Renger F Witkamp

Renger F Witkamp
Wageningen University & Research | WUR · Division of Human Nutrition

PhD

About

297
Publications
51,706
Reads
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6,407
Citations
Citations since 2016
94 Research Items
3376 Citations
20162017201820192020202120220200400600
20162017201820192020202120220200400600
20162017201820192020202120220200400600
20162017201820192020202120220200400600
Additional affiliations
May 2006 - present
Wageningen University & Research
Position
  • Wageningen University
Description
  • Professor and chair in Nutrition and Pharmacology, combining research and teaching in medical nutrition and the interfaces between foods and medicines.
April 1996 - November 2010
TNO Pharma
Position
  • TNO
December 1988 - April 1996
Utrecht University, Faculty of Veterinary Medicine
Position
  • Professor (Associate)
Education
August 1977 - December 1987
Utrecht University
Field of study
  • Biology (Biochemistry) and Pharmacy (Pharmacology)

Publications

Publications (297)
Article
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Prenylated phenolics are antimicrobials found in liquorice (Glycyrrhiza spp.). Liquorice spent is a by-product rich in prenylated phenolics obtained after water extraction of roots, and is currently not valorised. We analysed the prenylated phenolics composition of spent extracts from Glycyrrhiza glabra, G. inflata, and G. uralensis, their antimicr...
Article
Background: Cachexia-anorexia syndrome is a complex metabolic condition characterized by skeletal muscle wasting, reduced food intake and prominent involvement of systemic and central inflammation. Here, the gut barrier function was investigated in pancreatic cancer-induced cachexia mouse models by relating intestinal permeability to the degree of...
Chapter
The adequate quantification of endocannabinoids and related N-acylethanolamines can be complex due to their low endogenous levels, structural diversity, and metabolism. Therefore, advanced analytical approaches, involving LC–MS, are required to quantify these molecules in plasma, tissues, and other matrices. It has been shown that endocannabinoid c...
Article
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Gamma-aminobutyric acid (GABA) and its precursor glutamate play signaling roles in a range of tissues. Both function as neurotransmitters in the central nervous system, but they also modulate pancreatic and...
Article
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We studied the mechanistic and biological origins of anti-inflammatory poly-unsaturated fatty acid-derived N-acylethanolamines using synthetic bifunctional chemical probes of docosahexaenoyl ethanolamide (DHEA) and arachidonoyl ethanolamide (AEA) in RAW264.7 macrophages stimulated with 1.0 μg mL-1 lipopolysaccharide. Using a photoreactive diazirine...
Article
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Purpose Trials aiming to lower homocysteine by B-vitamin supplementation have reported mixed results on slowing cognitive decline. We investigated if efficacy of B-vitamin supplementation is affected by baseline plasma omega-3 fatty acid levels. Methods This post-hoc analysis of the B-proof trial included 191 adults aged 65 years or older with bas...
Article
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Arabinoxylans of various structures and sources have shown to possess the ability to induce a range of immune responses in different cell types in vitro and in vivo. Although the underlying mechanisms remain to be fully established, several studies point towards the involvement of activation of pattern recognition receptors (PRRs). Activation of sp...
Article
Traditional foods and diets can provide health benefits beyond their nutrient composition because of the presence of bioactive compounds. In various traditional healthcare systems, diet-based approaches have always played an important role, which has often survived until today. Therefore, investigating traditional foods aimed at health promotion co...
Article
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Targeted exercise combined with nutritional and pharmacological strategies is commonly considered to be the most optimal strategy to reduce the development and progression of cachexia. For COPD patients, this multi-targeted treatment has shown beneficial effects. However, in many, physical activity is seriously hampered by frailty and fatigue. In t...
Article
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Background: Pulmonary hypertension (PH) is a rare progressive and lethal disease affecting pulmonary arteries and heart function. The disease may compromise the nutritional status of the patient, which impairs their physical performance. This study aimed to determine the prevalence of micronutrient deficiencies in pulmonary arterial hypertension (...
Article
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Metabolic syndrome increases the risk of vascular dementia and other neurodegenerative disorders. Recent studies underline that platelets play an important role in linking peripheral with central metabolic and inflammatory mechanisms. In this narrative review, we address the activation of platelets in metabolic syndrome, their effects on neuronal p...
Article
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Demonstrating in an unambiguous manner that a diet, let alone a single product, ‘optimizes’ health, presents an enormous challenge. The least complicated is when the starting situation is clearly suboptimal, like with nutritional deficiencies, malnutrition, unfavourable lifestyle, or due to disease or ageing. Here, desired improvements and interven...
