Functional impact of high protein intake on healthy elderly people.

Am J Physiol Endocrinol Metab. 2008 Aug 12;

Authors: Walrand S, Short KR, Bigelow ML, Sweatt A, Hutson SM, Nair KS

Decline in muscle mass, protein synthesis and mitochondrial function occur with age and amino acids are reported to enhance both muscle protein synthesis and mitochondrial function. It is unclear whether increasing dietary protein intake corrects postabsorptive muscle changes in aging. We determined whether a 10-day diet of high (HP, 3.0 g protein/kg FFM*d) versus usual protein intake (UP, 1.5 g protein/kg FFM*d) favourably affects mitochondrial function, protein metabolism and nitrogen balance or adversely affects insulin sensitivity and glomerular filtration rate (GFR) in 10 healthy younger (24 +/- 1 years) and 9 older (70 +/- 2 years) participants in a randomized crossover study. Net daily nitrogen balance increased equally in young and older but postabsorptive catabolic state also increased as indicated by higher whole body protein turnover and leucine oxidation with no change in protein synthesis. Maximal muscle mitochondrial ATP production rate was lower in older people, with no change occurred with diet. GFR was lower in older people and response to HP was significantly different between the two groups with a significant increase occurring only in younger people thus, widening the differences in GFR between the young and older. In conclusion a short-term high protein diet increased net daily nitrogen balance but increased the postabsorptive use of protein as a fuel. HP did not enhance protein synthesis or muscle mitochondrial function in either young or older. Additionally, widening differences in GFR between young and older is potential cause of concern in using HP diet in older people. Key words: dietary protein, protein metabolism, mitochondrial function, kidney function, aging.

PMID: 18697911 [PubMed - as supplied by publisher]

Aging and Alexithymia: Association With Reduced Right Rostral Cingulate Volume.

Am J Geriatr Psychiatry. 2008 Aug 12;

Authors: Paradiso S, Vaidya JG, McCormick LM, Jones A, Robinson RG

Objectives: Previous studies have linked alexithymia to an inability to process emotions appropriately. Older persons show changes in emotion processing and have higher alexithymia scores. Because the anterior cingulate cortex (ACC) is one of the regions showing earlier decline in late-life, and alexithymia seems to be related to a dysfunction in right hemisphere regions including the ACC subserving affective processes, the present study sought to test the hypothesis that reduced ACC volume accounts for the association between older age and alexithymia. Design: Correlation analyses between functionally distinct ACC subregions, age and alexithymia features. Setting: University of Iowa. Participants: Twenty-four healthy volunteers aged between 24 and 79 years. Measurements: Psychiatric and neuropsychological assessment and assessment of alexithymia using the 20-item Toronto Alexithymia Scale. High-resolution magnetic resonance imaging, and in-house developed methods for ACC parcellation. Results: Older age directly correlated with higher overall alexithymia and reduced bilateral rostral and right dorsal ACC gray matter volume. Furthermore, higher alexithymia scores correlated with reduced right rostral ACC volume. This correlation seems to be influenced primarily by Factor 3 of the alexithymia scale measuring diversion of attention to external details in place of internal feelings. Conclusions: These results suggest that alexithymia in older age may be a result of structural changes in the right rostral ACC.

PMID: 18697882 [PubMed - as supplied by publisher]

World Congress on Biomimetics, Artificial Muscles and Nano-Bio 2007.

