Renal hemodynamics in newly presenting non-insulin dependent diabetes mellitus

Fluid shear stress stimulates ATP release without regulating purinergic gene expression in the renal inner medullary collecting duct

In the kidney, the flow rate of the pro-urine through the renal tubules is highly variable. The tubular epithelial cells sense these variations in pro-urinary flow rate in order to regulate various physiological processes, including electrolyte reabsorption. One of the mechanosensitive pathways activated by flow is the release of ATP, which can then act as a autocrine or paracrine factor. Increased ATP release is observed in various kidney diseases, among others autosomal dominant polycystic kidney disease (ADPKD). However, the mechanisms underlying flow-induced ATP release in the collecting duct, especially in the inner medullary collecting duct, remain understudied. Using inner medullary collecting duct 3 (IMCD3) cells in a microfluidic setup, we show here that administration of a high flow rate for 1 min results in an increased ATP release compared to a lower flow rate. Although the ATP release channel pannexin-1 contributed to flow-induced ATP release in Pkd1-/- IMCD3 cells, it did not in wildtype IMCD3 cells. In addition, flow application increased the expression of the putative ATP release channel connexin-30.3 (CX30.3) in wildtype and Pkd1-/- IMCD3 cells. However, CX30.3 knockout IMCD3 cells exhibited a similar flow-induced ATP release as wildtype IMCD3 cells, suggesting that CX30.3 does not drive flow-induced ATP release in wildtype IMDC3 cells. Collectively, our results show differential mechanisms underlying flow-induced ATP release in wildtype and Pkd1-/- IMCD3 cells and further strengthen the link between ADPKD and pannexin-1-dependent ATP release.

The Role of Macula Densa Nitric Oxide Synthase 1 Beta Splice Variant in Modulating Tubuloglomerular Feedback

Abnormalities in renal electrolyte and water excretion may result in inappropriate salt and water retention, which facilitates the development and maintenance of hypertension, as well as acid-base and electrolyte disorders. A key mechanism by which the kidney regulates renal hemodynamics and electrolyte excretion is via tubuloglomerular feedback (TGF), an intrarenal negative feedback between tubules and arterioles. TGF is initiated by an increase of NaCl delivery at the macula densa cells. The increased NaCl activates luminal Na-K-2Cl cotransporter (NKCC2) of the macula densa cells, which leads to activation of several intracellular processes followed by the production of paracrine signals that ultimately result in a constriction of the afferent arteriole and a tonic inhibition of single nephron glomerular filtration rate. Neuronal nitric oxide (NOS1) is highly expressed in the macula densa. NOS1β is the major splice variant and accounts for most of NO generation by the macula densa, which inhibits TGF response. Macula densa NOS1β-mediated modulation of TGF responses plays an essential role in control of sodium excretion, volume and electrolyte hemostasis, and blood pressure. In this article, we describe the mechanisms that regulate macula densa-derived NO and their effect on TGF response in physiologic and pathologic conditions. © 2023 American Physiological Society. Compr Physiol 13:4215-4229, 2023.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Renoprotective Mechanism of Sodium-Glucose Cotransporter 2 Inhibitors: Focusing on Renal Hemodynamics

Diabetic kidney disease (DKD) is a prevalent renal complication of diabetes mellitus that ultimately develops into end-stage kidney disease (ESKD) when not managed appropriately. Substantial risk of ESKD remains even with intensive management of hyperglycemia and risk factors of DKD and timely use of renin-angiotensin-aldosterone inhibitors. Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce hyperglycemia primarily by inhibiting glucose and sodium reabsorption in the renal proximal tubule. Currently, their effects expand to prevent or delay cardiovascular and renal adverse events, even in those without diabetes. In dedicated renal outcome trials, SGLT2 inhibitors significantly reduced the risk of composite renal adverse events, including the development of ESKD or renal replacement therapy, which led to the positioning of SGLT2 inhibitors as the mainstay of chronic kidney disease management. Multiple mechanisms of action of SGLT2 inhibitors, including hemodynamic, metabolic, and anti-inflammatory effects, have been proposed. Restoration of tubuloglomerular feedback is a plausible explanation for the alteration in renal hemodynamics induced by SGLT2 inhibition and for the associated renal benefit. This review discusses the clinical rationale and mechanism related to the protection SGLT2 inhibitors exert on the kidney, focusing on renal hemodynamic effects.

Role of the macula densa sodium glucose cotransporter type 1-neuronal nitric oxide synthase-tubuloglomerular feedback pathway in diabetic hyperfiltration

An increase of glomerular filtration rate (GFR) is a common observation in early diabetes and is considered a key risk factor for subsequent kidney injury. However, the mechanisms underlying diabetic hyperfiltration have not been fully clarified. Here, we tested the hypothesis that macula densa neuronal nitric oxide synthase (NOS1) is upregulated via sodium glucose cotransporter type 1 (SGLT1) in diabetes, which then inhibits tubuloglomerular feedback (TGF) promoting glomerular hyperfiltration. Therefore, we examined changes in cortical NOS1 expression and phosphorylation, nitric oxide production in the macula densa, TGF response, and GFR during the early stage of insulin-deficient (Akita) diabetes in wild-type and macula densa-specific NOS1 knockout mice. A set of sophisticated techniques including microperfusion of juxtaglomerular apparatus in vitro, micropuncture of kidney tubules in vivo, and clearance kinetics of plasma fluorescent-sinistrin were employed. Complementary studies tested the role of SGLT1 in SGLT1 knockout mice and explored NOS1 expression and phosphorylation in kidney biopsies of cadaveric donors. Diabetic mice had upregulated macula densa NOS1, inhibited TGF and elevated GFR. Macula densa-selective NOS1 knockout attenuated the diabetes-induced TGF inhibition and GFR elevation. Additionally, deletion of SGLT1 prevented the upregulation of macula densa NOS1 and attenuated inhibition of TGF in diabetic mice. Furthermore, the expression and phosphorylation levels of NOS1 were increased in cadaveric kidneys of diabetics and positively correlated with blood glucose as well as estimated GFR in the donors. Thus, our findings demonstrate that the macula densa SGLT1-NOS1-TGF pathway plays a crucial role in the control of GFR in diabetes.

Insulin Resistance is Associated with Clinical Manifestations of Diabetic Kidney Disease (Glomerular Hyperfiltration, Albuminuria, and Kidney Function Decline)

Clinical features of diabetic kidney disease include glomerular hyperfiltration, albuminuria, and kidney function decline towards End-Stage Kidney Disease (ESKD). There are presently neither specific markers of kidney involvement in patients with diabetes nor strong predictors of rapid progression to ESKD. Serum-creatinine-based equations used to estimate glomerular filtration rate are notoriously unreliable in patients with diabetes. Early kidney function decline, reduced glomerular filtration rate, and proteinuria contribute to identifying diabetic patients at higher risk for rapid kidney function decline. Unlike proteinuria, the elevation of urinary albumin excretion in the range of microalbuminuria is frequently transient in patients with diabetes and does not always predict progression towards ESKD. Although the rate of progression of kidney function decline is usually accelerated in the presence of proteinuria, histological lesions of diabetes and ESKD may occur with normal urinary albumin excretion. No substantial reduction in the rate of ESKD associated with diabetes has been observed during the last decades despite intensified glycemic control and reno-protective strategies, indicating that existing therapies do not target underlying pathogenic mechanisms of kidney function decline. Very long-term effects of sodium-glucose transporters- 2 inhibitors and glucagon-like peptide-1 analogs remain to be defined. In patients with diabetes, glucagon secretion is typically elevated and induces insulin resistance. Insulin resistance is consistently and strongly associated with clinical manifestations of diabetic kidney disease, suggesting that reduced insulin sensitivity participates in the pathogenesis of the disease and may represent a therapeutic objective. Amelioration of insulin sensitivity in patients with diabetes is associated with cardioprotective and kidney-protective effects.

Association of Glomerular Hyperfiltration and Cardiovascular Risk in Middle-Aged Healthy Individuals

IMPORTANCE

Glomerular hyperfiltration is associated with increased risk of cardiovascular disease in high-risk conditions, but its significance in low-risk individuals is uncertain.

OBJECTIVE

To determine whether glomerular hyperfiltration is associated with increased cardiovascular risk in healthy individuals.

DESIGN, SETTING, AND PARTICIPANTS

This was a prospective population-based cohort study, for which enrollment took place from August 2009 to October 2010, with follow-up available through March 31, 2016. Analysis of the data took place in October 2019. The cohort was composed of 9515 healthy individuals, defined as individuals without hypertension, diabetes, cardiovascular disease, estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m2, or statin and/or aspirin use, identified among 20 004 patients aged 40 to 69 years with health information accessed through the CARTaGENE research platform.

EXPOSURES

Individuals with glomerular hyperfiltration (eGFR >95th percentile after stratification for sex and age) were compared with individuals with normal filtration rate (eGFR 25th-75th percentiles).

