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Osteoarthritis (OA) is a common disease in dogs with severe impact on their welfare. The multimodal management of OA includes feeding therapeutic diets and nutraceuticals to slow down OA progression. Collagen hydrolysates (CH) are a nutritional supplement that may exert anabolic effects on osteoarthritic joint cartilage as well as disease-modifying effects. After oral intake, CH is absorbed, mainly as amino acids, di- and tripeptides that are transported amongst others to the joint. In addition to reducing cartilage degradation, CH metabolites may reduce synovial inflammation and subchondral bone sclerosis during OA. Preliminary evidence in dogs suffering from the consequences of OA support the clinical efficacy of CH with reported reductions in lameness. However, effects on biomarker level of cartilage metabolism and inflammation are inconclusive. Additionally, current studies show a lack of standardised dosing regimens and the use of not validated outcomes. Future work should therefore elucidate further on the bioavailability of CH in dogs in order to establish adequate dosing recommendations. Furthermore, high-quality placebo-controlled randomised controlled trials are essential to dstudies have evaluated the cetermine the clinical efficacy of CH to reduce lameness, prevent OA progression and thereby improve the level of evidence., (© 2024 The Author(s). Journal of Animal Physiology and Animal Nutrition published by Wiley‐VCH GmbH.)

Background: A healthy skin provides protection against intrinsic and extrinsic factors. Skin aging is characterized by structural and morphological alterations affecting skin health, integrity, and functionality, resulting in visible aging signs., Aim: The primary objective of this study was to assess the effect of a collagen peptide dietary supplement on skin aging in the East Asian population., Methods: Eighty-five healthy women, aged from 43 to 65 years old, were randomly assigned to the collagen supplement (CP, 5 g) or placebo (maltodextrin, 5 g) group. To standardize daily skin care, the volunteers in both groups used a specific face cream for 28 days prior to and throughout the supplementation period, creating an equal baseline for the assessment of the efficacy of CP on several skin parameters. At baseline, day 28 and day 84, the following hallmarks of skin and nail aging were assessed: dermis density, skin moisture and elasticity, wrinkle visibility, beauty perception, and nail color., Results: After 84 days, a significant improvement of dermis density and skin moisture was observed in the collagen peptides group compared to the placebo group. Positive effects on skin elasticity, wrinkle visibility, nail color, and overall beauty perception were already observed within 28 days of supplementation in the CP group, while the same effects in the placebo group were only observed after 84 days., Conclusion: Taken together, these results show that, in addition to a standardized skin care, daily supplementation with 5 g of collagen peptides positively affects visible signs of skin and nail aging in the East Asian population., (© 2024 Rousselot BV. Journal of Cosmetic Dermatology published by Wiley Periodicals LLC.)

In response to nutrients, intestinal L- and K-cells naturally secrete glucagon-like peptide 1 (GLP-1). GLP-1 regulates postprandial blood glucose by increasing insulin secretion, slowing down gastric emptying and inducing satiety. A selection of specifically developed collagen hydrolysates was screened for their ability to enhance natural GLP-1 production in vitro. The best performing hydrolysate, H80 (Nextida GC), was orally administered at different doses to lean, normoglycemic mice and overweight, prediabetic mice. Lean mice were acutely challenged 45 min before an oral glucose load. While daily supplemented for 6 weeks, prediabetic mice were acutely challenged at day 21 and 34. Oral glucose tolerance, plasma insulin and GLP-1 levels were assessed, and a gastric emptying assay performed in prediabetic mice. H80 significantly lowered the blood glucose response in lean and prediabetic mice, at a 4 g/kg dose (-25% and -36%, respectively), compared to vehicle. In chronically supplemented, prediabetic mice, acute H80 administration slowed down gastric emptying (-60%) after 21 days and increased plasma insulin (+166%) after 35 days of supplementation. H80 increased plasma active GLP-1 in lean (+217%) and prediabetic (+860%) mice. Overall, the data indicate that the specific collagen hydrolysate, H80, has significant GLP-1-mediated effects on oral glucose tolerance in lean and prediabetic mice. Furthermore, effects on postprandial glucose tolerance were evaluated in a small, human, proof of concept study. H80 reduced the postprandial glucose response at a 5 g dose in healthy, normoglycemic and prediabetic participants. Oral supplementation with H80 might thus be a promising strategy to maintain normal glucose tolerance., Competing Interests: Elien Gevaert, Sara Vleminckx, Janne Prawitt and Nicolina Virgilio are employees of Rousselot BV. Estelle Grasset, François Briand, Thierry Sulpice are employees of Physiogenex SAS, Christiane Schön is an employee of BioTeSys GmbH., (© 2024 Rousselot BV. Food Science & Nutrition published by Wiley Periodicals LLC.)

Background: Collagen hydrolysates (CH) in functional foods and supplements are dietary sources of amino acids (AAs) and di-and tripeptides linked to various health benefits. This study aimed to investigate the single-dose bioavailability of skin- and hide-derived CH from fish, porcine and bovine origin with different molecular weights (bovine 2,000 and 5,000 Da)., Methods: A randomized, double-blind crossover clinical study was performed with healthy volunteers assessing the plasma concentration of free and peptide-bound hydroxyproline (Hyp) as well as selected peptides reported to be abundantly present in collagen., Results: The pharmacokinetic endpoints demonstrated comparable uptake of free Hyp from all CH. A higher amount of total compared to free Hyp indicated the uptake of substantial amounts of Hyp-containing di- or tripeptides., Conclusion: Independently of source and molecular weight, all CH yielded relevant plasma concentrations of the investigated metabolites. Larger studies are needed to estimate an ideal level of selected circulating metabolites needed to trigger distinct physiological reactions in target tissues., Competing Interests: NV, BS, SV, CIFS, and JP were employed by the Rousselot BV. CS and YM were employed by the BioTeSys GmbH. FH and AK were employed by the Triskelion., (Copyright © 2024 Virgilio, Schön, Mödinger, van der Steen, Vleminckx, van Holthoon, Kleinnijenhuis, Silva and Prawitt.)

