Insulin resistance, hyperinsulinemia, and renal injury: mechanisms and implications

Elevated plasma magnesium and calcium may be associated with shorter telomeres in older South Australian women

Telomeres are structures that cap the ends of chromosomes. The integrity of the telomere structure and its DNA hexamer (TTAGGG)n repeat sequence is critical for protecting the ends of chromosomes from degradation and in maintaining overall chromosomal stability. Currently, there are limited data on the influence that nutrition has on telomere length. Recent studies have suggested that micronutrients may influence telomere length. Here we examined the relationship between telomere length in lymphocytes and plasma calcium, magnesium, selenium and zinc status in a healthy cohort of younger and older adults. We report a negative association between telomere length and both plasma calcium and magnesium levels, (r=-0.47, P=0.03 and r=-0.61, P=0.001 respectively), in older females; Intriguingly Ca/Mg ratio was positively associated with telomere length (r=0.55, P=0.007). These relationships were not observed in the younger adults, nor in the older males. In conclusion, our study provides preliminary evidence suggesting that levels of plasma magnesium and calcium may impact on telomere length in lymphocytes in older women.

Obesity and metabolic syndrome in kidney transplantation

The epidemic of obesity and metabolic syndrome (MS) contributes to the rapid growth of chronic kidney disease (CKD) and end-stage renal disease (ESRD). There is a reverse epidemiology, known as the "obesity paradox," in ESRD patients receiving maintenance dialysis. Obese patients are routinely referred for kidney transplant, and they have more surgical and medical complications than non-obese patients. However, compared to dialysis, kidney transplant provides a survival benefit for obese patients. After kidney transplant, obese patients tend to gain more body weight, and non-obese patients can develop new-onset obesity/MS. Obesity/MS is not only associated with serious morbidities, but also compromises the long-term graft and patient survival. The immunosuppressive drugs commonly used as maintenance therapy, including corticosteroids, calcineurin inhibitors and mammalian target-of-rapamycin inhibitors, contribute to obesity/MS. Development of novel immunosuppressive drugs free of metabolic adverse effects is needed, so that the full potential and benefits of kidney transplantation can be realized.

Hepatitis C virus itself is a causal risk factor for chronic kidney disease beyond traditional risk factors: a 6-year nationwide cohort study across Taiwan

Background

Hepatitis C virus (HCV) infection and chronic kidney disease (CKD) have high prevalences in Taiwan and worldwide, but the role of HCV infection in causing CKD remains uncertain. This cohort study aimed to explore this association.

Methods

This nationwide cohort study examined the association of HCV with CKD by analysis of sampled claims data from Taiwan National Health Insurance Research Database from 1998 to 2004. ICD-9 diagnosis codes were used to identify diseases. We extracted data of 3182 subjects who had newly identified HCV infection and no traditional CKD risk factors and data of randomly selected 12728 matched HCV-uninfected control subjects. Each subject was tracked for 6 years from the index date to identify incident CKD cases. Cox proportional hazard regression was used to determine the risk of CKD in the HCV-infected and control groups.

Results

The mean follow-up durations were 5.88 years and 5.92 years for the HCV-infected and control groups, respectively. Among the sample of 15910 subjects, 251 subjects (1.6%) developed CKD during the 6-year follow-up period, 64 subjects (2.0%) from the HCV-infected group and 187 subjects (1.5%) from the control group. The incidence rate of CKD was significantly higher in the HCV-infected group than in the control group (3.42 vs. 2.48 per 1000 person-years, p = 0.02). Multivariate analysis indicated that the HCV-infected group had significantly greater risk for CKD (adjusted hazard ratio: 1.75, 95% CI: 1.25-2.43, p = 0.0009). This relationship also held for a comparison of HCV-infected and HCV-uninfected subjects who were younger than 70 years and had none of traditional CKD risk factors.

Conclusions

HCV infection is associated with increased risk for CKD beyond the well-known traditional CKD risk factors. HCV patients should be informed of their increased risk for development of CKD and should be more closely monitored.

Effects of a new SGLT2 inhibitor, luseogliflozin, on diabetic nephropathy in T2DN rats

This study examined the effect of long-term control of hyperglycemia with a new sodium glucose cotransporter 2 inhibitor, luseogliflozin, given alone or in combination with lisinopril on the progression of renal injury in the T2DN rat model of type 2 diabetic nephropathy. Chronic treatment with luseogliflozin (10 mg/kg/day) produced a sustained increase in glucose excretion and normalized blood glucose and glycosylated hemoglobin levels to the same level as seen in the rats treated with insulin. It had no effect on blood pressure. In contrast, lisinopril (10 mg/kg/day) reduced mean blood pressure from 140 to 113 mmHg. Combination therapy significantly reduced blood pressure more than that seen in the rats treated with lisinopril. T2DN rats treated with vehicle exhibited progressive proteinuria, a decline in glomerular filtration rate (GFR), focal glomerulosclerosis, renal fibrosis, and tubular necrosis. Control of hyperglycemia with luseogliflozin prevented the fall in GFR and reduced the degree of glomerular injury, renal fibrosis, and tubular necrosis. In contrast, control of hyperglycemia with insulin had no effect on the progression of renal disease in T2DN rats. Reducing blood pressure with lisinopril prevented the fall in GFR and reduced proteinuria and the degree of glomerular injury and tubular necrosis. Combination therapy reduced the degree of glomerular injury, renal fibrosis, and tubular necrosis to a greater extent than administration of either drug alone. These results suggest that control of hyperglycemia with luseogliflozin slows the progression of diabetic nephropathy more than that seen with insulin, and combination therapy is more renoprotective than administration of either compound alone.

Diabetic nephropathy: traditional to proteomic markers

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes and it is defined as a rise in the urinary albumin excretion (UAE) rate and abnormal renal function. Currently, changes in albuminuria are considered a hallmark of onset or progression of DN. However, some patients with diabetes have advanced renal pathological changes and progressive kidney function decline even if urinary albumin levels are in the normal range, indicating that albuminuria is not the perfect marker for the early detection of DN. The present article provides an overview of the literature reporting some relevant biomarkers that have been found to be associated with DN and that potentially may be used to predict the onset and/or monitor the progression of nephropathy. In particular, biomarkers of renal damage, inflammation, and oxidative stress may be useful tools for detection at an early stage or prediction of DN. Proteomic-based biomarker discovery represents a novel strategy to improve diagnosis, prognosis and treatment of DN; however, proteomics-based approaches are not yet available in most of the clinical chemistry laboratories. The use of a panel with a combination of biomarkers instead of urinary albumin alone seems to be an interesting approach for early detection of DN, including markers of glomerular damage (e.g., albumin), tubular damage (e.g., NAG and KIM-1), inflammation (e.g., TNF-α) and oxidative stress (e.g., 8-OHdG) because these mechanisms contribute to the development and outcomes of this disease.

The risk factors of mild decline in estimated glomerular filtration rate in a community-based population

OBJECTIVES

The study aimed to analyze the relationship between metabolic variables and estimated glomerular filtration rate (eGFR) and explore the potential risk factors for a mildly reduced eGFR in a community-based population.

DESIGN AND METHODS

Cross-sectional study in 643 adults without a history of kidney disease whose eGFR levels were greater than 60 mL/min/1.73 m(2) according to the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI). Anthropometric measurements, blood pressure, fasting lipid profile and levels of fasting and post-load glucose, insulin, serum creatinine and uric acid (UA) were tested. The eGFR was calculated, and the correlations between eGFR and each variable were analyzed.

