Abdominal fat and insulin resistance in normal and overweight women: Direct measurements reveal a strong relationship in subjects at both low and high risk of NIDDM

Comparison of dual-energy x-ray absorptiometric and anthropometric measures of adiposity in relation to adiposity-related biologic factors

Dual-energy x-ray absorptiometry (DXA) can provide accurate measurements of body composition. Few studies have compared the relative validity of DXA measures with anthropometric measures such as body mass index (BMI) and waist circumference (WC). The authors compared correlations of DXA measurements of total fat mass and fat mass percent in the whole body and trunk, BMI, and WC with obesity-related biologic factors, including blood pressure and levels of plasma lipids, C-reactive protein, and fasting insulin and glucose, among 8,773 adults in the National Health and Nutrition Examination Survey (1999-2004). Overall, the magnitudes of correlations of BMI and WC with the obesity-related biologic factors were similar to those of fat mass or fat mass percent in the whole body and trunk, respectively. These observations were largely consistent across different age, gender, and ethnic groups. In addition, in both men and women, BMI and WC demonstrated similar abilities to distinguish between participants with and without the metabolic syndrome in comparison with corresponding DXA measurements. These data indicate that the validity of simple anthropometric measures such as BMI and WC is comparable to that of DXA measurements of fat mass and fat mass percent, as evaluated by their associations with obesity-related biomarkers and prevalence of metabolic syndrome.

Intrinsic depot-specific differences in the secretome of adipose tissue, preadipocytes, and adipose tissue-derived microvascular endothelial cells

OBJECTIVE

Visceral adipose tissue (VAT) is more closely linked to insulin resistance than subcutaneous adipose tissue (SAT). We conducted a quantitative analysis of the secretomes of VAT and SAT to identify differences in adipokine secretion that account for the adverse metabolic consequences of VAT.

RESEARCH DESIGN AND METHODS

We used lectin affinity chromatography followed by comparison of isotope-labeled amino acid incorporation rates to quantitate relative differences in the secretomes of VAT and SAT explants. Because adipose tissue is composed of multiple cell types, which may contribute to depot-specific differences in secretion, we isolated preadipocytes and microvascular endothelial cells (MVECs) and compared their secretomes to those from whole adipose tissue.

RESULTS

Although there were no discrete depot-specific differences in the secretomes from whole adipose tissue, preadipocytes, or MVECS, VAT exhibited an overall higher level of protein secretion than SAT. More proteins were secreted in twofold greater abundance from VAT explants compared with SAT explants (59% versus 21%), preadipocytes (68% versus 0%), and MVECs (62% versus 15%). The number of proteins in the whole adipose tissue secretome was greater than the sum of its cellular constituents. Finally, almost 50% of the adipose tissue secretome was composed of factors with a role in angiogenesis.

CONCLUSIONS

VAT has a higher secretory capacity than SAT, and this difference is an intrinsic feature of its cellular components. In view of the number of angiogenic factors in the adipose tissue secretome, we propose that VAT represents a more readily expandable tissue depot.

Insulin resistance independently influences arterial stiffness in normoglycemic normotensive postmenopausal women

OBJECTIVE

Cardiovascular disease risk increases after menopause, which may be related to insulin resistance, and arterial stiffness is a significant predictor of atherosclerosis. We investigated the relationships among insulin resistance, adiponectin, and arterial stiffness in normoglycemic normotensive postmenopausal women.

METHODS

From 9,555 participants who had routine health checkups, 455 normoglycemic normotensive postmenopausal women were enrolled. Serum concentrations of glucose, total cholesterol, triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) and adiponectin were measured. Insulin resistance was estimated by the insulin resistance index of homeostasis model assessment (HOMA-IR). Pulse wave velocity (PWV) was evaluated to assess arterial stiffness.

RESULTS

The women were stratified into three groups according to their HOMA-IR values, and comparisons were made among the three groups. There were significant differences in metabolic parameters between the groups. The mean age, body mass index, waist circumference, fasting plasma glucose, TG, systolic blood pressure (SBP), diastolic blood pressure (DBP), aortic PWV, and peripheral PWV increased sequentially with the degree of insulin resistance. Meanwhile, HDL-C and adiponectin levels decreased with the worsening of insulin resistance. Age, body mass index, fasting plasma glucose, TG, insulin, SBP, HOMA-IR, aortic PWV, and peripheral PWV were significantly higher in women with central obesity, and HDL-C and adiponectin were significantly lower in women with central obesity. Aortic PWV and peripheral PWV were significantly correlated with age, waist circumference, total cholesterol, SBP, DBP, insulin, and HOMA-IR, but adiponectin was not associated with PWV. The results of multiple regression analysis indicated that SBP, DBP, and insulin resistance were independently correlated with PWV.

CONCLUSIONS

Insulin resistance was independently associated with PWV in normoglycemic normotensive postmenopausal women.

MRI assessment of lean and adipose tissue distribution in female patients with Cushing's disease

OBJECTIVE

Chronic hypercortisolemia due to Cushing's disease (CD) results in abnormal adipose tissue (AT) distribution. Whole-body magnetic resonance imaging (MRI) was used to examine lean and AT distribution in female patients with CD to further understand the role of glucocorticoid excess in the development of abnormal AT distribution and obesity.

DESIGN

Cross-sectional and case-control study.

PATIENTS

Fifteen women with CD and 12 healthy controls.

MEASUREMENTS

Mass of skeletal muscle (SM) and AT in the visceral (VAT), subcutaneous (SAT), and intermuscular (IMAT) compartments from whole-body MRI and serum levels of insulin, glucose, and leptin were measured.

RESULTS

CD patients had leptin values that correlated to total AT (TAT) and SAT (P < 0.05) but not to VAT. CD patients had higher VAT/TAT ratios (P < 0.01) and lower SAT/TAT ratios (P < 0.05) compared to controls. TAT, VAT, and trunk SAT (TrSAT) were greater in CD patients (P < 0.01). SM was less in CD (P < 0.001) but IMAT was not different.

CONCLUSIONS

TAT, VAT, trSAT, and the proportion of AT in the visceral depot were greater in CD although the proportion in the subcutaneous depot was less. SM was less but IMAT was not different. These findings have implications for understanding the role of cortisol in the abnormal AT distribution and metabolic risk seen in patients exposed to chronic excess glucocorticoids.

Imaging body composition in obesity and weight loss: challenges and opportunities

Obesity is a threat to public health worldwide primarily due to the comorbidities related to visceral adiposity, inflammation, and insulin resistance that increase risk for type 2 diabetes and cardiovascular disease. The translational research portfolio that originally described these risk factors was significantly enhanced by imaging techniques, such as dual-energy X-ray absorptiometry (DEXA), computed tomography (CT), and magnetic resonance imaging (MRI). In this article, we briefly review the important contributions of these techniques to understand the role of body composition in the pathogenesis of obesity-related complications. Notably, these imaging techniques have contributed greatly to recent findings identifying gender and racial differences in body composition and patterns of body composition change during weight loss. Although these techniques have the ability to generate good-quality body composition data, each possesses limitations. For example, DEXA is unable to differentiate type of fat, CT has better resolution but provides greater ionizing radiation exposure, and MRI tends to require longer imaging times and specialized equipment for acquisition and analysis. With the serious need for efficacious and cost-effective therapies to appropriately identify and treat at-risk obese individuals, there is greater need for translational tools that can further elucidate the interplay between body composition and the metabolic aberrations associated with obesity. In conclusion, we will offer our perspective on the evolution toward an ideal imaging method for body composition assessment in obesity and weight loss, and the challenges remaining to achieve this goal.

A family history of type 2 diabetes increases risk factors associated with overfeeding

AIMS/HYPOTHESIS

The purpose of the study was to test prospectively whether healthy individuals with a family history of type 2 diabetes are more susceptible to adverse metabolic effects during experimental overfeeding.

METHODS

We studied the effects of 3 and 28 days of overfeeding by 5,200 kJ/day in 41 sedentary individuals with and without a family history of type 2 diabetes (FH+ and FH- respectively). Measures included body weight, fat distribution (computed tomography) and insulin sensitivity (hyperinsulinaemic-euglycaemic clamp).

