Obesity and cancer: a gut microbial connection

NON-ALCOHOLIC FATTY LIVER DISEASE AND EXTRA-HEPATIC CANCER: A NARRATIVE REVIEW

BACKGROUND

Recently, significant associations between non-alcoholic fatty liver disease (NAFLD) and extra-hepatic cancer have been reported.

OBJECTIVE

To carry out a comprehensive review of the current evidence in the literature on the association between NAFLD and extra-hepatic cancer.

METHODS

A narrative literature review was performed through an online search for the MeSH terms "fatty liver" and "cancer" in MEDLINE (via PubMed) and LILACS (via BVS). Original studies that described the impact of NAFLD on different types of extra-hepatic malignancies were included.

RESULTS

After careful analysis, nine prospective cohort studies, one retrospective cohort study, three case-control studies, and three cross-sectional studies were selected.

CONCLUSION

There is consistent evidence on the association between NAFLD and extra-hepatic carcinogenesis, especially in relation to colorectal, gastric, pancreatic, breast, prostate, and bladder cancers.

Role of probiotics in managing various human diseases, from oral pathology to cancer and gastrointestinal diseases

The imbalance of microbial composition and diversity in favor of pathogenic microorganisms combined with a loss of beneficial gut microbiota taxa results from factors such as age, diet, antimicrobial administration for different infections, other underlying medical conditions, etc. Probiotics are known for their capacity to improve health by stimulating the indigenous gut microbiota, enhancing host immunity resistance to infection, helping digestion, and carrying out various other functions. Concurrently, the metabolites produced by these microorganisms, termed postbiotics, which include compounds like bacteriocins, lactic acid, and hydrogen peroxide, contribute to inhibiting a wide range of pathogenic bacteria. This review presents an update on using probiotics in managing and treating various human diseases, including complications that may emerge during or after a COVID-19 infection.

Obesity, cancer, and response to immune checkpoint inhibitors: Could the gut microbiota be the mechanistic link?

Immune checkpoint inhibitors (ICI) have deeply changed the therapeutic management of a broad spectrum of solid tumors. Recent observations showed that obese patients receiving ICIs might have better outcomes than those with normal weight, while obesity was historically associated with a worse prognosis in cancer patients. Of note, obesity is associated with alterations in the gut microbiome profile, which interacts with immune and inflammatory pathways, both at the systemic and intratumoral levels. As the influence of the gut microbiota on the response to ICI has been repeatedly reported, a specific gut microbiome profile in obese cancer patients may be involved in their better response to ICI. This review summarizes recent data on the interactions between obesity, gut microbiota, and ICIs. In addition, we highlight possible pathophysiological mechanisms supporting the hypothesis that gut microbiota could be one of the links between obesity and poor response to ICIs.

Anthocyanin actions at the gastrointestinal tract: Relevance to their health benefits

Anthocyanins (AC) are flavonoids abundant in the human diet, which consumption has been associated to several health benefits, including the mitigation of cardiovascular disease, type 2 diabetes, non-alcoholic fatty liver disease, and neurological disorders. It is widely recognized that the gastrointestinal (GI) tract is not only central for food digestion but actively participates in the regulation of whole body physiology. Given that AC, and their metabolites reach high concentrations in the intestinal lumen after food consumption, their biological actions at the GI tract can in part explain their proposed local and systemic health benefits. In terms of mechanisms of action, AC have been found to: i) inhibit GI luminal enzymes that participate in the absorption of lipids and carbohydrates; ii) preserve intestinal barrier integrity and prevent endotoxemia, inflammation and oxidative stress; iii) sustain goblet cell number, immunological functions, and mucus production; iv) promote a healthy microbiota; v) be metabolized by the microbiota to AC metabolites which will be absorbed and have systemic effects; and vi) modulate the metabolism of GI-generated hormones. This review will summarize and discuss the latest information on AC actions at the GI tract and their relationship to overall health benefits.

Mechanistic insights into zearalenone-accelerated colorectal cancer in mice using integrative multi-omics approaches

Zearalenone (ZEA), a secondary metabolite of Fusarium fungi found in cereal-based foods, promotes the growth of colon, breast, and prostate cancer cells in vitro. However, the lack of animal studies hinders a deeper mechanistic understanding of the cancer-promoting effects of ZEA. This study aimed to determine the effect of ZEA on colon cancer progression and its underlying mechanisms. Through integrative analyses of transcriptomics, metabolomics, metagenomics, and host phenotypes, we investigated the impact of a 4-week ZEA intervention on colorectal cancer in xenograft mice. Our results showed a twofold increase in tumor weight with the 4-week ZEA intervention. ZEA exposure significantly increased the mRNA and protein levels of BEST4, DGKB, and Ki67 and the phosphorylation levels of ERK1/2 and AKT. Serum metabolomic analysis revealed that the levels of amino acids, including histidine, arginine, citrulline, and glycine, decreased significantly in the ZEA group. Furthermore, ZEA lowered the alpha diversity of the gut microbiota and reduced the abundance of nine genera, including Tuzzerella and Rikenella. Further association analysis indicated that Tuzzerella was negatively associated with the expression of BEST4 and DGKB genes, serum uric acid levels, and tumor weight. Additionally, circulatory hippuric acid levels positively correlated with tumor weight and the expression of oncogenic genes, including ROBO3, JAK3, and BEST4. Altogether, our results indicated that ZEA promotes colon cancer progression by enhancing the BEST4/AKT/ERK1/2 pathway, lowering circulatory amino acid concentrations, altering gut microbiota composition, and suppressing short chain fatty acids production.

