All-trans retinoic acid ameliorates inflammatory response mediated by TLR4/NF-κB during initiation of diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of renal failure worldwide and its complications have become a public health problem. Inflammation, oxidative stress and fibrosis play central roles in the progression of DN that lead to renal failure. Potential deleterious effect of inflammation in early evolution of DN is not fully disclosed. Therefore, it is relevant to explore therapies that might modulate this process in order to reduce DN progression. We explored the beneficial effect of all-trans retinoic acid (ATRA) in early inflammation in glomeruli, proximal and distal tubules in streptozotocin (STZ)-induced diabetes. ATRA was administered (1 mg/kg daily by gavage) on days 3 to 21 after STZ administration. It was found that 21 days after STZ injection, diabetic rats exhibited proteinuria, increased natriuresis and loss of body weight. Besides, diabetes induced an increase in interleukins [IL-1β, IL-1α, IL-16, IL-13, IL-2; tumor necrosis factor alpha (TNF-α)] and transforming growth factor-beta 1 (TGF-β1), chemokines (CCL2, CCL20, CXCL5 and CXCL7), adhesion molecules (ICAM-1 and L-selectin) and growth factors (GM-CSF, VEGF, PDGF) in glomeruli and proximal tubules, whereas ATRA treatment remarkably ameliorated these alterations. To further explore the mechanisms through which ATRA decreased inflammatory response, the NF-κB/p65 signaling mediated by TLR4 was studied. We found that ATRA administration attenuates the TLR4/NF-κB inflammatory signaling and prevents NF-κB nuclear translocation in glomeruli and proximal tubules.     

COX-2 but Not mPGES-1 Contributes to Renal PGE2 Induction and Diabetic Proteinuria in Mice with Type-1 Diabetes

Prostaglandin E2 (PGE2) has been implicated to play a pathogenic role in diabetic nephropathy (DN) but its source remains unlcear. To elucidate whether mPGES-1, the best characterized PGE2 synthase, was involved in the development of DN, we examined the renal phenotype of mPGES-1 KO mice subjected to STZ-induced type-1 diabetes. After STZ treatment, mPGES-1 WT and KO mice presented the similar onset of diabetes as shown by similar elevation of blood glucose. Meanwhile, both genotypes of mice exhibited similar increases of urinary and renal PGE2 production. In parallel with this comparable diabetic status, the kidney injury indices including the urinary albumin excretion, kidney weight and the kidney histology (PAS staining) did not show any difference between the two genotypes. By Western-blotting and quantitative qRT-PCR, mPGES-1, mPGES-2, cPGES and 15-hydroxyprostaglandin dehydrogenase (15-PGDH) remain unaltered following six weeks of diabetes. Finally, a selective COX-2 inhibitor celecoxib (50 mg/kg/day) was applied to the STZ-treated KO mice, which resulted in significant reduction of urinary albumin excretion (KO/STZ: 141.5±38.4 vs. KO/STZ + Celebrex: 48.7±20.8 ug/24 h, p<0.05) and the blockade of renal PGE2 induction (kidney: KO/STZ: 588.7±89.2 vs. KO/STZ + Celebrex: 340.8±58.7 ug/24 h, p<0.05; urine: KO/STZ 1667.6±421.4 vs. KO/STZ + Celebrex 813.6±199.9 pg/24 h, p<0.05), without affecting the blood glucose levels and urine volume. Taken together, our data suggests that an as yet unidentified prostaglanind E synthase but not mPGES-1 may couple with COX-2 to mediate increased renal PGE2 sythsesis in DN.     

