Lack of impact of angiotensin-converting enzyme gene polymorphism and salt intake on insulin resistance and limb blood flow

OBJECTIVES

We postulated the mechanism for the association between angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and insulin sensitivity might relate to changes in blood flow regulation. We studied the association of this polymorphism with insulin action, and insulin-mediated changes in limb blood flow (LBF), under conditions of high and low salt intake. We also studied effects of genotype and salt loading on renin-angiotensin-aldosterone system (RAAS) activity.

MATERIALS/METHODS

Twenty people with (10 I/I; 10 D/D) and 23 without (10 I/I; 13 D/D), type 2 diabetes were studied during 6 days of 40 mmol/day and 220 mmol/day sodium diet in a randomized, double-blind cross-over fashion. On the sixth day of each condition, we measured 24-h blood pressure, plasma volume, LBF and insulin sensitivity during hyperinsulinaemic clamp at low (40 mU/m(2) /min) and high (600 mU/m(2) /min) dose insulin infusion.

RESULTS

Salt intake variation produced greater effects on the renin-angiotensin-aldosterone system than ACE genotype. Diabetes status and insulin infusion were associated with differences in the metabolic clearance rate of glucose, (P < 0·001 for each) and insulin infusion increased LBF (P < 0·001). However, ACE genotype and salt intake had no consistent impacts on either variable in nondiabetic and diabetic subgroups, or in the combined group.

CONCLUSIONS

Reported differences in insulin sensitivity between ACE genotypes were not found in this study under strict regulation of sodium intake. Insulin sensitivity was also unaffected in either group by sodium loading. ACE genotype and salt status do not impact on insulin sensitivity through changes in limb blood flow during hyperinsulinaemia.

Expression Profiling of Purified Normal Human Luminal and Myoepithelial Breast Cells

The normal duct-lobular system of the breast is lined by two epithelial cell types, inner luminal secretory cells and outer contractile myoepithelial cells. We have generated comprehensive expression profiles of the two normal cell types, using immunomagnetic cell separation and gene expression microarray analysis. The cell-type specificity was confirmed at the protein level by immunohistochemistry in normal breast tissue. New prognostic markers for survival were identified when the luminal- and myoepithelial-specific molecules were evaluated on breast tumor tissue microarrays. Nuclear expression of luminal epithelial marker galectin 3 correlated with a shorter overall survival in these patients, and the expression of SPARC (osteonectin), a myoepithelial marker, was an independent marker of poor prognosis in breast cancers as a whole. These data provide a framework for the interpretation of breast cancer molecular profiling experiments, the identification of potential new diagnostic markers, and development of novel indicators of prognosis.

cDNA microarray analysis of genes associated with ERBB2 (HER2/neu) overexpression in human mammary luminal epithelial cells

To investigate changes in gene expression associated with ERBB2, expression profiling of immortalized human mammary luminal epithelial cells and variants expressing a moderate and high level of ERBB2 has been carried out using cDNA microarrays corresponding to approximately 6000 unique genes/ESTs. A total of 61 significantly up- or downregulated (2.0-fold) genes were identified and further validated by RT-PCR analysis as well as microarray comparisons with a spontaneously ERBB2- overexpressing breast cancer cell line and ERBB2-positive primary breast tumors. The expression and clinical relevance of proteins predicted to be associated with ERBB2 overexpression in breast cancers were analysed together with their clinical relevance by antibody screening using a tissue array. Differentially regulated genes include those involved in cell-matrix interactions including proline 4-hydroxylase (P4HA2), galectin 1 (LGALS1) and galectin 3 (LGALS3), fibronectin 1 (FN1) and p-cadherin (CDH3), and cell proliferation (CRIP1, IGFBP3) and transformation (S100P, S100A4). A number of genes associated with MYC signalling were also differentially expressed, including NDRG1, USF2 and the epithelial membrane proteins 1 and 3 (EMP1, EMP3). These data represent profiles of the transcriptional changes associated with ERBB2-related pathways in the breast, and identify novel and potentially useful targets for prognosis and therapy.

