Synergistic Phytochemicals Fail to Protect Against Ovariectomy Induced Bone Loss in Rats

Menopause induces a loss of bone as a result of estrogen deficiency. Despite pharmaceutical options for the treatment of osteopenia and osteoporosis, many aging women use dietary supplements with estrogenic activity to prevent bone loss and other menopausal-related symptoms. Such supplements are yet to be tested for efficacy against a Food and Drug Administration (FDA) approved medication for menopausal bone loss such as zoledronic acid (ZA). The postmenopausal rat model was used to investigate the efficacy of various synergistic phytochemical blends mixed into the diet for 16 weeks. Retired-breeder, Fischer 344 rats were randomly assigned to sham or ovariectomy surgery and 4 treatment groups: ZA; genistein supplementation; and a low dose and high dose blend of genistein, resveratrol, and quercetin. Ovariectomy resulted in a loss of both trabecular and cortical bone which was prevented with ZA. The phytochemical blends tested were unable to reverse these losses. Despite the lack of effectiveness in preventing bone loss, a significant dose-response trend was observed in the phytochemical-rich diets in bone adipocyte number compared to ovariectomized control rats. Data from this study indicate that estrogenic phytochemicals are not as efficacious as ZA in preventing menopausal-related bone loss but may have beneficial effects on bone marrow adiposity in rats.

Adipocyte nuclei captured from VAT and SAT

Background

Obesity-related comorbidities are thought to result from the reprogramming of the epigenome in numerous tissues and cell types, and in particular, mature adipocytes within visceral and subcutaneous adipose tissue, VAT and SAT. The cell-type specific chromatin remodeling of mature adipocytes within VAT and SAT is poorly understood, in part, because of the difficulties of isolating and manipulating large fragile mature adipocyte cells from adipose tissues.

Methods

We constructed MA-INTACT (Mature Adipocyte-Isolation of Nuclei TAgged in specific Cell Types) mice using the adiponectin (ADIPOQ) promoter (ADNp) to tag the surface of mature adipocyte nuclei with a reporter protein. The SUN1mRFP1Flag reporter is comprised of a fragment of the nuclear transmembrane protein SUN1, the fluorescent protein mRFP1, and three copies of the Flag epitope tag.

Results

Mature adipocyte nuclei were rapidly and efficiently immuno-captured from VAT and SAT (MVA and MSA nuclei, respectively), of MA-INTACT mice. MVA and MSA nuclei contained 1,000 to 10,000-fold higher levels of adipocyte-specific transcripts, ADIPOQ, PPARg2, EDNRB, and LEP, relative to uncaptured nuclei, while the latter expressed higher levels of leukocyte and endothelial cell markers IKZF1, RETN, SERPINF1, SERPINE1, ILF3, and TNFA. MVA and MSA nuclei differentially expressed several factors linked to adipogenesis or obesity-related health risks including CEBPA, KLF2, RETN, SERPINE1, and TNFA. The various nuclear populations dramatically differentially expressed transcripts encoding chromatin remodeler proteins regulating DNA cytosine methylation and hydroxymethylation (TETs, DNMTs, TDG, GADD45s) and nucleosomal histone modification (ARID1A, KAT2B, KDM4A, PRMT1, PRMT5, PAXIP1). Remarkably, MSA and MVA nuclei expressed 200 to 1000-fold higher levels of thermogenic marker transcripts PRDM16 and UCP1.

Conclusions

The MA-INTACT mouse enables a simple way to perform cell-type specific analysis of highly purified mature adipocyte nuclei from VAT and SAT and increases the statistical significance of data collected on adipocytes. Isolated VAT and SAT adipocyte nuclei expressed distinct patterns of transcripts encoding chromatin remodeling factors and proteins relevant to diabetes, cardiovascular disease, and thermogenesis. The MA-INTACT mouse is an useful model to test the impact of caloric intake, dietary nutrients, exercise, and pharmaceuticals on the epigenome-induced health risks of obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/s40608-016-0112-6) contains supplementary material, which is available to authorized users.

Subsets of Visceral Adipose Tissue Nuclei with Distinct Levels of 5-Hydroxymethylcytosine

The reprogramming of cellular memory in specific cell types, and in visceral adipocytes in particular, appears to be a fundamental aspect of obesity and its related negative health outcomes. We explored the hypothesis that adipose tissue contains epigenetically distinct subpopulations of adipocytes that are differentially potentiated to record cellular memories of their environment. Adipocytes are large, fragile, and technically difficult to efficiently isolate and fractionate. We developed fluorescence nuclear cytometry (FNC) and fluorescence activated nuclear sorting (FANS) of cellular nuclei from visceral adipose tissue (VAT) using the levels of the pan-adipocyte protein, peroxisome proliferator-activated receptor gamma-2 (PPARg2), to distinguish classes of PPARg2-Positive (PPARg2-Pos) adipocyte nuclei from PPARg2-Negative (PPARg2-Neg) leukocyte and endothelial cell nuclei. PPARg2-Pos nuclei were 10-fold enriched for most adipocyte marker transcripts relative to PPARg2-Neg nuclei. PPARg2-Pos nuclei showed 2- to 50-fold higher levels of transcripts encoding most of the chromatin-remodeling factors assayed, which regulate the methylation of histones and DNA cytosine (e.g., DNMT1, TET1, TET2, KDM4A, KMT2C, SETDB1, PAXIP1, ARID1A, JMJD6, CARM1, and PRMT5). PPARg2-Pos nuclei were large with decondensed chromatin. TAB-seq demonstrated 5-hydroxymethylcytosine (5hmC) levels were remarkably dynamic in gene bodies of various classes of VAT nuclei, dropping 3.8-fold from the highest quintile of expressed genes to the lowest. In short, VAT-derived adipocytes appear to be more actively remodeling their chromatin than non-adipocytes.

DNA cytosine hydroxymethylation levels are distinct among non-overlapping classes of peripheral blood leukocytes

BACKGROUND

Peripheral blood leukocytes are the most commonly used surrogates to study epigenome-induced risk and epigenomic response to disease-related stress. We considered the hypothesis that the various classes of peripheral leukocytes differentially regulate the synthesis of 5-methylcytosine (5mCG) and its removal via Ten-Eleven Translocation (TET) dioxygenase catalyzed hydroxymethylation to 5-hydroxymethylcytosine (5hmCG), reflecting their responsiveness to environment. Although it is known that reductions in TET1 and/or TET2 activity lead to the over-proliferation of various leukocyte precursors in bone marrow and in development of chronic myelomonocytic leukemia and myeloproliferative neoplasms, the role of 5mCG hydroxymethylation in peripheral blood is less well studied.

RESULTS

We developed simplified protocols to rapidly and reiteratively isolate non-overlapping leukocyte populations from a single small sample of fresh or frozen whole blood. Among peripheral leukocyte types we found extreme variation in the levels of transcripts encoding proteins involved in cytosine methylation (DNMT1, 3A, 3B), the turnover of 5mC by demethylation (TET1, 2, 3), and DNA repair (GADD45A, B, G) and in the global and gene-region-specific levels of DNA 5hmCG (CD4+ T cells≫CD14+ monocytes>CD16+ neutrophils>CD19+ B cells>CD56+ NK cells>Siglec8+ eosinophils>CD8+ T cells).

