Post-exercise Effects and Long-Term Training Adaptations of Hormone Sensitive Lipase Lipolysis Induced by High-Intensity Interval Training in Adipose Tissue of Mice

Abstract

Although studies have proven that high-intensity interval training (HIIT) shows a comparable effect to moderate-intensity continuous training (MICT) on reducing body fat, especially visceral fat, the mechanism is still unclear. Since MICT consumes more fat during exercise, the mechanism of HIIT weight loss may be related to post-exercise effects, long-term adaptive changes, and hormone sensitive lipase (HSL). The objective of this study was to compare the post-effects of acute exercise, long-term adaptive changes on HSL activity, and catecholamine-induced lipolysis between HIIT and MICT. Following a 14-week high-fat diet (HFD), obese female C57Bl/6 mice were divided into acute exercise groups (one time training, sacrificed at rest and 0, 1, and 12 h after exercise, n = 49), -L groups (12-week long-term training, 12-h fasting, n = 21), and -C groups (12-week training, primary adipocytes were isolated and stimulated by catecholamine in vitro, n = 18). MICT or HIIT treadmill protocols (running distance matched) were carried out during training. Comparison of acute exercise effects by two-way ANOVA showed no time × group interaction effect, however, a significant increase in HSL-Ser563 (at 0 and 1 h) and Ser660 phosphorylation (at 0, 1, and 12 h) in inguinal (subcutaneous) fat was only observed in HIIT mice (p < 0.05 vs. rest), but not in MICT mice. The periuterine (visceral) fat HSL expression and phosphorylation of HIIT mice was similar to or lower than MICT mice. After long-term training, 12-h fasting significantly increased periuterine fat Ser563 phosphorylation in HIIT mice (p < 0.05), but there was no change in MICT mice. Under stimulation of catecholamine in vitro, isolated primary adipocytes from periuterine fat of long-term HIIT mice showed a higher Ser563 increase than that found in MICT mice (p < 0.05). The quantity of triglyceride (TG) lipid bonds (representing lipolysis level) was significantly lower after HIIT than MICT (p < 0.05). The results indicate that (1) acute HIIT can induce an increase of HSL phosphorylation in subcutaneous fat lasting at least 12 h, implying longer post-exercise lipolysis than MICT and (2) long-time HIIT has a better effect on improving catecholamine resistance of visceral adipocytes caused by a HFD, which allows fat to be mobilized more easily when stimulated.

Comparison of visceral fat lipolysis adaptation to high-intensity interval training in obesity-prone and obesity-resistant rats

“…Another reasonable hypothesis is that due to the intense load of HIIT, during the recovery period, adipose tissue would release more lipid for gluconeogenesis, ketogenesis or tissue healing [ 24 ], which suggests that HIIT promotes adaptive catabolism of adipose tissue. Studies have verified the increase in β-AR and lipolysis in adipocytes after long-term HIIT [ 26 , 28 ], supporting the hypothesis of adaptive changes in SNS lipolytic pathway. As mentioned earlier, when facing catabolic stress, OP individuals are more likely to show adaptation (fat is lost easily), while OR individuals are more likely to maintain homeostasis [ 35 , 36 ].…”

“…This phenomenon may be related closely to the difference between obesity phenotypes in adipose catabolism. Previous experiments have found that the fat loss effect of HIIT is related to the activation lipolysis [ 26 – 28 , 31 ]. Because gene polymorphisms underlie individual differences in food intake, PA and adipose metabolism, we hypothesised that OP and OR individuals show different adaptive changes to HIIT, especially in lipolysis regulated by the SNS.…”

“…The distance of each HIIT was equal to 45 min of running at medium speed. See our previous study for more details [ 28 ].…”

“…To determine whether ISO-induced lipolysis is activated through β3-AR, SR59230a (MedChemExpress, USA, 100 nM), a selective antagonist, was added alongside 10 µM ISO. The methods of isolation and in vitro stimulation have been published previously [ 28 , 30 ]. The amount of glycerol released by cells—a marker of lipolysis—was measured by using an enzyme labelling kit (Jiancheng Bio, China).…”

“…HIIT increases the levels of β3-AR messenger RNA (mRNA) [ 26 ] and hormone-sensitive lipase (HSL, a catecholamine-regulated key lipolytic enzyme) [ 27 ] after NE stimulation in vitro. Moreover, the visceral adipocytes of mice subjected to HIIT show stronger HSL phosphorylation and TG hydrolysis [ 28 ], which means that VAT could be mobilised more easily during hunger, cold or stress. However, whether HIIT has different effects on OP and OR individuals remains unclear.…”