The Role of the Gut Microbiome in Diabetes and Obesity-Related Kidney Disease.

Diabetic kidney disease (DKD) is a progressive disorder, which is increasing globally in prevalence due to the increased incidence of obesity and diabetes mellitus. Despite optimal clinical management, a significant number of patients with diabetes develop DKD. Hence, hitherto unrecognized factors are likely to be involved in the initiation and progression of DKD. An extensive number of studies have demonstrated the role of microbiota in health and disease. Dysregulation in the microbiota resulting in a deficiency of short chain fatty acids (SCFAs) such as propionate, acetate, and butyrate, by-products of healthy gut microbiota metabolism, have been demonstrated in obesity, type 1 and type 2 diabetes. However, it is not clear to date whether such changes in the microbiota are causative or merely associated with the diseases. It is also not clear which microbiota have protective effects on humans. Few studies have investigated the centrality of reduced SCFA in DKD development and progression or the potential therapeutic effects of supplemental SCFAs on insulin resistance, inflammation, and metabolic changes. SCFA receptors are expressed in the kidneys, and emerging data have demonstrated that intestinal dysbiosis activates the renal renin-angiotensin system, which contributes to the development of DKD. In this review, we will summarize the complex relationship between the gut microbiota and the kidney, examine the evidence for the role of gut dysbiosis in diabetes and obesity-related kidney disease, and explore the mechanisms involved. In addition, we will describe the role of potential therapies that modulate the gut microbiota to prevent or reduce kidney disease progression.

Semicarbazide-sensitive amine oxidase inhibition ameliorates albuminuria and glomerulosclerosis but does not improve tubulointerstitial fibrosis in diabetic nephropathy.

Semicarbazide-sensitive amine oxidase (SSAO) is an enzyme with a unique dual function in controlling inflammation as well as reactive oxygen species (ROS) generation. We have demonstrated benefit of SSAO inhibition in acute kidney fibrosis. However the function of SSAO in chronic kidney disease (CKD) and diabetic kidney disease (DKD) is yet to be determined. We aimed to assess the effectiveness of a SSAO inhibitor (SSAOi; PXS-4728A) as an antifibrotic agent using a diabetic model of CKD. Diabetic mice were treated with SSAOi for 24 weeks and outcomes compared with untreated diabetic mice and telmisartan treated animals as a standard of care comparator. Extracellular matrix markers, fibronectin and oxidative stress, were downregulated in diabetic mice treated with SSAOi compared with untreated diabetic mice. Expression of the pan-leukocyte marker CD45 was also supressed by SSAOi. SSAO inhibition in diabetic mice resulted in a significant reduction in glomerulosclerosis and associated albuminuria compared to untreated diabetic mice. However, the effect of SSAO inhibition was less obvious in the tubulointerstitial compartment than in the glomeruli. Therefore, SSAO may be a potential target for diabetic glomerulosclerosis.

Impact of maternal e-cigarette vapor exposure on renal health in the offspring.

Maternal smoking during pregnancy is a significant risk factor of renal pathology in the offspring. E-cigarettes are perceived to be a safe option and are increasingly used by pregnant women either continuously during pregnancy or as a replacement for tobacco cigarettes. This study aimed to determine the effects of replacing tobacco cigarettes with e-cigarettes during pregnancy, and continuous e-cigarette use during pregnancy on the offspring's kidneys. Female Balb/c mice were exposed to either air (sham) or tobacco cigarette smoke (SE) for 6 weeks prior to mating, during gestation and lactation. A subset of the "SE group" received e-cigarette vapor (containing nicotine) after mating until pups weaned. Additional female mice were continuously exposed to e-vapor (either with or without nicotine) for 6 weeks prior to mating until pups weaned. Kidneys and urine from the male offspring were assessed at postnatal day 1, day 20 (weaning), and 13 weeks of age (adulthood). E-cigarette replacement was less detrimental to renal development and albuminuria than continuous SE during pregnancy. However, continuous e-vapor exposure during pregnancy increased markers of oxidative stress, inflammation, and fibrosis in the adult offspring, independent of nicotine. E-cigarette use during pregnancy confers future risk to the offspring's kidneys.

