White adipose tissue (WAT) stores triglycerides and is crucial to maintaining the body's energy balance. Attributed to its plasticity, WAT can undergo dynamic remodeling in response to chronic energy excess. As obesity increases, alterations in the quantity and function of progenitor and immune cells result in fibrosis and inflammation in the WAT. Hence, metabolic dysfunction becomes more severe. In a recent study, HFD feeding significantly increased the gene expressions of bone morphogenetic protein 2 (BMP2), acidic fibroblast growth factor (FGF1), and basic fibroblast growth factor (FGF2) in macrophages. It was found in a fibrotic environment that the factors stimulated the growth of progenitor cells and the expression of fibrotic genes but suppressed adipogenesis. We looked at how these ligands affect fat metabolism, including adipogenesis, fibrosis, and thermogenesis. We also found out how these ligands affect the way progenitor cells change. By conducting proliferation and differentiation experiments on the 3T3-L1 cell model in vitro with these ligands supplemented at different phases, we demonstrated these ligands' influence 3T3-L1 preadipocytes and adipocytes genotype and phenotype. Based on this research, it was found that BMP2 stimulates adipogenesis by making cells multiply and differentiate. FGF1 exhibits different phasic influences on adipogenesis. FGF1 suppresses the preadipocyte differentiation phase but promotes cell proliferation, which increases the cell confluence speed and might lead to earlier differentiation of adipocytes. FGF2 added in the proliferation phase did not have much effect on adipogenesis. FGF2 might promote preadipocyte commitment during the adipocyte-genesis stage of differentiation phase but the comprehensive effect remains ambiguous.

Atherosclerotic cardiovascular disease is a leading cause of death worldwide. Dysregulation of vascular redox state plays a crucial role in the atherosclerotic process. Increased production of vascular superoxide (O2·-) and other reactive oxygen species (ROS) leads to endothelial dysfunction, a key early step in atherogenesis. Adipose tissue is a source of vasoactive, hormone-like molecules which are termed adipokines. One of the most important adipokines is adiponectin. Adiponectin has been shown to have antioxidant, anti-atherosclerotic effects in cell culture studies and animal models. However, its role in human cardiovascular disease has not been extensively investigated. More specifically, its effects on the human vascular wall and the mechanisms regulating its synthesis in adipose tissue have not been studied before in humans. The aim of my thesis is to explore the role of adiponectin in human atherosclerosis. This was achieved through use of the Oxford CABG Bioresource: a well-phenotyped cohort and tissue bank of patients undergoing cardiac surgery. By employing a range of in vivo and ex vivo techniques, I demonstrate for the first time in humans that adiponectin has direct antioxidant effects in the vascular wall, by directly suppressing pro-oxidant vascular enzymes and restoring redox balance. These effects persist in type 2 diabetes, presence of which is linked to reduced circulating adiponectin levels. Indeed, a variety of stimuli affect adiponectin synthesis in human adipose tissue, with brain natriuretic peptide being a major driver of adiponectin synthesis. However, different adipose tissue depots demonstrate diverse responses to stimuli affecting adiponectin synthesis, owing to their functional and morphological differences. Of particular interest is the fact that synthesis of adiponectin in perivascular adipose tissue is driven by the oxidative stress status of the underlying vessel. This observation led me to document for the first time in humans the existence of a reciprocal, two-way interaction between perivascular adipose tissue and the vascular wall: high vascular oxidative stress leads to release of factors with the ability to up-regulate adiponectin expression in perivascular adipose tissue, acting as a local paracrine defence mechanism attempting to restore vascular redox state. My thesis provides proof-of-concept for this novel cross-talk between adipose tissue and the vascular wall. This can have significant impact in designing new therapeutic strategies against atherosclerosis.

Fettvävnaden är en viktig regulator för ämnesomsättningen och uppvisar en komplex cellulär arkitektur som påverkar olika fysiologiska och patologiska processer. Dess heterogena natur är relativt ostrukturerad och består huvudsakligen av bräckliga feta adipocyter och immunceller. Dessa komplikationer försvårar studier av mikroarkitekturen - som är avgörande för att förstå dess beteende - vilket nyligen har gynnats av teknik med rumslig upplösning, som möjliggör studier av genomiska profiler samtidigt som informationen från vävnaden bevaras. I detta arbete undersöks kromatindynamiken i fettvävnad med hjälp av den nyutvecklade Spatial Assay for Transposase-Accessible Chromatin med sekvensering med hög genomströmning (Spatial ATAC-seq). Med fokus på subkutan vit fettvävnad samlades prover in från en individ som led av fetma före och fem år efter en bariatrisk operation för att studera förändringar i samband med betydande viktnedgång. Studien omfattar detaljer för både experimentella protokoll och avancerade beräkningsverktyg för dataanalys, inklusive användning av en utvecklingsversion av Semla-paketet för att integrera data om rumslig tillgänglighet och kromatintillgänglighet. Analysen visade på en mångsidig cellulär arkitektur och distinkta genomiska egenskaper i vävnaden, vilket framhävde förekomsten av specifika celltyper som AdipoLEP-liknande adipocyter och infiltrerande immunceller. Denna studie visade att det är möjligt att tillämpa Spatial ATAC-seq för att undersöka de molekylära mekanismerna i fettvävnad som ligger till grund för metabol hälsa och sjukdom, särskilt i samband med fetma och viktminskning. / Adipose tissue is a critical regulator of metabolism, exhibiting a complex cellular architecture that influences various physiological and pathological processes. Its heterogeneous nature is relatively unstructured, mainly formed by fragile fatty adipocytes and immune cells. These intricacies complicate the study of its microarchitecture – crucial for understanding its behaviour – which has recently benefitted from spatially resolved technologies, that enable the study of genomic profiles while keeping the information from the tissue. This work explores the chromatin dynamics of adipose tissue using the newly developed Spatial Assay for Transposase-Accessible Chromatin with high throughput sequencing (Spatial ATAC-seq). Focusing on subcutaneous white adipose tissue, samples were collected from an individual suffering from obesity before and five years after bariatric surgery to study changes associated with significant weight loss. The study comprises details for both experimental protocols and advanced computational tools for data analysis, including the use of a development version of Semla package to integrate spatial and chromatin accessibility data. The analysis revealed a diverse cellular architecture and distinct genomic features across the tissue, highlighting the presence of specific cell types such as AdipoLEP-like adipocytes and infiltrating immune cells. This study demonstrated the feasibility of applying Spatial ATAC-seq in investigating the molecular mechanisms of adipose tissue underlying metabolic health and disease, particularly in the context of obesity and weight loss.