Association between CLOCK 3111 T/C polymorphism with ghrelin, GLP-1, food timing, sleep and chronotype in overweight and obese Iranian adults.

backgroundCircadian Locomotor Output Cycles Kaput (CLOCK), an essential element of the positive regulatory arm in the human biological clock, is involved in metabolic regulation. The aim was to investigate the behavioral (sleep duration, food timing, dietary intake, appetite and chronobiologic characteristics) and hormonal (plasma ghrelin and Glucagon-like peptide-1 concentrations) factors that could explain the previously reported association between the CLOCK 3111 T/C SNP and obesity.

methodsThis cross-sectional study included 403 subjects, overweight and/or obesity, aged 20- 50 years from Iran. The CLOCK rs1801260 data were measured by the PCR-RFLP method. Dietary intake, food timing, sleep duration, appetite and Chrono-type were assessed using validated questionnaires. Ghrelin and GLP-1 were measured by ELIZA in plasma samples. Participants were also divided into three groups based on BMI. Logistic regression models and general linear regression models were used to assess the association between CLOCK genotype and study parameters. Univariate linear regression models were used to assess the interaction between CLOCK and VAS, Food timing, chronotype and sleep on food intakes.

resultsAfter controlling for confounding factors, there was a significant difference between genotypes for physical activity (P = 0.001), waist circumference (P˂0.05), BMI (˂0.01), weight (P = 0.001), GLP-1 (P = 0.02), ghrelin (P = 0.04), appetite (P˂0.001), chronotype (P˂0.001), sleep (P˂0.001), food timing (P˂0.001), energy (P˂0.05), carbohydrate (P˂0.05) and fat intake (P˂0.001). Our findings also show that people with the minor allele C who ate lunch after 3 PM and breakfast after 9 AM are more prone to obesity (P˂0.05). furthermore, there was significant interactions between C allele carrier group and high appetite on fat intake (Pinteraction = 0.041), eat lunch after 3 PM on energy intake (Pinteraction = 0.039) and morning type on fat intake (Pinteraction = 0.021).

conclusionSleep reduction, changes in ghrelin and GLP-1 levels, changes in eating behaviors and evening preference that characterized CLOCK 3111C can all contribute to obesity. Furthermore, the data demonstrate a clear relationship between the timing of food intake and obesity. Our results support the hypothesis that the influence of the CLOCK gene may extend to a wide range of variables related to human behaviors.