Time-of-Day Adrenal Modulation of Corticosterone Synthesis is Affected by Sex and Diet but Not by Proanthocyanidins in Rat.

SCOPE: The aim of this study is to investigate the effect of time-of-day on serum hormones and gene expression in adrenal glands, studying the impact of sex, obesogenic diet, and timing of proanthocyanidins administration, with a focus on glucocorticoids synthesis by this gland. METHODS AND RESULTS: Female and male rats, assigned to a standard chow or a cafeteria diet-fed group, receive a daily oral dose of a grape seed proanthocyanidin extract (GSPE), or a vehicle (when light is turned on, or when light is turned off). Corticosterone, estradiol, and testosterone serum levels, and the expression analysis of clock genes and genes related to corticosterone synthesis pathway, are assessed. Serum hormone levels exhibited a marked time-of-day effect also see in the expression of scavenger receptor class B member 1 (Scarb1) and cyp11b genes. The correlation between these two genes and period circadian regulator 2 (Per2) is also extended to other clock genes, although to a lesser extent: cryptochrome (Cry) and nuclear receptor subfamily 1 group D member 1 (Rev-erba). CONCLUSION: The strong correlations found suggest an important role of local Per2 (but also of Cry and Rev-erbA) in regulating the expression of the enzymes involved in the corticosterone synthesis pathway. The expression of clock genes in adrenals is influenced by sex and diet but not by GSPE.

Administration time effect of dietary proanthocyanidins on the metabolome of Fischer 344 rats is sex- and diet-dependent.

Proanthocyanidins (PAs) are one of the most commonly ingested polyphenols in the human diet, with a wide range of beneficial health effects. Remarkably, PAs have been reported to influence core and peripheral clock genes expression, and their effects may change in a time-of-day dependent manner. Therefore, the aim of this study was to investigate whether the capacity of PAs to modulate the metabolome is conditioned by the time-of-day in which these compounds are consumed in a diet- and sex-dependent manner. To do this, a grape seed proanthocyanidin extract (GSPE) was administered to female and male Fischer 344 rats at ZT0 (in the morning) and ZT12 (at night) and the GSPE administration time effect was evaluated on clock genes expression, melatonin hormone and serum metabolite levels in a healthy and obesogenic context. The results showed an administration time effect of GSPE on the metabolome in a sex and diet-dependent manner. Specifically, there was an effect on amino acid, lipid and cholate metabolite levels that correlated with the central clock genes expression. Therefore, this study shows a strong influence of sex and diet on the PAs effects on the metabolome, modulated in turn by the time-of-day.

Circulating oestradiol determines liver lipid deposition in rats fed standard diets partially unbalanced with higher lipid or protein proportions.

The ingestion of excess lipids often produces the accumulation of liver fat. The modulation of diet energy partition affects this process and other metabolic responses, and oestrogens and androgens are implied in this process. Ten-week-old male and female rats were fed with either standard rat chow (SD), SD enriched with coconut oil (high-fat diet, HF), SD enriched with protein (high-protein diet, HP) or a 'cafeteria' diet (CAF) for 1 month. HF and CAF diets provided the same lipid-derived percentage of energy (40 %), HP diet protein energy derived was twice (40 %) that of the SD. Animals were killed under anaesthesia and samples of blood and liver were obtained. Hepatic lipid content showed sex-related differences: TAG accumulation tended to increase in HF and CAF fed males. Cholesterol content was higher only in the CAF males. Plasma oestradiol in HF and HP males was higher than in CAF. Circulating cholesterol was inversely correlated with plasma oestradiol. These changes agreed with the differences in the expression of some enzymes related to lipid and energy metabolism, such as fatty acid synthetase or phosphoglycolate phosphatase. Oestrogen protective effects extend to males with 'normal' diets, that is, not unbalanced by either lipid or protein, but this protection was not enough against the CAF diet. Oestradiol seems to actively modulate the liver core of 2C-3C partition of energy substrates, regulating cholesterol deposition and lactate production.

