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The prevalence of diabetes around the world has reached epidemic proportions and is projected to increase to 642 million people by 2040. Diabetes is already the leading cause of end-stage kidney disease (ESKD) in most developed countries, and the growth in the number of people with ESKD around the world parallels the increase in diabetes. The presence of kidney disease is associated with a markedly elevated risk of cardiovascular disease and death in people with diabetes. Several new therapies and novel investigational agents targeting chronic kidney disease patients with diabetes are now under development. This conference was convened to assess our current state of knowledge regarding optimal glycemic control, current antidiabetic agents and their safety, and new therapies being developed to improve kidney function and cardiovascular outcomes for this vulnerable population.

Tubular atrophy and interstitial fibrosis, important in progression of renal diseases, including diabetic (D) and cyclosporine-induced (CSA) nephropathy, have been considered irreversible. Normoglycemia for 10 years following pancreas transplantation alone (PTA) reversed D glomerulopathy lesions. This study quantified tubular, interstitial, and arteriolar parameters in PTA recipients. Kidney function studies and biopsies were performed in eight non-uremic type I D patients (pts) at 5 and 10 years after PTA. Renal biopsies were analyzed by morphometric analysis. All pts were normoglycemic and insulin independent and received CSA during the study. Cortical interstitial volume fraction was increased at 5 years (0.31+/-0.07 vs normal 0.15+/-0.02, P0.01) and decreased at 10 years post-PTA (0.23+/-0.03, P0.02 vs 5 years). There was a reduction in the volume fraction of interstitial collagen and cells per cortical tissue, measured using electron microscopy, from 5 (0.126+/-0.061 and 0.103+/-0.026, respectively) to 10 years (0.079+/-0.031, P0.05, and 0.074+/-0.018, P0.05, respectively). The volume fraction of tubules which were atrophic (AT) was abnormal at 5 years (0.160+/-0.090) and decreased from 5 to 10 years (0.044+/-0.034, P0.02), apparently due to AT reabsorption. The index of arteriolar hyalinosis did not change during the study (1.30+/-0.22 and 1.34+/-0.33 at 5 and 10 years, respectively, nonsignificant). This study demonstrates, for the first time in humans, that interstitial expansion is reversible and that atrophic tubules can be reabsorbed. In contrast, there was no improvement in the arteriolar lesions. Whether this is due to long-term normoglycemia, reduction of CSA dose or other mechanisms is unclear.

Cystatin C is a more sensitive marker than creatinine for the estimation of GFR in type 2 diabetic patients. Background Glomerular filtration rate (GFR) is the best overall index of renal function in health and disease. Inulin and 51Cr-EDTA plasma clearances are considered the gold standard methods for estimating GFR. Unfortunately, these methods require specialized technical personnel over a period of several hours and high costs. In clinical practice, serum creatinine is the most widely used index for the noninvasive assessment of GFR. Despite its specificity, serum creatinine demonstrates an inadequate sensitivity, particularly in the early stages of renal impairment. Recently, cystatin C, a low molecular mass plasma protein freely filtered through the glomerulus and almost completely reabsorbed and catabolized by tubular cells, has been proposed as a new and very sensitive serum marker of changes in GFR. This study was designed to test whether serum cystatin C can replace serum creatinine for the early assessment of nephropathy in patients with type 2 diabetes. Methods The study was performed on 52 Caucasian type 2 diabetic patients. Patients with an abnormal albumin excretion rate (AER) were carefully examined to rule out non-diabetic renal diseases by ultrasonography, urine bacteriology, microscopic urine analysis, and kidney biopsy. Serum creatinine, serum cystatin C, AER, serum lipids, and glycosylated hemoglobin (HbA1c) were measured. GFR was estimated by the plasma clearance of 51Cr-EDTA. In addition the Cockcroft and Gault formula (Cockcroft and Gault estimated GFR) was calculated. Results Cystatin C serum concentration progressively increased as GFR decreased. The overall relationship between the reciprocal cystatin C and GFR was significantly stronger (r = 0.84) than those between serum creatinine and GFR (r = 0.65) and between Cockcroft and Gault estimated GFR and GFR (r = 0.70). As GFR decreased from 120 to 20 mL/min/1.73 m2, cystatin C increased more significantly that serum creatinine, giving a stronger signal in comparison to that of creatinine over the range of the measured GFR. The maximum diagnostic accuracy of serum cystatin C (90%) was significantly better than those of serum creatinine (77%) and Cockcroft and Gault estimated GFR (85%) in discriminating between type 2 diabetic patients with normal GFR (!80 mL/min per 1.73 m2) and those with reduced GFR (!80 mL/min/1.73 m2). In particular, the cystatin C cut-off limit of 0.93 mg/L corresponded to a false-positive rate of 7.7% and to a false-negative rate of 1.9%; the serum creatinine cut-off limit of 87.5 μmol/L corresponded to a false-positive rate of 5.8% and to a false-negative rate of 17.0%. Conclusions Cystatin C may be considered as an alternative and more accurate serum marker than serum creatinine or the Cockcroft and Gault estimated GFR in discriminating type 2 diabetic patients with reduced GFR from those with normal GFR.

