Severe obesity and the impact of medical weight loss on estimated glomerular filtration rate

Nutritional assessment and medical dietary therapy for management of obesity in patients with non-dialysis chronic kidney disease: a practical guide for endocrinologist, nutritionists and nephrologists. A consensus statement from the Italian society of endocrinology (SIE), working group of the club nutrition-hormones and metabolism; the Italian society of nutraceuticals (SINut), club ketodiets and nutraceuticals "KetoNut-SINut"; and the Italian society of nephrology (SIN)

PURPOSE

Chronic kidney disease (CKD) is a serious health concern with an estimated prevalence of about 13.4% worldwide. It is cause and consequence of various comorbidities, including cardiovascular diseases. In parallel, common pathological conditions closely related to ageing and unhealthy dietary habits increase the risk of CKD development and progression, including type 2 diabetes and obesity. Among these, obesity is either independent risk factor for new onset kidney disease or accelerates the rate of decline of kidney function by multiple mechanisms. Therefore, the role of diets aimed at attaining weight loss in patients with obesity is clearly essential to prevent CKD as to slow disease progression. Various dietary approaches have been licensed for the medical dietary therapy in CKD, including low-protein diet and Mediterranean diet. Interestingly, emerging evidence also support the use of low-carbohydrate/ketogenic diet (LCD/KD) in these patients. More specifically, LCD/KDs may efficiently promote weight loss, improve metabolic parameters, and reduce inflammation and oxidative stress, resulting in a dietary strategy that act globally in managing collateral conditions that are directly and indirectly related to the kidney function.

CONCLUSION

This consensus statement from the Italian Society of Endocrinology (SIE), working group of the Club Nutrition - Hormones and Metabolism; the Italian Society of Nutraceuticals (SINut), Club Ketodiets and Nutraceuticals "KetoNut-SINut"; and the Italian Society of Nephrology (SIN) is intended to be a guide for Endocrinologist, Nutritionists and Nephrologist who deal with the management of patients with obesity with non-dialysis CKD providing a practical guidance on assessing nutritional status and prescribing the optimal diet in order to best manage obesity to prevent CKD and its progression to dialysis.

Long-term kidney outcomes of semaglutide in obesity and cardiovascular disease in the SELECT trial

The SELECT trial previously reported a 20% reduction in major adverse cardiovascular events with semaglutide (n = 8,803) versus placebo (n = 8,801) in patients with overweight/obesity and established cardiovascular disease, without diabetes. In the present study, we examined the effect of once-weekly semaglutide 2.4 mg on kidney outcomes in the SELECT trial. The incidence of the pre-specified main composite kidney endpoint (death from kidney disease, initiation of chronic kidney replacement therapy, onset of persistent estimated glomerular filtration rate (eGFR) < 15 ml min-1 1.73 m-2, persistent ≥50% reduction in eGFR or onset of persistent macroalbuminuria) was lower with semaglutide (1.8%) versus placebo (2.2%): hazard ratio (HR) = 0.78; 95% confidence interval (CI) 0.63, 0.96; P = 0.02. The treatment benefit at 104 weeks for eGFR was 0.75 ml min-1 1.73 m-2 (95% CI 0.43, 1.06; P < 0.001) overall and 2.19 ml min-1 1.73 m-2 (95% CI 1.00, 3.38; P < 0.001) in patients with baseline eGFR <60 ml min-1 1.73 m-2. These results suggest a benefit of semaglutide on kidney outcomes in individuals with overweight/obesity, without diabetes.ClinicalTrials.gov identifier: NCT03574597 .

The 10-Year Effects of Intensive Lifestyle Intervention on Kidney Outcomes

Rationale & Objective

Limited data exist on longitudinal kidney outcomes after nonsurgical obesity treatments. We investigated the effects of intensive lifestyle intervention on kidney function over 10 years.

Study Design

Post hoc analysis of Action for Health in Diabetes (Look AHEAD) randomized controlled trial.

Setting & Participants

We studied 4,901 individuals with type 2 diabetes and body mass index of ≥25 kg/m2 enrolled in Look AHEAD (2001-2015). The original Look AHEAD trial excluded individuals with 4+ urine dipstick protein, serum creatinine level of >1.4 mg/dL (women), 1.5 mg/dL (men), or dialysis dependence.

Exposures

Intensive lifestyle intervention versus diabetes support and education (ie, usual care).

Outcome

Primary outcome was estimated glomerular filtration rate (eGFR, mL/min/1.73 m2) slope. Secondary outcomes were mean eGFR, slope, and mean urine albumin to creatinine ratio (UACR, mg/mg).

