Effect of body composition on redox homeostasis at rest and in response to exercise: The case of underfat women

Combined effects of green tea supplementation and eccentric exercise on nuclear factor erythroid 2-related factor 2 activity

PURPOSE

This study investigated whether combining eccentric exercise and green tea supplementation synergistically increased nuclear factor erythroid 2-related factor 2 (NRF2) activity, a transcription factor responsible for coordinating endogenous antioxidant expression.

METHODS

In a double-blinded, randomized, between-subjects design, 24 males (mean [SD]; 23 [3] years, 179.6 [6.1] cm, 78.8 [10.6] kg) performed 100 drop jumps following a 6 days supplementation period with either green tea (poly)phenols (n = 12; 500 mg·d-1) or a placebo (n = 12; inulin). NRF2/antioxidant response element (ARE) binding in peripheral blood mononuclear cells (PBMCs), catalase (CAT) and glutathione reductase (GR) activity, 8-hydroxy-2'-deoxyguanosine (8-OHdG) excretion, and differential leukocyte counts were measured pre-, post-, 1 h and 24 h post-exercise.

RESULTS

Exercise did not increase NRF2/ARE binding (p = 0.12) (fold change vs rest: green tea = [post] 0.78 ± 0.45, [1 h] 1.17 ± 0.54, [24 h] 1.06 ± 0.56; placebo = [post] 1.40 ± 1.50, [1 h] 2.98 ± 3.70, [24 h] 1.04 ± 0.45). Furthermore, CAT activity (p = 0.12) and 8-OHdG excretion (p = 0.42) were unchanged in response to exercise and were not augmented by green tea supplementation (p > 0.05 for all). Exercise increased GR activity by 30% (p = 0.01), however no differences were found between supplement groups (p = 0.51). Leukocyte and neutrophil concentrations were only elevated post-exercise (p < 0.001 for all).

CONCLUSION

Eccentric exercise, either performed alone or in conjunction with green tea supplementation, did not significantly increase NRF2 activity in PBMCs.

TRIAL REGISTRATION NUMBER

osf.io/kz37g (registered: 15/09/21).

Challenges of considering both extremities of the weight status spectrum to better understand obesity: insights from the NUTRILEAN project in constitutionally thin individuals

BACKGROUND/OBJECTIVES

While the physiology of obesity has been so extensively investigated to date, only an extremely small number of studies (less than 50) have focused on the other extremity of the weight spectrum: constitutional thinness. Yet, this important state of underweight in the absence of any eating disorders provides a mirror model of obesity that might be particularly insightful in understanding obesity. Nevertheless, important methodological and recruitment-related issues appear when it comes to this complex constitutionally thin phenotype, as experienced by our research group with the realization of the ongoing NUTRILEAN clinical trial. To face this challenge, the present paper aims at identifying, analyzing, and discussing the quality of such recruitment processes in publications about constitutional thinness.

METHODS

In this order, a group of experts collectively created a new grading system to assess the level of rigour and quality achieved by each study based on different criteria.

RESULTS

The main results were that (i) metabolic-related biasing criteria were poorly observed despite being crucial, (ii) recruitment processes were not detailed enough and with sufficient explicitness, and (iii) recruiting among already identified patients would be associated with both higher sample sizes and better scores of quality.

CONCLUSIONS

The present work encourages investigators to adopt a high level of rigour despite the complexity and duration of recruitment processes for this specific population, and readers to pay close attention to the quality of recruitment when interpreting the data. To better understand obesity and its physiological adaptations, it seems essential not only to compare it to normal-weight conditions, but also to the other extremity of the weight status spectrum represented by constitutional thinness.

