Levels Of Lipid Classes Research Articles

APOE genotype‐specific lipidomic signatures in primary human hepatocytes

AbstractBackgroundApolipoprotein E (APOE) is primarily responsible for cholesterol homeostasis in the periphery and in the brain through independently regulated pathways, as it does not cross the blood‐brain barrier (BBB). Carriers of the APOE ε4 allele have a 3‐ to 15‐fold higher risk of developing Alzheimer’s disease (AD). Recently, we demonstrated that hepatic APOE4 was associated with alterations in AD‐relevant brain functions, suggesting clinical significance of plasma APOE, 90% of which is derived from the liver. How APOE genotype affects the hepatic lipidome is yet unknown. In this study, we assessed APOE genotype‐specific lipidomic profiles of primary human hepatocytes and their association with hepatic APOE.MethodWe conducted a lipidomic analysis of primary human hepatocytes isolated from 77 subjects by use of Ultra Performance Liquid Chromatography‐Tandem Mass Spectrometry. Lipid class levels over age across ε2/ε3, ε3/ε3 and ε3/ε4 genotypes were assessed using Pearson correlation analysis and between‐group comparisons for lipid class and species levels, controlled for demographic variables, were performed using one‐way ANOVA with Tukey HSD correction for multiple comparisons. We assessed hepatic APOE levels by ELISA in order to compare APOE expression between APOE genotypes and investigate correlations with lipid levels.ResultWe found APOE allele‐specific lipidomic patterns over age and between groups. APOE genotype differentially modulated the relationship between age and lipid levels across multiple lipid classes. The ε4 carriers had higher acylcarnitines (AC) and acylphosphatidylglycerol (AcylPG) as a class, as well as higher medium and long‐chain ACs, AcylPG, bis(monoacylglycerol)phosphate (BMP), monoacylglycerol and diacylglycerol species compared to ε2 carriers. Hepatocyte APOE levels decreased with age in the whole cohort, but correlated with monoacylglycerols (MG) and phosphatidylcholine (PC) only in ε4 carriers. We observed no differences in APOE hepatocyte levels specific to genotype or sex of the donor.ConclusionAPOE genotype dictates a differential lipidome in primary human hepatocytes but has no effect on APOE levels. The lipids involved suggest mitochondrial dysfunction with accompanying alterations in neutral lipid storage, reflective of a general disturbance of free fatty acid metabolism in human hepatocytes with the ε4 allele.

Role of Lipids of the Evergreen Shrub Ephedra monosperma in Adaptation to Low Temperature in the Cryolithozone

Lipids are the fundamental components of cell membranes and they play a significant role in their integrity and fluidity. The alteration in lipid composition of membranes has been reported to be a major response to abiotic environmental stresses. Seasonal dynamics of membrane lipids in the shoots of Ephedra monosperma J.G. Gmel. ex C.A. Mey. growing in natural conditions of permafrost ecosystems was studied using HPTLC, GC-MS and ESI-MS. An important role of lipid metabolism was established during the autumn-winter period when the shoots of the evergreen shrub were exposed to low positive (3.6 °C), negative (-8.3 °C) and extremely low temperatures (-38.4 °C). Maximum accumulation of phosphatidic acid (PA), the amount of which is times times greater than the sum of phosphatidylcholine and phosphatidylethanolamine (PC + PE) was noted in shoots of E. monosperma in the summer-autumn period. The autumn hardening period (3.6 °C) is accompanied by active biosynthesis and accumulation of membrane lipids, a decrease of saturated 34:1 PCs, 34:1 PEs and 34:1 PAs, and an increase in unsaturated long-chain 38:5 PEs, 38:6 PEs, indicating that the adaptation of E. monosperma occurs not at the level of lipid classes but at the level of molecular species. At a further decrease of average daily air temperature in October (-8.3 °C) a sharp decline of PA level was registered. At an extreme reduction of environmental temperature (-38.4 °C) the content of non-bilayer PE and PA increases, the level of unsaturated fatty acids (FA) rises due to the increase of C18:2(Δ9,12) and C18:3(Δ9,12,15) acids and the decrease of C16:0 acids. It is concluded that changes in lipid metabolism reflect structural and functional reorganization of cell membranes and are an integral component of the complex process of plant hardening to low temperatures, which contributes to the survival of E. monosperma monocotyledonous plants in the extreme conditions of the Yakutia cryolithozone.

