Gut microbiota alterations associated with reduced bone mineral density in older adults.
Rheumatology (Oxford, England). 2019;58(12):2295-2304
Plain language summary
Osteoporosis, characterised by reduced bone density or ‘brittle bones’ affects a significant number of individuals over the age of 50 worldwide. Contributing factors include calcium and vitamin D deficiency and the presence of other inflammatory conditions. The composition of gut bacteria, the gut microbiome, plays an important role in immune activity and changes in composition have been associated with other inflammatory conditions. This cohort study of 181 individuals at high risk of reduced bone density and fractures, aimed to determine whether different gut microbiota composition is associated with bone density. Dexa scans and faecal samples were used as part of the assessment and confounding factors of diet, BMI, supplementation and medication were included in the analysis. The authors of the study found 6 species of gut bacteria that were significantly altered in numbers in the groups with osteoporosis and osteopenia, after controlling for confounding factors, and suggest that they could be used as markers of disease risk or progression and as a therapeutic target. Nutrition Practitioners working with bone density can focus on supporting the gut microbiome as part of their nutrition protocols.
OBJECTIVE To investigate compositional differences in the gut microbiota associated with bone homeostasis and fractures in a cohort of older adults. METHODS Faecal microbiota profiles were determined from 181 individuals with osteopenia (n = 61) or osteoporosis (n = 60), and an age- and gender-matched group with normal BMD (n = 60). Analysis of the 16S (V3-V4 region) amplicon dataset classified to the genus level was used to identify significantly differentially abundant taxa. Adjustments were made for potential confounding variables identified from the literature using several statistical models. RESULTS We identified six genera that were significantly altered in abundance in the osteoporosis or osteopenic groups compared with age- and gender-matched controls. A detailed study of microbiota associations with meta-data variables that included BMI, health status, diet and medication revealed that these meta-data explained 15-17% of the variance within the microbiota dataset. BMD measurements were significantly associated with alterations in the microbiota. After controlling for known biological confounders, five of the six taxa remained significant. Overall microbiota alpha diversity did not correlate to BMD in this study. CONCLUSION Reduced BMD in osteopenia and osteoporosis is associated with an altered microbiota. These alterations may be useful as biomarkers or therapeutic targets in individuals at high risk of reductions in BMD. These observations will lead to a better understanding of the relationship between the microbiota and bone homeostasis.
What is the effect of a Mediterranean compared with a Fast Food meal on the exercise induced adipokine changes? A randomized cross-over clinical trial.
PloS one. 2019;14(4):e0215475
Plain language summary
Unhealthy dietary intake and sedentary behaviour in a genetically susceptible individual have been associated with adipokine dysregulation (adipokines are small proteins secreted by the fat tissue) resulting both in adverse metabolic and immune responses. The aim of this study was to evaluate the effect of a Mediterranean (MdM) compared with a Fast Food (FFM) iso-energy meal on the acute exercise-induced adipokine changes. The study is a double-blind randomised crossover clinical trial. Participants (n = 46) were randomly assigned to the intervention order in a double-blinded fashion, stratified by asthma diagnosis. Outcomes were measured blinded to the participant’s allocation order. Results indicate that MdM may blunt the adipsin (an adipokine) immediate response and potentiate its exercise induced increase in comparison with a FFM. MdM slightly attenuated the exercise induced cortisol increase. Authors conclude that their findings highlight the importance of the pre-exercise dietary intake on both the immune and metabolic response to acute exercise.
