Obesity promotes colonic stem cell expansion during cancer initiation

Dysregulation of cellular membrane homeostasis as a crucial modulator of cancer risk

Cellular membranes serve as an epicentre combining extracellular and cytosolic components with membranous effectors, which together support numerous fundamental cellular signalling pathways that mediate biological responses. To execute their functions, membrane proteins, lipids and carbohydrates arrange, in a highly coordinated manner, into well-defined assemblies displaying diverse biological and biophysical characteristics that modulate several signalling events. The loss of membrane homeostasis can trigger oncogenic signalling. More recently, it has been documented that select membrane active dietaries (MADs) can reshape biological membranes and subsequently decrease cancer risk. In this review, we emphasize the significance of membrane domain structure, organization and their signalling functionalities as well as how loss of membrane homeostasis can steer aberrant signalling. Moreover, we describe in detail the complexities associated with the examination of these membrane domains and their association with cancer. Finally, we summarize the current literature on MADs and their effects on cellular membranes, including various mechanisms of dietary chemoprevention/interception and the functional links between nutritional bioactives, membrane homeostasis and cancer biology.

Dietary regulation of intestinal stem cells in health and disease

Diet is a critical regulator for physiological metabolism and tissue homeostasis, with a close relation to health and disease. As an important organ for digestion and absorption, the intestine comes into direct contact with many dietary components. The rapid renewal of its mucosal epithelium depends on the continuous proliferation and differentiation of intestinal stem cells (ISCs). The function and metabolism of ISCs can be controlled by a variety of dietary patterns including calorie restriction, fasting, high-fat, ketogenic, and high-sugar diets, as well as different nutrients including vitamins, amino acids, dietary fibre, and probiotics. Therefore, dietary interventions targeting ISCs may make it possible to prevent and treat intestinal disorders such as colon cancer, inflammatory bowel disease, and radiation enteritis. This review summarised recent research on the role and mechanism of diet in regulating ISCs, and discussed the potential of dietary modulation for intestinal diseases.

Dysregulation of cholesterol metabolism in cancer progression

Cholesterol homeostasis has been implicated in the regulation of cellular and body metabolism. Hence, deregulated cholesterol homeostasis leads to the development of many diseases such as cardiovascular diseases, and neurodegenerative diseases, among others. Recent studies have unveiled the connection between abnormal cholesterol metabolism and cancer development. Cholesterol homeostasis at the cellular level dynamically circulates between synthesis, influx, efflux, and esterification. Any dysregulation of this dynamic process disrupts cholesterol homeostasis and its derivatives, which potentially contributes to tumor progression. There is also evidence that cancer-related signals, which promote malignant progression, also regulate cholesterol metabolism. Here, we described the relationship between cholesterol metabolism and cancer hallmarks, with particular focus on the molecular mechanisms, and the anticancer drugs that target cholesterol metabolism.

Obesity and cancer stem cells: Roles in cancer initiation, progression and therapy resistance

Obesity, the global pandemic since industrialization, is the number one lifestyle-related risk factor for premature death, which increases the incidence and mortality of various diseases and conditions, including cancer. In recent years, the theory of cancer stem cells (CSCs), which have the capacity for self-renewal, metastasis and treatment resistance, has been bolstered by increasing evidence. However, research on how obesity affects CSCs to facilitate cancer initiation, progression and therapy resistance is still in its infancy, although evidence has already begun to accumulate. Regarding the ever-increasing burden of obesity and obesity-related cancer, it is pertinent to summarize evidence about the effects of obesity on CSCs, as elucidating these effects will contribute to the improvement in the management of obesity-related cancers. In this review, we discuss the association between obesity and CSCs, with a particular focus on how obesity promotes cancer initiation, progression and therapy resistance through CSCs and the mechanisms underlying these effects. In addition, the prospect of preventing cancer and targeting the mechanisms linking obesity and CSCs to reduce cancer risk or to improve the survival of patients with cancer is considered.

Molecular genetics of early-onset colorectal cancer

Early-onset colorectal cancer (EOCRC) has been rising in global prevalence and incidence over the past several decades. Environmental influences, including generational lifestyle changes and rising obesity, contribute to these increased rates. While the rise in EOCRC is best documented in western countries, it is seen throughout the world, although EOCRC may have distinct genetic mutations in patients of different ethnic backgrounds. Pathological and molecular characterizations show that EOCRC has a distinct presentation compared with later-onset colorectal cancer (LOCRC). Recent studies have identified DNA, RNA, and protein-level alterations unique to EOCRC, revealing much-needed biomarkers and potential novel therapeutic targets. Many molecular EOCRC studies have been performed with Caucasian and Asian EOCRC cohorts, however, studies of other ethnic backgrounds are limited. In addition, certain molecular characterizations that have been conducted for LOCRC have not yet been repeated in EOCRC, including high-throughput analyses of histone modifications, mRNA splicing, and proteomics on large cohorts. We propose that the complex relationship between cancer and aging should be considered when studying the molecular underpinnings of EOCRC. In this review, we summarize current EOCRC literature, focusing on sporadic molecular alterations in tumors, and their clinical implications. We conclude by discussing current challenges and future directions of EOCRC research efforts.

