Elevated Blood Interleukin-6 Levels in Hyperketonemic Type 1 Diabetic Patients and Secretion by Acetoacetate-Treated Cultured U937 Monocytes

Abstract

OBJECTIVE -Diabetic patients have elevated blood levels of interleukin-6 (IL-6), which is known to increase inflammation and the development of vascular disease and atherosclerosis. This study examined the hypothesis that ketosis increases the circulating levels of IL-6 in type 1 diabetic patients as well as the secretion of IL-6 in vitro in a cell culture model using U937 monocytes.RESEARCH DESIGN AND METHODS -Fasting blood was obtained from type 1 diabetic patients and healthy siblings. To examine the effect of ketosis, U937 monocytes were cultured with ketone bodies (acetoacetate [AA], ␤-hydroxybutyrate [BHB]) in the presence or absence of high glucose levels in the medium at 37°C for 24 h. IL-6 was determined by the sandwich enzyme-linked immunosorbent assay method, and intracellular reactive oxygen species (ROS) generation was detected using dihydroethidium dye. RESULTS-The blood level of IL-6 was higher in hyperketonemic (HK) diabetic patients than in normoketonemic (NK) diabetic patients (P Ͻ 0.05) and normal control subjects (P Ͻ 0.05). There was a significant correlation between ketosis and IL-6 levels (r ϭ 0.36, P Ͻ 0.04, n ϭ 34) in the blood of diabetic patients. Cell culture studies found that exogenous addition of the ketone body AA, but not BHB, increases IL-6 secretion and ROS generation in U937 cells. N-acetylcysteine (NAC) prevented the IL-6 secretion in acetoacetate-treated U937 monocytes.CONCLUSIONS -This study demonstrates that hyperketonemia increases IL-6 levels in the blood of type 1 diabetic patients and that NAC can inhibit IL-6 secretion by U937 monocytic cells cultured in a ketotic medium. Diabetes Care 26:2139 -2143, 2003I nterleukin-6 (IL-6), which is secreted by macrophages, lymphocytes, and other cells (1), is an important cytokine that can initiate events leading to atherogenesis by induction of adhesion molecules, monocyte-endothelial interactions, and inflammation injury (1-5). Anti-IL-6 therapy significantly prevents the inflammatory process in mice (6). The role of IL-6 in vascular inflammation has also been shown using IL-6 knockout mice that exhibit resistance to splanchnic artery occlusion shock (6), and in studies (7) that show increased levels of lipid peroxidation and inflammation in mice that overexpress IL-6. This suggests that elevated blood levels of IL-6 are associated with the development of vascular inflammation and atherosclerosis (1,2).IL-6 levels in blood are higher or similar in diabetic patients compared with normal subjects (4,8 -10). Cell culture studies have shown that high glucose concentrations can increase the IL-6 secretion in cultured monocytes (4,11,12). In addition to hyperglycemia, type 1 diabetic patients frequently experience ketosis (hyperketonemia) from excessive fat breakdown because body fuel is derived mainly from fat when the body is in a state of insulin deficiency (13). The blood concentration of ketone bodies (acetoacetate [AA], ␤-hydroxybutyrate [BHB]) may reach 10 mmol/l in patients with severe ketosis, as compared with levels of Ͻ0.5 ...

Acetoacetate Accelerates Muscle Regeneration and Ameliorates Muscular Dystrophy in Mice

“…However, AA differs from 3HB in that it also has unique functions in various biological processes, such as insulin release in vitro, generation of free oxygen radicals, lipid peroxidation, and activation of the ERK1/2 and p38 MAPK signaling pathways (45,46,49). In this report, we demonstrate for the first time that AA-mediated promotion of muscle cell proliferation is not a generalized ketone body effect but instead is specific to AA.…”

“…AA also stimulates chaperone-mediated autophagy (47) and down-regulates the expression of ATP-binding cassette transporter A1 (ABCA1) in vitro (48). AA, but not 3HB, promotes the secretion of interleukin (IL)-6 in cultured U937 monocytic cells (49). Interestingly, in neural cells, AA exerts its protective effect against glutamate-induced oxidative stress on HT22 cells and rat primary hippocampal neurons by decreasing glutamate-induced production of reactive oxygen species (50).…”

Modulatory effect of berberine on adipose tissue PPARγ, adipocytokines and oxidative stress in high fat diet/ streptozotocin-induced diabetic rats

“…Furthermore, BBR supplementation in rats increased the expression of sirtuin 1 (SIRT1), a deacetylase with antioxidant activity (Gomes et al, 2012). In conjunction with oxidative stress, pro-inflammatory cytokines are elevated in the blood of both diabetic animals and human patients (Jain et al, 2003;Mahmoud et al, 2012). Increased pro-inflammatory cytokines including IL-6 lead to reduction in IRS-1 tyrosine phosphorylation and association with phosphatidylinositol (PI)-3 kinase, inhibition of Akt activation (Bastard et al, 2000;Senn et al, 2002) and suppressed lipoprotein lipase (LPL) activity (Greenberg et al, 1992).…”

Cytokine response to diabetic ketoacidosis (DKA) in children with type 1 diabetes (T1DM)

“…It has been previously reported that hyperglycaemia increases serum concentrations of IL-6 [11,12] possibly through augmented production in monocytes [11,13]. Thus patients with diabetes have elevated blood levels of IL-6, which, together with TNF-α are known to increase inflammation and the development of vascular disease and atherosclerosis, possibly by increasing oxidative stress [12,14,15,16]. In children with T1DM, IL-6 levels were found to be statistically significantly increased in the group with long T1DM duration, as well as in those newly diagnosed, when compared with healthy controls [6,9], with the highest levels in the newly diagnosed patients [9].…”

“…Although there are some previous studies on the role of cytokines in the development of long-term diabetes complications [6,9,12,14,15,16], there is only one study on the fluctuation of cytokines during the metabolic crisis of DKA in children with T1DM [6], including limited number of patients. The aim of the present study was to monitor serum levels of pro-inflammatory cytokines IL-1β, IL-2, IL-6, IL-8 and TNF-α and the anti-inflammatory cytokine IL-10 at different time-points during the management of DKA, as markers of the risk of development of its acute complications.…”