The impact of metabolic and blood pressure control on incidence and progression of nephropathy. A 10-year study of 385 type 2 diabetic patients

Sex-Related Aspects in Diabetic Kidney Disease-An Update

Differences between the sexes exist in many diseases, and in most cases, being a specific sex is considered a risk factor in the development and/or progression. This is not quite so clear in diabetic kidney disease (DKD), the development and severity of which depends on many general factors, such as the duration of diabetes mellitus, glycemic control, and biological risk factors. Similarly, sex-specific factors, such as puberty or andro-/menopause, also determine the microvascular complications in both the male and female sex. In particular, the fact that diabetes mellitus itself influences sex hormone levels, which in turn seem to be involved in renal pathophysiology, highlights the complexity of the question of sex differences in DKD. The major objective of this review is to summarize and simplify the current knowledge on biological sex-related aspects in the development/progression but also treatment strategies of human DKD. It also highlights findings from basic preclinical research that may provide explanations for these differences.

Interaction effect of blood glucose and pressure on the risk of chronic kidney disease: a population-based prospective cohort study

OBJECTIVE

To evaluate the interaction effect of blood glucose and blood pressure on the risk of chronic kidney disease (CKD).

METHODS

31,165 subjects were selected without CKD at baseline and had completed the first follow-up from "Jinchang cohort". Cox regression model and restricted cubic splines functions were used to evaluate the effects of blood glucose or pressure on the incidence of CKD and dose-response relationship after adjusting for confounding covariates. Synergic effect was assessed by the multiplicative or additive interaction scale.

RESULTS

Among 31,165 subjects, 1307 new-onset CKD were observed during 68905.78 person-years follow-up, and the incidence density was 18.97 per 1000 person-years. The risk of CKD gradually increased with the increase of blood pressure in diabetes, pre-diabetes and normal groups (P_trend < 0.05). And, the risk was greatest when SBP/DBP reached ≥150/≥110 mmHg in three groups, and HRs (95% CI) were 1.610 (1.070-2.422), 2.142 (1.396-3.288) and 2.455 (1.941-3.106), respectively. Additionally, among hypertension, pre-hypertension and normal groups, the risk of CKD increased by 16.0%, 14.3% and 25.2% for each 1 mmol/L of FPG. When FPG level was more than 9.0 mmol/L, the risk was greatest and adjusted HRs (95% CI) were 2.856 (2.176-3.748), 2.979 (1.828-4.854) and 7.520 (4.517-12.519). Furthermore, the risk was highest when hypertension was accompanied by diabetes (HR = 4.915, 95% CI: 3.923-6.157). This analysis supported a less than multiplicative effect (HR = 0.634, 95% CI: 0.417-0.964) for the interaction term of diabetes and hypertension, while there was no additive interaction towards CKD in all interaction term.

CONCLUSIONS

Blood glucose and pressure were independent risk factors in incidence of CKD, but there was only a negative multiplicative interaction between hypertension and diabetes, but no additive interaction effect between them.

Influence of Sex on the Progression of Chronic Kidney Disease

The role that sex plays in the development and progression of chronic kidney disease remains a subject of controversy. The lack of clarity in this important area reflects complex interactions between biological factors and cultural and socioeconomic influences that impact the relationship between sex and renal disease. Certainly, additional observational studies are indicated; however, innovative approaches are required to isolate biological processes from cultural influences. Despite these limitations, available data suggest that the progression of renal disease is slower in women than in men and that this sexual dimorphism is primarily due to direct actions of sex hormones on cellular metabolism. The extent to which differences in lifestyle factors between the sexes influence sexual dimorphism in the progression of chronic kidney disease remains to be elucidated.

Estrogens do not protect, but androgens exacerbate, collagen accumulation in the female mouse kidney after ureteric obstruction

AIMS

Controversy surrounds the gender basis of progression in chronic kidney disease. Unfortunately, most experimental studies addressing this question do not distinguish between direct effects of estrogen and indirect activation of estrogen receptors through conversion of testosterone to 17β-estradiol by aromatase. We examined the pathogenesis of renal fibrosis in female aromatase knockout (ArKO) mice, which lack circulating and stored estrogens, while having normal levels of testosterone.

