Relationship between visceral fat, steroid hormones and insulin sensitivity in premenopausal obese women

Relationship of the neutrophil/lymphocyte ratio with cardiovascular risk markers in premenopausal and postmenopausal women

Introduction

Cardiovascular disease is more frequent in postmenopausal women. Atherosclerosis is associated with inflammation and the neutrophil/lymphocyte ratio (NLR) is a marker of inflammation whose behavior in postmenopause is unknown.

Aim of the study

To know the relationship of the NLR with cardiovascular risk markers in premenopausal and postmenopausal women.

Material and methods

Premenopausal and postmenopausal women were studied, in all of them a complete hemogram and the NLR, platelet/lymphocyte ratio (PLR) were calculated, also glucose and lipids levels were measured. In all of them subcutaneous and visceral fat, carotid intima-media thickness (IMT), epicardial fat were measured by ultrasound Also baseline and and after flow-mediated stimulus the arterial diameter, the pulsatility index and the resistive index of the brachial artery were measured by ultrasound. The results are reported with medians and intervals, Mann-Whitney U and Spearman correlation analysis were performed.

Results

Eighty two patients were recruited, 41 premenopausal and 41 postmenopausal. When comparing both groups there was no difference in glucose, lipids, NLR, PLR, carotid IMT, epicardial fat, subcutaneous fat, visceral fat or Doppler parameters of the brachial artery.

Conclusion

NLR was not different between premenopausal and postmenopausal women but abnormal PLR was greater in those postmenopausal with vasomotor symptoms.

Abdominal adiposity contributes to adverse glycemic control and albuminuria in Chinese type 2 diabetic patients: A cross-sectional study

BACKGROUND

Abdominal adipose tissue plays an important role in the development of type 2 diabetes. However, few data have suggested its role in the prognosis of diabetes. This study aimed to investigate the association between waist-hip ratio (WHR), glycemic control, and early nephropathy in Chinese type 2 diabetic patients.

METHODS

A cross-sectional study was conducted in 1709 previously- and newly-diagnosed diabetic patients nested in a cohort study consisting of 10 375 participants aged ≥40 years in Shanghai, China. General characteristics through questionnaire, anthropometric measures, and biochemical results were recorded. Statistical analysis was performed by SPSS v20.0.

RESULTS

Each quartile increase in WHR was significantly associated with a fasting plasma glucose (FPG) ≥ 126 mg/dl [OR (95% CI):1.18 (1.06-1.30)], an HbA1c ≥ 7.0% [1.21 (1.08-1.35)], and a HOMA-IR ≥ 2.5 [1.30 (1.16-1.46)] after multivariable adjustments. WHR was not associated with a 2h PG ≥ 200mg/dl [1.13 (0.97-1.31)]. The risk for increased albuminuria (UACR ≥10.18mg/g) was also significantly associated with higher WHR after adjustment for HbA1c [1.14 (1.02-1.27)]. However, no significant relationship was seen between WHR and an estimated glomerular filtration rate < 90 ml/min per 1.73 m² . Interactions of sex, or physical activity with WHR in association with glycemic control and increased albuminuria were found (P values for interaction <0.05).

CONCLUSIONS

These data demonstrated an independent role of abdominal adipose tissue in glycemic control and renal complications of type 2 diabetes. Interventions aiming to reduce abdominal adipose tissue may have additional benefits.

Cortisol Measures Across the Weight Spectrum

CONTEXT

There are conflicting reports of increased vs decreased hypothalamic-pituitary-adrenal (HPA) activation in obesity; the most consistent finding is an inverse relationship between body mass index (BMI) and morning cortisol. In anorexia nervosa (AN), a low-BMI state, cortisol measures are elevated.

OBJECTIVE

This study aimed to investigate cortisol measures across the weight spectrum.

DESIGN AND SETTING

This was a cross-sectional study at a clinical research center.

PARTICIPANTS

This study included 60 women, 18-45 years of age: overweight/obese (OB; N = 21); AN (N = 18); and normal-weight controls (HC; N = 21).