Growth phenotype of cultured skin fibroblasts from IDDM patients with and without nephropathy and overactivity of the Na+/H+ antiporter. An increased activity of the Na+/H+ antiporter in cells from patients with insulin-dependent diabetes mellitus (IDDM) has been proposed as a potential marker of nephropathy. We evaluated Na+/H+ antiporter activity and its relationship to DNA and protein synthesis in cultured skin fibroblasts from patients with IDDM classified as having either overt nephropathy or absence of nephropathy on the basis of urinary albumin excretion and kidney biopsy findings. In IDDM patients with overt nephropathy, Na+/H+ antiporter activity in serum stimulated cells was increased as compared to cells from control subjects (9.62 ± 0.89 vs. 5.67 ± 0.97mmol H+/min, P < 0.005, respectively) and cells from IDDM patients without nephropathy (7.22 ± 0.67mmol H+/min, P < 0.025). By contrast, in cells made quiescent by serum deprivation Na+/H+ antiporter activity was lower than in serum-stimulated cells and there were no significant differences between the three groups. DNA synthesis assessed by [3H] thymidine incorporation was increased in the IDDM group with nephropathy as compared to the group without nephropathy (138 ± 14 vs. 105 ± 13 cpm/1000 cells, respectively, P < 0.05) and as compared to control subjects (65 ± 11 cpm/1000 cells, P < 0.001). By contrast, protein synthesis assessed by [14C] L-leucine incorporation was not increased in fibroblasts from IDDM patients with nephropathy, suggesting that cellular hypertrophy is not a feature of their altered growth phenotype. After chronic inhibition of the Na+/H+ antiporter using EIPA (25 µm), [3H] thymidine incorporation was reduced by about 20% both in cells from IDDM patients and controls. This parameter therefore remained higher in cells from IDDM patients with nephropathy than in those from controls (81 ± 16 vs. 40 ± 6 cpm/1000 cells, P < 0.05), while in cells from IDDM patients without nephropathy [3H] thymidine incorporation after EIPA (56 ± 7.0 cpm/1000 cells) was intermediate between cells from controls and IDDM patients with nephropathy. We argue that cultured skin fibroblasts from IDDM patients, with nephropathy display an abnormal growth phenotype characterized by cell hyperplasia. This growth phenotype is associated with overactivity of the Na+/H+ antiporter during serum stimulation but not when cells are made quiescent and persists after inhibition of the Na+/H+ antiporter. Our data, therefore, further shows that overactivity of the Na+/H+ antiporter is not required for the expression of the altered growth phenotype of cultured skin fibroblasts from IDDM patients with nephropathy.

Renal interstitial expansion in insulin-dependent diabetes mellitus. Eighty-four patients with insulin-dependent diabetes mellitus had studies of renal function and quantitative renal morphometry including mesangial volume fraction (Vv mes/glom ), index of arteriolar hyalinosis, percentage of globally sclerosed glomeruli (%GS), and interstitial volume fraction for total renal cortex (Vv int/T ). There was significant correlation among these four parameters, and all four structural parameters correlated with glomerular filtration rate and the log of urinary albumin excretion. Stepwise multiple regression analysis showed that Vv mes/glom and Vv int/T were additive, suggesting that they are partially independent. Arteriolar hyalinosis and %GS did not improve the correlations further. We hypothesize that V vmes/glom , Vv int/T , arteriolar hyalinosis, and %GS represent multiple but probably interrelated pathologic mechanisms leading to the functional disturbances of diabetic nephropathy. Longitudinal studies of patients with diabetes and studies of patients with diseases producing interstitial expansion in the absence of glomerular disease may help clarify the independent role of interstitial expansion in the kidney disease of diabetes mellitus.