Modulation of Food Intake by Differential TAS2R Stimulation in Rat.

Metabolic surgery modulates the enterohormone profile, which leads, among other effects, to changes in food intake. Bitter taste receptors (TAS2Rs) have been identified in the gastrointestinal tract and specific stimulation of these has been linked to the control of ghrelin secretion. We hypothesize that optimal stimulation of TAS2Rs could help to modulate enteroendocrine secretions and thus regulate food intake. To determine this, we have assayed the response to specific agonists for hTAS2R5, hTAS2R14 and hTAS2R39 on enteroendocrine secretions from intestinal segments and food intake in rats. We found that hTAS2R5 agonists stimulate glucagon-like peptide 1 (GLP-1) and cholecystokinin (CCK), and reduce food intake. hTAS2R14 agonists induce GLP1, while hTASR39 agonists tend to increase peptide YY (PYY) but fail to reduce food intake. The effect of simultaneously activating several receptors is heterogeneous depending on the relative affinity of the agonists for each receptor. Although detailed mechanisms are not clear, bitter compounds can stimulate differentially enteroendocrine secretions that modulate food intake in rats.

Modulation of SHBG binding to testosterone and estradiol by sex and morbid obesity.

OBJECTIVE: Sex hormone-binding globulin (SHBG) binds and transports testosterone and estradiol in plasma. The possibility that SHBG is a mixture of transporting proteins has been postulated. We analyzed in parallel the effects of obesity status on the levels and binding capacity of circulating SHBG and their relationship with testosterone and estradiol. DESIGN: Anthropometric measures and plasma were obtained from apparently healthy young (i.e. 35 ± 7 years) premenopausal women (n = 32) and men (n = 30), with normal weight and obesity (BMI >30 kg/m2). METHODS: SHBG protein (Western blot), as well as the plasma levels of testosterone, estradiol, cortisol and insulin (ELISA) were measured. Specific binding of estradiol and testosterone to plasma SHBG was analyzed using tritium-labeled hormones. RESULTS: Significant differences in SHBG were observed within the obesity status and gender, with discordant patterns of change in testosterone and estradiol. In men, testosterone occupied most of the binding sites. Estrogen binding was much lower in all subjects. Lower SHBG of morbidly obese (BMI >40 kg/m2) subjects affected testosterone but not estradiol. The ratio of binding sites to SHBG protein levels was constant for testosterone, but not for estradiol. The influence of gender was maximal in morbid obesity, with men showing the highest binding/SHBG ratios. CONCLUSIONS: The results reported here are compatible with SHBG being a mixture of at least two functionally different hormone-binding globulins, being affected by obesity and gender and showing different structure, affinities for testosterone and estradiol and also different immunoreactivity.

Long-term increased carnitine palmitoyltransferase 1A expression in ventromedial hypotalamus causes hyperphagia and alters the hypothalamic lipidomic profile.

Lipid metabolism in the ventromedial hypothalamus (VMH) has emerged as a crucial pathway in the regulation of feeding and energy homeostasis. Carnitine palmitoyltransferase (CPT) 1A is the rate-limiting enzyme in mitochondrial fatty acid ß-oxidation and it has been proposed as a crucial mediator of fasting and ghrelin orexigenic signalling. However, the relationship between changes in CPT1A activity and the intracellular downstream effectors in the VMH that contribute to appetite modulation is not fully understood. To this end, we examined the effect of long-term expression of a permanently activated CPT1A isoform by using an adeno-associated viral vector injected into the VMH of rats. Peripherally, this procedure provoked hyperghrelinemia and hyperphagia, which led to overweight, hyperglycemia and insulin resistance. In the mediobasal hypothalamus (MBH), long-term CPT1AM expression in the VMH did not modify acyl-CoA or malonyl-CoA levels. However, it altered the MBH lipidomic profile since ceramides and sphingolipids increased and phospholipids decreased. Furthermore, we detected increased vesicular γ-aminobutyric acid transporter (VGAT) and reduced vesicular glutamate transporter 2 (VGLUT2) expressions, both transporters involved in this orexigenic signal. Taken together, these observations indicate that CPT1A contributes to the regulation of feeding by modulating the expression of neurotransmitter transporters and lipid components that influence the orexigenic pathways in VMH.

