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2.
J Physiol ; 2020 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-32198893

RESUMO

KEY POINTS: Night time/active phase food restriction for 6 hr impaired glucose intolerance in young male and female mice. Females displayed increased capacity for lipogenesis and triglyceride storage in response to a short daily fast. Females had lower fasting insulin levels and an increased potential for utilizing fat for energy through ß-oxidation compared to males. The need for the inclusion of both sexes, and the treatment of sex as an independent variable, is emphasized within the context of this fasting regime. ABSTRACT: There is growing interest in understanding the mechanistic significance and benefits of fasting physiology in combating obesity. Increasing the fasting phase of a normal day can promote restoration and repair mechanisms that occur during the post-absorptive period. Most studies exploring the effect of restricting food access on mitigating obesity have done so with a large bias towards the use of male mice. Here, we disentangle the roles of sex, food intake and food withdrawal in the response to a short-term daily fasting intervention, where food was removed for six hours in the dark/active phase of young, 8-week old mice. We showed that the removal of food during the dark phase impaired glucose tolerance in males and females, possibly due to the circadian disruption induced by this feeding protocol. Although both sexes demonstrated similar patterns of food intake, body composition and various metabolic markers, there were clear sex differences in the magnitude and extent of these responses. While females displayed enhanced capacity for lipogenesis and triglyceride storage, they also had low fasting insulin levels and an increased potential for utilizing available energy sources such as fat for energy through ß-oxidation. Our results highlight the intrinsic biological and metabolic disparities between male and female mice, emphasizing the growing need for the inclusion of both sexes in scientific research. Furthermore, our results illustrate sex-specific metabolic pathways that regulate lipogenesis, obesity and overall metabolic health. This article is protected by copyright. All rights reserved.

3.
Obesity (Silver Spring) ; 28(4): 822-829, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32144892

RESUMO

OBJECTIVE: The aim of this study was to test the protein leverage hypothesis in a cohort of youth with obesity. METHODS: A retrospective study was conducted in a cohort of youth with obesity attending a tertiary weight management service. Validated food questionnaires revealed total energy intake (TEI) and percentage of energy intake from carbohydrates (%EC), fats (%EF), and proteins (%EP). Individuals with a Goldberg cutoff ≥ 1.2 of the ratio of reported TEI to basal metabolic rate from fat-free mass were included. A subgroup had accelerometer data. Statistics included modeling of percentage of energy from macronutrients and TEI, compositional data analysis to predict TEI from macronutrient ratios, and mixture models for sensitivity testing. RESULTS: A total of 137 of 203 participants were included (mean [SD] age 11.3 [2.7] years, 68 females, BMI z score 2.47 [0.27]). Mean TEI was 10,330 (2,728) kJ, mean %EC was 50.6% (6.1%), mean %EF was 31.6% (4.9%), and mean %EP was 18.4% (3.1%). The relationship between %EP and TEI followed a power function (L coefficient -0.48; P < 0.001). TEI was inversely associated with increasing %EP. In the subgroup with < 60 min/d of moderate to vigorous physical activity (n = 48), lower BMI z scores were associated with higher %EP and moderate %EC. CONCLUSIONS: In youth with obesity, protein dilution by either carbohydrates or fats increases TEI. Assessment of dietary protein may be useful to assist in reducing TEI and BMI in youth with obesity.

4.
Br J Nutr ; : 1-24, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-31983360

RESUMO

Nutritional therapy is a cornerstone of burns management. The optimal macronutrient intake for wound healing after burn injury has not been identified, although high-energy, high-protein diets are favoured. This study aimed to identify the optimal macronutrient intake for burn wound healing. The Geometric Framework (GF) was used to analyse wound healing after a 10% TBSA contact burn in mice ad libitum fed one of 11 high-energy diets, varying in macronutrient composition with protein (P5%-60%), carbohydrate (C20%-75%) and fat (F20%-75%). In the GF study, the optimal ratio for wound healing was identified as a moderate-protein, high-carbohydrate diet with a protein:carbohydrate:fat (P:C:F) ratio of 1:4:2. High-carbohydrate intake was associated with lower mortality, improved body weight and a beneficial pattern of body fat reserves. Protein intake was essential to prevent weight loss and mortality, but a protein intake target of ~7 kJ/day (~15% of energy intake) was identified, above which no further benefit was gained. High-protein intake was associated with delayed wound healing and increased liver and spleen weight. As the GF study demonstrated that an initial very high-protein intake prevented mortality, a very high-protein, moderate-carbohydrate diet (P40:C42:F18) was specifically designed. The dynamic diet study was also designed to combine and validate the benefits of an initial very high-protein intake for mortality, and subsequent moderate-protein, high-carbohydrate intake for optimal wound healing. The dynamic feeding experiment showed switching from an initial very high-protein diet to the optimal moderate-protein, high-carbohydrate diet accelerated wound healing whilst preventing mortality and liver enlargement.

