Retromer revisited: Evolving roles for retromer in endosomal sorting.

The highly conserved retromer complex has been linked to cargo retrieval from endosomes to the trans-Golgi network. In this issue, Kvainickas et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201702137) and Simonetti et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201703015) fundamentally question the current retromer model and demonstrate that in mammalian cells, the individual retromer subcomplexes have functionally diverged to organize multiple distinct sorting pathways.

Adiponectin administration prevents weight gain and glycemic profile changes in diet-induced obese immune deficient Rag1-/- mice lacking mature lymphocytes.

BACKGROUND: Obesity is associated with chronic low-grade inflammation leading to insulin resistance and diabetes. Adiponectin is an adipokine that regulates inflammatory responses. The aim of our study was to investigate whether any effects of adiponectin against obesity and insulin-resistance may depend on the adaptive immune system. METHODS: We treated high-fat-diet fed Rag1-/- mice lacking mature lymphocytes with adiponectin over 7weeks and investigated alterations in their metabolic outcome and inflammatory state. RESULTS: Adiponectin protects from weight gain despite a small compensatory stimulation of energy intake in mice lacking an adaptive immune system. Additionally, adiponectin protects from dysglycemia. Minor alterations in the macrophage phenotype, but not in the circulating cytokine levels, may contribute to the protective role of adiponectin against hyperglycemia and diabetes. CONCLUSION: Adiponectin or agents increasing adiponectin may be a promising therapeutic option against obesity and hyperglycemia in immune-deficient populations.

NECAP2 controls clathrin coat recruitment to early endosomes for fast endocytic recycling.

Endocytic recycling returns receptors to the plasma membrane following internalization and is essential to maintain receptor levels on the cell surface, re-sensitize cells to extracellular ligands and for continued nutrient uptake. Yet, the protein machineries and mechanisms that drive endocytic recycling remain ill-defined. Here, we establish that NECAP2 regulates the endocytic recycling of EGFR and transferrin receptor. Our analysis of the recycling dynamics revealed that NECAP2 functions in the fast recycling pathway that directly returns cargo from early endosomes to the cell surface. In contrast, NECAP2 does not regulate the clathrin-mediated endocytosis of these cargos, the degradation of EGFR or the recycling of transferrin along the slow, Rab11-dependent recycling pathway. We show that protein knockdown of NECAP2 leads to enlarged early endosomes and causes the loss of the clathrin adapter AP-1 from the organelle. Through structure-function analysis, we define the protein-binding interfaces in NECAP2 that are crucial for AP-1 recruitment to early endosomes. Together, our data identify NECAP2 as a pathway-specific regulator of clathrin coat formation on early endosomes for fast endocytic recycling.

Down-regulation of malignant potential by alpha linolenic acid in human and mouse colon cancer cells.

Omega-3 fatty acids (also called ω-3 fatty acis or n-3 fatty acid) are polyunsaturated fatty acids (PUFAs) with a double bond (C=C) at the third carbon atom from the end of the carbon chain. Numerous test tube and animal studies have shown that omega-3 fatty acids may prevent or inhibit the growth of cancers, suggesting that omega-3 fatty acids are important in cancer physiology. Alpha-linolenic acid (ALA) is one of an essential omega-3 fatty acid and organic compound found in seeds (chia and flaxseed), nuts (notably walnuts), and many common vegetable oils. ALA has also been shown to down-regulate cell proliferation of prostate, breast, and bladder cancer cells. However, direct evidence that ALA suppresses to the development of colon cancer has not been studied. Also, no previous studies have evaluated whether ALA may regulate malignant potential (adhesion, invasion and colony formation) in colon cancer cells. In order to address the questions above, we conducted in vitro studies and evaluated whether ALA may down-regulate malignant potential in human (HT29 and HCT116) and mouse (MCA38) colon cancer cell lines. We observed that treatment with 1-5 mM of ALA inhibits cell proliferation, adhesion and invasion in both human and mouse colon cancer cell lines. Interestingly, we observed that ALA did not decrease total colony numbers when compared to control. By contrast, we found that size of colony was significantly changed by ALA treatment when compared to control in all colon cancer cell lines. We suggest that our data enhance our current knowledge of ALA's mechanism and provide crucial information to further the development of new therapies for the management or chemoprevention of colon cancer.