RESULTS

The subjects were divided into two groups by using 90 mL/min/1.73 m(2) as the cut-off value of the eGFR. In the lower eGFR group, the age, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), waist circumference (WC), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), fasting plasma glucose (FPG), 2 h post-load plasma glucose (2 h-PG) levels and UA were significantly increased, and the incidences of hypertension, diabetes, obesity, hypertriglyceridemia and hypercholesterolemia were also higher (P<0.05). A multiple linear stepwise regression analysis showed that the WC, SBP, FPG and UA were independently correlated with the eGFR after adjusting for the other covariables.

CONCLUSIONS

The WC, SBP, FPG and UA were closely related to the eGFR in the subjects whose eGFR levels were greater than 60 mL/min/1.73 m(2). The increased WC, SBP, FPG and UA may be the main risk factors for a mildly reduced eGFR.

The association between cystatin C and incident type 2 diabetes is related to central adiposity

BACKGROUND

Cystatin C has recently been shown to be associated with incident type 2 diabetes. This study aims to validate this association and to study the impact of baseline adiposity.

METHODS

We investigated the 3-year diabetes incidence in 2849 participants from the French Data of an Epidemiological Study on the Insulin Resistance syndrome study, without overt kidney disease. Odds ratios (ORs) associated with cystatin C were adjusted for classical diabetes risk factors and interactions between cystatin C and these risk factors were studied.

RESULTS

Baseline serum cystatin C was significantly associated with incident diabetes on univariate analysis (OR/1 SD of log cystatin C: 1.74; 95% confidence interval [CI] 1.33-2.28; P=0.0001) and after adjustment for age and gender (OR 1.55; 95% CI 1.15-2.10; P=0.0039). This association was independent of serum creatinine-derived measures of baseline renal function and independent of fasting plasma glucose and HbA1c. When body mass index (BMI), waist circumference or baseline insulin resistance index were used as covariates, there was an interaction with cystatin C level. Cystatin C was associated only with incident diabetes for people with BMI, waist circumference or insulin resistance index≥median value with OR (95% CIs), respectively: 1.35 (0.98-1.84, P=0.0625); 1.39 (1.01-1.91, P=0.0441) and 1.41 (1.02-1.94, P=0.0398).

CONCLUSIONS

Cystatin C was associated with 3-year incident diabetes but only in people with central adiposity or insulin resistance. This should be considered in further studies assessing the clinical relevance of its prognostic value.

Serum fetuin-A levels related with microalbuminuria in diet-induced obese rats

The aim of the study was to investigate the association between elevated serum fetuin-A and increased urine albumin excretion in obese rats, and whether increased urine albumin excretion was modified by improving hepatic steatosis and lipid metabolism disorder. Male Wistar rats 4 weeks in age were randomly divided into three groups and fed with normal chow (control group), high-fat chow (obesity group), or high-fat chow plus fenofibrate (fenofibrate group). After 24 weeks, both body weight and visceral fat/body weight ratio in obese rats were higher than in controls. A difference in serology markers and pathology associated with hepatic steatosis was also found among the three groups. Serum fetuin-A and the expression of NF- κ B in the liver were increased, while serum adiponectin was decreased in obese rats in comparison to controls (P < 0.01). Urinary albumin/creatinine ratio (ACR) was increased in the obesity group compared to controls (P < 0.01). The fenofibrate intervention reduced serum fetuin-A and NF- κ B expression in the liver and increased serum adiponectin compared to obese rats and was accompanied by decrease in ACR. A positive correlation was found between ACR and fetuin-A (r = 0.602, P < 0.01), and a negative correlation was found between ACR and adiponectin (r = -0.635, P < 0.01). We conclude that elevated fetuin-A levels are associated with microalbuminuria in obese rats, and abnormal albuminuria is reversible by improving hepatic steatosis.

Dendrobium moniliforme Attenuates High-Fat Diet-Induced Renal Damage in Mice through the Regulation of Lipid-Induced Oxidative Stress

Obesity is an important and preventable risk factor for renal disease. The administration of an antioxidant with a lipid-lowering effect is an important therapeutic approach for kidney disease in obese patients. The present study was conducted to examine whether methanolic extract of Dendrobium moniliforme (DM), one of the most famous traditional medicines used in many parts of the world, has an antioxidant effect in vitro and an ameliorative effect on high-fat diet (HFD)-induced alterations such as renal dysfunction and lipid accumulation in vivo. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of DM extract (IC50 = 29.6 μg/mL) was increased in a dose-dependent manner. The LLC-PK1 kidney cell damage induced by oxidative stress was significantly inhibited by the treatments with DM extract. In the animal study, DM extract (200 mg/kg) was orally administered every day for nine weeks to HFD-fed mice, and its effect was compared with that of metformin. The administration of DM extract decreased the elevated serum glucose, total cholesterol concentration and renal lipid accumulation in HFD-fed mice. It also ameliorated renal dysfunction biomarkers including serum creatinine and renal collagen IV deposition. Taken together, these results provide important evidence that DM extract exhibits a pleiotropic effect on obesity induced parameters and exerted a renoprotective effect in HFD-fed mice.

Serum uric acid independently predicts cardiovascular events in advanced nephropathy

BACKGROUND

Chronic kidney disease (CKD) is associated with increased risk for cardiovascular (CV) disease and is also associated with elevated uric acid, which is emerging as a nontraditional CV risk factor. We therefore evaluated uric acid as a risk factor for CV disease in subjects presenting to nephrologists with CKD who were not on medications known to alter endothelial function.

METHODS

303 subjects with stage 3-5 CKD were followed for a mean of 39 months (range 6-46) and assessed for fatal and nonfatal CV events. Hyperuricemia was defined as uric acid >6.0 mg/dl for women and >7.0 mg/dl for men. In addition to other CV risk factors, endothelial function (flow-mediated dilatation), inflammatory markers (hsCRP), and insulin resistance (HOMA index and fasting insulin levels) were included in the analysis. We evaluated the association between uric acid and flow-mediated dilatation with linear regression. The impact of uric acid on composite CV events was assessed with Cox regression analysis.

RESULTS

Of a total of 303 patients, 89 had normouricemia and 214 had hyperuricemia. Both fatal (32 of 214 vs. 1 of 89 subjects) and combined fatal and nonfatal (100 of 214 vs. 13 of 89 subjects) CV events were more common in subjects with hyperuricemia compared with normal uric acid levels, and this was independent of estimated glomerular filtration rate, traditional CV risk factors including diabetes, hypertension and BMI, and nontraditional risk factors (hsCRP and endothelial function). The 46-month survival rate was 98.7% in the group with low uric acid compared to 85.8% in patients with high uric acid (p = 0.002).

CONCLUSIONS

Hyperuricemia is an independent risk factor for CV events in subjects presenting with CKD who are not on medications known to alter endothelial function.

