PCSK9 inhibition with alirocumab reduces lipoprotein(a) levels in nonhuman primates by lowering apolipoprotein(a) production rate.

Therapeutic antibodies targeting proprotein convertase subtilisin kexin type 9 (PCSK9) (e.g. alirocumab) lower low-density lipoprotein cholesterol (LDL-C) and lipoprotein (a) [Lp(a)] levels in clinical trials. We recently showed that PCSK9 enhances apolipoprotein(a) [apo(a)] secretion from primary human hepatocytes but does not affect Lp(a) cellular uptake. Here, we aimed to determine how PCSK9 neutralization modulates Lp(a) levels in vivoSix nonhuman primates (NHP) were treated with alirocumab or a control antibody (IgG1) in a crossover protocol. After the lowering of lipids reached steady state, NHP received an intravenous injection of [2H3]-leucine, and blood samples were collected sequentially over 48 h. Enrichment of apolipoproteins in [2H3]-leucine was assessed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Kinetic parameters were calculated using numerical models with the SAAMII software. Compared with IgG1, alirocumab significantly reduced total cholesterol (TC) (-28%), LDL-C (-67%), Lp(a) (-56%), apolipoprotein B100 (apoB100) (-53%), and apo(a) (-53%). Alirocumab significantly increased the fractional catabolic rate of apoB100 (+29%) but not that of apo(a). Conversely, alirocumab sharply and significantly reduced the production rate (PR) of apo(a) (-42%), but not significantly that of apoB100, compared with IgG1, respectively.In line with the observations made in human hepatocytes, the present kinetic study establishes that PCSK9 neutralization with alirocumab efficiently reduces circulating apoB100 and apo(a) levels by distinct mechanisms: apoB primarily by enhancing its catabolism and apo(a) primarily by lowering its production.

Comprehensive HPTLC Fingerprinting for Quality Control of an Herbal Drug - The Case of Angelica gigas Root.

The quality of herbal drugs is usually controlled using several tests recommended in a monograph. HPTLC is the method of choice for identification in many pharmacopoeias. If combined with a suitable reference material for comparison, HPTLC can provide information beyond identification and thus may simplify quality control. This paper describes, as a proof of concept, how HPTLC can be applied to define specifications for an herbal reference material and to control the quality of an herbal drug according to these specifications. Based on multiple batches of cultivated Angelica gigas root, a specific HPTLC method for identification was optimized. This method can distinguish 27 related species. It also can detect the presence of mixtures of A. gigas with two other Angelica species traded as "Dang gui" and is suitable as well for quantitative assessment of samples in a test for minimum content of the sum of decursin and decursinol angelate. The new concept of "comprehensive HPTLC fingerprinting" is proposed: HPTLC fingerprints (images), which are used for identification, are converted into peak profiles and the intensities of selected zones are quantitatively compared to those of the corresponding zones of the reference material. Following a collaborative trial involving three laboratories in three countries, the method was applied to check the quality of further candidates for establishing an appropriate reference material. In conclusion, this case demonstrates that a single HPTLC analysis can provide information about identity, purity, and minimum content of markers of an herbal drug.

Short Term Palmitate Supply Impairs Intestinal Insulin Signaling via Ceramide Production.

The worldwide prevalence of metabolic diseases is increasing, and there are global recommendations to limit consumption of certain nutrients, especially saturated lipids. Insulin resistance, a common trait occurring in obesity and type 2 diabetes, is associated with intestinal lipoprotein overproduction. However, the mechanisms by which the intestine develops insulin resistance in response to lipid overload remain unknown. Here, we show that insulin inhibits triglyceride secretion and intestinal microsomal triglyceride transfer protein expression in vivo in healthy mice force-fed monounsaturated fatty acid-rich olive oil but not in mice force-fed saturated fatty acid-rich palm oil. Moreover, when mouse intestine and human Caco-2/TC7 enterocytes were treated with the saturated fatty acid, palmitic acid, the insulin-signaling pathway was impaired. We show that palmitic acid or palm oil increases ceramide production in intestinal cells and that treatment with a ceramide analogue partially reproduces the effects of palmitic acid on insulin signaling. In Caco-2/TC7 enterocytes, ceramide effects on insulin-dependent AKT phosphorylation are mediated by protein kinase C but not by protein phosphatase 2A. Finally, inhibiting de novo ceramide synthesis improves the response of palmitic acid-treated Caco-2/TC7 enterocytes to insulin. These results demonstrate that a palmitic acid-ceramide pathway accounts for impaired intestinal insulin sensitivity, which occurs within several hours following initial lipid exposure.

Luminal lipid regulates CD36 levels and downstream signaling to stimulate chylomicron synthesis.

