OBJECTIVE-Hepatic steatosis is common in type 2 diabetes. It is causally linked to the features of the metabolic syndrome, liver cirrhosis, and cardiovascular disease. Experimental data have... Show moreOBJECTIVE-Hepatic steatosis is common in type 2 diabetes. It is causally linked to the features of the metabolic syndrome, liver cirrhosis, and cardiovascular disease. Experimental data have indicated that increased liver fat may impair hepatic perfusion and metabolism. The aim of the current study was to assess hepatic parenchymal perfusion, together with glucose and fatty acid metabolism, in relation to hepatic triglyceride content. RESEARCH DESIGN AND METHODS-Fifty-nine men with well controlled type 2 diabetes and 18 age-matched healthy normoglycemic men were studied using positron emission tomography to assess hepatic tissue perfusion, insulin-stimulated glucose, and fasting fatty acid metabolism, respectively, in relation to hepatic triglyceride content, quantified by proton magnetic resonance spectroscopy. Patients were divided into two groups with hepatic triglyceride content below (type 2 diabetes-low) or above (type 2 diabetes-high) the median of 8.6%. RESULTS-Type 2 diabetes-high patients had the highest BMI and A1C and lowest whole-body insulin sensitivity (ANOVA, all P < 0.001). Compared with control subjects and type 2 diabetes-low patients, type 2 diabetes-high patients had the lowest hepatic parenchymal perfusion (P = 0.004) and insulin-stimulated hepatic glucose uptake (P = 0.013). The observed decrease in hepatic fatty acid influx rate constant, however, only reached borderline significance (P = 0.088). In type 2 diabetic patients, hepatic parenchymal perfusion (r = -0.360, P = 0.007) and hepatic fatty acid influx rate constant (r = -0.407, P = 0.007) correlated inversely with hepatic triglyceride content. In a pooled analysis, hepatic fat correlated with hepatic glucose uptake (r = -0.329, P = 0.004). CONCLUSIONS-In conclusion, type 2 diabetic patients with increased hepatic triglyceride content showed decreased hepatic parenchymal perfusion and hepatic insulin mediated glucose uptake, suggesting a potential modulating effect of hepatic fat on hepatic physiology. Diabetes 59:2747-2754, 2010 Show less
Declercq, J.; Kumar, A.; Diepen, J.A. van; Vroegrijk, I.O.C.M.; Gysemans, C.; Pietro, C. di; ... ; Verfaillie, C.M. 2010
OBJECTIVE-It is believed that an organism remains normoglycemic despite an increase in the beta-cell mass because of decreased insulin production by beta-cells on a per-cell basis However, some... Show moreOBJECTIVE-It is believed that an organism remains normoglycemic despite an increase in the beta-cell mass because of decreased insulin production by beta-cells on a per-cell basis However, some transgenic mouse models with beta-cell hyperplasia suggest that insulin production remains excessive and that normoglycemia is maintained by insulin resistance METHODS-Here, we investigated the effect of an increased beta-cell mass on glycemia and insulin resistance by grafting excess normal islets in normoglycemic mice, as well as using targeted PLAG1 expression in beta-cells, which leads to beta-cell expansion. RESULTS-In both models, fasting plasma insulin levels were increased, even though animals were normoglycemic. After an intraperitoneal glucose tolerance test, plasma insulin levels increased, which was associated with improved glucose clearing Under these conditions, normoglycemia is maintained by hepatic insulin resistance as demonstrated by hyperinsulinemic euglycemic clamp experiments. CONCLUSIONS-In conclusion, we demonstrate that when excess beta-cells are grafted, insulin production on a per beta-cell basis is not sufficiently decreased, leading to hyperinsulinemia and hepatic insulin resistance. This observation might be important for the design of stem cell-based islet replacement therapies. Diabetes 59:1957-1965, 2010 Show less
OBJECTIVE-Type I diabetes results from selective T-cell-mediated destruction of the insulin-producing beta-cells in the pancreas. In this process, islet epitope-specific CD8(+) T-cells play a... Show moreOBJECTIVE-Type I diabetes results from selective T-cell-mediated destruction of the insulin-producing beta-cells in the pancreas. In this process, islet epitope-specific CD8(+) T-cells play a pivotal role. Thus, monitoring of multiple islet-specific CD8(+) T-cells may prove to be valuable for measuring disease activity, progression, and intervention. Yet, conventional detection techniques (ELISPOT and HLA tetramers) require many cells and are relatively insensitive. RESEARCH DESIGN AND METHODS-Here, we used a combinatorial quantum dot major histocompatibility