(P20-059-25) Effects of Pork Belly Fat, Grain-Fed, Grass-Fed Beef Tallow on Glucose Homeostasis and Insulin Resistance in High Fat Fed Mice

Objectives: The objective of this study was to compare the effect of major animal-derived fats (pork and beef) on glucose homeostasis in diet-induced obese (DIO) mice. Additionally, whether ruminant-derived fatty acids can attenuate whole-body insulin resistance in DIO mice to test the efficacy of natural compounds against pre- and type 2 diabetes.

Methods: All animal procedures were reviewed and approved by UC Davis’ IACUC Committee (protocol #: 23582). For 16 weeks, 75 six-week-old male C57BL/6J mice were fed either a low-fat diet (LFD; 10% kcal total fat), control lard (CL; 45% kcal total fat), grain-fed tallow (GN; 45% kcal total fat), or grass-fed tallow (GS; 45% kcal total fat). Pork lard was derived from commercial pork belly fat. Whole grain- and grass-fed tallow was sourced from cuts containing edible back fat. Fat sources were rendered and incorporated into a purified rodent pellet diet. Body weight and food intake were measured weekly. At weeks 7 and 13, blood sampling via tail vein was performed in fed and 12-hour fasted animals. On week 14, an insulin tolerance test (ITT) was performed then a glucose tolerance test (GTT) on week 15. Animals were sacrificed on week 16 in which various tissues were collected. Data were analyzed using an ordinary one-way ANOVA, followed by a Kruskal-Wallis test of multiple comparisons using GraphPad Prism (v.10.4.0)

Results: All HFD groups had increased (P < 0.01) body weight gain compared to mice fed LFD at week 16. Body weight gain was similar (P >0.05) within HFD. In week 13, CL had increased (P < 0.01) fasted blood glucose, while all HFD had elevated fasted insulin, and HOMA-IR compared to LFD. Cumulative energy intake in GN and GS was significantly higher than LFD  (P < 0.01), but not CL (P >0.05) group. Furthermore, food conversion efficiency of GS was significantly different from CL and LFD (P < 0.01), but not GN (P >0.05). All HFD groups had significantly greater (P < 0.01) area under the curve (AUC) than LFD for ITT and GTT; however, GS had a significantly lower (P < 0.01) AUC than CL for GTT.

Conclusions: Neither type of fat (beef or pork) significantly improved markers of glucose homeostasis and did not have significant differences between parameters related to hyperinsulinemia and hyperglycemia.

Funding Sources: Funding for this study was provided by the UC Davis Clear Center.