Leptin stimulates proliferation and TGF-beta expression in renal glomerular endothelial cells: potential role in glomerulosclerosis [seecomments]

Metabolic syndrome and chronic kidney disease

PURPOSE OF REVIEW

The association of the metabolic syndrome (MetS) with cardiovascular risk, mortality, type 2 diabetes mellitus, stroke, nonfatty liver disease and gout is well known. However, the association of the MetS with chronic kidney disease (CKD) is now emerging. This review discusses the epidemiology, pathology and potential mechanisms for the relationship of MetS with CKD.

RECENT FINDINGS

Studies show that patients with MetS have a 2.5-fold higher risk of developing CKD. The risk of microalbuminuria is also increased two-fold in the MetS. Renal dysfunction becomes apparent long before the appearance of hypertension or diabetes in MetS. Compared with healthy controls, patients with MetS have increased microvascular disease-tubular atrophy, interstitial fibrosis, arterial sclerosis and global and segmental sclerosis. Studies suggest that the renal fibrosis seen in MetS might be caused by a constellation of insulin resistance, hypertension, dyslipidemias and inflammation, and result in a heightened expression of adipocytokines, angiotensin and inflammatory cytokines such as interleukin-6 and tumour necrosis factor-alpha.

SUMMARY

Despite the strong association of MetS with CKD, a causal relationship has not been proven. More studies are needed to precisely elucidate the mechanisms that might lead upstream factors such as insulin resistance, hypertension, dyslipidemia and inflammation to cause renal fibrosis.

The adipose tissue as an endocrine organ

During the past 2 decades, results of both basic science and clinical studies have changed the physicians' views about adipocyte pathophysiology. Since leptin was discovered in 1994, white adipose tissue was recognized as an endocrine organ and an important source of biologically active substances with local and/or systemic action called adipokines. Inappropriate secretion of several adipokines by the excessive amount of white adipose tissue seems to participate in the pathogenesis of obesity-related pathologic processes including endothelial dysfunction, inflammation, atherosclerosis, diabetes mellitus, and chronic kidney disease. In this review endocrine action of selected adipokines (mainly leptin and adiponectin) in the context of kidney diseases is discussed. Specifically, the role of these adipokines in malnutrition, chronic kidney disease progression, and pathogenesis of cardiovascular complications is presented.

Overview of the physiology and pathophysiology of leptin with special emphasis on its role in the kidney

The adipocyte product leptin is a pleiotropic adipokine and hormone, with a role extending beyond appetite suppression and increased energy expenditure. This review summarizes the biology of the leptin system and the roles of its different receptors in a multitude of cellular functions in different organs, with special emphasis on the kidney. Leptin's physiological functions as well as deleterious effects in states of leptin deficiency or hyperleptinemia are emphasized. Chronic hyperleptinemia can increase blood pressure through the sympathetic nervous system and renal salt retention. The concept of selective leptin resistance in obesity is emerging, whereby leptin's effect on appetite and energy expenditure is blunted, with a concomitant increase in leptin's other effects as a result of the accompanying hyperleptinemia. The divergence in response likely is explained by different receptors and post-receptor activating mechanisms. Chronic kidney disease is a known cause of hyperleptinemia. There is an emerging view that the effect of hyperleptinemia on the kidney can contribute to the development and/or progression of chronic kidney disease in selective resistance states such as in obesity or type 2 diabetes mellitus. The mechanisms of renal injury are likely the result of exaggerated and undesirable hemodynamic influences as well as profibrotic effects.

The biological consequence of obesity on the kidney

Obesity is a worldwide epidemic that is associated with several health issues, including kidney diseases. A specific kidney disease, referred to as obesity-related glomerulopathy, has been described in earlier publications. Obesity can affect the prognosis of other types of kidney diseases. Body-weight reduction with caloric restriction is an essential therapy, although strictly controlling food intake coupled with an appropriate evaluation is challenging. Low birthweight can be an important factor for obesity and results in kidney dysfunction. In this review, we analyse the consequences of obesity on kidney prognosis and potential strategies for combating obesity-associated kidney injury.

Direct and indirect effects of obesity on the kidney

Over the last few decades, much of the world has experienced an epidemic of obesity. In the year 2008, 1.4 billion people worldwide were overweight, and 500 million were obese. Even more alarming is a fact that in the year 2010, 40 million children under the age of 5 years were overweight or obese. In the same time period, the incidence of CKD has also increased worldwide. Obesity has been recognized as a driving force of another global epidemic-diabetes, the leading cause of ESRD. Recent studies are confirming that in addition to risk associated with diabetes per se, increased body mass index is independently linked to increased risk for various kidney disorders, prominently CKD, but also renal cell carcinoma and nephrolithiasis. The purpose of this article is to review current knowledge regarding adverse effects of obesity on the kidney.

Chronic kidney disease, obesity, and hypertension: the role of leptin and adiponectin

Chronic kidney disease is a major public health problem and characterized by a progressive loss in renal function over a period of months or years as defined by structural or functional abnormalities of the kidney. Several elements contribute to determine a progression of the kidney injury, inducing a worsening of renal damage and accelerating the decline of renal function: obesity and hypertension are two known factors of kidney progression. Remarkable improvements have been recently achieved in the study of the endocrine features of the adipose tissue and have been able to produce hormone-like peptides named adipokines or adipocytokines. Among these adipocytokines, which represent a link between obesity, hypertension, and chronic nephropathy, leptins and adiponectin appear to play an important role. Leptin not only is a prohypertension element (renal progression factor) through the activation sympathetic nervous, but also is able to induce prosclerotic effects directly on the kidney. In contrast, a decline of adiponectin levels has been shown to be related to a picture of hypertension: an endothelial dysfunction has been described as the main pathogenic mechanism responsible for this phenomenon.

Leptin as a link between the immune system and kidney-related diseases: leading actor or just a coadjuvant?

Food intake and nutritional status modify the physiological responses of the immune system to illness and infection and regulate the development of chronic inflammatory processes, such as kidney disease. Adipose tissue secretes immune-related proteins called adipokines that have pleiotropic effects on both the immune and neuroendocrine systems, linking metabolism and immune physiology. Leptin, an adipose tissue-derived adipokine, displays a variety of immune and physiological functions, and participates in several immune responses. Here, we review the current literature on the role of leptin in kidney diseases, linking adipose tissue and the immune system with kidney-related disorders. The modulation of this adipose hormone may have a major impact on the treatment of several immune- and metabolic-related kidney diseases.

