High-Fat Nutritional Challenge Reshapes Circadian Signatures in Murine Extraorbital Lacrimal Glands

Abstract

Purpose A high-fat diet (HFD) increases the risk of developing many systemic diseases; however, the effects of high fat intake on lacrimal gland functions and the molecular mechanisms underlying these effects are unknown. We explored the effects of an HFD on the circadian rhythms of the extraorbital lacrimal glands (ELGs). Methods Male C57BL/6J mice maintained on a 12/12-hour light/dark cycle were fed an ad libitum HFD or normal chow (NC) for 2 weeks. The ELGs were collected from euthanized animals every 3 hours throughout the circadian cycle (24 hours). Using high-throughput RNA-sequencing (RNA-Seq), we studied the circadian transcriptomic profile of the ELGs. Circadian oscillations in cell size, secretion response, lipid deposition, and immune cell trafficking of the ELGs were also analyzed. Results An HFD modulated the circadian transcriptomic profile of the ELGs, including the composition, phase, and amplitude of cyclical transcript oscillations, and affected the associated signaling pathways at spatiotemporal levels. HFD feeding significantly altered the normal rhythmic oscillations of ELG cell size, immune cell trafficking, secretion response, and lipid deposition. After dietary reversal in HFD-fed animals, the activity, core temperature, and lipid accumulation in lacrimal glands recovered partially to the level of NC-fed animals. However, the average cell size of the ELGs, the recruitment of immune cells, and the rhythm of lacrimal secretion did not return to the levels of the NC-fed group. Conclusions HFD perturbation interferes with the cyclical transcriptomic profile, cell size, immune cell trafficking, and secretion function of the ELGs with a strikingly high sensitivity.

High-fat intake reshapes the circadian transcriptome profile and metabolism in murine meibomian glands

“…The normal chow (NC) group mice were provided with standard NC with 9% kcal fat (Trophic Animal Feed High-Tech Co., Ltd., Nantong, China) for 4 weeks. The HFD group mice were provided with HFD with 60% kcal fat (Trophic Animal Feed High-Tech Co., Ltd., Nantong, China) for 4 weeks ( Figure 1A ), as previously described ( 26 ). RNA-Seq data for circadian analysis were collected at eight time points throughout the circadian cycle (3-h intervals) ( Figure 1B ).…”

“…For each ZT point, RNA-Seq analysis was performed using three biological replicates ( 15 , 30 ). Library preparation and sequencing for the total RNA of MGs were performed according to our previous report ( 26 , 30 , 32 ). In brief, total RNA was quantified using a NanoDrop spectrophotometer (Thermo Fisher Scientific, MA, USA).…”

“…The circadian genes of MGs were identified using the JTK_CYCLE algorithm in R software, as previously described ( 26 , 30 , 32 ). The time-ordered fragments per kilobase of exon model per million mapped fragments (FPKM) of all MG genes were imported into the algorithm.…”

“…Biological processes and molecular function annotations of MG genes were performed using KEGG, GO, PSEA, and GSEA, as previously described ( 26 , 30 , 32 ). KEGG and GO enrichment analysis were performed by online bioinformatic platform Dr. Tom, 2 an online software developed by Beijing Genomic Institute (BGI) ( 36 ).…”

“…Similarly, the altered composition of high-calorie diets poses a challenge to the physiological function of ocular tissues and the development of disease ( 25 ). Metabolic stress from a high-calorie diet can remarkably alter the circadian activity of the cornea and lacrimal gland and the composition of the transcriptome that controls these activities ( 26 ). Furthermore, preliminary data suggest that a high-fat diet (HFD) promotes the onset and development of dry eye disease through the induction of an inflammatory response in the lacrimal gland ( 27 , 28 ).…”