Variable impact of tizanidine on the medium latency reflex of upper and lower limbs

Sudden limb displacement evokes a complex sequence of compensatory muscle activity. Following the short-latency reflex and preceding voluntary reactions is an epoch termed the medium-latency reflex (MLR) that could reflect spinal processing of group II muscle afferents. One way to test this possibility is oral ingestion of tizanidine, an alpha-2 adrenergic agonist that inhibits the interneurons transmitting group II signals onto spinal motor neurons. We examined whether group II afferents contribute to MLR activity throughout the major muscles that span the elbow and shoulder. MLRs of ankle muscles were also tested during walking on the same day, in the same participants as well as during sitting in a different group of subjects. In contrast to previous reports, the ingestion of tizanidine had minimal impact on MLRs of arm or leg muscles during motor actions. A significant decrease in magnitude was observed for 2/16 contrasts in arm muscles and 0/4 contrasts in leg muscles. This discrepancy with previous studies could indicate that tizanidine's efficacy is altered by subtle changes in protocol or that group II afferents do not substantially contribute to MLRs.

The effect of long-term bisphosphonate therapy on trabecular bone strength and microcrack density

Objectives

Bisphosphonates (BP) are the first-line treatment for preventing fragility fractures. However, concern regarding their efficacy is growing because bisphosphonate is associated with over-suppression of remodelling and accumulation of microcracks. While dual-energy X-ray absorptiometry (DXA) scanning may show a gain in bone density, the impact of this class of drug on mechanical properties remains unclear. We therefore sought to quantify the mechanical strength of bone treated with BP (oral alendronate), and correlate data with the microarchitecture and density of microcracks in comparison with untreated controls.

Methods

Trabecular bone from hip fracture patients treated with BP (n = 10) was compared with naïve fractured (n = 14) and non-fractured controls (n = 6). Trabecular cores were synchrotron scanned and micro-CT scanned for microstructural analysis, including quantification of bone volume fraction, microarchitecture and microcracks. The specimens were then mechanically tested in compression.

Results

BP bone was 28% lower in strength than untreated hip fracture bone, and 48% lower in strength than non-fractured control bone (4.6 MPa vs 6.4 MPa vs 8.9 MPa). BP-treated bone had 24% more microcracks than naïve fractured bone and 51% more than non-fractured control (8.12/cm²vs 6.55/cm²vs 5.25/cm²). BP and naïve fracture bone exhibited similar trabecular microarchitecture, with significantly lower bone volume fraction and connectivity than non-fractured controls.

Conclusion

BP therapy had no detectable mechanical benefit in the specimens examined. Instead, its use was associated with substantially reduced bone strength. This low strength may be due to the greater accumulation of microcracks and a lack of any discernible improvement in bone volume or microarchitecture. This preliminary study suggests that the clinical impact of BP-induced microcrack accumulation may be significant.

Cite this article: A. Jin, J. Cobb, U. Hansen, R. Bhattacharya, C. Reinhard, N. Vo, R. Atwood, J. Li, A. Karunaratne, C. Wiles, R. Abel. The effect of long-term bisphosphonate therapy on trabecular bone strength and microcrack density. Bone Joint Res 2017;6:602–609. DOI: 10.1302/2046-3758.610.BJR-2016-0321.R1.

Age-dependent relationships between body mass index and mortality: Singapore longitudinal ageing study

OBJECTIVES

The relationship between body mass index (BMI) with mortality risk, in particular the BMI category associated with the lowest all-cause and CVD-and-stroke mortality and the BMI threshold for defining overweight or obesity in older persons is controversial. This study investigated the age-dependent associations of BMI categories with all-cause and cardiovascular disease (CVD) and stroke mortality.

METHOD

Prospective cohort study (Singapore Longitudinal Ageing Studies) of older adults aged 55 and above, followed up from 2003 to 2011. Participants were 2605 Chinese with baseline BMI and other variables. Outcome Measurement: Mortality hazard ratios (HR) for all-cause and CVD and stroke mortality.

RESULTS

Overall, BMI showed a U-shaped relationship with all-cause and CVD and stroke mortality, being lowest at Normal Weight-II category (BMI 23.0-24.9 kg/m2). Most evidently among the middle-aged (55-64 years), all-cause mortality risks relative to Normal Weight-II were elevated for underweight (<BMI 18.5; HR = 4.92, p<0.0138), Normal Weight-I (BMI 18.5-22.9; HR = 3.41, p = 0.0149), and Overweight-Obese (BMI>30.0; HR = 4.05,p = 0.0423). Among the old (≥65 years), however, Overweight and Obese categories were not significantly associated with increased all-cause mortality (HR from 0.98 to 1.29), but Overweight-Obese was associated with increased CVD and stroke mortality (HR = 10.0, p = 0.0086).

CONCLUSION

BMI showed a U-shaped relationship with mortality. Among older persons aged 65 and above, the overweight-or-obese category of BMI was not associated with excess all-cause mortality.

Abstract 5318: Intake of tea and tea flavonoids, coffee and caffeine in relation to risk of lung cancer - the Singapore Chinese Health Study

Background: Coffee and tea are widely consumed beverages. Tea flavonoids have been shown to inhibit lung tumorigenesis in in-vitro and animal models. Conversely, coffee contains complex mixtures of biochemically active compounds that may have genotoxic and mutagenic properties. However, previous epidemiologic studies have shown inconsistent results on tea and coffee in relation to lung cancer risk.

Methods: The association between intake of tea and coffee, and their active compounds, and risk of lung cancer was investigated in the Singapore Chinese Health Study, a population-based prospective cohort of 63,257 Singaporean Chinese men and women aged 45-74 years at enrollment from 1993 through 1998. Information on demographic, lifestyle and habitual diet was collected through in-person interviews using a structured questionnaire which included a validated food-frequency questionnaire. The intake of caffeine and tea flavonoids was estimated for each participant based on the Singapore Food Composition Database, which was developed for this cohort and provided 96 nutritional and non-nutritional values per 100 grams of the edible portion for each of 165 surveyed foods and beverages specific for the study population. Flavonoids predominantly from black tea included theaflavin, thearubigin, theaflavin-3-3’-digallate, theaflavin-3’-gallate and theaflavin-3-gallate while those predominantly from green tea included catechin, epigallocatechin, epicatechin, epicatechin-3-gallate and epigallocatechin-3-gallate. Incident lung cancer cases were identified via record linkage with the nationwide cancer registry through 31 December 2013. Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations with adjustment for potential confounders.

Results: Compared to non-daily coffee drinkers, HR (95% CI) of lung cancer for those consuming 1 and 2 or more cups of coffee per day was 1.16 (1.00-1.34) and 1.29 (1.02-1.64), respectively (P for trend=0.029). Among ever smokers, black tea was inversely associated with risk of lung cancer (P for trend=0.037). HR (95% CI) was 0.83 (0.69-1.00) for the highest third of consumers (average 1.5 cups/day) compared to non-black tea drinkers. Consistently, flavonoids predominantly from black tea were also inversely associated with lung cancer risk (P for trend=0.045). This risk reduction with black tea and their major flavonoids was only observed in ever smokers and not in never smokers. There was no statistically significant association for lung cancer risk with total caffeine, green tea or flavonoids predominantly from green tea, regardless of smoking status.

Conclusions: Coffee may increase the risk of developing lung cancer, and this effect does not seem to be mediated by its caffeine content. Conversely, black tea and flavonoids found mainly in black tea may reduce the risk of lung cancer among ever smokers.

Citation Format: Wei Jie Seow, Aizhen Jin, Jian-Min Yuan, Woon-Puay Koh. Intake of tea and tea flavonoids, coffee and caffeine in relation to risk of lung cancer - the Singapore Chinese Health Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5318. doi:10.1158/1538-7445.AM2017-5318

Abstract 2273: Serum choline, methionine, betaine, dimethylglycine, and trimethylamine-N-oxide in relation to pancreatic cancer risk in two nested case-control studies in Asian populations

Background: Choline, methionine, and betaine are methyl group donors associated with DNA methylation. Diets deficient in choline and methionine have been shown to promote pancreatic carcinogenesis in experimental animals. We have previously reported an inverse association between dietary intake of choline and pancreatic cancer risk in a prospective cohort of Singapore Chinese. In the present study biomarkers of dietary choline and other methyl donor nutrients were evaluated in relation to pancreatic cancer risk.

