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A S Krolewski

Publications and source records attributed to A S Krolewski.

At least 19 recordsLinked to original sources
PubMed2006

Polymorphisms in the gene encoding hepatocyte nuclear factor-4alpha and susceptibility to type 2 diabetes in a Polish population.

Recently, several association studies of type 2 diabetes mellitus (T2DM) and the hepatocyte nuclear factor (HNF)-4alpha gene were reported with conflicting results. Our aim was to search for association between two polymorphisms of HNF-4alpha and T2DM in Polish Caucasians. The study groups comprised of 461 T2DM cases and 366 controls. Genotype-quantitative trait analyses were based on the oral glucose tolerance test (OGTT), glucose and insulin results, and comprised 310 glucose-tolerant subjects. All individuals were genotyped for two HNF-4alpha polymorphisms. The frequencies of the minor alleles were as follows: 19.2% in T2DM vs. 17.6% in controls for rs2144908; and 20.6% vs. 20.1% for rs4810424, respectively. The distributions of alleles, genotypes, and haplotypes of the HNF-4alpha polymorphisms did not differ between the study groups (lowest P = 0.41). None of the examined SNPs showed an association in control subjects with quantitative traits of fasting plasma glucose, fasting insulin, as well as plasma glucose and insulin 2 hours after glucose load in OGTT. We conclude that both examined polymorphisms in HNF-4alpha are not associated with T2DM and prediabetic phenotypes in Polish Caucasian study groups of this size.

Blood Glucose↗
PubMed2006

A genome-wide linkage scan for genes controlling variation in urinary albumin excretion in type II diabetes.

The main hallmark of diabetic nephropathy is elevation in urinary albumin excretion. We performed a genome-wide linkage scan in 63 extended families with multiple members with type II diabetes. Urinary albumin excretion, measured as the albumin-to-creatinine ratio (ACR), was determined in 426 diabetic and 431 nondiabetic relatives who were genotyped for 383 markers. The data were analyzed using variance components linkage analysis. Heritability (h2) of ACR was significant in diabetic (h2=0.23, P=0.0007), and nondiabetic (h2=0.39, P=0.0001) relatives. There was no significant difference in genetic variance of ACR between diabetic and nondiabetic relatives (P=0.16), and the genetic correlation (rG=0.64) for ACR between these two groups was not different from 1 (P=0.12). These results suggested that similar genes contribute to variation in ACR in diabetic and nondiabetic relatives. This hypothesis was supported further by the linkage results. Support for linkage to ACR was suggestive in diabetic relatives and became significant in all relatives for chromosome 22q (logarithm of odds, LOD=3.7) and chromosome 7q (LOD=3.1). When analyses were restricted to 59 Caucasian families, support for linkage in all relatives increased and became significant for 5q (LOD=3.4). In conclusion, genes on chromosomes 22q, 5q and 7q may contribute to variation in urinary albumin excretion in diabetic and nondiabetic individuals.

Adult↗
PubMed2006

Examination of PPP1R3B as a candidate gene for the type 2 diabetes and MODY loci on chromosome 8p23.

The product of the PPP1R3B gene (G(L)) is the regulatory subunit of PP1 - a serine/threonine phosphatase involved in the modulation of glycogen synthesis in the liver and skeletal muscle. The PPP1R3B gene is located on chromosome 8p23 in a region that has been linked with type 2 diabetes and maturity-onset diabetes of the young (MODY). We examined whether sequence variants at the PPP1R3B locus are responsible for the linkage with diabetes observed at this location. RT-PCR analysis revealed the existence of two alternative promoters. These and the two exons of this gene were sequenced in the probands of 13 Joslin families showing the strongest evidence of linkage at 8p23. A total of 20 variants were observed: two in the 5' flanking region, one in the intron (9 bp 5' of exon 2), and 17 in the 3' UTR. The intronic variant generated a new acceptor splice site, resulting in an alternative splice variant with a longer 5' UTR. However, neither this nor other variants segregated with diabetes in the 13 'linked' families. Furthermore, allele frequencies were similar in 90 family probands from the Joslin Study and 347 unrelated controls. Thus, genetic variability in the PPP1R3B gene does not appear to contribute to diabetes in our mostly Caucasian families. However, a role cannot be excluded in other populations such as the Japanese, among whom linkage to diabetes is also observed at 8p23 and a non-synonymous mutation has been detected in the PPP1R3B gene.