Diabetes induced renal complications by leukocyte activation of nuclear factor κ-B and its regulated genes expression

Type 2 diabetes mellitus (T2D) is a metabolic disorder characterized by inappropriate insulin function. Despite wide progress in genome studies, defects in gene expression for diabetes prognosis still incompletely identified. Prolonged hyperglycemia activates NF-κB, which is a main player in vascular dysfunctions of diabetes. Activated NF-κB, triggers expression of various genes that promote inflammation and cell adhesion process. Alteration of pro-inflammatory and profibrotic gene expression contribute to the irreversible functional and structural changes in the kidney resulting in diabetic nephropathy (DN). To identify the effect of some important NF-κB related genes on mediation of DN progression, we divided our candidate genes on the basis of their function exerted in bloodstream into three categories (Proinflammatory; NF-κB, IL-1B, IL-6, TNF-α and VEGF); (Profibrotic; FN, ICAM-1, VCAM-1) and (Proliferative; MAPK-1 and EGF). We analyzed their expression profile in leukocytes of patients and explored their correlation to diabetic kidney injury features. Our data revealed the overexpression of both proinflammatory and profibrotic genes in DN group when compared to T2D group and were associated positively with each other in DN group indicating their possible role in DN progression. In DN patients, increased expression of proinflammatory genes correlated positively with glycemic control and inflammatory markers indicating their role in DN progression. Our data revealed that the persistent activation NF-κB and its related genes observed in hyperglycemia might contribute to DN progression and might be a good diagnostic and therapeutic target for DN progression. Large-scale studies are needed to evaluate the potential of these molecules to serve as disease biomarkers.     

C3a Receptor Antagonist Ameliorates Inflammatory and Fibrotic Signals in Type 2 Diabetic Nephropathy by Suppressing the Activation of TGF-β/smad3 and IKBα Pathway

Objective

Diabetic nephropathy (DN) is a serious complication for patients with diabetes mellitus (DM). Emerging evidence suggests that complement C3a is involved in the progression of DN. The aim of this study was to investigate the effect of C3a Receptor Agonist (C3aRA) on DN and its potential mechanism of action in rats with type 2 diabetes mellitus (T2DM).

Methods

T2DM was induced in SD rats by a high fat diet (HFD) plus repeated low dose streptozocin (STZ) injections. T2DM rats were treated with vehicle or C3aRA for 8 weeks. Biochemical analysis, HE and PAS stains were performed to evaluate the renal function and pathological changes. Human renal glomerular endothelial cells (HRGECs) were cultured and treated with normal glucose (NG), high glucose (HG), HG+C3a, HG+C3a+C3aRA and HG+C3a+BAY-11-7082 (p-IKBα Inhibitor) or SIS3 (Smad3 Inhibitor), respectively. Real-time PCR, immunofluorescent staining and western blot were performed to detect the mRNA and protein levels, respectively.

Results

T2DM rats showed worse renal morphology and impaired renal function compared with control rats, including elevated levels of serum creatinine (CREA), blood urea nitrogen (BUN) and urine albumin excretion (UACR), as well as increased levels of C3a, C3aR, IL-6, p-IKBα, collagen I, TGF-β and p-Smad3 in the kidney of T2DM rats and C3a-treated HRGECs. In contrast, C3aRA treatment improved renal function and morphology, reduced CREA, UACR and the intensity of PAS and collagen I staining in the kidney of T2DM rats, and decreased C3a, p-IKBα, IL-6, TGF-β, p-Smad3 and collagen I expressions in HRGECs and T2DM rats.

Conclusion

C3a mediated pro-inflammatory and pro-fibrotic responses and aggravated renal injury in T2DM rats. C3aRA ameliorated T2DN by inhibiting IKBα phosphorylation and cytokine release, and also TGF-β/Smad3 signaling and ECM deposition. Therefore, complement C3a receptor is a potential therapeutic target for DN.     

