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Lien entre glucides et cancer du colon

26/07/2014 | Etudes Perte de poids et Etudes Anti-âge

 

Gut Microbial Metabolism Drives Transformation of Msh2-Deficient Colon Epithelial Cells
Cell Volume 158, Issue 2, p288–299, 17 July 2014     Antoaneta Belcheva

Highlights

•Gut microbiota induce colon cancer in genetically sensitized MSH2-deficient mice
•Reduced dietary carbohydrates decreased polyp frequency in APCMin/+MSH2−/− mice
•The carbohydrate metabolite butyrate induces colon cancer in APCMin/+MSH2−/− mice
•MSH2 regulates β-catenin activity and/or transit-amplifying cell differentiation

The etiology of colorectal cancer (CRC) has been linked to deficiencies in mismatch repair and adenomatous polyposis coli (APC) proteins, diet, inflammatory processes, and gut microbiota. However, the mechanism through which the microbiota synergizes with these etiologic factors to promote CRC is not clear. We report that altering the microbiota composition reduces CRC in APCMin/+MSH2−/− mice, and that a diet reduced in carbohydrates phenocopies this effect. Gut microbes did not induce CRC in these mice through an inflammatory response or the production of DNA mutagens but rather by providing carbohydrate-derived metabolites such as butyrate that fuel hyperproliferation of MSH2−/− colon epithelial cells. Further, we provide evidence that the mismatch repair pathway has a role in regulating β-catenin activity and modulating the differentiation of transit-amplifying cells in the colon. These data thereby provide an explanation for the interaction between microbiota, diet, and mismatch repair deficiency in CRC induction.

Impact hormonal du d-aspartate

26/07/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Aux vues du large spectre d’effets sur le système endocrinien, on comprends pourquoi certains ont vite regretté d’avoir joué avec le d-aspartate

Current knowledge of d-aspartate in glandular tissues

Maria Maddalena Di Fiore
Amino Acids August 2014, Volume 46, Issue 8, pp 1805-1818

Free d-aspartate (d-Asp) occurs in substantial amounts in glandular tissues. This paper reviews the existing work on d-Asp in vertebrate exocrine and endocrine glands, with emphasis on functional roles. Endogenous d-Asp was detected in salivary glands. High d-Asp levels in the parotid gland during development suggest an involvement of the amino acid in the regulation of early developmental phases and/or differentiation processes. d-Asp has a prominent role in the Harderian gland, where it elicits exocrine secretion through activation of the ERK1/2 pathway. Interestingly, the increase in NOS activity associated with d-Asp administration in the Harderian gland suggests a potential capability of d-Asp to induce vasodilatation.
In mammals, an increase in local concentrations of d-Asp facilitates the secretion of anterior pituitary hormones, i.e., PRL, LH and GH, whereas it inhibits the secretion of POMC/α-MSH from the intermediate pituitary and of oxytocin from the posterior pituitary. d-Asp also acts as a negative regulator for melatonin synthesis in the pineal gland. Further, d-Asp can stereo-specifically modulate the production of sex steroids, thus taking part in the endocrine control of reproductive activity. Although d-Asp receptors remain to be characterized, gene expression of NR1 and NR2 subunits of NMDAr responds to d-Asp in the testis.

Je ne comprends pas pourquoi il n’y a pas de supplément méga-dosé en bétaïne?

26/07/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

j’en parlais déjà dans le Monde du Muscle. La bétaïne est utilisée depuis des lustres pour faire prendre du muscle aux animaux. Pourquoi n’a t’on pas des suppléments apportant 10 ou 20 g de bétaïne?

Effects of betaine on performance and body composition: a review of recent findings and potential mechanisms
Jason M. Cholewa     Amino Acids August 2014, Volume 46, Issue 8, pp 1785-1793

Betaine is a methyl derivative of glycine first isolated from sugar beets. Betaine consumed from food sources and through dietary supplements presents similar bioavailability and is metabolized to di-methylglycine and sarcosine in the liver. The ergogenic and clinical effects of betaine have been investigated with doses ranging from 500 to 9,000 mg/day. Some studies using animal models and human subjects suggest that betaine supplementation could promote adiposity reductions and/or lean mass gains. Moreover, previous investigations report positive effects of betaine on sports performance in both endurance- and resistance-type exercise, despite some conflicting results. The mechanisms underlying these effects are poorly understood, but could involve the stimulation of lipolysis and inhibition of lipogenesis via gene expression and subsequent activity of lipolytic-/lipogenic-related proteins, stimulation of autocrine/endocrine IGF-1 release and insulin receptor signaling pathways, stimulation of growth hormone secretion, increased creatine synthesis, increases in protein synthesis via intracellular hyper-hydration, as well as exerting psychological effects such as attenuating sensations of fatigue. However, the exact mechanisms behind betaine action and the long-term effects of supplementation on humans remain to be elucidated. This review aims to describe evidence for the use of betaine as an ergogenic and esthetic aid, and discuss the potential mechanisms underlying these effects.

