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

BACKGROUND: Obesity, oxidative stress and inflammation, by triggering insulin resistance, may contribute to the accumulation of hepatic fat, and this accumulation by lipotoxicity can lead the organ to fail. Because obesity is growing at an alarming rate and, worryingly, in a precocious way, the present study aimed to investigate the effects of moderate physical training performed from childhood to adulthood on liver fat metabolism in rats. METHODS: Twenty rats that were 28 days old were divided into two groups: control (C) and trained (T). The C Group was kept in cages without exercise, and the T group was submitted to swimming exercise for 1 hour/day, 5 days/week from 28 to 90 days of age (8 weeks) at 80% of the anaerobic threshold determined by the lactate minimum test. At the end of the experiment, the body weight gain, insulin sensitivity (glucose disappearance rate during the insulin tolerance test), concentrations of free fatty acids (FFA) and triglycerides (TG) and hepatic lipogenic rate were analyzed. For the statistical analysis, the Student t-test was used with the level of significance preset at 5%. RESULTS: The T group showed lower body weight gain, FFA concentrations, fat accumulation, hepatic lipogenic rate and insulin resistance. CONCLUSION: The regular practice of moderate physical exercise from childhood can contribute to the reduction of obesity and insulin resistance and help prevent the development of accumulation of hepatic fat in adulthood.

Effects of swimming training on tissue glycogen content in experimental thyrotoxic rats.

Thyrotoxicosis, a condition in which there is an excessive amount of circulating thyroid hormones, leads to reduced glycogen content in different tissues. In this study we analyzed the effects of aerobic swimming training on liver, heart, and skeletal muscle glycogen content in experimentally induced thyrotoxicosis. Wistar male rats were divided into euthyroid sedentary (ES, n = 12), euthyroid trained (ET, n = 11), thyrotoxic sedentary (TS, n = 12), and thyrotoxic trained (TT, n = 10) groups. Thyrotoxic groups received daily i.p. doses of T4 (sodium levothyroxine, 25 µg/100 g body mass) through the experimental period, and trained groups swam for 1 h at 80% of the aerobic-anaerobic transition intensity, 5 days/week for 4 weeks. Heart and liver glycogen stores were ∼30% lower in T4 treated compared with nontreated groups, but were not changed by training status. On the other hand, glycogen content in mixed fiber type gastrocnemius of TT was 1.5- to 2.3-fold greater than those in other groups, whereas no significant differences were found for the slow soleus muscle. Increased gastrocnemius but not soleus, liver, or heart glycogen indicates that in mild long-term thyrotoxicosis chronic swimming affects glycogen stores in a tissue-specific manner.

Aerobic capacity of rats recovered from fetal malnutrition with a fructose-rich diet.

The objective of this study was to analyze the aerobic capacity, through the maximal lactate steady-state (MLSS) protocol, of rats subjected to fetal protein malnutrition and recovered with a fructose-rich diet. Pregnant adult Wistar rats that were fed a balanced (17% protein) diet or a low-protein (6% protein) diet were used. After birth, the offspring were distributed into groups according to diet until 60 days of age: balanced (B), balanced diet during the whole experimental period; balanced-fructose (BF), balanced diet until birth and fructose-rich diet (60% fructose) until 60 days; low protein-balanced (LB), low-protein diet until birth and balanced diet until 60 days; and low protein-fructose (LF), low protein diet until birth and fructose-rich diet until 60 days. It was verified that the fructose-rich diet reduced body growth, mainly in the BF group. There was no difference among the groups in the load corresponding to the MLSS (B, 7.5+/-0.5%; BF, 7.4+/-0.6%; LB, 7.7+/-0.4%; and LF, 7.7+/-0.6% relative to body weight). However, the BF group presented higher blood lactate concentrations (4.8+/-0.9 mmol.L(-1)) at 25 min in the load corresponding to the MLSS (B, 3.2+/-0.9 mmol.L(-1); LB, 3.4+/-0.9 mmol.L(-1); and LF, 3.2+/-1.0 mmol.L(-1)). Taken together, these results indicate that the ability of young rats to perform exercise was not altered by intrauterine malnutrition or a fructose-rich diet, although the high fructose intake after the balanced diet in utero increased blood lactate during swimming exercises in rats.

Non-exhaustive test for aerobic capacity determination in swimming rats.

The aim of this study was to describe a double-bout exercise test for non-exhaustive aerobic capacity determination in swimming rats. Adult rats were submitted to 4 swimming tests at different intensities (4%, 6%, 7%, and 8% of body mass), with intervals of 48 h between them. Two exercise bouts of equal intensity lasting 5 min were performed, separated by 2 min with blood collection for lactate analysis. For each intensity, delta lactate was determined by subtracting lactate concentration at the end of the first effort from the lactate at the end of the second effort. Individual linear interpolation of delta lactate concentration enabled determination of a "null" delta, equivalent to the critical load (CL). Maximal lactate steady state (MLSS) was also determined. The estimated CL was of 4.8% body mass and the MLSS was observed at 100% of CL, with blood lactate of 5.20 mmol/L. At 90%, blood lactate stabilized, with a progressive increase to 110% CL. These results offer a potential determination of aerobic capacity in swimming rats.

Exercício contínuo e intermitente: efeitos do treinamento e do destreinamento sobre a gordura corporal de ratos obesos / Continuous and intermittent exercise: effects of training and detraining on body fat in obese rats

O exercício contínuo tem sido recomendado na prevenção e no tratamento da obesidade mas o emprego do exercício intermitente é discutível. No presente estudo, são apresentados resultados referentes à composição química corporal de ratos obesos submetidos ao treinamento contínuo e intermitente e subseqüente destreinamento. Foram utilizados ratos, Wistar, recém-nascidos, que receberam glutamato monossódio (MSG), via subcutânea, 4mg/g peso corporal (p.c.), a cada dois dias nos primeiros 14 dias de vida. Após o desmame, foram separados em 3 grupos: MSG-SED (sedentário), MSG-CONT (contínuo=natação, 45 min/dia, 5 dias/semana, com sobrecarga de 5 por cento p.c. por 10 semanas) e MSG-INT (intermitente= natação, 15s de atividade/15s de repouso, num total de 45min, 5 dias/semana, com sobrecarga de 15por cento p.c.). Como controles foram utilizados ratos que receberam salina (SAl) separados em 3 grupos: SAL-SED, SAL-CONT e SAL-INT. Os animais foram avaliados imediatamente após 10 semanas de treinamento e 8 semanas depois de sua interrupção. Os ratos MSG mostraram maiores teores de gordura na carcaça bem como peso e tamanho celular no tecido adiposo epididimal que os SAL, comprovando a eficácia da droga em causar obesidade. O treinamento intermitente atenuou o acúmulo de lactato durante o exercício nos ratos SAL e MSG em relação aos sedentários, indicando melhora do condicionamento aeróbio. Ambos os protocolos reduziram o ganho de peso dos ratos SAL e MSG e o teor de gordura da carcaça dos ratos MSG. Os efeitos dos dois protocolos foram transitórios, uma vez que após o destreinamento os benefícios observados foram revertidos