Butyrylcholinesterase and lipid metabolism: Possible dual role in metabolic disorders

Butyrylcholinesterase (BChE), an enzyme primarily found in the liver, plasma, and brain, has been recognized for its role in the hydrolysis of choline esters. Recent studies have shed light on its involvement in lipid metabolism, revealing its potential as a crucial player in maintaining lipid homeostasis. However, the interactions between external factors and BChE activity in lipid metabolic pathways remain a complex subject of study. This review summarizes the current knowledge regarding BChE activity and lipid metabolism and seeks to clarify the nature of this relationship as causal or consequential. Evidence supports the role of BChE in energy homeostasis disruption, such as obesity and related metabolic disorders, where it exhibits lipolytic activity and mediates fatty acid use and storage. The unexpected functions of BChE in lipoprotein synthesis and the impact of polymorphic variants of the BCHE gene suggest a central role in lipid metabolism; however, further investigation is needed to confirm and describe these functions, especially considering the metabolic context. Furthermore, exploring therapeutic interventions in lipid metabolism disorders contributes to elucidating their implications on BChE activity, but attention to the metabolic status and genotypes as possible factors in this interaction is needed. In summary, further research in this field holds promise for improving our understanding of the complex interplay between BChE and lipid metabolism, and its potential clinical applications. However, the available data corroborate the dual role of BChE activity, both as a critical responsive element to metabolic challenges and as a predisposition factor to metabolic diseases.

Animal model of Alzheimer's disease induced by streptozotocin: New insights about cholinergic pathway

Alzheimer's disease (AD) is of multifactorial origin, and still presents several gaps regarding its development and progression. Disorders of the cholinergic system are well known to be involved in the pathogenesis of AD, characterized by increased acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and decreased acetyltransferase (ChAT) enzymatic activities. Late onset AD (LOAD) animal model induced by intracerebroventricular injection of streptozotocin (icv-STZ) showed promising results in this context, due to the similarity with the pathophysiology of human LOAD. Thus, this study aimed to assess the long-term effects of icv-STZ on the cholinergic system, through the measuring of AChE and BChE enzymatic activities in hippocampus, prefrontal cortex and liver of animals euthanized 30 and 120-days after the icv-STZ. Regarding the cholinergic response to icv-STZ, the 30-days and 120-days STZ-induced rats exhibit decreased AChE and BChE activities only in the hippocampus. The cognitive deficit was more consistent in the 30-days post icv-STZ animals, as was the weight loss. This is the first study to investigate the long-term effects (more than 60 days) of the icv-STZ on AChE and BChE activities, and our results, as well as those of a recent study, suggest that the cholinergic system may not be compromised by icv-STZ, at least in the long term, which means that this model may not be the best model for studying the cholinergic system in AD or that it is informative only for a short period.

Neurodevelopmental regression, severe generalized dystonia, and metabolic acidosis caused by POLR3A mutations

OBJECTIVE

To expand the clinical phenotype of POLR3A mutations by assessing the functional consequences of a missense and a splicing acceptor mutation.

METHODS

We performed whole-exome sequencing for identification of likely pathogenic mutations in a 9-year-old female patient with severe generalized dystonia, metabolic acidosis, leukocytosis, hypotonia, and dysphagia. Brain MRI showed basal ganglia atrophy and presence of lactate and lipid peaks by [1H]-magnetic resonance spectroscopy. Expression levels of Pol III target genes were measured by quantitative real-time (qRT)-PCR to study the pathogenicity of the biallelic mutations in patient fibroblasts.

RESULTS

The patient is a compound heterozygous for a novel missense c.3721G>A (p.Val1241Met) and the splicing region c.1771-6C>G mutation in POLR3A, the gene coding for the catalytic subunit of RNA polymerase III (Pol III). Aberrant splicing was observed for the c.1771-6C>G mutation. Decreased RNA expression levels of Pol III targets (HNRNPH2, ubiquitin B, lactotransferrin, and HSP90AA1) were observed in patient fibroblasts with rescue to normal levels by overexpression of the wild-type protein but not by the p.Val1241Met variant.

