Arachidonic acid and docosahexaenoic acid levels correlate with the inflammation proteome in extremely preterm infants

BACKGROUND & AIM

Clinical trials supplementing the long-chain polyunsaturated fatty acids (LCPUFAs) docosahexaenoic acid (DHA) and arachidonic acid (AA) to preterm infants have shown positive effects on inflammation-related morbidities, but the molecular mechanisms underlying these effects are not fully elucidated. This study aimed to determine associations between DHA, AA, and inflammation-related proteins during the neonatal period in extremely preterm infants.

METHODS

A retrospective exploratory study of infants (n = 183) born below 28 weeks gestation from the Mega Donna Mega trial, a randomized multicenter trial designed to study the effect of DHA and AA on retinopathy of prematurity. Serial serum samples were collected after birth until postnatal day 100 (median 7 samples per infant) and analyzed for phospholipid fatty acids and proteins using targeted proteomics covering 538 proteins. Associations over time between LCPUFAs and proteins were explored using mixed effect modeling with splines, including an interaction term for time, and adjusted for gestational age, sex, and center.

RESULTS

On postnatal day one, 55 proteins correlated with DHA levels and 10 proteins with AA levels. Five proteins were related to both fatty acids, all with a positive correlation. Over the first 100 days after birth, we identified 57 proteins to be associated with DHA and/or AA. Of these proteins, 41 (72%) related to inflammation. Thirty-eight proteins were associated with both fatty acids and the overall direction of association did not differ between DHA and AA, indicating that both LCPUFAs similarly contribute to up- and down-regulation of the preterm neonate inflammatory proteome. Primary examples of this were the inflammation-modulating cytokines IL-6 and CCL7, both being negatively related to levels of DHA and AA in the postnatal period.

CONCLUSIONS

This study supports postnatal non-antagonistic and potentially synergistic effects of DHA and AA on the inflammation proteome in preterm infants, indicating that supplementation with both fatty acids may contribute to limiting the disease burden in this vulnerable population.

CLINICAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT03201588).

Enteral supplementation with arachidonic and docosahexaenoic acid and pulmonary outcome in extremely preterm infants

Enteral supplementation with arachidonic acid (AA) and docosahexaenoic acid (DHA) in extremely preterm infants has shown beneficial effects on retinopathy of prematurity and pulmonary outcome whereas exclusive DHA supplementation has been associated with increased pulmonary morbidity. This secondary analysis evaluates pulmonary outcome in 204 extremely preterm infants, randomized to receive AA (100 mg/kg/day) and DHA (50 mg/kg/day) enterally from birth until term age or standard care. Pulmonary morbidity was primarily assessed based on severity of bronchopulmonary dysplasia (BPD). Serum levels of AA and DHA during the first 28 days were analysed in relation to BPD. Supplementation with AA:DHA was not associated with increased BPD severity, adjusted OR 1.48 (95 % CI 0.85-2.61), nor with increased need for respiratory support at post menstrual age 36 weeks or duration of oxygen supplementation. Every 1 % increase in AA was associated with a reduction of BPD severity, adjusted OR 0.73 (95 % CI 0.58-0.92). In conclusion, in this study, with limited statistical power, enteral supplementation with AA:DHA was not associated with an increased risk of pulmonary morbidity, but higher levels of AA were associated with less severe BPD. Whether AA or the combination of AA and DHA have beneficial roles in the immature lung needs further research.

The development of blood protein profiles in extremely preterm infants follows a stereotypic evolution pattern

BACKGROUND

Preterm birth is the leading cause of neonatal mortality and morbidity. Early diagnosis and interventions are critical to improving the clinical outcomes of extremely premature infants. Blood protein profiling during the first months of life in preterm infants can shed light on the role of early extrauterine development and provide an increased understanding of maturation after extremely preterm birth and the underlying mechanisms of prematurity-related disorders.

