Relationship between cardiovascular dysfunction and hyperglycemia in streptozotocin-induced diabetes in rats

Streptozotocin (STZ)-induced diabetes in rats is characterized by cardiovascular dysfunction beginning 5 days after STZ injection, which may reflect functional or structural autonomic nervous system damage. We investigated cardiovascular and autonomic function, in rats weighing 166 ± 4 g, 5-7, 14, 30, 45, and 90 days after STZ injection (N = 24, 33, 27, 14, and 13, respectively). Arterial pressure (AP), mean AP (MAP) variability (standard deviation of the mean of MAP, SDMMAP), heart rate (HR), HR variability (standard deviation of the normal pulse intervals, SDNN), and root mean square of successive difference of pulse intervals (RMSSD) were measured. STZ induced increased glycemia in diabetic rats vs control rats. Diabetes reduced resting HR from 363 ± 12 to 332 ± 5 bpm (P < 0.05) 5 to 7 days after STZ and reduced MAP from 121 ± 2 to 104 ± 5 mmHg (P = 0.007) 14 days after STZ. HR and MAP variability were lower in diabetic vs control rats 30-45 days after STZ injection (RMSSD decreased from 5.6 ± 0.9 to 3.4 ± 0.4 ms, P = 0.04 and SDMMAP from 6.6 ± 0.6 to 4.2 ± 0.6 mmHg, P = 0.005). Glycemia was negatively correlated with resting AP and HR (r = -0.41 and -0.40, P < 0.001) and with SDNN and SDMMAP indices (r = -0.34 and -0.49, P < 0.01). Even though STZ-diabetic rats presented bradycardia and hypotension early in the course of diabetes, their autonomic function was reduced only 30-45 days after STZ injection and these changes were negatively correlated with plasma glucose, suggesting a metabolic origin.

Effect of D-alpha-tocopherol on tubular nephron acidification by rats with induced diabetes mellitus

The objective of the present study was to determine if treatment of diabetic rats with D-alpha-tocopherol could prevent the changes in glomerular and tubular function commonly observed in this disease. Sixty male Wistar rats divided into four groups were studied: control (C), control treated with D-alpha-tocopherol (C + T), diabetic (D), and diabetic treated with D-alpha-tocopherol (D + T). Treatment with D-alpha-tocopherol (40 mg/kg every other day, ip) was started three days after diabetes induction with streptozotocin (60 mg/kg, ip). Renal function studies and microperfusion measurements were performed 30 days after diabetes induction and the kidneys were removed for morphometric analyses. Data are reported as means ± SEM. Glomerular filtration rate increased in D rats but decreased in D + T rats (C: 6.43 ± 0.21; D: 7.74 ± 0.45; D + T: 3.86 ± 0.18 ml min-1 kg-1). Alterations of tubular acidification observed in bicarbonate absorption flux (JHCO3) and in acidification half-time (t/2) in group D were reversed in group D + T (JHCO3, C: 2.30 ± 0.10; D: 3.28 ± 0.22; D + T: 1.87 ± 0.08 nmol cm-2 s-1; t/2, C: 4.75 ± 0.20; D: 3.52 ± 0.15; D + T: 5.92 ± 0.19 s). Glomerular area was significantly increased in D, while D + T rats exhibited values similar to C, suggesting that the vitamin prevented the hypertrophic effect of hyperglycemia (C: 8334.21 ± 112.05; D: 10,217.55 ± 100.66; D + T: 8478.21 ± 119.81µm²). These results suggest that D-alpha-tocopherol is able to protect rats, at least in part, from the harmful effects of diabetes on renal function.