Purpose: The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints., Methods: In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk 1 ) with sleep complaints (Athens Insomnia Scale, 9 ± 2) consumed CP (15 g·day 1 ) or a placebo control (CON) 1 h before bedtime for 7 nights. Sleep quality was measured with subjective sleep diaries and actigraphy for 7 nights; polysomnographic sleep and core temperature were recorded on night 7. Cognition, inflammation, and endocrine function were measured on night 7 and the following morning. Subjective sleepiness and fatigue were measured on all 7 nights. The intervention trials were separated by ≥ 7 days and preceded by a 7-night familiarisation trial., Results: Polysomnography showed less awakenings with CP than CON (21.3 ± 9.7 vs. 29.3 ± 13.8 counts, respectively; P = 0.028). The 7-day average for subjective awakenings were less with CP vs. CON (1.3 ± 1.5 vs. 1.9 ± 0.6 counts, respectively; P = 0.023). The proportion of correct responses on the baseline Stroop cognitive test were higher with CP than CON (1.00 ± 0.00 vs. 0.97 ± 0.05 AU, respectively; P = 0.009) the morning after night 7. There were no trial differences in core temperature, endocrine function, inflammation, subjective sleepiness, fatigue and sleep quality, or other measures of cognitive function or sleep (P > 0.05)., Conclusion: CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints., (© 2023. The Author(s).)

Background: Joint discomfort is a widespread and growing problem in active adults. The rising interest in preventative nutrition has increased the demand for supplements reducing joint discomfort. Protocols assessing the effect of a nutritional intervention on health commonly involve a series of face-to-face meetings between participants and study staff that can weigh on resources, participant availabilities, and even increase dropout rates. Digital tools are increasingly added to protocols to facilitate study conduct, but fully digitally run studies are still scarce. With the increasing interest in real-world studies, the development of health apps for mobile devices to monitor study outcomes is of great importance., Objective: The purpose of this real-world study was to develop a specific mobile app, Ingredients for Life, to conduct a 100% digital study testing the effectiveness of a hydrolyzed cartilage matrix (HCM) supplement on joint discomfort in a heterogeneous group of healthy, active consumers., Methods: The Ingredients for Life mobile app using a visual analog scale was specifically developed to monitor the variation in joint pain after exercise by the study participants. A total of 201 healthy and physically active women and men (18-72 years old) with joint pain completed the study over a period of 16 weeks. Participants were randomly allocated to the study groups and did not receive any dietary or lifestyle advice. Each participant indicated one area of joint pain and logged the type and duration of their weekly activities. They received blinded study supplements and took a daily regimen of 1 g of HCM (HCM group) or 1 g of maltodextrin (placebo group) for 12 weeks while weekly logging joint pain scores in the app. This was followed by a 4-week washout period during which participants continued reporting their joint pain scores (until the end of week 16)., Results: Joint pain was reduced within 3 weeks of taking a low dosage of HCM (1 g/day), regardless of gender, age group, and activity intensity when compared with the placebo group. After stopping supplementation, joint pain scores gradually increased but still remained significantly lower than those of the placebo group after 4 weeks of washout. The low dropout rate (<6% of participants, mainly in the placebo group) demonstrates that the digital study was well received by the study population., Conclusions: The digital tool allowed us to measure a heterogeneous group of active adults in a real-world setting (without any lifestyle intervention), thus promoting inclusivity and diversity. With low dropout rates, it demonstrates that mobile apps can generate qualitative, quantifiable, real-world data showcasing supplement effectiveness. The study confirmed that the oral intake of a low dose (1 g/day) of HCM led to a significant reduction of joint pain from 3 weeks after starting supplementation., (©Christie Newman, Els Adriaens, Nicolina Virgilio, Sara Vleminckx, Sara de Pelsmaeker, Janne Prawitt, Catarina I F Silva. Originally published in JMIR Formative Research (https://formative.jmir.org), 03.04.2023.)

Purpose: We examined the effects of collagen peptides (CP) supplementation on exercise-induced gastrointestinal (GI) stress., Methods: In a randomized, crossover design, 20 volunteers (16 males: [Formula: see text]O 2max , 53.4 ± 5.9 ml·kg -1 ) completed 3 trials: a non-exercise rest trial, with no supplement (REST) and then an exercise trial with CP (10 g·day -1 ) or placebo control (CON) supplements, which were consumed for 7 days prior to, and 45 min before, a 70 min run at 70-90% of [Formula: see text]O 2max . Outcome measures included urinary lactulose and rhamnose (L/R), intestinal fatty acid binding protein (I-FABP), lipopolysaccharide (LPS), anti-LPS antibody, monocyte-chemoattractant protein-1 (MCP-1), interleukin (IL) 6 and 8, cortisol, alkaline phosphatase (ALP) (measured pre, 10 min post and 2 h post) and subjective GI symptoms., Results: There were no differences in heart rate, perceived exertion, thermal comfort, or core temperature during exercise in the CP and CON trials (all P > 0.05). I-FABP was higher in CP (2538 ± 1221 pg/ml) and CON (2541 ± 766 pg/ml) vs. REST 2 h post (1893 ± 1941 pg/ml) (both P < 0.05). LPS increased in CON vs. REST 2 h post (+ 71.8 pg/ml; P < 0.05). Anti-LPS antibody decreased in CON and CP vs. REST at post (both P < 0.05). There were no differences in MCP-1, IL-6, and IL-8 between the CP and CON trials (all P > 0.05), and no differences in L/R or GI symptoms between CON and CP (all P > 0.05)., Conclusion: Collagen peptides did not modify exercise-induced changes in inflammation, GI integrity or subjective GI symptoms but LPS was higher in CON 2 h post-exercise and thus future studies may be warranted., (© 2022. The Author(s).)