Clustering of risk factors in hypertensive insulin-dependent diabetics with high sodium-lithium countertransport. Diabetic nephropathy is more common in patients with a positive family history of hypertension and with elevated red blood cell sodium-lithium countertransport, a marker of risk for essential hypertension. To evaluate whether there is a relationship between this cation transport system and indicators of risk of renal and cardiovascular complications in diabetic patients before the development of clinical proteinuria, we studied 31 type 1 (insulin-dependent) diabetic patients with arterial hypertension, without clinical proteinuria and 12 normotensive normoalbuminuric diabetic patients. Sodium-lithium countertransport activity was significantly higher in hypertensive patients (0.43 ± 0.03 mmol/1 RBC x hr) than in normotensive patients (0.23 ± 0.03; P < 0.001). To better explore the nature of the association between this transport system and arterial hypertension, hypertensive patients were divided in two groups, with high (>0.41 mmol/1 RBC x hr) or normal (

Cyclosporine associated lesions in native kidneys of diabetic pancreas transplant recipients. Five years of normoglycemia following pancreas transplantation (PT) does not ameliorate glomerular lesions in patients with their own kidneys and with long-term insulin-dependent diabetes (IDDM) (Lancet 342:1193,1993). All these patients received cyclosporine (CsA) as part of their immunosuppression. Here we examined the relationship of CsA dose and blood levels to the presence and severity of CsA-associated renal lesions and changes in renal function in these PT patients. Renal biopsies were taken before (0) and two and five years after PT from 13 non-uremic IDDM patients and were compared with baseline and five year biopsies from 10 IDDM controls (C). CsA dose was reduced from 10 ± 3 mg/kg/day in the first month to 5 ± 2 in the fifth year post-PT. Creatinine clearance (CCr) decreased by 34% at one year post-PT and was stable thereafter, and did not change in C. The decline in CCr from 0 to one year Was related to CsA blood levels and dose (P < 0.005) at one year. Cortical interstitial volume fraction [Vv(Int/Cortex)], the index of tubular atrophy, and % sclerotic glomeruli increased significantly from 0 to five years post-PT (P < 0.005, 0.01 and 0.001, respectively), but did not change in C. There was no significant change from 0 to two years post-PT in these lesions, while there was a clear progression from two to five years. Mean CsA dose and blood levels in the first year post-PT correlated with the increase (Δ) in Vv(Int/Cortex) at five years (P < 0.05 for both). The best predictor of Δ Vv(Int/Cortex) was the change in CCr over the first year post-PT (P < 0.003). In conclusion, in five years serious tubulointerstitial and glomerulosclerotic lesions developed in PT recipients on CsA therapy, but not in IDDM C. These lesions were best predicted by the decline in CCr and CsA blood levels and dose during the first year post-PT. Despite early CsA dose reductions, and stabilization of CCr, structural lesions progressed from two to five years post-PT.

In patients with diabetes, glycemic improvement by sodium-glucose cotransporter-2 inhibition depends on the kidney's ability to filter glucose. Dapagliflozin, a sodium-glucose cotransporter-2 inhibitor, reduces hyperglycemia in patients with diabetes and normal or mildly impaired renal function. In this randomized, double-blind, placebo-controlled study we assessed daily treatment with dapagliflozin in 252 patients with inadequately controlled type 2 diabetes and moderate renal impairment. The primary endpoint, the mean change in HbA1c, was not statistically different from placebo after 24 weeks (-0.41% and -0.44% for 5- and 10-mg doses, respectively, and -0.32% for placebo). The mean weight change from baseline was -1.54 and -1.89kg for the 5- and 10-mg doses, respectively, and +0.21kg for placebo. The mean systolic and diastolic blood pressure decreased in the dapagliflozin groups compared to placebo. Through 104 weeks, 13 patients receiving dapagliflozin and no patients receiving placebo experienced bone fracture. At 1 week, the mean serum creatinine increased with dapagliflozin 5mg (+0.13mg/dl) and 10mg (+0.18mg/dl) and did not change further after 104 weeks. Mean serum electrolytes did not change in any group, and there were fewer episodes of hyperkalemia with dapagliflozin than placebo. Thus, in patients with moderate renal impairment, dapagliflozin did not improve glycemic control, but reduced weight and blood pressure.

