Effect of drastic weight loss after bariatric surgery on renal parameters in extremely obese patients: long-term follow-up

Protective role for kidney TREM2high macrophages in obesity- and diabetes-induced kidney injury

Diabetic kidney disease (DKD), the most common cause of kidney failure, is a frequent complication of diabetes and obesity, and yet to date, treatments to halt its progression are lacking. We analyze kidney single-cell transcriptomic profiles from DKD patients and two DKD mouse models at multiple time points along disease progression-high-fat diet (HFD)-fed mice aged to 90-100 weeks and BTBR ob/ob mice (a genetic model)-and report an expanding population of macrophages with high expression of triggering receptor expressed on myeloid cells 2 (TREM2) in HFD-fed mice. TREM2high macrophages are enriched in obese and diabetic patients, in contrast to hypertensive patients or healthy controls in an independent validation cohort. Trem2 knockout mice on an HFD have worsening kidney filter damage and increased tubular epithelial cell injury, all signs of worsening DKD. Together, our studies suggest that strategies to enhance kidney TREM2high macrophages may provide therapeutic benefits for DKD.

Integrated miRNA-mRNA Analysis Reveals Critical miRNAs and Targets in Diet-Induced Obesity-Related Glomerulopathy

This study aimed to investigate obesity-related glomerulopathy (ORG) at cellular, structural, and transcriptomic levels. Thirty Wistar rats were randomized into two groups: 15 rats were fed with a standard diet (SD-rats), and 15 rats were fed with a high-fat diet (HFD-rats). After 10 weeks, the weight, kidney function, histological features, and transcriptomic changes were assessed. HFD-rats gained significantly more weight (55.8% vs. 29.2%; p < 0.001) and albuminuria (10,384.04 ng/mL vs. 5845.45 ng/mL; p < 0.001) compared to SD-rats. HFD-rats exhibited early stages of ORG, with predominant mesangial matrix increase and podocyte hypertrophy (PH). These lesions correlated with differentially expressed (DE) genes and miRNAs. Functional analysis showed that miR-205, which was DE in both the kidneys and urine of HFD-rats, negatively regulated the PTEN gene, promoting lipid endocytosis in podocytes. The downregulation of PTEN was proved through a higher PTEN/nephrin ratio in the SD-rats and the presence of lipid vacuoles in HFD-podocytes. This study has found a specific targetome of miRNAs and gene expression in early stages of ORG. Also, it emphasizes the potential value of miR-205 as a urinary biomarker for detecting podocyte injury in ORG, offering a tool for early diagnosis, and opening new avenues for future therapeutic research of obesity-related glomerulopathy.

Podocytes from hypertensive and obese mice acquire an inflammatory, senescent, and aged phenotype

Patients with hypertension or obesity can develop glomerular dysfunction characterized by injury and depletion of podocytes. To better understand the molecular processes involved, young mice were treated with either deoxycorticosterone acetate (DOCA) or fed a high-fat diet (HFD) to induce hypertension or obesity, respectively. The transcriptional changes associated with these phenotypes were measured by unbiased bulk mRNA sequencing of isolated podocytes from experimental models and their respective controls. Key findings were validated by immunostaining. In addition to a decrease in canonical proteins and reduced podocyte number, podocytes from both hypertensive and obese mice exhibited a sterile inflammatory phenotype characterized by increases in NLR family pyrin domain containing 3 (NLRP3) inflammasome, protein cell death-1, and Toll-like receptor pathways. Finally, although the mice were young, podocytes in both models exhibited increased expression of senescence and aging genes, including genes consistent with a senescence-associated secretory phenotype. However, there were differences between the hypertension- and obesity-associated senescence phenotypes. Both show stress-induced podocyte senescence characterized by increased p21 and p53. Moreover, in hypertensive mice, this is superimposed upon age-associated podocyte senescence characterized by increased p16 and p19. These results suggest that senescence, aging, and inflammation are critical aspects of the podocyte phenotype in experimental hypertension and obesity in mice.NEW & NOTEWORTHY Hypertension and obesity can lead to glomerular dysfunction in patients, causing podocyte injury and depletion. Here, young mice given deoxycorticosterone acetate or a high-fat diet to induce hypertension or obesity, respectively. mRNA sequencing of isolated podocytes showed transcriptional changes consistent with senescence, a senescent-associated secretory phenotype, and aging, which was confirmed by immunostaining. Ongoing studies are determining the mechanistic roles of the accelerated aging podocyte phenotype in experimental hypertension and obesity.

Obesity, Hyperfiltration, and Early Kidney Damage: A New Formula for the Estimation of Creatinine Clearance

CONTEXT

Glomerular hyperfiltration may represent a direct pathogenetic link between obesity and kidney disease. The most widely used methods to estimate creatine clearance such as Cockroft-Gault (CG), Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) have not been validated in subjects with obesity.

OBJECTIVE

The performance of prediction formulas was compared with measured creatinine clearance (mCrCl) in subjects with obesity.

METHODS

The study population included 342 patients with obesity (mean BMI 47.6 kg/m2) without primary kidney disease. A urine collection was performed over 24 hours for measurement of CrCl.

RESULTS

mCrCl increased with body weight. The CG formula showed an overestimation at high CrCl, whereas an underestimation resulted from CKD-EPI and MDRD. To improve the accuracy of estimated CrCl (eCrCl), a new CG-based formula was developed:53+0.7×(140-Age)×Weight/(96xSCr)×(0.85iffemale)A cut-off point for BMI of 32 kg/m2 was identified, at which the new formula may be applied to improve eCrCl.

CONCLUSION

In patients with obesity the glomerular filtration rate increases with body weight, and it is associated with the presence of albuminuria, suggesting an early kidney injury. We propose a novel formula that improves the accuracy of eCrCl to avoid missed diagnoses of hyperfiltration in patients with obesity.

The Effect of Chronic Kidney Disease or End-stage Kidney Disease on Perioperative Outcomes and Healthcare Utilization in Patients Undergoing Bariatric Surgery

BACKGROUND

As chronic kidney disease (CKD) has a higher prevalence in patients with obesity, there is an increasing need to understand the safety of bariatric surgery for patients with advanced CKD. This study determined if short-term bariatric surgical outcomes and healthcare utilization differ in patients with advanced CKD.

METHODS

A retrospective analysis of the Healthcare Cost and Utilization Project National Inpatient Sample (NIS) was performed. Patients with obesity who underwent bariatric surgery from 2015 to 2019 were included. Patients without CKD, with CKD, and end-stage kidney disease (ESKD) were compared for outcome differences. Univariate and multivariable regression was used to determine the association between perioperative outcomes to CKD status.

RESULTS

The unadjusted analysis found significantly higher mortality and overall complication rate in CKD and ESKD patients, however, after adjustment for confounders, only the ICU admission rate remained significantly higher for patients CKD compared to non-CKD patients (odds ratio 4.21, 95% CI [3.29-5.39]). Length of stay was longer for patients with CKD (mean difference (MD) 0.14 days, 95% CI, [0.04, 0.23]) and patients with ESKD (MD 0.27 days, 95% CI, [0.10, 0.43]) compared to non-CKD patients. Patients with ESKD had higher admission costs compared to non-CKD patients (MD $1982.65).

CONCLUSION

Patients with CKD and ESKD have increased healthcare utilization and higher rates of ICU admission after bariatric surgery compared to non-CKD patients. Otherwise, there is no significant difference in other post-operative complications and mortality. Bariatric surgery may therefore be safely offered to this patient population in hospitals with on-site ICU capacity.