5' Untranslated Regions↗
PubMed2005

Molecular genetic approaches for studying the etiology of diabetic nephropathy.

A critical challenge faced by clinical nephrologists today is the escalating number of patients developing end stage renal disease, a major proportion of which is attributed to diabetic nephropathy (DN). The need for new measures to prevent and treat this disease cannot be overemphasized. To this end, modern genetic approaches provide powerful tools to investigate the etiology of DN. Human studies have already established the importance of genetic susceptibility for DN. Several major susceptibility loci have been identified using linkage studies. In addition, linkage studies in rodents have pinpointed promising chromosomal segments that influence renal traits. Besides augmenting our understanding of disease pathogenesis, these animal studies may facilitate the cloning of disease susceptibility genes in man through the identification of homologous regions that contribute to renal disease. In human diabetes, various genes have been evaluated for their risk contribution to DN. This widespread strategy has been propelled by our knowledge of the glucose-activated pathways underlying DN. Evidence has emerged that a true association does indeed exist for some candidate genes. Furthermore, the in vivo manipulation of gene expression has shown that these genes can modify features of DN in transgenic and knockout rodent models, thus corroborating the findings from human association studies. Still, the exact molecular mechanisms involving these genes remain to be fully elucidated. This formidable task may be accomplished by continuing to harness the synergy between human and experimental genetic approaches. In this respect, our review provides a first synthesis of the current literature to facilitate this challenging effort.

Animals↗
PubMed2002

Risk of diabetes in siblings of index cases with Type 2 diabetes: implications for genetic studies.

AIMS: The goal was to estimate the sibling recurrence-risk ratio for Type 2 diabetes in families with diabetes occurring in middle age. Because diabetes aetiology involves environmental exposures and genetic susceptibility, we sought to identify determinants of the recurrence risk. METHODS: We surveyed patients diagnosed at ages 35-59 years (n = 563) to obtain information on the occurrence of diabetes in their relatives, particularly siblings (n = 1675). Age-specific prevalences of diabetes in the US population were used for comparison. RESULTS: The overall sibling recurrence-risk ratio for diabetes was low, about 1.8 in the Joslin families and even lower in three other studies that were reanalysed for comparison. In all studies, the diabetes risk in siblings of index cases without a history of diabetes in a parent was similar to that in the general population, suggesting that genetic factors contributed to the occurrence of diabetes in only a minority of these siblings. The fact that recurrence-risk ratios were elevated only in families with one or two diabetic parents indicates that susceptibility to Type 2 diabetes is transmitted primarily through an affected parent. In addition, the sibling recurrence-risk ratios were elevated even further in families with diabetes in both a parent and grandparent of the index case, and in siblings of non-obese index cases (percent ideal body weight < 120%). CONCLUSIONS: The selection of families with non-obese index cases and vertical transmission of diabetes through three generations may improve the success of efforts to map susceptibility genes for Type 2 diabetes.

Adult↗
PubMed2001

Mutation screening of the neurogenin-3 gene in autosomal dominant diabetes.

We investigated whether genetic variability in neurogenin-3, a basic helix-loop-helix transcription factor that is expressed in the developing pancreas, contributes to the etiology of maturity-onset diabetes of the young or other forms of autosomal dominant diabetes. Ninety-one probands of families with autosomal dominant diabetes were screened for neurogenin-3 mutations by dideoxy fingerprinting. Three sequence differences were identified: a polymorphism not affecting the amino acid sequence (L75L), a CA insertion/deletion in intron 1 (-44ins/del), and a C to T transition causing a serine to phenylalanine substitution (S199F). None of these sequence differences were more frequent in the family probands than in 179 nondiabetic controls. In contrast, allele 199F was weakly, but significantly, associated with common type 2 diabetes (199F frequencies = 0.436 in 132 cases with type 2 diabetes vs. 0.346 in the family probands and 0.346 in controls; P = 0.05). The relative risk of type 2 diabetes for 199F carriers was 1.7 (95% confidence interval, 1.04-2.7). We conclude that sequence differences in the neurogenin-3 gene do not play a major role in the development of autosomal dominant diabetes. Rather, they might contribute to common type 2 diabetes, although this finding must be replicated in other populations.

