Multiple Roles of Sirtuin 6 in Adipose Tissue Inflammation

Adipose tissue (AT) inflammation is strongly associated with obesity-induced insulin resistance. When subjected to metabolic stress, adipocytes become inflamed and secrete a plethora of cytokines and chemokines, which recruit circulating immune cells to AT. Although sirtuin 6 (Sirt6) is known to control genomic stabilization, aging, and cellular metabolism, it is now understood to also play a pivotal role in the regulation of AT inflammation. Sirt6 protein levels are reduced in the AT of obese humans and animals and increased by weight loss. In this review, we summarize the potential mechanism of AT inflammation caused by impaired action of Sirt6 from the immune cells’ point of view. We first describe the properties and functions of immune cells in obese AT, with an emphasis on discrete macrophage subpopulations which are central to AT inflammation. We then highlight data that links Sirt6 to functional phenotypes of AT inflammation. Importantly, we discuss in detail the effects of Sirt6 deficiency in adipocytes, macrophages, and eosinophils on insulin resistance or AT browning. In our closing perspectives, we discuss emerging issues in this field that require further investigation.

SPA0355 prevents ovariectomy-induced bone loss in mice

Estrogen withdrawal in post-menopausal women leads to overactivation of osteoclasts, which contributes to the development of osteoporosis. Inflammatory cytokines are known as one of mechanisms of osteoclast activation after estrogen deficiency. SPA0355 is a thiourea derivative that has been investigated for its antioxidant and anti-inflammatory activities. However, its efficacy in bone resorption has not been previously investigated. The aim of this study was to investigate the impact of SPA0355 on the development of osteoporosis and to explore its mode of action. In vitro experiments showed that SPA0355 inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis in primary bone marrow-derived macrophages. This effect appears to be independent of estrogen receptor activation as ICI 180,782 failed to abrogate its effects on osteoclasts. Further signaling studies revealed that SPA0355 suppressed activation of the MAPKs, Akt, and NF-κB pathways. SPA0355 also increased osteoblastic differentiation, as evidenced by its effects on alkaline phosphatase activity and mineralization nodule formation. Intraperitoneal administration of SPA0355 to ovariectomized mice prevented bone loss, as verified by three-dimensional images and bone morphometric parameters derived from µCT analysis. Noticeably, SPA0355 did not show hepatotoxicity and nephrotoxicity and also had little effect on hematological parameters. Taken together, the results indicate that SPA0355 may protect against bone loss in ovariectomized mice by stimulation of osteoblast differentiation and by inhibition of osteoclast resorption. Therefore, SPA0355 is a safe and potential candidate for management of postmenopausal osteoporosis.

Smad4 controls bone homeostasis through regulation of osteoblast/osteocyte viability

Regulation of osteoblast and osteocyte viability is essential for bone homeostasis. Smad4, a major transducer of bone morphogenetic protein and transforming growth factor-β signaling pathways, regulates apoptosis in various cell types through a mitochondrial pathway. However, it remains poorly understood whether Smad4 is necessary for the regulation of osteoblast and osteocyte viability. In this study, we analyzed Smad4Δ(Os) mice, in which Smad4 was subjected to tissue-specific disruption under the control of the 2.3-kb Col1a1 promoter, to understand the functional significance of Smad4 in regulating osteoblast/osteocyte viability during bone formation and remodeling. Smad4Δ(Os) mice showed a significant increase in osteoblast number and osteocyte density in the trabecular and cortical regions of the femur, whereas osteoclast activity was significantly decreased. The proliferation of osteoblasts/osteocytes did not alter, as shown by measuring 5′-bromo-2′deoxyuridine incorporation. By contrast, the percentage of TUNEL-positive cells decreased, together with a decrease in the Bax/Bcl-2 ratio and in the proteolytic cleavage of caspase 3, in Smad4Δ(Os) mice. Apoptosis in isolated calvaria cells from Smad4Δ(Os) mice decreased after differentiation, which was consistent with the results of the TUNEL assay and western blotting in Smad4Δ(Os) mice. Conversely, osteoblast cells overexpressing Smad4 showed increased apoptosis. In an apoptosis induction model of Smad4Δ(Os) mice, osteoblasts/osteocytes were more resistant to apoptosis than were control cells, and, consequently, bone remodeling was attenuated. These findings indicate that Smad4 has a significant role in regulating osteoblast/osteocyte viability and therefore controls bone homeostasis.

