Validation of steady-state insulin sensitivity indices in chronic kidney disease

Dysmetabolic markers predict outcomes in autosomal dominant polycystic kidney disease

BACKGROUND

Overweight and obesity were recently associated with a poor prognosis in patients with autosomal dominant polycystic kidney disease (ADPKD). Whether the metabolic consequences of obesity as defined by the metabolic syndrome (MS) are also linked with disease progression remains untested.

METHODS

Eligible ADPKD patients with different stages of CKD (n = 105) and 105 non-diabetic controls matched for CKD stage were enrolled in the study. Groups were evaluated at baseline for presence of MS, blood markers of metabolism, homeostasis model assessment of insulin resistance (HOMA-IR) score, and biochemical markers of inflammation (hs-CRP, IL-1β, IL-6, TNF-α and PON-1). MS was defined according to the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III). Patients were followed for 12 months and progression defined as a decrease in baseline eGFR > 10%.

RESULTS

MS and hypertension were more prevalent amongst ADPKD patients than in the control group. Meanwhile, markers of inflammation such as hs-CRP (3.63 [3.45-5.17] vs. 4.2 [3.45-8.99] mg/dL; p = 0.014), IL-6 (21.65 [14.1-27.49] vs. 24.9 [16.23-39.4] pg/mL; p = 0.004) and IL-1β (21.33 [15.8-26.4] vs. 26.78 [18.22-35] pg/mL; p < 0.001) levels were all more elevated in ADPKD patients than in non-diabetic CKD subjects. In multivariate analysis having a truncating PKD1 mutation predicted (OR 1.25 [1.09-1.43]; p = 0.002) fulfilling the MS criteria. Finally, ADPKD patients fulfilling MS criteria had a significantly more rapid progression during 12 months of follow-up than did those that did not (OR 3.28 [1.09-9.87]; p = 0.035).

CONCLUSIONS

Our data supports the notion that dysmetabolisms part of the ADPKD phenotype and associated with a poor outcome, especially in patients with a truncating PKD1 mutation.

Hyperhomocysteinemia Associated with Low Muscle Mass, Muscle Function in Elderly Hemodialysis Patients: An Analysis of Multiple Dialysis Centers

Background

The hyperhomocysteinemia was with high prevalence and has been considered as a risk factor for cardiovascular disease in hemodialysis patients. These patients also experienced a high risk of muscle wasting caused by the comorbidity, malnutrition, and low physical activity. We investigated the associations of homocysteinemia with muscle mass, muscle function in elderly hemodialysis patients.

Methods

A clinical cross-sectional study was conducted on 138 hemodialysis patients aged 65 years and above in seven hospital-based hemodialysis centers in Taiwan. The data on anthropometry, laboratory, and 3-day dietary intake was examined. The skeletal muscle mass (SMM) was measured by the bioelectrical impedance analysis; the SMM was adjusted by height or weight as SMM_Ht2 (kg/m²) and SMM_Wt (%). Muscle function was defined as handgrip strength (HGS) (kg) measured by handgrip dynamometer. Statistical analyses were conducted using simple regression and multivariable stepwise regression analysis.

Results

In the total sample, 74.6 % of hemodialysis patients were hyperhomocysteinemia (≥ 15 μmol/L). The means of SMM_Ht2, SMM_Wt, arm lean mass, hand grip strength, and muscle quality were 8.7 ± 1.2, 37.7 ± 5.6, 1.7 ± 0.5, 21.1 ± 7.4, and 10.0 ± 3.0, respectively. The multivariable stepwise regression analysis showed that homocysteinemia level was significantly inversely associated with SMM_Wt (B-coeff. = -0.03, p = 0.02) in hemodialysis patients above 65 years old, but not with muscle function.

Conclusions

Hyperhomocysteinemia is common and associated with decreased muscle mass in the elderly hemodialysis patients. Future studies are suggested to explore the impact of the homocysteine-lowering therapy on muscle decline.

