Measured GFR in murine animal models: review on methods, techniques, and procedures.

Chronic kidney disease (CKD) is one of the most common chronic diseases worldwide, with increasing rates of morbidity and mortality. Thus, early detection is essential to prevent severe adverse events and the progression of kidney disease to an end stage. Glomerular filtration rate (GFR) is the most appropriate index to evaluate renal function in both clinical practice and basic medical research. Several animal models have been developed to understand renal disease induction and progression. Specifically, murine models are useful to study the pathogenesis of renal damage, so a reliable determination of GFR is essential to evaluate the progression of CKD. However, as in clinical practise, the estimation of GFR in murine by levels of serum/urine creatinine or cystatin-C could not be accurate and needed other more reliable methods. As an alternative, the measurement of GFR by the clearance of exogenous markers like inulin, sinistrin, 51Cr-EDTA, 99mTc-DTPA, 125I-iothalamate, or iohexol could be performed. Nevertheless, both approaches-estimation or measurement of GFR-have their limitations and a standard method for the GFR determination has not been defined. Altogether, in this review, we aim to give an overview of the current methods for GFR assessment in murine models, describing each methodology and focusing on their advantages and limitations.

The Role of Vascular Lesions in Diabetes Across a Spectrum of Clinical Kidney Disease.

INTRODUCTION: The clinical-histologic correlation in diabetic nephropathy is not completely known. METHODS: We analyzed nephrectomy specimens from 90 patients with diabetes and diverse degrees of proteinuria and glomerular filtration rate (GFR). RESULTS: Thirty-six (40%) subjects had normoalbuminuria, 33 (37%) microalbuminuria, and 21 (23%) non-nephrotic proteinuria. Mean estimated GFR (eGFR) was 65±23 (40% <60 ml/min per 1.73 m2). About 170 glomeruli per patient were analyzed, and all samples included vascular tissue. Six subjects (7%) were classified in diabetic nephropathy class I, 61 (68%) in class II-a, 13 (14%) in class II-b, 9 (10%) class III, and 1 (1%) in class IV. Eighty percent to 90% of those with normoalbuminuria or microalbuminuria were classified in class II-a or II-b and <10% in class III; 52% of those with proteinuria were in class II-a, 15% in class II-b, and 19% in class III. Nodular sclerosis (57%) and mesangial expansion (15%) were more frequent in cases with proteinuria than in normoalbuminuria (28% and 8%; P = 0.028 and 0.017). About 20% to 30% of all cases, regardless the level of albuminuria or proteinuria or the histologic class had tubular atrophy, interstitial fibrosis, or inflammation in >10% to 20% of the sample. Moderate hyalinosis and arteriolar sclerosis were observed in 80% to 100% of cases with normoalbuminuria, microalbuminuria, proteinuria, as well as in class I, II, or III. CONCLUSIONS: Weak correspondence between analytical parameters and kidney histology was found. Thus, disease may progress undetected from the early clinical stages of the disease. Finally, vascular damage was a very common finding, which highlights the role of ischemic intrarenal disease in diabetes.

Obesity and metabolic syndrome induce hyperfiltration, glomerulomegaly, and albuminuria in obese ovariectomized female mice and obese male mice.

OBJECTIVE: Obese patients with metabolic syndrome have a high risk of chronic kidney disease. The prevalence of obesity, metabolic syndrome, and insulin resistance increase in women after menopause, as does the risk of chronic kidney disease. This may indicate an interaction between obesity, metabolic syndrome, and menopause in the induction of renal damage. However, the pathogenesis of kidney disease in postmenopausal obese women is poorly understood. METHODS: We investigated the interaction of an obesogenic diet and menopause on renal dysfunction in ovariectomized and non-ovariectomized lean (n = 8 and 17) and obese (n = 12 and 20) female mice. Obese (n = 12) and lean (n = 10) male mice were also studied. Glucose metabolism, insulin resistance, and kidney function were evaluated with gold standards procedures. Changes in kidney histology and lipid deposition were analyzed. Females had a lower number of glomeruli than males at baseline. RESULTS: Only female ovariectomized obese animals developed insulin resistance, hyperglycemia, and kidney damage, evidenced as glomerulomegaly, glomerular hyperfiltration, and increased urinary albumin excretion, despite a similar increase in weight than obese non-ovariectomized female mice. Male obese mice developed hyperglycemia, insulin resistance, and hyperfiltration without major renal histological changes. Males on high fat diet showed higher renal lipid content and females on high fat diet (ovariectomized or non-ovariectomized) showed higher total cholesterol content than males. CONCLUSIONS: In mice, there is a clear interplay between obesity, metabolic syndrome, and menopause in the induction of kidney damage.