Background: The effect of dietary collagen on managing digestive symptoms is currently lacking in the literature., Objective: To gain a better understanding of this issue, we conducted a 2-phase mixed methods study., Methods: Phase 1 was a mixed methods design to explore current attitude and practice among consumers and health care practitioners. The findings were used to design an 8-week phase 2 digital study called Gutme! conducted in the United States in healthy female volunteers (BMI>25 kg/m 2 ). Our aim was, first, to determine the feasibility of conducting a fully digital mixed methods study; second, the study explored the effect of an 8-week daily supplementation of 20 g dietary collagen peptide (Peptan) on digestive symptoms. Phase 2 was a prospective, open-label, longitudinal, single-arm study. Participation involved 2 weeks of baseline tracking (digestive symptoms, mood, stool, and lifestyle) using an app, followed by 8 weeks of tracking and taking 20 g collagen peptide supplement split into 2 dosages per day. Participants were required to complete a web-based symptom questionnaire at baseline, week 2, and week 8, as well as participate in 2 scheduled video interviews., Results: Phase 1 revealed that consumer awareness of collagen for digestive health is low (64/204, 31.4%). Among the dietitians prescribing collagen for their patients, the most common dosage was 20 g a day with notable effects after 6 weeks of intake. Within the phase 2 study, of the 40 recruited participants, 14 (35%) completed the full course of supplementation. The findings indicate that 93% (13/14) of those who completed the study experienced a reduction in digestive symptoms, which included bloating., Conclusions: A mixed methods digital study design is feasible and acceptable for collecting relevant data in a real-life setting. The use of a 20 g daily collagen peptide supplement may reduce bloating and improve mild digestive symptoms in otherwise healthy female adults in the absence of any other dietary or lifestyle interventions., Trial Registration: ClinicalTrials.gov NCT04245254; https://clinicaltrials.gov/ct2/show/NCT04245254., (©Mariette Abrahams, Rochez O’Grady, Janne Prawitt. Originally published in JMIR Formative Research (https://formative.jmir.org), 31.05.2022.)

Protein hydrolysates are an important part of the human diet. Often, they are prepared from milk, soy, or collagen. In the present study, four different collagen hydrolysates were tested, varying in the average molecular weight and the animal source. Three types of samples, the dissolved start products, in vitro generated dialysates (containing the digested components that are potentially available for small intestinal absorption), and human serum collected after product ingestion, were analyzed using LC-MS to compare the state of the hydrolysates before and after absorption, i.e., uptake into the blood. It was found that the composition of the collagen hydrolysates prior to and after ingestion was highly complex and dynamic, which made it challenging to predefine a strategy for a targeted analysis. Therefore, we implemented a new analytical approach to first map hydrolysate data sets by performing non-targeted LC-MS analysis followed by non-targeted and targeted data analysis. It was shown that the insight gained by following such a top down (data) analytical workflow could be crucial for defining a suitable targeted setup and considering data trends beyond the defined targets. After having defined and performed a limited targeted analysis, it was found that, in our experimental setup, Hyp-Gly and especially Pro-Hyp contributed significantly as carrier to the total Hyp increase in blood after ingestion of collagen hydrolysate. Graphical abstract.

Collagen proteins are crucial components of the bone matrix. Since collagen-derived products are widely used in the food and supplement industry, one may raise the question whether collagen-enriched diets can provide benefits for the skeleton. In this study, we designed an innovative approach to investigate this question taking into account the metabolites that are formed by the digestive tract and appear in the circulation after ingestion of hydrolysed collagen. Blood samples collected in clinical and pre-clinical trials following ingestion and absorption of hydrolysed collagen were processed and applied on bone-related primary cell cultures. This original ex vivo methodology revealed that hydrolysed collagen-enriched serum had a direct impact on the behaviour of cells from both human and mouse origin that was not observed with controls (bovine serum albumin or hydrolysed casein-enriched serum). These ex vivo findings were fully in line with in vivo results obtained from a mouse model of post-menopausal osteoporosis. A significant reduction of bone loss was observed in mice supplemented with hydrolysed collagen compared to a control protein. Both the modulation of osteoblast and osteoclast activity observed upon incubation with human or mouse serum ex vivo and the attenuation of bone loss in vivo, clearly indicates that the benefits of hydrolysed collagen for osteoporosis prevention go beyond the effect of a simple protein supplementation., Competing Interests: Fabien Wauquier, Henri Granel, Audrey Daneault, Gael Rochefort, Jérome Guicheux, Adeline Blot, Nathalie Meunier and Yohann Wittrant have no conflict of interest to declare. Janne Prawitt and Véronique Fabien-Soulé work for Rousselot and provided the hydrolysed collagens.

