Oral leptin supplementation throughout lactation in rats prevents later metabolic alterations caused by gestational calorie restriction.

OBJECTIVES: Calorie-restriction during gestation in rats has been seen to produce lasting detrimental effects in the offspring, affecting energy balance control and other related metabolic functions. Our aim was to assess whether leptin supplementation throughout lactation may prevent the dysmetabolic phenotype in adulthood associated with gestational calorie restriction. METHODS: Three groups of male Wistar rats were followed: the offspring of ad libitum fed dams (controls); the offspring of 20% calorie-restricted dams during gestation (CR); and CR rats supplemented with physiological doses of leptin throughout lactation (CR-Leptin). Pups were weaned with a standard diet (SD) until 4 months of age, and then half of the animals of each group were moved to a Western diet (WD) until 6 months of age. Body weight and food intake were recorded. Energy expenditure, locomotive activity, blood parameters, liver triglycerides (TG), and gene expression and specific proteins in liver and white adipose tissue (WAT) were measured in adulthood. RESULTS: Adult CR rats, but not CR-Leptin rats, displayed greater adiposity index and feed efficiency (both under SD) than controls, along with lower locomotive activity and energy expenditure, higher HOMA-IR index and greater circulating TG and leptin levels. CR animals also exhibited increased values of the respiratory exchange ratio and more severe signs of hepatic steatosis under WD than CR-Leptin animals. Gene expression analysis revealed that CR, but not CR-Leptin, animals displayed indicators of lower capacity for WAT expansion, along with decreased lipogenesis and lipolytic capacity under SD, and impaired lipogenic response of the liver to WD feeding, in accordance with diminished insulin sensitivity and WAT leptin signaling. CONCLUSIONS: Oral leptin supplementation in physiological doses throughout lactation in rats prevents most of the detrimental effects on energy homeostasis and metabolic alterations in adulthood caused by inadequate fetal nutrition.

Maternal consumption of a cafeteria diet during lactation in rats leads the offspring to a thin-outside-fat-inside phenotype.

BACKGROUND AND OBJECTIVE: The suckling period is a critical phase of development, in which maternal overnutrition may program the susceptibility of developing chronic diseases and disorders, such as obesity and metabolic alterations, in adult life. Here, we questioned whether the consumption of a cafeteria diet throughout lactation in rats affects the macronutrient composition of milk and whether it results in permanent metabolic effects in the offspring. METHODS: Nursing rats were fed a control diet or a cafeteria diet during lactation. Milk was obtained at different time points of lactation. Offspring (males and females) were weaned onto a control diet until the age of 6 months. Circulating parameters were measured under ad libitum feeding and under 12-h fasting conditions at weaning and at 3 and 6 months of age. An oral glucose tolerance test (OGTT) was performed at 3 and 6 months of age. RESULTS: Rats fed a cafeteria diet during lactation consumed an unbalanced diet, with lower protein and higher fat content versus controls, which was reflected in the composition of the milk. The offspring of rats fed a cafeteria diet during lactation showed lower body weight and lower lean mass, but greater fat accumulation, compared with controls. They also displayed hyperleptinaemia, altered lipid profile and impaired response to an OGTT. CONCLUSION: Maternal consumption of a cafeteria diet throughout lactation in rats produces lasting effects in the metabolic health of their offspring, which are not associated with a higher body weight but with a greater fat accumulation, similarly to the thin-outside-fat-inside phenotype.

Transcriptome analysis in blood cells from children reveals potential early biomarkers of metabolic alterations.