Intratumor Microbiome in Neuroendocrine Neoplasms: A New Partner of Tumor Microenvironment? A Pilot Study

Neuroendocrine neoplasms (NENs) are rare neoplasms with heterogeneous clinical behavior. Alteration in human microbiota was reported in association with carcinogenesis in different solid tumors. However, few studies addressed the role of microbiota in NEN. We here aimed at evaluating the presence of bacterial infiltration in neuroendocrine tumoral tissue. To assess the presence of bacteria, 20 specimens from pancreatic NEN (pan-NEN) and 20 from intestinal NEN (I-NEN) were evaluated through Fluorescent In situ Hybridization and confocal microscopy. Demographic data, pre-operative investigations, operative findings, pathological diagnosis, follow-up, and survival data were evaluated. Among I-NEN, bacteria were detected in 15/20 (75%) specimens, with high variability in microbial distribution. In eight patients, a high infiltration of microorganisms was observed. Among pan-NEN, 18/20 (90%) showed microorganisms’ infiltration, with a homogeneous microbial distribution. Bacterial localization in pan-NEN was observed in the proximity of blood vessels. A higher bacterial infiltration in the tumoral specimen as compared with non-tumoral tissue was reported in 10/20 pan-NEN (50%). No significant differences were observed in mean bacterial count according to age, sex, ki67%, site, tumor stage. Mean bacterial count did not result to be a predictor of disease-specific survival. This preliminary study demonstrates the presence of a significant microbiota in the NEN microenvironment. Further research is needed to investigate the potential etiological or clinical role of microbiota in NEN.

Adherence to the Danish food-based dietary guidelines and risk of colorectal cancer: a cohort study

BACKGROUND

National dietary guidelines contribute to primary prevention of a wide range of diseases. Yet, the importance of adhering to the Danish dietary guidelines for colorectal cancer prevention is unclear.

METHODS

We used the Danish Diet, Cancer and Health cohort (n = 55,744) to investigate adherence to the Danish dietary guidelines and the risk of colorectal cancer. Cox proportional hazard models were used to estimate hazard ratios (HRs) for colorectal cancer and subtypes across the Danish Dietary Guidelines Index score (ranging 0-6 points, 6 being the greatest adherence). Effect modification by BMI was explored on multiplicative and additive scales.

RESULTS

During a median follow-up of 18.9 years, 1030 men and 849 women developed colorectal cancer. Higher index scores were associated with a lower risk of colorectal cancer (HR 0.66; 95% confidence interval (CI) 0.53, 0.84, highest (≥5) versus lowest index score (<3 points) group). Similar inverse associations were observed between index scores and colon cancer. The risk difference was -0.8% (95% CI: -1.6, -0.1) among the overweight/obese group and 0.1% (95% CI: -0.7, 1.0) in the normal weight group for high compared to low adherence.

CONCLUSION

Adherence to the Danish Dietary Guidelines was associated with a lower risk of colorectal cancer, particularly among people with overweight/obesity.

Expected and paradoxical effects of obesity on cancer treatment response

Obesity, whose prevalence is pandemic and continuing to increase, is a major preventable and modifiable risk factor for diabetes and cardiovascular diseases, as well as for cancer. Furthermore, epidemiological studies have shown that obesity is a negative independent prognostic factor for several oncological outcomes, including overall and cancer-specific survival, for several site-specific cancers as well as for all cancers combined. Yet, a recently growing body of evidence suggests that sometimes overweight and obesity may associate with better outcomes, and that immunotherapy may show improved response among obese patients compared with patients with a normal weight. The so-called 'obesity paradox' has been reported in several advanced cancer as well as in other diseases, albeit the mechanisms behind this unexpected relationship are still not clear. Aim of this review is to explore the expected as well as the paradoxical relationship between obesity and cancer prognosis, with a particular emphasis on the effects of cancer therapies in obese people.

Nutrition and cellular senescence in obesity-related disorders

Adequate nutrition is vital for immune homeostasis. However, the incidence of obesity is increasing worldwide due to the adoption of the Western diet and a sedentary lifestyle. Obesity is associated with chronic inflammation which alters the function of adipose tissue, liver, pancreas, and the nervous system. Inflammation is related to cellular senescence, distinguished by irreversible cell cycle arrest. Senescent cells secrete the senescence-associated secretory phenotype (SASP) which contains pro-inflammatory factors. Targeting processes in senescence might have a salutary approach to obesity. The present review highlights the impact of an unhealthy diet on tissues affected by obesity, and the mechanisms that promote the consequent inflammation and senescence.

Association between body mass index and colorectal adenomas: Findings from a case-control study in Vietnam

Colorectal cancer is a leading cancer worldwide and in Vietnam. Adenomas (adenomatous polyps) is an important precursor of colorectal cancer. There is currently no study to determine the modifiable risk factors for colorectal adenomas, including body mass index (BMI) in Vietnam. We conducted an individually matched case-control study of 1149 colorectal adenomas and 1145 controls in a large-scale colorectal screening program involving 103 542 individuals aged 40-75 years old in Hanoi, Vietnam. Conditional logistic regression was used to evaluate the association between BMI and colorectal adenomas prevalence, after controlling for potential confounders. Overall, comparing to normal weight (ie, 18.5-22.9 kg/m² ), underweight (ie, BMI < 18.5) was associated with a non-statistically significant increased prevalence of colorectal adenomas (odd ratio [OR] = 1.29 and 95% confident interval [CI]: 0.88-1.87). This association became significant among male (OR = 1.98, 95% CI: 1.20-3.27), male who were ever smokers (OR = 2.59, 95% CI: 1.33-5.03), nonregular exercise (OR = 2.44, 95% CI: 1.26-4.73) and individuals with cardiometabolic disorders (OR = 3.46, 95% CI: 1.19-10.00). The association between underweight and colorectal adenomas did not vary by smoking status, drinking status, family history of cancer, adenomas types or cardiometabolic disorders. No association was observed among obese individuals (BMI ≥ 25). In the population with low prevalence of obesity, we found that the association between BMI and colorectal adenomas followed a reversed J-shape that underweight was associated with increased prevalence. Further studies are, therefore, warranted to replicate our results and to investigate the biologic mechanism the effect of underweight on colorectal adenomas prevalence.

Gut Microbiota and Gynecological Cancers: A Summary of Pathogenetic Mechanisms and Future Directions

Over the past 20 years, important relationships between the microbiota and human health have emerged. A link between alterations of microbiota composition (dysbiosis) and cancer development has been recently demonstrated. In particular, the composition and the oncogenic role of intestinal bacterial flora has been extensively investigated in preclinical and clinical studies focusing on gastrointestinal tumors. Overall, the development of gastrointestinal tumors is favored by dysbiosis as it leads to depletion of antitumor substances (e.g., short-chain fatty acids) produced by healthy microbiota. Moreover, dysbiosis leads to alterations of the gut barrier, promotes a chronic inflammatory status through activation of toll-like receptors, and causes metabolic and hormonal dysregulations. However, the effects of these imbalances are not limited to the gastrointestinal tract and they can influence gynecological tumor carcinogenesis as well. The purpose of this Review is to provide a synthetic update about the mechanisms of interaction between gut microbiota and the female reproductive tract favoring the development of neoplasms. Furthermore, novel therapeutic approaches based on the modulation of microbiota and their role in gynecological oncology are discussed.

