Eveliina Munukka

Antibacterial effects and dissolution behavior of six bioactive glasses

Dissolution behavior of six bioactive glasses was correlated with the antibacterial effects of the same glasses against sixteen clinically important bacterial species. Powdered glasses (<45 microm) were immersed in simulated body fluid (SBF) for 48 h. The pH in the solution inside the glass powder was measured in situ with a microelectrode. After 2, 4, 27, and 48 h, the pH and concentration of ions after removing the particles and mixing the SBF were measured with a normal glass pH electrode and ICP-OES. The bacteria were cultured in broth with the glass powder for up to 4 days, after which the viability of the bacteria was determined. The antibacterial effect of the glasses increased with increasing pH and concentration of alkali ions and thus with increased dissolution tendency of the glasses, but it also depended on the bacterium type. The changes in the concentrations of Si, Ca, Mg, P, and B ions in SBF did not show statistically significant influence on the antibacterial property. Bioactive glasses showed strong antibacterial effects for a wide selection of aerobic bacteria at a high sample concentration (100 mg/mL). The antibacterial effects increased with glass concentration and a concentration of 50 mg/mL (SA/V 185 cm(-1)) was required to generate the bactericidal effects. Understanding the dissolution mechanisms of bioactive glasses is essential when assessing their antibacterial effects.

Toll‐like receptor 5 in obesity: The role of gut microbiota and adipose tissue inflammation

This study aimed at establishing bacterial flagellin‐recognizing toll‐like receptor 5 (TLR5) as a novel link between gut microbiota composition, adipose tissue inflammation, and obesity.

Toll-like Receptor 5 in Obesity: The Role of Gut Microbiota and Adipose Tissue Inflammation

This study aimed at establishing bacterial flagellin‐recognizing toll‐like receptor 5 (TLR5) as a novel link between gut microbiota composition, adipose tissue inflammation, and obesity.

Gut-adipose tissue axis in hepatic fat accumulation in humans

BACKGROUND & AIMS Recent evidence suggests that in animals gut microbiota composition (GMC) affects the onset and progression of hepatic fat accumulation. The aim of this study was to investigate in humans whether subjects with high hepatic fat content (HHFC) differ in their GMC from those with low hepatic fat content (LHFC), and whether these differences are associated with body composition, biomarkers and abdominal adipose tissue inflammation. METHODS Hepatic fat content (HFC) was measured using proton magnetic resonance spectroscopy ((1)H MRS). Fecal GMC was profiled by 16S rRNA fluorescence in situ hybridization and flow cytometry. Adipose tissue gene expression was analyzed using Affymetrix microarrays and quantitative PCR. RESULTS The HHFC group had unfavorable GMC described by lower amount of Faecalibacterium prausnitzii (FPrau) (p<0.05) and relatively higher Enterobacteria than the LHFC group. Metabolically dysbiotic GMC associated with HOMA-IR and triglycerides (p<0.05 for both). Several inflammation-related adipose tissue genes were differentially expressed and correlated with HFC (p<0.05). In addition, the expression of certain genes correlated with GMC dysbiosis, i.e., low FPrau-to-Bacteroides ratio. CONCLUSIONS HHFC subjects differ unfavorably in their GMC from LHFC subjects. Adipose tissue inflammation may be an important link between GMC, metabolic disturbances, and hepatic fat accumulation.

Fermentable fibres condition colon microbiota and promote diabetogenesis in NOD mice

Aims/hypothesisGut microbiota (GM) and diet both appear to be important in the pathogenesis of type 1 diabetes. Fermentable fibres (FFs), of which there is an ample supply in natural, diabetes-promoting diets, are used by GM as a source of energy. Our aim was to determine whether FFs modify GM and diabetes incidence in the NOD mouse.MethodsFemale NOD mice were weaned to a semisynthetic diet and the effects of FF supplementation on diabetes incidence and insulitis were evaluated. Real-time quantitative PCR was employed to determine the effects imposed to gene transcripts in the colon and lymph nodes. Changes to GM were analysed by next-generation sequencing.ResultsNOD mice fed semisynthetic diets free from FFs were largely protected from diabetes while semisynthetic diets supplemented with the FFs pectin and xylan (PX) resulted in higher diabetes incidence. Semisynthetic diet free from FFs altered GM composition significantly; addition of PX changed the composition of the GM towards that found in natural-diet-fed mice and increased production of FF-derived short-chain fatty acid metabolites in the colon. The highly diabetogenic natural diet was associated with expression of proinflammatory and stress-related genes in the colon, while the semisynthetic diet free from FFs promoted Il4, Il22, Tgfβ and Foxp3 transcripts in the colon and/or pancreatic lymph node. PX in the same diet counteracted these effects and promoted stress-related IL-18 activation in gut epithelial cells. 16S RNA sequencing revealed each diet to give rise to its particular GM composition, with different Firmicutes to Bacteroidetes ratios, and enrichment of mucin-degrading Ruminococcaceae following diabetes-protective FF-free diet.Conclusions/interpretationFFs condition microbiota, affect colon homeostasis and are important components of natural, diabetes-promoting diets in NOD mice.

