Urinary excretion of N-acetyl-beta-D-glucosaminidase during normal pregnancy

Association between two common environmental toxicants (phthalates and melamine) and urinary markers of renal injury in the third trimester of pregnant women: The Taiwan Maternal and Infant Cohort Study (TMICS)

BACKGROUND

Exposure to either melamine or phthalate, two common toxicants, during pregnancy may cause adverse health effects, including kidney damage.

OBJECTIVES

We investigated the independent and interactive effect of exposure to melamine and phthalates, particularly di-(2-ethylhexyl) phthalate (DEHP), on markers of early renal injury in women their third trimester of pregnancy in one nationwide birth cohort, the Taiwan Maternal and Infant Cohort Study (TMICS).

METHODS

Between October, 2012 and May, 2015, participants were administered questionnaires, physical examinations, and blood and urine tests during their third trimester. One-spot overnight urine specimens were used to simultaneously measure melamine, 11 phthalate metabolites, and two markers of renal injury, microalbumin and N-acetyl-beta-D-glucosaminidas (NAG). Estimated daily DEHP intake was calculated based on measurement of three urinary DEHP metabolites. Microalbuminuria was defined as having a urinary albumin/creatinine ratio (ACR) higher than 3.5 mg/mmol.

RESULTS

Total 1433 pregnant women were analyzed. The median value for urinary melamine was 0.63 μg/mmol Cr and estimated DEHP intake was 1.84 μg/kg/day. We found subjects in the highest quartile of estimated DEHP intake to have significantly higher urinary ACR (β = 0.095, p = 0.043) and the prevalence of microalbuminuria (adjusted OR = 1.752, 95% confidence interval = 1.118-2.746), compared to those in the lowest quartile. In addition, there was a significant interactive effect between urinary melamine and estimated DEHP intake on urinary ACR and NAG.

CONCLUSION

Our results suggest these two ubiquitous chemicals together may be associated with markers of early kidney injury in pregnant women.

Increases in urinary creatinine and blood pressure during early pregnancy in pre-eclampsia

BACKGROUND

It is important to predict the development of pre-eclampsia (PE) during early pregnancy to prevent its occurrence later on. In this study, we studied urinary biochemical parameters and blood pressure (BP) during and after pregnancy to find useful parameters for predicting PE.

METHODS

A case-control study was performed in 25 PE patients and 172 normotensive pregnant women. Twelve biochemical parameters were measured in spot urine, and the systolic and diastolic BPs were measured using an automated device during pregnancy and six to eight weeks after birth.

RESULTS

A multiple logistic regression analysis showed that the combinations of urinary creatinine (Cr) and systolic BP (SBP) in the first trimester of pregnancy (8.9 +/- 2.6 weeks), and of urinary inorganic phosphorus (IP)/Cr and SBP in the second trimester of pregnancy (19.0 +/- 1.6 weeks) were useful for predicting PE. The area under the curve in the receiver operator characteristic curve of the combination of urinary Cr and SBP in the first trimester was 0.85 (95% confidence interval [CI] 0.74-0.96), and that of the combination of urinary IP/Cr and SBP in the second trimester was 0.91 (95% CI: 0.86-0.97). When used 249 mg/dL in urinary Cr and 128 mmHg in SBP as their cut-off points, the combination in the first trimester increased the accuracy (sensitivity 75% and specificity 95%) in predicting PE, as compared with that of urinary Cr (29%, 99%) or SBP (50%, 98%).

CONCLUSIONS

Combination of urinary Cr and SBP in early pregnancy and that of urinary IP/Cr and SBP in mid-pregnancy are useful for the prediction of PE.

Changes in urinary excretion of six biochemical parameters in normotensive pregnancy and preeclampsia

We evaluated renal functions by urinary biochemical parameters in normotensive pregnancy and preeclampsia. The parameters are expected to be altered resulting from different abnormalities of renal glomeruli and tubules. We chose N-acetyl-beta-d-glucosaminidase (NAG), beta2-microglobulin (beta2MG), total protein (TP), albumin (Alb), urea nitrogen (UN), uric acid (UA), and creatinine (Cr). Urinary excretion of these biochemical parameter concentrations (relative to Cr) was measured simultaneously in first morning fasting urine samples from 27 healthy nonpregnant women (group 1), 32 women with normotensive pregnancies (group 2), and 26 women with preeclampsia (group 3). The average gestational age at entry was 36 weeks. Serum UN and serum UA also were measured. All the ratios were significantly higher in group 2 than in group 1. The NAG-to-Cr, TP-to-Cr, and Alb-to-Cr ratios were significantly higher in group 3 than in group 2. In contrast, the UN-to-Cr and UA-to-Cr ratios were significantly lower in group 3 than in group 2. The percent increase in the beta2MG-to-Cr ratio in group 2 relative to that in group 1 was the highest, followed by percent increases in the NAG-to-Cr, TP-to-Cr, Alb-to-Cr, UA-to-Cr, and UN-to-Cr ratios. In contrast, the percent increase in the Alb-to-Cr ratio in group 3 relative to that in group 2 was the highest, followed by percent increases in the TP-to-Cr, NAG-to-Cr, beta2MG-to-Cr, UA-to-Cr, and UN-to-Cr ratios. The percent increases in the NAG-to-Cr and beta2MG-to-Cr ratios rose markedly in normotensive pregnancy, whereas percent increases of the Alb-to-Cr and TP-to-Cr ratios were far greater in preeclampsia than in normotensive pregnancy. Renal tubular damage and reabsorption dysfunction may be impaired markedly even in normotensive pregnancy, and further deterioration in reabsorption dysfunction may be slight in preeclampsia. Renal glomerular permeability of TP and Alb may be enhanced in normotensive pregnancy and markedly enhanced in preeclampsia.

Increased excretion of N-acetyl-beta-D-glucosaminidase and beta2-microglobulin in gestational week 30

BACKGROUND

Little is known about when the urinary excretion of a combination of N-acetyl-beta-D-glucosaminidase (NAG) and beta2-microglobulin (beta2MG) concentration [relative to creatinine (Cr)] reaches maximal values during uncomplicated normotensive pregnancy. This study was thus designed to analyze when urinary excretion of biochemical parameters was increased during normotensive pregnancy.

METHODS

NAG, beta2MG, total protein, albumin, and Cr were simultaneously measured in random (untimed) midstream urine samples from 22 healthy nonpregnant women and from 82 normotensive pregnant women (22 in gestational week 20, 25 in week 30, and 35 in week 37).

RESULTS

NAG/Cr and beta2MG/Cr ratios were significantly higher (P < 0.01-0.05) in the normotensive pregnant women in gestational week 30 than in the nonpregnant control subjects and normotensive pregnant women in gestational week 20. The NAG/Cr and beta2MG/Cr ratios showed maximal values in gestational week 30. The total protein/Cr ratio was significantly higher in gestational weeks 20, 30, and 37 than in the control subjects. The albumin/Cr ratio was significantly higher in women in gestational week 30 and 37 than in women in gestational week 20 and in the control subjects.

CONCLUSIONS

The excretion of both NAG and beta2MG relative to Cr was increased and showed the maximal values in gestational week 30 during normotensive pregnancy. The increase in a tubular enzyme (NAG) might be caused by renal tubular damage, and that in a low molecular weight protein (beta2MG) might result from decreased renal tubular reabsorption. These findings suggest that renal tubular damage and reabsorption dysfunction were increased in gestational week 30.