The relationship between glucose control and the development and progression of diabetic nephropathy

PS-MPs promotes the progression of inflammation and fibrosis in diabetic nephropathy through NLRP3/Caspase-1 and TGF-β1/Smad2/3 signaling pathways

BACKGROUND

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication of diabetes and the leading cause of end-stage renal disease (ESRD). Understanding the progressive etiology of DN is critical for the development of effective health policies and interventions. Recent research indicated that polystyrene microplastics (PS-MPs) contaminate our diets and accumulate in various organs, including the liver, kidneys, and muscles.

METHODS

In this study, ten-week-old db/db mice and db/m mice were fed. Besides, db/db mice were divided into two groups: PS-MPs group (oral administration of 0.5 µm PS-MPs) and an H2O group, and they were fed for three months. A type II diabetes model was established using db/db mice to investigate the effects of PS-MPs on body weight, blood glucose level, renal function, and renal fibrosis.

RESULTS

The results demonstrated that PS-MPs significantly exacerbated various biochemical indicators of renal tissue damage, including fasting blood glucose, serum creatinine, blood urea nitrogen, and blood uric acid. Additionally, PS-MPs worsened the pathological alterations and degree of fibrosis in renal tissue. An increased oxidative stress state and elevated levels of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1) were identified. Furthermore, PS-MPs significantly enhanced renal fibrosis by inhibiting the transition from epithelial cells to mesenchymal cells, specifically through the inhibition of the TGF-β/Smad signaling pathway. The expression levels of NOD-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), Caspase-1, and cleaved Caspase-1, which are inflammasome proteins, were significantly elevated in the PS-MPs group.

CONCLUSION

The findings suggested that PS-MPs could aggravate kidney injury and renal fibrosis in db/db mice by promoting NLRP3/Caspase-1 and TGF-β1/Smads signaling pathways. These findings had implications for elucidating the role of PS-MPs in DN progression, underscoring the necessity for additional research and public health interventions.

A systematic review and meta-analysis of randomized control trials of vitamin D supplementation in diabetic nephropathy

Objective

The aim of this study is to explore the correlation between vitamin D and diabetic nephropathy.

Methods

Relevant evidences were searched from PubMed, Embase, Web of Science, Ovid and China Knowledge Resource Integrated (CNKI), Wanfang Data Knowledge Service Platform databases (WANFANG), and VIP dating from inception to December 2019 to obtain the randomized controlled trials (RCTs) of vitamin D in the treatment of diabetic nephropathy. According to inclusion and exclusion criteria, two researchers independently screened the literature, extracted data, and evaluated the quality of included studies. Rev Man 5.3 software was used to conduct statistical analysis.

Results

A total of 10 studies involving 651 patients were identified. These studies were finally included into the meta-analysis. A meta-analysis results showed that vitamin D is the protection factor in diabetic nephropathy, the group treated with vitamin D did better than the traditional drug and the placebo group. After taking vitamin D, the level of vitamin D in the patient’s body increased significantly. Pooled results showed that there was a significant difference for vitamin D (MD = 38.24, 95%CI = 32.69–43.79, p < 0.001.) The patient had a significant decrease in urinary protein; the difference was statistically significant (MD = − 180.92, 95%CI = − 212.67 to − 149.16, p < 0.001). The blood creatinine content decreased obviously (MD = − 17.13, 95%CI = − 27.88 to − 6.37, p < 0.01). However, most of the included studies did not report the quality of life and adverse reactions of patients, making it impossible to analyze these measures.

Conclusion

This study showed that vitamin D played an active role in the treatment of diabetic nephropathy and can be used in future clinical applications. However, there are still some studies of low quality in the included studies, so it is suggested that clinical and scientific researchers carry out more high-quality, large sample, multi-center randomized controlled trials (RCTS) to provide more evidence-based medical evidence for future studies on vitamin D treatment of diabetic nephropathy.