Pretransplant HbA1c and Glucose Metabolism Parameters in Predicting Posttransplant Diabetes Mellitus and Their Course in the First 6 Months After Living-Donor Renal Transplant

OBJECTIVES

Posttransplant diabetes mellitus is a common and serious metabolic complication after renal transplant. Patients with uremia are known to have abnormal glucose metabolism characterized by insulin resistance and defects in insulin secretion, which are ameliorated to some extent with renal replacement therapy and more so with renal transplant. However, the diabetogenicity of calcineurin inhibitors compounds this state of dysglycemia and promotes the development of diabetes in some patients. It is not clear whether pretransplant dysglycemia is a risk factor for posttransplant diabetes mellitus and, if so, which between insulin resistance and pancreatic β-cell dysfunction is a major determinant in predicting posttransplant diabetes mellitus. Here, we examined the roles of the pretransplant oral glucose tolerance test, glycated hemoglobin (HbA1c) levels, and homeostatic model assessment-derived insulin resistance and beta-cell function in the prediction of posttransplant diabetes mellitus and the course of these indexes posttransplant. Our aim was to examine the correlations between these factors and their changes posttransplant with the development of posttransplant diabetes mellitus.

MATERIALS AND METHODS

Pretransplant fasting blood was drawn from patients for plasma glucose, insulin, C-peptide, and HbA1c levels, which was followed by a 2-hour oral glucose tolerance test. After transplant, patients were followed for 6 months to detect posttransplant diabetes mellitus. Serum insulin, C-peptide, and glycated hemoglobin levels were reexamined in patients with posttransplant diabetes mellitus at 1 and 6 months.

RESULTS

Twenty-one patients (29%) developed posttransplant diabetes mellitus. Pretransplant HbA1c was associated with development of posttransplant diabetes mellitus (odds ratio 27.04) on logistic regression. Homeostatic model assessment-derived insulin resistance improved significantly at 6 months posttransplant, whereas beta-cell function remained lower than pretransplant levels in patients with posttransplant diabetes mellitus.

CONCLUSIONS

Pretransplant HbA1c may be used as a predictive marker for posttransplant diabetes mellitus. Insulin resistance but not beta-cell function improves in patients with posttransplant diabetes mellitus at 6 months posttransplant.

Investigating the Effect of Glucose on Aortic Pulse Wave Velocity Using Pancreatic Clamping Methodology

Aortic stiffness, determined by carotid-femoral pulse wave velocity (cfPWV), independently predicts cardiovascular outcomes. Recent studies suggest that glucose levels influence arterial stiffness indices. It is not clear, however, whether glucose affects cfPWV independently of glucoregulatory hormones. The aim of this study was to utilize a pancreatic clamping approach to determine whether plasma glucose independently predicts cfPWV. Healthy participants ( N = 10) underwent pancreatic clamping to control glucose at varying concentrations using a 20% dextrose infusion while suppressing endogenous glucagon, insulin, and growth hormone by octreotide and replacing the hormones intravenously to achieve basal concentrations. Tonometric cfPWV, blood pressure, heart rate, plasma glucose, glucagon, insulin, growth hormone, and vasoactive biomarkers were measured. Plasma glucose levels of 150 mg/dl at 1 hr and 200 mg/dl at 2 hr postbaseline were achieved. There were no significant changes in cfPWV (5.8 m/s at 0 hr, 5.9 m/s at 1 hr, and 5.9 m/s at 2 hr) with increased glucose levels. There were small increases in insulin secretion. A definitive role for glucose in cfPWV modulation was not determined; there is a potential role for insulin as a cfPWV modulator. Continued efforts in clarifying the independent roles of glucose and insulin can elucidate novel vessel-related targets for cardiovascular disease prevention and management in patients with impaired glucose tolerance and diabetes.

