Exploring the Transformative Effects of Calorie Restriction on the Lacrimal Gland

Abstract

Purpose : Dry eye disease, a tear-dysfunctional disease affecting millions worldwide, can be caused by age-related dysfunction of the lacrimal gland (LG). Aging is associated with a decrease of secretory cells and chronic inflammation, leading to tissue deterioration and fibrosis. Calorie restriction (CR) has demonstrated efficacy in mitigating inflammation and extending lifespan across various organisms. In aged rats, CR has been shown to improve LG function and morphology. In mice, dry-eye signs appear during early senescence (10-14 months). This study explores the prophylactic potential of calorie restriction in preserving LG function in middle-aged mice.

Methods : Female C57BL/6J mice were subjected to early 40% CR from 6 months (6M) to 11M. LGs were excised for histology and bulk RNA sequencing was performed. Corneal barrier function was measured as the uptake of a fluorescent dye (n = 6). RNA samples from ad libitum (n=4) and CR (n=4) mice were sequenced. Fastq files from RNAseq were uploaded on ROSALIND® for processing and Differentially Expressed Genes (DEGs) and their Fold Changes (FC) were calculated by DEseq2. DEGs (using log2(FC) = ± log2(1.5) and FDR = 0.05 as cutoffs) lists were uploaded to Metascape to identify the biological pathways significantly modified in CR LGs.

Results : The preventive CR scheme blunted the age-related dry eye phenotype compared to the ad-libitum group by preventing corneal barrier disruption. RNAseq of LGs subjected to CR identified 589 significant DEGs (259 downregulated and 330 upregulated). Upregulated genes were involved in circadian rhythm and in secretory functions like ion channels, transporters, ribosomal proteins, and protein glycosylation. Other pathways enriched in CR-upregulated genes were related to lipid metabolism such as mitochondrial beta-oxidation and fatty acid biosynthesis. Downregulated pathways in CR included genes involved in immune activation, B-cell receptor signaling, adaptive immune system, and extracellular matrix remodeling and metalloproteinases.

Conclusions : Our results indicate that CR can prevent the increase in age-related cytokine production and decrease LG inflammation. CR restored circadian clock-related genes, improved mitochondrial function, enhanced secretory activity, reduced inflammation, and prevented fibrosis in the LG, similar to other organs. Further studies are needed to evaluate the molecular regulators enabling CR-mediated protection.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.