Adipokines and the cardiovascular system: mechanisms mediating health and disease

This review focuses on the role of adipokines in the maintenance of a healthy cardiovascular system, and the mechanisms by which these factors mediate the development of cardiovascular disease in obesity. Adipocytes are the major cell type comprising the adipose tissue. These cells secrete numerous factors, termed adipokines, into the blood, including adiponectin, leptin, resistin, chemerin, omentin, vaspin, and visfatin. Adipose tissue is a highly vascularised endocrine organ, and different adipose depots have distinct adipokine secretion profiles, which are altered with obesity. The ability of many adipokines to stimulate angiogenesis is crucial for adipose tissue expansion; however, excessive blood vessel growth is deleterious. As well, some adipokines induce inflammation, which promotes cardiovascular disease progression. We discuss how these 7 aforementioned adipokines act upon the various cardiovascular cell types (endothelial progenitor cells, endothelial cells, vascular smooth muscle cells, pericytes, cardiomyocytes, and cardiac fibroblasts), the direct effects of these actions, and their overall impact on the cardiovascular system. These were chosen, as these adipokines are secreted predominantly from adipocytes and have known effects on cardiovascular cells.

The effect of weight loss in obesity and chronic kidney disease

Several epidemiologic investigations have confirmed that obesity is a significant risk factor for the appearance of proteinuria and end-stage kidney disease in a normal population. Weight loss induced by low-calorie diets, physical exercise, or bariatric surgery is accompanied by an important antiproteinuric effect. Reduction in proteinuria is already observed after a few weeks from the onset of weight loss and it is evident even in patients with modest weight losses. Reduction in proteinuria by weight loss has been described in chronic proteinuric nephropathies of different etiologies. The mechanisms through which weight loss may reverse proteinuria are likely to be plural: better control of blood pressure, improvement of serum lipid profile, improvement of insulin sensitivity, better glycemic control in diabetes patients, decrease of circulating leptin levels, reversal of glomerular hyperfiltration, and decreased activation of the renin-angiotensin-aldosterone system.

Relationship between plasma leptin levels and clinical outcomes of pediatric traumatic brain injury

High plasma leptin level has been associated with mortality after adult intracerebral hemorrhage. The present study was undertaken to investigate the plasma leptin concentrations in children with traumatic brain injury and to analyze the correlation of leptin with pediatric traumatic brain injury outcome. Plasma leptin concentration of eighty-nine healthy children and 142 children with acute severe traumatic brain injury was measured by enzyme-linked immunosorbent assay. Twenty-six patients (18.3%) died and 42 patients (29.6%) had an unfavorable outcome (Glasgow outcome scale score of 1-3) at 6 months after traumatic brain injury. Upon admission, plasma leptin level in patients was substantially higher than that in healthy controls. A forward stepwise logistic regression selected plasma leptin level as an independent predictor for 6-month mortality and unfavorable outcome of patients. A receiver operating characteristic curve analysis showed plasma leptin level better predicted 6-month mortality and unfavorable outcome. The prognostic value of leptin was similar to that of Glasgow Coma scale score for 6-month clinical outcomes. Thus, plasma leptin level represents a novel biomarker for predicting 6-month clinical outcome in children with traumatic brain injury.

Relationship between Plasma Leptin Level and Chronic Kidney Disease

Background. Leptin is an adipose tissue-derived hormone shown to be related to several metabolic, inflammatory, and hemostatic factors related to chronic kidney disease. Recent animal studies have reported that infusion of recombinant leptin into normal rats for 3 weeks fosters the development of glomerulosclerosis. However, few studies have examined the association between leptin and CKD in humans. Therefore, we examined the association between plasma leptin levels and CKD in a representative sample of US adults. Methods. We examined the third National Health and Nutrition Examination Survey participants >20 years of age (n = 5820, 53.6% women). Plasma leptin levels were categorized into quartiles (≤4.3 Fg/L, 4.4-8.7 Fg/L, 8.8-16.9 Fg/L, >16.9 Fg/L). CKD was defined as a glomerular filtration rate of <60 mL/min/1.73 m(2) estimated from serum creatinine. Results. Higher plasma leptin levels were associated with CKD after adjusting for age, sex, race/ethnicity, education, smoking, alcohol intake, body mass index (BMI), diabetes, hypertension, and serum cholesterol. Compared to quartile 1 of leptin (referent), the odds ratio (95% confidence interval) of CKD associated with quartile 4 was 3.31 (1.41 to 7.78); P-trend = 0.0135. Subgroup analyses examining the relation between leptin and CKD by gender, BMI categories, diabetes, and hypertension status also showed a consistent positive association. Conclusion. Higher plasma leptin levels are associated with CKD in a representative sample of US adults.

Early improvement in albuminuria in non-diabetic patients after Roux-en-Y bariatric surgery

BACKGROUND

Obesity is a growing epidemic in the USA that has been shown to be associated with chronic kidney disease and albuminuria. Bariatric surgery is an effective means of achieving long-term weight loss and improvements in metabolic derangements including albumin excretion over the long term.

METHODS

We report changes in urinary albumin excretion levels in the early post-operative period for a euglycemic, predominantly Hispanic American cohort undergoing Roux-en-Y gastric bypass surgery.

RESULTS

Our cohort of 38 patients was largely female (89.5%) and predominantly Hispanic (76.3%) with a mean BMI of 46 ± 8.0 kg/m(2). Over half (53.3%) of the patients with significant preoperative albumin excretion in our cohort lowered their albumin excretion levels to <20 mg/g of creatinine. This early reduction in albumin excretion in our cohort correlated significantly with the level of albumin excretion preoperatively but not with the degree of weight loss experienced in this early post-operative period.

CONCLUSIONS

Improvements in microalbuminuria in the early post-operative period after Roux-en-Y surgery may result from an interplay between changes in gastrointestinal hormones, insulin sensitivity, blood pressure, and adipose tissue-and needs further study.

