Progressive Renal Decline: The New Paradigm of Diabetic Nephropathy in Type 1 Diabetes

On the basis of extensive studies in Joslin Clinic patients over 25 years, we propose a new model of diabetic nephropathy in type 1 diabetes. In this model, the predominant clinical feature of both early and late stages of diabetic nephropathy is progressive renal decline, not albuminuria. Progressive renal decline (estimated glomerular filtration rate loss >3.5 mL/min/year) is a unidirectional process that develops while patients have normal renal function. It progresses at an almost steady rate until end-stage renal disease is reached, albeit at widely differing rates among individuals. Progressive renal decline precedes the onset of microalbuminuria, and as it continues, it increases the risk of proteinuria. Therefore, study groups ascertained for microalbuminuria/proteinuria are enriched for patients with renal decline (decliners). We found prevalences of decliners in 10%, 32%, and 50% of patients with normoalbuminuria, microalbuminuria, and proteinuria, respectively. Whether the initial lesion of progressive renal decline is in the glomerulus, tubule, interstitium, or vasculature is unknown. Similarly unclear are the initiating mechanism and the driver of progression. No animal model mimics progressive renal decline, so etiological studies must be conducted in humans with diabetes. Prospective studies searching for biomarkers predictive of the onset and rate of progression of renal decline have already yielded positive findings that will help to develop not only accurate methods for early diagnosis but also new therapeutic approaches. Detecting in advance which patients will have rapid, moderate, or minimal rates of progression to end-stage renal disease will be the foundation for developing personalized methods of prevention and treatment of progressive renal decline in type 1 diabetes.     

Dealing with diabetic nephropathy

Nephropathy may develop in patients with type 1 diabetes because poor glycemic control produces effects that eventually lead to glomerular scarring and renal failure. The worse and more prolonged the hyperglycemia, the greater the risk of diabetic nephropathy. In patients with type 2 diabetes, hyperglycemia, as well as insulin resistance and generalized vascular disease, is involved in the pathogenesis of nephropathy. The glomerular changes of early diabetic nephropathy can be identified only by renal biopsy or by testing for microalbuminuria. Once macroalbuminuria occurs (albumin excretion rate, > 300 mg/day), usually after type 1 diabetes has been present for 10 to 15 postpubertal years, end-stage renal disease is almost inevitable. However, aggressive control of hypertension in diabetic patients without microalbuminuria helps avoid nephropathy, and tight glycemic control in those with microalbuminuria can avoid or delay its onset. Even when macroalbuminuria is present, treatment can prolong renal function. Aggressive antihypertensive therapy, especially with ACE inhibitors, can reduce renal decline by half. Avoiding circumstances that may damage the kidneys (e.g., use of radiocontrast materials or nephrotoxic drugs, dehydration, hyperlipidemia, urinary tract infection, buildup of AGEs) is critical. Some treatment methods are controversial (dietary protein restriction) or still under investigation (use of injected or oral heparin) but may help delay renal transplantation or dialysis.     

APOE polymorphism and the progression of diabetic nephropathy in Japanese subjects with type 2 diabetes: results of a prospective observational follow-up study

OBJECTIVE: The aim of this study is to clarify the conflicting results of the epsilon2/epsilon3/epsilon4 APOE polymorphism as a risk factor on diabetic nephropathy by a cohort study. RESEARCH DESIGN AND METHODS: A total of 429 Japanese subjects with type 2 diabetes and with normoalbuminuria (n = 299) or with microalbuminuria (n = 130) were enrolled in a prospective observational follow-up study during 1995-1998 and followed until 2001 (for at least 3 years). The endpoint was the occurrence of a renal event defined as the progression to a higher stage of diabetic nephropathy. RESULTS: During the study (the mean follow-up period: 4.4 +/- 1.0 years), 31 of 429 subjects progressed: 21 from normoalbuminuria to microalbuminuria and 10 from microalbuminuria to overt proteinuria. The allele frequency of the APOE polymorphism was significantly different between the progressors and the nonprogressors. Eight of 42 epsilon2 carriers (19%) progressed, whereas 23 of 387 noncarriers (6%) progressed with a relative risk of 3.2 (95% CI 1.5-6.7). When subjects were stratified by renal status at baseline, each relative risk for the progression in the epsilon2 carriers was 2.7 (0.99-7.4) in those with normoalbuminuria and 4.2 (1.3-13.3) in those with microalbuminuria. Furthermore, when analyzed only in subjects with normoalbuminuria and short duration of diabetes (<15 years) at baseline, the risk in the epsilon2 carriers became higher to 3.2 (1.2-8.8). CONCLUSIONS: Our follow-up study indicates that the epsilon2 allele of the APOE polymorphism is a prognostic risk factor for both the onset and the progression of diabetic nephropathy in Japanese type 2 diabetes.     