MEASURES

HPA dynamics were assessed by urinary free cortisol, mean overnight serum cortisol obtained by pooled frequent sampling every 20 minutes from 2000-0800 h, 0800 h serum cortisol and cortisol-binding globulin, morning and late-night salivary cortisol, and dexamethasone-CRH testing. Body composition and bone mineral density (BMD) were assessed by dual-energy x-ray absorptiometry.

RESULTS

Cortisol measures demonstrated a U-shaped relationship with BMI, nadiring in the overweight-class I obese range, and were similarly associated with visceral adipose tissue and total fat mass. Mean cortisol levels were higher in AN than OB. There were weak negative linear relationships between lean mass and some cortisol measures. Most cortisol measures were negatively associated with postero-anterior spine and total hip BMD.

CONCLUSIONS

Cortisol measures are lowest in overweight-class I obese women-lower than in lean women. With more significant obesity, cortisol levels increase, although not to as high as in AN. Therefore, extreme underweight and overweight states may activate the HPA axis, and hypercortisolemia may contribute to increased adiposity in the setting of caloric excess. Hypercortisolemia may also contribute to decreased BMD and muscle wasting in the setting of both caloric restriction and excess.

Relation of skinfold thickness and visceral fat with the endothelial function in Mexican postmenopausal women

OBJECTIVE

To determine the relationship between skinfolds and visceral fat with vascular reactivity according to body weight, fat distribution and time since menopause in Mexican postmenopausal women.

MATERIAL AND METHODS

In postmenopausal women, tricipital, suprailiac and subscapular skinfolds as well as blood pressure were measured, and body mass index (BMI) and waist-hip ratio (WHR) were calculated. Brachial artery Doppler ultrasound at baseline and after the hyperemic stimulus was done and Doppler parameters were assessed. For statistical analysis, Pearson and Spearman correlation analysis, as well as Student t were used.

RESULTS

Sixty-six postmenopausal women were studied; age was 54.5 ± 7.4 years. Skinfold thickness was related with subcutaneous and visceral fat. In all groups, the arterial diameter increased after the hyperemic stimulus among 6.5% and 9% of women. The pulsatility index decreased in the whole group and in those with BMI ≤ 27, WHR ≤ 0.85 and time since menopause ≤ 10 years. Negative correlations were observed between the percentage of change in arterial dilatation and the subscapular skinfold and subcutaneous fat in the whole group and in the subgroups with BMI > 27 and WHR > 0.85.

CONCLUSIONS

Skinfolds are indirectly related with visceral fat, and skinfold thickness permit to conclude about impact in endothelial environment.

Diurnal salivary cortisol is associated with body mass index and waist circumference: the Multiethnic Study of Atherosclerosis

OBJECTIVE

Neuroendocrine abnormalities, such as activation of the hypothalamic-pituitary-adrenal (HPA) axis, are associated with obesity; however, few large-scale population-based studies have examined HPA axis and markers of obesity. We examined the cross-sectional association of the cortisol awakening response (CAR) and diurnal salivary cortisol curve with obesity.

DESIGN AND METHODS

The Multiethnic Study of Atherosclerosis Stress Study includes 1,002 White, Hispanic, and Black men and women (mean age 65 ± 9.8 years) who collected up to 18 salivary cortisol samples over 3 days. Cortisol profiles were modeled using regression spline models that incorporated random parameters for subject-specific effects. Cortisol curve measures included awakening cortisol, CAR (awakening to 30-min postawakening), early decline (30 min to 2-h postawakening), late decline (2-h postawakening to bedtime), and the corresponding areas under the curve (AUC). Body mass index (BMI) and waist circumference (WC) were used to estimate adiposity.

RESULTS

For the entire cohort, both BMI and WC were negatively correlated with awakening cortisol (P < 0.05), AUC during awakening rise, and early decline and positively correlated to the early decline slope (P < 0.05) after adjustments for age, race/ethnicity, gender, diabetes status, socioeconomic status, β-blockers, steroids, hormone replacement therapy, and smoking status. No heterogeneities of effects were observed by gender, age, and race/ethnicity.

CONCLUSIONS

Higher BMI and WC are associated with neuroendocrine dysregulation, which is present in a large population sample, and only partially explained by other covariates.