Visceral Obesity, Metabolic Syndrome, and Esophageal Adenocarcinoma

Esophageal adenocarcinoma (EAC) represents an exemplar of obesity-associated carcinogenesis, with a progressive increase in EAC risk with increased body mass index. In this context, there is increased focus on visceral adipose tissue and associated metabolic dysfunction, including hypertension, diabetes mellitus and hyperlipidemia, or combinations of these in the metabolic syndrome. Visceral obesity (VO) may promote EAC via both directly impacting on gastro-esophageal reflux disease and Barrett's esophagus, as well as via reflux-independent effects, involving adipokines, growth factors, insulin resistance, and the microbiome. In this review these pathways are explored, including the impact of VO on the tumor microenvironment, and on cancer outcomes. The current evidence-based literature regarding the role of dietary, lifestyle, pharmacologic and surgical interventions to modulate the risk of EAC is explored.

Bi-Directional interactions between microbiota and ionizing radiation in head and neck and pelvic radiotherapy - clinical relevance

Purpose: Rapid developments in high throughput screening technology for the detection and identification of the human microbiota have helped in understanding its influence on human health and disease. In the recent past, several seminal studies have demonstrated the influence of microbiota on outcomes of therapy-associated radiation exposure. In this review, we highlight the concepts related to the mechanisms by which radiation alters the microbiota composition linked with radiation-associated toxicity in head and neck and pelvic regions. We further discuss specific microbial changes that can be employed as a biomarker for radiation and tumor response.Conclusion: Knowledge of the influence of microbiota in radiation response and advances in microbiota manipulation techniques would help to design personalized treatment augmenting the efficacy of radiotherapy.

My career development with Ames test: A personal recollection

I first became acquainted with the Ames test at the very beginning of my career in 1978, when my task at the National Institute of Health Sciences (Tokyo) was to screen for mutagenicity of food additives used in Japan, using the Ames test. I also used this test to research the metabolic activation mechanisms of chemical carcinogens, in particular, the analgesic drug, phenacetin. This chemical was not mutagenic in Salmonella typhimurium TA100 with standard 9000 × g supernatant of liver homogenates (S9) from rat but was mutagenic with hamster S9. It was revealed that hamster S9 had much higher deacetylation activities than rat S9, which accounts for the species difference. Then, my work was focused on molecular biology. We cloned the genes encoding nitroreductase and acetyltransferase in Salmonella typhimurium TA1538. Plasmids carrying these genes made strain TA98 more sensitive to mutagenic nitroarenes and aromatic amines. Because of their high sensitivity, the resulting strains such as YG1021 and YG1024 are widely used to monitor mutagenic nitroarenes and aromatic amines in complex mixtures. Later, we disrupted the genes encoding DNA polymerases in TA1538 and classified chemical mutagens into four classes depending on their use of different DNA polymerases. I was also involved in the generation of gpt delta transgenic rodent gene mutation assays, which examine the results of the Ames test in vivo. I have unintentionally developed my career under the influence of Dr. Ames and I would like to acknowledge his remarkable achievements in the field of environmental mutagenesis and carcinogenesis.

(-)-Epicatechin and NADPH oxidase inhibitors prevent bile acid-induced Caco-2 monolayer permeabilization through ERK1/2 modulation

Secondary bile acids promote gastrointestinal (GI) tract permeabilization both in vivo and in vitro. Consumption of high fat diets increases bile acid levels in the GI tract which can contribute to intestinal permeabilization and consequent local and systemic inflammation. This work investigated the mechanisms involved in bile acid (deoxycholic acid (DCA))-induced intestinal epithelial cell monolayer permeabilization and the preventive capacity of (-)-epicatechin (EC). While EC prevented high fat diet-induced intestinal permeabilization in mice, it did not mitigate the associated increase in fecal/cecal total and individual bile acids. In vitro, using differentiated Caco-2 cells as a model of epithelial barrier, EC and other NADPH oxidase inhibitors (VAS-2870 and apocynin) mitigated DCA-induced Caco-2 monolayer permeabilization. While EC inhibited DCA-mediated increase in cell oxidants, it did not prevent DCA-induced mitochondrial oxidant production. Prevention of DCA-induced ERK1/2 activation with EC, VAS-2870, apocynin and the MEK inhibitor U0126, also prevented monolayer permeabilization, stressing the key involvement of ERK1/2 in this process and its redox regulation. Downstream, DCA promoted myosin light chain (MLC) phosphorylation which was related to MLC phosphatase (MLCP) inhibition by ERK1/2. DCA also decreased the levels of the tight junction proteins ZO-1 and occludin, which can be related to MMP-2 activation and consequent ZO-1 and occludin degradation. Both events were prevented by EC, NADPH oxidase and ERK1/2 inhibitors. Thus, DCA-induced Caco-2 monolayer permeabilization occurs mainly secondary to a redox-regulated ERK1/2 activation and downstream disruption of TJ structure and dynamic. EC's capacity to mitigate in vivo the gastrointestinal permeabilization caused by consumption of high-fat diets can be in part related to its capacity to inhibit bile-induced NADPH oxidase and ERK1/2 activation.

Mitochondrial-related gene associated to obesity can be modulated by in utero hyperglycemic environment

We investigated whether mitochondrial-related genes and proteins are modulated by hyperglycemia promoted by gestational diabetes (GDM), thereby increasing neonate obesity predisposition. 19 healthy pregnant women, 16 pregnant women with GDM and their respective neonates were enrolled. Additionally, 19 obese and 19 eutrophic adults were recruited as a reference population. Umbilical cord, peripheral blood and placental (villous and decidua) tissues were collected to evaluate SOD2, PPAR-α and PPARGC-1β and their respective protein expressions. Data from the reference population confirmed that the three genes and proteins were overexpressed in blood cells of obese compared to eutrophic subjects. Only SOD2 was found upregulated in placental villous (fetal side) tissue of GDM women. Therefore, our findings showed an interaction between the hyperglycemic environment and SOD2 modulation, but also indicated that none of the three genes is useful as potential biomarkers for obesity development.

