Timing of Breakfast, Lunch, and Dinner. Effects on Obesity and Metabolic Risk.

(1) Background: Eating is fundamental to survival. Animals choose when to eat depending on food availability. The timing of eating can synchronize different organs and tissues that are related to food digestion, absorption, or metabolism, such as the stomach, gut, liver, pancreas, or adipose tissue. Studies performed in experimental animal models suggest that food intake is a major external synchronizer of peripheral clocks. Therefore, the timing of eating may be decisive in fat accumulation and mobilization and affect the effectiveness of weight loss treatments. (2) Results: We will review multiple studies about the timing of the three main meals of the day, breakfast, lunch and dinner, and its potential impact on metabolism, glucose tolerance, and obesity-related factors. We will also delve into several mechanisms that may be implicated in the obesogenic effect of eating late. Conclusion: Unusual eating time can produce a disruption in the circadian system that might lead to unhealthy consequences.

Modifiable lifestyle behaviors, but not a genetic risk score, associate with metabolic syndrome in evening chronotypes.

Evening chronotype associates with health complications possibly via lifestyle factors, while the contribution of genetics is unknown. The aim was to study the relative contributions of genetics, lifestyle, and circadian-related physiological characteristics in metabolic risk of evening chronotype. In order to capture a biological contribution to chronotype, a genetic-risk-score (GRS), comprised of 15 chronotype-related variants, was tested. Moreover, a wide range of behavioral and emotional eating factors was studied within the same population. Chronotype, lifestyle, and metabolic syndrome (MetS) outcomes were assessed (n = 2,126), in addition to genetics (n = 1,693) and rest-activity/wrist-temperature rhythms (n = 100). Evening chronotype associated with MetS and insulin resistance (P < 0.05), and several lifestyle factors including poorer eating behaviors, lower physical activity and later sleep and wake times. We observed an association between higher evening GRS and evening chronotype (P < 0.05), but not with MetS. We propose a GRS as a tool to capture the biological component of the inter-individual differences in chronotype. Our data show that several modifiable factors such as sedentary lifestyle, difficulties in controlling the amount of food eaten, alcohol intake and later wake and bed times that characterized evening-types, may underlie chronotype-MetS relationship. Our findings provide insights into the development of strategies, particularly for evening chronotype.

Serotonin-transporter promoter polymorphism modulates the ability to control food intake: Effect on total weight loss.

SCOPE: The biggest challenge for losing weight is the ability to control the amount of food eaten; the tendency to overeat is called disinhibition. Our aims were to determine whether (a) the SLC6A4-promoter variant (5-HTTLPR) relates to disinhibition; (b) this association could affect total weight-loss during a behavioral/dietary treatment for obesity. METHODS AND RESULTS: A total of 2961 subjects attended voluntarily five weight-loss clinics; a subsample (n = 624) was recruited for SLC6A4 genotyping. Total weight-loss, emotional-eating-score and disinhibition-score were examined. We observed that: (a) the reduced ability to control food intake (disinhibition) is implicated in the impairment to lose weight; (b) SLC6A4-promoter variant is implicated in disinhibition. S carriers (low-expressing) of the SLC6A4-promoter variant had a lower inhibition capacity and showed more failure (1.6 times) to control the amount of food eaten than LL (p < 0.05); other factors such as eating while bored, overeating after work at night, or craving for specific foods were associated to the SLC6A4 genotype (p < 0.05); (c) The combination of disinhibition (high disinhibition) and genetics (S carrier) had a higher impact on total weight loss than each factor separately. CONCLUSIONS: SLC6A4-promoter variant is associated with the ability to control food intake and interacts with emotional eating to modulate total weight loss.

Genes Clock. Ritmos circadianos y predisposición a obesidad / Clock genes. Circadian rhythms and predisposition to obesity

