Influence of Factors Altering Gastric Microbiota on Bariatric Surgery Metabolic Outcomes.

Little is known about the influence of gastric microbiota on host metabolism, even though the stomach plays an important role in the production of hormones involved in body weight regulation and glucose homeostasis. Proton pump inhibitors (PPIs) and Helicobacter pylori alter gut microbiota, but their impact on gastric microbiota in patients with obesity and the influence of these factors on the metabolic response to bariatric surgery is not fully understood. Forty-one subjects with morbid obesity who underwent sleeve gastrectomy were included in this study. The H. pylori group was established by the detection of H. pylori using a sequencing-based method (n = 16). Individuals in whom H. pylori was not detected were classified according to PPI treatment. Gastric biopsy specimens were obtained during surgery and were analyzed by a high-throughput-sequencing method. Patients were evaluated at baseline and 3, 6, and 12 months after surgery. ß-Diversity measures were able to cluster patients according to their gastric mucosa-associated microbiota composition. H. pylori and PPI treatment are presented as two important factors for gastric mucosa-associated microbiota. H. pylori reduced diversity, while PPIs altered ß-diversity. Both factors induced changes in the gastric mucosa-associated microbiota composition and its predicted functions. PPI users showed lower percentages of change in the body mass index (BMI) in the short term after surgery, while the H. pylori group showed higher glucose levels and lower percentages of reduction in body weight/BMI 1 year after surgery. PPIs and H. pylori colonization could modify the gastric mucosa-associated microbiota, altering its diversity, composition, and predicted functionality. These factors may have a role in the metabolic evolution of patients undergoing bariatric surgery. IMPORTANCE The gut microbiota has been shown to have an impact on host metabolism. In the stomach, factors like proton pump inhibitor treatment and Helicobacter pylori haven been suggested to alter gut microbiota; however, the influence of these factors on the metabolic response to bariatric surgery has not been fully studied. In this study, we highlight the impact of these factors on the gastric microbiota composition. Moreover, proton pump inhibitor treatment and the presence of Helicobacter pylori could have an influence on bariatric surgery outcomes, mainly on body weight loss and glucose homeostasis. Deciphering the relationship between gastric hormones and gastric microbiota and their contributions to bariatric surgery outcomes paves the way to develop gut manipulation strategies to improve the metabolic success of bariatric surgery.

Gut Microbiota: The Missing Link Between Helicobacter pylori Infection and Metabolic Disorders?

Helicobacter pylori (H. pylori) is a gram-negative bacterium that infects approximately 4.4 billion individuals worldwide. Although the majority of infected individuals remain asymptomatic, this bacterium colonizes the gastric mucosa causing the development of various clinical conditions as peptic ulcers, chronic gastritis and gastric adenocarcinomas and mucosa-associated lymphoid tissue lymphomas, but complications are not limited to gastric ones. Extradigestive pathologies, including metabolic disturbances such as diabetes, obesity and nonalcoholic fatty liver disease, have also been associated with H. pylori infection. However, the underlying mechanisms connecting H. pylori with extragastric metabolic diseases needs to be clarified. Notably, the latest studies on the topic have confirmed that H. pylori infection modulates gut microbiota in humans. Damage in the gut bacterial community (dysbiosis) has been widely related to metabolic dysregulation by affecting adiposity, host energy balance, carbohydrate metabolism, and hormonal modulation, among others. Taking into account that Type 2 diabetic patients are more prone to be H. pylori positive, gut microbiota emerges as putative key factor responsible for this interaction. In this regard, the therapy of choice for H. pylori eradication, based on proton pump inhibitor combined with two or more antibiotics, also alters gut microbiota composition, but consequences on metabolic health of the patients has been scarcely explored. Recent studies from our group showed that, despite decreasing gut bacterial diversity, conventional H. pylori eradication therapy is related to positive changes in glucose and lipid profiles. The mechanistic insights explaining these effects should also be addressed in future research. This review will deal with the role of gut microbiota as the linking factor between H. pylori infection and metabolic diseases, and discussed the impact that gut bacterial modulation by H. pylori eradication treatment can also have in host's metabolism. For this purpose, new evidence from the latest human studies published in more recent years will be analyzed.

