Protein kinase A regulatory subunits in human adipose tissue: decreased R2B expression and activity in adipocytes from obese subjects.
Protein kinase A regulatory subunits in human adipose tissue: decreased R2B expression and activity in adipocytes from obese subjects.
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作者：
Mantovani G;Bondioni S;Alberti L;Gilardini L;Invitti C;Corbetta S;Zappa MA;Ferrero S;Lania AG;Bosari S;Beck-Peccoz P;Spada A
在人脂肪细胞中，cAMP依赖性途径介导源自β-肾上腺素能激活的信号，因此在重要代谢过程的调节中发挥关键作用，即，脂肪分解和产热。环磷酸腺苷的作用主要由蛋白激酶A（PKA）介导，其R2 B调节亚型在小鼠脂肪组织中表达最多，在那里它可以防止饮食诱导的肥胖和脂肪肝的发展。该研究的目的是调查肥胖和非肥胖受试者脂肪组织中R2 B表达、PKA活性和脂解的可能差异。研究设计和方法-通过免疫组织化学、蛋白质印迹和实时PCR方法对20例非肥胖和67例肥胖患者的皮下和内脏脂肪组织样本中不同PKA调节亚基的表达进行评估。PKA活性和甘油释放分别在总蛋白提取物和从新鲜组织样品分离的脂肪细胞中进行评价。RT-PCR表达技术表明，R2 B是最丰富的调控蛋白，无论是在mRNA水平还是在蛋白水平。有趣的是，肥胖患者的皮下和内脏脂肪组织中R2 B mRNA水平显著低于非肥胖患者，并且与BMI、腰围、胰岛素水平和胰岛素抵抗的稳态模型评估呈负相关。此外，基础和刺激PKA活性和甘油释放显着降低内脏脂肪组织从肥胖患者，然后非肥胖受试者。结论：我们的研究结果首次表明，在人类脂肪组织中，R2 B表达和PKA激活存在重要的BMI相关差异，这可能是肥胖症患者对β-肾上腺素能激活的不同脂解反应的多种决定因素之一。
OBJECTIVE—In human adipocytes, the cAMP-dependent pathway mediates signals originating from β-adrenergic activation, thus playing a key role in the regulation of important metabolic processes, i.e., lipolysis and thermogenesis. Cyclic AMP effects are mainly mediated by protein kinase A (PKA), whose R2B regulatory isoform is the most expressed in mouse adipose tissue, where it protects against diet-induced obesity and fatty liver development. The aim of the study was to investigate possible differences in R2B expression, PKA activity, and lipolysis in adipose tissues from obese and nonobese subjects. RESEARCH DESIGN AND METHODS—The expression of the different PKA regulatory subunits was evaluated by immunohistochemistry, Western blot, and real-time PCR in subcutaneous and visceral adipose tissue samples from 20 nonobese and 67 obese patients. PKA activity and glycerol release were evaluated in total protein extract and adipocytes isolated from fresh tissue samples, respectively. RESULTS—Expression techniques showed that R2B was the most abundant regulatory protein, both at mRNA and protein level. Interestingly, R2B mRNA levels were significantly lower in both subcutaneous and visceral adipose tissues from obese than nonobese patients and negatively correlated with BMI, waist circumference, insulin levels, and homeostasis model assessment of insulin resistance. Moreover, both basal and stimulated PKA activity and glycerol release were significantly lower in visceral adipose tissue from obese patients then nonobese subjects. CONCLUSIONS—Our results first indicate that, in human adipose tissue, there are important BMI-related differences in R2B expression and PKA activation, which might be included among the multiple determinants involved in the different lipolytic response to β-adrenergic activation in obesity.