Factors influencing bariatric surgery outcomes

The outcomes of bariatric surgery, while often impressive, are not universally satisfactory; they vary from patient to patient and from operation to operation. Between 20-30% of patients experience suboptimal weight loss or substantial weight regain early in their postoperative course. Confronted with this chronic disease, and given that failures are difficult to manage, it is essential to better characterize obesity preoperatively, considering other metrics beyond just the body mass index (BMI), to select the best candidates for surgery and optimize the benefit/risk ratio. Based on the data of the most recent studies on bariatric surgery, our objective is to identify the predictive factors of weight loss as well as the risk factors of failure. Our analysis indicates that the choice of the surgical technique, age, initial BMI, ethnic origin, the presence of eating disorders and metabolic factors all have an impact on weight-loss outcomes after bariatric surgery. Thus, it is of major importance to carefully select patients during a preoperative multidisciplinary discussion in order to optimize weight loss and metabolic outcomes.

Novel insights in classic versus relative glomerular hyperfiltration and implications on pharmacotherapy

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) assessment and its estimation (eGFR) is a long-lasting challenge in medicine and public health. Current eGFR formulae are indexed for standardized body surface area (BSA) of 1.73 m2, ignoring persons and populations wherein the ratio of BSA or metabolic rate to nephron number might be different, due to increased BSA, increased metabolic rate or reduced nephron number. These equations are based on creatinine, cystatin C or a combination of the two, which adds another confounder to eGFR assessment. Unusually high GFR values, also known as renal hyperfiltration, have not been well defined under these equations.

RECENT FINDINGS

Special conditions such as solitary kidney in kidney donors, high dietary protein intake, obesity and diabetes are often associated with renal hyperfiltration and amenable to errors in GFR estimation. In all hyperfiltration types, there is an increased intraglomerular pressure that can be physiologic, but its persistence over time is detrimental to glomerulus leading to progressive glomerular damage and renal fibrosis. Hyperfiltration might be underdiagnosed due to BSA standardization embedded in the formula. Hence, timely intervention is delayed. Reducing intraglomerular pressure in diabetes can be achieved by SGLT2 inhibitors or low protein diet to reverse the glomerulopathy process.

SUMMARY

Accurate identification of glomerular hyperfiltration as a pre-CKD condition needs accurate estimation of GFR in the above normal range should establish a threshold for timely intervention.

Bariatric surgery for diabetic comorbidities: A focus on hepatic, cardiac and renal fibrosis

Continuously rising trends in diabetes render this disease spectrum an epidemic proportion worldwide. As the disease progresses, the pathological effects of diabetes may impair the normal function of several vital organs, eventually leading to increase the risk of other diabetic comorbidities with advanced fibrosis such as non-alcoholic fatty liver disease, diabetic cardiomyopathy, and diabetic kidney disease. Currently, lifestyle changes and drug therapies of hypoglycemic and lipid-lowering are effective in improving multi-organ function, but therapeutic efficacy is difficult to maintain due to poor compliance and drug reactions. Bariatric surgery, including sleeve gastrectomy and Roux-en-Y gastric bypass surgery, has shown better results in terms of prognosis for diabetes through long-term follow-up. Moreover, bariatric surgery has significant long-term benefits on the function of the heart, liver, kidneys, and other organs through mechanisms associated with reversal of tissue fibrosis. The aim of this review is to describe the impact of type 2 diabetes mellitus on hepatic, cardiac and renal fibrosis and to summarize the potential mechanisms by which bariatric surgery improves multiple organ function, particularly reversal of fibrosis.

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.

The SSLepR mutant rat represents a novel model to study obesity-induced renal injury before puberty

Prepubertal obesity (PPO) has emerged as a major health problem over the past few decades and is a risk factor for the development of proteinuria. The current study investigated whether the development of renal injury in the obese SSLepR mutant strain occurs before puberty. When determining the temporal changes in serum sex hormones in female and male SS and SSLepR mutant rats between 4 and 10 wk of age, we only observed significant increases in estradiol and testosterone levels in female and male SS rats at 10 wk of age than at 4 wk of age. The results suggest that studying both strains between 4 and 8 wk of age is appropriate to study the effects of PPO on renal injury in this model. Proteinuria was significantly higher in SSLepR mutant rats as opposed to the values observed in SS rats at 8 wk of age, and we did not observe any sex differences in proteinuria in either strain. The kidneys from the SSLepR mutant rats displayed significant glomerular and tubular injury and renal fibrosis versus the values measured in SS rats without any sex differences. Overall, we observed increased immune cell infiltration in the kidneys from SSLepR mutant rats compared with SS rats. Interestingly, female SSLepR mutant rats displayed significant increases in not only M1 macrophages (proinflammatory) but also M2 macrophages (anti-inflammatory) versus male SSLepR mutant rats. These results suggest the SSLepR mutant rat may be a useful model to study early progression of obesity-related renal injury before the onset of puberty.

Glomerular hyperfiltration

Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.

Improvement of Renal Function After Bariatric Surgery: a Systematic Review and Meta-analysis

BACKGROUND/OBJECTIVE

The effect of bariatric surgery in renal function varies and the postoperative benefit time point remains unclear. We aim to assess the changes of renal function after bariatric surgery (BS) in different postoperative periods and subgroups.

METHODS

We searched the databases of PubMed and Cochrane from inception to December 14, 2020. Articles included in the study were drawn from all recipients of BS that provided assessments of renal function pre and post-surgery. Meta-analysis was performed to compare glomerular filtration rate (GFR), serum creatinine, albumin-to-creatinine ratio (ACR), and albuminuria before and after BS.

RESULTS

The study included 49 articles involving 8515 patients. Compared with pre-operative renal function, the overall analysis showed that bariatric surgery significantly reduced serum creatinine levels, ACR, and albuminuria. There was significant increase of GFR in the CKD subgroup, yet a noticeable decrease in the hyperfiltration subgroup. The most significant improvement in GFR was seen 6-12 months after BS, while ACR dropped most dramatically 12-24 months after BS.

CONCLUSIONS

Bariatric surgery can improve renal function in obese patients with kidney dysfunction, especially 1 year after surgery.

Renoprotective role of bariatric surgery in patients with established chronic kidney disease

Background

Bariatric surgery (BS) has been postulated as the most effective measure for weight reduction. Weight loss improves metabolic parameters and exerts changes in renal function that lead to the amelioration of absolute or relative glomerular hyperfiltration, a condition that may be renoprotective in the long term. However, few studies have demonstrated the influence of BS in patients with severe obesity and chronic kidney disease (CKD). Our objective was to analyse the evolution of renal function, adipose tissue–derived molecules and inflammatory parameters in patients with CKD after BS.

Methods

This is an observational and prospective study. Thirty patients were screened and 12 were included between January 2016 and January 2018 with a 24-month follow-up. Glomerular filtration rate (GFR) was determined by plasma iohexol clearance. Adipokines, cytokines, circulating hormones and fibrotic parameters were evaluated before and 12 months after BS using the Bioplex system.

Results

The mean age was 50.6 years and 58.3% were males. Seven patients had a body mass index >40 kg/m² and 66.7% were diabetic. Twenty-four months following BS there was a significant decrease in body weight (36.4%). Proteinuria decreased by 63.7 ± 28.2%. Measured GFR significantly diminished from before surgery to Month 24 after surgery (94 ± 44 to 79 ± 44 mL/min, P = 0.03). There was a significant decrease in adipocyte-derived molecules (leptin and vifastin) as well as in pro-inflammatory cytokines [interleukin (IL)-1β, tumour necrosis factor α, IL-6 and monocyte chemoattractant protein-1] and other circulating factors (vascular endothelial growth factor and transforming growth factor β isoforms).

Conclusions

BS is an effective option to prevent kidney damage in obese subjects with CKD due to the improvement of glomerular hyperfiltration, adipocyte cytokines metabolic and inflammatory parameters.

