Effects of high-fat diet and losartan on renal cortical blood flow using contrast ultrasound imaging

Obesity-related glomerulopathy: Current approaches and future perspectives

Obesity-related glomerulopathy (ORG) is a silent comorbidity which is increasing in incidence as the obesity epidemic escalates. ORG is associated with serious health consequences including chronic kidney disease, end-stage renal disease (ESRD), and increased mortality. Although the pathogenic mechanisms involved in the development of ORG are not fully understood, glomerular hemodynamic changes, renin-angiotensin-aldosterone system (RAAS) overactivation, insulin-resistance, inflammation and ectopic lipid accumulation seem to play a major role. Despite albuminuria being commonly used for the non-invasive evaluation of ORG, promising biomarkers of early kidney injury that are emerging, as well as new approaches with proteomics and metabolomics, might permit an earlier diagnosis of this disease. In addition, the assessment of ectopic kidney fat by renal imaging could be a useful tool to detect and evaluate the progression of ORG. Weight loss interventions appear to be effective in ORG, although large-scale trials are needed. RAAS blockade has a renoprotective effect in patients with ORG, but even so, a significant proportion of patients with ORG will eventually progress to ESRD despite therapeutic efforts. It is noteworthy that certain antidiabetic agents such as sodium-glucose cotransporter 2 inhibitors (SGLT2i) or glucagon-like peptide-1 receptor agonists (GLP-1 RAs) could be useful in the treatment of ORG through different pleiotropic effects. In this article, we review current approaches and future perspectives in the care and treatment of ORG.

High Fat Diet Dysbiotic Mechanism of Decreased Gingival Blood Flow

The gut microbiome has a very important role in human health and its influence on the development of numerous diseases is well known. In this study, we investigated the effect of high fat diet (HFD) on the onset of dysbiosis, gingival blood flow decreases, and the periodontal matrix remodeling. We established a dysbiosis model (HFD group) and probiotic model by Lactobacillus rhamnosus GG (LGG) treatment for 12weeks. Fecal samples were collected 24h before mice sacrificing, while short chain fatty acids (SCFA) analysis, DNA extraction, and sequencing for metagenomic analysis were performed afterwards. After sacrificing the animals, we collected periodontal tissues and conducted comprehensive morphological and genetic analyses. While HFD reduced Bacteroidetes, SCFA, and gingival blood flow, this type of diet increased Firmicutes, lipopolysaccharide (LPS) binding protein, TLR4, pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), matrix metalloproteinases (MMP-2 and MMP-9) expression, and also altered markers of bone resorption (OPG and RANKL). However, LGG treatment mitigated these effects. Thus, it was observed that HFD increased molecular remodeling via inflammation, matrix degradation, and functional remodeling and consequently cause reduced gingival blood flow. All of these changes may lead to the alveolar bone loss and the development of periodontal disease.

Weight-gain induced changes in renal perfusion assessed by contrast-enhanced ultrasound precede increases in urinary protein excretion suggestive of glomerular and tubular injury and normalize after weight-loss in dogs

Early detection of obesity-related glomerulopathy in humans is challenging as it might not be detected by routine biomarkers of kidney function. This study's aim was to use novel kidney biomarkers and contrast-enhanced ultrasound (CEUS) to evaluate the effect of obesity development and weight-loss on kidney function, perfusion, and injury in dogs. Sixteen healthy lean adult beagles were assigned randomly but age-matched to a control group (CG) (n = 8) fed to maintain a lean body weight (BW) for 83 weeks; or to a weight-change group (WCG) (n = 8) fed the same diet to induce obesity (week 0-47), to maintain stable obese weight (week 47-56) and to lose BW (week 56-83). At 8 time points, values of systolic blood pressure (sBP); serum creatinine (sCr); blood urea nitrogen (BUN); serum cystatin C (sCysC); urine protein-to-creatinine ratio (UPC); and urinary biomarkers of glomerular and tubular injury were measured. Glomerular filtration rate (GFR) and renal perfusion using CEUS were assayed (except for week 68). For CEUS, intensity- and time-related parameters representing blood volume and velocity were derived from imaging data, respectively. At 12-22% weight-gain, cortical time-to-peak, representing blood velocity, was shorter in the WCG vs. the CG. After 37% weight-gain, sCysC, UPC, glomerular and tubular biomarkers of injury, urinary immunoglobulin G and urinary neutrophil gelatinase-associated lipocalin, respectively, were higher in the WCG. sBP, sCr, BUN and GFR were not significantly different. After 23% weight-loss, all alterations were attenuated. Early weight-gain in dogs induced renal perfusion changes measured with CEUS, without hyperfiltration, preceding increased urinary protein excretion with potential glomerular and tubular injury. The combined use of routine biomarkers of kidney function, CEUS and site-specific urinary biomarkers might be valuable in assessing kidney health of individuals at risk for obesity-related glomerulopathy in a non-invasive manner.