Circulating fetuin-A levels are not affected by short and long-term energy deprivation and/or by leptin administration.

OBJECTIVE: Fetuin-A may mediate cross-talk between the liver and adipose tissue. We studied the physiologic regulation of fetuin-A and explored its potential regulation by leptin. DESIGN AND METHODS: Fetuin-A levels were measured in three interventional studies as well as in in vitro experiments. Study 1: 15 lean subjects received placebo or physiologic replacement-dose recombinant human leptin (metreleptin) following short term complete caloric deprivation to induce severe hypoleptinemia; Study 2: 7 women with relative leptin deficiency due to strenuous exercise or low weight received 3 months of metreleptin; Study 3: 17 women with relative leptin deficiency were randomized to receive metreleptin or placebo over 9 months. In study 4 human hepatoma Hep G2 cells were treated with leptin. Fetuin-A mRNA expression and secretion were measured. RESULTS: Complete caloric deprivation significantly decreased leptin but had no effect on fetuin-A levels. Normalizing leptin levels with metreleptin in hypoleptinemic subjects had no effect on circulating fetuin-A levels. Leptin treatment had no effect on fetuin-A mRNA expression and secretion in vitro. CONCLUSIONS: Circulating fetuin-A levels are not affected by short and long-term energy deprivation. Furthermore, both in vivo and in vitro experiments confirm that fetuin-A is not regulated by leptin.

Chemerin levels as predictor of acute coronary events: a case-control study nested within the veterans affairs normative aging study.

OBJECTIVE: Chemerin is a recently identified adipocytokine that has been positively correlated with the presence and severity of coronary artery disease (CAD). However, no studies have examined circulating chemerin levels as a predictor of acute coronary syndrome (ACS). The purpose of this study is to evaluate whether chemerin levels predict the onset of ACS. MATERIALS/METHODS: We studied 90 men whose serum had been collected at least 2 years before the development of ACS, and 162 controls matched with the cases in a 1:2 fashion for age and year of collection. The mean age of the cohort was 66.3±9.6 years (range 34-84 years). Serum chemerin levels were measured with a commercially available enzyme-linked immunosorbent assay. RESULTS: Age was positively associated with chemerin levels (r=0.39, p<0.001). Logistic regression analysis, adjusting for years since blood collection, demonstrated a null association between chemerin levels and the odds ratio for development of ACS (OR: 0.99, 95% CI [0.99-1.001]). This association remained null after adjusting for age (OR: 0.99 95% CI [0.99-1.001]). CONCLUSIONS: Although cross-sectional and case-control studies suggest a positive association between chemerin levels and CAD, we demonstrate that chemerin levels do not predict the development of ACS.

Circulating alanine transaminase (ALT) and γ-glutamyl transferase (GGT), but not fetuin-A, are associated with metabolic risk factors, at baseline and at two-year follow-up: the prospective Cyprus Metabolism Study.