Combined MMF and insulin therapy prevents renal injury in experimental diabetic rats

Conventional therapies for diabetic mellitus are not effective in preventing the progression from early diabetic nephropathy (DN) to end-stage renal disease. The role of inflammation in the pathogenesis of DN has been implicated both clinically and experimentally, which provides an alternative therapeutic target for DN. Anti-inflammatory impact of mycophenolate mofetil (MMF) alone and in combination with insulin had been observed in a rat model of experimental DN. In this study, the diabetic rats were subjected to different treatments. Compared to control, the expression levels of CD68, NGF, and NF-κB p65, as determined immunohistochemically, were elevated in diabetic rats. Treatment with combined MMF/insulin is associated with a significant reduction in renal tissue of NGF and NF-κB p65 expression, macrophage infiltration. It also partially improved the renal function and attenuated renal hypertrophy at early stage of DN. CD68 was found to positively correlate with urinary albumin excretion and NGF. The combined use of MMF/insulin seemed to offer more protections in rats with experimental diabetic renal injury, and the protective effects of MMF might be due to its anti-inflammatory actions through inhibition of NF-κB activation and reduction of T cells and macrophage infiltration and/or other kidney chemokine productions.     

FGF1ΔHBS delays the progression of diabetic nephropathy in late-stage type 2 diabetes mouse model by alleviating renal inflammation,fibrosis, and apoptosis

Elderly adults are at higher risk for developing diabetic complications including diabetic nephropathy (DN), contributing to excess morbidity and mortality in elderly individuals. A non-mitogenic variant of fibroblast growth factor 1 (FGF1^ΔHBS) was demonstrated to prevent DN in an early-stage (2-month-old) type 2 diabetes (T2D) mouse model. The present study aimed to investigate the potential therapeutic effects of FGF1^ΔHBS against the progression of renal dysfunction in a late-stage T2D mouse model with established DN. Nine-month-old db/db mice were administered FGF1^ΔHBS every other day for 3 months. db/db mice at 12-month-old without FGF1^ΔHBS treatment exhibited high blood glucose level and elevated urine albumin-to-creatinine ratio. FGF1^ΔHBS treatment effectively reversed hyperglycemia, delayed the development of renal dysfunction, and reduced kidney size and weight. Furthermore, FGF1^ΔHBS treatment significantly prevented the progression of renal morphologic impairment. FGF1^ΔHBS treatment demonstrated anti-inflammatory and anti-fibrotic effects, with significantly decreased protein levels of key pro-inflammatory cytokines and pro-fibrotic factors in kidney. Moreover, FGF1^ΔHBS treatment greatly decreased apoptosis of renal tubular cells, accompanied by significant downregulation of the proapoptotic protein and upregulation of the antiapoptotic protein and peroxisome proliferator-activated receptor α (PPARα) expression in kidney. Mechanistically, FGF1^ΔHBS treatment directly protected mouse proximal tubule cells against palmitate-induced apoptosis, which was abolished by PPARα inhibition. In conclusion, this study demonstrated that FGF1^ΔHBS delays the progression of renal dysfunction likely through activating PPARα to prevent renal tubule cell death in late-stage T2D, exhibiting a promising translational potential in treating DN in elderly T2D individuals by ameliorating renal inflammation, fibrosis and apoptosis.     

Lysophosphatidic acid receptor 1 inhibitor,AM095, attenuates diabetic nephropathy in mice by downregulation of TLR4/NF-κB signaling and NADPH oxidase

Diabetic nephropathy (DN) is one of the major long-term complications of diabetes. Lysophosphatidic acid (LPA) signaling has been implicated in renal fibrosis. In our previous study, we found that the LPA receptor 1/3 (LPAR1/3) antagonist, ki16425, protected against DN in diabetic db/db mice. Here, we investigated the effects of a specific pharmacological inhibitor of LPA receptor 1 (LPA1), AM095, on DN in streptozotocin (STZ)-induced diabetic mice to exclude a possible contribution of LPAR3 inhibition. AM095 treatment significantly reduced albuminuria and the albumin to creatinine ratio and significantly decreased the glomerular volume and tuft area in the treated group compared with the STZ-vehicle group. In the kidney of STZ-induced diabetic mice, the expression of LPAR1 mRNA and protein was positively correlated with oxidative stress. AM095 treatment inhibited LPA-induced reactive oxygen species production and NADPH oxidase expression as well as LPA-induced toll like receptor 4 (TLR4) expression in mesangial cells and in the kidney of STZ-induced diabetic mice. In addition, AM095 treatment suppressed LPA-induced pro-inflammatory cytokines and fibrotic factors expression through downregulation of phosphorylated NFκBp65 and c-Jun N-terminal kinases (JNK) in vitro and in the kidney of STZ-induced diabetic mice. Pharmacological or siRNA inhibition of TLR4 and NADPH oxidase mimicked the effects of AM095 in vitro. In conclusion, AM095 is effective in preventing the pathogenesis of DN by inhibiting TLR4/NF-κB and the NADPH oxidase system, consequently inhibiting the inflammatory signaling cascade in renal tissue of diabetic mice, suggesting that LPAR1 antagonism might provide a potential therapeutic target for DN.     