MAIN OUTCOMES AND MEASURES

Adverse cardiovascular events were defined as a composite of cardiovascular mortality, myocardial infarction, unstable angina, heart failure, stroke, and transient ischemic attack. Risk of adverse cardiovascular events was assessed using Cox and fractional polynomial regressions and propensity score matching.

RESULTS

From the 20 004 CARTaGENE participants, 9515 healthy participants (4050 [42.6%] male; median [interquartile range] age, 50.4 [45.9-55.6] years) were identified. Among these, 473 had glomerular hyperfiltration (median [interquartile range] eGFR, 112 [107-115] mL/min/1.73 m2) and 4761 had a normal filtration rate (median [interquartile range] eGFR, 92 [87-97] mL/min/1.73 m2). Compared with the normal filtration rate, glomerular hyperfiltration was associated with an increased cardiovascular risk (hazard ratio, 1.88; 95% CI, 1.30-2.74; P = .001). Findings were similar with propensity score matching. The fractional polynomial regression showed that only the highest eGFR percentiles were associated with increased cardiovascular risk. The cardiovascular risk of individuals with glomerular hyperfiltration was similar to that of the 597 participants with an eGFR between 45 and 60 mL/min/1.73 m2 (hazard ratio, 0.90; 95% CI, 0.56-1.42; P = .64).

CONCLUSIONS AND RELEVANCE

These findings suggest that glomerular hyperfiltration is independently associated with increased cardiovascular risk in middle-aged healthy individuals. This risk profile appears to be similar to stage 3a chronic kidney disease.

Synergistic Impact of Diabetes and Hypertension on the Progression and Distribution of Glomerular Histopathological Lesions

BACKGROUND

Diabetes and hypertension share renal histopathological features, such as arterial lesions and glomerular hypertrophy, that have not been investigated in relation to the blood pressure status of diabetic subjects. The severity of glomerular lesions varies across locations of the renal cortex, which may be further affected by diabetes and/or hypertension.

METHODS

Histopathological lesions in different parts of the renal cortex of autopsy kidneys were evaluated and analyzed based on medical histories of diabetes and hypertension.

RESULTS

This study included a total of 82 Japanese autopsies composed of normotensive nondiabetics (n = 31), hypertensive nondiabetics (n = 28), normotensive diabetics (n = 14), and hypertensive diabetics (n = 9). There were no differences in age, sex, renal function, or body size among groups. In both the superficial and juxtamedullary cortices, increased glomerular volume (GV) was significantly associated with either diabetes or hypertension. In addition, diabetes and hypertension showed a significant interaction with GV regardless of the cortical location. Values for global glomerulosclerosis (GGS) and arteriolar hyalinosis (AH) were associated with diabetes but not with hypertension. Only values for GGS consistently showed cortical surface superiority. The zonal distribution of AH, GV, or other diabetic glomerular lesions differed among the lesions depending on the presence or absence of hypertension.

CONCLUSIONS

These results imply that diabetes and hypertension synergistically enhance glomerular hypertrophy across all layers of the human renal cortex. The process is closely associated with the severity of GGS and AH predominantly associated with diabetes.

Macula Densa SGLT1-NOS1-Tubuloglomerular Feedback Pathway, a New Mechanism for Glomerular Hyperfiltration during Hyperglycemia

BACKGROUND

Glomerular hyperfiltration is common in early diabetes and is considered a risk factor for later diabetic nephropathy. We propose that sodium-glucose cotransporter 1 (SGLT1) senses increases in luminal glucose at the macula densa, enhancing generation of neuronal nitric oxide synthase 1 (NOS1)-dependent nitric oxide (NO) in the macula densa and blunting the tubuloglomerular feedback (TGF) response, thereby promoting the rise in GFR.

METHODS

We used microperfusion, micropuncture, and renal clearance of FITC-inulin to examine the effects of tubular glucose on NO generation at the macula densa, TGF, and GFR in wild-type and macula densa-specific NOS1 knockout mice.

RESULTS

Acute intravenous injection of glucose induced hyperglycemia and glucosuria with increased GFR in mice. We found that tubular glucose blunts the TGF response in vivo and in vitro and stimulates NO generation at the macula densa. We also showed that SGLT1 is expressed at the macula densa; in the presence of tubular glucose, SGLT1 inhibits TGF and NO generation, but this action is blocked when the SGLT1 inhibitor KGA-2727 is present. In addition, we demonstrated that glucose increases NOS1 expression and NOS1 phosphorylation at Ser1417 in mouse renal cortex and cultured human kidney tissue. In macula densa-specific NOS1 knockout mice, glucose had no effect on NO generation, TGF, and GFR.

CONCLUSIONS

We identified a novel mechanism of acute hyperglycemia-induced hyperfiltration wherein increases in luminal glucose at the macula densa upregulate the expression and activity of NOS1 via SGLT1, blunting the TGF response and promoting glomerular hyperfiltration.

Impaired fasting glucose is associated with lower glomerular filtration rate decline among men but not women -a large cohort study from Israel

OBJECTIVES

Early stages of diabetes are associated with an increased glomerular filtration rate (GFR). Little is known, however, about the change in GFR among patients with impaired fasting glucose (IFG). We aimed to evaluate the yearly decline rate of GFR among IFG patients.

METHODS

A retrospective analysis of a large cohort of subjects attending a medical screening center in Israel. Patients with diabetes mellitus and patients with decreased estimated GFR (eGFR) were excluded. We divided the cohort into 2 subgroups; Healthy controls and impaired fasting control subjects. For each group, we calculated the average yearly estimated GFR decline (ΔeGFR). The results were adjusted for age, BMI, hypertension and smoking status.

RESULTS

8176 subjects met the inclusion criteria. The median follow up time was 4.8 years (range 2.0 to 13.4). For the whole cohort (men and women), yearly ΔeGFR was -0.68 among healthy controls, and - 0.47 among IFG patients (p = .003). Among men, average yearly ΔeGFR in healthy controls and IFG patients was -0.7 and - 0.4, respectively (p = .0002). All results remained significant after adjusting for age, BMI, hypertension, smoking status and level of HDL and triglycerides. In contrast, among IFG women there was no significant difference in ΔeGFR in comparison with healthy women.

CONCLUSIONS

Impaired fasting glucose is associated with a decreased rate of GFR reduction compared with healthy subjects. This effect is gender dependent - observed in men but not in women. A mechanism of glomerular hyperfiltration might be involved.

Glucose dilates renal afferent arterioles via glucose transporter-1

Glomerular hyperfiltration occurs during the early stage of diabetes. An acute glucose infusion increases glomerular filtration rate. The involvement of tubuloglomerular feedback response and direct effect of glucose on the afferent arterioles (Af-Arts) have been suggested. However, the signaling pathways to trigger Af-Art dilatation have not been fully identified. Therefore, in the present study we tested our hypothesis that an increase in glucose concentration enhances endothelial nitric oxide synthesis activity and dilates the Af-Arts via glucose transporter-1 (GLUT1) using isolated mouse Af-Arts with perfusion. We isolated and microperfused the Af-Arts from nondiabetic C57BL/6 mice. The Af-Arts were preconstricted with norepinephrine (1 µM). When we switched the d-glucose concentration from low (5 mM) to high (30 mM) in the perfusate, the preconstricted Af-Arts significantly dilated by 37.8 ± 7.1%, but L-glucose did not trigger the dilation. GLUT1 mRNA was identified in microdisserted Af-Arts measured by RT-PCR. Changes in nitric oxide (NO) production in Af-Art were also measured using fluorescent probe when ambient glucose concentration was increased. When the d-glucose concentration was switched from 5 to 30 mM, NO generation in Af-Art was significantly increased by 19.2 ± 6.2% (84.7 ± 4.1 to 101.0 ± 9.3 U/min). l-Glucose had no effect on the NO generation. The GLUT1-selective antagonist 4-[({[4-(1,1-Dimethylethyl)phenyl]sulfonyl}amino)methyl]- N-3-pyridinylbenzamide and the nitric oxide synthase inhibitor N^G-nitro-l-arginine methyl ester blocked the high glucose-induced NO generation and vasodilation. In conclusion, we demonstrated that an increase in glucose concentration dilates the Af-Art by stimulation of the endothelium-derived NO production mediated by GLUT1.

