Chapter 3 Folate Deprivation, the Methionine Cycle, and Alzheimer's Disease

Association between Alzheimer's disease, MAPT gene mutation and some biochemical biomarkers

Alzheimer's Disease (AD) is a multifactorial neurodegenerative disease and there is still no definitive treatment today. Early diagnosis of the disease is important, but there are almost no biomarkers that can be used in early diagnosis. The cerebrospinal fluid used in the diagnosis of the disease is not sufficient and is very difficult to obtain. Therefore, blood biomarkers that are less costly, less invasive, easily accessible, and can be used in long-term studies would be a better alternative. The aim of this study is to determine the relationship between Alzheimer's Disease and P301L MAPT gene mutation, homocysteine, folate and uric acid. 101 Alzheimer's patients and 101 healthy individuals were included in this study. Mutation analysis was performed using the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method with blood samples taken from the subjects. There was no significant difference between the patient and control groups in terms of homocysteine (p = 0.771), folate (p = 0.366) and uric acid (p = 0.860). When the genotypes were compared between the patient and control groups in terms of MAPT gene mutation (P301L), no statistically significant difference was detected (p = 0.081). There are very few studies in the literature investigating the relationship between Alzheimer's disease and P301L MAPT gene mutation. Additionally, there is no study investigating the relationship between Alzheimer's disease and homocysteine, folate, uric acid and P301L MAPT mutation in the Turkish population. We believe that this study has shed light on future studies.

High water temperature raised the requirements of methionine for spotted seabass (Lateolabrax maculatus)

This study evaluated the effects of dietary methionine level and rearing water temperature on growth, antioxidant capacity, methionine metabolism, and hepatocyte autophagy in spotted seabass (Lateolabrax maculatus). A factorial design was used with six methionine levels [0.64, 0.85, 1.11, 1.33, 1.58, and 1.76%] and two temperatures [moderate temperature (MT): 27 ℃, and high temperature (HT): 33 ℃]. The results revealed the significant effects of both dietary methionine level and water temperature on weight gain (WG) and feed efficiency (FE), and their interaction effect was found on WG (P < 0.05). In both water temperatures tested, fish WG increased with increasing methionine level up to 1.11% and decreased thereafter. The groups of fish reared at MT exhibited dramatically higher WG and FE than those kept at HT while an opposite trend was observed for feed intake. Liver antioxidant indices including reduced glutathione and malondialdehyde (MDA) concentrations, and catalase and superoxide dismutase (SOD) activities remarkably increased in the HT group compared to the MT group. Moreover, the lowest MDA concentration and the highest SOD activity were recorded at methionine levels between 1.11% and 0.85%, respectively, regardless of water temperatures. Expression of methionine metabolism-related key enzyme genes (mat2b, cbs, ms, and bhmt) in the liver was increased at moderate methionine levels, and higher expression levels were detected at MT compared to HT with the exception of ms gene relative expression. Relative expression of hepatocyte autophagy-related genes (pink1, atg5, mul1, foxo3) and hsp70 was upregulated by increasing methionine level up to a certain level and decreased thereafter and increasing water temperature led to significantly enhanced expression of hsp70. In summary, HT induced heat stress and reduced fish growth, and an appropriate dietary methionine level improved the antioxidant capacity and stress resistance of fish. A second-order polynomial regression analysis based on the WG suggested that the optimal dietary methionine level for maximum growth of spotted seabass is 1.22% of the diet at 27 ℃ and 1.26% of the diet at 33 ℃, then 1.37 g and 1.68 g dietary methionine intake is required for 100 g weight gain at 27 ℃ or 33 ℃, respectively.

Improvement of cognitive performance by a nutraceutical formulation: Underlying mechanisms revealed by laboratory studies

Cognitive decline, decrease in neuronal function and neuronal loss that accompany normal aging and dementia are the result of multiple mechanisms, many of which involve oxidative stress. Herein, we review these various mechanisms and identify pharmacological and non-pharmacological approaches, including modification of diet, that may reduce the risk and progression of cognitive decline. The optimal degree of neuronal protection is derived by combinations of, rather than individual, compounds. Compounds that provide antioxidant protection are particularly effective at delaying or improving cognitive performance in the early stages of Mild Cognitive Impairment and Alzheimer's disease. Laboratory studies confirm alleviation of oxidative damage in brain tissue. Lifestyle modifications show a degree of efficacy and may augment pharmacological approaches. Unfortunately, oxidative damage and resultant accumulation of biomarkers of neuronal damage can precede cognitive decline by years to decades. This underscores the importance of optimization of dietary enrichment, antioxidant supplementation and other lifestyle modifications during aging even for individuals who are cognitively intact.