CONCLUSIONS

Mutations in the POLR3A gene cause POLR3A-related hypomyelinating leukodystrophy with or without oligodontia or hypogonadotropic hypogonadism (HLD7, OMIM: 607694) and neonatal progeroid syndrome (OMIM: 264090), both with high phenotypic variability. We demonstrated the pathogenicity of c.1771-6C>G and c.3721G>A mutations causing an early-onset disorder. The phenotype of our patient expands the clinical presentation of POLR3A-related mutations and suggests a new classification that we propose designating as Neurodevelopmental Disorder with Regression, Abnormal Movements, and Increased Lactate.

IL18 Gene Polymorphism Influences Age of Onset of DM1 in African Ancestry Brazilians

The aim of this study was to investigate the relationship of two single nucleotide polymorphisms (SNPs) in the interleukin-18 ( IL18 ) gene (rs187238, g.-137G > C; rs1946518, g.-607C > A) and one SNP of the IL12B gene (rs3212227 g.*159A > C, 3'UTR) with the age of onset for type 1 diabetes mellitus (DM1). A total of 1,101 patients with DM1 enrolled in 13 centers from different regions of Brazil were genotyped with TaqMan assay and classified according to the ancestry. Our results show that an SNP in IL18 gene could be associated with DM1 age onset, taking into account that this studied variation affects gene expression.

Effects of polymorphisms in APOB, APOE, HSD11β1, PLIN4, and ADIPOQ genes on lipid profile and anthropometric variables related to obesity in children and adolescents

Genes can influence lipid profile and anthropometric variables related to obesity. The present study aimed to verify if variants of the APOE, APOB, ADIPOQ, HSD11β1, and PLIN4 genes are associated with lipid levels or anthropometric variables in a sample comprised of 393 Euro-Brazilian children and adolescents. DNA was genotyped by TaqMan allelic discrimination assay. The ε4 and ε2 alleles of the APOE gene were associated respectively with lower high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels (p=0.015 and p=0.012, respectively), while the ε3 allele was associated with higher abdominal circumference (p=0.0416) and excess weight (p=0.0001). The G allele (rs846910) of the HSD11β1 gene was also associated with excess weight (p=0.039). No other association was found. Our results indicate that the ε4 and ε2 alleles could contribute to lower HDL-C and LDL-C levels, respectively, furthermore, the ε3 allele and the G allele (rs846910) of HSD11β1 gene may be risk factors for excess of weight.These findings are very important because we observed that some genetic variants influence the lipid profile and anthropometric variables early in life.

Plasma butyrylcholinesterase activity: a possible biomarker for differential diagnosis between Alzheimer's disease and dementia with Lewy bodies?

Butyrylcholinesterase (BChE) is an enzyme encoded by BCHE gene, responsible for secondary hydrolysis of the acetylcholine. K and -116A BCHE variants were associated with decrease in plasma BChE activity, and their influence has been investigated in diseases with a cholinergic deficit such as Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). In order to check the influence of BCHE genetic variants on enzymatic activity, all patients and controls were genotyped for K and -116A variants. We found lower plasma BChE activity in DLB patients compared to elderly controls and to AD independent of the presence of K or -116A variants. Our results suggest that the reduction of total plasma BChE activity is probably associated with a feedback mechanism and provides a future perspective of using this enzyme as a possible plasmatic marker for differential diagnosis between AD and DLB.

Butyrylcholinesterase: K variant, plasma activity, molecular forms and rivastigmine treatment in Alzheimer's disease in a Southern Brazilian population

Alzheimer's disease (AD) is a neurodegenerative disorder in which there is a decline of cholinergic function. The symptomatic AD treatment involves the use of ChEIs (cholinesterase inhibitors) as rivastigimine, a dual inhibitor. The human butyrylcholinesterase (BChE) is an enzyme that has specific roles in cholinergic neurotransmission and it has been associated with AD. In the serum, BChE is found in four main molecular forms: G1 (monomer); G1-ALB (monomer linked to albumin); G2 (dimer); and G4 (tetramer). The interaction between the products of BCHE gene and CHE2 locus results in CHE2 C5+ and CHE2 C5- phenotypes. CHE2 C5+ phenotype and BChE-K are factors that influence on BChE activity. This work aimed to verify the proportions of BChE molecular forms, total and relative activity in 139 AD patients and 139 elderly controls, taking into account K variant, CHE2 locus, rivastigmine treatment and clinical dementia rating (CDR) of AD patients. Phenotypic frequencies of CHE2 C5+ and frequency of the carriers of the K allele were similar between groups. Total BChE activity in plasma was significantly lower in AD patients than in elderly controls. Furthermore, we found that reduction on plasma BChE activity is associated directly with AD progression in AD patients and that rivastigmine treatment has a stronger effect on BChE activity within the CDR2 group. The reduction in BChE activity did not occur proportionally in all molecular forms. Multiple regression analysis results confirmed that AD acts as the main factor in plasma BChE activity reduction and that severe stages are related with an even greater reduction. These findings suggest that the reduction of total plasma BChE and relative BChE molecular forms activity in AD patients is probably associated with a feedback mechanism and provides a future perspective of using this enzyme as a possible plasmatic secondary marker for AD.

