Central vs. peripheral metabolic control of estrous cycles in Syrian hamsters. I. Lipoprivation

1997 ◽  
Vol 272 (1) ◽  
pp. R400-R405 ◽  
Author(s):  
J. E. Schneider ◽  
A. J. Hall ◽  
G. N. Wade
Keyword(s):  
Fatty Acid ◽  
Metabolic Control ◽  
Metabolic Energy ◽  
Acid Oxidation ◽  
Inhibitory Effects ◽  
Critical Signal ◽  
Estrous Cycles ◽  
Syrian Hamsters ◽  
Sham Surgery ◽  
Circulating Levels

Metabolic energy availability has profound effects on reproduction in a wide variety of species. We have been studying the effects of fasting on estrous cycles in Syrian hamsters as a model system for metabolic control of reproduction. In previous experiments, a 48-h period of fasting inhibited estrous cycles in lean, but not fat, hamsters. In fat hamsters the effects of fasting may have been offset by the presence of high circulating levels of free fatty acids mobilized from lipids in adipose tissue. Consistent with this idea fat hamsters treated with the inhibitor of fatty acid oxidation methyl palmoxirate (MP) showed fasting-induced anestrus. Experiment 1 was designed to examine whether vagally transmitted signals are critical for the inhibitory effects of fasting and MP treatment. Lean or fat hamsters that had received bilateral subdiaphragmatic vagotomy or sham surgery were fasted and treated with MP or vehicle. In vagotomized and sham-operated hamsters, estrous cycles were inhibited in lean fasted hamsters and in fat fasted hamsters treated with MP, but not in fat fasted hamsters treated with vehicle. Thus the results of experiment 1 indicated that vagally transmitted signals about peripheral fatty acid availability are not critical for the effects of these particular metabolic challenges on estrous cycles in Syrian hamsters. In experiment 2, hamsters without food were allowed to ingest pure glucose or fructose solutions or vegetable shortening. One-half of each group was treated with an inhibitor of glucose utilization, 2-deoxy-D-glucose (2-DG), or vehicle. If ingestion of fructose or shortening, but not glucose, had protected hamsters from 2-DG-induced anestrus, this might have indicated that peripheral fuel availability is critical for anestrus. On the contrary, 2-DG treatment induced anestrus regardless of the type of fuel ingested. Neither experiment yielded results that implicated changes in peripheral fuel availability as a critical signal in metabolic control of estrous cycles.

Metabolic influences on satiety in rats receiving parenteral nutrition

1994 ◽  
Vol 266 (2) ◽  
pp. R381-R386 ◽  
Author(s):  
J. L. Beverly ◽  
M. M. Meguid ◽  
Z. J. Yang ◽  
M. X. Yue ◽  
B. L. Fetterman
Keyword(s):  
Fatty Acid ◽  
Food Intake ◽  
Parenteral Nutrition ◽  
Metabolic Energy ◽  
Acid Oxidation ◽  
Relative Importance ◽  
Phase 2 ◽  
Light Phase ◽  
Single Intraperitoneal Injection ◽  
And Control

Food intake is reduced during parenteral nutrition (PN) proportionally to the amount of calories or composition of the solution infused. The relative importance of infused glucose and lipid, 50 and 30% of PN kilocalories, respectively, in reducing food intake during PN was examined. Glycolysis, fatty acid oxidation, or both were acutely disrupted with 2-deoxy-D-glucose (2-DG) and mercaptoacetate (MA). Rats receiving intravenous infusions of saline or a PN solution providing 100% of total daily calories (PN-100) received a single intraperitoneal injection of saline, 2-DG, and/or MA during the early light phase. 2-DG (1.4 or 2.2 mmol/kg) did not initiate feeding in PN-100 rats, although hyperglycemia was evident in all rats 1 h after 2-DG. Food intake of PN-100 rats after MA (0.4 mmol/kg) was approximately 50% that of control rats. When 2-DG (1.4 mmol/kg) and MA (0.4 mmol/kg) were administered concomitantly, PN-100 and control rats consumed the same amount of food. During PN-100, rats appeared to be more sensitive to losing metabolic energy derived from lipid than from glucose.

