Despite longstanding excitement and progress toward understanding liquid-liquid phase separation in natural and artificial membranes, fundamental questions have persisted about which molecules are required for this phenomenon. Except in extraordinary circumstances, the smallest number of components that has produced large-scale, liquid-liquid phase separation in bilayers has stubbornly remained at three: a sterol, a phospholipid with ordered chains, and a phospholipid with disordered chains. This requirement of three components is puzzling because only two components are required for liquid-liquid phase separation in lipid monolayers, which resemble half of a bilayer. Inspired by reports that sterols interact closely with lipids with ordered chains, we tested whether phase separation would occur in bilayers in which a sterol and lipid were replaced by a single, joined sterol-lipid. By evaluating a panel of sterol-lipids, some of which are present in bacteria, we found a minimal bilayer of only two components (PChemsPC and diPhyPC) that robustly demixes into micron-scale, liquid phases. It suggests an additional role for sterol-lipids in nature, and it reveals a membrane in which tie-lines (and, therefore, the lipid composition of each phase) are straightforward to determine and will be consistent across multiple laboratories.

To investigate the effect of freeze-thaw (FT) process on the yield and quality of tiger nut oil, tiger nuts were subjected to 0-12 cycles of FT treatment. Results indicated that FT treatment ruptured the cell structure of tiger nut, resulting in an increase in oil yield. Acid value (2.09-2.42 mg KOH/g) and peroxide value (0.40-0.42 mmol/kg) increased with the number of FT cycles, but the increments were small. Likewise, slight differences in fatty acid composition and thermal properties between control and FT-treated samples were observed. FT treatment remarkably increased the bioactive components (e.g., vitamin E, sterols, chlorophyll and carotenoids) in the oil and extended the oxidation induction time from 1.2 to 5.57 h. FT treatment altered the volatile composition of tiger nut oil, increasing the relative content of heterocycles and pyrazines such as 2-methoxy-4-vinylphenol, trimethylpyrazine and tetramethylpyrazine. It was suggested that FT treatment prior to oil extraction was beneficial to improve the oil yield and quality.

Cholesterol is an essential component of cellular membranes, crucial for maintaining their structural and functional integrity. It is especially important for nervous tissues, including the retina, which rely on high amounts of plasma membranes for the transmission of the nervous signal. While cholesterol is by far the most abundant sterol, the retina also contains cholesterol precursors and metabolites, especially oxysterols, which are bioactive molecules. Cholesterol lack or excess is deleterious and some oxysterols are known for their effect on neuron survival. Cholesterol homeostasis must therefore be maintained. Retinal glial cells, especially Müller cells, the principal glial cells of the vertebrate retina, provide mechanical, nutritional, and metabolic support for the neighboring neurons. Several pieces of evidence indicate that Müller cells are major actors of cholesterol homeostasis in the retina, as it is known for other glial cells in the brain. This process is based on a close cooperation with neurons, and sterols can be signaling molecules participating in glia-neuron interactions. While some implication of cholesterol in age-related macular degeneration is now recognized, based on epidemiological and laboratory data, evidence for its role in glaucoma is still scarce. The association between cholesterolemia and glaucoma is controversial, but experimental data suggest that sterols could take part in the pathological processes. It has been demonstrated that Müller glial cells are implicated in the development of glaucoma through an ambivalent reactive retinal gliosis process. The early steps contribute to maintaining retinal homeostasis and favor the survival of ganglion cells, which are targeted during glaucoma. If gliosis persists, dysregulation of the neuroprotective functions, cytotoxic effects of gliotic Müller cells and disruption of glia-neuron interactions lead to an acceleration of ganglion cell death. Sterols could play a role in the glial cell response to glaucomatous injury. This represents an understudied but attractive topic to better understand glaucoma and conceive novel preventive or curative strategies. The present review describes the current knowledge on i) sterol metabolism in retinal glial cells, ii) the potential role of cholesterol in glaucoma, and iii) the possible relationships between cholesterol and oxysterols, glial cells and glaucoma. Focus is put on glia-neuron interactions.

