Comparison of test performance of two commonly used multiplex assays to measure micronutrient and inflammatory markers in serum:results from a survey among pregnant women in South Africa

The combined sandwich-ELISA (s-ELISA; VitMin Lab, Germany) and the Quansys Q-Plex™ Human Micronutrient Array (7-Plex) are multiplex serum assays that are used to assess population micronutrient status in low-income countries. We aimed to compare the agreement of five analytes, α-1-acid glycoprotein (AGP), C-reactive protein (CRP), ferritin, retinol binding protein 4 (RBP4), and soluble transferrin receptor (sTfR) as measured by the 7-Plex and the s-ELISA. Serum samples were collected between March 2016 and December 2017. Pregnant women (n=249) were recruited at primary healthcare clinics in Johannesburg and serum samples were collected between March 2016 and December 2017. Agreement between continuous measurements was assessed by Bland-Altman plots and concordance measures. Agreement in classifications of deficiency or inflammation was assessed by Cohen's kappa. Strong correlations (r&gt;0.80) were observed between the 7-Plex and s-ELISA for CRP and ferritin. Except for CRP, the 7-Plex assay gave consistently higher measurements than the s-ELISA. With the exception of CRP (Lin's ρ=0.92), there was poor agreement between the two assays, with Lin's ρ &lt;0.90. Discrepancies of test results difference between methods increased as the serum concentrations rose. Cohen's kappa for all the five analytes was &lt;0.81 and ranged from slight agreement (vitamin A deficiency) to substantial (inflammation, iron deficiency) agreement. The 7-Plex 1.0 is a research and or surveillance tool with potential for use in low-resource laboratories but cannot be used interchangeably with the s-ELISA. Further optimising and validation is required to establish its interchangeability with other validated methods.</p

Effects of zinc fortification on the plasma fatty acid composition of Beninese school children : a randomised, double-blind controlled trial

MSc (Nutrition), North-West University, Potchefstroom Campus, 2017Introduction The lack of a specific and sensitive zinc (Zn) status biomarker is problematic. The linoleic acid: dihomo-γ-linolenic acid (LA:DGLA) ratio has been suggested by some researchers to be a Zn status marker. This is because Zn and fatty acids (FA) are known to interact, as Zn and FA deficient individuals present similar symptoms and physical manifestations. Although the mechanism by which Zn and FA interact is not fully understood, it is suggested that they interact through the FA synthesis pathway. Zn deficiency is suggested to impair the activity of desaturase enzymes, (desaturase enzymes are responsible for the conversion of essential fatty acids into longer-chain polyunsaturated FA) thereby causing a decrease in tissue long chain polyunsaturated metabolites. Zn supplementation in Zn deficient rats is known to affect their FA status, but little is known about effects of Zn fortification on the FA status in humans. There is also limited data on the FA status of African children as well as data on Zn and FA interactions in humans. Therefore the main aim of this study was to investigate whether there were associations between baseline plasma Zn and plasma total phospholipid FA composition, as well as to assess the effect of Zn fortified water on the plasma total phospholipid FA composition of rural Beninese school children aged between 6 and 10 years. Methods. In a 20-week double blind randomised controlled trial, Beninese school children from a low-income rural setting aged between 6 and 10 years (n = 185) were randomly assigned to receive either a 300ml daily portion of Zn-fortified filtered water delivering 2.8 mg Zn (Zn+filter) or non-fortified filtered water (Filter). Plasma total phospholipid FA composition was determined using capillary gas chromatography and plasma Zn (PZn) analysis by atomic absorption spectrometry. Associations between Zn and FA were examined at baseline. Furthermore, the effect of Zn fortification on plasma FA composition was analysed in the total group, as well as in the Zn deficient and sufficient children and in girls and boys separately. Results and discussion. At baseline, plasma Zn correlated positively with DGLA (r = 0.209; p = 0.010) and the DGLA:LA ratio (r = 0.327; p < 0.001). There was a significant inverse association between plasma Zn and linoleic acid (LA) (r = –0.229; p = 0.005) and the arachidonic: dihomo-γ-linolenic acid (ARA:DGLA) ratio (r = –0.257; p<0.001). At baseline, LA (p = 0.017), eicosapentaenoic acid (EPA) (p = 0.002), n-3 docosapentaenoic acid (DPA) (p = 0.020), adrenic acid (p = 0.010) and the ARA:LA ratio (p = 0.020) differed between boys and girls. In Zn sufficient boys, gamma-linolenic acid (GLA) was higher (p = 0.020) and the DGLA:GLA ratio tended to be higher (p = 0.059) than in Zn deficient boys. Zn fortification increased nervonic acid (p = 0.048) and tended to reduce LA (p = 0.068) in all children. Zn deficient children had a significantly higher nervonic acid composition (p = 0.019) after Zn fortification, whilst no significant effect was found in Zn sufficient children (p = 0.382). Fortification did not improve the plasma total phospholipid FA composition differently in boys and girls. Conclusion. The findings from this research therefore supports that the LA:DGLA (or DGLA:LA) ratio could be a possible biomarker for Zn status. Our results further demonstrated that Zn filtered fortified water had an effect on the plasma total phospholipid FA composition of children, and even more so in Zn deficient children, thereby indicating that elongation and desaturation might be improved by Zn. The plasma total phospholipid FA composition was affected more by Zn deficiency in boys than in girls. However, further research is required to fully confirm these results, as well to examine the underlying mechanisms that exist between Zn and FA in humansMaster

