Immunoreactive insulin and obesity in women.

The authors investigated basal and glucose stimulated (50 g by mouth) IRI values in women with normal weight and obese women (58) under conditions of balanced body-weight and after its reduction. The body composition was determined (from body density), and from specimens of subcutaneous abdominal adipose tissue also the size of fat cells and their total number. In obese women significantly higher IRI levels (basal and stimulated) were found as compared with controls and these values had a marked tendency towards normalization after reduction of body weight. The authors found significant relations between IRI values and the degree of obesity, fat content and lean body mass. The closest correlation was found between the stimulated IRI values and Broca's index (r = +0.8227). Between the loss of body-weight and body fat and between changes of IRI in obese subjects no significant relations were found. Investigation of the relationship of IRI and the size and total number of fat cells revealed marked associations between basal values and the sum of stimulated IRI values and the size of the fat cell. Relations between IRI and the total number of fat cells were not significant. When investigating the relationship between the incidence of obesity in the family and IRI values it was revealed that the group of obese women with obese mothers, as compared with the group who had neither parent obese, had a significantly higher basal IRI value and IRI value after stimulation with glucose during the 120th and 180th minute, the higher basal value in the group with an obese father was not significant. After weight reduction the differences between basal and stimulated IRI values were not significant.     

The size of large adipose cells is a predictor of insulin resistance in first-degree relatives of type 2 diabetic patients

Early studies reported that the size of adipose cells correlates with insulin resistance. However, a recent study comparing moderately obese, sensitive and resistant subjects, with comparable BMI (~30), did not detect any significant difference in the size of the large cells, but rather a smaller proportion of large cells in the resistant subjects, suggesting impaired adipogenesis. We hypothesize that a decreased proportion, rather than the size, of large adipose cells is also associated with insulin resistance in first-degree relatives of type 2 diabetic patients. Thirty-five leaner (BMI 18-34) subjects who were relatively healthy were recruited. Insulin sensitivity was measured by the euglycemic, hyperinsulinemic clamp. Needle biopsies of abdominal subcutaneous fat were assayed for adipose cell size by fitting the cell size distribution with two exponentials and a Gaussian function. The fraction of large cells was defined as the area of the Gaussian peak and the size of the large cells was defined as its center (c(p)). Glucose infusion rate (GIR) and c(p) were negatively correlated, but insulin sensitivity and the proportion of large cells were not correlated. BMI and c(p) were also strongly correlated, but a relationship of modest correlation between the cell size and insulin resistance was still significant after correcting for BMI. In contrast to moderately obese subjects, in the first-degree relatives of type 2 diabetic patients both BMI and the size of the large adipose cells predict the degree of insulin resistance; no correlation is found between the proportion of large adipose cells and insulin resistance.     

Scanning electron microscopy of very small fat cells and mature fat cells in human obesity

To determine the effect of obesity on the size distribution of fat cell populations in human adipose tissue, omental fat tissue biopsies were obtained from lean, moderately obese, and massively obese patients. The size distributions of adipocytes from lean and obese fat tissues examined by the scanning electron microscopic method were bimodal, consisting of populations of very small fat cells and mature fat cells, in contrast to collagenase-derived isolated cells that showed only the large mature fat cells. The very small fat cell population represented 21 to 26% of the total fat cell number in the lean and in both obese groups. In contrast, preparations of human fat cells isolated by the collagenase method systematically excluded the very small fat cells. In massive obesity, both cell populations participated in the hyperplastic growth but only the larger mature fat cells increased in size, implying that these two cell populations differ in their physiological role.     

