Chronic cold exposure causes left ventricular hypertrophy that appears to be physiological

Area of Science:

• Cardiology
• Physiology
• Environmental Health

Background:

• Winter cold increases energy demands for thermoregulation.
• Small rodents experience profound cardiac hypertrophy (2-3x exercise levels) due to cold exposure.
• The nature and implications of cold-induced cardiac hypertrophy for winter mortality are unclear.

Purpose of the Study:

• Characterize cold-induced cardiac hypertrophy.
• Compare it to exercise-induced (physiological) and hypertension-induced (pathological) hypertrophy.
• Investigate its relevance to winter mortality in small rodents.

Main Methods:

• Induce cardiac hypertrophy via chronic cold exposure in rodents.
• Assess hypertrophy reversal upon return to warm temperatures.
• Analyze cardiac gene expression and mitochondrial enzyme activity.
• Compare gene expression profiles with exercise-trained rodents.

Main Results:

• Cold-induced cardiac hypertrophy was largely reversible upon rewarming.
• Metabolic rates increased, but pathological gene expression and mitochondrial enzyme activities were absent.
• Gene expression patterns showed similarities, though not identity, to exercise-induced hypertrophy.
• Decreased expression of fatty acid oxidation genes was observed.

Conclusions:

• Cold-induced cardiac hypertrophy closely resembles physiological hypertrophy.
• This process involves enhanced metabolic rate without pathological markers.
• Heart failure is unlikely to cause winter mortality in small rodents.
• Identifies a novel pathway for studying cardiac growth.