A comparison of the assessment and management of cardiometabolic risk in patients with and without type 2 diabetes mellitus in Canadian primary care.

AIM: To investigate the cardiometabolic risk (CMR) assessment and management patterns for individuals with and without type 2 diabetes mellitus (T2DM) in Canadian primary care practices. METHODS: Between April 2011 and March 2012, physicians from 9 primary care teams and 88 traditional non-team practices completed a practice assessment on the management of 2461 patients >40 years old with no clinical evidence of cardiovascular disease and diagnosed with at least one of the following risk factor-T2DM, dyslipidaemia or hypertension. RESULTS: There were 1304 individuals with T2DM and 1157 without. Pharmacotherapy to manage hyperglycaemia, dyslipidaemia and hypertension was widely prescribed. Fifty-eight percent of individuals with T2DM had a glycated haemoglobin (HbA1c) ≤7.0%. Amongst individuals with dyslipidaemia, median low-density lipoprotein cholesterol (LDL-C) was 1.8 mmol/l for those with T2DM and 2.8 mmol/l for those without. Amongst individuals with hypertension, 30% of those with T2DM achieved the <130/80 mmHg target, whereas 60% of those without met the <140/90 mmHg target. The composite glycaemic, LDL-C and blood pressure (BP) target outcome was achieved by 12% of individuals with T2DM. Only 17% of individuals with T2DM and 11% without were advised to increase their physical activity. Dietary modifications were recommended to 32 and 10% of those with and without T2DM, respectively. CONCLUSIONS: Patients at elevated CMR were suboptimally managed in the primary care practices surveyed. There was low attainment of recommended therapeutic glycaemic, lipid and BP targets. Advice on healthy lifestyle changes was infrequently dispensed, representing a missed opportunity to educate patients on the long-term benefits of lifestyle modification.

Dietary cholesterol and other nutritional considerations in people with diabetes.

BACKGROUND: Nutrition therapy is an integral component of lifestyle intervention and self-management of people with diabetes. The goals of nutrition therapy are to optimise or maintain quality of life, physiological and mental health, and to prevent and treat acute and long-term complications of diabetes, the associated comorbid conditions and concomitant disorders. Monitoring dietary cholesterol consumption and salt intake are important nutritional aspects to lower the risk for and treatment of cardiovascular disease and hypertension. AIMS: To evaluate the role of nutritional therapy and notably the effect of egg consumption on cardiovascular disease (CVD) risk in people with diabetes. METHODOLOGY: Literature review of nutritional therapy and clinical studies on egg consumption and CVD risk for people with diabetes were conducted and appraised. RESULTS: The Harvard Egg Study on two large prospective US cohorts found that eating one or more eggs a day had no adverse effects on lipid profile or cardiovascular disease risk in men or women. Similar findings were observed in the NHANES-I and Physicians' Health Study. The only exception was people with diabetes, where CVD was increased with eating more than one egg per day. CONCLUSIONS: Consumption of one or more eggs per day is associated with an elevated risk of coronary heart disease in people with diabetes. The mechanism for this association remains unknown but should be explored in randomised clinical trials.

Release of mitogenic factors by cultured preadipocytes from massively obese human subjects.

In this study, possible paracrine factors in adipose tissue from lean and obese subjects were sought. Conditioned media were prepared by incubation in alpha minimum essential medium of adipocyte precursors derived from lean and massively obese subjects. Adipocyte-precursor-derived conditioned media from the obese stimulated replication of cultured rat perirenal adipocyte precursors by about fourfold over control. The effect of media conditioned by precursors derived from lean subjects was much less evident. The mitogenicity of conditioned media was abolished by trypsin, indicating the protein nature of the mitogenic factor(s). Sephacryl S-200 chromatography of adipocyte-precursor-derived conditioned media from obese subjects revealed one major active fraction with molecular masses in the range of 25,000-40,000. Our results demonstrate that adipocyte precursors derived from massively obese subjects release factors mitogenic on cultured rat adipocyte precursors. These principles may act as paracrine factors contributing to the development of the adipocyte hyperplasia characteristic of massive obesity.

Induction of preadipocyte differentiation by mature fat cells in the rat.

