Publications by authors named "Thomas Ammann"

9 Publications

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Longitudinal Physical Activity Change During Hemodialysis and Its Association With Body Composition and Plasma BAIBA Levels.

Front Physiol 2019 25;10:805. Epub 2019 Jun 25.

Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy.

Low physical activity is frequent in end stage renal disease. We evaluated the longitudinal change in physical activity and its barriers in hemodialysis (HD) patients and the association between the patterns of physical activity change, body composition, and beta-aminoisobutyric acid (BAIBA), as circulating myokine. This is an observational study, where HD patients were considered in a 24-month follow-up. We assessed overtime the change of physical inactivity and its barriers by validated questionnaires, body composition by bioimpedance analysis, muscle strength by hand-dynamometer, and plasma BAIBA levels by liquid chromatography spectrometry. Parametric and non-parametric analyses were performed, as appropriate. Out of the 49 patients studied at baseline, 39 completed the first-year follow-up, and 29 completed the second year. At month 12, active patients had higher intracellular water (ICW) ( = 0.001) and cellular mass ( < 0.001), as well as at month 24 ( = 0.012, = 0.002; respectively) with respect to inactive. A significant reduction in ICW was shown at month 12 ( = 0.011) and month 24 ( = 0.014) in all patients. The barrier "reduced walking ability" was more frequent in inactive patients with respect to active at month 12 ( = 0.003) and at month 24 ( = 0.05). At month 24, plasma BAIBA levels were higher among active patients with respect to inactive ( = 0.043) and a correlation was seen between muscle strength and ICW ( = 0.51, = 0.005); normalizing BAIBA per body mass index, we found it lower with respect to baseline ( = 0.004), as well as after correcting per ICW ( = 0.001), as marker of muscle mass. A high prevalence of physical inactivity persisted during a 24-month follow-up in this cohort. We found an association between physical activity and a decline in marker of muscularity and reduced plasma BAIBA levels.
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http://dx.doi.org/10.3389/fphys.2019.00805DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603089PMC
June 2019

The metabolite beta-aminoisobutyric acid and physical inactivity among hemodialysis patients.

Nutrition 2017 Feb 30;34:101-107. Epub 2016 Jul 30.

Department of Clinical Medicine, Sapienza University of Rome, Rome, Italy.

Objective: Physical inactivity is frequent in patients on hemodialysis (HD), and represents a reliable predictor of morbidity and mortality. Beta-aminoisobutyric acid (BAIBA) is a contraction-induced myokine, the plasma levels of which increase with exercise and are inversely associated with metabolic risk factors. The aim of this study was to ascertain whether physical inactivity and clinical parameters relate to plasma BAIBA levels in this patient population.

Methods: Adult patients on HD were included, and the presence of physical inactivity was assessed. BAIBA levels were measured in these patients and in healthy individuals. We assessed barriers to physical activity, including 23 items regarding psychophysical and financial barriers. Body composition was assessed by bioimpedance and muscle strength by handgrip dynamometer. Nonparametric tests and logistic regression analyses were performed.

Results: Forty-nine patients on HD were studied; 49% were physically active and 51% were inactive. Of the patients, 43 reported barriers to physical activity and 61% of inactive patients reported three or more barriers. BAIBA levels were lower in patients on HD with respect to controls (P < 0.001). Stratifying HD patients as active and inactive, both groups showed significantly lower BAIBA levels versus controls (P = 0.0005, P < 0.001, respectively). Nondiabetic patients on HD showed increased BAIBA levels compared with diabetic patients (P < 0.001). Patients on HD endorsing the two most frequent barriers showed lower BAIBA levels than those not reporting these barriers (P = 0.006). Active patients showed higher intracellular water (%) (P = 0.008), and active and inactive patients showed significant correlation between total body muscle mass and handgrip strength (P = 0.04, P = 0.005, respectively).

Conclusions: Physical inactivity is highly prevalent among patients on HD and BAIBA correlates with barriers to physical activity reported by inactive patients.
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http://dx.doi.org/10.1016/j.nut.2016.07.012DOI Listing
February 2017

Impact of early colonizers on in vitro subgingival biofilm formation.