Oleoyl-estrone.

Oleoyl-estrone (OE) is a powerful slimming agent that is also present in plasma and adipose tissue, where it is synthesized. It acts through the formation of a derivative W. OE effects (and W levels) are proportional to the dose. OE reduces food intake but maintains energy expenditure (thermogenesis). The energy gap is fulfilled with adipose tissue fat, sparing body protein and maintaining glycemia (and glycogen) with lower insulin and leptin levels. OE (in fact W) acts through specific receptors, different from those of estrogen. OE increases cholesterol catabolism, reducing hypercholesterolemia in obese rats. The main metabolic effect on adipose tissue is lowering of lipid synthesis, maintaining unchanged the intracellular lipolytic processes; the imbalance favors the progressive loss of fat, which is largely used by the muscle. OE administration induces additive effects with other antiobesity agents, such as ß(3)-adrenergic agonists, forcing a massive loss of lipid. Corticosteroids markedly limit OE action by altering the liver control of lipogenesis. OE also inhibits the action of 17ß-hydroxysteroid dehydrogenase, decreasing the synthesis of ß-estradiol and testosterone. Discontinuous treatment allows for maximal efficacy both in rats and humans. OE has the advantage that the loss of fat is maintained and does not require additional dietary limitations.

Oleoyl-estrone is a precursor of an estrone-derived ponderostat signal.

Oleoyl-estrone (OE) is a powerful anti-obesity compound that decreases food intake, decreases insulin resistance and circulating cholesterol. OE stimulates a severe loss of body fat by decreasing adipose tissue lipid synthesis and maintaining lipolysis. Therefore, the body economy loses lipid energy because energy expenditure is maintained. This study analyses the discrepancy between OE effects and the distribution of labelled OE in plasma. Estrone radioimmunoassay of organic solvent plasma extracts of rats treated with OE showed the massive presence of acyl-estrone, but saponification did not release estrone, but containing similar unknown compound. Analysis of label distribution in plasma after oral gavages of (3)H-OE showed the presence of a more hydrophilic compound than OE or any estrogen as well as (3)H(2)O, formed from (3)H-OE in the acidic stomach medium. OE was not attached to a specific transporter in plasma. Through serum HPLC analysis we found W, a labelled derivative more hydrophilic than OE or estrone. The results were confirmed using (14)C-OE. HPLC-MS/MS studies showed that plasma OE levels were one order of magnitude lower than those of W. When liver cell cytosols from rats laden with (3)H-OE were incubated with nuclei from untreated rats, the OE-derived label (i.e., Ws) was found attached to nuclear DNA. Neither estradiol nor estrone interfered with its binding. W is a fairly hydrophilic compound of low molecular weight containing the estrone nucleus, but it is not an ester because saponification or esterases do not yield estrone as OE does. It is concluded that OE acts through its conversion to W, its active form; which binds to a nuclear receptor different from that of estrogen. The estimated W serum levels are proportional to the pharmacological OE effects in vivo. We postulate W as a new type of hormone that exerts the full range of in vivo effects thus far attributed to OE. The full identification of W is anticipated to open the way for the development of new OE-like anti-obesity drugs.

Comparative effects of oleoyl-estrone and a specific beta3-adrenergic agonist (CL316, 243) on the expression of genes involved in energy metabolism of rat white adipose tissue.

