Pyruvate dehydrogenase kinase 1 and 2 deficiency reduces high-fat diet-induced hypertrophic obesity and inhibits the differentiation of preadipocytes into mature adipocytes

Obesity is now recognized as a disease. This study revealed a novel role for pyruvate dehydrogenase kinase (PDK) in diet-induced hypertrophic obesity. Mice with global or adipose tissue-specific PDK2 deficiency were protected against diet-induced obesity. The weight of adipose tissues and the size of adipocytes were reduced. Adipocyte-specific PDK2 deficiency slightly increased insulin sensitivity in HFD-fed mice. In studies with 3T3-L1 preadipocytes, PDK2 and PDK1 expression was strongly increased during adipogenesis. Evidence was found for epigenetic induction of both PDK1 and PDK2. Gain- and loss-of-function studies with 3T3-L1 cells revealed a critical role for PDK1/2 in adipocyte differentiation and lipid accumulation. PDK1/2 induction during differentiation was also accompanied by increased expression of hypoxia-inducible factor-1α (HIF1α) and enhanced lactate production, both of which were absent in the context of PDK1/2 deficiency. Exogenous lactate supplementation increased the stability of HIF1α and promoted adipogenesis. PDK1/2 overexpression-mediated adipogenesis was abolished by HIF1α inhibition, suggesting a role for the PDK-lactate-HIF1α axis during adipogenesis. In human adipose tissue, the expression of PDK1/2 was positively correlated with that of the adipogenic marker PPARγ and inversely correlated with obesity. Similarly, PDK1/2 expression in mouse adipose tissue was decreased by chronic high-fat diet feeding. We conclude that PDK1 and 2 are novel regulators of adipogenesis that play critical roles in obesity. Obesity: Effects of different forms of key enzyme The discovery that two forms of a key enzyme appear to play a critical role in fat production triggered by overeating might lead to new approaches to prevent and treat obesity. Hyeon-Ji Kang at Kyungpook National University, Daegu, South Korea, and colleagues in South Korea and the USA examined the role of the enzymes pyruvate dehydrogenase kinase types 1 and 2 (PDK1/2). PDK enzymes regulate the activity of a multi-enzyme complex that catalyzes a key step in the use of glucose to provide energy stores for cells. Mice deficient in PDK2 were protected from diet-induced obesity, and PDK 1 and 2 activity was increased during the generation of fat cells. Studies using mice and human fat tissue confirmed that the enzymes regulate the development and growth of fat cells. Drugs inhibiting PDK enzymes might combat obesity.