Plasma Corticosterone, Motor Activity and Metabolic Circadian Patterns in Streptozotocin-Induced Diabetic Rats

Abstract

Experiments were conducted in male rats to study the effects of streptozotocin-induced diabetes on circadian rhythms of (a) plasma corticosterone concentrations; (b) motor activity; and (c) metabolic patterns. Animals were entrained to LD cycles of 12:12 hr and fed ad libitum. A daily rhythm of plasma corticosterone concentrations was found in controls animals with peak levels at 2400 hr and low values during the remaining hours. This rhythm was statistically confirmed by the cosinor method and had an amplitude of 3.37 micrograms/100 ml and the acrophase at 100 hr. A loss of the normal circadian variation was observed in diabetic animals, with a nadir at the onset of light period and high values throughout the remaining hours; cosinor analysis of these data showed no circadian rhythm, delete and a higher mean level than controls. As expected, normal rats presented most of their motor activity during the dark period with 80% of total daily activity; the cosinor method demonstrated a circadian rhythm with an amplitude of 60% of the mean level and the acrophase at 0852 hr. Both diabetic and control rats showed a similar activity during the light phase, but diabetic animals had less activity than controls during the night and their percentage of total daily activity was similar in both phases of the LD cycle (50% for each one). With the cosinor method we were able to show the persistence of a circadian rhythm in the motor activity of diabetic rats, but with a mesor and amplitude lower than in controls (amplitude rested at 60% of the mean level) and its acrophase advanced to 0148 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

The insulin–melatonin antagonism: studies in the LEW.1AR1-iddm rat (an animal model of human type 1 diabetes mellitus)

“…Continuous lines, control; dashed lines, diabetic; dotted lines, diabetic+insulin [35,36] and, more recently, Stebelova et al [37]. Moreover, opposite results on diurnal variations in plasma insulin, leptin, glucocorticoids, growth and thyroid hormones, glucose and fatty acids, as well as on the sympathetic neuronal activity, have been reported by other investigators [38][39][40][41].…”

Circadian Signatures in Rat Liver: From Gene Expression to Pathways

“…Insulin. Daily oscillation of insulin secretion and glucose tolerance are lost in patients with type 2 diabetes [73,74], as are daily variations in plasma corticosterone levels and locomotor activity in streptozotocin-induced diabetic rats [75,76]. These results suggest that loss of circadian rhythmicity of glucose metabolism may contribute to the development of metabolic disorders, such as type 2 diabetes [74][75][76][77][78].…”

Effect of a high-fat diet on food intake and hypothalamic neuropeptide gene expression in streptozotocin diabetes.

“…Conversely, in the diabetic state, reduced CNS insulin concentrations are proposed to result in the elevation of hypothalamic NPY activity, which in turn produces hyperphagia (7). In contrast to reduced insulin levels, plasma corticosterone concentrations are elevated in diabetic relative to nondiabetic rats (20,21), and this occurs despite the reduction in PVN CRH expression (7). Moreover, corticosterone administration to diabetic rats increases both ARC NPY expression and food intake in a dose-dependent manner (22).…”