In this study we investigated the influence of mature adipocytes, derived from rat adipose tissue, on the replication and differentiation of preadipocytes in primary culture. Mature fat did not inhibit preadipocyte replication within the 6-d period studied. Preadipocyte differentiation, as assessed by both cytoplasmic lipid accretion and an increase in glycerophosphate dehydrogenase (GPDH) activity, was significantly stimulated by the presence of mature fat tissue or isolated adipocytes. The proportion of cells containing visible lipid droplets by oil red O staining was 47 +/- 10 to 58 +/- 10% (depending on the site of origin of the preadipocytes) when cocultured with mature fat compared with less than 1 to 2 +/- 1% when cultured in medium alone, while GPDH activity was 344 +/- 9 compared with 43 +/- 3 nM NADH/min per mg protein, respectively. This effect was not due to release of triacylglycerols from damaged adipocytes. Fatty acids added to the medium promoted lipid accumulation but did not stimulate a rise in GPDH activity. We concluded that mature adipocytes may release factor(s) that promote preadipocyte differentiation (and maturation).

Generation and characterization of a proton microbeam for experimental radiosurgery.

A proton microbeam has been developed to support various research endeavors. Test subjects may be irradiated from any angle with respect to the vertical because the beamline is contained within a rotating gantry used for human patients. Converting from the treatment to experimental arrangement is quick and straightforward as is the reverse. Using a series of collimators, the final beam diameter at the surface of the subject is 1 mm. The depth from the surface to the Bragg peak in water is 15 mm. Fluence distributions perpendicular to the beam axis were determined by scanning radiographic film exposed at various depths with a scanner having a pixel size of 84.7 microm. The depth dose integrated over the beam area was measured using a parallel plate ionization chamber. Central axis depth doses were calculated by multiplying the ionization chamber signal by the ratio of film doses for the central axis pixels to the integrated beam doses at each depth. A Faraday cup was used to confirm the dose at the surface while TLDs, diodes, and film were used to verify the dose at depth. The usefulness of this beamline for experimental situations has been demonstrated in a feline neurological study. The dosimetry techniques are useful for narrow beams such as used for functional radiosurgery treatments of humans.

Development of insulin resistance in the JCR:LA-cp rat: role of triacylglycerols and effects of MEDICA 16.

The JCR:LA-cp rat develops an extreme obese/insulin-resistant syndrome such that by 12 weeks of age, there is no longer any insulin-mediated glucose turnover. At 4 weeks of age, obese and lean rats have essentially identical basal and insulin-mediated glucose uptake in skeletal muscle. By 8 weeks of age, however, the obese rats no longer exhibit such intake. Plasma insulin concentrations in the normal fed state show only small increases up to 4 weeks, with a rapid rise to a marked hyperinsulinemia thereafter, with an age at half-development of 5.5 weeks. Plasma triacylglycerol concentrations in fed obese rats are elevated at 3 weeks and rise rapidly thereafter. The triacylglycerol content of skeletal muscle is significantly elevated in the obese rats at 4 weeks of age. Histological examination of Oil Red O-stained muscle tissue and transmission electron microscopy shows the presence of intracellular lipid droplets. Treatment with the potent triacylglycerol-lowering agent MEDICA 16 (beta,beta'-tetramethylhexadecanedioic acid) from 6 weeks of age reduces plasma lipids markedly, but it reduces body weight and insulin resistance only modestly. In contrast, treatment with MEDICA 16 from the time of weaning at 3 weeks of age results in the normalization of food intake and body weight to over 8 weeks of age. The development of hyperinsulinemia is also delayed until 8.5 weeks of age, and insulin levels remain strongly reduced. Plasma triacylglycerol concentrations remain at the same level as in lean rats, and neither an elevated muscle triacylglycerol content nor intracellular lipid droplets are found at 4 weeks of age. The results indicate that insulin resistance develops in the young animals and is not directly due to a genetically determined defect in insulin metabolism. The mechanism of induction instead appears to be related to an exaggerated triacylglycerol metabolism.

Effect of acarbose on insulin sensitivity in elderly patients with diabetes.

