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  1. Teh JL, Abdul Rahman SF, Domnic G, Satiyasilan L, Chear NJY, Singh D, et al.
    BMC Res Notes, 2021 Aug 13;14(1):310.
    PMID: 34389056 DOI: 10.1186/s13104-021-05727-0
    OBJECTIVE: The spheroid model provides a physiological platform to study cancer cell biology and drug sensitivity. Usage of bovine collagen I for spheroid assays is costly especially when experiments are conducted in 24-well plates, as high volume of bovine collagen I is needed. The aim of the study was to downsize spheroid assays to a microfluidic 3D cell culture chip and compare the growth, invasion and response to drug/compound of spheroids embedded in the 3D chip to spheroids embedded in 24-well plates.

    RESULTS: Spheroids generated from nasopharyngeal carcinoma cell line HK-1 continuously grew and invaded into collagen matrix in a 24-well plate. Similar observations were noticed with spheroids embedded in the 3D chip. Large spheroids in both 24-well plate and the 3D chip disintegrated and invaded into the collagen matrix. Preliminary drug sensitivity assays showed that the growth and invasion of spheroids were inhibited when spheroids were treated with combination of cisplatin and paynantheine at high concentrations, in a 24-well plate. Comparable findings were obtained when spheroids were treated with the same drug combination in the 3D chip. Moving forward, spheroid assays could be performed in the 3D chip in a more high-throughput manner with minimal time and cost.

  2. Leong Bin Abdullah MFI, Tan KL, Mohd Isa S, Yusoff NS, Chear NJY, Singh D
    PLoS One, 2020;15(6):e0234639.
    PMID: 32525924 DOI: 10.1371/journal.pone.0234639
    BACKGROUND AND AIM: Kratom, or Mitragyna speciosa Korth., is a tropical plant that has been reported to exhibit opioid-like effects. Although opioids have been demonstrated to alter the lipid profile of regular users, data on the lipid-altering effects of kratom are scarce. This study aimed to compare the fasting lipid profile of regular kratom users to that of healthy subjects who do not use kratom. It also determined the association between various characteristics of kratom users and the serum triglycerides, total cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels of regular kratom users.

    METHODS: A total of 200 participants (n = 100 kratom users and n = 100 healthy subjects who do not use kratom) were recruited for this analytical cross-sectional study. Data on sociodemographic status, kratom use characteristics, cigarette smoking, physical activity, body mass index (BMI), fasting serum lipid profile, and liver function were collected from all participants.

    RESULTS: The liver parameters of the study participants were within normal range. The serum total cholesterol and LDL of kratom users were significantly lower than those of healthy subjects who do not use kratom. There were no significant differences in the serum triglyceride and HDL levels. However, higher average daily frequency of kratom use and increasing age were associated with increased serum total cholesterol among kratom users. Other kratom use characteristics such as age of first kratom intake, duration of kratom use, and quantity of daily kratom intake were not associated with increased serum triglyceride, total cholesterol, LDL, and HDL levels.

    CONCLUSIONS: Our findings suggest regular kratom consumption was not linked to elevated serum lipids, except when there is a higher frequency of daily kratom intake. However, the study was limited by the small sample size, and hence a more comprehensive study with larger sample size is warranted to confirm the findings.

  3. Saref A, Suraya S, Singh D, Grundmann O, Narayanan S, Swogger MT, et al.
    J Ethnopharmacol, 2019 Jun 28;238:111876.
    PMID: 31014959 DOI: 10.1016/j.jep.2019.111876
    ETHNOPHARMACOLOGICAL RELEVANCE: Mitragyna speciosa (Korth.) is a traditional medicinal plant widely used in Southeast Asia for its opioid-like effects. Although kratom produces analgesia through binding of mitragynine and other alkaloids at the mu-opioid receptor (MOR), the association of long-term kratom use with adverse opioid-like effects remains unknown.

    AIM OF THE STUDY: To determine the self-reported prevalence and severity of opioid-related adverse effects after kratom initiation in a cohort of illicit opioid users.

    MATERIALS AND METHODS: A total of 163 illicit opioid users with current kratom use history were recruited through convenience sampling from the northern states of Peninsular Malaysia. Face-to-face interviews were conducted using a semi-structured questionnaire.

    RESULTS: Respondents were all males, majority Malays (94%, n = 154/163), with a mean age of 37.10 years (SD = 10.9). Most were single (65%, n = 106/163), had 11 years of education (52%, n = 85/163) and employed (88%, n = 144/163). Half reported using kratom for over >6 years (50%, n = 81/163), and 41% consumed >3 glasses of kratom daily (n = 67/163). Results from Chi-square analysis showed kratom initiation was associated with decreased prevalence of respiratory depression, constipation, physical pain, insomnia, depression, loss of appetite, craving, decreased sexual performance, weight loss and fatigue.

    CONCLUSIONS: Our findings indicate that kratom initiation (approximately 214.29 mg of mitragynine) was associated with significant decreases in the prevalence and severity of opioid adverse effects.

  4. Leong Abdullah MFI, Tan KL, Narayanan S, Yuvashnee N, Chear NJY, Singh D, et al.
    Clin Toxicol (Phila), 2021 May;59(5):400-408.
    PMID: 32870119 DOI: 10.1080/15563650.2020.1812627
    OBJECTIVES: Little is known about the cardiotoxic effects of kratom (Mitragyna speciosa Korth.), a medicinal plant. This analytical cross-sectional study investigated the prevalence of electrocardiogram (ECG) abnormalities and QTc intervals in regular kratom users compared with non-kratom-using control subjects.