Comparison of Visceral Adipose Tissue Mass in Adult African Americans and Whites**

OBJECTIVE

Previous studies have reported racial differences in the amount of visceral adipose tissue (VAT), a risk factor for metabolic diseases. These results are equivocal and have not controlled for hormonal influences on VAT mass. This study was designed to measure the extent to which race is associated with VAT, controlling for total adipose tissue (TAT) mass and testosterone.

RESEARCH METHODS AND PROCEDURES

Using a cross-sectional study design, we measured TAT mass using DXA, VAT and subcutaneous adipose tissue mass using magnetic resonance imaging, and sex hormones using radioimmunoassay in 224 African-American and white men and women.

RESULTS

White men had increased VAT mass, even when controlling for TAT and age, compared with African-American men. White women also had a higher VAT mass compared with African-American women, but only when controlling for TAT and age. When multiple linear regression was used to evaluate the racial differences in VAT mass in a subset of subjects (n=80), controlling for sex hormones, it was found that white men, but not women, had increased VAT mass compared with their African-American counterparts.

DISCUSSION

Based on the results of this study, we conclude that, when controlling for TAT, sex hormone levels, and age, white men, but not women, have more VAT mass than African-American men and women. Additional studies are needed to explore possible environmental and genetic influences on fat distribution relative to race and sex.

Pleiotropic Effects of Genes for Insulin Resistance on Adiposity in Baboons

OBJECTIVE

Previous research has suggested a genetic contribution to the development of insulin resistance and obesity. We hypothesized that the same genes influencing insulin resistance might also contribute to the variation in adiposity.

RESEARCH METHODS AND PROCEDURES

A total of 601 (200 male, 401 female) adult baboons (Papio hamadryas) from nine families with pedigrees ranging in size from 43 to 121 were used in this study. Plasma insulin, glucose, C-peptide, and adiponectin were analyzed, and homeostasis model assessment of insulin resistance (HOMA IR) was calculated. Fat biopsies were collected from omental fat tissue, and triglyceride concentration per gram of fat tissue was determined. Body weight and length were measured, and BMI was derived. Univariate and bivariate quantitative genetic analyses were performed using SOLAR.

RESULTS

Insulin, glucose, C-peptide, and adiponectin levels, HOMA IR, triglyceride concentration of fat tissue, body weight, and BMI were all found to be significantly heritable, with heritabilities ranging from 0.15 to 0.80. Positive genetic correlations (r(G)s) were observed for HOMA IR with C-peptide (r(G) = 0.88 +/- 0.10, p = 0.01), triglyceride concentration in fat tissue (r(G) = 0.86 +/- 0.33, p = 0.02), weight (r(G) = 0.50 +/- 0.20, p = 0.03), and BMI (r(G) = 0.64 +/- 0.22, p = 0.02).

DISCUSSION

These results suggest that a set of genes contributing to insulin resistance also influence general and central adiposity phenotypes. Further genetic research in a larger sample size is needed to identify the common genes that constitute the genetic basis for the development of insulin resistance and obesity.

Visceral adiposity after tibolone use

OBJECTIVE

To evaluate the differences in visceral fat between women using tibolone and those not using tibolone.

METHODS

Sixty-five healthy postmenopausal women were included in the study: 26 who were taking tibolone (2.5 mg/day); and 39 who were not receiving tibolone treatment. Anthropometric measurements were performed, with subcutaneous and visceral fat measured via ultrasound. Differences between the groups were determined via Student t test.

RESULTS

There were no significant differences in age (P=0.796), weight (P=0.256), height (P=0.456), body mass index (P=0.08), waist circumference (P=0.420), or waist-hip ratio (P=0.1) between the groups. Hip circumference was significantly lower in the study group than in the control group (97.7 ± 12.2 cm vs 103 ± 8.1cm; P<0.04). There were no significant differences between the groups in subcutaneous fat measurements (P=0.56). There were significantly lower visceral fat measurements (2.8 ± 1.1cm vs 3.9 ± 1.6 cm; P<0.004) and a significantly lower visceral fat-subcutaneous fat ratio (1.1 ± 0.3 vs 1.5 ± 0.7; P<0.005) in the study group than in the control group.