Bioinspir Biomim. 2008 Jul 31;3(3):30202

Authors: Otero TF

Life-biological cells and organs-combines technological elegance with great efficiency in transforming chemical energy at constant temperature into functions. Inside any living cell thousands of simultaneous reactions occur. Every reaction promotes changes in intramolecular and intermolecular interactions. Most of those reactions link conformational changes of biopolymers with ionic and electronic movements pushing water flow. Living cells are constituted by reactive, soft and wet materials. Actuation of natural organs such as muscles involves, moreover, a chemical reaction (ATP hydrolysis). Simultaneous sensing processes provide living creatures with a perfect consciousness of both the characteristics of the mechanical movements and their interactions with the environment: they are intelligent devices. Nowadays models of the chemical kinetics do not include any quantification of either the changes in the molecular interactions inside the system during reaction or structural information about the conformational changes of enzymes or reactive proteins. From our point of view this is one the most important scientific challenges for the 21st century, involving responses to questions related to life, health and illness. Those responses, due to the magnitude of the challenge, can only be explored by cooperative work involving chemists, physicists, engineers, biologists or clinicians. Many technological advances developed by humans are inspired by biological systems, organs or devices present in living creatures. The main difference between human technology and natural organs is changes in chemical composition occurring inside the wet natural organ during actuation: they are reactive, soft and wet materials. Our artificial machines are constructed from dry materials that keep their composition constant under actuation. This is the context designed for the consecutive World Congresses on Biomimetics, Artificial Muscles and Nano-Bio, and more specifically for the fourth such one held in Torre Pacheco, Spain, on 6-9 November 2007: www.upct.es/~nano-bio/index.htm. Any attempt to produce biomimetic devices must include chemically reactive materials including water and ions. Considering that biological organs include biopolymers and that their actuation is triggered by a nervous pulse (electrical pulse), polymers and electric pulses are included in most of the devices. When those devices produce mechanical energy and macroscopic movements they are called artificial muscles: electromechanical when they do not include chemical reactions or electrochemomechanical when chemical reactions support the actuation. Advances in electromechanical artificial muscles consisting of a film of ionic polymer-metal nano-composites coated with two metallic electrodes are presented by Shahinpoor's group. When the polymer chains are influenced by physical or chemical variables from the environment, the triple layer produces an electrical signal proportional to the shifted variable and the device becomes, alternatively, a sensor. The contributions from Kaneto's and Otero's groups present two complementary aspects of electrochemomechanical wet devices where the conformational energy keeps the central role in training, fatigue and aging effects studied by repeat oxidation-reduction cycles under tensile loads, and for the unique simultaneous actuation and sensing abilities of those devices, mimicking those from natural organs. Consideration of the chemical reaction allows the quantification of the conformational energy as a constituent of the activation energy. The electrochemical reaction promotes in conducting polymers a progressive change in the potential gap between occupied and unoccupied electronic levels, the gap energy coming into the visible region. Thin films change their light absorbance under electrochemical control (chameleonic material) and Padilla shows that the maximum contrast is achieved with film of an intermediate thickness. The sensing abilities of artificial polymers are extended to natural crustacyanin proteins, extracted by Aldissi's group from lobster shells, that sense infrared radiation and can be used as an electro-optic thermal sensing device, having both high sensitivity and fast response, which is enhanced by the deposition process. The Toh group presents alumina membranes which allow selective transport of charged proteins, similar to biological membranes, by controlling the potential gradient between Pt deposited on both membrane surfaces. The Tozzi group presents a robust intelligent implantable robot based on shape memory alloys to restore the pump function of the atrium in patients suffering from chronic atrial fibrillation. The 4th World Congress on Biomimetics, Artificial Muscles and Nano-Bio was dedicated to the memory of Professor A MacDiarmid who had accepted both his participation as a plenary lecturer at the congress and his nomination as honorary doctor by the Universidad Politécnica de Cartagena. Unfortunately he passed away some months before the beginning of the meeting, depriving us of his clever lecture and of his permanent support in developing new aspects of conducting polymers. During the meeting we enjoyed a beautiful ceremony where Professor Yoshihito Osada received an honorary doctorate from the Universidad Politécnica de Cartagena, paying tribute to his outstanding contribution in the field. Finally, thanks are due to the editorial and production team of Bioinspiration & Biomimetics for their continued support and management of the review and preparation process in an entirely efficient and professional manner. Thanks are due to those institutions that have contributed in different ways to the final success of the meeting: MEC, ISE, UPCT, IBERNAM and the Autonomous Government of the Murcia Region. Special thanks go to all the participants who have contributed to this issue of Bioinspiration & Biomimetics at the forefront of steps towards the biomimetics of materials, properties and models.

