Serum insulin, proinsulin and proinsulin/insulin ratio in type 2 diabetic patients: as an index of beta-cell function or insulin resistance.
BACKGROUND
Although insulin resistance and decreased insulin secretion are characteristics of established type 2 DM, which of these metabolic abnormalities is the primary determinant of type 2 DM is controversial. It is also not well known how insulin resistance and beta cell dysfunction influence serum insulin, proinsulin, proinsulin/insulin ratio in type 2 DM.


METHODS
We compared serum insulin, proinsulin and proinsulin/insulin ratio in type 2 diabetic patients and control subjects. We also investigated the relationship between serum insulin, proinsulin and proinsulin/insulin ratio and several biochemical markers which represent insulin resistance or beta cell function.


RESULTS
Insulin, proinsulin and proinsulin/insulin ratio were significantly higher in type 2 DM than control(p < 0.001). In diabetic patients, total insulin level was correlated with urinary albumin excretion rates(r = 0.224, p = 0.025) and body mass index(r = 0.269, p = 0.014). Proinsulin level was correlated with fasting C-peptide(r = 0.43, p = 0.002), postprandial 2 hour blood glucose(r = 0.213, p = 0.05) and triglyceride(r = 0.28, p = 0.022). Proinsulin/insulin ratio was positively correlated with fasting C-peptide(r = 0.236, p = 0.031), fasting blood glucose (r = 0.264, p = 0.015), postprandial 2 hour blood glucose(r = 0.277, p = 0.001) and triglyceride(r = 0.428, p < 0.001). In control subjects, insulin level was correlated with triglyceride(r = 0.366, p = 0.002). Proinsulin/insulin ratio was correlated with age(r = 0.241, p = 0.044).


CONCLUSIONS
The serum levels of insulin and proinsulin seem to be associated with several markers of insulin resistance. Whereas proinsulin/insulin ratio might represent beta cell function rather than insulin resistance. But more studies are needed to clarify the mechanisms of elevated proinsulin/insulin ratio in type 2 DM.
Kim
N H
NH
Department of Internal Medicine, College of Medicine, Korea University, Seoul, Korea.
Kim
D L
DL
Choi
K M
KM
Baik
S H
SH
Choi
D S
DS
D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000209:etiology; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D007515:Islets of Langerhans / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011384:Proinsulin / Q000097:blood*; D013453:Sulfonylurea Compounds / Q000494:pharmacology
D007328:Insulin; D013453:Sulfonylurea Compounds; D011384:Proinsulin