Validation of insulin sensitivity surrogate indices and prediction of clinical outcomes in individuals with and without impaired renal function. Kidney Int. 2014;86:383-391. [PMID: 24476695 DOI: 10.1038/ki.2014.1]

The U-shape relationship between insulin resistance-related indexes and chronic kidney disease: a retrospective cohort study from National Health and Nutrition Examination Survey 2007-2016

BACKGROUND

There is ongoing debate on the correlation between chronic kidney disease (CKD) and insulin resistance (IR)-related indices. Our objective was to explore the prognostic ability of IR-related indexes for the prevalence of CKD, as well as the mortality from all causes and cardiovascular disease (CVD) in CKD patients.

METHODS

The data used in this study came from the National Health and Nutrition Examination Survey (NHANES). Binary logistic regression analysis, Cox proportional hazards model, and restricted cubic spline (RCS) were used to analyze the relationship between IR-related indexes, including metabolic score of IR (METS-IR), homeostatic model assessment for IR (HOMA-IR), triglyceride glucose index (TyG), triglyceride glucose-waist-to-height ratio (TyG-WHtR), triglyceride glucose-body mass index (TyG-BMI), with CKD and its all-cause mortality and CVD mortality. Subgroup analysis was performed to test the stability of the results. Finally, the predictive power of IR-related indexes for CKD was tested by the receiver operating characteristic (ROC) curve.

RESULTS

Among the recruited 10,660 participants, 15.42% were CKD patients. All IR-related indexes were found to be nonlinearly correlated to the prevalence of CKD in the study. When the TyG index was higher than 9.05, it was positively associated with CKD (OR: 1.77, 95% CI 1.44-2.18). Moreover, increased TyG-WHtR level was correlated with a greater prevalence of CKD when it was higher than 4.3 (OR: 1.31, 95% CI 1.19-1.45). Other IR-related indexes (METS-IR, HOMA-IR, and TyG-BMI) showed fewer notable correlations with CKD. The association of IR-related indexes and the prevalence of CKD remained consistent in most subgroups (P for interactions > 0.05). TyG-WHtR was also the predictor of all-cause mortality in CKD patients (HR: 1.34, 95% CI 1.14-1.58), while other IR-related indexes were not correlated with the all-cause mortality or CVD mortality in CKD patients (P > 0.05). Otherwise, ROC curves showed that TyG-WHtR had more robust diagnostic efficacy than other IR-related indexes (METS-IR, HOMA-IR, TyG, and TyG-BMI) in predicting CKD (area under the curve: 0.630, 95% CI 0.615-0.644).

CONCLUSIONS

IR-related biomarkers (METS-IR, HOMA-IR, TyG, and TyG-BMI) were positively correlated with the prevalence of CKD. Moreover, TyG-WHtR enhanced CKD and its all-cause mortality prediction. In patients with elevated levels of IR-related indexes, the early detection and intervention of IR may reduce the occurrence of CKD and the prognosis of CKD patients.

Triglyceride Glucose Index as an Indicator of Cardiovascular Risk in Syrian Refugees

Background

The triglyceride glucose (TyG) index is a quick and inexpensive approach to measure insulin resistance. The aim of this study was to evaluate the TyG index's ability to predict cardiovascular risk and determine the TyG index cutoff values in Syrian refugees.

Methods

A retrospective research study was conducted with 756 Syrian refugees. Data on demographics and clinical laboratory assessments were obtained from refugee's files. The formula Ln [fasting triglycerides (mg/dL) × fasting plasma glucose (mg (dL)/2] was used to calculate the TyG index. The Framingham risk score was used to calculate ten-year cardiovascular risk. The TyG index cutoff point was determined using the receiver operating characteristic curve (ROC).

Results

Included participants had a mean age of 56.76 ± 10.78 years and a mean body mass index (BMI) of 27.42 ± 4.03 kg/m2. 28.57% of the subjects were smokers, and the majority were female (56.75%). A significant moderate correlation was observed between TyG index and Framingham score (r = 0.428, p < 0.001). ROC curve analysis for TyG index and Framingham score showed an area under the curve (AUC) of 0.741 (95% CI = 0.691-0.791; p < 0.001). The cutoff value of the TyG index to recognize intermediate/high risk Framingham risk score was 9.33, with a sensitivity of 64.3%, and specificity of 75.0%.

Conclusion

Our findings determine that, given a TyG index cutoff value of 9.33, the TyG index has a predictive ability to assess ten-year cardiovascular risk by comparison to the Framingham risk score in a high-risk group of Syrian refugees and can be used as an independent indicator of cardiovascular risk.

Outcomes With Finerenone in Patients With Chronic Kidney Disease and Type 2 Diabetes by Baseline Insulin Resistance

OBJECTIVE

To explore whether insulin resistance, assessed by estimated glucose disposal rate (eGDR), is associated with cardiorenal risk and whether it modifies finerenone efficacy.

RESEARCH DESIGN AND METHODS

In FIDELITY (N = 13,026), patients with type 2 diabetes, either 1) urine albumin-to-creatinine ratio (UACR) of ≥30 to <300 mg/g and estimated glomerular filtration rate (eGFR) of ≥25 to ≤90 mL/min/1.73 m2 or 2) UACR of ≥300 to ≤5,000 mg/g and eGFR of ≥25 mL/min/1.73 m2, who also received optimized renin-angiotensin system blockade, were randomized to finerenone or placebo. Outcomes included cardiovascular (cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure) and kidney (kidney failure, sustained decrease of ≥57% in eGFR from baseline, or renal death) composites. eGDR was calculated using waist circumference, hypertension status, and glycated hemoglobin for 12,964 patients.

RESULTS

Median eGDR was 4.1 mg/kg/min. eGDR

CONCLUSIONS

Insulin resistance was associated with increased cardiovascular (but not kidney) risk and did not modify finerenone efficacy.

