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PubMed1980

Glucagon kinetics in fasting: physiological elevations in serum 3,5,3'-triiodothyronine increase the metabolic clearance rate of glucagon.

We have attempted to determine if the elevated plasma glucagon concentration and delayed MCR of glucagon (MCRg) observed during caloric restriction are related to the decreased serum T3 that also occurs during fasting. Twelve obese subjects received a 3-h iv glucagon infusion during a 4-day fed period (1000 kCal/day) and again on approximately the third fasting day. Five patients fasted without receiving exogenous T3 (control group), whereas seven subjects fasted but also received 5 micrograms T3 orally every 4 h (T3 group) to maintain approximately the same serum T3 levels in the fed and fasting periods. Glucagon production rates (GPR) were derived by multiplying the MCRg by the respective basal plasma glucogon concentrations. In the control group, the MCRg was 442 +/- 55 ml/m2 . min in the postabsorptive state and decreased to 312 +/- 49 ml/m2 . min (P < 0.025) during fasting, whereas in the T3-treated group, the postabsorptive MCRg was 304 +/- 22 ml/m2 . min and increased during fasting to 417 +/- 47 ml/m2 . min (P < 0.025). The GPRs in the control group were statistically unaltered between the fed (27.7 +/- 3.0 ng/m2 . min) and fasted (22.9 +/- 1.8 ng/m2 . min) intervals, but GPR increased from 37.9 +/- 6.1 ng/m2 . min during fasting to 49.2 +/- 9.1 ng/m2 . min when T3 was administered (5 micrograms every 4 h). The net plasma glucose increment in response to glucagon decreased from 18 mg/dl (fed) to 5 mg/dl (fast) in the control patients and from 10 mg/dl (fed) to 7 mg/dl (fast) in the T3-treated subjects. In the T3-treated patients, serum T3 averaged 124 ng/dl during both feeding and fasting, and rT3 was 55 +/- 6 ng/dl during feeding and 49 +/- 5 ng/dl during fasting. In summary, the results from this study indicate that during fasting 1) slight physiological alterations in serum T3 influence the MCRg, and 2) T3 increases the GPR and blocks the customary fasting-induced rise in rT3. Conceivably, decreased T3 is an early event in the fasting state which serves to decrease the MCRg, a process which subsequently regulates glucose homeostasis.

Adult↗
PubMed2006

Decreased insulin response in dairy cows following a four-day fast to induce hepatic lipidosis.

Negative energy balance has been implicated in the development of fatty liver, insulin resistance, and impaired health in dairy cows. A 4-d fasting model previously was reported to increase liver triglycerides more than 2.5-fold. The purpose of the present study was to evaluate insulin response in this fasting model. Nonlactating, nonpregnant Holstein cows were fasted for 4 d (6 cows) or fed continuously as control cows (4 cows). Samples were collected 5 d before fasting, during fasting, and immediately after the 4-d fast, 8 d after the fast, and 16 d after the fast. Fasted cows had greater liver triglyceride content (49.4 vs. 16.2 mg/g, wet-weight basis) at the end of the fasting period compared with control cows. Fasted cows also had increased plasma nonesterified fatty acid (NEFA) concentrations (1.24 vs. 0.21 mmol/L) and increased plasma beta-hydroxybutyrate (BHBA) concentrations at the end of the fasting period. Liver triglyceride, plasma NEFA, and plasma BHBA in fasted cows returned to prefasting concentrations by the end of the experiment. Plasma glucose concentrations were not affected by fasting. Plasma insulin concentrations were decreased (6.3 vs. 14.1 microU/mL) and insulin-stimulated blood glucose reduction was decreased (24.9 vs. 48.6%) in the fasted cows compared with control cows at the end of the fast, indicating reduced insulin response. Insulin response was negatively correlated with plasma NEFA and liver triglycerides. Decreased insulin response may be an important complication of negative energy balance and hepatic lipidosis.

3-Hydroxybutyric Acid↗
PubMed2006

Influence of short-term fasting during the luteal phase of the estrous cycle on ovarian follicular development during the ensuing proestrus of ewes.

