Adiponectin gene expression and plasma values in obese women during very-low-calorie diet. Relationship with cardiovascular risk factors and insulin resistance

Short-Term Physiological Effects of a Very Low-Calorie Ketogenic Diet: Effects on Adiponectin Levels and Inflammatory States

Adipose tissue is a multifunctional organ involved in many physiological and metabolic processes through the production of adipokines and, in particular, adiponectin. Caloric restriction is one of the most important strategies against obesity today. The very low-calorie ketogenic diet (VLCKD) represents a type of caloric restriction with very or extremely low daily food energy consumption. This study aimed to investigate the physiological effects of a VLCKD on anthropometric and biochemical parameters such as adiponectin levels, as well as analyzing oligomeric profiles and cytokine serum levels in obese subjects before and after a VLCKD. Twenty obese subjects were enrolled. At baseline and after eight weeks of intervention, anthropometric and biochemical parameters, such as adiponectin levels, were recorded. Our findings showed a significant change in the anthropometric and biochemical parameters of these obese subjects before and after a VLCKD. We found a negative correlation between adiponectin and lipid profile, visceral adipose tissue (VAT), C-reactive protein (CRP), and pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), which confirmed the important involvement of adiponectin in metabolic and inflammatory diseases. We demonstrated the beneficial short-term effects of a VLCKD not only in the treatment of obesity but also in the establishment of obesity-correlated diseases.

Comparison of visceral adipose tissue DNA methylation and gene expression profiles in female adolescents with obesity

BACKGROUND

Epigenetic changes in visceral adipose tissue (VAT) with obesity and their effects on gene expression are poorly understood, especially during emergent obesity in youth. The current study tested the hypothesis that methylation and gene expression profiles of key growth factor and inflammatory pathways are altered in VAT from obese compared to non-obese youth.

METHODS

VAT samples from adolescent females grouped as Lean (L; n = 15; age = 15 ± 3 years, BMI = 21.9 ± 3.0 kg/m2) or Obese (Ob; n = 15, age = 16 ± 2 years, BMI = 45.8 ± 9.8 kg/m2) were collected. Global methylation (n = 20) and gene expression (N = 30) patterns were profiled via microarray and interrogated for differences between groups by ANCOVA (p < 0.05), followed by biological pathway analyses.

RESULTS

Overlapping differences in methylation and gene expression in 317 genes were found in VAT from obese compared to lean groups. PI3K/AKT Signaling (p = 1.83 × 10-6; 11/121 molecules in dataset/pathway) was significantly overrepresented in Ob VAT according to pathway analysis. Upregulations in the PI3K/AKT signaling pathway mRNAs TFAM (p = 0.03; fold change = 1.8) and PPP2R5C (p = 0.03, FC = 2.6) were confirmed via qRT-PCR.

CONCLUSION

Our analyses show obesity-related differences in DNA methylation and gene expression in visceral adipose tissue of adolescent females. Specifically, we identified methylation site/gene expression pairs differentially regulated and mapped these differences to pathways including PI3K/AKT signaling, suggesting that PI3K/AKT signaling pathway dysfunction in obesity may be driven in part by changes in DNA methylation.

BARIATRIC ENDOCRINOLOGY AND VERY-LOW-CALORIE MEAL PLANS

ABBREVIATIONS

PSMF = protein-sparing modified fast; VLCMP = very-low-calorie meal plans.

Expansion of Bone Marrow Adipose Tissue During Caloric Restriction Is Associated With Increased Circulating Glucocorticoids and Not With Hypoleptinemia

Bone marrow adipose tissue (MAT) accounts for up to 70% of bone marrow volume in healthy adults and increases further in clinical conditions of altered skeletal or metabolic function. Perhaps most strikingly, and in stark contrast to white adipose tissue, MAT has been found to increase during caloric restriction (CR) in humans and many other species. Hypoleptinemia may drive MAT expansion during CR but this has not been demonstrated conclusively. Indeed, MAT formation and function are poorly understood; hence, the physiological and pathological roles of MAT remain elusive. We recently revealed that MAT contributes to hyperadiponectinemia and systemic adaptations to CR. To further these observations, we have now performed CR studies in rabbits to determine whether CR affects adiponectin production by MAT. Moderate or extensive CR decreased bone mass, white adipose tissue mass, and circulating leptin but, surprisingly, did not cause hyperadiponectinemia or MAT expansion. Although this unexpected finding limited our subsequent MAT characterization, it demonstrates that during CR, bone loss can occur independently of MAT expansion; increased MAT may be required for hyperadiponectinemia; and hypoleptinemia is not sufficient for MAT expansion. We further investigated this relationship in mice. In females, CR increased MAT without decreasing circulating leptin, suggesting that hypoleptinemia is also not necessary for MAT expansion. Finally, circulating glucocorticoids increased during CR in mice but not rabbits, suggesting that glucocorticoids might drive MAT expansion during CR. These observations provide insights into the causes and consequences of CR-associated MAT expansion, knowledge with potential relevance to health and disease.

Adiponectin and energy homeostasis

White adipose tissue (WAT) is the premier energy depot. Since the discovery of the hormonal properties of adipose-secreted proteins such as leptin and adiponectin, WAT has been classified as an endocrine organ. Although many regulatory effects of the adipocyte-derived hormones on various biological systems have been identified, maintaining systemic energy homeostasis is still the essential function of most adipocyte-derived hormones. Adiponectin is one adipocyte-derived hormone and well known for its effect in improving insulin sensitivity in liver and skeletal muscle. Unlike most other adipocyte-derived hormones, adiponectin gene expression and blood concentration are inversely associated with adiposity. Interestingly, recent studies have demonstrated that, in addition to its insulin sensitizing effects, adiponectin plays an important role in maintaining energy homeostasis. In this review, we summarize the progress of research about 1) the causal relationship of adiposity, energy intake, and adiponectin gene expression; and 2) the regulatory role of adiponectin in systemic energy metabolism.

Weight loss is more important than the diet type in improving adiponectin levels among overweight/obese adults

OBJECTIVE

The study objective was to compare the effect of a standard calorie- and fat-restricted diet (STD-D) and a calorie- and fat-restricted lacto-ovo-vegetarian diet (LOV-D) on total and high-molecular-weight (HMW) adiponectin levels after 6 months of behavioral intervention.

DESIGN

This study is an ancillary study to a randomized clinical trial.

SUBJECTS

Subjects included 143 overweight/obese adults (STD-D = 79; LOV-D = 64).

INTERVENTION

Both groups received the same standard behavioral intervention; the only difference was that LOV-D participants were instructed to eliminate meat, poultry, and fish from their diet.

MEASURES

Weight, dietary intake with the 3-day food diary, and total and HMW adiponectin levels were measured.

RESULTS

Both groups significantly increased total (STD-D +7.2 ± 17.8%; LOV-D +9.4 ± 21.8%) and HMW adiponectin levels (STD-D +18.5 ± 32.9%; LOV-D +15.8 ± 34.5%; ps < 0.05) with no significant differences between the groups. We found significant associations between weight loss and increases in total (β (SE) = -.071(.27); p = 0.003) and HMW adiponectin (β (SE) = -1.37(.47); p = 0.001) levels independent of the diet type. Weight loss at the higher quartile was associated with improvements of adiponectin levels (p < 0.05).

CONCLUSION

Weight loss was associated with increased total and HMW adiponectin levels regardless of the diet type. Enhancing weight loss may be a means to improve adiponectin levels.