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Key Words Collapse

MESH Headings

• Humans
• Diabetes Mellitus, Type 2/complications
• Diabetes Mellitus, Type 2/drug therapy
• Insulin Resistance
• Double-Blind Method
• Renal Insufficiency, Chronic/complications
• Glucose/therapeutic use
• Insulins/therapeutic use
• Naphthyridines

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Grants

• P30 DK111024 NIDDK NIH HHS
• Bayer

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Affiliation(s)

Thomas Ebert Medical Department III – Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
Stefan D. Anker Department of Cardiology of German Heart Center Charité; Institute of Health Center for Regenerative Therapies, German Centre for Cardiovascular Research partner site Berlin, Charité Universitätsmedizin, Berlin, Germany
Luis M. Ruilope Cardiorenal Translational Laboratory and Hypertension Unit, Institute of Research imas12, Madrid, Spain CIBER-CV, Hospital Universitario 12 de Octubre, Madrid, Spain Faculty of Sport Sciences, European University of Madrid, Madrid, Spain
Paola Fioretto Department of Medicine, University of Padua, Italy
Vivian Fonseca Tulane University Health Sciences Center, New Orleans, LA
Guillermo E. Umpierrez Division of Endocrinology, Emory University School of Medicine, Atlanta, GA
Andreas L. Birkenfeld Department of Diabetology, Endocrinology and Nephrology, University Clinic, Tübingen, Germany Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, University of Tübingen, Tübingen, Germany German Center for Diabetes Research, Neuherberg, Germany
Robert Lawatscheck Clinical Research, Bayer AG, Berlin, Germany
Charlie Scott Data Science and Analytics, Bayer PLC, Reading, U.K
Katja Rohwedder Medical Affairs, Bayer AG, Berlin, Germany
Peter Rossing Steno Diabetes Center Copenhagen, Herlev, Denmark Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
FIDELIO-DKD and FIGARO-DKD Investigators

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Non-linear relationship between baseline fasting blood glucose and mortality in peritoneal dialysis patients, a retrospective cohort study

Background

The relationship between baseline fasting blood glucose (bFBG) and mortality in peritoneal dialysis (PD) patients has been the subject of debate, with limited exploration of the non-linear relationship between bFBG and death in these patients.

Methods

This retrospective study categorized patients into four groups based on their bFBG using quartiles. Baseline clinical data at the initiation of dialysis were compared. Survival curves were plotted, and subgroup analyses were stratified by relevant covariates. To address the non-linear relationship, curve fitting and a threshold effect analysis were performed.

Results

The study included 379 PD patients with a median follow-up of 41.8 (22.6, 60.1) months. The COX proportional hazards model showed an association between bFBG and the risk of death after adjusting for confounding factors [hazard ratio (HR): 1.22, 95% CI: 1.05-1.41, P = 0.009]. Stratified analyses indicated a stable correlation between bFBG and mortality. The Kaplan-Meier curve analysis revealed significant differences in survival rates among different groups based on bFBG levels (P < 0.01). The curve fitting analysis revealed a U-shaped relationship between bFBG and mortality, with an inflection point at approximately 5.1 mmol/L.

Conclusion

Our study has demonstrated a non-linear relationship between bFBG and mortality in PD patients. Additionally, we have found that the optimal bFBG value associated with the lowest risk of mortality is approximately 5.1 mmol/L.

Brain-derived neurotrophic factor associated with kidney function

BACKGROUND

We examined the relationship between brain-derived neurotrophic factor (BDNF) and chronic kidney disease (CKD).

METHODS

First, a cross-sectional study was conducted in 480 participants without known diabetes. An oral glucose tolerance test (OGTT) was administered after overnight fasting, and blood samples were collected at 0, 30, and 120 min. Second, a total of 3003 participants were enrolled for the case-control genetic analysis. After assigning them to a case or a control group based on age and CKD status, we investigated the association between BDNF gene variants and susceptibility to CKD.

RESULTS

A higher fasting serum BDNF quartile was significantly associated with a lower prevalence of CKD (P value for trend  < 0.001). Based on the receiver operating characteristic analysis, the fasting BDNF level had a larger area under the curve for differentiating CKD (0.645, 95% CI 0.583‒0.707) than the BDNF levels at both 30 min (0.547, 95% CI 0.481‒0.612) and 120 min (0.598, 95% CI 0.536‒0.661). A significantly lower CKD prevalence (odds ratio = 0.30, 95% CI 0.12‒0.71) was observed in the highest quartile of fasting BDNF level than that in the lowest quartile, whereas no interquartile differences were observed for BDNF levels determined at 30 or 120 min during the OGTT. Furthermore, BDNF-associated variants, including rs12098908, rs12577517, and rs72891405, were significantly associated with CKD.

CONCLUSIONS

The BDNF level at fasting, but not at 30 and 120 min after glucose intake, was an independent indicator of CKD. In addition, significant associations were observed between three BDNF gene variants and CKD.

Serum Lipopolysaccharide-Binding Protein Levels and Cardiovascular Events in Hemodialysis Patients: A Prospective Cohort Study

INTRODUCTION

Patients with end-stage kidney disease (ESKD) exhibit an elevated cardiovascular risk. Chronic inflammation is one of the main mechanisms of cardiovascular disease (CVD). Lipopolysaccharide has been proposed as a link between systemic inflammation and CVD. Herein, we evaluated whether lipopolysaccharide-binding protein (LBP), a surrogate marker of lipopolysaccharide and consequent inflammation, is associated with cardiovascular events in ESKD.

METHODS

We performed a prospective cohort study of maintenance hemodialysis patients. Baseline serum LBP levels were categorized into tertiles and also modeled continuously for analyses. Cox regression methods were used to evaluate the association of serum LBP levels with cardiovascular events.

