Deficiency of p62/Sequestosome 1 Causes Hyperphagia Due to Leptin Resistance in the Brain

Harumi Harada, Eiji Warabi, Taizo Matsuki, Toru Yanagawa, Kosuke Okada, Junya Uwayama, Akira Ikeda, Kazuhiro Nakaso, Kyoko Kirii, Noriko Noguchi, Hiroki Bukawa, Richard C. M. Siow, Giovanni E. Mann, Junichi Shoda, Tetsuro Ishii, Takeshi Sakurai

The cytoplasmic regulatory protein p62 (Sequestosome 1/A170) is known to modulate various receptor-mediated intracellular signaling pathways. p62 deficiency was shown to result in mature-onset obesity in mice, but the mechanisms underlying this abnormality remained unclear. Here we report that hyperphagia due to central leptin resistance is the cause of obesity in p62(-/-) mice. We found that these mice show hyperphagia. Restriction of food to the amount eaten by wild-type mice prevented excess body weight gain and fat accumulation, suggesting that overfeeding is the primary cause of obesity in p62(-/-) mice. Brain-specific p62 deficiency caused mature-onset obesity to the same extent as in p62(-/-) mice, further supporting a neuronal mechanism as the major cause of obesity in these mice. Immunohistochemical analysis revealed that p62 is highly expressed in hypothalamic neurons, including POMC neurons in the arcuate nucleus. Central leptin resistance was observed even in young preobese p62(-/-) mice. We found a defect in intracellular distribution of the transcription factor Stat3, which is essential for the action of leptin, in p62(-/-) mice. These results indicate that brain p62 plays an important role in bodyweight control by modulating the central leptin-signaling pathway and that lack of p62 in the brain causes leptin resistance, leading to hyperphagia. Thus, p62 could be a clinical target for treating obesity and metabolic syndrome.