Implication of adipocytes from subcutaneous adipose tissue and fatty acids in skin inflammation caused by λ-carrageenin in gilthead seabream (Sparusaurata)

The role of subcutaneous adipose tissue adipocytes and the effects of fatty acids on carrageenan-induced skin inflammation in gilthead seabream (Sparus aurata) were studied. Fish were injected intramuscularly with phosphate-buffered saline (control) or λ-carrageenin (1%), and skin samples collected at the injection site at 3 and 6 h post-injection (p.i.) were processed for histological study. In addition, the presence and levels of lipid classes, fatty acid methyl esters (FAME) and eicosanoids were evaluated in the skin samples obtained from the injected areas. Histological results indicated an increase in adipocyte area in fish sampled at 3 h p.i. with λ-carrageenin compared to fish in the control group. Furthermore, the frequency of adipocytes between 4500 and 5000 μm2 was increased at 6 h in the λ-carrageenin group compared to the control group. Analysis of lipid classes found that fish injected with λ-carrageenan showed increased free fatty acid (FFA) and sphingomyelin content at 3 and 6 h, respectively, compared to the control group. An increase in saturated fatty acids (SFA), n-6 polyunsaturated fatty acids (PUFA), and a decrease in the values of monounsaturated fatty acids (MUFA), n-3 PUFA and minor fatty acids were observed in fish skin at 6 h after λ-carrageenin injection, with respect to the values obtained in the control group. Regarding the analysis of eicosanoids, an increase in hydroxyeicosatetraenoic acid (5-HETE) was detected in the skin of fish at 6 h post-carrageenin injection compared to the control group. The presented results indicate the contribution of adipocytes and fatty acids in the development and regulation of the inflammatory response triggered by λ-carrageenin in gilthead seabream skin.

Identification of novel lipid biomarkers in xmrk- and Myc-induced models of hepatocellular carcinoma in zebrafish

BackgroundHepatocellular carcinoma (HCC) is the predominant form of liver cancer and is accompanied by complex dysregulation of lipids. Increasing evidence suggests that particular lipid species are associated with HCC progression. Here, we aimed to identify lipid biomarkers of HCC associated with the induction of two oncogenes, xmrk, a zebrafish homolog of the human epidermal growth factor receptor (EGFR), and Myc, a regulator of EGFR expression during HCC.MethodsWe induced HCC in transgenic xmrk, Myc, and xmrk/Myc zebrafish models. Liver specimens were histologically analyzed to characterize the HCC stage, Oil-Red-O stained to detect lipids, and liquid chromatography/mass spectrometry analyzed to assign and quantify lipid species. Quantitative real-time polymerase chain reaction was used to measure lipid metabolic gene expression in liver samples. Lipid species data was analyzed using univariate and multivariate logistic modeling to correlate lipid class levels with HCC progression.ResultsWe found that induction of xmrk, Myc and xmrk/Myc caused different stages of HCC. Lipid deposition and class levels generally increased during tumor progression, but triglyceride levels decreased. Myc appears to control early HCC stage lipid species levels in double transgenics, whereas xmrk may take over this role in later stages. Lipid metabolic gene expression can be regulated by either xmrk, Myc, or both oncogenes. Our computational models showed that variations in total levels of several lipid classes are associated with HCC progression.ConclusionsThese data indicate that xmrk and Myc can temporally regulate lipid species that may serve as effective biomarkers of HCC progression.

Lipidomic profiling in patients with heavily pretreated castration-resistant prostate cancer.

