In vivo Polycystin-1 interactome using a novel Pkd1 knock-in mouse model.

PKD1 is the most commonly mutated gene causing autosomal dominant polycystic kidney disease (ADPKD). It encodes Polycystin-1 (PC1), a putative membrane protein that undergoes a set of incompletely characterized post-transcriptional cleavage steps and has been reported to localize in multiple subcellular locations, including the primary cilium and mitochondria. However, direct visualization of PC1 and detailed characterization of its binding partners remain challenging. We now report a new mouse model with HA epitopes and eGFP knocked-in frame into the endogenous mouse Pkd1 gene by CRISPR/Cas9. Using this model, we sought to visualize endogenous PC1-eGFP and performed affinity-purification mass spectrometry (AP-MS) and network analyses. We show that the modified Pkd1 allele is fully functional but the eGFP-tagged protein cannot be detected without signal amplification by secondary antibodies. Using nanobody-coupled beads and large quantities of tissue, AP-MS identified an in vivo PC1 interactome, which is enriched for mitochondrial proteins and components of metabolic pathways. These studies suggest this mouse model and interactome data will be useful to understand PC1 function, but that new methods and brighter tags will be required to track endogenous PC1.

Mechanisms of Cyst Development in Polycystic Kidney Disease.

Autosomal dominant polycystic kidney disease is the most common inherited cause of end-stage kidney disease worldwide. Most cases result from mutation of either of 2 genes, PKD1 and PKD2, which encode proteins that form a probable receptor/channel complex. Studies suggest that a loss of function of the complex below an indeterminate threshold triggers cyst initiation, which ultimately results in dysregulation of multiple metabolic processes and downstream pathways and subsequent cyst growth. Noncell autonomous factors may also promote cyst growth. In this report, we focus primarily on the process of early cyst formation and factors that contribute to its variability with brief consideration of how new studies suggest this process may be reversible.

Exercise Training Prevents High Fructose-Induced Hypertension and Renal Damages in Male Dahl Salt-Sensitive Rats.

INTRODUCTION: High-fructose diet (HFr) causes metabolic syndrome, and HFr-induced hypertension and renal damage are exaggerated in Dahl salt-sensitive (DS) rats. Exercise training (Ex) has antihypertensive and renal protective effects in rats fed HFr; however, there has been little discussion about the DS rats, which exhibit metabolic disturbances. This study thus examined the effects of Ex on DS rats fed HFr. METHODS: Male DS rats were divided into three groups. The control group was fed a control diet, and both the HFr group and the HFr-Ex group were fed an HFr (60% fructose). The HFr-Ex group also underwent treadmill running (20 m·min -1 , 60 min·d -1 , 5 d·wk -1 ). After 12 wk, renal function, histology, and renin-angiotensin system were examined. RESULTS: HFr increased blood pressure, urinary albumin, and creatinine clearance, and Ex inhibited these increases. HFr induced glomerular sclerosis, podocyte injury, afferent arteriole thickening, and renal interstitial fibrosis, and Ex ameliorated them. HFr reduced plasma renin activity, and Ex further reduced the activity. HFr also increased the expression of angiotensinogen, renin, angiotensin-converting enzyme (ACE), and angiotensin II type 1 receptor, and Ex restored the ACE expression to the control levels. HFr decreased the expression of ACE2, angiotensin II type 2 receptor, and Mas receptor, and Ex restored the ACE2 and Mas receptor expressions to the control levels and further decreased the angiotensin II type 2 receptor expression. HFr increased the ACE activity and decreased the ACE2 activity, and Ex restored these activities to the control levels. CONCLUSIONS: Ex prevents HFr-induced hypertension and renal damages in DS rats. The changes in renal renin-angiotensin system may be involved in the mechanism of the antihypertensive and renal protective effects of Ex.

Facile synthesis of Cu N-lauroyl sarcosinate nanozymes with laccase-mimicking activity and identification of toxicity effects for C. elegans.

