Dietary Sterols Research Articles

Plant Sterol-Enriched Palm Oil Intervention to Improve Lipid Profile and Inflammation Status in Hyperlipidemic Individuals.

Background: Cardiovascular diseases, including coronary heart disease (CHD), are currently positioned among the leading causes of mortality globally. Risk factors of CHD include, among others, hypercholesterolemia and elevations in systemic inflammation. Functional foods enriched with compounds showing cholesterol-lowering effects are considered one among various dietary and lifestyle intervention strategies to tackle this problem. A CHD-preventive effect of dietary plant sterols has been broadly discussed, not only due to their ability to reduce blood cholesterol level, but also to their proven anti-inflammatory potential. Palm oil is one of the most widely consumed edible oils in the world. Despite its widespread use, especially in Asian countries, no study has been conducted using palm oil as a vehicle for plant sterols. Methods: The aim of the placebo-controlled double-blinded trial presented here was, therefore, to evaluate the effect of palm oil enriched with plant sterols, used as a cooking oil, on lipid profile and systemic inflammation marker in 100 adult hyperlipidemic residents of Bogor, Indonesia. Results: The study has shown a significant reduction in total cholesterol and LDL cholesterol level in study subjects consuming plant sterol-enriched palm oil as a replacement for usual palm oil for cooking, with no similar effect on CRP levels. Conclusions: The study suggests that, along with a healthy diet and lifestyle promotion, incorporating plant sterols in palm oil used for cooking may be an effective strategy to reduce cardiovascular risks in hyperlipidemic individuals.

Genetic characterization of candidate ecdysteroid kinases in Drosophila melanogaster.

Ecdysteroids are major hormones in insects and control molting, growth, reproduction, physiology, and behavior. The biosynthesis of ecdysteroids such as 20-hydroxyecdysone (20E) from dietary sterols is well characterized, but ecdysteroid catabolism is poorly understood. Ecdysteroid kinases (EcKs) mediate the reversible phosphorylation of ecdysteroids, which has been implicated in ecdysteroid recycling during embryogenesis and reproduction in various insects. However, to date, only 2 EcK-encoding genes have been identified, in the silkworm Bombyx mori and the mosquito Anopheles gambiae. Previously, we identified 2 ecdysteroid kinase-like (EcKL) genes-Wallflower (Wall) and Pinkman (pkm)-in the model fruit fly Drosophila melanogaster that are orthologs of the ecdysteroid 22-kinase gene BmEc22K. Here, using gene knockdown, knockout, and misexpression, we explore Wall and pkm's possible functions and genetically test the hypothesis that they encode EcKs. Wall and pkm null mutants are viable and fertile, suggesting that they are not essential for development or reproduction, whereas phenotypes arising from RNAi and somatic CRISPR appear to derive from off-target effects or other artifacts. However, misexpression of Wall results in dramatic phenotypes, including developmental arrest, and defects in trachea, cuticle, and pigmentation. Wall misexpression fails to phenocopy irreversible ecdysteroid catabolism through misexpression of Cyp18a1, suggesting that Wall does not directly inactivate 20E. Additionally, Wall misexpression phenotypes are not attenuated in Cyp18a1 mutants, strongly suggesting that Wall is not an ecdysteroid 26-kinase. We hypothesize that the substrate of Wall in this misexpression experiment and possibly generally is an unknown, atypical ecdysteroid that plays essential roles in Drosophila development, and may highlight aspects of insect endocrinology that are as-yet uncharacterized. We also provide preliminary evidence that CG5644 encodes an ecdysteroid 22-kinase conserved across Diptera.

In vivo functional analysis of the cotton bollworm Helicoverpa armigera 24-dehydrocholesterol reductase (HaDHCR24) in phytosterol metabolism.

