Intra-individual variability of long-chain fatty acids (C12-C24) in plasma and red blood cells

Heterogeneity in the response to n-3 polyunsaturated fatty acids

PURPOSE OF REVIEW

A central goal in the study of long chain n-3 polyunsaturated fatty acids (PUFA) is to translate findings from the basic sciences to the population level to improve human health and prevent chronic diseases. A tenet of this vision is to think in terms of precision medicine and nutrition, that is, stratification of individuals into differing groups that will have different needs across the lifespan for n-3 PUFAs. Therefore, there is a critical need to identify the sources of heterogeneity in the human population in the dietary response to n-3 PUFA intervention.

RECENT FINDINGS

We briefly review key sources of heterogeneity in the response to intake of long chain n-3 PUFAs. These include background diet, host genome, composition of the gut microbiome, and sex. We also discuss the need to integrate data from newer rodent models (e.g. population-based approaches), multi -omics, and analyses of big data using machine learning and data-driven cluster analyses.

SUMMARY

Accounting for vast heterogeneity in the human population, particularly with the use of big data integrated with preclinical evidence, will drive the next generation of precision nutrition studies and randomized clinical trials with long-chain n-3 PUFAs.

Inherited causes of exocrine pancreatic insufficiency in pediatric patients: clinical presentation and laboratory testing

Pediatric patients with exocrine pancreatic insufficiency (EPI) have symptoms that include abdominal pain, weight loss or poor weight gain, malnutrition, and steatorrhea. This condition can be present at birth or develop during childhood for certain genetic disorders. Cystic fibrosis (CF) is the most prevalent disorder in which patients are screened for EPI; other disorders also are associated with pancreatic dysfunction, such as hereditary pancreatitis, Pearson syndrome, and Shwachman-Diamond syndrome. Understanding the clinical presentation and proposed pathophysiology of the pancreatic dysfunction of these disorders aids in diagnosis and treatment. Testing pancreatic function is challenging. Directly testing aspirates produced from the pancreas after stimulation is considered the gold standard, but the procedures are not standardized or widely available. Instead, indirect tests are often used in diagnosis and monitoring. Although indirect tests are more widely available and easier to perform, they have inherent limitations due to a lack of sensitivity and/or specificity for EPI.

Quantitation of Fatty Acids in Serum/Plasma and Red Blood Cells by Gas Chromatography-Negative Chemical Ionization-Mass Spectrometry

Quantitation of long-chain fatty acids in serum/plasma and red blood cells is a useful diagnostic tool in the evaluation of nutritional status and assessment of risk for essential fatty acid deficiency (EFAD). Serum/plasma has been the traditional sample type for this method, yet it requires prolonged fasting which is not compatible with some patient populations. More recently, red blood cells have become an important sample type due to less intraindividual variability and obviating the need for fasting. Here we present a method for the quantitation of 22 fatty acids in serum/plasma or red blood cells. Fatty acids are hydrolyzed and extracted from the biological matrix, followed by derivatization with pentafluorobenzyl bromide and subsequent analysis by gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS).

Long-term variability and change trend of systolic blood pressure and risk of type 2 diabetes mellitus in middle-aged Japanese individuals: findings of the Aichi Workers' Cohort Study

Studies have reported that short-term blood pressure (BP) variability (BPV) is associated with type 2 diabetes mellitus (T2DM) incidence, but the association with long-term BPV remains unclear. The present study investigated the associations of long-term BPV as well as the time trend of BP changes over time with the incidence of T2DM. This study followed a cohort of 3017 Japanese individuals (2446 male, 571 female) aged 36-65 years from 2007 through March 31, 2019. The root-mean-square error (RMSE) and the slope of systolic BP (SBP) change regressed on year were calculated individually using SBP values obtained from 2003 to baseline (2007). A multivariable Cox proportional hazard model was applied to estimate hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) for tertiles of SBP RMSE and continuous SBP slopes adjusted for age, sex, smoking status, regular exercise, sodium intake, family history of diabetes, sleep disorder, body mass index (BMI), SBP, and fasting blood glucose (FBG) at baseline, and BMI slope from 2003 to 2007. The highest RMSE tertile compared to the lowest was associated with a significantly higher incidence of T2DM after adjusting for covariates (HR: 1.79, 95% CI: 1.15, 2.78). The slope was also significantly associated with T2DM incidence until baseline SBP and FBG were adjusted (HR: 1.03, 95% CI: 0.99, 1.07). In conclusion, long-term SBP variability was significantly associated with an increased incidence of T2DM independent of baseline age, sex, BMI, SBP, FBG, lifestyle factors and BMI slope from 2003 until baseline.

