Effects of Exercise Training on Hepatic Microsomal Triglyceride Transfer Protein Content in Rats

Abstract

Microsomal triglyceride transfer protein (MTP) is a protein that exerts a central regulatory role in very-low-density lipoprotein (VLDL) assembly and secretion. The purpose of the study was to investigate the effects of an exercise-training program on hepatic content of MTP and its relation to hepatic VLDL-triglyceride (VLDL-TG) production in response to lipid infusion. Female rats either fed a standard (SD) or an obesity-induced high-fat (HF; 43% as energy) diet for 8 weeks were subdivided into sedentary (Sed) and trained (Tr) groups. Exercise training consisted of continuous running on a motor-driven rodent treadmill 5 times/week for 8 weeks. At the end of this period, all rats in the fasted state were intravenously infused with a 20% solution of Intralipid for 3 h followed by an injection of Triton WR1339 to block lipoprotein lipase. An additional control group consisting of Sed rats fed the SD diet was infused with saline (0.9% NaCl). Plasma TG accumulation was thereafter measured during 90 min to estimate VLDL-TG production. Under HF diet, hepatic MTP content and plasma TG accumulation after Triton blockade (thus reflecting VLDL-TG synthesis and secretion) were not changed in Sed rats, whereas liver TG content was highly increased (approximately 90%; p<0.01). On the other hand, training reduced liver MTP protein content in both SD (-18%) and HF (-23%) fed rats (p<0.05). Plasma VLDL-TG accumulation was also lower (p<0.05) in Tr than in Sed rats fed the HF diet. This effect was not observed in SD fed rats. Furthermore, the exercise training-induced decrease in VLDL-TG production in HF rats was associated with a decrease in liver TG levels. It is concluded that in addition to a reduction in liver TG content, exercise training reduces VLDL synthesis and/or secretion in HF fed rats probably via MTP regulation.

Can the Intermittent Training Generate Alterations on the Liver Tissue of Rats Submitted to a Hyperlipidic Diet?

“…However, the EO group had a differentiating factor, in addition to diet; intermittent training. The results of Chapados et al (2009) corroborate the findings of this study, stating that coupled with a reduction in the content of triacylglycerides in the liver, physical training reduces the synthesis of VLDL (Very Low Density Lipoprotein) in fed rats which have had obesity induced by high fat levels, via microsomal triglyceride transfer protein.…”

A Novel Mechanism for Decreasing Plasma Lipid Level from Imidazoline I-1 Receptor Activation in High Fat Diet-fed Mice

“…Blood samples were collected from the retro-orbital sinuses of each group. Blood samples were then centrifuged at 3 000 rpm for 10 min and stored at − 80 ° C for further experiments [16] . The determination of plasma lipid level was carried out according to a previous study [17] .…”

Ten weeks of aerobic training does not result in persistent changes in VLDL triglyceride turnover or oxidation in healthy men

“…In untrained individuals, a single bout of exercise reduces fasting VLDL-TG concentration the following day relative to both the intensity and the amount of exercise (4, 5,metabolism are plausible. Animal studies indicate that long-term endurance training is associated with decreased hepatic VLDL-TG secretion (13,14,15). Human studies, however, show somewhat divergent results.…”

“…In this study, we investigated the impact of a 10-week training intervention in healthy, sedentary men on plasma VLDL-TG and FFA kinetics and oxidation using i.v. infusion of [1-14 C]VLDL-TG and [9, H]palmitate in combination with measurements of plasma isotopic specific activity (SA) and exhaled 14 CO 2 before and after the 10-week intervention period.…”