CNS & Neurological Disorders - Drug Targets - Volume 13, Issue 3, 2014

Imbalances in gut microbiota are associated with metabolic disorder, which are a group of obesity-related metabolic abnormalities that increase an individual’s risk of developing type 2 diabetes (T2D) and Alzheimer’s disease (AD). Although a number of risk factors have been postulated that may trigger the development of AD, the root cause of this disease is still a matter of debate. This review further investigates the etiology of AD by accumulating the current role played by gut microbiota in human, and trying to establish an inter-link between T2D and AD pathogenesis. There is a growing body of evidence which suggests that obesity is associated with alteration in the normal gut flora, reduced bacterial diversity, metabolic pathways and altered representation of bacterial genes. Obesity and T2D are considered to be induced as a result of changes within the composition of gut microbiota. The evidence gathered so far clearly advocates the involvement of gut microbes in causing obesity, a state of chronic and low-grade inflammation. Hence, understanding the microbiota of the gut is significant in relation to inflammation, as it is a key contributor for diabetes which has a direct relation to the AD pathogenesis. Comparative analysis of gut microbiota may enable further novel insight into the complex biology of AD, which is very important in order to take preventive measure such as early diagnosis, identification of new therapeutic targets and development of novel drugs.

This review presents a concise update on the inhibitors of the neuroenzyme, acetylcholinesterase (AChE; EC 3.1.1.7). AChE is a serine protease, which hydrolyses the neurotransmitter, acetylcholine into acetate and choline thereby terminating neurotransmission. Molecular interactions (mode of binding to the target enzyme), clinical applications and limitations have been summarized for each of the inhibitors discussed. Traditional inhibitors (e.g. physostigmine, tacrine, donepezil, rivastigmine etc.) as well as novel inhibitors like various physostigmine-derivatives have been covered. This is followed by a short glimpse on inhibitors derived from nature (e.g. Huperzine A and B, Galangin). Also, a discussion on ‘hybrid of pre-existing drugs’ has been incorporated. Furthermore, current status of therapeutic applications of AChEinhibitors has also been summarized.

Objectives: The present study compares the role and significance of non-high density lipoproteins (non-HDL) cholesterol level in pre-diabetic and diabetic patients. This study also compares non-HDL cholesterol level between males and females and with different age groups as well. Methods: An observational study was conducted among 3830 randomly selected individuals to envisage the association of non-HDL cholesterol and other lipid parameters with age, gender, and diabetic status. On the basis of health status, the subjects were classified as diabetic, pre-diabetic and normal. Fasting blood samples were collected and analyzed on Roche p-800 modular system. Total cholesterol, high density lipoproteins (HDL), low density lipoproteins (LDL) and fasting triglycerides were also measured. From the above mentioned parameters, the level of non-HDL cholesterol level was also calculated. Results: Significant association was observed with non-HDL cholesterol level and all other studied lipid parameters (total cholesterol, HDL, LDL and triglycerides) compared with age and gender of the subjects studied. Moreover, the calculated non-HDL level, total cholesterol and triglycerides were found to be significantly co-related with diabetic status of the patients involved in the study. However, HDL and LDL values did not show any significant association with diabetic status of the patients. Conclusion: In this study, we found that age and gender of the studied subjects are associated with non-HDL cholesterol. Moreover, our data clearly indicates the positive association of non-HDL cholesterol level with pre-diabetic and diabetic status of the patients. Based on our study, we recommend estimation of non-HDL level in routine clinical practice to differentiate pre-diabetic and diabetic patients.

