Association between obesity and kidney disease: a systematic review and meta-analysis

The failure of glomerular filtration rate estimating equations among obese population

BACKGROUND

Obesity is a major public health with increasing numbers of obese individuals are at risk for kidney disease. However, the validity of serum creatinine-based glomerular filtration rate (GFR) estimating equations in obese population is yet to be determined.

METHODS

We evaluated the performance of the reexpressed Modification of Diet in Renal Disease (MDRD), reexpressed MDRD with Thai racial factor, Thai estimated GFR (eGFR) as well as Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations among obese patients, defined as body mass index (BMI) ≥25 kg/m2 with the reference measured GFR (mGFR) determined by 99mTc-diethylene triamine penta-acetic acid (99mTc-DTPA) plasma clearance method. Serum creatinine levels were measured using standardized enzymatic method simultaneously with GFR measurement. The statistical methods in assessing agreement for continuous data including total deviation index (TDI), concordance correlation coefficient (CCC), and coverage probability (CP) for each estimating equation were compared with the reference mGFR. Accuracy within 10% representing the percentage of estimations falling within the range of ±10% of mGFR values for all equations were also tested.

RESULTS

A total of 240 Thai obese patients were finally recruited with mean BMI of 31.5 ± 5.8 kg/m2. In the total population, all eGFR equations underestimated the reference mGFR. The average TDI values were 55% indicating that 90% of the estimates falling within the range of -55 to +55% of the reference mGFR. The CP values averaged 0.23 and CCC scores ranged from 0.75 to 0.81, reflecting the low to moderate levels of agreement between each eGFR equation and the reference mGFR. The proportions of patients achieving accuracy 10% ranged from 23% for the reexpressed MDRD equation to 33% for the Thai eGFR formula. Among participants with BMI more than 35 kg/m2 (n = 48), the mean error of all equations was extremely wide and significantly higher for all equations compared with the lower BMI category. Also, the strength of agreement evaluated by TDI, CCC, and CP were low in the subset of patients with BMI ≥35 kg/m2.

CONCLUSION

Estimating equations generally underestimated the reference mGFR in subjects with obesity. The overall performance of GFR estimating equations demonstrated poor concordance with the reference mGFR among individuals with high BMI levels. In certain clinical settings such as decision for dialysis initiation, the direct measurements of GFR are required to establish real renal function among obese population.

Association between weight status, metabolic syndrome, and chronic kidney disease among middle-aged and elderly Chinese

BACKGROUND AND AIMS

Obesity often initiates or coexists with certain metabolic abnormalities. This study sought to examine the independent and joint relations of weight and metabolic syndrome (MetS) with incident chronic kidney disease (CKD) among Chinese elderly people.

METHODS AND RESULTS

A total of 15,229 participants (mean age: 62.8 years) from the Dongfeng-Tongji cohort with complete baseline questionnaire and medical examination data were followed from 2008 to 2010 to 2013. All participants were categorized into four phenotypes: metabolically healthy non-overweight/obesity (MHNO), metabolically healthy overweight/obesity (MHO), metabolically unhealthy non-overweight/obesity (MUNO), metabolically unhealthy overweight/obesity (MUO). Multivariable-adjusted logistic regression models were applied to estimate the odds ratios (ORs) and confidence intervals (CIs) of four phenotypes with the risk of incident CKD, which was defined as estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m². A total of 1151 CKD cases were identified during a mean of 4.6-year follow-up. After adjusting for potential confounders, both overweight/obesity and MetS were associated with higher risk of CKD, and the ORs (95% CI) were 1.32 (1.15-1.52) and 1.50 (1.31-1.73), respectively. The risk of CKD was progressively higher in MHO (1.31, 1.09-1.57), MUNO (1.54, 1.22-1.93), and MUO (2.05, 1.73-2.42) as compared with MHNO phenotype, without significant multiplicative interaction between overweight/obesity and MetS (P_interaction = 0.906). These associations were slightly stronger among those aged >60 years or with baseline diabetes.

CONCLUSION

Both overweight/obesity and MetS were associated with an increased risk of CKD. It is worth noting that MHO and MUNO also have an elevated risk. Maintaining both normal weight and healthy metabolic profile is recommended.

Dietary Fermented Soy Extract and Oligo-Lactic Acid Alleviate Chronic Kidney Disease in Mice via Inhibition of Inflammation and Modulation of Gut Microbiota

Chronic kidney disease (CKD) is a global epidemic with an increasing prevalence worldwide. Effective preventive strategies are urgently needed. This study aimed to investigate the effect of nutraceutical components, a fermented soybean product (ImmuBalance, IMB) and an oligo-lactic acid product (LAP), on the prevention of adenine-induced CKD in mice. Female C57BL/6 mice were randomly assigned into following experimental groups: negative control; model control; and models treated with IMB at 250 or 1000 mg/kg body weight (BW), LAP at 1000 or 2000 mg/kg BW, and IMB/LAP combinations. The CKD model was established by intraperitoneal injection of adenine daily for 4 weeks, and treatments started 2 weeks before adenine injection and ended after 10 weeks. Compared with the model control, the treatments did not significantly alter the body weight or food intake. Both IMB and LAP, especially their combination, significantly inhibited tubular dilation, tubulointerstitial degeneration or atrophy, interstitial chronic inflammation and acute inflammation in the kidneys of CKD mice, and significantly decreased serum cystatin C levels. IMB or LAP significantly reversed CKD-associated increases of circulating and kidney levels of inflammatory cytokines, circulating levels of kidney injury biomarkers, and kidney levels of stem cell biomarkers, and significantly reversed CKD-associated reduction of cecum Clostridium leptum group. Our results suggest that dietary supplementation of IMB or LAP may significantly delay the development and/or progression of CKD.

The role of overweight and obesity in adverse cardiovascular disease mortality trends: an analysis of multiple cause of death data from Australia and the USA

BACKGROUND

In recent years, there have been adverse trends in premature cardiovascular disease (CVD) mortality rates (35-74 years) in the USA and Australia. Following long-term declines, rates in the USA are now increasing while falls in Australia have slowed rapidly. These two countries also have the highest adult obesity prevalence of high-income countries. This study investigates the role of overweight and obesity in their recent CVD mortality trends by using multiple cause of death (MCOD) data-direct individual-level evidence from death certificates-and linking the findings to cohort lifetime obesity prevalence.

METHODS

We identified overweight- and obesity-related mortality as any CVD reported on the death certificate (CVD MCOD) with one or more of diabetes, chronic kidney disease, obesity, lipidemias or hypertensive heart disease (DKOLH-CVD), causes strongly associated with overweight and obesity. DKOLH-CVD comprises 50% of US and 40% of Australian CVD MCOD mortality. Trends in premature age-standardized death rates were compared between DKOLH-CVD and other CVD MCOD deaths (non-DKOLH-CVD). Deaths from 2000 to 2017 in the USA and 2006-2016 in Australia were analyzed. Trends in in age-specific DKOLH-CVD death rates were related to cohort relative lifetime obesity prevalence.

RESULTS

Each country's DKOLH-CVD mortality rate rose by 3% per annum in the most recent year, but previous declines had reversed more rapidly in Australia. Non-DKOLH-CVD mortality in the USA increased in 2017 after declining strongly in the early 2000s, but in Australia it has continued declining in stark contrast to DKOLH-CVD. There were larger increases in DKOLH-CVD mortality rates at successively younger ages, strongly related with higher relative lifetime obesity prevalence in younger cohorts.

CONCLUSIONS

The increase in DKOLH-CVD mortality in each country suggests that overweight and obesity has likely been a key driver of the recent slowdown or reversal of CVD mortality decline in both countries. The larger recent increases in DKOLH-CVD mortality and higher lifetime obesity prevalence in younger age groups are very concerning and are likely to adversely impact CVD mortality trends and hence life expectancy in future. MCOD data is a valuable but underutilized source of data to track important mortality trends.