Nanozyme is a material with enzyme-like catalytic activity, which has been widely used in environmental, antibacterial, and other fields of research. However, there are few reports on the toxicity of nanozymes. In this work, nanozymes co-assembled from sodium N-lauroyl sarcosinate (Ls) and Cu ions possess a Cu(i)-Cu(ii) electron transfer system similar to that of natural laccases. Reaction kinetic studies show that the catalyst follows a typical Michaelis-Menten model. Cu-N-lauroyl sarcosinate nanozyme (Cu-Ls NZ) possess excellent laccase-like activity to oxidize a variety of phenol-containing substrates, such as phenol, 4-iodophenol, and 2,4,5-trichlorophenol. To evaluate the toxicity of the material, the nematode C. elegans was exposed to various concentrations of Cu-Ls NZ. Effects on physiological levels were determined. The results showed that high doses of Cu-Ls NZ increased the amount of reactive oxygen species (ROS), decreased the locomotor activity of nematodes, and inhibited their larval growth.

Extension of the alkyl chain length to adjust the properties of laccase-mimicking MOFs for phenolic detection and discrimination.

2-Methylimidazole (MIM) is a classic organic ligand that shows excellent thermal stability and chemical robustness and is widely used in ZIFs. Recently, transformations of MOFs have been realized by using metals or ligands. In this study, we propose a new strategy-adjusting MIM by extending the alkyl chain length -to change the properties of related MOFs. Furthermore, we used copper as the metal core to replace zinc to mimic the active sites of laccases (electron transfer between copper and imidazole ring). As a result, the nanostructures transformed from nanoleaves to nanovesicles, which changed the Cu(II)/Cu(I) ratio from 3.7 to 1.7, as well as the lattice constant (decreased the diffraction angle) and enzyme-like activity (inhibition). In addition, we revealed that superoxidase anions were the main factors responsible for its laccase-like activity. We applied it to detect and discriminate phenolics. Laccase-mimicking activity was best at pH 7.0. When compared to protein laccase, the Cu-MeIm nanozyme had a greater Vmax at the same mass concentration. It was used to identify and distinguish phenolics. In the presence of Cu-MeIm nanozymes, the linear range is 0.1-2 mM and the detection limit of 2,4-DCP is 0.034 mM.

Febuxostat ameliorates high salt intake-induced hypertension and renal damage in Dahl salt-sensitive rats.

OBJECTIVE: Several clinical studies have reported that xanthine oxidoreductase inhibitors have antihypertensive and renal protective effects but their mechanisms have not been fully determined. This study aims to clarify these mechanisms by examining the effects of febuxostat, which is a novel selective xanthine oxidoreductase inhibitor, in Dahl salt-sensitive rats. METHODS: Eight-week-old male Dahl salt-sensitive rats were fed a normal salt (0.6% NaCl) or high salt (8% NaCl) diet for 8 weeks. A portion of the rats that were fed high salt diet were treated with febuxostat (3 mg/kg per day) simultaneously. Additionally, acute effects of febuxostat (3 mg/kg per day) were examined after high salt diet feeding for 4 or 8 weeks. RESULTS: Treatment with febuxostat for 8 weeks attenuated high salt diet-induced hypertension, renal dysfunction, glomerular injury, and renal interstitial fibrosis. Febuxostat treatment reduced urinary excretion of H2O2 and malondialdehyde and renal thiobarbituric acid reactive substances content. High salt diet increased xanthine oxidoreductase activity and expression in the proximal tubules and medullary interstitium. Febuxostat completely inhibited xanthine oxidoreductase activity and attenuated the high salt diet-increased xanthine oxidoreductase expression. Febuxostat transiently increased urine volume and Na+ excretion without change in blood pressure or urinary creatinine excretion after high salt diet feeding for 4 or 8 weeks. CONCLUSION: Febuxostat ameliorates high salt diet-induced hypertension and renal damage with a reduction of renal oxidative stress in Dahl salt-sensitive rats. The antihypertensive effect of febuxostat may be mediated in part by diuretic and natriuretic action.

High Fructose-Induced Hypertension and Renal Damage Are Exaggerated in Dahl Salt-Sensitive Rats via Renal Renin-Angiotensin System Activation.

