Brian S. Snyder

Consumption of cross-linked resistant starch (RS4XL) on glucose and insulin responses in humans.

Objective. The objective was to compare the postprandial glycemic and insulinemic responses to nutrition bars containing either cross-linked RS type 4 (RS4XL) or standard wheat starch in normoglycemic adults (n = 13; age = 27 ± 5 years; BMI = 25 ± 3 kg/m2). Methods. Volunteers completed three trials during which they consumed a glucose beverage (GLU), a puffed wheat control bar (PWB), and a bar containing cross-linked RS4 (RS4XL) matched for available carbohydrate content. Serial blood samples were collected over two hours and glucose and insulin concentrations were determined and the incremental area under the curve (iAUC) was calculated. Results. The RS4XL peak glucose and insulin concentrations were lower than the GLU and PWB (P < .05). The iAUC for glucose and insulin were lower following ingestion of RS4 compared with the GLU and PWB trials. Conclusions. These data illustrate, for the first time, that directly substituting standard starch with RS4XL, while matched for available carbohydrates, attenuated postprandial glucose and insulin levels in humans. It remains to be determined whether this response was due to the dietary fiber and/or resistant starch aspects of the RS4XL bar.

The effects of antioxidants on microvascular oxygenation and blood flow in skeletal muscle of young rats

Alterations of skeletal muscle redox state via antioxidant supplementation have the potential to impact contractile function and vascular smooth muscle tone. The effects of antioxidants on the regulation of muscle O2 delivery–O2 utilization ( ) matching (which sets the microvascular partial pressure of O2; ) in young healthy muscle are not known. Therefore, the purpose of this study was to test the effects of acute antioxidant supplementation on rat spinotrapezius muscle force production, blood flow, and (phosphorescence quenching). Anaesthetized male Fischer 344 × Brown Norway rats (6–8 months old) had their right spinotrapezius muscles either exposed for measurement of blood flow and (n= 13) or exteriorized for measurement of muscle force production (n= 6). Electrically stimulated 1 Hz twitch contractions (∼7–9 V) were elicited for 180 s, and measurements were made before and after acute intra‐arterial antioxidant supplementation (76 mg kg−1 ascorbic acid, 52 mg kg−1 tempol) dissolved in saline and infused over 30 min. The principal effects of antioxidants were a ∼25% decrease (P < 0.05) in contracting spinotrapezius muscle force production concurrent with reductions in muscle blood flow and at rest and during contractions (P < 0.05 for both). Antioxidant supplementation reduced the resting baseline (before, 29.9 ± 1.2 mmHg; after, 25.6 ± 1.3 mmHg; P < 0.05), and this magnitude of depression was sustained throughout the rest‐to‐exercise transition (steady‐state value before, 16.4 ± 0.7 mmHg; after, 13.6 ± 0.9 mmHg; P < 0.05). In addition, the time constant of the decrease was reduced after antioxidant supplementation (before, 23.4 ± 4.3 s; after, 15.6 ± 2.7 s; P < 0.05). These results demonstrate that antioxidant supplementation significantly impacts the control of in young rats at rest and during contractions.