Effects of exercise on the circulating concentrations of irisin in healthy adult individuals: A review

Effect of Exercise Interventions on Irisin and Interleukin-6 Concentrations and Indicators of Carbohydrate Metabolism in Males with Metabolic Syndrome

Irisin (IR) is a biomarker that is associated with metabolic syndrome (MetS). However, the available evidence on the association of IR, physical activity, and MetS status are contradictory. Therefore, the present study aimed to investigate the effect of exercise intervention on IR and interleukin-6 (IL-6) levels and indicators of carbohydrate metabolism in males with MetS. The study included 62 males with MetS (age 36.6 ± 6.9 years, BMI 33.6 ± 4.4 kg/m²) randomly assigned to: examined group 1 (EG1, n = 21) with aerobic exercise intervention, examined group 2 (EG2, n = 21) with combined aerobic and resistance exercise intervention, both for 12 weeks, and the control group (CG, n = 20) without intervention. Anthropometric measurements, body composition (body fat [BF], fat free mass [FFM]) as well as a biochemical blood analysis (irisin [IR], interleukin-6 [IL-6], insulin [INS] and glucose [GL]) were performed at baseline, 6 and 12 weeks of intervention, and 4 weeks after ending the intervention (follow-up). Intergroup and intragroup comparisons were performed. In EG1, an increase in IR level was observed as well as decreases in IL-6, BF, and GL levels in relation to the initial measurement. In EG2, decreases in IL-6, BF, and INS levels were observed as well as an increase in FFM level. In CG, no changes were found. Aerobic-resistance exercise led to a greater reduction in the concentrations of IL-6 and INS and more favorable changes in body composition (BF and FFM) than the use of aerobic training alone in males with MetS.

Exerkines and long-term synaptic potentiation: Mechanisms of exercise-induced neuroplasticity

Physical exercise may improve cognitive function by modulating molecular and cellular mechanisms within the brain. We propose that the facilitation of long-term synaptic potentiation (LTP)-related pathways, by products induced by physical exercise (i.e., exerkines), is a crucial aspect of the exercise-effect on the brain. This review summarizes synaptic pathways that are activated by exerkines and may potentiate LTP. For a total of 16 exerkines, we indicated how blood and brain exerkine levels are altered depending on the type of physical exercise (i.e., cardiovascular or resistance exercise) and how they respond to a single bout (i.e., acute exercise) or multiple bouts of physical exercise (i.e., chronic exercise). This information may be used for designing individualized physical exercise programs. Finally, this review may serve to direct future research towards fundamental gaps in our current knowledge regarding the biophysical interactions between muscle activity and the brain at both cellular and system levels.

Multifactorial Mechanism of Sarcopenia and Sarcopenic Obesity. Role of Physical Exercise, Microbiota and Myokines

Obesity and ageing place a tremendous strain on the global healthcare system. Age-related sarcopenia is characterized by decreased muscular strength, decreased muscle quantity, quality, and decreased functional performance. Sarcopenic obesity (SO) is a condition that combines sarcopenia and obesity and has a substantial influence on the older adults’ health. Because of the complicated pathophysiology, there are disagreements and challenges in identifying and diagnosing SO. Recently, it has become clear that dysbiosis may play a role in the onset and progression of sarcopenia and SO. Skeletal muscle secretes myokines during contraction, which play an important role in controlling muscle growth, function, and metabolic balance. Myokine dysfunction can cause and aggravate obesity, sarcopenia, and SO. The only ways to prevent and slow the progression of sarcopenia, particularly sarcopenic obesity, are physical activity and correct nutritional support. While exercise cannot completely prevent sarcopenia and age-related loss in muscular function, it can certainly delay development and slow down the rate of sarcopenia. The purpose of this review was to discuss potential pathways to muscle deterioration in obese individuals. We also want to present the current understanding of the role of various factors, including microbiota and myokines, in the process of sarcopenia and SO.

