Vitamin K deficiency of germfree mice caused by feeding standard purified diet sterilized by gamma-irradiation.

Germfree mice died when they were fed a purified diet of AIN-76 formula sterilized by gamma-irradiation. Vitamin K deficiency was suspected and this study was performed to confirm the cause of the death. Germfree mice were fed purified diets of AIN-76 or AIN-93M formula, which were pelleted and sterilized by gamma-irradiation at a dose of 50 kGy. One half of the mice fed the AIN-76 diet died within two weeks and the surviving animals were also in poor health, while 91% of mice fed the AIN-93M diet survived. No hemorrhage was observed grossly in any organs of the surviving animals. Histologically, degeneration with inflammatory cell infiltration was observed as well as hemorrhage and fibrosis in the heart muscles of mice fed the AIN-76 diet. No microscopic lesions were observed in the other organs. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were extremely prolonged when mice were fed the AIN-76 diet. The animals totally recovered when they were intragastrically administered 1 microg/day of vitamin K(3) from the third day of feeding of the AIN-76 diet, except for PT and APTT which were still slightly longer than in mice fed the AIN-93M diet. The concentration of vitamin K(3) supplied in the AIN-76 diet decreased to an undetectable level after gamma-irradiation, while the AIN-93M diet contained 240 microg/kg of vitamin K(1). These results indicate that the deaths of the germfree mice fed the gamma-irradiated AIN-76 diet were caused by vitamin K deficiency. Vitamin K deficiency may cause fatal degeneration of cardiac muscle cells.     

Carbohydrate supercompensation and muscle glycogen utilization during exhaustive running in highly trained athletes

Three female and three male highly trained endurance runners with mean maximal oxygen uptake (VO2max) values of 60.5 and 71.5 ml.kg-1.min-1, respectively, ran to exhaustion at 75%-80% of VO2max on two occasions after an overnight fast. One experiment was performed after a normal diet and training regimen (Norm), the other after a diet and training programme intended to increase muscle glycogen levels (Carb). Muscle glycogen concentration in the gastrocnemius muscle increased by 25% (P less than 0.05) from 581 mmol.kg-1 dry weight, SEM 50 to 722 mmol.kg-1 dry weight, SEM 34 after Carb. Running time to exhaustion, however, was not significantly different in Carb and Norm, 77 min, SEM 13 vs 70 min, SEM 8, respectively. The average glycogen concentration following exhaustive running was 553 mmol.kg-1 dry weight, SEM 70 in Carb and 434 mmol.kg-1 dry weight, SEM 57 in Norm, indicating that in both tests muscle glycogen stores were decreased by about 25%. Periodic acid-Schiff staining for semi-quantitative glycogen determination in individual fibres confirmed that none of the fibres appeared to be glycogen-empty after exhaustive running. The steady-state respiratory exchange ratio was higher in Carb than in Norm (0.92, SEM 0.01 vs 0.89, SEM 0.01; P less than 0.05). Since muscle glycogen utilization was identical in the two tests, the indication of higher utilization of total carbohydrate appears to be related to a higher utilization of liver glycogen. We have concluded that glycogen depletion of the gastrocnemius muscle is unlikely to be the cause of fatigue during exhaustive running at 75%-80% of VO2max in highly trained endurance runners. Furthermore, diet- and training-induced carbohydrate super-compensation does not appear to improve endurance capacity in such individuals.     