Modelling and Simulation of Biochemical Processes Using Petri Nets

Systems composed of many components which interact with each other and lead to unpredictable global behaviour, are considered as complex systems. In a biological context, complex systems represent living systems composed of a large number of interacting elements. In order to study these systems, a precise mathematical modelling was typically used in this context. However, this modelling has limitations in the structural understanding and the behavioural study. In this sense, formal computational modelling is an approach that allows to model and to simulate dynamical properties of these particular systems. In this paper, we use Hybrid Functional Petri Net (HFPN), a Petri net extension dedicated to study and verify biopathways, to model and study the Methionine metabolic pathway. Methionine and its derivatives play significant roles in human bodies. We propose a set of simulations for the purpose of studying and analysing the Methionine pathway’s behaviour. Our simulation results have shown that several important abnormalities in this pathway are related to sever diseases such as Alzheimer’s disease, cardiovascular disease, cancers and others.

Methionine and/or Methionine Sulfoxide Alter Ectoenzymes Activities in Lymphocytes and Inflammatory Parameters in Serum from Young Rats: Acute and Chronic Effects

In this study we investigated the effect of acute and chronic treatment with Met and/or methionine sulfoxide (MetO) on ectonucleotidases and cholinesterases activities from lymphocytes and purine derivatives compounds, C-protein reactive, interleukin-10, interleukin-6, and tumor necrosis factor-α levels in serum of young rats. Adenosine triphosphate hydrolysis was decreased in lymphocytes 1 h after treatment by MetO and Met + MetO. However, adenosine triphosphate and adenosine diphosphate hydrolysis in lymphocytes was increased in the groups MetO and Met + MetO and adenosine deaminase activity was increased in MetO 3 h after the treatment. Acetylcholinesterase activity was increased in lymphocytes after 3 h and 21 days of treatment by MetO and Met + MetO, while serum butyrycholinesterase activity was decreased after 1 h and 21 days of treatment in the same groups. In chronic treatment, interleukin-6 and tumor necrosis factor-α level were increased, while that interleukin-10 level was decreased by Met, MetO, and Met + MetO when compared to control group. C-protein reactive level was increased by MetO and Met + MetO. Adenosine triphosphate and adenosine monophosphate levels were reduced in all amino acids treated groups, while adenosine diphosphate and hypoxanthine were enhanced by MetO and Met + MetO. Adenosine and xanthine were reduced in the MetO group, whereas inosine levels were decreased in the MetO and Met + MetO groups. These findings help to understand the inflammatory alterations observed in hypermethioninemia.

Vitamin Supplementation as an Adjuvant Treatment for Alzheimer's Disease

Alzheimer's Disease (AD) is a slowly progressing neurodegenerative disorder representing a major health concern worldwide. This disorder is characterised by progressive dementia and cognitive decline. The pathological hallmarks of AD include the presence of Aβ plaques and tau neurofibrils. Research has shown that oxidative stress represents a major risk factor associated with AD pathology. Accumulation of Aβ plaques and relative lack of antioxidant defence mechanisms, including cellular antioxidant enzymes and dietary antioxidants like vitamins, assist in the exacerbation of oxidative stress. Reactive Oxygen Species (ROS) produced as the result of oxidative stress, that increase structural and functional abnormalities in brain neurons, which then manifests as dementia and decline in cognition. Data from numerous epidemiological studies suggests that nutrition is one of the most important yet modifiable risk factors for AD. Since oxidative stress contributes a great deal in the development and progression of AD, anything that could attenuate oxidative stress would help in decreasing the prevalence and incidence of AD. There is increasing evidence that supports the use of different antioxidant as an adjuvant treatment for AD. Vitamins are one such antioxidant that can be used as an adjuvant in AD treatment. This paper will focus on the evidence, based on current literature, linking the use of vitamin supplementations as an adjuvant treatment for AD.

Nutritional determinants of cognitive aging and dementia

The objective of this review is to provide an overview of nutritional factors involved in cognitive aging and dementia with a focus on nutrients that are also important in neurocognitive development. Several dietary components were targeted, including antioxidant nutrients, dietary fats and B-vitamins. A critical review of the literature on each nutrient group is presented, beginning with laboratory and animal studies of the underlying biological mechanisms, followed by prospective epidemiological studies and randomised clinical trials. The evidence to date is fairly strong for protective associations of vitamin E from food sources, the n-3 fatty acid, DHA, found in fish, a high ratio of polyunsaturated to saturated fats, and vitamin B12 and folate. Attention to the level of nutrient intake is crucial for interpreting the literature and the inconsistencies across studies. Most of the epidemiological studies that observe associations have sufficient numbers of individuals who have both low and adequate nutrient status. Few of the randomised clinical trials are designed to target participants who have low baseline status before randomising to vitamin supplement treatments, and this may have resulted in negative findings. Post-hoc analyses by some of the trials reveal vitamin effects in individuals with low baseline intakes. The field of diet and dementia is a relatively young area of study. Much further work needs to be done to understand dietary determinants of cognitive aging and diseases. Further, these studies must be particularly focused on the levels of nutrient intake or status that confer optimum or suboptimal brain functioning.