OBJECTIVE: To study the effect of acarbose, an alpha-glucosidase inhibitor, on insulin release and insulin sensitivity in elderly patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: Elderly patients with type 2 diabetes were randomly treated in a double-blind fashion with placebo (n = 23) or acarbose (n = 22) for 12 months. Before and after randomization, subjects underwent a meal tolerance test and a hyperglycemic glucose clamp study designed to measure insulin release and sensitivity. RESULTS: After 12 months of therapy there was a significant difference in the change in fasting plasma glucose levels (0.2 +/- 0.3 vs. -0.5 +/- 0.2 mmol/l, placebo vs. acarbose group, respectively; P < 0.05) and in incremental postprandial glucose values (-0.4 +/- 0.6 vs. -3.5 +/- 0.6 mmol/l, placebo vs. acarbose group, P < 0.001) between groups. There was a significant difference in the change in HbA(1c) values in response to treatment (0.4 +/- 0.2 vs. -0.4 +/- 0.1%, placebo vs. acarbose group, P < 0.01). The change in fasting insulin in response to treatment (-2 +/- 2 vs. -13 +/- 4 pmol/l, placebo vs. acarbose group, P < 0.05) and incremental postprandial insulin responses (-89 +/- 26 vs. -271 +/- 59 pmol/l, placebo vs. acarbose group, P < 0.01) was also significantly different between groups. During the hyperglycemic clamps, glucose and insulin values were similar in both groups before and after therapy However, there was a significant difference in the change in insulin sensitivity in response to treatment between the placebo and the acarbose groups (0.001 +/- 0.001 vs. 0.004 +/- 0.001 mg/kg x min(-1) [pmol/l](-1), respectively, P < 0.05) CONCLUSIONS: Acarbose increases insulin sensitivity but not insulin release in elderly patients with diabetes.

Purification of a pituitary polypeptide that stimulates the replication of adipocyte precursors in culture.

A bovine anterior pituitary polypeptide that stimulates the replication of rat and human adipocyte precursors has been purified. Its Mr is 44 000-53 000 and its isoelectric point is 9.8-10.3. While pituitary basic fibroblast growth factor is equally mitogenic on adipocyte precursors and skin fibroblasts, the polypeptide described here is selectively more active on the precursors. We postulate that this adipocyte growth factor plays a physiological role by modulating the number of adipocyte precursors.

Exaggerated replication in culture of adipocyte precursors from massively obese persons.

The characteristics of omental adipocyte precursors from massively obese patients, whose average body weights were 231% (range 70--369) of reference values, were studied in propagating culture. When compared to cells from lean subjects, the adipocyte precursors from 34 massively obese patients replicated at a significantly higher rate (p less than 0.001). Excessive replication persisted throughout the first five subcultures. Thus, this characteristic is inherent in the cells, and may reflect the operation of genetic factors in this subgroup of the obese population.

Extracellular matrix components secreted by microvascular endothelial cells stimulate preadipocyte differentiation in vitro.

Paracrine interaction between preadipocytes and microvascular endothelial cells may play a role in the regulation of adipose tissue growth. We report here a study of the effect of extracellular matrix factors secreted by microvascular endothelial cells, derived from adipose tissue, on preadipocyte differentiation in primary culture. Extracellular matrix components (EC) were prepared by differential centrifugation of medium conditioned by microvascular endothelial cells (CM). Preadipocyte differentiation was assessed by enumerating cells containing Oil-Red-O-stainable neutral lipids and by assaying cellular triacylglycerol (TG) content and glycerol-3-phosphate dehydrogenase (GPDH) specific activity. Both supernatant (containing soluble components) and pelleted (containing large complexes of EC) fractions of CM stimulated preadipocyte differentiation. When the supernatant fraction was used, the proportion of cells containing visible lipid droplets was 29% +/- 3% of total preadipocytes in the presence of extracellular complexes, as compared with 6% +/- 1% under control conditions. This differentiation induction was associated with fourfold increases in TG content and GPDH specific activity. Neither the supernatant nor the pelleted fraction of EC affected the maximal differentiation induced by hormonal stimulation in serum-supplemented or serum-free media. The major EC, fibronectin, laminin, and collagen IV, had no effect on differentiation when added individually to culture medium. Collection of CM under hyperglycemic (18 mmol/L glucose) compared with control (6 mmol/L glucose) conditions reduced the stimulatory effect of extracellular complexes by twofold, suggesting decreased or altered production by endothelial cells. The present findings demonstrate that microvascular endothelial cells release EC that promote preadipocyte differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional differences in the replication rate of cultured rat microvascular endothelium from retroperitoneal and epididymal fat pads.