The membrane glycoprotein CD36 binds nanomolar concentrations of long chain fatty acids (LCFA) and is highly expressed on the luminal surface of enterocytes. CD36 deficiency reduces chylomicron production through unknown mechanisms. In this report, we provide novel insights into some of the underlying mechanisms. Our in vivo data demonstrate that CD36 gene deletion in mice does not affect LCFA uptake and subsequent esterification into triglycerides by the intestinal mucosa exposed to the micellar LCFA concentrations prevailing in the intestine. In rodents, the CD36 protein disappears early from the luminal side of intestinal villi during the postprandial period, but only when the diet contains lipids. This drop is significant 1 h after a lipid supply and associates with ubiquitination of CD36. Using CHO cells expressing CD36, it is shown that the digestion products LCFA and diglycerides trigger CD36 ubiquitination. In vivo treatment with the proteasome inhibitor MG132 prevents the lipid-mediated degradation of CD36. In vivo and ex vivo, CD36 is shown to be required for lipid activation of ERK1/2, which associates with an increase of the key chylomicron synthesis proteins, apolipoprotein B48 and microsomal triglyceride transfer protein. Therefore, intestinal CD36, possibly through ERK1/2-mediated signaling, is involved in the adaptation of enterocyte metabolism to the postprandial lipid challenge by promoting the production of large triglyceride-rich lipoproteins that are rapidly cleared in the blood. This suggests that CD36 may be a therapeutic target for reducing the postprandial hypertriglyceridemia and associated cardiovascular risks.

Gut microbiota and fermentation-derived branched chain hydroxy acids mediate health benefits of yogurt consumption in obese mice.

Meta-analyses suggest that yogurt consumption reduces type 2 diabetes incidence in humans, but the molecular basis of these observations remains unknown. Here we show that dietary yogurt intake preserves whole-body glucose homeostasis and prevents hepatic insulin resistance and liver steatosis in a dietary mouse model of obesity-linked type 2 diabetes. Fecal microbiota transplantation studies reveal that these effects are partly linked to the gut microbiota. We further show that yogurt intake impacts the hepatic metabolome, notably maintaining the levels of branched chain hydroxy acids (BCHA) which correlate with improved metabolic parameters. These metabolites are generated upon milk fermentation and concentrated in yogurt. Remarkably, diet-induced obesity reduces plasma and tissue BCHA levels, and this is partly prevented by dietary yogurt intake. We further show that BCHA improve insulin action on glucose metabolism in liver and muscle cells, identifying BCHA as cell-autonomous metabolic regulators and potential mediators of yogurt's health effects.

Psychobiotics for Patients with Chronic Gastrointestinal Disorders Having Anxiety or Depression Symptoms.

PURPOSE: Using psychobiotics to modify the gut microbiome has been shown to improve the anxiety and depression situation of patients with chronic gastrointestinal (GI) symptoms. This study evaluated changes in depression, anxiety, GI symptomss and side effects when patients used a multispecies probiotics product. PATIENTS AND METHODS: A single-center uncontrolled trial was conducted in patients with chronic GI symptoms, anxiety and depression who used a multispecies probiotics product. The patients were screened for anxiety and depression symptoms using the Hospital Anxiety and Depression Scale (HADS). Those who had a component score of 8 or higher were given the multispecies probiotics product for 2 months and followed up after 1 and 2 months. All data are collected and managed in a case report form. RESULTS: Eighty-three patients were enrolled, with a mean age (SD) of 43.9 (12.3) years; 73.5% of the patients were female. Of these patients, 8 met the Rome IV criteria for irritable bowel syndrome. The HADS scores displayed significant improvement at follow-up. The mean (SD) total HADS scores were 20.0 (6.3), 7.2 (5.4), and 4.9 (5.1) at baseline, 1 month, and 2 months, respectively. Quality of life also improved significantly. A small proportion (<5%) of patients developed mild symptoms, including fullness, diarrhea, and sleep complaints. CONCLUSION: After 2 months using the probiotic product, the symptoms of anxiety and depression improved significantly. Mild gastrointestinal or constitutional symptoms developed in some patients.

Deregulated Lipid Sensing by Intestinal CD36 in Diet-Induced Hyperinsulinemic Obese Mouse Model.

