Adipokine levels are altered by shiftwork: a preliminary study

Shiftwork is often associated with metabolic diseases, and in the past few years, several cytokines have been postulated to contribute to various diseases, including insulin resistance. The aim of this study was to compare the concentrations of adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in samples of young adult men exposed to a fixed (i) night shift (n = 9), working from 22:00 to 06:00 h; (ii) early morning shift (n = 6), working from 06:00 to 14:00 h; and (iii) day shift (n = 7), working from 08:00 to 17:00 h. The fixed night-shift and early-morning-shift samples were considered collectively as a shiftworker group given their work times. Blood samples were collected during the regular working day at 4-h intervals over the course of 24 h, thus totaling six samples. Morphological and physical activity parameters did not differ between the three groups. Total energy intake was lowest on the early morning shifts (p < .03). Both shiftworker groups ingested a significantly higher percentage of fat (p < .003) and a lower percentage of carbohydrate (p < .0005) than the day group. The early morning group had a lower mean 24-h level of adiponectin than the other two groups (p = .016), and both the early morning and night groups exhibited higher mean 24-h levels of TNF-α than the day group (p = .0001). The 24-h mean levels of IL-6 did not differ significantly between the groups (p = .147). None of the groups exhibited a significant circadian effect on adiponectin (p = .829), TNF-α (p = .779), or IL-6 (p = .979) levels. These results indicate that individuals who are enrolled in shiftwork are susceptible to alterations in the secretion of cytokines that are involved in insulin resistance and cardiovascular disease, both of which are known to affect this population.