BACKGROUND Adipose tissue-derived adipokines are pro-inflammatory cytokines involved in metabolic-related diseases and can be influenced by diet and exercise. We aimed to compare the effect of a Mediterranean (MdM) compared with Fast Food (FFM) meal on the exercise induced adipokines changes. METHODS In a double blinded cross over trial, 46 participants were randomly assigned to one of two standardized iso-energy pre-exercise meals: FFM or MdM-type. Three hours after each meal, participants completed a treadmill exercise test (EC). Serum adiponectin, resistin, PAI-1, lipocalin-2/NGAL and adipsin were determined by Luminex magnetic bead immunoassay. Wilcoxon signed rank test compared changes before/after meal and before/after EC and a linear mixed model evaluated the effect of meals on the adipokine response to exercise, adjusted for confounders. RESULTS Thirty-nine participants (mean age of 25, with a standard deviation of 5 years) completed the trial (56% females). For both interventions, a significant reduction of adipsin after each meal and a significant increase of lipocalin, PAI-1, adipsin and resistin, after exercise was observed. When exercise was preceded by a MdM meal a higher increase in adipsin levels was seen. CONCLUSION Acute exercise induced an increase of circulatory levels of adipsin, resistin, lipocalin and PAI-1, but not adiponectin. A pre-exercise Mediterranean meal potentiated the increase of adipsin after the exercise test, which possibly relates to the immune regulatory role of adipsin. These changes suggest a cross-talk between the immune and metabolic immediate response to exercise and its modulation by the pre-exercise diet composition.
Brain-Behavior-Immune Interaction: Serum Cytokines and Growth Factors in Patients with Eating Disorders at Extremes of the Body Mass Index (BMI) Spectrum.
Plain language summary
Eating disorders such as anorexia, binge eating and night-time eating cause great fluctuations in body mass and have also been shown to alter the immune system, and more specifically markers of inflammation called cytokines. In this observational study of 90 patients with known eating disorders, the researchers tried to identify how much BMI, ‘underweightness’ and malnutrition influenced the body’s pro-inflammatory response and upset the normal immune response. They found that many inflammatory cytokines were elevated in the blood samples taken, a likely response to the conditions of stress in the body. These cytokines are known to interact with the nervous system and were also influenced by other common symptoms such as depression. They were able to group the differences in cytokines for anorexia nervosa, binge-eating disorder, post-dinner eating, night-eating, sweet-eating and fasting. These markers of dysfunctional eating behaviours may help form part of a therapeutic approach to treating eating disorders based on supporting the immune response and reducing inflammation to stabilise metabolic processes. Future studies in a larger population of patients is necessary to determine the relevance of these findings.
Alterations of the immune system are known in eating disorders (EDs), however the importance of cytokine balance in this context has not been clarified. We compared cytokines and growth factors at opposite ends of BMI ranges, in 90 patients classified in relation to BMI, depressive and EDs comorbidities. Serum concentrations of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF), and epidermal growth factor (EGF) were determined by a biochip analyzer (Randox Labs). Differences were calculated through ANOVA. Possible predictors of higher cytokine levels were evaluated through regression analysis. IL-1α, IL-10, EGF, and IFN-γ were altered individuals with anorexia nervosa (AN) and binge eating disorder (BED). Night-eating was associated with IL-8 and EGF levels, IL-10 concentrations with post-dinner eating and negatively with sweet-eating, long fasting with higher IFN-γ levels. IL-2 increase was not linked to EDs, but to the interaction of depression and BMI. Altogether, for the first time, IL-1α, IL-10, EGF, and IFN-γ were shown to differ between AN and HCs, and between AN and individuals with obesity with or without BED. Only IL-2 was influenced by depression. Dysfunctional eating behaviors predicted abnormal concentrations of IL-10, EGF, IL-8 and IFN-γ.
The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise.
Journal of the International Society of Sports Nutrition. 2019;16(1):7
Plain language summary
According to previous studies, strenuous exercise may contribute towards an imbalance in Th1/Th2 cytokines that are secreted by the immune system, resulting in an impairment of the immune system. The main aim of this study was to analyse the effect of L-theanine on cytokines of the immune system and establish the role of L-Theanine as immunomodulatory. This double blind randomised study recruited 20 men from the Polish rowing team. The subjects were randomised to the supplemented group and placebo group. The supplemented group received gelatine capsules with 150 mg L-theanine extract whilst the placebo group received visually identical capsules with corn starch. The participants in the study were asked to take two capsules per day for 6 weeks. Athletes from both the groups did not differ significantly in terms of their mean age, body height, body weight and years of training. After 24 hour recovery, the athletes in the supplemented group showed lower amount of cytotoxic cell. The authors concluded based on the study that supplementation with L- theanine in athletes exposed to strenuous exercise had beneficial effect.