Method: Two case-control studies were nested within the Shanghai Cohort Study (129 cases and 258 matched controls) and the Singapore Chinese Health Study (58 cases and 104 matched controls). Concentrations of choline, methionine, betaine, dimethylglycine (DMG), and trimethylamine-N-oxide (TMAO) were

measured by LC-MS/MS in pre-diagnostic serum samples. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression method with adjustment for potential confounders.

Results: Choline, methionine, and betaine were moderately associated with each other (spearman correlation coefficient: 0.28 ~0.43). In the pooled analysis, serum choline, betaine, and methionine were inversely associated with risk of pancreatic cancer, while TMAO, an oxidative metabolite of choline produced by gut microbiota, was positively associated with risk of pancreatic cancer. Compared with the lowest quartile, ORs (95%CIs) of pancreatic cancer for the highest quartiles of choline, methionine, betaine, and TMAO were 0.37 (0.17-0.80), 0.39 (0.22-0.69), 0.49 (0.28-0.85), and 1.60 (0.94-2.74), respectively (all Ps for trend &lt; 0.05). DMG was not associated with pancreatic cancer risk.

Conclusion: The novel inverse associations of serum choline, methionine, and betaine with risk of pancreatic cancer support the notion that methyl groups related to DNA methylation may modulate the risk of pancreatic cancer development. The positive association between TMAO and pancreatic cancer risk suggested gut microbiota may play an important role in pancreatic carcinogenesis.

Citation Format: Joyce Huang, Lesley Butler, Øivind Midttun, Renwei Wang, Aizhen Jin, Yu-Tang Gao, Per Ueland, Woon-Puay Koh, Jian-Min Yuan. Serum choline, methionine, betaine, dimethylglycine, and trimethylamine-N-oxide in relation to pancreatic cancer risk in two nested case-control studies in Asian populations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2273. doi:10.1158/1538-7445.AM2017-2273

Abstract 2274: Extreme telomere length was associated with gastric adenocarcinoma risk: The Singapore Chinese Health Study

Background: Evidence regarding extreme telomere length and increased gastric cancer risk has been limited in retrospective case-control study setting which was potentially subjected to selection bias and reverse causality. We conducted a prospective analysis in an Eastern Asian population to examine the hypothesis that extreme telomere length is associated with increased risk of gastric adenocarcinoma.

Methods: Among 63,257 participants of the Singapore Chinese Health Study, a population-based prospective cohort of Chinese men and women aged 45-74 years recruited between 1993 and 1998, 28,219 provided baseline blood samples. We used quantitative polymerase chain reaction (PCR) method to quantify relative telomere length determined by the ratio of telomere repeat copy number (T) to single-copy gene for albumin (S) (i.e., TSR) on all subjects. The present analysis included 24,846 subjects with valid TSR values after excluding samples with insufficient DNA (n = 1,908) and/or patients with prevalent cancer at baseline blood draw (n = 1,465). As of December 31, 2014, 191 study participants who were free of cancer developed gastric adenocarcinoma. The information on demographic and lifestyle characteristics was collected using structured questionnaires at baseline and two follow-up interviews. Cox proportional

hazard regression method was used to estimate hazard ratio (HR) and the corresponding 95% confidence interval (CI) of developing gastric adenocarcinoma for different levels of decile TSR. Restricted cubic spline (RCS) analysis was applied to examine the nonlinear relationship between TSR level and gastric adenocarcinoma risk.

Results: The RCS analysis revealed a U-shaped relationship between TSR and gastric adenocarcinoma risk (p-value for non-linear association=0.009). Compared with the 4th decile, HR (95% CI) for the lowest and highest deciles of TSR 2.27 (1.17-4.40) and 1.98 (0.95-4.13), respectively after adjusting for age, sex, education, interview year, dialect group and smoking status.

Conclusions: This was the first prospective analysis of TSR and risk of developing gastric adenocarcinoma in a general population. The study demonstrates both extreme short and long telomere length to be associated with significantly increased risk of gastric adenocarcinoma. These results suggest a complex relationship between telomere length and gastric cancer risk.

Citation Format: Zhensheng Wang, Woon-Puay Koh, Aizhen Jin, Renwei Wang, Jian-Min Yuan. Extreme telomere length was associated with gastric adenocarcinoma risk: The Singapore Chinese Health Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2274. doi:10.1158/1538-7445.AM2017-2274

Abstract 2267: A prospective assessment for telomere length in relation to risk of cancer in the Singapore Chinese Health Study

Background: Telomeres are crucial in the maintenance of chromosome integrity and genomic stability. A critically short telomere length can trigger cell to enter replicative senescence with a result of cell death; alternatively, cells continue to divide if death does not occur, which results in genomic instability and chromosomal abnormality. A series of epidemiological studies have examined the association between telomere length and the risk of cancers, but the findings remain conflicting.

Methods: Among 63,257 participants of the Singapore Chinese Health Study, a population-based prospective cohort of Chinese men and women aged 45-74 years recruited from 1993 through 1998, 28,219 provided baseline blood samples. We used quantitative polymerase chain reaction (PCR) method to quantify relative telomere length determined by the ratio of telomere repeat copy number (T) to single-copy gene for albumin (S) (i.e., TSR) on all subjects. The present analysis included 24,847 subjects with valid TSR values after excluding samples with insufficient DNA (n = 1,908) and/or patients with prevalent cancer at baseline blood draw (n =1,464). As of December 31, 2015, 3,778 participants developed cancer, including 722 colorectal cancer, 599 lung cancer, and 412 breast cancer. Cox models were used to estimate hazard ratio (HR) and 95% confidence interval (CI) of developing any cancer and these selected specific cancer types for different quintiles of TSR.

Results: Women had a 5.7% higher TSR value than men (P&lt;0.0001). Age, level of education, number of cigarettes/day, years of smoking, and pack-years of smoking were all inversely associated with TSR (P&lt;0.0001). High TSR was associated, in a dose-dependent manner, with significantly increased risk of total cancer and breast, colorectal and lung cancer. Compared with the lowest quintile, the HRs (95% CIs) of total cancer for the 2nd, 3rd, and 4th, and 5th quintile of TSR were 1.03 (0.89, 1.20), 1.08 (0.93-1.26), 1.15 (0.98-1.34), and 1.36 (1.16-1.58), respectively, after adjustment for age, sex, education and smoking (Ptrend=0.001). The corresponding HRs (95% CIs) were 1.21 (0.72-2.03), 1.59 (0.97-2.60), 1.59 (1.04-2.75) and 1.62 (0.99-2.66) for breast cancer (Ptrend=0.023); 1.44 (1.03-2.00), 1.10 (0.76-1.59), 1.32 (0.92-1.90) and 1.88 (1.32-2.66) for colorectal cancer (Ptrend=0.004); and 1.41 (0.98-2.05), 1.37 (0.93-2.02), 1.31 (0.86-1.99) and 1.88 (1.26-2.81) for lung cancer (Ptrend=0.010).

Conclusions: This prospective cohort study demonstrates that longer telomere length is associated with significantly increased risk of total and major cancers in a general population. These results suggest a complex role of telomere in the development of cancer.

Citation Format: Jian-Min Yuan, Renwei Wang, Kenneth Beckman, Aizhen Jin, Woon-Puay Koh. A prospective assessment for telomere length in relation to risk of cancer in the Singapore Chinese Health Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2267. doi:10.1158/1538-7445.AM2017-2267

Increased body mass index is a risk factor for end-stage renal disease in the Chinese Singapore population

The relationship between body mass index (BMI) and end-stage renal disease (ESRD) is confounded by co-morbidities associated with both conditions. Furthermore, the association at low range BMI is controversial. We studied this association in the Singapore Chinese Health Study, a population-based prospective cohort that recruited Singaporean Chinese men and women 45-74 years of age from 1993 to 1998. Self-reported weight, height, lifestyle factors, usual diet, and medical history were collected via an interviewer-administered questionnaire. Incident ESRD cases were identified via record linkage with the nationwide ESRD registry. The computed Cox proportional hazard regression was adjusted for potential risk factors. After an average follow-up of 15.5 years, 827 incident ESRD cases were identified. Compared with a normal BMI of 18.5 to under 23 kg/m², the hazard ratios and (95% confidence intervals) of ESRD risk for BMIs under 18.5, 23 to under 27.5, and 27.5 kg/m² or more were 0.54 (0.37-0.79), 1.40 (1.20-1.64) and 2.13 (1.74-2.59), respectively. This significantly trended, linear, dose-dependent association was only present among those with no history of diabetes, hypertension, coronary heart disease, and stroke at baseline, but not significantly among those with any of these co-morbidities. Thus, BMI itself is a risk factor for ESRD in the general population and this association is present in those without pre-existing diabetes, hypertension, coronary heart disease, and stroke.