Nuestra fisiología cambia durante el día y diversas hormonas muestran ritmicidad circadiana. La alteración de este patrón normal se denomina Cronodisrupción (CD). Recientemente se ha demostrado que la CD se relaciona con la obesidad. Aunque existen diversos factores que producen la CD, un aspecto importante a considerar es el fallo en nuestro reloj interno. Así, estudios realizados en animales de experimentación muestran que mutaciones en los genes reloj se asocian a la obesidad. En humanos estas mutaciones son poco frecuentes (<1% de la población). Sin embargo, es bastante común tener variaciones genéticas en un solo nucleótido (SNP) que explican las diferencias en nuestra vulnerabilidad a la enfermedad. Se conocen varios SNPs en los genes reloj que se asocian a la obesidad y a la pérdida de peso. Teniendo en cuenta que la genética está detrás de la CD, la cuestión es: ¿estamos predestinados? A lo largo de estas líneas descubriremos cómo la respuesta nutrigenética y epigenética es: ‘NO, no estamos predestinados’. A través de la nutrigenética sabemos que nuestros comportamientos pueden interactuar con nuestros genes y pueden disminuir el efecto nocivo de una variante de riesgo específico. A partir de la epigenética el mensaje es más positivo: al cambiar nuestros comportamientos podemos cambiar nuestro genoma. Según esto, proponemos modificar el ‘qué, cómo y cuándo comemos’ como una herramienta eficaz para disminuir nuestro riesgo genético, y así disminuir la CD y la obesidad. Es por tanto esta un área muy novedosa y prometedora en la prevención y tratamiento de la obesidad (AU)

Our physiology changes throughout the day and several physiological hormones display circadian rhythmicity. The alteration of this normal pattern is called chronodisruption (CD). In recent years it has been demonstrated that CD is related to obesity. Although several factors may be causing CD, one important aspect to consider is the failure in our internal clock. Indeed, studies performed in mutant animals have demonstrated that mutations in clock genes are related to obesity. In humans, mutations are rare (<1 % of the population). Nevertheless, it is rather common to have genetic variations in one single nucleotide (SNP) which underlie differences in our vulnerability to disease. Several SNPs in clock genes are related to obesity and weight loss. Taking into account that genetics is behind CD, the questions is: are we predestinated? We will see along these lines that nutrigenetics and epigenetics answer: ‘NO, we are not predestinated’. Through nutrigenetics we know that our behaviours may interact with our genes and may decrease the deleterious effect of one specific risk variant. From epigenetics the message is even more positive: it is demonstrated that by changing our behaviours we can change our genome. Herein, we propose modifying ‘what, how, and when we eat’ as an effective tool to decrease our genetic risk, and as a consequence to diminish CD and decrease obesity. This is a novel and very promising area in obesity prevention and treatment (AU)

Lunch eating predicts weight-loss effectiveness in carriers of the common allele at PERILIPIN1: the ONTIME (Obesity, Nutrigenetics, Timing, Mediterranean) study.

BACKGROUND: We propose that eating lunch late impairs the mobilization of fat from adipose tissue, particularly in carriers of PERILIPIN1 (PLIN1) variants. OBJECTIVE: The aim was to test the hypothesis that PLIN1, a circadian lipid-stabilizing protein in the adipocyte, interacts with the timing of food intake to affect weight loss. DESIGN: A total of 1287 overweight and obese subjects [229 men and 1058 women; mean ± SD body mass index (in kg/m2): 31 ± 5] who attended outpatient obesity clinics were enrolled in the ONTIME (Obesity, Nutrigenetics, Timing, Mediterranean) study. Timing of food intake was estimated with a validated questionnaire. Anthropometric variables and PLIN1 genotypes were analyzed, including 6209T>C (rs2289487), 11482G>A (rs894160), 13041A>G (rs2304795), and 14995A>T (rs1052700). The main outcomes were effectiveness of the program and weight-loss progression during 28 wk of treatment. RESULTS: The PLIN1 locus was associated with variability in response to a weight-loss program. Specifically, carrying the minor C allele at the PLIN1 6209T>C was associated with better weight-loss response (P = 0.035). The probability of being a better responder [percentage of weight loss ≥7.5% (median)] was 33% higher among C than among TT carriers (OR: 1.32; 95% CI: 1.05, 1.67; P = 0.017). We found an interaction of PLIN1 × food timing between the 14995A>T variant and timing of lunch eating for total weight loss (P = 0.035). Among AA carriers, eating late was associated with less weight loss (P < 0.001), whereas time of eating did not influence weight loss among TT carriers (P = 0.326). CONCLUSIONS: Variability at the PLIN1 locus is associated with variability in weight loss. Moreover, eating late is related to lower weight-loss effectiveness among carriers of the AA genotype at the PLIN1 14995A>T variant. These results contribute to our ability to implement more precise and successful obesity treatments. The ONTIME study was registered at clinicaltrials.gov as NCT02829619.

Methylation on the Circadian Gene BMAL1 Is Associated with the Effects of a Weight Loss Intervention on Serum Lipid Levels.

