Outline

  • Abstract
  • Abbreviations
  • Keywords
  • 1. Introduction
  • 2. Materials and Methods
  • 2.1. Subjects
  • 2.2. Ogtt
  • 2.3. Euglycemic Hyperinsulinemic Clamp Test
  • 2.4. Principle of the Autoregressive Model
  • 2.5. Calculation of Autoregressive Coefficients and New Insulin Sensitivity Index: Oral Glucose Insulin Sensitivity Index (gsi)
  • 2.6. Simulation of Plasma Glucose Response to the Increment of Insulin
  • 2.7. Insulin Sensitivity Index from Clamp Data
  • 2.8. Ethics
  • 2.9. Statistical Analysis
  • 3. Results
  • 4. Discussion
  • Appendix A. Calculation of Autoregressive Coefficients
  • Appendix B.
  • References

رئوس مطالب

  • چکیده
  • کلیدواژه ها
  • مقدمه
  • 2. مواد و روش کار
  • 2.1 افراد
  • 2.2 OGTT
  • 2.3 تست کلامپ هایپرانسولیمینیک یوگلیسمیک
  • 2.4 اصل مدل خود همبسته
  • 2.5 محاصبه ضریب خود همبسته و شاخص جدید حساسیت به انسولین
  • 2.6. شبیه سازی پاسخ گلوکز پلاسما به افزایش انسولین
  • 2.7 شاخص حساسیت انسولین از داده های کلامپ
  • 2.8 اصول اخلاقی
  • 2.9 تحلیل آماری
  • 3. نتایج
  • ضمیمه A. محاسبه ضریب خودهمبسته
  • ضمیمه B

Abstract

A new insulin sensitivity index was devised on the basis of an autoregressive model and its validity was investigated.

Using data from the 75-g oral glucose tolerance test (OGTT), 115 subjects were divided into 3 groups: 40 with normal glucose tolerance, 34 with impaired glucose tolerance, and 41 with type 2 diabetes mellitus. The new insulin sensitivity index: oral glucose insulin sensitivity index (GSI) was calculated from five sets of plasma glucose and insulin levels obtained at 0, 30, 60, 90 and 120 min during OGTT using a formula based on an autoregressive model. Forty-three of the 115 subjects were examined for insulin sensitivity index (ISI) by euglycemic hyperinsulinemic clamp.

GSI decreased in the order of normal glucose tolerance group > impaired glucose tolerance group > diabetic group. There was a significant correlation between GSI and the ISI derived from euglycemic hyperinsulinemic clamp study data in all 43 subjects who underwent both tests (r = 0.72; P < 0.0001). The ISI calculated by previous methods poorly correlated with the ISIs obtained by euglycemic hyperinsulinemic clamp study.

In conclusion, this new insulin sensitivity index based on the data obtained from OGTT using an autoregressive model is comparable to an insulin sensitivity index by euglycemic hyperinsulinemic clamp technique and may be superior to previous indexes that have been devised to determine insulin sensitivity from OGTT data.

Keywords: - - - -

Conclusions

The simulated plasma glucose response to an increment of plasma insulin (1 μU/mL) in each of the three groups was expressed in Fig. 2. These curves were created by using Eq. (4) (see Appendix B) and the clinical data were obtained during the OGTT. After the insulin spike, the plasma glucose level declined in each group and the decrease at 30 min corre-sponded to —c’ in Eq. (3), that is GSI. The GSI was significantly lower in the impaired glucose tolerance group than in the normal glucose tolerance group (1.47 ± 0.16 vs. 0.72 ± 0.08, Fig. 3), and tended to be lower in the diabetic group than in the impaired glucose tolerance group (0.72 ± 0.08 vs. 0.62 ± 0.08, P = ns, Fig. 3). There was a significant correlation between our new GSI and the ISI (clamp) (r = 0.72, P < 0.0001, n = 43) (Fig. 4). There was also a significant correlation between the two indexes in each of the groups (normal glucose tolerance group: r = 0.73, P = 0.001, n = 15; impaired glucose tolerance group: r = 0.71, P < 0.01, n = 12; and diabetic group: r = 0.78, P < 0.0001, n = 16). Insulin sensitiv-ity indexes that are based on OGTT data and published by other [4,8] were poorly correlated with the ISI (clamp) (Fig. 5). The r values were significantly lower than that of our GSI (P < 0.0001).

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