BACKGROUND: The combination of oleoyl-estrone (OE) and a selective beta3-adrenergic agonist (B3A; CL316,243) treatment in rats results in a profound and rapid wasting of body reserves (lipid). METHODS: In the present study we investigated the effect of OE (oral gavage) and/or B3A (subcutaneous constant infusion) administration for 10 days to overweight male rats, compared with controls, on three distinct white adipose tissue (WAT) sites: subcutaneous inguinal, retroperitoneal and epididymal. Tissue weight, DNA (and, from these values cellularity), cAMP content and the expression of several key energy handling metabolism and control genes were analyzed and computed in relation to the whole site mass. RESULTS: Both OE and B3A significantly decreased WAT mass, with no loss of DNA (cell numbers). OE decreased and B3A increased cAMP. Gene expression patterns were markedly different for OE and B3A. OE tended to decrease expression of most genes studied, with no changes (versus controls) of lipolytic but decrease of lipogenic enzyme genes. The effects of B3A were widely different, with a generalized increase in the expression of most genes, including the adrenergic receptors, and, especially the uncoupling protein UCP1. DISCUSSION: OE and B3A, elicit widely different responses in WAT gene expression, end producing similar effects, such as shrinking of WAT, loss of fat, maintenance of cell numbers. OE acted essentially on the balance of lipolysis-lipogenesis and the blocking of the uptake of substrates; its decrease of synthesis favouring lipolysis. B3A induced a shotgun increase in the expression of most regulatory systems in the adipocyte, an effect that in the end favoured again the loss of lipid; this barely selective increase probably produces inefficiency, which coupled with the increase in UCP1 expression may help WAT to waste energy through thermogenesis. CONCLUSIONS: There were considerable differences in the responses of the three WAT sites. OE in general lowered gene expression and stealthily induced a substrate imbalance. B3A increasing the expression of most genes enhanced energy waste through inefficiency rather than through specific pathway activation. There was not a synergistic effect between OE and B3A in WAT, but their combined action increased WAT energy waste.

Oleoyl-estrone increases adrenal corticosteroid synthesis gene expression in overweight male rats.

Oleoyl-estrone (OE) induces a marked loss of body fat in rats by maintaining energy expenditure, body protein and blood glucose despite decreasing food intake. OE increases glucocorticoids, but they arrest OE lipid-mobilization. We studied here whether OE induces a direct effect on adrenal glands function as part of this feedback regulation. Dietary overweight male rats were given oral 10nmol/g OE gavages for ten days. A group (PF) of pair-fed to OE rats, and controls received vehicle-only gavages. OE rats lost slightly more body than PF, but had larger adrenal glands. Tissue corticosterone levels, and gene expressions for glucocorticoid-synthesizing enzymes were increased in OE versus controls and PF; thus, we assumed that adrenal growth affected essentially its cortex since OE also lowered the expression of the medullar catecholamine synthesis enzyme genes. Serum corticosterone was higher in PF than in OE and controls, but liver expression of corticosteroid-disposing steroid 5alpha-reductase was 3x larger in OE than PF and controls. Circulating glucocorticoids changed little under OE, in spite of higher adrenal gland and liver content, hinting at modulation of glucocorticoid turnover as instrumental in their purported increased activity. In conclusion, we have observed that OE considerable enhanced the expression of the genes controlling the synthesis of glucocorticoids from cholesterol in the rat and increasing the adrenal glands' corticosterone, size and cellularity, but also the liver disposal of corticosteroids, suggesting that OE increases corticosterone synthesis and degradation (i.e. serum turnover), a process not driven by limited energy availability but directly related to the administration of OE.

Gene expression modulation of rat liver cholesterol metabolism by oleoyl-estrone.

