EXPRESSION OF GUANINE-NUCLEOTIDE-BINDING PROTEINS IN LEAN AND OBESE INSULIN-RESISTANT MICE

To examine whether G proteins were affected in the obese insulin-resis tant state, the level of various G proteins (alpha(i1), alpha(i2), alp ha(i3), alpha(0), and alpha(s)) was assessed by immunodetection in lea n and experimentally induced obese mice. Crude membranes were prepared from adipose tissues, muscle, liver, kidney and brain. G(alpha)-subun its were similar in lean and obese animals in brain, kidney, skeletal or heart muscle. Hepatic G(alpha s), G(alpha i2) and G(alpha i3) subun its were markedly elevated in obese mice. When total tissue contents w ere considered, interscapular brown adipose tissue and epididymal fat pads from obese animals contained more alpha(i2), than the lean tissue s, while alpha(i1) alpha(i3) and alpha(s) were similar in both groups. However, when expressed per mg of membrane protein, alpha(i1), alpha( i3) and alpha(s) were decreased and alpha(i2), was normal in white adi pose tissue of obese animals. Thus the expression of the G protein alp ha-subunits seems to be regulated by tissue-specific factors rather th an by circulating factors.