The circadian clock system has been linked to the onset and development of obesity and some accompanying comorbidities. Epigenetic mechanisms, such as DNA methylation, are putatively involved in the regulation of the circadian clock system. The aim of this study was to investigate the influence of a weight loss intervention based on an energy-controlled Mediterranean dietary pattern in the methylation levels of 3 clock genes, BMAL1, CLOCK, and NR1D1, and the association between the methylation levels and changes induced in the serum lipid profile with the weight loss treatment. The study sample enrolled 61 women (body mass index = 28.6 ± 3.4 kg/m(2); age: 42.2 ± 11.4 years), who followed a nutritional program based on a Mediterranean dietary pattern. DNA was isolated from whole blood obtained at the beginning and end point. Methylation levels at different CpG sites of BMAL1, CLOCK, and NR1D1 were analyzed by Sequenom's MassArray. The energy-restricted intervention modified the methylation levels of different CpG sites in BMAL1 (CpGs 5, 6, 7, 9, 11, and 18) and NR1D1 (CpGs 1, 10, 17, 18, 19, and 22). Changes in cytosine methylation in the CpG 5 to 9 region of BMAL1 with the intervention positively correlated with the eveningness profile (p = 0.019). The baseline methylation of the CpG 5 to 9 region in BMAL1 positively correlated with energy (p = 0.047) and carbohydrate (p = 0.017) intake and negatively correlated with the effect of the weight loss intervention on total cholesterol (p = 0.032) and low-density lipoprotein cholesterol (p = 0.005). Similar significant and positive correlations were found between changes in methylation levels in the CpG 5 to 9 region of BMAL1 due to the intervention and changes in serum lipids (p < 0.05). This research describes apparently for the first time an association between changes in the methylation of the BMAL1 gene with the intervention and the effects of a weight loss intervention on blood lipids levels.

Common type 2 diabetes risk variant in MTNR1B worsens the deleterious effect of melatonin on glucose tolerance in humans.

AIMS: The common MTNR1B genetic variant rs10830963 is associated with an increased risk of type 2 diabetes (T2D). To date, no experimental study has tested the effect of the MTNR1B variant on glucose metabolism in humans during exposure of the melatonin receptors to their ligand. The aim of this study was to investigate whether this MTNR1B variant influenced the effect of melatonin (5mg) on glucose tolerance assessed by an oral glucose tolerance test (OGTT; 75 g) at different times of the day (morning and evening) as compared to a placebo. METHODS: Seventeen normoglycemic women (24 ± 6 years; BMI 23.0 ± 3.3 kg/m(2)) completed the study (11 carriers of the risk allele [CG] and 6 noncarriers [CC]). RESULTS: The effect of melatonin on glucose tolerance depended on the genotype. In the morning, the effect of melatonin (melatonin-placebo) on the glucose area under the curve (AUC) above baseline differed significantly (P=0.036) between the carriers and noncarriers. This effect of melatonin in the carriers was six times as large as that in the noncarriers. The MTNR1B SNP explained over one-quarter (26%) of the inter-individual differences in the effect of melatonin on glucose AUC. However, in the evening, the effect of melatonin on glucose AUC of the carriers and noncarriers did not differ significantly (P>0.05). CONCLUSIONS: MTNR1B rs10830963 risk variant worsens the effect of melatonin on glucose tolerance, suggesting the importance of genotyping and personalized recommendations, especially in people consuming food when melatonin levels are elevated. Large-scale studies in vulnerable populations are necessary to translate these results into real-world, clinically relevant recommendations.

Métodos cronobiológicos en las encuestas alimentarias: criterios de aplicación e interpretación de resultados / Methods for monitoring the functional status of the circadian system in dietary surveys studies: application criteria and interpretation of results

En 1996, la Cumbre Mundial sobre la Alimentación reafirmó el derecho inalienable de los habitantes del mundo a tener acceso a una alimentación adecuada, inocua y nutritiva, y se planteó como meta disminuir a la mitad el número de personas subnutridas en el mundo para el año 2015, es decir, este año que iniciamos. Diversos países y organizaciones se plantean la necesidad de consensuar y desarrollar indicadores para la medición de la inseguridad alimentaria en los hogares. Disponer de un método de medición simple pero con base científica para identificar los grupos de población de mayor vulnerabilidad nutricional, se considera una herramienta básica para poder implementar estrategias que permitan afrontar el problema de un forma efectiva (AU)

