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Endocrine Reviews 27(7):762–778
Copyright © 2006 by The Endocrine Society
doi: 10.1210/er.2006-0033

Adipose Tissue-Derived Factors: Impact on Health
and Disease
Maria E. Trujillo and Philipp E. Scherer
Departments of Cell Biology and Medicine, Diabetes Research and Training Center, Albert Einstein College of Medicine,
1300 Morris Park Avenue,Bronx, New York 10461
The endocrine functions of the adipose organ are widely studied
at this stage. The adipose organ, and in particular adipocytes,
communicate with almost all other organs. Although some adipose tissue pads assume the functions as distinct “miniorgans,”
adipocytes can also be present in smaller numbers interspersed
with other cell types. Although fat pads have thepotential to
have a significant systemic impact, adipocytes may also affect
neighboring tissues through paracrine interactions. These local
or systemic effects are mediated through lipid and protein factors. The protein factors are commonly referred to as adipokines. Their expression and posttranslational modifications can
undergo dramatic changes under different metabolic conditions.

Due to thefact that none of the mutations that affect
adipose tissue trigger embryonic lethality, the study of adipose tissue physiology lends itself to genetic analysis in
mice. In fact, life in the complete absence of adipose tissue
is possible in a laboratory setting, making even the most
extreme adipose tissue phenotypes genetically amenable to
be analyzed by disruption of specific genes oroverexpression of others.
Here, we briefly discuss some basic aspects of adipocyte
physiology and the systemic impact of adipocyte-derived
factors on energy homeostasis. (Endocrine Reviews 27:
762–778, 2006)

I. Introduction

I. Introduction

T

II. Complexity of the Adipose Organ
A. Cellular composition
B. Adipose tissue depots
C. Gender differences in adipose organ function
III.Adipocytes and the Regulation of Energy Storage
A. Lipid deposition
B. Adipogenesis
C. Lipid mobilization and utilization
IV. Endocrine Function of the Adipose Organ
A. Adiponectin
B. Resistin
C. Additional adipokines
V. Adipose Tissue: Paracrine Effects
A. TNF
B. IL-6
C. Adipose tissue and the immune system
D. Acute phase reactants
E. Hyperglycemia-induced inflammatory response
F.Toll-like receptors
G. The FAT-ATTAC mouse: a novel mouse model for the
study of adipose tissue physiology
VI. Concluding Remarks

HE ADIPOCYTE IS unique among cells in that one organelle, the lipid droplet, encompasses greater than
95% of the entire cell body. This lipid droplet serves as a
storage vessel for triglycerides that can be released through
lipolysis and added to by the process oftriglyceride synthesis. Because the lipid droplet can assume such a large portion
of the entire adipocyte, increases in lipid storage result in
increased fat cell size. In fact, the capacity for triglyceride
storage by the adipocyte is quite impressive because fat cells
range from 25–200 m in diameter. Hence, the adipocyte is
traditionally viewed as a cell that is primarily involved inenergy storage. However, it is now clear that the adipocyte
has additional roles with the remaining 5% of its cellular
mass. It has an exceptionally active secretory pathway whose
function is not only to release products of conventional
housekeeping genes, but also to release many endocrine and
paracrine factors commonly referred to as adipokines. The
endocrine functions allow the adipocyte toregulate processes in peripheral tissues such as the liver and the central
nervous system such as the hypothalamus. The paracrine
effects of adipokines have an impact on neighboring adipocytes as well as other local cell types within adipose tissue.

First Published Online October 20, 2006
Abbreviations: AdipoR, Adiponectin receptor; AMPK, AMP kinase;
BAT, brown adipose tissue; COX-2,...