Losartan Alleviates Renal Fibrosis and Inhibits Endothelial-to-Mesenchymal Transition (EMT) Under High-Fat Diet-Induced Hyperglycemia

The endothelial-to-mesenchymal transition (EMT) of glomerular vascular endothelial cells is considered to be pivotal in diabetic nephropathy (DN). The risk of DN can be decreased by losartan, but the potential molecular mechanism(s) are not fully understood. Extensive data show that the EMT occurs in proximal tubular endothelial cells resulting in an endothelial phenotype switch (fibrotic matrix accumulation), consequently enhancing the development of renal interstitial fibrosis. Here, we found that losartan significantly ameliorated DN-induced renal fibrosis progression via inhibition of the EMT in mice. In vivo experiments suggested that losartan significantly alleviated microalbuminuria and pathologic changes under high-fat diet-induced hyperglycemia. Immunohistochemistry indicated that losartan suppressed the EMT in glomeruli. In addition, losartan decreased oxidative stress damage and inhibited the transforming growth factor (TGF)-β1/Smad pathway. Furthermore, consistent changes were detected in vitro where losartan markedly inhibited the EMT and TGF-β1/Smad pathway induced by high glucose in glomerular endothelial cells. Together, these results suggested that losartan could alleviate the EMT in glomeruli via inhibition of oxidative stress damage and the TGF-β1/Smad signaling pathway under hyperglycemia.

Evaluation of inducible nitric oxide synthase inhibition on kidney function and structure in high-fat diet-induced kidney disease

NEW FINDINGS

What is the central question of this study? The metabolic pathways regulating the effects of obesity on the kidney remain unknown. We sought to determine whether inducible nitric oxide synthase (iNOS) is involved in the underlying mechanisms of high-fat diet-induced kidney disease using a specific iNOS inhibitor, N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL). What is the main finding and its importance? We did not demonstrate an upregulation of iNOS renal expression after high caloric intake, suggesting that iNOS might not be a crucial player in the development of obesity-induced kidney disease. Although L-NIL treatment clearly ameliorated systemic metabolic parameters, the effect on loss of renal function, impairment of tubular integrity, oxidative stress and inflammation appeared to be more moderate. Central obesity is related to caloric excess, promoting deleterious cellular responses in targeted organs. Nitric oxide (NO) has been determined as a key player in the pathogenesis of metabolic diseases. Here, we investigated the implication of inducible NO synthase (iNOS) in the development of obesity-induced kidney disease. C57Bl/6 male mice were randomized to a low-fat diet (LFD) or a high-fat diet (HFD) and treated with N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL), a specific iNOS inhibitor, for 16 weeks. Mice fed an HFD exhibited a significant increase in body weight, fasting blood glucose and plasma concentrations of non-esterified fatty acids, triglyceride and insulin. Inhibition of iNOS prevented these changes in mice fed an HFD. Interestingly, the significant increase in albuminuria and mesangial matrix expansion were not ameliorated with L-NIL, whereas a significant decrease in proteinuria, N-acetyl-β-d-glucosaminidase excretion and renal triglyceride content were found, suggesting that iNOS inhibition is more suitable for tubular function than glomerular function. The urinary concentration of hydrogen peroxide, a stable product of reactive oxygen species production, that was found to be increased in mice fed an HFD, was significantly reduced with L-NIL. Finally, despite a moderate effect of L-NIL on inflammatory processes in the kidney, we demonstrated a positive impact of this treatment on adipocyte hypertrophy and on adipose tissue inflammation. These results suggest that inhibition of iNOS leads to a moderate beneficial effect on kidney function in mice fed an HFD. Further studies are needed for better understanding of the role of iNOS in obesity-induced kidney disease.

