Type 2 diabetic nephropathy: never too early to treat?

Deciphering the Efficacy and Mechanisms of Chinese Herbal Medicine for Diabetic Kidney Disease by Integrating Web-Based Biochemical Databases and Real-World Clinical Data: Retrospective Cohort Study

Background

Diabetic kidney disease (DKD) is one of the most crucial causes of chronic kidney disease (CKD). However, the efficacy and biomedical mechanisms of Chinese herbal medicine (CHM) for DKD in clinical settings remain unclear.

Objective

This study aimed to analyze the outcomes of DKD patients with CHM-only management and the possible molecular pathways of CHM by integrating web-based biomedical databases and real-world clinical data.

Methods

A total of 152,357 patients with incident DKD from 2004 to 2012 were identified from the National Health Insurance Research Database (NHIRD) in Taiwan. The risk of mortality was estimated with the Kaplan-Meier method and Cox regression considering demographic covariates. The inverse probability of treatment weighting was used for confounding bias between CHM users and nonusers. Furthermore, to decipher the CHM used for DKD, we analyzed all CHM prescriptions using the Chinese Herbal Medicine Network (CMN), which combined association rule mining and social network analysis for all CHM prescriptions. Further, web-based biomedical databases, including STITCH, STRING, BindingDB, TCMSP, TCM@Taiwan, and DisGeNET, were integrated with the CMN and commonly used Western medicine (WM) to explore the differences in possible target proteins and molecular pathways between CHM and WM. An application programming interface was used to assess these online databases to obtain the latest biomedical information.

Results

About 13.7% (20,947/131,410) of patients were classified as CHM users among eligible DKD patients. The median follow-up duration of all patients was 2.49 years. The cumulative mortality rate in the CHM cohort was significantly lower than that in the WM cohort (28% vs 48%, P<.001). The risk of mortality was 0.41 in the CHM cohort with covariate adjustment (99% CI 0.38-0.43; P<.001). A total of 173,525 CHM prescriptions were used to construct the CMN with 11 CHM clusters. CHM covered more DKD-related proteins and pathways than WM; nevertheless, WM aimed at managing DKD more specifically. From the overrepresentation tests carried out by the online website Reactome, the molecular pathways covered by the CHM clusters in the CMN and WM seemed distinctive but complementary. Complementary effects were also found among DKD patients with concurrent WM and CHM use. The risk of mortality for CHM users under renin-angiotensin-aldosterone system (RAAS) inhibition therapy was lower than that for CHM nonusers among DKD patients with hypertension (adjusted hazard ratio [aHR] 0.47, 99% CI 0.45-0.51; P<.001), chronic heart failure (aHR 0.43, 99% CI 0.37-0.51; P<.001), and ischemic heart disease (aHR 0.46, 99% CI 0.41-0.51; P<.001).

Conclusions

CHM users among DKD patients seemed to have a lower risk of mortality, which may benefit from potentially synergistic renoprotection effects. The framework of integrating real-world clinical databases and web-based biomedical databases could help in exploring the roles of treatments for diseases.

High Glucose Impairs Insulin Signaling in the Glomerulus: An In Vitro and Ex Vivo Approach

Objective

Chronic hyperglycaemia, as seen in type II diabetes, results in both morphological and functional impairments of podocytes in the kidney. We investigated the effects of high glucose (HG) on the insulin signaling pathway, focusing on cell survival and apoptotic markers, in immortalized human glomerular cells (HGEC; podocytes) and isolated glomeruli from healthy rats.

Methods and Findings

HGEC and isolated glomeruli were cultured for various time intervals under HG concentrations in the presence or absence of insulin. Our findings indicated that exposure of HGEC to HG led to downregulation of all insulin signaling markers tested (IR, p-IR, IRS-1, p-Akt, p-Fox01,03), as well as to increased sensitivity to apoptosis (as seen by increased PARP cleavage, Casp3 activation and DNA fragmentation). Short insulin pulse caused upregulation of insulin signaling markers (IR, p-IR, p-Akt, p-Fox01,03) in a greater extent in normoglycaemic cells compared to hyperglycaemic cells and for the case of p-Akt, in a PI3K-dependent manner. IRS-1 phosphorylation of HG-treated podocytes was negatively regulated, favoring serine versus tyrosine residues. Prolonged insulin treatment caused a significant decrease of IR levels, while alterations in glucose concentrations for various time intervals demonstrated changes of IR, p-IR and p-Akt levels, suggesting that the IR signaling pathway is regulated by glucose levels. Finally, HG exerted similar effects in isolated glomeruli.

