TMEM2 is a bona fide hyaluronidase possessing intrinsic catalytic activity.

Transmembrane protein 2 (TMEM2) was originally identified as a membrane-anchored protein of unknown function. We previously demonstrated that TMEM2 can degrade hyaluronan (HA). Furthermore, we showed that induced global knockout of Tmem2 in adult mice results in rapid accumulation of incompletely degraded HA in bodily fluids and organs, supporting the identity of TMEM2 as a cell surface hyaluronidase. In spite of these advances, no direct evidence has been presented to demonstrate the intrinsic hyaluronidase activity of TMEM2. Here, we directly establish the catalytic activity of TMEM2. The ectodomain of TMEM2 (TMEM2ECD) was expressed as a His-tagged soluble protein and purified by affinity and size-exclusion chromatography. Both human and mouse TMEM2ECD robustly degrade fluorescein-labeled HA into 5 to 10 kDa fragments. TMEM2ECD exhibits this HA-degrading activity irrespective of the species of TMEM2 origin and the position of epitope tag insertion. The HA-degrading activity of TMEM2ECD is more potent than that of HYAL2, a hyaluronidase which, like TMEM2, has been implicated in cell surface HA degradation. Finally, we show that TMEM2ECD can degrade not only fluorescein-labeled HA but also native high-molecular weight HA. In addition to these core findings, our study reveals hitherto unrecognized confounding factors, such as the quality of reagents and the choice of assay systems, that could lead to erroneous conclusions regarding the catalytic activity of TMEM2. In conclusion, our results demonstrate that TMEM2 is a legitimate functional hyaluronidase. Our findings also raise cautions regarding the choice of reagents and methods for performing degradation assays for hyaluronidases.

Machine learning diagnosis by immunoglobulin N-glycan signatures for precision diagnosis of urological diseases.

Early diagnosis of urological diseases is often difficult due to the lack of specific biomarkers. More powerful and less invasive biomarkers that can be used simultaneously to identify urological diseases could improve patient outcomes. The aim of this study was to evaluate a urological disease-specific scoring system established with a machine learning (ML) approach using Ig N-glycan signatures. Immunoglobulin N-glycan signatures were analyzed by capillary electrophoresis from 1312 serum subjects with hormone-sensitive prostate cancer (n = 234), castration-resistant prostate cancer (n = 94), renal cell carcinoma (n = 100), upper urinary tract urothelial cancer (n = 105), bladder cancer (n = 176), germ cell tumors (n = 73), benign prostatic hyperplasia (n = 95), urosepsis (n = 145), and urinary tract infection (n = 21) as well as healthy volunteers (n = 269). Immunoglobulin N-glycan signature data were used in a supervised-ML model to establish a scoring system that gave the probability of the presence of a urological disease. Diagnostic performance was evaluated using the area under the receiver operating characteristic curve (AUC). The supervised-ML urologic disease-specific scores clearly discriminated the urological diseases (AUC 0.78-1.00) and found a distinct N-glycan pattern that contributed to detect each disease. Limitations included the retrospective and limited pathological information regarding urological diseases. The supervised-ML urological disease-specific scoring system based on Ig N-glycan signatures showed excellent diagnostic ability for nine urological diseases using a one-time serum collection and could be a promising approach for the diagnosis of urological diseases.

Management of bladder cancer in older patients.

Evidence has shown that patients with bladder cancer are diagnosed at a much older age compared with those with other cancers. Given that co-morbidities and frailty are prevalent in older patients with advanced bladder cancer, they are easily excluded from randomized controlled trials. As little evidence has been available regarding assessment tools for frailty, the management of those patients remains challenging. This weakness is strongly manifested in muscle-invasive bladder cancer. Despite radical cystectomy is the standard of care for bladder cancer, there is an extensive undertreatment of older adult patients with potentially curative muscle-invasive bladder cancer. However, it is also true that radical cystectomy is often unsuitable for vulnerable or frail patients. Bladder preservation using trimodality therapy has been utilized as an alternative option, but the appropriate selection criteria for trimodality therapy remain unclear. Cisplatin-based regimens have been the first choice for advanced disease among eligible patients. Moreover, immunotherapy appears to have similar benefits and tolerability in both older and younger patients. Furthermore, palliative or supportive interventions need to be initiated earlier in patients with metastatic disease. Accumulating evidence suggests that frailty may play a key role in the selection of treatment modalities. Older patients should be considered for standard treatment based on frailty and not chronological age. Moreover, older patients with bladder cancer need to undergo geriatric assessment for proper decision-making.