Diabetes mellitus (DM) is characterized by hyperglycemia either due to deficient insulin production (Type 1 Diabetes mellitus) or peripheral insulin resistance of the cells (Type 2 Diabetes mellitus). Both Type 1 Diabetes mellitus and Type 2 Diabetes mellitus are more prevalent and efforts are directed to actively control these metabolic syndromes. Currently, Alzheimer’s disease (AD), is gaining popularity as ‘Type 3 diabetes’ or ‘Diabetes of the brain’ and it is now evident that this neurodegenerative disease has multiple shared pathology with DM. Alarming is the fact that the incidence of AD might double within the next two decades, and this is certain to cause devastating effects not only to the afflicted individual or the family, but also to the global economy. Methods to either delay the onset or inhibit the progression of AD are therefore necessary. Progressive dementia, increased deposition of amyloid- β protein, neurofibrillary tangles and neuritic plaques in the brain are some of the hallmarks of AD. More understanding of the disease at the cellular and molecular level will enable identifying the possible targets for intervention and pave way for either development of novel or modification of the existing therapeutic options. In this work we have performed semantic data mining analysis on a large collection of most recently published data and identified an updated list of common genes expressed in DM and AD. Functional analysis of these genes revealed both existing and missing links involved in a bigger network associated with both disease conditions. Thus we argue that computational analysis methods help not only in understanding the mechanistic links but also in narrowing down precise targets (genes, proteins, metabolites and signalling pathways) and provide the base for both disease intervention and development of therapeutic options.

Parkinson’s disease (PD) is the second most common neurodegenerative disease afflicting about 1% of people over 65 years old and 4-5% of people over 85 years. It is proposed that a cascade of deleterious factors is set in motion within that neuron made not of one, but rather of multiple factors such as free radicals, excitotoxicity, neuroinflammation, and apoptosis to cite only some of the most salient. In this scenario, chronic systemic inflammation, as well as impaired mitochondrial metabolism, have also been suspected of playing a role in the development of type-2 diabetes, and the possibility of a shared pathophysiology of PD and type-2 diabetes has been proposed. The discussion about the interactions between PD and type-2 diabetes mellitus began in the 1960’s and there is still controversy. Insulin and dopamine may exert reciprocal regulation hence; hypoinsulinemia induced by streptozotocin decreased the amounts of dopamine transporter and tyrosine hydroxylase transcripts in the substantia nigra pars compacta. Accordingly, dopamine depletion in the striatum is able to decreases insulin signaling in basal ganglia, indicating that, perhaps, PD may be considered as a risk factor for the development of type-2 diabetes mellitus. In this sense, it is described that peroxisome proliferator-activated receptor-γ, ATP-sensitive K+ channels, AMP-activated protein kinase, glucagon-like peptide-1 and dipeptidyl peptidase-4 are important therapeutic targets for PD and reinforces the association with diabetes. Therefore, the objective of the present review is to contextualize the mutual pathophysiological interactions between PD and type-2 diabetes mellitus, as well as the potential common treatments.

Diabetes mellitus type 2 is a metabolic disorder characterized by high blood glucose due to insulin deficiency or resistance. Alzheimer's disease (AD) is a complex neurodegenerative disease leading to irreversible loss of neurons, intellectual abilities, memory and reasoning. The worldwide prevalence of diabetes and AD in elderly population is a major public health concern. Interestingly, both health issues are unraveling the puzzling links. The clinico-pathological relationship between diabetes and AD has been reported at genomic and proteomic levels. The association of virus infection in type 2 diabetes mellitus and AD has been reported in few recent studies, some have shown direct evidence of virus infection in diabetes and AD while other have shown that diabetes increases the risk of developing AD. This review aims to summarize the association of few common viruses like Hepatitis C Virus and Herpes Simplex Virus-1 which affects both these two age-related devastating diseases. We also discuss the pathological links of Influenza virus, Cytomegalovirus, West Nile virus, Enterovirus, Herpes Simplex Virus-2, Hepatitis viruses in diabetes and Influenza virus, Picornavirus and Borna disease virus in AD. Establishing such relationships and defining their common pathogenesis and patho-physiological mechanisms may lead to new concepts and paths for developing novel preventive strategies and pharmacological treatment options for diabetes and AD. This study may aid in future for the identification of a single or a panel of likely blood-based viral biomarkers for early diagnosis of diabetes and AD with high sensitivity and specificity.