Analytical Approach

Linear mixed-effects models with random slopes and intercepts to evaluate the association between randomization arms and within-individual repeated measures of eGFR and UACR. We tested for effect modification by baseline eGFR.

Results

At baseline, mean eGFR was 89, and 83% had a normal UACR. Over 10 years, there was no difference in eGFR slope (+0.064 per year; 95% CI: -0.036 to 0.16; P = 0.21) between arms. Slope or mean UACR did not differ between arms. Baseline eGFR, categorized as eGFR of <80, 80-100, or >100, did not modify the intervention's effect on eGFR slope or mean.

Limitations

Loss of muscle may confound creatinine-based eGFR.

Conclusions

In patients with type 2 diabetes and preserved kidney function, intensive lifestyle intervention did not change eGFR slope over 10 years. Among participants with baseline eGFR <80, lifestyle intervention had a slightly higher longitudinal mean eGFR than usual care. Further studies evaluating the effects of intensive lifestyle intervention in people with kidney disease are needed.

Obesity and glomerular filtration rate

Obesity has received considerable attention in general medicine and nephrology over the last few years. This condition increases the risk of metabolic syndrome, diabetes mellitus, hypertension, and dyslipidemia, which are the main risk factors for developing chronic kidney disease (CKD). Kidney damage caused by obesity can be explained by many mechanisms, such as sympathetic nervous and renin-angiotensin-aldosterone systems activation, mechanical stress, hormonal unbalance, as well as inflammatory cytokines production. Even though creatinine-based glomerular filtration rate (GFR) equations in obese individuals have been validated (Salazar-Corcoran and CKD-MCQ), changes in body weight after bariatric surgery (BS) leads to changes in creatininemia, affecting its reliability. Thus, an average between creatine and cystatin-based GFR equations would be more appropriate in this setting. Bariatric surgery can reverse diabetes mellitus and improve hypertension, which are the main causes of CKD. Conclusion: GFR can be affected by obesity and BS, and its value should be cautiously evaluated in this setting.

Creatinine-Based Definition of Kidney Disease in the Charlson Comorbidity Index May Underestimate Prognosis in Males Compared to an Estimated Glomerular Filtration Rate Definition

(1) Background: The Charlson comorbidity index allocates two points for chronic kidney disease (CKD) if serum creatinine is above 3.0 mg/dL (270 µmol/L). However, contemporary CKD staging is based on the estimated glomerular filtration rate (eGFR) derived from population-based equations. The aim of this study was to determine the correlation between eGFR and the creatinine threshold of the Charlson comorbidity index for defining CKD. (2) Methods: We conducted a cross-sectional study of 664 patients with established CKD attending general nephrology clinics over 6 months. Dialysis patients and kidney transplant recipients were excluded. (3) Results: The median age was 68 years, and 58% of the participants were male. By modeling with fractional polynomial regression, we estimated that a creatinine of 270 µmol/L corresponded with an eGFR of 14.8 mL/min/1.73 m2 for females and 19.4 mL/min/m2 for males. We also estimated that an eGFR of 15 mL/min/1.73 m2 (threshold which defines Stage 5 CKD) corresponded to a serum creatinine of 275 µmol/L for females and 342 µmol/L for males. After applying these sex-specific creatinine thresholds, 39% of males and 3% of females in our CKD study population who scored points for CKD in the Charlson comorbidity index had not yet reached Stage 5 CKD. (4) Conclusions: There is a significant difference in the creatinine threshold to define Stage 5 CKD between males and females, with a bias for greater allocation of Charlson index points for CKD to males despite similar eGFR levels between the sexes. Further research could examine if replacing creatinine with eGFR improves the performance of the Charlson comorbidity index as a prognostic tool.

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.

Heart failure in obesity: insights from proteomics in patients treated with or without weight-loss surgery

BACKGROUND

Obesity is associated with incident heart failure (HF), but the underlying mechanisms are unclear.

METHODS

We performed a nested case-control study within the Swedish-Obese-Subjects study, by identifying 411 cases who developed HF and matched them with respect to age, sex, weight-loss-surgery and length of follow-up with 410 controls who did not develop HF. In analyses corrected for multiple testing, we studied 182 plasma proteins known to be related to cardiovascular disease to investigate whether they could add to the understanding of the processes underlying obesity-related HF.