Adenovirus-mediated expression of SIK1 improves hepatic glucose and lipid metabolism in type 2 diabetes mellitus rats

Aim

In this study, we investigated the role and mechanism of Salt-induced kinase 1 (SIK1) in regulation of hepatic glucose and lipid metabolism in a high-fat food (HFD) and streptozocin (STZ)-induced type 2 diabetes mellitus (T2DM) rat model.

Methods

A diabetic rat model treated with HFD plus low-dose STZ was developed and was transduced to induce a high expression of SIK1 in vivo via a tail-vein injection of a recombinant adenoviral vector. The effects on hepatic glucogenetic and lipogenic gene expression, systemic metabolism and pathological changes were then determined.

Results

In T2DM rats, SIK1 expression was reduced in the liver. Overexpression of SIK1 improved hyperglycaemia, hyperlipidaemia and fatty liver, reduced the expression of cAMP-response element binding protein (CREB)-regulated transcription co-activator 2 (CRTC2), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), pS577 SIK1, sterol regulatory element binding-protein-1c (SREBP-1c) and its target genes, including acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), and increased the expression of SIK1, pT182 SIK1 and pS171 CRTC2 in diabetic rat livers with the suppression of gluconeogenesis and lipid deposition.

Conclusion

SIK1 plays a crucial role in the regulation of glucose and lipid metabolism in the livers of HFD/STZ-induced T2DM rats, where it suppresses hepatic gluconeogenesis and lipogenesis by regulating the SIK1/CRTC2 and SIK1/SREBP-1c signalling pathways. Strategies to activate SIK1 kinase in liver would likely have beneficial effects in patients with T2DM and nonalcoholic fatty liver disease (NAFLD).

Vitamin D receptor gene polymorphisms in association with diabetic nephropathy: a systematic review and meta-analysis

Background

A large amount of researches have demonstrated that vitamin D receptor (VDR) gene polymorphisms are associated with diabetic nephropathy (DN) risk in diabetes mellitus (DM) patients. Nevertheless, the results are inconclusive and inconsistent.

Methods

We screened PubMed, Embase, Chinese National Knowledge Infrastructure and Chinese Wanfang databases for those relevant studies updated in May 2016.

Results

7 studies involving 2564 subjects were recruited. We evaluated the genotypic and allelic differences between DN patients and DM controls. Overall analysis showed that no significant association was found among the ApaI, BsmI, FokI,TaqI gene polymorphisms and DN susceptibility in diabetic patients (all P values > 0.05). In the stratified analysis, TT genotype was related to DN susceptibility in Asians (TT vs Tt + tt: OR =2.21, 95% CI: 1.05–4.67, p = 0.04). The sensitivity analysis showed that the results in overall populations, Caucasians and Asians were dependable.

Conclusions

No significant association was found among the ApaI, BsmI, FokI, TaqI polymorphisms and DN risk in overall populations, the TaqI variants might related to DN susceptibility in Asians. Further researches are required to testify our meta-analysis.

Sitagliptin ameliorates high glucose-induced cell proliferation and expression of the extracellular matrix in glomerular mesangial cells

Diabetic nephropathy (DN) is one of the most important causes that leads to end-stage renal disease and the efficacy of strategies currently available for the prevention of DN remains unsatisfactory. Sitagliptin (SIT), which is a dipeptidyl peptidase-4 inhibitor, exhibited a modest beneficial effect on glycated hemoglobin levels and is capable of ameliorating renal ischemia reperfusion injury. By determining the expression of transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), collagen type IV (ColIV) and fibronectin (FN) levels in high glucose-cultured glomerular mesangial cells (MCs), the present study aimed to assess the anti-proliferative and anti-fibrotic effects of SIT on the therapeutic potential for the prevention of DN and its mechanism. Specifically, cell proliferation was determined via cell counting kit-8 assay, and the expression levels of TGF-β1 and CTGF mRNA were detected by reverse transcription polymerase chain reaction analysis. Furthermore, the secretion of TGF-β1, CTGF, ColIV and FN proteins was measured via enzyme-linked immunosorbent assays. The results demonstrated that high glucose induced the proliferation of MCs and enhanced the expression of TGF-β1, CTGF, ColIV and FN. Furthermore, treatment with SIT inhibited cell proliferation and the expression of TGF-β1, CTGF, ColIV and FN induced by high glucose. In conclusion, SIT inhibits cell proliferation and the expression of the major extracellular matrix proteins induced by high glucose, indicating its value for treating or relieving DN.

