OBJECTIVE: To investigate whether acute feeding induces changes in circulating leptin levels in humans and whether these changes vary according to nycthemeral cycle. METHODS: First experiment. Eighteen male subjects were given a fatty meal at 08.00 h. Blood sampling was performed for 10 h following this meal. Second experiment. Thirteen male subjects were given either a mixed meal or remained fasting either at night (starting at 01.00 h) or during the day (starting at 13.00 h). Blood samples were drawn every hour for a period of 8 h. RESULTS: First experiment. Serum leptin levels increased progressively from a mean (s.d.) baseline of 3.8 AE 2.2 ngaml to a value of 4.5 AE 2.7 ngaml (P`0.01) 8 h after the fatty meal. Second experiment. During the day, serum leptin levels increased progressively from 2.65 AE 1.7 to 3.34 AE 2.2 ngaml (P`0.001) 6 h after the test-meal and decreased from 2.68 AE 1.5 to 1.9 AE 1.1 ngaml (P`0.001) 8 h after the beginning of the fasting experiment. Similar results were obtained at night. No statistically signi®cant differences in leptin levels were observed between day and night sessions in response to feeding (mean area under the curve: 3.0 AE 4.1 vs 4.1 AE 4.1 ngaml) and fasting (72.9 AE 2.2 vs 71.5 AE 2.2 ngaml). CONCLUSION: In two independent experiments, human serum leptin levels increase following food intake. This response is not in¯uenced by nycthemeral cycle.

The goal of the present study was to assess the influence of mealtime on postprandial lipemia. Thirteen healthy subject aged 19-32 y were given the same meal at night (0100) or during the day (1300) in random order: the meal contained 40% of estimated daily energy expenditure. Blood samples were drawn at baseline and hourly for 8 h after the meal. Serum total cholesterol, very-low-density-lipoprotein cholesterol (VLDL-C), low-density-lipoprotein cholesterol (LDL-C), high-density-lipoprotein cholesterol (HDL-C), triacylglycerols, VLDL-triacylglycerols, apolipoprotein (apo) A-I, and apo B were measured at each time point. In a subgroup of seven subjects a control fasting reference line was measured according to the same nocturnal and diurnal time schedule. The mean postprandial concentrations of triacylglycerol (P < 0.001), VLDL-triacylglycerol (P < 0.001), and VLDL-C (P < 0.001) were higher at night than during the day. In contrast, mean cholesterol (P < 0.01), LDL-C (P < 0.01), HDL-C (P < 0.001), apo A-I (P < 0.001), and apo B (P < 0.001) concentrations were lower after the night meal than after the day meal. The magnitude of the postprandial response was estimated by the area between the fasting and postprandial curves. The triacylglycerol and VLDL-triacylglycerol responses were not significantly different between night and day. The VLDL-C (P < 0.01) response was greater and LDL-C (P < 0.0001) and HDL-C (P < 0.01) responses were lower at night than during the day. These results indicate that circadian factors specifically affect serum cholesterol transport. Apo B (P < 0.01) and apo A-I (P < 0.01) responses followed LDL-C and HDL-C changes during the day but were dissociated from lipoprotein responses at night, suggesting that circadian apolipoprotein regulation is dissociated from that of serum lipids. The results of the present study indicate that postprandial lipid, lipoprotein, and apolipoprotein concentrations are affected by circadian factors.

Mental stress is associated with increased concentrations of postprandial triacylglycerol-rich lipoprotein fractions. Therefore, postprandial hyperlipidemia is one possible mechanism contributing to the higher risk of ischemic heart disease in stressed people.

Grâce à une vision précise des détails et une perception tactile spécifique du bec, une volaille apprend, dès ses premières heures de vie, à associer les caractéristiques sensorielles des particules alimentaires à leurs effets nutritionnels. Le choix particulaire est très rapide et précis, mais il peut également changer avec l’expérience sensorielle que l’animal a de l’aliment. La taille et la dureté des particules déterminent une vitesse d’ingestion dont les conséquences zootechniques réelles dépendent de l’environnement. Exposées à des conditions d’élevage variées ou constantes, les volailles s’adaptent plus ou moins vite à un changement d’aliment. Le type d’élevage peut donc modifier sensiblement la perception et les conséquences de la granulométrie du régime. Cela rend difficile l’établissement de normes de besoin des animaux. La collaboration entre technologues et nutritionnistes permet la mise au point de nouvelles méthodes évaluant ce que les volailles perçoivent réellement de la texture et de la forme des particules. L’étude du comportement alimentaire est utile pour suivre, au laboratoire et directement en élevage, l’incidence d’ajustements technologiques, et pour développer de nouveaux modes de distribution des aliments. Nutrition et détection sensorielle interagissent sur les trois phases du comportement alimentaire : identification, préhension et ingestion de l’aliment. Une conception efficace de la technologie alimentaire intégrée à l’élevage devrait distinguer chacune de ces trois étapes.

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(1995), Daabete & Metab], the factorial method (MFact) [Visser et al (1995), Metab] and the heart rate recording method (MHR) [Ceesay et al (1989), Br

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