INCREASED HEPATIC MONOACYLGLYCEROL ACYLTRANSFERASE ACTIVITY IN STREPTOZOTOCIN-INDUCED DIABETES - CHARACTERIZATION AND COMPARISON WITH ACTIVITIES FROM ADULT AND NEONATAL RAT-LIVER
N. Mostafa et al., INCREASED HEPATIC MONOACYLGLYCEROL ACYLTRANSFERASE ACTIVITY IN STREPTOZOTOCIN-INDUCED DIABETES - CHARACTERIZATION AND COMPARISON WITH ACTIVITIES FROM ADULT AND NEONATAL RAT-LIVER, Biochimica et biophysica acta, 1169(2), 1993, pp. 189-195
Hepatic monoacylglycerol acyltransferase (EC 2.3.1.22) (MGAT) is a dev
elopmentally-expressed activity associated with physiological periods
characterized by high rates of lipolysis and dependence on fatty acids
for energy production. During these periods, MGAT may help to retain
essential fatty acids selectively. In streptozotocin-diabetes, mean MG
AT-specific activity increased 11.8-fold. We characterized microsomal
MGAT activity from diabetic and control adult rats, and compared these
adult activities with the high neonatal activity. Compared with the a
ctivity in neonatal liver, adult MGAT activity was more thermolabile,
had a markedly different pH profile, and responded differently to incu
bation with bovine serum albumin, phospholipids, and MnCl2. Adult diab
etic MGAT activity was also stimulated 2-fold by albumin and was marke
dly thermolabile, but was not inhibited by phospholipid. Diabetic MGAT
activity had some properties that combined characteristics observed i
n adult and neonatal microsomes: a pH dependence that was optimal at p
H 7.0 but that plateaued between pH 7.0 and 9.5, and neither stimulati
on nor inhibition after incubation with MnCl2. Diabetic MGAT acylated
monoalkylglycerols more readily than did either the neonatal or the ad
ult MGAT activities. The enhanced expression of hepatic MGAT activity
in diabetes is consistent with its postulated role in retaining essent
ial fatty acids during lipolysis.