Increased glucose synthesis in renal tubule fragments from hyperthyroid rats

Rates of glucose synthesis from several substrates were examined in renal tubule fragments from hyperthyroid rats. A hyperthyroid state was induced by daily intraperitoneal injections of thyroxine (T-4) (100 mu g/100 g body weight) for 14 days. At the end of the experimental period, plasma triiodothyronine and T-4 levels were six and eight times higher, respectively, than initial values. Hyperthyroid rats gained less weight and had lower blood glucose despite an increased food intake. In both control and hyperthyroid rats, rates of glucose production by renal tubule fragments were higher with glutamine and glycerol than with lactate, alanine, or glutamate. T-4 treatment induced a significant increase in the de novo glucose synthesis from all substrates, except glutamine. The highest percent increase was obtained with alanine (64%), compared with 31-40% for glutamate, lactate, and glycerol. The T-4 treatment induced increase in glucose synthesis by renal tubule fragments suggests that renal gluconeogenesis contributes to enhance glucose production in hyperthyroidism

Gluconeogenesis and glucose replacement rate during long-term fasting of Japanese quails

Gluconeogenic activity and kinetic parameters of glucose metabolism were estimated during the different phases of prolonged food deprivation in quails. Gluconeogenic activity, estimated from the rate of increase of incorporation of (HCO3-)-C-14 into circulating glucose, was significantly higher in fasted quails than in fed birds, whatever the period of food deprivation. However, gluconeogenic activity during phase II, although higher than in the fed state, was significantly lower than in quails fasted for 2 days (phase I) or in those on the final (phase III) period of starvation. Gluconeogenic activity did not differ significantly in birds from phases I and III. Rates of glucose replacement, estimated with [6-H-3]-glucose, were very high (20.5 mg . kg(-1). min(-1)) in fed quails and were markedly reduced (to about 42% of fed values) by fasting, no difference being observed between quails fasted for 2 and 5 days. Because of the poor condition of the birds, glucose replacement rates could not be measured during phase III. The present data are the first to provide direct evidence for the changes in gluconeogenesis which occur during prolonged food deprivation

Resistance to diabetogenic drugs in carnivorous or in animals fed high protein diets

info:eu-repo/semantics/publishe

Energy metabolism and fasting in male and female insectivorous bats Molossus molossus (Chiroptera: Molossidae)

Metabolic adaptations induced by 24 and 48 hours of fasting were investigated in male and female insectivorous bats (Molossus molossus Pallas, 1766). For this purpose, plasma glucose, non esterified fatty acids (NEFA), glycogen, protein and lipids concentrations in liver and muscles were obtained. Data presented here demonstrate that fed bats showed plasma glucose levels similar to those reported for other mammal species. In response to fasting, glycemia was decreased only in 48 hours fasted females. Plasma NEFA levels were similar in both sexes, and did not exhibit any changes during fasting. Considering the data from energy reserve variations, fed females presented an increased content of liver glycogen as well as higher breast muscle protein and limbs lipids concentrations, compared to fed males. In response to fasting, liver and muscle glycogen levels remained unchanged. Considering protein and lipid reserves, only females showed decreased values following fasting, as seen in breast, limbs and carcass lipids and breast muscle protein reserves, but still fail to keep glucose homeostasis after 48 hours without food. Taken together, our data suggest that the energy metabolism of insectivorous bats may vary according to sexual differences, a pattern that might be associated to different reproduction investments and costs between genders