中草药干预糖尿病肾病炎症的作用

随着糖尿病发病率逐年升高,糖尿病肾病成为导致慢性肾脏疾病和终末期肾脏疾病的主要原因。而目前控制血糖及抑制肾素-血管紧张素系统的药物治疗,并不能有效防止糖尿病肾病进展。近年来发现,慢性低水平炎症和免疫系统激活在糖尿病性肾病的发生及发展中起着至关重要的作用。明确糖尿病肾病进展中的炎症机制将有助于确定新的潜在靶点及研发抗炎治疗策略。越来越多的证据表明,中药治疗可以有效改善糖尿病性肾病的高血糖和蛋白尿,并能延缓其进展成为终末期肾病。糖尿病肾病动物实验和体外研究证实中药复方、中草药提取物和中药单体具有调节炎症介质的作用。本文旨在归纳总结文献中与糖尿病肾病肾损伤相关的炎症分子和途径,并探讨中草药靶向抗炎治疗糖尿病肾病的作用。     

Therapeutic Effects of Tangshen Formula on Diabetic Nephropathy in Rats

Objective

Inflammation and fibrosis are essential promoters in the pathogenesis of diabetic nephropathy (DN) in type 2 diabetes. The present study examined the anti-inflammation and anti-fibrosis effect of Tangshen Formula (TSF), a traditional Chinese medicine, on DN.

Research Design and Methods

Protective role of TSF in DN was examined in a rat model of type 2 DN that was established by high-fat diet-fed and low-dose-streptozotocin injection. TSF was suspended in 0.5% CMC-Na solution and delivered by oral gavage at a dosage of 1.67g/Kg body weight/day. The therapeutic effects and mechanisms of TSF on diabetic kidney injury were examined.

Results

We found that TSF treatment for 20 weeks attenuated DN by significantly inhibiting urinary excretion of albumin and renal histological injuries. These beneficial effects were associated with an inactivation of NF-κB signaling, thereby blocking the upregulation of pro-inflammatory cytokines (IL-1β, TNFα), chemokine (MCP-1), and macrophage infiltration in the TSF-treated rats with type 2 DN. In addition, TSF treatment also inactivated TGF-β/Smad3 signaling and therefore suppressed renal fibrosis including expressions of fibronectin, collagen I, and collagen IV. Further studies revealed that the inhibitory effect of TSF on TGF-β/Smad3 and NF-κB signaling in DN was associated with inhibition of Smurf2-dependent ubiquitin degradation of Smad7.

Conclusions

The present study reveals that TSF has therapeutic potential for type 2 DN in rats. Blockade of NF-κB-driven renal inflammation and TGF-β/Smad3-mediated renal fibrosis by preventing the Smurf2-mediated Smad7 degradation pathway may be mechanisms through which TSF inhibits type 2 DN.     