Dyslipidemia in patients with type 2 diabetes. relationships between lipids, kidney disease and cardiovascular disease.

Type 2 diabetes mellitus is a leading cause of morbidity and mortality. Cardiovascular disease (CVD) is the most prevalent complication and primarily accounts for the excess morbidity and mortality in diabetic patients, but microvascular complications, such as kidney disease and retinopathy, are frequent and contribute to the total disease burden. Lipid abnormalities in patients with type 2 diabetes are a major problem and associated with the increased risk of CVD. The most common pattern of dyslipidemia in these patients consists of elevated levels of triglycerides and low levels of high-density lipoprotein cholesterol. Low-density lipoprotein levels in these patients are often similar to that of the nondiabetic population, although there may be important qualitative differences in the pattern that contribute to the increased risk of CVD. Abnormal levels of urinary albumin occur in 30-40% of patients with type 2 diabetes and the presence of kidney disease enhances the mortality from CVD. Microalbuminuria, an early marker of diabetic nephropathy, is an independent risk factor for CVD. The increased levels of urinary albumin secretion may represent a more generalized vascular damage than renal microvascular injury alone. This Review focuses on the significance of diabetic dyslipidemia and microalbuminuria to CVD risk as well as to kidney complications. We also discuss the role of aggressive therapy to ameliorate vascular injury in the diabetic patient and reduce or prevent the cardiovascular and renal consequences of the disease.     

Diabetic nephropathy in patients with type 1 diabetes mellitus.

Proteinuria has been recognized in association with diabetes mellitus as early as the 18th century. This form of renal disease is known as diabetic nephropathy. It is now clear that diabetic nephropathy is the principal cause of end stage renal disease (ESRD) in the western world. According to reports by the United States Renal Data System (USRDS), in the past two decades there has been a continual increase in the incidence of ESRD among patients with diabetes. Many patients have diabetes that progresses to diabetic nephropathy, which is often not discovered until overt nephropathy is present. Many of the complications of diabetes could be minimized if patients received a comprehensive health maintenance program that includes vigorous cardiac risk reduction, routine eye examinations; routine foot examinations; screening and treatment for microalbuminuria, optimal hypertension management; and improved glycemic control. Hence, the key is not only prudent screening of these patients, but referral as well. Using a case study approach, this article illustrates the care of patients with diabetic nephropathy in type 1 diabetes mellitus.     

Progression to overt nephropathy in type 2 diabetes: the Casale Monferrato Study

OBJECTIVE: The first sign of diabetic nephropathy is microalbuminuria, but its predictive role of progression to overt nephropathy in type 2 diabetes has not yet been clarified. The aims of this study were to assess during 7 years of follow-up the incidence rate of overt nephropathy and the predictive role of microalbuminuria and other baseline variables (blood pressure, lipids, fibrinogen, uric acid, smoking, and HbA(1c) cumulative average during follow-up). RESEARCH DESIGN AND METHODS: A prospective population-based study was performed in Casale Monferrato, Italy, including 1,253 type 2 diabetic patients recruited at baseline (1991-1992), 765 with normoalbuminuria (albumin excretion rate [AER] <20 microg/min) and 488 with microalbuminuria (AER 20-200 microg/min). All measurements were centralized. A nested case-control study within the cohort was performed, selecting four control subjects, frequency matched for age and attained individual time of follow-up with each case. Conditional regression analysis was performed to assess variables independently associated with risk of progression to overt nephropathy. RESULTS: Of 1,253 total patients, 1,103 (88.0%) were included in the follow-up examination (median 5.33 years); their age and duration of disease at baseline were 68.4 +/- 10.5 years and 10.4 +/- 6.6 years, respectively. Cases of overt nephropathy were 202, giving an incidence rate of 37.0/1,000 person-years (95% CI 32.3-42.6). In conditional logistic regression analyses, microalbuminuria provided a 42% increased risk with respect to normoalbuminuria (95% CI 0.98-2.06), independently of duration of diabetes, hypertension, and systolic blood pressure. Other variables independently associated with progression to overt nephropathy were HbA(1c) cumulative average (P = 0.002), apolipoprotein B (P = 0.013), fibrinogen (P = 0.02), and HDL cholesterol (P = 0.03). CONCLUSIONS: Of type 2 diabetic patients, 3.7% progress every year to overt nephropathy. Microalbuminuria is associated with a 42% increased risk of progression to overt nephropathy. Other independent predictors are HbA(1c), HDL cholesterol, apolipoprotein B, and fibrinogen.     

