Lipid-induced mononuclear cell cytokine secretion in the development of metabolic aberration and androgen excess in polycystic ovary syndrome.

STUDY QUESTION: What is the effect of saturated fat ingestion on mononuclear cell (MNC) TNFα, IL-6 and IL-1ß secretion and circulating IL-6 levels in women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWER: Women with PCOS exhibit increases in MNC-derived TNFα, IL-6 and IL-1ß secretion and circulating IL-6 following saturated fat ingestion even in the absence of obesity, and these increases are linked to metabolic aberration and androgen excess. WHAT IS KNOWN ALREADY: Cytokine excess and metabolic aberration is often present in PCOS. STUDY DESIGN, SIZE, DURATION: A cross-sectional design was used in this study of 38 reproductive-age women. PARTICIPANTS/MATERIALS, SETTING, METHODS: Groups of 19 reproductive-age women with PCOS (10 lean, 9 obese) and 19 ovulatory controls (10 lean, 9 obese) participated in this study that was performed at a tertiary academic medical centre. TNFα, IL-6 and IL-1ß secretion was measured from cultured MNC, and IL-6 was measured in plasma from blood sampling while fasting and 2, 3 and 5 h after saturated fat ingestion. Insulin sensitivity was determined using the Matsuda index following an oral glucose tolerance test. Androgen secretion was evaluated with blood sampling while fasting and 24, 48 and 72 h after an HCG injection. MAIN RESULTS AND THE ROLE OF CHANCE: Lean and obese women with PCOS exhibited lipid-induced incremental AUC increases in MNC-derived TNFα (489-611%), IL-6 (333-398%) and IL-1ß (560-695%) secretion and in plasma IL-6 levels (426-474%), in contrast with lean control subjects. In both PCOS groups, insulin sensitivity was lower (42-49%) and androgen secretion after HCG injection was greater (63-110%) compared with control subjects. The MNC-derived TNFα, IL-6 and IL-1ß and circulating IL-6 responses were inversely associated with insulin sensitivity and directly associated with fasting lipids and androgen secretion after HCG injection. LIMITATIONS, REASONS FOR CAUTION: The sample size of each of the four study groups was modest following group assignment of subjects by body mass. WIDER IMPLICATIONS OF THE FINDINGS: This study showcases the unique pro-inflammatory contribution of circulating MNC in the development of metabolic aberration and androgen excess in PCOS. STUDY FUNDING/COMPETING INTEREST(S): This research was supported by grant R01 DK107605 to F.G. from the National Institutes of Health, the Indiana Clinical and Translational Sciences Institute Clinical Research Center which is funded in part by grant UL1TR002529 from the National Institutes of Health, National Center for Advancing Translational Sciences, Clinical and Translational Sciences Award, and the Indiana University Center for Diabetes and Metabolic Diseases funded by grant P30 DK097512 from the National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. No conflicts of interest, financial or otherwise, are declared by the authors. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov NCT01489319.

Effect of experimental change in children's sleep duration on television viewing and physical activity.

BACKGROUND: Paediatric observational studies demonstrate associations between sleep, television viewing and potential changes in daytime activity levels. OBJECTIVE(S): To determine whether experimental changes in sleep lead to changes in children's sedentary and physical activities. METHODS: Using a within-subject counterbalanced design, 37 children 8-11 years old completed a 3-week study. Children slept their typical amount during a baseline week and were then randomized to increase or decrease mean time in bed by 1.5 h/night for 1 week; the alternate schedule was completed the final week. Children wore actigraphs on their non-dominant wrist and completed 3-d physical activity recalls each week. RESULTS: Children reported watching more television (p < 0.001) and demonstrated lower daytime actigraph-measured activity counts per epoch (p = 0.03) when sleep was decreased (compared with increased). However, total actigraph-measured activity counts accrued throughout the entire waking period were higher when sleep was decreased (and children were awake for longer) than when it was increased (p < 0.001). CONCLUSION(S): Short sleep during childhood may lead to increased television viewing and decreased mean activity levels. Although additional time awake may help to counteract negative effects of short sleep, increases in reported sedentary activities could contribute to weight gain over time.

