Therapeutic effects of PPARα agonists on diabetic retinopathy in type 1 diabetes models

Retinal vascular leakage, inflammation, and neovascularization (NV) are features of diabetic retinopathy (DR). Fenofibrate, a peroxisome proliferator-activated receptor a (PPARa) agonist, has shown robust protective effects against DR in type 2 diabetic patients, but its effects on DR in type 1 diabetes have not been reported. This study evaluated the efficacy of fenofibrate on DR in type 1 diabetes models and determined if the effect is PPARa dependent. Oral administration of fenofibrate significantly ameliorated retinal vascular leakage and leukostasis in streptozotocin-induced diabetic rats and in Akita mice. Favorable effects on DR were also achieved by intravitreal injection of fenofibrate or another specific PPARa agonist. Fenofibrate also ameliorated retinal NV in the oxygen-induced retinopathy (OIR) model and inhibited tube formation and migration in cultured endothelial cells. Fenofibrate also attenuated overexpression of intercellular adhesion molecule-1, monocyte chemoattractant protein-1, and vascular endothelial growth factor (VEGF) and blocked activation of hypoxia-inducible factor-1 and nuclear factor-?B in the retinas of OIR and diabetic models. Fenofibrate's beneficial effects were blocked by a specific PPARa antagonist. Furthermore, Ppara knockout abolished the fenofibrate-induced downregulation of VEGF and reduction of retinal vascular leakage in DR models. These results demonstrate therapeutic effects of fenofibrate on DR in type 1 diabetes and support the existence of the drug target in ocular tissues and via a PPARa-dependent mechanism.

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.

Metabolism of very low- and low-density lipoproteins isolated from normolipidaemic type 2 (non-insulin-dependent) diabetic patients by human monocyte-derived macrophages

The very low- and low-density lipoprotein fractions were isolated from 16 normolipidaemic Type 2 (non-insulin-dependent) diabetic patients in good to fair glycaemic control and from corresponding age-, sex-, and race-matched, non-diabetic control subjects. Rates of cholesteryl ester synthesis averaged 268 +/- 31 vs 289 +/- 40 pmol 14C-cholesteryl oleate.mg cell protein-1.20 h-1 for very low- and 506 +/- 34 vs 556 +/- 51 pmol 14C-cholesteryl oleate.mg cell protein-1.20 h-1 for low-density lipoproteins isolated from the Type 2 diabetic patients and control subjects, respectively, when they were incubated with human macrophages. A group of approximately one-third of the patients was selected for separate analyses because very low-density lipoproteins isolated from these patients did stimulate more cholesteryl ester synthesis when incubated with macrophages. There were no significant differences in the lipid composition of the lipoproteins isolated from the three groups of subjects. The relative proportion of apoprotein C to apoprotein E was significantly decreased (p less than 0.002) in the very low-density lipoproteins from diabetic patients and was further decreased in samples from these selected diabetic patients. The apoprotein C-I content of very low-density lipoproteins isolated from diabetic patients was increased compared to control subjects and was further increased in samples from the selected diabetic patients (p less than 0.02). There were no significant differences in the proportions of apoproteins C-III-0, C-III-1, or C-III-2 among the three groups. These studies suggest that in normolipidaemic Type 2 diabetic patients, the apoprotein composition of VLDL is abnormal and this may alter VLDL macrophage interactions and thus contribute to the increased prevalence of atherosclerosis in diabetic patients.

Interaction of very-low-density lipoprotein isolated from type I (insulin-dependent) diabetic subjects with human monocyte-derived macrophages

Very-low-density lipoproteins (VLDL) (density less than 1.006 g/mL) were isolated from type I (insulin-dependent) diabetic patients in good to fair glycemic control and from age-, sex-, and race-matched, nondiabetic, control subjects. VLDL were incubated with human, monocyte-derived macrophages obtained from nondiabetic donors, and the rates of cellular cholesteryl ester synthesis and cholesterol accumulation were determined. VLDL isolated from diabetic patients stimulated significantly more cholesteryl ester synthesis than did VLDL isolated from control subjects (4.04 +/- 1.01 v 1.99 +/- 0.39 nmol 14C-cholesteryl oleate synthesized/mg cell protein/20 h; mean +/- SEM, P less than .05). The stimulation of cholesteryl ester synthesis in macrophages incubated with VLDL isolated from diabetic patients was paralleled by a significant increase in intracellular cholesteryl ester accumulation (P less than .05). The increase in cholesteryl ester synthesis and accumulation in macrophages were mediated by a significant increase in the receptor mediated, high affinity degradation (2.55 +/- 0.23 v 2.12 +/- 0.20 micrograms degraded/mg cell protein/20 h) and accumulation (283 +/- 35 v 242 +/- 33 ng/mg cell protein/20 h) of 125I-VLDL isolated from diabetic patients compared with VLDL from control subjects. To determine if changes in VLDL apoprotein composition were responsible for the observed changes in cellular rates of cholesteryl ester synthesis and accumulation, we also examined the apoprotein composition of the VLDL from both groups. There were no significant differences between the apoproteins B, E, and C content of VLDL from both groups. We also determined the chemical composition of VLDL isolated from both groups of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of cholesteryl ester synthesis in human monocyte-derived macrophages by low-density lipoproteins from type 1 (insulin-dependent) diabetic patients:the influence of non-enzymatic glycosylation of low-density lipoproteins

