There is a need to standardize the NDF procedure. Procedures have varied because of the use of different amylases in attempts to remove starch interference. The original Bacillus subtilis enzyme Type IIIA (XIA) no longer is available and has been replaced by a less effective enzyme. For fiber work, a new enzyme has received AOAC approval and is rapidly displacing other amylases in analytical work. This enzyme is available from Sigma (Number A3306; Sigma Chemical Co., St. Louis, MO). The original publications for NDF and ADF (43, 53) and the Agricultural Handbook 379 (14) are obsolete and of historical interest only. Up to date procedures should be followed. Triethylene glycol has replaced 2-ethoxyethanol because of reported toxicity. Considerable development in regard to fiber methods has occurred over the past 5 yr because of a redefinition of dietary fiber for man and monogastric animals that includes lignin and all polysaccharides resistant to mammalian digestive enzymes. In addition to NDF, new improved methods for total dietary fiber and nonstarch polysaccharides including pectin and beta-glucans now are available. The latter are also of interest in rumen fermentation. Unlike starch, their fermentations are like that of cellulose but faster and yield no lactic acid. Physical and biological properties of carbohydrate fractions are more important than their intrinsic composition.

The means by which vaginal microbiomes help prevent urogenital diseases in women and maintain health are poorly understood. To gain insight into this, the vaginal bacterial communities of 396 asymptomatic North American women who represented four ethnic groups (white, black, Hispanic, and Asian) were sampled and the species composition characterized by pyrosequencing of barcoded 16S rRNA genes. The communities clustered into five groups: four were dominated by Lactobacillus iners, L. crispatus, L. gasseri, or L. jensenii, whereas the fifth had lower proportions of lactic acid bacteria and higher proportions of strictly anaerobic organisms, indicating that a potential key ecological function, the production of lactic acid, seems to be conserved in all communities. The proportions of each community group varied among the four ethnic groups, and these differences were statistically significant [χ(2)(10) = 36.8, P < 0.0001]. Moreover, the vaginal pH of women in different ethnic groups also differed and was higher in Hispanic (pH 5.0 ± 0.59) and black (pH 4.7 ± 1.04) women as compared with Asian (pH 4.4 ± 0.59) and white (pH 4.2 ± 0.3) women. Phylotypes with correlated relative abundances were found in all communities, and these patterns were associated with either high or low Nugent scores, which are used as a factor for the diagnosis of bacterial vaginosis. The inherent differences within and between women in different ethnic groups strongly argues for a more refined definition of the kinds of bacterial communities normally found in healthy women and the need to appreciate differences between individuals so they can be taken into account in risk assessment and disease diagnosis.

Incorporation of 1.9% beta-disodium glycerophosphate (GP) into a complex medium resulted in improved growth by lactic streptococci at 30 C. The medium, called M17, contained: Phytone peptone, 5.0 g; polypeptone, 5.0 g; yeast extract, 2.5 g; beef extract, 5.0 g; lactose, 5.0 g; ascorbic acid, 0.5 g; GP, 19.0 g; 1.0 M MgSO(4).7H(2)O, 1.0 ml; and glass-distilled water, 1,000 ml. Based on absorbance readings and total counts, all strains of Streptococcus cremoris, S. diacetilactis, and S. lactis grew better in M17 medium than in a similar medium lacking GP or in lactic broth. Enhanced growth was probably due to the increased buffering capacity of the medium, since pH values below 5.70 were not reached after 24 h of growth at 30 C by S. lactis or S. cremoris strains. The medium also proved useful for isolation of bacterial mutants lacking the ability to ferment lactose; such mutants formed minute colonies on M17 agar plates, whereas wild-type cells formed colonies 3 to 4 mm in diameter. Incorporation of sterile GP into skim milk at 1.9% final concentration resulted in enhanced acid-producing activity by lactic streptococci when cells were inoculated from GP milk into skim milk not containing GP. M17 medium also proved superior to other media in demonstrating and distinguishing between lactic streptococcal bacteriophages. Plaques larger than 6 mm in diameter developed with some phage-host combinations, and turbid plaques, indicative of lysogeny, were also easily demonstrated for some systems.

