Estimating the diagnostic accuracy of the ankle-brachial pressure index for detecting peripheral arterial disease in people with diabetes: A systematic review and meta-analysis

AIM

To systematically evaluate research investigating the accuracy of the ankle-brachial index (ABI) for diagnosing peripheral artery disease (PAD) in people with diabetes, as the accuracy is thought to be reduced in this cohort.

METHODS

A database search of EBSCO Megafile Premier, Embase and The Cochrane Library was conducted to 28 February 2019. Prospective and retrospective investigations of the diagnostic accuracy of the ABI for PAD in people with diabetes using an imaging reference standard were eligible. Sensitivity and specify of the ABI and bivariate meta-analysis against reference tests, or a standard summary receiver operating curve analysis (SROC) was performed.

RESULTS

Thirty-three studies met the inclusion criteria. ABI was compared with angiography in 12 studies and with colour duplex ultrasound (CDUS) in 21 studies. A SROC analysis of studies using angiography as the reference standard found a diagnostic odds ratio (DOR) of 9.06 [95% confidence interval (CI) 3.61 to 22.69], and area under the curve (AUC) of 0.76 (95% CI 0.66 to 0.86). Bivariate analysis of studies using CDUS demonstrated mean sensitivity of 0.60 (95% CI 0.48 to 0.71; P = 0.097) and mean specificity of 0.87 (95% CI 0.78 to 0.92; P < 0.001) with a DOR of 9.76 (95% CI 5.24 to 18.20; P < 0.0001) and AUC 0.72.

CONCLUSIONS

These results suggest the ABI has a high specificity but lower sensitivity in detecting imaging diagnosed PAD in people with diabetes. The low probability of the testing being able to rule diagnosis in or out suggest that the ABI has limited effectiveness for early detection of PAD in this cohort.

Metabolic syndrome in type 1 diabetes and its association with diabetes complications

AIM

To assess the prevalence of metabolic syndrome in type 1 diabetes, and its age-related association with diabetes complications.

METHODS

Australian National Diabetes Information Audit and Benchmarking (ANDIAB) was a well-established quality audit programme. It provided cross-sectional data on people attending specialist diabetes services across Australia. We determined the prevalence of metabolic syndrome (WHO criteria) in adults with type 1 diabetes and its associations with diabetes complications across age groups.

RESULTS

Metabolic syndrome prevalence was 30% in 2120 adults with type 1 diabetes. Prevalence increased with age: 21% in those aged <40 years, 35% in those aged 40-60 years, and 44% in those aged >60 years (P<0.001), which was driven by an increase in hypertension rate. Metabolic syndrome was associated with a higher prevalence of microvascular, macrovascular and foot complications, with the greatest impact at a younger age. The odds ratio for macrovascular complications with metabolic syndrome, compared with without, was 5.9 (95% CI 2.1-16.4) in people aged <40 years, 2.7 (95% CI 1.7-4.2) in those aged 40-60 years, and 1.7 (95% CI 1.1-2.7) in those aged >60 years (all P < 0.05). Metformin use was higher in those with metabolic syndrome (16% vs 4%; P<0.001).

CONCLUSIONS

In this large Australian cohort, metabolic syndrome was common in type 1 diabetes and identified people at increased risk of the spectrum of diabetes complications, particularly in young to middle-aged adults. Potential clinical implications are that therapies targeting insulin resistance in this high-risk group may reduce diabetes complications and should be explored.

Young-onset type 2 diabetes and younger current age: increased susceptibility to retinopathy in contrast to other complications

BACKGROUND

Type 2 diabetes diagnosed during youth and early adulthood is aggressive and associated with a high burden of vascular complications. The increase in complications is often attributed to long disease duration and poor metabolic control. Whether people with young-onset type 2 diabetes are inherently more susceptible to long-term complications than those diagnosed in later adulthood is unclear.

METHODS

Prospective data from 3322 individuals, diagnosed between the age of 15 and 70 years and collected 10-25 years after diabetes diagnosis, were analysed. The cross-sectional associations between age at diagnosis and microvascular and macrovascular complications were analysed using logistic regression models, adjusted for duration of diabetes exposure and metabolic risk factors including blood pressure, cholesterol and updated mean HbA_1c .

RESULTS

The prevalence of retinopathy was highest in those with young-onset type 2 diabetes (diagnosed at age 15 to <40 years). After 10-15 years' diabetes duration, the adjusted odds ratio for retinopathy in this population was 2.8 (95% CI 1.9-4.1; reference group those diagnosed at 60 to <70 years of age). The odds of retinopathy remained higher in people with young-onset type 2 diabetes after longer durations of diabetes exposure; the odds decreased with increasing age at diagnosis. This pattern was not observed in models of other complications: after 10-15 years' diabetes exposure, the adjusted odds ratios for albuminuria, peripheral neuropathy and macrovascular disease in people with young-onset type 2 diabetes were 0.5 (95% CI 0.4-0.8), 0.7 (95% CI 0.5-1.1) and 0.2 (95% CI 0.1-0.3), respectively.

CONCLUSION

After accounting for disease duration and other important confounders, people with type 2 diabetes diagnosed in youth and early adulthood (or with a younger current age) appeared to be inherently more susceptible to retinopathy. For other complications, adjusted risk appears highest in the oldest age of diagnosis group. These data have screening and treatment target implications.

The emerging role of skeletal muscle extracellular matrix remodelling in obesity and exercise

Skeletal muscle extracellular matrix remodelling has been proposed as a new feature associated with obesity and metabolic dysfunction. Exercise training improves muscle function in obesity, which may be mediated by regulatory effects on the muscle extracellular matrix. This review examined available literature on skeletal muscle extracellular matrix remodelling during obesity and the effects of exercise. A non-systematic literature review was performed on PubMed of publications from 1970 to 2015. A total of 37 studies from humans and animals were retained. Studies reported overall increases in gene and protein expression of different types of collagen, growth factors and enzymatic regulators of the skeletal muscle extracellular matrix in obesity. Only two studies investigated the effects of exercise on skeletal muscle extracellular matrix during obesity, with both suggesting a regulatory effect of exercise. The effects of exercise on muscle extracellular matrix seem to be influenced by the duration and type of exercise training with variable effects from a single session compared with a longer duration of exercise. More studies are needed to elucidate the mechanisms behind skeletal muscle extracellular matrix remodelling during obesity and the effects of exercise.