Article
Objectives The neurotransmitters γ-aminobutyric acid (GABA) and glutamic acid are present in many common components of our diet like for example tomato. Recent research suggests that oral supplementation of especially GABA can have relevant health effects with regard to diabetes and blood pressure. As of yet it is unclear whether these neurotransmi...
Article
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Beta-glucans enable functional reprogramming of innate immune cells, a process defined as “trained immunity”, which results in enhanced host responsiveness against primary (training) and/or secondary infections (resilience). Trained immunity holds great promise for promoting immune responses in groups that are at risk ( e.g. elderly and patients)....
Article
Background: We investigated whether pre-operative and post-operative levels of inflammation markers, which have mechanistically been linked to colorectal cancer (CRC) progression, were associated with recurrence and all-cause mortality in CRC patients. Methods: Methods: Data of two prospective cohort studies were used. For the current analysis,...
Article
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Background: Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders. Its pathophysiology is diverse and variable, involving disturbed gut–brain interactions, altered motility and secretion, visceral hypersensitivity, increased intestinal permeability, immune activation, and changes in gut microbiota. Complaints experienc...
Article
Background: Although epidemiological studies suggest a protective role of B vitamins and omega-3 (ω-3) fatty acids in cognitive decline, findings from intervention studies are conflicting. Mechanistic studies suggest that the ω-3 (n-3) fatty acid status can modulate the effects of B vitamins on cognitive decline. Objectives: We investigated the...
Article
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Docosahexaenoyl ethanolamide (DHEA), the ethanolamine conjugate of the n-3 long chain polyunsaturated fatty acid docosahexaenoic acid, is endogenously present in the human circulation and in tissues. Its immunomodulating properties have been (partly) attributed to an interaction with the cyclooxygenase-2 (COX-2) enzyme. Recently, we discovered that...
Article
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Low carbohydrate, high fat (LCHF) diets are followed by athletes, but questions remain regarding effects of LCHF on metabolic adaptation, exercise-induced stress, immune function and their time-course. In this cross-over study, 14 recreational male athletes (32.9 ± 8.2 years, VO2max 57.3 ± 5.8 mL/kg/min) followed a two week LCHF diet (<10 En% carbo...
Article
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Fatigue is very common among colorectal cancer (CRC) patients. We examined the association between adherence to the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) lifestyle recommendations and fatigue among stage I-III CRC patients, and whether inflammation mediated this association. Data from two prospective cohort s...
Article
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Introduction Supplements with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are generally oil-based formulations containing their triacylglycerols, phospholipids or ethyl-esters (EE). Recently, a L-lysine salt of carboxylic EPA and DHA became available (Lys-FFA), which necessitated to study its oral absorption and plasma kinetics in hu...
Article
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Gamma-aminobutyric acid (GABA) and its precursor glutamic acid are important neurotransmitters. Both are also present in peripheral tissues and the circulation, where abnormal plasma concentrations have been linked to specific mental disorders. In addition to endogenous synthesis, GABA and glutamic acid can be obtained from dietary sources. An incr...
Article
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Introduction: Strenuous physical stress induces a range of physiological responses, the extent depending, among others, on the nature and severity of the exercise, a person's training level and overall physical resilience. This principle can also be used in an experimental set-up by measuring time-dependent changes in biomarkers for physiological...
Preprint
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Background Cancer cachexia is a complex and multi-factorial syndrome. As currently available therapeutic options are limited, more in-depth knowledge on cachexia pathophysiology and the underlying molecular mechanisms remains warranted. Studies with animal models provide useful insights but they only mimic the human situation to a certain degree. F...
Article
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Background Calcitriol, the active form of vitamin D, may inhibit colorectal cancer (CRC) progression, which has been mechanistically linked to an attenuation of a pro-inflammatory state. The present study investigated the associations between circulating 25 hydroxy vitamin D 3 (25(OH)D 3 ) levels and inflammatory markers (IL10, IL8, IL6, TNFα and h...
Article
Common dietary fatty acids, including palmitic acid, stearic acid, oleic acid, and polyunsaturated fatty acids, have been studied in the context of overall dietary fat and shown to impact on several types of behaviors, most prominently cognitive behaviors and ingestive behaviors. The independent effects of these fatty acids have been less well-deli...
Chapter
Een adequate vitamine-inname is zeker niet vanzelfsprekend, en deficiënties door bijvoorbeeld ondervoeding, eenzijdige voeding, medicijngebruik of andere factoren blijven wereldwijd een probleem. Voor sommige vitamines is de optimale inname of concentratie nog steeds onderwerp van discussie. In dit hoofdstuk ligt de nadruk op de fysiologische aspec...