H. pylori Eradication Treatment Causes Alterations in the Gut Microbiota and Blood Lipid Levels.

Background: The gut microbiome plays an important role in the lipid metabolism. Antibiotic treatment causes changes in the intestinal microbiota. Our objective was to explore the relationship between changes in the intestinal microbiota and the level of plasma high density lipoprotein cholesterol (HDL) and low density lipoprotein cholesterol (LDL). Methods: Prospective case-control study with Helicobacter pylori-positive patients undergoing eradication therapy with omeprazole, clarithromycin, and amoxicillin. Stool and blood samples were obtained from 20 controls (H. pylori negative) and 40 patients before and 2 months after antibiotic treatment. Gut microbiota was determined through 16S rRNA amplicon sequencing (Illumina MiSeq). Results: Eradication treatment for H. pylori increased the HDL levels, and caused changes in gut microbiota profiles. An unfavorable lipid profiles (high LDL and low HDL levels) was associated with a low microbial richness and an increase of the Bacteroidetes phylum. Prevotella copri, Lachonobacterium, and Delsufovibrio were positively associated with HDL while Rikenellaceae was negatively associated with HDL after completing antibiotic treatment. Conclusions: Helicobacter pylori eradication treatment could improve lipid metabolism in relation with an increase in the HDL. Changes in the abundance of specific bacteria, such as P. copri, Lachonobacterium, Delsufovibrio, and Rikenellaceae could be associated with change in the plasma HDL levels.

Mucosa-associated microbiota in the jejunum of patients with morbid obesity: alterations in states of insulin resistance and metformin treatment.

BACKGROUND: Stool samples have been widely used to evaluate gut microbiota; however, little is known about the composition of human small intestinal microbiota and the alterations provoked by insulin resistance. OBJECTIVE: To describe the composition of jejunal microbiota in morbidly obese patients, as well as its link with insulin resistance and metformin treatment. SETTING: Virgen de la Victoria University Hospital and Regional University Hospital, Málaga, Spain. METHODS: Jejunal biopsies from 46 morbidly obese patients were analyzed by next-generation sequencing method. Patients were classified in the following 3 groups: low homeostasis model assessment of insulin resistance index (HOMA-IR) value, high HOMA-IR value, and metformin-treated type 2 diabetes patients (T2D-metf). RESULTS: Richness (q = .011) together with Proteobacteria (W = 2), Fusobacteria (W = 2), and Bacteroidetes (W = 1) phyla were significantly higher in high HOMA-IR compared with low HOMA-IR group. At family level, several differences were found between low HOMA-IR and T2D-metf group, being the most important the higher abundance of Halomonadacea in T2D-metf group (W = 22). PICRUSt analysis showed that predicted genes involved in trimethylamine-N-oxide biosynthesis pathway could be increased in jejunal microbiota of T2D-metf group compared with the low HOMA-IR group, while indole biosynthesis pathway could be increased in the low HOMA-IR group compared with the high HOMA-IR group. CONCLUSION: An increase in richness and an enrichment in Proteobacteria, Fusobacteria, and Bacteroidetes was observed in jejunal from morbidly obese patients with high insulin resistance. Halomonadaceae family was significantly increased in metformin-treated patients. Functional analysis of predicted metagenome suggests that trimethylamine-N-oxide biosynthesis pathway could be increased in the jejunal microbiota of T2D-meft group, while indole biosynthesis pathway could be increased in low HOMA-IR group. These results contribute to the increase in the scarce knowledge about the mucosal microbiota of the hardly accessible small intestine.