Short-term fasting of mature ewes during diestrus results in increased serum concentrations of progesterone and a delayed pre-ovulatory surge release of LH. To determine if these changes in reproductive hormones influence subsequent follicular development, mature ewes observed in estrus were assigned randomly to control (n=10) or fasted (n=15) groups. Control ewes had ad libitum access to feed, whereas fasted ewes were not fed from day 7 through 11 of their estrous cycle. Daily blood samples were collected from control and fasted ewes throughout the fasting period. Fasting increased (P<0.001) serum concentrations of progesterone (4.4 ng/mL versus 2.7 ng/mL [+/-0.3]). On day 12, all ewes were treated with 10mg of PGF(2alpha) and fasted ewes were returned to ad libitum feed. Ovaries were collected from ewes (n=5 each group) at 0 and 72 h following PGF(2alpha) in control and 0, 72 and 96 h in fasted ewes. Ovaries were weighed and small (< or =2mm), medium (3-4mm), and large (> or =5mm) follicles were enumerated. Total numbers of follicles were less (P<0.001) in fasted than fed ewes (14.6 versus 30.2 [+/-2.2]) at 0 h, but did not differ (P=0.9) when numbers of follicles were compared at similar times before the anticipated LH surge (i.e., at 72 h versus 96 h in control and fasted ewes, respectively). Within follicular size class, numbers of small and medium follicles were decreased (P=0.04) at 0 h in fasted ewes. Numbers of large follicles did not differ (P=1.0) between groups. Although numbers of small and medium ovarian follicles in fasted ewes recovered by 96 h to values comparable to fed ewes at 72 h following PGF(2alpha), serum concentrations of estradiol 17beta (P=0.08) and FSH (P=0.06) tended to be decreased in fasted ewes before the anticipated surge release of LH. Pituitary content of LH and FSH also tended to be lower (P< or =0.09) at 96 h in fasted ewes than at 72 h in control ewes, but did not differ (P> or =0.4) at hour 0 following PGF(2alpha). Hypothalamic and stalk median eminence contents of GnRH were not influenced (P> or =0.2) by fasting at any time period. Fasting during the luteal phase perturbs gonadotropin secretion and may influence fertility by causing a delay in ovarian follicle development.

Animals↗
PubMed2004

Fast food consumption of U.S. adults: impact on energy and nutrient intakes and overweight status.

OBJECTIVE: To compare the diet quality and overweight status of free-living adults, ages 20 years and older, grouped based on their fast food intake status. METHODS: USDA's 1994 to 1996 Continuing Survey of Food Intakes by Individuals (CSFII 1994-1996) data was used. Three separate analyses were conducted: (1) effect of fast food on diet quality of males and females based on day-one data, (2) comparison of dietary and overweight status of adults who ate fast food on one- two- or none of survey days and (3) within-person analysis comparing energy and macronutrient intakes of adults who ate fast food on one of the two survey days. SUDAAN software package was used in pair-wise mean comparisons and regression analyses (alpha = 0.05). RESULTS: At least one in four adults reported eating fast food. The diet of males and females who consumed fast food was high in energy and energy density. Fast food provided more than one-third of the day's energy, total fat and saturated fat; and was high in energy density. Negligible amounts of milk and fruits, but substantially large amounts of non-diet carbonated soft drinks were reported consumed at fast food places. After controlling for age, gender, socio-economic and demographic factors, energy and energy density increased and micronutrient density decreased with frequency of fast food consumption. Adults who reported eating fast food on at least one survey day had higher mean body mass index values than those who did not eat fast food on both survey days. A small, but significant, positive association was seen between fast food consumption and overweight status. Within-person comparisons showed that energy intakes were higher on a fast food day than on a non-fast food day. CONCLUSION: Fast food consumption was associated with a diet high in energy and energy density and low in essential micronutrient density. Frequent fast food consumption may contribute to weight gain.

Adult↗
PubMed2006

Perceptions of the application of fast-track surgical principles by general surgeons.

INTRODUCTION: Fast-track surgery is a novel approach which uses a multimodal package of changes to traditional surgical care to reduce the stress response evoked by surgery allowing for enhanced recovery times. The depth of understanding and application of fast-track principles to general surgical practice by consultant surgeons is unknown. MATERIALS AND METHODS: 'Core management features' central to published fast-track general surgical studies were identified following a comprehensive Medline literature search. The knowledge and application of these features were examined in a postal questionnaire sent to 116 general surgeons in a single region. RESULTS: Of respondents, 31% indicated they were currently using fast-track surgery (the 'fast-trackers'). The number of fast-track compliant responses was calculated for each consultant (range, 1-12 of 14). Mean scores for 'fast-trackers' of 8.45 (+/- 2.188) and 'non-fast-trackers' of 6.16 (+/- 2.352) showed no significant differences (P > 0.6). The 'fast-trackers' median estimated length of stay (LOS) was 5 days (inter-quartile range [IQR], 4-7) which was significantly lower than the 7 day (IQR 6-8) LOS estimates given by the 'non-fast-trackers' (P < 0.01). CONCLUSIONS: Despite estimating reduced LOS, no significant difference in total fast-track compliant responses was found between the 'fast-tracker' and 'non-fast-tracker' groups. The 'fast-trackers' estimated LOS of 5 days is 2.5 times the 2 day LOS reported in the published fast-track studies. A significant gap exists between the perception and realisation of fast-track methodology amongst general surgeons.

Analgesia↗
PubMed2000

Evaluation of bone contusions with fat-saturated fast spin-echo proton-density magnetic resonance imaging.

