The effect of bariatric surgery on renal function and disease: a focus on outcomes and inflammation

The Impact of Early-Stage Chronic Kidney Disease on Weight Loss Outcomes After Gastric Bypass

PURPOSE

Weight loss achieved through bariatric metabolic surgery was demonstrated to be effective at reversing chronic kidney dysfunction associated with obesity-related glomerulopathy. However, robust data on how pre-operative kidney status impacts on bariatric metabolic surgery weight loss outcomes is still lacking. The aim of this study was to evaluate the impact of kidney dysfunction on weight loss outcomes after bariatric metabolic surgery.

METHODS

Patients with obesity to be submitted to gastric bypass surgery underwent a pre-operative evaluation of creatinine clearance, estimated glomerular filtration rate (eGFR), proteinuria, and albuminuria in 24-hour urine. Body mass index (BMI), % total weight loss (%TWL), and % excess BMI loss (%EBMIL) were assessed at 6 and 12 months after surgery.

RESULTS

Before surgery, patients (N=127) had a mean BMI of 39.6 ± 3.0 kg/m2, and 56.7% (n=72) had a creatinine clearance > 130 mL/min, 23.6% (n= 30) presented proteinuria > 150 mg/24h, and 15.0% (n= 19) presented albuminuria > 30 mg/24h. After surgery, the mean BMI was 27.7 kg/m2 and 25.0 kg/m2 at 6 and 12 months, respectively (p<0.0001). The %TWL was lower in patients with pre-operative eGFR < percentile 25 (34.4 ± 5.8% vs 39.4 ± 4.9%, p=0.0007, at 12 months). There were no significant correlations between weight loss metrics and pre-operative creatinine clearance rate, proteinuria, or albuminuria.

CONCLUSION

Early-stage chronic kidney disease (G2) has a negative impact on short-term weight loss outcomes after bariatric metabolic surgery, albeit in a magnitude inferior to the clinically relevant threshold.

Effect of Bariatric Surgery on Albuminuria in Non-Diabetic Non-Hypertensive Patients with Severe Obesity: a Short-Term Outcome

Background

Obesity is a risk factor for chronic kidney disease and albuminuria. Despite the well-documented obesity association with diabetes mellitus and hypertension, its predisposition to albuminuria is not related to these comorbidities, and, in some times, its occurrence is independent of DM or hypertension.

Purpose of the study

The present study aimed to evaluate bariatric surgery effect on albuminuria in patients with severe obesity with no DM or hypertension.

Materials and methods

The study consisted of 137 patients with extreme obesity and albuminuria scheduled for bariatric surgery and did not have diabetes or hypertension. They underwent an assessment for 24-h urinary albumin at baseline (T0) and 6 months postoperatively (T2).

Results

Albuminuria remission occurred in 83% of patients; there was a statistically highly significant difference between the baseline and the 6-month postoperative in the 24-h urinary albumin assessment. Weight loss and BMI at T2 were independent predictors of albuminuria remission.

Conclusion

The current work emphasizes the importance and promising role of bariatric surgery as an effective weight reduction management method in improving albuminuria, an early sign of chronic kidney disease, and a potential risk factor for cardiovascular disease.

Adiponectin receptor agonist AdipoRon ameliorates renal inflammation in diet-induced obese mice and endotoxin-treated human glomeruli ex vivo

AIMS/HYPOTHESIS

Chronic low-grade inflammation with local upregulation of proinflammatory molecules plays a role in the progression of obesity-related renal injury. Reduced serum concentration of anti-inflammatory adiponectin may promote chronic inflammation. Here, we investigated the potential anti-inflammatory and renoprotective effects and mechanisms of action of AdipoRon, an adiponectin receptor agonist.

METHODS

Wild-type DBA/2J mice were fed with high-fat diet (HFD) supplemented or not with AdipoRon to model obesity-induced metabolic endotoxaemia and chronic low-grade inflammation and we assessed changes in the glomerular morphology and expression of proinflammatory markers. We also treated human glomeruli ex vivo and human podocytes in vitro with AdipoRon and bacterial lipopolysaccharide (LPS), an endotoxin upregulated in obesity and diabetes, and analysed the secretion of inflammatory cytokines, activation of inflammatory signal transduction pathways, apoptosis and migration.