Metabolism and Colorectal Cancer

Reprogrammed metabolism is a hallmark of colorectal cancer (CRC). CRC cells are geared toward rapid proliferation, requiring nutrients and the removal of cellular waste in nutrient-poor environments. Intestinal stem cells (ISCs), the primary cell of origin for CRCs, must adapt their metabolism along the adenoma-carcinoma sequence to the unique features of their complex microenvironment that include interactions with intestinal epithelial cells, immune cells, stromal cells, commensal microbes, and dietary components. Emerging evidence implicates modifiable risk factors related to the environment, such as diet, as important in CRC pathogenesis. Here, we focus on describing the metabolism of ISCs, diets that influence CRC initiation, CRC genetics and metabolism, and the tumor microenvironment. The mechanistic links between environmental factors, metabolic adaptations, and the tumor microenvironment in enhancing or supporting CRC tumorigenesis are becoming better understood. Thus, greater knowledge of CRC metabolism holds promise for improved prevention and treatment.

Elevated ATGL in colon cancer cells and cancer stem cells promotes metabolic and tumorigenic reprogramming reinforced by obesity

Obesity is a worldwide epidemic associated with increased risk and progression of colon cancer. Here, we aimed to determine the role of adipose triglyceride lipase (ATGL), responsible for intracellular lipid droplet (LD) utilization, in obesity-driven colonic tumorigenesis. In local colon cancer patients, significantly increased ATGL levels in tumor tissue, compared to controls, were augmented in obese individuals. Elevated ATGL levels in human colon cancer cells (CCC) relative to non-transformed were augmented by an obesity mediator, oleic acid (OA). In CCC and colonospheres, enriched in colon cancer stem cells (CCSC), inhibition of ATGL prevented LDs utilization and inhibited OA-stimulated growth through retinoblastoma-mediated cell cycle arrest. Further, transcriptomic analysis of CCC, with inhibited ATGL, revealed targeted pathways driving tumorigenesis, and high-fat-diet obesity facilitated tumorigenic pathways. Inhibition of ATGL in colonospheres revealed targeted pathways in human colonic tumor crypt base cells (enriched in CCSC) derived from colon cancer patients. In CCC and colonospheres, we validated selected transcripts targeted by ATGL inhibition, some with emerging roles in colonic tumorigeneses (ATG2B, PCK2, PGAM1, SPTLC2, IGFBP1, and ABCC3) and others with established roles (MYC and MUC2). These findings demonstrate obesity-promoted, ATGL-mediated colonic tumorigenesis and establish the therapeutic significance of ATGL in obesity-reinforced colon cancer progression.

The tumor suppression theory of aging

Despite continued increases in human life expectancy, the factors determining the rate of human biological aging remain unknown. Without understanding the molecular mechanisms underlying aging, efforts to prevent aging are unlikely to succeed. The tumor suppression theory of aging introduced here proposes somatic mutation as the proximal cause of aging, but postulates that oncogenic transformation and clonal expansion, not functional impairment, are the relevant consequences of somatic mutation. Obesity and caloric restriction accelerate and decelerate aging due to their effect on cell proliferation, during which most mutations arise. Most phenotypes of aging are merely tumor-suppressive mechanisms that evolved to limit malignant growth, the dominant age-related cause of death in early and middle life. Cancer limits life span for most long-lived mammals, a phenomenon known as Peto's paradox. Its conservation across species demonstrates that mutation is a fundamental but hard limit on mammalian longevity. Cell senescence and apoptosis and differentiation induced by oncogenes, telomere shortening or DNA damage evolved as a second line of defense to limit the tumorigenic potential of clonally expanding cells, but accumulating senescent cells, senescence-associated secretory phenotypes and stem cell exhaustion eventually cause tissue dysfunction and the majority, if not most, phenotypes of aging.

Anti-inflammatory and -apoptotic effects of a long-term herbal extract treatment on DSS-induced colitis in mice fed with high AGEs-fat diet

Background

Obesity is associated with many comorbidities including inflammatory bowel disease (IBD). We investigated prophylactic effects of an herbal extract (HE) on the DSS-induced colitis mice challenged with high AGEs-fat diet 60% (HFD).

Methods

Six-week-old C57BL/6 male mice were fed with either HFD (8 groups, 6 mice in each group), or normal diet (ND) (8 groups, 6 mice in each group). After 6 weeks, animals received HE (combination of turmeric, ginger, boswellia and cat’s claw extract) for 7 weeks in three doses (high dose (0.6 mg/g); low dose (0.15 mg/g) and mid dose (0.3 mg/g)). Next, mice were subjected to 2.5% DSS in drinking water. Control mice received ND and instead of HE and DSS they received distilled water. Obesity index markers were determined, H&E staining and TUNEL assay evaluated apoptosis. Colonic expressions of IL-6, RAGE, AGER1, Sirt1, Bax, Bcl2, ZO-1 and P53 were determined.

Results

HE ameliorated colitis in HFD mice by reducing colonic myeloperoxidase activity (by 2.3-fold), macrophage accumulation (by 2.6-fold) and mRNA expression of IL-6 (by 2.3-fold) in HFD mice. Moreover, HE restored ZO-1 (by 2.7-fold), prevented apoptosis and maintained immune homeostasis. HE reduced activation of NF-κB protein (by 1.3-fold) through decreasing RAGE (by 1.93-fold) and up-regulation of Sirt1 (by 7.71-fold) and prevented down-regulation of DDOST (by 6.6-fold) in HFD mice.

