Browsing by Subject "PPAR gamma"

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The role of NLRC5 in obesity
(2024) Bauer, Sarah Katharina; Kufer, Thomas
Obesity and its associated morbidities are major global health problems. It has become evident in the last decades that the state of obesity is intimately linked with our immune system. Pattern recognition receptors (PRRs), the main sensor molecules of the innate immune system, were shown to play an essential role in the pathology of obesity and its associated morbidities. Among others, members of the nucleotide-binding and oligomerization domain (NOD) -like receptors (NLRs), a family of cytosolic PRRs, were associated with the obesity-accompanying low-grade inflammatory response contributing to obesity-associated morbidities. NLRC5 is a NLR protein functioning as key transcriptional regulator of major histocompatibility complex (MHC) class I genes responsible for antigen presentation. Recent observations now suggest novel roles of NLRC5 in metabolic trades, but so far, no confirmation of these singular observations is available, and the underlying mechanisms remain elusive. The aim of this thesis was to characterize the role of the NLR protein NLRC5 in obesity. To this end, two Nlrc5 deficient mouse lines (Nlrc5 deltaExon4-7 and Nlrc5 deltaExon4) were subjected to high-fat diet (HFD) feeding and phenotypic, morphological, and biochemical analyses were performed. Female Nlrc5 deltaExon4-7 mice presented with higher body and adipose tissue (AT) weight gain and larger adipocytes compared to wildtype (WT) animals. This phenotype, however, could not be recapitulated in the Nlrc5 deltaExon4 mouse line. Microbiome analysis revealed subtle alterations of the faecal microbiome by diet:genotype interactions. To further characterize the effect of NLRC5 deficiency on adipocyte differentiation, the CRISPR/Cas9 gene editing system was used to modify Nlrc5 expression in the 3T3-L1 preadipocyte cell line. Using inducible HeLa cell lines with stable GFP-NLRC5 expression we showed NLRC5 to interact with the master regulator of adipogenesis peroxisome proliferator-activated receptor y (PPARy) and to enhance the expression of PPARy target genes. In addition, a contribution of NLRC5 to PPARy’s anti-inflammatory actions was revealed using NLRC5 deficient THP-1 macrophage-like cells and bone marrow-derived macrophages from Nlrc5 deltaExon4-7 mice. To elucidate the mechanism behind the synergy between NLRC5 and PPARy, reporter gene and chromatin immunoprecipitation (ChIP) assays were performed. Lastly, the expression of multiple NLR family members was correlated with body mass index (BMI) in obese human patients and investigated in the adipose tissue and liver of HFD-fed mice, the latter revealing Nlrp10 to be highly upregulated by HFD feeding. Taken together, this thesis provides a comprehensive characterization of Nlrc5 deficient mice on HFD and reveals a function of NLRC5 as transcriptional co-regulator of PPARy targets and its anti-inflammatory properties. In addition, this work provides first insights into the potential mechanism behind the synergistic transcriptional regulation by NLRC5 and PPARy and extends the knowledge on the regulation of NLR expression by HFD feeding.