Single immediate instillation of chemotherapy is associated with decreased recurrence and progression in patients with high-risk non-muscle-invasive bladder cancer who receive adjuvant induction bacillus Calmette-Guérin therapy.

OBJECTIVES: To investigate whether a single intravesical instillation of chemotherapy is associated with improved oncological outcomes in patients with high-risk non-muscle-invasive bladder cancer who receive adjuvant induction bacillus Calmette-Guérin therapy. METHODS: This multi-institutional retrospective study included 205 patients with high-risk non-muscle-invasive bladder cancer who received adjuvant induction bacillus Calmette-Guérin therapy. Patients were divided into two groups: those who received the combined therapy of a single instillation of chemotherapy plus subsequent adjuvant induction bacillus Calmette-Guérin therapy (combined therapy group), and those who received adjuvant induction bacillus Calmette-Guérin therapy alone (bacillus Calmette-Guérin monotherapy group). Multivariable analyses using the inverse probability of treatment weighting method and Fine-Gray competing risk regression models were performed to evaluate the impact of a single instillation of chemotherapy on intravesical recurrence-free survival and muscle-invasive bladder cancer-free survival. RESULTS: Among the 205 patients, 130 (63%) and 75 (37%) were classified as the combined therapy and bacillus Calmette-Guérin monotherapy groups, respectively. Multivariable analyses using the inverse probability of treatment weighting method showed that a single instillation of chemotherapy was significantly associated with longer intravesical recurrence-free survival (hazard ratio 0.279; P < 0.001) and muscle-invasive bladder cancer-free survival (hazard ratio 0.078; P < 0.001). Fine-Gray competing risk regression model revealed that a single instillation of chemotherapy was associated with a significantly lower probability of intravesical recurrence and muscle-invasive bladder cancer progression, with an adjusted subdistribution hazard ratio of 0.477 (P = 0.008) and 0.261 (P = 0.043), respectively. CONCLUSION: A single intravesical instillation of chemotherapy may be a potential treatment option in patients with high-risk non-muscle-invasive bladder cancer who receive adjuvant induction bacillus Calmette-Guérin therapy.

Effect of active anticancer therapy on serologic response to SARS-CoV-2 BNT162b2 vaccine in patients with urothelial and renal cell carcinoma.

OBJECTIVES: To evaluate the serologic response to the BNT162b2 messenger ribonucleic acid vaccine in patients with urothelial carcinoma and renal cell carcinoma. METHODS: Between June 2021 and November 2021, we retrospectively evaluated blood samples from 60 healthy controls (control group), 57 patients with urothelial carcinoma, and 28 patients with renal cell carcinoma who had received two doses of the BNT162b2 vaccine at Hirosaki University Hospital. We determined the immunoglobulin G antibody titers against the severe acute respiratory syndrome coronavirus 2 spike receptor-binding domain. Seropositivity was defined as ≥15 U/mL. We investigate factors associated with antibody titers and seropositivity in the patients with urothelial carcinoma and renal cell carcinoma. RESULTS: Antibody titers in the control, urothelial carcinoma, and renal cell carcinoma groups were 813, 431, and 500 U/mL, respectively. Seropositivity was 100%, 90%, and 96% in the control, urothelial carcinoma, and renal cell carcinoma groups, respectively. Of the 85 patients, 37 of 57 (65%) and 21 of 28 (75%) were actively undergoing anticancer treatment for urothelial carcinoma and renal cell carcinoma, respectively. Anti-severe acute respiratory syndrome coronavirus 2 spike immunoglobulin G antibody titers and seropositivity was not significantly different between the patients with urothelial carcinoma and renal cell carcinoma. Anti-severe acute respiratory syndrome coronavirus 2 spike immunoglobulin G antibody titers were not significantly associated with active anticancer therapy or steroid treatment for immune-related adverse events. Univariable logistic regression analysis revealed that older age and metastatic disease were significantly and negatively associated with seropositivity. CONCLUSIONS: Patients with urothelial carcinoma or renal cell carcinoma exhibited an adequate antibody response to the BNT162b2 vaccine. Active anticancer therapy was not significantly associated with seropositivity following vaccination with severe acute respiratory syndrome coronavirus 2 BNT162b2 in patients with urothelial carcinoma and renal cell carcinoma.