Role of insulin resistance indices in predicting new-onset diabetes after kidney transplantation

New-onset diabetes mellitus (NODAT) is a serious complication following renal transplantation. In this cohort study, we studied 118 nondiabetic renal transplant recipients to examine whether indices of insulin resistance and secretion calculated before transplantation and at 3 months post-transplantation are associated with the development of NODAT within 1 year. We also analysed the long-term impact of early diagnosed NODAT. Insulin indices were calculated using homeostasis model assessment (HOMA) and McAuley's Index. NODAT was diagnosed using fasting plasma glucose. Median follow-up was 11 years. The cumulative incidence of NODAT at 1 year was 37%. By logistic regression, recipient age (per year) was the only significant pretransplant predictor of NODAT (OR 1.04, CI 1.009-1.072), while age (OR 1.04, CI 1.005-1.084) and impaired fasting glucose (OR 2.97, CI 1.009-8.733) were significant predictors at 3 months. Pretransplant and 3-month insulin resistance and secretion indices did not predict NODAT. All-cause mortality was significantly higher in recipients developing NODAT within 1 year compared with those remaining nondiabetic (44% vs. 22%, log-rank P = 0.008). By Cox's regression analysis, age (HR 1.075, CI 1.042-1.110), 1-year creatinine (HR 1.007, CI 1.004-1.010) and NODAT within 3 months (HR 2.4, CI 1.2-4.9) were independent predictors of death. In conclusion, NODAT developing early after renal transplantation was associated with poor long-term patient survival. Insulin indices calculated pretransplantation using HOMA and McAuley's Index did not predict NODAT.

Risk factors for peripheral arterial disease among patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have an increased risk for developing peripheral arterial disease (PAD). The aim of this study was to examine the cross-sectional association between novel risk factors and prevalent PAD in patients with CKD. A total of 3,758 patients with estimated glomerular filtration rates of 20 to 70 ml/min/1.73 m(2) who participated in the Chronic Renal Insufficiency Cohort (CRIC) study were included in the present analysis. PAD was defined as an ankle-brachial index <0.9 or a history of arm or leg revascularization. After adjustment for age, gender, race, cigarette smoking, physical activity, history of hypertension and diabetes, pulse pressure, high-density lipoprotein cholesterol, estimated glomerular filtration rate, and CRIC clinical sites, several novel risk factors were significantly associated with PAD. For example, odds ratios for a 1-SD higher level of risk factors were 1.18 (95% confidence interval [CI] 1.08 to 1.29) for log-transformed high-sensitivity C-reactive protein, 1.18 (95% CI 1.08 to 1.29) for white blood cell count, 1.15 (95% CI 1.05 to 1.25) for fibrinogen, 1.13 (95% CI 1.03 to 1.24) for uric acid, 1.14 (95% CI 1.02 to 1.26) for glycosylated hemoglobin, 1.11 (95% CI 1.00 to 1.23) for log-transformed homeostasis model assessment of insulin resistance, and 1.35 (95% CI 1.18 to 1.55) for cystatin C. In conclusion, these data indicate that inflammation, prothrombotic state, oxidative stress, insulin resistance, and cystatin C were associated with an increased prevalence of PAD in patients with CKD. Further studies are warranted to examine the causal effect of these risk factors on PAD in patients with CKD.

Modulation of vitamin D signaling is a potential therapeutic target to lower cardiovascular risk in chronic kidney disease

While it is true that many traditional cardiovascular risk factors are amenable to intervention in chronic kidney disease (CKD), the results of intervention may not be as efficacious as those obtained in the general population. Thus, there may also be a unique milieu established in CKD, which causes excess cardiovascular disease (CVD) burden by mechanisms that are as yet not fully recognized. Recently, vitamin D has sparked widespread interest because of its potential favorable benefits on CVD. However, the mechanisms for how vitamin D may improve CVD risk markers and outcomes have not been fully elucidated. Furthermore, hypovitaminosis D is highly prevalent in the CKD cohort. Given this background, we hypothesize that low vitamin D status may act as a new CVD risk marker, and modulation of vitamin D signaling may be a potential therapeutic target to lower cardiovascular risk in CKD. The data presented in this review support that the low vitamin D status may be linked with the high cardiovascular risk in CKD, based on both the biological effects of vitamin D itself on the cardiovascular system, and the cross-actions between vitamin D signaling and the multiple metabolic pathways. Considering the high prevalence of hypovitaminosis D, limited natural vitamin D food sources, and reduced sun exposure in CKD patients, recommendations for treatment of hypovitaminosis D mainly focus on exogenous supplementation with vitamin D and its analogues. Although promising, when to start therapy, the route of administration, the dose, and the duration remain need to be discussed.

