Age-related changes of calbindin D-28k-immunoreactive neurons in the myenteric plexus of gerbil duodenum

Cellular changes in the enteric nervous system during ageing

The intrinsic neurons of the gut, enteric neurons, have an essential role in gastrointestinal functions. The enteric nervous system is plastic and continues to undergo changes throughout life, as the gut grows and responds to dietary and other environmental changes. Detailed analysis of changes in the ENS during ageing suggests that enteric neurons are more vulnerable to age-related degeneration and cell death than neurons in other parts of the nervous system, although there is considerable variation in the extent and time course of age-related enteric neuronal loss reported in different studies. Specific neuronal subpopulations, particularly cholinergic myenteric neurons, may be more vulnerable than others to age-associated loss or damage. Enteric degeneration and other age-related neuronal changes may contribute to gastrointestinal dysfunction that is common in the elderly population. Evidence suggests that caloric restriction protects against age-associated loss of enteric neurons, but recent advances in the understanding of the effects of the microbiota and the complex interactions between enteric ganglion cells, mucosal immune system and intestinal epithelium indicate that other factors may well influence ageing of enteric neurons. Much remains to be understood about the mechanisms of neuronal loss and damage in the gut, although there is evidence that reactive oxygen species, neurotrophic factor dysregulation and/or activation of a senescence associated phenotype may be involved. To date, there is no evidence for ongoing neurogenesis that might replace dying neurons in the ageing gut, although small local sites of neurogenesis would be difficult to detect. Finally, despite the considerable evidence for enteric neurodegeneration during ageing, and evidence for some physiological changes in animal models, the ageing gut appears to maintain its function remarkably well in animals that exhibit major neuronal loss, indicating that the ENS has considerable functional reserve.

Small intestinal disorders in the elderly

The topic of gastroenterology (GI) in the elderly has been extensively reviewed. It takes special skill, patience and insight to interview the elderly, as well as to appreciate their altered physiology and interpretation of their presenting symptoms and signs, often against an extreme background of complex medical problems. The maldigestion and malabsorption coupled with altered motility contributes to the development of malnutrition. There generally a decrease of function of the GI tract, but there may be loss of adaptability in response to changes in diet or nutritional stress. Pathological alterations which might lead to minor overall intestinal functional variations in the young because of a normal process of adaptation, may lead to much more serious events in the elderly.