[Use of proinsulin analysis for estimates of insulin resistance].
BACKGROUND
According to contemporary estimates diabetes is present in 120 million subjects. This disease is associated with the incidence of a number of very serious organ complications and very frequently is diagnosed late (several years after its development). Because despite increased diagnostic and therapeutic efforts the number of diabetic patients is increasing, new diagnostic and therapeutic means are sought. Evidence was provided that some complications of diabetes develop not only in case of poor compensation but also in hyperinsulinaemia (hypertension, ischaemic heart and coronary artery disease etc.). In clinical practice it is however possible to assess hyperinsulinaemia or incipient insulin resistance only with difficulty because classical examinations (insulin and C-peptide on fasting) have a very low specificity and sensitivity. Therefore for estimation of insulin resistance loading tests are used (e.g. examination of insulin after stimulation with glucose, or C-peptide after stimulation with glucagon, insulin tolerance and suppression tests, or in research projects so-called minimal models or clamp techniques). Any loading test is however demanding from the aspect of time, money, technical aspects and staff and therefore possibilities are sought how to estimate the degree of insulin resistance and sensitivity in a specimen of biological material under basal conditions. OBJECTIVE OF INVESTIGATION: Because in the literature only sporadically assessment of intact proinsulin is mentioned as the ideal marker of insulin resistance under basal conditions, the authors decided to assess the relations between intact proinsulin (PI) and other biochemical parameters in patients with type 2 diabetes and dyslipidaemia (200 probands) and to assess whether PI correlates with the results of loading tests (modified oGTT with calculation of the sum and delta-insulin--120 probands).


RESULTS
It was revealed that PI (contrary to insulin, C-peptide and total proinsulin) correlates with the results of the loading test characterizing insulin resistance (sum and delta insulin, correlation coefficient 0.84) (n=120 subjects). It was furthermore found that probands (n=200 subjects) who are followed up on account of type 2 diabetes or dyslipidaemia (or both) differ from the control group (n=20 subjects) as regards biochemical parameters only in the PI concentration (dispensarized patients have higher levels, p>0.99), whereby in other standard basal characteristics of insulin secretion and resistance the groups did not differ. The differences were correlated with HOMA models of insulin secretion and resistance and no correlations were found. The PI concentration in this group correlated significantly with the cholesterol, fibrinogen and triacylglycerol concentration. No relations were found between the values of intact proinsulin with C-peptide and insulin.


CONCLUSIONS
Based on the results of their study the authors assume that examination of intact proinsulin is a valid "basal" indicator of insulin resistance. From the results ensues also that intact proinsulin is probably a very good predictor as regards the risk of development of cardiovascular disease.
Stejskal
D
D
Oddĕlení klinické biochemie a hematologie Nemocnice, Sternberk.
Pastorková
R
R
Bartek
J
J
Růzicka
V
V
Horalík
D
D
D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism; D007333:Insulin Resistance; D024821:Metabolic Syndrome / Q000378:metabolism*; D008875:Middle Aged; D011384:Proinsulin / Q000097:blood*
D011384:Proinsulin