Methylglyoxal (MG) is a reactive metabolite involved in diabetes and aging through the formation of protein adducts. Less is known about the extent that MG and its metabolic product S-d-lactoylglutathione (LGSH) form adducts with cell metabolites. Using a 'symmetric' isotope-labeled and reactivity-based metabolomics approach in living cells, we found over 200 adducts and, surprisingly, discovered that 10 of the most abundant are lactoylated amino acids mainly derived from LGSH. The most abundant adduct d-Lac-Cys is formed rapidly between LGSH and cysteine, whereas the diastereoisomer l-Lac-Cys is formed directly from MG and cysteine, assigning cysteine with both glyoxalase 1-like and glyoxalase 2-like activity. Cellular cysteine and MG dynamically regulate d-Lac-Cys and l-Lac-Cys levels and the adducts are increased in diabetes, suggesting their use as novel biomarkers. Lastly, cysteine amides, as proxies for protein cysteines, also undergo lactoylation by MG and LGSH, suggesting the existence of two additional pathways for nonenzymatic lactoylation of proteins.

Autoreactivity of the complement system may escalate the development of diabetic nephropathy. We used the BTBR OB mouse model of type 2 diabetes to investigate the role of the complement factor mannan-binding lectin (MBL) in diabetic nephropathy. Female BTBR OB mice (n = 30) and BTBR non-diabetic WT mice (n = 30) were included. Plasma samples (weeks 12 and 21) and urine samples (week 19) were analyzed for MBL, C3, C3-fragments, SAA3, and markers for renal function. Renal tissue sections were analyzed for fibrosis, inflammation, and complement deposition. The renal cortex was analyzed for gene expression (complement, inflammation, and fibrosis), and isolated glomerular cells were investigated for MBL protein. Human vascular endothelial cells cultured under normo- and hyperglycemic conditions were analyzed by flow cytometry. We found that the OB mice had elevated plasma and urine concentrations of MBL-C (p < 0.0001 and p < 0.001, respectively) and higher plasma C3 levels (p < 0.001) compared to WT mice. Renal cryosections from OB mice showed increased MBL-C and C4 deposition in the glomeruli and increased macrophage infiltration (p = 0.002). Isolated glomeruli revealed significantly higher MBL protein levels (p < 0.001) compared to the OB and WT mice, and no renal MBL expression was detected. We report that chronic inflammation plays an important role in the development of DN through the binding of MBL to hyperglycemia-exposed renal cells.

Mannan-binding lectin (MBL) initiates the lectin pathway of complement and has been linked to albuminuria and mortality in diabetes. We hypothesize that MBL-associated serine protease 2 (MASP-2) deficiency will protect against diabetes-induced kidney damage. Male C57BL/6J MASP-2 knockout (Masp2(-/-)) mice and wildtype (WT) mice were divided into a diabetic group and a non-diabetic group. Renal hypertrophy, albumin excretion, mesangial area and specific mRNA expressions in the renal cortex were measured after 8 and 12 weeks of diabetes. By two-way ANOVA it was tested if MASP-2 modulated the renal effects of diabetes, that is interaction. After 12 weeks of diabetes Masp2(-/-) diabetic mice had a smaller mesangium at 21.1% of the glomerular area (95% CI 19.7, 22.6) compared with WT diabetic mice, 25.2% (23.2, 27.2), p(interaction) = 0.001. After 8 weeks of diabetes, plasma cystatin C was 261.5 ng/mL (229.6, 297.8) in the WT diabetic group compared to 459.9 ng/mL (385.7, 548.3) in non-diabetic WT mice, p < 0.001. By contrast, no difference in plasma cystatin C levels was found between the Masp2(-/-) diabetic mice, 288.2 ng/mL (260.6, 318.6) and Masp2(-/-) non-diabetic mice, 293.5 ng/mL (221.0, 389.7), p = 0.86 and p(interaction) = 0.001. We demonstrated a protective effect of MASP-2 deficiency on mesangial hypertrophy after 12 weeks of diabetes and an effect on plasma cystatin C level. MASP-2 deficiency did, however, fail to protect against diabetic-induced alterations of kidney weight, albuminuria and renal mRNA expression of fibrotic- and oxidative stress markers.