CONCLUSION

Postmenopausal women who use tibolone have lower visceral fat measurements than do woman of similar age who do not use tibolone.

Early nutrition and adult health: Perspectives for international and community nutrition programs and policies

Recent economic changes throughout the world, either development or crises and recessions, have prompted a host of nutrition related problems, including a decreased prevalence of undernutrition, an increase in the prevalence of diet related diseases, widespread food insecurity as crop prices increase, and so on. In addition, evidence is mounting that suggests that exposure to poor nutrition early in life is a predisposing factor for chronic diseases in adulthood. Thus, the role of international or community nutrition professionals is vital to not only studying and understanding the interplay between economics, food policy, and health, but also to improving the ability to intervene and prevent many problems related to food insecurity in developed and developing countries. The purpose of this review is to outline and describe these issues as a means to open discussion on how to best alleviate major nutrition problems in the world.

Effects of dietary energy source and physical conditioning on insulin sensitivity and glucose tolerance in standardbred horses

REASONS FOR PERFORMING STUDY

There is evidence that adaptation to diets rich in nonstructural carbohydrates (NSC) contributes to the development of insulin resistance in horses. To date, however, no study in horses has examined the effects of physical conditioning on diet-associated alterations in insulin sensitivity and glucose tolerance.

OBJECTIVES

To examine the effects of adaptation to concentrate feeds rich in NSC or fat on insulin sensitivity and glucose tolerance in horses, both in the sedentary state and after a subsequent period of physical conditioning.

METHODS

Fourteen mature Standardbred horses underwent both a euglycaemic-hyperinsulinaemic clamp (EHC) and oral glucose tolerance test (OGTT) after each of the following phases: Baseline - fed only forage cubes for 3 weeks; Diet horses were randomly assigned to receive either a high NSC (S) concentrate or a high fat concentrate (F) with forage cubes for 6 weeks; and Diet x Exercise - horses remained on the assigned ration and underwent a 7 week period of physical conditioning. An incremental exercise test was performed before, and after, the Diet x Exercise phase for measurement of the peak rate of oxygen consumption (VO2peak).

RESULTS

In both diet groups, there was an approximately 10% increase in mean VO2peak after physical conditioning. The mean rate of glucose disposal (M) per unit of serum insulin (I) during the EHC [M/I ratio] in S horses was 30% lower (P<0.05) in the Diet phase when compared to Baseline, but not different from Baseline after physical conditioning. The S diet also resulted in a greater (P<0.05) OGTT insulin response (area under the insulin vs. time curve, AUC(INS)) in both Diet and Diet x Exercise phases when compared to Baseline. In F, insulin sensitivity (mean M/I ratio) and glucose tolerance were unchanged during the study.

CONCLUSIONS AND POTENTIAL RELEVANCE

Feeding a diet rich in NSC for 6 weeks resulted in decreased insulin sensitivity and impaired glucose tolerance. Physical conditioning lessened the effects of the high NSC diet on insulin sensitivity, as evidenced by the return to baseline M/I, but did not mitigate the impaired glucose tolerance. Decreased insulin sensitivity has been implicated in the development of obesity and laminitis in horses and the present findings provide support for avoidance of concentrates with high NSC in the dietary management of horses at risk for the development of these conditions.

Adrenal gland volume and dexamethasone-suppressed cortisol correlate with total daily salivary cortisol in African-American women

CONTEXT

Population-based studies of associations between subclinical hypercortisolism and risk for disease states, such as type 2 diabetes mellitus, have been difficult to assess because of imprecise measures of glucocorticoid exposure. Alternative measures (salivary cortisol and adrenal gland volume) have not been systematically compared with 24-h urine free cortisol (UFC) in a healthy population.

OBJECTIVE

Our objectives were: 1) to determine whether 24-h UFC and total daily salivary cortisol correlated with each other, adrenal gland volume, and salivary cortisol after dexamethasone suppression and 2) to evaluate the association of adrenal gland volume with salivary cortisol after dexamethasone suppression.

DESIGN, SETTING, AND PARTICIPANTS

This was a cross-sectional study of 20 healthy, premenopausal African-American women aged 18-45 yr.

