Modification of Muscle-Related Hormones in Women with Obesity: Potential Impact on Bone Metabolism

Effects of weight loss rate on myostatin and follistatin dynamics in patients with obesity

Background

Exercise-induced cytokines involved in controlling body composition include myostatin (MST) and follistatin (FST), both of which are influenced by physical activity. This study investigated changes in body composition and physical activity during a weight loss program, as well as the impact on serum MST and FST levels at various weight loss rates.

Methods

A total of 126 patients with obesity who completed a 6-month weight loss program were divided into three groups based on weight loss rate (%): low (< 3%), middle (3-10%), and high (≥10%). The International Physical Activity Questionnaire was used for assessing physical activity, whereas dual X-ray absorptiometry was used to determine body composition. Serum MST and FST levels were measured using the enzyme-linked immunosorbent assay.

Results

The middle and high groups showed a significant decrease in percent body fat and a significant increase in percent lean body mass and physical activity. Serum MST levels increased significantly in all three groups, although FST levels reduced significantly only in the middle group. After adjusting for sex and body composition, changes in peak oxygen intake (β = -0.359) and serum FST levels (β = -0.461) were identified as independent factors for the change in MST levels in the low group. Sex (β = -0.420) and changes in MST levels (β = -0.525) were identified as independent factors for the change in serum FST levels in the low group, whereas in the high group, sitting time (β = -0.600) during the weight loss program was identified as an independent factor for change in serum FST levels.

Conclusion

Serum MST levels in patients with obesity increased significantly following the weight loss program, independent of weight loss rate. In contrast, serum FST levels reduced significantly only in the 3-10% weight loss group. These findings indicate that MST and FST secretion dynamics may fluctuate in response to physical activity, while also reflecting feedback regulation of body composition and metabolism during weight reduction.

Effect of Nutritional Deprivation after Sleeve Gastrectomy on Bone Mass, Periostin, Sclerostin and Semaphorin 4D: A Two-Year Longitudinal Study

Bariatric surgery induces bone loss, but the exact mechanisms by which this process occurs are not fully known. The aims of this 2-year longitudinal study were to (i) investigate the changes in areal bone mineral density (aBMD) and bone turnover markers following sleeve gastrectomy (SG) and (ii) determine the parameters associated with the aBMD variations. Bone turnover markers, sclerostin, periostin and semaphorin 4D were assessed before and 1, 12 and 24 months after SG, and aBMD was determined by DXA at baseline and after 12 and 24 months in 83 patients with obesity. Bone turnover increased from 1 month, peaked at 12 months and remained elevated at 24 months. Periostin and sclerostin presented only modest increases at 1 month, whereas semaphorin 4D showed increases only at 12 and 24 months. A significant aBMD decrease was observed only at total hip regions at 12 and 24 months. This demineralisation was mainly related to body weight loss. In summary, reduced aBMD was observed after SG in the hip region (mechanical-loading bone sites) due to an increase in bone turnover in favour of bone resorption. Periostin, sclerostin and semaphorin 4D levels varied after SG, showing different time lags, but contrary to weight loss, these biological parameters did not seem to be directly implicated in the skeletal deterioration.

Serum Follistatin Levels are Independently Associated with Exercise Tolerance in Patients with Obesity

OBJECTIVE

Follistatin (FST)/myostatin (MST) myokine-signaling axis is important for muscle metabolism and pathogenesis of obesity. FST, mainly secreted by skeletal muscle and liver, inhibits MST and affects skeletal muscle synthesis. This study aimed to identify the characteristics of myokines and independent predictors of serum FST levels in patients with obesity.

METHODS

In this retrospective cross-sectional study, 226 patients (mean age, 46.6 years; men, 35.4%) with obesity who initially visited an outpatient clinic between June 2014 and September 2020, were included and classified into obesity (25.0 ≤ body mass index (BMI) < 35.0 kg/m2) and severe obesity (BMI ≥35 kg/m2) groups based on the guidelines of the Japan Society for the Study of Obesity. Body composition was measured using bioelectrical impedance analysis and computed tomography. Muscle strength, exercise tolerance, metabolic parameters, and myokines were measured, including serum levels of FST, MST, irisin, and brain-derived neurotrophic factor.

RESULTS

Serum FST levels were significantly higher in the severe obesity group than in the obesity group (median: 768.4 vs. 895.1 pg/mL, P = 0.020). However, the levels of other myokines showed no significant differences between the groups. In Model 1, which included factors that significantly correlated with FST levels, stepwise multivariate regression analysis revealed peak oxygen uptake (VO2) as an independent predictor of FST levels based on the significance of the univariate analysis. Additionally, Model 2 was analyzed by adding myokine level to Model 1, revealing that peak VO2, MST, and irisin levels were independent predictors of FST levels.

CONCLUSION

Serum FST levels were higher in patients in the severe obesity group compared to those in the obesity group. There was an independent association between low exercise tolerance and elevated serum FST levels.

