Regulation of macrophage migration inhibitory factor (MIF) expression by glucose and insulin in adipocytes in vitro.

BACKGROUND: It has been reported that macrophage migration inhibitory factor (MIF) stimulated insulin secretion from pancreatic islet beta-cells in an autocrine manner, which suggests its pivotal role in the glucose metabolism. According to this finding, we evaluated MIF expression in cultured adipocytes and epididymal fat pads of obese and diabetic rats to investigate its role in adipose tissue. MATERIALS AND METHODS: The murine adipocyte cell line 3T3-L1 was used to examine MIF mRNA expression and production of MIF protein in response to various concentrations of glucose and insulin. Epididymal fat pads of Otsuka Long-Evans Tokushima fatty (OLETF) and Wistar fatty rats, animal models of obesity and diabetes, were subjected to Northern blot analysis to determine MIF mRNA levels. RESULTS: MIF mRNA of 3T3-L1 adipocytes was up-regulated by costimulation with glucose and insulin. Intracellular MIF content was significantly increased by stimulation, whereas its content in the culture medium was decreased. When the cells were treated with cytochalasin B, MIF secretion in the medium was increased. Pioglitazone significantly increased MIF content in the culture medium of 3T3-L1 cells. However, MIF mRNA expression of both epididymal fat pads of OLETF and Wistar fatty rats was down-regulated despite a high plasma glucose level. The plasma MIF level of Wistar fatty rats was significantly increased by treatment with pioglitazone. CONCLUSION: We show here that the intracellular glucose level is critical to determining the MIF mRNA level as well as its protein content in adipose tissue. MIF is known to play an important role in glucose metabolism as a positive regulator of insulin secretion. In this context, it is conceivable that MIF may affect the pathophysiology of obesity and diabetes.     

Regulation of lipoprotein lipase activity and mRNA content in rat epididymal adipose tissue in vitro by recombinant tumour necrosis factor.

Tumour necrosis factor (TNF) has previously been shown to decrease lipoprotein lipase (LPL) activity and mRNA levels in 3T3-L1 cells and in adipose tissue from rats and guinea pigs when injected in vivo, but not to alter LPL activity in human adipocytes incubated in vitro. The effect of recombinant human TNF on LPL activity and mRNA levels in rat epididymal adipose tissue incubated in vitro was examined. LPL activity and mRNA levels fell in adipose tissue taken from fed rats and incubated in Krebs-Henseleit bicarbonate medium with glucose. The addition of insulin and dexamethasone prevented these falls. TNF (400 ng/ml) produced a fall of approx. 50% in LPL activity after 2 h of incubation and of approx. 30% in LPL mRNA levels after 3 h. TNF did not decrease LPL activity in isolated adipocytes. These results demonstrate that rat adipose tissue incubated in vitro is responsive to TNF whereas isolated adipocytes are not.     

Effect of PPAR-delta agonist on the expression of visfatin, adiponectin, and resistin in rat adipose tissue and 3T3-L1 adipocytes

It has been recently reported that activation of PPAR-delta, by specific agonists or genetic manipulation, alleviates dyslipidemia, hyperglycemia, and insulin resistance in animal models of obesity and type 2 diabetes. The purpose of the present study was to determine whether the PPAR-delta agonist has a direct effect on adipokines in visceral adipose tissue of rats and in cultured adipocytes. We examined the expression of visfatin, adiponectin, and resistin mRNA in visceral adipose tissue of Wistar rats fed a high-fat diet and 3T3-L1 adipocytes treated with PPAR-delta agonist (L-165041). Body weight and biochemical measurements were performed. Rats fed a high-fat diet showed a greater increase in body weight than those fed a standard diet (P<0.05), and treatment with L-165041 (10 mg/kg/day) significantly decreased weight gain (P<0.05). The concentration of total cholesterol was lower, and HDL cholesterol was higher in L-165041-treated rats (P<0.05). In the visceral adipose tissue of L-165041-treated rats, visfatin and adiponectin mRNA levels significantly increased compared to those of the untreated rats (P<0.05). However, the expression of resistin decreased in the L-165041-treated rats. Furthermore, in cultured 3T3-L1 adipocytes, the level of visfatin and adiponectin mRNA was up-regulated in response to L-165041 treatment for nine days. By contrast, resistin mRNA levels were down-regulated by L-165041 treatment. The present study provides a novel evidence to suggest that the PPAR-delta agonist has regulatory effects on a variety of adipokines, and these effects might explain some of their metabolic function.     

