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Tagiyeva Fakhriya Alamdar, Doctor of Philosophy in Medicine, Department of Obstetrics and Gynecology II Azerbaijan Medical University, Baku, Azerbaijan E-mail: fehriya@yandex.ru
PECULIARITIES OF LIPID EXCHANGE IN PREGNANT WOMEN WITH OBESITY
Abstract. Obesity often causes aggravated pregnancy, childbirth and the postpartum period. At the same time, serious changes are noted in lipid metabolism. With the progression of pregnancy, abdominal obesity in women is a risk factor for the development of pathological dyslipidemia. Keywords: pregnancy, obesity, lipids, fat metabolism.
Physiological pregnancy is accompanied by significant changes in the metabolism in the woman's body, which is associated with the characteristics of the hormonal background and is aimed at maintaining the normal growth and development of the fetus [3; 9]. At the same time, lipid metabolism undergoes the main changes [2]. During this period, there is a slight increase in the concentration of neutral fat, cholesterol and lipids in the blood of the woman, which reflects the adaptation processes taking place during pregnancy and is aimed at creating optimal conditions for the development of the fetus [5; 6; 7].
Currently, the important role of lipids in maintaining homeostasis during pregnancy is known. Violations of their exchange determine the changes that occur in the "mother -placenta - fetus" system. The content of lipids in the blood increases in a wavy manner as pregnancy progresses due to the inhibition of lipase activity under the influence of estrogens and hyperinsulinemia. By the end of pregnancy, there is an increase in total cholesterol, high and low density lipoproteins and triglycerides compared with pre-pregnancy levels [1; 4].
Obesity, as extragenital pathology, often causes aggravated pregnancy, childbirth and the postpartum period [8].
The high frequency of obstetric pathology is explained by the violation of adaptive and compensatory-protective mechanisms, the breakdown of the activity of regulatory systems that occur during obesity. Determining the levels and dynamics of changes in lipid metabolism during the gestation period in pregnant women with obesity is of particular interest.
The purpose of this study was to evaluate the dynamics of lipid metabolism changes in pregnant women with obesity.
Materials and methods
A total of 265 pregnant women with abdominal obesity and lipid metabolism disorders before pregnancy (main group) were under observation. The gestational age was determined by anamnestic data (the date of the last menstruation, the first appearance at the antenatal clinic) and the results of ultrasound fetometry. The work is based on clinical and anthropometric results of studies of 213 and clinical and laboratory results of studies of 52 pregnant women with obesity.
When registered for dispensary registration of pregnancy, all women were subjected to traditional anthropometric research with height (cm) and weight (kg) measurements, followed by calculation of body mass index (BMI). Obesity was diagnosed based on the calculation of the BMI index using the formula:
BMI = body weight (kg)/height (m2)
The criteria for inclusion of patients in the main group were BMI values above 25 kg/m2. We also measured waist circumference (WC) and hips circumference (HC) and then calculated the ratio WC/HC. Obesity was regarded as abdominal with a waist circumference of more than 80 cm and WC/HC ratio > 0.85. The control group consisted of 80 healthy pregnant women with a BMI before pregnancy of 18.5-25 kg/m2. The values of the studied parameters obtained in this group were used as a starting point of comparison as physiologically normal values.
The state of fat metabolism was assessed according to lipid profile. In accordance with the goal, 52 pregnant women carried out the determination of the concentration of total cholesterol (TC), triglycerides (TG), low density lipoproteins (LDL) and high density lipoproteins (HDL). The study was performed three times during pregnancy - at 8-12, 18-20 and 34-36 weeks of gestation. Blood samples were taken from the ulnar vein in the morning on an empty stomach 12-14 hours after a meal. High and low density lipoproteins were determined by a homogeneous method, total cholesterol and triglycerides - by an enzymatic colorimetric method. The atherogenic index was calculated using the formula:
AI = (TC - HDL)/ HDL
The ratio of HDL/LDL was also determined and the concentration of very low density lipoproteins (VLDL) was calculated by the formula:
VLDL = TG/2.18
Statistical data analysis was performed using the MedCalc statistical software package for biomedical research. The evaluation of the obtained results was carried out by methods of
statistical description and testing of statistical hypotheses. For comparison of normally distributed values, the Student's t-test was used; if the distribution differs from the normal, the non-parametric Mann-Whitney test (U-test) was used. The data for the parametric distribution are presented as mean values of the measured value and standard error (M ± m). Evaluation of the strength and relationship between phenomena or signs was carried out using the Pearson pair-correlation coefficient (r). The critical value of the level of statistical significance (p) in testing null hypotheses was taken to be 0.05.
Results and discussion
A normal pregnancy is accompanied by profound metabolic changes in the body of a woman, which for a number of
reasons turn into pathological conditions. However, serious changes are often observed in lipid metabolism.