Excess CO2 is generated when lactate is increased during exercise because its [H+] is buffered primarily by HCO-3 (22 ml for each meq of lactic acid). We developed a method to detect the anaerobic threshold (AT), using computerized regression analysis of the slopes of the CO2 uptake (VCO2) vs. O2 uptake (VO2) plot, which detects the beginning of the excess CO2 output generated from the buffering of [H+], termed the V-slope method. From incremental exercise tests on 10 subjects, the point of excess CO2 output (AT) predicted closely the lactate and HCO-3 thresholds. The mean gas exchange AT was found to correspond to a small increment of lactate above the mathematically defined lactate threshold [0.50 +/- 0.34 (SD) meq/l] and not to differ significantly from the estimated HCO-3 threshold. The mean VO2 at AT computed by the V-slope analysis did not differ significantly from the mean value determined by a panel of six experienced reviewers using traditional visual methods, but the AT could be more reliably determined by the V-slope method. The respiratory compensation point, detected separately by examining the minute ventilation vs. VCO2 plot, was consistently higher than the AT (2.51 +/- 0.42 vs. 1.83 +/- 0.30 l/min of VO2). This method for determining the AT has significant advantages over others that depend on regular breathing pattern and respiratory chemosensitivity.

There is increasing, but largely indirect, evidence pointing to an effect of commensal gut microbiota on the central nervous system (CNS). However, it is unknown whether lactic acid bacteria such as Lactobacillus rhamnosus could have a direct effect on neurotransmitter receptors in the CNS in normal, healthy animals. GABA is the main CNS inhibitory neurotransmitter and is significantly involved in regulating many physiological and psychological processes. Alterations in central GABA receptor expression are implicated in the pathogenesis of anxiety and depression, which are highly comorbid with functional bowel disorders. In this work, we show that chronic treatment with L. rhamnosus (JB-1) induced region-dependent alterations in GABA(B1b) mRNA in the brain with increases in cortical regions (cingulate and prelimbic) and concomitant reductions in expression in the hippocampus, amygdala, and locus coeruleus, in comparison with control-fed mice. In addition, L. rhamnosus (JB-1) reduced GABA(Aα2) mRNA expression in the prefrontal cortex and amygdala, but increased GABA(Aα2) in the hippocampus. Importantly, L. rhamnosus (JB-1) reduced stress-induced corticosterone and anxiety- and depression-related behavior. Moreover, the neurochemical and behavioral effects were not found in vagotomized mice, identifying the vagus as a major modulatory constitutive communication pathway between the bacteria exposed to the gut and the brain. Together, these findings highlight the important role of bacteria in the bidirectional communication of the gut-brain axis and suggest that certain organisms may prove to be useful therapeutic adjuncts in stress-related disorders such as anxiety and depression.

The production and regeneration of bacterial protoplasts promoted the loss of three different plasmid-specified traits in Streptococcus lactis subsp. diacetylactis strains. The loss of five different plasmids, including small multicopy molecules, was readily detected in Streptococcus lactis 712 by screening lysates of random protoplast regenerants on agarose gels. In this strain sequential rounds of protoplast regeneration were used to produce a plasmid-free strain and derivatives carrying only single molecules from the plasmid complement. During these experiments a 33-megadalton plasmid, pLP712, was found to encode genes for lactose and protein utilization. Only this plasmid was required for normal growth and acid production in milk; the remaining four plasmids appeared to be cryptic. Lactose-defective derivatives of a strain carrying only pLP712 were readily isolated. Although these derivatives included instances of plasmid loss, deletions of pLP712 were frequently found. Many different deleted derivatives of pLP712, including some in which the lactose or protein utilization determinant or both were lost, were isolated. The molecular instability of pLP712 largely accounted for previous observations of plasmid complements in S. lactis 712 after lactose determinant curing or transfer by conjugation and transduction. Curing of cryptic molecules from multiple plasmid complements by protoplast regeneration may prove to be generally valuable in lactic streptococci and other gram-positive species.