Effects of the fructose analog, 2,5-anhydro-D-mannitol, on food intake and estrous cyclicity in Syrian hamsters

1997 ◽  
Vol 272 (3) ◽  
pp. R935-R939
Author(s):  
J. E. Schneider
Keyword(s):  
Food Intake ◽  
Plasma Glucose ◽  
Acid Oxidation ◽  
Estrous Cycles ◽  
Syrian Hamsters ◽  
Glucose Levels ◽  
Fuel Metabolism ◽  
Increase Food Intake ◽  
Estrous Cyclicity ◽  
Estrous Cycling

Hyperphagia and anovulation are both triggered by prior food deprivation or other treatments that decrease intracellular availability of metabolic fuels in most species studied. Syrian hamsters fail to show compensatory hyperphagia, but do show anestrus in response to these energetic challenges. In the present experiments, we examined food intake, plasma glucose levels, and estrous cyclicity in Syrian hamsters in response to 2,5-anhydro-D-mannitol (2,5-AM), a fructose analog that is thought to trigger eating in rats by depleting intracellular levels of ATP. In experiment 1, female estrous cycling hamsters were treated with 100, 200, 400, or 800 mg/kg 2,5-AM or the vehicle by intraperitoneal injection. Food intake was measured 1, 2, 4, 8, and 24 h after treatment. There were no statistically significant increases in food intake in response to any dose of 2,5-AM. In experiment 2, blood samples were drawn at 0, 1, 3, 5, 7, and 25 h after hamsters were treated with 0 or 400 mg/kg 2,5-AM. 2,5-AM treatment resulted in a mild but significant decrease in plasma glucose levels similar to those seen in 2,5-AM-treated rats, suggesting that 2,5-AM has similar effects on fuel metabolism in rats and hamsters. In experiment 3, hamsters received 2,5-AM, 2,5-AM plus the fatty acid oxidation inhibitor methyl palmoxirate, or vehicle every 6 h over the first 48 h of the estrous cycle and were tested for indexes of estrous cyclicity at the end of the cycle. All hamsters showed normal estrous cycles, regardless of treatment. If 2,5-AM has similar metabolic consequences in rats and hamsters, the present results suggest that decreased intracellular levels of ATP and mild hypoglycemia do not increase food intake or inhibit estrous cyclicity in Syrian hamsters.

STUDIES OF FATTY ACID OXIDATION: 4. THE EFFECTS OF FATTY ACIDS ON THE OXIDATION OF OTHER METABOLITES

1956 ◽  
Vol 34 (6) ◽  
pp. 1211-1225 ◽  
Author(s):  
P. G. Scholefield
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Respiratory Activity ◽  
Tricarboxylic Acid Cycle ◽  
Rat Kidney ◽  
Brain Mitochondria ◽  
Acid Oxidation ◽  
Inhibitory Effects ◽  
Kidney Mitochondria ◽  
Low Concentrations

Fatty acids inhibit the oxidation of pyruvate by rat-kidney mitochondria but the extent of inhibition depends upon the nature and amount of agent added to stimulate the oxidation. The longer chain fatty acids are more effective inhibitors and, in general, the even-numbered fatty acids show greater inhibitory effects than the adjacent odd-numbered fatty acids. Under conditions where 2, 4-dinitrophenol (DNOP) and the fatty acids separately have little effect on the respiratory activity of rat-kidney mitochondria with pyruvate as substrate, the addition of both fatty acid and DNOP results in an extensive inhibition. At low concentrations the fatty acids are oxidized by rat-kidney mitochondria but at concentrations of 10−3 M and higher they inhibit their own oxidation, the oxidation of pyruvate, and those of the acids of the tricarboxylic acid cycle. The oxidation of pyruvate by rat-brain mitochondria is insensitive to decanoate but both the fumarate- and DNOP-stimulated oxidations of pyruvate are sensitive to the presence of decanoate. In contrast, Nembutal inhibits both the oxidation of pyruvate alone and the fumarate-stimulated oxidation of pyruvate. Possible mechanisms for the observed inhibitory effects of fatty acids are discussed.