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Immunological Pattern in IgA Nephropathy.

The current gold-standard diagnostic technique for IgA nephropathy (IgAN), the leading form of primary glomerulonephritis, is renal biopsy. CD89 (the main IgA receptor) is expressed on the surface of monocytes and plays a role in disease pathogenesis. Immunocomplexes formed by sCD89 (soluble form) and Gd-IgA1 are related to disease prognosis. We hypothesize that reduced CD89 surface expression on monocytes may be a marker of disease severity. We aimed to analyze leukocyte subpopulations in peripheral blood and CD89 surface expression on monocytes in a prospective study of 22 patients and 12 healthy subjects (HS). Leukocyte subpopulations and CD89 expression were analyzed by flow cytometry. IgAN patients had a higher percentage of activated and effector memory CD4+ and CD8+ T lymphocytes, a lower percentage of transitional B lymphocytes and plasmablasts, and a higher percentage of CD56dimCD16+ NK cells and myeloid dendritic cells compared with HS. Correlations between reduced CD89 expression levels on nonclassical monocytes, histological findings of a poor prognosis on renal biopsy and baseline renal function were observed. IgAN patients show a characteristic immunological pattern in peripheral blood. A reduced expression level of CD89 on nonclassical monocytes identifies patients with a worse renal prognosis.

The estimation of GFR and the adjustment for BSA in overweight and obesity: a dreadful combination of two errors.

BACKGROUND: Obesity is an established risk factor for renal disease and for disease progression. Therefore, an accurate determination of renal function is necessary in this population. Renal function is currently evaluated by estimated glomerular filtration rate (GFR) by formulas, a procedure with a proven high variability. Moreover, the adjustment of GFR by body surface area (BSA) confounds the evaluation of renal function. However, the error of using estimated GFR adjusted by BSA has not been properly evaluated in overweight and obese subjects. METHODS: We evaluated the error of 56 creatinine- and/or cystatin-C-based equations and the adjustment of GFR by BSA in 944 subjects with overweight or obesity with or without chronic kidney disease (CKD). The error between estimated (eGFR) and measured GFR (mGFR) was evaluated with statistics of agreement: the total deviation index (TDI), the concordance correlation coefficient (CCC) and the coverage probability (cp). RESULTS: The error of eGFR by any equation was common and wide: TDI averaged 55%, meaning that 90% of estimations ranged from -55 to 55% of mGFR. CCC and cp averaged 0.8 and 26, respectively. This error was comparable between creatinine and cystatin-C-based formulas both in obese or overweight subjects. The error of eGFR was larger in formulas that included weight or height. The adjustment of mGFR or eGFR led to a relevant underestimation of renal function, reaching at least 10 mL/min in 25% of the cases. CONCLUSIONS: In overweight and obese patients, formulas failed in reflecting real renal function. In addition, the adjustment for BSA led to a relevant underestimation of GFR. Both errors may have important clinical consequences. Thus, whenever possible, the use of a gold standard method to measure renal function is recommended. Moreover, the sense of indexing for BSA should be re-considered and probably abandoned.

Consequences of morbid obesity on the kidney. Where are we going?

Obesity and morbid obesity are modifiable risk factors for the development and progression of kidney disease. Obesity has reached epidemic proportions and is currently an important health problem in Europe, so it is necessary to develop therapeutic and preventive strategies. The obesity-related glomerulopathy has been defined as a secondary form of focal segmental glomerulosclerosis, and its most characteristic feature is glomerulomegaly. The renal evolution of patients with obesity-related glomerulopathy (ORG) who have not been treated is unfavourable. However, morbidly obese patients with ORG that underwent bariatric surgery and drastic weight loss had a better outcome. Many inflammatory factors have been implicated in the pathogenic mechanism of renal disease in obesity. Hypoadiponectinaemia, hyperleptinaemia and hyperaldosteronism have been associated with glomerular injury in obese patients. The application of modern techniques has provided important insights that increase the current understanding of ORG. However, further investigation is needed.

Low Insulin-Like Growth Factor-1 Level in Obesity Nephropathy: A New Risk Factor?