OBJECTIVE: To comparatively evaluate traditional liver tests and fetuin A as predictors of cardiometabolic risk, we studied associations between serum alanine transaminase (ALT), γ-glutamyl transferase (GGT), aspartate aminotransferase (AST) and fetuin-A and anthropometric, metabolic, and cardiovascular parameters cross-sectionally at baseline, and prospectively, after 2-years of follow-up. RESEARCH DESIGN AND METHODS: 616 randomly enrolled young healthy participants in the Cyprus Metabolism Study, including all 93 subjects who participated in the follow-up study 2 years after baseline assessment, were included in this study. RESULTS: In the cross-sectional study, serum ALT and GGT were strongly correlated with anthropometric, cardiovascular, and metabolic variables, while serum AST was only correlated with waist circumference and waist-to-hip ratio. Fetuin-A was correlated with anthropometric variables, systolic blood pressure (SBP), insulin, and homeostasis model of assessment-insulin resistance (HOMA-IR) in the unadjusted model. In the fully adjusted model, both serum ALT and GGT levels remained positively correlated with total and low-density lipoprotein (LDL) cholesterol. GGT levels also remained correlated with triglycerides. ALT levels remained strongly positively correlated with insulin (r=0.17, p<.0001) and HOMA-IR (r=0.16, p=0.0001). Serum fetuin-A levels were no longer significantly correlated with any variables. Prospectively, ALT and GGT were predictors of anthropometric variables and LDL cholesterol, while baseline levels of AST and fetuin-A were not predictors of any variables at 2-year follow-up. CONCLUSIONS: We confirmed associations of ALT and GGT levels but failed to demonstrate an independent association between fetuin-A and cardiometabolic risk factors in young healthy men. Traditional liver tests (LFTs) are thus better than fetuin-A predictors of metabolic risk factors cross-sectionally and prospectively in young healthy adults.

Irisin mRNA and circulating levels in relation to other myokines in healthy and morbidly obese humans.

OBJECTIVE: Skeletal muscle is considered to be an endocrine organ that secretes a number of myokines including follistatin (FST), myostatin (MSTN), activin A, and the newly identified irisin. Irisin's biology and function exhibit similarities with the functions of the FST-MSTN-activin A axis. It remains unknown whether there is any interplay among these molecules. The aim of this study is to examine potential associations of irisin with the FST, MSTN, and activin A axis. METHODS: Two observational studies were performed to evaluate the associations of irisin with the other three peptides. Study A included 150 healthy males aged 18.48±0.16 years with BMI 23.18±3.75 kg/m(2). Fasting serum samples were used to measure the levels of the molecules of interest. Study B included 14 morbidly obese individuals, candidates for bariatric surgery, aged 53.14±8.93 years with BMI 50.18±10.63 kg/m(2). Blood samples were obtained after an overnight fast. Eight out of the 14 participants consented to an optional thigh biopsy during their bariatric surgery. Using the above blood and tissue samples, we measured circulating levels and muscle mRNA of irisin, FST, MSTN, and activin A. RESULTS: We report that FNDC5 mRNA in muscle is positively correlated with FST mRNA expression in morbidly obese subjects (ρ=0.93, P<0.001). We also found that circulating irisin is positively correlated with FST circulating levels among lean subjects (ρ=0.17, P=0.05) while this association was suggestive among the obese (ρ=0.56, P=0.07). CONCLUSION: The newly identified myokine irisin may be positively associated with FST at both the mRNA and circulating protein level.

Chemerin is expressed mainly in pancreas and liver, is regulated by energy deprivation, and lacks day/night variation in humans.

OBJECTIVE: Chemerin is an adipocyte-secreted hormone and has recently been associated with obesity and the metabolic syndrome. Although studies in rodents have outlined the aspects of chemerin's function and expression, its physiology and expression patterns are still to be elucidated in humans. METHODS: To evaluate for any day/night variation in chemerin secretion, we analyzed hourly serum samples from six females in the fed state. To examine whether energy deprivation affects chemerin levels, and whether this could be mediated through leptin, we analyzed samples from the same subjects in the fasting state while administering either placebo or leptin. To evaluate for any potential dose-effect relationship between leptin and chemerin, we administered increasing metreleptin doses to five females. A tissue array was used to study the expression of chemerin in different human tissues. Ex vivo treatment of human fat explants from three subjects with leptin was carried out to evaluate for any direct effect of leptin on adipocyte chemerin secretion. RESULTS: Chemerin does not display a day/night variation, while acute energy deprivation resulted in a significant drop in circulating chemerin levels by ∼42%. The latter was unaltered by metreleptin administration, and leptin administration did not affect the secretion of chemerin by human adipose tissue studied ex vivo. Chemerin was expressed primarily in the pancreas and liver. Chemerin receptor showed increased expression in the lymph nodes and the spleen. CONCLUSIONS: We outline for the first time chemerin expression and physiology in humans, which are different from those in mice.

