Lactose and Fructo-oligosaccharides Increase Visceral Sensitivity in Mice via Glycation Processes, Increasing Mast Cell Density in Colonic Mucosa

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is characterized by abdominal pain, bloating, and erratic bowel habits. A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) can reduce symptoms of IBS, possibly by reducing microbial fermentation products. We investigated whether ingestion of FODMAPs can induce IBS-like visceral hypersensitivity mediated by fermentation products of intestinal microbes in mice.

METHODS

C57Bl/6 mice were gavaged with lactose, with or without the antiglycation agent pyridoxamine, or saline (controls) daily for 3 weeks. A separate group of mice were fed a diet containing fructo-oligosaccharides, with or without pyridoxamine in drinking water, or a normal chow diet (controls) for 6 weeks. Feces were collected and analyzed by 16S ribosomal RNA gene sequencing and bacterial community analyses. Abdominal sensitivity was measured by electromyography and mechanical von Frey filament assays. Colon tissues were collected from some mice and analyzed by histology and immunofluorescence to quantify mast cells and expression of advanced glycosylation end-product specific receptor (AGER).

RESULTS

Mice gavaged with lactose or fed fructo-oligosaccharides had increased abdominal sensitivity compared with controls, associated with increased numbers of mast cells in colon and expression of the receptor for AGER in proximal colon epithelium. These effects were prevented by administration of pyridoxamine. Lactose and/or pyridoxamine did not induce significant alterations in the composition of the fecal microbiota. Mass spectrometric analysis of carbonyl compounds in fecal samples identified signatures associated with mice given lactose or fructo-oligosaccharides vs controls.

CONCLUSIONS

We found that oral administration of lactose or fructo-oligosaccharides to mice increases abdominal sensitivity, associated with increased numbers of mast cells in colon and expression of AGER; these can be prevented with an antiglycation agent. Lactose and/or pyridoxamine did not produce alterations in fecal microbiota of mice. Our findings indicate that preventing glycation reactions might reduce abdominal pain in patients with IBS with sensitivity to FODMAPs.

[Angioedema and urticaria]

Angiœdema (AE) is the clinical expression of urticaria (U) which occurs when urticaria is located within the subcutis. It is a syndrome characterized by a sudden and limited subcutaneous and/or submucous swelling. The updated classification of urticaria distinguishes acute and chronic urticaria. Chronic urticaria is spontaneous (CSU) or inducible (CIU). Angioedema in chronic urticaria is rarely allergic, but most of the time caused by a non-specific histamine release from activated mast-cell (non IgE mediated reaction). Angioedemas are recurrent, concomitant or not with wheals. They appear skin-coloured, sometimes slightly rosy, non-inflammatory, and more painful than itchy. They are transient, ephemeral, migrant, last most of the time a few hours (< 24 or 48h) and disappear without after-effects. They are considered "deep urticaria" and wheals "superficial urticaria". When AE or wheals last more than 6 weeks (with or without free intermission), it is called chronic urticaria. Angioedema can be elicited or worsened by physical factors (cold urticaria, exercise, heat, solar, vibratory, aquagenic, delayed pressure urticaria…) and /or drugs (as aspirin, nonsteroid anti-inflammatory drugs, morphine, antibiotics…). The treatment of histaminergic angioedemas of chronic urticaria is based on modern second generation antihistamines (anti H1). In allergic acute urticaria only, additional treatment for anaphylaxis can be used if needed (grade 2 to 4). In chronic urticaria, steroids should be avoided : they can make symptoms worse and long-lasting because of corticosteroid dependence.