The TUDID Study - Background and Design of a Prospective Cohort.

Prevalence of both type 1 and type 2 diabetes mellitus is growing worldwide and one major cause for morbidity and mortality. However, not every patient develops diabetes-related complications, but causes for the individual susceptibility are still not fully understood. As a platform to address this, we initiated the TUDID (TUebingen DIabetes Database) study, a prospective, monocentric, observational study that includes adults with diabetes mellitus who are treated in the inpatient clinic of a University Hospital in southern Germany. Besides a thorough clinical examination and extensive laboratory tests (with integrated biobanking), major study focuses are the kidneys, the eyes, the vasculature as well as cognition and mood where standardized investigations for early stages for diabetes complications are performed. Analyses of the data generated by this precise characterization of diabetes-related complications will contribute to our understanding of the development and course of such complications, and thus facilitate the implementation of tailored treatment options that can reduce the risk and severity of diabetes-related complications.

Influence of Spinal Cord Stimulation on Insulin Sensitivity in Chronic Pain Patients.

BACKGROUND AND OBJECTIVE: This prospective, sham-controlled, randomized, cross-over study (NCT03637075), was designed to test the hypothesis that spinal cord stimulation (SCS) for the treatment of pain can also improve glucose metabolism and insulin sensitivity when compared to sham stimulation. METHODS: Ten non-diabetic participants (5 females, mean age 48.8 years) who had an SCS system implanted for the treatment of chronic neuropathic pain were studied. Whilst applying a hyperinsulinemic-euglycemic clamp, sham-stimulation and tonic stimulation were performed for 45 min (n=4) or 60 min (n=6) in each case randomly. The insulin sensitivity index and pain levels were determined. A second investigation, BurstDR stimulation was also conducted and the result was compared to that of sham stimulation (cross-over design). RESULTS: The insulin sensitivity improved significantly under the tonic stimulation when compared to the sham stimulation (p=0.037). BurstDR stimulation independently did not lead to a significantly improved insulin sensitivity compared to that after sham stimulation (p=0.16). We also examined the pain during the test and found no significant difference between sham and tonic stimulation (p=0.687). CONCLUSION: The results of this study show that tonic stimulation used for the treatment of pain could also improve glucose metabolism and insulin sensitivity. Further investigations are required to investigate the clinical relevance of the role of glucose metabolism in diabetic chronic pain participants and its underlying mechanisms.

Reproducibility and discrimination of different indices of insulin sensitivity and insulin secretion.

AIMS: Insulin sensitivity and insulin secretion can be estimated by multiple indices from fasting blood samples or blood samples obtained during oral glucose tolerance tests. The test-retest reliability of these indices in repeated measurements within the same individuals can strongly vary. METHODS: We analyzed data of persons without diabetes who underwent two repeated OGTTs. For each measurement pair, we calculated multiple commonly used indices for the assessment of insulin secretion and insulin sensitivity. We then evaluated the coefficient of variation (standard deviation/mean) and discriminant ratio for each index. RESULTS: 89 persons underwent two OGTTs with a median interval of 86 days (IQR 64-249). Among indices of insulin sensitivity derived from fasting blood samples, the revised quantitative insulin sensitivity check index had the smallest coefficient of variation (2.8 ± 2.1%) whereas the C-peptide based homeostasis model assessment 2 had the highest discriminant ratio (1.97 (1.65-2.39)). As for insulin sensitivity indices that are based on OGTT, the oral glucose insulin sensitivity index had the smallest coefficient of variation (6.5 ± 5.1%). The highest discriminant ratio was found for the non-esterified fatty acids-based insulin sensitivity index (NEFA-ISI, 2.70 (2.30-3.22)). For the assessment of insulin secretion from fasting variables, the lowest mean coefficient of variation was found for C-peptide based homeostasis model assessment 2 beta with 10.8 ± 8% and the highest discriminant ratio for the C-peptide / Glucose-Ratio (2.18 (1.84-2.63)). Among indices assessing insulin secretion from an OGTT, the lowest coefficient of variation was found for the ratio of the areas under the C-peptide and glucose curves from 0 to 120 minutes with 11.3 ± 9.7%. CONCLUSION: The data reveal large differences in the reproducibility and the discrimination capability of different indices that assess insulin sensitivity or insulin secretion. Our findings can aid the selection of an appropriate index in clinical studies.

Determinants of hepatic insulin clearance - Results from a Mendelian Randomization study.

