PSV-21 Short-term and long-term effects of beef tallow enriched with trans-vaccenic acid and rumenic acid on glucose homeostasis in mice feed a high-fat diet.

Trans-vaccenic acid (VA, trans-11-18:1) and rumenic acid (RA, cis-9, trans-11-18:2) are the predominant rumen-derived trans fatty acids found in beef fat from cattle fed forage-based diets. Unlike industrial trans fatty acids, these two are considered beneficial, as they have been associated with health benefits, such as a decreased risk of type 2 diabetes (T2D). The objective of this study was to compare the effects of VA+RA-enriched tallow (ET) from steers finished on a forage-based diet containing 15% extruded flaxseeds with a control tallow (CT) from beef cattle finished on a typical corn-grain-based ration on glucose homeostasis in high-fat diet-induced obese mice, which are considered a translatable model for prediabetes. Forty-eight male 6-week-old C57BL/6J mice were randomly assigned to one of four treatments for 20 weeks: a low-fat (10% Cal from fat) diet containing CT (LFD-CT), a low-fat diet containing ET (LFD-ET), a high-fat (45% Cal from fat) diet containing CT (HFD-CT), or a high-fat diet containing ET (HFD-ET). Body weight and food intake were measured weekly. At weeks 10 and 20, blood samples were collected from fed and 12-hour fasted mice to test for blood glucose and insulin concentrations. Fasted blood glucose and insulin levels were used to calculate the homeostatic model assessment for insulin resistance (HOMA-IR). At weeks 16 and 19, glucose tolerance tests (GTT) and insulin tolerance tests (ITT) were performed, respectively. Both HFD treatments resulted in greater (P< 0.01) fasted blood glucose and insulin concentrations, as well as HOMA-IR, compared to the LFD treatments at week 10. The HFD-ET group showed lower (P< 0.05) fasted insulin concentrations and HOMA-IR compared to the HFD-CT group at week 10. By week 19, both HFD treatments resulted in significantly greater (P< 0.01) body weight gain, fasted blood glucose, insulin, HOMA-IR, and area under the curve (AUC) for ITT and GTT compared to the LFD groups. However, no significant differences were observed within the LFD and HFD groups. Our findings suggest that beef fat enriched with VA and RA can prevent hyperinsulinemia and insulin resistance in the short term, but these effects are not sustained in the long term.