complex multimer technique to simultaneously monitor the presence of HLA-A2 restricted insulin B10-18, prepro-insulin (PPI)(15-24), islet antigen (IA)-2(797-805), GAD65(114-123) islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)(265-973), and prepro islet amyloid polypeptide (ppIAPP)(5-13)-specific CD8(+) T-cells in recent-onset diabetic patients, their siblings, healthy control subjects, and islet cell transplantation recipients. RESULTS-Using this kit, islet autoreactive CD8(+) T-cells recognizing insulin B10-18, IA-2(797-805), and IGRP(265-273) were shown to be frequently detectable in recent-onset diabetic patients but rarely in healthy control subjects; PPI15-24 proved to be the most sensitive epitope. Applying the "Diab-Q-kit" to samples of islet cell transplantation recipients allowed detection of changes of autoreactive T-cell frequencies against multiple islet cell-derived epitopes that were associated with disease activity and correlated with clinical outcome. CONCLUSIONS-A kit was developed that allows simultaneous detection of CD8(+) T-cells reactive to multiple HLA-A2-restricted beta-cell epitopes requiring limited amounts of blood, without a need for in vitro culture, that is applicable on stored blood samples. Diabetes 59:1721-1730, 2010 Show less
OBJECTIVE-To investigate the relationship between fasting glucose levels, insulin resistance, and cognitive impairment in old age. Diabetes is associated with cognitive impairment in older people.... Show moreOBJECTIVE-To investigate the relationship between fasting glucose levels, insulin resistance, and cognitive impairment in old age. Diabetes is associated with cognitive impairment in older people. However, the link between elevated fasting glucose levels and insulin resistance in nondiabetic individuals, and the risk of cognitive impairment is unclear. RESEARCH DESIGN AND METHODS-We analyzed data from, in total, 8,447 participants in two independent prospective studies: the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER), 5,019 participants, aged 69-84 years, and the Rotterdam Study, 3,428 participants, aged 61-97 years. Fasting glucose levels were assessed at baseline in both studies; fasting insulin levels were assessed in the Rotterdam Study only. Cognitive function was assessed in both studies at baseline and during follow-up. RESULTS-Subjects with diabetes had impaired cognitive function at baseline. In contrast, in people without a history of diabetes, there was no clear association between baseline fasting glucose levels and executive function and memory, nor was there a consistent relationship between elevated baseline fasting glucose levels and the rate of cognitive decline in either cohort. Insulin resistance (homeostasis model assessment index) was also unrelated to cognitive function and decline. CONCLUSIONS-Elevated fasting glucose levels and insulin resistance are not associated with worse cognitive function in older people without a history of diabetes. These data suggest either that there is a threshold for effects of dysglycemia on cognitive function or that factors other than hyperglycemia contribute to cognitive impairment in individuals with frank diabetes. Diabetes 59:1601-1607, 2010 Show less
OBJECTIVE-Regulatory T-cells (Tregs) recognizing islet autoantigens are proposed as a key mechanism in the maintenance of self-tolerance and protection from type 1 diabetes. To date, however,... Show moreOBJECTIVE-Regulatory T-cells (Tregs) recognizing islet autoantigens are proposed as a key mechanism in the maintenance of self-tolerance and protection from type 1 diabetes. To date, however, detailed information on such cells in humans, and insight into their mechanisms of action, has been lacking. We previously reported that a subset of CD4 T-cells secreting high levels of the immunosuppressive cytokine interleukin-10 (11,10) is significantly associated with late onset of type 1 diabetes and is constitutively present in a majority of nondiabetic Here, we test the hypothesis that these T-cells represent a naturally generated population of Tregs capable of suppressing proinflammatory T-cell responses. RESEARCH DESIGN AND METHODS-We isolated and cloned islet-specific IL-10-secreting CD4(+) T-cells from nondiabelie individuals after brief ex vivo exposure to islet autoantigens using cytokine capture technology and examined their phenotype and regulatory potential. RESULTS-Islet-specific IL-10 CD4 T-cells are potent suppressors of Th1 effector cells, operating through a linked suppression mechanism in which there is an absolute requirement for the cognate antigen of both the regulatory and effector T-cells to be presented by the same antigen-presenting cell (APC). The regulatory T-cells secrete perforin and granzymes, and suppression is associated with the specific killing of APCs presenting antigen to effector T-cells. CONCLUSIONS-This hitherto undescribed population of islet autoantigen-specific Tregs displays unique characteristics that offer exquisite specificity and control over the potential for pathological autoreactivity and may provide a suitable target with which to strengthen beta-cell-specific tolerance. Diabetes 59: 1451-1460, 2010 Show less