H. pylori Eradication Treatment Alters Gut Microbiota and GLP-1 Secretion in Humans.

Changes in the intestinal microbial community and some metabolic disturbances, including obesity and type2 diabetes, are related. Glucagon-like peptide-1 (GLP-1) regulates glucose homeostasis. Microbiota have been linked to incretin secretion. Antibiotic use causes changes in microbial diversity and composition. Our aim was to evaluate the relationship between microbiota changes and GLP-1 secretion. A prospective case-control study with a Helicobacter pylori-positive patient model involving subjects under eradication therapy (omeprazole, clarithromycin, and amoxicillin). Forty patients with H. pylori infection and 20 matched participants, but negative for H. pylori antigen. Patients were evaluated before and two months after treatment. We analyzed anthropometric measurements, carbohydrate metabolism, lipid profile, and C-reactive protein. Gut microbiota composition was analyzed through 16S rRNA amplicon sequencing (IlluminaMiSeq). Eradication treatment for H. pylori decreased bacterial richness (Chao1, p = 0.041). Changes in gut microbiota profiles were observed at phylum, family, genus and species levels. GLP-1 secretion and variables of carbohydrate metabolism were improved. Correlations were seen between GLP-1 changes and variations within microbial community abundances, specifically Bifidobacterium adolescentis, the Lachnobacterium genus, and Coriobacteriaceae family. A conventional treatment to eradicate H. pylori could improve carbohydrate metabolism possibly in relation with an increase in GLP-1 secretion. GLP-1 secretion may be related to alterations in intestinal microbiota, specifically Lachnobacterium, B. adolescentis and Coriobacteriaceae.

Methylation patterns of Vegfb promoter are associated with gene and protein expression levels: the effects of dietary fatty acids.

PURPOSE: We have investigated the epigenetic regulation by dietary fatty acids of Vegfb levels in rats' white adipose tissue and 3T3-L1 cells. METHODS: A group of rats were assigned to three diets, each one with a different composition of saturated, monounsaturated and polyunsaturated fatty acids. Samples of white adipose tissues were taken for the methylation and expression studies. Additionally, 3T3-L1 cells were treated with palmitic, oleic, and linoleic fatty acids. After treatment, cells were harvested and genetic material was extracted for the analysis of Vegfb levels. RESULTS: We report evidence of changes in the methylation levels of the CpG island at the Vegfb promoter and in the Vegfb expression levels in vivo and in vitro by dietary fatty acid, with the main contribution of the linoleic fatty acid. Vegfb promoter methylation levels were closely related to the Vegfb gene expression. CONCLUSION: According to our results, the regulation of Vegfb gene expression by dietary fatty acids may be mediated, at least in part, by epigenetic modifications on Vegfb promoter methylation. Considering the deep association between angiogenesis and tissue growth, we suggest the nutriepigenetic regulation of Vegfb as a key target in the control of the adipose tissue expansion.

Plasma selenium levels and oxidative stress biomarkers: a gene-environment interaction population-based study.

The role of selenium exposure in preventing chronic disease is controversial, especially in selenium-repleted populations. At high concentrations, selenium exposure may increase oxidative stress. Studies evaluating the interaction of genetic variation in genes involved in oxidative stress pathways and selenium are scarce. We evaluated the cross-sectional association of plasma selenium concentrations with oxidative stress levels, measured as oxidized to reduced glutathione ratio (GSSG/GSH), malondialdehyde (MDA), and 8-oxo-7,8-dihydroguanine (8-oxo-dG) in urine, and the interacting role of genetic variation in oxidative stress candidate genes, in a representative sample of 1445 men and women aged 18-85 years from Spain. The geometric mean of plasma selenium levels in the study sample was 84.76 µg/L. In fully adjusted models the geometric mean ratios for oxidative stress biomarker levels comparing the highest to the lowest quintiles of plasma selenium levels were 0.61 (0.50-0.76) for GSSG/GSH, 0.89 (0.79-1.00) for MDA, and 1.06 (0.96-1.18) for 8-oxo-dG. We observed nonlinear dose-responses of selenium exposure and oxidative stress biomarkers, with plasma selenium concentrations above ~110 µg/L being positively associated with 8-oxo-dG, but inversely associated with GSSG/GSH and MDA. In addition, we identified potential risk genotypes associated with increased levels of oxidative stress markers with high selenium levels. Our findings support that high selenium levels increase oxidative stress in some biological processes. More studies are needed to disentangle the complexity of selenium biology and the relevance of potential gene-selenium interactions in relation to health outcomes in human populations.