Preventive effects of Moringa oleifera (Lam) on hyperlipidemia and hepatocyte ultrastructural changes in iron deficient rats

The effects of Moringa oleifera (MO), Moringaceae on hyperlipidemia and hepatocyte ultrastructural changes caused by iron deficiency were investigated. Four-week-old male Wistar-strain rats were fed a control diet based on AIN-93G (C), an iron deficient diet (FeD), a FeD + 0.5% MO (FeD-m) diet, or a FeD + MO 1% (FeD-M) diet for 4 weeks. It was found that MO reduced iron-deficient diet-induced increases in serum and hepatic lipids with dose-dependent increases of serum quercetin and kaempherol, but did not prevent anemia. By electron microscopy, in iron deficient hepatocytes, slightly swollen mitochondria and few glycogen granules were observed, but glycogen granules increased and mitochondria were normalized by treatment with MO. Furthermore, lipoproteins were observed in the Golgi complex under treatment with MO. These results suggest a possible beneficial effect of MO in the prevention of hyperlipidemia and ultrastructural changes in hepatocytes due to iron-deficiency.     

Preventive Effects of Moringa oleifera (Lam) on Hyperlipidemia and Hepatocyte Ultrastructural Changes in Iron Deficient Rats

The effects of Moringa oleifera (MO), Moringaceae on hyperlipidemia and hepatocyte ultrastructural changes caused by iron deficiency were investigated. Four-week-old male Wistar-strain rats were fed a control diet based on AIN-93G (C), an iron deficient diet (FeD), a FeD + 0.5% MO (FeD-m) diet, or a FeD + MO 1% (FeD-M) diet for 4 weeks. It was found that MO reduced iron-deficient diet-induced increases in serum and hepatic lipids with dose-dependent increases of serum quercetin and kaempherol, but did not prevent anemia. By electron microscopy, in iron deficient hepatocytes, slightly swollen mitochondria and few glycogen granules were observed, but glycogen granules increased and mitochondria were normalized by treatment with MO. Furthermore, lipoproteins were observed in the Golgi complex under treatment with MO. These results suggest a possible beneficial effect of MO in the prevention of hyperlipidemia and ultrastructural changes in hepatocytes due to iron-deficiency.     

Low glycogen and branched-chain amino acid ingestion do not impair anaplerosis during exercise in humans.

We examined the hypothesis that increasing the rate of branched-chain amino acid (BCAA) oxidation, during conditions of low glycogen availability, reduces the level of muscle tricarboxylic acid cycle intermediates (TCAI) by placing a carbon "drain" on the cycle at the level of 2-oxoglutarate. Six men cycled at approximately 70% of maximal oxygen uptake for 15 min under two conditions: 1) low preexercise muscle glycogen (placebo) and 2) low glycogen combined with BCAA ingestion. We have previously shown that BCAA ingestion increased the activity of branched-chain oxoacid dehydrogenase, the rate-limiting enzyme for BCAA oxidation in muscle, compared with low glycogen alone [M. L. Jackman, M. J. Gibala, E. Hultman, and T. E. Graham. Am. J. Physiol. 272 (Endocrinol. Metab. 35): E233-E238, 1997]. Muscle glycogen concentration was 185 +/- 22 and 206 +/- 22 mmol/kg dry wt at rest for the placebo and BCAA-supplemented trials, respectively, and decreased to 109 +/- 18 and 96 +/- 10 mmol/kg dry wt after exercise. The net increase in the total concentration of six measured TCAI ( approximately 95% of TCAI pool) during exercise was not different between trials (3.97 +/- 0. 34 vs. 3.88 +/- 0.34 mmol/kg dry wt for the placebo and BCAA trials, respectively). Muscle 2-oxoglutarate concentration decreased from approximately 0.05 at rest to approximately 0.03 mmol/kg dry wt after exercise in both trials. The magnitude of TCAI pool expansion in both trials was similar to that seen previously in subjects who performed an identical exercise bout after a normal mixed diet [M. J. Gibala, M. A. Tarnopolsky, and T. E. Graham. Am. J. Physiol. 272 (Endocrinol. Metab. 35): E239-E244, 1997]. These data suggest that increasing the rate of BCAA oxidation has no measurable effect on muscle TCAI during exercise with low glycogen in humans. Moreover, it appears that low resting glycogen per se does not impair the increase in TCAI during moderate exercise.     

