Conjugated linoleic acid evokes de-lipidation through the regulation of genes controlling lipid metabolism in adipose and liver tissue.

Conjugated linoleic acid (CLA) is a unique lipid that elicits dramatic reductions in adiposity in several animal models when included at < or = 1% of the diet. Despite a flurry of investigations, the precise mechanisms by which conjugated linoleic acid elicits its dramatic effects in adipose tissue and liver are still largely unknown. In vivo and in vitro analyses of physiological modifications imparted by conjugated linoleic acid on protein and gene expression suggest that conjugated linoleic acid exerts its de-lipidating effects by modulating energy expenditure, apoptosis, fatty acid oxidation, lipolysis, stromal vascular cell differentiation and lipogenesis. The purpose of this review shall be to examine the recent advances and insights into conjugated linoleic acid's effects on obesity and lipid metabolism, specifically focused on changes in gene expression and physiology of liver and adipose tissue.

Dehydroepiandrosterone alters the growth of stromal vascular cells from human adipose tissue.

OBJECTIVE: The purpose of this study was to determine if the antiobesity actions of dehydroepiandrosterone (DHEA) observed in vivo are due to an influence on the proliferation and differentiation of primary cultures of stromal-vascular (SV) cells isolated from human adipose tissue. DESIGN: SV cells were isolated from subcutaneous adipose tissue obtained from a young adult female undergoing elective liposuction. For the proliferation assay (Experiment 1), cultures were fed proliferation media containing 0, 5, 25 or 100 microM DHEA for 3d. At the end of this treatment period, cultures were either prepared for counting or for determining their metabolic activity using the Alamar Blue staining procedure. For the differentiation assays (Experiment 2), cultures were fed differentiation media containing 0, 25 or 50 microM DHEA for 20 d. At the end of this treatment period, cultures were either prepared for lipid staining using Oil Red O or for marker enzyme analysis (glycerol-3-phosphate dehydrogenase activity; GPDH). To determine if the stimulatory effects of DHEA on SV cell differentiation were dependent on the presence of thiazolidinediones (Experiment 3), cultures of differentiating SV cells were incubated in the presence and absence of BRL 49653 and either 0, 25 or 50 microM DHEA. RESULTS: In Experiment 1, cultures treated with 25 and 100 microM DHEA had fewer cells than cultures treated with either 0 or 5 microM DHEA. Alamar Blue staining decreased as the level of DHEA in the cultures increased. In Experiment 2, cultures treated with DHEA had more lipid and GPDH activity than control cultures. In Experiment 3, cultures treated with BRL 49653 had more triglyceride than cultures treated without BRL 49653. Likewise, cultures treated with DHEA had more triglyceride than their non-DHEA controls. Regardless of the BRL status, cultures supplemented with DHEA had more triglyceride than control cultures. CONCLUSION: These data suggest that in cultures of SV cells from human adipose tissue, DHEA supplementation attenuates proliferation and enhances differentiation. These data support the hypothesis that DHEA directly attenuates preadipocyte proliferation in humans as we previously demonstrated in primary cultures of pig and rat SV cells and in cultures of 3T3-L1 preadipocytes. In contrast, DHEA stimulated the differentiation of human preadipocytes, which is contrary to its actions in differentiating cultures of preadipocytes from animals.

Dehydroepiandrosterone and related steroids alter 3T3-L1 preadipocyte proliferation and differentiation.