Sensitivity of fatty acid desaturation and elongation to plasma zinc concentration: a randomised controlled trial in Beninese children

Zn status may affect fatty acid (FA) metabolism because it acts as a cofactor in FA desaturase and elongase enzymes. Zn supplementation affects the FA desaturases of Zn-deficient rats, but whether this occurs in humans is unclear. We evaluated the associations between baseline plasma Zn (PZn) concentration and plasma total phospholipid FA composition, as well as the effect of daily consumption of Zn-fortified water on FA status in Beninese children. A 20-week, double-blind randomised controlled trial was conducted in 186 school age children. The children were randomly assigned to receive a daily portion of Zn-fortified, filtered water delivering on average 2·8mg Zn/d or non-fortified filtered water. Plasma total phospholipid FA composition was determined using capillary GLC and PZn concentrations by atomic absorption spectrometry. At baseline, PZn correlated positively with dihomo-γ-linolenic acid (DGLA, r 0·182; P=0·024) and the DGLA:linoleic acid (LA) ratio (r 0·293; P<0·000), and negatively with LA (r −0·211; P=0·009) and the arachidonic acid:DGLA ratio (r −0·170; P=0·036). With the intervention, Zn fortification increased nervonic acid (B: 0·109; 95% CI 0·001, 0·218) in all children (n 186) and more so in children who were Zn-deficient (n 60) at baseline (B: 0·230; 95% CI 0·023, 0·488). In conclusion, in this study, Zn-fortified filtered water prevented the reduction of nervonic acid composition in the plasma total phospholipids of children, and this effect was stronger in Zn-deficient children. Thus, Zn status may play an important role in FA desaturation and/or elongatio

Breast milk and erythrocyte fatty acid composition of lactating women residing in a peri‑urban South African township