RESULTS

A total of 360 hemodialysis patients were included in this analysis. During a median follow-up of 3.1 years, 90 (25.0%) patients had cardiovascular events. Patients in the upper tertile of serum LBP levels had a significantly greater risk of cardiovascular events (hazard ratio [HR] 4.87; 95% confidence intervals [CI], 2.12-11.15) than those in the lower tertile, independent of age, sex, hypertension, diabetes, CVD, dialysis vintage, body mass index, non-high-density lipoprotein cholesterol, albumin, phosphorus, high-sensitivity C-reactive protein, and interleukin-6. The association was consistent regardless of whether competing risk of death was accounted for (subdistribution HR 4.87; 95% CI, 1.96-12.11 for upper versus lower tertiles) or serum LBP was analysed as a continuous variable (HR 1.30; 95% CI, 1.02-1.66 per 1 SD increment).

CONCLUSIONS

Serum LBP levels were independently associated with cardiovascular events in heomodialysis patients. LBP might serve as a novel biomarker for CVD in ESKD.

Insulin Sensitivity After Living Donor Nephrectomy

BACKGROUND

The kidney is essential for glucose and insulin metabolism. Living kidney donors (LKDs) experience a reduction in glomerular filtration rate of 25 to 30 mL/min after donor nephrectomy. Little is known about the effect of glomerular filtration rate decline on insulin sensitivity in LKDs.

METHODS

We conducted a prospective pilot study on 9 LKDs (N = 9) who underwent dynamic metabolic testing (mixed meal tolerance test) to measure proxies of insulin sensitivity (homeostatic model assessment of insulin resistance, the area under curve [AUC] for insulin/glucose ratio, and Matsuda insulin sensitivity index) before and 3 months after donor nephrectomy. The primary outcome was the change in insulin sensitivity indices (delta [post-nephrectomy - pre-nephrectomy]).

RESULTS

Four of the donors had a body mass index (BMI) between 32.0 and 36.7 predonation. Post-donor nephrectomy, compared with prenephrectomy values, median insulin AUC increased from 60.7 to 101.7 hr*mU/mL (delta median 33.3, P = .04) without significant change in median glucose AUC levels from 228.9 to 209.3 hr*mg/dL (delta median 3.2, P = .77). There was an increase in the median homeostatic model assessment of insulin resistance from 2 to 2.9 (delta median 0.8, P = .03) and the AUC insulin/glucose ratio from 30.9 to 62.1 pmol/mmol (delta median 17.5, P = .001), whereas the median Matsuda insulin sensitivity index decreased from 5.9 to 2.9 (delta median -2, P = .05). The changes were more pronounced in obese (BMI >32) donors.

CONCLUSION

LKDs appear to have a trend toward a decline in insulin sensitivity post-donor nephrectomy in the short term, especially in obese donors (BMI >32). Further investigation with a larger sample size and longer follow-up is needed.

Nodular glomerulosclerosis in a kidney transplant recipient with impaired glucose tolerance: diabetic or idiopathic? A case report and literature review

Nodular glomerulosclerosis, typically diagnosed in patients with diabetes mellitus, has been reported in native kidneys of pre-diabetic patients but similar cases in kidney transplant recipients are lacking. We describe a case of nodular glomerulosclerosis in a kidney transplant recipient who had not been found to be diabetic despite regular screening and discuss the implications for the pathogenesis and diagnosis of nodular glomerulosclerosis and screening of post-transplant diabetes mellitus.

Association between the triglyceride-glucose index and diabetic nephropathy in patients with type 2 diabetes: A cross-sectional study

Aims/Introduction

The triglyceride–glucose (TyG) index has been proposed as a reliable and simple marker of insulin resistance. We investigated the association between TyG index and diabetic nephropathy (DN) in patients with type 2 diabetes.

Materials and Methods

A consecutive case series of 682 adult patients with type 2 diabetes hospitalized in the Department of Endocrinology at the Tongji Hospital (Wuhan, Hubei, China) from January 2007 to December 2009 was included in this cross‐sectional analysis. Receiver operating characteristics curve analysis, correlation analysis and multiple logistic regression analysis were carried out.

Results

A total of 232 (34.0%) participants were identified with DN. Compared with the non‐DN group, the DN group had longer disease duration, and higher bodyweight, systolic blood pressure, diastolic blood pressure, glycated hemoglobin, triglycerides, total cholesterol, serum uric acid, 24 h‐urinary albumin, TyG index and homeostasis model assessment 2 estimates for insulin resistance (HOMA2‐IR; P < 0.05 for each). The TyG index with an optimal cut‐off point >9.66 showed a higher area under the receiver operating characteristic curve of 0.67 (P = 0.002) than HOMA2‐IR (area under the curve 0.61, P = 0.029) on receiver operating characteristic curve analysis for DN identification. Additionally, the TyG index positively correlated with the levels of metabolic indicators (bodyweight, glycated hemoglobin, triglycerides, total cholesterol, serum uric acid, fasting glucose and HOMA2‐IR) and natural logarithmic 24 h‐urinary albumin (P < 0.05 for each), but not natural logarithm of estimated glomerular filtration rate. On multiple regression analysis, an increased TyG index was shown to be an independent risk factor (odds ratio 1.91, P = 0.001) for DN.

Conclusions

The TyG index was independently associated with DN in patients with type 2 diabetes, and was a better marker than HOMA2‐IR for identification of DN in type 2 diabetes patients.

Insulin: Trigger and Target of Renal Functions

Kidney function in metabolism is often underestimated. Although the word “clearance” is associated to “degradation”, at nephron level, proper balance between what is truly degraded and what is redirected to de novo utilization is crucial for the maintenance of electrolytic and acid–basic balance and energy conservation. Insulin is probably one of the best examples of how diverse and heterogeneous kidney response can be. Kidney has a primary role in the degradation of insulin released in the bloodstream, but it is also incredibly susceptible to insulin action throughout the nephron. Fluctuations in insulin levels during fast and fed state add another layer of complexity in the understanding of kidney fine-tuning. This review aims at revisiting renal insulin actions and clearance and to address the association of kidney dysmetabolism with hyperinsulinemia and insulin resistance, both highly prevalent phenomena in modern society.

