Development of liver fibrosis during aging: effects of caloric restriction

Liver is the central metabolic organ of the body and diet is considered one of the main environmental factors that can impact on aging liver. In the elderly stage liver function is relatively well conserved although there are a variety of not well defined morphological changes related to liver fibrosis which is commonly associated with an inflammatory state. The aim of this paper is to study these alterations during the physiological process of aging in Wistar rats and also test if caloric restriction (CR) could ameliorate them. As fibrosis is associated to hepatic stellate cell (HSC) function we also analyzed these cells during aging. Livers from five groups of male Wistar rats (3-, 8-, 24-months old ad libitum and 8- and 24-months caloric restricted rats) were used in this study. Histological analysis, expression of genes implicated in liver fibrosis and the status of inflammatory step-pathways as p38 mitogen-activated protein kinase (p38-MAPK), c-Jun N-terminal kinase (JNK) and the nuclear factor kappa B (NFkB) isoforms, p50 and p65, in cytosolic and nuclear fractions were performed. During elderly, associated with morphological change of HSC, there is a progressive increase in collagen deposition due to an inhibition in collagen degradation. Higher expression of cytokines and the activation of inflammatory pathways are associated with aging. CR ameliorates these circumstances being more effective when it started in middle age. In conclusion elderly stage is associated to a mild fibrotic and inflammatory state in the liver which could be ameliorated after CR.