Iron overload potentiates diet-induced hypercholesterolemia and reduces liver PPAR-α expression in hamsters

Iron stores and lipids are related to the development of cardiovascular disease. Given that peroxisome proliferator-activated receptor alpha (PPAR-α) regulates important physiological processes that impact lipid and glucose homeostasis, we decided to investigate the effects of iron overload on serum lipids and the liver expression of PPAR-α, 3-hydroxy-3-methylglutaryl coenzyme A reductase, and cholesterol 7α-hydroxylase. Hamsters were divided into four groups. The standard group (S) was fed the AIN-93M diet, the SI group was fed the diet and iron injections, the hypercholesterolemic group (H) was fed a standard diet containing cholesterol, and the HI group was fed a high-cholesterol diet and iron injections. Serum cholesterol in the HI group was higher than in the H group. Gene expression analysis of PPAR-α showed that the HI group had a lower PPAR-α expression than H. These data show that iron, when associated with a high-fat diet, can cause increased serum cholesterol levels, possibly due to a reduction in PPAR-α expression.     

Prevention of mammary tumorigenesis by intermittent caloric restriction: does caloric intake during refeeding modulate the response?

Chronic caloric restriction (CCR) prevents mammary tumorigenesis in rodents, but a protective effect for intermittent caloric restriction (ICR) is less well documented. We recently reported that ICR reduced mammary tumor (MT) incidence of mouse mammary tumor virus-transforming growth factor (MMTV-TGF)-alpha mice to a greater extent than did CCR. Here, we repeated this protocol and obtained serum and tissue samples. Ad libitum (AL) MMTV-TGF-alpha mice were fed AIN-93M diet. Beginning at 10 weeks of age, ICR mice received isocaloric AIN-93M-mod diet (2-fold increases in protein, fat, vitamins, and minerals) at 50% of ad libitum for 3 weeks followed by 3 weeks refeeding with AIN-93M diet. CCR mice were pair-fed AIN-93M:AIN-93M-mod (2:1) matching intakes for restriction/refeeding cycles. Mice were sacrificed for MT size, at 79 (end of 12th restriction) or at 80 (1 week after 12th refeeding) weeks of age. AL and ICR-80 mice had heavier body weights than ICR-79 and CCR mice (P < 0.0001). Cumulative food intakes of ICR and CCR mice were reduced 12% and 15% versus AL mice (P < 0.0001). However, ICR mice consumed significantly (P < 0.0001) more food than did AL mice during refeeding. MT incidence was 84%, 13%, and 27% for AL, ICR, and CCR mice, respectively. MT weight (P < 0.0011) and number (P < 0.01) were higher for AL mice compared with ICR and CCR mice. AL and ICR-80 mice had similar serum IGF-I levels, but only AL values were higher than those of ICR-79 and CCR mice (P < 0.0017). ICR mice had more MT DNA breaks compared with AL and CCR mice, suggesting enhanced apoptosis (P < 0.02). AL mice had higher mammary fat pad ObR and ObRb leptin receptor mRNA expression than did ICR and CCR mice (P < 0.001), but there was no effect on MTs. These results confirm that ICR prevents development of MTs to a greater extent than does CCR, although "overeating" during refeeding may compromise this protection.     

The effect of purified compared with nonpurified diet on bone changes induced by hindlimb suspension of female rats

