|Year : 2017 | Volume
| Issue : 1 | Page : 9-14
Evaluation of lipid profile in cord blood of full-term Nigerian newborn infants
Lawal W Umar1, Ibrahim S Aliyu2, Shehu A Akuyam2
1 Department of Paediatrics, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
2 Department of Chemical Pathology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
|Date of Web Publication||6-Mar-2018|
Lawal W Umar
Department of Paediatrics, Ahmadu Bello University Teaching Hospital, Zaria
Background: Blood lipid profiles are known to be under the influence of genetic and environmental factors, with considerable age variation. While lipid levels are generally lower in childhood and may predict future risk for atherosclerosis, normal ranges in cord blood have not been fully evaluated in developing countries.
Objective: To evaluate the cord blood lipid profiles for full-term newborn infants.
Materials and Methods: A descriptive cross-sectional study was performed at Ahmadu Bello University Teaching Hospital, Zaria, involving 71 term newborn infants. At delivery, cord blood was collected and serum separated by centrifugation. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were measured using Selectra XL AutoAnalyser (HUMAN Gesellschaft für Biochemica und Diagnostica mbH, Wiesbaden, Germany), while the atherogenic index of plasma (AIP) was calculated from the lipid fractions. Using a standardised pro forma, obstetric and demographic data, and cord blood lipid levels were collected. Data were analysed using the Statistical Package for Social Sciences version 20.0 software (SPSS Inc., Chicago, Illinois, USA), and results were presented in tables and charts. A P value of <0.05 was considered as significant.
Results: There were 38 males and 33 females. The mean TC, TG, HDL-C and LDL-C were 1.87 ± 0.10, 0.57 ± 0.05, 0.70 ± 0.04 and 1.02 ± 0.07 mmol/L, respectively. The mean TG concentration is lower while the LDL-C is higher than the standard reference values. The AIP was −0.09. Neither gender nor anthropometric differences were observed.
Conclusion: This study has defined the cord blood lipid profile and reference ranges for full-term newborn infants, with no sex or anthropometric differences. Further studies are recommended to determine values for pre- and post-term infants.
Keywords: Atherogenic index, lipid profile, newborn infants, term infants
|How to cite this article:|
Umar LW, Aliyu IS, Akuyam SA. Evaluation of lipid profile in cord blood of full-term Nigerian newborn infants. Sub-Saharan Afr J Med 2017;4:9-14
|How to cite this URL:|
Umar LW, Aliyu IS, Akuyam SA. Evaluation of lipid profile in cord blood of full-term Nigerian newborn infants. Sub-Saharan Afr J Med [serial online] 2017 [cited 2018 Jun 19];4:9-14. Available from: http://www.ssajm.org/text.asp?2017/4/1/9/226659
| Introduction|| |
Serum lipid profile characterises the pattern of concentration of key compounds of lipid metabolism, mainly triglycerides (TG), total cholesterol (TC) and its sub-types, the low-density lipoproteins cholesterol (LDL-C) and high-density lipoproteins cholesterol (HDL-C). Whereas the distribution of the serum levels of these lipid fractions has been widely studied and normative values established for both adults and children in developed countries,,, such values are not as extensively studied especially for newborn infants in developing countries. However, a number of studies in children and adolescents from different countries have shown wide variations in serum lipids, affirming the influence of genetic, age and environmental factors in their physiology.,,,,, A familial tendency to high blood TC levels and a risk of coronary vascular disease (CVD) are known to exist and are believed to be a reflection of the interplay between genetic and environmental factors., Whereas a wide variation exists in cord blood lipid reference ranges for full-term newborn infants in developing countries,,,,,, compared to established international reference standard, such ranges were found to be consistently higher in pre-term infants compared to their pre-term counterparts.,,,,,