Adolescent↗
PubMed2001

Type 2 diabetes locus on 12q15. Further mapping and mutation screening of two candidate genes.

We recently reported evidence of a novel type 2 diabetes locus placed on chromosome 12q15 between markers D12S375 and D12S1684 (Diabetes 48:2246-2251, 1999). Four multigenerational families having logarithm of odds (LOD) scores >1.0 in the original analysis were genotyped for 11 additional markers in this interval to refine this mapping; this allowed us to narrow the linked region to the interval between markers D12S1693 and D12S326. In a multipoint parametric analysis using the VITESSE software, the LOD score for linkage at this location reached 3.1 in one of these families. This interval contains the gene for protein tyrosine phosphatase receptor type R (PTPRR)--a protein that may be involved in both insulin secretion and action. After determining PTPRR exon-intron structure, we identified several polymorphisms in this gene but no mutation segregating with diabetes. The search for mutations was also negative for carboxypeptidase M (CPM)--another candidate gene mapped to this region. In summary, our data provide further evidence for the existence of a type 2 diabetes locus on chromosome 12q15. This locus, however, does not appear to correspond to the PTPRR or CPM, although a contribution of mutations in regulatory regions cannot be excluded at this time.

Adolescent↗
PubMed2001

A nonlinear effect of hyperglycemia and current cigarette smoking are major determinants of the onset of microalbuminuria in type 1 diabetes.

Cigarette smoking and poor glycemic control are risk factors for diabetic nephropathy in type 1 diabetes. However, the specifics of the relation of these risk factors to the onset of this complication have not been elucidated. To investigate these issues, we followed for 4 years 943 Joslin Clinic patients aged 15-44 years with type 1 diabetes who had normoalbuminuria during the 2-year baseline period. Microalbuminuria developed in 109 of the 943 individuals, giving an incidence rate of 3.3/100 person-years. The risk of onset of microalbuminuria was predicted somewhat more precisely by the measurements during the 1st and 2nd years preceding onset than by all the measurements during the longer (4-year) interval, suggesting attenuation of the impact of past hyperglycemia over time. Point estimates of the incidence rate (per 100 person-years) according to quartiles of HbA(1c) during the 1st and 2nd years preceding the outcome were 1.3 in the 1st, 1.5 in the 2nd, 3.1 in the 3rd, and 6.9 in the 4th (P = 1.3 x 10(-9)). Point estimates of the incidence rate (per 100 person-years) according to smoking status were 7.9 for current smokers, 1.8 for past smokers, and 2.2 for those who had never smoked (P = 2.0 x 10(-7)). In a multiple logistic model, the independent effects of HbA(1c) level and cigarette smoking remained highly significant, but their magnitudes were reduced. Using the same covariates in a generalized additive model, we examined the shape of the relationship between HbA(1c) and onset of microalbuminuria and found significant nonlinearity in the logarithm of odds scale (P = 0.04). The slope was steeper with HbA(1c) >8% than <8%. Furthermore, the change in the slope was magnified among current smokers. In conclusion, patients with type 1 diabetes who smoke and have an HbA(1c) >8% have the highest risk of onset of microalbuminuria.

Adolescent↗
PubMed2000

Polymorphisms of human paraoxonase 1 gene (PON1) and susceptibility to diabetic nephropathy in type I diabetes mellitus.

