How do mice cope with hunger? - briefly
Mice respond to food scarcity by reducing their metabolic rate, mobilizing stored fat, and entering brief torpor to conserve energy. They also intensify exploratory and foraging activity, using olfactory cues to locate limited resources.
How do mice cope with hunger? - in detail
Mice respond to food scarcity through a combination of physiological, behavioral, and molecular adjustments that preserve energy and maintain vital functions.
When nutrients become limited, basal metabolic rate declines. Thermogenesis in brown adipose tissue is suppressed, and peripheral vasoconstriction reduces heat loss, allowing body temperature to fall modestly without triggering full torpor. This controlled hypothermia conserves glucose and fatty acids for essential organs.
Hormonal signals shift rapidly. Circulating leptin drops, relieving inhibition of neuropeptide Y (NPY) and agouti‑related peptide (AgRP) neurons in the arcuate nucleus. These orexigenic pathways increase appetite and drive foraging activity. Simultaneously, glucagon rises, promoting glycogenolysis and gluconeogenesis, while insulin secretion diminishes to limit peripheral glucose uptake.
Behaviorally, mice reduce non‑essential movements, limit grooming, and spend more time near potential food sources. Exploration patterns become more focused, with increased use of olfactory cues to locate hidden caches. In social colonies, dominant individuals may prioritize feeding, while subordinate mice accept temporary deprivation, reducing competition for scarce resources.
At the cellular level, skeletal muscle and liver cells up‑regulate AMP‑activated protein kinase (AMPK), enhancing fatty‑acid oxidation and inhibiting anabolic pathways. Autophagy accelerates, recycling intracellular components to supply amino acids and energy. Gene expression analyses reveal heightened transcription of fasting‑responsive genes such as Pparα, Foxo1, and Atg5.
Gut microbiota composition also changes. Species capable of fermenting complex polysaccharides increase in relative abundance, producing short‑chain fatty acids that serve as an alternative energy source for colonocytes and contribute to systemic metabolic signaling.
If deprivation persists, mice may enter a state of daily torpor: body temperature drops 5–10 °C for several hours, metabolic rate falls by up to 70 %, and locomotor activity ceases. Recovery occurs promptly upon refeeding, with rapid restoration of glycogen stores and normalization of hormone levels.
Collectively, these mechanisms enable mice to survive periods of limited food availability while retaining the capacity to resume normal growth and reproduction once resources are restored.