Diabetes mellitus is an independent risk factor in the development of atherosclerosis. In this study we aimed to demonstrate whether there is an abnormal interaction between low-density lipoproteins from diabetic patients and human macrophages. We measured cholesteryl ester synthesis and cholesteryl ester accumulation in human monocyte-derived macrophages (obtained from non-diabetic donors) incubated with low density lipoproteins from Type 1 (insulin-dependent) diabetic patients in good or fair glycaemic control. Low density lipoproteins from the diabetic patients stimulated more cholesteryl ester synthesis than low density lipoproteins from non-diabetic control subjects (7.19 +/- 1.19 vs 6.11 +/- 0.94 nmol/mg cell protein/20 h, mean +/- SEM, p less than 0.05). The stimulation of cholesteryl ester synthesis by low density lipoproteins isolated from diabetic patients was paralleled by a significant increase in intracellular cholesteryl ester accumulation (p less than 0.02). There were no significant differences in the lipid composition of low density lipoproteins between the diabetic and control groups. Non-enzymatic glycosylation of low density lipoproteins was higher in the diabetic group (p less than 0.01) and correlated significantly with cholesteryl ester synthesis (r = 0.58). Similarly, low-density lipoproteins obtained from non-diabetic subjects and glycosylated in vitro stimulated more cholesteryl ester synthesis in macrophages than control low density lipoproteins. The increase in cholesteryl ester synthesis and accumulation by cells exposed to low density lipoproteins from diabetic patients seems to be mediated by an increased uptake of these lipoproteins by macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)

The combined effect of diabetes and ionising radiation on the retinal vasculature of the rat

The clinical impression that pre-existing diabetes exacerbates radiation injury to the retinal vasculature was studied in STZ diabetic rats. Half of 2 groups of streptozotocin (STZ)-induced diabetic rats and 1 group of normal animals had their right eyes irradiated with 1000 cGy of 90 KVP x-rays. The prevalence of acellular capillaries in trypsin digests of the retinal vasculature was quantified for each of the 6 groups of animals at 6.5 months post-irradiation. The prevalence of acellular capillaries in both non-irradiated diabetic groups was significantly higher than in controls while the irradiated animals in each of the three main categories showed a statistically significant increase compared to their non-irradiated equivalents. However, the net increase in acellular capillaries following irradiation was much greater in rats with an 8 month term of pre-existing diabetes (180%) than in those which had only been diabetic for 3 months (36%). The results of this study suggest a synergistic relationship between pre-existing diabetes and ionising radiation in the development of retinal vasculopathy, and that the potentiation of the vascular damage is dependent on the duration of diabetes prior to radiation exposure.

Prevention of retinal capillary basement membrane thickening in diabetic dogs by a non-steroidal anti-inflammatory drug

AIMS/HYPOTHESIS: To investigate the effect of treatment with the non-steroidal anti-inflammatory drug Sulindac on the early vascular pathology of diabetic retinopathy in the dog, and it's effect on recognised biochemical indices of hyperglycaemia-related pathophysiology. METHODS: Experimental diabetes (streptozotocin/alloxan) was induced in 22 male beagle dogs and 12 of the animals were assigned at random to receive oral Sulindac (10 mg/kg daily). Age- and sex-matched control animals were maintained as non-diabetic controls. After 4 years, several morphological parameters were quantified in the retinal microvasculature of each animal group using an established stereological method. Also, the following diabetes-associated biochemical parameters were analysed: accumulation of advanced glycation end products (AGEs), red blood cell polyol levels and antioxidant status. RESULTS: Diabetes increased red blood cell sorbitol levels when compared to non-diabetic controls (p<or =0.05), however, there was no difference in sorbitol levels between the untreated and the treated diabetic animals. No significant differences were found in red blood cell myoinositol levels between the three groups of animals. Pentosidine and other AGEs were increased two- to three-fold in the diabetic animals (p<or =0.001) although treatment with Sulindac did not affect their accumulation in diabetic skin collagen or alter diabetes-induced rises in plasma malondialdehyde. Retinal capillary basement membrane volume was significantly increased in the untreated diabetic dogs compared to non-diabetic controls or Sulindac-treated diabetic animals (p<or =0.0001). CONCLUSION/INTERPRETATION: This study has confirmed the beneficial effect of a non-steroidal anti-inflammatory drug on the early vascular pathology of diabetic retinopathy. However the treatment benefit was not dependent on inhibition of polyol pathway activity, advanced glycation, or oxidative stress.

