Abstract P181: Contrasting Effects of High Fat Diet and DOCA-salt on Primary Neuronal Cilia

Abstract

Virtually, every mammalian cell is equipped with an antenna like primary cilium, a cell surface protrusion that is thought to act as a sensory organelle. Many of the rare genetic disorders that cause shorter, absent or disrupted cilia are associated with obesity and cardiovascular dysfunction in humans and rodents, which suggest that cilia length contribute to energy balance and cardiovascular homeostasis. Here, we examined the length of the primary neuronal cilia in the brain nuclei that contribute to metabolic and cardiovascular regulation in high fat diet-induced obese (DIO) mice and DOCA-salt mice. Cilia length was examined by adenylate cyclase 3 (AC3) immunostaining, followed by confocal 3D reconstruction, and quantification by IMARIS imaging analysis software. Analysis of the cilia length and distribution showed reduced frequency of cilia that are over 10 μm in the brain of DIO mice compared to control mice fed normal diet fed mice (17.02±1.36% vs 23.78±1.15%, p=0.032). Interestingly, the most pronounced difference in cilia length was observed in the dorsomedial hypothalamus with the DIO mice displaying significantly shorter cilia (6.90±0.06 μm) relative to controls (7.32±0.14μm in controls, n=5/group p<0.05). Conversely, we found that average neuronal cilia length was elongated in 3-week DOCA-salt treated mice compared to sham group. The number of primary neuronal cilia that are over 10 μm was significantly increased in DOCA-salt mice by 8% (p=0.0114). On the other hand, the number of cilia that are 4-5 μm in length was significantly decreased in DOCA-salt mice compared to sham controls (11.73±1.70% vs 18.73±2.02%, p=0.0385). The supraoptic nucleus was the only nucleus that displayed difference in the length of cilia that are 5-10 μm in length (7.46±0.24 μm vs 6.76±0.15μm, n=5/group, p=0.0509). Our data demonstrate plasticity of neuronal cilia in response to high fat diet and DOCA-salt treatment in defined brain regions. Our results raise the possibility that primary neuronal cilia may function as part of environmental surveillance system in the brain that control energy homeostasis and cardiovascular function. Further analysis of the role of primary neuronal cilia in cardiovascular regulation is underway.