Insulin therapy does not interfere with venous endothelial function evaluation in patients with type 2 diabetes mellitus

Hypoglycemic agents and potential anti-inflammatory activity

Current literature shows an association of diabetes and secondary complications with chronic inflammation. Evidence of these immunological changes include altered levels of cytokines and chemokines, changes in the numbers and activation states of various leukocyte populations, apoptosis, and fibrosis during diabetes. Therefore, treatment of diabetes and its complications may include pharmacological strategies to reduce inflammation. Apart from anti-inflammatory drugs, various hypoglycemic agents have also been found to reduce inflammation that could contribute to improved outcomes. Extensive studies have been carried out with thiazolidinediones (peroxisome proliferator-activated receptor-γ agonist), dipeptidyl peptidase-4 inhibitors, and metformin (AMP-activated protein kinase activator) with each of these classes of compounds showing moderate-to-strong anti-inflammatory action. Sulfonylureas and alpha glucosidase inhibitors appeared to exert modest effects, while the injectable agents, insulin and glucagon-like peptide-1 receptor agonists, may improve secondary complications due to their anti-inflammatory potential. Currently, there is a lack of clinical data on anti-inflammatory effects of sodium–glucose cotransporter type 2 inhibitors. Nevertheless, for all these glucose-lowering agents, it is essential to distinguish between anti-inflammatory effects resulting from better glucose control and effects related to intrinsic anti-inflammatory actions of the pharmacological class of compounds.

Effect of acute inspiratory muscle exercise on blood flow of resting and exercising limbs and glucose levels in type 2 diabetes

To evaluate the effects of inspiratory loading on blood flow of resting and exercising limbs in patients with diabetic autonomic neuropathy. Ten diabetic patients without cardiovascular autonomic neuropathy (DM), 10 patients with cardiovascular autonomic neuropathy (DM-CAN) and 10 healthy controls (C) were randomly assigned to inspiratory muscle load of 60% or 2% of maximal inspiratory pressure (PImax) for approximately 5 min, while resting calf blood flow (CBF) and exercising forearm blood flow (FBF) were measured. Reactive hyperemia was also evaluated. From the 20 diabetic patients initially allocated, 6 wore a continuous glucose monitoring system to evaluate the glucose levels during these two sessions (2%, placebo or 60%, inspiratory muscle metaboreflex). Mean age was 58 ± 8 years, and mean HbA1c, 7.8% (62 mmol/mol) (DM and DM-CAN). A PImax of 60% caused reduction of CBF in DM-CAN and DM (P<0.001), but not in C, whereas calf vascular resistance (CVR) increased in DM-CAN and DM (P<0.001), but not in C. The increase in FBF during forearm exercise was blunted during 60% of PImax in DM-CAN and DM, and augmented in C (P<0.001). Glucose levels decreased by 40 ± 18.8% (P<0.001) at 60%, but not at 2%, of PImax. A negative correlation was observed between reactive hyperemia and changes in CVR (Beta coefficient = -0.44, P = 0.034). Inspiratory muscle loading caused an exacerbation of the inspiratory muscle metaboreflex in patients with diabetes, regardless of the presence of neuropathy, but influenced by endothelial dysfunction. High-intensity exercise that recruits the diaphragm can abruptly reduce glucose levels.

Reduced endothelial function in the skin in Southeast Asians compared to Caucasians

BACKGROUND

The reaction of vascular endothelial cells to occlusion and heat in Southeast Asian Indians (SAI) compared to Caucasians (C) has not been studied, although genetic differences are found in endothelial cells between the races.

MATERIAL/METHODS

Ten C and Ten SAI (<35 years old) male and female subjects participated. There was no difference in the demographics of the subjects except that the SAI group had been in the United States for 6 months; C was natives to the US. Endothelial function was assessed by the response of the circulation (BF) to local heating and the response to vascular occlusion. The effects of local heat on circulation in the skin on the forearm was assessed by applying heat for 6 minutes at temperatures, 38, 40 and 42°C on 3 separate days. On different days, vascular occlusion was applied for 4 minutes to the same arm and skin blood flow was measured for 2 minutes after occlusion; skin temperature was either 31°C or 42°C.

RESULTS

When occlusion was applied at a skin temperature of 31°C, the BF response to occlusion was significantly lower in the SAI cohort compared to C (peak BF C = 617 ± 88.2 flux, SAE = 284 ± 73 flux). The same effect was seen at skin temperatures of 42°C. The circulatory response to heat was also significantly less in SAI compared to C at each temperature examined (p<0.05)(for temperatures of 38, 40 and 42°C, peak blood flow for C was 374.7 ± 81.2, 551.9 ± 91.3 and 725.9 ± 107 flux respectively and 248.5 ± 86.2, 361.4 ± 104.3 and 455.3 ± 109.7 flux respectively for SAI. (p<0.05).

CONCLUSIONS

Thus there seems to be big differences in these 2 populations in endothelial response to these stressors. The difference may be due to genetic variations between the 2 groups of subjects.

Effects of diabetes on myocardial capillary density and serum angiogenesis biomarkers in male rats

INTRODUCTION

Cardiovascular disease is one of the main causes of mortality and morbidity in diabetic patients. This study evaluated the effects of diabetes on myocardial capillary density and several serum angiogenic factors including nitric oxide, vascular endothelial growth factor, and soluble vascular endothelial growth factor receptors.

METHODS

Twelve male rats were divided into two groups: control and diabetic (n = 6 each). Diabetes was induced with a single dose of streptozotocin (50 mg/kg). After 21 days, capillary density in the myocardial tissue was evaluated using immunohistochemical staining and is reported as capillaries per mm². Blood samples were collected before and after the induction of diabetes.

RESULTS

In the diabetic group, serum nitric oxide and soluble vascular endothelial growth factor receptor 2 concentrations were lower than the levels in the control group, while the level of soluble vascular endothelial growth factor receptor 1 was significantly higher. There was no significant change in the serum vascular endothelial growth factor concentration between the diabetic and control groups; however, the ratio of vascular endothelial growth factor to vascular endothelial growth factor receptor 1 was significantly lower in the diabetic animals. The myocardial capillary density was also lower in the diabetic group compared with the control group (1549 ± 161 vs. 2156 ± 202/mm², respectively).

CONCLUSION

Reduced serum nitric oxide and vascular endothelial growth factor receptor 2 levels, increased serum vascular endothelial growth factor receptor 1 levels and a lower vascular endothelial growth factor to vascular endothelial growth factor receptor 1 ratio may be responsible for the decreased myocardial capillary density in diabetic rats.