Urine output as one of the most important features in differentiating in-hospital death among patients receiving extracorporeal membrane oxygenation: a random forest approach

BACKGROUND

It is common to support cardiovascular function in critically ill patients with extracorporeal membrane oxygenation (ECMO). The purpose of this study was to identify patients receiving ECMO with a considerable risk of dying in hospital using machine learning algorithms.

METHODS

A total of 1342 adult patients on ECMO support were randomly assigned to the training and test groups. The discriminatory power (DP) for predicting in-hospital mortality was tested using both random forest (RF) and logistic regression (LR) algorithms.

RESULTS

Urine output on the first day of ECMO implantation was found to be one of the most predictive features that were related to in-hospital death in both RF and LR models. For those with oliguria, the hazard ratio for 1 year mortality was 1.445 (p < 0.001, 95% CI 1.265-1.650).

CONCLUSIONS

Oliguria within the first 24 h was deemed especially significant in differentiating in-hospital death and 1 year mortality.

Risk stratification and cost-effectiveness analysis of adult patients receiving extracorporeal membrane oxygenation

RATIONALE, AIMS, AND OBJECTIVES

A more effective allocation of critical care resources is important as the cost of intensive care increases. A model has been developed to predict the probability of in-hospital death among patients who received extracorporeal membrane oxygenation (ECMO). Cost-effectiveness analyses (CEA) were performed regarding the relationship between hospitalization expenses and predicted survival outcomes.

METHODS

Adult patients who received ECMO in a medical center in Taiwan (2005-2016) were included. A logistic regression model was applied to a spectrum of clinical measures obtained before and during ECMO institutions to identify the risk variables for in-hospital mortality. CEA were reported as a predictive risk in quintiles and defined as the cost of each quality-adjusted life-year (QALY). The distribution of the cost-effectiveness ratio (CER) was measured by the ellipse and acceptability curve methods.

RESULTS

A total of 919 patients (659 males, mean age: 53.7 years) were enrolled. Ten variables emerged as significant predictors of in-hospital death. The area under the receiver operating characteristic curve was 0.75 (95% confidence interval: 0.72-0.79). In-hospital and total follow-up times were 40,366 and 660,205 person-days, respectively. The total in-hospital expense was $31,818,701 USD and the total effectiveness was 1687.3 QALY. For the lowest to the highest risk quintile, the mean mortality risks were 0.30, 0.48, 0.61, 0.75, and 0.88, and mean adjusted CER were $24,230, $43,042, $54,929, $84,973, and $149,095 per QALY, respectively.

CONCLUSIONS

The efficient allocation of limited and costly resources is most important when one is forced to decide between groups of critically ill patients. The current analyses of ECMO outcomes should assist in identifying candidates with the greatest prospect for survival while avoiding futile treatments.

Vitamin D status in relation to inflammatory risk and albuminuria associated with polycyclic aromatic hydrocarbon exposure in the US population

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with both systematic inflammation and renal dysfunction. Reports have suggested that anti-inflammatory properties of vitamin D may provide protection against renal injury. This cross-sectional study tested the hypothesis that serum 25-hydroxyvitamin D [25(OH)D] moderates the inflammation and albuminuria associated with PAH exposure. Data were obtained from 5,982 subjects aged 20-79 years in the National Health and Nutrition Examination Survey (2001-2010). PAH exposure was estimated by urinary PAH metabolites. Inflammation was defined as serum C-reactive protein (CRP) > 3 mg/L and albuminuria as urinary albumin-to-creatinine ratio > 30 mg/g. The results found that greater PAH exposure was linked with inflammation and albuminuria. Individuals with PAH exposure also tended to have lower 25(OH)D and lower vitamin D was associated with both elevated CRP (Odds ratio [OR] = 1.28, 95% confidence interval [CI] = 1.07-1.54) and urinary albumin (1.35, 95%CI = 1.03-1.77) for any given PAH exposure. Those with lower serum 25(OH)D-to-urinary PAH ratios were likewise at a greater risk of elevated CRP and albuminuria. The findings support prior suggestions that exposure to PAHs is associated with inflammation and albuminuria but suggests further that the risk is higher when vitamin D is lower. Thus, nutritional status becomes an important variable in PAH risk assessment.

Evaluation of lead body burden in US adolescents

The objective was to examine key determinants in the body burden of lead in adolescents as lead poisoning remains a major public health challenge. Data from 2,925 teenagers aged 12-18 older in the National Health and Nutrition Examination Survey (NHANES), 1999-2012 were analyzed. Lead in both blood and urine was significantly correlated among individuals. Despite higher blood lead in males, urinary lead measures corrected for dilution were similar between male and female adolescents. Thus, the urine-to-blood ratio was approximately 30% lower in male than female adolescents, suggesting that differences in renal disposal contributed to the greater body burden for young males. Differences in urinary lead disposal appear to be a key determinant in lead accumulation and thus, the degree of lead poisoning. Direct renal studies should be conducted to determine mechanisms and potential solutions.

Analysis of mortality risk following receipt of implantable cardioverter defibrillators in patients with and without heart failure

BACKGROUND

Patients covered by the Taiwan National Health Insurance (NHI) program are eligible to receive an implantable cardioverter defibrillator (ICD) if diagnosed with heart failure (HF) or were at high risk of sudden cardiac death. The study was designed to evaluate the prognoses for ICD recipients with respect to contributory risks.

METHODS

ICD recipients (N=2138) from Taiwan's NHI database, for the 11-year period 2004-2014 were identified and assigned to no heart failure (NHF, n=978) or heart failure groups (HF, n=1160). The mortality rates were reported and survival trends were compared between groups.

RESULTS

The mean age of these patients was 61.8±15.2 years and 69% were men. The HF group was older (65 vs. 58 years) and had significantly more comorbidities. Pharmaceutical and medical resource utilization was also uniformly higher within the HF group. The 30-day (1.8%) and 1-year (18.4%) mortality rates among the HF patients were 3-4 times higher than in the NHF group (log rank p=0.006 and p<0.001, respectively). A coexistent major diseases score was consistently associated with a progressive mortality risk in ICD recipients overall.

CONCLUSIONS

Of those receiving ICDs, the prognosis for HF patients is poorer than for those in the NHF group which most likely reflects the fact that the HF patients were generally older with more complicated medical conditions as evident by the association between multiple major organ dysfunction and an increased risk of death.