Tumors contain oxygenated and hypoxic regions, so the tumor cell population is heterogeneous. Hypoxic tumor cells primarily use glucose for glycolytic energy production and release lactic acid, creating a lactate gradient that mirrors the oxygen gradient in the tumor. By contrast, oxygenated tumor cells have been thought to primarily use glucose for oxidative energy production. Although lactate is generally considered a waste product, we now show that it is a prominent substrate that fuels the oxidative metabolism of oxygenated tumor cells. There is therefore a symbiosis in which glycolytic and oxidative tumor cells mutually regulate their access to energy metabolites. We identified monocarboxylate transporter 1 (MCT1) as the prominent path for lactate uptake by a human cervix squamous carcinoma cell line that preferentially utilized lactate for oxidative metabolism. Inhibiting MCT1 with alpha-cyano-4-hydroxycinnamate (CHC) or siRNA in these cells induced a switch from lactate-fueled respiration to glycolysis. A similar switch from lactate-fueled respiration to glycolysis by oxygenated tumor cells in both a mouse model of lung carcinoma and xenotransplanted human colorectal adenocarcinoma cells was observed after administration of CHC. This retarded tumor growth, as the hypoxic/glycolytic tumor cells died from glucose starvation, and rendered the remaining cells sensitive to irradiation. As MCT1 was found to be expressed by an array of primary human tumors, we suggest that MCT1 inhibition has clinical antitumor potential.

Macrophages have an important role in the maintenance of tissue homeostasis. To perform this function, macrophages must have the capacity to monitor the functional states of their 'client cells': namely, the parenchymal cells in the various tissues in which macrophages reside. Tumours exhibit many features of abnormally developed organs, including tissue architecture and cellular composition. Similarly to macrophages in normal tissues and organs, macrophages in tumours (tumour-associated macrophages) perform some key homeostatic functions that allow tumour maintenance and growth. However, the signals involved in communication between tumours and macrophages are poorly defined. Here we show that lactic acid produced by tumour cells, as a by-product of aerobic or anaerobic glycolysis, has a critical function in signalling, through inducing the expression of vascular endothelial growth factor and the M2-like polarization of tumour-associated macrophages. Furthermore, we demonstrate that this effect of lactic acid is mediated by hypoxia-inducible factor 1α (HIF1α). Finally, we show that the lactate-induced expression of arginase 1 by macrophages has an important role in tumour growth. Collectively, these findings identify a mechanism of communication between macrophages and their client cells, including tumour cells. This communication most probably evolved to promote homeostasis in normal tissues but can also be engaged in tumours to promote their growth.

Poly(lactic-co-glycolic acid) (PLGA) is one of the most successfully developed biodegradable polymers. Among the different polymers developed to formulate polymeric nanoparticles, PLGA has attracted considerable attention due to its attractive properties: (i) biodegradability and biocompatibility, (ii) FDA and European Medicine Agency approval in drug delivery systems for parenteral administration, (iii) well described formulations and methods of production adapted to various types of drugs e.g. hydrophilic or hydrophobic small molecules or macromolecules, (iv) protection of drug from degradation, (v) possibility of sustained release, (vi) possibility to modify surface properties to provide stealthness and/or better interaction with biological materials and (vii) possibility to target nanoparticles to specific organs or cells. This review presents why PLGA has been chosen to design nanoparticles as drug delivery systems in various biomedical applications such as vaccination, cancer, inflammation and other diseases. This review focuses on the understanding of specific characteristics exploited by PLGA-based nanoparticles to target a specific organ or tissue or specific cells.

Lactic acid-producing bacteria are associated with various plant and animal niches and play a key role in the production of fermented foods and beverages. We report nine genome sequences representing the phylogenetic and functional diversity of these bacteria. The small genomes of lactic acid bacteria encode a broad repertoire of transporters for efficient carbon and nitrogen acquisition from the nutritionally rich environments they inhabit and reflect a limited range of biosynthetic capabilities that indicate both prototrophic and auxotrophic strains. Phylogenetic analyses, comparison of gene content across the group, and reconstruction of ancestral gene sets indicate a combination of extensive gene loss and key gene acquisitions via horizontal gene transfer during the coevolution of lactic acid bacteria with their habitats.

