Sex and sex steroids: impact on the kinetics of fatty acids underlying body shape

Influence of the different hormonal status changes during their life on fat mass localisation in women: a narrative review

CONTEXT

Independently of the total body fat mass, upper body fat mass deposition is strongly associated with cardiometabolic comorbidities. The mechanisms underlying fat mass localisation are not fully understood, but evidences indicate sex-specific fat mass distribution. Currently, data on women are scarce and the link between hormonal status changes during their life and fat mass distribution is overlooked.

METHOD

For this narrative review, literature data were extracted from the PubMed and CENTRAL databases to examine the relationship between hormonal status and adipose tissue localisation in women.

RESULTS

Menopause strongly influences fat mass localisation, while the effect of the menstrual cycle phases, oral contraception use and pregnancy has not been unambiguously determined.

CONCLUSION

Reliable data are lacking on the relationship between hormonal variations throughout the lifespan and body fat mass localisation in women. Future studies should take into account the hormonal status of women to reduce the risk of cardiometabolic diseases.

Age- and sex-related trends in body composition among Beijing adults aged 20-60 years: a cross-sectional study

BACKGROUND

Obesity is the most serious global epidemic and body composition is the main indicator to evaluate obesity. This study aimed to investigate the changing trends of body composition by age and gender in Beijing adults aged 20-60 years and explore the distribution of obesity rates in different age groups of both sexes under different evaluation criteria.

METHODS

A total of 24,948 adults aged 20-60 years in Beijing, including 10,225 males and 14,192 females, were included, divided into four age groups (20-29, 30-39, 40-49, and ≥ 50 years) with each decade of age as an age group. Body composition indicators (BMI, fat mass, BF%, muscle mass, visceral fat area, and WHR) were measured in all subjects.

RESULTS

BMI and total fat mass peaked in males aged 40-49 years (BMI = 25.75 kg/m2, total fat mass = 17.70 kg). Female BMI, fat mass and BF% all increased significantly with age (p < 0.01). Total muscle peaked in males aged 30-39 years and decreased significantly thereafter (p < 0.0001). Visceral fat area and WHR increased significantly with age in both sexes (p < 0.0001). Age was significantly positively correlated with BMI, BF%, fat mass, WHR, and visceral fat area in both sexes (p < 0.0001), and age was negatively correlated with muscle mass in males (standard β =  - 0.14, p < 0.0001) while positive in female (standard β = 0.05, p < 0.0001). Under the BMI criterion, the obesity rate peaked at 27.33% in males at the age of 20-29 years. Under the BF% criterion, the obesity rate peaked at 17.41% in males at the age of 30-39 years, and increased in females with age. The central obesity rate of both sexes increased with age under the criteria of WHR and visceral fat area.

CONCLUSION

The results of this study reveal that age- and sex-related patterns of body composition and obesity change among Beijing adults aged 20-60 years may differ across age groups and that such patterns of change should be considered when developing public health strategies.

Sex Affects Regional Variations in Subcutaneous Adipose Tissue T Cells but not Macrophages in Adults with Obesity

OBJECTIVE

The inflammatory environment in lower-body subcutaneous adipose tissue (SAT) has been largely unexplored. This study aimed to examine the effects of region (upper body vs. lower body) and sex on SAT immune cell profiles in young adults with obesity.

METHODS

Abdominal (AB) and femoral (FEM) SAT was collected from 12 males (mean [SEM] age = 30.8 [1.4] years; mean [SEM] BMI = 34.1 [1.1] kg/m² ) and 22 females (mean [SEM] age = 30.6 [0.6] years; mean [SEM] BMI = 34.0 [0.7] kg/m² ) with obesity via needle aspiration. Flow cytometry was used to quantify macrophage (CD68+) and T-cell (CD3+) subpopulations in the stromovascular fraction of each SAT region.

RESULTS

Females had a greater proportion of most T-cell types (CD3+CD4+CD45RA+, CD3+CD4+CD45RA-, and CD3+CD8+CD45RA+) in FEM compared with AB SAT, while males had similar proportions in both regions. Regardless of sex, the M1-like macrophage population (CD68+CD206-) was proportionally higher in AB SAT than in FEM SAT.

