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2. Eigenvalues of neutral networks: interpolating between hypercubes

Author

Reeves, T., Farr, R. S., Blundell, J., Gallagher, A., and Fink, T. M. A.

Subjects
Mathematics - Spectral Theory
Abstract

A neutral network is a subgraph of a Hamming graph, and its principal eigenvalue determines its robustness: the ability of a population evolving on it to withstand errors. Here we consider the most robust small neutral networks: the graphs that interpolate pointwise between hypercube graphs of consecutive dimension (the point, line, line and point in the square, square, square and point in the cube, and so on). We prove that the principal eigenvalue of the adjacency matrix of these graphs is bounded by the logarithm of the number of vertices, and we conjecture an analogous result for Hamming graphs of alphabet size greater than two.

Published
2015

3. Regular neutral networks outperform robust ones by reaching their top growth rate more quickly

Author

Blundell, J. R., Gallagher, A., and Fink, T. M. A

Subjects
Quantitative Biology - Populations and Evolution
Abstract

We study the relative importance of "top-speed" (long-term growth rate) and "acceleration" (how quickly the long-term growth rate can be reached) in the evolutionary race to increase population size. We observe that fitness alone does not capture growth rate: robustness, a property of neutral network shape, combines with fitness to include the effect of deleterious mutations, giving growth rate. Similarly, we show that growth rate alone does not capture population size: regularity, a different property of neutral network shape, combines with growth rate to include the effect of higher depletion rates early on, giving size. Whereas robustness is a function of the principal eigenvalue of the neutral network adjacency matrix, regularity is a function of the principal eigenvector. We show that robustness is not correlated with regularity, and observe in silico the selection for regularity by evolving RNA ribozymes. Despite having smaller growth rates, the more regular ribozymes have the biggest populations.

Published
2012

4. Buckling of semiflexible filaments under compression

Author

Blundell, J. R. and Terentjev, E. M.

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

A model for filament buckling at finite temperatures is presented. Starting from the classical worm-like chain model under constant compression, we use a mean-field approach for filament inextensibility to find the complete partition function. We find that there is a simple interpolation formula that describes the free energy of chains or filaments as a function of end-to-end separation, which spans the whole range of filament stiffnesses. Using this formula we study the buckling transition of semiflexible filaments and find that kinetics plays an important role. We propose that the filament buckling is essentially the first order transition governed by the kinetics of escaping a local free energy minimum. A simple model for the kinetics is put forward, which shows the critical buckling force for a filament is reduced by a fraction that has a universal scaling with temperature with an exponent 0.56.

Published
2009

5. Affine model of stress stiffening in semiflexible filament networks

Author

Blundell, J. R. and Terentjev, E. M.

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Statistical Mechanics
Abstract

We present a revised theoretical study of the affine assumption applied to semiflexible networks. Drawing on simple models of semiflexible worm-like chains we derive an expression for the probability distribution of crosslink separations valid at all separations. This accounts for both entropic and mechanical filament stretching. From this we obtain the free energy density of such networks explicitly as a function of applied strain. We are therefore able to calculate the elastic moduli of such networks for any imposed strain or stress. We find that accounting for the distribution of cross-link separations destroys the simple scaling of modulus with stress that is well known in single chains, and that such scaling is sensitive to the mechanical stretch modulus of individual filaments. We compare this model to three experimental data sets, for networks of different types of filaments, and find that a properly treated affine model can successfully account for the data. We find that for networks of stiffer filaments, such as F-actin, to fit data we require a much smaller effective persistence length than usually assumed to be characteristic of this filament type. We propose that such an effectively reduced rigidity of filaments might be a consequence of network formation., Comment: 11 pages, 9 figures

Published
2008

6. The theory of semiflexible filaments and their networks

Author

Blundell, J.

