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Dive into the research topics where Alexander Tong Boon Tan is active.

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Featured researches published by Alexander Tong Boon Tan.


Journal of Gastroenterology and Hepatology | 2013

Non‐alcoholic fatty liver disease in diabetics – prevalence and predictive factors in a multiracial hospital clinic population in Malaysia

Wah-Kheong Chan; Alexander Tong Boon Tan; Shireene Ratna Vethakkan; Pei-Chien Tah; Anushya Vijayananthan; Khean-Lee Goh

There is currently no published study comparing prevalence of non‐alcoholic fatty liver disease (NAFLD) and associated factors among diabetics of different ethnicity in the Asia‐Pacific region.


Endocrine Practice | 2013

Hypothalamic germinoma masquerading as superior mesenteric artery (SMA) syndrome.

Vethakkan; Venugopal Y; Alexander Tong Boon Tan; S. S. Paramasivam; Jeyakantha Ratnasingam; Razak Ra; Alias A; Kassim F; Karen Choong

OBJECTIVE To report a case of superior mesenteric artery (SMA) syndrome secondary to hypothalamic germinoma. METHODS We describe the clinical presentation, diagnostic work-up, management, and clinical course of a patient admitted with SMA syndrome who was subsequently found to have a hypothalamic germinoma. RESULTS An adolescent boy was admitted to the surgical ward with progressive weight loss over a 2 year period and postprandial vomiting. He was diagnosed with SMA syndrome based on evidence of proximal duodenal dilatation, extrinsic compression of the distal duodenum, and a narrowed aortomesenteric angle (16°). Investigations performed to exclude thyrotoxicosis unexpectedly revealed secondary hypothyroidism and further evaluation demonstrated evidence of pan-hypopituitarism. Psychiatric evaluation excluded anorexia nervosa and bulimia. Magnetic resonance imaging (MRI) of the brain revealed a heterogeneously enhancing hypothalamic lesion, but a normal pituitary gland. Hormone replacement with hydrocortisone, desmopressin, testosterone, and thyroxine resulted in weight gain and resolution of gastrointestinal symptoms. A transventricular endoscopic biopsy subsequently confirmed a hypothalamic germinoma and he was referred to an oncologist. CONCLUSION SMA syndrome secondary to severe weight loss is an uncommon cause of upper gastrointestinal obstruction. While there have been reports of poorly controlled diabetes mellitus and thyrotoxicosis manifesting as SMA syndrome, there are no published reports to date of SMA syndrome secondary to hypothalamic/pituitary disease. Management of SMA syndrome is conservative, as symptoms of intestinal obstruction resolve with weight gain following treatment of the underlying cause. Awareness of this uncommon presentation of endocrine cachexia/hypothalamic disease will prevent unnecessary laparotomies and a misdiagnosis of an eating disorder.


Asia Pacific Journal of Clinical Nutrition | 2013

Effects of sun exposure on 25(OH) vitamin D concentration in urban and rural women in Malaysia.

Musa Nurbazlin; Winnie Siew Swee Chee; Pendek Rokiah; Alexander Tong Boon Tan; Yee Yean Chew; Abd Rahman Siti Nusaibah; Siew Pheng Chan

Ultraviolet B sunlight exposure is a primary source of vitamin D. There have been reports of low vitamin D status amongst the Malaysian population despite it being a tropical country. This study was conducted to determine the influence of sun exposure on 25(OH)D concentrations in urban and rural women in Malaysia and factors predicting 25(OH)D concentrations. Women aged above 45 years were recruited from urban (n=107) and rural areas (n=293). Subjects were interviewed regarding their outdoor activities and usual outdoor attire over the previous week. 25(OH)D concentrations were analyzed using the vitamin D3 (25-OH) electrochemiluminescence immunoassay. Median (Q1-Q3) age of the participants was 57 (53-61) years old. Median (Q1-Q3) 25(OH)D concentration of rural women was significantly higher [69.5 (59.0-79.1) nmol/L] compared to urban women [31.9 (26.1- 45.5) nmol/L] (p<0.001). Rural women spent more time in the sun compared to urban women (7.83 (3.67-14.7) vs 2.92 (1.17-4.92) hours, p<0.001), although the fraction of body surface area (BSA) exposed to sunlight was significantly higher in the urban group [0.21 (0.21-0.43) vs 0.12 (0.07-0.17), p<0.001]. The calculated sun index (hours of sun exposure per week × fraction of BSA) was significantly higher in rural [0.89 (0.42-1.83)] compared to urban women [0.72 (0.26-1.28)], p=0.018. In the stepwise linear regression, rural dwelling increased the serum 25(OH)D by 31.74 nmol/L and 25(OH)D concentrations increased by 1.93 nmol/L for every unit increment in sun index. Urban women in Malaysia had significantly lower vitamin D status compared to rural women. Rural dwelling and sun index were key factors influencing vitamin D status in Malaysian women.


