Bile Acid-Microbiome Interaction Promotes Gastric Carcinogenesis

Bile reflux gastritis (BRG) is associated with the development of gastric cancer (GC), but the specific mechanism remains elusive. Here, a comprehensive study is conducted to explore the roles of refluxed bile acids (BAs) and microbiome in gastric carcinogenesis. The results show that conjugated BAs, interleukin 6 (IL-6), lipopolysaccharide (LPS), and the relative abundance of LPS-producing bacteria are increased significantly in the gastric juice of both BRG and GC patients. A secondary BA, taurodeoxycholic acid (TDCA), is significantly and positively correlated with the LPS-producing bacteria in the gastric juice of these patients. TDCA promotes the proliferation of normal gastric epithelial cells (GES-1) through activation of the IL-6/JAK1/STAT3 pathway. These results are further verified in two mouse models, one by gavage of TDCA, LPS, and LPS-producing bacteria (Prevotella melaninogenica), respectively, and the other by bile reflux (BR) surgery, mimicking clinical bile refluxing. Moreover, the bile reflux induced gastric precancerous lesions observed in the post BR surgery mice can be prevented by treatment with cryptotanshinone, a plant-derived STAT3 inhibitor. These results reveal an important underlying mechanism by which bile reflux promotes gastric carcinogenesis and provide an alternative strategy for the prevention of GC associated with BRG.

The microbial metabolome in metabolic-associated fatty liver disease

Metabolism-associated fatty liver disease (MAFLD) is defined as the presence of excess fat in the liver in the absence of excess alcohol consumption and metabolic dysfunction. It has also been described as the hepatic manifestation of metabolic syndrome. The incidence of MAFLD has been reported to be 43-60% in diabetics, ~90% in patients with hyperlipidemia, and 91% in morbidly obese patients. Risk factors that have been associated with the development of MAFLD include male gender, increasing age, obesity, insulin resistance, diabetes, and hyperlipidemia. All of these risk factors have been linked to alterations of the gut microbiota, that is, gut dysbiosis. MAFLD can progress to non-alcoholic steatohepatitis with the presence of inflammation and ballooning, which can deteriorate into cirrhosis, MAFLD-related hepatocellular carcinoma, and liver failure. In this review, we will be focused on the role of the gut microbial metabolome in the development, progression, and potential treatment of MAFLD.

Hyocholic acid species improve glucose homeostasis through a distinct TGR5 and FXR signaling mechanism

Hyocholic acid (HCA) and its derivatives are found in trace amounts in human blood but constitute approximately 76% of the bile acid (BA) pool in pigs, a species known for its exceptional resistance to type 2 diabetes. Here, we show that BA depletion in pigs suppressed secretion of glucagon-like peptide-1 (GLP-1) and increased blood glucose levels. HCA administration in diabetic mouse models improved serum fasting GLP-1 secretion and glucose homeostasis to a greater extent than tauroursodeoxycholic acid. HCA upregulated GLP-1 production and secretion in enteroendocrine cells via simultaneously activating G-protein-coupled BA receptor, TGR5, and inhibiting farnesoid X receptor (FXR), a unique mechanism that is not found in other BA species. We verified the findings in TGR5 knockout, intestinal FXR activation, and GLP-1 receptor inhibition mouse models. Finally, we confirmed in a clinical cohort, that lower serum concentrations of HCA species were associated with diabetes and closely related to glycemic markers.

Conjugated secondary 12α-hydroxylated bile acids promote liver fibrogenesis

BACKGROUND

Significantly elevated serum and hepatic bile acid (BA) concentrations have been known to occur in patients with liver fibrosis. However, the roles of different BA species in liver fibrogenesis are not fully understood.

METHODS

We quantitatively measured blood BA concentrations in nonalcoholic steatohepatitis (NASH) patients with liver fibrosis and healthy controls. We characterized BA composition in three mouse models induced by carbon tetrachloride (CCl4), streptozotocin-high fat diet (STZ-HFD), and long term HFD, respectively. The molecular mechanisms underlying the fibrosis-promoting effects of BAs were investigated in cell line models, a 3D co-culture system, and a Tgr5 (HSC-specific) KO mouse model.

FINDINGS

We found that a group of conjugated 12α-hydroxylated (12α-OH) BAs, such as taurodeoxycholate (TDCA) and glycodeoxycholate (GDCA), significantly increased in NASH patients and liver fibrosis mouse models. 12α-OH BAs significantly increased HSC proliferation and protein expression of fibrosis-related markers. Administration of TDCA and GDCA directly activated HSCs and promoted liver fibrogenesis in mouse models. Blockade of BA binding to TGR5 or inhibition of ERK1/2 and p38 MAPK signaling both significantly attenuated the BA-induced fibrogenesis. Liver fibrosis was attenuated in mice with Tgr5 depletion.

INTERPRETATION

Increased hepatic concentrations of conjugated 12α-OH BAs significantly contributed to liver fibrosis via TGR5 mediated p38MAPK and ERK1/2 signaling. Strategies to antagonize TGR5 or inhibit ERK1/2 and p38 MAPK signaling may effectively prevent or reverse liver fibrosis.

FUNDINGS

This study was supported by the National Institutes of Health/National Cancer Institute Grant 1U01CA188387-01A1, the National Key Research and Development Program of China (2017YFC0906800); the State Key Program of National Natural Science Foundation (81430062); the National Natural Science Foundation of China (81974073, 81774196), China Postdoctoral Science Foundation funded project, China (2016T90381), and E-institutes of Shanghai Municipal Education Commission, China (E03008).

