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.

Ovarian reserve in women with Type 1 diabetes in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study

Markers of ovarian reserve such as anti-Müllerian hormone (AMH) are used in the management of fertility and prediction of menopause. Although women with type 1 diabetes have a high prevalence of reproductive disorders, no studies have examined whether markers of ovarian reserve are associated with randomization to intensive insulin therapy and subsequent markers of glycemic control. Using data from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study, we found that the strongest predictor of AMH was chronologic age, and that diabetes-specific variables such as randomization to intensive therapy, insulin dose, and glycemic control were not associated with AMH concentrations.

Insulin secretion measured by stimulated C-peptide in long-established Type 1 diabetes in the Diabetes Control and Complications Trial (DCCT)/ Epidemiology of Diabetes Interventions and Complications (EDIC) cohort: a pilot study

AIMS

To evaluate whether clinically relevant concentrations of stimulated C-peptide in response to a mixed-meal tolerance test can be detected after almost 30 years of diabetes in people included in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications cohort.

METHODS

Mixed-meal tolerance tests were performed in a sample of 58 people. C-peptide levels were measured using a chemiluminescent immunoassay. This sample size assured a high probability of detecting C-peptide response if the true prevalence was at least 5%, a level that would justify the subsequent assessment of C-peptide in the entire cohort.

RESULTS

Of the 58 participants, 17% showed a definite response, defined as one or more post-stimulus concentrations of C-peptide > 0.03 nmol/l, and measurable concentrations were found in all participants.

CONCLUSIONS

These results show that a stimulated C-peptide response can be measured in some people with long-term Type 1 diabetes. Further investigation of all participants in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications study will help relate long-term residual C-peptide response to glycaemia over time and provide insight into the relevance of this response in terms of insulin dose, severe hypoglycaemia, retinopathy, nephropathy and macrovascular disease. Establishing the clinical relevance of long-term C-peptide responses is important in understanding the impact that therapy to preserve or improve β-cell function may have in patients with long-term Type 1 diabetes.

Association of inflammation with worsening HOMA-insulin resistance

AIMS/HYPOTHESIS

We examined the cross-sectional and longitudinal relationships between C-reactive protein (CRP), a marker of low-grade inflammation, and insulin resistance and whether the association was independent of obesity and oxidative stress.

METHODS

CRP and insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR]) data were obtained in a population-based, prospective observational study, Coronary Artery Risk Development in Young Adults (CARDIA), during 1992-2006.

RESULTS

CRP showed a significant positive association with insulin resistance, both cross-sectionally and longitudinally (5 year follow-up). The estimated increment in HOMA-IR was 0.34 log(e)(pmol/l x [mmol/l]/156.25) (p value for trend <0.0001) in the highest vs lowest CRP quartiles in cross-sectional analysis, whereas the corresponding estimate was 0.12 (p trend <0.0001) in the highest vs lowest CRP quartiles longitudinally over 5 years. The gradient of HOMA-IR across CRP was attenuated but remained statistically significant after controlling for body fat measurements (0.06 in the highest vs lowest CRP in both cross-sectional [p value for trend = 0.001] and longitudinal analyses [p value for trend = 0.01]), and was little changed by further adjustment for oxidative stress markers (F(2)-isoprostanes and oxidised LDL). There were consistent increments in the levels of HOMA-IR with increasing concentrations of CRP over time. In contrast, higher HOMA-IR did not predict future increases in CRP. Findings were similar using fibrinogen as the predictor variable.

CONCLUSIONS/INTERPRETATION

Although a substantial portion of this association was explained by obesity, CRP was independently related to concurrent and future insulin resistance.

Renal function and rate of hip bone loss in older men: the Osteoporotic Fractures in Men Study

Older men with reduced renal function are at increased risk of hip bone loss. Given the robustness of this association across different measures and a growing body of literature, our findings indicate that clinicians should take into account renal function when evaluating older men for osteoporosis risk and bone loss. Future randomized controlled trials should test whether interventions in this high risk population are effective in preventing bone loss and decreasing fracture incidence.

INTRODUCTION

Studies examining whether kidney impairment, not requiring dialysis, is associated with osteoporosis have reported conflicting results.

