Purificación Gómez-Abellán

Timing of food intake predicts weight loss effectiveness

Background:There is emerging literature demonstrating a relationship between the timing of feeding and weight regulation in animals. However, whether the timing of food intake influences the success of a weight-loss diet in humans is unknown.Objective:To evaluate the role of food timing in weight-loss effectiveness in a sample of 420 individuals who followed a 20-week weight-loss treatment.Methods:Participants (49.5% female subjects; age (mean±s.d.): 42±11 years; BMI: 31.4±5.4 kg m−2) were grouped in early eaters and late eaters, according to the timing of the main meal (lunch in this Mediterranean population). 51% of the subjects were early eaters and 49% were late eaters (lunch time before and after 1500 hours, respectively), energy intake and expenditure, appetite hormones, CLOCK genotype, sleep duration and chronotype were studied.Results:Late lunch eaters lost less weight and displayed a slower weight-loss rate during the 20 weeks of treatment than early eaters (P=0.002). Surprisingly, energy intake, dietary composition, estimated energy expenditure, appetite hormones and sleep duration was similar between both groups. Nevertheless, late eaters were more evening types, had less energetic breakfasts and skipped breakfast more frequently that early eaters (all; P<0.05). CLOCK rs4580704 single nucleotide polymorphism (SNP) associated with the timing of the main meal (P=0.015) with a higher frequency of minor allele (C) carriers among the late eaters (P=0.041). Neither sleep duration, nor CLOCK SNPs or morning/evening chronotype was independently associated with weight loss (all; P>0.05).Conclusions:Eating late may influence the success of weight-loss therapy. Novel therapeutic strategies should incorporate not only the caloric intake and macronutrient distribution—as is classically done—but also the timing of food.

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.

Clock genes are implicated in the human metabolic syndrome

Background:Clock genes play a role in adipose tissue (AT) in animal experimental models. However, it remains to be elucidated whether these genes are expressed in human AT.Objective:We investigated the expression of several clock genes, Bmal1, Per2 and Cry1, in human AT from visceral and subcutaneous abdominal depots. A second objective was to elucidate whether these clock genes expressions were related to the metabolic syndrome features.Methods:Visceral and subcutaneous AT samples were obtained from morbid obese men (n=8), age: 42±13 years and body mass index⩾40 kg/m2, undergoing laparoscopic surgery due to obesity. Biopsies were taken as paired samples at the beginning of the surgical process (1100 hour). Metabolic syndrome features such as waist circumference, plasma glucose, triglycerides, total cholesterol, high-density lipoprotein cholesterol and low-density lipoprotein (LDL) cholesterol were also studied. Homeostasis model assessment index of insulin resistance was also calculated. The expression of the different clock genes, hBmal1, hPer2 and hCry1, was determined by quantitative real-time PCR.Results:Clock genes were expressed in both human AT depots. hBmal1 expression was significantly lower than hPer2 and hCry1 in both AT (P<0.001). All genes were highly correlated to one another in the subcutaneous fat, while no correlation was found between Bmal1 and Per2 in the visceral AT. Clock genes AT expression was associated with the metabolic syndrome parameters: hPer2 expression level from visceral depot was inversely correlated to waist circumference (P<0.01), while the three clock genes studied were significantly and negatively correlated to total cholesterol and LDL cholesterol (P<0.01).Conclusion:We have demonstrated for the first time in humans that clock genes are expressed in both subcutaneous and visceral fat. Their association with abdominal fat content and cardiovascular risk factors may be an indicator of the potential role of these clock genes in the metabolic syndrome disturbances.

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 Sequenoms 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. (Author correspondence: garaulet@um.es)

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 11β‐hydroxysteroid dehydrogenase 1 (h11βHsd1) and the transcription factor peroxisome proliferator activated receptor γ (hPPARγ) are part of the clock controlled genes. AT biopsies were obtained from morbid obese patients (BMI ≥40 kg/m2) (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 hPPARγ 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.

Meal timing affects glucose tolerance, substrate oxidation and circadian-related variables: A randomized, crossover trial

Background/Objectives:Timing of food intake associates with body weight regulation, insulin sensitivity and glucose tolerance. However, the mechanism is unknown. The aim of this study was to investigate the effects of changes in meal timing on energy-expenditure, glucose-tolerance and circadian-related variables.Subjects/Methods:Thirty-two women (aged 24±4 years and body mass index 22.9±2.6 kg m−2) completed two randomized, crossover protocols: one protocol (P1) including assessment of resting-energy expenditure (indirect-calorimetry) and glucose tolerance (mixed-meal test) (n=10), the other (P2) including circadian-related measurements based on profiles in salivary cortisol and wrist temperature (Twrist) (n=22). In each protocol, participants were provided with standardized meals (breakfast, lunch and dinner) during the two meal intervention weeks and were studied under two lunch-eating conditions: Early Eating (EE; lunch at 13:00) and Late Eating (LE; lunch 16:30).Results:LE, as compared with EE, resulted in decreased pre-meal resting-energy expenditure (P=0.048), a lower pre-meal protein-corrected respiratory quotient (CRQ) and a changed post-meal profile of CRQ (P=0.019). These changes reflected a significantly lower pre-meal utilization of carbohydrates in LE versus EE (P=0.006). LE also increased glucose area under curve above baseline by 46%, demonstrating decreased glucose tolerance (P=0.002). Changes in the daily profile of cortisol and Twrist were also found with LE blunting the cortisol profile, with lower morning and afternoon values, and suppressing the postprandial Twrist peak (P<0.05).Conclusions:Eating late is associated with decreased resting-energy expenditure, decreased fasting carbohydrate oxidation, decreased glucose tolerance, blunted daily profile in free cortisol concentrations and decreased thermal effect of food on Twrist. These results may be implicated in the differential effects of meal timing on metabolic health.

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.

Circadian Expression of Adiponectin and Its Receptors in Human Adipose Tissue

Adiponectin is one of the most clinically relevant cytokines associated with obesity. However, circadian rhythmicity of adiponectin in human adipose tissue (AT) has not been analyzed. To assess whether the mRNA levels of adiponectin and its receptors (ADIPOR1 and ADIPOR2) might show daily circadian rhythms in visceral and sc fat explants obtained from morbid obese women, visceral and sc abdominal AT biopsies (n = 6) were obtained from morbidly obese women (body mass index >or=40 kg/m(2)). Anthropometric variables were measured and fasting plasma glucose, lipid, and lipoprotein concentrations were analyzed. To investigate rhythmic expression pattern, AT explants were cultured during 24 h, and gene expression was analyzed at the following times: 0800, 1400, 2000, and 0200 h, using quantitative real-time PCR. All genes investigated showed a circadian rhythmicity and oscillated accurately and independently of the suprachiasmatic nucleus in both AT explants (P < 0.05). Adiponectin gene expression fluctuated in the same phase as its receptors. Correlation analyses between the genetic circadian oscillation and components of the metabolic syndrome revealed that adiposity and abdominal obesity correlated with a decrease in adiponectin and adiponectin receptors ADIPOR1 and ADIPOR2 amplitude (P < 0.05). Visceral fat showed a trend toward a phase delay and dampening of the mRNA amplitude of adiponectin as compared with sc fat. The mRNA expression of adiponectin and its receptors showed 24-h rhythmicity in human AT from morbidly obese patients.

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/m2). 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. J. Cell. Physiol. 226: 2075–2080, 2011.

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.