OBJECTIVES: The development of effective strategies to prevent childhood obesity and its comorbidities requires new, reliable early biomarkers. Here, we aimed to identify in peripheral blood cells potential transcript-based biomarkers of unhealthy metabolic profile associated to overweight/obesity in children. METHODS: We performed a whole-genome microarray analysis in blood cells to identify genes differentially expressed between overweight and normal weight children to obtain novel transcript-based biomarkers predictive of metabolic complications. RESULTS: The most significant enriched pathway of differentially expressed genes was related to oxidative phosphorylation, for which most of genes were downregulated in overweight versus normal weight children. Other genes were involved in carbohydrate metabolism/glucose homoeostasis or in lipid metabolism (for example, TCF7L2, ADRB3, LIPE, GIPR), revealing plausible mechanisms according to existing biological knowledge. A set of differentially expressed genes was identified to discriminate in overweight children those with high or low triglyceride levels. CONCLUSIONS: Functional microarray analysis has revealed a set of potential blood-cell transcript-based biomarkers that may be a useful approach for early identification of children with higher predisposition to obesity-related metabolic alterations.

Leptin intake in suckling rats restores altered T3 levels and markers of adipose tissue sympathetic drive and function caused by gestational calorie restriction.

BACKGROUND: Maternal calorie restriction during gestation in rats has been associated with altered white adipose tissue (WAT) sympathetic innervation and function in offspring. Here, we aimed to investigate whether supplementation with oral leptin (a breast milk component) throughout the lactation period may revert the aforementioned adverse programming effects. METHODS: Three groups of male and female rats were studied at the postnatal day 25: the offspring of control dams, the offspring of 20% calorie-restricted dams during pregnancy (CR) and CR rats supplemented with physiological doses of leptin throughout lactation (CR-Leptin). Tyrosine hydroxylase (TH) levels and its immunoreactive area, and mRNA expression levels of lipid metabolism-related genes and of deiodinase iodothyronine type II (Dio2) were determined in WAT. Triiodothyronine (T3) levels were determined in the blood. RESULTS: In CR males, leptin treatment restored the decreased TH levels and its immunoreactive area in WAT, and partially normalized expression levels of genes related to lipolysis and fatty acid oxidation (adipose triglyceride lipase, hormone-sensitive lipase, carnitine palmitoyltransferase 1b and peroxisome proliferator-activated receptor gamma coactivator 1-alpha). Leptin treatment also reverted the decreased T3 plasma levels and WAT lipoprotein lipase mRNA levels occurring in CR males and females, and the decreased Dio2 mRNA levels in CR females. CONCLUSIONS: Leptin supplementation throughout the lactation period reverts the malprogrammed effects on WAT structure and function induced by undernutrition during pregnancy. These findings support the relevance of the intake of leptin during lactation, bearing clear characteristics of essential nutrient, and provide a strategy to treat and/or prevent the programmed trend to obesity acquired by inadequate fetal nutrition.

Cafeteria diet overfeeding in young male rats impairs the adaptive response to fed/fasted conditions and increases adiposity independent of body weight.

OBJECTIVE: We analyzed the effects of a short exposure to a cafeteria diet during early infancy in rats on their metabolic response to fed/fasting conditions in key tissues involved in energy homeostasis. METHODS: Ten-day-old male pups were fed a control or a cafeteria diet for 12 days and then killed under ad libitum feeding conditions or 12 h fasting. The expression of key genes related to energy metabolism in liver, retroperitoneal white adipose tissue (WAT) and hypothalamus were analyzed. RESULTS: Despite no differences in body weight, cafeteria-fed animals had almost double the fat mass of control rats. They also showed higher food intake, higher leptinemia and altered hypothalamic expression of Neuropetide Y, suggesting a dysfunction in the control of food intake. Unlike controls, cafeteria-fed animals did not decrease WAT expression of Pparg, sterol regulatory element binding transcription factor 1 or Cidea under fasting conditions, and displayed lower Pnpla2 expression than controls. In liver, compared with controls, cafeteria animals presented: (i) lower expression of genes related with fatty acid uptake and lipogenesis under ad libitum-fed conditions; (ii) higher expression of fatty acid oxidation-related genes and glucokinase under fasting conditions; (iii) greater expression of leptin and insulin receptors; and higher protein levels of insulin receptor and the pAMPK/AMPK ratio. CONCLUSION: A short period of exposure to a cafeteria diet in early infancy in rat pups is enough to disturb the metabolic response to fed/fasting conditions in key tissues involved in energy homeostasis, particularly in WAT, and hence induces an exacerbated body fat accumulation and increased metabolic risk, with no apparent effects on body weight.