Possible Role of Triacylglycerol-Rich Lipoproteins in the Down-Regulation of Adipose Obese mRNA Expression in Rats Re-Fed a High-Fat Diet

Summary The large amount of absorbed dietary lipid after feeding a high-fat diet is mainly transported as triacylglycerol (TG)-rich lipoproteins (TRL) in the post-prandial blood and is subsequently distributed to peripheral tissues including adipose and muscle tissues. An in vivo and an in vitro study were conducted to investigate the possible role of post-prandial TRL after high fat feeding in the regulation of obese (ob) gene expression. Adult male Wistar rats were fasted for 48 h and re-fed either a fat-free/high-carbohydrate diet or a high-fat diet for 2, 4, or 8 h and plasma glucose, insulin, TG, and leptin as well as ob mRNA expression in epididymal fat pads were examined. Rats re-fed the high-fat diet had significantly higher plasma TG (p<0.05) and lower plasma leptin and adipose ob mRNA (p<0.05) than those fed the fat-free/high-carbohydrate diet; however, plasma glucose and insulin concentrations were not significantly different between the two groups. Plasma lipid analysis found large amount of TRL in rats fed with high-fat diet; however, only very small amount of the TRL was found in rats fed with fat-free/high-carbohydrate diet. We speculated that TRL might involve in regulation of ob gene expression. To further examine the regulation of TRL on ob mRNA expression, differentiated 3T3-L1 adipocytes were treated with TRL collected from rats fed 5 ml soybean oil by gastric intubations. TRL down-regulated ob mRNA not only in a dose and time dependent manner but also in the presence of insulin in 3T3-L1 adipocytes. These results suggest a possible role of TRL in the down-regulation of adipose ob mRNA expression and may account, at least in part, for the previous observations that short-term high fat feeding resulted in lower plasma leptin.     

Cyclin-dependent kinase inhibitor, p21WAF1/CIP1, is involved in adipocyte differentiation and hypertrophy, linking to obesity, and insulin resistance

Both adipocyte hyperplasia and hypertrophy are determinant factors for adipocyte differentiation during the development of obesity. p21(WAF1/CIP1), a cyclin-dependent kinase inhibitor, is induced during adipocyte differentiation; however, its precise contribution to this process is unknown. Using both in vitro and in vivo systems, we show that p21 is crucial for maintaining adipocyte hypertrophy and obesity-induced insulin resistance. The absence of p21 in 3T3-L1 fibroblasts by RNA-mediated interference knockdown or in embryonic fibroblasts from p21(-/-) mice impaired adipocyte differentiation, resulting in smaller adipocytes. Despite normal adipose tissue mass on a normal diet, p21(-/-) mice fed high energy diets had reduced adipose tissue mass and adipocyte size accompanied by a marked improvement in insulin sensitivity. Knockdown of p21 in enlarged epididymal fat of diet-induced obese mice and also in fully differentiated 3T3-L1 adipocytes caused vigorous apoptosis by activating p53. Thus, p21 is involved in both adipocyte differentiation and in protecting hypertrophied adipocytes against apoptosis. Via both of these mechanisms, p21 promotes adipose tissue expansion during high fat diet feeding, leading to increased downstream pathophysiological consequences such as insulin resistance.     

