Novel Linkage Peaks Discovered for Diabetic Nephropathy in Individuals With Type 1 Diabetes

Genome-wide association studies (GWAS) and linkage studies have had limited success in identifying genome-wide significantly linked regions or risk loci for diabetic nephropathy (DN) in individuals with type 1 diabetes (T1D). As GWAS cohorts have grown, they have also included more documented and undocumented familial relationships. Here we computationally inferred and manually curated pedigrees in a study cohort of >6,000 individuals with T1D and their relatives without diabetes. We performed a linkage study for 177 pedigrees consisting of 452 individuals with T1D and their relatives using a genome-wide genotyping array with >300,000 single nucleotide polymorphisms and PSEUDOMARKER software. Analysis resulted in genome-wide significant linkage peaks on eight chromosomal regions from five chromosomes (logarithm of odds score >3.3). The highest peak was localized at the HLA region on chromosome 6p, but whether the peak originated from T1D or DN remained ambiguous. Of other significant peaks, the chromosome 4p22 region was localized on top of ARHGAP24, a gene associated with focal segmental glomerulosclerosis, suggesting this gene may play a role in DN as well. Furthermore, rare variants have been associated with DN and chronic kidney disease near the 4q25 peak, localized on top of CCSER1.     

Modulation of hepatic glucose production by non-esterified fatty acids in Type 2 (non-insulin-dependent) diabetes mellitus

Summary To study the effect of changes in plasma non-esterified fatty acid concentration on suppression of hepatic glucose production by insulin eight Type 2 (non-insulin-dependent) diabetic patients participated in three euglycaemic, hyperinsulinaemic (108pmol · m^2–1 · min^–1) clamp studies combined with indirect calorimetry and infusion of [3-³H]-glucose and [1-¹⁴C]palmitate; (1) a control experiment with infusion of NaCl 154 mmol/l, (2) heparin was infused together with insulin, and (3) an antilipolytic agent, Acipimox, was administered at the beginning of the experiment. Six healthy volunteers participated in the control experiment. Plasma non-esterified fatty acid concentrations during the insulin clamp were in diabetic patients: (1) 151±36 mol/1, (2) 949±178 mol/l, and (3) 65±9 mol/l; in healthy control subjects 93±13 mol/l. Non-esterified fatty acid transport rate, oxidation and non-oxidative metabolism were significantly higher during the heparin than during the Acipimox experiment (p<0.001). Suppression of hepatic glucose production by insulin was impaired in the diabetic compared to control subjects (255±42 vs 51±29 mol/min, p<0.01). Infusion of heparin did not affect the suppression of hepatic glucose production by insulin (231±49 mol/min), whereas Acipimox significantly enhanced the suppression (21±53 mol/min, p<0.001 vs 154 mmol/l NaCl experiment). We conclude that insulin-mediated suppression of hepatic glucose production is not affected by increased non-esterified fatty acid availability. In contrast, decreased non-esterified fatty acid availability enhances the suppression of hepatic glucose production by insulin.     

Pre-eclampsia but not pregnancy-induced hypertension is a risk factor for diabetic nephropathy in type 1 diabetic women

Aims/hypothesis Our aim was to study whether pre-eclampsia and pregnancy-induced hypertension are predictors of diabetic nephropathy in type 1 diabetic women. Materials and methods A total of 203 type 1 diabetic women, who were pregnant between 1988 and 1996 and followed at the Department of Obstetrics and Gynaecology in Helsinki, were re-assessed after an average of 11 years within the nationwide, multi-centre Finnish Diabetic Nephropathy Study. Diabetic nephropathy was defined as microalbuminuria, macroalbuminuria or end-stage renal disease. Results Patients with prior pre-eclampsia had diabetic nephropathy more often than patients with a normotensive pregnancy (diabetic nephropathy vs normal albumin excretion rate: 41.9% vs 8.9%; p<0.001), whereas patients with a history of pregnancy-induced hypertension did not (10.3% vs 8.9%; p=0.81). CHD was more prevalent in patients with a history of pre-eclampsia than in patients with a normotensive pregnancy (12.2% vs. 2.2%; p=0.03). Pre-eclampsia (odds ratio [OR] 7.7, 95% CI 1.6-36.1; p=0.01) and HbA_1c (OR 2.0, 95% CI 1.1-3.8; p<0.05) were associated with incident diabetic nephropathy even when adjusted for follow-up time, BMI, smoking, diabetes duration and age. Conclusions/interpretation These data suggest that a history of pre-eclamptic pregnancy but not pregnancy-induced hypertension is associated with an elevated risk of diabetic nephropathy. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible to authorised users.     