Impact of Bariatric Surgery on Male Sexual Health: a Prospective Study

BACKGROUND

Obesity is a worldwide prevalent problem which negatively affects most of the human body systems. Male sexual dysfunction is a frequent problem in obese individuals. Nowadays, bariatric surgery is the most successful way for the management of morbid obesity. Recent research has concluded that it has a significant improving effect on sexual function.

AIM OF THE STUDY

This study aimed to assess the long-term effect of bariatric surgery on male sexual function.

PATIENTS AND METHODS

Sixty-six male patients indicated for bariatric surgery were enrolled in this prospective study. Only forty-eight of them completed the study. Patients were invited to fill the International Index of Erectile Function (IIEF) questionnaire twice, preoperatively (T1) and 12 months postoperatively (T2). Simultaneously, patients' serum testosterone levels were assayed.

RESULTS

At T2, the patients showed highly significant increase in the IIEF scores and the serum testosterone levels (p<0.001). Only weight and BMI were significant predictors of the IIEF scores. The same factors as well as the patients' age were predictors of the serum testosterone levels.

CONCLUSION

Bariatric surgery improves male sexual health. It is associated with significant increase in IIEF score and serum testosterone levels.

The Impact of Bariatric Surgery on Renal Function: a Retrospective Analysis of Short-Term Outcomes

PURPOSE

Obesity and diabetes mellitus are now leading causes of chronic kidney disease. Our study investigated the effects of bariatric surgery on estimated glomerular filtration (eGFR) and urinary microalbumin/creatinine ratio (ACR) in morbidly obese patients.

MATERIALS AND METHODS

The clinical materials for patients who underwent bariatric surgery were retrospectively analyzed with a 6-month follow-up period between January 1, 2018, and June 1, 2020. The eGFR (ml/min) was calculated using the Cockcroft-Gault formula equation. The urinary ACR was measured during the follow-up. Body mass index (BMI, kg/m²), percent weight loss (%WL), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were recorded during the follow-up.

RESULTS

Sixty-one patients who underwent bariatric surgery-laparoscopic Roux-en-Y gastric bypass (LRYGB; n = 22) and laparoscopic sleeve gastrectomy (LSG; n = 39)-were included in this study. The eGFR of both groups decreased at the follow-up outpatient visits (p < 0.001), although eGFR did not differ between the two groups. Unexpectedly, the ACR increased in the first month after LSG (p < 0.01) but decreased with a descending trend with no significant difference (p > 0.05) throughout the remaining follow-up period. Interestingly, ACR showed a descending trend with no significant difference during the follow-up in the LRYGB group (p > 0.05). The SBP and DBP decreased after bariatric surgery, with no significant difference between the two groups (p > 0.05).

CONCLUSION

Bariatric surgery is associated with improvements in postoperative renal function 6 months following surgery. The different alterations in ACR following LSG and LRYGB procedures demonstrate the underlying mechanism.

Feasibility and impact of laparoscopic sleeve gastrectomy after renal transplantation on comorbidities, graft function and quality of life

Background

The aim of this study is to clarify the feasibility and effect of laparoscopic sleeve gastrectomy (LSG) on comorbidities, graft function and quality of life in patients who underwent renal transplantation (RT).

Methods

This is a retrospective review of five patients who underwent LSG after RT. Demographic data, anthropometric parameters, the effect on comorbidities, postoperative course, immunosuppressive medications, causes of RT, renal function, the survival of graft, and quality of life after SG in obese patients with a history of RT were assessed using BAROS–Moorhead–Ardelt survey

Results

From September 2015 to September 2019, 5 renal transplant patients underwent LSG; three female, and two male. Median body mass index (BMI) decreased from 42.17 kg/m² (range 36–55) before surgery to 28.16 kg/m² (range 25–42) after surgery. Improvement in blood pressure, triglyceride, and cholesterol levels was observed, and all cases were able to decrease their medications. Insulin was stopped and replaced with linagliptin in all diabetic patients. Graft function improved, and proteinuria level decreased in all cases. All patients reported to have an excellent quality of life.

Conclusion

LSG showed excellent outcomes in this high-risk group of patients regarding comorbidities, graft function and quality of life

Bariatric Surgery Induces a Differential Effect on Plasma Aldosterone in Comparison to Dietary Advice Alone

BACKGROUND AND OBJECTIVES

The pathophysiological mechanisms linking weight loss to blood pressure (BP) reduction are not completely understood. The objective of this study was to compare the effect of weight loss after Roux-en-Y gastric bypass (RYGB) on BP, renin-angiotensin-aldosterone system (RAAS), and urinary electrolytes excretion to those of dietary advice.

METHODS

This was a case-control prospective study including obese patients referred for RYGB (cases) and obese receiving diet advice only (controls). Ambulatory BP, plasma renin activity (PRA), plasma aldosterone concentration (PAC), and urinary electrolytes were measured before (M0) and after intervention (M3: 3 months and M12: 12 months).

RESULTS

Twenty-five patients were included in the RYGB group and twelve patients in the control group. After 12 months, weight loss (-42 ± 11.5 vs -12.3 ± 6.3 kg in the control group, p=0.001) and decrease in PAC were more pronounced in the RYGB group (-34 ± 76 vs +14 ± 45 pg/ml in the control group, p=0.002). There was no difference in PRA between both groups (-0.08 ± 1.68 vs 0.01 ± 0.37 ng/ml/h, p=0.31). Sodium excretion was more marked in the RYGB group after 3 months only (-89 ± 14.9 vs -9.9 ± 27.9 mmol/day, p=0.009). The decrease in SBP was similar between both groups (-6.9 ± 9.9 vs -7.1 ± 11.9 mmHg in the control group, p=0.96).

CONCLUSIONS

Bariatric-induced weight loss induces a progressive decrease in PAC independently of PRA and sodium excretion. Whether this decrease in PAC affects target organ damage in the long term remains to be determined.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT02218112.

Reduction of oxidative stress on DNA and RNA in obese patients after Roux-en-Y gastric bypass surgery-An observational cohort study of changes in urinary markers

Increased oxidative stress in obesity and diabetes is associated with morbidity and mortality risks. Levels of oxidative damage to DNA and RNA can be estimated through measurement of 8-oxo-7,8-dihydro-2´-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) in urine. Both markers have been associated with type 2 diabetes, where especially 8-oxoGuo is prognostic for mortality risk. We hypothesized that Roux-en-Y gastric bypass (RYGB) surgery that has considerable effects on bodyweight, hyperglycemia and mortality, might be working through mechanisms that reduce oxidative stress, thereby reducing levels of the urinary markers. We used liquid chromatography coupled with tandem mass spectrometry to analyze the content of 8-oxodG and 8-oxoGuo in urinary samples from 356 obese patients treated with the RYGB-procedure. Mean age (SD) was 44.2 (9.6) years, BMI was 42.1 (5.6) kg/m2. Ninety-six (27%) of the patients had type 2 diabetes. Excretion levels of each marker before and after surgery were compared as estimates of the total 24-hour excretion, using a model based on glomerular filtration rate (calculated from cystatin C, age, height and weight), plasma- and urinary creatinine. The excretion of 8-oxodG increased in the first months after RYGB. For 8-oxoGuo, a gradual decrease was seen. Two years after RYGB and a mean weight loss of 35 kg, decreased hyperglycemia and insulin resistance, excretion levels of both markers were reduced by approximately 12% (P < 0.001). For both markers, mean excretion levels were about 30% lower in the female subgroup (P < 0.0001). Also, in this subgroup, excretion of 8-oxodG was significantly lower in patients with than without diabetes. We conclude, that oxidative damage to nucleic acids, reflected in the excretion of 8-oxodG and 8-oxoGuo, had decreased significantly two years after RYGB-indicating that reduced oxidative stress could be contributing to the many long-term benefits of RYGB-surgery in obesity and type 2 diabetes.

