Study protocol
The effect of inflammatory markers on the vitamin B6 status measurements during pregnancy.
BACKGROUND
Vitamin B6 is essential for healthy pregnancy. Low maternal vitamin B6 status has been related to various pregnancy complications such as early pregnancy loss (Ronnenberg et al, 2007) and increased risk of anaemia (Hisano et al, 2010). This suggests that it is important vitamin B6 status to be monitored throughout pregnancy. Plasma pyridoxal phosphate (PLP) is the primary form of circulating vitamin B6 and the most frequently used biomarker for assessment of vitamin B6 status in different population groups. However, the validity of plasma PLP as a vitamin B6 status measurement in pregnancy is uncertain as plasma PLP values within the deficiency range are frequently found in pregnancy, but without the presence of any clinical signs of B6 deficiency (Contractor & Shane,1970; Cikot 2001;Bjorke-Monsen et al, 2013). On the other hand, pregnancy is a physiological condition associated with a low grade inflammation as maternal inflammatory response is necessary for the implantation of the fertilised egg into the uterus as well as for the successful progression of pregnancy (Palm et al, 2013). Increased concentrations of inflammatory factors like different cytokines and C-reactive protein (CRP) are reported in various studies in women with uncomplicated pregnancy (Belo et al, 2005; Palm et al, 2013; Christiaens et al, 2008). However, evidence from investigations in non-pregnant cohorts showed that inflammatory conditions and increased levels of inflammatory factors in the circulation are inversely associated with plasma PLP concentrations (Friso et al, 2001; Morris et al, 2010). Thus, it possible that the low plasma PLP concentrations found in pregnancy is related to the existing low-grade inflammation, however, this hypothesis has never been examined.
AIM
The aim of this work is to use existing samples to determine the effect of inflammatory markers on the vitamin B6 status measurements during pregnancy.
METHODS
Pregnancy samples: Within the FASSTT study (Folic Acid Supplementation during the Second and Third Trimesters of pregnancy (FASSTT); Project name ‘Folate utilisation during pregnancy and lactation - implications for dietary recommendations for folate and related b-vitamins in women of reproductive age’ (ORECNI Ref 05/Q2008/21; Approved by South West 1 in 2005; PI Dr K Pentieva) healthy pregnant women (n=226); aged 18-35 years; recruited from the NHSCT between September 2005 and December 2007) were followed from gestational week 14 till delivery. Blood samples were taken at 14th and 36th gestational week and umbilical cord blood samples were collected upon delivery. All blood samples were analysed for plasma PLP.
Control samples: Within the project entitled ‘A vitamin B12 intervention study in women’ (UUREC ref 04/39; PI Dr K Pentieva) healthy non-pregnant women aged 18-35 were recruited from the Ulster staff and student population between September 2004 and June 2006 in order to proceed to an intervention study with vitamin B12. At baseline (before the start of the intervention) women provided blood samples which were analysed for plasma PLP concentration.
Laboratory methods
For the purpose of the project described above we plan to analyse the following samples for plasma C-Reactive Protein (CRP) concentrations:
- Plasma samples from FASSTT study (pregnant women): n=218 (14th GW); n=119 (36th GW)
- Plasma samples from baseline B12 study (non-pregnant women): n=114
Vitamin B6 status marker (plasma PLP) concentrations already measured will be standardised using CRP results and results in pregnant women (FASSTT study) compared to those in age matched non-pregnant controls (B12 study).
Ethical issues
- Ethical permission:The FASSTT study was approved by a Health Research Authority (HRA) ethics board and was closed in December 2011. The B12 study was approved by UREC and closed in September 2006. All samples therefore fall under the University license.
- Consent: The proposed work falls under the original consent provided by the participant.
- FASSTT study:Within the PIS the purpose of the study was ‘…to look at the effect of folic acid supplementation in the later stages of pregnancy and to assess the effect of folic acid supplementation on pregnancy on homocysteine and the health of you and your baby.’
- B12 study:…to investigate whether vitamin 12 supplementationimproves blood concentrations of the vitamin, to a level which is associated with the decrease risk of disease.’
Within both studies no details on measures of health to be measured in the blood sample were given.
- Duty of care:
- FASSTT study:given that pregnancy is a physiological condition associated with raised inflammation CRP results will not be directly associated with current health.
- B12 study: as these samples were collected between 2006-2006 findings from this CRP analysis will no longer be relevant to health.
References:
Ronnenberg et al. Am J Epidemiol 2007; 166:304-12
Hisano et al. Eur J ClinNutr2010;64:221-3.
Contractor & ShaneAm J ObstetGynecol1970;107:635-40.
Cikot et al. Br J Nutr2001;85:49-58.
Bjorke-Monsen et al. MolNutr Food Res 2013; 57:645-52.
Palm et al. ActaObstetGynecol 2013; 92:601-5.
Belo et al. Eur J ObstetGynecolReprodBiol 2005; 123:46-51.
Christiaens et al. J ReprodImmunol 2008; 79:50-7.
Friso et al. Circulation 2001; 103:2788-2791.
Morris et al. J Nutr 2010; 140:103-110.