The anatomy of adipose tissue in captive Macaca monkeys and its implications for human biology

In a sample of 31 sedentary, ad libitum-fed monkeys, most specimens had less than 5% adipose tissue by weight. Total fatness correlated closely with the number of adipocytes per kilogram lean body mass, but not at all with mean adipocyte volume, except in specimens below 5% fat. The total number of adipocytes per kilogram of lean body mass increased more than tenfold in the most obese specimens. These data suggest that, like humans but in contrast to laboratory rodents, adipocyte proliferation, not adipocyte enlargement, is the chief mechanism of adipose tissue expansion except in very lean monkeys. Adipose tissue was found in all the typical mammalian depots and in the superficial abdominal paunch, which enlarged disproportionately in obese specimens, forming an almost continuous layer over most of the body. Site-specific differences in the activities of some glycolytic enzymes were similar to those of other mammals. Adipocytes in the paunch depot showed biochemical properties in common with those in the groin depots. The distribution and cellularity of adipose tissue in normal humans were similar to those of exceptionally obese monkeys. Many of the interspecific and sex differences can be attributed to the much greater abundance of adipose tissue in humans, and may not be associated with hair reduction or aquatic habits. Some minor changes in the size or shape of certain adipose depots may have arisen recently under sexual selection. The relevance of laboratory rodents as animal models of human obesity is assessed from comparison of the cellular structure, anatomical distribution and enzyme profiles of adipose tissue in monkeys with those of human and other mammals.     

Cellularity of adipose depots in the genetically obese Zucker rat

Cell size and number of three adipose depots, epididymal, retroperitoneal, and subcutaneous, were determined during growth of the obese Zucker rat ("fatty") and nonobese Zucker control. Cellularity of these depots in the adult "fatty" was compared with that in nonobese controls and in nonobese Zucker rats made obese by ventromedial hypothalamic lesions. Epididymal and retroperitoneal depots in the nonobese rat grew by cell enlargement and increase in cell number until the 14th wk, when number became fixed; further increase in depot size occurred by cell enlargement. The subcutaneous depot added cells until the 26th wk. In the Zucker "fatty," cell number increased until the 26th wk in all depots, accompanied by extreme cell enlargement. The enlarged adipose depots of the adult Zucker "fatty," when compared with the nonobese control, are the result of both hypertrophy and hyperplasia. Depot enlargement in the lesioned animal is the result of hypertrophy. "Fatties" have more cells in adipose depots than do lesioned rats. Genetic obesity in the Zucker rat is clearly different from the obesity produced by hypothalamic lesioning.     

Preadipocyte Number in Omental and Subcutaneous Adipose Tissue of Obese Individuals

Objective: To determine the variation in preadipocyte isolation procedure and to assess the number and function of preadipocytes from subcutaneous and omental adipose tissue of obese individuals. Research Methods and Procedures: The preadipocyte number per gram of adipose tissue in the abdominal‐subcutaneous and abdominal‐omental adipose stores of 27 obese subjects with a BMI of 44 ± 10 kg/m² and an age of 40 ± 9 years was determined. Results: The assessment of the preadipocyte number was found to be labor intensive and error prone. Our data indicated that the number of stromal vascular cells (SVCs), isolated from the adipose tissue by collagenase digestion, was dependent on the duration of collagenase treatment and the size and the origin of the biopsy. In addition, the fat accumulation and leptin production by differentiated SVCs were dependent on the number of adherent SVCs (aSVCs) in the culture plate and the presence of proteins derived from serum and peroxisome proliferator‐activated receptor ligands. Discussion: Using our standardized isolation and differentiation protocol, we found that the number of SVCs, aSVCs, leptin production, and fat accumulation still varied considerably among individuals. Interestingly, within individuals, the number of SVCs, aSVCs, and the leptin production by differentiating aSVCs from both the subcutaneous and the omental fat depots were associated, whereas fat accumulation was not. In obese to severely obese subjects, differences in BMI and age could not explain differences in SVCs, aSVCs, leptin production, and fat accumulation.     

Role of CC chemokine receptor 2 in bone marrow cells in the recruitment of macrophages into obese adipose tissue

