Elsevier

Metabolism

Volume 58, Issue 4, April 2009, Pages 443-448
Metabolism

Proinflammatory cytokines in response to insulin-induced hypoglycemic stress in healthy subjects

https://doi.org/10.1016/j.metabol.2008.10.018Get rights and content

Abstract

Hyperglycemic crises of diabetic ketoacidosis and nonketotic hyperglycemia are associated with elevation of counterregulatory hormones and proinflammatory cytokines, markers of lipid peroxidation, and oxidative stress. To investigate if other conditions besides hyperglycemia could evoke such a prompt increase in cytokine levels, lipid peroxidation, and oxidative stress markers, we induced hypoglycemic stress by standard insulin tolerance test and measured proinflammatory cytokines, markers of lipid peroxidation, reactive oxygen species (ROS), and counterregulatory hormones. Insulin tolerance test was performed in 13 healthy male subjects with no history of infection, cardiovascular risk factors, or abnormal glucose. At baseline and at 30, 45, 60, 120, and 240 minutes after insulin injection, the following parameters were measured: glucose, cortisol, corticotropin, epinephrine (EP), norepinephrine (NE), growth hormone, tumor necrosis factor (TNF)–α, interleukin (IL) 1β, IL-6, IL-8, free fatty acids, white blood cells, lipid peroxidation markers by thiobarbituric acid assay, and ROS by dichlorofluorescein method. The peak value of white blood cell count at 120 minutes was significantly associated with the peak values of NE at 30 minutes and cortisol at 60 minutes. By comparing the area under the curve of measured parameters, EP emerged as significant predictor of TNF-α (P = .05) and IL-8 (P = .027). Cortisol emerged as predictor of IL-1β significantly (P = .05). Corticotropin predicted area under the curve of IL-6 with borderline significance (P = .06). In the present study, insulin-induced hypoglycemia in nondiabetic male subjects is associated with increased proinflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8), markers of lipid peroxidation, ROS, and leukocytosis. Elevations of NE, EP, corticotropin, and cortisol in hypoglycaemia are associated with the elevation of the proinflammatory cytokines and leukocytosis.

Introduction

We have documented that severe hyperglycemia of diabetic ketoacidosis (DKA) or nonketotic hyperglycemia provokes elevation of counterregulatory hormones, proinflammatory cytokines (tumor necrosis factor [TNF]–α, interleukin [IL]-6, IL-8, and IL-1β), markers of reactive oxygen species (ROS) measured by dichlorofluorescein (DCF) or lipid peroxidation measured as malondialdehyde (MDA), cardiac risk factors including C-reactive protein, and free fatty acids (FFA). These parameters, which are 2- to 3-fold higher than normal, return to normal values within 24 hours of insulin therapy and resolution of hyperglycemia and dehydration [1]. We had previously suggested that these prompt responses to elevation of cytokines and counterregulatory hormones may be due to either anti-inflammatory effects of insulin or, more likely, responses to stress of hyperglycemia. Because patients with diabetes on antidiabetic agents experience hyperglycemia and hypoglycemia, these excursions may provoke various responses in the body. We have chosen hypoglycemia in distinction to hyperglycemia to investigate if such a stress would also produce similar responses to that of hyperglycemia. Herein, we present the results of insulin-induced hypoglycemia in 13 nondiabetic male subjects.

Section snippets

Participants

Healthy male subjects with no history of current infection, cardiovascular risk factors, metabolic syndrome, or abnormal glucose metabolism were invited to participate in the study that was approved by the ethics committee of Endocrinology and Metabolism Research Center of Tehran University. On admission, after physical examination including measuring the vital signs, blood was drawn between 8:00 and 9:00 am for the following tests: complete metabolic profile, cell blood counts with

Results

Table 1 demonstrates the baseline characteristics of the participants. During the ITT, no severe adverse events were detected; and infusion of 50% glucose was not required during the study, as hypoglycemia less than 30 mg/dL or intolerable hypoglycemic symptoms did not occur in any of participants. The mean nadir of hypoglycemia was 38.2 ± 4.3 mg/dL, which was recorded at 30 minutes. The levels of counterregulatory hormones (GH, ACTH, EP, and NE), WBC, proinflammatory cytokines, FFA, MDA, and

Discussion

In this study, we have demonstrated the responses of body to the stress of hypoglycemia; these include the well-known responses of counterregulatory hormones [2], [3] and previously unknown elevation of proinflammatory cytokines, markers of lipid peroxidation and ROS, as well as leukocytosis.

Based on the present findings, EP is a predictor of TNF-α and IL-8. Cortisol predicts the change of IL-1β. Corticotropin predicts IL-6 with borderline significance. Norepinephrine and cortisol are

Acknowledgment

We are grateful to our volunteers, whose participation made this study possible, and to Ms Brenda Scott for her secretarial assistance, Ms Cat Casey for her depiction of the results in the 5 figures, and Mr John Crisler for his assistance in laboratory assays.

None of the authors have any financial interests that might conflict with this study.

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