Analytical and biological variation of biomarkers of oxidative stress during the menstrual cycle

Urinary Biopyrrin Levels and Their Relationship with the Menstrual Cycle and Concomitant Symptoms Among Healthy Nonpregnant Women of Reproductive Age: A Cohort Study

Background

Urinary biopyrrin (UBP) is an oxidative metabolite formed from the reaction of bilirubin with reactive oxygen species. Previous studies have explored the relationship between UBP levels and certain diseases or pregnancy. However, UBP levels in healthy nonpregnant women have not been well examined. We aimed to clarify the representative value of UBP in healthy nonpregnant women and explore its relationship with menstrual cycles and concomitant symptoms.

Methods

We included healthy, nonpregnant Japanese women aged 20-39 years with normal body mass index and menstrual cycle. In total, 1260 urine samples collected during 43 menstrual cycles of 36 women were analyzed to determine the representative values and reference intervals of UBP levels. The correlation between daily UBP levels and the order of the day was explored, and median UBP levels of 5-day clusters were compared using Friedman and Mann-Whitney U tests. These analyses were also conducted in women with concomitant symptoms during the menstrual cycle.

Results

The median UBP level in all samples was 0.2291 (reference: 0.0102-2.9335) μmol/gCr. There was no significant relationship between the median UBP level and menstrual cycle, regardless of the presence of self-manageable symptoms during or before menstruation.

Conclusions

The representative UBP value and its reference interval can serve as standards for comparison with other populations. Our findings suggest that the UBP level may be an objective oxidative stress indicator that is less sensitive to menstrual cycle and concomitant symptoms. UBP levels in healthy nonpregnant women could be assessed regardless of the menstrual cycle and concomitant symptoms.

Toxic elements in follicular fluid adversely influence the likelihood of pregnancy and live birth in women undergoing IVF

STUDY QUESTION

Are follicular fluid (FF), arsenic (As), mercury (Hg), cadmium (Cd) and lead (Pb) concentrations associated with IVF outcomes among women undergoing IVF?

SUMMARY ANSWER

There was a non-linear association between higher FF Hg concentration and a lower likelihood of biochemical pregnancy and live birth. Higher FF Pb concentration was also associated with a lower probability of live birth.

WHAT IS KNOWN ALREADY

Previous research suggests that toxic elements may affect fertility among couples conceiving with and without assistance. However, the results have been inconsistent, possibly related in part to exposure misclassification. Very few studies have used ovarian FF to measure toxic elements, as it requires an invasive collection procedure, yet it may offer a more accurate estimate of a biologically effective dose than blood or urine.

STUDY DESIGN SIZE DURATION

This is a prospective study of 56 women undergoing IVF, from October 2015 to June 2017. FF was collected for analysis on the day of oocyte retrieval.

PARTICIPANTS/MATERIALS SETTING METHODS

As, Cd, Hg and Pb were determined in 197 FF specimens, using inductively coupled plasma tandem mass spectrometry. FF glutathione peroxidase, glutathione reductase, total glutathione-S-transferase, superoxide dismutase, arylesterase and paraoxonase (PON1p) activities were measured using kinetic enzyme assays.

MAIN RESULTS AND THE ROLE OF CHANCE

Non-linear associations were detected, in which the probabilities of biochemical pregnancy (P = 0.05) and live birth (P = 0.05) were lower in association with FF Hg greater than ∼0.51 µg/l Hg, adjusted for age, race, cigarette smoking and recent seafood consumption. Higher FF Pb was also associated with a lower likelihood of live birth (relative risk (RR) = 0.68, 95% CI: 0.46, 1.00; P = 0.05). We also found a suggestive, although imprecise, antagonizing mediating effect of PON1p activity on the association between FF Pb and live birth (-28.3%; 95% CI: -358%, 270%).

LIMITATIONS REASONS FOR CAUTION

The results should be interpreted judiciously given the limited sample size and difficulty accounting for correlated data in generalized additive models and mediation analyses. Additionally, women undergoing IVF are highly selected with respect to age and socioeconomic status, and so the generalizability of the results may be limited.

WIDER IMPLICATIONS OF THE FINDINGS

Overall, the results suggest that FF Hg was associated with a lower likelihood of biochemical pregnancy and live birth, with a potential threshold effect, and that higher FF Pb was associated with a lower probability of live birth. These results may help to guide clinical recommendations for limiting the exposure of patients to Hg and Pb and ultimately improve IVF success rates.

STUDY FUNDING/COMPETING INTERESTS

This work was funded in part by the National Institute of Environmental Health Sciences (NIEHS), grant number 1R56ES023886-01, to the University at Albany (M.S.B.), and in part by the National Institute of Environmental Health Sciences (NIEHS), grant number 1U2CES026542-01, to the Wadsworth Center (P.J.P.). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Intra-Individual Variation and Reliability of Biomarkers of the Antioxidant Defense System by Considering Dietary and Lifestyle Factors in Premenopausal Women

Epidemiological studies frequently rely on a single biomarker measurement to assess the relationship between antioxidant status and diseases. This bears an inherent risk for misclassification, if the respective biomarker has a high intra-individual variability. The present study investigates the intra-individual variation and reliability of enzymatic and non-enzymatic biomarkers of the antioxidant system in premenopausal women. Forty-four apparently healthy females provided three consecutive fasting blood samples in a four-week rhythm. Analyzed blood biomarkers included Trolox equivalent antioxidant capacity (TEAC), catalase, glutathione peroxidase, glutathione, vitamin C, bilirubin, uric acid, coenzyme Q10, tocopherols, carotenoids and retinol. Intra- and inter-individual variances for each biomarker were estimated before and after adjusting for relevant influencing factors, such as diet, lifestyle and use of contraceptives. Intraclass correlation coefficient (ICC), index of individuality, reference change value and number of measurements needed to confine attenuation in regression coefficients were calculated. Except for glutathione and TEAC, all biomarkers showed a crude ICC ≥ 0.50 and a high degree of individuality indicating that the reference change value is more appropriate than population-based reference values to scrutinize and classify intra-individual changes. Apart from glutathione and TEAC, between 1 and 9 measurements were necessary to reduce attenuation in regression coefficients to 10%. The results indicate that the majority of the assessed biomarkers have a fair to very good reliability in healthy premenopausal women, except for glutathione and TEAC. To assess the status of the antioxidant system, the use of multiple measurements and biomarkers is recommended.

A methodology for examining the association between plasma volume and micronutrient biomarker mass and concentration in healthy eumenorrheic women

BACKGROUND

Accurate estimation and interpretation of nutritional biomarker concentrations are important in nutritional research, clinical care, and public health surveillance. Plasma volume (PV) may affect the interpretation of plasma biomarkers but is rarely measured. We aimed to examine the association between plasma volume (PV) and micronutrient biomarker concentrations and mass as part of pilot work to develop methods.

