Acute regulation of 5′-AMP-activated protein kinase by long-chain fatty acid,glucose and insulin in rat primary adipocytes

Palmitate increased AMPK (5′-AMP-activated protein kinase) activity, glucose utilization and 2-DOG (2-deoxyglucose) transport in rat adipocytes. All three effects were blocked by the AMPK inhibitor Compound C, leading to the conclusion that in response to an increase in long-chain NEFA (non-esterified fatty acid) concentration AMPK mediated an enhancement of adipocyte glucose transport, thereby providing increased glycerol 3-phosphate for FA (fatty acid) esterification to TAG (triacylglycerol). Activation of AMPK in response to palmitate was not due to an increase in the adipocyte AMP:ATP ratio. Glucose decreased AMPK activity and effects of palmitate and glucose on AMPK activity were antagonistic. While insulin had no effect on basal AMPK activity insulin did decrease AMPK activity in the presence of palmitate and also decreased the percentage effectiveness of palmitate to increase the transport of 2-DOG. It is suggested that activation of adipocyte AMPK by NEFA, as well as decreasing the activity of hormone-sensitive lipase, could modulate adipose tissue dynamics by increasing FA esterification and, under certain circumstances, FA synthesis.     

Anti-diabetic properties of Daphniphyllum macropodum fruit and its active compound

We evaluated in vitro anti-diabetic activities of 497 native plants of Jeju Island (South Korea) by measuring the induction of adipocyte differentiation. Among the plants, Daphniphyllum macropodum fruit extract (DME) had the highest peroxisome proliferator-activated receptor γ (PPARγ) agonist activity and was therefore selected as a potential source of anti-diabetic agents. To elucidate the active components of DME, constituent compounds were purified and their effects on the adipocyte differentiation were studied. Using activity-guided fractionation, four compounds were isolated from DME and their adipogenic effects were evaluated. Among the compounds isolated, 5,7-dihydroxychromone potently induced the differentiation of mouse 3T3-L1 preadipocytes. DME and 5,7-dihydroxychromone increased PPARγ and liver X receptor α (LXRα) mRNA expression levels. To determine whether the adipogenic effects we observed might affect serum glucose levels, we undertook in vivo experiment using streptozotocin-/high-fat diet-induced type 2 diabetes mouse model. DME supplementation reduced serum glucose, total cholesterol, and triacylglycerol levels in diabetes mice. These results suggest that DME may be useful for the prevention and treatment of type 2 diabetes mellitus. Moreover, it was proposed that 5,7-dihydroxychromone isolated from DME is one of the active compounds that may contribute to regulate blood glucose levels.     

Cytokines, macrophage lipid metabolism and foam cells: implications for cardiovascular disease therapy

Cardiovascular disease is the biggest killer globally and the principal contributing factor to the pathology is atherosclerosis; a chronic, inflammatory disorder characterized by lipid and cholesterol accumulation and the development of fibrotic plaques within the walls of large and medium arteries. Macrophages are fundamental to the immune response directed to the site of inflammation and their normal, protective function is harnessed, detrimentally, in atherosclerosis. Macrophages contribute to plaque development by internalizing native and modified lipoproteins to convert them into cholesterol-rich foam cells. Foam cells not only help to bridge the innate and adaptive immune response to atherosclerosis but also accumulate to create fatty streaks, which help shape the architecture of advanced plaques. Foam cell formation involves the disruption of normal macrophage cholesterol metabolism, which is governed by a homeostatic mechanism that controls the uptake, intracellular metabolism, and efflux of cholesterol. It has emerged over the last 20 years that an array of cytokines, including interferon-γ, transforming growth factor-β1, interleukin-1β, and interleukin-10, are able to manipulate these processes. Foam cell targeting, anti-inflammatory therapies, such as agonists of nuclear receptors and statins, are known to regulate the actions of pro- and anti-atherogenic cytokines indirectly of their primary pharmacological function. A clear understanding of macrophage foam cell biology will hopefully enable novel foam cell targeting therapies to be developed for use in the clinical intervention of atherosclerosis.     