Impact of chronic kidney disease definition on assessment of its incidence and risk factors in patients with newly diagnosed type 1 and type 2 diabetes in the UK: A cohort study using primary care data from the United Kingdom

AIM

To estimate the incidence and risk factors of chronic kidney disease (CKD) in patients with newly-diagnosed diabetes using different CKD definitions.

METHODS

Using UK primary care data, patients with diabetes (type 1, 4691; type 2, 109,365) and no CKD were followed to identify newly-diagnosed CKD, classified by a broad and narrow CKD definition (to capture diabetes-induced CKD, termed diabetic kidney disease, DKD). Adjusted incidence rates of CKD/DKD were calculated, and risk factors identified using Cox regression.

RESULTS

There were 404 CKD cases and 147 DKD cases among patients with type 1 diabetes (T1D), and 29,104 CKD cases, 9284 DKD cases among patients with type 2 diabetes (T2D). Adjusted incidence rates of CKD per 100 years were 5.4 (T1D) and 5.5 (T2D); for DKD they were 1.9 and 1.5, respectively. Risk factors for CKD/DKD were older age, high social deprivation, obesity, cardiovascular disease, hypertension and smoking. Poor glycaemic control in the year after diabetes diagnosis was a strong predictor of CKD/DKD occurrence beyond this first year, and a risk factor for CKD/DKD in T2D.

CONCLUSIONS

CKD and DKD remain common in diabetics in the decade after diagnosis. Early prevention of T2D and aggressive treatment of risk factors is urgent.

The Short-Term Renal Effects of Bariatric Surgery: A Comparative Study Between Sleeve Gastrectomy and One Anastomosis Gastric Bypass Operations Among Egyptian Patients With Severe Obesity

PURPOSE

Obesity is a major health problem with many renal sequelae. Bariatric surgery (BS) has become the treatment of choice for severe obesity. This study was conducted to assess the short-term renal effects of BS and to compare such effects between two distinct forms of BS.

MATERIALS AND METHODS

A single-center non-randomized prospective observational study was conducted on 57 patients with severe obesity. Two distinct forms of BS have been performed; laparoscopic sleeve gastrectomy (LSG) and laparoscopic one anastomosis gastric bypass (OAGB). Anthropometric measurements, 24-h urinary creatinine clearance (CL_Cr), protein and oxalate excretion, and abdominal fat tissue analysis by computerized tomography were performed prior to surgery and 6 months later.

RESULTS

LSG and OAGB were performed in 47 and 10 participants, respectively. BS resulted in pronounced reduction of body mass index (- 27.1% ± 7.11), with no substantial weight loss discrepancy between LSG and OAGB. The median percent change in 24-h urinary CL_Cr and protein and oxalate excretion were - 35.7, - 42.2, and - 5.8, respectively. The median (IQR) percent change of urinary oxalate excretion was - 11.1 (- 22.6, - 1.4) and 113.08 (82.5, 179.7) for LSG and OAGB, respectively (p < 0.001). The subcutaneous abdominal fat surface area has been found to be the significant predictor of the persistence of glomerular hyperfiltration after BS.

CONCLUSION

Both LSG and OAGB can alleviate many of the obesity-related pathological renal changes. However, postoperative hyperoxaluria remains a serious issue particularly in OAGB. Detailed radiological abdominal fat tissue analysis by CT may aid in predicting the renal outcome following BS.

Ameliorative Effects of Bredemolic Acid on Markers Associated with Renal Dysfunction in a Diet-Induced Prediabetic Rat Model

Recently, studies have shown that renal dysfunction is associated not only with overt diabetes but also with the preceding stage known as prediabetes. Diet and pharmacological interventions are the therapeutic approaches to managing prediabetes, but the compliance in combining the two interventions is low. Hence, the efficacy of pharmacological intervention is reduced without diet modification. In our previous study, we established that bredemolic acid (BA) ameliorated glucose homeostasis via increased GLUT 4 expression in the skeletal muscle of prediabetic rats in the absence of diet intervention. However, the effects of bredemolic acid on renal function in prediabetic condition are unknown. Therefore, this study was aimed at investigating the ameliorative effects of bredemolic acid on renal dysfunction in a diet-induced prediabetic rat model. Thirty-six Sprague-Dawley male rats (150-180 g) were divided into two groups: the nonprediabetic (n = 6) and prediabetic (n = 30) groups which were fed normal diet (ND) and high-fat high-carbohydrate (HFHC) diet, respectively, for 20 weeks. After the 20^th week, the prediabetic groups were subdivided into prediabetic control (PD) and 4 other prediabetic groups which were treated with either BA (80 mg/kg) or metformin (MET, 500 mg/kg) for further 12 weeks (21^st to 32^nd). Plasma, urine, and kidney samples were collected for biochemical analysis. The untreated prediabetic (PD) rats presented increased fluid intake and urine output; increased creatinine, urea, and uric acid plasma concentrations; albuminuria; proteinuria; sodium retention; potassium loss; increased aldosterone and kidney injury molecule (KIM-1) concentration; and increased urinary podocin mRNA expression. However, BA administration attenuated the renal markers and oxidative stress and decreased the urinary podocin mRNA expression. In conclusion, BA administration, regardless of diet modification, attenuates renal dysfunction in an experimentally induced prediabetic state.

Peri-renal fat thickness is positively associated with the urine albumin excretion rate in patients with type 2 diabetes

BACKGROUNDS

Albuminuria, the earliest clinical manifestation of diabetic kidney disease (DKD), is a major prognostic indicator of renal progression. Obesity itself is associated with the development of DKD and accelerates its progression. Accumulation of peri-renal fat on the kidneys can damage kidney function. Measuring the perirenal fat thickness (PFT) by ultrasound is a non-invasive method to measure ectopic fat deposition on the kidney. In this study, we aim to obtain the association between albuminuria and PFT.

METHODS

Eighty-nine subjects with type 2 diabetes mellitus (T2DM) were enrolled. Albuminuria was defined as a urine albumin-to-creatinine ratio (UACR) ≧30 mg/g. Measurement of the PFT was performed by B-mode ultrasound (Toshiba SSA-680A) and determined from the surface of the abdominal musculature to the surface of kidney. Pearson correlation coefficients were determined to test the significant independent relationship between the PFT and demographic, anthropometric and laboratory parameters.

RESULTS

Patients were divided into those with (n = 66) and without (n = 23) albuminuria. PFT (odds ratio [OR], 19.3; 95% CI, 2.25-165.00; p = 0.01) was significantly correlated with albuminuria based on multiple logistic regression analysis. Additionally, linear regression confirmed that degree of albuminuria has a positive association with the PFT (r = 0.233; p = 0.03).

CONCLUSIONS

Our study showed that an increased PFT is positively associated with the albuminuria among patients with T2DM. Our findings suggest that measurement of the PFT may represent a helpful tool to assess the risk of developing albuminuria in patients with T2DM.

Carnosine and Kidney Diseases: What We Currently Know?

Carnosine (beta-alanyl-L-histidine) is an endogenously synthesised dipeptide which is present in different human tissues e.g. in the kidney. Carnosine is degraded by enzyme serum carnosinase, encoding by CNDP1 gene. Carnosine is engaged in different metabolic pathways in the kidney. It reduces the level of proinflammatory and profibrotic cytokines, inhibits advanced glycation end products' formation, moreover, it also decreases the mesangial cell proliferation. Carnosine may also serve as a scavenger of peroxyl and hydroxyl radicals and a natural angiotensin-converting enzyme inhibitor. This review summarizes the results of experimental and human studies concerning the role of carnosine in kidney diseases, particularly in chronic kidney disease, ischemia/reperfusion-induced acute renal failure, diabetic nephropathy and also drug-induced nephrotoxicity. The interplay between serum carnosine concentration and serum carnosinase activity and polymorphism in the CNDP1 gene is discussed. Carnosine has renoprotective properties. It has a promising potential for the treatment and prevention of different kidney diseases, particularly chronic kidney disease which is a global public health issue. Further studies of the role of carnosine in the kidney may offer innovative and effective strategies for the management of kidney diseases.