5.
Chronobiol Int ; 37(2): 218-226, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31934814

RESUMO

Objective measures of circadian disruption are difficult to capture in a free-living environment hence the importance of validating subjective measures of jetlag. We aimed to assess the internal consistency of the 15-item Liverpool Jetlag Scale and its convergent and divergent validity with indicators of fatigue and anxiety in a large sample of air passengers. Online survey of passengers was conducted after travel on a range of long-haul flights. Jetlag was captured using the Liverpool scale, fatigue was measured using the Vitality subscale of the Short-Form Health Survey (SF-36), and the presence of anxiety or worry before, during, and after flight was self-reported. Inter-item correlations and Cronbach's alpha were calculated to assess the internal consistency of the scale. Exploratory factor analysis was used to examine whether the scale was consistent with one underlying construct of circadian disruption. Correlations between fatigue and anxiety (flying, situational, symptoms) with jetlag were used to assess convergent and divergent validity. Linear regression was used to determine the most important symptoms contributing to subjective jetlag rating. N = 460 passengers (57% female, mean age 50, SD 16 years) were surveyed. Cronbach's alpha indicated high internal reliability (alpha = 0.85). Jetlag was more strongly correlated with fatigue (rho = 0.47) than any type of anxiety (rho = 0.10-0.22). Exploratory factor analysis indicated responses were consistent with four factors: (i) fatigue/daytime impairment, (ii) sleep disturbance, (iii) changes in appetite and (iv) changes in bowel function. Regression analysis indicated that only changes in concentration, sleep time, fatigue, sleep quality and frequency of bowel motions were independent correlates of subjective jetlag (R2 = 27%). The Liverpool Jetlag Scale is internally consistent and demonstrates the expected relationships with fatigue and anxiety. Patterns of response are not consistent with all items being derived from one underlying factor, i.e. circadian disruption. Further, not all items contributed to the jetlag rating, suggesting the single-item rating may be useful for capturing the subjective experience of jetlag, whilst a total jetlag score is useful for also capturing circadian symptoms considered by passengers to be unrelated to jetlag. Validation of subjective jetlag against objective measures of circadian disruption is required.

6.
J Anim Ecol ; 89(2): 460-470, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31658371

RESUMO

Immunity and nutrition are two essential modulators of individual fitness. However, while the implications of immune function and nutrition on an individual's lifespan and reproduction are well established, the interplay between feeding behaviour, infection and immune function remains poorly understood. Asking how ecological and physiological factors affect immune responses and resistance to infections is a central theme of eco-immunology. In this study, we used the fruit fly, Drosophila melanogaster, to investigate how infection through septic injury modulates nutritional intake and how macronutrient balance affects survival to infection by the pathogenic Gram-positive bacterium Micrococcus luteus. Our results show that infected flies maintain carbohydrate intake, but reduce protein intake, thereby shifting from a protein-to-carbohydrate (P:C) ratio of ~1:4 to ~1:10 relative to non-infected and sham-infected flies. Strikingly, the proportion of flies dying after M. luteus infection was significantly lower when flies were fed a low-P high-C diet, revealing that flies shift their macronutrient intake as means of nutritional self-medication against bacterial infection. These results are likely due to the effects of the macronutrient balance on the regulation of the constitutive expression of innate immune genes, as a low-P high-C diet was linked to an upregulation in the expression of key antimicrobial peptides. Together, our results reveal the intricate relationship between macronutrient intake and resistance to infection and integrate the molecular cross-talk between metabolic and immune pathways into the framework of nutritional immunology.

