Feeding and circadian clocks

Misalignment of Circadian Rhythms in Diet-Induced Obesity

The biological clocks of the circadian timing system coordinate cellular and physiological processes and synchronize them with daily cycles. While the central clock in the suprachiasmatic nucleus (SCN) is mainly synchronized by the light/dark cycles, the peripheral clocks react to other stimuli, including the feeding/fasting state, nutrients, sleep-wake cycles, and physical activity. During the disruption of circadian rhythms due to genetic mutations or social and occupational obligations, incorrect arrangement between the internal clock system and environmental rhythms leads to the development of obesity. Desynchronization between the central and peripheral clocks by altered timing of food intake and diet composition leads to uncoupling of the peripheral clocks from the central pacemaker and to the development of metabolic disorders. The strong coupling of the SCN to the light-dark cycle creates a situation of misalignment when food is ingested during the "wrong" time of day. Food-anticipatory activity is mediated by a self-sustained circadian timing, and its principal component is a food-entrainable oscillator. Modifying the time of feeding alone greatly affects body weight, whereas ketogenic diet (KD) influences circadian biology, through the modulation of clock gene expression. Night-eating behavior is one of the causes of circadian disruption, and night eaters have compulsive and uncontrolled eating with severe obesity. By contrast, time-restricted eating (TRE) restores circadian rhythms through maintaining an appropriate daily rhythm of the eating-fasting cycle. The hypothalamus has a crucial role in the regulation of energy balance rather than food intake. While circadian locomotor output cycles kaput (CLOCK) expression levels increase with high-fat diet-induced obesity, peroxisome proliferator-activated receptor-alpha (PPARα) increases the transcriptional level of brain and muscle aryl hydrocarbon receptor nuclear translocator (ARNT)-like 1 (BMAL1) in obese subjects. In this context, effective timing of chronotherapies aiming to correct SCN-driven rhythms depends on an accurate assessment of the SCN phase. In fact, in a multi-oscillator system, local rhythmicity and its disruption reflects the disruption of either local clocks or central clocks, thus imposing rhythmicity on those local tissues, whereas misalignment of peripheral oscillators is due to exosome-based intercellular communication.Consequently, disruption of clock genes results in dyslipidemia, insulin resistance, and obesity, while light exposure during the daytime, food intake during the daytime, and sleeping during the biological night promote circadian alignment between the central and peripheral clocks. Thus, shift work is associated with an increased risk of obesity, diabetes, and cardiovascular diseases because of unusual eating times as well as unusual light exposure and disruption of the circadian rhythm.

Oleic acid regulates the circadian rhythm of adipose tissue in obesity

The effect of oleic acid (OA) on the regulation of the circadian rhythm present in human visceral (VAT) and subcutaneous (SAT) adipose tissue from patients with morbid obesity has not been analyzed yet. VAT and SAT explants from patients with morbid obesity were incubated with OA to analyze the circadian regulation of clock and other genes related to lipid metabolism (SREBP-1c, FAS, LPL and CPT1), and their association with baseline variables and the improvement of these patients after bariatric surgery. There were significant differences in amplitude and acrophase in VAT with respect to SAT. In VAT, body weight negatively correlated with BMAL1 and CRY1 amplitude, and REVERBα acrophase; body mass index (BMI) negatively correlated with REVERBα acrophase; and waist circumference negatively correlated with PER3 acrophase. In SAT, BMI negatively correlated with CLOCK amplitude, and CLOCK, REVERBα and CRY2 MESOR; and waist circumference negatively correlated with PER3 amplitude and acrophase. A greater short-term improvement of body weight, BMI and waist circumference in patients with morbid obesity after bariatric surgery was associated with a lower CRY1 and CRY2 amplitude and an earlier PER1 and PER3 acrophase in SAT. OA produced a more relevant circadian rhythm and increased the amplitude of most clock genes and lipid metabolism-related genes. OA regulated the acrophase of most clock genes in VAT and SAT, placing CLOCK/BMAL1 in antiphase with regard to the other genes. OA increased the circadian rhythmicity, although with slight differences between adipose tissues. These differences could determine its different behavior in obesity.

