Category Archives: Studies

Le ventre, notre deuxième cerveau

[Documentaire] Le ventre, notre deuxième cerveau
Link du replay :
http://www.arte.tv/fr/videos/048696-000-A/le-ventre-notre-deuxieme-cerveau

Image initialement trouvée sur : http://future.arte.tv/fr/ventre-deuxieme-cerveau/le-ventre-en-quelques-chiffres

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Back pain and discs

“Journal of Anatomy 2010 Volume 217 Issue 1, Pages 1 – 15

Intervertebral disc, sensory nerves and neurotrophins: who is who in discogenic pain?

José García-Cosamalón
Journal of Anatomy 2010 Volume 217 Issue 1, Pages 1 – 15

The normal intervertebral disc (IVD) is a poorly innervated organ supplied only by sensory (mainly nociceptive) and postganglionic sympathetic (vasomotor efferents) nerve fibers. Interestingly, upon degeneration, the IVD becomes densely innervated even in regions that in normal conditions lack innervation. This increased innervation has been associated with pain of IVD origin. The mechanisms responsible for nerve growth and hyperinnervation of pathological IVDs have not been fully elucidated. Among the molecules that are presumably involved in this process are some members of the family of neurotrophins (NTs), which are known to have both neurotrophic and neurotropic properties and regulate the density and distribution of nerve fibers in peripheral tissues. NTs and their receptors are expressed in healthy IVDs but much higher levels have been observed in pathological IVDs, thus suggesting a correlation between levels of expression of NTs and density of innervation in IVDs. In addition, NTs also play a role in inflammatory responses and pain transmission by increasing the expression of pain-related peptides and modulating synapses of nociceptive neurons at the spinal cord. This article reviews current knowledge about the innervation of IVDs, NTs and NT receptors, expression of NTs and their receptors in IVDs as well as in the sensory neurons innervating the IVDs, the proinflammatory role of NTs, NTs as nociception regulators, and the potential network of discogenic pain involving NTs.

Source: http://www.michaelgundill.com/blog/223

Airport scans radiations: be careful

Radiation risks cited in full-body airport scans

Full-body airport security scanners manufactured by Torrance-based Rapiscan Inc. expose the skin to high radiation levels that may lead to cancer and other health problems, according to researchers from the University of California, San Francisco.

Particularly at risk, the researchers said, are travelers who are pregnant, elderly or have weakened immune systems.

The machines emit X-ray energy levels that would be safe if they were distributed throughout the body, but a majority of that energy is delivered to the skin and underlying tissue at levels that “may be dangerously high,” the researchers wrote last month to the White House Office of Science and Technology.

Two Rapiscan backscatter machines have been tested over the past two years at Los Angeles International Airport, with more expected to arrive by the end of the year as part of a nationwide deployment.

“These scanners work because of the energy level of X-rays being concentrated on one area of the body,” said David Agard, a professor of biochemistry and biophysics at UC San Francisco and one of the four researchers who raised concerns about the machines.

“The numbers are small, mind you, so it’s not like this is a chest X-ray by any means,” Agard said. “But it is an increment of radiation that isn’t trivial.”

Executives at Rapiscan’s office in Torrance referred inquiries to the company’s spokesman in Arlington, Va., who did not return four phone calls seeking

comment.

However, officials with the Department of Homeland Security defended the use of Rapiscan’s backscatter machines, which are 9 feet long and 6” feet wide and bounce low-level X-rays off airlines passengers to peek underneath clothes as a secondary security screening measure.

While radiation exposure should be avoided, the amount of energy emitted from the machines is equal to two minutes in flight at cruising altitude, said Dr. Alex Garza, chief medical officer for the Department of Homeland Security.

Travelers who do not wish to be screened can still opt for a full-body pat-down, Garza said.

“The radiation exposure risk of backscatter imaging technology is so low, it’s almost negligible,” Garza said. “We take very seriously our duty to deploy technology to prevent terrorist attacks and protect the American people; however, we will not compromise on the safety to the public in meeting that goal.”