SIRT1 Attenuates Kidney Disorders in Male Offspring Due to Maternal High-Fat Diet.

Maternal obesity has been associated with kidney disorders in male offspring. Our previous studies have demonstrated that Sirtuin (SIRT)1, an essential regulator of metabolic stress responses, is suppressed in the offspring as the result of maternal high-fat diet (HFD) consumption, which is likely to underpin the adverse metabolic and renal outcomes. To examine if SIRT1 overexpression or activation early in life can protect the offspring kidney, wild-type (WT) and transgenic (Tg) offspring were born to the same diet-induced obese female C57BL/6 mice through breeding with hemizygous SIRT1-transgenic (Tg) male mice and examined for renal pathological changes. In separate experiments, SIRT1 activator SRT1720 (25 mg/kg/2 days i.p) was administrated in WT offspring over 6 weeks of postnatal high-fat diet exposure. The results show that offspring born to obese dams have increased kidney weight, higher levels of renal triglycerides, and increased expression of oxidative stress, inflammatory, and fibrotic markers, as well as increased albuminuria compared to offspring of control dams. Both SIRT1 overexpression and SRT1720 treatment attenuated renal lipid contents and expression of lipogenesis, oxidative stress, and inflammatory markers; however, fibrosis was modestly reduced and albuminuria was not affected. The findings suggest that SIRT1 therapy can ameliorate some pathological mechanisms of kidney programming due to maternal obesity but may not be sufficient to prevent the resulting chronic kidney injury.

SIRT1 overexpression attenuates offspring metabolic and liver disorders as a result of maternal high-fat feeding.

KEY POINTS: Maternal high-fat diet (MHF) consumption led to metabolic and liver disorders in male offspring, which are associated with reduced sirtuin (SIRT)1 expression and activity in the offspring liver SIRT1 overexpression in MHF offspring reduced their body weight and adiposity and normalized lipid metabolic markers in epididymal and retroperitoneal adipose tissues SIRT1 overexpression in MHF offspring improved glucose tolerance, as well as systemic and hepatic insulin sensitivity SIRT1 overexpression ameliorated MHF-induced lipogenesis, oxidative stress and fibrogenesis in the liver of offspring. ABSTRACT: Maternal obesity can increase the risk of metabolic disorders in the offspring. However, the underlying mechanism responsible for this is not clearly understood. Previous evidence implied that sirtuin (SIRT)1, a potent regulator of energy metabolism and stress responses, may play an important role. In the present study, we have shown, in C57BL/6 mice, that maternal high-fat diet (HFD) consumption can induce a pre-diabetic and non-alcoholic fatty liver disease phenotype in the offspring, associated with reduced SIRT1 expression in the hypothalamus, white adipose tissues (WAT) and liver. Importantly, the overexpression of SIRT1 in these offspring significantly attenuated the excessive accumulation of epididymal (Epi) white adipose tissue (WAT) and retroperitoneal (Rp)WAT (P < 0.001), glucose intolerance and insulin resistance (both P < 0.05) at weaning age. These changes were associated with the suppression of peroxisome proliferator-activated receptor gamma (PPAR)γ (P < 0.01), PPARγ-coactivator 1-alpha (P < 0.05) and sterol regulatory element-binding protein-1c in EpiWAT (P < 0.01), whereas there was increased expression of PPARγ in RpWAT (P < 0.05). In the liver, PPARγ mRNA expression, as well as Akt protein expression and activity, were increased (P < 0.05), whereas fatty acid synthase and carbohydrate response element binding protein were downregulated (P < 0.05), supporting increased insulin sensitivity and reduced lipogenesis in the liver. In addition, hepatic expression of endogenous anti-oxidants, including glutathione peroxidase 1 and catalase, was increased (P < 0.01 and P < 0.05 respectively), whereas collagen and fibronectin deposition was suppressed (P < 0.01). Collectively, the present study provides direct evidence of the mechanistic significance of SIRT1 in maternal HFD-induced metabolic dysfunction in offspring and suggests that SIRT1 is a promising target for fetal reprogramming.

