左旋甲状腺素替代治疗对亚临床甲状腺功能减退大鼠脂肪细胞因子表达的影响

Effect of levothyroxine replacement therapy on adipocyte expression in subclinical hypothyroidism rats

目的观察亚临床甲状腺功能减退症（SCH）大鼠脂肪细胞因子[脂联素（APN）、趋化因子chemerin、肿瘤坏死因子a（TNF-a）]的表达变化，以及左旋甲状腺素（L-T4）替代治疗的影响。方法65只雄性Wistar大鼠，按体质量采用随机数字表法分为5组，即对照组（n=10）、SCHA组（n=15）、SCHB组（n=15）、SCHC组（n=15）及巩治疗组（SCH＋L-T4，n=10）。SCHA、B、C组大鼠分别以5、15、20mg·kg-1·d-1他巴唑灌胃；SCH＋L-T4组大鼠先以20mg·kg-1·d-1他巴唑灌胃，约8周后，以6μg·kg-1·d-1的L-T4同时灌胃（50μg／片），造模时间为16周。采用酶联免疫吸附试验测定5组大鼠血清APN、趋化因子chemerin、TNF—α水平；实时定量PCR及蛋白免疫印迹法检测大鼠内脏脂肪组织APN、趋化因子chemerin、TNF—α mRNA及蛋白表达水平。结果与对照组比较[（202．20±17．27）、（143．70±18．46）ng／L，（114．69±4．18）μg／L]，SCHA、B、C组大鼠血清趋化因子chemerin水平明显升高[（314．33±16．80）、（355．00±17．10）、（365．00±11．63）ng／L，P均〈0．05]，TNF-α水平也明显升高[（222．60±14．13）、（279．20±12．79）、（288．30±15．89）ng／L，P均〈0．05]，而APN水平明显降低[（77．21±3．08）、（68．58±2．92）、（59．45±2．41）μg／L，P均〈0．05]；与SCHC组比较，SCH＋L-T4治疗组趋化因子chemerin、TNF-α水平[（260．07±10．80）、（178．40±10．29）ng／L]降低，APN水平[（102．35±3．17）μg／L]升高（P均〈0．05）。SCHA、B、C组大鼠APNmRNA、蛋白水平明显低于对照组（P均〈0．05）；SCH＋L-T4组APN mRNA、蛋白水平明显高于SCHC组（P均〈0．05）。SCHA、B、C组趋化因子chemerin和TNF—α mRNA、蛋白水平高于对照组（P均〈0．05）；但SCH＋巩组大鼠趋化因子chemerin和TNF—α mRNA、蛋白水平明显低于SCHC组（P均〈0．05）。结论SCH大鼠血清趋化因子chemerin、TNF—α表达水平升高．APN水平下降．L-T4替代治疗可明显改善上述变化。

Objective To observe the changes of adiponectin （APN）, chemerin and tumor necrosis factor-α （TNF--α） in subclinical hypothyroidism （SCH） rats, and to clarify the effect of L-thyroxine （L-T4） replacement therapy. Methods Sixty-five male Wistar rats were randomly divided into five groups via the random number table method： control group （n = 10）, SCH group A （n = 15）, SCH group B （n = 15）, SCH group C （n = 15） and L-T4 treatment group （SCH ＋ L-T4, n = 10）. Rats in groups SCH A, B and C were fed with 5, 15 and 20 mg·kg-1·d-1 methimazole （MMI） once daily by gavage. The rats in SCH ＋ L-T4 group were given 20 mg ·kg-1· d-1 MMI once daily through gavage, after 8 weeks, 6 μg· kg-1· d-1 of L-T4 was intragastrieally added （50 μg/tablet） and the model was completed at the 16th week. The levels of serum APN, chemerin and TNF-α were measured via the enzyme linked immunosorbent assay （ELISA） method. The mRNA and protein levels of APN, chemerin and TNF-α in visceral adipose tissue of 5 groups were determined by real-time PCR （RT-PCR） and Western blotting, respectively. Results Compared with the control group [（202.20 ± 17.27） ng/L, （143.70 ± 18.46） ng/L, （114.69 ± 4.18） μg/L], the serum chemerin levels in the SCH A, B, C groups were significantly higher [（314.33 ±16.80）, （355.00 ± 17.10）, （365.00 ± 11.63） ng/L, P 〈 0.05] and TNF-α levels also increased significantly [（222.60 ± 14.13）, （279.20 ± 12.79）, （288.30 ± 15.89） ng/L, P 〈 0.05], and APN levels were significantly decreased [（77.21 ± 3.08）, （68.58 ± 2.92）, （59.45 ± 2.41） p,g/L, P 〈 0.05]; but compared with SCH group C, the levels of ehemerin and TNF-α in the SCH ＋ L-T4 group were decreased [（260.07 ± 10.80）, （178.40 ± 10.29） ng/L] and the level of APN [（102.35 ±3.17） μg/L] was increased （P〈 0.05）. The mRNA and protein levels of APN in SCH A, B, C groups were significantly lower than those in the control group （P 〈 0.05）. The APN mRNA and protein levels in the SCH ＋ L-T4 group were significantly higher than those in the SCH group C （P 〈 0.05）. The mRNA and protein levels of chemerin and TNF-α in the SCH A, B, C groups were higher than those in the control group （P 〈 0.05）. However, the mRNA and protein levels of chemerin and TNF-α in the SCH ＋ L-T4 group were significantly lower than those in the SCH group C （P 〈 0.05）. Conclusion The expression levels of serum chemerin and TNF-α in SCH rats have increased, and APN levels decreased, but L-T4 can ameliorate these changes.