7.
Curr Biol ; 30(1): 135-142.e4, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31839453

RESUMO

Achieving nutritional homeostasis is crucial for the fitness of all living organisms [1]. Using "collective wisdom," ants have been shown to excel at making rapid and appropriate decisions under various contexts [2, 3], including foraging [4-7]. Ants often use pheromone trails to share information about food resources [8-10], a process allowing them to focus their foraging activity on the best food source available [7, 11-14]. However, what constitutes the best food source depends on the nutritional context of the colony in relation to its food environment [15]. In this study, we exposed ant colonies to various nutrient deficiencies and observed their compensatory nutritional responses. Ants were deprived of carbohydrate, sterol, protein, a subset of amino acids, or a single amino acid. We found that ants were rapidly able to match their foraging decisions to their nutritional needs, even if the deficiency concerned a single amino acid. An individual-based model demonstrates that these impressive feats of nutritional compensation can emerge from the iterative process of trail-laying behavior, which relies on a simple individual decision: to eat or not to eat. Our results show that, by adjusting their feeding behavior at the individual level, ants sustain homeostasis at the colony level.

8.
J Insect Physiol ; 120: 103983, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31747550

RESUMO

Many animals have been shown to select among nutritionally complementary foods to reach a specific balance of nutrients that optimizes key life history traits. Nutritional ecology theory, however, predicts that an animal with a diet that is very stable in its composition, and with nutritional requirements that do not vary in their balance through time, would not need to display such mechanisms of regulation. Here we use the Australian termite Nasutitermes exitiosus as a model to test this prediction for the first time. We used the nutritional geometric framework to investigate the regulation of carbohydrate and protein, as well as the effects on foraging behaviour of protein type and group caste composition and size. Our results support the prediction of nutritional ecology, as termites failed to actively defend a well-defined macronutrient ratio. Termites maintained food collection relatively constant across protein type and group composition, and only appear to vary their collection by avoiding diets too rich in protein.

9.
J Gerontol A Biol Sci Med Sci ; 75(2): 348-356, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-30955034

RESUMO

BACKGROUND: The objective of the study is to evaluate the prospective associations between antioxidant intake and incident frailty among older Australian men aged ≥75 years. METHODS: Seven hundred and ninety-four men participated in a detailed diet history interview at the Concord Health and Ageing in Men Project (CHAMP) study third wave (considered baseline nutrition here) and 781 men participated at the fourth wave (considered 3-year follow-up here). The main outcome measurement was incident frailty at 3-year follow-up, using the Cardiovascular Health Study definition. Dietary adequacy of antioxidant intake was assessed by comparing participants' median intakes of four dietary antioxidants (vitamin A, E, C, and zinc) to the nutrient reference values (NRVs). Attainment of the NRVs was incorporated into a dichotomized variable "poor" (meeting ≤2 antioxidants) or "good" (meeting ≥3 antioxidants) as the independent variable using the cut-point method. Also, intakes of each individual dietary antioxidant at baseline nutrition were categorized into quartiles. Analyses were performed using multinomial logistic regression. RESULTS: Incidence of pre-frailty was 53.0% and frailty was 6.4% at 3-year follow-up. Poor dietary antioxidant intake (meeting ≤2) at baseline nutrition was associated with incident frailty at 3-year follow-up in unadjusted (OR: 2.59 [95% CI: 1.47, 4.59, p = .001]) and adjusted (OR: 2.46 [95% CI: 1.10, 5.51, p = .03]) analyses. The lowest quartile of vitamin E intake (<7.08 mg/d) was significantly associated with incident frailty (OR: 2.46 [95% CI: 1.01, 6.00, p = .05]). CONCLUSIONS: Poor antioxidant intake, particularly vitamin E, is a plausible factor associated with incident frailty among older men. This supports the need for clinical trials of diets rich in antioxidants or possibly low-dose antioxidant supplements, for prevention of frailty.