Development and validation of a liquid chromeatography-tandem mass spectrometry method for simultaneous quantification of medium- and long-chain saturated fatty acids in hamster plasma samples

RATIONALE

Saturated fatty acids (SFAs) are associated with many diseases in humans. Developing a reliable analytical method to analyze SFAs in plasma is essential to understand their biological activities. An ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC/MS/MS) method has been developed for the quantification of medium- and long-chain SFAs (M/LCSFAs) in hamster plasma.

METHODS

We compared three methods (DOLE, Folch and MTBE) for extracting M/LCSFAs from plasma. The M/LCSFA derivatives were separated using a C₁₈ column. The method was validated and applied to analyze M/LCSFA concentrations in normal-fat diet (NFD) and high-fat diet (HFD) hamster plasma.

RESULTS

Among the three extraction methods, the DOLE method had the highest extraction recovery and was simple to operate with a short incubation time. All of the calibration curves exhibited good linear relationships (r ≥ 0.9958). The results for selectivity, accuracy, precision, matrix effects and recovery were all within the acceptance criteria. In HFD hamster plasma, the concentration of M/LCSFAs with even-carbon chain length was significantly increased.

CONCLUSIONS

A simple, robust and reproducible method for the simultaneous quantification of M/LCSFAs by UHPLC/MS/MS was developed and validated. The method gave successfully quantification of M/LCSFAs in plasma samples from NFD and HFD hamsters.

Long-Chain Polyunsaturated Fatty Acid Concentrations and Association with Weight Gain in Pregnancy

Lower concentrations of omega-3 (ω-3) and higher concentrations of omega-6 (ω-6) have been associated with excess weight in adults; however, the information on this relationship in pregnancy remains in its infancy. This study aimed to investigate the association between plasma levels of ω-3 and ω-6 long-chain polyunsaturated fatty acids (PUFAs) and weight gain during the gestational period. This is a prospective cohort study involving 185 pregnant women registered with the prenatal services of a municipality in the northeast of Brazil. The dosage of the serum concentration of fatty acids and the anthropometric measurements were carried out at the baseline, and the women’s weight information in the first, second, and third trimesters was collected from their pregnancy cards. Serum fatty acids were determined with the help of gas chromatography. The response variable of this study is the latent variable weight gain in pregnancy, derived from three variables: gestational weight in the first, second, and third trimesters. The main exposure was the plasma concentrations of PUFAs. Structural equation modeling was used for the data analysis. The mean age of the pregnant women was 26.74 years old (SD: 5.96 years). Most of the women had not completed high school (84%) and had a low income (70.86%). It was observed that the ω-3 PUFAs, represented by ALA plasm (alpha-linolenic acid), DHA (docosahexaenoic acid), and the EPA/ALA ratio (eicosapentaenoic acid to alpha-linolenic acid ratio), were negatively associated with the weight gain during pregnancy construct (−0.20, −0.12, and −0.14, respectively). Meanwhile, the PUFAs represented by the ratio between the ω-6 category acids ARA and LA (arachidonic acid and linoleic acid) had a direct and positive association (0.22) with that construct. Excess maternal weight gain was associated with ω-3 and ω-6 plasma levels. The women with the greatest gestational weight gain were the ones that presented the highest ARA/LA ratio (ω-6) and the lowest plasma concentrations of ALA, DHA, and EPA/ALA ratio (ω-3).