Alzheimer's disease is a progressive degenerative disease of the brain marked by gradual and irreversible declines in cognitive functions. Acetylcholinesterase (AChE) plays a biological role in the termination of nerve impulse transmissions at cholinergic synapses by rapid hydrolysis of its substrate, "acetylcholine". The deficit level of acetylcholine leads to deprived nerve impulse transmission. Thus the cholinesterase inhibitors would reverse the deficit in acetylcholine level and consequently may reverse the memory impairments, which is characteristic of the Alzheimer's disease. The molecular interactions between AChE and Carnosic acid, a well known antioxidant substance found in the leaves of the rosemary plant has always been an area of interest. Here in this study we have performed in silico approach to identify carnosic acid derivatives having the potential of being a possible drug candidate against AChE. The best candidates were selected on the basis of the results of different scoring functions.

Acetylcholinesterase (AChE) is a primary target for Alzheimer’s therapy while recently sodium glucose cotransporter 2 (SGLT2) has gained importance as a potential target for Type 2 Diabetes Mellitus (T2DM) therapy. The present study emphasizes the molecular interactions between a new Food and Drug Administration (FDA) approved antidiabetic drug ‘Invokana’ (chemically known as Canagliflozin) with AChE and SGLT2 to establish a link between the treatment of T2DM and Alzheimer’s Disease (AD). Docking study was performed using ‘Autodock4.2’. Both hydrophobic and π-π interactions play an important role in the correct positioning of Canagliflozin within SGLT2 and catalytic site (CAS) of AChE to permit docking. Free energy of binding (δG) for ‘Canagliflozin-SGLT2’ interaction and ‘Canagliflozin - CAS domain of AChE’ interaction were found to be -10.03 kcal/mol and -9.40 kcal/mol, respectively. During ‘Canagliflozin-SGLT2’ interaction, Canagliflozin was found to interact with the most important amino acid residue Q457 of SGLT2. This residue is known for its interaction with glucose during reabsorption in kidney. However, ‘Canagliflozin-CAS domain of AChE’ interaction revealed that out of the three amino acids constituting the catalytic triad (S203, H447 and E334), two amino acid residues (S203 and H447) interact with Canagliflozin. Hence, Invokana (Canagliflozin) might act as a potent dual inhibitor of AChE and SGLT2. However, scope still remains in the determination of the three-dimensional structure of SGLT2-Canagliflozin and AChE-Canagliflozin complexes by X-ray crystallography to validate the described data. Since the development of diabetes is associated with AD, the design of new AChE inhibitors based on antidiabetic drug scaffolds would be particularly beneficial. Moreover, the present computational study reveals that Invokana (Canagliflozin) is expected to form the basis of a future dual therapy against diabetes associated neurological disorders.

The present study elucidates molecular interactions of human acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and 5-lipoxygenase (5-LPO) with a novel natural ligand Galangin (GAL); and also with the well-known ligands Bisnorcymserine (BNC) and Cymserine for comparison. Docking between these ligands and enzymes were performed using ‘Autodock4.2’. It was found that hydrophobic interactions play an important role in the correct positioning of BNC within the ‘catalytic site’ of AChE, BuChE and 5-LPO to permit docking while hydrogen bonds are significant in case of cymserine for the same. However, only polar interactions are significant in the correct positioning of GAL within the ‘catalytic site’ of AChE, BuChE and 5-LPO to permit docking. Such information may aid in the design of versatile AChE, BuChE and 5 LPO-inhibitors, and is expected to aid in safe clinical use of above ligands. Scope still remains in the determination of the three-dimensional structure of AChE-GAL, BuChE-GAL and 5-LPO-GAL complex by X-ray crystallography to certify the described data. Moreover, the present study confirms that GAL is a more efficient inhibitor of human brain AChE compared to BNC and cymserine, while in case of 5-LPO and human brain BuChE, BNC is a more efficient inhibitor compared to GAL and cymserine with reference to δG and Ki values.

