Diabetic microvascular complications: can patients at risk be identified? A review

Heat-shock protein gene polymorphisms and the risk of nephropathy in patients with Type 2 diabetes

HSPs (heat-shock proteins) are molecular chaperones synthesized under stress conditions, and are involved in renal cell survival and matrix remodelling in acute and chronic renal diseases. In the present study, we investigated whether the HSP70 gene polymorphisms affect susceptibility to DN (diabetic nephropathy) in patients with T2DM (Type 2 diabetes mellitus). The study group consisted of 452 patients with nephropathy. Two control subgroups involved 340 healthy individuals and 132 patients with T2DM lasting > or =10 years who were free of nephropathy. Subjects were genotyped for the HSP70-1 +190 G/C and -110 A/C, HSP70-2 +1267 A/G and HSP70-hom +2437 T/C polymorphisms by PCR, followed by digestion with restriction endonucleases. There were no statistically significant differences in genotype distribution between patients with T2DM with DN and controls for the HSP70-hom polymorphism. Significant differences were observed for HSP70-1 and HSP70-2 polymorphisms. CC homozygotes of the -110 and +190 HSP70-1 polymorphisms were more frequent in patients with T2DM with DN compared with healthy controls (22 compared with 6% and 15 compared with 6.5% respectively; P<0.01). The OR (odds ratio) for the risk allele was 2.17 [95% CI (confidence interval), 1.73-2.72] for the -110 A/C and 1.74 (95% CI, 1.40-2.15) for +190 G/C polymorphisms. A strong association with DN was found for the +1267 HSP70-2 polymorphism. The GG genotype and the G allele were associated with DN, with the OR for the G allele being 4.77 (95% CI, 3.81-5.96). All GG homozygotes in the patient group had higher LDL (low-density lipoprotein)-cholesterol levels than AA homozygotes (P<0.01), suggesting that the observed effect might be associated with this cardiovascular risk factor. These patients progressed faster to end-stage renal failure than those with other genotypes. In conclusion, our results indicate that the HSP70-1 and HSP70-2 polymorphisms are associated with renal complications in T2DM and may be useful in identifying patients with increased risk of DN.

Prevalence and determinants of albuminuria in a cohort of diabetic patients in Lebanon

BACKGROUND AND OBJECTIVES

Few data are available on the extent of albuminuria in diabetic populations in the Middle East generally and in Lebanon specifically. We conducted this study to determine the prevalence of albuminuria and its major risk factors in a cohort of diabetic patients in Lebanon.

PATIENTS AND METHODS

Diabetic patients followed in the outpatient department at the American University of Beirut Medical Center (AUBMC) were included in a prospective observational study. AUBMC is a tertiary referral center and the outpatient department typically handles patients of low socioeconomic status with advanced disease. Patients were classified according to their urinary albumin-to-creatinine ratio (ACR) as having normoalbuminuria (ACR<30 mg/g creatinine), microalbuminuria (ACR=30 to <300 mg/g creatinine), or macroalbuminuria (ACR > or =300 mg/g creatinine). The three groups were compared to analyze the association between albuminuria and its risk factors. In addition, independent predictors of albuminuria were determined using multivariate logistic regression and presented as an odds ratio.

RESULTS

Microalbuminuria and macroalbuminuria were present in 33.3% and 12.7% of 222 patients (mean age 56.4 years, mean deviation of diabetes 8.6 years, 58.7% women, 43.8% obese), respectively. Factors significantly associated with microalbuminuria included glycemic control, insulin use, and total and LDL cholesterol. Those associated with macroalbuminuria included in addition to glycemic control and insulin use, duration of diabetes, hypertension, elevated mean arterial pressure (MAP), and presence of neuropathy, retinopathy and peripheral vascular disease by bivariate analysis. Only glycemic control was an independent risk factor for both in addition to MAP and retinopathy for macroalbuminuria by multivariate analysis.