Investigation of potential mechanisms regulating protein expression of hepatic pyruvate dehydrogenase kinase isoforms 2 and 4 by fatty acids and thyroid hormone

Liver contains two pyruvate dehydrogenase kinases (PDKs), namely PDK2 and PDK4, which regulate glucose oxidation through inhibitory phosphorylation of the pyruvate dehydrogenase complex (PDC). Starvation increases hepatic PDK2 and PDK4 protein expression, the latter occurring, in part, via a mechanism involving peroxisome proliferator-activated receptor-alpha (PPARalpha). High-fat feeding and hyperthyroidism, which increase circulating lipid supply, enhance hepatic PDK2 protein expression, but these increases are insufficient to account for observed increases in hepatic PDK activity. Enhanced expression of PDK4, but not PDK2, occurs in part via a mechanism involving PPAR-alpha. Heterodimerization partners for retinoid X receptors (RXRs) include PPARalpha and thyroid-hormone receptors (TRs). We therefore investigated the responses of hepatic PDK protein expression to high-fat feeding and hyperthyroidism in relation to hepatic lipid delivery and disposal. High-fat feeding increased hepatic PDK2, but not PDK4, protein expression whereas hyperthyroidism increased both hepatic PDK2 and PDK4 protein expression. Both manipulations decreased the sensitivity of hepatic carnitine palmitoyltransferase I (CPT I) to suppression by malonyl-CoA, but only hyperthyrodism elevated plasma fatty acid and ketone-body concentrations and CPT I maximal activity. Administration of the selective PPAR-alpha activator WY14,643 significantly increased PDK4 protein to a similar extent in both control and high-fat-fed rats, but WY14,643 treatment and hyperthyroidism did not have additive effects on hepatic PDK4 protein expression. PPARalpha activation did not influence hepatic PDK2 protein expression in euthyroid rats, suggesting that up-regulation of PDK2 by hyperthyroidism does not involve PPARalpha, but attenuated the effect of hyperthyroidism to increase hepatic PDK2 expression. The results indicate that hepatic PDK4 up-regulation can be achieved by heterodimerization of either PPARalpha or TR with the RXR receptor and that effects of PPARalpha activation on hepatic PDK2 and PDK4 expression favour a switch towards preferential expression of PDK4.

Up-regulation of pyruvate dehydrogenase kinase isoform 4 (PDK4) protein expression in oxidative skeletal muscle does not require the obligatory participation of peroxisome-proliferator-activated receptor alpha (PPARalpha)

In insulin deficiency, increased lipid delivery and oxidation suppress skeletal-muscle glucose oxidation by inhibiting pyruvate dehydrogenase complex (PDC) activity via enhanced protein expression of pyruvate dehydrogenase kinase (PDK) isoform 4, which phosphorylates (and inactivates) PDC. Signalling via peroxisome-proliferator-activated receptor alpha (PPARalpha) is an important component of the mechanism enhancing hepatic and renal PDK4 protein expression. Activation of PPARalpha in gastrocnemius, a predominantly fast glycolytic (FG) muscle, also increases PDK4 expression, an effect that, if extended to all muscles, would be predicted to drastically restrict whole-body glucose disposal. Paradoxically, chronic activation of PPARalpha by WY14,643 treatment improves glucose utilization by muscles of insulin-resistant high-fat-fed rats. In the resting state, oxidative skeletal muscles are quantitatively more important for glucose disposal than FG muscles. We evaluated the participation of PPARalpha in regulating PDK4 protein expression in slow oxidative (SO) skeletal muscle (soleus) and fast oxidative-glycolytic (FOG) skeletal muscle (anterior tibialis) containing a high proportion of oxidative fibres. In the fed state, acute (24 h) activation of PPARalpha by WY14,643 in vivo failed to modify PDK4 protein expression in soleus, but modestly enhanced PDK4 protein expression in anterior tibialis. Starvation enhanced PDK4 protein expression in both muscles, with the greater response in anterior tibialis. WY14,643 treatment in vivo during starvation did not further enhance upregulation of PDK4 protein expression in either muscle type. Enhanced PDK4 protein expression after starvation was retained in SO and FOG skeletal muscles of PPARalpha-deficient mice. Our data indicate that PDK4 protein expression in oxidative skeletal muscle is regulated by a lipid-dependent mechanism that is not obligatorily dependent on signalling via PPARalpha.