Low alanine aminotransferase levels and higher number of cardiovascular events in people with Type 2 diabetes: analysis of the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study

AIMS

To determine whether alanine aminotransferase or gamma-glutamyltransferase levels, as markers of liver health and non-alcoholic fatty liver disease, might predict cardiovascular events in people with Type 2 diabetes.

METHODS

Data from the Fenofibrate Intervention and Event Lowering in Diabetes study were analysed to examine the relationship between liver enzymes and incident cardiovascular events (non-fatal myocardial infarction, stroke, coronary and other cardiovascular death, coronary or carotid revascularization) over 5 years.

RESULTS

Alanine aminotransferase measure had a linear inverse relationship with the first cardiovascular event occurring in participants during the study period. After adjustment, for every 1 sd higher baseline alanine aminotransferase measure (13.2 U/l), the risk of a cardiovascular event was 7% lower (95% CI 4-13; P = 0.02). Participants with alanine aminotransferase levels below and above the reference range 8-41 U/l for women and 9-59 U/l for men, had hazard ratios for a cardiovascular event of 1.86 (95% CI 1.12-3.09) and 0.65 (95% CI 0.49-0.87), respectively (P = 0.001). No relationship was found for gamma-glutamyltransferase.

CONCLUSIONS

The data may indicate that in people with Type 2 diabetes, which is associated with higher alanine aminotransferase levels because of prevalent non-alcoholic fatty liver disease, a low alanine aminotransferase level is a marker of hepatic or systemic frailty rather than health.

Lower serum fibroblast activation protein shows promise in the exclusion of clinically significant liver fibrosis due to non-alcoholic fatty liver disease in diabetes and obesity

Non-alcoholic fatty liver disease (NAFLD) is common in diabetes and obesity but few have clinically significant liver fibrosis. Improved risk-assessment is needed as the commonly used clinical-risk algorithm, the NAFLD fibrosis score (NFS), is often inconclusive.

AIMS

To determine whether circulating fibroblast activation protein (cFAP), which is elevated in cirrhosis, has value in excluding significant fibrosis, particularly combined with NFS.

METHODS

cFAP was measured in 106 with type 2 diabetes who had transient elastography (Cohort 1) and 146 with morbid obesity who had liver biopsy (Cohort 2).

RESULTS

In Cohort 1, cFAP (per SD) independently associated with median liver stiffness (LSM) ≥ 10.3 kPa with OR of 2.0 (95% CI 1.2-3.4), p=0.006. There was 0.12 OR (95% CI 0.03-0.61) of LSM ≥ 10.3 kPa for those in the lowest compared with the highest FAP tertile (p=0.010). FAP levels below 730 pmol AMC/min/mL had 95% NPV for LSM ≥ 10.3 kPa and reclassified 41% of 64 subjects from NFS 'indeterminate-risk' to 'low-risk'. In Cohort 2, cFAP (per SD), associated with 1.7 fold (95% CI 1.1-2.8) increased odds of significant fibrosis (F ≥ 2), p=0.021, and low cFAP reclassified 49% of 73 subjects from 'indeterminate-risk' to 'low-risk'.

CONCLUSIONS

Lower cFAP, when combined with NFS, may have clinical utility in excluding significant fibrosis in diabetes and obesity.

Congestive heart failure presence predicts delayed healing of foot ulcers in diabetes: An audit from a multidisciplinary high-risk foot clinic

AIMS

This retrospective study aimed to investigate both established and less well-explored factors as potential predictive variables for failed and delayed ulcer healing.

METHODS

Patients with type 1 or 2 diabetes with foot ulceration presenting consecutively to, and then subsequently managed at, a multidisciplinary, high-risk foot clinic were followed until ulcer healing, amputation or death. Data comprised prospective standardised documentation at each visit and retrospective collection from hospital records, and included patient demographics, comorbidities, laboratory variables, and ulcer infection, depth and area at each presentation. Multiple regression analysis was used to determine independent predictors of failure to heal and delayed healing.

RESULTS

Of the 107 consecutive patients studied, 95 (89%) healed overall, 50 (47%) had healed in 12 weeks and the mean healing rate was a 10% decrease in ulcer area per week. Amongst all variables examined, comorbid congestive heart failure (CHF) was the only factor independently predictive of all measured outcomes of failure to heal overall, delayed healing at 12 weeks, and reduced healing rate. Ulcer infection at presentation, longer duration of antibiotic use, and liver enzyme abnormalities of raised ALT and AST:ALT<1 (each suggestive of non-alcoholic fatty liver disease), were also predictive of poor ulcer outcomes.

CONCLUSIONS

Comorbid congestive cardiac failure is predictive of delayed foot ulcer healing rate as well as a lower probability of healing overall. Liver enzyme abnormalities also predicted delayed ulcer healing outcomes. The mechanisms underlying these associations with foot ulcer outcomes in diabetes are unclear. Further studies are needed to determine the role of systematic routine documentation of heart failure and its severity, and then targeting of heart failure to potentially aid the management of foot ulcers in diabetes.

Topically applied connective tissue growth factor/CCN2 improves diabetic preclinical cutaneous wound healing: potential role for CTGF in human diabetic foot ulcer healing

AIMS/HYPOTHESIS

Topical application of CTGF/CCN2 to rodent diabetic and control wounds was examined. In parallel research, correlation of CTGF wound fluid levels with healing rate in human diabetic foot ulcers was undertaken.

METHODS

Full thickness cutaneous wounds in diabetic and nondiabetic control rats were treated topically with 1 μg rhCTGF or vehicle alone, on 2 consecutive days. Wound healing rate was observed on day 14 and wound sites were examined for breaking strength and granulation tissue. In the human study across 32 subjects, serial CTGF regulation was analyzed longitudinally in postdebridement diabetic wound fluid.

RESULTS

CTGF treated diabetic wounds had an accelerated closure rate compared with vehicle treated diabetic wounds. Healed skin withstood more strain before breaking in CTGF treated rat wounds. Granulation tissue from CTGF treatment in diabetic wounds showed collagen IV accumulation compared with nondiabetic animals. Wound α-smooth muscle actin was increased in CTGF treated diabetic wounds compared with untreated diabetic wounds, as was macrophage infiltration. Endogenous wound fluid CTGF protein rate of increase in human diabetic foot ulcers correlated positively with foot ulcer healing rate (r = 0.406; P < 0.001).

