Role of leptin, ghrelin, angiotensin II and orexins in 3T3 L1 preadipocyte cells proliferation and oxidative metabolism.

There is now growing evidence that the reactive oxygen species have an influence on proliferation and antioxidative status of various cell types. The aim of the study was to investigate the effects of different concentrations of leptin, ghrelin, angiotensin II and orexins on proliferation, culture medium malondialdehyde (MDA) levels and antioxidative enzymes activities: superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) in 3T3 L1 preadipocytes cell culture. Cell proliferation was measured using [(3)H]tymidine incorporation. In 3T3-L1 cells leptin caused a significant reduction in proliferation (by 36%) compared to control. Ghrelin increased preadipocyte proliferation, and the effect was stronger in higher dose (by 39%), while proproliferatory effect of angiotensin II was stronger in lower doses (by 47%). All used doses of orexin A significantly increased 3T3 L1 cell proliferation (from 21% to 160%), while orexin B caused a marked reduction (from 35% to 70%) of this proliferation. The effects of both orexins were dose-dependent. Leptin and ghrelin increased activity of SOD, CAT, GSH-Px and decreased level of MDA. Angiotensin II treatment stimulated only SOD and CAT activities. Influence of orexins was different on various enzymes. Orexin A increased MDA levels, while orexin B caused a marked decrease in MDA levels. Our results strongly suggest the effects of appetite affecting hormones such as leptin and ghrelin on proliferation and antioxidative enzyme activities of preadipocyte cell lines. Orexin A was found to be the most efficient proliferative-signalling hormone, while orexin B revealed the most significant inhibitory effect on preadipocytes proliferation.

Influence of melatonin on cell proliferation, antioxidative enzyme activities and lipid peroxidation in 3T3-L1 preadipocytes--an in vitro study.

Melatonin, acting via MT1, MT2 and MT3 membrane receptors, influences central and peripheral regulatory mechanisms of energy homeostasis in mammals. In peripheral tissues, it evokes the pro-proliferative effect in a number of normal cells. Moreover, this hormone inhibits lipolysis in subcutaneous adipocytes in vitro and reduces free oxygen metabolites-induced damage acting directly, as a free radical scavenger, and indirectly, by stimulation of antioxidative enzyme activities. The aim of the study was to examine the effects of melatonin on cell proliferation, antioxidative enzyme activities and malondialdehyde (MDA) concentration in 3T3-L1 preadipocyte cell culture. We found that melatonin (10(-3) and 10(-6) M/L) stimulated cell proliferation in dose- and time-depending manner, and this effect was inhibited by a relatively selective MT2 receptor antagonist - luzindole (10(-4) M/L). Melatonin, increased activities of manganese containing and copper-zinc containing superoxide dismutase (MnSOD and Cu/ZnSOD) isoenzymes, catalase, glutathione reductase and glutathione peroxidase after 24 h of incubation. In contrast, after 48 h of incubation, activities of all studied enzymes were lower than in the control group. There were no changes in MDA concentrations after 24 h of incubation, whereas, in melatonin-treated media, after 48 h of the experiment, MDA level was significantly decreased. Our results demonstrate that melatonin, acting via MT2 receptors, stimulates proliferation of 3T3-L1 preadipocytes and this action could be due to the enhancement in antioxidative enzyme activities and attenuation of lipid peroxidation by this indole.

Effect of extremely low frequency of electromagnetic fields on cell proliferation, antioxidative enzyme activities and lipid peroxidation in 3T3-L1 preadipocytes--an in vitro study.

The exposure to extremely low frequency electromagnetic field (ELF-MF, frequencies less than 200-300 Hz) can alter the transcription and translation of genes, influence the cell proliferation rate and affect enzyme activities. Moreover, the hypothesis that ELF-MF increases free oxygen metabolites generation has been proposed. Since recent in vivo studies suggest that electric and magnetic fields are able to affect adipose cells metabolism. The aim of the study was to examine the effects of ELF-MF (frequency of basic impulse 180-195 Hz, induction 120 microT) on cell proliferation, antioxidative enzyme activities and malondialdehyde (MDA) concentration in 3T3-L1 preadipocyte cell culture. We found that ELF-MF application lasting 36 minutes daily failed to influence cell count after 24h and 48 h of incubation. After 24 h, in the ELF-MF treated group, manganese- and copper-zinc-containing superoxide dismutase (MnSOD and Cu/ZnSOD) isoenzymes media activities were decreased, catalase activity was increased, whereas there were no significant differences in glutathione peroxidase (GSH-Px) and glutathione reductase (GSSG-Rd) activities in comparison to the control. After 48 h of incubation, all enzyme activities were reduced, except for GSSG-Rd, in which no changes were noticed. MDA concentration at 24 h after incubation with the exposure to ELF-MF was significantly higher in comparison to the control, without ELF-MF. After 48 h of incubation, MDA levels were significantly lower in both groups with no differences between the groups without and with ELF-MF. We conclude that ELF-MF influences antioxidative enzyme activities and increases lipid peroxidation in 3T3-L1 preadipocyte cultures.