Medical media have published many reports recently about the effects of different cytokines on human health. Just a few years ago, during the "swine flu" panic, one read about how some people's exaggerated immune respose -- dubbed a "cytokine storm" -- was what made H1N1 lethal for them and not for others. A team of Japanese and Chinese researchers recently won the Ig Nobel prize for their discovery that some types of music produce a preferable cytokine response in the bodies of mice with transplanted hearts. The latest news on cytokines is that they are linked to the way aging manifests itself in the human body.
What is a cytokine? It is a small protein secreted by a cell; types of cytokines include lymphokines, monokines, chemokines, and interleukins. Some cytokines are characterized as "pro-inflammatory"; the best-known of these are interleukin one-beta (IL-1β), interleukin six (IL-6), tumor necrosis factor alpha (TNF-α, or cachexin). These cytokines promote inflammation in response to infection or injury, and may be responsible for the sensation of pain.
In an article published on September 16, 2013, in the Canadian Medical Association Journal, researchers elucidate the manner in which pro-inflammatory cytokines, particularly IL-6, affect the aging process. During the research, the team measured the levels of IL-6 in a group of middle-aged individuals at the beginning of a five-year period and at the end. Ten years after the end of the five-year period, the researchers used hospital data and clinical examination data to compile information about these subjects' mortality, chronic disease, and levels of functioning, and used this information to categorize each individual as one of four phenotypes. The four phenotypes are: successful aging, cardiovascular incident (fatal or non-fatal), non-cardiovascular-related death, and normal aging. The individuals deemed to fit the "successful aging" phenotype were free from major chronic disease and had what the researchers deemed to be "optimal physical, mental, and cognitive functioning."
As one might expect, just over 60% of the study participants fell into the "normal aging" category. Slightly more than 10% had cardiovascular events, and just under five percent died from non-cardiovascular-related causes. Just under 24% were considered to be successfully aging. Individuals who had high levels of IL-6 ("high" being greater than 2 ng per liter of blood) at the two measurement points (beginning and end of the five-year-period) were roughly half as likely to be "successfully aging" as those who did not, and were more likely to have died during the ten-year follow-up period and more likely to have a cardiovascular event during the ten-year follow-up period.
The researchers concluded that chronic inflammation is associated with poor aging, and that measurements of IL-6 concentration should be used by clinicians to guide their treatment of aging patients.