The purpose of this study was to compare the bone changes induced by unloading in rats fed different diets, because space flight studies use a semipurified diet, whereas space flight simulation studies typically use nonpurified diets. Female Sprague-Dawley rats were fed a purified American Institute of Nutrition (AIN) 93G diet or a standard nonpurified diet and kept ambulatory or subjected to unloading by hindlimb suspension (HLS) for 38 days. Bone mineral content (BMC), mechanical strength, and factors related to the diet that affect bone (i.e., urinary calcium excretion, estradiol, and corticosterone) were measured. Average food intakes (grams per day) differed for diets, but caloric intake (kilocalories per day) and the final body masses of treatment groups were similar. The HLS-induced decrease in femoral BMC was not statistically different for rats fed a nonpurified diet (-8.6%) compared with a purified AIN-93G diet (-11.4%). The HLS-induced decrease in femoral mechanical strength was not statistically different for rats fed a nonpurified diet (-24%) compared with a purified AIN-93G diet (-31%). However, bone lengths were decreased (P < 0.05) in rats fed a nonpurified diet compared with a purified diet. Plasma estradiol levels were lower (P < 0.05) in the HLS/AIN-93G group but similar in the HLS and ambulatory rats fed a nonpurified diet. Plasma estradiol was related to femoral BMC (r = 0.85, P < 0.01). Urinary calcium excretion was higher (P < 0.05) in rats fed a nonpurified diet than those fed a purified AIN-93G diet, which is consistent with the higher level of calcium in the nonpurified diet. Urinary corticosterone levels were higher (P < 0.05) in rats fed a nonpurified diet than rats fed the AIN-93G diet. Although the osteopenia induced by unloading was similar in both diet groups, there were differences in longitudinal bone growth, calcium excretion, plasma estradiol levels, and urinary corticosterone levels. Results indicate that the type of standard diet used is an important factor to consider when measuring bone end points.     

Lactobacilluscollinoides JCM1123T: effects on mouse plasma cholesterol and isoflavonoids in the caecum

The effects of Lactobacillus collinoides JCM1123^T on plasma cholesterol levels, isoflavonoids in the caecum and faecal flora were assessed in adult mice. L. collinoides JCM1123^T altered the equol production status in in vitro incubation of daidzein with faecal flora of mice. In in vivo investigation, mice were fed an AIN-93M purified diet for 13 days, and then randomly divided into two groups of seven animals each. All mice were fed an AIN-93M diet for 6 days; then the diet was replaced with a 0.05% daidzein diet, the mice received a 0.05% daidzein diet for 4 days. Two groups of mice were administered either L. collinoides JCM1123^T (the experimental group) or a physiological saline solution (the control group) daily for 10 days and dissection was performed on the following day. The total plasma cholesterol concentration was significantly higher in the control group than in the experimental group. The amount of daidzein present in the caecum was significantly higher in the control group than in the experimental group. Significantly higher numbers of lactobacilli were observed in the experimental group than in the control group. Our data suggest that the administration of L. collinoides is likely to influence the metabolism of isoflavonoids and endogenous cholesterol via changes in the gastrointestinal environment.     

Muscle glycogen repletion after exercise in trained normal and diabetic rats

We hypothesize that training results in a faster and greater repletion of glycogen in skeletal muscles of normal and diabetic rats. Normal male Sprague-Dawley rats (100-140 g) were divided into two groups--one to train by treadmill running for 10 wk and the other to remain sedentary. Forty-eight hours after the last training session the rats of both groups were exercised to exhaustion. One subgroup of each was fed oral glucose (3 g/kg) at exhaustion and killed 60 min later. The other was killed at exhaustion. The glycogen concentration of soleus, plantaris, and red and white gastrocnemius was determined in all rats. The trained group had higher glycogen levels after glucose feeding in all muscles (P less than 0.002) and repleted their muscle glycogen more rapidly (P less than 0.05). However, in diabetic rats (45 mg streptozotocin/kg body wt) the trained and sedentary rats have similar glycogen levels and glycogen repletion rates in all muscles. Compared with the normal trained rats, the diabetic trained rats had slower glycogen repletion rates (P less than 0.05).     

