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PubMedDate not supplied

Fasting decreases the content of D-chiroinositol in human skeletal muscle.

Two classes of inositol phosphoglycans have been implicated as second messengers of insulin, one that activates pyruvate dehydrogenase and contains D-chiroinositol, and one that inhibits cyclic AMP-dependent protein kinase and contains myoinositol. We examined the effects of a 3-day fast on muscle contents of inositols in healthy humans. An oral glucose tolerance test was performed and a biopsy was obtained from the quadriceps femoris muscle after an overnight fast and after a 72-hour fast. The 72-hour fast significantly increased plasma glucose (1.5- to 2-fold) and insulin (2- to 4-fold) after glucose ingestion versus the values after the overnight fast, indicating the manifestation of peripheral insulin resistance. The 72-hour fast resulted in an approximately 20% decrease in the muscle content of D-chiroinositol (P < 0.02), but no change in the myoinositol content. These data demonstrate that fasting specifically decreases the muscle content of D-chiroinositol in human muscle and this may contribute to the finding that insulin-mediated activation of pyruvate dehydrogenase is attenuated after short-term starvation.

Adult↗
PubMedDate not supplied

Anatomical and histological changes in the alimentary tract of migrating blackcaps (Sylvia atricapilla): a comparison among fed, fasted, food-restricted, and refed birds.

During northward migration, blackcaps that arrive to refuel at stopover sites in Israel's Negev Desert have reduced masses of organs that are important in food digestion and assimilation. We tested several predictions from the general hypothesis that smaller organs of digestion (small intestine and pancreas) and nutrient assimilation (liver) bring about a lower capacity to consume food and that the organs must be restored before blackcaps can feed and digest at a high rate. We used a fasting protocol to create a group of blackcaps with reduced intestine and liver mass (reduced by 45% and 36%, respectively) compared with controls fed ad lib. Because most of the small intestine's biochemical digestive capacity reside in enterocytes found on villi, we predicted and found that reduced intestinal mass in fasted blackcaps related mainly to changes in enterocytes rather than other cells and tissues such as nonabsorptive crypt cells or underlying muscle. Because migrating blackcaps that stop over to feed begin to increase in body mass only 2 d after arrival, we predicted and found a similar recovery period in blackcaps that were first fasted but then refed--the organ mass, structure, function, and ability to consume food was restored after 2 d of feeding. Another group of food-restricted blackcaps (fed at one-third ad lib. level) lost similar amounts of body mass as fasted blackcaps but had much greater capacity to consume food than fasted blackcaps, and so we predicted that they would exhibit little or no reduction in alimentary organs relative to controls fed ad lib. A surprising result was that, as in fasted blackcaps, in food-restricted blackcaps, the decreases in masses of small intestine, liver, and pancreas were proportionally greater than the decreases in body mass or in masses of nonalimentary organs (heart, pectoralis). Food restriction, like fasting, caused a decrease in amount of intestinal mucosa and an alteration in the phenotype of enterocytes. These results are thus not consistent with the general hypothesis, and although they can be rationalized by assuming that blackcaps fed ad lib. have excess digestive capacity, it may also be that the physiological process or processes limiting very high feeding rate lie elsewhere than in the digestive system.

Adaptation, Physiological↗
PubMed2006

Angiotensin II and aldosterone increase with fasting in breeding adult male northern elephant seals (Mirounga angustirostris).

The renin-angiotensin-aldosterone system (RAAS) appears to contribute significantly to osmoregulation of fasting northern elephant seal (Mirounga angustirostris) pups; however, RAAS has not been characterized in fasting adult seals. Therefore, this study examined the contribution of RAAS to water turnover rates in fasting adult male northern elephant seals. Blood samples were obtained twice during their breeding fast at an interval of 6.5 wk, and water efflux rate was estimated by isotopic dilution during the same period. Serum electrolytes (Na+, K+, Cl-) and osmolality were unaltered between the two sampling periods, indicating ionic and osmotic homeostasis during the fast. Despite the lack of an increase in vasopressin, serum angiotensin II and aldosterone were increased and were significantly and positively correlated. Changes in aldosterone concentration and water efflux rate were significantly and negatively correlated, suggesting that the greater the increase in aldosterone, the smaller the loss of water. Adult male seals maintain ionic and osmotic homeostasis similar to that of fasting weaned pups, and this homeostasis appears to be mediated, at least in part, by RAAS, which probably contributes to increased water retention as well. The hormonal mechanisms by which northern elephant seals maintain water and electrolyte balance during fasting conditions appear to be similar regardless of age.