Evaluation of the role of peroxisome-proliferator-activated receptor alpha in the regulation of cardiac pyruvate dehydrogenase kinase 4 protein expression in response to starvation, high-fat feeding and hyperthyroidism

Inactivation of cardiac pyruvate dehydrogenase complex (PDC) after prolonged starvation and in response to hyperthyroidism is associated with enhanced protein expression of pyruvate dehydrogenase kinase (PDK) isoform 4. The present study examined the potential role of peroxisome-proliferator-activated receptor alpha (PPARalpha) in adaptive modification of cardiac PDK4 protein expression after starvation and in hyperthyroidism. PDK4 protein expression was analysed by immunoblotting in homogenates of hearts from fed or 48 h-starved rats, rats rendered hyperthyroid by subcutaneous injection of tri-iodothyronine and a subgroup of euthyroid rats maintained on a high-fat/low-carbohydrate diet, with or without treatment with the PPARalpha agonist WY14,643. In addition, PDK4 protein expression was analysed in hearts from fed, 24 h-starved or 6 h-refed wild-type or PPARalpha-null mice. PPARalpha activation by WY14,643 in vivo over the timescale of the response to starvation failed to up-regulate cardiac PDK4 protein expression in rats maintained on standard diet (WY14,643, 1.1-fold increase; starvation, 1.8-fold increase) or influence the cardiac PDK4 response to starvation. By contrast, PPARalpha activation by WY14,643 in vivo significantly enhanced cardiac PDK4 protein expression in rats maintained on a high-fat diet, which itself increased cardiac PDK4 protein expression. PPARalpha deficiency did not abolish up-regulation of cardiac PDK4 protein expression in response to starvation (2.9-fold increases in both wild-type and PPARalpha-null mice). Starvation and hyperthyroidism exerted additive effects on cardiac PDK4 protein expression, but PPARalpha activation by WY14,643 did not influence the response of cardiac PDK4 protein expression to hyperthyroidism in either the fed or starved state. Our data support the hypothesis that cardiac PDK4 protein expression is regulated, at least in part, by a fatty acid-dependent, PPARalpha-independent mechanism and strongly implicate a fall in insulin in either initiating or facilitating the response of cardiac PDK4 protein expression to starvation.

Peroxisome-proliferator-activated receptor-alpha (PPARalpha) deficiency leads to dysregulation of hepatic lipid and carbohydrate metabolism by fatty acids and insulin

The aim of the present study was to determine whether peroxisome-proliferator-activated receptor-alpha (PPARalpha) deficiency disrupts the normal regulation of triacylglycerol (TAG) accumulation, hepatic lipogenesis and glycogenesis by fatty acids and insulin using PPARalpha-null mice. In wild-type mice, hepatic TAG concentrations increased (P<0.01) with fasting (24 h), with substantial reversal after refeeding (6 h). Hepatic TAG levels in fed PPARalpha-null mice were 2.4-fold higher than in the wild-type (P<0.05), increased with fasting, but remained elevated after refeeding. PPARalpha deficiency also impaired hepatic glycogen repletion (P<0.001), despite normal insulin and glucose levels after refeeding. Higher levels of plasma insulin were required to support similar levels of hepatic lipogenesis de novo ((3)H(2)O incorporation) in the PPARalpha-null mice compared with the wild-type. This difference was reflected by corresponding changes in the relationship between plasma insulin and the mRNA expression of the lipogenic transcription factor sterol-regulatory-element-binding protein-1c, and that of one of its known targets, fatty acid synthase. In wild-type mice, hepatic pyruvate dehydrogenase kinase (PDK) 4 protein expression (a downstream marker of altered fatty acid catabolism) increased (P<0.01) in response to fasting, with suppression (P<0.001) by refeeding. Although PDK4 up-regulation after fasting was halved by PPARalpha deficiency, PDK4 suppression after refeeding was attenuated. In summary, PPARalpha deficiency leads to accumulation of hepatic TAG and elicits dysregulation of hepatic lipid and carbohydrate metabolism, emphasizing the importance of precise control of lipid oxidation for hepatic fuel homoeostasis.

