Oxidative Stress and Cardiovascular Risk in Type 1 Diabetes Mellitus: Insights From the DCCT/EDIC Study

Background

Hyperglycemia leading to increased oxidative stress is implicated in the increased risk for the development of macrovascular and microvascular complications in patients with type 1 diabetes mellitus.

Methods and Results

A random subcohort of 349 participants was selected from the DCCT / EDIC (Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications) cohort. This included 320 controls and 29 cardiovascular disease cases that were augmented with 98 additional known cases to yield a case cohort of 447 participants (320 controls, 127 cases). Biosamples from DCCT baseline, year 1, and closeout of DCCT , and 1 to 2 years post‐ DCCT ( EDIC years 1 and 2) were measured for markers of oxidative stress, including plasma myeloperoxidase, paraoxonase activity, urinary F 2α isoprostanes, and its metabolite, 2,3 dinor‐8 iso prostaglandin F 2α . Following adjustment for glycated hemoblobin and weighting the observations inversely proportional to the sampling selection probabilities, higher paraoxonase activity, reflective of antioxidant activity, and 2,3 dinor‐8 iso prostaglandin F 2α , an oxidative marker, were significantly associated with lower risk of cardiovascular disease (−4.5% risk for 10% higher paraoxonase, P <0.003; −5.3% risk for 10% higher 2,3 dinor‐8 iso prostaglandin F 2α , P =0.0092). In contrast, the oxidative markers myeloperoxidase and F 2α isoprostanes were not significantly associated with cardiovascular disease after adjustment for glycated hemoblobin. There were no significant differences between DCCT intensive and conventional treatment groups in the change in all biomarkers across time segments.

Conclusions

Heightened antioxidant activity (rather than diminished oxidative stress markers) is associated with lower cardiovascular disease risk in type 1 diabetes mellitus, but these biomarkers did not change over time with intensification of glycemic control.

Clinical Trial Registration

URL : https://www.clinicaltrials.gov . Unique identifiers: NCT 00360815 and NCT 00360893.

Analysis of TCR Vbeta repertoire and cytokine gene expression in patients with idiopathic dilated cardiomyopathy

Although the etiopathogenesis of idiopathic dilated cardiomyopathy (IDC) is still unclear, it is widely accepted that a complex interplay between viral infections and immune mechanisms is the basis of disease genesis. Previously, we showed that heart-infiltrating T cells of patients suffering from acute, fulminant Coxsackie virus B3+-IDC shared a preferential usage of three variable gene segments of the T cell receptor beta chain-(TCR-Vbeta) encoding families Vbeta3, 7 and 13.1. This indicated the possible presence of a superantigen-driven immune response. Here, we further investigated the IDC immunological scenario by analysing different phenotypes of heart-infiltrating cells: TCR repertoires, cytokine expression and presence of enterovirus-specific antigens. IDC patients who underwent heart transplantation at different times after the onset of heart failure were studied. A cardiac infiltrate of CD4+ and CD8+ T cells was present together with activated macrophages. Furthermore, the same Vbeta gene families, previously found to be skewed in hearts from fulminant cases of CVB3+-IDC, together with two additional Vbeta gene families, Vbeta1 and 5B, were increased. IL-1beta, IL-2, IL-6 and IFN-gamma were expressed in the myocardium while others, like IL-4 were not. In conclusion, an orchestrated complex of immune mechanisms seems to be the basis of IDC etiopathogenesis.

Idiopathic dilated cardiomyopathy: a superantigen-driven autoimmune disease

BACKGROUND

Many cases of idiopathic dilated cardiomyopathy (IDC) result from an inflammatory myocarditis. The specific immunological mechanisms are not yet defined. Various autoimmune diseases are associated with superantigen-triggered immune responses, resulting in massive T-cell activation and tissue damage. We studied 3 cases in a search for evidence that such a phenomenon is also implicated in IDC.

METHODS AND RESULTS

Myocardial, lymph node, and thymic tissue samples were obtained from IDC patients who were undergoing heart transplantation. Infiltrating immune-cell phenotypes and gene expression of T-cell receptor (TCR) alpha- and beta-chain variable (Valpha and Vbeta) regions were analyzed by immunostaining and polymerase chain reaction. Similar technical approaches were used to assay the tissues for the presence of coxsackievirus B (CVB). In all the specimens analyzed, an overexpression of the TCR Vbeta3, Vbeta7, and Vbeta13.1 gene families was detected among the infiltrating T cells. These tissues were also found to be CVB3-positive. In vitro exposure of peripheral blood mononuclear cells to lysates of cells infected with CVB3 was capable of stimulating expansion of the same TCR Vbeta families. The TCR Valpha repertoire was never found to be skewed.

