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. Author manuscript; available in PMC: 2011 Mar 23.
Published in final edited form as: Cytokine. 2008 Aug 23;44(1):141–148. doi: 10.1016/j.cyto.2008.07.004

Treatment with an Interleukin 1 beta antibody improves glycemic control in diet induced obesity

O Osborn 1, SE Brownell 1, M Sanchez-Alavez 1, D Salomon 2, H Gram 3, T Bartfai 1
PMCID: PMC3063393  NIHMSID: NIHMS269887  PMID: 18723371

Abstract

The proinflammatory cytokine Interleukin 1 beta (IL-1β) is elevated in obese individuals and rodents and it is implicated in impaired insulin secretion, decreased cell proliferation and apoptosis of pancreatic beta cells. In this study we describe the therapeutic effects by an IL-1β antibody to improve glucose control in hyperglycemic mice with diet induced obesity. After 13wks of treatment the IL-1β antibody treated group showed reduced glycated hemoglobin (*P = 0.049), reduced serum levels of proinsulin (*P = 0.015), reduced levels of insulin and smaller islet size (*P = 1.65E-13) relative to the control antibody treated group. Neutralization of IL-1β also significantly reduced serum amyloid A (SAA) which is an indicator of inflammation-induced acute phase response (*P = 0.024). While there was no improvement of obesity, a significant improvement of glycemic control and of beta cell function is achieved by this pharmacological treatment which may slow/prevent disease progression in Type 2 Diabetes.

Keywords: Interleukin 1 beta, Interleukin 1 alpha, diabetes, obesity, hyperglycemia

Introduction

Type 2 Diabetes mellitus (T2D) is a complex progressive disease with a rapidly increasing incidence as a consequence of the dramatic rise in obesity (1). Obesity is characterized by expansion of white adipose tissue, by elevated leptin levels and by a state of chronic mild inflammation (2–4). The adipose tissue is an active secretory organ that produces and releases a variety of proinflammatory (IL-1β, leptin, TNF-alpha, IL-6) and anti-inflammatory proteins (IL-10, Interleukin-1 receptor antagonist, IL-1Ra) (Juge-Aubry 2003) whose circulating levels rise as adipose tissue expands. The increased release and action of these cytokines at both the local and systemic level are thought to be involved in the development of insulin resistance (5–14). T2D develops in individuals who lose the ability to produce sufficient quantities of insulin to maintain normoglycemia in the presence of insulin resistance. The prevention and treatment of T2D are major medical goals that involve the preservation of the pancreatic islets and their ability to secrete insulin, sensitization of the target tissue to insulin and if needed administration of exogenous insulin. Obesity is a major risk factor for T2D but the exact molecular and cellular mechanisms by which the different components of obesity affect insulin production and sensitivity are not fully known. The obesity associated inflammation has been highlighted as a possible link in the transition from obesity and insulin resistance to T2D (15).

IL-1β can be produced by many cell types including adipocytes, macrophages, endothelial cells, neurons, microglia and pancreatic beta cells (16–18). The pancreatic expression of IL-1β is induced in high glucose concentrations (19) and IL-1β has well described cytotoxic effects which lead to impaired insulin secretion, decreased cell proliferation and apoptosis of the pancreatic beta cells (19–25). IL-1 can also induce the expression of its own gene (26–28).

IL-1Ra is an anti-inflammatory cytokine that is also produced by white adipose tissue, (17), the pancreas (29) and which competitively binds to the IL-1 receptor (30) and blocks the IL-1 mediated signaling. IL-1Ra concentration has been shown to be reduced in the pancreatic islets of patients with T2D (31). In obese humans, serum IL-1Ra levels have been shown to be elevated 3–8 fold (13). It has also been suggested that elevated circulating IL-1Ra in obesity is likely to represent a protective response to the rise of the cytotoxic IL-1β. This rise has however some deleterious effects since IL-1Ra also increases insulin resistance of muscle (15) and blocks the IL-1β activation of lipolysis (32).

