Prolonged postweaning protein restriction induces gut dysbiosis and colonic dysfunction in male mice

Insufficient or imbalanced protein can disrupt gut microbiota, potentially compromising gut barrier function and increasing health risks. Herein, we investigated the effects of protein restriction on cecal microbiota and colon morphofunction in male mice. From 30 to 120 days of age, <i>C57Bl/6</i> mice were fed a control protein diet [14% protein, control (C) group] or a low-protein diet [6% protein, protein-restricted (R) group]. At the end of the experimental period, R mice exhibited typical features of undernutrition, such as reduced body weight, hypoalbuminemia, and hypoproteinemia. In addition, despite the hyperphagia displayed in the R group, these mice presented a decreased amount of excreted feces and less energy content in feces. Cecal microbiota analysis demonstrated that protein restriction led to reductions in Shannon and Simpson indices and, therefore, dysbiosis. This effect was accompanied by morphological modifications in the proximal colon of R mice, such as <i>1</i>) reduction in the total area of neurons of myenteric plexus; <i>2</i>) increased number of goblet cells, with mucin droplets less developed; <i>3</i>) reductions in crypt depth and diameter; <i>4</i>) decreases in gene expressions for mucins and in the tight junction proteins expression; <i>5</i>) enhanced paracellular permeability and expression of pro-inflammatory cytokines (tumor necrosis factor α, toll-like receptor 4, interferon γ, interleukin 1β, and interleukin 6), decreased anti-inflammatory cytokines (interleukins 4 and 10) in the colon, and increased plasma LPS binding protein concentrations. Therefore, protein restriction induced gut dysbiosis and may result in structural and functional negative impacts on the proximal colon barrier against luminal bacteria.<b>NEW & NOTEWORTHY</b> Prolonged postweaning protein restriction induced gut dysbiosis and led to a reduced neuron area in the myenteric plexus, with increased but underdeveloped goblet cells. Protein restriction decreased colonic crypt depth and diameter, and increased paracellular permeability due to lower expression of mucin-related genes and tight junction proteins. The diminished barrier function resulted in systemic inflammation, evidenced by elevated plasma LPS-binding protein and pro-inflammatory markers in the colon.