Signalling pathways identified in salivary glands from primary Sjögren’s syndrome patients reveal enhanced adipose tissue development

A characteristic feature of primary Sjögren’s syndrome (pSS) is the destruction of salivary and lacrimal glands mediated by mononuclear cell infiltration. Adipocytes can also occupy a large portion of the salivary gland (SG) tissue area, although little is known about their significance in pSS. We have previously investigated adipose tissue infiltration in SG biopsies from pSS patients and non-SS sicca controls. Our findings indicated the distinct incidence of adipose tissue replacement in pSS patients, where adipocytes were detected in interleukin (IL) 6 rich regions. We now aimed to examine the development of adipocytes in the SG microenvironment, and delineate their possible involvement in immune reactions. A microarray analysis was performed on SG from 6 pSS patients and 6 non-SS controls, where the expression levels of genes involved in adipose tissue development, inflammatory responses, and lymphoma development were assessed. Real-time PCR was carried out on SG from 14 pSS patients and 15 non-SS controls to account for IL6, IL10, and IL17 mRNA levels. Immunohistochemical staining of frozen SG tissue using IL17 was also conducted. Our results indicate signalling pathways identified in SG of pSS patients displayed genes leading to prominent adipose tissue development and reduced mitochondrial fatty acid beta-oxidation (ARID5B, OXCT1, BDH1, SOX8, HMGCS2, FTO, ECHS1, PCCA, ACADL and ACADVL), inflammatory responses (IL1R1, IL7R, IL10RA, IL15, IL18RAP, CCL2, CCL5, CCL22, CXCR6, CD14, and CD48), and lymphoma development via JAK-STAT signalling (STAT2, TYK2, EBI3, FAS, TNFRSF1B, MAP3K8, HMOX1, LTB, TNF, STAT1, and BAK1). Genes involved in interferon production and signalling were also detected (IRF1, IRF9, and IRF7), in addition to IL6, IL10, and IL17. Higher mRNA levels of IL6, IL17 and IL10 were observed in the SG of pSS patients compared to controls. Moreover, IL17 positive cells were detected mostly interstitially in the SG and around adipocytes, also within the focal infiltrates. In conclusion, adipocyte development seems to be more prominent in the SG of pSS patients, where adipose tissue replacement is also evident. Whether this is due to disease progression, or the repair process, remains to be investigated. Detection of IL17 positive adipocytes in the target organ suggests their involvement in immune reactions.     

Nutritional Ingredients Modulate Adipokine Secretion and Inflammation in Human Primary Adipocytes

Nutritional factors such as casein hydrolysates and long chain polyunsaturated fatty acids have been proposed to exert beneficial metabolic effects. We aimed to investigate how a casein hydrolysate (eCH) and long chain polyunsaturated fatty acids could affect human primary adipocyte function in vitro. Incubation conditions with the different nutritional factors were validated by assessing cell vitality with lactate dehydrogenase (LDH) release and neutral red incorporation. Intracellular triglyceride content was assessed with Oil Red O staining. The effect of eCH, a non-peptidic amino acid mixture (AA), and long-chain polyunsaturated fatty acids (LC-PUFAs) on adiponectin and leptin secretion was determined by enzyme-linked immunosorbent assay (ELISA). Intracellular adiponectin expression and nuclear factor-κB (NF-κB) activation were analyzed by Western blot, while monocyte chemoattractant protein-1 (MCP-1) release was explored by ELISA. The eCH concentration dependently increased adiponectin secretion in human primary adipocytes through its intrinsic peptide bioactivity, since the non-peptidic mixture, AA, could not mimic eCH’s effects on adiponectin secretion. Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and DHA combined with arachidonic acid (ARA) upregulated adiponectin secretion. However, only DHA and DHA/ARA exerted a potentanti-inflammatory effect reflected by prevention of tumor necrosis factor-α (TNF-α) induced NF-κB activation and MCP-1 secretion in human adipocytes. eCH and DHA alone or in combination with ARA, may hold the key for nutritional programming through their anti-inflammatory action to prevent diseases with low-grade chronic inflammation such as obesity or diabetes.     