Myeloid deletion of SIRT1 suppresses collagen-induced arthritis in mice by modulating dendritic cell maturation

The type III histone deacetylase silent information regulator 1 (SIRT1) is an enzyme that is critical for the modulation of immune and inflammatory responses. However, the data on its role in rheumatoid arthritis (RA) are limited and controversial. To better understand how SIRT1 regulates adaptive immune responses in RA, we evaluated collagen-induced arthritis (CIA) in myeloid cell-specific SIRT1 knockout (mSIRT1 KO) and wild-type (WT) mice. Arthritis severity was gauged on the basis of clinical, radiographic and pathologic scores. Compared with their WT counterparts, the mSIRT1 KO mice exhibited less severe arthritis, which was less destructive to the joints. The expression levels of inflammatory cytokines, matrix metalloproteinases and ROR-γT were also reduced in the mSIRT1 KO mice compared with the WT mice and were paralleled by reductions in the numbers of Th1 and Th17 cells and CD80- or CD86-positive dendritic cells (DCs). In addition, impaired DC maturation and decreases in the Th1/Th17 immune response were observed in the mSIRT1 KO mice. T-cell proliferation was also investigated in co-cultures with antigen-pulsed DCs. In the co-cultures, the DCs from the mSIRT1 KO mice showed decreases in T-cell proliferation and the Th1/Th17 immune response. In this study, myeloid cell-specific deletion of SIRT1 appeared to suppress CIA by modulating DC maturation. Thus, a careful investigation of DC-specific SIRT1 downregulation is needed to gauge the therapeutic utility of agents targeting SIRT1 in RA.

Polyphenols isolated from Broussonetia kazinoki prevent cytokine-induced beta-cell damage and the development of type 1 diabetes

The axis of nuclear factor kappaB (NF-kappaB)-inducible NO synthase (iNOS)-nitric oxide plays a key role in cytokine- and streptozotocin-mediated pancreatic beta-cell damage. In this study, we investigated the effects of kazinol C and isokazinol D isolated from Broussonetia kazinoki on the beta-cell viability and function. RINm5F cells and primary islets were used for in vitro and ex vivo cytokine toxicity experiments, respectively. For type 1 diabetes induction, mice were injected with multiple low-dose streptozotocin (MLDS). Cytokine-induced toxicity was completely abolished in both RINm5F cells and islets that were pretreated with either kazinol C or isokazinol D. Both kazinols inhibited the NF-kappaB signaling pathway, thereby inhibiting cytokine-mediated iNOS induction, nitric oxide production, apoptotic cell death and defects in insulin secretion. Moreover, the occurrence of diabetes in MLDS-treated mice was efficiently attenuated in kazinol-pretreated mice. Immunohistochemical analysis revealed that the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive apoptotic cells and nuclear p65-positive cells were significantly decreased in kazinol-pretreated mice. Our results suggest that kazinol C and isokazinol D block the NF-kappaB pathway, thus reducing the extent of beta-cell damage. Therefore, kazinol C and isokazinol D may have therapeutic value in delaying pancreatic beta-cell damage in type 1 diabetes.

Correction: Neuroradiological and Neurophysiological Characteristics of Patients With Dyskinetic Cerebral Palsy

We found that one phrase should be corrected.