Study of the vascular endothelium has been greatly facilitated by the development of specific cell culture systems isolated from various tissues. We report herein a simple method for establishing a propagating cell culture system of microvascular endothelial cells derived from rat adipose tissue. In addition to the characteristic cobblestone appearance on light microscopy, the microvascular endothelial cells in culture also demonstrated the presence of other markers for large vessel endothelia. Electron microscopy revealed endothelium-specific Weibel-Palade bodies and abundant pinocytotic vesicles. Both retroperitoneal and epididymal endothelia demonstrated the presence of factor VIII antigen by immunofluorescent staining and prostacyclin production. Although there was no appreciable morphological difference between cultured retroperitoneal and epididymal microvascular endothelia, the replication rate of the former was significantly higher than that of the latter (P less than .05). Excessive replication of endothelial cells may play a role in the regional differences of adipose tissue mass in an organism.

Arachidonic acid metabolites of the lipoxygenase as well as the cyclooxygenase pathway may be involved in regulating preadipocyte differentiation.

Conditions that trigger preadipocyte differentiation in vivo have yet to be elucidated. To investigate the role of endogenous arachidonic acid (AA) metabolites on adipose tissue growth, rat preadipocytes in primary culture were induced to differentiate using medium conditioned by isolated mature adipocytes (ACM). Differentiation was determined by assay of glycerol-3-phosphate dehydrogenase (GPDH). When collected in the presence of indomethacin (10 nmol/L) to inhibit prostaglandin (PG) synthesis by adipocytes, ACM induced greater differentiation (GPDH activity, 405 +/- 68 nmol NADH used/min/mg protein) than when indomethacin was added postcollection to inhibit preadipocyte PG synthesis (205 +/- 24, P < .05) or ACM alone (304 +/- 55). This suggested that PGs released by adipocytes inhibited differentiation, whereas those released by preadipocytes appeared to act in an autocrine manner to stimulate differentiation. However, 24-hour collections of ACM contained 125 pmol/L PGE2 and 900 pmol/L PGI2, concentrations too low to promote differentiation when added exogenously. Nordihydroguaiaretic acid (NDGA; 10 pmol/L), an inhibitor of lipoxygenase (LOX), stimulated the ACM-induced increase in GPDH activity (ACM, 99 +/- 13; ACM + NDGA, 369 +/- 130). In contrast, when differentiation was induced by a hormonal cocktail (MIX), including insulin and corticosterone, NDGA decreased GPDH activity (MIX, 329 +/- 66; MIX + NDGA, 142 +/- 40; P < .03). We concluded that preadipocyte differentiation within adipose tissue may be subject to both positive and negative regulators derived from AA metabolism resulting from both LOX and cyclooxygenase (COX) activity.

Acarbose in the treatment of elderly patients with type 2 diabetes.

AIMS: To study the effect of acarbose, an alpha-glucosidase inhibitor, on glycemic control in elderly patients with type 2 diabetes. METHODS: Elderly patients with type 2 diabetes treated with diet alone were randomly treated in a double-blind fashion with placebo (n=99) or acarbose (n=93) for 12 months. RESULTS: After 12 months of therapy, there was a statistically significant difference in the change in glycated haemoglobin (HbA(1c)) (-0.6%) in the acarbose group versus placebo, as well as in the incremental post-prandial glucose values (-2.1 mmol h/l) and mean fasting plasma glucose (-0.7 mmol/l). Although there was no effect of acarbose on insulin release, there was a clear effect of acarbose to decrease relative insulin resistance (-0.8) (HOMA method). In addition, acarbose was generally well tolerated and safe in the elderly; most discontinuations were due to gastrointestinal side effects such as flatulence and diarrhea. There were no cases of hypoglycemia reported, and no clinically relevant changes in laboratory abnormalities or vital signs during the study. CONCLUSIONS: Acarbose improves the glycemic profile and insulin sensitivity in elderly patients with type 2 diabetes who are inadequately controlled on diet alone.