OBJECTIVE: To evaluate the efficacy of fast spin-echo proton-density magnetic resonance imaging (MRI) with fat saturation sequences in the evaluation of bone contusions at the knee. METHODS: Analysis of 46 consecutive knee MRI examinations performed on patients referred from a sports medicine clinic after knee trauma. All examinations included coronal fast spin-echo proton-density fat saturation, fast spin-echo proton-density and fast spin-echo T2-weighted sequences. All 3 coronal sequences were blindly reviewed independently of each other by 3 experienced musculoskeletal radiologists to identify and grade bone contusions. RESULTS: Thirty-five bone contusions were identified in 24 patients. All bone contusions were identified on fast spin-echo proton-density fat saturation sequences, which was significantly greater than the percentage identified on either fast spin-echo T2-weighted sequences (21/35, 60%, p < 0.001) or fast spin-echo proton-density sequences (10/35, 29%, p < 0.001). Fourteen (40%) of the contusions were identified only on the fast spin-echo proton-density fat saturation sequences. The average grade of contusion for all 35 examinations was also significantly higher on the fast spin-echo proton-density fat saturation sequences than on the fast spin-echo proton-density and fast spin-echo T2-weighted sequences (p < 0.05). CONCLUSION: Fast spin-echo proton-density fat saturation sequences are more sensitive in the detection of bone contusions than fast spin-echo proton-density and fast spin-echo T2-weighted sequences. Assessment of other structures in the knee with fast spin-echo proton-density fat saturation MRI provides good spatial resolution and adequate T2-weighted information. It may have advantages over the more heavily T2-weighted fast spin-echo T2 fat saturation and inversion recovery sequences.

Adult↗
PubMed2003

Preoperative fasting for adults to prevent perioperative complications.

BACKGROUND: Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents during surgery, thus reducing the risk of regurgitation/aspiration. Recent guidelines have recommended a shift in fasting policy from the standard 'nil by mouth from midnight' approach to more relaxed policies which permit a period of restricted fluid intake up to a few hours before surgery. The evidence underpinning these guidelines however, was scattered across a range of journals, in a variety of languages, used a variety of outcome measures and methodologies to evaluate fasting regimens that differed in duration and the type and volume of intake permitted during a restricted fasting period. Practice has been slow to change. OBJECTIVES: To systematically review the effect of different preoperative fasting regimens (duration, type and volume of permitted intake) on perioperative complications and patient wellbeing (including aspiration, regurgitation and related morbidity, thirst, hunger, pain, nausea, vomiting, anxiety) in different adult populations. SEARCH STRATEGY: Electronic databases, conference proceedings and reference lists from relevant articles were searched for studies of preoperative fasting in August 2003 and experts in the area were consulted. SELECTION CRITERIA: Randomised controlled trials which compared the effect on postoperative complications of different preoperative fasting regimens on adults were included. DATA COLLECTION AND ANALYSIS: Details of the eligible studies were independently extracted by two reviewers and where relevant information was unavailable from the text attempts were made to contact the authors. MAIN RESULTS: Thirty eight randomised controlled comparisons (made within 22 trials) were identified. Most were based on 'healthy' adult participants who were not considered to be at increased risk of regurgitation or aspiration during anaesthesia. Few trials reported the incidence of aspiration/regurgitation or related morbidity but relied on indirect measures of patient safety i.e. intra-operative gastric volume and pH. There was no evidence that the volume or pH of participants' gastric contents differed significantly depending on whether the groups were permitted a shortened preoperative fluid fast or continued a standard fast. Fluids evaluated included water, coffee, fruit juice, clear fluids and other drinks (e.g. isotonic drink, carbohydrate drink). Participants given a drink of water preoperatively were found to have a significantly lower volume of gastric contents than the groups that followed a standard fasting regimen. This difference was modest and clinically insignificant. There was no indication that the volume of fluid permitted during the preoperative period (i.e. low or high) resulted in a difference in outcomes from those participants that followed a standard fast. Few trials specifically investigated the preoperative fasting regimen for patient populations considered to be at increased risk during anaesthesia of regurgitation/aspiration and related morbidity. REVIEWER'S CONCLUSIONS: There was no evidence to suggest a shortened fluid fast results in an increased risk of aspiration, regurgitation or related morbidity compared with the standard 'nil by mouth from midnight' fasting policy. Permitting patients to drink water preoperatively resulted in significantly lower gastric volumes. Clinicians should be encouraged to appraise this evidence for themselves and when necessary adjust any remaining standard fasting policies (nil-by-mouth from midnight) for patients that are not considered 'at-risk' during anaesthesia.

Adult↗
PubMed2006

A comparison of glycemic effects of glimepiride, repaglinide, and insulin glargine in type 2 diabetes mellitus during Ramadan fasting.

