Toward a more standardised and accurate evaluation of glycemic response to foods: recommendations for portion size calculation.

This study aimed at evaluating the adequacy of calculation methods for portions to be provided to subjects in clinical trials evaluating glycemic response to foods. Portion sizes were calculated for 140 food samples, based on Nutrition Facts labels (current practice) and actual available carbohydrate content (current recommendation), and compared against the amount of monosaccharides yielded by the digestive breakdown of their actual available carbohydrate content (basis for glycemic response to food). The current practice can result in significant under- or over-feeding of carbohydrates in 10% of tested cases, as compared to the targeted reference dosage. The method currently recommended can result in significantly inadequate yields of monosaccharides in 24% of tested cases. The current and recommended calculation methods do not seem adequate for a standardised evaluation of glycemic response to foods. It is thus recommended to account for the amount of absorbable monosaccharides of foods for portion size calculation.

Glycerol-3-phosphate acyltransferase-1 gene ablation results in altered thymocyte lipid content and reduces thymic T cell production in mice.

Glycerol 3-phosphate acyltransferase-1 (GPAT-1) catalyzes the initial and rate-limiting step in de novo glycerophospholipid and triacylglycerol (TAG) biosynthesis. We have previously shown that peripheral T cell proliferation and cytokine production is altered in GPAT-1 gene-ablated (KO) mice. This finding is important in light of the reduction in GPAT-1 activity associated with aged T cells. To determine if the mechanism for altered peripheral T cell function is linked to altered T cell development, we assessed thymic function in 3, 6 and 16-week old GPAT-1 KO compared to wild type (WT) mice. At 16 weeks of age, there was a significant reduction in thymic T cell production in KO compared to WT mice but not at 6 weeks of age. The reduced thymic T cell production was associated with altered thymic development as confirmed by increased numbers of double-negative (DN) thymocytes and a significant reduction in the double positive (DP) thymocytes suggesting a developmental block at the DN stage. This change was accompanied by an increase in the single positive CD4 subset. These changes were associated with reduced glycerophospholipid mass while thymic cortex and medulla architecture was not altered by GPAT-1 KO. Taken together, these data suggest that GPAT-1 deletion is capable of reducing the number of new T cells produced via alterations in membrane receptor function rather than by causing deleterious changes within the thymic microenvironment explaining in part the observed alterations in peripheral T cell function.

Resveratrol inhibits the deleterious effects of diet-induced obesity on thymic function.

Obesity is associated with an increased risk of infectious diseases. It has been shown to have deleterious effects on cell-mediated immunity, including reducing thymocyte numbers and altering responses of thymocytes to pathogens. In the current study, we examined the efficacy of the antiobesity phytochemical resveratrol in preventing the deleterious effects of a high-fat diet on thymic anatomy and function. Compared to C57Bl/6 male mice fed a low-fat diet, mice on a high-fat diet had a significant increase in thymic weight and lipid content, and a disrupted anatomy, including a reduction of the medullary compartment and absence of a corticomedullary junction. There were a decrease in thymic cellularity and mature T-cell output, and a disrupted T-cell maturation, as evidenced by increased double-negative and decreased single- and double-positive thymocytes. Mice that had been fed resveratrol along with a high-fat diet had a dose-dependent reversal in all these parameters. Western blots from thymi showed that obese mice had lower levels of the key stimulators of lipid metabolism, phospho-5' adenosine monophosphate-activated protein kinase and its downstream target, carnitine palmitoyl transferase-1; this was restored to normal levels in resveratrol-fed mice. Resveratrol also reversed an increase in glycerol-3-phosphate acyltransferase-1, the enzyme that catalyzes the first step in triglycerol synthesis. Taken together, these results indicate that resveratrol is a potent inhibitor of the deleterious effects of diet-induced obesity on thymic anatomy and function, and this may hold promise in preventing obesity-related deficits in cell-mediated immunity.

In vitro antioxidant capacity and anti-inflammatory activity of seven common oats.

Oats are gaining increasing scientific and public interest for their purported antioxidant-associated health benefits. Most reported studies focused on specific oat extracts or particular oat components, such as ß-glucans, tocols (vitamin E), or avenanthramides. Studies on whole oats with respect to antioxidant and anti-inflammatory activities are still lacking. Here the antioxidant and anti-inflammatory activities from whole oat groats of seven common varieties were evaluated. All oat varieties had very similar oxygen radical absorption capacity compared with other whole grains. In an anti-inflammatory assay, oat variety CDC Dancer inhibited tumor necrosis factor-α induced nuclear factor-kappa B activation by 27.5% at 2 mg/ml, whereas variety Deiter showed 13.7% inhibition at a comparable dose. Avenanthramide levels did not correlate with the observed antioxidant and anti-inflammatory activities. Further investigations are needed to pinpoint the specific antioxidant and anti-inflammatory compounds, and potential synergistic and/or matrix effects that may help explain the mechanisms of oat's anti-inflammatory actions.