Changes in Weight and Glucose Can Protect Against Progression in Early Diabetes Independent of Improvements in ß-Cell Function.

CONTEXT: Evidence-based strategies to prevent progression of dysglycemia in newly diagnosed type 2 diabetes are needed. OBJECTIVE: To undertake a secondary analysis of the Early Diabetes Intervention Program (EDIP) in order to understand the features that were protective against worsening glycemia. DESIGN: EDIP was a randomized, placebo-controlled trial. SETTING: Two university diabetes centers. PATIENTS: A total of 219 overweight individuals with fasting glucose < 7.8 mmol/L and 2-hour oral glucose tolerance test (OGTT) glucose > 11.1 mmol/L. INTERVENTIONS: Acarbose versus placebo, on a background of dietary recommendations, with quarterly visits to assess glycemia and intervention adherence for up to 5 years. MAIN OUTCOME MEASURES: Progression of fasting glucose ≥ 7.8 mmol/L on two consecutive quarterly visits. Cox proportional hazards modeling and ANOVA were performed to evaluate determinants of progression. RESULTS: Progression-free status was associated with reductions in weight, fasting glucose, 2-hour OGTT glucose, and increases in the high-density lipoprotein/triglyceride ratio. The reduction in fasting glucose was the only effect that remained significantly associated with progression-free status in multivariable Cox modeling. The reduction in fasting glucose was in turn primarily associated with reductions in weight and in 2-hour OGTT glucose. Acarbose treatment did not explain these changes. CONCLUSIONS: In early diabetes, reductions in glucose, driven by reductions in weight, can delay progressive metabolic worsening. These observations underscore the importance of lifestyle management including weight loss as a tool to mitigate worsening of glycemia in newly diagnosed diabetes.

Assessment of myocardial metabolic flexibility and work efficiency in human type 2 diabetes using 16-[18F]fluoro-4-thiapalmitate, a novel PET fatty acid tracer.

Altered myocardial fuel selection likely underlies cardiac disease risk in diabetes, affecting oxygen demand and myocardial metabolic flexibility. We investigated myocardial fuel selection and metabolic flexibility in human type 2 diabetes mellitus (T2DM), using positron emission tomography to measure rates of myocardial fatty acid oxidation {16-[(18)F]fluoro-4-thia-palmitate (FTP)} and myocardial perfusion and total oxidation ([(11)C]acetate). Participants underwent paired studies under fasting conditions, comparing 3-h insulin + glucose euglycemic clamp conditions (120 mU·m(-2)·min(-1)) to 3-h saline infusion. Lean controls (n = 10) were compared with glycemically controlled volunteers with T2DM (n = 8). Insulin augmented heart rate, blood pressure, and stroke index in both groups (all P < 0.01) and significantly increased myocardial oxygen consumption (P = 0.04) and perfusion (P = 0.01) in both groups. Insulin suppressed available nonesterified fatty acids (P < 0.0001), but fatty acid concentrations were higher in T2DM under both conditions (P < 0.001). Insulin-induced suppression of fatty acid oxidation was seen in both groups (P < 0.0001). However, fatty acid oxidation rates were higher under both conditions in T2DM (P = 0.003). Myocardial work efficiency was lower in T2DM (P = 0.006) and decreased in both groups with the insulin-induced increase in work and shift in fuel utilization (P = 0.01). Augmented fatty acid oxidation is present under baseline and insulin-treated conditions in T2DM, with impaired insulin-induced shifts away from fatty acid oxidation. This is accompanied by reduced work efficiency, possibly due to greater oxygen consumption with fatty acid metabolism. These observations suggest that improved fatty acid suppression, or reductions in myocardial fatty acid uptake and retention, could be therapeutic targets to improve myocardial ischemia tolerance in T2DM.

Failure of hyperglycemia and hyperinsulinemia to compensate for impaired metabolic response to an oral glucose load.