The purpose of the present study was to determine if the anti-adipogenic effects of dehydroepiandrosterone (DHEA) are mediated solely by DHEA or by one or more of its downstream metabolites. In Experiment 1, preconfluent proliferating cultures of 3T3-L1 preadipocytes were incubated for either 24 or 72 h with 0, 1, 5 or 25 microM DHEA, DHEA sulfate (DHEAS), testosterone, estrone and 17beta-estradiol. Pregnenolone, a precursor of DHEA(S), was also tested at these concentrations. After 24 h of incubation, DHEAS, 17beta-estradiol and estrone at the 1 microM level stimulated preadipocyte proliferation. In contrast, DHEA and 17beta-estradiol at the 25 microM level attenuated proliferation to a greater extent than all other steroids. After 72 h of incubation, DHEA and 17beta-estradiol at the 25 microM level attenuated proliferation to a greater extent than all other steroids. In Experiment 2, post-confluent cultures of differentiating 3T3-L1 preadipocytes were incubated for 6 days with 0, 5, 30, or 60 microM levels of these steroids. Preadipocyte differentiation, as assessed by lipid content and glycerol-3-phosphate dehydrogenase activity, decreased markedly when treated with 30 and 60 microM DHEA, 17beta-estradiol, estrone and pregnenolone. In contrast, DHEAS had no impact on preadipocyte proliferation or differentiation. These results suggest that the anti-adipogenic actions of DHEA in adipose tissue may be mediated, in part, by one or more of its distal metabolites, including 17beta-estradiol.

Dehydroepiandrosterone reduces proliferation and differentiation of 3T3-L1 preadipocytes.

The purpose of these studies was to determine whether the antiobesity actions of dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS) observed in vivo are due to an influence on proliferation and/or differentiation in monolayer cultures of 3T3-L1 preadipocytes. For the proliferation study (Exp. 1), cells were grown in plating medium containing DHEA at 0, 5, 25, 50, or 100 microM for 1-4 d. DHEAS was added at the 100 microM level only. For the differentiation study (Exp. 2), cultures were grown in plating medium containing DHEA at 0, 5, 30, 60, 120, or 240 microM for 2-6 d. DHEAS was added at the 240 microM level only. In Exp. 3, the effect of DHEA on mature adipocytes was determined by exposing adipocytes grown in plating medium to DHEA at 0, 75, 125, and 250 microM for 1-4 d. In Exp. 1, preadipocyte proliferation decreased as the level of DHEA increased in cultures of 3T3-L1 cells. DHEAS had no effect on preadipocyte proliferation. The antiproliferative effect of DHEA was partially reversed by the addition of 1 microM mevalonic acid to proliferating cultures containing 25 microM DHEA. In Exp. 2, preadipocyte differentiation decreased as the level of DHEA in the cultures increased. In contrast, neither DHEAS nor mevalonic acid treatment influenced preadipocyte differentiation decreased as the level and duration of DHEA treatment increased in cultures of mature adipocytes. These data support the hypothesis that DHEA, but not DHEAS, is the active form of the steroid that attenuates obesity via altering preadipocyte proliferation and differentiation. The addition of 1 microM mevalonic acid to cultures of 3T3-L1 preadipocytes partially reversed DHEA's antiproliferative effects.

Dehydroepiandrosterone-sulfate (DHEAS) reduces adipocyte hyperplasia associated with feeding rats a high-fat diet.

OBJECTIVE: To determine if chronic administration of a low level of dehydroepiandrosterone-sulfate (DHEAS) (10 micrograms/ml drinking water) attenuates adiposity in male Osborne-Mendel rats fed low-fat (11% of kcals) vs high fat (46% of kcals) diets. DESIGN: Rats were randomly assigned to one of four treatment groups for 6 wk in this 2 x 2 factorial study. The main effects tested were diet (low vs high fat) and DHEAS (- or +). SUBJECTS: Male Osborne-Mendel rats (initial body wt approximately 265 g). MEASUREMENTS: Adipocyte mass, size and number from two major fat depots (retroperitoneal, epididymal); mass of one subcutaneous adipose depot (inguinal); serum levels of triglycerides, insulin, glucose and DHEAS; brown adipose tissue (BAT) mass; body weight gain, food and water consumption, and residual carcass composition. RESULTS: DHEAS treatment had no effect on weight gain, food consumption or water intake. DHEAS-treated rats fed the high-fat diet had smaller fat pads containing fewer adipocytes and less carcass lipid than the non DHEAS-treated rats fed the high-fat diet. In contrast, DHEAS-treated rats fed the low-fat diet had similar levels of adipose tissue mass and cellularity compared to control animals fed the low-fat diet. CONCLUSION: Administration of a low dose of DHEAS (10 micrograms/ml or 0.8 mg/kg body wt/d) in the drinking water of young male Osborne-Mendel rats fed a high-fat diet for 6 wk reduced carcass lipid, fat depot mass and retroperitoneal and epididymal adipocyte number compared to their high-fat-fed cohorts. In this study, the antiobesity effects of DHEAS were specific to the level of dietary fat used.