METHODS

We have investigated the blood protein profiles during the first months of life in preterm infants on the role of early extrauterine development. The blood protein levels were analyzed using next generation blood profiling on 1335 serum samples, collected longitudinally at nine time points from birth to full-term from 182 extremely preterm infants.

RESULTS

The protein analysis reveals evident predestined serum evolution patterns common for all included infants. The majority of the variations in blood protein expression are associated with the postnatal age of the preterm infants rather than any other factors. There is a uniform protein pattern on postnatal day 1 and after 30 weeks postmenstrual age (PMA), independent of gestational age (GA). However, during the first month of life, GA had a significant impact on protein variability.

CONCLUSIONS

The unified pattern of protein development for all included infants suggests an age-dependent stereotypic development of blood proteins after birth. This knowledge should be considered in neonatal settings and might alter the clinical approach within neonatology, where PMA is today the most dominant age variable.

Modification of serum fatty acids in preterm infants by parenteral lipids and enteral docosahexaenoic acid/arachidonic acid: A secondary analysis of the Mega Donna Mega trial

BACKGROUND & AIM

Preterm infants risk deficits of long-chain polyunsaturated fatty acids (LCPUFAs) that may contribute to morbidities and hamper neurodevelopment. We aimed to determine longitudinal serum fatty acid profiles in preterm infants and how the profiles are affected by enteral and parenteral lipid sources.

METHODS

Cohort study analyzing fatty acid data from the Mega Donna Mega study, a randomized control trial with infants born <28 weeks of gestation (n = 204) receiving standard nutrition or daily enteral lipid supplementation with arachidonic acid (AA):docosahexaenoic acid (DHA) (100:50 mg/kg/day). Infants received an intravenous lipid emulsion containing olive oil:soybean oil (4:1). Infants were followed from birth to postmenstrual age 40 weeks. Levels of 31 different fatty acids from serum phospholipids were determined by GC-MS and reported in relative (mol%) and absolute concentration (μmol l-1) units.

RESULTS

Higher parenteral lipid administration resulted in lower serum proportion of AA and DHA relative to other fatty acids during the first 13 weeks of life (p < 0.001 for the 25th vs the 75th percentile). The enteral AA:DHA supplement increased the target fatty acids with little impact on other fatty acids. The absolute concentration of total phospholipid fatty acids changed rapidly in the first weeks of life, peaking at day 3, median (Q1-Q3) 4452 (3645-5466) μmol l-1, and was positively correlated to the intake of parenteral lipids. Overall, infants displayed common fatty acid trajectories over the study period. However, remarkable differences in fatty acid patterns were observed depending on whether levels were expressed in relative or absolute units. For example, the relative levels of many LCPUFAs, including DHA and AA, declined rapidly after birth while their absolute concentrations increased in the first week of life. For DHA, absolute levels were significantly higher compared to cord blood from day 1 until postnatal week 16 (p < 0.001). For AA, absolute postnatal levels were lower compared to cord blood from week 4 throughout the study period (p < 0.05).

CONCLUSIONS

Our data show that parenteral lipids aggravate the postnatal loss of LCPUFAs seen in preterm infants and that serum AA available for accretion is below that in utero. Further research is needed to establish optimal postnatal fatty acid supplementation and profiles in extremely preterm infants to promote development and long-term health.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov, identifier: NCT03201588.

Costs associated with retinopathy of prematurity: a systematic review and meta-analysis

OBJECTIVES

To review and analyse evidence regarding costs for retinopathy of prematurity (ROP) screening, lifetime costs and resource use among infants born preterm who develop ROP, and how these costs have developed over time in different regions.

DESIGN

Systematic review and meta-analysis DATA SOURCES: PubMed and Scopus from inception to 23 June 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Included studies presented costs for ROP screening and the lifetime costs (including laser treatment and follow-up costs) and resource use among people who develop ROP. Studies not reporting on cost calculation methods or ROP-specific costs were excluded.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers screened for inclusion and extracted data, including items from a published checklist for quality assessment used for bias assessment, summary and random-effects meta-analysis for treatment costs. Included studies were further searched to identify eligible references and citations.