Purpose To investigate the level and localization of the multifunctional receptor sortilin in the diabetic retina, as well as the effect of sortilin inhibition on retinal neurodegeneration in experimental diabetes. Methods The localization of sortilin and colocalization with the p75 neurotrophin receptor (p75NTR) and Müller cell (MC) markers were determined using immunofluorescence on retinal sections from human patients with diabetes and streptozotocin-induced diabetic C57BL/6J male mice. In the diabetic mice, levels were further quantified using Western blot and quantitative PCR. Therapeutic studies were performed on diabetic mice using intravitreally injected anti-sortilin antibodies. Neuroprotection was evaluated in vivo by optical coherence tomography and by quantification of retinal ganglion cells (RGCs) in flat mounts. Results Increased levels of sortilin were observed in human and murine diabetic retinas compared with nondiabetic control retinas. Sortilin was highly localized to retinal MCs, and, notably, colocalization with p75NTR was only seen in diabetic retinas. A remarkable protective effect of sortilin inhibition on inner retinal cells was observed in diabetic mice. At eight weeks after diabetes induction, inner retinal thickness was reduced by 9.7% (−12.7%, −6.6%; P < 0.0001; n = 11−12) in the PBS-injected control group compared with the anti-sortilin injected group. Similarly, the count of RGCs was reduced by 20.5% (−30.8%, −10.2%; P = 0.0009) in the PBS-injected control group compared with the anti-sortilin–injected group. Conclusions Sortilin is upregulated in the diabetic retina, and sortilin inhibition effectively protects against neuronal loss. Thus sortilin emerges as a novel pharmacological target in diabetic retinal neurodegeneration—an important early event in the pathogenesis of diabetic retinopathy.

Significance: The metabolic disorder, diabetes mellitus, results in microvascular complications, including diabetic kidney disease (DKD), which is partly believe to involve disrupted energy generation in the kidney, leading to injury that is characterized by inflammation and fibrosis. An increasing body of evidence indicates that the innate immune complement system is involved in the pathogenesis of DKD; however, the precise mechanisms remain unclear. Recent Advances: Complement, traditionally thought of as the prime line of defense against microbial intrusion, has recently been recognized to regulate immunometabolism. Studies have shown that the complement activation products, Complement C5a and C3a, which are potent pro-inflammatory mediators, can mediate an array of metabolic responses in the kidney in the diabetic setting, including altered fuel utilization, disrupted mitochondrial respiratory function, and reactive oxygen species generation. In diabetes, the lectin pathway is activated via autoreactivity toward altered self-surfaces known as danger-associated molecular patterns, or via sensing altered carbohydrate and acetylation signatures. In addition, endogenous complement inhibitors can be glycated, whereas diet-derived glycated proteins can themselves promote complement activation, worsening DKD, and lending support for environmental influences as an additional avenue for propagating complement-induced inflammation and kidney injury. Critical Issues: Recent evidence indicates that conventional renoprotective agents used in DKD do not target the complement, leaving this web of inflammatory stimuli intact. Future Directions: Future studies should focus on the development of novel pharmacological agents that target the complement pathway to alleviate inflammation, oxidative stress, and kidney fibrosis, thereby reducing the burden of microvascular diseases in diabetes. Antioxid. Redox Signal. 37, 781–801.

Introduction Accumulating evidence support that mannan-binding lectin (MBL) is a promising prognostic biomarker for risk-stratification of diabetic micro- and macrovascular complications. Serum MBL levels are predominately genetically determined and depend on MBL genotype. However, Type 1 diabetes (T1D) is associated with higher MBL serum levels for a given MBL genotype, but it remains unknown if this is also the case for patients with T2D. In this study, we evaluated the impact of MBL genotypes on renal function trajectories serum MBL levels and compared MBL genotypes in newly diagnosed patients with T2D with age- and sex-matched healthy individuals. Furthermore, we evaluated differences in parameters of insulin resistance within MBL genotypes. Methods In a cross-sectional study, we included 100 patients who were recently diagnosed with T2D and 100 age- and sex-matched individuals. We measured serum MBL levels, MBL genotype, standard biochemistry, and DEXA, in all participants. A 5-year clinical follow-up study was conducted, followed by 12-year data on follow-up biochemistry and clinical status for the progression to micro- or macroalbuminuria for the patients with T2D. Results We found similar serum MBL levels and distribution of MBL genotypes between T2D patients and healthy individuals. The serum MBL level for a given MBL genotype did not differ between the groups neither at study entry nor at 5-year follow-up. We found that plasma creatinine increased more rapidly in patients with T2D with the high MBL expression genotype than with the medium/low MBL expression genotype over the 12-year follow-up period (p = 0.029). Serum MBL levels did not correlate with diabetes duration nor with HbA1c. Interestingly, serum MBL was inversely correlated with body fat percentage in individuals with high MBL expression genotypes both at study entry (p=0.0005) and 5-years follow-up (p=0.002). Discussion Contrary to T1D, T2D is not per se associated with increased MBL serum level for a given MBL genotype or with diabetes duration. Serum MBL was inversely correlated with body fat percentage, and T2D patients with the high MBL expression genotype presented with deterioration of renal function.