Supplementation with conjugated linoleic acids extends the adiponectin deficit during early lactation in dairy cows

Decreasing insulin sensitivity (IS) in peripheral tissues allows for partitioning nutrients towards the mammary gland. In dairy cows, extensive lipid mobilization and continued insulin resistance (IR) are typical for early lactation. Adiponectin, an adipokine, promotes IS. Supplementation with conjugated linoleic acids (CLA) in rodents and humans reduces fat mass whereby IR and hyperinsulinemia may occur. In dairy cows, CLA reduce milk fat, whereas body fat, serum free fatty acids and leptin are not affected. We aimed to investigate the effects of CLA supplementation on serum and adipose tissue (AT) adiponectin concentrations in dairy cows during the lactation driven and parity modulated changes of metabolism. High yielding cows (n=33) were allocated on day 1 post partum to either 100 g/day of a CLA mixture or a control fat supplement (CON) until day 182 post partum. Blood and subcutaneous (sc) AT (AT) biopsy samples were collected until day 252 post partum to measure adiponectin. Serum adiponectin decreased from day 21 pre partum reaching a nadir at calving and thereafter increased gradually. The distribution of adiponectin molecular weight forms was neither affected by time, parity nor treatment. Cows receiving CLA had decreased serum adiponectin concentrations whereby primiparous cows responded about 4 weeks earlier than multiparous cows. The time course of adiponectin concentrations in sc AT (corrected for residual blood) was similar to serum concentrations, without differences between CLA and CON. CLA supplementation attenuated the post partum increase of circulating adiponectin thus acting towards prolongation of peripartal IR and drain of nutrients towards the mammary gland.

Recombinant human adiponectin as a potential protein for treating diabetic tendinopathy promotes tenocyte progenitor cells proliferation and tenogenic differentiation in vitro

Adiponectin is an adipocyte-secreting hormone that increases cell sensitivity to insulin. It has been previously demonstrated that this hormone protects against Type II Diabetes and, is found to concurrently promote cell proliferation and differentiation. It is postulated that diabetic patients who suffer from tendinopathy may benefit from using adiponectin, which not only improves the metabolism of diabetic ridden tenocytes but also promotes progenitor cell proliferation and differentiation in tendons. These changes may result in tendon regeneration, which, in diabetic tendinopathy, is difficult to treat. Considering that such findings have yet to be demonstrated, a study was thus conducted using diabetic ridden human tenocyte progenitor cells (TPC) exposed to recombinant adiponectin in vitro. TPC were isolated from tendons of diabetic patients and exposed to 10 μg/ml adiponectin. Cell proliferation rate was investigated at various time points whilst qPCR were used to determine the tenogenic differentiation potential. The results showed that adiponectin significantly reduced blood glucose in animal models. The proliferation rate of adiponectin-treated TPCs was significantly higher at 6, 8 and 10 days as compared to untreated cells (p<0.05). The levels of tenogenic genes expression (collagen I, III, tenomodulin and scleraxis) were also significantly upregulated; whilst the osteogenic (Runx2), chondrogenic (Sox9) and adipogenic (PPARУγ) gene expressions remained unaltered. The results of this study suggest that adiponectin is a potential promoter that not only improves diabetic conditions, but also increases tendon progenitor cell proliferation and differentiation. These features supports the notion that adiponectin may be potentially beneficial in treating diabetic tendinopathy.

Adaptation of human adipose tissue to hypocaloric diet

Hypocaloric diet is a key component of the weight-reducing treatment of obesity and obesity-related disorders. Hypocaloric diets and the associated weight reduction promote improvement of metabolic profile of obese individuals. Among the mechanisms that underlie this beneficial metabolic outcome, the diet-induced modifications of morphological and functional characteristics of human adipose tissue (AT) are believed to have an important role. Prospective studies of hypocaloric weight-reducing dietary intervention demonstrate effects on adipocyte metabolism, namely lipolysis and lipogenesis, and associated changes of the adipocyte size. The endocrine function of AT, which involves cytokine and adipokine production by adipocytes, as well as by cells of stromavascular fraction, is also regulated by dietary intervention. Related inflammatory status of AT is modulated also as a consequence of the changes in recruitment of immune cells, mainly macrophages, in AT. Here, we give an overview of metabolic and endocrine modifications in human AT induced by a variety of hypocaloric diets.

Omental gene expression of adiponectin correlates with degree of insulin sensitivity before and after gastric bypass surgery

BACKGROUND

Circulating adiponectin is known to correlate negatively with insulin resistance in patients with obesity and diabetes. The aim of this study was to assess the effect of gastric bypass (GB) surgery on adiponectin gene expression in subcutaneous and omental adipose tissues.

METHODS

Adipose tissues and plasma were obtained from 25 subjects undergoing GB surgery, 15 non-obese subjects, and 12 subjects after GB surgery. Real-time quantitative reverse transcription polymerase chain reaction was used for analysis of the adipose tissues. Adiponectin expression was normalized for glyceraldehyde 3-phosphate dehydrogenase and expressed as percentage of subject-matched subcutaneous expression which was given an arbitrary value of 100%. Insulin resistance was assessed by the homeostatic model assessment (HOMA). Circulating adiponectin was assayed by ELISA.

RESULTS

Omental adiponectin gene expression was fivefold higher in subjects after GB when compared with age-matched morbidly obese subjects before GB (P < 0.01). There were no statistical differences in omental adiponectin gene expression observed in subjects after GB and age-matched non-obese subjects. For the entire cohort of subjects, there was a significant negative correlation between omental adiponectin expression and insulin resistance expressed by HOMA values (r = -0.62, P < 0.001). Circulating adiponectin was significantly lower (P < 0.05) in the obese group than in the non-obese and post-GB groups.

CONCLUSIONS

Omental adiponectin gene expression significantly increases after GB surgery reaching levels equal to age-matched non-obese subjects. Omental adiponectin expression has a significant negative correlation with the insulin resistance status.

A comparative study on the expression, purification and functional characterization of human adiponectin in Pichia pastoris and Escherichia coli

Adiponectin is one of the most bioactive substances secreted by adipose tissue and is involved in the protection against metabolic syndrome, artherosclerosis and type II diabetes. Research into the use of adiponectin as a promising drug for metabolic syndromes requires production of this hormone in high quantities considering its molecular isoforms. The objective of this study is to produce recombinant human adiponectin by Pichia pastoris (P-ADP) as a cheap and convenient eukaryotic expression system for potential application in pharmaceutical therapy. For comparison, adiponectin was also expressed using the Escherichia coli (E-ADP) expression system. Adiponectin was constructed by overlap-extension PCR, and cloned in standard cloning vector and hosts. Recombinant expression vectors were cloned in the P. pastoris and E. coli host strains, respectively. SDS-PAGE and western blotting were used to detect and analyse expressed recombinant protein in both systems. Adiponectin was purified by affinity chromatography and quantified using the Bradford Assay. The results of this study indicated that P-ADP quantity (0.111 mg/mL) was higher than that of E-ADP (0.04 mg/mL) and both were produced in soluble form. However, P-ADP was able to form high molecular weights of adiponectin molecules, whilst E-ADP was not able to form isoforms higher than trimer. In addition, P-ADP was more active in lowering blood glucose compared with E-ADP. The two types of proteins were equally efficient and significantly decreased blood triglyceride and increased high density lipoprotein. We conclude that P. pastoris is able to produce high quantity of bioactive adiponectin for potential use in treatment of metabolic syndromes.

Changes in gene expression profile in human subcutaneous adipose tissue during significant weight loss

OBJECTIVE

To analyze the expression of peroxisome proliferator-activated receptor-γ1 and 2 (PPARγ1 and 2), 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), and leptin in adipose tissue (AT) of obese women during weight loss following Roux-en-Y gastric bypass (RYGB) and to compare these levels with those obtained in AT of nonobese subjects.

METHODS

Gene expression was determined by real-time RT-PCR prior to surgery and at 3, 6, and 12 months after RYGB.

RESULTS

All obese patients lost weight, reaching a mean BMI of 29.3 ± 1.0 kg/m(2) at 1 year after surgery (-33.9 ± 1.5% of their initial body weight). In obese subjects leptin and 11βHSD1 were over-expressed, whereas PPARγ1 was expressed at lower levels compared to controls. After surgery, leptin and 11βHSD1 gene expression decreased, whereas PPARγ1 expression increased. At 12 months after RYGB, these 3 genes had reached levels similar to the controls. In contrast, PPARγ2 gene expression was not different between groups and types of tissue and remained unchanged during weight loss. We found a positive correlation between BMI and levels of gene expression of leptin and 11βHSD1.

