Role of hyperlipidemia in progressive renal disease: focus on diabetic nephropathy

Effect of hydroxyethyl starch on drug stability and release of semaglutide in PLGA microspheres

The degradation of peptide drugs limits the application of peptide drug microspheres. Structural changes of peptides at the water-oil interface and the destruction of their spatial structure in the complex microenvironment during polymer degradation can affect drug release and in vivo biological activity. This study demonstrates that adding hydroxyethyl starch (HES) to the internal aqueous phase (W1) significantly enhances the stability of semaglutide and optimizes its release behavior in PLGA microspheres. The results showed that this improvement was due to a spontaneous exothermic reaction (ΔH = -132.20 kJ mol-1) facilitated by hydrogen bonds. Incorporating HES into the internal aqueous phase using the water-in-oil-in-water (W1/O/W2) emulsion method yielded PLGA microspheres with a high encapsulation rate of 94.38 %. Moreover, microspheres with HES demonstrated well-controlled drug release over 44 days, unlike the slower and incomplete release in microspheres without HES. The optimized h-MG2 formulation achieved a more complete drug release (83.23 %) and prevented 30.65 % of drug loss compared to the HES-free microspheres within the same period. Additionally, the optimized semaglutide microspheres provided nearly three weeks of glycemic control with adequate safety. In conclusion, adding HES to the internal aqueous phase improved the in-situ drug stability and release behavior of semaglutide-loaded PLGA microspheres, effectively increasing the peptide drug payload in PLGA microspheres.

Hypertriglyceridemia is associated with decline of estimated glomerular filtration rate and risk of end-stage kidney disease in a real-word Italian cohort: Evidence from the TG-RENAL Study

BACKGROUND

This analysis investigated the role of hypertriglyceridemia on renal function decline and development of end-stage kidney disease (ESKD) in a real-world clinical setting.

METHODS

A retrospective analysis using administrative databases of 3 Italian Local Health Units was performed searching patients with at least one plasma triglyceride (TG) measurement between 2013 and June 2020, followed-up until June 2021. Outcome measures included reduction in estimated glomerular filtration rate (eGFR) ≥30% from baseline and ESKD onset. Subjects with normal (normal-TG), high (HTG) and very high TG levels (vHTG) (respectively <150 mg/dL, 150-500 mg/dL and >500 mg/dL) were comparatively evaluated.

RESULTS

Overall 45,000 subjects (39,935 normal-TGs, 5,029 HTG and 36 vHTG) with baseline eGFR of 96.0 ± 66.4 mL/min were considered. The incidence of eGFR reduction was 27.1 and 31.1 and 35.1 per 1000 person-years, in normal-TG, HTG and vHTG subjects, respectively (P<0.01). The incidence of ESKD was 0.7 and 0.9 per 1000 person-years, in normal-TG and HTG/vHTG subjects, respectively (P<0.01). Univariate and multivariate analyses revealed that HTG subjects had a risk of eGFR reduction or ESKD occurrence (composite endpoint) increased by 48% compared to normal-TG subjects (adjusted OR:1.485, 95%CI 1.300-1.696; P<0.001). Moreover, each 50 mg/dL increase in TG levels resulted in significantly greater risk of eGFR reduction (OR:1.062, 95%CI 1.039-1.086 P<0.001) and ESKD (OR:1.174, 95%CI 1.070-1.289, P = 0.001).

CONCLUSIONS

This real-word analysis in a large cohort of individuals with low-to-moderate cardiovascular risk suggests that moderate-to-severe elevation of plasma TG levels is associated with a significantly increased risk of long-term kidney function deterioration.

Atherogenic dyslipidemia and diabetic nephropathy

Chronic kidney disease is associated with altered lipid metabolism and lipid accumulation. Although it is though that hyperlipemia is a consequence of kidney dysfunction, several lines of evidence support that hyperlipidemia may contribute to the onset and progression of kidney disease, also in diabetes. This review describes the results of recent observational studies supporting the concept that glucose is only partly responsible for kidney damage onset, while a cluster of factors, including hypertriglyceridemia and low HDL-cholesterol, could play a relevant role in inducing onset and progression of DKD. We also report the results of randomized clinical trials investigating in type 2 diabetic patients the role of drug improvement of hypertriglyceridemia on renal outcomes. Finally, we discuss putative mechanisms linking hyperlipidemia (i.e. hypertriglyceridemia or low HDL cholesterol) with kidney disease.

Protective Effect of Hydroxysafflor Yellow A on Nephropathy by Attenuating Oxidative Stress and Inhibiting Apoptosis in Induced Type 2 Diabetes in Rat

Diabetic nephropathy (DN) is a serious complication of diabetes mellitus, and its prevalence has been increasing all over the world, which is also the leading cause of end-stage renal failure. Hydroxysafflor yellow A (HSYA) is the main active chemical component of Carthamus tinctorius L., and it is commonly used in patients with cardiovascular and cerebrovascular diseases in China. The aim of this study was to investigate the renal protective effects and molecular mechanisms of HSYA on high-fat diet (HFD) and streptozotocin- (STZ-) induced DN in rats. The DN rats were treated with HSYA for eight weeks. We assessed creatinine (CR), urea nitrogen (UN), glomerular volume, podocyte number, renal inflammation, oxidative stress, and cells apoptosis markers after HSYA treatment. The number of apoptotic cells was measured by the TUNEL assay, and apoptosis-related proteins BAX, caspase-3, and BCL-2 in the renal tissue were analyzed by western blot. The treatment with HSYA significantly decreased fasting blood glucose, CR, UN, and blood lipid profile, including triglyceride and total and low-density lipoprotein cholesterol, even though it did not change the rats' body weights. The western blot results indicated that HSYA reversed the upregulation of BAX and caspase-3 and significantly increased BCL-2 in renal tissue. Moreover, the levels of TNF-α and the inflammatory products, including free fatty acids (FFA) and lactic dehydrogenase (LDH) in the HSYA group, were significantly decreased. For the oxidative stress marker, the superoxide dismutase (SOD) markedly increased in the HSYA treatment group, while the malondialdehyde (MDA) in the serum and kidney tissue evidently decreased. In conclusion, HSYA treatment preserved kidney function in diabetic nephropathy in the HFD- and STZ-induced rats. The potential mechanism of renal protective effect of HSYA might be through inhibiting oxidative stress, reducing inflammatory reaction, and attenuating renal cell apoptosis. Our studies present a promising use for Hydroxysafflor yellow A in the treatment of type 2 diabetes mellitus.

Diabetic nephropathy: an insight into molecular mechanisms and emerging therapies

Introduction: Diabetic kidney disease (DKD) is a major cause of morbidity and mortality in diabetes and is the most common cause of proteinuric and non-proteinuric forms of end-stage renal disease (ESRD). Control of risk factors such as blood glucose and blood pressure is not always achievable or effective. Significant research efforts have attempted to understand the pathophysiology of DKD and develop new therapies. Areas covered: We review DKD pathophysiology in the context of existing and emerging therapies that affect hemodynamic and metabolic pathways. Renin-angiotensin system (RAS) inhibition has become standard care. Recent evidence for renoprotective activity of SGLT2 inhibitors and GLP-1 agonists is an exciting step forward while endothelin receptor blockade shows promise. Multiple metabolic pathways of DKD have been evaluated with varying success; including mitochondrial function, reactive oxygen species, NADPH oxidase (NOX), transcription factors (NF-B and Nrf2), advanced glycation, protein kinase C (PKC), aldose reductase, JAK-STAT, autophagy, apoptosis-signaling kinase 1 (ASK1), fibrosis and epigenetics. Expert opinion: There have been major advances in the understanding and treatment of DKD. SGLT2i and GLP-1 agonists have demonstrated renoprotection, with novel therapies under evaluation. Addressing the interaction between hemodynamic and metabolic pathways may help achieve prevention, attenuation or even reversal of DKD.