Long-term pharmacotherapy for obesity and overweight.

BACKGROUND: Worldwide prevalence rates of obesity and overweight are rising and safe and effective treatment strategies are urgently needed. A number of anti-obesity agents have been studied in short-term clinical trials, but long-term efficacy and safety need to be established. OBJECTIVES: To assess/compare the effects and safety of approved anti-obesity medications in clinical trials of at least one-year duration. SEARCH STRATEGY: MEDLINE, EMBASE, the Cochrane Controlled Trials Register, the Current Science Meta-register of Controlled Trials, and reference lists of original studies and reviews were searched. Date of last search was December 2002. Drug manufacturers and two obesity experts were contacted in to detect unpublished trials. No language restrictions were imposed. SELECTION CRITERIA: Double-blind, randomised controlled weight loss and weight maintenance trials of approved anti-obesity agents that 1) enrolled adult overweight or obese patients, 2) included a placebo control group or compared two or more anti-obesity drugs 3) used an intention-to-treat analysis, and 4) had a minimum follow-up period of one year. Abstracts and pseudo-randomised trials were not included. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed all potentially relevant citations for inclusion and methodological quality. The primary outcome measure was weight loss. MAIN RESULTS: Of the eight anti-obesity agents investigated, only orlistat and sibutramine trials met inclusion criteria. Eleven orlistat weight loss studies (four of which reported a second year weight maintenance phase) and five sibutramine studies (three weight loss and two weight maintenance trials) were included. Attrition rates averaged 33% during the weight loss phase of orlistat trials and 43% in sibutramine studies. All patients received lifestyle modification as a co-intervention. Compared to placebo, orlistat-treated patients lost 2.7 kg (95% CI: 2.3 kg to 3.1 kg) or 2.9% (95% CI: 2.3 % to 3.4%) more weight and patients on sibutramine experienced 4.3 kg (95% CI: 3.6 kg to 4.9 kg) or 4.6% (95% CI: 3.8% to 5.4%) greater weight loss. The number of patients achieving ten percent or greater weight loss was 12% (95% CI: 8% to 16%) higher with orlistat and 15% (95% CI: 4% to 27%) higher with sibutramine therapy. Weight loss maintenance results were similar. Orlistat caused gastrointestinal side effects and sibutramine was associated with small increases in blood pressure and pulse rate. REVIEWERS' CONCLUSIONS: Studies evaluating the long-term efficacy of anti-obesity agents are limited to orlistat and sibutramine. Both drugs appear modestly effective in promoting weight loss; however, interpretation is limited by high attrition rates. Longer and more methodologically rigorous studies of anti-obesity drugs that are powered to examine endpoints such as mortality and cardiovascular morbidity are required to fully evaluate any potential benefit of such agents.

Long-term pharmacotherapy for obesity and overweight.