CONCLUSION

Albuminuria is highly prevalent among this cohort of diabetic patients in Lebanon. Both glycemic control and blood pressure need to be better targeted in its management.

Toll-like receptor 4 gene polymorphism and early onset of diabetic retinopathy in patients with type 2 diabetes

Toll-like receptor 4 (TLR4) is an important mediator of innate immunity. Type 2 diabetes (DM2) might be associated with changed innate immune response. We investigated whether the polymorphisms in the TLR4 gene are associated with diabetic retinopathy (DR). The study group of 864 patients with DM2 and 420 healthy individuals were genotyped. In the patient group 352 subjects were diagnosed with DR. Out of the remaining 512, 140 had DM2 for > or = 10 years but no DR. In the DM2 group 7.4% of patients were heterozygous for the Asp299Gly polymorphism compared with 6.5% controls. For Thr399Ile polymorphism there were 7.2% heterozygotes vs 6.2% controls. In most cases, the linkage disequilibrium between the minor alleles Gly299 and Ile399 was confirmed. Increased frequency of both heterozygous genotypes was observed in patients with retinopathy (11.2% for the Asp299Gly). The frequency of the G allele was significantly higher in patients with early onset retinopathy (n = 80) vs patients without DR (odds ratio = 5.0, and 95% confidence interval = 2.33-10.71). In contrast, in the entire retinopathy group, the odds ratio for the G allele was 1.88 (95% confidence interval = 0.93-3.79). In the multivariate logistic regression analysis, the G allele of Asp299Gly was an independent risk factor of early onset DR (p < 0.001). In conclusion, our results suggest an association between the Asp299Gly polymorphism of the TLR4 gene and early onset of DR in the DM2 patients. Thus the G allele may be a predictor of increased risk of retinopathy.

Economic outcomes associated with microvascular complications of type 2 diabetes mellitus: results from a US claims data analysis

BACKGROUND

Patients with diabetes mellitus have been shown to be at high risk for both macrovascular and microvascular complications (MVC). Recent studies have focused on MVC and their effect on the healthcare system, but limited published data exist on long-term costs associated with MVC in patients with type 2 diabetes mellitus (T2DM).

OBJECTIVE

The objective of this study was to compare resource utilization and medical costs over a 12-month period among patients diagnosed with T2DM with versus without MVC in a managed-care population.

METHODS

Patients aged >/=18 years, diagnosed with T2DM between 1 January 2003 and 31 December 2004 were identified in an administrative claims database of approximately 55 million beneficiaries in private and public health plans. The date of the first T2DM diagnosis during this period was the 'index date' for each patient. All patients had to have a minimum of 12 months of continuous enrolment both prior to and following the index date. MVC was identified during the 12 months prior to the first T2DM diagnosis and these patients were matched (1 : 2) by age, sex and ten co-morbid conditions to those with no evidence of MVC during the entire study period.

RESULTS

Among the 15 326 MVC patients included in the study, 61% had a history of peripheral neuropathy, 28% diabetic retinopathy and 19% nephropathy. Compared with 30 652 patients without MVC, the MVC patients were more likely to use oral antidiabetics and insulin and had a higher co-morbidity score. Over 12 months, patients with MVC had more (mean 0.3 vs 0.2; p < 0.001) and longer (mean length of stay 1.79 days vs 0.85 days; p < 0.001) hospital stays; physician office visits (19.7 vs 13.7; p < 0.001); and prescriptions for oral antidiabetic (6.3 vs 5.6 scripts; p < 0.001) and insulin (0.7 vs 0.2 scripts; p < 0.001) use. Average total costs per patient over 12 months were $US14 414 with MVC versus $US8669 without MVC (p < 0.001).

CONCLUSIONS

This study indicates that in patients with T2DM, MVC is associated with significant consumption of healthcare resources. Mean total costs with MVC were almost double those of patients without MVC over a 12-month period.