CYP2A6 genetic polymorphisms and biomarkers of tobacco smoke constituents in relation to risk of lung cancer in the Singapore Chinese Health Study

Cytochrome P450 2A6 (CYP2A6) catalyzes the metabolism of nicotine and the tobacco-specific lung carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Genetic variation in CYP2A6 may affect smoking behavior and contribute to lung cancer risk. A nested case-control study of 197 lung cancer cases and 197 matched controls was conducted within a prospective cohort of 63 257 Chinese men and women in Singapore. Quantified were five genetic variants of CYP2A6 (*1A, *4, *7, *9 and *12) and urinary metabolites of nicotine [total nicotine, total cotinine, total trans-3'-hydroxycotinine (3HC)] and NNK (total NNAL, free NNAL, NNAL-glucuronide, NNAL-N-glucuronide, and NNAL-O-glucuronide). Higher urinary metabolites of nicotine and NNK were significantly associated with a 2- to 3-fold increased risk of lung cancer after adjustment for smoking intensity and duration. Lower CYP2A6-determined nicotine metabolizer status was significantly associated with a lower ratio of total 3HC over total cotinine, lower total nicotine equivalent and reduced risk of developing lung cancer (all Ptrend < 0.001). Compared with normal metabolizers, odds ratios (95% confidence intervals) of developing lung cancer for intermediate, slow and poor metabolizers determined by CYP2A6 genotypes were 0.85 (0.41-1.77), 0.55 (0.28-1.08) and 0.32 (0.15-0.70), respectively, after adjustment for smoking intensity and duration and urinary total nicotine equivalents. Thus the reduced risk of lung cancer in smokers with lower CYP2A6 activity may be explained by lower consumption of cigarettes, less intense smoking and reduced CYP2A6-catalyzed activation of the tobacco-specific lung carcinogen NNK.

Composite protective lifestyle factors and risk of developing gastric adenocarcinoma: the Singapore Chinese Health Study

BACKGROUND

Incidence of gastric cancer is the highest in Eastern Asia. Multiple modifiable lifestyle factors have been identified as risk factors for gastric cancer. However, their aggregated effect on the risk of gastric cancer has not been examined among populations with high prevalence of Helicobacter pylori.

METHODS

A study was conducted to examine the association between multiple lifestyle factors together and the risk of developing gastric adenocarcinoma in the Singapore Chinese Health Study, a prospective cohort of 63 257 men and women between 45 and 74 years enroled during 1993-1998. Composite score of cigarette smoking, alcohol consumption, obesity, dietary pattern, and sodium intake at baseline was assessed with hazard ratio (HR) and 95% confidence interval (CI) of gastric adenocarcinoma using Cox regression method.

RESULTS

Higher healthy composite lifestyle scores were significantly associated with reduced risk of gastric adenocarcinoma in a dose-dependent manner. Hazard ratios (95% CIs) for total, cardia, and non-cardia gastric adenocarcinoma for the highest (score 5) vs lowest composite score (score 0/1/2) were 0.42 (0.31-0.57), 0.22 (0.10-0.47), and 0.55 (0.39-0.78), respectively (all Ptrend<0.001). These lifestyles together accounted for 48% of total gastric adenocarcinoma cases in the study population. The inverse association was observed in both genders, and remained after exclusion of first 5 years of follow-up.

CONCLUSIONS

The inverse association between the aggregated healthy lifestyle factors and the risk of gastric adenocarcinoma is in dose-dependent manner in this highly H. pylori-exposed population. These lifestyle factors together may account for up to half of disease burden in this study population.

Serum B6 vitamers (pyridoxal 5'-phosphate, pyridoxal, and 4-pyridoxic acid) and pancreatic cancer risk: two nested case-control studies in Asian populations

BACKGROUND

Vitamin B6 is an important enzymatic cofactor in pathways relevant for the development of pancreatic cancer. In order to evaluate vitamin B6 as a preventive factor for pancreatic cancer, a biomarker approach is needed to overcome the limitations inherent in self-reported dietary information.

METHODS

To determine whether levels of serum B6 vitamers, including pyridoxal 5'-phosphate (PLP), pyridoxal (PL), 4-pyridoxic acid (PA), and the PA/(PLP + PL) ratio (PAr), were associated with risk of pancreatic cancer, two nested case-control studies of 187 incident pancreatic cancer cases and 258 individually matched controls were conducted within two prospective cohorts of 81,501 participants in Shanghai, China, and Singapore. PLP, PL, and PA were quantified in pre-diagnostic serum samples. Odds ratios and 95% confidence intervals (CIs) were calculated using conditional logistic regression with adjustment for potential confounders.

RESULTS

The median (5th-95th percentiles) concentrations of serum PLP among control subjects of the Shanghai and Singapore cohorts were 25.7 (10.0-91.7) nmol/L and 58.1 (20.8-563.0) nmol/L, respectively. In pooled analyses, high serum PLP was associated with a reduced risk of pancreatic cancer (P for trend = 0.048); the adjusted odds ratio for the highest category of PLP (>52.4 nmol/L) was 0.46 (95% CI 0.23, 0.92) compared to vitamin B6 deficiency (<20 nmol/L). No associations were found for serum PL, PA, or PAr with pancreatic cancer risk.

CONCLUSIONS

Higher concentrations of PLP may protect against the development of pancreatic cancer. The protective effect may be more apparent in populations with low concentrations of circulating vitamin B6.

Heel reconstruction with parallel fibular osteoseptocutaneous flap

Reconstruction of heel defects can be challenging and requires careful consideration in restoring both the functional and aesthetic deficit. This study assessed the use of parallel fibular osteoseptocutaneous flap to repair composite heel defects. Follow-up of the 4 patients included in this study ranged from 24 months to 3 years after their operation. The flap survival rate was 100% in all patients, with good coverage of the heel defects. Postoperative complication was one -superficial wound infection. Union of the graft with the host bone was achieved in all patients at an average of 6 months (range : 5-10 m/onths). The parallel fibular osteoseptocutaneous flap is thus a reliable means of reconstruction of composite bone and soft-tissue -defect in the heel region.

Red Meat Intake and Risk of ESRD

Randomized controlled trials suggest that protein restriction may retard the progression of CKD toward ESRD. However, the effects of dietary protein intake level and the food sources of dietary protein on the risk of ESRD in the general population remain unclear. We investigated these effects in the Singapore Chinese Health Study, a prospective population-based cohort that recruited 63,257 Chinese adults aged 45-74 years from 1993 to 1998. We collected habitual diet information via a validated semiquantitative food frequency questionnaire and identified ESRD via record linkage with a nationwide registry. In all, 951 cases of ESRD occurred over a mean follow-up of 15.5 years. Regarding total protein intake, compared with the lowest quartile, the three higher quartiles combined had a hazard ratio for ESRD of 1.24 (95% confidence interval [95% CI], 1.05 to 1.46), but the dose-dependent association across the quartiles was not statistically significant (P_trend=0.16). Red meat intake strongly associated with ESRD risk in a dose-dependent manner (hazard ratio for highest quartile versus lowest quartile,1.40 [95% CI, 1.15 to 1.71; P_trend<0.001]). Intake of poultry, fish, eggs, or dairy products did not associate with risk of ESRD. In substitution analysis, replacing one serving of red meat with other food sources of protein associated with a maximum relative risk reduction of 62.4% (95% CI, 33.1 to 78.9; P<0.01). Our study shows that red meat intake may increase the risk of ESRD in the general population and substituting alternative sources of protein may reduce the incidence of ESRD.

Dietary fatty acids and risk of hepatocellular carcinoma in the Singapore Chinese health study

BACKGROUND & AIM

Lipidomic signature of lipid metabolism suggests that omega-6 polyunsaturated fatty acids (PUFA) may play a role in oncogenesis of hepatocellular carcinoma (HCC). Hence, we examined the association between dietary fatty acids and risk of HCC.

