Eli Ipp

Genome-wide scans for diabetic nephropathy and albuminuria in multiethnic populations: The Family Investigation of Nephropathy and Diabetes (FIND)

The Family Investigation of Nephropathy and Diabetes (FIND) was initiated to map genes underlying susceptibility to diabetic nephropathy. A total of 11 centers participated under a single collection protocol to recruit large numbers of diabetic sibling pairs concordant and discordant for diabetic nephropathy. We report the findings from the first-phase genetic analyses in 1,227 participants from 378 pedigrees of European-American, African-American, Mexican-American, and American Indian descent recruited from eight centers. Model-free linkage analyses, using a dichotomous definition for diabetic nephropathy in 397 sibling pairs, as well as the quantitative trait urinary albumin-to-creatinine ratio (ACR), were performed using the Haseman-Elston linkage test on 404 microsatellite markers. The strongest evidence of linkage to the diabetic nephropathy trait was on chromosomes 7q21.3, 10p15.3, 14q23.1, and 18q22.3. In ACR (883 diabetic sibling pairs), the strongest linkage signals were on chromosomes 2q14.1, 7q21.1, and 15q26.3. These results confirm regions of linkage to diabetic nephropathy on chromosomes 7q, 10p, and 18q from prior reports, making it important that genes underlying these peaks be evaluated for their contribution to nephropathy susceptibility. Large family collections consisting of multiple members with diabetes and advanced nephropathy are likely to accelerate the identification of genes causing diabetic nephropathy, a life-threatening complication of diabetes.

Diabetes, Metformin, and Breast Cancer in Postmenopausal Women

PURPOSE Emerging evidence suggests that metformin may reduce breast cancer incidence, but reports are mixed and few provide information on tumor characteristics. Therefore, we assessed associations among diabetes, metformin use, and breast cancer in postmenopausal women participating in Womens Health Initiative clinical trials. PATIENTS AND METHODS In all, 68,019 postmenopausal women, including 3,401 with diabetes at study entry, were observed over a mean of 11.8 years with 3,273 invasive breast cancers diagnosed. Diabetes incidence status was collected throughout follow-up, with medication information collected at baseline and years 1, 3, 6, and 9. Breast cancers were confirmed by review of central medical records and pathology reports. Cox proportional hazards regression, adjusted for breast cancer risk factors, compared breast cancer incidence in women with diabetes who were metformin users or nonusers with breast cancer incidence in women without diabetes. RESULTS Compared with that in women without diabetes, breast cancer incidence in women with diabetes differed by diabetes medication type (P = .04). Women with diabetes receiving medications other than metformin had a slightly higher incidence of breast cancer (hazard ratio [HR], 1.16; 95% CI, 0.93 to 1.45), and women with diabetes who were given metformin had lower breast cancer incidence (HR, 0.75; 95% CI, 0.57 to 0.99). The association was observed for cancers positive for both estrogen receptor and progesterone receptor and those that were negative for human epidermal growth factor receptor 2. CONCLUSION Metformin use in postmenopausal women with diabetes was associated with lower incidence of invasive breast cancer. These results can inform future studies evaluating metformin use in breast cancer management and prevention.

Pulsatile Insulin Secretion in Isolated Rat Islets

The pancreas secretes insulin in an oscillatory fashion, but the precise site of the pacemaker for pulsatile insulin secretion has not been identified. These studies were designed to determine whether islets also secrete insulin in a pulsatile fashion if they are isolated from their pancreatic milieu. Isolated rat islets (80–100) were perifused 8 h in culture medium after overnight incubation, and samples were collected at 3.3-min intervals. Insulin secretion was evaluated for pulsatility with the Clifton Cycle Detection Program. Perifusion of islets was associated with a spontaneous, persistent, and regular pulsatility of insulin secretion, which was observed in all conditions tested. Perifusion with medium containing 5.5 mM glucose (n = 11) demonstrated oscillations with a mean periodicity of 17.6 ±1.1 min and a mean amplitude of 4.8 ± 0.4 μU/ml when overall mean insulin concentration was 16.7 ± 2.4 μU/ml. When the glucose concentration was 16.7 mM (n = 9), overall mean insulin concentration was 54.4 ± 2.6 μU/ml, with increases in periodicity (22.0 ±1.3 min) and amplitude (10.7 ± 0.5 μU/ml). All measurements were significantly different from those observed during perifusion with 5.5 mM glucose (P < 0.02−0.001). Theophylline (1 mM) also enhanced the overall mean insulin concentration and amplitude (69.4 ± 10.4 and 14.2 ±1.2 μU/ml, respectively) compared with control studies without theophylline (16.7 ± 5.3 and 4.3 ± 0.5 μU/ml) (P < 0.01). The period of the cycle was also increased from 17.5 ± 1.1 to 26.4 ± 6.3 min, but this was not significantly different from the control group. When glucose was delivered in rhythmic fashion with a period of 40 min, the characteristics of the insulin cycling approximated those of the glucose oscillation rather than the spontaneously generated insulin pulsatility. We conclude that a pacemaker for pulsatile insulin secretion is located within the islets of Langerhans and is subject to influence by both glucose concentration and pattern of delivery and cAMP-mediated mechanisms.

