Compared with other cancers, diabetes mellitus is more closely associated with hepatocellular carcinoma (HCC). However, whether hyperglycemia is associated with hepatic carcinogenesis remains uncertain. In this study, we investigate the effect of hyperglycemia on HCC development. Mice pretreated with 7,12-dimethylbenz (a) anthracene were divided into three feeding groups: normal diet (Control), high-starch diet (Starch), and high-fat diet (HFD) groups. In addition, an STZ group containing mice that were fed a normal diet and injected with streptozotosin to induce hyperglycemia was included. The STZ group demonstrated severe hyperglycemia, whereas the Starch group demonstrated mild hyperglycemia and insulin resistance. The HFD group demonstrated mild hyperglycemia and severe insulin resistance. Multiple HCC were macroscopically and histologically observed only in the HFD group. Hepatic steatosis was observed in the Starch and HFD groups, but levels of inflammatory cytokines, interleukin (IL)-6, tumor necrosis factor-alpha, and IL-1 beta, were elevated only in the HFD group. The composition of gut microbiota was similar between the Control and STZ groups. A significantly higher number of Clostridium cluster XI was detected in the feces of the HFD group than that of all other groups; it was not detectable in the Starch group. These data suggested that hyperglycemia had no effect on hepatic carcinogenesis. Different incidences of HCC between the Starch and HFD groups may be attributable to degree of insulin resistance, but diet-induced changes in gut microbiota including Clostridium cluster XI may have influenced hepatic carcinogenesis. In conclusion, in addition to the normalization of blood glucose levels, diabetics may need to control insulin resistance and diet contents to prevent HCC development. (C) 2015 The Authors. Published by Elsevier Inc.