Biomarker for early renal microvascular and diabetic kidney diseases

Recognition of early stage of diabetic kidney disease, under common practice using biomarkers, namely microalbuminuria, serum creatinine level above 1 mg/dL and accepted definition of diabetic kidney disease associated with creatinine clearance value below 60 mL/min/1.73 m2, is unlikely. This would lead to delay treatment associated with therapeutic resistance to vasodilator due to a defective vascular homoeostasis. Other alternative biomarkers related to the state of microalbuminuria is not sensitive to screen for early diabetic kidney disease (stages I, II). In this regard, a better diagnostic markers to serve for this purpose are creatinine clearance, fractional excretion of magnesium (FE Mg), cystatin C. Recently, renal microvascular disease and renal ischemia have been demonstrated to correlate indirectly with the development of diabetic kidney disease and its function. Among these are angiogenic and anti-angiogenic factors, namely VEGF, VEGF receptors, angiopoietins and endostatin. With respect to therapeutic prevention, implementation of treatment at early stage of diabetic and nondiabetic kidney disease is able to restore renal perfusion and function.

Metabolic risk factors in nondiabetic adolescents with glomerular hyperfiltration

BACKGROUND

In adults, glomerular hyperfiltration is associated with abnormalities related to metabolic syndrome (MetS). We investigated if glomerular hyperfiltration was associated with metabolic abnormalities in US adolescents without diabetes.

METHODS

We analyzed data from the National Health and Nutrition Examination Survey, a nationally representative sample of US adolescents ages 12-17 years. Estimated glomerular filtration rate (eGFR) was determined using the bedside Schwartz equation; adolescents with hyperfiltration (eGFR >120 mL/min/1.73 m 2 ) were compared to those with normal eGFR (90-120 mL/min/1.73 m 2 ). We calculated mean levels of factors related to MetS, insulin resistance and diabetes risk, adjusting for age, race/ethnicity, sex, socioeconomic status, and BMI z -score.

RESULTS

Overall, 11.8% of US adolescents had hyperfiltration [95% confidence interval (CI) 10.6-13.0]. Hyperfiltration prevalence varied by race (20.2% in Hispanics versus 9.8% non-Hispanic whites and 7.4% non-Hispanic blacks; P< 0.001). Compared to those with normal eGFR, adolescents with hyperfiltration had higher adjusted mean levels of triglyceride (83 versus 77 mg/dL; P = 0.05), fasting insulin (15.1 versus 12.9; P< 0.001) and homeostatic model assessment of insulin resistance (3.52 versus 3.01; P = 0.001). These differences persisted after adjusting for BMI z- score. Adolescents with hyperfiltration had increased odds for hypertriglyceridemia [odds ratio 1.58 (95% CI 1.11-2.23)]. These relationships varied by racial/ethnic group.

CONCLUSIONS

Glomerular hyperfiltration is associated with hypertriglyceridemia and increased insulin resistance independent of BMI z- score in a nationally representative sample of US adolescents. Hispanic adolescents are more likely to have hyperfiltration than other racial/ethnic groups. These findings could have significance in evaluations of renal function and MetS in adolescents to identify related risks and target interventions.

Liver Fat, Hepatic Enzymes, Alkaline Phosphatase and the Risk of Incident Type 2 Diabetes: A Prospective Study of 132,377 Adults

Previous studies have reported inconsistent results of the associations of alanine transaminase (ALT), aspartate transaminase (AST), gamma-glutamyltransferase (GGT) and alkaline phosphatase (ALP) with incident type 2 diabetes (diabetes hereafter). We aimed to resolve the controversy by taking nonalcoholic fatty liver disease (NAFLD) into account. The study population comprised 132,377 non-diabetic individuals (64,875 men and 67,502 women) aged 35–79 who had two or more health examinations during 1996–2014. A total of 6,555 incident diabetes (3,734 men and 2,821 women) were identified, on average, over 5.8 years of follow-up. Cox regression was used to calculate the hazard ratio (HR) for incident diabetes, adjusting for classical confounders. The risk of incident diabetes was significantly associated with NAFLD [HR = 2.08 (men) and 2.65 (women)]. Elevated ALT, AST, GGT and ALP were also significantly associated with the increased risk of diabetes, with HRs of 1.27, 1.23, 1.58 and 1.37, respectively, in men, and 1.56, 1.18, 1.48 and 1.44, respectively in women. Our results suggest that NAFLD, ALT, AST, GGT and ALP are independent predictors for incident diabetes in both men and women.

Pre-sarcopenia is associated with renal hyperfiltration independent of obesity or insulin resistance: Nationwide Surveys (KNHANES 2008-2011)

Renal hyperfiltration is closely linked to cardiometabolic disorders, and it may increase the mortality risk of the general population. Despite the well-established association between cardiometabolic diseases and sarcopenia, the relationship between renal hyperfiltration and sarcopenia has not yet been assessed.This population-based, cross-sectional study used a nationally representative sample of 13,800 adults from the 2008 to 2011 Korea National Health and Nutrition Examination Survey. Renal hyperfiltration was defined as the age- and sex-specific glomerular filtration rate above the 90th percentile in subjects with normal kidney function (>60 mL/min/1.73 m). Appendicular skeletal muscle (ASM), measured by dual-energy x-ray absorptiometry, was used to assess pre-sarcopenia, which the international consensus defines as both ASM per se and ASM that was adjusted for the body mass index and the height.A total of 1402 (10.2%) participants were classified as having renal hyperfiltration. The prevalence of pre-sarcopenia ranged from 11.6% to 33.0%, by definition. Individuals with pre-sarcopenia had higher risks of renal hyperfiltration compared to those without pre-sarcopenia (10.9% vs 17.4%, P < .001; odds ratio [OR] = 1.71, 95% confidential interval [CI] = 1.48-1.99, P < .001). Multiple logistic regression analyses also demonstrated this independent association between pre-sarcopenia and renal hyperfiltration, following adjustment for confounding factors such as insulin resistance and obesity (OR = 1.84, 95% CI = 1.57-2.15, P < .001).In the general population of healthy individuals, pre-sarcopenia might be associated with renal hyperfiltration independent of obesity or insulin resistance.

Different effects of linagliptin and sitagliptin on blood pressure and renal function in Japanese patients with type 2 diabetes mellitus

Aims

To compare and evaluate effects of two DPP-4 inhibitors with different excretion routes on systemic and renal hemodynamics in Japanese patients with type 2 diabetes mellitus.

Methods

Seventy-three outpatients with type 2 diabetes who had been treated by 50 mg/day of sitagliptin (S) for at least 1 year were enrolled and prescribed 5 mg/day of linagliptin (L) instead of S for the next 1 year.

Results

After the initiation of S, the systolic and diastolic blood pressure decreased significantly. However, after switching to L for 1 year they increased significantly and returned to a comparable level as those before S treatment. The increase in serum creatinine or uric acid levels and the decrease in eGFR after S initiation were completely stopped or reversed after switching to L. The change in eGFR after the initiation of S was negatively correlated with the eGFR value at 1 year before switching.

Conclusions

The administration of S had an obvious effect on the systemic or renal hemodynamics in contrast to the fact that the administration of L had no effect on these parameters. It is thus important to use these agents with different excretion routes, properly taking the patients' renal function into account.

Estimated Glomerular Filtration Rate and Albuminuria Are Associated with Biomarkers of Cardiac Injury in a Population-Based Cohort Study: The Maastricht Study

BACKGROUND

Chronic kidney disease (CKD) is associated with an increased cardiovascular disease mortality risk. It is, however, less clear at what point in the course from normal kidney function to CKD the association with cardiovascular disease appears. Studying the associations of estimated glomerular filtration rate (eGFR) and albuminuria with biomarkers of (subclinical) cardiac injury in a population without substantial CKD may clarify this issue.

METHODS

We examined the cross-sectional associations of eGFR and urinary albumin excretion (UAE) with high-sensitivity cardiac troponin (hs-cTn) T, hs-cTnI, and N-terminal probrain natriuretic-peptide (NT-proBNP) in 3103 individuals from a population-based diabetes-enriched cohort study.

RESULTS

After adjustment for potential confounders, eGFR and UAE were associated with these biomarkers of cardiac injury, even at levels that do not fulfill the CKD criteria. For example, eGFR 60-<90 mL · min^-1 ·(1.73 m²)^-1 [vs ≥90 mL · min^-1 · (1.73 m²)^-1] was associated with a [ratio (95% CI)] 1.21 (1.17-1.26), 1.14 (1.07-1.20), and 1.19 (1.12-1.27) times higher hs-cTnT, hs-cTnI, and NT-proBNP, respectively. The association of eGFR with hs-cTnT was statistically significantly stronger than that with hs-cTnI. In addition, UAE 15-<30 mg/24 h (vs <15 mg/24 h) was associated with a 1.04 (0.98-1.10), 1.08 (1.00-1.18), and 1.07 (0.96-1.18) times higher hs-cTnT, hs-cTnI, and NT-proBNP, respectively.

CONCLUSIONS

eGFR and albuminuria were already associated with biomarkers of (subclinical) cardiac injury at levels that do not fulfill the CKD criteria. Although reduced renal elimination may partly underlie the associations of eGFR, these findings support the concept that eGFR and albuminuria are, over their entire range, associated with cardiac injury.