RESULTS

Body weight was increased compared with baseline at 3 and 28 days in both groups (p < 0.001), FH+ individuals having gained significantly more weight than FH- individuals at 28 days (3.4 +/- 1.6 vs 2.2 +/- 1.4 kg, p < 0.05). Fasting serum insulin and C-peptide were increased at 3 and 28 days compared with baseline in both groups, with greater increases in FH+ than in FH- for insulin at +3 and +28 days (p < 0.01) and C-peptide at +28 days (p < 0.05). Fasting glucose also increased at both time points, but without a significant group effect (p = 0.1). Peripheral insulin sensitivity decreased in the whole cohort at +28 days (54.8 +/- 17.7 to 50.3 +/- 15.6 micromol min(-1) [kg fat-free mass](-1), p = 0.03), and insulin sensitivity by HOMA-IR decreased at both time points (p < 0.001) and to a greater extent in FH+ than in FH- (p = 0.008). Liver fat, subcutaneous and visceral fat increased similarly in the two groups (p < 0.001).

CONCLUSIONS

Overfeeding induced weight and fat gain, insulin resistance and hepatic fat deposition in healthy individuals. However, individuals with a family history of type 2 diabetes gained more weight and greater insulin resistance by HOMA-IR. The results of this study suggest that healthy individuals with a family history of type 2 diabetes are predisposed to adverse effects of overfeeding.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00562393

FUNDING

The study was funded by the National Health and Medical Research Council (NHMRC), Australia (no. #427639).

Effects of four Bifidobacteria on obesity in high-fat diet induced rats

AIM: To compare the effects of four Bifidobacteria strains (Bifidobacteria L66-5, L75-4, M13-4 and FS31-12, originated from normal human intestines) on weight gain, lipid metabolism, glucose metabolism in an obese murine model induced by high-fat diet.

METHODS: Forty-eight Sprague-Dawley rats were randomly divided into six groups. Control group received standard chow, model group received high-fat diet, and intervention groups received high-fat diet added with different Bifidobacteria strains isolated from healthy volunteers’ fresh feces. All rats were executed at the 6th weekend. Body weight (BW), obese indexes, oral glucose tolerance test, serum and liver lipid and serum insulin (INS) were tested. Liver lipid deposition was classified pathologically.

RESULTS: Compared with the model group, B. M13-4 improved BW gains (264.27 ± 26.91 vs 212.55 ± 18.54, P = 0.001) while B. L66-5 induced a decrease in BW (188.47 ± 11.96 vs 212.55 ± 18.54, P = 0.043). The rest two strains had no significant change in BW. All the four strains can reduce serum and liver triglyceride and significantly alleviate the lipid deposition in liver. All strains showed a trend of lowing serum and liver total cholesterol while B. L66-5 and B. FS31-12 did so more significantly. In addition, all the four strains showed no significant differences in serum INS and glucose level.

CONCLUSION: The response of energy metabolism to administration of Bifidobacteria is strain dependent. Different strains of Bifidobacteria might drive different directions of fat distribution.

Effect of regional fat loss assessed by DXA on insulin resistance and dyslipidaemia in obese women

OBJECTIVE

To investigate the impact of reduction in total fat mass (FM) and regional FMs on indices of insulin resistance and dyslipidaemia in obese women (BMI > 30 kg/m(2)) after a 1-year weight loss (WL) program; and, secondly, to investigate the potential predictive effect of baseline insulin resistance on reduction in total and regional FMs.

MATERIAL AND METHODS

In 35 women with > 4 kg weight loss, body composition by DXA (dual X-ray absorptiometry), fasting insulin, C-Peptide, insulin resistance (HOMA-IR), insulin sensitivity (QUICKI), metabolic clearance rate (MCRestOGTT) and serum lipids were assessed.

RESULTS

Mean WL was 9.6%; trunk and leg FM were reduced proportionally (14.9-14.7%). Improvement in HOMA-IR was 34.7%, insulin 30.7%, QUICKI 8.6% and MCRest OGTT 74%. The reduction in total, trunk and leg FM were similarly correlated with improvement in indices of insulin resistance (p < 0.001-0.05) and also with initial HOMA-IR (p = 0.000-0.02). In linear regressions improvement in HOMA-IR was similarly related with these FMs (p = 0.008), and initial HOMA predicted loss of trunk FM (p = 0.01). In multivariate analysis improvement in HOMA-IR was explained by loss of total FM (R(2) = 0.20, p = 0.004); improvement of QUICKI by loss of leg FM (R(2) = 0.33, p < 0.001).

CONCLUSION

Loss of leg FM and trunk FM had similar importance for the improvement in insulin resistance. Baseline HOMA-IR predicted the potential for reduction in trunk FM.

Prader-Willi syndrome is associated with activation of the innate immune system independently of central adiposity and insulin resistance

BACKGROUND

Subjects with Prader-Willi syndrome (PWS) have a reduced life expectancy due to cardiovascular disease. Increased systemic low-grade inflammation is postulated as a contributor, despite reported lower visceral fat mass and increased insulin sensitivity.

OBJECTIVES

Our aim was to compare inflammatory markers and arterial stiffness in PWS and adiposity-matched obese control subjects.

DESIGN

We conducted a cross-sectional cohort study comparing 12 PWS subjects, 12 obese subjects matched for percentage body fat and central abdominal fat mass, and 10 healthy normal-weight subjects.

MAIN OUTCOME MEASURES

Dual-energy x-ray absorptiometry was used to assess body composition, flow cytometry to quantify activation markers on immun e cells, and ELISA for measurement of C-reactive protein, adiponectin, and IL-6. Insulin resistance was estimated by homeostasis model assessment and arterial stiffness by applanation tonometry.

RESULTS

PWS and obese subjects had similarly increased homeostasis model assessment and arterial stiffness. Nevertheless, PWS subjects showed significantly higher IL-6 (4.9 + or - 1.0 vs. 2.5 + or - 0.4 pg/ml; P = 0.02) and nonsignificantly higher C-reactive protein (10.5 + or - 3.2 vs. 4.0 + or - 1.0 ng/ml; P = 0.08). Neutrophil activation markers CD66b and CD11b were higher in PWS compared to obese subjects (P < 0.01), reflecting an activated innate immune system. These markers were positively related to central adiposity in lean and obese subjects (r = 0.49; P < 0.05), but not in PWS subjects.

CONCLUSIONS

PWS subjects compared to adiposity-matched obese subjects demonstrate similar insulin resistance but increased low-grade inflammation. The dissociation of inflammation and central adiposity suggests that activation of innate immunity may be either a specific genetic feature of PWS or linked to the commonly associated obstructive sleep apnea syndrome, and might offer a treatment target to reduce cardiovascular disease.

Sex differences in regional body fat distribution from pre- to postpuberty

Few large studies have evaluated the emergence of sexual dimorphism in fat distribution with appropriate adjustment for total body composition. The objective of this study was to determine the timing and magnitude of sex differences in regional adiposity from early childhood to young adulthood. Regional fat distribution was measured using dual-energy X-ray absorptiometry (trunk and extremity fat using automatic default regions and waist and hip fat using manual analysis) in 1,009 predominantly white participants aged 5-29 years. Subjects were divided into pre (Tanner stage 1), early (Tanner stages 2-3), late (Tanner stages 4-5), and post (males > or =20 years and females > or =18 years) pubertal groups. Sexual dimorphism in trunk fat (adjusted for extremity fat) was not apparent until late puberty, when females exhibited 17% less (P < 0.001) trunk fat than males. By contrast, sex differences in waist fat (adjusted for hip fat) were apparent at each stage of puberty, the effect being magnified with age, with prepubertal girls having 5% less (P = 0.027) and adult women having 48% less (P < 0.0001) waist fat than males. Girls had considerably more peripheral fat whether measured as extremity or hip fat at each stage. Sex differences in regional adiposity were significantly greater in young adults than in late adolescence. Exclusion of overweight participants did not materially affect the estimates. Sexual dimorphism in fat patterning is apparent even prepubertally with girls having less waist and more hip fat than boys. The magnitude of the sex difference is amplified with maturation, and particularly from late puberty to early adulthood.