Activation of nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3) inflammasome has been reported in diabetic complications including diabetic kidney disease (DKD). However, it remains unknown if NLRP3 inhibition is renoprotective in a clinically relevant interventional approach with established DKD. We therefore examined the effect of the NLRP3-specific inhibitor MCC950 in streptozotocin-induced diabetic mice to measure the impact of NLRP3 inhibition on renal inflammation and associated pathology in DKD. We identified an adverse effect of MCC950 on renal pathology in diabetic animals. Indeed, MCC950-treated diabetic animals showed increased renal inflammation and macrophage infiltration in association with enhanced oxidative stress as well as increased mesangial expansion and glomerulosclerosis when compared with vehicle-treated diabetic animals. Inhibition of the inflammasome by MCC950 in diabetic mice led to renal up-regulation of markers of inflammation (Il1β, Il18 and Mcp1), fibrosis (Col1, Col4, Fn1, α-SMA, Ctgf and Tgfβ1) and oxidative stress (Nox2, Nox4 and nitrotyrosine). In addition, enhanced glomerular accumulation of pro-inflammatory CD68 positive cells and pro-oxidant factor nitrotyrosine was identified in the MCC950-treated diabetic compared with vehicle-treated diabetic animals. Collectively, in this interventional model of established DKD, NLRP3 inhibition with MCC950 did not show renoprotective effects in diabetic mice. On the contrary, diabetic mice treated with MCC950 exhibited adverse renal effects particularly enhanced renal inflammation and injury including mesangial expansion and glomerulosclerosis.

BACKGROUND:Diabetic nephropathy (DN) is a serious complication of diabetes and a common cause of end stage renal failure. Insulin-like growth factor (IGF)-signaling has been implicated in DN, but is mechanistically poorly understood. Here, we assessed the activity of the metalloproteinase PAPP-A, an activator of IGF activity, and its possible interaction with the endogenous PAPP-A inhibitors stanniocalcin (STC)-1 and -2 in the mammalian kidney under normal and hyperglycemic conditions. METHODS AND RESULTS:Immunohistochemistry demonstrated that PAPP-A, its proteolytic substrate IGF binding protein-4, STC1 and STC2 are present in the human kidney. Endogenous inhibited complexes of PAPP-A (PAPP-A:STC1 and PAPP-A:STC2) were demonstrated in media conditioned by human mesangial cells (HMCs), suggesting that PAPP-A activity is regulated by the STCs in kidney tissue. A method for the selective detection of active PAPP-A in tissue was developed and a significant increase in glomerular active PAPP-A in human diabetic kidney relative to normal was observed. In DN patients, the estimated glomerular filtration rate correlated with PAPP-A activity. In diabetic mice, glomerular growth was reduced when PAPP-A activity was antagonized by adeno-associated virus-mediated overexpression of STC2. CONCLUSION:We propose that PAPP-A activity in renal tissue is precisely balanced by STC1 and STC2. An imbalance in this equilibrium causing increased PAPP-A enzymatic activity potentially contributes to the development of DN, and thus, therapeutic targeting of PAPP-A activity may represent a novel strategy for its treatment.