CONCLUSIONS

Our data taken together suggest a potential hierarchy of responsiveness among classes of leukocytes with CD4+, CD8+ T cells and CD14+ monocytes being the most distinctly poised for a rapid methylome response to physiological stress and disease.

Isoproterenol Increases Uncoupling, Glycolysis, and Markers of Beiging in Mature 3T3-L1 Adipocytes

Beta-adrenergic activation stimulates uncoupling protein 1 (UCP1), enhancing metabolic rate. In vitro, most work has studied brown adipocytes, however, few have investigated more established adipocyte lines such as the murine 3T3-L1 line. To assess the effect of beta-adrenergic activation, mature 3T3-L1s were treated for 6 or 48 hours with or without isoproterenol (10 and 100 μM) following standard differentiation supplemented with thyroid hormone (T3; 1 nM). The highest dose of isoproterenol increased lipid content following 48 hours of treatment. This concentration enhanced UCP1 mRNA and protein expression. The increase in UCP1 following 48 hours of isoproterenol increased oxygen consumption rate. Further, coupling efficiency of the electron transport chain was disturbed and an enhancement of glycolytic rate was measured alongside this, indicating an attempt to meet the energy demands of the cell. Lastly, markers of beige adipocytes (protein content of CD137 and gene transcript of CITED1) were also found to be upregulated at 48 hours of isoproterenol treatment. This data indicates that mature 3T3-L1 adipocytes are responsive to isoproterenol and induce UCP1 expression and activity. Further, this finding provides a model for further pharmaceutical and nutraceutical investigation of UCP1 in 3T3-L1s.

A 72-hour high fat diet increases transcript levels of the neuropeptide galanin in the dorsal hippocampus of the rat

Background

Recent evidence identifies the hippocampus, a brain structure commonly associated with learning and memory, as key to the regulation of food intake and the development and consequences of obesity. Intake of a high fat diet (HFD) results in altered consumptive behavior, hippocampal damage, and cognitive deficits. While many studies report the effects of HFD after chronic consumption and in the instance of obesity, few examine the events that occur following acute HFD consumption. In this study, male rats were fed either a control diet (10% fat by kcal) or HFD (45% fat by kcal) for 72 h. At the end of the 72-h period, serum and tissues were collected and weighed. Brains were rapidly frozen or formalin-fixed in preparation for qRT-PCR or immunohistochemistry, respectively.

Results

Acute intake of HFD resulted in higher serum levels of leptin and cholesterol, with no significant changes in final body weight or adipose tissue mass. In the dorsal hippocampus, transcription of the neuroprotective peptide galanin was significantly upregulated along with a trend for an increase in brain-derived neurotrophic factor and histone deacetylase 2 in the rats fed HFD. In the ventral hippocampus, there was a significant increase in histone deacetylase 4 and a decrease in galanin receptor 1 in this group. Results from immunohistochemistry validate strong presence of the galanin peptide in the CA1/CA2 region of the dorsal hippocampus.

Conclusions

These results provide evidence for a distinct response in specific functional regions of the hippocampus following acute HFD intake.

A dietary phytochemical blend prevents liver damage associated with adipose tissue mobilization in ovariectomized rats

OBJECTIVE

Menopausal reduction in estrogen causes increased adipose accumulation, leading many to turn to dietary supplements to prevent and treat such changes. Enhanced adipose mobilization stimulated by some supplements can increase the risk of non-alcoholic fatty liver disease (NAFLD). Cytoprotective and anti-obesity compounds may prevent the lipotoxicity associated with mobilization.

METHODS

A phytochemical blend was tested in aged, ovariectomized rats. Rats were given the AIN-93M basal diet or a diet containing varying doses of phytochemicals with 2.4 IU/g vitamin D [diet 1: 1000 mg/kg genistein (G); diet 2: 500 mg/kg (G), 200 mg/kg resveratrol (R), and 1000 mg/kg quercetin (Q); diet 3: 1000 mg/kg (G), 400 mg/kg (R), and 2000 mg/kg (Q)].

RESULTS

Serum free fatty acids and hepatic triglycerides were elevated with diets 2 and 3. Despite this increase, the phytochemical blends did not increase apoptotic, cell repair, or remodeling gene expression. The highest phytochemical dose prevented increases in serum alanine aminotransferase.

CONCLUSIONS

Adverse hepatic effects secondary to ovariectomy were mitigated through the inclusion of a dietary phytochemical blend in aged ovariectomized rats. The use of such compounds may not only help with weight management and disease risk in menopausal women, but may also prevent the lipotoxicity in NAFLD.

Acute exposure to high-fat diets increases hepatic expression of genes related to cell repair and remodeling in female rats

High-fat diets (HFD) promote the development of both obesity and fatty liver disease through the up-regulation of hepatic lipogenesis. Insulin resistance, a hallmark of both conditions, causes dysfunctional fuel partitioning and increases in lipogenesis. Recent work has demonstrated that systemic insulin resistance occurs in as little as the first 72 hours of an HFD, suggesting the potential for hepatic disruption with HFD at this time point. The current study sought to determine differences in expression of lipogenic genes between sexes in 3-month-old male and female Long-Evans rats after 72 hours of a 40% HFD or a 17% fat (chow) diet. Owing to the response of estrogen on hepatic signaling, we hypothesized that a sexual dimorphic response would occur in the expression of lipogenic enzymes, inflammatory cytokines, apoptotic, and cell repair and remodeling genes. Both sexes consumed more energy when fed an HFD compared with their low fat-fed controls. However, only the males fed the HFD had a significant increase in body fat. Regardless of sex, HFD caused down-regulation of lipogenic and inflammatory genes. Interestingly, females fed an HFD had up-regulated expression of apoptotic and cell repair-related genes compared with the males. This may suggest that females are more responsive to the acute hepatic injury effects caused by HFDs. In summary, neither male nor female rats displayed disrupted hepatic metabolic pathways after 72 hours of the HFD treatment. In addition, female rats appear to have protection from increases in fat deposition, possibly due to increased caloric expenditure; male rats fed an HFD were less active, as demonstrated by distance traveled in their home cage.