Early activated Th-1 type and dominantly diverse natural killer T (CD3⁺CD161⁺Vα24⁻) cells in bone marrow among visceral leishmaniasis patients

Lipid antigens of Leishmania donovani-like lipophosphoglycans (LPG) are demonstrated to be a potent ligand for natural killer T (NKT) cell activation. Little is known about the phenotype or function of these cells and their trafficking pattern to the bone marrow (BM) of visceral leishmaniasis (VL) patients. Their precise role in humans still requires pathological validation. The study included 42 parasitologically confirmed patients (mean age 24.80 ± 16.26 years; range 3-70 years; 25 males and 17 females), 33 healthy contact subjects (family/non-family members) and normal BM specimens (NBM; n = 9). Enumeration of NKT cells and quantification of parasites (before and after therapy) were performed for the recruited patients. Results established that non-CD1d restricted, diverse cells are the dominant population among resident but not enriched NKT (CD3⁺CD161⁺) cells at the disease site (BM). Expression profiles for various markers are indicative of their early activated (CD69⁺, CD62L^low, CD11a^high) CCR5⁺ phenotype at the BM. Functionally, BM-derived NKT cells were dominantly producing IFN-γ in response to L. donovani antigen in vitro. Given these observations, these data indicate that CD3⁺CD161⁺ diverse NKT cells are heterogeneous in function and of the dominant Th-1 phenotype at the disease site.     

Adipose-specific disruption of autotaxin enhances nutritional fattening and reduces plasma lysophosphatidic acid

Autotaxin (ATX) is a secreted lysophospholipase D that generates the lipid mediator lysophosphatidic acid (LPA). ATX is secreted by adipose tissue and its expression is enhanced in obese/insulin-resistant individuals. Here, we analyzed the specific contribution of adipose-ATX to fat expansion associated with nutritional obesity and its consequences on plasma LPA levels. We established ATX(F/F)/aP2-Cre (FATX-KO) transgenic mice carrying a null ATX allele specifically in adipose tissue. FATX-KO mice and their control littermates were fed either a normal or a high-fat diet (HFD) (45% fat) for 13 weeks. FATX-KO mice showed a strong decrease (up to 90%) in ATX expression in white and brown adipose tissue, but not in other ATX-expressing organs. This was associated with a 38% reduction in plasma LPA levels. When fed an HFD, FATX-KO mice showed a higher fat mass and a higher adipocyte size than control mice although food intake was unchanged. This was associated with increased expression of peroxisome proliferator-activated receptor (PPAR)γ2 and of PPAR-sensitive genes (aP2, adiponectin, leptin, glut-1) in subcutaneous white adipose tissue, as well as in an increased tolerance to glucose. These results show that adipose-ATX is a negative regulator of fat mass expansion in response to an HFD and contributes to plasma LPA levels.     

