Maintenance of adiponectin attenuates insulin resistance induced by dietary conjugated linoleic acid in mice

Conjugated linoleic acid (CLA) causes insulin resistance and hepatic steatosis in conjunction with depletion of adipokines in some rodent models. Our objective was to determine whether the maintenance of adipokines, mainly leptin and adiponectin, by either removing CLA from diets or using an adiponectin enhancer, rosiglitazone (ROSI), could attenuate CLA-induced insulin resistance. Male C57BL/6 mice were consecutively fed two experimental diets containing 1.5% CLA mixed isomer for 4 weeks followed by a diet without CLA for 4 weeks. CLA significantly depleted adiponectin but not leptin and was accompanied by hepatic steatosis and insulin resistance. These effects were attenuated after switching mice to the diet without CLA along with restoration of adiponectin. To further elucidate the role of adiponectin in CLA-mediated insulin resistance, ROSI was used in a subsequent study in male ob/ob mice fed either control (CON) or CLA diet. ROSI maintained significantly higher adiponectin levels in CON- and CLA-fed mice and prevented the depletion of epididymal adipose tissue and the development of insulin resistance. In conclusion, we show that insulin resistance induced by CLA may be related more to adiponectin depletion than to leptin and that maintaining adiponectin levels alone either by removing CLA or using ROSI can attenuate these effects.     

Comparison of the rapid pro-apoptotic effect of trans-ß-nitrostyrenes with delayed apoptosis induced by the standard agent 5-fluorouracil in colon cancer cells

Trans-beta-nitrostyrene (TBNS) has been reported to be a potent inhibitor of protein phosphatases PTB1 and PP2A and to display a pro-apoptotic effect even in multidrug resistant tumour cells. Here we compared the anti-tumour potential of TBNS with 5-fluorouracil (5-FU) as the standard chemotherapeutic agent for colorectal cancer in LoVo cells. Resistance to 5-FU based therapy might be a consequence of 5-FU's delayed effect requiring long-term effective concentrations in the tumour tissue. Thus, alternatives like platin containing drugs with a more rapid effect have been introduced recently. Compared to 5-FU TBNS displayed a faster cytotoxic and pro-apoptotic effect. A 50% decrease in viability was observed already after 8 h with TBNS while 5-FU displayed no significant effect before 48 h. DNA fragmentation and caspase-3 assays confirmed the more rapid apoptotic effect of TBNS. Since apoptosis affects individual cells these results about a rapidly induced apoptosis were further studied on a single cell level in microscopic assays of caspase-3 and caspase-8 activation. Adducts of trans-beta-nitrostyrene displayed an anti-tumour effect comparable to TBNS which suggests the possibility of creating adducts with optimised tissue targeting. Finally, the calculation of a drug combination index displayed a synergistic effect for the combination of TBNS and 5-FU in Lovo as well as in HT-29 and HCT116 colon cancer cells.     

KSRP is critical in governing hepatic lipid metabolism through controlling Per2 expression

Hepatic lipid metabolism is controlled by integrated metabolic pathways. Excess accumulation of hepatic TG is a hallmark of nonalcoholic fatty liver disease, which is associated with obesity and insulin resistance. Here, we show that KH-type splicing regulatory protein (KSRP) ablation reduces hepatic TG levels and diet-induced hepatosteatosis. Expression of period 2 (Per2) is increased during the dark period, and circadian oscillations of several core clock genes are altered with a delayed phase in Ksrp^−/− livers. Diurnal expression of some lipid metabolism genes is also disturbed with reduced expression of genes involved in de novo lipogenesis. Using primary hepatocytes, we demonstrate that KSRP promotes decay of Per2 mRNA through an RNA-protein interaction and show that increased Per2 expression is responsible for the phase delay in cycling of several clock genes in the absence of KSRP. Similar to Ksrp^−/− livers, both expression of lipogenic genes and intracellular TG levels are also reduced in Ksrp^−/− hepatocytes due to increased Per2 expression. Using heterologous mRNA reporters, we show that the AU-rich element-containing 3′ untranslated region of Per2 is responsible for KSRP-dependent mRNA decay. These findings implicate that KSRP is an important regulator of circadian expression of lipid metabolism genes in the liver likely through controlling Per2 mRNA stability.     

