Participants.

Eighteen young (19–29 yr; n = 9 males and 9 females) and 20 middle- to older-aged (57–82 yr; n = 10 males and 10 females) individuals were recruited from a larger study examining aging, exercise training, and insulin sensitivity (10). A detailed description of subject inclusion/exclusion criteria was published previously (10). Briefly, all participants were nonsmokers and participated in <1 h/wk of organized physical activity. Individuals with diabetes, heart disease, and metabolic disorders and those taking lipid-altering medications were excluded. In an attempt to study a representative population reflective of the “normal” aging process, BMI was between the 25th and 75th percentiles of the US population for the respective decade of age (38). Written, informed consent was obtained, and the protocol was in accordance with the Declaration of Helsinki and approved by the East Carolina University Policy and Review Committee on Human Research.