To evaluate the circadian system status of the subject may be of special interest in nutrition. Particularly for those studies related to the assessment of diseases related to malnutrition, as it is the case of most of the degenerative diseases such as obesity, cancer, or cardiovascular diseases. For this purpose, one of the approaches consists to measure a) the external synchronizers of the internal clock, such as light intensity, and changes from fasting to eating and from resting to activity. Indeed, “chronodisruptors” have been defined as “exogenous and endogenous exposures or effectors which are chronobiologically active and can thus disrupt the timing and order. Another approach to assess the circadian system health is to measure the b) outputs of the internal clock (circadian marker rhythms). Among such outputs, the rhythm of body temperature, motor activity, melatonin, cortisol and clock gene expression are the most commonly used. From the genetic perspective, we are now able to measure failures in the internal clock, in order to assess c) the genetics of the molecular clock. Indeed, new nutrigenetics techniques are giving us the opportunity to measure the association between different genetic variants of our clock genes and several illnesses such as obesity, cardiovascular diseases, diabetes or cancer. In addition to these techniques, selfreported questionnaires based in the morning-evening preferences have been developed as complementary procedures to assess human chronotypes (AU)

Acute melatonin administration in humans impairs glucose tolerance in both the morning and evening.

STUDY OBJECTIVES: To study the effect of melatonin administration on glucose metabolism in humans in the morning and evening. DESIGN: Placebo-controlled, single-blind design. SETTING: Laboratory assessments. PARTICIPANTS: 21 healthy women (24 ± 6 y; body mass index: 23.0 ± 3.3 kg/m(2)). INTERVENTIONS: Glucose tolerance was assessed by oral glucose tolerance tests (OGTT; 75 g glucose) on 4 occasions: in the morning (9 AM), and evening (9 PM); each occurring 15 minutes after melatonin (5 mg) and placebo administration on 4 non-consecutive days. MEASUREMENTS AND RESULTS: Melatonin administration impaired glucose tolerance. When administered in the morning, melatonin significantly increased the incremental area under the curve (AUC) and maximum concentration (Cmax) of plasma glucose following OGTT by 186% and 21%, respectively, as compared to placebo; while in the evening, melatonin significantly increased glucose AUC and Cmax by 54% and 27%, respectively. The effect of melatonin on the insulin response to the OGTT depended on the time of day (P < 0.05). In the morning, melatonin decreased glucose tolerance primarily by decreasing insulin release, while in the evening, by decreasing insulin sensitivity. CONCLUSIONS: Acute melatonin administration in humans impairs glucose tolerance in both the morning and evening. When administering melatonin, the proximity to meal timing may need to be considered, particularly in those at risk for glucose intolerance.

Evening physical activity alters wrist temperature circadian rhythmicity.

The adequate time to perform physical activity (PA) to maintain optimal circadian system health has not been defined. We studied the influence of morning and evening PA on circadian rhythmicity in 16 women with wrist temperature (WT). Participants performed controlled PA (45 min continuous-running) during 7 days in the morning (MPA) and evening (EPA) and results were compared with a no-exercise-week (C). EPA was characterized by a lower amplitude (evening: 0.028 ± 0.01 °C versus control: 0.038 ± 0.016 °C; p < 0.05) less pronounced second-harmonic (power) (evening: 0.41 ± 0.47 versus morning: 1.04 ± 0.59); and achrophase delay (evening: 06:35 ± 02:14 h versus morning: 04:51 ± 01:11 h; p < 0.05) as compared to MPA and C. Performing PA in the late evening might not be as beneficial as in the morning.

Timing of food intake and obesity: a novel association.

Recent studies link energy regulation to the circadian clock at the behavioral, physiological and molecular levels, emphasizing that the timing of food intake itself may have a significant role in obesity. In this regards, there is emerging literature in animals demonstrating a relationship between the timing of feeding and weight regulation. Unusual feeding time can produce a disruption of the circadian system which might produce unhealthy consequences in humans. In a longitudinal study, we recently showed that the timing of the main meal was predictive of weight loss during a 20-week dietary intervention and that this effect was independent from total 24-h caloric intake. The importance of caloric distribution across the day on weight loss therapy was supported by a recent 12-week experimental study showing that subjects assigned to high caloric intake during breakfast lost significantly more weight than those assigned to high caloric intake during the dinner. Furthermore, one of the most influential discoveries relevant for this area of research in the last years is the presence of an active circadian clock in different organs related to food intake. This is the case for stomach, intestine, pancreas or liver. New data also suggest that there is a temporal component in the regulation of adipose tissue functions. Thus, a specific temporal order in the daily patterns of adipose tissue genes appears to be crucial for adipose tissue to exclusively either accumulate fat or to mobilize fat at the proper time. Taking into account that feeding is the source of energy for adipose tissue, the time of feeding, particularly for high-energy content meals, may be decisive, and changes in this timing could have metabolic consequences for the development of obesity and for weight loss.