Range of adiposity and cardiorenal syndrome

Obesity and obesity-related co-morbidities, diabetes mellitus, and hypertension are among the fastest-growing risk factors of heart failure and kidney disease worldwide. Obesity, which is not a unitary concept, or a static process, ranges from alterations in distribution to the amount of adiposity. Visceral adiposity, which includes intraabdominal visceral fat mass and ectopic fat deposition such as hepatic, cardiac, or renal, was robustly associated with a greater risk for cardiorenal morbidity than subcutaneous adiposity. In addition, morbid obesity has also demonstrated a negative effect on cardiac and renal functioning. The mechanisms by which adipose tissue is linked with the cardiorenal syndrome (CRS) are hemodynamic and mechanical changes, as well neurohumoral pathways such as insulin resistance, endothelial dysfunction, nitric oxide bioavailability, renin-angiotensin-aldosterone, oxidative stress, sympathetic nervous systems, natriuretic peptides, adipokines and inflammation. Adiposity and other associated co-morbidities induce adverse cardiac remodeling and interstitial fibrosis. Heart failure with preserved ejection fraction has been associated with obesity-related functional and structural abnormalities. Obesity might also impair kidney function through hyperfiltration, increased glomerular capillary wall tension, and podocyte dysfunction, which leads to tubulointerstitial fibrosis and loss of nephrons and, finally, chronic kidney disease. The development of new treatments with renal and cardiac effects in the context of type 2 diabetes, which improves mortality outcome, has highlighted the importance of CRS and its prevalence. Increased body fat triggers cellular, neuro-humoral and metabolic pathways, which create a phenotype of the CRS with specific cellular and biochemical biomarkers. Obesity has become a single cardiorenal umbrella or type of cardiorenal metabolic syndrome. This review article provides a clinical overview of the available data on the relationship between a range of adiposity and CRS, the support for obesity as a single cardiorenal umbrella, and the most relevant studies on the recent therapeutic approaches.

[Changes in metabolic parameters and glomerular filtration rate in patients with morbid obesity after bariatric surgery]

AIM

To study the effect of weight loss in the short term after bariatric surgery (BO) on metabolic parameters and glomerular filtration rate (GFR) in patients with morbid obesity.

MATERIALS AND METHODS

We studied 40 adult (over 18 years) patients with morbid obesity who underwent bariatric surgery. Metabolic indices and calculated GFR according to the CKD-EPI formula in patients before and after bariatric surgery were compared.

RESULTS

In the whole group of operated patients, the average body mass index (BMI) after surgery decreased from 45.8 to 30.5 kg/m2. In 11 (92%) patients with impaired carbohydrate metabolism, remission of diabetes mellitus was achieved and sugar-lowering drugs were canceled. In patients with baseline GFR90 ml/min/1.73 m2 after surgery, there is a tendency towards a decrease in GFR, probably due to a decrease in hyperfiltration. In patients with baseline GFR90 ml/min/1.73 m2 after surgery, a statistically significant increase in the level of GFR was noted. The greater metabolic efficacy of combined operations (mini-gastric bypass, biliopancreatic diversion) in relation to the correction of carbohydrate and fat metabolism was revealed.

CONCLUSION

Obesity is a modifiable risk factor for decreased kidney function and the progression of chronic kidney disease. Bariatric surgery is an effective treatment for morbid obesity. The study proved the positive effect of weight loss after BO on renal function, including by improving the course of diseases associated with obesity.

Kidney injury molecule-1: A potential marker of renal recovery after laparoscopic sleeve gastrectomy

Background

Bariatric surgeries were reported to improve diabetes and hypertension; however, the effect on renal recovery has not been fully explored. The aim of this study was to evaluate the effect of laparoscopic sleeve gastrectomy (LSG) in morbidly obese patients on renal function, degree of albuminuria, and kidney injury molecule-1 (KIM-1) level.

Methods

This was a prospective observational study conducted at Mansoura University Hospitals from January to June 2017. Forty-four morbidly obese patients (29 females and 15 males) who met the 1991 WHO criteria for obesity surgery were included. Patients underwent surgical LSG for treatment of morbid obesity, and all were followed for 6 months after surgery. Demographic, clinical, and laboratory data were collected and compared before and after surgery. Primary endpoints were the differences of albuminuria, estimated glomerular filtration rate (eGFR) and serum KIM-1 between baseline (pre-surgery) and 6-month post-surgery values.

Results

Six-month post-surgery data showed significant reduction of body mass index, HbA1c, microalbuminuria, and serum KIM-1, and a significant increase in eGFR (all, P < 0.001). The serum KIM-1 level positively correlated with microalbuminuria and serum creatinine (r = 0.596, P = 0.001 and r = 0.402, P = 0.034, respectively). Postoperative data showed that patients with microalbuminuria had significantly lower eGFR and higher KIM-1 values than those without microalbuminuria (P = 0.003 and 0.049, respectively).

Conclusion

We showed potential benefits of LSG against obesity-associated kidney damage. This is evidenced by improving eGFR and reducing levels of both KIM-1 and microalbuminuria. The serum level of KIM-1 may be a potential marker for renal recovery after LSG.

Albuminuria in Patients with Morbid Obesity and the Effect of Weight Loss Following Bariatric Surgery

BACKGROUND AND OBJECTIVES

Patients with morbid obesity are at an increased risk for cardiovascular and renal complications, which are not only linked to traditional cardiovascular risk factors. Thus, we evaluated (a) the prevalence of albuminuria in non-diabetic and diabetic morbidly obese patients and (b) the effect of weight loss following bariatric surgery.

MATERIAL AND METHODS

We included 1307 patients (77% women, mean age 40 ± 12 years, BMI 45.6 ± 6.6 kg/m²) in a cross-sectional study. A subgroup (n = 318) was followed up for 2 years after bariatric surgery. Weight, cardiovascular risk markers and a 75-g glucose tolerance test were determined. Albuminuria was assessed by collecting 24-h urine on three consecutive days.

RESULTS

In the cross-sectional study, the prevalence of microalbuminuria was 16.0% (n = 209), of macroalbuminuria 3.1% (n = 41). The chi-square for the association of albuminuria and diabetes was 31.937 (p < 0.001). Of all patients with albuminuria, 42.0% exhibited normal glucose tolerance. In a multivariate regression analysis, systolic blood pressure (beta = 0.236; p < 0.001), log fasting insulin (beta = 0.309; p < 0.001) and log 2-h postprandial insulin (beta = - 0.173; p = 0.033) were predictive risk factors for albuminuria. Longitudinally, albumin excretion decreased significantly from 11.1 (6.4, 18.4 mg/24 h) to 7.8 mg/24 h (4.9, 13.0 mg/24 h; p < 0.001). In the group with albuminuria preoperatively, albumin excretion decreased from 65.7 (38.2, 147.1 mg/24 h) to 13.5 mg/24 h (8.4, 36.8 mg/24 h; p < 0.001). After adjusting for age, sex and baseline albuminuria, patients with lower creatinine clearance showed a smaller decrease of albuminuria (beta = 0.117; p = 0.021).

CONCLUSION

A substantial portion of patients with morbid obesity exhibits microalbuminuria, nearly half of those present with normal glucose tolerance. After weight loss, we found a significant decrease of albuminuria, potentially indicating or even contributing to the known reduction of cardiovascular mortality after bariatric surgery.

