Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes

Postprandial hyperglycaemia and vascular damage--the benefits of acarbose

Traditional risk factors do not fully explain the increased risk of cardiovascular disease (CVD) in diabetes. Epidemiology shows that hyperglycaemia is a continuous CVD risk factor and that two-hour postprandial glucose levels are more strongly associated with CVD than fasting glucose. Good glycaemic control is proven to reduce the risk of microvascular complications, but equivalent evidence for CVD risk reduction is lacking. However, in the Study to Prevent Non-Insulin Dependent Diabetes Mellitus (STOP-NIDDM), acarbose reduced the risk of diabetes in those with impaired glucose tolerance by 36% (p=0.0017) and the risk of any cardiovascular event by 49% (p=0.0326) versus placebo. Furthermore, a meta-analysis of trials of acarbose in patients with type 2 diabetes suggests a significant reduction of CVD events. This review examines evidence that postprandial hyperglycaemia plays a major role in vascular damage, particularly through non-traditional risk factors such as oxidative stress and subclinical inflammation, and how acarbose may prevent this damage.

Epidemiological data on postprandial glycaemia

There are few studies on the effects of postprandial hyperglycaemia, and usually it is assumed that its effects are the same as those of post-glucose-load hyperglycaemia, following a standard 75 g oral glucose tolerance test. There is some evidence from a study with blood drawn following ingestion of a standardised "diabetes screening product" or a 75 g oral glucose load, that the glucose concentrations during the 2-hour period of these two tests are highly correlated. There is epidemiological evidence that the 2-hour post-load-glucose is more predictive of cardiovascular mortality than fasting glucose, but it would appear that they are equally predictive of retinopathy. While hyperglycaemia is related with cardiovascular mortality, clinical trials lowering glucose levels in type 2 diabetic patients, have not succeeded in reducing cardiovascular disease rates, in contrast to the beneficial effects on micro-vascular disease. STOP-NIDDM, a clinical trial testing the prevention of type 2 diabetes, used the glucose lowering agent acarbose, a drug which lowers postprandial glucose. There was a beneficial effect on cardiovascular outcomes, however, the number of events was extremely small and the study was not designed to test this effect. Confirmatory studies are required before it is possible to conclude that acarbose is effective in cardiovascular prevention, and that indeed it is the treatment of postprandial glucose which is beneficial. The cardiovascular disease in diabetic patients may be due to the presence of other cardiovascular risk factors associated with diabetes.

Should diabetic patients be asked to test their blood glucose 90 to 120 minutes after the beginning of their meals?

There are three distinct objectives in reducing the post-prandial blood glucose peaks: 1st to reduce the risk of foetal macrosomia in pregnancy, 2nd to reduce cardiovascular morbi-mortality, 3rd to lower the HbA1c. With 6-7 glycaemic controls per day and fractionning their meals, motivated women with gestational diabetes reach this goal. But there is no data today directly proving that post-prandial glycaemia is specifically related to the development of micro and macrovascular complications. So to reduce the cardiovascular risk, there are more arguments in favour of lowering HbA1c or prescribing statins than in prescribing a hypoglycaemic drug acting selectively on post-prandial glycaemia. Lastly, to reduce HbA1c near to the goal of 7%, the most important is to reduce the preprandial glycaemia below 1.20 g/l. The patients must be required to monitor their post-prandial glycaemia 2 hours after the beginning of the meal only when the aim is to lower the HbA1c below 7% or 6.5%, for example during pregnancy, or in case of discrepancy between glycaemia at 8 a.m. and 7 p.m. (below 1.20 g/)l and HbA1c (above 7%). In other cases, in type 2 diabetes, two glycaemias per day, fasting and vesperal, seems sufficient.

New-onset diabetes and risk of all-cause and cardiovascular mortality: the Cardiovascular Health Study

OBJECTIVE

Cardiovascular risk associated with new-onset diabetes is not well characterized. We hypothesized that risk of all-cause and cardiovascular mortality would be similar among participants with and without new-onset diabetes in the first years of follow-up and rise over time for new-onset diabetes.

