Mohammed I. Hawa

Identification of Type 1 Diabetes–Associated DNA Methylation Variable Positions That Precede Disease Diagnosis

Monozygotic (MZ) twin pair discordance for childhood-onset Type 1 Diabetes (T1D) is ∼50%, implicating roles for genetic and non-genetic factors in the aetiology of this complex autoimmune disease. Although significant progress has been made in elucidating the genetics of T1D in recent years, the non-genetic component has remained poorly defined. We hypothesized that epigenetic variation could underlie some of the non-genetic component of T1D aetiology and, thus, performed an epigenome-wide association study (EWAS) for this disease. We generated genome-wide DNA methylation profiles of purified CD14+ monocytes (an immune effector cell type relevant to T1D pathogenesis) from 15 T1D–discordant MZ twin pairs. This identified 132 different CpG sites at which the direction of the intra-MZ pair DNA methylation difference significantly correlated with the diabetic state, i.e. T1D–associated methylation variable positions (T1D–MVPs). We confirmed these T1D–MVPs display statistically significant intra-MZ pair DNA methylation differences in the expected direction in an independent set of T1D–discordant MZ pairs (P = 0.035). Then, to establish the temporal origins of the T1D–MVPs, we generated two further genome-wide datasets and established that, when compared with controls, T1D–MVPs are enriched in singletons both before (P = 0.001) and at (P = 0.015) disease diagnosis, and also in singletons positive for diabetes-associated autoantibodies but disease-free even after 12 years follow-up (P = 0.0023). Combined, these results suggest that T1D–MVPs arise very early in the etiological process that leads to overt T1D. Our EWAS of T1D represents an important contribution toward understanding the etiological role of epigenetic variation in type 1 diabetes, and it is also the first systematic analysis of the temporal origins of disease-associated epigenetic variation for any human complex disease.

Mechanism of Metformin Action in Non-Insulin-Dependent Diabetes

The mechanism of action of metformin was studied by comparing glucose turnover before and after a 75-g oral glucose load in 10 nonobese men with noninsulin-dependent diabetes mellitus (NIDDM) during metformin and placebo therapy by the combined application of the forearm and double-isotope techniques. During the study, 9 of the 10 patients were regularly receiving glibenclamide therapy. In 5 of the men, the first study was performed during metformin therapy, and the second study was done during placebo administration; in the other 5 subjects, the order was reversed. The interval between the studies was at least 3 mo. The metformin dosage was 1 g twice daily in 9 of the patients and 850 mg thrice daily in the 10th subject. In the basal state, metformin administration reduced plasma glucose levels from 172 ± 14 to 103 ± 9 mg/dl (P < .005), hepatic glucose output (HGO) from 2.67 ± 0.15 to 2.20 ± 0.20 mg · kg−1 · min−1 (P < .02), and forearm glucose uptake (FGU) from 0.106 ± 0.18 to 0.039 ± 0.016 mg · 100 ml−1 forearm · min−1 (P < .005), whereas insulin (23 ± 6 μU ml) and lactate (1.56 ± 0.18 mM) levels were unchanged. Although the oral glucose tolerance curve (OGTC) was significantly lowered by metformin, the incremental area under the curve and the insulin response were unchanged. The systemic appearance of ingested glucose was unaffected by metformin; 64 ± 2% of the load was recovered peripherally in 3 h. The rise in FGU and total glucose disappearance in 3 h after glucose loading was unaffected by metformin. From 0 to 180 min after glucose loading, HGO was suppressed by 45.3 and 44.5% of the corresponding basal value without and with metformin treatment, respectively. Peak lactate levels were noted 90 min after glucose loading and were increased during metformin treatment from 2.10 ± 0.23 to 2.92 ± 0.32 mM (P < .05). We conclude that 1) metformin markedly lowers the OGTC in NIDDM; 2) lowering of the OGTC is due entirely to a fall in the basal glucose concentration; and 3) because fasting insulin levels were unchanged, the reduction in basal HGO and fasting glucose concentrations by metformin is the result of a druginduced increase in hepatic insulin sensitivity.