Examining the association between oral health status and dementia: A nationwide nested case-controlled study

Alzheimer’s disease as a consequence of chronic brain inflammation mediated by infectious microbes including the oral microbiome continues to attract support. Taiwan’s National Insurance database was used to evaluate associations between dental health and Alzheimer’s disease; 209,112 new cases of Alzheimer’s disease were matched 1:4 with 836,448 dementia-free controls to test the hypothesis that better dental health would be associated with less occurrence of dementia. Ten year dental records and conditional logistic regression models were used to estimate the odds ratios associated with Alzheimer’s disease. Subgroup analyses compared vascular Alzheimer’s disease and sporadic Alzheimer’s disease. As the population aged, Alzheimer’s disease diagnoses were more frequent with a 10 fold upward inflection after 60. Nearly 56% of sporadic Alzheimer’s disease patients were women but less than 50% had vascular Alzheimer’s disease. Comorbidities were 10–20% higher in the Alzheimer’s disease patients than in controls, but stroke, chronic infection, and pneumonia were 40–45% more common in the vascular Alzheimer’s disease patients. Heart disease, hypertension, diabetes, stroke, peripheral artery disease, pneumonia, and herpetic disease (HSV) were all associated with higher odds of Alzheimer’s disease. HSV was not a factor in the vascular Alzheimer’s disease. Routine dental procedures tended to lower odds ratios. Root canals and extractions that restore oral homeostasis were associated with lower odds of dementia. However, when extractions exceeded four, the odds of Alzheimer’s disease rose. The fact that Alzheimer’s disease was not associated with periodontal procedures per se but with more frequent periodontal emergencies suggested again a chronic issue. Dental health costs suggest that good dental care was associated with lower odds of Alzheimer’s disease except for radiographic costs which were consistently associated with higher odds, independent of oral health. Common comorbid conditions were associated with higher odds of Alzheimer’s disease and oral health care was associated with lower odds, providing support for the hypothesis that the oral microbiome is a factor in the development of Alzheimer’s disease.

Impact statement

This study clearly demonstrates the power and value of a nationally applied digital medical record. Longitudinal studies of gradually developing pathologies like dementia have often been limited by sample size and narrow and incomplete medical histories. The Taiwan National Insurance database provides an unparalleled opportunity for detailed analyses of associations between current medical conditions and a spectrum of prior medical and dental events. The temporal impact of the database will only become more important as the past historical record progressively expands going forward. The inclusion of dental records in assessing the relationship with subsequent dementia is very important because this information is often unavailable or dependent on subject recall. This study clearly establishes associations between a variety of suspected cardiovascular and metabolic factors and the odds of dementia. A critical outcome should include the design of targeted interventions and the subsequent assessment of their efficacy.

Cardioprotection by intermittent hypoxia conditioning: evidence, mechanisms, and therapeutic potential

The calibrated application of limited-duration, cyclic, moderately intense hypoxia-reoxygenation increases cardiac resistance to ischemia-reperfusion stress. These intermittent hypoxic conditioning (IHC) programs consistently produce striking reductions in myocardial infarction and ventricular tachyarrhythmias after coronary artery occlusion and reperfusion and, in many cases, improve contractile function and coronary blood flow. These IHC protocols are fundamentally different from those used to simulate sleep apnea, a recognized cardiovascular risk factor. In clinical studies, IHC improved exercise capacity and decreased arrhythmias in patients with coronary artery or pulmonary disease and produced robust, persistent, antihypertensive effects in patients with essential hypertension. The protection afforded by IHC develops gradually and depends on β-adrenergic, δ-opioidergic, and reactive oxygen-nitrogen signaling pathways that use protein kinases and adaptive transcription factors. In summary, adaptation to intermittent hypoxia offers a practical, largely unrecognized means of protecting myocardium from impending ischemia. The myocardial and perhaps broader systemic protection provided by IHC clearly merits further evaluation as a discrete intervention and as a potential complement to conventional pharmaceutical and surgical interventions.

Association between thyroid dysfunction and dysglycaemia: a prospective cohort study

AIMS

To compare the incidence of hyperglycaemia among participants with low, elevated and normal serum thyroid-stimulating hormone concentration, as well as the incidence of abnormal thyroid function test results among participants with normal blood glucose and those with hyperglycaemia.

METHODS

In a prospective study, a cohort of 72 003 participants with normal, low and elevated serum thyroid-stimulating hormone concentration were followed from the study beginning to the first report of diabetes and prediabetes. A proportional hazards regression model was used to calculate the hazard ratios and 95% CIs for each outcome, adjusting for age, sex, education level, smoking, alcohol consumption and obesity. Analyses for the association between dysglycaemia and incident abnormal thyroid function test were also conducted.

RESULTS

During a median 2.6 year follow-up, the incident rates for dysglycaemia, particularly prediabetes, were substantially higher in participants with elevated thyroid-stimulating hormone concentrations at baseline, while the rates for participants with normal and low thyroid-stimulating hormone were similar. After controlling for risk factors, participants with elevated thyroid-stimulating hormone retained a 15% increase in risk of prediabetes (adjusted hazard ratio 1.15, 95% CI 1.04-1.26), but were not at greater risk of diabetes (adjusted hazard ratio 0.96, 95% CI 0.64-1.44). By contrast, participants with normal and low thyroid-stimulating hormone concentrations had similar dysglycaemia risks. Participants with diabetes and prediabetes were not at greater risks of developing abnormal thyroid function test results when compared with participants with euglycaemia.

CONCLUSIONS

People with elevated serum thyroid-stimulating hormone concentration are at greater risk of developing prediabetes. Whether this includes a greater risk of developing frank diabetes may require an extended period of follow-up to clarify.

Metabolic syndrome is associated with an increased incidence of subclinical hypothyroidism - A Cohort Study

Prior cross-sectional analyses have demonstrated an association between subclinical hypothyroidism and metabolic syndrome and selected components. However, the temporal relation between metabolic syndrome and declining thyroid function remains unclear. In a prospective study, an unselected cohort of 66,822 participants with and without metabolic syndrome were followed. A proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% CIs for hypothyroidism. Exploratory analyses for the relation between components of metabolic syndrome and declining thyroid function were also undertaken. During an average follow-up of 4.2 years, the incident rates for subclinical hypothyroidism were substantially higher in participants who began the study with metabolic syndrome compared with metabolically normal controls. After controlling for risk factors, patients with metabolic syndrome were at a 21% excess risk of developing subclinical hypothyroidism (adjusted HR 1.21; 95% CI 1.03–1.42). When individual components were analyzed, an increased risk of subclinical hypothyroidism was associated with high blood pressure (1.24; 1.04–1.48) and high serum triglycerides (1.18; 1.00–1.39), with a trend of increasing risk as participants had additional more components. Individuals with metabolic syndrome are at a greater risk for developing subclinical hypothyroidism, while its mechanisms and temporal consequences of this observation remain to be determined.

No increased risk of hospitalization for heart failure for patients treated with dipeptidyl peptidase-4 inhibitors in Taiwan

BACKGROUND

Saxagliptin has been reported to be associated with an increased risk of hospitalization for heart failure (HF). The objective of this study was to test whether the increased risk is drug specific or a class effect for dipeptidyl peptidase-4 (DPP-4) inhibitors.

METHODS

Diabetic patients prescribed sitagliptin, saxagliptin, and vildagliptin between 2011 and 2013 were identified from Taiwan's National Health Insurance (NHI) claims database. The outcome of interest was the first hospitalization for HF. The patients were followed for one year from drug initiation to outcome occurrence, death, or study termination (December 31, 2013). A Cox proportional hazards regression model was used to calculate the hazard ratios (HR) and their 95% confidence intervals, using sitagliptin as the reference group.