RESEARCH DESIGN AND METHODS

The Cardiovascular Health Study (CHS) is a longitudinal study of cardiovascular risk factors in adults aged > or =65 years. We used CHS participants to define a cohort (n = 282) with new-onset diabetes during 11 years of follow-up. New-onset diabetes was defined by initiation of antidiabetes medication or by fasting plasma glucose >125 mg/dl among CHS participants without diabetes at study entry. Three CHS participants without diabetes were matched for age, sex, and race to each participant with new-onset diabetes at the time of diabetes identification (n = 837). Survival analysis provided adjusted hazard ratios (HRs) for all-cause and cardiovascular mortality.

RESULTS

During a median of 5.9 years of follow-up, there were 352 deaths, of which 41% were cardiovascular. In adjusted analyses, new-onset diabetes was associated with an HR of 1.9 (95% CI 1.4-2.5) for all-cause and 2.2 (1.4-3.4) for cardiovascular mortality compared with no diabetes. Mortality risks were elevated within 2 years of onset, especially cardiovascular risk (4.3 [95% CI 1.7-10.8]), and did not increase over time.

CONCLUSIONS

Our findings indicate that there may be a mortality differential soon after diabetes onset in older adults and suggest that long-term macrovascular damage from atherosclerosis may not be primarily responsible for increased risk.

Microalbuminuria

Microalbuminuria, originally described more than 3 decades ago as a predictor of nephropathy in patients who had type 1 diabetes mellitus and associated with higher cardiovascular risk, is now linked with increased risk for cardiovascular events rather than progression to end-stage kidney disease. This article reviews the role of microalbuminuria in the context of atherosclerotic vascular disease. It presents the methods for microalbuminuria assessment in clinical practice, its relations with other cardiovascular risk factors, and the pathophysiologic associations between microalbuminuria and vascular damage. In addition, this article discusses the prognostic significance of microalbuminuria for cardiovascular disease as well as existing therapeutic interventions for reducing urine albumin excretion in patients who are at high cardiovascular risk.

National Stroke Association guidelines for the management of transient ischemic attacks

OBJECTIVE

Transient ischemic attacks are common and important harbingers of subsequent stroke. Management varies widely, and most published guidelines have not been updated in several years. We sought to create comprehensive, unbiased, evidence-based guidelines for the management of patients with transient ischemic attacks.

METHODS

Fifteen expert panelists were selected based on objective criteria, using publication metrics that predicted nomination by practitioners in the field. Prior published guidelines were identified through systematic review, and recommendations derived from them were rated independently for quality by the experts. Highest quality recommendations were selected and subsequently edited by the panelists using a modified Delphi approach with multiple iterations of questionnaires to reach consensus on new changes. Experts were provided systematic reviews of recent clinical studies and were asked to justify wording changes based on new evidence and to rate the final recommendations based on level of evidence and quality. No expert was allowed to contribute to recommendations on a topic for which there could be any perception of a conflict of interest.

RESULTS

Of 257 guidelines documents identified by systematic review, 13 documents containing 137 recommendations met all entry criteria. Six iterations of questionnaires were required to reach consensus on wording of 53 final recommendations. Final recommendations covered initial management, evaluation, medical treatment, surgical treatment, and risk factor management.

INTERPRETATION

The final recommendations on the care of patients with transient ischemic attacks emphasize the importance of urgent evaluation and treatment. The novel approach used to develop these guidelines is feasible, allows for rapid updating, and may reduce bias.

Cardiovascular disease risk in youth with diabetes mellitus

In the United States, cardiovascular disease is the leading cause of mortality in adults with diabetes over age 30 years. Studies in persons without diabetes have shown that atherosclerosis, a central factor in cardiovascular disease, begins in childhood and the presence of cardiovascular disease risk factors in youth lead to increased cardiovascular disease risk in adults. Therefore, youth with diabetes are at increased risk for developing cardiovascular disease as adults and there is a role for risk factor screening and addressing modifiable factors to lower cardiovascular disease risk starting in childhood. This paper reviews the literature on traditional cardiovascular disease risk factors in youth with diabetes including hyperglycemia, hypertension, dyslipidemia, smoking, obesity and family history of cardiovascular disease with an emphasis on type 1 diabetes as well as current American Diabetes Association guidelines for screening and treatment of modifiable risk factors. Current roles of inflammatory markers and measures of subclinical vascular changes such as arterial stiffness are also discussed.