Although diabetics may be exempted from Ramadan fasting, many patients still insist on this worship. Aim of the present study is to compare the effects of glimepiride, repaglinide, and insulin glargine in type 2 diabetics during Ramadan fasting on the glucose metabolism. Patients, who were willing to fast, were treated with glimepiride (n=21), repaglinide (n=18), and insulin glargine (n=10). Sixteen non-fasting control type 2 diabetics matched for age, sex, and body mass index were also included. Fasting blood glucose (FBG), post-prandial blood glucose (PBG), HbA1c, and fructosamine as well as lipid metabolism were evaluated in pre-Ramadan, post-Ramadan, and 1-month post-Ramadan time points. There was no significant change from pre-Ramadan in FBG, PBG, and HbA1c variables in fasting diabetics at post-Ramadan and 1-month post-Ramadan. However, PBG was found higher in non-fasting control diabetics at post-Ramadan and 1-month post-Ramadan (p<0.05 and p<0.001, respectively). In fructosamine levels, a significant increase was noted both in fasting group and non-fasting group at 1-month post-Ramadan (p<0.01 for all). However, no significant difference was found in the comparison of the changes in fructosamine levels between fasting group and non-fasting group. Risk of hypoglycemia did not significantly differ between fasting and non-fasting diabetics. There was no significant difference between three drug therapies regarding glucose metabolism and rate of hypoglycemia. No adverse effects on plasma lipids were noted in fasting diabetics. In this fasting sample of patients with type 2 diabetes, glimepiride, repaglinide, and insulin glargine did not produce significant changes in glucose and lipid parameters.

Adult↗
PubMed1976

Blood metabolites and glucose metabolism in the fed and fasted chicken.

The effect of fasting on blood metabolites and glucose metabolism in the chicken was studied. Parameters of glucose metabolism were estimated in vivo using a single injection of [2-3H]-glucose or [6-3H]-glucose in combination with [U-14C]-glucose. Plasma glucose, blood lactate and blood acetoacetate levels were not significantly changed in chickens fasted for 72 hours. Pyruvate levels in chickens fasted for 24 hours were higher than those observed in blood from birds fasted 0 to 72 hours. Further, the lactate to pyruvate ratio was lower in chickens fasted for 24 to 72 hours than in fed chickens. Fasting chickens for 24 or 72 hours resulted in three- to fivefold increase in blood beta-hydroxybutyrate levels and a significant increase in beta-hydroxybutyrate to acetoacetate ratio. Plasma levels of alanine and serine were increased after a 24 hour fast but were not further changed when fasting was extended to 72 hours. Plasma aspartate and glutamate levels were not significantly changed in chickens fasted for 24 hours but were markedly decreased in chickens fasted for 72 hours. Plasma levels of glycine were significantly lower in chickens fasted 24 or 72 hours than in fed birds. Glucose replacement rates estimated with [2-3H]-glucose in chickens fasted 0,24 and 72 hours were 14.3, 9.1 and 9.4 mg glucose/minute/kg body weight, respectively. Fasting up to 72 hours did not influence the total body glucose mass in the chickens. The degree of glucose-carbon recycling in 24-hour fasted chickens estimated by using [2-3H]- and [U-14C]-glucose or [6-3H]- and [U-14C]-glucose averaged 42% to 52% and 27% to 30%, respectively. These observations indicate that rate of glucose utilization in the chicken is rapid and that substantial recycling of glucose carbon occurs in fasted chickens.

Amino Acids↗
PubMed1993

Lack of a role of the hypothalamic-pituitary-adrenal axis in the fasting-induced suppression of luteinizing hormone secretion in adult male rhesus monkeys (Macaca mulatta).