Follistatin Is Associated with Bone Mineral Density in Lean Adolescent Girls with Increased Physical Activity

Follistatin is a member of the activin-follistatin-inhibin hormonal system and is proposed to affect bone metabolism. However, data regarding the effect of follistatin on bone are relatively scarce and contradictory in humans. The purpose of the current study was to investigate possible associations of serum follistatin concentration with bone mineral characteristics in lean and physically active adolescent girls. Bone mineral density, body composition, resting energy expenditure and different energy homeostasis hormones in serum including follistatin, leptin and insulin were investigated. Significant relationships (p < 0.05) between serum follistatin (1275.1 ± 263.1 pg/mL) and whole-body (WB) bone mineral content (r = 0.33), WB areal bone mineral density (aBMD) (r = 0.23) and lumbar spine (LS) aBMD (r = 0.29) values were observed. Serum follistatin remained associated with LS aBMD independent of body fat and lean masses (r = 0.21; p < 0.05). However, the follistatin concentration explained only 3% (R² × 100; p = 0.049) of the total variance in LS aBMD values. In conclusion, serum follistatin concentrations were associated with bone mineral values in lean adolescent girls with increased physical activity. Follistatin was an independent predictor of lumbar spine areal bone mineral density, which predominantly consists of trabecular bone.

Serum vitamin D status and circulating irisin levels in older adults with sarcopenia

Background

Emerging evidence suggests sarcopenia, which is involved in the serum vitamin D deficiency and development of abnormal muscle metabolism, is predominately centered in the general older population. In the present study, we aimed to explore the relationship between the level of serum vitamin D and irisin concentrations in the older adults with sarcopenia.

Methods

A cross-sectional study was conducted which included 422 sarcopenia participants (146 males and 276 females). Sarcopenia was assessed according to the recommended diagnostic criteria of the Asia Working Group for Sarcopenia (AWGS). The levels of serum 25-hydroxyvitamin D (25(OH)D), 25-hydroxyvitamin D₂ (25(OH)D₂) and 25-hydroxyvitamin D₃ (25(OH)D₃) were determined by LC-MS/MS. Irisin levels were measured by enzyme-linked immunosorbent assay (ELISA). The relationship between serum concentration of vitamin D and irisin were determined using multiple linear regression analysis.

Results

After adjustment for potential confounding factors, a significant and positive relationship between changes in irisin across 25(OH)D, and 25(OH)D₃ was observed (standard regression coefficients of 0.150 and 0.151, respectively, P < 0.05). However, no significant relationship was observed between serum vitamin D concentrations and irisin levels in males.

Conclusions

This study demonstrated that a higher level of serum vitamin D is independently related to the increment of irisin in sarcopenia females, not in males. These investigations need to be verified in other large-scale prospective studies.

Modification of bone mineral density, bone geometry and volumetric BMD in young women with obesity

BACKGROUND

Most obese women with low-trauma fractures present normal areal bone mineral density (aBMD), suggesting that other bone parameters are more determinant for fracture risk in these patients.

OBJECTIVES

(i) Determine the effects of obesity in young women on areal bone mineral density (aBMD), bone geometry, strength, and volumetric BMD determined by advanced DXA-based methods; (ii) model the profiles of bone parameters for each population with age; and (iii) determine the factors related to body composition (i.e. lean tissue mass and fat mass) potentially implicated in the "bone adaptation" in the femoral region.

SUBJECTS AND METHODS

Two hundred and twenty adolescent and young women from 18 to 35 years old were enrolled in this study: 128 patients with obesity and 92 age-matched (±6 months) normal-weight controls. aBMD was determined with DXA, whereas hip geometry and strength parameters were assessed by hip structural analysis (HSA) and volumetric BMD by 3D-SHAPER® software.

RESULTS

Compared with controls, subjects with obesity presented significantly higher aBMD at all bone sites, but the difference was greater at hip compared with lumbar spine or radius. Bone size estimates (i.e. cortical thickness), as well as strength estimates (i.e. cross-sectional area) were higher at all femoral subregions including femoral neck, intertrochanteric region and femoral shaft in young women with obesity. In whole proximal femur and all femoral compartments, vBMD was also higher in subjects with obesity, but the difference between groups was greater for cortical vBMD compared with trabecular vBMD. When hip bone parameters were modelled for each group from individual values, maximal values were reached between 20 and 26 years in both groups but, whatever the age, subjects with obesity presented higher values than controls. In both groups, lean body mass (LBM) was the parameter most positively associated with the greatest number of bone parameters studied.

CONCLUSION

Our study confirmed that young women with obesity presented higher aBMD, better hip geometry and greater strength compared with normal-weight controls. Additionally, cortical and trabecular compartments measured by 3D-SHAPER® were favourably and concomitantly modified. However, it remains to be demonstrated whether the evaluation of these new parameters would provide better prediction of fracture risk in this population than aBMD.