More than 80 years ago, the renowned biochemist Otto Warburg described how cancer cells avidly consume glucose and produce lactic acid under aerobic conditions. Recent studies arguing that cancer cells benefit from this phenomenon, termed the Warburg effect, have renewed discussions about its exact role as cause, correlate, or facilitator of cancer. Molecular advances in this area may reveal tactics to exploit the cancer cell's "sweet tooth" for cancer therapy.

Bacteriocins are bacterially produced antimicrobial peptides with narrow or broad host ranges. Many bacteriocins are produced by food-grade lactic acid bacteria, a phenomenon which offers food scientists the possibility of directing or preventing the development of specific bacterial species in food. This can be particularly useful in preservation or food safety applications, but also has implications for the development of desirable flora in fermented food. In this sense, bacteriocins can be used to confer a rudimentary form of innate immunity to foodstuffs, helping processors extend their control over the food flora long after manufacture.

In past two decades poly lactic-co-glycolic acid (PLGA) has been among the most attractive polymeric candidates used to fabricate devices for drug delivery and tissue engineering applications. PLGA is biocompatible and biodegradable, exhibits a wide range of erosion times, has tunable mechanical properties and most importantly, is a FDA approved polymer. In particular, PLGA has been extensively studied for the development of devices for controlled delivery of small molecule drugs, proteins and other macromolecules in commercial use and in research. This manuscript describes the various fabrication techniques for these devices and the factors affecting their degradation and drug release.

The 3,308,274-bp sequence of the chromosome of Lactobacillus plantarum strain WCFS1, a single colony isolate of strain NCIMB8826 that was originally isolated from human saliva, has been determined, and contains 3,052 predicted protein-encoding genes. Putative biological functions could be assigned to 2,120 (70%) of the predicted proteins. Consistent with the classification of L. plantarum as a facultative heterofermentative lactic acid bacterium, the genome encodes all enzymes required for the glycolysis and phosphoketolase pathways, all of which appear to belong to the class of potentially highly expressed genes in this organism, as was evident from the codon-adaptation index of individual genes. Moreover, L. plantarum encodes a large pyruvate-dissipating potential, leading to various end-products of fermentation. L. plantarum is a species that is encountered in many different environmental niches, and this flexible and adaptive behavior is reflected by the relatively large number of regulatory and transport functions, including 25 complete PTS sugar transport systems. Moreover, the chromosome encodes >200 extracellular proteins, many of which are predicted to be bound to the cell envelope. A large proportion of the genes encoding sugar transport and utilization, as well as genes encoding extracellular functions, appear to be clustered in a 600-kb region near the origin of replication. Many of these genes display deviation of nucleotide composition, consistent with a foreign origin. These findings suggest that these genes, which provide an important part of the interaction of L. plantarum with its environment, form a lifestyle adaptation region in the chromosome.

Targeted uptake of therapeutic nanoparticles in a cell-, tissue-, or disease-specific manner represents a potentially powerful technology. Using prostate cancer as a model, we report docetaxel (Dtxl)-encapsulated nanoparticles formulated with biocompatible and biodegradable poly(D,L-lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-b-PEG) copolymer and surface functionalized with the A10 2'-fluoropyrimidine RNA aptamers that recognize the extracellular domain of the prostate-specific membrane antigen (PSMA), a well characterized antigen expressed on the surface of prostate cancer cells. These Dtxl-encapsulated nanoparticle-aptamer bioconjugates (Dtxl-NP-Apt) bind to the PSMA protein expressed on the surface of LNCaP prostate epithelial cells and get taken up by these cells resulting in significantly enhanced in vitro cellular toxicity as compared with nontargeted nanoparticles that lack the PSMA aptamer (Dtxl-NP) (P < 0.0004). The Dtxl-NP-Apt bioconjugates also exhibit remarkable efficacy and reduced toxicity as measured by mean body weight loss (BWL) in vivo [body weight loss of 7.7 +/- 4% vs. 18 +/- 5% for Dtxl-NP-Apt vs. Dtxl-NP at nadir, respectively (mean +/- SD); n = 7]. After a single intratumoral injection of Dtxl-NP-Apt bioconjugates, complete tumor reduction was observed in five of seven LNCaP xenograft nude mice (initial tumor volume of approximately 300 mm3), and 100% of these animals survived our 109-day study. In contrast, two of seven mice in the Dtxl-NP group had complete tumor reduction with 109-day survivability of only 57%. Dtxl alone had a survivability of only 14%. Saline and nanoparticles without drug were similarly nonefficacious. This report demonstrates the potential utility of nanoparticle-aptamer bioconjugates for a therapeutic application.