Reduced risk for chronic kidney disease after recovery from metabolic syndrome: A nationwide population-based study

Background

Metabolic syndrome (MetS) is linked to various chronic comorbidities, including chronic kidney disease (CKD). However, few large studies have addressed whether recovery from MetS is associated with reduction in the risks of such comorbidities.

Methods

This nationwide population-based study in Korea screened 10,664,268 people who received national health screening ≥ 3 times between 2012 and 2016. Those with a history of major cardiovascular events or preexisting CKD were excluded. We classified study groups into four, according to the course of MetS state, as defined by the harmonizing criteria. The main study outcome was incidental CKD (estimated glomerular filtration rate < 60 mL/min/1.73 m² which was persistent until the last health exams). The study outcomes were investigated using multivariable logistic regression analysis, which was adjusted for clinical variables and the previous severity of MetS.

Results

Four study groups included 6,315,301 subjects: 4,537,869 people without MetS, 1,034,605 with chronic MetS, 438,287 who developed MetS, and 304,540 who recovered from preexisting MetS. Those who developed MetS demonstrated higher risk of CKD (adjusted odds ratio [OR], 1.26 [1.23-1.29]) than did those who did not develop MetS. In contrast, MetS-recovery was associated with decreased risk of CKD (adjusted OR, 0.84 [0.82-0.86]) than that in people with chronic MetS. Among the MetS components, change in hypertension was associated with the largest difference in CKD risk.

Conclusion

Reducing or preventing MetS may reduce the burden of CKD on a population-scale. Clinicians should consider the clinical importance of altering MetS status for risk of CKD.

Educational case: a patient with proteinuria

This is an educational case suitable for all readers, but aimed particularly at trainees preparing for MRCP. Using the example of a patient presenting to clinic with proteinuria, aspects of differential diagnosis, pathology and management are explored.

The fat mass, estimated glomerular filtration rate, and chronic inflammation in type 2 diabetic patients

BACKGROUND

The aim of the study was to analyze the degree of obesity and its associations with age, gender, inflammation, an estimated glomerular filtration rate (eGFR), and liver function in type 2 diabetes mellitus (T2DM) patients.

METHODS

A total of 874 consecutive adult Caucasian T2DM patients from outpatient diabetic clinic were included in the study. The relative fat mass (RFM) and body mass index (BMI) were used as obesity markers. Serum creatinine and cystatin C were used for the GFR estimation. Serum high-sensitive C-reactive protein (hsCRP) was used as the indicator of inflammation.

RESULTS

The median, interquartile range (IQR) of RFM in females was higher than that in males (44.8 (42.3-47.2) % vs 31.3 (28.8-34.1) %, respectively; P < .0001). The median (IQR) of BMI in females was no higher than that in males (30 (27-34) kg/m2 vs 30 (27-34), respectively; P = .5152). The obesity prevalence was 99% in males and 98% in females according to RFM. BMI recognized obesity in 51% males and 53% females. RFM was positively associated with hsCRP in both males (rs  = .296, P < .0001) and females (rs  = .445, P < .0001). ALT was positively correlated with eGFRcys in both males (rs  = .379, P < .0001) and females (rs  = .308, P < .0001).

CONCLUSION

The RFM equation leads to higher obesity prevalence compared to BMI. Women have higher RFM compared to men. The kidney function was positively correlated with ALT serum concentrations.

Single-Nephron GFR in Patients With Obesity-Related Glomerulopathy

Introduction

Obesity-related glomerulopathy (ORG) is a slowly progressive kidney disease occurring in association with obesity. It is characterized histopathologically by glomerulomegaly, likely caused by single-nephron hyperfiltration that has not been demonstrated in humans because of technical difficulty in measuring single-nephron glomerular filtration rate (SNGFR) in the clinical setting.

Methods

Total glomerular number per kidney, with or without global glomerulosclerosis, was estimated by the combination of cortical volume assessment via unenhanced computed tomography and biopsy-based stereology. Mean glomerular volume was calculated from the measured area of glomerular tufts. Both SNGFR and single-nephron urinary protein excretion (SNUPE) were estimated by dividing values for estimated glomerular filtration rate and urinary protein excretion by the number of nonsclerotic glomeruli. Living kidney donors were used as healthy controls.

Results

A total of 48 ORG patients with average nonsclerotic glomerular numbers of 456,000 ± 235,000 per kidney were included. The values for SNGFR in ORG patients with chronic kidney disease (CKD) stages 1 and 2 were higher than for nonobese and obese controls (97 ± 43 vs. 59 ± 21 vs. 64 ± 21 nl/min, respectively, P = 0.001). Nonsclerotic glomerular number decreased with advancing stages of renal functional impairment. The presence of ORG with more advanced CKD stages was associated with lower SNGFR and marked elevation in SNUPE levels, with no difference in the mean glomerular volume between the stages.

Conclusions

These results provide functional evidence for single-nephron hyperfiltration in patients with ORG, and identify compensatory failure to maintain effective SNGFR as a feature of advanced-stage ORG.

Impact of Preoperative Anemia on Postoperative Kidney Function Following Laparoscopic Bariatric Surgery

BACKGROUND

Preoperative anemia is a risk factor for acute kidney failure after high-risk surgeries. We assessed the impact of preoperative anemia on kidney function in an obese Asian population after laparoscopic bariatric surgery.

METHODS

Patient characteristics, comorbidities, type of surgery, perioperative profiles, eGFR, and micronutrition were retrospectively reviewed in 341 patients with obesity undergoing bariatric surgery. All patients, who had a preoperative estimated glomerular filtration rates (eGFR) ≥ 90 mL/min/1.73 m², were followed for 1 year and assigned to one of two groups: anemia or non-anemia group. Preoperative anemia was determined based on hemoglobin concentration.

RESULTS

The Pearson's correlation coefficient between preoperative body mass index (BMI) and preoperative eGFR of all patients was 0.169 (p = 0.005). Preoperatively, there were no significant differences in age, BMI, and eGFR between the anemia (n = 38) and non-anemia groups (n = 303). Patients in the anemia group had lower hemoglobin concentration at baseline, 1 month, and 12 months after surgery than those in the non-anemia group. Postoperative eGFR levels at 1 month (p = 0.993) and 1 year (p = 0.118) as well as hospital stay (p = 0.941) were comparable between the two groups. However, the percentage weight loss was significantly higher in the non-anemia group than that in the anemia group 1 year after bariatric surgery (30.0 ± 7.3% vs. 27.0 ± 8.1%; p = 0.041).

CONCLUSIONS

Preoperative anemia did not negatively impact kidney function following laparoscopic bariatric surgery during the 12-month follow-up. Considering the potential adverse impact of anemia on postoperative weight loss, preoperative correction of anemia may be recommended.

Underweight Increases the Risk of End-Stage Renal Diseases for Type 2 Diabetes in Korean Population: Data From the National Health Insurance Service Health Checkups 2009-2017

OBJECTIVE

There is a controversy over the association between obesity and end-stage renal disease (ESRD) in people with or without type 2 diabetes; therefore, we examined the effect of BMI on the risk of ESRD according to glycemic status in the Korean population.

RESEARCH DESIGN AND METHODS

The study monitored 9,969,848 participants who underwent a National Health Insurance Service health checkup in 2009 from baseline to the date of diagnosis of ESRD during a follow-up period of ∼8.2 years. Obesity was categorized by World Health Organization recommendations for Asian populations, and glycemic status was categorized into the following five groups: normal, impaired fasting glucose (IFG), newly diagnosed diabetes, diabetes <5 years, and diabetes ≥5 years.