One day of fasting suppresses pulsatile LH secretion in adult male rhesus monkeys. In the present study, we determined whether the hypothalamic-pituitary-adrenal (HPA) axis is activated by 1 day of fasting, and if there is any evidence that an increase in the activity of the HPA axis causes the fasting-induced suppression of LH secretion. In the first experiment, blood samples were collected at 15-min intervals from nine monkeys for 24 h (0800-0800 h) on a day of normal feeding (animals fed a single daily meal at 1100 h) and again on a day of fasting (animals not fed their daily meal) to assess changes in LH and cortisol secretion caused by fasting. LH secretion on the day of fasting (4.44 +/- 0.85 LH pulses/24 h) was significantly suppressed compared to that on a day of normal feeding (7.67 +/- 0.74 LH pulses/24 h; P < or = 0.01), and there was a slight, but significant, rise in plasma cortisol levels from 17.86 +/- 2.29 to 25.14 +/- 2.74 micrograms/dl (measured at 1400 h) that was evident soon after the meal was missed on the day of fasting. However, within individual animals, there was no correlation between the rise in plasma cortisol levels and the decrease in LH secretion observed on a day of fasting (r = 0.37). A second experiment was performed to determine whether the small rise in plasma cortisol levels that occurred on a day of fasting was capable of suppressing LH secretion. Hydrocortisone acetate (HCA) was administered to six normally fed monkeys, creating a rise in plasma cortisol levels somewhat greater than the levels occurring during fasting (HCA treatment, 44.51 +/- 1.48 micrograms/dl; fasting, 18.42 +/- 1.62 micrograms/dl; measured between 1100-2400 h). However, HCA treatment had no effect on LH secretion, suggesting that the rise in cortisol that occurs during fasting does not cause LH suppression. To determine whether increased secretion of the neuropeptides that provide the central drive to the adrenal axis causes the suppression of LH secretion during fasting, six animals were treated with dexamethasone (0.25 mg/kg, im) on a day of fasting to inhibit the activity of the glucocorticoid-sensitive CRH neurons of the adrenal axis via increased glucocorticoid negative feedback. Dexamethasone treatment caused a marked suppression of circulating cortisol levels (to approximately 1.0 micrograms/dl), but it did not prevent the fasting-induced suppression of pulsatile LH secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗
PubMed1998

Reduction of hepatic insulin-like growth factor I (IGF-I) messenger ribonucleic acid (mRNA) during fasting is associated with diminished splicing of IGF-I pre-mRNA and decreased stability of cytoplasmic IGF-I mRNA.

The mechanisms by which fasting decreases liver insulin-like growth factor I (IGF-I) messenger RNA (mRNA) abundance have not been defined completely. In the present study, we have examined the effects of fasting in rats on hepatic IGF-I gene transcription, IGF-I pre-mRNA splicing, and cytoplasmic IGF-I mRNA stability. Using the in vitro nuclear run-on transcription technique, we observed that fasting did not change IGF-I gene transcription activity [76 +/- 32 densitometric units (DU) for fasted vs. 58 +/- 23 DU for control-fed rats; P = 0.1], whereas IGF-binding protein-1 (IGFBP-1) gene transcription, a positive control, was increased more than 2-fold (729 +/- 157 DU for fasted vs. 261 +/- 56 DU for control-fed rats; P < 0.05). This implies that fasting-induced reduction of liver IGF-I mRNA is due to events other than a decreased rate of IGF-I gene transcription. By measuring nonspliced (pre-mRNA) and spliced IGF-I transcripts in liver nuclear RNA using ribonuclease protection assays, we found that IGF-I pre-mRNA was increased in fasted rats (measured as the percentage of beta-actin: 34.0 +/- 5.5% for fasted vs. 8.1 +/- 3.8% for control-fed rats; P < 0.01), whereas spliced IGF-I transcript remained unchanged (measured as the percentage of beta-actin: 60.9 +/- 9.2% for fasted vs. 79.0 +/- 6.2% for control-fed rats; P = 0.75). We then compared this pattern of splicing to IGF-I pre-mRNA splicing in hypophysectomized rats subjected to GH stimulation and to IGFBP-1 pre-mRNA splicing in the same fasting experiment. One hour after GH injection, we observed a coordinate increase in both nonspliced and spliced IGF-I transcripts in liver nuclei of hypophysectomized rats. Fasting increased both IGFBP-1 pre-mRNA and spliced transcript. Taken together, these results indicate that the increase in IGF-I pre-mRNA in liver nuclei during fasting is caused by delayed pre-mRNA splicing, rather than increased IGF-I gene transcription. To examine the possible effect of fasting on hepatic IGF-I mRNA stability, we used an in vitro model of nutrient deprivation (fewer amino acids in culture medium) of rat hepatocyte primary culture. Each of the three major IGF-I mRNA species exhibited a shortened half-life in the amino acid-deprived media. The 7.5-kb IGF-I mRNA, however, was degraded faster than the two smaller IGF-I mRNA species. This may indicate that fasting decreases the stability of liver IGF-I mRNA in vivo. In summary, these results suggest that fasting regulates hepatic IGF-I gene expression mainly at the posttranscriptional level by delaying IGF-I pre-mRNA splicing, which attenuates mature IGF-I mRNA generation, and by accelerating the rate of degradation of IGF-I mRNA in cytoplasm.

Actins↗
PubMed1998

Fasting-induced increase in type II iodothyronine deiodinase activity and messenger ribonucleic acid levels is not reversed by thyroxine in the rat hypothalamus.

