The stimulating effect of 3′,5′-(cyclic)adenosine monophosphate and lipolytic hormones on 3-O-methylglucose transport and Ca release in adipocytes and skeletal muscle of the rat

(1) In order to assess the possible role of 3′,5′-(cyclic)adenosine monophosphate (cAMP) in the control of glucose transport, the effect of the nucleotide or agents known to increase its intracellular concentration on sugar transport or ⁴⁵Ca²⁺ washout were characterized in epididymal fat pads, free fat cells and soleus muscles of the rat. (2) When added to the incubation medium, cAMP (0.1–2.0 mM) stimulated 3-O-[¹⁴C]methylglucose washout from fat pads. This effect was abolished by cytochalasin B, and additive to that induced by submaximal (10–25 μU/ml), but not by supramaximal (10 mU/ml) concentrations of insulin. (3) cAMP (2 mM) stimulated the conversion of [U-¹⁴C]glucose into CO₂ and triacylglycerols. This effect was additive to that of insulin (100 μU/ml). (4) ACTH, glucagon, adrenaline, noradrenaline and salbutamol, which are all known to increase the cAMP content of adipose tissue, stimulated the washout of 3-O-[¹⁴C]methylglucose and ⁴⁵Ca²⁺ from preloaded fat pads. The fractional losses of the two isotopes were significantly correlated (P < 0.001, r = 0.73). (5) In free fat cells, adrenaline (10⁻⁶ M) and salbutamol (10⁻⁵ M) stimulated the uptake of 3-O-[¹⁴C]methylglucose, and salbutamol (10⁻⁵ M) did not interfere with the stimulating effect of insulin (25 μU/ml) on sugar uptake. (6) In rat soleus muscles, adrenaline and salbutamol produced a dose-dependent stimulation of the washout of 3-O-[¹⁴C]methylglucose and ⁴⁵Ca²⁺. The effect of adrenaline on sugar efflux was abolished by propranolol. (7) It is concluded that the activation of the glucose transport system by insulin is unlikely to be mediated by a drop in the cellular concentration of cAMP. An increase in cAMP brought about by β-adrenoceptor agonists or lipolytic hormones may induce a mobilization of calcium ions from cellular pools into the cytoplasm, which in turn leads to the activation of the glucose transport system demonstrated in the present as well as in several earlier studies.     

Direct Action of Insulin on Plasma Membrane ATPase Activity in Human Lymphocytes

LITTLE is known about the effects of insulin on lymphocytes. Helmreich and Eisen¹ concluded that it has insignificant effects, but others^2–5 have made a case for a role in inflammatory and immunological responses. We^6,7 have demonstrated that noradrenaline enhances the uptake of both glucose and potassium by lymphocytes, as does insulin in several tissues. We have associated this action of noradrenaline with a direct effect on membrane adenosine triphosphatase (ATPase) activity⁷. The observation⁸ that insulin bound to ‘Sepharose’ polymers enhances glucose transport while in contact only with the plasma membrane indicated that insulin might have a direct action similar to that of noradrenaline on membrane ATPase. The observations reported here show that insulin stimulates ATPase activity and glucose uptake in the lymphocyte and suggest a relationship between membrane ATPase activity and glucose transport.     