GLP-1 promotes angiogenesis in human endothelial cells in a dose-dependent manner, through the Akt, Src and PKC pathways.

INTRODUCTION: Novel anti-diabetic medications that mimic or augment the physiological actions of GLP-1 improve cardiovascular risk factors in diabetics and GLP-1 has been proposed to have a beneficial role in the cardiovascular system. GLP-1 may have a direct cardioprotective role by decreasing infarct size and protecting from ischemia-reperfusion injury while prolonging survival in rodent models. The mechanisms underlying these observations remain largely unknown. In vitro studies suggest that GLP-1 may promote endothelial cell proliferation, but no study to date has evaluated a potential direct effect of GLP-1 on angiogenesis. SPECIFIC AIM: To evaluate whether GLP-1 affects angiogenesis in humans and to elucidate underlying molecular mechanisms. MATERIAL AND METHODS: We utilized a 3D culture system where spherules of human umbilical vein endothelial cells (HUVECs) embedded in a collagen scaffold were treated with escalating doses of human recombinant GLP-1 (50-2000 nmol/L) and the formation of new vessels was observed and quantified. Signaling inhibitors were utilized to identify molecular pathways through which GLP-1 promotes angiogenesis. RESULTS: We demonstrate that GLP-1 promotes angiogenesis in a dose-dependent manner. The maximum effect on angiogenesis was observed at a GLP-1 dose of 500 nmol/L, while increased angiogenesis occurred in response to doses ranging from 200 nmol/L to 1000 nmol/L. Pre-treatment of the system with Akt inhibitor IV, Bisindolylmaleimide (PKC inhibitor) and src inhibitor I resulted in a significant decrease of the GLP-1 induced angiogenesis. CONCLUSIONS: This is the first study to demonstrate that GLP-1 promotes angiogenesis in a HUVEC three dimensional in vitro model. This effect requires pharmacological doses and is mediated through the Akt, PKC and src pathways.

Gender dimorphism and lack of day/night variation or effects of energy deprivation on undercarboxylated osteocalcin levels in humans.

OBJECTIVE: Undercarboxylated osteocalcin (ucOC) is a bone marker with potent metabolic effects. Leptin regulates Esp gene expression and osteocalcin carboxylation in animal models. We aim to elucidate day/night patterns of ucOC levels, whether short-term and/or chronic energy deprivation alters ucOC levels, and whether leptin may mediate these changes in humans. DESIGN AND METHODS: Twelve healthy males and females were studied for 72 h in the fed state to study day/night pattern of ucOC. The six female subjects were also studied in a crossover interventional study in the fasting state for 72 h with administration of either placebo or metreleptin in physiological doses. Blood samples were obtained hourly from 0800 a.m. on day 3 until 0800 a.m. on day 4. In a separate study, eleven obese subjects who underwent bariatric surgery were followed for 24 weeks to examine the effects of postsurgery weight loss on ucOC levels. RESULTS: Males have higher ucOC levels compared to females. There is no day/night variation pattern of circulating ucOC in humans. Short-term and chronic energy deprivation or leptin administrations do not alter ucOC levels. CONCLUSIONS: The hypothesis that ucOC plays a role in energy homeostasis or of leptin in regulating ucOC in humans is not supported.

Abdominal obesity, independent from caloric intake, accounts for the development of intestinal tumors in Apc(1638N/+) female mice.