There is a critical balance between the levels of the proinflammatory cytokine IL-1β and the endogenous receptor antagonist IL-1Ra at the level of the IL-1R1 receptors which has been shown to play a role in the susceptibility and severity of many diseases including arthritis, inflammatory bowel disease, kidney diseases, leukemia, cancer, osteoporosis, infectious diseases and diabetes (33, 34). Over 100 fold higher levels of IL-1Ra over IL-1β are necessary to functionally inhibit the effects of IL-1 on target cells (35) in pharmacological settings for example during IL-1Ra therapy in inflammation. Administration of the soluble interleukin 1 receptor to sequester IL-1β has also been shown to have protective effects on pancreatic islets of non obese diabetic mice (36). These findings prompted us to investigate the role of IL-1β in vivo on the development of obesity, inflammation, and insulin resistance in a mouse model of diet-induced obesity, which appear to mimic human disease more closely than genetic mouse models of obesity.

To specifically address the role of IL-1β in obesity, we employed an anti- mouse IL-1β monoclonal antibody (37) with demonstrated activity in vivo (38). Previous studies have employed recombinant IL-1Ra which blocks the biological activity on IL-1 receptor of both IL-1β and IL-1α. However, different roles have been assigned to IL-1α and IL-1β in the mouse (39–41), suggesting that both isoforms are not redundant. In order to specifically determine the long-term effects of IL-1β neutralization on the development of obesity, insulin responsiveness and blood glucose homeostasis C57Bl/6 mice were treated for 13 weeks with IL-1β antibody or control antibody, and the pharmacological effects were assessed in diet induced obese (DIO) mice and lean mice. DIO mice were characterized by high circulating insulin, leptin, IL-1Ra and showed somewhat increased insulin resistance and glucose intolerance (Table 1.)

Table 1. Characterization of obese and lean mice.

Mice on a high fat diet (HF) have higher body weight with increased levels of insulin, leptin, glycated hemoglobin and IL1Ra when compared with mice on a low fat diet (LF). All parameters were determined after 13 weeks of treatment, at 19 weeks of age, in 7–8 mice per group.

Obese Lean P value
Body weight (g) 42.88 ± 2.35 30.24 ± 0.84 *0.00017
Insulin (ng/ml) 5.04 ± 1.04 1.75 ± 0.46 0.05827
Leptin (ng/ml) 38.99 ± 1.17 9.28 ± 2.51 *3.84187E-08
Glycated Hb (%) 4.9 ± 0.17 4.2 ± 0.08 *0.00227
IL1Ra (pg/ml) 1459 ± 179 1163 ± 137 0.21122
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Materials and Methods

Mice and diets

C57BL/6 wild type male mice used in this study were bred and maintained in the animal research facility at the Scripps Research Institute (The Scripps Research Institute, LA Jolla, CA). All procedures were approved by the Institutional Animal Care and Use Committee of the Scripps Research Institute. Mice were housed in groups of 4 and fed ad libitum with mouse breeder diet composed of 11% fat, 17% Protein, 3.5% fiber (S-2335 Mouse Breeder, gross energy kcal 4.39 kcal/g). At 6 weeks of age mice were randomly divided into two diet groups. The high fat (HF) group received a diet containing 60% fat, 20% carbohydrate and 20% protein (D12492, 5.24 kcal/g). The low fat (LF) diet contained 10% fat, 70% carbohydrate and 20% Protein (D12450B, 3.85 kcal/g). Both diets were otherwise identical and manufactured by Research Diets, New Brunswick, NJ. Mice were further subdivided into groups that received either IL-1β antibody treatment (Ab) or control antibody treatment (C-Ab). The sizes of each treatment group were: HF + Ab, n = 12; HF + C-Ab, n = 8; LF + Ab, n = 8; LF + C-Ab, n = 8.

Immuno-neutralization of IL-1β

Mouse monoclonal antibody raised against mouse IL-1β with a 300pM affinity was administered intraperitoneally weekly in 150 μL volume at a dose of 10 μg per g body weight. This monoclonal antibody was derived from the 1400.24.17 antibody described by Geiger et al by class switch from IgG1 to IgG2a. As isotype control a mouse monoclonal IgG2a antibody raised against cyclosporine A in a 150 μl volume was given intraperitoneally at a dose of 10 μg per g body weight.

