**Potential Benefits of Selenium Supplementation in Reducing Insulin Resistance in Patients with Cardiometabolic Diseases: A Systematic Review and Meta-Analysis**

**Jiahui Ouyang 1,†, Yajie Cai 1,†, Yewen Song 1, Zhuye Gao 1,2, Ruina Bai 1,2,\* and Anlu Wang 1,2,\***

<sup>1</sup> Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing 100091, China

<sup>2</sup> National Clinical Research Center for Chinese Medicine Cardiology, Xiyuan Hospital,

China Academy of Chinese Medical Sciences, Beijing 100091, China

**\*** Correspondence: brntcl@126.com (R.B.); wanganlu@bucm.edu.cn (A.W.)

† These authors contributed equally to this work.

**Abstract:** Background: Selenium is a trace element that has been reported to be effective in regulating glucose and lipid metabolism. However, there is conflicting evidence from different clinical trials of selenium supplementation in treating cardiometabolic diseases (CMDs). Objective: This metaanalysis aimed to identify the effects of selenium supplementation on insulin resistance, glucose homeostasis, and lipid profiles in patients with CMDs. Methods: Randomized controlled trials (RCTs) of selenium supplementation for treating CMDs were screened in five electronic databases. Insulin levels, homeostatic model assessment of insulin resistance (HOMA-IR), fasting plasma glucose (FPG), and glycosylated hemoglobin A1C (HbA1c) were defined as the primary outcome markers, and lipid profiles were considered the secondary outcome markers. Results: Ten studies involving 526 participants were included in the meta-analysis. The results suggested that selenium supplementation significantly reduced serum insulin levels (standardized men difference [SMD]: −0.53; 95% confidence interval [CI] [−0.84, −0.21], *p* = 0.001, *I* <sup>2</sup> = 68%) and HOMA-IR (SMD: <sup>−</sup>0.50, 95% CI [−0.86, −0.14], *p* = 0.006, *I* <sup>2</sup> = 75%) and increased high-density lipoprotein cholesterol (HDL-C) levels (SMD: 0.97; 95% CI [0.26, 1.68], *p* = 0.007, *I* <sup>2</sup> = 92%), but had no significant effect on FPG, total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and very low-density lipoprotein cholesterol (VLDL-C). Conclusion: Current evidence supports the beneficial effects of selenium supplementation on reducing insulin levels, HOMA-IR, and increasing HDL-C levels. Selenium supplementation may be an effective strategy for reducing insulin resistance in patients with CMDs. However, more high-quality clinical studies are needed to improve the certainty of our estimates.

**Keywords:** selenium; cardiometabolic disease; insulin resistance; diabetes mellitus; cardiovascular disease; systematic review; meta-analysis