Effects of acute administration of dehydroepiandrosterone-sulfate on adipose tissue mass and cellularity in male rats.

OBJECTIVE: To determine if short term (2 week) treatment of growing male rats with low levels of dehydroepiandrosterone-sulfate (DHEAS) can reduce adiposity and serum triglycerides. DESIGN: Rats were administered either normal drinking water or drinking water supplemented with 10 (D10) or 100 (D100) micrograms/ml DHEAS for 14 d. SUBJECTS: Twenty-one male Sprague-Dawley rats (initial body weight 280 g). MEASUREMENTS: Adipocyte mass, size and number from three major fat depots (retroperitoneal, epididymal, inguinal); serum levels of triglycerides, insulin, IGF-1 and DHEAS; brown adipose tissue (BAT) mass, uncoupling protein content and enzyme activity; body weight gain, food and water consumption; carcass composition. RESULTS: DHEAS treatment had no effect on weight gain, food consumption or water intake. In contrast, rats treated with both levels of DHEAS had lighter fat pads, fewer epididymal and retroperitoneal adipocytes, less carcass lipid, lower levels of serum triglycerides and greater BAT mass and UCP content than control rats. Moreover, rats administered 100 micrograms/ml DHEAS had smaller and fewer epididymal adipocytes and fewer inguinal adipocytes than the D10 and the control rats. CONCLUSION: Acute treatment of growing male rats with low levels (10 micrograms/ml drinking water or 0.7 mg/kg body wt/d) of DHEAS reduces carcass lipid, adipose tissue mass and cellularity as well as serum triglycerides without altering food intake and body weight gain or causing hepatomegaly.

Vitamin E attenuates myocardial oxidative stress induced by DHEA in rested and exercised rats.

Sixty-four male Sprague-Dawley rats were randomly assigned to one of eight treatment groups to determine whether vitamin E (VitE) could help protect the heart from oxidative stress induced by either dehydroepiandrosterone (DHEA) or exercise. Oxidative stress was indicated by lipid peroxidation [i.e., thiobarbituric acid-reactive substances (TBARS)] and two scavenger enzymes. VitE supplementation (250 IU VitE/kg of diet) was given to one-half of the rats. DHEA acetate (0.35 mol/kg body wt) was injected intraperitoneally to one-half of the animals while the others were injected with corn oil vehicle. All treatments lasted for 5 wk. Next, 32 rats were randomly assigned to run for 1 h on a motorized rodent treadmill at 21 m/min up a 12% grade and then were killed. The remaining rats were killed at rest. Exercise increased TBARS in heart independent of treatment (1.94 +/- 0.12 vs. 2.43 +/- 0.11 nmol/mg protein). VitE attenuated the amount of TBARS in heart when DHEA was given. DHEA significantly increased TBARS in heart. Total and selenium-dependent glutathione peroxidase activities in heart were unaffected by any treatment. DHEA increased catalase activity at rest. Exercise increased catalase activity (71.5 +/- 7.9 vs. 97.4 +/- 9.5 mu mol x min-1 x mg protein-1); however, when VitE was given, the response to exercise was attenuated (74.1 +/- 8.4 vs. 80.9 +/- 9.9 mu mol center dot min-1 x mg protein-1). These results suggest that aerobic exercise and DHEA are mild oxidative stressors on the heart and that VitE supplementation can be beneficial in attenuating these combined stressors on the heart.

Hypolipidemic agents alter hepatic mitochondrial respiration in vitro.