OBJECTIVE: Since oleoyl-estrone (OE) decreases circulating cholesterol in the rat, we analyzed the response to OE treatment of hepatic gene expressions related with cholesterol metabolism. METHODS: Male overweight rats treated with oral OE (10 nmol/g daily) were compared with a pair-fed (PF) group and controls fed ad libitum. Serum parameters and liver lipid and cholesterol contents were measured. Total tissue RNA was used for real-time PCR analysis of the gene expression of enzymes and regulatory factors of liver cholesterol metabolism. Cholesterol-7α-hydroxylase and ABC transporter A1 protein levels were estimated by Western blot. RESULTS: Pair-feeding and OE treatment reduced the expression of 3-hydroxy-3-methyl-glutaryl-CoA synthase. OE increased the expression of the LDL receptor. Cholesterol disposal, through bile acids synthesis, was increased in PF and more markedly in OE rats. Gene expressions of the ABC transporter A1 and apolipoproteins A1 and E were increased in OE rats. The expression of liver X receptor was lower in PF than in OE and controls. CONCLUSION: The rapid disappearance of circulating cholesterol elicited by OE is consequence of: (1) decreased mevalonate pathway activity, (2) a higher expression of the LDL-receptor, and (3) the activation of the oxidation of cholesterol to form bile acids as a consequence of the higher cholesterol concentrations found in liver, also affected by energy availability.

Different modulation by dietary restriction of adipokine expression in white adipose tissue sites in the rat.

BACKGROUND: White adipose tissue (WAT) is a disperse organ acting as energy storage depot and endocrine/paracrine controlling factor in the management of energy availability and inflammation. WAT sites response under energy-related stress is not uniform. In the present study we have analyzed how different WAT sites respond to limited food restriction as a way to better understand the role of WAT in the pathogenesis of the metabolic syndrome. METHODS: Overweight male rats had their food intake reduced a 40% compared with free-feeding controls. On day ten, the rats were killed; circulating glucose, insulin, leptin, adiponectin, triacylglycerols and other parameters were measured. The main WAT sites were dissected: mesenteric, retroperitoneal, epididymal and subcutaneous inguinal, which were weighed and frozen. Later all subcutaneous WAT was also dissected and weighed. Samples were used for DNA (cellularity) analysis and mRNA extraction and semiquantitarive RT-PCR analysis of specific cytokine gene expressions. RESULTS: There was a good correlation between serum leptin and cumulative WAT leptin gene mRNA, but not for adiponectin. Food restriction reduced WAT size, but not its DNA content (except for epididymal WAT). Most cytokines were correlated to WAT site weight, but not to DNA. There was WAT site specialization in the differential expression (and probably secretion) of adipokines: subcutaneous WAT showed the highest concentration for leptin, CD68 and MCP-1, mesenteric WAT for TNFalpha (and both tissues for the interleukins 1beta and 6); resistin was highly expressed in subcutaneous and retroperitoneal WAT. CONCLUSION: Food restriction induced different patterns for mesenteric and the other WAT sites, which may be directly related to both the response to intestine-derived energy availability, and an inflammatory-related response. However, retroperitoneal WAT, and to a lower extent, subcutaneous and epididymal, reacted decreasing the expression of inflammatory markers and the signaling of decreased energy availability in their stores. The varying cytokine expression patterns highlight the fact that WAT sites show different inflammatory and signaling responses to energy availability; they are too much different to simply extend to the whole-body WAT the findings of one or even a couple of sites.

Oleoyl-estrone affects lipid metabolism in adrenalectomized rats treated with corticosterone through modulation of SREBP1c expression.

Oleoyl-estrone (OE) elicits a decrease in body fat, which is blocked by glucocorticoids. In order to analyze this counterregulatory effect, we studied the effects of oral OE on adrenalectomized female rats simultaneously receiving corticosterone (subcutaneous pellets). Circulating corticosteroids, liver glycogen, lipids and the expressions in whole liver, soleus muscle, interscapular brown adipose tissue (BAT), and the inguinal and periovaric white adipose tissue (WAT) of genes controlling lipid metabolism were analyzed. Corticosterone reversed OE lipid mobilization, storing fat in liver and subcutaneous WAT. This was not simply the predominance of corticosteroid enhancement of lipogenesis against OE inhibition, but a synergy to enhance lipogenesis. Periovaric WAT showed a different effect, with corticosterone inhibiting OE arrest of lipogenic gene expressions. The data presented suggests that interaction of OE and glucocorticoids (and the metabolic response) depends on the organ or WAT site; there was a direct relationship on the direction and extent of change of SREBP1c expression with those of important energy and lipid handling genes. Our results confirm that corticosterone blocks - and even reverses - OE effects on body lipids in a dose-dependent way, a process mediated, at least in part, by modulation of SREBP1c expression.