Aldosterone↗
PubMed1997

Effects of fasting and glucose infusion on basal and overnight leptin concentrations in normal-weight women.

The plasma concentration of leptin is reduced in association with chronic energy restriction and weight loss in humans, but little is known about the acute effects of fasting and glucose infusion on leptin. In this study, plasma leptin, insulin, glucose, and fatty acid concentrations were measured daily in 14 healthy, normal-weight, female volunteers aged 24 +/- 4 y with a body mass index (kg/m2) of 24.2 +/- 3.6 during a 4-d fast. The mean plasma leptin concentration decreased by 54 +/- 8% with fasting (P = 0.0006, ANOVA). In a stepwise-regression model, the change in leptin concentration with fasting correlated most significantly with the change in insulin (R2 = 0.48, P = 0.0057) and to a lesser extent with the change in body fat by bioimpedance analysis (R2 = 0.19, P = 0.03). Plasma leptin concentrations measured every 20 min from 2000 to 0800 on the fourth night of the fast did not show a time-dependent rise. A continuous intravenous infusion of 5% glucose providing 1414 +/- 323 kJ/d (338 +/- 78 kcal/d) was begun after 4 d of fasting in seven subjects who continued to fast for an additional 6 d. Within 24 h of the glucose infusion, leptin concentrations increased significantly by 80 +/- 52% (P < 0.05). These data show the sensitivity of plasma leptin concentrations to small changes in energy supply and suggest a basic role of substrate metabolism in the short-term regulation of leptin.

Adult↗
PubMed2003

Blunted lipolytic response to fasting in abdominally obese women: evidence for involvement of hyposomatotropism.

BACKGROUND: Abdominal obesity is associated with a blunted lipolytic response to fasting that may contribute to the preservation of adipose tissue mass. OBJECTIVE: To further explore the pathophysiology of blunted lipolysis during fasting in obesity, we simultaneously measured lipolysis and distinct neuroendocrine regulatory hormones in abdominally obese and normal-weight (NW) women. DESIGN: Eight abdominally obese [x +/- SD body mass index (BMI; in kg/m(2)): 32.1 +/- 2.6] and 6 NW (BMI: 22.7 +/- 1.5) women were studied during the last 8 h of a 20-h fast. The glycerol appearance rate and the serum and plasma concentrations of insulin, leptin, cortisol, and growth hormone were measured regularly. RESULTS: At 13 h of fasting, the mean (+/-SD) glycerol appearance rate corrected for fat mass was greater in NW women than in obese women (7.2 +/- 1.0 and 5.1 +/- 0.6 micro mol.kg(-1).min(-1), respectively; P = 0.001). After a 20-h fast, lipolysis increased to 8.9 +/- 1.5 mmol.kg(-1).min(-1) in NW women (23%), whereas it did not change significantly in obese women (-2%). Fasting decreased insulin concentrations by approximately 30% in both groups, but it did not induce significant changes in leptin concentrations. Mean cortisol concentrations and urinary catecholamine excretion were comparable in both groups. However, mean plasma growth hormone concentrations were higher in NW women than in obese women (1.81 +/- 0.98 compared with 0.74 +/- 0.52 mU/L; P = 0.046). The relative change in lipolysis tended to correlate with mean plasma growth hormone concentrations (r = 0.515, P = 0.059). CONCLUSION: Abdominal obesity-associated hyposomatotropism may be involved in the blunted increase in lipolysis during fasting.

Abdomen↗
PubMed1986

Effects of fasting on ketone body concentrations in healthy men of different ages.

This work was performed to assess age effects on fasting-induced hyperketonemia and to determine if measurement of cerebral glucose utilization by positron emission tomography after 6 to 8 hr of fasting is associated with hyperketonemia that could influence cerebral glucose metabolism. Acetoacetate and 3-hydroxybutyrate were assayed in venous blood from healthy men of various ages, subjected to an 18-hr fast. At 18 hr of fasting but not at 14 hr or earlier, 3-hydroxybutyrate concentrations were correlated significantly with age; concentrations of acetoacetate and 3-hydroxybutyrate were significantly higher than at earlier times in the fast, p less than or equal to .05, with elevations of 82% and 214% over baseline, respectively. Acetoacetate and 3-hydroxybutyrate concentrations were higher on the day when cerebral glucose utilization was determined than after a comparable fast at another time. The observed level of hyperketonemia, however, would not substantially influence cerebral glucose metabolism. The findings indicate that aging is associated with increased susceptibility to fasting-induced hyperketonemia.