REV-ERB-ALPHA circadian gene variant associates with obesity in two independent populations: Mediterranean and North American.

SCOPE: Despite the solid connection between REV-ERB and obesity, the information about whether genetic variations at this locus may be associated with obesity traits is scarce. Therefore our objective was to study the association between REV-ERB-ALPHA1 rs2314339 and obesity in two independent populations. METHODS AND RESULTS: Participants were 2214 subjects from Spanish Mediterranean (n = 1404) and North American (n = 810) populations. Anthropometric, biochemical, dietary, and genotype analyses were performed. We found novel associations between the REV-ERB-ALPHA1 rs2314339 genotype and obesity in two independent populations: in Spanish Mediterranean and North American groups, the frequency of the minor-allele-carriers (AA+ AG) was significantly lower in the "abdominally obese" group than in those of the "nonabdominally obese" group (p < 0.05). Minor allele carriers had lower probability of abdominal obesity than noncarriers, and the effect was of similar magnitude for both populations (OR ≈ 1.50). There were consistent associations between REV-ERB-ALPHA1 genotype and obesity-related traits (p < 0.05). Energy intake was not significantly associated with REV-ERB-ALPHA1 rs2314339. However, physical activity significantly differed by genotype. A significant interaction between the REV-ERB-ALPHA1 variant and monounsaturated-fatty-acids (MUFA) intake for obesity was also detected in the Mediterranean population. CONCLUSION: This new discovery highlights the importance of REV-ERB-ALPHA1 in obesity and provides evidence for the connection between our biological clock and obesity-related traits.

Chronobiology and obesity.

Chronobiology is a word derived from three Greek stems: kronos for time, bios for life and logos for study. From microarrays studies, now it is accepted that 10-30% of the human genome is under the control of circadian molecular clocks. This implies that most behavioral, physiological and biochemical variables display circadian rhythms in their expression. In its simplest form, circadian clocks are composed of a set of proteins that generate self-sustained circadian oscillations. The molecular clock comprises two transcription factors, CLOCK and BMAL1, whereas PERs and CRYs are responsible for the negative limb. One of the most important questions related to the circadian system and obesity, was to elucidate if adipose tissue displayed circadian rhythmicity or whether it had an internal peripheral clock. Our group of research has provided an overall view of the internal temporal order of circadian rhythms in human adipose tissue. A new concept related to illness is Chronodisruption (CD). It is defined as a relevant disturbance of the internal temporal order of physiological and behavioral circadian rhythms. In our modern society, CD may be common in several conditions such as jet lag, shift work, light at night, or social jet lag. In addition clock gene polymorphisms and aging may have also chronodisruptive effects. Our group has also demonstrated that Obesity and CD are also highly interconnected. With the help of chronobiology we can reach a new view of obesity considering not only "what" are the factors involved in obesity, but also "when" these factors are produced.

Cronobiología es una palabra de origen griego: kronos significa tiempo, bios, vida y logos, estudio. A partir de los estudios de microarrays, se acepta en la actualidad que del 10 al 30% del genoma humano queda bajo el control de relojes moleculares circadianos. Este implica que la expresión de la mayor parte de las variables de la conducta, psicológicas y bioquímicas muestran ritmos circadianos. En su forma más sencilla, los relojes circadianos están compuestos por un conjunto de proteínas que generan oscilaciones circadianas auto-mantenidas. El reloj molecular comprende dos factores de trascripción, CLOCK y BMAL1, mientras que los PERs y los CRYs son responsables de la fracción negativa. Una de las preguntas más importantes relacionadas con el sistema circadiano y la obesidad fue dilucidar si el tejido adiposo mostraba un ritmo circadiano o si poseía un reloj periférico interno. Nuestro grupo de investigación proporcionó una visión de conjunto del orden temporal interno de los ritmos circadianos del tejido adiposo humano. Un nuevo concepto relacionado con la enfermedad es el de cronodisrupción (CD). Se define como una alteración relevante del orden temporal interno de los ritmos circadianos fisiológicos y conductuales. En nuestra sociedad moderna, la CD podría ser frecuente en diversos trastornos como el jet lag, el trabajo a turnos, la luz nocturna o el jet lag social. Además, los polimorfismos de los genes horarios y el envejecimiento también podrían tener efectos de cronodisrupción. Nuestro grupo también ha demostrado que la obesidad y la CD están muy interconectadas. Con la ayuda de la cronobiología podemos llegar a un nuevo enfoque de la obesidad, considerando no solamente "cuáles" son los factores implicados en la obesidad, sino también "cuándo" se producen estos factores.

