Figure 1.
Growth curve of euthyroid (Eu), hypothyroid (Hypo), and hypothyroid rats treated with T2 (Hypo+T2).
The arrows indicate initiation of T2 treatment. Although the standard error for each data point is less than 2%, these bars were omitted for a better representation.
Table 1.
Effect of hypothyroidism and T2 administration to hypothyroid rats on rat resting energy expenditure and on the contribution of different tissues to rat total body weight.
Figure 2.
Effects of hypothyroidism and T2 administration to Hypo rats on BAT morphology.
(A) Representative tissue sections showing different cellular shapes within BAT parenchyma, and (B) the different distribution of lipid droplets inside the multilocular (ML) adipocytes. Scale bars: 60 μm in (A); 10 μm in (B). (C) Quantification of ML, paucilocular (PL), and unilocular (UL) cells within the tissue, as well as lipid droplet diameters and areas of ML adipocytes *P<0.05 versus Eu; #P<0.05 versus Hypo.
Figure 3.
Effects of hypothyroidism and T2 administration to Hypo rats on BAT sympathetic innervation.
(A) Parenchymal noradrenergic innervation was detected by immunohistochemistry. Single TH immunoreactive fibers were closely associated with brown adipocytes (arrows) and with a small arteriole (a). Scale bar: 10 μm. (B) Bar chart showing the number of parenchymal TH immunoreactive fibers per adipocyte. *P<0.05 versus Eu; #P<0.05 versus Hypo.
Figure 4.
Effects of hypothyroidism and T2 administration to Hypo rats on BAT vascularization.
(A) Vascular endothelial cells were visualized by isolectin (BS-1) immunostaining. Scale bar: 10 μm. (B) Bar charts showing the number of BS-1 immunoreactive capillaries per adipocyte. *P<0.05 versus Eu; #P<0.05 versus Hypo.
Figure 5.
Effects of hypothyroidism and T2 administration to Hypo rats on tissue mitochondrial content and oxidative capacity.
(A) Mitochondrial protein/100 mg tissue, (B) cytochrome oxidase (COX) activity, (C) citrate synthase activity, and (D) VDAC1 content detected in whole BAT lysates. Data in the bar chart are represented as means ± standard error of the mean from five independent experiments, each performed in duplicate. *P<0.05 versus Eu; #P<0.05 versus Hypo. (E) Representative COX IV immunoreactivity in BAT. Scale bar: 40 μm.
Figure 6.
Dose-dependent effect of in vitro addition of T2 on cytochrome oxidase (COX) activity in Hypo BAT homogenates.
Values represented means ± standard error of the mean from five independent experiments, each performed in duplicate. *P<0.05 versus 0 M.
Figure 7.
Effects of hypothyroidism and T2 administration to Hypo rats on mitochondrial respiration rate.
(A) Mitochondrial respiration evaluated in whole homogenates energized with α-glycerophosphate. (B) Mitochondrial respiration evaluated in isolated mitochondria in the absence and presence of 1 mM GDP. (C) An increase in oxygen consumption rate caused by addition of arachidonic acid to GDP inhibited-mitochondria. Values represented as means ± standard error of the mean from five independent experiments, each performed in duplicate. *P<0.05 versus Eu; #P<0.05 versus Hypo.
Figure 8.
Effects of hypothyroidism and of T2 administration to hypothyroid rats on BAT UCP1 content.
(A) Immunohistochemistry for UCP1 in representative sections of BAT. Inset: enlargement of the framed area showing an intensely stained PL cell (arrow). Scale bar represents 40 μm.
(B) Representative western blots and quantification of the signals of UCP1 protein levels detected in the whole lysate and at the mitochondrial levels. For total lysate, each lane contained 15 μg of protein from a single rat. Bar charts show quantifications of the signals (expressed relative to the value for the euthyroid controls obtained from 5 rats). *P<0,05 vs Eu, #P<0,05 vs hypo
Figure 9.
Effects of hypothyroidism and of T2 administration to Hypo rats on nuclear and mitochondrial PGC1-α content.
Representative western blots and quantification of the signals are shown. Each lane contained 15 μg of protein from a single rat. Bar charts show quantifications of the signals (expressed relative to the value for the Euthyroid controls obtained from 5 rats). Values represent mean ± SE * P <0.05 vs. Eu. #P<0.05 vs. Hypo.
Figure 10.
Effects of T3 administration to Hypo rats on (A) BAT weight, (B) Cytochrome oxidase (COX) activity, (C) mitochondrial respiration, and (D) UCP1 content in Hypo rats.
(D) Representative Western blots and histogram of UCP1 protein levels in whole lysates (15 μg of protein/rat/lane). The bar charts shows blot signal quantification relative to Eu (n = 5 rats). *P<0.05 versus Hypo.
Figure 11.
Effects of T3 administration to Hypo rats on nuclear and mitochondrial PGC1-α content.
Representative Western blots and respective histograms of respective lysates. Each lane was loaded with 15 μg protein from a single rat. The bar charts show blot signal quantification relative to Hypo (n = 5 rats). Values represent mean ± standard error of the mean. #P<0.05 versus hypo