Yolanda Sanz

Gut microbiota composition is associated with body weight, weight gain and biochemical parameters in pregnant women.

Obesity is associated with complications during pregnancy and increased health risks in the newborn. The objective of the present study was to establish possible relationships between gut microbiota, body weight, weight gain and biochemical parameters in pregnant women. Fifty pregnant women were classified according to their BMI in normal-weight (n 34) and overweight (n 16) groups. Gut microbiota composition was analysed by quantitative real-time PCR in faeces and biochemical parameters in plasma at 24 weeks of pregnancy. Reduced numbers of Bifidobacterium and Bacteroides and increased numbers of Staphylococcus, Enterobacteriaceae and Escherichia coli were detected in overweight compared with normal-weight pregnant women. E. coli numbers were higher in women with excessive weight gain than in women with normal weight gain during pregnancy, while Bifidobacterium and Akkermansia muciniphila showed an opposite trend. In the whole population, increased total bacteria and Staphylococcus numbers were related to increased plasma cholesterol levels. Increased Bacteroides numbers were related to increased HDL-cholesterol and folic acid levels, and reduced TAG levels. Increased Bifidobacterium numbers were related to increased folic acid levels. Increased Enterobacteriaceae and E. coli numbers were related to increased ferritin and reduced transferrin, while Bifidobacterium levels showed the opposite trend. Therefore, gut microbiota composition is related to body weight, weight gain and metabolic biomarkers during pregnancy, which might be of relevance to the management of the health of women and infants.

Interactions of gut microbiota with functional food components and nutraceuticals

The human gut is populated by an array of bacterial species, which develop important metabolic and immune functions, with a marked effect on the nutritional and health status of the host. Dietary component also play beneficial roles beyond basic nutrition, leading to the development of the functional food concept and nutraceuticals. Prebiotics, polyunsaturated fatty acids (PUFAs) and phytochemicals are the most well characterized dietary bioactive compounds. The beneficial effects of prebiotics mainly relay on their influence on the gut microbiota composition and their ability to generate fermentation products (short-chain fatty acids) with diverse biological roles. PUFAs include the omega-3 and omega-6 fatty acids, whose balance may influence diverse aspects of immunity and metabolism. Moreover, interactions between PUFAs and components of the gut microbiota may also influence their biological roles. Phytochemicals are bioactive non-nutrient plant compounds, which have raised interest because of their potential effects as antioxidants, antiestrogenics, anti-inflammatory, immunomodulatory, and anticarcinogenics. However, the bioavailability and effects of polyphenols greatly depend on their transformation by components of the gut microbiota. Phytochemicals and their metabolic products may also inhibit pathogenic bacteria while stimulate the growth of beneficial bacteria, exerting prebiotic-like effects. Therefore, the intestinal microbiota is both a target for nutritional intervention and a factor influencing the biological activity of other food compounds acquired orally. This review focuses on the reciprocal interactions between the gut microbiota and functional food components, and the consequences of these interactions on human health.

Interplay Between Weight Loss and Gut Microbiota Composition in Overweight Adolescents

The aim of this study was to determine the influence of an obesity treatment program on the gut microbiota and body weight of overweight adolescents. Thirty‐six adolescents (13–15 years), classified as overweight according to the International Obesity Task Force BMI criteria, were submitted to a calorie‐restricted diet (10–40%) and increased physical activity (15–23 kcal/kg body weight/week) program over 10 weeks. Gut bacterial groups were analyzed by quantitative real‐time PCR before and after the intervention. A group of subjects (n = 23) experienced >4.0 kg weight loss and showed significant BMI (P = 0.030) and BMI z‐score (P = 0.035) reductions after the intervention, while the other group (n = 13) showed <2.0 kg weight loss. No significant differences in dietary intake were found between both groups. In the whole adolescent population, the intervention led to increased Bacteroides fragilis group (P = 0.001) and Lactobacillus group (P = 0.030) counts, and to decreased Clostridium coccoides group (P = 0.028), Bifidobacterium longum (P = 0.031), and Bifidobacterium adolescentis (P = 0.044) counts. In the high weight–loss group, B. fragilis group and Lactobacillus group counts also increased (P = 0.001 and P = 0.007, respectively), whereas C. coccoides group and B. longum counts decreased (P = 0.001 and P = 0.044, respectively) after the intervention. Total bacteria, B. fragilis group and Clostridium leptum group, and Bifidobacterium catenulatum group counts were significantly higher (P < 0.001–0.036) while levels of C. coccoides group, Lactobacillus group, Bifidobacterium, Bifidobacterium breve, and Bifidobacterium bifidum were significantly lower (P < 0.001–0.008) in the high weight–loss group than in the low weight–loss group before and after the intervention. These findings indicate that calorie restriction and physical activity have an impact on gut microbiota composition related to body weight loss, which also seem to be influenced by the individuals microbiota.

