Displaying publications 1 - 20 of 29 in total

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  1. Aravind SR, Al Tayeb K, Ismail SB, Shehadeh N, Kaddaha G, Liu R, et al.
    Curr Med Res Opin, 2011 Jun;27(6):1237-42.
    PMID: 21506631 DOI: 10.1185/03007995.2011.578245
    To determine the incidence of hypoglycaemia during Ramadan in Muslim subjects with type 2 diabetes treated with a sulphonylurea.
  2. Lea AJ, Clark AG, Dahl AW, Devinsky O, Garcia AR, Golden CD, et al.
    PLoS Biol, 2023 Sep;21(9):e3002311.
    PMID: 37695771 DOI: 10.1371/journal.pbio.3002311
    Noncommunicable diseases (NCDs) are on the rise worldwide. Obesity, cardiovascular disease, and type 2 diabetes are among a long list of "lifestyle" diseases that were rare throughout human history but are now common. The evolutionary mismatch hypothesis posits that humans evolved in environments that radically differ from those we currently experience; consequently, traits that were once advantageous may now be "mismatched" and disease causing. At the genetic level, this hypothesis predicts that loci with a history of selection will exhibit "genotype by environment" (GxE) interactions, with different health effects in "ancestral" versus "modern" environments. To identify such loci, we advocate for combining genomic tools in partnership with subsistence-level groups experiencing rapid lifestyle change. In these populations, comparisons of individuals falling on opposite extremes of the "matched" to "mismatched" spectrum are uniquely possible. More broadly, the work we propose will inform our understanding of environmental and genetic risk factors for NCDs across diverse ancestries and cultures.
  3. Lea AJ, Clark AG, Dahl AW, Devinsky O, Garcia AR, Golden CD, et al.
    ArXiv, 2023 Feb 13.
    PMID: 36713247
    Globally, we are witnessing the rise of complex, non-communicable diseases (NCDs) related to changes in our daily environments. Obesity, asthma, cardiovascular disease, and type 2 diabetes are part of a long list of "lifestyle" diseases that were rare throughout human history but are now common. A key idea from anthropology and evolutionary biology-the evolutionary mismatch hypothesis-seeks to explain this phenomenon. It posits that humans evolved in environments that radically differ from the ones experienced by most people today, and thus traits that were advantageous in past environments may now be "mismatched" and disease-causing. This hypothesis is, at its core, a genetic one: it predicts that loci with a history of selection will exhibit "genotype by environment" (GxE) interactions and have differential health effects in ancestral versus modern environments. Here, we discuss how this concept could be leveraged to uncover the genetic architecture of NCDs in a principled way. Specifically, we advocate for partnering with small-scale, subsistence-level groups that are currently transitioning from environments that are arguably more "matched" with their recent evolutionary history to those that are more "mismatched". These populations provide diverse genetic backgrounds as well as the needed levels and types of environmental variation necessary for mapping GxE interactions in an explicit mismatch framework. Such work would make important contributions to our understanding of environmental and genetic risk factors for NCDs across diverse ancestries and sociocultural contexts.
  4. Li C, Lawrance EL, Morgan G, Brown R, Greaves N, Krzanowski J, et al.
    Int Rev Psychiatry, 2022 08;34(5):563-570.
    PMID: 36165755 DOI: 10.1080/09540261.2022.2097005
    The climate and ecological crisis will constitute the defining public health challenge of the twenty-first century, posing an unprecedented global threat to all determinants of health, and to healthcare delivery systems. We believe that mental health professionals have a crucial role to play in responding to this crisis. Whilst responding to the mental health consequences of the climate crisis will remain a key role for us as mental health professionals, we argue that our remit goes beyond this, and should include advancing public understanding of the climate crisis, highlighting its impact on physical and mental wellbeing, and advocating for systemic changes to limit its impending harms. This paper is an urgent call to action for all mental health professionals to take up a role in the context of the climate and ecological crisis. This paper will describe the relationship between mental health and climate change, and frame it within wider systemic and conceptual frameworks. It will demonstrate that as mental health professionals we are well placed to act as leaders of change-arguing that we have a duty to do so-and suggest actions that can be implemented depending on interests, skill sets and opportunities.
