Prevalence, associated risk factors; and patient and economic impact of multiple sensory impairment in a multi-ethnic elderly population in Singapore: the PIONEER study.

BACKGROUND: To determine the prevalence, risk factors; and impact on patient health and economic outcomes across the laterality spectrum of multiple sensory impairment (MSI) in a multi-ethnic older Asian population. METHODS: In this population-based study of Singaporeans aged ≥ 60 years, MSI was defined as concomitant vision (visual acuity > 0.3 logMAR), hearing (pure-tone air conduction average > 25 dB), and olfactory (score < 12 on the Sniffin' Sticks test) impairments across the spectrum of laterality (any, unilateral, combination [of unilateral and bilateral], and bilateral). RESULTS: Among 2,057 participants (mean ± SD 72.2 ± 0.2 years; 53.1% female), the national census-adjusted prevalence rates of any, unilateral, combination, and bilateral MSI were 20.6%, 1.2%, 12.2%, and 7.2%, respectively. Older age, male gender, low socioeconomic status (SES), and smoking (all p < 0.05) were independently associated with higher likelihood of any MSI. Compared to those with no sensory loss, those with MSI had significantly decreased mobility (range 5.4%-9.2%), had poor functioning (OR range 3.25-3.45) and increased healthcare costs (range 4-6 folds) across the laterality spectrum. Additionally, bilateral MSI had a significant decrease in HRQoL (5.5%, p = 0.012). CONCLUSIONS: MSI is a highly prevalent medical condition, with 1 in 5; and almost 1 in 10 community-dwelling older Asians having any and bilateral MSI, respectively, with a higher likelihood in men, smokers, and those with low SES. Critically, MSI has a substantial negative impact on patient health and economic outcomes across the laterality spectrum. Sensory testing is critical to detect and refer individuals with MSI for management to improve their functional independence and QoL.

The prevalence patterns and risk factor profiles of poor muscle health and its associated components in multiethnic older Asians: The PIONEER study.

BACKGROUND: We aim to determine the multiethnic patterns of the prevalence and associated factors of poor muscle health and its associated components in older Chinese, Malays, and Indian Asian adults. METHODS: We included 2199 participants (mean age ± SD: 72.9 ± 8.3 years; 54.3% female) from the baseline assessment of the Population Health and Eye Disease Profile in Elderly Singaporeans (PIONEER; 2017-2022) cohort study. Poor muscle health was defined as the presence of either low muscle mass (DEXA), or low muscle strength (handgrip strength), or low physical performance (gait speed). Its components include poor muscle function (low muscle strength and/or low physical performance without low muscle mass), pre-sarcopenia (low muscle mass only), and any sarcopenia (low muscle mass with low muscle strength and/or low physical performance). Sociodemographic, clinical, and lifestyle factors were assessed using biochemistry, clinical tests, and validated questionnaires. Regression models were utilized to evaluate the independent risk factors of poor muscle health and its components. RESULTS: The national census-adjusted prevalence of poor muscle health (88%) was similar across the three ethnic groups. However, Chinese individuals had higher prevalence of pre-sarcopenia and any sarcopenia, and a lower prevalence of poor muscle function compared with Indians or Malays. We observed ethnic differences in modifiable risk factors (low physical activity, diabetes, osteoporosis, and obesity) of poor muscle health and its components. Although obesity was protective of pre-sarcopenia (RRR = 0.19, 95% CI: 0.11, 0.36) and any sarcopenia (RRR = 0.29, 95% CI: 0.18, 0.47) in the overall population and across ethnic groups, it was associated with 1.7 times (95% CI: 1.07, 2.67) the likelihood of poor muscle function in the entire population. CONCLUSIONS: Almost 90% of community dwelling Singaporean aged ≥60 years have poor muscle health across the three ethnic groups with ethnic disparities in modifiable risk factors, highlighting an urgent need for community-wide targeted interventions to promote muscle health.

Effect of atropine 0.01% on progression of myopia.