Post-exercise ketosis and the glycogen content of liver and muscle in rats on a high carbohydrate diet

Post-exercise ketosis is known to be suppressed by physical training and by a high carbohydrate diet. As a result it has often been presumed, but not proven, that the development of post-exercise ketosis is closely related to the glycogen content of the liver. We therefore studied the effect of 1 h of treadmill running on the blood 3-hydroxybutyrate and liver and muscle glycogen concentrations of carbohydrate-loaded trained (n = 72) and untrained rats (n = 72). Resting liver and muscle glycogen levels were 25%-30% higher in the trained than in the untrained animals. The resting 3-hydroxybutyrate concentrations of both groups of rats were very low: less than 0.08 mmol.l-1. Exercise did not significantly influence the blood 3-hydroxybutyrate concentrations of trained rats, but caused a marked post-exercise ketosis (1.40 +/- 0.40 mmol.l-1 h after exercise) in the untrained animals, the time-course of which was the approximate inverse of the changes in liver glycogen concentration. Interpreting the results in the light of similar data obtained after a normal and low carbohydrate diet it has been concluded that trained animals probably owe their relative resistance to post-exercise ketosis to their higher liver glycogen concentrations as well as to greater peripheral stores of mobilizable carbohydrate.     

Effect of infusing branched-chain amino acid during incremental exercise with reduced muscle glycogen content

The aim of this study was to investigate whether, when muscle glycogen is reduced, a pre-exercise infusion of branched-chain amino acids (BCAA) modifies exercise performance or the metabolic and respiratory responses to incremental exercise. Six moderately trained volunteers took part in the following protocol on two occasions. On day 1, at 9 a.m. in the postabsorptive state, they performed a graded incremental exercise (increases of 35 W every 4 min) to exhaustion (Ex-1). A meal of 1,000 kcal (4,200 kJ; 60% protein, 40% fat) was consumed at 12 p.m. No food was then allowed until the end of the experiment (20–21 h later). A 90-min period of exercise at alternating high and moderate intensities, designed to deplete muscle glycogen, was performed between 6 p.m. and 7.30 p.m. The morning after (day 2), the subjects randomly received either a mixed solution of BCAA (260 mg × kg^–1 × h^–1 for 70 min), or saline. They then repeated the graded incremental exercise to exhaustion (Ex-2). Metabolic and respiratory measurements suggested a muscle glycogen-depleted state had been achieved. No significant differences were observed in total work performed, maximal oxygen uptake or plasma ammonia, alanine, and blood pyruvate concentrations in the two treatments. After BCAA infusion, higher blood lactate concentrations were observed at maximal power output in comparison with those during saline [BCAA 4.97 (SEM 0.41) mmol × l^–1, Saline 3.88 (SEM 0.47) mmol × l^–1,P < 0.05]. In summary, in conditions of reduced muscle glycogen content, after a short period of fasting, BCAA infusion had no significant effect on the total work that could be performed during a graded incremental exercise.     

Deficiency of dietary EAA preferentially inhibits mRNA translation of ribosomal proteins in liver of meal-fed rats

The goal of these studies was to investigate the mechanisms by which amino acid supply regulates global rates of protein synthesis as well as the translation of ribosomal protein (rp) mRNAs in liver. In the experiments conducted, male weanling rats were trained over a 2-wk period to consume their daily food intake within 3 h. On day 14, rats were fed the control diet or an isocaloric, isonitrogenous diet lacking glycine, tryptophan, leucine, or the branched-chain amino acids (BCAA) for 1 h. Feeding Trp-, Leu-, or BCAA-deficient diets resulted in significant reductions in serum insulin, hepatic protein synthesis, eukaryotic initiation factor 2B (eIF2B) activity, and phosphorylation of eIF4E-binding protein 1 (4E-BP1) and ribosomal protein S6 kinase (S6K1). Phosphorylation of eIF2alpha was inversely related to eIF2B activity under all conditions. Alterations in the hepatic synthesis of rp were assessed by changes in the distribution of rp (S4, S8, L26) mRNAs across sucrose density gradients and compared with non-rp (beta-actin, albumin) mRNAs. In all dietary treatments, non-rp mRNAs were mostly polysome associated. Conversely, the proportion of rp mRNAs residing in polysomes was two- to fivefold less in rats fed diets lacking tryptophan, leucine, or BCAA compared with rats fed the control diet. Total hepatic abundance of all mRNAs examined did not differ among treatment groups. For all parameters examined, there were no differences between rats fed the glycine-deficient diet and rats fed the control diet. The data suggest that essential amino acid (EAA) deficiency inhibits global rates of liver protein synthesis via a block in translation initiation. Additionally, the translation of rp mRNAs is preferentially repressed in association with decreased S6K1 phosphorylation.     