Transplantation or removal of intra-abdominal adipose tissue prevents age-induced glucose insensitivity

Increases in intra-abdominal fat, a common feature associated with aging, is an established risk factor for insulin resistance, diabetes and the metabolic syndrome. To examine the direct contribution of intra-abdominal fat in the pathophysiology of insulin resistance we altered fat volume via removal or transplantation in a naturally occurring age-induced moderate model of obesity and insulin resistance. This was accomplished by bilateral removal of epididymal white adipose tissue (Lipx) or transplantation of donor fat into the intra-abdominal side of the peritoneal cavity of 28-week old rats. Control animals received sham surgery. Glucose tolerance was evaluated at baseline and 4 and 8weeks post-surgery in all groups, and fasting insulin and leptin were additionally measured in 28-week old rats. In addition, fasted and fed triglyceride, cholesterol and fatty acid concentrations were measured. Before surgery 28-week old rats weighed more and were glucose intolerant compared with 8-week old controls. Both Lipx and transplantation significantly prevented age-induced decreases in glucose tolerance, with Lipx causing improvement at 4weeks which declined by 8weeks; and with a significant transplantation improvement at 8weeks only. Lipx significantly increased insulin secretion 15min after a bolus injection of 0.75mg/kg dextrose at 4 and 8weeks compared with controls, while transplantation caused a significant ( approximately 220%) increase in fasted leptin level at 4weeks only. Taken together, these data suggest that surgical removal or addition of intra-abdominal fat prevents age-induced insulin resistance by different mechanisms and is a suitable model to investigate naturally occurring obesity.

Obesity in women

Obesity carries a unique disease burden on women and is influenced by a variety of biological, hormonal, environmental, and cultural factors. Reproductive transitions, such as pregnancy and menopause, increase the risk for obesity. Psychologically, obese women experience greater weight-related stigma and discrimination and are at increased risk for depression than obese men. Women are also particularly susceptible to psychological stress, sleep debt, and lack of physical activity, all of which are risk factors for the development of excess weight. Obesity risk is increased among women with psychiatric disorders and those who use certain psychotropic medications. Obesity treatment should take into consideration degree of obesity, health risks, past weight loss attempts, and individual differences in motivation and readiness for treatment.

Polycystic ovary syndrome and weight management

Polycystic ovary syndrome (PCOS) is a common condition in women of reproductive age, and has reproductive, metabolic and psychological implications. Weight gain and obesity worsen the features of PCOS, while weight loss improves the features of PCOS. While there are potential barriers to successful weight management in young women who do not suffer from PCOS, women with PCOS may experience additional barriers. Weight management strategies in younger women with or without PCOS should encompass both the prevention of excess weight gain and achieving and maintaining a reduced weight through multidisciplinary lifestyle management, comprising dietary, exercise and behavioral therapy, as well as attention to psychosocial stress and practical and physiological barriers to weight management. Further research is warranted in the examination of specific barriers to weight management in women with PCOS, as well as in the determination of optimal components of lifestyle weight management interventions in young women in order to facilitate long-term compliance.

Sex differences in the association of regional fat distribution with the severity of obstructive sleep apnea

STUDY OBJECTIVES

To describe sex differences in the associations between severity of obstructive sleep apnea (OSA) and measures of obesity in body regions defined using both dual-energy absorptiometry and traditional anthropometric measures in a sleep-clinic sample.

DESIGN

A prospective case-series observational study.

SETTING

The Western Australian Sleep Health Study operating out of the Sir Charles Gairdner Hospital Sleep Clinic, Perth, Western Australia.

PARTICIPANTS

Newly referred clinic patients (60 men, 36 women) suspected of having OSA.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Obstructive sleep apnea severity was defined by apnea-hypopnoea index from laboratory-based overnight polysomnography. Body mass index, neck, waist and hip circumference, neck-to-waist ratio, and waist-to-hip ratio were measured. Dual energy absorptiometry measurements included percentage fat and lean tissue. Multivariate regression models for each sex were developed. In women, percentage of fat in the neck region and body mass index together explained 33% of the variance in apnea-hypopnea index. In men, percentage of fat in the abdominal region and neck-to-waist ratio together accounted for 37% of the variance in apnea-hypopnea index.

CONCLUSIONS

Regional obesity is associated with obstructive sleep apnea severity, although differently in men and women. In women, a direct influence of neck fat on the upper airway patency is implicated. In men, abdominal obesity appears to be the predominant influence. The apnea-hypopnea index was best predicted by a combination of Dual Energy Absorptiometry-measured mass and traditional anthropometric measurements.

Maternal metabolism and obesity: modifiable determinants of pregnancy outcome

BACKGROUND

Obesity among pregnant women is highly prevalent worldwide and is associated in a linear manner with markedly increased risk of adverse outcome for mother and infant. Obesity in the mother may also independently confer risk of obesity to her child. The role of maternal metabolism in determining these outcomes and the potential for lifestyle modification are largely unknown.

METHODS

Relevant studies were identified by searching PubMed, the metaRegister of clinical trials and Google Scholar without limitations. Sensitive search strategies were combined with relevant medical subject headings and text words.

RESULTS

Maternal obesity and gestational weight gain have a significant impact on maternal metabolism and offspring development. Insulin resistance, glucose homeostasis, fat oxidation and amino acid synthesis are all disrupted by maternal obesity and contribute to adverse outcomes. Modification of lifestyle is an effective intervention strategy for improvement of maternal metabolism and the prevention of type 2 diabetes and, potentially, gestational diabetes.

CONCLUSIONS

Maternal obesity requires the development of effective interventions to improve pregnancy outcome. Strategies that incorporate a detailed understanding of the maternal metabolic environment and its consequences for the health of the mother and the growth of the child are likely to identify the best approach.

Epidemiological Investigation of Metabolic Syndrome and Analysis of Relevant Factors in North-Eastern China

This epidemiological study was conducted to investigate the prevalence of metabolic syndrome and associated risk factors in Chinese subjects from Dehui in northeastern China. Using a random sampling method, a questionnaire was completed by 3785 permanent residents aged 18-72 years and relevant clinical data were collected from each subject. Binary multivariate logistic regression analysis was used to identify factors that were significantly associated with metabolic syndrome. Based on the International Diabetes Federation definition, the prevalence of metabolic syndrome was 22.4%, which is higher than that of the general Chinese population. Metabolic syndrome occurred more frequently in females and the prevalence gradually increased with age. Living in an urban setting and being female, > 50 years old, overweight, having total cholesterol ≥ 5.18 mmol/l, low-density lipoprotein cholesterol ≥ 3.1 mmol/l, and a fatty liver were significant risk factors associated with metabolic syndrome.

Practical guidance on intensification of insulin therapy with BIAsp 30: a consensus statement

BACKGROUND

Basal insulin and premix insulin are commonly prescribed first-line insulin therapies for patients failing to maintain glycaemic control on oral therapy. When control on these insulins starts to drift, premix analogues, such as biphasic insulin aspart 30/70 (BIAsp 30), are a simple and effective tool for intensification as they can be injected up to three-times daily (TID). However, at present, international recommendations for intensification of insulin therapy using premix analogues are limited and specific guidance on dosing is not available for many scenarios.

METHODS

In October 2008, an international expert panel met to review the current guidelines for insulin intensification with BIAsp 30 in patients with type 2 diabetes, with the aim of developing practical guidance for general and specialist practitioners.

RESULTS

Simple treatment algorithms have been developed for (i) patients on basal insulin (human or analogue) once daily or twice daily (BID) who need intensification to BIAsp 30 BID, and (ii) patients on BIAsp 30 once daily or BID who can be intensified to BIAsp 30 BID or TID. As well as these algorithms, specific guidance has been provided on dose transfer (from basal insulin to BIAsp 30), dose split (when intensifying from once daily to BID), and combination oral therapies. In addition, a guide to dose titration is included.

CONCLUSIONS

The guidelines presented here should enable general or specialist practitioners to use BIAsp 30 to intensify the insulin therapy of patients failing on basal insulin or BIAsp 30 once or twice daily.

A high mixed protein diet reduces body fat without altering the mechanical properties of bone in female rats

Long-term consumption of high-protein (HP) diets at 35% of energy is postulated to negatively influence bone health. Previous studies have not comprehensively examined the biochemical, physical, and biomechanical properties of bone required to arrive at this conclusion. Our objective in this study was to examine the long-term effect of a HP diet on bone metabolism, mass, and strength in rats. Adult female Sprague-Dawley rats (n = 80) were randomized to receive for 4, 8, 12, or 17 mo a normal-protein (NP) control diet (15% of energy) or a HP diet (35% of energy). Diets were balanced for calcium because the protein sources were rich in calcium. At each time point, measurements included weight, body composition, and bone mass using dual-energy X-ray absorptiometry, mechanical strength at the mid-diaphysis of femur and tibia, microarchitecture of femurs using microcomputerized tomography and serum osteocalcin, carboxy-terminal crosslinks of type I collagen (CTX), insulin-like growth factor-1 (IGF-1), leptin, and adiponectin. Effects of diet, time, and their interaction were tested using factorial ANOVA. The HP diet resulted in lower body weight, total body, and abdominal fat and higher lean mass. Serum leptin and adiponectin were greater in HP-fed than in NP-fed rats, but IGF-1 did not differ between the groups. Whereas the HP diet resulted in higher relative bone mineral content (g/kg) in the femur, tibia, and vertebrae, serum osteocalcin and CTX and bone internal architecture and biomechanical strength were unaffected. In conclusion, HP diets at 35% of energy lower body fat content without hindering the mechanical and weight-bearing properties of bone.