RESULTS

In total, 15 studies reported ROP screening costs, and 13 reported lifetime costs (either treatment and/or follow-up costs) for infants with ROP. The range for screening costs (10 studies) was US$5-US$253 per visit, or US$324-US$1072 per screened child (5 studies). Costs for treatment (11 studies) ranged from US$38 to US$6500 per child. Four studies reported healthcare follow-up costs (lifetime costs ranging from US$64 to US$2420, and 10-year costs of US$1695, respectively), and of these, three also reported lifetime costs for blindness (range US$26 686-US$224 295) using secondary cost data. Included papers largely followed the quality assessment checklist items, thus indicating a low risk of bias.

CONCLUSION

The costs of screening for and treating ROP are small compared with the societal costs of resulting blindness. However, little evidence is available for predicting the effects of changes in patient population, screening schedule or ROP treatments.

PROSPERO REGISTRATION NUMBER

CRD42020208213.

Preterm infant circulating sex steroid levels are not altered by transfusion with adult male plasma: a retrospective multicentre cohort study

OBJECTIVE

To determine if plasma transfusions with male donor plasma to very preterm infants affect circulatory levels of sex steroids.

DESIGN AND PATIENTS

Retrospective multicentre cohort study in 19 infants born at gestational age <29 weeks requiring plasma transfusion during their first week of life.

SETTING

Three neonatal intensive care units in Sweden.

MAIN OUTCOME MEASURES

Concentrations of sex steroids and sex hormone-binding globulin (SHBG) in donor plasma and infant plasma measured before and after a plasma transfusion and at 6, 12, 24 and 72 hours.

RESULTS

The concentrations of progesterone, dehydroepiandrosterone and androstenedione were significantly lower in donor plasma than in infant plasma before the transfusion (median (Q1-Q3) 37.0 (37.0-37.0), 1918 (1325-2408) and 424 (303-534) vs 901 (599-1774), 4119 (2801-14 645) and 842 (443-1684) pg/mL), while oestrone and oestradiol were higher in donor plasma (17.4 (10.4-20.1) and 16.0 (11.7-17.2) vs 3.1 (1.1-10.2) and 0.25 (0.25-0.25) pg/mL). Median testosterone and dihydrotestosterone (DHT) levels were 116-fold and 21-fold higher in donor plasma than pre-transfusion levels in female infants, whereas the corresponding difference was not present in male infants. Plasma sex steroid levels were unchanged after completed transfusion compared with pre-transfusion levels, irrespective of the gender of the receiving infant. The SHBG concentration was significantly higher in donor than in recipient plasma (22.8 (17.1-33.5) vs 10.2 (9.1-12.3) nmol/L) before transfusion but did not change in the infants after the transfusion.

CONCLUSIONS

A single transfusion of adult male plasma to preterm infants had no impact on circulating sex steroid levels.

Maternal n-3 Polyunsaturated Fatty Acid Enriched Diet Commands Fatty Acid Composition in Postnatal Brain and Protects from Neonatal Arterial Focal Stroke