Hypolipidemic effect of the edible mushroom Agaricus blazei in rats subjected to a hypercholesterolemic diet

The effects of Agaricus blazei intake on the lipid profile of animals fed a hypercholesterolemic diet were evaluated. Thirty-two female Fisher rats were divided into four groups and given the standard AIN-93 M diet (C), this diet?+?1 % A. blazei (CAb), a hypercholesterolemic diet with 25 % soybean oil and 1 % cholesterol (H) or this diet?+?1 % A. blazei (HAb) for 6 weeks. Food intake, weight gain, liver and serum lipid profiles, activity of aminotransferases [alanine aminotransferase (ALT) and aspartate aminotransferase (AST)], and creatinine and urea levels as well as abdominal fat weight were measured. Histological analysis of kidney and liver tissue was also performed. The HAb group had a higher food intake, but a lower weight gain as compared to group H. This resulted in a significant decrease in abdominal fat weight, to values close to those of groups C and CAb. Supplementing the hypercholesterolemic diet with A. blazei promoted a significant reduction in total and non-HDL cholesterol, as well as in the atherogenic index, as compared to group H, and this effect was more pronounced in the serum. There was no hepatotoxic effect caused by the supplementation of the diets with the mushroom. We conclude that in our experimental model and in the concentration used, A. blazei was effective in improving the lipid profile of the animals.     

Portal-drained viscera and hepatic fluxes of branched-chain amino acids do not account for differences in circulating branched-chain amino acids in rats fed arginine-deficient diets

Summary Concentrations and fluxes of amino acids across the portal-drained viscera (PDV) and liver were assessed in rats fed a meal of one of three arginine-deficient diets containing either alanine or the arginine precursors, ornithine or citrulline. A previous report included findings of seven arginine-related amino acids and indicated that only the citrulline-containing diet protected blood arginine concentrations. In the present report we extend these findings and note that the concentrations and fluxes of the non-arginine-related amino acids showed remarkable consistency across diet groups. However, total branched-chain amino acid (BCAA) concentrations of arterial blood were higher in rats fed the - Arg/+ Ala and the - Arg/+ Orn diets than in rats fed the control (+ Arg) diet. The elevated BCAA correlated with higher circulating concentrations of other essential amino acids but were inversely correlated with arginine concentrations. PDV and hepatic fluxes of BCAA were not different across diet groups, indicating that amino acid absorption and hepatic utilization of BCAA were generally comparable across diet groups. Hepatic concentrations of 14 of 22 measured amino acids, including total BCAA, were correlated with their arterial concentrations. The circulating concentrations and net PDV and hepatic fluxes of rats fed the control diet were comparable to our previous observations in fed rats and illustrate the role of the liver in utilization of diet-derived essential amino acids.Abbreviations PDV portal-drained viscera - BCAA branched-chain amino acids - SSA 5-sulfosalicylic acid - PBF portal blood flow - HBF hepatic blood flow - SELSM pooled standard errors of least squares means - TAA total amino acids - NEAA nonessential amino acids - EAA essential amino acids - LNAA large neutral amino acids Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee by the US Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.     

Glucose uptake is increased in trained vs. untrained muscle during heavy exercise.