Politicians called for a wide deployment of the body imaging scanners nationwide just weeks after a 23-year-old Nigerian national allegedly tried to light an explosive device aboard a Northwest Airlines flight from Amsterdam to Detroit on Christmas Day. Authorities have said the machines would have been able to detect the explosives, which were hidden in the man’s underwear.

The Transportation Security Administration is expected to install 450 backscatter machines at LAX and 10 other airports across the country by the end of the year, funded by the American Recovery and Reinvestment Act.

At a cost of $190,000 each, the scanners produce intimate images that obscure the faces of passengers, but natural curves and crevices are seen clearly enough to detect hidden weapons or explosives. The graphic portraits are immediately deleted after they are viewed by security screeners in a remote, enclosed area away from passengers.

The National Council on Radiation Protection and Measurements released a statement last week that said a traveler would need to go through 2,500 body scans annually—or 10 times a day for a year—to meet the annual effective dose.

Researchers at UC San Francisco said that comparing the X-ray levels emitted from the machines to cosmic ray exposure during flights is “misleading.”

“Air travel cosmic rays are understood in terms of whole body volume doses, while these airport scanners deposit their energy directly into the skin,” Agard said. “We’re not trying to be alarmist, but cautious, and we would like the government to test these machines before they are put into wide use.”

Officials with the U.S. Food and Drug Administration said they found no problems with Rapiscan’s backscatter machines during tests conducted with the National Institute of Standards Technology and the Johns Hopkins University Applied Physics Laboratory.

The FDA is expected to respond to concerns raised by the team of UC San Francisco researchers sometime next month.

“We took their question seriously, but these machines are safe for the general public, including sensitive groups cited by UC San Francisco,” said Daniel Kassiday, an FDA specialist in radiation hazards. “The risk levels are extremely low, but communicating risk is never an easy thing when it comes to radiation.”

Source: http://www.michaelgundill.com/blog/218

Are myonuclei forever?

Are myonuclei forever?

Bruusgaard J.C., Johansen I.B., Egner I.M., Gundersen K.
J Muscle Res Cell Motil (2009) 30: 324

“Muscle size and force is mainly altered by changing the cross-sectional area of each muscle fibre. Muscle fibres contain multiple nuclei, and it has generally been assumed that each nucleus supports a certain cytoplasmic domain, and that some myonuclei are lost by a selective apoptosis during atrophy, while new nuclei are added from satellite cells during hypertrophy. We have recently used novel in vivo time lapse techniques to demonstrate that the number of myonuclei are constant during inactivity-atrophy. We have now used similar techniques to study overload-hypertrophy. A 53% increase in the number of nuclei was observed after 6–10 days after the overload intervention and this preceded the hypertrophy that commenced after 8 days. The newly added nuclei were persistence even if the fibres were subjected to subsequent denervation for up to 3 months: the number of nuclei remained as high in the severely atrophic, inactive fibres, as in normally innervated, overloaded muscles. Thus, the overload episode induced a permanently elevated number of nuclei. This effect might explain the observations that previously strength trained individuals are easily retrained. This phenomenon has been dubbed ‘‘muscle memory’’, and has previously been attributed to motor learning. Since anabolic steroids also increase the number of myonuclei, our findings might have an impact on the suspension periods of athletes after a doping offence.”

Source: http://www.michaelgundill.com/blog/178

Omega-3 against polyps

Colorectal polyps, while benign most of the time, can become cancerous tumors. Individuals with familial adenomatous polyposis (FAP) possess a genetic mutation that results in the development of multiple polyps and a greatly increased risk of colorectal cancer. Randomized trials have demonstrated a colorectal cancer-protective effect for the nonsteroidal anti-inflammatory sunlindac and the COX-2 inhibitors celecoxib and rofecoxib in FAP patients. However, COX-2 inhibitors are associated with cardiovascular toxicity in older users and may not be entirely safe in younger patients as well.