Purpose: Myopia is the most common type of refractive error and the leading cause of functional visual loss. Increased risk of myopic maculopathy, retinal detachment, glaucoma and cataract has been seen with a myopia of as low as -1D. This study was done to determine the effect of atropine 0.01% eye drops on the progression of myopia in children >5 years. Methods: This was a single-blind, prospective, randomized case-control study which included children of 5-15 years with myopia of >2D and were divided into treatment group (group 1) and placebo group (group 2). Children under treatment group were treated with application of 0.01% atropine at night. Children with history of any ocular surgery, chronic ophthalmic illness, squint and amblyopia were excluded from the study. The follow-up for myopia progression was done for two years. Results: This study showed a significant difference in increase of spherical equivalent and axial length among treatment and placebo groups after a duration of two years. Total duration of follow up was twenty-four months. Mean increase in axial length of group 1 and 2 was 0.115 mm and 0.32 mm, respectively. Mean increase in refraction of groups 1 and 2 was -0.30 D and -0.88 D, respectively, showing significant change in axial length and refraction (P < 0.0001). Conclusion: This study supports the use of atropine 0.01% eye drops in reducing the progression of myopia.

Different impact of early and late stages irreversible eye diseases on vision-specific quality of life domains.

To determine the differential impact of the irreversible eye diseases on vision-related quality of life (VRQoL) in a multi-ethnic Asian population. 2652 participants from the Singapore Epidemiology of Eye Disease Study, with any of the following early and late-stage eye conditions including age-related macular degeneration (AMD, n = 158), diabetic retinopathy (DR, n = 105; non vision threatening [non-VTDR]; VTDR), glaucoma (n = 57) and myopic macular degeneration (MMD, n = 106), or none of the above (controls, 2226 [83.9%]) were included. Rasch-scaled scores of the Emotional well-being Mobility and Reading subscales of the Impact of Vision Impairment (IVI) questionnaire, collectively referred to as "VRQoL" were assessed. Multivariable linear regression analyses and pairwise comparisons adjusting for age, gender, ethnicity, socio-economic status, BMI, smoking, alcohol use, presence of systemic diseases and presenting VI were performed to assess and compare the impact of the presence and severity of each eye condition on the three IVI domains. Multivariable adjusted pairwise comparisons of VRQoL between early stages of the four eye diseases showed no significant differences (all P > 0.05). For late stage diseases, individuals with VTDR had significantly larger decrements in Emotional well-being compared to glaucoma (ß - 0.81; 95% CI - 1.47 to - 0.16) and MMD (ß - 1.17; 95% CI - 2.16 to - 0.18); and Reading decrements compared to glaucoma (ß - 0.66; 95% CI - 1.22 to - 0.11). When compared to late glaucoma, individuals with late AMD (ß - 0.76; 95% CI - 1.50 to - 0.01) had significantly larger IVI Mobility subscale decrements. VTDR and late AMD, appear to have the greatest impact on VRQoL, compared to late glaucoma and MMD, suggesting a differential impact of late-stage eye disease categorization on VRQoL.

Probing the Interaction of Selonsertib with Human Serum Albumin: In silico and In vitro Approaches.

INTRODUCTION: Selonsertib, the most recently developed selective inhibitor of apoptosis signal-regulating kinase 1. We elucidated the binding characteristics, mechanism of interaction, and dynamic behaviors of selonsertib with human serum albumin (HSA), a major circulatory transport protein. METHODS: Different biophysical approaches (fluorescence quenching and isothermal titration calorimetry (ITC) were combined with various in silico techniques to examine the binding of selonsertib to HSA. Molecular docking results, analysis of molecular dynamics trajectories, and essential dynamics investigations indicated the stable binding of selonsertib to HSA. Further in vitro studies were performed to validate the observed interaction. RESULTS: ITC results confirmed the robust binding and high affinity of selonsertib and HSA. Likewise, the fluorescence quenching results highlighted the binding affinity of selonsertib and HSA. Collectively, our findings offer deeper insight into the binding mechanism of selonsertib and HSA, emphasizing the selonsertib-mediated structural changes within HSA, along with a comprehensive rationale for the biological transport and accumulation of selonsertib in the blood plasma. CONCLUSION: Therefore, considering the bioavailability and effectiveness of selonsertib, assessing the interactions of this inhibitor with carrier proteins is crucial to elucidate its biological processes at the molecular level. This evidence carries the considerable scientific potential for future drug design.