Wogonin suppresses osteopontin expression in adipocytes by activating PPARα

Aim:

Wogonin (5,7-dihydroxy-8-methoxyflavone), a major bioactive compound of the flavonoid family, is commonly extracted from the traditional Chinese medicine Scutellaria baicalensis and possesses antioxidant and anti-inflammatory activities and is assumed to have anti-diabetes function. Indeed, a current study has shown that it can possibly treat metabolic disorders such as those found in db/db mice. However, the underlying molecular mechanism remains largely unclear. The aim of this study was to investigate the impact of wogonin on osteopontin (OPN) expression in adipose tissue from type 1 diabetic mice and in 3T3-L1 adipocytes.

Methods:

Type 1 diabetes was induced by streptozotocin (STZ) injection. 3T3-L1 preadipocytes were converted to 3T3-L1 adipocytes through treatment with insulin, dexamethasone, and 3-isobutyl-1-methylxanthine (IBMX). Western blot analysis and RT-PCR were performed to detect protein expression and mRNA levels, respectively.

Results:

Wogonin treatment suppressed the increase in serum OPN levels and reduced OPN expression in adipose tissue from STZ-induced type 1 diabetic mice. Administration of wogonin enhanced PPARα expression and activity. Silencing of PPARα diminished the inhibitory effects of wogonin on OPN expression in 3T3-L1 adipocytes. Furthermore, the levels of c-Fos and phosphorylated c-Jun were reduced in wogonin-treated adipose tissue and 3T3-L1 adipocytes. In addition, wogonin treatment dramatically mitigated p38 MAPK phosphorylation. Pharmacological inhibition of p38 MAPK by its specific inhibitor SB203580 increased PPARα activity and decreased OPN expression.

Conclusion:

Our results suggest that wogonin downregulated OPN expression in adipocytes through the inhibition of p38 MAPK and the sequential activation of the PPARα pathway. Given the adverse effects of high OPN levels on metabolism, our results provide evidence for the potential administration of wogonin as a treatment for diabetes.     

Mature adipocytes in bone marrow protect myeloma cells against chemotherapy through autophagy activation

A major problem in patients with multiple myeloma is chemotherapy resistance, which develops in myeloma cells upon interaction with bone marrow stromal cells. However, few studies have determined the role of bone marrow adipocytes, a major component of stromal cells in the bone marrow, in myeloma chemotherapy resistance. We reveal that mature human adipocytes activate autophagy and upregulate the expression of autophagic proteins, thereby suppressing chemotherapy-induced caspase cleavage and apoptosis in myeloma cells. We found that adipocytes secreted known and novel adipokines, such as leptin and adipsin. The addition of these adipokines enhanced the expression of autophagic proteins and reduced apoptosis in myeloma cells. In vivo studies further demonstrated the importance of bone marrow-derived adipocytes in the reduced response of myeloma cells to chemotherapy. Our findings suggest that adipocytes, adipocyte-secreted adipokines, and adipocyte-activated autophagy are novel targets for combatting chemotherapy resistance and enhancing treatment efficacy in myeloma patients.     

Calorie restriction counteracts the impairment of adipocyte insulin-stimulated lipogenesis in aging rats, but not that induced by dexamethasone treatment

In order to detect metabolic derangements that could be implicated in the pathogenesis of age-related insulin resistance, insulin-stimulated lipogenesis was investigated in isolated adipocytes from 24-month-old Sprague-Dawley rats, and the protective influence of caloric restriction was assessed. For comparison, the effects of glucocorticoid administration, used as a pharmacological tool to alter insulin sensitivity, were also studied. Caloric restriction consisted in a 40% reduction of the daily food intake of controls starting at 3 months of age. Dexamethasone (0.13 mg/kg/day) was administered for 14 days prior to sacrifice to both ad libitum-fed and dietary-restricted aging rats. Three-month-old animals, treated or untreated with dexamethasone, served as young controls. The results showed a significant age-related decrease of insulin-stimulated lipogenesis, which was fully prevented by a lifelong regimen of dietary restriction. Dexamethasone treatment markedly reduced insulin-stimulated lipogenesis in adipocytes isolated from all groups of rats, including those submitted to calorie restriction. In conclusion, our data indicate that the mechanism by which aging alters adipose tissue insulin-induced lipogenesis is reversed by dietary intervention and appears to be different from that triggered by dexamethasone. This particular defect might contribute to an imbalance of fat distribution among tissues that could induce or aggravate peripheral insulin resistance in old age.     