The importance of local formation of T3 in the feedback effect of the thyroid gland on hypothalamic TRH-producing cells has been established. Primary failure of the thyroid gland results in a fall in circulating T4 and T3 levels, leading to an elevation in the production and release of TRH in the hypothalamic paraventricular nucleus. In contrast, during short term fasting, declining plasma levels of thyroid hormones coincide with suppressed TRH production and release. In the brain, the prevalent enzyme that converts T4 to T3 is type II iodothyronine deiodinase (DII). The present study was undertaken to determine whether a differential hypothalamic expression of type II deiodinase may exist in fasted rats and in animals that are hypothyroid due to the failure of the thyroid gland. Using in situ hybridization, we assessed type II deiodinase messenger RNA (mRNA) levels in the hypothalamus of rats that were control euthyroid, hyperthyroid (T4), hypothyroid induced by propylthiouracil (PTU), and fasted. A group of fasted rats also received exogenous T4. DII mRNA was detected around the third ventricle, including the ependymal layer and adjacent periventricular regions as well as in the arcuate nucleus and the external layer of the median eminence. Quantitative in situ hybridization analysis demonstrated that PTU treatment and short term fasting resulted in significant elevations in DII messenger levels compared with those in euthyroid controls. Three weeks of PTU administration induced a consistent decline in circulating T3 and undetectable T4 levels, whereas 3 days of fasting resulted in only a 50% fall in the concentration of serum thyroid hormones. Interestingly, however, the expression of the DII mRNA was more than 2-fold higher in fasted animals compared with the values in PTU-treated rats. Furthermore, although T4 administration repressed DII mRNA expression in euthyroid animals, the same treatment had no effect on the fasting-induced elevations of DII message. To assess whether DII enzymatic activity is also affected during food deprivation, hypothalami were dissected out, and DII activity was measured in control euthyroid, fasted, and fasted plus T4-treated rats. To determine whether comparable changes in plasma thyroid hormone levels induced by fasting and PTU treatment could have affected DII enzymatic activity in a similar manner, animals were injected ip with PTU for 5 days to decrease plasma thyroid hormones to levels similar to those caused by fasting. DII enzymatic assay showed a significant increase in DII activity in fasted and fasted plus T4-treated animals compared with those in euthyroid controls and PTU-treated rats. No significant changes were found in PTU-treated rats compared with euthyroid animals. These data indicate that during short term fasting, a signal of nonthyroid origin underlies the robust elevation of DII production and activity in the hypothalamus. Thus, we propose that during the initial phase of food deprivation, an increased negative thyroid feedback exists on the hypothalamus due to locally formed T3. This local hyperthyroidism may, in turn, induce the suppression of TRH under these conditions.

Animals↗
PubMed1989

Effect of triiodothyronine on leucine kinetics, metabolic rate, glucose concentration and insulin secretion rate during two weeks of fasting in obese women.

We investigated the effect of the fasting-induced reduction in triiodothyronine (T3) on metabolic changes that occur during fasting. In five obese women (T3 group) the serum T3 level during a 2200 kcal/day diet was 3.34 +/- 0.23 nmol/l while taking 20 micrograms T3 8-hourly, 0.65 +/- 0.04 after one week of fasting while not taking T3, and 2.9 +/- 0.3 after a second week of fasting while taking T3 20 micrograms 8-hourly. In three other obese women (control group) who did not take T3, T3 concentrations decreased during fasting and remained low at the end of both the first and second week of fasting. In the T3 group, resting metabolic rate (RMR) (O2 ml/min) decreased 11.7 percent at the end of one week of fasting, but then increased by 5.3 percent at the end of the second week of fasting, whereas in the control group RMR decreased by 13.1 percent after one week of fasting and a further fall of 13.3 percent occurred by the end of the second week of fasting. The RMR at the end of 2 weeks of fasting of the control group was significantly lower (P less than 0.05) than predicted using the equation of Dore, whereas that of the T3 group was as predicted using the same equation. The changes in leucine flux, leucine oxidation and non-oxidative portion of leucine flux were not different during fasting between the T3 group and the control group. Plasma concentrations of glucose, insulin and C-peptide increased from the end of one week of fasting to the end of 2 weeks of fasting in the T3 group, whereas they decreased in the control group. It is concluded that the changes in T3 concentration during fasting affected RMR, glucose metabolism and insulin secretion but failed to influence leucine metabolism.

Adult↗
PubMed1996

[Relationship between fasting glycemia, serum peptide C, insulin, growth hormone and plasma glucagon in acromegaly].