CONCLUSIONS/INTERPRETATION

These data collectively increasingly substantiate a functional role for CTGF in human diabetic foot ulcers.

Age of diabetes diagnosis and diabetes duration associate with glycated haemoglobin

An earlier age of diagnosis (r=-0.28, p<0.0001) and longer duration of type 2 diabetes (r=0.26, p<0.0001) were each found to correlate with higher HbA1c level, on analysis of a diabetes centre database in people under regular shared care. When combined, these biological variables strongly associate with the current HbA1c level.

Thyroid autoimmunity in Type 1 diabetes: systematic review and meta-analysis

AIMS

To review the incidence and evidence for screening for thyroid autoimmunity and thyroid dysfunction in Type 1 diabetes.

METHODS

Systematic review and meta-analysis. Inclusion criteria were prospective cohort studies screening for thyroid autoimmunity and/or dysfunction (defined as an abnormal thyroid-stimulating hormone level) in Type 1 diabetes. Exclusion criteria included pregnancy and thyroid dysfunction before diabetes onset. Outcomes examined were: incidence of thyroid autoimmunity and/or dysfunction; association between thyroid autoimmunity and dysfunction; and cost-effectiveness. Data sources were MEDLINE, EMBASE, the Cochrane Library, manual searching and contact with authors, with limitations to English language and human studies. Meta-analysis was performed using random effects models.

RESULTS

We identified 14 eligible studies, involving 2972 young people and 789 adults with Type 1 diabetes. Follow-up ranged from 1-18 years. None of the studies were of good methodological quality (Newcastle Ottowa Scale score > 7). The incidence of thyroid dysfunction (11 studies) ranged from 27 (95% CI 15-45) to 246 (95% CI 118-453) per 10 000 patient-years and thyroid autoimmunity (four studies) from 13 (95% CI 0.3-71) to 326 (95% CI 194-510). The risk of thyroid dysfunction was higher in those with thyroid autoimmunity: summary risk ratio 25 (95% CI 9-71) and was higher in children (49, 95% CI 16-150) compared with adults (7, 95% CI 3-13). No studies examined cost-effectiveness of screening.

CONCLUSIONS

There is a markedly increased risk of thyroid dysfunction in people with Type 1 diabetes and thyroid autoimmunity. The optimal method or frequency of screening could not be determined from available data. Future studies should examine whether screening improves clinical outcomes in this population.

Blood β-hydroxybutyrate vs. urine acetoacetate testing for the prevention and management of ketoacidosis in Type 1 diabetes: a systematic review

AIM

Diabetic ketoacidosis is a life-threatening complication of Type 1 diabetes. Blood β-hydroxybutyrate testing is now widely available as an alternative to urine acetoacetate testing for detecting ketosis. The aim of this study was to review the effectiveness of capillary or serum β-hydroxybutyrate compared with urine acetoacetate testing in prevention and management of diabetic ketoacidosis.

METHODS

MEDLINE, EMBASE, EBM Reviews, The Cochrane Library and CINAHL (until April 2012, no language restrictions, studies in humans) were searched for experimental and observational studies comparing the effectiveness of blood β-hydroxybutyrate and urine acetoacetate testing. Outcomes examined were prevention of diabetic ketoacidosis, time to recovery from diabetic ketoacidosis, healthcare costs and patient or caregiver satisfaction. Additional sources included reference lists, conference proceedings and contact with experts in the field.

RESULTS

Four studies (two randomized controlled trials and two cohort studies) met eligibility criteria, including 299 participants across 11 centres. Risk of bias was low to moderate. Blood ketone testing compared with urine testing was associated with reduced frequency of hospitalization (one study), reduced time to recovery from diabetic ketoacidosis (three studies), cost benefits (one study) and greater satisfaction (one study, intervention group only). No study assessed prevention of diabetic ketoacidosis. Meta-analysis could not be performed because of heterogeneity in study design and published data.

CONCLUSIONS

There is evidence suggesting that blood β-hydroxybutyrate testing is more effective than urine acetoacetate testing in reducing emergency department assessment, hospitalization and time to recovery from diabetic ketoacidosis, as well as potentially lowering healthcare expenditure. Further research in both young people and adults is needed.

Diabetes and nonalcoholic Fatty liver disease: a pathogenic duo

Recent data increasingly support a complex interplay between the metabolic condition diabetes mellitus and the pathologically defined nonalcoholic fatty liver disease (NAFLD). NAFLD predicts the development of type 2 diabetes and vice versa, and each condition may serve as a progression factor for the other. Although the association of diabetes and NAFLD is likely to be partly the result of a "common soil," it is also probable that diabetes interacts with NAFLD through specific pathogenic mechanisms. In particular, through interrelated metabolic pathways currently only partly understood, diabetes appears to accelerate the progression of NAFLD to nonalcoholic steatohepatitis, defined by the presence of necroinflammation, with varying degrees of liver fibrosis. In the research setting, obstacles that have made the identification of clinically significant NAFLD, and particularly nonalcoholic steatohepatitis, difficult are being addressed with the use of new imaging techniques combined with risk algorithms derived from peripheral blood profiling. These techniques are likely to be used in the diabetes population in the near future. This review examines the pathogenic links between NAFLD and diabetes by exploring the epidemiological evidence in humans and also through newer animal models. Emerging technology to help screen noninvasively for differing pathological forms of NAFLD and the potential role of preventive and therapeutic approaches for NAFLD in the setting of diabetes are also examined.

The management of Type 2 diabetes: a survey of Australian general practitioners

OBJECTIVE

To explore how clinical and demographic variables impact on the management of diabetes mellitus in general practice.

DESIGN

A structured vignette survey was conducted in Australia. This included nine vignettes chosen at random from 128 developed around seven clinical variables. Respondents were asked to recommend a change in treatment and make specific recommendations. A random sample of general practitioners (GPs) were recruited. Two diabetologists involved in the development of national guidelines also participated.