Effects of a grapeseed procyanidin extract (GSPE) on insulin resistance

Flavonoids are beneficial compounds against risk factors for metabolic syndrome, but their effects and the mechanisms on glucose homeostasis modulation are not well defined. In the present study, we first checked the efficacy of grapeseed procyanidin extract (GSPE) for stimulating glucose uptake in insulin-resistant 3T3-L1 adipocytes. Results show that when resistance is induced with chronic insulin treatment, GSPE maintain a higher stimulating capacity than insulin. In contrast, when dexamethasone is used as the resistance-inducing agent, GSPE is less effective. Next we evaluated how effective different GSPE treatments are at improving glucose metabolism in hyperinsulinemic animals (fed a cafeteria diet). GSPE reduced plasma insulin levels. The lower dose (25 mg GSPE/kg body weight per day) administered for 30 days improved the HOmeostasis Model Assessment-insulin resistance index. This was accompanied by down-regulation of Pparg2, Glut4 and Irs1 in mesenteric white adipose tissue. Similarly, a chronic GSPE treatment of insulin-resistant 3T3-L1 adipocytes down-regulated the mRNA levels of those adipocyte markers, although cells were still able to respond to the acute stimulation of glucose uptake.In summary, 25 mg/kg body weight per day of GSPE has a positive long-term effect on glucose homeostasis, and GSPE could be targeted at adipose tissue, where it might directly stimulate glucose uptake. This work also highlights the need to carefully consider the bioactive dose, since a higher dose does not necessarily correlate to a greater positive effect.     

Grape pomace extract induced beige cells in white adipose tissue from rats and in 3T3-L1 adipocytes

This study investigated the effects of a grape pomace extract (GPE) rich in phenolic compounds on brown-like adipocyte induction and adiposity in spontaneously hypertensive (SHR) and control normotensive Wistar–Kyoto (WKY) rats fed a high-fat diet (HFD). HFD consumption for 10 weeks significantly increased epididymal white adipose tissue (eWAT) in WKY but not in SHR rats. Supplementation with GPE (300 mg/kg body weight/day) reduced adipocyte diameter and increased levels of proteins that participate in adipogenesis and angiogenesis, i.e., peroxisome-proliferator activated receptor gamma (PPARγ), vascular endothelial grow factor-A (VEGF-A) and its receptor 2 (VEGF-R2), and partially increased the uncoupling protein 1 (UCP-1) in WKY. In both strains, GPE attenuated adipose inflammation. In eWAT from SHR, GPE increased the expression of proteins involved in adipose tissue “browning,” i.e., PPARγ-coactivator-1α (PGC-1α), PPARγ, PR domain containing 16 (PRDM16) and UCP-1. In primary cultures of SHR adipocytes, GPE-induced UCP-1 up-regulation was dependent on p38 and ERK activation. Accordingly, in 3T3-L1 adipocytes treated with palmitate, the addition of GPE (30 μM) activated the β-adrenergic signaling cascade (PKA, AMPK, p38, ERK). This led to the associated up-regulation of proteins involved in mitochondrial biogenesis (PGC-1α, PPARγ, PRDM16 and UCP-1) and fatty acid oxidation (ATGL). These effects were similar to those exerted by (−)-epicatechin and quercetin, major phenolic compounds in GPE. Overall, in HFD-fed rats, supplementation with GPE promoted brown-like cell formation in eWAT and diminished adipose dysfunction. Thus, winemaking residues, rich in bioactive compounds, could be useful to mitigate the adverse effects of HFD-induced adipose dysfunction.     