This study examined whether consuming collagen peptides (CP) before and after strenuous exercise alters markers of muscle damage, inflammation and bone turnover. Using a double-blind, independent group's design, 24 recreationally active males consumed either 20 g day -1 of CP or a placebo control (CON) for 7 days before and 2 days after performing 150 drop jumps. Maximal isometric voluntary contractions, countermovement jumps (CMJ), muscle soreness (200 mm visual analogue scale), pressure pain threshold, Brief Assessment of Mood Adapted (BAM +) and a range of blood markers associated with muscle damage, inflammation and bone turnover C-terminal telopeptide of type 1 collagen (β-CTX) and N-terminal propeptides of type 1 pro-collagen (P1NP) were measured before supplementation (baseline; BL), pre, post, 1.5, 24 and 48 h post-exercise. Muscle soreness was not significantly different in CP and CON (P = 0.071) but a large effect size was evident at 48 h post-exercise, indicative of lower soreness in the CP group (90.42 ± 45.33 mm vs. CON 125.67 ± 36.50 mm; ES = 2.64). CMJ height recovered quicker with CP than CON at 48 h (P = 0.050; CP 89.96 ± 12.85 vs. CON 78.67 ± 14.41% of baseline values; ES = 0.55). There were no statistically significant effects for the other dependent variables (P > 0.05). β-CTX and P1NP were unaffected by CP supplementation (P > 0.05). In conclusion, CP had moderate benefits for the recovery of CMJ and muscle soreness but had no influence on inflammation and bone collagen synthesis.

Osteoporosis is a chronic and asymptomatic disease characterized by low bone mass and skeletal microarchitectural deterioration, increased risk of fracture, and associated comorbidities most prevalent in the elderly. Due to an increasingly aging population, osteoporosis has become a major health issue requiring innovative disease management. Proteins are important for bone by providing building blocks and by exerting specific regulatory function. This is why adequate protein intake plays a considerable role in both bone development and bone maintenance. More specifically, since an increase in the overall metabolism of collagen can lead to severe dysfunctions and a more fragile bone matrix and because orally administered collagen can be digested in the gut, cross the intestinal barrier, enter the circulation, and become available for metabolic processes in the target tissues, one may speculate that a collagen-enriched diet provides benefits for the skeleton. Collagen-derived products such as gelatin or hydrolyzed collagen (HC) are well acknowledged for their safety from a nutritional point of view; however, what is their impact on bone biology? In this manuscript, we critically review the evidence from literature for an effect of HC on bone tissues in order to determine whether HC may represent a relevant alternative in the design of future nutritional approaches to manage osteoporosis prevention.

Osteoarthritis (OA) is a degenerative joint disease for which there are no disease modifying therapies. Thus, strategies that offer chondroprotective or regenerative capability represent a critical unmet need. Recently, oral consumption of a hydrolyzed type 1 collagen (hCol1) preparation has been reported to reduce pain in human OA and support a positive influence on chondrocyte function. To evaluate the tissue and cellular basis for these effects, we examined the impact of orally administered hCol1 in a model of posttraumatic OA (PTOA). In addition to standard chow, male C57BL/6J mice were provided a daily oral dietary supplement of hCol1 and a meniscal-ligamentous injury was induced on the right knee. At various time points post-injury, hydroxyproline (hProline) assays were performed on blood samples to confirm hCol1 delivery, and joints were harvested for tissue and molecular analyses were performed, including histomorphometry, OARSI and synovial scoring, immunohistochemistry and mRNA expression studies. Confirming ingestion of the supplements, serum hProline levels were elevated in experimental mice administered hCol1. In the hCol1 supplemented mice, chondroprotective effects were observed in injured knee joints, with dose-dependent increases in cartilage area, chondrocyte number and proteoglycan matrix at 3 and 12 weeks post-injury. Preservation of cartilage and increased chondrocyte numbers correlated with reductions in MMP13 protein levels and apoptosis, respectively. Supplemented mice also displayed reduced synovial hyperplasia that paralleled a reduction in Tnf mRNA, suggesting an anti-inflammatory effect. These findings establish that in the context of murine knee PTOA, daily oral consumption of hCol1 is chondroprotective, anti-apoptotic in articular chondrocytes, and anti-inflammatory. While the underlying mechanism driving these effects is yet to be determined, these findings provide the first tissue and cellular level information explaining the already published evidence of symptom relief supported by hCol1 in human knee OA. These results suggest that oral consumption of hCol1 is disease modifying in the context of PTOA.

Background: Skin dryness and an accelerated fragmentation of the collagen network in the dermis are hallmarks of skin aging. Nutrition is a key factor influencing skin health and consequently its appearance. A wide range of dietary supplements is offered to improve skin health. Collagen peptides are used as a bioactive ingredient in nutricosmetic products and have been shown in preclinical studies to improve skin barrier function, to induce the synthesis of collagen and hyaluronic acid, and to promote fibroblast growth and migration. Our aim was to investigate the effect of oral supplementation with specific collagen peptides on skin hydration and the dermal collagen network in a clinical setting., Methods: Two placebo-controlled clinical trials were run to assess the effect of a daily oral supplementation with collagen peptides on skin hydration by corneometry, on collagen density by high-resolution ultrasound and on collagen fragmentation by reflectance confocal microscopy. Human skin explants were used to study extracellular matrix components in the presence of collagen peptides ex vivo., Results: Oral collagen peptide supplementation significantly increased skin hydration after 8 weeks of intake. The collagen density in the dermis significantly increased and the fragmentation of the dermal collagen network significantly decreased already after 4 weeks of supplementation. Both effects persisted after 12 weeks. Ex vivo experiments demonstrated that collagen peptides induce collagen as well as glycosaminoglycan production, offering a mechanistic explanation for the observed clinical effects., Conclusion: The oral supplementation with collagen peptides is efficacious to improve hallmarks of skin aging., (© 2015 The Authors. Journal of Cosmetic Dermatology Published by Wiley Periodicals, Inc.)