Effect of food restriction on adipose tissue in spontaneously diabetic Torii fatty rats

Spontaneously Diabetic Torii-fa/fa (SDT fatty) rat is a new model of obese type 2 diabetes. SDT fatty rat exhibits obesity associated with hyperphagia. In this study, SDT fatty rats were subjected to pair-feeding with SDT-+/+ (SDT) rats from 6 to 22 weeks of age. The ratio of visceral fat weight to subcutaneous fat weight (V/S) decreased at 12 weeks of age in the pair-feeding rats. The intraperitoneal fat weight such as epididymal and retroperitoneal fat weight decreased, whereas mesenteric fat weight had no change. Cell size of the epididymal fat in the pair-feeding rats tended to decrease. Glucose oxidation level in epididymal fat in the pair-feeding rats at 12 weeks of age was recovered to a similar level with that in SDT rats. These results indicated that SDT fatty rat is a useful model to evaluate the functional or the morphological features in adipose tissue and develop a novel drug for antiobesity.

Visceral fat dominant distribution in male type 2 diabetic patients is closely related to hepatic insulin resistance, irrespective of body type

Background

All previous studies that investigated the association between abdominal fat distribution and insulin resistance evaluated subcutaneous and visceral fat area and/or volume, but these values were not related to the body type of each subject. In the present study we have examined the association between abdominal fat distribution and peripheral (muscle)/hepatic sensitivity to insulin using the visceral to abdominal subcutaneous fat area ratio (VF/SF ratio) in male patients with type 2 diabetes mellitus. This ratio defines the predominancy of visceral or subcutaneous abdominal adiposity, independent of the body type of each individual.

Methods

Thirty-six type 2 diabetic male patients underwent a euglycemic insulin clamp (insulin infusion rate = 40 mU/m²·min) with 3-³H-glucose to measure insulin-mediated total body (primarily reflects muscle) glucose disposal (TGD) and suppression of endogenous (primarily reflects liver) glucose production (EGP) in response to a physiologic increase in plasma insulin concentration. Abdominal subcutaneous (SF) and intraabdominal visceral fat (VF) areas were quantitated with magnetic resonance imaging (MRI) at the level of L_4–5.

Results

TGD and TGD divided by steady state plasma insulin concentration during the insulin clamp (TGD/SSPI) correlated inversely with body mass index (BMI), total fat mass (FM) measured by ³H₂O, SF and VF areas, while VF/SF ratio displayed no significant relationship with TGD or TGD/SSPI. In contrast, EGP and the product of EGP and SSPI during the insulin clamp (an index hepatic insulin resistance) correlated positively with VF/SF ratio, but not with BMI, FM, VF or SF.

Conclusion

We conclude that, independent of the individual's body type, visceral fat dominant accumulation as opposed to subcutaneous fat accumulation is associated with hepatic insulin resistance, whereas peripheral (muscle) insulin resistance is more closely related to general obesity (i.e. higher BMI and total FM, and increased abdominal SF and VF) in male patients with type 2 diabetes.

Sexual differences in the control of energy homeostasis

The prevalence of obesity has reached epidemic proportion with enormous costs in both human lives and healthcare dollars spent. Obesity-related metabolic disorders are much lower in premenopausal women than men; however, there is a dramatic increase following menopause in women. The health risks associated with obesity vary depending on the location of adipose tissue. Adipose tissue distributed in the abdominal visceral carry a much greater risk for metabolic disorders than does adipose tissue distributed subcutaneously. There are distinct sex-dependent differences in the regional fat distribution, women carry more fat subcutaneously whereas men carry more fat viscerally. Males and females differ with respect to their regulation of energy homeostasis. Peripheral adiposity hormones such as leptin and insulin as well as sex hormones directly influence energy balance. Sexual dimorphisms in energy balance, body fat distribution, and the role sex hormones have in mediating these differences are the focus of this review.

Abdominal visceral adiposity in the first trimester predicts glucose intolerance in later pregnancy

OBJECTIVE

To assess whether abdominal adiposity in early pregnancy is associated with a higher risk of glucose intolerance at a later gestational stage.

RESEARCH DESIGN AND METHODS

Subcutaneous and visceral fat was measured with ultrasonography at approximately 12 weeks' gestation. A 50-g glucose challenge test (GCT) was performed between 24 and 28 weeks' gestation. The risk of having a positive GCT (>or=7.8 mmol/l) was determined in association with subcutaneous and visceral adipose tissue depths above their respective upper-quartile values relative to their bottom three quartile values.

RESULTS

Sixty-two women underwent GCTs. A visceral adipose tissue depth above the upper quartile value was significantly associated with a positive GCT in later pregnancy (adjusted odds ratio 16.9 [95% CI 1.5-194.6]). No associations were seen for subcutaneous adipose tissue.

CONCLUSIONS

Measurement of visceral adipose tissue depth in early pregnancy may be associated with glucose intolerance later in pregnancy.

Rimonabant prevents additional accumulation of visceral and subcutaneous fat during high-fat feeding in dogs

We investigated whether rimonabant, a type 1 cannabinoid receptor antagonist, reduces visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in dogs maintained on a hypercaloric high-fat diet (HHFD). To determine whether energy expenditure contributed to body weight changes, we also calculated resting metabolic rate. Twenty male dogs received either rimonabant (1.25 mg.kg(-1).day(-1), orally; n = 11) or placebo (n = 9) for 16 wk, concomitant with a HHFD. VAT, SAT, and nonfat tissue were measured by magnetic resonance imaging. Resting metabolic rate was assessed by indirect calorimetry. By week 16 of treatment, rimonabant dogs lost 2.5% of their body weight (P = 0.029), whereas in placebo dogs body weight increased by 6.2% (P < 0.001). Rimonabant reduced food intake (P = 0.027), concomitant with a reduction of SAT by 19.5% (P < 0.001). In contrast with the VAT increase with placebo (P < 0.01), VAT did not change with rimonabant. Nonfat tissue remained unchanged in both groups. Body weight loss was not associated with either resting metabolic rate (r(2) = 0.24; P = 0.154) or food intake (r(2) = 0.24; P = 0.166). In conclusion, rimonabant reduced body weight together with a reduction in abdominal fat, mainly because of SAT loss. Body weight changes were not associated with either resting metabolic rate or food intake. The findings provide evidence of a peripheral effect of rimonabant to reduce adiposity and body weight, possibly through a direct effect on adipose tissue.

Effects of cevoglitazar, a dual PPARalpha/gamma agonist, on ectopic fat deposition in fatty Zucker rats

AIM

By acting as both insulin sensitizers and lipid-lowering agents, dual-acting peroxisome proliferator-activated receptors alpha/gamma (PPARalpha/gamma) agonists may be used to improve glucose tolerance in type 2 diabetic patients without inducing adiposity and body weight gain. Here, in an animal model of obesity and insulin resistance, the metabolic response to cevoglitazar, a dual PPARalpha/gamma, was characterized using a combination of in vivo and ex vivo magnetic resonance methodologies and compared to treatment effects of fenofibrate, a PPARalpha agonist, and pioglitazone, a PPARgamma agonist.

METHODS

Four groups of fatty Zucker rats: (i) Vehicle; (ii) fenofibrate 150 mg/kg; (iii) pioglitazone 30 mg/kg; and (iv) cevoglitazar 5 mg/kg were investigated before and after treatment. Animals were fed a fat-enriched (54% kcal fat) diet for 6 weeks, 2 weeks high of fat-exposure alone followed by a 4-week dosing period.

RESULTS AND CONCLUSIONS

Cevoglitazar was as effective as pioglitazone at improving glucose tolerance. However, unlike pioglitazone, both fenofibrate and cevoglitazar reduced BW gain and adiposity, independent of food intake. All three treatment regimens normalized intramyocellular lipids. Metabolic profiling showed that in the muscle cevoglitazar improves the lipid profile via both PPARalpha- and PPARgamma-mediated mechanisms. Pioglitazone reduced hepatic lipid accumulation, while cevoglitazar and fenofibrate reduced hepatic lipid concentration below baseline levels (p < 0.05). Metabolic profiling showed that in the liver, cevoglitazar functions largely through PPARalpha agonism resulting in increased beta-oxidation. Cevoglitazar only induced small changes to the lipid composition of visceral fat. In subcutaneous fat, however, cevoglitazar induced changes similar to those observed with fenofibrate suggesting export of fatty acids from this depot.

