The melanocortin 3 receptor: a novel mediator of exercise-induced inflammation reduction in postmenopausal women?

Exercise Is Medicine: How Do We Implement It?

Exercise is well known to have beneficial effects on various disease states. In this paper, we broadly describe the fundamental concepts that are shared among various disease states, including obesity, type 2 diabetes (T2D), cardiovascular disease (CVD), heart failure (HF), cancer, and psychological well-being, and the beneficial effects of exercise training within these concepts. We highlight issues involved in implementing exercise recommendations and describe the potential impacts and challenges to medical professionals and patients. Problems are identified and discussed with respect to the future roles of professionals in the current built environment with its limited infrastructure to support current physical activity recommendations.

Linking Physical Activity to Breast Cancer Risk via Inflammation, Part 1: The Effect of Physical Activity on Inflammation

The protective effect of physical activity on breast cancer incidence may partially be mediated by inflammation. Systematic searches of Medline, EMBASE, and SPORTDiscus were performed to identify intervention studies, Mendelian randomization studies, and prospective cohort studies that examined the effects of physical activity on circulating inflammatory biomarkers in adult women. Meta-analyses were performed to generate effect estimates. Risk of bias was assessed, and the Grading of Recommendations Assessment, Development, and Evaluation system was used to determine the overall quality of the evidence. Thirty-five intervention studies and one observational study met the criteria for inclusion. Meta-analyses of randomized controlled trials (RCT) indicated that, compared with control groups, exercise interventions reduced levels of C-reactive protein (CRP) [standardized mean difference (SMD) = -0.27, 95% confidence interval (CI) = -0.62 to 0.08), tumor necrosis factor alpha (TNFα, SMD = -0.63, 95% CI = -1.04 to -0.22), interleukin-6 (IL6, SMD = -0.55, 95% CI = -0.97 to -0.13) and leptin (SMD = -0.50, 95% CI = -1.10 to 0.09). Owing to heterogeneity in effect estimates and imprecision, evidence strength was graded as low (CRP, leptin) or moderate (TNFα and IL6). High-quality evidence indicated that exercise did not change adiponectin levels (SMD = 0.01, 95% CI = -0.14 to 0.17). These findings provide support for the biological plausibility of the first part of the physical activity-inflammation-breast cancer pathway.

Effects of resistance training on body weight and body composition in older adults: An inter-individual response difference meta-analysis of randomized controlled trials

Whether true inter-individual response differences (IIRD) occur as a result of resistance training on body weight and body composition in older adults with overweight and obesity is not known. To address this gap, data from a previous meta-analysis representing 587 men and women (333 resistance training, 254 control) ≥ 60 years of age nested in 15 randomized controlled trials of resistance training ≥ 8 weeks were included. Resistance training and control group change outcome standard deviations treated as point estimates for body weight and body composition (percent body fat, fat mass, body mass index in kg.m2, and lean body mass) were used to calculate true IIRD from each study. True IIRD as well as traditional pairwise comparisons were pooled using the inverse-variance (IVhet) model. Both 95% confidence intervals (CI) and prediction intervals (PI) were calculated. While statistically significant improvements were found for body weight and all body composition outcomes (p < 0.05 for all), no statistically significant IIRD was observed for any of the outcomes (p > 0.05 for all) and all 95% PIs overlapped. Conclusions: While resistance training is associated with improvements in body weight and body composition in older adults, the lack of true IIRD suggests that factors other than training response variation (random variation, physiological responses associated with behavioral changes that are not the result of resistance training) are responsible for the observed variation in body weight and body composition.

α-MSH is partially involved in the immunomodulation of Nile tilapia (Oreochromis niloticus) antibacterial immunity

α-Melanocyte-stimulating hormone (α-MSH) is a well-studied neuropeptide controlling skin and hair color. Besides, numerous immunomodulation roles of α-MSH were recorded in humans and mice. However, the regulatory effects of α-MSH in teleost immunity haven't been well elucidated. In this study, several precursor molecules of α-MSH (POMCs) and its receptors (MCRs) in Nile tilapia (Oreochromis niloticus) were characterized, and their expression characteristics and specific functions on antibacterial immunity were determined. Overall, POMCs and MCRs were principally detected in the brain, skin, and liver, and were remarkably promoted post Streptococcus agalactiae infection. However, tiny POMCs and MCRs were observed in tilapia immune organs (head kidney and spleen) or lymphocytes, and no evident immunomodulation effect was detected in vitro. Moreover, the in vivo challenge experiments revealed that α-MSH protects tilapia from bacterial infection by regulating responses in the brain and intestine. This study lays theoretical data for a deeper comprehension of the immunomodulation mechanisms of teleost α-MSH and the evolutional process of the vertebrate melanocortin system.