Impact of a Community-Based Weight Loss Program on Renal Function

Introduction Obesity is associated with increased morbidity and mortality and is an independent risk factor for the development and progression of chronic kidney disease (CKD). This study investigated the effect of a community-based, lifestyle-focused, weight-loss intervention on renal function among participants at baseline following 12 weeks of therapy.  Methods A retrospective analysis of adults enrolled in a weight management program from 2009 to 2014 was conducted. Participants consumed at least 800 kilocalories per day in meal replacements, attended weekly behavioral education classes, and expended approximately 300 kilocalories per day in physical activity. The primary outcome was the association of weight loss and changes in glomerular filtration rate (GFR). Secondary outcomes included changes in blood sugar levels, lipid parameters, blood pressure, and the use of medication for hypertension and diabetes mellitus.  Results Of the 71 participants, 63.4% were female, the average weight was 289 pounds, the average body mass index (BMI) of 53, and baseline GFR 47 ml/min/1.73m². Following 12 weeks of the intervention, 76.1% of participants improved in CKD stage, 22.4% remained within the same stage, and 1.5% progressed to a higher stage (3A to 3B). Analysis revealed a correlation between weight loss and improved GFR (p=0.0006). Improvements were noted in blood sugar levels, blood pressure, and lipids (p<0.05). Medications were reduced in 61.8% of participants for hypertension and 83.3% for diabetes. Conclusions A significant correlation was observed between weight loss and improved renal function, with most participants improving in CKD stage. Participants also improved in markers of chronic disease and required fewer medications. When controlling for both diabetes and hypertension, the effect of improved renal function persisted.

SHORT TERM EFFECT OF LAPAROSCOPIC SLEEVE GASTRECTOMY ON CLINICAL, RENAL PARAMETERS AND URINARY NGAL LEVELS IN DIABETIC AND NON DIABETIC OBESITY

Background

Although diseases such as diabetes, hypertension, obstructive sleep apnea and hyperlipidemia are clearly documented as obesity associated diseases, it is not well-known whether obesity causes renal pathologies. The aim of the present study was to evaluate the effect of weight loss following laparoscopic sleeve gastrectomy on clinical, renal parameters and urinary Neutrophil gelatinase-associated lipocalin (NGAL) levels in diabetic and non-diabetic obese patients.

Methods

Nineteen morbidly obese patients (10 diabetic and 9 non diabetic) who underwent laparoscopic sleeve gastrectomy were evaluated clinically (anthropometric measurements) and biochemically before surgery and at 6 months from surgery.

Results

Significant decreases in weight, BMI, FPG, PPG and HbA1c levels were observed in the diabetic group when the baseline and 6th month parameters of the patients were compared. There was also a significant decrease in SBP and DBP. At 6^th month following laparoscopic sleeve gastrectomy, renal parameters such as creatinine, mAlb/creatinine, NGAL/creatinine did not differ in the diabetic group. In the nondiabetic group, serum creatinine levels were significantly decreased, but other renal parameters such as mAlb/creatinine and NGAL/creatinine were not significantly different.

Conclusions

Our findings revealed significant decreases in weight, body mass index and glycemic parameters after sleeve gastrectomy in diabetic and non-diabetic patients, while no significant alteration was noted in renal functions, urinary NGAL and microalbumin levels.

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.

Reduction in Urinary Chemokine (C-C Motif) Ligand 2 (CCL2) After Surgery-Induced Weight Loss

Kidney dysfunction, a deleterious effect of obesity, is now recognized as a relevant health risk. Chemokine (C-C Motif) Ligand 2 (CCL2) is one of the critical chemokines that play a vital role in the development of obesity-related metabolic disease. We aim to measure the changes in urinary CCL2 in our patients before and after their bariatric procedure and examine the correlation between CCL2 and renal function. A prospective cohort study was conducted at our teaching university hospital. Ethics approval was obtained from our institutional review board. Patients with a BMI of ≥37.5 kg/m² with no history of renal disease were included. They underwent single anastomosis gastric bypass (SAGB), Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG), all performed via laparoscopic approach. Venous blood and urine samples were obtained preoperatively and six months after surgery. A total of 58 patients were recruited, with SG being performed in 74.1% of patients. At six-months follow-up, median (IQR) body weight reduced from 101.35 kgs (20.25) to 76.95 kg (24.62) p < 0.001. The mean (SD) estimated glomerular filtration rate (eGFR) improved from 96.26 ± 14.97 to 108.06 ± 15.00 mL/min/1.73 m², p < 0.001. The median (IQR) urinary CCL2 levels reduced from 15.2 pg/ml (10.77) to 4.30 pg/ml (4.27) p < 0·001. There is a significant correlation between the reduction of BMI and the reduction of urinary CCL2 (r = −0.220, p = 0.048). We also found a significant correlation between the reduction of urinary CCL2 with the reduction of urine ACR (r = −0.240, p = 0.035). Urinary CCL2 is a promising biomarker that can be used to assess improvement in renal function in obese patients after bariatric surgery.

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.

The effect of a multidisciplinary weight loss program on renal circadian rhythm in obese adolescents

Adolescent obesity is a serious health problem associated with many comorbidities. Obesity-related alterations in circadian rhythm have been described for nocturnal blood pressure and for metabolic functions. We believe renal circadian rhythm is also disrupted in obesity, though this has not yet been investigated. This study aimed to examine renal circadian rhythm in obese adolescents before and after weight loss.In 34 obese adolescents (median age 15.7 years) participating in a residential weight loss program, renal function profiles and blood samples were collected at baseline, after 7 months, and again after 12 months of therapy. The program consisted of dietary restriction, increased physical activity, and psychological support. The program led to a median weight loss of 24 kg and a reduction in blood pressure. Initially, lower diurnal free water clearance (- 1.08 (- 1.40-- 0.79) mL/min) was noticed compared with nocturnal values (0.75 (- 0.89-- 0.64) mL/min). After weight loss, normalization of this inverse rhythm was observed (day - 1.24 (- 1.44-1.05) mL/min and night - 0.98 (- 1.09-- 0.83) mL/min). A clear circadian rhythm in diuresis rate and in renal clearance of creatinine, solutes, sodium, and potassium was seen at all time points. Furthermore, we observed a significant increase in sodium clearance. Before weight loss, daytime sodium clearance was 0.72 mL/min (0.59-0.77) and nighttime clearance was 0.46 mL/min (0.41-0.51). After weight loss, daytime clearance increased to 0.99 mL/min (0.85-1.17) and nighttime clearance increased to 0.78 mL/min (0.64-0.93).Conclusion: In obese adolescents, lower diurnal free water clearance was observed compared with nocturnal values. Weight loss led to a normalization of this inverse rhythm, suggesting a recovery of the anti-diuretic hormone activity. Both before and after weight loss, clear circadian rhythm of diuresis rate and renal clearance of creatinine, solutes, sodium, and potassium was observed.What is Known:• Obesity-related alterations in circadian rhythm have been described for nocturnal blood pressure and for metabolic functions. We believe renal circadian rhythm is disrupted in obesity, though this has not been investigated yet.What is New:• In obese adolescents, an inverse circadian rhythm of free water clearance was observed, with higher nighttime free water clearance compared with daytime values. Weight loss led to a normalization of this inverse rhythm, suggesting a recovery of the anti-diuretic hormone activity.• Circadian rhythm in diuresis rate and in the renal clearance of creatinine, solutes, sodium, and potassium was preserved in obese adolescents and did not change after weight loss.

Long-Term Impact of Bariatric Surgery on Renal Outcomes at a Community-Based Publicly Funded Bariatric Program: The Regina Bariatric Study

Background:

Obesity is recognized as an independent risk factor for chronic kidney disease through multiple direct and indirect biological pathways. Bariatric surgery is a proven, effective method for sustained weight loss. However, there is a relative paucity of data on the impact of bariatric surgery on renal outcomes.