The fetus is strongly dependent on nutrients from the mother, including polyunsaturated fatty acids (PUFA). In adult animals, n-3 PUFA ameliorates stroke-mediated brain injury, but the modulatory effects of different PUFA content in maternal diet on focal arterial stroke in neonates are unknown. This study explored effects of maternal n-3 or n-6 enriched PUFA diets on neonatal stroke outcomes. Pregnant mice were assigned three isocaloric diets until offspring reached postnatal day (P) 10–13: standard, long-chain n-3 PUFA (n-3) or n-6 PUFA (n-6) enriched. Fatty acid profiles in plasma and brain of mothers and pups were determined by gas chromatography–mass spectrometry and cytokines/chemokines by multiplex protein analysis. Transient middle cerebral artery occlusion (tMCAO) was induced in P9-10 pups and cytokine and chemokine accumulation, caspase-3 and calpain-dependent spectrin cleavage and brain infarct volume were analyzed. The n-3 diet uniquely altered brain lipid profile in naïve pups. In contrast, cytokine and chemokine levels did not differ between n-3 and n-6 diet in naïve pups. tMCAO triggered accumulation of inflammatory cytokines and caspase-3-dependent and -independent cell death in ischemic-reperfused regions in pups regardless of diet, but magnitude of neuroinflammation and caspase-3 activation were attenuated in pups on n-3 diet, leading to protection against neonatal stroke. In conclusion, maternal/postnatal n-3 enriched diet markedly rearranges neonatal brain lipid composition and modulates the response to ischemia. While standard diet is sufficient to maintain low levels of inflammatory cytokines and chemokines under physiological conditions, n-3 PUFA enriched diet, but not standard diet, attenuates increases of inflammatory cytokines and chemokines in ischemic-reperfused regions and protects from neonatal stroke.

Association of Docosahexaenoic Acid and Arachidonic Acid Serum Levels With Retinopathy of Prematurity in Preterm Infants

IMPORTANCE

Supplementing preterm infants with long-chain polyunsaturated fatty acids (LC-PUFA) has been inconsistent in reducing the severity and incidence of retinopathy of prematurity (ROP). Furthermore, few studies have measured the long-term serum lipid levels after supplementation.

OBJECTIVE

To assess whether ROP severity is associated with serum levels of LC-PUFA, especially docosahexaenoic acid (DHA) and arachidonic acid (AA), during the first 28 postnatal days.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study analyzed the Mega Donna Mega study, a randomized clinical trial that provided enteral fatty acid supplementation at 3 neonatal intensive care units in Sweden. Infants included in this cohort study were born at a gestational age of less than 28 weeks between December 20, 2016, and August 6, 2019.

MAIN OUTCOMES AND MEASURES

Severity of ROP was classified as no ROP, mild or moderate ROP (stage 1-2), or severe ROP (stage 3 and type 1). Serum phospholipid fatty acids were measured through gas chromatography-mass spectrometry. Ordinal logistic regression, with a description of unadjusted odds ratio (OR) as well as gestational age- and birth weight-adjusted ORs and 95% CIs, was used. Areas under the curve were used to calculate mean daily levels of fatty acids during postnatal days 1 to 28. Blood samples were obtained at the postnatal ages of 1, 3, 7, 14, and 28 days.

RESULTS

A total of 175 infants were included in analysis. Of these infants, 99 were boys (56.6%); the median (IQR) gestational age was 25 weeks 5 days (24 weeks 3 days to 26 weeks 6 days), and the median (IQR) birth weight was 785 (650-945) grams. A higher DHA proportion was seen in infants with no ROP compared with those with mild or moderate ROP or severe ROP (OR per 0.5-molar percentage increase, 0.49 [95% CI, 0.36-0.68]; gestational age- and birth weight-adjusted OR, 0.66 [95% CI, 0.46-0.93]). The corresponding adjusted OR for AA levels per 1-molar percentage increase was 0.83 (95% CI, 0.66-1.05). The association between DHA levels and ROP severity appeared only in infants with sufficient AA levels, suggesting that a mean daily minimum level of 7.8 to 8.3 molar percentage of AA was necessary for a detectable association between DHA level and less severe ROP.

CONCLUSIONS AND RELEVANCE

This cohort study found that higher mean daily serum levels of DHA during the first 28 postnatal days were associated with less severe ROP even after adjustment for known risk factors, but only in infants with sufficiently high AA levels. Further studies are needed to identify LC-PUFA supplementation strategies that may prevent ROP and other morbidities.

Sphingolipidomics of serum in extremely preterm infants: Association between low sphingosine-1-phosphate levels and severe retinopathy of prematurity

BACKGROUND

Extremely preterm infants are at risk of developing retinopathy of prematurity (ROP) that can cause impaired vision or blindness. Changes in blood lipids have been associated with ROP. This study aimed to monitor longitudinal changes in the serum sphingolipidome of extremely preterm infants and investigate the relationship to development of severe ROP.