Inflammation and oxidative stress in obesity-related glomerulopathy

Obesity-related glomerulopathy is an increasing cause of end-stage renal disease. Obesity has been considered a state of chronic low-grade systemic inflammation and chronic oxidative stress. Augmented inflammation in adipose and kidney tissues promotes the progression of kidney damage in obesity. Adipose tissue, which is accumulated in obesity, is a key endocrine organ that produces multiple biologically active molecules, including leptin, adiponectin, resistin, that affect inflammation, and subsequent deregulation of cell function in renal glomeruli that leads to pathological changes. Oxidative stress is also associated with obesity-related renal diseases and may trigger the initiation or progression of renal damage in obesity. In this paper, we focus on inflammation and oxidative stress in the progression of obesity-related glomerulopathy and possible interventions to prevent kidney injury in obesity.

Inflammation and metabolic dysfunction: links to cardiovascular diseases

Abdominal obesity is a major risk factor for cardiovascular disease, and recent studies highlight a key role of adipose tissue dysfunction, inflammation, and aberrant adipokine release in this process. An increased demand for lipid storage results in both hyperplasia and hypertrophy, finally leading to chronic inflammation, hypoxia, and a phenotypic change of the cellular components of adipose tissue, collectively leading to a substantially altered secretory output of adipose tissue. In this review we have assessed the adipo-vascular axis, and an overview of adipokines associated with cardiovascular disease is provided. This resulted in a first list of more than 30 adipokines. A deeper analysis only considered adipokines that have been reported to impact on inflammation and NF-κB activation in the vasculature. Out of these, the most prominent link to cardiovascular disease was found for leptin, TNF-α, adipocyte fatty acid-binding protein, interleukins, and several novel adipokines such as lipocalin-2 and pigment epithelium-derived factor. Future work will need to address the potential role of these molecules as biomarkers and/or drug targets.

Early postnatal hyperalimentation impairs renal function via SOCS-3 mediated renal postreceptor leptin resistance

Early postnatal hyperalimentation has long-term implications for obesity and developing renal disease. Suppressor of cytokine signaling (SOCS) 3 inhibits phosphorylation of signal transducer and activator of transcription (STAT) 3 and ERK1/2 and thereby plays a pivotal role in mediating leptin resistance. In addition, SOCS-3 is induced by both leptin and inflammatory cytokines. However, little is known about the intrinsic-renal leptin synthesis and function. Therefore, this study aimed to elucidate the implications of early postnatal hyperalimentation on renal function and on the intrinsic-renal leptin signaling. Early postnatal hyperalimentation in Wistar rats during lactation was induced by litter size reduction at birth (LSR) either to LSR10 or LSR6, compared with home cage control male rats. Assessment of renal function at postnatal day 70 revealed decreased glomerular filtration rate and proteinuria after LSR6. In line with this impairment of renal function, renal inflammation and expression as well as deposition of extracellular matrix molecules, such as collagen I, were increased. Furthermore, renal expression of leptin and IL-6 was up-regulated subsequent to LSR6. Interestingly, the phosphorylation of Stat3 and ERK1/2 in the kidney, however, was decreased after LSR6, indicating postreceptor leptin resistance. In accordance, neuropeptide Y (NPY) gene expression was down-regulated; moreover, SOCS-3 protein expression, a mediator of postreceptor leptin resistance, was strongly elevated and colocalized with NPY. Thus, our findings not only demonstrate impaired renal function and profibrotic processes but also provide compelling evidence of a SOCS-3-mediated intrinsic renal leptin resistance and concomitant up-regulated NPY expression as an underlying mechanism.

Effects of apelin and leptin on renal functions following renal ischemia/reperfusion: An experimental study

The present study aimed to investigate the effects of apelin and leptin on renal functions following renal ischemia/reperfusion (I/R). A total of 32 rats were divided into four groups. The control group was not induced with ischemia, but was administered normal saline intraperitoneally. Normal saline, apelin and leptin were administered intraperitoneally to the I/R, ischemia/reperfusion and apelin (I/R+A) and ischemia/reperfusion and leptin (I/R+L) groups, in turn for three days prior to the surgical procedure. Blood and urine samples were obtained after 24 h of reperfusion, and scintigraphic examination was performed. Renal damage was evaluated histopathologically. Urea levels of the I/R+L and I/R+A groups were comparable, but were higher compared to that of the control group. The I/R group had the highest urea levels (control, 27±2; I/R, 120±15; I/R+A, 75±10; I/R+L, 80±11; p<0.001). Creatinine levels were higher in all three ischemic groups compared to the control group. Glomerular filtration rate values of the I/R+A and I/R+L groups were not significantly, but numerically higher compared to that of the I/R group. No pathological damage was observed in any of the animals in the control group. In the I/R group, two animals had moderate and six had severe renal damage, while three had moderate and one had severe renal damage in the I/R+L group. In the I/R+A group, moderate renal damage was found in one animal, while none had severe renal damage. This study demonstrates the functional and histopathological protective effects of leptin and apelin against renal I/R injury.

Leptin's regulation of obesity-induced cardiac extracellular matrix remodeling

Obesity-induced remodeling of cardiac extracellular matrix (ECM) leads to myocardial fibrosis and ultimately diastolic dysfunction. Leptin, an adipocyte hormone, is emerging as a novel mechanistic link between obesity and heart diseases. Despite the known essential role of leptin in hepatic and renal fibrosis, the in vivo effects of leptin on cardiac ECM remodeling remain unclear. Our objective was to define the role of leptin as a key mediator of pro-fibrogenic responses in the heart. In vitro administration of leptin to primary cardiofibroblasts resulted in significant stimulation of pro-collagen Iα ( 1 ) and a decrease in pro-matrix metalloproteinase (MMP)-8, -9 and -13 gene expressions at 24 h. To study the in vivo pro-fibrotic effect, leptin was administrated to C57BL/6 and leptin-deficient ob/ob mice for 8 weeks. With exogenous leptin ob/ob mice displayed passive diastolic filling dysfunction, coincided with significant increase in myocardial collagen compared with ob/ob controls. We also observed a marked stimulation of pro-collagen IIIα ( 1 ) and suppression of pro-MMP-8, TIMP-1 and -3 gene expressions in leptin-treated ob/ob mice. Our findings suggest pro-fibrotic effects of leptin in the heart, primarily through the predominance of collagen synthesis over degradation.

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.

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.

