Nooshin Naghavi

Thermoregulatory responses are attenuated after fructose but not glucose intake.

PURPOSE We examined whether plasma hyperosmolality induced by oral monosaccharide intake attenuated thermoregulatory responses and whether the responses were different between fructose and glucose. METHODS Ten healthy young subjects performed three trials in a sitting position in an artificial climate chamber (ambient temperature, 28°C; relative humidity, 40%). After resting for 10 min, the subjects drank 300 mL of water alone (control), or 300 mL of water supplemented with 75 g fructose or 75 g glucose. Twenty minutes later, they were heated passively by immersing the lower legs in water at 42°C for 60 min. Plasma osmolality (Posm), sodium ([Na+]p) and insulin concentrations ([Ins]p), and percent change in plasma volume (%ΔPV) were measured, and esophageal temperature (Tes) thresholds for cutaneous vasodilation (THCVC) and sweating (THSR) at the forearm were determined. RESULTS Posm was significantly increased by fructose and glucose intake compared with water alone, although %ΔPV and [Na+]p were not significantly different among the three trials. [Ins]p was significantly higher after glucose intake than after fructose or water alone. THCVC and THSR were significantly higher after fructose intake than after glucose intake, which showed similar values to water intake. CONCLUSIONS These results suggest that the Tes threshold for thermoregulation is elevated after fructose intake, indicating the attenuation of thermoregulatory responses, whereas it is not attenuated after glucose intake. These results provide a novel insight to better determine the carbohydrate component of oral rehydration fluids for preventing dehydration and/or heat disorders.

Forced respiration during the deeper water immersion causes the greater inspiratory muscle fatigue in healthy young men.

[Purpose] The purpose of the present study was to evaluate the effect of water immersion at different water depths on respiratory function and the effect of inspiratory load breathing (ILB) during water immersion at different water depths on respiratory muscle strength evaluated by maximum inspiratory and expiratory pressures (PImax and PEmax, respectively). [Subjects] Eight healthy men participated randomly in three trials. [Methods] All sessions were conducted with the participants in a sitting position immersed in a water bath. We evaluated respiratory function, PImax and PEmax during submersion at three different levels of water depth (umbilicus; 4th-rib; or clavicle, CL) and after subsequent 15-min ILB. [Results] Decreases in vital capacity and expiratory reserve volume from baseline by water immersion were significantly greater in the CL trial than those in the other trials. In the CL trial, PImax was immediately reduced after ILB compared to that at baseline, and the reduction was significantly greater than those in the other trials. PEmax was not affected by ILB in any of the trials. [Conclusion] Forced respiration during deeper water immersion caused greater inspiratory muscle fatigue in healthy young men.

The combination of exercise training and Zataria multiflora supplementation increase serum irisin levels in postmenopausal women

Background We examined the effect of antioxidant supplementation and exercise on irisin within postmenopausal women. Methods Forty-eight participants (age: 55.7 ± 4.9 years; weight: 68.0 ± 6.3 kg; BMI 27.0 ± 2.7; mean ± SD) were randomized into four groups for the eight week intervention: control group (CG; n = 12), resistance training group (RTG; n = 12), supplementation with Zataria multiflora group (ZG; n = 12), or supplementation with Z. multiflora and resistance training group (ZRTG; n = 12). RTG and ZRTG performed circuit resistance training, and both ZG and ZRTG consumed 500 mg of Z. multiflora every day during the intervention. Blood samples were taken 48 hours before and after the intervention. Results There was a significant difference in irisin at post-training, with greater levels in ZRTG compared to CG. A significant increase was noted for irisin at post-training compared to pre-training for ZG, RTG, and ZRTG. Moreover, we identified a significant decrease in malondialdehyde in the RTG and ZRTG groups and increase in glutathione in the ZG, RTG, and ZRTG groups when compared to CG. Conclusion These findings showed that exercise, Z. multiflora supplementation or their combination led to an increase in irisin.

Intranasal insulin administration does not modulate incretin secretion, gastric emptying, and appetite in healthy young adults

Intranasal insulin (INS) administration reduces food intake and body weight in humans. It remains unclear whether the intranasal delivery of INS to the brain affects incretin secretion via the brain–gut axis. In the present study, we examined the effect of intranasal INS administration on glucagon-like peptide-1 (GLP-1) secretion, gastric emptying, and appetite. Thirteen normal-weight, healthy, young volunteers (age 21.2 ± 2.9 (SD) years) participated in a randomized single-blind, crossover study. Sixteen puffs of regular INS (10 IU; total dose, 160 IU) or normal saline as a placebo (0.1 mL, with a total dose of 1.6 mL) were intranasally administered in a random order after an overnight fast. Afterward, a fixed meal test, including 1,500 mg paracetamol to measure gastric emptying, was performed in each participant. Blood glucose, INS, the active form of GLP-1, paracetamol, and postprandial satiety (measured using the visual analog scale) levels were evaluated during the 180-min meal test. Meal intake similarly induced the elevation of blood glucose, INS, and GLP-1 levels in both trials. The total increases in blood glucose, INS, and GLP-1 levels during the meal test evaluated by the area under the curve were not different between the trials. Gastric emptying velocity and postprandial satiety were not significantly different either. In conclusion, we could find no significant effect of intranasal delivery of INS to the brain on postprandial GLP-1 secretion, gastric emptying, or postprandial satiety in the present study with healthy young adults.