Transplantation of betacellulin-transduced islets improves glucose intolerance in diabetic mice

Type 1 diabetes is an autoimmune disease caused by permanent destruction of insulin-producing pancreatic beta cells and requires lifelong exogenous insulin therapy. Recently, islet transplantation has been developed, and although there have been significant advances, this approach is not widely used clinically due to the poor survival rate of the engrafted islets. We hypothesized that improving survival of engrafted islets through ex vivo genetic engineering could be a novel strategy for successful islet transplantation. We transduced islets with adenoviruses expressing betacellulin, an epidermal growth factor receptor ligand, which promotes beta-cell growth and differentiation, and transplanted these islets under the renal capsule of streptozotocin-induced diabetic mice. Transplantation with betacellulin-transduced islets resulted in prolonged normoglycemia and improved glucose tolerance compared with those of control virus-transduced islets. In addition, increased microvascular density was evident in the implanted islets, concomitant with increased endothelial von Willebrand factor immunoreactivity. Finally, cultured islets transduced with betacellulin displayed increased proliferation, reduced apoptosis and enhanced glucose-stimulated insulin secretion in the presence of cytokines. These experiments suggest that transplantation with betacellulin-transduced islets extends islet survival and preserves functional islet mass, leading to a therapeutic benefit in type 1 diabetes.

Neuroradiological and Neurophysiological Characteristics of Patients With Dyskinetic Cerebral Palsy

OBJECTIVE: To investigate neuroradiological and neurophysiological characteristics of patients with dyskinetic cerebral palsy (CP), by using magnetic resonance imaging (MRI), voxel-based morphometry (VBM), diffusion tensor tractography (DTT), and motor evoked potential (MEP). METHODS: Twenty-three patients with dyskinetic CP (13 males, 10 females; mean age 34 years, range 16-50 years) were participated in this study. Functional evaluation was assessed by the Gross Motor Functional Classification System (GMFCS) and Barry-Albright Dystonia Scale (BADS). Brain imaging was performed on 3.0 Tesla MRI, and volume change of the grey matter was assessed using VBM. The corticospinal tract (CST) and superior longitudinal fasciculus (SLF) were analyzed by DTT. MEPs were recorded in the first dorsal interossei, the biceps brachii and the deltoid muscles. RESULTS: Mean BADS was 16.4+/-5.0 in ambulatory group (GMFCS levels I, II, and III; n=11) and 21.3+/-3.9 in non-ambulatory group (GMFCS levels IV and V; n=12). Twelve patients showed normal MRI findings, and eleven patients showed abnormal MRI findings (grade I, n=5; grade II, n=2; grade III, n=4). About half of patients with dyskinetic CP showed putamen and thalamus lesions on MRI. Mean BADS was 20.3+/-5.7 in normal MRI group and 17.5+/-4.0 in abnormal MRI group. VBM showed reduced volume of the hippocampus and parahippocampal gyrus. In DTT, no abnormality was observed in CST, but not in SLF. In MEPs, most patients showed normal central motor conduction time. CONCLUSION: These results support that extrapyramidal tract, related with basal ganglia circuitry, may be responsible for the pathophysiology of dyskinetic CP rather than CST abnormality.

Neuroradiological and Neurophysiological Characteristics of Patients With Dyskinetic Cerebral Palsy

OBJECTIVE: To investigate neuroradiological and neurophysiological characteristics of patients with dyskinetic cerebral palsy (CP), by using magnetic resonance imaging (MRI), voxel-based morphometry (VBM), diffusion tensor tractography (DTT), and motor evoked potential (MEP). METHODS: Twenty-three patients with dyskinetic CP (13 males, 10 females; mean age 34 years, range 16-50 years) were participated in this study. Functional evaluation was assessed by the Gross Motor Functional Classification System (GMFCS) and Barry-Albright Dystonia Scale (BADS). Brain imaging was performed on 3.0 Tesla MRI, and volume change of the grey matter was assessed using VBM. The corticospinal tract (CST) and superior longitudinal fasciculus (SLF) were analyzed by DTT. MEPs were recorded in the first dorsal interossei, the biceps brachii and the deltoid muscles. RESULTS: Mean BADS was 16.4+/-5.0 in ambulatory group (GMFCS levels I, II, and III; n=11) and 21.3+/-3.9 in non-ambulatory group (GMFCS levels IV and V; n=12). Twelve patients showed normal MRI findings, and eleven patients showed abnormal MRI findings (grade I, n=5; grade II, n=2; grade III, n=4). About half of patients with dyskinetic CP showed putamen and thalamus lesions on MRI. Mean BADS was 20.3+/-5.7 in normal MRI group and 17.5+/-4.0 in abnormal MRI group. VBM showed reduced volume of the hippocampus and parahippocampal gyrus. In DTT, no abnormality was observed in CST, but not in SLF. In MEPs, most patients showed normal central motor conduction time. CONCLUSION: These results support that extrapyramidal tract, related with basal ganglia circuitry, may be responsible for the pathophysiology of dyskinetic CP rather than CST abnormality.