Bile acids are signalling molecules, which activate the transmembrane receptor TGR5 and the nuclear receptor FXR. BA sequestrants (BAS) complex bile acids in the intestinal lumen and decrease intestinal FXR activity. The BAS-BA complex also induces glucagon-like peptide-1 (GLP-1) production by L cells which potentiates β-cell glucose-induced insulin secretion. Whether FXR is expressed in L cells and controls GLP-1 production is unknown. Here, we show that FXR activation in L cells decreases proglucagon expression by interfering with the glucose-responsive factor Carbohydrate-Responsive Element Binding Protein (ChREBP) and GLP-1 secretion by inhibiting glycolysis. In vivo, FXR deficiency increases GLP-1 gene expression and secretion in response to glucose hence improving glucose metabolism. Moreover, treatment of ob/ob mice with the BAS colesevelam increases intestinal proglucagon gene expression and improves glycaemia in a FXR-dependent manner. These findings identify the FXR/GLP-1 pathway as a new mechanism of BA control of glucose metabolism and a pharmacological target for type 2 diabetes.

Background & Aims: Peroxisome proliferator-activated receptors (PPARs) have been implicated in non-alcoholic steatohepatitis (NASH) pathogenesis, mainly based on animal data. Gene expression data in NASH patients are scarce. We studied liver PPARα, β/δ, and γ expression in a large cohort of obese patients assessed for presence of NAFLD at baseline and 1 year follow-up., Methods: Patients presented to the obesity clinic underwent a hepatic work-up. If NAFLD was suspected, liver biopsy was performed. Gene expression was studied by mRNA quantification. Patients were reassessed after 1 year., Results: 125 patients were consecutively included in the study, of which 85 patients had paired liver biopsy taken at 1 year of follow-up. Liver PPARα expression negatively correlated with the presence of NASH (p=0.001) and with severity of steatosis (p=0.003), ballooning (p=0.001), NASH activity score (p=0.008) and fibrosis (p=0.003). PPARα expression was positively correlated to adiponectin (R(2)=0.345, p=0.010) and inversely correlated to visceral fat (R(2)=-0.343, p<0.001), HOMA IR (R(2)=-0.411, p<0.001) and CK18 (R(2)=-0.233, p=0.012). Liver PPARβ/δ and PPARγ expression did not correlate with any histological feature nor with glucose metabolism or serum lipids. At 1 year, correlation of PPARα expression with liver histology was confirmed. In longitudinal analysis, an increase in expression of PPARα and its target genes was significantly associated with histological improvement (p=0.008)., Conclusion: Human liver PPARα gene expression negatively correlates with NASH severity, visceral adiposity and insulin resistance and positively with adiponectin. Histological improvement is associated with an increase in expression of PPARα and its target genes. These data might suggest that PPARα is a potential therapeutic target in NASH., (Copyright © 2015. Published by Elsevier B.V.)

Atopic dermatitis (AD) is a chronic allergic dermatosis characterized by epidermal thickening and dermal inflammatory infiltrates with a dominant Th2 profile during the acute phase, whereas a Th1 profile is characteristic of the chronic stage. Among chemokines and chemokine receptors associated with inflammation, increased levels of CX3CL1 (fractalkine) and its unique receptor, CX3CR1, have been observed in human AD. We have thus investigated their role and mechanism of action in experimental models of AD and psoriasis. AD pathology and immune responses, but not psoriasis, were profoundly decreased in CX3CR1-deficient mice and upon blocking CX3CL1-CX3CR1 interactions in wild-type mice. CX3CR1 deficiency affected neither antigen presentation nor T cell proliferation in vivo upon skin sensitization, but CX3CR1 expression by both Th2 and Th1 cells was required to induce AD. Surprisingly, unlike in allergic asthma, where CX3CL1 and CX3CR1 regulate the pathology by controlling effector CD4(+) T cell survival within inflamed tissues, adoptive transfer experiments established CX3CR1 as a key regulator of CD4(+) T cell retention in inflamed skin, indicating a new function for this chemokine receptor. Therefore, although CX3CR1 and CX3CL1 act through distinct mechanisms in different pathologies, our results further indicate their interest as promising therapeutic targets in allergic diseases., (© 2014 Staumont-Sallé et al.)

Intestinal bile acid (BA) sequestration efficiently lowers plasma glucose concentrations in type 2 diabetes (T2D) patients. Because BAs act as signaling molecules via receptors, including the G protein-coupled receptor TGR5 and the nuclear receptor FXR (farnesoid X receptor), to regulate glucose homeostasis, BA sequestration, which interrupts the entero-hepatic circulation of BAs, constitutes a plausible action mechanism of BA sequestrants. An increase of intestinal L-cell glucagon-like peptide-1 (GLP-1) secretion upon TGR5 activation is the most commonly proposed mechanism, but recent studies also argue for a direct entero-hepatic action to enhance glucose utilization. We discuss here recent findings on the mechanisms of sequestrant-mediated glucose lowering via an increase of splanchnic glucose utilization through entero-hepatic FXR signaling., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The nuclear bile acid receptor farnesoid X receptor (FXR) is an important transcriptional regulator of bile acid, lipid, and glucose metabolism. FXR is highly expressed in the liver and intestine and controls the synthesis and enterohepatic circulation of bile acids. However, little is known about FXR-associated proteins that contribute to metabolic regulation. Here, we performed a mass spectrometry-based search for FXR-interacting proteins in human hepatoma cells and identified AMPK as a coregulator of FXR. FXR interacted with the nutrient-sensitive kinase AMPK in the cytoplasm of target cells and was phosphorylated in its hinge domain. In cultured human and murine hepatocytes and enterocytes, pharmacological activation of AMPK inhibited FXR transcriptional activity and prevented FXR coactivator recruitment to promoters of FXR-regulated genes. Furthermore, treatment with AMPK activators, including the antidiabetic biguanide metformin, inhibited FXR agonist induction of FXR target genes in mouse liver and intestine. In a mouse model of intrahepatic cholestasis, metformin treatment induced FXR phosphorylation, perturbed bile acid homeostasis, and worsened liver injury. Together, our data indicate that AMPK directly phosphorylates and regulates FXR transcriptional activity to precipitate liver injury under conditions favoring cholestasis.