The MCP-1 (monocyte chemoattractant protein-1)/CCR2 (CC motif chemokine receptor-2) pathway may play a role in macrophage infiltration into obese adipose tissue. Here we investigated the role of CCR2 in the recruitment of bone marrow-derived macrophages into obese adipose tissue in vitro and in vivo. Using the TAXIScan device, which can measure quantitatively the directionality and velocity of cell migration at time lapse intervals in vitro, we demonstrated that bone marrow cells (BMCs) from wild type mice migrate directly toward MCP-1 or culture medium conditioned by adipose tissue explants of genetically obese ob/ob mice, which are efficiently suppressed by pharmacological blockade of CCR2 signaling. The number of F4/80-positive macrophages was reduced in the adipose tissue from high fat diet-fed obese KKAy or ob/ob mice treated with a CCR2 antagonist propagermanium relative to vehicle-treated groups. We also found that the number of macrophages is reduced in the adipose tissue from ob/ob mice reconstituted with CCR2(-/-) BMCs (ob/ob + CCR2(-/-) BMCs) relative to those with CCR2+/+ BMCs (ob/ob + CCR2+/+ BMCs). Expression of mRNAs for CD11c and TLR4 (Toll-like receptor 4) markers of proinflammatory M1 macrophages was also decreased in the adipose tissue from ob/ob + CCR2(-/-) BMCs relative to ob/ob + CCR2+/+ BMCs, whereas mannose receptor and CD163, markers of anti-inflammatory M2 macrophages, were unchanged. This study provides in vivo and in vitro evidence that CCR2 in bone marrow cells plays an important role in the recruitment of macrophages into obese adipose tissue.     

Studies on Human Adipose Cells in Culture: Relation of Cell Size and Cell Multiplication to Donor Age

In an effort to test the adipose hyperplasia theory of obesity in humans, adipose cells, derived from anterior abdominal walls of human infants and children, were grown in synthetic medium (McCoy's 5A Medium) supplemented with 20% fetal calf serum. Adipose cells which became delipidinized in culture were found to be capable of division and the rate and number of cell divisions was age dependent. Cells of infants under 1 yr of age and cells derived from early adolescent children divided to varying degrees in culture. Adipose cells from children aged 1-10 yr showed no cell division. Cell division was never observed in a lipid-laden adipocyte. Measurements of cell diameter showed that after the first year of life, cell size increased progressively with age. During the first year adipose cell size appeared to reflect the rapid hyperplasia of the first 3 mo, reaching smallest size at 3-12 mo but increasing thereafter.     

Mobilization of fatty acids in genetically obese rats

The mobilization of fatty acids has been studied in genetically obese rats of the Zucker strain and in control obese animals with bilateral destructive lesions in the hypothalamus. The body weight and size of adipose cells did not differ significantly between the genetically obese rats and the obese controls. Weight loss in control and genetically obese rats was identical during a 1 month fast. The release of glycerol and the rise in free fatty acids in adipose tissue incubated in vitro were similar in tissue from genetic and hypothalamic obese rats. Epinephrine, theophylline, and dibutyryl cyclic adenosine monophosphate all augmented lipolysis, and the effects were usually greater in the tissues from genetically obese rats.     

Increased Death of Adipose Cells,a Path to Release Cell‐Free DNA Into Systemic Circulation of Obese Women

Remodeling of adipose tissue is required to support the expansion of adipose mass. In obesity, an increased death of adipocytes contributes to the accelerated cellular turnover. We have shown that obesity in pregnancy is associated with metabolic and immune alterations in the adipose tissue. In this study, we characterized the mechanisms responsible for increased death of adipose cells of pregnant obese women and its functional consequences. We postulated that a higher turnover of dead cells in white adipose tissue of obese women would translate into release of cell‐free DNA (cfDNA) into their systemic circulation. Increase in adipose mass of obese compared to lean women results from a lesser number of hypertrophic adipocytes and an accumulation of macrophages in the stromal vascular fraction (SVF). The adipocytes of obese displayed enhanced necrosis with a loss of perilipin staining at the plasma membrane. Apoptosis was prominent in SVF cells with an increased expression of caspase 9 and caspase 3 and a higher rate of terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate nick end‐labeling (TUNEL) positive CD68 macrophages in obese vs. lean. Whereas circulating fetal cfDNA concentrations were not changed, there was a twofold increase in circulating glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) cfDNA and adipose tissue GAPDH mRNA in obese women. The maternal systemic GAPDH cfDNA was positively correlated with BMI and gestational weight gain. These data suggest that the active remodeling of adipose tissue of obese pregnant women results in an increased release of cfDNA of maternal origin into the circulation.     