Chronobiology and obesity / Cronobiología y obesidad

Chronobiology is a word derived from three Greekstems: kronos for time, bios for life and logos for study. From microarrays studies, now it is accepted that 10-30%of the human genome is under the control of circadian molecular clocks. This implies that most behavioral, physiological and biochemical variables display circadian rhythms in their expression. In its simplest form, circadian clocks are composed of a set of proteins that generate selfsustained circadian oscillations. The molecular clock comprises two transcription factors, CLOCK and BMAL1,whereas PERs and CRYs are responsible for the negative limb. One of the most important questions related to the circadian system and obesity, was to elucidate if adipose tissue displayed circadian rhythm city or whether it had an internal peripheral clock. Our group of research has provided an overall view of the internal temporal order of circadian rhythms in human adipose tissue. A new concept related to illness is Chronodisruption(CD). It is defined as a relevant disturbance of the internal temporal order of physiological and behavioral circadian rhythms. In our modern society, CD may be common inseveral conditions such as jet lag, shift work, light at night, or social jet lag. In addition clock gene polymorphisms and aging may have also chronodisruptive effects. Our group has also demonstrated that Obesity and CD are also highly interconnected. With the help of chronobiology we can reach a new view of obesity considering notonly “what” are the factors involved in obesity, but also “when” these factors are produced (AU)

Cronobiología es una palabra de origen griego: kronos significa tiempo, bios, vida y logos, estudio. A partir de los estudios de microarrays, se acepta en la actualidad que del 10 al 30% del genoma humano queda bajo el control de relojes moleculares circadianos. Este implica que la expresión de la mayor parte de las variables de la conducta, psicológicas y bioquímicas muestran ritmos circadianos. En su forma más sencilla, los relojes circadianos están compuestos por un conjunto de proteínas que generan oscilaciones circadianas auto-mantenidas. El reloj molecular comprende dos factores de trascripción, CLOCK y BMAL1, mientras que los PERs y los CRYs son responsables de la fracción negativa. Una de las preguntas más importantes relacionadas con el sistema circadiano y la obesidad fue dilucidar si el tejido adiposo mostraba un ritmo circadiano o si poseía un reloj periférico interno. Nuestro grupo de investigación proporcionó una visión de conjunto del orden temporal interno de los ritmos circadianos del tejido adiposo humano. Un nuevo concepto relacionado con la enfermedad es el de cronodisrupción (CD). Se define como una alteración relevante del orden temporal interno de los ritmos circadianos fisiológicos y conductuales. En nuestra sociedad moderna, la CD podría ser frecuente en diversos trastornos como el jet lag, el trabajo a turnos, la luz nocturna o eljet lag social. Además, los polimorfismos de los genes horarios y el envejecimiento también podrían tener efectos de cronodisrupción. Nuestro grupo también ha demostrado que la obesidad y la CD están muy interconectadas. Con la ayuda de la cronobiología podemos llegara un nuevo enfoque de la obesidad, considerando no solamente “cuáles” son los factores implicados en la obesidad, sino también “cuándo” se producen estos factores (AU)

Glucocorticoids affect 24 h clock genes expression in human adipose tissue explant cultures.