The molecular signaling of exercise and obesity in the microbiota-gut-brain axis

Obesity is one of the major pandemics of the 21st century. Due to its multifactorial etiology, its treatment requires several actions, including dietary intervention and physical exercise. Excessive fat accumulation leads to several health problems involving alteration in the gut-microbiota-brain axis. This axis is characterized by multiple biological systems generating a network that allows bidirectional communication between intestinal bacteria and brain. This mutual communication maintains the homeostasis of the gastrointestinal, central nervous and microbial systems of animals. Moreover, this axis involves inflammatory, neural, and endocrine mechanisms, contributes to obesity pathogenesis. The axis also acts in appetite and satiety control and synthesizing hormones that participate in gastrointestinal functions. Exercise is a nonpharmacologic agent commonly used to prevent and treat obesity and other chronic degenerative diseases. Besides increasing energy expenditure, exercise induces the synthesis and liberation of several muscle-derived myokines and neuroendocrine peptides such as neuropeptide Y, peptide YY, ghrelin, and leptin, which act directly on the gut-microbiota-brain axis. Thus, exercise may serve as a rebalancing agent of the gut-microbiota-brain axis under the stimulus of chronic low-grade inflammation induced by obesity. So far, there is little evidence of modification of the gut-brain axis as a whole, and this narrative review aims to address the molecular pathways through which exercise may act in the context of disorders of the gut-brain axis due to obesity.

Analysis of real-time PCR Melanocortin 3 (MC3R) gene expression to identify new biomarkers inflammation in tuberculosis

Background

Diagnosis of tuberculosis (TB) in the era of technological sophistication requires accuracy and speed to provide as much information as possible so that TB treatment can be carried out quickly and precisely. New studies have also begun to be carried out to diagnose TB, one of which is by examining genes, either by looking at polymorphisms, mutations, or expressions. Several previous studies have confirmed the association of MC3R and TB genes with polymorphisms; MC3R is a gene that participates in the regulation of the inflammatory process and is also found in macrophages; therefore, we tried to analyze gene expression in the active TB group, household contacts, and healthy controls for looked at the differences between the three groups and confirmed the correlation of MC3R with TB by seeing which group's gene expression increased the most expression of the three groups so that the results can be considered as a TB diagnostic biomarker in the future.

Methods

This study included 122 people, 49 patients with confirmed TB, 46 close relatives of patients, and 27 healthy controls. This study used a real-time PCR technique to analyze MC3R gene expression in the three groups, and all data were analyzed using Bio-Rad CFXTM software version 3.1 and one-way ANOVA using SPSS 21.0.

Results

The value of MC3R gene expression in the active TB group increased 3.6-fold in the healthy group (p = 0.143), and that of gene expression in the healthy control group increased 1.09-fold in the healthy group (p = 0.007).

Conclusion

There is a relationship between MC3R and TB based on the results of gene expression analysis that increased in the active TB group compared to the household contact group and healthy controls.

Resistance training effectiveness on body composition and body weight outcomes in individuals with overweight and obesity across the lifespan: A systematic review and meta-analysis