The management of hyperglycemia in individuals with type 2 diabetes and impaired kidney function remains challenging because the pharmacological options are limited especially when estimated glomerular filtration rate (eGFR) is below 30 ml/min per 1.73 m2. The effects and safety of GLP-1 receptor agonists in type 2 diabetes have been investigated in several clinical trials, including in patients with moderately and severely impaired kidney function as recruited in the AWARD-7 study1Tuttle K.R. Lakshmanan M.C. Rayner B. et al.Dulaglutide versus insulin glargine in patients with type 2 diabetes and moderate-to-severe chronic kidney disease (AWARD-7): a multicentre, open-label, randomised trial.Lancet Diabetes Endocrinol. 2018; 6: 605-617https://doi.org/10.1016/S2213-8587(18)30104-9Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar as well as in those with moderately impaired kidney function as described in the PIONEER-5 study.2Mosenzon O. Blicher T.M. Rosenlund S. et al.Efficacy and safety of oral semaglutide in patients with type 2 diabetes and moderate renal impairment (Pioneer 5): a placebo-controlled, randomised, phase 3a trial.Lancet Diabetes Endocrinol. 2019; 7: 515-527https://doi.org/10.1016/S2213-8587(19)30192-5Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar In this issue of Kidney International Reports, Cherney et al.3Cherney D.Z. Hadjadj S. Lawson J. et al.Hemoglobulin A1c reduction with the GLP-1 receptor agonist semaglutide is independent of baseline eGFR: post hoc analysis of the SUSTAIN and Pioneer programs.Kidney Int Rep. 2022; 7: 2345-2355Abstract Full Text Full Text PDF Scopus (1) Google Scholar have extended our knowledge about the treatment with GLP-1 receptor agonists in type 2 diabetic subjects with renal impairment by performing a post hoc analysis of data from the SUSTAIN and PIONEER trials. In their analysis of the data from more than 8000 type 2 diabetic subjects in the SUSTAIN and PIONEER studies, the authors compared the glucose-lowering efficacy of subcutaneously and orally administered semaglutide across a broad range of renal impairment. In these study populations the authors found similar effects on glycemic control of semaglutide across subgroups of eGFR varying from chronic kidney disease (CKD) stage 1 to 4. This supplements previous evidence of the efficacy of this particular GLP-1 receptor agonist in those type 2 diabetic patients with impaired kidney function. The safety of semaglutide was also assessed in this population where side effects from other glucose lowering agents have been reported to be increased. Indeed, more serious adverse effects were reported among patients with eGFR lower than 60 ml/min per 1.73 m2 as compared to patients with higher eGFR. It is important to appreciate that the study did not statistically compare the event rates of adverse effects in semaglutide treated patients versus placebo or the active comparator treated patients. Gastrointestinal side effects were common among semaglutide treated patients ranging from 16% to 56% but did not appear to be related to eGFR. Moreover, patients treated with semaglutide tended to more frequently discontinue treatment than patients treated with placebo or an active comparator. In addition, discontinuation of semaglutide treatment occurred more often in patients with lower eGFR as compared to those with a higher eGFR but a similar pattern of increased discontinuation in those subjects with a lower GFR was also seen in patients treated with placebo or the active comparator. Data on mortality were available from the SUSTAIN 6 and PIONEER 6 studies. Although more patients died in the groups with eGFR <60 ml/min per 1.73 m2 as one would predict, this increase in mortality was observed in both semaglutide and placebo treated patients. Treatment with semaglutide induced a loss in body weight across the eGFR subgroups ranging from −2.9% to −8.2% in all the trials except for the PIONEER 5 study in which patients with eGFR ≥60 ml/min per 1.73 m2 did not either lose or gain weight during the study. In SUSTAIN 6 and 10 and PIONEER 5 and 6 trials, the authors found a statistically significant interaction between change in body weight and eGFR subgroup with the signal of weight loss being more pronounced in those individuals with lower eGFR. Systolic and diastolic blood pressure decreased in semaglutide treated patients compared with placebo or the active comparator across the trials, with the authors reporting no evidence of an interaction between effects on blood pressure and baseline eGFR. The post hoc design of the analyses of the SUSTAIN and PIONEER data comes with several limitations, as acknowledged by the authors, including the necessity to interpretate the results cautiously because the trials were not designed to specifically compare outcomes among different eGFR subgroups. In this context, for example, baseline hemoglobin A1c differed among the eGFR subgroups. This difference in hemoglobin A1c could influence the treatment effects on glycemic control although the differences appear to have been minor. Nevertheless, the overall conclusion of the study is consistent with an earlier post hoc analysis of data from 8 trials studying once weekly exenatide, including patients with type 2 diabetes and CKD stage 2 and 3.4Guja C. Frias J.P. Suchower L. et al.Safety and efficacy of exenatide once weekly in participants with Type 2 diabetes and Stage 2/3 chronic kidney disease.Diabetes Ther. 2020; 11: 1467-1480https://doi.org/10.1007/s13300-020-00815-zCrossref PubMed Scopus (2) Google Scholar As in the present report examining semaglutide, the effect of exenatide with regards to reduction in hemoglobin A1c did not differ between certain eGFR subgroups, specifically CKD 2 versus CKD 3 patients.4Guja C. Frias J.P. Suchower L. et al.Safety and efficacy of exenatide once weekly in participants with Type 2 diabetes and Stage 2/3 chronic kidney disease.Diabetes Ther. 2020; 11: 1467-1480https://doi.org/10.1007/s13300-020-00815-zCrossref PubMed Scopus (2) Google Scholar Furthermore, exenatide treatment induced a decrease in systolic blood pressure and body weight, which was similar in the 2 CKD groups.4Guja C. Frias J.P. Suchower L. et al.Safety and efficacy of exenatide once weekly in participants with Type 2 diabetes and Stage 2/3 chronic kidney disease.Diabetes Ther. 2020; 11: 1467-1480https://doi.org/10.1007/s13300-020-00815-zCrossref PubMed Scopus (2) Google Scholar In conclusion, despite the limitations due to the post hoc design of the study we consider that the data presented affords diabetologists and nephrologists a degree of optimism as reflected by both the safety and efficacy of GLP-1 receptor agonists, thereby representing a viable therapeutic option for the population of type 2 diabetic patients with reduced GFR. All the authors declared no competing interests. Hemoglobin A1c Reduction With the GLP-1 Receptor Agonist Semaglutide Is Independent of Baseline eGFR: post hoc Analysis of the SUSTAIN and PIONEER ProgramsKidney International ReportsVol. 7Issue 11PreviewGlucagon-like peptide-1 receptor agonists (GLP-1RAs) are effective treatments for reducing hemoglobin A1c (HbA1c) in people with type 2 diabetes (T2D), including those with reduced kidney function. Full-Text PDF Open Access

