K. Willems van Dijk

Exendin-4 decreases liver inflammation and atherosclerosis development simultaneously by reducing macrophage infiltration

The aetiology of inflammation in the liver and vessel wall, leading to non‐alcoholic steatohepatitis (NASH) and atherosclerosis, respectively, shares common mechanisms including macrophage infiltration. To treat both disorders simultaneously, it is highly important to tackle the inflammatory status. Exendin‐4, a glucagon‐like peptide‐1 (GLP‐1) receptor agonist, reduces hepatic steatosis and has been suggested to reduce atherosclerosis; however, its effects on liver inflammation are underexplored. Here, we tested the hypothesis that exendin‐4 reduces inflammation in both the liver and vessel wall, and investigated the common underlying mechanism.

Obesity is marked by distinct functional connectivity in brain networks involved in food reward and salience.

We hypothesized that brain circuits involved in reward and salience respond differently to fasting in obese versus lean individuals. We compared functional connectivity networks related to food reward and saliency after an overnight fast (baseline) and after a prolonged fast of 48 h in lean versus obese subjects. We included 13 obese (2 males, 11 females, BMI 35.4 ± 1.2 kg/m(2), age 31 ± 3 years) and 11 lean subjects (2 males, 9 females, BMI 23.2 ± 0.5 kg/m(2), age 28 ± 3 years). Resting-state functional magnetic resonance imaging scans were made after an overnight fast (baseline) and after a prolonged 48 h fast. Functional connectivity of the amygdala, hypothalamus and posterior cingulate cortex (default-mode) networks was assessed using seed-based correlations. At baseline, we found a stronger connectivity between hypothalamus and left insula in the obese subjects. This effect diminished upon the prolonged fast. After prolonged fasting, connectivity of the hypothalamus with the dorsal anterior cingulate cortex (dACC) increased in lean subjects and decreased in obese subjects. Amygdala connectivity with the ventromedial prefrontal cortex was stronger in lean subjects at baseline, which did not change upon the prolonged fast. No differences in posterior cingulate cortex connectivity were observed. In conclusion, obesity is marked by alterations in functional connectivity networks involved in food reward and salience. Prolonged fasting differentially affected hypothalamic connections with the dACC and the insula between obese and lean subjects. Our data support the idea that food reward and nutrient deprivation are differently perceived and/or processed in obesity.

Menopause impacts the relation of plasma adiponectin levels with the metabolic syndrome

Abstract.  Henneman P, Janssens ACJW, Carola Zillikens M, Frolich M, Frants RR, Oostra BA, van Duijn CM, van Dijk KW (Leiden University Medical Center, Leiden; Erasmus Medical Center, Rotterdam, The Netherlands). Menopause impacts the relation of plasma adiponectin levels with the metabolic syndrome. J Intern Med 2010; 267: 402–409.

Gender-dependent effects of high-fat lard diet on cardiac function in C57Bl/6J mice

Increased availability of fatty acids released from insulin-resistant adipose tissue may lead to excess fatty acid uptake in nonadipose organs, including the heart. Accumulation of toxic fatty acid intermediates may affect cardiac function. Our aim was to identify to which extent high-fat diet feeding leads to alterations in cardiac function and whether this depends on gender and (or) duration of high-fat diet feeding. Male and female C57Bl/6J mice (n = 8 per group) of 12 to 16 weeks old were fed a low-fat (10% energy) or high-fat (45% energy) lard diet for 6 or 12 weeks. Plasma lipid levels, echocardiography, and left ventricular pressure-volume relationships were obtained at 2, 1, and 0 weeks before termination, respectively. In both male and female mice, the high-fat diet increased body weight and plasma lipid content. At 10 weeks, significant increases were observed for plasma total cholesterol (males: +44%; females: +86%), phospholipids (+16% and +34%), and triglycerides (+27% and +53%) (all p < 0.001). In male mice, but not in female mice, the high-fat diet significantly affected cardiac function at 12 weeks with increased end-systolic volume (25.4 ± 6.2 vs. 17.0 ± 6.7 µL, p < 0.05), increased end-systolic pressure (72.1 ± 6.9 vs. 63.6 ± 6.9 mm Hg, p < 0.01), and decreased ejection fraction (61.2% ± 4.5% vs. 68.1% ± 3.7%, p < 0.01), indicating reduced systolic function. Multiple linear regression analysis indicated a significant diet-gender interaction for end-systolic volume and ejection fraction. In conclusion, high-fat diet feeding increased body weight and plasma lipid levels in male and in female mice, but resulted in impairment of cardiac function only in males.

Adipocyte telomere length associates negatively with adipocyte size, whereas adipose tissue telomere length associates negatively with the extent of fibrosis in severely obese women

Telomere length can be considered as a biological marker for cell proliferation and aging. Obesity is associated with adipocyte hypertrophy and proliferation as well as with shorter telomeres in adipose tissue. As adipose tissue is a mixture of different cell types and the cellular composition of adipose tissue changes with obesity, it is unclear what determines telomere length of whole adipose tissue. We aimed to investigate telomere length in whole adipose tissue and isolated adipocytes in relation to adiposity, adipocyte hypertrophy and adipose tissue inflammation and fibrosis. Telomere length was measured by real-time PCR in visceral adipose tissue, and isolated adipocytes of 21 obese women with a waist ranging from 110 to 147 cm and age from 31 to 61 years. Telomere length in adipocytes was shorter than in whole adipose tissue. Telomere length of adipocytes but not whole adipose tissue correlated negatively with waist and adipocyte size, which was still significant after correction for age. Telomere length of whole adipose tissue associated negatively with fibrosis as determined by collagen content. Thus, in extremely obese individuals, adipocyte telomere length is a marker of adiposity, whereas whole adipose tissue telomere length reflects the extent of fibrosis and may indicate adipose tissue dysfunction.