Relationships among natriuresis, atrial natriuretic peptide and insulin in insulin-dependent diabetes. Insulin-dependent diabetic patients have a large exchangeable body sodium pool, secondary to sodium retention. The pathogenesis of impaired natriuresis in insulin dependent diabetes remains to be elucidated. The present study examines the role of hyperinsulinemia, impaired atrial natriuretic release, and resistance to atrial natriuretic peptide action in determining sodium retention in normotensive and hypertensive insulin-dependent diabetic patients. Eight insulin-dependent diabetic patients had significantly higher daily sodium excretion rate (147 ± 16mmol/day; mean ± SE) during conventional insulin treatment (daily plasma glucose: 11.6 ± 1.2 mmol/liter; daily plasma insulin: 27 ± 3 μU/ml) than during intensified insulin treatment (daily sodium excretion rate: 91 ± 12, P < 0.01; daily plasma glucose: 6.8 ± 0.7, P < 0.01; daily plasma insulin: 44 ± 4, P < 0.01). Daily sodium excretion rate was also significantly lower (107 ± 13, P < 0.01) in the same diabetic patients during intensified insulin treatment along with hyperglycemic clamp (daily plasma glucose: 12.8 ± 0.3, NS; plasma insulin 48 ± 4, P < 0.01). Seven control subjects had lower extracellular liquid volume than eight insulin-dependent diabetic patients (11.0 ± 0.8 1/ 1.73m2 vs. 14.8 ± 0.9, P < 0.05) and also had baseline plasma atrial natriuretic peptide concentrations (18 ± 5 pg/ml vs. 37 ± 4, P < 0.05). Atrial natriuretic peptide response to saline challenge was blunted in insulin-dependent diabetic patients when saline was administered on the basis of body surface area (90mmol/1.73 m2 · 90 min) but not when administered on the basis of extracellular liquid volume (ECV) (8.2 mmol/liter ECV · 90 min). Continuous infusion of atrial natriuretic peptide in the same control and diabetic subjects (0.06 µg/kg min · 120 min) resulted in similar circulating concentrations of the hormone but in significantly lower sodium excretion rate in diabetic (from 185 ± 19 to 193 ± 21 µmol/1.73m2 · min) than in control subjects (199 ± 14 to 341 ± 22, P < 0.01). Natriuretic action of atrial natriuretic peptide was similarly impaired in a group of eighteen hypertensive insulin-dependent diabetic patients in comparison with a matched group of seven hypertensive control patients. Angiotensin converting enzyme inhibitor treatment in these hypertensive diabetic patients decreased extracellular liquid volume and improved natriuretic response to atrial natriuretic peptide. We conclude that refractoriness to natriuretic action rather than impaired release of atrial natriuretic peptide can further deteriorate sodium retention in insulin dependent diabetes. This altered hormonal behavior could be primarily due to insulin-induced sodium retention and extracellular liquid volume expansion.

Sequential renal biopsies in insulin-dependent diabetic patients: Structural factors associated with clinical progression. Quantitative structural studies in native kidneys of IDDM patients have almost all been cross sectional, and little is known regarding the dynamics of progression of structural lesions in relation to clinical progression. It has been suggested that interstitial may be more important than glomerular changes in determining functional outcome. This study evaluated renal structure in sequential biopsies from IDDM patients with established renal lesions to determine whether glomerular, arteriolar and interstitial changes progress together and in concordance with measures of renal function. Eleven long-term IDDM patients [age 29 ± 10 years, duration 17 ± 7 years (mean ± SD)] had renal function studies and kidney biopsies performed at two occasions 5.6 ± 1.6 years apart. HbA1 as well as creatinine clearance (CCr) did not change over this time; albumin excretion rate (AER) increased from 12 (6 to 280) to 19 (5 to 2462) [median (range)] mg/24hr (P < 0.03). AER increased in the three patients with abnormal albuminuria at first observation, and two normoalbuminuric patients became microalbuminuric. Blood pressure (BP) did not change; however, the number of patients on antihypertensive therapy increased from 1 to 5. All structural parameters were abnormal at first evaluation. Mesangial fractional volume [Vv(mes/glom)] and mean glomerular volume increased and the surface density of the peripheral glomerular basement membrane (GBM) decreased, while GBM width did not change over the five years of the study. Also, arteriolar hyalinosis lesions progressed, while the fractional volume of cortical interstitium [Vv(interstitium/cortex)] and the percent of globally sclerosed glomeruli did not change. The only structural change that correlated with the increasing AER was the change in Vv(mes/glom). Changes in structural parameters, AER or CCr did not significantly correlate with baseline BP or change in BP over the five years. Although based on a small number of patients, this study suggests that at the stage of disease where renal lesions are established and where some IDDM patients are in transition to microalbuminuria or early clinical nephropathy, continuing mesangial expansion is the central variable. Interstitial changes were not occurring over this time. Progressive interstitial expansion at the later stages of diabetic nephropathy may thus be consequent to advanced diabetic glomerular injury.