The Distinctive Serum Metabolomes of Gastric, Esophageal and Colorectal Cancers

Simple Summary

Cancer of the stomach, esophagus and colon are often fatal. Ways are being sought to establish patient-friendly screening tests that would allow these cancers to be detected earlier. Examination of the metabolomics results of cancer patient’s serum for certain metabolites unique for a particular cancer was the goal of this review. From studies conducted within the past five years several metabolites were found to be changed in cancer compared to non-cancer patients for each of the three cancers. Further confirmation of what was discovered in this review coupled with establishment of standard protocols may allow for cancer screening on patient blood samples to become routine clinical tests.

Abstract

Three of the most lethal cancers in the world are the gastrointestinal cancers—gastric (GC), esophageal (EC) and colorectal cancer (CRC)—which are ranked as third, sixth and fourth in cancer deaths globally. Early detection of these cancers is difficult, and a quest is currently on to find non-invasive screening tests to detect these cancers. The reprogramming of energy metabolism is a hallmark of cancer, notably, an increased dependence on aerobic glycolysis which is often referred to as the Warburg effect. This metabolic change results in a unique metabolic profile that distinguishes cancer cells from normal cells. Serum metabolomics analyses allow one to measure the end products of both host and microbiota metabolism present at the time of sample collection. It is a non-invasive procedure requiring only blood collection which encourages greater patient compliance to have more frequent screenings for cancer. In the following review we will examine some of the most current serum metabolomics studies in order to compare their results and test a hypothesis that different tumors, notably, from EC, GC and CRC, have distinguishing serum metabolite profiles.

Targeting the alternative bile acid synthetic pathway for metabolic diseases

The gut microbiota is profoundly involved in glucose and lipid metabolism, in part by regulating bile acid (BA) metabolism and affecting multiple BA-receptor signaling pathways. BAs are synthesized in the liver by multi-step reactions catalyzed via two distinct routes, the classical pathway (producing the 12α-hydroxylated primary BA, cholic acid), and the alternative pathway (producing the non-12α-hydroxylated primary BA, chenodeoxycholic acid). BA synthesis and excretion is a major pathway of cholesterol and lipid catabolism, and thus, is implicated in a variety of metabolic diseases including obesity, insulin resistance, and nonalcoholic fatty liver disease. Additionally, both oxysterols and BAs function as signaling molecules that activate multiple nuclear and membrane receptor-mediated signaling pathways in various tissues, regulating glucose, lipid homeostasis, inflammation, and energy expenditure. Modulating BA synthesis and composition to regulate BA signaling is an interesting and novel direction for developing therapies for metabolic disease. In this review, we summarize the most recent findings on the role of BA synthetic pathways, with a focus on the role of the alternative pathway, which has been under-investigated, in treating hyperglycemia and fatty liver disease. We also discuss future perspectives to develop promising pharmacological strategies targeting the alternative BA synthetic pathway for the treatment of metabolic diseases.

Anti-Adipogenic Effect of Theabrownin Is Mediated by Bile Acid Alternative Synthesis via Gut Microbiota Remodeling

Theabrownin is one of the most bioactive compounds in Pu-erh tea. Our previous study revealed that the hypocholesterolemic effect of theabrownin was mediated by the modulation of bile salt hydrolase (BSH)-enriched gut microbiota and bile acid metabolism. In this study, we demonstrated that theabrownin ameliorated high-fat-diet (HFD)-induced obesity by modifying gut microbiota, especially those with 7α-dehydroxylation on the species level, and these changed microbes were positively correlated with secondary bile acid (BA) metabolism. Thus, altered intestinal BAs resulted in shifting bile acid biosynthesis from the classic to the alternative pathway. This shift changed the BA pool by increasing non-12α-hydroxylated-BAs (non-12OH-BAs) and decreasing 12α-hydroxylated BAs (12OH-BAs), which improved energy metabolism in white and brown adipose tissue. This study showed that theabrownin was a potential therapeutic modality for obesity and other metabolic disorders via gut microbiota-driven bile acid alternative synthesis.

Gut microbiota alterations are distinct for primary colorectal cancer and hepatocellular carcinoma

Colorectal cancer (CRC) and hepatocellular carcinoma (HCC) are the second and third most common causes of death by cancer, respectively. The etiologies of the two cancers are either infectious insult or due to chronic use of alcohol, smoking, diet, obesity and diabetes. Pathological changes in the composition of the gut microbiota that lead to intestinal inflammation are a common factor for both HCC and CRC. However, the gut microbiota of the cancer patient evolves with disease pathogenesis in unique ways that are affected by etiologies and environmental factors. In this review, we examine the changes that occur in the composition of the gut microbiota across the stages of the HCC and CRC. Based on the idea that the gut microbiota are an additional "lifeline" and contribute to the tumor microenvironment, we can observe from previously published literature how the microbiota can cause a shift in the balance from normal → inflammation → diminished inflammation from early to later disease stages. This pattern leads to the hypothesis that tumor survival depends on a less pro-inflammatory tumor microenvironment. The differences observed in the gut microbiota composition between different disease etiologies as well as between HCC and CRC suggest that the tumor microenvironment is unique for each case.