174 Background: Despite the advent of chemotherapy and androgen-receptor signaling inhibitors (ARSi), patients with metastatic castration-resistant prostate cancer (mCRPC) still show poor prognosis and reduced survival. The selective pressure induced by treatments favors the activation of alternative metabolic pathways that allow the persistence of cancer cells in unfavorable conditions. This study aimed at assessing the lipidomic profiles of patients with mCRPC, in order to identify lipid species potentially useful to predict for prognosis and response to therapies. Methods: Plasma samples were collected from patients with mCRPC who were starting a first-line treatment for mCRPC (1L) (n = 30) and from those who had already received at least two lines of treatment for mCRPC ( > 2L) (n = 19), including at least one ARSi and a taxane. Lipids were extracted from plasma samples using a modified Matyash method employing a mix of cold MeOH and MTBE and containing a mix of deuterated standards (Splash Lipidomix). Lipids were then analyzed with an untargeted lipidomic approach using an UHPLC Vanquish system coupled with a Q-Exactive Plus instrument. T-test was then applied to identify lipid species and classes that were differentially expressed in 1L vs < 2L patients. Results: We identified and quantified a total of 907 plasma lipids. Overall, 68 lipid species were significantly dysregulated in > 2L compared to 1L plasma samples. 56 species were found to be upregulated, whereas 12 were downregulated, with a fold change (FC) > 1.3 or < 0.75 and a p-value < 0.05. At the level of lipid classes, > 2L patients showed higher levels of acylcarnitine (CAR), diacylglycerols (DG), phosphatidylethanolamine (PE) and triacylglycerols (TG). The following lipids showed the highest FC: DG28:2 = 4.2; CAR14:0 = 3.7; CAR20:1 = 2.6; CAR18:0 = 2.3; PE40:6 = 2.3. Conversely, significantly lower levels of specific phosphatidylcholines (PC) and sterols (ST) were found in > 2L compared to 1L patients. The following species showed the lowest FC: PCO-39:3 = 0.52; ST29:1;O;S = 0.55; PC36:5 = 0.55; PC36.4 = 0.60. These results suggest that patients with strongly pretreated mCRPC show higher levels of lipid species involved in the switch between the glucose and fatty acid metabolism. We also found a dysregulation of ceramides and sphingomyelins which are well-known lipid species involved in apoptosis and cancer progression. Specific lipids warrant further investigation to be used as potential prognostic and predictive biomarkers in patients with mCRPC. Conclusions: Using a quantitative mass spectrometry approach, we investigated the dysregulation of lipids and lipid metabolism in mCRPC patients at different disease stages. We found that specific lipid species show differential levels in patients pretreated with ARSi and chemotherapy, compared to those who are naïve to these treatments, paving the way for further investigations in this field.

Lipid remodeling associated with chitooligosaccharides-induced heat tolerance of marine macroalgae Gracilariopsis lemaneiformis

Heat stress is a detrimental environmental factor limiting the growth and productivity of Gracilariopsis lemaneiformis, one of the most important economic marine red algae, and its adverse effects are expected to increase in the near future due to global warming. Thus, understanding the heat stress response of G. lemaneiformis and enhancing its ability to adapt to high temperatures have become of critical importance to aquaculture development. Previous study found that chitooligosaccharides (COS) can effectively alleviate the adverse effects of heat stress and enhance the heat tolerance of G. lemaneiformis. Although membrane lipids are of fundamental importance to the survival of plants under abiotic stress, whether membrane lipid adjustment is associated with COS-induced thermotolerance of G. lemaneiformis and possible related mechanism are still unclear. In this work, the variations of the lipid metabolic pathways of G. lemaneiformis in response to COS and subsequent heat stress are investigated. As manifested by transcriptomic profiles, the expression of genes involved in glycerolipid metabolism, glycerophospholipid metabolism, fatty acid metabolism, and alpha-linolenic acid metabolism were significantly enhanced in COS-induced thermotolerant G. lemaneiformis. Consistently, lipidomics analysis further revealed that glycerolipids of G. lemaneiformis, such as monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulfoquinovosyldiacylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid were significantly accumulated in response to COS and subsequent heat stress. Elevated unsaturation levels of lipid classes and free fatty acids might also be an effective strategy for improving thermotolerance in COS-induced G. lemaneiformis. Notably, jasmonic acid and ethylene have potential roles in the regulation of the COS-induced heat resistance of G. lemaneiformis. These results not only advance our understanding of the molecular mechanisms underlying the survival strategy of G. lemaneiformis under heat stress but also pave the way for the molecular breeding of the thermotolerant G. lemaneiformis.

Macrophage maturation from blood monocytes is altered in people with HIV, and is linked to serum lipid profiles and activation indices: A model for studying atherogenic mechanisms.

