Although mortality in old age has significantly decreased over the last fifty years in the developed world, there still remains a large inter-individual variability in ageing trajectories,... Show more Although mortality in old age has significantly decreased over the last fifty years in the developed world, there still remains a large inter-individual variability in ageing trajectories, morbidity and mortality. In the three parts of this thesis, we examined three interacting systems that have been identified as contributing to a slower pace of ageing, namely glucose/insulin metabolism (part I), the thyroid axis (part II), and the autonomic nervous system (part III). We found that familial longevity is associated with a stronger association of insulin parameters with microstructural brain parameters, and by higher TSH secretion, in the absence of differences in basal energy metabolism or differences in heart rate and its variability. Using specialized MRI techniques, we showed that subtle changes in microstructural brain parenchymal homogeneity in relation to insulin can be detected, even in brain tissue that appears normal on conventional MR imaging sequences. Insulin (rather than glucose), seemed to be a stronger indicator of micro- structural brain integrity in normo-glycemic older adults. Furthermore, intranasal application of insulin improved brain perfusion in parietal and occipital gray matter and in the thalamus of older adults. These results deepen our understanding of the physiological mechanisms and processes that underlie the ageing process. Show less