Bone quality and strength are greater in growing male rats fed fructose compared with glucose

Optimization of peak bone mass during adolescence is important for osteoporosis prevention. Studies in rodents and humans have demonstrated the harmful effects of sugar intake on bone health. With the high levels of sucrose in the diets of adolescents, it is necessary to understand the influence of glucose and fructose on growing bones. This study compared the effects of dietary glucose and fructose on bone formation, microarchitecture, and strength. Because of the different metabolic effects of glucose and fructose, we hypothesized that their individual effects on bone would be different. Eighteen male Sprague-Dawley rats (age, 60 days) were randomly assigned to high-fructose (n = 9; 40% fructose, 10% glucose) or high-glucose diet (n = 9; 50% glucose) for 12 weeks. Bone measurements included histology and histomorphometry of trabecular bone in the distal femur and a 3-point bending test of the whole tibia. Whole liver mass and postprandial serum glucose, insulin, and triglycerides were used to assess differences in energy metabolism between the diets. There were no differences in food intake, body weight, or visceral adiposity between groups, but fructose consumption led to heavier livers (P = .001) and elevated serum triglycerides (P = .00). The distal femurs of fructose-fed rats had greater bone volume (bone volume/total volume; P = .03), lower bone surface (bone surface/bone volume; P = .02), and thicker trabeculae (trabecular thickness; P = .01). The tibias of the fructose-fed rats also withstood a greater maximum flexure load (P = .032). These results indicate that consumption of the high-fructose diet resulted in stronger bones with enhanced microarchitecture than consumption of the high-glucose diet.

Bioactive flavonoid p-hydroxycinnamic acid stimulates osteoblastogenesis and suppresses adipogenesis in bone marrow culture

The bioactive flavonoid p-hydroxycinnamic acid (HCA), which is an intermediate-metabolic substance in plants and fruits, is synthesized from tyrosine. The biological effect of HCA is poorly understood. Among cinnamic acid and its related compounds, HCA has a specific-anabolic effect on bone, being found to stimulate osteoblastogenesis and to inhibit osteoclastogenesis through the suppression of NF-κB signaling, thereby preventing bone loss. Bone marrow mesenchymal stem cells give rise to ostoblasts and adipocytes. HCA might therefore have effects on osteoblastogenesis and adipogenesis in bone marrow culture. This study demonstrates (1) that HCA has stimulatory effects on osteoblastogenesis and mineralization and suppressive effects on adipogenesis in mouse bone marrow culture and (2) that HCA depresses adipogenesis in mouse 3T3-L1 preadipocytes in vitro. Such effects of HCA might be involved in the differentiation of mesenchymal stem cells.

The Mediation of Hepatic Lipogenesis Through Estrogens

Estrogens have been shown to protect against various diseases and disastrous metabolic consequences of poor diets. Although a large body of research demonstrates estrogen's ability to control food intake, adipogenesis, and oxidative stress, research regarding the effects of estrogens on hepatic lipogenesis, steatosis, and non-alcoholic fatty liver disease is only now accumulating. Estrogen deficiency in both human and rodent models directly results in the upregulation of hepatic lipogenic signaling - in both serum and hepatic triglyceride content - which leads to the development of fatty liver. In all models, estrogen replacement completely reverses these outcomes. Similar to the endogenous estrogen hormone, plant-derived phytoestrogens also appear to have beneficial effects related to prevention of hepatic lipogenic signaling and steatosis in rodent models. Additionally, such compounds can completely overcome the hepatic consequences that result from estrogen deficiency. While published research strongly supports that estrogens, both endogenous and exogenous, can protect against hepatic lipogenic signaling that can contribute to the development of non-alcoholic fatty liver diseases and adverse weight gain, little research exists on elucidating the mechanism behind this protection. Various pathways have been suggested, including manipulation of both leptin and signal transducer and activator of transcription 3 (STAT3) signaling. However, the discovery of x-box protein 1 elicits the identification of another potential pathway through which estrogen may be working. While the supportive work is strong, further research is needed to determine the mechanism behind the protection by estrogens from hepatic lipogenesis and associated diseases.

Adenovirus 36, adiposity, and bone strength in late-adolescent females

Adenovirus 36 (Ad36) is the only adenovirus to date that has been linked with obesity in humans. Our previous studies in late-adolescent females suggest that excess weight in the form of fat mass is associated with lower cortical bone strength. The purpose of this study was to assess the relationship between Ad36-specific antibodies, adiposity, and bone strength in our sample of late-adolescent females. A cross-sectional study of 115 females aged 18 to 19 years was performed. Participants were classified according to adiposity by dual-energy X-ray absorptiometry (body fat percentage as normal-fat [ < 32% body fat; n = 93] or high-fat [ ≥ 32% body fat; n = 22]), and according to the presence of Ad36-specific neutralizing antibodies. Peripheral quantitative computed tomography measured bone parameters at the 4% (trabecular bone) and 20% (cortical bone) site, and muscle cross-sectional area (MCSA) at the 66% site, from the distal metaphyses of the radius and the tibia. Bone strength was determined from volumetric bone mineral density and bone geometry to calculate bone strength index (BSI; trabecular site) and polar strength-strain index (SSI; cortical site). After adjustment for MCSA and limb length, radial SSI was lower in Ad36+  versus Ad36- subjects from the high-fat group (p < 0.03), but not the normal-fat group. No significant differences were observed between groups in tibial SSI or BSI. These data support an association of adiposity and cortical bone strength at the radius with the presence of neutralizing antibodies to Ad36 in late-adolescent females.

Exogenous regucalcin suppresses osteoblastogenesis and stimulates adipogenesis in mouse bone marrow culture

Regucalcin plays a pivotal role in regulating intracellular calcium homeostasis and consequently has a profound effect on multiple intracellular signal transduction pathways. The regucalcin transgenic rat displays pronounced bone loss and hyperlipidemia. Consistent with these effects exogenous regucalcin has been shown to promote osteoclastogenesis in mouse bone marrow cultures and to suppress the differentiation and mineralization of MC3T3 osteoblast precursors. Regucalcin may induce hyperlipidemia in vivo by suppressing osteoblast differentiation and stimulating adipogenesis in bone marrow mesenchymal stem cells. The present study demonstrates that exogenous regucalcin suppresses differentiation to osteoblasts and stimulates adipogenesis in mouse bone marrow cell culture ex vivo. Moreover, exogenous regucalcin was found to enhance adipogenesis stimulated by insulin which is involved in the extracellular signal-related kinase pathway in 3T3-L1 adipocytes in vitro.

Influence of Dietary Conjugated Linoleic Acid and Fat Source on Body Fat and Apoptosis in Mice*

OBJECTIVE

To determine whether altered dietary essential fatty acid (linoleic and arachidonic acid) concentrations alter sensitivity to conjugated linoleic acid (CLA)-induced body fat loss or DNA fragmentation.

RESEARCH METHODS AND PROCEDURES

Mice were fed diets containing soy oil (control), coconut oil [essential fatty acid deficient (EFAD)], or fish oil (FO) for 42 days, and then diets were supplemented with a mixture of CLA isomers (0.5% of the diet) for 14 days. Body fat index, fat pad and liver weights, DNA fragmentation in adipose tissue, and fatty acid profiles of adipose tissue were determined.

