Endothelin receptor antagonism improves glucose tolerance and adipose tissue inflammation in an experimental model of systemic lupus erythematosus

Abstract

Endothelin-1 (ET-1) is elevated in patients with systemic lupus erythematosus (SLE), an autoimmune disease characterized by high rates of hypertension, renal injury, and cardiovascular disease. SLE is also associated with an increased prevalence of obesity and insulin resistance compared to the general population. In the present study, we tested the hypothesis that elevated ET-1 in SLE contributes to obesity and insulin resistance. For these studies, we used the NZBWF1 mouse model of SLE, which develops obesity and insulin resistance on a normal chow diet. To test this hypothesis, we treated control (NZW) and SLE (NZBWF1) mice with vehicle, atrasentan (ET_A receptor antagonist, 10 mg/kg/day), or bosentan (ET_A/ET_B receptor antagonist, 100 mg/kg/day) for 4 wk. Neither treatment impacted circulating immunoglobulin levels, but treatment with bosentan lowered anti-dsDNA IgG levels, a marker of SLE disease activity. Treatment with atrasentan and bosentan decreased glomerulosclerosis, and atrasentan lowered renal T-cell infiltration. Body weight was lower in SLE mice treated with atrasentan or bosentan. Endothelin receptor antagonism also improved hyperinsulinemia, homeostatic model assessment for insulin resistance, and glucose tolerance in SLE mice. Adipose tissue inflammation was also improved by endothelin receptor blockade. Taken together, these data suggest a potential therapeutic benefit for SLE patients with obesity and insulin resistance.NEW & NOTEWORTHY SLE is an autoimmune disease that is associated with obesity, insulin resistance, and elevated endothelin-1. The present study demonstrated that pharmacological inhibition of endothelin receptors decreased body weight, insulin resistance, and adipose tissue inflammation in a murine model of SLE. The therapeutic potential of endothelin receptor antagonists to treat obesity-related diseases and pathophysiological conditions, such as autoimmune diseases and insulin resistance, has become increasingly clear.

Keywords: adipose; autoimmunity; endothelin-1; insulin resistance; lupus; obesity.

Graphical abstract

Figure 1.

Effect of endothelin receptor antagonism on circulating immunoglobulins and autoantibodies. Circulating immunoglobulins and autoantibodies were assessed by ELISA at the conclusion of the study. A: total IgG. B: total IgM. C: double-stranded DNA (anti-dsDNA) IgG. ATR, atrasentan; BOS, bosentan; SLE, systemic lupus erythematosus; Veh, vehicle. *P < 0.05, by two-way ANOVA followed by Tukey’s post hoc test to determine significance. Animals per group: Control-Veh, n = 10; Control-ATR, n = 11; Control-BOS, n = 11; SLE-Veh, n = 9; SLE-ATR, n = 10; SLE-BOS, n = 8.

Figure 2.

Endothelin receptor antagonism decreases glomerulosclerosis. A: urinary albumin, as measured by an albumin ELISA at the conclusion of the study. B: urine output, each point is the average of 4 weekly measurements for an individual animal (Control-Veh: n = 10; Control-ATR: n = 11; Control-BOS: n = 11; SLE-Veh: n = 9; SLE-ATR: n = 10, SLE-BOS: n = 8). C: glomerulosclerosis index (n = 5–6 animals per group). D: representative images of glomerulosclerosis (×20) from paraffin-embedded kidneys stained with hematoxylin and eosin. ATR, atrasentan; BOS, bosentan; SLE, systemic lupus erythematosus; Veh, vehicle. *P < 0.05; ***P < 0.001 by two-way ANOVA followed by Tukey’s post hoc test to determine significance.

Figure 3.

