In one set, the probands (n = 11) had no evidence of diabetic nephropathy, with normal creatinine clearance and a urinary albumin excretion rate below 45 mg per day.
Diabetic nephropathy (defined as urinary albumin excretion greater than 300 mg/24 hr) was found in 7 out of 21 siblings to patients with nephropathy and 3 out of 30 siblings to normoalbuminuric patients (P less than 0.04).
The observation suggests that changes in transglomerular albumin traffic are demonstrable prior to the onset of diabetes and diabetic nephropathy in subjects with a potential genetic predisposition to these conditions.
In our case-control study, we assessed the prevalence of hypertension among parents of 73 IDDM patients with diabetic nephropathy (DN+; persistent albuminuria > 200 microg/min or > 300 mg/24 h) and 73 IDDM patients without diabetic nephropathy (DN-; urinary albumin excretion < 20 microg/min or < 30 mg/24 h).
Thus, in a large ethnically homogeneous cohort of diabetic subjects, our data show: (1) a significant association of C708/T polymorphism with microalbuminuria in long-term diabetes and with both lower plasma ANP levels and widespread albumin leakage; and (2) a strong association between ScaI polymorphism and both diabetic nephropathy and plasma ANP concentrations.
Since advanced glycation end products (AGEs; AGE-albumin) and in particular carboxymethyllysine (CML) are known to play a central role in diabetic nephropathy, we studied the activation of nuclear factor kappaB (NF-kappaB) in tubular epithelial cells in vivo and in vitro by AGE-albumin and CML.
Genomic DNA was obtained from 659 patients: 307 with normal urinary albumin excretion despite diabetes duration of >15 years (control subjects) and 352 with advanced diabetic nephropathy, of whom 200 had persistent proteinuria and 152 had end-stage renal disease (ESRD).
Thus, the association between the RAGE -374 T/A homozygous AA genotype and cardiovascular disease as well as albumin excretion in type 1 diabetic patients with poor metabolic control suggests a gene-environment interaction in the development of diabetic nephropathy and cardiovascular complications.
To test this hypothesis we searched for association between the A-->G (-3862) variant in UCP1, the insertion/deletion (I/D) polymorphism in exon 8 in UCP2, and the C-->T (-55) polymorphism in UCP3 and diabetic nephropathy in 218 diabetic patients with normal urinary albumin excretion rate (AER), 216 with micro- or macroalbuminuria, and in 106 control subjects without a family history of diabetes.
A total of 458 cases with diabetic nephropathy (albumin excretion >300 mg/24h) and 319 controls with persistent normoalbuminuria (<30 mg/24h), despite > or =20 years of diabetes duration at follow-up were identified.
A total of 441 cases with diabetic nephropathy (albumin excretion > or =300 mg/24 h) and 314 controls with persistent normoalbuminuria (<30 mg/24 h), despite diabetes of duration > or =20 years, were identified.
An albumin excretion rate (AER) of 20-200 microg/min (n=73) was considered as incipient DN, and an AER >200 microg/min was considered as overt DN (n=48).
Thirdly, reno-protective effects of PPARγ ligands, especially on reducing urinary albumin, have been observed in both animals and human not only in diabetic nephropathy but also in non-diabetic renal diseases.
We showed that heparanase is a target gene of the diabetic nephropathy mediators albumin and advanced glycation end-product, so it may be relevant to the progression of diabetic nephropathy.