Cardiovascular Disease and Diabetic Kidney Disease

Diabetic kidney disease commonly is associated with an increased risk of cardiovascular disease. There are traditional common risk factors for both conditions including hypertension and poor glycemic control. However, it is likely that there are other pathophysiological mechanisms that explain the clinical phenomenon of increased cardiovascular disease in diabetic patients with chronic kidney and vice versa. Current management of both conditions includes aggressive glucose and blood pressure control. The protective role of treating dyslipidemia has been shown for cardiovascular disease, but the results for renal disease are not as clear. The advent of new classes of glucose-lowering agents such as sodium glucose co-transporter2 inhibitors and glucagon-like peptide-1 agonists has resulted in impressive effects on both cardiovascular and renal disease in diabetes. However, how these drugs act independently of glucose lowering to confer both kidney and cardiovascular protection has not been fully elucidated. Nevertheless, these new treatments provide optimism for reducing both microvascular and macrovascular complications in diabetes, which represent the major causes of morbidity and premature mortality in this condition.

9-O-benzoyl-substituted berberine exerts a triglyceride-lowering effect through AMPK signaling pathway in human hepatoma HepG2 cells

Berberine is an isoquinoline alkaloid extracted from Rhizoma coptidis and shows anti-hyperlipidemia effect in vivo and in vitro. We previously found that berberine could decrease the intracellular triglyceride content in human hepatoma HepG2 cells through activation of AMP-activated protein kinase (AMPK), a major regulator of lipid metabolism. Herein, to find a more effective agent, several berberine analogues (A1-A13) were isolated and synthesized, and the triglyceride-lowering effects and potential mechanisms were investigated in HepG2 cells. Among these berberine analogues, 9-O-benzoyl-substituted berberine (A13) showed strong affinity to AMPK and significantly up-regulated the levels of phospho-Thr172 AMPK α subunit. Meanwhile, A13 reduced the cellular triglyceride levels. Furthermore, A13 could mediate the mRNA levels of downstream proteins involved in triglyceride synthesis and fatty acid oxidation of AMPK signaling pathway. These results suggested that A13 exerts a triglyceride-lowering effect via stimulation of AMPK pathway, which may be beneficial to regulate hyperlipidemia.

Carnosic acid improves diabetic nephropathy by activating Nrf2/ARE and inhibition of NF-κB pathway

BACKGROUND

Diabetic nephropathy (DN), one of the most serious complications of diabetes, is the leading cause of morbidity and mortality of end-stage renal disease. Our previous research found that carnosic acid (CA) or rosemary extract can effectively improve glucose and lipid metabolism disorder by inhibiting SREBPs.

PURPOSE

In this study, we aimed to explore the therapeutic effects of CA on the DN.

METHODS

The mice glomerular mesangial cells (mGMCs) were used to evaluate the anti-oxidative and anti-inflammation effects of CA under high glucose (HG) condition. Furthermore, db/db mice and streptozotocin (STZ)-induced diabetic mice were used to investigate the effects of CA against DN in vivo.

RESULTS

The results showed that CA activated Nrf2, inhibited NF-κB pathway and regulated related downstream genes in mGMC under HG condition. A 14-week treatment of mice with CA reduced water uptake and urine volume, attenuated diabetes-induced albuminuria, increased urine creatinine, and subsequently improved the glomerular sclerosis and mesangial expansion in db/db mice. Similarly, a 20-week oral administration of CA improved kidney damage in STZ-induced diabetic mice. In addition, CA inhibited the expression of profibrotic factors, such as TGF-β1, fibronectin and E-cadherin. Compared to irbesartan, CA exerted better glucose lowering effect, and in kidney, CA was more potent to reduce fibronectin and E-cadherin expression. In all the animal experiment, CA did not lead to abnormal damages to other tissues.

CONCLUSION

These findings suggest that CA is a safe compound which exerts the protective effects on diabetes-induced kidney complications.

The apolipoprotein E (APOE) gene and the risk of diabetic nephropathy (DN): a meta-analysis in East Asian populations

Background: Several studies have examined the association between DN and the APOE gene, but the results have been inconsistent. Objective: Determine whether APOE is a risk factor for DN by a meta-analysis. Methods: A meta-analysis was performed using all findings of 16 similar case-control studies in East Asian to evaluate the effect of APOE as a risk factor for DN. Several electronic databases were searched for relevant articles up to 2009. After data collection, a meta-analysis was used to assess heterogeneity, combine results and evaluate variations by using software STATA SE 9.0. Publication bias was examined by the Egger’s linear regression test and fail-safe number. Results: The meta-analysis showed that the ε2 allele almost doubled the risk of DN in East Asians (pooled ORs [95% CI]: 1.85 [1.49-2.29]). In contrast, studies relating the ε4 allele to DN risk were very heterogeneous and the pooled ORs were 1.05 [95% CI: 0.72-1.52]. In the subgroup meta-analysis, ε4 was substantially related to an increased risk for DN in studies conducted in China (pooled ORs [95% CI]: 1.51 [1.11-2.06]), which was different from previous results. However, the higher risk of DN associated with ε4 was not found in Japanese or Korean populations (pooled ORs [95% CI]: 0.46 [0.27-0.80] and 0.58 [0.09-3.55], respectively). Conclusion: The ε2 allele conferred a higher risk of DN in East Asians, and no significant result was obtained with the ε4 allele.

Comparison between Atorvastatin and Rosuvastatin in Renal Function Decline among Patients with Diabetes

BACKGROUND

Although the beneficial effects of statin treatment in dyslipidemia and atherosclerosis have been well studied, there is limited information regarding the renal effects of statins in diabetic nephropathy. We aimed to investigate whether, and which, statins affected renal function in Asian patients with diabetes.

METHODS

We enrolled 484 patients with diabetes who received statin treatment for more than 12 months. We included patients treated with moderate-intensity dose statin treatment (atorvastatin 10 to 20 mg/day or rosuvastatin 5 to 10 mg/day). The primary outcome was a change in estimated glomerular filtration rate (eGFR) during the 12-month statin treatment, and rapid renal decline was defined as a >3% reduction in eGFR in a 1-year period.

RESULTS

In both statin treatment groups, patients showed improved serum lipid levels and significantly reduced eGFRs (from 80.3 to 78.8 mL/min/1.73 m² for atorvastatin [P=0.012], from 79.1 to 76.1 mL/min/1.73 m² for rosuvastatin [P=0.001]). A more rapid eGFR decline was observed in the rosuvastatin group than in the atorvastatin group (48.7% vs. 38.6%, P=0.029). Multiple logistic regression analyses demonstrated more rapid renal function loss in the rosuvastatin group than in the atorvastatin group after adjustment for other confounding factors (odds ratio, 1.60; 95% confidence interval, 1.06 to 2.42).

CONCLUSION

These results suggest that a moderate-intensity dose of atorvastatin has fewer detrimental effects on renal function than that of rosuvastatin.