Unlabelled: An independent role of nonalcoholic fatty liver disease (NAFLD) in the development of cardiovascular disease has been suggested, probably mediated through increased levels of prothrombotic factors. Therefore, we examined whether NAFLD is linked to a prothrombotic state, independently of metabolic risk factors in a large single-center cohort of overweight/obese patients. Patients presenting to the obesity clinic underwent a detailed metabolic and liver assessment, including an extensive panel of coagulation factors. If NAFLD was suspected, a liver biopsy was proposed. A series of 273 consecutive patients (65% female) with a liver biopsy were included (age, 44 ± 0.76 years; body mass index: 39.6 ± 0.40 kg/m(2)). Increase in fibrinogen, factor VIII, and von Willebrand factor and decrease in antithrombin III correlated with metabolic features, but not with liver histology. Levels of plasminogen activator inhibitor-1 (PAI-1) increased significantly with increasing severity of steatosis (P < 0.001), lobular inflammation (P < 0.001), ballooning (P = 0.002), and fibrosis (P < 0.001). Patients with nonalcoholic steatohepatitis had significantly higher PAI-1 values than those with normal liver (P < 0.001). In multiple regression, including anthropometric and metabolic parameters, steatosis remained an independent predictor of PAI-1 levels, explaining, together with fasting C-peptide and waist circumference, 21% of the variance in PAI-1. No consistent correlations with histology were found for the other coagulation factors., Conclusion: In obesity, NAFLD severity independently contributes to the increase in PAI-1 levels, whereas other coagulation factors are unaltered. This finding might, in part, explain the increased cardiovascular risk associated with NAFLD., (© 2013 by the American Association for the Study of Liver Diseases.)

The α-1-acid glycoprotein/orosomucoids (ORMs) are members of the lipocalin protein family. Encoded by 3 polymorphic genes in mouse (2 in man, 1 in rat), ORMs are expressed in hepatocytes and function as acute-phase proteins secreted in plasma under stressful conditions. In addition to their role of nanocarrier, ORMs are involved in several pathophysiological processes such as immunosuppression, cardioprotection, and inflammatory bowel disease. The nuclear bile acid receptor farnesoid X receptor (FXR) regulates bile acid homeostasis and lipid and glucose metabolism and is an important modulator of enterohepatic functions. Here we report that hepatic FXR deletion in mice affects the expression of several members of the lipocalin family, among which ORMs are identified as direct FXR target genes. Indeed, a FXR response element upstream of the mouse Orm1 promoter was identified to which hepatic, but not ileal, FXR can bind and activate ORM expression in vitro and in vivo. However, ORMs are regulated in a species-specific manner because the ORM cluster is regulated by FXR neither in human nor rat cell lines. Consistent with these data, chromatin immunoprecipitation sequencing analysis of the FXR genomic binding sites did not detect any FXR response element in the vicinity of the human or rat ORM gene cluster. Thus, bile acids and their cognate nuclear receptor, FXR, are regulators of ORM expression, with potential implications for the species-specific metabolic and inflammation control by FXR because the expression of the proinflammatory genes in epididymal white adipose tissue was dependent on liver FXR activation.

Dyslipidemia is an important risk factor for cardiovascular disease (CVD) and atherosclerosis. When dyslipidemia coincides with other metabolic disorders such as obesity, hypertension, and glucose intolerance, defined as the metabolic syndrome (MS), individuals present an elevated risk to develop type 2 diabetes (T2D) as well as CVD. Because the MS epidemic represents a growing public health problem worldwide, the development of therapies remains a major challenge. Alterations of bile acid pool regulation in T2D have revealed a link between bile acid and metabolic homeostasis. The bile acid receptors farnesoid X receptor (FXR) and TGR5 both regulate lipid, glucose, and energy metabolism, rendering them potential pharmacological targets for MS therapy. This review discusses the mechanisms of metabolic regulation by FXR and TGR5 and the utility relevance of natural and synthetic modulators of FXR and TGR5 activity, including bile acid sequestrants, in the treatment of the MS.