Primary proximal tubule hyperreabsorption and impaired tubular transport counterregulation determine glomerular hyperfiltration in diabetes: a modeling analysis

Glomerular hypertension and hyperfiltration in early diabetes are associated with development and progression of diabetic kidney disease. The tubular hypothesis of diabetic hyperfiltration proposes that it is initiated by a primary increase in sodium (Na) reabsorption in the proximal tubule (PT) and the resulting tubuloglomerular feedback (TGF) response and lowering of Bowman space pressure (P_Bow). Here we utilized a mathematical model of the human kidney to investigate over acute and chronic timescales the mechanisms responsible for the magnitude of the hyperfiltration response. The model implicates that the primary hyperreabsorption of Na in the PT produces a Na imbalance that is only partially restored by the hyperfiltration induced by TGF and changes in P_Bow Thus secondary adaptations are needed to restore Na balance. This may include neurohumoral transport regulation and/or pressure-natriuresis (i.e., the decrease in Na reabsorption in response to increased renal perfusion pressure). We explored the role of each tubular segment in contributing to this compensation and the consequences of impairment in tubular compensation. The simulations indicate that impaired secondary downregulation of transport potentiated the rise in glomerular hypertension and hyperfiltration needed to restore Na balance at a given level of primary PT hyperreabsorption. Therefore, we propose for the first time that both the extent of primary PT hyperreabsorption and the degree of impairment of the distal tubular responsiveness to regulatory signals determine the level of glomerular hypertension and hyperfiltration in the diabetic kidney, thereby extending the tubule-centric concept of diabetic hyperfiltration and potential therapeutic approaches beyond the proximal tubule.

Glomerular Hyperfiltration in Diabetes: Mechanisms, Clinical Significance, and Treatment

An absolute, supraphysiologic elevation in GFR is observed early in the natural history in 10%-67% and 6%-73% of patients with type 1 and type 2 diabetes, respectively. Moreover, at the single-nephron level, diabetes-related renal hemodynamic alterations-as an adaptation to reduction in functional nephron mass and/or in response to prevailing metabolic and (neuro)hormonal stimuli-increase glomerular hydraulic pressure and transcapillary convective flux of ultrafiltrate and macromolecules. This phenomenon, known as glomerular hyperfiltration, classically has been hypothesized to predispose to irreversible nephron damage, thereby contributing to initiation and progression of kidney disease in diabetes. However, dedicated studies with appropriate diagnostic measures and clinically relevant end points are warranted to confirm this assumption. In this review, we summarize the hitherto proposed mechanisms involved in diabetic hyperfiltration, focusing on ultrastructural, vascular, and tubular factors. Furthermore, we review available evidence on the clinical significance of hyperfiltration in diabetes and discuss currently available and emerging interventions that may attenuate this renal hemodynamic abnormality. The revived interest in glomerular hyperfiltration as a prognostic and pathophysiologic factor in diabetes may lead to improved and timely detection of (progressive) kidney disease, and could provide new therapeutic opportunities in alleviating the renal burden in this population.

Sodium and Its Role in Cardiovascular Disease - The Debate Continues

Guidelines have recommended significant reductions in dietary sodium intake to improve cardiovascular health. However, these dietary sodium intake recommendations have been questioned as emerging evidence has shown that there is a higher risk of cardiovascular disease with a low sodium diet, including in individuals with type 2 diabetes. This may be related to the other pleotropic effects of dietary sodium intake. Therefore, despite recent review of dietary sodium intake guidelines by multiple organizations, including the dietary guidelines for Americans, American Diabetes Association, and American Heart Association, concerns about the impact of the degree of sodium restriction on cardiovascular health continue to be raised. This literature review examines the effects of dietary sodium intake on factors contributing to cardiovascular health, including left ventricular hypertrophy, heart rate, albuminuria, rennin-angiotensin-aldosterone system activation, serum lipids, insulin sensitivity, sympathetic nervous system activation, endothelial function, and immune function. In the last part of this review, the association between dietary sodium intake and cardiovascular outcomes, especially in individuals with diabetes, is explored. Given the increased risk of cardiovascular disease in individuals with diabetes and the increasing incidence of diabetes worldwide, this review is important in summarizing the recent evidence regarding the effects of dietary sodium intake on cardiovascular health, especially in this population.

Effect of Sitagliptin on Kidney Function and Respective Cardiovascular Outcomes in Type 2 Diabetes: Outcomes From TECOS

OBJECTIVE

To evaluate chronic kidney disease (CKD) and cardiovascular outcomes in TECOS (Clinical trial reg. no. NCT00790205, clinicaltrials.gov) participants with type 2 diabetes and cardiovascular disease treated with sitagliptin, a dipeptidyl peptidase 4 inhibitor, according to baseline estimated glomerular filtration rate (eGFR).

RESEARCH DESIGN AND METHODS

We used data from 14,671 TECOS participants assigned in a double-blind design to receive sitagliptin or placebo added to existing therapy, while aiming for glycemic equipoise between groups. Cardiovascular and CKD outcomes were evaluated over a median period of 3 years, with participants categorized at baseline into eGFR stages 1, 2, 3a, and 3b (≥90, 60-89, 45-59, or 30-44 mL/min/1.73 m², respectively).

RESULTS

Participants with eGFR stage 3b were older, were more often female, and had a longer duration of diabetes. Four-point major adverse cardiovascular event rates increased with lower baseline eGFR (3.52, 3.55, 5.74, and 7.34 events/100 patient-years for stages 1-3b, respectively). Corresponding adjusted hazard ratios for stages 2, 3a, and 3b versus stage 1 were 0.93 (95% CI 0.82-1.06), 1.28 (1.10-1.49), and 1.39 (1.13-1.72), respectively. Sitagliptin therapy was not associated with cardiovascular outcomes for any eGFR stage (interaction P values were all >0.44). Kidney function declined at the same rate in both treatment groups, with a marginally lower but constant eGFR difference (-1.3 mL/min/1.73 m²) in those participants who were assigned to sitagliptin. Treatment differences in these eGFR values remained after adjustment for region, baseline eGFR, baseline HbA_1c, time of assessment, and within-study HbA_1c levels.

CONCLUSIONS

Impaired kidney function is associated with worse cardiovascular outcomes. Sitagliptin has no clinically significant impact on cardiovascular or CKD outcomes, irrespective of baseline eGFR.

Association of Retinoid X Receptor Alpha Gene Polymorphism with Clinical Course of Chronic Glomerulonephritis

Background

Vitamin D (VD), VD binding protein, VD receptor (VDR), and retinoids are involved in pathogenesis of chronic glomerulonephritis (ChGN). We aimed to compare distribution of VD pathway gene polymorphisms in ChGN patients showing glomerular filtration rate (GFR) category 1–3, GFR category 5D, and healthy controls in order to elucidate the role of VD-related polymorphisms in the course of ChGN.

Material/Methods

GFR category 1–3 ChGN patients (n=195), GFR category 5D ChGN patients (n=178), and controls (n=751) underwent testing for polymorphisms of genes encoding VD binding protein (GC, rs2298849, rs7041, rs1155563), VDR (VDR, rs2228570, rs1544410), and retinoid X receptor alpha (RXRA, rs10776909, rs10881578, rs749759).

Results

Among GFR 1–3 subjects possessing TT genotype of RXRA rs10776909, 75% of patients had nephrotic syndrome, and 37.5% had glomerular hyperfiltration defined as GFR >140 ml/min/1.73 m², and, consequently, serum creatinine was lower in these patients compared to the remaining subjects (0.67±0.26 vs. 0.94±0.34, P=0.014). In GFR category 5D ChGN patients, frequencies of RXRA rs10776909 allele T (25% vs. 19%) and CT+TT (46% vs. 34%) were higher compared to frequencies of respective variants in controls (P_trend=0.004, P_genotype=0.008).

Conclusions

RXRA rs10776909 allele T is specifically involved in the pathogenesis of ChGN. This risk allele may be also associated with worse clinical course of ChGN.

CLINICAL COURSE OF DIABETIC RETINOPATHY IN KOREAN TYPE 2 DIABETES AFTER BARIATRIC SURGERY: A Pilot Study

PURPOSE

To assess the changes in diabetic retinopathy (DR) in Type 2 diabetes (T2DM) patients after bariatric surgery.

METHODS

Consecutive 20 patients with T2DM who underwent bariatric surgery and were followed for at least 12 months were enrolled. The case history was reviewed retrospectively, and laboratory data were assessed at baseline and every 3 months postoperatively. Two retinal specialists evaluated the severity of DR with dilated fundus examination preoperatively and postoperatively. Factors associated with DR progression were assessed.

RESULTS

During the follow-up period, 2 of 12 patients without DR and 2 of 3 patients with mild nonproliferative DR before surgery developed moderate nonproliferative DR. All five patients with moderate nonproliferative DR or worse preoperatively had progression requiring intervention. Preexisting DR (P = 0.005) and albuminuria (P = 0.01) were identified as associated with DR progression. Six patients (30%) entered remission of T2DM, but remission of T2DM could not halt the DR progression.