CONCLUSIONS

A superantigen-mediated immune response is involved in human heart disease. CVB3 may directly or indirectly trigger this response, suggesting a possible mechanistic link between CVB infection and myocarditis development progressing to IDC.

Appraising boardroom performance

Rare is the company that does not periodically review the performance of its staff, business units, and suppliers. But rare, as well, is the company that does such a review of one of its most important contributors--its board of directors. Reviewing a board's performance is not an easy proposition: it has to be done by the members themselves, people who generally have many other responsibilities and whose time is always at a premium. But done properly, appraisals can help boards become more effective by clarifying individual and collective responsibilities. They can help improve the working relationship between a company's board and its senior management. They can help ensure a healthy balance of power between the board and the CEO. And, once in place, an appraisal process is difficult to dismantle, making it harder for a new CEO to dominate a board or avoid being held accountable for poor performance. Done properly is the key here, though. Done incorrectly, board appraisals can degenerate into self-serving evaluations or unpleasant, time-wasting exercises. Worse, they can evolve into rigid mechanical processes that discourage innovation. In fact, all of the approaches the authors observed in two years of research were incomplete. The authors have therefore drawn on the strengths of several different approaches to synthesize a best-practice process that is both rigorous and comprehensive.

Evidence for superantigen involvement in insulin-dependent diabetes mellitus aetiology

Insulin-dependent diabetes mellitus (IDDM) is a T-cell-mediated autoimmune disease whose onset is believed to be triggered by unknown environmental factors acting on a predisposing genetic background. Islet-infiltrating T (IIT) cells from two IDDM patients, who had died at the onset of the disease from brain swelling as a complication of ketoacidosis, were analysed. The results provided evidence for the involvement of a pancreatic islet cell membrane-bound superantigen as a diabetes aetiopathogenetic factor. There was a selective expansion of a T-cell receptor (TCR) variable segment of the beta-chain (V beta 7) in these IIT cells in association with unselected V alpha-chain segments; extensive junctional diversity of the TCR V beta 7 chains; and evidence of positive selection, after exposure to diabetic islet cell membrane preparations, of V beta 7+ T-cell clones among peripheral blood lymphocytes from non-diabetic individuals.

Significance of antibody to hepatitis B core antigen in blood donors as determined by their serologic response to hepatitis B vaccine

Because large numbers of volunteer blood donors may be disqualified for "false-positive" results on tests for antibody to hepatitis B core antigen (anti-HBc), a more specific definition of anti-HBc enzyme immunoassay (EIA)-reactive was evaluated, including only those donor samples that were "strongly" reactive (sample-to-cutoff absorbance ratio, < 0.45). Results using this definition and other anti-HBc test methods were compared to the serologic response (antibody to hepatitis B surface antigen [anti-HBsAg]) to hepatitis B vaccination. Fifty-eight volunteer blood donors who had previously been deferred as donors, because of reactive anti-HBc tests (all other blood screening tests were negative, including those for HBsAg and anti-HBsAg) on two occasions, were vaccinated for hepatitis B. It was assumed that an anamnestic response to vaccine indicated past infection with hepatitis B, while a primary response to vaccine indicated lack of past infection. One (2%) of 43 donors with a historically "weak" anti-HBc (reactive absorbance ratio, > or = 0.45) had an anamnestic response to vaccine, compared to 8 (53%) of 15 with historically "strong" anti-HBc (reactive absorbance ratio, < 0.45) (p < 0.005). Anti-HBc testing using the microparticle EIA method also correlated well with hepatitis B vaccination results. The use of a narrower definition of "reactive" for anti-HBc EIA testing yielded much more specific, but slightly less sensitive, results.

Acute profound dystonia in infants with glutaric acidemia

Acute profound dystonia developed in three previously well infants who were found to have glutaryl-CoA dehydrogenase deficiency in cultured skin fibroblasts. Two patients had excessive urinary excretion of glutaric acid, but one did not. Neuroradiologic studies performed in all three patients at the onset of their illnesses revealed large CSF-containing spaces both within the sylvian fissures and anterior to the temporal lobes. Pathologic examination of the brain of one patient demonstrated cerebral and cerebellar atrophy, shrinkage of the putamen, and white matter vacuolation. Glutaric acidemia may be a common cause of acquired persistent dystonia or choreoathetosis in infancy.