OBJECTIVE: To evaluate whether the augmented insulin and glucose response to a glucose challenge is sufficient to compensate for defects in glucose utilization in obesity and type 2 diabetes, using a breath test measurement of integrated glucose metabolism. METHODS: Non-obese, obese normoglycemic and obese type 2 diabetic subjects were studied on 2 consecutive days. A 75g oral glucose load spiked with ¹³C-glucose was administered, measuring exhaled breath ¹³CO2 as an integrated measure of glucose metabolism and oxidation. A hyperinsulinemic euglycemic clamp was performed, measuring whole body glucose disposal rate. Body composition was measured by DEXA. Multivariable analyses were performed to evaluate the determinants of the breath ¹³CO2. RESULTS: Breath ¹³CO2 was reduced in obese and type 2 diabetic subjects despite hyperglycemia and hyperinsulinemia. The primary determinants of breath response were lean mass, fat mass, fasting FFA concentrations, and OGTT glucose excursion. Multiple approaches to analysis showed that hyperglycemia and hyperinsulinemia were not sufficient to compensate for the defect in glucose metabolism in obesity and diabetes. CONCLUSIONS: Augmented insulin and glucose responses during an OGTT are not sufficient to overcome the underlying defects in glucose metabolism in obesity and diabetes.

Effect of acarbose to delay progression of carotid intima-media thickness in early diabetes.

BACKGROUND: The anti-diabetic agent acarbose reduces postprandial glucose excursions. We have evaluated the effect of randomized treatment with acarbose on the progression of carotid intima-media thickness (IMT) in early diabetes. METHODS: The Early Diabetes Intervention Program was a randomized trial of acarbose versus placebo in 219 participants with early diabetes characterized by glucose values over 11.1 mmol/L 2 h after a 75 g oral glucose load and a mean HbA1c of 6.3%. IMT was measured at baseline and yearly. Follow-up was discontinued if participants progressed to the study glucose endpoints; IMT readings were available for a median of 2 years, with 72 subjects followed for 5 years. RESULTS: Progressive increases in IMT were seen in both treatment groups, but progression was reduced in participants randomized to acarbose (p = 0.047). In age, sex and smoking-adjusted analyses, IMT progression was associated with greater fasting and oral glucose tolerance test-excursion glucose, fasting insulin, cholesterol and glycated low-density lipoprotein concentrations. IMT progression was reduced with study-related changes in weight, insulin and non-esterified fatty acids; these features were more strongly associated with reduced IMT progression than acarbose treatment. Despite strong associations of baseline glycemia with IMT progression, study-related changes in glucose were not important determinants of IMT progression. CONCLUSIONS: Acarbose can delay progression of carotid intima-media thickness in early diabetes defined by an oral glucose tolerance test. Glucose, weight, insulin and lipids contributed to risk of progression but reductions in glycemia were not major determinants of reduced rate of IMT progression. Vascular benefits of acarbose may be independent of its glycemic effects.

Fat-induced membrane cholesterol accrual provokes cortical filamentous actin destabilisation and glucose transport dysfunction in skeletal muscle.

AIMS/HYPOTHESIS: Diminished cortical filamentous actin (F-actin) has been implicated in skeletal muscle insulin resistance, yet the mechanism(s) is unknown. Here we tested the hypothesis that changes in membrane cholesterol could be a causative factor, as organised F-actin structure emanates from cholesterol-enriched raft microdomains at the plasma membrane. METHODS: Skeletal muscle samples from high-fat-fed animals and insulin-sensitive and insulin-resistant human participants were evaluated. The study also used L6 myotubes to directly determine the impact of fatty acids (FAs) on membrane/cytoskeletal variables and insulin action. RESULTS: High-fat-fed insulin-resistant animals displayed elevated levels of membrane cholesterol and reduced F-actin structure compared with normal chow-fed animals. Moreover, human muscle biopsies revealed an inverse correlation between membrane cholesterol and whole-body glucose disposal. Palmitate-induced insulin-resistant myotubes displayed membrane cholesterol accrual and F-actin loss. Cholesterol lowering protected against the palmitate-induced defects, whereas characteristically measured defects in insulin signalling were not corrected. Conversely, cholesterol loading of L6 myotube membranes provoked a palmitate-like cytoskeletal/GLUT4 derangement. Mechanistically, we observed a palmitate-induced increase in O-linked glycosylation, an end-product of the hexosamine biosynthesis pathway (HBP). Consistent with HBP activity affecting the transcription of various genes, we observed an increase in Hmgcr, a gene that encodes 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. In line with increased HBP activity transcriptionally provoking a membrane cholesterol-based insulin-resistant state, HBP inhibition attenuated Hmgcr expression and prevented membrane cholesterol accrual, F-actin loss and GLUT4/glucose transport dysfunction. CONCLUSIONS/INTERPRETATION: Our results suggest a novel cholesterolgenic-based mechanism of FA-induced membrane/cytoskeletal disorder and insulin resistance.