Plasma Triglycerides and HDL-C Levels Predict the Development of Diabetic Kidney Disease in Subjects With Type 2 Diabetes: The AMD Annals Initiative

OBJECTIVE

Despite the achievement of blood glucose, blood pressure, and LDL cholesterol (LDL-C) targets, the risk for diabetic kidney disease (DKD) remains high among patients with type 2 diabetes. This observational retrospective study investigated whether diabetic dyslipidemia-that is, high triglyceride (TG) and/or low HDL cholesterol (HDL-C) levels-contributes to this high residual risk for DKD.

RESEARCH DESIGN AND METHODS

Among a total of 47,177 patients attending Italian diabetes centers, 15,362 patients with a baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m², normoalbuminuria, and LDL-C ≤130 mg/dL completing a 4-year follow-up were analyzed. The primary outcome was the incidence of DKD, defined as either low eGFR (<60 mL/min/1.73 m²) or an eGFR reduction >30% and/or albuminuria.

RESULTS

Overall, 12.8% developed low eGFR, 7.6% an eGFR reduction >30%, 23.2% albuminuria, and 4% albuminuria and either eGFR <60 mL/min/1.73 m² or an eGFR reduction >30%. TG ≥150 mg/dL increased the risk of low eGFR by 26%, of an eGFR reduction >30% by 29%, of albuminuria by 19%, and of developing one abnormality by 35%. HDL-C <40 mg/dL in men and <50 mg/dL in women were associated with a 27% higher risk of low eGFR and a 28% risk of an eGFR reduction >30%, with a 24% higher risk of developing albuminuria and a 44% risk of developing one abnormality. These associations remained significant when TG and HDL-C concentrations were examined as continuous variables and were only attenuated by multivariate adjustment for numerous confounders.

CONCLUSIONS

In a large population of outpatients with diabetes, low HDL-C and high TG levels were independent risk factors for the development of DKD over 4 years.

Exendin-4 Ameliorates Lipotoxicity-induced Glomerular Endothelial Cell Injury by Improving ABC Transporter A1-mediated Cholesterol Efflux in Diabetic apoE Knockout Mice

ATP-binding cassette transporter A1 (ABCA1), which promotes cholesterol efflux from cells and inhibits inflammatory responses, is highly expressed in the kidney. Research has shown that exendin-4, a glucagon-like peptide-1 receptor (GLP-1R) agonist, promotes ABCA1 expression in multiple tissues and organs; however, the mechanisms underlying exendin-4 induction of ABCA1 expression in glomerular endothelial cells are not fully understood. In this study we investigated the effect of exendin-4 on ABCA1 in glomerular endothelial cells of diabetic kidney disease (DKD) and the possible mechanism. We observed a marked increase in glomerular lipid deposits in tissues of patients with DKD and diabetic apolipoprotein E knock-out (apoE^-/-) mice by Oil Red O staining and biochemical analysis of cholesterol. We found significantly decreased ABCA1 expression in glomerular endothelial cells of diabetic apoE^-/- mice and increased renal lipid, cholesterol, and inflammatory cytokine levels. Exendin-4 decreased renal cholesterol accumulation and inflammation and increased cholesterol efflux by up-regulating ABCA1. In human glomerular endothelial cells, GLP-1R-mediated signaling pathways (e.g. Ca²⁺/calmodulin-dependent protein kinase, cAMP/PKA, PI3K/AKT, and ERK1/2) were involved in cholesterol efflux and inflammatory responses by regulating ABCA1 expression. We propose that exendin-4 increases ABCA1 expression in glomerular endothelial cells, which plays an important role in alleviating renal lipid accumulation, inflammation, and proteinuria in mice with type 2 diabetes.

Protective effect of thymol on high fat diet induced diabetic nephropathy in C57BL/6J mice

Obesity is one of several factors implicated in chronic kidney disease (CKD). Thymol, a monoterpene phenolic compound found in the oils of thyme with multiple biological properties especially antidiabetic activity. The present study was undertaken to evaluate the thymol against diabetic nephropathy by high fat diet (HFD)-induced diabetic C57BL/6J mice. After 10 weeks of continuous dietary intervention, HFD (fat- 35.2%) to mice presented characteristic features of progressive nephropathy by significant increased in kidney weight, blood, and urinary parameters, glomerulosclerosis, oxidative stress, hyperlipidemia and subsequent renal injuries. After intragastric administration of thymol (40 mg/kg BW) daily for the subsequent 5 weeks significantly decreased the blood, urinary parameters and kidney weight. Thymol inhibited the activation of transforming growth factor-β1 (TGF-β1) and vascular endothelial growth factor (VEGF). Also, significantly increased the antioxidants and suppresses the lipid peroxidation markers in erythrocytes and kidney tissue compared to the diabetic mice. Thymol downregulated the expression level of sterol regulatory element binding protein-1c (SREBP-1c) and reduced the lipid accumulation in renal. Histopathological study of kidney tissues showed that extracellular mesangial matrix expansion, glomerulosclerosis in diabetic mice were suppressed by thymol. Further, our results indicate that administration of thymol afforded remarkable protection against HFD-induced diabetic nephropathy.

Coadministration of alloxan and nicotinamide in rats produces biochemical changes in blood and pathological alterations comparable to the changes in type II diabetes mellitus

BACKGROUND

In the present study, thirty six male Sprague Dawley rats were randomly divided into six groups and were injected with varying doses of alloxan (Ax) and nicotinamide (NA). The serum levels of glucose, insulin, and adiponectin were measured weekly up to 4 weeks.

RESULTS

Elevated levels of glucose were observed in all groups on days 7, 14, 21, and 28, except in groups a and f (control). The serum insulin levels were significantly elevated in groups b and c on day 7, when compared with that in group f, whereas a decrease in the serum insulin levels was observed in groups d and e on days 21 and 28. The adiponectin levels showed inconsistencies on days 7 and 14. However, significant decrease in the adiponectin levels was observed on days 21 and 28. Histological section of the pancreas showed mild (group a), moderate (group b) to severe (groups c, d, and e) degenerative changes. Concomitant fatty changes in the liver and inflammatory infiltration of the kidney were markedly observed in all the treated groups, when compared to control.

CONCLUSION

These results suggested that the use of selective combination of Ax120 + NA50 injection demonstrated type II diabetes mellitus in rats.

Renoprotective effect of myricetin restrains dyslipidemia and renal mesangial cell proliferation by the suppression of sterol regulatory element binding proteins in an experimental model of diabetic nephropathy

Myricetin is a natural flavonoid used in various health management systems. In this present study myricetin tested to evaluate the effect on lipids and lipid metabolism enzymes in normal and streptozotocin (STZ) with cadmium (Cd) induced diabetic nephrotoxic rats. Diabetic nephrotoxic rats were significantly (P<0.05) increased the levels of urinary albumin and lipid profiles: total cholesterol (TC), triglycerides (TGs), free fatty acids (FFAs), phospholipids (PLs), low density lipoprotein (LDL), very low-density lipoproteins (VLDL), and decreased in the levels of high-density lipoproteins (HDL). In addition, the activity of lipoprotein lipase (LPL) and lecithin cholesterol acyl transferase (LCAT) were decreased significantly, whereas the 3-hydroxy 3-methylglutaryl coenzyme A (HmgCoA) reductase activity was increased. The upregulation of sterol regulatory element binding protein-1a (SREBP-1a), SREBP-1c, SREBP-2, transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF) and downregulation peroxisome proliferator-activated receptor alpha (PPAR-α) proteins expression levels were noticed. An administration of myricetin (1.0 mg/kg body weight (b/w)) for 12 weeks was brought the above parameters towards normal level. Histopathological study of kidney samples showed that extracellular mesangial matrix expansion, glomerulosclerosis and interstitial fibrosis in diabetic nephrotoxic rats was suppressed by myricetin treatment. Further our results indicate that administration of myricetin afforded remarkable protection against STZ-Cd induced alterations in lipid metabolism and thereby reduced the diabetic nephropathy in experimental rats.