  5. Trautmann A, Vivarelli M, Samuel S, Gipson D, Sinha A, Schaefer F, et al.
    Pediatr Nephrol, 2020 Aug;35(8):1529-1561.
    PMID: 32382828 DOI: 10.1007/s00467-020-04519-1
    Idiopathic nephrotic syndrome newly affects 1-3 per 100,000 children per year. Approximately 85% of cases show complete remission of proteinuria following glucocorticoid treatment. Patients who do not achieve complete remission within 4-6 weeks of glucocorticoid treatment have steroid-resistant nephrotic syndrome (SRNS). In 10-30% of steroid-resistant patients, mutations in podocyte-associated genes can be detected, whereas an undefined circulating factor of immune origin is assumed in the remaining ones. Diagnosis and management of SRNS is a great challenge due to its heterogeneous etiology, frequent lack of remission by further immunosuppressive treatment, and severe complications including the development of end-stage kidney disease and recurrence after renal transplantation. A team of experts including pediatric nephrologists and renal geneticists from the International Pediatric Nephrology Association (IPNA), a renal pathologist, and an adult nephrologist have now developed comprehensive clinical practice recommendations on the diagnosis and management of SRNS in children. The team performed a systematic literature review on 9 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, formulated recommendations and formally graded them at a consensus meeting, with input from patient representatives and a dietician acting as external advisors and a voting panel of pediatric nephrologists. Research recommendations are also given.
  6. Karunanithi P, Murali MR, Samuel S, Raghavendran HRB, Abbas AA, Kamarul T
    Carbohydr Polym, 2016 08 20;147:294-303.
    PMID: 27178935 DOI: 10.1016/j.carbpol.2016.03.102
    Presence of sulfated polysaccharides like heparan sulphate has often been implicated in the regulation of chondrogenesis. However, recently there has been a plethora of interest in the use of non-animal extracted analogs of heparan sulphate. Here we remodeled alginate (1.5%) by incorporating fucoidan (0.5%), a natural sulphated polysaccharide extracted from seaweeds to form a composite hydrogel (Al-Fu), capable of enhancing chondrogenesis of human mesenchymal stromal cells (hMSCs). We confirmed the efficiency of fucoidan incorporation by FTIR and EDX analysis. Further, its ability to support hMSC attachment and chondrogenic differentiation was confirmed by SEM, biochemical glycosaminoglycan quantification, real-time quantitative PCR and immunocytochemical analyses of chondrogenic markers Sox-9, Collagen II, Aggrecan and COMP. Effect of Al-Fu hydrogel on hMSC hypertrophy was also confirmed by the downregulation of hypertrophic genes Collagen X and Runx2. This composite scaffold can hence be used as a cartilage biomimetic biomaterial to drive hMSC chondrogenesis and for other cartilage repair based therapies.
  7. Samuel S, Ahmad RE, Ramasamy TS, Karunanithi P, Naveen SV, Murali MR, et al.
    PeerJ, 2016;4:e2347.
    PMID: 27651984 DOI: 10.7717/peerj.2347