Biological effects of sulphated insulin in adipocytes and hepatocytes

Summary The binding affinity of sulphated insulin compared with unmodified, neutral insulin has been reported to be approximately four times lower in human and rat adipocytes but over twenty times lower in rat hepatocytes. In the present study the biological action of sulphated insulin was assesed in rat hepatocytes and human and rat adipocytes. To achieve half-maximal stimulation of fatty acid synthesis in rat hepatocytes about twenty one times higher concentrations of sulphated than neutral insulin were required (15.07±5.50 vs 0.71±0.34 nmol/l), this ratio being similar to the ratio of binding affinity in rat hepatocytes. In human adipocytes, half-maximal stimulation of initial rates of glucose uptake was observed at 11.6±5.1 vs 2.9±1.3 pmol/l for sulphated and neutral insulin respectively, and half-maximal inhibition of lipolysis at 31.0±13.5 vs 7.3+2.5 pmol/I respectively. These data are consistent with the four-fold lower binding affinity of sulphated insulin to human adipocytes. However, in rat adipocytes the biological potency of sulphated insulin was found to be much lower than anticipated from the binding data, half-maximal stimulation of initial rates of glucose uptake being observed at 757±299 vs 35±13 pmol/l respectively and half-maximal inhibition of lipolysis at 35.9±12.1 vs 1.5±0.5 pmol/l respectively. Thus, in rat adipocytes, approximately 22 times the concentration of sulphated insulin was required to achieve equivalent biological effect. A discrepancy between binding affinity and biological action with respect to sulphated insulin was identified in rat adipocytes but not human adipocytes nor rat hepatocytes suggesting differences in the binding-action linkage in these cells.     

Measurements of glycolytic flux rate in brown adipocytes. Effects of insulin, noradrenaline and streptozotocin diabetes

Glycolytic flux was estimated in brown adipocytes by [3-3H]-glucose detritiation. Without insulin the process was slightly stimulated by noradrenaline or palmitate. Insulin stimulated glucose detritiation by 4-fold. Noradrenaline stimulated the process in the presence of insulin and synergism between these hormones was observed. Palmitate did not stimulate glucose detritiation in the presence of insulin suggesting that the effect of noradrenaline is not secondary to stimulation of lipolysis. With insulin, cells from streptozotocin-diabetic rats showed lower rates of glucose detritiation. Extracts from these cells also had lower maximum activities of phosphofructokinase.     

Insulin stimulation of glucose transport and metabolism in a human Wilms' tumor-derived myoblast-like cell Line: Modulation of hormone effects by glucose deprivation

The effects of insulin and glucose on parameters of metabolism were investigated in myoblast-like (MBL) cells, a human myoblast-like cell line derived from a Wilms' tumor. Insulin responses were studied after 4 hr pre-incubation in serum free media, with or without 5 mM glucose. Insulin was added during the last 2 hr. Glucose starvation markedly increased basal glucose transport (measured as 2-deoxyglucose uptake) as well as the net uptake of [¹⁴C]glucose and [¹⁴C]glucose incorporation into glycogen. Insulin stimulated net glucose uptake and incorporation into glycogen in a dose-dependent manner in glucose-fed and starved cells. These insulin responses were markedly enhanced in glucose-starved cells. Insulin accelerated 2-deoxyglucose transport in glucose-fed cells but did not further stimulate basal glucose transport in glucose-deprived cells. Insulin increased the incorporation of [³H]leucine into protein in glucose-fed or -starved MBL cells equally. The dose of insulin required for half-maximal insulin responses was similar for all parameters studied. Cycloheximide did not prevent the increased basal glucose incorporation in glucose-starved cells, but markedly inhibited the insulin response, while in glucose-fed cells, cycloheximide stimulated basal glucose incorporation. We conclude that MBL cells resemble fibroblasts in their insulin-independent stimulation of glucose transport in response to glucose-deprivation; when provided with glucose, they respond to insulin like fibroblasts. However, after brief glucose-starvation, the stimulated glucose transport system is no longer insulin-responsive in MBL cells, while pathways leading to the synthesis of macromolecules demonstrate preserved or enhanced stimulation by insulin, suggesting that these cells may serve as models to study the regulation of receptor-response coupling by the metabolic milieu.     

Alterations in response of rat white adipocytes to insulin, noradrenaline, corticotropin and glucagon after adrenalectomy. Correction of these changes by adenosine deaminase.