Is constitutional thinness really different from anorexia nervosa? A systematic review and meta-analysis

A growing interest in constitutional thinness has been observed in the last decades, but the publications however cover various fields of study and report equivocal results. The present work systematically reviewed any clinical trials enrolling participants with constitutional thinness and bibliographic researches were performed between December 2018 and June 2020. From a total of 1 212 records initially identified, 402 records were removed as duplicates, 381 articles were excluded based on titles or abstracts and 390 references were excluded against eligibility criteria. Thirty-nine articles were finally included in the systematic review. The results showed that constitutionally thin people seem to be underweight but not underfat and present a fat-free mass as blunted as anorexic patients, despite being a little less underweight. The meta-analysis confirmed that constitutionally thin people present normal energy intake and revealed a trend toward a higher resting metabolic rate to fat-free mass ratio which suggests a highly metabolic fat-free mass. Contrary to patients with anorexia nervosa, constitutionally thin people present normal levels of insulin-like growth factor 1, estradiol, growth hormone, follicle-stimulating hormone, and luteinizing hormone. An intermediate level of leptin between anorexic and control participants was however observed in constitutional thinness. While all the studies reported normal free triiodothyronine and cortisol levels in constitutionally thin individuals, a higher fasting free triiodothyronine level (p = 0.033) and a lower 24 h mean cortisol level (p = 0.005) were observed for the first time. Present results give robust evidence that constitutionally thin people present an atypical phenotype highly different from anorexia nervosa.

Does Obesity Affect the Severity of Exercise-Induced Muscle Injury?

This literature review investigates the effects of obesity on exercise-induced muscle injury and reexamines the potential mechanisms of exercise-induced muscle injury related to obesity. Several studies reported that high body mass index and percent body fat can significantly affect the markers of muscle injury after exercise, including maximal strength, delayed onset muscle soreness, creatinine kinase level, and myoglobin level. The potential mechanisms resulting in these outcomes include structural changes in the cell membrane induced by high fat levels, increased inflammatory responses due to adipose tissues, reduced muscle satellite cell activation and myogenesis due to lipid overload, differences in muscle fiber distributions, and sedentary behaviors. These mechanisms, however, must be verified through more research. As obesity is a potential risk factor increasing the severity of exercise-induced muscle injuries, the exercise intensity and duration for obese patients must be carefully selected, and a preconditioning intervention (e.g., low-intensity eccentric training) may be considered before or during the early stages of the exercise program.

Eccentric exercise per se does not affect muscle damage biomarkers: early and late phase adaptations

PURPOSE

Acute high-intensity unaccustomed eccentric exercise performed by naive subjects is accompanied by disturbances in muscle damage biomarkers. The aim of the study was to investigate whether a causal relationship indeed exists between eccentric exercise and muscle damage.

METHODS

Twenty-four men randomly assigned into a concentric only or an eccentric-only training group and performed 10 weeks of isokinetic resistance exercise (one session/week of 75 maximal knee extensors actions). Physiological markers of muscle function and damage (i.e., range of motion, delayed onset muscle soreness, isometric, concentric and eccentric peak torque) were assessed prior to and 1-3 and 5 days post each session. Biochemical markers of muscle damage (creatine kinase) and inflammation (C-reactive protein) were measured prior and 2 days post each session.

RESULTS

After the first bout, eccentric exercise induced greater muscle damage compared to concentric exercise; however, during the nine following sessions, this effect progressively diminished, while after the 10th week of training, no alterations in muscle damage biomarkers were observed after either exercise protocol. Additionally, strength gains at the end of the training period were comparable between the two groups and were mode-specific.

CONCLUSION

(1) eccentric exercise per se does not affect muscle damage biomarkers; (2) muscle damage occurs as a result of muscle unaccustomedness to this action type; (3) exercise-induced muscle damage is not a prerequisite for increased muscle strength. Collectively, we believe that muscle unaccustomedness to high-intensity eccentric exercise, and not eccentric exercise per se, is the trigger for muscle damage as indicated by muscle damage biomarkers.