Objective:

The primary objective was to evaluate the change in urine albumin/creatinine ratio (ACR) in patients undergoing bariatric surgery, at 12 months after the procedure. Secondary objectives were to determine the changes in ACR at (6 and 24 months), estimated glomerular filtration rate (eGFR; 6, 12, and 24 months), and hemoglobin A1c (HbA1c); 12 and 24 months) after the procedure.

Design:

This observational retrospective cohort study included consecutive obese patients who underwent bariatric surgery.

Setting:

Provincial Bariatric Surgery Clinic at the Regina General Hospital, Saskatchewan.

Patients:

This study includes 471 consecutive obese adult patients who underwent bariatric surgery between 2008 and 2015.

Measurements:

We studied the impact of bariatric surgery on body mass index (BMI), renal outcomes (urine ACR and eGFR) and metabolic outcomes (fasting glucose, total cholesterol, low-density lipoprotein, triglycerides, and HbA1c) in 471 patients.

Methods:

Patients were followed for 2 years postsurgery in the bariatric clinic. Mixed linear models that accounted for the repeated nature of the data were used to access changes in outcomes over time.

Results:

Patients were predominantly female (81%) with a mean age (±SD) of 46 ± 10 years. Most patients (87%) had a BMI > 40 kg/m² and 81% of the patients underwent Roux-en-Y gastric bypass. The mean BMI decreased from 47.7 ± 7.8 kg/m² at baseline to 37.1 ± 7.9 kg/m² at 6 months and 34.8 ± 8.8 kg/m² at 12 months. In a subcohort of patients with microalbuminuria, ACR showed an improvement from a median [interquartile] value of 5.1 [3.7-7.5] mg/mmol at baseline to 2.3 [1.2-3.6] mg/mmol at 6 months (P = .007), to 1.4 [0.9-3.7] mg/mmol at 2-year follow-up (P < .001). Similarly, eGFR increased in patients with microalbuminuria from 109 ± 10 mL/min/1.73 m² at baseline to 120 ± 36 mL/min/1.73 m² at 2-year follow-up (P = .013). There were statistically significant reductions in triglycerides, fasting glucose, and HbA1c.

Limitations:

This was a retrospective chart review, with the lack of a control group. Patients with eGFR less than 60 mL/min/1.73 m² were not considered for surgery, and we had to measure renal outcomes predominantly on the presence of proteinuria.

Conclusions:

Our results suggest bariatric surgery significantly decreased weight and consequently improved renal and metabolic outcomes (eGFR, ACR, fasting glucose, cholesterol, and triglycerides) in patients with elevated BMI.

The Effects of Bariatric Surgery on Renal Outcomes: a Systematic Review and Meta-analysis

BACKGROUND/OBJECTIVE

Although promising, data regarding the renal impact and safety of bariatric surgery (BS) are insufficient. We aimed at investigating the benefits and harms of BS for weight loss on kidney function.

METHODS

A systematic review and meta-analysis of observational studies reporting data about the impact of BS (any techniques) on serum/plasma creatinine, creatinine clearance, glomerular filtration rate (GFR), proteinuria, nephrolithiasis, and need for renal replacement therapy (RRT)) was performed. Obese adults (non-chronic kidney disease (CKD), CKD or transplanted patients) that underwent BS for weight loss were included. After searching MEDLINE (inception to August 2017), the Cochrane Library (Issue 10-12, October 2017), and the websiteclinicaltrials.gov (August 2017), data were extracted and summarized using a random-effects model.

RESULTS

The final analysis included 23 cohort studies, comprising 3015 participants. Compared with renal function before treatment, BS significantly decreased serum creatinine level (mean difference (MD), - 0.08 mg dl^-1; 95% confidence interval (CI), - 0.10 to - 0.06); p < 0.001) and proteinuria (MD, - 0.04 g 24 h^-1; 95% CI, - 0.06 to - 0.02; p < 0.001) in the overall group. GFR significantly improved 6 months or more after BS both in the hyperfiltration and CKD subgroups. Renal function also tended to improve in renal transplant patients. Data on nephrolithiasis and the need for RRT were scarce or not reported.

CONCLUSIONS

BS apparently has positive effects on kidney function and tends to normalize GFR across different categories of renal impairment (hyperfiltration and CKD patients).

Effect of weight loss on the estimated glomerular filtration rates of obese patients at risk of chronic kidney disease: the RIGOR-TMU study

BACKGROUND

Weight-reduction therapies, including bariatric surgery (BS), are standard treatments for severely obese patients with type 2 diabetes; however, the outcomes of these therapies are inconclusive for obese patients with chronic kidney disease (CKD). This study aimed to investigate the effects of BS or non-surgical interventions on the estimated glomerular filtration rate (eGFR) and to determine whether BS can be recommended for renal function preservation based on body mass index (BMI) and eGFR changes in obese patients with CKD.

METHODS

This study used data from the weight Reduction Intervention on GFR in Obese Patients with Renal Impairment-Taipei Medical University (TMU) study, which was a large, long-term, propensity score-matched cohort study based on clinical data from patients who registered at weight-reduction centres at TMU and its affiliated hospitals from 2008 to 2016. The patients were stratified according to whether they had undergone BS and into the mild, moderate, and high CKD risk groups using the Kidney Disease: Improving Global Outcomes guidelines. The primary outcome was the eGFR calculated using the Taiwan Chronic Kidney Disease-Epidemiology Collaboration equation. Cox regression models were used to determine hazard ratios (HRs) for eGFR decreases ≥25%.

RESULTS

A total of 4332 obese patients were enrolled in this study. After propensity score matching, 1620 patients, including 60.2% women, with a mean age of 36.5 (9.9) years were divided into BS or non-surgery groups (n = 810 per group). The overall mean eGFRs increased by 4.4 (14) mL/min·1.73 m² and decreased by 6.4 (16.0) mL/min·1.73 m² in the BS and non-surgery groups, respectively. The decrease in BMI in the BS and non-surgery groups were 2.5 and 1.3 kg/m² , respectively. In the moderate/high CKD risk BS group, a significant correlation was evident between an increased eGFR and a reduced BMI (Spearman's correlation -0.229, P < 0.001). The Cox regression analysis showed that the BS group had a significantly lower risk of an eGFR decline ≥25% at 12 months [adjusted HR (aHR) 0.47, P = 0.03). After BS, obese patients with hypertension or albuminuria had significantly lower risks of eGFR declines ≥25% (aHR 0.37, P = 0.02 and aHR 0.13, P = 0.0018, respectively).

CONCLUSIONS

Bariatric surgery was associated with eGFR preservation in all obese patients and, particularly, in those with moderate-to-high CKD risks. A longer term outcome study is warranted to determine the benefits of BS for CKD patients.

The impact of chronic kidney disease on bariatric perioperative outcome: a MBSAQIP matched analysis

BACKGROUND

Morbid obesity is considered a strong independent risk factor for chronic kidney disease (CKD), and bariatric surgery remains the most effective treatment for obesity-related co-morbidities. Previous large database analyses have suggested that CKD does not independently increase the risk of adverse outcomes after bariatric surgery. The safety of elective bariatric surgery in this patient population remains unclear. To this end, we compared 30-day outcomes in this patient population after laparoscopic sleeve gastrectomy or Roux-en-Y gastric bypass.

OBJECTIVES

To compare 30-day outcomes in CKD patients after laparoscopic sleeve gastrectomy or gastric bypass.

SETTING

University Hospital, United States.

METHODS

Using the Metabolic and Bariatric Surgery Accreditation Quality Improvement Program database, we identified patients with CKD who underwent laparoscopic sleeve gastrectomy or Roux-en-Y gastric bypass in 2015 or 2016. An unmatched cohort analysis, a propensity-matched analysis, and a case-control, matched-cohort analysis was performed of patients with and without CKD.