RESULTS

Underweight was associated with a higher risk of ESRD in all participants after adjustment for all covariates. In the groups with IFG, newly diagnosed type 2 diabetes, diabetes duration <5 years, and diabetes ≥5 years, the hazard ratio (HR) of the underweight group increased with worsening glycemic status (HR 1.431 for IFG, 2.114 for newly diagnosed diabetes, 4.351 for diabetes <5 years, and 6.397 for diabetes ≥5 years), using normal weight with normal fasting glucose as a reference. The adjusted HRs for ESRD were also the highest in the sustained underweight group regardless of the presence of type 2 diabetes (HR 1.606 for nondiabetes and 2.14 for diabetes).

CONCLUSIONS

Underweight showed more increased HR of ESRD according to glycemic status and diabetes duration in the Korean population. These associations also persisted in the group with sustained BMI during the study period.

Abdominal obesity phenotypes and risk of kidney function decline: Tehran Lipid and Glucose Study

OBJECTIVE

Obesity and related health risk in different obesity phenotypes has always been a controversial subject. The present study was conducted with the aim of investigating the risk of kidney function decline (KFD) incidence in different abdominal obesity phenotypes.

METHODS

In this prospective observational cohort study, 7002 individuals (56.1% female), aged ≥20 years, were followed for the incidence of KFD defined as 40% decline in eGFR. Abdominal obesity was defined based on waist circumference cut-offs ≥89/91cm for men/women, respectively. Metabolic health was defined as ≤1 criterion of the metabolic syndrome criteria, according to the Joint Interim Statement (JIS) definition.

RESULTS

At baseline 4273 individuals (61.0%) were abdominally obese, among whom, 1188 (27.8%) belonged to the metabolically healthy abdominal obese (MHAO) phenotype. Totally, 251 incidences of KFD was indicated throughout the 12-year follow-up. After adjusting for the confounding variables, MHAO phenotype was not associated with increased risk of KFD in both males and females. Furthermore, results indicated that hazard ratios (HRs) for incidence of KFD did not increase in males with unhealthy obesity phenotypes. However, females with metabolically unhealthy abdominal obese (MUAO) phenotype had increased risk of KFD.

CONCLUSION

Findings of this study indicated that MHAO phenotype was not associated with KFD incidence, regardless of the participants gender. Furthermore, MUAO phenotype was associated with higher risk of KFD only in females. Further studies with longer follow up and larger sample size are needed to shed more light upon the regarded relationship and the influential role of gender.

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.

Podocyte-specific deletion of tubular sclerosis complex 2 promotes focal segmental glomerulosclerosis and progressive renal failure

Obesity can initiate and accelerate the progression of kidney diseases. However, it remains unclear how obesity affects renal dysfunction. Here, we show that a newly generated podocyte-specific tubular sclerosis complex 2 (Tsc2) knockout mouse model (Tsc2Δpodocyte) develops proteinuria and dies due to end-stage renal dysfunction by 10 weeks of age. Tsc2Δpodocyte mice exhibit an increased glomerular size and focal segmental glomerulosclerosis, including podocyte foot process effacement, mesangial sclerosis and proteinaceous casts. Podocytes isolated from Tsc2Δpodocyte mice show nuclear factor, erythroid derived 2, like 2-mediated increased oxidative stress response on microarray analysis and their autophagic activity is lowered through the mammalian target of rapamycin (mTOR)-unc-51-like kinase 1 pathway. Rapamycin attenuated podocyte dysfunction and extends survival in Tsc2Δpodocyte mice. Additionally, mTOR complex 1 (mTORC1) activity is increased in podocytes of renal biopsy specimens obtained from obese patients with chronic kidney disease. Our work shows that mTORC1 hyperactivation in podocytes leads to severe renal dysfunction and that inhibition of mTORC1 activity in podocytes could be a key therapeutic target for obesity-related kidney diseases.

Metabolic abnormalities, but not obesity per se, associated with chronic kidney disease in a Taiwanese population

BACKGROUND AND AIMS

It is inconclusive whether obesity itself or metabolic abnormalities are linked to chronic kidney disease (CKD). The aim of this study was to examine the association between different subtypes of obesity and metabolic abnormalities with CKD in adults.

METHODS AND RESULTS

This study enrolled 14,983 eligible subjects stratified into metabolically healthy normal weight (MHNW), metabolically healthy overweight (MHOW), metabolically healthy obesity (MHO), metabolically unhealthy normal weight (MUNW), metabolically unhealthy overweight (MUOW), and metabolically unhealthy obesity (MUO) according to body mass index and metabolic syndrome status (ATP-III criteria). The metabolic healthy phenotype was defined as the absence of both metabolic syndrome and any known diabetes, coronary artery disease, stroke, hypertension or dyslipidemia. Early and advanced CKD were defined as eGFR<60, proteinuria, or structural abnormalities as detected by renal sonography. The prevalence of CKD was 2.5, 3.0, 4.0, 10.6, 9.5, and 10.5% in subjects with MHNW, MHOW, MHO, MUNW, MUOW, and MUO, respectively. In the multivariate analysis, the MUNW (OR:2.22, P < 0.001), MUOW (OR:2.22, P < 0.001), and MUO (OR:2.45, P < 0.001) groups were associated with early CKD. For advanced CKD, the OR was 2.56 (P < 0.001), 2.31 (P < 0.001), and 3.49 (P < 0.001) in the MUNW, MUOW, and MUO groups, respectively. The associated risks of early and advanced CKD were not significant in the MHOW and MHO group. MUOW and MUO were associated with higher risk of CKD compared with MHOW and MHO after adjusting other variables.

CONCLUSIONS

Metabolic abnormalities, but neither overweight nor obesity, were associated with a higher risk of CKD in adults.

Effect of laparoscopic sleeve gastrectomy on renal function in obese patients

BACKGROUND

To investigate the clinical efficacy and mechanism of laparoscopic sleeve gastrectomy (LSG) in improving renal function in obese patients.

METHODS

We retrospectively reviewed the anthropometric indices (waist circumference, hip circumference and body mass index (BMI)), renal function indices (serum creatinine, urea and urinary albumin:creatinine ratio (UACR)), serum inflammatory indices (C-reactive protein, interleukin-6 and tumour necrosis factor-α) and an adipose factor (leptin) in 50 patients with obesity (BMI ≥32.5 kg/m² ) who underwent LSG in our hospital from January 2018 to January 2019.

RESULTS

Patients constituted 23 men and 27 women, with an average age of 32.5 ± 8.7 years and BMI of 43.99 ± 8.29 kg/m² . Body weight and BMI 1 month post-operatively were significantly lower than preoperatively (P < 0.05), and the renal function indices serum creatinine, urea and UACR, improved significantly 3 months post-operatively (P < 0.05). C-reactive protein, interleukin-6 and tumour necrosis factor-α levels improved significantly 3 months post-operatively (P < 0.05), while leptin levels decreased significantly 1 month post-operatively (P < 0.05). Six months post-operatively, the remission rates for type 2 diabetes mellitus, sleep apnoea syndrome and hypertension were 83.8%, 92.9% and 88.6%, respectively.

CONCLUSIONS

LSG led to body weight loss and significantly improved serum creatinine, urea and UACR values in patients with obesity, which may be related to changes in adipocytokines and inflammatory factors, post-operatively. LSG is expected to become a new treatment to prevent or treat renal insufficiency caused by obesity.

