Abstract
Recent advances on the influence of cold exposure on energy metabolism in animals
and humans are summarized. Although the cold-induced enhancements in carbohydrate
metabolism have been the focus of numerous studies, it was only recently that pieces
of evidence from animal studies have suggested that cold exposure exerts an insulin-like
effect on peripheral tissue glucose uptake, which appears to proceed primarily via
insulin-independent pathways. Interestingly, this phenomenon was observed in insulin-sensitive
tissues of warm- as well as cold-adapted rats. Whereas previous human studies have
concentrated on the cold-induced changes in basal levels of hormones and metabolic
substrates, recent work from our laboratory has demonstrated that exposure to cold
at rest shifts substrate utilization from mainly lipids at thermal neutrality to carbohydrates,
representing the main fuel for shivering thermo-genesis. Further investigation has
revealed that the marked increment in carbohydrate oxidation in cold-exposed humans
is derived from a greater utilization of both circulating glucose and intramuscular
glycogen. With respect to lipid metabolism, recent studies have shown that the cold-induced
increase in lipid oxidation in man is fuelled primarily by the fatty acids released
from white adipose tissue triglycerides (TG) and possibly intramuscular TG, not plasma
TG. One practical application of this work on energy metabolism in the cold resides
in the pharmacological approach to improve cold tolerance, where pharmacological agents
that alter energy metabolism and substrate utilization could be used to enhance cold
thermogenesis and produce warmer body temperatures.
Key words
Animals - carbohydrate - humans - lipid - substrate utilization
