Effect of aging on the expression of peroxisome proliferator-activated receptor gamma and the possible relation to insulin resistance.
BACKGROUND
The morbidity of insulin resistance tends to increase with aging. However, studies on molecular mechanisms underlying insulin resistance in aging process is still in paucity.


OBJECTIVE
The effect of aging on peroxisome proliferator-activated receptor gamma (PPARgamma) expression, and in addition, the possible association of PPARgamma expression with insulin resistance in aging process were investigated.


METHODS
The minimal model technique (MMT) based on frequently sampled intravenous glucose tolerance test was adopted and SI and glucose effectiveness of young and aged rats were compared. RT-PCR and Western blot were used to determine the expression of PPARgamma at mRNA and protein level in adipose tissue and skeletal muscle, as well as in human colic omentum, respectively.


RESULTS
MMT result implied existence of various degrees of insulin resistance in aged rats. The expression of PPARgamma at both mRNA and protein levels in adipose tissue of aged rats dramatically decreased; consequently, the expression of its target gene lipoprotein lipases mRNA also markedly decreased compared with those in young rats. Furthermore, the level of PPARgamma mRNA and glucose transporter-4 mRNA in skeletal muscle of aged rats attenuated significantly. The expression of PPARgamma mRNA in omental adipose tissue of old men was significantly decreased, accompanied by a tendency of higher insulin resistance index, compared with those of the young.


CONCLUSIONS
Aging may be associated with diminished PPARgamma expression affecting insulin resistance in the aged individuals.
Ye
Ping
P
Department of Geriatric Cardiology, Chinese PLA General Hospital, Beijing, China. yeping@sina.com
Zhang
Xiu-Jin
XJ
Wang
Zhao-Jun
ZJ
Zhang
Cheng
C
D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D016022:Case-Control Studies; D015870:Gene Expression; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007333:Insulin Resistance / Q000235:genetics*; D008071:Lipoprotein Lipase / Q000235:genetics / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D047495:PPAR gamma / Q000096:biosynthesis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
D051275:Glucose Transporter Type 4; D047495:PPAR gamma; D012333:RNA, Messenger; D008071:Lipoprotein Lipase