Coronary artery calcification, serum lipids, lipoproteins, and peripheral inflammatory markers in adolescents and young adults with type 1 diabetes

OBJECTIVE

To determine whether coronary artery calcification (CAC), elevated fasting lipids, and lipoproteins and peripheral inflammatory markers are present in insulin-dependent diabetic adolescents and young adults several years after diagnosis.

STUDY DESIGN

Hispanic insulin-dependent diabetics (n = 32) diagnosed a mean of 7.8 +/- 4.5 years ago (range, 3 to 16 years), with a mean glycosylated hemoglobin concentration at the time of the study of 8.8% +/- 2.3% and a mean chronological age of 16.1 +/- 4.4 years, were evaluated. Healthy patients (n = 15) with a chronological age (CA) of 15.2 +/- 2.2 years served as control subjects. CAC was assessed by multiple slice computed tomography, and total CAC score in Agatston units was calculated. Fasting lipids, C-reactive protein, apolipoprotein (Apo) A, Apo B, and metalloproteinase-9 (MMP-9) concentrations were measured in all subjects.

RESULTS

Neither adolescents with type 1 diabetes nor healthy control subjects presented with evidence of CAC. Fasting lipids, Apo A, Apo B, CRP, and MMP-9 concentrations were similar between diabetic subjects and control subjects. However, 34.4% and 25.0% of our type 1 diabetic subjects had elevated total and LDL cholesterol levels (>200 and >130 mg/dL, respectively), whereas 15.6% and 28.1% had elevated triglyceride and Apo B concentrations (>150 mg/dL and >100 mg/dL, respectively). In addition, 28.1% and 34.4% presented with elevated CRP and MMP-9 levels (>2 mg/L and >80 ng/mL, respectively). Total, LDL and HDL cholesterol, triglycerides, Apo B, CRP, and MMP-9 concentrations correlated positively with duration of the disease and with glycosylated hemoglobin levels.

CONCLUSIONS

Although the study adolescents with type 1 diabetes did not present any radiologic evidence of CAC at this stage of the disease, they remain a high-risk group for the development of microvascular and macrovascular artery disease, as risk factors such as elevated lipoproteins and proinflammatory markers are already present in a significant percentage of patients studied.

New therapies aimed at the preservation or restoration of beta cell function in type 1 diabetes

Type 1 diabetes is caused by an immune-mediated destruction of the insulin-secreting beta cells in the pancreas. The disease can become clinically apparent at any age. At diagnosis, there is invariably some residual beta cell function and more so in adults than in children. Recent studies--including one conducted mainly in Belgium--have provided proof of principle that short-term anti-T-cell antibody treatment is able to preserve residual beta cell function for at least 18 months. The resultant stabilizing effect on metabolic control is expected to delay or limit chronic complications in these patients. With a similar goal in mind, nonuremic C-peptide negative patients are offered beta cell transplantation. The outcome of these implants looks promising but their final applicability hinges on finding ways to induce immune tolerance to the donor beta cells. A widespread application, however, will only occur if the shortage of viable human donor cells can be overcome. Both xenotransplantation and stem cell therapy provide possible strategies to solve this problem and represent areas of intense investigation. The ultimate goal is prevention of clinical disease. Studies by the Belgian Diabetes Registry and others in first degree family members of type 1 diabetic patients have refined the identification of individuals at very high risk of hyperglycaemia so that new immunological treatments can be tested in the prediabetic phase.

Animal models of type 2 diabetes: clinical presentation and pathophysiological relevance to the human condition

The prevalence of diabetes throughout the world has increased dramatically over the recent past, and the trend will continue for the foreseeable future. One of the major concerns associated with diabetes relates to the development of micro- and macrovascular complications, which contribute greatly to the morbidity and mortality associated with the disease. Progression of the disease from prediabetic state to overt diabetes and the development of complications occur over many years. Assessment of interventions designed to delay or prevent disease progression or complications in humans also takes years and requires tremendous resources. To better study both the pathogenesis and potential therapeutic agents, appropriate animal models of type 2 diabetes (T2D) mellitus are needed. However, for an animal model to have relevance to the study of diabetes, either the characteristics of the animal model should mirror the pathophysiology and natural history of diabetes or the model should develop complications of diabetes with an etiology similar to that of the human condition. There appears to be no single animal model that encompasses all of these characteristics, but there are many that provide very similar characteristics in one or more aspects of T2D in humans. Use of the appropriate animal model based on these similarities can provide much needed data on pathophysiological mechanisms operative in human T2D.