Insects have to obtain sterols from food due to the inability to synthesize this essential nutrient de novo. For lepidopteran insects, they can convert a variety of phytosterols into cholesterol to meet their growth needs. The final step of the cholesterol biosynthesis is the metabolism of desmosterol catalyzed by 24-dehydrocholesterol reductase (DHCR24). In this study, we identified a DHCR24 homolog in the cotton bollworm Helicoverpa armigera, designated as H. armigera 24-dehydrocholesterol reductase (HaDHCR24)-1. The quantitative expression analyses indicated that HaDHCR24-1 was highly enriched in the midgut where dietary sterol uptake occurs. Compared to the control, the DHCR24-1 mutant larvae generated by clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 technology accumulated more desmosterol in the gut, while the content of cholesterol was significantly reduced. A similar phenomenon was observed when the DHCR24 inhibitor, amiodarone, was applied to the insects. Moreover, DHCR24-1 played an important role for the usage of β-sitosterol, a major sterol in plants, in H. armigera, and loss of function of DHCR24-1 resulted in higher mortality on β-sitosterol. However, the DHCR24 homolog does not necessarily exist in the genomes of all insects. The loss of this gene occurred more frequently in the insects feeding on animals, which further support the role of DHCR24-1 in using phytosterols. This gene may have important potential in developing new strategies to control herbivory pests in Lepidoptera and other insect orders.

Life history of rotifers under temporally heterogeneous dietary sterol conditions

Life history of rotifers under temporally heterogeneous dietary sterol conditions

Association of ABCG5 and ABCG8 Transporters with Sitosterolemia.

Sitosterolemia is a rare genetic lipid disorder, mainly characterized by the accumulation of dietary xenosterols in plasma and tissues. It is caused by inactivating mutations in either ABCG5 or ABCG8 subunits, a subfamily-G ATP-binding cassette (ABCG) transporters. ABCG5/G8 encodes a pair of ABC half transporters that form a heterodimer (G5G8). This heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the hepatobiliary and transintestinal secretion of cholesterol and dietary plant sterols to the surface of hepatocytes and enterocytes, promoting the secretion of cholesterol and xenosterols into the bile and the intestinal lumen. In this way, ABCG5/G8 function in the reverse cholesterol transport pathway and mediate the efflux of cholesterol and xenosterols to high-density lipoprotein and bile salt micelles, respectively. Here, we review the biological characteristics and function of ABCG5/G8, and how the mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis, among other features.

Mandibular glands secrete 24-methylenecholesterol into honey bee (Apis mellifera) food jelly

Honey bee (Apis mellifera) workers feed their larvae with food jelly that is secreted by specialized glands in their heads – the hypopharyngeal and the mandibular glands. Food jelly contains all the nutrients the larvae need to develop into adult honey bees, including essential dietary sterols. The main sterol in food jelly, 24-methylenecholesterol (24MC), is pollen-derived and delivered in food jelly to the larvae in a complex with two proteins, major royal jelly protein 1 (MRJP1) and apisim. Whereas the proteins are synthesized in the hypopharyngeal glands, the sterol-secreting gland has not been identified. We here identified the mandibular glands as sterol-secreting gland for food jelly production by direct detection of the four main honey bee sterols (24MC, campesterol, β-sitosterol and isofucosterol). Furthermore, 24MC seems to be specifically enriched in the mandibular glands, thereby ensuring that food jelly contains the amounts of 24MC necessary for complex formation with MRJP1 and apisimin.

Association of dietary intake of polyphenols, lignans, and phytosterols with immune-stimulating microbiota and COVID-19 risk in a group of Polish men and women.

Devastating consequences of COVID-19 disease enhanced the role of promoting prevention-focused practices. Among targeted efforts, diet is regarded as one of the potential factors which can affect immune function and optimal nutrition is postulated as the method of augmentation of people's viral resistance. As epidemiological evidence is scarce, the present study aimed to explore the association between dietary intake of total polyphenols, lignans and plant sterols and the abundance of immunomodulatory gut microbiota such as Enterococcus spp. and Escherichia coli and the risk of developing COVID-19 disease. Demographic data, dietary habits, physical activity as well as the composition of body and gut microbiota were analyzed in a sample of 95 young healthy individuals. Dietary polyphenol, lignan and plant sterol intakes have been retrieved based on the amount of food consumed by the participants, the phytochemical content was assessed in laboratory analysis and using available databases. For all investigated polyphenols and phytosterols, except campesterol, every unit increase in the tertile of intake category was associated with a decrease in the odds of contracting COVID-19. The risk reduction ranged from several dozen percent to 70 %, depending on the individual plant-based chemical, and after controlling for basic covariates it was statistically significant for secoisolariciresinol (OR = 0.28, 95% CI: 0.11-0.61), total phytosterols (OR = 0.47, 95% CI: 0.22-0.95) and for stigmasterols (OR = 0.34, 95% CI: 0.14-0.72). We found an inverse association between increased β-sitosterol intake and phytosterols in total and the occurrence of Escherichia coli in stool samples outside reference values, with 72% (OR = 0.28, 95% CI: 0.08-0.86) and 66% (OR = 0.34, 95% CI: 0.10-1.08) reduced odds of abnormal level of bacteria for the highest compared with the lowest tertile of phytochemical consumption. Additionally, there was a trend of more frequent presence of Enterococcus spp. at relevant level in people with a higher intake of lariciresinol. The beneficial effects of polyphenols and phytosterols should be emphasized and these plant-based compounds should be regarded in the context of their utility as antiviral agents preventing influenza-type infections.