Association between age-related sensory impairment with sarcopenia and its related components in older adults: a systematic review.

Sensory impairments and sarcopenia are both highly prevalent age-related conditions, with the former having been postulated to contribute to the pathogenesis of the latter condition. Confirming this hypothesis may therefore help to better inform strategies for early treatment and intervention of sarcopenia. We performed a systematic review of the current literature examining the relationships between four major sensory impairments [vision (VI), hearing (HI), smell (SI), and taste (TI)] with (i) sarcopenia; and (ii) its associated components (low handgrip strength, slow gait speed, and low muscle mass). PubMed, EMBASE, CINAHL, and Cochrane Library databases were searched for observational studies investigating the relationship of VI, HI, SI, and TI with sarcopenia, low handgrip strength, slow gait speed, and low muscle mass, in adults aged 50 years or older, from inception until 24 May 2021. The risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale. This study was registered with PROSPERO, reference CRD42021247967. Ten cross-sectional and three longitudinal population-based studies of community-dwelling adults (N = 68 235) were included, with five studies investigating more than one sensory impairment. In total, 8, 6, 3, and 1 studies investigated the relationship between VI, HI, SI, and TI and sarcopenia and its related components, respectively. Follow-up duration for the longitudinal studies ranged from 4 to 11 years. All studies had a low or moderate risk of bias. We found that the presence of VI and SI, but not TI, independently increased the odds of sarcopenia. In addition, VI and SI were each independently associated with low muscle mass; and VI, HI, and SI were each independently associated with slow gait speed. However, we found inconclusive evidence for the associations between VI, HI and SI, and low handgrip strength. Our systematic review suggests a potential association between the presence of single or multiple sensory impairments and a greater likelihood of sarcopenia and/or deficits in its associated components, especially for VI, HI, and SI. Prospective studies are needed to untangle the relationship between sensory impairment and sarcopenia to better inform clinical guidelines for disease prevention and management.

Comparison of efficacy of lignocaine, ropivacaine, and bupivacaine in pain control during extraction of mandibular posterior teeth.

BACKGROUND: The management of pain during extraction of mandibular third molars is an important requisite to achieve patient comfort and to obtain desired result in an effective manner. There are various anesthetics that can be used to achieve regional or local anesthetic effect in this regard. AIM: The aim of this study was to compare the efficacy of 2% lignocaine with 1:80,000 adrenaline, 0.75% ropivacaine and bupivacaine in pain control during extraction of mandibular posterior teeth. MATERIALS AND METHODS: This prospective, cross-sectional study included 300 study participants indicated for mandibular third molar surgical extractions. The study subjects were categorized into three broad groups - (a) Group I (n = 100): Third molar extractions performed using 2% Lignocaine with 1: 80,000 epinephrine; (b) Group II (n = 100): This group included subjects who underwent extractions of mandibular third molars using 0.75% ropivacaine and (c) Group III (n = 100): This group included patients who underwent extractions of mandibular third molars with bupivacaine. Inclusion criteria were: (a) partially impacted mandibular third molars which were symptomatic; (b) written informed consent. Exclusion criteria were - (a) any systemic diseases and/or undergoing any medication for same; (b) subjects not willing for extraction after clinical and radiographic examination and opinion and (c) subjects undergoing orthodontic therapy. Subject response for pain was recorded using - (a) visual analog scale (VAS) and (b) Verbal Rating scale (VRS). Postoperative pain was assessed using requirement of analgesics after extraction. SPSS version 21.0 was employed as statistical software. Statistical tool used was the Analysis of Variance test which was used for determining statistical significance which was set at a P value of lesser than 0.05 (significant). RESULTS: On analysis of visual analog scale (VAS), it was observed that in Group I (2% Lignocaine with 1:80,000), no pain during the extraction procedure was demonstrated in 30 study participants while minimal or less pain was present in 70 patients, while in Group II (0.75% ropivacaine), 90 patients presented with no pain while ten patients had presented with minimal amount of pain during tooth extraction. While on the other hand, Group III patients whose mandibular third molars were extracted using local anesthesia by injecting bupivacaine, lack of any pain was observed in 69 patients while minimal pain was noted in 31 individuals. While making statistical comparison between three groups, a significant P = 0.03 was observed. Also, postoperative pain was noted in 60% of cases who underwent extraction using 2% lignocaine (Group I), 10% patients who had third molar extractions under Bupivacaine anesthesia presented with pain whereas none of the patients (0%), demonstrated the presence of pain following third molar extraction. CONCLUSION: 0.75% Ropivacaine is the most effective local anesthetic agent that can be used for extracting mandibular third molars due to its effective pain control both during and following the procedure when compared to 2% lignocaine and bupivacaine.