MAIN METHODS

ArKO mice and their wild-type (ArWT) counterparts were subjected to unilateral ureteric obstruction (UUO), with kidney tissue collected at day(D) 0, 3 and 9 post-UUO. Effects of 5α-dihydrotestosterone (DHT) administration on each genotype were also studied. Tissue was assessed biochemically and histochemically for fibrosis. Western blot analysis was used to measure α-smooth muscle actin (α-SMA) expression and TGF-β1 signalling. Matrix metalloproteinase-2 (MMP-2) activity was measured by zymography.

KEY FINDINGS

UUO increased collagen content over time (p<0.05 (D3) and p<0.01 (D9) vs day 0), with no difference between genotypes in qualitative (collagen IV staining) and quantitative (hydroxyproline concentration) analyses. Systemic administration of non-aromatizable DHT increased collagen content after 3days of UUO in both genotypes. This was not paralleled by any change in α-SMA (myofibroblast burden) or TGF-β1 signalling but was commensurate with DHT reducing MMP2 activity in both genotypes (p<0.05 vs genotype controls).

SIGNIFICANCE

Physiological concentrations of estrogens do not protect the injured kidney from fibrosis progression. Androgens rather than estrogens are the relevant factor involved in regulating disease-related renal scarring in this model.

Risk factors for perioperative complications in hand-assisted laparoscopic donor nephrectomy

Living donor kidney transplant is the preferred treatment for end-stage renal disease; however, the shortage of kidney donors remains a big problem. One of the major reasons for the shortage of living donors is the risk of potentially serious surgical complications of a procedure in which the donor has no personal medical benefit. Therefore it is important to understand the risk factors for perioperative complications associated with donor nephrectomy. Hand-assisted laparoscopic donor nephrectomy is the preferred approach for kidney procurement in many medical centers. This review gives an overview of the risk factors in donor nephrectomy and more specifically in hand-assisted laparoscopic donor nephrectomy.

Sex differences in hypertension-related renal and cardiovascular diseases in Italy: the I-DEMAND study

AIM

The aim of this study is to evaluate the differences in the prevalence of chronic kidney disease (CKD) and of cardiovascular risk factors and diseases between men and women participating in the Italy Developing Education and awareness on MicroAlbuminuria in patients with hyperteNsive Disease (I-DEMAND) study.

METHODS

This is an observational, cross-sectional, multicenter study aimed at assessing prevalence and correlates of CKD among Italian hypertensive patients attending out-patient referral clinics. CKD was defined as glomerular filtration rate (GFR) less than 60 ml/min per 1.73 m(2) [Modification of Diet in Renal Disease (MDRD) study equation and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation] and/or urine albumin-to-creatinine ratio of at least 2.5 mg/mmol in men and of at least 3.5 mg/mmol in women or both. Left-ventricular hypertrophy (LVH) was diagnosed by either ECG or echocardiography.

RESULTS

A total of 3558 study patients with renal data available were considered for this analysis: mean age was 61 ± 4 years and 37% had diabetes mellitus. Female patients (n = 1636, 46%) were older, with a greater prevalence of obesity and lower prevalence of smoking. The prevalence of concomitant coronary artery and peripheral artery diseases, but not of hypertension, diabetes mellitus, or heart failure, was lower in women than in men. The overall prevalence of albuminuria (21 vs. 32%; P = 0.001) and of microalbuminuria (16 vs. 23%; P = 0.001) was lower in women than in men. In women the prevalence of a reduced GFR estimated by both MDRD (33 vs. 21%; P = 0.001) and CKD-EPI equations (32 vs. 23%; P = 0.001) was higher than in men. CKD prevalence was similar in women and men (44 vs. 41%; P = 0.095 and 43 vs. 43%; P = 0.475, respectively, when MDRD and CKD-EPI eGFR estimations were used). The prevalence of LVH (diagnosed by either ECG or echocardiography) was similar in men and women (18 vs. 20%; P = 0.12).The main independent determinants of CKD were age, glycemia, uricemia, pulse pressure, hypertension duration, and previous cardiovascular diseases in men, and increasing age, glycemia, uricemia, pulse pressure, and a lower BMI in women.