INTRODUCTION: IGF-1 (insulin-like growth factor-1) is a hormone involved in cell growth and other important processes. In the kidney, IGF-1 has a stimulating effect, increasing the blood flow and glomerular filtration rate. Although many experimental animal studies regarding the role of IGF-1 in the kidney have been conducted, few human studies are available in the literature. Obesity is a cause of renal failure, and several glomerular lesions associated with obesity have been described. However, no studies regarding the levels of IGF-1 in morbidly obese patients with renal injury associated with obesity have been conducted. AIM: To determine the serum IGF-1 concentrations in morbidly obese patients with normal renal function but with different types of early obesity-related glomerular lesions and to evaluate the possible relationship between IGF-1 and the presence of renal lesions. METHODS: Eighty morbidly obese patients with renal biopsy, including 11 patients with no evidence of renal lesion, 17 patients with single glomerulomegaly, 21 patients with single podocyte hypertrophy, 10 patients with glomerulomegaly and podocyte hypertrophy, 5 patients with focal segmental hyalinosis, and 16 patients with increased mesangial matrix and/or mesangial proliferation, participated in this study. Biological parameters, including serum IGF-1 concentrations with the standard deviation score for age (SDS-IGF-1), were determined for all patients. RESULTS: Eighty patients (50 women and 30 men) with a mean BMI of 52.63 ± 8.71 and a mean age of 42.40 ± 9.45 years were included in this study. IGF-1, IGF-1 SDS and IGF-1BP3 levels according to the renal injury were compared (normal glomeruli: IGF-1 = 190.17 ± 72.46; glomerulomegaly: IGF-1 = 122.3 ± 50.05; podocyte hypertrophy: IGF-1 = 119.81 ± 60.34; focal segmental hyalinosis: IGF-1 170.98 ± 100.83, increased mesangial matrix and/or mesangial proliferation: IGF-1 117.73 ± 63.87). Statistically significant differences were observed between serum levels of IGF-1 and between the levels of SDS-IGF-1 by comparing the group without glomerular lesion with the group formed by patients with any type of glomerular injury. Logistic regression analysis was performed, with the dependent variable defined as the glomerular injury. In the multivariate analysis, only SDS-IGF-1 was associated with glomerular injury, and low levels of IGF-1 SDS were a risk factor for kidney injury. CONCLUSIONS: Our study demonstrates that low IGF-1 serum levels are associated with renal lesions in morbidly obese patients without overt clinical renal manifestations.

Long-Term Normal Renal Function after Drastic Weight Reduction in Patients with Obesity-Related Glomerulopathy.

AIMS: No long-term studies of renal function evolution in morbidly obese (MO) patients after weight loss are available. The aim of our work was to ascertain the long-term influence of drastic weight reduction on renal function in MO patients with obesity-related glomerular lesions. METHODS: 92 MO patients with normal renal function and biopsy evidence of mild obesity-related glomerulopathy underwent bariatric surgery (BS) and subsequent drastic weight loss. A long-term prospective follow-up (mean duration: 76 ± 42 months) was carried out. Basal renal biopsies and basal and long-term metabolic and renal function studies were performed in all cases. Linear mixed models were applied. RESULTS: Blood pressure dropped early after BS and remained stable thereafter. Creatinine clearance and BMI fell in the first 2 years, rose slightly after 5 years and then remained stable. Serum creatinine and albuminuria decreased throughout the follow-up period. Renal function and albuminuria evolution showed non-significant differences in relation to the number of glomerular lesions. CONCLUSIONS: Drastic weight loss in BS-treated MO patients with pre-surgical normal renal function and mild obesity-related glomerular lesions is associated with short- and long-term maintenance of normal renal function and improvement in both arterial hypertension and albuminuria.

Hypogonadotropic hypogonadism in morbidly obese males is reversed after bariatric surgery.