10.
Nutr Healthy Aging ; 5(2): 111-117, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31763496

RESUMO

BACKGROUND: Sirtuin 1 (SIRT1) is a NAD+-dependent enzyme that has important roles in many biological processes involved in aging, including cell growth and repair, inflammation, and energy regulation. SIRT1 activity is modulated in response to certain nutritional interventions that increase healthspan and longevity in rodents, including calorie restriction (CR) and intermittent fasting (IF). In addition to positively influencing cardiometabolic health, SIRT1 is important for brain health and may be critical in the preservation of memory processes that deteriorate during aging. OBJECTIVE: To investigate the role of brain-associated SIRT1 expression in the acquisition of fear memory in mice at 45 and 65 weeks of age. METHODS: Mice with brain-specific knock-out or overexpression of Sirt1 were assessed on a fear conditioning paradigm to determine the role of SIRT1 in fear memory acquisition. RESULTS: In the current study, mice lacking the expression of brain SIRT1 could not learn the fear conditioning paradigm during training, context, or cue phases. CONCLUSIONS: The results of the study indicate that SIRT1 expression in the brain is critical for the formation of fear memory in male mice at two distinct ages, highlighting the essential role of SIRT1 in fear memory acquisition during aging.

11.
Nat Metab ; 1(5): 532-545, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31656947

RESUMO

Elevated branched chain amino acids (BCAAs) are associated with obesity and insulin resistance. How long-term dietary BCAAs impact late-life health and lifespan is unknown. Here, we show that when dietary BCAAs are varied against a fixed, isocaloric macronutrient background, long-term exposure to high BCAA diets leads to hyperphagia, obesity and reduced lifespan. These effects are not due to elevated BCAA per se or hepatic mTOR activation, but rather due to a shift in the relative quantity of dietary BCAAs and other AAs, notably tryptophan and threonine. Increasing the ratio of BCAAs to these AAs resulted in hyperphagia and is associated with central serotonin depletion. Preventing hyperphagia by calorie restriction or pair-feeding averts the health costs of a high BCAA diet. Our data highlight a role for amino acid quality in energy balance and show that health costs of chronic high BCAA intakes need not be due to intrinsic toxicity but, rather, a consequence of hyperphagia driven by AA imbalance.

12.
J Evol Biol ; 32(10): 1106-1116, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31385640

RESUMO

As females and males have different roles in reproduction, they are expected to require different nutrients for the expression of reproductive traits. However, due to their shared genome, both sexes may be constrained in the regulation of nutrient intake that maximizes sex-specific fitness. Here, we used the Geometric Framework for nutrition to examine the effect of macronutrient and micronutrient intakes on lifespan, fecundity and cuticular hydrocarbons (CHCs) that signal mate quality to prospective mates in female field crickets, Teleogryllus oceanicus. In addition, we contrasted nutritional effects on life-history traits between males and females to determine how sex differences influence nutrient regulation. We found that carbohydrate intake maximized female lifespan and protein intake influenced CHC expression, while early life fecundity (cumulative fecundity at day 21) and lifetime fecundity were dependent on both macronutrient and micronutrient intakes. Fecundity required different nutrient blends to those required to optimize sperm viability in males, generating the potential for sexual conflict over macronutrient intake. The regulation of protein (P) and carbohydrate (C) intakes by virgin and mated females initially matched that of males, but females adjusted their intake to a higher P:C ratio, 1P:2C, that maximized fecundity as they aged. This suggests that a sex-specific, age-dependent change in intake target for sexually mature females, regardless of their mating status, adjusts protein consumption in preparation for oviposition. Sex differences in the regulation of nutrient intake to optimize critical reproductive traits in female and male T. oceanicus provide an example of how sexual conflict over nutrition can shape differences in foraging between the sexes.

13.
Nutrients ; 11(8)2019 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412601

RESUMO

Protein and branched-chain amino acid (BCAA) intake are associated with changes in circulating BCAAs and influence metabolic health in humans and rodents. However, the relationship between BCAAs and body composition in both species is unclear, with many studies questioning the translatability of preclinical findings to humans. Here, we assessed and directly compared the relationship between circulating BCAAs, body composition, and intake in older mice and men. Body weight and body fat were positively associated with circulating BCAA levels in both mouse and human, which remained significant after adjustments for age, physical activity, number of morbidities, smoking status, and source of income in the human cohort. Macronutrient intakes were similarly associated with circulating BCAA levels; however, the relationship between protein intake and BCAAs were more pronounced in the mice. These findings indicate that the relationship between circulating BCAAs, body composition, and intakes are comparable in both species, suggesting that the mouse is an effective model for examining the effects of BCAAs on body composition in older humans.


