Dose-dependent effects of the once-daily GLP-1 receptor agonist lixisenatide in patients with Type 2 diabetes inadequately controlled with metformin:a randomized, double-blind, placebo-controlled trial

To evaluate the dose-response relationship of lixisenatide (AVE0010), a glucagon-like peptide-1 (GLP-1) receptor agonist, in metformin-treated patients with Type 2 diabetes.

Cross-sectional associations of C-reactive protein with vascular risk factors and vascular complications in the DCCT/EDIC cohort

To determine the relationships between C-reactive protein (CRP) levels and features of Type 1 diabetes.

Increased serum pigment epithelium-derived factor is associated with microvascular complications, vascular stiffness and inflammation in Type 1 diabetes

To determine in Type 1 diabetes patients if levels of pigment epithelium-derived factor (PEDF), an anti-angiogenic, anti-inflammatory and antioxidant factor, are increased in individuals with complications and positively related to vascular and renal dysfunction, body mass index, glycated haemoglobin, lipids, inflammation and oxidative stress.

Advanced glycation end-products and methionine sulphoxide in skin collagen of patients with type 1 diabetes

We determined whether oxidative damage in collagen is increased in (1) patients with diabetes; (2) patients with diabetic complications; and (3) subjects from the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) study, with comparison of subjects from the former standard vs intensive treatment groups 4 years after DCCT completion.

Apolipoprotein C-III protein concentrations and gene polymorphisms in type 1 diabetes:associations with lipoprotein subclasses

Serum apolipoprotein C-III (apoCIII) concentration and apoCIII gene polymorphisms have been shown to be a risk factor for cardiovascular disease; however, the underlying mechanisms remain unclear. In addition, no studies have been performed that address these issues in type 1 diabetes. The current study investigated apoCIII protein and apoCIII gene variation in a normotriglyceridemic (82 +/- 57 mg/dL) population of patients with type 1 diabetes, the Diabetes Control and Complications Trial/Epidemiology of Diabetes Intervention and Complications (DCCT/EDIC) cohort. Blood samples were obtained in 409 patients after an overnight fast. Serum apoCIII concentration was highly correlated with multiple changes in lipids and lipoproteins that resulted in an adverse cardiovascular disease risk profile. Higher apoCIII concentrations were associated (P <.0001) with increased triglycerides (r = 0.78), total (r = 0.61) and low-density lipoprotein (LDL) (r = 0.40) cholesterol, apoA-I (r = 0.26), and apoB (r = 0.50), and these relationships persisted after controlling for age, gender, body mass index (BMI), and hemoglobin A1c (HbA1c). Nuclear magnetic resonance (NMR) lipoprotein subclass analyses demonstrated that apoCIII was correlated with an increase in very-low-density lipoprotein (VLDL) subclasses (P = .0001). There also was a highly significant positive relationship between serum apoCIII concentration and the LDL particle concentration in both men (r = 0.49, P = .001) and women (r = 0.40, P = .001), and a highly significant negative relationship between serum apoCIII levels and average LDL particle size in both men (r = -0.37, P = .001) and women (r = -0.22, P = .001) due primarily to an augmentation in the small L1 subclass (r = 0.42, P = .0001). Neither the T(-455) --> C polymorphism affecting an insulin response element in the apoCIII gene promoter nor a SacI polymorphism in the 3'UTR were associated with any alterations in circulating apoCIII concentrations, serum lipids, apolipoprotein concentrations, lipoprotein composition, or parameters measured by NMR lipoprotein subclass analyses. In summary, elevated apoCIII concentration was associated with risk factors for cardiovascular disease in normolipidemic type 1 diabetic patients through associated changes in lipoprotein subfraction distributions, which were independent of apoCIII genotype.

In vivo glycated low-density lipoprotein is not more susceptible to oxidation than nonglycated low-density lipoprotein in type 1 diabetes

It has been suggested that low-density lipoprotein (LDL) modified by glycation may be more susceptible to oxidation and thus, enhance its atherogenicity. Using affinity chromatography, LDL glycated in vivo (G-LDL) and relatively nonglycated. (N-LDL) subfractions can be isolated from the same individual. The extent of and susceptibility to oxidation of N-LDL compared with G-LDL was determined in 15 type 1 diabetic patients. Total LDL was isolated and separated by boronate affinity chromatography into relatively glycated (G-) and nonglycated (N-) subfractions. The extent of glycation, glycoxidation, and lipoxidation, lipid soluble antioxidant content, susceptibility to in vitro oxidation, and nuclear magnetic resonance (NMR)-determined particle size and subclass distribution were determined for each subfraction. Glycation, (fructose-lysine) was higher in G-LDL versus N-LDL, (0.28 +/- 0.08 v 0.13 +/- 0.04 mmol/mol lysine, P <.0001). However, levels of glycoxidation/lipoxidation products and of antioxidants were similar or lower in G-LDL compared with N-LDL and were inversely correlated with fructose-lysine (FL) concentrations in G-LDL, but positively correlated in N-LDL. In vitro LDL (CuCl2) oxidation demonstrated a longer lag time for oxidation of G-LDL than N-LDL (50 +/- 0.16 v 37 +/- 0.15 min, P <.01), but there was no difference in the rate or extent of lipid oxidation, nor in any aspect of protein oxidation. Mean LDL particle size and subclass distribution did not differ between G-LDL and N-LDL. Thus, G-LDL from well-controlled type 1 diabetic patients is not more modified by oxidation, more susceptible to oxidation, or smaller than relatively N-LDL, suggesting alternative factors may contribute to the atherogenicity of LDL from type 1 diabetic patients.