Gut Microbiota Analysis Results Are Highly Dependent on the 16S rRNA Gene Target Region, Whereas the Impact of DNA Extraction Is Minor

Next-generation sequencing (NGS) is currently the method of choice for analyzing gut microbiota composition. As gut microbiota composition is a potential future target for clinical diagnostics, it is of utmost importance to enhance and optimize the NGS analysis procedures. Here, we have analyzed the impact of DNA extraction and selected 16S rDNA primers on the gut microbiota NGS results. Bacterial DNA from frozen stool specimens was extracted with 5 commercially available DNA extraction kits. Special attention was paid to the semiautomated DNA extraction methods that could expedite the analysis procedure, thus being especially suitable for clinical settings. The microbial composition was analyzed with 2 distinct protocols: 1 targeting the V3-V4 and the other targeting the V4-V5 area of the bacterial 16S rRNA gene. The overall effect of DNA extraction on the gut microbiota 16S rDNA profile was relatively small, whereas the 16S rRNA gene target region had an immense impact on the results. Furthermore, semiautomated DNA extraction methods clearly appeared suitable for NGS procedures, proposing that application of these methods could importantly reduce hands-on time and human errors without compromising the validity of results.

Factors Controlling Antibacterial Properties of Bioactive Glasses

Factors controlling the antibacterial ability of three bioactive glasses were studied by comparing the changes in the SBF during immersion of the glasses with their response to four microorganisms. After immersion of 100 mg/ml fine powder (<45μm) of the glasses in the SBF for 1, 2, 4, 8, 16, 27 and 48 hours, the immersion solutions were filtered and the pH in the bulk solution was measured. Ionic concentrations of Na, K, Ca, Mg, P and Si ions in the immersion solutions were determined by ICP-OES. The antibacterial activity of the glasses showed good correlation with the changes of the pH values in the SBF solutions. No correlation was found between the ionic concentration and the antibacterial ability of the three glasses against the four tested microorganisms. The results suggest that, the antimicrobial effect of the glass powder against the microorganisms tested is mostly dependent on the increase of the pH in the solution to values detrimental for the bacteria growth.

Comparison of Antibacterial Effect of Three Bioactive Glasses

Antibacterial effects of three powdered bioactive glasses were compared by measuring the pH of the simulated body fluid in immediate contact with the glass powder particles and by cultivating four microorganisms in the powder-solution mixtures. After individual cultivation with the microorganisms the bioactive glasses showed ability to kill bacteria, but the effects were very dependent on glass composition and on the microorganism as well as on cultivation time. The results indicated that antimicrobial property of bioactive glasses correlates with their ability to change the pH of the body fluid in immediate contact with the glass. However, the increase in pH is not the only factor influencing the antimicrobial properties.

Effect of Ion Release on Antibacterial Activity of Melt-Derived and Sol-Gel-Derived Reactive Ceramics

Four different bioreactive ceramics were prepared using a sol-gel method and a standard melting process. The aim was to study antibacterial effect of these materials on the growth of Staphylococcus epidermidis. The dissolution (Si and Ca ions) of fine (≤ 45 !m) ceramic powders in a tryptone soya broth (TSB) was investigated. Also the pH changes in TSB solution were measured. In addition the adherence of Enterococcus faecalis (Ef) to materials was investigated. The bacterial adhesion was studied using scanning electron microscopy (SEM). In the bacterial and the adhesion test, CaPSiO2 and S53P4 had the strongest antimicrobial effect against studied bacteria. It was shown that bioreactive sol-gel derived ceramic with sufficient high Ca ion release (> 270 ppm) can reach strong antibacterial effect also at lower pH values (< 9.6).

Faecalibacterium prausnitzii treatment improves hepatic health and reduces adipose tissue inflammation in high-fat fed mice

Faecalibacterium prausnitzii is considered as one of the most important bacterial indicators of a healthy gut. We studied the effects of oral F. prausnitzii treatment on high-fat fed mice. Compared to the high-fat control mice, F. prausnitzii-treated mice had lower hepatic fat content, aspartate aminotransferase and alanine aminotransferase, and increased fatty acid oxidation and adiponectin signaling in liver. Hepatic lipidomic analyses revealed decreases in several species of triacylglycerols, phospholipids and cholesteryl esters. Adiponectin expression was increased in the visceral adipose tissue, and the subcutaneous and visceral adipose tissues were more insulin sensitive and less inflamed in F. prausnitzii-treated mice. Further, F. prausnitzii treatment increased muscle mass that may be linked to enhanced mitochondrial respiration, modified gut microbiota composition and improved intestinal integrity. Our findings show that F. prausnitzii treatment improves hepatic health, and decreases adipose tissue inflammation in mice and warrant the need for further studies to discover its therapeutic potential.