Cerebral Venous Thrombosis in Acute Lymphoblastic Leukemia with Severe COVID-19: a Case Report.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has brought an unprecedented upheaval in our health-care systems. Amongst the many challenges posed by the disease, increased risk of thromboembolism has presented a distinct new front for increased mortality and morbidity. While there are multiple documented evidences for the same, the exact mechanism, knowledge of groups at-risk, and mitigation strategies are evolving. We present a case of a young individual who was diagnosed with acute lymphoblastic leukemia (ALL), was started on appropriate chemotherapy, and subsequently developed severe COVID-19 pneumonia. He was treated for COVID-19 pneumonia and recovered from the illness. However, his recovery from COVID-19 was further complicated by cortical venous sinus thrombosis (CVT). Contrast enhanced magnetic resonance imaging (CEMRI) brain and magnetic resonance venography (MRV) revealed the diagnosis of CVT with hemorrhagic parenchymal changes. He was managed with therapeutic anticoagulation and cerebral decongestants and was subsequently shifted to oral anticoagulant therapy. While the case was managed at a tertiary care setting, it opened up the question of identifying the high-risk groups and to formulate guidelines for extended thromboprophylaxis in these patients.

Targeting the Sphingosine Kinase/Sphingosine-1-Phosphate Signaling Axis in Drug Discovery for Cancer Therapy.

Sphingolipid metabolites have emerged as critical players in the regulation of various physiological processes. Ceramide and sphingosine induce cell growth arrest and apoptosis, whereas sphingosine-1-phosphate (S1P) promotes cell proliferation and survival. Here, we present an overview of sphingolipid metabolism and the compartmentalization of various sphingolipid metabolites. In addition, the sphingolipid rheostat, a fine metabolic balance between ceramide and S1P, is discussed. Sphingosine kinase (SphK) catalyzes the synthesis of S1P from sphingosine and modulates several cellular processes and is found to be essentially involved in various pathophysiological conditions. The regulation and biological functions of SphK isoforms are discussed. The functions of S1P, along with its receptors, are further highlighted. The up-regulation of SphK is observed in various cancer types and is also linked to radio- and chemoresistance and poor prognosis in cancer patients. Implications of the SphK/S1P signaling axis in human pathologies and its inhibition are discussed in detail. Overall, this review highlights current findings on the SphK/S1P signaling axis from multiple angles, including their functional role, mechanism of activation, involvement in various human malignancies, and inhibitor molecules that may be used in cancer therapy.

Vision, vision-specific functioning and mobility, and their relationship with clinically assessed cognitive impairment.