Polyunsaturated fatty acid metabolites as novel lipidomic biomarkers for noninvasive diagnosis of nonalcoholic steatohepatitis

Lipotoxicity is a key mechanism thought to be responsible for the progression of nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH). Noninvasive diagnosis of NASH is a major unmet clinical need, and we hypothesized that PUFA metabolites, in particular arachidonic acid (AA)-derived eicosanoids, in plasma would differentiate patients with NAFL from those with NASH. Therefore, we aimed to assess the differences in the plasma eicosanoid lipidomic profile between patients with biopsy-proven NAFL versus NASH versus normal controls without nonalcoholic fatty liver disease (NAFLD; based on MRI fat fraction <5%). We carried out a cross-sectional analysis of a prospective nested case-control study including 10 patients with biopsy-proven NAFL, 9 patients with biopsy-proven NASH, and 10 non-NAFLD MRI-phenotyped normal controls. We quantitatively compared plasma eicosanoid and other PUFA metabolite levels between NAFL versus NASH versus normal controls. Utilizing a uniquely well-characterized cohort, we demonstrated that plasma eicosanoid and other PUFA metabolite profiling can differentiate between NAFL and NASH. The top candidate as a single biomarker for differentiating NAFL from NASH was 11,12-dihydroxy-eicosatrienoic acid (11,12-diHETrE) with an area under the receiver operating characteristic curve (AUROC) of 1. In addition, we also found a panel including 13,14-dihydro-15-keto prostaglandin D₂ (dhk PGD2) and 20-carboxy arachidonic acid (20-COOH AA) that demonstrated an AUROC of 1. This proof-of-concept study provides early evidence that 11,12-diHETrE, dhk PGD2, and 20-COOH AA are the leading eicosanoid candidate biomarkers for the noninvasive diagnosis of NASH.     

Nrf2激动剂CDDO-Im对高脂饮食诱导的肥胖小鼠肝脏脂肪变性的影响

摘要 目的：探究Nrf2激动剂CDDO-Im对高脂饮食诱导的肥胖小鼠肝脏脂肪变性的作用。方法：33只雄性C57BL/6J小鼠随机分为两组：一组16只饲喂普通饲料,另一组17只饲喂高脂饲料建立肥胖模型。造模成功后将小鼠随机分成四组：普通饲料溶剂对照组（Control ND组）、普通饲料Nrf2激动剂组（Nrf2(+) ND组）、高脂饲料溶剂对照组（Control HFD组）和高脂饲料Nrf2激动剂组（Nrf2(+) HFD组）。分别给予Nrf2激动剂CDDO-Im和等体积溶剂灌胃干预6周后,检测各组小鼠血清甘油三酯（TG）、总胆固醇（T-CHO）和低密度脂蛋白-胆固醇（LDL-C）。苏木素-伊红（HE）染色观察肝脏组织形态学变化。RT-qPCR检测肝脏Nrf2下游抗氧化基因Nqo1、Ho1和Gclc的mRNA表达水平,Western Blot检测肝脏NQO1、HO-1和GCLC的蛋白表达水平。结果：与正常小鼠相比,肥胖小鼠的体重、TG和LDL-C升高（P＜0.05）,肝脏脂肪变性增加,GCLC的蛋白表达水平降低（P＜0.05）。在肥胖小鼠中,与溶剂对照组相比,Nrf2激动剂组小鼠的体重、血清TG降低（P＜0.05）,肝脏脂肪变性减轻,Nqo1和Gclc的mRNA表达水平升高（P＜0.05）,NQO1和GCLC的蛋白表达水平升高（P＜0.05）。结论：Nrf2激动剂CDDO-Im可改善高脂饮食诱导的肥胖小鼠肝脏脂肪变性,可能与Nrf2激动剂CDDO-Im激活抗氧化基因的表达来减轻肝细胞氧化应激有关。     

Vibrational spectroscopy-based quantification of liver steatosis

The liver plays a central role in lipid metabolism, and abnormal lipid accumulation in the liver is a key feature of Non-Alcoholic Fatty Liver Disease. In experimental studies, quantification of liver steatosis is commonly based on lipids staining or biochemical analysis. Here, we present a spectroscopic approach for quantitative analysis of the lipid content in the freeze-dried liver. The method is based on vibrational spectroscopy (Raman and infrared) measurements applied for Partial Least Squares (PLS) regression modeling. The obtained PLS models show a good correlation of the spectroscopic data with the reference histological evaluation of steatosis based on Oil Red O (ORO)-stained images of liver cross sections. Vibrational spectroscopy with PLS-based modeling described here represents a useful approach for the fast assessment of the liver steatosis in a small sample of freeze-dried liver tissue. In conclusion, our work demonstrates the easy-to-use method that can be applied in laboratory routine as a beneficial alternative to the established ORO staining.     