CONCLUSION

Gene expression of leptin, PPARγ1, and 11βHSD1 in AT is modified in human obesity. This default is completely corrected by RYGB.

Influence of quercetin-rich onion peel extracts on adipokine expression in the visceral adipose tissue of rats

We examined the effects of quercetin-rich onion peel extract supplementation on adipokine expressions from adipose tissues in a diet-induced obese animal model. Male Sprague-Dawley rats (n = 24) were randomly assigned into control (n = 8), high fat diet (HF, n = 8) and high fat diet with onion peel extract (HFOE, n = 8). After 8 weeks, serum biochemical parameters, weights of adipose tissues (epididymal, perirenal and mesenteric fats) and adipokine mRNA levels (adiponectin, IL (interleukin)-6 and visfatin) along with PPAR (peroxisome proliferator-activated receptor) γ2 from adipose tissues were measured. After the 8 week supplementation, mesenteric fat weights were lower in the HFOE group than the HF group (p < 0.05). Adiponectin mRNA levels (mesenteric fats) were remarkably higher in the HFOE group than the other groups (p < 0.05 for both). Levels of PPARγ2 mRNA (mesenteric fats) were significantly higher in the HF group (p < 0.05) than those in the control group, but those in the HFOE group were not different from those in the control group. The IL-6 mRNA levels (perirenal and mesenteric fats) were higher in the HF and HFOE groups, but those in the HFOE group were slightly lower than those in the HF group. In conclusion, quercetin-rich onion peel extract supplementation influenced adipokine expressions, particularly from mesenteric fat, addressing the modulatory effect of this substance on obesity-induced inflammation.

Reliability of leptin, but not adiponectin, as a biomarker for diet-induced weight loss in humans

Calorie restriction (CR)-induced weight loss has been shown to lower the risk of chronic disease in obese individuals. Although the mechanisms that link weight loss to disease risk reduction remain unclear, evidence suggests adipokines may play a role. What has yet to be determined, however, is the dose-response effect of body weight loss and visceral fat mass loss on adipokines. Accordingly, this review examines how varying degrees of CR-induced weight loss (i.e., >10%, 5-10%, and <5% from baseline) impact plasma levels and expression of adiponectin, leptin, resistin, interleukin 6 (IL-6), interleukin 8 (IL-8), monocyte chemotactic protein 1 (MCP-1), and retinol-binding protein 4 (RBP-4). The dose-response relationship between visceral fat mass loss and adipokine profile improvement will also be explored. Results from this review demonstrate that even mild weight loss induced by CR may have beneficial effects on leptin levels, but it has no clear impact on adiponectin, resistin, IL-6, IL-8, MCP-1, or RBP-4 concentrations.

Adipokines and dietary interventions in human obesity

Obesity is a multisystem disorder associated with cardiovascular and metabolic complications. According to recent studies, it is characterized as a condition of low-grade inflammation with altered adipose tissue function and secretion of various adipokines. One of the strategies in obesity treatment is dietary intervention (DI) that could modulate cytokine levels in a favourable way. The aim of this review was to summarize the results of studies performed in the last 13 years investigating DI programmes accompanied with weight loss in relation to profile of adipokines at different level (adipose tissue mRNA, adipose tissue secretion and circulating level) and identify whether modulations of adipokines are implicated in the positive effects of DIs. The overall finding is that DIs leading to 5-10% weight loss modulate production of certain adipokines and generally induce improvement of clinical parameters, e.g. insulin sensitivity, but the amelioration of obesity complications is not coherent with the pattern of adipokine regulation, except maybe for leptin. Global analysis of the adipose tissue secretome and measurement of panels of adipokines may prove more informative than studies on individual molecules.

Differences in AMPK expression between subcutaneous and visceral adipose tissue in morbid obesity

Adenine monophosphate (AMP) activated protein kinase (AMPK) is an important regulator of obesity. The objective of the present work was to study and compare AMPK protein expression in visceral vs. subcutaneous adipose tissue of morbid obese subjects and to correlate it with adipose tissue characteristics. We selected a total population of 17 extreme obese (BMI>or=40 kg/m2) aged 42.8+/-10.2 years were included in this study. We measured anthropometric and body composition parameters. Adiponectin expression by qRT-PCR, isoproterenol-stimulated lipolytic rates, and AMPK alpha subunits expression by Western blot in adipose tissue explants were determined. Finally plasma concentrations of glucose, triacylglycerols, total cholesterol, HDL-c, LDL-c and insulin were also measured. Our results showed that AMPK alpha expression was higher in subcutaneous than in visceral tissue. A positive correlation between AMPK expression and adiponectin expression in human subcutaneous adipose tissue was observed. Furthermore, a positive correlation between AMPK expression and isoproterenol evoked upregulation of lipolysis rate was also observed. In conclusion, AMPK alpha expression differed according to adipose tissue location. The positive correlation between subcutaneous adipose tissue AMPK and adiponectin or the evoked lipolysis rate could indicate a protective role of AMPK in this tissue, counteracting insulin resistance in morbid obese patients.

Degree of weight loss required to improve adipokine concentrations and decrease fat cell size in severely obese women

Adipose tissue physiology plays an important role in mediating disease risk. Weight loss in obese individuals improves indicators of adipocyte physiology. However, the minimum degree of weight loss required to elicit improvements remains unknown. The objective of the present study was to determine the minimum weight loss required to improve adipokine profile and decrease fat cell size in severely obese women. Thirteen severely obese women (body mass index, 50 +/- 3 kg/m(2); age, 35 +/- 1 years) consumed a low-calorie diet for 3 weeks with the goal of losing 5% of their initial weight. Subjects were divided into 2 weight loss groups posttreatment: less than 5% weight loss and 5% to 10% weight loss. Body weight was reduced (P < .05) in both groups (-1.4 +/- 1.0 and -6.8 +/- 0.6 kg, respectively). Adiponectin concentrations increased (P < .05) by 20% in the 5% to 10% weight loss group only. Likewise, leptin and resistin decreased (P < .05) by 37% and 27%, respectively, in the group that lost more weight. Visceral and subcutaneous fat cell size was 41% and 37% smaller (P < .01), respectively, in the 5% to 10% weight loss group. Smaller visceral adipocyte size was related to lower insulin (r = 0.82, P = .01) and glucose (r = 0.58, P = .04) concentrations posttreatment. These findings suggest that a minimum weight loss of 5% is required to improve adipokine profile and decrease fat cell size in severely obese women. These changes in adipocyte physiology may be linked to reductions in metabolic disease risk in this population.

Secretion of adiponectin multimeric complexes from adipose tissue explants is not modified by very low calorie diet

OBJECTIVE

Adiponectin is a protein abundantly secreted by the adipose tissue (AT). Plasma adiponectin levels are decreased in obese, insulin-resistant, and type 2 diabetic patients. Various multimeric complexes, i.e. high-, middle-, and low-molecular weight isoforms (HMW, MMW and LMW), are present in plasma. Here, we investigated the effect of weight reducing diet on the distribution of adiponectin isoforms in plasma and on their secretion in AT explants from obese subjects.

DESIGN

A total of 20 obese subjects (age 37.8+/-7.3 years, body mass index 33.9+/-5.0 kg/m(2)) underwent eight weeks of very low-calorie diet (VLCD). A needle biopsy of subcutaneous abdominal AT and blood samples were taken before and after dietary intervention. AT explants were incubated in culture medium for 4 h. ELISA assay and western blot analyses were used to identify adiponectin complexes in culture media and in plasma.

RESULTS

The distribution of adiponectin polymers in plasma was different from that secreted in human AT explants. Before VLCD, the relative amount of HMW isoform was 75.5+/-9.1% of total adiponectin in culture media and 52.2+/-11.2% in plasma. Despite the diet-induced weight loss and improvement of insulin sensitivity, VLCD neither induced change in total adiponectin level nor in the ratio of HMW to total adiponectin in plasma and in culture media of AT explants.