AIMS: to examine firstly whether CLOCK exhibits a circadian expression in human visceral (V) and subcutaneous (S) adipose tissue (AT) in vitro as compared with BMAL1 and PER2, and secondly to investigate the possible effect of the glucocorticoid analogue dexamethasone (DEX) on positive and negative clock genes expression. SUBJECTS AND METHODS: VAT and SAT biopsies were obtained from morbid obese women (body mass index ≥ 40 kg/m(2)) (n = 6). In order to investigate rhythmic expression pattern of clock genes and the effect of DEX on CLOCK, PER2 and BMAL1 expression, control AT (without DEX) and AT explants treated with DEX (2 hours) were cultured during 24 h and gene expression was analyzed at the following times: 10:00 h, 14:00 h, 18:00 h, 22:00 h, 02:00 h and 06:00 h, using qRT-PCR. RESULTS: CLOCK, BMAL1 and PER2 expression exhibited circadian patterns in both VAT and SAT explants that were adjusted to a typical 24 h sinusoidal curve. PER2 expression (negative element) was in antiphase with respect to CLOCK and in phase with BMAL1 expression (both positive elements) in the SAT (situation not present in VAT). A marked effect of DEX exposure on both positive and negative clock genes expression patterns was observed. Indeed, DEX treatment modified the rhythmicity pattern towards altered patterns with a period lower than 24 hours in all genes and in both tissues. CONCLUSIONS: 24 h patterns in CLOCK and BMAL1 (positive clock elements) and PER2 (negative element) mRNA levels were observed in human adipose explants. These patterns were altered by dexamethasone exposure.

CLOCK, PER2 and BMAL1 DNA methylation: association with obesity and metabolic syndrome characteristics and monounsaturated fat intake.

The circadian clock system instructs 24-h rhythmicity on gene expression in essentially all cells, including adipocytes, and epigenetic mechanisms may participate in this regulation. The aim of this research was to investigate the influence of obesity and metabolic syndrome (MetS) features in clock gene methylation and the involvement of these epigenetic modifications in the outcomes. Sixty normal-weight, overweight and obese women followed a 16-weeks weight reduction program. DNA methylation levels at different CpG sites of CLOCK, BMAL1 and PER2 genes were analyzed by Sequenom's MassARRAY in white blood cells obtained before the treatment. Statistical differences between normal-weight and overweight + obese subjects were found in the methylation status of different CpG sites of CLOCK (CpGs 1, 5-6, 8 and 11-14) and, with lower statistical significance, in BMAL1 (CpGs 6-7, 8, 15 and 16-17). The methylation pattern of different CpG sites of the three genes showed significant associations with anthropometric parameters such as body mass index and adiposity, and with a MetS score. Moreover, the baseline methylation levels of CLOCK CpG 1 and PER2 CpGs 2-3 and 25 correlated with the magnitude of weight loss. Interestingly, the percentage of methylation of CLOCK CpGs 1 and 8 showed associations with the intake of monounsaturated and polyunsaturated fatty acids. This study demonstrates for the first time an association between methylation status of CpG sites located in clock genes (CLOCK, BMAL1 and PER2) with obesity, MetS and weight loss. Moreover, the methylation status of different CpG sites in CLOCK and PER2 could be used as biomarkers of weight-loss success, particularly CLOCK CPGs 5-6.

Aspectos cronobiológicos de la obesidad y el síndrome metabólico / Chronobiological aspects of obesity and metabolic syndrome

Los ritmos circadianos (aproximadamente 24 horas) están ampliamente caracterizados a nivel molecular y su generación se realiza gracias a la expresión de varios «genes reloj» y mediante la regulación de sus productos proteicos. Mientras que la adaptación general de los organismos a los ciclos ambientales de luz-oscuridad se lleva a cabo principalmente por el reloj central del núcleo supraquiasmático, este mecanismo de reloj molecular es funcional en varios órganos y tejidos. Algunos estudios muestran que un fallo del sistema circadiano (cronodisrupción [CD]) puede ser la causa de las manifestaciones del síndrome metabólico. Esta revisión resume, (1) cómo los relojes moleculares coordinan el metabolismo y su papel específico en el adipocito; (2) aspectos genéticos y evidencias científicas de la obesidad como enfermedad cronobiológica, y (3) CD, sus causas y consecuencias patológicas. Finalmente, se discuten ideas sobre el uso de la cronobiología en el tratamiento de la obesidad(AU)

Circadian rhythms (approximately 24h) are widely characterized at molecular level and their generation is acknowledged to originate from oscillations in expression of several clock genes and from regulation of their protein products. While general entrainment of organisms to environmental light-dark cycles is mainly achieved through the master clock of the suprachiasmatic nucleus in mammals, this molecular clockwork is functional in several organs and tissues. Some studies have suggested that disruption of the circadian system (chronodisruption (CD)) may be causal for manifestations of the metabolic syndrome. This review summarizes (1) how molecular clocks coordinate metabolism and their specific role in the adipocyte; (2) the genetic aspects of and scientific evidence for obesity as a chronobiological illness; and (3) CD and its causes and pathological consequences. Finally, ideas about use of chronobiology for the treatment of obesity are discussed(AU)

[Chronobiological aspects of obesity and metabolic syndrome]. / Aspectos cronobiológicos de la obesidad y el síndrome metabólico.

