Opposite Effects of Voluntary Physical Exercise on β3-Adrenergic Receptors in the White and Brown Adipose Tissue

Abstract

Catecholamine effects via β3-adrenergic receptors are important for the metabolism of the adipose tissue. Physical exercise is a core component of antiobesity regimens. We have tested the hypothesis that voluntary wheel running results in enhancement of β3-adrenergic receptor gene expression in the white and brown adipose tissues. The secondary hypothesis is that dietary tryptophan depletion modifies metabolic effects of exercise. Male Sprague-Dawley rats were assigned for sedentary and exercise groups with free access to running wheels for 3 weeks. All animals received normal control diet for 7 days. Both groups were fed either by low tryptophan (0.04%) diet or by control diet (0.2%) for next 2 weeks. The β3-adrenergic receptor mRNA levels in response to running increased in the retroperitoneal and epididymal fat pads. The gene expression of uncoupling protein-1 (UCP-1) was increased in the brown, while unchanged in the white fat tissues. Unlike control animals, the rats fed by low tryptophan diet did not exhibit a reduction of the white adipose tissue mass. Tryptophan depletion resulted in enhanced concentrations of plasma aldosterone and corticosterone, but had no influence on exercise-induced adrenal hypertrophy. No changes in β3-adrenergic receptor and cell proliferation measured by 5-bromo-2′-deoxyuridine incorporation in left heart ventricle were observed. The reduced β3-adrenergic receptor but not enhanced uncoupling protein-1 gene expression supports the hypothesis on hypoactive brown adipose tissue during exercise. Reduction in dietary tryptophan had no major influence on the exercise-induced changes in the metabolic parameters measured.

Human white-fat thermogenesis: Experimental and meta-analytic findings

“…Four of the studies in humans [16][17][18]39] together with data from study 5 provided data for a meta-analysis showing no effect of chronic exercise on UCP1 mRNA (p > 0.05; no data were available to test this hypothesis for UCP1 protein expression). Seven of the studies in animals identified in the systematic review that used a normal diet [11][12][13][14][15]40,41] provided data for a meta-analysis showing no effect of chronic exercise on UCP1 mRNA (p > 0.05). An additional meta-analysis using data from four studies [11,[42][43][44] for UCP1 protein expression showed a significant impact of chronic exercise in normal diet animals (Std = 0.41, CI = −0.01-0.83, p = 0.05, Figure 5).…”

Effect of Repeated Predator Scent Exposure on Excitability of Serotonin Neurons and Stress Markers in Rats

“…Concentration and purity of mRNA preparations was measured by absorption spectroscopy described previously [42,43]. Primers (Table 1) were used at a concentration of 0.25 pmol/μl.…”

Is Exercise a Match for Cold Exposure? Common Molecular Framework for Adipose Tissue Browning

“…Lactate, a glycolytic byproduct whose concentration increases after acute high-intensity exercise to 15-25 mmol/L in blood [175] and up to ~40 mmol/L in skeletal muscle [176], is imported into cells through proton-linked monocarboxylate transporters (MCTs) [177]. MCT1 increases strongly in BAT after exercise [81] and is similarly upregulated in WAT after cold exposure [178], enabling increased lactate flux into adipocytes. Carriere et al reported that lactate treatment (5-25 mmol/L) is a strong and selective enhancer of UCP1 activity in WAT and BAT, potentially serving as an adaptive response to mitigate redox imbalance and acidosis [72].…”