CONCLUSIONS

The profile of adiponectin polymeric isoforms secreted by AT explants into culture media differs from the plasma profile. A dietary intervention leading to weight loss and improvement of insulin sensitivity was not associated with modifications of AT secretion of total or HMW adiponectin.

Effect of diet on the low-grade and chronic inflammation associated with obesity and metabolic syndrome

Adipose tissue is an active endocrine and paracrine organ that releases a large number of cytokines and biomarkers, which are involved in the development of chronic diseases. These effects have been attributed to direct or indirect mechanisms acting on insulin resistance, inflammation and endothelial dysfunction. In addition, the expression and secretion of these biomarkers in various tissues can be influenced by dietary patterns, with an effect on inflammatory status. In this context, following an energy-balanced diet, moderate in carbohydrates, high in oleic and omega-3 fatty acids, and low in saturated and trans fatty acids, with high intake of fruits and legumes and moderate alcohol consumption, appears to have beneficial effects on the inflammatory state associated with obesity and the manifestations of metabolic syndrome. However, the long-term impact of habitual intake and the mechanisms involved in distinct physiological and pathological conditions remain unclear.

Effects of weight loss on visceral and abdominal subcutaneous adipose tissue blood-flow and insulin-mediated glucose uptake in healthy obese subjects

OBJECTIVE

Rapid weight loss with very-low-calorie diet (VLCD) is known to improve insulin sensitivity and decrease adipose tissue masses. The aim was to investigate the effects of VLCD on adipose tissue regional glucose uptake (rGU) and perfusion and their association with adipokines.

RESEARCH DESIGN AND METHODS

Sixteen healthy obese (body mass index 33+/-1.1 kg/m(2)) subjects underwent VLCD for 6 weeks. RGU and perfusion were measured using [(18)F]-fluoro-deoxy-glucose, [(15)O]H(2)O and positron emission tomography.

RESULTS

Blood-flow and rGU expressed per gram of adipose tissue were higher in visceral fat compared to abdominal subcutaneous fat (P<0.01 for both). Dieting decreased weight by 11+/-0.9 kg (P<0.0001). Visceral adipose fat decreased by 25% (P<0.001) and abdominal subcutaneous fat by 16% (P<0.001). Whole body insulin sensitivity increased by 33% (P<0.01). Perfusion of both fat depots decreased (P<0.001), while rGU remained unchanged. Among the adipokines, leptin and interleukin-6 levels seemed to be associated with abdominal subcutaneous and intra-abdominal adipose tissue insulin resistance but not with adipose tissue perfusion.

CONCLUSIONS

Abdominal adipose tissue perfusion and rGU are not related in obesity. Rapid weight loss decreases perfusion through adipose tissue depots but has no influence on rGU demonstrating the 'sink' role of adipose tissue.

Insulin effect on adipose tissue (AT) adiponectin expression is regulated by the insulin resistance status of the patients

OBJECTIVE

The objective of the present study was to determine a possible depot-specific effect of insulin-stimulation on adiponectin gene expression in adipose tissue (AT) explants from subcutaneous and visceral AT. A secondary aim was to analyse the associations of adiponectin plasma levels, as well as control and insulin-stimulated gene expression levels with different features of the metabolic syndrome.

DESIGN

Visceral and subcutaneous AT biopsies were obtained from 20 subjects (10 men and 10 women) with morbid obesity. Metabolic syndrome and other clinical features were studied. Adiponectin expression from isolated adipocytes was measured both in control and after insulin-stimulation conditions by quantitative PCR.

RESULTS

Subcutaneous adipocytes expressed significantly higher amounts of adiponectin mRNA than visceral tissue (P = 0.027). Insulin increased adiponectin expression specifically in the omental tissue (P = 0.011). In these patients, waist : hip ratio was directly correlated with adiponectin expression in the visceral depot (r = 0.660; P = 0.014), while fasting glucose levels were inversely associated with adiponectin mRNA in the subcutaneous tissue (r =-0.604; P = 0.022). Adiponectin expression after addition of insulin was positively correlated with some metabolic risk factors (cholesterol, LDL-cholesterol, insulin, C-peptide). Interestingly, local insulin induced an up-regulation of adiponectin expression in the AT of those patients with higher metabolic syndrome disturbances.

CONCLUSIONS

Our results clearly demonstrate that insulin exerts a stimulating effect on adiponectin gene expression in a depot-specific manner. The AT response to insulin stimulus depends on the physiopathological situation, being higher in those individuals with impaired insulin-sensitivity and lipid metabolism.

Do calorie restriction or alternate-day fasting regimens modulate adipose tissue physiology in a way that reduces chronic disease risk?

Adipose tissue physiology plays an important role in the development of several obesity-related disorders. Dietary restriction regimens, i.e., daily calorie restriction (CR) or alternate-day fasting (ADF), have been shown to decrease the risk of these disorders. Whether changes in adipose mass or physiology are required for the beneficial effects of CR or ADF is an important question. Accordingly, this review summarizes the effects of CR and ADF regimens on parameters of adipose physiology, i.e., adipose tissue morphology, triglyceride metabolism, and adipokine release, and attempts to link these changes to indicators of chronic disease risk.

Total adiponectin and adiponectin multimeric complexes in relation to weight loss-induced improvements in insulin sensitivity in obese women: the NUGENOB study

AIM

Adiponectin increases insulin sensitivity, protects arterial walls against atherosclerosis, and regulates glucose metabolism, and is decreased in obese, insulin resistant, and type 2 diabetic patients. Adiponectin circulates in plasma as high, medium, and low molecular weight forms (HMW, MMW, and LMW). The HMW form was suggested to be closely associated with insulin sensitivity. This study investigated whether diet-induced changes in insulin sensitivity were associated with changes in adiponectin multimeric complexes.

SUBJECTS

Twenty obese women with highest and twenty obese women with lowest diet induced changes in insulin sensitivity (responders and non-responders respectively), matched for weight loss (body mass index (BMI)=34.5 (s.d. 2.9) resp. 36.5 kg/m(2) (s.d. 4.0) for responders and non-responders), were selected from 292 women who underwent a 10-week low-caloric diet (LCD; 600 kcal/d less than energy requirements). Plasma HMW, MMW, and LMW forms of adiponectin were quantified using Western blot method.

RESULTS

LCD induced comparable weight reduction in responders and non-responders by 8.2 and 7.6 kg. Homeostasis model assessment insulin resistance index decreased by 48.1% in responders and remained unchanged in non-responders. Total plasma adiponectin and the quantity of HMW and MMW remained unchanged in both groups, while LMW increased by 16.3% in non-responders. No differences between both groups were observed at baseline and after the study. Total plasma adiponectin, MMW, and LMW were negatively associated with fasting insulin levels at baseline.

CONCLUSION

No differences in total plasma adiponectin, HMW, MMW, and LMW forms were observed between responders and non-responders following 10-week LCD, suggesting that adiponectin is not a major determinant of weight loss-induced improvements in insulin sensitivity.

Adiponectin, obesity and atherosclerosis

The circulating protein adiponectin has been the subject of immense interest ever since it was first discovered in the mid-1990s. The protein is uniquely produced and secreted by mature adipocytes and is believed to have important anti-inflammatory and anti-diabetic effects; low levels have been shown to be predictive of future type 2 diabetes and cardiovascular disease. This review discusses adiponectin in relation to obesity, inflammation, insulin resistance and atherosclerosis.

Regulation of inflammation-related genes in human adipose tissue

The identification of a moderate increase in circulating inflammatory factors in obese subjects, the description of changes in inflammatory gene expression in adipose tissue (AT) and the discovery that macrophage cells infiltrate AT are observations contributing to the concept that human obesity is a chronic inflammatory illness. This concept has led to some revision of the physiopathology of obesity and of its related metabolic and cardiovascular co-morbidities. Low-grade inflammation in the AT and the subsequent production of specific biomarkers could actually link expanded fat mass to obesity complications. This review aims at providing an overview of the current knowledge brought up by human gene expression studies, notably those performed on a large scale in AT depots. The regulation of specific biomarkers related to inflammation and putative new candidates (i.e. cathepsins and serum amyloid A) is discussed in the context of weight loss programmes based on calorie restriction and physical exercise. The foreseen clinical and technological challenges are also summarized.