Increased conversion of glucose to lactic acid associated with decreased mitochondrial respiration is a unique feature of tumors first described by Otto Warburg in the 1920s. Recent evidence suggests that the Warburg effect is caused by oncogenes and is an underlying mechanism of malignant transformation. Using a novel approach to measure cellular metabolic rates in vitro, the bioenergetic basis of this increased glycolysis and reduced mitochondrial respiration was investigated in two human cancer cell lines, H460 and A549. The bioenergetic phenotype was analyzed by measuring cellular respiration, glycolysis rate, and ATP turnover of the cells in response to various pharmacological modulators. H460 and A549 cells displayed a dependency on glycolysis and an ability to significantly upregulate this pathway when their respiration was inhibited. The converse, however, was not true. The cell lines were attenuated in oxidative phosphorylation (OXPHOS) capacity and were unable to sufficiently upregulate mitochondrial OXPHOS when glycolysis was disabled. This observed mitochondrial impairment was intimately linked to the increased dependency on glycolysis. Furthermore, it was demonstrated that H460 cells were more glycolytic, having a greater impairment of mitochondrial respiration, compared with A549 cells. Finally, the upregulation of glycolysis in response to mitochondrial ATP synthesis inhibition was dependent on AMP-activated protein kinase activity. In summary, our results demonstrate a bioenergetic phenotype of these two cancer cell lines characterized by increased rate of glycolysis and a linked attenuation in their OXPHOS capacity. These metabolic alterations provide a mechanistic explanation for the growth advantage and apoptotic resistance of tumor cells.

Lactococcus lactis is a nonpathogenic AT-rich gram-positive bacterium closely related to the genus Streptococcus and is the most commonly used cheese starter. It is also the best-characterized lactic acid bacterium. We sequenced the genome of the laboratory strain IL1403, using a novel two-step strategy that comprises diagnostic sequencing of the entire genome and a shotgun polishing step. The genome contains 2,365,589 base pairs and encodes 2310 proteins, including 293 protein-coding genes belonging to six prophages and 43 insertion sequence (IS) elements. Nonrandom distribution of IS elements indicates that the chromosome of the sequenced strain may be a product of recent recombination between two closely related genomes. A complete set of late competence genes is present, indicating the ability of L. lactis to undergo DNA transformation. Genomic sequence revealed new possibilities for fermentation pathways and for aerobic respiration. It also indicated a horizontal transfer of genetic information from Lactococcus to gram-negative enteric bacteria of Salmonella-Escherichia group.

Measurement of pH in tissue has shown that the microenvironment in tumors is generally more acidic than in normal tissues. Major mechanisms which lead to tumor acidity probably include the production of lactic acid and hydrolysis of ATP in hypoxic regions of tumors. Further reduction in pH may be achieved in some tumors by administration of glucose (+/- insulin) and by drugs such as hydralazine which modify the relative blood flow to tumors and normal tissues. Cells have evolved mechanisms for regulating their intracellular pH. The amiloride-sensitive Na+/H+ antiport and the DIDS-sensitive Na+-dependent HCO3-/Cl- exchanger appear to be the major mechanisms for regulating pHi under conditions of acid loading, although additional mechanisms may contribute to acid extrusion. Mitogen-induced initiation of proliferation in some cells is preceded by cytoplasmic alkalinization, usually triggered by stimulation of Na+/H+ exchange; proliferation of other cells can be induced without prior alkalinization. Mutant cells which lack Na+/H+ exchange activity have reduced or absent ability to generate solid tumors; a plausible explanation is the failure of such mutant cells to withstand acidic conditions that are generated during tumor growth. Studies in tissue culture have demonstrated that the combination of hypoxia and acid pHe is toxic to mammalian cells, whereas short exposures to either factor alone are not very toxic. This interaction may contribute to cell death and necrosis in solid tumors. Acidic pH may influence the outcome of tumor therapy. There are rather small effects of pHe on the response of cells to ionizing radiation but acute exposure to acid pHe causes a marked increase in response to hyperthermia; this effect is decreased in cells that are adapted to low pHe. Acidity may have varying effects on the response of cells to conventional anticancer drugs. Ionophores such as nigericin or CCCP cause acid loading of cells in culture and are toxic only at low pHc; this toxicity is enhanced by agents such as amiloride or DIDS which impair mechanisms involved in regulation of pHi. It is suggested that acid conditions in tumors might allow the development of new and relatively specific types of therapy which are directed against mechanisms which regulate pHi under acid conditions.