Moderate calorie restriction during gestation programs offspring for lower BAT thermogenic capacity driven by thyroid and sympathetic signaling.

BACKGROUND: Maternal calorie restriction during pregnancy programs offspring for later overweight and metabolic disturbances. Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis and has recently emerged as a very likely target for human obesity therapy. OBJECTIVE: Here we aimed to assess whether the detrimental effects of undernutrition during gestation could be related to impaired thermogenic capacity in BAT and to investigate the potential mechanisms involved. METHODS: Offspring of control and 20% calorie-restricted rats (days 1-12 of pregnancy) (CR) were studied at the age of 25 days. Protein levels of uncoupling protein 1 (UCP1) and tyrosine hydroxylase (TyrOH); mRNA levels of lipoprotein lipase (LPL), carnitine palmitoyltransferase 1 (CPT1) and deiodinase iodothyronine type II (DIO2) in BAT; and blood parameters including thyroid hormones, were determined. The response to 24-h cold exposure was also studied by measuring body temperature changes over time, and final BAT UCP1 levels. RESULTS: Compared with controls, CR animals displayed in BAT lower UCP1 and TyrOH protein levels and lower LPL and CPT1 mRNA levels; they also showed lower triiodothyronine (T3) plasma levels. CR males, but not females, revealed lower DIO2 mRNA levels than controls. When exposed to cold, CR rats experienced a transient decline in body temperature, but the values were reestablished after 24 h, despite having lower UCP1 levels than controls. CONCLUSIONS: These results suggest that BAT thermogenic capacity is diminished in CR animals, involving impaired BAT sympathetic innervation and thyroid hormone signaling. These alterations make animals more sensitive to cold and may contribute to long-term outcomes of gestational calorie restriction in promoting obesity and related metabolic alterations.

Impact of virologic breakthrough and HBIG regimen on hepatitis B recurrence after liver transplantation.

The availability of hepatitis B immune globulin (HBIG) and several oral antiviral therapies has reduced but not eliminated hepatitis B virus (HBV) recurrence. We aimed to determine the rate of HBV recurrence after orthotopic liver transplantation (OLT) in relation to virologic breakthrough pre-OLT and HBIG regimens post-OLT. Data from the NIH HBV-OLT database were analyzed. A total of 183 patients transplanted between 2001 and 2007 followed for a median of 42 months (range 1-81) post-OLT were studied. At transplant, 29% were hepatitis B e antigen (HBeAg) (+), 38.5% had HBV DNA > 5 log(10) copies/mL, 74% were receiving antiviral therapy. Twenty-five patients experienced virologic breakthrough before OLT. Post-OLT, 26%, 22%, 40% and 12% of patients received intravenous (IV) high-dose, IV low-dose, intramuscular low-dose and a finite duration of HBIG, respectively as maintenance prophylaxis. All but two patients also received antiviral therapy. Cumulative rates of HBV recurrence at 1 and 5 years were 3% and 9%, respectively. Multivariate analysis showed that listing HBeAg status and HBV DNA level at OLT were the only factors associated with HBV recurrence. In conclusion, low rates of HBV recurrence can be accomplished with all the HBIG regimens used when combined with antiviral therapy including patients with breakthrough pre-OLT as long as rescue therapy is administered pre- and post-OLT.

Leptin intake during the suckling period improves the metabolic response of adipose tissue to a high-fat diet.