DDOST, PRKCSH and LGALS3, which encode AGE-receptors 1, 2 and 3, respectively, are not associated with diabetic nephropathy in type 1 diabetes

Aims/hypothesis  

The AGE receptors 1, 2 and 3, which are encoded by DDOST, PRKCSH and LGALS3, respectively, may be involved in the pathogenesis of diabetic complications. We sought to find out whether these genes are associated with diabetic nephropathy, cardiovascular disease and type 1 diabetes or related quantitative traits.     

Decreased expression of heat shock protein 72 in skeletal muscle of patients with type 2 diabetes correlates with insulin resistance

Oxidative stress has been ascribed a role in the pathogenesis of diabetes and its complications, and stress proteins have been shown to protect organisms in vitro and in vivo against oxidative stress. To study the putative role of one of the most abundant cytoprotective stress proteins, inducible cytoplasmic 72-kDa-mass heat shock protein (Hsp-72), in the pathogenesis of diabetes, we measured its mRNA concentration in muscle biopsies from six type 2 diabetic patients and six healthy control subjects (protocol 1) as well as in 12 twin pairs discordant for type 2 diabetes and 12 control subjects undergoing a euglycemic-hyperinsulinemic clamp in combination with indirect calorimetry (protocol 2). The amount of Hsp-72 mRNA in muscle was significantly lower in type 2 diabetic patients than in healthy control subjects (in protocol 1: 5.2 +/- 2.2 vs. 53 +/- 32 million copies of Hsp-72 mRNA/microg total RNA, n = 6, P = 0.0039; in protocol 2: 3.2 +/- 3.3 vs. 43 +/- 31 million copies of Hsp-72 mRNA/microg total RNA, n = 12, P = 0.0001). Hsp-72 mRNA levels were also markedly reduced in the nondiabetic co-twins compared with healthy control subjects (5.8 +/- 5.0 vs. 43 +/- 31, n = 12, P = 0.0001), but they were also statistically significantly different from their diabetic co-twins when the difference between the pairs was compared (P = 0.0280). Heat shock protein mRNA content in muscle of examined patients correlated with the rate of glucose uptake and other measures of insulin-stimulated carbohydrate and lipid metabolism. In conclusion, the finding of decreased levels of Hsp-72 mRNA in skeletal muscle of patients with type 2 diabetes and its relationship with insulin resistance raises the question of whether heat shock proteins are involved in the pathogenesis of skeletal muscle insulin resistance in type 2 diabetes.     

Haplotype construction of the FRDA gene and evaluation of its role in type II diabetes

A GAA-repeat in the X25 gene is causing Friedreich's ataxia (FRDA), a common neurodegenerative disease and >20% of FRDA patients develop type II diabetes (T2D). Linkage has previously been detected between T2D and chromosome 9p13-q21, the region that harbours the X25 gene, but association studies of this gene in T2D have been contradicting. Here, we examined whether genetic variation in the X25 gene is associated with risk for T2D. The GAA-repeat and 18 single nucleotide polymorphisms (SNPs) covering the X25 gene were genotyped in 220 trios in which the affected offspring had abnormal glucose tolerance. Any nominally significant findings were examined in an independent sample consisting of 523 individuals with T2D and 326 healthy controls. Previously reported results were analysed together with our data using a meta-analysis approach. There was no association between the GAA-repeat and T2D susceptibility in our study, which was supported by the meta-analysis including all previous publications. One SNP (rs2498429), 8.2 kb downstream of X25, was nominally associated with T2D in the trios (P=0.02) and showed a trend of association in the same direction in the case-controls (P=0.08; combined permuted P=0.01). Further analysis showed that the nine-marker haplotype containing the rare allele of rs2498429 was nominally associated with T2D in the trios (P<0.01) as well as in the case-controls (P=0.03). In conclusions, this study excludes a role of genetic variation within the X25 gene, but instead suggests that genetic variation downstream the X25 gene, may increase risk for T2D.     