The antihypertensive effect of cysteine

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease and kidney failure. Essential hypertension results from a combination of genetic and lifestyle factors. One such lifestyle factor is diet, and its role in the control of blood pressure has come under much scrutiny. Just as increased salt and sugar are known to elevate blood pressure, other dietary factors may have antihypertensive effects. Studies including the Optimal Macronutrient Intake to Prevent Heart Disease (OmniHeart) study, Multiple Risk Factor Intervention Trial (MRFIT), International Study of Salt and Blood Pressure (INTERSALT) and Dietary Approaches to Stop Hypertension (DASH) study have demonstrated an inverse relationship between dietary protein and blood pressure. One component of dietary protein that may partially account for its antihypertensive effect is the nonessential amino acid cysteine. Studies in hypertensive humans and animal models of hypertension have shown that N-acetylcysteine, a stable cysteine analogue, lowers blood pressure, which substantiates this idea. Cysteine may exert its antihypertensive effects directly or through its storage form, glutathione, by decreasing oxidative stress, improving insulin resistance and glucose metabolism, lowering advanced glycation end products, and modulating levels of nitric oxide and other vasoactive molecules. Therefore, adopting a balanced diet containing cysteine-rich proteins may be a beneficial lifestyle choice for individuals with hypertension. An example of such a diet is the DASH diet, which is low in salt and saturated fat; includes whole grains, poultry, fish and nuts; and is rich in vegetables, fruits and low-fat dairy products.

Biology of metabolic syndrome in a vascular patient

Metabolic syndrome is highly prevalent in vascular patients and has a significant impact on the outcomes of vascular interventions. It comprises of a set of metabolically driven risk factors, including truncal obesity, dyslipidemia, elevated blood pressure and elevated fasting blood glucose. Increased insulin resistance within the context of obesity and hypertension contributes to atherogenic dyslipidemia, hyperglycemia, and prothrombotic and proinflammatory states which lead to the adverse impact of metabolic syndrome on the response to injury and on atherosclerotic disease progression. This review focuses on the complex biology of metabolic syndrome and its relevance to management of vascular patients, including outcomes and implications for the coronary, cerebrovascular and lower-extremity vascular beds.

Insulin resistance, cystatin C, and mortality among older adults

OBJECTIVE

Insulin resistance is a risk factor for cardiovascular and noncardiovascular diseases. Impaired kidney function is linked with insulin resistance and may affect relationships of insulin resistance with health outcomes.

RESEARCH DESIGN AND METHODS

We performed a cohort study of 3,138 Cardiovascular Health Study participants (age ≥ 65 years) without diabetes. Insulin sensitivity index (ISI) was calculated from fasting and 2-h postload insulin and glucose concentrations. Associations of ISI and fasting insulin concentration with all-cause mortality were tested using Cox proportional hazards models, adjusting for demographic variables, prevalent cardiovascular disease, lifestyle variables, waist circumference, and LDL cholesterol. Subsequent models were additionally adjusted for or stratified by glomerular filtration rate estimated using serum cystatin C (eGFR).

RESULTS

A total of 1,810 participants died during the 14.7-year median follow-up. Compared with the highest quartile of ISI, the lowest quartile (most insulin resistant) was associated with 21% (95% CI 6-41) and 11% (-3 to 29) higher risks of death without and with adjustment for eGFR, respectively. Compared with the lowest quartile of fasting insulin concentration, the highest quartile was associated with 22% (4-43) and 4% (-12 to 22) higher risks of death without and with adjustment for eGFR, respectively. Similar attenuation by eGFR was observed when blood pressure, triglycerides, HDL cholesterol, and C-reactive protein were included in models.

CONCLUSIONS

Insulin resistance measured as ISI or fasting insulin concentration is associated with increased risk of death among older adults, adjusting for conventional confounding characteristics. Impaired kidney function may mediate or confound this relationship.

The metabolic syndrome and risk of chronic kidney disease: pathophysiology and intervention strategies

Metabolic syndrome is characterized by a clustering of cardiovascular risk factors, including abdominal obesity, elevated blood pressure and glucose concentrations, and dyslipidemia. The presence of this clinical entity is becoming more pervasive throughout the globe as the prevalence of obesity increases worldwide. Moreover, there is increased recognition of the complications and mortality related to this syndrome. This paper looks to examine the link between metabolic syndrome and the development of chronic kidney disease.

Impaired renal function in morbid obese patients with nonalcoholic fatty liver disease

INTRODUCTION AND AIMS

Obesity is a common risk factor for nonalcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD). NAFLD and CKD have been associated in many epidemiological studies. We hypothesize that more severe liver disease, namely nonalcoholic steatohepatitis (NASH), is related with further renal impairment. We aimed to evaluate if changes in renal function were present in morbid obese patients with NAFLD.

METHODS

Prospective and consecutive recruitment of morbid obese patients with biopsy proven NAFLD obtained during bariatric surgery. Renal function was evaluated with CKD-Epidemiology Collaboration estimated glomerular filtration rate (eGFR). Plasmatic adiponectin, leptin and active ghrelin concentrations were determined.

RESULTS

One hundred and forty-eight patients were included of whom 25% had NASH and 75% simple steatosis. NASH patients were older, with higher body mass index and had more frequently metabolic syndrome and lower eGFR (97 ± 22 vs 106 ± 16 ml/min/1.73(2), P = 0.035). NASH conferred an odds ratio (OR) 3.0 (1.3-7.0) for eGFR < 90 and OR 9.7 (1.0-96.4) for eGFR < 60 ml/min/1.73(2). eGFR < 90 ml/min/1.73(2) associated with aspartate aminotransferase [OR 2.9 (1.1-7.6)] and γ-glutamyl transpeptidase elevation [OR 3.0 (1.3-7.2)], NASH [OR 3.0 (1.3-7.0)], any lobular inflammatory activity [OR 3.0 (1.3-7.0)] and severe fibrosis [OR 3.4 (1.1-10.8)]. Neither eGFR nor liver histology was associated with adipokines levels.

CONCLUSIONS

In morbid obese patients, NASH, particularly lobular inflammation and advanced fibrosis, associates with mild decreases in eGFR, suggesting a common inflammatory link between liver and renal lesion.

Circulatory syndrome: an evolution of the metabolic syndrome concept!

The metabolic syndrome has been a useful, though controversial construct in clinical practice as well as a valuable model in order to understand the interactions of diverse cardiovascular risk factors. However the increasing importance of the circulatory system in particular the endothelium, in both connecting and controlling organ function has underlined the limitations of the metabolic syndrome definition. The proposed "Circulatory Syndrome" is an attempt to refine the metabolic syndrome concept by the addition of recently documented markers of cardiovascular disease including renal impairment, microalbuminuria, arterial stiffness, ventricular dysfunction and anaemia to more classic factors including hypertension, dyslipidemia and abnormal glucose metabolism; all of which easily measured in clinical practice. These markers interact with each other as well as with other factors such as aging, obesity, physical inactivity, diet and smoking. The final common pathways of inflammation, oxidative stress and hypercoagulability thereby lead to endothelial damage and eventually cardiovascular disease. Nevertheless, the Circulatory (MARC) Syndrome, like its predecessor the metabolic syndrome, is only a small step toward an understanding of these complex and as yet poorly understood markers of disease.