BACKGROUND The aim of this study was to analyze the response of selected components of the immune system in rowers to maximal physical exercise, and to verify if this response could be modulated by supplementation with L-theanine. METHOD The double-blind study included 20 members of the Polish Rowing Team. The subjects were randomly assigned to the supplemented group (n = 10), receiving 150 mg of L-theanine extract for 6 weeks, or to the placebo group (n = 10). The participants performed a 2000-m test on a rowing ergometer at the beginning (1st examination) and at the end of the supplementation period (2nd examination). Blood samples were obtained from the antecubital vein before each exercise test, 1 min after completing the test, and after a 24-h recovery. Subpopulations of T regulatory lymphocytes (Tregs) (CD4+/CD25+/CD127-), cytotoxic lymphocytes (CTLs) (CD8+/TCRαβ+), natural killer (NK) cells (CD3-/CD16+/CD56+) and TCRδγ-positive (Tδγ) cells were determined by means of flow cytometry. The levels of interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 10 (IL-10), interferon gamma (INF-ɤ) and total antioxidant capacity (TAC) were determined with commercially available diagnostic kits. RESULTS Supplementation with L-theanine contributed to a significant post-exercise decrease in IL-10 concentration, which was reflected by higher values of IL-2 to IL-10 and IFN-γ to IL-10 ratios. Moreover, a significant post-recovery decrease in CTL count, Treg to NK and Treg to CTL ratios was observed in the supplemented group. CONCLUSION Despite the decrease in the number of some cytotoxic cells (CTLs) and an increase in the proportion of Tregs to CTLs, supplementation with LTE seems to exert a beneficial effect on a disrupted Th1/Th2 balance in elite athletes, as shown by the decrease in IL-10 concentration.
Vitamin C and Immune Function.
Plain language summary
Vitamin C is essential to immune function and performs several crucial roles supporting cellular function in both the innate and adaptive immune system. Low storage capacity means a regular intake of a minimum 100-200mg of Vit C daily is necessary for adequate plasma levels. A potent antioxidant, Vit C can readily donate electrons as part of its immuno-protective role protecting against oxidative damage. VitC is a cofactor for the transportation of fatty acids into the cell mitochondria as well as numerous gene regulatory enzymes, including those involved in the cardiovascular response to infection. Structurally, Vit C supports barrier integrity and wound healing and concentrations of the vitamin accumulate in the epidermis. White leukocyte cells actively accumulate intracellular stores of Vit C indicating an important role in immune signalling. Neutrophils use Vit C to help migration to infection sites in the body and it enhances the differentiation and proliferation of B- and T-cells. Vit C has been shown to moderate inflammatory cytokines and reduce infection severity and longevity. Specifically, supplementation with high dose Vit C appears to be able to both prevent and ameliorate respiratory and systemic infections such as pneumonia. In summary, optimal levels of Vit C are necessary for proper immune function and resistance to infections.
Vitamin C is an essential micronutrient for humans, with pleiotropic functions related to its ability to donate electrons. It is a potent antioxidant and a cofactor for a family of biosynthetic and gene regulatory enzymes. Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system. Vitamin C supports epithelial barrier function against pathogens and promotes the oxidant scavenging activity of the skin, thereby potentially protecting against environmental oxidative stress. Vitamin C accumulates in phagocytic cells, such as neutrophils, and can enhance chemotaxis, phagocytosis, generation of reactive oxygen species, and ultimately microbial killing. It is also needed for apoptosis and clearance of the spent neutrophils from sites of infection by macrophages, thereby decreasing necrosis/NETosis and potential tissue damage. The role of vitamin C in lymphocytes is less clear, but it has been shown to enhance differentiation and proliferation of B- and T-cells, likely due to its gene regulating effects. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections. In turn, infections significantly impact on vitamin C levels due to enhanced inflammation and metabolic requirements. Furthermore, supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections. Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100-200 mg/day), which optimize cell and tissue levels. In contrast, treatment of established infections requires significantly higher (gram) doses of the vitamin to compensate for the increased inflammatory response and metabolic demand.