Skeletal muscle of females and males with constitutional thinness: a low intramuscular lipid content and oxidative profile

Constitutional thinness (CT) is a nonpathological state of underweight. The current study aimed to explore skeletal muscle energy storage in individuals with CT and to further characterize muscle phenotype at baseline and in response to overfeeding. Thirty subjects with CT (15 females, 15 males) and 31 normal-weight control subjects (16 females, 15 males) participated in the study. Histological and enzymological analyses were performed on muscle biopsy specimens before and after overfeeding. In the skeletal muscle of CT participants compared with controls, we observed a lower content of intramuscular triglycerides for type I (-17%, p < 0.01) and type IIA (-14%, p < 0.05) muscle fibers, a lower glycogen content for type I (-6%, p < 0.01) and type IIA (-5%, p < 0.05) muscle fibers, a specific fiber-type distribution, a marked muscle hypotrophy (-20%, p < 0.001), a low capillary-to-fiber ratio (-19%, p < 0.001), and low citrate synthase activity (-18%, p < 0.05). In response to overfeeding, CT participants increased their intramuscular triglycerides content in type I (+10%, p < 0.01) and type IIA (+9%, p < 0.01) muscle fibers. CT individuals seem to present an unusual muscle phenotype and different adaptations to overfeeding compared with normal-weight individuals, suggesting a specific energy metabolism and muscle adaptations. ClinicalTrials.gov registration no. NCT02004821. Novelty Low intramuscular triglycerides and glycogen content in skeletal muscle of constitutionally thin individuals. Low oxidative capacity, low capillary supply, and fiber hypotrophy in skeletal muscle of constitutionally thin individuals. Increase in intramuscular triglycerides in constitutional thinness in response to overfeeding.

Effect of Body Fat Percentage on Muscle Damage Induced by High-Intensity Eccentric Exercise

This study aimed to investigate the impact of percent body fat (%BF) on muscle damage after high-intensity eccentric exercise. Thirty healthy male undergraduates (mean age: 22.0 ± 2 years, height: 176.9 ± 5 cm, weight: 75.8 ± 11.6 kg) participated in this study, and they were classified according to their %BF into a high %fat group (HFG, ≥20%, n = 15) and a low %fat group (LFG, ≤15%, n = 15). For eccentric exercise, two sets of 25 reps were performed on a modified preacher curl machine using the elbow flexor muscle. Maximal isometric strength, muscle soreness (passive and active), creatine kinase (CK), and myoglobin (Mb) were measured as indices of muscle damage. The data were analyzed with repeated measures ANOVA. The results show that there is a significant group–time interaction for both CK and Mb after eccentric exercise (p = 0.007, p = 0.015, respectively), with a greater increase in the HFG than in the LFG. However, there was no significant group–time interaction for maximal isometric strength and muscle soreness (passive and active) (p > 0.05). These results suggest that %BF is a factor that alters the muscle damage indices CK and Mb, which indicate membrane disruption, after eccentric exercise.

Definition and diagnosis of constitutional thinness: a systematic review

The existing literature about the definition and diagnostic criteria of constitutional thinness (CT) appears equivocal. The present work systematically reviewed the criteria used in the diagnosis of adult individuals with CT (PROSPERO registration number: CRD42019138236). Five electronic bibliographic databases were searched between December 2018 and November 2019: MEDLINE, Embase, CENTRAL (Cochrane Library), Google Scholar and Clinical Trials. Search terms were combined with Medical Subject Headings terms. The search strategy included any clinical trials that enrolled adults with CT. Studies were systematically excluded if the state of thinness was not due to a well-identified constitutional origin. From the 689 references after duplicate removal, 199 studies were excluded based on title and 164 based on abstract. According to the inclusion and exclusion criteria, 291 other studies were removed. Finally, thirty-five studies remained at the end of the process. The analysis of these studies showed high heterogeneity in the diagnostic criteria of CT. A real need emerged to adopt a common terminology and to systematically exclude potential non-constitutional origins of thinness such as eating disorders, associated pathology or over-exercising, with validated tools. Weight history, physiological menses and weight gain resistance are also important criteria to consider. The present systematic review revealed that our medical and scientific approaches of CT need to be harmonised in terms of terminology and diagnostic criteria. Although further studies are needed, we finally proposed recommendations and a decision tree to help in the recognition and diagnosis of CT.