Moderate physical activity from childhood contributes to metabolic health and reduces hepatic fat accumulation in adult rats

Exercise decreases CLK2 in the liver of obese mice and prevents hepatic fat accumulation

The accumulation of fatty acids in the liver associated with obesity condition is also known as nonalcoholic fatty liver disease (NAFLD). The impaired fat oxidation in obesity condition leads to increased hepatic fat accumulation and increased metabolic syndrome risk. On the other hand, physical exercise has been demonstrated as a potent strategy in the prevention of NAFLD. Also, these beneficial effects of exercise occur through different mechanisms. Recently, the Cdc2-like kinase (CLK2) protein was associated with the suppression of fatty acid oxidation and hepatic ketogenesis. Thus, obese animals demonstrated elevated levels of hepatic CLK2 and decreased fat acid oxidation. Here, we explored the effects of chronic physical exercise in the hepatic metabolism of obese mice. Swiss mice were distributed in Lean, Obese (fed with high-fat diet during 16 weeks) and Trained Obese group (fed with high-fat diet during 16 weeks and exercised (at 60% exhaustion velocity during 1 h/5 days/week) during 8 weeks. In our results, the obese animals showed insulin resistance, increased hepatic CLK2 content and increased hepatic fat accumulation compared to the Lean group. Otherwise, the chronic physical exercise improved insulin resistance state, prevented the increased CLK2 in the liver and attenuated hepatic fat accumulation. In summary, these data reveal a new protein involved in the prevention of hepatic fat accumulation after chronic physical exercise. More studies can evidence the negative role of CLK2 in the control of liver metabolism, contributing to the improvement of insulin resistance, obesity, and type 2 diabetes.

Physical activity: benefit or weakness in metabolic adaptations in a mouse model of chronic food restriction?

In restrictive-type anorexia nervosa (AN) patients, physical activity is usually associated with food restriction, but its physiological consequences remain poorly characterized. In female mice, we evaluated the impact of voluntary physical activity with/without chronic food restriction on metabolic and endocrine parameters that might contribute to AN. In this protocol, FRW mice (i.e., food restriction with running wheel) reached a crucial point of body weight loss (especially fat mass) faster than FR mice (i.e., food restriction only). However, in contrast to FR mice, their body weight stabilized, demonstrating a protective effect of a moderate, regular physical activity. Exercise delayed meal initiation and duration. FRW mice displayed food anticipatory activity compared with FR mice, which was strongly diminished with the prolongation of the protocol. The long-term nature of the protocol enabled assessment of bone parameters similar to those observed in AN patients. Both restricted groups adapted their energy metabolism differentially in the short and long term, with less fat oxidation in FRW mice and a preferential use of glucose to compensate for the chronic energy imbalance. Finally, like restrictive AN patients, FRW mice exhibited low leptin levels, high plasma concentrations of corticosterone and ghrelin, and a disruption of the estrous cycle. In conclusion, our model suggests that physical activity has beneficial effects on the adaptation to the severe condition of food restriction despite the absence of any protective effect on lean and bone mass.

Prenatal programming of obesity in a swine model of leptin resistance: modulatory effects of controlled postnatal nutrition and exercise

The main role of early nutritional programming in the current rise of obesity and associated diseases is well known. However, translational studies are mostly based in postnatal food excess and, thus, there is a paucity of information on the phenotype of individuals with prenatal deficiencies but adequate postnatal conditions. Thus, we assessed the effects of prenatal programming (comparing descendants from females fed with a diet fulfilling 100 or only 50% of their nutritional requirements for pregnancy) on gene expression, patterns of growth and fattening, metabolic status and puberty attainment of a swine model of obesity/leptin resistance with controlled postnatal nutrition and opportunity of exercise. Maternal restriction was related to changes in the relationships among gene expression of positive (insulin-like growth factors 1 and 2) and negative (myostatin) regulators of muscle growth, with negative correlations in gilts from restricted pregnancies and positive relationships in the control group. In spite of these differences, the patterns of growth and fattening and the metabolic features during juvenile growth were similar in control gilts and gilts from restricted pregnancies. Concomitantly, there was a lack of differences in the timing of puberty attainment. However, after reaching puberty and adulthood, females from restricted pregnancies were heavier and more corpulent than control gilts, though such increases in weight and size were not accompanied by increases in adiposity. In conclusion, in spite of changes in gene expression induced by developmental programming, the propensity for higher weight and adiposity of individuals exposed to prenatal malnutrition may be modulated by controlled food intake and opportunity of physical exercise during infant and juvenile development.

Critical load estimation in young swimming rats using hyperbolic and linear models

We analysed the viability of critical load (CL) and anaerobic swimming capacity (ASC) estimation by different mathematical models and the effects of varying the number/intensity of predictive trials on these parameters in young swimming rats. After familiarised to swimming, 9 male animals had time to exhaustion (TEX) accessed in efforts against 9, 11, 13 and 15% of their body mass (bm). CL and ASC were calculated by the hyperbolic load vs. TEX (Hyp) as well as linear load vs. 1/TEX (Lin1) and load·TEX vs. TEX (Lin2) models. Moreover, parameters derived from the 11 possible combinations of 2, 3 or 4 efforts using the Lin1 regression were compared. The Lin1 model resulted in a lower R2 compared to Lin2 and Hyp methods (0.968±0.010 vs. 0.995±0.004 and 0.988±0.013; P<0.05), but no significant differences were found between models regarding CL (7.8±1.2, 7.9±1.1 and 7.8±1.0% bm) or ASC (526±129, 521±104 and 534±117% bm?s). Except for the atypical CL (1.4 ± 4.2% bm) and ASC (1079 ± 383% bm⋅s) from trials against 13 and 15% bm, varying the number/intensity of predictive bouts had no significant effects on parameter estimates. The observed viability and robustness of CL and ASC estimation by different mathematical models in young swimming Wistar rats suggest the load-time relationship as an interesting tool to investigate the physiological mechanisms underlying exercise tolerance in laboratory rodents.