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

Abstract

The proinflammatory cytokine Interleukin 1 beta (IL-1beta) 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-1beta antibody to improve glucose control in hyperglycemic mice with diet-induced obesity. After 13 weeks of treatment the IL-1beta 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-1beta 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.

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

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.

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

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

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.

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

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

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

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)

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.

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

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.

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

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.