Maternal L-carnitine supplementation ameliorates renal underdevelopment and epigenetic changes in male mice offspring due to maternal smoking.

OBJECTIVES: Epidemiological and animal studies showed that L-carnitine (LC) supplementation can ameliorate oxidative stress-induced tissues damage. We have previously shown that maternal cigarette smoke exposure (SE) can increase renal oxidative stress in newborn offspring with postnatal kidney underdevelopment and renal dysfunction in adulthood, which were normalised by LC administration in the SE dams during pregnancy. Exposure to an adverse intrauterine environment may lead to alteration in the epigenome, a mechanism by which adverse prenatal conditions increase the susceptibility to chronic disease later in life. The current study aimed to determine whether maternal SE induces epigenetic changes in the offspring's kidney are associated with renal underdevelopment, and the protective effect of maternal LC supplementation. METHOD: Female Balb/c mice (7 weeks) were exposed to cigarette smoke (SE) or air (Sham) for 6 weeks prior to mating, during gestation and lactation. A subgroup of the SE dams received LC via drinking water (SE + LC, 1.5 mmol/L) throughout gestation and lactation. Male offspring were studied at postnatal day (P)1, P20, and 13 weeks. RESULTS: Maternal SE altered the expression of renal development markers glial cell line-derived neurotrophic factor and fibroblast growth factor 2, which were associated with increased renal global DNA methylation and DNA methyltransferase 1 mRNA expression at birth. These disorders were reversed by maternal LC administration. CONCLUSION: The effect of maternal SE on renal underdevelopment involves global epigenetic alterations from birth, which can be prevented by maternal LC supplementation.

Lysyl oxidase-like 2 inhibition ameliorates glomerulosclerosis and albuminuria in diabetic nephropathy.

Diabetic nephropathy is characterised by the excessive amount of extracellular matrix in glomeruli and tubulointerstitial space. Lysyl oxidase-like 2 (LOXL2) is elevated in renal fibrosis and known to play key roles in ECM stabilisation by facilitating collagen cross-links, epithelial to mesenchymal transition and myofibroblast activation. Thus, targeting LOXL2 may prove to be a useful strategy to prevent diabetic nephropathy. We explored the renoprotective effect of a selective small molecule LOXL2 inhibitor (PXS-S2B) in a streptozotocin-induced diabetes model. Diabetic mice were treated with PXS-S2B for 24 weeks and outcomes compared with untreated diabetic mice and with telmisartan treated animals as comparator of current standard of care. Diabetic mice had albuminuria, higher glomerulosclerosis scores, upregulation of fibrosis markers and increased renal cortical LOXL2 expression. Treatment with PXS-S2B reduced albuminuria and ameliorated glomerulosclerosis. This was associated with reduced expression of glomerular fibronectin and tubulointerstitial collagen I. The renoprotective effects of both PXS-S2B and telmisartan were more marked in the glomerular compartment than in the tubulointerstitial space. The study reveals that LOXL2 inhibition was beneficial in preserving glomerular structure and function. Thus, LOXL2 may be a potential therapeutic target in diabetic nephropathy.

MitoQ supplementation prevent long-term impact of maternal smoking on renal development, oxidative stress and mitochondrial density in male mice offspring.