Monocyte/macrophage chemokine receptor CCR2 mediates diabetic renal injury

Monocyte/macrophage recruitment correlates strongly with the progression of renal impairment in diabetic nephropathy (DN). C-C chemokine receptor (CCR)2 regulates monocyte/macrophage migration into injured tissues. However, the direct role of CCR2-mediated monocyte/macrophage recruitment in diabetic kidney disease remains unclear. We report that pharmacological blockade or genetic deficiency of CCR2 confers kidney protection in Ins2(Akita) and streptozotocin (STZ)-induced diabetic kidney disease. Blocking CCR2 using the selective CCR2 antagonist RS504393 for 12 wk in Ins2(Akita) mice significantly attenuated albuminuria, the increase in blood urea nitrogen and plasma creatinine, histological changes, and glomerular macrophage recruitment compared with vehicle. Furthermore, mice lacking CCR2 (CCR2(-/-)) mimicked CCR2 blockade by reducing albuminuria and displaying less fibronectin mRNA expression and inflammatory cytokine production compared with CCR2(+/+) mice, despite comparable blood glucose levels. Bone marrow-derived monocytes from CCR2(+/+) or CCR2(-/-) mice adoptively transferred into CCR2(-/-) mice reversed the renal tissue-protective effect in diabetic CCR2(-/-) mice as evaluated by increased urinary albumin excretion and kidney macrophage recruitment, indicating that CCR2 is not required for monocyte migration from the circulation into diabetic kidneys. These findings provide evidence that CCR2 is necessary for monocyte/macrophage-induced diabetic renal injury and suggest that blocking CCR2 could be a novel therapeutic approach in the treatment of DN.     

骨形态发生蛋白-7及抑制性Smads在糖尿病肾病发生发展中的表达变化

本文采用免疫组化、Western blot及荧光实时定量PCR方法,动态观察链脲佐菌素（streptozocin,STZ）诱导的大鼠糖尿病肾病（diabetic nephropathy,DN）发生早期肾脏骨形态发生蛋白-7（bone morphogenetic protein-7,BMP-7）、Smad6、Smad7蛋白及mRNA表达。结果显示,在正常及DN大鼠肾小管均有BMP-7、Smad6、Smad7蛋白表达,以胞浆表达为主。DN大鼠BMP-7、Smad6蛋白表达较正常大鼠明显增多（P〈0．05）,且BMP-7的mRNA表达呈先增加后降低的状态;而Smad7蛋白和mRNA的表达均呈先增加后降低的状态。转化生长因子-β1（transforming growth factor-β1,TGF-β1）及Ⅰ型胶原（collagen typeⅠ,COL-Ⅰ）mRNA在DN大鼠肾脏表达较正常大鼠明显增多（P〈0．05）,且随着糖尿病进展有逐渐增加的趋势。结果提示,作为TGF-β超家族信号分子的一员,BMP-7信号及抑制性Smad通路在DN肾纤维化发生早期可能起重要的反馈性抑制作用。     

Genipin inhibits mitochondrial uncoupling protein 2 expression and ameliorates podocyte injury in diabetic mice

Diabetic nephropathy (DN) is one of the most common causes of end stage renal disease (ESRD) in China, which requires renal replacement therapy. Recent investigations have suggested an essential role of podocyte injury in the initial stage of DN. This study investigated the potential therapeutic role of genipin, an active extract from a traditional Chinese medicine, on progression of DN in diabetic mice induced by intraperitoneally injection of streptozocin (STZ). In diabetic mice, orally administration of genipin postponed the progression of DN, as demonstrated by ameliorating body weight loss and urine albumin leakage, attenuating glomerular basement membrane thickness, restoring the podocyte expression of podocin and WT1 in diabetic mice. The protective role of genipin on DN is probably through suppressing the up-regulation of mitochondrial uncoupling protein 2 (UCP2) in diabetic kidneys. Meanwhile, through inhibiting the up-regulation of UCP2, genipin restores podocin and WT1 expression in cultured podocytes and attenuates glucose-induced albumin leakage through podocytes monolayer. Therefore, these results revealed that genipin inhibited UCP2 expression and ameliorated podocyte injury in DN mice.     

