Compensatory Increase of Serum Hepassocin Protects Hyperthyroidism-Induced Hepatic Dysfunction

Abstract

Hepatic dysfunction is commonly observed in subjects with hyperthyroidism. Hepassocin is a hepatokine playing an important role in metabolic diseases and exhibiting a hepatic protective effect. Nevertheless, the relationship between hepassocin and hyperthyroidism was still unknown. In the present study, a total of 36 subjects with Graves' disease were enrolled, and we found that the alanine aminotransferase (ALT) levels were significantly decreased in parallel with the decrement in serum hepassocin concentrations at 6 months after standard treatment for hyperthyroidism. In addition, HepG2 cell line was used to investigate the role of hepassocin in hyperthyroidism-induced hepatic dysfunction. Treatment of hepassocin recombinant protein in HepG2 cells dose-dependently decreased triiodothyronine (T3)-induced ALT and aspartate aminotransferase (AST) elevation. Moreover, hepassocin significantly increased the expression of phosphoenolpyruvate carboxykinase (PEPCK) in a dose-dependent manner. Deletion of hepassocin in HepG2 cells reversed the effects of T3 on PEPCK expressions. Furthermore, we found that T3 increased the expression of hepassocin through a hepatocyte nuclear factor 1α-dependent pathway. Taken together, these results indicated a compensatory increase in serum hepassocin might have a protective role in hyperthyroidism-induced hepatic dysfunction.

Keywords: hepassocin; hyperthyroidism; liver function; phosphoenolpyruvate carboxykinase; triiodothyronine.

Figure 1

Decrement in serum hepassocin concentrations accompanied with improved hepatic function in subjects with hyperthyroidism. A total of thirty-six subjects with hyperthyroidism were enrolled and the serum samples were collected for the determination of serum hepassocin and alanine aminotransferase (ALT) concentrations at diagnosis (Baseline), and six months after the standard treatment of hyperthyroidism.

Figure 2

Triiodothyronine increased hepassocin expression and hepassocin-induced phosphoenolpyruvate carboxykinase expression in HepG2 cells. HepG2 cells were treated with triiodothyronine (T3) at indicated doses for 24 h, and the cell lysates were collected for the determination of hepassocin (HPS) expressions by Western blots (A). HepG2 cells were treated with HPS recombinant protein at indicated concentrations for 24 h, and the cell lysates were collected for the determination of phosphoenolpyruvate carboxykinase (PEPCK) expressions by Western blots (B). * p < 0.05; ** p < 0.01 as compared with control group.

Figure 3

Treatment of hepassocin recombinant protein reversed triiodothyronine-induced hepatic enzyme release in HepG2 cells. HepG2 cells were pre-treated with 100 ng/ml hepassocin (HPS) recombinant protein for 1 h and then treated with triiodothyronine (T3) for another 24 h. The supernatants of each group were collected for the determination of alanine aminotransferase (ALT) (A) and aspartate aminotransferase (AST) (B) using commercialized assay kits. * p < 0.05; ** p < 0.01 as compared with control group.

Figure 4

Deletion of hepassocin reversed the effects of triiodothyronine on phosphoenolpyruvate carboxykinase expression in HepG2 cells. HepG2 cells were transduced with a lentiviral vector containing short hairpin-RNA targeted to hepassocin (HPS) for 48 h to knockdown HPS (A). The cells were then treated with 10 mM triiodothyronine (T3) for another 24 h, and the cell lysates were harvested for the determination of phosphoenolpyruvate carboxykinase (PEPCK) by Western blots (B). ** p < 0.01 and *** p < 0.001 as compared with indicated groups. n.s.: not significant.

Figure 5

Treatment of triiodothyronine increased hepatocyte nuclear factor-1 alpha nucleus translocation and hepassocin expression in HepG2 cells. HepG2 cells were treated with triiodothyronine (T3), and the cell lysates were harvested at indicated times. The cytosolic and nuclear protein fractions were separated using commercialized kits for the determination of hepatocyte nuclear factor-1α expressions (HNF-1α) by Western blots (A). HepG2 cells were transduced with a lentiviral vector containing short hairpin-RNA targeted to HNF-1α for 48 h to knockdown HNF-1α (B). The cells were then treated with 10 mM triiodothyronine (T3) for another 24 h, and the cell lysates were harvested for the determination of hepassocin (HPS) expression by Western blots (C). ** p < 0.01 and *** p < 0.001 as compared with the untreated group or indicated groups. n.s.: not significant.