BACKGROUND: The intake of leptin during the suckling period protects against obesity and improves insulin and central leptin sensitivity in adult rats. OBJECTIVE: We analyzed whether leptin treatment to neonates may also improve later peripheral leptin sensitivity in adipose tissue under high-fat (HF) diet conditions. DESIGN: Male rats were supplemented with a daily oral dose of leptin or the vehicle (controls) during the suckling period. After weaning, animals were fed a normal-fat or an HF diet until the age of 6 months. At this age, mRNA and protein levels of the long-form leptin receptor (OB-Rb) and the expression of other genes related with energy metabolism were measured in various adipose depots (inguinal, mesenteric and retroperitoneal). RESULTS: HF-diet feeding resulted in lower OB-Rb mRNA and protein levels in internal depots in controls but not in leptin-treated animals; these animals maintained OB-Rb mRNA and protein levels under HF-diet conditions in these depots, particularly in the mesenteric one, and this was accompanied by increased expression of genes related with energy uptake (GLUT4, CD36), fatty acid oxidation (peroxisome proliferator activated receptor-alpha (PPARalpha), CPT1, UCP3) and lipogenesis (PPARgamma, GPAT). Leptin-treatment also ameliorated HF-diet-induced hepatic fat accumulation occurring in control animals. CONCLUSION: Leptin treatment during the suckling period may improve the lasting effects of HF-diet feeding on leptin receptor abundance in the adipose tissue and increase its oxidative capacity, resulting in a better handling and partitioning of excess fuel. This, together with the described improvement of central leptin sensitivity, may explain why these animals are more protected against diet-induced obesity and its metabolic-related disorders.

Moderate caloric restriction during gestation results in lower arcuate nucleus NPY- and alphaMSH-neurons and impairs hypothalamic response to fed/fasting conditions in weaned rats.

AIM: We aimed to characterize the developmental programming effects of moderate caloric restriction during early pregnancy on factors involved in hypothalamic control of energy balance. METHODS: Twenty-five-days-old offspring Wistar rats from 20% caloric restricted dams (from 1 to 12 days of pregnancy) (CR) and from control dams were studied under fed and 12 h fasting conditions. Morphometric studies on arcuate nucleus (ARC) and determinations of circulating parameters and hypothalamic levels of neuropeptide Y (NPY), proopiomelanocortin (POMC), long-form leptin receptor (ObRb), insulin receptor (InsR) and suppressor of cytokine signalling-3 (SOCS-3) mRNA were performed. RESULTS: CR animals did not show different body weight with respect to their controls, but presented higher food intake. They exhibited lower neuropeptide Y- and alpha-melanocyte-stimulating hormone-neurons (decreases of 18 and 13% in males, and 10 and 18% in females respectively) and lower total cells (decrease of 3% in males and 18% in females) in ARC. Under fed conditions, CR animals presented lower circulating leptin and ghrelin levels (decreases of 37 and 43% in males, and 15 and 34% in females respectively); furthermore, hypothalamic POMC, NPY (only in females), ObRb and InsR mRNA levels were reduced (39, 16 and 26% in males, and 112, 33, 61 and 56% in females), and those of SOCS-3 were increased (86% in males and 74% in females). Unlike control animals, under fasting conditions, ObRb, InsR and POMC mRNA levels did not decrease in CR females, and NPY mRNA decreased instead of increase in CR males. CONCLUSIONS: Moderate caloric restriction during gestation affects offspring hypothalamic structure and function, impairing its response to fed/fasting conditions, which suggests a predisposition to insulin and leptin resistance.

Majocchi's granuloma after antithymocyte globulin therapy in a liver transplant patient.

Majocchi's granuloma (MG) is an atypical and uncommon presentation of dermatophytic infection involving the invasion of dermal and subcutaneous tissue by fungal organisms. It usually begins as a suppurative folliculitis and may culminate in the development of widespread granulomas. Immunosuppressed patients are at increased risk, especially those with T-cell deficiencies. We describe a case of inguinal MG in a liver transplant patient who had received antithymocyte globulin for acute rejection.