Excessive production of renal reactive oxygen species (ROS) play a major role in diabetic kidney disease (DKD). Here, we provide key novel findings demonstrating the predominant pathological role of the prooxidant enzyme NADPH oxidase-NOX5 in DKD, independent of the previously characterised NOX4 pathway. In diabetic patients, we found increased expression of renal NOX5 in association with enhanced ROS formation and upregulation of ROS-sensitive factors EGR-1 (early growth response 1), PKC-α (protein kinase C- α) and a key metabolic gene involved in redox balance, TXNIP (thioredoxin-interacting protein). In preclinical models of DKD, overexpression of NOX5 in Nox4 deficient mice enhances kidney damage by increasing albuminuria and augmenting renal fibrosis and inflammation via enhanced ROS formation and the modulation of EGR1, TXNIP, ERK1/2, PKC-α and PKC-ε. In addition, the only first in class NOX inhibitor, GKT137831 appears to be ineffective in the presence of NOX5 expression in diabetes. In vitro, silencing of NOX5 in human mesangial cells attenuated high glucose induced upregulation of EGR1, PKC-α, and TXNIP as well as markers of inflammation (TLR4 and MCP-1) and fibrosis (CTGF and collagens I and III) via reduction in ROS formation. Collectively, these findings identify NOX5 as a superior target in human DKD compared to other NOX isoforms such as NOX4 which may have been overinterpreted in previous rodent studies.

H-ficolin recognizes patterns on microorganisms and stressed cells and can activate the lectin pathway of the complement system. We aimed to assess H-ficolin in relation to the progression of diabetic kidney disease (DKD), all-cause mortality, diabetes-related mortality, and cardiovascular events. Event rates per 10-unit H-ficolin-increase were compared in an observational follow-up of 2,410 individuals with type 1 diabetes from the FinnDiane Study. DKD progression occurred in 400 individuals. The unadjusted hazard ratio (HR) for progression was 1.29 (1.18–1.40) and 1.16 (1.05–1.29) after adjustment for diabetes duration, sex, HbA1c, systolic blood pressure, and smoking status. After adding triglycerides to the model, the HR decreased to 1.07 (0.97–1.18). In all, 486 individuals died, including 268 deaths of cardiovascular causes and 192 deaths of complications to diabetes. HRs for all-cause mortality and cardiovascular mortality were 1.13 (1.04–1.22) and 1.05 (0.93–1.17), respectively, in unadjusted analyses. These estimates lost statistical significance in adjusted models. However, the unadjusted HR for diabetes-related mortality was 1.19 (1.05–1.35) and 1.18 (1.02–1.37) with the most stringent adjustment level. Our results, therefore, indicate that H-ficolin predicts diabetes-related mortality, but neither all-cause mortality nor fatal/non-fatal cardiovascular events. Furthermore, H-ficolin is associated with DKD progression, however, not independently of the fully adjusted model.