MAIN OUTCOME MEASURES

Salivary cortisol was assessed at six time points throughout the day simultaneous with 24-h UFC collection. Adrenal gland volume was measured by computed tomography scan. Dexamethasone-suppressed salivary cortisol was measured at 0800 h after administration of 0.5 mg dexamethasone at 2300 h the prior evening.

RESULTS

Dexamethasone-suppressed salivary cortisol levels correlated strongly with individual, timed salivary cortisol measurements, total daily salivary cortisol (rs=0.75; P=0.0001; n=20), and adrenal gland volume (rs=0.66; P=0.004; n=17). Total daily salivary cortisol and adrenal gland volume also correlated (rs=0.46; P=0.04; n=19). In contrast, 24-h UFC levels did not correlate with any of the other hypothalamic-pituitary-adrenal axis measures.

CONCLUSION

A dexamethasone suppression test or adrenal gland volume may be alternative measures for characterizing subtle subclinical hypercortisolism in healthy adults.

Indexes of abdominal adiposity in patients with type 2 diabetes

OBJECTIVE

To assess the relationship of waist circumference and weight/height ratio with height, and their association with components of the metabolic syndrome, in Type 2 diabetic patients.

DESIGN

multicenter cross-sectional survey on a cohort enrolled in a prospective observational study.

SUBJECTS

13,232 patients (6816 women and 6416 men) with Type 2 diabetes, not currently affected by macrovascular complications.

MEASUREMENTS

height, weight, waist and hip circumference, waist/hip and waist/height ratios.

RESULTS

waist circumference was significantly correlated with height after adjustment for potential confounders (adjusted r=0.19 and 0.23 in women and men, respectively), while waist/height ratio showed an inverse correlation with height (r=-0.14 and -0.15, respectively). Elevated waist/height ratio was more predictive of hypertension and hypertriglyceridemia, than waist circumference or waist/hip ratio.

CONCLUSIONS

Waist circumference is correlated with height; thresholds for waist circumference could need adjustment for height. Waist/height ratio, although inversely correlated with height, could be a better predictor of abnormalities associated with abdominal adiposity than waist circumference alone.

Abdominal adipose tissue distribution and metabolic risk

It is now established that waist circumference remains a significant predictor of disease and metabolic risk independent of obesity measured by body mass index. These observations are reinforced by a large body of evidence implicating abdominal obesity measured by imaging modalities in the pathogenesis of numerous metabolic risk factors. However, the extent to which abdominal subcutaneous or visceral adipose tissue (AT) independently contribute to the established association between abdominal obesity and metabolic risk remains a subject of considerable research. Discrepancies in the literature may be partially explained by methodological issues, as currently there is no accepted definition for either visceral or abdominal subcutaneous AT. Accordingly, there is confusion concerning how best to measure these depots in metabolic and descriptive studies. Further, despite numerous studies linking abdominal AT depots with metabolic risk factors, the underlying mechanisms remain unclear. The primary purpose of this review is to examine the independent contribution of visceral and abdominal subcutaneous AT to the aetiology of obesity-related health risk. We begin by considering specific methodological issues with respect to the current classification of abdominal AT as measured by imaging methods. When necessary, we present original data to reinforce important concepts not suitably addressed in the literature. We conclude with a consideration of proposed mechanisms that may link abdominal adiposity and metabolic risk.

The dysmetabolic syndrome, insulin resistance and increased cardiovascular (CV) morbidity and mortality in type 2 diabetes: aetiological factors in the development of CV complications