Losartan in diabetic nephropathy

Diabetic nephropathy has become the single most important cause of end-stage renal disease in the USA, Europe and Japan. The earliest marker of incipient diabetic nephropathy is the transition of normoalbuminuria to microalbuminuria at an albumin excretion rate of 20 μg/min. Human studies in patients both with and without diabetic kidney diseases have shown that the severity of baseline proteinuria is an important predictor of the rate of loss of renal function. Moreover, the reduction in protein excretion rate when patients with nephropathies are being treated with antihypertensive agents predicts the efficacy of subsequent renoprotection. Experimental and clinical observations provide the rationale for targeting the renin–angiotensin system as a renoprotective approach in diabetic and nondiabetic proteinuric nephropathies. Losartan (Cozaar^®, Merck Sharpe and Dohme) is a potent, orally active and highly specific angiotensin-type 1 receptor blocker. In addition to its antihypertensive efficacy, losartan decreases the left ventricular mass index in patients with hypertension, left ventricular end-diastolic and end-systolic volume in subjects with heart failure and prevents cardiovascular morbidity and death, predominantly stroke, independent of blood pressure reduction. Short-term studies in Type 1 diabetic patients with overt nephropathy have demonstrated that losartan and angiotensin-converting enzyme inhibitors have similar beneficial effects on albumin excretion rate, blood pressure and renal hemodynamics. Losartan also lowered albumin excretion rate in microalbuminuric patients with Type 2 diabetes mellitus. Moreover, the large multicenter Reduction of End points in Noninsulin dependent diabetes mellitus with the Angiotensin II Antagonist Losartan (RENAAL) trial has shown that blockade of angiotensin-type 1 receptor with losartan is superior to conventional antihypertensive therapy in slowing the progression of overt Type 2 diabetic nephropathy. Together, data from clinical trials demonstrate the beneficial effect of angiotensin-type 1 receptor blockers, including losartan, in the primary and secondary prevention of renal disease progression in diabetic patients. Nevertheless, it can be expected that the positive results achieved so far with this class of drugs may be further implemented by including angiotensin-type 1 receptor antagonists as a part of the multidrug approach that may hold more promise for the future of renoprotection in diabetic patients with chronic nephropathy.     

Losartan in diabetic nephropathy

Diabetic nephropathy has become the single most important cause of end-stage renal disease in the USA, Europe and Japan. The earliest marker of incipient diabetic nephropathy is the transition of normoalbuminuria to microalbuminuria at an albumin excretion rate of 20 microg/min. Human studies in patients both with and without diabetic kidney diseases have shown that the severity of baseline proteinuria is an important predictor of the rate of loss of renal function. Moreover, the reduction in protein excretion rate when patients with nephropathies are being treated with antihypertensive agents predicts the efficacy of subsequent renoprotection. Experimental and clinical observations provide the rationale for targeting the renin-angiotensin system as a renoprotective approach in diabetic and nondiabetic proteinuric nephropathies. Losartan (Cozaar, Merck Sharpe and Dohme) is a potent, orally active and highly specific angiotensin-type 1 receptor blocker. In addition to its antihypertensive efficacy, losartan decreases the left ventricular mass index in patients with hypertension, left ventricular end-diastolic and end-systolic volume in subjects with heart failure and prevents cardiovascular morbidity and death, predominantly stroke, independent of blood pressure reduction. Short-term studies in Type 1 diabetic patients with overt nephropathy have demonstrated that losartan and angiotensin-converting enzyme inhibitors have similar beneficial effects on albumin excretion rate, blood pressure and renal hemodynamics. Losartan also lowered albumin excretion rate in microalbuminuric patients with Type 2 diabetes mellitus. Moreover, the large multicenter Reduction of End points in Noninsulin dependent diabetes mellitus with the Angiotensin II Antagonist Losartan (RENAAL) trial has shown that blockade of angiotensin-type 1 receptor with losartan is superior to conventional antihypertensive therapy in slowing the progression of overt Type 2 diabetic nephropathy. Together, data from clinical trials demonstrate the beneficial effect of angiotensin-type 1 receptor blockers, including losartan, in the primary and secondary prevention of renal disease progression in diabetic patients. Nevertheless, it can be expected that the positive results achieved so far with this class of drugs may be further implemented by including angiotensin-type 1 receptor antagonists as a part of the multidrug approach that may hold more promise for the future of renoprotection in diabetic patients with chronic nephropathy.     

