0080 DIURNAL VARIATION OF PLASMA LYSOPHOSPHATIDYL LIPIDS IN HEALTHY NON-OBESE OLDER ADULTS

Abstract Introduction: Disruption of daily rhythms in energy expenditure has been implicated in metabolic dysfunction. The rhythmic control of lipid metabolism and its temporal coordination with rest-activity and food intake have been studied in young adults, but remain poorly understood in older adults who are at greater risk for metabolic disorders. Lysophosphatidyl lipids (LPLs) are a class of membrane phosphatidyl lipids reported to exhibit diurnal variation. We characterized the effects of rest-activity and timing of food intake on LPLs in healthy older adults studied in controlled laboratory conditions. Methods: As part of a larger study, blood samples from eight healthy non-obese older adults (56–69, 4 women) were collected every 4h for 24h. Participants had a 10h scheduled sleep episode followed by 14 h of wakefulness with controlled posture and activity, during which time three calorie/nutrient controlled meals (breakfast, lunch, dinner) were served. Plasma lipid profiling was done by liquid chromatography-high resolution mass spectrometry. Eighteen LPLs were identified based on their m/z in both positive and negative ionization modes. Rhythmicity was tested by fitting a cosinor model; two-way ANOVA was used to test the effects of rest-activity and fasting (>8h since last meal) on LPL levels. Results: All 18 LPLs showed rhythmicity (p