METHODS

We used data from the Singapore Chinese Health Study, a population-based prospective cohort of 63 257 Chinese men and women aged 45-74 years enrolled between 1993 and 1998. Information on current diet assessed via a validated semi-quantitative food frequency questionnaire, medical history and lifestyle factors were obtained through in-person interview, and incidence of HCC recorded through 31 Dec 2010. We also examined the association between dietary fatty acids and HCC risk using a case-control set of 92 cases and 274 controls with available serological biomarkers of chronic infections with hepatitis B virus (HBV) and hepatitis C virus (HCV) nested within this cohort.

RESULTS

Among the dietary fat components examined, which included saturated, monounsaturated, omega-3 and omega-6 PUFA, only omega-6 PUFA intake displayed a dose-dependent, positive association with HCC risk (p for trend = 0.02). Compared to the lowest quartile, the hazard ratio for the highest quartile intake was 1.49 [(95% confidence interval (CI):1.08-2.07)]. In the nested case-control study, only among individuals negative for serology markers of chronic infection with HBV or HCV, those who consumed above median levels of dietary omega-6 PUFA had increased HCC risk (odds ratio = 4.36, 95% CI = 1.59-11.94) compared to those with lower intake.

CONCLUSION

Dietary omega-6 PUFA may be implicated in the risk of non-viral hepatitis related HCC.

Ecological analyses of the associations between injury risk and socioeconomic status, geography and Aboriginal ethnicity in British Columbia, Canada

BACKGROUND

The current study examines what factors contribute to higher injury risk among Aboriginal peoples, compared to the total British Columbia (BC) population. We explore socioeconomic, geographic, and cultural factors, and combinations of these factors, that contribute to increased injury risk for Aboriginal peoples. This follows from our previously reported findings of improvements in injury risk over time for both the total and Aboriginal populations.

DATA AND METHODS

We use provincial population-based linked health care databases of hospital discharge records. We identify three population groups: total BC population, and Aboriginal populations living off-reserve, or on-reserve. For each group we calculate age and gender-standardized relative risks (SRR) of injury-related hospitalization, relative to the total population of BC, for two 5-year time periods (1999-2003, and 2004-2008). We use custom data from the 2001 and 2006 long-form Censuses that described income, education, employment, housing conditions, proportion of urban dwellers, proportion of rural dwellers, and prevalence of Aboriginal ethnicity. We use multivariable linear regression to examine the associations between the census characteristics and SRR of injury.

RESULTS

The best-fitting model was an excellent fit (R(2) = 0.905, p < 0.001) among the three population groups within Health Service Delivery Areas of BC. We find indicators in all three categories (socioeconomic, geographic, and cultural) are associated with disparity in injury risk. While the socioeconomic indicators (income, education, housing, employment) were shown to be highly correlated, only living in housing that needs major repair and occupational hazardousness, along with rural residence and Aboriginal ethnicity, remained in the final model. Our data show that cultural density is not associated with injury risk for Aboriginal peoples, and that living off-reserve is associated with reduced injury by improving socioeconomic and geographic conditions (compared to living on-reserve). Finally, our analyses show that Aboriginal status itself is associated with injury risk.

CONCLUSIONS

Our findings confirm previous research indicating that geographical differences differentiate injury risk, including for Aboriginal populations, and that socioeconomic determinants are associated with health risks. Our analyses showing that Aboriginal status itself contributes to injury risk is new, but we can only speculate about pathway, and whether the causes are direct or indirect.

Reproductive factors, hormone use and gastric cancer risk: The Singapore Chinese Health Study

Gastric cancer incidence varies greatly worldwide, but is consistently twice as high in men than in women. The hormone-related factors hypothesized to be associated with lower risk of gastric cancer in women have not been fully explored in populations with a high background risk of gastric cancer. The Singapore Chinese Health Study (SCHS) is a prospective cohort study in which 34,022 of the participants enrolled between 1993 and 1998 were women between 45 and 74 years of age. Information on reproductive histories, hormone replacement therapy (HRT) and oral contraceptive (OC) use was collected through in-person interviews at baseline. As of December 31, 2013, 269 incident gastric cancer cases were identified. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to evaluate gastric cancer risk associations. Older age at natural menopause (≥55 versus <45 years: HR = 0.50, 95% CI: 0.25-0.99), type of menopause (other versus natural: HR = 0.48, 95% CI: 0.27-0.87) and greater years of menstrual cycling (fourth versus first quartile: HR = 0.67, 95% CI: 0.46-0.96) were associated with a decreased risk of gastric cancer. Ever use of OCs and HRT was also associated with reduced risk of gastric cancer; the multivariable-adjusted HRs (95% CIs) were 0.40 (0.17-0.90) for use of HRT >3 years and 0.67 (0.47-0.94) for ever use of OCs, compared with never use. Reproductive factors associated with a longer window of fertility and the use of exogenous hormones were shown to reduce gastric cancer development in a cohort of Chinese women with a high background risk of gastric cancer.

Homocysteine induces glyceraldehyde-3-phosphate dehydrogenase acetylation and apoptosis in the neuroblastoma cell line Neuro2a

High plasma levels of homocysteine (Hcy) promote the progression of neurodegenerative diseases. However, the mechanism by which Hcy mediates neurotoxicity has not been elucidated. We observed that upon incubation with Hcy, the viability of a neuroblastoma cell line Neuro2a declined in a dose-dependent manner, and apoptosis was induced within 48 h. The median effective concentration (EC₅₀) of Hcy was approximately 5 mM. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) nuclear translocation and acylation has been implicated in the regulation of apoptosis. We found that nuclear translocation and acetylation of GAPDH increased in the presence of 5 mM Hcy and that higher levels of acetyltransferase p300/CBP were detected in Neuro2a cells. These findings implicate the involvement of GAPDH in the mechanism whereby Hcy induces apoptosis in neurons. This study highlights a potentially important pathway in neurodegenerative disorders, and a novel target pathway for neuroprotective therapy.

Dietary Intake of One-Carbon Metabolism-Related Nutrients and Pancreatic Cancer Risk: The Singapore Chinese Health Study

BACKGROUND

Nutrients involved in one-carbon metabolism are hypothesized to protect against pancreatic cancer development.

METHODS

The Singapore Chinese Health Study database was used to prospectively examine the association between intake of one-carbon metabolism-related nutrients and pancreatic cancer risk. Between 1993 and 1998, 63,257 men and women ages 45 to 74 years were enrolled into the cohort. The daily intakes of the following one-carbon metabolism-related nutrients were assessed at enrollment using a 165-item food frequency questionnaire: betaine, choline, folate, and vitamins B2, B6, and B12. Multivariable HRs and 95% confidence intervals (CI) for pancreatic cancer risk associated with dietary intakes of one-carbon metabolism-related nutrients were calculated.

RESULTS

As of December 2013, 271 incident pancreatic cancer cases were identified during an average of 16.3 years of follow-up. Higher intakes of vitamin B6 and choline were associated with statistically significant decreases in the risk of developing pancreatic cancer. Compared with the lowest quartile, HRs (95% CIs) for the highest quartiles of vitamin B6 and choline were 0.52 (0.36-0.74; P trend = 0.001) and 0.67 (0.48-0.93; P trend = 0.04), respectively. There were no clear associations between the other one-carbon metabolism-related nutrients and pancreatic cancer risk.

CONCLUSION

Our study suggests that higher intake of vitamin B6 and choline may lower the risk of pancreatic cancer.

IMPACT

Our prospective findings are consistent with the in vivo evidence for protective roles of vitamin B6 and choline on pancreatic cancer development.

Mortality of older persons living alone: Singapore Longitudinal Ageing Studies

BACKGROUND

We investigated the association of living alone with mortality among older persons, independently of marital, health and other factors, and explored its effect modification by age group, sex, marital status and physical functional disability.

METHOD

Using data from 8 years of mortality follow up (1 September 2003 to 31 December 2011) of 2553 participants in the Singapore Longitudinal Ageing Studies (SLAS) cohort, we estimated hazard ratio (HR) of mortality associated with living alone using Cox proportional hazard models.

RESULTS

At baseline, 7.4 % (N = 189) of the participants were living alone, and 227 (8.9 %) died during the follow up period. Living alone was significantly associated with mortality 1.66 (95 % CI, 1.05-2.63), controlling for health status (hypertension, diabetes, chronic lung disease, stroke, heart disease, kidney failure, IADL-ADL disability and depressive symptoms), marital status and other variables (age, sex, housing type). Possible substantive effect modification by sex (p for interaction = 0.106) and marital status (p for interaction <0.115) were observed: higher among men (HR = 2.36, 95 % CI, 1.24-4.49) than women (HR = 1.14, 95 % CI, 0.58-2.22), and among single, divorce or widowed (HR = 2.26, 95 % CI, 1.24-4.10) than married individuals (HR = 0.83, 95 % CI, 0.30-2.31).