Adult-Onset Autoimmune Diabetes in Europe Is Prevalent With a Broad Clinical Phenotype: Action LADA 7

OBJECTIVE Specific autoantibodies characterize type 1 diabetes in childhood but are also found in adult-onset diabetes, even when initially non–insulin requiring, e.g., with latent autoimmune diabetes (LADA). We aimed to characterize adult-onset autoimmune diabetes. RESEARCH DESIGN AND METHODS We consecutively studied 6,156 European diabetic patients attending clinics within 5 years of diagnosis (age range, 30–70 years) examined cross-sectionally clinically and for GAD antibodies (GADA) and antibodies to insulinoma-associated antigen-2 (IA-2A) and zinc-transporter 8 (ZnT8A). RESULTS Of 6,156 patients, 541 (8.8%) had GADA and only 57 (0.9%) IA-2A or ZnT8A alone. More autoantibody-positive than autoantibody-negative patients were younger, leaner, on insulin (49.5 vs. 13.2%), and female (P < 0.0001 for each), though LADA patients (9.7% of total) did not show categorically distinct clinical features from autoantibody-negative type 2 diabetes. Similarly, more GADA patients with high (>200 World Health Organization IU) (n = 403) compared with low (n = 138) titer were female, lean, and insulin treated (54.6 vs. 39.7%) (P < 0.02 for each). Autoantibody-positive patients usually had GADA (541 of 598; 90.5%) and had LADA more often than type 1 autoimmune diabetes (odds ratio 3.3). CONCLUSIONS Adult-onset autoimmune diabetes emerges as a prevalent form of autoimmune diabetes. Our results indicate that adult-onset autoimmune diabetes in Europe encompasses type 1 diabetes and LADA in the same broad clinical and autoantibody-positive spectrum. At diagnosis, patients with adult-onset autoimmune diabetes are usually non–insulin requiring and clinically indistinguishable from patients with type 2 diabetes, though they tend to be younger and leaner. Only with screening for autoantibodies, especially GADA, can they be identified with certainty.

Adult-Onset Autoimmune Diabetes in Europe Is Prevalent With a Broad Clinical Phenotype Action LADA 7

OBJECTIVE Specific autoantibodies characterize type 1 diabetes in childhood but are also found in adult-onset diabetes, even when initially non–insulin requiring, e.g., with latent autoimmune diabetes (LADA). We aimed to characterize adult-onset autoimmune diabetes. RESEARCH DESIGN AND METHODS We consecutively studied 6,156 European diabetic patients attending clinics within 5 years of diagnosis (age range, 30–70 years) examined cross-sectionally clinically and for GAD antibodies (GADA) and antibodies to insulinoma-associated antigen-2 (IA-2A) and zinc-transporter 8 (ZnT8A). RESULTS Of 6,156 patients, 541 (8.8%) had GADA and only 57 (0.9%) IA-2A or ZnT8A alone. More autoantibody-positive than autoantibody-negative patients were younger, leaner, on insulin (49.5 vs. 13.2%), and female (P < 0.0001 for each), though LADA patients (9.7% of total) did not show categorically distinct clinical features from autoantibody-negative type 2 diabetes. Similarly, more GADA patients with high (>200 World Health Organization IU) (n = 403) compared with low (n = 138) titer were female, lean, and insulin treated (54.6 vs. 39.7%) (P < 0.02 for each). Autoantibody-positive patients usually had GADA (541 of 598; 90.5%) and had LADA more often than type 1 autoimmune diabetes (odds ratio 3.3). CONCLUSIONS Adult-onset autoimmune diabetes emerges as a prevalent form of autoimmune diabetes. Our results indicate that adult-onset autoimmune diabetes in Europe encompasses type 1 diabetes and LADA in the same broad clinical and autoantibody-positive spectrum. At diagnosis, patients with adult-onset autoimmune diabetes are usually non–insulin requiring and clinically indistinguishable from patients with type 2 diabetes, though they tend to be younger and leaner. Only with screening for autoantibodies, especially GADA, can they be identified with certainty.