The Interplay Between Nutrition and Stress in Pregnancy: Implications for Fetal Programming of Brain Development

Growing evidence supports an important role for the intrauterine environment in shaping fetal development and subsequent child health and disease risk. The fetal brain is particularly plastic, whereby even subtle changes in structure and function produced by in utero conditions can have long-term implications. Based on the consideration that conditions related to energy substrate and likelihood of survival to reproductive age are particularly salient drivers of fetal programming, maternal nutrition and stress represent the most commonly, but independently, studied factors in this context. However, the effects of maternal nutrition and stress are context dependent and may be moderated by one another. Studies examining the effects of the bidirectional nutrition-stress interplay in pregnancy on fetal programming of brain development are beginning to emerge in the literature. This review incorporates all currently available animal and human studies of this interplay and provides a synthesis and critical discussion of findings. Nine of the 10 studies included here assessed nutrition-stress interactions and offspring neurodevelopmental or brain development outcomes. Despite significant heterogeneity in study design and methodology, two broad patterns of results emerge to suggest that the effects of prenatal stress on various aspects of brain development may be mitigated by 1) higher fat diets or increased intake and/or status of specific dietary fats and 2) higher dietary intake or supplementation of targeted nutrients. The limitations of these studies are discussed, and recommendations are provided for future research to expand on this important area of fetal programming of brain development.

Meagre's melatonin profiles under captivity: circadian rhythmicity and light sensitiveness

The present study reveals the first characterization of the plasma melatonin rhythms of the meagre (Argyrosomus regius) under aquaculture conditions. Melatonin levels were monitored during a 24 h cycle under a photoperiod of 16 L:8D and under constant darkness (DD), respectively to characterize the daily rhythm of this indoleamine and to test its endogenous origin. Besides, to identify which light intensities are perceived as night or day by this species, the degree of inhibition of nocturnal melatonin production caused by increasing intensities of light was tested (3.3, 5.3, 10.5, and 120 μW/cm²), applying 1 h light pulses at Mid-Dark. The result for melatonin daily rhythm in plasma showed a typical profile: concentration remained low during all daytime points, increasing greatly during dark points, with maximum values at 16:00 and 22:00 h, zeitgeber time. Under DD conditions, the plasma melatonin profile persisted, with a similar acrophase but with a lower amplitude between subjective day and night periods, indicating this rhythm as being endogenously driven. Moreover, meagre seemed to be very sensitive to dim levels of illumination during the night, since an intensity of just 3.3 μW/cm² inhibited melatonin production. However, only the pulse of 5.3 μW/cm² caused a melatonin drop till daytime concentrations. Thus, the threshold of light detection by the pineal organ was suggested as being located between 3.3 and 5.3 μW/cm². Such results are an added value for this species biology knowledge, and in consequence to its adaptation to aquaculture conditions, allowing the improvement of culture husbandry protocols.

Circadian Rhythms in Diet-Induced Obesity

The biological clocks of the circadian timing system coordinate cellular and physiological processes and synchronizes these with daily cycles, feeding patterns also regulates circadian clocks. The clock genes and adipocytokines show circadian rhythmicity. Dysfunction of these genes are involved in the alteration of these adipokines during the development of obesity. Food availability promotes the stimuli associated with food intake which is a circadian oscillator outside of the suprachiasmatic nucleus (SCN). Its circadian rhythm is arranged with the predictable daily mealtimes. Food anticipatory activity is mediated by a self-sustained circadian timing and its principal component is food entrained oscillator. However, the hypothalamus has a crucial role in the regulation of energy balance rather than food intake. Fatty acids or their metabolites can modulate neuronal activity by brain nutrient-sensing neurons involved in the regulation of energy and glucose homeostasis. The timing of three-meal schedules indicates close association with the plasma levels of insulin and preceding food availability. Desynchronization between the central and peripheral clocks by altered timing of food intake and diet composition can lead to uncoupling of peripheral clocks from the central pacemaker and to the development of metabolic disorders. Metabolic dysfunction is associated with circadian disturbances at both central and peripheral levels and, eventual disruption of circadian clock functioning can lead to obesity. While CLOCK expression levels are increased with high fat diet-induced obesity, peroxisome proliferator-activated receptor (PPAR) alpha increases the transcriptional level of brain and muscle ARNT-like 1 (BMAL1) in obese subjects. Consequently, disruption of clock genes results in dyslipidemia, insulin resistance and obesity. Modifying the time of feeding alone can greatly affect body weight. Changes in the circadian clock are associated with temporal alterations in feeding behavior and increased weight gain. Thus, shift work is associated with increased risk for obesity, diabetes and cardio-vascular diseases as a result of unusual eating time and disruption of circadian rhythm.

