRF1-MPC1 axis is involved in HCC progression and could be a promising target for HCC treatment.

NT-PGC-1α deficiency attenuates high-fat diet-induced obesity by modulating food intake, fecal fat excretion and intestinal fat absorption

Transcriptional coactivator PGC-1α and its splice variant NT-PGC-1α regulate metabolic adaptation by modulating many gene programs. Selective ablation of PGC-1α attenuates diet-induced obesity through enhancing fatty acid oxidation and thermogenesis by upregulation of NT-PGC-1α in brown adipose tissue (BAT). Recently, we have shown that selective ablation of NT-PGC-1α reduces fatty acid oxidation in BAT. Thus, the objective of this study was to test our hypothesis that NT-PGC-1α^−/− mice would be more prone to diet-induced obesity. Male and female NT-PGC-1α^+/+ (WT) and NT-PGC-1α^−/− mice were fed a regular chow or 60% high-fat (HF) diet for 16 weeks. Contrary to our expectations, both male and female NT-PGC-1α^−/− mice fed HFD were protected from diet-induced obesity, with more pronounced effects in females. This lean phenotype was primarily driven by reduced dietary fat intake. Intriguingly, HFD-fed female, but not male, NT-PGC-1α^−/− mice further exhibited decreased feed efficiency, which was closely associated with increased fecal fat excretion and decreased uptake of fatty acids by the intestinal enterocytes and adipocytes with a concomitant decrease in fatty acid transporter gene expression. Collectively, our results highlight the role for NT-PGC-1α in regulating whole body lipid homeostasis under HFD conditions.

Mitochondrial Metabolism in the Intestinal Stem Cell Niche-Sensing and Signaling in Health and Disease

Mitochondrial metabolism, dynamics, and stress responses in the intestinal stem cell niche play a pivotal role in regulating intestinal epithelial cell homeostasis, including self-renewal and differentiation. In addition, mitochondria are increasingly recognized for their involvement in sensing the metabolic environment and their capability of integrating host and microbial-derived signals. Gastrointestinal diseases such as inflammatory bowel diseases and colorectal cancer are characterized by alterations of intestinal stemness, the microbial milieu, and mitochondrial metabolism. Thus, mitochondrial function emerges at the interface of determining health and disease, and failure to adapt mitochondrial function to environmental cues potentially results in aberrant tissue responses. A mechanistic understanding of the underlying role of mitochondrial fitness in intestinal pathologies is still in its infancy, and therapies targeting mitochondrial (dys)function are currently lacking. This review discusses mitochondrial signaling and metabolism in intestinal stem cells and Paneth cells as critical junction translating host- and microbe-derived signals into epithelial responses. Consequently, we propose mitochondrial fitness as a hallmark for intestinal epithelial cell plasticity, determining the regenerative capacity of the epithelium.

Reprogramming Oxidative Phosphorylation in Cancer: A Role for RNA-Binding Proteins

Significance: Cancer is a major disease imposing high personal and economic burden draining large part of National Health Care and Research budgets worldwide. In the last decade, research in cancer has underscored the reprogramming of metabolism to an enhanced aerobic glycolysis as a major trait of the cancer phenotype with great potential for targeted therapy. Recent Advances: Mitochondria are essential organelles in metabolic reprogramming for controlling the production of biological energy through oxidative phosphorylation (OXPHOS) and the supply of metabolic precursors that sustain proliferation. In addition, mitochondria are critical hubs that integrate different signaling pathways that control cellular metabolism and cell fate. The mitochondrial ATP synthase plays a fundamental role in OXPHOS and cellular signaling. Critical Issues: This review overviews mitochondrial metabolism and OXPHOS, and the major changes reported in the expression and function of mitochondrial proteins of OXPHOS in oncogenesis and in cellular differentiation. We summarize the prominent role that RNA-binding proteins (RNABPs) play in the sorting and localized translation of nuclear-encoded mRNAs that help define the mitochondrial cell-type-specific phenotype. Moreover, we emphasize the mechanisms that contribute to restrain the activity and expression of the mitochondrial ATP synthase in carcinomas, and illustrate that the dysregulation of proteins that control energy metabolism correlates with patients' survival. Future Directions: Future research should elucidate the mechanisms and RNABPs that promote the specific alterations of the mitochondrial phenotype in carcinomas arising from different tissues with the final aim of developing new therapeutic strategies to treat cancer.