To investigate the effect of maternal MitoQ treatment on renal disorders caused by maternal cigarette smoke exposure (SE). We have demonstrated that maternal SE during pregnancy increases the risk of developing chronic kidney disease (CKD) in adult offspring. Mitochondrial oxidative damage contributes to the adverse effects of maternal smoking on renal disorders. MitoQ is a mitochondria-targeted antioxidant that has been shown to protect against oxidative damage-related pathologies in many diseases. Female Balb/c mice (8 weeks) were divided into Sham (exposed to air), SE (exposed to cigarette smoke) and SEMQ (exposed to cigarette smoke with MitoQ supplemented from mating) groups. Kidneys from the mothers were collected when the pups weaned and those from the offspring were collected at 13 weeks. Maternal MitoQ supplementation during gestation and lactation significantly reversed the adverse impact of maternal SE on offspring's body weight, kidney mass and renal pathology. MitoQ administration also significantly reversed the impact of SE on the renal cellular mitochondrial density and renal total reactive oxygen species in both the mothers and their offspring in adulthood. Our results suggested that MitoQ supplementation can mitigate the adverse impact of maternal SE on offspring's renal pathology, renal oxidative stress and mitochondrial density in mice offspring.

SRT1720 attenuates obesity and insulin resistance but not liver damage in the offspring due to maternal and postnatal high-fat diet consumption.

Recent studies indicate that sirtuin-1 (SIRT1), an important metabolic sensor and regulator of life span, plays a mechanistic role in maternal obesity-induced programming of metabolic disorders in the offspring. In this study we investigate whether SIRT1 activation in early childhood can mitigate metabolic disorders due to maternal and postnatal high-fat feeding in mice. Male offspring born to chow-fed (MC) or high fat diet-fed dams (MHF) were weaned onto postnatal chow or high-fat diet and treated with SRT1720 (25 mg/kg ip every 2 days) or vehicle control for 6 wk and examined for metabolic disorders. MHF exacerbated offspring body weight and insulin resistance in the offspring exposed to postnatal HFD (OHF). These metabolic changes were associated with reduced hepatic lipid droplet accumulation but increased plasma levels of alanine aminotransferase (ALT), a marker of liver damage. SRT1720 significantly decreased offspring body weight, adiposity, glucose intolerance, and hyperleptinemia due to OHF and reversed hyperinsulinemia and adipocyte hypertrophy due to the additive effects of MHF. Although SRT1720 suppresses liver lipogenesis, inflammation, and oxidative stress markers, it also reduces antioxidants and increased liver collagen deposition in OHF offspring independent of MHF. Hepatic steatosis was attenuated only in MC/OHF offspring in association with elevated plasma ALT levels. The study suggests that postnatal SRT1720 administration can mitigate obesity and insulin resistance in the offspring due to maternal and postnatal HFD exposure. However, the possibility of liver toxicity needs to be further examined.

The renal consequences of maternal obesity in offspring are overwhelmed by postnatal high fat diet.

AIMS/HYPOTHESIS: Developmental programming induced by maternal obesity influences the development of chronic disease in offspring. In the present study, we aimed to determine whether maternal obesity exaggerates obesity-related kidney disease. METHODS: Female C57BL/6 mice were fed high-fat diet (HFD) for six weeks prior to mating, during gestation and lactation. Male offspring were weaned to normal chow or HFD. At postnatal Week 8, HFD-fed offspring were administered one dose streptozotocin (STZ, 100 mg/kg i.p.) or vehicle control. Metabolic parameters and renal functional and structural changes were observed at postnatal Week 32. RESULTS: HFD-fed offspring had increased adiposity, glucose intolerance and hyperlipidaemia, associated with increased albuminuria and serum creatinine levels. Their kidneys displayed structural changes with increased levels of fibrotic, inflammatory and oxidative stress markers. STZ administration did not potentiate the renal effects of HFD. Though maternal obesity had a sustained effect on serum creatinine and oxidative stress markers in lean offspring, the renal consequences of maternal obesity were overwhelmed by the powerful effect of diet-induced obesity. CONCLUSION: Maternal obesity portends significant risks for metabolic and renal health in adult offspring. However, diet-induced obesity is an overwhelming and potent stimulus for the development of CKD that is not potentiated by maternal obesity.

Impact of maternal cigarette smoke exposure on brain and kidney health outcomes in female offspring.