Obesity alters the peripheral circadian clock in the aorta and microcirculation

OBJECTIVE

Perturbation of daily rhythm increases cardiovascular risk. The aim of this study was to determine whether obesity alters circadian gene expression and microvascular function in lean mice and obese (db/db) mice.

METHODS

Mice were subjected to normal LD or DD to alter circadian rhythm. Metabolic parameters and microvascular vasoreactivity were evaluated. Array studies were conducted in the am and pm cycles to assess the rhythmicity of the entire genomics. Rhythmic expression of specific clock genes (Bmal1, Clock, Npas2, Per1, Per2, and Cry1), clock output genes (dbp), and vascular relaxation-related genes (eNOS, GTPCH1) were assessed.

RESULTS

Obesity was associated with metabolic dysfunction and impaired endothelial dilation in the microvasculature. Circadian rhythm of gene expression was suppressed 80% in both macro- and microcirculations of obese mice. Circadian disruption with DD increased fasting serum glucose and HbA1c in obese but not lean mice. Endothelium-dependent dilation was attenuated in obese mice and in lean mice subjected to DD. Rhythmic expression of per1 and dbp was depressed in obesity. Expression of eNOS expression was suppressed and GTPCH1 lost rhythmic expression both in obesity and by constant darkness.

CONCLUSION

These results suggest that obesity reduces circadian gene expression in concert with impaired endothelial function. The causal relationship remains to be determined.

Effects of constant light during perinatal periods on the behavioral and neuronal development of mice with or without dietary lutein

Constant light conditions (LL) carry a risk of disrupting the biological clock of developing animals. Our purpose in this study was to investigate what disorders occur in animals receiving an LL stress during the late embryonic and suckling periods as compared with animals housed in dark-light (14 h-10 h) conditions (DL). In addition, we examined ameliorating effects against the disorder by the oral administration of lutein as an antioxidant. LL caused hypertrophy of the spleen and induced a higher expression of serotonin transporter (5HTT) in the corpus striatum and hippocampus in 15-day-old pups. In 9-week-old offspring, LL caused abnormal behavior in the elevated plus-maze test. The expression levels of 5HTT in the brain of the LL group changed to lower than those in DL group. The oral administration of lutein lessened the abnormality in behavior and 5HTT expression in the hippocampus to a certain degree although the expression levels of 5HTT in the corpus striatum were not altered by lutein diet. LL also induced disorders in the maternal brain with lower expression levels of 5HTT and neuregulin 1. These results indicate that LL during the perinatal periods may induce some neuronal abnormalities in both offspring and mothers that may be partially ameliorated by dietary lutein as an antioxidant.

Diet and our genetic legacy in the recent anthropocene: a Darwinian perspective to nutritional health

Nutrient-gene research tends to focus on human disease, although such interactions are often a by-product of our evolutionary heritage. This review explores health in this context, reframing genetic variation/epigenetic phenomena linked to diet in the framework of our recent evolutionary past. This "Darwinian/evolutionary medicine" approach examines how diet helped us evolve among primates and to adapt (or fail to adapt) our metabolome to specific environmental conditions leading to major diseases of civilization. This review presents updated evidence from a diet-gene perspective, portraying discord that exists with respect to health and our overall nutritional, cultural, and activity patterns. While Darwinian theory goes beyond nutritional considerations, a significant component within this concept does relate to nutrition and the mismatch between genes, modern diet, obesogenic lifestyle, and health outcomes. The review argues that nutritional sciences should expand knowledge on the evolutionary connection between food and disease, assimilating it into clinical training with greater prominence.