Vascular endothelial markers, von Willebrand factor and thrombomodulin index, are specifically elevated in type 2 diabetic patients with nephropathy: comparison of primary renal disease

To elucidate the hypothesis that albuminuria in diabetic subjects reflects widespread vascular damage, plasma markers for vascular endothelial damage was measured in diabetic subjects with various degrees of albuminuria and compared to results in patients with primary renal disease. The groups consisted of 31 non-diabetic patient controls with normoalbuminuria, 109 type 2 diabetic patients with normo- micro- and macro-albuminuria, and 16 proteinuric patients with primary renal disease. Endothelial markers, plasma von Willebrand factor (vWF) and thrombomodulin (TM), were measured by enzyme-linked immunosolvent assay and enzyme immunoassay (EIA) methods, respectively. Plasma vWF levels were similar in controls (119+/-7%, mean+/-S.E.M.) and diabetic patients with normoalbuminuria (139+/-6), but significantly elevated in diabetic patients with microalbuminuria (174+/-11) and macroalbuminuria (204+/-17), while the level was not increased in patients with primary renal disease (124+/-11). Because plasma TM level was strongly affected by kidney function, TM index (TM (FU/ml)/serum creatinine (mg %)) was used as an endothelial marker. The TM index was substantially increased in diabetic patients with overt nephropathy compared with controls (5.29+/-2.98 vs. 2.35+/-0.85), whereas this was not observed in patients with primary renal disease (3.25+/-0.29). Both vWF and TM index were significantly higher in diabetic patients with retinopathy than in the patients without retinopathy. These results suggest that generalized vascular endothelial damage occurs in diabetic nephropathy including the microalbuminuric stage, which is not attributed to kidney damage per se.     

Urinary connective tissue growth factor excretion in patients with type 1 diabetes and nephropathy

OBJECTIVE: Excretion of growth factors in the urine has been implicated in the pathogenesis of tubulointerstitial disease that characterizes proteinuric renal disease. In this cross-sectional study, we sought to examine the urinary excretion of the profibrotic cytokine connective tissue growth factor (CTGF) in type 1 diabetic patients with incipient and overt diabetic nephropathy. RESEARCH DESIGN AND METHODS: We recruited 31 subjects with type 1 diabetes from a hospital diabetes outpatient clinic. Of these, 10 subjects were normoalbuminuric, 8 were microalbuminuric and not receiving ACE inhibitor treatment, and 13 were macroalbuminuric, 8 of whom were receiving ACE inhibitor treatment. Urinary CTGF NH(2)-terminal fragment (CTGF-N) was determined by enzyme-linked immunosorbent assay and expressed relative to urinary creatinine. RESULTS: Urinary CTGF-N was closely correlated with the degree of albuminuria (r = 0.76, P < 0.001). In comparison with normoalbuminuric subjects, urinary CTGF-N was increased 10- and 100-fold in micro- and untreated macroalbuminuric subjects, respectively (CTGF-N-to-creatinine ratio: normoalbuminuria 0.23 x// 1.3 ng/mg, microalbuminuria 2.1 x// 1.7 ng/mg, untreated macroalbuminuria 203 x// 3.8 ng/mg, and geometric mean x// tolerance factor; P < 0.05 for normoalbuminuria versus microalbuminuria, P < 0.001 for microalbuminuria versus macroalbuminuria). Urinary CTGF-N was lower (<30-fold) in macroalbuminuric subjects treated with ACE inhibitors (6.5 x// 1.7 ng/mg; P < 0.01 vs. untreated macroalbuminuria) compared with their untreated counterparts. CONCLUSIONS: In this cross-sectional study, the magnitude of urinary CTGF-N excretion was related to the severity of diabetic nephropathy. In the context of its known profibrotic actions, these findings suggest that CTGF may contribute to the chronic tubulointerstitial fibrosis that accompanies proteinuric renal disease. Prospective and interventional studies will be needed to determine whether urinary CTGF-N may provide a reliable surrogate marker of renal injury and a meaningful indicator of response to therapy.     

Urinary κ and λ immunoglobulin light chains in normoalbuminuric type 2 diabetes mellitus patients

Background and Aim: Kidney disease is one of the major chronic microvascular complications of diabetes. Tubular involvement may precede glomerular involvement and the appearance of microalbuminuria. The aim of the study was to evaluate quantitatively immunoglobulin light chains (IgLCs), kappa and lambda excretion in the urine of patients with type 2 diabetes mellitus with normoalbuminuria and with microalbuminuria compared to control group. Results: Urinary IgLCs levels of the control group were significantly lower than diabetic patients with normoalbuminuria and diabetic patients with albuminuria. IgLCs were significantly associated with the duration of disease and negatively with estimated glomerular filtration rate. Conclusion: Type 2 diabetic patients can have significantly raised concentrations of urinary IgLCs before microalbuminuria or renal disease occurs. Further investigations are recommended to assess LC evaluation in the early management of diabetic renal disease. J. Clin. Lab. Anal. 25:229–232, 2011. © 2011 Wiley‐Liss, Inc.     