3-Hydroxybutyric Acid↗
PubMed1977

Fasting-induced hypoglycemia in experimentally malnourished rats.

The ability to withstand a fasting stress as related to glucose homeostasis was studied in malnourished rats. Young male Wistar rats were fed a low-protein (D), or a low-protein, low-energy diet (M) containing, respectively, 4% protein with 70% carbohydrate (D) and 4% protein and 45% carbohydrate (M). They were compared with rats fed a control diet with 18% protein and 70% carbohydrate (C). All diets contained 8% fat. After consuming the respective diets for 4 weeks, the rats were either killed or fasted for 24 or 48 hours. Hypoglycemia developed in the malnourished rats upon fasting, but not in those receiving a complete diet. Malnourished rats had a higher blood glycine level after 4 weeks of dietary treatment. There was a marked decrease of circulating alanine and glutamate-glutamine after 48 hours of fasting in all rats. There were no differences in lysine, histidine, glycine and serine-valine. Protein malnutrition produced an increase in brain lysine, gamma-aminobutyric acid, glycine and alanine, and of glycine and alanine in liver. In contrast, D and M rats showed a depletion in muscle lysine, alanine, serine-valine and glutamate-glutamine. The fasting stress produced no changes in brain or muscle glycogen. However, liver glycogen of rats fed the D and M diets was below that of rats fed the C diet for 4 weeks. In addition, after 48 hours of fasting the C rats mobilized more exhaustively their glycogen stores that the M rats. These data suggest that in chronic malnutrition, rats may maintain their glucose homeostasis by mobilization of muscular gluconeogenic amino acids through proteolysis or de novo synthesis. Rats which were fed protein and protein-energy-deficient diets lacked adequate liver glycogen stores and their overall gluconeogenic capacity was exceeded during fasting with resultant hypoglycemia.

Adaptation, Physiological↗
PubMed1977

Influence of prolonged fasting in the dog on glucose turnover and blood metabolites.

Glucose turnover and blood metabolites were measured in eight adult female beagles in the fed state, at 1 day of fasting, and at 7, 14, and 21 days of fasting. Glucose utilization decreased significantly from 1 to 7 days of fasting, but remained constant from 7 to 21 days, while blood ketones and plasma free fatty acids rose significantly during the same period. Plasma alanine, serine, and glycine fell with fasting, with the greatest decrease in alanine levels occurring between 7 to 14 days. Plasma branched chain amino acids rose significantly with fasting. It was concluded that the shifts in plasma metabolites and decreased glucose utilization could be indicative of decreased energy demands of the fasting dogs and/or a shift in substrate utilization with progressive fasting.

Amino Acids↗
PubMed1978

Hepatic synthesis and urinary excretion of alpha2u-globulin by male rats: diurnal rhythm and response to fasting and refeeding.

The urine of sexually mature male rats contains a protein of hepatic origin, alpha2u-globulin, not found in the urine of immature or female rats; output of this protein is greatly reduced by fasting. We have examined the effects of feeding and of fasting for various lengths of time on urinary output and hepatic synthesis of alpha2u-globulin. Rats eating ad libitum showed diurnal rhythms of urinary alpha2u-globulin excretion reaching maxima between 2000 and 0800 hours, thus coinciding with the daily feeding period of the rat. Fasting for 12 hours extinguished this diurnal rhythm. When fasting was prolonged up to 36 hours, urinary excretion of alpha2u-globulin was reduced to very low levels. Hepatic synthesis of alpha2u-globulin under these nutritional conditions was investigated by incubating liver polyribosomes with [3H]leucine and a preparation of soluble enzymes for protein synthesis and separating the labeled alpha2u-globulin peptides by immunoprecipitation followed by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. By this technique, it was shown that only membrane-bound ribosomes in the livers of mature male rats make this protein. Semi-quantitative measurement suggested that the proportion of liver polyribosomes synthesizing alpha2u-globulin was unchanged after 12 hours of fasting, but was reduced after 24 and 36 hours of fasting. It is proposed that the diurnal rhythm in alpha2u-globulin output in the urine represents translational control of its synthesis in the liver, whereas the more extensive reduction with prolonged fasting is partly due to a selective reduction in transcription of the messenger RNA for this protein.

Alpha-Globulins↗
PubMed1979

The effect of long-term fasting on the branched chain acylcarnitines and branched chain carnitine acyltransferases.

