Fasting levels of appetite regulating hormones predict caloric intake at breakfast in a group of Chilean adolescents / Los niveles en ayunas de hormonas reguladoras del apetito predicen la ingesta energética en el desayuno en adolescentes

BACKGROUND: Appetite regulation is integral to food intake and is modulated by complex interactions between internal and external stimuli. Hormonal mechanisms which stimulate or inhibit intake have been characterized, but the physiologic effects of serum levels of such hormones in short-term appetite regulation have received little attention. AIM: To evaluate whether fasting levels of orexigenic/anorexigenic hormones were associated with energy intake at breakfast, served soon after drawing a fasting blood sample, in a group of adolescents. MATERIAL AND METHODS: Anthropometry, body composition and fasting blood levels of leptin, insulin, ghrelin, and orexin-A were measured in 655 Chilean adolescents aged 16.8 ± 0.3 years (52% males). Energy intake was measured at a semi-standardized breakfast. Associations between hormone levels and energy intake were studied using multivariate linear models. RESULTS: Thirty nine percent of participants were overweight/ obese. After an overnight fast, median values for leptin, insulin, ghrelin and orexin-A were 7.3 ng/mL, 6.7 IU/dL, 200.8 pg/mL, and 16.1 pg/mL, respectively. Participants ate on average 637 ± 239 calories at breakfast. In multivariable models, insulin levels were inversely and independently associated with caloric intake at breakfast (β = −18.65; p < 0.05), whereas leptin, ghrelin and orexin-A levels were positively and independently associated with intake: β= 5.56, β = 0.34 and β = 8.40, respectively, p < 0.05. CONCLUSIONS: Fasting leptin, ghrelin and orexin-A were positively associated with energy intake during breakfast provided soon after the blood draw. Insulin was negatively associated with energy intake. Modifiable factors influencing levels of appetite regulating hormones could be a potential target for influencing food intake.

ANTECEDENTES: La regulación del apetito es parte integral de la ingesta alimentaria y es modulada por complejas interacciones entre estímulos internos y externos. Se han caracterizado los mecanismos hormonales que estimulan o inhiben la ingesta, pero los efectos fisiológicos de los niveles séricos de tales hormonas en la regulación del apetito a corto plazo han recibido poca atención. OBJETIVO: Evaluar si los niveles en ayunas de hormonas orexigénicas/ anorexigénicas se asocian con la ingesta energética en el desayuno, entregado inmediatamente después de una muestra de sangre en ayunas, en un grupo de adolescentes. MATERIAL Y MÉTODO: Se efectuaron mediciones antropométricas, composición corporal y medición de niveles en ayunas de leptina, insulina, grelina y orexina-A en 655 adolescentes de 16,8 ± 0,26 años. La ingesta energética se midió en un desayuno semiestandarizado. Se estudiaron las asociaciones entre los niveles hormonales y la ingesta energética mediante modelos lineales multivariados. RESULTADOS: Los valores de leptina, insulina, grelina y orexina-A fueron 7,3 ng/mL, 6,7 UI/dL, 200,8 pg/mL y 16,1 pg/mL respectivamente. Los participantes comieron un promedio de 637 ± 239 calorías en el desayuno. Los niveles de insulina se asociaron inversa e independientemente con la ingesta del desayuno (β = −18,65; p < 0,05), mientras que los niveles de leptina, grelina y orexina-A se asociaron positiva e independientemente con la ingesta: β = 5,65; β = 0,34; β = 8,40, (p < 0,05). CONCLUSIONES: La leptina, grelina y orexina-A en ayunas se asociaron positivamente con la ingesta de energía durante el desayuno proporcionado poco después de la muestra de sangre. La insulina se asoció negativamente con la ingesta de energía. Los factores modificables que influyen en las hormonas reguladoras del apetito podrían ser un objetivo potencial para influir en la ingesta de alimentos.