Conclusions

HE ameliorated colitis in prophylactic in HFD mice and it was, at least partly, due to the restoration of the gut integrity, suppression of inflammation and apoptosis via modulation of colonic Sirt1, RAGE and DDOST signaling.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00603-x.

High-fat diet-activated fatty acid oxidation mediates intestinal stemness and tumorigenicity

Obesity is an established risk factor for cancer in many tissues. In the mammalian intestine, a pro-obesity high-fat diet (HFD) promotes regeneration and tumorigenesis by enhancing intestinal stem cell (ISC) numbers, proliferation, and function. Although PPAR (peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to facilitate these effects, their exact role is unclear. Here we find that, in loss-of-function in vivo models, PPARα and PPARδ contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Pharmacologic and genetic disruption of CPT1A (the rate-controlling enzyme of mitochondrial FAO) blunts the HFD phenotype in ISCs. Furthermore, inhibition of CPT1A dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression. These findings demonstrate that inhibition of a HFD-activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.

AdipoRon and Other Adiponectin Receptor Agonists as Potential Candidates in Cancer Treatments

The high mortality rate together with an ever-growing number of annual cases have defined neoplastic disorders as “the real 21st-century disease”. Its dubious distinction also results from conventional therapy failure, which has made cancer an orphan disease. Therefore, innovative and alternative therapeutic strategies are mandatory. The ability to leverage human naturally occurring anti-tumor defenses has always represented a fascinating perspective, and the immuno blockage approval in cancer treatment represents in timeline the latest success. As a multifunctional organ, adipose tissue releases a large amount of adipokines having both carcinogenic and antitumor properties. The negative correlation between serum levels and risk for developing malignancies, as well as the huge number of existing preclinical studies, have identified adiponectin as a potential anticancer adipokine. Nevertheless, its usage in clinical has constantly clashed with the inability to reproduce a mimic synthetic compound. Between 2011 and 2013, two distinct adiponectin receptor agonists were recognized, opening new scenarios even in cancer. Here, we review the first orally active adiponectin receptor agonists AdipoRon, from the discovery to the anticancer evidence. Including our latest findings in osteosarcoma models, we summarize AdipoRon and other existing agonists state-of-art, questioning about the feasibility assessment of this strategy in cancer treatment.

Obesity and intestinal stem cell susceptibility to carcinogenesis

Background

Obesity is a top public health problem associated with an increase in colorectal cancer incidence. Stem cells are the chief cells in tissue homeostasis that self-renew and differentiate into other cells to regenerate the organ. It is speculated that an increase in stem cell pool makes cells susceptible to carcinogenesis. In this review, we looked at the recent investigations linking obesity/high-fat diet-induced obesity to intestinal carcinogenesis with regard to intestinal stem cells and their niche.

Findings

High-fat diet-induced obesity may rise intestinal carcinogenesis by increased Intestinal stem cells (ISC)/progenitor’s population, stemness, and niche independence through activation of PPAR-δ with fatty acids, hormonal alterations related to obesity, and low-grade inflammation. However, these effects may possibly relate to the interaction between fats and carbohydrates, and not a fatty acid per se. Nonetheless, literature studies are inconsistency in their results, probably due to the differences in the diet components and limitations of genetic models used.

Conclusion

High-fat diet-induced obesity affects carcinogenesis by changing ISC proliferation and function. However, a well-matched diet and the reliable colorectal cancer models that mimic human carcinogenesis is necessary to clearly elucidate the influence of high-fat diet-induced obesity on ISC behavior.

Nutritional Control of Intestinal Stem Cells in Homeostasis and Tumorigenesis

Food and nutrition have a profound impact on organismal health and diseases, and tissue-specific adult stem cells play a crucial role in coordinating tissue maintenance by responding to dietary cues. Emerging evidence indicates that adult intestinal stem cells (ISCs) actively adjust their fate decisions in response to diets and nutritional states to drive intestinal adaptation. Here, we review the signaling mechanisms mediating the dietary responses imposed by caloric intake and nutritional composition (i.e., macronutrients and micronutrients), fasting-feeding patterns, diet-induced growth factors, and microbiota on ISCs and their relevance to the beginnings of intestinal tumors.

Roles of Adipokines in Digestive Diseases: Markers of Inflammation, Metabolic Alteration and Disease Progression

Adipose tissue is a highly dynamic endocrine tissue and constitutes a central node in the interorgan crosstalk network through adipokines, which cause pleiotropic effects, including the modulation of angiogenesis, metabolism, and inflammation. Specifically, digestive cancers grow anatomically near adipose tissue. During their interaction with cancer cells, adipocytes are reprogrammed into cancer-associated adipocytes and secrete adipokines to affect tumor cells. Moreover, the liver is the central metabolic hub. Adipose tissue and the liver cooperatively regulate whole-body energy homeostasis via adipokines. Obesity, the excessive accumulation of adipose tissue due to hyperplasia and hypertrophy, is currently considered a global epidemic and is related to low-grade systemic inflammation characterized by altered adipokine regulation. Obesity-related digestive diseases, including gastroesophageal reflux disease, Barrett's esophagus, esophageal cancer, colon polyps and cancer, non-alcoholic fatty liver disease, viral hepatitis-related diseases, cholelithiasis, gallbladder cancer, cholangiocarcinoma, pancreatic cancer, and diabetes, might cause specific alterations in adipokine profiles. These patterns and associated bases potentially contribute to the identification of prognostic biomarkers and therapeutic approaches for the associated digestive diseases. This review highlights important findings about altered adipokine profiles relevant to digestive diseases, including hepatic, pancreatic, gastrointestinal, and biliary tract diseases, with a perspective on clinical implications and mechanistic explorations.

