Muscle Mass, Quality, and the Menopause: Sex-specific Strategies to Mitigate Sarcopenia in Ageing Populations

Overview

Aging causes muscles to often become smaller and weaker resulting in physical frailty and functional impairments, such as difficulty raising from a chair, dressing, and preparing meals. In the UK there is a growing aged population with those \>65y expected to increase from 18% of the population in 2016, to 26% by 2066. As such, age related muscle mass loss and functional impairments represents one of the largest problems facing the health care services. There is an urgent need to develop strategies to reduce healthcare costs and improve health and wellbeing with age. These strategies must be targeted, as evidence suggests that the loss in muscle size and strength is different between men and women throughout the aging process. For example, older women have greater levels of physical disability that includes difficulties in walking around the home, getting out of a bed or chair, and eating, compared with men. These sex differences with ageing are unclear, yet the greater levels of physical disability could be the result of the menopause. The menopause describes a change in the sex hormone environment that is a part of normal female ageing. Physical disability can be further enhanced by an increase in body fat during the menopause in the face of decreasing muscle mass. Currently, there is a lack of understanding as to how these changes in body composition occur, with no effective treatments against muscle mass loss. The aims of this project are to increase understanding on how the menopause impacts muscle mass regulation. In addition, the investigators will use novel magnetic resonance imaging (MRI) techniques to map the distribution of newly created fat, and qualitative interviews to better understand how resistance exercise therapy (RET) can be incorporated into the daily lives of postmenopausal women.

The age-related loss of muscle mass and function (sarcopenia) inevitably results in physical frailty and functional impairments, such as difficulty raising from a chair, dressing, and preparing meals. With a rapidly growing aged population (those \>65y increasing from 18% of the population in 2016, to 26% by 2066), sarcopenia represents one of the largest problems facing health care services. Excess healthcare costs associated with sarcopenia are rapidly growing and were estimated to be £2.5 billion in 2016. There is an urgent need to develop strategies to mitigate sarcopenia to reduce healthcare costs and improve health and wellbeing with age. These strategies must be targeted, as evidence suggests that there is sexual dimorphism in ageing and the development of sarcopenia. Sarcopenia develops earlier in women, resulting in greater levels of physical disability that includes difficulties in walking, getting out of a chair, and eating, compared with men. The mechanistic sex differences with ageing are unclear, yet the earlier prevalence of sarcopenia in women coincides with the menopause. In addition, physical disability can be further exacerbated by an increase in adiposity during the menopause in the face of decreasing muscle mass. This change in body composition includes ectopic fat infiltration into muscle that is associated with decreased muscle performance, however, currently, there is a lack of understanding as to how these changes in body composition occur. Understanding the underlying mechanisms that bring about change in physiological systems is key in the development of interventions. Muscle mass is controlled by the balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). With age, many of the signals that increase MPS (i.e., nutrient intake and activity) become less effective, resulting in negative protein balance and muscle loss. Since muscle loss is accelerated after the menopause in women, there must be a greater imbalance between MPS and MPB. The measurement of MPS and MPB can be achieved using stable isotope tracer techniques that can be followed throughout the body. However, there is a lack of research into the mechanistic effects of the menopause on muscle mass regulation. In addition to measures of muscle protein turnover, the investigators have recently used stable isotope tracer techniques alongside MRI scanning to image deuterium incorporation within lipid. the investigators will use these techniques to image newly created fat to further understanding of body composition changes in post-menopausal women. Resistance exercise therapy (RET) currently offers the most effective strategy to mitigate muscle mass loss and improve body composition with ageing, by increasing MPS, promoting muscle hypertrophy, and building strength8. However, older women display blunted muscle hypertrophy in response to RET (when compared to younger women, and older men), and it is not known how the menopause affects hypertrophic responses to exercise. Further, for any intervention to have a meaningful impact, it must be effectively incorporated by postmenopausal women into their daily lives. The investigators have conducted an evaluation of physical activity interventions for post-menopausal women, which revealed that women going through the menopause want more evidence-based guidance on how much and what type of exercise they should be doing, and on whether exercise can alleviate menopausal symptoms and prevent muscle loss. Aims: To investigate the effects of the menopause on muscle mass regulation, changes in body composition, and assess the acceptability and effectiveness of RET.