Cellular cholesterol transport proteins in diabetic nephropathy

Background

Lipid accumulation has been shown to accelerate renal injury, and the intracellular accumulation of lipids may be caused by alterations in synthesis as well as lipid uptake and efflux. We have investigated the role of cellular cholesterol transport proteins including adenosine triphosphate binding cassette transporter A1 (ABCA1), G1 (ABCG1) and scavenger receptor class B type I (SR-BI) in diabetic nephropathy.

Methods

Protein expression and the ability to mediate cholesterol efflux of ABCA1, ABCG1 and SR-BI was determined in human renal mesangial cells and proximal tubular epithelial cells cultured under normal or high glucose conditions. Renal expression of these cholesterol transporters was examined in a murine model of streptozotocin-induced type 1 diabetes.

Results

ABCA1, ABCG1 and SR-BI were expressed in both human renal mesangial cells and proximal tubular epithelial cells, and mediated cholesterol efflux to apolipoprotein AI and HDL. In vitro, hyperglycemia reduced the expression and the ability to mediate cholesterol efflux of all three cholesterol transporters (p<0.05). In vivo studies showed that intra-renal accumulation of lipids was increased in diabetic mice, particularly in mice with nephropathy. This was associated with a significant reduction in the expression of ABCA1, ABCG1 and SR-BI in the kidneys. These changes were already seen in diabetic mice without nephropathy and preceded the development of nephropathy. Diabetic mice with nephropathy had the lowest level of these cholesterol transporters.

Conclusion

Inducing diabetes with streptozotocin significantly reduced renal expression of ABCA1, ABCG1 and SR-BI. Defects in cholesterol export pathway in renal cells could therefore promote cholesterol accumulation and might contribute to the development of diabetic nephropathy.

Most appropriate animal models to study the efficacy of statins: a systematic review

BACKGROUND

In animal models and clinical trials, statins are reported as effective in reducing cholesterol levels and lowering the risk of cardiovascular diseases. We have aggregated the findings in animal models - mice, rats and rabbits - using the technique of systematic review and meta-analysis to highlight differences in the efficacy of statins.

MATERIALS AND METHODS

We searched Medline and Embase. After examining all eligible articles, we extracted results about total cholesterol and other blood parameters, blood pressure, myocardial infarction and survival. Weighted and standard mean difference random effects meta-analysis was used to measure overall efficacy in prespecified species, strains and subgroups.

RESULTS

We included in systematic review 161 animal studies and we analysed 120 studies, accounting for 2432 animals. Statins lowered the total cholesterol across all species, although with large differences in the effect size: -30% in rabbits, -20% in mice and -10% in rats. The reduction was larger in animals fed on a high-cholesterol diet. Statins reduced infarct volume but did not consistently reduce the blood pressure or effect the overall survival. Few studies considered strains at high risk of cardiovascular diseases or hard outcomes.

CONCLUSIONS

Although statins showed substantial efficacy in animal models, few preclinical data considered conditions mimicking human pathologies for which the drugs are clinically indicated and utilized. The empirical finding that statins are more effective in lowering cholesterol derived from an external source (i.e. diet) conflicts with statin's supposed primary mechanism of action.

Statins in chronic kidney disease and kidney transplantation

HMG-CoA reductase inhibitors (statins) have been shown to improve cardiovascular (CV) outcomes in the general population as well as in patients with cardiovascular disease (CVD). Statins' beneficial effects have been attributed to both cholesterol-lowering and cholesterol-independent "pleiotropic" properties. By their pleiotropic effects statins have been shown to reduce inflammation, alleviate oxidative stress, modify the immunologic responses, improve endothelial function and suppress platelet aggregation. Patients with chronic kidney disease (CKD) exhibit an enormous increase in CVD rates even from early CKD stages. As considerable differences exist in dyslipidemia characteristics and the pathogenesis of CVD in CKD, statins' CV benefits in CKD patients (including those with a kidney graft) should not be considered unequivocal. Indeed, accumulating clinical evidence suggests that statins exert diverse effects on dialysis and non-dialysis CKD patients. Therefore, it seems that statins improve CV outcomes in non-dialysis patients whereas exert little (if any) benefit in the dialysis population. It has also been proposed that dyslipidemia might play a causative role or even accelerate renal injury. Moreover, ample experimental evidence suggests that statins ameliorate renal damage. However, a high quality randomized controlled trial (RCT) and metaanalyses do not support a beneficial role of statins in renal outcomes in terms of proteinuria reduction or retardation of glomerular filtration rate (GFR) decline.

Antihyperglycemic, antihyperlipidemic, and renoprotective effects of Chlorella pyrenoidosa in diabetic rats exposed to cadmium

OBJECTIVE

The objective of the present study is to evaluate the antihyperlipidemic effect of Chlorella pyrenoidosa in diabetic rats exposed to cadmium (Cd).

MATERIALS AND METHODS

Group 1 and 2 rats were treated as control and C. pyrenoidosa control. Group 3 and 4 rats were given single injection of streptozotocin (40 mg/kg b.w; i.p) followed by Cd (0.6 mg/kg b.w; s.c) for 5 days per week for a total period of 90 days. In addition, group 4 rats alone were treated with C. pyrenoidosa throughout the study period of 90 days. Assessments of plasma glucose, insulin, lipid profile and renal function markers were performed in control and experimental rats along with histological examination of kidney tissues.

RESULTS

Diabetic rats exposed to Cd showed increased levels of plasma glucose and decreased levels of plasma insulin accompanied by the significantly elevated levels of tissue lipids viz., total cholesterol, triglyceride, free fatty acid, and phospholipids compared with control rats. Alterations in lipoproteins (low density lipoprotein-C, very low density lipoprotein-C, and high density lipoprotein-C) levels were also observed.

DISCUSSION

Elevated levels of urinary albumin, creatinine, and blood urea nitrogen confirmed the onset of renal dysfunction in unsupplemented diabetic rats exposed to Cd.

CONCLUSION

C. pyrenoidosa (100 mg/kg body weight) supplemented diabetic nephropathic rats showed near normal biochemical profile and well preserved renal histology that substantiate the antihyperglycemic, antihyperlipidemic, and renoprotective effects of C. pyrenoidosa in diabetic rats exposed to Cd.

Lipid droplet accumulation is associated with an increase in hyperglycemia-induced renal damage: prevention by liver X receptors

Dyslipidemia is a frequent component of the metabolic disorder of diabetic patients contributing to organ damage. Herein, in low-density lipoprotein receptor-deficient hyperlipidemic and streptozotozin-induced diabetic mice, hyperglycemia and hyperlipidemia acted reciprocally, accentuating renal injury and altering renal function. In hyperglycemic-hyperlipidemic kidneys, the accumulation of Tip47-positive lipid droplets in glomeruli, tubular epithelia, and macrophages was accompanied by the concomitant presence of the oxidative stress markers xanthine oxidoreductase and nitrotyrosine, findings that could also be evidenced in renal biopsy samples of diabetic patients. As liver X receptors (LXRα,β) regulate genes linked to lipid and carbohydrate homeostasis and inhibit inflammatory gene expression in macrophages, the effects of systemic and macrophage-specific LXR activation were analyzed on renal damage in hyperlipidemic-hyperglycemic mice. LXR stimulation by GW3965 up-regulated genes involved in cholesterol efflux and down-regulated proinflammatory/profibrotic cytokines, inhibiting the pathomorphology of diabetic nephropathy, renal lipid accumulation, and improving renal function. Xanthine oxidoreductase and nitrotyrosine levels were reduced. In macrophages, GW3965 or LXRα overexpression significantly suppressed glycated or acetylated low-density lipoprotein-induced cytokines and reactive oxygen species. Specifically, in mice, transgenic expression of LXRα in macrophages significantly ameliorated hyperlipidemic-hyperglycemic nephropathy. The results demonstrate the presence of lipid droplet-induced oxidative mechanisms and the pathophysiologic role of macrophages in diabetic kidneys and indicate the potent regulatory role of LXRs in preventing renal damage in diabetes.

