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Dietary vitamin A status affects energy metabolism. The present study explored the effect of all‐trans retinoic acid (ATRA) on the expression levels of molecules and metabolites of brown adipocytes. Chronic ATRA treatment was initiated during the early stage (days 0‐8) or late stage (days 8‐12) of adipogenesis. Treatment with ATRA during the early and late stage of adipogenesis resulted in an increase in the expression level of Ucp1 and Cidea, genes highly expressed in brown adipocytes, on day 8 and day 12, respectively, whereas expression of Pgc‐1α, another gene expressed during brown adipogenesis, was unaffected by ATRA. Non‐targeted metabolomic analyses indicated that the pathways related to the glucose metabolism were affected by ATRA, irrespective of the differentiation stage. Cellular levels of glucose 6‐phosphate, fructose 6‐phosphate, citric acid, and succinic acid decreased after ATRA treatment on days 8 and 12. In contrast, glucose level was higher in ATRA‐treated cells on day 8, but it was lower on day 12. ATRA decreased the cellular level of aconitic acid, fumaric acid, and malic acid on day 12 but not on day 8. Furthermore, ATRA increased the expression level of Hxk2 and downregulated the expressions of G6pdh and Pfkl/Pfkp on day 8 but not on day 12. Together, the results indicate that the chronic treatment with ATRA stimulated the formation of activated brown adipocytes, eventually leading to alterations in the levels of cellular metabolites related to glucose metabolism. Significance of the study: Significance of the study treatment with all‐trans retinoic acid (ATRA) during the early and late stage of adipogenesis increased the expression of Ucp1 and Cidea, genes highly expressed in brown adipocytes, on day 8 and day 12. Cellular levels of glucose 6‐phosphate, fructose 6‐phosphate, citric acid, and succinic acid decreased after ATRA treatment on days 8 and 12. In contrast, glucose level was higher in ATRA‐treated cells on day 8, but it was lower on day 12. The present results indicate that ATRA stimulated the formation of activated brown adipocytes, eventually leading to alterations in the levels of cellular metabolites related to glucose metabolism. [ABSTRACT FROM AUTHOR]

Activity of brown/beige adipocytes is higher in women than in men. The expression level of uncoupling protein 1 (UCP1) is largely consistent with the thermogenic activity in brown/beige adipocytes. The present study examined the direct effects of sex hormones on Ucp1 expression in brown adipocytes and beige adipocytes, which were differentiated from HB2 brown preadipocytes and 3T3‐L1 white preadipocytes, respectively; treatment with estradiol or testosterone was used during the early (days 0‐8) or late stage (days 8‐12) of brown adipogenesis and beige adipogenesis. On day 8 or day 12, cells were treated with or without isoproterenol (Iso), an agonist for the β‐adrenergic receptor, for 4 hours. Furthermore, the sex of cells was examined; the sex‐determining region y gene, which is located on the y chromosome, was present in HB2 cells, but not in 3T3‐L1 cells, suggesting that HB2 cells and 3T3‐L1 cells are male and female cells, respectively. Treatment with 17β‐estradiol during the early stage of brown adipogenesis enhanced the responsiveness to Iso on Ucp1 induction, whereas treatment during the late stage of brown adipogenesis decreased Ucp1 expression in unstimulated brown adipocytes. Estradiol decreased Iso‐induced Ucp1 expression during the early stage of beige adipogenesis. Treatment with testosterone during the early stage of brown adipogenesis did not affect Ucp1 expression but increased the responsiveness to Iso on Ucp1 induction by the treatment during the late stage of brown adipogenesis. The present results suggest that sex hormones modulate the expression level of Ucp1 in brown/beige adipocytes in a stage‐dependent manner. Direct effects of sex hormones in brown/beige adipogenesis were evaluated. Treatment with 17β‐estradiol during the early stage of brown adipogenesis enhanced the responsiveness to isoproterenol (Iso), an agonist for the β‐adrenergic receptor, on Ucp1 induction, whereas treatment during the late stage of brown adipogenesis decreased Ucp1 expression in unstimulated brown adipocytes. Estradiol decreased Iso‐induced Ucp1 expression during the early stage of beige adipogenesis. Testosterone during the late stage of brown adipogenesis increased the responsiveness to Iso on Ucp1 induction. Sex hormones modulate the expression level of Ucp1 in brown/beige adipocytes in a stage‐dependent manner. [ABSTRACT FROM AUTHOR]