Medicinal Mushrooms: Their Bioactive Components, Nutritional Value and Application in Functional Food Production-A Review.

Medicinal mushrooms, e.g., Lion's Mane (Hericium erinaceus (Bull.) Pers.), Reishi (Ganoderma lucidum (Curtis) P. Karst.), Chaga (Inonotus obliquus (Ach. ex Pers.) Pilát), Cordyceps (Ophiocordyceps sinensis (Berk.) G.H. Sung, J.M. Sung, Hywel-Jones and Spatafora), Shiitake (Lentinula edodes (Berk.) Pegler), and Turkey Tail (Trametes versicolor (L.) Lloyd), are considered new-generation foods and are of growing interest to consumers. They are characterised by a high content of biologically active compounds, including (1,3)(1,6)-β-d-glucans, which are classified as dietary fibre, triterpenes, phenolic compounds, and sterols. Thanks to their low-fat content, they are a low-calorie product and are classified as a functional food. They have a beneficial effect on the organism through the improvement of its overall health and nutritional level. The biologically active constituents contained in medicinal mushrooms exhibit anticancer, antioxidant, antidiabetic, and immunomodulatory effects. In addition, these mushrooms accelerate metabolism, help fight obesity, and slow down the ageing processes thanks to their high antioxidant activity. The vast therapeutic properties of mushrooms are still not fully understood. Detailed mechanisms of the effects of medicinal mushrooms on the human organism still require long-term clinical studies to confirm their nutraceutical effects, their safety of use, and their dosage. Medicinal mushrooms have great potential to be used in the design of innovative functional foods. There is a need for further research on the possibility of incorporating mushrooms into food products to assess the interactions of their bioactive substances with ingredients in the food matrix. This review focuses on the properties of selected medicinal mushrooms and their effects on the human organism and presents current knowledge on the possibilities of their use in the production of functional foods.

Sterol Regulation of Development and 20-Hydroxyecdysone Biosynthetic and Signaling Genes in Drosophila melanogaster.

Ecdysteroids are crucial in regulating the growth and development of insects. In the fruit fly Drosophila melanogaster, both C27 and C28 ecdysteroids have been identified. While the biosynthetic pathway of the C27 ecdysteroid 20-hydroxyecdysone (20E) from cholesterol is relatively well understood, the biosynthetic pathway of C28 ecdysteroids from C28 or C29 dietary sterols remains unknown. In this study, we found that different dietary sterols (including the C27 sterols cholesterol and 7-dehydrocholesterol, the C28 sterols brassicasterol, campesterol, and ergosterol, and the C29 sterols β-sitosterol, α-spinasterol, and stigmasterol) differentially affected the expression of 20E biosynthetic genes to varying degrees, but similarly activated 20E primary response gene expression in D. melanogaster Kc cells. We also found that a single dietary sterol was sufficient to support D. melanogaster growth and development. Furthermore, the expression levels of some 20E biosynthetic genes were significantly altered, whereas the expression of 20E signaling primary response genes remained unaffected when flies were reared on lipid-depleted diets supplemented with single sterol types. Overall, our study provided preliminary clues to suggest that the same enzymatic system responsible for the classical C27 ecdysteroid 20E biosynthetic pathway also participated in the conversion of C28 and C29 dietary sterols into C28 ecdysteroids.