[Physiological mechanisms in the development of adiposity]. / Physiologische Mechanismen in der Entwicklung von Adipositas.

The phenomenon of the so-called "obesity pandemic" having arisen over the last decades has to be, in large part, attributed to changes of lifestyle and the associated changes in dietary habits and physical activity observed world-wide. The resulting interference in energy homeostasis plays a central role in the development of obesity in a large proportion of the population worldwide. In this article, current knowledge about central biological mechanisms of energy intake, energy storage, and energy expenditure is summarized. This includes, for example, the feeling of hunger/satiety, lipid turnover with the two components of lipolysis and lipogenesis, adipogenesis, as well as energy-consuming processes like (adaptive) thermogenesis, resting metabolic rate, and physical activity energy expenditure. Based on examples, the possible influence of genetic polymorphisms contributing to the development of adiposity are illustrated.

Maternal diet, rather than obesity itself, has a main influence on milk triacylglycerol profile in dietary obese rats.

Triacylglycerols (TG) in milk derive from different sources, and their composition may be influenced by both maternal diet and obesity. We used two rat models to ascertain potential changes in TG composition in milk associated to maternal intake of an obesogenic diet during lactation and to distinguish them from the effects attributable to maternal adiposity. Milk samples were obtained from dams fed a cafeteria diet during lactation (CAF) and from dams made obese by cafeteria diet feeding, with dietary normalization before gestation (PCaf). Levels of specific TG species in milk collected at different time points of lactation were determined by shotgun lipidomics. CAF and PCaf dams presented a greater adiposity than their respective controls. The principal component analysis of TG peaks showed a clear separation between milk from CAF dams and milk from control and Pcaf dams, already evident at 5 days of lactation. Milk from CAF dams was enriched with TG species with greater number of carbons and double bonds and reduced in TG with lower number of carbons. TG composition of milk from Pcaf dams was similar to controls, although specific differences were observed at day 5 of lactation. Thus, the intake of a cafeteria diet during lactation, rather than maternal adiposity, alters milk composition. This effect is avoided with dietary normalization before gestation, although the remaining fat reserves may also influence TG composition at initial stages of lactation. Therefore, normalization of maternal diet prior to pregnancy should be considered as a strategy for achieving optimal milk composition.

Liver retransplantation: a single-center outcome and financial analysis.

Retransplantation of the liver (re-OLTx) accounts for approximately 10% of all liver transplants in the United States. The decision to offer a patient a second liver transplant has significant financial, ethical, and outcome implications. This large, single-center experience describes some outcome and financial data to consider when making this decision. One thousand three liver transplants were performed in 921 patients at our center. Patients were divided into adult and pediatric groups, and further by whether they received a single transplant or more than one. Overall survival, variation in survival by timing of re-OLTx, and survival in adults with hepatitis C were investigated, as were hospital charges and cost of re-OLTx. Adults, but not children, had a significant decrement in survival following a second transplant. Second transplants more than double the cost of the initial transplant, but there is a significantly higher cost associated with early retransplantation compared to the cost associated with late retransplantation (costs of first and second transplants included in both cases). This difference is due to a longer length of stay and associated cost in the ICU. Adult patients retransplanted early have the same overall survival compared to those done late. The sample size of the adult HCV re-OLTx population was too small to reach statistical significance despite their observed poorer outcome.

TAS1R3 and UCN2 Transcript Levels in Blood Cells Are Associated With Sugary and Fatty Food Consumption in Children.