    METHODS: We enrolled regular kratom users and non-kratom-using control subjects from three communities. Demographic data, clinical data, kratom use characteristics, and ECG findings were recorded. The mitragynine content of kratom juice was quantified using a validated gas chromatography-mass spectrometry (GC-MS) method.

    RESULTS: A total of 200 participants (100 kratom users and 100 control subjects) participated in this study. The prevalence of ECG abnormalities in kratom users (28%) did not differ from that of control subjects (32%). Kratom use was not associated with ECG abnormalities, except for significantly higher odds of sinus tachycardia (OR = 8.61, 95% CI = 1.06-70.17, p = 0.035) among kratom users compared with control subjects. The odds of observing borderline QTc intervals were significantly higher for kratom users compared with control subjects, regardless of the age of first use, the duration of use, the daily quantity consumed, and the length of time that had elapsed between last kratom use and ECG assessment. Nevertheless, there were no differences in the odds of having prolonged QTc intervals between kratom users and controls. The estimated average daily intake of mitragynine consumed by kratom users was 434.28 mg.

    CONCLUSION: We found no link between regular kratom use and electrocardiographic abnormalities with an estimated average daily intake of 434.28 mg of mitragynine.

  5. Singh D, Murugaiyah V, Hamid SBS, Kasinather V, Chan MSA, Ho ETW, et al.
    J Ethnopharmacol, 2018 Jul 15;221:30-36.
    PMID: 29626673 DOI: 10.1016/j.jep.2018.04.005
    ETHNOPHARMACOLOGICAL RELEVANCE: Mitragyna speciosa (Korth.) also known as kratom, is a native medicinal plant of Southeast Asia with opioid-like effects. Kratom tea/juice have been traditionally used as a folk remedy and for controlling opiate withdrawal in Malaysia. Long-term opioid use is associated with depletion in testosterone levels.

    AIM OF THE STUDY: Since kratom is reported to deform sperm morphology and reduce sperm motility, we aimed to clinically investigate the testosterone levels following long-term kratom tea/juice use in regular kratom users.

    METHODS: A total of 19 regular kratom users were recruited for this cross-sectional study. A full-blood test was conducted including determination of testosterone level, follicle stimulating hormone (FSH) and luteinizing hormone (LH) profile, as well as hematological and biochemical parameters of participants.

    RESULTS: We found long-term kratom tea/juice consumption with a daily mitragynine dose of 76.23-94.15 mg did not impair testosterone levels, or gonadotrophins, hematological and biochemical parameters in regular kratom users.

    CONCLUSION: Regular kratom tea/juice consumption over prolonged periods (>2 years) was not associated with testosterone impairing effects in humans.

  6. Singh D, Müller CP, Murugaiyah V, Hamid SBS, Vicknasingam BK, Avery B, et al.
    J Ethnopharmacol, 2018 Mar 25;214:197-206.
    PMID: 29248450 DOI: 10.1016/j.jep.2017.12.017
    ETHNOPHARMACOLOGICAL RELEVANCE: Kratom (Mitragyna speciosa Korth.) from the Rubiaceae family is an indigenous tropical medicinal tree of Southeast Asia. Kratom leaves have been used for decades in Malaysia and Thailand in traditional context for its perceived vast medicinal value, and as a mild stimulant among manual labourers. Kratom consumption has been reported to cause side-effects in kratom users.

    AIM OF THE STUDY: To evaluate kratom's effects towards hematological and clinical-chemistry parameters among regular kratom users in Malaysia.

    METHODS: A total of 77 subjects (n=58 regular kratom users, and n=19 healthy controls) participated in this cross-sectional study. All the surveys were conducted through face-to-face interview to elicit subject's socio-demographic characteristics and kratom use history. A full-blood test was also administered. Laboratory analysis was conducted using GC-MS to determine mitragynine content in the acquired kratom samples in order to relate mitragynine consumption with possible alterations in the blood parameters of kratom users.

    RESULTS: Findings showed that there were no significant differences in the hematological and clinical-chemistry parameters of traditional kratom users and healthy controls, except for HDL and LDL cholesterol values; these were found to be above the normal reference range for the former. Similarly, long-term kratom consumption (>5 years), and quantity of daily kratom use (≥3 ½ glasses; mitragynine content 76.3-114.8mg) did not appear to alter the hematological and biochemical parameters of kratom users.

    CONCLUSION: These data suggest that even long-term and heavy kratom consumption did not significantly alter the hematological and clinical-chemistry parameters of kratom users in a traditional setting.

  7. Singh D, Narayanan S, Müller CP, Swogger MT, Chear NJY, Dzulkapli EB, et al.
    J Ethnopharmacol, 2019 Apr 06;233:34-40.
    PMID: 30594604 DOI: 10.1016/j.jep.2018.12.038
    ETHNOPHARMACOLOGICAL RELEVANCE: The leaves of Mitragyna speciosa (Korth.) or kratom have been traditionally used in Malaysia and Thailand mainly to enhance work productivity, as a folk remedy for treating common ailments, and as a mood enhancer.

    AIM OF THE STUDY: This present study sought to investigate kratom use motives among regular kratom users in Malaysia.

    MATERIALS AND METHODS: A total of 116 regular kratom users were recruited for this cross-sectional survey. The Drinking Motives Questionnaire (DMQ) was administered to measure kratom use motives.

    RESULTS: Our results indicate that heavy (>3 glasses daily, each glass contains 48.24-50.4 mg of mitragynine) kratom use was associated with coping (t87.09 =3.544, p 3 glasses daily) kratom consumption (p 3 glasses daily) kratom consumption among regular kratom users in traditional, rural settings.

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