Circadian leptin, insulin and cortisol rhythms in obese subjects

Sugary beverage consumption mediates the relationship between late chronotype, sleep duration, and weight increase among undergraduates: a cross-sectional study

BACKGROUND

The study aimed to explore whether sugary beverage consumption is a key mediator of late chronotype, sleep duration, and weight increase in college students in China.

METHODS

The cross-sectional study was conducted in four universities using a sample of 800 undergraduate students recruited by cluster sampling. A self-reported questionnaire was given out to collect information, including the characteristic of social demography, state of physical exercise and sugary beverage intake, the types of chronotype, and psychological conditions. Then, two structural equation models (SEMs) were constructed to test the mediating effect of sugary beverage consumption.

RESULTS

The significant indirect effect of sugary beverage consumption was found between chronotype and BMI (effect = - 0.03, SE = 0.01, 95% CI [- 0.05, - 0.02]) and between sleep duration and BMI (effect = - 0.12, SE = 0.05, 95% CI [- 0.16, - 0.09]). In addition, physical exercise and psychological condition also play mediating effects between chronotype and BMI (effect = - 0.04, SE = 0.01, 95% CI [- 0.06, - 0.01] and effect = - 0.03, SE = 0.02, 95% CI [- 0.05, - 0.01]), but their mediating effect was not found between sleep duration and BMI.

CONCLUSION

Preventive measures should be taken to decrease student's sugary beverage consumption, improve physical exercise, and increase individual well-being to avoid the harmful effects of eveningness. Moreover, the issue of short sleep duration among college students may be further investigated in future research.

Caffeinated Drinks Intake, Late Chronotype, and Increased Body Mass Index among Medical Students in Chongqing, China: A Multiple Mediation Model

Background: This paper investigates the problems regarding caffeinated drinks intake, late chronotype, and increased body mass index (BMI) among medical students at a Chinese university. Methods: This cross-sectional study was conducted in 2018 with 616 medical students from Chongqing Medical University in Chongqing, China, whose information were collected by a self-reported questionnaire that included four sections: Demographic characteristics; Caffeinated drinks intake and physical state; Morningness-Eveningness Questionnaire; Depression Anxiety Stress Scale 21. Multiple mediation analyses were conducted to test the impact of late chronotype on increased BMI through caffeinated drinks consumption through two models. Results: The significantly mediated effect of caffeinated drinks consumption was revealed (estimate: -0.01, SE = 0.01, 95% CI [-0.02, -0.01]), and which played a positive role in linking late chronotype (B = -0.01, SE = 0.01, p < 0.001) and increased BMI (B = 1.37, SE = 0.21, p < 0.01), but their significant association did not be found in reversed model. In addition, physical activity and inactivity times demonstrated significant indirect effects in the two models. Conclusions: Interventions should focus on reducing caffeinated drinks intake and sedentary behavior time, enhancing physical activity among medical students.

Time-dependent effects of leptin on food intake and locomotor activity in goldfish

The present study investigates the possible circadian dependence of leptin effects on food intake, locomotor activity, glycemia and plasma cortisol levels in goldfish (Carassius auratus). Fish were maintained under 12L:12D photoperiod and subjected to two different feeding schedules, one group fed during photophase (10:00) and the other one during scotophase (22:00). Leptin or saline were intraperitoneally injected at two different times (10:00 or 22:00), coincident or not with the meal time. To eliminate the entraining effect of the light/dark cycle, goldfish maintained under 24h light (LL) were fed and leptin-injected at 10:00. A reduction in food intake and locomotor activity and an increase in glycemia were found in goldfish fed and leptin-injected at 10:00. No significant changes in circulating cortisol were observed. Those effects were not observed when leptin was administered during the scotophase, regardless the feeding schedule; neither in fish maintained under LL, suggesting that a day/night cycle would be necessary to observe the actions of leptin administered during the photophase. Changes in locomotor activity and glycemia were only observed in goldfish when leptin was injected at daytime, coincident with the feeding schedule, suggesting that these leptin actions could be dependent on the feeding time as zeitgeber. In view of these results it appears that the circadian dependence of leptin actions in goldfish can be determined by the combination of both zeitgebers, light/dark cycle and food. Our results point out the relevance of the administration time when investigating regulatory functions of hormones.