Dissociation between adipose tissue expression and serum levels of adiponectin during and after diet-induced weight loss in obese subjects with and without the metabolic syndrome

The study aimed to examine if dysmetabolic subjects (MetS+) have lower adiponectin gene expression and lower circulating adiponectin levels than non-dysmetabolic obese subjects (MetS-) at baseline, if adiponectin expression and adiponectin concentration rise more in the dysmetabolic group during weight loss, and if v-SNARE Vti1a (vesicle transport soluble NSF attachment protein receptor vps10p tail interacting 1a) expression increases during the weight loss, as a mechanism for increased adiponectin secretion. Twenty-one obese MetS+ and 19 obese MetS- subjects underwent a very low-energy diet for 16 weeks followed by 2 weeks of refeeding. Abdominal subcutaneous adipose tissue biopsies and blood samples were taken before, during, and after dieting for DNA microarray, reverse transcriptase-polymerase chain reaction, and biochemical analyses. Serum adiponectin was also assessed in a sex- and age-matched healthy, nonobese reference group. Weight decreased by 26.3+/-9.8 kg in the MetS+ group and 28.2+/-8.4 kg in the MetS- group with concomitant reductions in insulin, hemoglobin A1c, and triglycerides that were more pronounced in the MetS+ group. Initially, the MetS+ subjects had lower serum adiponectin, but the differences disappeared at week 8, with a continuous increase in serum adiponectin throughout the study in both groups to a level that was higher than in the reference group. The expression of adiponectin and v-SNARE Vti1a did not differ between the groups or over time. In conclusion, obese subjects with the metabolic syndrome had lower circulating adiponectin than subjects without the syndrome. Weight loss increased serum levels of adiponectin without a parallel increase in adiponectin gene expression. The mechanisms involved in the regulation of adiponectin levels merits further investigation.

Addition of medroxyprogesterone acetate to conjugated equine estrogens results in insulin resistance in adipose tissue

The purpose of this study was to determine if the insulin resistance we have previously reported in surgically postmenopausal primates treated with combined hormone therapy (HT) is due in part to effects on adipose tissue. Eighty-seven ovariectomized monkeys were fed a moderately atherogenic diet (0.28 mg cholesterol per kilocalorie [0.07 mg/kJ]) and randomized to receive no hormones (control, n = 29), estrogen therapy (ET, conjugated equine estrogens, 0.625 mg/d human equivalent; n = 29), or HT (ET + medroxyprogesterone acetate, 2.5 mg/d human equivalent; n = 29) in the diet for 2 years. Fasting glycemic measures were made at baseline and at the end of treatment. Circulating adiponectin measures, insulin tolerance tests, glucose tolerance tests, and isolated adipocyte glucose uptake assays were performed at the end of the trial. Hormone therapy-treated animals were insulin resistant, as determined by greater fasting insulin concentrations (P = .008), greater homeostasis model assessment of insulin resistance (HOMA-R) value (P = .005) and slower glucose disposal after insulin administration (K(ITT); P = .02) when compared with controls. Subcutaneous adipocytes from HT-treated monkeys had a greater ED(50) for insulin (P = .04) and lower maximal glucose uptake per cell (P < .001) compared with controls, suggesting impaired adipocyte insulin sensitivity. Adipocytes were smaller (P = .001) and adiponectin concentrations were greatest in the ET group (P = .02), with no difference between controls and HT-treated monkeys. In conclusion, estrogen therapy resulted in smaller adipocyte size and greater adiponectin concentrations than control or HT. Hormone therapy resulted in impaired insulin sensitivity and adipocyte glucose uptake compared with controls, whereas there was no difference between ET and controls. Because no adverse effects were found with ET alone, it is likely that the progestin, medroxyprogesterone acetate, resulted in the negative effects of the combined HT regimen on whole-body insulin sensitivity, which were mediated, in part, by reductions in adipose tissue responses to insulin.

Adiponectin: saving the starved and the overfed

The incidence of the metabolic syndrome, type 2 diabetes and cardio- and cerebrovascular disease is increasing in the Western world. The adipocyte derived protein adiponectin is thought to have a protective role against these conditions. But why is it so? Is it reasonable to believe that we have adiponectin to gain protection from welfare related diseases? Humans have had a far deadlier foe throughout history than obesity and sedentariness and that is starvation. During starvation, the body is catabolic in order to provide fuel. Catabolism is also seen in patients with advanced cardiac or renal failure, type 1 diabetes and anorexia. These subjects have higher adiponectin levels than controls. In this article, I will put forward the hypothesis that the adiponectin system evolved in order to help us to survive periods of malnourishment.

Effect of marked weight loss on adiponectin gene expression and plasma concentrations

OBJECTIVE

Adiponectin is the most abundant protein secreted by adipose tissue and is inversely associated with adiposity and insulin resistance. The aim of this study was to evaluate the hypothesis that marked weight loss, induced by gastric bypass surgery (GBS), would increase adiponectin gene expression in both upper and lower subcutaneous body fat and increase plasma adiponectin concentration.

RESEARCH METHODS AND PROCEDURES

Adiponectin subcutaneous abdominal and femoral adipose tissue gene expression, determined by using quantitative reverse transcriptase-polymerase chain reaction, and adiponectin plasma concentrations, determined by using enzyme-linked immunosorbent assay, were evaluated in six extremely obese women (BMI = 57.1 +/- 4.1 kg/m2) before and 1 year after GBS.

RESULTS

After GBS, subjects lost 36 +/- 5% of their initial body weight and showed increased insulin sensitivity, manifested by a marked decrease in homeostasis model assessment of insulin resistance from 10.7 +/- 4.1 to 1.4 +/- 0.3 (p < 0.05). Adiponectin gene expression increased 8- to 15-fold in subcutaneous abdominal and femoral adipose tissues (p < 0.05). Plasma adiponectin concentrations increased from 5.2 +/- 0.9 to 8.4 +/- 1.2 mug/mL (p < 0.05).

DISCUSSION

These data show that marked weight loss induced by GBS increases adiponectin gene expression in both upper- and lower-body subcutaneous fat. The increase in adipose tissue adiponectin production resulted in an increase in plasma adiponectin concentrations, which likely contributed to the decrease in insulin resistance observed after weight loss.

Clinical aspects of obesity in the gynecological endocrinologicaly practice

Obesity is epidemic of 21st century, its visceral form is associated with increased risk for type 2 diabetes, cardiovascular disease, hypertension and increased mortality due to consequences of the disease. This type of obesity is a common diagnostic and therapeutic problem in gynecological practice. This especially concerns polycystic ovary disease, in which this type of obesity with its metabolic consequences is one of the important factors in etiology and additionally may lead to remote metabolic and cardiovascular problems. Another group of women in which this type of obesity plays an important role are climacteric women in whom redistribution of adipose tissue with increase in visceral fat deposit occurs. On the basis of current viewpoints and own experiences, the authors propose a diagnostic-therapeutic algorithm in women with visceral obesity and polycystic ovary disease or climacteric period. In case with cardiovascular risk factors (waist circumference over than 80cm, serum triglycerides over 1.7mmol/l, HDL cholesterol lower than 1.0mmol/l, blood pressure over 130/85mmHg and fast serum glucose levels over 100mg/dl) the therapeutic model focuses on the recognize risk factors. It must be considered that diet and physical activity play a very important role in the therapy.

