Whm Saris

Regulation of average 24h human plasma leptin level; the influence of exercise and physiological changes in energy balance.

OBJECTIVE: The effects of short-term moderate physiological changes in energy flux and energy balance, by exercise and over- or underfeeding, on a 24 h plasma leptin profile, were investigated.DESIGN: Subjects were studied over 24 h in four randomized conditions: no exercise\energy balance (energy intake (EI)=;energy expenditure (EE)=;11.8±0.8 MJ); exercise\energy balance (EI=;EE=;15.1±0.6 MJ); exercise\negative energy balance (EI=;11.8±0.8 MJ, EE=;15.1±0.8 MJ); exercise\positive energy balance (EI=;18.6±0.7 MJ, EE=;15.1±0.6 MJ).SUBJECTS: Eight healthy, lean men (age: 23.5±7.0 y, body fat 14.1±5.4%, body mass index (BMI): 21.4±2.3 kg\m2).MEASUREMENTS: Blood was sampled every hour during the daytime (09.00–23.00 h) and every two hours during the night (01.00–09.00 h) for analysis of plasma leptin, insulin, glucose, FFA and catecholamines.RESULTS: Plasma leptin levels were highest around 01.00 h (mean±s.e.m. 4.9±2.0 ng\ml) and lowest around 11.00 h. (2.3±0.7 ng\ml). An increased 24 h EE, induced by exercise under conditions of energy balance, significantly decreased the peak and average 24 h plasma leptin concentration. A positive energy balance, by overfeeding, resulted in a significantly higher amplitude of the 24 h plasma leptin curve, compared to a condition of energy balance.CONCLUSION: Exercise decreases peak and average 24 h plasma leptin concentration and a moderately positive energy balance increases the amplitude of the 24 h plasma leptin profile. These effects are not acute, but are manifest within 24 h. The variations of average 24 h FFA and average 24 h glucose concentrations almost fully explained the variation in average 24 h leptin concentration across trials.

INCREASED SYSTOLIC BLOOD PRESSURE AFTER MILD COLD AND REWARMING: RELATION TO COLD-INDUCED THERMOGENESIS AND AGE

Aim:  Higher winter mortality in elderly has been associated with augmented systolic blood pressure (SBP) response and with impaired defense of core temperature. Here we investigated whether the augmented SBP upon mild cold exposure remains after a rewarming period, and whether SBP changes are linked to thermoregulation. Therefore, we tested the following hypotheses: cold‐induced increase in SBP (1) remains augmented after rewarming in elderly compared to young adults (2) is related to non‐shivering thermogenesis (NST) upon mild cold (3) is related to vasoconstriction upon mild cold.