Comparison of the antilipolytic effects of an A1 adenosine receptor partial agonist in normal and diabetic rats

Introduction and Aims: Elevated plasma free fatty acid (FFA) concentrations play a role in the pathogenesis of type 2 diabetes (2DM). Antilipolytic agents that reduce FFA concentrations may be potentially useful in the treatment of 2DM. Our previous observation that CVT‐3619 lowered plasma FFA and triglyceride concentrations in rats and enhanced insulin sensitivity in rodents with dietary‐induced forms of insulin resistance suggested that it might be of use in the treatment of patients with 2DM. The present study was undertaken to compare the antilipolytic effects of CVT‐3619 in normal (Sprague Dawley, SD) and Zucker diabetic fatty (ZDF) rats. Results: ZDF rats had significantly higher fat pad weight, glucose, insulin and FFA concentrations than those of SD rats. EC₅₀ values for forskolin‐stimulated FFA release from isolated adipocytes from SD and ZDF rats were 750 and 53 nM, respectively (p < 0.05). Maximal forskolin stimulation of FFA release was significantly (p < 0.01) less in ZDF rats (133 ± 60 μM) compared with SD rats (332 ± 38 μM). EC₅₀ values for isoproterenol to increase lipolysis in adipocytes from SD and ZDF rats were 2 and 7 nM respectively. Maximal isoproterenol‐stimulated lipolysis was significantly (p < 0.01) lower in adipocytes from ZDF rats (179 ± 23 μM) compared with SD rats (343 ± 27 μM). Insulin inhibited lipolysis in adipocytes from SD rats with an IC₅₀ value of 30 pM, whereas adipocytes from ZDF rats were resistant to the antilipolytic actions of insulin. In contrast, IC₅₀ values for CVT‐3619 to inhibit the release of FFA from SD and ZDF adipocytes were essentially the same (63 and 123 nM respectively). CVT‐3619 inhibited lipolysis more than insulin in both SD (86 vs. 46%, p < 0.001) and ZDF (80 vs. 13%, p < 0.001) adipocytes. In in vivo experiments, CVT‐3619 (5 mg/kg, PO) lowered FFA to a similar extent in both groups. Plasma concentrations of CVT‐3619 were not different in SD and ZDF rats. There was no significant difference in the messenger RNA expression of the A₁ receptors relative to β‐actin expression in adipocytes from SD (0.98 ± 0.2) and ZDF rats (0.99 ± 0.3). Conclusion: The antilipolytic effects of CVT‐3619 appear to be independent of insulin resistance and animal model.     

阿托伐他汀对血脂异常兔血清和脂肪细胞分泌肿瘤坏死因子-α的影响

目的观察阿托伐他汀干预对血脂异常兔血清及脂肪细胞分泌肿瘤坏死因子-α(TNF-α)的影响,并探讨其可能机制。方法10只新西兰大白兔给予高胆固醇饮食饲养8周后,随机分为高胆固醇组和阿托伐他汀组,每组5只。另选普通饮食12周兔5只作为对照组。12周末,取腹股沟皮下脂肪组织行脂肪细胞培养,酶联免疫吸附法检测血清及脂肪细胞培养液中TNF-α水平。半定量逆转录聚合酶链反应测定脂肪细胞TNF-αmRNA的表达。结果阿托伐他汀干预4周能明显降低血脂异常兔血清总胆固醇、低密度脂蛋白胆固醇、TNF-α水平和脂肪细胞TNF-αmRNA表达量(P<0.05)。阿托伐他汀呈剂量依赖性降低脂肪细胞TNF-α表达和分泌。结论阿托伐他汀降低血脂异常兔血清TNF-α水平,其机制可能与其调脂及抑制脂肪细胞TNF-α的分泌有关。