Prevalence and determinants of albuminuria in a cohort of diabetic patients in Lebanon

BACKGROUND AND OBJECTIVES

Few data are available on the extent of albuminuria in diabetic populations in the Middle East generally and in Lebanon specifically. We conducted this study to determine the prevalence of albuminuria and its major risk factors in a cohort of diabetic patients in Lebanon.

PATIENTS AND METHODS

Diabetic patients followed in the outpatient department at the American University of Beirut Medical Center (AUBMC) were included in a prospective observational study. AUBMC is a tertiary referral center and the outpatient department typically handles patients of low socioeconomic status with advanced disease. Patients were classified according to their urinary albumin-to-creatinine ratio (ACR) as having normoalbuminuria (ACR<30 mg/g creatinine), microalbuminuria (ACR=30 to <300 mg/g creatinine), or macroalbuminuria (ACR > or =300 mg/g creatinine). The three groups were compared to analyze the association between albuminuria and its risk factors. In addition, independent predictors of albuminuria were determined using multivariate logistic regression and presented as an odds ratio.

RESULTS

Microalbuminuria and macroalbuminuria were present in 33.3% and 12.7% of 222 patients (mean age 56.4 years, mean deviation of diabetes 8.6 years, 58.7% women, 43.8% obese), respectively. Factors significantly associated with microalbuminuria included glycemic control, insulin use, and total and LDL cholesterol. Those associated with macroalbuminuria included in addition to glycemic control and insulin use, duration of diabetes, hypertension, elevated mean arterial pressure (MAP), and presence of neuropathy, retinopathy and peripheral vascular disease by bivariate analysis. Only glycemic control was an independent risk factor for both in addition to MAP and retinopathy for macroalbuminuria by multivariate analysis.

CONCLUSION

Albuminuria is highly prevalent among this cohort of diabetic patients in Lebanon. Both glycemic control and blood pressure need to be better targeted in its management.

Association of organochlorine pesticides with peripheral neuropathy in patients with diabetes or impaired fasting glucose

OBJECTIVE

Recent epidemiological studies have shown that background exposure to persistent organic pollutants (POPs)--xenobiotics accumulated in adipose tissue--is strongly associated with type 2 diabetes. Hyperglycemia is the cause of long-term complications of diabetes as well as diabetes itself, and POPs are well-known neurotoxicants. This study was performed to explore whether POPs are associated with peripheral neuropathy, a common long-term complication of diabetes, in people with glucose abnormalities.

RESEARCH DESIGN AND METHODS

We studied cross-sectional associations of peripheral neuropathy with 25 POPs, each of which were detectable in at least 60% of study subjects, in 246 subjects aged >or=40 years with diabetes or impaired fasting glucose (IFG) using National Health and Nutrition Examination Survey 1999-2002 datasets.

RESULTS

Among five subclasses of POPs, organochlorine pesticides showed a strong dose-response relation with prevalence of peripheral neuropathy; adjusted ORs were 1.0, 3.6, and 7.3 (P for trend <0.01), respectively, across three categories of serum concentrations of organochlorine pesticides. Furthermore, when we restricted the analyses to 187 participants with A1C <7%, the adjusted ORs were still 1.0, 3.9, and 6.7 (P for trend <0.01). Organochlorine pesticides were also strongly associated with the prevalence of A1C >or=7%; adjusted ORs were 1.0, 2.5, and 5.0 (P for trend <0.01). Specific POPs belonging to organochlorine pesticides showed similar positive associations.

CONCLUSIONS

This study suggests that background exposure to organochlorine pesticides may be associated with higher risk of peripheral neuropathic complications among those with glucose abnormalities, even beyond the influence of diabetes itself.