Cord blood TC levels are generally lower in full-term infants than that in pre-term newborns while the full-term levels approximate to one-third of adult values, with 50–60% proportion for LDL-C and 40–50% for HDL-C. It has been suggested that inadequate enzymatic activity (lipoprotein lipase, hepatic lipase and lecithin cholesterol acyl-transferase), in near term neonates compared with their term counterparts, is partly responsible for higher serum lipids in pre-term infants.,, Plasma depletion of cholesterol that occurs at term appears to have inverse correlation with an increase in LDL-C uptake by the foetal adrenal gland for steroid hormone synthesis. Since HDL-C is not metabolized efficiently by the adrenals, the fall in HDL-C levels at term may be attributed to an increased maturity of these enzymes and their activity., The pathogenesis of atherosclerosis has been described to begin early in life and high concentrations of lipoproteins in pre-term newborn have been associated with the risk of developing CVD later in life.,,, Among indices that are derivable from the ratios of concentrations of blood lipid parameters, the atherogenic index of plasma (AIP), the logarithm of the ratio TG/HDL-C, was shown to be predictive of risk of atherosclerosis in cord blood and sera of participants at birth, through infancy, childhood, adolescence to adult life.,,
Plasma TC rises rapidly from a mean of 68 mg/dl (1.80 mmol/L) at birth to nearly twice that by the end of the neonatal period., A gradual rise in TC continues and at puberty, reaching 160 mg/dl (4.14 mmol/L) when the levels transiently drop (in males due to a reduction of HDL and in females due to a reduction in LDL). While high cord blood lipids in pre-term newborn infants may predict atherogenic risk, a correlation was found between lower levels in full-term newborns and risk of late onset neonatal sepsis, attributed to defective TG-mediated neutralisation of lipopolysaccharides, suggesting a prognostic significance of cord blood and neonatal lipid evaluation.
Although reports of studies on reference ranges of cord blood lipid profiles abound from both developed and developing countries, there are only a few studies involving measurements of cord blood lipids in Nigeria, and all of which are from the southern part of the country., The aim of our study is to assess the cord blood lipid profile of full-term normal birth weight newborn infants in northern Nigeria and determine the reference ranges in our locality.
| Objectives of the study|| |
The objectives were to assess the cord blood lipid profile and determine the normal reference ranges for full-term normal birth weight newborn infants.
| Materials and methods|| |
A total of 71 (38 males and 33 females) full-term singleton newborn infants delivered at the Labour Ward, to pregnant women who attended antenatal care clinic of Ahmadu Bello University Teaching Hospital (ABUTH), Zaria were enrolled. Informed consent for inclusion into the study was obtained from these women after the nature of the study was explained to them in the language they best understood.
Relevant medical and obstetric history was obtained from pregnant women who presented in labour, and their antenatal medical records were studied to identify those whose medical/obstetric history and newborn characteristics fulfil the inclusion criteria. The enrolment of participants was conducted in a consecutive manner between January 15, 2011 and May 15, 2011. A total of 238 deliveries were conducted in the facility during this period, out of which seventy-one pregnant women and their newborns that satisfied the eligibility criteria were selected.
Newborn infants delivered between 37 and 42 completed weeks of gestation (calculated from the first day of mother’s last day of menstrual period to the date of birth) were included. All infants whose birth weight fell between 2.51 and 3.99 kg, and whose mothers consented were also considered as eligible.
Newborn infants whose parent declined consent were excluded from the study. Similarly, newborns whose birth weight was 2.50 kg or less and those whose birth weight was 4.00 kg or more, those whose mothers had past medical history/record of either alcoholism, smoking, hypertension, heart disease, diabetes mellitus or oral contraceptive use and those who had no antenatal care at the study facility were also excluded from the study. Also excluded were women who presented with multiple pregnancy.
Physical examination, anthropometry and gestational age assessment
Physical examination and anthropometric measurements were taken for each newborn. Weights were measured to the nearest 0.1 kg within two hours of delivery and with baby naked, using Seca electronic weighing scale, while crown-heel length was measured using an infantometer to the nearest 0.1 cm. Body mass index (BMI) was calculated using the formula BMI = weight (kg)/height (cm). Gestational age was assessed using the mother’s facility ANC record card correlated with use of Dubowitz criteria.