RESULTS

A total of 239,669 patients, including 159,330 sitagliptin, 38,561 saxagliptin, and 41,778 vildagliptin initiators, were included in the analysis. With a follow-up period ranging from 269days (vildagliptin) to 313days (sitagliptin), the crude incidence rate of HF was 2.77, 2.63, and 1.91 per 100 person-years for sitagliptin, saxagliptin, and vildagliptin, respectively. Saxagliptin had a similar risk (HR: 0.98, 95% CI: 0.91-1.06) to sitagliptin, while vildagliptin was associated with a lower risk of HF (HR: 0.85, 95% CI: 0.78-0.93). Auxiliary analyses using acarbose (n=130,800) as a reference group consistently showed no increased risk of HF associated with DDP-4 inhibitors.

CONCLUSION

Three DPP-4 inhibitors studied seem to be safe regarding the risk of HF, while the reduced risk of vildagliptin might be a spurious association or a chance finding.

Survival Analysis After Extracorporeal Membrane Oxygenation in Critically Ill Adults

Background—

Extracorporeal membrane oxygenation (ECMO) provides circulatory and respiratory support for patients with severe acute cardiopulmonary failure. The objective of this study was to examine the survival outcomes for patients who received ECMO.

Methods and Results—

Adult patients who received ECMO from September 1, 2002, to December 31, 2012, were identified from the Taiwan National Health Insurance Database associated with coronary artery bypass graft surgery, myocardial infarction/cardiogenic shock, injury, and infection/septic shock. A Cox regression model was used to determine hazard ratios and to compare 30-day and 1-year survival rates with the myocardial infarction/cardiogenic shock group used as the reference. The mean±SD age of the 4227-patient cohort was 57±17 years, and 72% were male. The overall mortalities were 59.8% and 76.5% at 1 month and 1 year. Survival statistics deteriorated sharply when ECMO was required for >3 days. Acute (30-day) survival was more favorable in the infection/septic shock (n=1076; hazard ratio, 0.61; 95% confidence interval, 0.55–0.67), coronary artery bypass graft surgery (n=1077; hazard ratio, 0.68; 95% confidence interval, 0.61–0.75), and injury (n=369, hazard ratio, 0.82; 95% confidence interval, 0.70–0.95) groups. The extended survival rapidly approached an asymptote near 20% for the infection/septic shock, myocardial infarction/cardiogenic shock (n=1705), and coronary artery bypass graft surgery groups. The pattern of survival for the injury group was somewhat better, exceeding 30% at year-end.

Conclusions—

Regardless of initial pathology, patients requiring ECMO were critically ill with similar guarded prognoses. Those in the trauma group had somewhat better outcomes. Determining the efficacy and cost-effectiveness of ECMO should be a critical future goal.

Fetal Growth, Obesity, and Atopic Disorders in Adolescence: a Retrospective Birth Cohort Study

BACKGROUND

Developmental status at birth and subsequent obesity have been implicated in the development of childhood atopic dermatitis (AD) and allergic rhinitis (AR).

METHODS

The current study analysed the cohort data of 74 688 junior high school students from a national retrospective birth cohort study in Taiwan. A random 10% sample was selected from singleton livebirths with complete data on the analytical variables of interest. Atopic disorders, including AD and AR, were assessed by questionnaires (International Study of Asthma and Allergies in Childhood). Logistic regression analyses were applied with adjustments for related risk factors.

RESULTS

Among subjects mainly 13-15 years of age, the estimated prevalence was 7.6% for AD and 22.4% for AR. While the role of fetal growth in allergic disorders was less evident, the risk of developing AD and AR were both influenced by a combination of fetal growth status and adolescent body mass index (BMI). Compared with those with normal fetal growth and school-aged BMI, the risk of developing AD increased 64% among adolescents with both restricted fetal growth and high BMI (odds ratio 1.64, 95% confidence interval 1.37, 1.97). The risk for this combination was higher than that for either restricted fetal growth or high BMI alone. Nevertheless, the overall interaction between BMI and fetal growth status on atopic disorders did not reach statistical significance.

CONCLUSIONS

Excessive weight gain could be an important risk factor related to developing atopic dermatitis and allergic rhinitis during adolescence, especially among infants born small for gestational age.

Different Angiotensin-converting enzyme inhibitors and the associations with overall and cause-specific mortalities in patients with hypertension

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors have been widely used in the treatment of hypertension, but the comparative effectiveness in reducing mortality among different drugs is seldom reported.

METHODS

We identified hypertensive patients who started captopril, enalapril, lisinopril, fosinopril, perindopril, ramipril, or imidapril therapy from Taiwan's National Health Insurance database between 1 January 2004 and 31 December 2009. Overall and cause-specific mortalities were ascertained through a linkage to Taiwan's National Death Registry. Patients were followed from the initiation of ACE inhibitors to death, disenrollment, or study termination (31 December 2010). A Cox proportional hazard regression model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI), using ramipril as the reference group.

RESULTS

A total of 989,489 hypertensive patients were included, with a mean follow-up ranging from 3.5 years for imidapril to 4.5 years for enalapril. Captopril initiators had the highest overall mortality rate (117.8 per 1,000,000 person-days) as compared to other ACE inhibitors (54.3-79.4 per 1,000,000 person-days). Patients who started captopril therapy had a significantly increased risk of overall mortality (HR: 1.28, 95% CI: 1.24-1.31) when compared with ramipril. Enalapril (HR: 1.08, 95% CI: 1.05-1.11) and fosinopril (HR: 1.08, 95% CI: 1.05-1.12) were also associated with a modestly increased risk. No difference in mortality was found for lisinopril, perindopril, and imidapril, as compared with ramipril.

CONCLUSIONS

There are differences in the mortality risk associated with different ACE inhibitors. However, potential residual confounding effects might still exist.

Low serum zinc is associated with elevated risk of cadmium nephrotoxicity

BACKGROUND

Despite animal evidence suggests that zinc modulates cadmium nephrotoxicity, limited human data are available.

OBJECTIVE

To test the hypothesis that low serum zinc concentrations may increase the risk of cadmium-mediated renal dysfunction in humans.

METHODS

Data from 1545 subjects aged 20 or older in the National Health and Nutrition Examination Survey (NHANES), 2011-2012 were analyzed. Renal function was defined as impaired when estimated glomerular filtration rate (eGFR) fell below 60 ml/min/1.73 m(2) and/or the urinary albumin-to-creatinine ratio surpassed 2.5 in men and 3.5mg/mmol in women.

RESULTS

Within the study cohort, 117 subjects had reduced eGFR and 214 had elevated urinary albumin. After adjusting for potential confounders, subjects with elevated blood cadmium (>0.53 μg/L) were more likely to have a reduced eGFR (odds ratio [OR]=2.21, 95% confidence interval [CI]: 1.09-4.50) and a higher urinary albumin (OR=2.04, 95% CI: 1.13-3.69) than their low cadmium (<0.18 μg/L) peers. In addition, for any given cadmium exposure, low serum zinc is associated with elevated risk of reduced eGFR (OR=3.38, 95% CI: 1.39-8.28). A similar increase in the odds ratio was observed between declining serum zinc and albuminuria but failed to reach statistical significance. Those with lower serum zinc/blood cadmium ratios were likewise at a greater risk of renal dysfunction (p<0.01).

CONCLUSIONS

This study results suggest that low serum zinc concentrations are associated with an increased risk of cadmium nephrotoxicity. Elevated cadmium exposure is global public health issue and the assessment of zinc nutritional status may be an important covariate in determining its effective renal toxicity.