Effectiveness of Electroacupuncture for Simple Obesity: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

To evaluate the effectiveness of electroacupuncture in the treatment of simple obesity.

METHODS

Randomized clinical trials concerning electroacupuncture as a treatment of simple obesity published prior to October 31, 2019, were searched in the following Chinese and English databases: Chinese National Knowledge Infrastructure (CNKI), WanFang Database, China Science and Technology Journal Database (VIP), Chinese Biomedical Literature Database (CBM), PubMed, Cochrane Library, Web of Science, and Scopus. After data collection and quality evaluation, meta-analysis was performed using RevMan 5.3 software and Stata 15.0 software.

RESULTS

A total of 13 studies involving 937 patients with simple obesity were included in the meta-analysis. Results revealed that the total effective rate (RR = 1.29, 95% CI [1.13, 1.48]; P=0.0002), BMI (MD = -1.82, 95% CI [-2.21, -1.43]; P < 0.000), waist circumference (MD = -2.39, 95% CI [-3.95, -0.84]; P=0.003), hip circumference (MD = 0.31, 95% CI [-2.37, 2.99]; P=0.82), waist-hip ratio (MD = -0.05, 95% CI [-0.07, -0.03]; P < 0.00), and body fat rate (MD = -1.56, 95% CI [-2.35, -0.78]; P=0.0001) in the electroacupuncture group were superior to those in the control group. Analysis of acupoint clustering and correlation using SPSS 24.0 and Clementine 12.0 revealed the highest statistical support for acupoint groups CV12-CV4 and CV12-ST25-CV4, while ST36-CV12-ST25, SP6, and ST40-ST24-SP15-ST37-CV4 were found to be validly clustered acupoints.

CONCLUSION

For treating simple obesity, electroacupuncture is superior to other interventions such as acupuncture, acupoint catgut embedding therapy, and simple lifestyle modification for improvement in body fat rate, waist circumference, and waist-hip ratio, although not hip circumference. Acupoint analysis revealed that ST25, CV12, CV4, SP6, and ST36 can form the basis for electroacupuncture therapy for the treatment of simple obesity.

Oleic acid-induced NOX4 is dependent on ANGPTL4 expression to promote human colorectal cancer metastasis

Background: Colorectal cancer (CRC) progression and related mortality are highly associated with metabolic disorders. However, the molecular mechanism involved in the regulation of hyperlipidemia-associated CRC metastasis remains unclear. This study aimed to investigate the effects of angiopoietin-like 4 (ANGPTL4) on NADPH oxidase 4 (NOX4) expression and reactive oxygen species (ROS) production, which might provide new targets for improving outcomes in patients with hyperlipidemia-associated CRC metastasis.

Methods: The clinical relevance of relationship between NOX4 expression and ANGPTL4 was examined in CRC patients by the Oncomine and TCGA data set. Expressions of NOX4, epithelial-mesenchymal transition (EMT) markers, and gene regulation of NOX4 in free fatty acids (FFAs)-treated CRC cells were determined. The FFAs-triggered metastatic ability of CRC cells under treatments of antioxidants or knockdown of NOX4, ANGPTL4, and MMPs was evaluated in vitro and in vivo. In addition, effects of antioxidants and depletion of metastasis-associated molecules on the correlation between ROS production and FFAs-promoted CRC metastasis were also clarified.

Results: In this study, we found that the induction of NOX4, followed by the increased ROS was essential for oleic acid (OA)-promoted CRC cell metastasis. The depletion of ANGPTL4 significantly inhibited c-Jun-mediated transactivation of NOX4 expression, accompanied with reduced levels of ROS, MMP-1, and MMP-9, resulting in the disruption of OA-promoted CRC cell metastasis. Moreover, knockdown of ANGPTL4, NOX4, MMP-1, and MMP-9 or the treatment of antioxidants dramatically inhibited circulating OA-enhanced tumor cell extravasation and metastatic seeding of tumor cells in lungs, indicating that the ANGPTL4/NOX4 axis was critical for dyslipidemia-associated tumor metastasis.

Conclusion: The coincident expression of NOX4 and ANGPTL4 in CRC tumor specimens provides the insight into the potential therapeutic targets for the treatment of dyslipidemia-associated CRC metastasis.

Life style factors, tumor cell plasticity and cancer stem cells

Cancers are heterogeneous tissues and a layer of heterogeneity is determined by the presence of cells showing stemness traits, known as cancer stem cells (CSCs). Evidence indicates that CSCs are important players in tumor development, progression and relapse. Oncogenic transformation of normal stem cells can give rise to CSCs, but CSCs can also originate from de-differentiation of bulk tumor cells. Thus, factors promoting the increase of normal stem cell pools or stimulating the acquisition of stemness features by tumor cells can have serious consequences on cancer origin and progression. In this review, we will first give an overview of the CSC model of cancer development and we will then discuss the role of life style factors, such as high caloric diet, alcohol drinking and smoking, on the widening of stem cell pools and the induction of CSC features in tumors. Finally, we will discuss some healthy life style factors that can help to prevent cancer.