Shifts in clostridia, bacteroides and immunoglobulin-coating fecal bacteria associated with weight loss in obese adolescents

Objective:To evaluate the effects of a multidisciplinary obesity treatment programme on fecal microbiota composition and immunoglobulin-coating bacteria in overweight and obese adolescents and their relationship to weight loss.Design:Longitudinal intervention study based on both a calorie-restricted diet (calorie reduction=10–40%) and increased physical activity (calorie expenditure=15–23 kcal/kg body weight per week) for 10 weeks.Participants:Thirty-nine overweight and obese adolescents (BMI mean 33.1 range 23.7–50.4; age mean 14.8 range, 13.0–16.0).Measurements:BMI, BMI z-scores and plasma biochemical parameters were measured before and after the intervention. Fecal microbiota was analyzed by fluorescent in situ hybridization. Immunoglobulin-coating bacteria were detected using fluorescent-labelled F(ab′)2 antihuman IgA, IgG and IgM.Results:Reductions in Clostridium histolyticum and E. rectale-C. coccoides proportions significantly correlated with weight and BMI z-score reductions in the whole adolescent population. Proportions of C. histolyticum, C. lituseburense and E. rectale-C. coccoides dropped significantly whereas those of the Bacteroides-Prevotella group increased after the intervention in those adolescents who lost more than 4 kg. Total fecal energy was almost significantly reduced in the same group of adolescents but not in the group that lost less than 2.5 kg. IgA-coating bacterial proportions also decreased significantly in participants who lost more than 6 kg after the intervention, paralleled to reductions in C. histolyticum and E. rectale-C. coccoides populations. E. rectale-C. coccoides proportions also correlated with weight loss and BMI z-score reduction in participants whose weight loss exceeded 4 kg.Conclusions:Specific gut bacteria and an associated IgA response were related to body weight changes in adolescents under lifestyle intervention. These results suggest interactions between diet, gut microbiota and host metabolism and immunity in obesity.

Specific duodenal and faecal bacterial groups associated with paediatric coeliac disease.

Aims: To identify specific gut bacteria associated with coeliac disease (CD) at diagnosis and after treatment with a gluten-free diet (GFD) in a paediatric population. Methods: 30 and 18 faecal samples from untreated and treated CD patients and 25 and 8 biopsy samples from untreated and treated CD patients, respectively, were analysed. In addition, 30 faecal and 8 biopsy samples from control children were evaluated for comparative purposes. Gut bacterial groups were quantified by real-time PCR. Results: Bacteroides and Clostridium leptum groups were more abundant in faeces and biopsies of CD patients than in controls regardless of the stage of the disease. E coli and Staphylococcus counts were also higher in faeces and biopsies of non-treated CD patients than in those of controls, but their levels were normalised after treatment with a GFD. Bifidobacterium levels were lower in faeces of both groups of CD patients and in biopsies of untreated CD patients compared to controls. Similar bacterial groups were related to CD in biopsies and faeces, indicating that faecal microbiota partly reflects that of the small intestine in CD patients, and could constitute a convenient biological index of this disorder. Conclusions: Duodenal and faecal microbiota is unbalanced in children with untreated CD and only partially restored after long-term treatment with a GFD, constituting a novel factor linked to this disorder.

Differential immunomodulatory properties of Bifidobacterium logum strains : relevance to probiotic selection and clinical applications

Modulation of host immunity is one of the proposed benefits of the consumption of probiotics. Nonetheless, comparative studies on the immunological properties that support the selection of strains of the same species for specific health benefits are limited. In this study, the ability of different strains of Bifidobacterium longum to induce cytokine production by peripheral blood mononuclear cells (PBMCs) has been evaluated. Live cells of all B. longum strains greatly stimulated regulatory cytokine interleukin (IL)‐10 and proinflammatory cytokine tumour necrosis factor (TNF)‐α production. Strains of the same species also induced specific cytokine patterns, suggesting that they could drive immune responses in different directions. The probiotic strain B. longum W11 stimulated strongly the production of T helper 1 (Th1) cytokines while B. longum NCIMB 8809 and BIF53 induced low levels of Th1 cytokines and high levels of IL‐10. The effects of cell‐surface components obtained by sonication of B. longum strains overall confirm the effects detected by stimulation of PBMCs with live cells, indicating that these components are important determinants of the immunomodulatory activity of B. longum. Genomic DNA of some strains stimulated the production of the Th1 and pro‐inflammatory cytokines, interferon (IFN)‐γ and TNF‐α, but not that of IL‐10. None of the cell‐free culture supernatants of the studied strains was able to induce TNF‐α production, suggesting that the proinflammatory component of these strains is associated mainly with structural cell molecules. The results suggest that despite sharing certain features, some strains can perform a better functional role than others and their careful selection for therapeutic use is desirable.

The impact of probiotic on gut health.