Metabolic Syndrome and Autoimmune Diabetes: Action LADA 3

OBJECTIVE—The purpose of this study was to estimate whether prevalence of metabolic syndrome in adult European diabetic patients is associated with type of diabetes. RESEARCH DESIGN AND METHODS—A consecutive series of patients attending hospital-based diabetes clinics were assessed for the frequency of metabolic syndrome and compared with population-based control subjects as part of the Action LADA study. In total, 2,011 subjects (aged 30–70 years) were studied, including 1,247 patients with recent-onset type 2 diabetes without glutamic acid decarboxylase autoantibodies (GADAs), 117 non–insulin-requiring patients with GADAs who had not received insulin therapy for at least 6 months after diagnosis (designated latent autoimmune diabetes of adults [LADA]), 288 type 1 diabetic patients, and 359 normal subjects. RESULTS—Frequency of metabolic syndrome was significantly different in patients with type 1 diabetes (31.9%) and LADA (41.9%) (P = 0.015) and in both conditions was less frequent than in type 2 diabetic patients (88.8%) (P < 0.0001 for each). Eliminating glucose as a variable, the prevalence of metabolic syndrome was similar in patients with autoimmune diabetes (type 1 diabetes and/or LADA) (17.3%) and control subjects (23.7%) but remained more common in type 2 diabetic patients (47.8%) (P = 0.001 for all groups). In both type 1 diabetic patients and those with LADA, individual components of metabolic syndrome were similar but less common than in type 2 diabetic patients (P < 0.0001 for each). CONCLUSIONS—The prevalence of metabolic syndrome is significantly higher in type 2 diabetic patients than in patients with LADA or adults with type 1 diabetes. Excluding glucose as a variable, metabolic syndrome is not more prevalent in patients with autoimmune diabetes than in control subjects. Metabolic syndrome is not a characteristic of autoimmune diabetes.

Buccals are likely to be a more informative surrogate tissue than blood for epigenome-wide association studies

There is increasing evidence that interindividual epigenetic variation is an etiological factor in common human diseases. Such epigenetic variation could be genetic or non-genetic in origin, and epigenome-wide association studies (EWASs) are underway for a wide variety of diseases/phenotypes. However, performing an EWAS is associated with a range of issues not typically encountered in genome-wide association studies (GWASs), such as the tissue to be analyzed. In many EWASs, it is not possible to analyze the target tissue in large numbers of live humans, and consequently surrogate tissues are employed, most commonly blood. But there is as yet no evidence demonstrating that blood is more informative than buccal cells, the other easily accessible tissue. To assess the potential of buccal cells for use in EWASs, we performed a comprehensive analysis of a buccal cell methylome using whole-genome bisulfite sequencing. Strikingly, a buccal vs. blood comparison reveals > 6X as many hypomethylated regions in buccal. These tissue-specific differentially methylated regions (tDMRs) are strongly enriched for DNaseI hotspots. Almost 75% of these tDMRs are not captured by commonly used DNA methylome profiling platforms such as Reduced Representational Bisulfite Sequencing and the Illumina Infinium HumanMethylation450 BeadChip, and they also display distinct genomic properties. Buccal hypo-tDMRs show a statistically significant enrichment near SNPs associated to disease identified through GWASs. Finally, we find that, compared with blood, buccal hypo-tDMRs show significantly greater overlap with hypomethylated regions in other tissues. We propose that for non-blood based diseases/phenotypes, buccal will be a more informative tissue for EWASs.