Brown adipocytes dissipate chemical energy in the form of heat through the expression of mitochondrial uncoupling protein 1 (Ucp1); Ucp1 expression is further upregulated by the stimulation of β-adrenergic receptors in brown adipocytes. An increase in energy expenditure by activated brown adipocytes potentially contributes to the prevention of or therapeutics for obesity. The present study examined the effects of milk by-products, buttermilk and butter oil, on brown adipogenesis and the function of brown adipocytes. The treatment with buttermilk modulated brown adipogenesis, depending on the product tested; during brown adipogenesis, buttermilk 1 inhibited the differentiation of HB2 brown preadipocytes. In contrast, buttermilk 3 and 5 increased the expression of Ucp1 in the absence of isoproterenol (Iso), a β-adrenergic receptor agonist, suggesting the stimulation of brown adipogenesis. In addition, the Iso-induced expression of Ucp1 was enhanced by buttermilk 2 and 3. The treatment with buttermilk did not affect the basal or induced expression of Ucp1 by Iso in HB2 brown adipocytes, except for buttermilk 5, which increased the basal expression of Ucp1. Conversely, butter oil did not significantly affect the expression of Ucp1, irrespective of the cell phase of HB2 cells, ie, treatment during brown adipogenesis or of brown adipocytes. The results of the present study indicate that buttermilk is a regulator of brown adipogenesis and suggest its usefulness as a potential food material for antiobesity. [ABSTRACT FROM AUTHOR]

The ingestion of capsaicin, the principle pungent component of red and chili peppers, induces thermogenesis, in part, through the activation of brown adipocytes expressing genes related to mitochondrial biogenesis and uncoupling such as peroxisome proliferator-activated receptor (Ppar) γ coactivator-1α (Pgc-1α) and uncoupling protein 1 (Ucp1). Capsaicin has been suggested to induce the activation of brown adipocytes, which is mediated by the stimulation of sympathetic nerves. However, capsaicin may directly affect the differentiation of brown preadipocytes, brown adipocyte function, or both, through its significant absorption. We herein demonstrated that Trpv1, a capsaicin receptor, is expressed in brown adipose tissue, and that its expression level is increased during the differentiation of HB2 brown preadipocytes. Furthermore, capsaicin induced calcium influx in brown preadipocytes. A treatment with capsaicin in the early stage of brown adipogenesis did not affect lipid accumulation or the expression levels of Fabp4 (a gene expressed in mature adipocytes), Pparγ2 (a master regulator of adipogenesis) or brown adipocyte-selective genes. In contrast, a treatment with capsaicin in the late stage of brown adipogenesis slightly increased the expression levels of Fabp4, Pparγ2 and Pgc-1α. Although capsaicin did not affect the basal expression level of Ucp1, Ucp1 induction by forskolin was partially inhibited by capsaicin, irrespective of the dose of capsaicin. The results of the present study suggest the direct effects of capsaicin on brown adipocytes or in the late stage of brown adipogenesis. [ABSTRACT FROM AUTHOR]

Carnosine, which is abundant in meat, is a dipeptide composed of β-alanine and histidine, known to afford various health benefits. It has been suggested that carnosine can elicit an anti-obesity effect via induction and activation of brown/beige adipocytes responsible for non-shivering thermogenesis. However, the relationship between carnosine and brown/beige adipocytes has not been comprehensively elucidated. We hypothesized that β-alanine directly modulates brown/beige adipogenesis and performed an in vitro assessment to test this hypothesis. HB2 brown preadipocytes were differentiated using insulin from day 0. Cells were treated with various concentrations of β-alanine (12.5–100 μM) during adipogenesis (days 0–8) and differentiation (days 8–10). Then, cells were further stimulated with or without forskolin, an activator of the cAMP-dependent protein kinase pathway, on day 8 or day 10 for 4 h before harvesting. We observed that HB2 cells expressed molecules related to the transport and signal transduction of β-alanine. Treatment with β-alanine during brown adipogenesis dose-dependently enhanced forskolin-induced Ucp1 expression; this was not observed in differentiated brown adipocytes. Consistent with these findings, treatment with β-alanine during days 0–8 increased phosphorylation levels of CREB in forskolin-treated HB2 cells. In addition, β-alanine treatment during brown adipogenesis increased the expression of Pparα , known to induce brown/beige adipogenesis, in a dose-dependent manner. These findings revealed that β-alanine could target HB2 adipogenic cells and enhance forskolin-induced Ucp1 expression during brown adipogenesis, possibly by accelerating phosphorylation and activation of CREB. Thus, β-alanine, a carnosine-constituting amino acid, might directly act on brown adipogenic cells to stimulate energy expenditure. [ABSTRACT FROM AUTHOR]

