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.

Free-Living Humans Cross Cardiovascular Disease Risk Categories Due to Daily Rhythms in Cholesterol and Triglycerides

“…The American College of Cardiology recently released a recommendation stating that TC and HDL-c “vary little between the fasting and non-fasting state” [65], implying that variability of these outputs is not relevant for interpreting clinical results. This conflicts with the variability observed in this cohort, and those of previous studies [26272829343536], in which fasting state and/or time of day play a role. Additionally, recommendations on which biomarkers take precedence in risk evaluation vary considerably by country [1966] and by year [946].…”

“…There is substantial evidence to suggest that lipids, including TC and triglycerides, have a daily rhythm in humans [26272829] and in rodent models [30313233]. In humans, laboratory-based lipidomic and metabolomic studies have illustrated circadian control of a large number of lipid blood factors, including fatty acids, triacylglycerides, glycerophospholipids, sterolipids and sphingolipids [333435].…”

“…In a third study of 17 individuals, sampled every 4 hours for 24 hours, effects of time but not significant sine fits were observed [38]. Additionally, in 2016, a cohort of 173 observed significant change by time of day in TC by drawing blood every six hours for 24 hours in laboratory conditions [27]. At least two other human studies have demonstrated approximately 24-hour rhythms in serum cholesterol components in elderly populations in laboratory conditions, but have disagreed as to the presence of a triglyceride rhythm [39].…”

The aging clock: circadian rhythms and later life

“…12, 14). Many metabolic rhythms exhibit progressive dampening with age (76,81,82). These changes are underscored by evidence of age-related decreases in the amplitude of clock gene expression rhythms in clocks outside of the master pacemaker (83,84).…”

Effect of Gender, Age, Diet and Smoking Status on the Circadian Rhythm of Serum Uric Acid of Healthy Indians of Different Age Groups

“…Serum was separated and uric was measured spectrophotometrically [17]. Other biochemical variables of these volunteers have recently been published separately [18,19].…”