METHODS

Nine healthy women with regular menstrual cycles provided fasting blood samples to measure micronutrient biomarkers. Indocyanine green was injected, and five timed blood draws were taken from 2 to 5 min to measure PV. Visits were scheduled around menstrual cycle day 2. Retinol, 25-hydroxyvitamin D, riboflavin, alpha-tocopherol, zinc, copper, magnesium, manganese, cobalt, iron, and ferritin concentrations were measured in serum. Total circulating micronutrient biomarker mass was calculated from PV and concentration.

RESULTS

The mean PV was 2067 ±  470 mL. PV correlated positively with concentration of iron (r = 0.87, P = 0.005); other correlations were weaker with p > 0.05. PV and total mass of retinol (r = 0.90), 25(OH)D (r = 0.75), zinc (r = 0.88), copper (r = 0.83), magnesium (r = 0.93), manganese (r = 0.72), and iron (r = 0.92) were strongly correlated (all p < 0.05). PV was positively correlated with circulating micronutrient mass for most biomarkers, implying that concentrations are maintained at different volumes of plasma. Larger studies are needed to further examine these relationships.

CONCLUSION

Though there appear to be some association between micronutrient biomarker mass and plasma volume, we are unable to draw a firm conclusion about any relationship from these results because of the small sample size. We consider these findings as a preliminary analysis to establish methods for future studies.

Application of an analytical framework for multivariate mediation analysis of environmental data

Diverse toxicological mechanisms may mediate the impact of environmental toxicants (phthalates, phenols, polycyclic aromatic hydrocarbons, and metals) on pregnancy outcomes. In this study, we introduce an analytical framework for multivariate mediation analysis to identify mediation pathways (q = 61 mediators) in the relationship between environmental toxicants (p = 38 analytes) and gestational age at delivery. Our analytical framework includes: (1) conducting pairwise mediation for unique exposure-mediator combinations, (2) exposure dimension reduction by estimating environmental risk scores, and (3) multivariate mediator analysis using either Bayesian shrinkage mediation analysis, population value decomposition, or mediation pathway penalization. Dimension reduction demonstrates that a one-unit increase in phthalate risk score is associated with a total effect of 1.07 lower gestational age (in weeks) at delivery (95% confidence interval: 0.48-1.67) and eicosanoids from the cytochrome p450 pathway mediated 26% of this effect (95% confidence interval: 4-63%). Eicosanoid products derived from the cytochrome p450 pathway may be important mediators of phthalate toxicity.

Role of Anti-Inflammatory, Reactive Oxygen Species Scavenging Activity and Nematicidal Properties of Myrtle Berry Seeds on Helminthiasis Treatment

This study was undertaken to investigate the involvement of the reactive oxygen species (ROS) and proinflammatory cytokine production in the pathogenicity of gastrointestinal nematode Heligmosomoides polygyrus in mice and also the protective effect of myrtle (Myrtus communis L.) berry seeds aqueous extract (MBSAE). With this aim, Swiss Albino mice were divided into four groups of 10 animals each: control, helminthiasis, helminthiasis + MBSAE, and helminthiasis + Albendazole. The animals were infected with infective third larval stage (L3) of H. polygyrus by oral administration. Mice were treated with bidistilled water, MBSAE (100 mg/kg, b.w., p.o.) or Albendazole (100 mg/kg, b.w., p.o.). We have demonstrated that MBSAE (100 mg/kg, b.w., p.o.) significantly reduced the total mean adult worms compared with the infected and nontreated group. Moreover, hematological parameters, intestinal ROS such as hydrogen peroxide (H₂O₂), hydroxyl radical (OH^•), and superoxide anion (O₂^•-), as well as serum cytokines such as interleukin (IL)-1β and IL-6 were analyzed. We have shown that H. polygyrus infection has disrupted all these biochemical parameters and that MBSAE treatment has significantly corrected these disturbances. The effect of plant extract was comparable to the standard drug albendazole. Therefore, MBSAE appeared to be a promising agent for the control of intestinal helminthiasis.

Urinary levels of environmental phenols and parabens and antioxidant enzyme activity in the blood of women

BACKGROUND

The balance between oxidative stress and antioxidant enzymes is one biological mechanism by which environmental and lifestyle exposures affect health outcomes. Yet, no studies have examined the relationship between environmental phenolic compounds and parabens or their mixtures in relation to antioxidant enzyme activity in women of reproductive age.

METHODS

Sixteen environmental phenols and parabens were measured in urine 2-5 times across two months of follow-up in 143 women aged 18-44 years. Four antioxidant enzymes, erythrocyte and plasma glutathione peroxidase (eGPx, pGPx), glutathione reductase (GSHR), superoxide dismutase (SOD) were measured in plasma. Linear mixed models were adjusted for age, body mass index, race, and creatinine and were weighted with inverse probability of exposure weights. Multi-chemical exposures were estimated using hierarchical principal component analysis (PCA).

RESULTS

In line with our hypothesis that environmental phenols and parabens would be associated with decreased antioxidant enzymes, butyl, benzyl, ethyl, and propyl parabens were associated with lower levels of eGPx. Methyl paraben, 2,4-dichlorophenol and 2,5-dichlorophenol were associated with reduced SOD. 2,4,6-trichlorophenol was associated with increased levels of pGPx and GSHR. Several parabens were associated with modest decreases in eGPx and SOD, biomarkers of antioxidant defense. Increases in pGPx and GSHR were noted in relation to butyl and ethyl parabens. Co-exposures to parabens were associated with decreased eGPx (β = -1.08, 95% CI: -1.74, -0.43) in principal components mixed models, while co-exposure to benzophenones-3 and -1 were associated with increased eGPx (β = 0.92, 95% CI: 0.20, 1.64).

CONCLUSION

These findings indicate that nonpersistent chemicals altered antioxidant enzyme activity. Further human studies are necessary to delineate the relationship between environmental phenol and paraben exposures with erythrocyte and plasma activities of antioxidant enzymes.