CONCLUSION

Living alone was associated with increased mortality, independently of marital, health and other variables. The impact of living alone on mortality appeared to be stronger among men and those who were single, divorced or married.

Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone

A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications.

Combined supercontinuum source with >200 W power using a 3 × 1 broadband fiber power combiner

We report an incoherently combined near-infrared supercontinuum (SC) source with >200  W output power using a 3×1 broadband fiber power combiner. A broadband fiber power combiner is designed and theoretically investigated. The power transmission efficiencies of light at different wavelengths of the combiner are calculated, and the combiner is verified to be capable of combining broadband sources efficiently. Then a combiner is fabricated. Three ∼70  W near-infrared SC sources are constructed and then, using the combiner, a >200  W near-infrared SC source is obtained. Conclusively, using incoherently combining method we can obtain a high-power SC source, and the thermo-management can be realized easily. We believe that this is a suitable method to obtain a higher-power SC source.

Abstract 863: Exogenous hormone use was inversely associated with gastric cancer risk among women: The Singapore Chinese Health Study

Background: There is a 23-fold difference in gastric cancer incidence worldwide between high- and low-risk populations. In all regions, gastric cancer incidence is two-fold higher among men, compared with women. Although higher prevalence of established risk factors in men may explain some of the sex disparity, a protective role of high lifelong exposure to estrogens may contribute to the lower gastric cancer incidence for women. There have been few prospective data evaluating associations with gastric cancer risk for markers of estrogen exposure in high-risk populations.

Methods: In the Singapore Chinese Health Study, 34,022 women between 45 and 74 years of age were recruited as cohort participants between 1993 and 1998. By December 2013, 315 incident gastric cancer cases were identified. Information about menstrual and reproductive histories, as well as oral contraceptive (OC) and hormone replacement therapy (HRT) use was collected at the baseline interview. Cox proportional hazard regression was performed to obtain the adjusted hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) for menstrual and reproductive factors and exogenous hormone use with gastric cancer risk. In secondary analyses, a nested case-control study was conducted in which Helicobacter (H.) pylori infection and atrophic gastritis status were evaluated in conditional logistic regression models as potential confounders on the association between hormone-related factors and gastric cancer risk.

Results: Compared with nonusers, ever use of HRT (HR = 0.55; 95%CI: 0.26, 1.18), OCs (HR = 0.69; 95%CI: 0.51, 0.95) and HRT and/or OCs (HR = 0.67; 95%CI: 0.49-0.92) was associated with a lower risk of gastric cancer. A statistically significant trend with increasing age at first OC use was observed for gastric cancer risk, compared with nonusers (P for trend = 0.013). The HRs (95% CIs) for ≤25, 26-30 and &gt;30 years of age, compared with nonusers were 0.85 (0.50, 1.46), 0.76 (0.48, 1.21), and 0.54 (0.31, 0.92), respectively. There were no associations with other menstrual or reproductive factors including number of births, years of menstrual cycling, or age at menopause. The inverse associations with ever HRT and/or OC use for gastric cancer risk remained after further adjusting for H. pylori infection and atrophic gastritis status.

Conclusion: In a high-risk study population, ever use of exogenous hormones was associated with a statistically significant decrease in gastric cancer risk, independent of established risk factors. These results support the notion that high exposure to estrogens may contribute to the lower incidence of gastric cancer in women compared with men.

Citation Format: Zhensheng Wang, Anna H. Wu, Woon-Puay Koh, Aizhen Jin, Renwei Wang, Jian-Min Yuan, Lesley M. Butler. Exogenous hormone use was inversely associated with gastric cancer risk among women: The Singapore Chinese Health Study. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 863. doi:10.1158/1538-7445.AM2015-863

Physical activity and risk of end-stage kidney disease in the Singapore Chinese Health Study

AIM

To explore the relationship between physical activity and risk of end-stage kidney disease (ESKD).

METHODS

We analysed data on a prospective cohort of 59,552 Chinese adults aged 45-74 years enrolled in the Singapore Chinese Health Study. Information on physical activity was collected with a structured questionnaire. Physically active individuals were defined as those who engaged in any moderate activities for 2 h or more per week and any strenuous activities 30 min or more per week. Incident ESKD was identified via record linkage with the Singapore Registry of Birth and Death and Singapore Renal Registry. Cox proportional hazards regression method was used for analysis for risk of incident ESKD alone or ESKD plus death associated with physical activity.

RESULTS

During a median follow-up of 15.3 years, a total of 642 incident ESKD occurred, and 9808 study participants died. A 24% lower adjusted risk of ESKD (hazard ratio: 0.76; 95% confidence interval: 0.62-0.93) was associated with moderate or strenuous physical activities compared with no regular physical activity. This association appeared to be dose dependent with the lowest risk for subjects at highest intensity of physical activity (P trend <0.003). Similar results were observed for risk of ESKD plus death.

CONCLUSION

Higher levels of physical activity are associated with lower risk of ESKD. Our findings highlight the role of physical activity for prevention of ESKD, which deserves further evaluation in intervention trials.

Serum estrogen receptor bioactivity and breast cancer risk among postmenopausal women

The estrogen levels of Asian women are different from those of Western women, and this could affect estrogen receptor (ER) bioactivity and breast cancer risk. We conducted a case-control study in 169 postmenopausal breast cancer cases and 426 matched controls nested within a population-based prospective cohort study, the Singapore Chinese Health Study, to evaluate the serum levels of estrogens and their receptor (ERα and ERβ)-mediated estrogenic activities in relation to breast cancer risk. Breast cancer cases had higher levels of estrogens and ER-mediated bioactivities in baseline serum than the controls. Compared with those in the lowest quartile, women in the highest quartile for estrone (E1) or ERα-mediated bioactivity had increased breast cancer risk. After additional adjustment for ERβ bioactivity, free estradiol, and E1 levels, serum ERα-mediated bioactivity remained associated with increased breast cancer risk. Compared with those in the lowest quartile, women in the highest quartile for ERα-mediated bioactivity had an odds ratio of 2.39 (95% CI=1.17-4.88; P for trend=0.016). Conversely, the positive association between E1 and cancer risk became null after adjustment for ERα-mediated bioactivity, suggesting that the effect of E1 could be mediated through ERα. Factor(s) contributing to increased ERα-mediated estrogenic bioactivity in serum and its role as a predictor for breast cancer risk need to be validated in future studies.

Coffee intake and gastric cancer risk: the Singapore Chinese health study

BACKGROUND

Despite experimental evidence showing chemopreventive effects of coffee-related compounds on gastric carcinogenesis, epidemiologic studies generally do not support coffee-gastric cancer associations. Observational data are lacking among high-risk populations with sufficient regular coffee consumption.

METHODS

We examined the association between caffeinated coffee intake and gastric cancer risk in a population-based cohort that enrolled 63,257 Chinese men and women ages 45 to 74 years between 1993 and 1998 in Singapore. Incident gastric cancer cases (n = 647) were identified after a mean follow-up of 14.7 years. Biomarkers of Helicobacter pylori (H. pylori) infection were measured in a subset of gastric cancer cases with blood collected before cancer diagnosis and their matched controls.

RESULTS

In the total cohort, daily versus nondaily coffee intake was associated with a statistically nonsignificant decrease in gastric cancer risk [HR = 0.85; 95% confidence interval (CI), 0.69-1.04]. In women, the inverse association strengthened and reached statistical significance (HR = 0.63; 95% CI, 0.46-0.87). In analyses restricted to never smokers and nondrinkers of alcohol, inverse associations strengthened in the total cohort (HR = 0.69; 95% CI, 0.52-0.91) and in women (HR = 0.52; 95% CI, 0.37-0.74). There was no coffee-gastric cancer risk association among men, regardless of smoking status or alcohol consumption. Similar results were observed in the nested case-control study after adjustment for H. pylori infection.

CONCLUSION

Daily coffee consumption may reduce the risk of gastric cancer in high-risk populations, especially among women.

IMPACT

Research aimed at identifying the compounds in coffee that may protect against gastric carcinogenesis is warranted.