Effects of astragalosides from Radix Astragali on high glucose-induced proliferation and extracellular matrix accumulation in glomerular mesangial cells

Diabetic nephropathy (DN) exhibits a deteriorating course that may lead to end-stage renal failure. Astragalosides have been clinically tested for the treatment of DN, but the mechanism is unclear at present. In this study, the effects of astragalosides were investigated on high glucose-induced proliferation and expression of transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), type IV collagen (colIV) and fibronectin (FN) in glomerular mesangial cells (MCs). Cell proliferation was determined by 5-bromo-2'-deoxyuridine assay, and the expression of TGF-β1, CTGF, colIV and FN mRNA and proteins in MCs was detected by reverse transcription-polymerase chain reaction and ELISA assay, respectively. The results showed that high glucose clearly induced the proliferation of MCs and increased the expression of TGF-β1, CTGF, colIV and FN. Treatment with 50, 100, 200 µg/ml astragalosides inhibited cell proliferation and the expression of TGF-β1, CTGF, colIV and FN induced by high glucose. Thus, it is concluded that astragalosides inhibit the increased cell proliferation and expression of major extracellular matrix proteins that are induced by high glucose, indicating their value for the prophylaxis and therapy of DN.

Impact of intensive treatment on serum methylglyoxal levels among individuals with screen-detected type 2 diabetes: the ADDITION-Denmark study

AIMS

Methylglyoxal (MG) has been implicated in the development of micro- and macrovascular diabetic complications, but it remains unclear how current treatments of type 2 diabetes affect its circulating levels.

METHODS

In the Danish arm of the ADDITION trial, we (a) described serum MG levels at baseline and at 6-year follow-up among individuals with screen-detected type 2 diabetes, (b) examined the effect of intensive multifactorial treatment compared with routine care on MG, (c) examined the associations between MG and risk factors at baseline and at follow-up and (d) examined the associations between changes in MG and changes in risk factors.

RESULTS

Patients in both treatment arms experienced a significant decline in MG from baseline to follow-up, with no effect of allocation to intensive treatment. In cohort analyses, MG was associated with smoking and fasting glucose at baseline and smoking and LDL cholesterol at follow-up. Compared with patients receiving no lipid-lowering treatment, patients receiving lipid-lowering treatment had higher MG at follow-up, and those initiating lipid-lowering treatment experienced a less pronounced decline in MG.

CONCLUSIONS

Further studies are required to explore any possible effects of the observed decrease in MG in type 2 diabetes patients as well as the potential interplay between MG, lipids, lipid-lowering treatment and smoking.

The molecular mechanism of rhein in diabetic nephropathy

Diabetic nephropathy (DN) is characterized by unclear pathogenesis. Recent medical data shows that the incidence of DN rises year by year. Rhein is the main compositions of rhubarb, a traditional Chinese medicinal plant, which plays an active role in kidney protection. The prophylaxis and phytotherapeutic effects of rhein are due to its anti-inflammatory and antifibrosis properties. Here, we shed light on the renal protective role of rhein in diabetes mellitus (DM) with a particular focus on the molecular basis of this effect.

