Nutritional effects on NF-kappaB/IkappaB activity in weight-gaining and -losing rats.
BACKGROUND
We had previously reported metabolic abnormalities in TNF-treated weight-gaining (WG) rats, associated with increased soluble and membrane TNF receptors.


OBJECTIVE
On the basis of these findings, we hypothesized that stabilization of TNF in circulation in WG animals by these receptors augmented the action of TNF. TNF influences cellular function through the activation of NF-kappaB, by its release from IkappaBalpha and translocation to the nucleus where it regulates gene transcription. This study was designed to determine whether NF-kappaB binding was increased in WG rats in comparison with weight-losing (WL) rats.


METHODS
Twenty two male Wistar rats weighing 200-220 g were fed a liquid-defined formula diet for 10 days and divided as follows: (i) WG rats (n = 11) receiving an energy density of 0.35 MJ per 60 ml and (ii) WL rats (n = 11) receiving an energy density of 0.09 MJ per 60 ml. Nuclear extracts from heart, liver, lung, spleen and gastrocnemius were used for NF-kappaB measurements by electrophoretic mobility shift assay. Tissue lysates from heart and lung were used for IkappaBalpha measurements by Western blot analysis.


RESULTS
There was increased NF-kappaB binding in the lung and heart extracts of the WG rats as compared with WL rats. There was no difference in the binding activity between WG and WL rats in the spleen, liver and gastrocnemius extracts. In lung and heart lysates, IkappaBalpha protein expression was decreased in WG rats as compared with the WL rats. We conclude that there is increased organ-specific TNF activity in WG rats because of increased binding of NF-kappaB to the nucleus and reduced IkappaBalpha levels in the lung and heart.


CONCLUSIONS
The findings are consistent with increased TNF activity resulting in the release of NF-kappaB from the NF-kappaB/IkappaBalpha complex and translocation to the nucleus. The nuclear translocation of NF-kappaB observed in the heart and lung suggests that nutrition may influence the action of TNF in these vital organs in sepsis. This finding is potentially of great significance, as pulmonary and cardiac failure are the main causes of death in sepsis.
Raina
Nilima
N
Department of Nutrition , University of Toronto, Ontario, M5S 1A8, Toronto, Canada. nilima42@hotmail.com
Jeejeebhoy
Khursheed N
KN
D000818:Animals; D004247:DNA / Q000378:metabolism; D020672:I-kappa B Proteins / Q000502:physiology*; D008168:Lung / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology*; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015430:Weight Gain / Q000502:physiology*; D015431:Weight Loss / Q000502:physiology*
D020672:I-kappa B Proteins; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D004247:DNA