Gene expression modulation of liver energy metabolism by oleoyl-oestrone in overweight rats.

We intended to determine how the liver copes with the massive handling of lipids induced by OE (oleoyl-oestrone), as well as to characterize and differentiate the actual OE effects from those that may be only the consequence of decreased food intake. Thus we used male rats treated with oral OE (10 nmol/g per day) compared with a vehicle only PF (pair-fed) group and controls fed ad libitum (vehicle only). Plasma parameters, and total liver lipids, glycogen, DNA and total mRNA were measured. RNA was extracted and used for real-time PCR analysis of the gene expression of enzymes and regulatory factors of liver energy metabolism. Most hepatic proteins showed similar gene expressions in OE and controls, but the differences widened between OE and PF rats, showing that OE effects could not be merely attributed to a lower energy intake. The liver of OE-treated rats largely maintained its ability to mobilize glucose for the synthesis of fats; this was achieved in part by a peculiar combination of regulative modifications that facilitate both fatty acid disposal and restrained glucose utilization under conditions of limited food supply but ample availability of internal energy stores. In conclusion, the results presented suggest that the effect of OE on liver metabolism may be (at least in part) mediated through an insulin-sensitivity-dependent modulation of the expression of SREBP-1c (sterol-regulatory-element-binding protein-1c), resulting in the unique combined effect of mildly increased (or maintained) glucose disposal but also limited enhancement of lipogenesis.

Site-related white adipose tissue lipid-handling response to oleoyl-estrone treatment in overweight male rats.

BACKGROUND: Oleoyl-estrone (OE) decreases energy intake while maintaining glucose homeostasis, and energy expenditure at the expense of body fat. White adipose tissue (WAT) depots behave differently under starvation, postprandial state and pharmacologically induced lipolysis. AIM OF THE STUDY: To understand the mechanism of massive lipid loss from WAT elicited by OE treatment. METHODS: We used overweight male rats. Rats receiving OE (10 nmol/g) gavages were compared with controls and a pair-fed group. Whole fat pads from the mesenteric, retroperitoneal, epididymal and inguinal subcutaneous sites were excised and analyzed for lipid, DNA, mRNA and the expression of lipogenic, fatty acid transporters and lipase genes. RESULTS: In OE and pair-fed rats, WAT weights decreased, with the limited loss of cells. Patterns of gene expression in most WAT sites were similar for OE and PF, suggesting a shared mechanism of fat mobilization, but in mesenteric WAT, PF increased lipogenic and fatty acid transporter gene expressions. However, OE inhibited lipogenic expressions more deeply than PF. CONCLUSIONS: White adipose tissue sites showed different expression patterns, hinting at relatively specialized functions in fat storage; thus, single site analyses cannot be extrapolated to whole WAT. Differences between mesenteric and the other sites suggest that 'visceral fat' should be reserved for this site only, and not applied to other abdominal fat depots (epididymal, retroperitoneal).

Short-term oral oleoyl-estrone decreases the expression of ghrelin in the rat stomach.

Oleoyl-estrone (OE) mobilizes body fat and decreases food intake. The precise mechanism of its modulation of appetite is unknown. Since the effects of OE on food intake appear early, here we studied the effect of OE on the expression of gut peptides that affect short-term ingestive behavior: ghrelin, leptin, CCK, PYY, and GLP-1. Two hours after a single OE dose, adult male rats were killed and their stomach fundus and intestine sections were dissected and processed for real-time PCR amplification. Semi-quantitative estimation of gene mRNA tissue levels showed that OE markedly decreased ghrelin expression in the stomach; leptin mRNA was unchanged; CCK mRNA decreased in the proximal intestine while PYY and GLP-1 expression in the intestine was not altered. Our results indicate that the short-term decrease in food intake induced by OE may be essentially the consequence of a marked decrease in the expression of ghrelin in the stomach.

