Melatonin secretion is impaired in women with preeclampsia and an abnormal circadian blood pressure rhythm

Figures & data

Table 1. Clinical and laboratory features of women with normal pregnancy (NP, n = 20), preeclampsia (PE, n = 31), dippers (n = 10) and non-dippers (n = 21) with preeclampsia, during pregnancy.

	Pregnant women			Pregnant women with preeclampsia (PE)
	NP (n = 20)	PE (n = 31)	p^a	Dippers (n = 10)	Non-dippers (n = 21)	p^a
Age(years)	29.9 ± 5.7	29.1 ± 5.1	0.601	28.2 ± 7.2	29.6 ± 3.9	0.306
Gestational age (weeks)	35.5 ± 2.5	34.8 ± 3	0.558	34.7 ± 3.9	35.1 ± 2.7	0.819
Primigravidity [n (%)]	12 (60)	22 (71)	0.545^b	6 (60)	16 (76.2)	0.417^b
Severe PE [n (%)]	n.a.	10 (32.3)	n.a.	1 (10)	9 (42.9)	0.106^b
BMI(kg/m^2)	26 ± 1	30 ± 2.3	0.000	28.3 ± 1.5	30 ± 2.3	0.002
Daytime MAP (mmHg)	84.3 ± 6.9	110.5 ± 4.1	0.000	108.5 ± 3.4	111.5 ± 4.1	0.048
Night time MAP (mmHg)	73.6 ± 6	104.8 ± 7.5	0.000	96 ± 4	109 ± 4.5	0.000
Creatinine (mg/dL)	0.74 ± 0.13	0.81 ± 0.17	0.135	0.82 ± 1.7	0.81 ± 1.8	0.849
Urea (mg/dL)	19.7 ± 5.7	23.6 ± 7.5	0.093	21.2 ± 7.7	24.9 ± 7.3	0.204
Uric acid (mg/dL)	3.9 ± 0.78	6.5 ± 1.28	0.000	5.9 ± 1.1	6.8 ± 1.3	0.072
Proteinuria (mg/d)	70 ± 56	2022 ± 2286	0.000	956 ± 607	2530 ± 2614	0.079

Note: Data are mean ± SD. Serum creatinine in mg/dL may be converted to μmol/L by multiplying by 88.4; urea in mg/dL to mmol/L by multiplying by 0.357; uric acid in mg/dL to μmol/L by multiplying by 59.48.

^aMann–Whitney U test was used for assessing the differences between the two groups.

^bFor categorical data a Fisher’s exact test was performed.

Figure 1. Daytime and night time levels of melatonin (A; pg/mL) and 6-Sulfatoxymelatonin (B; 6-SMT; ng/mL) in the two groups of women with preeclampsia, that is, dippers (n = 10) and non-dippers (n = 21), during pregnancy. Note: * represents a statistically significant difference between the night time and daytime levels within the respective group (p < 0.01) and the # a statistically significant difference of the respective day or night time levels between the two groups (dippers and non-dippers; p < 0.01).

Table 2. Binomial logistic regression analysis showed that night time serum melatonin (model 1) and 6-sulfatoxymelatonin (model 2) as measures of melatonin secretion were independent predictors of blood pressure dipping status in women with preeclampsia (n = 31).

Binomial logistic regression
Model 1					Model 2
	OR	p	95% CI for OR			OR	p	95% CI for OR
Melatonin (pg/mL)	0.911	0.035*	0.835	0.993	6-SMT (ng/mL)	0.866	0.026*	0.762	0.983
Age (years)	1.180	0.238	0.896	1.554	Age (years)	1.239	0.233	0.872	1.760
Gestational age (weeks)	1.592	0.176	0.811	3.122	Gestational age (weeks)	1.854	0.210	0.707	4.861
BMI (kg/m^2)	2.699	0.143	0.714	10.203	BMI (kg/m^2)	6.825	0.074	0.833	55.921
Log proteinuria (mg/d)	0.157	0.460	0.010	2.141	log Proteinuria (mg/d)	0.865	0.958	0.040	19.513
Constant	0.0	0.124			Constant	0.0	0.071

Note: Dipping status was the outcome variable and independent variables (covariates) were the BMI (kg/m²), proteinuria (mg/d) and serum melatonin (pg/mL; model 1) or 6-sulfatoxymelatonin (6-SMT ng/mL; model 2). Proteinuria was not following a normal distribution and therefore it was inserted after logarithmical transformation in order to increase stability of the model. Odds ratio (OR) was calculated as the antilogarithm of the b-coefficient of each independent variable (expb), (*p < 0.05).

Figure 2. Daytime and night time levels of melatonin (A; pg/mL) and 6-sulfatoxymelatonin (B; 6-SMT; ng/mL) in the two groups of women with preeclampsia, that is, dippers (n = 21) and non-dippers (n = 10), 2 months after delivery. Note: * represents a statistically significant difference between the night time and daytime levels within the respective group (p < 0.01) and the # a statistically significant difference of the respective day or night time levels between the two groups (dippers and non-dippers; p < 0.01).