Chapter
In dit hoofdstuk komen eerst de voedingsnormen voor vitamines, de begrippen aanbevolen dagelijkse hoeveelheid (ADH) en adequate inname (AI), en de wijze waarop deze tot stand komen aan de orde. Wat de inname van afzonderlijke nutriënten vanuit de voeding betreft heeft zich de afgelopen decennia een belangrijke verandering in denken en beleidsontwik...
Article
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Background: Higher concentrations of 25-hydroxyvitamin D3 [25(OH)D3] at diagnosis are associated with a lower mortality risk in colorectal cancer (CRC) patients. However, magnesium and calcium are important in vitamin D metabolism. Objectives: We aimed to investigate 25(OH)D3, magnesium, or calcium and their interaction among patients with CRC i...
Article
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Activation of peroxisome proliferator-activated receptor gamma (PPARγ) elicits anti-proliferative effects on different tumor cells, including those derived from breast cancer. PPARγ is also expressed in several cells of the breast tumor microenvironment, among which tumor associated macrophages (TAMs) play a pivotal role in tumor progression and me...
Article
Vitamin D metabolites, including 25-hydroxyvitamin D3 (25(OH)D3), may inhibit colorectal cancer (CRC) progression. Here we investigated cross-sectional and longitudinal associations of demographic, lifestyle and clinical characteristics with 25(OH)D3 serum concentrations in CRC patients at diagnosis and six months later. In 1,201 newly-diagnosed st...
Article
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Background: Dietary supplementation with leucine and fish oil rich in omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) has previously been shown to reduce cachexia-related outcomes in C26 tumour-bearing mice. To further explore associated processes and mechanisms we investigated changes in plasma Ca2+ levels, the invo...
Article
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A large body of evidence suggests that dietary n-3 polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), contribute to a reduced inflammatory tone thereby lowering the risk for several chronic and degenerative diseases. Different mechanisms have been proposed to explain these anti-inflammatory ef...
Article
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Cyclooxygenase 2 (COX-2) plays a key role in the regulation of inflammation by catalyzing the oxygenation of PUFAs to prostaglandins (PGs) and hydroperoxides. Next to this, COX-2 can metabolize neutral lipids, including endocannabinoid-like esters and amides. We developed an LC-HRMS-based human recombinant (h)COX-2 screening assay to examine its ab...
Article
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Pulmonary arterial hypertension (PAH) is characterized by remodelling of the pulmonary arteries and right ventricle (RV), which leads to functional decline of cardiac and skeletal muscle. This study investigated the effects of a multi-targeted nutritional intervention with extra protein, leucine, fish oil and oligosaccharides on cardiac and skeleta...
Article
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The genetically encoded calcium sensor protein Cameleon YC3.6 has previously been applied for functional G protein-coupled receptor screening using receptor cell arrays. However, different types of sensors are available, with a wide range in [Ca2+] sensitivity, Hill coefficients, calcium binding domains and fluorophores, that could potentially impr...
Article
Notwithstanding the ongoing debate on their full potential in health and disease, there is general consensus that n-3 PUFAs play important physiological roles. Increasing dietary n-3 PUFA intake results in increased DHA and EPA content in cell membranes as well as an increase in n-3 derived oxylipin and -endocannabinoid concentrations, like fatty a...
Article
Background Magnesium is essential for health and performance. Sub-optimal levels have been reported for older persons. In addition, physical exercise is known to temporally decrease magnesium blood concentrations. Objective To investigate these observations in conjunction we assessed total (tMg) and ionized magnesium (iMg) concentrations in plasma...
Article
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Introduction Prevalence of type 2 diabetes (T2D) is increasing rapidly and lifestyle interventions to reverse diabetes are seen as a possible solution to stop this trend. New practice-based evidence is needed to gain more insight in the actual, and above all scientific, basis for these claims. Methods This observational study with a pretest post-t...
Article
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In this study, two capsaicin analogues, N-eicosapentaenoyl vanillylamine (EPVA) and N-docosahexaenoyl vanillylamine (DHVA), were enzymatically synthesized from their corresponding n-3 long chain polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both dietary relevant components. The compounds significantly reduc...