RESULTS

The EFAD diet decreased (p < 0.05) linoleic and arachidonic acid in mouse adipose tissue but did not affect body fat. Dietary CLA caused a reduction (p < 0.05) in body fat. Mice fed the EFAD diet and then supplemented with CLA exhibited a greater reduction (p < 0.001) in body fat (20.21% vs. 6.94% in EFAD and EFAD + CLA-fed mice, respectively) compared with mice fed soy oil. Dietary FO decreased linoleic acid and increased arachidonic acid in mouse adipose tissue. Mice fed FO or CLA were leaner (p < 0.05) than control mice. FO + CLA-fed mice did not differ in body fat compared with FO-fed mice. Adipose tissue apoptosis was increased (p < 0.001) in CLA-supplemented mice and was not affected by fat source.

DISCUSSION

Reductions in linoleic acid concentration made mice more sensitive to CLA-induced body fat loss only when arachidonic acid concentrations were also reduced. Dietary essential fatty acids did not affect CLA-induced DNA fragmentation.

Green Tea Polyphenol Epigallocatechin Gallate Inhibits Adipogenesis and Induces Apoptosis in 3T3-L1 Adipocytes

OBJECTIVE

Green tea catechins have been shown to promote loss of body fat and to inhibit growth of many cancer cell types by inducing apoptosis. The objective of this study was to determine whether epigallocatechin gallate (EGCG), the primary green tea catechin, could act directly on adipocytes to inhibit adipogenesis and induce apoptosis.

RESEARCH METHODS AND PROCEDURES

Mouse 3T3-L1 preadipocytes and mature adipocytes were used. To test the effect of EGCG on viability, cells were incubated for 3, 6, 12, or 24 hours with 0, 50, 100, or 200 microM EGCG. Viability was quantitated by MTS assay. To determine the effect of EGCG on apoptosis, adipocytes were incubated for 24 hours with 0 to 200 microM EGCG, then stained with annexin V and propidium iodide and analyzed by laser scanning cytometry. Both preadipocytes and adipocytes were also analyzed for apoptosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. To determine the effect of EGCG on adipogenesis, maturing preadipocytes were incubated during the 6-day induction period with 0 to 200 microM EGCG, then stained with Oil-Red-O and analyzed for lipid content.

RESULTS

EGCG had no effect on either viability or apoptosis of preconfluent preadipocytes. EGCG also did not affect viability of mature adipocytes; however, EGCG increased apoptosis in mature adipocytes, as demonstrated by both laser scanning cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling assays. Furthermore, EGCG dose-dependently inhibited lipid accumulation in maturing preadipocytes.

DISCUSSION

These results demonstrate that EGCG can act directly to inhibit differentiation of preadipocytes and to induce apoptosis of mature adipocytes and, thus, could be an important adjunct in the treatment of obesity.

Central (ICV) leptin injection increases bone formation, bone mineral density, muscle mass, serum IGF-1, and the expression of osteogenic genes in leptin-deficient ob/ob mice

Both central and peripheral leptin administrations reduce body weight, food intake, and adiposity in ob/ob mice. In this study we compared effects of intracerebroventricular (ICV) and subcutaneous (SC) administration of leptin on bone metabolism in the appendicular and axial skeleton and adipose tissue gene expression and determined the effects of ICV leptin on bone marrow gene expression in ob/ob mice. In experiment 1, leptin (1.5 or 0.38 µg/d) or control was continuously injected ICV for 12 days. Gene expression analysis of femoral bone marrow stromal cells showed that expression of genes associated with osteogenesis was increased after ICV injection, whereas those associated with osteoclastogenesis, adipogenesis, and adipocyte lipid storage were decreased. In experiment 2, leptin was injected continuously ICV (0.0 or 1.5 µg/d) or SC (0.0 or 10 µg/d) for 12 days. In both experiments, regardless of mode of administration, leptin decreased body weight, food intake, and body fat and increased muscle mass, bone mineral density, bone mineral content, bone area, marrow adipocyte number, and mineral apposition rate. Serum insulin was decreased, whereas serum osteocalcin, insulin-like growth factor 1, osteoprotegerin, pyridinoline, and receptor activator of nuclear factor κB ligand concentrations were increased. In experiment 2, expression of genes in adipose tissue associated with apoptosis, lipid mobilization, insulin sensitivity, and thermogenesis was increased, whereas expression of genes associated with cell differentiation and maturation was decreased regardless of mode of administration. Thus ICV injection of leptin promotes expression of pro-osteogenic factors in bone marrow, leading to enhanced bone formation in ob/ob mice.

Preventing bone loss and weight gain with combinations of vitamin D and phytochemicals

Vitamin D and certain natural compounds have been shown to regulate both lipid metabolism and bone formation. Treatments that prevent or reverse age-related increase in bone marrow adiposity could both increase new bone formation and inhibit bone destruction. We tested the hypothesis that dietary supplementation with combinations of vitamin D and phytochemicals inhibits bone loss and decreases adiposity to a greater extent than control or vitamin D-alone diets. Aged ovariectomized female rats (12 months old, n=50, initial body weight=240 g) were given control (AIN-93M diet), vitamin D (2,400 IU/kg), or vitamin D plus resveratrol (16, 80, or 400 mg/kg of diet [low, medium, and high dose, respectively]), quercetin (80, 400, or 2,000 mg/kg of diet), and genistein (64, 256, or 1,040 mg/kg of diet) for 8 weeks. The high-dose treatment (vitamin D+400 mg/kg resveratrol+2,000 mg/kg quercetin+1,040 mg/kg genistein) reduced body weight gain (P<.05) and the fat pad weights (P<.05). This treatment also increased the serum concentration of insulin-like growth factor-1 (P<.05) and the bone mineral content of the femur. Micro-computed tomography and histomorphometric analyses indicated that the high-dose treatment prevented loss of trabecular bone (P<.05) and reduced marrow adipocytes (P<.001) and osteoclasts (P<.05) compared with the control and vitamin D alone (P<.05). We conclude that aged ovariectomized female rats supplemented with vitamin D combined with genistein, quercetin, and resveratrol had improved bone mineral density and reduced body weight gain and a significant decrease in bone marrow adipocytes. The synergistic effects of a combination of phytochemicals with vitamin D may be effective in reducing bone loss and weight gain after menopause.

Synergism between resveratrol and other phytochemicals: implications for obesity and osteoporosis

Resveratrol, a phytoalexin, has gained much attention recently due to its effects on sirtuins. While the anti-cancer properties of resveratrol have been extensively investigated, the anti-adipogenic and osteogenic effects of resveratrol are also gaining considerable interest. The finding that resveratrol supplementation mimics caloric restriction prompted researchers to study the effects of resveratrol on lipid metabolism. Mesenchymal stem cells are the precursors for both adipocytes and osteoblasts. In the aging population, differentiation to adipocytes dominates over the differentiation to osteoblasts in bone marrow, contributing to the increased tendency for fractures to occur in the elderly. Thus, an inverse relationship exists between adipocytes and osteoblasts in the bone marrow. Resveratrol acts on several molecular targets in adipocytes and osteoblasts leading to a decrease in adipocyte number and size and an increase in osteogenesis. Furthermore, resveratrol in combination with genistein and quercetin synergistically decreased adipogenesis in murine and human adipocytes. A recent in vivo study showed that phytochemicals including resveratrol in combination with vitamin D prevented weight gain and bone loss in a postmenopausal rat model. Therefore, combinations of resveratrol with other phytochemicals may lead to potential novel potent therapies for both obesity and osteoporosis.