A novel method for quantitative myocardial contrast echocardiography in mice

The small size of the mouse heart frequently imparts technical challenges when applying conventional in vivo imaging methods for assessing heart function. Here, we describe the use of high-frequency ultrasound imaging in conjunction with a size-tuned blood pool contrast agent for quantitatively assessing myocardial perfusion in living mice. A perflurocarbon microbubble formulation exhibiting a narrow size distribution was developed, and echogenicity was assessed at 18 MHz in vitro. Adult mice were subjected to permanent ligation of the left anterior descending artery. Ultrasound imaging was performed on day 7, and a cohort of intact mice was used as a control. Parasternal long-axis cine clips were acquired at 18 MHz before and after contrast administration. Reduced ejection fraction and increased end-systolic volume were observed in infarcted compared with control mice. In control animals, washin of the contrast agent was visible in all myocardial segments. Reduced contrast enhancement was observed in apical-posterolateral regions of all infarcted mice. A novel method for reslicing of the imaging data through the time domain provided a two-dimensional presentation of regional contrast agent washin, enabling convenient identification of locations exhibiting altered perfusion. Myocardial segments exhibiting diminished contractility were observed to have correspondingly low relative myocardial perfusion. The contrast agent formulation and methods demonstrated here provide the basis for simplifying routine in vivo estimation of infarct size in mice and may be particularly useful in longitudinal evaluation of revascularization interventions and assessment of peri-infarct ischemia. NEW & NOTEWORTHY Murine myocardial contrast echocardiography frequently suffers from poor sensitivity to contrast. Here, we formulated a novel size-tuned microbubble contrast agent and validated it for use with ultra-high-frequency ultrasound. A novel data method for evaluating myocardial perfusion based on reslicing the imaging data through the time domain is presented.

Hemodynamics as Measured With Color Doppler Sonography in Early-Stage Obesity-Related Nephropathy in Children

OBJECTIVES

We retrospectively studied hemodynamic changes in the interlobar artery to assess the clinical value of color Doppler sonography for detecting preclinical obesity-related nephropathy.

METHODS

Color Doppler renal sonography was performed in 52 children with obesity-related nephropathy and 51 control children with simple obesity. The interlobar artery resistive index (RI) was measured and compared with clinical data and laboratory indicators.

RESULTS

The left RI (mean ± SD, 0.65 ± 0.05 versus 0.60 ± 0.08; t = 3.85), right RI (0.64 ± 0.03 versus 0.59 ± 0.02; t = 10.00), and mean RI (0.64 ± 0.05 versus 0.59 ± 0.06; t = 5.00) revealed large statistically significant increases in the obesity-related nephropathy group (all P < .01). In the obesity-related nephropathy group, a positive correlation was found between the mean RI and 24-hour urine trace albumin (r = 0.47; P < .01), triglycerides (r = 0.98; P < .01), and body mass index (r = 0.28; P < .05). The 24-hour urine trace albumin and triglycerides were higher in the obesity-related nephropathy group than the control group (P < .05). In the control group, a mild positive correlation was also found between the mean RI and body mass index (r = 0.24; P < .05).

CONCLUSIONS

Color Doppler sonography successfully indicated renal hemodynamic changes and has diagnostic value for early-stage obesity-related nephropathy.

Potential involvement of PPAR α activation in diminishing the hepatoprotective effect of fenofibrate in NAFLD: Accuracy of non- invasive panel in determining the stage of liver fibrosis in rats

BACKGROUND

Although Fenofibrate (FF) is a hypolipedmic drug and one of the PPARα agonists which is a drug target for non alcoholic liver disease (NAFLD), no studies had investigated its potential hepatic effects in such cases.

AIM

To compare between the effect of FF and Gemfibrozil (GF) on the prognosis of NAFLD in rats.