Insulin resistance often clusters with other cardiovascular risk factors, such as obesity, impaired glucose tolerance (IGT), hypertension, dyslipidaemia and impaired fibrinolysis. Collectively, these endocrine and metabolic disturbances are described as the dysmetabolic syndrome, which is also commonly called the "insulin resistance syndrome", the "metabolic syndrome", or "syndrome X". Insulin resistance, working in concert with the other components of the dysmetabolic syndrome, induces deleterious changes to the vascular endothelium and lipid profiles that directly and indirectly promote the progression of atherosclerosis. Insulin resistance in adipocytes, leading to decreased suppression of lipolysis by insulin, may be especially important in this regard. Reduced suppression of lipolysis by insulin in obese subjects is associated with increased levels of fatty acids that damage the arterial wall and promote atherosclerosis. The lipid profiles of insulin-resistant subjects are often characterised by the appearance of hypertriglyceridaemia and small, dense LDL-cholesterol, together with low HDL-cholesterol. In addition, adipocytes are highly active endocrine organs and secrete a range of substances that reduce insulin sensitivity further. The net result of these derangements is a vicious circle, wherein the development of insulin resistance is strongly associated with atherogenic lipid profiles and endothelial dysfunction which, in turn, exacerbates insulin resistance. The consequences for the individual with dysmetabolic syndrome include an increased risk of cardiovascular disease of up to 4-fold compared with subjects without the dysmetabolic syndrome.

A path model of chronic stress, the metabolic syndrome, and coronary heart disease

OBJECTIVE

We tested a theoretical stress model cross-sectionally and prospectively that examined whether relationships of chronic stress, psychophysiology, and coronary heart disease (CHD) varied in older adult men (N = 47), older adult women not using hormone replacement therapy (HRT) (N = 64), and older adult women using HRT (N = 41).

METHOD

Structural equations examined relationships of CHD with 1) chronic stress (caring for a spouse with Alzheimer's disease and patient functioning), 2) vulnerability (anger and hostility), 3) social resources (supports), 4) psychological distress (burden, sleep problems, and low uplifts), 5) poor health habits (high-caloric, high-fat diet and limited exercise), and 6) the metabolic syndrome (MS) (blood pressure, obesity, insulin, glucose, and lipids).

RESULTS

Caregiver men had a greater prevalence of CHD (13/24) than did noncaregiver men (6/23) (p <.05) 27 to 30 months after study entry. This was influenced by pathways from caregiving to distress, distress to the MS, and the MS to CHD. In men, poor health habits predicted the MS 15 to 18 months later, and the MS predicted new CHD cases over 27 to 30 months. In women, no "caregiving-CHD" relationship occurred; however, 15 to 18 months after study entry women not using HRT showed "distress-MS" and "MS-CHD" relationships. In women using HRT, associations did not occur among distress, the MS, and CHD, but poor health habits and the MS were related.

CONCLUSIONS

In older men, pathways occurred from chronic stress to distress to the metabolic syndrome, which in turn predicted CHD. Older women not using HRT showed fewer pathways than men; however, over time, distress, the MS, and CHD were related. No psychophysiological pathways occurred in older women using HRT.

Insulin-leptin-visceral fat relation during weight loss

INTRODUCTION

The relation between insulin-leptin-visceral fat axis during weight loss has not been studied previously.

AIMS

To evaluate the insulin, leptin, and abdominal adiposity relation during weight loss in patients with upper body obesity.

METHODOLOGY

Twenty volunteers (7 men, 13 women) with mean age 50.6+/-6.3 (SD) and upper body obesity (weight 105.4+/-12.3 kg, BMI 35.9+/-2.5 kg/m2) were recruited. Participants were enrolled in a one-arm clinical study using a calorie-deficient diet and an escalating dose regimen of sibutramine, starting with 5 mg daily and increasing in 5-mg increments to 20 mg per day. Body weight, insulin, leptin, glucose, lipids, abdominal computed tomography (CT), and total body electrical conductance (TOBEC) were measured serially at weeks 0, 4, 8, 12, and 24.

RESULTS

Eighteen patients completed the 6-month study: one man and one woman discontinued because of adverse events. With diet and sibutramine, body weight was significantly and continuously reduced throughout the 6-month study. There was a 16.0% (p = 0.0001) reduction in body weight (p < 0.001) and 22.5% (p = 0.0001) decrease in total body fat mass. Abdominal CT scans showed a 28.3% (p = 0.0001) reduction in total abdominal fat, a 26.0% (p = 0.0001) reduction in subcutaneous fat (p < 0.001), and a 31.0% (p = 0.0003) reduction in visceral fat (p < 0.001). There was a 32.0% (p = 0.0008) reduction in leptin levels and 37.9% (p = 0.0001) reduction in insulin levels between baseline and week 4, but no further significant reduction in leptin and insulin levels was observed for the duration of the study. There was a significant correlation between insulin and leptin concentrations throughout the study (p = 0.0001). Leptin was presented as a function of insulin measured at the same time. Significant associations between visceral abdominal fat, subcutaneous fat, and leptin were also observed.