Effect of polymorphisms of the MTHFR and APOE genes on susceptibility to diabetes and severity of diabetic retinopathy in Brazilian patients

Diabetes mellitus (DM) is a highly prevalent complex genetic disorder. There has been a worldwide effort in the identification of susceptibility genes for DM and its complications, and the 5-10-methylenetetrahydrofolate reductase (MTHFR) and apolipoprotein-E (APOE) genes have been considered good candidate susceptibility genes to this condition. The objectives of the present study were to determine if the 677T MTHFR and epsilon2/epsilon3/epsilon4 APOE alleles are risk factors for DM and for severity of diabetic retinopathy (DR). A total of 248 individuals were studied: 107 healthy individuals and 141 diabetic patients (46 with type 1 diabetes and 95 with type 2 diabetes), who also had DR (81 with non-proliferative DR and 60 with proliferative DR). The polymorphisms were analyzed by PCR followed by digestion with restriction enzyme or the single-nucleotide primer extension method. No evidence of association between the 677TT genotype of MTHFR gene and DM [cases: TT = 10/95 (10.6%); controls: TT = 14/107 (13%)] or with severity of DR was observed [cases: TT = 5/60 (8.5%); controls: TT = 9/81 (11.1%); P > 0.05]. We also did not find evidence of an association between APOE alleles and proliferative DR (epsilon2, epsilon3 and epsilon4 in cases: 9, 76, and 15%, and in controls: 5, 88, and 12%, respectively) but the carriers of epsilon2 allele were more frequent among patients with type 2 DM and DR than in controls [cases: 15/95 (15.8%); controls: 7/107 (6.5%); P < 0.05]. Therefore, our results suggest that the epsilon2 allele/APOE might be a risk factor for diabetes in the Brazilian population.

Proliferative diabetic retinopathy is associated with microalbuminuria in patients with type 2 diabetes

Diabetic retinopathy is one of the leading causes of blindness in working-age individuals. Diabetic patients with proteinuria or those on dialysis usually present severe forms of diabetic retinopathy, but the association of diabetic retinopathy with early stages of diabetic nephropathy has not been entirely established. A cross-sectional study was conducted on 1214 type 2 diabetic patients to determine whether microalbuminuria is associated with proliferative diabetic retinopathy in these patients. Patients were evaluated by direct and indirect ophthalmoscopy and grouped according to the presence or absence of proliferative diabetic retinopathy. The agreement of diabetic retinopathy classification performed by ophthalmoscopy and by stereoscopic color fundus photographs was 95.1% (kappa = 0.735; P < 0.001). Demographic information, smoking history, anthropometric and blood pressure measurements, glycemic and lipid profile, and urinary albumin were evaluated. On multiple regression analysis, diabetic nephropathy (OR = 5.18, 95% CI = 2.91-9.22, P < 0.001), insulin use (OR = 2.52, 95% CI = 1.47-4.31, P = 0.001) and diabetes duration (OR = 1.04, 95% CI = 1.01-1.07, P = 0.011) were positively associated with proliferative diabetic retinopathy, and body mass index (OR = 0.90, 95% CI = 0.86-0.96, P < 0.001) was negatively associated with it. When patients with macroalbuminuria and on dialysis were excluded, microalbuminuria (OR = 3.3, 95% CI = 1.56-6.98, P = 0.002) remained associated with proliferative diabetic retinopathy. Therefore, type 2 diabetic patients with proliferative diabetic retinopathy more often presented renal involvement, including urinary albumin excretion within the microalbuminuria range. Therefore, all patients with proliferative diabetic retinopathy should undergo an evaluation of renal function including urinary albumin measurements.

Secondary prevention of type 1 diabetes mellitus: stopping immune destruction and promoting ß-cell regeneration

Type 1 diabetes mellitus results from a cell-mediated autoimmune attack against pancreatic ß-cells. Traditional treatments involve numerous daily insulin dosages/injections and rigorous glucose control. Many efforts toward the identification of ß-cell precursors have been made not only with the aim of understanding the physiology of islet regeneration, but also as an alternative way to produce ß-cells to be used in protocols of islet transplantation. In this review, we summarize the most recent studies related to precursor cells implicated in the regeneration process. These include embryonic stem cells, pancreas-derived multipotent precursors, pancreatic ductal cells, hematopoietic stem cells, mesenchymal stem cells, hepatic oval cells, and mature ß-cells. There is controversial evidence of the potential of these cell sources to regenerate ß-cell mass in diabetic patients. However, clinical trials using embryonic stem cells, umbilical cord blood or adult bone marrow stem cells are under way. The results of various immunosuppressive regimens aiming at blocking autoimmunity against pancreatic ß-cells and promoting ß-cell preservation are also analyzed. Most of these regimens provide transient and partial effect on insulin requirements, but new regimens are beginning to be tested. Our own clinical trial combines a high dose immunosuppression with mobilized peripheral blood hematopoietic stem cell transplantation in early-onset type 1 diabetes mellitus.