Diabetes-related microvascular and macrovascular diseases in the physical therapy setting

Physical therapists commonly treat people with diabetes for a wide variety of diabetes-associated impairments, including those from diabetes-related vascular disease. Diabetes is associated with both microvascular and macrovascular diseases affecting several organs, including muscle, skin, heart, brain, and kidneys. A common etiology links the different types of diabetes-associated vascular disease. Common risk factors for vascular disease in people with diabetes, specifically type 2 diabetes, include hyperglycemia, insulin resistance, dyslipidemia, hypertension, tobacco use, and obesity. Mechanisms for vascular disease in diabetes include the pathologic effects of advanced glycation end product accumulation, impaired vasodilatory response attributable to nitric oxide inhibition, smooth muscle cell dysfunction, overproduction of endothelial growth factors, chronic inflammation, hemodynamic dysregulation, impaired fibrinolytic ability, and enhanced platelet aggregation. It is becoming increasingly important for physical therapists to be aware of diabetes-related vascular complications as more patients present with insulin resistance and diabetes. The opportunities for effective physical therapy interventions (such as exercise) are significant.

Promoter polymorphism of the erythropoietin gene in severe diabetic eye and kidney complications

Significant morbidity and mortality among patients with diabetes mellitus result largely from a greatly increased incidence of microvascular complications. Proliferative diabetic retinopathy (PDR) and end stage renal disease (ESRD) are two of the most common and severe microvascular complications of diabetes. A high concordance exists in the development of PDR and ESRD in diabetic patients, as well as strong familial aggregation of these complications, suggesting a common underlying genetic mechanism. However, the precise gene(s) and genetic variant(s) involved remain largely unknown. Erythropoietin (EPO) is a potent angiogenic factor observed in the diabetic human and mouse eye. By a combination of case-control association and functional studies, we demonstrate that the T allele of SNP rs1617640 in the promoter of the EPO gene is significantly associated with PDR and ESRD in three European-American cohorts [Utah: P = 1.91 x 10(-3); Genetics of Kidneys in Diabetes (GoKinD) Study: P = 2.66 x 10(-8); and Boston: P = 2.1 x 10(-2)]. The EPO concentration in human vitreous body was 7.5-fold higher in normal subjects with the TT risk genotype than in those with the GG genotype. Computational analysis suggests that the risk allele (T) of rs1617640 creates a matrix match with the EVI1/MEL1 or AP1 binding site, accounting for an observed 25-fold enhancement of luciferase reporter expression as compared with the G allele. These results suggest that rs1617640 in the EPO promoter is significantly associated with PDR and ESRD. This study identifies a disease risk-associated gene and potential pathway mediating severe diabetic microvascular complications.

Lipid-lowering therapy and peripheral sensory neuropathy in type 2 diabetes: the Fremantle Diabetes Study

AIMS/HYPOTHESIS

The aim of this study was to assess the relationships between lipid-lowering therapy and the prevalence and incidence of peripheral sensory neuropathy in type 2 diabetes mellitus.

METHODS

We analysed data from an observational cohort study, the Fremantle Diabetes Study (FDS), specifically, (1) a cross-sectional sample comprising 1,237 FDS participants with type 2 diabetes mellitus, and (2) a longitudinal subgroup of 531 individuals who had attended six consecutive annual assessments. Neuropathy was identified using the clinical portion of the Michigan Neuropathy Screening Instrument.

RESULTS

At entry, the cross-sectional sample had a mean +/- SD age of 63.8+/-11.3 years, 48.7% were men, median (interquartile range) diabetes duration was 4.0 (1.0-9.0) years, and 30.9% had peripheral neuropathy. Fibrates and statins were used by 3.5 and 6.8%, respectively. Multiple logistic regression analysis showed that older age, longer diabetes duration, central adiposity, increased height, higher fasting serum glucose, albuminuria and aboriginality were significant independent positive predictors of prevalent neuropathy, while systolic blood pressure and fibrate use (odds ratio 0.30, 95% CI 0.10-0.86; p=0.025) were negatively associated. In the longitudinal subgroup, fibrate and statin use increased to 10.4 and 36.5%, respectively, over 5 years. In time-dependent Cox proportional hazards modelling, fibrate use [hazard ratio (HR) 0.52, 95% CI 0.27-0.98] and statin use (HR 0.65, 95% CI 0.46-0.93) were significant determinants of incident neuropathy (p <or= 0.042).