Endothelin receptor antagonism decreases renal immune cell infiltration in systemic lupus erythematosus (SLE) mice. Data for individual cell populations are expressed as the percentage of total CD45⁺ cells. A: percentage of CD45⁺ cells among gated renal cells. B: percentage of CD3⁺CD4⁺ T cells. C: percentage of CD3⁺CD8⁺ T cells. D: percentage of CD45R⁺ B cells. E: percentage of F4/80⁺ macrophages. ATR, atrasentan; BOS, bosentan; Veh, vehicle. **P < 0.01 by two-way ANOVA followed by Tukey’s post hoc test to determine significance. Animals per group: Control-Veh, n = 10; Control-ATR, n = 11; Control-BOS, n = 11; SLE-Veh, n = 9; SLE-ATR, n = 10; SLE-BOS, n = 8.

Figure 4.

Effect of endothelin receptor antagonism on body weight, body composition, and circulating adipokines. Adipokines were assessed in fasted mice at the conclusion of the study. A: weekly body weights over the course of the study. B: percent change in body weight at the conclusion of the study. C: fat mass percent at the conclusion of the study assessed using Echo MRI. D: lean mass percent at the conclusion of the study assessed using Echo MRI. E: circulating adiponectin. F: circulating leptin. ATR, atrasentan; BOS, bosentan; SLE, systemic lupus erythematosus; Veh, vehicle. *P < 0.05; **P < 0.01 by two-way ANOVA followed by Tukey’s post hoc test to determine significance. Animals per group: Control-veh, n = 10; Control-ATR, n = 11; Control-BOS, n = 11; SLE-Veh, n = 9; SLE-ATR, n = 10; SLE-BOS, n = 8.

Figure 5.

Effect of endothelin receptor antagonism on circulating lipids. Plasma was collected from fasted mice at the conclusion of the study. A: cholesterol (c). B: HDL-c. C: LDL-c. D: nonesterified fatty acids. E: triglycerides. ATR, atrasentan; BOS, bosentan; SLE, systemic lupus erythematosus; Veh, vehicle. Animals per group: Control-veh, n = 10; Control-ATR, n = 11; Control-BOS, n = 11; SLE-Veh, n = 9; SLE-ATR, n = 10; SLE-BOS, n = 8.

Figure 6.

Endothelin receptor antagonism improves glucose tolerance in systemic lupus erythematosus (SLE) mice. A: fasting blood glucose. B: insulin. C: homeostatic model assessment for insulin resistance (HOMA-IR). D: oral glucose tolerance test of control mice (OGTT). E: oral glucose tolerance test of SLE mice. F: calculated area under the curve (AUC) of OGTT for each animal in all groups. G: insulin tolerance test (ITT) of control mice. H: insulin tolerance test of SLE mice. I: calculated AUC of ITT for each animal in all groups. ATR, atrasentan; BOS, bosentan; Veh, vehicle. *P < 0.05; **P < 0.01 by two-way ANOVA followed by Tukey’s post hoc test to determine significance. Animals per group: Control-veh, n = 10; Control-ATR, n = 11; Control-BOS, n = 11; SLE-Veh, n = 9; SLE-ATR, n = 10; SLE-BOS, n = 8.

Figure 7.

Endothelin receptor antagonism decreases T cells in visceral adipose tissue. Data for individual cell populations are expressed as the percentage of total CD45⁺ cells. A: percentage of CD45⁺ immune cells in adipose tissue. B: percentage of eosinophils. C: percentage of macrophages. D: Percentage of neutrophils. E: percentage of B cells. F: percentage of CD4⁺ T cells. G: percentage of CD8⁺ T cells. ATR, atrasentan; BOS, bosentan; SLE, systemic lupus erythematosus; Veh, vehicle. *P < 0.05; **P < 0.001 by two-way ANOVA followed by Tukey’s post hoc test to determine significance. Animals per group: Control-veh, n = 10; Control-ATR, n = 11; Control-BOS, n = 11; SLE-Veh, n = 9; SLE-ATR, n = 10; SLE-BOS, n = 8.