Serum lipoproteins in the diabetes control and complications trial/epidemiology of diabetes intervention and complications cohort:associations with gender and glycemia

To relate the nuclear magnetic resonance (NMR)-determined lipoprotein profile, conventional lipid and apolipoprotein measures, and in vitro oxidizibility of LDL with gender and glycemia in type 1 diabetes.

3-Deoxyfructose concentrations are increased in human plasma and urine in diabetes

3-Deoxyglucosone (3-DG) is a reactive dicarbonyl sugar thought to be a key intermediate in the nonenzymatic polymerization and browning of proteins by glucose. 3-DG may be formed in vivo from fructose, fructose 3-phosphate, or Amadori adducts to protein, such as N epsilon-fructoselysine (FL), all of which are known to be elevated in body fluids or tissues in diabetes. Modification of proteins by 3-DG formed in vivo is thought to be limited by enzymatic reduction of 3-DG to less reactive species, such as 3-deoxyfructose (3-DF). In this study, we have measured 3-DF, as a metabolic fingerprint of 3-DG, in plasma and urine from a group of diabetic patients and control subjects. Plasma and urinary 3-DF concentrations were significantly increased in the diabetic compared with the control population (0.853 +/- 0.189 vs. 0.494 +/- 0.072 microM, P <0.001, and 69.9 +/- 44.2 vs. 38.7 +/- 16.1 nmol/mg creatinine, P <0.001, respectively). Plasma and urinary 3-DF concentrations correlated strongly with one another, with HbA1c (P <0.005 in all cases), and with urinary FL (P <0.02 and P = 0.005, respectively). The overall increase in 3-DF concentrations in plasma and urine in diabetes and their correlation with other indexes of glycemic control suggest that increased amounts of 3-DG are formed in the body during hyperglycemia in diabetes and then metabolized to 3-DF. These observations are consistent with a role for increased formation of the dicarbonyl sugar 3-DG in the accelerated browning of tissue proteins in diabetes.

Platelet plasminogen activator inhibitor 1 in patients with type II diabetes

To compare platelet plasminogen activator inhibitor 1 (PAI-1) concentration in type II diabetic patients and healthy control subjects.

Accumulation of Maillard reaction products in skin collagen in diabetes and aging

To investigate the contribution of glycation and oxidation reactions to the modification of insoluble collagen in aging and diabetes, Maillard reaction products were measured in skin collagen from 39 type 1 diabetic patients and 52 nondiabetic control subjects. Compounds studied included fructoselysine (FL), the initial glycation product, and the glycoxidation products, N epsilon-(carboxymethyl) lysine (CML) and pentosidine, formed during later Maillard reactions. Collagen-linked fluorescence was also studied. In nondiabetic subjects, glycation of collagen (FL content) increased only 33% between 20 and 85 yr of age. In contrast, CML, pentosidine and fluorescence increased five-fold, correlating strongly with age. In diabetic patients, collagen FL was increased threefold compared with nondiabetic subjects, correlating strongly with glycated hemoglobin but not with age. Collagen CML, pentosidine and fluorescence were increased up to twofold in diabetic compared with control patients: this could be explained by the increase in glycation alone, without invoking increased oxidative stress. There were strong correlations among CML, pentosidine and fluorescence in both groups, providing evidence for age-dependent chemical modification of collagen via the Maillard reaction, and acceleration of this process in diabetes. These results support the description of diabetes as a disease characterized by accelerated chemical aging of long-lived tissue proteins.