A randomized, double-blinded trial, described in an article published online on March 18, 2010 in the journal Gut, included 55 men and women with FAP who had undergone removal of their colons to prevent the development of colorectal cancer. Participants received two capsules twice daily of enteric-coated eicosapentaenoic acid free fatty acid (EPA-FFA) or placebo capsules for 6 months. The omega-3 fatty acid EPA has been shown to have an anticancer activity in cultured colorectal cancer cells and in other studies.

Subjects underwent endoscopic examination of the rectum at the beginning of the trial and at the conclusion of the treatment period, during which the number and size of polyps in a defined area were measured. There was a 2.6 fold increase in mucosal EPA levels in those who received the free fatty acid compared with the placebo. While the number of polyps in both groups was similar at baseline, they increased by 9.7 percent in those who received a placebo while decreasing by 12.4 percent in the EPA group, resulting in an average 22.4 reduction in polyp number in the EPA group compared to the placebo group. Polyp size, as assessed by the sum of polyp diameters, increased by 17.2 percent among those who received a placebo and decreased by 12.6 percent in the EPA group, which represents an average 29.8% decrease in the group that received EPA compared with the placebo group.

The authors remark that the reduction in the number and size of polyps in a short intervention period suggests that the activity elicited by EPA consists of a combination of regression of existing polyps and prevention of new growth. They note that delivery of the fatty acid in enteric-coated capsules could explain the absence of minor upper gastrointestinal effects in the current trial’s participants, which have been reported with prolonged use of omega-3 polyunsaturated fatty acids.

The study shares similar methodology with a trial involving the COX-2 inhibitor celecoxib, which also documented a decrease in polyp number among those who received active treatment. “EPA-FFA has chemopreventative efficacy in FAP, to a degree similar to that previously observed with selective cyclo-oxygenase-2 inhibitors,” the authors conclude. “EPA holds promise as a colorectal cancer chemoprevention agent with a favorable safety profile.”

Source: http://www.michaelgundill.com/blog/168

Excessive fructose and metabolic syndrome features

Excessive fructose intake induces the features of metabolic syndrome in healthy adult men: role of uric acid in the hypertensive response
International Journal of Obesity (2010) 34, 454–461; doi:10.1038/ijo.2009.259; published online 22 December 2009

S E Perez-Pozo, J Schold, T Nakagawa
“Background: Excessive fructose intake causes metabolic syndrome in animals and can be partially prevented by lowering the uric acid level. We tested the hypothesis that fructose might induce features of metabolic syndrome in adult men and whether this is protected by allopurinol. Methods: A randomized, controlled trial of 74 adult men who were administered 200 g fructose daily for 2 weeks with or without allopurinol. Primary measures included changes in ambulatory blood pressure (BP), fasting lipids, glucose and insulin, homeostatic model assessment (HOMA) index, body mass index and criteria for metabolic syndrome. Results: The ingestion of fructose resulted in an increase in ambulatory BP (7±2 and 5±2 mm Hg for systolic (SBP) and diastolic BP (DBP), P<0.004 and P<0.007, respectively). Mean fasting triglycerides increased by 0.62±0.23 mmol l−1 (55±20 mg per 100 ml), whereas high-density lipoprotein cholesterol decreased by 0.06±0.02 mmol l−1 (2.5±0.7 mg per 100 ml), P<0.002 and P<0.001, respectively. Fasting insulin and HOMA indices increased significantly, whereas plasma glucose level did not change. All liver function tests showed an increase in values. The metabolic syndrome increased by 25–33% depending on the criteria. Allopurinol lowered the serum uric acid level (P<0.0001) and prevented the increase in 24-h ambulatory DBP and daytime SBP and DBP. Allopurinol treatment did not reduce HOMA or fasting plasma triglyceride levels, but lowered low-density lipoprotein cholesterol relative to control (P<0.02) and also prevented the increase in newly diagnosed metabolic syndrome (0–2%, P=0.009). Conclusions: High doses of fructose raise the BP and cause the features of metabolic syndrome. Lowering the uric acid level prevents the increase in mean arterial blood pressure. Excessive intake of fructose may have a role in the current epidemics of obesity and diabetes.

