Circadian Aspects of Postprandial Metabolism

Abstract

Time-dependent variations in the hormonal and metabolic responses to food are of importance to human health, as postprandial metabolic responses have been implicated as risk factors in a number of major diseases, including cardiovascular disease. Early work reported decreasing glucose tolerance in the evening and at night with evidence for insulin resistance at night. Subsequently an endogenous circadian component, assessed in constant routine (CR), as well as an influence of sleep time, was described for glucose and insulin. Plasma triacylglycerol (TAG), the major lipid component of dietary fat circulating after a meal, also appears to be influenced by both the circadian clock and sleep time with higher levels during biological night (defined as the time between the onset and offset of melatonin secretion) despite identical hourly nutrient intake. These time-dependent differences in postprandial responses have implications for shiftworkers. In the case of an unadapted night shift worker, meals during work time will be taken during biological night. In simulated night shift conditions the TAG response to a standard meal, preceded by either a low-fat or a high-fat premeal, was higher after a nighttime meal than during a daytime meal, and the day/night difference was larger in men than in women. In real night shift workers in Antarctica, insulin, glucose, and TAG all showed an increased response after a nighttime meal (second day of night shift) compared to a daytime meal. Night shift workers are reported to have an approximately 1.5 times higher incidence of heart disease risk and also demonstrate higher TAG levels compared with matched dayworkers. As both insulin resistance and elevated circulating TAG are independent risk factors for heart disease, it is possible that meals at night may contribute to this risk.

Quantitative Genetic Analysis of Sleep inDrosophila melanogaster

“…Our correlation data suggest that the differences in male and female sleep patterns may be related to sexspecific differences in metabolic needs (Montooth et al 2003;Morgan et al 2003;De Luca et al 2005). The relatively high genetic correlations that we observed between sleep and energy stores may reflect the fact that large metabolic changes occur with high probability with the introduction of single P-element insertions in flies, implying that large numbers of genes influence metabolism (Clark et al 1995).…”

Second meal effects of dietary calcium and vitamin D

“…This diurnal change was evident at all levels of circulating glucose, although the amplitude was greater at higher glucose concentrations (Boden et al, 1996). Other investigators have also reported circadian variations in insulin sensitivity, glucose tolerance and postprandial metabolism (Lee et al, 1992;Morgan et al, 2003). Given the variety of study designs and the lack of meal standardization, the basis and magnitude of sequential effects deserves further investigation.…”

Lipidomics reveals diurnal lipid oscillations in human skeletal muscle persisting in cellular myotubes cultured in vitro

“…In humans, diurnal variations in glucose tolerance have long been described (18), and rhythmic profiles of plasma glucose, insulin, and triglycerides have been detected (19,20). Furthermore, a lipidomic analysis of human plasma has shown that ∼18% of all lipid profiles oscillate in a circadian manner independent of sleep and food intake (19).…”