Blood sample collection and processing
Blood specimen was collected from the placental end of the cord immediately after the delivery of the placenta for each baby. The cord was cleaned with methylated spirit and allowed to dry. Blood was then taken using sterile 5 ml syringe and 23G needle, transferred into a plain specimen bottle and allowed to clot. The specimen was then centrifuged for 5 min at 1000×g. to separate serum, which was then transferred into Bijou bottle and stored at −20°C until the time for analysis.
The Health Research Ethics Committee of ABUTH, Zaria approved the study.
Reagents and test kits
The reagents and diagnostic kits used include CHOL Liquicolor reagent, TG Liquicolor reagent, Precipitant for HDL-C determination, CHOL, HDL-C and TG standards. All reagents were obtained from HUMAN Gesellschaft für Biochemica und Diagnostica mbH (Wiesbaden, Germany). Quality control kits for low, medium and high labels of total CHOL, HDL-C and TG were obtained from RANDOX Diagnostics Laboratory (Crumlin, County Antrim, UK) and were ran with each batch of test analysis.
Serum concentrations of TC, HDL-C and TG were measured by enzymatic colorimetric method of Eggstein. Serum LDL-C was estimated using Friedewald formula, while AIP was determined using the formula: AIP = Log [TG/HDL-C], or Logarithm of TG divided by HDL-C.,,
All the findings from clinical, anthropometric and laboratory information were entered into a standardised study pro forma and data were entered for statistical analysis into the Statistical Package for the Social Sciences version 9.0 software for Windows (SPSS Inc., Chicago, IL, USA). Student’s t-test was employed for the comparison of gestational age, anthropometric parameters, BMI and serum lipids between males and females. One-way analysis of variance was employed for the comparison of mean values of serum lipids and anthropometric measurements. Correlations between sex and serum lipids as well as between BMI and serum lipids were made using Pearson’s linear correlation analysis. A P-value equal to or less than 0.05 (P ≤ 0.05) was considered as statistically significant.
| Results|| |
Anthropometric measurements and cord blood lipids
Seventy-one newborn infants aged 37–42 weeks of completed gestation (mean 37.9 ± 0.22) born to eligible pregnant women were studied. [Table 1] shows the sex distribution, anthropometric parameters and mean (±SD) values of their cord blood lipids. There were no significant differences in their anthropometric parameters (P > 0.05). There were also no statistically significant differences in the lipid values and the AIP between female and male newborn infants as derived from the formula Log10 [TG/HDL-C] (P > 0.05).
|Table 1: Mean Anthropometric parameters and cord blood lipid values of study subjects by sex (mean ± SEM)|
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Reference ranges of cord blood lipids of study population
The reference ranges of serum lipid values stratified by sex are shown in [Table 2]. These range of values represent cord blood lipid concentrations between 2.5th and 97.5th percentiles.
|Table 2: Reference ranges of cord blood lipid values (2.5–97.5th percentiles) of 71 study subjects|
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Relationship between cord blood lipids with body mass index and gestational age
The relationship between cord blood lipid profile with BMI and gestational age of the study population is presented in [Table 3]. The results did not show any significant correlations between the cord blood lipid profile with neither the BMI nor the gestational age (P > 0.05).
|Table 3: Relationship of cord blood lipids with BMI and gestational age of study subjects|
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Comparison with newborn lipid profiles with International reference standard
[Table 4] shows a comparison of the mean concentrations of cord blood lipid values obtained for the 71 study participants, along with the international reference standards (Nelson Textbook of Pediatrics), and values from a report in Nigeria. The concentration of TC approximates to, while those for TG, LDL-C and HDL-C concentrations differ from that of the international reference standard. The concentrations of HDL-C are closest between our value and that reported by Ayoola et al., while TG, TC and LDL-C concentrations differ widely.
|Table 4: Newborn lipid profiles of 71 study subjects − comparison with mean international reference and a report in Nigeria|
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AIP as calculated from the formula Log10 (TG/HDL-C) is −0.09, which is also lower than both the calculated value for the international reference standard and the calculated value from the report of Ayoola et al., cited in [Table 4].
| Discussion|| |
This study has found the mean values and reference ranges for cord blood lipids in newborn infants in Zaria, northern Nigeria, which are at variance with the mean international reference values. The mean values of cord blood lipids were also at variance with those reported in a previous study from the southern Nigeria, except for almost similar values of HDL-C. The variations may be a reflection of the genetic and intrauterine environmental influences previously reported to interact in different ways.,, However, the implication of this could be that reference values for lipid profiles would need to be determined with larger studies for different environments in developing countries.
