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stress and apoptosis
peroxisome proliferators-activated receptors (PPARs) are a family of at least three
nuclear receptors (q ßlõ and 7) which belong to the superfamily of steroid-thyroid
nuclear receptors (Dreyer eI al. 1992; Issemann and Green 1990)'
ppARs were first time cloned in an attempt to identify molecular mediators of
peroxisome proliferation in liver of rodents (Issemann and Green 1990). konically,'
despite their name, recent studies have confirmed that both PPAR-ô and PPAR-"y do not
respond to the activation of peroxisome proliferators. It is also shown that PPAR receptor
are involved in the regulation of a number of metabolic processes such as regulation of
cholesterol metabolism, insulin sensitivity, cardiac energy metabolism and control of
apoptosis (Barger and Kelly 2000; Diep and Schiffrin 2001; Fruchart et al.200I; Guerre-
Millo et al. 2001). Until recently the action of PPARs was thought to be limited by their
distribution, however more recent studies have identified the presence of PPAR receptors
in a number of different tissues and cell types. Although, distribution of PPAR's is found
to be almost ubiquitous, the differences in the expression of PPAR isoforms in number
organs and organic systems may indicate their specific function.
V.a.Distribution and function of PPAR receptors
ppAR cv was found to be widely expressed in tissues with high fatty acid
oxidation capacity such as hepatocytes, cardiac myocytes, kidney cortex and skeletal
myocytes (Braissant et al. 1996; Su et al. 1998). PPAR ßlõ are ubiquitously expressed in
number of tissues, however the distribution of these receptors was found to follow the
distribution of ppAR a with the highest levels recorded in the heart (Kliewer et al' 1994;
Takahashi and Kawad a 2001). The expression of PPAR "y is limited to brown and white
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