AIMS/HYPOTHESIS: Besides insulin resistance, type 2 diabetes associates with decreased hepatic insulin clearance (HIC). We now tested for causal relationship of HIC to liver fat accumulation or features of the metabolic syndrome. METHODS: HIC was derived from oral glucose tolerance tests with the "Oral C-peptide and Insulin Minimal Models" (n = 3311). Liver fat was quantified by magnetic resonance spectroscopy (n = 1211). Mendelian Randomization was performed using established single nucleotide polymorphisms (SNPs; 115 for liver fat, 155 alanine-aminotransferase, 37 insulin sensitivity, 37 insulin secretion, 72 fasting insulin, 5285 BMI, 163 visceral fat, 270 waist circumference, 442 triglycerides, 620 HDL-Cholesterol, 193 C-reactive protein, 53 lipodystrophy-like phenotypes). RESULTS: HIC associated inversely with liver fat (p < 0.003) and insulin sensitivity (p < 0.0001). Both liver fat and HIC were independently associated with insulin sensitivity (p < 0.0001). Neither liver fat nor alanine-aminotransferase were causally linked to HIC, as indicated by Mendelian Randomization (Nliver fat = 1054, NHIC = 2254; Nalanineaminotranferase = 1985, NHIC = 2251). BMI-related SNPs were causally associated with HIC (NBMI = 2772, NHIC = 2259, p < 0.001) but not waist circumference-SNPs (NSNPs-waist circumference = 2751, NHIC = 2280). Genetically determined insulin sensitivity was not causally related to HIC (Ninsulin sensitivity = 2752, NHIC = 2286). C-reactive protein and HDL were causally associated with HIC, with higher C-reactive protein and lower HDL leading to higher HIC (NC-reactive protein = 2660, NHIC = 2240; NHDL = 2694, NHIC = 2275). CONCLUSIONS: This Mendelian Randomization analysis does not support a causal link between hepatic steatosis and HIC. Other components of the metabolic syndrome seem to compensate peripheral hyperinsulinemia by increasing hepatic insulin extraction.

Clinical Impact of the TCF7L2 Gene rs7903146 Type 2 Diabetes Mellitus Risk Polymorphism in Women with Gestational Diabetes Mellitus: Impaired Glycemic Control and Increased Need of Insulin Therapy.

BACKGROUND: The single nucleotide polymorphism in TCF7L2 rs7903146 is associated with an increased risk of type 2 diabetes mellitus and gestational diabetes mellitus. Mechanisms by which this mutation acts, and its impact on the clinical course of the diseases remain unclear. Here we investigated the clinical impact of the T risk allele in women with gestational diabetes mellitus. METHODS: We genotyped the C/T polymorphism in 164 Caucasian women with GDM (German n=114; Greek n=50). The impact of the T allele on the results of the 75g oral-glucose-tolerance-test, and on the required therapy (diet/lifestyle or insulin) was investigated. RESULTS: During oral-glucose-tolerance-test, women harboring the T allele displayed significantly higher glucose values at 60 min (p=0.034) and were more likely to require insulin therapy even after adjusting for confounders, such as BMI and age. CONCLUSION: These results provide evidence that the T risk allele in TCF7L2 rs7903146 is associated with failure in early postprandial glycemic control and requirement of insulin therapy in women with gestational diabetes mellitus, even after adjusting for confounding factors such BMI and age.

Genetic Variation in the 11ß-hydroxysteroid-dehydrogenase 1 Gene Determines NAFLD and Visceral Obesity.

CONTEXT/OBJECTIVE: Acute pharmacological inhibition of 11ß-hydroxysteroid-dehydrogenase 1 (11ß-HSD1), which converts cortisone into the much more potent cortisol in peripheral tissues, results in reduction of total, visceral, and liver fat but not insulin resistance. We now investigated whether lifelong alterations of 11ß-HSD1 activity similarly affect these cardiometabolic risk parameters by studying single-nucleotide polymorphisms (SNPs) in the 11ß-HSD1-coding gene (HSD11B1). DESIGN/METHODS: Liver fat content was measured by 1H-magnetic resonance spectroscopy and total and visceral fat mass by 1H-magnetic resonance tomography in 327 subjects. Insulin sensitivity (IS) was estimated during an oral glucose tolerance test and the euglycemic, hyperinsulinemic clamp (n = 219). Nine SNPs covering the whole HSD11B1 gene were genotyped. RESULTS: After correction for multiple testing, liver fat content strongly correlated with three SNPs, rs2235543, rs12565406, and rs4844880 (P = .0002, P = .001, and P = .0009, respectively), independently of gender and age. There was a nominal association of these SNPs with hepatic IS but only of rs4844880 with whole-body IS. Subjects homozygous for the major allele had an adjusted odds ratio of 2.16 (95% confidence interval [CI] 1.23-3.90) for rs2235543, 2.06 (95% CI 1.08-4.13) for rs12565406, and 1.95 (95% CI 1.13-3.49) for rs4844880 for having nonalcoholic fatty liver disease compared with carriers of the minor allele. Less strong associations of these SNPs with visceral fat mass were observed. In liver biopsies, carriers of the minor alleles of rs2235543 and rs12565406 had significantly lower HSD11B1 mRNA expression (n = 105, P = .034 and P = .0086, respectively). CONCLUSIONS: 11ß-HSD1 may be an important enzyme in the pathogenesis of fatty liver and visceral obesity and a promising target for their treatment.