Novel molecular targets for prevention of obesity and osteoporosis

Evidence from both epidemiological studies and basic research suggests that obesity and osteoporosis are interrelated. Though there is an increase in the prevalence of these disorders, a limited number of treatments are available, one of the reasons being the complexity of the pathways involved and difficulty in identifying a single molecular target. Due to adverse effects of pharmaceuticals, intake of herbal drugs by patients without a physician's recommendation is increasing globally. Lack of success with targeted monotherapy has encouraged scientists to determine whether combinations of phytochemicals that interfere with numerous cell-signaling pathways can be a more effective approach to treat complex diseases. For example, evidence is emerging that specific combinations of phytochemicals are far more effective than single compounds in decreasing adipogenesis and promoting bone formation. Since multiple pathways are dysfunctional in obesity and osteoporosis, an ideal approach for preventing and treating these diseases may be to use a combination of phytochemicals to address several targets simultaneously.

Effect of resveratrol on fat mobilization

Higher levels of body fat are associated with increased risk for development of numerous adverse health conditions. Phytochemicals are potential agents to inhibit differentiation of preadipocytes, stimulate lipolysis, and induce apoptosis of existing adipocytes, thereby reducing adipose tissue mass. Resveratrol decreased adipogenesis and viability in maturing preadipocytes; these effects were mediated not only through down-regulating adipocyte specific transcription factors and enzymes but also by genes that modulate mitochondrial function. Additionally, resveratrol increased lipolysis and reduced lipogenesis in mature adipocytes. In addition, combining resveratrol with other natural products produced synergistic activities from actions on multiple molecular targets in the adipocyte life cycle. Treatment of mice with resveratrol alone was shown to improve resistance to weight gain caused by a high-fat diet. Moreover, dietary supplementation of aged ovariectomized rats with a combination of resveratrol and vitamin D, quercetin, and genistein not only decreased weight gain but also inhibited bone loss. Combining several phytochemicals, including resveratrol, or using them as templates for synthesizing new drugs, provides a large potential for using phytochemicals to target adipocyte adipogenesis, apoptosis, and lipolysis.

Leptin modulated changes in adipose tissue protein expression in ob/ob mice

Comparative proteomic analyses were performed in adipose tissue of leptin-deficient ob/ob mice treated with leptin or control buffer in order to identify the protein expression changes as the potential targets of leptin. Mice were treated with either phosphate-buffered saline (control) or 10 µg/day leptin for 14 days via subcutaneous osmotic minipumps. Total protein from white adipose tissue was extracted and labeled with different fluorescent cyanine dyes for analysis by two-dimensional difference gel electrophoresis (DIGE). Spots that were differentially expressed and appeared to have sufficient material for mass spectrometry analysis were picked and digested with trypsin and subjected to MALDI-TOF MS for protein identification. Twelve functional protein groups were found differentially expressed in adipose tissue of leptin-treated vs. control ob/ob mice, including molecular chaperones and redox proteins such as calreticulin (CALR), protein disulfide isomerase-associated 3 (PDIA3), prohibitin (PHB), and peroxiredoxin-6 (PRDX6); cytoskeleton proteins such as β actin, desmin, and α-tubulin; and some other proteins. The mRNA levels of CALR, PDIA3, and PHB were measured by real-time reverse transcription-PCR and found to be upregulated (P < 0.05), consistent with the fold change in protein expression level. Our findings suggest that leptin's effects on lipid metabolism and apoptosis may be mediated in part by alterations in expression of molecular chaperones and redox proteins for regulating endoplasmic reticulum stress and cytoskeleton proteins for regulating mitochondrial morphology.

Bone and fat relationships in postadolescent black females: a pQCT study

Despite adolescent black females experiencing the highest rates of obesity, the effect of excess fat mass on bone structure and strength in this population is unknown. Our findings in postadolescent black females suggest that excess weight in the form of fat mass may adversely influence cortical bone structure and strength.

INTRODUCTION

Although adolescent obesity has been associated with reduced bone structure and strength in white females, this relationship has not been studied in adolescent black females, a population experiencing the highest rates of obesity. Our objective was to compare bone structure and strength between postadolescent black females with normal and high levels of adiposity.

METHODS

Black females with ≤ 32% body fat were classified as normal body fat (NF; n = 33, aged 19.3 ± 1.3 years); females exceeding this cutoff were classified as high body fat (HF; n = 15, aged 19.0 ± 1.1 years). Using peripheral quantitative computed tomography, tibial and radial bones were scanned at the 4% (trabecular) and 20% (cortical) sites from the distal metaphyses. Fat-free soft-tissue mass (FFST) and %body fat were assessed by dual-energy X-ray absorptiometry.

RESULTS

After controlling for either FFST or body weight, the HF vs. NF group had lower total cross-sectional area (CSA; 9-17%), cortical CSA (6-15%), and strength-strain index (SSI; 13-24%) at the cortical site of the tibia (all p < 0.05). At the cortical site of the radius, the HF vs. NF group had lower total CSA (14%, p = 0.03), cortical CSA (9%, p = 0.04), and SSI (15%, p = 0.07) after control for body weight. There were no group differences in either the FFST-adjusted cortical bone values at the radius or in the trabecular bone parameters (body weight- or FFST-adjusted) at the tibia and radius.

CONCLUSIONS

Consistent with our adiposity and bone data in late-adolescent white females, our findings in black females entering adulthood also suggest that obesity may adversely influence cortical bone strength.

Comparisons of trabecular and cortical bone in late adolescent black and white females

Few childhood studies have investigated racial differences in volumetric bone mineral density (vBMD), bone geometry, and bone strength indices measured by three-dimensional bone imaging. The purpose of this study was to compare trabecular and cortical bone parameters at the radius and tibia between late adolescent white and black females using peripheral quantitative computed tomography (QCT). White (n = 25) and black females (n = 25), 18-19 years of age, were pair-matched for age, height, and fat-free soft tissue mass. Peripheral QCT scans were obtained at the 4% (trabecular bone), 20% (cortical bone), and 66% [muscle cross-sectional area (CSA)] sites from the distal metaphyses. Bone strength was determined from vBMD and bone geometry to calculate bone strength index (BSI; trabecular site) and polar strength-strain index (SSI; cortical site). Radial SSI was not different between groups; however, blacks had greater radial BSI (P = 0.02) than whites. After adjustment for the longer forearm in blacks, the greater radial BSI in blacks no longer remained. At the tibia, blacks versus whites had greater bone strength at the trabecular and cortical bone sites (BSI, P = 0.03; SSI, P = 0.04, respectively). When controlling for differences in tibial length and muscle CSA, the higher estimates of bone strength persisted in blacks versus whites (BSI, P = 0.01; SSI, P = 0.02). Our data suggest that when differences in body size are considered, late adolescent black versus white females have a stronger bone profile, due to greater bone geometry and vBMD, at the trabecular and cortical regions of the tibia but not at the radius.