Gut microbial dysbiosis associates hepatocellular carcinoma via the gut-liver axis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies in the world. Gut microbiota has been demonstrated to play a critical role in liver inflammation, chronic fibrosis, liver cirrhosis, and HCC development through the gut-liver axis.

DATA SOURCES

Recently there have been several innovative studies investigating gut microbial dysbiosis-mediated enhancement of HCC through the gut-liver axis. Literatures from January 1998 to January 2018 were searched in the PubMed database using the keywords "gut microbiota" and "hepatocellular carcinoma" or "liver cancer", and the results of experimental and clinical studies were analyzed.

RESULTS

Gut microbial dysbiosis accompanies the progression of alcoholic liver disease, non-alcoholic fatty liver disease and liver cirrhosis, and promotes HCC progression in an experimental mouse model. The immune system and key factors such as Toll-like receptor 4 are involved in the process. There is evidence for gut microbial dysbiosis in hepatitis virus-related HCC patients.

CONCLUSIONS

Gut microbial dysbiosis is closely associated with hepatic inflammation disease and HCC through the gut-liver axis. With the enhanced understanding of the interactions between gut microbiota and liver through the gut-liver axis, new treatment strategies for HCC are being developed.

Environmental Factors, Gut Microbiota, and Colorectal Cancer Prevention

The substantial burden of colorectal cancer and increasing trend in young adults highlight the importance of lifestyle modification as a complement to screening for colorectal cancer prevention. Several dietary and lifestyle factors have been implicated in the development of colorectal cancer, possibly through the intricate metabolic and inflammatory mechanisms. Likewise, as a key metabolic and immune regulator, the gut microbiota has been recognized to play an important role in colorectal tumorigenesis. Increasing data support that environmental factors are crucial determinants for the gut microbial composition and function, whose alterations induce changes in the host gene expression, metabolic regulation, and local and systemic immune response, thereby influencing cancer development. Here, we review the epidemiologic and mechanistic evidence regarding the links between diet and lifestyle and the gut microbiota in the development of colorectal cancer. We focus on factors for which substantial data support their importance for colorectal cancer and their potential role in the gut microbiota, including overweight and obesity, physical activity, dietary patterns, fiber, red and processed meat, marine omega-3 fatty acid, alcohol, and smoking. We also briefly describe other colorectal cancer-preventive factors for which the links with the gut microbiota have been suggested but remain to be mechanistically characterized, including vitamin D status, dairy consumption, and metformin use. Given limitations in available evidence, we highlight the need for further investigations in the relationship between environmental factors, gut microbiota, and colorectal cancer, which may lead to development and clinical translation of potential microbiota-based strategies for cancer prevention.

BCL2 and miR-181a transcriptional alterations in umbilical-cord blood cells can be putative biomarkers for obesity

Several findings suggest that in utero stressor stimuli can alter fetal development by promoting transcriptional changes, and predisposing the neonate to diseases later in life. This study aimed to investigate whether a hyperglycemic environment in pregnant women with gestational diabetes mellitus (GDM) is able to cause fetal genetic alterations and predispose neonates to obesity. Transcriptional alteration of SIRT1, TP53 and BCL2 genes, miR-181a (a SIRT1 or BCL2 regulator) and telomere length were evaluated in placental and umbilical-cord blood cells. Healthy (HP; n = 20) and GDM (n = 20) pregnant women and their respective neonates were included in the study. Additionally, obese (n = 20) and eutrophic (n = 20) adults also participated as reference populations. Gene expression data showed down-regulation of BCL2 in umbilical-cord and peripheral blood cells from GDM neonates and obese adults, respectively. The miR-181a was down-regulated only in umbilical-cord blood cells of GDM neonates. Telomere length presented no significant difference. In conclusion, our study demonstrated that the GDM hyperglycemic intrauterine environment promotes transcriptional alterations in BCL2 and miR-181a in neonate umbilical-cord blood cells. Furthermore, both GDM neonates and obese subjects share the same transcriptional alteration in BCL2. Considering the relationship between obesity development and the functions regulated by these two genes, BCL2 and miR-181a could be adopted as potential biomarkers for childhood obesity. However, further study designs are recommended to confirm this hypothesis.

Microbiota effects on cancer: from risks to therapies

Gut microbiota, a group of 1014 bacteria, eukaryotes and virus living in gastrointestinal tract, is crucial for many physiological processes in particular plays an important role in inflammatory and immune reactions. Several internal and external factors can influence this population, and shifts in their composition, have been demonstrated to contribute and affect different diseases. During dysbiosis several bacteria related to inflammation, one of the most necessary factors in carcinogenesis; it has been shown that some bacterial strains through deregulation of different signals/pathways may affect tumor development through the production of many factors. Gut microbiota might be considered as a holistic hub point for cancer development: direct and indirect involvements have been studying in several neoplasms such as colon rectal cancer, hepatocellular carcinoma and breast cancer. This review discuss over the evidence of crosstalk between gut microbiota and cancer, its ability to modulate chemotherapy, radiotherapy and immunotherapy, and the possibility that the intestinal microbial is a new target for therapeutic approaches to improve the prognosis and quality of life of cancer patients.

Cellular senescence in gastrointestinal diseases: from pathogenesis to therapeutics

Senescence is a durable cell cycle arrest that can be induced in response to various stress factors, such as telomere erosion, DNA damage or the aberrant activation of oncogenes. In addition to its well-established role as a stress response programme, research has revealed important physiological roles of senescence in nondisease settings, such as embryonic development, wound healing, tissue repair and ageing. Senescent cells secrete various cytokines, chemokines, matrix remodelling proteases and growth factors, a phenotype collectively referred to as the senescence-associated secretory phenotype. These factors evoke immune responses that, depending on the pathophysiological context, can either prevent or even fuel disease and tumorigenesis. Remarkably, even the gut microbiota can influence senescence in various organs. In this Review, we provide an introduction to cellular senescence, addressed particularly to gastroenterologists and hepatologists, and discuss the implications of senescence for the pathogenesis of malignant and nonmalignant gastrointestinal and hepatobiliary diseases. We conclude with an outlook on how modulation of cellular senescence might be used for therapeutic purposes.