The liver is a major target of injury in obese patients. Non-alcoholic fatty liver disease (NAFLD) is present in 60-90% of obese Americans and can range from simple steatosis to the more severe non-alcoholic steatohepatitis (NASH). The onset of a chronic inflammatory reaction marks the progression from simple steatosis to NASH and the expansion of adipose tissue is strongly associated with angiogenesis. Therefore, we determined the serum concentration of inflammatory [tumor necrosis factor alpha (TNFα) and interleukin 6 (IL6)] and angiogenic [vascular endothelial growth factor A (VEGF)] cytokines and soluble VEGF receptors 1 and 2 (sVEGFR1, sVEGFR2) in the serum of an obese population with simple steatosis and NASH compared to healthy controls. Moreover, we determined the TNFα, IL6, VEGF, VEGFR1 and VEGFR2 gene expression in the liver of these simple steatosis and NASH patients. The population consisted of 30 obese patients, which were diagnosed with simple steatosis and 32 patients with NASH and compared to 30 age-and-sex matched healthy controls. Mean serum TNFα levels were elevated in the serum of simple steatosis and NASH patients compared to healthy controls, reaching significance in NASH patients. IL6 was significantly increased in simple steatosis and NASH patients compared to the healthy controls. VEGF levels were significantly elevated in patients with simple steatosis and borderline significantly elevated in NASH patients compared to the serum levels of healthy control subjects. The concentration of sVEGFR1 was significantly increased in serum of simple steatosis and NASH patients compared to controls. sVEGFR2 concentration was not significantly different in the three groups. TNFα mRNA expression was higher in NASH patients compared to simple steatosis patients. Hepatic gene expression of VEGF, VEGFR1 and VEGFR2 were slightly decreased in NASH patients compared to simple steatosis patients. These data indicate the involvement of inflammatory (TNFα and IL6), angiogenic (VEGF) cytokines and sVEGFR1 in the pathophysiology of NAFLD., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Today, we are witnessing a rising incidence of obesity worldwide. This increase is due to a sedentary life style, an increased caloric intake and a decrease in physical activity. Obesity contributes to the appearance of type 2 diabetes, dyslipidemia and cardiovascular complications due to atherosclerosis, and nephropathy. Therefore, the development of new therapeutic strategies may become a necessity. Given the metabolism controlling properties of nuclear receptors in peripheral organs (such as liver, adipose tissues, pancreas) and their implication in various processes underlying metabolic diseases, they constitute interesting therapeutic targets for obesity, dyslipidemia, cardiovascular disease and type 2 diabetes. The recent identification of the central nervous system as a player in the control of peripheral metabolism opens new avenues to our understanding of the pathophysiology of obesity and type 2 diabetes and potential novel ways to treat these diseases. While the metabolic functions of nuclear receptors in peripheral organs have been extensively investigated, little is known about their functions in the brain, in particular with respect to brain control of energy homeostasis. This review provides an overview of the relationships between nuclear receptors in the brain, mainly at the hypothalamic level, and the central regulation of energy homeostasis. In this context, we will particularly focus on the role of PPARα, PPARγ, LXR and Rev-erbα., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objective: Bile acids (BA) participate in the maintenance of metabolic homeostasis acting through different signaling pathways. The nuclear BA receptor farnesoid X receptor (FXR) regulates pathways in BA, lipid, glucose, and energy metabolism, which become dysregulated in obesity. However, the role of FXR in obesity and associated complications, such as dyslipidemia and insulin resistance, has not been directly assessed., Research Design and Methods: Here, we evaluate the consequences of FXR deficiency on body weight development, lipid metabolism, and insulin resistance in murine models of genetic and diet-induced obesity., Results: FXR deficiency attenuated body weight gain and reduced adipose tissue mass in both models. Surprisingly, glucose homeostasis improved as a result of an enhanced glucose clearance and adipose tissue insulin sensitivity. In contrast, hepatic insulin sensitivity did not change, and liver steatosis aggravated as a result of the repression of β-oxidation genes. In agreement, liver-specific FXR deficiency did not protect from diet-induced obesity and insulin resistance, indicating a role for nonhepatic FXR in the control of glucose homeostasis in obesity. Decreasing elevated plasma BA concentrations in obese FXR-deficient mice by administration of the BA sequestrant colesevelam improved glucose homeostasis in a FXR-dependent manner, indicating that the observed improvements by FXR deficiency are not a result of indirect effects of altered BA metabolism., Conclusions: Overall, FXR deficiency in obesity beneficially affects body weight development and glucose homeostasis., (© 2011 by the American Diabetes Association.)

Type 2 diabetes (T2D) is a growing health problem worldwide, but the currently available strategies for therapy and prevention are insufficient. Recent observations indicate that bile acid homeostasis is altered in T2D. Bile acids are metabolic regulators that act as signaling molecules through receptor-dependent and -independent pathways. The most prominent signaling molecules mediating bile acid signaling are the nuclear receptor farnesoid X receptor (FXR) and the membrane receptor TGR5. Both are implicated in the regulation of lipid, glucose, and energy metabolism. Dysregulation of these pathways might contribute to the development of T2D and associated complications. Interestingly, data from studies with bile acids or bile acid sequestrants indicate that the manipulation of bile acid homeostasis might be an attractive approach for T2D therapy. In this review, we summarize the mechanisms of bile acid-mediated metabolic control that might be relevant in the pathogenesis of T2D.

Objective: Hypertriglyceridemia and fatty liver are common in patients with type 2 diabetes, but the factors connecting alterations in glucose metabolism with plasma and liver lipid metabolism remain unclear. Apolipoprotein CIII (apoCIII), a regulator of hepatic and plasma triglyceride metabolism, is elevated in type 2 diabetes. In this study, we analyzed whether apoCIII is affected by altered glucose metabolism., Methods and Results: Liver-specific insulin receptor-deficient mice display lower hepatic apoCIII mRNA levels than controls, suggesting that factors other than insulin regulate apoCIII in vivo. Glucose induces apoCIII transcription in primary rat hepatocytes and immortalized human hepatocytes via a mechanism involving the transcription factors carbohydrate response element-binding protein and hepatocyte nuclear factor-4α. ApoCIII induction by glucose is blunted by treatment with agonists of farnesoid X receptor and peroxisome proliferator-activated receptor-α but not liver X receptor, ie, nuclear receptors controlling triglyceride metabolism. Moreover, in obese humans, plasma apoCIII protein correlates more closely with plasma fasting glucose and glucose excursion after oral glucose load than with insulin., Conclusions: Glucose induces apoCIII transcription, which may represent a mechanism linking hyperglycemia, hypertriglyceridemia, and cardiovascular disease in type 2 diabetes.