Effects of losartan on whole body, skeletal muscle and vascular insulin responses in obesity/insulin resistance without hypertension.

AIMS: Renin-angiotensin system antagonists have been found to improve glucose metabolism in obese hypertensive and type 2 diabetic subjects. The mechanism of these effects is not well understood. We hypothesized that the angiotensin receptor antagonist losartan would improve insulin-mediated vasodilation, and thereby improve insulin-stimulated glucose uptake in skeletal muscle of insulin-resistant subjects. METHODS: We studied subjects with obesity and insulin resistance but without hypertension, hypercholesterolaemia or dysglycaemia [age 39.0 ± 9.6 yr (mean ± SD), body mass index (BMI) 33.2 ± 5.9 kg/m(2) , BP 115.8 ± 12.2/70.9 ± 7.2 mmHg, LDL 2.1 ± 0.5 mmol/l]. Subjects were randomized to 12 weeks' double-blind treatment with losartan 100 mg once daily (n = 9) or matching placebo (n = 8). Before and after treatment, under hyperinsulinaemic euglycaemic clamp conditions we measured whole-body insulin-stimulated glucose disposal, insulin-mediated vasodilation, and insulin-stimulated leg glucose uptake by the limb balance technique. RESULTS: Whole-body insulin-stimulated glucose disposal was not significantly increased by losartan. Insulin-mediated vasodilation was augmented following both treatments [increase in leg vascular conductance: pretreatment 0.7 ± 0.3 l/min/mmHg (losartan, mean ± SEM) and 0.9 ± 0.3 (placebo), posttreatment 1.0 ± 0.4 (losartan) and 1.3 ± 0.6 (placebo)] but not different between treatment groups (p = 0.53). Insulin's action to augment nitric oxide (NO) production and to augment endothelium-dependent vasodilation was also not improved. Leg glucose uptake was not significantly changed by treatments, and not different between groups (p = 0.11). CONCLUSIONS: These findings argue against the hypothesis that losartan might improve skeletal muscle glucose metabolism by improving insulin-mediated vasodilation in normotensive insulin-resistant obese subjects. The metabolic benefits of angiotensin receptor blockers may require the presence of hypertension in addition to obesity-associated insulin resistance.

mRNA concentrations of MIF in subcutaneous abdominal adipose cells are associated with adipocyte size and insulin action.

OBJECTIVE: To determine whether the mRNA concentrations of inflammation response genes in isolated adipocytes and in cultured preadipocytes are related to adipocyte size and in vivo insulin action in obese individuals. DESIGN: Cross-sectional inpatient study. SUBJECTS: Obese Pima Indians with normal glucose tolerance. MEASUREMENTS: Adipocyte diameter (by microscope technique; n=29), expression of candidate genes (by quantitative real-time PCR) in freshly isolated adipocytes (monocyte chemoattractant protein (MCP) 1 and MCP2, macrophage inflammatory protein (MIP) 1alpha, MIP1beta and MIP2, macrophage migration inhibitory factor (MIF), tumor necrosis factor alpha, interleukin (IL) 6 and IL8; n=22) and cultured preadipocytes (MCP1, MIP1alpha, MIF, IL6 and matrix metalloproteinase 2; n=33) from subcutaneous abdominal adipose tissue (by aspiration biopsy, n=34), body fat by dual-energy X-ray absorptiometry, glucose tolerance by 75 g oral glucose tolerance test and insulin action by euglycemic-hyperinsulinemic clamp (insulin infusion rate 40 mU m(-2) min(-1)) (all n=34). RESULTS: MIF was the only gene whose expression in both freshly isolated adipocytes and cultured preadipocytes was positively associated with adipocytes diameter and negatively associated with peripheral and hepatic insulin action (all P<0.05). In multivariate analysis, the association between adipocyte MIF mRNA concentrations and adipocytes diameter was independent of the percentage of body fat (P=0.03), whereas adipocyte MIF mRNA concentrations, but not adipocyte diameter, independently predicted peripheral insulin action. The mRNA expression concentrations of the MIF gene in adipocytes were not associated with plasma concentrations of MIF, but were negatively associated with plasma adiponectin concentrations (P=0.004). In multivariate analysis, adipocyte MIF RNA concentrations (P=0.03) but not plasma adiponectin concentrations (P=0.4) remained a significant predictor of insulin action. CONCLUSIONS: Increased expression of MIF gene in adipose cells may be an important link between obesity characterized by enlarged adipocytes and insulin resistance in normal glucose tolerant people.