Characteristics of α2,3-sialyl N-glycosylated PSA as a biomarker for clinically significant prostate cancer in men with elevated PSA level.

BACKGROUND: The presence of glycosylated isoforms of prostate-specific antigen (PSA) in prostate cancer (PC) cells is a potential marker of their aggressiveness. We characterized the origin of α2,3-sialylated prostate-specific antigen (S23PSA) by tissue-based sialylation-related gene expression and studied the performance of S23PSA density (S23PSAD) alone and in combination with multiparametric magnetic resonance imaging (MRI) for the detection of clinically significant prostate cancer in men with elevated PSA. METHODS: Tissue-based quantification of S23PSA and sialyltransferase and sialidase gene expression was evaluated in 71 radical prostatectomy specimens. The diagnostic performance of S23PSAD was studied in 1099 men retrospectively enrolled in a multicenter systematic biopsy (SBx) cohort. We correlated the S23PSAD with Prostate Imaging Reporting and Data System (PI-RADS) scores in 98 men prospectively enrolled in a single-center MRI-targeted biopsy (MRI-TBx) cohort. The primary outcome was the PC-diagnostic performance of the S23PSAD, the secondary outcome was the avoidable biopsy rate of S23PSAD combined with DRE and total PSA (tPSA), and with or without PI-RADS. RESULTS: S23PSA was significantly higher in Gleason pattern 4 and 5 compared with benign prostate tissue. In the retrospective cohort, the performance of S23PSAD for detecting PC was superior to tPSA or PSA density (PSAD) (AUC: 0.7758 vs. 0.6360 and 0.7509, respectively). In the prospective cohort, S23PSAD was superior to tPSA, PSAD, and PI-RADS (AUC: 0.7725 vs. 0.5901, 0.7439 and 0.7305, respectively), and S23PSAD + PI-RADS + DRE + tPSA was superior to DRE + tPSA+PI-RADS with avoidance rate of MRI-TBx (13% vs. 1%) at 30% risk threshold. CONCLUSIONS: The diagnostic performance of S23PSAD was superior to conventional strategies but comparable to mpMRI.

Association between the baseline frailty and quality of life in patients with prostate cancer (FRAQ-PC study).

BACKGROUND: The association between baseline frailty and health-related quality of life (HRQOL) in patients with prostate cancer (PC) remains unknown. METHODS: We retrospectively evaluated the association of pretreatment frailty with HRQOL in 409 patients with PC from February 2017 to April 2020. Frailty and HRQOL were evaluated using the geriatric 8 (G8) screening tool and QLQ-C30 questionnaire, respectively. The primary objective was comparison of G8 and QOL scores between the localized diseases (M0 group) and metastatic castration-sensitive PC (mCSPC group). Secondary objectives were to study the association of G8 and QOL scores in each group and effect of frailty (G8 ≤ 14) on worse QOL. RESULTS: The median age of patients was 70 years. There were 369 (surgery: 196, radiotherapy: 156, androgen deprivation therapy alone: 17) patients in the M0 and 40 patients in the mCSPC groups. There was a significant difference between the M0 and mCSPC groups in the G8 score (14.5 vs. 12.5), functioning QOL (94 vs. 87), global QOL (75 vs. 58), and 100-symptom QOL (94 vs. 85) scores. G8 scores were significantly associated with functioning, global, and 100-symptom QOL scores in both M0 and mCSPC groups. The multivariable logistic regression analyses showed that frailty (G8 ≤ 14) was significantly associated with worse global QOL, functioning QOL, and 100-symptom QOL scores. CONCLUSION: The baseline frailty and HRQOL were significantly different between the localized and metastatic disease. The baseline frailty was significantly associated with worse HRQOL in patients with PC.

A Longitudinal Study of Bidirectional Relationships between Sleep Disorder and Frequency of Nocturia: Results from the Iwaki Health Promotion Project.

