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.

Obesity aggravates acute kidney injury resulting from ischemia and reperfusion in mice

In critically ill patients, overweight and obesity are associated with acute respiratory distress syndrome and acute kidney injury (AKI). However, the effect of obesity on ischemia-reperfusion injury (IRI)-induced AKI is unknown. We hypothesized that obesity would aggravate renal IRI in mice. We fed mice a standard or high-fat diet for eight weeks. The mice were divided into four groups and submitted to sham surgery or IRI: obese, normal, normal + IRI, obese, and obese + IRI. All studies were performed 48 h after the procedures. Serum glucose, cholesterol, and creatinine clearance did not differ among the groups. Survival and urinary osmolality were lower in the obese + IRI group than in the normal + IRI group, whereas urinary neutrophil gelatinase-associated lipocalin levels, tubular injury scores, and caspase 3 expression were higher. Proliferating cell nuclear antigen expression was highest in the obese + IRI group, as were the levels of oxidative stress (urinary levels of thiobarbituric acid-reactive substances and renal heme oxygenase-1 protein expression), whereas renal Klotho protein expression was lowest in that group. Expression of glutathione peroxidase 4 and peroxiredoxin 6, proteins that induce lipid peroxidation, a hallmark of ferroptosis, was lower in the obese + IRI group. Notably, among the mice not induced to AKI, macrophage infiltration was greater in the obese group. In conclusion, greater oxidative stress and ferroptosis might aggravate IRI in obese individuals, and Klotho could be a therapeutic target in those with AKI.

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.

A high Diabetes Risk Reduction Score (DRRS) is associated with a better cardio-metabolic profile among obese individuals

BACKGROUND

Dietary indices and scores are valuable predictive markers against chronic diseases. Several previous studies have revealed the beneficial effects of diabetes risk reduction score (DRRS) against diabetes and cancer incidence. However, its association with metabolic abnormalities among obese individuals have not been revealed before. In the current study, we aimed to investigate the association between DRRS and metabolic risk factors among obese individuals.

METHODS

In the current cross-sectional study, 342 obese individuals [Body mass index (BMI) ≥ 30 kg/m2] aged 20-50 years were included. Dietary intake was assessed by a validated semi-quantitative food frequency questionnaire (FFQ) of 168 food items and DRRS was calculated. Metabolic syndrome (MetS) was defined based on the guidelines of the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III). Enzymatic methods were used to assess serum lipids, glucose, and insulin concentrations. Blood pressure was measured by a sphygmomanometer and body composition with bioelectrical impedance analysis (BIA).

RESULTS

Those with a higher adherence to DRRS had a significantly higher intake of energy, fiber, and lower protein compared with those in the lower quartiles. Moreover, lower intakes of trans fats, meat, sugar sweetened beverages (SSB), and glycemic index (GI) with higher intakes of fruits, cereal fiber, polyunsaturated fatty acids/ saturated fatty acids (PUFA/ SFA) ratio, coffee, and nuts were observed in the highest versus lowest DRRS categories. Lower systolic blood pressure, diastolic blood pressure, triglyceride and, higher high-density lipoprotein values were observed in higher DRRS categories. Logistic regression analysis showed that hypertension was significantly associated with adherence to DRRS among obese individuals, the odds ratio (OR) was 0.686 (95% confidence interval [CI], 0.26-0.84) after adjustment for potential confounders. But the risk of other components of MetS was not significantly associated with higher quartiles of adherence to DRRS. Also, a non-significantly lower prevalence of MetS was observed in the higher quartile of DRRS.

CONCLUSIONS

According to the results of the current study, higher DRRS was associated with lower blood pressure, modified serum lipids, and lower Mets prevalence. Further studies in different populations are warranted for better generalization of the obtained findings.

Obesity Pillars Roundtable: Body mass index and body composition in Black and Female individuals. Race-relevant or racist? Sex-relevant or sexist?

Background

Body mass index (BMI or weight in kilograms/height in meters2) is the most common metric to diagnose overweight and obesity. However, a body composition analysis more thoroughly assesses adiposity, percent body fat, lean body mass (i.e., including skeletal muscle), and sometimes bone mineral density. BMI is not an accurate assessment of body fat in individuals with increased or decreased muscle mass; the diagnostic utility of BMI in individuals is also influenced by race and sex.

Methods

Previous Obesity Pillars Roundtables addressed the diagnostic limitations of BMI, the importance of android and visceral fat (especially among those with South and East Asian ancestry), and considerations of obesity among individuals who identify as Hispanic, diverse in sexual-orientation, Black, Native American, and having ancestry from the Mediterranean and Middle East regions. This roundtable examines considerations of BMI in Black and female individuals.

Results

The panelists agreed that body composition assessment was a more accurate measure of adiposity and muscle mass than BMI. When it came to matters of race and sex, one panelist felt: "race is a social construct and not a defining biology." Another felt that: "BMI should be a screening tool to prompt further evaluation of adiposity that utilizes better diagnostic tools for body composition." Regarding bias and misperceptions of resistance training in female individuals, another panelist stated: "I have spent my entire medical career taking care of women and have never seen a woman unintentionally gain 'too much' muscle mass and bulk up from moderate strength training."