Lack of relationship between glycemic control and bone mineral density in type 2 diabetes mellitus

We assessed the effect of chronic hyperglycemia on bone mineral density (BMD) and bone remodeling in patients with type 2 diabetes mellitus. We investigated 42 patients with type 2 diabetes under stable control for at least 1 year, 22 of them with good metabolic control (GMC: mean age = 48.8 ± 1.5 years, 11 females) and 20 with poor metabolic control (PMC: mean age = 50.2 ± 1.2 years, 8 females), and 24 normal control individuals (CG: mean age = 46.5 ± 1.1 years, 14 females). We determined BMD in the femoral neck and at the L2-L4 level (DEXA) and serum levels of glucose, total glycated hemoglobin (HbA1), total and ionic calcium, phosphorus, alkaline phosphatase, follicle-stimulating hormone, intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25-OH-D), insulin-like growth factor I (IGFI), osteocalcin, procollagen type I C propeptide, as well as urinary levels of deoxypyridinoline and creatinine. HbA1 levels were significantly higher in PMC patients (12.5 ± 0.6 vs 7.45 ± 0.2% for GMC and 6.3 ± 0.9% for CG; P < 0.05). There was no difference in 25-OH-D, iPTH or IGFI levels between the three groups. BMD values at L2-L4 (CG = 1.068 ± 0.02 vs GMC = 1.170 ± 0.03 vs PMC = 1.084 ± 0.02 g/cm²) and in the femoral neck (CG = 0.898 ± 0.03 vs GMC = 0.929 ± 0.03 vs PMC = 0.914 ± 0.03 g/cm²) were similar for all groups. PMC presented significantly lower osteocalcin levels than the other two groups, whereas no significant difference in urinary deoxypyridine was observed between groups. The present results demonstrate that hyperglycemia is not associated with increased bone resorption in type 2 diabetes mellitus and that BMD is not altered in type 2 diabetes mellitus.

Sleep deprivation reduces the lymphocyte count in a non-obese mouse model of type 1 diabetes mellitus

The objective of the present study was to determine whether sleep deprivation (SD) would promote changes in lymphocyte numbers in a type 1 diabetes model (non-obese diabetic, NOD, mouse strain) and to determine whether SD would affect female and male NOD compared to Swiss mice. The number of lymphocytes in peripheral blood after 24 and 96 h of SD (by multiple platform method) or equivalent period of time in home-cage controls was examined prior to the onset of diabetes. SD for 96 h significantly reduced lymphocytes in male Swiss mice compared to control (8.6 ± 2.1 vs 4.1 ± 0.7 10³/µL; P < 0.02). In male NOD animals, 24- and 96-h SD caused a significant decrease of lymphocytes compared to control (4.4 ± 0.3 vs 1.6 ± 0.5; P < 0.001 and 4.4 ± 0.3 vs 0.9 ± 0.1 10³/µL; P < 0.00001, respectively). Both 24- and 96-h SD induced a reduction in the number of lymphocytes in female Swiss (7.5 ± 0.5 vs 4.5 ± 0.5, 4.4 ± 0.6 10³/µL; P < 0.001, respectively) and NOD mice (4 ± 0.6 vs 1.8 ± 0.2, 1.2 ± 0.4 10³/µL; P < 0.01, respectively) compared to the respective controls. Loss of sleep induced lymphopenia in peripheral blood in both genders and strains used. Since many cases of autoimmunity present reduced numbers of lymphocytes and, in this study, it was more evident in the NOD strain, our results suggest that SD should be considered a risk factor in the onset of autoimmune disorders.