Lyoniresinol 3α-O-β-D-Glucopyranoside-Mediated Hypoglycaemia and Its Influence on Apoptosis-Regulatory Protein Expression in the Injured Kidneys of Streptozotocin-Induced Mice

Averrhoa carambola L. (Oxalidaceae) root (ACLR) has a long history of use in traditional Chinese medicine for treating diabetes and diabetic nephropathy (DN). (±)-Lyoniresinol 3α-O-β-D-glucopyranoside (LGP1, LGP2) were two chiral lignan glucosides that were isolated from the ACLR. The purpose of this study was to investigate the effect of LGP1 and LGP2-mediated hypoglycaemia on renal injury in streptozotocin (STZ)-induced diabetic mice. STZ-induced diabetic mice were administrated LGP1 and LGP2 orally (20, 40, 80 mg/kg body weight/d) for 14 days. Hyperglycaemia and the expression of related proteins such as nuclear factor-κB (NF-κB), caspase-3, -8, -9, and Bcl-associated X protein (Bax) were markedly decreased by LGP1 treatment. However, LGP2 treatment had no hypoglycaemic activity. Diabetes-dependent alterations in the kidney such as glomerular hypertrophy, excessive extracellular matrix amassing, and glomerular and tubular basement membrane thickening were improved after 14 days of LGP1 treatment. B cell lymphoma Leukaemia-2 (Bcl-2) expression was reduced in the STZ-induced diabetic mouse kidneys but was enhanced by LGP1 treatment. These findings suggest that LGP1 treatment may inhibit diabetic nephropathy progression and may regulate several pharmacological targets for treating or preventing diabetic nephropathy.     

Bradykinin B2 receptor gene polymorphism is associated with altered urinary albumin/creatinine values in diabetic patients

Diabetic nephropathy (DN) is an important microvascular complication of both insulin-dependent and non-insulin-dependent diabetes mellitus. Considerable evidence exists that genetic predisposition is a major determinant in the development of DN. Progress in the understanding of the kinin receptor gene expression indicates their relevance in nephrology and renal pathology. In order to investigate whether clinically relevant polymorphisms of the kinin receptor genes contribute to the genetic predetermination of the renal complication of diabetes, we have initiated a retrospective study with a mixed population of 49 type 1 and 112 type 2 diabetic patients who have been followed for several years by an endocrinologist and (or) nephrologist with periodical functional tests relevant to DN (microalbuminuria, serum and urinary creatinine). The allelic frequencies of four kinin receptor polymorphisms, including three B2R polymorphisms (the C/T-58 promoter polymorphism, the exon 2 and exon 1 polymorphisms, all of them with assumed clinical significance) and the putative nephroprotective (G/C-699) B1R promoter polymorphism, were analyzed in all recruited diabetic patients. Our results indicate a significant association of the B2R exon 1 (+/-) genotype with increased urinary albumin/creatinine values (P = 0.026) and serum creatinine levels (P = 0.028). More importantly, the (+) allele of B2R exon 1 polymorphism was associated very significantly with lower albumin/creatinine values in these patients (P = 0.0087). Thus, the B2R exon 1 polymorphism may represent a susceptibility marker for nephropathy progression in diabetic patients.     

miR-218 regulates diabetic nephropathy via targeting IKK-β and modulating NK-κB-mediated inflammation