Increased levels of conjugated bile acids are associated with human bile reflux gastritis

Bile acids (BAs) play essential roles in facilitating lipid digestion and absorption in the intestine. Gastric BAs were attributed to abnormal refluxing from duodenal compartments and correlated with the occurrence of gastric inflammation and carcinogenesis. However, the differences in gastric BAs between physiologically compromised and healthy individuals have not been fully investigated. In this study, gastric juice was collected from patients clinically diagnosed as gastritis with/without bile reflux and healthy subjects for BA profiles measurements. As a result, we found that the conjugated BAs became prominent components in bile reflux juice, whereas almost equal amounts of conjugated and unconjugated BAs existed in non-bile reflux and healthy juice. To investigate whether gastric BA changes were regulated by hepatic BA synthesis, C57BL/6J mice were intervened with GW4064/resin to decrease/increase hepatic BA synthesis. The results revealed that changes of gastric BAs were coordinated with hepatic BA changes. Additionally, gastric BAs were detected in several healthy mammals, in which there were no obvious differences between the conjugated and unconjugated BAs. Pigs were an exception. Thus, increased levels of conjugated BAs are associated with human bile reflux gastritis. Gastric conjugated BAs could become a panel of biomarkers to facilitate diagnosis of pathological bile reflux.

Serum metabolite profiles are associated with the presence of advanced liver fibrosis in Chinese patients with chronic hepatitis B viral infection

BACKGROUND

Accurate and noninvasive diagnosis and staging of liver fibrosis are essential for effective clinical management of chronic liver disease (CLD). We aimed to identify serum metabolite markers that reliably predict the stage of fibrosis in CLD patients.

METHODS

We quantitatively profiled serum metabolites of participants in 2 independent cohorts. Based on the metabolomics data from cohort 1 (504 HBV associated liver fibrosis patients and 502 normal controls, NC), we selected a panel of 4 predictive metabolite markers. Consequently, we constructed 3 machine learning models with the 4 metabolite markers using random forest (RF), to differentiate CLD patients from normal controls (NC), to differentiate cirrhosis patients from fibrosis patients, and to differentiate advanced fibrosis from early fibrosis, respectively.

RESULTS

The panel of 4 metabolite markers consisted of taurocholate, tyrosine, valine, and linoelaidic acid. The RF models of the metabolite panel demonstrated the strongest stratification ability in cohort 1 to diagnose CLD patients from NC (area under the receiver operating characteristic curve (AUROC) = 0.997 and the precision-recall curve (AUPR) = 0.994), to differentiate fibrosis from cirrhosis (0.941, 0.870), and to stage liver fibrosis (0.918, 0.892). The diagnostic accuracy of the models was further validated in an independent cohort 2 consisting of 300 CLD patients with chronic HBV infection and 90 NC. The AUCs of the models were consistently higher than APRI, FIB-4, and AST/ALT ratio, with both greater sensitivity and specificity.

CONCLUSIONS

Our study showed that this 4-metabolite panel has potential usefulness in clinical assessments of CLD progression in patients with chronic hepatitis B virus infection.

Expert insights: The potential role of the gut microbiome-bile acid-brain axis in the development and progression of Alzheimer's disease and hepatic encephalopathy

Recent epidemiological and molecular studies have linked the disruption of cholesterol homeostasis to increased risk for developing Alzheimer's disease (AD). Emerging evidence also suggests that brain cholesterol accumulation contributes to the progression of hepatic encephalopathy (HE) via bile acid (BA)-mediated effects on the farnesoid X receptor. In this perspective paper, we reviewed several recently published studies that suggested a role for the gut microbiota transformation of BAs as a factor in AD and HE development/progression. We hypothesize that in addition to cholesterol elimination pathways, alteration of the gut microbiota and subsequent changes in both the serum and brain BA profiles are mechanistically involved in the development of both AD and HE, and thus, are a potential target for the prevention and treatment of the two diseases. Our understanding of the microbiome-BAs-brain axis in central nervous system disease is still evolving, and critical questions regarding the emerging links among central, peripheral, and intestinal metabolic failures contributing to brain health and disease during aging have yet to be addressed.

Dysregulated bile acid signaling contributes to the neurological impairment in murine models of acute and chronic liver failure

BACKGROUND

Hepatic encephalopathy (HE), a severe neuropsychiatric complication, is associated with increased blood levels of ammonia and bile acids (BAs). We sought to determine (1) whether abnormally increased blood BAs in liver cirrhotic patients with HE is caused by elevation of apical sodium-dependent BA transporter (ASBT)-mediated BA reabsorption; and (2) whether increased BA reabsorption would exacerbate ammonia-induced brain injuries.

METHODS

We quantitatively measured blood BA and ammonia levels in liver cirrhosis patients with or without HE and healthy controls. We characterized ASBT expression, BA profiles, and ammonia concentrations in a chronic liver disease (CLD) mouse model induced by streptozotocin-high fat diet (STZ-HFD) and an azoxymethane (AOM) - induced acute liver failure (ALF) mouse model. These two mouse models were treated with SC-435 (ASBT inhibitor) and budesonide (ASBT activator), respectively.

FINDINGS

Blood concentrations of ammonia and conjugated BAs were substantially increased in cirrhotic patients with HE (n = 75) compared to cirrhotic patients without HE (n = 126). Pharmacological inhibition of the enterohepatic BA circulation using a luminal- restricted ASBT inhibitor, SC-435, in mice with AOM-induced ALF and STZ-HFD -induced CLD effectively reduced BA and ammonia concentrations in the blood and brain, and alleviated liver and brain damages. Budesonide treatment induced liver and brain damages in normal mice, and exacerbated these damages in AOM-treated mice.

INTERPRETATION

ASBT mediated BA reabsorption increases intestinal luminal pH and facilitates conversion of intestinal ammonium to ammonia, leading to abnormally high levels of neurotoxic ammonia and cytotoxic BAs in the blood and brain. Inhibition of intestinal ASBT with SC-435 can effectively remove neurotoxic BAs and ammonia from the bloodstream and thus, mitigate liver and brain injuries resulting from liver failure.

