Hepatitis C virus infection and diabetes: direct involvement of the virus in the development of insulin resistance.
OBJECTIVE
Epidemiological studies have suggested a linkage between type 2 diabetes and chronic hepatitis C virus (HCV) infection. However, the presence of additional factors such as obesity, aging, or cirrhosis prevents the establishment of a definite relationship between these 2 conditions.


METHODS
A mouse model transgenic for the HCV core gene was used.


RESULTS
In the glucose tolerance test, plasma glucose levels were higher at all time points including in the fasting state in the core gene transgenic mice than in control mice, although the difference was not statistically significant. In contrast, the transgenic mice exhibited a marked insulin resistance as revealed by the insulin tolerance test, as well as significantly higher basal serum insulin levels. Feeding with a high-fat diet led to the development of overt diabetes in the transgenic mice but not in control mice. A high level of tumor necrosis factor-alpha, which has been also observed in human chronic hepatitis C patients, was considered to be one of the bases of insulin resistance in the transgenic mice, which acts by disturbing tyrosine phosphorylation of insulin receptor substrate-1. Moreover, administration of an anti-tumor necrosis factor-alpha antibody restored insulin sensitivity.


CONCLUSIONS
The ability of insulin to lower the plasma glucose level in the HCV transgenic mice was impaired, as observed in chronic hepatitis C patients. These results provide a direct experimental evidence for the contribution of HCV in the development of insulin resistance in human HCV infection, which finally leads to the development of type 2 diabetes.
Department of Internal Medicine, Graduate School of Medicine, University of Tokyo, Japan.
Yoshizumi
Y
Shintani
Hajime
H
Fujie
Hideyuki
H
Miyoshi
Takeya
T
Tsutsumi
Kazuhisa
K
Tsukamoto
Satoshi
S
Kimura
Kyoji
K
Moriya
Kazuhiko
K
Koike
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000821:virology*; D004041:Dietary Fats / Q000008:administration & dosage; D015309:Glucose Clamp Technique; D016174:Hepacivirus / Q000378:metabolism*; D006526:Hepatitis C / Q000150:complications* / Q000473:pathology / Q000503:physiopathology*; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D007515:Islets of Langerhans / Q000473:pathology; D008099:Liver / Q000503:physiopathology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*
D000906:Antibodies; D001786:Blood Glucose; D004041:Dietary Fats; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D010750:Phosphoproteins; D014409:Tumor Necrosis Factor-alpha; D014758:Viral Core Proteins; D014443:Tyrosine