**Background:** Wolfram syndrome (WS) is a rare monogenic neurodegenerative disease caused by biallelic mutations in WFS1, leading to juvenile-onset diabetes, optic atrophy, and neuropsychiatric complications. The renin-angiotensin-aldosterone system (RAAS) regulates critical functions including fluid balance and blood pressure, and its dysregulation is implicated in neurodegenerative disorders. Previous work by the authors showed that Wfs1 deficiency alters RAAS components in peripheral tissues and that the GLP-1R agonist liraglutide (LIR) can modulate these changes. This study aimed to examine RAAS component expression in the hippocampus and brain stem of aged WS rats and to test whether LIR and the BDNF mimetic 7,8-dihydroxyflavone (7,8-DHF) could reverse any observed alterations.
**Methods:** Nine-month-old male Wfs1-deficient rats and wild-type (WT) littermates were treated daily for 3.5 months with LIR (0.4 mg/kg), 7,8-DHF (5 mg/kg), LIR+7,8-DHF, or vehicle. Additionally, age-matched treatment-naïve WS and WT rats (12.5–13 months old) were taken directly from home cages without any experimental manipulation. Hippocampi and brain stems were collected, and mRNA expression of eight RAAS genes (Ace, Ace2, Agtr1a, Agtr1b, Agtr2, Bdkrb1, Bdkrb2, Mas1) was measured by qPCR normalized to Hprt1. Statistical analysis used one-way ANOVA with Dunnett’s test or unpaired t-test; p<0.05 was considered significant.
**Key Results:** In the hippocampus of vehicle-treated WS rats, Agtr1a, Agtr1b, Agtr2, and Bdkrb1 were significantly downregulated compared to vehicle-treated WT rats (p<0.0001 for each). This downregulation was not rescued by any treatment (LIR, 7,8-DHF, or combination). In WT animals, these same genes were significantly downregulated across all treatment groups relative to vehicle (p<0.05). No significant genotype or treatment differences were observed for Bdkrb2, Ace, Ace2, or Mas1 in the hippocampus of treated animals. In the brain stem, no significant differences were found for any gene between genotypes or treatment groups.
In treatment-naïve rats, hippocampal expression of Ace, Ace2, and Mas1 was significantly downregulated in WS compared to WT (p<0.01 for Ace and Ace2; p<0.001 for Mas1), while Agtr1a, Agtr1b, Agtr2, and Bdkrb1 showed no significant differences. In the brain stem of treatment-naïve rats, Ace was significantly upregulated (p<0.05) and Agtr2 significantly downregulated (p<0.05) in WS versus WT.
**Clinical Implications:** These findings demonstrate that Wfs1 deficiency leads to region-specific alterations in hippocampal RAAS gene expression under chronic stress conditions, but not in the absence of prolonged experimental stress. The inability of LIR or 7,8-DHF to normalize these changes suggests that their previously reported neuroprotective effects in WS are mediated through RAAS-independent pathways. The study underscores the critical influence of chronic stress on RAAS regulation in WS and the need to control for procedural stress in experimental designs. The downregulation of protective RAAS components (Agtr2, Bdkrb1) may contribute to neurodegeneration and neuropsychiatric symptoms in WS, while the altered Ace/Ace2/Mas1 axis in treatment-naïve animals points to early disturbances in angiotensin processing. These results highlight potential therapeutic targets within the RAAS for WS, but also indicate that current drug candidates may not act through this system.