Rethinking the bile acid/gut microbiome axis in cancer

Dietary factors, probiotic agents, aging and antibiotics/medicines impact on gut microbiome composition leading to disturbances in localised microbial populations. The impact can be profound and underlies a plethora of human disorders, including the focus of this review; cancer. Compromised microbiome populations can alter bile acid signalling and produce distinct pathophysiological bile acid profiles. These in turn have been associated with cancer development and progression. Exposure to high levels of bile acids, combined with localised molecular/genome instability leads to the acquisition of bile mediated neoplastic alterations, generating apoptotic resistant proliferation phenotypes. However, in recent years, several studies have emerged advocating the therapeutic benefits of bile acid signalling in suppressing molecular and phenotypic hallmarks of cancer progression. These studies suggest that in some instances, bile acids may reduce cancer phenotypic effects, thereby limiting metastatic potential. In this review, we contextualise the current state of the art to propose that the bile acid/gut microbiome axis can influence cancer progression to the extent that classical in vitro cancer hallmarks of malignancy (cell invasion, cell migration, clonogenicity, and cell adhesion) are significantly reduced. We readily acknowledge the existence of a bile acid/gut microbiome axis in cancer initiation, however, in light of recent advances, we focus exclusively on the role of bile acids as potentially beneficial molecules in suppressing cancer progression. Finally, we theorise that suppressing aggressive malignant phenotypes through bile acid/gut microbiome axis modulation could uncover new and innovative disease management strategies for managing cancers in vulnerable cohorts.

Diet, Gut Microbiota, and Colorectal Cancer Prevention: A Review of Potential Mechanisms and Promising Targets for Future Research

Diet plays an important role in the development of colorectal cancer. Emerging data have implicated the gut microbiota in colorectal cancer. Diet is a major determinant for the gut microbial structure and function. Therefore, it has been hypothesized that alterations in gut microbes and their metabolites may contribute to the influence of diet on the development of colorectal cancer. We review several major dietary factors that have been linked to gut microbiota and colorectal cancer, including major dietary patterns, fiber, red meat and sulfur, and obesity. Most of the epidemiologic evidence derives from cross-sectional or short-term, highly controlled feeding studies that are limited in size. Therefore, high-quality large-scale prospective studies with dietary data collected over the life course and comprehensive gut microbial composition and function assessed well prior to neoplastic occurrence are critically needed to identify microbiome-based interventions that may complement or optimize current diet-based strategies for colorectal cancer prevention and management.

Microbes and Cancer

Commensal microorganisms (the microbiota) live on all the surface barriers of our body and are particularly abundant and diverse in the distal gut. The microbiota and its larger host represent a metaorganism in which the cross talk between microbes and host cells is necessary for health, survival, and regulation of physiological functions locally, at the barrier level, and systemically. The ancestral molecular and cellular mechanisms stemming from the earliest interactions between prokaryotes and eukaryotes have evolved to mediate microbe-dependent host physiology and tissue homeostasis, including innate and adaptive resistance to infections and tissue repair. Mostly because of its effects on metabolism, cellular proliferation, inflammation, and immunity, the microbiota regulates cancer at the level of predisposing conditions, initiation, genetic instability, susceptibility to host immune response, progression, comorbidity, and response to therapy. Here, we review the mechanisms underlying the interaction of the microbiota with cancer and the evidence suggesting that the microbiota could be targeted to improve therapy while attenuating adverse reactions.

Non-alcoholic fatty liver disease and colorectal cancer

As a significant cause of cancer death worldwide, colorectal cancer (CRC) is still one of the most common cancers in the world. The most efficient strategies to reduce CRC incidence include identifying risk factors for CRC and performing a preventive colonoscopy in high-risk populations. Some well-established risk factors for CRC development include hereditary syndromes and inflammatory bowel disease. Of note, in recent years, attention has been given to new evidence indicating that more than 75%-95% of CRC occurs in individuals with little or no genetic risk. For these individuals, the risk for CRC is associated with their lifestyle and dietary factors, including central obesity, overweight and physical inactivity. Recently, evidence demonstrated a connection between non-alcoholic fatty liver disease (NAFLD) and CRC. Insulin resistance and metabolic syndrome (MetS) are common risks that NAFLD and colorectal neoplasms share. The incidence of NAFLD is increasing in parallel with an increasing prevalence of MetS and obesity. Consequently, the question arises: will the incidence of CRC increase together with this dramatic increase in obesity, MetS and ultimately NAFLD prevalence? Recent studies of adenomatous polyps, CRC and NAFLD are discussed in this manuscript.

Association between body mass index and osteoporosis in women from northwestern Rio Grande do Sul

OBJECTIVE

To investigate the association between body mass index (BMI) and bone mineral density (BMD) in postmenopausal women.

METHODS

Observational study with postmenopausal women who underwent bone densitometry in Palmeira das Missões - RS. Sociodemographic data, risk for osteoporosis and food intake were assessed through a specific form. BMI was calculated according to WHO criteria. The assessment of BMD was performed by dual-energy X-ray absorptiometry (DXA) and classified according to WHO. Statistical analysis was performed using prevalence ratios (PR) and their respective 95% confidence intervals for the factors studied. Variables associated with p<0.20 with the different outcomes (osteopenia and osteoporosis) were included in a Poisson regression model with robust variance to adjust for potential confounding factors. A 5% significance level was considered.

RESULTS

393 postmenopausal women with a mean age of 59.6±8.2 years participated. After the adjustments, the normal weight women had 1.2 times the prevalence of osteopenia of obese women (PR=1.2; CI 95% 1.3-1.5). Considering osteoporosis, the PR of euthophic women was twice the PR of obese women (PR=2; CI 95% 1.4-2.9) and was 1.7 times greater for overweight group compared to obese category (PR=1.7; CI 95% 1.2-2.5).