Conclusions

These results suggest that HG compromises the insulin signaling pathway in the glomerulus, promoting a proapoptotic environment, with a possible critical step for this malfunction lying at the level of IRS-1 phosphorylation; thus we herein demonstrate glomerular insulin signaling as another target for investigation for the prevention and/ or treatment of diabetic nephropathy.

The effect of RAAS blockade on the progression of diabetic nephropathy

The renin-angiotensin-aldosterone system (RAAS) has a key role in the regulation of blood pressure, sodium and water balance, and cardiovascular and renal homeostasis. In diabetic nephropathy, excessive activation of the RAAS results in progressive renal damage. RAAS blockade using angiotensin-converting-enzyme inhibitors or angiotensin-receptor blockers is the cornerstone of treatment of diabetic renal disease. Alternative RAAS-blockade strategies include renin inhibition and aldosterone blockade. Data from small initial studies of these agents are promising. However, single-agent interventions do not fully block the RAAS and patients treated with these therapies remain at high residual renal risk. Approaches to optimize drug responses include dietary changes and increasing dosages. The theoretically attractive option of combining different RAAS interventions has also been tested in clinical trials but long-term outcomes were disappointing. However, dual RAAS blockade might represent a good therapeutic option for specific patients. A better knowledge of the pathophysiology of the RAAS is crucial to fully understand the mechanisms of action of RAAS blockers and to exploit their renoprotective effects. Moreover, lifestyle interventions or diagnostic tools might be used to optimize RAAS blockade and identify those patients who are most likely to benefit from the therapy.

Angiotensin II receptor blocker pretreatment of rats undergoing sudden renal ablation

BACKGROUND

Subtotal nephrectomy (N) in rats results in progressive hypertension, proteinuria and renal lesions. Renin-angiotensin system blockade initiated at N prevents these changes; treatments failing to reduce hypertension and proteinuria do not.

METHODS

Ten Munich-Wistar rats underwent 1&frac12; surgical N; eight littermates were pretreated with losartan (L) only for 6 weeks prior to 1&frac12; N (N + L). Pretreated (n = 8; C + L) and untreated controls (C; n = 8) had sham operations.

RESULTS

Over 6 months, N and N + L rats developed ∼80% increase in glomerular filtration rate per nephron over C and C + L, P < 0.001). Hypertension (intra-arterial mean blood pressure 116 ± 6.8 mmHg in N rats versus 102 ± 3.2 in C, 104 ± 8.4 in C + L, and 104 ± 8.4 in N + L rats, P < 0.001 for all) and proteinuria (120 ± 20 mg/day in N versus 39 ± 10 in C, 34 ± 8 in C + L and 35 ± 8 in N + L, P < 0.001 for all) developed only in N. Focal segmental glomerulosclerosis (FSGS) (%) at 6 months was 20 ± 8 in N and 17.5 ± 8 in N + L (ns) and <1 in C and C + L (P < 0.001 versus N and N + L). Interstitial fractional volume (Vv), 4.0 ± 1.7% in C and 4.4 ± 1.6% in C + L (ns), was similarly increased to 7.5 ± 2.5% in N and 9.0 ± 3.9% in N+L (P < 0.04 versus C and C + L). Atrophic tubule Vv was increased by >300% in N and N + L over C and C + L (P < 0.02 for all). Glomerular volume doubled in N and N + L (P < 0.001). Podocyte foot process effacement was greater in N and NL than in C or C + L (P ≤ 0.02 for all). Thus, L given for 6 weeks prior to 1&frac12; N prevented hypertension and proteinuria over the subsequent 6 months without reducing glomerular hypertrophy, hyperfiltration or interstitial, tubular or FSGS lesions or foot process effacement.

CONCLUSIONS

These studies dissociated systemic hypertension and proteinuria from the renal lesions in this model. Durable effects of losartan on blood pressure and proteinuria likely represent epigenetic processes.