See Clinical Research on Page 2392 See Clinical Research on Page 2392 Advances in our understanding of the pathogenesis of diabetic nephropathy are severely hampered by our limited knowledge as to how kidney histopathological changes mirror clinically available markers, such as urinary albumin excretion and estimated glomerular filtration rate and vice versa. A significant obstacle in this regard has been the low number of renal biopsy specimens obtained in clinical practice as part of diagnosing and monitoring diabetic nephropathy. This is particularly relevant over the last 20 years when most clinicians have considered the limited gain and potential risk of performing kidney biopsies. Thus, in clinical practice, the diagnosis of diabetic nephropathy has remained mostly based on the clinical course of the renal impairment where diabetes duration, glycemic control, and the presence of other complications are key factors when considering if the renal disease is due to diabetes per se. By contrast kidney biopsies are usually restricted to the setting of atypical clinical presentations where there is uncertainty as to the etiology of the kidney impairment, even in the presence of diabetes. In the article “Renal Histology in Patients with Type 2 Diabetes, Normoalbuminuria, Microalbuminuria or Proteinuria, Normal or Reduced Renal Function: The Hidden Role Of Vascular Lesions” featured in this issue of Kidney International Reports, Rodríguez et al.1Rodrigues R. Renal histology in patients with type 2 diabetes, normoalbuminuria, microalbuminuria or proteinuria, normal or reduced renal function: the hidden role of vascular lesions.Kidney Int Rep. 2021; (In press)PubMed Google Scholar present their evaluation of a unique set of renal specimens obtained from nephrectomy specimens of 90 patients. In their study, the much larger samples than seen with a routine renal biopsy allow for the examination of about 170 glomeruli per patient, including vascular tissue. The authors aimed to help fill the important knowledge gap in our understanding of the relationship between renal histopathology and clinical markers of kidney disease. This study confirms the dissociation between the clinical presentation of kidney function and renal histopathology. This is consistent with previous reports, including the seminal study by Fioretto et al.2Fioretto P. Mauer M. Brocco E. et al.Patterns of renal injury in NIDDM patients with microalbuminuria.Diabetologia. 1996; 39: 1569-1576Crossref PubMed Scopus (356) Google Scholar Furthermore, this study has also revealed widespread vascular disease including in patients with preserved kidney function as well as in those with normal urinary albumin excretion as previously reported in a recent Japanese study.3Furuichi K. Shimizu M. Hara A. et al.Diabetic nephropathy: a comparison of the clinical and pathological features between the CKD risk classification and the classification of diabetic nephropathy 2014 in Japan.Intern Med. 2018; 57: 3345-3350Crossref PubMed Scopus (13) Google Scholar As a consequence of the kidney specimens obtained in the present study including a broader representation of glomeruli and vascular tissue, Rodríguez et al.1Rodrigues R. Renal histology in patients with type 2 diabetes, normoalbuminuria, microalbuminuria or proteinuria, normal or reduced renal function: the hidden role of vascular lesions.Kidney Int Rep. 2021; (In press)PubMed Google Scholar were able to show with greater accuracy the glomerular and vascular histopathology in patients across the clinical spectrum of chronic kidney disease stages. Thus, this study has highlighted that estimated glomerular filtration rate and urinary albumin excretion often fail to reveal developing kidney structural lesions. The authors found that patients with normal urinary albumin excretion frequently have advanced glomerular, tubular, as well as interstitial injury. For example, 10% to 20% of the patients with normal urinary albumin excretion had nodular glomerulosclerosis (class III diabetic nephropathy) as well as tubular lesions with atrophy, fibrosis, and inflammation. In addition, many patients with macroalbuminuria only had mild structural injury within the kidney. These changes may explain the dissociation frequently seen between urinary albumin excretion and kidney function, including why some diabetic patients lose kidney function despite not developing proteinuria.4MacIsaac R.J. Ekinci E.I. Progression of diabetic kidney disease in the absence of albuminuria.Diabetes Care. 2019; 42: 1842-1844Crossref PubMed Scopus (8) Google Scholar The study importantly also unmasked extensive vascular damage in patients with type 2 diabetes which was present even among patients with normal urinary albumin excretion and preserved estimated glomerular filtration rate. Of particular interest, 80% to 100% of the cases were found to have moderate hyalinosis and arteriolar sclerosis including in patients with normo- and microalbuminuria. Furthermore, these vascular lesions were seen across the diabetic nephropathy histopathological classes I, II, and III. The same moderate degree of tubular atrophy, interstitial fibrosis, and inflammation was observed across cases with class IIa, IIb, and III diabetic nephropathy. Thus, it is possible that renal vascular damage leads to these changes via ischemia independently of glomerular damage. The study adds knowledge to our understanding of diabetic nephropathy. However, the study has important limitations in part due to its cross-sectional design and recent developments in clinical practice regarding the changes in the use of glucose-lowering drugs. The histopathological impact of pharmaceutical interventions targeting disease development of diabetic nephropathy including the renin-angiotensin-aldosterone system blockade (which was administered to 58%, 64%, and 76% of patients with normo-, micro-, and macroalbuminuria, respectively) therefore remains to be clarified. In addition, the impact of glucagon-like peptide 1–receptor agonists and sodium glucose cotransporter 2 inhibitors cannot be assessed in the present study as only a few patients were treated with these drugs; yet in the contemporary management of type 2 diabetes, these newer drug classes are increasingly being recommended to those subjects with or at risk for diabetic kidney disease. Furthermore, only a few cases in the study were diagnosed with diabetic retinopathy, that is, 3%, 6%, and 20% of the patients with normo-, micro- and macroalbuminria, respectively. The diagnosis of diabetic retinopathy was based on existing medical records and the low prevalence is therefore most likely due to a low level of detection rather than an effect of selection bias with retinopathy commonly associated with increased renal disease in most rigorous epidemiological studies in type 2 diabetes. Another cause of concern is the inability by study design to distinguish diabetes-related effects on kidney histopathology from those related to normal age-related effects on the kidney. In a subanalysis of the data, the authors compare cases involving patients aged more than 60 years old with those younger than 60 years old and noted that a higher fraction of the evaluated glomeruli exhibited total sclerosis (8%) in the older group as compared with the younger group (4%). Likewise, more patients in the older group had moderate fibrointimal thickening (89%) compared with the younger patients (67%) as evidence of arteriosclerosis. The authors concluded that these numbers are high and clinically relevant despite the differences between age groups and in part could reflect a diabetes-induced acceleration of the age-related kidney changes as previously suggested by others.5Guo J. Zheng H.J. Zhang W. et al.Accelerated kidney aging in diabetes mellitus.Oxid Med Cell Longev. 2020; 2020: 1234059Crossref PubMed Scopus (12) Google Scholar With this study, Rodríguez et al.1Rodrigues R. Renal histology in patients with type 2 diabetes, normoalbuminuria, microalbuminuria or proteinuria, normal or reduced renal function: the hidden role of vascular lesions.Kidney Int Rep. 2021; (In press)PubMed Google Scholar has added important knowledge to our understanding of diabetic nephropathy through their thorough and systematic evaluation of high-quality sections from nephrectomy specimens in patients with type 2 diabetes. The data indisputably have illustrated the complexity of the disease and the intriguing yet perplexing discordance between the clinical presentation of diabetic nephropathy and renal histopathology. This study has further highlighted our need for better tools for noninvasive prediction of kidney damage in diabetes. Future studies must investigate how novel markers of diabetic nephropathy mirror histopathology and disease progression. As emphasized by the authors, the results call for the application of novel unbiased approaches to assess renal pathology including urinary peptidomics, liquid-biopsies, and magnetic resonance imaging of renal microstructure, oxygenation, and metabolism.6Magalhaes P. Pejchinovski M. Markoska K. et al.Association of kidney fibrosis with urinary peptides: a path towards non-invasive liquid biopsies?.Sci Rep. 2017; 7: 16915Crossref PubMed Scopus (35) Google Scholar,7Selby N.M. Blankestijn P.J. Boor P. et al.Magnetic resonance imaging biomarkers for chronic kidney disease: a position paper from the European Cooperation in Science and Technology Action PARENCHIMA.Nephrol Dial Transplant. 2018; 33: ii4-ii14Crossref PubMed Scopus (55) Google Scholar The authors have declared no competing interests. The Role of Vascular Lesions in Diabetes Across a Spectrum of Clinical Kidney DiseaseKidney International ReportsVol. 6Issue 9PreviewThe clinical-histologic correlation in diabetic nephropathy is not completely known. Full-Text PDF Open Access