Whole-body repeated hyperthermia increases irisin and brain-derived neurotrophic factor: A randomized controlled trial

CONTEXT

Hyperthermia is known to be beneficial to patients affected by various diseases. Irisin is a key regulators of fat metabolism known to be released as response to cold. Brain Derived Neurotrophic Factor (BDNF) is a marker of neuroplasticity usually increased as response to acute exposure to human body stressors.

OBJECTIVE

Effect of a repeated hyperthermia exposure programme on changes in circulating irisin and serum BDNF in healthy humans.

DESIGN

Setting, Participants: Randomized, single-blind, cross-over trial in healthy humans conducted at Sechenov University Physiology Laboratory from April 2019. The treatment period was 2 weeks (wash-out 3 weeks). Researchers analysing serum biomarkers and questionnaires data were blinded to participants allocation. Participants were 20 healthy male (age 21.5 ± 2.1 years).

INTERVENTION

Hyperthermia exposure programme (WBPH) versus sham exposure (SHAM) to hyperthermia (10 sessions in two weeks).

MAIN OUTCOME MEASURE

Changes in irisin and BDNF before and after short hyperthermia exposure.

RESULTS

Twenty participants were analyzed. Irisin increased significantly in group WBPH only: 6.3 μg/ml (mean with SD = 1.6) compared to 5.4 μg/ml (SD = 1.7) in SHAM group; This value was also higher than baseline (5.0 mean with SD = 1.1) in WBPH. After 10 sessions mean change in BDNF was higher in WBPH group vs SHAM: BDNF was 28,263 (SD = 4213) pg/ml in WBPH group and 24,064 (SD = 5600) pg/ml in SHAM group. BDNF concentrations were significantly higher than baseline values in WBPH group only, 28,263 (SD 4213) vs 25,888 (SD 4316) pg/ml.

CONCLUSION

In healthy young humans a 2-week, ten sessions programme consisting of repeated exposure to hyperthermia resulted in a significantly higher increase of circulating Irisin and BDNF.

Effect of Chronic Resistance Training on Circulating Irisin: Systematic Review and Meta-Analysis of Randomized Controlled Trials

Irisin seems to play an important role in several chronic diseases, however, the interactions between chronic training and irisin are still unclear. The purpose of this systematic review and meta-analysis was to examine the effect of chronic resistance training on circulating irisin in adults. Literature search was conducted in PubMed, Web of Science and EBSCOhost (Academic Search Complete) until December 2020. Randomized controlled trials researching irisin levels after a resistance training program for at least 8 weeks among an adult population were eligible. Other inclusion criteria comprised recruiting a control group and reporting circulating irisin through ELISA kits. Cohen's d effect size and subgroup analyses (95% confidence level) were calculated using a random effects analysis model. Data of the seven included studies comprising 282 individuals showed an increasing and non-significant tendency after a resistance training program (d = 0.58, 95% CI: -0.25 to 1.40, p = 0.17). Subgroup analyses showed significant increases for the older adults group (p < 0.001) and when training is demanding and progressive in terms of intensity (p = 0.03). Data suggest that resistance training programs seem to increase circulating irisin, especially in older adults and in demanding and progressive training programs. However, more studies should be conducted using robust measurement methods, such as mass spectrometry, to better understand the interaction between chronic resistance exercise and irisin.

Taurine supplementation increases irisin levels after high intensity physical training in obese women

BACKGROUND

Irisin is a myokine/adipokine that under stimulus of physical exercise is able to improve thermogenic capacity in adipose tissue. Likewise, taurine supplementation has demonstrated similar effects on energy metabolism. Therefore, we hypothesized that taurine supplementation combined with physical training may induce an increase in irisin concentrations, optimizing energy metabolism in obese individuals.

OBJECTIVE

To evaluate if taurine supplementation associated with a high intensity physical training program increases irisin levels in obese women.