1. Adipocytes isolated from rats 6--9 days after adrenalectomy had significantly increased sensitivity to insulin action against noradrenaline-stimulated lipolysis. In the presence of adenosine deaminase there was no significant difference in insulin sensitivity between cells from adrenalectomized and sham-operated rats. 2. Adipocytes from adrenalectomized rats had decreased lipolytic responses to all concentrations of noradrenaline and glucagon tested and a decreased lipolytic response to low but not high concentrations of corticotropin. There was no difference in lipolytic response to theophylline after adrenalectomy. Adenosine deaminase corrected the differences in response to noradrenaline and glucagon resulting from adrenalectomy. 3. In the presence of adenosine deaminase rates of lipolysis, after stimulation by high concentrations of noradrenaline, glucagon, corticotropin or theophylline, were the same in cells from adrenalectomized or sham-operated rats. 4. These findings and previously reported effects of adenosine and adrenalectomy on adipocyte function are discussed. It is proposed that changes in adipocyte hormone responsiveness after adrenalectomy may result from changes in adenosine metabolism or release.     

Insulin action on adipocytes. Evidence that the anti-lipolytic and lipogenic effects of insulin are mediated by the same receptor.

1. The dose-response relationships of insulin stimulation of lipogenesis and inhibition of lipolysis were studied simultaneously by using rat adipocytes to determine whether these different effects of insulin are mediated through the same or different sets of receptors. 2. The sensitivity (defined as the concentration of insulin required to produce a half-maximal effect) of the stimulated lipogenic response to insulin was not significantly different from the sensitivity of the anti-lipolytic response to insulin. The addition of different adrenaline and glucose concentrations did not alter the half-maximal concentration of insulin required to inhibit lipolysis. 3. The specificities of the lipogenic and antilipolytic responses were studied by using insulin analogues. The sensitivities of the lipogenic and anti-lipolytic responses were the same for five chemically modified insulins and hagfish insulin, which have potencies compared with bovine insulin of between 3 and 90%. 4. Starving rats for 48h significantly increased the sensitivities of both the antilipolytic and lipogenic responses to insulin, but the changes in the sensitivities of both lipogenesis and anti-lipolysis returned to that of fed rats. 5. We conclude that insulin stimulates lipogenesis and inhibits lipolysis over the same concentration range. These observations provide powerful evidence that the different effects of insulin are mediated through the same set of receptors.     

Sensitivity of glucose uptake and lipolysis of white adipocytes of the rat to insulin and effects of some metabolites.

1. Insulin increased glucose uptake and inhibited lipolysis in white adipocytes of the rat over the same concentration range of the hormone: the half-maximal effects were observed at approx. 10 microunits of insulin/ml. Thus, contrary to previous reports, no difference in sensitivity of the two processes to insulin could be found, which suggests that both these effects of insulin are important in increasing the rate of glucose utilization after a meal. 2. Adenosine deaminase, which lowers the concentration of adenosine in the incubation medium, decreased the sensitivity of both processes (lipolysis and glucose uptake) to insulin: this suggests that adenosine increases the sensitivity of both processes. Similarly, lactate and 3-hydroxybutyrate increased the sensitivity of both processes (to the same extent) to insulin. It is suggested that this increased sensitivity will improve the response (of adipose tissue) to insulin on refeeding after a prolonged period of starvation (when the hydroxybutyrate concentration is high), and after a short burst of exercise, when the blood lactate concentration is high and when large amounts of glucose are produced from lactate via gluconeogenesis in the liver.     