Mitochondria in the pathogenesis of diabetes: a proteomic view

Diabetes mellitus is a complex metabolic disorder characterized by chronic hyperglycemia due to absolute or relative lack of insulin. Though great efforts have been made to investigate the pathogenesis of diabetes, the underlying mechanism behind the development of diabetes and its complications remains unexplored. Cumulative evidence has linked mitochondrial modification to the pathogenesis of diabetes and its complications and they are also observed in various tissues affected by diabetes. Proteomics is an attractive tool for the study of diabetes since it allows researchers to compare normal and diabetic samples by identifying and quantifying the differentially expressed proteins in tissues, cells or organelles. Great progress has already been made in mitochondrial proteomics to elucidate the role of mitochondria in the pathogenesis of diabetes and its complications. Further studies on the changes of mitochondrial protein specifically post-translational modifications during the diabetic state using proteomic tools, would provide more information to better understand diabetes.

Enalapril treatment restores the decreased proximal tubule reabsorption in response to acute volume expansion in diabetic rats

The renin-angiotensin system (RAS) plays an important role in the regulation of blood pressure, fluid and electrolyte homeostasis. The RAS is activated and renal interstitial hydrostatic pressure (RIHP) is decreased in diabetic rats. The objective of this study was to evaluate the roles of proximal tubule reabsorption and RAS in the decreased RIHP and blunted natriuretic and diuretic responses to acute saline volume expansion (VE) in diabetic rats. Enalapril was utilized to inhibit angiotensin II (AII) formation. Diabetes mellitus (DM) was induced by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 65 mg/kg). RIHP was measured by a polyethylene (PE) matrix that was chronically implanted in the left kidney. Fractional excretion of phosphate (FE(Pi)) and fractional excretion of lithium (FE(Li)) were used as indexes for proximal tubule reabsorption. VE significantly increased both FE(Li) and FE(Pi) in all groups of rats studied. However, the increase in FE(Li) (DeltaFE(Li)=17.26+/-3.83%) and FE(Pi) (DeltaFE(Pi)=7.38+/-2.37%) in diabetic rats (DC, n=12) were significantly lower as compared with those in nondiabetic control rats (NC, n=8; DeltaFE(Li)=32.15+/-4.71% and DeltaFE(Pi)=20.62+/-3.27%). The blunted increases in FE(Li) and FE(Pi) were associated with an attenuated increase in RIHP (DeltaRIHP) in DC (1.8+/-0.4 mm Hg) compared with NC rats (4.3+/-0.3 mm Hg). Enalapril treatment (25 mg/kg/day in drinking water) had no effect on nondiabetic rats (NE, n=8) as compared with untreated NC rats, but significantly improved RIHP response (DeltaRIHP) to VE in diabetic rats (DE, n=9; 2.8+/-0.5 mm Hg). Both DeltaFE(Li) and DeltaFE(Pi) were restored by enalapril treatment in diabetic rats and no significant differences were found in DeltaFE(Li) and DeltaFE(Pi) between DE (DeltaFE(Li)=26.81+/-4.94% and DeltaFE(Pi)=10.45+/-4.67%) and NC groups of rats in response to VE. These data suggest that the activated RAS and the decrease in RIHP may play an important role in the increased proximal tubule reabsorption, and the attenuated natriuretic and diuretic responses to acute volume expansion in diabetic rats.

Rhein reverses the diabetic phenotype of mesangial cells over-expressing the glucose transporter (GLUT1) by inhibiting the hexosamine pathway

BACKGROUND AND PURPOSE

Rhein, an anthraquinone compound isolated from rhubarb, has been proved effective in treatment of experimental diabetic nephropathy (DN). To explore the mechanism of its therapeutic effect on DN, rhein was tested for its effect on the hexosamine pathway.

EXPERIMENTAL APPROACH

The influence of rhein on cellular hypertrophy, fibronectin synthesis, glucose uptake, glutamine: fructose 6-phosphate aminotransferase (GFAT) activity, UDP-N-acetylglucosamine (UDP-GlcNAc) level and TGF-beta1 and p21 expression was evaluated in MCGT1 cells, a GLUT1 transgenic rat mesangial cell line. GFAT activity in normal rat mesangial cells in high glucose concentrations and in vitro was also measured.

