Relationship between erythrocyte insulinase activity and insulin resistance in patients with impaired glucose tolerance

Chenzhong LI; Suhua ZHANG; Yaoming XUE; Hongxin QIU

ABSTRACT

BACKGROUND:

Impaired glucose tolerance(IGT) is mainly related to genetic factors and environmental factors including excessive calorie intake and obesity. Insulin resistance(IR) plays a major role in the onset of IGT.

OBJECTIVE:

To investigate the relationship between erythrocyte insulinase activity(EIA) and IR in patients with IGT soas to provide theoretic basis for improving IR in patients with IGT by exercise.

DESIGN:

Observational and comparative study based on IGT patients as the subjects and adults with normal glucose tolerance as controls.

SETTING:

Department of endocrinology of a hospital affiliated to a military medical university.

SUBJECTS:

The study was conducted in the Department of Endocrinology of Nanfang Hospital, First Military Medical University of Chinese PLA, from January 2001 to April 2003. A total of 50 inpatients and outpatients with IGT, 26 males and 24 females aged(52 ± 7) years, were randomly selected. Inclusion criteria those whose diagnosis met the WHO 1999 for criteria oral glucose tolerance test (OGTT) and whose heart, liver and kidney functions and blood test were within the normal range without taking any antidiabetics. Exclusion criteria those who had liver and kidney diseases, infection, malignant tumor, coronary heart disease, cerebrovascular disorder and connective tissue disease. The patients with IGT were divided into 2 subgroups according to the presence of abnormal fasting plasma glucose (FPG).Subgroup A consisted of 20 patients (9 males and 11 females) with IGT accompanied with impaired FPG. Subgroup B was composed of 30 IGT patients (17 males and 13 females) with normal FPG. Twenty adults with normal glucose tolerance were set as control group(20 females and 10 males) with the age of(48 ± 12)years.

METHODS:

EIA was measured with the method of radioenzymatic assay in all subjects. Blood sugar, serum insulin and glycosylated hemoglobin were also measured, and homeostasis model analysis-insulin resistance (HOMA-IR) index was calculated for estimation of insulin sensitivity.MAIN OUTCOME

MEASURES:

The differences and correlation between EIA and HOMA-IR in IGT patients of each group.

RESULTS:

EIA, serum fasting insulin and HOMA-IR indexes of the patients with IGT were significantly higher than those of the controls ( P < 0.01 or P < 0.05) . EIA and HOMA-IR of the patients in subgroup A was significantly higher than those in subgroup B ( P < 0. 01 ). Linear regression analysis showed that EIA had significant positive correlation with serum fasting insulin, glycosylated hemoglobin and HOMA-IR indexes( r = 0.51, 0.44,0.49, P <0.01).

CONCLUSION:

The degradation rate of erythrocyte insulinase in patients with IGT tolerance is significantly higher than that of normal persons, and is closely related to the onset and development of insulin resistance.