Seasonal light hours modulate peripheral clocks and energy metabolism in mice

Except for latitudes close to the equator, seasonal variation in light hours can change dramatically between summer and winter. Yet investigations into the interplay between energy metabolism and circadian rhythms typically use a 12 h light:12 h dark photoperiod corresponding to the light duration at the equator. We hypothesized that altering the seasonal photoperiod affects both the rhythmicity of peripheral tissue clocks and energy homeostasis. Mice were housed at photoperiods representing either light hours in summer, winter, or the equinox. Mice housed at a winter photoperiod exhibited an increase in the amplitude of rhythmic lipid metabolism and a modest reduction in fat mass and liver triglyceride content. Comparing melatonin-proficient and -deficient mice, the effect of seasonal light on energy metabolism was largely driven by differences in the rhythmicity of food intake and not melatonin. Together, these data indicate that seasonal light impacts energy metabolism by modulating the timing of eating.

Comparative analysis of sperm DNA methylation supports evolutionary acquired epigenetic plasticity for organ speciation

Aim: To perform a comparative epigenomic analysis of DNA methylation in spermatozoa from humans, mice, rats and mini-pigs. Materials & methods: Genome-wide DNA methylation analysis was used to compare the methylation profiles of orthologous CpG sites. Transcription profiles of early embryo development were analyzed to provide insight into the association between sperm methylation and gene expression programming. Results: We identified DNA methylation variation near genes related to the central nervous system and signal transduction. Gene expression dynamics at different time points of preimplantation stages were modestly associated with spermatozoal DNA methylation at the nearest promoters. Conclusion: Conserved genomic regions subject to epigenetic variation across different species were associated with specific organ functions, suggesting their potential contribution to organ speciation and long-term adaptation to the environment.

Ablation of DNA-methyltransferase 3A in skeletal muscle does not affect energy metabolism or exercise capacity

In response to physical exercise and diet, skeletal muscle adapts to energetic demands through large transcriptional changes. This remodelling is associated with changes in skeletal muscle DNA methylation which may participate in the metabolic adaptation to extracellular stimuli. Yet, the mechanisms by which muscle-borne DNA methylation machinery responds to diet and exercise and impacts muscle function are unknown. Here, we investigated the function of de novo DNA methylation in fully differentiated skeletal muscle. We generated muscle-specific DNA methyltransferase 3A (DNMT3A) knockout mice (mD3AKO) and investigated the impact of DNMT3A ablation on skeletal muscle DNA methylation, exercise capacity and energy metabolism. Loss of DNMT3A reduced DNA methylation in skeletal muscle over multiple genomic contexts and altered the transcription of genes known to be influenced by DNA methylation, but did not affect exercise capacity and whole-body energy metabolism compared to wild type mice. Loss of DNMT3A did not alter skeletal muscle mitochondrial function or the transcriptional response to exercise however did influence the expression of genes involved in muscle development. These data suggest that DNMT3A does not have a large role in the function of mature skeletal muscle although a role in muscle development and differentiation is likely.

Skeletal muscle is a plastic tissue able to adapt to environmental stimuli such as exercise and diet in order to respond to energetic demand. One of the ways in which skeletal muscle can rapidly react to these stimuli is DNA methylation. This is when chemical groups are attached to DNA, potentially influencing the transcription of genes. We investigated the function of DNA methylation in skeletal muscle by generating mice that lacked one of the main enzymes responsible for de novo DNA methylation, DNA methyltransferase 3A (DNMT3A), specifically in muscle. We found that loss of DNMT3A reduced DNA methylation in muscle however this did not lead to differences in exercise capacity or energy metabolism. This suggests that DNMT3a is not involved in the adaptation of skeletal muscle to diet or exercise.

Long-term management of patients with symptoms of gastro-oesophageal reflux disease -- a Norwegian randomised prospective study comparing the effects of esomeprazole and ranitidine treatment strategies on health-related quality of life in a general practitioners setting

This article reports quality of life (QoL) aspects of a study that investigated the efficacy of three treatment regimens in gastro-oesophageal reflux disease patients. Following a 4-week symptom-control phase (esomeprazole 40 mg once daily), patients were randomised to 6 months' esomeprazole 20 mg once daily continuously (n = 658), on-demand (n = 634) or ranitidine 150 mg twice daily continuously (n = 610). Esomeprazole 40 mg once daily improved QoL during the symptom-control phase. At 6 months, both esomeprazole regimens were more effective than ranitidine in all dimensions of the Quality of Life in Reflux and Dyspepsia questionnaire (p < 0.0001). Esomeprazole continuous and on-demand led to a significant improvement in symptoms (Overall Treatment Evaluation questionnaire) compared with ranitidine (continuous: 80.2%, on-demand: 77.8%, vs. ranitidine 47.0%; p < 0.001). Esomeprazole once daily continuously maintained QoL better than esomeprazole on-demand and was associated with greater patient satisfaction. In conclusion, esomeprazole 20 mg once daily continuously and on-demand were more effective than ranitidine continuously for maintaining QoL.

Six-month management of patients following treatment for gastroesophageal reflux disease symptoms -- a Norwegian randomized, prospective study comparing the costs and effectiveness of esomeprazole and ranitidine treatment strategies in a general medical practitioners setting

This study assesses the difference in direct medical costs between on-demand treatment with esomeprazole 20 mg, continuous treatment with esomeprazole 20 mg once-daily and continuous treatment with ranitidine 150 mg twice-daily to prevent symptomatic relapse in patients with gastroesophageal reflux disease over 26 weeks. Two hundred eighty-one GP clinics in Norway enrolled 2156 patients to an open, randomized, parallel group, Norwegian society perspective study during 2000-2001. The total direct medical costs of each strategy were 171.9 Euros for on-demand esomeprazole (n = 634), 221.6 Euros for ranitidine (n = 610) and 248.8 Euros for continuous esomeprazole (n = 658). The total costs for on-demand and continuous esomeprazole treatment and ranitidine treatment were 221.5, 286.5 and 295.8 Euros, respectively. The highest proportion of costs was because of the study medication cost in each strategy. The on-demand and continuous treatment strategies with esomeprazole were found to be cost-effective, compared with ranitidine.