Atherosclerosis | 2015

Effects of amount and type of dietary fats on postprandial lipemia and thrombogenic markers in individuals with metabolic syndrome

Kim-Tiu Teng; Chee-Yan Chang; M.S. Kanthimathi; Alexander Tong Boon Tan; Kalanithi Nesaretnam

OBJECTIVE Postprandial lipemia has been reported to affect endothelial function by thrombogenic and inflammatory pathways. We set out to investigate the impact of a) specific amount (50 g vs 20 g fat), and b) type of fatty acids (saturated, monounsaturated or n-6 polyunsaturated fatty acids; SFA, MUFA, PUFA) on postprandial lipemia, thrombogenic and inflammatory factors in metabolic syndrome subjects. DESIGN 30 subjects (15 men, 15 women) participated in a double-blind, randomized crossover design study with both the subjects and investigators blinded to treatments. Blood samples were collected at fasting and 30 min, hourly interval for a total of 6 h. RESULTS As expected, lower triacylglycerol response was observed for low fat/high carbohydrate meal; whereas no difference was detected between the types of fatty acids. The incremental area under the curve (iAUC) for low fat/high carbohydrate meal was 70%, 81% and 61% lower than the SFA, MUFA and PUFA meals, respectively. The iAUC 0-6 h for triacylglycerol was 42% lower in women compared with the men (P = 0.024), with the similar trend observed for non-esterified fatty acids. There were significant meal × time interaction (P = 0.000) for plasma plasminogen activator inhibitor-1 and thromboxane B2 (P = 0.022) from baseline. No differences were observed between meals for plasma D-dimer, interleukin-6, interleukin-1β, tumor necrosis factor-α and high sensitivity C-reactive protein. CONCLUSION These data indicate that in metabolic syndrome subjects, only the amount of dietary fatty acids affects postprandial lipemia but both amount and type of dietary fats alter thrombogenic factors. TRIAL REGISTRATION The study was registered at Clinicaltrials.gov (NCT01571947).


Asia Pacific Journal of Clinical Nutrition | 2015

Low Physical Activity and Energy Dense Malaysian Foods are Associated with Non-Alcoholic Fatty Liver Disease in Centrally Obese but not in Non-Centrally Obese Patients with Diabetes Mellitus

Wah-Kheong Chan; Mbbs; Mrcp; Alexander Tong Boon Tan; MBChB; Shireene Ratna dVethakkan; MMed; MD ; Pei-Chien Tah; Anushya Vijayananthan; MRad; dKhean-Lee Goh; Frcp

OBJECTIVE To study the dietary intake and level of physical activity (PA) of patients with diabetes mellitus and the association with non-alcoholic fatty liver disease (NAFLD). METHODS Consecutive adult patients with type 2 diabetes mellitus seen in our hospital diabetes clinic were enrolled. The Global Physical Activity Questionnaire and a semi-quantitative food-frequency questionnaire were used to assess PA and dietary intake, respectively. Diagnosis of NAFLD was ultrasound-based and following exclusion of significant alcohol intake and other causes of chronic liver disease. RESULTS Data for 299 patients were analyzed (mean age 63.3±10.5 years old, 41.1% male). Prevalence of NAFLD was 49.2%. Patients with low PA were more likely to have NAFLD (OR=1.75, 95% CI=1.03-2.99, p=0.029). There was no significant difference in energy intake, intake of macronutrients and percentage energy intake from each macronutrient, high sugar food, high cholesterol food and high SFA food between patients with and without NAFLD. Among centrally obese patients, patients with low PA and in the highest quartile of percentage energy intake from fat (OR=4.03, 95% CI=1.12-15.0, p=0.015), high cholesterol food (OR=3.61, 95% CI=1.37-9.72, p=0.004) and high SFA food (OR=2.67, 95% CI=1.08-6.67, p=0.019) were most likely to have NAFLD. Among those who were not centrally obese, PA and percentage energy intake from fat, high cholesterol food and high SFA food was not associated with NAFLD. CONCLUSION Low PA and high percentage energy intake from fat, high cholesterol food and high SFA food is associated with NAFLD in centrally obese but not in non-centrally obese patients with diabetes mellitus.


Journal of Diabetes and Its Complications | 2017

Place of sodium-glucose cotransporter-2 inhibitors in East Asian subjects with type 2 diabetes mellitus: Insights into the management of Asian phenotype

Lee Ling Lim; Alexander Tong Boon Tan; Kevin Moses; Viraj Rajadhyaksha; Siew Pheng Chan

The burden of type 2 diabetes (T2DM) in East Asia is alarming. Rapid modernization and urbanization have led to major lifestyle changes and a tremendous increase in the prevalence of obesity, metabolic syndrome, and diabetes mellitus. The development of T2DM at a younger age, with lower body mass index, higher visceral adiposity, and more significant pancreatic beta-cell dysfunction compared to Caucasians are factors responsible for the increased prevalence of T2DM in East Asians. Sodium-glucose Cotransporter-2 (SGLT2) inhibitors (canagliflozin, dapaglifozin, empagliflozin, etc.) reduce renal glucose reabsorption, leading to favorable effects on glycemic, blood pressure, and weight control. The insulin-independent mechanism enables their use as monotherapy or combination therapy with insulin and other oral antidiabetic agents. The role of SGLT2 inhibitors in the management of T2DM among East Asians is an interesting area of research, given that East Asians have been proven to be uniquely different from Caucasians. This review provides comprehensive coverage of the available literature not only on the efficacy and safety, but also on the recent cardiovascular and renal outcomes of SGLT2 inhibitors, focusing among East Asians.