Background High-fructose diet (HFr) induces hypertension and renal damage. However, it has been unknown whether the HFr-induced hypertension and renal damage are exaggerated in subjects with salt sensitivity. We tested impacts of HFr in Dahl salt-sensitive (DS) and salt-resistant (DR) rats. Methods and Results Male DS and DR rats were fed control diet or HFr (60% fructose) with normal-salt content. After 12 weeks, plasma and urinary parameters, renal histological characteristics, and renal expression of renin-angiotensin system components were examined. Furthermore, effects of renin-angiotensin system inhibitors were also examined in DS rats fed the HFr. HFr elevated blood pressure in DS rats but not in DR rats. HFr increased urinary albumin and liver type fatty acid binding protein excretions in both rats, but the excretions were exaggerated in DS rats. HFr increased plasma lipids and uric acid in both rats, whereas HFr increased creatinine clearance in DS rats but not DR rats. Although HFr decreased plasma renin activity in DS rats, HFr-induced glomerular injury, afferent arteriolar thickening, and renal interstitial fibrosis were exaggerated in DS rats. HFr increased renal expression of angiotensinogen, renin, (pro)renin receptor, angiotensin-converting enzyme, and angiotensin II type 1 receptor in DS rat, whereas HFr increased only angiotensin-converting enzyme expression and decreased renin and angiotensin II type 1 receptor expressions in DR rats. Enalapril and candesartan attenuated the HFr-induced hypertension, albuminuria, glomerular hyperfiltration, and renal damage in DS rats. Conclusion HFr-induced hypertension and renal damage are exaggerated in DS rats via renal renin-angiotensin system activation, which can be controlled by renin-angiotensin system inhibitors.

Chronic Exercise Protects against the Progression of Renal Cyst Growth and Dysfunction in Rats with Polycystic Kidney Disease.

INTRODUCTION: Polycystic kidney disease (PKD) is a genetic disorder characterized by the progressive enlargement of renal epithelial cysts and renal dysfunction. Previous studies have reported the beneficial effects of chronic exercise on chronic kidney disease. However, the effects of chronic exercise have not been fully examined in PKD patients or models. The effects of chronic exercise on the progression of PKD were investigated in a polycystic kidney (PCK) rat model. METHODS: Six-week-old male PCK rats were divided into a sedentary group and an exercise group. The exercise group underwent forced treadmill exercise for 12 wk (28 m·min-1, 60 min·d-1, 5 d·wk-1). After 12 wk, renal function and histology were examined, and signaling cascades of PKD progression, including arginine vasopressin (AVP), were investigated. RESULTS: Chronic exercise reduced the excretion of urinary protein, liver-type fatty acid-binding protein, plasma creatinine, urea nitrogen, and increased plasma irisin and urinary AVP excretion. Chronic exercise also slowed renal cyst growth, glomerular damage, and interstitial fibrosis and led to reduced Ki-67 expression. Chronic exercise had no effect on cAMP content but decreased the renal expression of B-Raf and reduced the phosphorylation of extracellular signal-regulated kinase (ERK), mammalian target of rapamycin (mTOR), and S6. CONCLUSION: Chronic exercise slows renal cyst growth and damage in PCK rats, despite increasing AVP, with the downregulation of the cAMP/B-Raf/ERK and mTOR/S6 pathways in the kidney of PCK rats.

Metformin slows liver cyst formation and fibrosis in experimental model of polycystic liver disease.

Polycystic liver disease (PLD) is a hereditary liver disease in which the number of cysts increases over time, causing various abdominal symptoms and poor quality of life. Although effective treatment for PLD has not been established, we recently reported that long-term exercise ameliorated liver cyst formation and fibrosis with the activation of AMP-activated protein kinase (AMPK) in polycystic kidney (PCK) rats, a PLD model. Therefore, the aim of this study was to investigate whether metformin, an indirect AMPK activator, was effective in PCK rats. PCK rats were randomly divided into a control (Con) group and a metformin-treated (Met) group. The Met group was treated orally with metformin in drinking water. After 12 wk, liver function, histology, and signaling cascades of PLD were examined in the groups. Metformin did not affect the body weight or liver weight, but it reduced liver cyst formation, cholangiocyte proliferation, and fibrosis around the cyst. Metformin increased the phosphorylation of AMPK and tuberous sclerosis complex 2 and decreased the phosphorylation of mammalian target of rapamycin, S6, and extracellular signal-regulated kinase and the expression of cystic fibrosis transmembrane conductance regulator, aquaporin I, transforming growth factor-ß, and type 1 collagen without changes in apoptosis or collagen degradation factors in the liver. Metformin slows the development of cyst formation and fibrosis with the activation of AMPK and inhibition of signaling cascades responsible for cellular proliferation and fibrosis in the liver of PCK rats.NEW & NOTEWORTHY This study indicates that metformin, an indirect AMPK activator slows liver cyst formation and fibrosis in PLD rat model. Metformin attenuates excessive cell proliferation in the liver with the inactivation of mTOR and ERK pathways. Metformin also reduces the expression of proteins responsible for cystic fluid secretion and liver fibrosis. Metformin and AMPK activators may be potent drugs for polycystic liver disease.