CONCLUSIONS

Results showed that T-cell populations vary by SAT region in females but not males. Both sexes, however, have proportionately more proinflammatory macrophages in upper-body than in lower-body SAT. It remains to be seen how these unique immune cell profiles in males and females with obesity contribute to adipose tissue inflammation and metabolic disease risk.

Effect of Fat Mass Localization on Fat Oxidation During Endurance Exercise in Women

Independent of total body fat mass, predominant upper body fat mass distribution is strongly associated with cardio-metabolic comorbidities. However, the mechanisms underlying fat mass localization are not fully understood. Although a large body of evidence indicates sex-specific fat mass distribution, women are still excluded from many physiological studies and their specific features have been investigated only in few studies. Moreover, endurance exercise is an effective strategy for improving fat oxidation, suggesting that regular endurance exercise could contribute to the management of body composition and metabolic health. However, no firm conclusion has been reached on the effect of fat mass localization on fat oxidation during endurance exercise. By analyzing the available literature, this review wants to determine the effect of fat mass localization on fat oxidation rate during endurance exercise in women, and to identify future research directions to advance our knowledge on this topic. Despite a relatively limited level of evidence, the analyzed studies indicate that fat oxidation during endurance exercise is higher in women with lower upper-to-lower-body fat mass ratio than in women with higher upper-to-lower-body fat mass ratio. Interestingly, obesity may blunt the specific effect of upper and lower body fat mass distribution on fat oxidation observed in women with normal weight during endurance exercise. Studying and understanding the physiological responses of women to exercise are essential to develop appropriate physical activity strategies and ultimately to improve the prevention and treatment of cardio-metabolic diseases.

Effects of short-term sex steroid suppression on dietary fat storage patterns in healthy males

Hypogonadism in males is associated with increased body fat and altered postprandial metabolism, but mechanisms remain poorly understood. Using a cross‐over study design, we investigated the effects of short‐term sex hormone suppression with or without testosterone add‐back on postprandial metabolism and the fate of dietary fat. Eleven healthy males (age: 29 ± 4.5 year; BMI: 26.3 ± 2.1 kg/m²) completed two 7‐day study phases during which hormone levels were altered pharmacologically to produce a low sex hormone condition (gonadotropin releasing hormone antagonist, aromatase inhibitor, and placebo gel) or a testosterone add‐back condition (testosterone gel). Following 7 days of therapy, subjects were administered an inpatient test meal containing 50 μCi of [1‐¹⁴C] oleic acid. Plasma samples were collected hourly for 5 h to assess postprandial responses. Energy metabolism (indirect calorimetry) and dietary fat oxidation (¹⁴CO₂ in breath) were assessed at 1, 3, 5, 13.5, and 24 h following the test meal. Abdominal and femoral adipose biopsies were taken 24 h after the test meal to determine uptake of the labeled lipid. Postprandial glucose, insulin, free‐fatty acid, and triglyceride responses were not different between conditions (P > 0.05). Whole‐body energy metabolism was also not different between conditions at any time point (P > 0.05). Dietary fat oxidation trended lower (P = 0.12) and the relative uptake of ¹⁴C labeled lipid into femoral adipose tissue was greater (P = 0.03) in the low hormone condition. Short‐term hormone suppression did not affect energy expenditure or postprandial metabolism, but contributed to greater relative storage of dietary fat in the femoral depot. ClinicalTrials.gov Identifier: NCT03289559.

Sex-dependent Depot Differences in Adipose Tissue Development and Function; Role of Sex Steroids

Men and women are different in their fat mass and distribution pattern. The gynoid-type fat distribution, accumulation in lower-body, is considered to be protective while the android-type accumulation in upper-body, both in abdominal subcutaneous and visceral depots, is detrimental. Sex-dependent depot differences in adipose metabolic and endocrine functions are thought to contribute to the sexual disparity in fat distribution as well as its association with cardiometabolic risks. Although molecular details have not been completely elucidated, available evidence shows that sex steroid hormones are important factors governing sexual dimorphism in adipose tissue distribution and hence, risks for metabolic diseases. We will review sex-dependent heterogeneities in adipose tissue properties that can link their depot-specific biology to metabolic complications in men and women. In addition, we will also review how sex steroids regulate adipose tissue biology, both development and functional characteristics, with emphasis on their depot-dependent actions.

