Figure 2

The serum levels of IL6 in women and IFNγ in men decrease with increasing age. A group of 66 healthy subjects of Italian people, 33 men and 33 women (blood donors, laboratory staff and relative), were studied [28]. None of the subjects was receiving concurrent drug treatment including widely-used pharmaceuticals, such as salicylates and sex hormones (contraceptive pill, hormone replacement therapy). Distribution of age in male and female groups was the same (mean ± SD =41 ± 12 years, compared to mean ± SD = 41 ± 15 years, p = 0.14). In physiological systems components operate as a network and each component varies and co-varies dynamically with respect to one another. Therefore, the identification of physiological pathways, and correlated biomarkers can only be achieved through evaluations that take these fluctuations into account. Using the principal component analysis these authors plotted the network of vectors obtained by analyzing the data matrix of correlation/covariance coefficients of serum cytokines. In these plots, the angle between vectors is inversely proportional to the degree of correlation between vectors; the same vector direction indicates a positive correlation/covariance, the opposite vector direction indicates a negative correlation/covariance. This allows a visualization of the situation under study and is an excellent method for capturing significance from systems biology evaluations. The plots show that the serum levels of IL6 in women and IFNγ in men decrease with increasing age. The results of multiple regression analysis confirm that age could also be a significant independent factor for IFNγ (p = 0.01) and IL10 (p = 0.03) in men; whilst in women age appears to be significant for sIL6R (p = 0.002) and IFNγ (p = 0.04).