Chronic infection can cause slow progressive dementia, cortical atrophy and amyloid deposition in the atrophic form of general paresis. Due to the fact that specific bacterial ligands can increase the expression of proinflammatory molecules that can activate innate and adaptive immune systems, inflammation may play a significant role in the pathogenesis of Alzheimer’s disease (AD). Furthermore, there is a significant association between AD and various types of spirochete. Periodontitis is a prevalent and persistent peripheral infection that is associated with gram-negative anaerobic bacteria and is capable of showing localized and systemic infections in the host. Periodontal disease related pathogens and their inflammatory products contribute to systemic inflammation and the pathogenesis of AD. In this minireview, we propose a hypothetical link between periodontitis, type 2 diabetes and AD. We also present the possible mechanistic links between periodontitis-related inflammation, type 2 diabetes and AD. Since this condition is treatable, periodontitis may be a readily-modifiable risk factor for AD.

Alzheimer disease (AD) and type 2 diabetes mellitus (T2DM) are chronic health disorders that affect millions of people around the world. According to recent studies, there are molecular similarities in the inflammatory pathways involved in both AD and T2DM, which opens a new avenue for researchers with different perspectives to target the cause of these diseases rather than their obvious symptoms. Several links between inflammation, cardiovascular disease, T2DM and central nervous system disorders such as AD and Parkinson’s disease have been elucidated. Mutations in the hippocampal-β-amyloid precursor protein gene in genetically high-risk individuals have been shown to cause the early onset of AD symptoms. The overexpression of β-amyloid protein in the hippocampal region and the synaptotoxicity that occurs as a result have been considered a typical feature of AD and leads to neuronal loss and cognitive decline. However, the identity of the cellular components that cause the late onset of the disease seen in the majority of the cases is still unknown. Synaptic insults associated with neuronal dysfunction may involve several cascades and molecules, one of which has been hypothesized to be tyrosine hydroxylase (TH). The axons of the noradrenergic cells that project to the hippocampus appear to be affected by the β-amyloid protein, which subsequently contributes to TH loss in Alzheimer brain cells. In this review, we attempt to shed light on the important mechanisms involved in AD as well as T2DM such as inflammatory factors, abnormalities in the insulin signaling system and the possible role of the endocrine enzyme TH.

Alzheimer's disease (AD) and type 2 diabetes (T2D) are both prevalent in older individuals and have gained significant attention due to alarming rates of increase. The high incidences of these diseases pose a great socioeconomic burden and cause major public health concerns worldwide. A number of studies have established potential links between AD and T2D, supporting the hypothesis that T2D is linked with an increased risk of AD and that controlling diabetes could have a positive impact on the prevention of AD. At present, both diseases lack precise diagnostic approaches for early intervention and effective cure. Further, the currently available diagnostic tools for AD screening are insufficiently sensitive and robust for preventive measures. Although several drugs are used for the treatment of both these diseases, none of these drugs offers complete remission of the disease, merely symptomatic relief. Moreover, these drugs have limited efficacy because of problems such as conventional drug delivery systems beyond the blood brain barrier, a lack of target specificity and diminished potency. From this perspective, the emerging field of nanotechnology has offered new techniques and tools to overcome these challenges. In this review, we discuss the direct and indirect limitations of existing therapies and describe alternative potential nanotechnological approaches that could be utilized to overcome these limitations. New insight in the field of nanomedicine is necessary for early diagnosis, the development of novel drug therapies, the action of drugs and prevention, as well as for gaining an in-depth understanding of the complex biology of both diseases.

The present study emphasizes the molecular interactions between human brain acetylcholinesterase (AChE) and the natural ligand Huperzine-B and its comparison to ‘AChE-Tolserine interactions’. Docking between Huperzine-B and AChE was performed using ‘Autodock4.2’. Hydrophobic interactions and hydrogen bonds both play an equally important role in the correct positioning of Huperzine-B within the ‘catalytic site’ of AChE to permit docking. However, docking of Tolserine to AChE is largely dominated by hydrophobic interactions. Such information may aid in the design of versatile AChE-inhibitors, and is expected to aid in safe clinical use of Huperzine-B. Scope still remains in the determination of the three-dimensional structure of AChE-Huperzine-B complex by X-ray crystallography to validate the described data. Furthermore, this study confirms that Huperzine-B is a more efficient inhibitor of human brain AChE compared to tolserine with reference to Ki and δG values.

