Chronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues,... Show moreChronic energy surplus causes obesity and promotes insulin resistance and type 2 diabetes (T2D). A major contributor to insulin resistance is chronic, low-grade inflammation in metabolic tissues, also coined metaflammation. In this context, white adipose tissue and liver-resident innate and adaptive immune cells produce proinflammatory cytokines that exacerbate inflammation and inhibit canonical insulin signaling. Among them, macrophages and dendritic cells were shown to play central roles in metaflammation, although the environmental and cellular changes dictating proinflammatory activation in the context of obesity are not fully understood. This thesis describes novel mechanisms by which macrophages and dendritic cells control metabolic homeostasis in obese mice. In addition, we show that immunomodulatory molecules derived from parasitic worm eggs promote an immune response in metabolic tissues that maintains insulin sensitivity. Finally, we describe the pleiotropic beneficial effects of a novel plant-derived nutritional supplement on metaflammation and metabolic homeostasis in obese mice. Altogether, this work may provide new leads for interventions aimed at improving immunological control of metabolic dysfunctions. Show less
Rios-Morales, M.; Vieira-Lara, M.A.; Homan, E.; Langelaar-Makkinje, M.; Gerding, A.; Li, Z.; ... ; Bakker, B.M. 2022
Skeletal muscle insulin resistance is a key pathophysiological process that precedes the development of type 2 diabetes. Whereas an overload of long-chain fatty acids can induce muscle insulin... Show moreSkeletal muscle insulin resistance is a key pathophysiological process that precedes the development of type 2 diabetes. Whereas an overload of long-chain fatty acids can induce muscle insulin resistance, butyrate, a short -chain fatty acid (SCFA) produced from dietary fibre fermentation, prevents it. This preventive role of butyrate has been attributed to histone deacetylase (HDAC)-mediated transcription regulation and activation of mito-chondrial fatty-acid oxidation. Here we address the interplay between butyrate and the long-chain fatty acid palmitate and investigate how transcription, signalling and metabolism are integrated to result in the butyrate -induced skeletal muscle metabolism remodelling. Butyrate enhanced insulin sensitivity in palmitate-treated, insulin-resistant C2C12 cells, as shown by elevated insulin receptor 1 (IRS1) and pAKT protein levels and Slc2a4 (GLUT4) mRNA, which led to a higher glycolytic capacity. Long-chain fatty-acid oxidation capacity and other functional respiration parameters were not affected. Butyrate did upregulate mitochondrial proteins involved in its own oxidation, as well as concentrations of butyrylcarnitine and hydroyxybutyrylcarnitine. By knocking down the gene encoding medium-chain 3-ketoacyl-CoA thiolase (MCKAT, Acaa2), butyrate oxidation was inhibited, which amplified the effects of the SCFA on insulin sensitivity and glycolysis. This response was associated with enhanced HDAC inhibition, based on histone 3 acetylation levels. Butyrate enhances insulin sensitivity and induces glycolysis, without the requirement of upregulated long-chain fatty acid oxidation. Butyrate catabolism functions as an escape valve that attenuates HDAC inhibition. Thus, inhibition of butyrate oxidation indirectly prevents insulin resistance and stimulates glycolytic flux in myotubes treated with butyrate, most likely via an HDAC-dependent mechanism. Show less
Background and aims: The separate cardiovascular effects of type 2 diabetes and adiposity remain to be examined. This study aimed to investigate the role of insulin resistance in the relations of... Show moreBackground and aims: The separate cardiovascular effects of type 2 diabetes and adiposity remain to be examined. This study aimed to investigate the role of insulin resistance in the relations of visceral (VAT), abdominal subcutaneous (aSAT) adipose tissue and total body fat (TBF) to cardiovascular remodeling.Methods and results: In this cross-sectional analysis of the population-based Netherlands Epidemiology of Obesity study, 914 middle-aged individuals (46% men) were included. Participants underwent magnetic resonance imaging. Standardized linear regression coefficients (95%CI) were calculated, adjusted for potential confounding factors. All fat depots and insulin resistance (HOMA-IR), separate from VAT and TBF, were associated with lower mitral early and late peak filling rate ratios (E/A): -0.04 (-0.09;0.01) per SD (54 cm(2)) VAT; -0.05 (-0.10;0.00) per SD (94 cm(2)) aSAT; -0.09 (-0.16;-0.02) per