INTERACTION OF DAILY INJECTIONS AND SUBCUTANEOUS RESERVOIRS OF MELATONIN ON THE REPRODUCTIVE PHYSIOLOGY OF FEMALE SYRIAN HAMSTERS

1979 ◽  
Vol 91 (1) ◽  
pp. 59-69 ◽  
Author(s):  
C. Trakulrungsi ◽  
R. J. Reiter ◽  
W. K. Trakulrungsi ◽  
M. K. Vaughan ◽  
P. J. Waring-Ellis
Keyword(s):  
Luteinizing Hormone ◽  
Untreated Control ◽  
Light Period ◽  
Reproductive Physiology ◽  
Pituitary Hormone ◽  
Inhibitory Effects ◽  
Syrian Hamsters ◽  
First Report ◽  
Treatment Procedures ◽  
Circulating Levels

ABSTRACT This study investigated the ability of continuously available melatonin (from sc melatonin-beeswax pellets that were implanted bi-weekly) in overcoming the antigonadotrophic action of single daily melatonin (25 μg) injections given late in the light period to female Syrian hamsters kept in light:dark cycles of 14:10. The melatonin-beeswax pellets contained either 1, 50, 500 μg, 1 or 10 mg melatonin and 25 mg beeswax. Daily melatonin injections into hamsters implanted with beeswax only caused vaginal acyclicity in 60 % of the animals within 6 weeks. After 10 weeks of treatment, uterine weights and pituitary levels of immunoreactive prolactin were still greatly depressed. Beeswax pellets containing either 500 μg, 1 or 10 mg melatonin overcame the inhibitory effects of daily melatonin injections. Thus, the vaginal cycles and pituitary hormone levels of these animals were indistinguishable from those of untreated control animals. Beeswax pellets containing either 1 or 50 μg melatonin were incapable of counteracting the antigonadotrophic effects of daily injections of melatonin. This is the first report that continuously available melatonin can negate the effects of daily injections of melatonin in female hamsters. When measured after 10 weeks, none of the treatment procedures significantly influenced circulating levels of luteinizing hormone or prolactin.

Role of fatty acid oxidation in food intake and hunger motivation in Syrian hamsters

1988 ◽  
Vol 43 (5) ◽  
pp. 617-623 ◽  
Author(s):  
Jill E. Schneider ◽  
Sandra J. Lazzarini ◽  
Mark I. Friedman ◽  
George N. Wade
Keyword(s):  
Fatty Acid ◽  
Food Intake ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Syrian Hamsters ◽  
Hunger Motivation

Insulin-induced anestrus in Syrian hamsters

1991 ◽  
Vol 260 (1) ◽  
pp. R148-R152 ◽  
Author(s):  
G. N. Wade ◽  
J. E. Schneider ◽  
M. I. Friedman
Keyword(s):  
Food Intake ◽  
Body Fat ◽  
Significant Inhibition ◽  
Acid Oxidation ◽  
Estrous Cycles ◽  
Syrian Hamsters ◽  
Metabolic Fuel ◽  
Energy Demands ◽  
Estrous Cyclicity ◽  
Ad Libitum

In Syrian hamsters, reproduction is sensitive to the availability of metabolic fuels. Estrous cycles can be interrupted by brief periods of food deprivation, by pharmacological inhibition of glycolysis and fatty acid oxidation, or by increasing energy demands for thermoregulation. We predicted that manipulations that divert an excessive portion of the metabolic fuel supply into storage also should inhibit reproduction. Redirection of metabolic fuels from oxidation to storage was accomplished by treatment with protamine zinc insulin suspension (PZI). Syrian hamsters treated with PZI and fed ad libitum increased their food intake by approximately equal to 40% and body fat stores, but there was no effect on estrous cycles. When PZI-treated hamsters were limited to approximately equal to 110% of their preinjection food intake, they still fattened, and there was a significant inhibition of estrous cyclicity. Thus, in the absence of overeating, PZI-enhanced energy storage may lead to a shortage of oxidizable metabolic fuels with the result that reproduction is inhibited in favor of processes essential for survival (e.g., cellular maintenance, thermoregulation). It is unlikely that insulin-induced anestrus is due to actions of PZI unrelated to metabolic fuel partitioning, because the hormone had no effects on estrous cyclicity in ad libitum-fed hamsters. These findings are inconsistent with the hypothesis that nutritional infertility is due to the failure to maintain a minimum body fat content and raise the possibility that the infertility associated with some types of obesity could be due in part to a disorder of macronutrient partitioning.

