# Effect of circadian rhythm disruption on benign prostatic hyperplasia in rats

## TL;DR

Disrupted circadian rhythms may worsen prostate enlargement in rats by boosting cell growth and inflammation.

## Contribution

This study shows for the first time that circadian rhythm disruption accelerates benign prostatic hyperplasia in rats.

## Key findings

- CRD increased prostate weight, index, and epithelial thickness in rats.
- CRD altered immune and inflammatory pathways linked to prostate cell growth.
- Key genes like Itgad and Ccr7 were found to be highly correlated with CRD effects.

## Abstract

Benign prostatic hyperplasia (BPH) is a common condition in middle-aged and elderly men. Disrupted circadian rhythms (CRD) can directly influence aging, inflammation, metabolic syndrome, and hormonal changes—all of which are closely linked to BPH. This study aimed to investigate whether CRD accelerates prostatic hyperplasia in rats. Twenty male Sprague-Dawley (SD) rats were divided into two batches. A BPH model was established using mixed slow-release pellets of testosterone (T) and estradiol (E2). CRD was induced by continuous light exposure (Cle), while a 12-hour light/12-hour dark cycle defined the control (Con) group.

Rats were divided into T+E2 and T+E2+Cle groups. Initial and final body weight, prostate weight, and prostate index (PI) were recorded. Hematoxylin and eosin (H&E) staining was performed. Serum levels of dihydrotestosterone (DHT) and estradiol (E2) were measured by ELISA, and mRNA expression of circadian rhythm genes was assessed via qRT-PCR.

Rats were divided into Con and Cle groups. Body weight, prostate weight, and PI were recorded. H&E staining was used for pathological analysis. Ki-67 expression was assessed by immunohistochemistry (IHC). RNA sequencing (RNA-Seq) was used to investigate gene expression in prostate tissue, validated by qRT-PCR. Differentially expressed genes (DEGs) were analyzed using bioinformatics methods.

CRD significantly increased prostate weight, PI, and epithelial thickness; elevated serum DHT levels; and reduced E2 levels. qRT-PCR confirmed that CRD altered circadian gene expression.

CRD significantly increased PI and Ki-67 expression in the prostate. GO analysis revealed significant enrichment in immune response, external side of plasma membrane, and carbohydrate binding (p < 0.001). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed enrichment in cytokine-cytokine receptor interaction, viral protein interaction with cytokine and receptor, phenylalanine metabolism, and chemokine signaling pathways (p < 0.001). Gene set enrichment analysis (GSEA) indicated positive enrichment in voltage-gated calcium channel activity and type II diabetes mellitus. Protein–protein interaction (PPI) network analysis identified Itgad, Ccr7, CD27, Sell, CD69, Gzmb, IRF8, and KIrd1 as highly correlated genes.

These findings suggest that CRD may accelerate prostate cell growth by modulating immune and inflammatory responses, contributing to the development of benign prostatic hyperplasia.