To determine whether visceral fat (VF), independent of other confounders, is causally linked to intestinal tumorigenesis, we surgically removed visceral fat in Apc(1638/N+) mice. At 15 weeks of age, male and female Apc(1638/N+) mice were randomized to one of three groups: ad libitum, visceral fat removal (VF-) and ad libitum fed, or caloric restriction, and were studied for effects on tumorigenesis and survival. As compared with ad libitum, VF- and caloric restriction reduced macroadenomas to a similar extent (P < 0.05), but only caloric restriction significantly improved survival (P < 0.05). Given that a significant group × gender interaction was observed, we next examined males and females separately. In females, macroadenomas were markedly attenuated by VF- (1.33 ± 0.23 mean ± SE; P < 0.05), but not by caloric restriction (2.35 ± 0.25; P = 0.71), as compared with ad libitum (2.50 ± 0.34). In males, however, caloric restriction (1.71 ± 0.26; P < 0.01), but not VF- (2.94 ± 0.42; P = 0.29), reduced macroadenomas, as compared with ad libitum males (3.47 ± 0.30). In females, both VF- (P = 0.05) and caloric restriction (P < 0.01) improved survival, but not in male mice (P = 0.15). The benefits observed with caloric restriction were consistent with favorable metabolic adaptations, but protection conferred in VF- females was despite lower adiponectin levels (P < 0.05), and failure to reduce body mass, total adiposity, glucose, insulin, leptin, and chemokine (C-X-C motif) ligand 1 (CXCL-1) levels. In conclusion, these data provide the first causal evidence linking visceral fat to intestinal cancer risk, and suggest that factors, other than known metabolic mediators, may impact tumor development. Furthermore, these data emphasize that strategies designed to deplete visceral fat stores in humans should be considered in the prevention of intestinal cancer. Cancer Prev Res; 6(3); 177-87. ©2012 AACR.

Salutary effects of adiponectin on colon cancer: in vivo and in vitro studies in mice.

BACKGROUND: Obesity and a high-fat diet are associated with the risk and progression of colon cancer. Low adiponectin levels may play an important role in the development of colon and other obesity-related malignancies. No previous studies have directly investigated the mechanistic effects of adiponectin on colon cancer in the settings of obesity, a high-fat diet and/or adiponectin deficiency. OBJECTIVE: To investigate the effects of adiponectin on the growth of colorectal cancer in adiponectin-deficient or wild-type-C57BL/6 mice fed a low-fat or high-fat diet. RESULTS: Mice fed a high-fat-diet gained more weight and had larger tumours than mice fed a low-fat-diet. Adiponectin administration suppressed implanted tumour growth, causing larger central necrotic areas. Adiponectin treatment also suppressed angiogenesis assessed by CD31 staining and VEGFb and VEGFd mRNA expression in tumours obtained from mice fed a high-fat-diet and from adiponectin-deficient mice. Adiponectin treatment decreased serum insulin levels in mice on a high-fat-diet and increased serum-interleukin (IL)-12 levels in adiponectin-deficient mice. In vitro, it was found that adiponectin directly controls malignant potential (cell proliferation, adhesion, invasion and colony formation) and regulates metabolic (AMPK/S6), inflammatory (STAT3/VEGF) and cell cycle (p21/p27/p53/cyclins) signalling pathways in both mouse MCA38 and human HT29, HCT116 and LoVo colon cancer cell lines in a LKB1-dependent way. CONCLUSION: These new mechanistic and pathophysiology studies provide evidence for an important role of adiponectin in colon cancer. The data indicate that adiponectin or analogues might be useful agents in the management or chemoprevention of colon cancer.

Fibroblast growth factor 21 levels in young healthy females display day and night variations and are increased in response to short-term energy deprivation through a leptin-independent pathway.

