Variations in Risk of End-Stage Renal Disease and Risk of Mortality in an International Study of Patients With Type 1 Diabetes and Advanced Nephropathy.

OBJECTIVE: Patients with type 1 diabetes and diabetic nephropathy are targets for intervention to reduce high risk of end-stage renal disease (ESRD) and deaths. This study compares risks of these outcomes in four international cohorts. RESEARCH DESIGN AND METHODS: In the 1990s and early 2000s, Caucasian patients with type 1 diabetes with persistent macroalbuminuria in chronic kidney disease stages 1-3 were identified in the Joslin Clinic (U.S., 432), Finnish Diabetic Nephropathy Study (FinnDiane) (Finland, 486), Steno Diabetes Center Copenhagen (Denmark, 368), and INSERM (France, 232) and were followed for 3-18 years with annual creatinine measurements to ascertain ESRD and deaths unrelated to ESRD. RESULTS: During 15,685 patient-years, 505 ESRD cases (rate 32/1,000 patient-years) and 228 deaths unrelated to ESRD (rate 14/1,000 patient-years) occurred. Risk of ESRD was associated with male sex; younger age; lower estimated glomerular filtration rate (eGFR); higher albumin/creatinine ratio, HbA1c, and systolic blood pressure; and smoking. Risk of death unrelated to ESRD was associated with older age, smoking, and higher baseline eGFR. In adjusted analysis, ESRD risk was highest in Joslin versus reference FinnDiane (hazard ratio [HR] 1.44, P = 0.003) and lowest in Steno (HR 0.54, P < 0.001). Differences in eGFR slopes paralleled risk of ESRD. Mortality unrelated to ESRD was lowest in Joslin (HR 0.68, P = 0.003 vs. the other cohorts). Competing risk did not explain international differences in the outcomes. CONCLUSIONS: Despite almost universal renoprotective treatment, progression to ESRD and mortality in patients with type 1 diabetes with advanced nephropathy are still very high and differ among countries. Finding causes of these differences may help reduce risk of these outcomes.

Differential Gene Expression in Diabetic Nephropathy in Individuals With Type 1 Diabetes.

CONTEXT: Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD) in the United States. OBJECTIVE: The aim of this study was to determine whether there were skin fibroblast gene expression differences between subjects with type 1 diabetes (T1D) with or without DN. SETTING: This was a cross-sectional study conducted in the University of Minnesota. PATIENTS: Study volunteers were 100 former participants of Genetics of Kidneys in Diabetes: 40 were diabetic nephropathy (DN) Controls, normoalbuminuric after ≥ 15 years of T1D; and 60 were DN Cases, 25 with proteinuria and 35 with ESRD. INTERVENTION(S): Skin fibroblasts were grown in high glucose (HG) for five passages (approximately 6 weeks). MAIN OUTCOME MEASURE(S): SF gene expression was assessed by transcriptome sequencing using the Illumina HiSeq 2000 platform. Pathway analyses tested directionally consistent group differences within the Kyoto Encyclopedia of Genes and Genomes pathways. RESULTS: Eight pathways, all related to cell cycle and repair, were up-regulated in the DN Controls vs the DN Cases. These pathways markedly overlapped with the pathways up-regulated by HG in T1D monozygotic twins (MZT), but not in their non-T1D MZT. DN Cases showed statistical trends toward up-regulation of these pathways vs non-T1D MZT, but much less so than the DN Controls. CONCLUSIONS: Together, these data suggest that SF from T1D patients undergo epigenetic modifications resulting in increased expression of genes in healing and repair pathways. These responses, much more robust in patients protected from DN, suggest that epigenetic factors are important in DN risk.

JDRF perspective: bridging the gap-translational research to prevent progression of diabetic nephropathy.

For those with type 1 diabetes (T1D), the diagnosis of diabetic nephropathy predicts a significant negative impact on quality of life and mortality risk. Diabetic nephropathy is a huge component of the potential cost of diabetes both to the individual and society. For this reason, JDRF and others have prioritized programs aimed to advance our understanding of diabetic nephropathy and translate findings to benefit patients with T1D. Although the current standard of care has reduced the incidence of diabetic nephropathy, a significant proportion of those with T1D are still at risk for declining renal function and progression to end-stage renal disease. Carefully directed research is needed to discover and translate novel targets and biomarkers for diabetic nephropathy to improve the prognosis and outlook for those with T1D and at risk for end-stage renal disease.

The first bromodomain of Brdt, a testis-specific member of the BET sub-family of double-bromodomain-containing proteins, is essential for male germ cell differentiation.

Brdt is a testis-specific member of the distinctive BET sub-family of bromodomain motif-containing proteins, a motif that binds acetylated lysines and is implicated in chromatin remodeling. Its expression is restricted to the germ line, specifically to pachytene and diplotene spermatocytes and early spermatids. Targeted mutagenesis was used to generate mice carrying a mutant allele of Brdt, Brdt(Delta)(BD1), which lacks only the first of the two bromodomains that uniquely characterize BET proteins. Homozygous Brdt(Delta)(BD1/)(Delta)(BD1) mice were viable but males were sterile, producing fewer and morphologically abnormal sperm. Aberrant morphogenesis was first detected in step 9 elongating spermatids, and those elongated spermatids that were formed lacked the distinctive foci of heterochromatin at the peri-nuclear envelope. Quantitative reverse transcription (RT)-PCR showed threefold increased levels of histone H1t (Hist1h1t) in Brdt(Delta)(BD1/)(Delta)(BD1) testes and chromatin immunoprecipitation revealed that Brdt protein, but not Brdt(DeltaBD1) protein, was associated with the promoter of H1t. Intracytoplasmic sperm injection suggested that the DNA in the Brdt(Delta)(BD1) mutant sperm could support early embryonic development and yield functional embryonic stem cells. This is the first demonstration that deletion of just one of the two bromodomains in members of the BET sub-family of bromodomain-containing proteins has profound effects on in vivo differentiation.

Cyclin A1-deficient mice lack histone H3 serine 10 phosphorylation and exhibit altered aurora B dynamics in late prophase of male meiosis.

Male mice lacking cyclin A1 protein are sterile. Their sterility results from an arrest in the meiotic cell cycle of spermatocytes, which we now identify as occurring at late diplotene, immediately before diakinesis. The stage of arrest in cyclin A1-deficient mice is distinct from the arrest seen in spermatocytes that are deficient in its putative catalytic partner Cdk2, which occurs much earlier in pachytene. The arrest in cyclin A1-deficient spermatocytes is also accompanied by an unusual clustering of centromeric heterochromatin. Consistent with a possible defect in the centromeric region, immunofluorescent staining of cyclin A1 protein shows localization in the region of the centromere. Phosphorylation of histone H3 at serine 10 in pericentromeric heterochromatin, which normally occurs in late diplotene, is reduced in spermatocytes from heterozygous Ccna1(+/-) testes and completely absent in spermatocytes with no cyclin A1 protein. Concomitantly, the levels of pericentromeric aurora B kinase, known to phosphorylate histone H3 during meiosis, are partially reduced in spermatocytes from testes of heterozygous mice and further reduced in homozygous null spermatocytes. These data suggest a critical and concentration-dependent function for cyclin A1 in the pericentromeric region in late diplotene of meiosis, perhaps in assembly or function of the passenger protein complex.