Expression of the thermogenic nuclear hormone receptor coactivator PGC-1alpha is reduced in the adipose tissue of morbidly obese subjects.

Peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC1alpha) is an accessory protein which can potentiate the transcriptional activation function of many nuclear hormone receptors. Its tissue distribution and physiological studies suggest that its principal in vivo roles are to promote cold-induced thermogenesis, mitochondrial biogenesis, hepatic gluconeogenesis, and fatty acid beta-oxidation. It is expressed in the white adipose tissue of both humans and rodents, and in rodents it has been suggested to mediate in part the leptin-induced conversion of white adipocytes from fat storing to fat oxidising cells. In this study, quantitative real-time PCR has been used in human tissue to demonstrate that (1) PGC1alpha mRNA levels in subcutaneous fat are three-fold lower in morbidly obese than in slim subjects; (2) there are no differences in PGC1alpha mRNA between omental and subcutaneous mature adipocytes; (3) there is a robust induction of PGC1alpha expression during subcutaneous human preadipocyte differentiation ex vivo. Whether low PGC1alpha expression is a prelude to the development of obesity, or a consequence of that obesity, attempts to upregulate endogenous white adipose tissue expression may prove a valuable new avenue to explore in obesity therapy.

Leptin levels in type 2 diabetes: associations with measures of insulin resistance and insulin secretion.

Interactions between leptin and insulin have been shown previously, in vitro and in vivo. In this study, we evaluate the associations of leptin levels with insulin secretion and insulin sensitivity in type 2 diabetes. Fasting leptin levels, HbA 1c, glucose, insulin, C-peptide, intact and des-31,32-proinsulin were measured in 100 non-insulin-treated type 2 diabetic patients. Glucose, insulin and C-peptide were measured 2 hours after an oral glucose load. Insulin resistance and beta-cell function were calculated using HOMA. Leptin levels were found to be associated with all measures of beta-cell secretion: with fasting and 2 hours insulin and C-peptide, with intact and des-31,32-proinsulin concentrations, and with beta-cell secretion estimated with HOMA. This association was independent of age and body fat in women, but in men, associations with insulin and C-peptide weakened after controlling for fat mass, whereas those with intact and des-31,32-proinsulin disappeared. Fasting insulin and C-peptide levels were also significant in multiple regression analyses, besides gender and fat mass. Insulin resistance, as assessed by HOMA, was strongly correlated with leptin, also after correction for age and fat mass in both genders. We conclude that, besides fat mass and gender - the main determinants for leptin levels in type 2 diabetic subjects as in healthy subjects - insulin secretion and the degree of insulin resistance also seem to contribute significantly to leptin levels.

Serum leptin responses after acute resistance exercise protocols.

This study examined the acute effects of maximum strength (MS), muscular hypertrophy (MH), and strength endurance (SE) resistance exercise protocols on serum leptin. Ten young lean men (age = 23 +/- 4 yr; body weight = 79.6 +/- 5.2 kg; body fat = 10.2 +/- 3.9%) participated in MS [4 sets x 5 repetitions (reps) at 88% of 1 repetition maximum (1 RM) with 3 min of rest between sets], MH (4 sets x 10 reps at 75% of 1 RM with 2 min of rest between sets), SE (4 sets x 15 reps at 60% of 1 RM with 1 min of rest between sets), and control (C) sessions. Blood samples were collected before and immediately after exercise and after 30 min of recovery. Serum leptin at 30 min of recovery exhibited similar reductions from baseline after the MS (-20 +/- 5%), MH (-20 +/- 4%), and SE (-15 +/- 6%) protocols that were comparable to fasting-induced reduction in the C session (-12 +/- 3%) (P < 0.05). Furthermore, no differences were found in serum leptin among the MS, MH, SE, and C sessions immediately after exercise and at 30 min of recovery (P > 0.05). Cortisol was higher (P < 0.05) after the MH and SE protocols than after the MS and C sessions. Glucose and growth hormone were higher (P < 0.05) after exercise in the MS, MH, and SE protocols than after the C session. In conclusion, typical resistance exercise protocols designed for development of MS, MH, and SE did not result in serum leptin changes when sampled immediately or 30 min postexercise.