SD (8%) TBF; -0.11 (-0.17;-0.05) per 10-fold increase in HOMA-IR, whereas VAT and TBF were differently associated with left ventricular (LV) end-diastolic volume: -8.9 (-11.7;-6.1) mL per SD VAT; +5.4 (1.1;9.7) mL per SD TBF. After adding HOMA- IR to the model to evaluate the mediating role of insulin resistance, change in E/A was -0.02 (-0.07;0.04) per SD VAT; -0.03 (-0.08;0.02) per SD aSAT; -0.06 (- 0.13;0.01) per SD TBF, and change in LV end-diastolic volume was -7.0 (-9.7;-4.3) mL per SD VAT. In women, adiposity but not HOMA-IR was related to higher aortic arch pulse wave velocity.Conclusion: Insulin resistance was associated with reduced diastolic function, separately from VAT and TBF, and partly mediated the associations between adiposity depots and lower diastolic function. (C) 2020 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved. Show less
Heparanase is the predominant enzyme that cleaves heparan sulfate, the main polysaccharide in the extracellular matrix. While the role of heparanase in sustaining the pathology of autoimmune... Show moreHeparanase is the predominant enzyme that cleaves heparan sulfate, the main polysaccharide in the extracellular matrix. While the role of heparanase in sustaining the pathology of autoimmune diabetes is well documented, its association with metabolic syndrome/type 2 diabetes attracted less attention. Our research was undertaken to elucidate the significance of heparanase in impaired glucose metabolism in metabolic syndrome and early type 2 diabetes. Here, we report that heparanase exerts opposite effects in insulin-producing (i.e., islets) vs. insulin-target (i.e., skeletal muscle) compartments, sustaining or hampering proper regulation of glucose homeostasis depending on the site of action. We observed that the enzyme promotes macrophage infiltration into islets in a murine model of metabolic syndrome, and fosters beta-cell-damaging properties of macrophages activated in vitro by components of diabetogenic/obese milieu (i.e., fatty acids). On the other hand, in skeletal muscle (prototypic insulin-target tissue), heparanase is essential to ensure insulin sensitivity. Thus, despite a deleterious effect of heparanase on macrophage infiltration in islets, the enzyme appears to have beneficial role in glucose homeostasis in metabolic syndrome. The dichotomic action of the enzyme in the maintenance of glycemic control should be taken into account when considering heparanase-targeting strategies for the treatment of diabetes. Show less
Cardiovascular disease and diabetes are one of the leading causes of death worldwide. Multiple genetic and non-genetic factors play a role in this process. This dissertation aims to study the... Show moreCardiovascular disease and diabetes are one of the leading causes of death worldwide. Multiple genetic and non-genetic factors play a role in this process. This dissertation aims to study the interplay between genetic factors and lifestyle factors (eg sleep, nutrition, physical activity) with diseases such as cardiovascular disease and risk factors for cardiovascular disease (diabetes). For example, 12 blood biomarkers associated with insulin resistance have been identified, 5 of which are specifically much higher in subjects with diabetes. In addition, it appeared that a short sleep duration and poor sleep quality are associated with poorer lipids in the blood (eg cholesterol and LDL) and more insulin resistance. With regard to sleep, 59 new genetic variants have also been identified with regard to blood lipids (HDL, LDL, triglycerides). In addition, the results indicate that a better lifestyle can also help reduce the development of new cardiovascular diseases in people with an increased genetic risk. This is particularly interesting to prevent diseases in persons at high risk. All in all, this thesis has provided new insights into the various factors that are potentially important in the development of cardiovascular disease and diabetes. Show less
