Inconvenient relationship of haemoglobin A1c level with endothelial function in type 2 diabetes in a cross-sectional study

A six-month low-carbohydrate diet high in fat does not adversely affect endothelial function or markers of low-grade inflammation in patients with type 2 diabetes: an open-label randomized controlled trial

BACKGROUND

While a low-carbohydrate diet (LCD) reduces HbA1c in patients with type 2 diabetes (T2D), the associated high intake of fat may adversely affect cardiovascular risk factors. To address this, we examined the effect of a non-calorie-restricted LCD high in fat on endothelial function and markers of low-grade inflammation in T2D over 6 months.

METHODS

In an open-label randomized controlled trial, 71 patients with T2D were randomized 2:1 to either a LCD (< 20 E% carbohydrates, 50-60 E% fat) or a control diet (50-60 E% carbohydrates, 20-30 E% fat) for six months. Flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) were assessed by ultrasound in the brachial artery together with plasma interleukin-6 (IL-6) and serum high-sensitivity C-reactive protein (hsCRP) in the participants at baseline (n = 70) and after six months (n = 64).

RESULTS

The FMD and NID were unaltered in both groups after six months, and there were no between-group differences in change of either FMD (p = 0.34) or NID (p = 0.53) in response to the interventions. The circulating hsCRP and IL-6 levels decreased only in response to LCD (both p < 0.05). However, comparing changes over time with the control diet, the LCD did not reduce either IL-6 (p = 0.25) or hsCRP (p = 0.07) levels. The lack of changes in FMD and NID in response to LCD persisted after adjustment for cardiovascular risk factors.

CONCLUSION

A LCD high in fat for six months does not adversely affect endothelial function or selected markers of low-grade inflammation, which suggests that this nutritional approach does not increase the risk of cardiovascular disease. Trial registration ClinicalTrials.gov (NCT03068078).

Relationship between hemoglobin A1c level and flow-mediated vasodilation in patients with type 2 diabetes mellitus receiving antidiabetic drugs

Aims/Introduction

Diabetes mellitus is associated with endothelial dysfunction. However, it is still controversial as to whether antidiabetic drug treatment affects endothelial function. The purpose of this study was to evaluate the relationships of the hemoglobin A1c (HbA1c) level with flow‐mediated vasodilation (FMD) and nitroglycerine‐induced vasodilation (NID) in patients with type 2 diabetes mellitus who are receiving antidiabetic drugs.

Materials and Methods

The FMD was measured in 866 patients with type 2 diabetes mellitus who were receiving antidiabetic drugs (625 men and 241 women; mean age: 62 ± 10 years). The patients were divided into four groups according to HbA1c levels: <6.5, 6.5–6.9, 7.0–7.9, and ≥8.0%.

Results

There was an inverted U‐shaped pattern of association of the HbA1c level with the FMD at an HbA1c level of about 7% of the peak of FMD in patients with type 2 diabetes mellitus who were receiving antidiabetic drugs. The FMD was significantly smaller in the HbA1c <6.5% group than in the HbA1c 6.5–6.9% group and the HbA1c 7.0–7.9% group (P < 0.001 and P < 0.001, respectively). The FMD values were similar in the HbA1c <6.5% group and HbA1c ≥8.0% group (P = 0.10). There were no significant differences in NID among the four groups (P = 0.98).

Conclusions

These findings suggest that a low HbA1c <6.5% as well as a high HbA1c ≥8.0% is associated with endothelial dysfunction in patients with type 2 diabetes mellitus who are receiving antidiabetic drugs and that vascular smooth muscle function is similar in such patients regardless of the HbA1c level.