Clinical prediction of HBV and HCV related hepatic fibrosis using machine learning

Clinical prediction of advanced hepatic fibrosis (HF) and cirrhosis has long been challenging due to the gold standard, liver biopsy, being an invasive approach with certain limitations. Less invasive blood test tandem with a cutting-edge machine learning algorithm shows promising diagnostic potential.

In this study, we constructed and compared machine learning methods with the FIB-4 score in a discovery dataset (n = 490) of hepatitis B virus (HBV) patients. Models were validated in an independent HBV dataset (n = 86). We further employed these models on two independent hepatitis C virus (HCV) datasets (n = 254 and 230) to examine their applicability.

In the discovery data, gradient boosting (GB) stably outperformed other methods as well as FIB-4 scores (p < .001) in the prediction of advanced HF and cirrhosis. In the HBV validation dataset, for classification between early and advanced HF, the area under receiver operating characteristic curves (AUROC) of GB model was 0.918, while FIB-4 was 0.841; for classification between non-cirrhosis and cirrhosis, GB showed AUROC of 0.871, while FIB-4 was 0.830. Additionally, GB-based prediction demonstrated good classification capacity on two HCV datasets while higher cutoffs for both GB and FIB-4 scores were required to achieve comparable specificity and sensitivity.

Using the same parameters as FIB-4, the GB-based prediction system demonstrated steady improvements relative to FIB-4 in HBV and HCV cohorts with different cutoff values required in different etiological groups. A user-friendly web tool, LiveBoost, makes our prediction models freely accessible for further clinical studies and applications.

Strategy for an Association Study of the Intestinal Microbiome and Brain Metabolome Across the Lifespan of Rats

There is increased appreciation for the diverse roles of the microbiome-gut-brain axis on mammalian growth and health throughout the lifespan. Numerous studies have demonstrated that the gut microbiome and their metabolites are extensively involved in the communication between brain and gut. Association study of brain metabolome and gut microbiome is an active field offering large amounts of information on the interaction of microbiome, brain and gut but data size and complicated hierarchical relationships were found to be major obstacles to the formation of significant, reproducible conclusions. This study addressed a two-level strategy of brain metabolome and gut microbiome association analysis of male Wistar rats in the process of growth, employing several analytical platforms and various bioinformatics methods. Trajectory analysis showed that the age-related brain metabolome and gut microbiome had similarity in overall alteration patterns. Four high taxonomical level correlated pairs of "metabolite type-bacterial phylum", including "lipids-Spirochaetes", "free fatty acids (FFAs)-Firmicutes", "bile acids (BAs)-Firmicutes", and "Neurotransmitters-Bacteroidetes", were screened out based on unit- and multivariant correlation analysis and function analysis. Four groups of specific "metabolite-bacterium" association pairs from within the above high level key pairs were further identified. The key correlation pairs were validated by an independent animal study. This two-level strategy is effective in identifying principal correlations in big data sets obtained from the systematic multiomics study, furthering our understanding on the lifelong connection between brain and gut.

The Influence of Gut Microbial Metabolism on the Development and Progression of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is defined as the presence of excess fat in the liver parenchyma in the absence of excess alcohol consumption and overt inflammation. It has also been described as the hepatic manifestation of metabolic syndrome (Than NN, Newsome PN, Atherosclerosis. 239:192-202, 2015). The incidence of NAFLD has been reported to be 43-60% in diabetics, ~90% in patients with hyperlipidemia and 91% in morbidly obese patients (Than NN, Newsome PN, Atherosclerosis. 239:192-202, 2015, Machado M, Marques-Vidal P, Cortez-Pinto H, J Hepatol, 45:600-606, 2006, Vernon G, Baranova A, Younossi ZM, Aliment Pharmacol Ther, 34:274-285, 2011). The risk factors that have been associated with the development of NAFLD include male gender, increasing age, obesity, insulin resistance, diabetes and hyperlipidemia (Attar BM, Van Thiel DH, Sci World J, 2013:481893, 2013, Gaggini M, Morelli M, Buzzigoli E, DeFronzo RA, Bugianesi E, Gastaldelli A, Forum Nutr, 5:1544-1460, 2013). All of these risk factors have been linked to alterations of the gut microbiota, ie., gut dysbiosis (He X, Ji G, Jia W, Li H, Int J Mol Sci, 17:300, 2016). However, it must be pointed out that the prevalence of NAFLD in normal weight individuals without metabolic risk factors is ~16% (Than NN, Newsome PN, Atherosclerosis. 239:192-202, 2015). This fact has led some investigators to hypothesize that the gut microbiota can impact lipid metabolism in the liver independently of obesity-related metabolic factors (Marchesi JR, Adams DH, Fava F, Hermes GD, Hirschfield GM, Hold g, et al., Gut, 65:330 339, 2016) (Le Roy T, Llopis M, Lepage P, Bruneau A, Rabot S, Bevilacqua C, et al., Gut, 62:1787-1794, 2013). In this chapter, we will explore the effect of the gut microbiota on hepatic lipid metabolism and how this affects the development of NAFLD.

Bile acid is a significant host factor shaping the gut microbiome of diet-induced obese mice

Background

Intestinal bacteria are known to regulate bile acid (BA) homeostasis via intestinal biotransformation of BAs and stimulation of the expression of fibroblast growth factor 19 through intestinal nuclear farnesoid X receptor (FXR). On the other hand, BAs directly regulate the gut microbiota with their strong antimicrobial activities. It remains unclear, however, how mammalian BAs cross-talk with gut microbiome and shape microbial composition in a dynamic and interactive way.

