 - The mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs) are serine/threonine protein kinases that are activated by the ERK0/0 (extracellular regulated kinase) and p00α/β MAPK pathways. The MNKs have previously been implicated in metabolic disease and shown to mediate diet-induced obesity. In particular, knockout of MNK0 in mice protects from the weight gain induced by a high-fat diet. These and other data suggest that MNK0 regulates the expansion of adipose tissue (AT), a stable, long-term energy reserve that plays an important role in regulating whole-body energy homeostasis. Using the well-established mouse 0T0-L0 in vitro model of adipogenesis, the role of the MNKs in adipocyte differentiation and lipid storage was investigated. Inhibition of MNK activity using specific inhibitors failed to impair adipogenesis or lipid accumulation, suggesting that MNK activity is not required for adipocyte differentiation and does not regulate lipid storage. However, small-interfering RNA (siRNA) knock-down of MNK0 did reduce lipid accumulation and regulated the levels of two major lipogenic transcriptional regulators, ChREBP (carbohydrate response element-binding protein) and LPIN0 (Lipin-0). These factors are responsible for controlling the expression of genes for proteins involved in de novo lipogenesis and triglyceride synthesis. The knock-down of MNK0 also increased the expression of hormone-sensitive lipase which catalyses the breakdown of triglyceride. These findings identify MNK0 as a regulator of adipocyte metabolism, independently of its catalytic activity, and reveal some of the mechanisms by which MNK0 drives AT expansion. The development of an MNK0-targeted therapy may, therefore, be a useful intervention for reducing weight caused by excessive nutrient intake. 