BACKGROUND: The relationship between self-reported visual disability and cognitive impairment in older individuals is unclear. OBJECTIVE: To determine the relationship of vision-specific functioning (VSF), vision-specific mobility (VSM) and visual acuity (VA) with clinically assessed cognitive impairment in the Epidemiology of Dementia in Singapore study. DESIGN: Cross-sectional. SETTING: Population-based. SUBJECTS: Eight hundred and seventy-four adults aged ≥60 years at higher risk of possible cognitive impairment by the Abbreviated Mental Test and progressive forgetfulness question. METHODS: VSF and VSM were measured using Rasch-transformed continuous scores of two Impact of Vision Impairment questionnaire domains. Cognitive impairment was objectively determined using detailed neuropsychological testing and defined as no cognitive impairment (NCI), mild cognitive impairment-no dementia (CIND), moderate CIND only and moderate CIND or dementia. Associations were assessed using multinomial logistic regression models. RESULTS: Of the 874 participants (49.0% males, mean age (SD) 65.5 (7.0) years), 277, 281 and 316 had NCI, mild CIND and moderate CIND or dementia, respectively. Compared to NCI, the odds of moderate CIND, and moderate CIND or dementia increased for every SD worsening in VSF (OR: 1.44, 95% CI 1.14-1.82, and OR: 1.52, 95%CI 1.19-1.94, respectively) and VSM (OR: 1.42, 95%CI 1.11-1.81, and OR: 1.50, 95%CI 1.15-1.95). Similarly, the odds of mild CIND (OR: 1.62, 95%CI 1.19-2.22), moderate CIND (OR: 1.93, 95%CI 1.45-2.58), and moderate CIND or dementia (OR: 2.25, 95%CI 1.62-3.11) increased significantly with every SD worsening of VA. CONCLUSIONS: Our results emphasise the importance of interventions to prevent vision loss and improve quality of life to reduce likelihood of age-related cognitive decline.

Malignant prolongation of the QTc interval due to severe vitamin D deficiency: an unusual presentation.

Long QT syndrome with Torsades de Pointes (TdP) is a life-threatening polymorphic ventricular arrhythmia. The corrected QT (QTc) prolongation >500 milliseconds (ms) has been associated with TdP. Hypocalcaemia due to severe vitamin D deficiency is an uncommon cause of acquired long QT. We hereby present a case of a 40-year-old woman with sensorineural deafness and having symptoms of palpitations and presyncope. She had a QTc interval of 556 ms (reference range, QTc 451-470 ms in adult healthy woman) on 24-hour Holter analysis. Genetic analysis for congenital long QT syndrome was negative. She was diagnosed with severe hypocalcaemia secondary to severe vitamin D deficiency. After treatment with intravenous calcium gluconate, followed by oral vitamin D and calcium supplementation, the QTc became normalised and no further episode of palpitations or presyncope occurred. The causes of vitamin D deficiency was due to inadequate exposure to sunlight and a strict vegan diet.

Discovery of Harmaline as a Potent Inhibitor of Sphingosine Kinase-1: A Chemopreventive Role in Lung Cancer.

The sphingosine kinase-1/sphingosine-1-phosphate pathway is linked with the cancer progression and survival of the chemotherapy-challenged cells. Sphingosine kinase-1 (SphK1) has emerged as an attractive drug target, but their inhibitors from natural sources are limited. In this study, we have chosen harmaline, one of the ß-carboline alkaloids, and report its mechanism of binding to SphK1 and subsequent inhibition. Molecular docking combined with fluorescence binding studies revealed that harmaline binds to the substrate-binding pocket of SphK1 with an appreciable binding affinity and significantly inhibits the kinase activity of SphK1 with an IC50 value in the micromolar range. The cytotoxic effect of harmaline on non-small-cell lung cancer cells by MTT assay was found to be higher for H1299 compared to A549. Harmaline induces apoptosis in non-small-cell lung carcinoma cells (H1299 and A549), possibly via the intrinsic pathway. Our findings suggest that harmaline could be implicated as a scaffold for designing potent anticancer molecules with SphK1 inhibitory potential.

Mechanistic insights into the urea-induced denaturation of human sphingosine kinase 1.