Differential effects of adiposity on peroxisomal proliferator-activated receptor gamma1 and gamma2 messenger ribonucleic acid expression in human adipocytes.

Both genetic and pharmacological studies raise the possibility that a primary increase in the amount or activity of peroxisomal proliferator-activated receptor gamma (PPARgamma) in adipocytes could play a role in common types of human obesity. Using real-time RT-PCR assays we examined the relationship between body mass index (BMI) and PPARgamma isoform expression in freshly isolated human adipocytes. There were no consistent differences in the expression of either PPARgamma1 mRNA or PPARgamma2 mRNA between omental and sc adipocytes. In a group of 17 subjects (BMI range, 17-34 kg/m(2)) there was a strong and highly significant inverse correlation (r = -0.68; P < 0.005) between PPARgamma1 mRNA expression in adipocytes and BMI, whereas no significant relationship was apparent for PPARgamma2. In an independent study PPARgamma1 mRNA levels were decreased (1.1 +/- 0.1 vs. 3.7 +/- 0.8 arbitrary units; P < 0.01) in adipocytes from morbidly obese (BMI, 50.6 +/- 14.1 kg/m(2)) vs. lean (BMI, 21.1 +/- 1.0 kg/m(2)) subjects. In contrast, there was a significant increase in the expression of PPARgamma2 mRNA levels between the morbidly obese and lean groups (1.7 +/- 0.2 vs. 1.1 +/- 0.2 arbitrary units; P < 0.05). Treatment of isolated human adipocytes with TNFalpha resulted in a significant decrease in both PPARgamma1 and PPARgamma2 mRNA levels [40.6 +/- 5.5% relative to control (P = 0.01) and 60.9 +/- 24.8% (P = 0.02) respectively]. The strong inverse relationship between BMI and PPARgamma1 expression in human adipocytes is striking and may represent part of an autoregulatory mechanism restraining the expansion of individual adipocytes in states of positive energy balance. On the other hand, the increase in PPARgamma2 observed in adipocytes of morbidly obese individuals suggests a potential pathogenic effect of this isoform in promoting fat acquisition. Although an autocrine effect of the enhanced TNFalpha secretion seen with increasing obesity might play a role in the changes in PPARgamma1, this would not provide an explanation for the different relationship of PPARgamma2 to adiposity. The significance of the divergent effect of human adiposity on the two isoforms will require a greater understanding of the differential properties of the two isoforms and of the differences in the functions of their respective regulatory elements.

Regulation of leptin production.

Fat mass is the primary determinant of serum leptin in humans with energy intake and gender also having significant effects. Gender influences leptin production through the reproductive hormones. Glucose metabolism links food intake to leptin production and hexosamine biosynthesis appears to play a significant role in this process. Catecholamines inhibit leptin production and the sympathetic nervous system has been proposed to be the efferent arm of the leptin signal transduction pathway between adipose tissue and the central nervous system. Additional regulators of leptin production include glucocorticoids, cytokines and agonists of PPAR gamma. In addition to adipose tissue, leptin is produced in several other places including placenta, bone marrow, stomach, muscle and perhaps brain, thus increasing the number of potential regulatory roles for this hormone. Future work will be needed to fully elucidate the mechanisms regulating leptin synthesis/release in each tissue as well as its regulatory functions.

Resistin / Fizz3 expression in relation to obesity and peroxisome proliferator-activated receptor-gamma action in humans.