To systematically review and analyze the effects of resistance-based exercise programs on body composition, regional adiposity, and body weight in individuals with overweight/obesity across the lifespan. Using PRISMA guidelines, randomized controlled trials were searched in nine electronic databases up to December 2020. Meta-analyses were performed using random-effects model. One-hundred sixteen articles describing 114 trials (n = 4184 participants) were included. Interventions involving resistance training and caloric restriction were the most effective for reducing body fat percentage (ES = -3.8%, 95% CI: -4.7 to -2.9%, p < 0.001) and whole-body fat mass (ES = -5.3 kg, 95% CI: -7.2 to -3.5 kg, p < 0.001) compared with groups without intervention. Significant results were also observed following combined resistance and aerobic exercise (ES = -2.3% and -1.4 kg, p < 0.001) and resistance training alone (ES = -1.6% and -1.0 kg, p < 0.001) compared with no training controls. Resistance training alone was the most effective for increasing lean mass compared with no training controls (ES = 0.8 kg, 95% CI: 0.6 to 1.0 kg, p < 0.001), whereas lean mass was maintained following interventions involving resistance training and caloric restriction (ES = ~ - 0.3 kg, p = 0.550-0.727). Results were consistently observed across age and sex groups (p = 0.001-0.011). Reductions in regional adiposity and body weight measures were also observed following combined resistance and aerobic exercise and programs including caloric restriction (p < 0.001). In conclusion, this study provides evidence that resistance-based exercise programs are effective and should be considered within any multicomponent therapy program when caloric restriction is utilized in individuals with overweight or obesity.

Effects of Exercise on the Body Composition and Lipid Profile of Individuals with Obesity: A Systematic Review and Meta-Analysis

Background

Numerous researchers have worked to develop treatments for obesity; however, the prevalence of obesity continues to increase in many countries. Moreover, the effects of physical activity and exercise on obesity remain unclear. Therefore, it is necessary to perform a systematic review and meta-analysis to assess the relationship between exercise and obesity using mediator variables such as the mode of exercise.

Methods

Our review focuses on research tracking the effects of exercise on obesity conducted from 2007 to 2016 and available in any of three databases: Embase, PubMed, and EBSCO Academic Search Premier. The keywords used in the search were “exercise and obesity” and “exercise and obese.”

Results

The average size of the effects that exercise interventions have on body mass index (standardized mean difference [SMD], 0.533), waist circumference (SMD, 0.666), total cholesterol (SMD, 0.721), and triglyceride (TG; SMD, 0.603) were medium or larger. Exercise had greater effects on the outward appearance of obesity (body mass index, waist circumference) than on its practical factors (weight, % body fat). The effect of exercise on TG (SMD, 0.603) was larger than that on low-density lipoprotein (SMD, 0.406) and high-density lipoprotein (SMD, −0.222). Exercise duration (weeks of exercise) and intensity correlate better than exercise time (minutes per week) with a large and consistent improvement in adult obesity.

Conclusion

We suggest that individuals with obesity should exercise consistently to achieve significant improvements in their health.

Associations of the melanocortin 3 receptor C17A + G241A haplotype with body composition and inflammation in African-American adults

BACKGROUND

The MC3R haplotype C17A + G241A, which encodes a partially inactivated receptor, has high prevalence in individuals of predominately African ancestry. In pediatric cohorts, homozygosity for this common variant has been associated with obesity, reduced lean mass, and greater fasting insulin. However, metabolic and body composition measures have not been well studied in adults with this haplotype.

METHODS

A convenience sample of 237 healthy African-American adult volunteers was studied. TaqMan assays were used to genotype MC3R variants. Labs were drawn in the morning in the fasted state. Body composition data was obtained via dual-energy X-ray absorptiometry. An analysis of covariance was used to examine the associations of genotype with metabolic and body composition measures controlling for age and sex.

RESULTS

Individuals homozygous for the MC3R C17A + G241A haplotype had significantly greater body mass index, fat mass, fat mass percentage, and C-reactive protein, with reduced lean mass percentage as compared to heterozygous and wild-type participants (all ps < 0.05); fasting insulin was marginally nonsignificant between groups (p = 0.053). After adjusting for fat mass, laboratory differences no longer remained significant.

CONCLUSIONS

Homozygosity for MC3R C17A + G241A is associated with increased adiposity in African-American adults. Further studies are needed to elucidate the mechanisms behind these associations.