Vitamin D (VD) production-based microalgae biosynthesis presents various benefits including sustainability, fast expansion, and the capacity to generate substantial quantities. However, this approach suffers from serious challenges that require effective cultivation methods and extraction processes. Indeed, further researches are of significant interest to understand the biosynthesis pathways, enhance the processes, and ensure its viability. In this context, the present review focuses on an in-depth understanding of the chemistry of VD and its analogues and provides a comprehensive explanation of the biosynthesis pathways, precursors, and production methods. In addition, this work discusses the state of the art reflecting the recent advances researches and the global market of microalgae as a potential source of VD. In sum, this paper demonstrates that microalgae can efficiently biosynthesize various forms of VD, presenting a sustainable alternative for VD production.

The effectivity of utilization of exogenous sterols in the yeast Saccharomyces cerevisiae exposed to hypoxic stress is dependent on the sterol structure. The highly imported sterols include animal cholesterol or plant sitosterol, while ergosterol, typical of yeasts, is imported to a lesser extent. An elevated utilization of non-yeast sterols is associated with their high esterification and relocalization to lipid droplets (LDs). Here we present data showing that LDs and sterol esterification play a critical role in the regulation of the accumulation of non-yeast sterols in membranes. Failure to form LDs during anaerobic growth in media supplemented with cholesterol or sitosterol resulted in an extremely long lag phase, in contrast to normal growth in media with ergosterol or plant stigmasterol. Moreover, in hem1∆, which mimics anaerobiosis, neither cholesterol nor sitosterol supported the growth in an LD-less background. The incorporation of non-ergosterol sterols into the membranes affected fundamental membrane characteristics such as relative membrane potential, permeability, tolerance to osmotic stress and the formation of membrane domains. Our findings reveal that LDs assume an important role in scenarios wherein cells are dependent on the utilization of exogenous lipids, particularly under anoxia. Given the diverse lipid structures present in yeast niches, LDs fulfil a protective role, mitigating the risk of excessive accumulation of potentially toxic steroids and fatty acids in the membranes. Finally, we present a novel function for sterols in a model eukaryotic cell - alleviation of the lipotoxicity of unsaturated fatty acids.

Polyene macrolides are antifungal substances, which interact with cells in a sterol-dependent manner. While being widely used, their mode of action is poorly understood. Here, we employ ultraviolet-sensitive (UV) microscopy to show that the antifungal polyene natamycin binds to the yeast plasma membrane (PM) and causes permeation of propidium iodide into cells. Right before membrane permeability became compromised, we observed clustering of natamycin in the PM that was independent of PM protein domains. Aggregation of natamycin was paralleled by cell deformation and membrane blebbing as revealed by soft X-ray microscopy. Substituting ergosterol for cholesterol decreased natamycin binding and caused a reduced clustering of natamycin in the PM. Blocking of ergosterol synthesis necessitates sterol import via the ABC transporters Aus1/Pdr11 to ensure natamycin binding. Quantitative imaging of dehydroergosterol (DHE) and cholestatrienol (CTL), two analogues of ergosterol and cholesterol, respectively, revealed a largely homogeneous lateral sterol distribution in the PM, ruling out that natamycin binds to pre-assembled sterol domains. Depletion of sphingolipids using myriocin increased natamycin binding to yeast cells, likely by increasing the ergosterol fraction in the outer PM leaflet. Importantly, binding and membrane aggregation of natamycin was paralleled by a decrease of the dipole potential in the PM, and this effect was enhanced in the presence of myriocin. We conclude that ergosterol promotes binding and aggregation of natamycin in the yeast PM, which can be synergistically enhanced by inhibitors of sphingolipid synthesis.