INTRODUCTION: The causal relationship between sleep disorder and frequency of nocturia remains unclear. METHODS: We longitudinally evaluated sleep disorder and frequency of nocturia in 547 community-dwelling adults between baseline and 5-year follow-up. We included participants ≥50 years old who have no sleep disorder (the Pittsburgh Sleep Quality Index [PSQI] ≥ 5) nor nocturia (≥1). For 5 years, we evaluated the temporal changes in sleep disorder and nocturia and the bidirectional relationships between sleep disorder and nocturia. RESULTS: Of the 547 participants, we included 268 adults with a median age of 61 years in this study. Median PSQI and nocturia were significantly increased for 5 years from 2 to 3 and from 1 to 2, respectively. New onset of sleep disorder (PSQI > 5) and nocturia >1 was observed in 42 (16%) and 137 (51%) participants, respectively. The cross-lagged panel analysis showed that the path coefficient from PSQI to nocturia (ß = 0.22, p = 0.031) was significantly higher than that from nocturia to PSQI (ß = 0.02, p = 0.941). CONCLUSIONS: Our longitudinal study showed the effect of sleep disorder on nocturia was significant, although nocturia may not significantly worsen sleep disorder in community-dwelling adults.

Comparison of pembrolizumab with conventional chemotherapy after first-line platinum-based chemotherapy for advanced urothelial carcinoma in real-world practice: A multicenter retrospective study.

OBJECTIVES: To assess the clinical benefit of pembrolizumab as second-line therapy for advanced urothelial carcinoma. METHODS: We retrospectively compared the effects of pembrolizumab with those of conventional chemotherapy on the prognosis of patients with advanced urothelial carcinoma at six hospitals between January 2004 and August 2020. We compared the oncological outcomes between the patients treated with pembrolizumab and those treated with conventional chemotherapy using Kaplan-Meier curve analysis and multivariate Cox regression analysis with the inverse probability of treatment weighting method. RESULTS: The numbers of patients in the pembrolizumab and chemotherapy groups were 121 and 67, respectively. Patients in the pembrolizumab group were significantly older (median 72 vs 66 years, P = 0.001), and had poor Eastern Cooperative Oncology Group performance status (median 1 vs 0, P = 0.001). The unadjusted Kaplan-Meier curve analysis showed no significant differences in the median overall survival from the first-line chemotherapy (24.7 months vs 16.3 months, P = 0.159). Inverse probability of treatment weighting-adjusted multivariate Cox proportional hazards analyses showed a significant difference between the pembrolizumab and chemotherapy groups in overall survival (P = 0.003, hazard ratio 0.63). CONCLUSIONS: Despite the non-negligible age difference between the trial and our clinical practice, our study supports the benefit of second-line pembrolizumab over chemotherapy in real-world practice.

Inhibition of GIP signaling extends lifespan without caloric restriction.

AIMS/INTRODUCTION: Caloric restriction (CR) promotes longevity and exerts anti-aging effects by increasing Sirtuin production and activation. Gastric inhibitory polypeptide (GIP), a gastrointestinal peptide hormone, exerts various effects on pancreatic ß-cells and extra-pancreatic tissues. GIP promotes glucose-dependent augmentation of insulin secretion and uptake of nutrients into the adipose tissue. MATERIALS AND METHODS: Gipr-/- and Gipr+/+ mice were used for lifespan analysis, behavior experiments and gene expression of adipose tissue and muscles. 3T3-L1 differentiated adipocytes were used for Sirt1 and Nampt expression followed by treatment with GIP and α-lipoic acid. RESULTS: We observed that GIP receptor-knockout (Gipr-/-) mice fed normal diet showed an extended lifespan, increased exploratory and decreased anxiety-based behaviors, which are characteristic behavioral changes under CR. Moreover, Gipr-/- mice showed increased Sirt1 and Nampt expression in the adipose tissue. GIP suppressed α-lipoic acid-induced Sirt1 expression and activity in differentiated adipocytes. CONCLUSIONS: Although maintenance of CR is difficult, food intake and muscle endurance of Gipr-/- mice were similar to those of wild-type mice. Inhibition of GIP signaling may be a novel strategy to extend the lifespan of diabetic patients.

Presence of transient hydronephrosis immediately after surgery has a limited influence on renal function 1 year after ileal neobladder construction.

