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Activation of systemic, but not local, renin-angiotensin system is associated with upregulation of TNF-? during prolonged fasting in northern elephant seal pups.


ABSTRACT: Northern elephant seal pups naturally endure a 2-3 month post-weaning fast that is associated with activation of systemic renin-angiotensin system (RAS), a decrease in plasma adiponectin (Acrp30), and insulin resistance (IR)-like conditions. Angiotensin II (Ang II) and tumor necrosis factor-alpha (TNF-?) are potential causal factors of IR, while Acrp30 may improve insulin signaling. However, the effects of fasting-induced activation of RAS on IR-like conditions in seals are not well described. To assess the effects of prolonged food deprivation on systemic and local RAS, and their potential contribution to TNF-? as they relate to an IR condition, the mRNA expressions of adipose and muscle RAS components and immuno-relevant molecules were measured along with plasma RAS components. Mean plasma renin activity and Ang II concentrations increased by 89 and 1658%, respectively, while plasma angiotensinogen (AGT) decreased by 49% over the fast, indicative of systemic RAS activation. Prolonged fasting was associated with decreases in adipose and muscle AGT mRNA expressions of 69 and 68%, respectively, corresponding with decreases in tissue protein content, suggesting suppression of local AGT production. Muscle TNF-? mRNA and protein increased by 239 and 314%, whereas those of adipose Acrp30 decreased by 32 and 98%, respectively. Collectively, this study suggests that prolonged fasting activates a systemic RAS, which contributes to an increase in muscle TNF-? and suppression of adipose Acrp30. This targeted and tissue-specific regulation of TNF-? and Acrp30 is likely coordinated to synergistically contribute to the development of an IR-like condition, independent of local RAS activity. These data enhance our understanding of the adaptive mechanisms evolved by elephant seals to tolerate potentially detrimental conditions.

SUBMITTER: Suzuki M 

PROVIDER: S-EPMC4074259 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Activation of systemic, but not local, renin-angiotensin system is associated with upregulation of TNF-α during prolonged fasting in northern elephant seal pups.

Suzuki Miwa M   Vázquez-Medina José Pablo JP   Viscarra Jose A JA   Soñanez-Organis José G JG   Crocker Daniel E DE   Ortiz Rudy M RM  

The Journal of experimental biology 20130516 Pt 17


Northern elephant seal pups naturally endure a 2-3 month post-weaning fast that is associated with activation of systemic renin-angiotensin system (RAS), a decrease in plasma adiponectin (Acrp30), and insulin resistance (IR)-like conditions. Angiotensin II (Ang II) and tumor necrosis factor-alpha (TNF-α) are potential causal factors of IR, while Acrp30 may improve insulin signaling. However, the effects of fasting-induced activation of RAS on IR-like conditions in seals are not well described. T  ...[more]

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