Results

We quantitatively profiled small molecule metabolites derived from host-microbial co-metabolism in mice, demonstrating that BAs were the most significant factor correlated with microbial alterations among all types of endogenous metabolites. A high-fat diet (HFD) intervention resulted in a rapid and significant increase in the intestinal BA pool within 12 h, followed by an alteration in microbial composition at 24 h, providing supporting evidence that BAs are major dietary factors regulating gut microbiota. Feeding mice with BAs along with a normal diet induced an obese phenotype and obesity-associated gut microbial composition, similar to HFD-fed mice. Inhibition of hepatic BA biosynthesis under HFD conditions attenuated the HFD-induced gut microbiome alterations. Both inhibition of BAs and direct suppression of microbiota improved obese phenotypes.

Conclusions

Our study highlights a liver–BA–gut microbiome metabolic axis that drives significant modifications of BA and microbiota compositions capable of triggering metabolic disorders, suggesting new therapeutic strategies targeting BA metabolism for metabolic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-017-0462-7) contains supplementary material, which is available to authorized users.

The ratio of dihomo-γ-linolenic acid to deoxycholic acid species is a potential biomarker for the metabolic abnormalities in obesity

Bile acid (BA) signaling regulates fatty acid metabolism. BA dysregulation plays an important role in the development of metabolic disease. However, BAs in relation to fatty acids have not been fully investigated in obesity-related metabolic disorders. A targeted metabolomic measurement of serum BA and free fatty acid profiles was applied to sera of 381 individuals in 2 independent studies. The results showed that the ratio of dihomo-γ-linolenic acid (DGLA) to deoxycholic acid (DCA) species (DCAS) was significantly increased in obese individuals with type 2 diabetes (T2DM) from a case-control study and decreased in the remission group of obese subjects with T2DM after metabolic surgery. The changes were closely associated with their metabolic status. These results were consistently confirmed in both serum and liver of mice with diet-induced obesity, implying that such a metabolic alteration in circulation reflects changes occurring in the liver. In vitro studies of human liver L-02 cell lines under BA treatment revealed that DCA and its conjugated form, TDCA, significantly inhibited mRNA expression of fatty acid transport protein 5 in the presence of DGLA, which was involved in hepatocyte DGLA uptake. Thus, the DGLA:DCAS ratio may be a promising biomarker for metabolic abnormalities in obesity.-Lei, S., Huang, F., Zhao, A., Chen, T., Chen, W., Xie, G., Zheng, X., Zhang, Y., Yu, H., Zhang, P., Rajani, C., Bao, Y., Jia, W., Jia, W. The ratio of dihomo-γ-linolenic acid to deoxycholic acid species is a potential biomarker for the metabolic abnormalities in obesity.

High Throughput and Quantitative Measurement of Microbial Metabolome by Gas Chromatography/Mass Spectrometry Using Automated Alkyl Chloroformate Derivatization

The ability to identify and quantify small molecule metabolites derived from gut microbial-mammalian cometabolism is essential for the understanding of the distinct metabolic functions of the microbiome. To date, analytical protocols that quantitatively measure a complete panel of microbial metabolites in biological samples have not been established but are urgently needed by the microbiome research community. Here, we report an automated high-throughput quantitative method using a gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) platform to simultaneously measure over one hundred microbial metabolites in human serum, urine, feces, and Escherichia coli cell samples within 15 min per sample. A reference library was developed consisting of 145 methyl and ethyl chloroformate (MCF and ECF) derivatized compounds with their mass spectral and retention index information for metabolite identification. These compounds encompass different chemical classes including fatty acids, amino acids, carboxylic acids, hydroxylic acids, and phenolic acids as well as benzoyl and phenyl derivatives, indoles, etc., that are involved in a number of important metabolic pathways. Within an optimized range of concentrations and sample volumes, most derivatives of both reference standards and endogenous metabolites in biological samples exhibited satisfactory linearity (R² > 0.99), good intrabatch reproducibility, and acceptable stability within 6 days (RSD < 20%). This method was further validated by examination of the analytical variability of 76 paired human serum, urine, and fecal samples as well as quality control samples. Our method involved using high-throughput sample preparation, measurement with automated derivatization, and rapid GC/TOFMS analysis. Both techniques are well suited for microbiome metabolomics studies.

Sex-dependent effects on gut microbiota regulate hepatic carcinogenic outcomes

Emerging evidence points to a strong association between sex and gut microbiota, bile acids (BAs), and gastrointestinal cancers. Here, we investigated the mechanistic link between microbiota and hepatocellular carcinogenesis using a streptozotocin-high fat diet (STZ-HFD) induced nonalcoholic steatohepatitis-hepatocellular carcinoma (NASH-HCC) murine model and compared results for both sexes. STZ-HFD feeding induced a much higher incidence of HCC in male mice with substantially increased intrahepatic retention of hydrophobic BAs and decreased hepatic expression of tumor-suppressive microRNAs. Metagenomic analysis showed differences in gut microbiota involved in BA metabolism between normal male and female mice, and such differences were amplified when mice of both sexes were exposed to STZ-HFD. Treating STZ-HFD male mice with 2% cholestyramine led to significant improvement of hepatic BA retention, tumor-suppressive microRNA expressions, microbial gut communities, and prevention of HCC. Additionally the sex-dependent differences in BA profiles in the murine model can be correlated to the differential BA profiles between men and women during the development of HCC. These results uncover distinct male and female profiles for gut microbiota, BAs, and microRNAs that may contribute to sex-based disparity in liver carcinogenesis, and suggest new possibilities for preventing and controlling human obesity-related gastrointestinal cancers that often exhibit sex differences.