Lactic acid bacteria produce a variety of bacteriocins that have recently come under detailed investigation. The biochemical and genetic characteristics of these antimicrobial proteins are reviewed and common elements are discussed between the different classes of bacteriocins produced by these Gram-positive bacteria.

A characteristic feature of tumors is high production of lactic acid due to enhanced glycolysis. Here, we show a positive correlation between lactate serum levels and tumor burden in cancer patients and examine the influence of lactic acid on immune functions in vitro. Lactic acid suppressed the proliferation and cytokine production of human cytotoxic T lymphocytes (CTLs) up to 95% and led to a 50% decrease in cytotoxic activity. A 24-hour recovery period in lactic acid-free medium restored CTL function. CTLs infiltrating lactic acid-producing multicellular tumor spheroids showed a reduced cytokine production. Pretreatment of tumor spheroids with an inhibitor of lactic acid production prevented this effect. Activated T cells themselves use glycolysis and rely on the efficient secretion of lactic acid, as its intracellular accumulation disturbs their metabolism. Export by monocarboxylate transporter-1 (MCT-1) depends on a gradient between cytoplasmic and extracellular lactic acid concentrations and consequently, blockade of MCT-1 resulted in impaired CTL function. We conclude that high lactic acid concentrations in the tumor environment block lactic acid export in T cells, thereby disturbing their metabolism and function. These findings suggest that targeting this metabolic pathway in tumors is a promising strategy to enhance tumor immunogenicity.

Monocarboxylates such as lactate and pyruvate play a central role in cellular metabolism and metabolic communication between tissues. Essential to these roles is their rapid transport across the plasma membrane, which is catalysed by a recently identified family of proton-linked monocarboxylate transporters (MCTs). Nine MCT-related sequences have so far been identified in mammals, each having a different tissue distribution, whereas six related proteins can be recognized in Caenorhabditis elegans and 4 in Saccharomyces cerevisiae. Direct demonstration of proton-linked lactate and pyruvate transport has been demonstrated for mammalian MCT1-MCT4, but only for MCT1 and MCT2 have detailed analyses of substrate and inhibitor kinetics been described following heterologous expression in Xenopus oocytes. MCT1 is ubiquitously expressed, but is especially prominent in heart and red muscle, where it is up-regulated in response to increased work, suggesting a special role in lactic acid oxidation. By contrast, MCT4 is most evident in white muscle and other cells with a high glycolytic rate, such as tumour cells and white blood cells, suggesting it is expressed where lactic acid efflux predominates. MCT2 has a ten-fold higher affinity for substrates than MCT1 and MCT4 and is found in cells where rapid uptake at low substrate concentrations may be required, including the proximal kidney tubules, neurons and sperm tails. MCT3 is uniquely expressed in the retinal pigment epithelium. The mechanisms involved in regulating the expression of different MCT isoforms remain to be established. However, there is evidence for alternative splicing of the 5'- and 3'-untranslated regions and the use of alternative promoters for some isoforms. In addition, MCT1 and MCT4 have been shown to interact specifically with OX-47 (CD147), a member of the immunoglobulin superfamily with a single transmembrane helix. This interaction appears to assist MCT expression at the cell surface. There is still much work to be done to characterize the properties of the different isoforms and their regulation, which may have wide-ranging implications for health and disease. In the future it will be interesting to explore the linkage of genetic diseases to particular MCTs through their chromosomal location.