KEY RESULTS

Significantly increased fibronectin synthesis, cellular hypertrophy, much higher GFAT activity and UDP-GlcNAc level and increased TGF-beta1 and p21 expression were found in MCGT1 cells cultured in normal glucose concentration. Rhein treatment decreased all these features of MCGT1 cells but did not exert a direct effect on GFAT enzymatic activity.

CONCLUSIONS AND IMPLICATIONS

There was over-activity of the hexosamine pathway in MCGT1 cells, which may explain the higher expression of TGF-beta1 and p21, the cellular hypertrophy and the increased expression of extracellular matrix (ECM) components in the cells. By inhibiting the increased activity the hexosamine pathway, rhein decreased TGF-beta1 and p21 expression and thus contributed to the decreased cellular hypertrophy and ECM synthesis. Inhibition of the hexosamine pathway may be one of the mechanism through which rhein exerts its therapeutic role in diabetic nephropathy.

Microalbuminuria among Type 1 and Type 2 diabetic patients of African origin in Dar Es Salaam, Tanzania

Background

The prevalences and risk factors of microalbuminuria are not full described among black African diabetic patients. This study aimed at determining the prevalence of microalbuminuria among African diabetes patients in Dar es Salaam, Tanzania, and relate to socio-demographic features as well as clinical parameters.

Methods

Cross sectional study on 91 Type 1 and 153 Type 2 diabetic patients. Two overnight urine samples per patient were analysed. Albumin concentration was measured by an automated immunoturbidity assay. Average albumin excretion rate (AER) was used and were categorised as normalbuminuria (AER < 20 ug/min), microalbuminuria (AER 20–200 ug/min), and macroalbuminuria (AER > 200 ug/min). Information obtained also included age, diabetes duration, sex, body mass index, blood pressure, serum total cholesterol, high-density and low-density lipoprotein cholesterol, triglycerides, serum creatinine, and glycated hemoglobin A_1c.

Results

Overall prevalence of microalbuminuria was 10.7% and macroalbuminuria 4.9%. In Type 1 patients microalbuminuria was 12% and macroalbuminuria 1%. Among Type 2 patients, 9.8% had microalbuminuria, and 7.2% had macroalbuminuria. Type 2 patients with abnormal albumin excretion rate had significantly longer diabetes duration 7.5 (0.2–24 yrs) than those with normal albumin excretion rate 3 (0–25 yrs), p < 0.001. Systolic and diastolic blood pressure among Type 2 patients with abnormal albumin excretion rate were significantly higher than in those with normal albumin excretion rate, (p < 0.001).

No significant differences in body mass index, glycaemic control, and cholesterol levels was found among patients with normal compared with those with elevated albumin excretion rate either in Type 1 or Type 2 patients.

A stepwise multiple linear regression analysis among Type 2 patients, revealed AER (natural log AER) as the dependent variable to be predicted by [odds ratio (95% confidence interval)] diabetes duration 0.090 (0.049, 0.131), p < 0.0001, systolic blood pressure 0.012 (0.003–0.021), p < 0.010 and serum creatinine 0.021 (0.012, 0.030).

Conclusion

The prevalence of micro and macroalbuminuria is higher among African Type 1 patients with relatively short diabetes duration compared with prevalences among Caucasians. In Type 2 patients, the prevalence is in accordance with findings in Caucasians. The present study detects, however, a much lower prevalence than previously demonstrated in studies from sub-Saharan Africa. Abnormal AER was significantly related to diabetes duration and systolic blood pressure.

