Table 2.
The effect of inorganic nitrate on brain insulin action (A) and CBF response to nasal insulin during the placebo test day (B) in a randomized, double-blind, controlled crossover study with abdominally obese men1.
| A | Inorganic nitrate |
Placebo |
Mean difference |
Volume |
P-value 2 |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (mL/100 g/min) | (mL/100 g/min) | (mL/100 g/min) | (mm3) | |||||||||
| Treatment * insulin | Cluster 1 N | 2.7 | ± | 3.2 | −4.2 | ± | 4.9 | 7.0 | ± | 3.8 | 5296 | < 0.001 |
| Cluster 2 N | 3.2 | ± | 4.0 | −3.3 | ± | 4.2 | 6.5 | ± | 4.3 | 3592 | < 0.001 | |
| Cluster 3 N | 4.7 | ± | 2.8 | −1.2 | ± | 2.6 | 5.9 | ± | 3.2 | 1792 | < 0.001 | |
| Cluster 4 N | 4.3 | ± | 3.5 | −4.7 | ± | 5.0 | 9.0 | ± | 6.0 | 1096 | 0.007 | |
| Cluster 5 N | 4.5 | ± | 3.6 | −1.6 | ± | 3.4 | 6.1 | ± | 4.3 | 1024 | 0.012 | |
| B |
Pre-insulin | Post-insulin | Mean difference | Volume | P-value 2 | |||||||
| (mL/100 g/min) | (mL/100 g/min) | (mL/100 g/min) | (mm3) | |||||||||
| Insulin | Cluster 1I | 49.7 | ± | 10.5 | 53.2 | ± | 11.1 | 3.5 | ± | 2.4 | 1976 | < 0.001 |
| Cluster 2I | 47.1 | ± | 9.0 | 51.1 | ± | 9.0 | 4.0 | ± | 3.3 | 1336 | 0.002 | |
| Cluster 3I | 50.3 | ± | 10.9 | 53.3 | ± | 11.4 | 3.0 | ± | 1.9 | 1064 | 0.011 | |
| Cluster 4I | 41.8 | ± | 6.9 | 45.3 | ± | 7.0 | 3.6 | ± | 2.8 | 992 | 0.018 | |
| Cluster 5I | 50.6 | ± | 13.8 | 44.0 | ± | 12.4 | −6.5 | ± | 7.4 | 1368 | 0.001 | |
| Cluster 6I | 56.5 | ± | 14.1 | 51.1 | ± | 14.6 | −5.4 | ± | 4.3 | 952 | 0.023 | |
| Cluster 7I | 52.5 | ± | 16.8 | 45.9 | ± | 15.9 | −6.6 | ± | 5.9 | 944 | 0.025 | |
| Cluster 8I | 40.7 | ± | 9.4 | 35.1 | ± | 7.6 | −5.6 | ± | 5.1 | 872 | 0.042 | |
Values are shown as means ± SD. n = 18.
Clusters were the result of a voxel-wise analysis applying a repeated measures mixed effects analysis using a general linear model with a single-group paired difference (FLAME stage 1 and 2), and a Z-threshold of 2.3 (P < 0.05). Family-wise error correction was performed based on smoothness estimates. The effect of inorganic nitrate on brain insulin action (treatment * insulin) was assessed using the difference between the post-insulin and pre-insulin CBF-maps during the nitrate and placebo test day (cluster N). For evaluation of brain insulin action, the post-insulin and pre-insulin scans during the placebo test day were compared (Cluster I). Inorganic nitrate did not affect CBF when the scans after the nitrate and placebo pre-insulin administration were compared.