The effect of shifting food‐intake period on rat body weight and plasma levels of glucose, leptin, melatonin, cholesterol and triglyceride

Abstract

The suprachiasmatic nucleus of the hypothalamus receives photic information from the retina and contribute to the control of body functions and hormonal secretion in a rhythmic manner through day/night cycle. We hypothesized that disturbance of circadian rhythm by shifting food‐intake period may reflect on body metabolism‐related blood parameters and hence body weight. Hence, we investigated the effect of repeated shifting food intake (over a period of six weeks) on daily changes of rat body weight, food/water intake, feces output and plasma levels of glucose, leptin, melatonin, cholesterol and triglyceride. Two groups of male WKY rats weighing 150–180g were used. The first was subjected to a constant day/night of 12:12h of light/dark cycle (fixed light/day cycle throughout the experimental period; Fixed Group); whereas the second group was subjected to an alternating (every two weeks) pattern of light/dark‐dark/light cycle of 12:12h each (Shifted Group). The plasma glucose, triglycerides, leptin and melatonin levels as well as feces output, food intake showed significant differences between Shifted and Fixed Groups. However, body weight and other measured plasma parameters were not significantly different. It is concluded that rats may need more frequent shifting of food‐intake period to manifest more conclusive effects.