Differential expression of proteins in kidney, eye, aorta, and serum of diabetic and non-diabetic rats

Diabetes mellitus (DM) is a chronic progressive disease that often results in microvascular and macrovascular complications, yet its pathogenesis is not clear. Automated proteomic technology, coupled with powerful bioinformatics and statistical tools, can provide new insights into the molecular alterations implicated in DM. Following our previous findings of redox changes in the eye and aorta of diabetic rats, as well as the activities of different antioxidant enzymes during the development of DM, this study is further launched to find potential biomarkers by comparing the serum and tissue samples of 26 diabetic rats (8 weeks after streptozotocin [STZ] administration) with 29 normal controls using surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) technology. Eight potential biomarkers were found in the serum, one potential biomarker was found in the kidney and eye, respectively, whereas three potential biomarkers were discovered in the aorta. One of the serum biomarker candidates was found to match the C-reactive protein (CRP) in the Swiss-Prot knowledgebase. Further validation has been conducted by ELISA kit to confirm the role of CRP during the development of DM. To conclude, the increased level of CRP in diabetic serum demonstrated in this study indicates that the development of DM is associated with inflammation. This is also the first report demonstrating that some potential lysate biomarkers in the kidney, eye, and aorta may be involved in the development of diabetes and its complications. Further identification and evaluation of these potential biomarkers will help unravel the underlying mechanisms of the disease.

Glucose and diabetes: effects on podocyte and glomerular p38MAPK, heat shock protein 25, and actin cytoskeleton

Phosphorylated p38 (pp38) mitogen-activated protein kinase (MAPK) regulates heat shock protein 25 (HSP25), stabilizing fibrillar actin (FA) and preventing cleavage to G-actin (GA). Cultured podocytes (Pods) were exposed to glucose (5.5-50 mM)+/-p38MAPK inhibitor SB202190 (SB) or control SB202474 to assess the effects on FA/GA and Pod structure. The relationship of p38MAPK with in vivo Pod structure and albuminuria (Ualb) was assessed in rats with streptozotocin (SZ)-induced diabetes (DM) for 1 week, 1 month, and 4 months. High glucose induced concentration-dependent increases in pp38MAPK and phosphorylated HSP25 (pHSP25) maintained actin cytoskeleton. Inhibition by SB diminished pp38MAPK and pHSP25, decreased FA/GA, and altered FA and GA immunohistochemical appearance. In SZ-DM, glomerular pp38MAPK and biphosphorylated HSP25 were increased after 1 week, declining at 1 month, and at or below C values at 4 months. Glomerular FA/GA in DM was normal at 1 week, declining at 1 month, and low at 4 months. Ualb/creatinine was similar in DM vs C at 1 week, and increased at 1 and 4 months. Morphometry demonstrated progressively diminishing slit pore density in DM over time, denoting evolving effacement. There were strong correlations between slit membrane density and both glomerular biphosphorylated HSP25 and ln Ualb/cr ratio. The data suggest that increased pp38MAPK and pHSP25 comprise an acute adaptation to glycemic stress. Later depletion of DM may contribute to Pod structural alterations and Ualb.

High Ambient Glucose Levels Modulates the Production of MMP-9 and a5(IV) Collagen by Cultured Podocytes

Recent evidences have demonstrated an important role for glomerular visceral epithelial cell (podocyte) in the development and progression of diabetic nephropathy. We investigated the high-glucose (HG)-triggered signaling pathway and its role in matrix metalloproteinase (MMP) production in murine podocytes. The activity of 92-kDa (MMP-9) gelatinase, but not of 72 kDa (MMP-2), in an HG medium significantly increased during incubation of 2 to 3 days and decreased during incubation of more than 5 days revealed by Gelatin zymography. Opposite to the increases in MMP-9 activity, HG medium produced significant decreases in the protein levels of alpha5(IV) collagen. Changes in MMP-9 activity were associated with the same pattern as MMP-9 mRNA levels in podocytes exposed to HG media. HG medium rapidly activated ERK1/2 MAPK in podocytes. Moreover, ERK1/2 activation was required for HG-induced enhancement of MMP-9 activity and a decrease in the level of alpha5(IV) collagen. HG incubation rapidly induced an increase in the nuclear accumulation of Ets-1 protein. Blocking the ERK pathway suppressed HG-induced expression and nuclear accumulation of transcriptional factor Ets-1, and MMP-9 mRNA expression. We suggest that short- or long-term exposure to HG concentrations increases or decreases MMP-9 production and alpha5(IV) collagen expression in podocytes, this may contribute to the GBM abnormality caused by an imbalance in extracellular matrix (ECM) synthesis and degradation, and may play a critical role in the pathogenesis of proteinuria in diabetic nephropathy.

