Introduction
The aging with weight gain induces pathological changes in the liver, exacerbating non-alcoholic fatty liver disease (NAFLD). In the reproductive age, NAFLD is more prevalent and severe in males, however, NAFLD occurs at a higher rate among postmenopausal females. The liver and small bowel are closely interrelated through enterohepatic circulation, such that damage to the small bowel can significantly impact hepatic function. In small intestine, the expression of tight junction protein (TJP) in nearly associated with the development of NAFLD. The aim of this study was to investigate the effects of age and sex on hepatic steatosis and the small bowel under conditions of a high fructose, high-fat diet (HFHFD) in rats.
Aims & Methods
6-week-old male and female F344 rats divided into control and HFHFD groups, along with 2-year-old F344 rats. Over an 8-week period, the high fat diet (Raonbio, 60 kcal% fat) provided twice weekly and high fructose water (20%) gave once weekly for HFHFD groups. After 8 weeks, all animals were sacrificed, and both liver and small intestinal tissue were collected. All tissue samples were subjected to hematoxylin and eosin staining for histological analysis. RNA extraction from the jejunum mucosa was followed by qRT-PCR analysis to assess claudin-2 (cldn-2, one of TJP) gene expression.
Results
The body weight change (%) and the hepatic steatosis scores were significantly higher in the HFHFD groups compared to both male and female control groups (Table). Histological scores of old rat HFHFD groups were significantly higher than those of 6 week HFHFD groups, regardless of sex (Table). In terms of histological inflammation scores of old control group small bowel were higher than those of 6 week control group regardless of sex (Table). The jejunum villus/crypt ratio of 6-week-old rats significantly decreased only among males (Table). In contrast, in the 2-year-old groups, the villus/crypt ratio resulted in a reduction only among females and the mRNA expression of cldn-2 observed in females with significant elevation (Table).
|
| Weight | Steatosis score | Inflammation score | Jejunum villus/crypt length ratio | Cldn-2 mRNA expression |
| Duodenum | Jejunum | Ileum |
| Male | 6-week Con vs. 6-week HFHFD | increase
(p = 0.006) | increase
(p = 0.003)
| increase
(p = 0.072)
| increase
(p = 0.026)
| increase
(p = 0.049)
| decrease
(p = 0.072)
| - |
| 2-year Con vs. 2-year HFHFD | increase
(p = 0.006)
| increase
(p = 0.002)
| - | increase
(p = 0.015)
| - | - | - |
| 6-week Con vs. 2-year Con | - | - | increase
(p = 0.005)
| - | increase
(p = 0.022)
| - | - |
| 6-week HFHFD vs. 2-year HFHFD | - | increase
(p = 0.007)
| - | - | - | - | - |
| Female | 6-week Con vs. 6-week HFHFD
| increase
(p = 0.004)
| increase
(p = 0.002)
| - | increase
(p = 0.007)
| increase
(p = 0.104)
| - | increase
(p = 0.056)
|
2-year Con vs. 2-year HFHFD
| increase
(p = 0.004)
| increase
(p = 0.002)
| - | - | - | decrease
(p = 0.076)
| increase
(p = 0.005)
|
6-week Con vs. 2-year Con
| - | - | increase
(p = 0.007)
| increase
(p = 0.002)
| increase
(p = 0.002)
| - | - |
6-week HFHFD vs. 2-year HFHFD
| - | increase
(p = 0.011)
| - | - | - | - | - |
Con, control; HFHFD, high fructose high fat diet; Cldn-2, Claudin-2; vs., versus
Conclusion
Our data showed that high fructose, high-fat diet induced hepatic steatosis and inflammation of small bowel, especially in old rats. This indicates that NAFLD is related with damage of small bowel brush border membrane. The upregulated gene expression of cldn-2 (p = 0.005) and the decreased tendency of jejunum villus/crypt ratio (p = 0.076) in the aged females rats suggests a potential role of TJP in advancing NAFLD in postmenopausal females.
References
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