CONCLUSIONS/INTERPRETATION

These preliminary observational data suggest that therapy with a statin or a fibrate may protect against the development of diabetic peripheral sensory neuropathy, but there is a need for additional confirmatory evidence, preferably from randomised clinical trials.

Determination of urinary enzymes as a marker of early renal damage in diabetic patients

Diagnosis of diabetic nephropathy in the early stages is very important since there are no clinical signs or symptoms. Urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion has been recommended as a tubular dysfunction marker that elevates before other markers, such as microalbuminuria and a decrease in creatinine clearance. In this study, we compared excretion of urinary enzymes with other markers that are used routinely in diabetic nephropathy assessment. Urinary NAG, lactate dehydrogenase (LDH), alkaline phosphatase (AP) activities, urea, creatinine, and albumin, with levels of serum glucose and creatinine and whole blood glycosylated hemoglobin (HbA1c) were measured in 32 diabetes mellitus patients and 25 healthy subjects (controls). Notably, urinary NAG, AP, LDH excretion, and microalbuminuria in the diabetic patients group were significantly increased compared to those in the control groups (P<0.001, P<0.05, P<0.01, and P<0.01, respectively). Meanwhile, our results showed that the urinary NAG excretion had the highest sensitivity and specificity (100% and 87.5%, respectively) compared to other markers. We showed that measuring urinary NAG excretion could be useful for the assessment of renal failure in diabetes mellitus patients and confirmed the use of NAG as a routine screening test.

A predisposição genética para o desenvolvimento da microangiopatia no DM1

Acredita-se que o controle glicêmico e a duração do diabetes sejam os fatores de risco mais importantes para o desenvolvimento das microangiopatias diabéticas, contudo, as velocidades de progressão da nefropatia, da retinoaptia e da polineuropatia variam consideravelmente entre os pacientes. Além da presença de fatores de risco, como a hipertensão arterial, a dislipidemia e o fumo, existem evidências sugerindo que uma predisposição genética desempenha um papel na susceptibilidade para as complicações microvasculares. Com base na patogênese dessas complicações crônicas do diabetes, polimorfismos de vários genes candidatos que atuam em diferentes vias desse processo têm sido investigados, como os genes relacionados aos mecanismos dos danos induzidos pela hiperglicemia (os produtos finais de glicação avançada, o aumento na formação de espécies reativas de oxigênio e a atividade aumentada da via da aldose-redutase), os genes relacionados ao sistema renina-angiotensina; os genes que codificam a síntese das citoquinas, dos fatores de crescimento e dos seus receptores e dos transportadores de glicose entre muitos outros. Este artigo discute alguns estudos que corroboram com a importância da predisposição genética no desenvolvimento da microangiopatia diabética.

Vascular complications of diabetes in Lebanon: Experience at the American University of Beirut

Aim To examine the metabolic control and presence of

complications, among a cohort of diabetic patients in Lebanon. Method A total of 313 diabetic patients presenting for their usual care were screened in a cross-sectional manner for metabolic control and presence of complications at the American University of Beirut.

Results Only 235 subjects completed their data of whom 220 (93%) had type 2 diabetes with mean duration of disease of 8.2 (±6.6) years. Only 30% had haemoglobin A1C < 7%, and 35.5% had low-density lipoprotein Cholesterol < 2.6 mmol/L. About 50.5% were obese, 34.9% current smokers, and 40.7% had blood pressure ≥ 140/90 mmHg. Microvascular complications were present as 46.3, 39.9 and 33% for albuminuria, neuropathy, 33% for albuminuria, neuropathy, and retinopathy, respectively. Macrovascular complications were as follows: 19.3, 18.3 and 4.1% for coronary artery disease, peripheral vascular disease and cerebrovascular disease, respectively.