Source: http://www.michaelgundill.com/blog/164

Pycnogenol protects kidneys

Hypertension affects many strength athletes. Pycnogenol contributes to protect them.

Kidney flow and function in hypertension: protective effects of pycnogenol in hypertensive participants—a controlled study.

J Cardiovasc Pharmacol Ther. 2010 Mar;15(1):41-6. Cesarone MR, Belcaro G, Stuard S, Schönlau F, Di Renzo A, Grossi MG, Dugall M, Cornelli U, Cacchio M, Gizzi G, Pellegrini L.

“This study evaluated the effects of Pycnogenol as an adjunct to angiotensin-converting enzyme (ACE)-inhibitor ramipril treatment of hypertensive patients presenting with early signs of renal function problems. One group of 26 patients was medicated with 10 mg ramipril per day only; a second group of 29 patients took Pycnogenol in addition to the ACE inhibitor over a period of 6 months. At trial end, a lowered systolic and diastolic blood pressure was found in both groups, with a significant further reduction of diastolic pressure in the group given Pycnogenol in addition to ramipril. The major aim of this study was the investigation of kidney-protective effects of Pycnogenol. Urinary albumin decreased from 87 +/- 23 to 64 +/- 16 mg/d with ramipril only. Additional Pycnogenol lowered albumin significantly better from 91 +/- 25 to 39 +/- 13 mg/day (P

< .05). In both groups, serum creatinine was lowered; however, only in the combination treatment group did the effect reached statistical significance. In both groups, CRP levels decreased from 2.1 to 1.8 with ramipril and from 2.2 to 1.1 with the ramipril-Pycnogenol combination; the latter reached statistical significance. Kidney cortical flow velocity was investigated by Doppler color duplex ultrasonography. Both systolic and diastolic flow velocities increased significantly after 6 months medication with ramipril. The addition of Pycnogenol to the regimen statistically significantly further enhanced kidney cortical flow velocities, by 8% for diastolic flow and 12% for systolic flow, relative to values found for the group taking ramipril only. The

protective effects of Pycnogenol for initial kidney damage ound in this study warrant further research with a larger number of patients and over a longer period of time.

Source: michaelgundill.com

Leptin and muscle hypertrophy

Training increases muscles receptors density
(obviously, dieting is not good)

Muscle hypertrophy and increased expression of leptin receptors in the musculus triceps brachii of the dominant arm
in professional tennis players

Eur J Appl Physiol (2010) 108:749–758

Hugo Olmedillas · Joaquin Sanchis-Moysi

In rodents, endurance training increases leptin
sensitivity in skeletal muscle; however, little is known
about the effects of exercise on the leptin signalling system
in human skeletal muscle. Thus, to determine whether
chronic muscle loading increases leptin receptor (OBR170)
protein expression, body composition dual-energy
X-ray absorptiometry was assessed in nine professional
male tennis players (24 § 4 years old) and muscle biopsies
were obtained from the dominant (DTB) and non-dominant
(NDTB) arm triceps brachii (TB), and also from the right
vastus lateralis (VL). In each biopsy, the protein content of
OB-R170, perilipin A, suppressor of cytokine signalling 3
(SOCS3), protein tyrosine phosphatase 1B (PTP1B) and
signal transducer and activator of transcription 3 (STAT3)
phosphorylation were determined by western blot. The
DTB had 15% greater lean mass (P < 0.05) and 62%
greater OB-R170 protein expression (P < 0.05) than the
NDTB. SOCS3 and PTP1B protein expression was similar
in both arms, while STAT3 phosphorylation was reduced in
the NDTB. OB-R170 protein content was also higher in
DTB than in VL (P < 0.05). In summary, this study shows
that the functional isoform of the leptin receptor is up-regulated
in the hypertrophied TB. The latter combined with the
fact that both SOCS3 and PTP1B protein expression were
unaltered is compatible with increased leptin sensitivity in
this muscle. Our findings are also consistent with a role of
leptin signalling in muscle hypertrophy in healthy humans.