PLoS One 2013 5;8(12):e83090. Epub 2013 Dec 5.

Oral Microbiology and Immunology, Institute of Oral Biology, Center of Dental Medicine, University of Zürich, Zürich, Switzerland.

The aim of this study was to investigate the impact of early colonizing species on the structure and the composition of the bacterial community developing in a subgingival 10-species biofilm model system. The model included Streptococcus oralis, Streptococcus anginosus, Actinomycesoris, Fusobacterium nucleatum subsp. nucleatum, Veillonella dispar, Campylobacter rectus, Prevotella intermedia, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola. Based on literature, we considered Streptococcus oralis, Streptococcus anginosus, and Actinomyces oris as early colonizers and examined their role in the biofilms by either a delayed addition to the consortium, or by not inoculating at all the biofilms with these species. We quantitatively evaluated the resulting biofilms by real-time quantitative PCR and further compared the structures using confocal laser scanning microscopy following fluorescence in situ hybridisation. The absence of the early colonizers did not hinder biofilm formation. The biofilms reached the same total counts and developed to normal thickness. However, quantitative shifts in the abundances of individual species were observed. In the absence of streptococci, the overall biofilm structure appeared looser and more dispersed. Moreover, besides a significant increase of P. intermedia and a decrease of P. gingivalis , P. intermedia appeared to form filamented long chains that resembled streptococci. A. oris, although growing to significantly higher abundance in absence of streptococci, did not have a visible impact on the biofilms. Hence, in the absence of the early colonizers, there is a pronounced effect on P. intermedia and P. gingivalis that may cause distinct shifts in the structure of the biofilm. Streptococci possibly facilitate the establishment of P. gingivalis into subgingival biofilms, while in their absence P. intermedia became more dominant and forms elongated chains.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0083090PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3855599PMC
September 2014

Phenotypic diversity of multicellular filamentation in oral Streptococci.

PLoS One 2013 27;8(9):e76221. Epub 2013 Sep 27.

Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland ; Anthropological Institute and Museum, University of Zurich, Zurich, Switzerland.

Filamentous multicellular bacteria are among the most ancient multicellular organisms. They inhabit a great variety of environments and are present in the human body, including the oral cavity. Beside the selective advantages related to the larger size achieved through filamentation, the development of multicellular bacteria can be also driven by simple ecological factors such as birth and death rates at the cellular level. In order to extend earlier results obtained in aquatic species, we investigate the filamentation process of four different strains of oral streptococci, namely S. mutans, S. salivarius, S. oralis and S. anginosus. The results indicate differences in the capacities of different streptococcus species to form filaments, manifested in terms of length and the time-scale of filament elongation. The filamentation pattern of these oral streptococci resembles that of aquatic bacteria, whereby filaments reach a peak length during exponential growth and become short when the population reaches a steady state. Hence, this study validates that multicellularity can be an emergent property of filamentous bacteria of different ecological niches, and that phenotypic differences in filamentation can occur within species of the same genus, in this case oral streptococci. Moreover, given the role that specific oral streptococci can play in the etiology of oral diseases, these results can possibly open new perspectives in the study of the virulence properties of these species.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0076221PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3785443PMC
July 2014

Advancement of the 10-species subgingival Zurich biofilm model by examining different nutritional conditions and defining the structure of the in vitro biofilms.

BMC Microbiol 2012 Oct 5;12:227. Epub 2012 Oct 5.

Section of Oral Microbiology and Immunology, Institute of Oral Biology, Center of Dental Medicine, Plattenstrasse 11, 8032, Zürich, Switzerland.

Background: Periodontitis is caused by a highly complex consortium of bacteria that establishes as biofilms in subgingival pockets. It is a disease that occurs worldwide and its consequences are a major health concern. Investigations in situ are not possible and the bacterial community varies greatly between patients and even within different loci. Due to the high complexity of the consortium and the availability of samples, a clear definition of the pathogenic bacteria and their mechanisms of pathogenicity are still not available. In the current study we addressed the need of a defined model system by advancing our previously described subgingival biofilm model towards a bacterial composition that reflects the one observed in diseased sites of patients and analysed the structure of these biofilms.