Plant-based diets, insulin sensitivity and inflammation in elderly men with chronic kidney disease

BACKGROUND

In persons with CKD, adherence to plant-based diets is associated with lower risk of CKD progression and death, but underlying mechanisms are poorly characterized. We here explore associations between adherence to plant-based diets and measures of insulin sensitivity and inflammation in men with CKD stages 3-5.

METHODS

Cross-sectional study including 418 men free from diabetes, aged 70-71 years and with cystatin-C estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m² and not receiving kidney-specific dietetic advice. Information from 7-day food records was used to evaluate the adherence to a plant-based diet index (PBDi), which scores positively the intake of plant-foods and negatively animal-foods. Insulin sensitivity and glucose disposal rate were assessed with the gold-standard hyperinsulinemic euglycemic glucose clamp technique. Inflammation was evaluated by serum concentrations of C-reactive protein (CRP) and interleukin (IL)-6. Associations were explored through linear regression and restricted cubic splines.

RESULTS

The majority of men had CKD stage 3a. Hypertension and cardiovascular disease were the most common comorbidities. The median PBDi was 38 (range 14-55). Across higher quintiles of PBDi (i.e. higher adherence), participants were less often smokers, consumed less alcohol, had lower BMI and higher eGFR (P for trend <0.05 for all). Across higher PBDi quintiles, patients exhibited higher insulin sensitivity and lower inflammation (P for trend <0.05). After adjustment for eGFR, lifestyle factors, BMI, comorbidities and energy intake, a higher PBDi score remained associated with higher glucose disposal rate and insulin sensitivity as well as with lower levels of IL-6 and CRP.

CONCLUSION

In elderly men with non-dialysis CKD stages 3-5, adherence to a plant-based diet was associated with higher insulin sensitivity and lower inflammation, supporting a possible role of plant-based diets in the prevention of metabolic complications of CKD.

Obesity and Metabolic Syndrome in Kidney Transplantation: The Role of Dietary Fructose and Systemic Endotoxemia

BACKGROUND

The concepts that obesity is merely a consequence of overeating, and that metabolic health then reflects obesity, may be insufficient and potentially flawed. The role of fructose intake and metabolic endotoxemia has gained attention recently, but data in kidney transplantation are lacking. This study evaluated the risk factors for metabolic syndrome (MS), its components, and other associated markers in kidney transplant recipients (KTRs), focusing particularly on fructose intake and systemic endotoxemia.

METHODS

This cross-sectional observational study enrolled 128 KTRs longer than 1 year posttransplantation. Clinical, biochemical, anthropometric, and questionnaire assessments were undertaken.

RESULTS

Obesity (body mass index, ≥30 kg/m) and MS (International Diabetes Federation Definition) were found in 36.7% and 50% of KTRs, respectively. Both increased fructose intake (P = 0.01) and endotoxin level (P = 0.02) were independently associated with MS; and higher fructose intake was independently associated with obesity (P < 0.001). Specifically, increased fructose intake was associated with the central obesity (P = 0.01) and hyperglycemia (P < 0.001) criteria of MS, whereas higher endotoxin level was associated with the hypertriglyceridemia (P = 0.003) and low HDL cholesterol concentration (P = 0.002) criteria of MS. Neither saturated fat nor total caloric intakes were independently associated with obesity and MS; and neither obesity nor central obesity were independently associated with the dyslipidemia and hyperglycemia criteria of MS. Principal component analysis demonstrated relationships between higher levels of endotoxin, soluble endothelial selectin, triglycerides, and insulin resistance (r > 0.6), as well as relationships between increased fructose intake, inflammation, and blood glucose (r > 0.6).

CONCLUSIONS

Dietary modifications through decreasing fructose intake and addressing systemic endotoxemia are plausible targets for improving metabolic health of KTRs.

Insulin resistance and chronic kidney disease progression, cardiovascular events, and death: findings from the chronic renal insufficiency cohort study

BACKGROUND

Insulin resistance contributes to the metabolic syndrome, which is associated with the development of kidney disease. However, it is unclear if insulin resistance independently contributes to an increased risk of chronic kidney disease (CKD) progression or CKD complications. Additionally, predisposing factors responsible for insulin resistance in the absence of diabetes in CKD are not well described. This study aimed to describe factors associated with insulin resistance and characterize the relationship of insulin resistance to CKD progression, cardiovascular events and death among a cohort of non-diabetics with CKD.

METHODS

Data was utilized from Chronic Renal Insufficiency Cohort Study participants without diabetes (N = 1883). Linear regression was used to assess associations with insulin resistance, defined using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The relationship of HOMA-IR, fasting glucose, hemoglobin A1c (HbA1c), and C-peptide with CKD progression, cardiovascular events, and all-cause mortality was examined with Cox proportional hazards models.

RESULTS

Novel positive associations with HOMA-IR included serum albumin, uric acid, and hemoglobin A1c. After adjustment, HOMA-IR was not associated with CKD progression, cardiovascular events, or all-cause mortality. There was a notable positive association of one standard deviation increase in HbA1c with the cardiovascular endpoint (HR 1.16, 95% CI: 1.00-1.34).

CONCLUSION

We describe potential determinants of HOMA-IR among a cohort of non-diabetics with mild-moderate CKD. HOMA-IR was not associated with renal or cardiovascular events, or all-cause mortality, which adds to the growing literature describing an inconsistent relationship of insulin resistance with CKD-related outcomes.