Sphingosine kinase 1 (SphK1) plays a significant role in various cellular processes, including cell proliferation, apoptosis, and angiogenesis. SphK1 is considered as an attractive target for drug development owing to its connection with several diseases, including cancer. In the current work, the urea-induced unfolding of SphK1 was performed at pH 8.0 and 25 °C using CD and fluorescence spectroscopy. SphK1 follows a biphasic unfolding transition (N â‡Œ I â‡Œ D) with an intermediate (I) state populated around 4.0 M urea concentration. The circular dichroism ([θ]222) and fluorescence emission spectra (λmax) of SphK1 with increasing concentrations of urea were analyzed to calculate Gibbs free energy (ΔG0) for both the transitions (N â‡Œ I and I â‡Œ D). A significant overlap of both the transitions obtained by two spectroscopic properties ([θ]222 and λmax) was observed, indicating that both N â‡Œ I and I â‡Œ D transition follow two-step equilibrium unfolding pattern. Also, we performed 100 ns molecular dynamics (MD) simulations to get atomistic insights into the structural changes in SphK1 with increasing urea concentrations. Our results showed a consistent pattern of the SphK1 unfolding with increasing urea concentrations. Together, spectroscopic and MD simulation findings provide deep insights into the unfolding mechanism and conformational features of SphK1.

Identification of Potential Inhibitors of Calcium/Calmodulin-Dependent Protein Kinase IV from Bioactive Phytoconstituents.

Calcium/calmodulin-dependent protein kinase IV (CaMKIV) is an upstream regulator of CaMKK-CaMKIV signaling cascade that activates various transcription factors, thereby regulating several cellular activities including, neuronal communication and immune response. Owing to the abnormal expression in cancer and neurodegenerative diseases, the CaMKIV has been considered a potential drug target. In the present study, we checked the binding affinity of plant-derived natural compounds viz., quercetin, ellagic acid (EA), simvastatin, capsaicin, ursolic acid, DL-α-tocopherol acetate, and limonin towards CaMKIV. Molecular docking and fluorescence binding studies showed that EA and quercetin bind to the CaMKIV with a considerable affinity in comparison to other compounds. Enzyme inhibition assay revealed that both EA and quercetin inhibit CaMKIV activity with their IC50 values in the micromolar range. To get atomistic insights into the mode of interactions, inhibition mechanism, and the stability of the CaMKIV-ligand complex, a 100 ns MD simulation analysis was performed. Both EA and quercetin bind to the catalytically important residues of active site pocket of CaMKIV forming enough stabilizing interactions presumably inhibiting enzyme activity. Moreover, no significant structural change in the CaMKIV was observed upon binding of EA and quercetin. In conclusion, this study illustrates the application of phytoconstituents in the development of therapeutic molecules targeting CaMKIV having implications in cancer and neurodegenerative diseases after in vivo validation.

Design and Development of Novel Urea, Sulfonyltriurea, and Sulfonamide Derivatives as Potential Inhibitors of Sphingosine Kinase 1.

Sphingosine kinase 1 (SphK1) is one of the well-studied drug targets for cancer and inflammatory diseases. Recently discovered small-molecule inhibitors of SphK1 have been recommended in cancer therapeutics; however, selectivity and potency of first-generation inhibitors are great challenge. In search of effective SphK1 inhibitors, a set of small molecules have been designed and synthesized bearing urea, sulfonylurea, sulfonamide, and sulfonyltriurea groups. The binding affinity of these inhibitors was measured by fluorescence-binding assay and isothermal titration calorimetry. Compounds 1, 5, 6, and 7 showed an admirable binding affinity to the SphK1 in the sub-micromolar range and significantly inhibited SphK1 activity with admirable IC50 values. Molecular docking studies revealed that these compounds fit well into the sphingosine binding pocket of SphK1 and formed significant number of hydrogen bonds and van der Waals interactions. These molecules may be exploited as potent and selective inhibitors of SphK1 that could be implicated in cancer therapeutics after the required in vivo validation.

Identification of Sphingosine Kinase-1 Inhibitors from Bioactive Natural Products Targeting Cancer Therapy.