The CREB coactivator TORC2 is a key regulator of fasting glucose metabolism

Glucose homeostasis is regulated systemically by hormones such as insulin and glucagon, and at the cellular level by energy status. Glucagon enhances glucose output from the liver during fasting by stimulating the transcription of gluconeogenic genes via the cyclic AMP-inducible factor CREB (CRE binding protein). When cellular ATP levels are low, however, the energy-sensing kinase AMPK inhibits hepatic gluconeogenesis through an unknown mechanism. Here we show that hormonal and energy-sensing pathways converge on the coactivator TORC2 (transducer of regulated CREB activity 2) to modulate glucose output. Sequestered in the cytoplasm under feeding conditions, TORC2 is dephosphorylated and transported to the nucleus where it enhances CREB-dependent transcription in response to fasting stimuli. Conversely, signals that activate AMPK attenuate the gluconeogenic programme by promoting TORC2 phosphorylation and blocking its nuclear accumulation. Individuals with type 2 diabetes often exhibit fasting hyperglycaemia due to elevated gluconeogenesis; compounds that enhance TORC2 phosphorylation may offer therapeutic benefits in this setting.

Diabetes and hypertension: pathogenesis, prevention and treatment

Hypertension occurs in approximately 30% of patients with type 1 diabetes and from 50 to 80% of patients with type 2 diabetes. Although the pathogenesis of hypertension is distinct in each type, hypertension markedly enhances the already high risk of cardiovascular and renal disease in types 1 and 2 and implications for treatment are similar in both. The threshold for blood pressure treatment in diabetic patients is generally agreed to be 140/90 mm/hg with a target BP of < 130/80. So-called "lifestyle modifications" play an important role in therapy, particularly in type 2 patients, by decreasing blood pressure and improving other risk factors for cardiovascular disease. Indeed non-pharmacologic interventions have been demonstrated to prevent the development of type 2 diabetes in patients at high risk to develop the disease. Aggressive anti-hypertensive drug treatment is warranted given the high risk associated with the combination of diabetes and hypertension and the demonstrated effectiveness of anti-hypertensive treatment in reducing cardiovascular morbidity and mortality in this group of patients. ACE inhibitors and ARBs are the cornerstones of pharmacologic management, in no small part because of the renoprotective effects of these agents in antagonizing the development and progression of diabetic renal disease. Multiple agents, including diuretics, will usually be required to attain target blood pressure levels.

Diabetes care in remote northern Australian Indigenous communities

OBJECTIVE

To assess primary care processes and clinical characteristics of adults with diabetes in remote northern Australian Indigenous communities.

DESIGN

Clinical audit from diabetes registers in 21 remote primary healthcare centres in the Torres Strait Health Service District (n = 921), three in Cape York, Queensland (n = 252), and three in the Northern Territory (n = 194), between September 2002 and February 2003.

PARTICIPANTS AND SETTING

Aboriginal and Torres Strait Islander adults with diabetes who were receiving their routine diabetes care in these 27 centres.

MAIN OUTCOME MEASURES

Provision of regular checks for weight, blood pressure, glycaemia (HbA(1c)), proteinuria, lipid levels, renal function, eyes and feet, influenza and pneumococcal vaccination. Weight, blood pressure and glycaemic control.

RESULTS

Most routine diabetes checks were delivered according to recommended schedules, except for eye and foot checks in the NT. There were uniformly high rates of appropriate treatment for hypertension and albuminuria, but low rates of insulin treatment and self-monitoring despite a high mean HbA(1c) level (8.9%). Vaccination rates were low in the NT. Torres Strait Islanders with diabetes were significantly heavier than Aboriginals, but had lower mean diastolic blood pressure (77.3 mmHg compared with 79.5 mmHg) and lower prevalence of albuminuria and smoking.