Insulin resistance in chronic kidney disease

This review provides an overview of insulin resistance (IR) in patients with chronic kidney disease (CKD). IR is a pathological state in which target tissues fail to respond normally to insulin. IR is understood as a consequence of CKD and its prevalence rises particularly in advanced CKD stages. Mechanisms leading to IR are complex and multifactorial, involving post-receptor signaling defects, unhealthy lifestyles, metabolic acidosis, inflammation, oxidative stress, vitamin D deficiency, anemia, and uremic toxicity, as shown by human and experimental studies over the last 30 years. Whereas hyperinsulinemic euglycemic clamp is the gold standard, it is unpractical at the bedside, and either estimated IR indices by fasting glucose or insulin and oral glucose tolerance tests (OGTT) provide satisfactory estimates of IR also in patients with CKD. IR is likely to play a key role in the development of cardiometabolic complications, but not all studies associate IR with the risk of cardiovascular events and death. Various interventions at the level of lifestyle modifications, adaptations in dialysis therapy (such as use of icodextrin based solutions) and pharmacological strategies such as thiazolidinediones or vitamin D therapy may improve IR in patient with CKD.

Probing insulin sensitivity in diabetic kidney disease: is there a stronger role for functional imaging?

Clinical and experimental evidence support a cause-effect relationship between altered insulin signaling and development of kidney disease of metabolic and non-metabolic origin. However, the current criteria to measure and/or estimate the insulin resistance (IR) are available as research tool but are very difficult to implement in the clinical practice. Therefore, a better understanding of the key players contributing to IR may lead to the development of new non-invasive tools to assess organ-specific insulin sensitivity (IS). We will therefore first introduce the concept that IR and kidney disease may be causally linked as suggested by clinical and experimental studies. We will then, expand on the potential mechanisms leading to altered renal insulin signaling. After reviewing the limitation of currently available strategies to determine IR, this review article will focus on imaging techniques that could be utilized to determine renal IR and that could be tested to predict kidney disease development and progression.

Chronic Kidney Disease-Induced Insulin Resistance: Current State of the Field

PURPOSE OF REVIEW

Insulin resistance is an early complication of chronic kidney disease (CKD) associated with worsening cardiovascular outcomes. This review will evaluate mechanisms responsible for CKD-induced insulin resistance and therapies currently available.

RECENT FINDINGS

Recent mechanisms have been identified including SIRPα and specific E3 ubiquitin ligases causing insulin resistance in CKD. The hallmark finding in these mechanisms is degradation of the insulin receptor substrate 1 (IRS1) which impairs intracellular insulin signaling and ultimately metabolism. The mechanisms responsible for insulin resistance in CKD include inflammation, oxidative stress, elevations in aldosterone, angiotensin II, uremic toxins, and metabolic acidosis. Potential treatments currently available for CKD-induced insulin resistance include lifestyle modification and metformin. Potential future treatments may include glucagon-like peptide agonists, SGLT2 inhibitors, and thiazolidinediones. Investigations into molecular mechanisms responsible for insulin resistance in CKD may provide new therapeutic targets while current therapies may prevent the catabolic sequelae of CKD and ameliorate its cardiovascular consequences.

Insulin Sensitivity and Glucose Homeostasis Can Be Influenced by Metabolic Acid Load

Recent epidemiological findings suggest that high levels of dietary acid load can affect insulin sensitivity and glucose metabolism. Consumption of high protein diets results in the over-production of metabolic acids which has been associated with the development of chronic metabolic disturbances. Mild metabolic acidosis has been shown to impair peripheral insulin action and several epidemiological findings suggest that metabolic acid load markers are associated with insulin resistance and impaired glycemic control through an interference intracellular insulin signaling pathways and translocation. In addition, higher incidence of diabetes, insulin resistance, or impaired glucose control have been found in subjects with elevated metabolic acid load markers. Hence, lowering dietary acid load may be relevant for improving glucose homeostasis and prevention of type 2 diabetes development on a long-term basis. However, limitations related to patient acid load estimation, nutritional determinants, and metabolic status considerably flaws available findings, and the lack of solid data on the background physiopathology contributes to the questionability of results. Furthermore, evidence from interventional studies is very limited and the trials carried out report no beneficial results following alkali supplementation. Available literature suggests that poor acid load control may contribute to impaired insulin sensitivity and glucose homeostasis, but it is not sufficiently supportive to fully elucidate the issue and additional well-designed studies are clearly needed.

Normal-weight obesity and clinical outcomes in nondiabetic chronic kidney disease patients: a cohort study

Background

Normal-weight obesity (NWO), defined by a normal body mass index (BMI) and high body fat percentage, has been shown to be associated with cardiometabolic dysfunction and an increased risk of cardiovascular disease and mortality in the general population. However, little is known about the clinical implications of NWO among patients with chronic kidney disease (CKD).

Objective

The aim of this study was to assess the characteristics and outcomes of nondiabetic CKD patients with NWO.

Design

A total of 178 nondiabetic patients with stages 3-5 CKD were prospectively followed for a median of 4.9 y. The patients were classified into 3 different adiposity phenotypes: nonobese [BMI (in kg/m2) <25 and fat mass percentage (FM%) ≤25% for men or ≤35% for women], NWO (BMI <25 and FM% >25% for men or >35% for women), and preobese-obese (BMI ≥25). FM% was determined using the Body Composition Monitor, a multifrequency bioimpedance spectroscopy device. The outcome was a composite of cardiovascular events or all-cause mortality.

Results

The prevalence of NWO was 28.1% among nondiabetic CKD patients with a normal BMI. NWO patients were older, had lower lean body mass, and had higher plasma interleukin-6 concentrations than nonobese patients. However, homeostatic model assessment for insulin resistance levels did not differ between the 2 groups. NWO patients showed a significant 3-fold higher risk of the composite outcome (HR 2.96, 95% CI: 1.13, 7.77; P < 0.05) than did nonobese patients in the fully adjusted model. Preobese-obese patients were not at increased risk compared to nonobese patients.