Subjects
620.112
Abstract

A method devised by Edwards and Gupta for nematic polymers is implemented here for semiflexible filaments which enforces mean inextensibility. This linearises the path integral so that analytic results can be obtained. I argue that the expressions for the probability density obtained using this approach have merit – successfully reproducing the limiting cases of flexible and rigid chains – and have the advantage of being algebraically simple. I develop an algorithm based on the Metropolis method that can calculate the statistical properties of single chains subject to arbitrary interactions. I use this algorithm to check the analytical results obtained using the mean inextensibility approximation and find they are in close agreement. I highlight the applicability of the algorithm to arbitrary interactions by considering the statistical properties of a single chain which is stearically confined to a tube. I develop a model for the elasticity of semiflexible polymer networks based on the assumption of affine strain that uses the simple analytical expressions for probability densities obtained using mean inextensibility. Under such assumptions, I find that mechanical stretching of filaments must be considered in the network energy. This in turn implies that there are three distinct scaling regimes of the modulus which are relevant to stiff filament networks. I check the validity of the homogenous strain assumption by developing an algorithm capable of calculating the elasticity of a network of filaments subject to arbitrary strains and interaction energies. The effect thermal fluctuations, non-homogeneous deformations and variations in filament length have on elasticity is then explored. I find that all are in fact crucial in determining elasticity correctly, particularly at small strains.

Published
2011

14. Associations between high-metabolic rate organ masses and fasting hunger: a study using whole-body magnetic resonance imaging in healthy males

Author

Cassanova, N, Bosy-Westphal, A, Beaulieu, K, Finlayson, G, Stubbs, RJ, Blundell, J, Hopkins, M, and Müller, MJ

Subjects
Adult, Male, Magnetic Resonance Spectroscopy, Hunger, Experimental and Cognitive Psychology, Fasting, Magnetic Resonance Imaging, Behavioral Neuroscience, Young Adult, Glucose, Body Composition, Humans, Whole Body Imaging, Basal Metabolism, Insulin Resistance, Energy Metabolism
Abstract

Background: Fat-free mass (FFM) has been shown to be positively associated with hunger and energy intake, an association mediated by resting metabolic rate (RMR). However, FFM comprises a heterogeneous group of tissues with distinct metabolic rates, and it remains unknown how specific high-metabolic rate organs contribute to the degree of perceived hunger. Objective: To examine whether FFM and its anatomical components were associated with fasting hunger when assessed at the tissue-organ level. Design: Body composition (quantitative magnetic resonance and magnetic resonance imaging), RMR and whole-body glucose oxidation (indirect calorimetry), HOMA-index as a marker of insulin sensitivity, nitrogen balance and fasting hunger (visual analogue scales) were assessed in 21 healthy males (age = 25 ± 3y; BMI = 23.4 ± 2.1 kg/m2) after 3 days of controlled energy balance. Results: FFM (rs = 0.39; p = 0.09), RMR (rs = 0.52; p = 0.02) and skeletal muscle mass (rs = 0.57; p = 0.04), but not fat mass (rs = −0.01; p = 0.99), were positively associated with fasting hunger. The association between the combined mass of high-metabolic rate organs (i.e., brain, liver, kidneys and heart; rs = 0.58; p = 0.006) and fasting hunger was stronger than with FFM as a uniform body component. The strongest individual association was between liver mass and fasting hunger (rs = 0.51; p = 0.02). No associations were observed between glucose parameters, markers of insulin sensitivity and fasting hunger. The encephalic measure, an index of brain-to-body energy allocation, was negatively associated with fasting hunger (rs = −0.51; p = 0.02). Conclusions: Fasting hunger was more strongly associated with the combined mass of high-metabolic rate organs than with FFM as a uniform body component, highlighting the importance of integrating individual tissue-organ masses and their functional correlates into homeostatic models of human appetite. The association between liver mass and fasting hunger may reflect its role in ensuring the brain's basal energy needs are met.

Published
2022

15. Preliminary validation and principal components analysis of the Control of Eating Questionnaire (COEQ) for the experience of food craving

Author

Dalton, M., Finlayson, G., Hill, A., and Blundell, J.