OBJECTIVE: Fibroblast growth factor (FGF)-21 is an endocrine factor with potent metabolic effects. Its day-night patterns of secretion and/or its physiological response to energy deprivation and relationship to free fatty acids (FFAs) and/or leptin remain to be fully elucidated. We aim to elucidate day-night pattern of FGF-21 levels and its relationship to FFA, to assess whether energy deprivation alters its circulating patterns, and to examine whether leptin may mediate these changes. RESEARCH DESIGN AND METHODS: Six healthy lean females were studied for 72 h in a cross-over interventional study under three different conditions: on isocaloric diet and in a fasting state with administration of either placebo or metreleptin in physiological replacement doses. Blood samples were obtained hourly from 8:00 a.m. on day 4 until 8:00 a.m. on day 5. RESULTS: FGF-21 exhibited day-night variation pattern during the isocaloric fed state. Fasting significantly increased FGF-21 levels (P < 0.01) via a leptin-independent pathway. Day-night variation pattern in the fed state was lost on fasting. Leptin replacement in the hypoleptinemic state restored approximate entropy of FGF-21 time series but did not alter circulating levels. FGF-21 levels were closely cross-correlated with FFA levels in all three states. CONCLUSIONS: A day-night variation in the levels of FGF-21 exists in young lean females in the fed state. Energy deprivation increases FGF-21 levels via a leptin-independent pathway. The interaction between FGF-21 and starvation-induced lipolysis, as indicated by its close cross-correlations with FFA in both fed state and energy deprivation, needs to be studied further.

Secretion patterns of circulating osteoprotegerin and response to acute and chronic energy deprivation in young healthy adults.

INTRODUCTION: Osteoprotegerin (OPGN) is a bone-remodeling marker that is associated with various metabolic and vascular complications. Cross-sectional studies in humans have demonstrated an inverse association between leptin, a marker of energy sufficiency, and OPGN. The physiology of OPGN has not been fully elucidated to date. We thus aim to elucidate 1) whether OPGN levels exhibit any gender dimorphism or day/night secretion pattern; and 2) whether there is any effect of acute and/or chronic energy deprivation on its circulating levels and whether such effects are mediated through leptin. MATERIALS AND METHODS: Study A: To evaluate OPGN secretion patterns and OPGN response to acute energy deprivation, we studied 12 healthy subjects under three different conditions for 72 h-in the isocaloric fed state, and during a fasting state with administration of either placebo or metreleptin in replacement doses. Blood samples were obtained every 15 min and pooled hourly during the last 24 h of the study. Study B: To evaluate the effect of chronic energy deprivation on OPGN secretion, we measured its levels in 14 obese subjects before and during weight loss after bariatric surgery. RESULTS: OPGN levels exhibited a statistically significant (P < 0.01), albeit clinically limited in magnitude, day/night variation pattern in both genders (R(2) = 14.68%; 10.7-14.8% reduction with lower levels around 1600-1800 h; P < 0.01). Males had lower OPGN levels compared to females (1.81 ± 0.04 vs. 3.65 ± 0.07 pmol/liter; P < 0.001). Three days of fasting with either placebo or metreleptin administration did not change OPGN levels. OPGN levels did not change during bariatric surgery-induced weight loss. CONCLUSIONS: OPGN levels are lower in men and exhibit a statistically significant, albeit clinically limited in magnitude, day/night secretion pattern. Neither acute nor chronic energy deprivation leading to significant weight loss has any effects on OPGN levels. Nomenclature Comment: Use of the terms "circadian" and "day/night variation" is meant as follows: Circadian pattern is a functional term that implies a rhythm that has been proven to be regulated by the innate circadian apparatus (anatomical and/or molecular). Conversely, day/night variation pattern is a descriptive term that refers to serum levels that vary during a day, usually in a periodic fashion. It is not known whether this variation is an innate property of the organ that secretes this hormone or whether it is determined by exogenous factors.

Dietary walnuts inhibit colorectal cancer growth in mice by suppressing angiogenesis.