Background: South Asians generally have an unfavourable metabolic phenotype compared with white Caucasians, including central obesity and insulin resistance. The Wnt protein family interacts with... Show moreBackground: South Asians generally have an unfavourable metabolic phenotype compared with white Caucasians, including central obesity and insulin resistance. The Wnt protein family interacts with insulin signaling, and impaired Wnt signaling is associated with adiposity and type 2 diabetes mellitus. We aimed to investigate Wnt signaling in relation to insulin signaling in South Asians compared with white Caucasians.Methods: Ten Dutch South Asian men with prediabetes and overweight or obesity and 10 matched Dutch white Caucasians were included. Blood samples were assayed for the Wnt inhibitor sclerostin. Subcutaneous white adipose tissue (WAT) and skeletal muscle biopsies were assayed for Wnt and insulin signaling gene expression with quantitative reverse transcription polymerase chain reaction (Clinicaltrials.gov NCT02291458).Results: Plasma sclerostin was markedly higher in South Asians compared with white Caucasians (+65%, P < 0.01). Additionally, expression of multiple Wnt signaling genes and key insulin signaling genes were lower in WAT in South Asians compared with white Caucasians. Moreover, in WAT in both ethnicities, Wnt signaling gene expression strongly positively correlated with insulin signaling gene expression. In skeletal muscle, WNT10B expression in South Asians was lower, but expression of other Wnt signaling and insulin signaling genes was comparable between ethnicities. Wnt and insulin signaling gene expression also positively correlated in skeletal muscle, albeit less pronounced.Conclusion: South Asian men with overweight or obesity and prediabetes have higher plasma sclerostin and lower Wnt signaling gene expression in WAT compared with white Caucasians. We interpret that reduced Wnt signaling could contribute to impaired insulin signaling in South Asians. Show less
Metabolic disease has become pandemic in the developed world. Given our lack of understanding of its molecular pathology, we are often unable to diagnose patients before they reach an... Show moreMetabolic disease has become pandemic in the developed world. Given our lack of understanding of its molecular pathology, we are often unable to diagnose patients before they reach an irreversible state of diabetes or cardiovascular disease. Much research has been done on the role of insulin signaling in metabolic disease, as well as the resultant disturbed lipid homeostasis present in cardiovascular disease and atherosclerosis. Here we add to existing work by developing new tools and sketching out the pathology of dysregulated adipose insulin signaling. We discuss the mechanism of lipodystrophy by using adipocytes differentiated from patient-derived iPSCs. These cells mimic the clinical phenotype and hint at mechanism that reduced patients’ adipose tissue mass. In mice we find that if we knock out the adipose insulin receptor, there is disrupted adipose and liver metabolism. There is a protection from diet-induced obesity, but a dramatically reduced lifespan. We also establish a relationship between obesity and inflammation by transcriptomically assessing obese human adipocytes. We find that an immune factor is responsible for lipid droplet formation and content. Lastly, we develop a new differentiation and purification strategy for iPSC-derived hepatocytes, which we employ to in vitro model a SNP that protects against cardiovascular disease. Show less
The worldwide prevalence of obesity is steadily increasing. Obesity leads to insulin resistance and atherosclerosis, which are the pathologies underlying type 2 diabetes and cardiovascular disease,... Show moreThe worldwide prevalence of obesity is steadily increasing. Obesity leads to insulin resistance and atherosclerosis, which are the pathologies underlying type 2 diabetes and cardiovascular disease, respectively. Inflammation is an important factor connecting obesity to these disorders, but the exact mechanisms connecting obesity, the immune system, type 2 diabetes and cardiovascular disease are still under investigation. The research described in this thesis was performed 1) to gain more insight into the role of the immune system in obesity, dyslipidemia, insulin resistance and atherosclerosis, 2) to study whether inflammation contributes to the disadvantageous metabolic phenotype of a human population with a particularly high risk to develop type 2 diabetes and cardiovascular disease, and 3) to study the therapeutic potential of decreasing inflammation by pharmacological strategies to reduce obesity and improve glucose and lipid metabolism in pre-clinical models. The studies described in this thesis have increased our understanding of the role of inflammation in adipose tissue function and lipid metabolism during the development of type 2 diabetes and cardiovascular disease. Moreover, novel potential therapeutic strategies were identified to combat obesity, metabolic inflammation and associated metabolic disorders, such as treatment with interferons, salsalate and GPR120 agonists. Show less