Subjects
Principal components analysis -- Usage, Desire -- Health aspects, Food habits -- Health aspects, Food/cooking/nutrition, Health
Abstract

BACKGROUND/OBJECTIVES: The Control of Eating Questionnaire (CoEQ) comprises 21-items that are designed to assess the severity and type of food cravings an individual experiences over the previous 7 days. The CoEQ has been used in clinical trials as a multi-dimensional measure of appetite, craving and mood regulation however its underlying component structure has yet to be determined. The current paper has two aims;(1) to examine the psychometric properties, and internal consistency of the CoEQ; and (2) to provide a preliminary examination of the underlying components by exploring their construct and predictive validity. SUBJECTS/METHODS: Data were pooled from four studies in which a total 215 adults (80% women; Age = 29.7 ± 10.3; BMI = 26.5 ± 5.2) had completed the CoEQ alongside measures of psychometric eating behaviour traits, ad libitum food intake, and body composition. A principal components analysis (PCA) and parallel analysis was conducted to examine the underlying structure of the questionnaire. The resulting subscales were tested for internal consistency (Cronbach's a = 0.66-0.88). RESULTS: PCA revealed four components that explained 54.5% of the variance. The components were identified as: Craving Control, Positive Mood, Craving for Sweet, and Craving for Savoury. Associations between the underlying CoEQ subscales and measures of body composition and eating behaviour traits confirmed construct validity of the subscales. The associations between the subscales and snack food selection and intake of palatable snack foods supported the CoEQ's predictive validity. CONCLUSIONS: The CoEQ has good psychometric properties with a clear component structure and acceptable internal consistency. This preliminary validation supports the CoEQ as a measure of the experience of food cravings. European Journal of Clinical Nutrition (2015) 69, 1313-1317; doi: 10.1038/ejcn.2015.57; published online 8 April 2015, INTRODUCTION Food craving is defined as an intense desire to eat a specific food and has been associated with a loss of control over eating and poor weight management. For [...]

Published
2015
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16. The Psychobiology of Hunger – A Scientific Perspective

Author

Beaulieu, K and Blundell, J

Subjects
Philosophy, Energy expenditure, Expression (architecture), Energy (esotericism), fungi, digestive, oral, and skin physiology, Sensation, Perspective (graphical), food and beverages, Conscious State, Behavioral neuroscience, Cognitive psychology
Abstract

From a scientific perspective, hunger can be regarded as an identifiable conscious sensation which can be distinguished from other conscious states (e.g., pain, fear). The hunger state can be measured and is a marker of the existence of underlying biological processes. Measured hunger is functional and is normally associated with the act of eating. However, the conscious state of hunger, although driven physiologically, is not exclusively determined by biology; there is an environmental influence that can modulate its intensity and periodicity, and cultural factors that shape the appropriateness of the expression of hunger. Within a psychobiological framework, hunger can be considered as the expression of a ‘need state’ which mediates between biological requirements and environmental (nutritional) satisfaction. Our empirical studies show that hunger is clearly associated with biological signals (e.g., resting metabolic rate and some gastrointestinal peptides) and is central to the relationship between energy expenditure and energy intake.

Published
2020

18. Meta‐analysis of individual‐patient data from EVAR‐1, DREAM, OVER and ACE trials comparing outcomes of endovascular or open repair for abdominal aortic aneurysm over 5 years