Is childhood type 1 diabetes a wealth-related disease? An ecological analysis of European incidence rates

Aims/Hypothesis: To describe the epidemiology of childhood-onset Type 1 (insulin-dependent) diabetes in Europe, the EURODIAB collaborative group has established prospective, geographically-defined registers of children diagnosed under 15 years. A total of 16,362 cases were registered by 44 centres during the period 1989-1994. The registers cover a population of approximately 28 million children with most European countries represented. Methods In most centres a primary and a secondary source of ascertainment were used so that the completeness of registration could be assessed by the capture-recapture method. Ecological correlation and regression analyses were used to study the relationship between incidence and various environmental, health and economic indicators. Findings: The standardised average annual incidence rate during the period 1989-94 ranged from 3.2 cases per 100,000 per annum in the Former Yugoslavian Republic of Macedonia to 40.2 cases per 100,000 per annum in Finland. Indicators of national prosperity such as infant mortality (r= -0.64) and gross domestic product (r= 0.58) were most strongly and significantly correlated with incidence rate, and previously-reported associations with coffee consumption (r= 0.51), milk consumption (r= 0.58) and latitude (r= 0.40) were also observed. Conclusion/Interpretation: The wide variation in childhood type 1 diabetes incidence rates within Europe could be partially explained by indicators of national prosperity. These indicators could reflect differences in environmental risk factors such as nutrition or lifestyle that are important in determining a country's incidence rate.

Increased concentrations of the oxidative DNA adduct 7, 8-dihydro-8-oxo-2-deoxyguanosine in the germ-line of men with type 1 diabetes

The effects of diabetes mellitus on male reproductive health have not been clearly defined. A previous publication from this group reported significantly higher levels of nuclear DNA fragmentation and mitochondrial DNA deletions in spermatozoa from men with type 1 diabetes. This study compared semen profiles, sperm DNA fragmentation and levels of oxidative DNA modification in spermatozoa of diabetic and non-diabetic men. Semen samples from 12 non-diabetic, fertile men and 11 type 1 diabetics were obtained and subjected to conventional light microscopic semen analysis. Nuclear DNA fragmentation was assessed using an alkaline Comet assay and concentrations of 7,8-dihydro-8-oxo-2-deoxyguanosine (8-OHdG), an oxidative adduct of the purine guanosine, were assessed by high-performance liquid chromatography. Conventional semen profiles were similar in both groups, whilst spermatozoa from type 1 diabetics showed significantly higher levels of DNA fragmentation (44% versus 27%; P < 0.05) and concentrations of 8-OHdG (3.6 versus 2.0 molecules of 8-OHdG per 105 molecules of deoxyguanosine; P < 0.05). Furthermore, a positive correlation was observed between DNA fragmentation and concentrations of 8-OHdG per 105 molecules of deoxyguanosine (rs = 0.7, P < 0.05). The genomic damage evident in spermatozoa of type 1 diabetics may have important implications for their fertility and the outcome of pregnancies fathered by these individuals.

Nutrient regulation of pancreatic beta-cell function in diabetes: problems and potential solutions

increasing prevalence of obesity combined with longevity will produce an epidemic of Type 2 (non-insulin-dependent) diabetes in the next 20 years. This. disease is associated with defects in insulin secretion, specifically abnormalities of insulin secretory kinetics and pancreatic beta-cell glucose responsiveness. Mechanisms underlying beta-cell dysfunction include glucose toxicity, lipotoxicity and beta-cell hyperactivity. Defects at various sites in beta-cell signal transduction pathways contribute, but no single lesion can account for the common form of Type 2 diabetes. Recent studies highlight diverse beta-cell actions of GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). These intestinal hormones target the beta-cell to stimulate glucose-dependent insulin secretion through activation of protein kinase A and associated pathways. Both increase gene expression and proinsulin biosynthesis, protect against apoptosis and stimulate replication/neogenesis of beta-cells. Incretin hormones therefore represent an exciting future multi-action solution to correct beta-cell defect in Type 2 diabetes.

