(P04-029-25) Inulin Increases Lean Mass and Improves HOMA-IR in Mice Fed Standard AIN93 Diet but Not in High Fat Diets

Objectives: The objective of this study was to investigate whether fiber type altered the obesogenic effects of a high fat diet on body weight and glucose homeostasis. Our hypothesis was that inulin mitigates the obesogenic effects of high fat diets (46% energy, HF) and improves glucose homeostasis by reducing hepatic lipid content and altering the transcription of genes associated with fat metabolism in mice fed a high fat diet.

Methods: Inulin (IN) is a water soluble, fermentable fiber that is used in many foods and supplements as a prebiotic. To investigate whether the obesogenic effects of a HF were moderated by IN we employed a 2 X 2 design in which 14 male mice in each group were provided either a HF or a AIN93 diet (16% energy, NF) with either 10% of diet by weight as cellulose (CE) or 7% of diet by weight as inulin and 3% cellulose (IN) for 12 weeks.

Results: The HF increased body weight and adiposity equally in both HFCE and HFIN groups. Body weight was similar in NFCE and NFIN groups, but body fat mass was elevated after 12 weeks in the NFCE compared to NFIN. Lean mass correspondingly was increased in NFIN compared to NFCE (p < 0.05). Thus, there was an interaction between dietary fat content and fiber type in which body composition was altered by fiber type in NF diets but not in HF. Glucose homeostasis was improved by NF diets. Fasting glucose and insulin were reduced by IN (p < 0.01 and p< 0.03, respectively). Fiber type and dietary fat content interacted (p < 0.01) such that fasting serum insulin was reduced by NFIN compared to NFCE (p < 0.01) but did not differ in the HF-fed groups. HOMA-IR was reduced by both IN (p < 0.02) and NF feeding (p < 0.01) but no interaction was detected. IN reduced hepatic lipid content by 25.1% (p < 0.01), but no interactions between dietary fat content and fiber type were detected. Fiber type affected 14 of 41 transcripts involved in lipid metabolism with only two significant interactions between fiber type and fat content.

Conclusions: IN did not mitigate the obesogenic effects of HF, and glucose homeostasis was affected by IN only in the NF-fed groups without any interactions in hepatic lipid content between dietary fat content and fiber type. Thus, IN was only effective in improving glucose homeostasis in NF which was likely mediated by alterations in overall body composition, not liver fat content.

Funding Sources: U.S. Department of Agriculture, Agricultural Research Service