Adrian Pickar‐Oliver

Abstract Branched-chain amino acids (BCAA) and their cognate α-ketoacids (BCKA) are elevated in an array of cardiometabolic diseases. Here we demonstrate that the major metabolic fate of uniformly- 13 C-labeled α-ketoisovalerate ([U- 13 C]KIV) in the heart is reamination to valine. Activation of cardiac branched-chain α-ketoacid dehydrogenase (BCKDH) by treatment with the BCKDH kinase inhibitor, BT2, does not impede the strong flux of [U- 13 C]KIV to valine. Sequestration of BCAA and BCKA away from mitochondrial oxidation is likely due to low levels of expression of the mitochondrial BCAA transporter SLC25A44 in the heart, as its overexpression significantly lowers accumulation of [ 13 C]-labeled valine from [U- 13 C]KIV. Finally, exposure of perfused hearts to levels of BCKA found in obese rats increases phosphorylation of the translational repressor 4E-BP1 as well as multiple proteins in the MEK-ERK pathway, leading to a doubling of total protein synthesis. These data suggest that elevated BCKA levels found in obesity may contribute to pathologic cardiac hypertrophy via chronic activation of protein synthesis.

Cell engineering relies heavily on viral vectors for the delivery of molecular cargo into cells due to their superior efficiency compared to nonviral ones. However, viruses are immunogenic and expensive to manufacture, and have limited delivery capacity. Nonviral delivery approaches avoid these limitations but are currently inefficient for clinical applications. This work demonstrates that the efficiency of nonviral delivery of plasmid DNA, mRNA, Sleeping Beauty transposon, and ribonucleoprotein can be significantly enhanced through pretreatment of cells with the nondegradable sugars (NDS), such as sucrose, trehalose, and raffinose. The enhancement is mediated by the incorporation of the NDS into cell membranes, causing enlargement of lysosomes and formation of large (>500 nm) amphisome-like bodies (ALBs). The changes in subcellular structures redirect transport of cargo to ALBs rather than to lysosomes, reducing cargo degradation in cells. The data indicate that pretreatment of cells with NDS is a promising approach to improve nonviral cargo delivery in biomedical applications.