Selective modification of pyruvate dehydrogenase kinase isoform expression in rat pancreatic islets elicited by starvation and activation of peroxisome proliferator-activated receptor-alpha: implications for glucose-stimulated insulin secretion

The pyruvate dehydrogenase complex (PDC) has a pivotal role in islet metabolism. The pyruvate dehydrogenase kinases (PDK1-4) regulate glucose oxidation through inhibitory phosphorylation of PDC. Starvation increases islet PDK activity (Am J Physiol Endocrinol Metab 270:E988-E994, 1996). In this study, using antibodies against PDK1, PDK2, and PDK4 (no sufficiently specific antibodies are as yet available for PDK3), we identified the PDK isoform profile of the pancreatic islet and delineated the effects of starvation (48 h) on protein expression of individual PDK isoforms. Rat islets were demonstrated to contain all three PDK isoforms, PDK1, PDK2, and PDK4. Using immunoblot analysis with antibodies raised against the individual recombinant PDK isoforms, we demonstrated increased islet protein expression of PDK4 in response to starvation (2.3-fold; P < 0.01). Protein expression of PDK1 and PDK2 was suppressed in response to starvation (by 27% [P < 0.01] and 10% [NS], respectively). We demonstrated that activation of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) by the selective agonist WY14,643 for 24 h in vivo leads to specific upregulation of islet PDK4 protein expression by 1.8-fold (P < 0.01), in the absence of change in islet PDK1 and PDK2 protein expression but in conjunction with a 2.2-fold increase (P < 0.01) in islet PPAR-alpha protein expression. Thus, although no changes in islet PPAR-alpha expression were observed after the starvation protocol, activation of PPAR-alpha in vivo may be a potential mechanism underlying upregulation of islet PDK4 protein expression in starvation. We evaluated the effects of antecedent changes in PDK profile and/or PPAR-alpha activation induced by starvation or PPAR-alpha activation in vivo on glucose-stimulated insulin secretion (GSIS) in isolated islets. GSIS at 20 mmol/l glucose was modestly impaired on incubation with exogenous triglyceride (1 mmol/l triolein) ( approximately 20% inhibition; P < 0.05) in islets from fed rats. Starvation (48 h) impaired GSIS in the absence of triolein (by 57%; P < 0.001), but GSIS after the further addition of triolein did not differ significantly between islets from fed or starved rats. GSIS by islets prepared from WY14,643-treated fed rats did not differ significantly from that seen with islets from control fed rats, and the response to triolein addition resembled that of islets prepared from fed rather than starved rats. PPAR-alpha activation in vivo led to increased insulin secretion at low glucose concentrations. Our results are discussed in relation to the potential impact of changes in islet PDK profile on the insulin secretory response to lipid and of PPAR-alpha activation in the cause of fasting hyperinsulinemia.

Role of peroxisome proliferator-activated receptor-alpha in the mechanism underlying changes in renal pyruvate dehydrogenase kinase isoform 4 protein expression in starvation and after refeeding