Leg fat mass as measured by dual X-ray absorptiometry (DXA) impacts insulin resistance differently in obese women versus men

OBJECTIVE

To investigate the association between regional fat mass (FM) and insulin resistance and dyslipidaemia in obese women and men.

MATERIAL AND METHODS

Body composition was measured by dual-energy X-ray absorptiometry (DXA) in 109 obese women and 113 obese men. Insulin resistance was measured by (HOMA-IR); insulin sensitivity was estimated by metabolic clearance rate (MCRestOGTT) and insulin secretion by HOMAsecr. Serum lipids were assessed.

RESULTS

In women, leg FM was negatively (favourably) associated with HOMA-IR and cholesterol/HDL-cholesterol ratio (p<0.05). Trunk FM was positively (unfavourably) associated with HOMA-IR. Leg/trunk FM ratio was negatively associated with HOMA-IR (p<0.001), cholesterol/HDL-cholesterol ratio (p<0.001) and triglycerides (p<0.01); positively (favourably) with MCRestOGTT (p<0.01) and HDL-cholesterol (p<0.05). No associations were found in men. In women, multiple regression analysis demonstrated that leg/trunk FM ratio was the only explanatory FM for HOMA-IR and MCRestOGTT (R(2) = 0.23 and R(2) = 0.13, respectively; p<0.001), but postmenopausal status was also of importance (R(2) = 0.23, p = 0.019 and R(2) = 0.29, p = 0.015, respectively).

CONCLUSIONS

Leg FM has a favourable influence on insulin resistance and dyslipidaemia in obese women, but not demonstrated in this cohort of obese men.

The STEDMAN project: biophysical, biochemical and metabolic effects of a behavioral weight loss intervention during weight loss, maintenance, and regain

The Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) Project uses comprehensive metabolic profiling to probe biochemical mechanisms of weight loss in humans. Measurements at baseline, 2 and 4 weeks, 6 and 12 months included diet, body composition, metabolic rate, hormones, and 80 intermediary metabolites measured by mass spectrometry. In 27 obese adults in a behavioral weight loss intervention, median weight decreased 13.9 lb over the first 6 months, then reverted towards baseline by 12 months. Insulin resistance (HOMA) was partially ameliorated in the first 6 months and showed sustained improvement at 12 months despite weight regain. Ghrelin increased with weight loss and reverted to baseline, whereas leptin and PYY fell at 6 months and remained persistently low. NPY levels did not change. Factors possibly contributing to sustained improvement in insulin sensitivity despite weight regain include adiponectin (increased by 12 months), IGF-1 (increased during weight loss and continued to increase during weight regain), and visceral fat (fell at 6 months but did not change thereafter). We observed a persistent reduction in free fatty acids, branched chain amino acids, and related metabolites that may contribute to improved insulin action. These findings provide evidence for sustained benefits of weight loss in obese humans and insights into mechanisms.

Successful versus failed adaptation to high-fat diet-induced insulin resistance: the role of IAPP-induced beta-cell endoplasmic reticulum stress

OBJECTIVE

Obesity is a known risk factor for type 2 diabetes. However, most obese individuals do not develop diabetes because they adapt to insulin resistance by increasing beta-cell mass and insulin secretion. Islet pathology in type 2 diabetes is characterized by beta-cell loss, islet amyloid derived from islet amyloid polypeptide (IAPP), and increased beta-cell apoptosis characterized by endoplasmic reticulum (ER) stress. We hypothesized that IAPP-induced ER stress distinguishes successful versus unsuccessful islet adaptation to insulin resistance.

RESEARCH DESIGN AND METHODS

To address this, we fed wild-type (WT) and human IAPP transgenic (HIP) rats either 10 weeks of regular chow or a high-fat diet and prospectively examined the relations among beta-cell mass and turnover, beta-cell ER stress, insulin secretion, and insulin sensitivity.

RESULTS

A high-fat diet led to comparable insulin resistance in WT and HIP rats. WT rats compensated with increased insulin secretion and beta-cell mass. In HIP rats, in contrast, neither beta-cell function nor mass compensated for the increased insulin demand, leading to diabetes. The failure to increase beta-cell mass in HIP rats was the result of ER stress-induced beta-cell apoptosis that increased in proportion to diet-induced insulin resistance.

CONCLUSIONS

IAPP-induced ER stress distinguishes the successful versus unsuccessful islet adaptation to a high-fat diet in rats. These studies are consistent with the hypothesis that IAPP oligomers contribute to increased beta-cell apoptosis and beta-cell failure in humans with type 2 diabetes.

Physical activity, menopause, and quality of life: the role of affect and self-worth across time

OBJECTIVE

Physical activity has been shown to enhance quality of life (QOL); however, few investigations of these effects exist in women undergoing the menopausal transition. The present study examined the long-term effects of physical activity on menopause-related QOL and tested the mediating effects of physical self-worth and positive affect in this relationship.

METHODS

Middle-aged women previously enrolled in a 4-month randomized controlled trial involving walking and yoga, and a control group completed a follow-up mail-in survey 2 years after the end of the trial. The survey included a battery of psychological and physical activity measures, including measures of menopausal symptoms and menopause-related QOL. Longitudinal linear panel analysis was conducted within a covariance modeling framework to test whether physical self-worth and positive affect mediated the physical activity-QOL relationship over time.

RESULTS

At the end of the trial, physical activity and menopausal symptoms were related to physical self-worth and positive affect, and in turn, greater levels of physical self-worth and positive affect were associated with higher levels of menopause-related QOL. Analyses indicated that increases in physical activity and decreases in menopausal symptoms over the 2-year period were related to increases in physical self-worth (betas = 0.23 and -0.52, physical activity and menopausal symptoms, respectively) and, for symptoms, also to decreased positive affect (beta = -0.47), and both physical self-worth (beta = 0.34) and affect (beta = 0.43) directly influenced enhancements in QOL (R = 0.775).

CONCLUSIONS

The findings support the position that the effects of physical activity on QOL are mediated, in part, by intermediate psychological outcomes and that physical activity can have long-term benefits for women undergoing the menopausal transition.

Which comes first: atypical antipsychotic treatment or cardiometabolic risk?

OBJECTIVE

To provide an overview for practicing clinicians on the pharmacological basis of cardiometabolic risk induced by antipsychotic drugs in patients with serious mental illness, to propose hypotheses to explain these risks and to give tips for managing cardiometabolic risk during antipsychotic treatment.

METHOD

A MEDLINE search using terms for atypical antipsychotics (including individual drug names), metabolic, cardiovascular, weight gain and insulin resistance, cross-referenced with schizophrenia was performed on articles published between 1990 and May 2008.

RESULTS

Strong evidence exists for significant cardiometabolic risk differences among several antipsychotic agents. Histamine H1 and serotonin 5HT2C antagonism are associated with risk of weight gain, but receptor targets for dyslipidemia and insulin resistance have not yet been identified. Convincing data indicate that hypertriglyceridemia and insulin resistance may occur in the absence of weight gain with certain antipsychotics.

CONCLUSION

Although lifestyle and genetics may contribute independent risks of cardiometabolic dysfunction in schizophrenia and other serious mental illness, antipsychotic treatment also represents an important contributor to risk of cardiometabolic dysfunction, particularly for certain drugs and for vulnerable patients. Mental health professionals must learn to recognize the clinical signposts indicating antipsychotic-related cardiometabolic problems to forestall progression to type II diabetes, cardiovascular events and premature death.

