Postbiotic Stool Filtrates From Patients With Type 2 Diabetes Impair Mouse Intestinal Muscle Contractility Ex Vivo...

Type 2 diabetes (T2D) is associated with gastrointestinal dysfunction, enteric nervous system damage, and microbiome dysbiosis. We aimed to investigate whether filter-sterilized postbiotic stool filtrates (PSFs) from patients with prediabetes (PD) and T2D inhibit muscle contractions ex vivo, and whether T2D PSFs impair cholinergic enteric neurons in vivo.

Duodenojejunal muscularis from healthy mice were cultured with PSFs from patients with PD, T2D, or healthy subjects. Mouse PSFs served as control. PSFs of T2D patients or healthy subjects were intragastrically gavaged into healthy mice expressing GCaMP6f in cholinergic neurons. Stomachs and distal colons were used to assess cholinergic myenteric neuron activity via Ca²⁺ transient amplitudes, and myenteric neuronal cell density was determined by immunohistochemistry.

Prediabetes and T2D PSFs inhibited contractions and dissociated cells from duodenojejunal muscularis. These effects were reversed by endotoxin-binding filters and reduced by a protease inhibitor cocktail and heating. PSFs from T2D patients decreased gastrointestinal motility and increased the amplitude of Ca²⁺ transients in cholinergic myenteric neurons in the stomachs of male mice, but not female stomachs or distal colons of either sex. PSFs from healthy subjects increased neuronal density in the male stomach and colon, an effect absent in T2D PSF-treated male and all female mice.

These findings suggest that unidentified proteases and other molecules in the PSFs of PD and T2D patients contribute to gastrointestinal dysmotility by inhibiting muscle contractility and inducing cholinergic neuronal hyperactivity. PSFs from healthy male subjects contain neurotrophic factors that are reduced in T2D.