Effects of combined oleoyl-estrone and rimonabant on overweight rats.

Oleoyl-estrone (OE) decreases appetite, maintains energy expediture, induces lipolysis (sparing protein), and decreases cholesterolemia and insulin resistance. Rimonabant (SR141716) is a cannabinoid-receptor inhibitor that decreases appetite and mobilizes fat. We studied whether their combination improves their slimming effects. Male overweight rats received daily gavages of 5.3 mg/kg OE, 10 mg/kg rimonabant, or both drugs during 10 days. Body weight and composition, energy balance, adipose tissue weight, and serum hormones and metabolites were measured. OE halved food intake and maintained energy expenditure at the expense of body fat. Rimonabant effects on appetite and energy balance were less marked, resulting in lower lipid mobilization. OE and rimonabant followed the OE pattern, with no additive or synergic effects. Glycemia was maintained, but OE decreased insulin, GLP-1, and cholesterol, whilst rimonabant increased cholecystokinin and cholesterol, and decreased NEFA. Both drugs decreased leptin and triacylglycerols; ghrelin was unchanged. The results hint at different mechanisms of action of both drugs: we can assume that OE effects do not involve the cannabinoid pathway. OE does not seem to act, either, after 10 days, through the secretion of ghrelin or the intestinal appetite-controlling peptides tested.

Corticosterone inhibits the lipid-mobilizing effects of oleoyl-estrone in adrenalectomized rats.

Oleoyl-estrone (OE) is an adipose-derived signal that decreases energy intake and body lipid, maintaining energy expenditure and glycemic homeostasis. Glucocorticoids protect body lipid and the metabolic status quo. We studied the combined effects of OE and corticosterone in adrenalectomized female rats: daily OE gavages (0 or 10 nmol/g) and slow-release corticosterone pellets at four doses (0, 0.5, 1.7, and 4.8 mg/d). Intact and sham-operated controls were also included. After 8 d, body composition and plasma metabolites and hormones were measured. OE induced a massive lipid mobilization (in parallel with decreased food intake and maintained energy expenditure). Corticosterone increased fat deposition and inhibited the OE-elicited mobilization of body energy, even at the lowest dose. OE enhanced the corticosterone-induced rise in plasma triacylglycerols, and corticosterone blocked the OE-induced decrease in leptin. High corticosterone and OE increased insulin resistance beyond the effects of corticosterone alone. The presence of corticosterone dramatically affected OE effects, reversing its decrease of body energy (lipid) content, with little or no change on food intake or energy expenditure. The maintenance of glycemia and increasing insulin in parallel to the dose of corticosterone indicate a decrease in insulin sensitivity, which is enhanced by OE. The reversal of OE effects on lipid handling, insulin resistance, can be the consequence of a corticosterone-induced OE resistance. Nevertheless, OE effects on cholesterol were largely unaffected. In conclusion, corticosterone administration effectively blocked OE effects on body lipid and energy balance as well as insulin sensitivity and glycemia.

In rats, oral oleoyl-DHEA is rapidly hydrolysed and converted to DHEA-sulphate.