Influence of Aging on Hepatic and Peripheral Glucose Metabolism in Humans

Mechanisms of glucose intolerance with aging were studied by comparing the metabolic response to glucose ingestion in 10 young (20–23 yr) and 10 elderly (73–80 yr) normal men with the simultaneous application of the forearm and double-isotope techniques. The latter technique consisted of a primed-constant infusion of [3-3H]glucose followed by the administration of an oral glucose load (mean ± SE, 90.7 ± 0.7 g) containing [1-14C]glucose. Fasting plasma glucose and insulin concentrations were similar in young and elderly subjects, but in the elderly, glucose tolerance was markedly impaired. Although in the elderly the initial rise in insulin levels (∆, i.e., the incremental area under the curve) from 0 to 30 min was delayed (P < .02), the response from 0 to 45 min, 0 to 60 min, and thereafter equaled that in the young group, and from 90 to 240 min insulin concentrations in the elderly exceeded those in young subjects. Basal hepatic glucose output (HGO) was similar in young and elderly men (2.13 ± 0.10 and 1.97 ± 0.14 mg.· kg−1 · min−1, respectively). Similar proportional reductions in HGO from 0 to 270 min after glucose loading occurred in young (59.7 ± 10.3%) and elderly (50.3 ± 4.9%) subjects but was delayed in the elderly. Suppression of HGO was observed in the young 30 min after glucose ingestion (P < .02), but not before 60 min in the elderly subjects (P < .05). The systemic appearance of ingested glucose (0–270 min) was slowed with age (80.7 ± 3.1 and 66.9 ± 4.3% of the oral load in the young and elderly groups, respectively; P < .02). Initial increments in both total glucose disappearance (Rd) and forearm glucose uptake (FGU) from 0 to 60 min after glucose loading were decreased in the elderly (Rd, 4.1 ± 0.7 vs. 11.5 ± 1.3 g, P < .001; FGU, 17.2 ± 1.4 vs. 24.6 ± 2.5 md/dl forearm, P < .02). The overall increment (∆, 0–270 min) in Rd was reduced with age (47.2 ± 2.9 and 34.5 ± 3.6 g, P < .02 in the young and elderly, respectively), but the corresponding data for FGU were similar in the two groups. However, the ratios of ∆Rd and ∆FGU to the corresponding insulin responses (∆l), mainly reflecting peripheral insulin sensitivity, were reduced in the elderly (∆Rα/∆I, 1.3 ± 0.2 vs. 3.0 ± 0.6 U, P < .01; ∆FGU/∆I, 0.7 ± 0.1 vs. 1.2 ± 0.2 U, P < .05). Assessment of the relative contribution by the liver and peripheral tissues to age-related glucose intolerance suggested that the deficit in Rd was twofold greater than that due to the delayed fall in HGO. We conclude that age-related glucose intolerance 1) develops despite slowed glucose absorption; 2) is characterized by delays in the initial rise in insulin levels, the suppression of HGO, and the rise in peripheral glucose uptake; but 3) is predominantly the result of impaired peripheral glucose utilization. While the latter reflects increased tissue insulin resistance, the delayed fall in HGO may be mainly the consequence of delayed insulin secretion.

Pro- and anti-inflammatory cytokines in latent autoimmune diabetes in adults, type 1 and type 2 diabetes patients: Action LADA 4.

Aims/hypothesisSystemic pro- and anti-inflammatory cytokines are associated with both type 1 and type 2 diabetes, while their role in latent autoimmune diabetes in adults (LADA) is unclear. Therefore, we compared cytokine concentrations in patients with LADA, type 1 or type 2 diabetes and healthy individuals to test the hypothesis that differences of cytokine concentrations between all groups are attributable to diabetes type and BMI.MethodsThe pro-inflammatory cytokines IL-6 and TNF-α, and the anti-inflammatory cytokines IL-1 receptor antagonist (IL-1RA) and IL-10 were measured in 90 participants with type 1 diabetes, 61 with LADA, 465 with type 2 diabetes and 41 control participants using multiple regression models adjusted for BMI, sex, age, blood pressure and diabetes duration.ResultsPatients with type 2 diabetes had higher concentrations of systemic IL-1RA, IL-6 and TNF-α cytokines than patients with either LADA or type 1 diabetes (p < 0.0001 for all differences). Cytokine concentrations in controls were lower than those in all diabetes types (p < 0.04). Increased BMI was positively associated with higher systemic cytokine concentrations in all diabetes types (p < 0.0001). Despite the association of cytokines with anthropometric data, differences between diabetes forms persisted also after adjusting analysis for the confounders BMI, age, sex, disease duration and blood pressure (p < 0.04).Conclusions/interpretationAlthough body mass associates positively with pro- and anti-inflammatory cytokine levels, patients with type 2 diabetes have higher cytokine levels independent of the prevailing BMI. LADA and type 1 diabetes could not be distinguished by systemic cytokines.

