Meta-inflammation and endotoxemia in a highly translational porcine model of diet-induced obesity

Abstract

Meta-inflammation (chronic, low-grade systemic inflammation) is increasingly recognized as an essential link between obesity and the development of various noncommunicable diseases. However, large animal models for studying obesity-related meta-inflammation are lacking. Minipigs have great potential as models for human diseases, warranting investigation of the performance of the Göttingen minipig as a model for obesity-associated meta-inflammation. Here, we fed 26 pigs a high-fat, fructose and cholesterol diet (HFFC) or a standard diet (SD) for 103 days, resulting in the HFFC group having a 45% higher body weight and 16% larger abdominal circumference by the end of the experiment. Meta-inflammation was shown in the HFFC group by elevated serum concentrations of the acute phase protein C-reactive protein for more than 60 days during development of obesity, accompanied by increased numbers of circulating neutrophils and monocytes. Additional obesity-related abnormalities included dyslipidemia, hepatosteatosis and transcriptional changes to genes related to inflammation and metabolism in circulating leukocytes, liver and visceral adipose tissue. Notably, the transcription of genes related to lipid metabolism, namely ATP-binding cassette subfamily A member 1 (ABCA1) and ATP-binding cassette subfamily G member 1 (ABCG1), was elevated in liver, visceral adipose tissue and circulating leukocytes (ABCA1 only) in the HFFC group compared with the SD group. The development of obesity was accompanied by endotoxemia, indicated by a 2.5-fold increase in serum lipopolysaccharide concentration in the HFFC group compared with the SD group, suggesting increased intestinal permeability. In conclusion, the described Göttingen minipig model convincingly links diet-induced obesity, meta-inflammation and endotoxemia, achieved by short-duration HFFC dieting.

Fig. 1. Experimental setup.

Twenty-six Göttingen minipigs were divided into two equal groups and fed either the HFFC diet (n = 13) or the SD diet (n = 13) for 103 days. Blood samples were collected from all animals throughout the study. CRP concentrations were quantified on days 0, 20, 41, 62, 83 and 98. Lipid concentrations were quantified on days 0, 62, 83 and 98. White blood cell counts were performed on days 0 and 98. LPS concentrations were quantified on day 99. Gene expression in circulating leukocytes was quantified on days 0, 20, 41, 62, 83 and 98. Gene expression in liver tissue and VAT was quantified in four randomly selected pigs from each diet group on day 103. Created in BioRender. Henriksen, B. (2025) https://BioRender.com/25rsuz8.

Fig. 2. The HFFC diet induces an increase in BW and ABC in Göttingen minipigs.

From day 49 of the study, significantly increased BWs (left y axis) and ABC (right y axis) were observed in the HFFC group compared with the SD group. Statistical significance of differences between the HFFC (n = 13) and SD (n = 13) groups was determined with Welch’s t-test and Benjamini–Hochberg corrections (*P < 0.05, **P < 0.01, ***P < 0.001). Error bars show the s.e.m.

Fig. 3. The HFFC diet is associated with increased CRP serum concentrations in Göttingen minipigs.

Statistical significance of differences between the HFFC (n = 13) and SD (n = 13) groups was determined with Welch’s t-test and Benjamini–Hochberg corrections (**P < 0.01, ***P < 0.001). The bars and error bars represent the mean and s.e.m.

Fig. 4. The HFFC diet induces changes to circulating leukocytes and leads to endotoxemia and dyslipidemia.

a, Circulating neutrophil counts. b, Circulating monocyte counts. c, Serum LPS concentration (in endotoxin units (EU)) on day 99 after initiation of diet regimes. d, Circulating triglyceride concentrations. e, Circulating total cholesterol concentration. f, Circulating LDL concentrations. g, Circulating HDL concentrations. Statistical significance of differences between cell counts and lipid concentrations in the HFFC (n = 13) and SD (n = 13) group was determined using Welch’s t-test with Benjamini–Hochberg corrections applied for multiple testing (**P < 0.01, ***P < 0.001). Bars and error bars show the mean and s.e.m.

Fig. 5. The HFFC diet induces changes in gene expression in circulating leukocytes throughout the dieting period.

The expression of each gene is scaled to the expression level in the SD group on day 0. Statistical significance of differences between the HFFC (n = 13) and SD (n = 13) groups at individual time points was determined with Welch’s t-test and Benjamini–Hochberg corrections (*P < 0.05, **P < 0.01, ***P < 0.001). Bars and error bars show the mean and s.e.m.

Fig. 6. Macroscopic and microscopic changes observed in livers of HFFC-fed pigs.

a, Livers from pigs in the HFFC group displayed steatosis (right), while livers from pigs in the SD group were normal (left). Histopathological examination was performed on pigs from both the HFFC (n = 4) and SD (n = 4) groups. b, Histological analysis of the liver from an SD-fed pig. Arrowheads, sinusoidal space; star, central vein; arrow, portal arteriole. c, Liver from HFFC-fed pig. Arrowheads, microvesicular lipids; star, central vein; arrow, portal arteriole. d, Liver from HFFC-fed pig. Arrowheads, large lipid vacuoles; star, central vein; arrow: portal arteriole. Scale bars, 200 µm (b–d).