Association of body burden of mercury with liver function test status in the U.S. population

The majority of mercury (Hg) exposure in the US population is from consumption of fish contaminated with methylmercury (MeHg). Since inorganic Hg is the predominant form excreted in the feces and urine, hepatic biotransformation is a critical step in its normal clearance. This study was set to test the hypothesis that compromised liver function is associated with body burden of Hg as indirectly reflected by Hg sampled in blood and urine. From the National Health and Nutrition Examination Survey (NHANES, 2003-2008), 3769 adults aged 20 years and above were selected for analysis. Hepatic function was inferred from the three standard serum liver-related enzyme activities, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyltransferase (GGT). Multivariate regression models were used to examine the associations of interest. Although urinary Hg was significantly correlated with serum Hg, the blood-urinary Hg relationship was influenced by liver function, which is also a function of demographic and lifestyle factors (e.g., gender). Although the results were only marginally significant for examined enzymes (p=0.06-0.08), urinary Hg tended to be lower among subjects with elevated liver enzymes, as compared to those with normal enzyme measurements. Conversely, MeHg generally represents a higher fraction of the total circulating Hg among those with elevated liver enzyme levels, especially among participants with elevations in all three enzymes (p=0.01). In conclusion, this population-based study identified an association between liver function, serum Hg and urinary Hg. Urinalysis may not be the optimal approach to monitor Hg elimination toxicokinetics or Hg exposure, since the majority of Hg excretion is fecal and the fidelity of urinary excretion may depend on healthy liver function. Future prospective studies are warranted to expand these findings.

Low birth weight and environmental tobacco smoke increases the risk of wheezing in adolescents: a retrospective cohort study

Background

Low birth weight (LBW) and environmental tobacco smoke (ETS) exposure are each associated with wheezing in children. This study was designed to examine the combined association of LBW and ETS with wheezing.

Methods

A retrospective birth cohort analysis linked with a national survey of allergic disorders among 1,018,031 junior high school students in Taiwan (1995–1996) was analyzed. The reported incidence of wheezing (yes or no) and ETS exposure (4 categories: 0, 1–20, 21–40 and greater than or equal to 41 household cigarettes per day) were obtained from validated questionnaires. Multiple logistic regression models were used to assess the associations of interest.

Results

There were 844,003 (83%) subjects analyzed after the exclusion criteria. LBW was associated with an increased risk of reporting ever wheezing (odds ratio [OR] = 1.08, 95% confidence interval [CI] = 1.01–1.16), current wheezing (OR = 1.09, 95% CI = 1.00–1.20) and wheezing with exercise (OR = 1.11, 95% CI = 1.02–1.21) within the smoke-free cohort. Higher ETS exposure correlated to a higher risk of wheezing (ever, current and with exercise). With ETS exposure, adolescents from the lowest birth weight cohorts were more likely to report wheezing (ever, current and with exercise).

Conclusions

ETS and LBW each has been related to increasing public health risk for respiratory symptoms among adolescents. Furthermore, LBW may aggravate the risk among those exposed to ETS. LBW, ETS and associated respiratory impairments may deserve special attention as part of a comprehensive environmental health risk assessment directed toward prevention and intervention.

Examining the Association of Olmesartan and Other Angiotensin Receptor Blockers With Overall and Cause-Specific Mortality

Concerns about an increased cardiovascular risk with the angiotensin receptor blocker, olmesartan, prompted the current study to examine associations between olmesartan and other angiotensin receptor blockers with overall and cause-specific mortalities. We collected patients who started to use losartan, valsartan, irbesartan, candesartan, telmisartan, and olmesartan between January 1, 2004, and December 31, 2009, from Taiwan’s National Health Insurance claims database. Prescribed drug types, dosage, and other clinical information were collected. Overall mortality and cause-specific mortality were ascertained through linkages with Taiwan’s National Death Registry. Two follow-up analyses, labeled intention-to-treat and as-treated, were conducted. A Cox proportional hazard regression model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) using losartan as the reference group. A total of 690 463 subjects were included, with a mean follow-up ranging from a low of 2.8 years for olmesartan to a high of 4.1 years for irbesartan. Subjects who began with valsartan had a modest but significantly increased risk of overall mortality (HR, 1.04; 95% CI, 1.02–1.06) compared with losartan. Irbesartan (HR, 0.96; 95% CI, 0.94–0.99), candesartan (HR, 0.95; 95% CI, 0.92–0.99), telmisartan (HR, 0.93; 95% CI, 0.90–0.96), and olmesartan (HR, 0.93; 95% CI, 0.88–0.97) were associated with a slightly lower overall mortality risk than losartan. The analysis indicates that the differences in mortality risk among individual angiotensin receptor blockers were only marginal and thus less likely to be clinically important. Although uncontrolled confounding might still exist, olmesartan does not seem to increase cardiovascular risk compared with losartan.

Effect of Radiofrequency Catheter Ablation for Atrial Fibrillation on Morbidity and Mortality

Background—

This study examined the effect of radiofrequency catheter ablation (RFA) on reducing morbidity and mortality among patients with atrial fibrillation (AF).

Methods and Results—

A retrospective cohort of patients with AF without prior stroke or heart failure (HF) who underwent RFA between 2003 and 2009 was identified using Taiwan’s National Health Insurance claims database. Outpatients with AF who met the same enrollment criteria but did not receive RFA were matched (≤1:20) by hospitals and dates to serve as controls. Outcomes of interest were death, stroke, or hospitalization for HF. A proportional hazard Cox regression model adjusted by propensity scores (based on age, sex, hypertension, diabetes mellitus, comorbidities, medications, and medical resource utilization) was applied to estimate the hazard ratio and 95% confidence interval. A total of 846 patients with AF who received RFA and 11 324 matched AF controls were included, with a mean follow-up of 3.74 and 3.96 years, respectively. RFA was associated with a lower hazard for stroke (hazard ratio, 0.57; 95% confidence interval, 0.35–0.94; P =0.026). The reduction in the hazard for death and HF did not reach statistical significance (hazard ratio, 0.88; 95% confidence interval, 0.62–1.23; P =0.451 and hazard ratio, 0.78; 95% confidence interval, 0.55–1.12; P =0.185, respectively). Additional analysis using death as a competing risk showed similar results for stroke and HF.

Conclusions—

RFA did not reduce mortality or hospitalization for HF during the immediate 3.5-year follow-up. Although a beneficial effect on stroke prevention associated with RFA was suggested, residual confounding attributable to unmeasured factors remains a concern.

Associations of physical activity and dietary behaviors with children's health and academic problems

BACKGROUND

We examined the associations of physical activities and dietary behaviors with children's health and academic-behavioral problems.