Evaluation of microalbuminuria in obese children and its relation to metabolic syndrome

Several epidemiologic studies have clearly demonstrated that obesity increases the risk of kidney diseases. We have attempted to evaluate the association of obesity with albuminuria, an early marker of kidney disease, among obese children and its relation to metabolic syndrome. This study included 150 obese children. Blood pressure, fasting blood glucose, plasma insulin and the lipid profile were assessed. The homeostasis model assessment of insulin resistance (HOMA-IR) was used to calculate in vivo insulin resistance. Urinary albumin and creatinine were estimated. Microalbuminuria was detected in 22 (14.7%) of the obese children. Waist circumference, blood pressure, triglyceride, low-density lipoprotein (LDL), insulin resistance and fasting blood glucose were significantly higher in obese children with microalbuminuria than in those with normoalbuminuria and showed significant positive correlations with microalbuminuria. High-density lipoprotein (HDL) was significantly lower in obese children with microalbuminuria than in those with normoalbuminuria, with a significant negative correlation with microalbuminuria. We found that body mass index, abdominal obesity, hypertension, impaired fasting glucose level and insulin resistance significantly increased the odds of microalbuminuria in the obese children enrolled in this study. Moreover, high triglyceride, high LDL and low HDL were significantly associated with microalbuminuria. In our patient group, childhood obesity was a risk factor for the development of microalbuminuria, which in turn was significantly associated with metabolic syndrome and its different constituents.

Interleukin-10 expression induced by adeno-associated virus vector suppresses proteinuria in Zucker obese rats

Varying degrees of metabolic abnormalities mediated by chronic inflammation are implicated in the chronic glomerular injuries associated with obesity. Interleukin (IL)-10, a pleiotropic cytokine, exerts anti-inflammatory effects in numerous biological settings. In the present study, we explored the biological benefits of adeno-associated virus (AAV) vector-mediated sustained IL-10 expression against the pathological renal characteristics observed in Zucker fatty rats (ZFRs). We injected an AAV vector, encoding rat IL-10 or enhanced green fluorescent protein (GFP) into male ZFRs at 5 weeks of age. Subsequently, the renal pathophysiological changes were analyzed. Persistent IL-10 expression significantly reduced the urinary protein excretion of ZFRs compared with GFP expression (47.1±11.6 mg per mg·creatinine versus 88.8±30.0 mg per mg·creatinine, P<0.01). The serum levels of IL-10 negatively correlated with the urinary protein in AAV-treated rats (r=-0.78, P<0.01). Renal hypertrophy, increased widths in the glomerular basement membrane, and the lack of uniformity and regularity of the foot process of the visceral glomerular epithelial cells of ZFRs were significantly blunted by IL-10 expression. IL-10 also abrogated the downregulation of glomerular nephrin observed in ZFRs treated with the GFP vector. Our findings provide insights into the potential benefit of the anti-inflammatory effects of IL-10 on the overall management of glomerulopathy induced by the metabolic disorders associated with obesity.

Development rate of chronic kidney disease in hepatitis C virus patients with advanced fibrosis after interferon therapy

AIM

  The aim of this retrospective cohort study is to assess the development incidence and predictive factors for chronic kidney disease (CKD) after the termination of interferon therapy in hepatitis C virus (HCV) positive Japanese patients with liver cirrhosis.

METHODS

  A total of 650 HCV positive, liver cirrhotic patients who were treated with interferon and showed an estimated glomerular filtration rate (eGFR) of ≥60 mL/min per 1.73 m(2) after the termination of interferon therapy were enrolled. CKD was defined as an eGFR of <60 mL/min per 1.73 m(2) . End-stage-CKD was defined as an eGFR of <15 mL/min/1.73 m(2) . The primary goal is the new development of CKD and end-stage-CKD.

RESULTS

  Eighty-five patients developed CKD, and six patients progressed to end-stage-CKD. The development rate of CKD was 5.2% at the 5th year, 14.5% at the 10th year and 30.6% at the 15th year. Multivariate Cox proportional hazards analysis showed that CKD occurred when patients had age increments of 10 years (hazard ratio: 2.32; 95% confidence interval [CI] 1.61-3.35; P < 0.001), eGFR decrements of 10 mL/min per 1.73 m(2) (hazard ratio: 1.66; 95% CI 1.27-2.16; P < 0.001), hypertension (hazard ratio: 2.00; 95% CI 1.13-3.53; P = 0.017), diabetes (hazard ratio: 1.79; 95% CI 1.02-3.14; P = 0.042), and non-clearance of HCV (hazard ratio: 2.67; 95% CI 1.34-5.32; P = 0.005). The development rate of end-stage-CKD was 0.4% at the 5th year, 1.6% at the 10th year and 2.8% at the 15th year.

CONCLUSIONS

  The annual incidence for CKD among cirrhotic patients with HCV was determined to be about 1.0-1.5%. In addition, the annual incidence for end-stage-CKD is one order of magnitude lower than that of CKD.

Chronic kidney disease in postmenopausal women

Menopause is derived from the Greek words men (month) and pauses (cessation) and means permanent cessation of menstruation after the loss of ovarian activity. Chronic kidney disease (CKD) has recently been associated with cardiovascular events in several studies. CKD patients have a heavy burden of traditional cardiovascular risk factors in addition to a range of nontraditional risk factors such as inflammation and abnormal metabolism of calcium and phosphate. In this review, the association of CKD and cardiovascular disease (CVD), as well as of osteoporosis in postmenopausal women is discussed. CKD mineral and bone disorder, characterized by disturbances of calcium/phosphate/parathyroid hormone, bone abnormalities and vascular and soft tissue calcification, is highly prevalent in CKD and is a strong, independent predictor of bone fracture, CVD and death. Estrogen has been shown to: (a) decrease the expression of angiotensin type 1 receptors in vasculature and kidneys; (b) reduce the expression and activity of angiotensin-converting enzyme, and (c) cause the release of angiotensinogen substrate from the liver. However, the degree of activation or suppression of the renin-angiotensin-aldosterone system by estrogen has not been clearly established. Clinical data on the effects of estrogen therapy on bone mineral densities are extremely limited in the ESRD population. CVD is the most common cause of death in postmenopausal women with CKD and many contributing factors have been explored. Future research for prevention of CVD in postmenopausal women with CKD would focus on the biology of vascular calcification as well as bone loss.

Clinicopathological characteristics of obesity-associated focal segmental glomerulosclerosis

Obesity-related glomerulopathy (ORG) is a secondary form of focal segmental glomerulosclerosis (FSGS) occurring in obese patients with a body-mass index higher than 30 kg/m(2). It is typically manifested by nephrotic-range proteinuria without full nephrotic syndrome, and progressive renal insufficiency. Characteristic morphologic features include the consistent presence of glomerulomegaly, predominance of perihilar variant of FSGS, and the relatively mild fusion of visceral epithelial cell foot processes. The concept of podocyte depletion as a driver of the glomerular scarring in obesity-associated FSGS is well documented. The underlying mechanisms are likely to be related in part to the oxidative stress and the impairment of the integrity of the slit diaphragm and cell adhesion resulting mainly from angiotensin II and transforming growth factor-β. These proapoptotic cytokines are upregulated in obesity in response to insulin resistance, compensatory hyperinsulinemia and glomerular hyperfiltration-hypertension mediated mechanical stress. This review is designed to discuss the clinicopathologic features of obesity-associated FSGS, with a focus on the podocyte injury, which is involved in the onset and progression of the glomerulosclerotic process. Ultrastructural glomerular lesions are documented.

One-hour postload plasma glucose levels and left ventricular mass in hypertensive patients

OBJECTIVE

Left ventricular hypertrophy (LVH), an independent risk factor for cardiovascular (CV) morbidity and mortality, recognizes a multifactorial pathogenesis. A plasma glucose value ≥155 mg/dL for the 1-h postload plasma glucose during an oral glucose tolerance test (OGTT) identifies subjects with normal glucose tolerance (NGT) at high risk for type 2 diabetes. We addressed the question if glucose tolerance status, particularly 1-h postload plasma glucose levels, affects left ventricular mass (LVM) and cardiac geometry in essential hypertension.