Data on breast milk fatty acid (FA) composition in South African lactating women in relation to their FA status, as well as on potential compositional changes within feed, are limited. The aim of this study was to assess the FA composition of breast milk sampled at three time points within feed, and to determine associations with red blood cell (RBC) total phospholipid FA levels in lactating South African mothers of 2–4-month-old breastfed infants. FA composition (% total FAs) was analyzed in RBC total phospholipids, and in fore-, mid-feed and hind-milk samples of lactating mothers (n = 100) of Black African descent living in a peri‑urban township. The mean age of the lactating women was 27.8 ± 6.8 years. Geometric mean (95% CI) breast milk SFA, MUFA and PUFA contents were 37.7 (37.3,38.1), 28.5 (27.9, 28.8), and 23.5 (23.2, 24.5)%, respectively. Breast milk DHA and AA contents were 0.25 (0.24, 3.71) and 0.81 (0.79, 0.83)%, respectively, in fore-, mid- and hind-milk combined. Maternal RBC EPA, DHA and AA levels were 0.37 (0.34, 0.40), 3.8 (3.6, 4.0) and 15.4 (14.8, 16.1)%, respectively. Women who reported to consume fish often (n = 3) had significantly higher RBC EPA levels than women who consumed fish sometimes (n = 56), never (n = 14) or rarely (n = 19). Breast milk DHA positively correlated with maternal RBC DHA, while no correlations were found between breast milk AA and maternal RBC AA. Breast milk ALA and DHA contents were significantly higher in mid-feed [ALA= 0.8 (0.2, 0.2), DHA=0.3 (0.2, 0.3)] and hind-milk [ALA=0.8 (0.8, 0.9), DHA=0.3 (0.3, 0.3)] than foremilk [ALA=0.8 (0.7, 0.9), DHA=0.2 (0.2, 0.3)]. In contrast, LA and AA contents remained constant within feed. In this sample of peri‑urban South African lactating mothers, breast milk was low in DHA and high in AA compared to global means. Breast milk DHA was associated with maternal RBC status, while breast milk AA was not. We further showed that breast milk ALA and DHA increased, while LA and AA remained unchanged within feed. This suggests that n-3 PUFA maybe preferentially transferred to breast milk within feed through biomagnificatio

Sensitivity of fatty acid desaturation and elongation to plasma zinc concentration: a randomised controlled trial in Beninese children

ISSN:0007-1145ISSN:1475-266

Association of maternal diet, micronutrient status, and milk volume with milk micronutrient concentrations in Indonesian mothers at 2 and 5 months postpartum

BackgroundMaternal micronutrient deficits during preconception and pregnancy may persist during lactation and compromise human milk composition.ObjectiveWe measured micronutrient concentrations in human milk and investigated their association with maternal micronutrient intakes, status, and milk volume.MethodsInfant milk intake (measured via a deuterium dose-to-mother technique), milk micronutrient and fat concentrations, and maternal micronutrient intakes were assessed at 2 and 5&nbsp;mo postpartum in 212 Indonesian lactating mother-infant pairs. Maternal hemoglobin, ferritin, transferrin receptors, retinol binding protein (RBP), zinc, selenium, and vitamin B-12 were measured at 5 mo (n&nbsp;=&nbsp;163). Multivariate or mixed effects regression examined associations of milk micronutrient concentrations with maternal micronutrient intakes, status, and milk volume.ResultsPrevalence of anemia (15%), and iron (15% based on body iron), selenium (2.5%), and vitamin B-12 deficiency (0%) were low compared with deficiencies of zinc (60%) and vitamin A (34%). The prevalence of inadequate intakes was &gt;50% for 7 micronutrients at 2 and 5 mo. Median milk concentrations for most micronutrients were below reference values, and nearly all declined between 2 and 5 mo postpartum and were not associated substantially with milk volume (except for β-carotene, α-carotene, and β-cryptoxanthin). At 5 mo postpartum, associations between maternal micronutrient status and corresponding milk concentrations reported as mean percentage difference in human milk concentration for each unit higher maternal biomarker were significant for hemoglobin (1.9%), iron biomarkers (ranging from 0.4 to 7%), RBP (35%), selenium (70%), and vitamin B-12 (0.1%), yet for maternal intakes only a positive association with β-carotene existed.ConclusionsMost milk micronutrient concentrations declined during lactation, independent of changes in human milk production, and few were associated with maternal micronutrient intakes. The significant associations between maternal biomarkers and milk micronutrient concentrations at 5 mo warrant further study to investigate whether the declines in milk micronutrients are linked to shifts in maternal status