    Previous studies have shown that platelet concentrates used in conjunction with appropriate growth media enhance osteogenic differentiation of human mesenchymal stromal cells (hMSCs). However, their potential in inducing osteogenesis of hMSCs when cultured in serum free medium has not been explored. Furthermore, the resulting osteogenic molecular signatures of the hMSCs have not been compared to standard osteogenic medium. We studied the effect of infrequent supplementation (8-day interval) of 15% non-activated platelet-rich concentrate (PRC) in serum free medium on hMSCs proliferation and differentiation throughout a course of 24 days, and compared the effect with those cultured in a standard osteogenic medium (OM). Cell proliferation was analyzed by alamar blue assay. Gene expression of osteogenic markers (Runx2, Collagen1, Alkaline Phosphatase, Bone morphogenetic protein 2, Osteopontin, Osteocalcin, Osteonectin) were analyzed using Q-PCR. Immunocytochemical staining for osteocalcin, osteopontin and transcription factor Runx2 were done at 8, 16 and 24 days. Biochemical assays for the expression of ALP and osteocalcin were also performed at these time-points. Osteogenic differentiation was further confirmed qualitatively by Alizarin Red S staining that was quantified using cetylpyridinium chloride. Results showed that PRC supplemented in serum free medium enhanced hMSC proliferation, which peaked at day 16. The temporal pattern of gene expression of hMSCs under the influence of PRC was comparable to that of the osteogenic media, but at a greater extent at specific time points. Immunocytochemical staining revealed stronger staining for Runx2 in the PRC-treated group compared to OM, while the staining for Osteocalcin and Osteopontin were comparable in both groups. ALP activity and Osteocalcin/DNA level were higher in the PRC group. Cells in the PRC group had similar level of bone mineralization as those cultured in OM, as reflected by the intensity of Alizarin red stain. Collectively, these results demonstrate a great potential of PRC alone in inducing proliferation of hMSCs without any influence from other lineage-specific growth media. PRC alone has similar capacity to enhance hMSC osteogenic differentiation as a standard OM, without changing the temporal profile of the differentiation process. Thus, PRC could be used as a substitute medium to provide sufficient pool of pre-differentiated hMSCs for potential clinical application in bone regeneration.
  8. Samuel S, Ahmad RE, Ramasamy TS, Karunanithi P, Naveen SV, Kamarul T
    Platelets, 2019;30(1):66-74.
    PMID: 29090639 DOI: 10.1080/09537104.2017.1371287
    Platelet-rich concentrate (PRC), used in conjunction with other chondroinductive growth factors, have been shown to induce chondrogenesis of human mesenchymal stromal cells (hMSC) in pellet culture. However, pellet culture systems promote cell hypertrophy and the presence of other chondroinductive growth factors in the culture media used in previous studies obscures accurate determination of the effect of platelet itself in inducing chondrogenic differentiation. Hence, this study aimed to investigate the effect of PRC alone in enhancing the chondrogenic differentiation potential of human mesenchymal stromal cells (hMSC) encapsulated in three-dimensional alginate constructs. Cells encapsulated in alginate were cultured in serum-free medium supplemented with only 15% PRC. Scanning electron microscopy was used to determine the cell morphology. Chondrogenic molecular signature of hMSCs was determined by quantitative real-time PCR and verified at protein levels via immunohistochemistry and enzyme-linked immunosorbent assay. Results showed that the cells cultured in the presence of PRC for 24 days maintained a chondrocytic phenotype and demonstrated minimal upregulation of cartilaginous extracellular matrix (ECM) marker genes (SOX9, TNC, COL2, ACAN, COMP) and reduced expression of chondrocyte hypertrophy genes (Col X, Runx2) compared to the standard chondrogenic medium (p 
  9. Samuel S, Ahmad RE, Ramasamy TS, Manan F, Kamarul T
    Injury, 2018 Apr;49(4):775-783.
    PMID: 29503013 DOI: 10.1016/j.injury.2018.02.020
    BACKGROUND: It has been previously suggested that the use of regenerative promoters, which include bone marrow-derived mesenchymal stem cells (MSCs) or natural growth factors supplement such as platelet-rich concentrate (PRC) could promote cartilage regeneration. However, the notion that the concurrent use of both promoters may provide a synergistic effect that improves the repair outcome of focal cartilage injury has not been previously demonstrated. This study was thus conducted to determine whether the concomitant use of PRC could further enhance the reparative potential of MSCs encapsulated in alginate transplanted into focal cartilage injury in rabbits.