Alzheimer's disease, the most important neurodegenerative disorder, is an irreversible, age-dependent disease of the brain characterized by problems in progressive impairments in memory, language, reasoning, behavior and visuospatial skills. It is characterized by the deposition of amyloid beta peptide, forming compact fibrillar plaques and neurofibrillary tau tangles. Another major and much more prevalent cause of morbidity and mortality in world is diabetes especially type 2 diabetes mellitus. It is caused by a combination of resistance to insulin action and an inadequate compensatory insulin secretory response. Chronic wounds caused by antibiotic resistant bacterial infections that fail to heal are a common complication of diabetes mellitus and the most frequent reason for nontraumatic lower limb amputation. Holistically, these two diseases are linked at molecular level but the exact mechanism is a topic of debate. Bacteriophages are viruses infecting bacteria and lack ability to infect mammalian cells. They are neither causative agent for Alzheimer's disease or type 2 diabetes mellitus nor involved in their pathogenicity but promises for a novel divergent therapeutic approach. The great versatility of the phage system has led to the development of improved phage delivery vectors, as well as immunomodulation of anti-amyloid beta peptide response. Phages could also constitute valuable prophylaxis against bacterial infections, especially in immunocompromised patients like in the case of diabetes. Patients having diabetes have a high risk of developing foot ulcers which are difficult to be treated by antibiotics alone due to ever increasing antibiotic resistance strains. Combination therapy based on multiple phage and broad spectrum antibiotics holds great promise. The potential therapeutic phage therapy arises from its lack of natural tropism for mammalian cells, resulting in no adverse effects.

Meta-analysis methods exist for combining multiple microarray datasets. However, there are a wide range of issues associated with microarray meta-analysis and a limited ability to compare the performance of different metaanalysis methods. Using cDNA microarray technology (Partek Genomics Suite 6.6) and global pathway analysis with Ingenuity Pathway Analysis tool (IPA, Inc), we examined the transcript level in type 2 diabetes mellitus (T2DM) and Alzheimer’s disease (AD) patients and controls. To understand the molecular link between T2DM and AD, we compared the gene expression pattern and pathway involved. Microarray analysis identified 235 differentially expressed genes between T2DM patients and controls; and 834 between AD and controls at two fold change and a false discovery rate of 0.05. Significantly changed expression of “myeloid leukemia cell differentiation protein 1; RAS guanyl releasing protein 1; S100 calcium-binding protein A8; prostaglandin- endoperoxide synthase 2; parvalbumin; endoplasmic reticulum aminopeptidase 1; phosphoglycerate kinase 1; Eukaryotic translation initiation factor 3 subunit F; Interleukin-1 beta; tubulin, beta 2A; glycine receptor alpha 1 and ribosomal protein S24” genes were highly associated with T2DM, whereas “neuronal differentiation 6; G-protein coupled receptor 83; phosphoserine phosphatase; bobby sox homolog or HMG box -containing protein 2; Glutathione S-transferase theta 1; alpha-2-glycoprotein 1 zinc-binding; Heat shock 70kDa protein 1B; transportin 1, Acidic leucine-rich nuclear phosphoprotein 32 family member B; Nuclear factor of activated T-cells 5; inositol 1,4,5-trisphosphate 3-kinase B; prenylcysteine oxidase 1 like” were found to be strongly related with AD. We also found a set of differentially expressed genes; “ARP2 actin-related protein 2; Cell division control protein 42; cytoplasmic polyadenylation element binding protein 4; Early growth response protein 1; ectonucleotide pyrophosphatase/phosphodiesterase 5; folate receptor 1; glutamate-ammonia ligase; hydroxy-3-methylglutaryl-Coenzyme A reductase; 3-hydroxy-3- methylglutaryl-CoA synthase; interleukin 1 receptor- like 1; leukemia inhibitory factor receptor; metastasis associated lung adenocarcinoma transcript 1; pyruvate dehydrogenase kinase, isozyme 4; phosphoserine phosphatase, parvalbumin, and tubulin, beta 2A” to be present in both dataset. Altered regulation of intracellular signaling pathways, including Ephrin receptor, liver X receptor/ retinoid X receptor; interleukin 6; insulinlike growth factor 1; interleukin 10 and 14-3-3-mediated signaling pathways were associated with T2DM as well as Alzheimer-type pathology. Our findings implicate diabetic disorders in the pathogenesis of AD, and provide a basis for future candidate studies based on specific pathways.