Pulsatile growth hormone secretion in children with acute lymphoblastic leukemia after 1800 cGy cranial radiation

The relationship between intensity of central nervous system preventive therapy and the development of hypothalamic pituitary dysfunction is unclear in patients with acute lymphoblastic leukemia. In a previous report, we demonstrated uniform decreases in spontaneous secretion of growth hormone following 2400 cGy whole brain radiation. In this study, we measured basal growth hormone levels every 20 minutes over 24 hr in five survivors of childhood acute lymphoblastic leukemia treated with 1800 cGy cranial radiation. Four of the patients had been off therapy 2 9/12-4 3/12 years. Growth hormone secretion in these patients, as indicated by mean growth hormone concentration, pulse amplitude and frequency, was clearly greater than that seen following 2400 cGy and appeared to be normal compared with sex- and Tanner stage-matched literature controls. However, serial growth measurements showed significant decreases in height percentiles in two of these children. The fifth patient, who had already approached her adult height at the time of diagnosis, had been off therapy only 1 year and had a mean growth hormone level intermediate between those of normal controls and previously reported children treated with 2400 cGy. These data suggest (a) that the effect of radiation therapy on spontaneous pulsatile growth hormone secretion may be dose related, and (b) that short stature in a given patient may not be indicative of subnormal basal growth hormone levels. Further longitudinal investigation may clarify whether early transient changes in GH secretion occur that may normalize over time.

Comparable effects of 1800- and 2400-rad (18- and 24-Gy) cranial irradiation on height and weight in children treated for acute lymphocytic leukemia

To examine the effects of "low-dose" cranial irradiation on growth and to determine if one can predict patients in whom growth will be most affected, we studied 47 children with acute lymphocytic leukemia who had been treated with 2400 rad (24 Gy), 1800 rad (18 Gy), or no whole-brain irradiation. Serial measurements of height, weight, and weight for height were obtained by retrospective chart review. The effects of 1800 rad (18 Gy) and 2400 rad (24 Gy) treatment were indistinguishable. Height percentiles among irradiated patients decreased by a mean of 12% six months after diagnosis, and growth generally did not catch up. Moreover, although 33 irradiated patients maintained heights within the normal range, In 11 patients (33%) a dramatic falloff occurred such that by three years following diagnosis their height for age was more than 30 percentiles below the original value. These patients were all identifiable at six months since their height percentiles had already decreased by more than 15%. Although weight percentiles did not change following irradiation, the weight-for-height ratio increased and patients were relatively stockier three years after therapy than they had been at diagnosis. In patients who had received chemotherapy alone, the weight-for-height ratio also increased, but this appeared to be due to a disproportionate increase in weight. Longer follow-up and evaluation of larger cohorts of patients treated with 1800 rad (18 Gy) will be needed to confirm these results.

Why do children with diabetes die?

While the treatment of children with Type I diabetes mellitus has dramatically improved since the introduction of insulin in 1922, significant acute mortality still remains. To better ascertain the causes of death in younger children and adolescents with diabetes mellitus, a retrospective review was undertaken of diabetes associated mortality in the patient population followed at the Children's Hospital of Pittsburgh between the years 1950 and 1985. Fifty-five deaths were identified of which 20 occurred during the initial presentation of diabetes and 35 occurred between 2 months and 11 years following the diagnosis of diabetes mellitus. Diabetic ketoacidosis (DKA) was associated with 64% of the total mortality with 85% of the early onset and 54% of the late onset deaths being ketoacidosis related. Of these ketoacidosis associated deaths, cerebral edema was documented in 31%, or 20% of the total group mortality. Non ketoacidosis deaths in both early and late onset groups were caused by heterogeneous events. There were no deaths associated with the traditional late vascular complications of diabetes mellitus. Since diabetic ketoacidosis is a potentially preventable acute complication of diabetes mellitus and represented a predominant cause of mortality in these children, early recognition and prompt treatment might substantially reduce childhood mortality in patients with Type I diabetes mellitus.