People with HIV (PWH) are at increased risk for atherosclerotic cardiovascular disease (ASCVD). Proportions of vascular homing monocytes are enriched in PWH; however, little is known regarding monocyte-derived macrophages (MDMs) that may drive atherosclerosis in this population. We isolated PBMCs from people with and without HIV, and cultured these cells for 5 days in medium containing autologous serum to generate MDMs. Differential gene expression (DGE) analysis of MDMs from PWH identified broad alterations in innate immune signaling (IL-1β, TLR expression, PPAR βδ) and lipid processing (LXR/RXR, ACPP, SREBP1). Transcriptional changes aligned with the functional capabilities of these cells. Expression of activation markers and innate immune receptors (CD163, TLR4, and CD300e) was altered on MDMs from PWH, and these cells produced more TNFα, reactive oxygen species (ROS), and matrix metalloproteinases (MMPs) than did cells from people without HIV. MDMs from PWH also had greater lipid accumulation and uptake of oxidized LDL. PWH had increased serum levels of free fatty acids (FFAs) and ceramides, with enrichment of saturated FAs and a reduction in polyunsaturated FAs. Levels of lipid classes and species that are associated with CVD correlated with unique DGE signatures and altered metabolic pathway activation in MDMs from PWH. Here, we show that MDMs from PWH display a pro-atherogenic phenotype; they readily form foam cells, have altered transcriptional profiles, and produce mediators that likely contribute to accelerated ASCVD.

High-Performance Thin-Layer Chromatography Coupled with Electrospray Ionization Tandem Mass Spectrometry for Identifying Neutral Lipids and Sphingolipids in Complex Samples.

High-performance thin-layer chromatography was directly combined with electrospray mass spectrometry (ESI-MS) for structural identification issues below the level of lipid classes in complex samples through a portable, automated, elution-based interface. For samples as diverse as biodiesel and human plasma, separation conditions using Automated Multiple Development were selected in each case to provide lipid classes as zones narrow enough to ensure a direct transfer of them to ESI-MS. The respective zone of interest can be selected at will. ESI+ spectra of neutral lipids and sphingolipids showed sodium adducts when recorded from the plate. By using the described technique and ion-trap technology, the respective sodium adducts were fragmented. Sodium remained as the charge of the fragment ions and, thus, was useful for their structural identification through MSn. In this way, composition profiles of each class by ESI+-MS, and further identification of individual lipids and the molecular species belonging to each of them, were obtained by MS/MS and/or high-resolution MS. Thus, mono and diacylglycerides in ESI+ and fatty acids (in ESI-) were identified as low-concentration impurities in a fatty acid methyl ester-based biodiesel sample. Likewise, molecular species of sphingomyelins and globotriaosylceramides were unequivocally identified in human plasma samples.

Seasonal and interannual variation in the lipid content and composition of Euphausia superba Dana, 1850 (Euphausiacea) samples derived from the Scotia Sea fishery

The Antarctic krill (Euphausia superba Dana, 1850) is an important trophic link between phytoplankton and higher trophic levels. Knowledge of the lipid biochemistry of krill assists in understanding their seasonal biology and predicting their responses to ecological changes. We collected daily samples of krill from a commercial fishing vessel operating in the Atlantic Sector of the Southern Ocean from 2014 to 2016. We analysed the total lipid content of krill sampled every two weeks and the relative distribution of lipid class levels to examine seasonal trends. Krill total lipid content varied significantly within and between seasons and sexes. An annual sinusoidal trend was seen in total lipid content with the highest values in autumn and the lowest in spring (average 380 and 87 mg/g dry mass, respectively). Total lipids in krill increased during summer, peaking in autumn, with the total lipids in winter individuals decreasing towards spring. The relative distribution of lipid class levels varied between season and year. Levels of triacylglycerol showed the same seasonal trend as total lipid content, whilst phospholipid showed the inverse trend indicating the contrasting roles of these two dominant lipid classes. These data provide high-resolution information on the seasonality of krill lipid content and composition. This information has both ecological and commercial utility. ​

Prepartal overfeeding alters the lipidomic profiles in the liver and the adipose tissue of transition dairy cows