    METHODS: Artifically created full thickness cartilage defects were made on the weight-bearing region of medial femoral condyles in bilateral knees of New Zealand White rabbits (N = 30). After one month, the right knee was treated with either i) PRC (n = 10), ii) MSCs (n = 10), or, iii) a combination of PRC and MSCs (PRC + MSC) (n = 10), all encapsulated in alginate. The left knee remained untreated (control). Rabbits were sacrificed at 3 and 6 months after treatment. Cartilage tissue regeneration was accessed using ICRS morphologic scoring, histologic grading by O'Driscoll scoring, immunohistochemical staining and quantitative analysis of glycosaminoglycans (GAG) per total protein content.

    RESULTS: At 3 months, transplantation using PRC alone was equally effective as MSCs in inducing the repair of cartilage defects. However, PRC + MSC resulted in significantly higher ICRS and O'Driscoll scores (p 

  10. Shankar RR, Zeitler P, Deeb A, Jalaludin MY, Garcia R, Newfield RS, et al.
    Pediatr Diabetes, 2022 Mar;23(2):173-182.
    PMID: 34779087 DOI: 10.1111/pedi.13279
    OBJECTIVE: To assess the efficacy and safety of DPP-4 inhibition with sitagliptin in youth with type 2 diabetes (T2D).

    STUDY DESIGN: This was a 54-week, double-blind, randomized, controlled clinical trial evaluating the safety and efficacy of DPP-4 inhibition with sitagliptin 100 mg once daily as initial oral therapy in youth with T2D. The 190 participants, aged 10-17 years, had HbA1c 6.5%-10% (7.0%-10% if on insulin). All were negative for pancreatic autoantibodies and overweight/obese at screening or diagnosis. The trial was placebo controlled for the first 20 weeks, after which metformin replaced placebo. The primary efficacy endpoint was change from baseline in HbA1c at Week 20.

    RESULTS: Treatment groups were well balanced at baseline (mean ± SD HbA1c = 7.5% ± 1.0, BMI percentile = 97.1% ± 6.8, age = 14.0 years ± 2.0 [57.4% <15], 60.5% female). At Week 20, least squares mean changes from baseline in HbA1c were -0.01% (sitagliptin) and 0.18% (placebo); between-group difference (95% CI) = -0.19% (-0.68, 0.30), p = 0.448. At Week 54, the changes in HbA1c were 0.45% (sitagliptin) and -0.11 (placebo/metformin). There were no notable between-group differences in the adverse event profiles through Week 54.

    CONCLUSIONS: DPP-4 inhibition with sitagliptin did not provide significant improvement in glycemic control. In this study, sitagliptin was generally well tolerated with a safety profile similar to that reported in adults. (ClinicalTrials.gov: NCT01485614; EudraCT: 2011-002528-42).