METHODS

Sixty four rats were used and classified into two main groups. Group I (treated for 6 weeks): naïve, FF, GF groups and Group II (treated for 14 weeks and drugs were added at the last 6 weeks): Control, high fat diet (HFD) untreated, HFD+FF, HFD+FF+folic acid (FA) and HFD+GF groups. Body weight (BW), liver index (LI), renal perfusion test (RPT), glomerular filtration rate (GFR), serum creatinine (S.cr), plasma homocysteine (Hcy), liver function, non invasive markers of fibrosis and histopathology were done.

RESULTS

HFD produced significant increase (P<0.05) in BW, LI, S.cr, plasma Hcy, lipid profile and liver enzymes. It showed significant (P<0.05) decrease in GFR and RPT. These findings were correlated to the histopathology. FF through its effect on GFR and renal function induced significant increase in plasma Hcy and that decreased its effectiveness in managing NAFLD associated with hyperlipidemia. The addition of FA improved significantly its hypolipidemic and hepatotoxic effects.GF showed none of the above FF effects and this may be due to its low affinity to PPAR α.

CONCLUSIONS

There is preference of adding FA to FF or using GF instead in cases of NAFLD. Moreover, this work implies the enhanced liver fibrosis (ELF) panel diagnostic performance in diagnosis of any and moderate degree of fibrosis in rats with NAFLD.

Ultrasound-based imaging methods of the kidney-recent developments

In recent years, several novel ultrasound (US)-based techniques have emerged for kidney diagnostic imaging, including tissue stiffness assessment with elastography, Ultrasensitive Doppler techniques, and contrast-enhanced ultrasonography to assess renal microvascularization. Renal elastography has become available with the development of noninvasive quantitative techniques, following the rapidly growing field of liver fibrosis diagnosis. With the increased incidence of chronic kidney disease, noninvasive diagnosis of renal fibrosis can be of critical value. However, it is difficult to simply extend the application of US elastography from one organ to the other due to anatomic and technical issues. Today, renal elastography appears to be a promising application that, however, still requires optimization and validation. New ultrasensitive Doppler techniques improve the detection of slow blood flow and can be used alone or after administration of US contrast agents. These microbubble-based agents are extremely well tolerated and can be administered even in cases of impaired renal function. Despite the lack of approval, they improve the characterization of atypical renal masses, complex cystic renal masses, and peripheral vascular disorders. Dynamic contrast-enhanced US is based on quantification of the signal intensity from region of interest and mathematical fits of the time-intensity curves. Perfusion-related parameters can be extracted for the monitoring of vascular changes in the renal parenchyma and in tumors in order to evaluate drug response. This estimation of renal perfusion depends on many parameters that should be kept constant for follow-up studies, and, when possible, an internal reference should be used to normalize the measurements.

Short-Term High Fat Intake Does Not Significantly Alter Markers of Renal Function or Inflammation in Young Male Sprague-Dawley Rats

Chronic high fat feeding is correlated with diabetes and kidney disease. However, the impact of short-term high fat diets (HFD) is not well-understood. Six weeks of HFD result in indices of metabolic syndrome (increased adiposity, hyperglycemia, hyperinsulinemia, hyperlipidemia, hyperleptinemia, and impaired endothelium-dependent vasodilation) compared to rats fed on standard chow. The hypothesis was that short-term HFD would induce early signs of renal disease. Young male Sprague-Dawley rats were fed either HFD (60% fat) or standard chow (5% fat) for six weeks. Morphology was determined by measuring changes in renal mass and microstructure. Kidney function was measured by analyzing urinary protein, creatinine, and hydrogen peroxide (H₂O₂) concentrations, as well as plasma cystatin C concentrations. Renal damage was measured through assessment of urinary oxDNA/RNA concentrations as well as renal lipid peroxidation, tumor necrosis factor alpha (TNFα), and interleukin 6 (IL-6). Despite HFD significantly increasing adiposity and renal mass, there was no evidence of early stage kidney disease as measured by changes in urinary and plasma biomarkers as well as histology. These findings suggest that moderate hyperglycemia and inflammation produced by short-term HFD are not sufficient to damage kidneys or that the ketogenic HFD may have protective effects within the kidneys.