The sphingolipids galactosylceramide (GalCer), sulfatide (ST) and sphingomyelin (SM) are essential for myelin stability and function. GalCer and ST are synthesized mostly from C22‐C24 ceramides, generated by Ceramide Synthase 2 (CerS2). To clarify the requirement for C22‐C24 sphingolipid synthesis in myelin biosynthesis and stability, we generated mice lacking CerS2 specifically in myelinating cells (CerS2^ΔO/ΔO). At 6 weeks of age, normal‐appearing myelin had formed in CerS2^ΔO/ΔO mice, however there was a reduction in myelin thickness and the percentage of myelinated axons. Pronounced loss of C22‐C24 sphingolipids in myelin of CerS2^ΔO/ΔO mice was compensated by greatly increased levels of C18 sphingolipids. A distinct microglial population expressing high levels of activation and phagocytic markers such as CD64, CD11c, MHC class II, and CD68 was apparent at 6 weeks of age in CerS2^ΔO/ΔO mice, and had increased by 10 weeks. Increased staining for denatured myelin basic protein was also apparent in 6‐week‐old CerS2^ΔO/ΔO mice. By 16 weeks, CerS2^ΔO/ΔO mice showed pronounced myelin atrophy, motor deficits, and axon beading, a hallmark of axon stress. 90% of CerS2^ΔO/ΔO mice died between 16 and 26 weeks of age. This study highlights the importance of sphingolipid acyl chain length for the structural integrity of myelin, demonstrating how a modest reduction in lipid chain length causes exposure of a denatured myelin protein epitope and expansion of phagocytic microglia, followed by axon pathology, myelin degeneration, and motor deficits. Understanding the molecular trigger for microglial activation should aid the development of therapeutics for demyelinating and neurodegenerative diseases.

Background: Calorie restriction (CR) ameliorates preclinical models of multiple sclerosis (MS) via multiple mechanisms. These include decreased leptin, a proinflammatory adipokine, but mechanistic studies in humans are lacking. Tests of daily and intermittent CR (iCR) in people with MS (pwMS) showed improvements in fatigue and well-being measures. This trial studied the effects of 12-week iCR on metabolic, immunological, and clinical outcomes in pwMS.Method: Relapsing-remitting MS participants were randomised to iCR or a control group. Study visits were conducted at baseline, 6 and 12 weeks. The primary outcome was reduction in serum leptin levels at 12 weeks. Feasibility and safety were assessed by diet adherence and adverse events (AEs). Secondary outcomes included changes in anthropometric and body composition measures, metabolic and immunologic profiling, and clinical measures. Mixed effects linear regression models were used to evaluate outcome differences between and within groups over time.Results: Forty-two pwMS were randomised, 34 completed the study (17/group). Leptin serum levels at 12 weeks were significantly lower in the iCR versus the control group (mean decrease −6.98 µg/dL, 95% CI: −28.02 to 14.06; p=0.03). Adherence to iCR was 99.5% and 97.2% at 6 and 12 weeks, respectively, and no serious AEs were reported. An increase in blood CD45RO⁺regulatory T-cell numbers was seen after 6 weeks of iCR. Exploratory cognitive testing demonstrated a significant improvement in the Symbol Digit Modality Test Score in the iCR group at 12 weeks.Conclusions: iCR has the potential to benefit metabolic and immunologic profiles and is safe and feasible in pwMS.Trial registration number: NCT03539094.