Haplotype structure and genotype-phenotype correlations of the sulfonylurea receptor and the islet ATP-sensitive potassium channel gene region

The genes for the sulfonylurea receptor (SUR1; encoded by ABCC8) and its associated islet ATP-sensitive potassium channel (Kir6.2; encoded by KCNJ11) are adjacent to one another on human chromosome 11. Multiple studies have reported association of the E23K variant of Kir6.2 with risk of type 2 diabetes. Whether and how E23K itself-or other variant(s) in either of these two closely linked genes-influences type 2 diabetes remains to be fully determined. To better understand genotype-phenotype correlation at this important candidate gene locus, we 1) characterized haplotype structures across the gene region by typing 77 working, high-frequency markers spanning 207 kb and both genes; 2) performed association studies of E23K and nearby markers in >3,400 patients (type 2 diabetes and control) not previously reported in the literature; and 3) analyzed the resulting data for measures of insulin secretion. These data independently replicate the association of E23K with type 2 diabetes with an odds ratio (OR) in the new data of 1.17 (P = 0.003) as compared with an OR of 1.14 provided by meta-analysis of previously published, nonoverlapping data (P = 0.0002). We find that the E23K variant in Kir6.2 demonstrates very strong allelic association with a coding variant (A1369S) in the neighboring SUR1 gene (r(2) > 0.9) across a range of population samples, making it difficult to distinguish which gene and polymorphism in this region are most likely responsible for the reported association. We show that E23K is also associated with decreased insulin secretion in glucose-tolerant control subjects, supporting a mechanism whereby beta-cell dysfunction contributes to the common form of type 2 diabetes. Like peroxisome proliferator-activated receptor gamma, the SUR1/Kir6.2 gene region both contributes to the inherited risk of type 2 diabetes and encodes proteins that are targets for hypoglycemic medications, providing an intriguing link between the underlying mechanism of disease and validated targets for pharmacological treatment.     

Pharmacokinetic/pharmacodynamic models for the depletion of Vbeta5.2/5.3 T cells by the monoclonal antibody ATM-027 in patients with multiple sclerosis, as measured by FACS

AIMS: (i) To model the effects of the monoclonal antibody ATM-027 on the number of target cells and on the receptor density on the cell surface as measured by Fluorescence Activated Cell Sorter analysis, (ii) to investigate the effects of categorizing a continuous scale, and (iii) to simulate a phase II trial from phase I data in order to evaluate the predictive performance of the model by comparison with the actual trial results. METHODS: Based on the data from one phase I and one phase II study in multiple sclerosis (MS) patients, models were developed to characterize the pharmacokinetics and pharmacodynamics of the monoclonal antibody ATM-027 and its effects on Vbeta5.2/5.3+ T cells. The pharmacodynamic variables were the number of target T cells and the expression of its receptor. The latter was modelled in both a categorical and continuous way. The modelling was performed with a nonlinear mixed effects approach using the software NONMEM. The joint continuous models were used to simulate the phase II trial from the phase I data. RESULTS: The pharmacokinetics of ATM-027 were characterized by a two-compartment model with a total volume of distribution of 5.9 litres and a terminal half-life of 22.3 days (phase II parameter estimates) in the typical patient. Continuous receptor expression was modelled using an inhibitory sigmoidal Emax-model. Similar results from the phase I and phase II data were obtained, and EC50 was estimated to be 138 and 148 microg litre(-1), respectively. Categorical receptor expression was modelled using a proportional odds model, and the EC50 values obtained were highly correlated with those from the continuous model. The numbers of target T cells were also modelled and treatment with ATM-027 decreased the number of cells to 25.7% and 28.9% of their baseline values in the phase I and II trials, respectively. EC50s for the decrease in the number of T cells were 83 microg litre(-1) and 307 microg litre(-1), respectively. Simulations of the phase II trial from the phase I models gave good predictions of the dosing regimens administered in the phase II study. CONCLUSION: All aspects of effects of the monoclonal antibody ATM-027 on Vbeta5.2/5.3+ T cells were modelled and the phase II trial was simulated from phase I data. The effects of categorizing a continuous scale were also evaluated.