Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada.
Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Biomolecules. 2022 Dec 23;13(1):30. doi: 10.3390/biom13010030.
A decrease in the circulating levels of adiponectin in obesity increases the risk of metabolic complications, but the role of globular adiponectin, a truncated form produced by proteolytic cleavage, has not been defined. The objective of this investigation was to determine how globular adiponectin is generated and to determine whether this process impacts obesity. The cleavage of recombinant full-length adiponectin into globular adiponectin by plasma in vitro was used to identify Gly-93 as the N-terminal residue after proteolytic processing. The amino acid sequence of the cleavage site suggested thrombin was the protease responsible for cleavage, and inhibitors confirmed its likely involvement. The proteolytic site was modified, and this thrombin-resistant mutant protein was infused for 4 weeks into obese adiponectin-knockout mice that had been on a high-fat diet for 8 weeks. The mutation of the cleavage site ensured that globular adiponectin was not generated, and thus did not confound the actions of the full-length adiponectin. Mice infused with the mutant adiponectin accumulated less fat and had smaller adipocytes compared to mice treated with globular adiponectin, and concurrently had elevated fasting glucose. The data demonstrate that generation of globular adiponectin through the action of thrombin increases both adipose tissue mass and adipocyte size, but it has no effect on fasting glucose levels in the context of obesity.
循环脂联素水平在肥胖症中降低会增加代谢并发症的风险，但球形脂联素（一种通过蛋白水解切割产生的截断形式）的作用尚未确定。本研究的目的是确定球形脂联素的产生方式，并确定这一过程是否会影响肥胖。使用体外血浆将重组全长脂联素切割成球形脂联素，从而确定 Gly-93 是蛋白水解加工后的 N 端残基。切割位点的氨基酸序列提示凝血酶是负责切割的蛋白酶，抑制剂证实其可能参与其中。修饰了蛋白水解位点，并用这种对凝血酶有抗性的突变蛋白对高脂饮食 8 周的肥胖脂联素敲除小鼠输注 4 周。突变切割位点可确保不会产生球形脂联素，从而不会影响全长脂联素的作用。与用球形脂联素治疗的小鼠相比，输注突变脂联素的小鼠脂肪堆积减少，脂肪细胞变小，同时空腹血糖升高。这些数据表明，凝血酶作用下生成的球形脂联素增加了脂肪组织质量和脂肪细胞大小，但在肥胖的情况下对空腹血糖水平没有影响。