Decrease in skin collagen glycation with improved glycemic control in patients with insulin-dependent diabetes mellitus

Glycation, oxidation, and nonenzymatic browning of protein have all been implicated in the development of diabetic complications. The initial product of glycation of protein, fructoselysine (FL), undergoes further reactions, yielding a complex mixture of browning products, including the fluorescent lysine-arginine cross-link, pentosidine. Alternatively, FL may be cleaved oxidatively to form N(epsilon)-(carboxymethyl)lysine (CML), while glycated hydroxylysine, an amino-acid unique to collagen, may yield N(epsilon)-(carboxymethyl)hydroxylysine (CMhL). We have measured FL, pentosidine, fluorescence (excitation = 328 nm, emission = 378 nm), CML, and CMhL in insoluble skin collagen from 14 insulin-dependent diabetic patients before and after a 4-mo period of intensive therapy to improve glycemic control. Mean home blood glucose fell from 8.7 +/- 2.5 (mean +/- 1 SD) to 6.8 +/- 1.4 mM (P less than 0.005), and mean glycated hemoglobin (HbA1) from 11.6 +/- 2.3% to 8.3 +/- 1.1% (P less than 0.001). These changes were accompanied by a significant decrease in glycation of skin collagen, from 13.2 +/- 4.3 to 10.6 +/- 2.3 mmol FL/mol lysine (P less than 0.002). However, levels of browning and oxidation products (pentosidine, CML, and CMhL) and fluorescence were unchanged. These results show that the glycation of long-lived proteins can be decreased by improved glycemic control, but suggest that once cumulative damage to collagen by browning and oxidation reactions has occurred, it may not be readily reversed. Thus, in diabetic patients, institution and maintenance of good glycemic control at any time could potentially limit the extent of subsequent long-term damage to proteins by glycation and oxidation reactions.

Hemostatic alterations with exercise conditioning in NIDDM

Various parameters of coagulation and fibrinolysis were measured in 13 men (aged 54 +/- 3 yr) with non-insulin-dependent diabetes mellitus (NIDDM) before and after 12-14 wk of exercise training. Subjects exercised for 30 min 3 times/wk at 70% of maximum O2 consumption (VO2max). Training increased VO2max by 12.5% but did not alter body weight, relative body fat, blood pressure, cholesterol, triglycerides, or high-density lipoprotein cholesterol. Slight downward trends were apparent for fasting glucose and insulin, but glycosylated hemoglobin was unchanged. There were no changes in coagulation parameters of plasminogen, hematocrit, or alpha 2-antiplasmin. Plasma fibrinogen (303 +/- 24.2 vs. 256 +/- 12.3 mg/dl) and fibronectin (380 +/- 41.9 vs. 301 +/- 22.2 micrograms/ml) were significantly reduced (P less than 0.02) by exercise conditioning. Three assays of fibrinolytic activity (tissue plasminogen activator, euglobulin lysis time, and an isotopic measure of fibrinolysis) confirmed that neither basal fibrinolysis nor the fibrinolytic responses to venous occlusion and maximal exercise were significantly altered. Exercise conditioning may have antithrombotic effects in NIDDM by reducing plasma fibrinogen and fibronectin. Although the significance of the fall in fibronectin awaits further studies, the reduction in plasma fibrinogen gives a rationale for the use of exercise training in men with NIDDM.

Non-enzymatic glycosylation

Experience with the use of glycosylated haemoglobin throughout the 1980s has confirmed its uniqueness and usefulness as an objective index of long-term glycaemia in diabetes mellitus, and has enabled the definition of realistic and achievable targets for outpatient management. Measurement of glycosylated serum proteins yields information over a much shorter time-scale which may be particularly useful in diabetic pregnancy. The formation of advanced glycosylation end-products may provide a link between hyperglycaemia and chronic diabetic complications. Therapeutic inhibition or the promotion of alternative metabolic pathways, to yield inert glycosylated products, represents an innovative approach to the problem of preventing these complications.

Non-enzymatic glycosylation of skin collagen in patients with type 1 (insulin-dependent) diabetes mellitus and limited joint mobility

Forearm skin biopsies were obtained from diabetic subjects with and without limited joint mobility, and from non-diabetic control subjects. Collagen purified from these samples was assayed for non-enzymatic glycosylation. The level in all diabetic patients was significantly greater than that in control subjects (p less than 0.001), but those diabetic patients with limited joint mobility had a level of collagen glycosylation similar to that in those with normal joints (15.3 +/- 1.3 and 16.5 +/- 1.3 nmol fructose/10 mg protein, respectively; mean +/- SEM). Glycosylation of collagen in the diabetic patients correlated with glycosylated haemoglobin measured at the time of skin biopsy (r = 0.60). These results do not support the hypothesis that non-enzymatic glycosylation of collagen, as reflected by the ketoamine link, plays an important role in the development of limited joint mobility in diabetes.

Increased serum pigment epithelium derived factor levels in Type 2 diabetes patients

Serum PEDF levels (mean (S.D.)) were increased in 96 Type 2 diabetic vs. 54 non-diabetic subjects; 5.3 (2.8) vs. 3.2 (2.0)mug/ml, p