Gestational diabetes mellitus (GDM) decreases butyrylcholinesterase (BChE) activity and changes its relationship with lipids

Many conditions interfere with butyrylcholinesterase (BChE) activity, e.g., pregnancy or presence of the BCHE gene variant -116A can decrease activity whereas obesity and types I and II diabetes mellitus can increase activity. In this study, we examined BChE activity, -116A and 1615A BCHE gene variants, and anthropometric and biochemical variables associated with diabetes in patients with gestational diabetes mellitus (GDM) and in healthy pregnant women. BChE activity was measured spectrophotometrically using propionylthiocholine as substrate and genotyping of the -116 and 1615 sites of the BCHE gene was done with a TaqMan SNP genotyping assay. Three groups were studied: 150 patients with GDM, 295 healthy pregnant women and 156 non-pregnant healthy women. Mean BChE activity was significantly lower in healthy pregnant women than in women from the general population and was further reduced in GDM patients. BChE activity was significantly reduced in carriers of -116A in GDM patients and healthy pregnant women. Although GDM patients had a significantly higher mean body mass index (BMI) and triglycerides than healthy pregnant women, they had lower mean BChE activity, suggesting that the lowering effect of GDM on BChE activity was stronger than the characteristic enhancing effect of increased BMI and triglycerides.

Effects of physical exercise on butyrylcholinesterase in obese adolescents

The aim of the present study was to evaluate the effect of a 12 week program of physical exercise (PE) on butyrylcholinesterase (BChE) in obese adolescents. This study compared obese adolescents (N = 54) before and after PE, regarding the relative intensity (RI) and activity of different molecular forms (G1, G2, G4 and G1-ALB) of BChE found in plasma. Waist circumference (WC) and lipid profile were also assessed before and after PE. It was shown that before PE, mean plasma BChE activity was significantly higher in obese than in non-obese adolescents and that it was significantly reduced after PE, becoming similar to that found in non-obese adolescents. Lipid profile and WC also changed in response to PE. These results are consistent with studies that found a correlation between BChE and lipid metabolism and suggest that PE may have led to a physiological regularization of plasma BChE activity. Although mean BChE activity of each isoform was significantly reduced by PE, their RI did not change. This is in accordance with a previous suggestion that this proportion is maintained under factors such as obesity, and may therefore be important for BChE functions.

Investigation of Association between Susceptibility to Leprosy and SNPs inside and near the BCHE Gene of Butyrylcholinesterase

Leprosy is a chronic disease caused by Mycobacterium leprae and affects the skin and the peripheral nervous system. Butyrylcholinesterase is coded by the BCHE gene, and the atypical allele (70G; rs1799807) has been investigated as a leprosy risk factor, with conflicting results. The present study estimated the frequencies of variants of rs1799807 and of five additional SNPs at the BCHE gene or near it: rs1126680, rs1803274, rs2863381, rs4440084, and rs4387996. A total of 167 patients and 150 healthy controls were genotyped by TaqMan PCR. Significantly higher allelic (70G) and genotypic (70DG) frequencies in rs1799807 were found in the patient group, with odds ratio (OR) of 6.33 (1.40 to 28.53) for the heterozygote. This finding was replicated in a comparison of the cases against a control group of 361 blood donors. The present data suggest that the atypical BChE variant may predispose to leprosy per se.