SPA0355 attenuates ischemia/reperfusion-induced liver injury in mice

Hepatic ischemia/reperfusion (I/R) injury leads to oxidative stress and acute inflammatory responses that cause liver damage and have a considerable impact on the postoperative outcome. Much research has been performed to develop possible protective techniques. We aimed to investigate the efficacy of SPA0355, a synthetic thiourea analog, in an animal model of hepatic I/R injury. Male C57BL/6 mice underwent normothermic partial liver ischemia for 45 min followed by varying periods of reperfusion. The animals were divided into three groups: sham operated, I/R and SPA0355 pretreated. Pretreatment with SPA0355 protected against hepatic I/R injury, as indicated by the decreased levels of serum aminotransferase and reduced parenchymal necrosis and apoptosis. Liver synthetic function was also restored by SPA0355 as reflected by the prolonged prothrombin time. To gain insight into the mechanism involved in this protection, we measured the activity of nuclear factor-kappaB (NF-kappaB), which revealed that SPA0355 suppressed the nuclear translocation and DNA binding of NF-kappaB subunits. Concomitantly, the expression of NF-kappaB target genes such as IL-1beta, IL-6, TNF-alpha and iNOS was significantly downregulated. Lastly, the liver antioxidant enzymes superoxide dismutase, catalase and glutathione were upregulated by SPA0355 treatment, which correlated with the reduction in serum malondialdehyde. Our results suggest that SPA0355 pretreatment prior to I/R injury could be an effective method to reduce liver damage.

The efficacy of SPA0355 in protecting beta cells in isolated pancreatic islets and in a murine experimental model of type 1 diabetes

Cytokines activate several inflammatory signals that mediate beta-cell destruction. We recently determined that SPA0355 is a strong anti-inflammatory compound, thus reporting its efficacy in protecting beta cells from various insults. The effects of SPA0355 on beta-cell survival were studied in RINm5F cells and primary islets. The protective effects of this compound on the development of type 1 diabetes were evaluated in non-obese diabetic (NOD) mice. SPA0355 completely prevented cytokine-induced nitric oxide synthase (iNOS) expression and cytotoxicity in RINm5F cells and isolated islets. The molecular mechanism of SPA0355 inhibition of iNOS expression involves the inhibition of nuclear factor kappaB and Janus kinase signal transducer and activator of transcription pathways. The protective effects of SPA0355 against cytokine toxicity were further demonstrated by normal insulin secretion and absence of apoptosis of cytokine-treated islets. In experiments with NOD mice, the occurrence of diabetes was efficiently reduced when the mice were treated with SPA0355. Therefore, SPA0355 might be a valuable treatment option that delays the destruction of pancreatic beta cells in type 1 diabetes.

Inhibition of Janus activated kinase-3 protects against myocardial ischemia and reperfusion injury in mice

Recent studies have documented that Janus-activated kinase (JAK)-signal transducer and activator of transcription (STAT) pathway can modulate the apoptotic program in a myocardial ischemia/reperfusion (I/R) model. To date, however, limited studies have examined the role of JAK3 on myocardial I/R injury. Here, we investigated the potential effects of pharmacological JAK3 inhibition with JANEX-1 in a myocardial I/R model. Mice were subjected to 45 min of ischemia followed by varying periods of reperfusion. JANEX-1 was injected 1 h before ischemia by intraperitoneal injection. Treatment with JANEX-1 significantly decreased plasma creatine kinase and lactate dehydrogenase activities, reduced infarct size, reversed I/R-induced functional deterioration of the myocardium and reduced myocardial apoptosis. Histological analysis revealed an increase in neutrophil and macrophage infiltration within the infarcted area, which was markedly reduced by JANEX-1 treatment. In parallel, in in vitro studies where neutrophils and macrophages were treated with JANEX-1 or isolated from JAK3 knockout mice, there was an impairment in the migration potential toward interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), respectively. Of note, however, JANEX-1 did not affect the expression of IL-8 and MCP-1 in the myocardium. The pharmacological inhibition of JAK3 might represent an effective approach to reduce inflammation-mediated apoptotic damage initiated by myocardial I/R injury.