Desaturation of skeletal muscle structural and depot lipids in obese individuals during a very-low-calorie diet intervention

OBJECTIVE

This study investigated whether a very-lowcalorie dietary intervention (VLCD) may influence composition of skeletal muscle cell membrane phospholipid and composition and concentration of intramyocellular triglyceride (IMTG) in obese subjects. The working hypothesis proposed that a VLCD would decrease saturated fatty acids (FAs) and increase long-chain polyunsaturated FAs (LCPUFAs) in muscular structural lipids, as such changes have been associated with improved insulin sensitivity.

RESEARCH METHODS AND PROCEDURES

Skeletal muscle biopsies (vastus lateralis) were obtained from 13 obese subjects (nine women) before and after 8 weeks on VLCD (approximately 600 to 800 kcal/d). FA composition in muscle cell membrane phospholipid and concentration and FA composition of IMTG were determined by gas-liquid chromatography.

RESULTS

Baseline BMI was 36.0 +/- 3.4 kg/m2. Weight loss was 9.3 +/- 1.1 kg (8.8 +/- 1.1%; p < 0.0001); loss of adipose tissue was 5.9 +/- 0.9 kg (p < 0.0001). Insulin resistance (by homeostasis model assessment) decreased (-44 +/- 7%; p < 0.001). Muscle cell membrane phospholipid saturated FAs decreased (-3.2 +/- 1.3%; p < 0.05), whereas monounsaturated FAs (4.3 +/- 1.7%; p < 0.05), LCPUFAs (11 +/- 6%; p < 0.05), and the ratio of LCPUFAs to saturated FAs (12 +/- 5%; p < 0.05) increased. IMTG decreased, but not significantly (-5%). IMTG-saturated FAs decreased (-3.3 +/- 1.5%; p < 0.05), whereas LCPUFAn-3 (29 +/- 9%; p < 0.01), LCPUFAn-6 (33 +/- 9%; p < 0.01), and the ratio of LCPUFAs to saturated FAs (34 +/- 8%; p < 0.001) increased. Plasma total cholesterol (-15 +/- 6%; p < 0.05), low-density lipoprotein-cholesterol (-16 +/- 5%; p < 0.01), high-density lipoprotein-cholesterol (-8 +/- 2%; p < 0.01), and plasma triglyceride (-19 +/- 12%; p = 0.10) all decreased during the VLCD.

DISCUSSION

Desaturation of both muscle cell membrane phospholipid and IMTG was significant but modest during a VLCD in obese subjects. Further research must delineate whether such changes in skeletal muscle structural and depot lipid composition themselves are enough to promote the observed improvements in insulin action.

Dynamic strength training improves insulin sensitivity without altering plasma levels and gene expression of adipokines in subcutaneous adipose tissue in obese men

CONTEXT

Obesity is characterized by a low-grade inflammatory state, which could play a role in insulin resistance. Dynamic strength training improves insulin sensitivity.

OBJECTIVE

The objective of this study was to investigate, in obese subjects, whether the insulin sensitizing effect of dynamic strength training is associated with changes in plasma levels and gene expression of adipokines potentially involved in the development of insulin resistance.

DESIGN

Twelve obese male subjects were investigated before and at the end of 3 months of dynamic strength training. Insulin sensitivity was evaluated using euglycemic-hyperinsulinemic clamp. Blood samples and needle biopsy samples of sc abdominal adipose tissue were obtained. The plasma levels and adipose tissue mRNA levels of adiponectin, leptin, IL-1beta, IL-6, and TNF-alpha were determined.

RESULTS

The training induced an increase in the whole-body glucose disposal rate by 24% (P = 0.04). The body weight was not altered during the training. Plasma levels of leptin decreased during the training (16.6 +/- 6.3 vs. 13.1 +/- 5.7 ng/ml) by 21% (P < 0.02), whereas no change in plasma levels of other adipokines and C-reactive protein was observed. Gene expression of the investigated adipokines was not changed in sc adipose tissue during the training.

CONCLUSIONS

In obese subjects, the dynamic strength training resulted in an improvement of whole-body insulin sensitivity. The increase in insulin sensitivity was not associated with training-induced modifications of plasma levels or adipose tissue gene expression of adipokines supposedly involved in the development of insulin resistance.

Angiotensin II, corticosteroids, type II diabetes and the metabolic syndrome

Syndrome X, the Metabolic Syndrome, and type II diabetes are closely related diseases that share risk factors and symptoms, notably insulin resistance. Several factors have been proposed either to mediate the disease(s) or to be their causes, and most converge on the endocrine/paracrine functions of the adipocyte. A common feature of such systems is their relative autonomy from systemic negative feedback regulation, for example by the HPA axis. We draw particular attention to two such mechanisms, both of which are associated with, and can cause, insulin resistance: the extra-adrenal production of corticosteroids, and the tissue renin angiotensin system of the adipocyte. These show another feature: the inter-regulation of glucocorticoid action and the RAS by positive feedback. Cortisol enhances the expression of 11 beta-HSD 1, and also of angiotensinogen and angiotensin type 1 receptors. In turn, angiotensin can stimulate further corticosteroid production, from the adrenal and perhaps from extra-adrenal sources. The instability inherent in such positive loops could account for the progressive nature of the disease(s), suggesting ways to break the circle.

A polymorphism in the adiponectin gene influences adiponectin expression levels in visceral fat in obese subjects

OBJECTIVE

Reduced serum adiponectin levels have been found in obesity and type 2 diabetes and variations in the adiponectin gene (APM1) have been associated with type 2 diabetes and features of the metabolic syndrome in different populations.

STUDY DESIGN

Here, we investigated the expression of APM1 in adipose tissue and studied the relationship between variation in APM1 expression, the APM1 G276T polymorphism, the common PPARG Pro12Ala polymorphism and clinical features of 36 morbidly obese (body mass index (BMI) 41.5 +/- 4.9 kg/m2) nondiabetic subjects.

RESULTS

APM1 mRNA expression in visceral fat was correlated with serum adiponectin levels (r = 0.54, P = 0.012). In visceral, but not in subcutaneous, adipose tissue APM1 mRNA level was 38% higher among carriers of the APM1 G276T T allele (G/T and T/T) than among carriers of the G/G genotype (0.91 +/- 0.06 for G/T and T/T carriers vs 0.66 +/- 0.09 for G/G carriers, P = 0.013). Carriers of the T allele also had significantly higher body fat percent compared to G/G carriers (65 +/- 6 vs 56 +/- 10%, P = 0.011).

CONCLUSION

Our results indicate that genetic variation in APM1 influences the expression of the gene in visceral adipose tissue and suggest a potential role for such variation in regulation of body fat accumulation in obese subjects.

Effect of aerobic training on plasma levels and subcutaneous abdominal adipose tissue gene expression of adiponectin, leptin, interleukin 6, and tumor necrosis factor alpha in obese women

Adipocytokines secreted by adipose tissue are suggested to play a role in the development of obesity-related complications. Regular aerobic exercise has been shown to reduce the risk of metabolic complications in obese subjects. The aim of this study was to investigate the effect of aerobic training on gene expression in subcutaneous abdominal adipose tissue (SCAAT) and on plasma levels of several adipocytokines in obese women. Twenty-five obese sedentary premenopausal women (body mass index, 32.18 +/- 3.17 kg/m(2)) underwent a 12-week aerobic exercise program, with a frequency of 5 d/wk and intensity corresponding to 50% of individual maximal oxygen consumption (V(.-)(O(2)max)) consisting of 2 sessions per week of supervised aerobic exercise and 3 sessions per week of home-based exercise on a bicycle ergometer. Before and after the aerobic training, (V(.-)(O(2)max)) and body composition were measured and plasma and SCAAT biopsy samples (in a subgroup of 8 subjects) were obtained for determination of plasma and messenger RNA levels of adipocytokines (leptin, adiponectin, interleukin 6, tumor necrosis factor alpha). The aerobic training resulted in an increase of subjects' V o(2)max by 12.8% (24.6 +/- 3.9 vs 27.7 +/- 4.8 mL x min(-1) x kg(-1), P < .05). Body weight and fat mass were reduced by 5.9% (88.5 +/- 8.2 vs 83.3 +/- 7.7 kg, P < .001) and 6.4% (38.8 +/- 4.2% vs 36.3 +/- 4.6%, P < .001), respectively, and the revised QUantitative Insulin sensitivity ChecK Index (QUICKI) increased (0.43 +/- 0.06 vs 0.48 +/- 0.06, P < .05) during the aerobic training. No aerobic training-induced changes in messenger RNA levels of the investigated genes in SCAAT were observed. A decrease of plasma leptin (24.3 +/- 8.7 vs 18.1 +/- 8.3 ng/mL, P < .05) was detected, whereas plasma levels of other cytokines remained unchanged. In moderately obese females, 3 months' aerobic training did not promote changes in the adipose tissue gene expression or plasma levels of the adipocytokines (except for leptin) involved in a regulation of lipid and carbohydrate metabolism.