Adiposity and insulin resistance in nondiabetic hemodialysis patients: effects of high energy supplementation

BACKGROUND

In contrast to the general population, a higher body mass index is associated with better survival among hemodialysis patients. Theoretically, high energy supplementation in these patients ought to lead to weight gain over time, but the benefits of this strategy are unclear.

OBJECTIVE

The objective was to assess whether high energy supplementation in nondiabetic hemodialysis patients might adversely affect insulin resistance -- a known risk factor for cardiovascular disease.

DESIGN

We first investigated the association between body fat mass and insulin resistance (homeostasis model assessment of insulin resistance; HOMA-IR) in nondiabetic hemodialysis patients in a cross-sectional analysis (study 1). Of the 106 individuals studied, 55 were randomly assigned to either high energy supplementation (an extra 475 kcal/d; n = 28) or not (n = 27) for 12 wk to assess prospective changes in body fat mass and insulin resistance (study 2).

RESULTS

In study 1, body fat mass (P < 0.05) and C-reactive protein (CRP) (P < 0.05) each contributed independently to HOMA-IR. In study 2, 41 patients completed the study. The 20 patients who received high energy supplementation had a significantly greater increase in body fat mass (P < 0.05), CRP (P < 0.05), and HOMA-IR (P < 0.001) than did the 21 controls.

CONCLUSIONS

Body fat mass and CRP are primary determinants of insulin resistance in nondiabetic hemodialysis patients. High energy supplementation, because it increases adiposity and inflammation, exacerbates insulin resistance. A long-term study is needed to clarify the metabolic effects of high energy supplementation on cardiovascular disease outcomes in hemodialysis patients.

Role of fat mass and adipokines in chronic kidney disease

PURPOSE OF REVIEW

As traditional risk factors cannot alone explain the high prevalence and incidence of cardiovascular disease in chronic kidney disease, the complex of insulin resistance, oxidative stress, and endothelial dysfunction has increasingly been studied as an important non-traditional risk factor. Recent studies show that the adipose tissue is a complex organ with pleiotropic functions far beyond the mere storage of energy. Fat tissue secretes a number of adipokines including leptin and adiponectin, as well as cytokines, such as resistin, visfatin, tumor-necrosis factor-alpha and interleukin-6.

RECENT FINDINGS

Adipokine serum levels are markedly elevated in chronic kidney disease, likely due to a decreased renal excretion. Evidence suggests that these pluripotent signaling molecules may have multiple effects modulating insulin signaling, endothelial health and vascular outcome.

SUMMARY

Fat tissue is a storage depot for energy and a source of circulating signaling molecules. It plays an important role in the catabolic uremic milieu, and has been linked to systemic inflammation and uremic anorexia. Further research is needed to investigate the complex interactions between adipokine signaling networks and its effects on vascular health and outcome in chronic kidney disease.

Obesity in chronic kidney disease: good or bad?

Cardiovascular disease (CVD) remains the major cause of morbidity and mortality in chronic kidney disease (CKD) patients. As traditional risk factors cannot alone explain the high prevalence and incidence of CVD in this high-risk population, the complex of insulin resistance, oxidative stress, and endothelial dysfunction has increasingly been studied as important non-traditional risk factors. Recent studies show that the adipose tissue is a complex organ with functions far beyond the mere storage of energy. Indeed, it has recently been shown that fat tissue secretes a number of adipokines - including leptin, adiponectin and retinol-binding protein, as well as cytokines such as resistin, visfatin, tumor necrosis factor and interleukin-6. Adipokine serum levels are furthermore markedly elevated in CKD, likely due to a decreased renal excretion. Evidence suggests that these pluripotent signaling molecules may have multiple effects modulating insulin signaling, endothelial health and putatively CVD. As fat tissue is also a storage depot for energy, much needed in the catabolic milieu of uremia, further research is still needed to elucidate the likely complex interactions between these signaling networks, vascular health and outcome in this high-risk population.