CONTEXT: New types of dietary exposure biomarkers are needed to implement effective strategies for obesity prevention in children. Of special interest are biomarkers of consumption of food rich in simple sugars and fat because their intake has been associated with obesity development. Peripheral blood cells (PBCs) represent a promising new tool for identifying novel, transcript-based biomarkers. OBJECTIVE: This study aimed to study potential associations between the transcripts of taste receptor type 1 member 3 (TAS1R3) and urocortin II (UCN2) genes in PBCs and the frequency of sugary and fatty food consumption in children. DESIGN, SETTING, AND PARTICIPANTS: Four hundred sixty-three children from the IDEFICS cohort were selected to include a similar number of boys and girls, both normal-weight and overweight, belonging to eight European countries. MAIN OUTCOME MEASURES: Anthropometric parameters (measured at baseline and in a subset of 193 children after 2 years), food consumption frequency and transcript levels of TAS1R3 and UCN2 genes in PBCs were measured. RESULTS: Children with low-frequency consumption of sugary foods displayed higher TAS1R3 expression levels with respect to those with intermediate or high frequency. In turn, children with high-frequency consumption of fatty foods showed lower UCN2 expression levels with respect to those with low or intermediate frequency. Moreover, transcripts of TAS1R3 were related with body mass index and fat-mass changes after a 2-year follow-up period, with low expression levels of this gene being related with increased fat accumulation over time. CONCLUSION: The transcripts of TAS1R3 and UCN2 in PBCs may be considered potential biomarkers of consumption of sugary and fatty food, respectively, to complement data of food-intake questionnaires.

In vitro adsorption of amino acids onto isolated rat erythrocyte membranes.

Amino acids adsorbed onto blood cell membranes represent about 8% of the total amino acids in blood. The aim of this study was to determine the in vitro adsorption kinetics of different amino acids (L-alanine, glycine, L-glutamate, L-glutamine, L-phenylalanine and L-leucine) onto rat erythrocyte membranes and to assess the effect of 24-hr starvation on these adsorption kinetics. Isolated red cell membranes were incubated at 37 degrees C for 10 sec in the presence of 14C-amino acids--with different specific radioactivity--the radioactivity retained in the membrane fraction measured and kinetic parameters of amino acid adsorption determined. With the exception of glutamate, where the adsorption was negligible, all amino acids studied were adsorbed onto isolated red cell membranes, adhering to simple Michaelis-Menten kinetics. Km' values of glycine, phenylalanine and leucine adsorption in control rats (14.7 +/- 3.8 mM, 8.41 +/- 0.95 mM and 4.65 +/- 0.46 mM respectively, SEM, n = 6-8) decreased in response to 24-hr starvation, giving the following values: 0.792 +/- 0.122 mM, 5.32 +/- 0.82 mM and 3.53 +/- 0.31 mM respectively (SEM, n = 6-8), Vmax' value of glycine adsorption of control rats decreased (from 61.0 +/- 15.5 mmol/mol P/sec to 4.25 +/- 0.70 mmol/mol P/sec, SEM, n = 7) and that of leucine increased (from 13.5 +/- 1.0 mmol/mol P/sec to 18.9 +/- 2.0 mmol/mol P/sec, SEM, n = 7) as an effect of 24-hr starvation. This study shows that alanine, glycine, glutamine, phenylalanine and leucine, but not glutamate, adsorbed onto erythrocyte membranes according to Michaelis-Menten-like kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

The uncoupling protein, thermogenin.

The uncoupling protein (UCP) or thermogenin is a 33 kDa inner-membrane mitochondrial protein exclusive to brown adipocytes in mammals that functions as a proton transporter, allowing the dissipation as heat of the proton gradient generated by the respiratory chain and thereby uncoupling oxidative phosphorylation. Thermogenesis (heat production) in brown adipose tissue, which is activated in response to cold exposure or chronic overeating, depends largely on UCP activity. Norepinephrine, released from sympathetic terminals and acting via beta-adrenoceptors and cAMP, is the main positive regulator of both UCP synthesis and activity. Brown fat thermogenesis plays a critical role in thermoregulation and in overall energy balance, at least in rodents. Manipulation of thermogenesis, whether through UCP or through analogous uncoupling proteins, could be an effective strategy against obesity.