Abstract 447: Cholesterol Excretion In Whole-body And Liver-specific ABCG5 ABCG8-deficient Mice

Background: The ABCG5 ABCG8 sterol transporter is the body’s primary defense against the accumulation of dietary sterols. Loss of function mutations in ABCG5 or ABCG8 result in Sitosterolemia, a rare disorder that presents as familial hypercholesterolemia, but is distinguished by recessive genetics and the accumulation of phytosterols in plasma and tissues. Biliary cholesterol is reduced by greater than 80% in ABCG5 ABCG8-deficient mice, but fecal neutral sterols are unaffected, suggesting a G5G8-independent pathway for cholesterol excretion. The objectives of the present study were to determine the ability of whole-body and liver-specific G5G8-deficient mice to maintain fecal neutral sterol output when challenged with cholesterol -enriched diet and determine maximal rates of biliary cholesterol secretion. Methods: Wild-type, whole-body and liver-specific ABCG5 ABCG8-deficient mice were maintained on cereal-based mixed diet, a phytosterol-free purified diet, or a purified diet supplemented with 0.2% cholesterol. Following acclimatization to each diet, fecal neutral sterol output was determined over a three-day period by gas chromatography/mass spectrometry. Maximal biliary cholesterol secretion rates were determined by biliary diversion with bile acid infusion over a range of 0 to 1000 nmol/minute. Biliary lipid secretion was determined by enzymatic colorimetric assays and molecular coupling of cholesterol to bile acid and phospholipid secretion calculated by linear regression. Results & Conclusions: Whole-body G5G8-deficient mice exhibited a 40% reduction in fecal neutral sterol output compared to wild-type mice when maintained on cereal-based or purified, low cholesterol containing diets. Cholesterol feeding resulted in a 10-fold increase in fecal neutral sterols in wild-type mice, an effect not observed in G5G8-deficient mice. These data indicate that ABCG5 ABCG8 is indispensable in opposing the accumulation of dietary cholesterol and that alternative pathways cannot compensate for G5G8 deficiency.

Does sterol availability in a forested headwater stream constitute a nutritional constraint for macroinvertebrates?

ABSTRACT Headwater streams are characterised by predominantly heterotrophic functioning resulting from leaf litter input, but autochthonous primary production can also contribute to energy fluxes and the supply of nutrients. While much work has focused on the role of polyunsaturated fatty acids as essential nutrients, less attention has been paid to the significance of sterols in stream food webs. Yet these molecules are essential to arthropods that can only synthesise cholesterol from a limited range of dietary sterols. In a headwater stream, we tracked the transfer of dominant sterols from allochthonous and autochthonous resources to 5 benthic macroinvertebrates. Despite their formal functional feeding group, all the taxa tended to be opportunistic omnivores that relied on all available resources. These behaviours could be attributed to nutritional constraints in the stream food web, but these constraints were not related to the sterol supply from the different basal sources. Dominant sterols from detrital sources (leaf litter, fine benthic organic matter [FBOM]) and primary producers (epilithic biofilms, bryophytes) were all Δ5-sterols (β-sitosterol, campesterol, stigmasterol, epibrassicasterol). The levels of cholesterol detected in macroinvertebrates, as well as the presence of desmosterol, indicate efficient dealkylation activity of these Δ5-sterols. Leaf litter has consistently shown high β-sitosterol/stigmasterol ratios, giving it greater nutritional value than usually accepted. But bryophytes, and especially epilithic biofilms, contained cholesterol, providing a direct supply to invertebrates, thereby promoting their growth. Detrital particles (FBOM) colonised by microalgae could be the best-balanced diet to avoid sterol deficiencies due to their cholesterol content and high β-sitosterol/stigmasterol ratios.

Abstract P521: Association Between Dietary Phytosterols and Risk of Cardiovascular Disease Mortality in US Adults: Findings From the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994