RESULTS

125 (13.8%) GPs participated. Statistical analyses were used to generate outcome measures. GPs recommended a change in treatment for most (81.1%) cases; were less likely to prescribe a statin (68.5% GPs vs. 76.3% diabetologists), less likely to treat hypertension (66.7% vs.89%) and less likely to refer for lifestyle modification (82.3% vs. 96.5%). Significant disagreement occurred around prescribing or changing oral hypoglycaemics. No GP characteristics showed significant impact. The proportion of GPs who agreed with diabetiologists on dose and choice of drugs was 35.7% for statins, 49.6% for antihypertensives and 39.6% for oral hypoglycaemics.

CONCLUSIONS

There were significant differences between diabetologists and GPs on the management of diabetes. The survey suggests significant under-dosing by GPs. These findings warrant further investigation.

The danger of using inappropriate point-of-care glucose meters in patients on icodextrin dialysis

AIMS

Icodextrin is a glucose polymer used to maintain an osmotic gradient in peritoneal dialysis. Metabolites of icodextrin are known to cause overestimation of blood glucose in glucose meters using glucose dehydrogenase/pyrroloquinolinequinone systems. The aim of this study is to determine the extent of icodextrin interference in glucose meters using the newer glucose dehydrogenase/NAD or glucose oxidase systems. This has not been established previously.

METHODS

Fasting blood samples (n = 4) were spiked with either one icodextrin metabolite (maltose, maltotriose or maltotetraose) or a combination, at various blood concentrations expected during dialysis. Samples were tested in triplicate on: five glucose-meters, a Radiometer® (glucose oxidase/hydrogen peroxide) and laboratory (hexokinase) analysers. Each meter was also tested on blood from six patients undergoing dialysis. Accuracy was evaluated as % Bias = [(meter glucose - laboratory glucose)/laboratory glucose] × 100.

RESULTS

A single icodextrin metabolite affected glucose measurements and, in combination, the interferences were additive in the two Accu-Chek® and Optium® Xceed meters by > 10%. Amongst these meters, the Optium Xceed 5-s machine was less affected. Meters using glucose oxidase were least affected by interference. A similar trend in interference was observed in vivo.

CONCLUSION

While meters using glucose dehydrogenase/NAD are less affected by icodextrin metabolites, interference can still be demonstrated. The degree of interference can vary in different glucose meters using this enzyme/cofactor system, as seen in the Optium Xceed machines. Icodextrin is an important source of interference that sometimes even experienced professionals are unaware of and which leads to clinically significant errors in insulin dose adjustment. Awareness of this interference and selection of the most appropriate glucose meters are crucial to minimize this hazard.

Beyond ONTARGET: angiotensin-converting enzyme inhibition and angiotensin II receptor blockade in combination, a lesser evil in some?

AIM

Following the recent Ongoing Telmistartan Alone and in Combination With Ramipril Global Endpoint Trial (ONTARGET) finding of adverse renal outcomes, dual renin-angiotensin blockade has fallen out of favour, despite antihypertensive and antiproteinuric efficacy. However, in high-risk severe hypertension, not studied in ONTARGET, whether combination treatment should be withheld or withdrawn is not clear. We examine the renal effects of angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker (ARB) monotherapy versus combination therapy in patients with type 2 diabetes and varying degrees of hypertension.

METHODS

Subjects attending a hospital diabetes centre were selected as case (combination therapy, n = 120) and control (monotherapy, n = 480). Subjects were matched for age, gender, ethnicity, estimated glomerular filtration rate (eGFR), blood pressure (BP) and study duration. Patients were stratified by BP, hypertension stage 1 (BP < 160/100, n = 506) and stage 2 (≥160/100, n = 94), and by treatment group. Data were analysed for the primary renal outcome of eGFR decline ≥20 ml/min, over a median of 3.7 years.

RESULTS

In keeping with the ONTARGET study, for stage 1 hypertension, combination treatment is significantly worse than monotherapy for the primary outcome of eGFR decline ≥20 ml/min (20 vs. 10.7%, p = 0.01). In contrast, for stage 2 hypertension, this endpoint was reached less often for combination versus monotherapy (12.0 vs. 23.2%, p = 0.2). Combination treatment was also not detrimental in patients with proteinuria or eGFR < 60 ml/min and was associated with fewer macrovascular events.

CONCLUSION

Given that hypertension control is paramount and in the spirit of primum non nocere, these data are reassuring should clinicians choose to use ACE-I and ARB combination therapy in the very hypertensive diabetic patient.

Monocyte CD147 is induced by advanced glycation end products and high glucose concentration: possible role in diabetic complications

CD147 is a highly glycosylated transmembrane protein that is known to play a role in regulation of many protein families. It has the unique ability to maintain functional activity in both the membrane bound state and in the soluble form. CD147 is known to play a role in regulation of matrix metalloproteinase (MMP) expression, but whether its expression is affected by the diabetic milieu is not known, and its role in regulation of monocyte MMPs in this environment has not been investigated. Therefore, in this study we investigated the effect of advanced glycation end products (AGEs) and high glucose (HG; 25 mM), on monocyte CD147 expression. Culture of THP-1 monocytes in the presence of AGEs or HG significantly increased CD147 at the gene and protein level. THP-1 cell results were confirmed using freshly isolated monocytes from human volunteers. The effect of AGEs and HG on CD147 expression was also mimicked by addition of proinflammatory cytokines. Addition of AGEs or HG also increased expression of monocyte MMP-1 and MMP-9 but not MMP-2. This increase in MMPs was significantly attenuated by inhibition of CD147 using either a small interfering RNA or an anti-CD147 antibody. Inhibition of NF-κB or addition of antibodies to either TNF-α or the receptor for AGE (RAGE) each significantly prevented in a dose-dependent manner the induction of CD147 gene and protein by AGE and also decreased MMP-1 and MMP-9. This novel result shows that AGEs can induce monocyte CD147 expression, an effect mediated by inflammatory pathways and RAGE. Because MMPs play a role in monocyte migration, inhibition of their regulator CD147 may assist in the prevention of diabetic complications, particularly those where monocyte infiltration is an early initiating event.