Exome-sequencing in a large population-based study reveals a rare Asn396Ser variant in the LIPG gene associated with depressive symptoms

Despite a substantial genetic component, efforts to identify common genetic variation underlying depression have largely been unsuccessful. In the current study we aimed to identify rare genetic variants that might have large effects on depression in the general population. Using high-coverage exome-sequencing, we studied the exonic variants in 1265 individuals from the Rotterdam study (RS), who were assessed for depressive symptoms. We identified a missense Asn396Ser mutation (rs77960347) in the endothelial lipase (LIPG) gene, occurring with an allele frequency of 1% in the general population, which was significantly associated with depressive symptoms (P-value=5.2 × 10−08, β=7.2). Replication in three independent data sets (N=3612) confirmed the association of Asn396Ser (P-value=7.1 × 10−03, β=2.55) with depressive symptoms. LIPG is predicted to have enzymatic function in steroid biosynthesis, cholesterol biosynthesis and thyroid hormone metabolic processes. The Asn396Ser variant is predicted to have a damaging effect on the function of LIPG. Within the discovery population, carriers also showed an increased burden of white matter lesions (P-value=3.3 × 1−02) and a higher risk of Alzheimer’s disease (odds ration=2.01; P-value=2.8 × 10−02) compared with the non-carriers. Together, these findings implicate the Asn396Ser variant of LIPG in the pathogenesis of depressive symptoms in the general population.

Pharmacological Modulation of Dopamine Receptor D2-Mediated Transmission Alters the Metabolic Phenotype of Diet Induced Obese and Diet Resistant C57Bl6 Mice

High fat feeding induces a variety of obese and lean phenotypes in inbred rodents. Compared to Diet Resistant (DR) rodents, Diet Induced Obese (DIO) rodents are insulin resistant and have a reduced dopamine receptor D2 (DRD2) mediated tone. We hypothesized that this differing dopaminergic tone contributes to the distinct metabolic profiles of these animals. C57Bl6 mice were classified as DIO or DR based on their weight gain during 10 weeks of high fat feeding. Subsequently DIO mice were treated with the DRD2 agonist bromocriptine and DR mice with the DRD2 antagonist haloperidol for 2 weeks. Compared to DR mice, the bodyweight of DIO mice was higher and their insulin sensitivity decreased. Haloperidol treatment reduced the voluntary activity and energy expenditure of DR mice and induced insulin resistance in these mice. Conversely, bromocriptine treatment tended to reduce bodyweight and voluntary activity, and reinforce insulin action in DIO mice. These results show that DRD2 activation partly redirects high fat diet induced metabolic anomalies in obesity-prone mice. Conversely, blocking DRD2 induces an adverse metabolic profile in mice that are inherently resistant to the deleterious effects of high fat food. This suggests that dopaminergic neurotransmission is involved in the control of metabolic phenotype.

Obesity is associated with an altered autonomic nervous system response to nutrient restriction.

Heart rate variability (HRV) reflects the balance of activities of sympathetic and parasympathetic components of the autonomic nervous system. We compared HRV parameters in response to a prolonged fast in obese versus normal weight humans. In addition, the effect of weight‐loss was evaluated in obese individuals.

RP105 deficiency aggravates cardiac dysfunction after myocardial infarction in mice

BACKGROUND Toll-like receptor-4 (TLR4), a receptor of the innate immune system, is suggested to have detrimental effects on cardiac function after myocardial infarction (MI). RP105 (CD180) is a TLR4 homolog lacking the intracellular signaling domain that competitively inhibits TLR4-signaling. Thus, we hypothesized that RP105 deficiency, by amplifying TLR4 signaling, would lead to aggravated cardiac dysfunction after MI. METHODS AND RESULTS First, whole blood from RP105-/- and wild-type (WT) male C57Bl/6N mice was stimulated with LPS, which induced a strong inflammatory TNFα response in RP105-/- mice. Then, baseline heart function was assessed by left ventricular pressure-volume relationships which were not different between RP105-/- and WT mice. Permanent ligation of the left anterior descending coronary artery was performed to induce MI. Infarct sizes were analyzed by (immuno)histology and did not differ. Fifteen days post MI heart function was assessed and RP105-/- mice had significantly higher heart rate (+21%, P<0.01), end systolic volume index (+57%, P<0.05), end systolic pressure (+22%, P<0.05) and lower relaxation time constant tau (-12%, P<0.05), and a tendency for increased end diastolic volume index (+42%, P<0.06), compared to WT mice. In the area adjacent to the infarct zone, compared to the healthy myocardium, levels of RP105, TLR4 and the endogenous TLR4 ligand fibronectin-EDA were increased as well as the number of macrophages, however this was not different between both groups. CONCLUSION Deficiency of the endogenous TLR4 inhibitor RP105 leads to an enhanced inflammatory status and more pronounced cardiac dilatation after induction of MI, underscoring the role of the TLR4 pathway in post-infarction remodeling.

Specific and efficient targeting of adenovirus vectors to macrophages: application of a fusion protein between an adenovirus-binding fragment and avidin, linked to a biotinylated oligonucleotide.

The application of serotype 5 adenoviruses (Ad5) in macrophages is hampered by the absence of the endogenous coxsackie adenovirus receptor (CAR).