Sphingosine kinase 1 (SphK1) is an oncogenic lipid kinase that catalyzes the formation of sphingosine-1-phosphate via phosphorylation of sphingosine and known to play a crucial role in angiogenesis, lymphocyte trafficking, signal transduction pathways, and response to apoptotic stimuli. SphK1 has received attention because of its involvement in varying types of cancer and inflammatory diseases such as rheumatoid arthritis, diabetes, renal fibrosis, pulmonary fibrosis, asthma, and neurodegenerative disorders. In the malignancies of breast, lung, uterus, ovary, kidney, and leukemia, overexpression of SphK1 has been reported and thus considered as a potential drug target. In this study, we have performed virtual high-throughput screening of ∼90,000 natural products from the ZINC database to find potential SphK1-inhibitors. Initially, the hits were selected by applying absorption, distribution, metabolism, excretion, and toxicity properties, Lipinski's rule, and PAINS filters. Further, docking analysis was performed to estimate the binding affinities and specificity to find safe and effective preclinical leads against SphK1. Two compounds, ZINC05434006 and ZINC04260971, bearing appreciable binding affinity and SphK1 selectivity were selected for 100 ns molecular dynamics (MD) simulations under explicit water conditions. The all-atom MD simulation results suggested that the ZINC05434006 and ZINC04260971 binding induces a slight structural change and stabilizes the SphK1 structure. In conclusion, we propose natural compounds, ZINC05434006 and ZINC04260971, as potential inhibitors of SphK1, which may be further exploited as potential leads to develop effective therapeutics against SphK1-associated diseases including cancer after in vitro and in vivo validations.

Effect of pH on the structure and function of pyruvate dehydrogenase kinase 3: Combined spectroscopic and MD simulation studies.

Pyruvate dehydrogenase kinase-3 (PDK3) plays important role in the glucose metabolism and is associated with cancer progression, and thus being considered as an attractive target for cancer therapy. In this study, we employed spectroscopic techniques to study the structural and conformational changes in the PDK3 at varying pH conditions ranging from pH 2.0 to 12.0. UV/Vis, fluorescence and circular dichroism spectroscopic measurements revealed that PDK3 maintains its native-like structure (both secondary and tertiary) in the alkaline conditions (pH 7.0-12.0). However, a significant loss in the structure was observed under acidic conditions (pH 2.0-6.0). The propensity of aggregate formation at pH 4.0 was estimated by thioflavin T fluorescence measurements. To further complement structural data, kinase activity assay was performed, and maximum activity of PDK3 was observed at pH 7.0-8.0 range; whereas, its activity was lost under acidic pH. To further see conformational changes at atomistic level we have performed all-atom molecular dynamics at different pH conditions for 150 ns. A well defined correlation was observed between experimental and computational studies. This work highlights the significance of structural dependence of pH for wide implications in protein-protein interaction, biological function and drug design procedures.

Functional implications of pH-induced conformational changes in the Sphingosine kinase 1.

Sphingosine kinase 1 (SphK1) catalyzes the conversion of sphingosine to sphingosine-1-phosphate that acts as a bioactive signalling molecule, and regulates various cellular processes including lymphocyte trafficking, angiogenesis and response to apoptotic stimuli. Abnormal expression of SphK1 has been observed in a wide range of cancers highlighting their role in tumour growth and metastasis. This enzyme also plays a critical role in metabolic and inflammatory diseases, including pulmonary fibrosis, diabetic neuropathy and Alzheimer's disease. In the present study, we have investigated the structural and conformational changes in SphK1 at varying pH using various spectroscopic techniques. Consistent results were observed with the function of SphK1 at corresponding pH values. SphK1 maintains its secondary and tertiary structure in the pH range of 7.5-10.0. However, protein aggregation was observed in the acidic pH range (4.0-6.5). At pH 2.0, the SphK1 exists in the molten-globule state. Kinase assay also shows that SphK1 activity was optimal in the pH range of 7.5-8.5. To complement in vitro results, we have performed 100 ns molecular dynamics simulation to examine the effect of pH on the structural stability of SphK1 at molecular level. SphK1 maintains its native conformation in the alkaline pH range with some residual fluctuations detected at acidic pH. A considerable correlation was noticed between spectroscopic, enzymatic activity and MD simulation studies. pH dependent structural changes can be further implicated to understand its association with disease condition, and cellular homeostasis with respect to protein function under variable pH conditions.