Effects of Long-Term Exercise on Liver Cyst in Polycystic Liver Disease Model Rats.

BACKGROUND: Polycystic liver disease (PLD) is a hereditary liver disease with progressive enlargement of fluid-filled liver cysts, which causes abdominal discomfort and worsens quality of life. Long-term exercise has beneficial effects in various organs, but the effects of long-term exercise on PLD are unclear. Therefore, the aim of this study was to investigate whether long-term exercise inhibits liver cyst formation and fibrosis. METHODS: Polycystic kidney (PCK) rats, a model of PLD, were randomly divided into a sedentary group and a long-term exercise group, which underwent treadmill running for 12 wk (28 m·min, 60 min·d, 5 d·wk). Sprague-Dawley (SD) rats were set as a control group. After 12 wk, exercise capacity, histology, and signaling cascades of PLD were examined. RESULTS: Compared with control SD rats, PCK rats showed a low exercise capacity before exercise protocol. After 12 wk, the exercise improved the exercise capacity and ameliorated liver cyst formation and fibrosis. The exercise significantly decreased the number of Ki-67-positive cells; the expression of cystic fibrosis transmembrane conductance regulator, aquaporin 1, transforming growth factor ß, and type 1 collagen; and the phosphorylation of extracellular signal-regulated kinase, mammalian target of rapamycin and S6. It also increased the phosphorylation of AMP-activated protein kinase in the liver of PCK rats. CONCLUSIONS: The present results indicated that long-term moderate-intensity exercise ameliorates liver cyst formation and fibrosis with the inhibition of signaling cascades responsible for cellular proliferation and fibrosis in PCK rats.

Poor lower extremity function was associated with pre-diabetes and diabetes in older chinese people.

OBJECTIVE: To determine whether a relationship exists between performance-based physical assessments and pre-diabetes/diabetes in an older Chinese population. METHODS: Our study population comprised 976 subjects (mean ± SD age: 67.6±6.0 years; 44.5% men) from the Hangu area of Tianjin, China. Diabetes was defined by self-reporting of a physician's diagnosis, or a fasting plasma glucose level ≥126 mg/dL; and pre-diabetes was defined as a fasting plasma glucose level ≥100 mg/dL and <126 mg/dL. RESULTS: When all other variables were adjusted for, men needing longer to finish a Timed Up and Go Test and a decreased usual walking speed had higher odds of pre-diabetes (P for trend = 0.007 and 0.008, respectively) and diabetes (P for trend = 0.012 and 0.014, respectively). However, women needing longer to finish the test and a decreased usual walking speed had a higher odds of diabetes (P for trend = 0.020 and 0.034, respectively) but not of pre-diabetes. There was no apparent association between grip strength and pre-diabetes/diabetes in both sexes. CONCLUSIONS: In this study, poor lower extremity function was associated with pre-diabetes/diabetes in older people.

A pair of identified giant visual projection neurons demonstrates rhythmic activities before eclosion.

A small set of neurons acting as an internal clock in the Drosophila brain is critical for regulating circadian activities behavior and pre-adult development. However, the cell basis for the circadian rhythm in correlation with light sensitivity is not fully understood. Here we identified a pair of giant visual projection neurons located laterally to the calyx of the mushroom bodies, and investigated their electrophysiological, morphological characteristics, as well as the development pathways during eclosion. The typical morphology of these giant neurons showed the size of the soma (16.0±0.6 microns in diameter) and its processes. Interestingly during development, the three major branches shrunk significantly along with gradually decreased rhythmic spikes. Furthermore, the electrical activity of the giant visual projection neurons is circadian-regulated, shown with significantly higher resting membrane potential, increase in frequency of spontaneous action potential firing, and burst firing pattern during circadian day and night time. The similarities in the morphological characteristics with other visual projection neurons highly suggest that this neuron is a type of novel visual projection neurons in this area, which has special properties in light sensitivities and rhythmic activities. Our data provided supporting evidence for the visual projection neurons with light sensitivities, and pointed to the potential correlation of visual projection neurons and circadian rhythms during the eclosion period or an adaptive development for higher sensitivity of light in adult visual systems.