Anti-diabetic effect of Wen-pi-tang-Hab-Wu-ling-san extract in streptozotocin-induced diabetic rats

Objectives:

Wen-pi-tang-Hab-Wu-ling-san (WHW) is an oriental herbal prescription formulated using 14 herbs and has been used to cure chronic renal failure in Korean oriental medicine. In this study, we investigated the anti-diabetic effect of WHW in the streptozotocin-induced diabetic rats.

Materials and Methods:

Diabetes was induced by streptozotocin (STZ, 60 mg/kg, i.p.) in rats. WHW extract (100 mg/kg) was orally dosed once a day for four weeks. The results were compared with standard antidiabetic drug, glibenclamide (3 mg/kg, p.o).

Results:

Significant decrease in body weight and insulin levels and increase in blood glucose, triglycerides, urea nitrogen (BUN), and creatinine were detected in STZ-induced diabetic rats with disruption and disappearance of pancreatic and kidney cells and decrease in insulin producing beta cells. However, these diabetic changes were significantly inhibited by treatment with WHW extract. In the oral glucose tolerance test, the extract produced a significant decrease in glycemia 60 minutes after the glucose pulse.

Conclusions:

Based on these results, we suggest that WHW extract has favorable effects in protecting the STZ-induced hyperglycemia, renal damage, and beta-cell damage in rats.

Role of triglyceride-rich lipoproteins in renal injury

Dyslipidemia is implicated as a risk factor for the development of atherosclerosis. Specifically triglyceride-rich lipoproteins and their lipolysis products are shown to be proinflammatory and proapoptosis in both in vivo and in vitro studies with endothelium. However, the role of triglyceride-rich lipoproteins in the progression of kidney diseases is not clear. Epidemiology studies demonstrated a correlation between renal disease and blood lipids. Recent evidence suggests that the mechanism may involve cellular uptake of lipid and de novo lipogenesis. Further studies are needed to establish the relevance of these mechanistic studies in human pathophysiology.

New pharmacological treatments for improving renal outcomes in diabetes

Diabetic nephropathy is the most common and most rapidly growing cause of end-stage renal failure in developed countries. Diabetic nephropathy results from complex interactions between genetic, metabolic and hemodynamic factors. Improvements in our understanding of the pathogenesis of fibrosis associated with diabetic kidney disease have led to the identification of several novel targets for the treatment of diabetic nephropathy. Albuminuria is a useful clinical marker of diabetic nephropathy, as it can be used to predict a decline in renal function. A reduction in albuminuria might not, however, be reflective of a protective effect of therapies focused on ameliorating renal fibrosis. Although new strategies for slowing down the progression of several types of renal disease have emerged, the challenge of arresting the relentless progression of diabetic nephropathy remains. In this Review, we discuss novel pharmacological approaches that aim to improve the renal outcomes of diabetic nephropathy, including the use of direct renin inhibitors and statins. We also discuss the promise of using antifibrotic agents to treat diabetic nephropathy. The need for novel biomarkers of diabetic nephropathy is also highlighted.

Role of triglyceride-rich lipoproteins in diabetic nephropathy

Diabetic nephropathy is an increasingly important cause of morbidity and mortality worldwide. A large body of evidence suggests that dyslipidemia has an important role in the progression of kidney disease in patients with diabetes. Lipids may induce renal injury by stimulating TGF-beta, thereby inducing the production of reactive oxygen species and causing damage to the glomeruli and glomerular glycocalyx. Findings from basic and clinical studies strongly suggest that excess amounts of a variety of lipoproteins and lipids worsens diabetes-associated microvascular and macrovascular disease, increases glomerular injury, increases tubulointerstitial fibrosis, and accelerates the progression of diabetic nephropathy. The increasing prevalence of obesity, type 2 diabetes mellitus, and diabetic nephropathy means that interventions that can interrupt the pathophysiological cascade of events induced by lipoproteins and lipids could enable major life and cost savings. This Review discusses the structural, cellular, and microscopic findings associated with diabetic nephropathy and the influence of lipoproteins, specifically triglyceride-rich lipoproteins (TGRLs), on the development and perpetuation of diabetic nephropathy. Some of the accepted and hypothesized mechanisms of renal injury relating to TGRLs are also described.

Genetic diversity of the apolipoprotein E gene and diabetic nephropathy: a meta-analysis

In the past decade, a number of case-control studies have been carried out to investigate the relationship between the ApoE polymorphism and diabetic nephropathy. However, the results have been inconclusive. To investigate this inconsistency, we performed a meta-analysis of all available studies dealing with the relationship between the ApoE polymorphism and DN. The 23 studies in the meta- analysis included 6,012 diabetic patients with (n = 2,979) and without (n = 3,033) DN. The ApoE ε2 allele was significantly associated with DN (OR = 1.64, 95% CI: 1.26-2.13; P(Z) = 0.00027), whereas the ε4 allele was non-significantly associated with DN (OR = 0.93, 95% CI: 0.78-1.11; P(Z) = 0.418). However, significant heterogeneity was detected. In further subgroup analyses, genotyping methods, outcome of cases and duration of diabetes in controls were found to explain some of the heterogeneity. Genotypic analysis also found a strong association between the ε2 carriers and DN (OR = 1.61, 95% CI: 1.22-2.13; P(Z) = 0.001) and indicated that ε4 tended to have a marginally significant protective effect for DN (OR = 0.82, 95% CI: 0.65-1.03; P(Z) = 0.085). The results of our meta-analysis support a genetic association between the ApoE polymorphism and DN. ε2 increases the risk of DN in diabetes patients, while ε4 trends to be protective. These findings may have implications for therapeutic intervention in diabetic nephropathy.

Effect of atorvastatin on aldosterone production induced by glucose, LDL or angiotensin II in human renal mesangial cells

Nephropathy is a major complication of diabetes mellitus, thus development of rational therapeutic means is critical for improving public health. It was previously reported that human mesangial cells locally produced aldosterone, a steroid hormone that plays an important role in the development of diabetic nephropathy. The present experiments clarified the effect of glucose, LDL and angiotensin II, the molecules frequently elevated in patients with diabetic nephropathy, on aldosterone production in human primary mesangial cells. These cells expressed the CYP11B2 mRNA, a rate-limiting enzyme in the aldosterone biosynthesis. LDL and angiotensin II stimulated CYP11B2 mRNA expression in these cells, while a high concentration of glucose, angiotensin II and/or LDL increased aldosterone production. Importantly, atorvastatin (CAS 134523-03-8), an HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitor, strongly suppressed their effects on aldosterone production. Atorvastatin also suppressed positive effects of these compounds on the mRNA expression of the angiotensin II receptor type 1, thus atorvastatin exerted its negative effect in part through changing expression of this receptor. Since elevated levels of glucose and LDL, and increased action of the renin-angiotensin-aldosterone system is known to participate in the progression of diabetic nephropathy, it is speculated that the mesangial endocrine system that produces aldosterone locally is a promising therapeutic target for diabetic nephropathy where HMG-CoA reductase inhibitors provide a beneficial effect.