Introduction

The ob/ob mouse, which does not produce leptin,
and the db/db mouse, which lacks functional leptin
receptors, have lower muscle mass than comparable wildtype
lean mice (Madiehe et al. 2002; Trostler et al. 1979).
Leptin administration to these mice promotes muscle
hypertrophy (Madiehe et al. 2002; Sainz et al. 2009).

Thus, muscle loading facilitates the expression of leptin
receptors when accompanied by muscle hypertrophy, at
least in muscles with a high proportion of type 2 fibres, as
in the TB (Sanchís-Moysi et al. 2009).

In summary, this study shows that TB hypertrophy is
accompanied by up-regulation of the functional isoform of
the leptin receptor. Given the cross-talk between IGF-I signalling
and leptin signalling, this finding is compatible with
a role for leptin signalling in muscle hypertrophy in healthy
humans. Since hypertrophy occurred predominantly in type
2 fibres in the loaded TB and in type 1 fibres in the VL, our
findings are consistent with a greater increase in OB-Rb
content in hypertrophied type 2 muscle fibres.

Source: michaelgundill.com

Potassium citrate and recurrent stone formation

Impact of long-term potassium citrate therapy on urinary profiles and recurrent stone formation.
J Urol. 2009 Mar;181(3):1145-50. Robinson MR, Leitao VA, Haleblian GE, Scales CD Jr, Chandrashekar A, Pierre SA, Preminger GM.

Comprehensive Kidney Stone Center, Division of Urologic Surgery, Duke University Medical Center, Durham, North Carolina, USA.

“PURPOSE: Potassium citrate therapy has become one of the cornerstones of medical stone management. We elucidated the long-term effects of potassium citrate on urinary metabolic profiles and its impact on stone formation rates. MATERIALS AND METHODS: We performed a retrospective cohort study in patients treated at the Comprehensive Kidney Stone Center at our institution between 2000 and 2006. Patients with pre-therapy and post-therapy 24-hour urinary profiles available who remained on potassium citrate for at least 6 months were included in the analysis. RESULTS: Of the 1,480 patients with 24-hour urinary profiles 503 met study inclusion criteria. Mean therapy duration was 41 months (range 6 to 168). Overall a significant and durable change in urinary metabolic profiles was noted as soon as 6 months after the onset of therapy. These changes included increased urinary pH (5.90 to 6.46, p <0.0001) and increased urinary citrate (470 to 700 mg a day, p <0.0001). The stone formation rate also significantly decreased after the initiation of potassium citrate from 1.89 to 0.46 stones per year (p <0.0001). There was a 68% remission rate and a 93% decrease in the stone formation rate. CONCLUSIONS: Potassium citrate provides a significant alkali and citraturic response during short-term and long-term therapy with the change in urinary metabolic profiles sustained as long as 14 years of treatment. Moreover, long-term potassium citrate significantly decreases the stone formation rate, confirming its usefulness in patients with recurrent nephrolithiasis.

Source: michaelgundill.com

Glucosamine and chondroitin sulfate taken separately or in combination

The human pharmacokinetics of oral ingestion of glucosamine and chondroitin sulfate taken separately or in combination
C.G. Jackson, A.H. Plaas, J.D. Sandy, C. Hua, S. Kim-Rolands Osteoarthritis and Cartilage Volume 18, Issue 3, Pages 297-302 (March 2010)

“Objective
As part of the National Institutes of Health (NIH)-sponsored Glucosamine/Chondroitin sulfate Arthritis Intervention Trial (GAIT) our objective here was to examine (1) the pharmacokinetics (PK) of glucosamine (GlcN) and chondroitin sulfate (CS) when taken separately or in combination as a single dose in normal individuals (n=29) and (2) the PK of GlcN and CS when taken as a single dose after 3 months daily dosing with GlcN, CS or GlcN+CS, in patients with symptomatic knee pain (n=28).

