Lipectomy does not impair fattening induced by short photoperiods or high-fat diets in female Syrian hamsters.

Syrian hamsters (Mesocricetus auratus) exhibit seasonal fluctuations in body fat that are triggered by changes in photoperiod and/or diet. Body fat accumulates when hamsters are switched to a short photoperiod or high-fat diet. The effects of surgical reduction of adipose tissue (lipectomy) on these responses were tested in adult female hamsters. Dorsal-inguinal subcutaneous, parametrial, and retroperitoneal white adipose tissues were removed bilaterally from some hamsters, while others received sham surgery. Hamsters from each surgical group were then fed a high-fat diet for the next 12 or 30 weeks, or were exposed to a short photoperiod for 13 weeks. Restoration of previously excised pads was for the most part incomplete, yet all lipectomized hamsters fully regained total body lipid, which suggests compensatory hypertrophy in other depots. Consistent with this, we found a significant increase in the weight of the previously undisturbed axillary subcutaneous pad, but this increase was small and not sufficient to offset the deficits remaining in the regenerated pads. Thus, restoration of total body lipid mass was achieved by a general increase in deposition over all depots rather than a specific renewal of removed tissue. This ability to recover completely from lipectomy is similar to that previously reported in ground squirrels. In contrast, rats and mice are frequently unable to replace lost adipose tissue. Both hamsters and squirrels adjust their levels of body fat according to season, which may afford them an enhanced ability to recover from surgical reductions of adipose tissue.