The direct effects of three different classes of structurally diverse hypolipidemic agents on respiration were studied in mitochondria isolated from donor Sprague-Dawley rats. Two classes of peroxisome proliferators (i.e. plasticizers and hypolipidemic hormones and drugs) and one class of peroxisome inhibitors (i.e. anti-psychotic drugs) were studied. The phthalate ester plasticizers dibutylphthalate, ethylhexanoic acid and di(2-ethylhexyl) adipate, the hypolipidemic hormones or drugs dehydro-epiandrosterone (DHEA), thyroxine (T4), triiodothyronine (T3), gemfibrozil, clofibrate and naphthoflavone, and the anti-psychotic drugs chlorpromazine, thioridazine and fluphenazine were studied. As the dose of the plasticizer dibutylphthalate increased from 8 to 200 mumol/l, there was a decrease (P < 0.05) in state 3 (+ADP) respiration and in the respiratory control ratio for both substrates tested. The anti-psychotic drug chlorpromazine decreased state 3 malate + pyruvate-supported respiration and increased state 3 succinate-supported respiration. As the concentration of all three anti-psychotic drugs increased, there was a linear increase in state 4 respiration (-ADP) and a decrease in the respiratory control ratio for both substrates tested. As the dose of the hypolipidemic agents DHEA, gemfibrozil and T4 increased, there was a linear reduction in state 3 malate + pyruvate-supported respiration. However, when succinate was used as the substrate to support respiration, only the thyroid hormones significantly decreased state 3 respiration. Gemfibrozil, T4 and T3 increased state 4 respiration, regardless of the substrate used. As the dose of clofibrate, gemfibrozil, and the thyroid hormones increased, there was a linear reduction in the respiratory control ratio for both substrates tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Inverse relationship between peroxisomal and mitochondrial beta-oxidation in HepG2 cells treated with dehydroepiandrosterone and clofibric acid.

A transformed human hepatoma cell line was examined to determine if it was an appropriate model system for studying the mechanism of action of two peroxisome proliferators that lower blood lipids. Cultures of HepG2 cells were exposed to four different concentrations of either the hypolipidemic drug, clofibric acid (CLO), or the adrenal steroid, dehydroepiandrosterone (DHEA). Activities of two peroxisomal enzymes, palmitoyl-CoA oxidase and catalase, and two mitochondrial enzymes, carnitine palmitoyl-CoA transferase and succinate-INT-reductase, were measured in CLO- and DHEA-treated cells. In general, as the concentration of these hypolipidemic agents increased from 0 to 1000 microM, the specific activities of peroxisomal palmitoyl-CoA oxidase and catalase increased, and mitochondrial carnitine palmitoyl-CoA transferase and succinate-INT-reductase decreased. The activity of lactate dehydrogenase was significantly higher in the medium of cultures exposed to the 500 and 1000 microM concentration of DHEA compared with the control cultures, indicating the cytotoxic effects of this steroid at millimolar levels in vitro. In summary, the peroxisomal proliferators, DHEA and CLO, inversely altered peroxisomal and mitochondrial beta-oxidation in HepG2 cultures, but not to the extent reported for rat hepatocytes in vitro. In vitro concentrations of DHEA greater than 500 microM adversely affected the viability of HepG2 cells. The results of this study suggest that beta-oxidation in this human hepatoma cell line may not be as sensitive to hypolipidemic agents as are primary cultures of rat hepatocytes.

Rates of beta-oxidation of fatty acids of various chain lengths and degrees of unsaturation in highly purified peroxisomes isolated from rat liver.

Highly purified peroxisomes were obtained from the liver of untreated rats, and rates of peroxisomal beta-oxidation were measured using fatty acyl-CoAs differing in chain length and degree of unsaturation. A 20-24-fold purification of peroxisomes, indicated by the specific activities of the marker enzymes catalase and urate oxidase, respectively, was obtained from crude liver homogenate using differential centrifugation techniques followed by a 30% Nycodenz gradient separation. The use of a 30% Nycodenz gradient in the final step of purification was extremely effective (e.g. 5.5-fold reduction) in removing lysosomal contamination. The rate of peroxisomal beta-oxidation with lauroyl-CoA (C12:0) as substrate was the highest of all fatty acyl-CoAs tested. Butyryl-CoA (C4:0) was not oxidized by purified peroxisomes. In general, as chain length of the fatty acyl-CoAs increased above 12 carbons, the rates of beta-oxidation decreased.