Endocrine (plasma cortisol and glucose) and behavioral (locomotor and self-feeding activity) circadian rhythms in Senegalese sole (Solea senegalensis Kaup 1858) exposed to light/dark cycles or constant light

The existence of daily rhythms under light/dark (LD) cycles in plasma cortisol, blood glucose and locomotor and self-feeding activities, as well as their persistence (circadian nature) under constant light (LL), was investigated in Senegalese sole (Solea senegalensis). For the cortisol and glucose rhythms study, 48 soles were equally distributed in 8 tanks and exposed to a 12:12 LD cycle and natural water temperature (experiment 1). After an acclimation period, blood was sampled every 3 h until a 24-h cycle was completed. Blood glucose levels were measured immediately after sampling, while plasma cortisol was measured later by ELISA. In experiment 2, the fish were exposed to LL for 11 days, and after this period, the same sampling procedure was repeated. For the study of locomotor and self-feeding rhythms (experiment 3), two groups of sole were used: one exposed to LD and the other to LL. Each group was distributed within 3 tanks equipped with infrared photocells for the record of locomotor activity, and self-feeders for feeding behavior characterization. The results revealed a marked oscillation in cortisol concentrations during the daily cycle under LD, with a peak (35.65 ± 3.14 ng/ml) in the afternoon (15:00 h) and very low levels during the night (5.30 ± 1.09 ng/ml). This cortisol rhythm persisted under LL conditions, with lower values (mean cortisol concentration = 7.12 ± 1.11 ng/ml) and with the peak shifted by 3 h. Both rhythms were confirmed by COSINOR analysis (p < 0.05). The synchronizing role of temperature and feeding schedule, in addition to light, is also discussed. Diel rhythms of glucose were not evident in LD or LL. As to locomotor and self-feeding activity, a very marked rhythm was observed under LD, with higher activity observed during the night, with acrophases located at 2:14 and 3:37 h, respectively. The statistical significance of daily rhythms was confirmed by COSINOR analysis. Under LL, both feeding and locomotor rhythms persisted, with an endogenous period (τ) around 22.5 h. In short, our findings described for the first time the existence of circadian cortisol and behavioral circadian rhythms in flat fish. Such results revealed the importance of taking into account the time of day when assessing stress responses and evaluating physiological indicators of stress in fish.

Time estimation predicts mathematical intelligence

BACKGROUND

Performing mental subtractions affects time (duration) estimates, and making time estimates disrupts mental subtractions. This interaction has been attributed to the concurrent involvement of time estimation and arithmetic with general intelligence and working memory. Given the extant evidence of a relationship between time and number, here we test the stronger hypothesis that time estimation correlates specifically with mathematical intelligence, and not with general intelligence or working-memory capacity.

METHODOLOGY/PRINCIPAL FINDINGS

Participants performed a (prospective) time estimation experiment, completed several subtests of the WAIS intelligence test, and self-rated their mathematical skill. For five different durations, we found that time estimation correlated with both arithmetic ability and self-rated mathematical skill. Controlling for non-mathematical intelligence (including working memory capacity) did not change the results. Conversely, correlations between time estimation and non-mathematical intelligence either were nonsignificant, or disappeared after controlling for mathematical intelligence.

CONCLUSIONS/SIGNIFICANCE

We conclude that time estimation specifically predicts mathematical intelligence. On the basis of the relevant literature, we furthermore conclude that the relationship between time estimation and mathematical intelligence is likely due to a common reliance on spatial ability.

Folic Acid: Beyond Metabolism

Mandatory and discretionary fortification with folic acid is eliminating deficiency of this vitamin. Blood levels of the vitamin have never been higher, with hematologic folate values commonly exceeding the upper range of calibration. The synthetic analog (pteroylmonoglutamic acid) prevents neural tube defects and lowers homocysteine, both positive attributes, yet negative correlates of pteroylmonoglutamic acid are increasingly reported. These involve increased risk for common cancers (ie, colon, breast, prostate) and antimetabolite effects on natural killer cells and at dihydrofolate reductase, a critical gatekeeper enzyme. This review, however, takes a different, human ecological perspective, examining novel folate-related phenomena distinct from the classic metabolic role of the vitamin in maintaining health and well-being. An argument is developed that at molecular, cellular, and organism levels, folate is crucial to some important events that link light to life.

