Chronobiologic study of the GH-IGF1 axis and the ageing immune system

SummaryOne of the many systems that weakens as we age is our immune system and there is a reduction in the GH-IGF1 axis activity with increasing age. In this study we evaluated the immune system and the GH-IGF1 axis function in healthy ageing. CD3, CD4, CD20, CD25, HLA-DR and GH showed acrophase during the night, whereas CD8, CD16 and TCRγδ expressing cells showed acrophase during the day. MESOR of CD3 was higher in the old aged subjects, MESOR of CD20 and CD20 values at 14:00h and at 02:00h were higher in the young middle aged subjects, MESOR of CD25 and CD25 values at 10:00 were higher in the elderly subjects, MESOR of HLA-DR was higher in the young middle aged subjects, whereas MESOR of DR+T cells and HLA-DR at 02:00h were higher in the elderly subjects, MESOR of TCRγδ bearing cells was higher in the elderly subjects, GH value at 18:00h was also higher in the elderly subjects, and MESOR of IGF1 was higher in the young middle aged subjects. There was a statistically significant difference for the acrophases of CD25, HLA-DR and IGF1. There were different and opposing correlations among lymphocyte subpopulations and GH-IGF1 axis hormones in young and middle aged subjects in comparison with old aged subjects. Linear regression evidenced a statistically significant positive trend between age and the 24h mean of CD3 and CD25 and a statistically significant negative trend between age and the 24h mean of CD20 and GH. In conclusion, ageing is associated with an altered GH and IGF1 secretion, with decreased peripheral B cell compartment, increased peripheral T cell compartment and alterations of circadian rhythmicity.