Methods
The concentration of GlcN in the circulation was determined by established fluorophore-assisted carbohydrate electrophoresis (FACE) methods. The hydrodynamic size and disaccharide composition of CS chains in the circulation and dosage samples was determined by Superose 6 chromatography and FACE.

Results
We show that circulating levels of CS in human plasma are about 20μg/ml. Most significantly, the endogenous concentration and CS disaccharide composition were not detectably altered by ingestion of CS, when the CS was taken alone or in combination with GlcN. On the other hand, the Cmax (single-dose study) and AUC values (multiple-dose study) for ingested GlcN were significantly reduced by combination dosing with CS, relative to GlcN dosing alone.

Conclusions
We conclude that pain relief perceived following ingestion of CS probably does not depend on simultaneous or prior intake of GlcN. Further, such effects on joint pain, if present, probably do not result from ingested CS reaching the joint space but may result from changes in cellular activities in the gut lining or in the liver, where concentrations of ingested CS, or its breakdown products, could be substantially elevated following oral ingestion. Moreover, since combined dosing of GlcN with CS was found to reduce the plasma levels seen with GlcN dosing alone , any improved pain relief by combination dosing cannot be explained by higher circulating concentrations of GlcN.

Source: michaelgundill.com

Elastic bands improve squat

Kinetic and kinematic differences between squats performed with and without elastic bands
Israetel, MA, McBridem, JM, Nuzzo, JL, Skinner, JW, and Dayne, AM. J Strength Cond Res 24(1): 190-194, 2010

The purpose of this investigation was to compare kinetic and kinematic variables between squats performed with and without elastic bands equalized for total work. Ten recreationally weight trained males completed 1 set of 5 squats without (Wht) and with (Band) elastic bands as resistance. Squats were completed while standing on a force platform with bar displacement measured using 2 potentiometers. Electromyography (EMG) was obtained from the vastus lateralis. Average force-time, velocity-time, power-time, and EMG-time graphs were generated and statistically analyzed for mean differences in values between the 2 conditions during the eccentric and concentric phases. The Band condition resulted in significantly higher forces in comparison to the Wht condition during the first 25% of the eccentric phase and the last 10% of the concentric phase. However, the Wht condition resulted in significantly higher forces during the last 5% of the eccentric phase and the first 5% of the concentric phase in comparison to the Band condition. The Band condition resulted in significantly higher power and velocity values during the first portion of the eccentric phase and the latter portion of the concentric phase. Vastus lateralis muscle activity during the Band condition was significantly greater during the first portion of the eccentric phase and latter portion of the concentric phase as well. This investigation indicates that squats equalized for total work with and without elastic bands significantly alter the force-time, power-time, velocity-time, and EMG-time curves associated with the movements. Specifically, elastic bands seem to increase force, power, and muscle activity during the early portions of the eccentric phase and latter portions of the concentric phase.

Source: michaelgundill.com

Plasma Injection and Tendinopathy

A new study reveals that plasma injection would not be efficient against tendinopathy:

Platelet-Rich Plasma Injection for Chronic Achilles Tendinopathy
A Randomized Controlled Trial
Robert J. de Vos, MD; Adam Weir, MBBS; Hans T. M. van Schie, DVM, PhD; Sita M. A. Bierma-Zeinstra, PhD; Jan A. N. Verhaar, MD, PhD; Harrie Weinans, PhD; Johannes L. Tol, MD, PhD
JAMA. 2010;303(2):144-149.