Author

Powell, J. T., Sweeting, M. J., Ulug, P., Blankensteijn, J. D., Lederle, F. A., Becquemin, J.‐P., Greenhalgh, R. M., Greenhalgh, R. M., Beard, J. D., Buxton, M. J., Brown, L. C., Harris, P. L., Powell, J. T., Rose, J. D. G., Russell, I. T., Sculpher, M. J., Thompson, S. G., Lilford, R.J., Bell, P. R. F., Greenhalgh, R. M., Whitaker, S.C., Poole‐Wilson, the late P.A., Ruckley, C. V., Campbell, W. B., Dean, M. R. E., Ruttley, M. S. T., Coles, E. C., Powell, J. T., Halliday, A., Gibbs, S. J., Brown, L. C., Epstein, D., Sculpher, M. J., Thompson, S. G., Hannon, R. J., Johnston, L., Bradbury, A. W., Henderson, M. J., Parvin, S. D., Shepherd, D. F. C., Greenhalgh, R. M., Mitchell, A. W., Edwards, P. R., Abbott, G. T., Higman, D. J., Vohra, A., Ashley, S., Robottom, C., Wyatt, M. G., Rose, J. D. G., Byrne, D., Edwards, R., Leiberman, D. P., McCarter, D. H., Taylor, P. R., Reidy, J. F., Wilkinson, A. R., Ettles, D. F., Clason, A. E., Leen, G. L. S., Wilson, N. V., Downes, M., Walker, S. R., Lavelle, J. M., Gough, M. J., McPherson, S., Scott, D. J. A., Kessell, D. O., Naylor, R., Sayers, R., Fishwick, N. G., Harris, P. L., Gould, D. A., Walker, M. G., Chalmers, N. C., Garnham, A., Collins, M. A., Beard, J. D., Gaines, P. A., Ashour, M. Y., Uberoi, R., Braithwaite, B., Whitaker, S. C., Davies, J. N., Travis, S., Hamilton, G., Platts, A., Shandall, A., Sullivan, B. A., Sobeh, M., Matson, M., Fox, A. D., Orme, R., Yusef, W., Doyle, T., Horrocks, M., Hardman, J., Blair, P. H. B., Ellis, P. K., Morris, G., Odurny, A., Vohra, R., Duddy, M., Thompson, M., Loosemore, T. M. L., Belli, A. M., Morgan, R., Adiseshiah, M., Brookes, J. A. S., McCollum, C. N., Ashleigh, R., Aukett, M., Baker, S., Barbe, E., Batson, N., Bell, J., Blundell, J., Boardley, D., Boyes, S., Brown, O., Bryce, J., Carmichael, M., Chance, T., Coleman, J., Cosgrove, C., Curran, G., Dennison, T., Devine, C., Dewhirst, N., Errington, B., Farrell, H., Fisher, C., Fulford, P., Gough, M., Graham, C., Hooper, R., Horne, G., Horrocks, L., Hughes, B., Hutchings, T., Ireland, M., Judge, C., Kelly, L., Kemp, J., Kite, A., Kivela, M., Lapworth, M., Lee, C., Linekar, L., Mahmood, A., March, L., Martin, J., Matharu, N., McGuigen, K., Morris‐Vincent, P., Murray, S., Murtagh, A., Owen, G., Ramoutar, V., Rippin, C., Rowley, J., Sinclair, J., Spencer, S., Taylor, V., Tomlinson, C., Ward, S., Wealleans, V., West, J., White, K., Williams, J., Wilson, L., Grobbee, D. E., Blankensteijn, J. D., Bak, A. A. A., Buth, J., Pattynama, P. M., Verhoeven, E. L. G., van Voorthuisen, A. E., Blankensteijn, J. D., Balm, R., Buth, J., Cuypers, P. W. M., Grobbee, D. E., Prinssen, M., van Sambeek, M. R. H. M., Verhoeven, E. L. G., Baas, A. F., Hunink, M. G., van Engelshoven, J. M., Jacobs, M. J. H. M., de Mol, B. A. J. M., van Bockel, J. H., Balm, R., Reekers, J., Tielbeek, X., Verhoeven, E. L. G., Wisselink, W., Boekema, N., Heuveling, L. M., Sikking, I., Prinssen, M., Balm, R., Blankensteijn, J. D., Buth, J., Cuypers, P. W. M., van Sambeek, M. R. H. M., Verhoeven, E. L. G., de Bruin, J. L., Baas, A. F., Blankensteijn, J. D., Prinssen, M., Buth, J., Tielbeek, A.V., Blankensteijn, J. D., Balm, R., Reekers, J. A., van Sambeek, M. R. H. M., Pattynama, P., Verhoeven, E. L. G., Prins, T., van der Ham, A. C., van der Velden, J. J. I. M., van Sterkenburg, S. M. M., ten Haken, G. B., Bruijninckx, C. M. A., van Overhagen, H., Tutein