Effects of high-fat diet and intestinal aryl hydrocarbon receptor deletion on colon carcinogenesis

Consumption of a high-fat diet has been associated with an increased risk of developing colorectal cancer (CRC). However, the effects of the interaction between dietary fat content and the aryl hydrocarbon receptor (AhR) on colorectal carcinogenesis remain unclear. Mainly known for its role in xenobiotic metabolism, AhR has been identified as an important regulator for maintaining intestinal epithelial homeostasis. Although previous research using whole body AhR knockout mice has revealed an increased incidence of colon and cecal tumors, the unique role of AhR activity in intestinal epithelial cells (IECs) and modifying effects of fat content in the diet at different stages of sporadic CRC development are yet to be elucidated. In the present study, we have examined the effects of a high-fat diet on IEC-specific AhR knockout mice in a model of sporadic CRC. Although loss of AhR activity in IECs significantly induced the development of premalignant lesions, in a separate experiment, no significant changes in colon mass incidence were observed. Moreover, consumption of a high-fat diet promoted cell proliferation in crypts at the premalignant colon cancer lesion stage and colon mass multiplicity as well as β-catenin expression and nuclear localization in actively proliferating cells in colon masses. Our data demonstrate the modifying effects of high-fat diet and AhR deletion in IECs on tumor initiation and progression.NEW & NOTEWORTHY Through the use of an intestinal-specific aryl hydrocarbon receptor (AhR) knockout mouse model, this study demonstrates that the expression of AhR in intestinal epithelial cells is required to reduce the formation of premalignant colon cancer lesions. Furthermore, consumption of a high-fat diet and the loss of AhR in intestinal epithelial cells influences the development of colorectal cancer at various stages.

AdipoRon Attenuates Wnt Signaling by Reducing Cholesterol-Dependent Plasma Membrane Rigidity

The increasing prevalence of adult and adolescent obesity and its associated risk of colorectal cancer reinforces the urgent need to elucidate the underlying mechanisms contributing to the promotion of colon cancer in obese individuals. Adiponectin is an adipose tissue-derived adipokine, whose levels are reduced during obesity. Both epidemiological and preclinical data indicate that adiponectin suppresses colon tumorigenesis. We have previously demonstrated that both adiponectin and AdipoRon, a small-molecule adiponectin receptor agonist, suppress colon cancer risk in part by reducing the number of Lgr5+ stem cells in mouse colonic organoids. However, the mechanism by which the adiponectin signaling pathway attenuates colon cancer risk remains to be addressed. Here, we have hypothesized that adiponectin signaling supports colonic stem cell maintenance through modulation of the biophysical properties of the plasma membrane (PM). Specifically, we investigated the effects of adiponectin receptor activation by AdipoRon on the biophysical perturbations linked to the attenuation of Wnt-driven signaling and cell proliferation as determined by LEF luciferase reporter assay and colonic organoid proliferation, respectively. Using physicochemical sensitive dyes, Di-4-ANEPPDHQ and C-laurdan, we demonstrated that AdipoRon decreased the rigidity of the colonic cell PM. The decrease in membrane rigidity was associated with a reduction in PM free cholesterol levels and the intracellular accumulation of free cholesterol in lysosomes. These results suggest that adiponectin signaling plays a role in modulating cellular cholesterol homeostasis, PM biophysical properties, and Wnt-driven signaling. These findings are noteworthy because they may in part explain how obesity drives colon cancer progression.

Effects of high-fat diet-induced adipokines and cytokines on colorectal cancer development

Colorectal cancer (CRC) is the third most common tumor worldwide, and recent epidemiological studies have indicated that obesity contributes to the morbidity and mortality of CRC. Furthermore, obesity‐related adipokines have been shown to be closely related to the incidence of CRC, but the underlying mechanisms are unclear. Here, we investigated the effects of high‐fat diet‐induced adipokines and cytokines on the development of CRC in vitro and in vivo. For the in vivo assays, we divided 2‐week‐old C57BL/6J‐ApcMin/J male mice into three groups: normal‐fat diet (ND), high‐fat and high‐sugar feed (HFHS), and high‐fat and low‐sugar feed (HFLS). After 1 week, all mice were injected with 20 mg·kg⁻¹ 1,2‐dimethylhydrazine once weekly for 10 consecutive weeks. Body weight, liver weight, epididymal fat weight and blood glucose levels were greatly increased in HFHS and HFLS groups compared with the ND group, and the expression levels of some adipokines and cytokines were obviously higher in HFHS or HFLS mice compared with ND mice. For the in vitro assays, HCT116 CRC cells were treated with sera of ND, HFHS or HFLS groups, or serum‐free media as a negative control. We observed that sera derived from HFHS or HFLS mice that contain excess adipokines and cytokines promoted the proliferation, migration and invasion of HCT116 cells compared with the ND sera‐conditioned medium or serum‐free medium group. Therefore, high‐fat diet‐induced adipokines and cytokines may promote the progression of CRC in vivo and in vitro.

We investigated the effects of high‐fat diet‐induced adipokines and cytokines in the development of colorectal cancer. Some adipokines and cytokines were obviously higher in obese mice than in normal mice. Obesity‐induced adipokines and cytokines promoted the proliferation, migration and invasion of HCT116 cells. Therefore, high‐fat diet‐induced adipokines and cytokines may accelerate the progression of colorectal cancer.