Obesity and variants of the GHRL (ghrelin) and BCHE (butyrylcholinesterase) genes

Ghrelin coded by the GHRL gene is related to weight-gain, its deactivation possibly depending on its hydrolyzation by butyrylcholinesterase (BChE) encoded by the BCHE gene, an enzyme already associated with the body mass index (BMI). The aim was to search for relationships between SNPs of the GHRL and BCHE genes with BChE activity, BMI and obesity in 144 obese and 153 nonobese Euro-Brazilian male blood donors. In the obese individuals, a significant association with higher BChE activity, in the 72LM+72MM; –116GG genotype class (GHRL and BCHE genes, respectively) was noted. No significant differences were found otherwise, through comparisons between obese and control individuals, of genotype and allele frequencies in SNPs of the GHRL gene (Arg51Gln and Leu72Met), or mean BMI between 72LL and 72LM+72MM genotypes. Although there appears to be no direct relationship between the examined GHRL SNPs and BMI, the association of the 72M SNP with higher BChE activity in obese subjects probably points to a regulatory mechanism, thereby implying the influence of the GHRL gene on BChE expression, and a consequential metabolic role in the complex process of fat utilization.

Molecular forms of butyrylcholinesterase and obesity

This study compared obese (N = 134) and unobese (N = 92) male blood donors, regarding the relative intensity (RI) and activity of different molecular forms (G1, G2, G4 and G1-ALB) of butyrylcholinesterase (BChE, EC 3.1.1.8) found in plasma, thereby searching for an association between these variables with obesity and SNPs of exons 1 and 4 of the BCHE gene. It was shown that obese and unobese individuals do not differ in the RI of each BChE band, even when classifying the sample into three genotypes of exons 1 and 4 of the BCHE gene (-116GG/539AA, -116GG/539AT, -116GA/539AT). Although the mean BChE activity of each band was significantly higher in obese than in unobese blood donors, the proportions of BChE bands were maintained, even under the metabolic stress associated to obesity, thereby leading to infer that this proportion is somehow regulated, and may therefore be important for BChE functions.

Amplification and deletion of the ACHE and BCHE cholinesterase genes in sporadic breast cancer

Increasing evidence supports the involvement of acetylcholinesterase and butyrylcholinesterase in cell proliferation control and differentiation, reinforcing the hypothesis that these enzymes might have an influence in tumorigenesis. It has already been shown that the cholinesterase genes are structurally altered or aberrantly expressed in a variety of tumor types. In this study, amplifications and deletions in the ACHE and BCHE genes were investigated in sporadic breast tumors using real-time polymerase chain reaction and the relative quantification method. The majority of the tumor tissues showed a notable number of both deletions and amplifications: 65.7% and 22.9%, respectively, in BCHE and 45.7% and 31.4%, respectively, in ACHE. Deletion of the ACHE gene was significantly correlated with amplification of the protooncogene ERBB2. Tumor size was significantly higher when the ACHE gene was amplified, and the total number of alterations (amplifications plus deletions) of the BCHE gene was positively correlated with tumor malignancy grade.

Expression of three naturally occurring genetic variants (G75R, E90D, I99M) of the BCHE gene of human butyrylcholinesterase

The present paper examined the effects of three non synonymous BCHE mutations (G75R, E90D and /99M) on enzyme kinetic parameters obtained after the expression of the respective recombinant BChEs. The respective nucleotide substitution that characterizes each of the three variants was introduced into BCHE cDNA by site directed mutagenesis and transfected into human embryonic kidney 293 T cells and Chinese hamster ovary cells (for E90D). BChE catalysed hydrolysis of butyrylthiocoline (BTC) was measured by Ellman method. The expression results showed that: (1) the activity of the G75R enzyme represents approximately 45% of the wild-type activity, whereas that of the I99M enzyme does not differ from the wild-type; (2) the E90D enzyme presents a silent phenotype; disruption of the salt bridge between E90 and R42 may cause the enzyme to be rapidly degraded inside the cells. In homozygous form the E90D enzyme may confer increased susceptibility to succinylcholine, but may delay cognitive impairment in aged individuals. BChE genotyping may become important for estimating prognosis, and the knowledge of the genetic variants of BChE in a particular population may be useful for carrying out the genotyping assays.