Conclusions This study highlights the poor control and high prevalence of vascular complications among adult type 2 diabetic patients in Lebanon.

Stroke presentation in Type 2 diabetes and the metabolic syndrome

INTRODUCTION

The metabolic syndrome (MetS) is associated with macrovascular disease and an altered pattern of cerebrovascular disease. We investigated stroke subtype presentation in Type 2 diabetic (T2D) patients, and analysed patients with and without the MetS.

METHODS

We performed a retrospective analysis of 243 T2D patients with first presentation of stroke from our Diabetes Centre database. The MetS was diagnosed in patients with T2D and two or more additional risk factors (obesity, low HDL cholesterol, elevated triglycerides or hypertension). We analysed the clinical stroke subtype presentation, using the Oxford classification of stroke, into cortical and lacunar (small vessel disease) stroke.

RESULTS

The MetS was diagnosed in 151 T2D patients (62%), with 86 male and 65 female patients (age: 71.8+/-9.7). Comparing the MetS and non-MetS groups, the distribution of stroke subtypes adjusted for age and sex were: cortical stroke (13.2% versus 15.2%; P=0.56), lacunar stroke (43.7% versus 43.5%; P=0.87) and TIA (38.4% versus 39.1%; P=0.98). Lacunar stroke incidence was significantly higher compared to cortical stroke in both groups (P<0.001).

CONCLUSION

In this study of T2D patients, lacunar stroke (small vessel disease) was the most common stroke subtype in both patients with and without the MetS.

Delayed initiation of subcutaneous insulin therapy after failure of oral glucose-lowering agents in patients with Type 2 diabetes: a population-based analysis in the UK

AIMS

The aim of this retrospective cohort study was to estimate the time to insulin initiation in patients with Type 2 diabetes inadequately controlled on oral glucose-lowering agents (OGLAs).

METHODS

Insulin-naïve patients failing on OGLAs were identified from The Health Improvement Network database, which collects records from general practices throughout the UK. Patients were included if they were aged > or = 40 years, had concomitant prescriptions for > or = 2 OGLAs, and > or = 1 year of available records prior to the first occurrence of HbA(1c) > or = 8.0% after > or = 90 days of OGLA polytherapy at > or = 50% of maximum recommended dosages.

RESULTS

A total of 2501 eligible patients with Type 2 diabetes who had an HbA(1c) above the OGLA failure threshold of > or = 8.0% were identified (54.0% male; 30.9% aged 60-69 years). It was estimated that if all the eligible patients were followed for 5 years, 25% would initiate insulin within 1.8 years of OGLA failure (95% CI 1.6-2.0), and 50% within 4.9 years (95% CI 4.6-5.8). The presence of diabetes-related complications had no substantial impact on the time to insulin initiation.

CONCLUSIONS

This study found that 25% of patients with Type 2 diabetes had insulin initiation delayed for at least 1.8 years, and 50% of patients delayed starting insulin for almost 5 years after failure of glycaemic control with OGLA polytherapy, even in the presence of diabetes-related complications. Interventions that reduce this delay to insulin initiation are required to help achieve and maintain recommended glycaemic targets in patients with Type 2 diabetes.

21st Century treatment of diabetic retinopathy

Despite marked improvements in the treatment of diabetes and its retinal complications, diabetic retinopathy remains a leading cause of blindness and vision impairment in working-age adults. Control of blood glucose and blood pressure will remain important means to prevent the onset and progression of diabetic retinopathy. Current and improved surgical treatments, such as laser therapy and vitrectomy, have also proved highly effective in preventing major visual loss in advanced stages of retinopathy. In this review, emerging drug-based therapies (corticosteroids, somatostatin analogues, anti-VEGF agents, a specific PKCβ1/2 inhibitor [ruboxistaurin]), more effective inhibitors of aldose reductase, inhibitors of the renin-angiotensin system and anti-inflammatory agents that could help to preserve sight in the growing population of diabetic patients into the 21st Century are discussed.