Mechanisms of sympathoadrenal failure and hypoglycemia in diabetes

A reduced sympathoadrenal response, induced by recent antecedent hypoglycemia, is the key feature of hypoglycemia-associated autonomic failure (HAAF) and, thus, the pathogenesis of iatrogenic hypoglycemia in diabetes. Understanding of the mechanism(s) of that reduced response awaits new insight into its basic molecular, cellular, organ, and whole-body physiology and pathophysiology in experimental models. In this issue of the JCI, McCrimmon and colleagues report that application of urocortin I (a corticotrophin-releasing factor receptor-2 agonist) to the ventromedial hypothalamus reduces the glucose counterregulatory response to hypoglycemia in rats (see the related article beginning on page 1723). Thus, hypothalamic urocortin I release during antecedent hypoglycemia is, among other possibilities, a potential mechanism of HAAF.

An integrated graphic scheme for the display of insulin prescription and blood glucose information

OBJECTIVE

This study was undertaken to determine whether use of an integrated graphic scheme for the display of insulin prescription and blood glucose information has an impact on simulated decision-making in clinical practice.

METHODS

Five test cases representing patients treated with multiple daily insulin regimens were selected from a database of stored blood glucose readings. Five endocrinologists made treatment recommendations based on review of aggregated readings and corresponding insulin prescriptions. Twenty subjects were randomized to complete two sets of sequential real-time data management exercises. One set focused on evaluation of insulin prescriptions and readings printed as entries in logbooks. The other focused on evaluation of displays of insulin doses and readings plotted out according to an integrated graphic scheme of representation.

RESULTS

Subjects were more likely to make correct decisions in four out of five test cases after reviewing displays. Subjects were less likely to make incorrect decisions in all of five test cases after reviewing displays. Completion times were 30-66% shorter for exercises involving review of displays.

CONCLUSION

An integrated graphic scheme that associates representations of insulin doses with metaphor graphic displays of aggregated blood glucose readings may facilitate decisionmaking in clinical practice.

The apolipoprotein A-IV Gln360His polymorphism predicts progression of coronary artery calcification in patients with type 1 diabetes

AIMS/HYPOTHESIS

Individuals with type 1 diabetes have an increased incidence of coronary artery disease (CAD) and a higher risk of cardiovascular death compared with individuals of the same age in the general population. While chronic hyperglycaemia and insulin resistance partially explain excess CAD, little is known about the potential genetic determinants of accelerated coronary atherosclerosis in type 1 diabetes. The aim of the present study was to evaluate the association of apolipoprotein A-IV (APOA4) polymorphisms with coronary artery calcification (CAC) progression, a marker of subclinical atherosclerosis.

SUBJECTS AND METHODS

Two previously well-studied functional APOA4 polymorphisms resulting in the substitution of the amino acid Thr for Ser at codon 347 and Gln for His at codon 360 were genotyped in 634 subjects with type 1 diabetes and 739 non-diabetic control subjects, the participants of the prospective Coronary Artery Calcification in Type 1 Diabetes (CACTI) study.

RESULTS

The His360 allele was associated with a significantly higher risk of CAC progression among patients with type 1 diabetes (33.7 vs 21.2%, p=0.014), but not in the control subjects (14.1 vs 11.1%, p=0.42). Logistic regression analysis confirmed that the presence of the APOA4 His360 allele predicts an increased risk of progression of coronary atherosclerosis in adults with type 1 diabetes of long duration (odds ratio = 3.3, p=0.003 after adjustment for covariates associated with CAD risk). CONCLUSIONS /INTERPRETATION: This is the first report suggesting an association between the APOA4 Gln360His polymorphism and risk of CAC progression in subjects with type 1 diabetes. Additional studies are needed to explore potential interactions between APOA4 genotypes and metabolic/oxidative stress components of the diabetic milieu leading to rapid progression of atherosclerosis.