Association between obesity and risk of fracture, bone mineral density and bone quality in adults: A systematic review and meta-analysis

BACKGROUND

The association between obesity and fracture risk may be skeletal site- and sex-specific but results among studies are inconsistent. Whilst several studies reported higher bone mineral density (BMD) in patients with obesity, altered bone quality could be a major determinant of bone fragility in this population.

OBJECTIVES

This systematic review and meta-analysis aimed to compare, in men, premenopausal women and postmenopausal women with obesity vs. individuals without obesity: 1) the incidence of fractures overall and by site; 2) BMD; and 3) bone quality parameters (circulating bone turnover markers and bone microarchitecture and strength by advanced imaging techniques).

DATA SOURCES

PubMed (MEDLINE), EMBASE, Cochrane Library and Web of Science were searched from inception of databases until the 13th of January 2021.

DATA SYNTHESIS

Each outcome was stratified by sex and menopausal status in women. The meta-analysis was performed using a random-effect model with inverse-variance method. The risks of hip and wrist fracture were reduced by 25% (n = 8: RR = 0.75, 95% CI: 0.62, 0.91, P = 0.003, I2 = 95%) and 15% (n = 2 studies: RR = 0.85, 95% CI: 0.81, 0.88), respectively, while ankle fracture risk was increased by 60% (n = 2 studies: RR = 1.60, 95% CI: 1.52, 1.68) in postmenopausal women with obesity compared with those without obesity. In men with obesity, hip fracture risk was decreased by 41% (n = 5 studies: RR = 0.59, 95% CI: 0.44, 0.79). Obesity was associated with increased BMD, better bone microarchitecture and strength, and generally lower or unchanged circulating bone resorption, formation and osteocyte markers. However, heterogeneity among studies was high for most outcomes, and overall quality of evidence was very low to low for all outcomes.

CONCLUSIONS

This meta-analysis highlights areas for future research including the need for site-specific fracture studies, especially in men and premenopausal women, and studies comparing bone microarchitecture between individuals with and without obesity.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42020159189.

Follistatin secretion is enhanced by protein, but not glucose or fat ingestion, in obese persons independently of previous gastric bypass surgery

Follistatin is secreted from the liver and is involved in the regulation of muscle mass and insulin sensitivity via inhibition of activin A in humans. The secretion of follistatin seems to be stimulated by glucagon and inhibited by insulin, but only limited knowledge on the postprandial regulation of follistatin exists. Moreover, results on postoperative changes after Roux-en-Y gastric bypass (RYGB) are conflicting with reports of increased, unaltered, and lowered fasting concentrations of follistatin. In this study, we investigated postprandial follistatin and activin A concentrations after intake of isocaloric amounts of protein, fat, or glucose in subjects with obesity with and without previous RYGB to explore the regulation of follistatin by the individual macronutrients. Protein intake enhanced follistatin concentrations similarly in the two groups, whereas glucose and fat ingestion did not change postprandial follistatin concentrations. Concentrations of activin A were lower after protein intake compared with glucose intake in RYGB. Glucagon concentrations were also particularly enhanced by protein intake and tended to correlate with follistatin in RYGB. In conclusion, we demonstrated that protein intake, but not glucose or fat, is a strong stimulus for follistatin secretion in subjects with obesity and that this regulation is maintained after RYGB surgery.NEW & NOTEWORTHY Circulating follistatin and activin A were studied after intake of isocaloric protein, fat, or glucose drinks in subjects with obesity with and without previous Roux-en-Y gastric bypass (RYGB). Protein intake enhanced follistatin similarly in both groups, whereas glucose and fat ingestion did not change follistatin. Activin A was lower after protein compared with glucose in RYGB. The novel finding is that protein intake, but neither glucose nor fat, stimulates follistatin secretion independently of previous RYGB.

The production, detection, and origin of irisin and its effect on bone cells

Irisin is a muscle factor discovered in 2012 that plays an important role in many tissues, including bone. Eight years since its discovery, there are still many controversies regarding its molecular biology, detection, and effects on bone. This article summarizes the points raised to date, and discusses the mechanisms by which irisin regulates bone cells. The information reviewed here provides a useful foundation for future research.

The effects of gradual vs. rapid weight loss on serum concentrations of myokines and body composition in overweight and obese females

Context: Research has shown the modulations of Follistatin (FST) and Myostatin (MST) following weight loss.Objective: We evaluated the effects of gradual weight loss (GWL) and rapid weight loss (RWL) on serum MST, FST, and body composition in overweight and obese females.Materials and methods: Thirty-six overweight and obese females successfully completed the study interventions: GWL (n = 18) or RWL (n = 18). Serum MST and FST concentrations, as well as anthropometric measurements, were collected at baseline and at the conclusion of each weight loss intervention.Results: MST concentration significantly (p < .05) decreased in the GWL; while FST concentration, body fat percentage and skeletal muscle mass significantly declined in both conditions. The loss in skeletal muscle mass was significantly greater in RWL relative to GWL.Discussion and conclusion: GWL was more effective than RWL in preserving skeletal muscle mass in overweight and obese females. Moreover, GWL leads to declines in MST concentrations.