METHODS

double-blind study with 22 obese women (BMI 32.4 ± 2.0 kg/m², 36.6 ± 6.4 years and sedentary) who were randomly divided into two groups, control group (GC, n = 14), exercised and supplemented with placebo (3 g of starch), and taurine group (GTAU, n = 8), exercised and supplemented with taurine (3 g). The subjects performed high intensity physical training, Deep Water Running (DWR), for 8 weeks, 3 times/week, for 50 min per training session, at 70-85% maximum heart rate. Resting metabolic rate (RMR) was evaluated by indirect calorimetry, body composition by deuterium oxide, plasma taurine by HPLC, plasma irisin by Multiplex Kit, and food consumption by food records. The results were analyzed by an ANOVA two way repeated measures mixed model, with the Sidak post hoc (p < 0.05).

RESULTS

No changes were observed in body composition. DWR increased RMR independent of supplementation (p < 0.001) and irisin levels (pg/mL) showed a significant difference only in the GTAU in 1 h after exercise (p < 0.001).

CONCLUSION

DWR associated with taurine supplementation resulted in increased plasma irisin concentrations after physical training in obese adult women.

Irisin: A Hope in Understanding and Managing Obesity and Metabolic Syndrome

White adipose tissue (WAT) is an endocrine organ highly integrated in homeostasis and capable of establishing ways of communicating and influencing multiple metabolic processes. Brown adipose tissue promotes energy expenditure by incorporating the uncoupling protein 1 (UCP1), also known as thermogenin, which decouples cellular respiration and heat production, in the mitochondrial membranes. Recent data suggest the presence of a thermogenic cell formation from white adipocytes (beige or brite cells) with a potential role in preventing obesity and metabolic syndrome. The formation of these cells is influenced by physical exertion that induces expression of PPARγ coactivator-1 (PGC1) and downstream membrane protein, fibronectin type III domain-containing protein 5 (FNDC5) in skeletal muscle. Irisin, a thermogenic adipomyokine produced by FNDC5 cleavage is involved in the browning of adipose tissue. While animal studies are congruent with regard to the relationship between physical exertion and irisin release, the results from human studies are less than clear. Therefore, this review focuses on recent advances in our understanding of muscle and adipose tissue thermogenesis. Further, it describes the molecular mechanisms by which irisin impacts exercise, glucose homeostasis and obesity. Finally, the review discusses current gaps and controversies related to irisin release, its mode of action and its future potential as a therapeutic tool in managing obesity and metabolic syndrome.

The Exercise-Induced Irisin Is Associated with Improved Levels of Glucose Homeostasis Markers in Pregnant Women Participating in 8-Week Prenatal Group Fitness Program: A Pilot Study

Background

Both exercise and pregnancy influence serum irisin concentration.

Aim

To determine how the interaction of pregnancy and exercise affects irisin level and whether various patterns of exercise adherence had different effect on irisin concentration.

Methods

It was a one-group pretest-posttest study among 9 Caucasian nulliparous healthy women in normal pregnancy (age 23 ± 3 years, 21 ± 2 weeks of gestation; mean ± SD) who participated in 8-week group fitness program. Before and after exercise intervention, we determined serum concentrations of irisin and selected parameters of lipid profile and glucose homeostasis markers.

Results

In active women, irisin slightly decreased with the development of pregnancy. After 8 weeks of exercising, irisin correlated negatively with fasting glucose (R = -0.922; p = 0.001), glycated hemoglobin (R = -0.784; p = 0.012), and insulin concentrations (R = -0.845; p = 0.004). In women exercising below recommended level, we observed a significant drop in irisin concentration, whereas in women exercising at least three times a week this myokine slightly increased (31% difference; 90% confidence limits ±28; a large, clear effect).

Conclusions

Irisin stimulated by prenatal exercise may improve glucose homeostasis markers in healthy women and compensate for metabolic changes induced by pregnancy. Moreover, the frequency of exercise may regulate the changes in exercise-induced irisin concentration.