METHODS

We tested the hypothesis that reduced renal function in older men as manifested by higher concentrations of cystatin C or lower levels of estimated glomerular filtration rate (eGFR) is associated with higher rates of bone loss. We measured serum cystatin C, serum creatinine and total hip bone mineral density (BMD) at baseline in a cohort of 404 older men enrolled in the Osteoporotic Fractures in Men (MrOS) Study and followed them prospectively for an average of 4.4 years for changes in BMD. Associations between renal function and change in hip BMD were examined using linear regression.

RESULTS

In multivariable analysis, the mean rate of decline in total hip BMD showed an increase in magnitude with higher cystatin C concentration (mean annualized percent change -0.29, -0.34, -0.37 and -0.65% for quartiles 1 to 4; p for trend=0.004). Similarly, adjusted rates of hip bone loss were higher among men with lower eGFR as defined by the modification of diet in renal disease formula (mean annualized percent change -0.58, -0.39, -0.37, and -0.31 for quartiles 1 to 4; p for trend=0.02), but not among men with lower eGFR as defined by the Cockcroft-Gault formula (mean annualized percent change -0.47, -0.44, -0.31 and -0.43 for quartiles 1 to 4; p for trend=0.48).

CONCLUSIONS

Older men with reduced renal function are at increased risk of hip bone loss. Our findings suggest that health care providers should consider renal function when evaluating older men for risk factors for bone loss and osteoporosis.

Relationship between serum concentrations of persistent organic pollutants and the prevalence of metabolic syndrome among non-diabetic adults: results from the National Health and Nutrition Examination Survey 1999-2002

AIMS/HYPOTHESIS

We recently reported associations of some persistent organic pollutants (POPs) with both prevalence of type 2 diabetes and insulin resistance in a US population with background exposure to POPs. Restricted to non-diabetic participants, we now investigate the relationship between POPs and the metabolic syndrome, a prediabetic state.

MATERIALS AND METHODS

Cross-sectional associations were investigated in 721 non-diabetic participants aged > or =20 years. Nineteen POPs in five subclasses were selected because they were detectable in > or =60% of participants.

RESULTS

Among five POPs subclasses, organochlorine (OC) pesticides were most strongly and consistently associated with metabolic syndrome: adjusted odds ratios (ORs) of 1.0, 1.5, 2.3 and 5.3 across OC pesticide quartiles (p for trend <0.01). Dioxin-like polychlorinated biphenyls (PCBs) were also positively associated with adjusted ORs of 1.0, 1.1, 2.2 and 2.1 (p for trend = 0.01). However, non-dioxin-like PCBs showed an inverted U-shaped association with adjusted ORs of 1.0, 1.3, 1.8 and 1.0 (p for quadratic term <0.01). Associations of specific POPs varied across five components of the metabolic syndrome. OC pesticides were positively and significantly associated with four of the five components, especially elevated triacylglycerol and high fasting glucose, but not high blood pressure. PCBs were significantly associated with waist circumference, triacylglycerol and impaired fasting glucose. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans showed small but significant associations only with high blood pressure.

CONCLUSIONS/INTERPRETATION

This study suggests that the prevalence of a cluster of cardiovascular risk factors relates to background exposure to a mixture of POPs, several of which are also related to the prevalence of diabetes. POPs associated differentially with different components of the metabolic syndrome.

The combination oral and nutritional treatment of late-onset diabetes mellitus (CONTROL DM) trial results

OBJECTIVE

To examine the effect of short-term improvements in glycaemic control on brachial artery endothelial function as a marker of cardiovascular health.

METHODS

Persons with Type 2 diabetes who were poorly controlled on oral therapy were randomly assigned to monotherapy with repaglinide or combination therapy with repaglinide plus metformin. Brachial artery flow-mediated vasodilation was assessed by ultrasonography at randomization and following 16 weeks of therapy. The primary outcome was change in brachial artery endothelial function from baseline. Comparison of randomized groups was a secondary aim.

RESULTS

Eighty-six participants were randomized, and 83 were followed to study completion. Post occlusion brachial artery vasodilation was 3.74% at baseline and 3.82% following 16 weeks of therapy (P = 0.77). The treatment effect was 0.08% (95% CI: -0.48%, 0.64%). No difference was seen between treatment groups (P = 0.69). Overall, A1C was reduced from 8.3% to 7.0%, with a greater reduction in the combination therapy group (from 8.4% to 6.7%) than in the monotherapy group (from 8.3% to 7.3%, p for difference between groups = 0.01). Statistically significant reductions were observed in fasting glucose, and plasminogen activator inhibitor-1. Statistically significant increases were observed for fasting insulin, uric acid, weight and BMI.

