FGF-23 protects cell function and viability in murine pancreatic islets challenged by glucolipotoxicity.

The fibroblast growth factor FGF-23 is a member of the FGF-15/19 subfamily with hormonal functions. Besides its well-known role for bone mineralization, FGF-23 is discussed as a marker for cardiovascular disease. We investigated whether FGF-23 has any effects on the endocrine pancreas of mice by determining insulin secretion, electrical activity, intracellular Ca2+, and apoptosis. Acute application of FGF-23 (10 to 500 ng/ml, i.e., 0.4 to 20 nM) does not affect insulin release of murine islets, while prolonged exposure leads to a 21% decrease in glucose-stimulated secretion. The present study shows for the first time that FGF-23 (100 or 500 ng/ml) partially protects against impairment of insulin secretion and apoptotic cell death induced by glucolipotoxicity. The reduction of apoptosis by FGF-23 is approximately twofold higher compared to FGF-21 or FGF-15/19. In contrast to FGF-23 and FGF-21, FGF-15/19 is clearly pro-apoptotic under control conditions. The beneficial effect of FGF-23 against glucolipotoxicity involves interactions with the stimulus-secretion cascade of beta-cells. Electrical activity and the rise in the cytosolic Ca2+ concentration of islets in response to acute glucose stimulation increase after glucolipotoxic culture (48 h). Co-culture with FGF-23 further elevates the glucose-mediated effects on both parameters. Protection against apoptosis and glucolipotoxic impairment of insulin release by FGF-23 is prevented, when calcineurin is inhibited by tacrolimus or when c-Jun N-terminal kinase (JNK) is blocked by SP600125. In conclusion, our data suggest that FGF-23 can activate compensatory mechanisms to maintain beta-cell function and integrity of islets of Langerhans during excessive glucose and lipid supply.

Multiple sclerosis endophenotypes identified by high-dimensional blood signatures are associated with distinct disease trajectories.

One of the biggest challenges in managing multiple sclerosis is the heterogeneity of clinical manifestations and progression trajectories. It still remains to be elucidated whether this heterogeneity is reflected by discrete immune signatures in the blood as a surrogate of disease pathophysiology. Accordingly, individualized treatment selection based on immunobiological principles is still not feasible. Using two independent multicentric longitudinal cohorts of patients with early multiple sclerosis (n = 309 discovery and n = 232 validation), we were able to identify three distinct peripheral blood immunological endophenotypes by a combination of high-dimensional flow cytometry and serum proteomics, followed by unsupervised clustering. Longitudinal clinical and paraclinical follow-up data collected for the cohorts revealed that these endophenotypes were associated with disease trajectories of inflammation versus early structural damage. Investigating the capacity of immunotherapies to normalize endophenotype-specific immune signatures revealed discrete effect sizes as illustrated by the limited effect of interferon-ß on endophenotype 3-related immune signatures. Accordingly, patients who fell into endophenotype 3 subsequently treated with interferon-ß exhibited higher disease progression and MRI activity over a 4-year follow-up compared with treatment with other therapies. We therefore propose that ascertaining a patient's blood immune signature before immunomodulatory treatment initiation may facilitate prediction of clinical disease trajectories and enable personalized treatment decisions based on pathobiological principles.

Single-cell profiling reveals preferential reduction of memory B cell subsets in cladribine patients that correlates with treatment response.

Background: Cladribine is a highly effective immunotherapy that is applied in two short-term courses over 2 years and reduces relapse rate and disease progression in patients with relapsing multiple sclerosis (MS). Despite the short treatment period, cladribine has a long-lasting effect on disease activity even after recovery of lymphocyte counts, suggesting a yet undefined long-term immune modulating effect. Objectives: Our aim was to provide a more profound understanding of the detailed effects of cladribine, also with regard to the patients' therapy response. Design: We performed an open-labeled, explorative, prospective, single-arm study, in which we examined the detailed lymphocyte subset development of MS patients who received cladribine treatment over 2 years. Methods: We performed in-depth profiling of the effects of cladribine on peripheral blood lymphocytes by flow cytometry, bulk RNA sequencing of sorted CD4+ T cells, CD8+ T cells, and CD19+ B cells as well as single-cell RNA sequencing of peripheral blood mononuclear cells in a total of 23 MS patients before and at different time points up to 24 months after cladribine treatment. Data were correlated with clinical and cranial magnetic resonance imaging (MRI) disease activity. Results: Flow cytometry revealed a predominant and sustained reduction of memory B cells compared to other B cell subsets after cladribine treatment, whereas T cell subsets were slightly reduced in a more uniform pattern. The overall transcriptional profile of total blood B cells exhibited reduced expression of proinflammatory and T cell activating genes, while single-cell transcriptomics revealed that gene expression within each B cell cluster did not change over time. Stable patients displayed stronger reductions of selected memory B cell clusters as compared to patients with clinical or cerebral MRI disease activity. Conclusion: We describe a pronounced and sustained effect of cladribine on the memory B cell compartment, and the resulting change in B cell subset composition causes a significant alteration of B cell transcriptional profiles resulting in reduced proinflammatory and T cell activating capacities. The extent of reduction in selected memory B cell clusters by cladribine may predict treatment response.

Impact of disease-modifying therapies on humoral and cellular immune-responses following SARS-CoV-2 vaccination in MS patients.

The impact of distinct disease-modifying therapies (DMTs) on severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vaccination efficacy in patients with multiple sclerosis (MS) is still enigmatic. In this prospective comparative study, we investigated humoral and cellular immune-responses in patients with MS receiving interferon beta, natalizumab, and ocrelizumab pre-vaccination and 6 weeks post second SARS-CoV-2 vaccination. Healthy individuals and interferon beta-treated patients generated robust humoral and cellular immune-responses. Although humoral immune responses were diminished in ocrelizumab-treated patients, cellular immune-responses were reduced in natalizumab-treated patients. Thus, both humoral and cellular immune responses should be closely monitored in patients on DMTs. Whereas patients with a poor cellular immune-response may benefit from additional vaccination cycles, patients with a diminished humoral immune-response may benefit from a treatment with SARS-CoV-2 antibodies in case of an infection.