Obesity and the role of gut and adipose hormones in female reproduction

Reproductive function declines at both extremes of human energy balance. The relationship between obesity and reproductive function is complex and incompletely understood. The literature has established the negative impact of excess energy stores on ovulatory function and investigated the mechanisms whereby this occurs. Furthermore, weight loss in obese anovulatory women increases ovulation and conception. Obesity and anti-obesity therapy effects on the endometrium, implantation and early fetal development have received less attention. The discovery of adipokines and enterokines greatly expands the ability to investigate the relationship between obesity, therapies to produce weight loss and reproductive function. In this review, we discuss select adipose and enteric signals. We focus on in vitro, animal and human data that lend biological plausibility to adipokines and enterokines as mediators of obesity and reproduction. Very little published work exists that directly addresses adipocyte and enteric signals in this specific role; therefore, much of this review is on the basis of a synthesis of the literature in three areas: (i) in vitro and in vivo evidence regarding the reproductive effects of these signals; (ii) adipokine and enterokine changes that occur with weight-loss therapies, focusing on hypocaloric diets, bariatric surgery and drugs that target adipocyte or enteric signals and (iii) reproductive changes produced by these weight-loss therapies.

The association of SNP276G>T at adiponectin gene with circulating adiponectin and insulin resistance in response to mild weight loss

OBJECTIVE

The purpose of this study was to determine whether common single nucleotide polymorphisms (SNPs) at the adiponectin (ADIPOQ) locus influence changes in circulating adiponectin and the features of insulin resistance in response to a weight loss intervention.

SUBJECTS

In total, 294 nondiabetic/overweight-obese Koreans participated in a clinical intervention study lasting 12 weeks involving a caloric reduction of -300kcal/day.

METHODS

Plasma adiponectin, blood lipids, glucose and insulin concentrations were measured at baseline and after weight loss. Insulin resistance was estimated by homeostasis model assessment insulin resistance (HOMA-IR) derived from fasting glucose and insulin concentrations. We genotyped for three SNPs, 45T>G, 276G>T and -11377C>G.

RESULTS

At baseline, HOMA-IR was significantly higher in GG homozygotes than in carriers of the T allele at SNP276G>T of the adiponectin gene (P<0.05). With regard to SNP45T>G and SNP -11377C>G, we did not find any genotype related differences in baseline levels of HOMA-IR and adiponectin. In the 45/276 haplotype test, homozygous for the TG haplotype had significantly lower concentrations of plasma adiponectin (P<0.05). After the 12-week weight loss intervention, the significant decreases in HOMA-IR (P<0.001) and increases in adiponectin (P<0.01) were observed in GG homozygotes at SNP276, which were not shown in carriers of the T allele. Furthermore, there was a significant difference in the decreases in HOMA-IR between the GG homozygotes and carriers of the T allele at SNP276 (P<0.05). Regarding SNP45T>G and SNP -11377C>G, there was no association between SNP45T>G and SNP -11377C>G and decreases in HOMA-IR. In the 45/276 haplotype test, there was a significant difference in changes of adiponectin levels among those with different haplotype combinations (P<0.05).

CONCLUSION

The SNP276G>T of the ADIPOQ gene is associated with different responses of circulating adiponectin and insulin resistance to mild weight loss in overweight-obese subjects.

Adipokines: implications for female fertility and obesity

Obesity is associated with a diverse set of metabolic disorders, and has reproductive consequences that are complex and not well understood. The adipose tissue-produced leptin has dominated the literature with regards to female fertility complications, but it is pertinent to explore the likely role of other adipokines--adiponectin and resistin--as our understanding of their biological functions emerge. Leptin influences the developing embryo, the functioning of the ovary and the endometrium, interacts with the release and activity of gonadotrophins and the hormones that control their synthesis. In this review such biological actions and potential roles of the adipokines leptin, adiponectin and resistin are explored in relation to female fertility and the complexity of the obese metabolic state.

Energy balance adiposity and breast cancer - energy restriction strategies for breast cancer prevention

Excess adiposity over the pre- and postmenopausal years is linked to risk of postmenopausal breast cancer. Weight loss could potentially reduce risk amongst those with excess weight via beneficial effects on the hormonal (decreased circulating levels of oestradiol, testosterone, insulin) and secretory profiles of adipocytes (decreased production of leptin, tumour necrosis factor-alpha, interleukin 6 and increased production of adiponectin). Only modest reductions in adipose tissue are achieved and sustained with current weight loss programmes, which makes strategies to mitigate the adverse metabolic effect of adiposity a priority for cancer prevention. The adverse hormonal and secretory effects of adipose tissue are influenced substantially by acute changes in energy balance prior to changes in adiposity. Human and animal studies have shown dietary energy restriction to bring about favourable changes in circulating levels of insulin, leptin, sex hormone binding globulin, insulin-like growth factor-1, oestradiol, testosterone, reactive oxygen species, and the production and secretion of locally acting adipokines and inflammatory cytokines, that is, increased adiponectin and decreased interleukin-6. Achieving and sustaining energy restriction remains a difficult challenge. Intermittent energy restriction is a potential strategy for promoting periods of energy restriction on a long-term basis. Animal and human data suggest that intermittent energy restriction may have cancer preventative effects beyond that of chronic energy restriction and weight loss. Intermittent energy restriction may be a potential strategy for the primary prevention of breast cancer.

Adipose tissue: a regulator of inflammation

Adipose tissue is a highly active organ. In addition to storing calories as triglycerides, it also secretes a large variety of proteins, including cytokines, chemokines and hormone-like factors, such as leptin, adiponectin and resistin. Intriguingly, many, if not most, of these adipose-derived proteins have dual actions; cytokines have both immunomodulatory functions and act as systemic or auto-/paracrine regulators of metabolism, while proteins such as leptin and adiponectin are regulators of both metabolism and inflammation. The production of pro-atherogenic chemokines by adipose tissue is of particular interest since their local secretion, e.g. by perivascular adipose depots, may provide a novel mechanistic link between obesity and the associated vascular complications.

Transcriptomics applied to obesity and caloric restriction

Caloric restriction still remains the most efficient way to promote weight loss. Deciphering the molecular basis of adaptation to energy restriction is critical for the tailoring of new therapeutic strategies. This review focuses on the recent input of gene profiling on adipose tissue in obesity pathogenesis and on the new insights on adaptations occurring during very low caloric diet (VLCD) in humans. Hypocaloric diets improve a wide range of metabolic parameters including lipolytic efficiency, insulin sensitivity, and inflammatory profile. In the subcutaneous white adipose tissue (scWAT) the VLCD induced a decrease in the mRNA levels for the antilipolytic alpha2-adrenergic receptor associated with changes in catecholamine-induced adipocyte lipolytic capacity. The improvement in insulin sensitivity was not associated with a change in subcutaneous adipose tissue adiponectin gene expression or in its plasma level, suggesting that adiponectin is not involved in the regulation of VLCD-induced improvement of insulin sensitivity and that there is a small contribution of subcutaneous adipose tissue to plasma adiponectin levels. Pangenomic microarray studies in human scWAT revealed that a panel of inflammatory markers and acute phase reactants were over expressed in obese compared to lean subjects. Caloric restriction improved the inflammatory profile of obese subjects through a decrease of pro-inflammatory factors and an increase of anti-inflammatory molecules. These genes were mostly expressed in the stroma vascular fraction of the adipose tissue. Specific cell-type isolation and immunohistochemistry demonstrated that monocyte/macrophage lineage cells were responsible for the expression of both mRNA and protein inflammatory markers. The acute phase proteins serum amyloid A was highly expressed in mature adipocytes from obese subjects. Caloric restriction decreased both serum amyloid mRNA and circulating levels. Obesity now clearly appears as chronic low-grade inflammation state. Modulation of the inflammatory pathways may represent new therapeutic targets for the treatment of obesity-related complications.