Addition of dietary fat to cholesterol in the diets of LDL receptor knockout mice: effects on plasma insulin, lipoproteins, and atherosclerosis

The factors underlying cardiovascular risk in patients with diabetes have not been clearly elucidated. Efforts to study this in mice have been hindered because the usual atherogenic diets that contain fat and cholesterol also lead to obesity and insulin resistance. We compared plasma glucose, insulin, and atherosclerotic lesion formation in LDL receptor knockout (Ldlr(-/-)) mice fed diets with varying fat and cholesterol content that induced similar lipoprotein profiles. Ldlr(-/-) mice fed a high-fat diet developed obesity, mild hyperglycemia, hyperinsulinemia, and hypertriglyceridemia. Quantitative and qualitative assessments of atherosclerosis were unchanged in diabetic Ldlr(-/-) mice fed a high-fat diet compared with lean nondiabetic control mice after 20 weeks of diet. Although one group of mice fed diets for 40 weeks had larger lesions at the aortic root, this was associated with a more atherogenic lipoprotein profile. The presence of a human aldose reductase transgene had no effect on atherosclerosis in fat-fed Ldlr(-/-) mice with mild diabetes. Our data suggest that when lipoprotein profiles are similar, addition of fat to a cholesterol-rich diet does not increase atherosclerotic lesion formation in Ldlr(-/-) mice.

Acute coronary syndromes in patients with renal disease: what are the issues?

Patients with chronic kidney disease and acute coronary syndromes are at high risk for both bleeding and ischemic events. This risk increases with the severity of renal insufficiency. Management for acute coronary syndromes in the setting of kidney disease is a paradox; as the benefit of current treatment is high, so is the risk for complications. Patients with chronic renal disease are frequently excluded from randomized clinical trials, and therefore, the optimal treatment strategies are often speculative in this high-risk patient population. Additional research is needed to further refine the optimal management of patients with chronic kidney disease in the setting of acute coronary syndromes.

Implications of Chronic Kidney Disease for Dietary Treatment in Cardiovascular Disease

Chronic kidney disease (CKD) often accompanies cardiovascular disease (CVD). Trends foretelling a greater burden of CKD and CVD are largely a result of increasing frequencies of obesity, hypertension, and diabetes. Nutritional therapy occupies a critical role in reducing risk factors and preventing progressive damage to the kidneys and heart. Nutritional assessment and treatment should take into account both health concerns. This review examines several diet components and eating styles for efficacy in the treatment of these conditions. A variety of dietary regimens claim to provide health benefits, but rigorous scientific validation of long-term efficacy is frequently lacking. An urgent need exists for eating styles that reduce risk of chronic diseases and that are acceptable and achievable in free-living populations. We describe our ongoing study, a randomized controlled trial comparing the American Heart Association Step II diet and a Mediterranean diet, in survivors of a first myocardial infarction. The primary end point is a composite of mortality and major CVD events. Because many in this population have CKD, indicators of kidney damage and function are prespecified secondary end points. Results of this trial should provide insight into optimal dietary interventions for persons with both CVD and CKD.

Embryonic pig pancreatic tissue transplantation for the treatment of diabetes

BACKGROUND

Transplantation of embryonic pig pancreatic tissue as a source of insulin has been suggested for the cure of diabetes. However, previous limited clinical trials failed in their attempts to treat diabetic patients by transplantation of advanced gestational age porcine embryonic pancreas. In the present study we examined growth potential, functionality, and immunogenicity of pig embryonic pancreatic tissue harvested at different gestational ages.

METHODS AND FINDINGS

Implantation of embryonic pig pancreatic tissues of different gestational ages in SCID mice reveals that embryonic day 42 (E42) pig pancreas can enable a massive growth of pig islets for prolonged periods and restore normoglycemia in diabetic mice. Furthermore, both direct and indirect T cell rejection responses to the xenogeneic tissue demonstrated that E42 tissue, in comparison to E56 or later embryonic tissues, exhibits markedly reduced immunogenicity. Finally, fully immunocompetent diabetic mice grafted with the E42 pig pancreatic tissue and treated with an immunosuppression protocol comprising CTLA4-Ig and anti-CD40 ligand (anti-CD40L) attained normal blood glucose levels, eliminating the need for insulin.

CONCLUSIONS

These results emphasize the importance of selecting embryonic tissue of the correct gestational age for optimal growth and function and for reduced immunogenicity, and provide a proof of principle for the therapeutic potential of E42 embryonic pig pancreatic tissue transplantation in diabetes.

Closing the gap between clinical research and clinical practice: can outcome studies with thiazolidinediones improve our understanding of type 2 diabetes?