CONCLUSION

Renal abnormalities are present in a significant number of female hypertensive patients attending hypertension clinics. Prevalence of reduced eGFR and of microalbuminuria, associated risk factors, and clinical conditions are different between men and women, suggesting the need to develop specific therapeutic strategies to prevent renal dysfunction and reduce associated morbidity and mortality.

Tamm-Horsfall protein gene is associated with distal tubular dysfunction in patients with type 1 diabetes

OBJECTIVE

The first changes in the diabetic kidney are glycogen deposits in the epithelial cells of the thick ascending limb of Henle, which leads to decreased production of Tamm-Horsfall protein (THP). The production of THP is also influenced by nitric oxide (NO). The aims of this study were to investigate whether low excretion of THP, a sign of distal tubular dysfunction, in patients with type 1 diabetes was associated with polymorphisms in the THP gene and the endothelial NO synthase (eNOS) gene.

MATERIAL AND METHODS

Urine was collected from 301 patients with type 1 diabetes, 164 with normoalbuminuria, 91 with microalbuminuria and 46 with macroalbuminuria. Urinary THP concentration below median (3.12 mg/l) was defined as tubular dysfunction. Representative polymorphisms were analysed in the THP and eNOS genes.

RESULTS

Patients with tubular dysfunction had longer diabetes duration and higher blood pressure than patients without tubular dysfunction. Tubular dysfunction was common in patients with macroalbuminuria (70% of patients) and it was associated with the AA+AT genotypes of rs12444268 in the THP gene [odds ratio (OR) 1.8, 95% confidence interval (CI) 1.1-2.8], and the GG genotype of rs1799983 in the eNOS gene (OR 1.6, 95% CI 1.03-2.6). When adjusting for other associated factors, diabetes duration, glycosylated haemoglobin (HbA(1c)), mean arterial pressure and albuminuria, the THP rs12444268 and macroalbuminuria were independently associated with tubular dysfunction.

CONCLUSION

Distal tubular dysfunction was associated with the THP gene and macroalbuminuria in patients with type 1 diabetes.

Decreased urinary concentration of Tamm-Horsfall protein is associated with development of renal failure and cardiovascular death within 20 years in type 1 but not in type 2 diabetic patients

OBJECTIVE

The first changes in the diabetic kidney are glycogen deposits in the epithelial cells of the thick ascending limb of Henle. These cells produce Tamm-Horsfall protein (THP). Is low excretion of THP associated with the development of renal insufficiency or cardiovascular disease?

MATERIAL AND METHODS

Urine samples were collected at baseline in patients with type 1 (n = 131) and type 2 (n = 108) diabetes who were followed for a mean of 14 years (range 1-20 years) and 4.5 years (range 1-15 years), respectively.

RESULTS

Twenty percent of type 1 and 54% of type 2 diabetic patients died and 24% and 29%, respectively developed uraemia. A decreased urinary concentration of THP (u-THP) was associated with an eight-fold increased risk of renal failure and cardiovascular death in type 1 but not in type 2 diabetic patients, irrespective of the degree of albuminuria and glycosylated haemoglobin and blood pressure levels. There were no differences in the degrees of albuminuria, serum creatinine or u-THP between the two types of diabetic patients at baseline. Low u-THP occurred in 8% and 9% of normoalbuminuric type 1 and type 2 diabetic patients, respectively.

CONCLUSION

A decreased u-THP was associated with an eight-fold increased risk of cardiovascular death and uraemia in type 1 but not in type 2 diabetic patients.

Low-protein diet for diabetic nephropathy: a meta-analysis of randomized controlled trials

BACKGROUND

A low-protein diet (LPD) has been proposed for many years to delay the progression of diabetic nephropathy. However, the efficacy of an LPD with respect to renal outcome is disputed.

OBJECTIVE

We aimed to determine the effect of an LPD on renal function in patients with type 1 or 2 diabetic renal diseases by using a meta-analysis of randomized controlled trials.