Physiological adaptations in the energy metabolism of dairy cows during the periparturient period are partly mediated by insulin resistance (IR), which may subsequently induce metabolic disorders postpartum. The molecular mechanisms underlying IR in dairy cows are largely unknown. This study aimed to find a novel insight into the molecular mechanisms underlying IR in dairy cows during the periparturient period by analyzing the effects of prepartal overfeeding on the lipidomic profiles in the liver and adipose tissue (AT). Sixteen cows were allocated to controlled-energy and high-energy feeding groups. Lipidomic profiling was conducted on liver and adipose tissue samples collected at 8 days prior to the predicted parturition, and 1 day (only AT) and 9 days after the actual parturition. Five ceramides (Cers) were identified to be significantly increased by prepartal overfeeding in AT in the analysis of the variance between groups within time points. Principal component-linear discriminant analysis showed that lipidomic profiles between the feeding groups were mainly characterized by phosphatidylcholines (PC), phosphatidylethanolamines (PE), lysophophosphatidylcholines (LysoPC), and lysophosphatidylethanolamines (LysoPE) in the liver, and by Cer, PE, and phosphatidylinositols (PI) in AT. Lipid class levels indicated that prepartal overfeeding elevated the concentration of PE, PI, LysoPC, LysoPE, and sphingomyelin in the liver, and increased the concentration of Cer in AT during the periparturient period. Prepartal overfeeding significantly altered the concentrations of various sphingolipids, phospholipids, and lysophospholipids in the liver and AT of dairy cows during the periparturient period.

Blood plasma lipidomic signature of epicardial fat in healthy obese women.

A lipidomic approach was employed in a clinically well-defined cohort of healthy obese women to explore blood lipidome phenotype ascribed to body fat deposition, with emphasis on epicardial adipose tissue (EAT). The present investigation delivered a lipidomics signature of epicardial adiposity under healthy clinical conditions using a cohort of 40 obese females (age: 25-45 years, BMI: 28-40 kg/m(2) ) not showing any metabolic disease traits. Lipidomics analysis of blood plasma was employed in combination with in vivo quantitation of mediastinal fat depots by computerized tomography. All cardiac fat depots correlated to indicators of hepatic dysfunctions (ALAT and ASAT), which describe physiological connections between hepatic and cardiac steatosis. Plasma lipidomics encompassed overall levels of lipid classes, fatty acid profiles, and individual lipid species. EAT and visceral fat associated with diacylglycerols (DAG), triglycerides, and distinct phospholipid and sphingolipid species. A pattern of DAG and phosphoglycerols was specific to EAT. Human blood plasma lipidomics appears to be a promising clinical and potentially diagnostic readout for patient stratification and monitoring. Association of blood lipidomics signature to regio-specific mediastinal and visceral adiposity under healthy clinical conditions may help provide more biological insights into obese patient stratification for cardiovascular disease risks.

Aging bone marrow mesenchymal stromal cells have altered membrane glycerophospholipid composition and functionality

Human mesenchymal stem/stromal cells (hMSC) are increasingly used in advanced cellular therapies. The clinical use of hMSCs demands sequential cell expansions. As it is well established that membrane glycerophospholipids (GPL) provide precursors for signaling lipids that modulate cellular functions, we studied the effect of the donor's age and cell doublings on the GPL profile of human bone marrow MSC (hBMSC). The hBMSCs, which were harvested from five young and five old adults, showed clear compositional changes during expansion seen at the level of lipid classes, lipid species, and acyl chains. The ratio of phosphatidylinositol to phosphatidylserine increased toward the late-passage samples. Furthermore, 20:4n-6-containing species of phosphatidylcholine and phosphatidylethanolamine accumulated while the species containing monounsaturated fatty acids (FA) decreased during passaging. Additionally, in the total FA pool of the cells, 20:4n-6 increased, which happened at the expense of n-3 polyunsaturated FAs, especially 22:6n-3. The GPL and FA correlated with the decreased immunosuppressive capacity of hBMSCs during expansion. Our observations were further supported by alterations in the gene expression levels of several enzymes involved in lipid metabolism and immunomodulation. The results show that extensive expansion of hBMSCs harmfully modulates membrane GPLs, affecting lipid signaling and eventually impairing functionality.

