👤 Blokzijl Hans

Metabolic diseases such as obesity, type 2 diabetes mellitus (T2DM), dyslipidaemia, and metabolic dysfunction-associated steatotic liver disease (MASLD) are increasingly recognised as chronic inflammatory conditions driven in part by innate immune dysregulation. Among the metabolic factors implicated in this process, branched-chain amino acids (BCAAs) have emerged as key regulators linking nutrient sensing to immune cell function. Circulating BCAA concentrations are consistently elevated in these metabolic diseases. However, experimental and clinical studies also show that BCAA supplementation can improve metabolic and immune outcomes in specific contexts, revealing a paradoxical relationship between BCAA metabolism and inflammation. This narrative review examines how dysregulated BCAA metabolism and accumulation of branched-chain keto acids (BCKAs) shape the functional programming of innate immune cells across these conditions, including monocytes/macrophages, granulocytes, dendritic cells, and natural killer cells. Evidence indicates that the immunometabolic effects of BCAAs depend not solely on circulating concentrations but on the efficiency of their intracellular catabolism. When BCAA oxidation is preserved, these amino acids support mitochondrial metabolism and immune competence. Conversely, impaired catabolism leads to the accumulation of branched chain ketoacids, which activate inflammatory pathways and contribute to metabolic dysfunction. Resolving this paradox requires the need of targeting catabolic flux restoration rather than simple BCAA restriction or supplementation, and requires stratifying patients by enzymatic capacity, BCAA/BCKA ratios, and disease stage. Pharmacological modulators, including BCKDK inhibitors and BCAT1-targeted agents, show promise in simultaneously addressing metabolic and immune dysregulation. Show less

Zebrafish can achieve scar-free healing of heart injuries, and robustly replace all cardiomyocytes lost to injury via dedifferentiation and proliferation of mature cardiomyocytes. Previous studies suggested that Wnt/β-catenin signaling is active in the injured zebrafish heart, where it induces fibrosis and prevents cardiomyocyte cell cycling. Here, via targeting the destruction complex of the Wnt/β-catenin pathway with pharmacological and genetic tools, we demonstrate that Wnt/β-catenin activity is required for cardiomyocyte proliferation and dedifferentiation, as well as for maturation of the scar during regeneration. Using cardiomyocyte-specific conditional inhibition of the pathway, we show that Wnt/β-catenin signaling acts cell-autonomously to promote cardiomyocyte proliferation. Our results stand in contrast to previous reports and rather support a model in which Wnt/β-catenin signaling plays a positive role during heart regeneration in zebrafish. Show less

The mature aortic valve is composed of a structured trilaminar extracellular matrix that is interspersed with aortic valve interstitial cells (AVICs) and covered by endothelium. Dysfunction of the valvular endothelium initiates calcification of neighboring AVICs leading to calcific aortic valve disease (CAVD). The molecular mechanism by which endothelial cells communicate with AVICs and cause disease is not well understood. Using a co-culture assay, we show that endothelial cells secrete a signal to inhibit calcification of AVICs. Gain or loss of nitric oxide (NO) prevents or accelerates calcification of AVICs, respectively, suggesting that the endothelial cell-derived signal is NO. Overexpression of Notch1, which is genetically linked to human CAVD, retards the calcification of AVICs that occurs with NO inhibition. In AVICs, NO regulates the expression of Hey1, a downstream target of Notch1, and alters nuclear localization of Notch1 intracellular domain. Finally, Notch1 and NOS3 (endothelial NO synthase) display an in vivo genetic interaction critical for proper valve morphogenesis and the development of aortic valve disease. Our data suggests that endothelial cell-derived NO is a regulator of Notch1 signaling in AVICs in the development of the aortic valve and adult aortic valve disease. Show less