BACKGROUND: Worldwide prevalence rates of obesity and overweight are rising and safe and effective treatment strategies are urgently needed. A number of anti-obesity agents have been studied in short-term clinical trials, but long-term efficacy and safety need to be established. OBJECTIVES: To assess/compare the effects and safety of approved anti-obesity medications in clinical trials of at least one-year duration. SEARCH STRATEGY: MEDLINE, EMBASE, the Cochrane Controlled Trials Register, the Current Science Meta-register of Controlled Trials, and reference lists of original studies and reviews were searched. Date of last search was December 2002. Drug manufacturers and two obesity experts were contacted in to detect unpublished trials. No language restrictions were imposed. SELECTION CRITERIA: Double-blind, randomised controlled weight loss and weight maintenance trials of approved anti-obesity agents that 1) enrolled adult overweight or obese patients, 2) included a placebo control group or compared two or more anti-obesity drugs 3) used an intention-to-treat analysis, and 4) had a minimum follow-up period of one year. Abstracts and pseudo-randomised trials were not included. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed all potentially relevant citations for inclusion and methodological quality. The primary outcome measure was weight loss. MAIN RESULTS: Of the eight anti-obesity agents investigated, only orlistat and sibutramine trials met inclusion criteria. Eleven orlistat weight loss studies (four of which reported a second year weight maintenance phase) and five sibutramine studies (three weight loss and two weight maintenance trials) were included. Attrition rates averaged 33% during the weight loss phase of orlistat trials and 43% in sibutramine studies. All patients received lifestyle modification as a co-intervention. Compared to placebo, orlistat-treated patients lost 2.7 kg (95% CI: 2.3 kg to 3.1 kg) or 2.9% (95% CI: 2.3 % to 3.4%) more weight and patients on sibutramine experienced 4.3 kg (95% CI: 3.6 kg to 4.9 kg) or 4.6% (95% CI: 3.8% to 5.4%) greater weight loss. The number of patients achieving ten percent or greater weight loss was 12% (95% CI: 8% to 16%) higher with orlistat and 15% (95% CI: 4% to 27%) higher with sibutramine therapy. Weight loss maintenance results were similar. Orlistat caused gastrointestinal side effects and sibutramine was associated with small increases in blood pressure and pulse rate. REVIEWER'S CONCLUSIONS: Studies evaluating the long-term efficacy of anti-obesity agents are limited to orlistat and sibutramine. Both drugs appear modestly effective in promoting weight loss; however, interpretation is limited by high attrition rates. Longer and more methodologically rigorous studies of anti-obesity drugs that are powered to examine endpoints such as mortality and cardiovascular morbidity are required to fully evaluate any potential benefit of such agents.

Canadian Physicians' Use of Antiobesity Drugs and Their Referral Patterns to Weight Management Programs or Providers: The SOCCER Study.

Antiobesity pharmacotherapy and programs/providers that possess weight management expertise are not commonly used by physicians. The underlying reasons for this are not known. We performed a cross-sectional study in 33 Canadian medical practices (36 physicians) examining 1788 overweight/obese adult patients. The frequency of pharmacotherapy use and referral for further diet, exercise, behavioral management and/or bariatric surgery was documented. If drug treatment or referral was not made, reasons were documented by choosing amongst preselected categories. Logistic regression models were used to identify predictors of antiobesity drug use. No single antiobesity management strategy was recommended by physicians in more than 50% of patients. Referral was most common for exercise (49% of cases) followed by dietary advice (46%), and only 5% of eligible patients were referred for bariatric surgery. Significant predictors of initiating/continuing pharmacotherapy were male sex (OR 0.70; 95% CI 0.52-0.94), increasing BMI (1.02; 95% CI 1.01-1.03), and private drug coverage (1.78; 95% CI 1.39-2.29). "Not considered" and "patient refusal" were the main reasons for not initiating further weight management. We conclude that both physician and patient factors act as barriers to the use of weight management strategies and both need to be addressed to increase uptake of these interventions.

Perivascular adipose tissue-derived relaxing factors: release by peptide agonists via proteinase-activated receptor-2 (PAR2) and non-PAR2 mechanisms.