Recent clinical research has provided a wealth of information to support optimal management strategies in type 2 diabetes mellitus (T2DM). In particular, outcome studies appropriately have had an increasingly important impact on clinical decision-making. Additional, new data are required, however, to close the current gaps in clinical knowledge and improve patient outcomes in T2DM. These outcome studies are particularly important in assessing the long-term benefit of newer agents for which data are available for short-term glycaemic control, effects on lipids and some data on non-traditional cardiovascular risk markers, but outcome data for harder end points relevant to the natural history of T2DM, particularly beta-cell function, are lacking. Outcome studies such as ADOPT and DREAM are investigating the impact of thiazolidinediones (TZDs) on beta-cell function and disease progression in T2DM and impaired glucose tolerance, respectively, the results of which are eagerly anticipated. The primary focus of this article is on TZD outcome studies evaluating beta-cell function and disease progression.

Insulin resistance and atherosclerosis

Considerable evidence supports the association between insulin resistance and vascular disease, and this has led to wide acceptance of the clustering of hyperlipidemia, glucose intolerance, hypertension, and obesity as a clinical entity, the metabolic syndrome. While insulin resistance, by promoting dyslipidemia and other metabolic abnormalities, is part of the proatherogenic milieu, it is possible that insulin resistance itself in the vascular wall does not promote atherosclerosis. Recent findings suggest that insulin resistance and atherosclerosis could represent independent and ultimately maladaptive responses to the disruption of cellular homeostasis caused by the excess delivery of fuel.

Low-carbohydrate diet in type 2 diabetes. Stable improvement of bodyweight and glycemic control during 22 months follow-up

Background

Low-carbohydrate diets in the management of obese patients with type 2 diabetes seem intuitively attractive due to their potent antihyperglycemic effect.

We previously reported that a 20 % carbohydrate diet was significantly superior to a 55–60 % carbohydrate diet with regard to bodyweight and glycemic control in 2 non-randomised groups of obese diabetes patients observed closely over 6 months. The effect beyond 6 months of reduced carbohydrate has not been previously reported. The objective of the present study, therefore, was to determine to what degree the changes among the 16 patients in the low-carbohydrate diet group at 6-months were preserved or changed 22 months after start, even without close follow-up. In addition, we report that, after the 6 month observation period, two thirds of the patients in the high-carbohydrate changed their diet. This group also showed improvement in bodyweight and glycemic control.

Method

Retrospective follow-up of previously studied subjects on a low carbohydrate diet.

Results

The mean bodyweight at the start of the initial study was 100.6 ± 14.7 kg. At six months it was 89.2 ± 14.3 kg. From 6 to 22 months, mean bodyweight had increased by 2.7 ± 4.2 kg to an average of 92.0 ± 14.0 kg. Seven of the 16 patients (44%) retained the same bodyweight from 6 to 22 months or reduced it further; all but one had lower weight at 22 months than at the beginning. Initial mean HbA1c was 8.0 ± 1.5 %. After 6 and 12 months it was 6.6 ± 1.0 % and 7.0 ± 1.3 %, respectively. At 22 months, it was still 6.9 ± 1.1 %.

Conclusion

Advice on a 20 % carbohydrate diet with some caloric restriction to obese patients with type 2 diabetes has lasting effect on bodyweight and glycemic control.

Diabetic vascular disease: an experimental objective

It is well known that humans with diabetes have more atherosclerosis and its complications. The causes of this relationship are, however, unclear. Although recent data show that improved glycemic control reduces arterial disease in type 1 diabetes, other studies have shown that subjects with "prediabetes" have more cardiovascular disease before the development of hyperglycemia. Thus, either hyperglycemia and/or lack of insulin actions are toxic to arteries, or metabolic derangements exclusive of hyperglycemia are atherogenic. For >50 years animal models of diabetes and atherosclerosis have been used to uncover potential mechanisms underlying diabetes associated cardiovascular disease. Surprisingly, diabetes alone increases vascular disease in only a few select animal models. Increased atherosclerosis has been found in several animals and lines of genetically modified mice; however, diabetes often also leads to greater hyperlipidemia. This makes it difficult to separate the toxic effects of insulin lack and/or hyperglycemia from those caused by the lipids. These studies are reviewed, as well as more recent investigations using new methods to create diabetic-atherosclerotic models.

