A study titled “Years of endurance exercise training remodel abdominal subcutaneous adipose tissue in Adults with overweight or obesity” was published in the journal Nature Metabolism. For the study, a total of 52 participants were enrolled. 32 participants were selected and divided into two groups each of 16 participants. And in each group of 16, 8 were males and the other 8 were females. One group was labeled as sedentary or non-exercisers, and the other as exercises. People who did moderate and vigorous intensity exercise for >30 minutes for at least 4 days a week for 2 years were termed as exercisers. The participants selected for comparison were similar in age, sex, body weight, and BMI and had similar adiposity so that the comparisons could be made pairwise. As it was not possible to collect fresh aSAT samples from 32 participants, another cohort, consisting of 19 exercisers and 24 non-exercisers were selected to conduct ex vivo experiments. The participants were compensated for their participation in the study.
The criteria for the enrolment of the participants were:
Stable weight since 6 months before enrollment
Do not have a history of cardiovascular or metabolic disease
Females were premenopausal, not pregnant, and not lactating.1
SAMPLE COLLECTION:
2-3 days before the sample collection, the participants refrained from indulging in exercise. The subjects did overnight fasting by taking a standard dinner and a snack meal one day before the sample collection. The next day after the overnight fasting, the samples that were collected are
Blood samples by inserting an intravenous catheter into an antecubital vein in one arm
100mg core aSAT sample was collected from 10 cm distal to the umbilicus using a Bergstrom needle.
For exploratory ex vivo experiments, 800 mg of fresh aSAT samples were collected from another set of cohorts to quantify the angiogenic capacity and culture 3D spheroids.
The OGTT test was also done on subjects by drinking 75 g of glucose solution (Fisherbrand GTT beverage), and then blood samples were collected every 15 minutes for about 2 hours.
Immediately after collection, the aSAT sample was fixed in a 10% formalin solution for detailed analyses of histology, morphology, and structure of adipose, and the blood samples were centrifuged at 2000 g at 4 °C for 15 minutes. The analyses was done to determine two outcomes.
1. Primary outcome: effect of exercise on cardiometabolic health, adipose tissue structure, and adipose tissue proteomic profile. The primary outcome was assessed by pair-matching exercisers and non-exercisers for sex, adiposity, anthropometric, circulating markers for cardiometabolic health, adipose tissue structure and morphology, and adipose tissue proteomic profile.
2. Secondary outcome: effect of exercise on aSAT angiogenic capacity and regulation of lipid storage. The secondary outcome was between exercisers and non-exercisers by comparing the growth of neo-vasculature and markers of lipid storage capacity by conducting ex vivo experiments with fresh adipose tissue samples.
RESULTS:
The findings from the study carried out showed that:
Subject characteristics:
Self-reported physical activity behavior was ten-fold greater, and the peak volume of oxygen uptake was 25% higher in exercise.
Indices of insulin resistance of glucose metabolism and fatty acid release from adipose tissue were lower, whereas high-density lipoprotein was higher in exercisers.
Total adiponectin concentration was higher in exercisers.
aSAT capillarization:
Protein abundances of fatty acid binding protein (FABP4), a marker of adipocyte proliferation, were higher in exercisers.
The capillary density of aSAT accompanied by the greater protein abundance of vascular endothelial growth factor was higher in exercisers.
The collagen type Col6a found in adipocytes associated with metabolic abnormalities is lower in exercisers.
The protein abundance of MMP14 in adipose tissue, known to degrade Col6a, is higher in exercisers.
The protein abundance of TIMP1, an enzyme that inhibits MMPs, was higher in exercisers.
aSAT macrophages:
Protein abundances of adipose tissue macrophage (ATM) markers CD14 and CD206 were lower in exerciser aSAT samples.
Targeted immunoblot assays:
Protein abundances of the S3 and S6 ribosomes were greater in exercisers.
Protein abundances of oxidative phosphorylation subunits NDUFB8 (complex I), SDHB (complex II), UQCRC2 (complex III), and ATP5A (complex V) were greater in exercisers.
Protein abundances of key lipogenic regulators FASN and the active form of SREBP1 were significantly higher in exercisers.
Ex vivo functional assays:
BMI was similar in both groups.
Fat-free mass is significantly higher, whereas percentage body mass and fat mass were lower in exercisers.
The whole-body insulin sensitivity index and antilipolytic sensitivity to insulin assessed from a 2-hour oral glucose tolerance test (OGTT) were significantly higher in exercisers.
In the ex vivo assay, the neovascular growth after 11 days of incubation was found to be greater in aSAP samples of exercisers, which suggests greater angiogenic capacity.
3D cultured spheroids from exercisers showed greater lipid droplet size in exercisers.
DGAT1 mRNA expression was found to be greater in exercisers. mRNA expression of SREBF1 (coding gene for SREBP) and ITGAX increased significantly between day 20 and day 27 in exercisers. In addition, the mRNA expression of COL1 and TNF was significantly lower in exercisers.
Based on the findings and results from the study, if there are any abnormalities in the structure and metabolic function of abdominal subcutaneous adipose tissue (aSAT), it may indicate obesity-related health complications. The aSAT of exercisers has higher capillary density, lower Col6a abundance, and fewer macrophages. Additionally, exercisers have abundant angiogenic, ribosomal, mitochondrial, and lipogenic proteins. aSAT collected from exercisers has higher protein translation and lipogenesis phosphoproteins. Exploratory ex vivo experiments conducted in samples cultured from aSAT in exercisers demonstrate greater angiogenic capacity and higher lipid-storage capacity. Regular exercise plays an important role in obese and overweight individuals as it improves cardiometabolic health by enabling the remodeling of aSAT structure and proteomics profile.
According to an article, the study author, Dr. Jeffrey Horowitz, professor of movement studies in the school of kinesiology at the University of Michigan, was quoted as saying:3
“Living a physically active lifestyle, exercising regularly over time, makes our fat tissue a more accommodating place for extra energy under conditions when we do gain weight. Unfortunately, most of us, even regular exercisers, gain weight as we get older. If we have a greater capacity to store that in our fat tissue, less of it’ll go to our liver, less of it will go to our heart, less will go to all these other places that in excess can be really problematic.”Dr. Jeffrey Horowitz, Professor of Movement Studies, School of Kinesiology, University of Michigan
CONCLUSION:
It was found that exercisers when compared with non-exercisers if they were continuously exercising, had the additional capacity to store fat in adipose tissue as the subcutaneous fat tissue was flexible which allows more fat to be stored under skin because of the structural and morphological characteristics. This means that the fat instead of accumulating in and around the organs and increasing the risk of diseases gets stored in the adipose tissue, which is the safest place where the fat can be stored. Additionally, the study showed that the exercisers had more blood vessels, proteins that play a crucial role in metabolism, and fewer cells that can contribute to inflammation. Hence, regular exercise can lead to healthier fat, but a doctor must be consulted before implementing as exercising may be based on many factors.2
REFERENCES:
1. Ahn, C., Zhang, T., Yang, G., Rode, T., Varshney, P., Ghayur, S. J., Chugh, O. K., Jiang, H., & Horowitz, J. F. (2024). Years of endurance exercise training remodel abdominal subcutaneous adipose tissue in adults with overweight or obesity. Nature Metabolism.https://doi.org/10.1038/s42255-024-01103-x
2. Long-term exercisers have “healthier” belly fat, study reveals. (2024, September 10). https://medicalxpress.com/news/2024-09-term-healthier-belly-fat-reveals.html
3. https://edition.cnn.com/2024/09/10/health/exercise-fat-storage-wellness/index.html