BACKGROUND: Urinary tract obstruction and postoperative hydronephrosis are risk factor for renal function deterioration after orthotopic ileal neobladder construction. However, reports of relationship between transient hydronephrosis and renal function are limited. We assess the influence of postoperative transient hydronephrosis on renal function in patients with orthotopic ileal neobladder construction. METHODS: Between January 2006 and June 2013, we performed radical cystectomy in 164 patients, and 101 received orthotopic ileal neobladder construction. This study included data available from 64 patients with 128 renal units who were enrolled retrospectively. The hydronephrosis grade of each renal unit scored 0-4. The patients were divided into 4 groups according to the grade of hydronephrosis: control, low, intermediate, and high. The grade of postoperative hydronephrosis was compared with renal function 1 month and 1 year after surgery. RESULTS: There were no significant differences in renal function before surgery between groups. One month after surgery, the presence of hydronephrosis was significantly associated with decreased renal function. However, 1 year after urinary diversion hydronephrosis grades were improved significantly, and renal function was comparable between groups. Postoperative hydronephrosis at 1 month had no significant influence on renal function 1 year after ileal neobladder construction. Limitations include retrospective design, short follow-up periods, and a sample composition. CONCLUSIONS: The presence of transient hydronephrosis immediately after surgery may have limited influence on renal function 1 year after ileal neobladder construction.

Clinical relevance of aortic calcification in urolithiasis patients.

BACKGROUND: The aim of the present study is to investigate the clinical relevance of aortic calcification in urolithiasis patients. METHODS: Between January 2010 and September 2014, 1221 patients with urolithiasis were treated in Oyokyo Kidney Research Institute and Hirosaki University Hospital. Among these, 287 patients (Stone group) on whom adequate data were available were included in this retrospective study. We also selected 148 subjects with early stage (pT1N0M0) renal cell carcinoma from 607 renal cell carcinoma patients who underwent radical nephrectomy at Hirosaki University Hospital (Non-stone group) as control subjects. Validity of the Non-stone group was evaluated by comparison with pair-matched 296 volunteers from 1166 subjects who participated in the Iwaki Health Promotion Project in 2014. Thereafter, age, body mass index, aortic calcification index (ACI), renal function, serum uric acid concentrations, and comorbidities (diabetes, hypertension, or cardiovascular disease) were compared between the Non-stone and Stone groups. Independent factors for higher ACI and impaired renal function were assessed using multivariate logistic regression analysis. RESULTS: We confirmed relevance of Non-stone group patients as a control subject by comparing the pair-matched community-dwelling volunteers. Backgrounds of patients between the Non-stone and Stone groups were not significantly different except for the presence of hypertension in the Stone group. ACI was not significantly high in the Stone group compared with the Non-stone group. However, age-adjusted ACI was greater in the Stone group than the Non-stone group. Among urolithiasis patients, ACI was significantly higher in uric acid containing stone patients. The number of patients with stage 3B chronic kidney disease (CKD) was significantly higher in the Stone group than in the Non-stone group (12% vs. 4%, P = 0.008). Multivariate logistic regression analysis showed higher aortic calcification index (>13%), and being a stone former were independent factors for stage 3B CKD at the time of diagnosis. CONCLUSION: Aortic calcification and being a stone former had harmful influence on renal function. This study was registered as a clinical trial: UMIN: UMIN000022962.

Aortic calcification burden predicts deterioration of renal function after radical nephrectomy.

BACKGROUND: Radical nephrectomy for renal cell carcinoma (RCC) is a risk factor for the development of chronic kidney disease (CKD), and the possibility of postoperative deterioration of renal function must be considered before surgery. We investigated the contribution of the aortic calcification index (ACI) to the prediction of deterioration of renal function in patients undergoing radical nephrectomy. METHODS: Between January 1995 and December 2012, we performed 511 consecutive radical nephrectomies for patients with RCC. We retrospectively studied data from 109 patients who had regular postoperative follow-up of renal function for at least five years. The patients were divided into non-CKD and pre-CKD based on a preoperative estimated glomerular filtration rate (eGFR) of ≥60 mL/min/1.73 m2 or <60 mL/min/1.73 m2, respectively. The ACI was quantitatively measured by abdominal computed tomography before surgery. The patients in each group were stratified between low and high ACIs. Variables such as age, sex, comorbidities, and pre- and postoperative renal function were compared between patients with a low or high ACI in each group. Renal function deterioration-free interval rates were evaluated by Kaplan-Meier analysis. Factors independently associated with deterioration of renal function were determined using multivariate analysis. RESULTS: The median age, preoperative eGFR, and ACI in this cohort were 65 years, 68 mL/min/1.73 m2, and 8.3%, respectively. Higher ACI (≥8.3%) was significantly associated with eGFR decline in both non-CKD and pre-CKD groups. Renal function deterioration-free interval rates were significantly lower in the ACI-high than ACI-low strata in both of the non-CKD and pre-CKD groups. Multivariate analysis showed that higher ACI was an independent risk factor for deterioration of renal function at 5 years after radical nephrectomy. CONCLUSIONS: Aortic calcification burden is a potential predictor of deterioration of renal function after radical nephrectomy. TRIAL REGISTRATION: This study was registered as a clinical trial: UMIN000023577.