SEAWEED EXTRACTS AS A POTENTIAL TOOL FOR THE ATTENUATION OF OXIDATIVE DAMAGE IN OBESITY‐RELATED PATHOLOGIES1

Recent studies suggest that seaweed extracts are a significant source of bioactive compounds comparable to the dietary phytochemicals such as onion and tea extracts. The exploration of natural antioxidants that attenuate oxidative damage is important for developing strategies to treat obesity‐related pathologies. The objective of this study was to screen the effects of seaweed extracts of 49 species on adipocyte differentiation and reactive oxygen species (ROS) production during the adipogenesis in 3T3‐L1 adipocytes, and to investigate their total phenol contents and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activities. Our results show that high total phenol contents were observed in the extracts of Ecklonia cava (see Table 1 for taxonomic authors) (681.1 ± 16.0 μg gallic acid equivalents [GAE] · g^?1), Dictyopteris undulata (641.3 ± 70.7 μg GAE · g^?1), and Laurencia intermedia (560.9 ± 48.1 μg GAE · g^?1). In addition, DPPH radical scavenging activities were markedly higher in Sargassum macrocarpum (60.2%), Polysiphonia morrowii (55.0%), and Ishige okamurae (52.9%) than those of other seaweed extracts (P < 0.05). Moreover, treatment with several seaweed extracts including D. undulata, Sargassum micracanthum, Chondrus ocellatus, Gelidium amansii, Gracilaria verrucosa, and Grateloupia lanceolata significantly inhibited adipocyte differentiation and ROS production during differentiation of 3T3‐L1 preadipocytes. Furthermore, the production of ROS was positively correlated with lipid accumulation (R² = 0.8149). According to these preliminary results, some of the seaweed extracts can inhibit ROS generation, which may protect against oxidative stress that is linked to obesity. Further studies are required to determine the molecular mechanism between the verified seaweeds and ROS, and the resulting effects on obesity.

Table 1. List of Korean seaweed extracts of 49 species evaluated in this experiment.

Antimony resistance during Visceral Leishmaniasis: A possible consequence of serial mutations in ABC transporters of Leishmania species

Visceral Leishmaniasis is a macrophage associated disorder for the treatment of which antimony based drugs like SAG and SSG were the first choice in the recent past. The clinical value of antimony therapy is now declined against VL because increasing cases of Sodium Antimony Gluconate (SAG) resistance have reached outstanding proportion in Bihar, India. Within this context we looked into the protein sequences of ABC transporters of Leishmania spp associated with Visceral Leishmaniasis that are known to play a crucial role in the development of multidrug resistance (MDR). Our studies consisting of ClustalW, Phylogeny and TCOFFEE have pinpointed that ABC transporters have enormously diverged during the process of evolution even within the identical species strains resulting in insignificant homology and subdued conservation amongst the aminoacid residues. Moreover these amino acid residues remain susceptible to mutations in evolutionary era as indicated by high frequency of variations by the variability studies. Hence we predict that during the process of evolution a series of frequent mutations might have led to changes in the ABC transporters favorable to effluxing the drug thereby making the Leishmania species prone to resistance against the efficient first line drug SAG, used for combating VL. This selection has made them to survive efficiently in the adverse circumstances of antimony based antileishmanial therapy regime.     

灌胃和皮下注射脂肪膜蛋白卵黄抗体对大鼠生长和脂肪沉积的影响

目的：研究脂肪膜卵黄抗体不同处理对大鼠生长和脂肪沉积的影响。方法：选用140 g左右雌性SD大鼠96只,随机分成4组,分别灌胃阴性卵黄和含脂肪细胞膜蛋白抗体的阳性卵黄;皮下注射阴性卵黄和含脂肪细胞膜蛋白抗体的阳性卵黄。灌胃每3 d给予1 ml卵黄,皮下注射连续4 d经背部皮下多点注射1 ml卵黄,1月后同方式加强1次。75 d后屠宰并采集血样测定。结果：阳性卵黄处理后大鼠体重和摄食量无显著差异。灌胃阳性卵黄降低肠系膜脂指数、子宫周脂指数和肾脂肪囊指数（P〈0.05）;降低血清甘油三酯（P〈0.05）,升高血清游离脂肪酸（P〈0.01）;降低血清Leptin、胰岛素和TNF-α水平（P〈0.01或P〈0.05）,但对腓肠肌生长、血清总胆固醇无显著影响。皮下注射阳性卵黄提高腓肠肌指数（P〈0.05）;降低血清甘油三脂（P〈0.01）;降低血清Leptin（P〈0.01）,升高血清TNF-α（P〈0.05）;而对脂肪沉积、血清游离脂肪酸、总胆固醇和胰岛素无显著影响。结论：脂肪细胞膜蛋白卵黄抗体能有效改善机体组成,灌胃的效果优于皮下注射。