Butyrate is a natural substance present in biological liquids and tissues. The present paper aims to give an update on the biological role of butyrate in mammals, when it is naturally produced by the gastrointestinal microbiota or orally ingested as a feed additive. Recent data concerning butyrate production delivery as well as absorption by the colonocytes are reported. Butyrate cannot be detected in the peripheral blood, which indicates fast metabolism in the gut wall and/or in the liver. In physiological conditions, the increase in performance in animals could be explained by the increased nutrient digestibility, the stimulation of the digestive enzyme secretions, a modification of intestinal luminal microbiota and an improvement of the epithelial integrity and defence systems. In the digestive tract, butyrate can act directly (upper gastrointestinal tract or hindgut) or indirectly (small intestine) on tissue development and repair. Direct trophic effects have been demonstrated mainly by cell proliferation studies, indicating a faster renewal of necrotic areas. Indirect actions of butyrate are believed to involve the hormono-neuro-immuno system. Butyrate has also been implicated in down-regulation of bacteria virulence, both by direct effects on virulence gene expression and by acting on cell proliferation of the host cells. In animal production, butyrate is a helpful feed additive, especially when ingested soon after birth, as it enhances performance and controls gut health disorders caused by bacterial pathogens. Such effects could be considered for new applications in human nutrition

Aim: To assess the role of lactate as a precursor for butyrate biosynthesis in human colonic microflora. Methods and Results: Three human faecal microfloras were incubated in vitro with media supplemented with 30 mmol l )1 unenriched or 13 C-enriched lactate. Lactate metabolism and short-chain fatty acid (SCFA) production were quantified. Lactate conversion to butyrate was investigated by gas chromatography-mass spectrometry and the pathways involved were identified by 13 C nuclear magnetic resonance spectroscopy. All human faecal microfloras rapidly and completely fermented lactate, yielding approx. 19 mmol l )1 total SCFAs. However, the SCFA composition varied markedly between microfloras. Butyrate was the main end-product for two microfloras but not for the third (60 and 61% vs 27% of the net concentration of SCFA produced respectively). The latter was typified by its ability to produce propionate as a major product (37%), and valerate (3%). 13 C-Labelling showed that butyrate was produced through the acetyl-CoA pathway and that the three microfloras possessed significant differences in their metabolic pathways for lactate consumption. Conclusions: In contrast to the ruminal microflora, the human intestinal microflora can utilize both D D-and L L-lactate as precursors for butyrate synthesis. Inter-individual variation is found. Significance and Impact of the Study: This study suggests that the butyrogenic capability of colonic prebiotics could be related to lactate availability. These findings will direct the development of selection strategies for the isolation of new butyrate-producing bacteria among the lactate-utilizing bacteria present in the human intestinal microfloras.

The course of the conversion reaction during the electrochemical insertion/deinsertion of lithium in CuO thin film electrodes was surveyed by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The electrochemical processes were studied through the comprehensive acquisition and interpretation of XPS and Auger spectra (Cu 2p, O 1s, Cu LMM) recorded at different stages of the first cycle of a Li/CuO cell. The reduction process consisting of three main steps leads successively to Cu+ and Cu0 and involves a Li2O2 peroxide type phase as an intermediate, whereas Li2O is the main lithiated oxide at the end of the discharge. Only the two last steps appear reversible in charge. No evidence of Cu2+ was found at the end of the charge at 3.5 V/Li+/Li, showing the irreversibility of the first step in our experimental conditions. Complementary XPS depth profile analyses were performed to check the evolution of the active material composition over the thickness of the electrode.

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Weight gain in neutered cats was decreased by feeding an LF, low energy-dense diet. To prevent weight gain in cats after neutering, a suitable LF diet should be fed in carefully controlled meals rather than ad libitum.

Butyrate is recognised as efficient in healing colonic inflammation, but cannot be used as a long-term treatment. Dietary fibre that produces a high-butyrate level when fermented represents a promising alternative. We hypothesised that different types of dietary fibre do not have the same efficiency of healing and that this could be correlated to their fermentation characteristics. We compared short-chain fructo-oligosaccharides (FOS) and type 3 resistant starch (RS) in a previously described dextran sulfate sodium (DSS)-induced colitis model. Seventytwo Sprague -Dawley rats received water (control rats) or DSS (50 g DSS/l for 7 d then 30 g DSS/l for 7 (day 7) or 14 (day 14) d). The rats were fed a basal diet (BD), or a FOS or RS diet creating six groups: BD-control, BD-DSS, FOS-control, FOS-DSS, RS-control and RS-DSS. Caeco-colonic inflammatory injuries were assessed macroscopically and histologically. Short-chain fatty acids (SCFA) were quantified in caeco-colon, portal vein and abdominal aorta. At days 7 and 14, caecal and distal macroscopic and histological observations were improved in RS-DSS compared with BD-DSS and also with FOS-DSS rats. Caeco-colonic SCFA were reduced in FOS-DSS and RS-DSS groups compared with healthy controls. The amount of butyrate was higher in the caecum of the RS-DSS rats than in the BD-DSS and FOS-DSS rats, whereas distal butyrate was higher in FOS-DSS rats. Partially explained by higher luminal levels of SCFA, especially butyrate, the healing effect of RS confirms the involvement of some types of dietary fibre in inflammatory bowel disease. Moreover, the ineffectiveness of FOS underlines the importance of the type of dietary substrate.