Retinoic acid modulates retinoid X receptor alpha and retinoic acid receptor alpha levels of cultured brown adipocytes.

A novel potential regulatory pathway of brown adipose tissue (BAT) thermogenesis was recently recognized after identifying retinoic acid (RA) as a transcriptional activator of the uncoupling protein (UCP) gene. Here we provide evidence that the UCP responsiveness to RA in primary cultures of brown adipocytes involves RA receptor alpha (RAR alpha), and show, in the same system and also in CHO cells, that RA down-regulates the steady-state levels of RAR alpha and especially of retinoid X receptor alpha, suggesting autoregulation of the retinoid pathway and therefore supporting the idea of a physiological role for it in controlling the thermogenic capacity of BAT.

Opposite effects of feeding a vitamin A-deficient diet and retinoic acid treatment on brown adipose tissue uncoupling protein 1 (UCP1), UCP2 and leptin expression.

The relationship between interscapular brown adipose tissue (IBAT) thermogenic potential and vitamin A status was investigated by studying the effects of feeding a vitamin A-deficient diet and all-trans retinoic acid (tRA) treatment on body weight and IBAT parameters in mice. Feeding a vitamin A-deficient diet tended to trigger opposite effects to those of tRA treatment, namely increased body weight, IBAT weight, adiposity and leptin mRNA expression, and reduced IBAT thermogenic potential in terms of uncoupling protein 1 (UCP1) mRNA and UCP2 mRNA expression. The results emphasize the importance of retinoids as physiological regulators of brown adipose tissue.

Effect of selective beta-adrenoceptor stimulation on UCP synthesis in primary cultures of brown adipocytes.

Given the co-existence of the three beta-adrenoceptor (beta AR) subtypes (beta 1AR, beta 2AR and beta 3AR) in brown adipocytes, the present study was undertaken to determine the relative importance of these in the induction of UCP synthesis in mouse BAT precursor cells in primary culture. Cells at different stages of differentiation were exposed to different beta AR agonists: prenalterol (a selective beta 1AR agonist), salbutamol or clenbuterol (selective beta 2AR agonists), or BRL 37344 (a selective beta 3AR agonist). As with the endogenous agonist, noradrenaline, and the non-selective beta AR agonist, isoprenaline, all four beta AR agonists induced UCP in the confluent stage of the cells, but with different potencies, and with the highest induction being seen after clenbuterol or BRL 37344 treatment. Cells in the confluent stage of development were the most sensitive to the effects of the agonists, although clenbuterol and BRL 37344 induced a weak UCP synthesis in pre-confluent cells. None of these beta AR agonists were able to induce UCP synthesis in the post-confluent period. The responses to prenalterol and salbutamol were inhibited by propranolol at relatively low concentrations, suggesting their effects were mediated by beta 1AR and beta 2AR, respectively. However, propranolol was a particularly weak antagonist of BRL 37344 and, unexpectedly, of the clenbuterol UCP responses, which suggests that both induce UCP synthesis via the beta 3AR. In summary, the beta 3AR is the most important adrenoceptor coupled to the induction of UCP synthesis, although both beta 1AR and beta 2AR activation may make a contribution. However, all three beta AR subtypes do not become fully functional until cultured cells become confluent.

Decrease of the pool of amino acids adsorbed on blood cell membranes caused by starvation in rats.

The effect of 24 h starvation on the pool of amino acids adsorbed on the blood cell membranes was determined in Wistar rats. Aortic and iliac blood was analysed. 24 h starvation induced a significant decrease in the combined essential amino acids adsorbed on the blood cell membranes, in both arterial and venous blood, without affecting whole-blood levels (adsorbed + non-adsorbed). The same tendency was extended to most of the individual amino acids. This finding indicates that this pool of adsorbed amino acids has a rapid turnover and probably plays a physiological role in a situation of exogenous food deprivation.