Biology subjects

Willenbockel, H. F.

Publications and source records attributed to Willenbockel, H. F..

3 recordsLinked to original sources

bioRxiv2025

Itaconate is metabolized to 2-hydroxymethylsuccinate through a CoA-independent degradation pathway in mitochondria

The immunometabolite itaconate modulates cellular metabolism and is converted into structurally similar C5 dicarboxylates that require advanced analytics to decipher their metabolic fate. Here, we employ high-resolution mass spectrometry and tracing approaches and identify 2-hydroxymethylsuccinate (2HMS) as a previously unrecognized C5 dicarboxylate derived from itaconate. 2HMS synthesis occurs during inflammatory responses and upon itaconate treatment, as detected by 13C itaconate tracing. Pathway analysis reveals that methylglutaconyl-CoA hydratase (AUH) drives 2HMS synthesis through a CoA-independent conversion (CIC) pathway. This pathway is distinct from the CoA-dependent conversion (CDC) pathway that generates mesaconate and itaconyl-CoA influencing B12-dependent processes. In vivo inflammation studies reveal that adipose tissue prefers CIC to produce 2HMS and liver favors CDC-mediated mesaconate synthesis, highlighting tissue-specific itaconate degradation routes. This study identifies a new branch of itaconate metabolism, provides an analytical framework to resolve C5 dicarboxylate networks, and links 2HMS to inflammation and mitochondrial metabolism that might be targeted therapeutically.

cell biology↗

bioRxiv2025

Substrate availability and citrate alter TCA cycle metabolism and SLC13A3 in macrophage immune responses

Cell culture media are commonly formulated to enhance cell growth and often lack the physiological nutrient composition found in human blood plasma. The impact of substrate availability on immune cell metabolism and function remains incompletely understood. Here, we demonstrate that changes in culture medium composition affect mitochondrial metabolic pathways, immune responses, and transport in macrophages. Using mass spectrometry and stable isotope tracing, we identify citrate as a mediator linking extracellular substrate availability to intracellular metabolism. We also observe increased IL-6 secretion and elevated expression of plasma membrane transporter NaDC3 (SLC13A3) under physiological carbon source conditions that are reversed when citrate is excluded from the medium. Our findings demonstrate that extracellular substrate composition shapes macrophage immunometabolism and identify citrate as an extracellular signal that modulates immune responses. This work highlights the importance of physiologically relevant nutrient availability in studying and targeting immunometabolic pathways.

cell biology↗

bioRxiv2025

In vivo itaconate tracing reveals degradation pathway and turnover kinetics

Itaconate is an immunomodulatory metabolite that alters mitochondrial metabolism and immune cell function. This organic acid is endogenously synthesized via tricarboxylic acid (TCA) metabolism downstream of TLR signaling. Itaconate-based treatment strategies are being explored to mitigate numerous inflammatory conditions. However, little is known about the turnover rate of itaconate in circulation, the kinetics of its degradation, and the broader consequences on metabolism. By combining mass spectrometry and in vivo 13C itaconate tracing, we demonstrate that itaconate is rapidly eliminated from plasma, excreted via urine, and fuels TCA cycle metabolism specifically in the liver and kidneys. These studies further revealed that itaconate is converted into acetyl-CoA, mesaconate, and citramalate in mitochondria. Itaconate administration also influenced branched-chain amino acid metabolism and succinate levels, indicating a functional impact on succinate dehydrogenase (SDH) and methylmalonyl-CoA mutase (MUT) activity. Our findings uncovered a previously unknown aspect of the itaconate metabolism, highlighting its rapid catabolism in vivo that contrasts findings in cultured cells.

cell biology↗