Distribution of methionine between cells and incubation medium in suspension of rat hepatocytes

Methionine is an essential amino acid involved in many significant intracellular processes. Aberrations in methionine metabolism are associated with a number of complex pathologies. Liver plays a key role in regulation of blood methionine level. Investigation of methionine distribution between hepatocytes and medium is crucial for understanding the mechanisms of this regulation. For the first time, we analyzed the distribution of methionine between hepatocytes and incubation medium using direct measurements of methionine concentrations. Our results revealed a fast and reversible transport of methionine through the cell membrane that provides almost uniform distribution of methionine between hepatocytes and incubation medium. The steady-state ratio between intracellular and extracellular methionine concentrations was established within a few minutes. This ratio was found to be 1.06±0.38, 0.89±0.26, 0.67±0.16 and 0.82±0.06 at methionine concentrations in the medium of 64±19, 152±39, 413±55, and 1,204±104 μmol/L, respectively. The fast and uniform distribution of methionine between hepatocytes and extracellular compartments provides a possibility for effective regulation of blood methionine levels due to methionine metabolism in hepatocytes.

The logic of the hepatic methionine metabolic cycle

This review describes our current understanding of the "traffic lights" that regulate sulfur flow through the methionine bionetwork in liver, which supplies two major homeostatic systems governing cellular methylation and antioxidant potential. Theoretical concepts derived from mathematical modeling of this metabolic nexus provide insights into the properties of this system, some of which seem to be paradoxical at first glance. Cellular needs supported by this network are met by use of parallel metabolic tracks that are differentially controlled by intermediates in the pathway. A major task, i.e. providing cellular methylases with the methylating substrate, S-adenosylmethionine, is met by flux through the methionine adenosyltransferase I isoform. On the other hand, a second important function, i.e., stabilization of the blood methionine concentration in the face of high dietary intake of this amino acid, is achieved by switching to an alternative isoform, methionine adenosyltransferase III, and to glycine N-methyl transferase, which together bypass the first two reactions in the methionine cycle. This regulatory strategy leads to two metabolic modes that differ in metabolite concentrations and metabolic rates almost by an order of magnitude. Switching between these modes occurs in a narrow trigger zone of methionine concentration. Complementary experimental and theoretical analyses of hepatic methionine metabolism have been richly informative and have the potential to illuminate its response to oxidative challenge, to methionine restriction and lifespan extension studies and to diseases resulting from deficiencies at specific loci in this pathway.

Elevated cerebrospinal fluid and plasma homocysteine levels in ALS

BACKGROUND

High cerebrospinal fluid (CSF) and plasma levels of homocysteine (HC) have been reported in certain neurodegenerative disorders, such as Alzheimer's, Parkinson's diseases and, recently, amyotrophic lateral sclerosis (ALS).

OBJECTIVES

To assay the CSF and plasma levels of HC in ALS patients and controls, and to evaluate the relationship between HC levels and clinical variables of the disease.

METHODS

Cerebrospinal fluid from sixty-nine (M/F 1.87) and plasma from sixty-five ALS patients (M/F 1.83) were taken and stored at -80 degrees C until use. Controls (CSF = 55; plasma = 67) were patients admitted to our hospital for neurological disorders with no known relationship to HC changes. CSF and plasma from ALS patients and controls were obtained as a necessary step of the diagnostic workup. HC levels in CSF and plasma were assayed using a high performance liquid chromatograph (HPLC) and a fluorimeter detector.

RESULTS

The median level of total HC in the CSF of ALS patients was 0.46( )microM, significantly higher than that of the controls (0.24 microM, +91.6%, P < 0.001). A similar trend was observed when HC was assayed in plasma (ALS, 12.4 microM vs. controls, 7.26 microM, +70.8%, P < 0.001). The CSF and plasma HC levels showed no relationship with the disease progression, age at onset, and the site of onset.

CONCLUSIONS

Homocysteine is a biochemical marker in ALS, and it might be related to the pathophysiology of the disease.