Subclinical eating disorders and glycemic control in adolescents with type I diabetes

Several recent case reports have shown that anorexia nervosa and bulimia negatively affect glycemic control in diabetic patients. However, there have been no systematic studies to assess the prevalence of clinical or subclinical eating disorders among diabetic patients or to determine the impact of such disturbances on glycemic control. This study reports a survey of 202 adolescents, aged 12-18 yr, seen in the Diabetes Clinic, Children's Hospital of Pittsburgh, who were asked to complete the Binge Eating Scale (BES) and the EAT-26 questionnaire. Responses of diabetic patients to the EAT-26 questionnaire were compared with those of a nondiabetic control group and were related to measures of glycemic control. Diabetic subjects scored higher on the total EAT-26 than nondiabetic control subjects, ordinarily indicative of more eating pathology. However, diabetic subjects scored higher only on the dieting subscale of this questionnaire, probably reflecting adherence to the diabetes dietary regimen. Subjects with diabetes scored lower, or did not differ significantly, from nondiabetic control subjects on measures of oral control and bulimia. Among diabetic subjects, self-reported bulimic behaviors were related to poorer glycemic control. Patients with the highest scores on the BES had an average HbA1 of 13.1% compared with 11.8% for age- and sex-matched patients at the 50th percentile, and 10.8% for patients in the lowest 10th percentile. Further studies are needed to determine whether modification of these eating behaviors would improve glycemic control.

The glucokinase glucose sensor in human pancreatic islet tissue

The enzyme glucokinase controls glucose metabolism in islets and is proposed to be the glucose sensor in pancreatic beta-cells. This concept was developed from studies with rodents and it remained to be explored whether it also applies to man. Studies in man were hampered, however, by the difficulty in obtaining well-preserved pancreatic islet tissue and also because the high activity of hexokinase made it difficult to measure glucokinase. To overcome these obstacles, quantitative histochemical sampling techniques were developed allowing precise dissection of pure human islet tissue and a newly designed radiometric microassay was used, avoiding hexokinase interference, and providing the sensitivity necessary to measure the relatively low glucokinase activity in small samples of tissue obtained from brain-dead tissue donors. The present data indicate that glucokinase is present in human pancreatic islet tissue and is not found in the exocrine pancreas. The enzyme's Vmax with D-glucose as substrate was similar to the Vmax for glucose utilization reported previously for intact, isolated human islets and the enzyme's Km for D-glucose was about 5 mM. Since glucokinase was also present in islet tissue of hamster, mouse, and rat, it is suggested that the glucokinase-glucose sensor concept has general applicability and that it could explain many aspects of the physiology and pathology of glucose homeostasis. This well-defined pancreatic islet glucokinase-glucose sensor should, therefore, be incorporated in any comprehensive model of glucose homeostasis.

Polyol pathway activity and myo-inositol metabolism. A suggested relationship in the pathogenesis of diabetic neuropathy

Two major metabolic perturbations, increased polyol (sorbitol) pathway activity and reduced tissue myo-inositol content, are induced in peripheral nerve by hyperglycemia. Although they are commonly invoked as alternative biochemical pathogenetic mechanisms for diabetic neuropathy, their possible interrelationship has never been adequately explored. Therefore, we studied the effect of polyol pathway blockade with sorbinil, a specific inhibitor of aldose reductase, on nerve myo-inositol content in acutely streptozotocin-diabetic rats. Sorbinil administration completely prevented the fall in nerve myo-inositol, thereby implicating increased polyol pathway activity as a likely factor in the fall in nerve myo-inositol content in experimental diabetes.

Quantitative histochemical resolution of the oxidation-reduction and phosphate potentials within the simple hepatic acinus

Glycerin-3-P, commonly known as alpha-glycerophosphate and dihydroxyacetone phosphate (DHAP) were measured in well defined microscopic samples of the simple liver acinus allowing a comparison of the glycerin-3-P/dihydroxyacetone-P-ratios of Zones 1 and 3 as a measure of the free NAD+/NADH ratio. The ATP/ADP X Pi quotients were determined in these same microscopic areas of the liver acinus as a measure of the phosphate potential. Brief ischemia was used to disturb the system. The results indicate that the oxidation-reduction and phosphate potentials are uniform throughout the entire liver lobule.

Linear growth in a population of children with myelomeningocele

Short stature or total body length less than the third percentile for age was present in 51% of our children with myelomeningocele. It was particularly common in children with higher spinal lesions where 77% of the children with L3 and higher lesions had length measurements less than the 3rd percentile for age. None of the children with sacral lesions was of short stature. Associated musculoskeletal deformities of the spine, hips, and knees made total body length and upper to lower body segment ratio measurements both difficult to obtain and less than ideal parameters for assessing linear growth. Arm span measurements, however, were easily obtained in or out of braces and were greater than expected for length in 91% of children with short stature older than 3 years of age. This apparent sparing of arm span in many of our children makes it a valuable growth parameter when assessing linear growth and in turn an important diagnostic tool for the monitoring of total health in a population of children with myelomeningocele.