Safety and Efficacy of Fluvastatin in Hyperlipidemic Patients With Chronic Renal Disease

BACKGROUND

There are few reports on the safety and efficacy of long-term treatment with statins in patients with chronic renal disease and hyperlipidemia. We evaluated these subjects treated with fluvastatin.

METHODS

After a 4-week run-in period, a total of 80 patients with diabetic nephropathy or chronic glomerulonephritis were randomly allocated to receive dietary therapy and fluvastatin 20 mg/day (n=39), or dietary therapy alone (n=41) for a period of 48 weeks. Lipid parameters, rhabdomyolysis-related indicators, 24-hour urinary albumin excretion and creatinine clearance were measured. The pharmacokinetics of fluvastatin was examined in 8 patients.

RESULTS

Creatinine clearance and 24-hour urinary albumin excretion did not differ between the two groups. The peak serum fluvastatin concentration (Cmax) was 141+/-67 microg/L and the mean AUC0-6 h was 341+/-149 microgh/L. Fluvastatin treatment significantly lowered serum total cholesterol, low-density lipoprotein (LDL) cholesterol and apo-lipoprotein B concentrations by 16%, 25%, and 22%, respectively, compared with patients receiving dietary therapy alone. There were no significant differences in serum triglyceride and high-density lipoprotein (HDL) cholesterol concentrations between the two treatment groups. Serum creatine kinase and aldolase concentrations did not change throughout treatment in both groups.

CONCLUSIONS

Fluvastatin treatment significantly improved lipid parameters in patients with chronic renal disease. Fluvastatin was well tolerated, with no adverse effects on renal function and no muscular toxicity. However, the drug showed no direct renoprotective effects.

Role of PPARgamma in renoprotection in Type 2 diabetes: molecular mechanisms and therapeutic potential

DN (diabetic nephropathy) is a chronic disease characterized by proteinuria, glomerular hypertrophy, decreased glomerular filtration and renal fibrosis with loss of renal function. DN is the leading cause of ESRD (end-stage renal disease), accounting for millions of deaths worldwide. TZDs (thiazolidinediones) are synthetic ligands of PPARgamma (peroxisome-proliferator-activated receptor gamma), which is involved in many important physiological processes, including adipose differentiation, lipid and glucose metabolism, energy homoeostasis, cell proliferation, inflammation, reproduction and renoprotection. A large body of research over the past decade has revealed that, in addition to their insulin-sensitizing effects, TZDs play an important role in delaying and preventing the progression of chronic kidney disease in Type 2 diabetes. Although PPARgamma activation by TZDs is in general considered beneficial for the amelioration of diabetic renal complications in Type 2 diabetes, the underlying mechanism(s) remains only partially characterized. In this review, we summarize and discuss recent findings regarding the renoprotective effects of PPARgamma in Type 2 diabetes and the potential underlying mechanisms.

Lovastatin inhibits oxidized low-density lipoprotein-induced plasminogen activator inhibitor and transforming growth factor-beta1 expression via a decrease in Ras/extracellular signal-regulated kinase activity in mesangial cells

Oxidized low-density lipoprotein (Ox-LDL) might be involved in the progression of renal disease. Ox-LDL stimulation of plasminogen activator inhibitor-1 (PAI-1) expression via transforming growth factor-beta (TGF-beta)/Smad signaling in mesangial cells required activation of extracellular signal-regulated kinase (ERK). Mevalonate depletion by 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors, or statins, decreases the levels of farnesyl pyrophosphate (FPP) for isoprenylation of Ras. We postulate that statins may ameliorate the Ox-LDL-induced mesangial matrix accumulation by inhibiting Ras/ERK activation with subsequent downregulation of TGF-beta target genes. Quiescent mesangial cells were incubated for 18 h with and without the presence of lovastatin before 50 microg/mL of Ox-LDL treatment for 1 h. Lovastatin inhibited markedly the stimulatory effects of Ox-LDL on ERK1/2 activation, nuclear Smad3 expression, TGF-beta1 and PAI-1 mRNA and protein expression, and PAI-1 luciferase activity. These inhibitory effects of lovastatin were reversed almost completely by mevalonate or FPP. Similar to lovastatin, FTI-277, which is an inhibitor of Ras farnesylation, decreased the Ox-LDL-induced activation of ERK/Smad3 and induction of TGF-beta1/PAI-1. These results indicate that lovastatin prevents the Ox-LDL-induced Ras/ERK activation that results in inhibition of Smad3 activation in mesangial cells with subsequent downregulation of TGF-beta target genes. Thus, statins seem to have antifibrotic effects through their anti-TGF-beta response that are relevant in the treatment of chronic renal disease with dyslipidemia.

Atorvastatin Treatment in the Short Term: Does It Induce Renoprotection or Vasculoprotection in Renal Transplantation?

INTRODUCTION

Proteinuria and dyslipidemia are nonimmune risk factors implicated in the deterioration of kidney function and associated with an increased risk of accelerated atherogenesis. Statin therapy, used for cholesterol reduction, has shown a renoprotective effect in animal models, particularly in cases of proteinuria. This may occur through lipid-independent mechanisms, such as improved endothelial dysfunction/vascular biology, reduced inflammatory cytokine production (transforming growth factor-beta 1 [TGF-beta1]), and regulation of fibrogenic responses. We studied mechanisms of action of agents, such as statins, to change proteinuria, inflammatory parameters, and TGF-beta1 plasma levels in relation to vascular tone.

METHODS

Fifty-six kidney transplant recipients (30 men and 26 women of overall mean age 54 +/- 13 years) were treated posttransplantation with atorvastatin (10 mg/d) for 12 weeks without renin-angiotensin-system blockade drugs. Inflammatory variables, biochemical parameters, lipid profile, renal function, and TGF-beta1 levels were determined at baseline and at 3 months. Vascular stiffness was evaluated using pulse wave velocity (PWV).

RESULTS

Baseline TGF-beta1 plasma levels were higher among transplant recipients than healthy controls, namely 8.12 ng/mL (range, 5.82-13.12) to 2.55 (range, 1.78- 4.35) (P < .01). Furthermore, the levels remained higher after the treatment with atorvastatin, namely, 7.59 (range, 4.97-12.35) to 2.55 (range, 1.78-4.35) ng/mL (P < .01). Atorvastatin treatment significantly decreased total cholesterol as well as low-density lipoprotein cholesterol plasma levels, but did not modify mean blood pressure (MBP), proteinuria, creatinine clearance, or inflammatory factors. Reduction in TGF-beta1 plasma levels was statistically significant among patients with PWV >9.75 (m/s) (pathology reference value) namely, from 10.7 ng/mL (range, 7.02-13.98) to 6.7 (range, 3.96-11.94) (P = .038). Among older patients, atorvastatin significantly decrease TGF-beta1 plasma levels: from 9.5 ng/mL (range, 6.45-14.44) to 5.65 (range, 3.63-9.48; P < .05). The decreased TGF-beta1 was not related to changes in lipid profiles.