Comparison of metabolic risk factors between severely and very severely obese patients

Objective: A prospective clinical intervention study was performed to estimate the metabolic risk factors in patients with very severe obesity (VSO) vs. severe obesity (SO). Research Methods and Procedures: Two hundred twenty‐eight VSO (BMI ≥ 50 kg/m²) and 221 SO patients (BMI = 40 to 49.9 kg/m²) participated in the study (367 women and 82 men). Metabolic measurements included plasma lipids, glucose and insulin, hemoglobin A_1c, leptin, and sex hormones, as well as hepatic steatosis in a subgroup of patients. Subgroups of patients with non–insulin‐dependent diabetes and hyperlipidemia (HLP) were examined. Results: The most unexpected result of our study was that VSO men showed significantly better lipid profiles than SO men. Furthermore, 18% of VSO men had no metabolic aberrations, whereas all SO men did. The advantageous metabolic status of VSO men was associated with sex hormone changes that favor gynoid fat distribution. The beneficial metabolic situation with VSO seems to be sex specific for men. Discussion: This study shows that the metabolic situation in VSO is not more severe than in the less obese cohort. These findings distinctly differ from the positive associations that have previously been reported between BMI, lipids, and other metabolic indices among individuals whose BMI is <40 kg/m².     

Loss of stearoyl-CoA desaturase 1 rescues cardiac function in obese leptin-deficient mice

The heart of leptin-deficient ob/ob mice is characterized by pathologic left ventricular hypertrophy along with elevated triglyceride (TG) content, increased stearoyl-CoA desaturase (SCD) activity, and increased myocyte apoptosis. In the present study, using an ob/ob;SCD1^−/− mouse model, we tested the hypothesis that lack of SCD1 could improve steatosis and left ventricle (LV) function in leptin deficiency. We show that disruption of the SCD1 gene improves cardiac function in ob/ob mice by correcting systolic and diastolic dysfunction without affecting levels of plasma TG and FFA. The improvement is associated with reduced expression of genes involved in FA transport and lipid synthesis in the heart, as well as reduction in cardiac FFA, diacylglycerol, TG, and ceramide levels. The rate of FA β-oxidation is also significantly lower in the heart of ob/ob;SCD1^−/− mice compared with ob/ob controls. Moreover, SCD1 deficiency reduces cardiac apoptosis in ob/ob mice due to increased expression of antiapoptotic factor Bcl-2 and inhibition of inducible nitric oxide synthase and caspase-3 activities. Reduction in myocardial lipid accumulation and inhibition of apoptosis appear to be one of the main mechanisms responsible for improved LV function in ob/ob mice caused by SCD1 deficiency.     

Dietary cholesterol reverses resistance to diet-induced weight gain in mice lacking Niemann-Pick C1-Like 1

Niemann-Pick C1-Like 1 (NPC1L1) mediates intestinal cholesterol absorption. NPC1L1 knockout (L1-KO) mice were recently shown to be resistant to high-fat diet (HFD)-induced obesity in one study, which was contrary to several other studies. Careful comparison of dietary compositions in these studies implies a potential role of dietary cholesterol in regulating weight gain. To examine this potential, wild-type (WT) and L1-KO mice were fed one of three sets of diets for various durations: (1) a HFD without added cholesterol for 5 weeks; (2) a high-carbohydrate diet with or without added cholesterol for 5 weeks; or (3) a synthetic HFD with or without added cholesterol for 18 weeks. We found that L1-KO mice were protected against diet-induced weight gain only on a diet without added cholesterol but not on a diet containing 0.16% or 0.2% (w/w) cholesterol, an amount similar to a typical Western diet, regardless of the major energy source of the diet. Food intake and intestinal fat absorption were similar between the two genotypes. Intestinal cholesterol absorption was blocked, and fecal cholesterol excretion increased in L1-KO mice. Under all diets, L1-KO mice were protected from hepatosteatosis. In conclusion, increasing dietary cholesterol restores diet-induced weight gain in mice deficient in NPC1L1-dependent cholesterol absorption.