Diabetic renal disease in type 1 diabetes: aetiology and prevention

Urinary liver-type fatty acid binding protein is an independent predictor of stroke and mortality in individuals with type 1 diabetes

AIMS/HYPOTHESIS

In type 1 diabetes, cardiovascular disease (CVD) and diabetic nephropathy progress in parallel, thereby potentiating the risk of premature death during their development. Since urinary liver-type fatty acid binding protein (L-FABP) predicts the progression of diabetic nephropathy, the aim of this study was to investigate whether urinary L-FABP also predicts cardiovascular outcomes and mortality.

METHODS

We tested our hypothesis in a Finnish cohort of 2329 individuals with type 1 diabetes and a median follow-up of 14.1 years. The L-FABP to creatinine ratio was determined from baseline urine samples. The predictive value of urinary L-FABP was evaluated using Cox regression models, while its added predictive benefit for cardiovascular outcomes and mortality was evaluated using a panel of statistical indexes.

RESULTS

Urinary L-FABP predicted incident stroke independently of traditional risk factors (HR 1.33 [95% CI 1.20, 1.49]) and after further adjustment for eGFR (HR 1.28 [95% CI 1.14, 1.44]) or AER (HR 1.24 [95% CI 1.06, 1.44]). In addition, it predicted mortality independently of traditional risk factors (HR 1.34 [95% CI 1.24, 1.45]), and after adjustment for eGFR (HR 1.29 [95% CI 1.18, 1.39]) or AER (HR 1.22 [95% CI 1.09, 1.36]). Urinary L-FABP was as good a predictor as eGFR or AER, and improved the AUC for both outcomes on top of traditional risk factors, with no reclassification benefit (integrated discrimination improvement/net reclassification improvement) for stroke or mortality when AER or eGFR were added to traditional risk factors. However, urinary L-FABP was not a predictor of other cardiovascular endpoints (coronary artery disease, peripheral vascular disease and overall CVD events) when adjusted for the AER.

CONCLUSIONS/INTERPRETATION

Urinary L-FABP is an independent predictor of stroke and mortality in individuals with type 1 diabetes.

No detrimental effect on renal function during long-term use of fluvastatin in renal transplant recipients in the Assessment of Lescol in Renal Transplantation (ALERT) study

BACKGROUND

Concerns have recently been raised regarding a potential harmful effect of statins on renal function. This study investigated the effect of fluvastatin treatment on renal function in renal transplant recipients enrolled in the Assessment of Lescol in Renal Transplantation (ALERT) trial.

METHODS

ALERT was a randomized, double-blind, placebo-controlled study of the effect of fluvastatin, 40-80 mg daily (n = 1050) or placebo (n = 1052) on cardiac and renal outcomes in renal transplant recipients over a follow-up period of five to six years. The incidence of graft loss, changes in serum creatinine, calculated creatinine clearance and proteinuria, and the incidence of renal adverse events (AEs) were assessed in both treatment groups.

RESULTS

Fluvastatin treatment in ALERT had no significant effect compared with placebo on renal function, assessed by serum creatinine (overall adjusted mean +/- SEM: fluvastatin, 175.4 +/- 2.20 micromol/L; placebo, 172.7 +/- 2.20 micromol/L; p = 0.39), creatinine clearance (fluvastatin, 55.3 +/- 0.30 mL/min; placebo, 55.8 +/- 0.30 mL/min; p = 0.26) or proteinuria (fluvastatin, 0.58 +/- 0.03 g/24 h; placebo, 0.53 +/- 0.03 g/24 h; p = 0.31). There were no significant differences between treatment groups when the 283 patients suffering graft loss were excluded from the analysis. Fluvastatin also had no detrimental effect on creatinine clearance or proteinuria in the subgroup of 340 diabetic patients without graft loss in ALERT. No notable differences in the rate of renal or musculoskeletal AEs were observed between fluvastatin and placebo groups.

CONCLUSIONS

Fluvastatin had no detrimental effect on renal function, or the risk of renal AEs, in renal transplant recipients with or without diabetes enrolled in ALERT. Fluvastatin treatment for the prevention of cardiac events may therefore be used without fear of jeopardizing renal function.

Diabetes causes inhibition of glucose-6-phosphate dehydrogenase via activation of PKA, which contributes to oxidative stress in rat kidney cortex

The incidence of diabetic nephropathy has been increasing. Studies have shown that oxidative stress (due to increased oxidant production and/or decreased antioxidant activity) is a critical underlying mechanism. The principal intracellular reductant is NADPH whose production is mainly dependent on glucose-6-phosphate dehydrogenase (G6PD) activity. Our work in cultured cells previously showed that high glucose caused activation of protein kinase A (PKA) and subsequent phosphorylation and inhibition of G6PD activity and hence decreased NADPH (Zhang Z, Apse K, Pang J, and Stanton RC. J Biol Chem 275:40042-40047, 2000). The purpose of this study was to determine whether these findings occur in diabetic rats (induced by streptozotocin) compared with control. G6PD activity and accordingly NADPH levels and glutathione levels were significantly decreased in diabetic kidneys compared with control kidneys. Lipid peroxidation was significantly increased, which correlated with decreased G6PD activity (r = 0.48). G6PD expression was significantly reduced, which correlated with decreased G6PD activity (r = 0.72). PKA activity and serine phosphorylation of G6PD were significantly increased and were closely correlated with decreased G6PD activity (r = 0.51 for PKA activity; r = 0.93 for serine phosphorylation of G6PD). Insulin treatment and/or correction of hyperglycemia ameliorated the changes caused by diabetes. In conclusion, chronic hyperglycemia caused inhibition of G6PD activity via decreased expression and increased phosphorylation of G6PD, which therefore led to increased oxidative stress.