RESULTS

Of the 302,092 patients included in this study, 2362 (.7%) had CKD, of whom 837 (35.4%) required dialysis. CKD patients were older with significantly higher rates of co-morbid conditions. Hospital length of stay, intensive care unit admission, reoperation, readmission, bleeding, cardiopulmonary, infectious complications, and total morbidity were significantly higher in CKD patients. In propensity-matched and case-control matched analyses of 4006 patients and 2264 patients, respectively, poorer outcomes in CKD patients highlight it an independent risk factor for morbidity.

CONCLUSIONS

In contrast to previously reported large database analysis, CKD and dependence on dialysis independently increases the risk of 30-day adverse outcomes after primary bariatric surgery. The benefits conferred by bariatric surgery should be carefully weighed against the increased risk of complications in this challenging population.

Bariatric Surgery Reduces Elevated Urinary Mitochondrial DNA Copy Number in Patients With Obesity

OBJECTIVE

Obesity is an independent risk factor for chronic kidney disease. Recently, urinary mitochondrial DNA (mtDNA) has been used as a surrogate marker of mitochondrial damage in various kidney diseases. However, there are no data regarding its use in patients with obesity or the change in urinary mtDNA copy number after surgery.

DESIGN

We prospectively recruited age- and sex-matched healthy volunteers and patients with obesity (n = 22 in each group: nine men and 13 women). The copy number of urinary and serum mtDNA nicotinamide adenine dinucleotide dehydrogenase subunit-1 (mtND-1) and cytochrome-c oxidase 3 (mtCOX-3) was measured using quantitative PCR. We measured urinary mtDNA and body weight and carried out laboratory tests, 6 months after surgery.

RESULTS

Urinary mtND-1 copy number was significantly higher in the obese group than in healthy volunteers. However, urinary mtCOX-3 and serum ND-1 copy numbers in the obese group did not differ from that in the healthy volunteers. When patients with obesity were divided into two groups, according to their baseline mtND-1 copy number, bariatric surgery reduced the mtND-1 copy number (P = 0.006) in the high baseline mtDNA copy-number group. The change in urinary mtND-1 copy number was correlated with a change in urinary albumin (r = 0.478, P = 0.025).

CONCLUSIONS

Obesity is associated with elevated urinary mtND-1 copy number. Bariatric surgery reduces the elevated urinary mtND-1 copy number in patients with obesity. This suggests that bariatric surgery could attenuate mitochondrial damage in the kidney cells of patients with obesity.

Bariatric Surgery Modulates Urinary Levels of MicroRNAs Involved in the Regulation of Renal Function

Background: Obesity and diabetes cause chronic kidney disease with a common pathophysiology that is characterized by the accumulation of collagen in the extracellular matrix. Recent evidence has implicated the epithelial-to-mesenchymal transition (EMT) as a key step in this pathology with regulation by microRNAs. Weight loss leads to improvements in renal function; therefore, this study hypothesized that bariatric-surgery aided weight loss would lead to changes in urinary microRNAs involved in the regulation of renal function. Materials and methods: Twenty-four bariatric patients undergoing Roux-en-Y gastric bypass and sleeve gastrectomy donated urine pre-operatively and at 2-6 months and 1-2 years post-operatively. Urine samples were also obtained from 10 healthy weight and 7 morbidly obese non-surgical controls. Expression levels of kidney microRNAs were assessed in urine and the function of microRNAs was assessed through the in vitro transfection of HK-2 cells, a kidney proximal tubule cell line. Results: Levels of miR 192, miR 200a, and miR 200b were upregulated in urine following bariatric surgery. This increase was consistent across surgical type and diabetes status and was maintained and enhanced with time. Bariatric surgery alters urinary miR 192 expression from levels seen in morbidly obese patients to levels seen in healthy weight control patients. In mechanistic studies, the transfection of miR 192 in HK-2 cells increased miR 200a expression and decreased ZEB2, a key transcriptional promoter of kidney fibrosis. Conclusions: Bariatric surgery increased miR 192 and miR 200 urinary levels, key anti-fibrotic microRNAs that could contribute to a renal-protective mechanism and may be of value as urinary biomarkers following surgery. These findings suggest that urinary microRNAs may represent potential novel biomarkers for obesity-associated renal function.

Impact of obesity as an independent risk factor for the development of renal injury: implications from rat models of obesity

Diabetes and hypertension are the major causes of chronic kidney disease (CKD). Epidemiological studies within the last few decades have revealed that obesity-associated renal disease is an emerging epidemic and that the increasing prevalence of obesity parallels the increased rate of CKD. This has led to the inclusion of obesity as an independent risk factor for CKD. A major complication when studying the relationship between obesity and renal injury is that cardiovascular and metabolic disorders that may result from obesity including hyperglycemia, hypertension, and dyslipidemia, or the cluster of these disorders [defined as the metabolic syndrome, (MetS)] also contribute to the development and progression of renal disease. The associations between hyperglycemia and hypertension with renal disease have been reported extensively in patients suffering from obesity. Currently, there are several obese rodent models (high-fat diet-induced obesity and leptin signaling dysfunction) that exhibit characteristics of MetS. However, the available obese rodent models currently have not been used to investigate the impact of obesity alone on the development of renal injury before hypertension and/or hyperglycemia. Therefore, the aim of this review is to describe the incidence and severity of renal disease in these rodent models of obesity and determine which models are suitable to study the independent effects obesity on the development and progression of renal disease.

Bariatric Surgery can Reduce Albuminuria in Patients with Severe Obesity and Normal Kidney Function by Reducing Systemic Inflammation

BACKGROUND

Obesity causes renal problems including albuminuria. Bariatric surgery (BS) improves albuminuria. We investigated whether albuminuria is reduced by weight loss per se or by improved systemic inflammation induced by weight loss after BS.

METHODS

Patients older than 18 years who received BS in Soonchunhyang University Hospital from 01 January 2011 to 31 December 2011 were included. Other inclusion criteria included body mass index (BMI) ≥ 30 kg/m², creatinine level ≤ 1.0 mg/dL, and no overt proteinuria (trace amount or undetectable by dipstick). The patients were followed at 1 and 6 months after BS.

RESULTS

Forty-three patients were analyzed. Three patients were men, 10 patients had diabetes, and 12 patients had hypertension. All patients had normal renal function (creatinine ≤ 1.0 mg/dL), and estimated glomerular filtration rate was 115.7 ± 16.5 mL/min/1.73 m². There were significant reductions in body weight, BMI, high-sensitivity C-reactive protein (hs-CRP), and urine albumin-to-creatinine ratio (ACR). There were positive correlations between delta hs-CRP and delta body weight (r = 0.349, p = 0.043) or delta body mass index (BMI, r = 0.362, p = 0.035); between hs-CRP and body weight (r = 0.374, p = 0.001), BMI (r = 0.431, p < 0.001). Multivariate analysis using a linear mixed model demonstrated that hs-CRP (β = 0.5364, p = 0.026) was an independent risk factor affecting ACR.

CONCLUSIONS

Our study suggests that BS can reduce albuminuria in patients with severe obesity and normal kidney function by reducing systemic inflammation.

Microvascular Outcomes in Patients With Diabetes After Bariatric Surgery Versus Usual Care: A Matched Cohort Study

Background

Bariatric surgery improves glycemic control in patients with type 2 diabetes mellitus (T2DM), but less is known about microvascular outcomes.

Objective

To investigate the relationship between bariatric surgery and incident microvascular complications of T2DM.

Design

Retrospective matched cohort study from 2005 to 2011 with follow-up through September 2015.

Setting

4 integrated health systems in the United States.