Diabetic nephropathy (DN) is a common clinically relevant complication of diabetes that is associated with damage to the capillaries, yet the etiology of this condition remains unclear. Nuclear factor-kappa B (NF-κB) activation is known to be associated with DN-related inflammation and disease progression. Recent work indicated that microRNAs are diagnostic biomarkers of DN progression associated with inflammation in the progression of DN. miR-218 is known to play key regulatory roles in certain cancers in humans, while its influence on DN pathology remains uncertain. The present study, therefore, sought to assess how miR-218 influences the progression of disease in both a rat streptozotocin-induced model of DN and as well as an in vitro model system in which mouse podocytes were stimulated with high glucose levels. We found miR-218 to be markedly downregulated in both model systems relative to appropriate controls, and this downregulation was associated with IKK-β upregulation. In DN rat model, overexpressing miR-218 was sufficient to reduce renal injury. We further determined that podocyte proliferation was markedly impaired by glucose treatment, leading to the apoptotic death of these cells, and miR-218 mimics were able to reduce these phenotypes. Overexpressing miR-218 also significantly dampened inflammatory responses in this model system, as evidenced by reduced tumor necrosis factor-α, interleukin-6 (IL-6), IL-1β, and MCP-1 levels. We then confirmed that miR-218 targeting the messenger RNA encoding IKK-β using a dual-luciferase reporter assay. Together, our results provide clear evidence that miR-218 regulate NF-κB-mediated inflammation, which is central to DN progression.     

Schisandrin B alleviates diabetic nephropathy through suppressing excessive inflammation and oxidative stress

Diabetic nephropathy (DN) is a progressive kidney disease due to glomerular capillary damage in diabetic patients, with inflammation and oxidative stress implicated as crucial pathogenic factors. There is an urgent need to develop effective therapeutic drug. Natural medicines are rich resources for active lead compounds. They would provide new opportunities for the treatment of DN. The present study was designed to investigate the protective effects of Schisandrin B (SchB) on DN and to delineate the underlying mechanism. Oral administration of SchB in the diabetic mouse model significantly alleviated hyperglycemia-induced renal injury, which was accompanied by maintenance of urine creatinine and albumin levels at similar to those of control non-diabetic mice. Histological examination of renal tissue indicated that both development of fibrosis and renal cell apoptosis were dramatically inhibited by SchB. The protective effect of SchB on DN associated with suppression of inflammatory response and oxidative stress. These results strongly suggested that SchB could be a potential therapeutic agent for treatment of DN. Moreover, our findings provided a fuller understanding of the regulatory role of NF-κB and Nrf2 in DN, indicating that they could be important therapeutic targets.     

Impaired parathyroid hormone action on urinary phosphorus excretion in isolated perfused kidney of streptozotocin-induced diabetic rats.

To study the effects of diabetes on the renal actions of parathyroid hormone (PTH), we observed urinary excretion of cyclic adenosine monophosphate (cAMP) and phosphorus in isolated perfused rat kidney. Diabetic rats were kept for 7 days after an intraperitoneal injection of 70 mg/kg streptozotocin (STZ). STZ-induced diabetic rats were treated with a daily injection of 20 U/kg lente-type insulin for 7 days. Plasma albumin, calcium, phosphorus, and PTH levels were not different among normal control, diabetic and insulin-treated diabetic groups. In the control rat kidney, the addition of PTH increased urinary cAMP excretion from 8 +/- 3 to 190 +/- 49 pmol/5 min and urinary phosphorus excretion from 11.3 +/- 4.4 to 33.6 +/- 10.8 microg/5 min. In the STZ-diabetic rat kidney, basal urinary cAMP was impaired, and PTH altered neither urinary cAMP nor phosphorus excretion (from below 0.7 to below 0.7 pmol/5 min, and from 15.5 +/-4.5 to 13.6 +/- 8.1 microg/5 min, respectively). Insulin treatment completely recovered the PTH actions. These results show that insulinopenic diabetes induces PTH resistance in the kidney.     

Increased hyaluronidase activity in the kidney of streptozotocin-induced diabetic rats

We investigated changes in renal hyaluronidase activity in streptozotocin (STZ)-induced diabetic rats during the progression of diabetes. Prior to the study, we characterized rat renal hyaluronidase activity to find that its optimum pH is 3.5 and that it consists of two isomers of 73 and 63 kDa, as detected by zymography. Hyaluronidase activity was traced in one whole kidney and in the cortex and medulla of the other kidney up to the 18th week after STZ injection. Whole kidney hyaluronidase activity started to increase on day 3 and reached a maximum level 2.4 times that of the controls in the 3rd week. Cortical hyaluronidase showed a similar tendency to that of whole kidney hyaluronidase, while medullary hyaluronidase activity continued to increase until the 8th week, suggesting their different involvements in the progression of diabetic nephropathy. In zymography, the intensities of the two isomer bands increased with the progression of diabetes, but the intensity ratio did not change significantly and no new isomer band appeared. Renal HAase activity increased only in STZ-induced diabetic rats, but not in spontaneously diabetic Goto-Kakizaki rats still without remarkable renal disorder. Based on these findings, increased renal HAase activity may serve as a useful marker for diabetic nephropathy.     

