RESUMO
Central obesity is characterized by visceral adipose tissue (VAT) expansion, considered one of the main risk factors for metabolic complications. In recent years, new drugs have been studied for obesity treatment. Liraglutide (LGT), a GLP-1 agonist, decreases body weight, however, several mechanisms of action on VAT are still unknown. Aim: to study the effect of LGT on factors associated with VAT remodeling and mitochondrial dynamics in mice fed a high-fat diet (HFD). Methods: C57BL/6 mice were divided into Control (C) and HFD. After 15 weeks of feeding, each group was subdivided according to LGT administration for 5 weeks: C, C + LGT, HFD, and HFD + LGT. In epididymal AT (EAT) we evaluated histological and mitochondrial characteristics, vascularity, gelatinase activity (MMPs), and galectin-3 expression. Results: HFD presented larger adipocytes (p < 0.05), and lower vascular density and MMP-9 activity (p < 0.01) than C, while a major number of smaller adipocytes (p < 0.05) and an increase in vascularity (p < 0.001) and MMP-9 activity (p < 0.01) was observed in HFD + LGT. Collagen content was higher (p < 0.05) in EAT from HFD and decreased in HFD + LGT. In C, C + LGT, and HFD + LGT, mitochondria were predominantly tubular-shaped while in HFD mitochondria were mostly spherical (p < 0.001). Conclusion: LGT positively influences VAT behavior by modulating gelatinase activity, enhancing vascularization, and improving adipocyte histological characteristics. Additionally, LGT improves mitochondrial dynamics, a process that would favor VAT functionality.
RESUMO
The RNA-cleaving 8-17 DNAzyme, which is a metalloenzyme that depends on divalent metal ions for its function, is the most studied catalytic DNA in terms of its mechanism. By the end of 2017, a report of the crystal structure of the enzyme-substrate complex in the presence of Pb2+ probed some of the previous findings and opened new questions, especially around the participation of the metal ion in the catalytic mechanism and the promiscuity exhibited by the enzyme in terms of the metal cofactor required for catalysis. In this article we explore the role of the divalent metal ion in the mechanism of the 8-17 DNAzyme as a general acid, by measuring the influence of pH over the activity of a slower variant of the enzyme in the presence of Pb2+. We replaced G14, which has been identified as a general base in the mechanism of the enzyme, by the unnatural analog 2-aminopurine, with a lower pKa value of the N1 group. With this approach, we obtained a bell-shaped pH-rate profile with experimental pKa values of 5.4 and 7.0. Comparing these results with previous pH-rate profiles in the presence of Mg2+, our findings suggest the stabilization of the 5'-O leaving group by the hydrated metal ion acting as a general acid, in addition to the activation of the 2'-OH nucleophile by the general base G14.