Nolthenius, R. P., Hendriksz, T. R., Teijink, J. A. W., Odink, H. F., de Smet, A. A. E. A., Vroegindeweij, D., van Loenhout, R. M. M., Rutten, M. J., Hamming, J. F., Lampmann, L. E. H., Bender, M. H. M., Pasmans, H., Vahl, A. C., de Vries, C., Mackaay, A. J. C., van Dortmont, L. M. C., van der Vliet, A. J., Schultze Kool, L. J., Boomsma, J. H. B., van Dop, H. R., de Mol van Otterloo, J. C. A., de Rooij, T. P. W., Smits, T. M., Yilmaz, E. N., Wisselink, W., van den Berg, F. G., Visser, M. J. T., van der Linden, E., Schurink, G. W. H., de Haan, M., Smeets, H. J., Stabel, P., van Elst, F., Poniewierski, J., Vermassen, F. E. G., Lederle, F. A., Freischlag, J. A., Kohler, T. R., Latts, E., Matsumura, J., Padberg, F. T., Jr, Kyriakides, T. C., Swanson, K. M., Guarino, P., Peduzzi, P., Antonelli, M., Cushing, C., Davis, E., Durant, L., Joyner, S., Kossack, the late A., Kyriakides, T. C., LeGwin, Mary, McBride, V., OʼConnor, T., Poulton, J., Stratton, the late S., Zellner, S., Snodgrass, A. J., Thornton, J., Swanson, K. M., Haakenson, C. M., Stroupe, K.T., Jonk, Y., Hallett, J. W., Hertzer, N., Towne, J., Katz, D. A., Karrison, T., Matts, J. P., Marottoli, R., Kasl, S., Mehta, R., Feldman, R., Farrell, W., Allore, H., Perry, E., Niederman, J., Randall, F., Zeman, M., Beckwith, the late D., OʼLeary, T. J., Huang, G. D., Latts, E., Bader, M., Ketteler, E. R., Kingsley, D. D., Marek, J. M., Massen, R. J., Matteson, B. D., Pitcher, J. D., Langsfeld, M., Corson, J. D., Goff, J. M., Jr, Kasirajan, K., Paap, C., Robertson, D. C., Salam, A., Veeraswamy, R., Milner, R., Kasirajan, K., Guidot, J., Lal, B. K., Busuttil, S. J., Lilly, M. P., Braganza, M., Ellis, K., Patterson, M. A., Jordan, W. D., Whitley, D., Taylor, S., Passman, M., Kerns, D., Inman, C., Poirier, J., Ebaugh, J., Raffetto, J., Chew, D., Lathi, S., Owens, C., Hickson, K., Dosluoglu, H. H., Eschberger, K., Kibbe, M. R., Baraniewski, H. M., Matsumura, J., Endo, M., Busman, A., Meadows, W., Evans, M., Giglia, J. S., El Sayed, H., Reed, A. B., Ruf, M., Ross, S., Jean‐Claude, J. M., Pinault, G., Kang, P., White, N., Eiseman, M., Jones, the late R., Timaran, C. H., Modrall, J. G., Welborn, M. B., III, Lopez, J., Nguyen, T., Chacko, J. K. Y., Granke, K., Vouyouka, A. G., Olgren, E., Chand, P., Allende, B., Ranella, M., Yales, C., Whitehill, T. A., Krupski, the late W. C., Nehler, M. R., Johnson, S. P., Jones, D. N., Strecker, P., Bhola, M. A., Shortell, C. K., Gray, J. L., Lawson, J. H., McCann, R., Sebastian, M.W., Kistler Tetterton, J., Blackwell, C., Prinzo, P. A., Lee, N., Padberg, F. T., Jr, Cerveira, J. J., Lal, B. K., Zickler, R. W., Hauck, K. A., Berceli, S. A., Lee, W. A., Ozaki, C. K., Nelson, P. R., Irwin, A. S., Baum, R., Aulivola, B., Rodriguez, H., Littooy, F. N., Greisler, H., OʼSullivan, M. T., Kougias, P., Lin, P. H., Bush, R. L., Guinn, G., Bechara, C., Cagiannos, C., Pisimisis, G., Barshes, N., Pillack, S., Guillory, B., Cikrit, D., Lalka, S. G., Lemmon, G., Nachreiner, R., Rusomaroff, M., OʼBrien, E., Cullen, J. J., Hoballah, J., Sharp, W. J., McCandless, J. L., Beach, V., Minion, D., Schwarcz, T. H., Kimbrough, J., Ashe, L., Rockich, A., Warner‐Carpenter, J., Moursi, M., Eidt, J. F., Brock, S., Bianchi, C., Bishop, V., Gordon, I. L., Fujitani, R., Kubaska, S. M., III, Behdad, M., Azadegan, R., Ma