LAUSR

Free fatty acids (FFA) are a primary fuel source for heart and skeletal muscle, particularly during fasting. In addition, both high fat feeding and insufficient sleep have been shown to increase nocturnal FFA in animal and human models, respectively. However, findings from studies of insufficient sleep have been limited by a focus on male subjects. Furthermore, the impact of ad libitum food intake during insufficient sleep on FFA has not been examined. We therefore examined potential sex differences in circulating 24-hour FFA profiles during habitual sleep and insufficient sleep under ad libitum feeding conditions. Healthy adults (7 females: 23.6±3.2 y, BMI 22.1±1.1 kg/m 2 ; 7 males: 25.7±4.6 y, BMI 22.5±1.2 kg/m 2 ; mean±SD) were studied after five inpatient days consisting of 9h scheduled sleep per night at habitual bedtime and five inpatient days consisting of 5h scheduled sleep beginning 2 hours later than habitual bedtime in a crossover design. On the 5 th day in each condition, blood was sampled hourly beginning one hour after scheduled wake-time for 24 hours. In both conditions, participants were provided 3 scheduled meals and 2 snacks designed to provide approximately 130-150% of energy requirements, and had free access to snacks during scheduled waketime. Females showed a more robust FFA response to food intake during both habitual and insufficient sleep vs. men, likely due to positive energy balance for men in both conditions. In addition, both men and women displayed altered FFA patterns during insufficient sleep such that the nocturnal peak was later in the 24hour profile. We provide evidence of sex differences in 24-hour FFA profiles in response to overeating with and without insufficient sleep. The significance of these differences and how they may affect responses to sleep and/or metabolic perturbations is unknown. Future studies are necessary to determine whether differences in FFA may lead to sex differences in metabolic impairments in response to insufficient sleep. Disclosure J.L. Broussard: None. C.M. Depner: None. R. Markwald: None. R.H. Eckel: Advisory Panel; Self; Novo Nordisk Inc., Merck & Co., Inc. L. Perreault: Advisory Panel; Self; Novo Nordisk A/S. Speaker9s Bureau; Self; Novo Nordisk A/S. Advisory Panel; Self; Merck & Co., Inc.. Speaker9s Bureau; Self; Merck & Co., Inc., AstraZeneca, Janssen Pharmaceuticals, Inc., Boehringer Ingelheim Pharmaceuticals, Inc.. Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Advisory Panel; Self; Sanofi. Speaker9s Bureau; Self; Sanofi. J. Higgins: None. E. Melanson: None. K. Wright: Research Support; Self; Philips Respironics, CurAegis Technologies, Inc., Somalogics, National Institutes of Health, Pac-12, Office of Naval Research. Consultant; Self; National Heart, Lung, and Blood Institute, CurAegis Technologies, Inc., Circadian Therapeutics, LTD. Board Member; Self; Sleep Research Society. Consultant; Self; American Academy of Sleep Medicine, American Diabetes Association, American College of Chest Physicians.