CONCLUSIONS

Brachial artery endothelial function was not influenced by short-term improvements in glycaemic control. The CONTROL DM group was successful in lowering A1C. Future research should explore more intensive and longer-lasting improvements in glycaemic control on endothelial function. Some data previously published in abstract form (Diabetes 2001; 50 (Suppl. 2): A217).

Gamma-glutamyltransferase and diabetes--a 4 year follow-up study

AIMS/HYPOTHESIS

Gamma-glutamyltransferase (GGT) is located on the external surface of most cells and mediates the uptake of gluthathione, an important component of intracellular antioxidant defenses. An increase in GGT concentration has been regarded as a marker of alcohol consumption or liver disease. However, more subtle gradations in GGT could be informative because its expression is enhanced by oxidative stress and it could be released by several conditions inducing cellular stress. Recently, serum GGT concentrations have been associated with many cardiovascular disease risk factors or components of the insulin resistance syndrome. We did a prospective study with the hypothesis that serum GGT is a predictor of incident diabetes.

METHODS

A total of 4,088 healthy men working in a steel manufacturing company were examined in 1994 and 1998. Diabetes was defined as a serum fasting glucose concentration of more than 126 mg/dl or the use of diabetes medication.

RESULTS

There was a strong dose-response relation between serum GGT concentrations at baseline and the incidence of diabetes. In contrast to the 31% of men with GGT concentrations under 9 U/l, adjusted relative risks for incidence of diabetes for GGT concentrations 10-19, 20-29, 30-39, 40-49, and over 50 U/l were 8.0, 13.3, 12.6, 19.6 and 25.8, respectively. The associations of age and BMI with incident diabetes became stronger the higher the value of baseline serum GGT concentration.

CONCLUSION/INTERPRETATION

This study suggests that an increase in GGT concentration within its physiological range is a sensitive and early biomarker for the development of diabetes.

Prevention of cardiovascular and renal pathology of aging by the advanced glycation inhibitor aminoguanidine

Human aging is impacted severely by cardiovascular disease and significantly but less overtly by renal dysfunction. Advanced glycation endproducts (AGEs) have been linked to tissue damage in diabetes and aging, and the AGE inhibitor aminoguanidine (AG) has been shown to inhibit renal and vascular pathology in diabetic animals. In the present study, the effects of AG on aging-related renal and vascular changes and AGE accumulation were studied in nondiabetic female Sprague-Dawley (S-D) and Fischer 344 (F344) rats treated with AG (0.1% in drinking water) for 18 mo. Significant increases in the AGE content in aged cardiac (P < 0.05), aortic (P < 0.005), and renal (P < 0.05) tissues were prevented by AG treatment (P < 0.05 for each tissue). A marked age-linked vasodilatory impairment in response to acetylcholine and nitroglycerine was prevented by AG treatment (P < 0.005), as was an age-related cardiac hypertrophy evident in both strains (P < 0.05). While creatinine clearance was unaffected by aging in these studies, the AGE/ creatinine clearance ratio declined 3-fold in old rats vs. young rats (S-D, P < 0.05; F344, P < 0.01), while it declined significantly less in AG-treated old rats (P < 0.05). In S-D but not in F344 rats, a significant (P < 0.05) age-linked 24% nephron loss was completely prevented by AG treatment, and glomerular sclerosis was markedly suppressed (P < 0.01). Age-related albuminuria and proteinuria were markedly inhibited by AG in both strains (S-D, P < 0.01; F344, P < 0.01). These data suggest that early interference with AGE accumulation by AG treatment may impart significant protection against the progressive cardiovascular and renal decline afflicting the last decades of life.

Advanced glycation end products induce glomerular sclerosis and albuminuria in normal rats