Results: We further developed the growth media by systematic variation of key components resulting in improved stability and the firm establishment of spirochetes in the 10-species subgingival Zurich biofilm model. A high concentration of heat-inactivated human serum allowed the best proliferation of the used species. Therefore we further investigated these biofilms by analysing their structure by confocal laser scanning microscopy following fluorescence in situ hybridisation. The species showed mutual interactions as expected from other studies. The abundances of all organisms present in this model were determined by microscopic counting following species-specific identification by both fluorescence in situ hybridisation and immunofluorescence. The newly integrated treponemes were the most abundant organisms.

Conclusions: The use of 50% of heat-inactivated human serum used in the improved growth medium resulted in significantly thicker and more stable biofilms, and the quantitative representation of the used species represents the in vivo community of periodontitis patients much closer than in biofilms grown in the two media with less or no human serum. The appearance of T. denticola, P. gingivalis, and T. forsythia in the top layer of the biofilms, and the high abundance of T. denticola, reflects well the microbial situation observed at diseased sites. The improved model biofilms will allow further investigations of interactions between individual species and of the effects of atmospheric or nutritional changes, as well as interactions with tissue cells.
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http://dx.doi.org/10.1186/1471-2180-12-227DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3561252PMC
October 2012

Effect of intensive nutritional counseling and support on clinical outcomes of hemodialysis patients.

Nutrition 2012 Oct 1;28(10):1012-5. Epub 2012 May 1.

Department of Clinical Medicine, Sapienza University of Rome, Rome, Italy.

Objective: Protein-energy wasting is frequently found in patients on hemodialysis (HD). Anorexia and hypophagia contribute to malnutrition and increased morbidity and mortality, but the clinical impact of correcting hypophagia remains uncertain. We evaluated whether the correction of hypophagia influences morbidity and mortality in anorexic patients on HD.

Methods: Thirty-four patients on HD were enrolled in a 2-y follow-up program including regular nutritional assessments. Patients not meeting the nutritional requirements during the follow-up received nutritional counseling, consisting of advice, individually tailored diets, and, for a failed dietary intervention, artificial nutrition. Biochemical, anthropometric, and body composition parameters, morbidity, and mortality were recorded in all patients at 12 and 24 mo.

Results: At baseline, 14 patients (41%) were anorexic, and 20 patients (59%) were non-anorexic. Anorexic patients were hypophagic and presented with a decreased fat-free mass. After 12 and 24 mo, cholesterol, albumin, lymphocyte count, and body mass index did not differ between the groups, whereas fat-free mass (percentage) in supplemented anorexic patients significantly improved in no longer differing from non-anorexic patients (65.8 ± 4.4 versus 65.4 ± 8.9, respectively, P = NS; 65.8 ± 4.4 versus 66.7 ± 10.78, respectively, P = NS). Morbidity and mortality were not different between the two groups.

Conclusion: In patients on HD, nutritional counseling and nutritional support positively affect the nutritional status in hypophagic patients and make the risk of morbidity and mortality in anorexic patients comparable to those of non-anorexic patients.
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http://dx.doi.org/10.1016/j.nut.2012.01.008DOI Listing
October 2012

Subgingival biofilm structure.

Front Oral Biol 2012 11;15:1-16. Epub 2011 Nov 11.

Department of Oral Microbiology, University of Umeå, Umeå, Sweden.

Periodontitis is an inflammatory disease of the oral cavity initiated by a microbial biofilm (or 'dental plaque'). Subgingival biofilms in periodontal pockets are not easily analyzed without the loss of structural integrity. These subgingival plaques are structured communities of microorganisms with great phylogenetic diversity embedded in a self-produced extracellular polymeric matrix. For almost three decades, knowledge of the structure of plaque located below the gingival margin has been limited to landmark studies from the 1970s that were unaware of the breadth of microbial diversity we appreciate now. Only recently has technical progress - combining histology, confocal scanning fluorescent microscopy and fluorescent in situ hybridization to localize the most abundant species from different phyla and species associated with periodontitis - provided new insights into the architecture of subgingival biofilms. This review focuses on the structure and composition of subgingival biofilms and discusses current knowledge on the nature of the extracellular matrix. We describe further structural aspects of 'subgingival' biofilms produced in vitro that are gaining considerable interest as we search for models to investigate biofilm development, resistance to antibiotics, extracellular polymeric matrix composition and function, and reciprocal host-cell-to-biofilm interactions.
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http://dx.doi.org/10.1159/000329667DOI Listing
January 2012

Scent of danger: floc formation by a freshwater bacterium is induced by supernatants from a predator-prey coculture.