Mortality from cerebrovascular disease in a cohort of 23 000 patients with insulin-treated diabetes

Background and Purpose-Disease of the cardiovascular system is the main cause of long-term complications and mortality in patients with type I (insulin-dependent) and type 11 (non-insulin-dependent) diabetes. Cerebrovascular mortality rates have been shown to be raised in patients with type 11 diabetes but have not previously been reported by age and sex in patients with type I diabetes.

Variation and trends in incidence of childhood diabetes in Europe

Background To study the epidemiology of childhood-onset type 1 insulin-dependent diabetes in Europe, the EURODIAB collaborative group established in 1988 prospective geographically-defined registers of new cases diagnosed under 15 years of age. This report is based on 16 362 cases registered during the period 1989-94 by 44 centres representing most European countries and Israel and covering a population of about 28 million children.

Preconception care for women with diabetes: the midwife's role

Diabetes mellitus is a chronic illness which affects a significant number of childbearing women. Despite the potential for adverse consequences for both maternal and fetal wellbeing, few women with diabetes plan their pregnancies to ensure that they enter pregnancy in optimal health. Furthermore, whilst adverse pregnancy outcomes are well documented for women with type I diabetes, it is now apparent that an increasing number of women with type II diabetes are becoming pregnant with similar adverse associated risk. There is an increasing recognition that significant adverse pregnancy outcomes are determined prior to a woman initiating pregnancy care, many of which could be minimised with the introduction of preconception care. As formalised preconception care clinics remain scant across the United Kingdom, there is an urgent need to increase the opportunities for the provision of preconception care and advice to women with diabetes. Midwives are ideally placed to provide preconception advice to women and could provide the missing link in terms of preconception advice for women with diabetes.

SNP in the genome-wide association study hotspot on chromosome 9p21 confers susceptibility to diabetic nephropathy in type 1 diabetes

AIMS/HYPOTHESIS: Parental type 2 diabetes mellitus increases the risk of diabetic nephropathy in offspring with type 1 diabetes mellitus. Several single nucleotide polymorphisms (SNPs) that predispose to type 2 diabetes mellitus have recently been identified. It is, however, not known whether such SNPs also confer susceptibility to diabetic nephropathy in patients with type 1 diabetes mellitus. METHODS: We genotyped nine SNPs associated with type 2 diabetes mellitus in genome-wide association studies in the Finnish population, and tested for their association with diabetic nephropathy as well as with severe retinopathy and cardiovascular disease in 2,963 patients with type 1 diabetes mellitus. Replication of significant SNPs was sought in 2,980 patients from three other cohorts. RESULTS: In the discovery cohort, rs10811661 near gene CDKN2A/B was associated with diabetic nephropathy. The association remained after robust Bonferroni correction for the total number of tests performed in this study (OR 1.33 [95% CI 1.14, 1.56], p?=?0.00045, p (36tests)?=?0.016). In the meta-analysis, the combined result for diabetic nephropathy was significant, with a fixed effects p value of 0.011 (OR 1.15 [95% CI 1.02, 1.29]). The association was particularly strong when patients with end-stage renal disease were compared with controls (OR 1.35 [95% CI 1.13, 1.60], p?=?0.00038). The same SNP was also associated with severe retinopathy (OR 1.37 [95% CI 1.10, 1.69] p?=?0.0040), but the association did not remain after Bonferroni correction (p (36tests)?=?0.14). None of the other selected SNPs was associated with nephropathy, severe retinopathy or cardiovascular disease. CONCLUSIONS/INTERPRETATION: A SNP predisposing to type 2 diabetes mellitus, rs10811661 near CDKN2A/B, is associated with diabetic nephropathy in patients with type 1 diabetes mellitus.

Diabetes management in patients receiving palliative care

A literature review revealed no evidence-based guidelines specific to managing diabetes in the context of palliative care. The purpose of the current project was to describe the management practices of doctors and nurses caring for people with diabetes and advanced disease. Palliative care doctors, palliative care nurses, endocrinologists, and diabetes nurse educators participated in this study. A two-phase project was undertaken: 1) two focus groups, and 2) a cross-sectional survey using a self-completed questionnaire. The focus group and questionnaire data identified that doctors and nurses used a range of practices and blood glucose testing frequencies to control blood glucose based on experience and not according to a robust evidence base. Implications for practice include the importance of collaboration between diabetes and palliative care specialists, and the need to develop clinical management guidelines.