The ability of male rats to accumulate menaquinone-4 (MK-4) in tissues when fed a vitamin K-deficient diet supplemented with intraperitoneal phylloquinone (K) as the sole source of vitamin K for 14 d was assessed. In both conventionally housed controls and gnotobiotic rats, supplementation with the equivalent of 1500 microg vitamin K/kg diet increased (P < 0.001) tissue MK-4 concentrations above those of controls fed a vitamin K-deficient diet. MK-4 concentrations were approximately 5 ng/g (11 pmol/g) in liver, 14 ng/g in heart, 17 ng/g in kidney, 50 ng/g in brain and 250 ng/g in mandibular salivary glands of gnotobiotic rats. MK-4 concentrations in conventionally housed rats were higher than in gnotobiotic rats in heart (P < 0.01), brain (P < 0.01) and kidney (P < 0.05) but lower in salivary gland (P < 0.05). Cultures of a kidney-derived cell line (293) converted K to the expoxide of MK-4 in a manner that was dependent on both time of incubation and concentration of vitamin K in the media. A liver-derived cell line (H-35) was less active in carrying out this conversion. These data offer conclusive proof that the tissue-specific formation of MK-4 from K is a metabolic transformation that does not require bacterial transformation to menadione as an intermediate in the process.

CU were more likely than AO to drive over the .08 BAC driving limit (53% vs. 38%; p = .009) and after knowing they were too drunk to drive (57% vs. 44%; p = .025). CU were also more likely (56% vs. 35%; p = .000) to ride with an intoxicated driver while knowing it was unsafe. Conclusions/Importance: Combined-users are more likely to drive after drinking, drive while knowingly drunk, and participate in other high-risk behaviors such as heavy drinking that increase the potential for injury. Public policy makers and health professionals should focus prevention efforts to reduce high-risk combined-use behavior.

muscle insulin sensitivity improves with short-term reduction in calorie intake. The goal of this study was to evaluate changes in the abundance and phosphorylation of Akt1 and Akt2 as potential mechanisms for enhanced insulin action after 20 days of moderate calorie restriction [CR; 60% of ad libitum (AL) intake] in rat skeletal muscle. We also assessed changes in the abundance of SH2 domain-containing inositol phosphatase (SHIP2), a negative regulator of insulin signaling. Fisher 344 ϫ Brown Norway rats were assigned to an AL control group or a CR treatment group for 20 days. Epitrochlearis muscles were dissected and incubated with or without insulin (500 U/ml). Total Akt serine and threonine phosphorylation was significantly increased by 32 (P Ͻ 0.01) and 30% (P Ͻ 0.005) in insulin-stimulated muscles from CR vs. AL. Despite an increase in total Akt phosphorylation, there was no difference in Akt1 serine or Akt1 threonine phosphorylation between CR and AL insulin-treated muscles. However, there was a 30% decrease (P Ͻ 0.05) in Akt1 abundance for CR vs. AL. In contrast, there was no change in Akt2 protein abundance, and there was a 94% increase (P Ͻ 0.05) in Akt2 serine phosphorylation and an increase of 75% (P Ͻ 0.05) in Akt2 threonine phosphorylation of insulin-stimulated CR muscles compared with AL. There was no diet effect on SHIP2 abundance in skeletal muscle. These results suggest that, with brief CR, enhanced Akt2 phosphorylation may play a role in increasing insulin sensitivity in rat skeletal muscles. dietary restriction; insulin signaling; glucose transport; SH2 domain-containing inositol phosphatase; protein kinase B MODERATE CALORIE RESTRICTION [CR; 25-40% reduction in food intake compared with ad libitum (AL)] improves insulin action in a variety of species, including mice, rats, rhesus monkeys, and humans (2,22,24,28,39) and leads to enhanced insulin-stimulated glucose transport in skeletal muscle (9) with 20 days of calorie restriction (10,16,18,20). Skeletal muscle accounts for ϳ85% of insulin-stimulated blood glucose clearance (21), and glucose transport is a key rate-limiting step in muscle glucose utilization (48). Therefore, changes in skeletal muscle glucose metabolism are important for the enhanced, whole body insulin action seen with CR.Brief CR increases translocation of the glucose transporter GLUT4 to the cell membrane in skeletal muscle after insulin stimulation (17). The CR effect on glucose transport is specific to the insulin-mediated pathway, because there is no effect of diet on basal glucose transport or hypoxia-stimulated glucose transport (17). These findings suggest that CR acts on the insulinsignaling pathway, but the specific cellular mechanism leading to the CR enhancement on insulin-stimulated GLUT4 translocation has not yet been identified. With brief CR, there is no change in insulin receptor number and binding affinity (3) nor its tyrosine kinase activity (11), indicating a postinsulin receptor mechanism. Accordingly, we first performed a series of experiments focused ...