Assuntos
Envelhecimento/sangue , Aminoácidos de Cadeia Ramificada/sangue , Composição Corporal , Adiposidade , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Animais , Biomarcadores/sangue , Peso Corporal , Humanos , Estudos Longitudinais , Masculino , Camundongos Endogâmicos C57BL , Fatores Sexuais , Especificidade da Espécie , Fatores de Tempo
14.
Artigo em Inglês | MEDLINE | ID: mdl-31428789

RESUMO

Increased blood levels of branched chain amino acids (BCAAs) have been associated with cardiometabolic risk factors. Here we studied 918 community dwelling older men to determine the relationship between BCAAs and other amino acids with cardiometabolic risk factors, major cardiovascular endpoints (MACE) and mortality. BCAAs had robust associations with many adverse metabolic risk factors (increased glucose, insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), triglycerides; decreased HDL cholesterol). However, paradoxically, participants with lower levels of BCAAs had greater mortality and MACE possibly because increasing age and frailty, both of which were associated with lower BCAA levels, are powerful risk factors for these outcomes in older people. Overall, amino acids that were lowest in frail subjects (BCAAs, α-aminobutyric acid (AABA), histidine, lysine, methionine, threonine, tyrosine) were inversely associated with mortality and MACE. In conclusion, BCAAs are biomarkers for important outcomes in older people including cardiometabolic risk factors, frailty and mortality. In old age, frailty becomes a dominant risk factor for MACE and mortality.

15.
FEMS Microbiol Ecol ; 95(8)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31271418

RESUMO

Proteins and carbohydrates have profound impacts on the ecology of gut microbiota, but disentangling the single and interactive effects of different dietary constituents is challenging. Here, we used a multidimensional approach, the Geometric Framework, to study the interactions between nutrition and bacterial abundances with respect to protein and carbohydrate intakes in field cricket, Teleogryllus oceanicus. Our study revealed that species richness decreased as crickets consumed more macronutrients, and species evenness peaked at high intake of protein-rich diets. Sex and protein:carbohydrate (P:C) ratios in diets were the primary factors influencing the gut bacterial community, but most of the microbial operational taxonomic units (OTUs) that were significantly different between males and females were present in low abundance. In contrast, protein intake had a greater influence than carbohydrate consumption on the relative abundances of the core bacterial taxa, as an increase in dietary protein availability could remove the growth constraint imposed by limited nitrogen. Taken together, the use of the Geometric Framework provides a deeper insight into how nutritional intakes influence the relative abundances of gut microbes, and could be a useful tool to integrate the study of gut microbiome and fitness traits in a host.

16.
Obesity (Silver Spring) ; 27(8): 1225-1238, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31339001

RESUMO

Much attention has been focused on fats and carbohydrates as the nutritional causes of energy overconsumption and obesity. In 2003, a model of intake regulation was proposed in which the third macronutrient, protein, is not only involved but is a primary driver of calorie intake via its interactions with carbohydrates and fats. This model, called protein leverage, posits that the strong regulation of protein intake causes the overconsumption of fats and carbohydrates (hence total energy) on diets with a low proportion of energy from protein and their underconsumption on diets with a high proportion of protein. Protein leverage has since been demonstrated in a range of animal studies and in several studies of human macronutrient regulation, and its potential role in contributing to the obesity epidemic is increasingly attracting discussion. Over recent years, however, several misconceptions about protein leverage have arisen. Our aim in this paper is to briefly outline some key aspects of the underlying theory and clarify 10 points of misunderstanding that have the potential to divert attention from the substantive issues.

17.
Cell Rep ; 27(10): 2934-2947.e3, 2019 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-31167139

RESUMO

Reduced dietary protein intake induces adaptive physiological changes in macronutrient preference, energy expenditure, growth, and glucose homeostasis. We demonstrate that deletion of the FGF21 co-receptor ßKlotho (Klb) from the brain produces mice that are unable to mount a physiological response to protein restriction, an effect that is replicated by whole-body deletion of FGF21. Mice forced to consume a low-protein diet exhibit reduced growth, increased energy expenditure, and a resistance to diet-induced obesity, but the loss of FGF21 signaling in the brain completely abrogates that response. When given access to a higher protein alternative, protein-restricted mice exhibit a shift toward protein-containing foods, and central FGF21 signaling is essential for that response. FGF21 is an endocrine signal linking the liver and brain, which regulates adaptive, homeostatic changes in metabolism and feeding behavior during protein restriction.