The effect of fasting for 8 days on the levels of carnitine acyltransferases in heart, liver, liver mitochondria, skeletal muscle, skeletal muscle mitochondria, kidney, and testes in young adult male rats was determined. The specific activities of acetyl-, octanyl-, isobutyryl-, and isovaleryl-carnitine acyltransferase in mitochondria isolated from the livers of fasted animals were significantly higher than the levels of the transferases isolated from livers of fed animals. Similar results were obtained with the 500 x g supernatant fluids from liver. In contrast, the specific activities of carnitine acyltransferases of 500 x g supernatant fractions isolated from heart, skeletal muscle, kidney, and testes were the same for fed as fasted animals. The total carnitine content of liver, muscle, heart, and kidney was less in animals fasted for 8 days than in fed animals, but the amount/g of organ was higher in the animals fasted for 8 days. The amount of specific short-chain acylcarnitines in liver, muscle, and heart was determined for both fed and fasted animals. The amount of isobutyrylcarnitine and isovalerylcarnitine increased significantly in muscle from fasted animals. These data are consistent with the previous suggestion that carnitine may have a role in the metabolism of the branched-chain amino acids.

Acyltransferases↗
PubMed1979

Effect of adrenalectomy on liver lipid content of fasted rats.

The interrelationship between thyroid and adrenal hormones in the regulation of lipid accumulation of the liver during fasting was examined with the use of intact, sham operated and adrenalectomized (ADX) rats previously fed a high carbohydrate diet. Adrenalectomy depressed the lipid accumulation of the liver induced by fasting. This was restored by cortisone administration, but not by epinephrine injection. Lipid content of the liver during fasting tended to be decreased in rats made hyperthyroid by intraperitoneal injection of thyroxine compared to euthyroid-fasted rats. In rats made hypothyroid by oral administration of propylthiouracil, liver lipid content during fasting was significantly higher than that of euthyroid-fasted rats. These responses of liver lipid to thyroid activity were minimized in ADX rats. Cortisone tended to restore completely the liver response to thyroid activity. The maximal response of liver lipid to cortisone was obtained in hypothyroid-ADX rats. The injection of epinephrine alone did not cause any significant change in liver lipid content of ADX rats regardless of the thyroid status. These findings suggest that glucocorticoid must be present for thyroid function to exert its effect on the lipid accumulation of the liver induced by fasting.

Adrenalectomy↗
PubMed1981

Effects of fasting during pregnancy on maternal and fetal weight and body composition in well-nourished and undernourished rats.

The effect of a 2-day fast on fetal and maternal weight and composition was determined in ad libitum-fed and food-restricted pregnant and non-pregnant rats. Fasting between days 17 and 19 of gestation resulted in a greater loss of net maternal body weight in ad libitum-fed pregnant than in nonpregnant rats, and also a greater loss of body fat. In contrast, food-restricted pregnant rats, also fasted from day 17 to day 19 of gestation, maintained their net body weight and body fat during the fast as did nonpregnant rats fasted for the same length of time. Fetal weight was not significantly reduced by fasting in the ad libitum-fed rats but was reduced by 25% in the previously food-restricted rats. The results demonstrate that prior maternal nutritional status strongly influences the effects of fasting on the fetus and that maternal nutrient stores are not mobilized for fetal utilization even when fetal growth is markedly impaired.

Animals↗
PubMed1981

Tissue glutathione as a cyst(e)ine reservoir during fasting and refeeding of rats.

Previous reports suggest that liver glutathione serves as a cyst(e)ine reservoir in both starved rats and rats fed a cyst(e)ine-deficient diet. We investigated whether glutathione concentrations in other tissues also decrease and whether component amino acids of glutathione increase under such conditions. Tissue glutathione and free amino acid concentrations were measured in six groups of growing rats (120-150 g; four animals/group) during fasting and refeeding regimens. All animals were fed a rat stock diet ad libitum for 5 days. Two groups were than fasted for 24 or 48 hours, respectively. Other groups were fasted for 48 hours and then refed for 10, 24 or 48 hours respectively the stock diet. Significant changes (P less than or equal to 0.05) in liver and intestine glutathione concentrations were noted with 24 and 48-hour fasting, and a 24-hour refeeding was necessary to return concentrations to prefasting values. Muscle glutathione concentrations decreased slightly with fasting, but remained low with refeeding. Erythrocyte glutathione concentrations were independent of dietary treatment. Liver cysteine and glycine concentrations increased after 24 hours' fasting, but glutamate levels were not affected. The data indicate that liver and intestine glutathione serve as cyst(e)ine reservoirs during fasting. Since erythrocyte and muscle glutathione levels did not decrease, levels in these tissues cannot be used to measure cyst(e)ine status in premature infants fed parenterally.