Effect of experimental hyperglycaemia on renal haemodynamics in prediabetic patients with and without AT1 receptor blockade

BACKGROUND AND OBJECTIVES

To prevent diabetic nephropathy, knowledge about early renal impairment caused by a disturbed glucose homoeostasis is essential. The purpose of our study was to investigate haemodynamic changes of the kidney in subjects with impaired glucose tolerance (prediabetics, IGT) during experimental hyperglycaemia and the effect of angiotensin receptor blockade.

DESIGN

In our prospective case control study, we measured renal haemodynamics in 13 non-albuminuric males with normal kidney function and IGT (diagnosed by an oral glucose tolerance test, OGTT) and in 13 matched controls with a normoglycemic response in the OGTT. Glomerular filtration rate (GFR) was assessed by determination of sinistrin clearance; renal plasma flow (RPF) by para-aminohippuric acid clearance. All measurements were performed at rest and during hyperglycaemic stress testing (clamp technique; target blood glucose approximately 170 mg dL(-1)). We examined renal effects of valsartan (4 weeks 160 mg day(-1)) at rest and during experimental hyperglycaemia. Metabolic (glycosylated haemoglobin, adiponectin) and inflammatory (high sensitive C-reactive protein) parameters were compared with and without valsartan in both groups.

RESULTS

During experimental hyperglycaemia, GFR and RPF decreased significantly more in prediabetics compared with controls. Under valsartan, the hyperglycaemia induced decrease of GFR and RPF was blunted in part by valsartan. Hs-CRP and HbA1c were significantly higher in prediabetics when compared with controls and improved both under valsartan. Adiponectin was lower in prediabetics and increased significantly under valsartan.

CONCLUSIONS

Hyperglycaemia induces impairments of renal haemodynamics as well as inflammatory and metabolic parameters in subjects with impaired glucose tolerance, which improve under valsartan.

Telmisartan lowers albuminuria in type 2 diabetic patients treated with angiotensin enzyme inhibitors

PURPOSE

Angiotensin-converting-enzyme inhibitors (ACEIs) provide renal protection in patients with type 2 diabetes and microalbuminuria.

MATERIAL AND METHODS

In the presented study we followed 34 stable, type 2 diabetic patients with persistent albuminuria treated with maximal doses of ACEIs as a part of their anti-hypertensive treatment. Telmisartan--an angiotensin receptor blocker (ARB)--in a dose of 40 mg was added to the treatment and the patients were observed for 12 weeks. We measured creatinine clearance, 24-hour urinary albumin excretion, before and after 12 weeks of combined therapy.

RESULTS

The addition of telmisartan resulted in a significant reduction of albuminuria from median 157 to 67 mg/24h. No change in creatinine clearance was observed (93 vs 97 ml/min).

CONCLUSION

The addition of telmisartan to a maximum dose of ACEI is safe and results in further albuminuria decrease in patients with type 2 diabetes and incipient nephropathy.

The pathogenesis of diabetic nephropathy

Between 20% and 40% of patients with diabetes ultimately develop diabetic nephropathy, which in the US is the most common cause of end-stage renal disease requiring dialysis. Diabetic nephropathy has several distinct phases of development and multiple mechanisms contribute to the development of the disease and its outcomes. This Review provides a summary of the latest published data dealing with these mechanisms; it focuses not only on candidate genes associated with susceptibility to diabetic nephropathy but also on alterations in various cytokines and their interaction with products of advanced glycation and oxidant stress. Additionally, the interactions between fibrotic and hemodynamic cytokines, such as transforming growth factor beta1 and angiotensin II, respectively, are discussed in the context of new information concerning nephropathy development. We touch on the expanding clinical data regarding markers of nephropathy, such as microalbuminuria, and put them into context; microalbuminuria reflects cardiovascular and not renal risk. If albuminuria levels continue to increase over time then nephropathy is present. Lastly, we look at advances being made to enable identification of genetically predisposed individuals.

Improvement of renal function in type 2 diabetic nephropathy

BACKGROUND

Therapeutic failure in preventing renal disease progression in type 2 diabetic nephropathy (DN) is due to a failure in the early detection of DN by microalbuminuria and the inappropriate correction of renal hemodynamic maladjustment secondary to glomerular endothelial dysfunction.

METHODS

Thirty patients associated with normoalbuminuric type 2 DN were subject to the following studies: tubular function by means of fractional excretion of magnesium (FE Mg), vascular function by means of determining the circulating endothelial cell, VEGF, VEGF/TGF B ratio, and intrarenal hemodynamic studies.