Serum stearic acid/palmitic acid ratio as a potential predictor of diabetes remission after Roux-en-Y gastric bypass in obesity

Endogenous fatty acid metabolism that results in elongation and desaturation lipid products is thought to play a role in the development of type 2 diabetes mellitus (T2DM). In this study, we evaluated the potential of estimated elongase and desaturase activities for use as predictive markers for T2DM remission after Roux-en-Y gastric bypass (RYGB). The results of a targeted metabolomics approach from 2 independent studies were used to calculate 24 serum FA concentration ratios (product/precursor). Gene expression data from an open public data set was also analyzed. In a longitudinal study of 38 obese diabetic patients with RYGB, we found higher baseline stearic acid/palmitic acid (S/P) ratio. This ratio reflects an elovl6-encoded elongase enzyme activity that has been found to be associated with greater possibility for diabetes remission after RYGB [odds ratio, 2.16 (95% CI 1.10-4.26)], after adjustment for age, gender, body mass index, diabetes duration, glycosylated hemoglobin A1c, and fasting C-peptide. Our results were validated by examination of postsurgical elovl6 gene expression in morbidly obese patients. The association of S/P with the metabolic status of obese individuals was further validated in a cross-sectional cohort of 381 participants. In summary, higher baseline S/P was associated with greater probability of diabetes remission after RYGB and may serve as a diagnostic marker in preoperative patient assessment. - Zhao, L., Ni, Y., Yu, H., Zhang, P., Zhao, A., Bao, Y., Liu, J., Chen, T., Xie, G., Panee, J., Chen, W., Rajani, C., Wei, R., Su, M., Jia, W., Jia, W. Serum stearic acid/palmitic acid ratio as a potential predictor of diabetes remission after Roux-en-Y gastric bypass in obesity.

Enhanced Fructose Utilization Mediated by SLC2A5 Is a Unique Metabolic Feature of Acute Myeloid Leukemia with Therapeutic Potential

Rapidly proliferating leukemic progenitor cells consume substantial glucose, which may lead to glucose insufficiency in bone marrow. We show that acute myeloid leukemia (AML) cells are prone to fructose utilization with an upregulated fructose transporter GLUT5, which compensates for glucose deficiency. Notably, AML patients with upregulated transcription of the GLUT5-encoding gene SLC2A5 or increased fructose utilization have poor outcomes. Pharmacological blockage of fructose uptake ameliorates leukemic phenotypes and potentiates the cytotoxicity of the antileukemic agent, Ara-C. In conclusion, this study highlights enhanced fructose utilization as a metabolic feature of AML and a potential therapeutic target.

Tryptophan Predicts the Risk for Future Type 2 Diabetes

Recently, 5 amino acids were identified and verified as important metabolites highly associated with type 2 diabetes (T2D) development. This report aims to assess the association of tryptophan with the development of T2D and to evaluate its performance with existing amino acid markers. A total of 213 participants selected from a ten-year longitudinal Shanghai Diabetes Study (SHDS) were examined in two ways: 1) 51 subjects who developed diabetes and 162 individuals who remained metabolically healthy in 10 years; 2) the same 51 future diabetes and 23 strictly matched ones selected from the 162 healthy individuals. Baseline fasting serum tryptophan concentrations were quantitatively measured using ultra-performance liquid chromatography triple quadruple mass spectrometry. First, serum tryptophan level was found significantly higher in future T2D and was positively and independently associated with diabetes onset risk. Patients with higher tryptophan level tended to present higher degree of insulin resistance and secretion, triglyceride and blood pressure. Second, the prediction potential of tryptophan is non-inferior to the 5 existing amino acids. The predictive performance of the combined score improved after taking tryptophan into account. Our findings unveiled the potential of tryptophan as a new marker associated with diabetes risk in Chinese populations. The addition of tryptophan provided complementary value to the existing amino acid predictors.

Key Role for the 12-Hydroxy Group in the Negative Ion Fragmentation of Unconjugated C24 Bile Acids

Host-gut microbial interactions contribute to human health and disease states and an important manifestation resulting from this cometabolism is a vast diversity of bile acids (BAs). There is increasing interest in using BAs as biomarkers to assess the health status of individuals and, therefore, an increased need for their accurate separation and identification. In this study, the negative ion fragmentation behaviors of C24 BAs were investigated by UPLC-ESI-QTOF-MS. The step-by-step fragmentation analysis revealed a distinct fragmentation mechanism for the unconjugated BAs containing a 12-hydroxyl group. The unconjugated BAs lacking 12-hydroxylation fragmented via dehydration and dehydrogenation. In contrast, the 12-hydroxylated ones, such as deoxycholic acid (DCA) and cholic acid (CA), employed dissociation routes including dehydration, loss of carbon monoxide or carbon dioxide, and dehydrogenation. All fragmentations of the 12-hydroxylated unconjugated BAs, characterized by means of stable isotope labeled standards, were associated with the rotation of the carboxylate side chain and the subsequent rearrangements accompanied by proton transfer between 12-hydroxyl and 24-carboxyl groups. Compared to DCA, CA underwent further cleavages of the steroid skeleton. Accordingly, the effects of stereochemistry on the fragmentation pattern of CA were investigated using its stereoisomers. Based on the knowledge gained from the fragmentation analysis, a novel BA, 3β,7β,12α-trihydroxy-5β-cholanic acid, was identified in the postprandial urine samples of patients with nonalcoholic steatohepatitis. The analyses used in this study may contribute to a better understanding of the chemical diversity of BAs and the molecular basis of human liver diseases that involve BA synthesis, transport, and metabolism.

