title: Circadian Time Structure of Circulating Plasma Lipid Components in Healthy Indians of Different Age Groups.
abstract: The circadian rhythm of human circulating lipid components was studied under nearnormal tropical conditions in 162 healthy volunteers (103 males and 59 females; 7 to 75 years of age). They followed a diurnal activity from about 06:00 to about 22:00 and nocturnal rest. These volunteers were divided into four groups: Group A (7-20 years), Group B (21-40 years), Group C (41-60 years) and Group D (61-75 years), comprising 42, 60, 35 and 25 participants, respectively. A marked circadian rhythm was demonstrated for each studied variable in each group by population-mean cosinor analysis (almost invariably p < 0.001). Furthermore, circadian rhythm characteristics were compared among the 4 groups by parameter tests and regressed as a function of age, separately for males and females. A second-order polynomial characterized the MESOR of HDL cholesterol, phospholipids and total lipids, as well as the 24-h amplitude of total cholesterol and phospholipids. The 24-h amplitude of total lipids decreased linearly with age. The 24-h acrophase of the oldest age group (Group D) was advanced in the case of total cholesterol, HDL cholesterol, and total lipids, whereas that of phospholipids was delayed. Mapping the circadian rhythm (an important component of the broader time structure or chronome, which includes a. o., trends with age and extra-circadian components) of lipid components is needed to explore their role in the aging process in health.
authors.affiliation: Biochemistry Department, King George's Medical University, Lucknow, 226003 India.
authors.forename: Ranjana
authors.initials: R
authors.lastname: Singh
authors.affiliation: Biochemistry Department, SGRR Institute of Medical & Health Sciences, Dehradun, 248001 India.
authors.forename: Sumita
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Biochemistry Department, SGRR Institute of Medical & Health Sciences, Dehradun, 248001 India.
authors.forename: Raj K
authors.initials: RK
authors.lastname: Singh
authors.affiliation: Halberg Chronobiology Center, University of Minnesota, Minneapolis, MN 55455 USA.
authors.forename: Germaine
authors.initials: G
authors.lastname: Cornelissen
keywords: Aging process; Cholesterol; Circadian time structure; Healthy population; Phospholipids; Total lipids