Circulating Vascular Progenitor Cells in Patients With Type 1 Diabetes and Microalbuminuria

OBJECTIVE

Patients with type 1 diabetes and microalbuminuria are at increased risk of cardiovascular disease (CVD). Abnormalities in vascular progenitor cells, which participate in vascular repair, may be implicated in this susceptibility.

RESEARCH DESIGN AND METHODS

We studied the number and function of vascular progenitor cells in 22 type 1 diabetic patients with history of microalbuminuria (MA⁺) and 22 type 1 diabetic patients without history of microalbuminuria (MA⁻), of similar age, diabetes duration, glycemic control, renal function, and no history of CVD.

RESULTS

MA⁺ patients had lower circulating CD34⁺ and CD34⁺/CD133⁺ cell numbers compared with MA⁻ patients (P < 0.006). In in vitro functional assays, MA⁺ patients had a significantly lower number of colony-forming units and impaired vascular endothelial growth factor (VEGF)-A–mediated tube formation, when compared with MA⁻ patients (P < 0.01).

CONCLUSIONS

In type 1 diabetic patients with microalbuminuria, a marker of microvascular injury and a risk factor for CVD, circulating vascular progenitor cell number is reduced and function is impaired.The number of circulating endothelial progenitor cells inversely relates to cardiovascular disease (CVD) (1–3); microalbuminuria is one of the earliest manifestations of diabetic nephropathy and a marker of CVD (4). A subset of patients with type 1 diabetes is susceptible to diabetic nephropathy, a condition characterized by a higher risk of cardiovascular morbidity and mortality (4,5). Type 1 diabetic patients without complications have a lower number of circulating progenitor cells than healthy control subjects (6,7). To gain insight into the susceptibility to CVD in type 1 diabetes, we studied circulating vascular progenitor cell number and function in type 1 diabetic patients with and without microalbuminuria.     

Clinical features and health-care costs of diabetic nephropathy

The nephropathy complicating insulin-dependent diabetes mellitus (IDDM) has been well studied, but that complicating non-insulin-dependent diabetes mellitus (NIDDM) is less well defined. In patients with IDDM, the glomerular filtration rate is often increased early in the course of the disease, approaches normal with insulin therapy, but tends to remain slightly elevated throughout the ensuing 10-15 yr of insulin dependency. After the onset of overt azotemia, end-stage renal disease (ESRD) develops in approximately 5 yrs. Proteinuria may be intermittently positive in the earliest stages of diabetes, evolving into intermittent and then persistent microalbuminuria, which in turn blossoms into macroalbuminuria. Because 40-50% of IDDM patients develop proteinuria and two-thirds of this subpopulation develop ESRD, some 20-30% of any given cohort of IDDM patients eventually need dialysis or transplantation. Evidence indicates that diabetic nephropathy is associated with a greater incidence of eye, nerve, heart, and peripheral vascular disease. Nondiabetic renal disease complicating IDDM and NIDDM is associated with a lesser frequency and severity of these extrarenal manifestations. The prevalence of retinopathy increases with advancing nephropathy. Roughly two-thirds of the deaths from IDDM are related to renal failure, and most of the remainder are caused by associated cardiovascular disease. Transplantation from living relatives carries the best prognosis for survival, and little difference is seen between hemodialysis, peritoneal dialysis, and cadaver transplantation. The health-care costs of treating diabetic nephropathy are also reviewed.     

Effect of blood glucose and blood pressure control on progression of diabetic nephropathy

Although diabetic nephropathy is a slowly progressing, well studied disease, it is the most common cause of end stage renal disease in industrialized countries. Recently the first randomized controlled long term trials about microvascular complications in patients with type 2 diabetes have been published. Only seven years ago the first hallmark papers about metabolic control and ACE inhibition emerged. This review highlights the current status of prevention and therapy of diabetic nephropathy by metabolic and blood pressure control in type 1 and type 2 diabetic patients, depending on their stage of nephropathy (normo-, micro-, or macroalbuminuria). In patients with type 1 diabetes and normo- or microalbuminuria, strict metabolic control has been shown to slow the progression of nephropathy. In macroalbuminuric patients an aggressive antihypertensive treatment, preferably with an ACE inhibitor, is more important than the metabolic control. ACE inhibitor therapy has also been proven beneficial in microalbuminuric patients, but not yet in normotensive, non-albuminuric type 1 patients. Because of the high prevalence of hypertension in patients with type 2 diabetes, a strict antihypertensive treatment is more important than metabolic control for the prevention of progression of microvascular disease. Since most patients need a combination of antihypertensive medications a recommendation for a single substance class can not be given.     