Sex Differences in Diabetic Kidney Disease

While the global prevalence of both type 1 and type 2 diabetes mellitus is similar in men and women, the consequences of diabetes on associated end-organ complications, including diabetic kidney disease appear to be more sex-specific. Particularly, women with diabetes have higher mortality rates for diabetes-related deaths, and higher prevalence of diabetic kidney disease risk factors such as hypertension, hyperglycemia, obesity, and dyslipidemia. However, the evidence for the impact of sex on diabetic kidney disease prevalence and disease progression is limited and inconsistent. Although most studies agree that the protective effect of the female sex against the development of kidney disease is diminished in the setting of diabetes, the reasons for this observation are unclear. Whether or not sex differences exist in the risk of diabetic kidney disease is also unclear, with studies reporting either higher risk in men, women, or no sex differences. Despite the remaining controversies, some of the factors that associate with sex differences in the risk of diabetic kidney disease are age at onset, and type and duration of diabetes. There is growing appreciation of the importance of sex hormones in the regulation of renal function, with estrogens generally considered to be renoprotective. Although some progress has been made towards better understanding of the mechanisms by which sex hormones play a role in the pathophysiology of diabetic kidney disease, the translational potential of this knowledge is still underappreciated. A better understanding of sex differences in diabetic kidney disease may provide basis for personalized and sex-specific treatment of diabetic kidney disease.

A Coaching Program to Improve Dietary Intake of Patients with CKD: ENTICE-CKD

BACKGROUND AND OBJECTIVES

The dietary self-management of CKD is challenging. Telehealth interventions may provide an effective delivery method to facilitate sustained dietary change.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This pilot, randomized, controlled trial evaluated secondary and exploratory outcomes after a dietitian-led telehealth coaching intervention to improve diet quality in people with stage 3-4 CKD. The intervention group received phone calls every 2 weeks for 3 months (with concurrent, tailored text messages for 3 months), followed by 3 months of tailored text messages without telephone coaching, to encourage a diet consistent with CKD guidelines. The control group received usual care for 3 months, followed by nontailored, educational text messages for 3 months.

RESULTS

Eighty participants (64% male), aged 62±12 years, were randomized to the intervention or control group. Telehealth coaching was safe, with no adverse events or changes to serum biochemistry at any time point. At 3 months, the telehealth intervention, compared with the control, had no detectable effect on overall diet quality on the Alternative Health Eating Index (3.2 points, 95% confidence interval, -1.3 to 7.7), nor at 6 months (0.5 points, 95% confidence interval, -4.6 to 5.5). There was no change in clinic BP at any time point in any group. There were significant improvements in several exploratory diet and clinical outcomes, including core food group consumption, vegetable servings, fiber intake, and body weight.

CONCLUSIONS

Telehealth coaching was safe, but appeared to have no effect on the Alternative Healthy Eating Index or clinic BP. There were clinically significant changes in several exploratory diet and clinical outcomes, which require further investigation.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Evaluation of Individualized Telehealth Intensive Coaching to Promote Healthy Eating and Lifestyle in CKD (ENTICE-CKD), ACTRN12616001212448.

Metabolic Reprogramming in Autosomal Dominant Polycystic Kidney Disease: Evidence and Therapeutic Potential

Autosomal dominant polycystic kidney disease is characterized by progressive development and enlargement of kidney cysts, leading to ESKD. Because the kidneys are under high metabolic demand, it is not surprising that mounting evidence suggests that a metabolic defect exists in in vitro and animal models of autosomal dominant polycystic kidney disease, which likely contributes to cystic epithelial proliferation and subsequent cyst growth. Alterations include defective glucose metabolism (reprogramming to favor aerobic glycolysis), dysregulated lipid and amino acid metabolism, impaired autophagy, and mitochondrial dysfunction. Limited evidence supports that cellular kidney metabolism is also dysregulated in humans with autosomal dominant polycystic kidney disease. There are notable overlapping features and pathways among metabolism, obesity, and/or autosomal dominant polycystic kidney disease. Both dietary and pharmacologic-based strategies targeting metabolic abnormalities are being considered as therapies to slow autosomal dominant polycystic kidney disease progression and are attractive, particularly given the slowly progressive nature of the disease. Dietary strategies include daily caloric restriction, intermittent fasting, time-restricted feeding, a ketogenic diet, and 2-deoxy-glucose as well as alterations to nutrient availability. Pharmacologic-based strategies include AMP-activated kinase activators, sodium glucose cotransporter-2 inhibitors, niacinamide, and thiazolidenediones. The results from initial clinical trials targeting metabolism are upcoming and anxiously awaited within the scientific and polycystic kidney disease communities. There continues to be a need for additional mechanistic studies to better understand the role of dysregulated metabolism in autosomal dominant polycystic kidney disease and for subsequent translation to clinical trials. Beyond single-intervention trials focused on metabolic reprograming in autosomal dominant polycystic kidney disease, great potential also exists by combining metabolic-focused therapeutic approaches with compounds targeting other signaling cascades altered in autosomal dominant polycystic kidney disease, such as tolvaptan.

Bariatric surgery and kidney disease outcomes in severely obese youth

Bariatric surgery, an emerging treatment for severely obese youth with and without T2D, provides marked improvement in insulin resistance, beta-cell function, and central adiposity. Further, preliminary data suggest that bariatric surgery also results in significant improvement in markers of obesity-related nephropathy and DKD, beyond that which can be achieved with current medical interventions. Yet, the mechanisms whereby bariatric surgery attenuates kidney disease remain unclear. This review summarizes the data on the effects of bariatric surgery on obesity-related nephropathy and DKD in youth with and without T2D, in addition to potential mechanisms underlying the nephroprotective effects of weight loss surgery and how these may differ in Roux-en-Y gastric bypass vs. vertical sleeve gastrectomy. Finally, we discuss potential future non-surgical therapies to mitigate kidney disease.

Long-term outcomes in patients with obesity and renal disease after sleeve gastrectomy

Morbid obesity is a barrier to kidney transplant in patients with end-stage renal disease (ESRD). Laparoscopic sleeve gastrectomy (SG) is an increasingly considered intervention, but the safety and long-term outcomes are uncertain. We reviewed prospectively collected data on patients with ESRD and chronic kidney disease (CKD) undergoing SG from 2011 to 2018. There were 198 patients with ESRD and 45 patients with CKD (stages 1-4) who met National Institutes of Health guidelines for bariatric surgery and underwent SG; 72% and 48% achieved a body mass index of ≤ 40 and ≤ 35 kg/m² , respectively. The mean percentages of total weight loss and excess weight loss were 18.9 ± 10.8% and 38.2 ± 20.3%, respectively. SG reduced hypertension (85.8% vs 52.1%), decreased antihypertensive medication use (1.6 vs 1.0) (P < .01 each), and reduced incidence of diabetes (59.6% vs 32.5%, P < .01). Of the 71 patients with ESRD who achieved a body mass index of ≤ 40 kg/m² , 45 were waitlisted and received a kidney transplant, whereas 10 remain on the waitlist. Mortality rate after SG was 1.8 per 100 patient-years, compared with 7.3 for non-SG. Patients with stage 3a or 3b CKD exhibited improved glomerular filtration rate (43.5 vs 58.4 mL/min, P = .01). In conclusion, SG safely improves transplant candidacy while providing significant, sustainable effects on weight loss, reducing medical comorbidities, and possibly improving renal function in stage 3 patients.

Metabolic Surgery to Treat Obesity in Diabetic Kidney Disease, Chronic Kidney Disease, and End-Stage Kidney Disease; What Are the Unanswered Questions?

