👤 Erika Tarasco

The incidence of obesity and metabolic syndrome (MetS) has rapidly increased worldwide. Roux-en-Y gastric bypass (RYGB) achieves long-term weight loss and improves MetS-associated comorbidities. Using a mouse model with a humanized lipoprotein metabolism, we elucidated whether improvements in lipid and glucose metabolism after RYGB surgery are body weight loss-dependent or not. Male ApoE*3Leiden.CETP (ApoE3L.CETP) mice fed Western type diet for 6 weeks underwent RYGB or Sham surgery. Sham groups were either fed ad libitum or were body weight-matched (BWm) to the RYGB mice to discriminate surgical effects from body weight loss-associated effects. Before and after surgery, plasma was collected to assess the metabolic profile, and glucose tolerance and insulin sensitivity were tested. Twenty days after surgery, mice were sacrificed, and liver was collected to assess metabolic, histological and global gene expression changes after surgery. RYGB induced a marked reduction in body weight, which was also achieved by severe food restriction in BWm mice, and total fat mass compared to Sham ad libitum mice (Sham AL). Total cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C) and ceramide were strongly reduced 20 days after surgery in RYGB compared to BWm mice. Glucose tolerance and insulin sensitivity improved 13 days after surgery similarly in RYGB and BWm mice. Liver histology confirmed lipid reduction in RYGB and BWm mice while the transcriptomics data indicated altered genes expression in lipid metabolism. RYGB surgery improves glucose metabolism and greatly ameliorates lipid metabolism in part in a body weight-dependent manner. Given that ApoE3L.CETP mice were extensively studied to describe the MetS, and given that RYGB improved ceramide after surgery, our data confirmed the usefulness of ApoE3L.CETP mice after RYGB in deciphering the metabolic improvements to treat the MetS. Show less

Long-term exposure to excess dietary fat leads to obesity and the metabolic syndrome (MetS). The purpose of the present study was to identify global changes in liver gene expression and circulating miRNAs in a humanized mouse model of diet-induced MetS. Male apoE3L.CETP mice received a high-fat diet (HFD) or a low-fat diet (LFD) for different time periods and the progression of MetS pathology was monitored. A separate group of mice was divided into responders (R) or nonresponders (NR) and received HFD for 16 weeks. We found that mice receiving the HFD developed manifestations of MetS and displayed an increasing number of differentially expressed transcripts at 4, 8, and 12 weeks compared with mice receiving the LFD. Significantly changed genes were functionally annotated to metabolic diseases and pathway analysis revealed the downregulation of genes in cholesterol and fatty acid biosynthesis and upregulation of genes related to lipid droplet formation, which was in line with the development of hepatic steatosis. In the serum of the apoE3L.CETP mice we identified three miRNAs that were upregulated specifically in the HFD group. We found that responder mice have a distinct gene signature that differentiates them from nonresponders. Comparison of the two diet intervention studies revealed a limited number of common differentially expressed genes but the expression of these common genes was affected in a similar way in both studies. In conclusion, the characteristic hepatic gene signatures and serum miRNAs identified in the present study provide novel insights to MetS pathology and could be exploited for diagnostic or therapeutic purposes. Show less

The metabolic syndrome (MetS) is a major health issue worldwide and is associated with obesity, insulin resistance, and hypercholesterolemia. Several animal models were used to describe the MetS; however, many of them do not mimic well the MetS pathophysiology in humans. The ApoE*3Leiden.CETP mouse model overcomes part of this limitation, since they have a humanised lipoprotein metabolism and a heterogeneous response to MetS, similar to humans. The reported heterogeneity among them and their common classification refer to responder (R) and nonresponder (NR) mice; R mice show increased body weight, cholesterol, and triglycerides levels, whereas NR mice do not show this expected phenotype when fed a Western type diet. To define better the differences between R and NR mice, we focused on feeding behavior, body weight gain, glucose tolerance, and lipid parameters, and on an extensive pathological examination along with liver histology analysis. Our data confirmed that R mice resemble the pathological features of the human MetS: obesity, dysplipidemia, and glucose intolerance. NR mice do not develop the full dysmetabolic phenotype because of a severe inflammatory hepatic condition, which may heavily affect liver function. We conclude that R and NR mice are metabolically different and that NR mice have indications of severely impaired liver function. Hence, it is critical to identify and separate the respective mice to decrease data heterogeneity. Clinical chemistry and histological analysis should be used to confirm retrospectively the animals' classification. Moreover, we point out that NR mice may not be an appropriate control for studies involving ApoE*3Leiden.CETP R mice. NEW & NOTEWORTHY When compared with some other animal models, ApoE*3Leiden.CETP mice are better models to describe the metabolic syndrome. However, there is phenotypic heterogeneity between "responder" and "nonresponder" mice, the latter showing some evidence of hepatic pathology. A full phenotypic characterization and eventually postmortem analysis of the liver are warranted. Show less