The metabolic syndrome (MetS) greatly increases risk of cardiovascular disease and diabetes and is generally associated with abnormally elevated postprandial triglyceride levels. We evaluated intestinal synthesis of triglyceride-rich lipoproteins (TRL) in a mouse model of the MetS obtained by feeding a palm oil-rich high fat diet (HFD). By contrast to control mice, MetS mice secreted two populations of TRL. If the smaller size population represented 44% of total particles in the beginning of intestinal lipid absorption in MetS mice, it accounted for only 17% after 4 h due to the secretion of larger size TRL. The MetS mice displayed accentuated postprandial hypertriglyceridemia up to 3 h due to a defective TRL clearance. These alterations reflected a delay in lipid induction of genes for key proteins of TRL formation (MTP, L-FABP) and blood clearance (ApoC2). These abnormalities associated with blunted lipid sensing by CD36, which is normally required to optimize jejunal formation of large TRL. In MetS mice CD36 was not downregulated by lipid in contrast to control mice. Treatment of controls with the proteosomal inhibitor MG132, which prevented CD36 downregulation, resulted in blunted lipid-induction of MTP, L-FABP and ApoC2 gene expression, as in MetS mice. Absence of CD36 sensing was due to the hyperinsulinemia in MetS mice. Acute insulin treatment of controls before lipid administration abolished CD36 downregulation, lipid-induction of TRL genes and reduced postprandial triglycerides (TG), while streptozotocin-treatment of MetS mice restored lipid-induced CD36 degradation and TG secretion. In vitro, insulin treatment abolished CD36-mediated up-regulation of MTP in Caco-2 cells. In conclusion, HFD treatment impairs TRL formation in early stage of lipid absorption via insulin-mediated inhibition of CD36 lipid sensing. This impairment results in production of smaller TRL that are cleared slowly from the circulation, which might contribute to the reported association of CD36 variants with MetS risk.

PCSK9 Modulates the Secretion But Not the Cellular Uptake of Lipoprotein(a) Ex Vivo: An Effect Blunted by Alirocumab.

To elucidate how the proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor alirocumab modulates lipoprotein(a) [Lp(a)] plasma levels, the authors performed a series of Lp(a) uptake studies in primary human hepatocytes and dermal fibroblasts and measured Lp(a) secretion from human hepatocytes. They found that Lp(a) cellular uptake occurred in a low-density lipoprotein receptor-independent manner. Neither PCSK9 nor alirocumab altered Lp(a) internalization. By contrast, the secretion of apolipoprotein (a) from human hepatocytes was sharply increased by PCSK9, an effect that was reversed by alirocumab. They propose that PCSK9 does not significantly modulate Lp(a) catabolism, but rather enhances the secretion of Lp(a) from liver cells.

From fatty-acid sensing to chylomicron synthesis: role of intestinal lipid-binding proteins.

Today, it is well established that the development of obesity and associated diseases results, in part, from excessive lipid intake associated with a qualitative imbalance. Among the organs involved in lipid homeostasis, the small intestine is the least studied even though it determines lipid bioavailability and largely contributes to the regulation of postprandial hyperlipemia (triacylglycerols (TG) and free fatty acids (FFA)). Several Lipid-Binding Proteins (LBP) are expressed in the small intestine. Their supposed intestinal functions were initially based on what was reported in other tissues, and took no account of the physiological specificity of the small intestine. Progressively, the identification of regulating factors of intestinal LBP and the description of the phenotype of their deletion have provided new insights into cellular and molecular mechanisms involved in fat absorption. This review will discuss the physiological contribution of each LBP in the main steps of intestinal absorption of long-chain fatty acids (LCFA): uptake, trafficking and reassembly into chylomicrons (CM). Moreover, current data indicate that the small intestine is able to adapt its lipid absorption capacity to the fat content of the diet, especially through the coordinated induction of LBP. This adaptation requires the existence of a mechanism of intestinal lipid sensing. Emerging data suggest that the membrane LBP CD36 may operate as a lipid receptor that triggers an intracellular signal leading to the modulation of the expression of LBP involved in CM formation. This event could be the starting point for the optimized synthesis of large CM, which are efficiently degraded in blood. Better understanding of this intestinal lipid sensing might provide new approaches to decrease the prevalence of postprandial hypertriglyceridemia, which is associated with cardiovascular diseases, insulin resistance and obesity.

Intestinal absorption of long-chain fatty acids: evidence and uncertainties.

Over the two last decades, cloning of proteins responsible for trafficking and metabolic fate of long-chain fatty acids (LCFA) in gut has provided new insights on cellular and molecular mechanisms involved in fat absorption. To this systematic cloning period, functional genomics has succeeded in providing a new set of surprises. Disruption of several genes, thought to play a crucial role in LCFA absorption, did not lead to clear phenotypes. This observation raises the question of the real physiological role of lipid-binding proteins and lipid-metabolizing enzymes expressed in enterocytes. The goal of this review is to analyze present knowledge concerning the main steps of intestinal fat absorption from LCFA uptake to lipoprotein release and to assess their impact on health.