Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

Advisor

Lucy Liaw

Second Committee Member

Robert Koza

Third Committee Member

Anyonya Guntur

Additional Committee Members

Sergey Ryzhov

Kristy Townsend

Abstract

High fat diet (HFD) can contribute to diabetes and cardiovascular disease (CVD) in humans, and diabetes is a major risk factor for CVD. The comorbidity of these two metabolic disorders indicates shared mechanisms of pathology. As a component of the vasculature, perivascular adipose tissue (PVAT) regulates vasoreactivity and contributes to obesity-related vascular pathologies, such as atherosclerosis, through paracrine signaling. The Notch pathway plays fundamental roles in cell fate decisions and growth, and is involved in adipocyte metabolic homeostasis. Previous studies have shown that constitutive Notch signaling in adipose tissue promotes pathological conversion of aortic PVAT in mice fed a control diet, including increased lipid storage and reduced expression of thermogenic adipocyte markers in PVAT. However, it is unknown how Notch signaling regulates thermogenesis in PVAT and the downstream effects on cardiovascular function. A better understanding of Notch signaling in PVAT will advance our knowledge of molecular pathways that link local adipose tissue to the underlying blood vessel. This could lead to the development of therapeutic strategies targeting specific pathways in the PVAT to improve cardiovascular health.

Methods: N1ICD;Adipoq-Cre mice with constitutive activation of Notch signaling specifically in adipose tissue and RBPJ-kfl/fl .Adipoq-Cre mice with conditional loss-of-function of the Notch signaling transcription factor, RBPJ-k in adipose tissue were generated. Histological and physiological analyses were used to analyze mouse phenotypes. Proteomic analysis was performed to analyze pathways and proteins that are regulated by Notch signaling. Vessel wire myography was used to analyze vascular phenotypes ex vivo. Changes in gene and protein expression were further studied by Real-Time PCR (qPCR), immunoblot, and immunofluorescent analysis. To study Notch’s regulation of mitophagy, we isolated PVAT stromal vascular fractions from mito-QC mice and transfected them with adenovirus-associated viruses to overexpress Notch siganling. We also performed the Seahorse Assay to assess mitochondrial respiration in differentiated PVAT stromal vascular fractions in vitro.

Conclusions: We found that increased Notch signaling leads to PVAT whitening and impaired mitochondrial function. Furthermore, we found that Notch signaling activation leads to increased mitophagy, and oxidative stress in PVAT tissue, which also causes upregulated ferroptosis in PVAT adipocytes. These further lead to the loss of protective vasodilatory function of PVAT and pathology in PVAT adjacent vessels.

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