Serum MMP-7 is increased in diabetic renal disease and diabetic diastolic dysfunction

Circulating matrix metalloproteinase (MMP) levels may correlate with diabetic complications. Whether they are changed in early diabetic cardiomyopathy is not known and was examined in this study. TIMP-1 and collagen degradation products were also measured. Results from subjects with and without diastolic dysfunction were compared with those obtained for patients with varying stages of diabetic renal disease. Patients with type 2 diabetes with or without diastolic dysfunction with varying degrees of renal disease were recruited for this study. Age-matched non-diabetic subjects served as controls. MMPs (-1, -3 and -7) and TIMP-1 were measured by ELISA, MMP-2 and -9 by zymography and collagen degradation products by radioimmunoassay. Differences in the pattern of MMPs/TIMPs and collagen degradation products were observed. The most consistent change was in totalMMP-7, which was increased in those with diastolic dysfunction and those with macroalbuminuria. MMP-7 correlated with cardiac function (p<0.05 vs control, in those with diastolic dysfunction), and renal filtration function (p<0.05 vs control). In summary, we have identified novel relationships between serum MMP-7 and diabetic complications specifically in renal disease and in diastolic dysfunction. How increased circulating MMP-7 is associated with these diabetic microvascular complications and the significance of these findings will require prospective studies.

A novel primate model of delayed wound healing in diabetes: dysregulation of connective tissue growth factor

AIMS/HYPOTHESIS

Chronic non-healing wounds are a common complication of diabetes. Prolonged inflammation and decreased matrix accumulation may contribute. Connective tissue growth factor (CTGF) is induced during normal wound healing, but its regulation in diabetic wounds is unknown. We developed a primate model for the study of in vivo wound healing in baboons with long diabetes duration.

METHODS

Drum implants were placed subcutaneously into thighs of diabetic and non-diabetic control baboons. After 2 and 4 weeks the skin incision sites were removed for measurement of breaking strength and epithelial thickness. Drum implants were removed for analysis of granulation tissue and inflammatory cells, CTGF and tissue inhibitor of matrix metalloproteinase (TIMP-1). Degradation of added CTGF by wound fluid was also examined.

RESULTS

Healed incision site skin was stiffer (less elastic) in diabetic baboons and epithelial remodelling was slower compared with controls. Granulation tissue from diabetic baboons was reduced at 2 and 4 weeks, with increased vessel lumen areas at 4 weeks. Macrophages were reduced while neutrophils persisted in diabetic tissue. In diabetic wound tissue at 4 weeks there was less CTGF induced, as shown by immunohistochemistry, compared with controls. In contrast, immunoreactive fragments of CTGF were significantly increased in whole tissue lysate in diabetic baboons, suggesting that CTGF is redistributed in diabetes from granulation tissue into wound fluid. When recombinant human CTGF was co-incubated with wound fluid, increased CTGF degradation products were observed in both control and diabetic samples.

CONCLUSIONS/INTERPRETATION

This baboon model of wound healing reflects the abnormal microenvironment seen in human diabetic wounds and provides insights into the dysregulation of CTGF in diabetic wounds.

Mitochondrial DNA content in peripheral blood monocytes: relationship with age of diabetes onsetand diabetic complications

AIMS/HYPOTHESIS

We examined whether age of type 2 diabetes onset is related to mitochondrial DNA content in peripheral blood monocytes (PBMCs).

METHODS

PBMCs were isolated from 65 patients with type 2 diabetes. To minimise age as a confounder, only patients aged >or=50 years were studied. Sample mitochondrial DNA (mtDNA) content was determined by amplification of the mitochondrial gene CYT-B (also known as MT-CYB) and adjusted for single-copy nuclear control genes (36B4 [also known as RPLPO] and GAPDH).

RESULTS

Age of diabetes onset ranged from 25 to 69 years. There was a significant positive relationship between age of diabetes onset in quartiles and mtDNA content for the whole group (p = 0.02 for trend). When stratified by the presence of diabetes complications, a strong positive relationship was observed between age of diagnosis and mtDNA content for participants without diabetic complications (r = 0.7; p = 0.0002), but not for those with complications (r = -0.04; p = 0.8). Multivariate analysis confirmed age of onset and complication status as independent determinants. There was co-linearity between age of onset and disease duration, with similar relationships also seen between duration and mtDNA content.

CONCLUSIONS/INTERPRETATION

An earlier age of type 2 diabetes onset is associated with a lower PBMC mtDNA content, but only in patients without diabetes complications. This may reflect a differing biology of PBMC mtDNA in those with early-onset diabetes and those who are prone to complications. PBMC mtDNA depletion may accelerate diabetes onset; however the independent effect of diabetes duration remains to be evaluated.

Diastolic dysfunction and abnormalities of the microcirculation in type 2 diabetes

AIM

Diabetic cardiomyopathy is an increasingly recognized entity. The pathogenic factors that may contribute to its development, especially the earliest changes of diastolic dysfunction (DD), have not been clearly defined. Microvessel dysfunction and upregulation of profibrotic growth factors have been described as possible causes. The aim of this study was therefore to determine whether microvascular dysfunction and/or upregulation of the profibrotic connective tissue growth factor (CTGF) are associated with subclinical DD in subjects with type 2 diabetes.

METHODS

Forty subjects with type 2 diabetes and 20 age-matched non-diabetic controls, all of whom had no clinical evidence of ischaemic heart disease, cardiac failure or echo evidence of systolic ventricular dysfunction, were recruited. Microvascular function was measured by laser Doppler velocimetry, with examination of endothelium-dependent increase in blood flow following iontophoresis of acetylcholine (ACh) and endothelium-independent increase in blood flow in response to the nitric oxide donor sodium nitroprusside (SNP). CTGF levels were determined by Western immunoblotting.

RESULTS

DD determined on the basis of traditional echocardiographic criteria was similar in diabetic subjects compared with controls (28 vs. 20%, p = 0.5). Using left ventricular myocardial tissue Doppler-based indices for DD, the E/E' and the E'/A' ratios (where E is the flow related to early ventricular filling and E' and A' are early and late diastolic velocities, respectively) in diabetic subjects revealed evidence of more DD than controls (p = 0.046 and p = 0.007 respectively) . Comparing controls with no DD by conventional echocardiographic criteria (Group I), diabetes and no DD (Group II) and diabetes with DD (Group III), there was a significant trend in reduction of both endothelium-dependent (ACh fold change; p = 0.04) and endothelium-independent (SNP fold change; p = 0.0004) blood flow across the groups. The ACh and SNP responses, however, were not correlated significantly with quartiles of the E/E' ratio or the E'/A' ratio. CTGF plasma levels did not differ across the groups and CTGF did not correlate with parameters of microvascular function.

