When the Lupus Gut Loses Its Taste for Fiber
In people with lupus — and in lupus-prone mice — the gut microbiome shifts its carbohydrate catabolism away from dietary fiber and toward the host's own mucin lining, a change that coincides with the depletion of one bug: Faecalibacterium prausnitzii.
So researchers tried putting it back. Male B6.Sle1.Yaa mice (a lupus model driven by Sle1 plus a Tlr7-containing duplication) got a single F. prausnitzii strain, UT1, by gavage every 2 days, starting at 3 months — before disease — and continuing for up to 12 weeks. The treated microbiome drifted partway back toward that of healthy controls, restoring 17 of 86 disrupted species and roughly 40% of the depleted carbohydrate-degrading enzymes. Alongside that: more colonic regulatory T cells, fewer Th17 cells, lower anti-dsDNA antibodies, and smaller glomeruli with lower renal pathology scores.
The proposed mechanism is metabolic. Restored fiber digestion was accompanied by more pentose sugars — feeding an antioxidant pathway — and tryptophan catabolism that leaned toward indoleacetic and indoleacrylic acids, aryl hydrocarbon receptor ligands the authors say may support Tregs, rather than inflammatory indole. As they put it, "UT1 transcriptionally and metabolically reprograms the microbiome to potentially resist disease progression."
Worth holding lightly: this is a mouse intervention plus a reanalysis of human metagenomes, with treatment begun before disease onset. But it reframes lupus "dysbiosis" as a specific, traceable loss of carbohydrate-eating function rather than a shifting taxonomic headcount — a candidate mechanism, and maybe a target.
Source: Nature Communications
Fish Oil Got Into the Brain. That Wasn’t the Problem.
In a 24-month randomized trial of high-dose DHA in older adults at risk for dementia, the supplement did exactly what it was supposed to do biochemically — and still did not move cognition or brain structure.
The phase 2a PreventE4 trial randomized 365 adults aged 55 to 80 years with low dietary docosahexaenoic acid (DHA) intake and at least 1 dementia or cardiovascular risk factor to 2 g/day DHA or placebo. Nearly half were APOE ε4 carriers, the group expected to be trickier because APOE ε4 has been linked to altered omega-3 metabolism. By 6 months, DHA significantly increased the cerebrospinal fluid DHA/arachidonic acid ratio compared with placebo, with similar effects regardless of APOE ε4 status. But after 24 months, there were no treatment differences in hippocampal volume, cortical thickness, or cognitive performance.
Plot twist: one common explanation for prior null omega-3 trials — maybe the dose was too low, or the DHA never really reached the brain — looks less convincing here. As the authors put it, “brain delivery is not the limiting factor.”
Mechanistically, the authors point toward DHA metabolism, inflammatory and vascular risk, and possible downstream handling of fatty acids after delivery, rather than simple underdosing. Clinical takeaway: high-dose DHA may show target engagement, but this trial does not support expecting cognitive or structural brain benefit from DHA monotherapy over 2 years in similar nondemented older adults.
Source: eBioMedicine
The Foam Cells Were Not Just Background Noise
The lipid-stuffed microglia found in some progressive MS lesions may be more than passive debris collectors.
In a postmortem multi-omics study, researchers profiled 110 white matter samples from 28 donors with secondary progressive multiple sclerosis (MS) and 10 controls, then linked pathology data from 250 MS donors and 8,708 lesions to disease trajectory. A higher proportion of active and mixed active/inactive lesions containing foamy microglia/macrophages was associated with faster progression to EDSS 6 and EDSS 8, while nonfoamy active lesions were not. These foamy lesions carried a distinct molecular signature: cholesterol esters, oxylipins, lysosomal stress, phagocytosis, antigen presentation, B-cell infiltration, and IgG1.
The plot twist: this was not a classic inflammatory fireworks show. The authors reported no difference in prominent inflammatory markers, including TNF, IL-6, IFN-γ, and IL-1β, between foamy and nonfoamy lesions. As they wrote, “This finding may suggest that the foamy phenotype is not simply a byproduct of demyelination but a defining feature of lesion persistence and expansion.”
Mechanistically, the signal pointed toward disturbed lipid metabolism. MAGL, a lipid-metabolizing enzyme, emerged as a potential target, and MAGL inhibition improved lesion recovery in a mouse demyelination model. Clinically, this is not ready for biomarker use or treatment selection, but it does sharpen the progressive MS question: lipid-loaded microglia may be an important window into why some lesions smolder instead of resolve.
Source: Nature Neuroscience
The Workout That Didn’t Melt More Fat—but May Have Protected the Good Stuff
In healthy adults around age 72, HIIT did not dramatically outperform moderate exercise for fat loss—but it may have spared lean tissue in a way moderate training did not.
Researchers randomized 123 apparently healthy older adults to 6 months of supervised exercise 3 times weekly: treadmill-based high-intensity interval training (HIIT), moderate-intensity continuous training, or low-intensity balance/stretching/toning as an active control. Both HIIT and moderate training reduced fat mass more than the low-intensity control, and both showed significant reductions in visceral adipose tissue over 6 months. But the moderate group also had a decline in fat-free mass—the bucket that includes muscle and other lean tissues—while the HIIT group maintained it. At 6 months, the HIIT group showed a greater between-group difference in fat-free mass than the moderate group and was the only group with a net improvement in body fat percentage.
The plot twist: none of this was exactly body-composition fireworks. The authors wrote, “High-intensity training reduced fat and maintained lean mass in apparently healthy older adults,” but also noted the average changes were small and not clinically meaningful.
The why is still partly speculative: higher-intensity exercise may create more skeletal muscle loading and stimulate muscle protein synthesis, while moderate exercise may still help reduce fat and visceral adiposity.
Clinical takeaway: for healthy older adults who can safely tolerate it, HIIT may be worth considering as an aerobic option when preserving lean mass matters. But for meaningful body composition change, aerobic intensity alone probably is not the whole prescription.
Source: Maturitas