DESIGN

Medline, EMBASE, and the Cochrane Central Register of Controlled Trials were searched. Eight studies met the inclusion criteria for our meta-analysis: a duration of >6 mo, use of a randomized control group, availability of outcome data for changes in glomerular filtration rate (GFR) or creatinine clearance rate (CCR), and albuminuria or proteinuria in patients with type 1 or 2 diabetic nephropathy. Data were combined by means of a fixed-effects model. Weighted mean differences (WMD) were calculated for the change in GFR or CCR, glycated hemoglobin (HbA(1c)), and serum albumin between the LPD and control groups. A random-effects model was also used to calculate the standardized mean difference for the change in urinary albumin excretion or proteinuria.

RESULTS

Overall, a change in WMD for GFR or CCR was not significantly associated with an LPD, but a decrease in WMD for HbA(1c) was significant in the LPD group (P = 0.005). Although the benefit of LPD therapy on proteinuria was significant (P = 0.003), great heterogeneity was observed. In a subgroup analysis, LPD resulted in lower serum albumin concentrations.

CONCLUSION

LPD was not associated with a significant improvement of renal function in patients with either types 1 or 2 diabetic nephropathy.

Gender and human chronic renal disease

BACKGROUND

Gender affects the incidence, prevalence, and progression of renal disease. In animal models of the disease, female sex appears to modify the course of progression. Hormonal manipulation by male or female castration also changes the course of renal disease progression, suggesting direct effects of sex hormones in influencing the course of these maladies.

OBJECTIVE

This review examines the pertinent animal and human studies assessing the role of gender, and strives to shed light on the possible physiologic mechanisms underlying the effect of gender, on renal disease progression.

METHODS

A summary and evaluation of past and recent studies describing the rate of renal disease progression in animal models and humans as it pertains to gender is provided. In addition, studies elucidating the factors involved in the more modest renal progression rate in females are reviewed and conclusions drawn. Relevant English-language publications were identified by searching the PubMed database from January 1990 until November 2007 using the search terms gender, sex, renal disease, and kidney.

RESULTS

In polycystic kidney disease, membranous nephropathy, immunoglobulin A nephropathy, and "chronic renal disease of unknown etiology," men progress at a faster rate to end-stage renal failure than do women. In type 1 diabetes mellitus, there is evidence that males are more likely to manifest signs of renal disease, such as proteinuria. The factors involved in this gender disparity may include diet, kidney and glomerular size, differences in glomerular hemodynamics, and the direct effects of sex hormones. In many, but not all, animal models of renal disease, estrogens slow progression rate. Several studies have recently evaluated the effect of selective estrogen receptor modulators on renal function in humans.

CONCLUSION

Further studies assessing the factors involved in the gender disparity in renal disease progression and the effects of hormonal treatments are warranted.

The effects of induced diabetes and cutaneous Leishmania infection on the pharmacokinetics of antimony in hamsters

Patients with certain diseases appear to be at greater risk of developing adverse drug interactions, either because of the disease state itself or the drugs used to treat it. The effects of streptozotocin-induced diabetes and/or cutaneous Leishmania major infection on the pharmacokinetics of antimony (SbV) have now been investigated, in hamsters treated with sodium stibogluconate (Pentostam). The animals were randomly divided into five groups, each of 20 hamsters, known as D (for diabetes without leishmaniasis), DL (diabetes induced prior to the leishmaniasis), L (leishmaniasis without diabetes), LD (diabetes induced after leishmanial infection) and C (the control group, of animals with neither diabetes nor leishmaniasis). After its diabetes and/or leishmaniasis (if any) was established, each animal was given an intramuscular dose of sodium stibogluconate (80 mg/kg) each day for 3 weeks. Blood samples were collected after the first or last doses, to allow the pharmacokinetic parameters of SbV after single and multiple dosing to be compared. Although the between-dose interval (24 h) was more than 10 times longer than the terminal elimination rate constant (t1/2) at steady state, there was a significant increase in the mean peak SbV concentration (Cmax), as the result of multiple dosing, in all five groups (P<0.001 for each). The hamsters with diabetes showed the least accumulation of SbV in their blood, whether or not they were infected with L. major. In the non-diabetic animals of groups L and C, the apparent total clearance of SbV (CL/F) was decreased by multiple dosing, being, respectively, 34.5% and 23.0% lower after the 21st dose than after the first. An increase in urine volume was the reason for the significant increase in CL/F in group D (P<0.001), and this offset the decrease in CL/F seen in the L group, resulting in no change in CL/F in the animals of the DL group. Three weeks of antileishmanial treatment produced no significant reductions in the leishmanial lesions on the parasite-inoculated foot-pads of the hamsters in the L or DL groups but such reductions were detected in the animals of the LD group (P<0.001). In conclusion, it appears that the administration of SbV over a few weeks may cause renal toxicity and, in clinical use, should therefore be accompanied by the regular monitoring of renal function. A cautious increase in SbV dosing may be necessary for the effective treatment of L. major (and perhaps other species of Leishmania) in diabetic patients.

