Region-specific proteome changes of the intestinal epithelium during aging and dietary restriction

The small intestine is responsible for nutrient absorption and it is one of the most important interfaces between the environment and our body. During aging, changes in the structure of the epithelium lead to food malabsorption and reduced barrier function thus increasing disease risk in aging. The molecular drivers of these alterations remain poorly understood. Here, we compared the proteomes of small intestinal crypts from mice across different anatomical regions and age groups. We found that aging alters epithelial immune responses, metabolic networks and stem cell proliferation, and it is accompanied by a region-dependent skewing in the cellular composition of the intestinal epithelium. Of note, a short period of dietary restriction followed by re-feeding partially restores the epithelium to a youthful state by promoting the differentiation of intestinal stem cells (ISCs) towards the secretory lineage. Using in vitro and in vivo studies, we identify Hmgcs2 (3-hydroxy-3-methylglutaryl-CoA synthetase 2) – the rate limiting enzyme in the synthesis of ketone bodies – as a modulator of ISCs differentiation, which responds to dietary changes. This study provides an atlas of age-dependent proteome changes in defined regions of the intestinal epithelium and characterizes how young and old mice adapt to drastic changes of diet, such as dietary restriction and re-feeding.