Smoking and risk of kidney failure in the Singapore Chinese health study

Background

The relationship between smoking and risk of kidney failure, especially in people of Chinese origin, is not clear. We analyzed data from the Singapore Chinese Health Study to investigate whether smoking increases the risk of kidney failure.

Methods

The Singapore Chinese Health Study is a population-based cohort of 63,257 Chinese adults enrolled between 1993 and 1998. Information on smoking status was collected at baseline. Incidence of kidney failure was identified via record linkage with the nationwide Singapore Renal Registry until 2008. Kidney failure was defined by one of the following: 1) serum creatinine level of more than or equal to 500 µmol/l (5.7 mg/dl), 2) estimated glomerular filtration rate of less than 15 ml/min/1.73 m², 3) undergoing hemodialysis or peritoneal dialysis, 4) undergone kidney transplantation. Cox proportional hazard regression analysis was performed for the outcome of kidney failure after adjusting for age, education, dialect, herbal medications, body mass index, sex, physician-diagnosed hypertension and diabetes mellitus.

Results

The mean age of subjects was 55.6 years at baseline, and 44% were men. Overall 30.6% were ever smokers (current or former) at baseline. A total of 674 incident cases of kidney failure occurred during a median follow-up of 13.3 years. Among men, smokers had a significant increase in the adjusted risk of kidney failure [hazard ratio (HR): 1.29; 95% CI: 1.02–1.64] compared to never smokers. There was a strong dose-dependent association between number of years of smoking and kidney failure, (p for trend = 0.011). The risk decreased with prolonged cessation (quitting ≥10 years since baseline). The number of women smokers was too few for conclusive relationship.

Limitation

Information on baseline kidney function was not available.

Conclusions

Cigarette smoking is associated with increased risk of kidney failure among Chinese men. The risk appears to be dose- and duration-dependent and modifiable after long duration of cessation.

Comparison of testing approaches for Clostridium difficile infection at a large community hospital

Multiple diagnostic approaches are available for Clostridium difficile infection (CDI); current guidelines support two-step testing (2ST) as the preferred approach. We retrospectively evaluated the impact of switching from toxin enzyme immunoassay (EIA) to 2ST, and then to polymerase chain reaction (PCR), on CDI rates, test utilization and CDI treatment at a 900-bed tertiary care community teaching hospital. All inpatients tested for CDI between December 2008 and February 2011 were included. A positive toxin EIA or PCR was diagnostic of CDI; 2ST was performed using glutamate dehydrogenase EIA, followed by PCR if positive. Repeat tests within 8 weeks on the same patient were considered part of the same testing episode. Data were collected electronically and studied in aggregate from 9725 unique inpatients tested for CDI, representing 20 836 individual tests. PCR detected 41% more patients with CDI than toxin EIA (p <0.0001), and 15% more than 2ST (p 0.02), corresponding to higher hospital-onset and community-onset CDI rates. The number of CDI tests performed per patient decreased by 48% with PCR (p <0.0001) compared with toxin EIA. For patients with CDI, time to the first positive test result was shortest with PCR. For patients without CDI, a negative PCR, but not 2ST, was associated with 22% fewer CDI treatment days, compared with toxin EIA (p <0.0001). Compared with both toxin EIA and 2ST, PCR detected more CDI patients faster and with less frequent testing, and negative PCR results were associated with less empirical CDI treatment.

Predictors of decrease in ankle-brachial index among patients with diabetes mellitus

AIM

Screening for peripheral arterial disease, a complication among patients with diabetes, is performed by periodic assessment of ankle-brachial index. We aimed to study the degree of ankle-brachial index change over time and factors associated with significant change.

METHOD

We assessed difference between two ankle-brachial index measurements over time in a consecutive series of 82 patients with Type 2 diabetes. All patients had ankle-brachial index > 0.9 but ≤ 1.3 for the first measurement, and significant ankle-brachial index decrease was defined as a decrease of > 0.1 in the follow-up measurement compared with the baseline.

RESULTS

The mean follow-up duration was 27.6 (median 30.0) months. Significant ankle-brachial index decrease was seen in 20.7% of patients, including 5% with follow-up ankle-brachial index of ≤ 0.9, consistent with the diagnosis of peripheral arterial disease. After adjusting for age and gender, higher baseline HbA(1c) and serum creatinine levels, increase in follow-up serum LDL cholesterol levels compared with baseline and history of retinopathy were predictors of significant ankle-brachial index decrease.

CONCLUSIONS

Our study suggests that, within two years, one in five patients with diabetes and a normal ankle-brachial index may have significant progression of peripheral arterial disease. Annual ankle-brachial index assessment and better control of hyperlipidaemia may thus be required for at-risk patients with poor glycaemic control, renal impairment and retinopathy.

Serum free estradiol and estrogen receptor-α mediated activity are related to decreased incident hip fractures in older women

There is paucity of data from Asian women on the association between serum estrogens and osteoporotic hip fracture risk. We conducted a case-control study nested within a population-based prospective cohort, The Singapore Chinese Health Study, to evaluate serum estrogens levels, ERα-mediated estrogenic activity and hip fracture risk in postmenopausal Asian women. Among 35,298 women who were recruited between 1993 and 1998, 15,410 women donated blood for research between 1999 and 2004. From this subcohort, we identified 140 cases who subsequently suffered hip fracture after blood donation, and 278 age-matched controls. Serum levels of total estrone, estradiol and sex hormone binding globulin levels were measured in a blinded fashion among cases and controls. ERα-mediated estrogenic activity of serum samples was quantified using a sensitive ERα-driven cell bioassay. Women with hip fracture had lower serum estrogens than control women. Compared to the lowest quintile, women in the highest quintile of free estradiol exhibited a statistically significant 57% reduction in risk of hip fracture (95% confidence interval (CI), 6-80%), with a dose-dependent relationship (p for trend=0.021). High levels of ERα-mediated estrogenic activity were also associated with decreased risk of hip fracture (p for trend=0.048). Overall, women with relatively high levels of both free estradiol and ERα-mediated estrogenic activity had a 55% reduction in hip fracture risk (95% CI, 17-76%) compared to women with low levels of both. High levels of free estradiol and ERα-mediated estrogen activity in sera were associated with reduced hip fracture risk in Chinese postmenopausal women.

Abstract 632: Effect of body mass index on the association between smoking and risk of gastric cancer in the Singapore Chinese Health Study

Background: Tobacco smoking is an established risk factor for gastric cancer. Recently, reports have suggested high body mass index (BMI) as a significant risk factor for esophageal adenocarcinoma whereas the relationship with gastric cancer remains inconsistent. The aim of the current study is to evaluate two potentially modifiable factors, tobacco smoking and increased body mass index, as risk factors for gastric cancer among Singapore Chinese. Methods: We prospectively examined the association between smoking and BMI at baseline, and the risk of developing gastric cancer in the Singapore Chinese Health Study, a cohort of 63,257 middle-aged and older Chinese men and women enrolled between 1993 and 1998. Information on body weight, height, cigarette smoking and other lifestyle factors and diet was obtained through in-person interview at enrollment. BMI was calculated using weight in kg divided by height in meter squared (kg/m2). Incidence of cancer and death among cohort participants was obtained via linkage with nationwide registries. Results: As of 31 December 2009, 568 cohort participants who were free of cancer at baseline had developed gastric cancer. Compared to never smokers, current smokers had a 38% increase in risk of gastric cancer (95% confidence interval: 1.12-1.70), with a positive dose-response association between number of cigarettes per day (P for trend=0.002) and number of years of smoking (P for trend=0.005), and gastric cancer risk. After adjustment for cigarette smoking and other potential confounders, hazard ratios (95% confidence interval) of gastric cancer for subjects with BMI 20-&lt;24, 24-&lt;28 and 28+ kg/m2 were 1.30 (1.00-1.68), 1.19 (0.88-1.60), and 1.65 (1.14-2.40), respectively, relative to those with &lt;20 kg/m2 (P for trend=0.063). This dose-response association between increasing BMI and cancer risk was stronger for cardia cancer (P for trend =0.021) than for noncardia cancer (P for trend=0.19). In separate analyses in groups defined by BMI, hazard ratios (95% confidence interval) of gastric cancer for current smokers with BMI of β28, 24-&lt;28, 20-&lt;24, and &lt;20 kg/m2 were 1.11 (0.51-2.45), 1.08 (0.67-1.75), 1.52 (1.16-1.99), and 1.90 (1.05-3.43), respectively, as compared with nonsmokers. The positive dose-response associations between dose and duration of smoking, and gastric cancer risk were limited to lean subjects with BMI&lt;24 kg/m2 and not observed in the more obese subjects. Conclusion: Smokers with relatively low level of BMI had enhanced risk of gastric cancer compared to smokers with higher BMI. Our findings corroborate the hypothesis that lean smokers have increased oxidative DNA damage relative to their non-lean counterparts, which may in turn explain their heightened susceptibility to tobacco carcinogens-induced DNA damage in gastric carcinogenesis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 632. doi:1538-7445.AM2012-632