We describe the fatal course of a patient with initial symptoms of vomiting and nausea who developed symptoms of dystonia, encephalopathy, and coma. The cause of death was poisoning with 3-nitropropionic acid from coconut water spoiled with the fungus Arthrinium saccharicola. We present the clinical findings and forensic analysis.

Background: Previous studies suggest that NLRP3 inflammasome activation could have pathological relevance in diabetic kidney disease (DKD). A recent study demonstrated that NLRP3 inhibition in a preventional approach in db/db mice provided reno-protection, potentially via a ROS dependent mechanism. We aimed to examine the therapeutical potential of the NLRP3 inflammasome inhibitor, MCC950 in a more clinically relevant interventional approach in a model of DKD and its impact on renal pathology. Methods: Diabetes was induced by streptozotocin in ApoE-/- mice. A subgroup of control and diabetic mice was treated with MCC950 (5mg/kg/3 times/week). Treatment was commenced after 5 or 9 weeks of diabetes and continued for another 5 or 9 weeks for the assessment of renal gene expression as well its impact on albuminuria and renal morphology, respectively. Results: Diabetes-induced mesangial expansion was further increased in MCC950 treated diabetic mice when compared to untreated diabetic group (18.9±0.6% vs. 16.3±0.7%, respectively). MCC950 treated diabetic mice showed a trend of increased albuminuria when compared to untreated diabetic mice (43±9 vs. 31±5 ug/24hrs, respectively). Gene expression of markers of fibrosis (fibronectin, collagen IV, α-smooth muscle actin and PCNA) and pro-oxidant enzymes (Nox2 and Nox4) were upregulated in diabetic mice compared to nondiabetic controls. These changes were further upregulated in MCC950-treated diabetic mice when compared to untreated diabetic mice. In addition, mRNA expression of pro-inflammatory markers (MCP-1 and IL-6) were increased in untreated diabetic animals as compared to controls and MCC950 treatment did not show additional upregulation of these parameters. Conclusions: The present study indicates that inhibition of the NLRP3 inflammasome by MCC950 after establishment of disease, may not have a reno-protective effect. Our data rather shows an adverse effect of this drug at least in this model of DKD. Disclosure J.A. Østergaard: None. J.C. Jha: None. A. Sharma: None. A. Dai: None. M.E. Cooper: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim International GmbH, Mundipharma International. Research Support; Self; Boehringer Ingelheim International GmbH, Novo Nordisk A/S. Speaker’s Bureau; Self; AstraZeneca, Merck Sharp & Dohme Corp., Novartis AG, Sanofi-Aventis, Servier. J.B. de Haan: Research Support; Self; Bayer Inc., Reata Pharmaceuticals. K. Jandeleit-Dahm: None.