CONCLUSION

Obese women had lower prevalence of osteopenia compared with normal weight subjects and also with lower prevalence of osteoporosis as compared to normal- and overweight women.

Physiology, pathophysiology and therapeutic implications of enteroendocrine control of food intake

With the increasing prevalence of obesity and its associated comorbidities, strides to improve treatment strategies have enhanced our understanding of the function of the gut in the regulation of food intake. The most successful intervention for obesity to date, bariatric surgery effectively manipulates enteroendocrine physiology to enhance satiety and reduce hunger. Areas covered: In the present article, we provide a detailed overview of the physiology of enteroendocrine control of food intake, and discuss its pathophysiologic correlates and therapeutic implications in both obesity and gastrointestinal disease. Expert commentary: Ongoing research in the field of nutrient sensing by L-cells, as well as understanding the role of the microbiome and bile acid signaling may facilitate the development of novel strategies to combat the rising population health threat associated with obesity. Further refinement of post-prandial satiety gut hormone based therapies, including the development of chimeric peptides exploiting the pleiotropic nature of the gut hormone response, and identification of novel methods of delivery may hold the key to optimization of therapeutic modulation of gut hormone physiology in obesity.

Rhizoma Coptidis alkaloids alleviate hyperlipidemia in B6 mice by modulating gut microbiota and bile acid pathways

It is hypothesized that Rhizoma Coptidis (RC) alkaloids exert their hypolipidemic effects primarily by targeting the gastrointestinal tract and liver. Thus, this study was conducted to evaluate the antihyperlipidemic mechanisms of RC alkaloids (at a daily dose of 140mg/kg for 35days) in high-fat and high-cholesterol induced hyperlipidemic B6 mice. After treatment, serum lipid parameters were determined, the expression of lipid metabolism related genes and pathways such as the sterol regulatory element binding proteins (SREBPs) and bile acid signaling in mice were also investigated. Meanwhile, Illumina sequencing was used to investigate the differences in gut microbiota of B6 mice. The results indicated that RC alkaloids reduced the body weight gain and serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), total bile acids (TBA) and lipopolysaccharide of B6 mice. Liver fat deposition and epididymal adipose cell size were also deceased in therapy group. RC alkaloids feeding significantly promoted the abundance of Sporobacter termitidis, Alcaligenes faecalis, Akkermansia muciniphila in the gut of mice, whereas, the abundance of Escherichia coli, Desulfovibrio C21_c20, Parabacteroides distasonis was suppressed. The observed antihyperlipidemic effects of RC alkaloids can also be attributed to their action as agonists of FXR and TGR5, activators for SREBP2, LDLR, UCP2 and CYP7A1, inhibitors of HMGCR, TXNIP, TLR4 and JNK. Therefore, this study expands current knowledge on hypolipidemic mechanisms of RC alkaloids and presents new evidence supporting a key role for RC alkaloids as regulators of lipid homeostasis by modulation gut microbiota and hepatic lipid metabolism.

Non-Alcoholic Fatty Liver Disease and Extra-Hepatic Cancers

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease but the second cause of death among NAFLD patients are attributed to malignancies at both gastrointestinal (liver, colon, esophagus, stomach, and pancreas) and extra-intestinal sites (kidney in men, and breast in women). Obesity and related metabolic abnormalities are associated with increased incidence or mortality for a number of cancers. NAFLD has an intertwined relationship with metabolic syndrome and significantly contributes to the risk of hepatocellular carcinoma (HCC), but recent evidence have fuelled concerns that NAFLD may be a new, and added, risk factor for extra-hepatic cancers, particularly in the gastrointestinal tract. In this review we critically appraise key studies on NAFLD-associated extra-hepatic cancers and speculate on how NAFLD may influence carcinogenesis at these sites.

Risk factors for neuroendocrine neoplasms: a systematic review and meta-analysis

BACKGROUND

Neuroendocrine neoplasms (NENs) are rare cancers mainly of lung and digestive tract. Little is known on risk factors. The aim of this work is to define the risk factors for NEN development by extensive review and meta-analysis of published data.

METHODS

The search was conducted on Medline, Scopus, and Web of Science following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The Newcastle-Ottawa scale was used for study quality. Meta-analyses were conducted by primary site. Odds ratio (OR), hazard ratio, risk ratio, standardized incidence ratio, and associated 95% confidence intervals (CIs) were abstracted. Data were combined and analyses carried out for risk factors considered by at least two studies. Random-effects model was adopted for study variation.

RESULTS

Of 1535 extracted articles, 24 were enrolled. Meta-analyses were possible for pancreas, small intestine, and rectum. Risk for NEN associated with: (i) family history of cancer at all investigated sites (lung, stomach, pancreas, small intestine, appendix, and colon; OR 2.12 [95% CI 1.40-3.22, I(2) = 0.0%, P = 0.681] at meta-analysis in pancreas); (ii) body mass index (BMI) or diabetes (stomach, pancreas, and small intestine; OR of 2.76 [95% CI 1.65-4.64, I(2) = 58.5%, P = 0.090] for diabetes at meta-analysis in pancreas); (iii) cigarette smoking (lung, stomach, pancreas, and small intestine; OR of 1.34 [95% CI 1.10-1.63, I(2) = 0.0%, P = 0.780] and of 1.59 [95% CI 1.07-2.37, I(2) = 32.9%, P = 0.225] for smokers versus never-smokers at meta-analysis for pancreas and small intestine); (iv) alcohol consumption (pancreas and rectum; OR of 2.44 [95% CI 1.07-5.59, I(2) = 65.8%, P = 0.054] and of 1.53 [95% CI 0.99-2.35, I(2) = 0.0%, P = 0.630] for heavy drinkers versus never-drinkers at meta-analysis for pancreas and rectum).

CONCLUSIONS

Family history of cancer is the most relevant risk factor for NEN development at all investigated sites, followed by BMI and diabetes. Cigarette smoking and alcohol consumption are potential risk factors for selected anatomical sites.