RESULTS

FE Mg, circulating endothelial cells, and TGF B were abnormally elevated, and VEGF/TGF B ratio was decreased in these normoalbuminuric patients. The intrarenal hemodynamic study revealed a hemodynamic maladjustment characterized by a preferential constriction at the efferent arteriole and a reduction in peritubular capillary flow. Following treatment with vasodilators, a decrease in efferent arteriolar resistance and increase in peritubular capillary flow as well as glomerular clearance were observed.

CONCLUSION

FE Mg appears to be a more sensitive marker than microalbuminuria for the early detection of DN. Increased endothelial cell injury is reflected by enhanced circulating endothelial cell loss in conjunction with the increased TGF B and the decreased ratio between VEGF and TGF B. This is further supported by the dysfunctioning glomerular endothelium, which is characterized by hemodynamic maladjustment and a reduction in the peritubular capillary flow. A correction of such hemodynamic maladjustment by multidrug vasodilators effectively improves renal perfusion and restores renal function in type 2 DN.

Effects of Adrenomedullin on Cardiac Oxidative Stress and Collagen Accumulation in Aldosterone-Dependent Malignant Hypertensive Rats

We examined the effects of adrenomedullin on cardiac oxidative stress and collagen accumulation in aldosterone-dependent malignant hypertensive rats. Spontaneously hypertensive rats (SHRs) were treated with one of the following combinations for 4 weeks: tap water and vehicle [0.5% ethanol, subcutaneously (s.c.), n = 5], 1% NaCl in drinking water and vehicle (n = 8), 1% NaCl and aldosterone (0.75 microg/h s.c., n = 8), and 1% NaCl, aldosterone, and adrenomedullin (1.3 microg/kg/h s.c., n = 8). Systolic blood pressure (SBP) and left ventricular (LV) weight were higher in aldosterone-treated SHRs than vehicle- or vehicle/1% NaCl-treated SHRs. Thiobarbituric acid reactive substances (TBARS) levels and NADPH oxidase activity in LV tissues of aldosterone-treated SHRs were also higher than those of vehicle- or vehicle/1% NaCl-treated SHRs, and these changes were associated with increases in LV mRNA levels of p22phox, gp91phox, fibronectin, collagen types I and III, as well as collagen content. Treatment with adrenomedullin did not alter SBP or LV weight but attenuated aldosterone-induced increases in TBARS levels, NADPH oxidase activity, and mRNA levels of p22phox, gp91phox, fibronectin, collagen types I and III, as well as collagen content in LV tissues. These data suggest that NADPH oxidase-mediated reactive oxygen species production is involved in the pathogenesis of cardiac collagen accumulation in aldosterone-dependent malignant hypertensive rats and that the cardioprotective effects of adrenomedullin are mediated through the suppression of this pathway.

Epidemiology of diabetic nephropathy in Spain

BACKGROUND

The incidence of diabetes mellitus (DM) has increased persistently in recent years and is becoming an epidemic. Some have estimated that 4.4% of the world's population will be diabetic by the year 2030. The increase incidence of DM has been accompanied by an increased incidence in diabetic nephropathy (DN), the main cause of end-stage renal disease.

METHODS AND RESULTS

In 1996, a pharmaco-economic study estimated that 162,000 people in Spain had type 1 DM and 1,354,900 had type 2 DM. More recent studies have estimated that 6% to 10% of the Spanish population might be diabetic. This percentage is higher in some autonomous communities, such as Canarias, in which 12% of the population is thought to have DM. Based on these studies, we estimate that more than 33,000 residents of Canarias have DN associated with type 1 DM, and more than 405,000 have DN associated with type 2 DM. The percentage of diabetic patients starting renal replacement therapy each year is currently around 21% in Spain but much higher (35%) in Canarias, which equates to 78 patients per million population (pmp) per year. In Catalonia, the number of DM patients entering renal replacement therapy has increased from 8.6 pmp per year in 1984 to 32.4 pmp per year in 2003. We estimate that the systematic application of converting enzyme inhibitors or angiotensin receptor blockers could save more than 2.690 million over 15 years in Spain.

CONCLUSION

This epidemic could be prevented, or its impact reduced, through multifactorial and multidisciplinary early intervention, under the observance of guides, Spanish consensus documents, and clinical practice recommendations, together with an integrated educational program aimed at people with diabetes and the improvement of the standard of medical care.