A Diet High in Saturated Fat Results in Greater Increases in Splenic Tregs in Female vs Male Sprague Dawley Rats

Abstract

Background Diets high in saturated fats promote inflammation and are linked to the development of many cardiovascular diseases (CVD). Young females are typically protected from CVD vs males. However, epidemiological and basic science studies suggest that the cardiovascular protection in females is compromised by a high fat diet (HFD). Little is known regarding the impact of a HFD on T cells in males vs. females. Therefore, the current study tested the hypothesis that a HFD results in a more pro‐inflammatory T cell profile in females vs. males. Methods 26‐day‐old male and female Sprague Dawley rats (n=3–5 per group) were randomized to a control (Ctrl; 7.2% calories from fat) or HFD (36% of calories from fat) for 10 weeks. 24 hour food consumption was measured every 3 weeks. Body weights were measured weekly. At the end of the 10 week treatment, body fat composition was measured via NMR. Rats were euthanized and spleen were isolated for flow cytometric analysis of Pan T cells (CD3+), CD4+ T cells (CD3+CD4+), and T regulatory cells (Tregs; CD3+CD4+FOXP3+). Results Throughout the treatment, rats on HFD consumed more kcal from fat vs Ctrls (P<0.05). There were no differences in body weight between Ctrl and HFD rats of the same sex (P>0.05 at each time point), although males were heavier than females at all time points (P<0.05), Table 1. Following 10 weeks of treatment, HFD increased body fat percentage in both sexes vs Ctrl, (PDiet=0.01). Increases in body fat were similarly in both sexes (PSex=0.33; Pinteraction=0.37). At end of treatment, all groups had similar percentages of splenic CD3+ cells (Pdiet=0.27; Psex=0.14; Pinteraction=0.41). However, rats on a HFD had more CD4+ T cells vs Ctrl (PDiet=0.006). Moreover, females had more CD4+ T cells vs males (PSex=0.002; Pinteraction=0.09). HF females had the most splenic Tregs vs all groups (PDiet=0.28, PSex=0.09, PInteraction=0.007. Discussion This dietary model allows for investigation of the effects of a HFD on body composition and T cell count independent of obesity. Evidence in the literature suggests high anti‐inflammatory Tregs in female rats contributes to cardiovascular protection and decrease in renal Tregs compromises this protection. Thus, the increase in splenic Tregs in females on a HFD may show a compensatory increase to counteract the decreased renal Tregs observed in the literature. Future studies will test this hypothesis. Data following 0 and 10 weeks of dietary treatment expressed as means ± SEM. Assay Weeks of treatment Population Ctrl F HF‐F Ctrl‐M HF‐M Body weight (g) 0 73.25 ± 0.48 70 ± 1.05 83.2 ± 2.13 80.2 ± 1.07 10 254 ± 8.57 242.4 ± 11.05 411 ± 11.79 410.8 ± 13.72 Body fat percentage 10 7.94 ± 0.49 11.35 ± 1.23 7.84 ± 1.69 10.18 ± 0.82 Splenic T cells 10 CD3 21.5 ± 1.55 20.96 ± 2.02 25.9 ± 2.3 22.28 ± 0.65 CD4 73.48 ± 1.38 77.36 ± 2.85 58.8 ± 2.91 72.23 ± 2.44 Tregs 6.05 ± 0.31 8.47 ± 0.79 7.55 ± 0.92 5.63 ± 0.32