De la lutéine pour protéger le cerveau en plus des yeux?

25/07/2014 | Etudes Compléments alimentaires et Etudes Anti-âge

 

Macular Pigment, Visual Function, and Macular Disease among Subjects with Alzheimer’s Disease: An Exploratory Study
Journal Journal of Alzheimer’s Disease             July 02, 2014       John M. Nolan

Background: The macula (central retina) contains a yellow pigment, comprising the dietary carotenoids lutein (L), zeaxanthin (Z), and meso-zeaxanthin, known as macular pigment (MP). The concentrations of MP’s constituent carotenoids in retina and brain tissue correlate, and there is a biologically-plausible rationale, supported by emerging evidence, that MP’s constituent carotenoids are also important for cognitive function. Objective: To investigate if patients with Alzheimer’s disease (AD) are comparable to controls in terms of MP and visual function. Methods: 36 patients with moderate AD and 33 controls with the same age range participated. MP was measured using dual-wavelength autofluorescence (Heidelberg Spectralis®); cognitive function was assessed using a battery of cognition tests (including Cambridge Neuropsychological Test Automated Battery). Visual function was recorded by measuring best corrected visual acuity (BCVA) and contrast sensitivity (CS). Serum L and Z concentrations (by HPLC) and age-related macular degeneration (AMD, by retinal examination) status were also assessed. Results: In the AD group, central MP (i.e., at 0.23°) and MP volume were significantly lower than the control group (p < 0.001 for both), as were measures of BCVA, CS, and serum L and Z concentrations (p < 0.05, for all). Conclusion: AD patients were observed to exhibit significantly less MP, lower serum concentrations of L and Z, poorer vision, and a higher occurrence of AMD when compared to control subjects. A clinical trial in AD patients designed to investigate the impact of macular carotenoid supplementation with respect to MP, visual function, and cognitive function is merited.

Relationships between macular pigment optical density and cognitive function in unimpaired and mildly cognitively impaired older adults
Neurobiology of AgingVolume 35, Issue 7, Pages 1695–1699, July 2014   Lisa M. Renzi

Low carotenoid status (especially of the xanthophylls, lutein [L], and zeaxanthin [Z]) is common in older adults and has been associated with a number of degenerative diseases of the central nervous system ranging from retina (e.g., macular degeneration) to brain (e.g., Alzheimer’s disease). In this study, we tested whether retinal measures of L + Z (macular pigment optical density [MPOD]), used as a surrogate for brain L + Z levels, were related to cognitive function when comparing healthy older adults with mildly cognitively impaired older adults. Twenty-four subjects with mild cognitive impairment were compared with 24 matched controls. Subjects were matched with respect to age, body mass index, ethnicity, sex, and smoking status. Degree of cognitive impairment and cognitive ability was determined via structured clinical interview. MPOD was measured psychophysically. In healthy older adults, MPOD was only related to visual-spatial and constructional abilities (p = 0.04). For subjects with mild cognitive impairment (MCI), however, MPOD was broadly related to cognition including the composite score on the mini-mental state examination (p = 0.02), visual-spatial and constructional abilities (p = 0.04), language ability (p = 0.05), attention (p = 0.03), and the total scale on the Repeatable Battery for the Assessment of Neuropsychological Status (p = 0.03). It is possible that L/Z status may be more strongly related to cognition when individuals are considered with established onset of cognitive decline.


Lutein is the Predominant Carotenoid in Infant Brain: Preterm Infants Have Decreased Concentrations of Brain Carotenoids.

J Pediatr Gastroenterol Nutr. 2014 Mar 31. [Epub ahead of print] Vishwanathan R

Lutein and zeaxanthin are dietary carotenoids that may influence visual and cognitive development. The objective of this study was to provide the first data on distribution of carotenoids in the infant brain and compare concentrations in preterm and term infants.