Increased oxidative stress in the brain can lead to increased sympathetic tone that may further induce kidney dysfunction. Previously we have shown that maternal cigarette smoke exposure (SE) leads to significantly increased oxidative stress and inflammation in both brain and kidney, as well as reduced brain and kidney mitochondrial activity. This is closely associated with significant kidney underdevelopment and abnormal function in adulthood in the male offspring. This study aimed to investigate the impact of maternal SE on brain and kidney health in the female offspring. In this study, the mouse dams were exposed to two cigarettes, twice daily for 6 weeks prior to gestation, during pregnancy and lactation. Brains and kidneys from the female offspring were collected at 20 days (P20) and 13 weeks (W13) and were subject to further analysis. We found that mRNA expression of brain inflammatory markers interleukin-1 receptor and Toll-like receptor 4 were significantly increased in the SE offspring at both P20 and W13. Their brain mitochondrial activity markers were however increased at W13 with increased antioxidant activity. Kidney development and function in the female SE offspring were not different from the control offspring. We concluded that although brain inflammatory markers were upregulated in the SE female offspring, they were protected from some of the indicators of brain oxidative stress, such as endogenous antioxidant and mitochondrial dysfunction, as well as abnormal kidney development and function in adulthood.

Maternal Obesity Promotes Diabetic Nephropathy in Rodent Offspring.

Maternal obesity is known to increase the risk of obesity and diabetes in offspring. Though diabetes is a key risk factor for the development of chronic kidney disease (CKD), the relationship between maternal obesity and CKD has not been clearly defined. In this study, a mouse model of maternal obesity was employed to determine the impact of maternal obesity on development of diabetic nephropathy in offspring. Female C57BL/6 mice were fed high-fat diet (HFD) for six weeks prior to mating, during gestation and lactation. Male offspring were weaned to normal chow diet. At postnatal Week 8, offspring were randomly administered low dose streptozotocin (STZ, 55 mg/kg/day for five days) to induce diabetes. Assessment of renal damage took place at postnatal Week 32. We found that offspring of obese mothers had increased renal fibrosis, inflammation and oxidative stress. Importantly, offspring exposed to maternal obesity had increased susceptibility to renal damage when an additional insult, such as STZ-induced diabetes, was imposed. Specifically, renal inflammation and oxidative stress induced by diabetes was augmented by maternal obesity. Our findings suggest that developmental programming induced by maternal obesity has implications for renal health in offspring. Maternal obesity should be considered a risk factor for CKD.

Impact of maternal cigarette smoke exposure on brain inflammation and oxidative stress in male mice offspring.

Maternal cigarette smoke exposure (SE) during gestation can cause lifelong adverse effects in the offspring's brain. Several factors may contribute including inflammation, oxidative stress and hypoxia, whose changes in the developing brain are unknown. Female Balb/c mice were exposed to cigarette smoke prior to mating, during gestation and lactation. Male offspring were studied at postnatal day (P) 1, P20 and 13 weeks (W13). SE dams had reduced inflammatory mediators (IL-1ß, IL-6 and toll like receptor (TLR)4 mRNA), antioxidant (manganese superoxide dismutase (MnSOD)), and increased mitochondrial activities (OXPHOS-I, III and V) and protein damage marker nitrotyrosine. Brain hypoxia-inducible factor (HIF)1α and its upstream signalling molecule early growth response factor (EGR)1 were not changed in the SE dams. In the SE offspring, brain IL-1R, IL-6 and TLR4 mRNA were increased at W13. The translocase of outer mitochondrial membrane, and MnSOD were reduced at W13 with higher nitrotyrosine staining. HIF-1α was also increased at W13, although EGR1 was only reduced at P1. In conclusion, maternal SE increased markers of hypoxia and oxidative stress with mitochondrial dysfunction and cell damage in both dams and offspring, and upregulated inflammatory markers in offspring, which may render SE dams and their offspring vulnerable to additional brain insults.

Effect of GLP-1 Receptor Activation on Offspring Kidney Health in a Rat Model of Maternal Obesity.

