Prognostic values of α2-macroglobulin, fibrinogen and albumin in regards to mortality and frailty in old rats

The study aimed to determine if acute phase proteins (APP) are markers of frailty in old rats. We evaluated in male Wistar rats at 96 weeks of age (n = 72) whether single measurements of α2-macroglobulin, fibrinogen and albumin are predictive of mortality, body weight loss and inflammatory status during a 10-week follow-up period. Rats were clustered depending on levels of these APP at baseline. Rats with extremely high levels of α2-macroglobulin or fibrinogen (upper quartiles), or extremely low level of albumin (lower quartile), had an 11.6, 8.1 and 5.3-fold higher risk of mortality, respectively, than other rats. Body weight loss was negatively correlated with α2-macroglobulin, a trend was observed with fibrinogen (P = 0.08) but not with albumin. Rats with fibrinogen levels >4.0 g/L or α2-macroglobulin levels >91 mg/L (respective top halves) at 96 weeks of age had higher levels of α2-macroglobulin and fibrinogen and lower levels of albumin throughout the follow-up period and higher levels of sTNFR-1 and lipopolysaccharide-binding protein at 106 weeks of age. Highest levels of α2-macroglobulin, fibrinogen and lowest albumin were predictive of mortality, whereas moderate levels of α2-macroglobulin and fibrinogen were, according to body weight loss and inflammatory status, markers of frailty in old rats.