Characteristics and mechanisms of subcutaneous and visceral adipose tissue aging

Aging is one of the most significant health challenges worldwide and is a primary cause of chronic diseases and physiological decline.Among the myriad changes that occur with aging,alterations in adipose tissue distribution and function have gained considerable attention because of their profound impact on metabolic health and overall well-being.Subcutaneous adipose tissue(SAT)and visceral adipose tissue(VAT)are the two major depots of white adipose tissue,each with distinct roles in metabolism and health.Understanding the characteristics and underlying mechanisms of SAT and VAT is crucial for elucidating the aging process and developing strategies to promote healthy aging.This review focuses on delineating and analyzing the characteristics and intrinsic mechanisms underlying the aging of subcutaneous and visceral adipose tissue during the aging process,which can contribute to a better understanding of the aging process and enhance healthy aging.

Tissue-specific Gene Expression Changes Are Associated with Aging in Mice

Aging is a complex process that can be characterized by functional and cognitive decline in an individual. Aging can be assessed based on the functional capacity of vital organs and their intricate interactions with one another. Thus, the nature of aging can be described by focusing on a specific organ and an individual itself. However, to fully understand the complexity of aging,one must investigate not only a single tissue or biological process but also its complex interplay and interdependencies with other biological processes. Here, using RNA-seq, we monitored changes in the transcriptome during aging in four tissues(including brain, blood, skin and liver) in mice at9 months, 15 months, and 24 months, with a final evaluation at the very old age of 30 months.We identified several genes and processes that were differentially regulated during aging in both tissue-dependent and tissue-independent manners. Most importantly, we found that the electron transport chain(ETC) of mitochondria was similarly affected at the transcriptome level in the four tissues during the aging process. We also identified the liver as the tissue showing the largest variety of differentially expressed genes(DEGs) over time. Lcn2(Lipocalin-2) was found to be similarly regulated among all tissues, and its effect on longevity and survival was validated using its orthologue in Caenorhabditis elegans. Our study demonstrated that the molecular processes of aging are relatively subtle in their progress, and the aging process of every tissue depends on the tissue’s specialized function and environment. Hence, individual gene or process alone cannot be described as the key of aging in the whole organism.

Macrophage senescence in health and diseases

Macrophage senescence,manifested by the special form of durable cell cycle arrest and chronic low-grade inflammation like senescence-associated secretory phenotype,has long been consid-ered harmful.Persistent senescence of macrophages may lead to maladaptation,immune dysfunction,and finally the development of age-related diseases,infections,autoimmune diseases,and malignancies.However,it is a ubiquitous,multi-factorial,and dynamic complex phenomenon that also plays roles in remodeled processes,including wound repair and embryogenesis.In this review,we summarize some general molecular changes and several specific biomarkers during macrophage senescence,which may bring new sight to recognize senescent macrophages in different conditions.Also,we take an in-depth look at the functional changes in senescent macrophages,including metabolism,autophagy,polarization,phagocytosis,antigen presentation,and infiltration or recruitment.Furthermore,some degenerations and diseases associated with senescent macrophages as well as the mechanisms or relevant genetic regulations of senescent macrophages are integrated,not only emphasizing the possibility of regulating macrophage senescence to benefit age-associated diseases but also has an implication on the finding of potential tar-gets ordrugs clinically.