Introduction: Phytosterols (plant sterols) are naturally occurring components of plant food sources, including vegetable oils, nuts, cereals and legumes. Their chemical structure impedes intestinal cholesterol absorption and regular consumption has been related to lower serum low-density cholesterol (LDL-C), a causal risk factor for cardiovascular disease (CVD). The association between dietary plant sterol intake and CVD has yet to be determined. Objective: We aimed to examine the association of phytosterol consumption in the diet with cardiovascular mortality in US adults the National Health & Nutrition Examination Survey III (NHANES III), 1988-1994. Methods: We conducted a prospective cohort analysis on National Health and Nutrition Examination Survey (NHANES, 1988-1994 [III]), linked with the National Death Index mortality data (2015) to associate dietary phytosterol intake from 24h dietary recall data with CVD mortality. We included 13,004 adults aged ≥20 years who were non-pregnant, free of CVD at baseline and completed ≥1 24h dietary recall with plausible caloric intake data. We excluded individuals with death occurring within 1 year of baseline. We created a database quantifying the phytosterol content of foods in the 24h dietary recall data and estimated usual intake by quintiles using the NCI method. We determined the risk function by regression calibration and estimated CVD mortality risk between the 10 th (Q1) and 90 th (Q5) percentiles of usual intake. Data was adjusted for sex, age, smoking status and ethnicity. Results: Over a mean±SD follow-up period of 21.2±5.1y, 949 CVD deaths occurred in a population with a mean±SD age of 44.2±14.3y, BMI 26.7±4.7 kg/m 2 and mean dietary plant sterol usual intake of 272.3 mg/day. The top sources of dietary phytosterols were from potatoes 23%), wheat and other grains (21%) and beans, legumes and nuts (13%). Mean usual intake plant intake in the 10 th (Q1) and 90 th (Q5) percentiles of the population was 150.1 and 414.0 mg/day. The estimated relative risk for CVD mortality between Q1 (ref) and Q5 was 0.972 (p<0.05). Conclusions: Preliminary analyses suggest a CVD death risk reduction of 2.8% in the highest versus lowest intakes of dietary plant sterols in the US population. We plan to expand the multivariable model to include the Healthy Eating Index (diet quality) and assess stratification by healthful and unhealthful sources of phytosterols and linear and non-linear dose response analyses to determine the robustness of the association. OSF Registration: osf.io/da4sg Funding: Amgen Scholars Program, Canadian Institutes of Health Research (CIHR), Banting and Best Diabetes Centre (BBDC), Toronto 3D Knowledge Synthesis and Clinical Trials foundation

A Mixture of Dietary Plant Sterols at Nutritional Relevant Serum Concentration Inhibits Extrinsic Pathway of Eryptosis Induced by Cigarette Smoke Extract.

Cell death program of red blood cells (RBCs), called eryptosis, is characterized by activation of caspases and scrambling of membrane phospholipids with externalization of phosphatidylserine (PS). Excessive eryptosis confers a procoagulant phenotype and is implicated in impairment of microcirculation and increased prothrombotic risk. It has recently been reported that cigarette smokers have high levels of circulating eryptotic erythrocytes, and a possible contribution of eryptosis to the vaso-occlusive complications associated to cigarette smoke has been postulated. In this study, we demonstrate how a mixture of plant sterols (MPtS) consisting of β-sitosterol, campesterol and stigmasterol, at serum concentration reached after ingestion of a drink enriched with plant sterols, inhibits eryptosis induced by cigarette smoke extract (CSE). Isolated RBCs were exposed for 4 h to CSE (10-20% v/v). When RBCs were co-treated with CSE in the presence of 22 µM MPtS, a significant reduction of the measured hallmarks of apoptotic death like assembly of the death-inducing signaling complex (DISC), PS outsourced, ceramide production, cleaved forms of caspase 8/caspase 3, and phosphorylated p38 MAPK, was evident. The new beneficial properties of plant sterols on CSE-induced eryptosis presented in this work open new perspectives to prevent the negative physio-pathological events caused by the eryptotic red blood cells circulating in smokers.

Drosophila melanogaster females prioritise dietary sterols for producing viable eggs

Limiting calories or specific nutrients without malnutrition, otherwise known as dietary restriction (DR), has been shown to extend lifespan and reduce reproduction across a broad range of taxa. Our recent findings in Drosophila melanogaster show that supplementing flies on macronutrient-rich diets with additional cholesterol can extend lifespan to the same extent as DR, while also sustaining high egg production. Thus, DR may be beneficial for lifespan because it reduces egg production which in turn reduces the mother’s demand for sterols, thus supporting longer lifespan. It is also possible that mothers live longer and lay more eggs on high sterol diets because the diet triggers enhanced somatic maintenance and promotes egg production, but at the cost of diminished egg quality. To test this, we measured the viability of eggs and development of offspring from mothers fed either cholesterol-sufficient or cholesterol-limiting diets. We found that even when the mother’s diet was completely devoid of cholesterol, viable egg production persisted for ∼10 days. Furthermore, we show that sterol-supplemented flies with long lives lay eggs that have high viability and the same developmental potential as those laid by shorter lived mothers on sterol limiting diets. These findings suggest that offspring viability is not a hidden cost of lifespan extension seen in response to dietary sterol supplementation.