Importance: Although prolonged fasting has become increasingly popular, the favourable biological adaptations and possible adverse effects in humans have yet to be fully elucidated. Objective: To investigate the effects of a three-day water-only fasting, with or without exercise-induced glycogen depletion, on autophagy activation and the molecular pathways involved in cellular damage accumulation and repair in healthy humans. Design: A randomised, single-centre, two-period, two-sequence crossover trial. The primary outcome is autophagic activity, assessed as flux in peripheral blood mononuclear cells (PBMCs) measured in the context of whole blood. Secondary outcomes include changes in body composition, heart rate variability, endothelial function, and genomic, epigenomic, metabolomic, proteomic, and metagenomic adaptations to fasting in plasma, platelets, urine, stools, and PBMCs. Detailed profiling of circulating immune cell populations and their functional states will be assessed by flow cytometry. Setting: All clinical investigations will be undertaken at the Charles Perkins Centre Royal Prince Alfred Hospital clinic, University of Sydney, Australia. Participants: Twenty-four individuals aged 18 to 70 years, with a BMI of 20–40 kg/m², free of major health conditions other than obesity. Discussion: While autophagic flux induction through fasting has garnered interest, there is a notable lack of human studies on this topic. This trial aims to provide the most detailed and integrated analysis of how three days of prolonged water-only fasting, combined with glycogen-depleting exercise, affects autophagy activation and other crucial metabolic and molecular pathways linked to cellular, metabolic, and immune health. Insights from this study may pave the way for safe and effective strategies to induce autophagy, offering potential preventive interventions for a range of chronic conditions.

Tangential flow filtration (TFF) is an effective method for scalable EV isolation. Here, we describe and validate a reference protocol for TriPort-TFF, a laboratory-assembled TFF system featuring a three-port reservoir design enabling sample circulation, retentate return, and diafiltration. Constructed from individually sourced, commercially available components with detailed assembly and operating parameters, TriPort-TFF can be built at a lower cost than commercially integrated TFF platforms. We evaluated the system using conditioned media (CM) from human MDM cultured with EV-depleted human serum, human cerebral organoids in serum-free medium, and mouse BMDM cultured with EV-depleted foetal bovine serum (FBS) unstimulated or LPS-stimulated. The system reproducibly isolated EVs from all three sources, and biological replicates of BMDM showed distinct proteomic clusters between LPS-stimulated and unstimulated conditions. The requirement for subsequent size-exclusion chromatography (SEC) after TFF depended on the sample’s serum-presence. In serum-containing CM, TFF alone co-concentrated serum proteins alongside EVs, subsequent SEC improved the particle-to-protein ratio, reduced inter-replicate variability and improved proteomic depth. TFF alone in serum-free organoid CM already yielded higher particle-to-protein ratios than TFF-only preparations from serum-containing CM, with SEC further improving this ratio. TriPort-TFF offers an accessible system for EV-isolation that can be combined with SEC for diverse sample types.

Background: Calorie restriction (CR) ameliorates preclinical models of multiple sclerosis (MS) through reduction of inflammation. The aim of this trial was to study the effects of 12-week iCR on metabolic, immunological and clinical outcomes in people with MS (pwMS). Methods: Participants with relapsing-remitting MS were randomly assigned to intermittent CR (iCR) or a control group for 12 weeks. Primary outcome was change in leptin levels; secondary outcomes included changes in anthropometric and body composition measures, peripheral blood metabolic and immunologic profiling, and clinical measures. Mixed effects linear regression models were used to evaluate differences. Results: Forty-two pwMS were randomized, 34 completed the study (17 iCR and 17 control). Leptin levels decreased in the iCR group and were significantly lower in the iCR than the control group at 6 (mean difference 11.49 mg/dL, 95% CI 32.54, 9.54; P =0.01) and 12 weeks (6.97 mg/dL, 95% CI 28.02, 14.06; P =0.03). We observed a significant reduction of weight, body mass index and body adiposity measures over the 6 and 12-weeks in the iCR group. Immune profiling showed a significant increase in CD45RO ⁺ regulatory T cell numbers after 6 weeks of iCR. Lysophosphatidylcholine, lysophophatidylethanolamine and phosphatidylinositol lipid species were significantly increased after 12 weeks in the iCR group compared to baseline, and all three were higher at 12 weeks compared to controls. Exploratory cognitive testing demonstrated improvement in the symbol digit modality test score in the iCR group. Conclusions: Short term iCR is safe, feasible and can benefit metabolic and immunologic profiles in pwMS. ClinicalTrial.gov number: NCT03539094 (first patient screened on 11/14/17; first patient recruited on 1/29/2018; last patient recruited on 11/24/2021).