Metabolic and immune parameters at clinical onset of insulin-dependent diabetes: A population-based study☆

The age at diagnosis of insulin-dependent diabetes mellitus (type I DM) varies between childhood and adulthood. The aim of this study was to define the immunologic and metabolic characteristics of the disease according to the age at which it is diagnosed. We evaluated the residual beta-cell function (basal and stimulated C-peptide) and frequency of two major islet cell-related autoantibodies, glutamic acid decarboxylase (GAD) and tyrosine phosphatase-like molecule (IA-2ic), at the onset of type I DM. A population-based study was performed with 235 consecutive cases of recent-onset (<4 weeks) type I DM (ages 5 to 45 years) diagnosed in the Lazio region of central Italy. Five age groups were considered: patients diagnosed between ages 5 and 7 years (n = 10), 7 and 10 years (n = 38), 10 and 17 years (n = 94), 17 and 20 years (n = 17), and 20 and 45 years (n = 76). Patients diagnosed before puberty had significantly reduced C-peptide secretion compared with patients diagnosed at a later age (P < .02). Glycosylated hemoglobin (HbA1c) did not differ at diagnosis between the different age groups. Patients diagnosed at puberty or after required significantly less insulin compared with younger patients (P < .04). GAD antibodies were found in 65% and IA-2ic antibodies in 59% of patients. GAD antibodies tended to be more frequent in patients diagnosed after age 17 compared with younger patients (P = .05), while IA-2ic antibodies were not age-related. These data suggest that (1) the extent of beta-cell damage differs between patients diagnosed before and after puberty, the process being more destructive in children less than 7 years of age, when C-peptide levels are the lowest; and (2) residual beta-cell function at diagnosis is not influenced by the presence or absence of islet cell-related antibodies. These findings have implications for trials in type I DM diagnosis aimed at protecting beta cells from end-stage destruction and in attempts to prevent the disease in susceptible individuals.

Hypoxia increases Sca-1/CD44 co-expression in murine mesenchymal stem cells and enhances their adipogenic differentiation potential

Mesenchymal stem cells (MSCs) are usually cultured under normoxic conditions (21% oxygen). However, in vivo, the physiological “niches” for MSCs have a much lower oxygen tension. Because of their plasticity, stem cells are particularly sensitive to their environments, and oxygen tension is one developmentally important stimulus in stem cell biology and plays a role in the intricate balance between cellular proliferation and commitment towards differentiation. Therefore, we investigated here the effect of hypoxia (2% oxygen) on murine adipose tissue (AT) MSC proliferation and adipogenic differentiation. AT cells were obtained from the omental fat and AT-MSCs were selected for their ability to attach to the plastic dishes, and were grown under normoxic and hypoxic conditions. Prior exposure of MSCs to hypoxia led to a significant reduction of ex vivo expansion time, with significantly increased numbers of Sca-1+ as well as Sca-1+/CD44+double-positive cells. Under low oxygen culture conditions, the AT-MSC number markedly increased and their adipogenic differentiation potential was reduced. Notably, the hypoxia-mediated inhibition of adipogenic differentiation was reversible: AT-MSCs pre-exposed to hypoxia when switched to normoxic conditions exhibited significantly higher adipogenic differentiation capacity compared to their pre-exposed normoxic-cultured counterparts. Accordingly, the expression of adipocyte-specific genes, peroxisome proliferator activated receptor γ (Pparγ), lipoprotein lipase (Lpl) and fatty acid binding protein 4 (Fabp4) were significantly enhanced in hypoxia pre-exposed AT-MSCs. In conclusion, pre-culturing MSCs under hypoxic culture conditions may represent a strategy to enhance MSC production, enrichment and adipogenic differentiation.