Impaired insulin-mediated inhibition of lipolysis and glucose transport with aging

Regulation of hormone action with aging has been extensively studied; adipocytes provide an interesting model for some of these questions. We have compared the ability of insulin to stimulate glucose uptake and suppress lipolysis in adipocytes isolated from two month and twelve month-old rats. The ability of insulin to stimulate maximal glucose transport was decreased in adipocytes from the older rats (P less than 0.001); as well, insulin's EC50 was also higher (P less than 0.01) in these cells. Furthermore, these defects were present when insulin-stimulated glucose transport was measured in the presence or absence of adenosine deaminase which metabolizes endogenously released adenosine. Endogenously released adenosine is a stimulator of glucose transport and an inhibitor of lipolysis. Maximal suppression of isoproterenol-induced lipolysis by insulin was similar when adipocytes isolated from the two age groups were incubated in the absence of adenosine deaminase. However, maximal insulin-mediated suppression of lipolysis was found to be significantly decreased (P less than 0.001) in adipocytes isolated from older rats when the experiments were done in the presence of adenosine deaminase; also, insulin's EC50 was increased in these cells under these conditions (P less than 0.001). These results emphasize the importance of the adenosine receptor in modulating the response of isolated adipocytes to insulin, particularly for lipolysis, and document the presence of age-associated defects in insulin regulation of both glucose transport and lipolysis.     

Affinity change of the adipocyte receptor fails to alter insulin-stimulated glucose transport

Occupancy increased the affinity of the insulin receptor of the adipocyte. During the affinity change the half-maximal sensitivity of glucose transport to insulin stimulation was unaltered. Decreased maximum response of transport only occurred after the affinity change. There was not a simple relationship between receptor affinity and insulin stimulation of glucose transport in the adipocyte.     

Adenosine regulates the release of adrenocorticotropic hormone (ACTH) from cultured anterior pituitary cells

We have recently shown the presence of adenosine receptors coupled to adenylate cyclase in anterior pituitary and in the present studies we have investigated the effects of adenosine on ACTH release. The R-site specific analogs of adenosine such as N-Ethylcarboxamide adenosine (NECA), L-N⁶-phenylisopropyl adenosine (PIA), 2-chloro-adenosine (2-Cl-Ado) all stimulated ACTH release in a dose-dependent manner. NECA was the most potent analog and stimulated ACTH release by about 170% with an apparent Ka of 0.1 µM, whereas PIA and 2-Cl-Ado were less potent and stimulated the release by about 110% and 125% with an apparent Ka of 0.2 and 0.4 µ-M respectively. The stimulation of ACTH release by NECA was inhibited by 3-isobutyl-1-methylxanthine (IBMX). On the other hand, adenosine deaminase (ADA) treatment of the cells also stimulated ACTH release as well as adenylate cyclase activity by about 2-fold, suggesting that endogenous adenosine plays an inhibitory role in the release of ACTH. Other agents, such as corticotropin-releasing factor (CRF), vasoactive intestinal peptide (VIP) and forskolin (FSK) also stimulated ACTH release from these cells. In addition, the stimulation by an optimal concentration of NECA was almost additive with maximal stimulation caused by VIP and FSK. These data suggest that adenosine modulates ACTH release from anterior pituitary through its interaction with adenosine receptors coupled to adenylate cyclase.Abbreviations NECA N-Ethylcarboxamideadenosine - PIA L-N⁶-Phenylisopropyladenosine - 2-Cl-Ado 2-chloroadenosine - FSK Forskolin - VIP Vasoactive Intestinal Peptide - CRF Corticotropin Releasing Factor - ADA Adenosine Deaminase - IBMX 3-Isobutyl-1-methylxanthine     

Effects of phorbol esters on insulin receptor function and insulin action in hepatocytes: evidence for heterogeneity

We investigated the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator on insulin receptors and insulin action in freshly isolated and primary cultures of rat hepatocytes. PMA (1 x 10^–7 M) did not alter insulin receptor numbers or affinity either acutely or chronically but within 60 minute inactivated insulin stimulated tyrosine kinase of the insulin receptor. PKC activation inhibitied insulin (1 x 10^–7M) stimulation of glycogen and lipid synthesis with a decrease or no change in basal glycogenesis and lipogenesis respectively. However, PKC activation did not alter insulin stimulated or basal amino acid transport even though PCK activation inhibited insulin stimulation of the insulin. receptor tyrosine kinase. Thus, within one tissue, PKC activation has differential effect on insulin action depending on which pathway is examined. Furthermore, insulin stimulation of the insulin receptor tyrosine kinase may not be a necessary step for all insulin signaling pathways.     