Prediction and associations of preterm birth and its subtypes with eicosanoid enzymatic pathways and inflammatory markers

Endogenous signaling molecules derived from lipids, peptides, and DNA, are important regulators of physiological processes during pregnancy. The effect of their collective impact on preterm birth (delivery < 37 weeks gestation) is understudied. We aimed to characterize the associations and predictive capacity of an extensive panel of eicosanoids, immune biomarkers, oxidative stress markers, and growth factors towards preterm birth and its subtypes. We conducted a cross-sectional study of pregnant women (recruited < 15 weeks gestation) in the LIFECODES birth cohort, which included 58 cases of preterm birth and 115 controls that delivered term. Among the cases there were 31 cases who had a spontaneous preterm birth (cases who had spontaneous preterm labor and/or preterm premature rupture of membranes) and 25 that had preterm birth associated with aberrant placentation (cases who had preeclampsia and/or intrauterine growth restriction) and 2 cases that could not be sufficiently categorized as either. We analyzed single biomarker associations with each preterm birth outcome using multiple logistic regression. Adaptive elastic-net was implemented to perform a penalized multiple logistic regression on all biomarkers simultaneously to identify the most predictive biomarkers. We then organized biomarkers into biological groups and by enzymatic pathways and applied adaptive elastic-net and random forest to evaluate the accuracy of each group for predicting preterm birth cases. The majority of associations we observed were for spontaneous preterm birth, and adaptive elastic-net identified 5-oxoeicosatetraenoic acid, resolvin D1, 5,6-epoxy-eicsatrienoic acid, and 15-deoxy-12,14-prostaglandin J2 as most predictive. Overall, lipid biomarkers performed the best at separating cases from controls compared to other biomarker categories (adaptive elastic-net AUC = 0.78 [0.62, 0.94], random forest AUC = 0.84 [0.72, 0.96]). Among the enzymatic pathways that differentiate eicosanoid metabolites, we observed the highest prediction of overall preterm birth by lipoxygenase metabolites using random forest (AUC = 0.83 [0.69, 0.96]), followed by cytochrome p450 metabolites using adaptive elastic-net (AUC = 0.74 [0.52, 0.96]). In this study we translate biological hypothesis into the language of modern machine learning. Many lipid biomarkers were highly associated with overall and spontaneous preterm birth. Among eicosanoids, lipoxygenase and cytochrome p450 products performed best in identifying overall and spontaneous preterm birth. The combination of lipid biomarkers may have good utility in clinical settings to predict preterm birth.

Tampon use, environmental chemicals and oxidative stress in the BioCycle study

BACKGROUND

Tampons are used by up to 86% of US women and are a rarely considered potential source of pesticide and metal exposure. Tampons may be of particular concern given the likely higher absorption that occurs in the vagina. Our objective was to examine the potential associations between tampon use and metal concentrations, and biomarkers of inflammation and oxidative stress among healthy women.

METHODS

We used information from a prospective cohort of 259 regularly menstruating women, aged 18-44, followed for two menstrual cycles. Tampon use was assessed using information provided in participant study diaries. Metal concentrations were measured from a blood sample collected at enrollment. Oxidative stress and inflammation biomarker concentrations were determined from blood samples collected at up to 8 clinic visits for each cycle. Linear regression models were used to estimate associations of tampon use with metal exposure, and linear mixed models to estimate associations of tampon use with inflammation and oxidative stress biomarkers at different times during the menstrual cycle.

RESULTS

We observed non-significantly higher mean levels of mercury for tampon users compared to non-tampon users (exp(β) = 1.25, 95% CI = 0.93, 1.68). We found no evidence of an association between tampon use and inflammation biomarkers. We observed consistently higher isoprostane levels, an oxidative stress biomarker, among tampon users compared to non-tampon users (e.g. exp.(β) = 1.05, 95%CI = 0.96, 1.16, for the average isoprostane during the menstruating week); however, these results were not statistically significant.

CONCLUSIONS

While our results are not statistically significant, we observed suggestive associations between tampon use and elevated levels of mercury and oxidative stress biomarkers. Although our finding should be interpreted in light of our limitations, they indicate that tampons may be a source of exposure to metals and chemicals that have been largely ignored, and any related health effects are an important public health concern.

How stable is oxidative stress level? An observational study of intra- and inter-individual variability in urinary oxidative stress biomarkers of DNA, proteins, and lipids in healthy individuals

Oxidative stress in humans is affected by the health and nutritional status as well as exposure to external environmental factors. To evaluate the effects of external factors, an assessment of baseline levels as well as diurnal variations in oxidative stress status of healthy individuals is needed. In this study, we examined intra- and inter-individual variability of oxidative stress biomarkers (OSBs) of lipids (malondialdehyde [MDA] and four F₂-isoprostane isomers, namely, 8-isoprostaglandinF_2α [8-PGF_2α], 11β-prostaglandinF_2α [11-PGF_2α], 15(R)-prostaglandinF_2α [15-PGF_2α], and 8-iso,15(R)-prostaglandinF_2α [8,15-PGF_2α]); proteins (o,o'-dityrosine [diY]); and DNA (8-hydroxy-2'-deoxyguanosine [8-OHdG]) in urine from healthy individuals. The significance of creatinine correction, which is typically used to account for urinary dilution, on OSB concentrations was evaluated. Analysis of 515 urine samples, collected longitudinally from 19 healthy individuals daily for over a month, showed inter-individual coefficient of variation (CV) in concentrations from 112% for MDA to 272% for 15-PGF_2α. Intra-individual CV in concentrations ranged from 29% for 8-OHdG to 149% for 15-PGF_2α. MDA was the most abundant OSB found in urine. The intra- and inter-individual variability in F₂-isoprostane concentrations were higher than the values calculated for diY, 8-OHdG, and MDA. All seven OSB concentrations were significantly correlated with each other and with creatinine. Creatinine normalization of OSB concentrations improved predictability in OSB concentrations over time. Our results suggest that 8-OHdG, showing the highest ICC (0.96), yielded more reproducible measurements with a low CV, and is the most suitable biomarker of OSB in spot urine samples. The measured concentrations and diurnal variability in urinary OSB levels in healthy individuals reported in this study are useful as a benchmark for future toxicological and epidemiological studies.

Associations between PON1 enzyme activities in human ovarian follicular fluid and serum specimens

The importance of high-density lipoprotein (HDL) particle components to reproduction is increasingly recognized, including the constituent paraoxonase 1 (PON1). However, the reliability characteristics of PON1 enzymes in ovarian follicular fluid (FF) as biomarkers for clinical and epidemiologic studies have not been described. Therefore, we characterized PON1 enzymes in FF and serum and assessed the impact of the PON1 Q192R polymorphism on associations between enzyme activities in two compartments. We also evaluated associations between HDL particle size and enzyme activities. We collected FF and serum from 171 women undergoing in vitro fertilization. PON1 activities were measured as paraoxonase and arylesterase activities, and HDL particle size was determined by ¹H NMR spectrometry. Reliability indices for PON1 activities were characterized and we evaluated HDL particle sizes as predictors of PON1 enzyme activities. We found that PON1 enzyme activities were correlated between compartments, but higher in serum than in FF. For FF, the index of individuality (II) was low and the coefficient of variation (CV%) was high for paraoxonase activity overall (0.12 and 11.51%, respectively). However, IIs increased (0.33–1.30) and CV%s decreased (5.58%-8.52%) when stratified by PON1 Q192R phenotype. The intraclass correlation coefficient (ICC) for FF paraoxonase activity was high overall (0.89) but decreased when stratified by PON1 Q192R phenotype (0.43–0.75). We found similar, although more modest, patterns for FF arylesterase activity. For enzyme activities in serum, ICCs were close to 1.00 across all phenotypes. Additionally, different HDL particle sizes predicted PON1 enzyme activities according to PON1 Q192R phenotype. Overall, stratification by PON1 Q192R phenotype improved the reliability characteristics of FF PON1 enzymes as biomarkers for use in clinical investigations but diminished usefulness for epidemiologic studies. Thus, we recommend stratification by PON1 Q192R phenotype for clinical but not epidemiologic investigations, when employing FF PON1 enzyme activity biomarkers.

