Integrative Epigenomic and Transcriptomic Analysis Reveals Robust Metabolic Switching During Intermittent Fasting in the Brain

Intermittent fasting (IF) is a dietary regimen aimed to restrict energy intake via alternate periods of ad libitum food consumption and fasting, without compromise of nutritional composition intake. Prophylactic IF have been well-established in many animal studies to promote longevity as well as ameliorate the development and manifestation of age-related diseases such as cardiovascular, neurodegenerative as well as metabolic diseases. However, while vast experimental evidences have pointed out that IF is able to exert plethora effects against these diseases, understanding with regards to the underlying mechanisms remain in their infancy. Recently, an emerging area of research in the field of epigenetics have been shown to be a cornerstone in mediating the interaction between environmental factors and genome status. IF is a lifestyle intervention that may serves as potential environmental influences over the epigenome status of individuals. However, there is no current information available that shows that IF can induce epigenetic changes. Here, we show that IF is able to influence the modulation of histone H3 lysine 9 trimethylation (H3K9me3) epigenetic mark in C57/BL6 male mice cerebellum, which in turn helps to control a plethora of transcriptomic changes involved in robust metabolic switching processes commonly observed during IF. Interestingly, both epigenomic and transcriptomic modulation are still observed following a refeeding regimen, which may suggest the possibility of epigenetic maintenance induced by IF at this epigenetic locus. However, we found a loss of H3K9me3 maintenance of transcriptomic changes after abolishment of IF. Collectively, our study helps to characterize a novel mechanism of IF in the epigenetic-transcriptomic axis, which control a myriad of metabolic process changes that provide better understanding of IF-induced effects. Overall design: C57/BL6NTac male mice (InVivos Pte Ltd, Singapore) were raised to three-month-old with ad libitum access to food using standard Teklad Global 18% protein rodent diet (Envigo, United Kingdom) and water. Mice were then randomly assigned and subjected to ad libitum (AL) feeding, or IF for 16 h per day (IF16) or for 24 h on alternate days (i.e. 'every other day'; EOD) for three months. Mice placed under IF16 regimen had access to food at 7 am and then removed at 3pm for 16 h daily. For EOD regimen mice, food was provided at 7 am and removed at 7 am the next day for a further 24 h. All mice had AL access to water, with AL mice having free access to both food and water. During refeeding regimen, these three groups of mice were further subjected to AL access to both food and water for two months. Following which, ChIP and RNA sequencing are performed on these frozen samples.