Kallistatin/Serpina3c inhibits cardiac fibrosis after myocardial infarction by regulating glycolysis via Nr4a1 activation

BACKGROUND

Fibrotic remodeling is an essential aspect of heart failure. Human kallistatin (KS, mouse Serpina3c homologs) inhibits fibrosis after myocardial infarction (MI) but the specific underlying mechanism is unknown.

METHODS

A total of 40 heart failure patients (HFPs) were enrolled and their plasma KS was measured using ELISA. Serpina3c^-/- and C57BL/6 mice were used to construct the MI model. TGF-β1 or a hypoxic condition was established to interfere with the functioning of cardiac fibroblasts (CFs). RNA-seq was performed to assess the effect of Serpina3c on the transcriptome.

FINDINGS

The levels of KS were used as a predictor of readmission among the HFPs. Serpina3c expression decreased in MI hearts and CFs. Serpina3c^-/- led to the aggravation of MI fibrosis, and increased the proliferation of CFs. The overexpression of Serpina3c in CFs had the opposite effect. Glycolysis-related genes were significantly increased in Serpina3c^-/- group by RNA-seq. Enolase (ENO1), which is a key enzyme in glycolysis, increased most significantly. Inhibition of ENO1 could antagonize the promotion of Serpina3c^-/- on the proliferation of CFs. Co-IP was performed to verify the interaction between Serpina3c and Nr4a1. Serpina3c^-/- inhibited the acetylation of Nr4a1 and increased the degradation of Nr4a1. Activation of Nr4a1 could negatively regulate the expression of ENO1 and inhibited the proliferation of Serpina3c^-/- CFs in Serpina3c^-/- MI mice.

INTERPRETATION

Serpina3c inhibits the transcriptional activation of ENO1 by regulating the acetylation of Nr4a1, thereby reducing the fibrosis after MI by inhibiting glycolysis. Serpina3c is a potential target for prevention and treatment of heart failure after MI.

Serpina3c regulates adipose differentiation via the Wnt/β-catenin-PPARγ pathway

OBJECTIVE

The Serpin protein family plays an important role in regulating the functioning of the adipose tissue. This study aimed to study the underlying mechanisms of Serpina3c in regulating adipogenesis.

METHODS

We developed a Serpina3c knockout (Serpina3c^-/-) mouse model and Serpina3c knockdown and overexpression 3 T3-L1 preadipocyte models to evaluate the role of Serpina3c in adipose differentiation. Mice were fed on ND for 12-month or HFD for one month. The body weight, glucose tolerance, and insulin tolerance of the mice were subsequently measured. Lipid depositions and adipose tissue morphology were then detected using Oil red O staining and HE staining. qRT-PCR and Western blot were used to detect the expression of adipose differentiation transcription factors.

RESULTS

Serpina3c^-/- mice exhibited lower body weight and white adipose tissue (WAT) weight than WT mice after 12 months of being fed on ND. Additionally, there was an increase in serum and hepatic triglyceride (TG) levels in Serpina3c^-/- mice, without changes in glucose metabolism. Wnt/β-catenin was upregulated while PPARγ expression was decreased in knockout mice WAT. Impaired adipocyte differentiation caused by Serpina3c knockdown was reversed by IWR-1 and kallistatin through an increase in PPARγ expression. Serpina3c^-/- mice fed on HFD for one month had a lower body weight and WAT than WT, accompanied by increased lipid depositions in the liver and muscles and severe insulin resistance.

CONCLUSION

Serpina3c promotes adipogenesis and maintains normal fat function by inhibiting the Wnt/β-catenin pathway.

Serpina3c protects against high-fat diet-induced pancreatic dysfunction through the JNK-related pathway

BACKGROUND

Serpina3 is a member of the serine protease inhibitor family and is involved in the inflammatory response. In this study, we investigated the effect of Serpina3c on pancreatic function in hypercholesterolemic mice.

METHODS

To investigate the role of Serpina3c in hyperlipidaemia, Serpina3c knockout mice were bred with Apoe-knockout mice (on a C57BL/6 background) to generate heterozygous Serpina3c-Apoe double knockout (Serpina3c^+/-/Apoe^+/-) mice and were then bred to obtain homozygotes. C57BL/6, Serpina3c^-/-, Apoe^-/-, and Apoe^-/-Serpina3c^-/- mice were fed normal chow, and Apoe^-/- and Apoe^-/-Serpina3c^-/- mice were fed a high-fat diet (HFD). After feeding for 3 months, the mice were monitored for body weight, blood glucose, glucose tolerance, and insulin tolerance test (ITT). ELISA and immunohistochemistry were used to detect insulin levels and glucagon expression. Immunohistochemical staining for macrophages in the pancreas was also performed. Western blot analysis was performed on pancreatic tissues to detect the protein levels of insulin-associated molecules, the metalloproteinase MMP2, the tissue inhibitor TIMP2 and components of the JNK-related pathway.

RESULTS

Blood glucose levels, glucose tolerance, and ITT were not significantly different among the groups. Serpina3c knockout resulted in blood lipid abnormalities in mice under HFD conditions. Insulin secretion was decreased in Apoe^-/-Serpina3c^-/- mice compared with Apoe^-/- mice under normal chow conditions. In addition, Apoe^-/-Serpina3c^-/- mice exhibited increased insulin and glucagon secretion and expression after three months of HFD feeding, but insulin secretion was decreased in Apoe^-/-Serpina3c^-/- mice compared with Apoe^-/- mice after the fifth month of HFD feeding. Serpina3c knockout increased MMP2 protein levels, whereas TIMP2 levels in the pancreas were decreased. Furthermore, Serpina3c knockout significantly upregulated the number of macrophages in the pancreas under HFD conditions. The JNK/AKT/FOXO1/PDX-1 axis was found to be involved in Serpina3c-regulated insulin secretion.

CONCLUSION

These novel findings show that Serpina3c could play a protective role in insulin secretion partly through the JNK-related pathway under HFD conditions.