The mean TG, HDL-C, LDL-C and TC/HDL-C concentrations were higher in female newborn infants compared to their male counterparts except for TC, though the difference was not statistically significant. Similar to our findings, Aletayeb et al., and Kazemi and Sadeghzadeh, did not find any significant gender differences in cord blood lipid concentrations among newborns they studied. Comparison on sex differences between our findings and the studies from Nigeria by Ayoola et al., and Taylor et al., could not be made as these reports did not disaggregate the sex of newborns in their analysis. However, Mago et al., in India, found significantly higher LDL-C among female compared to male newborns. Our findings are in agreement with suggestions that, the influence of sex may not yet be a manifest on lipid levels in full-term newborn infants at birth.,
The mean cord blood TG level for newborns in our study is lower when compared to values reported in other findings from different parts of the world.,,, It is noteworthy also that the mean TG concentration reported by Ayoola et al., from southern Nigeria, even though slightly higher than the mean TG for newborns in our study, is similarly lower than the value in the international reference standard, and what was reported in these similar studies.,,, Conversely, the LDL-C in our findings is higher than what was reported in both the international reference standard, as well as in some other studies.,,, These observations may be suggestive of a trend of lower TG and higher LDL-C levels in cord blood in Nigerian newborns, which calls for further investigation with countrywide multicenter studies.
AIP of −0.09, a negative value obtained in our study, is suggestive of a little or no risk for atherosclerosis, nearly similar to that derived from the international reference standard ratio by application of the same formula., AIP is a predictor for the risk of atherosclerosis in future adult life, and values above 0.5 are associated with the high risk of atherosclerosis, respectively., Nwagha et al., have suggested that in situations where other atherogenic risk parameters namely TG and HDL-C are within normal limits, AIP is a reliable index that can predict the risk of atherosclerosis. The AIP of −0.09 obtained in our study may, thus, suggest minimal or no risk for the future development of atherosclerosis among our studied participants.
Our study found no correlation between cord blood lipid profile and BMI and gestational age, which are expected results, since the study participants are a homogenous group of normal birth weight infants born at term (37–42 weeks of gestation). Some studies on cord blood lipid profiles have reported positive correlation with anthropometric parameters, BMI and gestational age, after disaggregation of participants to pre-term, full-term and post-term subgroups.,,,,, These studies, generally found normal levels of cord blood lipids and AIPs below the cut-off values associated with the risk of atherosclerosis among full-term newborn infants with normal anthropometry compared to significantly higher relative concentrations of LDL-C and consequently higher AIPs among premature infants and those with smaller BMIs.,,,,
Some limitations of this study include a relatively small sample size and a narrow scope of study participants arising from non-inclusion of pre-term and post-term newborn infants in the evaluation.
| Conclusion|| |
This study has outlined the cord blood lipid profiles of full-term normal birth weight newborn infants in Zaria, which were similar irrespective of gender and size at birth, and whose concentrations differ from previously established international standard values published in a reference textbook. All the parameters were higher than those reported by studies in southern Nigeria, except for the TG, which was lower. The LDL-C fraction was higher than both the international reference standard, and that was previously reported in Nigeria. The TC concentration that we found is higher, even though closer to the international reference standard value. The risk of future atherosclerosis as determined by the AIP is low.
We recommend the conduct of a larger multicentre study including pre-term and post-term newborn infant categories and newborn infants with maternal risk factors for hyperlipidaemia.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]