Liver X receptors (LXRs) are nuclear receptors that play a crucial role in the transcriptional control of lipid metabolism. Pharmacological LXR activation is an attractive concept for the treatment of atherosclerosis. Genetic LXR deficiency in mice has been shown to have an effect on bone turnover and structure and LXR activation is known to influence the osteogenic differentiation of bone marrow stromal cells. Therefore, therapeutic pharmacological LXR activation may have relevant effects on bone. Here, using two synthetic LXR ligands, T0901317 and GW3965, we investigated the effect of LXR activation on murine osteoblasts and the influence of long-term LXR activation on bone in vivo in mice. Short term (48 h) in vitro treatment of primary murine osteoblasts with T0901317 resulted in a dose-dependent decrease of osteocalcin and alkaline phosphatase mRNA and protein. In vivo, a 6-day treatment of C57BL/6J mice with T0901317 led to a 40% reduction of serum osteocalcin concentrations. Long-term (12-week) oral administration of T0901317 or GW3965 influenced the expression of established LXR target genes in liver and intestine, but did not alter trabecular and cortical bone structure or bone turnover as determined by total skeleton radiography, histomorphometric analysis of lumbar vertebral trabecular bone, micro CT analysis of femur cortical bone and biochemical determination of bone formation and resorption markers. We conclude that short-term pharmacological LXR activation has the potential to profoundly influence osteoblast function, but that long-term LXR activation in vivo has no adverse effects on the murine skeleton., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Bile acids are not only intestinal detergents, but also act as signaling molecules to control bile acid and metabolic homeostasis. By binding to the nuclear receptor farnesoid X receptor (FXR) or the membrane receptor TGR5, bile acids regulate lipid, glucose, and energy metabolism. The removal of bile acids from the enterohepatic cycle by orally administered sequestrants, nonabsorbable resins that complex bile acids in the intestinal lumen, is an effective treatment to reduce plasma cholesterol concentrations in dyslipidemia. In diabetic patients, sequestrants further lower hyperglycemia, and are thus useful in glycemic control. Here, we review the signaling pathways involved in the glucose-regulatory function of bile acids and our current understanding of the mechanisms behind the glucose-lowering effect of bile acid sequestrants.

The bile acid receptor farnesoid X receptor (FXR) is expressed in adipose tissue, but its function remains poorly defined. Peroxisome proliferator-activated receptor-γ (PPARγ) is a master regulator of adipocyte differentiation and function. The aim of this study was to analyze the role of FXR in adipocyte function and to assess whether it modulates PPARγ action. Therefore, we tested the responsiveness of FXR-deficient mice (FXR(-/-)) and cells to the PPARγ activator rosiglitazone. Our results show that genetically obese FXR(-/-)/ob/ob mice displayed a resistance to rosiglitazone treatment. In vitro, rosiglitazone treatment did not induce normal adipocyte differentiation and lipid droplet formation in FXR(-/-) mouse embryonic fibroblasts (MEFs) and preadipocytes. Moreover, FXR(-/-) MEFs displayed both an increased lipolysis and a decreased de novo lipogenesis, resulting in reduced intracellular triglyceride content, even upon PPARγ activation. Retroviral-mediated FXR re-expression in FXR(-/-) MEFs restored the induction of adipogenic marker genes during rosiglitazone-forced adipocyte differentiation. The expression of Wnt/β-catenin pathway and target genes was increased in FXR(-/-) adipose tissue and MEFs. Moreover, the expression of several endogenous inhibitors of this pathway was decreased early during the adipocyte differentiation of FXR(-/-) MEFs. These findings demonstrate that FXR regulates adipocyte differentiation and function by regulating two counteracting pathways of adipocyte differentiation, the PPARγ and Wnt/β-catenin pathways.

There is a great demand for cell models to study human adipocyte function. Here we describe the adipogenic differentiation of a telomerase-immortalized human mesenchymal stem cell line (hMSC-Tert) that maintains numerous features of terminally differentiated adipocytes even after prolonged withdrawal of the peroxisome proliferator activated receptor gamma (PPARgamma) agonist rosiglitazone. Differentiated hMSC-Tert developed the characteristic monolocular phenotype of mature adipocytes. The expression of adipocyte specific markers was highly increased during differentiation. Most importantly, the presence of the PPARgamma agonist rosiglitazone was not required for the stable expression of lipoprotein lipase, adipocyte fatty acid binding protein and perilipin on mRNA and protein levels. Adiponectin expression was post-transcriptionally down-regulated in the absence of rosiglitazone. Insulin sensitivity as measured by insulin-induced phosphorylation of Akt and S6 ribosomal protein was also independent of rosiglitazone. In addition to commonly used adipogenic markers, we investigated further PPARgamma-stimulated proteins with a role in lipid metabolism. We observed an increase of lipoprotein receptor (VLDLR, LRP1) and apolipoprotein E expression during differentiation. Despite this increased expression, the receptor-mediated endocytosis of lipoproteins was decreased in differentiated adipocytes, suggesting that these proteins may have an additional function in adipose tissue beyond lipoprotein uptake.