Sex-dependent difference in the relationship between adipose-tissue cholesterol efflux and estradiol concentrations in young healthy humans

BACKGROUND

Impaired adipose tissue function and lower levels of high density lipoprotein cholesterol (HDL-C) have been implicated in the development of vascular dementia, and metabolic diseases such as hypertension, atherosclerosis, type 2 diabetes (T2D) and metabolic syndrome. Interestingly, both the substrate fluxes in adipose tissue and HDL-C concentration differ between men and women. Moreover, adipose tissue cholesterol efflux has been implicated in modulation of HDL-C levels. Thus, we aimed to determine if the association between serum estradiol levels and adipose tissue cholesterol efflux is sex-dependent.

METHOD

We evaluated the serum estradiol levels and adipose tissue cholesterol efflux in young healthy men (n=5) and women (n=3). Adipose tissue cholesterol efflux was determined using subcutaneous microdialysis probes. Linear regression analyses were used to determine the relationship between the parameters, p<0.05 was considered as statistically significant.

RESULTS

Our data demonstrated that serum estradiol levels directly associated with adipose tissue cholesterol efflux; however, the relationships may be sex-dependent. We discussed our results in the context of currently available data regarding sex-dependent variability in adipose tissue function and HDL-C metabolism as a potential contributor to higher rates of vascular dementia in men. Further research is required to understand the sex-dependent and -independent variabilities in adipose tissue metabolism to determine novel targets for interventions to prevent the development of vascular dementia.

Acute Female Hypogonadism Alters Adipose Tissue Fatty Acid Storage Factors and Chylomicronemia

CONTEXT

Chronic sex steroid deficiency has effects on adipose fatty acid (FA) storage mechanisms and fat oxidation, but the chronology of events are not well understood.

OBJECTIVE

The objective of the study was to examine the acute effects of female sex steroid suppression on cellular mechanisms affecting abdominal and femoral subcutaneous adipose tissue FA storage.

DESIGN

This study had a randomized, longitudinal, parallel study design.

SETTING

The study was conducted at the Mayo Clinic Clinical Research Unit.

PARTICIPANTS

Thirty-eight nonsmoking premenopausal women aged 18-50 years participated in the study.

INTERVENTION

The intervention included randomization to receive one of the following: 1) no treatment (control), 2) 3.75 mg of Lupron, or 3) 3.75 mg of Lupron and estrogen, but not progesterone, replacement for 49 days, resulting in at least 4 weeks of sex steroid suppression.

MAIN OUTCOME MEASURES

Body composition, fat cell size, postprandial chylomicron and nonchylomicron triglyceride concentrations, adipose tissue meal FA storage, direct free fatty acid storage, lipoprotein lipase, acyl CoA synthetase, and diacylglycerol acyltransferase activities, and CD36 content were measured.

RESULTS

Compared with the control group, the fed state femoral lipoprotein lipase activity was reduced in women taking Lupron and those taking Lupron and estrogen replacement. In addition, we observed significantly greater postprandial chylomicronemia in the Lupron group than in the other two groups. There were no differences in overall fat storage and oxidation. Depending on the mode of data expression (per unit lipid vs per 1000 adipocytes), there were modest changes in acyl CoA synthetase, diacylglycerol acyltransferase, and CD36 in response to acute sex hormone suppression.

CONCLUSIONS

Our results suggest estrogen and progesterone may have different effects on the regulation of FA metabolism and that acute sex steroid deficiency in women does not alter fat storage and oxidation.

Liver X receptors as regulators of metabolism

The liver X receptors (LXR) are crucial regulators of metabolism. After ligand binding, they regulate gene transcription and thereby mediate changes in metabolic pathways. Modulation of LXR and their downstream targets has appeared to be a promising treatment for metabolic diseases especially atherosclerosis and cholesterol metabolism. However, the complexity of LXR action in various metabolic tissues and the liver side effect of LXR activation have slowed down the interest for LXR drugs. In this review, we summarized the role of LXR in the main metabolically active tissues with a special focus on obesity and associated diseases in mammals. We will also discuss the dual interplay between the two LXR isoforms suggesting that they may collaborate to establish a fine and efficient system for the maintenance of metabolism homeostasis.