Aging Effects on Diaphragm Muscle Sarcopenia

The population at very old age is increasing dramatically throughout the world. Aging adults experience increased health and medical needs associated with debility and sarcopenia (i.e., muscle atrophy and force loss). Respiratory complications and diseases are common causes of morbidity and mortality in the elderly. Sarcopenia of respiratory muscles such as the diaphragm muscle (DIAm) may contribute to respiratory complications since the DIAm, the main inspiratory muscle in mammals, plays an important role in ventilation and generating the forces necessary to maintain airway clearance. Presently, there is limited information about aging effects into very old age. Specifically, whether DIAm sarcopenia is exacerbated in old age and if it will effect ventilation into very old age are presently unknown. We hypothesized that DIAm sarcopenia in very old mice (>30 mo; ~30% survival) will result in reduced DIAm force generation across motor behaviors, exhibit impaired ventilation, decreased isometric force, and reduced fiber cross‐sectional area compared to old (24 mo; ~80% survival), and young (6 mo, 100% survival). C57BL/6 × 129 female and male mice (n = 30) at 6 mo, 24 mo, and >30 mo were used to examine transdiaphragmatic pressure (Pdi) generation during eupnea, exposure to hypoxia‐hypercapnia, as well as higher force behaviors in airway occlusion, and/or bilateral phrenic stimulation. Ventilation was assessed using whole body plethysmography and venous blood gases. Isometric force was examined via physiological muscle force testing, and fiber cross‐sectional area was determined in immunohistochemically labeled sections across fiber types. There was a significant reduction in Pdi between young and old mice for higher force behaviors – tracheal occlusion and bilateral phrenic nerve stimulation, (p < 0.001); however, there was no further decline in Pdi for all behaviors between old and very old mice. There was no evidence of impaired ventilation (ventilatory parameters – respiratory rate, minute ventilation, or tidal volume) across age groups, and no evidence of differences between sex in any of the measurements. A loss of ability to generate higher levels of force necessary to maintain airway clearance may predispose older individuals to recurrent infection. Understanding the mechanisms of sarcopenia in old age will be important in mitigating the effects of aging on quality of life and maintaining the health span. Support or Funding Information This work was supported by grants R25‐GM075148, R01‐AG044615, and R01‐AG057052 from the National Institutes of Health. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .