Chronological changes in metabolism and functions of cultured adipocytes: a hypothesis for cell aging in mature adipocytes

Influence of epicardial adipose tissue inflammation and adipocyte size on postoperative atrial fibrillation in patients after cardiovascular surgery

Epicardial adipose tissue (EAT) is an active endocrine organ that is closely associated with occurrence of atrial fibrillation (AF). However, the role of EAT in the development of postoperative AF (POAF) remains unclear. We aimed to investigate the association between EAT profile and POAF occurrence in patients who underwent cardiovascular surgery. We obtained EAT samples from 53 patients to evaluate gene expression, histological changes, mitochondrial oxidative phosphorylation (OXPHOS) capacity in the EAT, and protein secretion in EAT-conditioned medium. EAT volume was measured using computed tomography scan. Eighteen patients (34%) experienced POAF within 7 days after surgery. Although no significant difference was observed in EAT profile between patients with and without POAF, logistic regression analysis identified that the mRNA expression levels of tumor necrosis factor-alpha (TNF-α) were positively correlated and adipocyte size in the EAT was inversely correlated with onset of POAF, respectively. Mitochondrial OXPHOS capacity in the EAT was not associated with POAF occurrence; however, it showed an inverse correlation with adipocyte size and a positive correlation with adiponectin secretion. In conclusion, changes in the secretory profile and adipocyte morphology of the EAT, which represent qualitative aspects of the adipose tissue, were present before the onset of AF.

Age-adjusted visceral adiposity index (VAI) is superior to VAI for predicting mortality among US adults: an analysis of the NHANES 2011-2014

BACKGROUND

The association of visceral adiposity with mortality in older adults is conflicting. Whether age influences the predicting ability of visceral adiposity (VAI) for mortality remains unknown. This study uncovered the relationship between age-adjusted visceral adiposity index and mortality through the data of NHANES 2011-2014.

METHODS

This study obtained data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. The age-adjusted visceral adiposity index (AVAI) scores were expressed as quartiles. Receiver operating characteristics (ROC) curve analysis was also applied to compare the predictive ability for mortality. Multivariate weighted Cox regression models were constructed to explore the association between AVAI and mortality. Kaplan-Meier survival curves were conducted for survival analyses. Smooth curve fittings and two-piecewise linear models were applied to explore the relationships between AVAI and mortality.

RESULTS

This study recruited 4281 subjects aged ≥ 18 years from the NHANES 2011-2014. The AUCs of AVAI were 0.82 (0.79, 0.86) and 0.89 (0.85, 0.92) for predicting all-cause mortality and cardiovascular mortality, which were superior to BMI, WC and VAI (all p < 0.05). AVAI is still an independent predictor for mortality adjusted for confounders. The associations of AVAI with all-cause and cardiovascular mortalities were dose-responsive, with higher AVAI scores indicating higher mortality risks.

CONCLUSION

Age significantly improves the ability of VAI for predicting all-cause and cardiovascular mortality. Age-adjusted VAI is independently associated with mortality risk, and thus could be considered a reliable parameter for assessing mortality risk.

Senescent adipocytes as potential effectors of muscle cells dysfunction: An in vitro model

Recently, there has been a growing body of evidence showing a negative effect of the white adipose tissue (WAT) dysfunction on the skeletal muscle function and quality. However, little is known about the effects of senescent adipocytes on muscle cells. Therefore, to explore potential mechanisms involved in age-related loss of muscle mass and function, we performed an in vitro experiment using conditioned medium obtained from cultures of mature and aged 3 T3-L1 adipocytes, as well as from cultures of dysfunctional adipocytes exposed to oxidative stress or high insulin doses, to treat C2C12 myocytes. The results from morphological measures indicated a significant decrease in diameter and fusion index of myotubes after treatment with medium of aged or stressed adipocytes. Aged and stressed adipocytes presented different morphological characteristics as well as a different gene expression profile of proinflammatory cytokines and ROS production. In myocytes treated with different adipocytes' conditioned media, we demonstrated a significant reduction of gene expression of myogenic differentiation markers as well as a significant increase of genes involved in atrophy. Finally, a significant reduction in protein synthesis as well as a significant increase of myostatin was found in muscle cells treated with medium of aged or stressed adipocytes compared to controls. In conclusion, these preliminary results suggest that aged adipocytes could influence negatively trophism, function and regenerative capacity of myocytes by a paracrine network of signaling.

Immuno-metabolic effect of pancreastatin inhibitor PSTi8 in diet induced obese mice: In vitro and in vivo findings

AIMS

Pancreastatin (PST), an anti-insulin peptide derived from chromogranin A. Its levels increase in cases of obesity, which contributes to adipose tissue inflammation and insulin resistance. This study aims to investigate the immunometabolic effect of PST inhibitor (PSTi8) against PST by using in vitro and in vivo finding.

MAIN METHODS

3T3-L1 cells were differentiated with or without PSTi8, and Oil Red O staining was performed. J774A.1 cells were used for macrophage polarization study. The diet-induced obesity and T2DM model was developed in C57BL/6 mice through high-fat diet for 8 weeks. Alzet osmotic pumps were filled with PSTi8 (release rate: 2 mg/kg/day) and implanted in mice for eight weeks. Further, insulin and glucose tolerance tests were performed. Liver and eWAT sections were stained with hematoxylin and eosin. FACS was used to measure mitochondrial ROS and membrane potential, while Oroboros O2k was used to measure oxygen consumption rate. Immunocytochemistry and qRT-PCR were done for protein and gene expression, respectively.

KEY FINDINGS

PSTi8 inhibited the expression of lipolytic genes and proteins in 3T3-L1 adipocytes. PSTi8 improved the inulin sensitivity, lipid profile, MMP, and OCR levels in the 3T3-L1 adipocyte and eWAT. It also increased the M1 to M2 macrophage polarization in J77A.1 cells and eWAT. Further, PSTi8 attenuated inflammatory CD4⁺ T, CD8⁺ T cells and increased the anti-inflammatory T-reg and eosinophil populations in the eWAT. It also reduced the expression of pro-inflammatory genes like Mcp1, Tnfα, and Il-6.

SIGNIFICANCE

Collectively, PSTi8 exerted its beneficial effect on adipose tissue inflammation and restored energy expenditure against diet-induced obesity.

The Role of Crosstalk between Adipose Cells and Myocytes in the Pathogenesis of Sarcopenic Obesity in the Elderly

As a result of aging, body composition changes, with a decline in muscle mass and an increase in adipose tissue (AT), which reallocates from subcutaneous to visceral depots and stores ectopically in the liver, heart and muscles. Furthermore, with aging, muscle and AT, both of which have recognized endocrine activity, become dysfunctional and contribute, in the case of positive energy balance, to the development of sarcopenic obesity (SO). SO is defined as the co-existence of excess adiposity and low muscle mass and function, and its prevalence increases with age. SO is strongly associated with greater morbidity and mortality. The pathogenesis of SO is complex and multifactorial. This review focuses mainly on the role of crosstalk between age-related dysfunctional adipose and muscle cells as one of the mechanisms leading to SO. A better understanding of this mechanisms may be useful for development of prevention strategies and treatments aimed at reducing the occurrence of SO.

Senolytic effects of quercetin in an in vitro model of pre-adipocytes and adipocytes induced senescence

The dysfunction of adipose tissue with aging and the accumulation of senescent cells has been implicated in the pathophysiology of chronic diseases. Recently interventions capable of reducing the burden of senescent cells and in particular the identification of a new class of drugs termed senolytics have been object of extensive investigation. We used an in vitro model of induced senescence by treating both pre-adipocytes as well as mature adipocytes with hydrogen peroxide (H₂O₂) at a sub-lethal concentration for 3 h for three consecutive days, and hereafter with 20 uM quercetin at a dose that in preliminary experiments resulted to be senolytic without cytotoxicity. H₂O₂ treated pre-adipocytes and adipocytes showed typical senescence-associated features including increased beta-galactosidase activity (SA-ß-gal) and p21, activation of ROS and increased expression of pro-inflammatory cytokines. The treatment with quercetin in senescent pre-adipocytes and adipocytes was associated to a significant decrease in the number of the SA-β-gal positive cells along with the suppression of ROS and of inflammatory cytokines. Besides, quercetin treatment decreased miR-155-5p expression in both models, with down-regulation of p65 and a trend toward an up-regulation of SIRT-1 in complete cell extracts. The senolytic compound quercetin could affect AT ageing by reducing senescence, induced in our in vitro model by oxidative stress. The downregulation of miRNA-155-5p, possibly through the modulation of NF-κB and SIRT-1, could have a key role in the effects of quercetin on both pre-adipocytes and adipocytes.

The Aging of Adipocytes Increases Expression of Pro-Inflammatory Cytokines Chronologically

Adipose tissue is a significant producer of pro-inflammatory cytokines in obese and old individuals. However, there is no direct evidence of whether and how aged adipocytes enhance the production of pro-inflammatory markers. We aimed to investigate whether the aging adipocytes increase pro-inflammatory markers. Swiss mouse embryonic-tissue-derived 3T3-L1 cells were differentiated into adipocytes and maintained for 60 days in the conditioned medium or 35 days in the unconditioned medium. Additionally, 20-month-old male C57BL/6 mice were fed a standard chow diet for 37 weeks until they were extremely aged, when ~75% of mice died because of aging. Accumulated lipids, pro-inflammatory markers, and nuclear factor kappa B (NF-κB) pathway markers from differentiated adipocytes were analyzed. Pro-inflammatory markers and NF-κB pathway markers of epididymal white adipose tissues (EWATs) and adipocytes from EWATs were also analyzed. We found that the aging adipocytes chronologically accumulated lipids and increased pro-inflammatory markers interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-alpha (TNF-α); at the same time, NF-κB p50 markers were also increased while IκBα protein was decreased significantly in conditioned medium. Similar results were observed when differentiated adipocytes were maintained in the unconditioned medium and the adipocytes from EWATs of aged mice. We demonstrated that aging augmented chronic inflammation through the NF-κB signaling pathway in adipocytes and adipose tissue.

How does adipose tissue contribute to inflammageing?

Across aging, white adipose tissue (WAT) undergoes significant changes in quantity and distribution, with an increase in visceral adipose tissue, ectopic fat deposition and a decline in gluteofemoral subcutaneous depot. In particular, WAT becomes dysfunctional with an increase in production of inflammatory peptides and a decline of those with anti-inflammatory activity and infiltration of inflammatory cells. Moreover, dysfunction of WAT is characterized by preadipocyte differentiation decline, increased oxidative stress and mitochondrial dysfunction, reduction in vascularization and hypoxia, increased fibrosis and senescent cell accumulation. WAT changes represent an important hallmark of the aging process and may be responsible for the systemic pro-inflammatory state ("inflammageing") typical of aging itself, leading to age-related metabolic alterations. This review focuses on mechanisms linking age-related WAT changes to inflammageing.

Histology and molecular biology studies on the expression and localization of angiopoietin-like protein 8 in human tissues

Angiopoietin-like protein (ANGPTL) 8 regulates the partitioning of triglycerides by inhibiting lipoprotein lipase in muscle and adipose tissues. ANGPTL8 is expressed in the liver and adipose tissue and secreted into the blood. However, the precise localization of ANGPTL8-expressing cells in these tissues remains unknown. The aim of the present study was to investigate the localization of ANGPTL8-expressing cells in human tissues. Using formalin-fixed paraffin-embedded human tissue specimens, the expression of ANGPTL8 was investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry (IHC) and in situ hybridization (ISH). The expression level of ANGPTL8 mRNA was the highest in the liver, followed by lipoma, hibernoma and normal adipose tissue. In the liver, wild type (KF809856) and two splice variants of ANGPTL8 mRNA (KF809857 and KF809858) were found to be expressed. The expression level of the splice variant KF809858, which produces a short form of ANGPTL8, accounted for <1% of ANGPTL8 in the liver. IHC revealed that ANGPTL8 was expressed in hepatocytes in zone 1 of the hepatic acinus in the liver. In the adipose tissue, mature adipocytes weakly expressed ANGPTL8, while immature adipocytes strongly expressed it. ISH confirmed ANGPTL8 mRNA expression in portal hepatocytes and immature adipocytes. ANGPTL8 was expressed in the cells, which actively uptake and metabolize triglycerides. In hibernoma, the ANGPTL8 protein and mRNA were homogeneously expressed in tumor cells. The expression of ANGPTL8 was associated with the differentiation state and activity of lipid metabolism in a subpopulation of cells in the liver and adipose tissue. The association may be helpful for the understanding of local metabolic state in organs and diseases associated with the lipid metabolism.

Mitochondrial Dysfunction in Adipocytes as a Primary Cause of Adipose Tissue Inflammation

Adipose tissue inflammation is considered a major contributing factor in the development of obesity-associated insulin resistance and cardiovascular diseases. However, the cause of adipose tissue inflammation is presently unclear. The role of mitochondria in white adipocytes has long been neglected because of their low abundance. However, recent evidence suggests that mitochondria are essential for maintaining metabolic homeostasis in white adipocytes. In a series of recent studies, we found that mitochondrial function in white adipocytes is essential to the synthesis of adiponectin, which is the most abundant adipokine synthesized from adipocytes, with many favorable effects on metabolism, including improvement of insulin sensitivity and reduction of atherosclerotic processes and systemic inflammation. From these results, we propose a new hypothesis that mitochondrial dysfunction in adipocytes is a primary cause of adipose tissue inflammation and compared this hypothesis with a prevailing concept that "adipose tissue hypoxia" may underlie adipose tissue dysfunction in obesity. Recent studies have emphasized the role of the mitochondrial quality control mechanism in maintaining mitochondrial function. Future studies are warranted to test whether an inadequate mitochondrial quality control mechanism is responsible for mitochondrial dysfunction in adipocytes and adipose tissue inflammation.

Differential effects of a combination of Hibiscus sabdariffa and Lippia citriodora polyphenols in overweight/obese subjects: A randomized controlled trial

Plant-polyphenols have shown the capacity to ameliorate obesity-induced metabolic disturbances, both in cell and animal models, where most therapeutic approaches have failed. On the basis of previous research, a dietary supplement containing 500 mg of a combination of polyphenolic extracts from Lippia citriodora L. and Hibiscus sabdariffa L. (LC-HS), in the context of an equilibrated isocaloric diet, was evaluated in a double blind, placebo-controlled and randomized trial in 56 obese/overweight subjects for two months. Compared to controls, the consumption of the LC-HS polyphenols showed significant improvements in body weight, abdominal circumference of overweight subjects (−6.79 ± 0.80 cm in overweight LC-HS group vs −1.85 ± 0.83 cm in controls, p < 0.001) and body fat % (−1.33 ± 0.15% in overweight LC-HS group vs −0.66 ± 0.17% in controls, p < 0.05). Heart rate and systolic blood pressure also presented significant improvements in overweight LC-HS participants. However, changes were more modest in obese subjects. Further, LC-HS extract significantly reduced lipid content and increased AMPK activity in a hypertrophied adipocyte cell model. Therefore, consumption of 500 mg/day of LC-HS extracts enriched in polyphenols for two months in the context of an isocaloric diet by overweight subjects decreased symptoms associated to obesity-related diseases. Modulation of fat metabolism in adipose tissue, probably mediated by AMPK activation, is proposed as a molecular target to be explored in future research.

Potential role of marine algae extract on 3T3-L1 cell proliferation and differentiation: an in vitro approach

Background

From ancient times, marine algae have emerged as alternative medicine and foods, contains the rich source of natural products like proteins, vitamins, and secondary metabolites, especially Chlorella vulgaris (C. vulgaris) contains numerous anti-inflammatory, antioxidants and wound healing substances. Type 2 diabetes mellitus is closely associated with adipogenesis and their factors. Hence, we aimed to investigate the chemical constituents and adipogenic modulatory properties of C. vulgaris in 3T3-L1 pre-adipocytes.

Results

We analysed chemical constituents in ethanolic extract of C. vulgaris (EECV) by LC–MS. Results revealed that the EECV contains few triterpenoids and saponin compounds. Further, the effect of EECV on lipid accumulation along with genes and proteins expressions which are associated with adipogenesis and lipogenesis were evaluated using oil red O staining, qPCR and western blot techniques. The data indicated that that EECV treatment increased differentiation and lipid accumulation in 3T3-L1 cells, which indicates positive regulation of adipogenic and lipogenic activity. These increases were associated with up-regulation of PPAR-γ2, C/EBP-α, adiponectin, FAS, and leptin mRNA and protein expressions. Also, EECV treatments increased the concentration of glycerol releases as compared with control cells. Troglitazone is a PPAR-γ agonist that stimulates the PPAR-γ2, adiponectin, and GLUT-4 expressions. Similarly, EECV treatments significantly upregulated PPAR-γ2, adiponectin, GLUT-4 expressions and glucose utilization. Further, EECV treatment decreased AMPK-α expression as compared with control and metformin treated cells.

Conclusion

The present research findings confirmed that the EECV effectively modulates the lipid accumulation and differentiation in 3T3-L1 cells through AMPK-α mediated signalling pathway.

Epigallocatechin Gallate Inhibits Mouse Mesenchymal Stem Cell Differentiation to Adipogenic Lineage

Epigallocatechin gallate (EGCG) is a major component of green tea polyphenols having a potent anti-oxidant potential. Besides inhibiting the growth of many cancer cell types and inducing proliferation and differentiation in keratinocytes, it has been shown to promote reduction of body fat. The fact that mesenchymal stem cells (MSCs) have ability to self-renew and differentiate into the cells of mesodermal lineages, such as fat and bone, it is, thus, possible that EGCG may directly be involved in affecting fat metabolism through its effect on mesenchymal stem cells. Hence, with this aim, the present study was designed to determine the effect of EGCG on mouse mesenchymal stem cells, C3H10T1/2 cells differentiation into adipocytes. To understand this process, the cells were incubated with varying concentrations of EGCG (1 μM, 5 μM, 10 μM, 50 μM) in the presence and /or absence of adipogenic medium for 9 days. The results demonstrated that, EGCG inhibited the cells proliferation, migration and also prevented their differentiation to adipogenic lineage. These effects were analyzed through the inhibition of wound healing activity, reduction in Oil red O stained cells, together with decrease in the expression of Adipisin gene following EGCG treatment. These observations thus demonstrated anti-adipogenic effect of EGCG with a possibility of its role in the therapeutic intervention of obesity.

Saffron with resistance exercise improves diabetic parameters through the GLUT4/AMPK pathway in-vitro and in-vivo

Saffron is consumed as food and medicine to treat several illnesses. This study elucidates the saffron effectiveness on diabetic parameters in-vitro and combined with resistance exercise in-vivo. The antioxidant properties of saffron was examined. Insulin secretion and glucose uptake were examined by cultured RIN-5F and L6 myotubes cells. The expressions of GLUT2, GLUT4, and AMPKα were determined by Western blot. Diabetic and non-diabetic male rats were divided into: control, training, extract treatment, training + extract treatment and metformin. The exercise and 40 mg/kg/day saffron treatments were carried out for six weeks. The antioxidant capacity of saffron was higher compare to positive control (P < 0.01). High dose of saffron stimulated insulin release in RIN-5F cells and improved glucose uptake in L6 myotubes. GLUT4 and AMPKα expressions increased in both doses of saffron (P < 0.01), whereas GLUT2 not changed (p > 0.05). Serum glucose, cholesterol, triglyceride, low-density lipoprotein, very low-density lipoprotein, insulin resistance, and glycated hemoglobin levels decreased in treated rats compared to untreated (p < 0.01). However, no significant differences were observed in the high-density lipoprotein, insulin, adiponectin, and leptin concentration levels in all groups (p > 0.05). The findings suggest that saffron consuming alongside exercise could improve diabetic parameters through redox-mediated mechanisms and GLUT4/AMPK pathway to entrap glucose uptake.

Mitochondrial function/dysfunction in white adipose tissue

The role of mitochondria in white adipocytes has long been neglected due in part to their lower abundance in these cells. However, accumulating evidence suggests that mitochondria are vital for maintaining metabolic homeostasis in white adipocytes because of their involvement in adipogenesis, fatty acid synthesis and esterification, branched-chain amino acid catabolism and lipolysis. It is therefore not surprising that white adipose tissue function can be perturbed by altering mitochondrial components or oxidative capacity. Moreover, studies in humans and animals with significantly altered fat mass, such as in obesity or lipoatrophy, indicate that impaired mitochondrial function in adipocytes may be linked directly to the development of metabolic diseases such as diabetes and insulin resistance. However, recent studies that specifically targeted mitochondrial function in adipocytes indicated dissociation between impaired mitochondrial oxidative capacity and systemic insulin sensitivity.

The influence of EPA and DHA on markers of inflammation in 3T3-L1 cells at different stages of cellular maturation

BACKGROUND

EPA and DHA have been reported to have anti-obesity and anti-inflammatory properties. Recent studies revealed that these positive actions of n-3 PUFA at least partially are connected with their influence on metabolism and secretory functions of the adipose tissue. However, their impact on old adipocytes is still poorly understood. Therefore the aim of the present study was to evaluate the influence of EPA and DHA on markers of inflammation in 3T3-L1 cells at different stages of cellular maturation.

METHODS

Young, mature and old differentiated 3T3-L1 adipocytes were cultured for 48 h in the presence of 100 μM EPA, or 50 μM DHA complexed to albumin, whereas in control conditions only albumin was added to the medium. The Oil Red O staining was used to confirm adipocytes differentiation, and measure triglycerides content in cells. The concentration of adipokines (interleukin 6, adiponectin and leptin) in conditioned media was measured using mouse-specific ELISA kits.

RESULTS

The fat accumulation in 3T3-L1 adipocytes was positively correlated with their age; however, EPA and DHA did not affect lipid accumulation on any stage of maturation. EPA and DHA increased the concentration of secreted adiponectin when compared with control, but only in the case of young adipocytes (58% and 35%, respectively). Moreover, EPA supplementation increased interleukin 6 concentration in conditioned medium, while DHA exerted an opposite effect on all stages of cellular maturation. Furthermore, EPA treatment increased leptin release from young cells, while DHA did not affect the secretion of this adipokine. In mature 3T3-L1 adipocytes both experimental factors decreased synthesis of leptin; however, in old cells no impact of these PUFA was noted.

CONCLUSIONS

In summary, age is an important determinant of fat accumulation in adipocytes and affects adipokines secretion by these cells. Moreover, the impact of investigated fatty acids: EPA and DHA on fat cells varies depending on the stage of maturation, and seems to be stronger in young cells than in mature and old ones. Docosahexaenoic acid exerts an anti-inflammatory action; however, on the basis of the obtained data it was not possible to determine whether eicosapentaenoic acid shows anti- or pro-inflammatory properties.

Adipose tissue, diet and aging

Age related increase in body fat mass, visceral adipose tissue (AT), and ectopic fat deposition are strongly related to worse health conditions in the elderly. Moreover, with aging higher inflammation in adipose tissue may be observed and may contribute to inflammaging. Aging may significantly affect AT function by modifying the profile of adipokines produced by adipose cells, reducing preadipocytes number and their function and increasing AT macrophages infiltration. The initiating events of the inflammatory cascade promoting a greater AT inflammatory profile are not completely understood. Nutrients may determine changes in the amount of body fat, in its distribution as well as in AT function with some nutrients showing a pro-inflammatory effect on AT. Evidences are sparse and quite controversial with only a few studies performed in older subjects. Different dietary patterns are the result of the complex interaction of foods and nutrients, thus more studies are needed to evaluate the association between dietary patterns and changes in adipose tissue structure, distribution and function in the elderly.

Triiodothyronine increases mRNA and protein leptin levels in short time in 3T3-L1 adipocytes by PI3K pathway activation

The present study aimed to examine the effects of thyroid hormone (TH), more precisely triiodothyronine (T3), on the modulation of leptin mRNA expression and the involvement of the phosphatidyl inositol 3 kinase (PI3K) signaling pathway in adipocytes, 3T3-L1, cell culture. We examined the involvement of this pathway in mediating TH effects by treating 3T3-L1 adipocytes with physiological (P=10nM) or supraphysiological (SI=100 nM) T3 dose during one hour (short time), in the absence or the presence of PI3K inhibitor (LY294002). The absence of any treatment was considered the control group (C). RT-qPCR was used for mRNA expression analyzes. For data analyzes ANOVA complemented with Tukey’s test was used at 5% significance. T3 increased leptin mRNA expression in P (2.26 ± 0.36, p< 0.001), SI (1.99 ±0.22, p< 0.01) compared to C group (1± 0.18). This increase was completely abrogated by LY294002 in P (1.31±0.05, p< 0.001) and SI (1.33±0.31, p< 0.05). Western blotting confirmed these results at protein level, indicating the PI3K pathway dependency. To examine whether leptin is directly induced by T3, we used the translation inhibitor cycloheximide (CHX). In P, the presence of CHX maintained the levels mRNA leptin, but was completely abrogated in SI (1.14±0.09, p> 0.001). These results demonstrate that the activation of the PI3K signaling pathway has a role in TH-mediated direct and indirect leptin gene expression in 3T3-L1 adipocytes.

Adipocyte size and cellular expression of caveolar proteins analyzed by confocal microscopy

Caveolae are abundant in adipocytes and are involved in the regulation of lipid accumulation, which is the main volume determinant of these cells. We have developed and applied a confocal microscopic technique for measuring individual cellular expression of the caveolar proteins cavin-1 and caveolin-1 along with the size of individual adipocytes. The technique was applied on collagenase isolated adipocytes from ad libitum fed Sprague-Dawley rats of different age (4–26 wk) and weight (103–629 g). We found that cellular expression of caveolar proteins was variable (SD of log expression in the range from 0.25 to 0.65). Regression analysis of protein expression on adipocyte size revealed that the expression of the caveolar proteins cavin-1 and caveolin-1 on adipocytes from individual rats was tightly related to adipocyte cell surface area (mean coefficient of regression was 0.83 for cavin and 0.77 for caveolin), indicating that caveolar density was the same in membranes from all cells within a biopsy. This intrinsic relation remained unchanged with animal age, but adipocytes from animals with increasing age showed a decrease in mean expression of caveolar proteins per unit cell surface. The different relation between adipocyte size and cellular expression levels of caveolar proteins within and between individuals of different age shows that caveolar density is an age-sensitive characteristic of adipocytes.

Synergism of plant-derived polyphenols in adipogenesis: perspectives and implications

Dietary polyphenols may exert their pharmacological effect via synergistic interactions with multiple targets. Putative effects of polyphenols in the management of obesity should be primarily evaluated in adipose tissue and consequently in well-documented cell model. We used Hibiscus sabdariffa (HS), a widely recognised medicinal plant, as a source of polyphenols with a number of salutary effects previously reported. We present here the full characterisation of bioactive components of HS aqueous extracts and document their effects in a model of adipogenesis from 3T3-L1 cells and in hypertrophic and insulin-resistant adipocytes. Aqueous extracts were up to 100 times more efficient in inhibiting triglyceride accumulation when devoid of fibre and polysaccharides. Significant differences were also observed in reactive oxygen species generation and adipokine secretion. We also found that, when polyphenols were fractionated and isolated, the benefits of the whole extract were greater than the sum of its parts, which indicated a previously unnoticed synergism. In conclusion, polyphenols have interactive and complementary effects, which suggest a possible application in the management of complex diseases and efforts to isolate individual components might be irrelevant for clinical medicine and/or human nutrition.

Historical perspectives in fat cell biology: the fat cell as a model for the investigation of hormonal and metabolic pathways

For many years, there was little interest in the biochemistry or physiology of adipose tissue. It is now well recognized that adipocytes play an important dynamic role in metabolic regulation. They are able to sense metabolic states via their ability to perceive a large number of nervous and hormonal signals. They are also able to produce hormones, called adipokines, that affect nutrient intake, metabolism and energy expenditure. The report by Rodbell in 1964 that intact fat cells can be obtained by collagenase digestion of adipose tissue revolutionized studies on the hormonal regulation and metabolism of the fat cell. In the context of the advent of systems biology in the field of cell biology, the present seems an appropriate time to look back at the global contribution of the fat cell to cell biology knowledge. This review focuses on the very early approaches that used the fat cell as a tool to discover and understand various cellular mechanisms. Attention essentially focuses on the early investigations revealing the major contribution of mature fat cells and also fat cells originating from adipose cell lines to the discovery of major events related to hormone action (hormone receptors and transduction pathways involved in hormonal signaling) and mechanisms involved in metabolite processing (hexose uptake and uptake, storage, and efflux of fatty acids). Dormant preadipocytes exist in the stroma-vascular fraction of the adipose tissue of rodents and humans; cell culture systems have proven to be valuable models for the study of the processes involved in the formation of new fat cells. Finally, more recent insights into adipocyte secretion, a completely new role with major metabolic impact, are also briefly summarized.

Impact of metabolic regulators on the expression of the obesity associated genes FTO and NAMPT in human preadipocytes and adipocytes

Background

FTO and NAMPT/PBEF/visfatin are thought to play a role in obesity but their transcriptional regulation in adipocytes is not fully understood. In this study, we evaluated the transcriptional regulation of FTO and NAMPT in preadipocytes and adipocytes by metabolic regulators.

Methodology and Principal Findings

We assessed FTO mRNA expression during human adipocyte differentiation of Simpson-Golabi-Behmel syndrome (SGBS) cells and primary subcutaneous preadipocytes in vitro and evaluated the effect of the metabolic regulators glucose, insulin, dexamethasone, IGF-1 and isoproterenol on FTO and NAMPT mRNA expression in SGBS preadipocytes and adipocytes. FTO mRNA levels were not significantly modulated during adipocyte differentiation. Also, metabolic regulators had no impact on FTO expression in preadipocytes or adipocytes. In SGBS preadipocytes NAMPT expression was more than 3fold induced by dexamethasone and isoproterenol and 1.6fold by dexamethasone in adipocytes. Complete glucose restriction caused an increase in NAMPT mRNA expression by more than 5fold and 1.4fold in SGBS preadipocytes and adipocytes, respectively.

Conclusion

FTO mRNA expression is not significantly affected by differentiation or metabolic regulators in human adipocytes. The stimulation of NAMPT expression by dexamethasone, isoproterenol and complete glucose restriction may indicate a regulation of NAMPT by metabolic stress, which was more pronounced in preadipocytes compared to mature adipocytes.

Higher adiponectin levels predict greater weight gain in healthy women in the Nurses' Health Study

Adiponectin and resistin's possible roles in weight regulation have received little attention. We tested the hypothesis that adipokine levels predict future weight gain in women in the Nurses' Health Study. Among women who provided blood samples in 1990, we studied 1,063 women who did not develop diabetes ("healthy") and 984 women who subsequently developed diabetes. Total and high-molecular-weight (HMW) adiponectin and resistin levels were measured using enzyme-linked immunosorbent assay. Women who did not developed diabetes had a mean BMI of 26.3 ± 6.0 kg/m(2) at baseline and gained 2.0 ± 6.1 kg over 4 years. Women who developed diabetes had a mean BMI of 30.1 ± 5.4 kg/m(2) at baseline, and gained 2.4 ± 7.1 kg over 4 years. In women who did not developed diabetes, higher baseline levels of total and HMW adiponectin were associated with significantly greater weight gain after adjustment for age, BMI, physical activity, diet, and other covariates: women in the highest quintile of total adiponectin gained 3.18 kg compared to women in the lowest quintile who gained 0.80 kg (fully adjusted; P for trend <0.0001). Adiponectin was not significantly associated with weight gain in women who subsequently developed diabetes. Resistin levels were not associated with weight gain in either women who did or did not develop diabetes during the follow-up. We conclude that elevated adiponectin levels are associated with higher weight gain in healthy women, independent of confounding risk factors. High adiponectin production by adipocytes might be a sign of "healthy" adipose tissue with further capacity to store fat.

White adipose tissue genome wide-expression profiling and adipocyte metabolic functions after soy protein consumption in rats

Obesity is associated with an increase in adipose tissue mass due to an imbalance between high dietary energy intake and low physical activity; however, the type of dietary protein may contribute to its development. The aim of the present work was to study the effect of soy protein versus casein on white adipose tissue genome profiling, and the metabolic functions of adipocytes in rats with diet-induced obesity. The results showed that rats fed a Soy Protein High-Fat (Soy HF) diet gained less weight and had lower serum leptin concentration than rats fed a Casein High-Fat (Cas HF) diet, despite similar energy intake. Histological studies indicated that rats fed the Soy HF diet had significantly smaller adipocytes than those fed the Cas HF diet, and this was associated with a lower triglyceride/DNA content. Fatty acid synthesis in isolated adipocytes was reduced by the amount of fat consumed but not by the type of protein ingested. Expression of genes of fatty acid oxidation increased in adipose tissue of rats fed Soy diets; microarray analysis revealed that Soy protein consumption modified the expression of 90 genes involved in metabolic functions and inflammatory response in adipose tissue. Network analysis showed that the expression of leptin was regulated by the type of dietary protein and it was identified as a central regulator of the expression of lipid metabolism genes in adipose tissue. Thus, soy maintains the size and metabolic functions of adipose tissue through biochemical adaptations, adipokine secretion, and global changes in gene expression.

eNOS plays a major role in adiponectin synthesis in adipocytes

Nitric oxide (NO) stimulates mitochondrial biogenesis. We recently reported that adiponectin synthesis is regulated by mitochondrial function in adipocytes. This study was undertaken to test the hypothesis that endothelial NO synthase (eNOS) plays an important role in adiponectin synthesis by producing NO and enhancing mitochondrial function in adipocytes. We examined the effects of eNOS knockdown on adiponectin synthesis in 3T3-L1 adipocytes and also examined plasma adiponectin levels and the mitochondria in adipose tissue of eNOS knockout (eNOS(-/-)) mice with and without chronic administration of a NO donor. In cultured 3T3-L1 adipocytes, eNOS siRNA decreased rosiglitazone-induced adiponectin secretion, which was associated with decreases in mitochondrial proteins and biogenesis factors. Plasma adiponectin concentrations were reduced in adult eNOS(-/-) mice compared with age-matched wild-type mice. Mitochondrial contents in adipose tissue were reduced in eNOS(-/-) mice, and this was associated with decreased expression of mitochondrial biogenesis factors, increased levels of 8-hydroxyguanosine, a biomarker of oxidative stress, and morphological abnormalities in mitochondria. Rosiglitazone-induced increases in adiponectin expression and mitochondrial content were also reduced significantly in eNOS(-/-) mice. Chronic administration of a NO donor reversed mitochondrial abnormalities and increased adiponectin expression in adipose tissue of eNOS(-/-) mice. eNOS plays an important role in adiponectin synthesis in adipocytes by increasing mitochondrial biogenesis and enhancing mitochondrial function.

Paradoxical coupling of triglyceride synthesis and fatty acid oxidation in skeletal muscle overexpressing DGAT1

OBJECTIVE

Transgenic expression of diacylglycerol acyltransferase-1 (DGAT1) in skeletal muscle leads to protection against fat-induced insulin resistance despite accumulation of intramuscular triglyceride, a phenomenon similar to what is known as the "athlete paradox." The primary objective of this study is to determine how DGAT1 affects muscle fatty acid oxidation in relation to whole-body energy metabolism and insulin sensitivity.

RESEARCH DESIGN AND METHODS

We first quantified insulin sensitivity and the relative tissue contributions to the improved whole-body insulin sensitivity in muscle creatine kisase (MCK)-DGAT1 transgenic mice by hyperinsulinemic-euglycemic clamps. Metabolic consequences of DGAT1 overexpression in skeletal muscles were determined by quantifying triglyceride synthesis/storage (anabolic) and fatty acid oxidation (catabolic), in conjunction with gene expression levels of representative marker genes in fatty acid metabolism. Whole-body energy metabolism including food consumption, body weights, oxygen consumption, locomotor activity, and respiration exchange ratios were determined at steady states.

RESULTS

MCK-DGAT1 mice were protected against muscle lipoptoxicity, although they remain susceptible to hepatic lipotoxicity. While augmenting triglyceride synthesis, DGAT1 overexpression also led to increased muscle mitochondrial fatty acid oxidation efficiency, as compared with wild-type muscles. On a high-fat diet, MCK-DGAT1 mice displayed higher basal metabolic rates and 5-10% lower body weights compared with wild-type littermates, whereas food consumption was not different.

CONCLUSIONS

DGAT1 overexpression in skeletal muscle led to parallel increases in triglyceride synthesis and fatty acid oxidation. Seemingly paradoxical, this phenomenon is characteristic of insulin-sensitive myofibers and suggests that DGAT1 plays an active role in metabolic "remodeling" of skeletal muscle coupled with insulin sensitization.

Adiponectin is associated with serum and adipose tissue fatty acid composition in rats

The objective of the present work is to analyse the relationships between changes in adiponectin and fatty acid composition in serum and adipose tissue in rats. Samples from serum and different adipose depots (periovarian, mesenteric and subcutaneous) were obtained from ageing rats (14- and 20-month-old) to determine fatty acid composition (gasliquid chromatography). In serum, insulin (radioimmunoassay) and adiponectin levels (enzyme-linked immunosorbent assay) were also measured, while adiponectin gene expression was analysed (real time-qPCR) in all fat depots. There were significant age-related reductions in adipose tissue saturated (SFA) and trans fatty acids and increases in monounsaturated fatty acids in parallel with diminished adiponectin expression in periovarian and mesenteric adipose tissue (p<0.05). Age-independent negative correlations were found between adiponectin gene expression in mesenteric adipose tissue and C12:0, C14:0 and C18:2 trans fatty acids (p<0.05). There was a positive association between serum adiponectin and adipose tissue oleic acid, while palmitoleic acid was negatively associated with adiponectin expression and positively correlated with insulin concentration. For the first time, positive relationships are reported between the proportion of n-6 polyunsaturated fatty acids (PUFA) in adipose tissue and adiponectin concentration and expression. In summary, adiponectin expression and serum levels are associated with fatty acid composition, with SFA, trans and palmitoleic fatty acids appearing as negative markers for adiponectin, and oleic acid and n-6 PUFA as positive ones. In addition, most associations were found in the visceral depots, highlighting the importance of visceral fat in the metabolic status.

Simvastatin suppresses leptin expression in 3T3-L1 adipocytes via activation of the cyclic AMP-PKA pathway induced by inhibition of protein prenylation

Simvastatin inhibits 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which catalyses conversion of HMG-CoA to mevalonate, a rate-limiting step in cholesterol synthesis. We demonstrated that simvastatin at 1 microM markedly inhibited adipocyte differentiation measured by Oil Red O staining in preadipocyte cells (3T3-L1), while expression of leptin, a marker of adipocyte differentiation, was suppressed by 1 muM simvastatin for up to 12 days of culture. Next, to elucidate mechanisms underlying the reduction of leptin expression induced by simvastatin, differentiated 3T3-L1 adipocytes were treated with various inhibitors with mevalonate or its metabolite in the presence or absence of simvastatin. Simvastatin time- and dose-dependently suppressed leptin mRNA expression. Heterogeneous nuclear RNA related to leptin mRNA was inhibited by 10 muM simvastatin, while stability of the mRNA was not changed by treatment with simvastatin in transcription-arrested 3T3-L1 cells. Simvastatin inhibition of leptin gene transcription was not abrogated by pre-treatment with cycloheximide, an inhibitor of protein synthesis. Addition of mevalonate or geranylgeranyl pyrophosphate (GGPP), a mevalonate metabolite, abolished simvastatin-induced inhibition of leptin expression in 3T3-L1 cells. Suppression of expression was observed upon addition of GGTI-298, a geranylgeranyl transferase I inhibitor, but not FTI-277, a farnesyl transferase inhibitor. Expression was suppressed by treatment with hydroxyfasudil, a protein prenylation inhibitor. Treatment with phosphatidylinositol 3-kinase (PI3K) inhibitors, LY294002 and wortmannin, reduced leptin expression in 3T3-L1 cells. Simvastatin dose-dependently increased intra-cellular cyclic AMP (cAMP) concentrations in 3T3-L1 cells, with maximal stimulation obtained at 10 muM. Addition of GGPP abolished simvastatin-induced stimulation of cAMP accumulation and protein kinase A (PKA) activity. H89, an inhibitor of PKA, completely abolished simvastatin-induced suppression of leptin expression. These results suggested that simvastatin reduced geranylgeranylprotein prenylation followed by deactivation of PI3K, leading to cAMP accumulation and subsequent activation of PKA in differentiated 3T3-L1 adipocytes. Finally, PKA inhibited leptin gene transcription without new protein synthesis.

Cloning of rabbit adiponectin and its relationship to age and high-cholesterol diet

Secreted by adipocytes, adiponectin is a collagen-like protein with significant roles in regulating the metabolism of glucose and fatty acids and in preventing atherosclerosis. However, information about adiponectin in rabbit is limited. In this study, we cloned rabbit ADIPOQ gene by RT-PCR using mRNA from adipose tissue and sequenced the open reading frame. The rabbit adiponectin sequence shares approximately 86.39% and 81.45% homology with those of humans and mice respectively, and 85.66% and 85.25% similarity with humans and mice proteins at the amino acid level respectively, based on the translated rabbit sequence and GenBank submissions of other species. We also evaluated ADIPOQ gene mRNA expression in adipose tissue in rabbits fed on high-cholesterol diet and in different age groups by real-time PCR. ADIPOQ gene mRNA expression was significantly different in different age rabbits and correlated positively with the level of plasma HDL in high-cholesterol diet rabbits. These results suggest similar function of ADIPOQ gene in rabbits as in other species and indicate the relationship between ADIPOQ gene mRNA expression and high-cholesterol diet and age.

The laminopathies: the functional architecture of the nucleus and its contribution to disease

Most inherited diseases are associated with mutations in a specific gene. Often, mutations in two or more different genes result in diseases with a similar phenotype. Rarely do different mutations in the same gene result in a multitude of seemingly different and unrelated diseases. Mutations in the Lamin A gene (LMNA), which encodes largely ubiquitously expressed nuclear proteins (A-type lamins), are associated with at least eight different diseases, collectively called the laminopathies. Studies examining how different tissue-specific diseases arise from unique LMNA mutations are providing unanticipated insights into the structural organization of the nucleus, and how disruption of this organization relates to novel mechanisms of disease.

High-fat diet-induced changes in body mass and hypothalamic gene expression in wild-type and leptin-deficient mice

We tested whether diet-induced obesity results from increased energy consumption, is associated with changes in expression of genes involved in leptin signal transduction, and is altered by hyperleptinemia. C57BL/6 mice were fed a low-fat diet (LFD) or high-fat diet (HFD) for up to 15 weeks. HFD mice weighed significantly more than LFD controls by 3 weeks, despite consuming less energy. HFD mice had significantly greater leptin, insulin, and glucose levels than LFD mice, suggesting leptin and insulin resistance. Adiponectin levels declined with age but were unaffected by diet. HFD was associated with altered hypothalamic expression of genes whose products regulate the activity or nuclear translocation of STAT3, an important mediator of leptin actions. Expression of two isoforms of the leptin receptor decreased at 15 weeks in hypothalami of HFD mice in a tissue-specific manner. The type of fat (saturated versus unsaturated) did not influence weight gain on an HFD, but animals on LFD gained significantly more weight and adiposity if the dietary fat consisted mostly of saturated fats; this occurred despite no difference in energy consumption or absorption. Replacement of leptin to leptin-deficient ob/ob mice decreased hypothalamic leptin receptor expression and did not prevent HFD-induced weight gain. It is concluded that (1) increased energy consumption is not required for HFD-induced obesity in C57BL/6 mice, (2) HFD results in weight gain partly by modulating hypothalamic leptin-signaling pathways, (3) saturated fats induce weight gain even when total fat content of the diet is low, and (4) the effects of HFD are manifest in the presence or absence of circulating leptin.

The trans-10, cis-12 isomer of conjugated linoleic acid decreases adiponectin assembly by PPARgamma-dependent and PPARgamma-independent mechanisms

The adipocyte-derived secretory protein adiponectin functions as an insulin-sensitizing agent. In plasma, adiponectin exists as low, medium, and high molecular weight oligomers. Treatment with trans-10, cis-12 conjugated linoleic acid (t-10, c-12 CLA) reduces levels of adiponectin as well as triglyceride (TG) in mice and adipocyte cell culture models. The aim of this study was to determine whether the effects of t-10, c-12 CLA on adiponectin and TG are mediated through modulation of the transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma). 3T3-L1 cells were treated either during or after differentiation into adipocytes with 100 microM t-10, c-12 CLA with or without 10 microM troglitazone, a PPARgamma agonist, or 1 microM GW9662, a PPARgamma antagonist, and adiponectin and TG levels were analyzed. Treatment with t-10, c-12 CLA reduced TG as well as cellular and secreted adiponectin levels and impaired the assembly of adiponectin oligomers. These changes were accompanied by decreases in PPARgamma mass. Troglitazone was able to reverse the t-10, c-12 CLA-mediated decrease in TG levels and restore the assembly of adiponectin oligomers but was unable to restore adiponectin synthesis. Conversely, treatment with GW9662 decreased TG mass and impaired adiponectin oligomer assembly but did not decrease total adiponectin mass. In a reporter assay, t-10, c-12 CLA appeared to be a partial PPARgamma agonist and prevented the stimulation of reporter activity by troglitazone. Therefore, the t-10, c-12 CLA isomer appears to alter adipocyte adiponectin metabolism through PPARgamma-dependent and PPARgamma-independent mechanisms.

Essential role of mitochondrial function in adiponectin synthesis in adipocytes

OBJECTIVE

Adiponectin is an important adipocytokine that improves insulin action and reduces atherosclerotic processes. The plasma adiponectin level is paradoxically reduced in obese individuals, but the underlying mechanism is unknown. This study was undertaken to test the hypothesis that mitochondrial function is linked to adiponectin synthesis in adipocytes.

RESEARCH DESIGN AND METHODS

We examined the effects of rosiglitazone and the measures that increase or decrease mitochondrial function on adiponectin synthesis. We also examined the molecular mechanism by which changes in mitochondrial function affect adiponectin synthesis.

RESULTS

Adiponectin expression and mitochondrial content in adipose tissue were reduced in obese db/db mice, and these changes were reversed by the administration of rosiglitazone. In cultured adipocytes, induction of increased mitochondrial biogenesis (via adenoviral overexpression of nuclear respiratory factor-1) increased adiponectin synthesis, whereas impairment in mitochondrial function decreased it. Impaired mitochondrial function increased endoplasmic reticulum (ER) stress, and agents causing mitochondrial or ER stress reduced adiponectin transcription via activation of c-Jun NH(2)-terminal kinase (JNK) and consequent induction of activating transcription factor (ATF)3. Increased mitochondrial biogenesis reversed all of these changes.

CONCLUSIONS

Mitochondrial function is linked to adiponectin synthesis in adipocytes, and mitochondrial dysfunction in adipose tissue may explain decreased plasma adiponectin levels in obesity. Impaired mitochondrial function activates a series of mechanisms involving ER stress, JNK, and ATF3 to decrease adiponectin synthesis.

Succination of Protein Thiols during Adipocyte Maturation

Although obesity is a risk factor for development of type 2 diabetes and chemical modification of proteins by advanced glycoxidation and lipoxidation end products is implicated in the development of diabetic complications, little is known about the chemical modification of proteins in adipocytes or adipose tissue. In this study we show that S-(2-succinyl)cysteine (2SC), the product of chemical modification of proteins by the Krebs cycle intermediate, fumarate, is significantly increased during maturation of 3T3-L1 fibroblasts to adipocytes. Fumarate concentration increased > or =5-fold during adipogenesis in medium containing 30 mm glucose, producing a > or =10-fold increase in 2SC-proteins in adipocytes compared with undifferentiated fibroblasts grown in the same high glucose medium. The elevated glucose concentration in the medium during adipocyte maturation correlated with the increase in 2SC, whereas the concentration of the advanced glycoxidation and lipoxidation end products, N(epsilon)-(carboxymethyl)lysine and N(epsilon)-(carboxyethyl)lysine, was unchanged under these conditions. Adipocyte proteins were separated by one- and two-dimensional electrophoresis and approximately 60 2SC-proteins were detected using an anti-2SC polyclonal antibody. Several of the prominent and well resolved proteins were identified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry. These include cytoskeletal proteins, enzymes, heat shock and chaperone proteins, regulatory proteins, and a fatty acid-binding protein. We propose that the increase in fumarate and 2SC is the result of mitochondrial stress in the adipocyte during adipogenesis and that 2SC may be a useful biomarker of mitochondrial stress in obesity, insulin resistance, and diabetes.

Adipogenic signaling in rat white adipose tissue: modulation by aging and calorie restriction

Alterations in adipogenesis could have significant impact on several aging processes. We previously reported that calorie restriction (CR) in rats significantly increases the level of circulating adiponectin, a distinctive marker of differentiated adipocytes, leading to a concerted modulation in the expression of key transcription target genes and, as a result, to increased fatty acid oxidation and reduced deleterious lipid accumulation in other tissues. These findings led us to investigate further the effects of aging on adipocytes and to determine how CR modulates adipogenic signaling in vivo. CR for 2 and 25 months, significantly increased the expression of PPARgamma, C/EBPbeta and Cdk-4, and partially attenuated age-related decline in C/EBPalpha expression relative to rats fed ad libitum (AL). As a result, adiponectin was upregulated at both mRNA and protein levels, resulting in activation of target genes involved in fatty acid oxidation and fatty acid synthesis, and greater responsiveness of adipose tissue to insulin. Moreover, CR significantly decreased the ratio of C/EBPbeta isoforms LAP/LIP, suggesting the suppression of gene transcription associated with terminal differentiation while facilitating preadipocytes proliferation. Morphometric analysis revealed a greater number of small adipocytes in CR relative to AL feeding. Immunostaining confirmed that small adipocytes were more strongly positive for adiponectin than the large ones. Overall these results suggest that CR increased the expression of adipogenic factors, and maintained the differentiated state of adipocytes, which is critically important for adiponectin biosynthesis and insulin sensitivity.