Effect of fat cell size, restrictive diet and diabetes on lipoprotein lipase release by human adipose tissue.

The lipoprotein lipase activity (LPLA) eluted from human adipose tissue was measured after percutaneous biopsy in the fasting state. A positive and significant correlation was found between LPLA per 10(6) cells or per cell surface unit and cell volume in 27 normal and obese subjects in weight balance and on maintenance diet. Such a correlation was also found in 13 diabetic subjects before treatment. In 11 obese subjects subjected to a restricted diet, LPLA dropped dramatically without a significant change in cell size, blunting the cell size effect. In diabetic subjects the LPLA per cell was significantly lower than in nondiabetic people with similar adipose cell volume.     

Inflammation Correlates With Markers of T‐Cell Subsets Including Regulatory T Cells in Adipose Tissue From Obese Patients

Accumulation of cytotoxic and T‐helper (T_h)1 cells together with a loss of regulatory T cells in gonadal adipose tissue was recently shown to contribute to obesity‐induced adipose tissue inflammation and insulin resistance in mice. Human data on T‐cell populations in obese adipose tissue and their potential functional relevance are very limited. We aimed to investigate abundance and proportion of T‐lymphocyte sub‐populations in human adipose tissue in obesity and potential correlations with anthropometric data, insulin resistance, and systemic and adipose tissue inflammation. Therefore, we analyzed expression of marker genes specific for pan‐T cells and T‐cell subsets in visceral and subcutaneous adipose tissue from highly obese patients (BMI >40 kg/m², n = 20) and lean to overweight control subjects matched for age and sex (BMI <30 kg/m²; n = 20). All T‐cell markers were significantly upregulated in obese adipose tissue and correlated with adipose tissue inflammation. Proportions of cytotoxic T cells and T_h1 cells were unchanged, whereas those of regulatory T cells and T_h2 were increased in visceral adipose tissue from obese compared to control subjects. Systemic and adipose tissue inflammation positively correlated with the visceral adipose abundance of cytotoxic T cells and T_h1 cells but also regulatory T cells within the obese group. Therefore, this study confirms a potential role of T cells in human obesity‐driven inflammation but does not support a loss of protective regulatory T cells to contribute to adipose tissue inflammation in obese patients as suggested by recent animal studies.     

Regional variation in adipose tissue lipolysis in lean and obese men.

Biopsies of adipose tissue were obtained from two subcutaneous regions (abdominal and femoral) in a sample of 54 men (32 obese and 22 lean subjects). Clonidine-induced antilipolysis in femoral adipose cells was similar in both groups, whereas subcutaneous abdominal adipocytes of obese individuals showed a higher alpha 2-adrenergic response than did subcutaneous abdominal adipose cells from lean subjects. In addition, epinephrine had a biphasic effect in subcutaneous abdominal adipocytes from obese individuals, as it induced antilipolysis at low concentrations, and a net lipolytic response at higher doses. In contrast, the physiological amine promoted lipolysis in subcutaneous abdominal adipose cells of lean subjects. Epinephrine- and clonidine-induced antilipolysis of subcutaneous abdominal adipocytes was positively associated with the level of subcutaneous abdominal fat measured by computed tomography (CT). Finally, men with a high alpha 2-adrenergic response of subcutaneous abdominal fat cells were fatter than those with a low alpha 2-adrenergic component. These results suggest that, in men with a wide range of body fatness, variations in the lipolytic response of subcutaneous abdominal adipose cells to epinephrine appear to involve changes in the functional balance between alpha 2- and beta-adrenoceptors.     

Free fatty acid release from human adipose tissue in relation to obesity -- effect of isoprenaline.

The capacity to release non-esterified acids and glycerol from the abdominal subcutaneous adipose tissue into a medium containing different concentrations of isoprenaline was studied in 21 adults with different body weight (14 obese, 7 controls). The obese had a significantly lower maximum adipokinetic capacity (expressed as pD2) than controls. The significant decrease in pD2 in the obese was found to depend on the stabilization of the weight while the dynamic pD2 stage values of the obese did not differ from those of controls. The hypothesis is expressed that lower pD2 values may be related to the smaller decrease of body fat during weight reduction.     