Four new mutations in the BCHE gene of human butyrylcholinesterase in a Brazilian blood donor sample

The genetic variation of human butyrylcholinesterase has been associated with height, body mass index, Alzheimer's disease, and response to xenobiotic agents. The present study reports four new mutations, found in the exon 2 of the BCHE gene, in a sample from 3001 Brazilian blood donors. The three nonsynonymous mutations and one synonymous mutation detected are: 223G-->C, G75R; 270A-->C, E90 D; 297T-->G, I99 M; 486T-->C, A162 A, respectively. All these variants are rare: 0.093+/-0.093% for the missense mutations and 0.137+/-0.137% for the synonymous mutation. A table with the 58 non-usual variants of butyrylcholinesterase is also presented.

Possible influence ofBCHE locus of butyrylcholinesterase on stature and body mass index

Butyrylcholinesterase activity has been shown to be positively associated with weight and body mass index (BMI). The present study was carried out to search for an association between variants of the BCHE gene and weight, stature, and BMI on the basis of means and variances compared between nonusual variants and their respective usual controls. Individuals bearing the atypical mutation (N = 52) did not differ from their usual phenotype controls (N = 104) in these parameters. The BCHE*U/BCHE*K individuals (N = 222) presented a significantly higher BMI variance than their BCHE*U/BCHE*U controls (N = 222, F = 1.40, P = 0.012). This higher BMI variance does not seem to be an isolated effect of the K mutation, but appears to be the result of an interaction between the K allele and the usual allele, since no such difference in variance was detected between BCHE*K/BCHE*K individuals (N = 23) and their BCHE*U/BCHE*U (N = 23) controls. These data may suggest a relation between variability in the BCHE locus itself and BMI. Individuals with the BCHE UF phenotype (N = 45) showed a significantly higher mean stature (about 3 cm more; P = 0.02) than their controls with the usual phenotype (N = 135). A role in cell proliferation has been proposed for BCHE, and since growth depends on the number of mitoses, it is not unexpected that variants of this enzyme may influence body stature in different ways. This study reports the first data on the relation of BCHE alleles to anthropometric characters.

Studies on a heterologous complex formed by human butyrylcholinesterase

An electrophoretic band with butyrylcholinesterase activity was detected in 71 CHE2 C5+ and 378 CHE2 C5- individuals and was named C4/5 in view of its similar mobility to either C4 or C5, depending on the pH of the agar gel used. The present data suggest that C4/5 is a heterologous complex of butyrylcholinesterase. Although the C4/5 band may have the same mobility as C5, depending on the conditions of electrophoresis, our hypothesis is that these two bands result from the association of BChE with different molecules.

Variability of the paraoxonase gene (PON1) in Euro- and Afro-Brazilians

The human high-density lipoprotein-associated paraoxonase (EC 3.1.1.2; PON1) plays a role in the hydrolysis of organophosphorus compounds and against the oxidative damage of low-density lipoprotein. In the present study, variants of PON1 (55 and 192) were investigated by PCR-RFLP and PCR-SSCA in Euro- (N = 101) and Afro-Brazilians (N = 70). The PON1*55 and PON1*192 allele frequencies were significantly different in these ethnic groups (p < 0.05 and p < 0.001, respectively). The genotype frequencies for PON1*55 (LL, LM, and MM) in Euro- and Afro-Brazilians were 33, 56, and 11% and 47, 49, and 4%, respectively. The genotype frequencies for PON1*192 were significantly different in Euro- and Afro-Brazilians (QQ, QR, RR: 48, 42, and 10% and 21, 52, and 27%, respectively; p < 0.001). The haplotype frequency distributions were also significantly different in Euro- (LQ = 30.20%; LR = 30.69%; and MQ = 39.11%) and Afro-Brazilians (LQ = 24.97%; LR = 46.46%; MQ = 22.18%; and MR = 6.39%; p < 0.001). Linkage disequilibrium (D) in relation to the maximum expected value was higher in Euro- (100%) than in Afro-Brazilians (58%). We suggest that the high linkage disequilibrium in Caucasians and Asians characterized by the absence or very low frequency of the MR haplotype is mainly due to genetic drift and possibly also to natural selection favoring the PON1*192Q allele or a variant in linkage disequilibrium with it. This seems to be the first study on the PON1 variability at the DNA level in South American samples and one of the few studies on individuals of mixed African origin.