Prevalence, determinants and association of unawareness of diabetes, hypertension and hypercholesterolemia with poor disease control in a multi-ethnic Asian population without cardiovascular disease.

BACKGROUND: To explore the prevalence and determinants of unawareness of diabetes, hypertension and hypercholesterolemia and its association with poor disease control in a multi-ethnic Asian population without cardiovascular disease (CVD). METHODS: We included 6904 Chinese, Malay and Indian individuals (mean age [SD] 58.2 [10.2] years; 52.6% female) with diabetes, hypertension and/or hypercholesterolemia from the cross-sectional population-based Singapore Epidemiology of Eye Diseases study (2004-2011). Diabetes was defined as random blood glucose ≥ 11.1 mmol/L or HbA1c > 6.5% or self-reported use of diabetes medication; hypertension as systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg or self-reported use of anti-hypertensive treatment; and hypercholesterolemia as total cholesterol ≥ 6.2 mmol/L or self-reported use of lipid-lowering medications. Unawareness was based on participants' answers to the questions: "Did your medical practitioner ever tell you that you have diabetes/hypertension/high cholesterol?" The determinants of unawareness, and its association with poor disease control, were assessed using multivariable binary logistic regression models adjusted for known potential confounders. RESULTS: Of the 2380 (34.5%), 5386 (78.0%) and 3607 (52.2%) with diabetes, hypertension and hypercholesterolemia, respectively, unawareness rates were 30.7%, 43.1% and 40.9%, respectively. Having a higher BMI, particularly if obese, and Malay ethnicity were associated with greater unawareness of diabetes; Malay and Indian ethnicities and current smoking with greater unawareness of hypertension; and education ≤6 years, current smoking, and blue collar jobs or unemployment with greater unawareness of hypercholesterolemia (all P < 0.05). Lack of awareness of each condition was independently associated with poorer disease control in the case of hypertension and hypercholesterolemia, while the converse was true for diabetes (all P < 0.05). CONCLUSIONS: Unawareness of diabetes, hypertension, or hypercholesterolemia is high in Singapore, with risk factors varying across all three diseases, although Malay ethnicity is a consistent one. Unawareness was also associated with poor management for hypertension and hypercholesterolemia. Public health education and screening programs should target at-risk individuals, especially Malays, to reduce the likelihood of incident CVD.

Evaluation of binding and inhibition mechanism of dietary phytochemicals with sphingosine kinase 1: Towards targeted anticancer therapy.

Sphingosine kinase 1 (SphK1) has recently gained attention as a potential drug target for its association with cancer and other inflammatory diseases. Here, we have investigated the binding affinity of dietary phytochemicals viz., ursolic acid, capsaicin, DL-α tocopherol acetate, quercetin, vanillin, citral, limonin and simvastatin with the SphK1. Docking studies revealed that all these compounds bind to the SphK1 with varying affinities. Fluorescence binding and isothermal titration calorimetric measurements suggested that quercetin and capsaicin bind to SphK1 with an excellent affinity, and significantly inhibits its activity with an admirable IC50 values. The binding mechanism of quercetin was assessed by docking and molecular dynamics simulation studies for 100 ns in detail. We found that quercetin acts as a lipid substrate competitive inhibitor, and it interacts with important residues of active-site pocket through hydrogen bonds and other non-covalent interactions. Quercetin forms a stable complex with SphK1 without inducing any significant conformational changes in the protein structure. In conclusion, we infer that quercetin and capsaicin provide a chemical scaffold to develop potent and selective inhibitors of SphK1 after required modifications for the clinical management of cancer.