Glutamic acid decarboxylase antibodies are indicators of the course, but not of the onset, of diabetes in middle-aged adults: the Atherosclerosis Risk in Communities Study

To efficiently examine the association of glutamic acid decarboxylase antibody (GADA) positivity with the onset and progression of diabetes in middle-aged adults, we performed a case-cohort study representing the ~9-year experience of 10,275 Atherosclerosis Risk in Communities Study participants, initially aged 45-64 years. Antibodies to glutamic acid decarboxylase (GAD65) were measured by radioimmunoassay in 580 incident diabetes cases and 544 non-cases. The overall weighted prevalence of GADA positivity (³1 U/mL) was 7.3%. Baseline risk factors, with the exception of smoking and interleukin-6 (P £ 0.02), were generally similar between GADA-positive and -negative individuals. GADA positivity did not predict incident diabetes in multiply adjusted (HR = 1.04; 95%CI = 0.55, 1.96) proportional hazard analyses. However, a small non-significant adjusted risk (HR = 1.29; 95%CI = 0.58, 2.88) was seen for those in the highest tertile (³2.38 U/mL) of positivity. GADA-positive and GADA-negative non-diabetic individuals had similar risk profiles for diabetes, with central obesity and elevated inflammation markers, aside from glucose, being the main predictors. Among diabetes cases at study's end, progression to insulin treatment increased monotonically as a function of baseline GADA level. Overall, being GADA positive increased risk of progression to insulin use almost 10 times (HR = 9.9; 95%CI = 3.4, 28.5). In conclusion, in initially non-diabetic middle-aged adults, GADA positivity did not increase diabetes risk, and the overall baseline profile of risk factors was similar for positive and negative individuals. Among middle-aged adults, with the possible exception of those with the highest GADA levels, autoimmune pathophysiology reflected by GADA may become clinically relevant only after diabetes onset.

Neutrophil function and metabolism in individuals with diabetes mellitus

Neutrophils act as first-line-of-defense cells and the reduction of their functional activity contributes to the high susceptibilityto and severity of infections in diabetes mellitus. Clinical investigations in diabetic patients and experimental studies in diabetic rats and mice clearly demonstrated consistent defects of neutrophil chemotactic, phagocytic and microbicidal activities. Other alterations that have been reported to occur during inflammation in diabetes mellitus include: decreased microvascular responses to inflammatory mediators such as histamine and bradykinin, reduced protein leakage and edema formation, reduced mast cell degranulation, impairment of neutrophil adhesionto the endothelium and migration to the site of inflammation, production of reactive oxygen species and reduced release of cytokines and prostaglandin by neutrophils, increased leukocyte apoptosis, and reduction in lymph node retention capacity. Since neutrophil function requires energy, metabolic changes (i.e., glycolytic and glutaminolytic pathways) may be involved in the reduction of neutrophil function observed in diabetic states. Metabolic routes by which hyperglycemia is linked to neutrophil dysfunction include the advanced protein glycosylation reaction, the polyol pathway, oxygen-free radical formation, the nitric oxide-cyclic guanosine-3'-5'monophosphate pathway, and the glycolytic and glutaminolytic pathways. Lowering of blood glucose levels by insulin treatment of diabetic patients or experimental animals has been reported to have significant correlation with improvement of neutrophil functional activity. Therefore, changes might be primarily linked to a continuing insulin deficiency or to secondary hyperglycemia occurring in the diabetic individual. Accordingly, effective control with insulin treatment is likely to be relevant during infection in diabetic patients.

The reciprocal interaction between sleep and type 2 diabetes mellitus: facts and perspectives

Type 2 diabetes mellitus is a systemic disease characterized by intolerance to glucose and peripheral resistance to insulin. This endocrine disease affects fundamental mechanisms of the central nervous system and jeopardizes the balance of vital functions such as the cardiovascular and circadian rhythm. The increased prevalence of metabolic disorders in our society is aggravated by endemic voluntary postponement of bedtime and by the current sedentary lifestyle, leading to epidemic proportions of obese people. Diabetes and chronic loss of sleep share the fact that both affect millions and one is detrimental to the other. Indeed, sleep deficits have marked modulatory effects on glucose metabolism and insulin sensitivity and foster metabolic syndrome that culminates in sleep disorders like restless syndrome and sleep apnea, which in turn lead to poor sleep quality. We examine the hypothesis that these two worldwide emerging disorders are due to two interlinked cycles. In our paradigm, we establish an intimate relationship between diabetes and sleep disturbances and postulate possible mechanisms that provide support for this conjecture. In addition, we propose some perspectives about the development of the reciprocal interaction between predictor components of metabolic syndrome and sleep disturbances that lead to poor sleep quality. The ability to predict the development and identify or associate a given mode of sleep disturbance to diabetes would be a valuable asset in the assessment of both. Furthermore, major advances in care coupled with healthy lifestyles can ensure a higher quality of life for people with diabetes.