Reliability and Validity of the Korean Version VISA-P Questionnaire for Patellar Tendinopathy in Adolescent Elite Volleyball Athletes

OBJECTIVE: To translate the English Victorian Institute of Sport Assessment for patellar tendinopathy (VISA-P) questionnaire into a Korean version and to determine the reliability and validity of the Korean version. METHODS: The English VISA-P questionnaire was translated into Korean according to the internationally recommended guidelines. Then, 28 adolescent elite volleyball athletes (average age, 16 years; range, 14 to 19 years) were asked to complete the questionnaire three times (before examination, after examination, and 1 week later) for reliability. They were evaluated through a physical examination and ultrasonography to diagnosis patellar tendinopathy. RESULTS: The internal consistency of the VISA-P questionnaire by Cronbach's alpha was 0.80 for the first, 0.78 for the second, and 0.79 for the third assessment. The intraclass correlation coefficient (ICC) between the first and second assessments was 0.97. The ICC between the second and third assessments was 0.96. The mean VISA-P scores were 67.6+/-15.7 for the patellar tendinopathy group (n=23) and 92.6+/-8.6 for the normal group (n=5). There were significantly lower VISA-P scores in the patellar tendinopathy group compared to the normal group. CONCLUSION: The translated Korean version VISA-P questionnaire has good internal consistency, test-retest reliability and validity. In addition, this study indicated that most adolescent elite volleyball athletes had patellar tendon problems. Therefore, the Korean version VISA-P is a useful self-administered outcome score of athletes with patellar tendinopathy.

Effect of 45degrees Reclining Sitting Posture on Swallowing in Patients with Dysphagia

PURPOSE: To determine the effect of a 45degrees reclining sitting posture on swallowing in patients with dysphagia. MATERIALS AND METHODS: Thirty-four patients with dysphagia were evaluated. Videofluoroscopic swallowing study was performed for each patient in 90degrees upright and in 45degrees reclining sitting posture. Patients swallowed 5 types of boluses twice: sequentially 2 mL thin liquid, 5 mL thin liquid, thick liquid, yogurt, and cooked rice. Data such as the penetration-aspiration scale (PAS), oral transit time (OTT), pharyngeal delay time (PDT), pharyngeal transit time (PTT), residue in valleculae and pyriform sinuses, premature bolus loss, and nasal penetration were obtained. RESULTS: The mean PAS on the 2 mL thin liquid decreased significantly in the 45degrees reclining sitting posture (p=0.007). The mean PAS on 5 mL thin liquid in the 45degrees reclining sitting posture showed decreasing tendency. The residue in valleculae decreased significantly for all boluses in the 45degrees reclining sitting posture (p<0.001, p=0.002, p=0.003, p<0.001, p=0.020, respectively). The residue in pyriform sinuses increased significantly on 5 mL thin liquid, thick liquid, and yogurt (p=0.031, p=0.020, p=0.002, respectively). There were no significant differences in OTT, PDT, PTT, premature bolus loss, and nasal penetration between both postures. CONCLUSION: PAS on 2 mL thin liquid and residue in valleculae on all types of boluses were decreased in a 45degrees reclining sitting posture. Therefore, we believe that the 45degrees reclining sitting posture on swallowing is beneficial for the patients with penetration or aspiration on small amounts of thin liquid and large amounts of residue in valleculae.