25-hydroxyvitamin D, insulin-like growth factor-I, and bone mineral accrual during growth

CONTEXT

The extent to which 25-hydroxyvitamin D [25(OH)D] and IGF-I influence bone mineral content (BMC) accrual from early to mid-puberty is unclear. OBJECTIVE, SETTING, AND PARTICIPANTS: This study sought to determine relationships among 25(OH)D, IGF-I, and BMC in community-dwelling prepubertal females (n = 76; aged 4-8 yr at baseline) over a period of up to 9 yr.

DESIGN

The hypothesis that changes in IGF-I vs. 25(OH)D are more strongly associated with BMC accrual was formulated after data collection. 25(OH)D and IGF-I were log-transformed and further adjusted using two-way ANOVA for differences in season and race. Linear mixed modeling (including a random subject-specific intercept and a random subject-specific slope on age) was employed to analyze the proportion of variance the transformed 25(OH)D and IGF-I variables explained for the bone outcomes.

RESULTS

IGF-I was more strongly associated with BMC accrual than 25(OH)D at the total body (R(2) = 0.874 vs. 0.809), proximal femur (R(2) = 0.847 vs. 0.771), radius (R(2) = 0.812 vs. 0.759), and lumbar spine (R(2) = 0.759 vs. 0.698). The rate of BMC accrual was positively associated with changes in IGF-I but negatively associated with 25(OH)D. When IGF-I and 25(OH)D were included in the same regression equation, 25(OH)D did not have a significant predictive effect on BMC accrual above and beyond that of IGF-I.

CONCLUSIONS

These prospective data in early adolescent females indicate that both 25(OH)D and IGF-I have a significant impact on bone mineral accrual; however, the positive association of IGF-I and BMC accrual is greater than the negative association of 25(OH)D and BMC accrual.

Phytochemicals and adipogenesis

Obesity is an increasing health problem all over the world. Phytochemicals are potential agents to inhibit differentiation of preadipocytes, stimulate lipolysis, and induce apoptosis of existing adipocytes, thereby reducing the amount of adipose tissue. Flavonoids and stilbenoids represent the most researched groups of phytochemicals with regards to their effect on adipogenesis, but there are also a number of in vitro and in vivo studies with phenolic acids, alkaloids, and vitamins, as well as other plant compounds. Although phytochemicals like epigallocatechin-3-gallate, genistein, and resveratrol reduce lipid accumulation and induce adipocyte apoptosis in vitro and reduce body weight and adipose tissues mass in animal models of diet-induced obesity, well-conducted clinical trials are lacking. Pharmacological doses are often used in vitro and when applied in physiological doses in animals or humans, the phytochemicals are often ineffective in affecting adipogenesis. However, by combining several phytochemicals or using them as templates for synthesizing new drugs, there is a large potential in targeting adipogenesis using phytochemicals.

Hepatic gene expression profiling reveals key pathways involved in leptin-mediated weight loss in ob/ob mice

Background

Leptin, a cytokine-like protein, plays an important role in the regulation of body weight through inhibition of food intake and stimulation of energy expenditure. Leptin circulates in blood and acts on the brain, which sends downstream signals to regulate body weight. Leptin therapy has been successful in treating leptin deficient obese patients. However, high levels of leptin have been observed in more common forms of obesity indicating a state of leptin resistance which limits the application of leptin in the treatment of obesity. If the central effect of leptin could be by-passed and genes which respond to leptin treatment could be regulated directly, new therapeutic targets for the treatment of obesity may be possible. The purpose of this study was to identify genes and subsequent pathways correlated with leptin-mediated weight loss.

Methodology/Principal Findings

We utilized microarray technology to compare hepatic gene expression changes after two types of leptin administration: one involving a direct stimulatory effect when administered peripherally (subcutaneous: SQ) and another that is indirect, involving a hypothalamic relay that suppresses food intake when leptin is administered centrally (intracerebroventricular: ICV). We identified 214 genes that correlate with leptin mediated weight loss. Several biological processes such as mitochondrial metabolic pathways, lipid metabolic and catabolic processes, lipid biosynthetic processes, carboxylic acid metabolic processes, iron ion binding and glutathione S-transferases were downregulated after leptin administration. In contrast, genes involved in the immune system inflammatory response and lysosomal activity were found to be upregulated. Among the cellular compartments mitochondrion (32 genes), endoplasmic reticulum (22 genes) and vacuole (8 genes) were significantly over represented.

Conclusions/Significance

In this study we have identified key molecular pathways and downstream genes which respond to leptin treatment and are involved in leptin-mediated weight loss. Many of these genes have previously been shown to be associated with obesity; however, we have also identified a number of other novel target genes. Further investigation will be required to assess the possible use of these genes and their associated protein products as therapeutic targets for the treatment of obesity.

Maternal high fat feeding and gestational dietary restriction: effects on offspring body weight, food intake and hypothalamic gene expression over three generations in mice

Excessive gestational weight gain and maternal obesity have both been associated with increased incidence of obesity and metabolic disorder in offspring in both humans and animal models. The objectives of this study were to determine (1) whether mild gestational food restriction during the third trimester (GFR) would alter food intake and growth parameters of offspring, (2) whether effects of GFR depended on diet (high fat [HF] vs chow), (3) whether effects of excessive gestational weight gain (WG) would become magnified across generations, and (4) whether diet and GFR would alter hypothalamic gene expression in adult offspring. Three generations of female C57BL/6 mice were fed chow or HF diet, mated at 11 weeks of age and assigned to ad libitum feeding or 25% GFR. Offspring were fed the same diet as their mothers. Results showed (1) maternal gestational WG was positively correlated with offspring WG. (2) HF offspring weighed less (p<0.01) at weaning (WWT) but gained more during the 8 weeks after weaning than chow-fed offspring (p<0.05), resulting in higher final body weights (BW) (p<0.01). (3) HF males from GFR mothers had higher WWT (p<0.05), but subsequent WG and final BW were less (p<0.05) compared to males from ad lib mothers. (4) In the HF group, GFR also resulted in decreased FI (p<0.05) and FE (p<0.07) in offspring, compared to offspring from ad lib mothers. (5) In generation 3, hypothalamic expression of tyrosine hydroxylase was lower in HF males from GFR mothers compared to HF males from ad lib mothers (p<0.05). In conclusion, gender and maternal GFR had independent effects on growth and FI, and hypothalamic gene expression was dependent on both gender and maternal GFR in HF offspring. Even mild food restriction of obese mothers during pregnancy may have beneficial effects in reducing the risk or degree of obesity in offspring.