The pyruvate dehydrogenase complex (PDC) occupies a strategic role in renal intermediary metabolism, via partitioning of pyruvate flux between oxidation and entry into the gluconeogenic pathway. Inactivation of PDC via activation of pyruvate dehydrogenase kinases (PDKs), which catalyze PDC phosphorylation, occurs secondary to increased fatty acid oxidation (FAO). In kidney, inactivation of PDC after prolonged starvation is mediated by up-regulation of the protein expression of two PDK isoforms, PDK2 and PDK4. The lipid-activated transcription factor, peroxisome proliferator-activated receptor-alpha (PPAR alpha), plays a pivotal role in the cellular metabolic response to fatty acids and is abundant in kidney. In the present study we used PPAR alpha null mice to examine the potential role of PPAR alpha in regulating renal PDK protein expression. In wild-type mice, fasting (24 h) induced marked up-regulation of the protein expression of PDK4, together with modest up-regulation of PDK2 protein expression. In striking contrast, renal protein expression of PDK4 was only marginally induced by fasting in PPAR alpha null mice. The present results define a critical role for PPAR alpha in renal adaptation to fasting, and identify PDK4 as a downstream target of PPAR alpha activation in the kidney. We propose that specific up-regulation of renal PDK4 protein expression in starvation, by maintaining PDC activity relatively low, facilitates pyruvate carboxylation to oxaloacetate and therefore entry of acetyl-CoA derived from FA beta-oxidation into the TCA cycle, allowing adequate ATP production for brisk rates of gluconeogenesis.

Fuel-sensing mechanisms integrating lipid and carbohydrate utilization

Fuel metabolism is highly regulated to ensure adequate energy for cellular function. The contribution of the major metabolic fuels--glucose, lactate and fatty acids (FAs)--often reflects their circulating levels. In addition, regulatory cross-talk and fuel-induced hormone secretion ensures appropriate and co-ordinate fuel utilization. Because its activity can either determine or reflect fuel preference (carbohydrate versus fat), the pyruvate dehydrogenase complex (PDC) occupies a pivotal position in fuel cross-talk. Active PDC permits glucose oxidation and allows the formation of mitochondrially derived intermediates (e.g. malonyl-CoA and citrate) that reflect fuel abundance. FA oxidation suppresses PDC activity. PDC inactivation by phosphorylation is catalysed by pyruvate dehydrogenase kinases (PDKs) 1-4, which are regulated differentially by metabolite effectors. Most tissues contain at least two and often three of the PDK isoforms. We develop the hypothesis that PDK4 is a "lipid status"-responsive PDK isoform facilitating FA oxidation and signalling through citrate formation. Substrate interactions at the level of gene transcription extend glucose-FA interactions to the longer term. We discuss potential targets for substrate-mediated transcriptional regulation in relation to selective PDK isoform expression and the influence of altered PDK isoform expression in fuel sensing, selection and utilization.

The influence of improved glycaemic control with insulin and sulphonylureas on acute phase and endothelial markers in Type II diabetic subjects

AIMS/HYPOTHESIS

Improved glycaemic control might reduce both microvascular and macrovascular complications of Type II diabetes (non-insulin-dependent) mellitus. To explore such possible mechanisms, we investigated the effects of intensive treatment on markers of endothelial dysfunction and of acute phase activation, using both sulphonylureas and insulin.

METHODS

In a randomised cross-over study we gave sulphonylureas or insulin each for a period of 16 weeks to 22 poorly controlled Type II diabetic subjects who were being treated by diet. There was a 4 week washout period between each treatment. Subjects were studied at baseline and at the end of each treatment.

RESULTS

Treatment with sulphonylureas and insulin resulted in similar improvements in glycaemic control (glycated haemoglobin, baseline: 11.8 [(SD 2.2)%; after sulphonylureas: 8.6 (1.2)%,p < 0.001; after insulin: 8.6 (1.2)%, p < 0.001] and in insulin sensitivity ¿metabolic clearance rate of glucose, baseline: median 1.75 [interquartile (IQ) range 1.41, 2.27] ml x kg(-1) x min(-1); after sulphonylureas: 2.41 (1.82, 3.01) ml x kg(-1) x min(-1), p = 0.001; after insulin: 2.23 (1.92, 2.75) ml x kg(-1) min(-1), p = 0.027¿. There were no significant changes in concentrations of endothelial markers von Willebrand factor, cellular fibronectin, thrombomodulin, tissue plasminogen activator, soluble E-selectin or soluble intercellular adhesion molecule-1 or in urinary albumin excretion rate after either treatment period. Concentrations of C-reactive protein were not significantly influenced by sulphonylureas but fell after insulin [baseline: median 4.50 (IQ range 1.37, 6.44) microg x ml(-1); sulphonylureas: 2.69 (0.88, 9.65) microg x ml(-1) (p = 0.53); insulin: 2.07 (1.16, 5.24) microg x ml(-1) (p = 0.017)]. There were, however, no significant effects of either treatment on circulating concentrations of fibrinogen (p = 0.28-0.34) or of the proinflammatory cytokines interleukin-6 or tumour necrosis factor-alpha (p = 0.65-0.79).