CONCLUSIONS

This study indicates that while there is a significant association between DD and measures of microvascular function, the relationship between endothelial dysfunction, CTGF and subtle measures of DD is not strong. Other factors are therefore likely to play an important role in the early pathogenesis of subclinical cardiac DD in type 2 diabetes.

Alterations in liver sinusoidal endothelium in a baboon model of type 1 diabetes

AIMS/HYPOTHESIS

Diabetes mellitus is associated with extensive vascular pathology, yet little is known about its long-term effects on liver sinusoidal endothelial cells (LSECs). Potential diabetic changes in LSECs are important because of the role played by fenestrations in the LSECs in hepatic disposition of lipoproteins.

MATERIALS AND METHODS

Surgical liver biopsies for electron microscopy and immunohistochemistry were obtained from baboons with long-standing streptozotocin-induced, insulin-treated diabetes mellitus and compared with those from age-matched control animals.

RESULTS

There was an increase in the thickness of LSECs (170 +/- 17 vs 123 +/- 10 nm, p < 0.01). Fenestrations in LSECs, as determined by overall porosity, were markedly reduced (1.4 +/- 0.1% vs 2.6 +/- 0.2%, p < 0.01). Increased numbers of stellate cells were seen on electron microscopy, and this finding was corroborated by increased smooth muscle actin expression. Diabetes mellitus was also associated with increased endothelial production of von Willebrand factor and caveolin-1.

CONCLUSIONS/INTERPRETATION

Diabetes mellitus in the non-human primate is associated with marked changes in LSECs, including a reduction in fenestrations. Such changes provide an additional and novel mechanism for impaired hepatic lipoprotein clearance and post-prandial hyperlipidaemia in diabetes mellitus.

The metabolic syndrome in type 2 diabetes: When does it matter?

AIMS

Young adults with type 2 diabetes (T2Dm) present the clinician with the problem of when to start therapies for the primary prevention of vascular disease and how to identify those at most vascular risk. We examine whether the metabolic syndrome (MetS) can be a useful clinical tool to stratify vascular risk in this context.

METHODS

Data were collected from 5928 subjects with T2Dm, and subjects were categorized as having MetS by World Health Organization criteria (body mass index criteria modified for Asians using >23 kg/m2). The prevalence of macrovascular disease was examined by MetS status and age.

RESULTS

The overall MetS prevalence was 72.3%. MetS was associated with an increased prevalence of ischaemic heart disease (IHD) (17.2% MetS vs. 11.6% no MetS, p < 0.0001), coronary artery bypass graft (7.6 vs. 4.7%, p < 0.0003), peripheral vascular disease (PVD) (4.7 vs. 3.7%, p = 0.08) and stroke (6 vs. 3.9%, p = 0.002) across all age groups. MetS subjects had an IHD prevalence equivalent to that seen in subjects who were one decade older without MetS. The most significant impact of MetS was for the age group of 40-49 years with much lesser impact seen with progressively increasing age [odds ratio (OR) = 2.1 for IHD in MetS compared with no MetS at age 40-50 years, p < 0.05; falling progressively to OR = 1.5 at age >70 years, p > 0.05]. Similar trends were seen for coronary artery by-pass graft (CABG) and PVD. There was a strong relationship between the number of MetS risk factors and IHD prevalence (r = 0.99, p = 0.0001).

CONCLUSIONS

These data suggest that MetS is particularly useful in stratifying vascular risk in younger T2Dm patients and in those with a high number of MetS components. For patients with MetS, especially those with a full house of MetS risk factors, commencing risk-lowering interventions 10 years earlier than their MetS-free counterparts could be considered.

Connective tissue growth factor mediates high glucose effects on matrix degradation through tissue inhibitor of matrix metalloproteinase type 1: implications for diabetic nephropathy

High glucose concentration inhibits matrix degradation and affects the activities of the enzymes responsible, the matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). Connective tissue growth factor (CTGF) expression is increased in diabetic nephropathy and is a downstream mediator of TGF-beta actions. However, whether CTGF regulates matrix degradation and the mechanism of effect in diabetes has not been reported. Human mesangial cells were cultured in media containing 5 or 25 mM glucose and, in some experiments, with recombinant human (rh)CTGF (0-1000 ng/ml) and/or appropriate neutralizing antibodies. Matrix degradation was inhibited by rhCTGF in a dose-dependent manner, and the decrease in matrix degradation caused by high glucose and by TGF-beta was significantly attenuated by addition of CTGF-neutralizing antibody (by 40.2 and 69.1%, respectively). Similar to 25 mM glucose, addition of rhCTGF increased MMP-2, TIMP-1, and TIMP-3 mRNA by 2.5-, 2.1-, and 1.6-fold, respectively (P < 0.05) but had no effect on membrane-type (MT)1-MMP or TIMP-2. Addition of TIMP-1 antibody to conditioned medium abolished the decrease in degradation caused by rhCTGF and partially prevented (by 79%) the glucose-induced inhibition of matrix degradation. In vivo studies of glomeruli from diabetic and control rats showed that intensive insulin treatment prevented the increase in expression of CTGF and TIMP-1 and attenuated the decreased matrix degradation seen in diabetes. In summary, CTGF inhibits matrix degradation by increasing TIMP-1 expression, and by this action it contributes to the inhibition of matrix breakdown by high glucose, implying that CTGF has a role in the reduced matrix degradation observed in diabetic nephropathy.

Advanced glycosylation end products up-regulate connective tissue growth factor (insulin-like growth factor-binding protein-related protein 2) in human fibroblasts: a potential mechanism for expansion of extracellular matrix in diabetes mellitus

Expansion of extracellular matrix with fibrosis occurs in many tissues as part of the end-organ complications in diabetes, and advanced glycosylation end products (AGE) are implicated as one causative factor in diabetic tissue fibrosis. Connective tissue growth factor (CTGF), also known as insulin-like growth factor-binding protein-related protein-2 (IGFBP-rP2), is a potent inducer of extracellular matrix synthesis and angiogenesis and is increased in tissues from rodent models of diabetes. The aim of this study was to determine whether CTGF is up-regulated by AGE in vitro and to explore the cellular mechanisms involved. AGE treatment of primary cultures of nonfetal human dermal fibroblasts in confluent monolayer increased CTGF steady state messenger RNA (mRNA) levels in a time- and dose-dependent manner. In contrast, mRNAs for other IGFBP superfamily members, IGFBP-rP1 (mac 25) and IGFBP-3, were not up-regulated by AGE. The effect of the AGE BSA reagent on CTGF mRNA was due to nonenzymatic glycosylation of BSA and, using neutralizing antisera to AGE and to the receptor for AGE, termed RAGE, was seen to be due to late products of nonenzymatic glycosylation and was partly mediated by RAGE. Reactive oxygen species as well as endogenous transforming growth factor-beta1 could not explain the AGE effect on CTGF mRNA. AGE also increased CTGF protein in the conditioned medium and cell-associated CTGF. Thus, AGE up-regulates the profibrotic and proangiogenic protein CTGF (IGFBP-rP2), a finding that may have significance in the development of diabetic complications.