The role of K121Q ENPP1 polymorphism in diabetes mellitus and its complications

The aim of the present study was to analyze the frequency of K121Q polymorphism in the ENPP1 gene of Brazilian subjects according to ethnic origin and to determine its possible association with diabetes mellitus (DM) and/or diabetic complications. A cross-sectional study was conducted on 1027 type 2 DM patients and 240 anonymous blood donors (BD). Ethnicity was classified based on self-report of European and African descent. The Q allele frequency was increased in African descendant type 2 DM patients (KK = 25.9%, KQ = 48.2%, and QQ = 25.9%) and BD (KK = 22.0%, KQ = 53.8%, and QQ = 24.2%) compared to European descendant type 2 DM patients (KK = 62.7%, KQ = 33.3%, and QQ = 4.1%) and BD (KK = 61.0%, KQ = 35.6%, and QQ = 3.4%). However, there was no difference in genotype distribution or Q allele frequency between diabetic and non-diabetic subjects (European descendants: DM = 0.21 vs BD = 0.21, P = 0.966, and African descendants: DM = 0.50 vs BD = 0.51, P = 0.899). In addition, there were no differences in clinical, laboratory or insulin resistance indices among the three genotypes. The prevalence of DM complications was also similar. In conclusion, K121Q polymorphism is more common among Afro-Brazilian descendants regardless of glycemic status or insulin sensitivity indices. Likewise, insulin sensitivity and DM chronic complications appear not to be related to the polymorphism in this sample.

Alloxan-induced diabetes delays repair in a rat model of closed tibial fracture

A closed fracture was performed on the left tibia of 3-month-old Wistar rats weighing 250 to 350 g that were either healthy (N = 24) or made diabetic with alloxan (N = 24) to investigate the effect of alloxan-induced diabetes on the course of bone fracture healing. Histomorphometric analysis of the fracture site was performed at 7, 14, 25, and 35 days. After 7 days, diabetic rats had significantly less cartilage (P = 0.045) and greater fibrous connective (P = 0.006) tissue formation at the fracture site compared to controls. In contrast, marked callus formation was seen in diabetic rats with significant osteogenesis (P = 0.011, P = 0.010, P = 0.010, respectively, for 14, 25, and 35 days) and chondrogenesis (P = 0.028, P = 0.033, P = 0.019) compared to controls. Radiographic analysis revealed a displaced fracture with poor bone fragment alignment and delayed consolidation at these times in the diabetic group. The levels of alkaline phosphatase were significantly higher in diabetic rats at 25 days (P = 0.009). These results suggest that the initial excessive formation of fibrous connective tissue associated with delay in chondrogenesis and osteogenesis may not provide suitable stability of the fractured site, contributing to the inappropriate alignment of fragments and an increase in the volume of callus in later stages of repair. The resulting displaced fracture in diabetic rats requires long periods for remodeling and complete bone consolidation.

Association of polymorphisms at the ADIPOR1 regulatory region with type 2 diabetes and body mass index in a Brazilian population with European or African ancestry