METHODS

This is a prospective study that included 47 infants born <28 gestational weeks. Serum samples were collected from cord blood and at postnatal days 1, 7, 14, and 28, and at postmenstrual weeks (PMW) 32, 36, and 40. Serum sphingolipids and phosphatidylcholines were extracted and analyzed by LC-MS/MS. Associations between sphingolipid species and ROP were assessed using mixed models for repeated measures.

RESULTS

The serum concentration of all investigated lipid classes, including ceramide, mono- di- and trihexosylceramide, sphingomyelin, and phosphatidylcholine displayed distinct temporal patterns between birth and PMW40. There were also substantial changes in the lipid species composition within each class. Among the analyzed sphingolipid species, sphingosine-1-phosphate showed the strongest association with severe ROP, and this association was independent of gestational age at birth and weight standard deviation score change.

CONCLUSIONS

The serum phospho- and sphingolipidome undergoes significant remodeling during the first weeks of the preterm infant's life. Low postnatal levels of the signaling lipid sphingosine-1-phosphate are associated with the development of severe ROP.

Effect of Enteral Lipid Supplement on Severe Retinopathy of Prematurity: A Randomized Clinical Trial

IMPORTANCE

Lack of arachidonic acid (AA) and docosahexaenoic acid (DHA) after extremely preterm birth may contribute to preterm morbidity, including retinopathy of prematurity (ROP).

OBJECTIVE

To determine whether enteral supplementation with fatty acids from birth to 40 weeks' postmenstrual age reduces ROP in extremely preterm infants.

DESIGN, SETTING, AND PARTICIPANTS

The Mega Donna Mega trial, a randomized clinical trial, was a multicenter study performed at 3 university hospitals in Sweden from December 15, 2016, to December 15, 2019. The screening pediatric ophthalmologists were masked to patient groupings. A total of 209 infants born at less than 28 weeks' gestation were tested for eligibility, and 206 infants were included. Efficacy analyses were performed on as-randomized groups on the intention-to-treat population and on the per-protocol population using as-treated groups. Statistical analyses were performed from February to April 2020.

INTERVENTIONS

Infants received either supplementation with an enteral oil providing AA (100 mg/kg/d) and DHA (50 mg/kg/d) (AA:DHA group) or no supplementation within 3 days after birth until 40 weeks' postmenstrual age.

MAIN OUTCOMES AND MEASURES

The primary outcome was severe ROP (stage 3 and/or type 1). The secondary outcomes were AA and DHA serum levels and rates of other complications of preterm birth.

RESULTS

A total of 101 infants (58 boys [57.4%]; mean [SD] gestational age, 25.5 [1.5] weeks) were included in the AA:DHA group, and 105 infants (59 boys [56.2%]; mean [SD] gestational age, 25.5 [1.4] weeks) were included in the control group. Treatment with AA and DHA reduced severe ROP compared with the standard of care (16 of 101 [15.8%] in the AA:DHA group vs 35 of 105 [33.3%] in the control group; adjusted relative risk, 0.50 [95% CI, 0.28-0.91]; P = .02). The AA:DHA group had significantly higher fractions of AA and DHA in serum phospholipids compared with controls (overall mean difference in AA:DHA group, 0.82 mol% [95% CI, 0.46-1.18 mol%]; P < .001; overall mean difference in control group, 0.13 mol% [95% CI, 0.01-0.24 mol%]; P = .03). There were no significant differences between the AA:DHA group and the control group in the rates of bronchopulmonary dysplasia (48 of 101 [47.5%] vs 48 of 105 [45.7%]) and of any grade of intraventricular hemorrhage (43 of 101 [42.6%] vs 42 of 105 [40.0%]). In the AA:DHA group and control group, respectively, sepsis occurred in 42 of 101 infants (41.6%) and 53 of 105 infants (50.5%), serious adverse events occurred in 26 of 101 infants (25.7%) and 26 of 105 infants (24.8%), and 16 of 101 infants (15.8%) and 13 of 106 infants (12.3%) died.