The impact of obesity, sex, and diet on hepatic glucose production in cats

Obesity is a risk factor for type 2 diabetes in cats. The risk of developing diabetes is severalfold greater for male cats than for females, even after having been neutered early in life. The purpose of this study was to investigate the role of different metabolic pathways in the regulation of endogenous glucose production (EGP) during the fasted state considering these risk factors. A triple tracer protocol using (2)H(2)O, [U-(13)C(3)]propionate, and [3,4-(13)C(2)]glucose was applied in overnight-fasted cats (12 lean and 12 obese; equal sex distribution) fed three different diets. Compared with lean cats, obese cats had higher insulin (P < 0.001) but similar blood glucose concentrations. EGP was lower in obese cats (P < 0.001) due to lower glycogenolysis and gluconeogenesis (GNG; P < 0.03). Insulin, body mass index, and girth correlated negatively with EGP (P < 0.003). Female obese cats had approximately 1.5 times higher fluxes through phosphoenolpyruvate carboxykinase (P < 0.02) and citrate synthase (P < 0.05) than male obese cats. However, GNG was not higher because pyruvate cycling was increased 1.5-fold (P < 0.03). These results support the notion that fasted obese cats have lower hepatic EGP compared with lean cats and are still capable of maintaining fasting euglycemia, despite the well-documented existence of peripheral insulin resistance in obese cats. Our data further suggest that sex-related differences exist in the regulation of hepatic glucose metabolism in obese cats, suggesting that pyruvate cycling acts as a controlling mechanism to modulate EGP. Increased pyruvate cycling could therefore be an important factor in modulating the diabetes risk in female cats.

Protective effect of leg fat against cardiovascular risk factors in obese premenopausal women

BACKGROUND AND AIMS

While the relationship between abdominal fat and cardiovascular risk (CVR) factors is well established, the possible protective role of peripheral fat against these factors has received less attention, particularly in severely obese individuals. The principal aim of this study was to analyse the relationship, if any, among amount of leg fat, CVR factors and body mass index (BMI) in obese premenopausal women.

METHODS AND RESULTS

Subjects were 80 obese premenopausal women. Body composition was measured by dual energy X-ray absorptiometry (DEXA); CVR factors (blood pressure, plasma lipids, glucose) were determined and anthropometric measurements (waist and hip circumferences) taken. In severely obese women (BMI>40 kg/m(2)) leg fat correlated negatively with CVR factors, whereas metabolic parameters were not significantly different from those of subjects with BMI<40 kg/m(2).

CONCLUSIONS

Leg fat seems to play a protective role against CVR factors in severely obese premenopausal women.

A stress signaling pathway in adipose tissue regulates hepatic insulin resistance

A high-fat diet causes activation of the regulatory protein c-Jun NH2-terminal kinase 1 (JNK1) and triggers development of insulin resistance. JNK1 is therefore a potential target for therapeutic treatment of metabolic syndrome. We explored the mechanism of JNK1 signaling by engineering mice in which the Jnk1 gene was ablated selectively in adipose tissue. JNK1 deficiency in adipose tissue suppressed high-fat diet-induced insulin resistance in the liver. JNK1-dependent secretion of the inflammatory cytokine interleukin-6 by adipose tissue caused increased expression of liver SOCS3, a protein that induces hepatic insulin resistance. Thus, JNK1 activation in adipose tissue can cause insulin resistance in the liver.

Prenatal nicotine exposure alters early pancreatic islet and adipose tissue development with consequences on the control of body weight and glucose metabolism later in life

Despite medical advice, 20-30% of female smokers continue to smoke during pregnancy. Epidemiological studies have associated maternal smoking with increased risk of obesity and type-2 diabetes in the offspring. In the present study, we investigated the impact of prenatal nicotine exposure (3 mg/kg in Sprague Dawley rats via osmotic Alzet minipumps) on the early endocrine pancreas and adipose tissue development in rat pups before weaning. Body weight, fat deposition, food intake and food efficiency, cold tolerance, spontaneous physical activity, glucose utilization, and insulin sensitivity were also examined at adulthood. Prenatal nicotine exposure led to a decrease in endocrine pancreatic islet size and number at 7 d of life (postnatal d 7), which corroborates with a decrease in gene expression of specific transcription factors such as pancreatic and duodenal homeobox 1, Pax-6, Nkx6.1, and of hormones such as insulin and glucagon. The prenatal nicotine exposure also led to an increase in epididymal white adipose tissue weight at weaning (postnatal d 21), and marked hypertrophy of adipocytes, with increased gene expression of proadipogenic transcription factors such as CAAT-enhancer-binding protein-alpha, peroxisome proliferator activated receptor-gamma, and sterol regulatory element binding protein-1C. These early tissue alterations led to significant metabolic consequences, as shown by increased body weight and fat deposition, increased food efficiency on high-fat diet, cold intolerance, reduced physical activity, and glucose intolerance combined with insulin resistance observed at adulthood. These results prove a direct association between fetal nicotine exposure and offspring metabolic syndrome with early signs of dysregulations of adipose tissue and pancreatic development.

A prospective observational study of obesity, body composition, and insulin resistance in 18 women with bipolar disorder and 17 matched control subjects

OBJECTIVE

Patients with bipolar disorder are at increased risk for diabetes and cardiovascular diseases, possibly because of more severe insulin resistance. The primary purpose of this study was to determine whether insulin resistance is characteristic of bipolar disorder.

METHOD

The Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) was performed in 18 women with DSM-IV bipolar I disorder, and results were compared to those of 17 matched controls. Other risk factors were compared, including blood pressure, blood lipids, and abdominal obesity by computed tomography (CT). Additionally, substrate utilization was measured by indirect calorimetry, and free-living energy expenditure was estimated using wearable activity monitors. All data were collected between February 2006 and December 2007.

RESULTS

Patients with bipolar disorder were no more insulin resistant than controls after accounting for generalized obesity (mean +/- SEM HOMA-IR = 2.7 +/- 0.7 vs. 2.5 +/- 0.7, for patients and controls, respectively; p = .79). Although blood lipid profiles were generally similar in patients and controls, obese patients had higher blood pressure than controls. Obese patients had more mean +/- SEM total abdominal fat (718.1 +/- 35.1 cm² vs. 607.4 +/- 33.6 cm²; p = .04), and tended (p = .06) to have more visceral abdominal fat. Patients oxidized 13% less fat during resting conditions, although their resting metabolic rate was similar to that of controls.

CONCLUSION

Women with bipolar I disorder were no more insulin resistant than matched controls after accounting for their level of obesity. However, they were more hypertensive, had higher amounts of abdominal obesity, and had reduced rates of fat oxidation. Therefore, women with bipolar I disorder may be at a heightened risk for future weight gain and concomitant risk for diabetes and cardiovascular disease.

The metabolic syndrome

The "metabolic syndrome" (MetS) is a clustering of components that reflect overnutrition, sedentary lifestyles, and resultant excess adiposity. The MetS includes the clustering of abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure and is associated with other comorbidities including the prothrombotic state, proinflammatory state, nonalcoholic fatty liver disease, and reproductive disorders. Because the MetS is a cluster of different conditions, and not a single disease, the development of multiple concurrent definitions has resulted. The prevalence of the MetS is increasing to epidemic proportions not only in the United States and the remainder of the urbanized world but also in developing nations. Most studies show that the MetS is associated with an approximate doubling of cardiovascular disease risk and a 5-fold increased risk for incident type 2 diabetes mellitus. Although it is unclear whether there is a unifying pathophysiological mechanism resulting in the MetS, abdominal adiposity and insulin resistance appear to be central to the MetS and its individual components. Lifestyle modification and weight loss should, therefore, be at the core of treating or preventing the MetS and its components. In addition, there is a general consensus that other cardiac risk factors should be aggressively managed in individuals with the MetS. Finally, in 2008 the MetS is an evolving concept that continues to be data driven and evidence based with revisions forthcoming.

Dual-energy X-ray absorptiometry (DXA) can accurately and nondestructively measure the body composition of small, free-living rodents

Dual-energy x-ray absorptiometry (DXA) is a nondestructive technique that can potentially measure specific components of whole-body composition in free-living and lab-raised animals. Our aim was to test the ability of DXA to measure the composition of a common arvicoline rodent, the northern red-backed vole (Clethrionomys rutilus). We used a DXA apparatus to obtain measurements of fat mass (FM), lean mass (LM),bone mineral content, bone mineral density, and fat-free mass(FFM) in carcasses of free-living and lab-raised voles. We then used chemical carcass analysis to derive predictive algorithms for actual values of FM, total body water, total protein, total mineral, LM, and FFM. Unexplained error in the equations for all voles grouped collectively ranged from R(2) = 0.82 to R(2) = 0.98. The DXA FM measurement had the highest coefficient of variation, and it was higher for free-living voles than for lab-raised voles. However, FM can be determined by difference with excellent precision by using the FFM equation (R(2) = 0.98). We also derived corrective terms for passive integrated transponder-tagged animals. Thus, DXA is a nonlethal, nondestructive tool capable of precisely and accurately measuring many specific parameters of whole-body composition in small free-living and lab-raised rodents.