RESULTS

In HFD-fed mice, AdipoRon attenuated renal inflammation, as demonstrated by reduced expression of glomerular activated NF-κB p65 subunit (NF-κB-p65) (70%, p < 0.001), TNFα (48%, p < 0.01), IL-1β (51%, p < 0.001) and TGFβ (46%, p < 0.001), renal IL-6 and IL-4 (21% and 20%, p < 0.05), and lowered glomerular F4/80-positive macrophage infiltration (31%, p < 0.001). In addition, AdipoRon ameliorated HFD-induced glomerular hypertrophy (12%, p < 0.001), fibronectin accumulation (50%, p < 0.01) and podocyte loss (12%, p < 0.001), and reduced podocyte foot process effacement (15%, p < 0.001) and thickening of the glomerular basement membrane (18%, p < 0.001). In cultured podocytes, AdipoRon attenuated the LPS-induced activation of the central inflammatory signalling pathways NF-κB-p65, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38-MAPK) (30%, 36% and 22%, respectively, p < 0.001), reduced the secretion of TNFα (32%, p < 0.01), and protected against podocyte apoptosis and migration. In human glomeruli ex vivo, AdipoRon reduced the LPS-induced secretion of inflammatory cytokines IL-1β, IL-18, IL-6 and IL-10.

CONCLUSIONS/INTERPRETATION

AdipoRon attenuated the renal expression of proinflammatory cytokines in HFD-fed mice and LPS-stimulated human glomeruli, which apparently contributed to the amelioration of glomerular inflammation and injury. Mechanistically, based on assays on cultured podocytes, AdipoRon reduced LPS-induced activation of the NF-κB-p65, JNK and p38-MAPK pathways, thereby impelling the decrease in apoptosis, migration and secretion of TNFα. We conclude that the activation of the adiponectin receptor by AdipoRon is a potent strategy to attenuate endotoxaemia-associated renal inflammation.

Pro-resolving lipid mediators: regulators of inflammation, metabolism and kidney function

Obesity, diabetes mellitus, hypertension and cardiovascular disease are risk factors for chronic kidney disease (CKD) and kidney failure. Chronic, low-grade inflammation is recognized as a major pathogenic mechanism that underlies the association between CKD and obesity, impaired glucose tolerance, insulin resistance and diabetes, through interaction between resident and/or circulating immune cells with parenchymal cells. Thus, considerable interest exists in approaches that target inflammation as a strategy to manage CKD. The initial phase of the inflammatory response to injury or metabolic dysfunction reflects the release of pro-inflammatory mediators including peptides, lipids and cytokines, and the recruitment of leukocytes. In self-limiting inflammation, the evolving inflammatory response is coupled to distinct processes that promote the resolution of inflammation and restore homeostasis. The discovery of endogenously generated lipid mediators - specialized pro-resolving lipid mediators and branched fatty acid esters of hydroxy fatty acids - which promote the resolution of inflammation and attenuate the microvascular and macrovascular complications of obesity and diabetes mellitus highlights novel opportunities for potential therapeutic intervention through the targeting of pro-resolution, rather than anti-inflammatory pathways.

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.

Central blood pressure in morbid obesity and after bariatric surgery

Various mechanisms are related to arterial hypertension in obesity. Central blood pressure (BP) seems to correlate more than peripheral BP with future cardiovascular risk. Bariatric surgery is an effective method to reduce BP along with weight loss in patients with morbid obesity. The study of the relationship between weight modification after bariatric surgery and ambulatory BP measurement, not only peripheral BP, but also central BP, could provide information regarding the mechanisms of organic damage associated with elevated BP in obesity. In this review we analyze the available evidence regarding the association between central BP with obesity and its modifications after bariatric surgery.

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.

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.

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.

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 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.

Renal experiences of bariatric surgery in patients with type 2 diabetes mellitus

The review addresses the questions of the literature devoted to the problem of the influence of bariatric surgery on the course of diabetic nephropathy in patients with diabetes mellitus type 2 after achieving a surgically induced remission. This approach was shown to have positive aspects, such as decrease in creatinine, decrease in albuminuria, an increase in GFR, normalization of glycemia and blood pressure, "incretin effect"’s influence on the kidneys. Descriptions of the currently expected pathogenetic mechanisms involved in achieving the observed improvement in microvascular complications of diabetes, namely diabetic kidney disease, are also described in details.