Quality-of-life evaluation during platinum-based neoadjuvant chemotherapies for urothelial carcinoma.

BACKGROUND: Although quality of life (QOL) is one of the most important considerations in patients treated with anticancer therapies, desirable regimens for neoadjuvant chemotherapy including QOL in locally advanced urothelial carcinoma remain unclear. The present study evaluated the influence of neoadjuvant platinum-based chemotherapy on QOL in patients with locally advanced urothelial carcinoma. METHODS: Between June 2013 and March 2016, 83 urothelial carcinoma patients who received two courses of neoadjuvant chemotherapy were enrolled in this prospective observational study. Neoadjuvant regimens included gemcitabine + cisplatin (GCis) or gemcitabine + carboplatin (GCb) therapies. As a primary endpoint, we assessed QOL changes in each group before and after chemotherapy using the Quality of Life questionnaire on days 1, 3, and 15 of each cycle. Secondary endpoints included toxicity, safety, weight loss, renal function decline, and tumor responses. RESULTS: QOL analyses were performed in 39 patients receiving GCis and in 44 patients receiving GCb. Appetite loss, role functioning, nausea/vomiting, physical, and fatigue deteriorated >10% from baseline in the GCis group but not in the GCb group. Constipation worsened, whereas scores for pain and emotional items improved in both groups. Objective response rates were 38.5 and 43.2% in the GCis and GCb groups, respectively. CONCLUSIONS: Both GCis and GCb regimens were feasible in terms of QOL. The GCb regimen may be associated with a better QOL status especially in regard to gastrointestinal symptoms.

Difference in toxicity reporting between patients and clinicians during systemic chemotherapy in patients with urothelial carcinoma.

OBJECTIVES: To compare toxicity reporting between patients and clinicians in the case of systemic chemotherapy for urothelial carcinoma. METHODS: Between June 2013 and March 2016, 100 urothelial carcinoma patients received two courses of chemotherapy of gemcitabine plus cisplatin or gemcitabine plus carboplatin, and they were prospectively enrolled in the present study. During chemotherapy, patients answered European Organization for the Research and Treatment of Cancer Quality-of-Life Questionnaire C30 quality-of-life questionnaires, including four toxicity-related symptoms (appetite loss, nausea, constipation and diarrhea). Clinicians evaluated adverse events using the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. Differences of toxicity reporting were compared between patients and clinicians. Logistic regression analyses were carried out to investigate potential factors for underreporting by clinicians. RESULTS: Toxicity underreporting was most frequently for diarrhea (44%), followed by appetite loss (39%), constipation (33%) and nausea (22%). In total, toxicity underreporting was observed in 72% of patients. Background-adjusted logistic regression analyses showed pretreatment quality-of-life items of global, symptomatic scores to be predictors for toxicity underreporting by clinicians. The limitations of the present study included its retrospective nature and small sample size. CONCLUSIONS: Toxicity underreporting by clinicians is frequent in urothelial carcinoma patients receiving systemic chemotherapy. Pretreatment quality-of-life evaluation is essential not only for quality-of-life evaluation, but also to identify potential individuals at risk for toxicity underreporting.

Stromal cell-derived factor-1 is upregulated by dipeptidyl peptidase-4 inhibition and has protective roles in progressive diabetic nephropathy.