Dietary Plant Sterols and Phytosterol-Enriched Margarines and Their Relationship with Cardiovascular Disease among Polish Men and Women: The WOBASZ II Cross-Sectional Study.

Dietary cholesterol has been suggested to increase the risk of cardiovascular disease (CVD). Phytosterols, present in food or phytosterol-enriched products, can reduce cholesterol available for absorption. The present study aimed to investigate the association between habitual intake of total and individual plant sterols (β-sitosterol, campesterol, and stigmasterol) or a diet combined with phytosterol-enriched products and CVD in a cross-section of Polish adults, participants of the Multicenter National Health Survey II (WOBASZ II). Among men (n = 2554), median intakes of plant sterols in terciles ranged between 183–456 mg/d and among women (n = 3136), 146–350 mg/d in terciles. The intake of phytosterols, when consumed with food containing phytosterols, including margarine, ranged between 184–459 mg/d for men and 147–352 mg/d for women. Among both men and women, beta-sitosterol intake predominated. Plant sterol intake was lower among both men and women with CVD (p = 0.016) compared to those without CVD. Diet quality, as measured by the Healthy Diet Index (HDI), was significantly higher in the third tercile of plant sterol intake for both men and women and the entire study group (p < 0.0001). This study suggests that habitual dietary intake of plant sterols may be associated with a lower chance of developing CVD, particularly in men.

Serum Phytosterols Are Not Associated with Inflammatory Markers in Two Cross-Sectional, Swiss Population-Based Studies (The CoLaus|PsyCoLaus Study).

Background: The association between inflammation and dietary sterols remains poorly assessed at the population level. Aims: To assess the possible association between serum levels of various phytosterols (PS) and inflammatory markers. Methods: Serum levels of six PS (campesterol, campestanol, stigmasterol, sitosterol, sitostanol, brassicasterol), four cholesterol synthesis markers (lathosterol, lanosterol, desmosterol, dihydroxylanosterol) and one cholesterol absorption marker (cholestanol) were measured together with levels of CRP, IL-6 and TNF-α in two cross-sectional surveys of a population-based, prospective study. Results: CRP levels were negatively associated with levels of cholestanol and of sterols of plant origin, although some associations were not statistically significant. CRP levels were positively associated with cholesterol synthesis markers in the first but not in the second follow-up. IL-6 levels were negatively associated with cholestanol in both follow-ups. No associations between IL-6 levels and PS were found in the first follow-up, while significant negative associations with campesterol, sitosterol, brassicasterol, sitostanol and campesterol:TC ratio were found in the second follow-up. TNF-α levels were negatively associated with cholestanol in both follow-ups. These associations did not withstand adjusting for sex, age, BMI and statin administration. Conclusions: In a population-based study, PS serum levels were not significantly associated with inflammatory markers.

Microalgal food sources greatly improve macroinvertebrate growth in detritus‐based headwater streams: Evidence from an instream experiment

Abstract In forested headwater streams, inconspicuous food resources such as epilithic microalgae can play a major role owing to their content of long chain polyunsaturated fatty acids (PUFAs) that are essential for macroinvertebrate development. Yet, the use of these resources and their consequences for consumers and life‐history traits remain scarcely studied, especially for non‐herbivorous taxa. Using instream mesocosms, we aimed to understand how two macroinvertebrate species, a shredder detritivore (Gammarus pulex) and a scraper (Rhithrogena semicolorata), use available organic resources under light versus shaded conditions (high and low amounts of phototrophic biofilm, respectively). We specifically focused on the origin of carbon (C) and essential lipids (PUFAs, sterols) assimilated by the two species and the effects of these compounds on their survival and growth. When autotrophic biofilms were available (mesocosms exposed to light), both species experienced significantly higher growth than in mesocosms placed in the dark. In Rhithrogena nymphs, the survival and imago emergence rates were positively affected by access to autotrophic biofilms. Using stable isotope analysis (δ13C and δ15N), we demonstrated that under dark conditions both macroinvertebrates assimilated C of detrital origin. Under light conditions, most of the C assimilated by R. semicolorata was derived from autotrophic biofilms and around 11% from fine detrital particles (FPOM). Gammarus pulex derived part of its C from detrital sources (mainly FPOM) and from autotrophic biofilms. The results of isotopic analyses (δ13C) on fatty acids (FAs) and sterols showed that the scraper Rhithrogena was entirely dependent on autotrophic biofilms to meet its dietary FAs and sterol requirements. In contrast, detrital sources were quantitatively important for G. pulex both in terms of C and sterol supply, irrespective of the conditions tested. For these consumers, microalgae seemed to be a complementary food source, but yet essential to cover a large part of their requirements in long‐chain PUFAs. This study clearly confirmed the ecological importance of autotrophic biofilms for two functional feeding groups of macroinvertebrates in headwater streams providing new insights on the trophic origin of sterols and long‐chain PUFAs in their diet.