CONCLUSIONS

Atorvastatin (10 mg/d) improved the lipid profile and moreover among older patients with worse PWV (>9.75 m/s), TGF-beta1 levels were significantly reduced. Our results suggested that statins displayed potent actions distinct from their hypolipidemic effects.

Apo E gene polymorphism on development of diabetic nephropathy

Type 2 diabetes causes premature morbidity and mortality due to the complications of atherosclerosis and diabetic nephropathy (DN). Polymorphism of Apo E gene is known to influence lipid metabolism. Apo E is polymorphic, consisting of three common isoforms (epsilon2, epsilon3 and epsilon4) encoded by three alleles (2, 3 and 4) in exon 4 on chromosome 19. The aim of this study was to investigate the effect of Apo E polymorphism as a prognostic risk factor for the development of DN. A total of 108 NIDDM patients were recruited from the Nephrology and Endocrinology Departments of our hospital. All subjects were divided into three groups: Group I: diabetes with nephropathy (n:37), group II: diabetes without nephropathy (n:71), group III: controls (n:46). Apo E genotypes were determined by real-time PCR. The epsilon4 allele frequency was significantly higher in-group I (10.8%) than in-group III (2.2%), (p < 0.05). In diabetics without nephropathy, the total cholesterol and LDL cholesterol levels were significantly lower in subjects with epsilon2 alleles than epsilon3 and epsilon4 alleles. In conclusion, the present prospective study indicates that the epsilon4 allele of the Apo E polymorphism is one of the prognostic risk factors involved in the development of DN with type 2 diabetes mellitus.

Lipids and diabetic nephropathy

Although several factors may mediate the development and progression of diabetic nephropathy, hyperlipidemia is now considered an independent and major determinant of progression of renal disease in diabetes. The following discussion focuses on the experimental evidence that incriminates hyperlipidemia as a pathogenic factor for diabetic nephropathy and the potential mechanisms that may mediate renal injury from hyperlipidemia, as well as the clinical studies involving therapeutic interventions for hyperlipidemia and their impact on progression of diabetic renal disease.

Lipids and diabetic renal disease

Diabetic nephropathy is commonly associated with dyslipidemia, but the role of lipids in the progression of this disorder remains unresolved. In particular, the role of lipid-lowering drugs, such as 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors and fibrates, as renoprotective agents is not clarified. Experimental studies have demonstrated that dietary lipids promote renal injury and that statins, independent of their lipid-lowering effects, confer renoprotection via effects on intrarenal hemodynamics and renal cytokine and chemokine expression. Clinical studies have in general been underpowered, but a recent meta-analysis and findings from the Heart Protection Study suggest that statins may be renoprotective. Nevertheless, with the convincing antiatherosclerotic effects of these agents, including in the setting of diabetes, they should be widely administered in the diabetic population with or at risk for nephropathy.

Pleiotropic effects of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors on renal function

Pleiotropic, or non-lipid-dependent, effects mediated by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have important clinical implications for the cardiovascular (CV) system. Atherosclerosis is an inflammatory process accompanied by increases in levels of plasma inflammatory markers and accumulation of immune cells within atherosclerotic plaques. Statins not only decrease serum lipid levels, but also inhibit signaling molecules at several points in inflammatory pathways. The anti-inflammatory effects and improved endothelial function associated with statin therapy are thought to be partly responsible for the reduction in CV morbidity and mortality. In analogy, patients with chronic kidney disease administered statins for CV risk reduction show evidence of improved renal function. However, whether statins confer similar protective benefits on the kidney has not been established. Several lines of evidence suggest that similar etiologic and pathological processes may be involved in CV and chronic kidney diseases. If inflammation and functional changes in the renovascular endothelium contribute to the progression of kidney disease, statins are likely to be effective in the treatment of renal disease. In this review, we critically consider emerging data indicating that statins may modulate renal function by altering the inflammatory response of the kidney and renal vasculature to dyslipidemia. Whether the amelioration of renal function by statins is separable from the lipid-lowering effects of these drugs still remains to be delineated. Other questions that remain to be addressed and issues that should be investigated also are presented.

Protective effects of bendazac lysine on early experimental diabetic nephropathy in rats

AIM

To investigate the preventive and protective effects of bendazac lysine (BDL) on experimental early diabetic nephropathy (DN) rats.

METHODS

After an early DN model was induced by streptozotocin, rats were administered BDL at doses of 100, 200, and 400 mg/kg for 8 weeks. Blood glucose, microalbuminuria, kidney index, total antioxidative capacity, laminin, advanced glycation end products (AGE), aldose reductase (AR) activity, and the relative quantity of transforming growth factor beta1 (TGF- beta1) mRNA were measured by different methods. The ultrastructural morphology was observed by transmission electron microscope.

RESULTS

The physical behaviors of early DN rats were hypopraxia, cachexia, and polyuria, while those treated with high doses of BDL were vibrant and vigorous. For BDL-treated DN rats, when compared with vehicle-treated DN rats, the blood glucose level and the intensity of oxidative stress were ameliorated. Also, the microalbuminuria level, AGE either in serum or in renal, and AR activity were significantly reduced. Furthermore, the expression of TGF-beta1 mRNA in the kidney cortex was declined and the thickness of glomerular base membrane was decreased significantly. The ultrastructure of glomerulus and mesangial matrix of BDL-treated DN rats were ameliorated.

CONCLUSION

BDL has protective effects on several pharmacological targets in the progress of DN and is a potential drug for the prevention of early DN.

The prevention of diabetic microvascular complications of diabetes: is there a role for lipid lowering?

The role of hyperglycemia in the development of microvascular complications of diabetes, such as nephropathy, retinopathy and neuropathy, has been well documented. Evidence is accumulating to support the concept that dyslipidemia can also contribute to the development of these complications. Lipid-lowering agents, such as statins, have been shown to prevent cardiovascular events in patients with diabetes. However, in addition to preventing macrovascular diseases, statins may also be able to retard the progression of microvascular complications of diabetes. Indeed, in addition to reducing lipid levels, these agents can improve endothelial function and reduce oxidative stress, which can improve microvascular function. These findings would provide further support for the use of lipid-lowering agents in patients with diabetes.

Pharmacokinetic properties of pravastatin in Mexicans: An open-label study in healthy adult volunteers

BACKGROUND

The pharmacokinetic properties of pravastatin, particularlyAUC and Cmax, are variable by population. A description of the pharmacokinetic properties of pravastatin in Mexican mestizos was not found in a search of MEDLINE/PubMed (key terms: pravastatin, Mexican, and pharmacokinetics; years: 1966-2005). Because Mexicans and Japanese have common ancestors (Mongoloid group), they also have a common gene pool. This gene pool was modified by genetic "bottlenecks" that occurred when these populations migrated to the Americas and when the Mexican population mixed with the Spanish population during the 16th and 17th centuries. Previous studies in Japanese subjects showed 5 main mutations on the hepatic drug transporter OATP-C, resulting in higher Cmax and AUC values compared with whites. In the Japanese population, the rates of expression of the (*) 1b and (*) 15 alleles were 46% and 15%, respectively.

OBJECTIVE

The aim of this study was to evaluate the pharmacokinetic propertiesof pravastatin in healthy Mexican mestizo volunteers and to compare them with those in white and Japanese populations described in the literature.

METHODS

This open-label, uncontrolled pilot study of the pharmacokineticproperties of pravastatin was conducted at the Division of Pharmacology, Center for Research and Advanced Studies, Mexico City, Mexico. Healthy, adult, Mexican volunteers received a single dose of pravastatin 10 mg PO (tablet). High-performance liquid chromatography was used to determine plasma pravastatin concentrations between 15 minutes and 12 hours after dosing.

