Altered basal C-peptide/insulin molar ratios in obese patients with fatty liver

To elucidate if the presence of fatty liver in obesity influences hepatic insulin extraction under basal conditions, serum immunoreactive insulin (IRI) and C-peptide immunoreactivity (CPR) were measured in 20 obese patients with normal glucose tolerance and in 8 normal subjects. The obese patients were subdivided into two groups matched for age and body weight according to the presence or absence of fatty liver: 8 obese patients without fatty liver (OBN) and 14 with fatty liver (OBF). Basal levels of IRI and CPR were significantly greater in the obese patients than in the normals, but were similar in the two obese groups. In the OBF group, the CPR/IRI molar ratios, a relative measure of hepatic insulin uptake, were significantly lower than in the other two groups, while the ratios of the normal and OBN groups were similar. The CPR/IRI molar ratios in all obese patients correlated well with the degree of fatty liver (r = 0.785, p less than 0.001). These results suggest that hepatic insulin extraction in a subgroup of obese patients is either reduced or indistinguishable from that of non-obese subjects, and that basal CPR/IRI molar ratio may serve as a useful indicator of the presence of fatty liver in simple obesity.