Murine Colonic Organoid Culture System and Downstream Assay Applications

Colonic organoids, three-dimensional colonic crypts grown in vitro that show realistic microanatomy, have many potential applications for studying physiology, developmental biology, and pathophysiology of intestinal diseases including inflammatory bowel disease and colorectal cancer. Here, we describe detailed protocols for mouse colonic crypt isolation, organoid culture, and downstream applications. Specific culture strategies including growth factor enriched Matrigel and Wnt and R-spondin conditioned media serve as key factors for enhancing the growth and cost efficiency of colonic organoid cultures.

Evaluating intrinsic and non-intrinsic cancer risk factors

Discriminating the contribution of unmodifiable random intrinsic DNA replication errors ('bad luck') to cancer development from those of other factors is critical for understanding cancer in humans and for directing public resources aimed at reducing the burden of cancer. Here, we review and highlight the evidence that demonstrates cancer causation is multifactorial, and provide several important examples where modification of risk factors has achieved cancer prevention. Furthermore, we stress the need and opportunities to advance understanding of cancer aetiology through integration of interaction effects between risk factors when estimating the contribution of individual and joint factors to cancer burden in a population. We posit that non-intrinsic factors drive most cancer risk, and stress the need for cancer prevention.

Nutritional Regulation of Intestinal Stem Cells

Dietary composition and calorie intake are major determinants of health and disease. Calorie restriction promotes metabolic changes that favor tissue regeneration and is arguably the most successful and best-conserved antiaging intervention. Obesity, in contrast, impairs tissue homeostasis and is a major risk factor for the development of diseases including cancer. Stem cells, the central mediators of tissue regeneration, integrate dietary and energy cues via nutrient-sensing pathways to maintain growth or respond to stress. We discuss emerging data on the effects of diet and nutrient-sensing pathways on intestinal stem cells, as well as their potential application in the development of regenerative and therapeutic interventions.

Omega-3 fatty acids, membrane remodeling and cancer prevention

Proteins are often credited as the macromolecule responsible for performing critical cellular functions, however lipids have recently garnered more attention as our understanding of their role in cell function and human health becomes more apparent. Although cellular membranes are the lipid environment in which many proteins function, it is now apparent that protein and lipid assemblies can be organized to form distinct micro- or nanodomains that facilitate signaling events. Indeed, it is now appreciated that cellular function is partly regulated by the specific spatiotemporal lipid composition of the membrane, down to the nanosecond and nanometer scale. Furthermore, membrane composition is altered during human disease processes such as cancer and obesity. For example, an increased rate of lipid/cholesterol synthesis in cancerous tissues has long been recognized as an important aspect of the rewired metabolism of transformed cells. However, the contribution of lipids/cholesterol to cellular function in disease models is not yet fully understood. Furthermore, an important consideration in regard to human health is that diet is a major modulator of cell membrane composition. This can occur directly through incorporation of membrane substrates, such as fatty acids, e.g., n-3 polyunsaturated fatty acids (n-3 PUFA) and cholesterol. In this review, we describe scenarios in which changes in membrane composition impact human health. Particular focus is placed on the importance of intrinsic lipid/cholesterol biosynthesis and metabolism and extrinsic dietary modification in cancer and its effect on plasma membrane properties.

The mechanisms linking obesity to colon cancer: An overview

Obesity, characterised as a chronic low-grade inflammation is a crucial risk factor for colon cancer. The expansion of the adipose tissue is related to elevated triglyceride and low-density lipoprotein (LDL) levels and hyperinsulinemia, which all are presumed mediators of the tumour development. Obesity is also believed to support carcinogenesis by activating the insulin/IGF-1 pathway. Moreover, obesity increases the level of proinflammatory cytokines (e.g. TNF-α, IL-1, and IL-6) and has a significant impact on selected adipokines. This paper briefly outlines the latest evidence of the linkage between the obesity and colon cancer and discusses its possible implication for the improvement of anticancer prevention and treatment strategies connected with nutrition.

Colonic aberrant crypt formation accompanies an increase of opportunistic pathogenic bacteria in C57BL/6 mice fed a high-fat diet

The increasing worldwide incidence of colon cancer has been linked to obesity and consumption of a high-fat Western diet. To test the hypothesis that a high-fat diet (HFD) promotes colonic aberrant crypt (AC) formation in a manner associated with gut bacterial dysbiosis, we examined the susceptibility to azoxymethane (AOM)-induced colonic AC and microbiome composition in C57/BL6 mice fed a modified AIN93G diet (AIN, 16% fat, energy) or an HFD (45% fat, energy) for 14 weeks. Mice receiving the HFD exhibited increased plasma leptin, body weight, body fat composition and inflammatory cell infiltration in the ileum compared with those in the AIN group. Consistent with the gut inflammatory phenotype, we observed an increase in colonic AC, plasma interleukin-6, tumor necrosis factor-α, monocyte chemoattractant protein-1 and inducible nitric oxide synthase in the ileum of the HFD-AOM group compared with the AIN-AOM group. Although the HFD and AIN groups did not differ in bacterial species number, the HFD and AIN diets resulted in different bacterial community structures in the colon. The abundance of certain short-chain fatty acid (SCFA) producing bacteria (e.g., Barnesiella) and fecal SCFA (e.g., acetic acid) content were lower in the HFD-AOM group compared with the AIN and AIN-AOM groups. Furthermore, we identified a high abundance of Anaeroplasma bacteria, an opportunistic pathogen in the HFD-AOM group. Collectively, we demonstrate that an HFD promotes AC formation concurrent with an increase of opportunistic pathogenic bacteria in the colon of C57BL/6 mice.