AIMS/HYPOTHESIS: Oxidative stress is a putative mechanism in the development of diabetic nephropathy. Paraoxonase gene 1 is an HDL-bound enzyme that protects tissues against oxidative damage. Three common polymorphisms of paraoxonase gene 1, T-107C in the promoter, Leu54Met and Gln192Arg, that modify paraoxonase activity have been associated with cardiovascular disease. This study aimed to find whether these polymorphisms also contribute to the development of diabetic nephropathy. METHODS: The association between diabetic nephropathy and these three polymorphisms was examined in a case-control study. For this purpose, genomic DNA was collected from 188 patients with Type I (insulin-dependent) diabetes mellitus and diabetic nephropathy and from 179 unrelated patients with Type I diabetes but without diabetic nephropathy despite the duration of diabetes of 15 or more years. RESULTS: The genotype and allele frequencies for each of the three polymorphisms (T-107C, Leu54Met and Gln192Arg) were similar in cases and control subjects. CONCLUSION/INTERPRETATION: The three polymorphisms in paraoxonase gene 1 that have been associated with serum levels of paraoxonase are not associated with diabetic nephropathy. We show that this genetically determined component of the antioxidant capacity of HDL does not play a critical part in the development of diabetic nephropathy.

Adult↗
PubMed2000

Aldose reductase gene polymorphisms and susceptibility to diabetic nephropathy in Type 1 diabetes mellitus.

AIMS: To investigate association and linkage between DNA sequence variants in the aldose reductase (AR) gene on chromosome 7q35 and diabetic nephropathy (DN) in Type 1 diabetes mellitus. METHODS: By sequencing the promoter region and 10 exons in eight DN cases and eight controls, a frequent bi-allelic polymorphism (C-106T) was discovered. This polymorphism and the known 5'ALR2 dinucleotide repeat polymorphism were genotyped in unrelated cases with advanced nephropathy (n = 221) and unrelated controls with normoalbuminuria (n = 193). For a family based study, 166 case-trios (case and both parents) and 83 control-trios (control and both parents) were also genotyped. RESULTS: In the case-control study, carriers of the Z-2 allele of the 5'ALR2 polymorphism had a significantly higher risk of DN than non-carriers (odds ratios: 1.6 for heterozygotes and 2.1 for homozygotes, P<0.05 for each). The same was true for carriers of the T allele of the C-106T polymorphism (odds ratios: 1.6 for heterozygotes and 1.9 for homozygotes, P<0.05 for each). Moreover, the haplotype carrying both risk alleles was in excess in DN cases. In the family study, transmission of risk alleles from heterozygous parents was consistent with the case-control study, excess transmission in case-trios and deficient in control-trios. CONCLUSIONS: Association between DN and two DNA sequence variants in the promoter region of the AR gene implicates the polyol pathway in the development of kidney complications in Type 1 diabetes mellitus. Further examination of the molecular mechanisms underlying these findings may provide insight into the pathogenesis of DN.

Adolescent↗
PubMed2000

Urinary albumin excretion in families with type 2 diabetes is heritable and genetically correlated to blood pressure.

UNLABELLED: Urinary albumin excretion in families with type 2 diabetes is heritable and genetically correlated to blood pressure. BACKGROUND: Levels of urinary albumin excretion (UAE) are used to define both the diagnosis of diabetic nephropathy and its progression. Predisposition to high blood pressure is also a risk factor for susceptibility to nephropathy, but its relationship with UAE in type 2 diabetes remains unclear. In this study, we have estimated heritabilities of UAE and blood pressure and their correlation attributable to genetic effects using 96 large families ascertained for type 2 diabetes. METHODS: In these families, 630 individuals with type 2 diabetes and 639 individuals with normoglycemia were examined. All of them had a determination of UAE as the urinary albumin creatinine ratio (ACR), a convenient index of UAE, together with blood pressure and other variables, such as age, sex, and body mass index. A variance components approach was used to estimate heritability and genetic correlations for ACR and systolic and diastolic blood pressures (SBP and DBP) after adjustment for relevant covariates. RESULTS: In the 96 pedigrees, 6481 usable pairs of relatives were identified. In the total collection of pairs, heritability for ACR (h2 = 0.27, P < 0.001) was similar to that for blood pressure. When only pairs of diabetic relatives were analyzed (N = 1732), the estimates of heritability increased slightly for ACR (h2 = 0.31), SBP (h2 = 0.33), and DBP (h2 = 0.23). A significant genetic correlation was found between ACR and SBP (rg 0.27) and DBP (rg 0.26) in all pairs of relatives (P < 0.001). In pairs of diabetic relatives, these values were higher for SBP and DBP, 0.38 and 0.52, respectively. CONCLUSION: In families with type 2 diabetes, UAE is a heritable trait, with a heritability similar to that for blood pressure. A significant genetic correlation between UAE and blood pressure, particularly in the presence of diabetes, indicates that these traits share common genetic determinants.