Maternal obesity is associated with an increased risk of chronic disease in offspring, including type 2 diabetes (T2D). Exendin-4 (Exd-4) activates the glucagon like peptide-1 (GLP-1) receptor thereby decreasing serum glucose levels and body weight. In addition, Exd-4 has been shown to reduce renal and cardiac complications in experimental models of T2D. We hypothesized that treatment with Exd-4 would ameliorate the detrimental effects of maternal and diet-induced obesity on renal characteristics in offspring. Female Sprague-Dawley rats were fed either normal or high-fat diet (HFD) for 6 weeks prior to pregnancy, during pregnancy and lactation, and their offspring were weaned to normal or HFD. The offspring were randomized to Exd-4 or placebo from weaning and their kidneys harvested at Week 9. We found that the kidneys of offspring from obese mothers, regardless of postnatal diet, had significantly increased markers of inflammation, oxidative stress and fibrosis. Exd-4 ameliorated the negative renal effects of maternal obesity and in particular, reduced renal inflammation, oxidative stress and fibrosis. In conclusion, maternal obesity has persisting effects on renal structure in the offspring. GLP-1 analogues are potentially useful for protecting against the deleterious effects of maternal obesity on renal physiology in offspring.

Saxagliptin reduces renal tubulointerstitial inflammation, hypertrophy and fibrosis in diabetes.

AIM: In addition to lowering blood glucose in patients with type 2 diabetes mellitus, dipeptidyl peptidase 4 (DPP4) inhibitors have been shown to be antifibrotic and anti-inflammatory. We have previously shown that DPP4 inhibition in human kidney proximal tubular cells exposed to high glucose reduced fibrotic and inflammatory markers. Hence, we wanted to demonstrate renoprotection in an in vivo model. METHODS: We used a type 1 diabetic animal model to explore the renoprotective potential of saxagliptin independent of glucose lowering. We induced diabetes in enos -/- mice using streptozotocin and matched glucose levels using insulin. Diabetic mice were treated with saxagliptin and outcomes compared with untreated diabetic mice. RESULTS: We provide novel data that saxagliptin limits renal hypertrophy, transforming growth factor beta-related fibrosis and NF-κBp65-mediated macrophage infiltration. Overall, there was a reduction in histological markers of tubulointerstitial fibrosis. There was no reduction in albuminuria or glomerulosclerosis. CONCLUSION: Our findings highlight the potential of DPP4 inhibition as additional therapy in addressing the multiple pathways to achieve renoprotection in diabetic nephropathy.

FXR expression is associated with dysregulated glucose and lipid levels in the offspring kidney induced by maternal obesity.

BACKGROUND: Maternal obesity is associated with dysregulation of glucose and lipid metabolism with consequent exposure of the fetus to an abnormal metabolic milieu. It is recognized that maternal obesity predisposes offspring to chronic kidney disease (CKD). We aimed to determine whether the nuclear Farnesoid X receptor (FXR), known to play a role in maintaining homeostasis of glucose and lipid metabolism, is involved in renal injury in offspring of obese mothers. METHODS: Maternal obesity was established in a rat model by feeding dams with high-fat diet prior to and during pregnancy and lactation. The offspring's kidneys were examined at postnatal Day 1and Day 20. Human kidney 2 (HK2) cells were exposed to high glucose with or without the FXR agonist GW4064 or when FXR mRNA was silenced. RESULTS: Glucose intolerance in the offspring of obese mothers was evident at weaning, with associated downregulation of renal FXR expression and upregulation of monocyte chemoattractant protein-1 (MCP-1) and transforming growth factor-ß1 (TGF-ß1). HK2 cells exposed to high glucose had reduced FXR expression and increased MCP-1, TGF-ß1, fibronectin and collagen IV expression, which was reversed in the presence of GW4064. FXR-silenced HK2 cells had amplified pro-inflammatory and pro-fibrotic markers under high glucose conditions. CONCLUSIONS: Maternal obesity influences renal expression of pro-inflammatory and fibrotic factors that predispose the offspring to CKD. This was associated with the downregulation of the renal FXR expression suggesting a potential protective role for FXR.

