Systemic and vascular inflammation in an in-vitro model of central obesity.

Metabolic disorders due to over-nutrition are a major global health problem, often associated with obesity and related morbidities. Obesity is peculiar to humans, as it is associated with lifestyle and diet, and so difficult to reproduce in animal models. Here we describe a model of human central adiposity based on a 3-tissue system consisting of a series of interconnected fluidic modules. Given the causal link between obesity and systemic inflammation, we focused primarily on pro-inflammatory markers, examining the similarities and differences between the 3-tissue model and evidence from human studies in the literature. When challenged with high levels of adiposity, the in-vitro system manifests cardiovascular stress through expression of E-selectin and von Willebrand factor as well as systemic inflammation (expressing IL-6 and MCP-1) as observed in humans. Interestingly, most of the responses are dependent on the synergic interaction between adiposity and the presence of multiple tissue types. The set-up has the potential to reduce animal experiments in obesity research and may help unravel specific cellular mechanisms which underlie tissue response to nutritional overload.

Acute Effects of Linagliptin on Progenitor Cells, Monocyte Phenotypes, and Soluble Mediators in Type 2 Diabetes.

CONTEXT: Circulating cells, including endothelial progenitor cells (EPCs) and monocyte subtypes, are involved in diabetic complications. Modulation of these cells may mediate additional benefits of glucose-lowering medications. OBJECTIVE: We assessed whether the dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin acutely modifies EPCs and monocyte subsets in patients with type 2 diabetes. DESIGN: This was a randomized, crossover, placebo-controlled trial. SETTING: The study was conducted at a tertiary referral diabetes outpatient clinic. PATIENTS: Forty-six type 2 diabetes patients with (n = 18) or without (n = 28) chronic kidney disease (CKD) participated in the study. INTERVENTION: Intervention included a 4-day treatment with linagliptin 5 mg or placebo during two arms separated by a 2-week washout. MAIN OUTCOME MEASURES: Before and after each treatment, we determined the levels of circulating progenitor cells (CD34, CD133, KDR) and monocyte subtypes (CD14/CD16, chemokine and scavenger receptors) and the concentrations of soluble mediators. RESULTS: Compared with placebo, linagliptin increased CD34(+)CD133(+) progenitor cells (placebo subtracted effect 40.4 ± 18.7/10(6); P = .036), CD34(+)KDR(+) EPCs (placebo subtracted effect 22.1 ± 10.2/10(6); P = .036), and CX3CR1(bright) monocytes (placebo subtracted effect 1.7 ± 0.8%; P = .032). Linagliptin abated DPP-4 activity by greater than 50%, significantly increased active glucagon-like peptide-1 and stromal cell-derived factor-1α, and reduced monocyte chemotactic protein-1, CCL22, and IL-12. Patients with CKD, as compared with those without, had lower baseline CD133(+) and CD34(+)CD133(+) cells and had borderline reduced CD34(+) and CD34(+)KDR(+) cells. The effects of linagliptin on progenitor cells and monocyte subtypes were similar in patients with or without CKD. Fasting plasma glucose, triglycerides and free fatty acids were unaffected. CONCLUSIONS: DPP-4 inhibition with linagliptin acutely increases putative vasculoregenerative and antiinflammatory cells. Direct effects of DPP-4 inhibition may be important to lower vascular risk in diabetes, especially in the presence of CKD.

Circulating Stem Cells Associate With Adiposity and Future Metabolic Deterioration in Healthy Subjects.

CONTEXT: Obesity and metabolic syndrome are associated with mild leukocytosis, but whether hematopoietic stem/progenitor cells (HSPCs) play a role in metabolic deterioration is unknown. OBJECTIVE: Our objective was to analyze the cross-sectional and longitudinal associations between CD34(+) HSPCs, adiposity, and metabolic syndrome features. DESIGN: This is a cross-sectional study on 242 participants, 155 of whom were followed and included in a longitudinal assessment. SETTING: This study took place in a tertiary referral center for metabolic diseases. PARTICIPANTS: Healthy working individuals attending a cardiovascular screening program (total n = 3158) and having a baseline measure of circulating CD34(+) cells participated. MAIN OUTCOME MEASURES: We collected demographic and anthropometric data, cardiovascular risk factors, and metabolic syndrome parameters. RESULTS: Participants (34.7% males, mean age 45.9 ± 0.5 years) were free from diabetes and cardiovascular disease. Cross-sectionally, absolute CD34(+) cell counts were directly correlated with body mass index and waist circumference, inversely correlated with high-density lipoprotein cholesterol and the quantitative insulin sensitivity check index, and were higher in individuals with the metabolic syndrome. The hematopoietic component contributed most to the association of CD34(+) cells with adiposity. During a 6.3-year follow-up, high absolute levels of CD34(+) cells were associated with increasing waist circumference, declining quantitative insulin sensitivity check index and high-density lipoprotein cholesterol, and with incidence of metabolic syndrome. Relative CD34(+) cell counts showed weaker associations with metabolic parameters than absolute levels, but were longitudinally associated with increasing waist circumference and metabolic syndrome development. CONCLUSIONS: A mild elevation of circulating CD34(+) progenitor cells, reflecting expansion of HSPCs, is associated with adiposity and future metabolic deterioration in healthy individuals.

Glucose and fatty acid metabolism in a 3 tissue in-vitro model challenged with normo- and hyperglycaemia.

Nutrient balance in the human body is maintained through systemic signaling between different cells and tissues. Breaking down this circuitry to its most basic elements and reconstructing the metabolic network in-vitro provides a systematic method to gain a better understanding of how cross-talk between the organs contributes to the whole body metabolic profile and of the specific role of each different cell type. To this end, a 3-way connected culture of hepatocytes, adipose tissue and endothelial cells representing a simplified model of energetic substrate metabolism in the visceral region was developed. The 3-way culture was shown to maintain glucose and fatty acid homeostasis in-vitro. Subsequently it was challenged with insulin and high glucose concentrations to simulate hyperglycaemia. The aim was to study the capacity of the 3-way culture to maintain or restore normal circulating glucose concentrations in response to insulin and to investigate the effects these conditions on other metabolites involved in glucose and lipid metabolism. The results show that the system's metabolic profile changes dramatically in the presence of high concentrations of glucose, and that these changes are modulated by the presence of insulin. Furthermore, we observed an increase in E-selectin levels in hyperglycaemic conditions and increased IL-6 concentrations in insulin-free-hyperglycaemic conditions, indicating, respectively, endothelial injury and proinflammatory stress in the challenged 3-way system.

An in vitro model of glucose and lipid metabolism in a multicompartmental bioreactor.

The energy balance in vivo is maintained through inter-organ cross-talk involving several different tissues. As a first step towards recapitulating the metabolic circuitry, hepatocytes, endothelial cells and adipose tissue were connected in a multicompartmental modular bioreactor to reproduce salient aspects of glucose and lipid metabolism in vitro. We first examined how the two-way cellular interplay between adipose tissue and endothelial cells affects glucose and lipid metabolism. The hepatocyte cell line HepG2 was then added to the system, creating a three-way connected culture, to determine whether circulating metabolite concentrations were normalized, or whether metabolic shifts, which may arise when endothelial cells and adipose tissue are placed in connection, were corrected. The addition of hepatocytes to the system prevented the drop in the concentrations of glucose, L-alanine and lactate, and the rise in that of free fatty acids. There was no significant change in glycerol levels in either of the connected cultures. The results show that connected cultures recapitulate complex physiological systemic processes, such as glucose and lipid metabolism, and that the HepG2 hepatocytes normalize circulating metabolites in this in vitro environment in the presence of other cell types.