Pros and cons of insulin administration on liver glucose metabolism in strength-trained healthy mice

Abstract

Non-diabetic individuals use hormones like insulin to improve muscle strength and performance. However, as insulin also leads the liver and the adipose tissue to an anabolic state, the purpose of this study was to investigate the effects of insulin on liver metabolism in trained non-diabetic Swiss mice. The mice were divided into four groups: sedentary treated with saline (SS) or insulin (SI) and trained treated with saline (TS) or insulin (TI). Training was made in a vertical stair, at 90% of the maximum load, three times per week. Insulin (0.3 U/kg body weight) or saline were given intraperitoneally five times per week. After eight weeks, tissue and blood were collected and in situ liver perfusion with glycerol+lactate or alanine+glutamine (4 mM each) was carried out. The trained animals increased their muscle strength (+100%) and decreased body weight gain (–11%), subcutaneous fat (–42%), mesenteric fat (–45%), and peritoneal adipocyte size (–33%) compared with the sedentary groups. Insulin prevented the adipose effects of training (TI). The gastrocnemius muscle had greater density of muscle fibers (+60%) and less connective tissue in the trained groups. Liver glycogen was increased by insulin (SI +40% and TI +117%), as well as liver basal glucose release (TI +40%). Lactate and pyruvate release were reduced to a half by training. The greater gluconeogenesis from alanine+glutamine induced by training (TS +50%) was reversed by insulin (TI). Insulin administration had no additional effect on muscle strength and reversed some of the lipolytic and gluconeogenic effects of the resistance training. Therefore, insulin administration does not complement training in improving liver glucose metabolism.

Resistance training with and without insulin administration: an analysis of the cardiac plexus and epicardial adipose tissue

“…Previous results from our research group using this same experimental model showed that there was a significant difference in relation to body weight, where trained animals (TS and TI) had less weight when compared to sedentary groups. Biochemical data showed that the use of insulin increased the dosage of hepatic glycogen and the release of basal glucose from the liver, and its use associated with training meant that the increase in exercise-induced gluconeogenesis was reduced (Pereira, et al, 2019).…”

“…Each week a new ML test was performed, but starting from the ML of the previous week, to adjust the training intensity. Mice from groups SS and SI were subjected to the ML test on the first and last week of the experimental period (Pereira, et al, 2019).…”

High-intensity interval resistance training (HIIRT) improves liver gluconeogenesis from lactate in Swiss mice

“…The trained groups were scheduled sequentially, so that no more than 10 mice were under training during a given period. The apparatus used for familiarization, training and maximal load (ML) tests, as well as the training protocol (load, frequency, format of the sessions and periods of training) were adapted from previous studies (Cassilhas et al, 2013;Muller et al, 2019;Neto et al, 2016;Pereira et al, 2019).…”

“…The training with vertical ladder and overload presents many advantages: easy handling and low cost; control of the training load; individualized training intensity; less discomfort and distress to the animal; the desired physiological response (that is, increased blood lactate levels) achieved easily and in shorter training sessions; and it can be used for continuous (Pereira et al, 2019) or interval (Muller et al, 2019) training formats.…”