Vitamin E effects on indexes of lipid peroxidation in muscle from DHEA-treated and exercised rats.

Sixty-four male Sprague-Dawley rats were randomly assigned to one of eight treatment groups to determine the effects of vitamin E (VitE), dehydroepiandrosterone (DHEA), and exercise on antioxidant status in plasma and skeletal muscle. Indexes of oxidative stress were determined by measuring two markers of lipid peroxidation and the activity of two free radical scavenging enzymes. One-half of the rats had their diets supplemented with 250 IU VitE/kg of diet. One-half of the rats were injected with 0.35 mol/kg body wt ip of DHEA-acetate, whereas the others were injected with vehicle. All treatments lasted 5 wk. Before being killed, one-half of each treatments group of rats was randomly assigned to run for 1 h on a motorized rodent treadmill at 21 m/min up a 12% grade. The other rats remained rested before being killed. Exercise increased thiobarbituric acid-reactive substances (TBARS) and lipid hydroperoxides in plasma and TBARS in red slow-twitch and white fast-twitch muscles. VitE reduced the amount of lipid hydroperoxides and TBARS in plasma and TBARS in all three muscle fiber types. VitE also reduced glutathione peroxidase (GPX) activity in plasma and red fast-twitch muscle. DHEA increased indexes of oxidative stress in plasma and white fast-twitch muscle. DHEA reduced GPX activity in plasma but increased GPX activity in all three muscle fiber types. These results indicate that aerobic exercise is a mild oxidative stressor with DHEA exacerbating this response and that VitE helps diminish this effect in certain muscle fiber types.

Is dehydroepiandrosterone an antiobesity agent?

The steroid hormone intermediate, DHEA, has been proposed as a therapeutic agent for the treatment of obesity. Its effects on lipogenesis, substrate cycling, peroxisome proliferation, mitochondrial respiration, protein synthesis, and thyroid hormone function have been reported. The results of these studies suggest that the antiobesity function of DHEA is not simply one of inhibiting fat synthesis and deposition but is one of affecting a number of pathways that contribute to the maintenance of the isoenergetic state rather than the promotion of positive energy balance.

Vitamin E alters hepatic antioxidant enzymes in rats treated with dehydroepiandrosterone (DHEA).

The effects of vitamin E on hepatic antioxidant enzymes and plasma indicators of tissue damage were studied in rats treated with dehydroepiandrosterone (DHEA). Thirty-two male Sprague-Dawley rats were randomly allotted to one of four groups of eight rats each. Rats were treated with DHEA [100 mg/(kg body wt.d), i.p.], vitamin E (1 g/kg diet), or DHEA+vitamin E, or were untreated (controls) for 5 wk. Treatment with DHEA reduced (P < 0.05) weight gain, fat pad weight and carcass lipid concentration and increased carcass protein and ash concentration compared with control rats. The DHEA-treated rats had significantly lower concentrations of serum triglycerides and total cholesterol, yet greater amounts of liver lipid, than did control rats. Supplementation of DHEA-treated rats with vitamin E had no significant effect on weight gain, carcass composition or plasma metabolites compared with rats treated with DHEA alone. The rate of hepatic peroxisomal fatty acid oxidation in DHEA-treated rats was approximately 240% of that in control or vitamin E-supplemented rats. The specific activities of enzymes that defend against oxidative stress (e.g., glutathione reductase, glutathione transferase, catalase) or are indicators of tissue damage (e.g., alanine and aspartate aminotransferases) were all significantly higher in DHEA-treated rats compared with control rats. Supplementation of DHEA-treated rats with vitamin E generally reduced these indices of oxidative stress compared with rats treated with DHEA alone, suggesting that vitamin E may have a protective effect against potential oxidative damage associated with DHEA treatment.