Features of the metabolic syndrome and the risk of cardiovascular disease

The metabolic syndrome is being increasingly recognized as an important risk factor for cardiovascular disease (CVD). While several clinical definitions have been proposed to identify patients with this syndrome, additional metabolic markers may be considered to improve one's ability to assess and predict the risk of CVD in this population. The objective of this short review is to provide an overview of the risk of CVD associated with specific features of the metabolic syndrome. The extent to which these markers may be used one day in clinical practice in primary prevention is also briefly discussed.

ROC analysis of subcutaneous adipose tissue topography (SAT-Top) in female coronary heart disease patients and healthy controls

The aim of this study was to investigate whether subcutaneous adipose tissue topography (SAT-Top) is different in female CHD patients (n=26) and healthy controls (n=36) matched to age, body size, weight, and BMI. The thicknesses of SAT layers were measured by LIPOMETER at 15 specified body sites. To calculate the power of the different body sites to discriminate between CHD women and healthy controls, receiver operating characteristic (ROC) curve analysis was performed. For each parameter, sensitivity and specificity were calculated at different cutoff points. CHD women showed a significant decrease to 78.36% (p=0.012) at body site 11-front thigh, 73.10% (p=0.012) at 12-lateral thigh, 72.20% (p=0.009) at 13-rear thigh, 66.43% (p<0.001) at 14-inner thigh, and 49.19% (p<0.001) at 15-calf. The best discriminators analysed by ROC curves between female CHD patients and healthy controls turned out to be calf and inner thigh (optimal cut off values: calf: 3.85 mm and inner thigh: 11.15 mm). Stepwise discriminant analysis identified the body sites calf, lateral chest, and inner thigh as significant. In conclusion, information was obtained on the extent to which SAT thickness at each measured body site is able to discriminate between the two subject groups. The good discrimination results obtained for the present dataset are encouraging enough to recommend applying LIPOMETER SAT-Top measurements in further studies to investigate individual risks for CHD.

The effect of a hypocaloric diet with and without exercise training on body composition, cardiometabolic risk profile, and reproductive function in overweight and obese women with polycystic ovary syndrome

CONTEXT

In overweight women with polycystic ovary syndrome (PCOS), the benefits of the addition of exercise to an energy-restricted diet in further improving cardiometabolic risk factors and reproductive function has not been extensively studied.

OBJECTIVE

The objective was to evaluate the effects of aerobic and aerobic-resistance exercise when combined with an energy-restricted high protein diet (5000-6000 kJ/d) on metabolic risk factors and reproductive function in women with PCOS.

DESIGN AND SETTING

A 20-wk outpatient, randomized, parallel study was conducted in a metropolitan research clinic.

PATIENTS AND INTERVENTION

Ninety-four overweight and obese women with PCOS (age 29.3 +/- 0.7 yr; body mass index 36.1 +/- 0.5 kg/m2) were randomized to diet only (DO; n = 30), diet and aerobic exercise (DA; n = 31), or diet and combined aerobic-resistance exercise (DC; n = 33).

MAIN OUTCOME MEASURES

Weight, body composition, cardiometabolic risk factors, hormonal status, menstrual cyclicity, and ovulatory function were assessed.

RESULTS

All interventions reduced weight (DO 8.9 +/- 1.6%, DA 10.6 +/- 1.7%, and DC 8.7 +/- 1.7%; P < 0.001) with no difference between treatments (P = 0.7, time x treatment). Fat mass decreased more (3 kg) and fat-free mass decreased less (2 kg) in DA and DC compared with DO (P < or = 0.03). Reductions in blood pressure (5.6/2.7 mm Hg), triglycerides (0.4 mmol/liter), total cholesterol (0.5 mmol/liter), low-density lipoprotein cholesterol (0.1 mmol/liter), glucose (0.2 mmol/liter), fasting insulin (4.3 mIU/liter), testosterone (0.4 nmol/liter), and free androgen index (2.8) (P < 0.001) and improvements in SHBG (7.0 nmol/liter) and reproductive function occurred in all groups, with no difference between treatments.

CONCLUSION

In overweight and obese women with PCOS, the addition of aerobic or combined aerobic-resistance exercise to an energy-restricted diet improved body composition but had no additional effect on improvements in cardiometabolic, hormonal, and reproductive outcomes relative to diet alone.

Factor analysis of metabolic syndrome components in obese women

BACKGROUND AND AIM

Factor analysis is a multivariate correlation technique that is frequently employed to characterise the clustering of intercorrelated abnormalities, which underlie the metabolic syndrome in cohorts of individuals with different characteristics. To our knowledge, it has never been used to identify the components of this syndrome in obese subjects. The purpose of this study was to use factor analysis to investigate the clustering of features, which characterise the metabolic syndrome, in a cohort of 552 obese women aged 18-83 years (mean body mass index: 43.0 kg/m(2)+/-5.7 SD).

METHODS AND RESULTS

Principal component analysis reduced ten correlated physiological variables, to four uncorrelated factors that explained 72.2% of the variance in the original parameters. These factors were interpreted as: (1) an insulin resistance factor, with positive loading of fasting serum insulin and homeostatic model assessment of insulin resistance; (2) a metabolic glucose/lipid factor, with positive loading of fasting plasma glucose, triglycerides, waist-to-hip ratio, and inverse loading of high density lipoprotein cholesterol; (3) a body mass factor, with positive loading of body mass and waist circumference; and (4) a blood pressure factor, with positive loading of systolic and diastolic blood pressure.

CONCLUSION

The identification of four independent factors is consistent with previous findings among samples of different populations and may also support, in obese women, the hypothesis that multiple physiological determinants are responsible for the abnormalities underlying the metabolic syndrome. Nonetheless, findings in this cohort of obese women suggest that the absolute degree of adiposity is not correlated with any tested component of the metabolic syndrome, but that the relative fat distribution is highly correlated with the development of hyperglycaemic and dyslipidaemic phenomena. Furthermore, insulin resistance appears to be a major factor in obese individuals, independent of other metabolic and anthropometic abnormalities.

Islet-1: a potentially important role for an islet cell gene in visceral fat

OBJECTIVE

To examine differences in gene expression between visceral (VF) and subcutaneous fat (SF) to identity genes of potential importance in regulation of VF.

METHODS AND PROCEDURES

We compared gene expression (by DNA array and quantitative PCR (qPCR)) in paired VF and SF adipose biopsies from 36 subjects (age 54 +/- 15 years, 15 men/21 women) with varying degrees of adiposity and insulin resistance, in chow and fat fed mice (+/- rosiglitazone treatment) and in c-Cbl(-/-) mice. Gene expression was also examined in 3T3-L1 preadipocytes during differentiation.

RESULTS

A twofold difference or more was found between VF and SF in 1,343 probe sets, especially for genes related to development, cell differentiation, signal transduction, and receptor activity. Islet-1 (ISL1), a LIM-homeobox gene with important developmental and regulatory function in islet, neural, and cardiac tissue, not previously recognized in adipose tissue was virtually absent in SF but substantially expressed in VF. ISL1 expression correlated negatively with BMI (r = -0.37, P = 0.03), abdominal fat (by dual energy X-ray absorptiometry, r = -0.44, P = 0.02), and positively with circulating adiponectin (r = 0.33, P = 0.04). In diet-induced obese mice, expression was reduced in the presence or absence of rosiglitazone. Correspondingly, expression was increased in the c-Cbl(-/-) mouse, which is lean and insulin sensitive (IS). ISL1 expression was increased sevenfold in 3T3-L1 preadipocytes during early (day 1) differentiation and was reduced by day 2 differentiation.

DISCUSSION

An important developmental and regulatory gene ISL1 is uniquely expressed in VF, probably in the preadipocyte. Our data suggest that ISL1 may be regulated by adiposity and its role in metabolic regulation merits further study.

