1998 |
Goel, Namni |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Sensory Stimuli Effects On Human Circadian Rhythms
Many elderly people complain of significant sleep disturbance. Complaints of multiple and prolonged awakenings and fragmented nocturnal sleep indicate that elderly individuals have difficulties in maintaining, rather than initiating sleep. Age-related changes in the circadian system underlie, at least in part, sleep disturbance. Timed exposure to bright light can alleviate such symptoms, although compliance to long-term treatments is poor. As such, alternatives and/or supplements to bright light are needed to relieve sleep disturbance. In humans, light phase shifts circadian rhythms according to a phase response curve. Nonphotic stimuli, such as social interaction, and sensory stimuli including auditory and olfactory cues, can also phase shift circadian rhythms in mammals and birds. Few studies have investigated rigorously whether nonphotic stimuli can affect human circadian rhythms. This study will determine whether an auditory stimulus, with an arousing component, can phase shift circadian rhythms in a sample of healthy male and female elderly (60+ yr old) subjects. An ancillary question will assess gender differences in response to auditory stimuli in the elderly. Subjects will spend two 4-day sessions in a sleep laboratory under constant dim light (less than 20 lux), receiving either a 2-h auditory stimulus or a control stimulus (absence of auditory cue) from 0100 h-0300 h on the second and third nights. Subjects will participate in both sessions, with presentation order counterbalanced among individuals. Polysomnographical sleep and core body temperature will be collected continuously and salivary melatonin samples will be obtained once each hour from 1800 h to 2400 h on Night 1 (baseline night) and Night 4 (post-stimulus night). To measure putative phase shifts, circadian phase of core body temperature minimum and the dim light melatonin onset (DLMO), before and after sensory stimulation, will be assessed in the control and experimental sessions. This study serves as the first essential step toward describing rigorously the effects of sensory stimuli on circadian rhythms in males and females. Completion of this project will allow for further exploration regarding the significance of nonphotic entrainers for the human circadian system, in particular as alternatives for relieving sleep disturbance in older subjects.
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0.957 |
2017 — 2021 |
Allison, Kelly C Goel, Namni |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Impact of Daytime Vs. Delayed Eating Schedule On Weight and Metabolic Markers Among Obese Persons: An Examination of Circadian Mechanisms @ University of Pennsylvania
Project Summary/Abstract Timed eating is recognized for its significant contribution to body weight regulation. Disruption of sleep-wake cycles from a predominantly diurnal (daytime) lifestyle to a delayed lifestyle leads to disrupted circadian rhythms and metabolic dysfunction. In our R21 (DK100787), we studied healthy, normal weight adults in a randomized, cross-over design comparing the effects of eating an isocaloric diet for 8 wks on a daytime vs a delayed schedule, with a constant sleep-wake cycle. Our preliminary results indicate weight, respiratory quotient, trunk fat, insulin, total cholesterol, and adiponectin decreased on the daytime schedule, while triglycerides and glucose increased on the delayed schedule. Also, in the daytime condition, the circadian phase of ghrelin was advanced and that of leptin was delayed, but melatonin phase remained unchanged vs. the delayed condition. Our results provide the first experimental evidence that daytime eating compared with delayed eating promotes weight loss and a positive profile for fuel oxidation and hormonal markers, and positively alters circadian rhythm phase in normal weight adults. Notably, the metabolic effects and their underlying circadian mechanisms of such eating patterns have not been investigated rigorously in experimental studies among obese populations. We hypothesize that a daytime compared with a delayed eating schedule, with constant sleep-wake and activity levels, will decrease weight, improve metabolic profiles and positively impact circadian-mediated responses in obese persons, decreasing the risk for developing metabolic syndrome and diabetes. Forty healthy men and women, ages 21- 50, with a BMI of 30-50 kg/m2 will participate in a free-living randomized cross-over experiment comparing a daytime eating schedule (0800h-1900h) to a delayed eating schedule (1200h-2300h), with comparable energy and macronutrient content, and constant sleep-wake periods (2300h-0700h) and exercise (<30 min/d, <3 d/wk). Our metabolic kitchen will provide all food for 8 wks during each condition, separated by a 2-wk washout. Protocol adherence will be monitored closely with food logs, weighing of food, pictures for portion size assessment of any outside food eaten, actigraphy, and daily self-reports of sleep-wake and exercise. Assessments will occur 4 times, pre- and post- each 8-wk eating condition, during which we will measure: weight, body composition, respiratory quotient and resting energy expenditure; fasting levels of insulin, glucose, cholesterol, triglycerides, adiponectin, non-esterified fatty acids and C reactive protein; and levels of leptin, ghrelin, melatonin, glucose and cortisol, and gene expression from peripheral blood every 4h (7 times over 24h) to show circadian rhythm phase changes between the eating conditions. We will also examine mechanisms underlying these changes through frequently sampled intravenous glucose tolerance testing to determine insulin sensitivity, pancreatic beta cell function, glucose effectiveness, and free fatty acid dynamics, and through subcutaneous white adipose tissue gene expression. This multi-faceted project will benefit from the investigators' expertise in eating behaviors/weight management, circadian and sleep biology, endocrinology and metabolism, and bioinformatics.
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