Targeted deletion of RasGRP1 impairs skin tumorigenesis

Ras is frequently activated in cutaneous squamous cell carcinoma, a prevalent form of skin cancer. However, the pathways that contribute to Ras-induced transformation have not been entirely elucidated. We have previously demonstrated that in transgenic mice, overexpression of the Ras activator RasGRP1 promotes the formation of spontaneous skin tumors and enhances malignant progression in the multistage carcinogenesis skin model that relies on the oncogenic activation of H-Ras. Utilizing a RasGRP1 knockout mouse model (RasGRP1 KO), we now show that lack of RasGRP1 reduced the susceptibility to skin tumorigenesis. The dependency on RasGRP1 was associated with a diminished response to the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Specifically, we found impairment of epidermal hyperplasia induced by TPA through keratinocyte proliferation. Using a keratinocyte cell line that carries a ras oncogenic mutation, we also demonstrated that RasGRP1 could further activate Ras in response to TPA. Thus, we propose that RasGRP1 upregulates signaling from Ras and contributes to epidermal tumorigenesis by increasing the total dosage of active Ras.

Improving recognition and management of acute kidney injury

Acute kidney injury (AKI) is currently suboptimally recognised and managed in the UK, despite its association with significant patient morbidity, mortality and consequent implications for healthcare economics. Our prospective study, performed in a large urban London hospital, demonstrated that the introduction of a specially designed care bundle can significantly improve documentation of baseline creatinine, assessment and optimisation of fluid status, performance of urine dip, withholding of nephrotoxic drugs, appropriate monitoring of urine output, prescription of renal drug doses, and appropriate consideration of a renal ultrasound and urinary protein-creatinine ratio. Improved compliance of appropriate investigations and initial treatments translated to decreased requirement for intensive care admission and a trend towards shorter length of stays.

Resonance Raman Studies of HOO−Co(III)Bleomycin and Co(III)Bleomycin: Identification of Two Important Vibrational Modes, ν(Co−OOH) and ν(O−OH)

Bleomycin is an antitumor agent whose cytotoxicity is dependent on its ability to bind DNA in the nucleus and effect double-stranded DNA cleavage, which is difficult for the cell to repair. In order for this DNA cleavage to occur, bleomycin must, through a series of reactions, form a low-spin Fe(III) complex, the putative "activated" form of the drug, HOO-Fe(III)bleomycin. The relative strengths of the bonds in the Fe(III)-OOH linkage have not been determined due to the weakness of the hydroperoxo-to-iron(III) charge-transfer transition. The much more stable HOO-Co(III)bleomycin has often been studied as a structural analogue of HOO-Fe(III)bleomycin, and hence, an understanding of the relative bond strengths in the Co-OOH linkage may serve to enhance our understanding of the analogous Fe-OOH linkage. In this report, we present resonance Raman data that identify two important vibrational modes in the Co-OOH linkage, the stretching modes, nu(Co-OOH) and nu(O-OH). Both of these vibrational modes were found to be unperturbed by complexation of the drug with calf thymus DNA. Advantage was also taken of the isostructural realtionship between Fe-bleomycin and Co-bleomycin to analyze and assign the high-frequency modes for HOO-Co(III)bleomycin and Co(III)bleomycin (A(2) and B(2)). These data could be useful for future studies of photoactivated Co-bleomycin and Co-bleomycin analogues in an attempt to characterize oxygen-independent DNA damage pathways.

Raman spectroscopy of an O(2)-Co(II)bleomycin-calf thymus DNA adduct: alternate polymer conformations

Bleomycin (Blm) is an antitumor agent which binds to specific sequences of DNA and as HO(2)-Fe(III)Blm causes single and double strand cleavage. In the present investigation, binding of O(2)-Co(II)Blm to a native DNA polymer, calf thymus DNA, was examined using conventional Raman spectroscopy. O(2)-Co(II)Blm is a model for O(2)-Fe(II)Blm, the direct precursor of HO(2)-Fe(III)Blm. Although the DNA polymer retained a predominant B-form structure, Raman spectral evidence was obtained for localized structural changes to A, C and Z-DNA forms. The presence of these alternate DNA forms within B-DNA implied the presence of B/A, B/C and B/Z junctions. The observed changes in DNA secondary structure were attributed to perturbation of structural water resulting from binding of O(2)-Co(II)Blm within the minor groove.

The presence of two modes of binding to calf thymus DNA by metal-free bleomycin: a low frequency Raman study

Double-stranded DNA is targeted by bleomycin in cancer cells and ambiguity exists as to its mode of DNA binding. A conventional Raman study was performed on drug/DNA complexes in which the low frequency spectral region (560-930 cm(-1)) was examined at two temperatures (19 and 30 degrees C). At 30 degrees C, a global Raman hypochromism was observed consistent with partial intercalation of the bithiazole moiety. At 19 degrees C, Raman hypochromism (increased base pair stacking) was detected for bands associated with GC base pairs while Raman hyperchromism (base pair destacking) was evident for bands associated with AT base pairs. These results suggest that intercalation of the bithiazole moiety occurs with greater disruption of the more efficiently stacked AT base pairs at the lower temperature. Evidence for minor groove binding was indicated by an increase in the population of bands corresponding to C3' endo sugar conformations resulting from drug induced local desolvation of the DNA polymer.