The gastrointestinal tract (GIT) microbiota plays an important role in host health due to its involvement in nutritional, immunologic and physiological functions. Microbial imbalances have been associated with enhanced risk of specific diseases. This observation has allowed the introduction of microorganisms as probiotics which are microbes with demonstrated health benefits in humans when ingested in foods. The mechanisms of action include the inhibition of pathogen growth by competition for nutritional sources and adhesion sites, secretion of antimicrobial substances, toxin inactivation. Consequently, the primary clinical interest in the application of probiotics has been in the prevention and treatment of gastrointestinal infections and antibiotic-associated diarrhea diseases. The well-characterized immunomodulatory potential of specific probiotic strains, beyond the effect on the composition of the microbiota, has been be used as innovative tools to alleviate intestinal inflammation, normalize gut mucosal dysfunction, and down-regulate hypersensitivity reactions. Clinical efficacy of specific probiotic strains has been demonstrated in, rotaviruss diarrhea, antibiotic associated diarrhea, irritable bowel syndrome and food allergies. Further, recent clinical and nutritional studies have uncovered the function of specific strains in energy metabolism and thereby have opened up new angles on their exploitation. However, as these processes are highly specific, it is important to characterize the properties of specific probiotic strains an in order to select the best strains or strain combinations for the target in question. Advances have prompted increased the interest of researchers and industry and new applications and targets are being discovered.

Dry-cured ham flavour: enzymatic generation and process influence

Abstract The processing of dry-cured ham is very complex and involves numerous biochemical reactions that are reviewed in this paper. Muscle proteins undergo an intense proteolysis resulting in a great number of small peptides and high amounts of free amino acids. The enzymes responsible of these changes are proteinases (cathepsins B, D, H and L and, to a less extent, calpains) and exopeptidases (peptidases and aminopeptidases). Muscle and adipose tissue lipids are also subject to intense lipolysis generating free fatty acids by the action of lipases that, in a second stage, are transformed to volatiles as a result of oxidation. Sensory profiles of dry-cured ham are strongly affected by these enzymatic reactions. In addition, the activity levels of the muscle enzymes significantly depend on the properties of raw ham, such as age and crossbreeding as well as the process conditions such as temperature, time, water activity, redox potential and salt content. Thus, the control of the muscle enzyme systems, mainly proteases and lipases, is essential for the optimal standardisation of the processing and/or enhancement of flavour quality of dry-cured ham.

Intestinal dysbiosis and reduced immunoglobulin-coated bacteria associated with coeliac disease in children

BackgroundCoeliac disease is a chronic intestinal inflammatory disorder due to an aberrant immune response to dietary gluten proteins in genetically predisposed individuals. Mucosal immune response through IgA secretion constitutes a first line of defence responsible for neutralizing noxious antigens and pathogens. The aim of this study was the characterization of the relationships between immunoglobulin-coated bacteria and bacterial composition of faeces of coeliac disease (CD) patients, untreated and treated with a gluten-free diet (GFD) and healthy controls.ResultsIgA-coated faecal bacterial levels were significantly lower in both untreated and treated CD patients than in healthy controls. IgG and IgM-coated bacterial levels were also significantly lower in treated CD patients than in untreated CD patients and controls. Gram-positive to Gram-negative bacteria ratio was significantly reduced in both CD patients compared to controls. Bifidobacterium, Clostridium histolyticum, C. lituseburense and Faecalibacterium prausnitzii group proportions were less abundant (P < 0.050) in untreated CD patients than in healthy controls. Bacteroides-Prevotella group proportions were more abundant (P < 0.050) in untreated CD patients than in controls. Levels of IgA coating the Bacteroides-Prevotella group were significantly reduced (P < 0.050) in both CD patients in comparison with healthy controls.ConclusionsIn CD patients, reduced IgA-coated bacteria is associated with intestinal dysbiosis, which altogether provide new insights into the possible relationships between the gut microbiota and the host defences in this disorder.

Intestinal luminal nitrogen metabolism: Role of the gut microbiota and consequences for the host

Alimentary and endogenous proteins are mixed in the small intestinal lumen with the microbiota. Although experimental evidences suggest that the intestinal microbiota is able to incorporate and degrade some of the available amino acids, it appears that the microbiota is also able to synthesize amino acids raising the view that amino acid exchange between the microbiota and host can proceed in both directions. Although the net result of such exchanges remains to be determined, it is likely that a significant part of the amino acids recovered from the alimentary proteins are used by the microbiota. In the large intestine, where the density of bacteria is much higher than in the small intestine and the transit time much longer, the residual undigested luminal proteins and peptides can be degraded in amino acids by the microbiota. These amino acids cannot be absorbed to a significant extent by the colonic epithelium, but are precursors for the synthesis of numerous metabolic end products in reactions made by the microbiota. Among these products, some like short-chain fatty acids and organic acids are energy substrates for the colonic mucosa and several peripheral tissues while others like sulfide and ammonia can affect the energy metabolism of colonic epithelial cells. More work is needed to clarify the overall effects of the intestinal microbiota on nitrogenous compound metabolism and consequences on gut and more generally host health.