Central leptin versus ghrelin: effects on bone marrow adiposity and gene expression

This study compared the central effects of ghrelin and leptin on body and bone marrow adiposity and gene expression in adipose tissue and bone marrow. Male Sprague-Dawley rats were injected intracerebroventricular (ICV) twice daily with control, 66 ng ghrelin (G66), 330 ng ghrelin (G330), or 5 μg leptin (L5) for 5 days. Food intake (FI) and body weight (BW) were measured daily. Gene expression in adipose tissue and bone marrow was assessed using RT-PCR. Leptin reduced FI (P < 0.05) and BW (P < 0.05), whereas ghrelin increased BW (P < 0.05) without affecting FI. Leptin decreased fat pad weights, whereas ghrelin (G330) increased fat pad weights (P < 0.05). In epididymal adipose tissue, leptin increased expression of lipolysis marker ADRB2 and thermogenesis marker MFN2 and decreased expression of adipogenic markers, FASN, SLC2A4, and SCD1, whereas ghrelin increased expression of FASN and SCD1. Leptin decreased bone marrow adipocyte size and number; however, ghrelin had no effect on these parameters. In whole bone marrow, leptin decreased expression of FASN and SCD1 and increased expression of DLK1, whereas ghrelin (G330) decreased expression of COL1A1. Thus, leptin induces similar changes in bone marrow and adipose tissue gene expression, reflecting the decreased adiposity in both compartments.

Anti-obesity effects of xanthohumol plus guggulsterone in 3T3-L1 adipocytes

Xanthohumol (XN) and guggulsterone (GS) have each been shown to inhibit adipogenesis and induce apoptosis in adipocytes. In the present study effects of the combination of XN + GS on 3T3-L1 adipocyte apoptosis and adipogenesis were investigated. Mature adipocytes were treated with XN and GS individually and in combination. XN and GS individually decreased cell viability, but XN + GS caused an enhanced decrease in viability and potentiated induction of apoptosis. Likewise, XN + GS caused a potentiated increase in caspase-3/7 activation, whereas neither of the compounds showed any effect individually. In addition, western blot analysis revealed that XN + GS increased Bax expression and decreased Bcl-2 expression, whereas individual compounds did not show any significant effect. XN and GS both decreased lipid accumulation. Individually, XN at 1.5 microM and GS at 3.12 microM decreased lipid accumulation by 26 +/- 4.5% (P < .001) each, whereas XN1.5 + GS3.12 decreased lipid accumulation by 78.2 +/- 1.8% (P < .001). Moreover, expression of the adipocyte-specific proteins was down-regulated with XN1.5 + GS3.12, but no effect was observed with the individual compounds. Finally, XN + GS caused an enhanced stimulation of lipolysis. Thus, combination of XN and GS is more potent in exerting anti-obesity effects than additive effects of the individual compounds.

Resveratrol induces apoptosis and inhibits adipogenesis in 3T3-L1 adipocytes

Resveratrol, a phytoallexin, has recently been reported to slow aging by acting as a sirtuin activator. Resveratrol also has a wide range of pharmacological effects on adipocytes. In this study, we investigated the effects of resveratrol on adipogenesis and apoptosis using 3T3-L1 cells. In mature adipocytes, 100 and 200 microM resveratrol decreased cell viability dose-dependently by 23 +/- 2.7%, and 75.3 +/- 2.8% (p < 0.0001), respectively, after 48 h treatment, and 100 microM resveratrol increased apoptosis by 76 +/- 8.7% (p < 0.0001). Resveratrol at 25 and 50 microM decreased lipid accumulation in maturing preadipocytes significantly by 43 +/- 1.27% and 94.3 +/- 0.3% (p < 0.0001) and decreased cell viability by 25 +/- 1.3% and 70.4 +/- 1.6% (p < 0.0001), respectively. In order to understand the anti-adipogenic effects of resveratrol, maturing 3T3-L1 preadipocytes were treated with 25 microM resveratrol and the change in the expression of several adipogenic transcription factors and enzymes was investigated using real-time RT-PCR. Resveratrol down-regulated the expression of PPAR gamma, C/EBP alpha, SREBP-1c, FAS, HSL, LPL and up-regulated the expression of genes regulating mitochondrial activity (SIRT3, UCP1 and Mfn2). These results indicate that resveratrol may alter fat mass by directly affecting cell viability and adipogenesis in maturing preadipocytes and inducing apoptosis in adipocytes and thus may have applications for the treatment of obesity.

Regulation of adipogenesis by medium-chain fatty acids in the absence of hormonal cocktail

We report here that octanoate and decanoate, 8-carbon and 10-carbon medium-chain fatty acids (MCFA), decreased adipogenesis in 3T3-L1 preadipocytes when treated with standard hormonal cocktail, but increased adipogenesis in a dose-dependent manner (with decanoate being more effective) when treated with basal media. Addition of dexamethasone to basal medium with either octanoate or decanoate further increased adipogenesis. In order to understand the adipogenic effects of MCFA in the absence of standard hormonal cocktail, postconfluent 3T3-L1 preadipocytes were treated with octanoate or decanoate, and the change in the expression of several adipogenic transcription factors and enzymes was investigated using real-time RT-PCR. Octanoate and decanoate up-regulated the mRNA expression of peroxisome-proliferator-activated receptor (PPAR) gamma, CCAAT/enhancer-binding protein (C/EBP) alpha, fatty-acid-binding protein, sterol-regulatory element binding protein 1c, lipoprotein lipase and hormone-sensitive lipase, and the protein expression of PPARgamma and C/EBPalpha, with decanoate being more effective. Moreover, the PPARgamma antagonist GW9662 inhibited MCFA-induced lipid accumulation by about 50%. Decanoate and octanoate, to a lesser degree, increased lipid accumulation, which was associated with an increase in glycerol-3-phosphate dehydrogenase activity. These results show that octanoate and decanoate may stimulate differentiation of preadipocytes, at least in part, by their influence on the expression of PPARgamma and other adipocyte-specific factors.

Effects of recombinant bovine somatotropin (rbST) and season on plasma and milk insulin-like growth factors I (IGF-I) and II (IGF-II) in lactating dairy cows

During two studies, effects of recombinant bovine somatotropin (rbST) on plasma and milk IGF's in cows adapted to summer (S; 12 cows) or winter (W; 12 cows) conditions were evaluated. Each study consisted of on-farm periods (30 days) followed by climatology chamber periods (CC; 30 days). Cows were given daily injections of rbST, Sometribove, USAN (25mg/day; 6 cows each study) or saline (control; 6 cows each study). During on-farm periods, blood and milk (am and pm) samples were collected once weekly. During CC periods, blood samples were collected every 2 days and milk samples (am and pm) were collected daily. Plasma IGF-I and IGF-II were increased in cows treated with rbST. A pronounced seasonal pattern in basal and rbST-stimulated plasma IGF-I but not IGF-II was detected. Higher basal and rbST-stimulated plasma IGF-I concentrations in S occurred despite large decreases in feed intake and energy balance. Milk IGF-I and IGF-II was not affected by rbST treatment or season. Although milk IGF-I and IGF-II concentrations were unaffected by rbST treatment, total IGF-output increased due to increased milk yield. The observed seasonal patterns in plasma IGF-I may be indicative of seasonal differences in the coupling of the somatotropin-IGF axis. In particular, we failed to detect an uncoupling of the somatotropin-IGF-I axis in S despite an induced negative energy balance during thermal stress.