Levels of urinary matrix metalloproteinase-9 (MMP-9) and renal injuries in patients with type 2 diabetic nephropathy

To determine correlations among the levels of urinary MMP-9 and type-IV collagen, hyperglycemia, urinary protein excretion, and renal injuries in patients with type 2 diabetic nephropathy, we measured levels of urinary MMP-9 and protein, blood urea nitrogen (BUN), serum creatinine (s-Cr), fasting plasma glucose (FPG), and glycohemoglobin A1c (HbA1c) in 47 diabetic patients and 14 healthy adults. Urinary type-IV collagen was also measured in 28 diabetic patients and seven healthy adults. Patients with diabetic nephropathy were divided into two groups: 1). patients with normoalbuminuria or microalbuminuria (0-299 mg/g.Cr; n=27), and 2). patients with macroalbuminuria (>300 mg/g.Cr; n=20). The mean level of urinary MMP-9 in group 2 was significantly higher than those in healthy adults (P<0.05), and the levels of urinary MMP-9 in patients with diabetic nephropathy increased in accordance with the clinical stage of the disease. The levels of urinary MMP-9 tended to be correlated with HbA1c in these patients, but the correlation was not statistically significant. The mean level of urinary type-IV collagen in group 2 of patients with diabetic nephropathy was significantly higher than that in group 1 and healthy adults. Levels of urinary type-IV collagen in patients with diabetic nephropathy also increased in accordance with the clinical stage of the disease. The results suggest that measurements of urinary MMP-9, as well as urinary type-IV collagen, may be useful for evaluating the degree of renal injuries in patients with type 2 diabetic nephropathy, especially in the early stage.     

Medical care costs associated with progression of diabetic nephropathy

OBJECTIVE

To estimate the direct medical costs of hypertensive patients with type 2 diabetes by the level of proteinuria and to evaluate the differences between patients whose nephropathy did and did not progress.

RESEARCH DESIGN AND METHODS

We identified 7,758 patients with diabetes and hypertension who had a urine albumin-to-creatinine ratio (UACR) during 2001–2003 and at least one follow-up UACR 3–5 years later. Patients were followed for up to 8 years for progression of nephropathy, which was defined by increasing levels of proteinuria: normoalbuminuria (UACR <30 mg/g), microalbuminuria (30–299 mg/g), macroalbuminuria (≥300 mg/g), and end-stage renal disease (dialysis or transplant). We calculated annualized inpatient, outpatient, pharmaceutical, and total medical costs incurred by patients after the baseline measure through 2008, comparing patients who did and did not progress to a higher nephropathy stage. We also compared pre- and postprogression costs among those whose nephropathy progressed.

RESULTS

Patients with normoalbuminuria who progressed to microalbuminuria experienced an annualized change in baseline costs that was $396 higher (P < 0.001) than those who maintained normal albuminuria ($902 vs. $506). Among those with microalbuminuria, progression was significantly associated with a $747 difference (P < 0.001) in annualized change in outpatient costs compared with no progression ($1,056 vs. $309). Among patients who progressed, costs were 37% higher following progression from normoalbuminuria to microalbuminuria ($10,188 vs. $7,424; P < 0.001), and 41% higher following progression from microalbuminuria to macroalbuminuria ($12,371 vs. $8,753; P < 0.001).