Exposure of animals to the anti-mouse IL-1β antibody was measured by a competitive ELISA using highly purified anti-idiotypic antibodies raised against the Fab fragment of the 1400.24.17 antibody. The anti-idiotypic antibody preparation was extensively depleted for cross-reactive antibodies to mouse immunoglobulin, thereby retaining specificity for the 1400.24.17 paratope. High levels of circulating antibody were present in the serum of treated animals independent of diet and body weight. Antibody concentration in serum at the end of the 13 week study was as 133 ± 5.6 μg/ml and 109 ± 11.0 μg/ml in the HF and LF groups, respectively with little variation between animals.

Insulin resistance test

The glucose reducing effect of insulin injection was assessed in non fasted mice. Baseline glucose levels are measured by withdrawing ~0.6 μl of blood from the tail from un-anesthesized mice before a load of human insulin was administered (1 unit/kg, i.p.; Sigma–Aldrich, St. Louis, MO). Further samples were collected 15, 30, 60, 90 and 120 mins after the insulin challenge. Blood glucose levels (in mg per deciliter) were determined by a glucometer (Glucometer, Rite Aid).

Glucose tolerance test

Mice were fasted for 16hr overnight and injected Intraperitoneally with glucose (D-glucose, anhydrous; Sigma–Aldrich, St. Louis, MO) (1.5 mg/g body wt) in sterile water. Blood samples were taken before the glucose administration and then 15, 30, 60, 90 and 120 min after injection). Blood glucose levels were determined by a glucometer (Glucometer, Rite Aid).

Glycated hemoglobin

Glycated hemoglobin (HbA1c) levels were measured using A1cNow Monitors as per manufacturers instructions (Metrika, Sunnyvale, CA).

Serum collection

Mice are anesthetized with 5% isoflurane and blood was drawn between 8AM and 11AM via retro-orbital bleeds using EDTA coated capillary tubes (Drummond, Broomall, PA, USA). Blood samples were placed immediately on ice and then allowed to clot for 2 hours at room temperature before centrifuging at 2000 X g at 4°C for 20 mins. Serum was removed and stored at −80°C until further analysis. Truncal blood was obtained after mice were killed.

ELISA measurements

All ELISAs were performed in duplicate according to manufacturer’s guidelines. Leptin and Insulin ELISA kits were obtained from Linco Research, St Charles, Missouri. The Proinsulin ELISA kit was obtained from Mercodia, Uppsala, Sweden. Serum Amyloid A (SAA) levels were determined using an ELISA kit from USBiological, Swampscott, MA.

Non-esterified fatty acid and Triglyceride determination in serum

Enzymatic colorimetric assays were performed as described by the manufacturer’s instructions, NEFA Wako NEFA-HR(2) Microtitre Procedure, and Wako-L-Type TG-H Microplate procedure, Wako Diagnostics (Richmond, VA).

Statistical Analysis

Levene’s test was applied to assess the equality of variance in different samples. When the distributions in each of the groups were normal the differences between the four groups of mice were tested using one-way analysis of variance (ANOVA) with Tukey post hoc testing. The two tailed independent student’s t-test was used to compare the effect of IL-1β antibody treatment with control antibody treatment in mice on a high fat diet when the variance between groups was unequal. All results are expressed as mean ± SEM. A value of P < 0.05 was considered statistically significant.

Histological examination of the pancreas

Whole explanted pancreata from 3 mice per treatment group were fixed in Zn formalin solution (Anatech, battle Creek, MI), embedded in paraffin and 10 consecutive 10-micron thick sections were cut and stained with haematoxylin/eosin for each animal studied. Serial images to cover the full area of all sections were taken on a Leica DM-IL microscope at the same 100 x magnification using a Nikon DS-L1 digital camera (1280×960 pixels/image). These images and all analysis as done in a fashion blinded to the treatment groups by one author (DRS). For the 6 animals studied the total images taken per pancreas were: 60, 73, 50, 133, 77, and 73. Images were then loaded into NIH ImageJ (ver. 1.38x), stacks created and the area of each islet in each section was measured by manually drawing around the islet perimeter with the measuring tool. The total number of islets measured per animal was: 113, 115, 85, 216, 147, 168 respectively and in the same order as the image numbers are listed above. ImageJ also calculated summary statistics of median islet area (in pixels) and SD.