Reversibility of diabetes mellitus: Narrative review of the evidence

The global disease burden of diabetes mellitus is high. It is well-established that prediabetes is reversible but it is unclear whether diabetes is reversible once it has been diagnosed. The objective of this narrative review is to review the evidence of reversibility of diabetes mellitus and stimulate interest in prolonged remission as a treatment target. The current evidence for bariatric surgery is stronger than intensive medical management and the evidence is stronger for type 2 diabetes patients compared with type 1 diabetes patients. It is also unclear whether non obese diabetes patients would benefit from such interventions and the duration of diabetes before diabetes become irreversible. Further research is needed in this area especially with regards to the subgroup of diabetes patient who will benefit from these interventions and the long term safety and efficacy remains unknown especially with intensive medical management.

Effect of bariatric surgery on diabetic nephropathy in obese type 2 diabetes patients in a retrospective 2-year study: A local pilot

PURPOSE

To determine the effects of bariatric surgery on albuminuria in obese patients with type 2 diabetes mellitus.

METHODS

Retrospective analyses of clinical records of obese patients with type 2 diabetes mellitus who had either micro- or macroalbuminuria and had undergone various bariatric surgery were retrieved from a local hospital database. Their clinical data from follow-up appointments including albuminuria were analysed.

RESULTS

Of the 46 subjects with type 2 diabetes mellitus, 15 subjects had diabetic nephropathy and had pre- and post-bariatric surgery urine albumin-to-creatinine ratio or urine protein-to-creatinine ratio data available for analysis; 13 out of the 15 subjects (86.7%) showed improvement of urine albumin-to-creatinine ratio or urine protein-to-creatinine ratio after surgery; 2 showed equivocal results; 9 of 13 subjects (69.2%) showed remission of diabetic nephropathy; 7 of these 9 patients had microalbuminuria before surgery, 2 had macroalbuminuria before surgery. There were significant improvements to glycosylated haemoglobin, fasting plasma glucose, blood pressure and body weight post surgery. The usage of insulin and oral medications dropped significantly post surgery for all subjects.

CONCLUSION

This study shows that bariatric surgery significantly improves diabetic nephropathy in obese type 2 diabetes mellitus subjects. The results suggest that in our local type 2 diabetes mellitus patients, it is possible not only to improve metabolic parameters, but also to reverse what may be considered established microvascular complications by means of bariatric surgery.

Anaesthetic Preparation of Obese Patients: Current Status on Optimal Work-up

PURPOSE OF REVIEW

With the prevalence of obesity rapidly growing, bariatric anaesthesia becomes everyday anaesthesia rather than a subspecialty. In this review, we are aiming to draw attention to this complex group of patients and their comorbidities, relevant to everyday practice for contemporary anaesthetists.

RECENT FINDINGS

We wanted to focus greatly on sleep-related breathing disorders, because preoperative screening, diagnosis and treatment of the aforementioned make a huge impact in the improvement of preoperative morbidity and mortality, including positive effects on the cardiovascular system. The overview is touching on main obesity-related comorbidities and guides the anaesthetist and associated health professionals on how to approach and manage them. A multidisciplinary approach widely used in bariatric care may be adopted in the care of obese patients in order to reduce preoperative morbidity and mortality. We advocate the early involvement of the anaesthetic team in the preoperative assessment of obese patients in order to achieve appropriate risk stratification and optimise the care.

Bariatric surgery is associated with renal function improvement

INTRODUCTION

Weight loss after bariatric surgery improves both blood pressure and glycemic control following surgery. The effect of bariatric surgery on renal function is not well characterized. In this study, we sought to quantify the change in renal function over time following surgery.

METHODS

We retrospectively reviewed all patients who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB) or laparoscopic sleeve gastrectomy (LSG) between 2012 and 2014 at our institution. The glomerular filtration rate (GFR, mL/min) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Body mass index (BMI, kg/m²) and percent weight loss (%WL) were calculated following the surgery.

RESULTS

A total of 149 patients who underwent bariatric surgery were included in this study: LRYGB (n = 86 and LSG (n = 63). In LRYGB group, baseline BMI (kg/m², ±SD) and GFR (mL/min, ±SD) were 48.5 ± 6.8 and 94.7 ± 23.8, respectively. In comparison, BMI and GFR were 49.1 ± 11.9 kg/m² and 93.1 ± 28.0 mL/min in the LSG group, respectively. Over the follow-up period (19.89 ± 10.93 months), the patients who underwent LRGYB lost a larger percentage of weight as compared to those in the LSG group (29.9 ± 11.7% vs 22.3 ± 10.7%; p = <0.0001). Overall, GFR improved in both LRYGB (101.0 ± 25.8 mL/min) and LSG groups (97.9 ± 25.8 mL/min) and was not significantly different between the two groups. Of patients with a GFR < 90 mL/min prior to weight loss surgery (n = 62), 42% had improvement of their GFR to > 90 mL/min postoperatively (p < 0.001). There was no relationship between weight loss percentage and GFR improvement (p = 0.8703).