Enhanced effects of xanthohumol plus honokiol on apoptosis in 3T3-L1 adipocytes

OBJECTIVE

To study the effects of xanthohumol (XN), a flavonoid found in hops (Humulus lupulus) and honokiol (HK), a lignan isolated from Magnolia officinalis, alone and in combination, on apoptotic signaling in 3T3-L1 adipocytes.

METHODS AND PROCEDURES

3T3-L1 mature adipocytes were incubated with various concentrations of XN and HK alone and in combination. Viability and apoptosis were quantified using an MTS-based cell viability assay and single-stranded DNA assay, respectively. Expression of apoptosis related proteins including cleaved poly(ADP-ribose) polymerase (PARP), cytochrome c, Bcl-2, caspase-3/7, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Akt was analyzed by western blotting.

RESULTS

Combinations of XN and HK significantly decreased viability and induced apoptosis in a dose-dependent manner and more than the additive responses to XN and HK alone. Western blot analysis showed an increase in cleaved PARP and cytochrome c release and decrease in expression of Bcl-2 protein by XN plus HK, whereas XN and HK individually had no effect. Furthermore, the combination of XN and HK activated PTEN and inactivated Akt by decreasing levels of phosphorylated PTEN and phosphorylated Akt.

DISCUSSION

We demonstrated that although XN and HK showed little or no effect as individual compounds, in combination (XN plus HK) they showed enhanced activity in inducing apoptosis via the cytochrome c/caspase-3/PARP and PTEN/Akt pathways in 3T3-L1 adipocytes.

Adipose tissue gene expression profiles in ob/ob mice treated with leptin

Leptin plays a critical role in regulating body weight, lipid metabolism, apoptosis and microvasculature of adipose tissue. To explore multiple signaling pathways of leptin action on adipose tissue, real-time PCR utilizing TaqMan low-density arrays was performed to compare mRNA expression in adipose tissue of ob/ob mice treated with vehicle or leptin (2.5 microg/d or 10 microg/d) for 14 days via subcutaneous osmotic minipumps. Of the 24 target genes selected for characterization, many were differentially expressed between control ob/ob mice and leptin-treated ob/ob mice. Increases in mRNA expression were found for hormone sensitive lipase (HSL), uncoupling protein 2 (UCP2), adrenergic receptor 3 (ADR3), mitofusin 2 (Mfn2), sirtuin 3 (Sirt3), transcription factor sterol regulatory element binding factor 1 (SREBF1), Bcl-2, Bax, Caspase 3, tumor necrosis factor alpha (TNFalpha), adiponectin and angiopoietin 2 (Ang-2). Decreases in expression were found for stearoyl-coenzyme A desaturase 1 (SCD1), fatty acid synthase (FAS), and retinol binding protein 4 (RBP4). There were no changes in expression of transcription factors involved in adipocyte differentiation (C/EBPalpha, PPARalpha, and PPARgamma). These results confirm that alterations in the expression of specific adipose tissue genes including those associated with the promotion of lipid mobilization, energy dissipation, and apoptosis may mediate leptin-induced fat loss in ob/ob mice.

CART deficiency increases body weight but does not alter bone strength

The regulation of bone metabolism mediated by leptin is a complex process that is not clearly understood. Recent studies suggest that CART (cocaine-amphetamine related transcript) is a significant neuronal co-factor when combined with leptin. CART deficiency is thought to result in low trabecular bone mass, but since leptin exerts contrasting effects on trabecular and cortical bone it is possible that cortical bone may not respond to the absence of CART signaling in the same manner as trabecular bone. We tested the hypothesis that CART deficiency decreases cortical bone mass, density, and strength by examining femora of adult wild-type mice (CART(+/+)) and CART-deficient mice (CART(-/-)). DEXA densitometry (PIXImus system) was used to measure whole-bone mineral content (BMC) and mineral density (BMD) from right femora, and pQCT used to calculate densitometric and geometric parameters from the femur midshaft. Femora were also tested in three-point bending, and sections of the tibia analyzed histologically to determine bone marrow adipocyte density (N.At./M.Ar) and endocortical osteoclast number (N.Oc/B.Pm). The control mice weighed less than the mice lacking CART (P<0.001), but mechanical testing data showed no differences (p>0.05) in ultimate force, energy to fracture, stiffness, or intrinsic properties such as ultimate stress, ultimate strain, or modulus. CART-deficient mice did not differ from normal controls in whole-femur BMC (p=0.09), BMD (p=0.19), midshaft cortical bone thickness (p=0.67), midshaft cortical bone area (p=0.59) or N.Oc/B.Pm (p=0.94), although CART deficiency was associated with a three-fold increase in bone marrow adipocyte density (p<0.001). Our data suggest that while the central, neuroendocrine regulation of bone mass via CART signaling may have effects on trabecular mass, absence of CART expression does not significantly alter cortical bone geometry, density, or strength.

Enhanced inhibition of adipogenesis and induction of apoptosis in 3T3-L1 adipocytes with combinations of resveratrol and quercetin

Certain flavonoids have been shown to have specific effects on biochemical and metabolic functions of adipocytes. In this study, we investigated the effects of combinations of resveratrol and quercetin on adipogenesis and apoptosis in 3T3-L1 cells. In maturing preadipocytes resveratrol and quercetin at 25 microM individually suppressed intracellular lipid accumulation by 9.4+/-3.9% (p<0.01) and 15.9+/-2.5%, respectively, (p<0.001). The combination of resveratrol and quercetin at the same dose, however, decreased lipid accumulation by 68.6+/-0.7% (p<0.001). In addition, combinations of resveratrol and quercetin at 25 microM significantly decreased the expression of peroxisome proliferators-activated receptor gamma (PPAR gamma) and CCAAT/enhancer-binding protein (C/EBP)alpha, both of which act as key transcription factors. In mature adipocytes resveratrol and quercetin at 100 microM individually decreased viability by 18.1+/-0.6% (p<0.001) and 15.8+/-1% (p<0.001) and increased apoptosis (100 microM) by 120.5+/-8.3% (p<0.001) and 85.3+/-10% (p<0.001) at 48 h, respectively. Combinations of resveratrol and quercetin further decreased viability (73.5+/-0.9%, p<0.001) and increased apoptosis (310.3+/-9.6%, p<0.001) more than single compounds alone. The combination of resveratrol and quercetin at 100 muM increased release of cytochrome c from mitochondria to cytosol and decreased ERK 1/2 phosphorylation. Taken together, our data indicate that combinations of resveratrol and quercetin can exert potential anti-obesity effects by inhibiting differentiation of preadipocytes and inducing apoptosis of mature adipocytes.