Effects of sodium butyrate on expression of members of the IGF-binding protein superfamily in human mammary epithelial cells

Dietary factors play an important role in both the development and prevention of human cancers, including breast carcinoma. One dietary micronutrient, sodium butyrate (NaB), is a major end product of dietary starch and fiber, produced naturally during digestion by anaerobic bacteria in the cecum and colon. NaB is a potent growth inhibitor and initiates cell differentiation for many cell types in vitro. In this study, we investigated the effects of NaB on three human mammary epithelial cells and regulation of the IGF axis, specifically, IGF-binding protein-3 (IGFBP-3), a known growth regulator in human mammary cells, and IGFBP-related protein 2 (IGFBP-rP2)/connective tissue growth factor. NaB inhibited DNA synthesis, as measured by [3H]thymidine incorporation, in estrogen-responsive (MCF-7) and estrogen-non-responsive (Hs578T) breast cancer cells, and normal human mammary epithelial cells (HMEC) to a similar degree (up to 90% inhibition at 1-10 mM concentrations). Treatment of cells with NaB induced histone hyperacetylation, suggesting that NaB exerts its biological effects, at least in part, as a histone deacetylase inhibitor in mammary epithelial cells. Treatment of Hs578T cells with NaB caused an induction of apoptotic cell death. NaB treatment resulted in increased levels of p21(Waf1/Cip1) mRNA and protein in Hs578T cells and distinct upregulation of p27(Kip1) in HMEC, suggesting that NaB activates different genes involved in cell cycle arrest, depending upon the cell type. In the same context, among the IGFBP superfamily members tested, NaB specifically upregulated the expression of IGFBP-3 and IGFBP-rP2. These two proteins are known to be involved in inhibition of mammary epithelial cell replication. Northern blot analysis showed that NaB treatment at 1-10 mM concentrations caused a dose-dependent stimulation of IGFBP-3 mRNA expression in cancerous cells and IGFBP-rP2 mRNA expression in both cancerous and non-cancerous cells. Protein data from Western ligand blot and immunoblot analyses demonstrated parallel results. In summary, we have demonstrated that NaB (i) uniformly suppresses DNA synthesis in both cancerous and non-cancerous mammary cells, and (ii) upregulates IGFBP-3 and IGFBP-rP2 mRNA and protein levels in cancerous and non-cancerous mammary cells. These results provide the first demonstration that butyrate regulates the IGFBP system in the human mammary system.

A purified bovine serum albumin preparation contains an insulin-like growth factor (IGF) binding protein-3 fragment that forms ternary complexes selectively with IGF-II and the acid-labile subunit

Among the six insulin-like growth factor binding proteins (IGFBP), only IGFBP-3 and IGFBP-5 form ternary complexes with IGFs and the acid-labile sunbunit (ALS). In a commercial, highly-purified BSA preparation, ternary complex formation was detected using radio-labeled IGF-II and human serum-derived ALS, with precipitation by ALS antiserum. In contrast, no complexes with radio-labeled IGF-I were detected under the same conditions. Size-fractionation of the BSA on Superose-12 showed the peak of ternary complex forming activity at approximately 30 kDa. To purify the active factor, a solution of the BSA was pumped onto a [Gly(1)]IGF-II affinity column, and eluted fractions were lyophilized and applied to a C18 HPLC column. The eluted fractions showing ternary complex forming activity maintained a preference for IGF-II in forming ternary complexes and a slight preference in forming binary complexes with IGF-II rather than IGF-I. By silver staining after non-reducing SDS-PAGE, the peak activity in the HPLC-eluted fractions appeared as 30 kDa and 21-24 kDa bands. Amino-terminal sequencing of this peak activity revealed bovine IGFBP-3. These results demonstrate that amino-terminal proteolyzed bovine IGFBP-3 is present in a highly purified BSA preparation. In contrast to intact human IGFBP-3 and IGFBP-5, this form of bovine IGFBP-3 forms ternary complexes preferentially with IGF-II rather than IGF-I.

A central domain binding site in insulin-like growth factor binding protein-5 for the acid-labile subunit

Like insulin-like growth factor binding protein-3 (IGFBP-3), IGFBP-5 forms a ternary complex with insulin-like growth factor (IGF)-I or IGF-II, and the acid-labile subunit (ALS). The study of IGFBP-5/IGFBP-6 chimeric proteins with amino-terminal and middle domain swaps, has revealed the existence of a site in the middle domain of IGFBP-5, that binds to ALS in the absence of the IGFBP-5 carboxy-terminal domain. An IGFBP-6 chimeric protein containing the central domain of IGFBP-5 complexed efficiently with ALS, and a carboxy-terminally truncated IGFBP-5 mutant, IGFBP-5'(1-169), also bound to ALS in the presence of IGFs, although with much less potency than full length rhIGFBP-5. In contrast to the latter, IGFBP-5(1-169) preferentially formed ternary complexes with IGF-II rather than IGF-I. These results indicate that a site which binds ALS exists in IGFBP-5 mutants which lack the IGFBP-5 carboxy-terminal domain.