Complete replacement of dietary fish oil with a vegetable oil blend affect liver lipid and plasma lipoprotein levels in Atlantic salmon (Salmo salar L.)

To study how hepatic lipid turnover and lipid transport may be affected by complete replacement of dietary fish oil (FO) with a vegetable oil blend (VO) from start feeding until the adult stages, Atlantic salmon (Salmo salar L.) were fed either 100% FO- or 100% VO-based diets (55% rapeseed oil, 30% palm oil and 15% linseed oil) from start feeding until 22 months. Liver and plasma lipoprotein lipid class levels and lipoprotein fatty acid composition were analysed through the seawater phase, whereas liver fatty acid composition, plasma cholesterol, triacylglycerol (TAG) and protein levels were analysed through both freshwater and seawater stages. Further, enzyme activity of liver fatty acid synthetase (FAS), NADH-isocitrate dehydrogenase, malic enzyme, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and expression of the gene Peroxisome proliferator-activated receptor γ (PPARγ) was analysed during both fresh water and seawater stages through the experiment. Dietary VO significantly increased salmon liver TAG and hence total liver lipid stores after 14 and 22 months of feeding. Further, after 22 months of feeding, plasma lipid levels and plasma low-density lipoprotein (LDL) levels were significantly decreased in VO-fed salmon compared with FO-fed fish. The same trend, although not statistically significant, was seen for plasma very low-density lipoprotein (VLDL). The activity of FAS was generally low throughout the experiment with the VO group having significantly lower activity after 16 months of feeding. The expression of PPARγ in livers increased prior to seawater transfer followed by a decrease, and then another increase towards the final sampling (22 months). Dietary vegetable oil replacement had no impact on PPARγ expression in salmon liver. In summary, liver TAG stores, plasma lipid and LDL levels were affected by dietary vegetable oil replacement in Atlantic salmon during a long–term feeding experiment. Current results indicate that high dietary vegetable oil inclusion increase hepatic TAG stores and decrease plasma lipid levels possible through decreased VLDL synthesis.

Lipid class and glycogen content of the lugworm Abarenicola pacifica in relation to age, growth rate and reproductive condition

We measured the levels of lipid classes (wax esters, triacylglycerides, free fatty acids, sterols, phospholipids) and levels of glycogen in a population of Abarenicola pacifica over a one-year period beginning shortly after recruitment. Glycogen and lipid contents were unrelated to growth rates as estimated by changes in average size of individuals in the cohort. There was no indication of seasonality in levels of any component, consistent with the hypothesis of Slobodkin and Richman that animals living in environments where food supplies are likely to be stable, such as subsurface deposit-feeders like A. pacifica, do not accumulate energy reserves. Instead, glycogen content increased gradually and most lipid classes decreased gradually over time. A notable exception was the triacylglyceride content, which showed a large increase associated with the formation of eggs. Triacylglyceride levels in older A. pacifica and in two other species of depositfeeding polychaetes showed similar trends. Measurement of triacylglyceride levels may provide an additional objective method, supplementing egg counts and egg size, of quantifying reproductive effort in deposit-feeders.

Impact of gamma-BHC on lipid class levels and their modulation by reproductive hormones in the freshwater catfish, Heteropneustes fossilis.

In the present study an attempt has been made to explore the effect of sublethal concentration of an organochlorine agricultural pesticide {gamma}-BHC (1,2,3,4,5,6-hexachlorocyclohexane) on phospholipids, free cholesterol and esterified cholesterol levels in liver, plasma, and ovary during reproductively active phases, i.e., preparatory and prespawning phases in the female catfish, Heteropneustes fossilis. Modulatory role of oLH-RH and mGTH on pesticides induced changes on above lipids were also evaluated.

Temperature-induced changes in the lipid molecular species of a thermophilic cyanobacterium, Mastigocladus laminosus.

Temperature-induced changes in lipid molecular species of a thermophilic cyanobacterium, Mastigocladus laminosus, were investigated. The cells were grown at 48°C phototrophically, and transferred at mid-log phase to 40°C and 55°C. The lipids in the cells grown at dilferent temperatures were extracted, analyzed, and compared. The cells acclimated to decreasing and increasing temperatures by altering the constituent longer fatty acids and lipid class levels. The variation in fatty acids caused great changes in molecular species of lipids. The ways of changing lipid molecular species may have differed among lipid classes. Thermal analysis of the lipids showed that thermograms of the membrane lipids were greatly affected by the growth temperature, suggesting that proper changes in the membrane fluidity are required.