Association studies between ADIPOR1 genetic variants and predisposition to type 2 diabetes (DM2) have provided contradictory results. We determined if two single nucleotide polymorphisms (SNP c.-8503G>A and SNP c.10225C>G) in regulatory regions of ADIPOR1 in 567 Brazilian individuals of European (EA; N = 443) or African (AfA; N = 124) ancestry from rural (quilombo remnants; N = 439) and urban (N = 567) areas. We detected a significant effect of ethnicity on the distribution of the allelic frequencies of both SNPs in these populations (EA: -8503A = 0.27; AfA: -8503A = 0.16; P = 0.001 and EA: 10225G = 0.35; AfA: 10225G = 0.51; P < 0.001). Neither of the polymorphisms were associated with DM2 in the case-control study in EA (SNP c.-8503G>A: DM2 group -8503A = 0.26; control group -8503A = 0.30; P = 0.14/SNP 10225C>G: DM2 group 10225G = 0.37; control group 10225G = 0.32; P = 0.40) and AfA populations (SNP c.-8503G>A: DM2 group -8503A = 0.16; control group -8503A = 0.15; P = 0.34/SNP 10225C>G: DM2 group 10225G = 0.51; control group 10225G = 0.52; P = 0.50). Similarly, none of the polymorphisms were associated with metabolic/anthropometric risk factors for DM2 in any of the three populations, except for HDL cholesterol, which was significantly higher in AfA heterozygotes (GC = 53.75 ± 17.26 mg/dL) than in homozygotes. We conclude that ADIPOR1 polymorphisms are unlikely to be major risk factors for DM2 or for metabolic/anthropometric measurements that represent risk factors for DM2 in populations of European and African ancestries.

Effect of air pollution on diabetes and cardiovascular diseases in São Paulo, Brazil

Type 2 diabetes increases the risk of cardiovascular mortality and these patients, even without previous myocardial infarction, run the risk of fatal coronary heart disease similar to non-diabetic patients surviving myocardial infarction. There is evidence showing that particulate matter air pollution is associated with increases in cardiopulmonary morbidity and mortality. The present study was carried out to evaluate the effect of diabetes mellitus on the association of air pollution with cardiovascular emergency room visits in a tertiary referral hospital in the city of São Paulo. Using a time-series approach, and adopting generalized linear Poisson regression models, we assessed the effect of daily variations in PM10, CO, NO2, SO2, and O3 on the daily number of emergency room visits for cardiovascular diseases in diabetic and non-diabetic patients from 2001 to 2003. A semi-parametric smoother (natural spline) was adopted to control long-term trends, linear term seasonal usage and weather variables. In this period, 45,000 cardiovascular emergency room visits were registered. The observed increase in interquartile range within the 2-day moving average of 8.0 µg/m³ SO2 was associated with 7.0% (95%CI: 4.0-11.0) and 20.0% (95%CI: 5.0-44.0) increases in cardiovascular disease emergency room visits by non-diabetic and diabetic groups, respectively. These data indicate that air pollution causes an increase of cardiovascular emergency room visits, and that diabetic patients are extremely susceptible to the adverse effects of air pollution on their health conditions.

Vascular complications of black patients with type 2 diabetes mellitus in Southern Brazil

Ethnicity has been shown to be associated with micro- and macrovascular complications of diabetes in European and North American populations. We analyzed the contribution of ethnicity to the prevalence of micro- and macrovascular complications in Brazilian subjects with type 2 diabetes attending the national public health system. Data from 1810 subjects with type 2 diabetes (1512 whites and 298 blacks) were analyzed cross-sectionally. The rates of ischemic heart disease, peripheral vascular disease, stroke, distal sensory neuropathy, and diabetic retinopathy were assessed according to self-reported ethnicity using multiple logistic regression models. Compared to whites, black subjects [odds ratio = 1.72 (95%CI = 1.14-2.6)] were more likely to have ischemic heart disease when data were adjusted for age, sex, fasting plasma glucose, HDL cholesterol, hypertension, smoking habit, and serum creatinine. Blacks were also more likely to have end-stage renal disease [3.2 (1.7-6.0)] and proliferative diabetic retinopathy [1.9 (1.1-3.2)] compared to whites when data were adjusted for age, sex, fasting plasma glucose, HDL cholesterol, hypertension, and smoking habit. The rates of peripheral vascular disease, stroke and distal sensory neuropathy did not differ between groups. The higher rates of ischemic heart disease, end-stage renal disease and proliferative diabetic retinopathy in black rather than in white Brazilians were not explained by differences in conventional risk factors. Identifying which aspects of ethnicity confer a higher risk for these complications in black patients is crucial in order to understand why such differences exist and to develop more effective strategies to reduce the onset and progression of these complications.