Endurance training increases muscle content of glucose transporter proteins (GLUT-4) but decreases glucose utilization during exercise at a given absolute submaximal intensity. We hypothesized that glucose uptake might be higher in trained vs. untrained muscle during heavy exercise in the glycogen-depleted state. Eight untrained subjects endurance trained one thigh for 3 wk using a knee-extensor ergometer. The subjects then performed two-legged glycogen-depleting exercise and consumed a carbohydrate-free meal thereafter to keep muscle glycogen concentration low. The next morning, subjects performed dynamic knee extensions with both thighs simultaneously at 60, 80, and until exhaustion at 100% of each thigh's peak workload. Glucose uptake was similar in both thighs during exercise at 60% of thigh peak workload. At the end of 80 and at 100% of peak workload, glucose uptake was on average 33 and 22% higher, respectively, in trained compared with untrained muscle (P < 0.05). Training increased the muscle content of GLUT-4 by 66% (P < 0. 05). At exhaustion, glucose extraction correlated significantly (r = 0.61) with total muscle GLUT-4 protein. Thus, when working at a high load with low glycogen concentrations, muscle glucose uptake is significantly higher in trained than in untrained muscle. This may be due to the higher GLUT-4 protein concentration in trained muscle.     

Promotion of lipid oxidation by selenate and selenite and indicators of lipid peroxidation in the rat

The AIN-93 reformulation of the AIN-76A rodent diet includes a change in selenium supplement from sodium selenite to sodium selenate to reduce dietary lipid peroxidation. A change to selenate as the standard form of Se in rat diets would render results from previous work using selenite less relevant for comparison with studies using the AIN-93 formulation. To critically examine the rationale for the AIN-93 recommendation, we prepared Torula yeast basal diets patterned as closely as possible after the AIN-93 formulation and supplemented with 0, 0.15 (adequate), or 2.0 (high) mg selenium/kg diet as sodium selenite or sodium selenate. Livers isolated from male Sprague-Dawley rats fed these diets for 15 wk showed no differences in thiobarbituric acid-reactive substances or lipid hydroperoxides measured with the ferrous oxidation in xylenol orange method. Lipids isolated from samples of high-selenate and high-selenite diets showed no differences in conjugated dienes. The addition of selenate or selenite to soybean oil did not result in an altered Oil Stability Index. These results demonstrate that selenate is not less likely than selenite to cause oxidation of other dietary components. Benefits of selenate over selenite in the diets of rodents remain to be demonstrated. Results included in this paper were presented at the meeting of Experimental Biology 98, San Francisco, CA, April 18–22, 1998, and published in abstract form (Moak, M. A., Johnson, B. L., & Christensen, M. J. [1998] On the AIN-93G recommendation for selenium. FASEB J. 12, A824).     

High-protein diets prevent steatosis and induce hepatic accumulation of monomethyl branched-chain fatty acids

The hallmark of nonalcoholic fatty liver disease is steatosis of unknown etiology. To test how dietary protein decreases steatosis, we fed female C57BL/6 J mice low-fat (8 en%) or high-fat (42 en%) combined with low-protein (11 en%), high-protein (HP; 35 en%) or extra-high-protein (HPX; 58 en%) diets for 3 weeks. The 35 en% protein diets reduced hepatic triglyceride, free fatty acid, cholesterol and phospholipid contents to ~50% of that in 11 en% protein diets. Every additional 10 en% protein reduced hepatic fat content ~1.5 g%. HP diets had no effect on lipogenic or fatty acid-oxidizing genes except Ppargc1α (+30%), increased hepatic PCK1 content 3- to 5-fold, left plasma glucose and hepatic glycogen concentration unchanged, and decreased inflammation and cell stress (decreased Fgf21 and increased Gsta expression). The HP-mediated decrease in steatosis correlated inversely with plasma branched-chain amino-acid (BCAA) concentrations and hepatic content of BCAA-derived monomethyl branched-chain fatty acids (mmBCFAs) 14-methylpentadecanoic (14-MPDA; valine-derived) and, to a lesser extent, 14-methylhexadecanoic acid (isoleucine-derived). Liver lipid content was 1.6- to 1.8-fold higher in females than in males, but the anti-steatotic effect of HP diets was equally strong. The strong up-regulation of PCK1 and literature data showing an increase in phosphoenolpyruvate and a decline in tricarboxylic acid cycle intermediates in liver reveal that an increased efflux of these intermediates from mitochondria represents an important effect of an HP diet. The HP diet-induced increase in 14-MPDA and the dietary response in gene expression were more pronounced in females than males. Our findings are compatible with a facilitating role of valine-derived mmBCFAs in the antisteatotic effect of HP diets.     