Linagliptin Limits High Glucose Induced Conversion of Latent to Active TGFß through Interaction with CIM6PR and Limits Renal Tubulointerstitial Fibronectin.

BACKGROUND: In addition to lowering blood glucose in patients with type 2 diabetes mellitus, dipeptidyl peptidase 4 (DPP4) inhibitors have been shown to be antifibrotic. We have previously shown that cation independent mannose-6-phosphate receptor (CIM6PR) facilitates the conversion of latent to active transforming growth factor ß1 (GFß1) in renal proximal tubular cells (PTCs) and linagliptin (a DPP4 inhibitor) reduced this conversion with downstream reduction in fibronectin transcription. OBJECTIVE: We wanted to demonstrate that linagliptin reduces high glucose induced interaction between membrane bound DPP4 and CIM6PR in vitro and demonstrate reduction in active TGFß mediated downstream effects in a rodent model of type 1 diabetic nephropathy independent of high glycaemic levels. MATERIALS AND METHODS: We used human kidney 2 (HK2) cells and endothelial nitric oxide synthase knock out mice to explore the mechanism and antifibrotic potential of linagliptin independent of glucose lowering. Using a proximity ligation assay, we show that CIM6PR and DPP4 interaction was increased by high glucose and reduced by linagliptin and excess mannose-6-phosphate (M6P) confirming that linagliptin is operating through an M6P-dependent mechanism. In vivo studies confirmed these TGFß1 pathway related changes and showed reduced fibronectin, phosphorylated smad2 and phosphorylated smad2/3 (pSmad2/3) with an associated trend towards reduction in tubular atrophy, which was independent of glucose lowering. No reduction in albuminuria, glomerulosclerotic index or cortical collagen deposition was observed. CONCLUSION: Linagliptin inhibits activation of TGFß1 through a M6P dependent mechanism. However this in isolation is not sufficient to reverse the multifactorial nature of diabetic nephropathy.

The role of Krüppel-like factor 4 in transforming growth factor-ß-induced inflammatory and fibrotic responses in human proximal tubule cells.

Krüppel-like factor 4 (KLF4) is known to mitigate inflammation in several cell types. Using human proximal tubule cells, the present study aimed to investigate the role of KLF4 in regulating transforming growth factor (TGF)-ß1 induced inflammatory and fibrotic responses. Human kidney proximal tubular cells were exposed to high glucose, or TGF-ß1 and KLF4 expressions were determined. Cells were then transfected with empty vector or KLF4 and exposed to 2-ng/mL TGF-ß1 for up to 72 h. Inflammatory proteins (macrophage migration inhibitory factor and monocyte chemoattractant protein-1) and pro-fibrotic proteins (fibronectin and collagen IV) were measured after 72 h by enzyme-linked immunosorbent assay and western blot, respectively. To determine the relevance to in vivo models of chronic kidney disease, KLF4 protein expression in streptozotocin-induced diabetic mice was determined. Krüppel-like factor 4 messenger RNA (mRNA) levels were significantly reduced in high glucose-treated human kidney proximal tubular cells. High glucose increased TGF-ß1 mRNA expression, which significantly increased migration inhibitory factor and monocyte chemoattractant protein-1 protein secretion. Transforming growth factor-ß1 significantly increased fibronectin and collagen IV protein expression. The overexpression of KLF4 significantly reduced TGF-ß-mediated increases in migration inhibitory factor and monocyte chemoattractant protein-1 but had no effect on TGF-ß-mediated fibronectin and collagen IV mRNA and protein expression. The levels of KLF4 mRNA were significantly reduced in the diabetic kidney, and diabetic animals had a significant reduction in renal tubular expression of KLF4 proteins. This data suggest that KLF4 reduces inflammation induced by TGF-ß1, suggesting a therapeutic role for KLF4 in diabetic nephropathy.