Context Tendon disorders comprise 30% to 50% of all activity-related injuries; chronic degenerative tendon disorders (tendinopathy) occur frequently and are difficult to treat. Tendon regeneration might be improved by injecting platelet-rich plasma (PRP), an increasingly used treatment for releasing growth factors into the degenerative tendon.

Objective To examine whether a PRP injection would improve outcome in chronic midportion Achilles tendinopathy.

Design, Setting, and Patients A stratified, block-randomized, double-blind, placebo-controlled trial at a single center (The Hague Medical Center, Leidschendam, the Netherlands) of 54 randomized patients aged 18 to 70 years with chronic tendinopathy 2 to 7 cm above the Achilles tendon insertion. The trial was conducted between August 28, 2008, and January 29, 2009, with follow-up until July 16, 2009.

Intervention Eccentric exercises (usual care) with either a PRP injection (PRP group) or saline injection (placebo group). Randomization was stratified by activity level.

Main Outcome Measures The validated Victorian Institute of Sports Assessment-Achilles (VISA-A) questionnaire, which evaluated pain score and activity level, was completed at baseline and 6, 12, and 24 weeks. The VISA-A score ranged from 0 to 100, with higher scores corresponding with less pain and increased activity. Treatment group effects were evaluated using general linear models on the basis of intention-to-treat.

Results After randomization into the PRP group (n = 27) or placebo group (n = 27), there was complete follow-up of all patients. The mean VISA-A score improved significantly after 24 weeks in the PRP group by 21.7 points (95% confidence interval [CI], 13.0-30.5) and in the placebo group by 20.5 points (95% CI, 11.6-29.4). The increase was not significantly different between both groups (adjusted between-group difference from baseline to 24 weeks, –0.9; 95% CI, –12.4 to 10.6). This CI did not include the predefined relevant difference of 12 points in favor of PRP treatment.

Conclusion Among patients with chronic Achilles tendinopathy who were treated with eccentric exercises, a PRP injection compared with a saline injection did not result in greater improvement in pain and activity.

Source: michaelgundill.com

10 g of Amino Acids decrease Myostatin production

Essential Amino Acids Increase MicroRNA-499, -208b, and -23a and Downregulate Myostatin and Myocyte Enhancer Factor 2C mRNA Expression in Human Skeletal Muscle Micah J. Drummond, Erin L. Glynn, Christopher S. Fry, Shaheen Dhanani, Elena Volpi and Blake B. Rasmussen Journal of Nutrition,Vol. 139, No. 12, 2279-2284, December 2009 Essential amino acids (EAA) stimulate muscle protein synthesis in humans. However, little is known about whether microRNAs (miRNA) and genes associated with muscle growth are expressed differently following EAA ingestion. Our purpose in this experiment was to determine whether miRNA and growth-related mRNA expressed in skeletal muscle are up- or downregulated in humans following the ingestion of EAA. We hypothesized that EAA would alter miRNA expression in skeletal muscle as well as select growth-related genes. Muscle biopsies were obtained from the vastus lateralis of 7 young adult participants (3 male, 4 female) before and 3 h after ingesting 10 g of EAA. Muscle samples were analyzed for muscle miRNA (miR-499, -208b, -23a, -1, -133a, and -206) and muscle-growth related genes [MyoD1, myogenin, myostatin, myocyte enhancer factor C (MEF2C), follistatin-like-1 (FSTL1), histone deacytylase 4, and serum response factor mRNA] before and after EAA ingestion using real-time PCR. Following EAA ingestion, miR-499, -208b, -23a, -1, and pri-miR-206 expression increased (P < 0.05). The muscle-growth genes MyoD1 and FSTL1 mRNA expression increased (P < 0.05), and myostatin and MEF2C mRNA were downregulated following EAA ingestion (P < 0.05). We conclude that miRNA and growth-related genes expressed in skeletal muscle are rapidly altered within hours following EAA ingestion. Further work is needed to determine whether these miRNA are post-transcriptional regulators of growth-related genes following an anabolic stimulus."

Source: michaelgundill.com