Insulin sensitivity of rates of glycolysis and glycogen synthesis in soleus,stripped soleus,epitrochlearis, and hemi-diaphragm muscles isolated from sedentary rats

The effect of insulin concentrations on the rates of glycolysis and glycogen synthesis in four different in vitro rat muscle preparations (intact soleus, stripped soleus, epitrochlearis, and hemi-diaphragm) were investigated: the concentrations of insulin that produced half-maximal stimulation of the rates of these two processes in the four muscle preparations were similar - about 100 muunits/ml. This is at least 10-fold greater than the concentration that produced half-maximal inhibition of lipolysis in isolated adipocytes. Since 100 muunits/ml insulin is outside the normal physiological range in the rat, it is suggested that, in vivo, insulin influences glucose utilization in muscle mainly indirectly, via changes in the plasma fatty acid levels and the 'glucose/fatty acid cycle'. Consequently the view that insulin stimulates glucose utilization in muscle mainly by a direct effect on membrane transport must be treated with caution.     

Effect of endothelin-1 on lipolysis in rat adipocytes

Objective : To explore the role of endothelin‐1 (ET‐1) on lipid metabolism, we examined the effect of ET‐1 on lipolysis in rat adipocytes. Research Methods and Procedure : Adipocytes isolated from male Sprague‐Dawley rats, weighing 400 to 450 grams, were incubated in Krebs‐Ringer buffer with or without 10^?7 M ET‐1 for various times or with various concentrations of ET‐1 for 4 hours; then glycerol release into the incubation medium was measured. In addition, selective ET_AR and ET_BR blockers were used to identify the ET receptor subtype involved. We also explored the involvement of cyclic adenosine monophosphate (cAMP) in ET‐1‐stimulated lipolysis using an adenylyl cyclase inhibitor and by measuring changes in intracellular cAMP levels in response to ET‐1 treatment. To further explore the underlying mechanism of ET‐1 action, we examined the involvement of the extracellular signal‐regulated kinase (ERK)‐mediated pathways. Results : Our results showed that ET‐1 caused lipolysis in rat adipocytes in a time‐ and dose‐dependent manner. BQ610, a selective ET_AR blocker, blocked this effect. The adenylyl cyclase inhibitor, 2′, 5′‐dideoxyadenosine, had no effect on ET‐1‐stimulated lipolysis. ET‐1 did not induce an increase in intracellular cAMP levels. In addition, ET‐1‐induced lipolysis was blocked by inhibition of ERK activation using PD98059. Coincubation of cells with ET‐1 and insulin suppressed ET‐1‐stimulated lipolysis. Discussion : These findings show that ET‐1 stimulates lipolysis in rat adipocytes through the ET_AR and activation of the ERK pathway. The underlying mechanism is cAMP‐independent. However, this non‐conventional lipolytic effect of ET‐1 is inhibited by the anti‐lipolytic effect of insulin.     

Effects of insulin and norepinephrine on glucose transport and metabolism in rat brown adipocytes. Potentiation by insulin of norepinephrine-induced glucose oxidation

