We developed an inexpensive, culturally sensitive diabetes prevention program that resulted in weight loss, improved HbA1c, and improved insulin resistance in a high-risk Latino population.

Lipoic acid (thiotic acid) is being used as a dietary supplement, and as a therapeutic agent, and is reported to have beneficial effects in disorders associated with oxidative stress, but its mechanism of action remains unclear. We present evidence that lipoic acid induces a substantial increase in cellular reduced glutathione in cultured human Jurkat T cells human erythrocytes, C6 glial cells, NB41A3 neuroblastoma cells, and peripheral blood lymphocytes. The effect depends on metabolic reduction of lipoic acid to dihydrolipoic acid. Dihydrolipoic acid is released into the culture medium where it reduces cystine. Cysteine thus formed is readily taken up by the neutral amino acid transport system and utilized for glutathione synthesis. By this mechanism lipoic acid enables cystine to bypass the xc- transport system, which is weakly expressed in lymphocytes and inhibited by glutamate. Thereby lipoic acid enables the key enzyme of glutathione synthesis, gamma-glutamylcysteine synthetase, which is regulated by uptake-limited cysteine supply, to work at optimum conditions. Flow cytometric analysis of freshly prepared human peripheral blood lymphocytes, using monobromobimane labeling of cellular thiols, reveals that lipoic acid acts mainly to normalize a subpopulation of cells severely compromised in thiol status rather than to increase thiol content beyond physiological levels. Hence lipoic acid may have clinical relevance in restoration of severely glutathione deficient cells.

The protective effect of vitamin E supplementation on exercise-induced oxidative damage was tested in 21 male volunteers. Nine young (22-29 yr) and 12 older (55-74 yr) sedentary male subjects participated in a double-blind protocol and received either 800 IU dl-alpha-tocopherol or a placebo daily. After 48 days, vitamin E supplementation significantly increased alpha-tocopherol in plasma and skeletal muscle. Subjects then performed a bout of eccentric exercise at 75% of their maximum heart rate by running down an inclined treadmill for 45 min. All vitamin E-supplemented subjects excreted less (P < 0.05) urinary thiobarbituric acid adducts after the exercise bout than placebo subjects at 12 days postexercise (35 and 18% above baseline in young and old supplemented groups, respectively, vs. 60 and 80% in young and old placebo groups, respectively). After exercise, the initial difference in alpha-tocopherol concentration of muscle between young placebo and vitamin E-supplemented groups was diminished and muscle lipid conjugated dienes tended to increase (P = 0.09) in placebo subjects. Placebo subjects had a significant decrease in major fatty acids of muscle biopsy taken immediately after exercise. When normalized for the hemoconcentration effects of exercise, the plasma concentration of vitamins E and C and uric acid showed no significant change. The alterations in fatty acid composition, vitamin E, and lipid conjugated dienes in muscle and in urinary lipid peroxides in controls after eccentric exercise are consistent with the concept that vitamin E provides protection against exercise-induced oxidative injury.

Background:The food matrix in which carotenoids are found affects their bioavailability. Lutein and zeaxanthin are abundant in egg yolks and accumulate in the macular region of the retina, where they may affect visual function. Objective: We sought to determine whether plasma lutein and zeaxanthin concentrations are elevated after dietary supplementation with egg yolk. Design: Eleven moderately hypercholesterolemic men and women consumed 2 separate baseline diets, which contained 29-33% of energy as total fat, with 20% of energy as either beef tallow or corn oil. These diets were supplemented with cooked chicken egg yolks (1.3 egg yolks/d for an intake of 10.4 MJ). Each subject consumed all 4 diets. Each diet was consumed for 4.5 wk, with a washout period of ≥ 2 wk between diet phases. At the end of each diet phase, fasting morning plasma samples were collected and stored for carotenoid analysis by HPLC. Commercial chicken egg yolks were analyzed for carotenoids and cholesterol. Results: Egg yolk supplementation of the beef tallow diet increased plasma lutein by 28% (P < 0.05) and zeaxanthin by 142% (P < 0.001); supplementation of the corn oil diet increased plasma lutein by 50% (P < 0.05) and zeaxanthin by 114% (P < 0.001). Changes in plasma lycopene and ␤-carotene were variable, with no consistent trend. Egg yolk supplementation increased plasma LDL-cholesterol concentrations by 8-11% (P < 0.05). Conclusions: Egg yolk is a highly bioavailable source of lutein and zeaxanthin. The benefit of introducing these carotenoids into the diet with egg yolk is counterbalanced by potential LDL-cholesterol elevation from the added dietary cholesterol.Am J Clin Nutr 1999;70:247-51.