BACKGROUND:Adverse activation of the complement cascade in the innate immune system appears to be involved in development of vascular complications in diabetes. Dipeptidyl peptidase-4 (DPP-4) is a cell surface serine protease expressed in a variety of tissues. DPP-4 inhibitors are widely used in treatment of type 2 diabetes and appear to yield beneficial pleiotropic effects beyond their glucose-lowering action, for example, renoprotective and anti-inflammatory properties, but the exact mechanisms remain unknown. We hypothesised that DPP-4 inhibitors block adverse complement activation by inhibiting complement-activating serine proteases.MATERIALS AND METHODS:We analysed the effects of 7 different DPP-4 inhibitors on the lectin and classical pathway of the complement system in vitro by quantifying complement factor C4b deposition onto mannan or IgG coated surfaces, respectively. Furthermore, plasma concentrations of mannan-binding lectin (MBL), soluble membrane attack complex (sMAC), and C4b deposition were quantified in 71 patients with a recent acute coronary syndrome and glucose disturbances, randomly assigned to sitagliptin 100 mg (n = 34) or placebo (n = 37) for 12 weeks.RESULTS:All the 7 DPP-4 inhibitors tested in the study directly inhibited functional activity of the lectin pathway in a dose-dependent manner with varying potency in vitro. In vivo, MBL, sMAC, and C4b declined significantly during follow-up in both groups without significant effect of sitagliptin.CONCLUSIONS:We demonstrated an inhibitory effect of DPP-4 inhibitors on the lectin pathway in vitro. The clinical relevance of this effect of DPP-4 inhibitors remains to be fully elucidated.

Aims/Hypothesis. The complications affecting the peripheral nervous system, associated with diabetes mellitus, have been the focus of considerable research. Comparably less research has focused upon the effect of diabetes upon the central nervous system. In this study, we investigate the effect of diabetes upon motor-neuron potentials evoked in the motor cortex of streptozotocin diabetic rats. Methods. In this study, we investigated the cortical-evoked motor-neuron potentials in streptozotocin-induced diabetic rats. Cortical potentials were evoked using direct current stimulation to the motor cortex, and the resulting evoked potentials were recorded in the sciatic nerve. As voluntary movement consists of repeated activation of muscles, repeated stimulation trials were used to determine the effect of diabetes upon the animals' ability to recuperate between stimulations. Results. Our findings showed that diabetes severely decreased the amplitude of cortical-evoked potentials and compromised the recuperation of motor neurons between activation. Conclusion/Interpretation. The reduced amplitude and weakened recuperation of diabetic motor neurons potentially may contribute to impaired transmission in motor pathways and thereby motor dysfunction.

We aimed at establishing a sensitive and robust assay for estimation of systemic complement activation at complement component C3 level in mouse and human plasma samples. In order to capture the activation products iC3b and C3dg in a specific and physiological relevant manner we utilized a construct consisting of the iC3b/C3dg-binding site of human complement receptor 2 (CR2) attached to an Fc-part of mouse IgG. This construct binds C3dg and iC3b from both mice and humans. We purified the CR2-IgG construct from mouse B myeloma cell line supernatants, J558L-CR2-IgG, by protein G affinity chromatography. The CR2-IgG construct was used for capturing C3 fragments in microtiter wells and an anti-mouse or an anti-human-C3 antibody was used for detection of bound C3 fragments. Initially we tested the specificity of the assays with the use of purified C3 fragments. Further, with the use of the CR2-based assay, we measured an up to three-fold higher signal in activated mouse serum as compared to non-activated mouse serum, whereas activated serum from a C3 knock-out mouse gave no signal. We tested in vivo generated samples from a mouse experiment; complement activation was induced by injecting cobra venom factor or heat aggregated IgG into C57bl6 mice, followed by withdrawal of EDTA blood samples at different time points and measurement of iC3b/C3dg. We observed a clear time-dependent distinction in signals between samples with expected high and low complement activation. Furthermore, with the use of the assay for human C3 fragments, we observed that patients with systemic lupus erythematosus (SLE) (n = 144) had significantly higher iC3b/C3dg levels as compared to healthy individuals (n = 144) (p < 0.0001). We present two functional immunoassays, that are able to measure systemic levels of the C3-activation products iC3b and C3dg in mice and humans. To our knowledge, these are the first assays for complement activation that use a physiological relevant capture construct such as CR2. These assays will be a relevant tool when investigating mouse models and human diseases involving the complement system.