Maternal protein restriction during early lactation induces GLUT4 translocation and mTOR/Akt activation in adipocytes of adult rats

Epidemiological and experimental studies have demonstrated that early postnatal nutrition has been associated with long-term effects on glucose homeostasis in adulthood. Recently, our group demonstrated that undernutrition during early lactation affects the expression and activation of key proteins of the insulin signaling cascade in rat skeletal muscle during postnatal development. To elucidate the molecular mechanisms by which undernutrition during early life leads to changes in insulin sensitivity in peripheral tissues, we investigated the insulin signaling in adipose tissue. Adipocytes were isolated from epididymal fat pads of adult male rats that were the offspring of dams fed either a normal or a protein-free diet during the first 10 days of lactation. The cells were incubated with 100 nM insulin before the assays for immunoblotting analysis, 2-deoxyglucose uptake, immunocytochemistry for GLUT4, and/or actin filaments. Following insulin stimulation, adipocytes isolated from undernourished rats presented reduced tyrosine phosphorylation of IR and IRS-1 and increased basal phosphorylation of IRS-2, Akt, and mTOR compared with controls. Basal glucose uptake was increased in adipocytes from the undernourished group, and the treatment with LY294002 induced only a partial inhibition both in basal and in insulin-stimulated glucose uptake, suggesting an involvement of phosphoinositide 3-kinase activity. These alterations were accompanied by higher GLUT4 content in the plasma membrane and alterations in the actin cytoskeleton dynamics. These data suggest that early postnatal undernutrition impairs insulin sensitivity in adulthood by promoting changes in critical steps of insulin signaling in adipose tissue, which may contribute to permanent changes in glucose homeostasis.     

Duration of feeding on a sucrose-rich diet determines metabolic and morphological changes in rat adipocytes.

In this work, we studied the effect of a short-term (3 wk) and a long-term (15 wk) administration of a sucrose-rich diet (SRD) to Wistar rats on the morphological aspects and metabolic function of the epididymal adipose tissue that may contribute to the mechanism underlying the impaired glucose homeostasis and insulin resistance. The present work showed the following. 1) There was both a moderate increase of basal lipolysis and a decrease of the antilipolytic action of insulin in the adipocytes of rats fed a SRD for 3 wk. Neither size alterations nor increases in adipose tissue mass were recorded in this period. 2) There was a significant (P < 0.05) increase of epididymal weight after 15 wk on a SRD as well as a hypertrophy of adipocytes with a clear alteration in the cell size distribution. This was accompanied by a significant increase (P < 0.05) of basal and stimulated lipolysis and a marked decrease (P < 0.05) of the antilipolytic action of insulin. Moreover, these changes appear together with a worsening of both impaired glucose homeostasis and insulin resistance. Our results also indicate that the length of time on the SRD plays an important role in the evolution of the adiposity and metabolic changes observed in the fat pad. Furthermore, the latter precedes the detection of adiposity.     

Mature adipocytes and perivascular adipose tissue stimulate vascular smooth muscle cell proliferation: effects of aging and obesity

Adipocytes and perivascular adipose tissue are emerging as regulators of vascular function. The effects of adipocytes and perivascular adipose tissue on human smooth muscle cell (SMC) proliferation were investigated. Conditioned medium was prepared from cultured premature and differentiated 3T3-L1 adipocytes and from periaortic adipose tissue from young (3 mo) and old (24 mo) Wistar-Kyoto (WKY) rats, lean and obese Zucker rats (3 mo), and WKY rats fed normal chow or a high-fat diet for 3 mo. Conditioned medium from differentiated (but not premature) adipocytes stimulated SMC proliferation, which was abolished by charcoal and proteinase K treatment but was resistant to heat, trypsin, or phospholipase B (to hydrolyze lysophosphatidic acid). Further experiments demonstrated that the growth factor(s) are hydrosoluble and present in the fraction of molecular mass >100 kDa. Moreover, conditioned medium from periaortic adipose tissue stimulated SMC proliferation, which was significantly enhanced in aged rats and in rats fed a high-fat diet but not in obese Zucker rats deficient in functional leptin receptors. In conclusion, mature adipocytes release hydrosoluble protein growth factor(s) with a molecular mass >100 kDa for SMCs. Perivascular adipose tissue stimulates SMC proliferation, which is enhanced in aged WKY and in high-fat, diet-induced obesity but not in leptin receptor-deficient obese Zucker rats. These adipocyte-derived growth factor(s) and the effect of perivascular adipose tissue may be involved in vascular disease associated with aging and obesity.     