METHODS

We employed a Community-wide Children's Health Assessment and Planning Survey to examine physical activity, healthy meals, health status, and academic-behavioral problems in 3708 children 7 to 14 years of age. Statistical associations were examined with chi-square test and logistic regression analysis; we calculated odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Among these children, 30.2% were overweight-obese, 11.0% had academic problems, and 7.9% had behavioral problems. Children classified as healthy eaters were more likely to exercise ≥4 days/week (79.1% vs 64.6%, OR: 2.08, 95% CI: 1.14 to 2.49), less likely to be overweight-obese (27.7% vs 44.6%, OR: 0.48, CI: 0.31 to 0.73), less likely to have academic problems (9.1% vs 16.1%, OR: 0.57, 95% CI: 0.41 to 0.79) and behavioral problems (6.9% vs 13.9%, OR: 0.46, 95% CI: 0.32 to 0.66) compared with their less healthy eating peers. Physical activity and healthy meals were associated with an improved health status (p < .001). However, the proportions of children taking unhealthy meals or choosing sedentary lifestyle increased as the cohorts progressed (p < .05) from childhood (7 to 8 years) to adolescence (13 to 14 years).

CONCLUSIONS

Healthy (or unhealthy) lifestyle behaviors are significantly interrelated. Children who take healthy meals and exercise often are associated with better health and fewer academic and behavioral problems. Unfortunately, taking unhealthy meals and sedentary lifestyle characterize a growing proportion of young adolescents. Thus, curbing unhealthy lifestyle behaviors should start in early childhood.

Increased risk of cancer mortality associated with cadmium exposures in older Americans with low zinc intake

Cadmium (Cd) exposure has been associated with increased cancer risk, and zinc (Zn) appears to reduce that risk. However, little is known about the combined influence of Cd and Zn on cancer risk. The aim of this study was to examine relationships between Cd exposure, Zn intake, and cancer mortality risks. The analyses used 5204 subjects aged 50 yr or older from the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) and the mortality follow-up through December 31, 2006. Cox proportional hazards models were used to test associations. In total, 569 cancer deaths were recorded during an average follow-up of 12.4 yr, including 155 from lung, 61 from prostate, and 26 from breast cancer. A positive association between Cd and cancer mortality risk was identified for both genders. Despite limited cause-specific deaths, the increased risk associated with Cd was significant for lung cancer in men. All-cause cancer mortality risk was significantly elevated among women with Zn intakes below the recommended dietary allowance (RDA) compared with women who met the RDA. The effect of low dietary Zn was not observed in men. Similar trends for prostate and breast cancer deaths were not significant. There was a significant inverse association between cancer deaths and the Zn-to-Cd ratio for both genders. Cd exposure is an important independent risk factor of cancer mortality in older Americans and the risk appears exaggerated in those with inadequate dietary Zn. Additional studies are required to elucidate the mechanism(s) by which Zn participates in the carcinogenic influence of Cd.

Body mass index may modify asthma prevalence among low-birth-weight children

Childhood asthma, a growing health concern, has been associated with low birth weight and elevated body mass index. This study tested the hypothesis that overweight and obese adolescents with a history of low birth weight are at even greater risk of developing asthma. A cohort of 75,871 junior high school students was screened for asthma during 1995-1996 in Taiwan. Birth weight and estimated gestational age were obtained from the birth registry. Logistic regression and simple regression analyses were adjusted for confounding variables. Asthma was more prevalent in those with birth weights below 3,000 g and higher adolescent body mass indexes. Furthermore, those with both characteristics were consistently most likely to have asthma. Whether the asthma diagnosis among low-birth-weight subjects was assigned by physicians or medical questionnaire, the risks were elevated for both overweight (physician diagnosis: odds ratio = 1.41; medical questionnaire: odds ratio = 1.25) and obese (physician diagnosis: odds ratio = 1.38; medical questionnaire: odds ratio = 1.47) boys as well as overweight (physician diagnosis: odds ratio = 1.63; medical questionnaire: odds ratio = 1.30) and obese (physician diagnosis: odds ratio = 1.44; medical questionnaire: odds ratio = 1.32) girls (P < 0.05). Low birth weight predisposes one to develop asthma, and excess body mass amplifies the risk. A sex difference was observed. This study suggests that prenatal care and nutritional counseling could reduce asthma prevalence.

Environmental exposure to dioxin-like compounds and the mortality risk in the U.S. population

BACKGROUND

Little is known about the mortality risk associated with chronic dioxin exposure in the general U.S. populations.

OBJECTIVE

To explore the association between dioxin-like chemicals and mortality risk in a large population-based cohort study.

METHODS

The analysis included 2361 subjects aged 40 years or older from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). Exposure to a mixture of dioxin-like chemicals, including dibenzo-p-dioxins, dibenzofurans, and polychlorinated biphenyls was estimated using toxic equivalency values (TEQs) calculated with 2005 World Health Organization toxic equivalency factors. All-cause and cause-specific mortalities were obtained from the NHANES-linked follow-up data through December 31, 2006. Cox proportional-hazards models were applied to assess the associations of interest.

RESULTS

A total of 242 deaths occurred during the follow-up period, including 75 from cardiovascular disease and 72 from cancer. There was an increased mortality risk associated with logarithmically expressed dioxin TEQs for all-cause deaths (hazard ratio=1.19, 95% confidence interval=1.02-1.39, p=0.02). Similar graded dose-response trends were found for cardiovascular and cancer mortality which did not reach statistical significance.

CONCLUSIONS

In general, higher dioxin exposure is associated with an increased mortality risk among subjects aged 40 and above. The cause-specific analyses and responsible mechanisms will require further investigation.

Higher body mass index may induce asthma among adolescents with pre-asthmatic symptoms: a prospective cohort study

Background

Limited studies have prospectively examined the role of body mass index (BMI) as a major risk factor for asthma during adolescence. This study investigates whether BMI is associated with increased risk of developing physician-diagnosed asthma during 12-month follow-up among adolescents with undiagnosed asthma-like symptoms at baseline.

Methods

A total of 4,052 adolescents with undiagnosed asthma-like symptoms at baseline were re-examined after a 12-month follow-up. Asthma cases were considered confirmed only after diagnosis by a physician based on the New England core and International Study of Asthma and Allergies in Childhood (ISAAC) criteria video questionnaires, and accompanying pulmonary function tests. Logistic regression analyses were used to evaluate the relationship of BMI and the risk of acquiring asthma.

Results

The results indicated that girls with higher BMI were at an increased risk of developing asthma during the 12-month follow-up. The odds ratios for girls developing physician-diagnosed asthma were 1.75 (95% CI = 1.18-2.61) and 1.12 (95% CI = 0.76-1.67), respectively, for overweight and obesity as compared to the normal weight reference group after adjustment for other covariates. A similar relationship was not observed for overweight and obese boys who were also significantly more active than their female counterparts.

Conclusions

Increased BMI exaggerates the risk of acquiring asthma in symptomatic adolescent females but not in adolescent males. Thus, gender is an important modifier of BMI-related asthma risk. Additional research will be required to determine whether the increased asthma risk results from genetic, physiological or behavioural differences.