Variability in follicular fluid high density lipoprotein particle components measured in ipsilateral follicles

PURPOSE

The purpose of this study was to examine the biological variability of follicular fluid (FF) high density lipoprotein (HDL) particle components measured in ipsilateral ovarian follicles.

METHODS

We collected FF from two ipsilateral follicles among six women undergoing in vitro fertilization (IVF). We measured concentrations of 19 FF HDL particle components, including HDL cholesterol, free cholesterol, four cholesteryl esters, phospholipids, triglycerides, paraoxonase and arylesterase activities, apolipoproteins A-1 and A-2 (ApoA-1 and ApoA-2), and seven lipophilic micronutrients, by automated analysis and with high-performance liquid chromatography. We assessed biological variability using two-stage nested analysis of variance and compared values with those previously published for contralateral follicles.

RESULTS

For most FF HDL analytes, there was little variability between follicles relative to the variability between women (i.e., %σ(2) F:%σ(2) B <0.5). Intraclass correlation coefficients were >0.80 for HDL cholesterol (0.82), phospholipids (0.89), paraoxonase (0.96), and arylesterase (0.91) activities, ApoA-1 (0.89), and ApoA-2 (0.90), and single specimen collections were required to estimate the subject-specific mean, demonstrating sufficient reliability for use as biomarkers of the follicular microenvironment in epidemiologic and clinical studies.

CONCLUSIONS

These preliminary results raise the possibility for tighter regulation of HDL in follicles within the same ovary vs. between ovaries. Thus, collection of a single FF specimen may be sufficient to estimate HDL particle components concentrations within a single ovary. However, our results should be interpreted with caution as the analysis was based on a small sample.

Systemic circulatory influences on retinal microvascular function in middle-age individuals with low to moderate cardiovascular risk

PURPOSE

To investigate the relationship between retinal microvascular reactivity, circulatory markers for CVD risk and systemic antioxidative defence capacity in healthy middle-aged individuals with low to moderate risk of CVD.

METHODS

Retinal vascular reactivity to flickering light was assessed in 102 healthy participants (46-60 years) by means of dynamic retinal vessel analysis (DVA). Other vascular assessments included carotid intima-media thickness (C-IMT) and blood pressure (BP) measurements. Total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG) and blood glutathione levels in its reduced (GSH) and oxidized (GSSG) forms were also determined for each participant, along with Framingham risk scores (FRS).

RESULTS

Retinal arterial baseline diameter fluctuation (BDF) was independently, significantly and negatively influenced by LDL-C levels (β = -0.53, p = 0.027). Moreover, the arterial dilation slope (SlopeAD ) was independently, significantly and positively associated with redox index (GSH: GSSG ratio, β = 0.28, p = 0.016), while the arterial constriction slope (SlopeAC ) was significantly and negatively influenced by blood GSH levels (β = -0.20, p = 0.042), and positively associated with FRS (β = 0.25, p = 0.009). Venous BDF and dilation amplitude (DA) were also negatively influenced by plasma LDL-C levels (β = -0.83, p = 0.013; and β = -0.22, p = 0.028, respectively).

CONCLUSIONS

In otherwise healthy individuals with low to moderate cardiovascular risk, retinal microvascular dilation and constriction responses to stress levels are influenced by systemic antioxidant capacity, and circulating markers for cardiovascular risk.

Tracing the trajectory of behavioral impairments and oxidative stress in an animal model of neonatal inflammation

Exposure to early-life inflammation results in time-of-challenge-dependent changes in both brain and behavior. The consequences of this neural and behavioral reprogramming are most often reported in adulthood. However, the trajectory for the expression of these various changes is not well delineated, particularly between the juvenile and adult phases of development. Moreover, interventions to protect against these neurodevelopmental disruptions are rarely evaluated. Here, female Sprague-Dawley rats were housed in either environmental enrichment (EE) or standard care (SC) and their male and female offspring were administered 50 μg/kg i.p. of lipopolysaccharide (LPS) or pyrogen-free saline in a dual-administration neonatal protocol. All animals maintained their respective housing assignments from breeding until the end of the study. LPS exposure on postnatal days (P) 3 and 5 of life resulted in differential expression of emotional and cognitive disruptions and evidence of oxidative stress across development. Specifically, social behavior was reduced in neonatal-treated (n)LPS animals at adolescence (P40), but not adulthood (P70). In contrast, male nLPS rats exhibited intact spatial memory as adolescents which was impaired in later life. Moreover, these males had decreased prefrontal cortex levels of glutathione at P40, which was normalized in adult animals. Notably, EE appeared to offer some protection against the consequences of inflammation on juvenile social behavior and fully prevented reduced glutathione levels in the juvenile prefrontal cortex. Combined, these time-dependent effects provide evidence that early-life inflammation interacts with other developmental variables, specifically puberty and EE, in the expression (and prevention) of select behavioral and molecular programs.

Evaluation of method performance for oxidative stress biomarkers in urine and biological variations in urine of patients with type 2 diabetes mellitus and diabetic nephropathy

Background

Oxidative stress biomarkers such as superoxide dismutase (CuZnSOD), catalase (CAT) and malondialdehyde (MDA) play an important role in the pathogenesis or progression of numerous diseases. Data regarding the biological variation and analytical quality specifications (imprecision, bias and total error) for judging the acceptability of method performance for oxidative stress biomarkers in urine are conspicuously lacking in the literature. Such data are important in setting analytical quality specifications, assessing the utility of population reference intervals (index of individuality) and assessing the significance of changes in serial results from an individual (reference change value; RCV).