Clinics and Research in Hepatology and Gastroenterology | 2014

Ultrasonography-diagnosed non-alcoholic fatty liver disease is not associated with prevalent ischemic heart disease among diabetics in a multiracial Asian hospital clinic population.

Wah-Kheong Chan; Alexander Tong Boon Tan; Shireene Ratna Vethakkan; Pei-Chien Tah; Anushya Vijayananthan; Khean-Lee Goh

BACKGROUND Non-alcoholic fatty liver disease (NAFLD) and cardiovascular diseases are both common among patients with diabetes mellitus. OBJECTIVE The aim of this study is to determine if ultrasonography-diagnosed NAFLD is associated with prevalent ischemic heart disease (IHD) among patients with diabetes mellitus. METHODS This is a cross-sectional study on consecutive patients seen at the Diabetic Clinic, University of Malaya Medical Centre. The medical record for each patient was reviewed for documented IHD. Patients without documented IHD but had symptoms and/or electrocardiographic changes suggestive of IHD were referred for cardiac evaluation. RESULTS Data for 399 patients were analyzed. Mean age was 62.8±10.5 years with 43.1% male. NAFLD and IHD were present in 49.6 and 26.6%, respectively. The prevalence of IHD among patients with and without NAFLD was 24.7 and 28.4%, respectively (P=0.414). The prevalence of IHD was highest among the Indians (34.1%) followed by the Malays (29.2%) and the Chinese (20.1%). No association was found between NAFLD and IHD when analyzed according to ethnicity. On multivariate analysis, independent factors associated with IHD were older age, lower levels of physical activity, greater waist circumference and higher serum glycated hemoglobin level. CONCLUSIONS Ultrasonography-diagnosed NAFLD was not associated with prevalent IHD among patients with diabetes mellitus in a multiracial Asian hospital clinic population.


Journal of Diabetes Investigation | 2017

Relationship of glycated hemoglobin, and fasting and postprandial hyperglycemia in type 2 diabetes mellitus patients in Malaysia

Lee Ling Lim; Alan Jm Brnabic; Siew Pheng Chan; Luqman Ibrahim; S. S. Paramasivam; Jeyakantha Ratnasingam; Shireene Ratna Vethakkan; Alexander Tong Boon Tan

Studies on the relative contributions of fasting and postprandial hyperglycemia (FH and PPH) to glycated hemoglobin (HbA1c) in patients with type 2 diabetes have yielded inconsistent results. We aimed to assess the relationship by using continuous glucose monitoring in a multi‐ethnic cohort.


The Journal of Clinical Endocrinology and Metabolism | 2013

Primary hyperparathyroidism: a rare cause of genu valgus in adolescence.

Jeyakantha Ratnasingam; Alexander Tong Boon Tan; Shireene Ratna Vethakkan; S. S. Paramasivam; L. Ibrahim; Lee Ling Lim; Karen Choong

A 15-year-old girl presented with a history of progressive genu valgus of both lower limbs. She had no other skeletal deformities or fractures. There was no significant family history, in particular none to suggest multiple endocrine neoplasia syndrome. Radiographs of the lower limbs confirmed severe bilateral genu valgus (Figure 1). Investigations revealed a markedly elevated serum corrected calcium of 12.4 mg/dL (normal, 8.8–10.4), phosphate of 2.8 mg/dL (normal, 3.4–5.8), alkaline phosphatase of 1136 IU/L (normal, 50–136), intact PTH of 1649 pg/ml (normal, 10–68), 25-hydroxyvitamin D of 28 ng/ml (normal, 9–52), and 24-hour urinary calcium of 196 mg/d (normal, 88–300). Further radiographs of the hand re-


Osteoporosis International | 2018

Reduced bone mineral density in human immunodeficiency virus-infected individuals: a meta-analysis of its prevalence and risk factors: supplementary presentation

S. S. L. Goh; Pauline Siew Mei Lai; Alexander Tong Boon Tan; Sasheela Ponnampalavanar

A meta-analysis was conducted to evaluate the prevalence of osteopenia/osteoporosis in human immunodeficiency virus (HIV)-infected individuals. The prevalence of osteopenia/osteoporosis in HIV-infected and antiretroviral therapy (ART)-treated individuals was significantly higher than respective controls. Evidence regarding bone loss within first year of HIV infection or ART initiation was preliminary.

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Jeyakantha Ratnasingam

University Malaya Medical Centre

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S. S. Paramasivam

University Malaya Medical Centre

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L. Ibrahim

University Malaya Medical Centre

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