Acute partial sleep deprivation increases food intake in healthy men

BACKGROUND

Acute partial sleep deprivation increases plasma concentrations of ghrelin and decreases those of leptin.

OBJECTIVE

The objective was to observe modifications in energy intake and physical activity after acute partial sleep deprivation in healthy men.

DESIGN

Twelve men [age: 22 +/- 3 y; body mass index (in kg/m(2)): 22.30 +/- 1.83] completed a randomized 2-condition crossover study. During the first night of each 48-h session, subjects had either approximately 8 h (from midnight to 0800) or approximately 4 h (from 0200 to 0600) of sleep. All foods consumed subsequently (jam on buttered toast for breakfast, buffet for lunch, and a free menu for dinner) were eaten ad libitum. Physical activity was recorded by an actimeter. Feelings of hunger, perceived pleasantness of the foods, desire to eat some foods, and sensation of sleepiness were also evaluated.

RESULTS

In comparison with the 8-h sleep session, subjects consumed 559 +/- 617 kcal (ie, 22%) more energy on the day after sleep restriction (P < 0.01), and preprandial hunger was higher before breakfast (P < 0.001) and dinner (P < 0.05). No change in the perceived pleasantness of the foods or in the desire to eat the foods was observed. Physical activity from 1215 to 2015 was higher after sleep restriction than after 8 h of sleep (P < 0.01), even though the sensation of sleepiness was more marked (P < 0.01).

CONCLUSIONS

One night of reduced sleep subsequently increased food intake and, to a lesser extent, estimated physical activity-related energy expenditure in healthy men. These experimental results, if confirmed by long-term energy balance measurements, suggest that sleep restriction could be a factor that promotes obesity. This trial was registered at clinicaltrials.gov as NCT00986492.

Food-entrainable circadian oscillators in the brain

Circadian rhythms in mammalian behaviour and physiology rely on daily oscillations in the expression of canonical clock genes. Circadian rhythms in clock gene expression are observed in the master circadian clock, the suprachiasmatic nucleus but are also observed in many other brain regions that have diverse roles, including influences on motivational and emotional state, learning, hormone release and feeding. Increasingly, important links between circadian rhythms and metabolism are being uncovered. In particular, restricted feeding (RF) schedules which limit food availability to a single meal each day lead to the induction and entrainment of circadian rhythms in food-anticipatory activities in rodents. Food-anticipatory activities include increases in core body temperature, activity and hormone release in the hours leading up to the predictable mealtime. Crucially, RF schedules and the accompanying food-anticipatory activities are also associated with shifts in the daily oscillation of clock gene expression in diverse brain areas involved in feeding, energy balance, learning and memory, and motivation. Moreover, lesions of specific brain nuclei can affect the way rats will respond to RF, but have generally failed to eliminate all food-anticipatory activities. As a consequence, it is likely that a distributed neural system underlies the generation and regulation of food-anticipatory activities under RF. Thus, in the future, we would suggest that a more comprehensive approach should be taken, one that investigates the interactions between multiple circadian oscillators in the brain and body, and starts to report on potential neural systems rather than individual and discrete brain areas.

Effects of fasting at different stages of lighting regimen on the proliferation of jejunal epithelial cells during rat pup weaning

The lifespan of intestinal epithelial cells is predetermined by the process of cell proliferation that occurs constantly in the crypt. The control of this process involves some endogenous factors, such as hormones, as well as exogenous factors, like food and natural light variations. These last two exogenous factors seem to be the major modulators of the cell proliferation process. Fasting treatment was conducted to assess the role of food and its effect on the metaphase index (MI) of the intestinal epithelium at different times and periods (light and dark) of the day. The effects of short- (5 hr) and long-term (25 hr) fasting on the MI in the jejunal epithelium of young rats were investigated at 09:00 h, 15:00 hr, 21:00 hr, and 02:00 hr using the arrested metaphases method. The present study demonstrates that 5 hr and 25 hr of fasting treatment decrease the MI at 09:00 hr. It was observed from MI analysis that there is an interaction between the fed/fasted status of the animal and the different times of the day. This result suggests that during the transition from youth to adulthood, the control of MI by the light/dark cycle seems to be more pronounced as compared with control by food intake at some periods of the day, although at other times food had a greater impact on the MI.