Sight-threatening retinopathy is associated with lower mortality in type 2 diabetic subjects: a 10-year observation study

AIMS

To study associations between diabetic retinopathy and development of stroke, myocardial infarction and death in type 2 diabetic patients.

METHODS

During a 10-year observation period, 363 type 2 diabetic patients (diagnosis > or =30 years of age) attending an outpatient clinic were studied regarding the prevalence and incidence of retinopathy and associated risk factors, i.e., (HbA(1c), blood pressure, albuminuria, plasma creatinine, age, sex and diabetes duration) in relation to the development of myocardial infarction, stroke and death. The degree of retinopathy was classified as no retinopathy, background or sight-threatening retinopathy, i.e., clinically significant macular edema, severe non-proliferative or proliferative retinopathy.

RESULTS

During the study period, 62 patients had had myocardial infarction, 54 stroke and 99 patients died. Patients with sight-threatening retinopathy at baseline (n=41) had a 2.2-fold increased (p<0.01) risk for death compared to patients with no or background retinopathy, even when controlled for medical risk factors. When adjusted for medical risk factors, patients with no retinopathy at baseline (n=226) who remained without retinopathy or developed background retinopathy (n=187) during the study period, had a 3.6-fold increased risk for death (95% CI, 1.1, 11.8), (p=0.03), compared to patients who developed sight-threatening retinopathy (n=39), while the incidence of myocardial infarction did not differ. More patients who developed sight-threatening retinopathy were treated with ACE inhibitors than patients who did not (41% versus 24%; p=0.03).

CONCLUSION

Despite more medical risk factors, patients who developed sight-threatening retinopathy had lower mortality compared to patients with no or background retinopathy at follow-up. More patients who developed sight-threatening retinopathy were treated with ACE inhibitors but this seemed not to have influenced the lower mortality rate in this group, whereas the use of ACE inhibitors in patients who did not develop sight-threatening retinopathy was connected with lower mortality rate.

The burden of new-onset diabetes mellitus after transplantation

The clinical impact of new-onset diabetes mellitus (NODM) is frequently underestimated by clinicians. NODM occurs in approximately 15-20% of renal transplant patients and 15% of liver transplant recipients. Diabetes after transplantation is a leading risk factor for cardiovascular events, with a higher prognostic value than in the non-transplant population. NODM also appears to have a negative influence on graft function, and graft survival rates after renal transplantation are significantly lower in patients who develop diabetes than in controls. Patient mortality following renal transplantation is generally found to be higher in patients with NODM, due to increased cardiovascular and peripheral vascular disease, accelerated graft deterioration and diabetes-related complications, notably infection. A renal registry analysis has reported an increase of 87% in risk of death following onset of NODM. There is also limited evidence that NODM is associated with increased risk of death in liver transplant patients. The relative incidence and severity of diabetic complications in transplant recipients have not been assessed rigorously in a clinical trial but registry data indicate that 20% of renal transplant patients with NODM experience at least one clinically significant diabetic complication within three years. Financially, the additional healthcare costs incurred over the first two years following onset of NODM amount to 21,500 dollars. Routine pre-transplant assessment of diabetic risk, with requisite modification of lifestyle, glycaemic monitoring and immunosuppressive regimens, and coupled with standardized, aggressive hypoglycaemic management as necessary, offers an important opportunity to alleviate the burden of NODM for transplant patients.

Factores que influyen en la aparición de la nefropatía diabética incipiente: estudio ESODIAH

BACKGROUND AND OBJECTIVE

High cholesterol levels might contribute to the presence of albuminuria. The objective of our study was to evaluate the influence of lipid levels on the development of incipient diabetic nephropathy. Secondary objectives were to evaluate the effects of diabetes control, high blood pressure, age, sex, years of diabetes evolution, body mass index and smoking.