CONCLUSION

Diabetic retinopathy progression can occur in patients with or without before DR after bariatric surgery, regardless of remission of T2DM. All patients with T2DM should be examined regularly by an ophthalmologist postoperatively, and more carefully patients with previous DR or albuminuria.

Abdominal Adipose Tissue was Associated with Glomerular Hyperfiltration among Non- Diabetic and Normotensive Adults with a Normal Body Mass Index

Glomerular hyperfiltration is recognized as an early marker of progressive kidney dysfunction in the obese population. This study aimed to identify the relationship between glomerular hyperfiltration and body fat distribution measured by computed tomography (CT) in healthy Korean adults. The study population included individuals aged 20-64 years who went a routine health check-up including an abdominal CT scan. We selected 4,378 individuals without diabetes and hypertension. Glomerular filtration rate was estimated using the CKD-EPI equation, and glomerular hyperfiltration was defined as the highest quintile of glomerular filtration rate. Abdominal adipose tissue areas were measured at the level of the umbilicus using a 16-detector CT scanner, and the cross-sectional area was calculated using Rapidia 2.8 CT software. The prevalence of glomerular hyperfiltration increased significantly according to the subcutaneous adipose tissue area in men (OR = 1.74 (1.16-2.61), P for trend 0.016, for the comparisons of lowest vs. highest quartile) and visceral adipose tissue area in women (OR = 2.34 (1.46-3.75), P for trend < 0.001) in multivariate analysis. After stratification by body mass index (normal < 23 kg/m2, overweight ≥ 23 kg/m2), male subjects with greater subcutaneous adipose tissue, even those in the normal BMI group, had a higher prevalence of glomerular hyperfiltration (OR = 2.11 (1.17-3.80), P for trend = 0.009). Among women, the significance of visceral adipose tissue area on glomerular hyperfiltration resulted from the normal BMI group (OR = 2.14 (1.31-3.49), P for trend = 0.002). After menopause, the odds ratio of the association of glomerular hyperfiltration with subcutaneous abdominal adipose tissue increased (OR = 2.96 (1.21-7.25), P for trend = 0.013). Subcutaneous adipose tissue areas and visceral adipose tissue areas are positively associated with glomerular hyperfiltration in healthy Korean adult men and women, respectively. In post-menopausal women, visceral adipose tissue area shows significant positive association with glomerular hyperfiltration as in men.

Early stage of vascular disease and diabetic kidney disease: an under-recognized entity

Early stage of vascular disease and diabetic kidney disease (DKD stages 1 and 2) has been under-recognized, under common practice worldwide. The lack of sensitive diagnostic marker leads to late diagnosis and a progression of underlying vascular disease associated with chronic renal ischemia, which eventually intensifies the magnitude of DKD damage. Treatment at this late stage fails to correct the renal ischemia, or restore renal function, due to the altered vascular homeostasis associated with an impaired nitric oxide production. In contrast to the above information, early recognition of vascular disease and DKD with sensitive diagnostic markers would be able to implement an effective prevention of progression of vascular disease and DKD. Treatment at early stage under environment favorable for adequate vascular homeostasis is able to correct the renal ischemia and improve the renal function.

Hyperfiltration in Indigenous Australians with and without diabetes

BACKGROUND

Hyperfiltration (HF) has been linked to the development of diabetic kidney disease (DKD), but the causative or predictive role of HF in the pathogenesis of DKD still remains unclear. To date, there have been no studies of HF in Indigenous Australians, a population with high rates of both diabetes and end-stage kidney disease. We aimed to compare the characteristics and frequency of HF in Indigenous Australians with and without type 2 diabetes.

METHODS

Indigenous Australian participants, recruited across five pre-defined strata of health, diabetes status and kidney function, had a reference glomerular filtration rate (GFR) measured using plasma disappearance of iohexol [measured GFR(mGFR)] over 4 h. HF was defined in various ways: (i) mGFR > 144 mL/min/1.73 m(2), which is mGFR > 1.96 × SD above the mean of the mGFR in non-diabetic participants with normal albuminuria and normal renal function (mGFR > 90 mL/min/1.73 m(2)); (ii) age-corrected mGFR (>144 mL/min/1.73 m(2)) to account for the effect of ageing on GFR in subjects over 40 years of age with cut-off 1 mL/min/1.73 m(2) lower for every year; (iii) mGFR > 144 mL/min, without correction for body surface area or age, as well as (iv) mGFR > 125 mL/min/1.73 m(2), without adjustment for age.

RESULTS

A total of 383 Indigenous participants, 125 with and 258 without diabetes, with mGFR > 90 mL/min/1.73 m(2) were studied. The proportion of participants with HF was 7% using mGFR > 144 mL/min/1.73 m(2), 11% using the age-adjusted definition, 19% using mGFR > 144 mL/min and 27% using mGFR > 125 mL/min/1.73 m(2). Diabetes was more common in participants with HF (40-74%) compared with normofiltering participants (28-31%), regardless of the definition of HF.

CONCLUSIONS

HF exists in Indigenous Australians with and without diabetes. A greater proportion of participants had diabetes in HF group compared with normofiltration group. Long-term follow-up of this cohort is necessary to determine if HF plays a role in the development of DKD and non-DKD.

Urodynamic Findings and Renal Function in Children with Neurogenic Bladder after Myelomeningocele

INTRODUCTION

Myelomeningocele (MMC) is a congenital central nervous system malformation caused by a failure of the neurulation process in early pregnancy. Patients with MMC present many abnormalities and the nervous, skeletal and urinary systems are the most affected. The aim of this study was to clinically evaluate patients with MMC, estimate renal and lower urinary tract (LUT) function and to ascertain whether urodynamic findings can predict the deterioration of urinary tract function.

MATERIALS AND METHODS

Medical records of 112 patients were gathered from a database and evaluated retrospectively. The data included age, sex, BMI Z-score WHO, physical activity, urodynamic parameters and diagnosis and renal function.

RESULTS

A total of 112 patients with MMC were enrolled in the study. There were no differences in age, sex, BMI Z-score WHO, physical activity, renal function and urodynamic findings (apart from cystometric capacity) between boys and girls. Detrusor overactivity was the most frequent urodynamic diagnosis in all groups of physical activity, level of lesion and in catheterized and non-catheterized children. The correlations between urodynamic findings and renal function tests were found.

CONCLUSIONS

Patients with neurogenic bladder after MMC most often present detrusor overactivity. LUT function is disturbed in all MMC patients independent of lesion level and physical activity.

Does nephrotoxicity exist in pediatric epileptic patients on valproate or carbamazepine therapy?

The aim of this study was to investigate the effects of valproate and carbamazepine, on renal glomerular and tubular functions. The patient group comprised 54 children with new-onset epilepsy treated with valproate (n = 30) and carbamazepine (n = 24). Twenty-six healthy children were in the control group. The serum creatinine and cystatin C levels and urinary excretion of N-acetyl-β-d-glucosaminidase (NAG) levels were measured and the glomerular filtration rate (GFR) was estimated. Serum creatinine and cystatin C concentrations were not different between patients and controls. The glomerular filtration rate of the patient groups were higher than those of the control group. Thus, both drugs probably lead to glomerular hyperfiltration and toxicity for glomerular functions. However, urinary N-acetyl-β-d-glucosaminidase/creatinine levels were significantly higher in patients receiving only valproate (6.1 ± 5). The difference between carbamazepine and control groups was not significant for urinary N-acetyl-β-d-glucosaminidase/creatinine levels. Our data suggest that valproate has adverse effects on renal tubular functions.

The impact of hyperfiltration on the diabetic kidney

More than two decades ago, hyperfiltration (HF) in diabetes was postulated to be a maladaptive response observed early in the course of diabetic kidney disease (DKD), which may eventually predispose to irreversible damage to nephrons and development of progressive renal disease. Despite this, the potential mechanisms leading to renal HF in diabetes are not fully understood, although several hypotheses have been proposed, including alterations in glomerular haemodynamic function and tubulo-glomerular feedback. Furthermore, the role of HF as a causative factor in renal disease progression is still unclear and warrants further prospective longer-term studies. Although HF has been entrenched as the first stage in the classic albuminuric pathway to end-stage renal disease in DKD, and HF has been shown to predict the progression of albuminuria in many, but not all studies, the concept that HF predisposes to the development of chronic kidney disease (CKD) stage 3, that is, glomerular filtration rate (GFR) decline to<60mL/min/1.73m(2), remains to be proved. Further long-term studies of GFR gradients therefore are required to establish whether HF ultimately leads to decreased kidney function, after adjustment for glycaemic control and other confounders. Whether reversal of HF with therapeutic agents is protective against reducing the risk of development of albuminuria and renal impairment is also worth investigating in prospective randomized trials.

