Table-II.
Literature Review of the Relationship Between Interleukin-15, Adipose Tissue and Skeletal Muscle.
| Authors (year published) | Methodology | Outcome measures (results) | Comments |
|---|---|---|---|
| Nielsen et al. (2008)9 | 199 subjects divided into 4 groups based on obesity and T2DM | Plasma IL-15 was negatively associated with total fat mass (p < .05), trunk fat mass (p < .01), & % fat mass (p < .05) in multiple regression analysis adjusting for age, sex, fitness level, and smoking. | IL-15 may contribute to regulation of trunk fat mass. |
| Barra et al. (2010)17 | Animal study to observe overexpression of IL-15 (IL-15tg), lack of IL-15 (IL-15-/-) upon adipose tissue | Overexpression of IL-15 (IL-15tg) was linked to lean body weight; lack of IL-15 (IL-15-/-) resulted in significant increase in weight gain without altering appetite. | IL-15 is involved in regulation of adipose tissue mass |
| Tamura et al. (2011)20 | 13 PA subjects performed 30 min endurance exercise at 70% maximum HR. Serum IL-15 pre- & post-exercise | Serum IL-15 increased significantly at 10 min & returned to resting level in 3 hr. Serum CK, biomarker for muscle damage, increased maximally 3 h post-exercise. | In response to endurance exercise, IL-15 may be released immediately and not related to muscle damage |
| Rinnov et al. (2014)5 | 12 week endurance training; 3 hr ergometer cycling. Plasma IL-15 & muscle biopsies before & after intervention | Endurance training induced 40% rise in basal skeletal muscle IL-15 protein content (p < .01). Acute exercise for 3-hr did not change muscle IL-15 or plasma IL-15 levels significantly. | IL-15 may take part in adaptation of skeletal muscle in response to endurance training. |
| Perez-Lopez et al. (2018a)19 | 14 subjects performed resistance exercise. Plasma IL-15 & muscle biopsies before & after exercise. | Serum IL-15 increased 5.3 fold immediately post-exercise (p < .001). Skeletal muscle IL-15Rα mRNA increased 2 fold 4 hours after exercise (p < .001). | In response to resistance exercise IL-15/IL-15Rα signaling pathway is activated in skeletal muscle |
| Perez-Lopez et al. (2018b)21 | 276 subjects divided into 5 groups based on PA, body mass and T2DM | Serum IL-15 & IL-15Rα was decreased in PA subjects compared to sedentary (p < .05) and increased in obese with T2DM compared to obese without T2DM (p < .05). | Circulating IL-15 and IL-15Rα are reduced in lean and obese PA subjects. IL-15Rα may play role in glucose metabolism |
| This Study (2018) | 133 subjects divided into 2 groups based on BMI. Physical activity & fitness levels assessed | Serum IL-15 was higher in lean subjects compared to obese (p < .01). Physically active had higher IL-15 compared to sedentary (p < .01). Post-exercise level of IL-15 was 12.7% higher in lean. | IL-15 correlates negatively with adiposity indices, especially visceral fat. Levels of IL-15 rise early after the start of exercise |
Abbreviations: BMI, body mass index; PA, physical activity; IL-15, Interleukin-15;
T2DM, type 2 diabetes mellitus; HR, heart rate; CK, creatine kinase