Participants

Patients aged 19 to 79 years with T2DM who had bariatric surgery (n = 4024) were matched on age, sex, body mass index, hemoglobin A1c level, insulin use, diabetes duration, and intensity of health care use up to 3 nonsurgical participants (n = 11 059).

Intervention

Bariatric procedures (76% gastric bypass, 17% sleeve gastrectomy, and 7% adjustable gastric banding) compared with usual care.

Measurements

Adjusted Cox regression analysis investigated time to incident microvascular disease, defined as first occurrence of diabetic retinopathy, neuropathy, or nephropathy.

Results

Median follow-up was 4.3 years for both surgical and nonsurgical patients. Bariatric surgery was associated with significantly lower risk for incident microvascular disease at 5 years (16.9% for surgical vs. 34.7% for nonsurgical patients; adjusted hazard ratio [HR], 0.41 [95% CI, 0.34 to 0.48]). Bariatric surgery was associated with lower cumulative incidence at 5 years of diabetic neuropathy (7.2% for surgical vs. 21.4% for nonsurgical patients; HR, 0.37 [CI, 0.30 to 0.47]), nephropathy (4.9% for surgical vs. 10.0% for nonsurgical patients; HR, 0.41 [CI, 0.29 to 0.58]), and retinopathy (7.2% for surgical vs. 11.2% for nonsurgical patients; HR, 0.55 [CI, 0.42 to 0.73]).

Limitation

Electronic health record databases could misclassify microvascular disease status for some patients.

Conclusion

In this large, multicenter study of adults with T2DM, bariatric surgery was associated with lower overall incidence of microvascular disease (including lower risk for neuropathy, nephropathy, and retinopathy) than usual care.

Primary Funding Source

National Institute of Diabetes and Digestive and Kidney Diseases.

Impact of bariatric surgery on cardiovascular and renal complications of diabetes: a focus on clinical outcomes and putative mechanisms

INTRODUCTION

Cardiovascular and renal disease accounts for a substantial proportion of the morbidity and mortality associated with obesity and type 2 diabetes mellitus (T2DM). Bariatric surgery is associated with improved long-term cardiovascular and renal outcomes.

AREAS COVERED

All major case-control, cohort, and randomized controlled trial studies of bariatric surgery in adults with T2DM were screened and data on prespecified cardiovascular and renal outcomes collated. Bariatric surgery reduces all-cause mortality and risk of cardiovascular disease, albuminuria and progressive chronic kidney disease. Patients with poorer glycemic control and established microvascular disease preoperatively may stand to benefit the most from the surgical approach. Reduced sympathetic drive, remission of glomerular hypertension, enhanced natriuresis, gut microbiota shifts, reduced systemic and renal inflammation, improved lipoprotein profiles, and reductions in chronic cardiac remodeling may all be implicated.

EXPERT COMMENTARY

Ongoing RCTs of bariatric surgery selectively recruiting patients with class 1 obesity and established microvascular complications of diabetes will help to better characterize which subgroups of patients benefit most from this effective therapy.

Nephrological aspects of surgical weight correction in morbid obesity

Obesity, including morbid obesity, is a growing worldwide problem. The adverse effect of obesity on the kidneys is associated with the development of comorbid conditions, such as insulin resistance (IR), metabolic syndrome (MS), diabetes mellitus (DM), arterial hypertension (AH), which are the recognized risk factors of chronic kidney disease (СKD). Obesity also causes direct kidney damage with the development of non-immune focal segmental glomerulosclerosis. The leading pathophysiological mechanisms of kidney damage in obesity are intrarenal hemodynamic disorders with the formation of hyperfiltration and damaging effects of adipokines produced by adipose tissue. Bariatric surgery (BS) has taken a leading position in the treatment of morbid obesity, demonstrating its effectiveness not only in long-term weight loss, but also in the correction of IR, MS, DM, AH. Nephroprotective effect of significant and persistent weight loss is caused by the elimination of hyperfiltration and damaging effect of adipokines. Results of the observational studies of the immediate and long-term effects of BS have demonstrated positive renal outcomes, in particular, the decrease in albuminuria/proteinuria, the improvement or stabilization of glomerular filtration rate, the delay of end-stage renal failure development; surgical correction of body weight in dialysis patients with morbid obesity lets them realize subsequent kidney transplantation. Large, randomized prospective studies with a longer follow-up are needed; analysis of the long-term renal consequences of BS in obesity patients with pre-existing renal impairment, including dialysis patients, is required; stratification of the BS risk of renal complications (acute kidney damage, nephrolithiasis, nephrocalcinosis) and effective strategy for managing these risks need to be developed.

Longitudinal assessment of renal function in native kidney after bariatric surgery

The epidemic of obesity parallels that of chronic kidney disease (CKD). Obesity worsens the course of CKD, mainly defined by an abnormal glomerular filtration rate (GFR). Patients with severe obesity stages (II and III with body mass index >35 kg/m²) are eligible for bariatric surgery (BS), which is the most efficient method of achieving durable weight loss. BS may reverse glomerular hyperfiltration and albuminuria, improve adipocytokine profile, and relieve diabetes and hypertension. Obesity remission after BS might prevent the progression of renal failure in populations with morbid obesity. However, evidence for the beneficial effect of BS on renal function is scant. This lack of knowledge is mainly due to methodologic reasons, which are addressed in this review. The reversibility of hyperfiltration due to the presence of functional renal reserve hampers the interpretation of changes in true GFR after BS. This true GFR is only obtained with the renal clearance of an exogenous filtration marker. Estimation of GFR is generally provided by prediction equations, namely by modification of diet in renal diseases or by chronic kidney disease-epidemiology collaborative group. These equations are not accurate because the serum levels of both creatinine and cystatin C depend on extrarenal factors, which are modified by BS. Comparing the slopes of measured GFR according to various durations of exposure with morbid obesity would be critical in providing reliable data. Herein, we review the current knowledge on the effects of BS on kidney function; we specify the methodologic issues and particularities of the dietary management of CKD patients to propose reliable directions for future clinical research.

Associations between body mass index and the risk of renal events in patients with type 2 diabetes

BACKGROUND/OBJECTIVES

We aimed to evaluate the relationship between BMI and the risk of renal disease in patients with type 2 diabetes in the Action in Diabetes and Vascular Disease: PreterAx and DiamicroN Modified-Release Controlled Evaluation (ADVANCE) study.

SUBJECTS/METHODS

Participants were divided into six baseline BMI categories: <18.5 (underweight, n = 58); ≥18.5 to <25 (normal, n = 2894); ≥25 to <30 (overweight, n = 4340); ≥30 to <35 (obesity grade 1, n = 2265); ≥35 to <40 (obesity grade 2, n = 744); and ≥40 kg/m2 (obesity grade 3, n = 294); those underweight were excluded. The composite outcome "major renal event" was defined as development of new macroalbuminuria, doubling of creatinine, end stage renal disease, or renal death. These outcomes and development of new microalbuminuria were considered individually as secondary endpoints.

RESULTS

During 5-years of follow-up, major renal events occurred in 487 (4.6%) patients. The risk increased with higher BMI. Multivariable-adjusted HRs (95% CIs), compared to normal weight, were: 0.91 (0.72-1.15) for overweight; 1.03 (0.77-1.37) for obesity grade 1; 1.42 (0.98-2.07) for grade 2; and 2.16 (1.34-3.48) for grade 3 (p for trend = 0.006). These findings were similar across subgroups by randomised interventions (intensive versus standard glucose control and perindopril-indapamide versus placebo). Every additional unit of BMI over 25 kg/m2 increased the risk of major renal events by 4 (1-6)%. Comparable results were observed with the risk of secondary endpoints.

CONCLUSIONS

Higher BMI is an independent predictor of major renal events in patients with type 2 diabetes. Our findings encourage weight loss to improve nephroprotection in these patients.