In vitro studies on the effects of dehydroepiandrosterone and corticosterone on hepatic steroid receptor binding and mitochondrial respiration.

1. The in vitro effects of dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEA-S) and related steroids on glucocorticoid corticosterone (GC) binding in hepatic cytosol and hepatic mitochondrial respiration were examined in male BHE/cdb and Sprague-Dawley (SD) rats. 2. The Kd and the IC50 for GC binding in SD rats were 5- and 2-fold higher, respectively, than in BHE/cdb rats. 3. Hepatic cytosol from BHE/cdb rats bound six times more [3H]-GC to receptors than that from SD rats. 4. The percentage displacement and Bmax of GC for its receptors were similar for the two strains of rats. 5. DHEA and DHEA-S did not displace GC from its receptors. 6. DHEA and related non-sulfated steroids decreased state 3 mitochondrial respiration, respiratory control and oxidative phosphorylation capacity in a dose-dependent manner with malate + pyruvate as substrate.

Antiobesity effects of dehydroepiandrosterone are mediated by futile substrate cycling in hepatocytes of BHE/cdb rats.

This study investigated the hypothesis that dehydroepiandrosterone (DHEA) functions as an antiobesity agent by promoting energy wastage via hepatic substrate cycling in prediabetic male BHE/cdb rats. Weanling BHE/cdb rats fed a 65% glucose diet were injected intraperitoneally daily with either DHEA (0.35 mol/kg body wt) or vehicle (1 mL/kg body wt) for 7 wk. The DHEA treatment significantly (P less than 0.05) reduced body weight gain. The DHEA-treated rats had epididymal and retroperitoneal fat pads that were 40% and 66% lighter, respectively, than those of control rats. The residual carcasses (i.e., minus fat pads, liver and ingesta) of DHEA-treated rats contained a significantly lower percentage of fat than those of control rats. The DHEA treatment significantly reduced fasting serum glucose and triglycerides without affecting total or HDL cholesterol. Isolated hepatocytes from DHEA-treated rats converted 2.5 times as much [U-14C]glucose to 14CO2 and one-half as much alanine to glucose as did hepatocytes from control rats. The DHEA treatment increased the specific activities of malic enzyme and lactate dehydrogenase 4.0- and 1.8-fold, respectively. Hepatocytes from DHEA-treated rats tended (P less than 0.08) to have lower phosphoenolpyruvate carboxykinase activities than hepatocytes from control rats. These data suggest that DHEA treatment exerts some of its antiobesity and antidiabetic effects in prediabetic, lipemic BHE/cdb rats by promoting hepatic glucose oxidation and reducing gluconeogenesis.

Further studies on the effects of dehydroepiandrosterone on hepatic metabolism in BHE rats.

Two experiments were conducted to determine the effects of dehydroepiandrosterone (DHEA) on de novo fatty acid synthesis and oxygen consumption in BHE rats fed a 65% glucose diet. In Experiment 1, starved glucose-refed rats were injected ip with 120 mg of DHEA/kg body wt and hepatic de novo fatty acid synthesis was measured. DHEA-treated rats synthesized less fatty acid in response to starvation refeeding than nontreated rats. In Experiment 2, weanling rats were fed the glucose diet for 4 weeks. One-hundred twenty milligrams of DHEA/kg were injected daily for 3 weeks. Body weight gain, epididymal fat pad weight, and carcass lipid were less in the DHEA-treated rats than in the control rats. Mitochondrial respiration was less and liver size was greater in DHEA-treated rats compared with control rats. Whole body oxygen consumption was increased in DHEA-treated rats, suggesting that this steroid might be stimulating futile energy cycles involving lipid and protein turnover possibly through its effect on glucocorticoid and thyroid hormone function.

Studies of 5'-deiodinase activity in rats differing in hepatic lipogenic activity.