BACKGROUND AND PURPOSE: We hypothesized that proteinase-activated receptor-2 (PAR2)-mediated vasorelaxation in murine aorta tissue can be due in part to the release of adipocyte-derived relaxing factors (ADRFs). EXPERIMENTAL APPROACH: Aortic rings from obese TallyHo and C57Bl6 intact or PAR2-null mice either without or with perivascular adipose tissue (PVAT) were contracted with phenylephrine and relaxation responses to PAR2-selective activating peptides (PAR2-APs: SLIGRL-NH(2) and 2-furoyl-LIGRLO-NH(2) ), trypsin and to PAR2-inactive peptides (LRGILS-NH(2) , 2-furoyl-OLRGIL-NH(2) and LSIGRL-NH(2) ) were measured. Relaxation was monitored in the absence or presence of inhibitors that either alone or in combination were previously shown to inhibit ADRF-mediated responses: L-NAME (NOS), indomethacin (COX), ODQ (guanylate cyclase), catalase (H(2) O(2) ) and the K(+) channel-targeted reagents, apamin, charybdotoxin, 4-aminopyridine and glibenclamide. KEY RESULTS: Endothelium-intact PVAT-free preparations did not respond to PAR2-inactive peptides (LRGILS-NH(2) , LSIGRL-NH(2) , 2-furoyl-OLRGIL-NH(2) ), whereas active PAR2-APs (SLIGRL-NH(2) ; 2-furoyl-LIGRLO-NH(2) ) caused an L-NAME-inhibited relaxation. However, in PVAT-containing preparations treated with L-NAME/ODQ/indomethacin together, both PAR2-APs and trypsin caused relaxant responses in PAR2-intact, but not PAR2-null-derived tissues. The PAR2-induced PVAT-dependent relaxation (SLIGRL-NH(2) ) persisted in the presence of apamin plus charybdotoxin, 4-aminopyridine and glibenclamide, but was blocked by catalase, implicating a role for H(2) O(2) . Surprisingly, the PAR2-inactive peptides, LRGILS-NH(2) and 2-furoyl-OLRGIL-NH(2) (but not LSIGRL-NH(2) ), caused relaxation in PVAT-containing preparations from both PAR2-null and PAR2-intact (C57Bl, TallyHo) mice. The LRGILS-NH(2) -induced relaxation was distinct from the PAR2 response, being blocked by 4-aminopyridine, but not catalase. CONCLUSIONS: Distinct ADRFs that may modulate vascular tone in pathophysiological settings can be released from murine PVAT by both PAR2-dependent and PAR2-independent mechanisms.

Regulation of new fat cell formation in rats: the role of dietary fats.

Factors that stimulate formation of new adipocytes during development of obesity are yet to be identified. We examined whether diet acts directly on preadipocytes to stimulate replication and differentiation or indirectly by interacting with adipocytes to release or modify local growth factors. Male Sprague-Dawley rats were fed chow or diets high in starch (HST), saturated (HFS) or polyunsaturated (HFP) fats until 5-7 months of age. We found that, compared to other diets, HFS induced acceleration of replication of preadipocytes in primary culture (doubling time of retroperitoneal-derived preadipocytes: HFS 17 +/- 1 versus chow 32 +/- 6 and HFP 29 +/- 3 h, P < 0.05). HFS stimulated greater expansion of retroperitoneal fat than HFP even when caloric intake was equal and increased adipocyte number threefold. Preadipocyte pool size in inguinal and retroperitoneal fat pads changed relative to fat pad weight in rats fed all diets compared to chow, suggesting that the balance between the number of cells capable of replicating and those terminally differentiated was perturbed. Differentiation of preadipocytes and release of adipocyte growth factors in vitro were unaffected by diet. We concluded that dietary saturated fats induced expansion of adipose tissue mass more effectively than polyunsaturated fats and that this may, in part, be achieved by acceleration of preadipocyte replication.

Effects of glucocorticoid hormones on lipid-synthetic enzymes from different adipose tissue regions and from liver.

The regional diversity of adipose tissue is dramatically accentuated in states of glucocorticoid excess, in which certain fat depots expand, while others contract. We have studied the molecular basis of this redistribution by determining the activity of fatty acid synthetase and enzymes catalyzing di- and tri-acylglycerol synthesis, in subcellular fractions from four adipose depots of rats injected with dexamethasone and from interscapular and epididymal adipocyte precursors after addition of either dexamethasone or corticosterone to confluent monolayers in secondary culture. Subcellular fractions from cervical and interscapular adipose tissue, as well as from cultured interscapular precursors, revealed a general increase in specific enzyme activity. The opposite trend was observed for retroperitoneal and epididymal fat tissue, as well as cultured epididymal precursors. Fatty acid synthetase and cytosolic phosphatidate phosphohydrolase appeared to be most responsive. The findings in culture indicate that the regional effects of glucocorticoids are partly independent of other circulating or neural factors. Injections of dexamethasone led to significantly enhanced specific activity of all the lipid-synthetic enzymes assayed in subcellular fractions from liver. Differences in hormonal influences between liver and certain fat tissue regions represent tissue specificity. In addition, the diverse effects of glucocorticoids on various adipose tissue depots indicate regional or "intratissue" specificity.