Association of body mass index with glomerular filtration rate in Japanese: a cross-sectional study in work-site population

It has been shown that aging and hypertension are important risk factors to promote renal damage. However, little data are available on the effect of obesity on the progression of renal damage, especially in young and middle-aged individuals. The aim of this study was to determine the association between body mass index (BMI) and renal function evaluated by estimated glomerular filtration rate (eGFR) in Japanese men. We studied the cross-sectional association of BMI with eGFR in 3872 Japanese men in a work-site population (18-64 y; mean age 42.1 ± 0.2 y). Estimated glomerular filtration rate was calculated by a novel equation for Japanese men. Estimated glomerular filtration rate was negatively correlated with age, systolic blood pressure (SBP), hemoglobin A1c (HbA1c), and BMI. We performed multiple regression analysis, controlling for factors, such as SBP, low-density lipoprotein-cholesterol, gamma-glutamyl transpeptidase, age, HbA1c, and uric acid. The association between age and eGFR was highly statistically significant. In addition, BMI was still significantly associated with eGFR independently of SBP. Moreover, mean eGFR, which was adjusted for age, SBP, HbA1c, serum uric acid, and gamma-glutamyl transpeptidase, decreased from 88.9 mL/min/1.73 m(2) in the first quartile of BMI to 87.5 mL/min/1.73 m(2) in the second, 86.9 mL/min/1.73 m(2) in the third, and 85.9 mL/min/1.73 m(2) in the fourth quartile (test for trend, P < .0001). These results show that a close relationship is present between obesity and decreased eGFR in Japanese men. Keeping appropriate body weight, in addition to appropriate blood pressure, in young and middle age may be important to prevent renal damage in older age.

Predictive performance of 12 equations for estimating glomerular filtration rate in severely obese patients

ABSTRACT Objective: Considering that the Cockcroft-Gault formula and the equation of diet modification in renal disease are amply used in clinical practice to estimate the glomerular filtration rate, although they seem to have low accuracy in obese patients, the present study intends to evaluate the predictive performance of 12 equations used to estimate the glomerular filtration rate in obese patients. Methods: This is a cross-sectional retrospective study, conducted between 2007 and 2008 and carried out at a university, of 140 patients with severe obesity (mean body mass index 44 ± 4.4 kg/m2). The glomerular filtration rate was determined by means of 24-hour urine samples. Patients were classified into one or more of the four subgroups: impaired glucose tolerance (n = 43), diabetic (n = 24), metabolic syndrome (n = 76), and/or hypertension (n = 66). We used bias, precision, and accuracy to assess the predictive performance of each equation in the entire group and in the subgroups. Results: In renal disease, Cockcroft-Gault's formula and the diet modification equation are not precise in severely obese patients (precision: 40.9 and 33.4, respectively). Sobh's equation showed no bias in the general group or in two subgroups. Salazar-Corcoran's and Sobh's equations showed no bias for the entire group (Bias: −5.2, 95% confidence interval (CI) = −11.4, 1.0, and 6. 2; 95%CI = −0.3, 12.7, respectively). All the other equations were imprecise for the entire group. Conclusion: Of the equations studied, those of Sobh and Salazar-Corcoran seem to be the best for estimating the glomerular filtration rate in severely obese patients analyzed in our study.

Therapeutic impact of leptin on diabetes, diabetic complications, and longevity in insulin-deficient diabetic mice

OBJECTIVE

The aim of the current study was to evaluate the long-term effects of leptin on glucose metabolism, diabetes complications, and life span in an insulin-dependent diabetes model, the Akita mouse.

RESEARCH DESIGN AND METHODS

We cross-mated Akita mice with leptin-expressing transgenic (LepTg) mice to produce Akita mice with physiological hyperleptinemia (LepTg:Akita). Metabolic parameters were monitored for 10 months. Pair-fed studies and glucose and insulin tolerance tests were performed. The pancreata and kidneys were analyzed histologically. The plasma levels and pancreatic contents of insulin and glucagon, the plasma levels of lipids and a marker of oxidative stress, and urinary albumin excretion were measured. Survival rates were calculated.

RESULTS

Akita mice began to exhibit severe hyperglycemia and hyperphagia as early as weaning. LepTg:Akita mice exhibited normoglycemia after an extended fast even at 10 months of age. The 6-h fasting blood glucose levels in LepTg:Akita mice remained about half the level of Akita mice throughout the study. Food intake in LepTg:Akita mice was suppressed to a level comparable to that in WT mice, but pair feeding did not affect blood glucose levels in Akita mice. LepTg:Akita mice maintained insulin hypersensitivity and displayed better glucose tolerance than did Akita mice throughout the follow-up. LepTg:Akita mice had normal levels of plasma glucagon, a marker of oxidative stress, and urinary albumin excretion rates. All of the LepTg:Akita mice survived for >12 months, the median mortality time of Akita mice.

CONCLUSIONS

These results indicate that leptin is therapeutically useful in the long-term treatment of insulin-deficient diabetes.

Bariatric surgery and renal function

Obesity causes a significant healthcare burden and has been shown to be an important risk factor in the development of cardiovascular disease, type 2 diabetes, and increasingly chronic kidney disease. Bariatric surgery is the most effective treatment for obesity and has been shown to drastically improve both blood pressure and diabetic control. However, the interaction of bariatric surgery and renal function is less clear. This review focuses on the effect of bariatric surgery on renal function both in the acute situation, with respect to acute kidney injury, and also on changes in renal function parameters post-bariatric surgery weight loss. The interaction of obesity, bariatric surgery, and nephrolithiasis as a precipitant of acute kidney injury will also be considered. The role of bariatric surgery in pre- and post-renal transplant recipients is discussed as well as possible mechanisms underlying the improvement in renal function.

Cardiovascular benefits of bariatric surgery in morbidly obese patients

Morbid obesity is associated with increased morbidity and represents a major healthcare problem with increasing incidence worldwide. Bariatric surgery is considered an effective option for the management of morbid obesity. We searched MEDLINE, Current Contents and the Cochrane Library for papers published on bariatric surgery in English from 1 January 1990 to 20 July 2010. We also manually checked the references of retrieved articles for any pertinent material. Bariatric surgery results in resolution of major comorbidities including type 2 diabetes mellitus, hypertension, dyslipidemia, metabolic syndrome, non-alcoholic fatty liver disease, nephropathy, left ventricular hypertrophy and obstructive sleep apnea in the majority of morbidly obese patients. Through these effects and possibly other independent mechanisms bariatric surgery appears to reduce cardiovascular morbidity and mortality. Laparoscopic Roux-en-Y gastric bypass (LRYGB) appears to be more effective than laparoscopic adjustable gastric banding (LAGB) in terms of weight loss and resolution of comorbidities. Operation-associated mortality rates after bariatric surgery are low and LAGB is safer than LRYGB. In morbidly obese patients bariatric surgery is safe and appears to reduce cardiovascular morbidity and mortality.