Regulation of fructose 2,6-bisphosphate concentration in white adipose tissue.

Injection of insulin to fed rats diminished the concentration of fructose 2,6-bisphosphate in white adipose tissue. Incubation of epididymal fat-pads or adipocytes with insulin stimulated lactate release and sugar detritiation and also decreased fructose 2,6-bisphosphate concentration. Such a decrease was, however, not observed in fat-pads from starved or alloxan-diabetic rats. Incubation of adipocytes from fed rats with various concentrations of glucose or fructose led to a dose-dependent rise in fructose 2,6-bisphosphate which correlated with lactate output and detritiation of 3-3H-labelled sugar. In adipocytes from fed rats, palmitate stimulated the detritiation of [3-3H]glucose without affecting lactate production and fructose 2,6-bisphosphate concentration. Incubation of epididymal fat-pads from fed rats in the presence of antimycin stimulated lactate output but decreased fructose 2,6-bisphosphate concentration. Changes in lipolytic rates brought about by noradrenaline, insulin, adenosine and corticotropin in adipocytes from fed rats were not related to changes in fructose 2,6-bisphosphate or to rates of lactate output. In fed rats, the activity of 6-phosphofructo-2-kinase was not changed after treatment of adipocytes with insulin, noradrenaline or adenosine. It is suggested that the decrease in fructose 2,6-bisphosphate concentration observed after insulin treatment can be explained by the increase in sn-glycerol 3-phosphate, an inhibitor of 6-phosphofructo-2-kinase.     

Augmentation of RBP4/STRA6 signaling leads to insulin resistance and inflammation and the plausible therapeutic role of vildagliptin and metformin

A role of Retinol Binding Protein-4 (RBP4) in insulin resistance is widely studied. However, there is paucity of information on its receptor viz., Stimulated by Retinoic Acid-6 (STRA6) with insulin resistance. To address this, we investigated the regulation of RBP4/STRA6 expression in 3T3-L1 adipocytes exposed to glucolipotoxicity (GLT) and in visceral adipose tissue (VAT) from high fat diet (HFD) fed insulin-resistant rats. 3T3-L1 adipocytes were subjected to GLT and other experimental maneuvers with and without vildagliptin or metformin. Real-time PCR and western-blot experiments were performed to analyze RBP4, STRA6, PPARγ gene and protein expression. Adipored staining and glucose uptake assay were performed to evaluate lipid and glucose metabolism. Oral glucose tolerance test (OGTT) and Insulin Tolerance Test (ITT) were performed to determine the extent of insulin resistance in HFD fed male Wistar rats. Total serum RBP4 was measured by quantitative sandwich enzyme-linked immunosorbent assay kit. Adipocytes under GLT exhibited significantly increased RBP4/STRA6 expressions and decreased insulin sensitivity/glucose uptake. Vildagliptin and metformin not only restored the above but also decreased the expression of IL-6, NFκB, SOCS-3 along with lipid accumulation. Furthermore, HFD fed rats exhibited significantly increased serum levels of RBP4 along with VAT expression of RBP4, STRA6, PPARγ, IL-6. These molecules were significantly altered by the vildagliptin/ metformin treatment. We conclude that RBP4/STRA6 pathway is primarily involved in mediating inflammation and insulin resistance in adipocytes and visceral adipose tissues under glucolipotoxicity and in insulin resistant rats.

Graphic abstract

     