Mammalian target of rapamycin (mTOR) senses changes in nutrient status and stimulates the autophagic process to recycle amino acids. However, the impact of nutrient stress on protein degradation beyond autophagic turnover is incompletely understood. We report that several metabolic enzymes are proteasomal targets regulated by mTOR activity based on comparative proteome degradation analysis. In particular, 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) synthase 1 (HMGCS1), the initial enzyme in the mevalonate pathway, exhibits the most significant half-life adaptation. Degradation of HMGCS1 is regulated by the C-terminal to LisH (CTLH) E3 ligase through the Pro/N-degron motif. HMGCS1 is ubiquitylated on two C-terminal lysines during mTORC1 inhibition, and efficient degradation of HMGCS1 in cells requires a muskelin adaptor. Importantly, modulating HMGCS1 abundance has a dose-dependent impact on cell proliferation, which is restored by adding a mevalonate intermediate. Overall, our unbiased degradomics study provides new insights into mTORC1 function in cellular metabolism: mTORC1 regulates the stability of limiting metabolic enzymes through the ubiquitin system.

Gas chromatography with mass spectrometry (GC/MS) and fractionation steps were used to determine the sterol patterns of red goji berries in detail. Twenty-five sterols were detected in fresh berries of two species (Lycium barbarum and L. chinense) from bushes grown in the botanical garden of the University of Hohenheim, and 20 sterols were identified. The rarely occurring campesta-5,24(25)-dienol, β-sitosterol, Δ5-avenasterol, campesterol, and cycloartenol represented >60 % of the total sterol content. Maturity and drying of fresh red goji berries caused small changes but did not affect the characteristic sterol pattern. This was confirmed by analyzing various commercial dried red goji berry samples from different sources. Separated flesh and seed samples revealed pronounced differences in the sterol pattern. A new method of merging GC/MS chromatograms showed that ∼75 % of the sterols were present in seeds and ∼25 % in flesh. The unique sterol profile may be exploited to authenticate red goji berries.

Cholesterol is a major lipid of the animal realm with many biological roles. It is an important component of cellular membranes and a precursor of steroid hormones and bile acids. It is particularly abundant in nervous tissues, and dysregulation of cholesterol metabolism has been associated with neurodegenerative diseases such as Alzheimer\'s and Huntington\'s diseases. Deciphering the pathophysiological mechanisms of these disorders often involves animal models such as mice and Drosophila. Accurate quantification of cholesterol levels in the chosen models is a critical point of these studies. In the present work, we compare two common methods, gas chromatography coupled to flame-ionization detection (GC/FID) and a cholesterol oxidase-based fluorometric assay to measure cholesterol in mouse brains and Drosophila heads. Cholesterol levels measured by the two methods were similar for the mouse brain, which presents a huge majority of cholesterol in its sterol profile. On the contrary, depending on the method, measured cholesterol levels were very different for Drosophila heads, which present a complex sterol profile with a minority of cholesterol. We showed that the enzyme-based assay is not specific for cholesterol and detects other sterols as well. This method is therefore not suited for cholesterol measurement in models such as Drosophila. Alternatively, chromatographic methods, such as GC/FID, offer the required specificity for cholesterol quantification. Understanding the limitations of the quantification techniques is essential for reliable interpretation of the results in cholesterol-related research.

In Japanese agricultural lands, nitrate-nitrogen contamination of soil and groundwater often occurs due to the application of livestock excrements and compost. Therefore, rural soils in Japan were sampled and analyzed for nitrate-nitrogen leaching, heavy metal content, and sterols associated with livestock excrement and compost to calculate contamination risk indicators. The results were analyzed using self-organizing maps and cluster analysis. Nitrate-nitrogen content using water extraction was detected in most of the sampled soils. In addition, many samples from areas that were already severely contaminated with nitrate-nitrogen showed particularly high concentrations. Coprostanol, an indicator of fecal contamination, was detected in more than half of the samples. The main source of nitrate-nitrogen contamination in these areas is livestock excrement and compost. Self-organization maps showed that areas with high nitrate-nitrogen contamination also corresponded to areas with high copper and zinc soil contents. The self-organization maps and cluster analysis resulted in five clusters: a nitrate-contaminated group mainly originating from livestock excrement and compost, a heavy metal-contaminated group, a general group, a nitrate-contaminated group mainly originating from chemical fertilizers, and a contaminated group with potentially hazardous substances requiring attention. Authorities and decision-makers can use the results to prioritize areas requiring remediation.