Effect of current and midlife obesity status on mortality risk in the elderly

The primary purpose of this study was to determine whether current and midlife obesity status provide independent information on mortality risk in elderly persons. Analyses were based on 3,238 participants from the original Framingham Heart Study (FHS) cohort who lived to at least 70 years of age and who had BMI measures from when they were in their 50s. Within this group of 70-year olds, obesity based on current BMI was associated with a 21% increased risk of mortality (P = 0.019) whereas obesity in 70-year olds based on BMI measures obtained at around 50 years of age was associated with a 55% increased risk of mortality (P < 0.0001). Compared to 70-year olds who were nonobese at both 50 and 70 years of age, mortality risk was increased by 47% (P < 0.001) in those who were obese at both 50 and 70 years of age, increased by 56% (P < 0.001) in those who were obese at 50 years of age and nonobese at 70 years of age, and not significantly different (P > 0.9) in those who were nonobese at 50 years of age and obese at 70 years of age. In summary, in this cohort of elderly adults, midlife and current BMI had independent effects on mortality risk. Specifically, although mortality risk was increased in obese older adults who were already obese at midlife, this was not the case for newly obese older adults. Conversely, nonobese older adults who were obese at midlife had an increased mortality risk. These observations imply that it is imperative to consider an elderly adult's BMI in context of their BMI at midlife.     

A Comparison of Body Size Evaluations of Obesity Surgery Patients and General Population Adults

RAND, COLLEEN S. W., JAQUELYN LISS RESNIK, AND ALEX M. C. MACGREGOR. A comparison of body size evaluations of obesity surgery patients and general population adults. Obes Res. Objective: To compare post-operative obesity surgery patients and general population adults in their assessments of a wide range of body sizes. Research Methods and Procedures: Obesity surgery patients (n = 274) and general population adults (n = 326) rated ideal and socially acceptable body sizes in separate arrays of babies, children, young adults, and middle-aged and older adults. Nine line figure drawings ranging from very thin to very obese were rated for each array. Results: Both groups selected the same ideal body size for all arrays except for babies. Both groups rejected obese and very thin body sizes as socially acceptable. However, the obesity surgery patients were more restrictive than general population adults in their ratings of socially acceptable body sizes. Current obesity status did not impact ratings for the patient or general population subjects. In the patient sample, time since surgery did not influence body size evaluations. Discussion: The study of body size ratings limited only to the “ideal” size may be misleading because it may mask subtle but meaningful differences between groups. The consistent difference in more restrictive ratings of obesity surgery patients compared to general population adults may be due to patients' greater psychological investment in endorsing the societal ideal body size. It may also be due to patients' status as peripheral group members of the normal weight community. The inability of some patients to maintain their post-operative weight loss may be particularly problematic for those who have defined “socially acceptable” body size most narrowly.     

Decrease in Serum Adiponectin Level Due to Obesity and Visceral Fat Accumulation in Children

Objective: To determine whether serum adiponectin is decreased in obesity and is restored toward normal level after treatment in children. Research Methods and Procedures: Subjects were 53 Japanese obese children, 33 boys and 20 girls (6 to 14 years old), and 30 age‐matched nonobese controls for measuring adiponectin (16 boys and 14 girls). Blood was drawn after an overnight fast, and the obese children were subjected to anthropometric measurements including waist and hip circumferences and skinfold thicknesses. Paired samples were obtained from 21 obese children who underwent psychoeducational therapy. Visceral adipose tissue area was measured by computed tomography. Adiponectin was assayed by an enzyme‐linked immunosorbent assay. Results: The serum levels of alanine aminotransferase, uric acid, triglyceride, total cholesterol, low‐density lipoprotein‐cholesterol, total cholesterol/high‐density lipoprotein‐cholesterol, apo B, apo B/apo A₁, and insulin in obese children were higher than the reference values. Serum adiponectin level was lower in the obese children than in the controls (6.4 ± 0.6 vs. 10.2 ± 0.8 mg/L, means ± SEM, p < 0.001). In 21 obese children whose percent overweight declined during therapy, the adiponectin level increased (p = 0.002). The adiponectin level was correlated inversely with visceral adipose tissue area in obese children (r = ?0.531, p < 0.001). The inverse correlations of adiponectin with alanine aminotransferase, uric acid, and insulin were significant after being adjusted for percentage overweight, percentage body fat, or sex. Discussion: Serum adiponectin level is decreased in obese children depending on the accumulation of visceral fat and is restored toward normal level by slimming.     