Effects of feeding schedule on locomotor activity rhythms and stress response in sea bream

Feeding cycles entrain biological rhythms, which enable animals to anticipate feeding times and so maximize food utilization and welfare. In this article, the effect of mealtime was investigated in two groups of sea bream (Sparus aurata): one group received a single daily meal at random times during the light period (random daytime feeding, RDF), whereas the other group received the meal during the light period but at the same time (scheduled daytime feeding, SDF). All the fish showed diurnal behavior, although the SDF group showed a lower percentage of diurnalism (84.4% vs. 79.5% in RDF and SDF respectively) and developed food anticipatory activity some hours before the mealtime. In addition, the mean daily locomotor activity of the RDF group was significantly higher than that of the SDF group (3132 vs. 2654 counts/day, respectively). Although the mean weight differed between both groups on day 30 (115.7 g and 125.6 g in RDF and SDF respectively), these differences had disappeared by day 60. Plasma cortisol and glucose significantly differed in both groups (cortisol: 71.8 vs. 8.7 ng/ml, glucose: 53.7 vs. 43.8 mg/dl in RDF and SDF, respectively), whereas lactate did not differ significantly. The results obtained suggest that altering the feeding time (scheduled vs. random) affects the behavior and physiology of sea bream, indicating that a single daily feeding cycle (compared to random) is beneficial for fish welfare because they can prepare themselves for the forthcoming feed.

Daily rhythm of serum lipase and alpha-amylase activity in fed and fasted dogs

The aim of the current study was to investigate the influence of feeding and fasting on the daily rhythm of serum lipase and alpha-amylase activity in dogs. Fourteen purebred Beagle dogs were housed in individual pens lined with wood shavings under a 12:12 light:dark cycle. The dogs were divided into 2 groups. Group A received normal feeding once a day, and group B was fasted starting 12 hr prior to the first blood collection. Water was available ad libitum. Blood samples were collected every 4 hr for 48 hr. Serum lipase and alpha-amylase activity were analyzed with standard kits by means of an ultraviolet spectrophotometer. Statistical analysis of the data was performed by 2-way analysis of variance and by single cosinor method. Results showed no statistical influence of feeding schedule on lipase and alpha-amylase and a robust daily rhythmicity of lipase and alpha-amylase in fed and fasted dogs. The current study could provide additional documentation of the structure of the dog circadian timing system and increase the necessary information related to the clinical approach to pancreatic diseases and to the therapeutic efficacy of timed administration of drugs or rations.

Recovery of exfoliated cells from the gastrointestinal tract of premature infants: a new tool to perform "noninvasive biopsies?"

To gain insight into specific gene expression in the gastrointestinal (GI) tract of preterm infants, we adapted a method to isolate exfoliated epithelial cells. Gastric residual fluid aspirates (n = 89) or stool samples (n = 10) were collected from 96 neonates (gestational age, 24-36 wk). Cells were characterized by microscopic observation, cytokeratin-18 immunodetection, and expression of transcripts. The human origin of cellular DNA was confirmed by amplification of specific X and Y chromosome sequences. Isolation yielded 100-500 cells per sample for gastric aspirates (n = 8) and 10-20 cells for fecal samples (n = 5). Epithelial origin was confirmed by immunodetection of cytokeratin 18. Analyses of reverse transcribed products, using two independent methods, from 15 gastric fluid and two stool samples showed that 18S-rRNA and transcripts of beta-actin, glyceraldehyde-3-phosphate dehydrogenase (gapdh), and period1 were in quantities corresponding to at least 10 cells. On 59 aspirates, we found beta-actin transcripts (all but one), cytokeratin 18 (eight positive of eight samples), SLC26-A7-1 (13 positive of 19 samples), period2 (17 positive of 17 samples), and clock (25 positive of 26 samples). Exfoliated cells can be recovered from gastric aspirates and fecal samples and serve as a tool to investigate the impact of therapeutic and nutritional regimens on the maturation of GI functions.