Knockout of toll-like receptor-4 attenuates the pro-inflammatory state of diabetes

Type 1 diabetes (T1DM) is associated with increased vascular complications and is a pro-inflammatory state. Recent findings have shown increased TLR2 and 4 expression, signaling, ligands, and functional activation in T1DM subjects compared to controls and further accentuated in T1DM with microvascular complications. Thus, the aim of this study was to examine if genetic deficiency of TLR4 attenuates the increased inflammation associated with T1DM using the streptozotocin-induced diabetic mouse model. C57BL/6 and TLR4(-/-) mice were obtained and studied in the native state and following induction of diabetes using streptozotocin. Diabetic (WT+STZ) mice had increased expression of both TLR2 and TLR4, while TLR4(-/-) STZ mice had increased expression only of TLR2, but not TLR4 compared to the non-diabetic mice TLR2 expression was significantly increased with STZ-induced diabetes and was unaffected by knockout of TLR4. Also, levels of MyD88, IRAK-1 protein phosphorylation, Trif, IRF3, and NF-κB activity were significantly reduced in TLR4(-/-) +STZ mice compared to the WT+STZ mice. WT+STZ mice exhibited significantly increased levels of serum and macrophage IL-1β, IL-6, KC/IL-8, IP-10, MCP-1, IFN beta and TNF-α compared to WT mice and this was significantly attenuated in TLR4(-/-) +STZ mice (P<0.01). Thus, TLR4 contributes to the pro-inflammatory state and TLR4KO attenuates inflammation in diabetes.     

Empagliflozin ameliorates type 2 diabetes mellitus-related diabetic nephropathy via altering the gut microbiota

BackgroundThe dysregulation of gut microbiota can be found in patients with type 2 diabetes mellitus (T2DM)-related diabetic nephropathy (DN). Inhibitors of sodium-glucose co-transporter 2 (SGLT2) were reported to affect gut microbiota. This study aimed to identify whether empagliflozin (EMPA) attenuated DN via regulating gut microbiota.Materials and methodsThe high-fat diet (HFD) combining streptozocin (STZ) injection was performed to induce DN in mice. The therapeutic effects of EMPA were observed by staining of renal tissues and urine albumin/creatinine ratio (UACR). Mouse feces were collected for 16S rRNA sequencing. Fecal short-chain fatty acids (SCFAs) and fecal and serum lipopolysaccharide (LPS) were determined. An antibiotic-ablated model was established to confirm the role of the gut microbiota in the actions of EMPA.ResultsEMPA reduced the elevation of blood glucose and UACR caused by HFD/STZ. It inhibited the thickening of the colonic crypt and restored goblet cells and the expressions of ZO-1 and Occludin. The 16S rRNA sequencing showed that the diversity of gut microbiota was reduced after HFD/STZ treatment, while it was restored after EMPA treatment. The LPS-producing bacteria, Oscillibacter, and the SCFA-producing bacteria, Bateroid and Odoribacter, were changed after EMPA administration. The therapeutic effects of EMPA on ABX-treated mice were reduced. Meanwhile, the level of fecal SCFAs was decreased, while the levels of fecal and serum LPS were elevated, in T2DM mice, and they were negated by the administration of EMPA.ConclusionEMPA ameliorates T2DM-related DN via altering the gut microbiota, especially reducing LPS-producing bacteria and increasing SCFA-producing bacteria.