COMP-Angiopoietin-1 Stimulates Synovial Proliferation but Suppresses Osteoclast by Enhancing Angiogenesis and Osteoblast Maturation in Collagen-Induced Arthritis

OBJECTIVE: Angiopoietin-1 (Ang1) is a potent angiogenic factor that can increase synovial angiogenesis and also enhance osteoblast maturation and bone formation. However, its role in rheumatoid arthritis (RA) has not been well documented. Thus, we investigated roles of Ang1 in collagen-induced arthritis (CIA). METHODS: A recombinant adenovirus carrying the gene that encodes either cartilage oligomeric matrix protein (AdCOMP)-Ang1 (a modified form of Ang1) or LacZ (AdLacZ) was injected intravenously into CIA mice. Clinical, radiological, histopathological, and immunofluorescent analyses were performed. Serum levels of receptor activators of nuclear factor kappaB ligand (RANKL) and osteoprotegerin (OPG) and expression of osteoblast maturation genes were analyzed. RESULTS: AdCOMP-Ang1-injected mice developed more severe inflammation than the AdLacZ-injected mice. However, there were no significant differences in cartilage damage and bone erosion. More PECAM-1-positive blood vessels were seen in the synovium of the AdCOMP-Ang1-injected mice than in those injected with AdLacZ. Interestingly, a lower number of TRAP-positive osteoclasts were observed in AdCOMP-Ang1-injected CIA mice than in the AdLacZ group when comparing sections obtained from joints showing similar synovial proliferation. The serum OPG/RANKL ratio and expression of osteoblast maturation genes, such as runt-related transcription factor 2, bone sialoprotein, type 1 collagen, osteopontin, and osterix, were significantly upregulated in the AdCOMP-Ang1 group. CONCLUSION: COMP-Ang1 facilitates arthritis onset and increases synovial inflammation, but enhances osteoblast maturation, which in turn inhibits osteoclastogenesis by increasing the OPG/RANKL ratio in CIA. Our results suggest that careful investigation is necessary to delineate the possible therapeutic use of COMP-Ang1 as an adjunctive agent, in combination with anti-inflammatory therapies, for the prevention of bone destruction in RA.

Inhibitory Effect of SPA0355, a Thiourea Analogue, on Inflammation and Alveolar Bone Loss in Rats with Ligature-Induced Periodontitis

It has been documented that SPA0355 exerts anti-inflammatory effects via the inhibition of nuclear factor-kappaB activation. In present study, we investigated the inhibitory effects of SPA0355 on periodontitis in an animal model. Periodontitis was induced by ligation of the cervix of the 1st molar in the left mandible in rats. After ligature, the rats were randomly divided into four groups and topically applied with SPA0355 (0.5, 1, and 2%) or the vehicle alone once daily for 10 days. Body weight and food intake were measured daily throughout the experimental period. At day 10 post-ligature, the infiltration of inflammatory cells and distance of the cementoenamel junction (CEJ) to the alveolar bone crest (ABC) in the distal area of ligatured tooth were estimated histopathologically. No changes in body weight or food intake were found between the control and SPA0355 groups. The degree of inflammation was decreased in all three SPA0355 application groups. A decrease CEJ-ABC distance was observed in the 0.5% and 1% SPA0355 groups. These results indicate that SPA0355 inhibits the infiltration of inflammatory cells and alveolar bone resorption and suggests its potential as a therapeutic agent for periodontitis.

Sulfuretin protects against cytokine-induced beta-cell damage and prevents streptozotocin-induced diabetes

NF-kappaB activation has been implicated as a key signaling mechanism for pancreatic beta-cell damage. Sulfuretin is one of the main flavonoids produced by Rhus verniciflua, which is reported to inhibit the inflammatory response by suppressing the NF-kappaB pathway. Therefore, we isolated sulfuretin from Rhus verniciflua and evaluated if sulfuretin could inhibit cytokine- or streptozotocin-induced beta-cell damage. Rat insulinoma RINm5F cells and isolated rat islets were treated with IL-1beta and IFN-gamma to induce cytotoxicity. Incubation of cells and islets with sulfuretin resulted in a significant reduction of cytokine-induced NF-kappaB activation and its downstream events, iNOS expression, and nitric oxide production. The cytotoxic effects of cytokines were completely abolished when cells or islets were pretreated with sulfuretin. The protective effect of sulfuretin was further demonstrated by normal insulin secretion of cytokine-treated islets in response to glucose. Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was further evidenced by immunohistochemical staining of islets. However, the diabetogenic effects of streptozotocin were completely prevented when mice were pretreated with sulfuretin. The anti-diabetogenic effects of sulfuretin were also mediated by suppression of NF-kappaB activation. Collectively, these results indicate that sulfuretin may have therapeutic value in preventing beta-cell damage.

