Considerable heterogeneity in the aging population has been observed. The exceptional longevity of individuals reaching 100 years old, so-called centenarians may be an example of life-long healthy aging, or added years may be spent in poor health with decreased physical and cognitive functioning. Current knowledge of the aging experience and the trajectories of physical and cognitive decline across various age groups are not well-understood, yet crucial to prevent spending added years in disease. Hence, the study objective is to develop the metabolic profile associated with aging-related disorders measured as the incidence of impaired functional capacity, cognitive function, and/or well-being.

Our lab developed a pulse method combining multiple stable tracers to study multiple metabolic pathways in the same individual simultaneously. By measuring whole-body metabolism in a large group of older adults, we may be able to unravel age-related deterioration in protein turnover (synthesis and breakdown) that contributes to impaired functional capacity. Metabolic profiles could explain differences in pathways in the aging process with a special interest in the metabolism of amino acids as they have been associated with aging-related disorders. Studies on the effect of aging on metabolism might serve as potential therapeutic targets.

Inclusion Criteria:

• Stable body-weight (± 5%) for the past 3 months
• Subject is judged to be in satisfactory health based on medical history, physical examination, and laboratory screening evaluations.
• Ability to walk, sit down and stand up independently or with walking mobility aids
• Ability to lie in a supine or elevated position for up to 3 hours
• Willingness and ability to comply with the protocol

Exclusion Criteria:

• Insulin dependent diabetes mellitus
• Established diagnosis of malignancy
• History of untreated metabolic diseases including hepatic or renal disorder
• Presence of acute illness or metabolically unstable chronic illness
• Presence of fever within the last 3 days
• Use of short course of oral corticosteroids within 4 weeks preceding study day
• Failure to give informed consent or Investigator's uncertainty about the willingness or ability of the subject to comply with the protocol requirements
• (Possible) pregnancy
• Already enrolled in another clinical trial and that clinical trial interferes with participating in this study

We will screen 200 subjects (to complete n=100). This number includes screen failures and drop-outs. We expect some dropout between screening and enrollment. Subjects who drop out prior to the successful completion of the study will be replaced. Data will be used up to the point of withdrawal. Age range: 50 years or older, inclusive; Ethnicity: all races and ethnicities.

Data may be shared upon request for up to 6 years beyond completion of the trial based on methods/proposal approved by both parties' institutional review committees. Individual participant data that underlie the results of the trial may be shared after de-identification (text, tables, figures, and appendices). Additional documents available per request include: study protocol, statistical analysis plan, and informed consent. Requests should be directed to Dr. Marielle Engelen (mpkj.engelen@ctral.org).