Adiponectin suppression of high-glucose-induced reactive oxygen species in vascular endothelial cells: evidence for involvement of a cAMP signaling pathway

Adiponectin is an abundant adipocyte-derived plasma protein with antiatherosclerotic effects. Vascular signal transduction by adiponectin is poorly understood and may involve 5'-AMP-activated protein kinase (AMPK), cAMP signaling, and other pathways. Hyperglycemia sharply increases the production of reactive oxygen species (ROS), which play a key role in endothelial dysfunction in diabetes. Because the recombinant globular domain of human adiponectin (gAd) reduces the generation of endothelial ROS induced by oxidized LDL, we sought to determine whether adiponectin could also suppress ROS production induced by high glucose in cultured human umbilical vein endothelial cells. Incubation in 25 mmol/l glucose for 16 h increased ROS production 3.8-fold (P<0.05), using a luminol assay. Treatment with gAd for 16 h suppressed glucose-induced ROS in a dose-dependent manner up to 81% at 300 nmol/l (P<0.05). The AMPK activator 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 1 mmol/l, 16 h) only partially decreased glucose-induced ROS by 22% (P<0.05). Cell pretreatment with AMPK inhibitors, however, failed to block the effect of gAd to suppress glucose-induced ROS, suggesting that the action of gAd was independent of AMPK. Interestingly, activation of cAMP signaling by treatment with forskolin (2 micromol/l) or dibutyryl-cAMP (0.5 mmol/l) reduced glucose-induced ROS generation by 43 and 67%, respectively (both P<0.05). Incubation with the cAMP-dependent protein kinase (PKA) inhibitor H-89 (1 micromol/l) fully abrogated the effect of gAd, but not that of AICAR, on ROS induced by glucose. gAd also increased cellular cAMP content by 70% in an AMPK-independent manner. Full-length adiponectin purified from a eukaryotic expression system also suppressed ROS induced by high glucose or by treatment of endothelial cells with oxidized LDL. Thus, adiponectin suppresses excess ROS production under high-glucose conditions via a cAMP/PKA-dependent pathway, an effect that has implications for vascular protection in diabetes.

Impaired Glucose Tolerance Increases Stroke Risk in Nondiabetic Patients With Transient Ischemic Attack or Minor Ischemic Stroke

Background and Purpose— Impaired glucose tolerance, an intermediate metabolic state between normal glucose and diabetes characterized by nonfasting glucose levels between 7.8 to 11.0 mmol/L, is associated with an increased stroke risk in patients with coronary heart disease. Whether impaired glucose tolerance increases the risk of stroke in patients with transient ischemic attack (TIA) or minor ischemic stroke is unknown.

Methods— In total, 3127 patients with a TIA or minor ischemic stroke participated in the Dutch TIA Trial, testing 2 different doses of aspirin and atenolol versus placebo. We estimated the risk of stroke and the risk of myocardial infarction or cardiac death in relation to baseline nonfasting glucose levels (mean 6.0, SD 2.2 mmol/L) with Cox proportional hazards regression analysis, adjusted for cardiovascular risk factors.

Results— During 2.6 years follow-up, 272 patients (9%) experienced a stroke and 200 (6%) a myocardial infarction or cardiac death. We found a J-shaped relationship between baseline nonfasting glucose levels and stroke risk. Stroke risk was nearly doubled in patients with impaired glucose tolerance (glucose 7.8 to 11.0 mmol/L) compared with those with normal glucose levels (hazard ratio [HR] 1.8, 95% CI, 1.1 to 3.0) and nearly tripled in diabetic patients (glucose ≥11.1 mmol/L; HR 2.8, 95% CI, 1.9 to 4.1). Patients with low glucose levels (<4.6 mmol/L) had a 50% increased stroke risk (HR 1.5, 95% CI, 1.0 to 2.2) compared with those with normal glucose levels. There was no association between glucose levels and risk of myocardial infarction or cardiac death.

Conclusion— Impaired glucose tolerance is an independent risk factor for future stroke in nondiabetic patients with TIA or minor ischemic stroke.

