Jong Youn Baik

In the previous study, the culture medium was treated with nicotinamide adenine dinucleotide (NAD⁺) under the hypothesis that NAD⁺ regeneration is a major factor causing excessive lactate accumulation in Chinese hamster ovary (CHO) cells. The NAD⁺ treatment improved metabolism by not only reducing the Warburg effect but also enhancing oxidative phosphorylation, leading to enhanced antibody production. Building on this, four NAD⁺ precursors – nicotinamide mononucleotide (NMN), nicotinic acid (NA), nicotinamide riboside (NR), and nicotinamide (NAM) – were tested to elevate intracellular NAD+ levels more economically. First, the ability of CHO cells to utilize both the salvage and Preiss‐Handler pathways for NAD⁺ biosynthesis was verified, and then the effect of NAD⁺ precursors on CHO cell cultures was evaluated. These precursors increased intracellular NAD⁺ levels by up to 70.6% compared to the non‐treated group. Culture analysis confirmed that all the precursors induced metabolic changes and that NMN, NA, and NR improved productivity akin to NAD⁺ treatment, with comparable integral viable cell density. Despite the positive effects such as the increase in the specific productivity and changes in cellular glucose metabolism, none of the precursors surpassed direct NAD⁺ treatment in antibody titer, presumably due to the reduction in nucleoside availability, as evidenced by the decrease in ATP levels in the NAD⁺ precursor‐treated groups. These results underscore the complexity of cellular metabolism as well as the necessity for further investigation to optimize NAD⁺ precursor treatment strategies, potentially with the supplementation of nucleoside precursors. Our findings suggest a feasible approach for improving CHO cell culture performances by using NAD⁺ precursors as medium and feed components for the biopharmaceutical production.

Polyamines such as putrescine (PUT), spermidine (SPD), and spermine (SPM) are amine group-containing biomolecules that regulate multiple intracellular func

Aerobic glycolysis and its by‐product lactate accumulation are usually associated with adverse culture phenotypes such as poor cell viability and productivity. Due to the lack of knowledge on underlying mechanisms and accompanying biological processes, the regulation of aerobic glycolysis has been an ongoing challenge in culture process development for therapeutic protein productivity. Nicotinamide adenine dinucleotide (NAD⁺), a coenzyme and co‐substrate in energy metabolism, promotes the conversion of inefficient glycolysis into an efficient oxidative phosphorylation (OXPHOS) pathway. However, the effect of NAD⁺ on Chinese hamster ovary (CHO) cells for biopharmaceutical production has not been reported yet. In this work, we aimed to elucidate the influence of NAD⁺ on cell culture performance by examining metabolic shifts and mAb productivity. The supplementation of NAD⁺ increased the intracellular concentration of NAD⁺ and promoted SIRT3 expression. Antibody titer and the specific productivity in the growth phase were improved by up to 1.82‐ and 1.88‐fold, respectively, with marginal restrictions on cell growth. NAD⁺ significantly reduced the accumulation of reactive oxygen species (ROS) and the lactate yield from glucose, determined by lactate accumulation versus glucose consumption (Y_LAC/GLC). In contrast, OXPHOS capacity and amino acid consumption rate increased substantially. Collectively, these results suggest that NAD⁺ contributes to improving therapeutic protein productivity in bioprocessing via inducing an energy metabolic shift.

Hye-Im Kang, and Jong Youn Baik. Korean Society for Biotechnology and Bioengineering Journal 2022;37:139-50. https://doi.org/10.7841/ksbbj.2022.37.4.139