THE ROLE OF LEPTIN AND CYTOKINES IN BODY WEIGHT REGULATION OF OLDER ADULTS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Weight loss in geriatric patients is a common and worrisome problem. The etiology of lack of appetite in the face of continued weight loss is unknown. Previous studies have shown an increase in mortality rates, frailty, and functional disability among older persons with involuntary weight loss. Other studies have reported possible dysregulation of energy intake in older men after calorie restriction as well as abnormalities in leptin homeostasis. The specific aims of the proposed project are to determine whether a period of moderate caloric restriction suppresses integrated diurnal plasma leptin levels (AUC-leptin) and resting energy expenditure (REE) in healthy older subjects to the same degree as in young adults, and to determine whether the compensatory increase in energy intake following a period of dietary energy restriction is as robust in older subjects as it is in young adults. The hypothesis is that older adults are unable to increase their energy intake and/or decrease their energy expenditure after a period of calorie restriction due to inappropriately elevated levels of leptin or pro-inflammatory cytokines. A cross-sectional comparison of healthy older and younger adults during an eight-week controlled diet intervention was performed. Two weeks of a weight-maintaining diet were followed in sequence by 2 weeks of 30% caloric reduction and 4 weeks of ad libitum (ad lib) food intake. Integrated 24-hour plasma leptin levels (AUC leptin), pro-inflammatory cytokine levels, DEXA scan for body composition, and resting energy expenditure (REE) were measured after each diet phase.