Red blood cell triglycerides - a unique pool that incorporates plasma free fatty acids and relates to metabolic health

Most research into red blood cell (RBC) lipids focuses on membrane phospholipids and their relationships to metabolic conditions and diet. Triglycerides (TGs) exist in most cells; the TG-fatty acids serve as readily available fuel for oxidative phosphorylation. Because RBCs lack mitochondria, they would not be expected to store fatty acids in TG. We followed up on a previous in vitro study that found FFA can be incorporated into RBC-TG by testing whether intravenously infused [U-¹³C]palmitate could be detected in RBC-TG. We also quantified RBC-TG fatty acid concentrations and profiles as they relate to plasma FFA and lipid concentrations. We found that 1) RBC-TG concentrations measured by glycerol and LC/MS were correlated (r = 0.77; P < 0.001) and averaged <50 nmol/ml RBC; 2) RBC-TG concentrations were stable over 18 h; 3) [U-¹³C]palmitate was detectable in RBC-TG from half the participants; 4) RBC-TGs were enriched in saturated fatty acids and depleted in unsaturated fatty acid compared with plasma FFA and previously reported RBC membrane phospholipids; 5) RBC-TG fatty acid profiles differed significantly between obese and nonobese adults; 6) weight loss altered the RBC-TG fatty acid profile in the obese group; and 7) the RBC-TG fatty acid composition correlated with plasma lipid concentrations. This is the first report showing that plasma FFA contributes to RBC-TG in vivo, in humans, and that the RBC-TG fatty acid profile is related to metabolic health. The storage of saturated fatty acids in RBC-TG stands in stark contrast to the highly unsaturated profile reported in RBC membrane phospholipids.

Establishing age-stratified red blood cell fatty acid reference ranges using model-based clustering and iterative application of the harris-boyd method

BACKGROUND

The current assessment of nutritional status and diagnosis of essential fatty acids deficiency (EFAD) utilizes the analysis of long-chain fatty acids (LCFAs) in serum or plasma; however, these concentrations do not represent habitual LCFA intake. LCFAs in red blood cells (RBCs) are less prone to intra-individual variability and exclude the need for fasting, which is unrealistic in pediatric populations. Our study objective was to characterize the RBC LCFA profiles in pediatric and adult reference populations and establish age-specific reference intervals (RIs).

METHODS

Twenty-one LCFAs in RBCs were measured in 523 pediatric and adult controls by gas chromatography-mass spectrometry. Model-based clustering was used to identify possible age subgroups. After removing outliers by the Tukey method, initial age subgroups were then compared using the Harris-Boyd method in an iterative manner. RIs (95%), with confidence intervals (90%), in the final age groups were established using parametric or non-parametric statistics.

RESULTS

Our data showed heterogeneous changes in the concentrations of most LCFAs and the EFAD biomarkers (mead acid, Triene/Tetraene ratio) during infancy. Model-based clustering identified six initial age subgroups per fatty acid, on average. Our application of the iterative Harris-Boyd method decreased the average number of age groups to three per fatty acid, with 13 total unique age cut-offs. Finally, using these age groups, we established age-specific RIs for 21 fatty acids, six group totals, and the Triene/Tetraene ratio.

CONCLUSION

Our study revealed significant age-dependent changes in RBC fatty acid profiles warranting separate pediatric and adults RIs. Model-based clustering and the iterative application of the Harris-Boyd method were successfully used to establish RBC fatty acid RIs for an objective assessment of long-term nutritional status in pediatric and adult populations.

Dairy Fat Intake, Plasma Pentadecanoic Acid, and Plasma Iso-heptadecanoic Acid Are Inversely Associated With Liver Fat in Children

OBJECTIVES

We sought to evaluate the relevance of pediatric dairy fat recommendations for children at risk for nonalcoholic fatty liver disease (NAFLD) by studying the association between dairy fat intake and the amount of liver fat. The effects of dairy fat may be mediated by odd chain fatty acids (OCFA), such as pentadecanoic acid (C15:0), and monomethyl branched chain fatty acids (BCFA), such as iso-heptadecanoic acid (iso-C17:0). Therefore, we also evaluated the association between plasma levels of OCFA and BCFA with the amount of liver fat.