  11. Wang B, Ngoi S, Wang J, Chong SS, Lee CG
    Mol. Pharmacol., 2006 Jul;70(1):267-76.
    PMID: 16608921
    The MDR1 multidrug transporter represents one of the better characterized drug transporters that play an important role in protecting the body against xenobiotic insults. Single nucleotide polymorphisms (SNPs) and SNP haplotypes within this gene have been variously associated with differences in MDR1 expression/function, drug response as well as disease susceptibility. Nonetheless, the effect of polymorphisms at the MDR1 promoter region on its promoter activity remains less characterized. Through the examination of approximately 1.5 kilobases of MDR1 promoter region from five populations, including the Chinese, Malays, Indians, European Americans, and African Americans, we identified eight low-frequency SNPs, of which only two were polymorphic in at least four of the five populations examined. The other SNPs are mainly population-specific, the majority of which occur only in the African-American population. Recapitulation of the various combinations of SNP haplotypes in vitro in promoter-reporter assays revealed a few notable trends. The African and European American-specific haplotypes tended to result in enhanced MDR1 promoter activity only in the human embryonic kidney (HEK) 293 cell line. Haplotype GCTAACC, which occurs at variable frequencies in all the populations examined, with Asians having much lower frequencies (<2%) compared with the European Americans/African Americans (>4%), affected MDR1 promoter activity differently in different cell lines. Compared with the commonest haplotype, GCTA-ACC haplotype resulted in a significant decrease in MDR1 promoter activity in HeLa cells (P < 0.05) but a significant increase in the same promoter activity in HEK293 cells (P < 0.05). These results suggest that the MDR1 promoter region is largely invariant but that different haplotypes have differential effects on the MDR1 promoter activity in different cell lines.
  12. Tang K, Ngoi SM, Gwee PC, Chua JM, Lee EJ, Chong SS, et al.
    Pharmacogenetics, 2002 Aug;12(6):437-50.
    PMID: 12172212
    The MDR1 multidrug transporter plays a key role in determining drug bioavailability, and differences in drug response exist amongst different ethnic groups. Numerous studies have identified an association between the MDR1 single nucleotide polymorphism (SNP) exon 26 3435C>T and differences in MDR1 function. We performed a haplotype analysis of the MDR1 gene in three major ethnic groups (Chinese, Malays and Indians) by examining 10 intragenic SNPs. Four were polymorphic in all three ethnic groups: one occurring in the non-coding region and three occurring in coding exons. All three coding SNPs (exon 12 1236C>T, exon 21 2677G>T/A and exon 26 3435C>T) were present in high frequency in each ethnic group, and the derived haplotype profiles exhibited distinct differences between the groups. Fewer haplotypes were observed in the Malays (n = 6) compared to the Chinese (n = 10) and Indians (n = 9). Three major haplotypes (> 10% frequency) were observed in the Malays and Chinese; of these, two were observed in the Indians. Strong linkage disequilibrium (LD) was detected between the three SNPs in all three ethnic groups. The strongest LD was present in the Chinese, followed by Indians and Malays, with the corresponding LD blocks estimated to be approximately 80 kb, 60 kb and 40 kb, respectively. These data strongly support the hypothesis that strong LD between the neutral SNP exon 26 3435C>T and a nearby unobserved causal SNP underlies the observed associations between the neutral SNP and MDR1 functional differences. Furthermore, strong LD between exon 26 3435T and different unobserved causal SNPs in different study populations may provide a plausible explanation for conflicting reports associating the same exon 26 3435T allele with different MDR1 functional changes.
  13. Perak AM, Khan SS, Colangelo LA, Gidding SS, Armstrong AC, Lewis CE, et al.
    J Am Soc Echocardiogr, 2021 04;34(4):388-400.
    PMID: 33212181 DOI: 10.1016/j.echo.2020.11.002
    BACKGROUND: Little is known about the timing of preclinical heart failure (HF) development, particularly among blacks. The primary aims of this study were to delineate age-related left ventricular (LV) structure and function evolution in a biracial cohort and to test the hypothesis that young-adult LV parameters within normative ranges would be associated with incident stage B-defining LV abnormalities over 25 years, independent of cumulative risk factor burden.

    METHODS: Data from the Coronary Artery Risk Development in Young Adults study were analyzed. Participants (n = 2,833) had a mean baseline age of 30.1 years; 45% were black, and 56% were women. Generalized estimating equation logistic regression was used to estimate age-related probabilities of stage B LV abnormalities (remodeling, hypertrophy, or dysfunction) and logistic regression to examine risk factor-adjusted associations between baseline LV parameters and incident abnormalities. Cox regression was used to assess whether baseline LV parameters associated with incident stage B LV abnormalities were also associated with incident clinical (stage C/D) HF events over >25 years' follow-up.