Effect of Selenium Supplementation on Expression of SIRT1 and PGC-1α Genes in Ulcerative Colitis Patients: a Double Blind Randomized Clinical Trial

Selenium (Se) supplementation may decrease the severity of ulcerative colitis (UC) through the activation of genes responsible for immune modulation. The present research was aimed to assess the effect of Se supplementation on the expression of silent information regulator 1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) in UC patients. In a double-blind randomized parallel clinical trial, 100 patients with mild-to-moderate active UC met inclusion criteria and divided into 2 groups of treatment (50 patients received selenomethionine [200 µg daily]) and placebo (50 patients received placebo [1 capsule daily]) for 10 weeks. The expression rates of SIRT1 and PGC-1α were examined in the peripheral blood mononuclear cell (PBMC) using the real-time polymerase chain reaction. There was no considerable difference in the mean of baseline demographic and clinical characteristics between groups. Also, there were no significant differences in total energy intake, macronutrients, and micronutrients between groups. The SIRT1 gene expression in the Se group was significantly increased compared to the placebo (p < 0.001). An increase in the expression of the PGC-1α gene in the Se group was not statistically significant. It seems that Se supplementation caused a significant decrease in the inflammatory response of the colon by a significant increase in the expression of the SIRT1 gene.

Manipulation of Mitochondrial Plasticity Changes the Metabolic Competition Between "Foe" and "Friend" During Tumor Malignant Transformation

Mitochondria as the cellular energy powerhouses provide a common site for multiple metabolic reactions in order to cover energy and biomolecule demands, thus integrating the diverse metabolic pathways to endow cells with metabolic adaptation. Mitochondrial plasticity is normally regulated by mitochondrial dynamics, mitochondrial metabolism and mitochondrial biogenesis. Given that tumor cells and T cells share the metabolic similarities of survival, proliferation, expansion as well as effector function, manipulation of mitochondrial plasticity would change the metabolic competition between “foe” and “friend” during tumor malignant progression. On the one hand, for “foe” tumor cells, mitochondrial plasticity provides the enhancement of tumor metastasis and the development of resistance to‘ diverse antitumor drugs. On the other hand, for “friend” T cells, mitochondrial plasticity promotes the generation of long-term memory T (T_M) cells and alleviates the exhaustion of tumor-infiltrating lymphocytes (TILs). Therefore, downregulation of mitochondrial plasticity of tumor cells through engineering tumor-targeting nanoparticles may effectively potentiate metabolic vulnerability and re-sensitize tumor to relevant therapeutic treatment. On the contrary, upregulation of mitochondrial plasticity of T cells through optimizing adoptive cellular immunotherapy (ACI) or chimeric antigen receptor (CAR)-T cell therapy would provide T cells with the robust metabolic fitness and the persistent immune function, thus blocking tumor metastasis and reoccurrence.

Integrated analysis of RNA-binding proteins in human colorectal cancer

Background

Although RNA-binding proteins play an essential role in a variety of different tumours, there are still limited efforts made to systematically analyse the role of RNA-binding proteins (RBPs) in the survival of colorectal cancer (CRC) patients.

Methods

Analysis of CRC transcriptome data collected from the TCGA database was conducted, and RBPs were extracted from CRC. R software was applied to analyse the differentially expressed genes (DEGs) of RBPs. To identify related pathways and perform functional annotation of RBP DEGs, Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were carried out using the database for annotation, visualization and integrated discovery. Protein-protein interactions (PPIs) of these DEGs were analysed based on the Search Tool for the Retrieval of Interacting Genes (STRING) database and visualized by Cytoscape software. Based on the Cox regression analysis of the prognostic value of RBPs (from the PPI network) with survival time, the RBPs related to survival were identified, and a prognostic model was constructed. To verify the model, the data stored in the TCGA database were designated as the training set, while the chip data obtained from the GEO database were treated as the test set. Then, both survival analysis and ROC curve verification were conducted. Finally, the risk curves and nomograms of the two groups were generated to predict the survival period.

Results

Among RBP DEGs, 314 genes were upregulated while 155 were downregulated, of which twelve RBPs (NOP14, MRPS23, MAK16, TDRD6, POP1, TDRD5, TDRD7, PPARGC1A, LIN28B, CELF4, LRRFIP2, MSI2) with prognostic value were obtained.

Conclusions

The twelve identified genes may be promising predictors of CRC and play an essential role in the pathogenesis of CRC. However, further investigation of the underlying mechanism is needed.