Animals↗
PubMed1986

Insulin and glucose responses to glucose injection in fed and fasted obese and lean sheep.

Effects of short-term fasting on the insulin and glucose responses to injected glucose were determined in obese (n = 6) and lean (n = 6) Dorset ewes that were fed a maintenance level of energy intake. Sheep were assigned by Latin-square design to be fasted for 0 (fed), 12 or 24 h before glucose (350 mg/kg) was injected via jugular cannula at 2000 h with at least 7 d between successive tests. Insulin and glucose were quantified in jugular plasma samples. Pretreatment concentrations of insulin were affected (P less than 0.005) only by body condition with higher mean values in obese (23.5 +/- 3.3 microU/ml) than in lean (9.4 +/- 1.0 microU/ml) sheep. Pretreatment concentrations of glucose (53.6 +/- 1.8 mg/dl) were unaffected by body condition and fasting. The insulin responses to glucose, whether determined as absolute levels or response areas above base-line levels, were greater (P less than 0.005) in obese than in lean sheep regardless of fasting period. Insulin and glucose concentrations after glucose injection in lean sheep were unaffected by fasting. In contrast, the insulin response to glucose was greater (P less than 0.005) in fed obese than 12- or 24-h fasted obese sheep while glucose levels in the fed sheep were similar to those in the fasted obese sheep. Thus, factors associated with feeding enhanced the insulin response to glucose in obese sheep. In addition, obesity in sheep was associated with insulin resistance because basal hyperinsulinemia coexisted with euglycemia and because fractional removal rates of injected glucose were similar in obese and lean sheep despite much greater concentrations of insulin in obese sheep.

Animals↗
PubMed2004

Comparison of amino acid oxidation and urea metabolism in haemodialysis patients during fasting and meal intake.

BACKGROUND: The PNA (protein equivalent of nitrogen appearance) is used to calculate protein intake from urea kinetics. One of the essential assumptions in the calculation of PNA is that urea accumulation in haemodialysis (HD) patients is equivalent to amino acid oxidation. However, urea is hydrolysed in the intestine and the resulting ammonia could be used metabolically. The magnitude and dependence on protein intake of this process are unknown in HD patients. METHODS: Seven HD patients were studied twice, 1 week apart, on a similar protocol. After an overnight fast, patients fasted in the morning and received meals in the afternoon. On one day, amino acid oxidation was measured by infusion of L-[1-(13)C]valine. Urea production, measured from the dilution of [(13)C]urea, and urea accumulation, calculated from the increase in plasma urea concentration multiplied by the urea dilution volume, were measured during the other day. PNA was calculated using standard equations. RESULTS: Amino acid oxidation and urea production were not significantly different during fasting. Urea accumulation during fasting was significantly lower than both amino acid oxidation and urea production. Urea accumulation during feeding remained significantly lower than amino acid oxidation. PNA was equal to the average of the urea accumulation values during fasting and feeding. CONCLUSION: We conclude that during fasting, urea accumulation is not associated with amino acid oxidation or urea production. During meal intake, amino acid oxidation, urea production and urea accumulation show acutely an almost identical increase. PNA represents the average of fasting and fed urea accumulation and is lower than average amino acid oxidation or urea production.

Amino Acids↗
PubMed2006

Fasting augments PCB impact on liver metabolism in anadromous arctic char.

Anadromous arctic char (Salvelinus alpinus) undertake short feeding migrations to seawater every summer and accumulate lipids, while the rest of the year is spent in fresh water where the accumulated lipid reserves are mobilized. We tested the hypothesis that winter fasting and the associated polychlorinated biphenyls' (PCBs) redistribution from lipid depots to critical tissues impair the liver metabolic capacity in these animals. Char were administered Aroclor 1254 (0, 1, 10, and 100 mg/kg body mass) orally and maintained for 4 months without feeding to mimic seasonal winter fasting, while fed groups (0 and 100 mg Aroclor 1254/kg) were maintained for comparison. A clear dose-related increase in PCB accumulation and cytochrome P4501A (CYP1A) protein content was observed in the livers of fasted fish. This PCB concentration and CYP1A response with the high dose of Aroclor were 1.5-fold and 3-fold greater in the fasted than in the fed fish, respectively. In fed fish, PCB exposure lowered liver glycogen content, whereas none of the other metabolic indicators were significantly affected. In fasted fish, PCB exposure depressed liver glycogen content and activities of glucose-6-phosphate dehydrogenase, alanine aminotransferase, lactate dehydrogenase, and phosphoenolpyruvate carboxykinase and elevated 3-hydroxyacylcoA dehydrogenase activity and glucocorticoid receptor protein expression. There were no significant impacts of PCB on heat shock protein 70 (hsp70) and hsp90 contents in either fed or fasted fish. Collectively, our study demonstrates that winter emaciation associated with the anadromous lifestyle predisposes arctic char to PCB impact on hepatic metabolism including disruption of the adaptive metabolic responses to extended fasting.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1999