Studies of the relationship of hepatic 5'-deiodinase activity to hepatic lipogenic capacity were conducted. Rats of the Zucker, BHE, and Sprague-Dawley strains were used. BHE and Sprague-Dawley rats were starved and refed a 65% glucose diet, whereas lean and obese Zucker rats were fed a stock diet; the rats were thus different in hepatic lipogenic capacity. After hepatic 5'-deiodinase activity was determined, we found that rats genetically predisposed to increased hepatic lipogenesis had less deiodinase activity than rats without this genetic feature. The role of the interaction between the thyroid hormones and glucocorticoid in the activity of hepatic deiodinase was also studied. Adrenalectomized (ADX) or intact BHE and Sprague-Dawley rats were injected with saline, thyroxine, or triiodothyronine and either saline or glucocorticoid. The normal Sprague-Dawley rats made predictable adjustments to their deiodinase activity when their hormonal status was manipulated, whereas the BHE rats responded as though these manipulations were corrections rather than additions or deletions.

Differential effects of adrenalectomy and starvation-refeeding on hepatic lipogenic responses to dehydroepiandrosterone and glucocorticoid in BHE and Sprague-Dawley rats.

The interaction of rat strain and glucocorticoid status on the dehydroepiandrosterone (DHEA)-mediated decrease in response to starvation-refeeding was studied. DHEA treatment of intact starved-refed Sprague-Dawley rats resulted in significantly lower hepatic lipid and glucose-6-phosphate dehydrogenase activity than observed in non-DHEA-treated rats. When Sprague-Dawley rats were adrenalectomized (ADX), the response to DHEA treatment was potentiated. If glucocorticoid was replaced, there was some amelioration of the DHEA effect in the ADX rats. Responses to DHEA in BHE rats subjected to the above paradigms were different. The responses of starved-refed BHE rats to DHEA were more pronounced and it appeared that glucocorticoid replacement was not as effective in overcoming DHEA in these rats. Thus, it appears that the comparative inhibition of the glucocorticoid-mediated response to starvation-refeeding by DHEA is strain dependent.

Strain differences in the dose-response curves of adrenalectomized, starved-refed rats to dehydroepiandrosterone (DHEA).

The effects of adrenalectomy and dehydroepiandrosterone (DHEA) doses (0, 15, 30, 60, 120 and 240 mg/kg/day ip) on hepatic enzyme activity and lipid content and on the amount of epididymal fat pad lipid were studied in starved-refed BHE and Sprague-Dawley rats. BHE rats had significantly greater relative liver size, glucose-6-phosphate dehydrogenase (G6PD) and malic enzyme (ME) activities, and percentage liver lipid but less epididymal fat pad lipid than Sprague-Dawley rats. Adrenalectomized (ADX) rats consumed significantly less food, gained less weight per day, and had less lipid in their livers and fat pads than intact rats. As the level of DHEA increased from 0 to 240 mg/kg/day there was a significant linear decrease in average daily weight gain, food intake, G6PD activity, and percentage liver lipid. At the 15 mg/kg/day dose, G6PD activity was significantly reduced without reductions in the other parameters measured. At the 120 mg/kg/day dose, however, weight gain, food intake, G6PD activity, and percentage liver lipid were significantly lower than that of the controls. At this dose DHEA treatment reduced food intake by 17% whereas it diminished average daily weight gain and G6PD activity by 30 and 56%, respectively. The 240 mg/kg/day dose of DHEA significantly reduced food intake, weight gain, liver lipid, G6PD activity, and ME activity. Intact and ADX BHE rats reduced their G6PD activity and liver lipid more rapidly than Sprague-Dawley rats as the level of DHEA administered increased. ADX Sprague-Dawley rats receiving DHEA had greater liver lipid content and enzyme activity than their intact counterparts whereas the reverse situation was true in BHE rats. These data indicate that the effect of DHEA on body weight gain, food intake, and hepatic and peripheral adiposity are dependent on the strain of rat, the adrenal status, and the DHEA dose.