Activation of PPARgamma induces profound multilocularization of adipocytes in adult mouse white adipose tissues

We sought to determine the effects of activation of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) on multilocularization of adipocytes in adult white adipose tissue (WAT). Male C57BL/6 normal, db/db, and ob/ob mice were treated with agonists of PPAR-gamma, PPAR-alpha, or beta3-adrenoceptor for 3 weeks. To distinguish multilocular adipocytes from unilocular adipocytes, whole-mounted adipose tissues were co-immunostained for perilipin and collagen IV. PPAR-gamma activation with rosiglitazone or pioglitazone induced a profound change of unilocular adipocytes into smaller, multilocular adipocytes in adult WAT in a time-dependent, dose-dependent, and reversible manner. PPAR-alpha activation with fenofibrate did not affect the number of locules or remodeling. db/db and ob/ob obese mice exhibited less multilocularization in response to PPAR-gamma activation compared to normal mice. Nevertheless, all adipocytes activated by PPAR-gamma contained a single nucleus regardless of locule number. Multilocular adipocytes induced by PPAR-gamma activation contained substantially increased mitochondrial content and enhanced expression of uncoupling protein-1, PPAR-gamma coactivator-1-alpha , and perilipin. Taken together, PPAR-gamma activation induces profound multilocularization and enhanced mitochondrial biogenesis in the adipocytes of adult WAT. These changes may affect the overall function of WAT.

Effect of xanthohumol on melanogenesis in B16 melanoma cells

Xanthohumol (XH), the principal prenylflavonoid of the hop plant (Humulus lupulus L.), dose-dependently inhibited isobutylmethylxanthine (IBMX)-induced melanogenesis in B16 melanoma cells, with little cytotoxicity at the effective concentrations. Decreased melanin content was accompanied by reduced tyrosinase enzyme activity, protein and mRNA expression. The levels of tyrosinase-related protein 1 and 2 mRNAs were decreased by XH. XH also inhibited alpha-melanocyte stimulating hormone- or forskolin-induced increases in melanogenesis, suggesting an action on the cAMP-dependent melanogenic pathway. XH downregulated the protein and mRNA expression of microphthalmia-associated transcription factor (MITF), a master transcriptional regulator of key melanogenic enzymes. These results suggest that XH might act as a hypo-pigmenting agent through the downregulation of MITF in the cAMP-dependent melanogenic pathway.

Effect of Hypoxia on the Melanogenesis of Murine B16 Melanoma Cells / 대한피부과학회지

BACKGROUND: Numerous reports suggest the role of oxygen in melanogenesis. However, little has been reported on the effect of a hypoxic environment on cellular melanogenesis. OBJECTIVE: The effect of low oxygen tension on cellular melanogenesis was investigated in B16 murine melanoma cells. METHODS: Using cells cultured under an ambient (21% O2) or hypoxic (5% O2) condition, melanin content and tyrosinase activity were measured spectrophotometrically. The expression of tyrosinase, tyrosinase-related protein (TRP)- 1, and TRP-2 were analyzed by RT-PCR and Western blot. RESULTS: Culture of cells under hypoxic conditions caused significant inhibition of isobutylmethylxanthine (IBMX)- induced increase of melanin content. No cytotoxicity was observed during the hypoxic culture periods. Decreased melanin content occurred through the decrease of tyrosinase protein and activity (p<0.01). The mRNA levels of tyrosinase and TRP-2 were also decreased by hypoxia, while that of TRP-1 was unchanged. Similar inhibitions of melanin content and tyrosinase activity were observed in the cells stimulated with dibutyryl-cAMP. CONCLUSION: IBMX-induced melanogenesis in B16 cells was significantly inhibited under hypoxic culture conditions, suggesting the important role of oxygen tension in cellular melanogenesis.