CONCLUSIONS AND RELEVANCE

This study found that, compared with standard of care, enteral AA:DHA supplementation lowered the risk of severe ROP by 50% and showed overall higher serum levels of both AA and DHA. Enteral lipid supplementation with AA:DHA is a novel preventive strategy to decrease severe ROP in extremely preterm infants.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03201588.

Analysis of Brain Injury Biomarker Neurofilament Light and Neurodevelopmental Outcomes and Retinopathy of Prematurity Among Preterm Infants

IMPORTANCE

Circulating levels of neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) are important in the course of brain injury in adults, but longitudinal postnatal circulating levels in preterm infants have not been investigated.

OBJECTIVES

To examine postnatal longitudinal serum levels of NfL and GFAP in preterm infants during the first 15 weeks of life and to explore possible associations between these biomarkers, neonatal morbidities, and neurodevelopmental outcomes at 2 years.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from 3 clinical studies, including 221 infants born before 32 weeks gestational age (GA) from 1999 to 2015; neurodevelopmental outcomes were evaluated in 120 infants. Data were collected at tertiary-level neonatal intensive care units in Gothenburg, Lund, and Uppsala, Sweden. Data analysis was conducted from January to October 2020.

EXPOSURE

Preterm birth.

MAIN OUTCOMES AND MEASURES

Serum NfL and GFAP levels, retinopathy of prematurity (ROP), intraventricular hemorrhage, and Bayley Scales of Infant Development II and III at 2 years of age, analyzed by multivariate logistic regression measured by odds ratio (OR), and receiver operating characteristic curve (ROC) analysis. Area under the curve (AUC) was also measured.

RESULTS

The 221 included infants (108 [48.9%] girls) had a mean (SD) GA at birth of 26.5 (2.1) weeks and a mean (SD) birth weight of 896 (301) grams. NfL levels increased after birth, remaining high during the first 4 weeks of life before declining to continuously low levels by postnatal age 12 weeks (median [range] NfL level at birth: 58.8 [11.5-1371.3] ng/L; 1 wk: 83.5 [14.1-952.2] ng/L; 4 wk: 24.4 [7.0-306.0] ng/L; 12 wk: 9.1 [3.7-57.0] ng/L). In a binary logistic regression model adjusted for GA at birth, birth weight SD score, Apgar status at 5 minutes, and mode of delivery, the NfL AUC at weeks 2 to 4 was independently associated with any ROP (OR, 4.79; 95% CI, 2.17-10.56; P < .001). In an exploratory analysis adjusted for GA at birth and sex, NfL AUC at weeks 2 to 4 was independently associated with unfavorable neurodevelopmental outcomes at 2 years corrected age (OR per 10-unit NfL increase, 1.07; 95% CI, 1.02-1.13; P = .01). Longitudinal GFAP levels were not significantly associated with neonatal morbidity or neurodevelopmental outcome.

CONCLUSIONS AND RELEVANCE

In this study, high NfL levels during the first weeks of life were associated with ROP and poor neurodevelopmental outcomes at 2 years of age. Associations between NfL and later neurovascular development in infants born prematurely should be investigated further.

Inflammatory Markers in Suction Blister Fluid: A Comparative Study Between Interstitial Fluid and Plasma

Background

Biomarker analysis allows for the detection and prediction of disease as well as health monitoring. The use of interstitial fluid (ISF) as a matrix for biomarkers has recently gained interest. This study aimed to compare levels of inflammatory markers in ISF from suction blister fluid (SBF) and plasma.

Methods

Plasma and SBF were collected from 18 healthy individuals. Samples were analyzed for 92 inflammation-related protein biomarkers by Proximity Extension Assay (PEA). Protein profiles in the two matrices were compared using traditional and multivariate statistics.

