Expression of guanine-nucleotide-binding proteins in lean and obese insulin-resistant mice

Abstract

To examine whether G proteins were affected in the obese insulin-resistant state, the level of various G proteins ( α i2, α i2, α i3, α o and α s) was assessed by immunodetection in lean and experimentally induced obese mice. Crude membranes were prepared from adipose tissues, muscle, liver, kidney and brain. G α-subunits were similar in lean and obese animals in brain, kidney, skeletal or heart muscle. Hepatic G αs, G αi2 and G αi3 subunits were markedly elevated in obese mice. When total tissue contents were considered, interscapular brown adipose tissue and epididymal fat pads from obese animals contained more α i2 than the lean tissues, while α i1, α i3 and α s were similar in both groups. However, when expressed per mg of membrane protein, α i1, α i3 and α s were decreased and α i2 was normal in white adipose tissue of obese animals. Thus the expression of the G protein α-subunits seems to be regulated by tissue-specific factors rather than by circulating factors.