Universität zu Köln

Jaure, Nathalie (2023). Understanding the impact of ageing and latelife dietary restriction on murine white adipose tissue with single-nucleus RNA sequencing. PhD thesis, Universität zu Köln.

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Abstract

Dietary restriction (DR), defined as reduced food intake without malnutrition, increases lifespan and improves health in most organisms including mammals. In mice, onset of DR late in life does not provide the same benefits as lifelong DR. While lifelong DR increases lifespan, late-onset DR initiated at 24 months of age does not extend survival. Mice lose their responsiveness in lifespan to DR between 16 and 20 months of age. The liver and white adipose tissue (WAT) are key organs for maintaining energy homeostasis. Interestingly, gene expression in the liver is fully responsive to the late-life DR switch, while most genes in the WAT do not change their expression in response to late-onset DR, indicating a memory of gene expression in the WAT. However, the cause of this memory effect and which cell types in the WAT contribute to memory formation is currently unknown. To address these questions, in my PhD project, I employed single-nuclei sequencing of WAT from control and DR animals at young and old age. Furthermore, I analyzed the WAT from animals that were switched from AL to DR at 16 and 20 months of age, to correlate the responsiveness in gene expression with the longevity of these animals. When I started my PhD thesis, there were no methods available to perform single-cell sequencing of the whole WAT including mature adipocytes, which due to their large size and fragile nature, cannot be analyzed by traditional single-cell sequencing approaches. Thus, I first optimized a protocol to isolate WAT nuclei and then tested which droplet-based single-cell RNA-seq platform would provide the best data quality. Based on the results from the pre-test, I generated a comprehensive single-nuclei landscape of the WAT under DR using 10X Chromium. The results showed that cell types were distributed in three super clusters including mature adipocytes, immune cells, and the stromal-vascular fraction containing stem cells and precursor cells. Only mature adipocytes clustered in different sub-groups depending on diet and age. Interestingly, I identified a cluster of mature adipocytes that was unique to the AL to DR switch at 16 months of age, but not present in the DR switch at 20 months. Gene expression analysis showed this cluster was enriched for pathways linked to insulin sensitivity and fat tissue homeostasis. This finding suggests that the earlier DR switch generates a partial reprogramming of the WAT in response XIII to DR, which is not the case when animals are switched to DR later in life. To confirm my findings, I validated the cell-type proportion changes observed in the SNuc-seq data, by deconvolution of a corresponding bulk RNA-seq data. In addition, by including additional time points in the bulk analysis, I provide evidence that the transcriptional flexibility of the WAT decreases with age. Finally, using the single-nuclei data, I show that dietary memory originates mainly from differences in gene expression of mature adipocytes but also from changes in the proportion of immune cells.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Jaure, Nathalie UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-718228
Date:	2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Biology of Ageing
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language white adipose tissue English single-cell English ageing English bioinformatics English
Date of oral exam:	10 January 2023
Referee:	Name Academic Title Partridge, Linda Professor Kloppenburg, Peter Professor
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/71822