Fasting augments lipid peroxidation during reperfusion after ischemia in the perfused rat liver.

OBJECTIVE: To test the hypothesis that fasting would aggravate postischemic lipid peroxidation in a perfused rat liver model. DESIGN: Prospective, randomized study in a rat perfused liver model. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Livers isolated from fed and fasted male Sprague-Dawley rats (n = 16) were exposed to 2.5 hrs of normothermic (38 degrees C) ischemia followed by 2 hrs of reperfusion. MEASUREMENTS AND MAIN RESULTS: Lipid peroxidation was measured by chemiluminescence and thiobarbituric acid reactive substances (TBARS). Injury parameters, potassium, lactate dehydrogenase efflux, and oxygen extraction were measured every 30 mins. Chemiluminescence and TBARS were greater in the fasted ischemic group during reperfusion. (fasted vs. fed: chemiluminescence, 946.8+/-205.5 [SEM] vs. 98.1+/-8.2 counts per second, p = .0004; thiobarbituric acid reactive substances, 1.11+/-0.25 vs. 0.21+/-0.032 nM/g of liver wt/min, p = .0019). Potassium efflux in the fasted group was greater than in the fed group. (1.568+/-0.082 vs. 1.28+/-0.079 microEq/g liver weight/min, p = .0184). Fasted livers extracted less oxygen after ischemia (1.94+/-0.22 vs. 1.14+/-0.46 microM/g liver wt/min, p = .0048). Lactate dehydrogenase levels showed no significant differences. CONCLUSION: Fasting augmented lipid peroxidation markedly. Nutrition may be an important mechanism that protects organs from oxidative injury.

Animals↗
PubMed1995

Fasting inhibits natriuretic peptides clearance receptor expression in rat adipose tissue.

OBJECTIVE AND DESIGN: The early phase of weight loss induced by fasting is associated with diuresis, natriuresis and reduction in blood pressure through unclear mechanisms. Atrial natriuretic peptide (ANP) is a cardiac hormone with potent natriuretic, diuretic and hypotensive effects mediated by 'biologically active' receptors (NPr-A). A second type of receptor mediates the clearance of ANP (the clearance receptor, NPr-C). Since NPr-C appears to be abundant in adipose tissue, we analysed NPr-C and NPr-A gene expression in white and brown adipose tissue (WAT and BAT) as well as in renal cortex of fasting rats. Plasma ANP, cyclic GMP and aldosterone were also measured. METHODS: Twelve male Wistar rats were deprived of food for about 50 h, and 12 other rats were fed ad libitum. Periepididymal WAT, interscapular BAT and left renal cortex were used for RNA extraction and northern blot analysis with rat NPr-C and NPr-A complementary DNA probes labelled with 32P-dCTP. Densitometric analysis of hybridization signals was corrected by beta actin expression before statistical analysis. Blood was drawn for ANP, cyclic GMP (cGMP) and aldosterone radioimmunoassays, which were also measured in a group of six rats deprived of food for 25 h. RESULTS: A dramatic decrease in NPr-C steady-state messenger RNA levels was observed both in WAT (about 3.6-fold, P < 0.001) and in BAT (about threefold, P < 0.01), but fasting did not affect the expression of NPr-A in adipose tissues. In the renal cortex NPr-C and NPr-A messenger RNA levels were unaffected by fasting. ANP and aldosterone levels were reduced after fasting whereas cyclic GMP was increased at 25 h, but the differences did not reach statistical significance. CONCLUSIONS: Fasting exerts a tissue-specific and gene-specific suppression of NPr-C gene expression in adipose tissue that appears to be accompanied by an increased biological activity of ANP. The natriuresis and diuresis and reduction of blood pressure induced by fasting might result from a reduced expression of NPr-C in adipose fat pads.

Adipose Tissue↗