Sympatholytic delta-2 opioid receptors moderate ganglionic vasomotor control

This study tested the hypothesis that enkephalin increases femoral vascular conductance via the delta-2 phenotype of the opioid receptor (DOR-2) within peripheral sympathetic ganglia. Graded pulses of methionine–enkephalin (ME) were administered (0.03–10 μg/kg) into the terminal aorta of anesthetized dogs proximal to lumbar arteries that perfuse vasomotor ganglia regulating femoral blood flow. Femoral vascular conductance increased sharply (ED50 = 2.6 × 10−9 mol/kg) accompanied by declines in arterial pressure and femoral vascular resistance. A dose-related increase in arterial pressure preceded each subsequent fall in pressure. The DOR-2 antagonist, naltriben (NTB), abrogated the hyperemic effect of ME (ID50 = 1.4 × 10−9 mol/kg). DOR-1 blockade (BNTX) was five-fold less effective. The hyperemic effect of ME was also enhanced when sympathetic activity was reflexly increased by bilateral carotid occlusion. The DOR-2 agonist, deltorphin II, produced exaggerated increases in conductance compared with ME that were also reduced by DOR-2 blockade. DOR-1 blockade eliminated the initial pressor responses, exaggerated the subsequent depressor response, increased baseline femoral conductance 10-fold and shifted the ME-mediated hyperemic threshold one dose lower from 0.3 to 0.1 μg/kg, providing indirect support for a competing DOR-1-mediated constriction. Extended exposure to DOR-1 blockade lowered the maximal ME increase in conductance by 30%, suggesting that BNTX reduces the available pool of DOR receptors. In summary, enkephalin mediates a robust hyperemic effect through sympatholytic ganglionic DOR-2 receptors and DOR-1 antagonist studies provide indirect evidence for constituent opposition from a proposed DOR-1-mediated sympathotonic constrictor pathway.

Cystatin C and long-term mortality among subjects with normal creatinine-based estimated glomerular filtration rates: NHANES III (Third National Health and Nutrition Examination Survey)

OBJECTIVES

The objective was to test the association of cystatin C (Cys-C) with long-term mortality risk in the subjects with normal creatinine-based estimated glomerular filtration rates (eGFR).

BACKGROUND

Cys-C has been proposed as a sensitive indicator of renal dysfunction that is associated with cardiovascular events. The predictive value of Cys-C for mortality risk (both cardiovascular and noncardiovascular) and its utility among persons with normal kidney function remains unclear.

METHODS

The analysis included 2,990 subjects over 40 years of age with normal eGFR who participated in NHANES III (Third National Health and Nutrition Examination Survey). Normal eGFR was defined by Modification of Diet in Renal Disease (MDRD) equation ≥60 ml/min/1.73 m(2). Serum Cys-C was categorized as high, medium, or low. In 1 analysis, the high and low groups were the top and bottom 10%, and in the second analysis, they were the upper and lower thirds. All-cause and cause-specific mortality were obtained from the NHANES III-linked follow-up file through December 31, 2006. Multivariate Cox regression models were applied to assess the association of interest.

RESULTS

Within an average of 13.7 years follow-up, 488 cardiovascular and 719 noncardiovascular deaths occurred. When the first and last deciles were compared, the relative risks were all increased statistically as follows: all-cause, 4.36 (95% confidence interval [CI]: 2.52 to 7.82); cardiovascular, 7.44 (95% CI: 3.06 to 18.1); cancer, 2.45 (95% CI: 0.85 to 7.04); and noncardiovascular 3.15 (95% CI: 1.53 to 6.49) mortalities. Relative risks all moderated to lower values when the comparisons were expanded to include the upper and lower thirds. Similar associations were still present when Cys-C was modeled on a continuous scale, suggesting a linear relationship between Cys-C and mortality outcomes.

CONCLUSIONS

Serum Cys-C is prognostic of long-term mortality in the subjects with relatively normal renal function, independent of MDRD eGFR and albuminuria.

Association of albuminuria and cancer mortality

BACKGROUND

The objective was to evaluate the association of albuminuria with cancer mortalities in adults ages 50 and older.

METHODS

A total of 6,112 adults ages 50 years and above without a history of cancer at baseline in the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) were included in the analysis. Albuminuria was measured with urinary albumin-to-creatinine ratio (UACR) in mg/mmol. Cancer mortality was obtained from the NHANES III-linked follow-up database (up to December 31, 2006). Cox-regression models were used to examine the associations of interest.

RESULTS

Albuminuria was present in 705 men (17.5%) and 592 women (14.3%). During an average follow-up of 149 months, 613 subjects died of cancers including 184 lung cancers, 65 colorectal cancers, 55 prostate cancers, and 309 other cancers. There was an increased mortality risk associated with logarithmically transformed UACR for all-cancer [relative risk (RR), 1.20; 95% confidence interval (CI), 1.06-1.36], lung cancer (RR, 1.22; 95% CI, 1.05-1.43), and prostate cancer mortality (RR, 1.40; 95% CI, 1.01-1.95) in men. No associations between UACR and cancer were apparent in women.

CONCLUSIONS

The analysis shows that albuminuria is associated with an increased risk of cancer death, specifically for all-cause, lung, and prostate cancers in men ages 50 and above.

IMPACT

Further studies are needed to explore the relationship between albuminuria and specific cancers. Understanding the biological link between albuminuria and cancer will be critical for determining whether albuminuria represents an early marker or a potential therapeutic target.

Sex, menopause, metabolic syndrome, and all-cause and cause-specific mortality--cohort analysis from the Third National Health and Nutrition Examination Survey

OBJECTIVE

This study assessed the mortality risk associated with metabolic syndrome (MetS) for participants from the Third National Health and Nutrition Examination Survey.

DESIGN, SETTING, AND PATIENTS

The study analyzed mortality data from 1364 men and 1321 women aged 40 yr and older based on their MetS status defined by National Cholesterol Education Program Adult Treatment Panel III. Subjects initially using insulin, oral hypoglycemic, antihypertensive, or lipid-lowering medications were excluded.

MAIN OUTCOME MEASURES

All-cause, cardiovascular, cardiac, and noncardiovascular mortality were obtained from the Third National Health and Nutrition Examination Survey-linked mortality follow-up file through December 31, 2000.

RESULTS

The prevalence of MetS was 33 and 29% for men and women, respectively. In the male subjects, there was no significant association between MetS and mortality. In the women, MetS was an independent risk factor for all-cause mortality [hazard ratio (HR) 1.84, 95% confidence interval (CI) 1.29-2.64, P = 0.001], cardiovascular mortality (HR 1.96, 95% CI 1.21-3.17, P = 0.007), cardiac mortality (HR 1.88, 95% CI 1.15-3.09, P = 0.01), and noncardiovascular mortality (HR 1.80, 95% CI 1.13-2.87, P = 0.01). The HR was stronger when postmenopausal women were analyzed separately and became nonsignificant in the premenopausal cohort. The sex-specific HR remained unchanged, regardless of the MetS criteria used or the inclusion of actively treated subjects.

CONCLUSIONS

MetS poses a significant increase in mortality risk through an observation period as long as 12 yr, primarily in postmenopausal women, that is not apparent in men and premenopausal women. Sex is an important effect modifier of all-cause and cause-specific death.

Cigarette smoking, cadmium exposure, and zinc intake on obstructive lung disorder

BACKGROUND AND OBJECTIVE

This study examined whether zinc intake was associated with lower risk of smoking-induced obstructive lung disorder through interplay with cadmium, one of major toxicants in cigarette smoke.

METHODS

Data were obtained from a sample of 6,726 subjects aged 40+ from the Third National Health and Nutrition Examination Survey. The forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were measured using spirometry. Gender-, ethnicity-, and age-specific equations were used to calculate the lower limit of normal (LLN) to define obstructive lung disorder as: observed FEV1/FVC ratio and FEV1 below respective LLN. Zinc intake was assessed by questionnaire. Logistic regression analysis was applied to investigate the associations of interest.

