Low–molecular-weight metabolites produced by intestinal microbiota play a direct role in health and disease. In this study, we analyzed the colonic luminal metabolome using capillary electrophoresis mass spectrometry with time-of-flight (CE-TOFMS) —a novel technique for analyzing and differentially displaying metabolic profiles— in order to clarify the metabolite profiles in the intestinal lumen. CE-TOFMS identified 179 metabolites from the colonic luminal metabolome and 48 metabolites were present in significantly higher concentrations and/or incidence in the germ-free (GF) mice than in the Ex-GF mice (p < 0.05), 77 metabolites were present in significantly lower concentrations and/or incidence in the GF mice than in the Ex-GF mice (p < 0.05), and 56 metabolites showed no differences in the concentration or incidence between GF and Ex-GF mice. These indicate that intestinal microbiota highly influenced the colonic luminal metabolome and a comprehensive understanding of intestinal luminal metabolome is critical for clarifying host-intestinal bacterial interactions.

Prevention of quality of life (QOL) deterioration is associated with the inhibition of geriatric diseases and the regulation of brain function. However, no substance is known that prevents the aging of both body and brain. It is known that polyamine concentrations in somatic tissues (including the brain) decrease with increasing age, and polyamine-rich foods enhance longevity in yeast, worms, flies, and mice, and protect flies from age-induced memory impairment. A main source of exogenous polyamines is the intestinal lumen, where they are produced by intestinal bacteria. We found that arginine intake increased the concentration of putrescine in the colon and increased levels of spermidine and spermine in the blood. Mice orally administered with arginine in combination with the probiotic bifidobacteria LKM512 long-term showed suppressed inflammation, improved longevity, and protection from age-induced memory impairment. This study shows that intake of arginine and LKM512 may prevent aging-dependent declines in QOL via the upregulation of polyamines.

Metabolomics is an emerging technology that reveals homeostatic imbalances in biological systems. Global determination of metabolite concentrations in body fluid and tissues provides novel anatomical aspects of pathological conditions that cannot be obtained from target-specific measurements. Here, we characterised metabolic imbalance in Watanabe heritable hyperlipidaemic rabbits as a model of hypercholesterolaemia. Using a mass spectrometry-based system, we measured a total of 335 metabolites in plasma and tissues (liver, aorta, cardiac muscle, and brain) from WHHL and healthy control rabbits. From the comparison between two metabolomic profiles, pathophysiological features including glutathione and phosphatidylcholine metabolism indicated the occurrence of oxidative stress in several tissues. Especially for the liver, imbalanced purine catabolism shed light on the transcriptional activation of xanthine oxidase, which is thought to act in absorbing or possibly triggering oxidative stress. We also applied this system to assess the therapeutic effects of simvastatin administration. After the treatment, a portion of the metabolomic features in pathological conditions showed alterations suggesting restoration of metabolism to the healthy condition. These changes were considered to be due to the pleiotropic action of statin, including antioxidant effects, rather than its main inhibitory action on cholesterol biosynthesis.

Recent studies suggest that intestinal microbiota influences gut-brain communication. In this study, we aimed to clarify the influence of intestinal microbiota on cerebral metabolism. We analyzed the cerebral metabolome of germ-free (GF) mice and Ex-GF mice, which were inoculated with suspension of feces obtained from specific pathogen-free mice, using capillary electrophoresis with time-of-flight mass spectrometry (CE-TOFMS). CE-TOFMS identified 196 metabolites from the cerebral metabolome in both GF and Ex-GF mice. The concentrations of 38 metabolites differed significantly (p < 0.05) between GF and Ex-GF mice. Approximately 10 of these metabolites are known to be involved in brain function, whilst the functions of the remainder are unclear. Furthermore, we observed a novel association between cerebral glycolytic metabolism and intestinal microbiota. Our work shows that cerebral metabolites are influenced by normal intestinal microbiota through the microbiota-gut-brain axis, and indicates that normal intestinal microbiota closely connected with brain health and disease, development, attenuation, learning, memory, and behavior.

ADP-ribose pyrophosphatase (ADPRase) catalyzes the divalent metal ion-dependent hydrolysis of ADP-ribose to ribose 5 -phosphate and AMP. This enzyme plays a key role in regulating the intracellular ADP-ribose levels, and prevents nonenzymatic ADP-ribosylation. To elucidate the pyrophosphatase hydrolysis mechanism employed by this enzyme, structural changes occurring on binding of substrate, metal and product were investigated using crystal structures of ADPRase from an extreme thermophile, Thermus thermophilus HB8. Seven structures were determined, including that of the free enzyme, the Zn 2؉ -bound enzyme, the binary complex with ADP-ribose, the ternary complexes with ADPribose and Zn 2؉ or Gd 3؉ , and the product complexes with AMP and Mg 2؉ or with ribose 5 -phosphate and Zn 2؉ . The structural and functional studies suggested that the ADP-ribose hydrolysis pathway consists of four reaction states: bound with metal (I), metal and substrate (II), metal and substrate in the transition state (III), and products (IV). In reaction state II, Glu-82 and Glu-70 abstract a proton from a water molecule. This water molecule is situated at an ideal position to carry out nucleophilic attack on the adenosyl phosphate, as it is 3.6 Å away from the target phosphorus and almost in line with the scissile bond.Nudix pyrophosphatases are widely distributed in nature and share a highly conserved amino acid sequence motif called the "Nudix motif " (GX 5 EX 7 REUXEEXGU, where U is one of the bulky hydrophobic amino acids I, L, or V), which adopts a unique loop-helix-loop structure (1). Enzymes in this family catalyze the hydrolysis of nucleoside diphosphates, linked to another moiety x. Their postulated role is to control the cellular concentration of toxic nucleoside diphosphate derivatives or physiological metabolites, accumulation of which could be harmful (1). ADP-ribose (ADPR) 1 is one such diphosphate derivative, which is produced enzymatically as part of the turnover of NAD ϩ , cyclic ADPR, ADP-ribosylated proteins, and poly-ADP-ribosylated proteins. Although certain proteins are posttranslationally modified by ADPR, high intracellular levels of ADPR could result in nonenzymatic ADP-ribosylation. This is a deleterious process that inactivates enzymes and could interfere with the recognition of enzymatic ADP-ribosylation (2). ADPR pyrophosphatases (ADPRases) catalyze the hydrolysis of ADPR to AMP and ribose 5Ј-phosphate to prevent ADPR accumulation.ADPRase activity has been detected in all three kingdoms (3-7), but the specificity for ADPR over other substrates and the selectivity of metal ions required for activity vary between species. The mechanism underlying the different substrate specificity and the metal dependence is unknown at both the structural and functional levels. Elucidation of these properties requires the study of ADPRases from numerous sources.In this article, we investigated the catalytic mechanism of ADPRase from an extreme thermophile, Thermus thermophilus HB8 (TtADPRase). In general, proteins isolated fr...