METHODS

Observational, cross-sectional, community-based sample of 237 children ages 8 to 17. Dairy fat intake was assessed by 3 24-hour dietary recalls. Plasma fatty acids were measured by gas chromatography-mass spectrometry. Main outcome was hepatic steatosis measured by whole liver magnetic resonance imaging proton density fat fraction (MRI-PDFF).

RESULTS

Median dairy fat intake was 10.6 grams/day (range 0.0--44.5 g/day). Median liver MRI-PDFF was 4.5% (range 0.9%-45.1%). Dairy fat intake was inversely correlated with liver MRI-PDFF (r = -0.162; P = .012). In multivariable log linear regression, plasma C15:0 and iso-C17:0 were inverse predictors of liver MRI-PDFF (B = -0.247, P = 0.048; and B = -0.234, P = 0.009).

CONCLUSIONS

Dairy fat intake, plasma C15:0, and plasma iso-C17:0 were inversely correlated with hepatic steatosis in children. These hypothesis-generating findings should be tested through clinical trials to better inform dietary guidelines.

Use of Fish Oil Intravenous Lipid Emulsions as Monotherapy in the Pediatric Intestinal Failure Patient: Beyond the Package Insert

In July 2018, an intravenous lipid emulsion (ILE) composed of 100% fish oil (Omegaven, Fresenius Kabi, Bad Homburg, Germany) received Food and Drug Administration (FDA) approval as a source of fatty acids and calories for infants and children with parenteral nutrition-associated cholestasis. This soy-free fat source is rich in ω-3 fatty acids and α-tocopherol and contains few phytosterols. In comparison to conventional soybean oil ILE, this emulsion appears to be less hepatotoxic. The purpose of this paper is to guide the practitioner on the use of this alternative fat source in clinical practice and augment the material contained in the current package insert. This paper addresses various topics including the identification of which patients would benefit from fish oil ILE, dosing, administration, monitoring, potential adverse effects, and management strategies for fish oil ILE.

Psd2 pea defensin shows a preference for mimetic membrane rafts enriched with glucosylceramide and ergosterol

Psd2 is a pea defensin with 47 amino acid residues that inhibits the growth of fungal species by an uncharacterized mechanism. In this work, Psd2 interactions with model membranes mimicking the lipid compositions of different organisms were evaluated. Protein-lipid overlay assays indicated that Psd2 recognizes Fusarium solani glucosylceramide (GlcCerF.solani) and ergosterol (Erg) in addition to phosphatidylcholine (POPC) and some phosphatidylinositol species, such as PtdIns (3)P, (5)P and (3,5)P2, suggesting that these lipids may play important roles as Psd2 targets. Assays using lipid vesicles were also performed to study the behaviour and dynamics that occur after peptide-membrane interactions. Surface plasmon resonance analysis showed that Psd2 has a higher affinity for pure POPC and POPC-based vesicles containing GlcCer and Erg at a 70:30 proportion than for vesicles containing cholesterol (Chol). Partition experiments by fluorescence spectroscopy showed a decrease in Trp42 quantum yield of Psd2 in the presence of GlcCerF.solani and Erg, individually or in simultaneously enriched membranes. The partition coefficient (Kp) obtained indicated a Psd2 partition preference for this vesicles, confirmed by quenching assays using acrylamide and 5/16-doxyl-stearic acid. Furthermore, we showed that the presence of C8C9 double bonds and a methyl group at position C9 of the sphingoid base backbone of GlcCer was relevant to Psd2 activity against Aspergillus nidulans. These results are consistent with the selectivity of Psd2 against fungi and its lack of toxicity in human erythrocytes. Psd2 represents a promising natural compound for the treatment of fungal infections.