Increased metabolic flexibility and complexity in a long-lived growth hormone insensitive mouse model

Area of Science:

• Metabolic physiology
• Aging research
• Systems biology

Background:

• The "loss of complexity" hypothesis suggests reduced physiological variability with aging or disease.
• Growth hormone receptor (GHR) signaling influences metabolism, aging, and lifespan.
• GHR gene deletion in mice (GHR(-/-)) leads to extended lifespan and altered metabolic function.

Purpose of the Study:

• To investigate the applicability of the "loss of complexity" hypothesis to metabolic patterns.
• To compare the complexity of locomotor activity and metabolic parameters between long-lived GHR(-/-) mice and wild-type controls.
• To identify metabolic differences associated with extended lifespan in GHR(-/-) mice.

Main Methods:

• Utilized approximate entropy to quantify the complexity of physiological fluctuations.
• Measured locomotor activity, energy expenditure, oxygen consumption (VO₂), and respiratory quotient.
• Compared complexity and metabolic patterns between GHR(-/-) mice and their wild-type littermates.

Main Results:

• GHR(-/-) mice demonstrated significantly greater metabolic complexity, characterized by increased irregularity in physiological fluctuations.
• Lower energy costs associated with locomotor activity were observed in GHR(-/-) mice.
• A stronger correlation between locomotor activity and respiratory quotient was found in GHR(-/-) mice.

Conclusions:

• The study supports the "loss of complexity" hypothesis in the context of metabolic patterns and aging.
• Metabolic complexity, assessed through physiological fluctuations, reveals distinct differences in GHR(-/-) mice.
• Findings suggest altered metabolic modulation and energy utilization strategies in long-lived GHR(-/-) mice.