Interleukin-1β inhibition for chronic kidney disease in obese mice with type 2 diabetes

An animal model with overt DKD is needed for preclinical study. Uninephrectomy is a common tool to accelerate kidney impairment but it has shortcomings such as lethality and kidney infection. Given that oxalate-rich diet is a convenient method to generate progressive nephrocalcinosis, tubular atrophy, and CKD in C56BL6 mice, we want to explore the possibility of using oxalate-rich diet as a substitutive and non-surgical approach to accelerate kidney impairment in db/db. We fed db/db mice of 14 weeks old with oxalate-rich diet or control diet for 30 days. We measured GFR every 10 days and analysed the crystal deposition in kidney after 30 days. We found that oxalate rich diet did not induce GFR loss and oxalate crystal deposition in kidney compared to mice with control diet. Inflammation is one of the center mechanisms leading to DKD. Infiltrated immune cells as well as renal resident cells release various cytokines which contribute to kidney function loss and structural alterations. Of the cytokines, IL-1β is a key mediator in amplifying inflammation, such as upregulating chemokines and other cytokines. IL-1β also contributes to kidney fibrosis. Thus IL-1β serves as a potential target for DKD. Previous studies have shown that NLRP3-dependent IL-1β from non-myeloid cell contribute to initiation and progression of DKD in diabetic mice, even though other studies suggested that non-myeloid cells may lack the ability to synthesis IL-1β. Our first aim was to investigate IL-1β expression and possible cellular location in kidney. We observed IL-1β expression was mildly increased in kidney biopsies from patients with diabetes at protein and mRNA level, as indicated by immunostaining and microarray, respectively. In a uninephrectomized db/db mice, IL-1β gene expression level was also increased. Furthermore, human biopsy immunostainings demonstrated that IL-1β was mainly located in infiltrated immune cells. Therefore, IL-1β expression was induced in DKD and was mainly expressed by immune cells. Since we observed IL-1β expression is increased in DKD, we hypothesized that targeting IL-1β has a renal protective effect on DKD in animal model of DKD. To test this hypothesis, we treated 18-week-old db/db mice undergoing uninephrectomy at the age of 8 weeks with anti-IL-1β IgG antibody or control IgG for 8 weeks. Mice treated with anti-IL-1β IgG preserved higher glomerular filtration rate but comparable albuminuria level to those treated with control IgG. On glomerular structural changes, anti-IL-1β antibody treatment did not affect glomerular tuft and Bowman’s capsule size, nor collagen deposition in glomeruli. However, anti-IL-1β showed higher podocyte account and higher expression levels of podocyte marker genes. IL-1β blockade also reduced infiltrated macrophages in glomeruli. On fibrosis, IL-1β blockade did not reduced alpha smooth muscle actin accumulation, but reduced fibrosis gene expression, such as Acta2 and Col4a3. In conclusion, (i) oxalate-rich diet did not induce massive oxalate crystal deposition in kidney nor GFR loss, thus is not a suitable method to generate overt DKD in db/db model. (ii) kidney IL-1β expression mildly increased in human diabetes, and mainly originated from immune cells. Targeting IL-1β by antibody generated a moderate effect on glomerular filtration rate decline, podocyte loss, and renal inflammation in type 2 diabetic mice with CKD. Whether these findings can translate into better outcomes also in human DKD remains to be determined

Integrability and asymptotics of positive solutions of a γ-Laplace system

AbstractIn this paper, we use the potential analysis to study the properties of the positive solutions of a γ-Laplace system in Rn−div(|∇u|γ−2∇u)=upvq,−div(|∇v|γ−2∇v)=vpuq. Here 1<γ⩽2, p,q>0 satisfy the critical condition p+q=γ⁎−1. First, the positive solutions u and v satisfy an integral system involving the Wolff potentials. We then use the method of regularity lifting to obtain an optimal integrability for this Wolff type integral system. Different from the case of γ=2, it is more difficult to handle the asymptotics since u and v have not radial structures. We overcome this difficulty by a new method and obtain the decay rates of u and v as |x|→∞. We believe that this new method is appropriate to deal with the asymptotics of other decaying solutions without the radial structures