A sterol-mediated gleaner-opportunist trade-off underlies the evolution of grazer resistance to cyanobacteria.

The human-caused proliferation of cyanobacteria severely impacts consumers in freshwater ecosystems. Toxicity is often singled out as the sole trait to which consumers can adapt, even though cyanobacteria are not necessarily toxic and the lack of nutritionally critical sterols in cyanobacteria is known to impair consumers. We studied the relative significance of toxicity and dietary sterol deficiency in driving the evolution of grazer resistance to cyanobacteria in a large lake with a well-documented history of eutrophication and oligotrophication. Resurrecting decades-old Daphnia genotypes from the sediment allowed us to show that the evolution and subsequent loss of grazer resistance to cyanobacteria involved an adaptation to changes in both toxicity and dietary sterol availability. The adaptation of Daphnia to changes in cyanobacteria abundance revealed a sterol-mediated gleaner-opportunist trade-off. Genotypes from peak-eutrophic periods showed a higher affinity for dietary sterols at the cost of a lower maximum growth rate, whereas genotypes from more oligotrophic periods showed a lower affinity for dietary sterols in favour of a higher maximum growth rate. Our data corroborate the significance of sterols as limiting nutrients in aquatic food webs and highlight the applicability of the gleaner-opportunist trade-off for reconstructing eco-evolutionary processes.

No association between serum phytosterols and inflammatory marker levels in a population-based study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation Background The association between inflammation and dietary sterols remains poorly assessed at the population level. Aims To assess the possible association between serum levels of various phytosterols (PS) and inflammatory markers. Methods Serum levels of six PS (campesterol, campestanol, stigmasterol, sitosterol, sitostanol, brassicasterol), four cholesterol synthesis markers (lathosterol, lanosterol, desmosterol, dihydrolanosterol) and one cholesterol absorption marker (cholestanol) were measured together with levels of CRP, IL-6 and TNF-alpha in two cross-sectional surveys of a population-based, prospective study. Results PS levels and their ratios to cholesterol were significantly positively correlated to other PS and cholesterol absorption marker and negatively correlated to cholesterol synthesis markers, with a good agreement between follow-ups. Bivariate correlations showed a generally negative, sometimes significant, association between PS levels (or PS:total cholesterol ratio) and CRP in both follow-ups. The association between PS (or PS:total cholesterol) and IL6 or TNF alpha was mostly negative and, for some PS, significant in the second follow-up (Figure). These associations did not withstand adjusting for confounding factors such as sex, age, BMI and statin administration. Conclusion In this population-based study, PS serum levels were not significantly associated with inflammatory markers.

Transcriptional Regulators of Ecdysteroid Biosynthetic Enzymes and Their Roles in Insect Development.

Steroid hormones are responsible for coordinating many aspects of biological processes in most multicellular organisms, including insects. Ecdysteroid, the principal insect steroid hormone, is biosynthesized from dietary cholesterol or plant sterols. In the last 20 years, a number of ecdysteroidogenic enzymes, including Noppera-bo, Neverland, Shroud, Spook/Spookier, Cyp6t3, Phantom, Disembodied, Shadow, and Shade, have been identified and characterized in molecular genetic studies using the fruit fly Drosophila melanogaster. These enzymes are encoded by genes collectively called the Halloween genes. The transcriptional regulatory network, governed by multiple regulators of transcription, chromatin remodeling, and endoreplication, has been shown to be essential for the spatiotemporal expression control of Halloween genes in D. melanogaster. In this review, we summarize the latest information on transcriptional regulators that are crucial for controlling the expression of ecdysteroid biosynthetic enzymes and their roles in insect development.