UNLABELLED: The aim of this study was to investigate interrelations among fasting glycaemia, serum C-peptide, insulin, growth hormone and plasma glucagon concentration in people with acromegaly. 22 patients with active acromegaly, 11 women and 11 men (group A) and 19 healthy people (group K) participated in the study. The oral glucose tolerance test was carried out in all participants. Blood glucose, serum C-peptide, growth hormone and plasma glucagon concentration was measured. 13 patients with acromegaly had normal glucose tolerance (group AT) and 9 had impaired glucose tolerance (group AN). Statistical analysis was performed using Student's test and regression analysis. The comparison of patients from group A and K showed, that serum growth hormone, C-peptide, insulin, blood glucose concentration in fasting state was higher in acromegaly. There were no differences in fasting plasma glucagon concentration between both groups. Fasting glycaemia was similar in patients AT and controls, but there were also higher fasting serum C-peptide and insulin concentrations in the AT group. Fasting blood glucose, serum C-peptide and insulin concentration was higher in AN group than in controls. There were no significant differences in the above parameters between AT and AN group. Analysis of regression showed the negative correlation of fasting serum growth hormone and blood glucose concentration in the group A and AT. However there was no correlation between other parameters and fasting glycaemia, in particular between fasting glycaemia and insulin concentration. Fasting glycaemia positively correlated with fasting serum insulin concentration in healthy men. The comparison of glycaemia and fasting concentration of some hormones in patients with acromegaly regarding their glucose tolerance, did not answer the question, which hormonal abnormality is the most specific for disturbances of carbohydrate metabolism in acromegaly. Therefore groups of patients with markedly high of hormones in fasting state concentrations were distinguished. There was no difference in fasting glycaemia in this people compared to patients with normal or moderately elevated concentrations of hormones studied. CONCLUSIONS: There is higher fasting glycaemia in patients with acromegaly compared to healthy men. Among them one can see subjects with normal glucose tolerance that is accompanied with high serum C-peptide and insulin concentration. Disturbances of glucose-insulin interregulation occur in these people.

Acromegaly↗
PubMed1997

[Medical aspects of fasting].

Fasting (arabic-savm) was proclaimed through islam, and thus it is an obligation for Holly Prophet Muhammad s.a.v.s.-Peace be to Him-in the second year after Hijra (in 624 after Milad-born of Isa a.s.). There is a month of fasting-Ramadan-each lunar (hijra) year. So, it was 1415th fasting this year. Former Prophets have brought obligative messages on fasting to their people; so there are also certain forms of fasting with other religions i.e. with Catholics, Jews, Orthodox. These kinds of fasting above differ from muslim fasting, but they also appear obligative. All revelations have brought fasting as obligative. From medical point of view, fasting has two basical components: psychical and physical. Psychical sphere correlate closely with its fundamental ideological message. Allah dz.s. says in Quran: "... Fasting is obligative for you, as it was obligative to your precedents, as to avoid sins; during very few days (II, II, 183 & 184)." Will strength, control of passions, effort and self-discipline makes a pure faithfull person, who purify its mind and body through fasting. Thinking about The Creator is more intensive, character is more solid; and spirit and will get stronger. We will mention the hadith saying: "Essaihune humus saimun!" That means: "Travellers at the Earth are fasters (of my ummet)." The commentary of this hadith, in the Collection of 1001 hadiths (Bin bir hadis), number 485, says: "There are no travelling dervishs or monks in islam; thus there is no such a kind of relligousity in islam. In stead, it is changed by fasting and constant attending of mosque. That was proclaimed as obligation, although there were few cases of travelling in the name of relligousity, like travelling dervishs and sheichs." In this paper, the author discusses medical aspects of fasting and its positive characteristics in the respect of healthy life style and prevention of many sicks. The author mentions positive influence of fasting to certain system and organs of human body. According the author, o basic messages of fasting could be a Roman poet's saying:" Mens sana in corpora sanum."

Fasting↗
PubMed1982

Resetting fast phases of head and eye and their linkage in the frog.

(1) Compensatory slow phase movements were evoked by optokinetic, vestibular and combined optokinetic and vestibular stimulation. Superimposed fast phases resetting the position of the head (in space) and of the eye (in head) were recorded with a magnetic field search coil in unrestrained and head fixed frogs, respectively. (2) Head fast phases recorded during optokinetic stimulation covaried in the frequency of their occurrence with slow phase head velocity. Their amplitude was large (average 18.9 +/- 8.9 degrees), maximal velocity increased with amplitude by 6.6 degrees/s/deg, and duration (average 230 +/- 33 ms) was almost independent on amplitude. (3) Ocular fast phases rarely occurred during sinusoidal stimulation and neither optokinetic after nystagmus nor postrotatory nystagmus were observed. Fast phases, evoked by constant velocity optokinetic or acceleratory stimuli, consisted of two components: a primary resetting fast phase and a smaller fast movement in the opposite direction. The primary fast phase had a small amplitude (average 2.2 +/- 1.3 degrees). In different stimulus conditions fast phase parameters were very similar. Maximal velocity increased by 6.5 degrees/s/deg. Duration (average 165 +/- 23.4 ms) was variable. (4) During ocular fast phases the vestibulo-collic and the optokinetic-collic reflexes were suppressed. The slow phase head velocity either became zero or a small head fast phase in the direction of the ocular fast phase occurred. Fast phase head movements were accompanied by an ocular fast phase or by a retraction of one or both eyes, depending on the amplitude of the head fast phase. At the end of a head fast phase eye position was always recentered.