Glomerular hyperfiltration increases the risk of developing microalbuminuria in diabetic children

An elevated glomerular filtration rate (GFR) is frequently detectable in type 1 diabetic children and adolescents and in those without any other evidence of incipient diabetic nephropathy. In 1982 we detected 23 patients with hyperfiltration (GFR > 140 ml/min per 1.73 m2), aged 9-15 years, with diabetes for longer than 4 years; 23 age- and sex-matched patients with diabetes of a similar duration and without hyperfiltration served as controls. Both groups were followed until March 1992, by assessing GFR every 12 months, albumin excretion rate every 6 months, blood pressure and glycated haemoglobin (HbA1) every 3 months. Dietary protein intake was similar in patients with hyperfiltration and in controls. No other drug except insulin was used throughout the study. The insulin regimen was similar in the two groups. There was no significant difference between the two groups regarding albumin excretion, blood pressure and HbA1 at the beginning of the study. Of the 23 patients with hyperfiltration, 7 developed persistent microalbuminuria (defined as an overnight albumin excretion rate > 30 micrograms/min per 1.73 m2 on at least 5 consecutive measurements); 2 of these patients had overt proteinuria. Only 1 of the diabetics with normal GFR developed persistent microalbuminuria. The positive predictive value for microalbuminuria of an initial GFR > 140 ml/min per 1.73 m2 was 63%; the negative predictive value of an initial GFR < 140 ml/min per 1.73 m2 was 94%. The increase of albumin excretion rate into the microalbuminuric range precedes the elevation of both systolic and diastolic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous subcutaneous insulin infusion (CSII) in children and adolescents with chronic poorly controlled type 1 diabetes mellitus

This study was undertaken to determine if continuous subcutaneous insulin infusion (CSII) could improve control, diminish episodes of diabetic ketoacidosis (DKA), decrease number of hospitalizations and save health care expenditure in children and adolescents with long-standing poorly controlled diabetes mellitus. A retrospective analysis was done of six patients with type 1 diabetes for 1-8 years, of whom 4 were non-adherent to the diabetic regimen (ages 12-16.5 years) and 2 of whom had brittle diabetes (ages 8.5 and 10 years). These patients were non-randomly placed on the MiniMed (Sylmar, CA) CSII system. The year prior to CSII was compared with the year during pump use. Glycoslyated hemoglobin (HbA1c), spot urinary microalbumin, total cholesterol, insulin dose, growth velocity, number of convulsions and hypoglycemic events, number of episodes of DKA, number of hospitalizations and total inpatient costs were compared for the 2 years. The year prior to CSII, mean HbA1c was 9.02% (S.D. = 0.86%), mean number of hospitalizations was 5.2/patient (S.D. = 4.6), mean number of hospital days was 20.8/patient (S.D. = 14.7) and mean cost was $29330/patient (S.D. = $22804). During 1 year of CSII, mean number of hospital days decreased to 5 days/patient (S.D. = 0.8, P = 0.016), mean number of hospitalizations (including DKA and pump initiation) decreased to 1.7/patient (S.D. = 0.7, P = 0.31), mean inpatient costs decreased to $12762/patient (S.D. = $5.950, P = 0.047). HbA1c, urinary microalbumin, cholesterol, insulin dose and growth velocity did not change in a statistically significant manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria in young Sudanese patients with type 1 diabetes

Overnight urinary albumin excretion (UAE) was measured in 51 patients, nine to 18 years old, with type 1 (insulin-dependent) diabetes mellitus and in 22 healthy subjects using radioimmunoassay. Thirteen diabetic patients (25.5%) had microalbuminuria defined as UAE rate between 20 and 200 microg/min. Eleven of these patients were over 13 years of age. This gives a frequency of microalbuminuria of 42% (11/26) in the diabetic children and adolescents in the age group 14-18 years. UAE rate was positively correlated with both age at diagnosis and duration of diabetes. Arterial blood pressure, systolic and diastolic, glycosylated hemoglobin (HbA1c) and insulin dosage U.kg- 1.day-1 were significantly higher (P<0.001) in the diabetic patients with microalbuminuria compared to the diabetic patients with normal UAE rate. Retinal changes were also more common in the microalbuminuric diabetic patients than in the diabetic patients without microalbuminuria (P<0.01). This study has revealed a high prevalence of microalbuminuria in young Sudanese patients with type 1 (insulin-dependent) diabetes mellitus and emphasized the importance of routine screening of diabetic children after the age of 12 years.