Moderate intensity physical activity prevents increased blood glucose concentrations, fat pad deposition and cardiac action potential prolongation following diet-induced obesity in a juvenile-adolescent rat model

Background

Both obesity and a lack of physical activity have been associated with an elevated risk of cardiovascular disease (CVD). The incidence of obesity is increasing, especially in juvenile-adolescents. While there is limited research examining the chronic effects of obesity in adolescent humans and animal models of this condition, little is also known concerning how moderate physical activity might prevent or attenuate secondary cardiovascular complications induced by obesity during adolescence. We investigated the effects of diet-induced obesity (consisting of a high-fat, high-carbohydrate diet (HFHC)) on biometric indices, vascular and airway function, cardiovascular function, systemic oxidative stress and markers of inflammation in a juvenile-adolescent rodent model. Four groups were used: control (CON), physical activity (PA) treated, HFHC and HFHC + PA (n = 16 per group). HFHC feeding started at 4 weeks of age for a period of 12 weeks. Physical activity treatment was initiated (PA and HFHC + PA groups) when the animals were 8 weeks of age, for 8 weeks.

Results

Physical activity in juvenile-adolescent healthy rats showed no change in comparison to the CON group in all experimental parameters except for increases in lipid peroxidation, decreases in inflammatory cytokines, improvements in vascular reactivity and decreased atrial responses to positive chronotropic agents. The HFHC animals were mildly hyperglycemic, hypertensive, displayed renal hypertrophy and showed increased retroperitoneal fat pad deposition compared to the CON group. HFHC + PA rats were also hypertensive, however showed improvements in cardiac electrophysiology, body weight, fat pad deposition and inflammatory signaling, in comparison to the HFHC fed rats and CON animals.

Conclusion

In conclusion, in a juvenile-adolescent animal model of diet-induced obesity engagement in physical activity is beneficial in reducing the inflammatory effects of obesity.

Long-term effects of maternal diabetes on blood pressure and renal function in rat male offspring

Aims/Hypothesis

Gestational diabetes mellitus (GDM) is increasing rapidly worldwide. Previous animal models were established to study consequences of offspring after exposure to severe intrauterine hyperglycemia. In this study we are aiming to characterize the blood pressure levels and renal function of male offspring obtained from diabetic mothers with moderate hyperglycemia.

Methods

We established a rat model with moderate hyperglycemia after pregnancy by a single intraperitoneal injection of streptozotocin (STZ). The male offspring were studied and fed with either normal diet or high salt diet after weaning. Arterial pressure and renal function were measured.

Results

Arterial pressure of male offspring increased from 12 weeks by exposure to intrauterine moderate hyperglycemia. At 20 weeks, high salt diet accelerated the blood pressure on diabetic offspring compared to diabetic offspring fed with normal diet. We found offspring exposed to intrauterine moderate hyperglycemia had a trend to have a higher creatinine clearance rate and significant increase of urinary N-acetyl-β-D-glucosaminidase (NAG) excretion indicating an early stage of nephropathy progression.

Conclusions/Interpretation

We observed the high blood pressure level and early renal dysfunction of male offspring obtained from diabetic mothers with moderate hyperglycemia. Furthermore, we investigated high salt diet after weaning on offspring exposed to intrauterine hyperglycemia could exacerbate the blood pressure and renal function. Renin angiotensin system (RAS) plays an important role in hypertension pathogenesis and altered gene expression of RAS components in offspring with in utero hyperglycemia exposure may account for the programmed hypertension. Therefore, our study provides evidence “fetal programming” of maternal diabetes is critical for metabolic disease development.

Not all inflammatory markers are linked to kidney function: results from a population-based study

BACKGROUND

Several studies have reported increased levels of inflammatory biomarkers in chronic kidney disease (CKD), but data from the general population are sparse. In this study, we assessed levels of the inflammatory markers C-reactive protein (hsCRP), tumor necrosis factor α (TNF-α), interleukin (IL)-1β and IL-6 across all ranges of renal function.

METHODS

We conducted a cross-sectional study in a random sample of 6,184 Caucasian subjects aged 35-75 years in Lausanne, Switzerland. Serum levels of hsCRP, TNF-α, IL-6, and IL-1β were measured in 6,067 participants (98.1%); serum creatinine-based estimated glomerular filtration rate (eGFR(creat), CKD-EPI formula) was used to assess renal function, and albumin/creatinine ratio on spot morning urine to assess microalbuminuria (MAU).

RESULTS

Higher serum levels of IL-6, TNF-α and hsCRP and lower levels of IL-1β were associated with a lower renal function, CKD (eGFR(creat) <60 ml/min/1.73 m(2); n = 283), and MAU (n = 583). In multivariate linear regression analysis adjusted for age, sex, hypertension, smoking, diabetes, body mass index, lipids, antihypertensive and hypolipemic therapy, only log-transformed TNF-α remained independently associated with lower renal function (β -0.54 ±0.19). In multivariate logistic regression analysis, higher TNF-α levels were associated with CKD (OR 1.17; 95% CI 1.01-1.35), whereas higher levels of IL-6 (OR 1.09; 95% CI 1.02-1.16) and hsCRP (OR 1.21; 95% CI 1.10-1.32) were associated with MAU.

CONCLUSION

We did not confirm a significant association between renal function and IL-6, IL-1β and hsCRP in the general population. However, our results demonstrate a significant association between TNF-α and renal function, suggesting a potential link between inflammation and the development of CKD. These data also confirm the association between MAU and inflammation.

Tc-99m diethylenetriamine pentaacetic acid (DTPA) renal function reserve estimation: is it a reliable predictive tool for assessment of preclinical renal involvement in scleroderma patients?

Prognosis of systemic sclerosis (SSc) depends on internal organ involvement. We assessed the value of renal function reserve (RFR) for the detection of preclinical nephropathy in scleroderma. Thirty SSc patients with normal serum creatinine and 30 healthy controls were included. Medsger disease severity score, glomerular filtration rate (GFR), and microalbuminuria were measured. Tc-99m DTPA was utilized for GFR measurement at baseline and after oral protein overload (stimulated GFR). RFR was calculated as the percentile increase of stimulated GFR. SSc patients had lower means of baseline GFR (P=0.001), stimulated GFR (P=0.004), RFR (P=0.046), and higher microalbuminuria (P=0.009) than controls. According to baseline GFR, SSc patients showed three categories-normal baseline GFR (n=12), hyperfiltration GFR (n=3), and reduced baseline GFR (n=15). In the former category, RFR was normal in 6/12 patients and abnormal in the remainders (50%). Hyperfiltration patients and those with reduced baseline GFR showed abnormal RFR. A statistically significant negative association was found between microalbuminuria versus stimulated GFR and RFR (r= -0.5, P=0.007 and r= -0.45, P=0.013, respectively). The majority of SSc patients with abnormal RFR had disease duration of ≥48 months (60% vs. 20%, P=0.008). All SSc patients with pulmonary hypertension had abnormal RFR, while reduced baseline GFR was noted in only 60%. A significant negative correlation was found between reduced baseline GFR and cumulative dose of corticosteroids in SSc patients (r= -0.4, P=0.022). RFR estimation could be a useful predictive marker for preclinical renal involvement in SSc patients so that early prophylactic measures and therapy modifications could be considered.

Glomerular hyperfiltration: definitions, mechanisms and clinical implications

Glomerular hyperfiltration is a phenomenon that can occur in various clinical conditions including kidney disease. No single definition of glomerular hyperfiltration has been agreed upon, and the pathophysiological mechanisms, which are likely to vary with the underlying disease, are not well explored. Glomerular hyperfiltration can be caused by afferent arteriolar vasodilation as seen in patients with diabetes or after a high-protein meal, and/or by efferent arteriolar vasoconstriction owing to activation of the renin-angiotensin-aldosterone system, thus leading to glomerular hypertension. Glomerular hypertrophy and increased glomerular pressure might be both a cause and a consequence of renal injury; understanding the renal adaptations to injury is therefore important to prevent further damage. In this Review, we discuss the current concepts of glomerular hyperfiltration and the renal hemodynamic changes associated with this condition. A physiological state of glomerular hyperfiltration occurs during pregnancy and after consumption of high-protein meals. The various diseases that have been associated with glomerular hyperfiltration, either per nephron or per total kidney, include diabetes mellitus, polycystic kidney disease, secondary focal segmental glomerulosclerosis caused by a reduction in renal mass, sickle cell anemia, high altitude renal syndrome and obesity. A better understanding of the mechanisms involved in glomerular hyperfiltration could enable the development of new strategies to prevent progression of kidney disease.

Renal complications of diabetes

INTRODUCTION

Diabetic nephropathy is a leading cause of chronic kidney disease (CKD) in the UK. These patients are at significantly increased risk of cardiovascular disease and of progression to end-stage renal disease. We review the epidemiology, pathogenesis and natural history of diabetic nephropathy and evaluate the therapeutic options available.