scholarly journals The SGLT2 inhibitor canagliflozin suppresses lipid synthesis and interleukin-1 beta in ApoE deficient mice

2020 ◽  
Vol 477 (12) ◽  
pp. 2347-2361
Author(s):  
Emily A. Day ◽  
Rebecca J. Ford ◽  
Jessie H. Lu ◽  
Rachel Lu ◽  
Lucie Lundenberg ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Blood Glucose ◽  
Energy Expenditure ◽  
Fatty Acid Oxidation ◽  
Liver Lipid ◽  
Sglt2 Inhibitor ◽  
Lipid Synthesis ◽  
Metabolic Energy ◽  
Metabolic Effects ◽  
Acid Oxidation

Sodium-glucose cotransporter 2 inhibitors such as canagliflozin lower blood glucose and reduce cardiovascular events in people with type 2 diabetes through mechanisms that are not fully understood. Canagliflozin has been shown to increase the activity of the AMP-activated protein kinase (AMPK), a metabolic energy sensor important for increasing fatty acid oxidation and energy expenditure and suppressing lipogenesis and inflammation, but whether AMPK activation is important for mediating some of the beneficial metabolic effects of canagliflozin has not been determined. We, therefore, evaluated the effects of canagliflozin in female ApoE−/− and ApoE−/−AMPK β1−/− mice fed a western diet. Canagliflozin increased fatty acid oxidation and energy expenditure and lowered adiposity, blood glucose and the respiratory exchange ratio independently of AMPK β1. Canagliflozin also suppressed liver lipid synthesis and the expression of ATP-citrate lyase, acetyl-CoA carboxylase and sterol response element-binding protein 1c independently of AMPK β1. Canagliflozin lowered circulating IL-1β and studies in bone marrow-derived macrophages indicated that in contrast with the metabolic adaptations, this effect required AMPK β1. Canagliflozin had no effect on the size of atherosclerotic plaques in either ApoE−/− and ApoE−/−AMPK β1−/− mice. Future studies investigating whether reductions in liver lipid synthesis and macrophage IL-1β are important for the cardioprotective effects of canagliflozin warrant further investigation.

Energy balance and brown adipose tissue thermogenesis during pregnancy in Syrian hamsters

1986 ◽  
Vol 250 (5) ◽  
pp. R845-R850 ◽  
Author(s):  
G. N. Wade ◽  
G. Jennings ◽  
P. Trayhurn
Keyword(s):  
Adipose Tissue ◽  
Energy Balance ◽  
Food Intake ◽  
Brown Adipose Tissue ◽  
Interscapular Brown Adipose Tissue ◽  
Estrous Cycles ◽  
Syrian Hamsters ◽  
Brown Adipose ◽  
Brown Adipose Tissue Thermogenesis ◽  
Circulating Levels

Energy balance and brown adipose tissue thermogenesis were examined during pregnancy in Syrian hamsters (Mesocricetus auratus). Neither estrous cycles nor pregnancy had any effect on food intake, but both were accompanied by significant changes in body weight. Despite their substantial weight gains (attributable to growth of fetuses and placentas), pregnant hamsters actually lost a mean of 48 kJ in carcass energy, whereas unmated controls gained 98 kJ over the same 15 days. During pregnancy hamsters exhibited an increase in protein deposition (almost entirely in the fetuses and placentas), but they lost nearly 40% of their body lipid. An apparent increase in energy expenditure occurred despite a highly significant decrease in brown adipose tissue thermogenesis during pregnancy. By day 15 of pregnancy (within 13 h of expected parturition) there were substantial decreases in interscapular brown adipose tissue weight (-59%), protein content (-54%), and cytochrome-c oxidase activity (-69%). These changes in brown adipose tissue were evident by day 4 of pregnancy and persisted through lactation. It is suggested that this suppression of brown adipose tissue function is due to increased circulating levels of prolactin and subsequently to the nutritional stress of conceptus growth in the absence of an increase in food intake.

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