    RESULTS: Probabilities of stage B LV abnormalities at ages 25 and 60 years were 10.5% (95% CI, 9.4%-11.8%) and 45.0% (95% CI, 42.0%-48.1%), with significant race-sex disparities (e.g., at age 60, black men 52.7% [95% CI, 44.9%-60.3%], black women 59.4% [95% CI, 53.6%-65.0%], white men 39.1% [95% CI, 33.4%-45.0%], and white women 39.1% [95% CI, 33.9%-44.6%]). Over 25 years, baseline LV end-systolic dimension indexed to height was associated with incident systolic dysfunction (adjusted odds ratio per 1 SD higher, 2.56; 95% CI, 1.87-3.52), eccentric hypertrophy (1.34; 95% CI, 1.02-1.75), concentric hypertrophy (0.69; 95% CI, 0.51-0.91), and concentric remodeling (0.68; 95% CI, 0.58-0.79); baseline LV mass indexed to height2.7 was associated with incident eccentric hypertrophy (1.70; 95% CI, 1.25-2.32]), concentric hypertrophy (1.63; 95% CI, 1.19-2.24), and diastolic dysfunction (1.24; 95% CI, 1.01-1.52). Among the entire cohort with baseline echocardiographic data available (n = 4,097; 72 HF events), LV end-systolic dimension indexed to height and LV mass indexed to height2.7 were significantly associated with incident clinical HF (adjusted hazard ratios per 1 SD higher, 1.56 [95% CI, 1.26-1.93] and 1.42 [95% CI, 1.14-1.75], respectively).

    CONCLUSIONS: Stage B LV abnormalities and related racial disparities were present in young adulthood, increased with age, and were associated with baseline variation in indexed LV end-systolic dimension and mass. Baseline indexed LV end-systolic dimension and mass were also associated with incident clinical HF. Efforts to prevent the LV abnormalities underlying clinical HF should start from a young age.

  14. Colangelo LA, Carroll AJ, Perak AM, Gidding SS, Lima JAC, Lloyd-Jones DM
    Psychosom Med, 2024 01 09;86(2):60-71.
    PMID: 38193784 DOI: 10.1097/PSY.0000000000001277
    OBJECTIVE: Depression is a risk factor for coronary heart disease and left ventricular hypertrophy (LVH) is a potent predictor of coronary heart disease events. Whether depression is associated with LVH has received limited investigation. This study assessed cross-sectional and 20-year longitudinal associations of depressive symptoms with LVH outcomes after accounting for important known confounders.

    METHODS: From 5115 participants enrolled in 1985-1986 in the Coronary Artery Risk Development in Young Adults Study, 2533 had serial measures of depressive symptoms and subsequent echocardiography to measure normal LV geometry, concentric remodeling, and LVH. The primary exposure variable was trajectories of the Center for Epidemiologic Studies Depression (CES-D) scale score from 1990-1991 to 2010-2011. Multivariable polytomous logistic regression was used to assess associations of trajectories with a composite LV geometry outcome created using echocardiogram data measured in 2010-2011 and 2015-2016. Sex-specific conflicting results led to exploratory models that examined potential importance of testosterone and sex hormone-binding globulin.

    RESULTS: Overall CES-D and Somatic subscale trajectories had significant associations with LVH for female participants only. Odds ratios for the subthreshold (mean CES-D ≈ 14) and stable (mean CES-D ≈ 19) groups were 1.49 (95% confidence interval = 1.05-2.13) and 1.88 (95% confidence interval = 1.16-3.04), respectively. For female participants, sex hormone-binding globulin was inversely associated with LVH, and for male participants, bioavailable testosterone was positively associated with concentric geometry.

    CONCLUSIONS: Findings from cross-sectional and longitudinal regression models for female participants, but not male ones, and particularly for Somatic subscale trajectories suggested a plausible link among depression, androgens, and LVH. The role of androgens to the depression-LVH relation requires additional investigation in future studies.

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