CONCLUSION

In this study, we found that leptin and insulin were related in weight loss. The data suggest that insulin may act as a strong regulator of leptin secretion during weight loss and that circulating leptin levels can be predicted by insulin level. Using sibutramine in conjunction with hypocaloric diet reduced body weight and decreased fat mass significantly. Visceral and subcutaneous abdominal fat depots were shown to decrease. Whether sibutramine exerts any selective reduction of visceral abdominal fat as opposed to total body fat mass will require further clinical investigation.

Body fat distribution and cardiovascular risk in normal weight women. Associations with insulin resistance, lipids and plasma leptin

OBJECTIVE

To systematically examine the correlations between insulin resistance, plasma leptin concentration, obesity and the distribution of fat assessed by anthropometry and magnetic resonance imaging in Asian women.

DESIGN

A cross sectional study of non-diabetic, normal weight women.

SUBJECTS

Twenty-one healthy women aged 38.8 y (s.d. 11.7) and BMI 22.6 kg/m2 (s.d. 2.3).

MEASUREMENTS

Intraperitoneal, retroperitoneal and subcutaneous abdominal fat volume was assessed by magnetic resonance imaging. Anthropometric data were collected. Total fat mass was assessed by bioelectric impedance analysis. Fasting serum lipids, insulin and plasma leptin were assayed.

RESULTS

Generalized obesity correlated with subcutaneous abdominal fat mass (r=0.83, P<0.001), but not with intra-abdominal fat mass. Both intraperitoneal fat mass and retroperitoneal fat mass increased with age (r=0.58, P=0.005 and r=0. 612, P=0.003, respectively). Abdominal subcutaneous fat mass was the most important determinant of insulin resistance and plasma leptin. Of the serum lipids, only fasting triglyceride correlated significantly with the waist-to-hip ratio.

CONCLUSIONS

It is possible that the large size of the subcutaneous depot compared to the intra-abdominal depot overwhelms any metabolic differences between adipose tissue from these two sites, resulting in the stronger correlation between insulin resistance and subcutaneous abdominal fat mass rather than intra-abdominal fat mass. On the other hand, the distribution of fat between subcutaneous fat depots may be important in the metabolic syndrome given the correlation of fasting triglyceride with waist to hip ratio but not with abdominal fat. However, the study population was small, younger and leaner compared to previous studies and we may not be able to generalize these results to all segments of the population. We confirm that subcutaneous fat mass is the major determinant of plasma leptin.

Association of total and central adiposity measures with fasting insulin in a biracial population of young adults with normal glucose tolerance: the CARDIA study

OBJECTIVE

To determine the association of computed tomography (CT)-measured visceral adipose tissue (AT) and other measures of adiposity with fasting insulin in a biracial (African American and Caucasian) study population of young adults.

RESEARCH METHODS AND PROCEDURES

The study population consisted of 251 young adults with normal glucose tolerance (NGT), ages 28-40 years, who were volunteers from the Birmingham, Alabama, and Oakland, California centers of the Coronary Artery Risk Development in Young Adults (CARDIA) study.

RESULTS

In regression models with total adiposity measures (body mass index or dual-energy X-ray absorptiometry-measured percent fat), visceral AT (measured as a cross-sectional area in cm2) was generally a stronger predictor of insulin than overall adiposity in all race/gender groups (partial correlation coefficients ranging from 0.31 to 0.47) except for black men, in whom the associations were nonsignificant. Partial correlation coefficients between waist circumference and insulin, controlling for percent fat, were nearly identical to those between visceral AT and insulin in women and in white men. Analyses performed on 2060 NGT CARDIA subjects who were not in this study of visceral AT showed significant correlations of waist circumference with insulin in all race/gender groups, including black men, and that black men in the visceral AT study group were significantly leaner than other black male CARDIA subjects.

DISCUSSION

We conclude that visceral AT was associated with fasting insulin in NGT participants in three of the four race/gender groups (black men excepted) and that waist circumference was a good surrogate for visceral AT in examining associations of central adiposity with fasting insulin.