Mooyaart, A.L.; Zutinic, A.; Bakker, S.J.L.; Grootendorst, D.C.; Kleefstra, N.; Valkengoed, I.G.M. van; ... ; Heer, E. de 2010
OBJECTIVE-The 5-5 homozygous CNDP1 (carnosinase) genotype is associated with a reduced risk of diabetic nephropathy. We investigated whether this association is sex specific and independent of... Show moreOBJECTIVE-The 5-5 homozygous CNDP1 (carnosinase) genotype is associated with a reduced risk of diabetic nephropathy. We investigated whether this association is sex specific and independent of susceptibility for type 2 diabetes. RESEARCH DESIGN AND METHODS-Three separate groups of 114, 90, and 66 patients with type 2 diabetes and diabetic nephropathy were included in this study and compared with 93 patients with type 2 diabetes for >15 years without diabetic nephropathy and 472 population control subjects. The diabetes control group was used to determine an association in the three patient groups separately, and the population control group was used to estimate the genotype risk [odds ratio (CI)] for the population in a pooled analysis. The population control subjects were also compared with 562 patients with type 2 diabetes without diabetic nephropathy to determine whether the association was independent of type 2 diabetes. The CNDP1 genotype was determined by fragment analysis after PCR amplification. RESULTS-The frequency of the 5-5 homozygous genotype was 28, 36, and 41% in the three diabetic nephropathy patient groups and 43 and 42% in the diabetic and population control subjects, respectively. The 5-5 homozygous genotype occurred significantly less frequently in women in all three patient groups compared with diabetic control subjects. The genotype risk for the population was estimated to be 0.5 (0.30-0.68) in women and 1.2 (0.77-1.69) in men. The 562 patients with type 2 diabetes without diabetic nephropathy did not differ from the general population (P = 0.23). CONCLUSIONS-This study suggests that the association between the CNDP1 gene and diabetic nephropathy is sex specific and independent of susceptibility for type 2 diabetes. Diabetes 59:1555-1559, 2010 Show less
OBJECTIVE-At least 20 type 2 diabetes loci have now been identified, and several of these are associated with altered beta-cell function. In this study, we have investigated the combined effects of... Show moreOBJECTIVE-At least 20 type 2 diabetes loci have now been identified, and several of these are associated with altered beta-cell function. In this study, we have investigated the combined effects of eight known beta-cell loci on insulin secretion stimulated by three different secretagogues during hyperglycemic clamps. RESEARCH DESIGN AND METHODS-A total of 447 subjects originating from four independent studies in the Netherlands and Germany (256 with normal glucose tolerance [NGT]/191 with impaired glucose tolerance [IGT]) underwent a hyperglycemic clamp. A subset had an extended clamp with additional glucagon-like peptide (GLP)-1 and arginine (n = 224). We next genotyped single nucleotide polymorphisms in TCF7L2, KCNJ11, CDKAL1, IGF2BP2, HHEX/IDE, CDKV2A/B, SLC30A8, and MTNR1B and calculated a risk allele score by risk allele counting. RESULTS-The risk allele score was associated with lower first-phase glucose-stimulated insulin secretion (GSIS) (P = 7.1 X 10(-6)). The effect size was equal in subjects with NGT and IGT. We also noted an inverse correlation with the disposition index (P = 1.6 X 10(-3)). When we stratified the study population according to the number of risk alleles into three groups, those with a medium- or high-risk allele score had 9 and 23% lower first-phase GSIS. Second-phase GSIS, insulin sensitivity index and GLP-1, or arginine-stimulated insulin release were not significantly different. CONCLUSIONS-A combined risk allele score for eight known beta-cell genes is associated with the rapid first-phase GSIS and the disposition index. The slower second-phase GSIS, GLP-1, and arginine-stimulated insulin secretion are not associated, suggesting that especially processes involved in rapid granule recruitment and exocytosis are affected in the majority of risk loci. Diabetes 59:287-292, 2010 Show less