CONCLUSION

A high proportion of Aboriginals and Torres Strait Islanders requiring treatment for high blood pressure and proteinuria are receiving it. However, there is dissonance between the relatively high rates of routine checks and apparent lack of therapeutic action on glycaemia. More intensive management of glycaemia, including improved nutrition, exercise and (probably) insulin, is required to reduce microvascular complications.

Effects of insulin on renal interstitial hydrostatic pressure and natriuretic response to volume expansion in diabetic rats

Diabetes mellitus (DM) is characterized by alterations in fluid balance and blood volume homeostasis. Renal interstitial hydrostatic pressure (RIHP) has been shown to play a critical role in mediating sodium and water excretion under various conditions. The objective of this study was to determine the effects of immediate and delayed initiation of insulin treatment on the restoration of the relationship between RIHP, natriuretic, and diuretic responses to acute saline volume expansion (VE) in diabetic rats. Diabetes was induced by an intraperitoneal injection of streptozotocin (STZ; 65 mg/kg body wt). Four groups of female Sprague-Dawley rats were studied: normal control group (C), untreated diabetic group (D), immediate insulin-treated diabetic group (DI; treatment with insulin for 2 wk was initiated immediately when diabetes was confirmed, which was 2 days after STZ injection), and delayed insulin-treated diabetic group (DDI; treatment with insulin for 2 wk was initiated 2 wk after STZ injection). RIHP and sodium and water excretions were measured before and during VE (5% body wt/30 min) in the four groups of anesthetized rats. VE significantly increased RIHP, fractional excretion of sodium (FENa), and urine flow rate (V) in all groups of rats. Basal RIHP, RIHP response to VE (ΔRIHP), and FENa and V responses to VE (ΔFENa and ΔV) were significantly lower in the D group compared with the C group of rats. ΔRIHP was significantly higher in both DI and DDI groups compared with D group but was similar to that of the C group of rats. While in the DI group the ΔFENa response to VE was restored, ΔFENa was significantly increased in DDI compared with D group, but it remained lower than that of the C group. In conclusion, insulin treatment initiated immediately after the onset of diabetes restores basal RIHP and RIHP, natriuretic, and diuretic responses to VE; however, delayed insulin treatment restores the basal RIHP and RIHP response to VE but does not fully restore the natriuretic response to VE.

A novel potential therapy for diabetic nephropathy and vascular complications: protein kinase C beta inhibition

Diabetic nephropathy is one of the most common microvascular complications of diabetes mellitus and the leading cause of end-stage renal disease in developed countries. Current treatment includes glycemic control, blood pressure control (with special emphasis on agents targeting the renin-angiotensin system), a low-protein (0.6 to 0.8 g/kg) diet, and the use of hypolipidemic agents. Although these therapeutic options may slow progression, the burden of disease remains large, and additional therapeutic agents are urgently needed. Ruboxistaurin (LY333531) mesylate is a bisindolylmaleimide that shows a high degree of specificity within the protein kinase C (PKC) gene family for inhibiting PKC beta isoforms. In animal models of diabetes, including the streptozotocin (STZ) rat, Lepr(db)/Lepr(db) mouse, and STZ-Ren 2 rat models, ruboxistaurin normalized glomerular hyperfiltration, decreased urinary albumin excretion, and reduced glomerular transforming growth factor-beta1 and extracellular matrix protein production. As a result, improvements were noted in mesangial expansion, glomerulosclerosis, tubulointerstitial fibrosis, and renal function. Other studies using less specific probes of PKC activity also have shown an important role for PKC in the development of diabetic nephropathy and a close relationship to pathways believed to be important in its pathogenesis. Inhibition of PKC beta, a common signaling molecule in diabetes-related renal and vascular injury, holds promise as a novel strategy to improve microvascular and macrovascular outcomes in diabetes. Such therapies are needed to reduce the occurrence of devastating diabetic complications.