• Rosiglitazone and BMP7 induces brown adipogenesis in C2C12 myogenic cells. • Formed adipocytes are not always UCP1-positive. • The differentiation is not mediated by known pathways to induce brown adipogenesis. • FGF pathway may be partly involved in the brown adipogenesis. Brown/beige adipocytes, which are derived from skeletal muscle/smooth muscle-lineage cells, consume excess energy as heat through the expression of mitochondrial uncoupling protein 1 (UCP1). Previous studies have shown that forced expression of PR/SET domain (PRDM)-16 or early B-cell factor (EBF)-2 induced UCP1-positive adipocytes in C2C12 myogenic cells. Here, we explored the culture conditions to induce Ucp1 expression in C2C12 cells without introducing exogenous genes. Treatment with rosiglitazone (a peroxisome proliferator-activated receptor (PPAR)-γ agonist), GW501516 (a PPARδ agonist), and bone morphogenetic protein (BMP)-7 for 8 days efficiently increased Ucp1 expression in response to treatment with forskolin, an activator of the protein kinase A pathway. BMP7 dose-dependently increased forskolin-induced Ucp1 expression in the presence of rosiglitazone and GW501516; however, GW501516 was not required for Ucp1 induction. Additionally, the structurally related proteins, BMP6 and BMP9, efficiently increased forskolin-induced Ucp1 expression in rosiglitazone-treated cells. UCP1 protein was localized in cells with lipid droplets, but adipocytes were not always positive for UCP1. Continuous treatment with BMP7 was needed for the efficient induction of Ucp1 by forskolin treatment. Significant expression of Prdm16 was not detected, irrespective of the treatment, and treatment with rosiglitazone, GW501516, and BMP7 did not affect the expression levels of Ebf2. Fibroblast growth factor receptor (Fgfr)- 3 expression levels were increased by BMP9 in rosiglitazone-treated cells, and molecules that upregulate Fgfr3 transcription partly overlapped with those that stimulate Ucp1 transcription. The present results provide basic information on the practical differentiation of myogenic cells to brown adipocytes. [ABSTRACT FROM AUTHOR]

The expression of uncoupling protein (UCP1) is up-regulated in mammalian brown adipocytes during cold exposure. However, a previous study revealed that UCP1 was highly expressed in the liver of common carps, and that the hepatic expression of UCP1 was down-regulated during cold exposure. The present study examined the effects of temperature on the recovery of UCP1 expression levels and the expression of genes involved in UCP1 transcription in the livers and kidneys of common carps. The hepatic and renal expressions of UCP1 were decreased by acclimation from 22 °C to 8 °C, and a subsequent increase in the water temperature from 8 °C to 28 °C recovered the renal, but not hepatic expression of UCP1. Changes in the expression of peroxisome proliferator-activator receptor (PPAR) γ, retinoid X receptor (RXR) α and PPARγ co-activator (PGC)-1α, genes that are involved in the expression of UCP1 in mammals, with ambient temperature indicated that the expressions of PPARγ and RXRα, but not expression of PGC-1α was decreased in response to cold exposure; the hepatic and renal expressions of PPARγ and RXRα recovered to basal levels with the cessation of cold exposure, although this was not complete for hepatic expression of PPARγ. The results of the present study indicate that a unique regulatory mechanism is responsible for the hepatic and renal expressions of carp UCP1 during cold exposure and subsequent reacclimation, and is distinct from that in murine brown adipocytes. [ABSTRACT FROM AUTHOR]

• UCP1 is a transporter responsible for nonshivering thermogenesis in mammalian brown/beige fat. • We identified four alternative splice variants of bovine Ucp1 (variant 1–4). • Bovine Ucp1 comprises a substantial proportion of variant 1/3. • The gene products from Ucp1 variant 2–4 are efficiently degraded by the proteasome system. [ABSTRACT FROM AUTHOR]

Abstract: Brown adipocytes, which regulate non-shivering thermogenesis, have been believed to exist in a limited number of mammalian species, and only under limited physiological conditions. Recent discoveries indicate that adult humans possess a significant number of functional brown adipocytes. This study explores the regulatory emergence of brown adipocytes in white adipose tissue (WAT) depots of fattening cattle. RT-PCR analyses indicated significant expression of Ucp1, a brown adipocyte-specific gene, in the WAT of 31-month-old Japanese Black steers. Immunohistochemical analysis revealed that Ucp1-positive small adipocytes were dispersed in the subcutaneous WAT. Next, we examined expression level of Ucp1 and other brown adipocyte-selective genes such as Pgc1α, Cidea, Dio2, Cox1, Cox7a1 and Cox8b in WAT of 30-month-old steers fed either diet with low protein/energy content (roughage diet) or that with high protein/energy content (concentrate diet) for 20months. Ucp1 expression in the subcutaneous WAT was significantly higher in the concentrate diet group than in the roughage diet group. Furthermore, the higher Ucp1 expression levels were limited to the subcutaneous WAT, and no differences between groups were detected in the mesenteric, perirenal, intermuscular or intramuscular WAT. Expression of Dio2, Cox1 and Cox8b was higher in the subcutaneous WAT but not in the mesenteric WAT of the concentrate diet group. Furthermore, expression of Prdm16, a positive regulator of differentiation toward brown adipocyte-lineage cells, and expression of leptin, a molecule that enhances activity of brown adipocytes, were significantly higher in the subcutaneous WAT of the concentrate diet group. This study demonstrates the presence of brown adipocytes in WAT depots of fattening cattle, and suggests the diet-related modulation of expression of genes predominantly expressed in brown adipocytes. [Copyright &y& Elsevier]