Materials and methods

20 patients with type 2 diabetes mellitus (T2DM), 20 patients with diabetic nephropathy (DN) and 14 healthy individuals as control were involved in this study. Timed first morning urine samples were taken from patients and healthy groups on the zero, 1st, 3rd, 5th, 7th, 15th and 30th days. Index of individuality and reference change value were calculated from within-subject and between-subject variations. Methods of oxidative stress biomarkers in human blood were adopted in human urine and markers were measured as spectrophotometrically. Also, analytical quality specifications for evaluation of the method performance were established for oxidative stress biomarkers in urine.

Results

Within-subject variations of oxidative stress biomarkers were significantly higher in patients with DN and T2DM compared to healthy subjects. MDA showed low individuality, and within-subject variances of MDA were larger than between-subject variances in all groups. However, CAT and CuZnSOD showed strong individuality, but within-subject variances of them were smaller than between-subject variances in all groups. RCVs of all analytes in diabetic patients were relatively higher, because of high within-subject variation, resulting in a higher RCV. Also, the described methodology achieves these goals, with analytical CVs of < 3.5% for all analytes. Goals for bias and total error were 6.0-7.9% and 12.5-23.3%, respectively.

Conclusions

RCVs concept for predicting the clinical status in diabetic patients represents an optimization of laboratory reporting and could be a valuable tool for clinical decision. Furthermore, for oxidative stress biomarkers’ measurements in urine, the desirable imprecision goals based on biological variation are obtainable by current methodologies.

Variability in the components of high-density lipoprotein particles measured in human ovarian follicular fluid: a cross-sectional analysis

OBJECTIVE

To assess the variability of follicular fluid (FF) high-density lipoprotein (HDL) particle components.

DESIGN

Cross-sectional design with assessment using two-stage nested analysis of variance.

SETTING

Reproductive health center.

PATIENT(S)

180 in vitro fertilization (IVF) patients.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Nineteen HDL components including HDL cholesterol and free (unesterified) and esterified forms, phospholipids, triglycerides, apolipoproteins A-1 and A-2, paraoxonase 1 (PON1) activities, and seven lipophilic vitamins and micronutrients.

RESULT(S)

We collected FF specimens from two contralateral follicles on the day of oocyte retrieval and analyzed them for HDL components, characterizing the analytes by age, body mass index (BMI), race and smoking. For some analytes, a majority of total measurement variability was attributed to sources between follicles, suggesting an important role for the integrity of the blood-follicle barrier and in situ remodeling of plasma-derived constituents. For other analytes, variability was mostly attributed to sources between women, likely indicative of plasma levels. Variability between follicles decreased with increasing age and differed by BMI and smoking, and generally were lower for Asians and women with diminished ovarian reserve.

CONCLUSION(S)

Substantial variability in FF HDL components exist between follicles among women undergoing IVF as well as between women by age, BMI, race, smoking, and infertility diagnosis.

Urinary phthalate metabolites among elementary school children of Korea: sources, risks, and their association with oxidative stress marker

Phthalates have been used in a variety of consumer products and hence frequently been detected in humans. Children are susceptible to endocrine disrupting chemicals such as phthalates, but only limited information is available on the sources of exposure and potential adverse health effects among children. In this study, elementary school students (n=39, aged 9-12 years) were recruited in Seoul, and first void urine samples were collected twice in three-day intervals. Then six phthalate metabolites were analyzed by high performance liquid chromatography with triple quadrupole tandem mass spectrometry. In addition, malondialdehyde (MDA) as an oxidative stress marker was measured. A questionnaire was conducted and information on food consumption and the use of plastic packaging or storage materials was gathered. The concentrations of phthalate metabolites varied substantially by sampling time even within the same subject, but all target metabolites were detected in 100% of the samples with the highest geometric mean of 107 μg/g-creatinine for mono-n-butyl phthalate (MnBP). Urinary levels of mono-isobutyl phthalate (MiBP), and MnBP among Korean children were 8 and 3 times greater than those reported for US children, but those of monoethyl phthalate (MEP) were about 5 times lower than those of US children. Estimated phthalate intakes were generally in safe range, but in 3-8% of the participating children, the hazard quotients greater than one were noted. Urinary MDA concentrations were significantly associated with several metabolite levels after adjusting covariates in regression model. Consumption of dairy products or meat, and use of a plastic material were significantly associated with the DEHP metabolites or MnBP levels in multivariate model. The results of this study provide evidence of the association between phthalate exposure and oxidative stress especially among the early teenagers, and identified major sources that can be applied to development of management plan for phthalate exposure among children.

Serum Retinol and Carotenoids in Association with Biomarkers of Insulin Resistance among Premenopausal Women

Objective. The aim of this study was to investigate how serum retinol and carotenoids (β-carotene, β-cryptoxanthin, lutein/zeaxanthin, lycopene) are associated with biomarkers of insulin resistance. Research Methods and Procedures. The BioCycle Study (2005–2007) is a prospective cohort of 259 healthy premenopausal women. Fasting serum samples were collected at up to sixteen clinic visits, from which retinol, carotenoids, insulin, glucose, and sex hormone-binding globulin (SHBG) were measured. Insulin resistance was estimated by the homeostasis model assessment (HOMA-IR). Linear mixed models were used to determine associations adjusting for age, race, body mass index (BMI), education, smoking, physical activity, triglycerides, and energy intake. Results. Retinol was positively associated with HOMA-IR (β = 0.19 (95% CI: 0.07, 0.32)) units per ug/mL increase in retinol; the relationship was driven by insulin (β = 0.20 (95% CI: 0.08, 0.31)). Retinol was inversely associated with SHBG (β = −0.22 (95% CI: −0.28, −0.16)). Although no significant associations were found between serum carotenoids and HOMA-IR, β-carotene was positively associated with SHBG and β-cryptoxanthin inversely with fasting plasma glucose. Conclusion. Results indicate a possible role for serum retinol in the pathogenesis of type 2 diabetes. However, they do not support a strong association between individual or total serum carotenoids and insulin resistance.

Analysis of oxidative stress during the menstrual cycle

BACKGROUND

Few data concerning the oxidative stress (OS) in plasma during the entire menstrual cycle of eumenorrheic women are available.

METHODS

OS was assessed in 20 healthy volunteers during the phase of the menstrual cycle by determining the plasmatic hydroperoxides levels (d-ROMs test). The assessment was performed every three days, starting from the first day (t1) up the end of the menstrual phase (t27). Concomitantly, the estrogen (E2) and progestin (P4) levels were determined at the same time intervals.

RESULTS

From a base value (t1) of 284 +/- 38.0 CARR.U., which is essentially within the normal range (<300 Carratelli units or CARR.U.), the OS levels progressively increased to 378 +/- 115 CARR.U. at t15, and then slightly decreased over the subsequent time but with average values >300 CARR.U. Analysis of the E2 levels showed that the maximum OS values were noticed near the estrogen peak, while remaining above the base levels, and then decreased during the progestin phase until returning to normal at the end of the menstrual cycle.

