Phospholipid fatty acids in soil—drawbacks and future prospects

The current opinion and position paper highlights (1) correct assignation of indicator phospholipid fatty acids (PLFA), (2) specificity and recycling of PLFA in microorganisms, and (3) complete extraction and detection of PLFA. The straight-chain PLFA 14:0, 15:0, 16:0, and 17:0 occur in all microorganisms, i.e., also in fungi and not only in bacteria. If the phylum Actinobacteria is excluded from the group of Gram-positive bacteria, all remaining bacteria belong to the bacterial phylum Firmicutes, which should be considered. The PLFA 16:1ω5 should be used as an indicator for the biomass of arbuscular mycorrhizal fungi (AMF) as there is no experimental evidence that they occur in marked amounts in Gram-negative bacteria. Fungal PLFA should embrace the AMF-specific 16:1ω5. In the presence of plants, ergosterol should be used instead of the PLFA 18:2ω6,9 and 18:1ω9 as fungal indicators for Mucoromycotina, Ascomycota, and Basidiomycota. The majority of indicator PLFA are not fully specific for a certain microbial group. This problem might be intensified by recycling processes during decomposition to an unknown extent. Soil handling and extraction conditions should be further optimized. The reliability and accuracy of gas chromatographic separation need to be regularly checked against unintentional variations. PLFA analysis will still be of interest over the next decades as an important independent control of DNA-based methods.

Changes of Plasma Phospholipid Fatty Acids Profiles in Pregnancy in Relation to the Diagnosis and Treatment of Gestational Diabetes Mellitus

Background Plasma phospholipid fatty acids (FAs) in early and mid-pregnancy have been prospectively related to gestational diabetes mellitus (GDM) risk. Yet, changes of FAs following GDM diagnosis and treatment and their implications for glucose metabolism and control remain understudied. Methods From the Eunice Kennedy Shriver National Institute Child Health and Human Development Fetal Growth Studies–Singleton Cohort of 2802 pregnant women, we ascertained 85 GDM cases using the Carpenter and Coustan criteria and 85 non-GDM controls after exclusion. Using plasma collected before (23–31 weeks) and after GDM diagnosis (33–39 weeks), we quantified 25 saturated, poly- and monounsaturated FAs levels. We estimated the fold change of FAs before and after GDM diagnosis, using multiple linear mixed models adjusting for confounders. Results Eight FAs showed significant fold changes from the baseline values (23–31 weeks) among GDM cases as compared to women without GDM. Five FAs showed reduced fold changes [myristic acid (14:0): β: −0.22 (95% CI: −0.30, −0.14), palmitic acid (16:0): β: −0.02 (95% CI: −0.04, −0.01), cis-palmitoleic acid (16:1n7): β: −0.15 (95% CI: −0.24, −0.05), alpha-linolenic acid (18:3n3): β: −0.19 (95% CI: −0.31, −0.07], and dihomo-gamma-linoleic acid (20:3n6): β:−0.16; 95% CI: −0.21, −0.11)], whereas 3 showed increases [heptadecanoic acid (17:0): β: 0.17 (95% CI: 0.11, 0.22), cis-vaccenic acid (18:1n7): β: 0.06 (95% CI: 0.03, 0.10), and arachidonic acid (20:4n6): β: 0.10 (95% CI: 0.06, 0.13)]. Conclusions Our study identified 8 FAs with unique patterns of change before and after GDM diagnosis that differed significantly between women with and without GDM. Our findings may shed light on the role of FA metabolism in the pathophysiology and disease management and progression of GDM. Clinical Trial Registry NCT00912132

Using Genetic Variants to Evaluate the Causal Effect of Plasma Phospholipid Fatty Acids on Breast Cancer and Prostate Cancer: A Mendelian Randomization Study

BackgroundObservational studies indicate that phospholipid fatty acids (FAs) have an impact on the etiology in cancers, but the results are conflicting. We aimed to investigate the causal association of phospholipid FAs with breast cancer and prostate cancer.MethodsFourteen single nucleotide polymorphisms (SNPs) were selected as instrumental variables to predict the level of 10 phospholipid FAs from Genome-wide association studies (GWAS). We obtained the summary statistics for the latest and largest GWAS datasets for breast cancer (113,789 controls and 133,384 cases) and prostate cancer (61,106 controls and 79,148 cases) from the Breast Cancer Association Consortium (BCAC) and Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome (PRACTICAL) consortium. Two-sample Mendelian randomization analysis was applied.ResultsThe results demonstrate that the 10 individual plasma phospholipid FAs are not significantly associated with breast cancer risk and prostate cancer risk.ConclusionThe evidence is insufficient to support the causal association of the 10 individual plasma phospholipid FAs with breast cancer and prostate cancer.

Extraction and methylation parameters of phospholipid fatty acid analysis and their effect on total yield and community structure

<p>Phospholipid fatty acids are membrane compounds of microbial cell walls and the structure of individual compounds is indicative for specific microbial groups. The extraction and analysis of phospholipid fatty acids in soils improved our understanding of factors driving microbial abundance and community composition. Despite the wide application of this method, important pitfalls persist which impede comparability of PLFA results between studies.</p><p>Here, we show that there was an effect of freeze-drying on the community composition. However, compared to the effect of using of old extraction solution (4 weeks) and two different methylation procedures, this effect seems negligible. Using old extraction solution, the overall yield of PLFA was 12% lower and and we observed significant differences in the relative abundances of functional microbial groups. But most importantly, base catalyzed methylation yielded 35% less PLFA compared to acid catalyzed methylation and the relative abundances of all microbial groups were completely different. Our results show that it is crucial to keep the analytical parameters constant to capture subtle treatment effects and that especially the use of different methylation methods prevents comparability between studies.</p>