CONCLUSION/INTERPRETATION

Markers of endothelial dysfunction and concentrations of proinflammatory cytokines in Type II diabetes are not influenced by improved glycaemic control over 16 weeks. Improved metabolic control with insulin could, however, be associated with reduced concentrations of the acute phase marker C-reactive protein.

beta-Adrenergic regulation of proinflammatory cytokines in humans

OBJECTIVES

To investigate the effects of beta-adrenergic stimulation on IL-6 secretion in humans, and to determine the potential contribution to this response of adipocytes and peripheral blood cells (PBC).

DESIGN

Experimental study in 8 human volunteers, and in vitro studies on murine adipocyte cell-line, 3T3.L1 and 3T3.F442A, and human PBC.

MEASUREMENTS

Plasma IL-6 and TNFalpha responses to isoprenaline infusion. Cytokine secretion from differentiated adipocyte cell-lines and PBC in response to isoprenaline.

RESULTS

Plasma IL-6 levels increased ninefold (median) by 180 min (baseline median 0.51 [interquartile range 0.47-1.4] vs 180 mins 4.53 [2.58-5.69] pg ml(-1), P=0.01). One hour after infusion, IL-6 levels (2.9 [1.27-3.98]) were lower than at 180 min (P=0.05), but higher than baseline (P=0.01). TNFalpha levels were unchanged. Differentiated adipocytes incubated in isoprenaline (0-0.1 microM) released significantly increased amounts of IL-6 whereas no response was elicited from PBC.

CONCLUSIONS

The induction of IL-6 observed in vivo may be attributed to the beta-adrenergic stimulation of IL-6 release specifically from adipocytes, as opposed to circulating blood cells.

Physiological relationships of uncoupling protein-2 gene expression in human adipose tissue in vivo

The physiological significance of changes in uncoupling protein-2 (UCP-2) gene expression is controversial. In this study we investigated the biochemical and functional correlates of UCP-2 gene expression in sc abdominal adipose tissue in humans in vivo. UCP-2 messenger ribonucleic acid expression was quantified by nuclease protection in adipose tissue from lean and obese humans in both the fasting and postprandial states. Plasma fatty acids, insulin, and leptin were all determined in paired samples from the superficial epigastric vein and radial artery, and local production rates were calculated from 133Xe washout. In the fasting state UCP-2 expression correlated inversely with body mass index (r = -0.45; P = 0.026), percent body fat (r = -0.41; P = 0.05), plasma insulin (r = -0.47; P = 0.02), epigastric venous fatty acids (r = -0.45; P = 0.04), and leptin (r = -0.50; P = 0.018). UCP-2 expression remained inversely related with plasma leptin after controlling for percent body (r = -0.45; P = 0.038). At 2 or 4 h postprandially, there were no significant relationships between UCP-2 expression and biochemical parameters. In conclusion, 1) UCP-2 messenger ribonucleic acid expression in sc adipose tissue is inversely related to adiposity and independently linked to local plasma leptin levels; and 2) UCP-2 expression is not acutely regulated by food intake, insulin, or fatty acids. Reduced UCP-2 expression may be a maladaptive response to sustained energy surplus and could contribute to the pathogenesis and maintenance of obesity.