Shaping functional gut microbiota using dietary bioactives to reduce colon cancer risk

Colon cancer is a multifactorial disease associated with a variety of lifestyle factors. Alterations in the gut microbiota and the intestinal metabolome are noted during colon carcinogenesis, implicating them as critical contributors or results of the disease process. Diet is a known determinant of health, and as a modifier of the gut microbiota and its metabolism, a critical element in maintenance of intestinal health. This review summarizes recent evidence demonstrating the role and responses of the intestinal microbiota during colon tumorigenesis and the ability of dietary bioactive compounds and probiotics to impact colon health from the intestinal lumen to the epithelium and systemically. We first describe changes to the intestinal microbiome, metabolome, and epithelium associated with colon carcinogenesis. This is followed by a discussion of recent evidence indicating how specific classes of dietary bioactives, prebiotics, or probiotics affect colon carcinogenesis. Lastly, we briefly address the prospects of using multiple 'omics' techniques to integrate the effects of diet, host, and microbiota on colon tumorigenesis with the goal of more fully appreciating the interconnectedness of these systems and thus, how these approaches can be used to advance personalized nutrition strategies and nutrition research.

Dietary Green Pea Protects against DSS-Induced Colitis in Mice Challenged with High-Fat Diet

Obesity is a risk factor for developing inflammatory bowel disease. Pea is unique with its high content of dietary fiber, polyphenolics, and glycoproteins, all of which are known to be health beneficial. We aimed to investigate the impact of green pea (GP) supplementation on the susceptibility of high-fat diet (HFD)-fed mice to dextran sulfate sodium (DSS)-induced colitis. Six-week-old C57BL/6J female mice were fed a 45% HFD or HFD supplemented with 10% GP. After 7-week dietary supplementation, colitis was induced by adding 2.5% DSS in drinking water for 7 days followed by a 7-day recovery period. GP supplementation ameliorated the disease activity index score in HFD-fed mice during the recovery stage, and reduced neutrophil infiltration, mRNA expression of monocyte chemoattractant protein-1 (MCP-1) and inflammatory markers interleukin (IL)-6, cyclooxygenase-2 (COX-2), IL-17, interferon-γ (IFN-γ), and inducible nitric oxide synthase (iNOS) in HFD-fed mice. Further, GP supplementation increased mucin 2 content and mRNA expression of goblet cell differentiation markers including Trefoil factor 3 (Tff3), Krüppel-like factor 4 (Klf4), and SAM pointed domain ETS factor 1 (Spdef1) in HFD-fed mice. In addition, GP ameliorated endoplasmic reticulum (ER) stress as indicated by the reduced expression of Activating transcription factor-6 (ATF-6) protein and its target genes chaperone protein glucose-regulated protein 78 (Grp78), the CCAAT-enhancer-binding protein homologous protein (CHOP), the ER degradation-enhancing α-mannosidase-like 1 protein (Edem1), and the X-box binding protein 1 (Xbp1) in HFD-fed mice. In conclusion, GP supplementation ameliorated the severity of DSS-induced colitis in HFD-fed mice, which was associated with the suppression of inflammation, mucin depletion, and ER stress in the colon.

Dietary Regulation of Adult Stem Cells

PURPOSE OF REVIEW

Dietary intake is a critical regulator of organismal physiology and health. Tissue homeostasis and regeneration are dependent on adult tissue stem cells that self-renew and differentiate into the specialized cell types. As stem cells respond to cues from their environment, dietary signals and nutrients influence tissue biology by altering the function and activity of adult stem cells. In this review, we highlight recent studies that illustrate how diverse diets such as caloric restriction, fasting, high fat diets, and ketogenic diets impact stem cell function and their microenvironments.

RECENT FINDINGS

Caloric restriction generally exerts positive effects on adult stem cells, notably increasing stem cell functionality in the intestine and skeletal muscle as well as increasing hematopoietic stem cell quiescence. Similarly, fasting confers protection of intestinal, hematopoietic, and neuronal stem cells against injury. High fat diets induce intestinal stem cell niche independence and stem-like properties in intestinal progenitors, while high fat diets impair hematopoiesis and neurogenesis.

SUMMARY

Caloric restriction and fasting are generally beneficial to adult stem cell function, while high fat diets impair stem cell function or create opportunities for tumorigenesis. However, the effects of each diet on stem cell biology are complex and vary greatly between tissues. Given the recent interest in developing dietary interventions or mimetics as therapeutics, further studies, including on ketogenic diets, will be essential to understand how adult stem cells respond to diet-induced signals and physiology.

Emerging Concepts Linking Obesity with the Hallmarks of Cancer

There is compelling epidemiological evidence linking obesity to many tumours; however, the molecular mechanisms fuelling this association are not clearly understood. Emerging evidence links changes in the tumour microenvironment with the obese state, and murine and human studies highlight the relevance of adipose stromal cells (ASCs), including immune cells, both at remote fat depots, such as the omentum, as well as in peritumoural tissue. These obesity-associated changes have been implicated in several hallmarks of cancer, including the chronic inflammatory state and associated cell signalling, epithelial-to-mesenchymal transition (EMT), tumour-related fibrosis, angiogenesis, and genomic instability. Here, we present a summary of developments over the past 5 years, with particular focus on the tumour microenvironment in the obese state.

