Endocrine and metabolic signaling in retroperitoneal white adipose tissue remodeling during cold acclimation

Abstract

The expression profiles of adiponectin, resistin, 5'-AMP-activated protein kinase α (AMPK α ), hypoxia-inducible factor-1 α (HIF-1 α ), and key enzymes of glucose and fatty acid metabolism and oxidative phosphorylation in rat retroperitoneal white adipose tissue (RpWAT) during 45-day cold acclimation were examined. After transient suppression on day 1, adiponectin protein level increased following sustained cold exposure. In parallel, on day 1, the protein level of HIF-1 α was strongly induced and AMPK α suppressed, while afterwards the reverse was seen. What is more, after an initial decrease on day 1, a sequential increase in pyruvate dehydrogenase, acyl-CoA dehydrogenase, cytochrome c oxidase, and ATP synthase and a decrease in acetyl-CoA carboxylase (from day 3) were observed. Similar to adiponectin, protein level of resistin showed a biphasic profile: it increased after days 1, 3, and 7 and decreased below the control after 21 days of cold-acclimation. In summary, the data suggest that adiponectin and resistin are important integrators of RpWAT metabolic response and roles it plays during cold acclimation. It seems that AMPK α mediate adiponectin effects on metabolic remodeling RpWAT during cold acclimation.

Figure 1

Time course of the changes in protein expression of adiponectin (Acrp30) (a) and resistin (b) in rat RpWAT during cold acclimation. Protein content is expressed relative to a control acclimated to room temperature, which was standardized as 100%. The results of the representative example from three observations are shown. Data were quantified as described in Section 2. The values represent the mean ± S.E.M. *Compared to control, *P < 0.05, **P < 0.01, and ***P < 0.001.

Figure 2

Protein levels of HIF-1α (a) and phospho-AMPKα (b) in rat RpWAT during cold acclimation. Protein content is expressed relative to a room temperature-acclimated control, which was standardized as 100%. The results of the representative example from three observations are shown. Data were quantified as described in Section 2. The values represent the mean ± S.E.M. *Compared to control, *P < 0.05, **P < 0.01, and ***P < 0.001.

Figure 3

Changes in GAPDH (a), PDH (b), ACADM (c), ACC (d), subunit IV of cytochrome c  oxidase (COX IV) (e), and ATP synthase (f) protein levels in rat retroperitoneal depot of white fat tissue after different time periods of cold exposure. Protein content is expressed relative to the control maintained at room temperature, which was standardized as 100%. The results of the representative example from three observations are shown. Data were quantified as described in Section 2. The values represent the mean ± S.E.M. *Compared to control, *P < 0.05, **P < 0.01, and ***P < 0.001.