CONCLUSIONS

Bariatric surgery was associated with improvement in postoperative renal function at almost two years following surgery but was not different for LRYGB versus LSG. The gain in GFR was independent of percentage of weight lost suggesting an alternate mechanism in the improvement of renal function other than weight loss alone.

Estimated GFR Before and After Bariatric Surgery in CKD

BACKGROUND

Several reviews have recently detailed the beneficial effects of weight loss surgery for kidney function. However, these studies have a number of limitations, including small sample size, few done in chronic kidney disease (CKD) stages 3 and 4, and many not including the main bariatric surgery procedures used in the United States today.

STUDY DESIGN

This was an observational retrospective cohort study comparing propensity score-matched bariatric surgery patients and nonsurgery control patients who were referred for, but did not have, surgery. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy were also compared using propensity matching.

SETTING & PARTICIPANTS

Patients (714 surgery patients; 714 controls) were from a large integrated health care system, a mean of 58±8 (SD) years old, and mostly women (77%) and non-Hispanic whites (56%) and had diabetes mellitus (66%) and/or hypertension (91%).

PREDICTOR

Predictors at the time of surgery or referral to surgery were age, sex, race/ethnicity, weight, and presence of diabetes and/or hypertension.

OUTCOMES

The primary outcome for this study was change in estimated glomerular filtration rate (eGFR) from serum creatinine level over a median 3-year follow-up period.

MEASUREMENTS

Serum creatinine was used to calculate eGFR using the CKD-EPI (CKD Epidemiology Collaboration) creatinine equation.

RESULTS

Surgery patients had 9.84 (95% CI, 8.05-11.62) mL/min/1.73m² greater eGFRs than controls at a median 3 years' follow-up and RYGB patients had 6.60 (95% CI, 3.42-9.78) mL/min/1.73m² greater eGFRs than sleeve gastrectomy patients during the same period.

LIMITATIONS

This study is limited by its nonrandomized observational study design, estimation of GFR, and large changes in muscle mass, which may affect serum creatinine level independent of changes in kidney function.

CONCLUSIONS

Bariatric surgery, especially the RYGB procedure, results in significant improvements for up to 3 years in eGFRs for patients with CKD stages 3 and 4.

The impact of bariatric surgery on estimated glomerular filtration rate in patients with type 2 diabetes: a retrospective cohort study

BACKGROUND

Diabetes mellitus is the most common cause of end-stage renal disease, which is associated with increased morbidity and mortality. The impact of bariatric surgery on chronic kidney disease is unclear.

OBJECTIVES

Our primary aim was to assess the impact of bariatric surgery on estimated glomerular filtration rate (eGFR) in type 2 diabetes (T2D) patients. Our secondary aim was to compare the impact of bariatric surgery versus routine care on eGFR in patients with T2D.

SETTING

University Hospital, United Kingdom.

METHODS

A retrospective cohort analysis of adults with T2D who underwent bariatric surgery at a single center between January 2005 and December 2012. Data regarding eGFR were obtained from electronic patients records. eGFR was calculated using the Modification of Diet in Renal Disease formula. Data regarding patients with T2D who did not undergo bariatric surgery ("routine care") were obtained from patients attending the diabetes clinic at the same center from 2009 to 2011.

RESULTS

One hundred sixty-three patients were included (mean age 48.5±8.8 yr; baseline body mass index 50.8±9.1 kg/m²) and were followed for 3.0±2.3 years. Bariatric surgery resulted in an improvement in eGFR (median [interquartile range] 86.0 [73.0-100.0] versus 92.0 [77.0-101.0] mL/min/1.73 m² for baseline versus follow-up, respectively; P = .003), particularly in patients with baseline eGFR≤60 mL/min/1.73 m² (48.0 [42.0-57.0] versus 61.0 [55.0-63.0] mL/min/1.73 m²; P = .004). After adjusting for baseline eGFR, glycated hemoglobin (HbA1C), body mass index, age, and gender, bariatric surgery was associated with higher study-end eGFR compared with routine care (B = 7.787; P< .001).

CONCLUSION

Bariatric surgery results in significant improvements in eGFR in T2D patients, particularly those with an eGFR≤60 mL/min/1.73 m², while routine care was associated with a decline in eGFR.

