Visceral adipose tissue-directed human kallistatin gene therapy improves adipose tissue remodeling and metabolic health in obese mice

Abstract

Objective: Adipose tissue remodeling is a dynamic process that is pathologically expedited in the obese state and is closely related to obesity-associated disease progression. This study aimed to explore the effects of human kallistatin (HKS) on adipose tissue remodeling and obesity-related metabolic disorders in mice fed with a high-fat diet (HFD).

Methods: Adenovirus-mediated HKS cDNA (Ad.HKS) and a blank adenovirus (Ad.Null) were constructed and injected into the epididymal white adipose tissue (eWAT) of 8-weeks-old male C57B/L mice. The mice were fed normal or HFD for 28 days. The body weight and circulating lipids levels were assessed. Intraperitoneal glucose tolerance test (IGTT) and insulin tolerance test (ITT) were also performed. Oil-red O staining was used to assess the extent of lipid deposition in the liver. Immunohistochemistry and HE staining were used to measure HKS expression, adipose tissue morphology, and macrophage infiltration. Western blot and qRT-PCR were used to evaluate the expression of adipose function-related factors.

Results: At the end of the experiment, the expression of HKS in the serum and eWAT of the Ad.HKS group was higher than in the Ad.Null group. Furthermore, Ad.HKS mice had lower body weight and decreased serum and liver lipid levels after four weeks of HFD feeding. IGTT and ITT showed that HKS treatment maintained balanced glucose homeostasis. Additionally, inguinal white adipose tissue (iWAT) and eWAT in Ad.HKS mice had a higher number of smaller-size adipocytes and had less macrophage infiltration than Ad.Null group. HKS significantly increased the mRNA levels of adiponectin, vaspin, and eNOS. In contrast, HKS decreased RBP4 and TNFα levels in the adipose tissues. Western blot results showed that local injection of HKS significantly upregulated the protein expressions of SIRT1, p-AMPK, IRS1, p-AKT, and GLUT4 in eWAT.

Conclusions: HKS injection in eWAT improves HFD-induced adipose tissue remodeling and function, thus significantly improving weight gain and dysregulation of glucose and lipid homeostasis in mice.

Keywords: Adipose tissue; High-fat diet; Human kallistatin; Metabolic disorders.