OBJECTIVE: Animal studies have demonstrated that dietary supplementation with flaxseed oil inhibits colorectal cancer growth. Recent data indicate that walnuts have strong antiproliferative properties against colon cancer cells in vitro but no previous study has assessed the effects of walnuts in vivo or performed a joint evaluation of flaxseed oil and walnuts. The aim of the present study was to examine the effect of dietary walnuts on colorectal cancer in vivo and to comparatively evaluate their efficacy in relation to flaxseed oil. METHODS: HT-29 human colon cancer cells were injected in 6-wk-old female nude mice. After a 1-wk acclimation period, mice (n = 48) were randomized to diets containing ∼19% of total energy from walnuts, flaxseed oil, or corn oil (control) and were subsequently studied for 25 d. RESULTS: Tumor growth rate was significantly slower in walnut-fed and flaxseed-fed mice compared with corn oil-fed animals (P < 0.05) by 27% and 43%, respectively. Accordingly, final tumor weight was reduced by 33% and 44%, respectively (P < 0.05 versus control); the differences between walnut and flaxseed diets did not reach significance. We found no differences among groups in metabolic and hormonal profile, serum antioxidant capacity, or inflammation (P > 0.05). However, walnuts and flaxseed oil significantly reduced serum expression levels of angiogenesis factors, including vascular endothelial growth factor (by 30% and 80%, respectively), and approximately doubled total necrotic areas despite smaller tumor sizes (P < 0.05 versus control). Dietary walnuts significantly decreased angiogenesis (CD34 staining; P = 0.017 versus control), whereas this effect did not reach significance in the flaxseed oil group (P = 0.454 versus control). CONCLUSION: We conclude that walnuts in the diet inhibit colorectal cancer growth by suppressing angiogenesis. Further studies are needed to confirm our findings in humans and explore underlying mechanisms.

Short-term walnut consumption increases circulating total adiponectin and apolipoprotein A concentrations, but does not affect markers of inflammation or vascular injury in obese humans with the metabolic syndrome: data from a double-blinded, randomized, placebo-controlled study.

Long-term consumption of walnuts is associated with lower cardiovascular disease risk in epidemiological studies, possibly through improvements in lipid profile and endothelial function. It remains to be elucidated how soon after initiation of walnut consumption beneficial effects on lipid profile and biomarkers of inflammation or vascular injury can be observed. Fifteen obese subjects (9 men and 6 women; age, 58 ± 2.5 years; body mass index, 36.6 ± 1.7 kg/m(2)) with the metabolic syndrome participated as inpatients in a randomized, double-blinded, placebo-controlled crossover study involving short-term placebo or walnut-enriched diet (48 g/d for 4 days). Apolipoproteins and markers of inflammation and vascular injury were measured before and after consumption of the experimental diets. Consumption of walnuts was associated with a statistically significant increase in serum apolipoprotein A concentrations (P = .03), but did not affect circulating levels of fetuin A, resistin, C-reactive protein, serum amyloid A, soluble intercellular adhesion molecules 1 and 3, soluble vascular cell adhesion protein 1, interleukins 6 and 8, tumor necrosis factor α, E-selectin, P-selectin, and thrombomodulin. Four days of walnut consumption (48 g/d) leads to mild increases in apolipoprotein A concentrations, changes that may precede and lead to the beneficial effects of walnuts on lipid profile in obese subjects with the metabolic syndrome.

Direct role of adiponectin and adiponectin receptors in endometrial cancer: in vitro and ex vivo studies in humans.

Low adiponectin levels are an independent risk factor for and mediate the effect of obesity on endometrial cancer in epidemiology studies. The direct or indirect mechanisms underlying these findings remain to be elucidated. We first examined the expression of adiponectin receptor 1 (AdipoR1) and 2 (AdipoR2) in normal human endometrium and in endometrial cancer tissues ex vivo. We then used KLE and RL95-2 human endometrial cancer cell lines in vitro to study relative expression of AdipoRs, to investigate the effect of adiponectin on activating intracellular signaling pathways, and to assess its potential to alter malignant properties. We report for the first time that the relative expression level of AdipoR1 is higher than AdipoR2 in human endometrial cancer tissue, but the expression of AdipoRs is not statistically different from nonneoplastic tissues. We also show for the first time in endometrial cancer cell lines in vitro that adiponectin suppresses endometrial cancer proliferation acting through AdipoRs. Adiponectin also increases the expression of the adaptor molecule LKB1, which is required for adiponectin-mediated activation of AMPK/S6 axis and modulation of cell proliferation, colony formation, adhesion, and invasion of KLE and RL95-2 cell lines. These novel mechanistic studies provide for the first time in vitro and ex vivo evidence for a causal role of adiponectin in endometrial cancer.