METHODS::

Voluntarily donated brain tissues from 30 infants who died during the first 1.5 years of life were obtained from the NICHD Brain and Tissue Bank. Tissues (hippocampus and prefrontal, frontal, auditory and occipital cortices) were extracted using standard lipid extraction procedures and analyzed using reverse phase HPLC.

RESULTS::

Lutein, zeaxanthin, cryptoxanthin and β-carotene were the major carotenoids found in the infant brain tissues. Lutein was the predominant carotenoid accounting for 59% of total carotenoids. Preterm infants (n = 8) had significantly lower concentrations of lutein, zeaxanthin and cryptoxanthin in their brain compared to term infants (n = 22) despite similarity in postmenstrual age. Among formula-fed infants, preterm infants (n = 3) had lower concentrations of lutein and zeaxanthin compared to term infants (n = 5). Brain lutein concentrations were not different between breast milk-fed (n = 3) and formula-fed (n = 5) term decedents. In contrast, term decedents with measurable brain cryptoxanthin, a carotenoid that is inherently low in formula, had higher brain lutein suggesting that type of feeding is an important determinant of brain lutein concentrations.

CONCLUSIONS::

These data reveal preferential accumulation and maintenance of lutein in the infant brain despite under representation in the typical infant diet. Further investigation on the impact of lutein on neural development in preterm infants is warranted.

Endurance et hypertrophie font-ils bon ménage!

22/07/2014 | Etudes Musculation

 

Is muscle hypertrophy following resistance exercise regulated by truncated splice variants of PGC-1α?
Christopher G.R. Perry   Acta Physiologica 2014 Accepted Article (Accepted, unedited articles published online and citable. The final edited and typeset version of record will appear in future.)

In this issue, the investigation by Lundberg et al revisited a classic question of how muscle hypertrophy occurs following resistance exercise but not endurance exercise in human skeletal muscle. A recent study suggested the master transcriptional co-activator PGC-1α, known for regulating multiple transcriptional programs encoding mitochondrial and other metabolic proteins following endurance exercise, may also regulate muscle hypertrophy after resistance exercise through a truncated variant termed PGC-1α4 (Ruas et al 2012). Based on these findings, Lundberg and colleagues reasoned this model would predict a greater expression of this splice variant following resistance exercise vs endurance exercise in human skeletal muscle

A PGC-1α isoform induced by resistance training regulates skeletal muscle hypertrophy.

Cell. 2012 Dec 7;151(6):1319-31.  Ruas JL

PGC-1α is a transcriptional coactivator induced by exercise that gives muscle many of the best known adaptations to endurance-type exercise but has no effects on muscle strength or hypertrophy. We have identified a form of PGC-1α (PGC-1α4) that results from alternative promoter usage and splicing of the primary transcript. PGC-1α4 is highly expressed in exercised muscle but does not regulate most known PGC-1α targets such as the mitochondrial OXPHOS genes. Rather, it specifically induces IGF1 and represses myostatin, and expression of PGC-1α4 in vitro and in vivo induces robust skeletal muscle hypertrophy. Importantly, mice with skeletal muscle-specific transgenic expression of PGC-1α4 show increased muscle mass and strength and dramatic resistance to the muscle wasting of cancer cachexia. Expression of PGC-1α4 is preferentially induced in mouse and human muscle during resistance exercise. These studies identify a PGC-1α protein that regulates and coordinates factors involved in skeletal muscle hypertrophy.

Truncated splice variant PGC-1α4 is not associated with exercise-induced human muscle hypertrophy.
Lundberg TR           Acta Physiol (Oxf). 2014 May 6.