Conclusions

Conveying the importance of race and sex regarding body composition has proven challenging, with the discussion sometimes devolving into misunderstandings or misinformation that may be perceived as racist or sexist. Body composition analysis is the ultimate diagnostic equalizer in addressing the inaccuracies and biases inherent in the exclusive use of BMI.

Vancomycin dosing in patients with obesity

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

Utilization of Cystatin C in the Outpatient Setting

INTRODUCTION

Serum creatinine is the traditional biomarker for estimating glomerular filtration rate (eGFR). Cystatin C is an alternative biomarker for which estimating equations exist. The use of cystatin C testing, and the interrelationships among the recently revised Chronic Kidney Disease Epidemiology (CKD-EPI) 2021 estimating equations, was evaluated in a national outpatient laboratory dataset.

METHODS

Cystatin C results reported on adults between November 2011 and June 2018 by Laboratory Corporation of America Holdings were examined, with classification of ordering providers and diagnostic codes. Updated eGFR results were calculated using the CKD-EPI 2021 equations for each sample with both cystatin C and creatinine values available. The Spearman correlation coefficients were calculated. Reclassification at clinically relevant cut-off values was examined.

RESULTS

There were 87,803 serum cystatin C levels among 55,360 patients; mean age 58 ± 17 years; 50% women. Cystatin C usage increased over time and was ordered for many indications. Among 73,367 samples with simultaneous creatinine and cystatin C, r = 0.84 between eGFR-creatinine and eGFR-cystatin. Correlations of eGFR-creatinine, eGFR-cystatin, and the averaged result of the two equations to the new combined equation were r = 0.94, r = 0.97, and r = 0.998, respectively (p < 0.001 for all). Use of combined/averaged equations tended to result in a higher eGFR and upclassification, compared to eGFR-creatinine.

CONCLUSION/DISCUSSION

Use of Cystatin C is increasing and has moved beyond the nephrology community and the original indications from the 2012 KDIGO guidelines. Community utilization of cystatin C measurement is likely to expand, and understanding of the relationships between estimating equations will help clinicians optimize their use in the outpatient setting.

Drug dosing in hospitalized obese patients with COVID-19

Obesity is highly prevalent in hospitalized patients admitted with COVID-19. Evidence based guidelines are available for COVID-19-related therapies but dosing information specific to patients with obesity is lacking. Failure to account for the pharmacokinetic alterations that exist in this population can lead to underdosing, and treatment failure, or overdosing, resulting in an adverse effect. The objective of this manuscript is to provide clinicians with guidance for making dosing decisions for medications used in the treatment of patients with COVID-19. A detailed literature search was conducted for medications listed in evidence-based guidelines from the National Institutes of Health with an emphasis on pharmacokinetics, dosing and obesity. Retrieved manuscripts were evaluated and the following prioritization strategy was used to form the decision framework for recommendations: clinical outcome data > pharmacokinetic studies > adverse effects > physicochemical properties. Most randomized controlled studies included a substantial number of patients who were obese but few had large numbers of patients more extreme forms of obesity. Pharmacokinetic data have described alterations with volume of distribution and clearance but this variability does not appear to warrant dosing modifications. Future studies should provide more information on size descriptors and stratification of data according to obesity and body habitus.

Creatinine Assessment in Non-Steady-State Conditions: A Critical Review

OBJECTIVES

To discuss methods for the assessment of creatinine clearance (Cl_cr) when serum creatinine (SCr) is not at steady state in order to estimate kidney function and apply the estimate to kidney function staging for clinical assessment or drug dosing.

DATA SOURCES

A PubMed search was conducted from 1976 to mid-January 2021 with other articles identified through review of bibliographies of retrieved articles and citations in Scopus.

STUDY SELECTION AND DATA EXTRACTION

Articles assessing Cl_cr under non-steady-state conditions and studies evaluating predictive equations were selected.

DATA SYNTHESIS

When SCr is systematically changing (ie, trending up or down), kinetic methods to estimate Cl_cr are appropriate. Estimates from kinetic methods should be individual based and not indexed to body surface area, and careful monitoring is required to confirm predictions as the situation evolves. Standard methods intended for steady-state conditions should not be used to estimate Cl_cr in patients with unstable SCr.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Creatinine continues to be a monitoring parameter of choice and is an important variable in all the commonly used equations for estimating Cl_cr and most important for estimating glomerular filtration rate. However, standard methods of estimating Cl_cr for medication dosing are not accurate under non-steady-state conditions.

CONCLUSION

The methods for kinetic clearance estimation and standards methods for clearance estimation, such as the Cockcroft-Gault equation, are mutually exclusive. There are no benefits of using the kinetic method in patients with stable SCr concentrations, and standard equations are not appropriate with unstable SCr concentrations.