Animals↗
PubMed2000

Differential effect of fasting on IGF-BPs in serum of young and adult rats and its implication to impaired skin GAG content.

During fasting or aging of animals there is a decreased content of skin glycosaminoglycans (GAGs). It has been found that the skin of adult rats contains about 60% of GAGs found in the skin of young animals. Fasting of both groups of animals (young and adult) resulted in decrease of GAG content. However, GAG content in the skin of fasted young rats decreased by 30% and in fasted adult rats by 15% only, compared to fed animals, respectively. The mechanism for the phenomena is not known. We considered insulin-like growth factor-I (IGF-I) as a potential candidate involved in regulation of GAG biosynthesis in both experimental models of animals. Adult rat sera were found to contain about 75% of IGF-I recovered from young rat sera. Fasting of both groups of animals resulted in dramatic decrease in serum IGF-I levels to about 50% of initial values. Since IGF-I activity and IGF-I serum half-life depends on the level of specific IGF-binding proteins (IGFBPs) we determined (i) relationship between main groups of IGFBPs, namely high molecular weight binding proteins (HMWBPs) and low molecular weight binding proteins (LMWBPs) and (ii) the amounts of IGF-I bound to respective proteins in the sera of all experimental animals. Control young rat serum was found to contain about 90% of HMWBPs and about 10% of LMWBPs as determined by ligand binding assay. In contrast, control adult rat serum contained about 60% of HMWBPs and about 40% of LMWBPs. Fasting of both groups of animals resulted in significant increase in serum levels of LMWBPs. Control young rat serum was found to contain about 8% IGF-I bound to LMWBPs while serum of control adult rats contained 18% IGF-I bound to these proteins. In sera of fasted young animals however, about 75% of the bound IGF-I was recovered from LMWBPs (about 60% of total serum IGF-I) while in sera of fasted adult animals only about 56% of the bound IGF-I was recovered from LMWBPs (about 50% of total serum IGF-I). Evidence was provided that during fasting of both groups of animals there is a significant decrease in serum BP-3 and dramatic increase in serum BP-1 concentrations, compared to respective controls. However, the concentration of BP-1 in serum of fasted young rats was increased by about 60 fold while in serum of fasted adult rats only by about 10 fold, compared to respective control animals. Negative correlation between skin GAG content and LMWBPs derived IGF-I during fasting of young (r = -0.943, p < 0.001) and adult ( r = -0.571, p < 0.01) rats was found. The data presented suggest that the effects of aging and fasting on decreased skin GAG content may be due to induction of LMWBPs that are known to (i) inhibit IGF-I dependent function and (ii) increase clearance of IGF-I from circulation. However, the effects of fasting are distinct in respect to young and adult rats suggesting that mechanisms involved in regulation of IGF-I bioactivity during aging are more complex that during fasting.

Age Factors↗
PubMed1994

Fast spin-echo MR in the detection of vertebral metastases: comparison of three sequences.

PURPOSE: To examine the relative capabilities for the detection of vertebral metastases of three available fast spin-echo sequences: T1-weighted fast spin-echo, short tau inversion recovery (STIR) fast spin-echo, and T2-weighted fast spin-echo sequences with chemical shift selective saturation pulse fat suppression. METHODS: Fourteen patients were evaluated prospectively over a 2-month period with T1-weighted fast spin-echo (four echo train, four acquisitions, 1 min 59 sec-2 min 37 sec). STIR fast spin-echo (16 echo train, four acquisitions, 2 min 30 sec-3 min 19 sec), and T2-weighted fast spin-echo (16 echo train, 4 acquisitions, 2 min 27 sec-3 min 16 sec). For all three pulse sequences, measurements were obtained of the signal intensities of normal marrow, abnormal marrow, fat, and noise posterior to the spine. Contrast-to-noise ratios were calculated for metastases in each case. Lesions were evaluated by three observers and rated for size, location, and conspicuity. RESULTS: Signal intensities of fat, normal marrow, and noise were highest for T1-weighted fast spin-echo sequences. STIR fast spin-echo and fat-suppressed T2-weighted fast spin-echo had approximately similar fat-suppression capabilities. Though contrast-to-noise ratios were highest overall for STIR fast spin-echo, the finding was not statistically significant and lesion conspicuity was deemed better with fat-suppressed T2-weighted fast spin-echo and T1-weighted fast spin-echo images. Discrete lesions were well identified on all three pulse sequences. CONCLUSION: Fast spin-echo sequences appear promising for the detection of vertebral metastases. Further work should be directed toward comparison with conventional spin-echo to determine whether fast spin-echo may replace conventional spin-echo sequences for evaluation of vertebral metastases.

Adult↗