PATIENTS AND METHOD

930 subjects were enrolled in an open observational prospective cohort study of subjects with type 2 diabetes mellitus and high cholesterol levels (ESODIAH study) for 2 years. In our nephropathy study we selected 590 patients who had albuminuria measurements done. In every 4-month interval visit we made a clinical evaluation and blood analysis including HbA1c, lipid profile and microalbuminuria. Statistical analysis included t-Student, chi2 test, and binary logistic regressions.

RESULTS

51.7% men, aged 62.08 years of age and with an evolution of their diabetes of 8.49 years were studied. 40.6% had microalbuminuria and 59.4% had normoalbuminuria. High HbA1c correlated with the presence of albuminuria (odds ratio [OR] = 1.3; 95% confidence interval [CI], 1.12-1.55; p = 0.001). The development of microalbuminuria was more frequent in younger (OR = 0.93; 95% CI, 0.89-0.98), smoker (OR = 3.19; 95% CI, 1.02-9.96), subjects with high systolic blood pressure (OR = 1.02; 95% CI, 1-1.05). Total cholesterol levels at the end of the study were higher in new microalbuminuric (group I) than normoalbuminuric patients (group II) (group I: 211.08 [34.75] mg/dl vs group II: 200.67 [30.50]; p = 0.042).

CONCLUSIONS

Tobacco, blood pressure and diabetes control influences the presence and development of microalbuminuria. More studies are required to study the influence of hypercholesterolemia.

Diabetes in Canadian Women

Health Issue

Diabetes mellitus (DM) is a chronic health condition affecting 4.8% of Canadian adults ≥ 20 years of age. The prevalence increases with age. According to the National Diabetes Surveillance System (NDSS) (1998–1999), approximately 12% of Canadians aged 60–74 years are affected. One-third of cases may remain undiagnosed. The projected increase in DM prevalence largely results from rising rates of obesity and inactivity.

Key Findings

DM in Canada appears to be more common among men than women. However, among Aboriginal Canadians, two-thirds of affected individuals are women. Although obesity is more prevalent among men than women (35% vs. 27%), the DM risk associated with obesity is greater for women. Socio-economic status is inversely related to DM prevalence but the income-related disparities are greater among women. Polycystic ovarian syndrome affects 5–7% of reproductive-aged women and doubles their risk for DM. Women with gestational diabetes frequently develop DM over the next 10 years.

Data Gaps and Recommendations

Studies of at risk ethnic/racial groups and women with gestational diabetes are needed. Age and culturally sensitive programs need to be developed and evaluated. Studies of low-income diabetic women are required before determining potential interventions. Lifestyle programs in schools and workplaces are needed to promote well-being and combat obesity/inactivity, together with lobbying of the food industry for needed changes. High depression rates among diabetic women influence self-care ability and health care expenditures. Health professionals need further training in the use of effective counseling skills that will assist people with DM to make and maintain difficult behavioural changes.

Cost-effective strategies in the prevention of diabetic nephropathy

A significant subgroup of patients with diabetes mellitus are predisposed to developing diabetic nephropathy and it is in this subgroup that other diabetes- related complications, and in particular greatly increased cardiovascular disease risk, are concentrated. The high personal, social and financial costs of managing end-stage renal failure and the other complications associated with diabetic nephropathy make a powerful case for screening and effective intervention programmes to prevent the condition or retard its progression. As major breakthroughs in finding genetic susceptibility factors remain elusive, screening efforts continue to be based on microalbuminuria testing, despite increasing recognition of its limitations as a positive predictor of nephropathy. Interventions have been extensively studied, but results remain conflicting. Economic evaluations of such screening and intervention programmes are essential for health planners, yet models of the cost/benefit ratio of such interventions often rely on a rather slim evidence base. Where economic models are developed, they are frequently based on those papers that propound the greatest clinical benefits of a given intervention, leading to a possible over-estimation of the advantages of the chosen approach. Furthermore, the benefits of even such generally accepted interventions as ACE inhibitor treatment are less firmly established than generally appreciated. Lifestyle interventions are instinctively attractive, but are by no means a low-cost option (as is often assumed by both medical professionals and politicians). This review critically assesses the evidence for clinical efficacy and economic benefit of microalbuminuria screening and interventions such as intensive glycaemic control, antihypertensive treatment, ACE inhibition and angiotensin receptor blockade, dietary protein restriction and lipid-modifying therapy. The various costs associated with diabetic nephropathy are so great that even expensive interventions may have a favourable cost/benefit ratio, provided they are truly effective.