Results

IL-1β Antibody Treatment Does Not Affect the Development of Obesity

After 13 weeks of IL-1β antibody treatment there was no significant effect on body weight when compared to the control antibody group (Fig. 1) although during the treatment there has been a lowered body weight gain observed in the antibody treated animals, the difference was not consistent throughout the 13 weeks of treatment.

Figure 1. The IL-1β antibody treatment did not affect the development of obesity.

Figure 1

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C57Bl6 mice at 6 weeks of age on a high fat (HF) or low fat (LF) diet were treated with IL-1β antibody (Ab) or control antibody (C-Ab) for 13 weeks. A slight trend is observed in lower body weight in both treated groups however, there is no significant difference in body weight between treatment groups at the end point of this study.

IL-1β Antibody Treatment Decreases Glycated Hemoglobin, Proinsulin and Insulin levels in Obese Mice

Glycated hemoglobin (HbA1c) levels are significantly higher in obese animals relative to lean animals (4.9% ± 0.17 versus 4.2% ± 0.08 *P = 0.005947) (Fig. 2A). IL-1β antibody treatment caused a statistically significant decrease in HbA1c levels in obese mice (0.45% *P = 0.049) and a similar trend was observed in the lean mice treated with IL-1β antibody (0.1%, P = 0.39). We did not observe a significant effect of the antibody treatment on plasma glucose concentrations (Fig. 3). However glycated hemoglobin provides a more robust, long term, integrated measure of glycemia that is not affected by acute, environmental conditions such as stress, anxiety and circadian behavior. The extent of protein glycation is dependent on the level of chronic exposure to glucose and expressed as a percentage of total HbA and thus can be used as a measure of the effectiveness of control of hyperglycemia over longer periods.

Figure 2. IL-1β antibody treatment decreases glycated hemoglobin, insulin and proinsulin levels in obese mice.

Figure 2

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A) Glycated hemoglobin was significantly reduced in antibody treated mice relative to control antibody treated mice. In obese mice a significant reduction of 0.45% HbA1c was observed (*P = 0.049). B) Proinsulin levels were reduced in obese animals in the IL-1β antibody treated group relative to the control treated group (*P = 0.015). C) Insulin was also reduced in the IL-1β antibody treated group relative to the control treated group. All parameters were measured at the end of the study after 13 weeks of treatment with IL-1β antibody (Ab) or control antibody (CAb) in mice on a high fat (HF) diet or low fat (LF) diet. The two tailed independent student’s t-test was used to compare the effect of IL-1β antibody treatment with control antibody treatment in mice on a high fat diet due to the unequal variance between these groups. Data in A-C are presented as mean ± SEM.

Figure 3. IL-1β antibody treatment had no significant effect on fasting plasma glucose.

Figure 3

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Fasting plasma glucose was measured after 11 weeks of treatment with IL-1β antibody (Ab) or control antibody (C-Ab) in mice on a high fat (HF) diet or low fat (LF) diet. Data are presented as mean ± SEM.

IL-1β antibody treatment caused a significant decline in proinsulin levels in obese mice (4.8 ± 0.85 to 2.1 ± 0.24 ng/ml *P = 0.015) relative to the control antibody treated group (Fig. 2B). A similar trend was observed in the lean mice treated with IL-1β antibody (4.7 ± 0.81 to 3.6 ± 0.90 ng/ml) (Fig. 2B). The trend towards reduced insulin levels in IL-1β antibody treated animals versus control antibody treated animals further confirms the therapeutic effects of the antibody treatment (Fig. 2C). Insulin levels were decreased upon IL-1β antibody treatment in the obese group (5.24 ± 1.4 versus 3.65 ± 0.59 ng/ml) and in the lean groups (1.75 ± 0.67 versus 0.51 ± 0.12 ng/ml) relative to the control antibody group. The ratio of proinsulin to insulin is often used as a marker of beta cell dysfunction; increased proinsulin over insulin ratio has been associated with obesity and insulin resistance (42–44).