SOURCES OF DATA

We searched Medline and PubMed for source articles relevant to diabetic nephropathy and CKD.

AREAS OF AGREEMENT

Early multifactorial intervention including strict blood pressure control, the use of angiotensin-converting enzyme (ACE) inhibitors or angiotensin two-receptor blockers (A2RB's) and good metabolic control attenuates cardiovascular risk and slows the rate of progression of renal disease.

AREAS OF CONTROVERSY

Current areas of uncertainty include the relative benefits of ACE inhibitors and A2RBs in combination, whether direct renin inhibitors are harmful in patients with diabetes and also the positioning of hypoglycaemic agents as renal function declines.

GROWING POINTS

What are the appropriate metabolic and blood pressure targets for patients with diabetes? AREAS TIMELY FOR DEVELOPMENT: Therapeutic strategies as kidney function declines.

Proteinuria in type 2 diabetic patients with renal impairment: the changing face of diabetic nephropathy

Type 2 diabetic nephropathy (type 2 DN) patients traditionally develop significant proteinuria prior to the development of renal impairment. However, this clinical paradigm, based on observations prior to the widespread usage of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB), has recently been questioned. 2,303 patients enrolled in the Sulodexide Overt Nephropathy Study (OVERT) were analyzed. Prior therapy with ACEi and/or ARB at the time of screening was recorded in 951 patients. 22% of patients had significant renal impairment with a PCR at screening of <500 mg/g. Therapy with ACEi and/or ARB at the time of screening was recorded in 94%, where prior medication data was available. In patients with type 2 DN and advanced renal impairment, levels of proteinuria below that which traditionally defines overt diabetic nephropathy, are found in more than one fifth of patients. We suggest that the high prevalence of ACEi and ARB usage in patients with type 2 DN may be effecting the traditional clinical paradigm of type 2 DN.

The clinical significance of hyperfiltration in diabetes

Glomerular filtration rate is commonly elevated in early diabetes and patients with this symptom are arbitrarily considered to have hyperfiltration. The prevalence of hyperfiltration in type 1 diabetes varies from less than 25% to more than 75%. The corresponding figures in type 2 diabetes are significantly lower, ranging between 0% and more than 40%. Several factors, methodological and biological, may contribute to the wide variation in estimates of hyperfiltration prevalence. Methodological differences in measurement and evaluation of GFR apply in particular to the handling of plasma disappearance curves of filtration markers. Biological factors that may influence GFR in the hyperfiltration range include glycaemic control, diabetes duration, BMI, sex, pubertal status in type 1 diabetes and age in type 2 diabetes. Hyperglycaemia may influence GFR and albuminuria, and may therefore confound the evaluation of hyperfiltration as an independent risk factor for diabetic nephropathy. Adequate assessment of the relationship between glycaemic control, GFR and AER therefore requires serial measurements of all three variables followed by multivariate analysis. A recent meta-analysis of ten type 1 diabetes studies concluded that the presence of hyperfiltration at baseline more than doubled the risk of developing micro- or macroalbuminuria at follow-up. However, not all studies allowed for confounding factors or regression dilution bias. Future studies will therefore need to address the independent role of hyperfiltration, not only in the evolution of albuminuria, but also in the subsequent decline of GFR.

Comparison of the prevalence of chronic kidney disease in Japanese patients with Type 1 and Type 2 diabetes

AIMS

The relationship between type of diabetes and risk of chronic kidney disease has not been studied in detail. We conducted this study to determine the prevalence of chronic kidney disease in Japanese adults with diabetes, with a particular emphasis on the comparison of Type 1 and Type 2 diabetes.

METHODS

We studied 3,575 Japanese patients with diabetes, 504 with Type 1 (mean +/- SD age 38 +/- 13 years; 350 women and 154 men) and 3071 with Type 2 diabetes (60 +/- 13 years; 1187 women and 1884 men). Prevalence rates of albuminuria [urinary albumin/creatinine ratio (> or = 30 mg/g], decreased estimated glomerular filtration rate (eGFR < 60 ml/min/1.73 m(2)) and chronic kidney disease (defined as albuminuria and/or decreased eGFR) were compared between the two diabetic groups.

RESULTS

The prevalence of albuminuria was higher in Type 2 than Type 1 diabetic patients by both Fisher's exact test (36.1 vs. 15.9%, P < 0.001) and multivariate logistic regression analysis [adjusted odds ratio (OR) = 1.482, 95% confidence interval (CI) = 1.050-2.091, P = 0.025]. The prevalence of decreased eGFR was also higher in Type 2 diabetic patients (25.2 vs. 7.9%, P < 0.001); however, the statistical significance disappeared after adjusting for covariates, including age (OR = 0.656, 95% CI = 0.395-1.088, P = 0.102). The prevalence of chronic kidney disease was also higher in Type 2 diabetic patients (46.0 vs. 19.1%, P < 0.001); however, the statistical significance disappeared in the multivariate analysis. CONCLUSIONS Type 2 diabetic patients are more than twice as likely as Type 1 diabetic patients to have chronic kidney disease due to an age-independent higher prevalence of albuminuria and age-dependent decreased eGFR.

Glomerular hyperfiltration and increased proximal sodium reabsorption in subjects with type 2 diabetes or impaired fasting glucose in a population of the African region

BACKGROUND. Glomerular hyperfiltration (GHF) is a well-recognized early renal alteration in diabetic patients. As the prevalence of GHF is largely unknown in populations in the African region with respect to normal fasting glucose (NFG), impaired fasting glucose (IFG) and type 2 diabetes [diabetes mellitus (DM)], we conducted a cross-sectional study in the Seychelles islands among families including at least one member with hypertension. METHODS. The glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and proximal tubular sodium reabsorption were measured using inulin, p-aminohippurate (PAH) and endogenous lithium clearance, respectively. Twenty-four-hour urine was collected on the preceding day. RESULTS. Of the 363 participants (mean age 44.7 years), 6.6% had IFG, 9.9% had DM and 63.3% had hypertension. The prevalence of GHF, defined as a GFR >140 ml/min, was 17.2%, 29.2% and 52.8% in NFG, IFG and DM, respectively (P trend <0.001). Compared to NFG, the adjusted odds ratio for GHF was 1.99 [95% confidence interval (CI) 0.73-5.44] for IFG and 5.88 (2.39-14.45) for DM. Lithium clearance and fractional excretion of lithium were lower in DM and IFG than NFG (P < 0.001). CONCLUSION. In this population of African descent, subjects with impaired fasting glucose or type 2 diabetes had a high prevalence of GHF and enhanced proximal sodium reabsorption. These findings provide further insight on the elevated incidence of nephropathy reported among African diabetic individuals.

Increased urinary orosomucoid excretion is not related to impaired renal function in patients with type 2 diabetes

OBJECTIVES

Increased urinary orosomucoid excretion rate (UOER) independently predicted cardiovascular mortality in patients with type 2 diabetes at 5-years of follow-up. To further explore UOER in relation to local renal physiological phenomena, we studied renal glomerular and tubular functions in patients with type 2 diabetes and normal or increased UOER.

METHODS

We performed a cross-sectional study of 40 patients with type 2 diabetes (normal UOER, n=16; increased UOER, n=24) who displayed no signs of cardiovascular disease and 21 healthy control persons. The renal clearance values of [(51)Cr]ethylenediaminetetraacetic acid ([(51)Cr]EDTA), lithium, orosomucoid, albumin, and sodium were measured.

RESULTS

Patients with type 2 diabetes had normal glomerular filtration rate (GFR) measured by [(51)Cr]EDTA clearance. The clearance value of orosomucoid was highly increased in patients with increased UOER. The clearance values of albumin were similar in patients with increased UOER and in healthy controls. Investigations of renal tubular function revealed normal and similar levels of lithium clearance and proximal and distal reabsorption of sodium and water. Serum values of orosomucoid were higher in patients with increased UOER than in healthy controls (P<.001), but were still within reference limits, suggesting chronic low-grade inflammation. UOER was associated with increasing values of orosomucoid clearance (P<.0001) independently of serum orosomucoid.

CONCLUSIONS

Patients with type 2 diabetes and increased UOER had normal GFR and showed no signs of renal glomerular or tubular dysfunction. We therefore hypothesize that increased levels of UOER may be caused by local renal production of orosomucoid due to chronic low-grade inflammation.

Is hyperfiltration associated with the future risk of developing diabetic nephropathy? A meta-analysis

AIMS/HYPOTHESIS

Glomerular hyperfiltration is a well-established phenomenon occurring early in some patients with type 1 diabetes. However, there is no consistent answer regarding whether hyperfiltration predicts later development of nephropathy. We performed a systematic review and meta-analysis of observational studies that compared the risk of developing diabetic nephropathy in patients with and without glomerular hyperfiltration and also explored the impact of baseline GFR.