Agas, C., Zalecki, K., Hoch, J. R., Carr, S. C., Acher, C., Schwarze, M., Tefera, G., Mell, M., Dunlap, B., Rieder, J., Stuart, J. M., Weiman, D. S., Abul‐Khoudoud, O., Garrett, H. E., Walsh, S. M., Wilson, K. L., Seabrook, G. R., Cambria, R. A., Brown, K. R., Lewis, B. D., Framberg, S., Kallio, C., Barke, R. A., Santilli, S. M., dʼAudiffret, A. C., Oberle, N., Proebstle, C., Johnson, L. L., Jacobowitz, G. R., Cayne, N., Rockman, C., Adelman, M., Gagne, P., Nalbandian, M., Caropolo, L. J., Pipinos, I. I., Johanning, J., Lynch, T., DeSpiegelaere, H., Purviance, G., Zhou, W., Dalman, R., Lee, J. T., Safadi, B., Coogan, S. M., Wren, S. M., Bahmani, D. D., Maples, D., Thunen, S., Golden, M. A., Mitchell, M. E., Fairman, R., Reinhardt, S., Wilson, M. A., Tzeng, E., Muluk, S., Peterson, N. M., Foster, M., Edwards, J., Moneta, G. L., Landry, G., Taylor, L., Yeager, R., Cannady, E., Treiman, G., Hatton‐Ward, S., Salabsky, the late B., Kansal, N., Owens, E., Estes, M., Forbes, B. A., Sobotta, C., Rapp, J. H., Reilly, L. M., Perez, S. L., Yan, K., Sarkar, R., Dwyer, S. S., Perez, S., Chong, K., Kohler, T. R., Hatsukami, T. S., Glickerman, D. G., Sobel, M., Burdick, T. S., Pedersen, K., Cleary, P., Back, M., Bandyk, D., Johnson, B., Shames, M., Reinhard, R. L., Thomas, S. C., Hunter, G. C., Leon, L. R., Jr, Westerband, A., Guerra, R. J., Riveros, M., Mills, J. L., Sr, Hughes, J. D., Escalante, A. M., Psalms, S. B., Day, N. N., Macsata, R., Sidawy, A., Weiswasser, J., Arora, S., Jasper, B. J., Dardik, A., Gahtan, V., Muhs, B. E., Sumpio, B. E., Gusberg, R. J., Spector, M., Pollak, J., Aruny, J., Kelly, E. L., Wong, J., Vasilas, P., Joncas, C., Gelabert, H. A., DeVirgillio, C., Rigberg, D. A., Cole, L., Becquemin, J.‐P., Marzelle, J., Becquemin, J.‐P., Sapoval, M., Becquemin, J.‐P., Favre, J.‐P., Watelet, J., Lermusiaux, P., Sapoval, M., Lepage, E., Hemery, F., Dolbeau, G., Hawajry, N., Cunin, P., Harris, P., Stockx, L., Chatellier, G., Mialhe, C., Fiessinger, J.‐N., Pagny, L., Kobeiter, H., Boissier, C., Lacroix, P., Ledru, F., Pinot, J.‐J., Deux, J.‐F., Tzvetkov, B., Duvaldestin, P., Watelet, J., Jourdain, C., David, V., Enouf, D., Ady, N., Krimi, A., Boudjema, N., Jousset, Y., Enon, B., Blin, V., Picquet, J., LʼHoste, P., Thouveny, F., Borie, H., Kowarski, S., Pernes, J.‐M., Auguste, M., Becquemin, J.‐P., Desgranges, P., Allaire, E., Marzelle, J., Kobeiter, H., Meaulle, P.‐Y., Chaix, D., Juliae, P., Fabiani, J. N., Chevalier, P., Combes, M., Seguin, A., Belhomme, D., Sapoval, M., Baque, J., Pellerin, O., Favre, J. P., Barral, X., Veyret, C., Watelet, J., Peillon, C., Plissonier, D., Thomas, P., Clavier, E., Lermusiaux, P., Martinez, R., Bleuet, F., C, Dupreix, Verhoye, J. P., Langanay, T., Heautot, J. F., Koussa, M., Haulon, S., Halna, P., Destrieux, L., Lions, C., Wiloteaux, S., Beregi, J. P., Bergeron, P., Pinot, J.‐J., Patra, P., Costargent, A., Chaillou, P., DʼAlicourt, A., Goueffic, Y., Cheysson, E., Parrot, A., Garance, P., Demon, A., Tyazi, A., Pillet, J.‐C., Lescalie, F., Tilly, G., Steinmetz, E., Favier, C., Brenot, R., Krause, D., Cercueil, J. P., Vahdat, O., Sauer, M., Soula, P., Querian, A., Garcia, O., Levade, M., Colombier, D., Cardon, J.‐M., Joyeux, A., Borrelly, P., Dogas, G., Magnan, P.‐É., Branchereau, A., Bartoli, J.‐M., Hassen‐Khodja, R., Batt, M., Planchard, P.‐F., Bouillanne, P.‐J., Haudebourg, P., Bayne, J., Gouny, P., Badra, A., Braesco, J., Nonent, M., Lucas, A., Cardon, A., Kerdiles, Y., Rolland, Y., Kassab, M., Brillu, C., Goubault, F., Tailboux, L., Darrieux, H., Briand, O., Maillard, J.‐C., Varty, K., and Cousins, C.