There were no statistically significant differences in body weight (Fig. 1) or leptin levels (Fig. 4) upon treatment with the IL-1β antibody. Measurement of fat deposits and pancreas and spleen weights at the end of this study showed no significant differences between IL-1β antibody and control treated animals (Fig. 5). During the subsequent measurements on weeks 1, 3, 7 and 11 of the antibody treatment we have at some time points found evidence of lowered glucose tolerance and improved insulin sensitivity in the IL-1β antibody treated obese animals, these results were not confirmed at each time point (Fig. 6). However we should emphasize the levels of glycated hemoglobin provide a superior chronic, averaged measure of serum glucose concentrations and these data clearly suggest an improvement of the glycemic control by the IL-1β antibody treatment. Non-esterified fatty acid (NEFA) concentrations were not significantly affected by IL-1β antibody treatment versus treatment with control antibody (Fig. 7A). The Triglyceride (TG) levels showed a trend towards increased levels in the IL-1β antibody treated group compared with the control antibody treated group (Fig. 7B).

Figure 4. IL-1β antibody treatment had no significant effect on leptin levels in obese or lean mice relative to control antibody treatment.

Figure 4

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Leptin levels in mice on a high fat (HF) diet were significantly higher than in mice on a low fat (LF) diet, *P < 0.01, One-way ANOVA, Tukey post hoc analysis. Leptin levels were measured after 13 weeks of treatment with IL-1β antibody (Ab) or control antibody (C-Ab) in mice on a high fat (HF) diet or low fat (LF) diet. Data are presented as mean ± SEM.

Figure 5. IL-1β antibody (Ab) treatment had no significant effect on adipogenesis in obese mice relative to control antibody treatment (C-Ab). B. IL-1β antibody treatment had no significant effect on the weight of the spleen or pancreas in obese or lean mice relative to control antibody treatment.

Figure 5

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The pancreas of the mice on a high fat (HF) diet was significantly larger than mice on a low fat (LF) diet, *P < 0.05, One-way ANOVA, Tukey post hoc analysis. Data are presented as mean ± SEM.

Figure 6. A. IL-1β antibody treatment does not significantly affect glucose tolerance in lean or obese mice after 11 weeks of antibody treatment. B. IL-1β antibody treatment does not significantly affect response to insulin challenge in obese or lean mice relative to control antibody treatment.

Figure 6

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A subtle trend in improvement in insulin action by antibody treatment is observed at some time points but this does not reach statistical significance. The insulin resistance test was performed after 11 weeks of IL-1β antibody treatment (Ab) or control antibody (C-Ab) in mice on a high fat (HF) diet or low fat (LF) diet. Data are presented as mean ± SEM.

Figure 7. A. Non-esterified fatty acid (NEFA) concentrations were not significantly affected by IL-1β antibody treatment. B. Triglyceride (TG) levels were slightly increased upon IL-1β antibody treatment (P = 0.23).

Figure 7

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NEFA and TG were measured after 13 weeks of treatment with IL-1β antibody (Ab) or control antibody (C-Ab) in mice on a high fat (HF) diet or low fat (LF) diet. Data are presented as mean ± SEM.

A morphological analysis of the islet sizes in the control antibody and IL-1β antibody treated lean and obese animals shows that 13 weeks of treatment with the IL-1β antibody leads to reduced islet size in the obese animals (*P = 1.65E-13) (Fig. 8).

Figure 8. Islet size was significantly decreased in the IL-1β antibody treated obese mice relative to control antibody treated obese mice.