Biological Variability of Albumin Excretion Rate and Albumin-to-Creatinine Ratio in Hypertensive Type 2 Diabetic Patients

The importance of measuring microalbuminuria is well established. However, only scanty data are available concerning the biological variability of albumin excretion in type 2 diabetic subjects. We report our experience from a large clinical trial of a new antihypertensive drug (Lercanidipine) designed to reduce albumin excretion and blood pressure in type 2 diabetic patients with hypertension and microalbuminuria. Eighty seven patients with persistent microalbuminuria were studied within 1 year of the clinical trial. The measurements were performed on blood and timed urine samples frozen at -80 degrees C and shipped to a central laboratory unit. Preliminary experiments were performed to assess albumin stability in urine under various conditions (4 degrees C, -20 degrees C and -80 degrees C), particularly with regard to the albumin/creatinine ratio. Urine samples can be stored up to 3 weeks at 4 degrees C or up to 2 months at -80 degrees C. The biological variability of the albumin excretion rate was 25.7%, while that of the albumin/creatinine ratio was 13.4%. These data are useful in defining the analytical goals of imprecision for microalbuminuria (CV = 13% for albumin, and CV = 6% for albumin/creatinine ratio). No correlation between albumin/creatinine ratio and HbA1c was found in the cohort of 61 microalbuminuric patients who completed the trial. The results of this study confirm that the albumin/ creatinine ratio is much more suitable for monitoring albumin excretion in longitudinal studies than the albumin excretion rate.

The streptozotocin-diabetic rat as a model of the chronic complications of human diabetes

BACKGROUND

Diabetes in humans induces chronic complications such as cardiovascular damage, cataracts and retinopathy, nephropathy and polyneuropathy. The most common animal model of human diabetes is streptozotocin (STZ)-induced diabetes in the rat.

METHODS

This project assessed cardiovascular, ocular and neuropathic changes over a period of 24 weeks post STZ administration in rats.

RESULTS

STZ-diabetic rats (n = 96) showed stable signs of diabetes (hyperglycaemia, increased water and food intake with no increase in bodyweight): 52% of untreated STZ-diabetic rats (n = 50) survived 24 weeks after STZ administration. STZ-diabetic rats were normotensive with slowly developing systolic and diastolic dysfunction and an increased ventricular stiffness. Ventricular action potential durations were markedly prolonged. STZ-diabetic rats developed stable tactile allodynia. Cataracts developed to presumed blindness at 16 weeks but proliferative retinopathy was not observed even after 24 weeks.

CONCLUSION

The chronic STZ-diabetic rat mimics many but not all of the chronic complications observed in the diabetic human. The chronic STZ-diabetic rat may be a useful model to test therapeutic approaches for amelioration of chronic diabetic complications in humans.

The role of gender in the progression of renal disease

The rate of progression of certain renal diseases in animals is greater in men than in women. In various animal models of renal disease, investigators have concluded that the presence of testosterone explains the worse course in men compared with women, whereas in other diseases, estrogen seems to confer protection for women. The gender disparity in renal disease progression found in animals is seen in certain human renal diseases, including chronic renal disease, membranous nephropathy, immunoglobin A nephropathy, and polycystic kidney disease. In humans, the differences between the genders in renal disease progression cannot be fully explained by differences in blood pressure or serum cholesterol levels. The underlying mechanisms for this gender disparity are potentially related to differences between the sexes in glomerular structure, glomerular hemodynamics, diet, variations in the production and activity of local cytokines and hormones, and/or the direct effect of sex hormones on kidney cells. Further investigation into the contribution of gender to renal disease progression may aid us in developing strategies for slowing this pathological process.