PMID: 18698111 [PubMed - as supplied by publisher]

Acquired hematopoietic stem cell defects determine B-cell repertoire changes associated with aging.

Proc Natl Acad Sci U S A. 2008 Aug 12;

Authors: Guerrettaz LM, Johnson SA, Cambier JC

Aging is associated with an inability to mount protective antibody responses to vaccines and infectious agents. This decline is associated with acquisition of defects in multiple cellular compartments, including B cells. While peripheral B-cell numbers do not decline with aging, the composition of the compartment appears to change, with loss of naïve follicular B cells, accumulation of antigen-experienced cells, and alteration of the antibody repertoire. The underlying cause of this change is unknown. We tested the hypothesis that aging-associated repertoire changes can be attributed directly to decreased B lymphopoiesis. Using an Ig transgenic model to report changes in the B-cell repertoire, we show that the reduced B-cell generative capacity of "aged" long-term reconstituting hematopoietic stem cells (LT-HSCs) alters the representation of antigen specificities in the peripheral B-cell repertoire. Further, we show that reconstitution using suboptimal numbers of fully functional LT-HSCs results in the generation of a similarly altered B-cell repertoire. This may be an important factor to consider when deciding the number of bone marrow cells to transplant in the clinical setting. In conclusion, when B lymphopoiesis is limited peripheral B-cell homeostasis is altered. This is reflected in reduced diversity of the B-cell repertoire, which likely reduces the protective quality of the immune response.

PMID: 18697924 [PubMed - as supplied by publisher]

Reduced citrulline availability by OTC-deficiency in mice is related to reduced nitric oxide production.

Am J Physiol Endocrinol Metab. 2008 Aug 12;

Authors: Luiking YC, Hallemeesch MM, de Jonge WJ, Lamers WH, Deutz NE

The amino acid arginine is the sole precursor for nitric oxide (NO) synthesis. We recently demonstrated that an acute reduction of circulating arginine does not compromise basal or lipopolysaccharide (LPS)-inducible NO production in mice. In the present study, we investigated the importance of citrulline availability in ornithine transcarbamoylase-deficient spf(ash) (OTCD) mice on NO production, using stable isotope techniques and C57BL6/J (wild-type) mice controls. Plasma amino acids and tracer-tracee ratios were measured by LC-MS. NO production was measured as the in vivo conversion of L-[guanidino -(15)N2]arginine to L-[guanidine-(15)N]citrulline; de novo arginine production as conversion of L-[ureido-(13)C-5,5-(2)H2]citrulline to L-[guanidino -(13)C-5,5-(2)H2]arginine. Protein metabolism was measured using L-[ring-(2)H5]phenylalanine and L-[ring-(2)H2]tyrosine. OTC deficiency caused a reduction of systemic citrulline concentration and production to 30-50% (P<0.001), reduced de novo arginine production (P<0.05), reduced whole-body NO production to 50% (P<0.005) and increased net protein breakdown by a factor 2-4 (P<0.001). NO production was 2-fold higher in female than in male OTCD mice, in agreement with the X-linked location of the OTC gene. In response to LPS treatment (10 mg/kg i.p.), circulating arginine increased in all groups (P<0.001), and NO production was no longer affected by the OTC deficiency due to increased net protein breakdown as a source for arginine. Our study shows that reduced citrulline availability is related to reduced basal NO production via reduced de novo arginine production. Under basal conditions this is probably c-NOS mediated NO production. When sufficient arginine is available after LPS stimulated net protein breakdown, NO production is unaffected by OTC deficiency. Key words: arginine, OTC, sepsis.

PMID: 18697914 [PubMed - as supplied by publisher]