👤 Brigitte Vollmar

Obesity and metabolic syndrome are associated with dysregulated hepatic lipid metabolism, contributing to metabolic dysfunction-associated steatotic liver disease (MASLD). Though lifestyle interventions such as a low-fat diet (LFD), treadmill (TM) exercise, and time-restricted feeding (TRF) reduce hepatic lipid accumulation, their combined effects on hepatic lipid composition and lipid metabolism-related gene regulation remain poorly understood. Here, we examined the individual and combined effects of LFD, TM, and/or TRF on liver function, comprehensive hepatic lipidomics, and lipid metabolism-related gene expression in diet-induced obese mice, thereby extending our previous work through detailed lipid class-specific analyses and assessment of interactive intervention effects. Among all interventions, LFD led to the greatest weight loss and normalized plasma aspartate aminotransferase (AST) as well as alanine aminotransferase (ALT) levels. Combined interventions, including TM and TRF, reduced markers of liver damage even under continued HFD conditions compared to HFD alone. LFD with TRF and/or TM decreased the expression of lipogenic genes (Srebf1, Lxrα, Apoe), while expression of genes further involved in lipid synthesis (Fasn and Hmgcr) tended to be increased when TM was combined with either LFD or HFD. β-oxidation-related genes (Ppara, Acox1, Cpt1a) were most downregulated in the LFD groups vs. the HFD + TM group, likely representing a metabolic adaptation to increased lipid mobilization. For the first time, lipidomics analysis demonstrated that in particular LFD alone or in combination with TM most effectively increased sphingomyelin (SM) and dihydrosphingomyelin (DHSM) as well as lysophosphatidylcholine (LPC) and phosphatidylcholine (PC), potentially reflecting compensatory lipid remodeling. Taken together, these findings highlight distinct and additive effects of combined lifestyle interventions on hepatic lipid composition and gene regulation, clearly delineating the novel contributions of the present study and supporting combined dietary and physical strategies as potential approaches to improve hepatic lipid homeostasis and mitigate MASLD development. Show less

Actin is a protein of central importance to many cellular functions. Its localization and activity are regulated by interactions with a high number of actin-binding proteins. In a yeast two-hybrid (Y2H) screening system, snail family transcriptional repressor 2 (SNAI2 or slug) was identified as a yet unknown potential actin-binding protein. We validated this interaction using immunoprecipitation and analyzed the functional relation between slug and actin. Since both proteins have been reported to be involved in DNA double-strand break (DSB) repair, we focused on their interaction during this process after treatment with doxorubicin or UV irradiation. Confocal microscopy elicits that the overexpression of actin fused to an NLS stabilizes complexes of slug and γH2AX, an early marker of DNA damage repair. Show less

The vacuolar ATPase (v-ATPase) is a proton pump, able to acidify intracellular compartments and the pericellular space. v-ATPase has extensively been studied in various functional contexts, e.g., migration of tumor cells, and inhibition of v-ATPase has been proven as intriguing novel therapeutic concept. Since the role of v-ATPase in endothelial cell migration and angiogenesis has scarcely been investigated, we examined the consequences of pharmacological inhibition of v-ATPase (by concanamycin) on proliferation, migration, VEGF-receptor 2 (VEGFR2) trafficking and signaling, as well as Notch-mediated transcription in endothelial cells [human microvascular endothelial cells (HMEC-1) and human umbilical vein endothelial cells (HUVEC)] Treatment of the cells with 3 or 10 nM of the v-ATPase inhibitor concanamycin for 48 h or longer inhibited proliferation and arrested cell cycle in the G2/M phase in HMEC-1, while a G1 phase arrest occurred in HUVEC. Already after 24 h these concentrations reduced migration (scratch assay, chemotactic gradient). Activation of the small GTPase Rac1 in freshly adherent cells was reduced by concanamycin. Downstream signaling of the VEGFR2 (phosphorylation of ERK1/2 and AKT), as well as autophosphorylation of VEGFR2 were inhibited. VEGFR2 on the cell surface was reduced, and sequestered in a lysosomal compartment. In addition, concanamycin blocked transcription of the Notch target genes Hey1 and Hey2 after stimulation with DLL4. Since the impaired signaling pathways (Rac-1, VEGFR2, Notch) all depend on vesicular recycling circuits, we conclude that the disturbance of these is the main mode of action of v-ATPase inhibition in endothelial cells, offering an attractive multi-factorial anti-angiogenic approach. Show less