Obesity-related glomerulopathy: clinical and pathologic characteristics and pathogenesis

The prevalence of obesity-related glomerulopathy is increasing in parallel with the worldwide obesity epidemic. Glomerular hypertrophy and adaptive focal segmental glomerulosclerosis define the condition pathologically. The glomerulus enlarges in response to obesity-induced increases in glomerular filtration rate, renal plasma flow, filtration fraction and tubular sodium reabsorption. Normal insulin/phosphatidylinositol 3-kinase/Akt and mTOR signalling are critical for podocyte hypertrophy and adaptation. Adipokines and ectopic lipid accumulation in the kidney promote insulin resistance of podocytes and maladaptive responses to cope with the mechanical forces of renal hyperfiltration. Although most patients have stable or slowly progressive proteinuria, up to one-third develop progressive renal failure and end-stage renal disease. Renin-angiotensin-aldosterone blockade is effective in the short-term but weight loss by hypocaloric diet or bariatric surgery has induced more consistent and dramatic antiproteinuric effects and reversal of hyperfiltration. Altered fatty acid and cholesterol metabolism are increasingly recognized as key mediators of renal lipid accumulation, inflammation, oxidative stress and fibrosis. Newer therapies directed to lipid metabolism, including SREBP antagonists, PPARα agonists, FXR and TGR5 agonists, and LXR agonists, hold therapeutic promise.

Present and future in the treatment of diabetic kidney disease

Diabetic kidney disease is the leading cause of end-stage renal disease. Albuminuria is recognized as the most important prognostic factor for chronic kidney disease progression. For this reason, blockade of renin-angiotensin system remains the main recommended strategy, with either angiotensin converting enzyme inhibitors or angiotensin II receptor blockers. However, other antiproteinuric treatments have begun to be studied, such as direct renin inhibitors or aldosterone blockers. Beyond antiproteinuric treatments, other drugs such as pentoxifylline or bardoxolone have yielded conflicting results. Finally, alternative pathogenic pathways are being explored, and emerging therapies including antifibrotic agents, endothelin receptor antagonists, or transcription factors show promising results. The aim of this review is to explain the advances in newer agents to treat diabetic kidney disease, along with the background of the renin-angiotensin system blockade.

Impact of perioperative management of glycemia in severely obese diabetic patients undergoing gastric bypass surgery

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is associated with rapid postsurgical improvement in glycemic control in patients with type 2 diabetes mellitus (T2 DM). However, there is little outcome-based evidence to guide the glycemic management of this patient group preoperatively.

OBJECTIVES

We conducted 2 pilot studies randomizing patients to assess the impact of intensive glucose management pre- and post-RYGB on clinical outcomes after surgery.

SETTING

University hospital.

METHODS

In the GLUCOSURG-pre randomized controlled trial (RCT), 34 obese T2 DM patients with glycated hemoglobin (HbA1 c) ≥8.5% (69 mmol/mol) undergoing RYGB were randomly assigned to receive either glucose optimization or no optimization 3 months preoperatively. In the GLUCOSURG-post RCT, 35 obese T2 DM patients on insulin were randomly assigned to either intensive or conservative glucose management up to 2 weeks post- RYGB. HbA1c at 1 year post-RYGB was the primary outcome.

RESULTS

In GLUCOSURG-pre, the HbA1 c at 1 year postsurgery was -3.0% (51.9 mmol/mol) in the optimized and -4.0% (45.4 mmol/mol) in the nonoptimized groups (P = .06). In GLUCOSURG-post, there were no significant differences in HbA1 c at 1 year postsurgery between the intensive and conservative groups [-2.4% (44.3 mmol/mol)] versus [-2.3% (44.3 mmol/mol), P = .73)].

CONCLUSIONS

Our pilot studies suggested that neither intensive management of glycemia in the 3 months pre- RYGB, nor the first 2 weeks post-RYGB resulted in better glycemic control one year after surgery. RYGB has substantial effects on glucose control, and additional intensive glucose-lowering interventions do not confer clinical benefits compared to conservative approaches.