. Calorie restriction increases muscle insulin action but not IRS-1-, IRS-2-, or phosphotyrosine-PI 3-kinase. Am J Physiol Endocrinol Metab 282: E270-E276, 2002; 10.1152/ajpendo.00232.2001.-Skeletal muscle insulin sensitivity improves with a moderate reduction in caloric intake. We studied possible mechanisms in calorie-restricted [CR: 60% ad libitum (AL) intake] compared with AL rats, utilizing a time-matched feeding protocol (3, 5, 10, or 20 days). Visceral fat mass was lower for CR vs. AL at 10 and 20 days, but insulin-stimulated muscle 3-O-methylglucose transport was higher in CR vs. AL rats only at 20 days. Fructose 6-phosphate (precursor for the hexosamine biosynthetic pathway, which has inverse relationship with insulin sensitivity) was reduced only at 3 days of CR. Insulin stimulation of insulin receptor substrate (IRS)-1-, IRS-2-, and antiphosphotyrosineassociated phosphatidylinositol 3-kinase (PI3K) was similar for CR and AL. A PI3K inhibitor, wortmannin, reduced insulin-stimulated 3-O-methylglucose transport to basal levels, regardless of diet. With brief time-matched CR, reduced visceral fat mass precedes increased insulin sensitivity; transient reduction in fructose 6-phosphate may trigger more persistent changes but does not coincide with enhanced insulin action; and PI3K is essential for insulin-stimulated 3-O-methylglucose transport in CR as well as AL rats, although insulin-stimulated PI3K is not significantly greater in CR compared with AL animals. glucose transport; food restriction; dietary restriction; insulin signaling MODERATE CALORIE RESTRICTION (CR; consuming 60-75% of ad libitum intake) improves insulin action, and a pivotal adaptation to CR is the enhanced insulin-stimulated glucose transport in skeletal muscle (18). Skeletal muscle accounts for most of the whole body insulin-mediated glucose clearance (14,19), and glucose transport appears to be the rate-limiting step of glucose metabolism in skeletal muscle (28). Little is known about the cellular mechanisms underlying this process. Elucidating these mechanisms has importance for both fundamental biology and clinical application. Our overall hypothesis is that CR induces changes in the skeletal muscle insulin-signaling pathway, secondary to changes in the metabolic milieu of the muscle (for example, changes in concentrations of key metabolites).In this study, our first goal was to evaluate the time course for CR effects on glucose transport. We previously characterized the time course for increased insulin sensitivity with brief CR and found increased glucose transport after 5 days of CR despite no significant reduction in visceral fat mass detected at 5 days of CR, suggesting that a substantial decline in this tissue mass was not essential for the improved insulin action (4). In that study, CR animals were provided their feed in a single daily allotment, whereas controls had continuous access to feed. With this conventional (once daily) feeding approach, CR rats eat all of their food within 2-3 h of being fed, whereas ad libitum-fe...

Previous studies have demonstrated enhanced insulin sensitivity in calorie-restricted [CR, fed 60% ad libitum (AL) one time daily] compared with AL-fed rats. To evaluate the effects of reduced food intake, independent of temporal differences in consumption, we studied AL (unlimited food access)-fed and CR (fed one time daily) rats along with groups temporally matched for feeding [fed 3 meals (M) daily]: MAL and MCR, eating 100 and 60% of AL intake, respectively. Insulin-stimulated glucose transport by isolated muscle was increased in MCR and CR vs. AL and MAL; there was no significant difference for MCR vs. CR or MAL vs. AL. Intramuscular triglyceride concentration, which is inversely related to insulin sensitivity in some conditions, did not differ among groups. Muscle concentration of UDP-N-acetylhexosamines [end products of the hexosamine biosynthetic pathway (HBP)] was lower in MCR vs. MAL despite unaltered glutamine-fructose-6-phosphate aminotransferase activity (rate-limiting enzyme for HBP). These results indicate that the CR-induced increase in insulin-stimulated glucose transport in muscle is attributable to an altered amount, not timing, of food intake and is independent of lower triglyceride concentration. They further suggest that enhanced insulin action might involve changes in HBP.