Obesity is a major factor in contemporary clinical practice in nephrology. Obesity accelerates the progression of both diabetic and non-diabetic chronic kidney disease and, in renal transplantation, both recipient and donor obesity increase the risk of allograft complications. Obesity is thus a major driver of renal disease progression and a barrier to deceased and living donor kidney transplantation. Large observational studies have highlighted that metabolic surgery reduces the incidence of albuminuria, slows chronic kidney disease progression, and reduces the incidence of end-stage kidney disease over extended follow-up in people with and without type 2 diabetes. The surgical treatment of obesity and its metabolic sequelae has therefore the potential to improve management of diabetic and non-diabetic chronic kidney disease and aid in the slowing of renal decline toward end-stage kidney disease. In the context of patients with end-stage kidney disease, although complications of metabolic surgery are higher, absolute event rates are low and it remains a safe intervention in this population. Pre-transplant metabolic surgery increases access to kidney transplantation in people with obesity and end-stage kidney disease. Metabolic surgery also improves management of metabolic complications post-kidney transplantation, including new-onset diabetes. Procedure selection may be critical to mitigate the risks of oxalate nephropathy and disruption to immunosuppressant pharmacokinetics. Metabolic surgery may also have a role in the treatment of donor obesity, which could increase the living kidney donor pool with potential downstream impact on kidney paired exchange programmes. The present paper provides a comprehensive coverage of the literature concerning renal outcomes in clinical studies of metabolic surgery and integrates findings from relevant mechanistic pre-clinical studies. In so doing the key unanswered questions for the field are brought to the fore for discussion.

The Effect of Metabolic Surgery on the Complications of Diabetes: What Are the Unanswered Questions?

It is now established that metabolic surgery (also known as bariatric surgery or obesity surgery) is an effective treatment for type 2 diabetes. Data from several randomized controlled trials have shown that surgery, when used as an adjunct to best medical therapy, is superior to medical therapy alone in achieving glycaemic and metabolic treatment targets in diabetes care. This has resulting in metabolic surgery being recommended as a treatment option for obesity-associated type 2 diabetes in national and international diabetes care guidelines. While the superior glycaemic effect of surgery is clear, the effect of surgery on the complications of diabetes is not fully understood. There are observational and epidemiological data that indicate a preventative effect in cohorts who do not have complications at baseline, as well as a positive effect on those with established diabetic kidney disease. However, there is a dearth of randomized controlled studies that specifically examine the effect of surgery on the complications of diabetes. Therefore, we should remain cautious in some cases, especially in those with retinopathy or neuropathy, as there is potential for deterioration of disease post-operatively. Further study is needed on this important topic. A lot is known, but there remain several unanswered questions. This article summarizes what we know about the effect of metabolic surgery on the complications of diabetes, poses some unanswered questions, and suggests how we could answer them.

Socio-Demographic Factors Affect the Prevalence of Hematuria and Proteinuria Among School Children in Hualien, Taiwan: A Longitudinal Localization-Based Cohort Study

Objective: Child hematuria/proteinuria is a risk factor for chronic kidney disease (CKD) in later life, and mass urinary screening could detect asymptomatic glomerulonephritis at an early stage. This study aimed to evaluate the longitudinal prevalence of hematuria/proteinuria and its association with socio-demographic factors among school children in Hualien, Taiwan. Methods: The study cohort consisted of first and fourth graders enrolled from 2008 to 2015 in Hualien. We combined the data from two consecutive health examinations to ensure the validity of the body mass index (BMI), urbanization, proteinuria, and hematuria grouping. Prevalence and health status differences between sex, age, BMI, and urbanization level were examined. Results: A total of 16,990 students within the same BMI and urbanization categories were included during the study interval. The prevalence of persistent hematuria was 1.0%. Fourth graders (odds ratio OR: 1.68, p = 0.002), girls (OR: 1.48, p = 0.014), and students from suburban/rural areas (OR: 1.99, and OR: 4.93, respectively; both p < 0.001) demonstrated higher hematuria risk. The prevalence of proteinuria was 0.2%. Fourth graders (OR: 4.44, p < 0.001) and students in suburban areas (OR: 0.27, p = 0.031) were associated with persistent proteinuria. After stratifying by age, the significant association remained. A higher risk of proteinuria was noted in underweight subjects (OR: 2.52, p = 0.023) among the fourth-grade students. Conclusion: The prevalence of hematuria/proteinuria in Hualien was higher than the average reported for Taiwan. Hematuria/proteinuria was significantly associated with sex, age, BMI, and urbanization. Our longitudinal results can provide information for future pediatric CKD prevention in Taiwan.

Childhood obesity: an overview of laboratory medicine, exercise and microbiome

In the last few years, a significant increase of childhood obesity incidence unequally distributed within countries and population groups has been observed, thus representing an important public health problem associated with several health and social consequences. Obese children have more than a 50% probability of becoming obese adults, and to develop pathologies typical of obese adults, that include type 2-diabetes, dyslipidemia and hypertension. Also environmental factors, such as reduced physical activity and increased sedentary activities, may also result in increased caloric intake and/or decreased caloric expenditure. In the present review, we aimed to identify and describe a specific panel of parameters in order to evaluate and characterize the childhood obesity status useful in setting up a preventive diagnostic approach directed at improving health-related behaviors and identifying predisposing risk factors. An early identification of risk factors for childhood obesity could definitely help in setting up adequate and specific clinical treatments.

Estimated Glomerular Filtration Rate Bias in Participants with Severe Obesity Regardless of Deindexation

OBJECTIVE

Morbid obesity is associated with a higher independent risk of chronic kidney disease (CKD). Estimated glomerular filtration rate (eGFR) has been evaluated in a limited number of study participants with severe obesity.

METHODS

A total of 706 measured GFR (mGFR) results from 598 participants with obesity (BMI ≥ 35 kg/m² ) were retrospectively collected. The performance of the Modification of Diet in Renal Disease (MDRD) equation, Chronic Kidney Disease-Epidemiology (CKD-EPI) equation, and deindexed eGFR were compared with mGFR from the gold standard technique (inuline or iohexol), adjusted (mGFRr) or nonadjusted (mGFR) to body surface area. Absolute bias, precision, and accuracy were calculated.

RESULTS

Mean mGFRr (58 ± 31 mL/min/1.73 m² ) was significantly different from CKD-EPI and MDRD (P < 0.001). Mean mGFR (nonindexed) (70 ± 40 mL/min) was significantly higher than mGFRr (P < 0.001). eGFR showed important biases and low accuracies for CKD-EPI and MDRD (10.7 ± 10.7 and 12.2 ± 13.7 mL/min/1.73 m² ; 78% vs. 75% respectively). Deindexation worsened bias and accuracy 30% (percentage of GFR estimates within 30% of mGFRr or mGFR) between eGFR and mGFR.

CONCLUSIONS

eGFR overestimates mGFR and is associated with important biases and inaccuracies in patients with severe obesity, and deindexing eGFR worsens the overestimation. These findings may have important implications in examining kidney function in patients with obesity.

Can childhood obesity influence later chronic kidney disease?

Childhood overweight and obesity affects more and more children. Whilst associations of childhood overweight with later outcomes such as hypertension, diabetes and cardiovascular disease have been well documented, less is known about the association of childhood overweight and obesity with kidney disease. We review the existing evidence for the association of childhood obesity with markers of childhood and adult kidney disease. Whilst there is some evidence for an association, studies have not been able to distinguish between childhood being a sensitive time to develop later kidney problems, or whether observed associations of childhood obesity with poor outcomes are driven by greater lifelong exposure to obesity.

Renal hemodynamics and fatty acid uptake: effects of obesity and weight loss

Human studies of renal hemodynamics and metabolism in obesity are insufficient. We hypothesized that renal perfusion and renal free fatty acid (FFA) uptake are higher in subjects with morbid obesity compared with lean subjects and that they both decrease after bariatric surgery. Cortical and medullary hemodynamics and metabolism were measured in 23 morbidly obese women and 15 age- and sex-matched nonobese controls by PET scanning of [¹⁵O]-H₂O (perfusion) and 14(R,S)-[¹⁸F]fluoro-6-thia-heptadecanoate (FFA uptake). Kidney volume and radiodensity were measured by computed tomography, cardiac output by MRI. Obese subjects were re-studied 6 mo after bariatric surgery. Obese subjects had higher renal volume but lower radiodensity, suggesting accumulation of water and/or lipid. Both cardiac output and estimated glomerular filtration rate (eGFR) were increased by ~25% in the obese. Total renal blood flow was higher in the obese [885 (317) (expressed as median and interquartile range) vs. 749 (300) (expressed as means and SD) ml/min of controls, P = 0.049]. In both groups, regional blood perfusion was higher in the cortex than medulla; in either region, FFA uptake was ~50% higher in the obese as a consequence of higher circulating FFA levels. Following weight loss (26 ± 8 kg), total renal blood flow was reduced (P = 0.006). Renal volume, eGFR, cortical and medullary FFA uptake were decreased but not fully normalized. Obesity is associated with renal structural, hemodynamic, and metabolic changes. Six months after bariatric surgery, the hemodynamic changes are reversed and the structural changes are improved. On the contrary, renal FFA uptake remains increased, driven by high substrate availability.

