Hepatic IRS1 and ß-catenin expression is associated with histological progression and overt diabetes emergence in NAFLD patients

Abstract

Background: Nonalcoholic fatty liver disease (NAFLD) is a risk factor for type 2 diabetes. Our aim was to investigate the relationship between NAFLD and impaired glucose metabolism in terms of insulin receptor substrate 1 and 2 (IRS1 and IRS2) expression in the liver.

Methods: Liver biopsy was performed at the University of Tokyo Hospital between November 2011 and March 2016 on 146 patients with NAFLD who were not being treated with any diabetes or dyslipidemia drugs. Among them, 63 underwent liver biopsy after an overnight fast, and 83 at 5 h after an oral glucose tolerance test (OGTT). Differences in messenger RNA (mRNA) levels of several glucose metabolism-related factors were determined and correlated with hepatic histological changes assessed by NAFLD activity score. We prospectively followed up with the patients until May 2017.

Results: Hepatic necroinflammation was significantly correlated with serum insulin levels and inversely correlated with IRS1 mRNA levels. In specimens obtained after an OGTT, hepatic necroinflammation and IRS1 expression correlated significantly with both peripheral and hepatic insulin resistance. We also found that hepatic β-catenin and glucokinase mRNA levels were elevated in patients undergoing liver biopsy after an OGTT, especially in those with less hepatic necroinflammation and a lower degree of fibrosis. A prospective cohort study showed that ballooning is the most significant risk factor for developing diabetes.

Conclusions: The decreased hepatic expression of IRS1 and β-catenin in NAFLD is linked to histological progression such as ballooning, and might lead to diabetes as a result of impaired glucose metabolism.

Keywords: Hyperinsulinemia; IRS1; Insulin resistance; NAFLD; Postprandial hyperglycemia.

Fig. 1

Relationship between steatohepatitis histology and glucose metabolism parameters, all of which were very strongly correlated with lobular inflammation and ballooning. Spearman’s rank correlation coefficient was used to examine these correlations. IRI immunoreactive insulin, HOMA-IR homeostasis model assessment for insulin resistance, HBA1c hemoglobin A1c

Fig. 2

Relationship between IRS1/2 levels and steatohepatitis histology and metabolism parameters. Spearman’s rank correlation coefficient was used to examine these correlations. a IRS1 and IRS2 mRNA expression and steatohepatitis histology. b IRS1 and IRS2 mRNA expression and glucose metabolism-related parameters. IRI, immunoreactive insulin, HOMA-IR homeostasis model assessment for insulin resistance, HBA1c hemoglobin A1c

Fig. 3

Glucose concentrations during 75-g oral glucose tolerance tests (OGTTs) stratified based on degree of lobular inflammation and ballooning and IRS1 and IRS2 mRNA levels

Fig. 4

Relationship between β-catenin or GCK mRNA levels and steatohepatitis histology. Spearman’s rank correlation coefficient was used to examine these correlations. Hepatic β-catenin and GCK mRNA levels were measured in specimens from patients undergoing liver biopsy at 5 h after oral glucose tolerance tests (OGTTs)

Fig. 5

Immunohistochemical staining of liver biopsies from representative nonalcoholic fatty liver disease patients. Patients A and B underwent liver biopsy 5 h after oral glucose tolerance tests (OGTT), whereas patients C and D underwent liver biopsy in a fasting state. a Patient A was a 44-year-old male with severe ballooning. b Patient B was a 31-year-old male, with no ballooning. c Patient C was a 47-year-old male and had severe ballooning. d Patient D was a 45-year-old male and had no ballooning. Liver biopsies were stained for β-catenin and IRS1. Positive immunoreactivity appears brown. Original magnification, ×100 or ×200