CONCLUSIONS

It may concludes that the healthy women go into OS for 2/3 of the menstrual cycle.

Self-report of fruit and vegetable intake that meets the 5 a day recommendation is associated with reduced levels of oxidative stress biomarkers and increased levels of antioxidant defense in premenopausal women

BACKGROUND

Oxidative stress has been associated with a variety of chronic diseases and reproductive disorders. Fruits and vegetables (F/V) may contribute to antioxidant vitamin and micronutrient levels and reduce oxidative stress.

OBJECTIVE

To investigate the effect of meeting the 5 A Day For Better Health Program recommendation for F/V consumption on biomarkers of oxidative damage and antioxidant defense.

DESIGN

In this longitudinal study, healthy premenopausal women (n=258) were followed for ≤2 menstrual cycles with ≤16 oxidative stress measures timed to cycle phase.

MAIN OUTCOME MEASURES

Plasma concentrations of F2-isoprostane, 9-hydroxyoctadecadieneoic acid, 13-hydroxyoctadecadieneoic acid, erythrocyte activity of superoxide dismutase, glutathione reductase, and glutathione peroxidase, as well as blood micronutrient concentrations were measured. Dietary intake was assessed by food frequency questionnaires (FFQs) (1 per cycle), and 24-hour recalls (≤4 per cycle).

STATISTICAL ANALYSES PERFORMED

Fruit and vegetable servings were dichotomized based on the recommendation to consume five servings of F/V each day. Linear mixed models with repeated measures were used to analyze lipid peroxidation markers, antioxidant vitamins, and antioxidant enzymes by cycle phase and in association with usual F/V intake.

RESULTS

For both 24-hour recall (timed to cycle phase) and cycle-specific FFQ, meeting the recommendation to consume five servings of F/V each day was associated with decreased F2-isoprostanes (24-hour recall β=-.10 [95% CI, -0.12 to -0.07]; FFQ β= -.14 [95% CI, -0.18 to -0.11]). Glutathione reductase was lower in association with typical consumption of five or more servings of F/V by FFQ but not in the phase-specific analysis. Higher levels of ascorbic acid, lutein, beta carotene, and beta cryptoxanthin were observed with both intake measures.

CONCLUSIONS

Meeting the 5 A Day For Better Health Program recommendation was associated with lower oxidative stress and improved antioxidant status in analyses of typical diet (via FFQ) and in menstrual cycle phase-specific analyses using 24-hour recalls. Green salads were commonly eaten and increasing intake of salads may be a useful strategy to influence oxidation in reproductive aged women.

Performance of multiplex cytokine assays in serum and saliva among community-dwelling postmenopausal women

Multiplexing arrays increase the throughput and decrease sample requirements for studies employing multiple biomarkers. The goal of this project was to examine the performance of Multiplex arrays for measuring multiple protein biomarkers in saliva and serum. Specimens from the OsteoPerio ancillary study of the Women’s Health Initiative Observational Study were used. Participants required the presence of at least 6 teeth and were excluded based on active cancer and certain bone issues but were not selected on any specific condition. Quality control (QC) samples were created from pooled serum and saliva. Twenty protein markers were measured on five multiplexing array panels. Sample pretreatment conditions were optimized for each panel. Recovery, lower limit of quantification (LLOQ) and imprecision were determined for each analyte. Statistical adjustment at the plate level was used to reduce imprecision estimates and increase the number of usable observations. Sample pre-treatment improved recovery estimates for many analytes. The LLOQ for each analyte agreed with manufacturer specifications except for MMP-1 and MMP-2 which were significantly higher than reported. Following batch adjustment, 17 of 20 biomarkers in serum and 9 of 20 biomarkers in saliva demonstrated acceptable precision, defined as <20% coefficient of variation (<25% at LLOQ). The percentage of cohort samples having levels within the reportable range for each analyte varied from 10% to 100%. The ratio of levels in saliva to serum varied from 1∶100 to 28∶1. Correlations between saliva and serum were of moderate positive magnitude and significant for CRP, MMP-2, insulin, adiponectin, GM-CSF and IL-5. Multiplex arrays exhibit high levels of analytical imprecision, particularly at the batch level. Careful sample pre-treatment can enhance recovery and reduce imprecision. Following statistical adjustments to reduce batch effects, we identified biomarkers that are of acceptable quality in serum and to a lesser degree in saliva using Multiplex arrays.

The biological variation of N-terminal pro-brain natriuretic peptide in postmenopausal women with type 2 diabetes: a case control study

BACKGROUND

The incidence of heart failure in type 2 diabetes is high and it has poorer prognosis when compared with patients without diabetes. Access to echocardiography is limited and alternative methods to identify early heart failure such as the measurement of natriuretic peptides levels have been proposed. However, their wide biological variation could limit their clinical utility. Our aim was to determine if the intrinsic biological variation of one of these peptides, N-terminal proBNP, is as wide in type 2 diabetes as it is in health and to calculate the critical difference values that could be utilised in clinical practice to ensure changes observed between two samples are due to intervention rather than to its biological variability.

METHODOLOGY/PRINCIPAL FINDINGS

12 postmenopausal women with diet controlled type 2 diabetes and without heart failure were compared with 11 control postmenopausal women without diabetes. N-terminal proBNP levels were measured on 10 occasions. The biological variation was calculated according to Fraser's methods. The mean NT-proBNP level was similar in both groups (mean ± standard deviation; type 2 diabetes, 10.7 pmol/L± 8.5 versus 8.49±6.0 pmol/L, p = 0.42). The biological variation was also similarly wide. The critical difference in patients with type 2 diabetes was between -70% and ±236%.

CONCLUSIONS

Type 2 diabetes does not appear to significantly influence the marked biological variation of N-terminal proBNP in postmenopausal women. The critical difference values reported in this study could be used to titrate therapy or monitor response to interventions although the change required in between samples is wide and this might limit its utility.

Impact of Serum Estradiol on Biomarkers of Oxidative Stress in Polycystic Ovary Syndrome and Ovulatory Women

Background

Estrogens are thought to possess antioxidant properties in vivo, with estradiol being the most biologically active and available. Unlike ovulatory women, those with polycystic ovary syndrome (PCOS) have a relative steady-state serum estradiol concentration across a typical month. To better understand the antioxidant role of serum estradiol in premenopausal women, we evaluated biomarkers of oxidative stress at two time points in both ovulatory and anovulatory cycles (ie, women with PCOS).