RESULTS

A total of 821 subjects were followed for 16 ± 6 years. Multivariable analysis adjusted for matching variables revealed that 32 proteins were significantly associated with HF. Twelve proteins were related to HF ≥ 80% of the time using a bootstrap resampling approach (false-discovery-rate [FDR] < 0.05): 11 were associated with increased HF-risk: TNFRSF10A*, ST6GAL1, PRCP, MMP12, TIMP1, CCL3, QPCT, ANG, C1QTNF1, SERPINA5 and GAL-9; and one was related to reduced HF-risk: LPL. An further 20 proteins were associated with onset of HF 50-80% of the time using bootstrap resampling (FDR < 0.05). A pathway analysis including all significant 32 proteins suggested that these biomarkers were related to inflammation, matrix remodeling, cardiometabolic hormones and hemostasis. Three proteins, C1QTNF1, FGF-21 and CST3, reflecting dyslipidemia and kidney disease, displayed a higher association with HF in patients who did not undergo weight-loss-surgery and maintained with obesity.

CONCLUSION

Pathways associated with HF in obesity include inflammation, matrix remodeling, cardiometabolic hormones and hemostasis; three protein biomarkers predicting HF appeared to be obesity-specific.

Glomerular hyperfiltration in morbid obesity: Role of the inflammasome signalling

AIM

Obesity is associated with glomerular hyperfiltration which may precede the development of overt renal damage. Few studies evaluated the link between inflammasome signalling and hyperfiltration. The aim is to evaluate the relationship between IL1-β/Caspase-1, insulin sensitivity and hyperfiltration in subjects with severe obesity, before and after weight loss.

METHODS

Forty-six patients with BMI > 35 kg/m² , without type-2-diabetes or hypertension, were evaluated at baseline and 6 months after bariatric surgery with oral glucose tollerance test, bioimpedance analysis and blood tests. The eGFR was calculated according to EPIcr-cys formula and insulin sensitivity by Oral Glucose Insulin Sensitivity. IL-1β/Caspase-1 were measured with the ELISA-kit. HF was defined as eGFR ≥ 140 ml/min (non-indexed for BSA).

RESULTS

Sixteen subjects at baseline had hyperfiltration, with a higher insulin resistance, BMI, lean mass and plasma levels of IL-1β/Caspase-1. After surgery, there was a reduction in BMI and improvement in insulin resistance in all patients. However, in 8 of 16 patients hyperfiltration persisted and IL-1β/Caspase-1 levels did not decrease (3.22 ± 0.79 vs. 3.13 ± 1.03 and 23.7 ± 12.1 vs. 20.6 ± 9.1, pre vs. post, pg/ml), while cytokines normalized in all the other patients in parallel with the eGFR. In a logistic regression model, correcting for the main covariates, lean mass and IL-1β before surgery (p = .01 and p = .03, respectively), were the only predictors of hyperfiltration.

CONCLUSION

Weight loss is effective in reducing hyperfiltration in most, but not all patients. Hyperfiltration remains unchanged in subjects who do not have a reduction in IL-1β/Caspase-1, suggesting a pathogenetic role of the inflammasome signalling in the early stages of nephropathy.

Assessment of kidney function: clinical indications for measured GFR

In the vast majority of cases, glomerular filtration rate (GFR) is estimated using serum creatinine, which is highly influenced by age, sex, muscle mass, body composition, severe chronic illness and many other factors. This often leads to misclassification of patients or potentially puts patients at risk for inappropriate clinical decisions. Possible solutions are the use of cystatin C as an alternative endogenous marker or performing direct measurement of GFR using an exogenous marker such as iohexol. The purpose of this review is to highlight clinical scenarios and conditions such as extreme body composition, Black race, disagreement between creatinine- and cystatin C-based estimated GFR (eGFR), drug dosing, liver cirrhosis, advanced chronic kidney disease and the transition to kidney replacement therapy, non-kidney solid organ transplant recipients and living kidney donors where creatinine-based GFR estimation may be invalid. In contrast to the majority of literature on measured GFR (mGFR), this review does not include aspects of mGFR for research or public health settings but aims to reach practicing clinicians and raise their understanding of the substantial limitations of creatinine. While including cystatin C as a renal biomarker in GFR estimating equations has been shown to increase the accuracy of the GFR estimate, there are also limitations to eGFR based on cystatin C alone or the combination of creatinine and cystatin C in the clinical scenarios described above that can be overcome by measuring GFR with an exogenous marker. We acknowledge that mGFR is not readily available in many centres but hope that this review will highlight and promote the expansion of kidney function diagnostics using standardized mGFR procedures as an important milestone towards more accurate and personalized medicine.