Juxtaglomerular body abnormalities in youth-onset diabetic subjects

The role of inflammation in diabetic kidney disease

Diabetic kidney disease (DKD) has been the leading cause of chronic kidney disease for over 20 years. Yet, over these two decades, the clinical approach to this condition has not much improved beyond the administration of glucose-lowering agents, renin-angiotensin-aldosterone system blockers for blood pressure control, and lipid-lowering agents. The proportion of diabetic patients who develop DKD and progress to end-stage renal disease has remained nearly the same. This unmet need for DKD treatment is caused by the complex pathophysiology of DKD, and the difficulty of translating treatment from bench to bed, which further adds to the growing argument that DKD is not a homogeneous disease. To better capture the full spectrum of DKD in our design of treatment regimens, we need improved diagnostic tools that can better distinguish the subgroups within the condition. For instance, DKD is typically placed in the broad category of a non-inflammatory kidney disease. However, genome-wide transcriptome analysis studies consistently indicate the inflammatory signaling pathway activation in DKD. This review will utilize human data in discussing the potential for redefining the role of inflammation in DKD. We also comment on the therapeutic potential of targeted anti-inflammatory therapy for DKD.

IL-17 and CD40 ligand synergistically stimulate the chronicity of diabetic nephropathy

Background

Early stages of diabetic nephropathy (DN) are characterized by an influx of inflammatory cells. Interactions between infiltrating T cells and podocytes may play an important role in the ongoing inflammatory response and remodelling. The aim of this study was to explore the role of IL-17 and CD40 ligand (CD40L) in DN.

Methods

The study design involved a case series. Kidney biopsy samples of 69 patients with type 2 diabetes were assessed for the presence of CD4+ IL-17+ T cells. The number of CD4+ IL-17+ T cells were counted and correlated with clinical and laboratory findings. Additionally, advanced glycation end-products (AGEs) were added to cultured podocytes to imitate diabetic conditions and thus to elucidate the role of CD4+ IL-17+ T cells in renal sclerosis.

Results

CD80 expression was detected in early phases of DN but was absent during diffused glomerurosclerosis in DN kidney specimens. In DN samples, CD40 expression was not only observed in most of the infiltrating cells, but also increased in podocytes and tubular epithelial cells. CD40L is locally expressed on infiltrating cells. CD4+ IL-17+ T cells were found in DN, and the number of CD4+ IL-17+ T cells was positively correlated with the deterioration in glomerular filtration rate (GFR). IL-17A was the key cytokine produced by CD4+ IL-17+ T cells. IL-17A levels were elevated in DN renal tissue and were correlated with declining GFR. IL-17 and CD40L synergistically enhanced IL-6, monocyte chemoattractant protein-1 (MCP-1), regulated on activation, normal T cell expressed and secreted (RANTES), transforming growth factor beta 1 (TGF-β1) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) production in vitro. AGEs induced podocyte activation with increasing expression of IL-17A, CD40 and TGF-β1 in vitro. Blockade with an anti-IL-17 monoclonal antibody reduced the expression of CD40 and TGF-β1, but increased the viability of cultured podocytes.

Conclusions

IL-17 and CD40L synergistically mediate the inflammatory response and remodelling associated with tissue injury and glomerular sclerosis in DN.

Immunity and inflammation in diabetic kidney disease: translating mechanisms to biomarkers and treatment targets

Increasing incidences of obesity and diabetes have made diabetic kidney disease (DKD) the leading cause of chronic kidney disease and end-stage renal disease worldwide. Despite current pharmacological treatments, including strategies for optimizing glycemic control and inhibitors of the renin-angiotensin system, DKD still makes up almost one-half of all cases of end-stage renal disease in the United States. Compelling and mounting evidence has clearly demonstrated that immunity and inflammation play a paramount role in the pathogenesis of DKD. This article reviews the involvement of the immune system in DKD and identifies important roles of key immune and inflammatory mediators. One of the most recently identified biomarkers is serum amyloid A, which appears to be relatively specific for DKD. Novel and evolving treatment approaches target protein kinases, transcription factors, chemokines, adhesion molecules, growth factors, advanced glycation end-products, and other inflammatory molecules. This is the beginning of a new era in the understanding and treatment of DKD, and we may have finally reached a tipping point in our fight against the growing burden of DKD.

Cellular and humoral immune responses in the early stages of diabetic nephropathy in NOD mice

This study was designed to examine immunopathology of diabetic nephropathy in non-obese diabetic (NOD) mice and to investigate the involvement of cellular and humoral immunity at various time points after diabetes onset. We found that the glomeruli of diabetic NOD mice were infiltrated with T and B cells, as well as CD11c+ dendritic cells, which had close contact with CD4+ and CD8+ T cells in the infiltrates. We also found that IgG deposits in the glomeruli of diabetic NOD mice were accompanied by the presence of complement C3. Moreover, the serum from diabetic mice contained autoantibodies directed towards components of the glomeruli and these antibodies were not present in non-diabetic NOD mice. The immune changes in the kidney occurred together with increasing kidney weight and urinary albumin excretion along with duration of diabetes. We provide evidence that infiltrating lymphocytes and anti-kidney autoantibodies may be involved in diabetic nephropathy in autoimmune diabetes in the NOD mouse. Understanding the role that the immune system plays in the pathogenesis of diabetic nephropathy could lead to identification of new strategies and/or additional therapeutic targets for prevention and treatment of diabetic nephropathy.

Juxtaglomerular apparatus T-cell infiltration affects glomerular structure in Type 1 diabetic patients

AIMS/HYPOTHESIS

Type 1 diabetes is an autoimmune disorder associated with T-cell mediated injury to multiple endocrine tissues. T-cell infiltration of the juxtaglomerular apparatus could be associated with changes in local renin angiotensin system activity and, thus, with changes in the renal microenvironment. We examined the frequency of juxtaglomerular apparatus T-cell infiltration early in Type 1 diabetes and tested whether this is associated with renal structure and function.

METHODS

We classified 89 Type 1 diabetic patients by immunohistochemical analysis as either juxtaglomerular apparatus T-cell positive ( n=37) or T-cell negative ( n=38). Borderline cases ( n=14) were not considered further.

RESULTS

T-cell positive patients had a shorter duration of diabetes (6.7+/-2.5 years) than T-cell negative patients (9.2+/-5.0 years, p=0.011) and lower albumin excretion rate, but they had a similar glomerular filtration rate and blood pressure. Renal biopsy morphometric analysis showed similar glomerular basement membrane width and mesangial fractional volume in these two groups. However, glomerular capillary surface density ( p=0.0012) and filtration surface per glomerulus ( p=0.0155) were greater in the T-cell positive patients.

CONCLUSION/INTERPRETATION

Increased filtration surface per glomerulus could be associated with glomerular filtration rate preservation in diabetes. Thus, juxtaglomerular apparatus immunologic injury in Type 1 diabetes patients could delay the clinical consequences of diabetic nephropathy.

Diabetic nephropathy: what causes to treat?

In summary, diabetic nephropathy is characterized by a multifactorial disease process. The present survey points to several factors that are treatable by available drugs. We must now consider prophylactic treatment of patients with poor metabolic control not only to lower blood glucose levels, but also to protect against the harmful effects of glucose. ACE inhibitors and several other available drugs have such effects.