Host tp53 mutation induces gut dysbiosis eliciting inflammation through disturbed sialic acid metabolism.

BACKGROUND: Host tp53 mutations are frequently found during the early stages of colitis-associated colorectal cancer (CAC), but whether such mutations induce gut microbiota dysbiosis and chronic intestinal inflammation that contributes to the development of CAC, remains unknown. RESULTS: We found that zebrafish tp53 mutant larvae exhibited elevated intestinal inflammation, by monitoring the NFκB activity in the mid-distal intestines of zebrafish larvae using an NFκB:EGFP transgenic reporter line in vivo as well as neutrophil infiltration into the intestine. This inflammation was due to dysbiotic gut microbiota with reduced diversity, revealed using both 16S rRNA amplicon sequencing and a germfree larva model. In this dysbiosis, Aeromonas spp. were aberrantly enriched as major pathobionts and exhibited the capacity for aggressive colonization in tp53 mutants. Importantly, the ex-germfree experiments supported the causality of the host tp53 mutation for inducing the inflammation. Transcriptome and high-performance liquid chromatography analyses of the host gastrointestinal tracts identified dysregulated sialic acid (SA) metabolism concomitant with increased host Neu5Gc levels as the key determinant of aberrant inflammation, which was reversed by the sialidase inhibitors oseltamivir and Philippin A. CONCLUSIONS: These results demonstrate a crucial role for host tp53 in maintaining symbiosis and immune homeostasis via SA metabolism. Disturbed SA metabolism via a tp53 mutation may be exploited by specific elements of the gut microbiome, eliciting both dysbiosis and inflammation. Manipulating sialometabolism may therefore provide an efficacious therapeutic strategy for tp53 mutation-induced dysbiosis, inflammation, and ultimately, related cancers. Video Abstract.

Aceneuramic Acid Extended Release Administration Maintains Upper Limb Muscle Strength in a 48-week Study of Subjects with GNE Myopathy: Results from a Phase 2, Randomized, Controlled Study.

BACKGROUND: GNE Myopathy (GNEM) is a progressive adult-onset myopathy likely caused by deficiency of sialic acid (SA) biosynthesis. OBJECTIVE: Evaluate the safety and efficacy of SA (delivered by aceneuramic acid extended-release [Ace-ER]) as treatment for GNEM. METHODS: A Phase 2, randomized, double-blind, placebo-controlled study evaluating Ace-ER 3 g/day or 6 g/day versus placebo was conducted in GNEM subjects (n = 47). After the first 24 weeks, placebo subjects crossed over to 3 g/day or 6 g/day for 24 additional weeks (dose pre-assigned during initial randomization). Assessments included serum SA, muscle strength by dynamometry, functional assessments, clinician- and patient-reported outcomes, and safety. RESULTS: Dose-dependent increases in serum SA levels were observed. Supplementation with Ace-ER resulted in maintenance of muscle strength in an upper extremity composite (UEC) score at 6 g/day compared with placebo at Week 24 (LS mean difference +2.33 kg, p = 0.040), and larger in a pre-specified subgroup able to walk ≥200 m at Screening (+3.10 kg, p = 0.040). After cross-over, a combined 6 g/day group showed significantly better UEC strength than a combined 3 g/day group (+3.46 kg, p = 0.0031). A similar dose-dependent response was demonstrated within the lower extremity composite score, but was not significant (+1.06 kg, p = 0.61). The GNEM-Functional Activity Scale demonstrated a trend improvement in UE function and mobility in a combined 6 g/day group compared with a combined 3 g/day group. Patients receiving Ace-ER tablets had predominantly mild-to-moderate AEs and no serious adverse events. CONCLUSIONS: This is the first clinical study to provide evidence that supplementation with SA delivered by Ace-ER may stabilize muscle strength in individuals with GNEM and initiating treatment earlier in the disease course may lead to better outcomes.

Human risk of diseases associated with red meat intake: Analysis of current theories and proposed role for metabolic incorporation of a non-human sialic acid.