Regulación circadiana, patrón horario de alimentación y sueño: Enfoque en el problema de obesidad / Circadian rhythms, eating patterns, and sleep: A focus on obesity

RESUMEN El reloj biológico determina la mantención de los ritmos circadianos en mamíferos, un tipo particular de ritmos biológicos de duración cercana a 24 horas. Existe una estrecha relación entre el funcionamiento del sistema circadiano, la alimentación y la regulación metabólica, lo que actualmente constituye un área de intensa investigación. En particular, la alteración de la ritmicidad circadiana a partir de modificaciones genéticas, conductuales o dietarias, lleva a trastornos comportamentales, ganancia de peso excesiva y alteraciones metabólicas. Algunos factores que contribuyen a la alteración o desajuste circadiano incluyen el jet-lag, el trabajo por turnos horarios, la desorganización temporal y restricción de sueño, y desorden del patrón horario de alimentación. Este trabajo resume la evidencia acerca de la influencia de los ritmos circadianos en procesos relacionados con la alimentación y las consecuencias metabólicas de su alteración. Se hace énfasis en las consecuencias de la alteración de los ritmos de alimentación-ayuno y de sueño-vigilia, y su relación con la ganancia de peso excesiva, la obesidad y trastornos metabólicos asociados, condiciones altamente prevalentes en sociedades occidentalizadas.

ABSTRACT In mammals, the biological clock is driven by circadian rhythms, a particular type of biological rhythm that last about 24 hours. There is a close relationship between the functioning of the circadian system, eating and metabolic regulation, which is currently an area of intense research. Alteration of circadian rhythmicity from genetic, behavioral or dietary modifications, leads to behavioral and metabolic disorders, and excessive weight gain. Factors that contribute to circadian disruption include, among others, jet lag, shift work, mistimed and restricted sleep, and irregular eating patterns. This review summarizes the evidence regarding the influence of circadian rhythms on eating processes and the metabolic consequences of circadian disruption. Special focus is on the consequences of disruption of regular eating-fasting and sleep-wake rhythms, and relationships with excessive weight gain, obesity and obesity-related metabolic disorders that are highly prevalent in westernized societies.

La reducción del sueño como factor de riesgo para obesidad / Sleep deprivation as a risk factor for obesity

Nocturnal sleep patterns may be a contributing factor for the epidemic of obesity. Epidemiologic ana experimental studies have reported that sleep restriction is an independent risk factor for weight gain and obesity. Moreover, sleep restriction is significantly associated with incidence and prevalence of obesity and several non-transmissible chronic diseases. Experimental sleep restriction is related to altered plasma leptin and ghrelin concentrations. Both hormones are directly related to appetite and satiety mechanisms. Also, a higher activity of the orexin/hypocretin system has been reported, as well as changes in glucose metabolism and autonomic nervous system. Some studies indicate that these endocrine changes could be associated with a higher diurnal food intake and preference for energy- dense foods. All these changes could result in a positive energy balance, leading to weight gain and a higher obesity risk in the long-term. The present article summarizes the epidemiologic and experimental evidence related to sleep deprivation and higher obesity risk. The possible mechanisms are highlighted.

Sleep in brain development

With the discovery of rapid eye movement (REM) sleep, sleep was no longer considered a homogeneous state of passive rest for the brain. On the contrary, sleep, and especially REM sleep, appeared as an active condition of intense cerebral activity. The fact that we get large amounts of sleep in early life suggested that sleep may play a role in brain maturation. This idea has been investigated for many years through a large number of animal and human studies, but evidence remains fragmented. The hypothesis proposed was that REM sleep would provide an endogenous source of activation, possibly critical for structural maturation of the central nervous system. This proposal led to a series of experiments looking at the role of REM sleep in brain development. In particular, the influence of sleep in developing the visual system has been highlighted. More recently, non-REM (NREM) sleep state has become a major focus of attention. The current data underscore the importance of both REM sleep and NREM sleep states in normal synaptic development and lend support to their functional roles in brain maturation. Both sleep states appear to be important for neuronal development, but the corresponding contribution is likely to be different.