Exercise and exhaustion effects on glycogen synthesis pathways

Gunderson, Hans, Nadja Wehmeyer, Diane Burnett, John Nauman,Cynthia Hartzell, and Scott Savage. Exercise and exhaustion effects on glycogen synthesis pathways. J. Appl.Physiol. 81(5): 2020-2026, 1996.FemaleSprague-Dawley rats were infused with [1-¹³C]glucose tomeasure the effect of endurance training and the effect of variousmetabolic conditions on pathways of hepatic glycogen synthesis. Fourmetabolic states [sedentary (S), trained (T), sedentary exhausted(SE), and trained exhausted (TE)] were studied. T and TE ratswere trained on a motor-driven treadmill (30 m/min, 15% grade, 1.0 h/day, 5 days/wk) for 8-10 wk. After a 24-h fast, SE and TE ratswere run to exhaustion (sedentary average = 78 min, trained average = 155 min) at a training pace and immediately infused with labeledglucose for 2 h. S and T rats were infused after a 24-h fast. Afterinfusion, tissues were removed and glycogen was isolated and hydrolyzedto glucose. The glucose was measured for distribution of¹³C by using nuclear magneticresonance. Glycogen was synthesized predominantly by the indirectpathway for all metabolic states, indicating that infused glucose wasfirst metabolized primarily in the peripheral tissue. Thedirect-pathway utilization was greater in rested S than in rested Tanimals (30 vs. 14%); however, for exhausted animals, the trained useof the direct pathway was greater (22 vs. 9%). Both TE and rested Tanimals utilize the indirect pathway a comparable amount. Sedentaryanimals, on the other hand, dramatically decreased utilization of thedirect pathway, with exhaustive exercise changing from 30 to 9%. Theresults indicate that endurance training modifies glucose utilizationduring glycogen synthesis after fasting and exhaustive exercise.

     

Branched‐chain amino acids prevent insulin‐induced hepatic tumor cell proliferation by inducing apoptosis through mTORC1 and mTORC2‐dependent mechanisms

Branched‐chain amino acids (BCAA) supplementation has been reported to suppress the incidence of liver cancer in obese patients with liver cirrhosis or in obese and diabetic model animals of carcinogenesis. Whether BCAA directly suppresses cell proliferation of hepatic tumor cells under hyperinsulinemic condition remain to be defined. The aim of this study was to investigate the effects of BCAA on insulin‐induced proliferation of hepatic tumor cells and determine the underlying mechanisms. BCAA suppressed insulin‐induced cell proliferation of H4IIE, HepG2 cells. In H4IIE cells, BCAA did not affect cell cycle progression but increased apoptosis by suppressing expressions of anti‐apoptotic genes and inducing pro‐apoptotic gene via inactivation of PI3K/Akt and NF‐κB signaling pathways. Further studies demonstrated that BCAA inhibited PI3K/Akt pathway not only by promoting negative feedback loop from mammalian target of rapamycin complex 1 (mTORC1)/S6K1 to PI3K/Akt pathway, but also by suppressing mTORC2 kinase activity toward Akt. Our findings suggest that BCAA supplementation may be useful to suppress liver cancer progression by inhibiting insulin‐induced PI3K/Akt and subsequent anti‐apoptotic pathway, indicating the importance of BCAA supplementation to the obese patients with advanced liver disease. J. Cell. Physiol. 227: 2097–2105, 2012. © 2011 Wiley Periodicals, Inc.