Diet and Chronic Kidney Disease

Kidney disease affects almost 15% of the US population, and prevalence is anticipated to grow as the population ages and the obesity epidemic continues due to Western dietary practices. The densely caloric Western diet, characterized by high animal protein and low fruit and vegetable content, has fueled the growth of chronic diseases, including chronic kidney disease. The glomerulus or filtering unit of the kidney is very susceptible to barotrauma, and diets high in animal protein impede the glomerulus' ability to protect itself from hemodynamic injury. High animal protein intake combined with low intake of fruits and vegetables also leads to a high net endogenous acid production requiring augmentation of ammonium excretion in order to prevent acidosis. This higher workload of the kidney to maintain a normal serum bicarbonate level may further exacerbate kidney disease progression. This article reviews the potential mechanisms whereby several key characteristics of the typical Western diet may impact kidney disease incidence and progression. Reducing animal protein intake and egg yolk and increasing intake of fruits and vegetables and fiber may prevent or delay end-stage renal disease, but few clinical trials have examined vegetarian diets for management of chronic kidney disease. More research is needed to determine optimal dietary patterns for the prevention of kidney disease and its progression.

Effect of different bariatric surgeries on dietary protein bioavailability in rats

Bariatric surgery may induce protein malabsorption, although data are scarce. This study aims at evaluating dietary protein bioavailability after different bariatric surgeries in rats. Diet-induced obese Wistar rats were operated for vertical sleeve gastrectomy (VSG) or Roux-en-Y gastric bypass (RYGB). The control group was composed of pair-fed, sham-operated rats (Sham). Two weeks after surgery, rats were fed a ¹⁵N protein meal. Protein bioavailability was assessed by determination of ¹⁵N recovery in the gastrointestinal tract and organs 6 h after the meal. Fractional protein synthesis rate (FSR) was assessed using a flooding dose of ¹³C valine. Weight loss was the highest in RYGB rats and the lowest in Sham rats. Surprisingly, RYGB (95.6 ± 0.7%) improved protein digestibility (P = 0.045) compared with Sham (93.5 ± 0.5%) and VSG (93.8 ± 0.6%). In contrast, ¹⁵N retained in the liver (P = 0.001) and plasma protein (P = 0.037) was lower than in Sham, with a similar trend in muscle (P = 0.052). FSR was little altered by bariatric surgery, except for a decrease in the kidney of RYGB (P = 0.02). The ¹⁵N distribution along the small intestinal tissue suggests that dietary nitrogen was considerably retained in the remodeled mucosa of RYGB compared with Sham. This study revealed that in contrast to VSG, RYGB slightly improved protein digestibility but altered peripheral protein bioavailability. This effect may be ascribed to a higher uptake of dietary amino acids by the remodeled intestine.NEW & NOTEWORTHY Using a sensitive ¹⁵N meal test, we found that gastric bypass slightly improved protein digestibility compared with sleeve gastrectomy or control but, in contrast, lowered protein retention in the liver and muscles. This paradox can be due to a higher uptake of dietary nitrogen by the intestinal mucosa that was hypertrophied. This study provides new insight on the digestive and metabolic fate of dietary protein in different models of bariatric surgery in rats.

Perirenal fat thickness is associated with metabolic risk factors in patients with chronic kidney disease

Background

Adipose tissue accumulation in specific body compartments has been associated with diabetes, hypertension and dyslipidemia. Perirenal fat (PRF) may lead to have direct lipotoxic effects on renal function and intrarenal hydrostatic pressure. This study was undertaken to explore the association of PRF with cardiovascular risk factors and different stages of chronic kidney disease (CKD).

Methods

We studied 103 patients with CKD of different stages (1 to 5). PRF was measured by B-mode renal ultrasonography in the distal third between the cortex and the hepatic border and/or spleen.

Results

The PRF thickness was greater in CKD patients with impaired fasting glucose than in those with normal glucose levels (1.10 ± 0.40 cm vs. 0.85 ± 0.39 cm, P < 0.01). Patients in CKD stages 4 and 5 (glomerular filtration rate [GFR] < 30 mL/min/1.73 m²) had the highest PRF thickness. Serum triglyceride levels correlated positively with the PRF thickness; the PRF thickness was greater in patients with triglyceride levels ≥ 150 mg/dL (1.09 ± 0.40 cm vs. 0.86 ± 0.36 cm, P < 0.01). In patients with a GFR < 60 mL/min/1.73 m², uric acid levels correlated positively with the PRF thickness (P < 0.05).

Conclusion

In CKD patients, the PRF thickness correlated significantly with metabolic risk factors that could affect kidney function.

Association between preterm birth and the renin-angiotensin system in adolescence: influence of sex and obesity

OBJECTIVES

Preterm birth appears to contribute to early development of cardiovascular disease, but the mechanisms are unknown. Prematurity may result in programming events that alter the renin-angiotensin system. We hypothesized that prematurity is associated with lower angiotensin-(1-7) in adolescence and that sex and obesity modify this relationship.

METHODS

We quantified angiotensin II and angiotensin-(1-7) in the plasma and urine of 175 adolescents born preterm and 51 term-born controls. We used generalized linear models to estimate the association between prematurity and the peptides, controlling for confounding factors and stratifying by sex and overweight/obesity.

RESULTS

Prematurity was associated with lower plasma angiotensin II (β: -5.2 pmol/l, 95% CI: -10.3 to -0.04) and angiotensin-(1-7) (-5.2 pmol/l, 95% CI: -8.4 to -2.0) but overall higher angiotensin II:angiotensin-(1-7) (3.0, 95% CI: 0.9-5.0). The preterm-term difference in plasma angiotensin-(1-7) was greater in women (-6.9 pmol/l, 95% CI: -10.7 to -3.1) and individuals with overweight/obesity (-8.0 pmol/l, 95% CI: -12.2 to -3.8). The preterm-term difference in angiotensin II:angiotensin-(1-7) was greater among those with overweight/obesity (4.4, 95% CI: 0.6-8.1). On multivariate analysis, prematurity was associated with lower urinary angiotensin II:angiotensin-(1-7) (-0.13, 95% CI: -0.26 to -0.003), especially among the overweight/obesity group (-0.38, 95% CI: -0.72 to -0.04).

CONCLUSION

Circulating angiotensin-(1-7) was diminished whereas urinary angiotensin-(1-7) was increased relative to angiotensin II in adolescents born preterm, suggesting prematurity may increase the risk of cardiovascular disease by altering the renin-angiotensin system. Perinatal renin-angiotensin system programming was more pronounced in women and individuals with overweight/obesity, thus potentially augmenting their risk of developing early cardiovascular disease.