Evaluation of diagnostic and predictive value of serum adipokines: Leptin, resistin and visfatin in postmenopausal breast cancer

Obesity is a well-known risk factor for cancer. The associations of obesity with postmenopausal breast cancer (PBC) have been previously proven in clinical studies. The mechanisms underlying these associations remain unexplained completely, however, adipose tissue as an endocrine organ producing adipokines may interfere with cancer development. The aim of this study is to investigate the diagnostic and predictive value of serum levels of leptin, resistin and visfatin with inflammatory and tumour markers in relation to anthropometrics, clinicopathological features of PBC. This study included 298 postmenopausal Saudi females categorised into three groups. One hundred and ten BC patients with age matched, 89 healthy control (HC) and 99 females with benign breast lesion (BBL). For all subjects CA15-3, hsCRP, resistin, visfatin and leptin were measured by ELISA. Serum levels of leptin, resistin and visfatin were significantly higher in BC compared to BBL and HC groups (p<0.05). Their levels were also significantly higher in advanced TNM stage, tumour size, LN invasion, histological grade and negative ER or PR cases. The most significant predictor of leptin level was ER (p<0.05). While for resistin and visfatin level the most significant independent predictor was LN invasion. ROC analysis for serum leptin revealed AUC=0.795; 95% CI, 0.724-0.866. Resistin showed AUC=0.875; 95% CI, 0.821-0.928. Meanwhile, visfatin greater than 12.2ng/mL demonstrated a sensitivity and specificity of 97.6% and 92.6%, respectively and AUC=0.724; 95% CI, 0.643-0.804. In conclusion serum leptin, resistin, and visfatin levels could be considered of potential diagnostic value for PBC and they would be independent predictors of LN invasion and ER negative PBC cases.

Obesity and increased risk of esophageal adenocarcinoma

There has been a substantial increase in the incidence of esophageal adenocarcinoma over the past 40 years. Meta-analyses of large prospective cohorts and population-based case-control studies demonstrate consistent associations between obesity and the development of adenocarcinoma of the esophagus and esophago-gastric junction, with an approximate doubling of risk of esophageal adenocarcinoma among patients who are obese, and an almost five-fold increased risk among those with BMI >40 kg/m². The pathologic precursor, specialized intestinal metaplasia in Barrett's esophagus, is also associated with increased adiposity. Epidemiologic evidence suggests that this cancer risk is not solely due to increased gastro-esophageal reflux, and that adipose tissue itself, in particular visceral adipose, may fuel carcinogenesis through the production of adipokines, cytokines, growth factors, and increased inflammation. The robust epidemiologic evidence linking obesity with esophageal adenocarcinoma makes it an exemplar model for investigating the molecular mechanisms underpinning obesity-associated malignant progression, which are discussed in this review.

Cancer: an emergent property of disturbed resource-rich environments? Ecology meets personalized medicine

For an increasing number of biologists, cancer is viewed as a dynamic system governed by evolutionary and ecological principles. Throughout most of human history, cancer was an uncommon cause of death and it is generally accepted that common components of modern culture, including increased physiological stresses and caloric intake, favor cancer development. However, the precise mechanisms for this linkage are not well understood. Here, we examine the roles of ecological and physiological disturbances and resource availability on the emergence of cancer in multicellular organisms. We argue that proliferation of 'profiteering phenotypes' is often an emergent property of disturbed, resource-rich environments at all scales of biological organization. We review the evidence for this phenomenon, explore it within the context of malignancy, and discuss how this ecological framework may offer a theoretical background for novel strategies of cancer prevention. This work provides a compelling argument that the traditional separation between medicine and evolutionary ecology remains a fundamental limitation that needs to be overcome if complex processes, such as oncogenesis, are to be completely understood.

Inter- and intra-individual variations in seasonal and daily stabilities of the human gut microbiota in Japanese

Relationships between human gut microbiota, dietary habits, and health/diseases are the subject of epidemiological and clinical studies. However, the temporal stability and variability of the bacterial community in fecal samples remain unclear. In this study, middle-aged Japanese male and female volunteers (n = 5 each) without disease were recruited from the Sakura Diet Study. Fecal samples and lifestyle information were collected in every quarter and at each defecation for 7 continuous days. Next-generation sequencing of 16S rDNA and hierarchical clustering showed no time trend and intra-individual differences in both fecal sample sets. Significant inter-individual variations in seasonal and daily fecal sample sets were detected for 24 and 23 out of 39 selected dominant genera (>0.1% of the total human gut microbiota; occupation rate >85%), respectively. Intra- to inter-individual variance ratios in 26 and 35 genera were significantly <1.0 for seasonal and daily stabilities. Seasonal variation in fermented milk consumption might be associated with Bifidobacterium composition, but not with Lactobacillus. For most of the dominant genera in the human gut microbiota, inter-individual variations were significantly larger than intra-individual variations. Further studies are warranted to determine the contributions of human gut microbiota to nutritional metabolism, health promotion, and prevention/development of diseases.

Screening for colorectal cancer in African Americans: determinants and rationale for an earlier age to commence screening

Colorectal cancer (CRC) screening is a cost-effective approach to reduce morbidity, mortality, and prevalence of CRC in populations. Current recommendations for asymptomatic populations begin screening at age 50 years, after which ~95% of cancers occur. Determinants that modify timing and frequency for screening include: personal/family history of adenomas or CRC, age of onset of lesions, and presence or potential to harbor high-risk conditions like inflammatory bowel disease (IBD), familial adenomatous polyposis (FAP), or Lynch syndrome. Although race, like family history, is heritable, it has not engendered inclusion in systematic screening recommendations despite multiple studies demonstrating disparity in the incidence and mortality from CRC, and the potential for targeted screening to reduce disparity. African Americans, when compared to Caucasians, have lower CRC screening utilization, younger presentation for CRC, higher CRC prevalence at all ages, and higher proportion of CRCs before age 50 years (~11 vs. 5%); are less likely to transmit personal/family history of adenomas or CRC that may change screening age; show excess of high-risk proximal adenomas, matched with 7-15% excess right-sided CRCs that lack microsatellite instability; show higher frequencies of high-risk adenomas for every age decile; and demonstrate genetic biomarkers associated with metastasis. These epidemiological and biological parameters put African Americans at higher risk from CRC irrespective of socioeconomic issues, like IBD, FAP, and Lynch patients. Including race as a factor in national CRC screening guidelines and commencing screening at an age earlier than 50 years seems rational based on the natural history and aggressive behavior in this population.