Hypoadiponectinaemia and high risk of type 2 diabetes are associated with adiponectin-encoding (ACDC) gene promoter variants in morbid obesity: evidence for a role of ACDC in diabesity

AIMS/HYPOTHESIS

Morbid obesity (BMI>40 kg/m(2)) affecting 0.5-5% of the adult population worldwide is a major risk factor for type 2 diabetes. We aimed to elucidate the genetic bases of diabetes associated with obesity (diabesity), and to analyse the impact of corpulence on the effects of diabetes susceptibility genes.

METHODS

We genotyped known single nucleotide polymorphisms (SNPs) in the adiponectin-encoding adipocyte C1q and collagen-domain-containing (ACDC) gene (-11,391G>A, -11,377C>G, +45T>G and +276G>T), the peroxisome proliferator-activated receptor gamma (PPARG) Pro12Ala SNP and ACDC exon 3 variants in 703 French morbidly obese subjects (BMI 47.6+/-7.4 kg/m(2)), 808 non-obese subjects (BMI<30 kg/m(2)) and 493 obese subjects (30< or =BMI<40 kg/m(2)).

RESULTS

Two 5'-ACDC SNPs -11,391G>A, -11,377C>G were associated with adiponectin levels (p=0.0003, p=0.008) and defined a "low-level" haplotype associated with decreased adiponectin levels (p=0.0002) and insulin sensitivity (p=0.01) and with a risk of type 2 diabetes that was twice as high (p=0.002). In contrast, the prevalence of the PPARG Pro12Ala was identical in diabetic and normoglycaemic morbidly obese subjects. The PPARG Pro12 allele only displayed a trend of association with type 2 diabetes in the non-obese group. ACDC exon 3 variants were associated with type 2 diabetes in the non-obese group only (odds ratio 7.85, p<0.0001). In contrast, the 5'-ACDC "low-level" haplotype was associated with type 2 diabetes in obese and morbidly obese subjects (odds ratio 1.73 and 1.92) but not in non-obese individuals.

CONCLUSIONS/INTERPRETATION

These data clarify the contribution of the 5'-ACDC SNPs to the risk of diabesity. Their interaction with corpulence suggests for the first time a different genetic profile of type 2 diabetes in morbidly obese patients compared with in less obese individuals.

Abdominal adipose tissue cytokine gene expression: relationship to obesity and metabolic risk factors

Adipose tissue is a major source of inflammatory and thrombotic cytokines. This study investigated the relationship of abdominal subcutaneous adipose tissue cytokine gene expression to body composition, fat distribution, and metabolic risk during obesity. We determined body composition, abdominal fat distribution, plasma lipids, and abdominal subcutaneous fat gene expression of leptin, TNF-alpha, IL-6, PAI-1, and adiponectin in 20 obese, middle-aged women (BMI, 32.7 +/- 0.8 kg/m2; age, 57 +/- 1 yr). A subset of these women without diabetes (n = 15) also underwent an OGTT. In all women, visceral fat volume was negatively related to leptin (r = -0.46, P < 0.05) and tended to be negatively related to adiponectin (r = -0.38, P = 0.09) gene expression. Among the nondiabetic women, fasting insulin (r = 0.69, P < 0.01), 2-h insulin (r = 0.56, P < 0.05), and HOMA index (r = 0.59, P < 0.05) correlated positively with TNF-alpha gene expression; fasting insulin (r = 0.54, P < 0.05) was positively related to, and 2-h insulin (r = 0.49, P = 0.06) tended to be positively related to, IL-6 gene expression; and glucose area (r = -0.56, P < 0.05) was negatively related to, and insulin area (r = -0.49, P = 0.06) tended to be negatively related to, adiponectin gene expression. Also, adiponectin gene expression was significantly lower in women with vs. without the metabolic syndrome (adiponectin-beta-actin ratio, 2.26 +/- 0.46 vs. 3.31 +/- 0.33, P < 0.05). We conclude that abdominal subcutaneous adipose tissue expression of inflammatory cytokines is a potential mechanism linking obesity with its metabolic comorbidities.

Adiponectin: action, regulation and association to insulin sensitivity

Adiponectin is a novel adipocyte-specific protein, which, it has been suggested, plays a role in the development of insulin resistance and atherosclerosis. Although it circulates in high concentrations, adiponectin levels are lower in obese subjects than in lean subjects. Apart from negative correlations with measures of adiposity, adiponectin levels are also reduced in association with insulin resistance and type 2 diabetes. Visceral adiposity has been shown to be an independent negative predictor of adiponectin. Thus, most features of the metabolic syndrome's negative associations with adiponectin have been shown. Adiponectin levels seem to be reduced prior to the development of type 2 diabetes, and administration of adiponectin has been accompanied by lower plasma glucose levels as well as increased insulin sensitivity. Furthermore, reduced expression of adiponectin has been associated with some degree of insulin resistance in animal studies indicating a role for hypoadiponectinaemia in relation to insulin resistance. The primary mechanisms by which adiponectin enhance insulin sensitivity appears to be through increased fatty acid oxidation and inhibition of hepatic glucose production. Adiponectin levels are increased by thiazoledinedione treatment, and this effect might be important for the enhanced insulin sensitivity induced by thiazolidinediones. In contrast, adiponectin levels are reduced by pro-inflammatory cytokines especially tumour necrosis factor-alpha. In summary, adiponectin in addition to possible anti-inflammatory and anti-atherogenic effects appears to be an insulin enhancer, with potential as a new pharmacologic treatment modality of the metabolic syndrome and type 2 diabetes.

Adipose tissue gene expression in obese subjects during low-fat and high-fat hypocaloric diets

AIMS/HYPOTHESIS

Adaptation to energy restriction is associated with changes in gene expression in adipose tissue. However, it is unknown to what extent these changes are dependent on the energy restriction as such or on the macronutrient composition of the diet.

METHODS

We determined the levels of transcripts for 38 genes that are expressed in adipose tissue and encode transcription factors, enzymes, transporters and receptors known to play critical roles in the regulation of adipogenesis, mitochondrial respiration, and lipid and carbohydrate metabolism. Two groups of 25 obese subjects following 10-week hypocaloric diet programmes with either 20-25 or 40-45% of total energy derived from fat were investigated. Levels of mRNA were measured by performing real-time RT-PCR on subcutaneous fat samples obtained from the subjects before and after the diets.

RESULTS

The two groups of subjects lost 7 kg over the duration of the diets. Ten genes were regulated by energy restriction; however, none of the genes showed a significantly different response to the diets. Levels of peroxisome proliferator-activated receptor gamma co-activator 1alpha mRNA were increased, while the expression of the genes encoding leptin, osteonectin, phosphodiesterase 3B, hormone-sensitive lipase, receptor A for natriuretic peptide, fatty acid translocase, lipoprotein lipase, uncoupling protein 2 and peroxisome proliferator-activated receptor gamma was decreased. Clustering analysis revealed new potential coregulation of genes. For example, the expression of the genes encoding the adiponectin receptors may be regulated by liver X receptor alpha.

CONCLUSIONS/INTERPRETATION

In accordance with the comparable loss of fat mass produced by the two diets, this study shows that energy restriction and/or weight loss rather than the ratio of fat: carbohydrate in a low-energy diet is of importance in modifying the expression of genes in the human adipose tissue.