New paradigms in the study of the cholinergic system and metabolic diseases: Acetyl-and-butyrylcholinesterase

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are enzymes that belong to the neuromuscular cholinergic system, their main function is to hydrolyze the neurotransmitter acetylcholine (ACh), through their hydrolysis these enzymes regulate the neuronal and neuromuscular cholinergic system. They have recently attracted considerable attention due to the discovery of new enzymatic and nonenzymatic functions. These discoveries have aroused the interest of numerous scientists, consolidating the relevance of this group of enzymes. Recent investigations have revealed a positive correlation between several risk factors for metabolic syndrome (MetS) and the expression of cholinesterases (ChE's), which underscore the impact of high ChE's activity on the pro-inflammatory state associated with MetS. In addition, the excessive hydrolysis of ACh and other choline esters (succinylcholine, propionylcholine, butyrylcholine, etc.) by both ChE's results in the overproduction of fatty acid precursor metabolites, which facilitate the synthesis of very low-density lipoproteins and triacylglycerols. Participation in these processes may represent the link between ChE's and metabolic disorders. However, further scientific research is required to fully elucidate the involvement of ChE's in metabolic diseases. This review aims to collect recent research studies that contribute to understanding the association between the cholinergic system and metabolic diseases.

Oxidative stress in the ovaries of mice chronically exposed to a low lead concentration: A generational approach

Lead (Pb) is a heavy metal that alters the oxidation-reduction balance, affecting reproductive health and transfer during pregnancy and lactation. However, the multigenerational impact of exposure to low concentrations of Pb on mammalian ovaries has not been assessed. This study evaluated general parameters, histology, redox state (RS), protein carbonylation (PC), lipid peroxidation (LP), and hormone concentrations in the ovaries of mice (CD1® ICR) of three successive generations with both unigenerational (E1) and multigenerational (E2) exposure to 0.2 ppm lead acetate through the drinking water and a control group. Body weight, food consumption, the number of born pups, and their weight after weaning were not significantly affected by Pb exposure in E1 and E2. However, the ovaries of three successive generations of the E1 group, in which only the F0 was exposed, showed alterations in the ovarian histoarchitecture, increase in follicular atresia, decrease in the number of available follicles, and a significant RS and PC elevation that were surprisingly similar to those observed in the E2 group. LP increased in the second generation of E1 and E2, while hormone concentration was not altered. This is the first demonstration that exposure to low concentration of Pb induces multigenerational histological alterations and oxidative stress in mouse ovaries, that the termination of this exposure does not ensure the safety of later generations and that the lack of modifications in general parameters may facilitate the silent development of pathologies that affect ovarian health.

Nicotinamide reduces inflammation and oxidative stress via the cholinergic system in fructose-induced metabolic syndrome in rats

AIMS

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) have been associated with risk factors for metabolic syndrome (MetS). Our objective was to evaluate the effect of nicotinamide (NAM) on the activities, expression and protein content of cholinesterases in a MetS model.

MAIN METHODS

MetS was induced in male rats administrating 40% fructose to the drinking water for 16 weeks. Additionally, from 5th week onward, the carbohydrate solution was replaced by NAM, at several concentrations for 5 h each morning for the next 12 weeks. In the 15th week, the glucose tolerance test was conducted, and blood pressure was measured. After the treatment period had concluded, the biochemical profile; oxidant stress; proinflammatory markers; and the activity, quantity and expression of cholinesterases were evaluated, and molecular docking analysis was performed.

KEY FINDINGS

The MetS group showed anthropometric, hemodynamic and biochemical alterations and increased cholinesterase activity, inflammation and stress markers. In the liver, cholinesterase activity and mRNA, free fatty acid, tumor necrosis factor-alpha (TNF-α), and thiobarbituric acid-reactive substance (TBARS) levels were increased, while reduced glutathione (GSH) levels were decreased. NAM partially or totally decreased risk factors for MetS, markers of stress and inflammation, and the activity (serum and liver) and expression (liver) of cholinesterases. Molecular docking analysis showed that NAM has a greater affinity for cholinesterases than acetylcholine (ACh), suggesting NAM as an inhibitor of cholinesterases.

SIGNIFICANCE

Supplementation with 40% fructose induced MetS, which increased the activity and expression of cholinesterases, oxidative stress and the inflammation. NAM attenuated these MetS-induced alterations and changes in cholinesterases.