Transplant options for patients with type 2 diabetes and chronic kidney disease

Chronic kidney disease (CKD) has become a real epidemic around the world, mainly due to ageing and diabetic nephropathy. Although diabetic nephropathy due to type 1 diabetes mellitus (T1DM) has been studied more extensively, the vast majority of the diabetic CKD patients suffer from type 2 diabetes mellitus (T2DM). Renal transplantation has been established as a first line treatment for diabetic nephropathy unless there are major contraindications and provides not only a better quality of life, but also a significant survival advantage over dialysis. However, T2DM patients are less likely to be referred for renal transplantation as they are usually older, obese and present significant comorbidities. As pre-emptive renal transplantation presents a clear survival advantage over dialysis, all T2DM patients with CKD should be referred for early evaluation by a transplant center. The transplant center should have enough time in order to examine their eligibility focusing on special issues related with diabetic nephropathy and explore the best options for each patient. Living donor kidney transplantation should always be considered as the first line treatment. Otherwise, the patient should be listed for deceased donor kidney transplantation. Recent progress in transplantation medicine has improved the “transplant menu” for T2DM patients with diabetic nephropathy and there is an ongoing discussion about the place of simultaneous pancreas kidney (SPK) transplantation in well selected patients. The initial hesitations about the different pathophysiology of T2DM have been forgotten due to the almost similar short- and long-term results with T1DM patients. However, there is still a long way and a lot of ethical and logistical issues before establishing SPK transplantation as an ordinary treatment for T2DM patients. In addition recent advances in bariatric surgery may offer new options for severely obese T2DM patients with CKD. Nevertheless, the existing data for T2DM patients with advanced CKD are rather scarce and bariatric surgery should not be considered as a cure for diabetic nephropathy, but only as a bridge for renal transplantation.

Therapeutic approaches to diabetic nephropathy--beyond the RAS

Despite improvements in glycaemic and blood pressure control, and the efficacy of renin-angiotensin system (RAS) blockade for proteinuria reduction, diabetic nephropathy is the most frequent cause of end-stage renal disease in developed countries. This finding is consistent with the hypothesis that key pathogenetic mechanisms leading to progression of renal disease are not modified or inactivated by current therapeutic approaches. Although extensive research has elucidated molecular signalling mechanisms that are involved in progression of diabetic kidney disease, a number of high-profile clinical trials of potentially nephroprotective agents have failed, highlighting an insufficient understanding of pathogenic pathways. These include trials of paricalcitol in early diabetic kidney disease and bardoxolone methyl in advanced-stage disease. Various strategies based on encouraging data from preclinical studies that showed renoprotective effects of receptor antagonists, neutralizing antibodies, kinase inhibitors, small compounds and peptide-based technologies are currently been tested in randomized controlled trials. Phase II clinical trials are investigating approaches targeting inflammation, fibrosis and signalling pathways. However, only one trial that aims to provide evidence for marketing approval of a potentially renoprotective drug (atrasentan) is underway-further research into the potential nephroprotective effects of novel glucose-lowering agents is required.

Predicting the glomerular filtration rate in bariatric surgery patients

BACKGROUND/AIMS

Identifying the best method to estimate the glomerular filtration rate (GFR) in bariatric surgery patients has important implications for the clinical care of obese patients and research into the impact of obesity and weight reduction on kidney health. We therefore performed such an analysis in patients before and after surgical weight loss.

METHODS

Fasting measured GFR (mGFR) by plasma iohexol clearance before and after bariatric surgery was obtained in 36 severely obese individuals. Estimated GFR was calculated using the Modification of Diet in Renal Disease equation, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation using serum creatinine only, the CKD-EPI equation using serum cystatin C only and a recently derived equation that uses both serum creatinine and cystatin C (CKD-EPIcreat-cystC) and then compared to mGFR.

RESULTS

Participants were primarily middle-aged white females with a mean baseline body mass index of 46 ± 9, serum creatinine of 0.81 ± 0.24 mg/dl and mGFR of 117 ± 40 ml/min. mGFR had a stronger linear relationship with inverse cystatin C before (r = 0.28, p = 0.09) and after (r = 0.38, p = 0.02) surgery compared to the inverse of creatinine (before: r = 0.26, p = 0.13; after: r = 0.11, p = 0.51). mGFR fell by 17 ± 35 ml/min (p = 0.007) following surgery. The CKD-EPIcreat-cystC was unquestionably the best overall performing estimating equation before and after surgery, revealing very little bias and a capacity to estimate mGFR within 30% of its true value over 80% of the time. This was true whether or not mGFR was indexed for body surface area.

CONCLUSIONS

In severely obese bariatric surgery patients with normal kidney function, cystatin C is more strongly associated with mGFR than is serum creatinine. The CKD-EPIcreat-cystC equation best predicted mGFR both before and after surgery.