Obesity in kidney transplantation affects renal function but not graft and patient survival

INTRODUCTION

The number of overweight and obese patients undergoing renal transplantation has increased dramatically over the past two decades. Studies on graft survival and posttransplantation complications have often yielded conflicting results. Some authors have reported similar results for graft and patient survivals between obese and normal weight patients, but with a marginally increased rate of postoperative complications. In contrast, other reports note higher percentage of graft losses as well as increased mortality. In our study, we analyzed early- and long-term outcomes among obese versus nonobese kidney transplant recipients.

PATIENTS AND METHODS

Between January 2000 and December 2008, we performed 563 cadaveric kidney transplantations. Recipients were classified in 1 of 5 groups based on their body mass index (BMI) at the time of transplantation: group A (n = 68; BMI < 18.5); group B (n = 310; 18.6 < BMI < 24.9); group C (n = 143; 25 < BMI < 29.9); group D (n = 32; 30 < BMI < 34.9); and group E (n = 10; BMI ≥ 35). The comparative analysis included patient and graft survivals, postoperative complications, onset of delayed graft function (DGF), acute rejection episodes, hospital stay, and serum creatinine values in the first 3 years posttransplantation.

RESULTS

At a mean follow-up of 53 months (range, 3-112 months), DGF was observed in 20 patients in group A (29.4%), 82 in group B (26.4%), 43 in group C (30%), 16 in group D (50%), and 4 in group E (40%). Nevertheless, obese patients (groups D and E) showed higher mean serum creatinine values and worse renal function at 6 months (P = .001), 1 year (P < .001), and 3 years (P = .001). Moreover, they were at increased risk of an acute rejection episode (P = .01) and more susceptible to cardiovascular and metabolic complications (P = .01). Morbidly obese patients displayed a higher incidence of postsurgical complications (P = .002). There were no differences in the incidences of chronic allograft nephropathy (CAN) or infectious complications. Despite the differences in morbidity among the 5 groups, we failed to observe significant differences in patient or graft survivals at 6, 12, 36, or 60 months.

CONCLUSION

Our findings suggested that obese patients should not be discriminated against simply based on the BMI. At our center, obese (BMI >35) transplantation candidates undergo a thorough cardiac evaluation, as well as pulmonary, endocrine, and nutritional counseling seeking to minimize medical and surgical complications and improve survival and quality of life.

Adiponectin and leptin in chronic kidney disease: causal factors or mere risk markers?

Experimental and clinical evidence implicates the 2 major adipose tissue cytokines, adiponectin (ADPN) and leptin (LEP), in renal damage. The interpretation of the link between these cytokines and renal outcomes is strictly context-sensitive. Albuminuria is a feature of renal disease in the ADPN null mouse and this alteration can be reversed by supplementing ADPN. Accordingly, in young normoalbuminuric obese individuals low ADPN is associated with higher albumin excretion rate. Conversely, high ADPN is associated with more severe proteinuria in chronic kidney disease patients, possibly underlying a protective response aimed at countering the high renal and cardiovascular risk of high proteinuria. LEP administration ameliorates insulin resistance in insulin-resistant patients with hereditary lipodystrophy--a disease characterized by severe LEP deficiency and renal disease--and the same intervention reverses both, insulin resistance and renal damage in a mouse model of LEP deficiency. However, LEP may exert noxious effects on the kidney (particularly renal fibrosis) if administered in conditions of LEP sufficiency or excess.

A comparison of novel and commonly-used indices of insulin sensitivity in African American chronic hemodialysis patients

BACKGROUND

Insulin resistance (IR) is highly prevalent in chronic hemodialysis (CHD) patients and is associated with poor cardiovascular outcomes. Hyperinsulinemic euglycemic glucose clamp (HEGC) is the gold standard for measuring IR. The comparison of commonly-used indirect indices of IR to HEGC has not been adequately performed in this population. Furthermore, the validity of newly proposed adipokine-based IR indices has not been explored.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is an observational study performed in a single center, involving 12 prevalent CHD patients (50 ± 9 years old, 100% African American, 33% women, body mass index of 34.4 ± 7.6 kg/m(2)) who were studied three consecutive times. IR was assessed by HEGC (glucose-disposal rate [GDR]), homeostatic model assessment of IR (HOMA-IR), HOMA-IR corrected by adiponectin (HOMA-AD), leptin adiponectin ratio (LAR), QUICKI, and the McAuley's index at each time point.

RESULTS

Eighty-three percent of the subjects displayed either glucose intolerance or overt insulin resistance by HEGC (GDR median, 5.71; interquartile range [IQR], 4.16, 6.81). LAR and HOMA-AD were the best correlates of IR measured by HEGC (r=-0.72, P<0.001, and -0.67, P<0.001), respectively. Fat percentage, interleukin-6, and adipokines (leptin, adiponectin, and resistin) were strongly associated with GDR. HEGC, LAR, and HOMA-AD had the best intraclass correlation coefficients.

CONCLUSION

IR is common in CHD patients. Adipokine-based indices are the best correlates of IR measurements by HEGC. HOMA-IR and QUICKI are reasonable alternatives. Use of these indices may allow better detection of alterations in insulin sensitivity in CHD patients.

