High-fat diet-induced hypertension is associated with a proinflammatory T cell profile in male and female Dahl salt-sensitive rats

Abstract

Evidence supports a sex difference in the impact of a high-fat diet (HFD) on cardiovascular outcomes, with male experimental animals exhibiting greater increases in blood pressure (BP) than female experimental animals. The immune system has been implicated in HFD-induced increases in BP, and there is a sex difference in T-cell activation in hypertension. The goal of this study was to determine the impact of HFD on BP and aortic and renal T cell profiles in male and female Dahl salt-sensitive (DSS) rats. We hypothesized that male DSS rats would have greater increases in BP and T cell infiltration in response to a HFD compared with female DSS rats. BP was measured by tail-cuff plethysmography, and aortic and renal T cells were assessed by flow cytometric analysis in male and female DSS rats on a normal-fat diet (NFD) or HFD from 12 to 16 wk of age. Four weeks of HFD increased BP in male and female DSS rats to a similar degree. Increases in BP were accompanied by increased percentages of CD4⁺ T cells and T helper (Th)17 cells in both sexes, although male rats had more proinflammatory T cells. Percentages of renal CD3⁺ and CD4⁺ T cells as well as Th17 cells were increased in both sexes by the HFD, although the increase in CD3⁺ T cells was greater in male rats. HFD also decreased the percentage of aortic and renal regulatory T cells in both sexes, although female rats maintained more regulatory T cells than male rats regardless of diet. In conclusion, both male and female DSS rats exhibit BP sensitivity to a HFD; however, the mechanisms mediating HFD-induced increases in BP may be distinct as male rats exhibit greater increases in the percentage of proinflammatory T cells than female rats. NEW & NOTEWORTHY Our study demonstrates that male and female Dahl salt-sensitive rats exhibit similar increases in blood pressure to a high-fat diet and an increase in aortic and renal T cells. These results are in contrast to studies showing that female rats remain normotensive and/or upregulate regulatory T cells in response to hypertensive stimuli compared with male rats. Our data suggest that a 4-wk high-fat diet has sex-specific effects on the T cell profile in Dahl salt-sensitive rats.

Keywords: T cells; aorta; inflammation; kidney; sex differences.

Fig. 1.

Flow cytometry gating strategy showing the selection of single cells and exclusion of cell debris based on forward scatter (FSC) and side scatter (SSC). T cells were analyzed based on the expression of CD3 and/or CD4. Total CD3⁺ T cells were further gated for expression of RAR-related orphan receptor-γt for T helper 17 cells, and CD3⁺CD4⁺ T cells were further gated for expression of Foxp3 for regulatory T cells (Tregs).

Fig. 2.

Blood glucose levels were continuously monitored in male (n = 5) and female (n = 6) Dahl salt-sensitive rats on a high-fat diet (HFD) from baseline until the end of the study (A). Spot glucose measurements were also performed periodically over the 4 wk of HFD (B), and the percent difference of the spot glucose readings compared with the telemetry readings was calculated to determine the accuracy of the telemetry data (C). All data are presented as means ± SE. Glucose telemetry and spot glucose data within each group were analyzed using repeated-measures ANOVA; between-group comparisons were made using t-tests. There were no significant differences.

Fig. 3.

Systolic blood pressure (BP) measured via tail cuff in male (n = 5) and female (n = 5–6) Dahl salt-sensitive rats expressed as the change (Δ) between baseline and after a 4-wk normal-fat diet (NFD) or high-fat diet (HFD; A), expressed as absolute values weekly in the HFD-fed group and at baseline and after 4 wk in the NFD-fed group (B) and expressed as the percent increase from baseline (C) in both treatment groups. One female rats on the NFD died before final BP measurements. All data are presented as means ± SE. Tail-cuff data within each group were analyzed using repeated-measures ANOVA. Δ and percent increases in systolic BP were compared using two-way ANOVA. +P < 0.05 vs. baseline in the same treatment group in both male and female rats; *P < 0.05 vs. same-sex NFD-fed control group; #P < 0.05 vs. female rats of same treatment group (NFD or HFD).

Fig. 4.

T cell profile in aortas with adherent fat intact of 16-wk-old male (n = 4–6) and female (n = 6) Dahl salt-sensitive rats treated with a control normal-fat diet (NFD) or high-fat diet (HFD). Shown are percentages of total T cells (A), CD4⁺ T cells (B), Foxp3⁺ T regulatory cells (Tregs; C), and related orphan receptor (ROR)γt⁺ T helper (Th)17 cells (D), IL-17⁺ cells (E), and IL-10⁺ cells (F). All data are expressed as means ± SE. Flow cytometric data were compared using two-way ANOVA.

Fig. 5.

T cell profile in kidneys of 16-wk-old male (n = 4–6) and female (n = 6) Dahl salt-sensitive rats treated with a control normal-fat diet (NFD) or high-fat diet (HFD). Shown are percentages of total T cells (A), CD4⁺ T cells (B), Foxp3⁺ T regulatory cells (Tregs; C), and related orphan receptor (ROR)γt⁺ T helper (Th)17 cells (D), IL-17⁺ cells (E), and IL-10⁺ cells (F). All data are expressed as means ± SE. Flow cytometric data were compared using two-way ANOVA.