The main objective of this thesis is to improve understanding of the role of helminth infections in the development of insulin resistance (IR), hence Type 2 Diabetes (T2D), in the light of... Show moreThe main objective of this thesis is to improve understanding of the role of helminth infections in the development of insulin resistance (IR), hence Type 2 Diabetes (T2D), in the light of increasing urbanization in Indonesia. Our large-scale cluster-randomized controlled trial was performed in a rural area of Indonesia, which is endemic for soil-transmitted helminth (STH), and has been previously reported to have a low prevalence of IR and T2D. In STH-infected subjects, as assessed by microscopy, 12-month anthelmintic treatment increased IR, which was mediated by an increase in BMI and leptin to adiponectin ratio, as well as reduction in eosinophil count. Next, we also aimed to assess the different metabolic profile between populations living in rural and urban area, and to study the relative protective effect of rural environment to high-fat diet (HFD). In comparison to those living in rural area, individuals living in urban area had higher whole body IR, which was mainly mediated by the higher adiposity and leptin level, which were progressively increased with increased duration of time spent in urban area. Different environmental factors (including past or current exposure to STH) did not seem to affect the metabolic response to HFD intervention, independent from adiposity. Show less
As the obesity epidemic is still increasing, strategies to prevent and treat obesity and related pathologies are in great demand. Obesity-induced inflammation is thought to contribute to the... Show moreAs the obesity epidemic is still increasing, strategies to prevent and treat obesity and related pathologies are in great demand. Obesity-induced inflammation is thought to contribute to the development of metabolic disorders. Therefore, inflammatory pathways that play a role in obesity-induced inflammation are potential promising targets in the treatment of metabolic disorders. Extensive knowledge on obesity-induced inflammation and the role of inflammatory pathways in the development of metabolic disorders can benefit the development of these therapeutic strategies. Mouse models are widely used to study obesity and related disorders, however, to what extent mouse-derived results translate to humans has not been studied extensively yet. Obesity-induced inflammation and its role in the development of insulin resistance, as well as the similarities of these processes between humans and mice, have been addressed in this thesis. The new findings described in this thesis will be summarized and discussed in the final chapter. Additionally, clinical implications of obesity-induced inflammation as target to treat metabolic disorders and future perspectives will be addressed. Show less
Non-alcoholic fatty liver disease (NAFLD) has rapidly become the most common cause of chronic liver disease, and its worldwide prevalence continues to increase in parallel of the obesity epidemic.... Show moreNon-alcoholic fatty liver disease (NAFLD) has rapidly become the most common cause of chronic liver disease, and its worldwide prevalence continues to increase in parallel of the obesity epidemic. NAFLD comprises a wide spectrum of liver damage ranging fat accumulation (steatosis) to steatosis with inflammation (non-alcoholic steatohepatitis, NASH), which can further progress to fibrosis. In particular patients with NASH have increased risk to develop other metabolic complications, such as cardiovascular disease.NAFLD is a complex disease, in which the origin and molecular mechanisms controlling the progression of simple steatosis to NASH remain poorly understood. Nevertheless, it is thought that inflammation is a critical component of NAFLD progression. This inflammation may be triggered by metabolic surplus (excess of energy or nutrients) and is also referred to as “metabolic inflammation”. White adipose tissue (WAT) is assumed to be largely involved in the development of metabolic inflammation. The studies described in this thesis contributed to the understanding of the role of WAT in the development of NAFLD and provide insight into the molecular processes that cause metabolic inflammation. Show less