Published
2017
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23. Brief exposure of neuronal cells to levels of short chain fatty acids observed in human systemic circulation impair the cell lipid metabolism resulting in associated cell death by apoptosis

Author

Blundell J, Michel L. Tremblay, Tiffany A. Fillier, Sukhinder K. Cheema, Shah S, Thu Huong Pham, Raymond Thomas, Isabelle Aubry, and Karen M. Doody

Subjects
Programmed cell death, chemistry.chemical_compound, medicine.anatomical_structure, Chemistry, Cellular respiration, Apoptosis, Cell, Lipidomics, medicine, Cardiolipin, Lipid metabolism, Lipidome, Cell biology
Abstract

Communication between gut microbiota and the brain is an enigma. Alterations in the gut microbial community affects enteric metabolite levels, such as SCFAs. SCFAs have been proposed as a possible mechanism through which the gut microbiome modulate brain health and function. This study analyzed for the first time the effects of SCFAs at levels reported in human systemic circulation on human neuronal cell energy metabolism, viability, survival and the brain lipidome. Cell and rat brain lipidomics was done using UHPLC-HESI-HRAMS/MS. Neuronal cells viability, survival and energy metabolism were analyzed via flow cytometer, immunofluorescence, and SeahorseXF platform. Lipidomics analysis demonstrated that SCFAs significantly remodeled the brain lipidome in vivo and in vitro. The most notable remodulation was observed in the metabolism of phosphatidylethanolamine plasmalogens, and mitochondrial lipids carnitine and cardiolipin. Increased mitochondrial mass, fragmentation, and hyperfusion occurred concomitant with the altered mitochondrial lipid metabolism resulting in decreased neuronal cell respiration, ATP production, and increased cell death. This suggests SCFAs at levels observed in human systemic circulation can adversely alter the brain lipidome and neuronal cell function potentially negatively impacting brain health outcomes.

