This is the first report showing that serum HMW-APN and C1q-APN as well as Total-APN, but not C1q, correlated with aging, and that multiple regression analysis identified age as well as BMI as significant determinants of C1q-APN.
As one possible mechanism, three major factors are involved in the control of circulating Total-APN levels; gender, body weight and renal function [4, 12, 13]. The present study found that advanced age is associated with decreased body weight (r=−0.1612, p=0.0003) and reduced renal function (r=−0.2168, p<0.0001, data not shown). These findings may provide an explanation for the increased adiponectin levels in elderly men.
Another possible mechanism is dysregulated production of adipocytokines in elderly subjects, especially hyperadiponectinemia, which is associated with normal aging process . The data suggests that age-related lipoatrophy may be the major factor for adipose tissue dysfunction in advanced age. Transgenic expression of human adiponectin blocked excessive fat accumulation and reduced morbidity and mortality rates in mice fed high-calorie diet, and prolonged the lifespan of normal mice, by inhibiting AKT signaling and chronic inflammation . Based on our recent studies [8, 16, 17], low Total-APN and high C1q-APN/Total-APN correlated with coronary artery disease, suggesting that adiponectin may protect against the development of atherosclerosis through the activation of the complement system and that it can modulate the self-defense system through its binding with C1q in the peripheral circulation. The present study demonstrates that high Total-APN and low C1q-APN/Total-APN ratio correlated positively, but not strongly, with aging (Figure 1). Recent study suggests that centenarians possess a different adiponectin isoform pattern . Taken together, high Total-APN levels and low C1q-APN/Total-APN ratio seems to inhibit aging-related phenotypes including atherosclerosis, and, at least partly, may live longer than others. Further longitudinal studies of larger populations of elderly subjects are required.