Glucose is an important fuel for rat brown adipose tissue in vivo and its utilization is highly sensitive to insulin. In this study, the different glucose metabolic pathways and their regulation by insulin and norepinephrine were examined in isolated rat brown adipocytes, using [6-14C]glucose as a tracer. Glucose utilization was stimulated for insulin concentrations in the range of 40-1000 microU/ml. Furthermore, the addition of adenosine deaminase (200 mU/ml) or adenosine (10 microM) did not alter insulin sensitivity of glucose metabolism. The major effect of insulin (1 mU/ml) was a respective 7-fold and 5-fold stimulation of lipogenesis and lactate synthesis, whereas glucose oxidation remained very low. The 5-fold stimulation of total glucose metabolism by 1 mU/ml of insulin was accompanied by an 8-fold increase in glucose transport. In the presence of norepinephrine (8 microM), total glucose metabolism was increased 2-fold. This was linked to a 7-fold increase of glucose oxidation, whereas lipogenesis was greatly inhibited (by 72%). In addition, norepinephrine alone did not modify glucose transport. The addition of insulin to adipocytes incubated with norepinephrine, induced a potentiation of glucose oxidation, while lipogenesis remained very low. In conclusion, in the presence of insulin and norepinephrine glucose is a oxidative substrate for brown adipose tissue. However the quantitative importance of glucose as oxidative fuel remains to be determined.     

Overexpression of lactate dehydrogenase A attenuates glucose-induced insulin secretion in stable MIN-6 β-cell lines

Since islet β-cells express little

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-lactate dehydrogenase (LDH) activity, we have examined the effects on these cells of LDH overexpression. In mock-transfected MIN6 β-cells, LDH activity was 38 nmol/min/mg protein, and 30 mM glucose stimulated secretion 10.4-fold. In two MIN6 cell clones stably overexpressing human LDH-A cDNA, insulin secretion was stimulated only 2.7- and 2.1-fold by high glucose. K⁺-stimulated insulin secretion was unaffected, and leucine stimulation enhanced, by LDH-A overexpression. LDH-A-overexpressing clones displayed unaltered activities of hexokinase, glucokinase, and malate dehydrogenase, slightly elevated plasma membrane lactate transport activity, and lowered insulin content. Low LDH activity would therefore appear important in β-cell glucose sensing.     

Regulation of fructose 2,6-bisphosphate concentration in white adipose tissue.

Injection of insulin to fed rats diminished the concentration of fructose 2,6-bisphosphate in white adipose tissue. Incubation of epididymal fat-pads or adipocytes with insulin stimulated lactate release and sugar detritiation and also decreased fructose 2,6-bisphosphate concentration. Such a decrease was, however, not observed in fat-pads from starved or alloxan-diabetic rats. Incubation of adipocytes from fed rats with various concentrations of glucose or fructose led to a dose-dependent rise in fructose 2,6-bisphosphate which correlated with lactate output and detritiation of 3-3H-labelled sugar. In adipocytes from fed rats, palmitate stimulated the detritiation of [3-3H]glucose without affecting lactate production and fructose 2,6-bisphosphate concentration. Incubation of epididymal fat-pads from fed rats in the presence of antimycin stimulated lactate output but decreased fructose 2,6-bisphosphate concentration. Changes in lipolytic rates brought about by noradrenaline, insulin, adenosine and corticotropin in adipocytes from fed rats were not related to changes in fructose 2,6-bisphosphate or to rates of lactate output. In fed rats, the activity of 6-phosphofructo-2-kinase was not changed after treatment of adipocytes with insulin, noradrenaline or adenosine. It is suggested that the decrease in fructose 2,6-bisphosphate concentration observed after insulin treatment can be explained by the increase in sn-glycerol 3-phosphate, an inhibitor of 6-phosphofructo-2-kinase.     

Glycogen synthesis stimulation by adenylate cyclase inhibition in rat epididymal adipocytes