Genome-Wide Scan for Estimated Glomerular Filtration Rate in Multi-Ethnic Diabetic Populations The Family Investigation of Nephropathy and Diabetes (FIND)

OBJECTIVE— Diabetic nephropathy, the most common cause of end-stage renal disease, aggregates in families and specific ethnic groups. Deconstructing diabetic nephropathy into intermediate, quantitative phenotypes may increase feasibility of detecting susceptibility loci by genetic screens. Glomerular filtration rate (GFR), which characterizes diabetic nephropathy, was employed as a quantitative trait in a preliminary whole-genome scan. RESEARCH DESIGN AND METHODS— Estimated GFR (eGFR) was calculated for 882 diabetic sibpairs (mean age 57 years) of African-American (25.6% of total), American Indian (8.6%), European-American (14.2%), and Mexican-American (51.6%) descent enrolled in the initial phase of the Family Investigation of Nephropathy and Diabetes (FIND). A whole-genome scan was performed using 404 microsatellite markers (average spacing 9 cM) and model-free linkage analysis. RESULTS— For all ethnicities combined, strong evidence for linkage was observed on chromosomes 1q43 (P = 3.6 × 10−3), 7q36.1 (P = 2.1 × 10−4), 8q13.3 (P = 4.6 × 10−4), and 18q23.3 (P = 2.7 × 10−3). Mexican-American families, who comprised the major ethnic subpopulation in FIND, contributed to linkage on chromosomes 1q43, 2p13.3, 7q36.1, 8q13.3, and 18q23.3, whereas African-American and American-Indian families displayed linkage peaks on chromosomes 11p15.1 and 15q22.3, respectively. CONCLUSIONS— We have demonstrated multiple chromosomal regions linked to eGFR in a multi-ethnic collection of families ascertained by a proband with diabetic nephropathy. Identification of genetic variants within these loci that are responsible for the linkage signals could lead to predictive tests or novel therapies for subsets of patients at risk for diabetic nephropathy.

Genome-Wide Scan for Estimated GFR in Multi-Ethnic Diabetic Populations: The Family Investigation of Nephropathy and Diabetes

OBJECTIVE— Diabetic nephropathy, the most common cause of end-stage renal disease, aggregates in families and specific ethnic groups. Deconstructing diabetic nephropathy into intermediate, quantitative phenotypes may increase feasibility of detecting susceptibility loci by genetic screens. Glomerular filtration rate (GFR), which characterizes diabetic nephropathy, was employed as a quantitative trait in a preliminary whole-genome scan. RESEARCH DESIGN AND METHODS— Estimated GFR (eGFR) was calculated for 882 diabetic sibpairs (mean age 57 years) of African-American (25.6% of total), American Indian (8.6%), European-American (14.2%), and Mexican-American (51.6%) descent enrolled in the initial phase of the Family Investigation of Nephropathy and Diabetes (FIND). A whole-genome scan was performed using 404 microsatellite markers (average spacing 9 cM) and model-free linkage analysis. RESULTS— For all ethnicities combined, strong evidence for linkage was observed on chromosomes 1q43 (P = 3.6 × 10−3), 7q36.1 (P = 2.1 × 10−4), 8q13.3 (P = 4.6 × 10−4), and 18q23.3 (P = 2.7 × 10−3). Mexican-American families, who comprised the major ethnic subpopulation in FIND, contributed to linkage on chromosomes 1q43, 2p13.3, 7q36.1, 8q13.3, and 18q23.3, whereas African-American and American-Indian families displayed linkage peaks on chromosomes 11p15.1 and 15q22.3, respectively. CONCLUSIONS— We have demonstrated multiple chromosomal regions linked to eGFR in a multi-ethnic collection of families ascertained by a proband with diabetic nephropathy. Identification of genetic variants within these loci that are responsible for the linkage signals could lead to predictive tests or novel therapies for subsets of patients at risk for diabetic nephropathy.

