Hydrogen (H₂) is colorless, odorless, and the lightest of gas molecules. Studies in the past ten years have indicated that H₂ is extremely important in regulating the homeostasis of the cardiovascular system and metabolic activity. Delivery of H₂ by various strategies improves cardiometabolic diseases, including atherosclerosis, vascular injury, ischemic or hypertrophic ventricular remodeling, intermittent hypoxia- or heart transplantation-induced heart injury, obesity and diabetes in animal models or in clinical trials. The purpose of this review is to summarize the physical and chemical properties of H₂, and then, the functions of H₂ with an emphasis on the therapeutic potential and molecular mechanisms involved in the diseases above. We hope this review will provide the future outlook of H₂-based therapies for cardiometabolic disease.

Background and Purpose: Septic cardiomyopathy, which is one of the features of multi-organ dysfunction in sepsis, is characterized by ventricular dilatation, reduced ventricular contractility, and reduction in ejection fraction and, if severe, can lead to death. To date, there is no specific therapy that exists, and its treatment represents a large unmet clinical need. Herein, we investigated the effects and underlying anti-inflammatory mechanisms of hydrogen gas in the setting of lipopolysaccharide (LPS)-induced cardiomyocytes injury. Experimental Approach: Hydrogen gas was intraperitoneally injected to mice in LPS plus hydrogen group and hydrogen group for 4 days. On fourth, LPS was given by intraperitoneal injection to mice in LPS group and to mice in LPS plus hydrogen group. In addition, H9c2 cardiomyocytes were treated with hydrogen-rich medium for 30 min before LPS. The transthoracic echocardiography was performed at 6 h post‐LPS to assess left ventricular end-systolic diameter (LVESD), left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (EF%), fractional shortening (FS%), left ventricular mass average weight (LV mass AW), and LV mass AW (Corrected). The histological and morphological analyses of left ventricular were performed by hematoxylin and eosin (H&E) staining and Masson’s trichrome staining. The mRNA levels of ANP and BNP were examined by PCR in vitro . The expression of cytokines were assayed by Enzyme Linked Immunosorbent Assay (ELISA) and PCR. Moreover, Western blotting was performed to examine the expression of TLR4, the activation of ERK1/2, p38, JNK, and the expression of NF-κB in nucleus after 6 h of LPS challenge in vivo and in vitro . Key Results: LPS induced cardiac dysfunction; hydrogen therapy improved cardiac function after LPS challenge. Furthermore, pretreatment with hydrogen resulted in cardioprotection during septic cardiomyopathy via inhibiting the expression of pro-inflammatory cytokines TNFα, IL-1β, and IL-18; suppressing the phosphorylation of ERK1/2, p38, and JNK; and reducing the nuclear translocation of NF-κB and the expression of TLR4 by LPS. Conclusion and Implications: Hydrogen therapy prevents LPS-induced cardiac dysfunction in part via downregulation of TLR4-mediated pro-inflammatory cytokines expression.

A previous study from our group has demonstrated that hydrogen administration can attenuate cardiovascular hypertrophy in vivo by targeting reactive oxygen species‑dependent mitogen‑activated protein kinase signaling. The aim of the present study is to determine the effect of hydrogen on cardiomyocyte autophagy during β‑adrenoceptor activation in vivo and in vitro. We prepared hydrogen‑rich medium, and the concentration of hydrogen was measured by using the MB‑Pt reagent method. For the in vitro study, H9c2 cardiomyocytes were stimulated with isoproterenol (ISO; 10 µM) for 5, 15 and 30 min, and then the protein expression levels of the autophagy marker microtubule‑associated protein 1 light chain 3β II (LC3B II) were examined by western blotting. The effect of hydrogen‑rich medium was then tested by pretreating the H9c2 cardiomyocytes with hydrogen‑rich medium for 30 min, then stimulating with ISO, and examining the protein expression levels of the autophagy marker LC3B II. For the in vivo study, mice received hydrogen (1 ml/100 g/day, by intraperitoneal injection) for 7 days prior to ISO administration (0.5 mg/100 g/day, by subcutaneous injection), and subsequently received hydrogen with or without ISO for another 7 days. Hypertrophic responses were examined by heart weight (HW) and heart weight/body weight (HW/BW) measurements. The protein expression of autophagy markers Beclin1, autophagy‑related protein 7 (Atg7) and LC3B II were examined. The results demonstrated that excessive autophagy occurred following 5 min of ISO stimulation in vitro. This enhanced autophagy was blocked by pretreatment with hydrogen‑rich medium. Furthermore, hydrogen improved the deteriorated hypertrophic responses and inhibited the enhanced autophagic activity mediated by ISO administration in vivo, as indicated by decreasing HW and HW/BW, and suppressing the protein expression levels of Beclin1, Atg7 and LC3B II. Therefore, the results of the present study demonstrated that hydrogen inhibited ISO‑induced excessive autophagy in cardiomyocyte hypertrophy models in vitro and in vivo.

Background: Familial hyperaldosteronism type 1 (FH1), previously known as glucocorticoid-remediable aldosteronism, was the first identified monogenic cause of primary aldosteronism. Patients classically develop hypertension at a young age and are at risk of premature vascular complications. A systematic review of FH1 was performed to determine long-term treatment outcomes. Methods: Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we conducted searches with a PICO framework using Embase, Medline, PubMed, Scopus, and Web of Science databases to identify patients with FH1 prescribed either no treatment with a minimum 3 months follow-up or medical treatment of at least 3 months duration. Results: A total of 99 FH1 cases were identified from 42 studies. Most had early-onset hypertension but variable hypokalemia, hyperaldosteronism, and hyporeninemia. Of the 62 cases with a reported age of FH1 diagnosis, median age was 18 to 17.6 years old. Of those treated, 72% received a glucocorticoid for long-term treatment compared with 22% receiving a potassium-sparing diuretic. Data on long-term treatment and disease side effects, complications, and outcomes were seldom reported. However, of 20 patients with reported complications, premature vascular complications were evident with the median age of diagnosis for left ventricular hypertrophy and hypertensive retinopathy 15 and 16.5 years old respectively, the youngest age of aortic dissection age 10 years, and those with reported cerebrovascular history had strokes or transient ischemic attacks before age 40 years. Conclusions: Major gaps in the literature around FH1 patients’ long-term treatment and disease outcomes still exist. Long-term outcome data are required to help inform clinicians of the best long-term treatment for FH1.