Cancer cells are able to overproduce lactic acid aerobically, whereas normal cells undergo anaerobic glycolysis only when deprived of oxygen. Tumor aerobic glycolysis was recognized about seven decades ago; however, its molecular basis has remained elusive. The lactate dehydrogenase-A gene (LDH-A), whose product participates in normal anaerobic glycolysis and is frequently increased in human cancers, was identified as a c-Myc-responsive gene. Stably transfected Rat1a fibroblasts that overexpress LDH-A alone or those transformed by c-Myc overproduce lactic acid. LDH-A overexpression is required for c-Myc-mediated transformation because lowering its level through antisense LDH-A expression reduces soft agar clonogenicity of c-Myc-transformed Rat1a fibroblasts, c-Myc-transformed human lymphoblastoid cells, and Burkitt lymphoma cells. Although antisense expression of LDH-A did not affect the growth of c-Myc-transformed fibroblasts adherent to culture dishes under normoxic conditions, the growth of these adherent cells in hypoxia was reduced. These observations suggest that an increased LDH-A level is required for the growth of a transformed spheroid cell mass, which has a hypoxic internal microenvironment. Our studies have linked c-Myc to the induction of LDH-A, whose expression increases lactate production and is necessary for c-Myc-mediated transformation.

In the exercising human, maximal oxygen uptake (VO2max) is limited by the ability of the cardiorespiratory system to deliver oxygen to the exercising muscles. This is shown by three major lines of evidence: 1) when oxygen delivery is altered (by blood doping, hypoxia, or beta-blockade), VO2max changes accordingly; 2) the increase in VO2max with training results primarily from an increase in maximal cardiac output (not an increase in the a-v O2 difference); and 3) when a small muscle mass is overperfused during exercise, it has an extremely high capacity for consuming oxygen. Thus, O2 delivery, not skeletal muscle O2 extraction, is viewed as the primary limiting factor for VO2max in exercising humans. Metabolic adaptations in skeletal muscle are, however, critical for improving submaximal endurance performance. Endurance training causes an increase in mitochondrial enzyme activities, which improves performance by enhancing fat oxidation and decreasing lactic acid accumulation at a given VO2. VO2max is an important variable that sets the upper limit for endurance performance (an athlete cannot operate above 100% VO2max, for extended periods). Running economy and fractional utilization of VO2max also affect endurance performance. The speed at lactate threshold (LT) integrates all three of these variables and is the best physiological predictor of distance running performance.

OBJECTIVE

Obesity alters gut microbiota ecology and associates with low-grade inflammation in humans. Roux-en-Y gastric bypass (RYGB) surgery is one of the most efficient procedures for the treatment of morbid obesity resulting in drastic weight loss and improvement of metabolic and inflammatory status. We analyzed the impact of RYGB on the modifications of gut microbiota and examined links with adaptations associated with this procedure.

METHODS

Gut microbiota was profiled from fecal samples by real-time quantitative PCR in 13 lean control subjects and in 30 obese individuals (with seven type 2 diabetics) explored before (M0), 3 months (M3), and 6 months (M6) after RYGB.

RESULTS

Four major findings are highlighted: 1) Bacteroides/Prevotella group was lower in obese subjects than in control subjects at M0 and increased at M3. It was negatively correlated with corpulence, but the correlation depended highly on caloric intake; 2) Escherichia coli species increased at M3 and inversely correlated with fat mass and leptin levels independently of changes in food intake; 3) lactic acid bacteria including Lactobacillus/Leuconostoc/Pediococcus group and Bifidobacterium genus decreased at M3; and 4) Faecalibacterium prausnitzii species was lower in subjects with diabetes and associated negatively with inflammatory markers at M0 and throughout the follow-up after surgery independently of changes in food intake.

CONCLUSIONS

These results suggest that components of the dominant gut microbiota rapidly adapt in a starvation-like situation induced by RYGB while the F. prausnitzii species is directly linked to the reduction in low-grade inflammation state in obesity and diabetes independently of calorie intake.