RESEARCH DESIGN AND METHODS

We enrolled 767 never-treated hypertensive subjects, 393 women and 374 men (mean age 49.6 ± 8.5 years). All patients underwent an OGTT for the evaluation of glucose tolerance and standard echocardiography. LVM was calculated using the Devereux formula and normalized by body surface area (LVM index [LVMI]). Insulin sensitivity was assessed by the Matsuda index. Among all participants, 514 had NGT, 168 had impaired glucose tolerance (IGT), and 85 had type 2 diabetes. According to the 1-h postload plasma glucose cutoff point of 155 mg/dL, we divided normotolerant subjects into two groups: NGT <155 mg/dL (n = 356) and NGT ≥155 mg/dL (n = 158).

RESULTS

Subjects in the NGT ≥155 mg/dL group had worse insulin sensitivity than subjects in the NGT <155 mg/dL group (Matsuda index 63.9 vs. 88.8; P < 0.0001). Men with NGT ≥155 mg/dL had a higher LVMI than men with NGT <155 mg/dL (126.6 vs. 114.3 g/m(2); P = 0.002) and a different LVH prevalence (41.1 vs. 25.8%; P < 0.0001). At multiple regression analysis, 1-h glucose resulted in the major determinant of LVMI in normotolerant, IGT, and diabetic groups.

CONCLUSIONS

These data show that NGT ≥155 mg/dL subjects, compared with NGT <155 mg/dL subjects, have a higher LVMI and a greater prevalence of LVH similar to that of IGT and diabetic patients.

High-fat diet induces an initial adaptation of mitochondrial bioenergetics in the kidney despite evident oxidative stress and mitochondrial ROS production

Obesity and metabolic syndrome are associated with an increased risk for several diabetic complications, including diabetic nephropathy and chronic kidney diseases. Oxidative stress and mitochondrial dysfunction are often proposed mechanisms in various organs in obesity models, but limited data are available on the kidney. Here, we fed a lard-based high-fat diet to mice to investigate structural changes, cellular and subcellular oxidative stress and redox status, and mitochondrial biogenesis and function in the kidney. The diet induced characteristic changes, including glomerular hypertrophy, fibrosis, and interstitial scarring, which were accompanied by a proinflammatory transition. We demonstrate evidence for oxidative stress in the kidney through 3-nitrotyrosine and protein radical formation on high-fat diet with a contribution from iNOS and NOX-4 as well as increased generation of mitochondrial oxidants on carbohydrate- and lipid-based substrates. The increased H(2)O(2) emission in the mitochondria suggests altered redox balance and mitochondrial ROS generation, contributing to the overall oxidative stress. No major derailments were observed in respiratory function or biogenesis, indicating preserved and initially improved bioenergetic parameters and energy production. We suggest that, regardless of the oxidative stress events, the kidney developed an adaptation to maintain normal respiratory function as a possible response to an increased lipid overload. These findings provide new insights into the complex role of oxidative stress and mitochondrial redox status in the pathogenesis of the kidney in obesity and indicate that early oxidative stress-related changes, but not mitochondrial bioenergetic dysfunction, may contribute to the pathogenesis and development of obesity-linked chronic kidney diseases.

Implications for kidney disease in obese children and adolescents

Increasing attention has been focused on the implications of obesity in adults on the development of kidney disease, but data on the obese pediatric population are lacking. The aim of this study was to investigate whether changes in various renal function indexes/markers, as expressed by the glomerular filtration rate [GFR, as estimated by the Schwartz formula (eGFR)], serum cystatin C (CysC) level, albumin excretion rate (AER), and modifications in nitric oxide (NO; an important modulator of renal function and morphology), urinary isoprostanes (markers of oxidative stress), and blood pressure (BP), can be detected in obese children and adolescents when compared to normal weight controls. Blood and urinary samples were collected to evaluate markers of renal function, serum and urinary NO, and urinary isoprostanes in 107 obese Caucasian subjects and 50 controls. Ambulatory BP monitoring (ABPM) was performed in all cases. Obesity was expressed by the body mass index standard deviation score (SDS-BMI), and insulin resistance by the homeostasis model assessment of insulin resistance (HOMA-IR). CysC and eGFR did not significantly differ between the two groups; AER was increased in obese children. CysC and GFR were related to HOMA-IR, and AER was related to HOMA-IR and SDS-BMI. Obese subjects had reduced NO levels and increased urinary isoprostanes and BP measurements; all three parameters were related to SDS-BMI and insulin resistance. ABPM showed an increased incidence of hypertension and non-dipping in the obese group. Based on our comparison of obese and nonobese children, we conclude that renal involvement is not an early clinically evident manifestation of adiposity in childhood, since no overt changes in eGFR and only a mild albuminuria were detected. A longer exposure to obesity is probably needed before renal function impairment appears.

Protective effect of Garcinia against renal oxidative stress and biomarkers induced by high fat and sucrose diet

BACKGROUND

Obesity became major health problem in the world, the objective of this work was to examine the effect of high sucrose and high fat diet to induce obesity on antioxidant defense system, biochemical changes in blood and tissue of control, non treated and treated groups by administration of Garcinia cambogia, and explore the mechanisms that link obesity with altered renal function.

METHODS

Rats were fed a standard control diet for 12 week (wk) or a diet containing 65% high sucrose (HSD) or 35% fat (HFD) for 8 wk and then HFD group divided into two groups for the following 4 wks. One group was given Garcinia+HFD, the second only high fat, Also the HSD divided into two groups, 1st HSD+Garcinia and 2nd HSD. Blood and renal, mesenteric, Perirenal and epididymal adipose tissues were collected for biochemical assays.

RESULTS

HFD and HSD groups of rats showed a significant increase in feed intake, Body weight (BW) and body mass index (BMI). Also there were significant increases in weights of mesenteric, Perirenal and epididymal adipose tissues in HFD and HSD groups.HFD and HSD affect the kidney by increasing serum urea and creatinine levels and decreased level of nitric oxide (NO) and increased blood glucose, low density lipoproteins (LDL), triacylglycerol (TG), total cholesterol (TC) and malondialdehyde (MDA). Glucose 6-phosphate dehydrogenase (G6PD) activities were significantly decreased in HFD while there were significant increases in HSD and HSD+G groups p ≤ 0.05 compared with control. Moreover, renal catalase activities and MDA levels were significantly increased while NO level was lowered. These changes improved by Garcinia that decreased the oxidative stress biomarkers and increased NO level.There were significant positive correlations among BMI, kidney functions (Creatinine and urea), TG and Oxidative markers (renal MDA and catalase).

CONCLUSIONS

Rats fed a diet with HFD or HSD showed, hypertriglyceridemia, increased LDL production, increased oxidative stress and renal alteration. Moreover, suggesting association between lipid peroxidation, obesity and nephropathy, while Garcinia ameliorated the damaging effects of the HFD or HSD and decreased feed intake, MDA level and decreased oxidative stress in renal tissues.