Genome-wide association study in a Chinese population with diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of preventable blindness in adults. To identify genetic contributions in DR, we studied 2071 type 2 diabetics. We first conducted a genome-wide association study of 1007 individuals, comparing 570 subjects with ≥8 years duration without DR (controls) with 437 PDR (cases) in the Chinese discovery cohort. Cases and controls were similar for HbA1c, diabetes duration and body mass index. Association analysis with imputed data identified three novel loci: TBC1D4-COMMD6-UCHL3 (rs9565164, P = 1.3 × 10(-7)), LRP2-BBS5 (rs1399634, P = 2.0 × 10(-6)) and ARL4C-SH3BP4 (rs2380261, P = 2.1 × 10(-6)). Analysis of an independent cohort of 585 Hispanics diabetics with or without DR though did not confirm these signals. These genes are still of particular interest because they are involved in insulin regulation, inflammation, lipid signaling and apoptosis pathways, all of which are possibly involved with DR. Our finding nominates possible novel loci as potential DR susceptibility genes in the Chinese that are independent of the level of HbA1c and duration of diabetes and may provide insight into the pathophysiology of DR.

Genome-Wide Association and Trans-ethnic Meta-Analysis for Advanced Diabetic Kidney Disease: Family Investigation of Nephropathy and Diabetes (FIND).

Diabetic kidney disease (DKD) is the most common etiology of chronic kidney disease (CKD) in the industrialized world and accounts for much of the excess mortality in patients with diabetes mellitus. Approximately 45% of U.S. patients with incident end-stage kidney disease (ESKD) have DKD. Independent of glycemic control, DKD aggregates in families and has higher incidence rates in African, Mexican, and American Indian ancestral groups relative to European populations. The Family Investigation of Nephropathy and Diabetes (FIND) performed a genome-wide association study (GWAS) contrasting 6,197 unrelated individuals with advanced DKD with healthy and diabetic individuals lacking nephropathy of European American, African American, Mexican American, or American Indian ancestry. A large-scale replication and trans-ethnic meta-analysis included 7,539 additional European American, African American and American Indian DKD cases and non-nephropathy controls. Within ethnic group meta-analysis of discovery GWAS and replication set results identified genome-wide significant evidence for association between DKD and rs12523822 on chromosome 6q25.2 in American Indians (P = 5.74x10-9). The strongest signal of association in the trans-ethnic meta-analysis was with a SNP in strong linkage disequilibrium with rs12523822 (rs955333; P = 1.31x10-8), with directionally consistent results across ethnic groups. These 6q25.2 SNPs are located between the SCAF8 and CNKSR3 genes, a region with DKD relevant changes in gene expression and an eQTL with IPCEF1, a gene co-translated with CNKSR3. Several other SNPs demonstrated suggestive evidence of association with DKD, within and across populations. These data identify a novel DKD susceptibility locus with consistent directions of effect across diverse ancestral groups and provide insight into the genetic architecture of DKD.

Genomewide Linkage Scan for Diabetic Renal Failure and Albuminuria: The FIND Study

Background: Diabetic nephropathy (DN) is a leading cause of mortality and morbidity in patients with type 1 and type 2 diabetes. The multicenter FIND consortium aims to identify genes for DN and its associated quantitative traits, e.g. the urine albumin:creatinine ratio (ACR). Herein, the results of whole-genome linkage analysis and a sparse association scan for ACR and a dichotomous DN phenotype are reported in diabetic individuals. Methods: A genomewide scan comprising more than 5,500 autosomal single nucleotide polymorphism markers (average spacing of 0.6 cM) was performed on 1,235 nuclear and extended pedigrees (3,972 diabetic participants) ascertained for DN from African-American (AA), American-Indian (AI), European-American (EA) and Mexican-American (MA) populations. Results: Strong evidence for linkage to DN was detected on chromosome 6p (p = 8.0 × 10–5, LOD = 3.09) in EA families as well as suggestive evidence for linkage to chromosome 7p in AI families. Regions on chromosomes 3p in AA, 7q in EA, 16q in AA and 22q in MA displayed suggestive evidence of linkage for urine ACR. The linkage peak on chromosome 22q overlaps the MYH9/APOL1 gene region, previously implicated in AA diabetic and nondiabetic nephropathies. Conclusion: These results strengthen the evidence for previously identified genomic regions and implicate several novel loci potentially involved in the pathogenesis of DN.