Silencing of tissue factor by antisense deoxyoligonucleotide prevents monocrotaline/LPS renal injury in mice

Tissue factor (TF) is involved in monocrotaline (MCT)/lipopolysaccharide (LPS) hepatotoxicity. It is not known whether MCT/LPS can cause renal toxicity and whether TF is involved in this toxicity. Thus, the present study was undertaken to investigate the potential renal toxicity after MCT/LPS co-treatment and the involvement of TF in this toxicity. MCT was delivered to ND4 male mice (200 mg/kg) per os followed 4 h later by treatment with LPS ip (6 mg/kg) to investigate its effect on kidney. We injected TF antisense oligonucleotide (TF-AS) intravenously (i.v) in mice prior to LPS treatment, to block TF, and measured their blood urea nitrogen (BUN), creatinine (CRE), alkaline phosphatase (ALP), and potassium. In MCT/LPS co-treated group, fibrin was detected on the glomerular capillary lumina, distal tubules of renal cortex, and the necrotic tubules of renal medulla. An elevation of BUN, creatinine, and the BUN/creatinine ratio was seen in mice with MCT/LPS co-treatment, compared to animals receiving LPS or MCT alone. Simultaneously, an aggressive tubular necrosis was seen in the medullary tubules in the same group which may account for the oliguria observed in these animals. Fourfold inductions in the plasma TF level was detected at 10 h after MCT/LPS co-treatment which increased to 18-fold at 24 h. Increased blood level of leptin, interleukin-6 (IL-6) and downregulation of tubular chemokine (C-X-C motif) ligand 16 (CXCL16) are characteristic features in MCT/LPS co-treated animal. On the other hand, mice injected with TF-AS in the presence of MCT/LPS co-treatment showed no elevation of the blood BUN, creatinine, potassium, and normal levels of the proinflammatory molecules. TF-AS injection significantly prevented glomerular and tubular fibrin deposition, tubular necrosis, and improvement of the animal survivability. Renal toxicity involving TF can be prevented successfully by the use of TF-AS.

Leptin promotes fibroproliferative acute respiratory distress syndrome by inhibiting peroxisome proliferator-activated receptor-γ

RATIONALE

Diabetic patients have a lower incidence of acute respiratory distress syndrome (ARDS), and those who develop ARDS are less likely to die. The mechanisms that underlie this protection are unknown.

OBJECTIVES

To determine whether leptin resistance, a feature of diabetes, prevents fibroproliferation after lung injury.

METHODS

We examined lung injury and fibroproliferation after the intratracheal instillation of bleomycin in wild-type and leptin-resistant (db/db) diabetic mice. We examined the effect of leptin on transforming growth factor (TGF)-β(1)-mediated transcription in primary normal human lung fibroblasts. Bronchoalveolar lavage fluid (BAL) samples from patients with ARDS and ventilated control subjects were obtained for measurement of leptin and active TGF-β(1) levels.

MEASUREMENTS AND MAIN RESULTS

Diabetic mice (db/db) were resistant to lung fibrosis. The db/db mice had higher levels of peroxisome proliferator-activated receptor-γ (PPARγ), an inhibitor of the transcriptional response to TGF-β(1), a cytokine critical in the pathogenesis of fibroproliferative ARDS. In normal human lung fibroblasts, leptin augmented the transcription of profibrotic genes in response to TGF-β(1) through a mechanism that required PPARγ. In patients with ARDS, BAL leptin levels were elevated and correlated with TGF-β(1) levels. Overall, there was no significant relationship between BAL leptin levels and clinical outcomes; however, in nonobese patients, higher BAL leptin levels were associated with fewer intensive care unit- and ventilator-free days and higher mortality.

CONCLUSIONS

Leptin signaling is required for bleomycin-induced lung fibrosis. Leptin augments TGF-β(1) signaling in lung fibroblasts by inhibiting PPARγ. These findings provide a mechanism for the observed protection against ARDS observed in diabetic patients.

The molecular mechanism of leptin secretion and expression induced by aristolochic acid in kidney fibroblast

Background

Leptin is a peptide hormone playing pivotal role in regulating food intake and energy expenditure. Growing evidence has suggested the pro-inflammatory and fibrogenic properties of leptin. In addition, patients with renal fibrosis have higher level of plasma leptin, which was due to the increased leptin production. Aristolochic acid (AA) is a botanical toxin characterized to associate with the development of renal fibrosis including tubulointerstitial fibrosis. However, whether leptin is upregulated to participate in AA-induced kidney fibrosis remain completely unknown.

Methodology/Principal Findings

In this study, leptin expression was increased by sublethal dose of AA in kidney fibroblast NRK49f determined by enzyme-linked immunosorbent assay and Western blot. Data from real-time reverse transcriptase-polymerase chain reaction revealed that leptin was upregulated by AA at transcriptional level. DNA binding activity of CCAAT enhancer binding protein α (C/EBP α), one of the transcription factors for leptin gene, was enhanced in DNA affinity precipitation assay and chromatin immunoprecipitation experiments. Knockdown of C/EBP α expression by small interfering RNA markedly reduced AA-induced leptin expression. Moreover, AA promoted Akt interaction with p-PDK1, and increased phosphorylated activation of Akt. Akt knockdown, and inhibition of Akt signaling by LY294002 and mTOR inhibitor rapamycin reduced leptin expression. Furthermore, treatment of LY294002 or rapamycin significantly suppressed AA-induced C/EBP α DNA-binding activity. These results suggest that Akt and C/EBP α activation were involved in AA-regulated leptin expression.

Conclusions/Significance

Our findings demonstrate the first that AA could induce secretion and expression of fibrogenic leptin in kidney fibroblasts, which reveal potential involvement of leptin in the progression of kidney fibrosis in aristolochic acid nephropathy.

[Renal consequences of obesity]

The steady increase in the prevalence of obesity contributes to the increase in the prevalence of chronic kidney disease, through renal damages associated with type-2 diabetes and hypertension. Obesity is also an independent risk factor for the kidney, since it is associated with an increased risk of albuminuria and glomerulosclerosis, and worsens the course of chronic kidney disease regardless of the primary renal disease. The existence of a metabolic syndrome, constant in type-2 diabetes, and associated with abdominal obesity, is not the only requirement for renal anomalies of which the translation is a functional hyperfiltration, a clinical microalbuminuria and histologically a glomerulomegaly and glomerulosclerosis. The estimated glomerular filtration rate (GFR) in obese patients is strongly influenced by the weight or indexation to body surface area, and it is logical to take into account the value of non-indexed GFR to assess renal risk and treatment effects, especially if they lead to weight loss. Hypertension is promoted by salt sensitivity, potentially reversible, and overactivity of the renin-angiotensin system (RAS) in part due to adipose tissue. The cytokines secreted by adipose tissue (adipokines), induce sympathetic hyperactivity through leptin, and low-grade inflammatory state that contributes to the development of glomerular sclerosis lesions, especially because a resistance to adiponectin. The treatment relies on weight loss, possibly through bariatric surgery, and antagonists of the RAS.

