INVESTIGADORES
PODEROSO Juan Jose
congresos y reuniones científicas
Título:
Mitochondrial nitric oxide is increased in the mice Ob-/- modelo of metabolic syndrome
Autor/es:
BARREYRO FJ, FINOCCHIETTO PV, FRANCO MC, HOLOD S, CARRERAS MC, PODEROSO JJ.
Lugar:
EEUU, Boston
Reunión:
Congreso; 57th Annual Meeting of the American Association for the Study of Liver Disease; 2006
Resumen:
Background and Aim: Insulin resistance (IR), the hallmark of non
aJcoholic fatíy liver disease (NAFLD), is associated with the increase
of visceral white adipose tissue (WAT). Although the mechanísm
is unknown, there are severa! reports about mitochondrial
abnormalities in metabolic tissues in IR, Nitric Oxide (NO) is a
pleiotropic signaling moiecule, with many of its effects on cell
function being elicited at the mitochondrial level. In different
tissues, Nitric Oxide Synthase traslocates to mitochondria ímt-
NOS)anc! synthesizes NO vectorially directed to the matrix. It is
noteworíhy that NO steady-state concentration modulates electrón
transfer, O2 uptake, and the reactive oxygen species yield.
VVe previously reported that Insulin increases the mtNOS activity.
Our aim is to determine the activity and expression of mtNOS in
WAT, Muscle and Liver of lepíin deficient Ob-/- mice. Meíhods:
VVe used Ob-/- and C57BL/6 VVT mice (6-9 mo oíd); were divided
in fwo subgroups with no intervention or receiving (6 ¡xg bid IP 4
days) leptin replacement. Epidydimal WAT, Muscle, and Liver
were exdsed and isolafion and purification of mitochondria was
done by differential centrifugation. Mitochondrial NO was determined
by flow citometry wiíh DAF, the expression of mtNOS by
Western Blot and KT-PCR and Mitochondrial Complex I-IV activities
were follovved spectrophotometrically. Complexes were separated
by BN-PAGE, and tyrosine nitration was detected by
Western Blot. Results: l)Ob-/- have a significant increase of mt-
NOS activity in accord to 3-fold increase of expression. 2) Complex
I Activity resulted markedly reduced in WAT (-81 %; p<0,05),
Muscle (-72%; p<0,05), and Liver (-61%; p<0,05) from Ob-/-; there
were no significant changos of the activity of Complexes II-IJI and
IV. 3) According to low activity, Complex I exhibited 3-4 fold
increased tyrosine nitration in WAT. Muscle and Liver mitochondria
from Ób-/-. 4) Leptin replacement completely normaliyed
mtNOS activity and Complex I activity, with significantly decreased
nitration at same level of control». Conclusions: a)Milochondria
of Ob-/- mice tissues are exposed to high NO matrix
concentration that conducís lo Complex 1 nitration and subsequent
reduced activity; b)Likewise, more than 60% Complex I
inhibition contributes to low Ob-/- O2 uptake and obesity; c)Enhanced
NO depends on high mtNOS expression and probably as
well on preliminary dala of our group indicating that leptin reduces
mtNOS activity and insulin increased mtNOS activity;
díthus, in mis rodent mode! of metabolic syndrome, mitochondrial
hypometabolísm should depend on the balance between
leptin deficiency and reduced sensitivity to insulin.