Ghrelin stimulates insulin-induced glucose uptake in adipocytes

The gastric and hypothalamic hormone ghrelin is the endogenous agonist of the growth hormone secretagogue receptor GHS-R1(a). Ghrelin stimulates growth hormone release and appetite via the hypothalamus. However, putative direct peripheral effects of ghrelin remain poorly understood. Rat adipose tissue expresses GHS-R1(a) mRNA, suggesting ghrelin may directly influence adipocyte function. We have investigated the effects of ghrelin on insulin-stimulated glucose uptake in isolated white adipocytes in vitro. RT-PCR confirmed the expression of GHS-R1(a) mRNA in epididymal adipose tissue. However, GHS-R1(a) expression was not detected in the peri-renal fat pads. Ghrelin increased insulin-stimulated deoxyglucose uptake in isolated white adipocytes extracted from the epididymal fat pads of male Wistar rats. Ghrelin 1000 nM significantly increased deoxyglucose uptake by 55% in the presence of 0.1 nM insulin. However, ghrelin administration in the absence of insulin had no effect on adipocyte deoxyglucose uptake, suggesting that ghrelin acts synergistically with insulin. Des-acyl ghrelin, a major circulating non-octanylated form of ghrelin, had no effect on insulin-stimulated glucose uptake. Furthermore, acylated ghrelin had no effect on deoxyglucose uptake in adipocytes from peri-renal fat pads suggesting that ghrelin may influence glucose uptake via the GHS-R1(a). Ghrelin therefore appears to directly potentiate adipocyte insulin-stimulated glucose uptake in selective adipocyte populations. Ghrelin may play a role in adipocyte regulation of glucose homeostasis.     

Effects of hypophysectomy and acute growth hormone treatment upon glucose metabolism in adipose tissues and isolated adipocytes of rats.

Glucose oxidation and incorporation into lipid were measured in epididymal adipose tissues and isolated adipose cells of normal and hypophysectomized rats in an effort to determine whether the acute hypoglycemic effect of a systemic growth hormone (GH) injection was related to alterations in the glucose metabolism of adipose tissue. The rats were fed rat chow or a high sucrose diet and received 100 mug GH intraperitoneally 30 minutes or three and one-half hours before sacrifice. Hypophysectomized rats showed a lower plasma glucose as compared with normal rats on both diets. Thirty minutes after a GH injection there was a further decrease of the plasma glucose which, however, was not present in those rats receiving GH three and one-half hours before sacrifice. Adipose tissues from hypophysectomized rats fed the high sucrose diet showed a blunted insulin sensitivity as compared with normal rats on a similar diet. The insulin sensitivity of these tissues was further decreased 30 minutes after a GH injection. Basal glucose metabolism of isolated adipocytes from hypophysectomized rats, as compared with normal rats, was depressed if they were fed rat chow, was at normal levels if they were fed the high sucrose diet and was increased if they were fed the sucrose diet and received triiodothyronine and cortisone supplements. No manipulations of diet or hormonal treatments made the isolated adipocyte from hypophysectomized rats sensitive to insulin either 30 minutes or three and one-half hours after a GH injection. Since basal glucose utilization is not enhanced by GH injection and both the blunted insulin sensitivity of adipose tissue and the absent insulin sensitivity of adipopocytes would be expected to produce hyperglycemia rather than hypoglycemia, it is concluded that immediate systemic effects of a GH injection on carbohydrate metabolism are not related to changes in glucose metabolism of the peripheral adipose tissues.     

Insulin and Chromium Picolinate Induce Translocation of CD36 to the Plasma Membrane Through Different Signaling Pathways in 3T3-L1 Adipocytes,and with a Differential Functionality of the CD36

Chromium picolinate (CrPic) has been indicated to activate glucose transporter 4 (GLUT4) trafficking to the plasma membrane (PM) to enhance glucose uptake in 3T3-L1 adipocytes. In skeletal and heart muscle cells, insulin directs the intracellular trafficking of the fatty acid translocase/CD36 to induce the uptake of cellular long-chain fatty acid (LCFA). The current study describes the effects of CrPic and insulin on the translocation of CD36 from intracellular storage pools to the PM in 3T3-L1 adipocytes in comparison with that of GLUT4. Immunofluorescence microscopy and immunoblotting revealed that both CD36 and GLUT4 were expressed and primarily located intracellularly in 3T3-L1 adipocytes. Upon insulin or CrPic stimulation, PM expression of CD36 increased in a similar manner as that for GLUT4; the CrPic-stimulated PM expression was less strong than that of insulin. The increase in PM localization for these two proteins by insulin paralleled LCFA ([1-¹⁴C]palmitate) or [³H]deoxyglucose uptake in 3T3-L1 adipocytes. The induction of the PM expression of GLUT4, but not CD36, or substrate uptake by insulin and CrPic appears to be additive in adipocytes. Furthermore, wortmannin completely inhibited the insulin-stimulated translocation of GLUT4 or CD36 and prevented the increased uptake of glucose or LCFA in these cells. Taken together, for the first time, these findings suggest that both insulin and CrPic induce CD36 translocation to the PM in 3T3-L1 adipocytes and that their translocation-inducing effects are not additive. The signaling pathway inducing the translocations is different, apparently resulting in a differential activity of CD36.     