Metabolic syndrome and outcomes after renal intervention

Metabolic syndrome significantly increases the risk for cardiovascular disease and chronic kidney disease. The increased risk for cardiovascular diseases can partly be caused by a prothrombotic state that exists because of abdominal obesity. Multiple observational studies have consistently shown that increased body mass index as well as insulin resistance and increased fasting insulin levels is associated with chronic kidney disease, even after adjustment for related disorders. Metabolic syndrome appears to be a risk factor for chronic kidney disease, likely due to the combination of dysglycemia and high blood pressure. Metabolic syndrome is associated with markedly reduced renal clinical benefit and increased progression to hemodialysis following endovascular intervention for atherosclerotic renal artery stenosis. Metabolic syndrome is associated with inferior early outcomes for dialysis access procedures.

Renal Doppler indices in diabetic children with insulin resistance syndrome

End-stage renal failure is still a leading cause of mortality among type 1 diabetes patients. Insulin resistance plays a larger role in type 1 diabetes disease process than is commonly recognized. Detection of diabetic nephropathy as early as possible currently offers the best chance of delaying or possibly preventing progression to end-stage disease. Renal resistive index (RI) and pulsatility index (PI), measured using renal Doppler ultrasonography, reflect intrarenal vascular resistance. The present work aimed at examining renal Doppler indices (RI and PI) in type 1 diabetic children and their relation to features of insulin resistance and other established parameters of early diabetic nephropathy as microalbuminuria. One hundred diabetic children with a mean age of 13.4 ± 2.9 yr and an average diabetes duration of (7.2 ± 2.5 yr) were included. Thirty healthy children served as controls. All renal Doppler indices were significantly higher in children with type 1 diabetes mellitus (p ≤ 0.01). The worst parameters were observed in children diagnosed with insulin resistance syndrome (IRS) (38%), hypertensive (12%), and obese (4%) children. Resistive index showed a significant correlation to blood pressure (r = 0.2, p = 0.04), waist-hip ratio (r = 0.5, p = 0.02), insulin dose (r = 0.2, p = 0.02) and estimated glucose disposal rate (r = -0.5, p = 0.01). No correlation was noted to microalbuminuria, HbA1c, or duration of diabetes. The present work concluded that renal Doppler indices are worse in diabetic children and particularly those with IRS. These children appear to be at graver risk for diabetic nephropathy. In these patients adding renal Doppler assessment to their work up, might diagnose diabetic nephropathy at a prealbuminuric stage.

Possible Link between Metabolic Syndrome and Chronic Kidney Disease in the Development of Cardiovascular Disease

Metabolic syndrome (MetS) is a clinical syndrome that consists of visceral obesity, dyslipidemia, hypertension, and impaired insulin sensitivity. Although individual components of MetS have been implicated in the development of chronic kidney disease (CKD), few studies have examined the effect of combinations of the components of MetS on the development of CKD and cardiovascular disease (CVD). The prevalence of MetS is increasing worldwide in both developing and developed countries, and early detection and treatment of MetS would be a cost-effective strategy for preventing the development of CKD. Visceral obesity and insulin resistance are two important features of MetS that may be associated with renal damage. Lifestyle modifications, including caloric restriction and exercise, are necessary to treat MetS. Initial antihypertensive therapy should consist of an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker. An improved understanding of the mechanism responsible for the association between MetS and renal damage should be helpful in determining the treatment regimens directed at cardiovascular and renal protection.

Risk factors for the development of albuminuria and renal impairment in type 2 diabetes--the Swedish National Diabetes Register (NDR)

BACKGROUND

The aim of this study was to identify clinical risk factors associated with the development of albuminuria and renal impairment in patients with type 2 diabetes (T2D). In addition, we evaluated if different equations to estimate renal function had an impact on interpretation of data. This was done in a nationwide population-based study using data from the Swedish National Diabetes Register.

METHODS

Three thousand and six hundred sixty-seven patients with T2D aged 30-74 years with no signs of renal dysfunction at baseline (no albuminuria and eGFR >60 mL/min/1.73 m(2) according to MDRD) were followed up for 5 years (2002-2007). Renal outcomes, development of albuminuria and/or renal impairment [eGFR < 60 mL/min/1.73 m(2) by MDRD or eCrCl > 60 mL/min by Cockgroft-Gault (C-G)] were assessed at follow-up. Univariate regression analyses and stepwise regression models were used to identify significant clinical risk factors for renal outcomes.

RESULTS

Twenty percent of patients developed albuminuria, and 11% renal impairment; thus, ~6-7% of all patients developed non-albuminuric renal impairment. Development of albuminuria or renal impairment was independently associated with high age (all P < 0.001), high systolic BP (all P < 0.02) and elevated triglycerides (all P < 0.02). Additional independent risk factors for albuminuria were high BMI (P < 0.01), high HbA1c (P < 0.001), smoking (P < 0.001), HDL (P < 0.05) and male sex (P < 0.001), and for renal impairment elevated plasma creatinine at baseline and female sex (both P < 0.001). High BMI was an independent risk factor for renal impairment when defined by MDRD (P < 0.01), but low BMI was when defined by C-G (P <  0.001). Adverse effects of BMI on HbA1c, blood pressure and lipids accounted for ~50% of the increase risk for albuminuria, and for 41% of the increased risk for renal impairment (MDRD).

CONCLUSIONS

Distinct sets of risk factors were associated with the development of albuminuria and renal impairment consistent with the concept that they are not entirely linked in patients with type 2 diabetes. Obesity and serum triglycerides are semi-novel risk factors for development of renal dysfunction and BMI accounted for a substantial proportion of the increased risk. The equations used to estimate renal function (MDRD vs. C-G) had an impact on interpretation of data, especially with regard to body composition and gender.

One-hour postload plasma glucose levels are associated with kidney dysfunction

BACKGROUND AND OBJECTIVES

A cutoff of 155 mg/dl for 1-hour postload plasma glucose (1hPG) during the oral glucose tolerance test (OGTT) is able to identify patients who are at high risk for type 2 diabetes and vascular atherosclerosis. We aimed to examine whether individuals with 1hPG ≥155 mg/dl are also at increased risk for chronic kidney disease (CKD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Atherosclerosis risk factors, OGTT, and estimated GFR by Chronic Kidney Disease Epidemiology Collaboration equation were analyzed in 1075 white individuals without diabetes.

RESULTS

The area under the receiver operating characteristic curve for 1hPG was the highest (0.700) compared with the areas under the receiver operating characteristic curve of 0, 30-minute, and 2-hour glucose concentrations. Individuals with 1hPG ≥155 mg/dl had a worse cardiometabolic risk profile, exhibiting significantly higher body mass index, BP, triglycerides, and fasting insulin levels and lower HDL, IGF-1 levels, and insulin sensitivity, than individuals with 1hPG <155 mg/dl. Estimated GFR was significantly lower in individuals with 1hPG ≥155 mg/dl. In a logistic regression model adjusted for age and gender, individuals with 1hPG ≥155 mg/dl showed an increased risk for CKD compared with individuals with 1hPG <155 mg/dl. When the logistic regression analysis was restricted to individuals who had normal glucose tolerance, those with 1hPG ≥155 mg/dl showed a higher risk for CKD compared with individuals with 1hPG <155 mg/dl.

CONCLUSIONS

These data suggest that a cutoff point of 155 mg/dl for the 1hPG during OGTT may be helpful in the identification of individuals who are at increased risk for CKD.

