Physiological role of adipose tissue: white adipose tissue as an endocrine and secretory organ

P Trayhurn, J H Beattie

    Research output: Contribution to journalLiterature review

    818 Citations (Scopus)

    Abstract

    The traditional role attributed to white adipose tissue is energy storage, fatty acids being released when fuel is required. The metabolic role of white fat is, however, complex. For example, the tissue is needed for normal glucose homeostasis and a role in inflammatory processes has been proposed. A radical change in perspective followed the discovery of leptin; this critical hormone in energy balance is produced principally by white fat, giving the tissue an endocrine function. Leptin is one of a number of proteins secreted from white adipocytes, which include angiotensinogen, adipsin, acylation-stimulating protein, adiponectin, retinol-binding protein, tumour neorosis factor alpha, interleukin 6, plasminogen activator inhibitor-1 and tissue factor. Some of these proteins are inflammatory cytokines, some play a role in lipid metabolism, while others are involved in vascular haemostasis or the complement system. The effects of specific proteins may be autocrine or paracrine, or the site of action may be distant from adipose tissue. The most recently described adipocyte secretory proteins are fasting-induced adipose factor, a fibrinogen-angiopoietin-related protein, metallothionein and resistin. Resistin is an adipose tissue-specific factor which is reported to induce insulin resistance, linking diabetes to obesity. Metallothionein is a metal-binding and stress-response protein which may have an antioxidant role. The key challenges in establishing the secretory functions of white fat are to identify the complement of secreted proteins, to establish the role of each secreted protein, and to assess the pathophysiological consequences of changes in adipocyte protein production with alterations in adiposity (obesity, fasting, cachexia). There is already considerable evidence of links between increased production of some adipocyte factors and the metabolic and cardiovascular complications of obesity. In essence, white adipose tissue is a major secretory and endocrine organ involved in a range of functions beyond simple fat storage.

    Original languageEnglish
    Pages (from-to)329-339
    Number of pages11
    JournalProceedings of the Nutrition Society
    Volume60
    Issue number3
    DOIs
    Publication statusPublished - Aug 2001

    Keywords

    • cytokines
    • fasting-induced adipose factor
    • leptin
    • metallothionein
    • resistin
    • plasminogen-activator inhibitor-1
    • renin-angiotensin system
    • stimulating protein ASP
    • receptor messenger-RNA
    • necrosis-factor-alpha
    • OB gene-expression
    • sympathetic nervous-system
    • circulating leptin levels
    • in-situ hybridization
    • insulin-resistance

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