High levels of tissue advanced glycation end products (AGEs) that result from the spontaneous modification of proteins by glucose occur in diabetes and aging. To address the potential pathogenic role of AGEs in the glomerulosclerosis of diabetes or nephrosclerosis of aging, doses of AGE-modified rat albumin (25 mg per kg per day, i.v.) sufficient to elevate circulating AGE levels to the range of diabetic serum were administered daily to healthy rats alone or in combination with the AGE inhibitor aminoguanidine. After 5 months, the AGE content of renal tissues in AGE-treated rats rose to 50% above controls (P < 0.025), whereas serum contained 2.8-fold greater AGE levels (P < 0.025). Light and electron microscopy of kidneys from AGE-treated rats revealed a more than 50% increase in glomerular volume compared to controls (P < 0.001), significant periodic acid/Schiff reagent-positive deposits, basement membrane widening, and mesangial extracellular matrix increase and indicated significant glomerulosclerosis compared to untreated (P < 0.002) or albumin-treated controls (P < 0.002). These changes were associated with significant loss of protein (P < 0.005) and albumin (P < 0.002) in the urine of AGE-treated rats compared to controls. Cotreatment with aminoguanidine markedly limited both the structural and functional defects. These in vivo data demonstrate that AGEs influence glomerular structure and function in a manner leading to glomerulosclerosis. The effects are AGE-specific, as they are ameliorated by a pharmacological AGE inhibitor, aminoguanidine.

Cancer home care in Montana

Availability of health care services in sparsely populated areas may be limited by fewer health care organizations and geographic separation. The purposes of this study were to identify unmet needs of individuals and families managing cancer in rural areas and examine cancer-related home care in rural areas. Issues of staffing, caseloads and service area for home health agencies (HHAs) and hospices were examined. HHAs registered with the Montana Association of Home Health Care Agencies and licensed hospices in Montana were mailed questionnaires with 92% of the HHAs and 90% of the hospices returning the questionnaires. Health providers identified a variety of unmet needs including personal care and respite. Agencies were small with approximately four full-time equivalent registered nurses for HHAs and one full-time equivalent registered nurse for hospices. Similarly, caseloads were also small with an average of 50 clients per month for HHAs and 11 clients per month for hospices. HHAs and hospices had large service areas with two of the HHAs each serving seven counties. Implications of these findings for research and practice are discussed.

The role of the pediatric nephrologist in the care of children with diabetes mellitus

The pediatric nephrologist has traditionally not been involved in the care of the diabetic child since diabetic nephropathy presents in adulthood. Recent studies suggest that diabetic kidney disease develops silently during childhood. Measurement of urinary albumin excretion (UAE) allows earlier detection of patients at risk of nephropathy, often in adolescence. In addition to diabetic nephropathy, diabetic children are at risk of urinary tract infections, renal papillary necrosis, and various forms of glomerulonephritis. The role of the pediatric nephrologist in the care of the child with diabetes might include advising on the administration and interpretation of screening for UAE and the measurement and interpretation of glomerular filtration rate, and blood pressure. Children with evidence of renal dysfunction should be evaluated and treated by the pediatric nephrologist. Frequently, renal biopsy will be necessary in these patients. Future research may allow the detection of diabetic kidney disease earlier in childhood, further expanding the role of the pediatric nephrologist. In particular, early renal biopsy may eventually be used to select those patients at risk of diabetic nephropathy for specific treatment alterations.

Skeletal muscle basement membrane in maturity-onset diabetes in the young

We have studied skeletal muscle capillary basement membrane width (CBMW) and intensity of skeletal muscle extracellular basement membrane staining for albumin and IgG in eight families with maturity-onset diabetes in the young (MODY). Ninety-two MODY patients were identified. Sixty-three of these patients, 33 relatives with nondiagnostic oral glucose tolerance studies, and 61 normoglycemic relatives were studied for glucose and insulin. Twenty-six of these MODY patients, 20 normoglycemic relatives, and 16 unrelated normal controls had skeletal muscle capillary morphologic studies. The muscle capillary basement membrane was significantly increased in MODY patients younger than 40 yr when compared with unrelated normal subjects and relatives of the same age (P less than 0.001). However, in these families, the CBMW of MODY patients showed no significant thickening with age (slope = 0.45, P less than 0.14), as expected and seen in the normal subjects and in the normoglycemic relatives of the patients (slope = 1.21, P less than 0.001). The slope derived from the linear regression of age and CBMW in MODY patients (0.45 +/- 0.29) was significantly less (P less than 0.05) than that of the nondiabetic subjects (1.21 +/- 0.19). The mean intensity of skeletal muscle extracellular basement membrane staining for albumin was higher in MODY patients (1.1 +/- 0.15) than in unrelated normal subjects (0.7 +/- 0.1, P less than 0.025) and normal MODY family members (0.6 +/- 0.08, P less than 0.01). The unexpected absence of basement membrane thickening with age in the MODY patients may explain the paucity of vascular complications that have been reported by some.(ABSTRACT TRUNCATED AT 250 WORDS)