Prevalence of childhood obesity is increasing. Insulin resistance is a consequence of childhood obesity, and it has a keyrole in the development of cardiometabolic complications, such as... Show more Prevalence of childhood obesity is increasing. Insulin resistance is a consequence of childhood obesity, and it has a keyrole in the development of cardiometabolic complications, such as diabetes mellitus. In the first part of this thesis, the epidemiology of insulin resistance has been described. Since there is no clear definition for insulin resistance, the prevalence of IR remains unclear. In addition, the use of IR in the screening for diabetes mellitus in obese children was evaluated. In the second part of the thesis, treatment of obese children with insulin resistance is discussed. In a randomized controlled trial of 18 months, children were treated with either metformin or placebo in addition to lifestyle intervention. Body mass index in children treated with metformin remained stable during the 18 months, whereas placebo-treated children had an increase in body mass index. Finally, the treatment with metformin under the strict circumstances of the clinical trial was compared to treatment with metformin in daily practice during 18 months. Both groups showed similar results regarding body mass index during metformin treatment. Show less
The main objective of this thesis was to unravel relationships between obesity, insulin resistance, hyperglycemia, and atherosclerosis. It is well-established that patients with type 2... Show more The main objective of this thesis was to unravel relationships between obesity, insulin resistance, hyperglycemia, and atherosclerosis. It is well-established that patients with type 2 diabetes have a 2- to 3-fold increased risk of cardiovascular disease. We investigated whether insulin resistance and hyperglycemia are associated with atherosclerosis and incident cardiovascular disease before the onset of type 2 diabetes. Obesity can be considered as a common cause of both insulin resistance and atherosclerosis. Therefore, we investigated to what extent associations between insulin resistance, hyperglycemia and atherosclerosis were explained by body fat. We further aimed to study the specific role of visceral fat in the development of insulin resistance and atherosclerosis, and directly assessed abdominal subcutaneous and visceral adipose tissue depots. Show less
In today__s world, more people die from complications of overweight than from underweight. But not all individuals are equally prone to develop metabolic complications, such as obesity and insulin... Show moreIn today__s world, more people die from complications of overweight than from underweight. But not all individuals are equally prone to develop metabolic complications, such as obesity and insulin resistance. This thesis focuses on the differences in the energy and fatty acid metabolism that play a role in the susceptibility for metabolic complications. We have investigated certain existing associations between genetic clues and a disturbed energy metabolism, in order to construct a more refined mechanism of action for this genetic association. This knowledge could be used to more precisely target the causal proteins and pathways involved in the development of obesity. We have also investigated the role of fatty acid metabolism in the fat tissue of obese humans and mice. In this way, we have found a direct link in both humans and mice between fatty acids and inflammation, which is relevant for metabolic diseases such as obesity and insulin resistance. Show less
Nearly one quarter of the world__s population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T... Show moreNearly one quarter of the world__s population is infected with helminth parasites. A common feature of helminth infections is the manifestation of a type 2 immune response, characterized by T helper 2 (Th2) cells. In addition to their involvement in anti-helminth immunity, recent studies have shown that components of the type 2 immune responses can have additional functions. For example, recent evidence indicates that multiple facets of the type 2 immune response can regulate tissue-specific metabolic processes and whole-body nutrient homeostasis, and protect against insulin resistance. In this work we use omega-1, a glycosylated RNase excreted from Schistsoma mansoni eggs with strong Th2-inducing capacities, to study the requirements that equip DCs for Th2 skewing. In addition, we analyse the effect of chronic S. mansoni infection and administration of S. mansoni-derived egg antigens on metabolic homeostasis in diet-induced obese mice. Elucidating how helminths generate Th2 responses and contribute to metabolic homeostasis will not only shed light on the mechanisms that promote control of parasite infection, but may provide valuable leads for the development of pharmaceutical agents for the treatment of metabolic disorders. Show less