Appl Environ Microbiol 2010 Sep 23;76(18):6156-63. Epub 2010 Jul 23.

Limnological Station, Institute of Plant Biology, University of Zürich, CH-8802 Kilchberg, Switzerland.

We investigated predator-prey interactions in a model system consisting of the bacterivorous flagellate Poterioochromonas sp. strain DS and the freshwater bacterium Sphingobium sp. strain Z007. This bacterial strain tends to form a subpopulation of grazing-resistant microscopic flocs, presumably by aggregation. Enhanced formation of such flocs could be demonstrated in static batch culture experiments in the presence of the predator. The ratio of aggregates to single cells reached >0.1 after 120 h of incubation in an oligotrophic growth medium. The inoculation of bacteria into supernatants from cocultures of bacteria and flagellates (grown in oligotrophic or in rich media) also resulted in a substantially higher level of floc formation than that in supernatants from bacterial monocultures only. After separation of supernatants on a C(18) cartridge, the aggregate-inducing activity could be assigned to the 50% aqueous methanolic fraction, and further separation of this bioactive fraction could be achieved by high-pressure liquid chromatography. These results strongly suggest the involvement of one or several chemical factors in the induction of floc formation by Sphingobium sp. strain Z007 that are possibly released into the surrounding medium by flagellate grazing.
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http://dx.doi.org/10.1128/AEM.01455-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2937497PMC
September 2010

Anorexia in hemodialysis patients: the possible role of des-acyl ghrelin.

Am J Nephrol 2007 8;27(4):360-5. Epub 2007 Jun 8.

Department of Clinical Medicine, University La Sapienza, Rome, Italy.

Background: Anorexia is frequently found in end-stage renal disease and is a reliable predictor of morbidity and mortality in hemodialysis (HD) patients. The pathogenesis of anorexia is complex and the appetite-modulating hormone ghrelin could be involved. Two forms of circulating ghrelin have been described: acylated ghrelin (<10% of circulating ghrelin) which promotes food intake, and des-acyl ghrelin which induces a negative energy balance. The aim of this cross-sectional study is to clarify whether anorexia and body weight change in HD patients relate to plasma des-acyl ghrelin levels.

Methods: 34 HD patients and 15 healthy controls were studied. The presence of anorexia was assessed by a questionnaire. Serum des-acyl ghrelin was measured in HD patients and in 15 body mass index-, sex- and age-matched controls by ELISA. Energy intake was assessed by a 3-day dietary diary, and fat-free mass (FFM) was evaluated by body impedance analysis. Data have been statistically analyzed and are presented as mean +/- SD.

Results: 14 patients (41%) were found to be anorexic, and 20 patients (59%) non-anorexic. Energy intake (kcal/day) was significantly lower in anorexic than in non-anorexic patients (1,682 +/- 241 vs. 1,972.50 +/- 490; p < 0.05). FFM (%) was lower in anorexic than in non-anorexic patients (65.8 +/- 4.4 vs. 70.9 +/- 8.7; p = 0.05). Plasma des-acyl ghrelin levels (fmol/ml) were significantly higher in HD patients than in controls (214.88 +/- 154.24 vs. 128.93 +/- 51.07; p < 0.05), and in anorexic HD patients than in non-anorexic (301.7 +/- 162.4 vs. 159.1 +/- 115.5; p < 0.01).

Conclusion: Anorexia is highly prevalent among HD patients and des-acyl ghrelin could be involved in its pathogenesis.
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http://dx.doi.org/10.1159/000103798DOI Listing
September 2007