Type 2 diabetes and the metabolic syndrome in children and adolescents

The prevalence rates of obesity, metabolic syndrome, and type 2 diabetes in children are increasing at an alarming rate. The potential impact of these conditions on the individual, the family, and society, especially in regard to the costs and utilization of health care resources, are very serious. Strategies aimed at reducing caloric intake, increasing caloric expenditure through regular exercise, and treating cardiovascular risk factors and type 2 diabetes early and aggressively are necessary to meet the challenges they impose.

Evidence-Based Protocol for Diabetic Foot Ulcers

BACKGROUND

Diabetic foot ulcers are the single biggest risk factor for nontraumatic foot amputations in persons with diabetes. Foot ulcers occur in 12 to 25 percent of persons with diabetes and precede 84 percent of all nontraumatic amputations in this growing population. Because of the high incidence of foot ulcers, amputations remain a source of morbidity and mortality in persons with diabetes. Strict adherence to evidence-based protocols as described herein will prevent the majority of these amputations.

METHODS

The collective experience of treating patients with neuropathic diabetic foot ulcers in four major diabetic foot programs in the United States and Europe was analyzed.

RESULTS

The following protocol was developed for patients with diabetic foot ulcers: (1) establishment of good communication among the patient, the wound healing team, and the primary medical doctor; (2) comprehensive, protocol-driven care of the entire patient, including hemoglobin A1c, microalbuminuria, and cholesterol as well as early treatment of retinopathy, nephropathy, and cardiac disease; (3) weekly objective measurement of the wound with digital photography, planimetry, and documentation of the wound-healing process using the Wound Electronic Medical Record, if available; (4) objective evaluation of blood flow in the lower extremities (e.g., noninvasive flow studies); (5) débridement of hyperkeratotic, infected, and nonviable tissue; (6) use of systemic antibiotics for deep infection, drainage, and cellulitis; (7) off-loading; (8) maintenance of a moist wound bed; (9) use of growth factor and/or cellular therapy if the wound is not healing after 3 weeks with this protocol; and (10) consideration of the use of vacuum-assisted therapy in complex wounds.

CONCLUSIONS

In diabetic foot ulcers, availability of the above modalities, in combination with early recognition and comprehensive treatment, ensures rapid healing, minimizes morbidity and mortality rates, and eliminates toe and limb amputations in the absence of ischemia and osteomyelitis.

Drug therapy of the metabolic syndrome: minimizing the emerging crisis in polypharmacy

The metabolic syndrome--a collection of factors associated with increased risk for cardiovascular disease and diabetes--is becoming increasingly common, largely as a result of the increase in the prevalence of obesity. Although it is generally agreed that first-line clinical intervention for the metabolic syndrome is lifestyle change, this is insufficient to normalize the risk factors in many patients, and so residual risk could be high enough to justify drug therapy. However, at present there are no approved drugs that can reliably reduce all of the metabolic risk factors over the long term, and so there is growing interest in therapeutic strategies that might target multiple risk factors more effectively, thereby minimizing problems with polypharmacy. This review summarizes current understanding of the nature of the metabolic syndrome, and discusses each of the risk factors of the metabolic syndrome as possible primary drug targets; potential secondary or tertiary targets are also considered.

Secrets of the lac operon. Glucose hysteresis as a mechanism in dietary restriction, aging and disease

Elevated blood glucose associated with diabetes produces progressive and apparently irreversible damage to many cell types. Conversely, reduction of glucose extends life span in yeast, and dietary restriction reduces blood glucose. Therefore it has been hypothesized that cumulative toxic effects of glucose drive at least some aspects of the aging process and, conversely, that protective effects of dietary restriction are mediated by a reduction in exposure to glucose. The mechanisms mediating cumulative toxic effects of glucose are suggested by two general principles of metabolic processes, illustrated by the lac operon but also observed with glucose-induced gene expression. First, metabolites induce the machinery of their own metabolism. Second, induction of gene expression by metabolites can entail a form of molecular memory called hysteresis. When applied to glucose-regulated gene expression, these two principles suggest a mechanism whereby repetitive exposure to postprandial excursions of glucose leads to an age-related increase in glycolytic capacity (and reduction in beta-oxidation of free fatty acids), which in turn leads to an increased generation of oxidative damage and a decreased capacity to respond to oxidative damage, independent of metabolic rate. According to this mechanism, dietary restriction increases life span and reduces pathology by reducing exposure to glucose and therefore delaying the development of glucose-induced glycolytic capacity.