Early development of adipose cell lipogenesis and glycerol utilization in Zucker obese rats.

A study of adipose cell metabolism was made at ages 5, 7, 10, and 14 wk of age in genetically obese Zucker rats. Adipose samples were surgically removed and used for in vitro adipose cell incubations and for characterization of enzyme patterns. Lipogenic capacity from glucose and enzymes normally associated with lipogenesis (malic enzyme, citrate cleavage enzyme and glucose-6-PO4 dehydrogenase) followed the same pattern of development. At 5 wk of age, the adipose cells of obese animals had a greater capacity for fat synthesis than the lean rats. At all other ages lipogenic activity and enzyme levels were either similar or less than the pair-fed lean littermates. Glycerol utilization by isolated fat cells was similar; however, adipose tissue glycerokinase was elevated in obese rats at 14 wk of age. It was concluded that there was no apparent change in specific lipogenic capacity of fat cells from the obese rat when compared to its lean littermate. It was also concluded that increased adipose glycerokinase activity in obese rats represented a secondary shift in metabolism.     

Pioglitazone Treatment Reduces Adipose Tissue Inflammation through Reduction of Mast Cell and Macrophage Number and by Improving Vascularity

Context and Objective

Adipose tissue in insulin resistant subjects contains inflammatory cells and extracellular matrix components. This study examined adipose pathology of insulin resistant subjects who were treated with pioglitazone or fish oil.

Design, Setting and Participants

Adipose biopsies were examined from nine insulin resistant subjects before/after treatment with pioglitazone 45 mg/day for 12 weeks and also from 19 subjects who were treated with fish oil (1,860 mg EPA, 1,500 mg DHA daily). These studies were performed in a clinical research center setting.

Results

Pioglitazone treatment increased the cross-sectional area of adipocytes by 18% (p = 0.01), and also increased capillary density without affecting larger vessels. Pioglitazone treatment decreased total adipose macrophage number by 26%, with a 56% decrease in M1 macrophages and an increase in M2 macrophages. Mast cells were more abundant in obese versus lean subjects, and were decreased from 24 to 13 cells/mm² (p = 0.02) in patients treated with pioglitazone, but not in subjects treated with FO. Although there were no changes in total collagen protein, pioglitazone increased the amount of elastin protein in adipose by 6-fold.

Conclusion

The PPARγ agonist pioglitazone increased adipocyte size yet improved other features of adipose, increasing capillary number and reducing mast cells and inflammatory macrophages. The increase in elastin may better permit adipocyte expansion without triggering cell necrosis and an inflammatory reaction.     

Triacylglycerol biosynthesis in the adipose tissue of the obese-hyperglycaemic mouse.

Obesity in obese-hyperglycaemic mouse is associated with an increase in number and size of adipocytes. Adipocytes from the obese mouse showed increased incorporation of [14C]acetate and[14C]glucose into triacylglycerol. This increased capacity of triacylglycerol formation was correlated with increased activities of various triacylglycerol-forming enzymes measured in the microsomal fraction of adipose tissue from obese mice. Microsomal fractions from lean and obese mice contained sn-glycerol 3-phosphate acyltransferase, phosphatidate phosphohydrolase and diacylglycerol acyltransferase. Phosphatidate phosphohydrolase was also detected in the soluble fraction. In the presence of Mg2+, the phosphatidate phsophohydrolase from the soluble and the microsomal fractions was active towards membrane-bound phosphatidate. Among the three enzymes studied here, the increase in Mg2+-dependent phosphatidate phosphohydrolase was most prominent in adipose tissue of obese mice.