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Background: The aim of the current study is to investigate the effect of leptin on cytoskeleton structures in both in vivo and in vitro model of diabetes. Materials and methods: For in vivo studies, leptin in different doses (240, and 480 mg/kg) was injected to the diabetic rats after 1-week of streptozotocin (STZ, 55 mg/kg) treatment. Leptin levels were analysed in serum, liver, and pancreas samples. Hepatic and pancreatic F- and G-actin expressions were determined by Western blotting. For in vitro studies, hepatic and pancreatic primary cell lines were obtained from the control rats. To these cultures, STZ (15 and 30 mM), leptin (50, 60 and 100 ng/mL), and their combinations were applied for 1, 3, and 4 weeks. After the treatment period, F-actin was visualised by the Alexa-fluor fluorescent dye. Results: Streptozotocin decreased the G-actin in both tissues in vivo. However, leptin caused a dose-dependent increase in G-actin levels while F-actin decreased in both tissues. Moreover, leptin caused the perimembranous condensation of actin filaments and amelioration of F-actin structures in vivo. A dose-dependent corruption of F-actin filament structures was observed in leptin-treated primary cells in vitro, while STZ also caused corruption of these filaments. Co-exposure of STZ and leptin caused the amelioration of F-actin filaments, while the perimembranous condensation was also observed as was in vivo study. Conclusions: Leptin therapy could be a candidate for diabetes, but it should not be ruled out as being important the severity of diabetes and leptin doses. (Folia Morphol 2019; 78, 2: 314–324)
Diphtheria toxin (DT) and its N-terminal fragment A (FA) catalyse the transfer of the ADP-ribose moiety of nicotinamide adenine dinucleotide (NAD) into a covalent linkage with eukaryotic elongation factor 2 (eEF2). DT-induced cytotoxicity is versatile, and it includes DNA cleavage and the depolymerisation of actin filaments. The inhibition of the ADP-ribosyltransferase (ADPrT) activity of FA did not affect the deoxyribonuclease activity of FA or its interaction with actin. The toxin entry rate into cells (HUVEC) was determined by measuring the ADP-ribosyltransferase activity. DT uptake was nearly 80% after 30 min. The efficiency was determined as Km = 2.2 nM; Vmax = 0.25 pmol.min−1. The nuclease activity was tested with hyperchromicity experiments, and it was concluded that G-actin has an inhibitory effect on DT nuclease activity. In thepresence of DT and mutant of diphtheria toxin (CRM197), F-actin depolymerisation was determined with gel filtration, WB and fluorescence techniques. In the presence of DT and CRM197, 60–65% F-actin depolymerisation was observed. An in vitro FA-actin interaction and F-actin depolymerisation were reported in our previous paper. The present study thus confirms the depolymerisation of actin cytoskeleton in vivo.
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