Albuminuria↗
PubMed2000

Risk of advanced diabetic nephropathy in type 1 diabetes is associated with endothelial nitric oxide synthase gene polymorphism.

UNLABELLED: Risk of advanced diabetic nephropathy in type 1 diabetes is associated with endothelial nitric oxide synthase gene polymorphism. BACKGROUND: Polymorphisms in the endothelial nitric oxide synthase gene (eNOS) may be implicated in the development of nephropathy in patients with type 1 or insulin-dependent diabetes mellitus (IDDM). METHODS: Three groups of IDDM patients were selected to study this hypothesis: cases with advanced diabetic nephropathy (N = 78), cases with overt proteinuria but normal serum creatinine (N = 74), and controls with normoalbuminuria despite 15 years of diabetes (N = 195). Parents of 132 cases and 53 controls were also examined and were used for the transmission disequilibrium test, a family-based study design to test association. RESULTS: We examined four eNOS polymorphisms, and two were associated with diabetic nephropathy in the case-control comparisons: a T to C substitution in the promoter at position -786 and the a-deletion/b-insertion in intron 4. For the former, the risk of developing advanced nephropathy was higher for C allele homozygotes than for the other two genotypes (odds ratio 2.8, 95% CI, 1.4 to 5.6). For the latter polymorphism, it was the a-deletion carriers that had the higher risk (odds ratio 2.3, 95% CI, 1.3 to 4.0) in comparison with noncarriers. Both polymorphisms were analyzed together as haplotypes in a family-based study using the transmission disequilibrium test. The C/a-deletion haplotype was transmitted from heterozygous parents to cases with advanced diabetic nephropathy with a significantly higher frequency than expected (P = 0.004). CONCLUSION: The findings of the case-control and family-based studies demonstrate clearly that DNA sequence differences in eNOS influence the risk of advanced nephropathy in type 1 diabetes.

Adolescent↗
PubMed2000

Progression of microalbuminuria to proteinuria in type 1 diabetes: nonlinear relationship with hyperglycemia.

While small clinical trials have shown that improved glycemic control reduces the risk of progression of microalbuminuria to proteinuria, two recent clinical trials did not confirm this finding. We sought to reconcile the contradictory evidence by examining the dose-response relationship between hyperglycemia and progression of microalbuminuria to proteinuria in individuals with type 1 diabetes and microalbuminuria (n = 312) who were followed for 4 years with repeated assessments of urinary albumin excretion. Since 33 patients did not participate in follow-up (10.6%), data for 279 patients were analyzed. Urinary albumin excretion level worsened to proteinuria in 40 (4.1 per 100 person-years). To examine the dose-response relationship, baseline HbA1c was divided into four roughly equal groups using the cut points 8, 9, and 10%. The incidence rate varied significantly among the four groups (P = 0.008). Among those with HbA1c <8.0%, the incidence rate of progression was only 1.3 per 100 person-years, while it was 5.1, 4.2, and 6.7 per 100 person-years in the three other groups. We used generalized additive models to examine the dose-response curve using HbA1c as a continuous variable and found that the risk of progression rises steeply between an HbA1c of 7.5-8.5% and then remains approximately constant across higher levels. In conclusion, the results of this study suggest that, in patients with microalbuminuria, the risk of progression to overt proteinuria can be reduced by improved glycemic control only if the HbA1c is maintained below 8.5%. Moreover, below that value, the risk declines as the level of HbA1c decreases.

Adolescent↗