Production of soluble tumor necrosis factor receptors by human subcutaneous adipose tissue in vivo

To investigate in vivo adipose tissue production of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and their soluble receptors: TNF receptor type I (sTNFR-I), TNF receptor type II (sTNFR-II), and IL-6 receptor (sIL-6R), we determined arteriovenous differences in their levels across abdominal subcutaneous adipose tissue in obese subjects. Subjects had a median (interquartile range) age of 44.5 (27-51.3) yr, body mass index (BMI) of 32.9 (26. 0-46.6) kg/m(2), and %body fat of 42.5 (28.5-51.2) %. Although there was not a significant difference in the arteriovenous concentrations of TNF-alpha (P = 0.073) or sTNFR-II (P = 0.18), the levels of sTNFR-I (P = 0.002) were higher in the vein compared with artery, suggesting adipose tissue production of this soluble receptor. There was a significant arteriovenous difference in IL-6 (P < 0.001) but not in its soluble receptor (P = 0.18). There was no relationship between TNF-alpha levels and adiposity indexes (r(s) = 0.12-0.22, P = not significant); however, levels of both its soluble receptor isomers correlated significantly with BMI and %body fat (sTNFR-I r(s) = 0.42-0.72, P < 0.001; sTNFR-II r(s) = 0.36-0.65, P < 0.05- <0. 001). IL-6 levels correlated significantly with both BMI and %body fat (r(s) = 0.51, P = 0.004, and r(s) = 0.63, P < 0.001), but sIL-6R did not. In conclusion, 1) soluble TNFR-I is produced by adipose tissue, and concentrations of both soluble isoforms correlate with the degree of adiposity, and 2) IL-6, but not its soluble receptor, is produced by adipose tissue and relates to adiposity.

Lack of evidence for secretion of plasminogen activator inhibitor-1 by human subcutaneous adipose tissue in vivo

Circulating plasminogen activator inhibitor-1 (PAI-1) levels are elevated in patients with coronary heart disease and may play an important role in atherothrombosis. Levels are also raised in obese, hypertriglyceridaemic, or insulin-resistant subjects, which predispose people to coronary heart disease. It is unclear, though, which organ is responsible for PAI-1 secretion, either in health or disease. We measured arteriovenous differences across a subcutaneous adipose tissue bed in 25 subjects without coronary heart disease, which, combined with measures of adipose tissue blood flow, provides synthetic rates. There was no net increase in levels of PAI-1 activity (median change 0.23, interquartile range -0.59, 1.21 IU x L(-1), p=0.30) or of PAI-1 antigen (mean change -0.01, SD+/-2.93 ng x mL(-1), p=0.98) in these subjects. Assuming homogeneous production of PAI-1 by all adipose tissue beds, the contribution of adipose tissue to PAI-1 activity is 3.1% (interquartile range, -11.7, +7.0%) and to PAI-1 antigen 1.6% (interquartile range -14.5, +7.3%). Arteriovenous difference of PAI-1 activity and antigen did not relate to measures of obesity, triglyceride, insulin, fatty acids, or circulating concentrations or adipose tissue production of tumour necrosis factor-alpha or interleukin-6. We conclude that, at least in healthy subjects, subcutaneous adipose tissue does not contribute significantly to circulating levels of PAI-1.

Does malnutrition in utero determine diabetes and coronary heart disease in adulthood? Results from the Leningrad siege study, a cross sectional study

OBJECTIVE

To investigate the relation between decreased maternal food intake and risk factors for coronary heart disease in adult life.

DESIGN

Cross sectional study.

SUBJECTS

169 subjects exposed to malnutrition in utero (intrauterine group) during the siege of Leningrad (now St Petersburg) in 1941-4; 192 subjects born in Leningrad just before rationing began, before the siege (infant group); and 188 subjects born concurrently with the first two groups but outside the area of the siege (unexposed group).

SETTING

Ott Institute of Obstetrics and Gynaecology, St Petersburg.

MAIN OUTCOME MEASURES

Development of risk factors for coronary heart disease and diabetes mellitus-obesity, blood pressure, glucose tolerance, insulin concentrations, lipids, albumin excretion rate, and clotting factors.