In pregnant women with obesity, significantly higher levels of TC, TG and VLDL in serum were detected at all periods of gestation, which is a result of their increased production. During the analysis of the dynamics of lipid profile indicators of the examined women, it was found that the average lipid levels increase in all pregnant women with an increase in the gestation period, while the concentration of atherogenic lipids represented by TC, TG, VLDL was significantly higher in women with obesity (p < 0.05). Along with this, HDL levels have a tendency to decrease (picture 1).
Picture 1. Dynamics of lipid profile in pregnant women with normal body weight and pregnant women with obesity
Table 1.- Blood lipid parameters in pregnant women at different periods (M ± m, min-max)
Lipid spectrum Observation groups
The main group (n = 52) The control group (n = 80) The main group (n = 52) The control group (n = 80) The main group (n = 52) The control group (n = 80)
8 - 12 weeks 18 - 20 weeks 34 - 36 weeks
TC mmol/l 4.96 ± 0.071* (4.51 - 5.58) 4.65 ± 0.039 (4.11 - 5.26) 5.78 ± 0.076* (5.11 - 6.43) 5.31 ± 0.055 (4.51 - 6.13) 6.06 ± 0.11** (5.28 - 6.97) 5.20 ± 0.052 (4.41 - 5.94)
LDL mmol/l 2.71 ± 0.027* (2.47 - 2.93) 2.56 ± 0.020 (2.26 - 2.84) 2.88 ± 0.034* (2.65 - 3.41) 2.79 ± 0.022 (2.48 - 3.15) 3.06 ± 0.034 (2.81 - 3.34) 3.07 ± 0.033 (2.57 - 3.48)
HDL mmol/l 1.81 ± 0.028 (1.63 - 2.07) 1.76 ± 0.022 (1.47 - 2.12) 1.75 ± 0.017 (1.60 - 1.90) 1.72 ± 0.012 (1.56 - 1.94) 1.49 ± 0.02 (1.32 - 1.63)** 1.66 ± 0.012 (1.52 - 1.86)
TG mmol/l 1.69 ± 0.036** (1.41 - 1.95) 1.00 ± 0.013 (0.82 - 1.22) 1.92 ± 0.027** (1.71 - 2.13) 1.33 ± 0.013 (1.17 - 1.55) 2.17 ± 0.026** (1.97 - 2.39) 1.42 ± 0.013 (1.24 - 1.64)
VLDL mmol/l 0.77 ± 0.04** (0.21 - 1.24) 0.46 ± 0.07 (0.35 - 1.21) 0.88 ± 0.09** (0.34 - 1.45) 0.61 ± 0.05 (0.42 - 1.33) 0.99 ± 0.08** (0.51 - 1.45) 0.65 ± 0.04 (0.49 - 1.37)
AI standard unit 1.74 ± 0.025 (0.27 - 2.69) 1.64 ± 0.077 (0.39 - 2.23) 2.30 ± 0.023** (1.76 - 2.65) 2.09 ± 0.045 (1.04 - 2.58) 3.07 ± 0.061** (1.12 - 3.38) 2.13 ± 0.038 (1.09 - 2.61)
HDL/LDL unit 0.66 ± 0.01 (0.37 - 0.89) 0.68 ± 0.05 (0.33 - 0.75) 0.61 ± 0.03 (0.35 - 0.77) 0.62 ± 0.05 (0.37 - 0.80) 0.48 ± 0.07 (0.31 - 0.62) 0.54 ± 0.06 (0.39 - 0.83)
Note: The differences are significant in relation to the control
The results of the analysis of the dynamics of lipid profile in terms of pregnancy in patients of the main and control groups are presented in (table 1).
TC content at 8-12 weeks of gestation was 4.96 ± 0.071 mmol/l in patients with obesity (in the control group - 4.65 ± 0.039 mmol/l, p < 0.05), the TG level was 1.69 ± 0.036mmol/l (in the control group-1.00 ± 0.013 mmol/l, p < 0.001). The content of VLDL in the early stages of gestation was 0.77 ± 0.04 mmol/l (in the control group - 0.46 ± ± 0.07 mmol/l, p < 0.001). The LDL values were 2.71 ± ± 0.027 mmol/l (in the control group - 2.56 ± 0.020 mmol/l, p < 0.05), HDL - 1.81 ± 0.028 mmol/l (in the control group -1.76 ± 0.022 mmol/l, p > 0.05), the value of the atherogenic index is 1.74 ± 0.025 standard units (in the control group -1.64 ± 0.077 sr. units, p > 0.05), the HDL/LDL ratio is 0.66 ± ± 0.01 units. (in the control group - 0.68 ± 0.05 units, p > 0.05).