Effect of resistance training on muscular strength and indicators of abdominal adiposity, metabolic risk, and inflammation in postmenopausal women: controlled and randomized clinical trial of efficacy of training volume

This study evaluated the effect of resistance training (RT) volume on muscular strength and on indicators of abdominal adiposity, metabolic risk, and inflammation in post-menopausal women (PW). Thirty-two volunteers were randomly allocated into the following three groups: control (CT, no exercise, n = 11), low-volume RT (LV, three sets/exercise, n = 10), and high-volume RT (HV, six sets/exercise, n = 11). The LV and HV groups performed eight exercises at 70 % of one maximal repetition, three times a week, for 16 weeks. Muscular strength and indicators of abdominal adiposity, metabolic risk, and inflammation were measured at baseline and after 16 weeks. No differences were found in baseline measures between the groups. The PW showed excess weight and fat percentage (F%), large waist circumference (WC), high waist-hip ratio (WHR), and hypercholesterolemia and borderline values of glycated hemoglobin (HbA1c%). Following the RT, a similar increase in muscle strength and reduction in F% from baseline were found in both trained groups. In HV, a decrease in total cholesterol, LDL-c, WC, and WHR was noted. Moreover, the HV showed a lower change (delta%) of interleukin-6 (IL-6) when compared to CT (HV = 11.2 %, P 25-75 = -7.6-28.4 % vs. CT = 99.55 %, P 25-75 = 18.5-377.0 %, p = 0.049). In LV, a decrease was noted for HbA1c%. There were positive correlations (delta%) between WHR and IL-6 and between IL-6 and TC. These results suggest that while a low-volume RT improves HbA1c%, F%, and muscular strength, a high-volume RT is necessary to improve indicators of abdominal adiposity and lipid metabolism and also prevent IL-6 increases in PW.

Structure-activity relationships of peptides incorporating a bioactive reverse-turn heterocycle at the melanocortin receptors: identification of a 5800-fold mouse melanocortin-3 receptor (mMC3R) selective antagonist/partial agonist versus the mouse melanocortin-4 receptor (mMC4R)

The melanocortin-3 (MC3) and melanocortin-4 (MC4) receptors regulate energy homeostasis, food intake, and associated physiological conditions. The melanocortin-4 receptor (MC4R) has been studied extensively. Less is known about specific physiological roles of the melanocortin-3 receptor (MC3R). A major obstacle to this lack of knowledge is attributed to a limited number of identified MC3R selective ligands. We previously reported a spatial scanning approach of a 10-membered thioether-heterocycle ring incorporated into a chimeric peptide template that identified a lead nM MC4R ligand. Upon the basis of those results, 17 compounds were designed and synthesized that focused upon modification in the pharmacophore domain. Notable results include the identification of a 0.13 nM potent 5800-fold mMC3R selective antagonist/slight partial agonist versus a 760 nM mMC4R full agonist (ligand 11). Biophysical experiments (two-dimensional (1)H NMR and computer-assisted molecular modeling) of this ligand resulted in the identification of an inverse γ-turn secondary structure in the ligand pharmacophore domain.

Melanocortin receptor expression is associated with reduced CRP in response to resistance training

The existing paradigm of exercise-induced decreases in chronic inflammation focuses on the expression of inflammatory receptors on systemic monocytes in response to exercise training, with the role of anti-inflammatory receptors largely ignored. Our recent preliminary studies indicate that the anti-inflammatory melanocortin receptors (MCRs) may play a role in modulating exercise-induced decreases in chronic inflammation. Here, we present a study designed to determine the effect of intense, resistance exercise training on systemic monocyte MCR expression. Because low-grade chronic inflammation is associated with elevated cardiometabolic risk in healthy populations and exercise decreases chronic inflammation, we investigated the associations between systemic monocyte cell surface expression of MCRs and inflammatory markers as a possible mechanism for the beneficial anti-inflammatory effects of resistance training. To this end, the present study includes 40 adults (aged 19-27 yr) and implements a 12-wk periodized, intensive resistance training intervention. Melanocortin 1 and 3 receptor expression on systemic monocytes and inflammatory markers, including C-reactive protein (CRP), interleukin (IL)-6, IL-1β, and IL-10, were measured before and after the intervention. Resistance training significantly altered MCR systemic monocyte cell surface expression, had no chronic effects on IL-6, IL-1β, or IL-10 expression, but significantly decreased CRP levels from a moderate to a low cardiovascular disease risk category. More specifically, decreased melanocortin 3 receptor expression significantly correlated with decreased CRP, independent of changes in adiposity. These data suggest that the observed responses in MCR expression and decreases in cardiovascular disease risk in response to resistance training represent an important anti-inflammatory mechanism in regulating exercise-induced decreases in chronic inflammation that occur independent of chronic changes in systemic cytokines.