High resolution melting curve analysis of DNA samples isolated by different DNA extraction methods.

BACKGROUND: High resolution melting is a post-PCR-based method for detecting DNA sequence variation by measuring changes in the melting of a DNA duplex. Melting of double-stranded DNA molecules is influenced by several factors. We evaluated the influence of the DNA isolation method in the melting curve analysis to detect genetic variations. METHODS: We isolated DNA from whole blood of 547 subjects by two different methods: Maxwell 16 Instrument and DNA FlexiGene Kit. A fragment of 159 bp was amplified and analyzed by high resolution melting. Those samples that showed a different melting curve pattern were sequenced. RESULTS: Of the samples extracted with the Maxwell 16 Instrument, 42% showed variation compared with 0.18% of the samples extracted with DNA FlexiGene Kit. After sequencing, we showed that all samples extracted with the Maxwell 16 Instrument were false positive except one, which coincided with the only sample that showed variation in those extracted with the DNA FlexiGene Kit. CONCLUSION: The method used to extract DNA is an important factor to consider in the analysis of melting curves obtained by high resolution melting, as it may influence the melting behaviour of the samples, giving false positive results in the detection of genetic variants.

Testosterone, SHBG and risk of type 2 diabetes in the second evaluation of the Pizarra cohort study.

AIM: To evaluate the association between serum levels of testosterone, sex hormone-binding globulin (SHBG) and calculated bioavailable testosterone (bioT), and the risk of type 2 diabetes mellitus (T2D) in a prospective cohort from southern Spain (Pizarra study). RESEARCH DESIGN AND METHODS: The study was performed in the Pizarra Cohort Study, a prospective study started in 1995 with a follow-up of 11 years. Anthropometric and metabolic variables were measured at baseline and at 6 and 11 years of follow-up. Total testosterone (TT), SHBG and calculated bioT were determined at the 6-year follow-up. RESULTS: The levels of TT and bioT in men were negatively associated with the risk of obesity, T2D and the metabolic syndrome. In women, the levels of TT and bioT were associated positively with the risk of insulin resistance. The levels of SHBG were associated negatively with the risk of T2D, obesity and insulin resistance in both men and women. For all groups, the association was higher at the 11-year follow-up. CONCLUSIONS: Low levels of testosterone and SHBG increase the risk of T2D in men, and high levels of testosterone increase the risk of insulin resistance in women. The association between TT levels and the risk of T2D is not completely independent of other variables, such as exposure time, adiposity, insulin resistance or SHBG levels. This study also shows that the different responses between men and women are probably because of the protective effect of SHBG, levels of which are higher in women than in men.

The -30G>A polymorphism of the glucokinase gene promoter is associated with obesity in a population from southern Spain.

The aim of this study was to test the hypothesis of an association between the -30G>A polymorphism of the promoter of the glucokinase gene and the prevalence and incidence of obesity. We studied the -30G>A polymorphism of the glucokinase gene promoter in 981 persons, of whom 866 were seen again 6 years later. All the persons underwent an oral glucose-tolerance test and the BMI (weight/height(2)) was recorded. The -30G>A polymorphism of the glucokinase gene promoter was studied using RFLP-PCR. At the initial study, the probability of having a BMI > or =25 in carriers of the A allele was significantly lower than expected by chance (odds ratio (OR) = 0.63; 95% confidence interval (CI) = 0.456-0.885). In those persons with a BMI > or =30 at the first study, the probability at 6 years of losing weight (reaching a BMI < 30) was greater in carriers of the A allele (OR = 0.22; 95% CI = 0.087-0.576). The increase in weight over these 6 years, taken as a continuous variable, was significantly less only in those persons who were originally obese (P = 0.018). In conclusion, in a population from southern Spain, carriers of the A allele of the -30G>A polymorphism in the promoter of the glucokinase gene had a lower risk for obesity and the likelihood of losing weight was greater in those obese persons who had the A allele (GA or AA).