Glutathione S-transferase (GST) gene polymorphisms, cigarette smoking and colorectal cancer risk among Chinese in Singapore

Cigarette smoking is a risk factor for colorectal cancer. Putative colorectal procarcinogens in tobacco smoke include polycyclic aromatic hydrocarbons and heterocyclic aromatic amines that are known substrates of glutathione S-transferases (GSTs). This study examined the influence of functional GST gene polymorphisms on the smoking-colorectal cancer association in a population known to be minimally exposed to dietary sources of these procarcinogens. Incident cases of colorectal cancer (n = 480) and matched controls (n = 1167) were selected from the Singapore Chinese Health Study, a population-based prospective cohort of 63 257 men and women who have been followed since 1993. We determined the deletion polymorphisms of GSTM1 and GSTT1 and the functional polymorphism at codon 105 of GSTP1 for each subject. A three level composite GST index was used to examine if GST profile affected a smoker's risk of developing colorectal cancer. While there was no statistically significant association between cigarette smoking and colorectal cancer risk among subjects absent of any at-risk GST genotypes, smokers possessing two to three at-risk GST genotypes exhibited a statistically significant increased risk of colorectal cancer compared with non-smokers (P = 0.0002). In this latter stratum, heavy smokers exhibited a >5-fold increased risk relative to never-smokers (odds ratio, 5.43; 95% confidence interval, 2.22-13.23). Subjects with one at-risk GST genotype displayed a statistically significant but weaker association with smoking. These findings suggest that GST gene polymorphisms influence interindividual susceptibility to smoking-associated colorectal cancer. Our data indicate an important role for GST enzymes in the detoxification of colorectal carcinogens in tobacco smoke.

BCR/ABL and IL-3 activate Rap1 to stimulate the B-Raf/MEK/Erk and Akt signaling pathways and to regulate proliferation, apoptosis, and adhesion

The Ras family small GTPase Rap1 is activated by hematopoietic cytokines, such as interleukin (IL)-3, to induce beta1 integrin-mediated cell adhesion or by the BCR/ABL fusion tyrosine kinase to stimulate the MEK/Erk signaling pathway. Here, we demonstrate that the abrogation of Rap1 activation by SPA-1, a Rap1-specific GAP, inhibits activation of B-Raf, MEK, Erk, and Akt in a murine hematopoietic cell line, Ton.B210, stimulated with IL-3 or inducibly expressing BCR/ABL. Furthermore, Rap1 inactivation had an inhibitory effects on proliferation and survival of Ton.B210 cells, which were more remarkable when cells were stimulated by BCR/ABL than by IL-3. Induction of BCR/ABL expression increased adhesion of Ton.B210 cells to fibronectin in a manner at least partly dependent on its kinase activity, and Rap1 inhibition by SPA-1 partially inhibited BCR/ABL-induced adhesion of cells. Thus, IL-3- or BCR/ABL-induced activation of Rap1 may play important roles in regulation of cell proliferation and survival through activation of the B-Raf/MEK/Erk and Akt signaling pathways and in induction of integrin-mediated cell adhesion. Furthermore, as compared with IL-3, BCR/ABL is more dependent on Rap1-mediated signaling to induce cell proliferation and survival and, thus, Rap1 may represent an attractive target for novel therapies for leukemias caused by BCR/ABL.

Nanofluidic channels fabrication and manipulation of DNA molecules

Nanofluidic channel arrays, which have a width of about 40 nm, depth of 60 nm and length of 50 mum, were created using a focused-ion-beam milling instrument on a silicon nitride film swiftly and exactly, as is necessary. Stained -DNA molecules were put inside these sub-100 nm conduits by capillary force and they were stretched and transferred along these conduits, which were dealt with activating reagent Brij aqueous solution in advance. The movements of DNA molecules in these channels were discussed. These nano-structure channels may be useful in the study and analysis of the statics as well as the dynamics of single biomolecules.

Ethnic differences in quality of life in adolescents among Chinese, Malay and Indians in Singapore

BACKGROUND

Health-related quality of life in adolescents and ethnic and cultural differences are not well characterized. We used the Quality of Life Questionnaire for Adolescents (QOLQA) to examine ethnic differences in reported QOL scores among Chinese, Malay and Indian ethnicities in Singapore.

METHODS

The 70-item QOLQA measuring five QOL domains (physical, psychological, independence, social and environmental) was administered to a random sample of 1363 school-children aged 10-15 years, representative of the ethnic composition of Singapore adolescents (Chinese 72%, Malays 20% and Indians 8%).

RESULTS

Indians reported the highest overall QOL (mean 3.71 +/- SD 0.54) compared to Chinese (3.59 +/- 0.43), p < 0.05, and Malays (3.58 +/- 0.44), p < 0.05. In particular, Indians had significantly higher psychological QOL scores (3.73 +/- 0.61) compared to Chinese (3.55 +/- 0.54), p < 0.01. On the other hand, Chinese scored highest on physical and independence domains (3.97 +/- 0.54), p < 0.01 compared to Malays (3.82 +/- 0.55). There were no statistically significant gender differences in QOL scores. QOL declined significantly from age 10 to 15 for overall score, psychological, physical (p < 0.01) and environmental (p < 0.05). Lower socio-economic status and the self-report of a significant health problem were significantly associated with lower overall QOL and most domains. These ethnic differences persisted after adjusting for differences in socio-economic and health status. Psychometric properties and known group construct validity appeared to be similar across different ethnic groups, but compared to Chinese (r = 0.39) or Malays (r = 0.39), Indians showed a higher correlation of psychological scores with physical score (r = 0.59) and with other domain scores.

CONCLUSION

Significant ethnic differences in reported adolescent quality of life among Chinese, Malays and Indians in Singapore that are independent of socioeconomic and health status suggest important cultural differences.

A strict-late viral promoter is a strong tumor-specific promoter in the context of an oncolytic herpes simplex virus

Confinement of transgene expression to target cells is highly desirable in gene therapy. Current strategies of transcriptional targeting to tumors usually rely on tissue-specific promoters to control gene expression. However, such promoters generally have much lower activity than the constitutive viral promoters. We have explored an alternative approach, using a strict-late viral promoter (UL38p) in the context of an oncolytic herpes simplex virus (HSV) for tumor-selective gene expression. As with many DNA viruses, the genomic transcription of HSV is a tightly regulated molecular cascade in which early and late phases of gene expression are separated by viral DNA replication. In particular, some of the late transcripts are categorized as strict-late, whose expression depends rigorously on the initiation of viral DNA replication. Our in vitro and in vivo characterization showed that in normal nondividing cells, where the oncolytic HSV has limited ability to replicate, the UL38p has minimal activity. However, in tumor or cycling cells where the virus can fully replicate, transgene expression from UL38p was almost as high as from the cytomegalovirus immediate-early promoter. These results suggest that delivery of therapeutic genes driven by UL38p through an oncolytic HSV may be an effective approach to gene therapy for malignant diseases.

Emergency department asthma: compliance with an evidence-based management algorithm

BACKGROUND

Recent surveys in emergency medicine departments show inadequacies in many aspects of acute asthma management.

OBJECTIVE

The objective of this study was to evaluate the adherence to management algorithm for acute asthma in the emergency department which focused on evidence-based treatment steps rather than documentation and patient classification.

METHODS

A retrospective audit of consecutive adult patients with acute exacerbations of asthma in the emergency medicine department of a university hospital managed in the context of a clinical algorithm.

RESULTS

We collated information from 344 episodes of acute asthma (94% of total) over a 4-month period. The first-line treatment was nebulised bronchodilators in 97%, combination of salbutamol and ipratropium bromide in 93% and the combination in recommended dosages in 87%. Systemic corticosteroid treatment was administered to 82% of patients. A further course of systemic corticosteroid was prescribed at discharge for 94% of patients. Overall, 93% of patients received some form of systemic corticosteroid treatment. The admission rate was 35.2%, and was significantly higher in women and the elderly. Of those who were admitted, 46.2% received > or = 3 nebulised treatments and 69% received intravenous hydrocortisone.