Recent studies in murine models suggest that resistin (also called Fizz3 [1]), a novel cysteine-rich protein secreted by adipocytes, may represent the long-sought link between obesity and insulin resistance (2). Furthermore, peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists appear to inhibit resistin expression in murine adipocytes, providing a possible explanation for the mode of action of this class of insulin sensitizers (2). Using a fluorescent real-time reverse transcriptase-polymerase chain reaction-based assay, we found that resistin mRNA levels in whole adipose tissue samples were increased in morbidly obese humans compared with lean control subjects. However, in freshly isolated human adipocytes, resistin mRNA levels were very low and showed no correlation with BMI. Resistin mRNA was undetectable in preadipocytes, endothelial cells, and vascular smooth muscle cells, but it was readily detectable in circulating mononuclear cells. Although exposure of human mononuclear cells to PPAR-gamma agonists markedly upregulated fatty acid-binding protein-4 expression, these agents had no effect on mononuclear cell resistin expression. Finally, resistin mRNA was undetectable in adipocytes from a severely insulin-resistant subject with a dominant-negative mutation in PPAR-gamma (3). We conclude that the recently described relationships of murine resistin/Fizz3 expression with obesity, insulin resistance, and PPAR-gamma action may not readily translate to humans. Further studies of this novel class of proteins are needed to clarify their roles in human metabolism.

Public housing, public health: health needs of public housing tenants.

OBJECTIVES: To determine the health needs of public housing tenants, measured in terms of self-reported health status, health risk factors and expressed need for health risk reduction intervention. METHOD: Face-to-face interviews were conducted with a randomly selected sample of public housing tenants in the Hunter Region of New South Wales. RESULTS: Of 463 contactable tenants, 329 consented to participate in the study. Participants were 2.5 times more likely to rate their health as fair or poor relative to the community generally, and visited a doctor twice as often. The prevalence of smoking was more than twice that of the community generally, and the prevalence of falls was approximately three times greater. Risk of injury due to domestic violence was approximately six times greater, and the risk of injury due to violence in other locations was more than double that in the community. Between a quarter and a half of the participants requested support to reduce their health risks. CONCLUSIONS: The findings suggest that public housing tenants are one of the more severely health-compromised groups in the Australian community. IMPLICATIONS: An urgent need exists for public health initiatives that are directed at improving not only the current markedly poorer health status of public housing tenants, but also the greater prevalence of health risk factors that predict a likely continuation of such differentials into the future.

Infant exposure to environmental tobacco smoke: a prevalence study in Australia.

OBJECTIVE: To determine: the prevalence of exposure to environmental tobacco smoke among infants aged 0-12 months in two child health care settings; the accuracy of parent report indicators of exposure; and the factors associated with exposure to environmental tobacco smoke. METHOD: Samples of consecutive parents of infants 12 months of age or younger who attended Hunter Region public child health and immunisation clinics were approached to complete a questionnaire and to allow a urine sample to be obtained from their infant during December and January 1998/99. Infant urine samples were analysed for cotinine and information obtained regarding the smoking status of household members, infant exposure to environmental tobacco smoke during the previous three days, and parent and infant characteristics and demographics. RESULTS: 85 (47%) [95% CI 40-54] infants in the combined sample had detectable levels of cotinine. Sensitivity of reported infant exposure of 86% was achieved through the combined measure of parent report of exposure and smoking status of households. The odds of exposure for infants of smoking parents were 14 times that of infants of nonsmokers [CI 5.26-50.0]. CONCLUSIONS: Almost half of the infants in this study had detectable levels of cotinine in their urine. Future interventions targeting infant exposure to environmental tobacco smoke should incorporate quit smoking strategies for both parents and other household members, as well as strategies for changing the pattern of smoking behaviour around infants. IMPLICATIONS: These findings suggest that existing community education strategies and passive smoking public policies are failing to protect this vulnerable population group.

Increasing the practice of health promotion initiatives by licensed premises.