Blueberry Peel Extracts Inhibit Adipogenesis in 3T3-L1 Cells and Reduce High-Fat Diet-Induced Obesity

This study examined the anti-obesity effect and mechanism of action of blueberry peel extracts (BPE) in 3T3-L1 cells and high-fat diet (HFD)-induced obese rats. The levels of lipid accumulation were measured, along with the changes in the expression of genes and proteins associated with adipocyte differentiation in 3T3-L1 cells. Evidenced by Oil-red O staining and triglyceride assay, BPE dose-dependently inhibited lipid accumulation at concentrations of 0, 50, and 200 µg/ml. BPE decreased the expression of the key adipocyte differentiation regulator C/EBPβ, as well as the C/EBPα and PPARγ genes, during the differentiation of preadipocytes into adipocytes. Moreover, BPE down-regulated adipocyte-specific genes such as aP2 and FAS compared with control adipocytes. The specific mechanism mediating the effects of BP revealed that insulin-stimulated phosphorylation of Akt was strongly decreased, and its downstream substrate, phospho-GSK3β, was downregulated by BPE treatment in 3T3-L1 cells. Together, these data indicated that BP exerted anti-adipogenic activity by inhibiting the expression of PPARγ and C/EBPβ and the Akt signaling pathway in 3T3-L1 adipocytes. Next, we investigated whether BP extracts attenuated HFD-induced obesity in rats. Oral administration of BPE reduced HFD-induced body weight gain significantly without affecting food intake. The epididymal or perirenal adipose tissue weights were lower in rats on an HFD plus BPE compared with the tissue weights of HFD-induced obese rats. Total cholesterol and triglyceride levels in the rats fed BPE were modestly reduced, and the HDL-cholesterol level was significantly increased in HFD plus BP-fed rats compared with those of HFD-fed rats. Taken together, these results demonstrated an inhibitory effect of BP on adipogenesis through the down-regulation of C/EBPβ, C/EBPα, and PPARγ and the reduction of the phospho-Akt adipogenic factor in 3T3-L1 cells. Moreover, BPE reduced body weight gain and inhibited fat accumulation in an HFD-induced animal model of obesity.     

Reducing effect of feeding powdered scallop shell on the body fat mass of rats

The lipolytic effect of powdered scallop shells was estimated in vitro and in vivo. The scallop shells consisted of 98% calcium carbonate and 2% organic compounds, the extracted organic components promoted lipolysis in 3T3-L1 adipocyte cells. Male Wistar rats were fed on an experimental diet containing either the scallop shell powder or calcium carbonate (control) for 28 d. Feeding the scallop shell powder resulted in a decrease in body weight and in the weight of white adipose tissue. While the organ weights of the liver, kidney, testis, pancreas, and spleen, and of the brown adipose tissue relative to the body weight were no different between the scallop shell powder diet and control diet, the white adipose tissue weight relative to the body weight significantly decreased in the rats fed on the scallop shell powder. The glycerol concentration in the serum increased in the rats fed on the scallop shell powder, suggesting that this promoted lipolysis in the adipose tissue. These results show that the organic components in the scallop shells induced the decrease in weight of the adipose tissue due to the promotion of lipolysis.