RESULTS

The analyses showed that an increased prevalence of obstructive lung disorder was observed among individuals with low zinc intake regardless of smoking status. The adjusted odds of lung disorder are approximately 1.9 times greater for subjects in the lowest zinc-intake tertile than those in the highest tertile (odds ratio = 1.89, 95% confidence interval = 1.22-2.93). The effect of smoking on lung function decreased considerably after adjusting for urinary cadmium. Protective association between the zinc-to-cadmium ratio (log-transformed) and respiratory risk suggests that zinc may play a role in smoking-associated lung disorder by modifying the influence of cadmium.

CONCLUSIONS

While zinc intake is associated with lower risk of obstructive lung disorder, the role of smoking cession and/or prevention are likely to be more important given their far greater effect on respiratory risk. Future research is warranted to explore the mechanisms by which zinc could modify smoking-associated lung disease.

Repeated arterial occlusion, delta-opioid receptor (DOR) plasticity and vagal transmission within the sinoatrial node of the anesthetized dog

Brief interruptions in coronary blood flow precondition the heart, engage delta-opioid receptor (DOR) mechanisms and reduce the damage that typically accompanies subsequent longer coronary occlusions. Repeated short occlusions of the sinoatrial (SA) node artery progressively raised nodal methionine-enkephalin-arginine-phenylalanine (MEAP) and improved vagal transmission during subsequent long occlusions in anesthetized dogs. The DOR type-1 (DOR-1) antagonist, BNTX reversed the vagotonic effect. Higher doses of enkephalin interrupted vagal transmission through a DOR-2 mechanism. The current study tested whether the preconditioning (PC) protocol, the later occlusion or a combination of both was required for the vagotonic effect. The study also tested whether evolving vagotonic effects included withdrawal of competing DOR-2 vagolytic influences. Vagal transmission progressively improved during successive SA nodal artery occlusions. The vagotonic effect was absent in sham animals and after DOR-1 blockade. After completing the PC protocol, exogenously applied vagolytic doses of MEAP reduced vagal transmission under both normal and occluded conditions. The magnitude of these DOR-2 vagolytic effects was small compared to controls and repeated MEAP challenges rapidly eroded vagolytic responses further. Prior DOR-1 blockade did not alter the PC mediated, progressive loss of DOR-2 vagolytic responses. In conclusion, DOR-1 vagotonic responses evolved from signals earlier in the PC protocol and erosion of competing DOR-2 vagolytic responses may have contributed to an unmasking of vagotonic responses. The data support the hypothesis that PC and DOR-2 stimulation promote DOR trafficking, and down regulation of the vagolytic DOR-2 phenotype in favor of the vagotonic DOR-1 phenotype. DOR-1 blockade may accelerate the process by sequestering newly emerging receptors.

Cholinergic location of δ-opioid receptors in canine atria and SA node

δ-Opioid receptors (DORs) are associated with ischemic preconditioning and vagal transmission in the sinoatrial (SA) node and atria. Although functional studies suggested that DORs are prejunctional on parasympathetic nerve terminals, their precise location remains unconfirmed. DORs were colocalized in tissue slices and synaptosomes from the canine right atrium and SA node along with cholinergic and adrenergic markers, vesicular acetylcholine transporter (VAChT), and tyrosine hydroxylase (TH). Synapsin I immunofluorescence verified the neural character of tissue structures and isolated synaptosomes. Acetylcholine and norepinephrine measurements suggested the presence of both cholinergic and adrenergic synaptosomes. Fluorescent analysis of VAChT and TH signals indicated that >80% of the synapsin-positive synaptosomes were of cholinergic origin and <8% were adrenergic. DORs colocalized 75–85% with synapsin in tissue slices from both atria and SA node. The colocalization was equally strong (85%) for nodal synaptosomes but less so for atrial synaptosomes (57%). Colocalization between DOR and VAChT was 75–85% regardless of the source. Overlap between DOR and TH was uniformly low, ranging from 8% to 17%. Western blots with synaptosomal extracts confirmed two DOR-positive bands at molecular masses corresponding to those reported for DOR monomers and dimers. The abundance of DOR was greater in nodal synaptosomes than in atrial synaptosomes, largely attributable to a greater abundance of monomers in the SA node. The abundant nodal and atrial DORs predominantly associated with cholinergic nerve terminals support the hypothesis that prejunctional DORs regulate vagal transmission locally within the heart.

Evidence that cardioprotection by postconditioning involves preservation of myocardial opioid content and selective opioid receptor activation

Opioids introduced at reperfusion (R) following ischemia (I) reduce infarct size much like postconditioning, suggesting the hypothesis that postconditioning increases cardiac opioids and activates local opioid receptors. Anesthetized male rats subjected to 30 min regional I and 3 h R were postconditioned with three cycles of 10 s R and 10 s reocclusion at onset of R. Naloxone (NL), its peripherally restricted analog naloxone methiodide, delta-opioid receptor (DOR) antagonist naltrindole (NTI), kappa-opioid receptor antagonist norbinaltorphimine (NorBNI), and mu-opioid receptor (MOR) antagonist H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP) were administered intravenously 5 min before R. The area at risk (AAR) was comparable among groups, and postconditioning reduced infarct size from 57 +/- 2 to 42 +/- 2% (P < 0.05). None of the antagonists alone altered infarct size. All antagonists abrogated postconditioning protection at higher doses. However, blockade of infarct sparing by postconditioning was lost, since tested doses of NL, NTI, NorBNI, and CTAP were lowered. The efficacy of NorBNI declined first at 3.4 micromol/kg, followed sequentially by NTI (1.1), NL (0.37), and CTAP (0.09), suggesting likely MOR and perhaps DOR participation. Representative small, intermediate, and large enkephalins in the AAR were quantified (fmol/mg protein; mean +/- SE). I/R reduced proenkephalin (58 +/- 9 vs. 33 +/- 4; P < 0.05) and sum total of measured enkephalins, including proenkephalin, peptide B, methionine-enkephalin, and methionine-enkephalin-arginine-phenylalanine (139 +/- 17 vs. 104 +/- 7; P < 0.05) compared with shams. Postconditioning increased total enkephalins (89 +/- 8 vs. 135 +/- 5; P < 0.05) largely by increasing proenkephalin (33 +/- 4 vs. 96 +/- 7; P < 0.05). Thus the infarct-sparing effect of postconditioning appeared to involve endogenously activated MORs and possibly DORs, and preservation of enkephalin precursor synthesis in the AAR.

Influence of BMI and gender on postprandial hormone responses

OBJECTIVE

Influences of gender and body weight on the hormonal response to eating are not well understood. This study was conducted to determine a convenient time-point to evaluate peak postprandial hormone responses and to test the hypothesis that gender and BMI interact to produce differences in postprandial secretion of selected humoral markers implicated in hunger and satiety.