The effects of adenylate cyclase inhibition on the transport of glucose and fructose and their incorporation into glycogen were investigated in order to assess the extent to which lowered cAMP levels can take part in the various components of glycogen synthesis regulation in isolated rat epididymal adipocytes. The dose-response characteristics of (R)-N-(2-phenylisopropyl)adenosine (PIA), a potent and specific adenylate cyclase inhibitor, on glycogen synthesis were compared with those effectively inhibiting lipolysis, a measure of functional cAMP levels. PIA had no effect on basal glucose or fructose transport but stimulated glucose and fructose incorporation into glycogen. Their respective incorporation was 10 and 69% of that achieved in the presence of insulin. These effects of PIA were shown to be in part the result of increased glycogen synthase I activity. PIA was 20% as effective as insulin in this action. Thus, were insulin to lower cAMP levels and/or inhibit cAMP-dependent protein kinase, this action would be irrelevant to glucose transport but would contribute to the stimulation of glycogen metabolism. However, an additional mechanism(s) involving neither increased glucose transport nor lowered cAMP levels is required to account for the full action of insulin. Fat cells in the absence of medium glucose and in the presence of 10(-7) M PIA and adenosine deaminase constitute a system functionally depleted of cAMP where this mechanism can be studied in isolation.     

Effects of theophylline on insulin receptors and insulin action in the adipocyte

Summary The effects of theophylline on insulin receptors and insulin action in isolated rat adipocytes were studied. Theophylline reduced insulin binding by a decrease of receptor affinity. As concentration-response curves revealed, the effect was paralleled by a reduction of the cellular ATP content. Basal as well as insulin-stimulated glucose transport (2-deoxyglucose and 3-O-methylglucose uptake) were inhibited by much smaller theophylline concentrations (0.15–0.6 mM ) than those necessary to reduce insulin binding and to lower ATP levels (1–4.8 mM), or to stimulate lipolysis (0.3-2.4 mM). Insulin fully antagonized the effect of theophylline on lipolysis but failed to reverse the inhibition of glucose transport completely. The results suggest that (a) theophylline impairs insulin action at a post-receptor level and, at higher concentrations, by a decrease of receptor binding, (b) the reduction of insulin receptor affinity probably reflects ATP depletion of the adipocyte, and (c) the xanthine inhibits glucose transport independently from its effects on lipolysis.     

Regulation of Lipolysis and Lipoprotein Lipase after Weight Loss in Obese,Postmenopausal Women

Objective: To test the hypothesis that the greater β‐adrenoceptor (β‐AR)‐stimulated lipolysis and sensitivity (half‐maximal lipolytic response) in abdominal (ABD) adipocytes, greater gluteal (GLT) adipose tissue‐lipoprotein lipase (AT‐LPL) activity, and dyslipidemia associated with obesity in older women are modifiable by weight loss (WL) and are not due to menopause or aging. Research Methods and Procedures: The metabolic effects of 6 months of hypocaloric diet and low‐intensity walking WL program on the regional regulation of in vitro lipolysis and AT‐LPL activity in subcutaneous ABD and GLT adipocytes were measured in 34 obese (48.7 ± 0.7% body fat, mean ± SE) postmenopausal (59 ± 1 years) white women. Results: The lipolytic responsiveness to the β‐AR agonist isoproterenol and basal lipolysis in the presence of 1 U/mL adenosine deaminase‐uninhibited (lipolysis) were greater (p < 0.01) in ABD than GLT adipocytes before and after WL, but there were no regional differences in postreceptor (dibutyryl 3′, 5′‐cyclic adenosine monophosphate)‐stimulated lipolysis. β‐AR sensitivity was greater in ABD than GLT adipocytes before (p < 0.01) but not after WL. Regional AT‐LPL did not change after WL, but the change in the activity of ABD (but not GLT) AT‐LPL correlated with the baseline adenosine deaminase‐uninhibited lipolysis (r = 0.38, p = 0.03). There were no relationships between the declines in plasma triglyceride or increases in high‐density lipoprotein cholesterol associated with WL and the changes in regional fat cell metabolism. Discussion: Thus, despite improving lipoprotein lipid profiles in obese, postmenopausal women, WL does not affect the regulation of regional fat metabolism, and a greater tonic inhibition of basal lipolysis by endogenous adenosine may increase the activity of AT‐LPL after WL and predispose older women to develop ABD adiposity.