RESULTS

There was no difference between the subjects exposed to starvation in utero and those starved during infant life in: (a) glucose tolerance (mean fasting glucose: intrauterine group 5.2 (95% confidence interval 5.1 to 5.3), infant group 5.3 (5.1 to 5.5), P = 0.94; mean 2 hour glucose: intrauterine group 6.1 (5.8 to 6.4), infant group 6.0 (5.7 to 6.3), P = 0.99); (b) insulin concentration; (c) blood pressure; (d) lipid concentration; or (e) coagulation factors. Concentrations of von Willebrand factor were raised in the intrauterine group (156.5 (79.1 to 309.5)) compared with the infant group (127.6 (63.9 to 254.8); P < 0.001), and female subjects in the intrauterine group had a stronger interaction between obesity and both systolic (P = 0.01) and diastolic (P = 0.04) blood pressure than in the infant group. Short adult stature was associated with raised concentrations of glucose and insulin 2 hours after a glucose load-independently of siege exposure. Subjects in the unexposed group had non-systematic differences in subscapular to triceps skinfold ratio, diastolic blood pressure, and clotting factors compared with the exposed groups.

CONCLUSIONS

Intrauterine malnutrition was not associated with glucose intolerance, dyslipidaemia, hypertension, or cardiovascular disease in adulthood. Subjects exposed to malnutrition showed evidence of endothelial dysfunction and a stronger influence of obesity on blood pressure.

Control of acyl-CoA carboxylase activity in mycobacteria

Acyl-CoA carboxylase activity in four pathogenic mycobacteria and Mycobacterium smegmatis was shown with both acetyl-CoA and propionyl-CoA substrates. Only very low activity was detected in mycobacteria grown in host tissues or on egg-based media rich in lecithin and avidin. This appeared to be a result of severe depression of activity, as strains which could be grown both in host tissue and egg-based media, and in the relatively simple Dubos or Sauton's media showed 8 to 120-fold higher activity in the simpler media.

Fatty acid oxidation and the beta-oxidation complex in Mycobacterium leprae and two axenically cultivable mycobacteria that are pathogens

Intact, non-growing Mycobacterium leprae, M. avium and M. microti oxidized a wide range of 1-14C-labelled fatty acids (C8 to C24) to 14CO2. Laurate (C12) was oxidized most rapidly, and its oxidation by M. leprae was inhibited by the antileprosy agents Dapsone, clofazamine and rifampicin. Key enzymes of beta-oxidation were detected in extracts from all three mycobacteria. All these activities (both in intact mycobacteria and the enzymes) were stimulated in M. avium grown in Dubos medium plus palmitate but activities in M. microti or M. avium grown either in Dubos medium with added liposomes or triolein, or in vivo were similar to those detected in the same strain grown in Dubos medium alone. M. avium could be grown in medium in which 95% of its fatty acyl elongase activity is acetyl-CoA dependent. In this medium growing M. avium organisms oxidized [1-14C]palmitate to 14CO2 but simultaneously elongated palmitate to C24 acids and even longer. Acetyl-CoA-dependent elongase activity is similar but clearly not identical to reversed beta-oxidation, but the exact point(s) of difference have not yet been identified.

Enzymes for biosynthesis de novo and elongation of fatty acids in mycobacteria grown in host cells: is Mycobacterium leprae competent in fatty acid biosynthesis?

Fatty acid synthetase activity in extracts of Mycobacterium leprae was equivalent to 1.7 pmol malonyl-CoA incorporated into fatty acid min-1 (mg protein)-1. This activity--if representative of living M. leprae organisms--is insufficient to enable them to synthesize their lipid requirements rapidly enough to support growth. The major activity for scavenging fatty acids in extracts of Mycobacterium microti and Mycobacterium avium, as well as in extracts of M. leprae, was acetyl-CoA-dependent fatty acyl-CoA 'elongase'. This activity was about four times higher in M. avium and M. microti grown in a medium which contained lipids, or when grown in mice, than in medium without added lipids. In contrast, the de novo fatty acid synthetase activity was repressed in M. avium and M. microti when grown in medium that contained lipids, or when grown in mice. These results are consistent with the hypothesis that mycobacteria grown in vivo preferentially scavenge lipids from the host cells, and suggest that a source of lipid should be included in media for attempted axenic isolation of M. leprae.