RESULTS

Twenty-four subjects (15 women, 9 men; mean age, 30.6 years)participated in the study. The mean (SD) Cmax was 9.5 (2.4) ng/mL; Tmax, 0.8 (0.3) hours; AUC0-∞ 35.7 (19.7) ng/mL - h; t1/2, 2.7 (1.1) hours; and mean residence time, 3.1 (1.1) hours. One volunteer (4%) had an AUC value that differed substantially from the rest of the study population, producing a bimodal distribution of the pharmacokinetic parameters. No adverse events were observed or reported during the trial.

CONCLUSIONS

In this small pilot study of the pharmacokinetic properties of pravastatin in Mexican mestizos, AUC was not statistically significantly different from previous studies, either in a white or Japanese population. However, we did not find the high values reported for Cmax in some Japanese subjects carrying recently reported mutations on the pravastatin transporter.

Protective effects of Astragalus saponin I on early stage of diabetic nephropathy in rats

Diabetic nephropathy (DN) has become the leading cause of end stage failure, but no renoprotective treatment has been very available for use in DN. Astragalus saponin I (AS I), a component extracted from Astragalus membranaceus BUNGE, was studied in experimental DN induced by administration of streptozotocin in male rats. The early DN rats were treated with 3 doses of AS I for 8 weeks to analyze its efficacy with different parameters. By comparison with vehicle-treated DN rats, the renal hypertrophy, the oxidative stress intensity, and the blood glucose level of DN rats were ameliorated by AS I. Also, the microalbuminuria level, advanced glycated end-products either in serum or in kidney cortex, and the aldose reductase activity were significantly reduced. Furthermore, the expression of transforming growth factor beta1 mRNA in kidney cortex by RT-PCR analysis was markedly declined. Both the relative grade of mesangium hyperplasia by microscopical observation and the thickness of glomerular base membrane by electron microscope measurement were decreased significantly. Therefore, the results suggest that AS I has therapeutic effects on several pharmacological targets in the progress of DN and is a potential drug for prevention of early stage DN.

ATORVASTATIN AMELIORATES RENAL TISSUE DAMAGE IN UNILATERAL URETERAL OBSTRUCTION

PURPOSE

The current study was done to determine whether atorvastatin, the HMGCoA (3-hydroxy-3-methylglutaryl CoA) reductase inhibitor, could decrease renal transforming growth factor-beta (TGF-beta) levels in unilateral ureteral obstruction (UUO) and concomitantly affect renal tissue damage in UUO.

MATERIALS AND METHODS

Atorvastatin (20 mg/kg) was administered to rats 1 day prior to UUO and every day thereafter. Kidneys were harvested at day 14 after UUO. Tissue TGF-beta was measured by bioassay using mink lung epithelial cells. Renal tubular proliferation and apoptosis were detected by immunostaining proliferating cell nuclear antigen and polyclonal antisingle strand DNA antibody, respectively. Fibrosis was assessed by measuring collagen deposition with trichrome stained slides. Interstitial leukocyte was detected by immunostaining CD45.

RESULTS

TGF-beta bioassay showed that the obstructed kidney in the control group contained significantly higher TGF-beta than the unobstructed kidney in the control group (mean +/- SD 79.1 +/- 48.5 vs 28.7 +/- 13.7 pg/mg tissue) and atorvastatin significantly decrease tissue TGF-beta in the obstructed kidney (53.4 +/- 37.0 pg/mg tissue). Immunostaining polyclonal antisingle strand DNA antibody demonstrated that the obstructed kidney in the control group has significantly more tubular apoptosis than the unobstructed counterpart (4.8 +/- 2.8 vs 2.1 +/- 1.2 nuclei per high power field) and atorvastatin significantly decreased renal tubular apoptosis in the obstructed kidney (1.1 +/- 0.7 nuclei per high power field). In addition, immunostaining proliferating cell nuclear antigen showed that the obstructed kidney in the atorvastatin group had significantly more renal tubular proliferation than the obstructed kidney in the control group (48.7 +/- 20.8 vs 17.3 +/- 10.6 per high power field). Control obstructed kidney showed significantly more fibrosis, which was also blunted by atorvastatin.

CONCLUSIONS

Atorvastatin significantly decreases tissue TGF-beta, resulting in a decrease in tubular damage and interstitial fibrosis. This suggests that atorvastatin is a promising agent for preventing renal tubular damage in UUO.

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.

An implication of hypertriglyceridemia in the progression of diabetic nephropathy in metabolically obese, normal weight patients with type 2 diabetes mellitus in Korea

This study was undertaken to investigate diverse risk factors affecting the progression of diabetic nephropathy (DN) by observing the changes of 24 h urinary albumin excretion (24 h UAE) in 90 abdominally obese, normal weight, type 2 diabetic patients with normo- or micro-albuminuria. Patients were divided into three groups according to the 24h UAE; normo-, micro-, and macro-albuminuria group. After 4 years of follow-up, patients were divided into either progression or non-progression group according to the changes of 24 h UAE. About 37% of the normo-albuminuria group and 18% of the micro-albumiuria group were classified into the progression group. The initial serum creatinine levels and the initial and follow-up post-prandial plasma glucose levels were significantly higher in the progression group than in the non-progression group. Most remarkably, the initial and follow-up serum triglyceride (TG) levels (190 +/- 132 versus 132 +/- 49 mg/dl and 191 +/- 124 versus 133 +/- 41 mg/dl, P < 0.01 in both) were significantly higher in the progression group than in the non-progression group, suggesting hypertriglyceridemia might be included in the progression factors of DN. The increases in 24-hour UAE were positively associated with the initial and follow-up post-prandial plasma glucose levels (P < 0.05 in both), the initial and follow-up serum creatinine levels (P < 0.05 in both), and the initial serum TG levels (P < 0.05). Whereas, insulin users or patients with retinopathy at follow-up (P < 0.05 in both) showed more rapid progression of albuminuria, ACE inhibitors or acarbose (P < 0.05 in both) use turned out to protect against it.

The role of lipids in the development of diabetic microvascular complications: implications for therapy

Dyslipidemia is a major factor responsible for coronary heart disease and its reduction decreases coronary risk in patients with diabetes mellitus. However, the association of dyslipidemia with microvascular complications and the effect of intervention with lipid-lowering therapy in diabetes have been less investigated. We present the systematic review of association and intervention studies pertaining to dyslipidemia and microvascular disease in diabetes and also review possible mechanisms. Dyslipidemia may cause or exacerbate diabetic retinopathy and nephropathy by alterations in the coagulation-fibrinolytic system, changes in membrane permeability, damage to endothelial cells and increased atherosclerosis. Hyperlipidemia is associated with faster decline in glomerular filtration rate and progression of albuminuria and nephropathy. Recent evidence also suggests a role of lipoprotein(a) in progression of retinopathy and nephropathy in patients with diabetes mellitus. Lipid-lowering therapy, using single agents or a combination of drugs may significantly benefit diabetic retinopathy and diabetic nephropathy. In particular, hydroxymethyl glutaryl coenzyme A reductase inhibitors may be effective in preventing or retarding the progression of microvascular complications because of their powerful lipid-lowering effects and other additional mechanisms. However, most of the data are based on short-term studies, and need to be ascertained in long-term studies. Until more specific guidelines are available, aggressive management of diabetic dyslipidemia, according to currently accepted guidelines, should be continued for the prevention of macrovascular disease which would also benefit microvascular complications.