BACKGROUND: The effect of weight loss by bariatric surgery on gonadal hormones in morbidly obese males is not entirely known. The main objective of the study was to analyze gonadal hormonal changes after weight loss. METHODS: An observational study was conducted before and after 12 months of weight loss at a clinical research center. Thirty-three men [age 40.5 ± 9.9, body mass index (BMI) 50.3 ± 6.1 kg/m(2)] undergoing bariatric surgery were included. The main outcome measures were as follows: changes in total (TT) and free testosterone (FT), estradiol (E2), sex hormone binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), anti-Müllerian hormone (AMH), inhibin B, and prolactin (PRL). RESULTS: Baseline prevalence of hypogonadism (defined by TT < 300 ng/dl or FT < 65 pg/ml) was 78.8 and 51.5%, respectively. Hypogonadal patients were older and showed inhibin B and AMH significantly lower than those with normal TT. BMI correlated negatively with TT, LH, and SHBG. Regression analyses showed a significant and independent association of hypogonadism with age (OR = 1.2, p = 0.01), BMI (OR = 1.3, p = 0.03), and AMH (OR = 0.4, p = 0.03) after adjustments. After 1 year, percentage of weight loss (%WL) was 18.8 ± 5.2%, and there was a significant increase of TT, FT, SHBG, and FSH and a decrease of E2 and PRL. Prevalence of persistent hypogonadism after surgery was 6% (low TT) and 15% (low FT). %WL was significantly associated with percent changes in SHBG (r = -0.4, p = 0.04), inhibin B (r = -0.4, p = 0.03), and AMH (r = -0.4, p = 0.01). Age and %WL were the only significant and independent parameters associated with %TT change. CONCLUSIONS: Obesity-associated hypogonadism is very prevalent in males with morbid obesity and is mostly reversed after sustained weight loss by bariatric surgery.

Effects of two variants of Roux-en-Y Gastric bypass on metabolism behaviour: focus on plasma ghrelin concentrations over a 2-year follow-up.

BACKGROUND: To study the effects of two variants of Roux-en-Y gastric bypass (RYGBP) on plasma ghrelin concentrations according to different exposure of gastric fundus to the nutrient pathway. METHODS: A prospective longitudinal 2-year follow-up study was conducted. Ninety-six morbidly obese (MO) patients (age range: 41.6 +/- 9.6 years, body mass index: 53 +/- 9.5 kg/m(2)) were assigned to two bariatric surgical (BS) procedures: one that preserves food contact with gastric fundus (ringed RYGBP, n = 50) and the other that avoids it (modified RYGBP, n = 46). Different anthropometric and biochemical parameters were studied, focusing on ghrelin concentrations at baseline and 6, 12, and 24 months post-BS. RESULTS: At 24 months post-BS, all metabolic parameters studied had improved in all patients compared with those at 1-year follow-up and baseline (p < 0.05). However, high-density lipoprotein cholesterol concentrations took 2 years to normalise in 80% of patients, interleukin-6 decreased significantly in relation to baseline only after 2 years from BS (p < 0.001), and tumour necrosis factor alpha concentrations did not significantly decrease during the 2 years of follow-up. Plasma ghrelin concentrations increased in both surgical groups compare to baseline during the first year (24.6% in modified RYGBP and 36.62% in ringed RYGBP) and remained stable at the second year of follow-up, with no statistical differences between groups. CONCLUSIONS: In the second year of follow-up after BS, morbidity continued to improve in MO patients despite a lesser weight loss in relation to the first year. An increase in plasma ghrelin concentrations was found, regardless of nutrient contact with gastric fundus. Furthermore, changes in plasma ghrelin concentrations appeared to be independent of weight loss.

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.

Effect of drastic weight loss after bariatric surgery on renal parameters in extremely obese patients: long-term follow-up.

Obesity is a health problem that is reaching epidemic proportions. Extreme obesity (body mass index [BMI] > or =40 kg/m2) is a type of obesity that usually does not respond to medical treatment, with surgery being the current treatment of choice. Extreme obesity is associated with cardiovascular disease, type 2 diabetes, dyslipidemia, and hypertension. Recently, obesity has been related with high rate of renal lesions, but renal function and renal parameters in extreme obesity scarcely are documented. The objective of this study was to evaluate the effect of weight loss after bariatric surgery (BS) on BP, renal parameters, and renal function in 61 extremely obese (EO) patients after 24 mo of follow-up. A total of 61 EO adults (37 women) were studied prospectively before and 24 mo after surgery. Control subjects were 24 healthy, normal-weight adults (15 women). Anthropometric, BP, and renal parameters were determined. Presurgery weight, BMI, GFR, 24-h proteinuria, and 24-h albuminuria were higher in the EO patients than in control subjects (P < 0.001). All parameters improved at 12 mo after BS. However, during the second year of follow-up, only 24-h albuminuria (P = 0.006) and BMI (P = 0.014) continued to improve. At 24 mo after BS, obesity-related renal alterations considerably improved. This improvement was observed mainly in the first year after surgery, when the majority of weight loss occurred. However, 24-h albuminuria still improves during the second year of follow-up. It is possible that this decrease in 24-h albuminuria is not GFR related but rather is attributable to the persistence of the decrease in BMI and to the improvement of other weight-related metabolic factors.