A truncated PGC-1α splice variant (PGC-1α4) has been implicated in the regulation of resistance exercise (RE)-induced muscle hypertrophy, and basal expression levels said to be augmented in response to concurrent aerobic (AE) and RE training.
AIM:
The current study investigated human muscle truncated and non-truncated PGC-1α transcripts in response to both acute and chronic RE, and with or without preceding AE (AE+RE).
METHODS:
Ten men performed 5 weeks of unilateral AE+RE and RE training. Before (untrained) and after (trained) this intervention, PGC-1α transcripts were assessed in vastus lateralis muscle biopsies obtained before and 3 h after acute RE, with or without preceding AE. Additionally, samples were collected 72 h after the last exercise bout of the training programme.
RESULTS:
The truncated splice variant increased (P < 0.05) its expression after acute exercise regardless of mode. However, the expression was greater (P < 0.05) after AE+RE than RE. Other PGC-1α transcripts showed similar response. Truncated transcripts originated from both the alternative and proximal promoter, and AE+RE increased PGC-1α expression from both promoter sites. RE induced transcripts from the alternative promoter only. PGC-1α expressions after acute exercise were comparable across isoforms in both untrained and trained muscle. Steady-state levels of isoforms were unchanged after 5-week training (P > 0.05). Exercise-induced expression of PGC-1α variants did not correlate with changes in muscle size or strength (P > 0.05).
CONCLUSION:
Our results do not support the view that truncated PGC-1α coordinates exercise-induced hypertrophy in human skeletal muscle. Rather, all PGC-1α isoforms appear to be regulated transiently in response to acute exercise and regardless of mode.

De la DMAA détectée dans une majorité de boosters d’importation

22/07/2014 |

 

Si ton booster à l’air trop fort pour être vrai, c’est probablement qu’il l’est (trop fort mais pas vrai)

Rapid assessment of the illegal presence of 1,3-dimethylamylamine (DMAA) in sports nutrition and dietary supplements using 1 H NMR spectroscopy.
Monakhova YB   Drug Test Anal. 2014 Jun 9. doi: 10.1002/dta.1677. [Epub ahead of print]

1,3-Dimethylamylamine (DMAA) is a stimulant that can be found in pre-workout sports nutrition and dietary supplements. This practice is illegal because DMAA is not a safe food ingredient but rather an unapproved medicinal compound due to its pharmacological action. In order to determine the DMAA content in such products, a nuclear magnetic resonance (NMR) spectroscopic method was developed and validated (DMAA was quantified as DMAA-HCl). For quantification, the collective integral from two of the methyl groups of the molecule in the range δ 0.92-0.84 ppm was used. The method was linear over the examined range of 1-21 g/kg (R2  = 0.9937). The recoveries from spiked concentrations (0.1-6 g/kg) ranged between 85% and 105% (96% on average), with a relative standard deviation (RSD) of 1% for an authentic sample. The detection limit was 0.03 g/kg and the quantification limit was 0.08 g/kg (calculated for 75 mg sample weight). The actual DMAA-HCl content in the sample was quantified using calibration curves (external standardization) or 3,5-dinitrobenzoic acid as single-point internal standard. The developed NMR methodology was applied for the analysis of 16 products, from which 9 samples were found positive (the DMAA-HCl concentration varied between 3.1 g/kg and 415 g/kg). The method can be recommended for routine use in food testing, customs or doping control laboratories.

Les estrogènes du houblon ont un effet durable

22/07/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Pharmacokinetics of Prenylated Hop Phenols in Women Following Oral Administration of a Standardized Extract of Hops

Richard B. van Breemen         Molecular Nutrition & Food Research 2014 Accepted Article

Women seeking alternatives to hormone replacement therapy for menopausal symptoms often try botanical dietary supplements containing extracts of hops (Humulus lupulus L.). Hops contain 8-prenylnaringenin (8-PN), a potent phytoestrogen, the related flavanones 6-prenylnaringenin (6-PN) and isoxanthohumol (IX), and the prenylated chalcone xanthohumol (XN).

Methods and results

After chemically and biologically standardizing an extract of spent hops to these marker compounds, an escalating dose study was carried out in menopausal women to evaluate safety and pharmacokinetics. 8-PN, 6-PN, IX, and XN, sex hormones, and prothrombin time (PT/INR) were determined in blood samples and/or 24-h urine samples. There was no effect on sex hormones or blood clotting. The maximum serum concentrations of the prenylated phenols were dose-dependent and were reached from 2 to 7 h, indicating slow absorption. The marker compounds formed glucuronides that were found in serum and urine. Secondary peaks at 5 h in the serum concentration-time curves indicated enterohepatic recirculation. The serum concentration-time curves indicated demethylation of IX to form 8-PN and cyclization of XN to IX. Slow absorption and enterohepatic recirculation contributed to half-lives exceeding 20 h.

Conclusion

This human study indicated long half-lives of the estrogenic and proestrogenic prenylated phenols in hops but no acute toxicity.

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