Conclusions

NWO was associated with the worst prognosis among the 3 different adiposity phenotypes in nondiabetic CKD patients. Our findings suggest the importance of using direct measures of adiposity for risk assessment in CKD patients who are normal-weight. This trial was registered at clinicaltrials.gov as NCT03285074.

Insulin resistance and vascular dysfunction in chronic kidney disease: mechanisms and therapeutic interventions

Insulin resistance (IR) is a novel cardiovascular risk factor that has been implicated in the pathogenesis of cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). Beyond its metabolic effects, insulin can potentially mediate the increased risk for CVD through its vasoactive properties. This review examines key clinical data and potential mechanisms linking IR and cardiovascular risk in CKD. While lifestyle interventions and pharmacotherapies with known insulin-sensitizing properties are promising therapeutic targets to reduce the CVD burden in this population, clinical trial data on the effect of insulin sensitization on vascular function in CKD are either lacking or conflicting and are limited by small sample size and short duration of intervention. Affirming the role of IR in lowering CVD risk in CKD will require prospective randomized controlled studies with sufficient sample size and hard clinical outcomes. Future research efforts should be directed at assessing the efficacy, safety and mechanisms by which novel insulin sensitizers such as bile acid sequestrant, selective and dual peroxisome proliferator-activated receptor modulators and modulators of gut microbiota and uraemic toxins alter vascular function in patients with CKD.

Chronic kidney disease and obesity bias surrogate estimates of insulin sensitivity compared with the hyperinsulinemic euglycemic clamp

Insulin sensitivity can be measured by procedures such as the hyperinsulinemic euglycemic clamp or by using surrogate indices. Chronic kidney disease (CKD) and obesity may differentially affect these measurements because of changes in insulin kinetics and organ-specific effects on insulin sensitivity. In a cross-sectional study of 59 subjects with nondiabetic CKD [estimated glomerular filtration rate: (GFR) <60 ml·min^-1·1.73 m²] and 39 matched healthy controls, we quantified insulin sensitivity by clamp (SI_clamp), oral glucose tolerance test, and fasting glucose and insulin. We compared surrogate insulin sensitivity indices to SI_clamp using descriptive statistics, graphical analyses, correlation coefficients, and linear regression. Mean age was 62.6 yr; 48% of the participants were female, and 77% were Caucasian. Insulin sensitivity indices were 8-38% lower in participants with vs. without CKD and 13-59% lower in obese compared with nonobese participants. Correlations of surrogate indices with SI_clamp did not differ significantly by CKD or obesity status. Adjusting for SI_clamp in addition to demographic factors, Matsuda index was 15% lower in participants with vs. without CKD (P = 0.09) and 36% lower in participants with vs. without obesity (P = 0.0001), whereas 1/HOMA-IR was 23% lower in participants with vs. without CKD (P = 0.02) and 46% lower in participants with vs. without obesity (P < 0.0001). We conclude that CKD and obesity do not significantly alter correlations of surrogate insulin sensitivity indices with SI_clamp, but they do bias surrogate measurements of insulin sensitivity toward lower values. This bias may be due to differences in insulin kinetics or organ-specific responses to insulin.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

The Stockholm CREAtinine Measurements (SCREAM) project: protocol overview and regional representativeness

BACKGROUND

We here describe the construction of the Stockholm CREAtinine Measurement (SCREAM) cohort and assess its coverage/representativeness of the Stockholm county in Sweden. SCREAM has the principal aims to estimate the burden and consequences of chronic kidney disease (CKD) and to identify inappropriate drug use (prescription of nephrotoxic, contraindicated or ill-dosed drugs).

METHODS

SCREAM is a repository of laboratory data of individuals, residing or accessing healthcare in the region of Stockholm, who underwent creatinine assessments between 2006-11. Laboratory tests were linked to administrative databases with complete information on socioeconomic status, demographic data, healthcare utilization, diagnoses, vital status and dispensed prescription medicines.

RESULTS

SCREAM identified 1 118 507 adult Stockholm citizens with available creatinine tests between 2006-11. This corresponded to 66% of the complete population in the region. Geographical coverage was uniform, ranging between 62 and 72% throughout its 26 municipalities. Population coverage was higher across older age strata (50% coverage for age range 18-44 years, >75% for 45-64 years and >90% coverage for ≥65 years). Of note, 97 and 98% of all individuals with a diagnosis of diabetes mellitus or cardiovascular disease, respectively, were captured by SCREAM. Further, 89% of all deaths registered in the period occurred in individuals with a creatinine test undertaken.

CONCLUSION

SCREAM represents the largest cohort to estimate the burden and healthcare implications of CKD in Sweden. The coverage and representativeness of the region of Stockholm was high and in accordance to both the commonness of creatinine assessment, and the medical indications for creatinine testing. The inclusion of individuals who sought medical care and had a creatinine test undertaken resulted in a slight over-representation of elderly and comorbid patients.

Insulin Resistance in Nondiabetic Peritoneal Dialysis Patients: Associations with Body Composition, Peritoneal Transport, and Peritoneal Glucose Absorption

BACKGROUND AND OBJECTIVES

Insulin resistance has been associated with cardiovascular disease in peritoneal dialysis patients. Few studies have addressed the impact of fast transport status or dialysis prescription on insulin resistance. The aim of this study was to test whether insulin resistance is associated with obesity parameters, peritoneal transport rate, and glucose absorption.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Insulin resistance was evaluated with homeostasis model assessment method (HOMA-IR), additionally corrected by adiponectin (HOMA-AD). Enrolled patients were prevalent nondiabetics attending at Santo António Hospital Peritoneal Dialysis Unit, who were free of hospitalization or infectious events in the previous 3 months (51 patients aged 50.4 ± 15.9 years, 59% women). Leptin, adiponectin, insulin-like growth factor-binding protein 1 (IGFBP-1), and daily glucose absorption were also measured. Lean tissue index, fat tissue index (FTI), and relative fat mass (rel.FM) were assessed using multifrequency bioimpedance. Patients were categorized according to dialysate to plasma creatinine ratio at 4 hours, 3.86% peritoneal equilibration test, and obesity parameters.

