The interconnectedness of ageing: does the convoy principal apply?

Abstract

The convoy principal states that any system is only as functional as its 'slowest' unit. As organisms are made up of interconnected networks of physiological systems, it is possible that this principle applies to the biology of ageing. Often biogerontology will focus either on organismal ageing (mechanisms associated with increased longevity of a lower model organism for example), ageing of an individual organ system (such as the cardiovascular/musculoskeletal/immune) or ageing at the cellular level (from telomere length to cellular senescence, with many different cell types being studied) without considering the interconnectedness between the three and importantly, between the separate units of the convoy; the different organs systems. Conceptually, research that aims to identify 'anti-ageing' therapies is often deemed to be reaching for a panacea that will arrest or slow down the ageing process as a whole, whereas the more realistic aim is to first identify how we can improve the performance of systems that are 'the slowest in the convoy'. This concept of improving the biological performance of individual ageing systems should be seen as achievable in the short term. Recent evidence on the use of rapamycin in improving the immune performance of older adults is an excellent case in point (Mannick, Del Giudice et al. 2014) and provides evidence of the first small steps towards an 'anti-ageing' drug in humans.In this special issue the latest knowledge about ageing of several systems is reviewed. Cobley et al (Cobley, Moult et al. 2014) provide fascinating insight into how exercise can support muscle function in older adults in their review of mitochondrial responses to physical activity in ageing muscle, providing a potential mechanism for the protective effect of exercise training on age-related musculoskeletal decline. This is supported by the review from Pararasa et al (Pararasa, Bailey et al. 2014) describing evidence for the role of adipose tissue and circulating free fatty acids in the increased insulin resistance, cardiovascular disease risk and inflammation in older adults. In a related article describing the mechanisms behind regulation of longevity role by the C. elegans FOXO transcription factor ortholog DAF-16 (Tullet 2014). These articles collectively provide novel insight into the role that energy homeostasis has on ageing and longevity.The interconnectedness of biological systems is key in maintaining normal function as we age. These connections can be physical or chemical and recent advances in the knowledge regarding extracellular vesicles and brain ageing are discussed (Smith, Leonardi et al. 2014). Additionally, the oft-ignored concept of circadian rhythm and ageing, specifically the most common joint disease of ageing osteoarthritis, is discussed here (Gossan, Boot-Handford et al. 2014) highlighting how