Detection of undiagnosed diabetes and prediabetic states in high-risk emergency department patients.

BACKGROUND Diabetes is often not diagnosed until complications appear, and one-third of those with diabetes may be undiagnosed. Prediabetes and diabetes are conditions in which early detection would be appropriate, because the duration of hyperglycemia is a predictor of adverse outcomes, and there are effective interventions to prevent disease progression and to reduce complications. OBJECTIVES The objectives were to determine the prevalence of diabetes mellitus and prediabetes in emergency department (ED) patients with an elevated random glucose or risk factors for diabetes but without previously diagnosed diabetes and to identify which at-risk ED patients should be considered for referral for confirmatory diagnostic testing. METHODS This two-part study was composed of a prospective 2-year cohort study, and a 1-week cross-sectional survey substudy, set in an urban ED in Los Angeles County, California. A convenience sample was enrolled of 528 ED patients without previously diagnosed diabetes with either 1) a random serum glucose > or = 140 mg/dL regardless of the time of last food intake or a random serum glucose > or = 126 mg/dL if more than 2 hours since last food intake or 2) at least two predefined diabetes risk factors. Measurements included presence of diabetes risk factors, ED glucose, cortisol, insulin and glycosylated hemoglobin (HbA(1c)), and 2-hour oral glucose tolerance test results, administered at 6-week follow-up. RESULTS Glycemic status was confirmed at follow-up in 256 (48%) of the 528 patients. Twenty-seven (11%) were found to have diabetes, 141 (55%) had prediabetes, and 88 (34%) had normal results. Age, ED glucose, HbA(1c), cortisol, and random serum glucose > or = 140 mg/dL were associated with both diabetes and prediabetes on univariate analysis. A random serum glucose > or = 126 mg/dL after 2 hours of fasting was associated with diabetes but not prediabetes; ED cortisol, insulin, age > or = 45 years, race, and calculated body mass index (BMI) were associated with prediabetes but not diabetes. In multivariable models, among factors measurable in the ED, the only independent predictor of diabetes was ED glucose, while ED glucose, age > or = 45 years, and symptoms of polyuria and polydipsia were independent predictors of prediabetes. All at-risk subjects with a random ED blood glucose > 155 mg/dL had either prediabetes or diabetes on follow-up testing. CONCLUSIONS A substantial fraction of this urban ED study population was at risk for undiagnosed diabetes and prediabetes, and among the at-risk patients referred for follow-up, the majority demonstrated diabetes or prediabetes. Notably, all patients with two risk factors and a random serum glucose > 155 mg/dL were later diagnosed with prediabetes or diabetes. Consideration should be given to referring ED patients with risk factors and a random glucose > 155 mg/dL for follow-up testing.

Accuracy of Plasma Glucose Measurements in the Hypoglycemic Range

OBJECTIVE This study was designed to evaluate three different enzymatic methods for glucose measurement in plasma samples with special emphasis on glucose concentrations in the hypoglycemic range. RESEARCH DESIGN AND METHODS Glucose dehydrogenase (Hemo- Cue analyzer), glucose oxidase (YSI analyzer), and hexokinase (Abbott analyzer) methods were used to measure plasma samples that were obtained during research studies. RESULTS Mean glucose concentrations (n = 240) were 5.3 ± 0.2, 5.4 ± 0.2, and 5.6 ± 0.2 mM (95.6 ± 3.9, 96.7 ± 3.9, and 101.6 ± 4.0 mg/dl) using glucose dehydrogenase, glucose oxidase, and hexokinase, respectively (NS). In the hypoglycemic range, mean glucose concentrations with each method retained the same hierarchy of measurements: 2.7 ± 0.05, 2.8 ± 0.04, and 2.9 ± 0.03 mM (48.4 ± 0.9, 50.6 ± 0.8, and 52.3 ± 0.6 mg/dl) by glucose dehydrogenase, glucose oxidase, and hexokinase, respectively (P < 0.005). Individual glucose dehydrogenase measurements (n = 240) correlated well with glucose oxidase and hexokinase, r = 0.99, and were considerably easier to perform at the bedside. The differences between the glucose measurement methods were consistent and similar in low, normal, and high concentration ranges. CONCLUSIONS We conclude that any interpretation or comparison of critical clinical and research measurements of glucose in different settings take into account methodological differences, particularly in the hypoglycemic range.