CONCLUSIONS

In the management of acute asthma, we found excellent compliance with specific treatment steps based upon clinical evidence. However, adherence to second-line treatment was less satisfactory. Nevertheless, whenever second-line treatment was complied with, reasonable outcomes were achieved. It may be more appropriate to emphasise evidence-based treatment rather than extensive documentation.

Human esophageal cancer cell death mediated by apoptosis-inducing nucleosides from CD57+HLA-DRbright natural suppressor cell line

We approached the induction of apoptosis in human esophageal cancer cells (T.Tn) by apoptosis-inducing nucleosides (AINs) from CD57+HLA-DRbright-natural suppressor (57.DR-NS) cell line originated in decidua. The 57.DR-NS cells generated apoptosis in T.Tn cells by AINs released into the cultures. We isolated a series of AINs by high performance liquid chromatography (HPLC) from 57.DR-NS cell culture fluids. Each AIN and its mixture induced apoptotic cell death in T.Tn cells, detected by DNA fragmentation in agarose gels, terminal deoxynucleotide transferase mediated dUTP-nick end labeling (TUNEL) method and accumulation of sub-G1 DNA content with flow cytometry. Furthermore, we found the occurrence of DNA strand breaks followed by the activation of caspase-3 during AINs-induced apoptosis in T.Tn cells. Thus, we validated that AINs could induce apoptosis in T.Tn cells mediated through DNA strand breaks and activation of caspase-3.

Gene expression of inducible nitric oxide synthase in injured spinal cord tissue

OBJECTIVE

To investigate gene expression of inducible nitric oxide synthase (iNOS) in injured spinal cord tissue of rats.

METHODS

Thirty-six adult Sprague-Dawley rats were divided randomly into six groups: a normal group and five injury groups, six animals in ea ch group. Animals in the injury groups were killed at 2, 6, 12, 24, 48 hours after injury, respectively. A compression injury model of spinal cord was established according to Nystrom B et al, and gene expression of iNOS in spinal cord tissue was examined by means of reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Gene expression of iNOS was not detectable in normal spinal cord tissue but was seen in the injury groups. The expression was gradually up -regulated, reaching the maximum at 24 hours. The expression at 48 hours began to decrease but was still significantly higher than that at 2 hours.

CONCLUSIONS

iNOS is not involved in the normal physiological activities of spinal cord. Expression of iNOS is up-regulated in spinal cord tissue in response to injury and the up-regulation exists mainly in the late stage after injury. Over-expression of iNOS may contribute to the l ate injury of spinal cord.

[Application of rapid detection for Mycobacterium tuberculosis with phage splitting assay]

OBJECTIVE

To study the significance of rapid identification for Mycobacterium tuberculosis with phage splitting assay.

METHODS

Strains of Mycobacterium tuberculosis, non-tuberculosis mycobacterium, non-mycobacterium and samples of sputum with pulmonary tuberculosis were rapidly detected by phage spot technique.

RESULTS

The strains of Mycobacterium tuberculosis H37Rv, bovis and africanum were all positive. The results of 10 strains of non-tuberculosis mycobacterium and 7 strains of non-mycobacterium were negative. All of 30 clinical isolates from the patients of the pulmonary tuberculosis were positive. 19 of 20 sputum specimen of pulmonary tuberculosis, which were all positive detected by smear and culture, were positive. There were 15 specimen positive in 21 sputum with negative tested by smear and positive by culture. Besides, 5 of 19 sputum specimen with negative by smear and culture were positive detected by this method.

CONCLUSION

The phage splitting assay can be used for rapid identification of Mycobacterium tuberculosis, which possesses high specificity and sensitivity for detection of Mycobacterium tuberculosis in sputum specimen.

Decontamination issues for chemical and biological warfare agents: how clean is clean enough?

The objective of this assessment is to determine what level of cleanup will be required to meet regulatory and stakeholder needs in the case of a chemical and/or biological incident at a civilian facility. A literature review for selected, potential chemical and biological warfare agents shows that dose information is often lacking or controversial. Environmental regulatory limits or other industrial health guidelines that could be used to help establish cleanup concentration levels for such agents are generally unavailable or not applicable for a public setting. Although dose information, cleanup criteria, and decontamination protocols all present challenges to effective planning, several decontamination approaches are available. Such approaches should be combined with risk-informed decision making to establish reasonable cleanup goals for protecting health, property, and resources. Key issues during a risk assessment are to determine exactly what constitutes a safety hazard and whether decontamination is necessary or not for a particular scenario. An important conclusion is that cleanup criteria are site dependent and stakeholder specific. The results of a modeling exercise for two outdoor scenarios are presented to reinforce this conclusion. Public perception of risk to health, public acceptance of recommendations based on scientific criteria, political support, time constraints, and economic concerns must all be addressed in the context of a specific scenario to yield effective and acceptable decontamination.

[Taxol-induced apoptosis in Jurkat T cell lymphoma cell line and its molecular mechanisms]

OBJECTIVE

To observe whether antimicrotubular drug taxol can induce apoptosis in Jurkat T cell lymphoma cell line and the role of bcl-2 gene family in this process.

METHODS

Different concentrations of taxol were used to treat Jurkat cells. Cell morphology was observed under light and electron microscope. Flow cytometry and electrophoresis were used to analyze DNA contents and DNA fragments. bcl-2 gene family proteins and mRNAs were studied by immunohistochemistry and semi-quantitative RT-PCR technique.

RESULTS

Taxol could inhibit Jurkat cell growth. Within a certain range of treating time and dose, cells were induced apoptosis with a time and dose related manner. The expressions of bax protein and mRNA were increased and bcl-x(s) mRNA became detectable after taxol treatment.

CONCLUSION

Taxol can specifically induce Jurkat cell apoptosis. It might provide a theoretical basis for clinical treatment and a good model for studying apoptotic gene modulation. Bax and bcl-x(s) participate in the taxol induced apoptosis of Jurkat cells.

[Studies on the toxicity of polymer of glycolide and lactide(PLGA) and the anti-fertility effect of levonorgestrel(LNG)]

PLGA(9:1), a chemical degraded from biomaterials, has been subjected to the tests of acute toxicity, irritations on conjunctiva and muscle, haemolysis in vitro and allergic reaction of mice and rats. The anti-fertility effect of PLGA-LNG microphere composite on the same animals also has been tested. The studies demonstrated that PLGA had fine biological compatibility without side effects such as toxicity, irritations on conjunctiva and muscle, pyrogenicity, haemolysis in vitro and allergic reaction. The contraception period of mice lasted 11.5, 34.6 and 81.2 days respectively after the subcutaneous (s.c.) injection of PLGA-LNG microphere which contains LNG 5, 10 and 20 mg/kg separately. The intramuscular(i.m.) injection of PLGA-LNG microphere containing LNG 13.6, 19.8 and 30 mg/kg respectively could keep the estrus of rats supressed for 76.3, 104.1 and 131.8 days. The injections of PLGA-LNG microphere through s.c. or i.m. showed more significant effects than the same dosages of PLGA-LNG micro-crystal. These results suggest that PLGA-LNG microphere injection has long-term anti-fertility effect.

Diet survey of two cultural groups in a coastal British Columbia community

OBJECTIVES

As part of a larger study of polychlorinated dibenzodioxin (PCDD) and dibenzofuran (PCDF) pollution, to describe and compare Aboriginal and non-Aboriginal residents' recalled diets.

METHODS

We surveyed a stratified random sample aged 25 to 64 years: forest products mill employees (n = 84), Aboriginal reserve residents (n = 78), and other residents (n = 80). We administered a questionnaire on intake of fish/seafood, wild game and plants, domesticated animal meat and eggs, dairy products, vegetable oils and cereals; age, gender, childbearing, lactation, residence and smoking. We measured height and weight.

RESULTS

Reserve residents ate less seafood, but more fish roe, eulachon grease, smoked salmon, clams and sea urchins, more deer organs, hamburger meat, pork, fried chicken, and hot-dogs, but less rabbit, beef steaks/roasts, high-fibre cereals, potato chips, bread, cheese and milk.

CONCLUSIONS

We cannot yet quantify PCDD and PCDF intakes. The wild food consumption data are unique and may be useful for risk assessments in the target population and similar communities.