Published
2021

35. Homeostatic and non-homeostatic appetite control along the spectrum of physical activity levels: An updated perspective

Author

Beaulieu, K, Hopkins, M, Blundell, J, and Finlayson, G

Subjects
0301 basic medicine, Appetite control, media_common.quotation_subject, Energy balance, Physical activity, 030209 endocrinology & metabolism, Experimental and Cognitive Psychology, Satiation, Biology, 03 medical and health sciences, Behavioral Neuroscience, 0302 clinical medicine, Environmental health, Homeostasis, Humans, Exercise, media_common, 030109 nutrition & dietetics, Appetite Regulation, Perspective (graphical), Appetite, Physical activity level, Overconsumption, Adipose Tissue, Energy Intake, Energy Metabolism
Abstract

The current obesogenic environment promotes physical inactivity and food consumption in excess of energy requirements, two important modifiable risk factors influencing energy balance. Habitual physical activity has been shown to impact not only energy expenditure, but also energy intake through mechanisms of appetite control. This review summarizes recent theory and evidence underpinning the role of physical activity in the homeostatic and non-homeostatic mechanisms controlling appetite. Energy intake along the spectrum of physical activity levels (inactive to highly active) appears to be J-shaped, with low levels of physical activity leading to dysregulated appetite and a mismatch between energy intake and expenditure. At higher levels, habitual physical activity influences homeostatic appetite control in a dual-process action by increasing the drive to eat through greater energy expenditure, but also by enhancing post-meal satiety, allowing energy intake to better match energy expenditure in response to hunger and satiety signals. There is clear presumptive evidence that physical activity energy expenditure can act as a drive (determinant) of energy intake. The influence of physical activity level on non-homeostatic appetite control is less clear, but low levels of physical activity may amplify hedonic states and behavioural traits favouring overconsumption indirectly through increased body fat. More evidence is required to understand the interaction between physical activity, appetite control and diet composition on passive overconsumption and energy balance. Furthermore, potential moderators of appetite control along the spectrum of physical activity, such as body composition, sex, and type, intensity and timing of physical activity, remain to be fully understood.

Published
2018

39. Rate and extent of compensatory changes in energy intake and expenditure in response to altered exercise and diet composition in humans

Author

Stubbs, R.J., Hughes, D.A., Johnstone, A.M., Whybrow, S., Horgan, G.W., King, N., and Blundell, J.

Subjects
Appetite -- Research, Exercise -- Health aspects, Biological sciences
Abstract

We assessed the effect of no exercise (Nex; control) and high exercise level (Hex; ~4 M J/day) and two dietary manipulations [a high-fat diet (HF; 50% of energy, 700 kJ/100 g) and low-fat diet (LF; 20% of energy, 300 kJ/100 g)] on compensatory changes in energy intake (EI) and energy expenditure (EE) over 7-day periods. Eight lean men were each studied four times in a 2 x 2 randomized design. El was directly quantified by weight of food consumed. EE was assessed by heart rate (HR) monitoring. Body weight was measured daily. Mean daily EE was 17.6 and 11.5 MJ/day (P < 0.001) on the pooled Hex and Nex treatments, respectively. EI was higher on HF diets (13.4 M J/day pooled) compared with the LF diets (9.0 MJ/day). Regression analysis showed that these energy imbalances induced significant compensatory changes in EB over time of ~0.3-0.4 MJ/day (P < 0.05). These were due to changes in both EI and EE in the opposite direction to the perturbation in energy balance. These changes were significant, small but persistent, amounting to ~0.2 and ~0.35 MJ/day for EI and EE, respectively. appetite; energy balance; high-fat diet; low-fat diet; feeding behavior

Published
2004

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