Allosteric inhibition of MTHFR prevents futile SAM cycling and maintains nucleotide pools in one-carbon metabolism.

Methylenetetrahydrofolate reductase (MTHFR) links the folate cycle to the methionine cycle in one-carbon metabolism. The enzyme is known to be allosterically inhibited by SAM for decades, but the importance of this regulatory control to one-carbon metabolism has never been adequately understood. To shed light on this issue, we exchanged selected amino acid residues in a highly conserved stretch within the regulatory region of yeast MTHFR to create a series of feedback-insensitive, deregulated mutants. These were exploited to investigate the impact of defective allosteric regulation on one-carbon metabolism. We observed a strong growth defect in the presence of methionine. Biochemical and metabolite analysis revealed that both the folate and methionine cycles were affected in these mutants, as was the transsulfuration pathway, leading also to a disruption in redox homeostasis. The major consequences, however, appeared to be in the depletion of nucleotides. 13C isotope labeling and metabolic studies revealed that the deregulated MTHFR cells undergo continuous transmethylation of homocysteine by methyltetrahydrofolate (CH3THF) to form methionine. This reaction also drives SAM formation and further depletes ATP reserves. SAM was then cycled back to methionine, leading to futile cycles of SAM synthesis and recycling and explaining the necessity for MTHFR to be regulated by SAM. The study has yielded valuable new insights into the regulation of one-carbon metabolism, and the mutants appear as powerful new tools to further dissect out the intersection of one-carbon metabolism with various pathways both in yeasts and in humans.

Curcumin and cancer biology: Focusing regulatory effects in different signalling pathways.

Cancer is the second-leading cause of death worldwide. Till date, many such effective treatments are available, for example chemotherapy, surgery, and radiation therapy, but there are severe associated side effects, such as increased infection risk, constipation, hair loss, anaemia, among others. Thus, the need for effective therapeutic strategies and screening methodology arises. Researchers around the world are increasingly trying to discover anticancer therapies with as few side effects as possible and many are now focusing on phytochemicals, like curcumin. Curcumin is a bright yellow substance isolated from the plant rhizomes of Curcuma longa L. To this molecule a high therapeutic benefit has been underlined, being able to alter the development of cancer by different mechanisms, such as regulating multiple microRNA expression, modifying a series of signalling pathways, that is, Akt, Bcl-2, PTEN, p53, Notch, and Erbb. Another major pathway that curcumin targets is the matrix metalloproteinase (MMP) gene expression. In fact, MMPs are responsible for the degradation of the cell-extracellular matrix, which can lead to the diseased condition and many different pathways contribute to its activity, such as JAK/STAT, NF-κB, MAPK/ERK, COX-2, ROS, TGF-ß, among others. In this review, we have attempted to describe the curcumin regulatory effect on different cell signalling pathways involved in the progression of different types of cancers.

A multi-threaded approach to genotype pattern mining for detecting digenic disease genes.

To locate disease-causing DNA variants on the human gene map, the customary approach has been to carry out a genome-wide association study for one variant after another by testing for genotype frequency differences between individuals affected and unaffected with disease. So-called digenic traits are due to the combined effects of two variants, often on different chromosomes, while individual variants may have little or no effect on disease. Machine learning approaches have been developed to find variant pairs underlying digenic traits. However, many of these methods have large memory requirements so that only small datasets can be analyzed. The increasing availability of desktop computers with large numbers of processors and suitable programming to distribute the workload evenly over all processors in a machine make a new and relatively straightforward approach possible, that is, to evaluate all existing variant and genotype pairs for disease association. We present a prototype of such a method with two components, Vpairs and Gpairs, and demonstrate its advantages over existing implementations of such well-known algorithms as Apriori and FP-growth. We apply these methods to published case-control datasets on age-related macular degeneration and Parkinson disease and construct an ROC curve for a large set of genotype patterns.

Evolution of tobacco control in India: a narrative review of the legislative and regulatory approach.