The role of stromal cell-derived factor-1 (SDF-1) in the pathogenesis of diabetic nephropathy and its modification by dipeptidyl peptidase-4 (DPP-4) inhibition are uncertain. Therefore, we studied this independent of glucagon-like peptide-1 receptor (GLP-1R) signaling using two Akita diabetic mouse models, the diabetic-resistant C57BL/6-Akita and diabetic-prone KK/Ta-Akita. Increased SDF-1 expression was found in glomerular podocytes and distal nephrons in the diabetic-prone mice, but not in kidneys from diabetic-resistant mice. The DPP-4 inhibitor linagliptin, but not the GLP-1R agonist liraglutide, further augmented renal SDF-1 expression in both Glp1r(+/+) and Glp1r(-/-) diabetic-prone mice. Along with upregulation of renal SDF-1 expression, the progression of albuminuria, glomerulosclerosis, periglomerular fibrosis, podocyte loss, and renal oxidative stress was suppressed in linagliptin-treated Glp1r(+/+) diabetic-prone mice. Linagliptin treatment increased urinary sodium excretion and attenuated the increase in glomerular filtration rate which reflects glomerular hypertension and hyperfiltration. In contrast, selective SDF-1 receptor blockade with AMD3100 reduced urinary sodium excretion and aggravated glomerular hypertension in the Glp1r(+/+) diabetic-prone mice. Thus, DPP-4 inhibition, independent of GLP-1R signaling, contributes to protection of the diabetic kidney through SDF-1-dependent antioxidative and antifibrotic effects and amelioration of adverse renal hemodynamics.

The protective roles of GLP-1R signaling in diabetic nephropathy: possible mechanism and therapeutic potential.

Glucagon-like peptide-1 (GLP-1) is a gut incretin hormone that has an antioxidative protective effect on various tissues. Here, we determined whether GLP-1 has a role in the pathogenesis of diabetic nephropathy using nephropathy-resistant C57BL/6-Akita and nephropathy-prone KK/Ta-Akita mice. By in situ hybridization, we found the GLP-1 receptor (GLP-1R) expressed in glomerular capillary and vascular walls, but not in tubuli, in the mouse kidney. Next, we generated C57BL/6-Akita Glp1r knockout mice. These mice exhibited higher urinary albumin levels and more advanced mesangial expansion than wild-type C57BL/6-Akita mice, despite comparable levels of hyperglycemia. Increased glomerular superoxide, upregulated renal NAD(P)H oxidase, and reduced renal cAMP and protein kinase A (PKA) activity were noted in the Glp1r knockout C57BL/6-Akita mice. Treatment with the GLP-1R agonist liraglutide suppressed the progression of nephropathy in KK/Ta-Akita mice, as demonstrated by reduced albuminuria and mesangial expansion, decreased levels of glomerular superoxide and renal NAD(P)H oxidase, and elevated renal cAMP and PKA activity. These effects were abolished by an adenylate cyclase inhibitor SQ22536 and a selective PKA inhibitor H-89. Thus, GLP-1 has a crucial role in protection against increased renal oxidative stress under chronic hyperglycemia, by inhibition of NAD(P)H oxidase, a major source of superoxide, and by cAMP-PKA pathway activation.

DPP-4 inhibition with alogliptin on top of angiotensin II type 1 receptor blockade ameliorates albuminuria via up-regulation of SDF-1α in type 2 diabetic patients with incipient nephropathy.

Dipeptidyl peptidase-4 (DPP-4) inhibitor is a new class of anti-diabetic drug which exerts its glucose-lowering action by suppressing the degradation of a gut incretin hormone glucagon-like peptide-1 (GLP-1). To elucidate whether treatment with stronger DPP-4 inhibitor on top of angiotensin II type 1 receptor blocker (ARB) provides greater renal protective effects, we performed a crossover study with two DPP-4 inhibitors, sitagliptin and alogliptin, in twelve type 2 diabetic patients with incipient nephropathy taking ARBs. This study consisted of three treatment periods: sitagliptin 50 mg/day for 4 weeks (first period), alogliptin 25 mg/day for 4 weeks (second period), and sitagliptin 50 mg/day for 4 weeks (third period). Significant changes in body mass index, blood pressure, serum lipids, serum creatinine, estimated glomerular filtration rate, and HbA1c were not observed among the three treatment periods. Reduced urinary levels of albumin and an oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG), increased urinary cAMP levels, and elevated plasma levels of stromal cell-derived factor-1α (SDF-1α) which is a physiological substrate of DPP-4 were observed after the switch from sitagliptin to a stronger DPP-4 inhibitor alogliptin. Given a large body of evidence indicating anti-oxidative action of cAMP and up-regulation of cellular cAMP production by SDF-1α, the present results suggest that more powerful DPP-4 inhibition on top of angiotensin II type 1 receptor blockade would offer additional protection against early-stage diabetic nephropathy beyond that attributed to glycemic control, via reduction of renal oxidative stress by SDF-1α-cAMP pathway activation.