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Peripheral Neuropathy and Hindlimb Paralysis in a Mouse Model of Adipocyte-Specific Knockout of Lkb1
Yan Xiong1, Jessica C Page2, Naagarajan Narayanan3
1Laboratory of Animal Fat Deposition and Muscle Development, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China; Department of Animal Sciences, Purdue University, West Lafayette, IN 47906, USA; Joint Laboratory of Lipid Metabolism, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Beijing 100193, China.
Abstract:
Brown adipose tissues (BAT) burn lipids to generate heat through uncoupled respiration, thus representing a powerful target to counteract lipid accumulation and obesity. The tumor suppressor liver kinase b1 (Lkb1) is a key regulator of cellular energy metabolism; and adipocyte-specific knockout of Lkb1 (Ad-Lkb1 KO) leads to the expansion of BAT, improvements in systemic metabolism and resistance to obesity in young mice. Here we report the unexpected finding that the Ad-Lkb1 KO mice develop hindlimb paralysis at mid-age. Gene expression analyses indicate that Lkb1 KO upregulates the expression of inflammatory cytokines in interscapular BAT and epineurial brown adipocytes surrounding the sciatic nerve. This is followed by peripheral neuropathy characterized by infiltration of macrophages into the sciatic nerve, axon degeneration, reduced nerve conductance, and hindlimb paralysis. Mechanistically, Lkb1 KO reduces AMPK phosphorylation and amplifies mammalian target-of-rapamycin (mTOR)-dependent inflammatory signaling specifically in BAT but not WAT. Importantly, pharmacological or genetic inhibition of mTOR ameliorates inflammation and prevents paralysis. These results demonstrate that BAT inflammation is linked to peripheral neuropathy.