Figure 8

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Pancreas images selected to visually show the significant differences measured for islet area between animals in the high fat diet/antibody-treated experimental group, HF + Ab, (A and B) and the high fat diet control group, HF + C-Ab, (C and D). A scale bar showing 100 microns is displayed in B. It is evident that the high fat diet animals have larger islets than the animals on the same diet but treated with the anti-IL-1β antibody. E. Islet size was significantly reduced in IL-1β antibody treated mice relative to control antibody treatment (*P = 1.65E-13). F. Pancreatic islets were divided into 5 size groups for IL-1β antibody and control antibody treated groups. Y-axis represents % of total islets distributed in each of the 5 size groups. This size distribution analysis shows IL-1β antibody treated groups have a trend towards smaller sized islets relative to the control antibody treatment where a higher percentage of larger islets were observed. Data are presented as mean ± SEM.

Discussion

Our study provided insight in the role of IL-1β in the development of obesity, insulin resistance, T2D and low grade inflammation in a mouse model of obesity. Increased HbA1c after 13 weeks on a HF diet indicated the development of T2D in these mice. Anti-IL-1β treatment reduced HbA1c significantly, (0.45% *P = 0.049) suggesting a beneficial effect on glucose tolerance and/or insulin resistance. In a study monitoring the effects of a potential diabetic therapy Zhao et al (2007) report a similarly low basal HbA1c level after 18 wks on a high fat diet, where treatment with an inhibitor of glycosphingolipid synthesis significantly improved glycemic control by reducing HbA1c by 0.8% (45). Other high impact papers (46), have cited similarly small reduction in HbA1c levels and these differences, by most endocrinologists, were deemed to be of clinical relevance if over extended time periods.

We could not show consistent improvement of insulin resistance or glucose tolerance, by anti-IL-1β treatment, which one could expect when HbA1c is improved. There are serious difficulties with the accuracy and reproducibility of mouse glucose tolerance and insulin resistance data as discussed by several authors (47–50). These methods do not provide precise estimates of insulin sensitivity or tissue specific glucose disposal and the possibility of hypoglycemia and ensuing counter regulatory homeostatic mechanisms have the potential to confound estimates of insulin sensitivity (49). However we should emphasize the levels of glycated hemoglobin, in which we observed a significant change, provide a superior chronic, averaged measure of serum glucose concentrations (51). Furthermore, we observed increased islet mass in obese mice and we reason that this might be due to a mechanism compensating decreased insulin sensitivity by increased overall insulin production by increasing the islet cell number. We speculate that the reduced islet size observed in anti-IL-1β antibody treated obese mice is due to better insulin sensitivity, resulting in lower insulin levels and less need to compensate insulin resistance by increasing insulin production via expanding the islet. It has been demonstrated that IL-1β can directly modulate the activity of IRS-1, the downstream substrate of the insulin receptor (52–55). We therefore reason that IL-1β blockade in diet induced obesity results directly in an increased insulin sensitivity at the cellular level by enhancing the activity of the insulin receptor-mediated signaling pathway.

IL-1β also appears to be an important mediator of low grade inflammation induced in obese animals, as neutralization of IL-1β significantly reduces SAA which is an indicator of inflammation-induced acute phase response (Fig. 9). The significant reduction of SAA is an important proof that IL-1β antibodies were efficacious.

Figure 9. Serum amyloid A (SAA) is significantly reduced (*P = 0.024) in obese animals treated with IL-1β.

Figure 9

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The reduction in SAA levels by IL-1β antibody treatment (Ab) relative to control antibody (C-Ab) treatment provides an additional measure of the presence and effectiveness of the IL-1β antibody at this dosing regimen. Data are presented as mean ± SEM.

Blockade of IL-1β signaling by sequestration of IL-1β does not significantly impact on weight gain of mice on HF or LF diets, suggesting that peripheral IL-1β is of minor importance for feeding behavior or glucose utilization. IL-1β is implicated in regulation of body composition and fat distribution, mainly through its effect on the regulation of appetite, lipolysis and energy metabolism (56, 57). A likely explanation for the lack of effect of IL-1β on body weight is that the extremely potent acute anorexic effect of IL-1β associated with acute phase responses like fever is observed only at high concentrations of IL-1β, i.e. at 10–20 fold elevated levels over un-stimulated levels, (58) and not in the 2–3 fold, chronically elevated range of IL-1β concentrations observed in obesity (59, 60).