Variation in the Phosphoinositide 3-Kinase Gamma Gene Affects Plasma HDL-Cholesterol without Modification of Metabolic or Inflammatory Markers.

OBJECTIVE: Phosphoinositide 3-kinase γ (PI3Kγ) is a G-protein-coupled receptor-activated lipid kinase mainly expressed in leukocytes and cells of the cardiovascular system. PI3Kγ plays an important signaling role in inflammatory processes. Since subclinical inflammation is a hallmark of atherosclerosis, obesity-related insulin resistance, and pancreatic ß-cell failure, we asked whether common genetic variation in the PI3Kγ gene (PIK3CG) contributes to body fat content/distribution, serum adipokine/cytokine concentrations, alterations in plasma lipid profiles, insulin sensitivity, insulin release, and glucose homeostasis. STUDY DESIGN: Using a tagging single nucleotide polymorphism (SNP) approach, we analyzed genotype-phenotype associations in 2,068 German subjects genotyped for 10 PIK3CG SNPs and characterized by oral glucose tolerance tests. In subgroups, data from hyperinsulinaemic-euglycaemic clamps, magnetic resonance spectroscopy of the liver, whole-body magnetic resonance imaging, and intravenous glucose tolerance tests were available, and peripheral blood mononuclear cells (PBMCs) were used for gene expression analysis. RESULTS: After appropriate adjustment, none of the PIK3CG tagging SNPs was significantly associated with body fat content/distribution, adipokine/cytokine concentrations, insulin sensitivity, insulin secretion, or blood glucose concentrations (p>0.0127, all; Bonferroni-corrected α-level: 0.0051). However, six non-linked SNPs displayed at least nominal associations with plasma HDL-cholesterol concentrations, two of them (rs4288294 and rs116697954) reaching the level of study-wide significance (p = 0.0003 and p = 0.0004, respectively). More precisely, rs4288294 and rs116697954 influenced HDL2-, but not HDL3-, cholesterol. With respect to the SNPs' in vivo functionality, rs4288294 was significantly associated with PIK3CG mRNA expression in PBMCs. CONCLUSIONS: We could demonstrate that common genetic variation in the PIK3CG locus, possibly via altered PIK3CG gene expression, determines plasma HDL-cholesterol concentrations. Since HDL2-, but not HDL3-, cholesterol is influenced by PIK3CG variants, PI3Kγ may play a role in HDL clearance rather than in HDL biogenesis. Even though the molecular pathways connecting PI3Kγ and HDL metabolism remain to be further elucidated, this finding could add a novel aspect to the pathophysiological role of PI3Kγ in atherogenesis.

Peroxisome proliferator-activated receptor gamma (PPARG) modulates free fatty acid receptor 1 (FFAR1) dependent insulin secretion in humans.

Genetic variation in FFAR1 modulates insulin secretion dependent on non-esterified fatty acid (NEFA) concentrations. We previously demonstrated lower insulin secretion in minor allele carriers of PPARG Pro12Ala in high-NEFA environment, but the mode of action could not been revealed. We tested if this effect is mediated by FFAR1 in humans. Subjects with increased risk of diabetes who underwent oral glucose tolerance tests were genotyped for 7 tagging SNPs in FFAR1 and PPARG Pro12Ala. The FFAR1 SNPs rs12462800 and rs10422744 demonstrated interactions with PPARG on insulin secretion. FFAR1 rs12462800 (p = 0.0006) and rs10422744 (p = 0.001) were associated with reduced insulin secretion in participants concomitantly carrying the PPARG minor allele and having high fasting FFA. These results suggest that the minor allele of the PPARG SNP exposes its carriers to modulatory effects of FFAR1 on insulin secretion. This subphenotype may define altered responsiveness to FFAR1-agonists, and should be investigated in further studies.