Cardiovascular disease in kidney transplant recipients: the prognostic value of inflammatory cytokine genotypes

BACKGROUND

Cardiovascular disease (CVD) represents the main cause of morbidity and mortality after renal transplantation. In view of the modern paradigm of atherosclerosis as an inflammatory disease, this study investigated the impact of inflammatory cytokine polymorphisms on posttransplant CVD.

METHODS

The association between cytokine polymorphisms and CVD was assessed in a case-control study to identify the differences in genotype distributions between kidney allografts with or without posttransplant CVD. To validate our results in two independent groups, we divided a cohort of 798 renal transplant recipients according to geographic area: an evaluation cohort of 478 patients from Emilia-Romagna and a validation cohort of 320 patients from the rest of Italy. Tumor necrosis factor (TNF)-alpha, transforming growth factor-beta1, interleukin (IL)-10, IL-6, interferon-gamma, and IL-8 polymorphisms were analyzed, and thereafter, the cytokine production genotype was assigned.

RESULTS

In the evaluation cohort, the patients in the CVD and no-CVD groups differed significantly in TNF-alpha and IL-10 genotype frequencies. Using multivariate analyses to test the association with CVD, the TNF-alpha high-producer genotype was associated with a significantly increased cardiovascular risk (odds ratio [OR]=4.41, 95% confidence interval (CI)=2.53-7.67). Conversely, the IL-10 high-producer genotype resulted protective against CVD (OR=0.07, 95% CI=0.02-0.29). These findings were confirmed in the validation cohort where the carriers of the TNF-alpha high-producer genotype proved to be at 2.45-fold increased cardiovascular risk (OR=2.45, 95% CI=1.29-4.63), whereas the IL-10 high-producer genotype was associated with a 0.08-fold reduced risk (OR=0.08, 95% CI=0.02-0.36).

CONCLUSIONS

This work suggests a prognostic value of TNF-alpha and IL-10 genotypes, which might represent cardiovascular risk markers in renal transplant.

Therapeutic potential of endothelin receptor antagonists for chronic proteinuric renal disease in humans

Diabetes and arterial hypertension continue to be the main causes of chronic renal failure in 2010, with a rising prevalence in part due to the worldwide obesity epidemic. Proteinuria is a main feature of chronic renal disease and mediated by defects in the glomerular filtration barrier and is as a good predictor of cardiovascular events. Indeed, chronic renal disease due to glomerulosclerosis is one of the important risk factors for the development of coronary artery disease and stroke. Glomerulosclerosis develops in response to inflammatory activation and increased growth factor production. Preclinical and first preliminary clinical studies provide strong evidence that endogenous endothelin-1 (ET-1), a 21-amino-acid peptide with strong growth-promoting and vasoconstricting properties, plays a central role in the pathogenesis of proteinuria and glomerulosclerosis via activation of its ET(A) subtype receptor involving podocyte injury. These studies have not only shown that endothelin participates in the disease processes of hypertension and glomerulosclerosis but also that features of chronic renal disease such as proteinuria and glomerulosclerosis are reversible processes. Remarkably, the protective effects of endothelin receptors antagonists (ERAs) are present even on top of concomitant treatments with inhibitors of the renin-angiotensin system. This review discusses current evidence for a role of endothelin for proteinuric renal disease and podocyte injury in diabetes and arterial hypertension and reviews the current status of endothelin receptor antagonists as a potential new treatment option in renal medicine.

Obesity is the major contributor to vascular dysfunction and inflammation in high-fat diet hypertensive rats

Obesity and hypertension are the two major risk factors that contribute to the progression of end-stage renal disease. To examine whether hypertension further exacerbates oxidative stress and vascular dysfunction and inflammation in obese rats, four groups of male Sprague-Dawley rats were fed either a normal (7% fat) or high-fat (36% fat) diet for 6 weeks and osmotic pumps were implanted to deliver ANG (angiotensin II) or vehicle for an additional 4 weeks.Treatment with the high-fat diet did not alter ANG-induced hypertension compared with the normal diet (174 +/- 6 compared with 170 +/- 5 mmHg respectively). Treatment with the high-fat diet increased body weight gain and plasma leptin levels and induced insulin resistance in normotensive and ANG-induced hypertensive rats. Plasma TBARS (thiobarbituric acid-reacting substances), a measure of oxidative stress, were elevated in high-fat diet-fed rats compared with controls (11.2 +/-1 compared with 8.4 +/- nmol/ml respectively) and was increased further in ANG-induced hypertensive rats fed a high-fat diet (18.8 +/-2.2 nmol/ml). Urinary nitrite excretion was also decreased in rats fed a high-fat diet without or with ANG infusion compared with controls. Afferent arteriolar relaxation to acetylcholine was impaired in rats fed the high-fat diet without or with ANG infusion. Renal cortical TNF-alpha(tumour necrosis factor-alpha), COX-2(cyclo-oxygenase-2) and phospho-IKK (inhibitor of nuclear factor k B kinase) expression increased in high-fat diet-fed rats compared with normal diet-fed rats. The increases in phospho-IKK and COX-2 expression were elevated further in ANG-induced hypertensive rats fed the high-fat diet.These results suggest that ANG-induced hypertension exacerbates oxidative stress and renal inflammation without further impairment in vascular dysfunction in high-fat diet-induced obesity.

Inflammatory cytokines as predictive markers for early detection and progression of diabetic nephropathy

Diabetic nephropathy is a major complication of diabetes mellitus and the leading cause of end-stage renal disease. Both hyperglycemia and hypertension (systemic and/or intraglomerular) are established causal factors for diabetic nephropathy. Nonetheless, there is growing evidence that activated innate immunity and inflammation are also contributing factors to the pathogenesis of diabetic nephropathy. This notion is based on increasing evidence indicating that both cytokines-chemokines and pro-fibrotic growth factors are important players in the progression of diabetic nephropathy, effectively accelerating and exacerbating inflammatory and fibrotic processes leading to end-stage renal disease. In this review, we focus on several predominant cytokines-chemokines as potential predictive markers for diabetic nephropathy. These cytokines-chemokines may also be helpful as biomarkers to monitor the progression of the disease and the impact of interventional modalities aimed at halting eventual manifestation of end-stage renal disease in diabetic patients.

Urinary albumin excretion, HMW adiponectin, and insulin sensitivity in type 2 diabetic patients undergoing bariatric surgery

BACKGROUND

Microalbuminuria portends an increased risk for renal and cardiovascular diseases in diabetes. In this pilot study, we determined the effect of weight loss induced by different types of bariatric surgery on albuminuria in severely obese type 2 diabetic (T2DM) subjects.

METHODS

Fifteen consecutive T2DM patients (9M/6F, 51+/-14 years, body mass index (BMI) 49+/-9 kg/m2, HbA1c 7.2+/-1.1 percent) undergoing either Roux-en-Y gastric bypass (RYGB; N=9) or other types of bariatric surgery (N=6) underwent determination of urine albumin/creatinine ratio (UACR) and adipokine and insulin sensitivity during a mixed meal tolerance test performed 2 weeks prior to and 6 months following surgery.