Urine and plasma concentrations of amino acids and plasma vitamin status differ, and are differently affected by salmon intake, in obese Zucker fa/fa rats with impaired kidney function and in Long-Evans rats with healthy kidneys

Kidney function affects amino acid metabolism and vitamin status. The aims of the present study were to investigate urine and plasma concentrations of amino acids as well as plasma vitamin status in rats with impaired renal function (Zucker fa/fa rats) and in rats with normal kidney function (Long-Evans rats), and to explore the effects of salmon intake on these parameters and potential biomarkers of salmon intake in both rat strains. Male rats were fed diets with casein as sole protein source (control diet) or 25 % protein from baked salmon and 75 % casein for 4 weeks. Urine concentrations of markers of renal function and most amino acids and plasma concentrations of most vitamins were higher, and plasma concentrations of several amino acids including arginine, total glutathione and most tryptophan metabolites were lower in Zucker fa/fa rats compared with Long-Evans rats fed the control diet. Concentrations of kidney function markers were lower after salmon intake only in Zucker fa/fa rats. A trend towards lower urine concentrations of amino acids was seen in both rat strains fed the salmon diet, but this was more pronounced in Long-Evans rats and did not reflect the dietary amino acid content. Urine 1-methylhistidine, 3-methylhistidine, trimethylamineoxide and creatine concentrations, and plasma 1-methylhistidine and creatine concentrations were higher after salmon intake in both rat strains. To conclude, concentrations of amino acids in urine and plasma as well as vitamin status were different in Zucker fa/fa and Long-Evans rats, and the effects of salmon intake differed by rat strain for some of these parameters.

Hand-Assisted Nephrectomy Predisposes Incisional Herniation in Obese Living Donors

BACKGROUND

Living kidney donation from donors with a body mass index (BMI) over 30 can bring risks for the donor and the recipients. In this retrospective study, we evaluated the effect of a donor's obesity on a donor's long-term surveillance and the recipient outcomes.

METHOD

We performed hand-assisted retroperitoneoscopic donor nephrectomy in 565 living kidney transplantations between February 2009 and December 2015. One hundred fifty-two donors (26.9%) had a BMI > 30 and were described as the obese group. Four hundred thirteen donors (73.1%) were described as the nonobese group and had a BMI < 30. Incision to kidney removal time, mean follow-up period, postoperative complications, weight gained after surgery, and serum creatinine level (postop day 1-end of follow-up) were recorded for the donors. Serum creatinine level (postop day 5-end of follow-up) and immediate function of transplanted kidney were recorded for the recipients.

RESULTS

The obese donors were older, and the female sex was dominant. Mean incision to kidney removal period was longer in the obese patients (P = .012). The mean follow-up period was 49.97 ± 28.40 months for the donors. There was no significant difference in donor kidney function between the groups. The incidence of herniation was significantly higher in the obese group (P = .021). There was no significant difference between the recipient early and late serum creatinine levels and slow and delayed graft functions after the transplantation.

CONCLUSION

Postoperative kidney functions concerning the outcomes of the obese and nonobese living donors were similar in our series. Donor BMI had no influence on early and late kidney functions of the recipients. There was no difference in postoperative complications, except incisional hernia, that was statistically more significant in the obese donors.

Protein intake is not associated with progression of diabetic kidney disease in patients without macroalbuminuria

BACKGROUND

Diabetic kidney disease is an important problem in individuals with diabetes. The effect of dietary protein intake on the renal function of patients with diabetes is controversial. Here, we sought to clarify the association between dietary protein intake and changes in the urinary albumin excretion (UAE) or estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes.

METHODS

In this retrospective cohort study, we included 144 patients (70 men, mean ± standard deviation of age 64 ± 10 years, and median (interquartile range) of UAE 15.0 (7.0-38.9) mg/gCr) without an eGFR less than 30 mL/min/1.73 m² and/or UAE greater than or equal to 300 mg/gCr. Changes in the UAE or eGFR were defined as (logarithms [UAE+1] or eGFR at follow-up minus logarithms [UAE+1] or eGFR at baseline examination)/follow-up duration (years). Habitual protein intake was estimated by a self-administered diet history questionnaire.

RESULTS

The median follow-up duration was 5 years. Protein intake (g/kg ideal body weight/day) was not associated with the change in the UAE (r = -0.130, p = 0.120) or change in the eGFR (r = -0.074, p = 0.381). Multiple linear regression analyses showed that after adjusting for covariates, the patients' protein intake was not associated with change in their UAE (standardized regression coefficient: 0.044, p = 0.732) or change in their eGFR (standardized regression coefficient: 0.250, p = 0.085).

CONCLUSIONS

Dietary protein intake does not influence changes in the UAE or eGFR among patients with type 2 diabetes without macroalbuminuria.

High-fat diet-induced obesity causes an inflammatory microenvironment in the kidneys of aging Long-Evans rats

Background

Obesity is a risk factor for chronic kidney disease (CKD). While the exact mechanisms remain unclear, inflammation may be a consequence of obesity that directly impacts the kidneys. The aim of this study was to examine the inflammatory status of the kidneys and potential ongoing renal damage, i.e., tubular damage and fibrosis after long-term obesity maintained through persistent consumption of a high-fat diet (HFD).

Results

Twenty-four-week-old male Long-Evans (LEV) rats were continuously fed a control diet (CD) or HFD for 51 weeks. The mean body weight was higher in HFD-fed rats than in control diet-fed rats and markedly elevated during the last 24 weeks. Blood analyses revealed no substantial alterations in renal functional parameters by HFD consumption but a substantial increase in creatine kinase, a muscle loss marker. Magnetic resonance imaging (MRI) was utilized to quantify rat quadriceps muscle mass. The data showed that HFD-induced obesity in LEV rats was accompanied by minor decreases in muscle mass and strength at 75 weeks of age. Rat kidney inflammatory status was evaluated using histological and immunohistological techniques. The number of foci with immune cell infiltrates and infiltrating monocytes/macrophages was significantly increased in HFD-fed rat kidneys at week 75. Renal fibrosis parameters, including glomerulosclerosis and tubular damage, were also markedly increased in renal tissues from HFD-fed rats compared to the controls. The significant increase in tubular protein casts in HFD-fed rat tissues indicated that renal function was already disturbed. Rat kidney inflammatory status was further evaluated using the simultaneous profiling of twenty-two inflammatory markers in kidney tissue extracts. Consistently, MCP-1 and eotaxin (CCL11) levels were elevated in obese LEV rat kidneys.

Conclusions

Compared to CD-fed rats, HFD-fed obese LEV rats show significant damage of renal structures with aging. These subtle changes may sensitize the kidneys to the development of progressive CKD.

Electronic supplementary material

The online version of this article (10.1186/s12950-019-0219-x) contains supplementary material, which is available to authorized users.

Obesity and long-term mortality risk among living kidney donors

BACKGROUND

Body mass index of living kidney donors has increased substantially. Determining candidacy for live kidney donation among obese individuals is challenging because many donation-related risks among this subgroup remain unquantified, including even basic postdonation mortality.

METHODS

We used data from the Scientific Registry of Transplant Recipients linked to data from the Centers for Medicare and Medicaid Services to study long-term mortality risk associated with being obese at the time of kidney donation among 119,769 live kidney donors (1987-2013). Donors were followed for a maximum of 20 years (interquartile range 6.0-16.0). Cox proportional hazards estimated the risk of postdonation mortality by obesity status at donation. Multiple imputation accounted for missing obesity data.

RESULTS

Obese (body mass index ≥ 30) living kidney donors were more likely male, African American, and had higher blood pressure. The estimated risk of mortality 20 years after donation was 304.3/10,000 for obese and 208.9/10,000 for nonobese living kidney donors. Adjusting for age, sex, race/ethnicity, blood pressure, baseline estimated glomerular filtration rate, relationship to recipient, smoking, and year of donation, obese living kidney donors had a 30% increased risk of long-term mortality compared with their nonobese counterparts (adjusted hazard ratio: 1.32, 95% CI: 1.09-1.60, P = .006). The impact of obesity on mortality risk did not differ significantly by sex, race or ethnicity, biologic relationship, baseline estimated glomerular filtration rate, or among donors who did and did not develop postdonation kidney failure.

CONCLUSION

These findings may help to inform selection criteria and discussions with obese persons considering living kidney donation.