Accretion of visceral fat and hepatic insulin resistance in pregnant rats

Insulin resistance (IR) is a hallmark of pregnancy. Because increased visceral fat (VF) is associated with IR in nonpregnant states, we reasoned that fat accretion might be important in the development of IR during pregnancy. To determine whether VF depots increase in pregnancy and whether VF contributes to IR, we studied three groups of 6-mo-old female Sprague-Dawley rats: 1) nonpregnant sham-operated rats (Nonpreg; n = 6), 2) pregnant sham-operated rats (Preg; n = 6), and 3) pregnant rats in which VF was surgically removed 1 mo before mating (PVF-; n = 6). VF doubled by day 19 of pregnancy (Nonpreg 5.1 +/- 0.3, Preg 10.0 +/- 1.0 g, P < 0.01), and PVF- had similar amounts of VF compared with Nonpreg (PVF- 4.6 +/- 0.8 g). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp in late gestation in chronically catheterized unstressed rats. Glucose IR (mg.kg(-1).min(-1)) was highest in Nonpreg (19.4 +/- 2.0), lowest in Preg (11.1 +/- 1.4), and intermediate in PVF- (14.7 +/- 0.6; P < 0.001 between all groups). During the clamp, Nonpreg had greater hepatic insulin sensitivity than Preg [hepatic glucose production (HGP): Nonpreg 4.5 +/- 1.3, Preg 9.3 +/- 0.5 mg.kg(-1).min(-1); P < 0.001]. With decreased VF, hepatic insulin sensitivity was similar to nonpregnant levels in PVF- (HGP 4.9 +/- 0.8 mg.kg(-1).min(-1)). Both pregnant groups had lower peripheral glucose uptake compared with Nonpreg. In parallel with hepatic insulin sensitivity, hepatic triglyceride content was increased in pregnancy (Nonpreg 1.9 +/- 0.4 vs. Preg 3.2 +/- 0.3 mg/g) and decreased with removal of VF (PVF- 1.3 +/- 0.4 mg/g; P < 0.05). Accretion of visceral fat is an important component in the development of hepatic IR in pregnancy, and accumulation of hepatic triglycerides is a mechanism by which visceral fat may modulate insulin action in pregnancy.

The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women

OBJECTIVE

To determine the effects of a 15-week high-intensity intermittent exercise (HIIE) program on subcutaneous and trunk fat and insulin resistance of young women.

DESIGN AND PROCEDURES

Subjects were randomly assigned to one of the three groups: HIIE (n=15), steady-state exercise (SSE; n=15) or control (CONT; n=15). HIIE and SSE groups underwent a 15-week exercise intervention.

SUBJECTS

Forty-five women with a mean BMI of 23.2+/-2.0 kg m(-2) and age of 20.2+/-2.0 years.

RESULTS

Both exercise groups demonstrated a significant improvement (P<0.05) in cardiovascular fitness. However, only the HIIE group had a significant reduction in total body mass (TBM), fat mass (FM), trunk fat and fasting plasma insulin levels. There was significant fat loss (P<0.05) in legs compared to arms in the HIIE group only. Lean compared to overweight women lost less fat after HIIE. Decreases in leptin concentrations were negatively correlated with increases in VO(2peak) (r=-0.57, P<0.05) and positively correlated with decreases in TBM (r=0.47; P<0.0001). There was no significant change in adiponectin levels after training.

CONCLUSIONS

HIIE three times per week for 15 weeks compared to the same frequency of SSE exercise was associated with significant reductions in total body fat, subcutaneous leg and trunk fat, and insulin resistance in young women.

Relationship of abdominal obesity measured by DXA and waist circumference with insulin sensitivity in Hispanic and non-Hispanic white individuals: the San Luis Valley Diabetes Study

BACKGROUND

To determine if dual-energy X-ray absorptiometry (DXA) measures of trunk fat, a user-defined abdominal region of interest (ROI) and waist circumference (WC) differ in their association with insulin sensitivity among Hispanics and non-Hispanic whites (NHW) or explain any ethnic differences in insulin sensitivity.

METHODS

A cross-sectional study of data collected (1997-98) as part of the longitudinal San Luis Valley Diabetes Study was utilized. There were 664 non-diabetic participants including 349 women (220 NHW, 139 Hispanic) and 305 men (197 NHW, 108 Hispanic), average age 63 years. Measurements included body mass index, WC and DXA measures of total and abdominal fat. Fasting glucose and insulin were used to estimate insulin sensitivity using the QUICKI index. A 2-h oral glucose tolerance test was used to classify participants with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT).

RESULTS

Among women with NGT, Hispanics had lower insulin sensitivity, with DXA trunk fat explaining the most variance in QUICKI and 54% of the ethnic difference in QUICKI after adjusting for total body fat and lean mass. Among men with NGT, there were no differences between Hispanics and NHW in insulin sensitivity or any differences in the association of the abdominal fat measures with insulin sensitivity. Among men and women with IGT, the fat distribution variables explained little variance in QUICKI.

CONCLUSIONS

DXA measures of trunk fat provide additional information over WC and the DXA abdominal ROI measure about ethnic differences in insulin sensitivity between older Hispanic and NHW women with NGT.

Regional body composition in college-aged Caucasians from anthropometric measures

BACKGROUND

Quantitating fat and lean tissue in isolated body regions may be helpful or required in obesity and health-outcomes research. However, current methods of regional body composition measurement require specialized, expensive equipment such as that used in computed tomography or dual energy x-ray absorptiometry (DEXA). Simple body size or circumference measurement relationships to body composition have been developed but are limited to whole-body applications. We investigated relationships between body size measurements and regional body composition.

METHODS

Using DEXA technology we determined the fat and lean tissue composition for six regions of the body in predominantly Caucasian, college-aged men (n = 32) and women (n = 67). Circumference measurements as well as body weight and height were taken for each individual. Equations relating body measurements to a respective regional fat and lean mass were developed using multiple regression analysis.

RESULTS

Multiple regression R2 values ranged from 0.4451 to 0.8953 and 0.1697 to 0.7039 for regional fat and lean mass relationships to body measurements, respectively.

CONCLUSION

The equations developed in this study offer a simple way of estimating regional body composition in a college-aged adult population. The parameters used in the equations are common body measurements that can be obtained with the use of a measuring tape and weight scale.

Glucocorticoid modulation of insulin signaling in human subcutaneous adipose tissue

CONTEXT

Glucocorticoid (GC) excess is characterized by central obesity, insulin resistance, and in some cases, type 2 diabetes. However, the impact of GC upon insulin signaling in human adipose tissue has not been fully explored.

OBJECTIVE

We have examined the effect of GC upon insulin signaling in both human sc primary preadipocyte cultures and a novel human immortalized sc adipocyte cell line (Chub-S7) and contrasted this with observations in primary cultures of human skeletal muscle.

DESIGN AND SETTING

This is an in vitro study characterizing the impact of GC upon insulin signaling in human tissues.

PATIENTS

Biopsy specimens were from healthy volunteers who gave their full and informed written consent.

INTERVENTIONS

Combinations of treatments, including GC, RU38486, and wortmannin, were used.

MAIN OUTCOME MEASURES

Insulin signaling cascade gene and protein expression and insulin-stimulated glucose uptake were determined.

RESULTS

In human adipocytes, pretreatment with GC induced a dose-dependent [1.0 (control); 1.2 +/- 0.1 (50 nm); 2.2 +/- 0.2 (250 nm), P < 0.01 vs. control; 3.4 +/- 0.2 (1000 nm), P < 0.001 vs. control] and time-dependent [1.0 (1 h); 3.2 +/- 2.0 (6 h); 9.1 +/- 5.9 (24 h), P < 0.05 vs. 1 h; 4.5 +/- 2.2 (48 h)] increase in insulin-stimulated protein kinase B/akt phosphorylation. In addition, whereas insulin receptor substrate (IRS)-1 protein expression did not change, IRS-1 tyrosine phosphorylation increased. Furthermore, GC induced IRS-2 mRNA expression (2.8-fold; P < 0.05) and increased insulin-stimulated glucose uptake [1.0 (control) 1.8 +/- 0.1 (insulin) vs. 2.8 +/- 0.2 (insulin + GC); P < 0.05]. In contrast, in primary cultures of human muscle, GC decreased insulin-stimulated glucose uptake [1.0 (control) 1.9 +/- 0.2 (insulin) vs. GC 1.3 +/- 0.1 (insulin + GC); P < 0.05].

CONCLUSIONS

We have demonstrated tissue-specific regulation of insulin signaling by GC. Within sc adipose tissue, GCs augment insulin signaling, yet in muscle GCs cause insulin resistance. We propose that enhanced insulin action in adipose tissue increases adipocyte differentiation, thereby contributing to GC-induced obesity.

Gastric emptying, diabetes, and aging

Gastric emptying is mildly slowed in healthy aging, although generally remains within the normal range for young people. The significance of this is unclear, but may potentially influence the absorption of certain drugs, especially when a rapid effect is desired. Type 2 diabetes is common in the elderly, but there is little data regarding its natural history, prognosis, and management. This article focuses on the interactions between gastric emptying and diabetes, how each is influenced by the process of aging, and the implications for patient management.