Rapidly cycling Lgr5+ stem cells are exquisitely sensitive to extrinsic dietary factors that modulate colon cancer risk

The majority of colon tumors are driven by aberrant Wnt signaling in intestinal stem cells, which mediates an efficient route toward initiating intestinal cancer. Natural lipophilic polyphenols and long-chain polyunsaturated fatty acids (PUFAs) generally suppress Wnt- and NF-κB- (nuclear factor-κ light-chain enhancer of activated B-cell) related pathways. However, the effects of these extrinsic agents on colonic leucine-rich repeat-containing G-protein-coupled receptor 5-positive (Lgr5⁺) stem cells, the cells of origin of colon cancer, have not been documented to date. Therefore, we examined the effect of n-3 PUFA and polyphenol (curcumin) combination on Lgr5⁺ stem cells during tumor initiation and progression in the colon compared with an n-6 PUFA-enriched control diet. Lgr5-EGFP-IRES-^creERT2 knock-in mice were fed diets containing n-6 PUFA (control), n-3 PUFA, n-6 PUFA+curcumin or n-3 PUFA+curcumin for 3 weeks, followed by 6 azoxymethane (AOM) injections, and terminated 17 weeks after the last injection. To further elucidate the effects of the dietary bioactives at the tumor initiation stage, Lgr5⁺ stem cells were also assessed at 12 and 24 h post AOM injection. Only n-3 PUFA+curcumin feeding reduced nuclear β-catenin in aberrant crypt foci (by threefold) compared with control at the progression time point. n-3 PUFA+curcumin synergistically increased targeted apoptosis in DNA-damaged Lgr5⁺ stem cells by 4.5-fold compared with control at 12 h and maximally reduced damaged Lgr5⁺ stem cells at 24 h, down to the level observed in saline-treated mice. Finally, RNAseq analysis indicated that p53 signaling in Lgr5⁺ stem cells from mice exposed to AOM was uniquely upregulated only following n-3 PUFA+curcumin cotreatment. These novel findings demonstrate that Lgr5⁺ stem cells are uniquely responsive to external dietary cues following the induction of DNA damage, providing a therapeutic strategy for eliminating damaged Lgr5⁺ stem cells to reduce colon cancer initiation.

Weight loss following diet-induced obesity does not alter colon tumorigenesis in the AOM mouse model

Obesity presents a significant public health concern given its association with increased cancer incidence, unfavorable prognosis, and metastasis. However, there is very little literature on the effects of weight loss, following obesity, on risk for colon cancer or liver cancer. Therefore, we sought to study whether intentional weight loss through diet manipulation was capable of mitigating colon and liver cancer in mice. We fed mice with a high-fat diet (HFD) comprised of 47% carbohydrates, 40% fat, and 13% protein for 20 wk to mimic human obesity. Subsequently, azoxymethane (AOM) was used to promote colon and liver carcinogenesis. A subset of obese mice was then switched to a low-fat diet (LFD) containing 67.5% carbohydrate, 12.2% fat, and 20% protein to promote intentional weight loss. Body weight loss and excess fat reduction did not protect mice from colon cancer progression and liver dysplastic lesion in the AOM-chemical-cancer model even though these mice had improved blood glucose and leptin levels. Intentional weight loss in AOM-treated mice actually produced histological changes that resemble dysplastic alterations in the liver and presented a higher percentage of F4/80⁺CD206⁺ macrophages and activated T cells (CD4⁺CD69⁺) in the spleen and lymph nodes, respectively. In addition, the liver of AOM-treated mice exposed to a HFD during the entire period of the experiment exhibited a marked increase in proliferation and pNF-κB activation. Altogether, these data suggest that intentional weight loss following chemical-induced carcinogenesis does not affect colon tumorigenesis but may in fact negatively impact liver repair mechanisms.

Obesity and hypertension

The imbalance between energy intake and expenditure is the main cause of excessive overweight and obesity. Technically, obesity is defined as the abnormal accumulation of ≥20% of body fat, over the individual's ideal body weight. The latter constitutes the maximal healthful value for an individual that is calculated based chiefly on the height, age, build and degree of muscular development. However, obesity is diagnosed by measuring the weight in relation to the height of an individual, thereby determining or calculating the body mass index. The National Institutes of Health have defined 30 kg/m² as the limit over which an individual is qualified as obese. Accordingly, the prevalence of obesity in on the increase in children and adults worldwide, despite World Health Organization warnings. The growth of obesity and the scale of associated health issues induce serious consequences for individuals and governmental health systems. Excessive overweight remains among the most neglected public health issues worldwide, while obesity is associated with increasing risks of disability, illness and death. Cardiovascular diseases, the leading cause of mortality worldwide, particularly hypertension and diabetes, are the main illnesses associated with obesity. Nevertheless, the mechanisms underlying obesity-associated hypertension or other associated metabolic diseases remains to be adequately investigated. In the present review, we addressed the association between obesity and cardiovascular disease, particularly the biological mechanisms linking obesity and hypertension.