BACKGROUND: Dehydroepiandrosterone (DHEA) released by adrenal glands may be converted to androgens and estrogens mainly in the gonadal, adipose, mammary, hepatic and nervous tissue. DHEA is also a key neurosteroid and has antiglucocorticoid activity. DHEA has been used for the treatment of a number of diseases, including obesity; its pharmacological effects depend on large oral doses, which effect rapidly wanes in part because of its short half-life in plasma. Since steroid hormone esters circulate for longer periods, we have studied here whether the administration of DHEA oleoyl ester may extend its pharmacologic availability by keeping high circulating levels. RESULTS: Tritium-labelled oleoyl-DHEA was given to Wistar male and female rats by gastric tube. The kinetics of appearance of the label in plasma was unrelated to sex; the pattern being largely coincident with the levels of DHEA-sulfate only in females, and after 2 h undistinguishable from the results obtained using labelled DHEA gavages; in the short term, practically no lipophilic DHEA label was found in plasma. After 24 h only a small fraction of the label remained in the rat organs, with a different sex-related distribution pattern coincident for oleoyl- and free- DHEA gavages. The rapid conversion of oleoyl-DHEA into circulating DHEA-sulfate was investigated using stomach, liver and intestine homogenates; which hydrolysed oleoyl-DHEA optimally near pH 8. Duodenum and ileum contained the highest esterase activities. Pure hog pancreas cholesterol-esterase broke down oleoyl-DHEA at rates similar to those of oleoyl-cholesterol. The intestinal and liver esterases were differently activated by taurocholate and showed different pH-activity patterns than cholesterol esterase, suggesting that oleoyl-DHEA can be hydrolysed by a number of esterases in the lumen (e.g. cholesterol-esterase), in the intestinal wall and the liver. CONCLUSION: The esterase activities found may condition the pharmacological availability (and depot effect) of orally administered steroid hormone fatty acid esters such as oleoyl-DHEA. The oral administration of oleoyl-DHEA in order to extend DHEA plasma availability has not been proved effective, since the ester is rapidly hydrolysed, probably in the intestine itself, and mainly converted to DHEA-sulfate at least in females.

Estimation of the metabolizable energy equivalence of dietary proteins.

BACKGROUND: Protein contributes significantly to the human daily energy budget. The high diversity in composition, digestibility and dietary proportion complicates the estimation of its actual energy contribution. In practical terms we continue using the energy equivalents estimated by Atwater. This results in a persistent source of imprecision in the calculation of dietary energy that at least can be partially corrected. AIM OF THE STUDY: We used experimentally obtained data to compute an algorithm that will allow to estimate the gross energy content of a protein which composition is known. The relationship between gross energy (i.e. bomb calorimeter-derived) of protein is not a direct correlate of its metabolic efficacy as energy supplier. Thus we estimated the metabolic energy yield (i.e. ATP equivalents) of amino acid residues, using the data to compute the estimated protein metabolic energy yield. Both approaches were to be used to propose a corrected protein energy equivalence factor that will increase the precision in the calculation of dietary protein energy, especially when information on protein composition is available. METHODS: The gross energy content of amino acids was measured with a bomb-calorimeter, and compared with that of glucose. Amino acid estimated metabolizable energy yield, in moles of ATP per mol of amino acid residue, was also calculated. The net heat yield of all amino acids were used to compute the theoretical heat production of albumin, collagen, gelatin and whole rat protein, which gross energy was also measured experimentally. The mean estimated energy yield (both gross and metabolizable) for each amino acid residue were used to compute the theoretical energy of a number of dietary protein sources which composition was available in the literature. RESULTS: Calculated energy yield of a few selected proteins coincided with the data directly measured in the bomb calorimeter. The computed gross energy yield and metabolizable energy yield for a number of dietary protein sources was estimated. There were minor differences between both parameters: the proportion of aromatic and branched chain amino acids was the main factor affecting the gross energy yield of a given protein; conversely, the higher proportion of nitrogen, especially, but not exclusively, related to arginine and glycine content correlated with lower metabolizable energy. These parameters, corrected by the gross and metabolizable energy of glucose were used to compute a mean energy equivalence for dietary protein: 19 kJ/g protein (i.e. 4.55 kcal/g protein). This value, higher than the current Atwater factor, does not include protein digestibility (as Atwater value did), but included the cost of nitrogen excretion. CONCLUSIONS: The methodology presented allows the approximate calculation of both the purported heat production of a protein (pure or mixture) for which we know its amino acid composition (and even get a good estimate if we only know its proportion of nitrogen), and its metabolic energy equivalence. We also propose the use of a new energy correlate of dietary protein; this can be further tuned if the proportion of nitrogen in the protein is known, and even further if its amino acid composition is available. As a consequence of its application to dietary proteins, their energy yield may be higher than usually considered, which may influence the calculations of energy balance.