CONCLUSIONS

Progression of nephropathy was strongly associated with higher subsequent medical care costs in hypertensive patients with diabetes. Greater prevention efforts may reduce the substantial economic burden of diabetic nephropathy.Complications add greatly to the already substantial costs of medical care for patients with type 2 diabetes, the majority of whom are hypertensive (1). As the leading cause of end-stage renal disease (ESRD), which ultimately requires kidney dialysis or transplant, late-stage diabetic nephropathy is the single largest contributor to these additional costs (2,3). Clearly, avoidance of ESRD would have enormous cost-savings implications. Using a mathematical model and data from the U.S. Renal Data System, Trivedi et al. (4) estimated that slowing the progression of chronic renal failure by 20% would save approximately $39 billion over 10 years. On an individual basis, the Reduction of End Points in Type 2 Diabetes With Angiotensin II Antagonist Losartan (RENAAL) study showed that treatment with losartan reduced the number of ESRD days by 33.6 per patient over 3.5 years, resulting in a net savings of $3,522 per patient (5). Although the RENAAL study observed reduced costs over all levels of baseline albuminuria (6), macroalbuminuria (urinary albumin-to-creatinine ratio [UACR] ≥300 mg/g) was a study entry criterion, and the basis for the cost reductions was estimated as a function of ESRD-free days. To our knowledge, no study to date has estimated the medical costs associated with earlier stages of diabetic nephropathy or the progression from normoalbuminuria to microalbuminuria to macroalbuminuria. Therefore, we undertook the current study to estimate, in a population-based sample of managed care members, the medical costs associated with baseline stages of diabetic nephropathy, and to compare medical costs of patients who did and did not progress from normoalbuminuria, microalbuminuria, or macroalbuminuria to a more severe stage of nephropathy.     

Early diabetic nephropathy: assessment and potential therapeutic interventions

End-stage renal failure secondary to diabetes has increasingly become a health and socioeconomic issue. Diabetic nephropathy is the major cause of death in type I insulin-dependent diabetic patients and accounts for approximately 25% of all patients beginning hemodialysis in the United States. Once diabetic nephropathy is well established, attempts to modify the relentless downward progression of the disease have been essentially unsuccessful. We focus on the early structural and functional changes that occur as a consequence of diabetic renal disease and examine the evidence for microalbuminuria as an early marker and predictor for future overt diabetic nephropathy. The rationale for different therapeutic interventions to alter the course of early diabetic nephropathy are discussed.     

Dissociation between urinary pyrraline and pentosidine concentrations in diabetic patients with advanced nephropathy

It has been reported that the concentrations of both pyrraline and pentosidine, well-characterized advanced glycation end products, are increased in the urine of diabetic patients. To determine factors that influence the urinary excretion of pyrraline or pentosidine, we compared pyrraline or pentosidine concentrations with glycemic-control indexes, urinary albumin excretion, and urinary β2-microglobulin in patients with type 2 diabetes. The study was conducted in 39 age-matched healthy control subjects and 50 diabetic patients, including 22 patients with normoalbuminuria, 15 with microalbuminuria, and 13 with macroalbuminuria. Both urinary pyrraline and pentosidine were measured in early-morning urine specimens with the use of high-pressure liquid chromatography. The urinary pentosidine concentration was significantly higher in diabetic patients than in control subjects (P < .01). In contrast, the urinary pyrraline concentration was significantly lower in diabetic patients than in control subjects (P < .001). Urinary pentosidine concentrations were greater in diabetic patients with macroalbuminuria and microalbuminuria than in those with normoalbuminuria. However, urinary pyrraline concentrations were significantly lower in diabetic patients with advanced nephropathy. Both the hemoglobin A_1c (HbA_1c) and the preceding year's mean HbA_1c were lower in patients with macroalbuminuria than in those with normoalbuminuria or microalbuminuria. Urinary pyrraline, but not pentosidine, showed a significantly positive correlation with the preceding year's mean HbA_1c (P<0.01). Multivariate analysis disclosed that urinary β-2-microglobulin was independently correlated with the urinary concentrations of pentosidine and pyrraline (P < .05 for both). We conclude that the urinary concentration of pentosidine is greater in diabetic patients with overt nephropathy, whereas the urinary pyrraline concentration is significantly lower in diabetic patients with overt nephropathy. Because urinary pyrraline is more directly influenced by glycemia than by pentosidine, the difference in glycemic control among diabetic patients with various grades of nephropathy may be responsible for a dissociation between urinary pyrraline and pentosidine concentrations in patients with overt diabetic nephropathy.     

Improved Pregnancy Outcome in Type 1 Diabetic Women With Microalbuminuria or Diabetic Nephropathy: Effect of intensified antihypertensive therapy?