Our results are in line with and further extend with mechanistic and pancreas histology data the conclusion from the Anakinra™ study in humans with T2D where the treatment effect of human IL-1Ra administered subcutaneously (Anakinra™) was the improvement of low grade inflammation and a lowering of HbA1c (46). A recent study in DIO mice (61) also demonstrated the protective effects of administration of IL-1Ra on beta cell survival and function with improved glucose tolerance and thus further validates the therapeutic potential of blocking IL-1 signaling for the treatment of diabetes. The Anakinra study involved obese and non-obese patients with established T2D however, while we and Sauter et al (2008) show that blockade of IL-1 signaling can delay/ prevent the development of diabetes. From the view point of continued research it is important that in non genetic animal models of obesity-insulin resistance-T2D spectrum; like the DIO mice, the results of a recent, much heralded human patient study were confirmed and thus we can now deepen our understanding of the cellular and molecular mechanisms involved in the human study (46) and can extend it to morphological examination of the pancreatic islet sizes (Fig. 8) and to other parameters not easily followed in humans.

Important differences between our study, using immunoneutralization of IL-1β by a high affinity antibody, and the studies using the recombinant IL-1Ra are that we remove the agonist from the IL-1 receptor rather than rely on sufficient dose of the antagonist to competitively block IL-1β activity. Approximately a 100 fold excess of IL1-Ra over IL-1β is necessary to block the effects of IL-1β on pancreatic islets (29) (35). As obesity develops IL-1β is elevated in hyperglycemic beta cells (19, 62) and thus very large quantities of IL-1Ra are necessary to compensate for this rise. Our study also shows that significant improvement of glycemic control is achieved by neutralization of the soluble IL-1β, without blocking the function of or neutralizing the action of IL-1α. IL-1α also competitively binds to the IL-1 receptor and contributes to IL-1 mediated cytotoxicity in the pancreas (63). In this study we have utilized the availability of a highly specific, high affinity tool to neutralize IL-1β in mice, in absence of similarly high affinity antibody to IL-1α we could not examine the contribution of IL-1α, although it is known that mice produce higher relative quantities of IL-1α than humans (64). It is therefore not excluded that blockade of IL-1α and IL-1β may be even more effective as in other murine inflammatory models but we may expect only a smaller contribution by IL-1α in analogy of studies with anti- IL-1α and IL-1β blockade (39–41). In any case, our study shows that blocking IL-1β is sufficient for a pharmacodynamic effect that IL-1α and IL-1β are not redundant in DIO. Thus the results permit focusing on IL-1β in the obesity and pancreatic damage context, while the earlier data on IL-1Ra having similar effects on glycemic control (46) did suggest that the effects of one or both IL-1 agonists has to be blocked, now we clearly can assign the majority of effects at the IL-1 receptor to IL-1β.

Our study shows that treatment with an IL-1β antibody represents a novel approach to improve glucose control in obesity. This therapeutic strategy protects the pancreas from the proinflammatory cytotoxic action of IL-1β in obese individuals and shifts the balance in favor of the antagonist IL-1Ra. Reduced levels of glycated hemoglobin, proinsulin and insulin in the IL-1β antibody treated group highlight the effectiveness of this treatment in the control of glycemia and improvement in beta cell function. IL-1β is also a key mediator of impaired function and destruction of pancreatic beta cells during the development of Type 1 Diabetes (19, 65). This study suggests IL-1β antibody has therapeutic potential in the treatment of T2D and may also have beneficial effects in other forms of diabetes where tight glucose control is essential in preventing induction of IL-1β and thus limiting beta cell destruction.

Acknowledgments

These studies were supported by funds from The Harold L Dorris Neurological Institute endowment and from grants from the Skaggs Institute of Chemical Biology; no funds were received from Novartis AG.

Footnotes

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