Urinary cystatin C as a potential risk marker for cardiovascular disease and chronic kidney disease in patients with obesity and metabolic syndrome

BACKGROUND AND OBJECTIVES

Obesity and metabolic syndrome (MS) increase the risk of cardiovascular disease (CVD), chronic kidney disease (CKD), and all-cause mortality. Serum cystatin C (S-CysC), a marker of GFR, has been shown to be associated with CVD and CKD. This study was designed to elucidate the association of urinary CysC (U-CysC), a marker of renal tubular dysfunction, with CVD and CKD risk factors in patients with obesity and MS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The U-CysC-creatinine ratio (UCCR) was examined in 343 Japanese obese outpatients enrolled in the multi-centered Japan Obesity and Metabolic Syndrome Study.

RESULTS

UCCR was positively correlated with urine albumin-creatinine ratio (UACR) and S-CysC and negatively correlated with estimated GFR (eGFR). Among obese patients, UCCR was significantly higher in MS patients than in non-MS patients. UCCR had significant correlations with the number of components of MS and arterial stiffness, all of which are CVD predictors, similarly to UACR (P<0.05). Interestingly, diet- and exercise-induced weight reduction for 3 months significantly decreased only UCCR among all of the renal markers examined (P<0.01), in parallel with the decrease in BMI, HbA1c, and arterial stiffness, suggesting the beneficial effect of weight reduction on renal tubular dysfunction.

CONCLUSIONS

This study demonstrates that UCCR is significantly associated with renal dysfunction, the severity of MS, arterial stiffness, and weight change in obese patients. The data of this study suggest that U-CysC could serve as a CVD and CKD risk factor in patients with obesity and MS.

Pro-inflammatory high-density lipoproteins and atherosclerosis are induced in lupus-prone mice by a high-fat diet and leptin

Atherosclerosis is accelerated in people with systemic lupus erythematosus, and the presence of dysfunctional, pro-inflammatory high-density lipoproteins is a marker of increased risk. We developed a mouse model of multigenic lupus exposed to environmental factors known to accelerate atherosclerosis in humans - high-fat diet with or without injections of the adipokine leptin. BWF1 mice were the lupus-prone model; BALB/c were non-autoimmune controls. High-fat diet increased total serum cholesterol in both strains. In BALB/c mice, non-high-density lipoprotein cholesterol levels increased; they did not develop atherosclerosis. In contrast, BWF1 mice on high-fat diets developed increased quantities of high-density lipoproteins as well as elevated high-density lipoprotein scores, indicating pro-inflammatory high-density lipoproteins; they also developed atherosclerosis. In the lupus-prone strain, addition of leptin increased pro-inflammatory high-density lipoprotein scores and atherosclerosis, and accelerated proteinuria. These data suggest that environmental factors associated with obesity and metabolic syndrome can accelerate atherosclerosis and disease in a lupus-prone background.

SPARC: a key player in the pathologies associated with obesity and diabetes

SPARC (secreted protein acidic and rich in cysteine, also known as osteonectin or BM-40) is a widely expressed profibrotic protein with pleiotropic roles, which have been studied in a variety of conditions. Notably, SPARC is linked to human obesity; SPARC derived from adipose tissue is associated with insulin resistance and secretion of SPARC by adipose tissue is increased by insulin and the adipokine leptin. Furthermore, SPARC is associated with diabetes complications such as diabetic retinopathy and nephropathy, conditions that are ameliorated in the Sparc-knockout mouse model. As a regulator of the extracellular matrix, SPARC also contributes to adipose-tissue fibrosis. Evidence suggests that adipose tissue becomes increasingly fibrotic in obesity. Fibrosis of subcutaneous adipose tissue may restrict accumulation of triglycerides in this type of tissue. These triglycerides are, therefore, diverted and deposited as ectopic lipids in other tissues such as the liver or as intramyocellular lipids in skeletal muscle, which predisposes to insulin resistance. Hence, SPARC may represent a novel and important link between obesity and diabetes mellitus. This Review is focused on whether SPARC could be a key player in the pathology of obesity and its related metabolic complications.

Genetic variation at selected SNPs in the leptin gene and association of alleles with markers of kidney disease in a Xhosa population of South Africa

BACKGROUND

Chronic kidney disease (CKD) is a significant public health problem that leads to end-stage renal disease (ESRD) with as many as 2 million people predicted to need therapy worldwide by 2010. Obesity is a risk factor for CKD and leptin, the obesity hormone, correlates with body fat mass and markers of renal function. A number of clinical and experimental studies have suggested a link between serum leptin and kidney disease. We hypothesised that variants in the leptin gene (LEP) may be associated with markers of CKD in indigenous black Africans.

METHODOLOGY/PRINCIPAL FINDINGS

Black South Africans of Xhosa (distinct cultural Bantu-speaking population) descent were recruited for the study and four common polymorphisms of the LEP (rs7799039, rs791620, rs2167270 and STS-U43653 [ENSSNP5824596]) were analysed for genotype and haplotype association with urine albumin-to-creatinine ratio (UACR), estimated glomerular filtration rate (eGFR), Serum creatinine (Scr) and serum leptin level. In one of the four single nucleotide polymorphisms (SNPs) we examined, an association with the renal phenotypes was observed. Hypertensive subjects with the T allele (CT genotype) of the ENSSNP5824596 SNP had a significantly higher eGFR (p = 0.0141), and significantly lower Scr (p = 0.0137). This was confirmed by haplotype analysis. Also, the haplotype GAAC had a modest effect on urine albumin-to-creatinine ratio in normotensive subjects (p = 0.0482).

CONCLUSIONS/SIGNIFICANCE

These results suggest that genetic variations of the LEP may be associated with phenotypes that are markers of CKD in black Africans.

