Circadian rhythms modulate the effect of eccentric exercise on rat soleus muscles

Effects of preconditioning with heat stress on acute exercise-induced intracellular signaling in male rat gastrocnemius muscle

Heat stress (HS) induces Akt/mTOR phosphorylation and FoxO3a signaling; however, whether a prior increase in heat shock protein 72 (HSP72) expression affects intracellular signaling following eccentric exercise remains unclear. We analyzed the effects of HS pretreatment on intramuscular signaling in response to acute exercise in 10-week-old male Wistar rats (n = 24). One leg of each rat was exposed to HS and the other served as an internal control (CT). Post-HS, rats were either rested or subjected to downhill treadmill running. Intramuscular signaling responses in the red and white regions of the gastrocnemius muscle were analyzed before, immediately after, or 1 h after exercise (n = 8/group). HS significantly increased HSP72 levels in both deep red and superficial white regions. Although HS did not affect exercise-induced mTOR signaling (S6K1/ERK) responses in the red region, mTOR phosphorylation in the white region was significantly higher in CT legs than in HS legs after exercise. Thr308 phosphorylation of Akt showed region-specific alteration with a decrease in the red region and an increase in the white region immediately after downhill running. Overall, a prior increase in HSP72 expression elicits fiber type-specific changes in exercise-induced Akt and mTOR phosphorylation in rat gastrocnemius muscle.

Timed exercise stabilizes behavioral rhythms but not molecular programs in the brain's suprachiasmatic clock

Timed daily access to a running-wheel (scheduled voluntary exercise; SVE) synchronizes rodent circadian rhythms and promotes stable, 24h rhythms in animals with genetically targeted impairment of neuropeptide signaling (Vipr2 ^-/- mice). Here we used RNA-seq and/or qRT-PCR to assess how this neuropeptide signaling impairment as well as SVE shapes molecular programs in the brain clock (suprachiasmatic nuclei; SCN) and peripheral tissues (liver and lung). Compared to Vipr2 ^+/+ animals, the SCN transcriptome of Vipr2 ^-/- mice showed extensive dysregulation which included core clock components, transcription factors, and neurochemicals. Furthermore, although SVE stabilized behavioral rhythms in these animals, the SCN transcriptome remained dysregulated. The molecular programs in the lung and liver of Vipr2 ^-/- mice were partially intact, although their response to SVE differed to that of these peripheral tissues in the Vipr2 ^+/+ mice. These findings highlight that SVE can correct behavioral abnormalities in circadian rhythms without causing large scale alterations to the SCN transcriptome.

Effect of exercises according to the circadian rhythm in type 2 diabetes: Parallel-group, single-blind, crossover study

BACKGROUND AND AIM

To evaluate the effectiveness of structured exercise appropriate the circadian rhythm in terms of blood sample test (BST), functionality and quality of life (QoL) in individuals with type 2 diabetes.

METHODS AND RESULTS

This was a parallel-group, single-blind, crossover study. Thirty individuals with type 2 diabetes aged 35-65 years were enrolled in the study and allocated into 2 groups as the Morning Chronotype (MC) Group (n = 15) and the Evening Chronotype (EC) Group (n = 15) using Morningness-Eveningness Questionnaire which was used to determine the chronotypes. Participants were evaluated in terms of BST, functionality and QoL at the beginning of the study (T0), at 6 (T1), 12 (T2), and 18 (T3) weeks after the study started. A structured exercise program for 3 days a week over 6 weeks was applied in accordance with the chronotypes (T1-T2) and cross-controlled for the chronotypes (T2-T3). Significant differences were found in favor of the exercise given at the appropriate time for the chronotype in all parameters in both groups within groups (T0-T1-T2-T3) (p < 0.05). In the time∗group interactions, exercise in accordance with the appropriate chronotype in both groups provided the highest statistical improvement in all parameters (p < 0.05).

CONCLUSION

It was concluded that structured exercise performed at the appropriate time for chronotype improves HbA_1c, fasting blood glucose, HDL-LDL cholesterol, triglyceride, total cholesterol, functionality and quality of life in type 2 diabetes. This variation in blood values was observed to reflect the quantitative effects of exercise administered according to the circadian rhythm in individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04427488). The protocol of the study was registered at ClinicalTrials.gov (NCT04427488).