RESULTS

Obesity was present in 49% of patients according to rel.FM. HOMA-IR correlated better with FTI than with body mass index. Significant correlations were found in obese, but not in nonobese patients, between HOMA-IR and leptin, leptin/adiponectin ratio (LAR), and IGFBP-1. HOMA-IR correlated with HOMA-AD, but did not correlate with glucose absorption or transport rate. There were no significant differences in insulin resistance indices, glucose absorption, and body composition parameters between fast and nonfast transporters. A total of 18 patients (35.3%) who had insulin resistance presented with higher LAR and rel.FM (7.3 [12.3, interquartile range] versus 0.7 [1.4, interquartile range], P<0.001, and 39.4 ± 10.1% versus 27.2 ± 11.5%, P=0.002, respectively), lower IGFBP-1 (8.2 ± 7.2 versus 21.0 ± 16.3 ng/ml, P=0.002), but similar glucose absorption and small-solute transport compared with patients without insulin resistance. FTI and LAR were independent correlates of HOMA-IR in multivariate analysis adjusted for glucose absorption and small-solute transport (r=0.82, P<0.001).

CONCLUSIONS

Insulin resistance in nondiabetic peritoneal dialysis patients is associated with obesity and LAR independent of glucose absorption and small-solute transport status. Fast transport status was not associated with higher likelihood of obesity or insulin resistance.

Molecular mechanisms of insulin resistance in chronic kidney disease

Insulin resistance refers to reduced sensitivity of organs to insulin-initiated biologic processes that result in metabolic defects. Insulin resistance is common in patients with end-stage renal disease but also occurs in patients with chronic kidney disease (CKD), even when the serum creatinine is minimally increased. Following insulin binding to its receptor, auto-phosphorylation of the insulin receptor is followed by kinase reactions that phosphorylate insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase (PI3K) and Akt. In fact, low levels of Akt phosphorylation (p-Akt) identifies the presence of the insulin resistance that leads to metabolic defects in insulin-initiated metabolism of glucose, lipids and muscle proteins. Besides CKD, other complex conditions (e.g., inflammation, oxidative stress, metabolic acidosis, aging and excess angiotensin II) reduce p-Akt resulting in insulin resistance. Insulin resistance in each of these conditions is due to activation of different, E3 ubiquitin ligases which specifically conjugate ubiquitin to IRS-1 marking it for degradation in the ubiquitin-proteasome system (UPS). Consequently, IRS-1 degradation suppresses insulin-induced intracellular signaling, causing insulin resistance. Understanding mechanisms of insulin resistance could lead to therapeutic strategies that improve the metabolism of patients with CKD.

Dysglycemia after renal transplantation: Definition, pathogenesis, outcomes and implications for management

New-onset diabetes after transplantation (NODAT) is major complication following renal transplantation. It commonly develops within 3-6 mo post-transplantation. The development of NODAT is associated with significant increase in risk of major cardiovascular events and cardiovascular death. Other dysglycemic states, such as impaired glucose tolerance are also associated with increasing risk of cardiovascular events. The pathogenesis of these dysglycemic states is complex. Older recipient age is a consistent major risk factor and the impact of calcineurin inhibitors and glucocorticoids has been well described. Glucocorticoids likely cause insulin resistance and calcineurin inhibitors likely cause β-cell toxicity. The impact of transplantation in incretin hormones remains to be clarified. The oral glucose tolerance test remains the best diagnostic test but other tests may be validated as screening tests. Possibly, NODAT can be prevented by administering insulin early in patients identified as high risk for NODAT. Once NODAT has been diagnosed altering immunosuppression may be acceptable, but creates the difficulty of balancing immunological with metabolic risk. With regard to hypoglycemic use, metformin may be the best option. Further research is needed to better understand the pathogenesis, identify high risk patients and to improve management options given the significant increased risk of major cardiovascular events and death.

Insulin resistance in chronic kidney disease: a step closer to effective evaluation and treatment

Accurate measurements are needed to target insulin resistance in CKD. Among older men with and without moderate CKD, Jia and colleagues compared insulin resistance estimated from glucose and insulin concentrations obtained while fasting or during an oral glucose tolerance test to insulin resistance measured by the gold standard hyperinsulinemic euglycemic clamp and tested associations of each with mortality. These findings move forward the study of insulin resistance in CKD and generate new questions for future work.

High blood glucose independent of pre-existing diabetic status predicts mortality in patients initiating peritoneal dialysis therapy

PURPOSE

Poor glycemic control associates with increased mortality in diabetic (DM) dialysis patients, but it is less well established whether high blood glucose (BG) independent of pre-existing diabetic status associates with mortality in dialysis patients. We assessed factors affecting BG at the start of peritoneal dialysis (PD) and its mortality-predictive impact in Korean PD patients.

METHODS

In 174 PD patients (55 % males, 56 % DM), BG, nutritional status, comorbidity (CMD), and residual renal function (RRF) were assessed in conjunction with dialysis initiation. Determinants of BG and its association with mortality after a mean follow-up period of 30 ± 24 months were analyzed.