Application of metagenomics in the human gut microbiome

There are more than 1000 microbial species living in the complex human intestine. The gut microbial community plays an important role in protecting the host against pathogenic microbes, modulating immunity, regulating metabolic processes, and is even regarded as an endocrine organ. However, traditional culture methods are very limited for identifying microbes. With the application of molecular biologic technology in the field of the intestinal microbiome, especially metagenomic sequencing of the next-generation sequencing technology, progress has been made in the study of the human intestinal microbiome. Metagenomics can be used to study intestinal microbiome diversity and dysbiosis, as well as its relationship to health and disease. Moreover, functional metagenomics can identify novel functional genes, microbial pathways, antibiotic resistance genes, functional dysbiosis of the intestinal microbiome, and determine interactions and co-evolution between microbiota and host, though there are still some limitations. Metatranscriptomics, metaproteomics and metabolomics represent enormous complements to the understanding of the human gut microbiome. This review aims to demonstrate that metagenomics can be a powerful tool in studying the human gut microbiome with encouraging prospects. The limitations of metagenomics to be overcome are also discussed. Metatranscriptomics, metaproteomics and metabolomics in relation to the study of the human gut microbiome are also briefly discussed.

Oxidative DNA damage in disease--insights gained from base excision repair glycosylase-deficient mouse models

Cellular components, including nucleic acids, are subject to oxidative damage. If left unrepaired, this damage can lead to multiple adverse cellular outcomes, including increased mutagenesis and cell death. The major pathway for repair of oxidative base lesions is the base excision repair pathway, catalyzed by DNA glycosylases with overlapping but distinct substrate specificities. To understand the role of these glycosylases in the initiation and progression of disease, several transgenic mouse models have been generated to carry a targeted deletion or overexpression of one or more glycosylases. This review summarizes some of the major findings from transgenic animal models of altered DNA glycosylase expression, especially as they relate to pathologies ranging from metabolic disease and cancer to inflammation and neuronal health.

Excess adiposity and gastrointestinal cancer

BACKGROUND

Excess adiposity is a risk factor for incidence of several gastrointestinal cancers, but it is unclear how these epidemiological observations translate into clinical practice.

METHODS

Critical appraisals and updated analyses of published systematic reviews were undertaken to quantify cancer risk associations better and to assess the impact of weight-reducing strategies (surgical and non-surgical) on cancer prevention.

RESULTS AND CONCLUSION

A large volume of evidence demonstrates that body mass index (BMI), as an approximation for general adiposity, is a risk factor for the development of oesophageal adenocarcinoma, and colorectal, hepatocellular, gallbladder and pancreatic cancers. A smaller volume of evidence demonstrates that indices of increased central adiposity (such as waist circumference) are associated with increased risk of oesophageal adenocarcinoma and colorectal cancer, but these indices are not necessarily better predictors of risk compared with BMI. Several biological mechanisms may explain these associations but each hypothesis has several caveats and weaknesses. There are few data that convincingly demonstrate significant reductions in risk of gastrointestinal cancers following weight-reducing strategies. In turn, there are many methodological pitfalls in this literature, which prevent conclusive interpretation. The lack of robust intermediary obesity-related biomarkers is an additional unresolved challenge for prevention trials. Novel underpinning mechanisms (for example, local ectopic fat) and more accurate methods to measure these intermediaries are sought and explored as the most optimistic research strategies for the future.

Resistin: insulin resistance to malignancy

Adipose tissue is recognized as an endocrine organ that secretes bioactive substances known as adipokines. Excess adipose tissue and adipose tissue dysfunction lead to dysregulated adipokine production that can contribute to the development of obesity-related co-morbidities. Among the various adipokines, resistin, which was initially considered as a determinant of the emergence of insulin resistance in obesity, has appeared as an important link between obesity and inflammatory processes. Several experimental and clinical studies have suggested an association between increased resistin levels and severe conditions associated with obesity such as cardiovascular disease and malignancies. In this review, we present the growing body of evidence that human resistin is an inflammatory biomarker and potential mediator of obesity-associated diseases. A common pathway seems to involve the combined alteration of immune and inflammatory processes that favor metabolic disturbances, atherosclerosis and carcinogenesis. The mode of action and the signaling pathways utilized by resistin in its interactions with target cells could involve oxidative and nitrosative stress. Therefore, resistin could function as a key molecule in the complications of obesity development and could potentially be used as a diagnostic and prognostic marker.

Mechanisms behind the link between obesity and gastrointestinal cancers

Obesity and obesity-related disorders such as non-alcoholic fatty liver disease (NAFLD), metabolic syndrome and type 2 diabetes exhibit an increased risk of developing various gastrointestinal cancers. These malignancies include mainly esophageal, gastric, colorectal, pancreatic and hepatocellular carcinoma. Whereas underlying pathomechanisms remain unclear, chronic inflammation accompanying obesity has evolved in the last years as a crucial contributing factor. Obesity is also commonly characterized by inflammation in the organ where those cancers appear. Various pathways might participate involving rather diverse components such as innate immunity, (adipo)-cytokines such as adiponectin or leptin, insulin, insulin-like growth factors, the gut's microbiota and others. An imbalance in these systems could substantially contribute to chronic inflammation and subsequent cancer development. Future studies have to elucidate in more detail underlying mechanisms in the development of obesity-related carcinogensis and potential therapeutic strategies besides weight loss.

The risk of colonic adenomas and colonic cancer in obesity

Increasing body fatness has been associated with an increased burden from colorectal cancer. An increased susceptibility spanning the entire continuum from precancerous adenomatous polyps to the development of colorectal cancer, poor outcome with treatment, and reduced survival when compared to those with normal body weight has been described. It is unknown which age period and which degree and duration of excess weight are associated with increased colorectal cancer risk. It is uncertain whether weight loss can reverse this risk. If it can, how long will the new lower or normal weight be maintained to effect enduring risk reduction? Furthermore, it is controversial whether the increased burden of colorectal cancer warrants earlier and/or more frequent screening for obese persons. This article reviews the relationship between obesity and colorectal neoplasia, explores the postulated mechanism of carcinogenesis, discusses interventions to reduce the burden of disease, and suggests future directions of research.