Circulating adiponectin is inversely associated with risk of thyroid cancer: in vivo and in vitro studies.

CONTEXT: Circulating adiponectin has been inversely associated with risk for several malignancies. Its association with thyroid cancer has not yet been evaluated. OBJECTIVE/METHODS: We measured circulating adiponectin levels in 175 thyroid carcinoma patients and 107 controls. We also examined the expression of adiponectin receptors (AdipoR1 and AdipoR2) using immunohistochemistry in 82 thyroid carcinoma tissues and using RT-qPCR in 40 human thyroid carcinoma tissues (32 papillary, six follicular/Hurthle, one anaplastic, one medullary), four normal human thyroid tissue specimens, and the BHP7 and SW579 thyroid cancer cell lines. We then utilized these thyroid cancer cell lines to investigate whether adiponectin could directly regulate cell cycle or apoptosis. RESULTS: Thyroid cancer patients had lower circulating adiponectin levels than controls (17.00 ± 6.32 vs. 19.26 ± 6.28 µg/ml; P < 0.001). Subjects in the highest tertile of circulating adiponectin concentrations had significantly lower odds of developing any type of thyroid carcinoma (odds ratio = 0.29; 95% confidence interval, 0.16-0.55), or papillary thyroid carcinoma (odds ratio = 0.27; 95% confidence interval, 0.14-0.55), before and after adjustment for potential confounders. Both thyroid carcinoma cell lines and tissues expressed AdipoR1 and AdipoR2. Recombinant adiponectin did not exert a clinically significant direct effect on cell cycle, proliferation, or apoptosis in thyroid cancer cell lines in vitro. CONCLUSIONS: Circulating adiponectin is independently and inversely associated with the risk of thyroid cancer. Human thyroid carcinomas and cell lines express adiponectin receptors. However, in the absence of a major direct effect of adiponectin on thyroid cancer cell lines in vitro, the negative association observed herein may be attributed to the metabolic effects of adiponectin.

Short-term energy deprivation alters activin a and follistatin but not inhibin B levels of lean healthy women in a leptin-independent manner.

CONTEXT: Leptin is a potent modulator of the hypothalamic-pituitary-gonadal axis mediating the effect of energy deprivation on several hypothalamic-pituitary-peripheral axes. Activin A, inhibin B, and follistatin (FST) also regulate the hypothalamic-pituitary-gonadal axis in humans. It remains unknown whether energy deprivation affects these hormone levels in a leptin-dependent or -independent manner. OBJECTIVE: We investigated 1) day-night variability patterns of activin, inhibin, and FST in the fed state, 2) whether their levels are affected by fasting, and 3) whether such an effect is mediated by leptin in physiological replacement or pharmacological doses. DESIGN: We conducted two studies in healthy, eumenorrheic females, each comprising three separate admissions. In study 1, six women were maintained for 72 h 1) on isocaloric diet, 2) fasting while receiving placebo, or 3) fasting while receiving metreleptin in physiological replacement doses. In study 2, five women were administered physiological or pharmacological metreleptin doses (0.01, 0.1, or 0.3 mg/kg i.v. four times daily). RESULTS: Neither activin A nor FST had a pulsatile or day-night variability pattern. Inhibin B levels were also nonpulsatile, but a trend toward a day-night pattern was noted. When compared with the fed state, inhibin B levels remained unchanged, whereas FST levels increased (P = 0.01) and activin A decreased (P = 0.01) in the fasting state. These changes were not corrected with metreleptin administered in replacement or pharmacological doses. CONCLUSIONS: Short-term energy deprivation alters levels of activin A and FST, but these effects are not mediated by leptin.