Increasing dietary leucine intake reduces diet-induced obesity and improves glucose and cholesterol metabolism in mice via multimechanisms

Leucine, as an essential amino acid and activator of mTOR (mammalian target of rapamycin), promotes protein synthesis and suppresses protein catabolism. However, the effect of leucine on overall glucose and energy metabolism remains unclear, and whether leucine has beneficial effects as a long-term dietary supplement has not been examined. In the present study, we doubled dietary leucine intake via leucine-containing drinking water in mice with free excess to either a rodent chow or a high-fat diet (HFD). While it produced no major metabolic effects in chow-fed mice, increasing leucine intake resulted in up to 32% reduction of weight gain (P < 0.05) and a 25% decrease in adiposity (P < 0.01) in HFD-fed mice. The reduction of adiposity resulted from increased resting energy expenditure associated with increased expression of uncoupling protein 3 in brown and white adipose tissues and in skeletal muscle, while food intake was not decreased. Increasing leucine intake also prevented HFD-induced hyperglycemia, which was associated with improved insulin sensitivity, decreased plasma concentrations of glucagon and glucogenic amino acids, and downregulation of hepatic glucose-6-phosphatase. Additionally, plasma levels of total and LDL cholesterol were decreased by 27% (P < 0.001) and 53% (P < 0.001), respectively, in leucine supplemented HFD-fed mice compared with the control mice fed the same diet. The reduction in cholesterol levels was largely independent of leucine-induced changes in adiposity. In conclusion, increases in dietary leucine intake substantially decrease diet-induced obesity, hyperglycemia, and hypercholesterolemia in mice with ad libitum consumption of HFD likely via multiple mechanisms.

Adiponectin in health and disease

Adipose tissue is an active metabolic tissue that secretes multiple metabolically important proteins, known as adipokines. Adiponectin is an important adipokine because of its beneficial effects on glucose and lipid metabolism. Low levels of adiponectin are associated with disease states such as diabetes and cardiovascular disease. Direct administration of adiponectin has been shown to be beneficial in animal models of diabetes, obesity and atherosclerosis. Adiponectin levels in humans can be increased through indirect methods such as weight loss or treatment with thiazolidinediones. This article will review the epidemiology and therapeutic options with adiponectin.

Modulation of adiponectin and leptin during refeeding of female anorexia nervosa patients

CONTEXT

Several studies assessed adiponectin levels in anorexia nervosa (AN) patients, however, data regarding the dynamics of changes in adiponectin levels during refeeding of these patients is limited and contradicting.

OBJECTIVE

Our objective was to assess adiponectin levels and the distribution of its different isoforms in AN patients before and after long-term refeeding, and to relate them to alterations in body mass index, leptin, insulin sensitivity, and additional endocrine parameters.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a longitudinal controlled study of 38 female adolescent malnourished AN inpatients, with 13 young, lean, healthy women serving as controls. Blood samples were obtained upon admission and thereafter at 1, 3, and 5 months (at target weight).

MAIN OUTCOME MEASURES

Changes in body mass index, leptin, adiponectin, insulin sensitivity, and adiponectin multimeric forms were measured.

RESULTS

At admission, leptin levels of AN patients were significantly lower, whereas insulin sensitivity (assessed by homeostasis model assessment-insulin resistance), adiponectin levels, and the ratio of high molecular weight (HMW) adiponectin to total adiponectin were significantly higher compared with controls. During weight recovery, leptin levels and homeostasis model assessment-insulin resistance increased significantly, whereas adiponectin and HMW adiponectin/total adiponectin ratio decreased significantly, to levels similar to controls. An initial increase in adiponectin levels was observed after 1 month of refeeding. There was no correlation between adiponectin and either T(4) or cortisol levels.

CONCLUSIONS

Our study demonstrates hyperadiponectinemia, increased adiponectin HMW isoform, and increased insulin sensitivity in adolescent AN female patients and reversal of these findings with weight rehabilitation. We hypothesize that increased adiponectin levels may have a protective role in maintaining energy homeostasis during extreme malnourishment.

Mild gestational diabetes in pregnancy and the adipoinsular axis in babies born to mothers in the ACHOIS randomised controlled trial

Background

Mild gestational diabetes is a common complication of pregnancy, affecting up to 9% of pregnant women. Treatment of mild GDM is known to reduce adverse perinatal outcomes such as macrosomia and associated birth injuries, such as shoulder dystocia, bone fractures and nerve palsies. This study aimed to compare the plasma glucose concentrations and serum insulin, leptin and adiponectin in cord blood of babies of women (a) without gestational diabetes mellitus (GDM), (b) with mild GDM under routine care, or (c) mild GDM with treatment.

Methods

95 women with mild GDM on oral glucose tolerance testing (OGTT) at one tertiary level maternity hospital who had been recruited to the ACHOIS trial at one of the collaborating hospitals and randomised to either Treatment (n = 46) or Routine Care (n = 49) and Control women with a normal OGTT (n = 133) were included in the study. Women with mild GDM (treatment or routine care group) and OGTT normal women received routine pregnancy care. In addition, women with treated mild GDM received dietary advice, blood glucose monitoring and insulin if necessary.

The primary outcome measures were cord blood concentrations of glucose, insulin, adiponectin and leptin.

Results

Cord plasma glucose was higher in women receiving routine care compared with control, but was normalized by treatment for mild GDM (p = 0.01). Cord serum insulin and insulin to glucose ratio were similar between the three groups. Leptin concentration in cord serum was lower in GDM treated women compared with routine care (p = 0.02) and not different to control (p = 0.11). Adiponectin was lower in both mild GDM groups compared with control (Treatment p = 0.02 and Routine Care p = 0.07), while the adiponectin to leptin ratio was lower for women receiving routine care compared with treatment (p = 0.08) and control (p = 0.05).

Conclusion

Treatment of women with mild GDM using diet, blood glucose monitoring and insulin if necessary, influences the altered fetal adipoinsular axis characteristic of mild GDM in pregnancy.

Plasma adiponectin concentrations in non-pregnant, normal and overweight pregnant women

AIMS

Adiponectin is an adipokine that has anti-diabetic, anti-atherogenic, anti-inflammatory and angiogenic properties. This hormone has been implicated in both the physiological adaptation to normal pregnancy and in obstetrical complications. The aims of this study were to determine normal maternal plasma concentrations of adiponectin throughout gestation and to explore the relationships between plasma adiponectin concentration, pregnancy, and maternal overweight.

METHODS

A cross-sectional study was designed to include normal pregnant (normal weight and overweight; 11-42 weeks of gestation), and non-pregnant women. Plasma adiponectin concentration was determined by immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Adiponectin was detectable in the plasma of all patients; (2) there was no significant differences in the median adiponectin concentration between pregnant and non-pregnant women; (3) plasma adiponectin concentrations were negatively correlated with gestational age only among normal weight pregnant women; and (4) overweight patients had significantly lower plasma adiponectin concentrations than normal weight women.

CONCLUSIONS

Consistent with the increased insulin resistance and weight gain that occur in pregnancy, adiponectin concentrations were negatively correlated with gestational age. The results of this study and the nomogram herein presented, can serve as the basis to explore the relationship between adiponectin and pregnancy complications and facilitate the clinical use of this important adipokine.