Article
Hydroxytyrosyl esters with short, medium and long acyl chains were evaluated for their ability to reduce nitric oxide (NO) production by lipopolysaccharide-stimulated RAW264.7 macrophages. Among the compounds tested, C18 esters, namely hydroxytyrosyl stearate (HtySte) and hydroxytyrosyl oleate (HtyOle), were found to decrease NO production in a con...
Article
Background: Hypomagnesemia has been associated with diabetes, cardiovascular disease, and other disorders. Drug use has been suggested as one of the risk factors for low magnesium (Mg) levels. In the elderly population, prone to polypharmacy and inadequate Mg intake, hypomagnesemia might be relevant. Therefore, we aimed to investigate associations...
Article
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Purpose: The aim of the present study was to assess the effect of prolonged and repeated exercise on iron metabolism in middle-aged adults and to compare differences between sexes. Methods: 50 male (58.9 ± 9.9 year) and 48 female (50.9 ± 11.2 year) individuals were monitored on 4 consecutive days at which they walked on average 8 h and 44 min pe...
Article
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The oral mucosa is the first immune tissue that encounters allergens upon ingestion of food. We hypothesized that the bio-accessibility of allergens at this stage may be a key determinant for sensitization. Light roasted peanut flour was suspended at various pH in buffers mimicking saliva. Protein concentrations and allergens profiles were determin...
Article
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Pulmonary arterial hypertension (PAH) is a progressive disease primarily affecting the pulmonary vasculature and heart. PAH patients suffer from exercise intolerance and fatigue, negatively affecting their quality of life. This review summarizes current insights in the pathophysiological mechanisms underlying PAH. It zooms in on the potential invol...
Article
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Background & aims: Plasma citrulline concentration is considered to be a marker for enterocyte metabolic mass and to reflect its reduction as may occur during intestinal dysfunction. Strenuous exercise can act as a stressor to induce small intestinal injury. Our previous studies suggest that this comprises the intestinal ability to produce citrull...
Article
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Persistent physical impairment is frequently encountered after critical illness. Recent data point towards mitochondrial dysfunction as an important determinant of this phenomenon. This narrative review provides a comprehensive overview of the present knowledge of mitochondrial function during and after critical illness and the role and potential t...
Article
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Cancer-induced cachexia has a negative impact on quality of life and adversely affects therapeutic outcomes and survival rates. It is characterized by, often severe, loss of muscle, with or without loss of fat mass. Insight in the pathophysiology of this complex metabolic syndrome and direct treatment options are still limited, which creates a rese...
Article
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Chinotto (Citrus myrtifolia Raf.) is a widely diffused plant native from China and its fruits have a wide-spread use in confectionary and drinks. Remarkably, only little has been reported thus far on its bioactive properties, in contrast to those of the taxonomically related bergamot (Citrus bergamia Risso). The present study aimed to investigate p...
Article
There is no evidence that Hippocrates, although being credited for it, ever literally stated 'let thy food be thy medicine and thy medicine be thy food'. However, yet in line with Hippocrates' philosophy, we are currently witnessing a reappraisal of the complementarity of nutrition and pharmacology. Recent studies not only underline the therapeutic...
Article
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Previous studies have shown that exercise‐induced changes in cytokine profiles depend on exercise duration and intensity. Studies are generally limited to a single day and insight in the time‐course during multiple days of exercise is lacking. Therefore, this study assessed cytokine responses during multiple days of moderate intensity exercise in m...
Article
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Background Adequate nutrition is essential during critical illness. However, providing adequate nutrition is often hindered by gastro-intestinal complications, including feeding intolerance. It is suggested that hyperosmolar medications could be causally involved in the development of gastro-intestinal complications. The aims of the present study w...
Article
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Background: Chemotherapeutic treatment is regularly accompanied by side-effects. Hydrophilic chemotherapeutics such as capecitabine and oxaliplatin (CAPOX), often used in colorectal cancer treatment, predominantly accumulate in non-adipose tissues. From this we hypothesized that body composition and fat infiltration in the muscle (muscle attenuatio...
Article
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Reverse-transfected cell arrays in microfluidic systems have great potential to perform large-scale parallel screening of G protein-coupled receptor (GPCR) activation. Here, we report the preparation of a novel platform using reverse transfection of HEK293 cells, imaging by stereo-fluorescence microscopy in a flowcell format, real-time monitoring o...
Article
Intake, absorption and synthesis of fatty acids, including those produced by the intestinal microbiota are tightly monitored via specific receptors and, indirectly through their conversion into a variety of signalling molecules. The resulting information is integrated and translated to different physiological processes, including the regulation of...
Article
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p>Background & aims: The increased consumption of fish oil enriched-products exposes a wide divers