Overload of nutrients can lead to diet-induced inflammation, also called metabolic inflammation, which is thought to play an important role in many metabolic diseases, including the development of... Show moreOverload of nutrients can lead to diet-induced inflammation, also called metabolic inflammation, which is thought to play an important role in many metabolic diseases, including the development of nonalcoholic fatty liver disease (NAFLD). NAFLD encompasses a spectrum of pathologies that range from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH) and fibrosis. The pathogenesis of NAFLD, including the sequence of events in time and the underlying mechanisms that initiate the transition from a fatty liver to NASH and fibrosis, remain poorly understood. Effective and reliable therapeutic approaches that are based on the understanding of the pathogenesis of NASH are therefore still lacking. In order to gain more insight into the mechanisms of NASH pathogenesis, we started with comparison of human NASH and experimental NASH. Subsequently, we provided evidence that activation of AP-1 and associated neutrophil infiltration is important for NAFL progression towards NASH and this can be induced experimentally by __metabolic__ dietary triggers of inflammation.Furthermore, we explored novel nutritional and pharmacological agents as potential strategies to combat NASH. Finally, we investigated the effects of high fat diet-induced metabolic overload on the liver in relation to inflammation in white adipose tissue and kidney, and the dysfunction of these tissues. Show less
Insulin-producing pancreatic _-cells are essential to maintain blood glucose levels within a narrow range. _-cells can adapt to an increased insulin demand by enhancing insulin secretion via... Show moreInsulin-producing pancreatic _-cells are essential to maintain blood glucose levels within a narrow range. _-cells can adapt to an increased insulin demand by enhancing insulin secretion via increased _-cell function and/or increased _-cell mass. Inadequate _-cell adaptation leads to hyperglycemia and eventually diabetes mellitus. Therefore, it is critical to understand how the _-cell mass is regulated. We investigated _- and _-cell adaptation in response to different metabolic changes. We found that _-cell adaptation in response to insulin resistance in mice, rats, and deceased organ donors was regionally heterogeneous throughout the pancreas. We also observed that the glucagon-producing _-cell mass adapts to metabolic changes, resulting in the maintenance of the _- to _-cell ratio. Furthermore, we show that treatment of normoglycemic mice with a glucagon-like-peptide-1 receptor agonist improved _-cell function and that this is associated with a decrease in _-cell mass in order to maintain normoglycemia. In mice fed a high-fat, low-carbohydrate ketogenic diet beta-cell adaptation failed, resulting in symptoms that are associated with diabetes in humans. Finally, we developed three high-throughput culture platforms for human islets to assess _-cell function that can be used in future studies to identify novel mechanisms involved in _- and _-cell adaptation. Show less
Tahapary, D.L.; Ruiter, K. de; Martin, I.; Lieshout, L. van; Guigas, B.; Soewondo, P.; ... ; Supali, T. 2015
People of South Asian origin have an increased risk of developing type 2 diabetes (T2D) and cardiovascular disease (CVD) compared to people of Western European descent. Not only is the prevalence... Show morePeople of South Asian origin have an increased risk of developing type 2 diabetes (T2D) and cardiovascular disease (CVD) compared to people of Western European descent. Not only is the prevalence of these diseases higher in South Asians, they also occur at a younger age and lower BMI, and have a more severe course. The high prevalence of T2D and CVD in South Asians, who comprise one fifth of the total world__s population, poses a major health and socioeconomic burden worldwide. The underlying cause of this excess risk is, however, still poorly understood. The studies described in this thesis were performed to gain more insight in the pathogenesis of T2D and CVD in South Asians and to provide new leads for preventive strategies and treatment options. For this purpose sophisticated techniques were used such as hyperinsulinemic-euglycemic clamp with stable isotopes, indirect calorimetry, skeletal muscle biopsies, MRI and spectroscopy, and brown fat quantification using PET-CT-imaging, combined with short-term dietary interventions, in healthy lean young adult men and overweight adult men. These studies have led to a number of promising areas for further research. It seems that not one, but multiple metabolic mechanisms have been affected, most likely due to gene-environment interactions. Show less