Licensees of all licensed premises in the Hunter Region of New South Wales, Australia, were offered free services to encourage adoption of health promotion initiatives relating to responsible service of alcohol, environmental tobacco smoke, healthy food choices, breast and cervical cancer prevention, and the prevention of HIV/AIDS. A total of 239 premises participated in the follow-up survey. Increases in prevalence ranged between 11% and 59% for alcohol-related initiatives. The prevalence of smoke-free areas and healthy food choices increased from 32% to 65% and 42% to 96%, respectively, and the provision of cancer prevention information increased from 3% to 59%. Licensed premises represent a particularly challenging sector for health promotion practitioners to work in. The results of this study suggest that the adoption of health promotion initiatives by licensed premises can be increased. A considerable opportunity therefore exists for health promotion practitioners to become more actively involved in facilitating the adoption of such initiatives in this setting.

Polymorphisms in the leptin receptor gene, body composition and fat distribution in overweight and obese women.

OBJECTIVE: Leptin is an adipocyte-secreted hormone involved in body weight regulation, acting through the leptin receptor, localised centrally in the hypothalamus as well as peripherally, amongst others on adipose tissue. The aim of this study was to evaluate whether polymorphisms in the leptin receptor (LEPR) gene were related to obesity and body fat distribution phenotypes, such as waist and hip circumferences and the amount of visceral and subcutaneous fat. METHODS: Three known LEPR polymorphisms, Lys109Arg, Gln223Arg and Lys656Asn, were typed on genomic DNA of 280 overweight and obese women (body mass index (BMI)>25), aged 18-60 y. General linear model (GLM) analyses were performed in 198 pre- and 82 postmenopausal women, adjusting the data for age and menopausal state, plus fat mass for the fat distribution phenotypes. RESULTS: No associations were found between the LEPR polymorphisms and BMI or fat mass. In postmenopausal women, carriers of the Asn656 allele had increased hip circumference (P=0.03), total abdominal fat (P=0.03) and subcutaneous fat (P=0.04) measured by CT scan. Total abdominal fat was also higher in Gln223Gln homozygotes (P=0.04). Also in postmenopausal women, leptin levels were higher in Lys109Lys homozygotes (P=0.02). CONCLUSION: In conclusion, polymorphisms in the leptin receptor gene are associated with levels of abdominal fat in postmenopausal overweight women. Since body fat distribution variables were adjusted for fat mass, these results suggest that DNA sequence variations in the leptin receptor gene play a role in fat topography and may be involved in the predisposition to abdominal obesity.

Hexosamines regulate leptin production in human subcutaneous adipocytes.

The hexosamine biosynthetic pathway has recently been proposed as a mechanism through which cells "sense" nutrient flux to regulate leptin release. This study was undertaken to examine the regulation of leptin production by hexosamines in human adipocytes. Adipose tissue UDP-N-acetylglucosamine, an end product of hexosamine biosynthesis, was elevated 3.2-fold, and ob messenger ribonucleic acid was elevated 2-fold in the sc adipose tissue of 17 obese [body mass index (BMI), 41.3+/-12.0 kg/m2; age, 31+/-5 yr] subjects compared to 14 lean (BMI, 23.4+/-1.6 kg/m2; age, 33+/-11 yr) subjects. Serum leptin was increased 2.7-fold in the obese subjects. A significant positive relationship was found between adipose tissue UDP-N-acetylglucosamine and BMI (Spearman correlation = 0.576; P = 0.0007) and between UDP-N-acetylglucosamine and serum leptin (Spearman correlation = 0.4650; P = 0.0145). Treatment of isolated sc adipocytes with 1 mmol/L glucosamine, an intermediate product in UDP-N-acetylglucosamine biosynthesis, increased leptin release 21.4+/-17.6% (mean +/- SD) over control (P = 0.0365) and 74.5+/-82.8% over control (P = 0.0271) in adipocytes from lean (BMI, 23.2+/-1.6 kg/m2; n = 6) and obese (BMI, 55.4+/-13.0 kg/m2,; n = 9) subjects, respectively, by 48 h of culture. Inhibition of UDP-N-acetylglucosamine biosynthesis with 6-diazo-5-oxo-norleucine reduced glucose-stimulated leptin release from cultured adipocytes 21.8+/-32.4% (P = 0.0395; n = 12) and ob gene expression 19.9+/-18.9% (P = 0.0208; n = 8) by 48 h of treatment. These findings suggest that hexosamine biosynthesis regulates leptin production in human adipose tissue.