Tobacco is the only consumer product that kills half its users yearly. The challenges posed by tobacco control are limitless especially in a country like India where in addition to smoked forms, other smokeless forms of tobacco are also highly prevalent. Apart from being a health hazard tobacco is also a great environmental hazard. Policies for controlling tobacco use also include policy to prevent people from second hand smoke, which is aimed at improvement of air quality. According to the National Non-Communicable Disease Monitoring Survey, 2017-18, daily tobacco use was 32.8% in adults (18-69 years) and 3.1% in adolescents (15-17 years). Overall reduction in tobacco users by 8.1 Million was seen from GATS-1 to GATS-2, and prevalence amongst youth decreased from 18.4 to 12.4%. GYTS-4 (2019) revealed that 8.5% of students, 9.6% of boys and 7.4% of girls-currently used any tobacco products. This makes tobacco control a priority in India. Tobacco control consists of different approaches such as educational, healthcare, legislative, regulatory and fiscal. In the present article we traverse nearly five decades and decode the evolution of legislative, regulatory and fiscal approaches to Tobacco Control in India. A critical evaluation of all these approaches is described in the format of the MPOWER strategy for Tobacco Control which stands for Monitoring Tobacco use, Preventing people from Second Hand Smoke, Offering help to quit, Waring regarding ill effects of tobacco, Enforcing bans and Raising taxes on tobacco products.

Thiol trapping and metabolic redistribution of sulfur metabolites enable cells to overcome cysteine overload.

Cysteine is an essential requirement in living organisms. However, due to its reactive thiol side chain, elevated levels of intracellular cysteine can be toxic and therefore need to be rapidly eliminated from the cellular milieu. In mammals and many other organisms, excess cysteine is believed to be primarily eliminated by the cysteine dioxygenase dependent oxidative degradation of cysteine, followed by the removal of the oxidative products. However, other mechanisms of tackling excess cysteine are also likely to exist, but have not thus far been explored. In this study, we use Saccharomyces cerevisiae, which naturally lacks a cysteine dioxygenase, to investigate mechanisms for tackling cysteine overload. Overexpressing the high affinity cysteine transporter, YCT1, enabled yeast cells to rapidly accumulate high levels of intracellular cysteine. Using targeted metabolite analysis, we observe that cysteine is initially rapidly interconverted to non-reactive cystine in vivo. A time course revealed that cells systematically convert excess cysteine to inert thiol forms; initially to cystine, and subsequently to cystathionine, S-Adenosyl-L-homocysteine (SAH) and S-Adenosyl L-methionine (SAM), in addition to eventually accumulating glutathione (GSH) and polyamines. Microarray based gene expression studies revealed the upregulation of arginine/ornithine biosynthesis a few hours after the cysteine overload, and suggest that the non-toxic, non-reactive thiol based metabolic products are eventually utilized for amino acid and polyamine biogenesis, thereby enabling cell growth. Thus, cells can handle potentially toxic amounts of cysteine by a combination of thiol trapping, metabolic redistribution to non-reactive thiols and subsequent consumption for anabolism.

Study on gluco-regulatory potential of glimepiride sulfonamide using in silico, in vitro and in vivo approaches.

Glimepiride sulfonamide (GS) is a drug intermediate to synthesize glimepiride (antidiabetic drug). We hypothesized that GS exerts gluco-regulatory effect because GS is comprised of the structural components of dipeptidyl peptidase-IV (DPP-IV) inhibitors sitagliptin and DPP-728and glimepiride (sulfonylurea based antidiabetic drug).We analyzed the drug-likeness and docking efficiency of GS with DPP-IV using in silico tools. Also DPP-IV inhibition assays were conducted in vitro. Gluco-regulatory potential and parameters of drug safety were evaluated on normal euglycemic and streptozotocin (STZ) induced diabetic rats. We observed strong drug-likeness and DPP-IV binding efficiency of GS. Similarly, profound DPP-IV inhibition was also observed in vitro. Studies on euglycemic and STZ induced diabetic rats revealed antidiabetic potential for GS without significant change in the studied toxicological parameters. Glimepiride sulfonamide has antidiabetic potential mainly through DPP-IV inhibition, but also through insulin stimulation and alpha-amylase inhibition.