Diurnal changes in lipolytic activity of isolated fat cells and their increased responsiveness to epinephrine and theophylline with meal feeding in rats.

Abstract

SummaryDiurnal changes in glycogen stores of adipose tissues and in vitro lipolytic activity of isolated epididymal fat cells, and their lipolytic responsiveness to epinephrine and theophylline were examined in rats adapted to a 2-h daily meal feeding (20.00-22.00h; darkness between 20.00-08.00h) for 3 weeks and in control rats fed ad libitum. The fat cells from both groups of animals showed the peak of lipolytic activity at the mid-dark period (03.00h), but the peak values and the average values at 6 or 7 time points examined within the 24-h feeding cycle were significantly higher (p<0.025) in meal-fed rats. Basal, epinephrine-stimulated, and epinephrine-induced lipolysis of fat cells from control rats showed diurnal changes, and the rhythms and their amplitude were affected by meal feeding. Changes in lipolytic activity of fat cells did not seem to relate directly to those of glycogen stores in adipose tissue. The over-all 24-h means of lipolytic activity of fat cells were significantly increased (p<0.001) with meal feeding. Mean cell size of epididymal fat pads was significantly smaller (p<0.001) in meal-fed rats, but lipolytic responsive ness to the graded concentrations of epinephrine and theophylline in the incubation medium was significantly greater (p<0.001) in meal-fed rats than in rats fed ad libitum. Thus, these findings suggest that lipolytic activity of the CAMP-hormone sensitive lipase system in fat cells might be increased with meal feeding in rats. Furthermore, the present results may give a new idea to consider the discrepancy that many workers have not been able to observe the increase in body fat deposition with meal feeding,

Plasma Leptin Levels in Rat Mother and Offspring during Pregnancy and Lactation

“…Late pregnancy is characterized by high plasma insulin levels and insulin resistance [8,33,34]. Therefore, the high plasma leptin levels found in pregnant rats occur in the presence of hyperphagia which indicates leptin resistance, increased lumbar adipose tissue weight, high plasma insulin levels, and insulin resistance, all of which are similar changes to those normally seen in human obesity [35][36][37].…”

Circadian rhythms in the development of obesity: potential role for the circadian clock within the adipocyte

“…However, Suzuki et al . reported that diurnal variations in the sensitivity of adipose to adrenaline‐induced lipolysis persisted ex vivo , suggesting that the intrinsic nature of the adipocyte exhibits a diurnal variation (63).…”

Body weight, metabolism and clock genes

“…Although circadian variations of adipose tissue metabolism have been shown to be influenced by external neuro-humoral factors [13,16], they can also be influenced internally by a peripheral circadian clock that acts on tissue metabolism and can alter adipocyte responsiveness in response to different stimuli during the day (for example, levels of glucose, insulin, fatty acids, melatonin) or can alter the capacity of lipolysis and lipogenesis [17,18]. …”