Circadian rhythms (approximately 24h) are widely characterized at molecular level and their generation is acknowledged to originate from oscillations in expression of several clock genes and from regulation of their protein products. While general entrainment of organisms to environmental light-dark cycles is mainly achieved through the master clock of the suprachiasmatic nucleus in mammals, this molecular clockwork is functional in several organs and tissues. Some studies have suggested that disruption of the circadian system (chronodisruption (CD)) may be causal for manifestations of the metabolic syndrome. This review summarizes (1) how molecular clocks coordinate metabolism and their specific role in the adipocyte; (2) the genetic aspects of and scientific evidence for obesity as a chronobiological illness; and (3) CD and its causes and pathological consequences. Finally, ideas about use of chronobiology for the treatment of obesity are discussed.

An approximation to the temporal order in endogenous circadian rhythms of genes implicated in human adipose tissue metabolism.

Although it is well established that human adipose tissue (AT) shows circadian rhythmicity, published studies have been discussed as if tissues or systems showed only one or few circadian rhythms at a time. To provide an overall view of the internal temporal order of circadian rhythms in human AT including genes implicated in metabolic processes such as energy intake and expenditure, insulin resistance, adipocyte differentiation, dyslipidemia, and body fat distribution. Visceral and subcutaneous abdominal AT biopsies (n=6) were obtained from morbid obese women (BMI≥40 kg/m(2) ). To investigate rhythmic expression pattern, AT explants were cultured during 24-h and gene expression was analyzed at the following times: 08:00, 14:00, 20:00, 02:00 h using quantitative real-time PCR. Clock genes, glucocorticoid metabolism-related genes, leptin, adiponectin and their receptors were studied. Significant differences were found both in achrophases and relative-amplitude among genes (P<0.05). Amplitude of most genes rhythms was high (>30%). When interpreting the phase map of gene expression in both depots, data indicated that circadian rhythmicity of the genes studied followed a predictable physiological pattern, particularly for subcutaneous AT. Interesting are the relationships between adiponectin, leptin, and glucocorticoid metabolism-related genes circadian profiles. Their metabolic significance is discussed. Visceral AT behaved in a different way than subcutaneous for most of the genes studied. For every gene, protein mRNA levels fluctuated during the day in synchrony with its receptors. We have provided an overall view of the internal temporal order of circadian rhythms in human adipose tissue.

Circadian rhythm of clock genes in human adipose explants.

To analyze in severely obese women the circadian expression of the clock genes hPer2, hBmal1, and hCry1 in explants from subcutaneous (SAT) and visceral (VAT) adipose tissue (AT), in order to elucidate whether this circadian clockwork can oscillate accurately and independently of the suprachiasmatic nucleus (SCN) and if glucocorticoid metabolism-related genes such as glucocorticoid receptor (hGr) and 11beta-hydroxysteroid dehydrogenase 1 (h11 beta Hsd1) and the transcription factor peroxisome proliferator activated receptor gamma (hPPAR gamma) are part of the clock controlled genes. AT biopsies were obtained from morbid obese patients (BMI > or =40 kg/m(2)) (n = 7). Anthropometric variables were measured and fasting plasma lipids and lipoprotein concentrations were analyzed. In order to carry out rhythmic expression analysis, AT explants were cultured during 24 h and gene expression was performed at the following times (T): 0, 6, 12, and 18 h, with quantitative real-time PCR. Clock genes oscillated accurately and independently of the SCN in AT explants. Their intrinsic oscillatory mechanism regulated the timing of other genes such as hPPAR gamma and glucocorticoid-related genes. Circadian patterns differed between VAT and SAT. Correlation analyses between the genetic circadian oscillation and components of the metabolic syndrome (MetS) revealed that subjects with a higher sagittal diameter showed an increased circadian variability in hPer2 expression (r = 0.91; P = 0.031) and hBmal1 (r = 0.90; P = 0.040). Data demonstrate the presence of peripheral circadian oscillators in human AT independently of the central circadian control mechanism. This knowledge paves the way for a better understanding of the circadian contribution to medical conditions such as obesity and MetS.