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Original Articles
- Thiazolidinediones on Insulin Resistance and Insulin Secretion in Obese Diabetic OLETF Rats.
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Jung hyun Noh, Seung hyun Hong, Kyoung hee Lee, Kyoung Min Min, Tae young Yang, Myung shik Lee, Kwang won Kim, Moon kyu Lee
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Korean Diabetes J. 2007;31(1):33-43. Published online January 1, 2007
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DOI: https://doi.org/10.4093/jkda.2007.31.1.33
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Abstract
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- BACKGROUND
Thiazolidinediones are synthetic peroxisome proliferator-activated receptor-gamma agonists that decrease insulin resistance but, as in vitro and in vivo studies suggest, may have direct beneficial effects on pancreatic beta cells. Here, we investigated the effects of thiazolidinediones (TZDs) on the insulin resistance, beta-cell mass and insulin secretion in obese diabetic OLETF rats. METHODS: We studied insulin resistance (by hyperinsulinemic euglycemic clamp) and insulin secretion (by hyperglycemic clamp) in TZDs administered OLETF and LETO rats. Histologic alterations of the islets were observed and beta-cell mass was also measured by point counting method. RESULTS: Chronic administration of troglitazone (TGZ, 0.15%) or pioglitazone (PGZ, 0.02%) prevented the development of glucose intolerance in OLETF rats, as assessed by oral glucose tolerance test. There was significant difference in submaximal glucose infusion rate between TGZ-treated and untreated OLETF rats during euglycemic clamp studies at 24 weeks of age. At 16 and 24 weeks of ages, beta-cell mass significantly increased in TGZ-treated OLETF rats compared to untreated animals. At 19 weeks and 30 weeks of age, first-phase insulin secretion was not different in PGZ-treated OLETF rats from untreated OLETF rats during hyperglycemic clamp study. At 30 weeks of age, late-phase insulin secretion was decreased in PGZ-treated OLETF rats compared to untreated OLETF rats. The expression of alpha-smooth muscle actin, a marker of activated pancreatic stellate cells that are involved in the fibrosis of the pancreas, in the islets was suppressed by TGZ treatment at 24 weeks of age. CONCLUSION: The treatment of TGZ prevented the development of diabetes, and increased insulin sensitivity and pancreatic beta-cell mass in OLETF rats. These results might be related with the suppression of pancreatic stellate cells. Insulin secretion was not affected by PGZ treatment.
- Limitation of Validity of Homeostasis Model Assessment as a Index of Insulin Resistance.
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Yong Seok Yun, Seok Won Park, Young Duk Song, Hyo Kyung Park, Oh Yoen Kim, Chul Woo Ahn, Jae Hyun Nam, Su Youn Nam, Bong Soo Cha, Chong Ho Lee, Sumg Gil Lim, Kyung Rae Kim, Hyun Chul Lee, Kap Bum Huh
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Korean Diabetes J. 2000;24(5):541-551. Published online January 1, 2001
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Abstract
- BACKGROUND
Homeostasis model assessment of insulin resistance (HOMAIR) had been proposed as a simple and inexpensive alternative to other complex procedures measuring insulin resistance. We evaluated the validity of HOMAIR, comparing to total glucose disposal rate measured by euglycemic clamp test in 63 subjects with normal glucose tolerance, 21 with impaired glucose tolerance and 47 with type 2 DM. METHODS: HOMAIR and HOMA cell function (Homeostasis model assessment of cell function) were calculated with formula described by Matthews [HOMAIR: fasting insulin ( U/mL) X fasting glucose (mmol/L) / 22.5, HOMA cell function: 20 X fasting insulin ( U/mL) / (fasting glucose (mmol/L) - 3.5)]. 2-hour euglycemic (5 mmol/L) hyper insulinemic (717 pmol/L) clamp test were carried out. RESULTS: The strong inverse correlation (r=-0.658, <0.001) was shown between log transformed HOMAIR and total glucose disposal rates. The agreement of two methodes in the categorization according to insulin resistance was moderate (weighed kappa=0.45). The magnitude of correlation coefficients were smaller in subjects with lower BMI (BMI < 23.7 kg/m2, r = -0.441 vs BMI > or = 23.7 kg/m2, r = -0.693, p = 0.0183), lower HOMA cell function (HOMA cell function < 57.2, r = -0.514 vs HOMA cell function > or = 57.2, r = -0.773, p = 0.0091) and higher fasting glucose levels (fasting glucose < 102 mg/dL, r = -0.697 vs fasting glucose > or = 102 mg/dL, r = -0.59, p = 0.0735). The results of correlation analysis was not significant in diabetics with lower BMI. CONCLUSION: Limitation of validity of HOMAIR should be carefully considered in subjects with lower BMI and lower fasting insulin to glucose levels, such as lean type 2 diabetes with insulin secretory defects.
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