One of the most consistent epidemiological associations between diet and human disease risk is the impact of red meat consumption (beef, pork, and lamb, particularly in processed forms). While risk estimates vary, associations are reported with all-cause mortality, colorectal and other carcinomas, atherosclerotic cardiovascular disease, type II diabetes, and possibly other inflammatory processes. There are many proposed explanations for these associations, some long discussed in the literature. Attempts to explain the effects of red meat consumption have invoked various red meat-associated agents, including saturated fat, high salt intake, Trimethylamine-N-oxide (TMAO) generation by microbiota, and environmental pollutants contaminating red meat, none of which are specific for red meat. Even the frequently mentioned polycyclic aromatic carcinogens arising from high temperature cooking methods are not red meat specific, as these are also generated by grilling poultry or fish, as well as by other forms of cooking. The traditional explanations that appear to be more red meat specific invoke the impact of N-nitroso compounds, heme iron, and the potential of heme to catalyze endogenous nitrosation. However, heme can be denatured by cooking, high levels of plasma hemopexin will block its tissue delivery, and much higher amounts of heme likely originate from red blood cell breakdown in vivo. Therefore, red meat-derived heme could only contribute to colorectal carcinoma risk, via direct local effects. Also, none of these mechanisms explain the apparent human propensity i.e., other carnivores have not been reported at high risk for all these diseases. A more recently proposed hypothesis involves infectious agents in beef from specific dairy cattle as agents of colorectal cancer. We have also described another mechanistic explanation for the human propensity for risk of red-meat associated diseases that is consistent with most observations: metabolic incorporation of a non-human sialic acid N-glycolylneuraminic acid (Neu5Gc) into the tissues of red meat consumers and the subsequent interaction with inflammation-provoking antibodies against this "xenoautoantigen". Overall, we conclude that while multiple mechanisms are likely operative, many proposed theories to date are not specific for red meat, and that the viral and xenoautoantigen theories deserve further consideration. Importantly, there are potential non-toxic dietary antidotes, if the xenoautoantigen theory is indeed correct.

Free Sialic Acid Acts as a Signal That Promotes Streptococcus pneumoniae Invasion of Nasal Tissue and Nonhematogenous Invasion of the Central Nervous System.

Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial meningitis and neurological sequelae in children worldwide. Acute bacterial meningitis is widely considered to result from bacteremia that leads to blood-brain barrier breakdown and bacterial dissemination throughout the central nervous system (CNS). Previously, we showed that pneumococci can gain access to the CNS through a nonhematogenous route without peripheral blood infection. This access is thought to occur when the pneumococci in the upper sinus follow the olfactory nerves and enter the CNS through the olfactory bulbs. In this study, we determined whether the addition of exogenous sialic acid postcolonization promotes nonhematogenous invasion of the CNS. Previously, others showed that treatment with exogenous sialic acid post-pneumococcal infection increased the numbers of CFU recovered from an intranasal mouse model of infection. Using a pneumococcal colonization model, an in vivo imaging system, and a multiplex assay for cytokine expression, we demonstrated that sialic acid can increase the number of pneumococci recovered from the olfactory bulbs and brains of infected animals. We also show that pneumococci primarily localize to the olfactory bulb, leading to increased expression levels of proinflammatory cytokines and chemokines. These findings provide evidence that sialic acid can enhance the ability of pneumococci to disseminate into the CNS and provide details about the environment needed to establish nonhematogenous pneumococcal meningitis.

Safety evaluation of the human-identical milk monosaccharide sialic acid (N-acetyl-d-neuraminic acid) in Sprague-Dawley rats.

N-Acetyl-d-neuraminic acid (Neu5Ac) is the predominant form of sialic acid (Sia) in humans, while other mammals express Sia as a mixture with N-glycolyl-d-neuraminic acid (Neu5Gc). Neu5Ac occurs in highest levels in the brain and in breast milk, and is therefore, coined a human-specific milk monosaccharide, and is thought to play an important nutritional role in the developing infant. Synthesized human-identical milk monosaccharide (HiMM) Neu5Ac is proposed for use in infant formulas to better simulate the free saccharides present in human breast milk. As part of the safety evaluation of HiMM Neu5Ac, a subchronic dietary toxicity study preceded by an in utero phase was conducted in Sprague-Dawley rats. Neu5Ac was without maternal toxicity or compound-related adverse effects on female reproduction and on the general growth and development of offspring at a maternal dietary level of up to 2%, equivalent to a dose of 1895mg/kg body weight (bw)/day. During the subchronic phase, no compound-related adverse effects were observed in first generation rats at dietary levels of up to 2% (highest level tested), corresponding to doses of 974 and 1246mg/kgbw/day in males and females, respectively. Neu5Ac also was non-genotoxic in a series of in vitro genotoxicity/mutagenicity tests. These results support the safe use of Neu5Ac both in infant formula and as a food ingredient at levels equivalent to those found naturally in human breast milk.

Effect of NMSO3 treatment in a murine model of human metapneumovirus infection.

BALB/c mice infected with human metapneumovirus (hMPV) were treated with the sulfated sialyl lipid NMSO3 (one dose of 50 mg kg(-1)) given at the time of infection. NMSO3 significantly reduced viral replication in the lungs, as well as hMPV-induced body weight loss, pulmonary inflammation and cytokine production, suggesting that antiviral treatment initiated at the beginning of viral infection can modify hMPV-induced disease.