Role of central leptin signaling in renal macrophage infiltration

Monocytes/macrophages are key mediators of wound repair, tissue remodeling, and inflammation. However, the molecular mechanisms underlying macrophage recruitment to the site of inflammation is not fully understood. Leptin acts directly on the hypothalamus, thereby regulating food intake and energy expenditure. The leptin receptor, a single transmembrane protein that belongs to the gp130 family of cytokine receptor superfamily, is expressed not only in the hypothalamus but in a variety of peripheral tissues, suggesting the role of leptin as a pro-inflammatory adipocytokine in peripheral tissues. Here, we show that deficiency of leptin signaling reduces renal macrophage infiltration after unilateral ureteral obstruction (UUO). Bone marrow transplantation studies using leptin signaling-deficient db/db mice revealed that leptin signaling in bone marrow cells may not play a major role in the UUO-induced renal macrophage infiltration. Interestingly, central leptin administration reverses the otherwise reduced UUO-induced renal macrophage infiltration in leptin-deficient ob/ob mice. This is effectively abolished by central co-administration of SHU9119, a melanocortin-3 receptor/melanocortin-4 receptor antagonist. This study demonstrates that central leptin administration in ob/ ob mice accelerates renal macrophage infiltration through the melanocortin system, thereby suggesting that the central nervous system, which is inherent to integrate information from throughout the organism, is able to control peripheral inflammation.

Involvement of visceral fat in the pathogenesis of albuminuria in patients with type 2 diabetes with early stage of nephropathy

BACKGROUND

Visceral obesity has been implicated in the pathogenesis of diabetic nephropathy. Waist circumference has been used as a surrogate measure of visceral fat mass; however, subcutaneous fat mass is also correlated with waist circumference. We therefore conducted this cross-sectional study to clarify the relationship between directly measured sizes of visceral and subcutaneous fat and microalbuminuria in patients with type 2 diabetes (T2DM).

METHODS

We studied a total of 208 adult Japanese individuals with T2DM, 99 women and 109 men, with a mean +/- standard deviation (SD) age of 56 +/- 13 years. Patients with macroalbuminuria, defined as a urinary albumin-to-creatinine ratio (ACR) >or=300 mg/g creatinine, and those with an estimated glomerular filtration rate <15 ml/min/1.73 m(2) were excluded. Visceral and subcutaneous fat areas were measured by abdominal computed tomography.

RESULTS

In the univariate correlational analysis, logarithmically transformed urinary ACR was significantly associated with visceral fat area (r = 0.14, p = 0.047) but not with subcutaneous fat area (r = 0.08, p = 0.237). In the multiple regression analysis with stepwise selection procedure, visceral fat area but not subcutaneous fat area was selected as an independent variable that was statistically associated with urinary ACR.

CONCLUSION

This cross-sectional study suggests that increased visceral but not subcutaneous fat is independently associated with microalbuminuria in Japanese adult patients with T2DM.

Leptin and the clinical cardiovascular risk

Obesity is a universal health problem of increasing prevalence and represents a major public health concern. Obesity is associated with a high risk of developing cardiovascular and metabolic diseases such as hypertension, coronary atherosclerosis, myocardial hypertrophy, diabetes, dyslipidemia, and increased cardiovascular morbidity and mortality. There has been an ongoing search for mediators between obesity and cardiovascular disease. Leptin is a novel and very promising molecule of research that may link these pathologic conditions. Since its discovery in 1994, major advances have been made in the understanding of neuroendocrine mechanisms regulating appetite, metabolism, adiposity, sympathetic tone and blood pressure. In this review, we discuss the physiological and pathophysiological roles of leptin in the causation of various cardiovascular diseases.

Resolution of renal inflammation: a new role for NF-kappaB1 (p50) in inflammatory kidney diseases

In renal tissue injury, activation of the transcription factor NF-kappaB has a central role in the induction of proinflammatory gene expression, which are involved in the development of progressive renal inflammatory disease. The function of NF-kappaB during the switch from the inflammatory process toward resolution, however, is largely unknown. Therefore, we assessed the time-dependent activation and function of NF-kappaB in two different models of acute nephritis. Our experiments demonstrate a biphasic activation of NF-kappaB in the anti-Thy-1 model of glomerulonephritis in rats and the LPS-induced nephritis in mice, with a first peak during the induction phase and a second peak during the resolution period. After induction of glomerular immune injury in rats, predominantly NF-kappaB p65/p50 heterodimer complexes are shifted to the nucleus whereas during the resolution phase predominantly p50 homodimers could be demonstrated in the nuclear compartment. In addition, we could demonstrate that p50 protein plays a pivotal role in the resolution of LPS-induced renal inflammation since NF-kappaB p50 knockout mice demonstrate significantly higher chemokine expression, prolonged renal inflammatory cell infiltration with consecutive tissue injury, and reduced survival. In conclusion, our studies indicate that NF-kappaB subunit p50 proteins have critical in vivo functions in immunologically mediated renal disease by downregulating inflammation during the resolution period.

Obesity, inflammation, and kidney disease

Obesity and extreme obesity are associated with a wide range of well known comorbidities (cardiovascular disease, dyslipidemia, hypertension, diabetes mellitus, metabolic syndrome). Recently, the association between obesity and renal involvement has been accepted since several epidemiological and pathological studies support this relationship. However, the physiopathological mechanism of this association is not completely understood. Different mechanisms have been implicated in the production of these renal lesions. Between them, metabolic alterations and inflammatory adipocytokines have been suggested. This paper is a review of the association between inflammatory adipocytokines or metabolic syndrome with renal involvement. We also briefly report our experience in a cohort of extremely obese patients.

Leptin induces migration and invasion of glioma cells through MMP-13 production

Leptin, the product of the obese gene, plays an important role in the regulation of body weight by coordinating metabolism, feeding behavior, energy balance, and neuroendocrine responses. However, regulation of leptin gene expression in the central nervous system is different from that in the adipocytes. In addition, leptin has been found in many tumor cell lines and has been shown to have mitogenic and angiogenic activity in a number of cell types. Glioma is the most common primary adult brain tumor with poor prognosis because of the spreading of tumor cell to the other regions of brain easily. Here we found that malignant C6 glioma cells expressed more leptin and leptin receptors than nonmalignant astrocytes. Furthermore, it was found that exogenous application of leptin enhanced the migration and invasion of C6 glioma cells. In addition, we found that the expression of matrix metalloproteinase-13 (MMP-13) but not of MMP-2 and MMP-9 was increased in response to leptin stimulation. The leptin-induced increase of cell migration and invasion was antagonized by MMP-13 neutralizing antibody or silencing MMP-13. The up-regulation of MMP-13 induced by leptin was mainly through p38 MAP kinase and NF-kappaB pathway. In addition, migration-prone sublines demonstrate that cells with increasing migration ability had more expression of MMP-13 and leptin. Taken together, these results indicate that leptin enhanced migration and invasion of C6 glioma cells through the increase of MMP-13 production.