With the progression of pregnancy, dyslipidemic changes intensified, including in the control group of women. Such an increase in lipid concentration in healthy women can be considered as a physiological phenomenon that promotes the growth and development of the fetus, enhanced steroidogenesis, as well as providing high energy demands of the pregnant woman.
Thus, with a gestation period of 18-20 weeks, the TC level in the serum of healthy pregnant women was 5.31 ± ± 0.055 mmol/l, TG - 1.33 ± 0.013 mmol/l, VLDL - 0.6 ± ± 0.05 mmol/l. These lipid profile in obese patients with gestational period changed as follows: TC - 5.78 ± 0.076
up: * -p < 0.05, ** -p < 0.001
mmol/l (p < 0.05), TG - 1.92 ± 0.02 mmol/l (p < 0.001), VLDL - 0.88 ± 0.09 mmol/l (p < 0.001). The level of LDL in the serum of pregnant women in the control group was 2.79 ± 0.022 mmol/l (in the main group - 2.88 ± 0.034 mmol/l, p < 0.05), HDL - 1.72 ± 0.012 mmol/l (in the main group -1.75 ± 0.017 mmol/l, p > 0.05), the value of the atherogenic index is 2,09 ± 0,045 sr. units (in the main group - 2.30 ± ± 0.023 standard units, p < 0.001), the HDL/LDL ratio is 0.62 ± ± 0.05 units (in the main group - 0.61 ± 0.03 units, p > 0.05).
When comparing lipid metabolism in women of the main and control groups at gestational age 34-36 weeks, statistically significant differences were found. The values of TC, TG, VLDL and atherogenicindex increase with obesity compared with the control group. Analysis of the lipid profile showed a significant increase in the level of TC in the serum of patients in the main group - 6.06 ± 0.11 mmol/l (in the control group -5.20 ± 0.052 mmol/l, p < 0.001), TG - 2.17 ± 0.026 mmol/l (in the control group - 1.42 ± 0.013 mmol/l, p < 0.001), VLDL - 0.99 ± 0.08 mmol/l (in the control group - 0.65 ± ± 0.04 mmol/l, p < 0.001). At the same time, the level of LDL in the serum of pregnant women of the main group was 3.06 ± ± 0.034 mmol/l (in the control group - 3.07 ± 0.033 mmol/l, p > 0.05), HDL - 1.49 ± 0.02 mmol/l (in the control group -1.66 ± 0.012 mmol/l, p < 0.001), the value of the atherogenic coefficient - 3.07 ± 0.061sr. units (in the control group - 2.13 ± ± 0.038 conv. units, p < 0.001), the HDL/LDL ratio is 0.48 ± ± 0.07 units. (in the control group - 0.54 ± 0.06 units, p > 0.05).
In order to assess the association of the studied clinical and metabolic parameters in pregnant women, a correlation analysis was conducted, during which there was a close relationship between the lipid profile and BMI. It was established that the growing imbalance of lipidogram indices was accompanied by an increase in BMI: TC (r = 0.251; p = 0.001), TG (r = 0.401; p = 0.002), VLDL (r = 0.365; p = 0.033), HDL (r = - 0.318; p = 0.002).
Analysis of the obtained results showed that lipid metabolism disorders have a close direct and inverse relationship with BMI and an increase in the duration of pregnancy. The development of pregnancy was accompanied by an increase in fat metabolism in the main group at 18-20 and 34-36 weeks of gestation, respectively: TC - by 16.5% and 22.1%, LDL - by 6.3% and 13.0%, TG - by 13.6% and 28.4%, VLDL - by 14.3% and 28.5%. We have revealed an inverse relationship between HDL levels and gestational age. So, if the level of HDL at the gestational age of 8-12 and 18-20 weeks did not have a significant difference (p > 0.05) with the level of the control group, then by the end of the gestation a significant decrease was observed. The decrease
in HDL values - by 3.3% and 17.6% during gestation led to a strongly marked increase in the atherogenic index by 32.1% and 76.4% in gestational age 18-20 weeks and 34-36 weeks, respectively. This index indicates the distribution of TC between HDL and atherogenic lipoprotein fractions. The antiatherogenic HDL/LDL ratio slightly decreased in the dynamics of pregnancy in obese women - by 7.5% and 27.2%, respectively.
Thus, the results of the study indicate a significant increase in total cholesterol, triglycerides, VLDL with a maximum level by the end of the gestation period in the group of pregnant women with obesity compared with patients with normal body weight. Along with this, there is a decrease in HDL levels, which is accompanied by an increase in the atherogenic potential of blood serum. Despite the fact that the metabolic changes occurring in the body of a pregnant woman are adaptive, they can play a role in the pathophysiological process of the development of pregnancy complications and impaired labor. With the progression of pregnancy, abdominal obesity in women is a risk factor for the development of pathological dyslipidemia.
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