Results

Out of 92 targeted proteins, 70 were successfully quantified in both plasma and SBF. Overall, plasma and SBF displayed distinct protein profiles with up to 40-fold difference in abundance of specific proteins. The levels of 25 proteins were significantly correlated between plasma and SBF and several of these were recognized as potential markers to monitor health using ISF.

Conclusions

Skin ISF and plasma have unique protein profiles but many inflammatory markers are proportionally related between the matrices at the individual level. ISF is a promising biofluid for the monitoring of biomarkers in clinical studies and routine analyses.

Lipid profiling of suction blister fluid: comparison of lipids in interstitial fluid and plasma

BACKGROUND

Recent technical advances in the extraction of dermal interstitial fluid (ISF) have stimulated interest in using this rather unexploited biofluid as an alternative to blood for detection and prediction of disease. However, knowledge about the presence of useful biomarkers for health monitoring in ISF is still limited. In this study, we characterized the lipidome of human suction blister fluid (SBF) as a surrogate for pure ISF and compared it to that of plasma.

METHODS

Plasma and SBF samples were obtained from 18 healthy human volunteers after an overnight fast. Total lipids were extracted and analyzed by liquid chromatography-tandem mass spectrometry. One hundred ninety-three lipid species covering 10 complex lipid classes were detected and quantified in both plasma and SBF using multiple reaction monitoring. A fraction of the lipid extract was subjected to alkaline transesterification and fatty acid methyl esters were analyzed by gas chromatography-mass spectrometry.

RESULTS

The total concentration of lipids in SBF was 17% of the plasma lipid concentration. The molar fraction of lipid species within lipid classes, as well as total fatty acids, showed a generally high correlation between plasma and SBF. However, SBF had larger fractions of lysophospholipids and diglycerides relative to plasma, and consequently less diacylphospholipids and triglycerides. Principal component analysis revealed that the interindividual variation in SBF lipid profiles was considerably larger than the within-subject variation between plasma and SBF.

CONCLUSIONS

Plasma and SBF lipid profiles show high correlation and SBF could be used interchangeably with blood for the analysis of major lipids used in health monitoring.

CSF neurogranin or tau distinguish typical and atypical Alzheimer disease

Objective

To assess whether high levels of cerebrospinal fluid neurogranin are found in atypical as well as typical Alzheimer's disease.

Methods

Immunoassays were used to measure cerebrospinal fluid neurogranin in 114 participants including healthy controls (n = 27), biomarker-proven amnestic Alzheimer's disease (n = 68), and the atypical visual variant of Alzheimer's (n = 19) according to international criteria. CSF total-tau, Aβ42, and neurofilament light concentrations were investigated using commercially available assays. All affected individuals had T1-weighted volumetric MR images available for analysis of whole and regional brain volumes. Associations between neurogranin, brain volumes, total-tau, Aβ42, and neurofilament light were assessed.

Results

Median cerebrospinal fluid neurogranin concentrations were higher in typical and atypical Alzheimer's compared to controls (P < 0.001 and P = 0.005). Both neurogranin and total-tau concentrations, but not neurofilament light and Aβ42, were higher in typical Alzheimer's compared to atypical patients (P = 0.004 and P = 0.03). There were significant differences in the left hippocampus and right and left superior parietal lobules in atypical patients, which were larger (P = 0.03) and smaller (P = 0.001 and P < 0.001), respectively, compared to typical patients. We found no evidence of associations between neurogranin and brain volumes but a strong association with total-tau (P < 0.001) and a weaker association with neurofilament light (P = 0.005).

Interpretation

These results show significant differences in neurogranin and total-tau between typical and atypical patients, which may relate to factors other than disease topography. The differential relationships between neurogranin, total-tau and neurofilament light in the Alzheimer's variants, provide evidence for mechanistically distinct and coupled markers of neurodegeneration.