RESEARCH METHODS AND PROCEDURES

Fasting blood glucose, insulin, leptin, ghrelin, glucagon-like peptide-1, and glucagon were measured in normal-weight (20 <or= BMI < 25 kg/m2) men (n = 10) and women (n = 9) and obese (BMI >or= 30 kg/m2) men (n = 9) and women (n = 11). A standard liquid meal was consumed, and humoral measurements were repeated every 10 minutes for 1 hour. Data were analyzed using repeated measures ANOVA with BMI and gender as main effects.

RESULTS

Obese subjects had delayed peak insulin responses (p = 0.004), whereas obese men had a delayed nadir ghrelin response (p = 0.05). Obese subjects had higher and more sustained postprandial glucose (p = 0.02), and greater fasting (p = 0.0004) and postprandial insulin (p = 0.0001). Ghrelin decreased after the meal (p = 0.003); the percent change from fasting tended to be reduced in obese subjects (p = 0.07). Men had greater fasting (p = 0.02) and postprandial (p = 0.03) glucagon and a subtle postprandial decline in plasma leptin (p = 0.01).

DISCUSSION

Peak hormone responses occurred 20 to 40 minutes after eating. Measurements made during this interval may be useful in evaluating postprandial response magnitude. Peak/nadir responses and time courses of postprandial responses are influenced by gender and BMI. Nutritional studies need to account for variability introduced by these factors.

Repeated δ1-opioid receptor stimulation reduces δ2-opioid receptor responses in the SA node

Ultra-low-dose methionine-enkephalin-arginine-phenylalanine improves vagal transmission (vagotonic) and decreases heart rate via δ1-opioid receptors within the sinoatrial (SA) node. Higher doses activate δ2-opioid receptors, interrupt vagal transmission (vagolytic), and reduce the bradycardia. Preconditioning-like occlusion of the nodal artery produced a vagotonic response that was reversed by the δ1-antagonist 7-benzylidenaltrexone (BNTX). The following study tested the hypothesis that extended δ1-opioid receptor stimulation reduces subsequent δ2-receptor responses. The δ2-agonist deltorphin II was introduced in the SA node by microdialysis to evaluate δ2 responses before and after infusion of the δ1-agonist TAN-67. TAN-67 reduced the vagolytic effect of deltorphin by two-thirds. When the δ1-antagonist BNTX was combined with TAN-67, the deltorphin response was preserved, suggesting that attrition of the prior response was mediated by δ1 activity. When TAN-67 was omitted in time control studies, some loss of δ2 responses was apparent in the absence of the δ1 treatment. This loss was also eliminated by BNTX, suggesting that the attenuation of the response after deltorphin alone was also the result of δ1 activity. Additional studies tested TAN-67 alone in the absence of prior deltorphin. When time controls were conducted without the initial deltorphin treatment, a robust vagolytic response was observed. When TAN-67 preceded the delayed deltorphin, the vagolytic response was eroded, indicating an independent effect of TAN-67. BNTX infused afterward was unable to restore the δ2 response. These data support the conclusion that the loss of the δ2 response resulted from reduced δ2 activity mediated by continued δ1-receptor stimulation and not the arithmetic consequence of increased competition from that same δ1 receptor.

The monosialosyl ganglioside GM-1 reduces the vagolytic efficacy of delta2-opioid receptor stimulation

The cardiac enkephalin, methionine-enkephalin-arginine-phenylalanine (MEAP), alters vagally induced bradycardia when introduced by microdialysis into the sinoatrial (SA) node. The responses to MEAP are bimodal; lower doses enhance bradycardia and higher doses suppress bradycardia. The opposing vagotonic and vagolytic effects are mediated, respectively, by delta(1) and delta(2) phenotypes of the same receptor. Stimulation of the delta(1) receptor reduced the subsequent delta(2) responses. Experiments were conducted to test the hypothesis that the delta-receptor interactions were mediated by the monosialosyl ganglioside GM-1. When the mixed agonist MEAP was evaluated after nodal GM-1 treatment, delta(1)-mediated vagotonic responses were enhanced, and delta(2)-mediated vagolytic responses were reduced. Prior treatment with the delta(1)-selective antagonist 7-benzylidenaltrexone (BNTX) failed to prevent attrition of the delta(2)-vagolytic response or restore it when added afterward. Thus the GM-1-mediated attrition was not mediated by delta(1) receptors or increased competition from delta(1)-mediated vagotonic responses. When GM-1 was omitted, deltorphin produced a similar but less robust loss in the vagolytic response. In contrast, however, to GM-1, the deltorphin-mediated attrition was prevented by pretreatment with BNTX, indicating that the decline in response after deltorphin alone was mediated by delta(1) receptors and that GM-1 effectively bypassed the receptor. Whether deltorphin has intrinsic delta(1) activity or causes the release of an endogenous delta(1)-agonist is unclear. When both GM-1 and deltorphin were omitted, the subsequent vagolytic response was more intense. Thus GM-1, deltorphin, and time all interact to modify subsequent delta(2)-mediated vagolytic responses. The data support the hypothesis that delta(1)-receptor stimulation may reduce delta(2)-vagolytic responses by stimulating the GM-1 synthesis.

Vagotonic effects of enkephalin are not mediated by sympatholytic mechanisms

This study examined the hypothesis that vagotonic and sympatholytic effects of cardiac enkephalins are independently mediated by different receptors. A dose-response was constructed by administering the delta-receptor opioid methionine-enkephalin-arginine-phenylalanine (MEAP) by microdialysis into the interstitium of the canine sinoatrial node during vagal and sympathetic stimulation. The right cardiac sympathetic nerves were stimulated as they exited the stellate ganglion at frequencies selected to increase heart rate approximately 35 bpm. The right cervical vagus was stimulated at frequencies selected to produce a two-step decline in heart rate of 25 and 50 bpm. A six-step dose-response was constructed by recording heart rates during nerve stimulation as the dose of MEAP was increased between 0.05 pmol/min and 1.5 nmol/min. Vagal transmission improved during MEAP at 0.5 pmol/min. However, sympathetically mediated tachycardia was unaltered with any dose of MEAP. In Study 2, a similar dose-response was constructed with the kappa-opioid receptor agonist trans(+/-)-3-4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide-HCl (U-50488H) to illustrate an independent sympatholytic effect and to verify its kappa-receptor character. U-50488H gradually suppressed the sympathetic tachycardia, with a significant effect obtained only at the highest dose (1.5 nmol/min). U-50488H had no effect on vagally mediated bradycardia. Surprisingly, the sympatholytic effect was not reversed by withdrawing U-50488H or by the subsequent addition of the kappa-antagonist 17,17'-(dichloropropylmethyl)-6,6',7,7'-6,6'-imino-7,7'-binorphinan-3,4',14,14'-tetroldi-hydrochloride (norBNI). Study 3 was conducted to determine whether the sympatholytic effect of U-50488H could be prevented by norBNI. NorBNI blocked the sympatholytic effect of the U50488H for 90 mins. When norBNI was discontinued afterward and U-50488H was continued alone, a sympatholytic effect emerged within 30 mins. Collectively these observations support the hypothesis that the vagotonic influence of MEAP is not dependent on a sympatholytic influence. Furthermore, the sympatholytic effect is mediated independently by kappa-receptors. The sympatholytic effect of sustained kappa-receptor stimulation appears to evolve gradually into a functional state not easily reversed.