Insulin-like growth factor-binding protein 5 complexes with the acid-labile subunit. Role of the carboxyl-terminal domain

We have recently shown that insulin-like growth factor (IGF)-binding protein 5 forms ternary complexes with IGF-I or IGF-II and the acid-labile subunit (ALS) (Twigg, S. M., and Baxter, R. C. (1998) J. Biol. Chem. 273, 6074-6079). Because IGF-binding protein 3 (IGFBP-3) binds to ALS through its basic carboxyl-terminal domain, we tested whether a homologous region present in IGFBP-5 is involved in IGFBP-5 binding to ALS. Chimeric peptides were generated by carboxyl-terminal domain interchange between recombinant human IGF-BP-5 and IGFBP-6, producing two IGFBP peptides designated 5-5-6 and 6-6-5. Determined by immunoprecipitation and by Superose chromatography, 6-6-5 formed ternary complexes, albeit less potently than IGF-BP-5. In contrast, 5-5-6, like IGFBP-6, did not form ternary complexes by these methods. Whereas 6-6-5, like IGFBP-6, had a marked preference for binary complex formation with IGF-II rather than IGF-I, it formed ternary complexes more efficiently with IGF-I, like IGF-BP-5. The glycosaminoglycans heparin and heparan sulfate bind to IGFBP-5 through its basic carboxyl-terminal domain. At high concentrations, these glycosaminoglycans inhibited ALS binding to binary complexed IGF-BP-5. In addition, in the absence of IGFs, IGFBP-5, a synthetic peptide representing the basic carboxyl-terminal sequence IGFBP-5(201-218), and the corresponding IGFBP-3 basic sequence IGFBP-3(215-232), competed weakly for ALS binding to covalent IGF-IGFBP-5 complex, as did a random-sequence synthetic peptide with the same composition as IGFBP-5(201-218). These findings are consistent with the basic carboxyl-terminal domain on IGFBP-5 being the principal site in IGFBP-5 that binds to ALS.

Insulin-like growth factor (IGF)-binding protein 5 forms an alternative ternary complex with IGFs and the acid-labile subunit

Up to 90% of circulating insulin-like growth factors (IGF-I and IGF-II) are carried in heterotrimeric complexes with a binding protein (IGFBP) and a liver-derived glycoprotein known as the acid-labile subunit. IGFBP-3 is considered unique among the six well characterized IGFBPs in its ability to complex with the acid-labile subunit. However, a basic carboxyl-terminal domain of IGFBP-3, known to be involved in its interaction with the acid-labile subunit, is shared by IGFBP-5, suggesting the possibility of ternary complexes containing IGFBP-5. We now demonstrate using three independent methods that human IGFBP-5, when occupied by IGF-I or IGF-II, forms ternary complexes of approximately 130 kDa with the acid-labile subunit. IGFBP-3 competes with approximately twice the potency of IGFBP-5 for the formation of such complexes. No other IGFBP complexes with the acid-labile subunit itself or competes with IGFBP-5 for complex formation. As observed for IGFBP-3, ternary complexes containing IGFBP-5 form preferentially in the presence of IGF-I, even though IGFBP-5 has a preferential affinity for IGF-II over IGF-I. By size fractionation chromatography, serum IGFBP-5 co-elutes predominantly with ternary complexes. The demonstration of IGFBP-5-containing ternary complexes indicates an unrecognized form of IGF transport in the circulation and an additional mechanism for regulating IGF bioavailability.

The molecular genetics of endocrine tumours

The molecular genetics of endocrine tumours is an area of great interest, due to the heterogeneity of endocrine tumour types, the association of hormone over-production in some cases, and the wide variation in tumour behaviour. Genes implicated fall into functional categories such as oncogenes, in which mutations tend to cause activation, and tumour suppressor genes, in which mutations lead to loss of function. Oncogenes include the receptor tyrosine kinases such as RET, signal transduction proteins and other molecules such as cell cycle regulators and nuclear proteins. Tumour suppressor genes include cell cycle regulators such as p53 and other molecules such as the MEN 1 gene. Loss of heterozygosity studies help in the initial localisation of the latter. Endocrine tumours, as with other tumours, develop as a result of a combination of genetic events, and in the paediatric age group they often occur in the setting of familial cancer syndromes. In this review we analyse the main genetic lesions which have been described in endocrine tumours. There has been an explosion of knowledge in the last 5 years including the identification of the causative genes for MEN 2 and most recently for MEN 1. Characterisation of such genes also aids in the study of somatic mutations in sporadic versions of the same tumour types as occur in the familial syndromes. Identification of a genetic predisposition to a certain tumour has management implications that are still to be clarified in most cases, although in the case of MEN 2 the guidelines for prophylactic thyroidectomy are generally well accepted.

Genetic testing for familial cancer. Consequences of RET proto-oncogene mutation analysis in multiple endocrine neoplasia, type 2

OBJECTIVE

To assess clinician use and acceptance of RET proto-oncogene mutation testing in multiple endocrine neoplasia, type 2 (MEN 2) family members.

DESIGN

A retrospective survey of clinicians managing 26 MEN 2 families with documented RET mutations to assess the effect of genetic screening on subsequent investigation and management of family members.

SETTING

Tertiary referral center for RET mutation testing.

MAIN OUTCOME MEASURES

The screening procedures used by clinicians and the altered incidence of C-cell hyperplasia vs medullary thyroid carcinoma in genetically as opposed to biochemically identified affected family members.

RESULTS

Among RET mutation-positive patients, thyroidectomy performed for clinical or biochemical indication disclosed medullary thyroid carcinoma in 44 (98%) of 45 patients and precursor C-cell hyperplasia in only 1 (2%) patient. When prophylactic thyroidectomy was performed based on a positive genetic result, medullary thyroid carcinoma occurred in 3 (43%) of 7 patients and C-cell hyperplasia in 4 (57%) of 7 patients (P < .001). RET mutation-negative patients were not subjected to further biochemical testing, but 4 had already undergone thyroidectomy based on abnormal results of pentagastrin stimulation tests, including 2 patients who were known to be RET mutation-negative at the time of surgery. RET mutation testing was well accepted and resulted in additional family members consenting to screening in more than 85% of families.

CONCLUSIONS

Genetic screening for RET proto-oncogene mutations in MEN 2 is a powerful diagnostic tool that enables prophylactic thyroidectomy to be performed in RET mutation-positive patients at an earlier stage of the disease process than does traditional biochemical screening.

The practical management of multiple endocrine neoplasia

Adbances in the identification and localization of the abnormal genes in the multiple endocrine neoplasia syndromes have provided new methods of identifying "at risk" individuals in these families. Genetic testing using linkage analysis in multiple endocrine neoplasia (MEN) 1 and direct mutation analysis of the RET protooncogene in MEN 2 is now available for these disorders. New management issues for these disorders have resulted, and a practical approach to these issues is discussed.