18.
Proc Biol Sci ; 286(1902): 20190393, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-31039722

RESUMO

Protein and calorie restrictions extend median lifespan in many organisms. However, studies suggest that among-individual variation in the age at death is also affected. Ultimately, both of these outcomes must be caused by effects of nutrition on underlying patterns of age-specific mortality (ASM). Using model life tables, we tested for effects of dietary macronutrients on ASM in mice ( Mus musculus). High concentrations of protein and fat relative to carbohydrates were associated with low life expectancy and high variation in the age at death, a result caused predominantly by high mortality prior to middle age. A lifelong diet comprising the ratio of macronutrients self-selected by mouse (in early adulthood) was associated with low mortality up until middle age, but higher late-life mortality. This pattern results in reasonably high life expectancy, but very low variation in the age at death. Our analyses also indicate that it may be possible to minimize ASM across life by altering the ratio of dietary protein to carbohydrate in the approach to old age. Mortality in early and middle life was minimized at around one-part protein to two-parts carbohydrate, whereas in later life slightly greater than equal parts protein to carbohydrate reduced mortality.

19.
Neurobiol Dis ; 130: 104481, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31136814

RESUMO

Aging is the greatest risk factor for most diseases including cancer, cardiovascular disorders, and neurodegenerative disease. There is emerging evidence that interventions that improve metabolic health with aging may also be effective for brain health. The most robust interventions are non-pharmacological and include limiting calorie or protein intake, increasing aerobic exercise, or environmental enrichment. In humans, dietary patterns including the Mediterranean, Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) and Okinawan diets are associated with improved age-related health and may reduce neurodegenerative disease including dementia. Rapamycin, metformin and resveratrol act on nutrient sensing pathways that improve cardiometabolic health and decrease the risk for age-associated disease. There is some evidence that they may reduce the risk for dementia in rodents. There is a growing recognition that improving metabolic function may be an effective way to optimize brain health during aging.

20.
Insect Biochem Mol Biol ; 109: 128-141, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30954680

RESUMO

Nutrition is vital to health and the availability of resources has long been acknowledged as a key factor in the ability to fight off parasites, as investing in the immune system is costly. Resources have typically been considered as something of a "black box", with the quantity of available food being used as a proxy for resource limitation. However, food is a complex mixture of macro- and micronutrients, the precise balance of which determines an animal's fitness. Here we use a state-space modelling approach, the Geometric Framework for Nutrition (GFN), to assess for the first time, how the balance and amount of nutrients affects an animal's ability to mount an immune response to a pathogenic infection. Spodoptera littoralis caterpillars were assigned to one of 20 diets that varied in the ratio of macronutrients (protein and carbohydrate) and their calorie content to cover a large region of nutrient space. Caterpillars were then handled or injected with either live or dead Xenorhabdus nematophila bacterial cells. The expression of nine genes (5 immune, 4 non-immune) was measured 20 h post immune challenge. For two of the immune genes (PPO and Lysozyme) we also measured the relevant functional immune response in the hemolymph. Gene expression and functional immune responses were then mapped against nutritional intake. The expression of all immune genes was up-regulated by injection with dead bacteria, but only those in the IMD pathway (Moricin and Relish) were substantially up-regulated by both dead and live bacterial challenge. Functional immune responses increased with the protein content of the diet but the expression of immune genes was much less predictable. Our results indicate that diet does play an important role in the ability of an animal to mount an adequate immune response, with the availability of protein being the most important predictor of the functional (physiological) immune response. Importantly, however, immune gene expression responds quite differently to functional immunity and we would caution against using gene expression as a proxy for immune investment, as it is unlikely to be reliable indicator of the immune response, except under specific dietary conditions.


Assuntos
Regulação da Expressão Gênica/imunologia , Imunidade Inata/genética , Proteínas de Insetos/genética , Proteínas de Insetos/imunologia , Spodoptera/genética , Spodoptera/imunologia , Animais , Dieta , Hemolinfa , Interações Hospedeiro-Patógeno , Larva/genética , Larva/crescimento & desenvolvimento , Larva/imunologia , Spodoptera/crescimento & desenvolvimento , Xenorhabdus/fisiologia
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