Iatroscan-measured profiles of dissolved and particulate marine lipid classes over the Scotian Slope and in Bedford Basin

The Chromarod-Iatroscan thin-layer chromatography-flame ionization detection (TLC-FID) system was used to measure lipid classes in the dissolved and suspended particulate fractions of seawater samples taken near the edge of the Scotian Shelf and in Bedford Basin, a small Nova Scotian inlet. Vertical profiles within the surface waters of these environments suggest considerable spatial heterogeneity in lipid class levels and warn against assuming any uniformity in the composition of dissolved or particulate matter. The levels of lipid classes measured below the pycnocline were about half the values observed above it. The highest levels of lipids were measured in the vicinity of pycnoclines.

Seasonal variations of the major lipid classes in relation to the reproductive activity of two species of clams raised in a common habitat: Tapes decussatus L. (Jeffreys, 1863) and T. philippinarum (Adams & Reeve, 1850)

The relative and absolute levels of four major lipid classes in an indigenous and an introduced adult clam population raised in a common habitat were determined over a 74-wk period. The standard animal of each population contained a low and stable amount of the fraction containing wax esters, hydrocarbons, and sterol esters. The absolute levels of triacylglycerols and phospholipids closely followed the indices of reproductive activity. Following the summer spawning a severe negative energy balance was observed throughout the winter. During this period, both triacylglycerols and phospholipid contributed to the maintenance energy, although the phospholipids' contribution was greater in both populations. A comparison of the seasonal variations of absolute and relative values underscores the advantages of absolute values in the calculation of lipid class levels. Although some specific differences were found in mean lipid class levels, the overall seasonal variations of the lipid classes were similar in both populations.

Storage and depletion of lipid components in the pyloric caeca and ovaries of the seastarAsterias rubens during its annual reproductive cycle

Detailed information is presented on the changes in lipid-class profiles (polar lipids, total neutral lipids, free sterols, steryl esters, triacylglycerols, neutral ether lipids and free fatty acids), which are manifest during the annual reproductive cycle of the seastarAsterias rubens for both the storage organs (pyloric caeca) and utilizing organs (ovaries). The ovaries appear to accumulate all individual lipid components proportional to progression of vitellogenesis. Pyloric caeca, in contrast, show variable lipid-class levels, probably due to more complex processes in these organs, operating simultaneously: digestion of food, accumulation of storage lipids, mobilization of stored lipids and their release. The results are discussed in terms of current knowledge on the role of lipids in echinoderm reproduction.

Effects of palm-kernel oil and sunflower-seed oil on serum lipids and atherogenesis in alloxan-diabetic rabbits

Groups of metabolically normal (controls) and alloxan-diabetic adult female rabbits were fed semi-synthetic diets containing 40 cal % palm-kernel oil (PKO) or sunflower-seed oil (SSO) for 54 weeks. In contrast to control rabbits fed PKO-diet, the alloxan-diabetic rabbits on this diet, developed no or only a negligible degree of atherosclerosis, although the serum levels of all lipid classes had increased in the diabetic rabbits above that of the controls during almost the whole experimental period. The diabetic rabbits and the controls fed SSO-diet were both free from any significant atherosclerotic involvement in spite of the fact that the SSO-diet appeared unable to suppress the very high levels of the various serum lipid classes induced by the diabetic state. On both diets, the diabetic rabbits showed a significantly higher cholesteryl linoleate/oleate ratio than the controls, which was caused by an increase in the cholesteryl linoleate level in the diabetics. No serious aorta atherosclerosis was found in rabbits with a cholesteryl linoleate/oleate ratio higher than 0.6, although no correlation was found between the atherosclerosis indices and these ratios at values lower than 0.6. Rabbits with cholesteryl linoleate/oleate ratios below 0.6 seemed to run a greater risk of developing atherosclerosis. It is suggested that insulin might be required for atherogenesis in addition to hyperlipemia and hypercholesterolemia.