Deletion of Ligand Dependent Corepressor-Like (LCoRL) Protects Against Diet-induced Obesity Deletion of Ligand Dependent Corepressor-Like (LCoRL) Protects Against Diet-induced Obesity

ABSTRACT OBJECTIVE: Genome Wide Association Studies (GWAS) in humans, dogs, and livestock have uncovered genes which may play a role in metabolism. However, functional analysis is required to link the metabolic phenotype with the associated gene. Here we identified the Ligand Dependent Corepressor-Like (LCoRL) as a potential metabolic regulator. METHOD: We used CRISPR/Cas9 approaches in mice to generate a Lcorl null allele (Lcorl-/-). We characterized Lcorl-/- mice by assessing body weight, body composition, food intake, and glucose homeostasis as well as assessing transcriptional changes in Lcorl-/- livers by RNA-sequencing. Finally, we challenged mice with a 60% high fat diet (HFD) and a treadmill exercise stress test. RESULTS: Mice homozygous for loss of Lcorl are viable and fertile. However, Lcorl-/- pups show stunted postnatal growth for the first few weeks of life. This is followed by a catchup growth, such that, Lcorl-/- mice are indistinguishable from wildtype littermates by 7-9 weeks of age. Three-week-old mice show reduced circulating insulin like growth factor-1 (IGF-1) levels without a change in pituitary Growth hormone (Gh) mRNA levels. Interestingly, Lcorl-/- mice remain lean compared to wildtype littermates as they age. This is associated with a decrease in daily food intake. Additionally, Lcorl-/- mice show no change in energy expenditure; however, Lcorl-/- mice show a greater amplitude of their respiratory exchange ratio (RER) compared to controls, suggesting differential usage of fat and carbohydrates across the light/dark cycle. This altered RER may result from the reduction in day-time food intake or disrupted mobilization of fat and carbohydrate stores. Consistent with enhanced metabolic health, Lcorl-/- mice also show improved glucose tolerance and insulin sensitivity. Finally, Lcorl-/- mice are protected against a 60% high fat diet challenge and show reduced exercise capacity in a stress test. CONCLUSION: This phenotypic characterization of the Lcorl-/- mouse reveals that LCoRL is a causal gene resulting in the changes in metabolism seen in GWAS in humans and livestock and provides novel mechanistic insights of a gene important in human disease and economically valuable traits in livestock. To investigate the role of Lcorl, we created a Lcorl global knockout model. We harvested tissues from Lcorl KO and wildtype mice and conducted RNA-Seq on their livers. We performed differential gene expression analysis on Lcorl KO vs WT livers.【摘要】 研究目的：针对人类、犬类及家畜开展的全基因组关联研究（Genome Wide Association Studies, GWAS）已发现若干可能参与代谢调控的基因，但需通过功能分析将代谢表型与相关基因建立因果关联。本研究鉴定出配体依赖性辅阻遏物样蛋白（Ligand Dependent Corepressor-Like, LCoRL）为潜在的代谢调控因子。 研究方法：本研究在小鼠体内采用CRISPR/Cas9技术构建Lcorl纯合敲除等位基因（Lcorl-/-）模型。通过检测体重、身体成分、食物摄入量、葡萄糖稳态，以及对Lcorl-/-小鼠肝脏开展RNA测序以分析转录组变化，对该模型进行表型表征。此外，本研究还通过60%高脂饮食（High Fat Diet, HFD）造模及跑台运动应激试验对小鼠进行应激挑战。 研究结果：Lcorl纯合敲除的小鼠可存活且具有生育能力。但Lcorl-/-幼鼠在出生后数周内出现生长迟缓，随后出现代偿性追赶生长，至7~9周龄时，其表型与野生型同窝小鼠无明显差异。3周龄的Lcorl-/-小鼠循环中胰岛素样生长因子-1（Insulin Like Growth Factor-1, IGF-1）水平降低，但垂体生长激素（Growth Hormone, Gh）的mRNA水平无显著变化。值得注意的是，随着年龄增长，Lcorl-/-小鼠始终保持较瘦的体型，这与每日食物摄入量降低相关。此外，Lcorl-/-小鼠的能量消耗无明显改变，但与对照组相比，其呼吸交换率（Respiratory Exchange Ratio, RER）的波动幅度更大，提示其在明暗周期中对脂肪与碳水化合物的利用模式存在差异。这种呼吸交换率的改变可能源于日间进食量减少，或是脂肪与碳水化合物储存的动员过程被打乱。与代谢健康改善的表型一致，Lcorl-/-小鼠的糖耐量与胰岛素敏感性均有所提升。最后，Lcorl-/-小鼠可抵御60%高脂饮食诱导的代谢异常，但在运动应激试验中表现出运动能力下降。 研究结论：本研究通过对Lcorl-/-小鼠的表型表征，证实LCoRL是导致人类及家畜全基因组关联研究中所发现的代谢改变的因果基因，同时为该基因在人类疾病及家畜经济性状中的作用机制提供了全新的研究视角。为探究Lcorl的功能，本研究构建了Lcorl全身敲除模型，采集该模型小鼠与野生型小鼠的组织样本，并对其肝脏开展RNA测序，进而进行差异基因表达分析。