Obesity and cardiovascular disease

Obesity, diabetes mellitus, and hypertension are common, interrelated medical problems in Westernized, industrialized societies. These interrelated medical conditions are associated with an increased risk of cardiovascular disease and are more prevalent in several minority groups, including African-American and Hispanic populations. The associated cardiovascular risks of these problems are more thoroughly addressed in another review in this supplement. Obesity markedly enhances the development of Type 2 diabetes. Moreover, it enhances the cardiovascular risk associated with other risk factors, such as hypertension and dyslipidemia. Weight reduction in association with an aerobic exercise program improves metabolic abnormalities and reduces blood pressure in individuals with diabetes and hypertension.

Insulin resistance and fat patterning with aging: relationship to metabolic risk factors for cardiovascular disease

Both insulin resistance and abdominal fat patterning are related to aging, and have been related to cardiovascular disease (CVD) risk factors such as dyslipidemia and hypertension. However, previous studies have not used direct methods to quantify the independent strength of the association of each of these two putative primary factors with metabolic outcomes. We quantified overall obesity by the body mass index (BMI) and used a previously validated magnetic resonance imaging (MRI) method to quantify abdominal fat in 63 healthy nondiabetic individuals aged 22 to 83 years. We also measured the glucose and insulin response to an oral glucose tolerance test and the insulin sensitivity ([SI] by modified minimal model analysis). Body fat patterning was evaluated by the waist to hip ratio (WHR) and by MRI, which allowed direct measurement of subcutaneous (SCF) and intraabdominal (IAF) fat depots at the umbilicus in these subjects. These independent parameters were related to risk factors for CVD (blood pressure, lipids, and lipoproteins) and to plasma concentrations of free fatty acids (FFAs). Measures of overall obesity (BMI), total fat [TF], and/or SCF measured at the abdomen by MRI), glucose/insulin metabolism and SI, and central fat patterning (WHR or IAF measured by MRI) were correlated with mean arterial pressure (MAP), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) levels in univariate analysis and after controlling for age and gender. An index of central fat patterning (WHR) added to the informativeness of the insulin area under the curve (IAUC) in explaining 24% of the variability in plasma TG concentration, but measures of overall obesity were not independently related. Both the BMI and TF contributed to the IAUC in explaining 32% to 34% of the variability in MAP, but central fat patterning was not independently related. No index of overall obesity, fat patterning, glucose/insulin metabolism, and/or SI, was independently related to the plasma concentration of HDL-C after controlling for any one of the other two. Direct measurement of glucose/insulin metabolism and SI, as well as fat patterning, provides information on their relative associations with CVD risk factors. The measures of glucose/insulin metabolism and SI were more consistently related to dyslipidemia and hypertension than were the overall obesity and fat patterning in this healthy population.

Establishing reference intervals for DPC's free testosterone radioimmunoassay

OBJECTIVE

To establish reference intervals for serum free testosterone for DPC's Free Testosterone assay.

METHODS

We used data from healthy subjects and patients to determine reference intervals by parametric and non-parametric methods after partitioning by sex and age.

RESULTS

In males, there was a significant decrease in free testosterone concentrations with age. Reference intervals derived from a combination of 2075 "healthy" and patients' results gave similar values by parametric and nonparametric methods. However, the subgroups failed the test for Gaussian distribution. For each decade from 20 years on and > or = 60 years, the intervals based on 2.5th and 97.5th percentiles were: 24.1-94.8, 25.0-89.3, 23.4-81.7, 22.5-80.4, and 21.5-74.3 pmol/L respectively, in females, there was little change with age. The frequency distribution of 1915 patients was positively skewed, and showed a wider range than "healthy." Using square roots of values gave a Gaussian distribution. The central 95% intervals based on 187 "healthy" subjects were: 0.5-8.1 and 0.0-6.4 pmol/L for 20-59 and > or = 60 years, respectively.

CONCLUSION

Developing reference intervals for free testosterone was complicated by the need to partition data by gender and age, difficulty in establishing disease in subjects and presence of physiological and other factors which can affect concentration in health and disease.