METHODS

A systematic review and meta-analysis was carried out. Cohort studies in type 1 diabetic participants were included if they contained data on the development of incipient or overt nephropathy with baseline measurement of GFR and presence or absence of hyperfiltration.

RESULTS

We included ten cohort studies following 780 patients. After a study median follow-up of 11.2 years, 130 patients had developed nephropathy. Using a random effects model, the pooled odds of progression to a minimum of microalbuminuria in patients with hyperfiltration was 2.71 (95% CI 1.20-6.11) times that of patients with normofiltration. There was moderate heterogeneity (heterogeneity test p = 0.05, measure of degree of inconsistency = 48%) and some evidence of funnel plot asymmetry, possibly due to publication bias. The pooled weighted mean difference in baseline GFR was 13.8 ml min(-1) 1.73 m(-2) (95% CI 5.0-22.7) greater in the group progressing to nephropathy than in those not progressing (heterogeneity test p < 0.01).

CONCLUSIONS/INTERPRETATION

In published studies, individuals with glomerular hyperfiltration were at increased risk of progression to diabetic nephropathy using study level data. Further larger studies are required to explore this relationship and the role of potential confounding variables.

Diabetic nephropathy in children and adolescents

Type 1 diabetes mellitus (T1DM) commonly occurs in childhood or adolescence, although the rising prevalence of type 2 diabetes mellitus (T2DM) in these age groups is now being seen worldwide. Diabetic nephropathy (DN) develops in 15-20% of subjects with T1DM and in similar or higher percentage of T2DM patients, causing increased morbidity and premature mortality. Although overt DN or kidney failure caused by either type of diabetes are very uncommon during childhood or adolescence, diabetic kidney disease in susceptible patients almost certainly begins soon after disease onset and may accelerate during adolescence, leading to microalbuminuria or incipient DN. Therefore, all diabetics warrant ongoing assessment of kidney function and screening for the earliest manifestations of renal injury. Pediatric health care professionals ought to understand about risk factors, strategy for prevention, method for screening, and treatment of early DN. This review considers each form of diabetes separately, including natural history, risk factors for development, screening for early manifestations, and strategy recommended for prevention and treatment of DN in children and adolescents.

Glomerular hyperfiltration in non-proteinuric and non-hypertensive Japanese type 2 diabetic patients

Glomerular hyperfiltration (GHF) may be an important factor in the initiation of glomerular damage and in predisposing diabetic patients to the later development of diabetic nephropathy (DN). Previous reports show wide range of prevalence of GHF in type 2 diabetic patients. This cross-sectional study was designed to determine the prevalence of GHF at an early stage of DN in Japanese type 2 diabetic patients and to investigate the relationships between clinical variables and GHF. We measured the glomerular filtration rate (GFR) using the plasma clearance of iohexol in 56 control subjects and 93 type 2 diabetic patients without hypertension or overt proteinuria. We used Altman's method to calculate the age-adjusted 95% reference ranges for GFR from the data of control subjects and classified GHF in type 2 diabetics from the reference ranges. Hyperfiltrators (defined as GFR > mean GFR + 1.96 S.D. of control subjects) was found in 17% patients (16/93). Other 77 patients (83%) were normofiltrators (defined as GFR< or = mean GFR + 1.96 S.D. of control subjects). GFR values, both in hyperfiltrators and normofiltrators, were 140.5 +/- 14.6 and 98.8 +/- 14.0 ml/min/1.73 m2, respectively. Age, sex, BMI, blood pressure, albumin excretion rate, and frequency of microalbuminuria did not differ between the hyperfiltrators and normofiltrators. Fasting plasma glucose and hemoglobin A1c were significantly higher in the hyperfiltrators than the normofiltrators (P<0.001 and 0.004, respectively). GHF exists among Japanese type 2 diabetic patients with no evidence of overt proteinuria or hypertension. Glycemic control might be a significant determinant of GHF in these patients.

Renal hyperfiltration in type 2 diabetes: effect of age-related decline in glomerular filtration rate

AIMS/HYPOTHESIS

We sought to characterise the effect of the age-related decline of GFR on hyperfiltration in type 2 diabetes and to identify clinical characteristics associated with hyperfiltration.

MATERIALS AND METHODS

GFR was measured in 662 type 2 diabetic patients by plasma disappearance of 99 m-technetium-diethylene-triamine-penta-acetic acid. The prevalence of hyperfiltration was calculated using both an age-unadjusted GFR threshold of >130 ml min(-1) 1.73 m(-2) and an age-adjusted threshold incorporating a decline of 1 ml min(-1) year(-1) after the age of 40. The hyperfiltering patients were compared with type 2 diabetic subjects who had a GFR between 90 and 130 ml min(-1) 1.73 m(-2) and were matched for age, sex and disease duration to allow for identification of modifiable factors associated with hyperfiltration.

RESULTS

The prevalence of hyperfiltration was 7.4% when age-unadjusted and 16.6% when age-adjusted definitions were used. The age-unadjusted vs -adjusted prevalence rates for hyperfiltration were 50 vs 50%, 12.9 vs 23.4% and 0.3 vs 9.0% for patients aged <40 years, 40 to 65 years and >65 years, respectively. Both the age-unadjusted and -adjusted hyperfiltration groups had lower mean diastolic blood pressure and lower serum creatinine levels than the control groups. Although the age-unadjusted hyperfiltration group had larger kidneys compared to the control group, this difference was no longer significant when the age-adjusted definition was used. There were no differences in HbA(1)c, mean arterial pressure, antihypertensive use, insulin therapy, dyslipidaemia, frequency of macro- or microvascular complications, BMI, urinary sodium, urea and albumin excretion between the groups.

CONCLUSIONS/INTERPRETATION

Hyperfiltration was still more common among younger patients with type 2 diabetes even after adjusting for the expected age-related decline in GFR. Hyperfiltration was associated with a lower mean diastolic blood pressure independent of age.

Microalbuminuria and abnormal ambulatory blood pressure in adolescents with type 2 diabetes mellitus

OBJECTIVE

To determine whether risk factors for cardiovascular disease and diabetic nephropathy, as evidenced by abnormalities of ambulatory blood pressure (ABP), dyslipidemia, and microalbuminuria (MA), are present in adolescents with type 2 diabetes mellitus (T2DM).

STUDY DESIGN

We enrolled 26 minority adolescents recently diagnosed with T2DM and 13 obese control subjects without diabetes mellitus. ABP monitoring was performed, and a 24-hour urine, a fasting lipid profile, blood urea nitrogen, creatinine, homocysteine, and hemoglobin A 1 c levels were obtained. The patients with T2DM underwent echocardiograms.

RESULTS

Forty percent of the patients with T2DM had MA (> or = 30 mg of microalbumin/day), compared with none of the control subjects ( P < .05). There were no significant differences between patients with T2DM who had MA and patients with T2DM who didn't have MA in demographics, characteristics, casual BP, echocardiographic findings, and hemoglobin A 1 c levels. Average daytime systolic BP was greater in patients with T2DM with MA than patients without MA (129 versus 121 mm Hg, P = .03) and compared with the control subjects (113 mm Hg, P = .01). Patients with MA had an average daytime systolic BP load that was higher than patients without MA (37.1 versus 5.1%, P = .008) and compared with the control subjects (2.6%, P < .001).

CONCLUSION

As in adults, adolescents with T2DM exhibit abnormalities of ABP, dyslipidemia, and microalbuminuria.

From secondary to primary prevention of progressive renal disease: The case for screening for albuminuria

Many subjects nowadays present with end-stage renal failure and its attendant cardiovascular complications without known prior renal damage. In this report we review the evidence available to strongly suggest that the present practice of secondary prevention in those with known prior renal disease should be extended to primary prevention for those subjects in the general population who are at risk for progressive renal failure, but who had never suffered from a primary renal disease. We show that such subjects can be detected by screening for albuminuria. Elevated urinary albumin loss is an indicator not only of poor renal, but also of poor cardiovascular prognosis. In addition to diabetic subjects who are at risk for albuminuria, we also show that hypertensive, obese, and smoking subjects are more susceptible. We suggest that therapies that have been shown to lower albumin excretion, such as ACE inhibitors, angiotensin II receptor antagonists, and statins be started early in such patients to prevent them from developing clinical renal disease and its attendant cardiovascular complications.

Diabetic nephropathy and retinopathy

Diabetic nephropathy and retinopathy are arguably the two most dreaded complications of diabetes. Together they contribute to serious morbidity and mortality. As they progress to end-stage renal disease and blindness, they impose enormous medical, economic,and social costs on both the patient and the health care system. Because nephropathy and retinopathy are frequently linked in patients,this article reviews their common and individual aspects of pathophysiology, clinical features, and management.