Methods

A total of 16 women (7 PCOS, 9 ovulatory) completed this study. Ovulatory women were tested on cycle day 3, and again on cycle day 21. Women with PCOS were tested at a random time and returned to the clinic 14 days later. At each visit, blood was collected for determination of malondialdehyde (MDA), hydrogen peroxide (H2O2) and Trolox Equivalent Antioxidant Capacity (TEAC). Estradiol, progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were also measured.

Results

There were no significant differences observed in any oxidative stress biomarker between ovulatory and PCOS women. Estradiol levels were positively correlated with TEAC in women with PCOS (r = 0.57; P = 0.03), but not in ovulatory women. While not statistically significant, negative correlations were noted between estradiol and MDA and estradiol and H2O2 in women with PCOS but not in ovulatory subjects.

Conclusions

Our data indicate that oxidative stress biomarkers do not differ between PCOS and ovulatory women. The changing estrogen level that occurs throughout ovulatory cycles does not appear to impact overall oxidative status when compared to the relative steady-state estradiol levels in PCOS subjects in our study. Furthermore, estradiol may be associated with antioxidant status and biomarkers of oxidative stress in women with PCOS but not in those with regular menstrual cycles.

Relation of blood cadmium, lead, and mercury levels to biomarkers of lipid peroxidation in premenopausal women

Exposures to cadmium, lead, and mercury are associated with adverse health effects, including cardiovascular disease, which may be promoted by lipid peroxidation. The authors examined cadmium, lead, and mercury in relation to plasma levels of F(2)-8α isoprostanes (isoprostane), 9-hydroperoxy-10,12-octadecadienoic acid (9-HODE), 13-hydroxy-9,11-octadecadienoic acid (13-HODE), and thiobarbituric acid reactive substances (TBARS) in 252 women from western New York State (2005-2007). Healthy premenopausal women were followed for ≤2 menstrual cycles, with biomarkers of lipid peroxidation being assessed ≤8 times per cycle. Metals were measured at baseline in whole blood. Linear mixed models were used to estimate the association between cadmium, lead, and mercury and lipid peroxidation biomarkers. Median cadmium, lead, and mercury levels were 0.30 μg/L, 0.86 μg/dL, and 1.10 μg/L, respectively. Blood cadmium, lead, and mercury were not associated with increases in isoprostane, TBARS, 9-HODE, or 13-HODE levels. Isoprostane levels decreased 6.80% (95% confidence interval: -10.40, -3.20) per 1% increase in mercury. However, after adjustment for a simulated strong confounding factor, such as precisely measured fish consumption, the observed association was attenuated, suggesting that this unexpected association could be attributable to unmeasured confounding. In this population of healthy premenopausal women with low exposure levels, cadmium, lead, and mercury were not associated with elevated lipid peroxidation biomarkers.

Biomonitoring for exposure to multiple trace elements via analysis of urine from participants in the study of metals and assisted reproductive technologies (SMART)

Humans are exposed to concentrations of multiple trace elements through a variety of background sources; many are suspected reproductive toxicants. Prior to investigating associations between trace elements and human reproductive health, potential biomarkers of exposure should be characterized by sources of variability in the population at risk. Factors influencing elemental exposure should also be identified to ensure their consideration as potential confounding variables. The principal aim of this study is to characterize sources of variability for 19 trace elements measured in urine specimens collected from 55 women and 36 male partners completing a 1st cycle of in vitro fertilization (IVF). Urine specimens were analyzed using a biomonitoring method based on inductively coupled plasma-mass spectrometry (ICP-MS). Randomly selected urine specimens (∼6%) were analyzed in duplicate, and these data were used to characterize sources of variability. Nine trace elements including As, Ba, Cd, Cs, Co, Cu, Mn, Mo, and Zn, were quantified in most specimens, indicating their utility in future epidemiologic studies of trace elements exposure and IVF outcomes. With few exceptions, normalizing urine using the traditional creatinine-correction procedure, or an alternative approach based on a linear regression model, increased residual variability only slightly. Sex and race appear to be important factors to consider in epidemiologic studies conducted in this population. Urine concentrations for most elements are similar to those reported in the 2005-2006 National Health and Nutrition Examination Survey (NHANES); however, differences in others may indicate regional trends or a unique exposure history for this infertile study population.

Effect of dietary fiber intake on lipoprotein cholesterol levels independent of estradiol in healthy premenopausal women

High-fiber diets are associated with improved lipid profiles. However, pre- and postmenopausal women respond differently to fiber intake, suggesting that endogenous estradiol mediates the effect. The authors' objective was to determine the direct effect of fiber intake on lipoprotein cholesterol levels independent of estradiol among premenopausal women. The BioCycle Study, a prospective cohort study conducted at the State University of New York at Buffalo from 2005 to 2007, followed 259 healthy women for up to 2 complete menstrual cycles. Serum lipoprotein and hormone levels were measured at 16 visits timed using fertility monitors. Fiber intake was assessed by 8 24-hour recalls. Marginal structural models with inverse probability weights for both lipoprotein and estradiol levels were used to estimate controlled direct effects of the highest category of fiber intake (≥22 g/day vs. <22 g/day) while accounting for age, body mass index, total energy, vitamin E intake, physical activity, luteinizing hormone, follicle-stimulating hormone, and progesterone. Reductions were observed in total and low density lipoprotein cholesterol in women with higher fiber intakes. Direct effects were greater than total effects. These analyses suggested that estradiol mediates at least part of the association between fiber and cholesterol among premenopausal women. More research is needed to elucidate the biologic mechanisms driving these associations.

Adherence to a Mediterranean diet and plasma concentrations of lipid peroxidation in premenopausal women

BACKGROUND

A Mediterranean diet has been associated with a reduced risk of cardiovascular disease and mortality. A possible mechanism is through a decrease in lipid peroxidation (LPO); however, evidence linking the Mediterranean diet with lower LPO in premenopausal women is sparse.

OBJECTIVE

We investigated whether adherence to a Mediterranean diet was associated with lower LPO concentrations in premenopausal women.

DESIGN

Two hundred fifty-nine healthy women aged 18-44 y were followed for ≤ 2 menstrual cycles. Plasma concentrations of F(2)-isoprostane (8-iso-PGF2α), 9-hydroxyoctadecadieneoic acid (9-HODE), and thiobarbituric acid reactive substances (TBARS) were measured ≤ 8 times per cycle at visits scheduled by using fertility monitors. Diet was assessed ≤ 4 times per cycle by using 24-h dietary recalls. The alternate Mediterranean Diet Score (aMED) (range: 0-9) was calculated on the basis of intake of vegetables, legumes, fruit, nuts, whole grains, red and processed meat, fish, and alcohol and the ratio of monounsaturated to saturated fat.