OBJECTIVE—To describe pregnancy outcome in type 1 diabetic women with normoalbuminuria, microalbuminuria, or diabetic nephropathy after implementation of an intensified antihypertensive therapeutic strategy.RESEARCH DESIGN AND METHODS—Prospective study of 117 pregnant women with type 1 diabetes. Antihypertensive therapy, mainly methyldopa, was given to obtain blood pressure <135/85 mmHg and urinary albumin excretion <300 mg/24 h. Blood pressure and A1C were recorded during pregnancy. The pregnancy outcome was compared with recently published studies of pregnant women with microalbuminuria or diabetic nephropathy.RESULTS—Antihypertensive therapy was given in 14 of 100 women with normoalbuminuria, 5 of 10 women with microalbuminuria, and all 7 women with diabetic nephropathy. Mean systolic blood pressure during pregnancy was 120 mmHg (range 101–147), 122 mmHg (116–135), and 135 mmHg (111–145) in women with normoalbuminuria, microalbuminuria, and diabetic nephropathy, respectively (P = 0.0095). No differences in mean diastolic blood pressure or A1C were detected between the groups. No women with microalbuminuria developed preeclampsia. The frequency of preterm delivery was 20% in women with normoalbuminuria and microalbuminuria in contrast to 71% in women with diabetic nephropathy (P < 0.01) where the median gestational age was 258 days (220–260). Compared with previous studies using less stringent antihypertensive therapeutic strategy and less strict metabolic control, gestational age was longer and birth weight was larger in our study.CONCLUSIONS—With intensified antihypertensive therapy and strict metabolic control, comparable pregnancy outcome was seen in type 1 diabetic women with microalbuminuria and normoalbuminuria. Although less severe than in previous studies, diabetic nephropathy was associated with more adverse pregnancy outcome.Type 1 diabetic women with microalbuminuria or diabetic nephropathy are at particular risk of poor pregnancy outcome (1–6). Diabetic nephropathy is associated with a high risk of gestational hypertension, preeclampsia, and preterm delivery (1–4,6). Likewise, preeclampsia and preterm delivery occur more frequently in type 1 diabetic women with microalbuminuria (3,5).Outside pregnancy, the importance of antihypertensive therapy with ACE inhibition to reduce the risk of renal complications is well documented in both type 1 diabetic patients with microalbuminuria (7) and diabetic nephropathy (8). To prevent development of hypertension and proteinuria, ACE inhibition has been documented to be effective even in normotensive diabetic women with microalbuminuria (7). However, ACE inhibition in early pregnancy has been associated with congenital malformations (9), while use late in pregnancy may cause fetal renal failure (10). ACE inhibition therefore should be discontinued before conception or as soon as pregnancy is confirmed (9). In diabetic women with microalbuminuria or diabetic nephropathy, the effect of antihypertensive therapy in relation to development and progression of hypertension and proteinuria during pregnancy seems promising when using antihypertensive drugs considered safe during pregnancy. However, this is only sparsely investigated (1,3,5).A retrospective study suggested that early intervention with antihypertensive therapy reduces the risk of preterm delivery in type 1 diabetic women with diabetic nephropathy (1).Previously, we found an association between early onset of antihypertensive therapy in pregnant type 1 diabetic women with microalbuminuria and a reduced prevalence of preterm delivery, probably due to a reduced prevalence of preeclampsia (5). Methyldopa was first-choice therapy based on reports of stable utero-placental blood flow, fetal hemodynamics (11,12), and long-term follow-up (13). Given that the prevalence of preterm delivery and preeclampsia was still high (5), we speculated that pregnant type 1 diabetic women with microalbuminuria or diabetic nephropathy would benefit from further intensified antihypertensive therapy in early pregnancy. Therefore, in 2004, we intensified our treatment strategy in early pregnancy in type 1 diabetic women with microalbuminuria or diabetic nephropathy.In this study, we describe the pregnancy outcome in type 1 diabetic women according to their degree of albuminuria after the implementation of an intensified antihypertensive therapeutic strategy.     

Significance of urinary type IV collagen in patients with diabetic nephropathy using a highly sensitive one-step sandwich enzyme immunoassay

Urinary concentrations of type IV collagen in patients with diabetic nephropathy were measured by a highly sensitive, one-step sandwich enzyme immunoassay. Samples from 298 patients with non-insulin-dependent diabetes mellitus (NIDDM) and 80 healthy controls were examined. In diabetic patients with macroalbuminuria or renal insufficiency, the concentrations of urinary type IV collagen were significantly higher than those of diabetic patients with normoalbuminuria or healthy controls (P < 0.001). Urinary type IV collagen concentration in diabetic patients with microalbuminuria was significantly higher than that in diabetic patients with normoalbuminuria or that in healthy controls (P < 0.001). In contrast, there were no significant changes in the concentration of serum type IV collagen between microalbuminuric patients and normoalbuminuric patients. The area under the receiver operating characteristic (ROD) curve for the urinary type IV collagen concentration was equivalent to that of urinary albumin. It was concluded that urinary type IV collagen concentration determined using this method might be a useful marker for the early detection of diabetic nephropathy. J. Clin. Lab. Anal. 11:110–116. © 1997 Wiley-Liss, Inc.