RESULTS

On Cox proportional hazards analysis comprising all patients, old age, high CMD score, presence of protein energy wasting, and low serum albumin (Salb) concentration were independent predictors of mortality but not a high-BG level, while in patients without pre-existing diabetic status, high BG, together with old age and high CMD score, was an independent predictor of mortality. After adjustment for age, CMD score, and Salb, the risk ratio for mortality increased by 12 % per 1 mg/dL increase in BG in the non-DM patients. Patient survival in patients without pre-existing diabetic status with high BG did not differ from DM patients, but the survival of patients with high BG was significantly lower than in patients with low BG. In patients without pre-existing diabetic status, in multiple regression analysis, high BG at initiation of PD associated with high age, high body mass index, and low RRF.

CONCLUSIONS

High blood glucose at initiation of PD associated with an increased mortality risk in PD patients without pre-existing diabetic status suggesting that blood glucose monitoring and surveillance of factors contributing to poor glycemic control are warranted in patients initiating PD therapy.

Kidney function, β-cell function and glucose tolerance in older men

CONTEXT

Kidney dysfunction induces insulin resistance, but it is unknown if β cell function is affected.

OBJECTIVE

To investigate insulin release (β cell function) and glucose tolerance following a standardized oral glucose tolerance test (OGTT) across kidney function strata.

SETTING AND DESIGN

Community-based cohort study from the Uppsala Longitudinal Study of Adult Men (ULSAM). PARTICIPANTS AND MAIN OUTCOME MEASURE: Included were 1015 nondiabetic Swedish men aged 70-71 years. All participants underwent OGTT and euglycaemic hyperinsulinaemic clamp (HEGC) tests, allowing determination of insulin sensitivity, β cell function, and glucose tolerance. Kidney function was estimated by cystatin C-algorithms. Mixed models were used to identify determinants of insulin secretion after the hyperglycemic load.

RESULTS

As many as 466 (46%) of participants presented moderate-advanced kidney disease. Insulin sensitivity (by HEGC) decreased across decreasing kidney function quartiles. After the OGTT challenge, however, β cell function indices (area under the curve for insulin release, the estimated first phase insulin release, and the insulinogenic index) were incrementally higher. Neither the oral disposition index nor the 2-h postload glucose tolerance differed across the kidney function strata. Mixed models showed that dynamic insulin release during the OGTT was inversely associated with kidney function, despite the correction for each individual's insulin sensitivity or its risk factors.

CONCLUSIONS

In older men, β cell function after a hyperglycemic load appropriately compensated the loss in insulin sensitivity that accompanies kidney dysfunction. As a result, the net balance between insulin sensitivity and β cell function was preserved.

Nonesterified fatty acids and cardiovascular mortality in elderly men with CKD

BACKGROUND AND OBJECTIVES

Although nonesterified fatty acids (NEFAs) are essential as energy substrate for the myocardium, an excess of circulating NEFAs can be harmful. This study aimed to assess plausible relationships between serum NEFA and mortality due to cardiovascular disease (CVD) in individuals with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a prospective cohort study from the third examination cycle of the Uppsala Longitudinal Study of Adult Men, a population-based survey of 1221 elderly men aged 70-71 years residing in Uppsala, Sweden. Data collection took place during 1991-1995. All participants had measures of kidney function; this study investigated 623 (51.7%) of these patients with manifest CKD (defined as either eGFR<60 ml/min per 1.73 m(2) or urine albumin excretion rate ≥20 µg/min). Follow-up for mortality was done from examination date until death or December 31, 2007. After a median follow-up of 14 years (interquartile range, 8-16.8), associations of NEFAs with mortality (related to all causes, CVD, ischemic heart disease [IHD], or acute myocardial infarction) were ascertained.

RESULTS

The median serum NEFA was 14.1 mg/dl (interquartile range, 11.3-17.8). No association was found with measures of kidney function. Diabetes and serum triglycerides were the only multivariate correlates of NEFA. During follow-up, 453 participants died, of which 209 deaths were due to CVD, including 88 IHD deaths, with 41 attributed to acute myocardial infarction (AMI). In fully adjusted covariates, serum NEFA was an independent risk factor for all-cause mortality (hazard ratio [HR] per log2 increase, 1.22; 95% confidence interval [95% CI], 1.00 to 1.48) and CVD-related death (HR, 1.51; 95% CI, 1.15 to 1.99), including both IHD (HR, 1.51; 95% CI, 1.00 to 2.32) and AMI mortality (HR, 2.08; 95% CI, 1.09 to 3.98).

CONCLUSIONS

Elevated serum NEFA associated with CVD mortality, and particularly with mortality due to AMI, in a homogeneous population of older men with moderate CKD.

Obesity--a disease with many aetiologies disguised in the same oversized phenotype: has the overeating theory failed?

Evolution has led to metabolic thrift in humans--a genetic heritage that, when exposed to the modern 'obesogenic' milieu with energy-dense food and a sedentary lifestyle, predisposes to obesity. The current paradigm that overeating of easily digestible carbohydrates and the resulting imbalance between energy in and out as the cause of overweight has recently been challenged. Indeed, studies suggest that the host response to various nutrients contributes to overeating and fat accumulation. Alterations in neurotransmitter functions, changes in the epigenome, dysbiosis of gut microbiota and effects of specific nutrients (or lack of such nutrients) on mitochondrial function and signalling pathways may promote fat accumulation independent of calories. Whereas nutrients that stimulate generation of uric acid (such as fructose and purine-rich food) cause insulin resistance and fat accumulation, other nutrients (such as antioxidants, plant food, probiotics, nuts, soy and omega-3) counteract the negative effects of a calorie-rich diet by salutary effects on mitochondrial biogenesis. Thus, the specific metabolic effects of different nutrients may be more important than its total energy content. By studying the impact of nutrients on mitochondrial health, as well as the trans-generational impact of nutrients during fetal life, and how specific bacterial species correlate with fat mass accumulation, new dietary targets for obesity management may emerge. Overeating and overshooting of calories could to a large extent represent a symptom rather than a cause of obesity; therefore, hypocaloric diets should probably not be the main, and certainly not the only, focus for treatment of the obese patient.