RESULTS

A 1-unit increase in aMED was associated with a 4.50% decrease in 8-iso-PGF2α concentrations (95% CI: -6.32%, -2.65%) and a 14.01% decrease in 9-HODE concentrations (95% CI: -17.88%, -9.96%) after adjustment for energy intake, age, race, body mass index, plasma ascorbic acid, and serum cholesterol. No significant association was observed between aMED and TBARS. A 1-unit increase in aMED was associated with a 1.39% increase (95% CI: 0.07%, 2.72%) in plasma ascorbic acid concentrations.

CONCLUSIONS

Adherence to a Mediterranean diet is associated with lower LPO and higher ascorbic acid concentrations. These results confirm that decreased LPO is a plausible mechanism linking a Mediterranean diet to reduced cardiovascular disease risk.

Cholesterol, endocrine and metabolic disturbances in sporadic anovulatory women with regular menstruation

BACKGROUND

Sporadic anovulation among regularly menstruating women is not well understood. It is hypothesized that cholesterol abnormalities may lead to hormone imbalances and incident anovulation. The objective was to evaluate the association between lipoprotein cholesterol levels and endocrine and metabolic disturbances and incident anovulation among ovulatory and anovulatory women reporting regular menstruation.

METHODS

The BioCycle Study was a prospective cohort study conducted at the University at Buffalo from September 2005 to 2007, which followed 259 self-reported regularly menstruating women aged 18-44 years, for one or two complete menstrual cycles. Sporadic anovulation was assessed across two menstrual cycles.

RESULTS

Mean total and low-density lipoprotein cholesterol and triglycerides levels across the menstrual cycles were higher during anovulatory cycles (mean difference: 4.6 (P = 0.01), 3.0 (P = 0.06) and 6.4 (P = 0.0002) mg/dl, respectively, adjusted for age and BMI). When multiple total cholesterol (TC) measures prior to expected ovulation were considered, we observed a slight increased risk of anovulation associated with increased levels of TC (odds ratio per 5 mg/dl increase, 1.07; 95% confidence interval, 0.99, 1.16). Sporadic anovulation was associated with an increased LH:FSH ratio (P = 0.002), current acne (P = 0.02) and decreased sex hormone-binding globulin levels (P = 0.005).

CONCLUSIONS

These results do not support a strong association between lipoprotein cholesterol levels and sporadic anovulation. However, sporadic anovulation among regularly menstruating women is associated with endocrine disturbances which are typically observed in women with polycystic ovary syndrome.

Procedures for determination of detection limits: application to high-performance liquid chromatography analysis of fat-soluble vitamins in human serum

BACKGROUND

Problems in the analysis of laboratory data commonly arise in epidemiologic studies in which biomarkers subject to lower detection thresholds are used. Various thresholds exist including limit of detection (LOD), limit of quantification (LOQ), and limit of blank (LOB). Choosing appropriate strategies for dealing with data affected by such limits relies on proper understanding of the nature of the detection limit and its determination. In this paper, we demonstrate experimental and statistical procedures generally used for estimating different detection limits according to standard procedures in the context of analysis of fat-soluble vitamins and micronutrients in human serum.

METHODS

Fat-soluble vitamins and micronutrients were analyzed by high-performance liquid chromatography with diode array detection. A simulated serum matrix blank was repeatedly analyzed for determination of LOB parametrically by using the observed blank distribution as well as nonparametrically by using ranks. The LOD was determined by combining information regarding the LOB with data from repeated analysis of standard reference materials (SRMs), diluted to low levels; from LOB to 2-3 times LOB. The LOQ was determined experimentally by plotting the observed relative standard deviation (RSD) of SRM replicates compared with the concentration, where the LOQ is the concentration at an RSD of 20%.

RESULTS

Experimental approaches and example statistical procedures are given for determination of LOB, LOD, and LOQ. These quantities are reported for each measured analyte.

CONCLUSION

For many analyses, there is considerable information available below the LOQ. Epidemiologic studies must understand the nature of these detection limits and how they have been estimated for appropriate treatment of affected data.

Ovarian function and cigarette smoking

Cigarette smoking has been implicated in reproductive outcomes including delayed conception, but mechanisms underlying these associations remain unclear. One potential mechanism is the effect of cigarette smoking on reproductive hormones; however, studies evaluating associations between smoking and hormone levels are complicated by variability of hormones and timing of specimen collection. We evaluated smoking among women participating in the BioCycle Study, a longitudinal study of menstrual cycle function in healthy, premenopausal, regularly menstruating women (n = 259). Fertility monitors were used to help guide timing of specimen collection. Serum levels of oestradiol, progesterone, follicle-stimulating hormone (FSH), luteinising hormone (LH) and total sex-hormone binding globulin (SHBG) across phases of the menstrual cycle were compared between smokers and non-smokers. We observed statistically significant phase-specific differences in hormone levels between smokers and non-smokers. Compared with non-smokers, smokers had higher levels of FSH in the early follicular phase and higher LH at menses after adjusting for potential confounding factors of age, race, body mass index, parity, vigorous exercise, and alcohol and caffeine intake through inverse probability of treatment weights. No statistically significant differences were observed for oestradiol, progesterone or SHBG. These phase-specific differences in levels of LH and FSH in healthy, regularly menstruating women who are current smokers compared with non-smokers reflect one mechanism by which smoking may influence fertility and reproductive health.

Oxidation, type 2 diabetes, and coronary heart disease: a complex interaction: findings from a population-based study

OBJECTIVE

The purpose of this study was to analyze the interrelationship among oxidation, myocardial infarction (MI), and type 2 diabetes in a population-based case-control study of MI.

RESEARCH DESIGN AND METHODS

Participants were 1,709 individuals from western New York: 257 women and men with incident MI and 1,452 healthy control subjects (aged 35-70 years). Lipid peroxidation was measured by plasma levels of thiobarbituric acid reactive substances (TBARS). History of type 2 diabetes was determined by self-reported history of medical diagnosis.

RESULTS

In multivariate analyses, there was no significant difference in TBARS levels between case and control subjects in both sexes. In subgroup analyses by diabetes status, diabetic subjects, regardless of MI status, exhibited significantly higher TBARS values than nondiabetic subjects. For diabetic women, TBARS values were 1.84 and 1.83 nmol/ml for case and control subjects, respectively. Values for nondiabetic women were 1.29 and 1.31 nmol/ml, respectively. In diabetic men, values were 1.65 and 1.97 nmol/ml for case and control subjects, respectively. Values for nondiabetic men were 1.36 and 1.36 nmol/ml, respectively.

CONCLUSIONS

Whereas type 2 diabetes may be an important correlate of lipid peroxidation, clinical coronary heart disease may not.