RESULTS

Following RYGB, there was a significant decrease in BMI ((-4.74)+/-(-5.05) kg/m2), fasting glucose, cholesterol, and leptin levels. Insulin sensitivity (Matsuda index [12.05+/-3.81, p=0.003]) and high molecular weight (HMW) adiponectin increased significantly along with a significant reduction in UACR (median, 36 mg/g [7-94] vs. 27 mg/g [5.5-42.5], p=0.01). The reduction in UACR following RYGB was inversely correlated with the Matsuda index (r=-0.74), p=0.02) and HMW adiponectin (r=(-0.67), p=0.04). In contrast, despite reduction in BMI ((-4.11)+/-(-4.10) kg/m2) following other types of bariatric surgery (n=6), there was no significant improvement in insulin sensitivity (0.88+/-2.40, p=0.63), UACR, or HMW adiponectin levels.

CONCLUSIONS

RYGB in severely obese DM subjects is associated with a reduction in albuminuria that correlates to the improvement in insulin sensitivity and HMW adiponectin. The data point to a need for larger studies to confirm these findings and evaluate the micro-macrovascular benefits including renal parenchymal benefits of different types of bariatric surgery in T2DM.

Postprandial hyperglycemia and hyperinsulinemia associated with renal arterio-arteriolosclerosis in chronic kidney disease

Hypertension has an important function in the formation of renal arterio-arteriolosclerosis. However, renal arterio-arteriolosclerosis is sometimes found in biopsy specimens of normotensive patients, which indicates unknown factors may contribute to renal arterio-arteriolosclerosis. In this study, we aimed to evaluate the effects of glucose metabolism/insulin resistance on renal arterio-arteriolosclerosis. Forty-eight patients with biopsy-proven non-diabetic chronic glomerular disease were included. Renal arterio-arteriolosclerosis was evaluated as the percentage of vessels showing hyaline changes or wall thickening. We correlated renal arterio-arteriolosclerosis with clinical parameters including indices obtained by 75 g oral glucose tolerance test. Of the 48 patients, 30 had hypertension. The results of univariate analysis showed significant association of renal arterio-arteriolosclerosis with hypertension, increased serum creatinine (S-Cr), hypertriglyceridemia, increased 2-h plasma glucose (PG) and increased 2-h plasma insulin (PI). In stepwise multiple regression analysis, hypertension (beta=0.344, P=0.009), S-Cr (beta=0.287, P=0.03) and 2-h PG (beta=0.274, P=0.03) were independently associated with renal arterio-arteriolosclerosis. Eleven of the 30 hypertensive patients did not have renal arterio-arteriolosclerosis. The hypertensive patients with renal arterio-arteriolosclerosis showed significantly higher 2-h PG (134+/-25 vs. 106+/-26 mg per 100 ml, P=0.008) and higher 2-h PI (67.7+/-34.9 vs. 48.3+/-30.0 microU ml(-1), P=0.04) compared with those without renal arterio-arteriolosclerosis, but the difference in S-Cr was not significant. Postprandial hyperglycemia and hyperinsulinemia may contribute to the formation of renal arterio-arteriolosclerosis independently of hypertension.

Body weight control by a high-carbohydrate/low-fat diet slows the progression of diabetic kidney damage in an obese, hypertensive, type 2 diabetic rat model

Obesity is one of several factors implicated in the genesis of diabetic nephropathy (DN). Obese, hypertensive, type 2 diabetic rats SHR/NDmcr-cp were given, for 12 weeks, either a normal, middle-carbohydrate/middle-fat diet (MC/MF group) or a high-carbohydrate/low-fat diet (HC/LF group). Daily caloric intake was the same in both groups. Nevertheless, the HC/LF group gained less weight. Despite equivalent degrees of hypertension, hyperglycemia, hyperlipidemia, hyperinsulinemia, and even a poorer glycemic control, the HC/LF group had less severe renal histological abnormalities and a reduced intrarenal advanced glycation and oxidative stress. Mediators of the renoprotection, specifically linked to obesity and body weight control, include a reduced renal inflammation and TGF-beta expression, together with an enhanced level of adiponectin. Altogether, these data identify a specific role of body weight control by a high-carbohydrate/low-fat diet in the progression of DN. Body weight control thus impacts on local intrarenal advanced glycation and oxidative stress through inflammation and adiponectin levels.

Diabetic nephropathy: a disorder of oxygen metabolism?

Chronic hypoxia induces sequential abnormalities in oxygen metabolism (for example, oxidative stress, nitrosative stress, advanced glycation, carbonyl stress, endoplasmic reticulum stress) in the kidneys of individuals with diabetes. Identification of these abnormalities improves our understanding of therapeutic benefits that can be achieved with antihypertensive agents, the control of hyperglycemia and/or hyperinsulinemia and the dietary correction of obesity. Key to the body's defense against hypoxia is hypoxia-inducible factor, the activity of which is modulated by prolyl hydroxylases (PHDs)-oxygen sensors whose inhibition may prove therapeutic. Renal benefits of small-molecule PHD inhibitors have been documented in several animal models, including those of diabetic nephropathy. Three different PHD isoforms have been identified (PHD1, PHD2 and PHD3) and their respective roles have been delineated in knockout mouse studies. Unfortunately, none of the current inhibitors is specific for a distinct PHD isoform. Nonspecific inhibition of PHDs might induce adverse effects, such as those associated with PHD2 inhibition. Specific disruption of PHD1 induces hypoxic tolerance, without angiogenesis and erythrocytosis, through the reprogramming of basal oxygen metabolism and decreased generation of oxidative stress in hypoxic mitochondria. A specific PHD1 inhibitor might, therefore, offer a novel therapy for abnormal oxygen metabolism not only in the diabetic kidney, but also in other diseases for which hypoxia is a final, common pathway.

Metabolic syndrome and chronic kidney disease

The prevalence of metabolic syndrome (MetS) is increasing worldwide in both developing and developed countries. Experimental and clinical studies have revealed that MetS plays an important role in the development of chronic kidney disease (CKD), which leads to end-stage renal disease. Emerging evidence also suggests that CKD may actually cause MetS since the kidney is an important organ of glucose and lipid homeostasis. Although multiple mechanisms have been shown to be involved in the pathogenesis of MetS, insulin resistance appears to be a central pathophysiological factor contributing to MetS. In this review we will discuss the association of MetS with insulin resistance and CKD, and the renal pathophysiological changes associated with MetS.

Alterations in L-arginine and inflammatory markers in type 2 diabetic patients with and without microalbuminuria

Low-grade inflammation is closely involved in the pathogenesis of type 2 diabetes and associated micro- and macrovascular complications. The nitric oxide (NO) precursor L-arginine, is relevant to diverse pathological conditions including type 2 diabetes and its complications. High sensitive-CRP (hs-CRP), neopterin and arginine levels were measured in 46 normoalbuminuric, 45 microalbuminuric type 2 diabetics and in 32 healthy controls in order to assess the relationship between markers of inflammation and L: -arginine. Hs-CRP concentrations were higher in microalbuminuric diabetic patients compared to normoalbuminuric patients and controls. Diabetics had higher serum and urine neopterin levels than controls. Urine neopterin and L-arginine levels differed significantly among diabetic patients with and without microalbuminuria. There were significant positive correlations between hs-CRP and BMI in healthy controls and diabetics with and without microalbuminuria. In microalbuminuric diabetics, hs-CRP correlated with microalbuminuria (MAU). Significant predictors for the development of microalbuminuria were higher postprandial glucose levels, lower creatinine clearance and lower serum L-arginine levels. Assessment of early markers of inflammation and endothelial function, such as neopterin and NO precursor L-arginine, may help to predict incipient nephropathy more accurately in type 2 diabetic patients.