Insulin-degrading enzyme (IDE) is a key protease involved in degrading insulin and amyloid peptides in human body. Several non-synonymous genetic mutations of IDE gene have been recently associated with susceptibility to both diabetes and Alzheimer’s diseases. However, the consequence of these mutations on the structure of IDE protein and its substrate binding characteristics is not well elucidated. The computational investigation of genetic mutation consequences on structural level of protein is recently found to be an effective alternate to traditional in vivo and in vitro approaches. Hence, by using a combination of empirical rule and support vector machine based in silico algorithms, this study was able to identify that the pathogenic nonsynonymous genetic mutations corresponding to p.I54F, p.P122T, p.T533R, p.P581A and p.Y609A have more potential role in structural and functional deviations of IDE activity. Moreover, molecular modeling and secondary structure analysis have also confirmed their impact on the stability and secondary properties of IDE protein. The molecular docking analysis of IDE with combinational substrates has revealed that peptide inhibitors compared to small non-peptide inhibitor molecules possess good inhibitory activity towards mutant IDE. This finding may pave a way to design novel potential small peptide inhibitors for mutant IDE. Additionally by un-translated region (UTR) scanning analysis, two regulatory pathogenic genetic mutations i.e., rs5786997 (3’ UTR) and rs4646954 (5’ UTR), which can influence the translation pattern of IDE gene through sequence alteration of upstream-Open Reading Frame and Internal Ribosome Entry Site elements were identified. Our findings are expected to help in narrowing down the number of IDE genetic variants to be screened for disease association studies and also to select better competitive inhibitors for IDE related diseases.

Alzheimer’s disease (AD) is a neurodegenerative disorder that leads to memory problems. It has been associated with type 2 diabetes mellitus at both the molecular and biochemical level. Pancreatic cells have molecular similarities to the brain at the transcriptomic and proteomic levels. Several genes have been reported to be responsible for both AD and diabetes. Currently, no proper treatment is available but various therapeutic approaches are utilized worldwide for the management of these disorders and may be nanoparticles and herbal treatment of Bacopa monnieri will make promise for the treatment of AD in future. The formation of amyloids in neurons and the formation of amylin in pancreatic cells are potential links between these two disorders, which can be silent killers.

The prevalence of Alzheimer’s disease (AD) is higher among type 2 diabetes mellitus (T2DM) patients. In T2DM patients, the progression of AD is more rapid. Furthermore, several pathophysiological pathways are common to AD and T2DM. Humanin is a recently introduced, mitochondrial-derived peptide with neuroprotective effects. Humanin can alter the mechanisms involved in AD and T2DM pathogenesis. Insulin resistance as well as oxidative stress has been shown to be associated with increased amyloid deposition in brain neurons and islet beta cells. Moreover, advanced glycation end products and lipid metabolism disorders are common pathways of oxidative stress and low-grade systemic inflammation in AD and T2DM. These common pathways may explain AD and T2DM pathogenesis and suggest common treatments for both diseases. Treatments for T2DM and AD attempt to slow cognitive decline, and recent investigations have focused on agents that may alter pathways common to AD and T2DM pathogenesis. Non-steroidal antiinflammatory drugs, such as interleukin-1 antagonists and statins, are possible drug candidates for both AD and T2DM.