A systematic approach toward the analysis of drug-DNA interactions using Raman spectroscopy: the binding of metal-free bleomycins A(2) and B(2) to calf thymus DNA

Bleomycins A(2) and B(2) are the two active components in the antineoplastic drug Blenoxane. DNA is targeted by this drug in cancer cells and the mode of action of this drug involves DNA binding. Ambiguity exists as to the way in which bleomycin binds to DNA. Raman spectroscopy was used to examine both calf thymus DNA and a bleomycin/DNA complex at two temperatures. A curvefitting technique was applied to these spectra for a spectral region obscured by many overlapping bands associated with the nucleotide bases in order to derive information about frequencies, bandwidths, and intensities of the vibrational modes in this region. This allowed identification and analysis of bands associated with specific assigned nucleotide base residues. Upon binding of bleomycin, several significant changes in bandwidth, intensities, and frequencies relative to uncomplexed DNA were observed consistently at both higher (30 degrees C) and lower (19 degrees C) temperature. The data presented here support at least a partial intercalation mode of binding for bleomycin that is temperature dependent and more pronounced at the more physiologically relevant temperature of 30 degrees C.

Resonance raman studies of heme structural differences in subunits of deoxy hemoglobin

Low frequency resonance Raman (RR) spectra are reported for deoxy hemoglobin (Hb), its isolated subunits, its analogue bearing methine-deuterated hemes in all four subunits (Hb-d(4)), and the hybrids bearing the deuterated heme in only one type of subunit, which are [alpha(d4)beta(h4)](2) and [alpha(h4)beta(d4)](2). Analyzed collectively, the spectra reveal subunit-specific modes that conclusively document subtle differences in structure for the heme prosthetic groups in the two types of subunits within the intact tetramer. Not surprisingly, the most significant spectral differences are observed in the gamma(7) mode that has a major contribution from out of plane bending of the methine carbons, a distortion that is believed to relieve strain in the high-spin heme prosthetic groups. The results provide convincing evidence for the utility of selectively labeled hemoglobin hybrids in unraveling the separate subunit contributions to the RR spectra of Hb and its various derivatives and for thereby detecting slight structural differences in the subunits.

Methanol poisoning. A rodent model with structural and functional evidence for retinal involvement

Methanol ingestion can lead to visual impairment, central nervous system dysfunction, or death. The extent of ocular involvement has been difficult to determine because the toxicity is restricted to humans and nonhuman primates due to species differences in methanol metabolism. A rodent model of methanol toxicity recently developed by us was used to evaluate retinal dysfunction in methanol poisoning. Formic acidemia and visual toxic reactions developed in methanol-intoxicated rats. Electroretinographic analysis indicated a significant early deficit in b-wave amplitude followed by a temporally delayed, lesser reduction in a-wave amplitude. Histologic evaluation of the eyes 60 hours after methanol administration revealed generalized retinal edema and vacuolation in the photoreceptors and retinal pigment epithelium. Ultrastructural examination showed swelling and disruption of the mitochondria in photoreceptor inner segments, optic nerve, and the retinal pigment epithelium. These studies document direct retinal involvement in this nonprimate model of methanol toxicity.

Liquid-chromatographic procedure for simultaneous analysis for eight benzodiazepines in serum

We describe an efficient extraction and liquid-chromatographic method for separating commonly encountered benzodiazepine drugs and their pharmacologically active metabolites. After a single extraction of the drugs from serum, chlordiazepoxide, demoxepam, N-desmethyl-chloriazepoxide, diazepam, N-desmethyldiazepam, N-desalkylflurazepam, oxazepam, and prazepam can be resolved and quantified by using a C18 reversed-phase "high-performance" column and a ternary-solvent gradient system. Three separate solutions [60 mmol/L ammonium acetate (pH 7.69), 60 mmol/L acetic acid (pH 2.8), and acetonitrile] were incorporated into a gradient mobile phase such that changes in pH and solvent composition occur. Complete chromatographic resolution of the benzodiazepines resulted, permitting quantification of all within 15 min. The standard curve is linear to at least 8 mg/L for each drug, and the detection limit for each was 0.05-0.10 mg/L. The day-to-day precision for both high and low concentrations yielded CVs of 5 to 9%. Extraction of each drug from serum was 95 to 100% complete. Exogenous and endogenous interferences are minimal. Finally, we circumvented the instability problem of benzodiazepine standards in solution by using a simple reduced-pressure drying process that produces a working standard that is stable for at least nine months.

Liquid-chromatographic procedure for simultaneous analysis for eight benzodiazepines in serum

We describe an efficient extraction and liquid-chromatographic method for separating commonly encountered benzodiazepine drugs and their pharmacologically active metabolites. After a single extraction of the drugs from serum, chlordiazepoxide, demoxepam, N-desmethyl-chloriazepoxide, diazepam, N-desmethyldiazepam, N-desalkylflurazepam, oxazepam, and prazepam can be resolved and quantified by using a C18 reversed-phase "high-performance" column and a ternary-solvent gradient system. Three separate solutions [60 mmol/L ammonium acetate (pH 7.69), 60 mmol/L acetic acid (pH 2.8), and acetonitrile] were incorporated into a gradient mobile phase such that changes in pH and solvent composition occur. Complete chromatographic resolution of the benzodiazepines resulted, permitting quantification of all within 15 min. The standard curve is linear to at least 8 mg/L for each drug, and the detection limit for each was 0.05-0.10 mg/L. The day-to-day precision for both high and low concentrations yielded CVs of 5 to 9%. Extraction of each drug from serum was 95 to 100% complete. Exogenous and endogenous interferences are minimal. Finally, we circumvented the instability problem of benzodiazepine standards in solution by using a simple reduced-pressure drying process that produces a working standard that is stable for at least nine months.