Outcomes of SGLT-2i and GLP-1RA Therapy Among Patients With Type 2 Diabetes and Varying NAFLD Status.

Importance: Nonalcoholic fatty liver disease (NAFLD) is a cardiovascular risk factor, but whether sodium-glucose cotransporter-2 inhibitors (SGLT-2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA) are associated with reduced cardiovascular risk in patients with type 2 diabetes (T2D) and concomitant NAFLD remains uncertain. Objective: To investigate the outcomes of SGLT-2i and GLP-1RA therapy among patients with T2D varied by the presence or absence of NAFLD. Design, Setting, and Participants: This retrospective, population-based, nationwide cohort study used an active-comparator new-user design. Two distinct new-user active-comparator cohorts of patients aged 40 years and older who initiated SGLT-2i or GLP-1RA were propensity score matched to patients who initiated dipeptidyl peptidase-4 inhibitors (DPP-4i). The study was conducted in South Korea from January 2013 to December 2020, and data analysis was conducted from October 2022 to March 2023. Main Outcomes and Measures: The main outcomes were (1) major adverse cardiovascular events (MACE), a composite end point of hospitalization for myocardial infarction, hospitalization for stroke, and cardiovascular death, and (2) hospitalization for heart failure (HHF). Cox proportional hazards models were used to estimate hazard ratios (HRs). The Wald test was applied to assess heterogeneity by NAFLD. Results: After 1:1 propensity score matching, 140 438 patients were retrieved in the first cohort (SGLT-2i vs DPP-4i; mean [SD] age, 57.5 [10.3] years; 79 633 [56.7%] male) and 34 886 patients were identified in the second cohort (GLP-1RA vs DPP-4i; mean [SD] age, 59.5 [10.5] years; 17 894 [51.3%] male). Compared with DPP-4i, SGLT-2i therapy was associated with a lower risk of MACE (HR, 0.78 [95% CI, 0.71-0.85]) and HHF (HR, 0.62 [95% CI, 0.48-0.81]). GLP-1RA therapy was associated with a decreased risk of MACE (HR, 0.49 [95% CI, 0.39-0.62]) but had statistically nonsignificant findings regarding HHF (HR, 0.64 [95% CI, 0.39-1.07]). Stratified analysis by NAFLD status yielded consistent results for SGLT-2i (MACE with NAFLD: HR, 0.73 [95% CI, 0.62-0.86]; without NAFLD: HR, 0.81 [95% CI, 0.72-0.91]; HHF with NAFLD: HR, 0.76 [95% CI, 0.49-1.17]; without NAFLD: HR, 0.56 [95% CI, 0.40-0.78]) and for GLP-1RA (MACE with NAFLD: HR, 0.49 [95% CI, 0.32-0.77]; without NAFLD: HR, 0.49 [95% CI, 0.37-0.65]; HHF with NAFLD: HR, 0.82 [95% CI, 0.38-1.76]; without NAFLD: HR, 0.54 [95% CI, 0.27-1.06]). Conclusions and Relevance: In this population-based cohort study, SGLT-2i therapy was associated with a decreased risk of MACE and HHF, while GLP-1RA therapy was associated with a decreased risk of MACE among patients with T2D, irrespective of baseline NAFLD status.

The involvement of TRPC3 channels in sinoatrial arrhythmias.

Atrial fibrillation (AF) is a significant contributor to cardiovascular morbidity and mortality. The currently available treatments are limited and AF continues to be a major clinical challenge. Clinical studies have shown that AF is frequently associated with dysfunction in the sino-atrial node (SAN). The association between AF and SAN dysfunction is probably related to the communication between the SAN and the surrounding atrial cells that form the SAN-atrial pacemaker complex and/or pathological processes that affect both the SAN and atrial simultaneously. Recent evidence suggests that Ca(2+) entry through TRPC3 (Transient Receptor Potential Canonical-3) channels may underlie several pathophysiological conditions -including cardiac arrhythmias. However, it is still not known if atrial and sinoatrial node cells are also involved. In this article we will first briefly review TRPC3 and IP3R signaling that relate to store/receptor-operated Ca(2+) entry (SOCE/ROCE) mechanisms and cardiac arrhythmias. We will then present some of our recent research progress in this field. Our experiments results suggest that pacing-induced AF in angiotensin II (Ang II) treated mice are significantly reduced in mice lacking the TRPC3 gene (TRPC3(-/-) mice) compared to wild type controls. We also show that pacemaker cells express TRPC3 and several other molecular components related to SOCE/ROCE signaling, including STIM1 and IP3R. Activation of G-protein coupled receptors (GPCRs) signaling that is able to modulate SOCE/ROCE and Ang II induced Ca(2+) homeostasis changes in sinoatrial complex being linked to TRPC3. The results provide new evidence that TRPC3 may play a role in sinoatrial and atrial arrhythmias that are caused by GPCRs activation.

ISL1 regulates peroxisome proliferator-activated receptor γ activation and early adipogenesis via bone morphogenetic protein 4-dependent and -independent mechanisms.

While adipogenesis is controlled by a cascade of transcription factors, the global gene expression profiles in the early phase of adipogenesis are not well defined. Using microarray analysis of gene expression in 3T3-L1 cells, we have identified evidence for the activity of 2,568 genes during the early phase of adipocyte differentiation. One of these, the ISL1 gene, was of interest since its expression was markedly upregulated 1 h after initiation of differentiation, with a subsequent rapid decline. Overexpression of ISL1 at early times during adipocyte differentiation but not at later times was found to profoundly inhibit differentiation. This was accompanied by moderate downregulation of peroxisome proliferator-activated receptor γ (PPARγ) levels, substantial downregulation of PPARγ downstream genes, and downregulation of bone morphogenetic protein 4 (BMP4) levels in preadipocytes. Readdition of BMP4 overcame the inhibitory effect of ISL1 on the expression of PPARγ but not aP2, a gene downstream of PPARγ, and BMP4 also partially rescued ISL1 inhibition of adipogenesis, an effect which is additive with rosiglitazone. These results suggest that ISL1 is intimately involved in early regulation of adipogenesis, modulating PPARγ expression and activity via BMP4-dependent and -independent mechanisms. Our time course gene expression survey sets the stage for further studies to explore other early and immediate regulators.

Distribution and functional role of inositol 1,4,5-trisphosphate receptors in mouse sinoatrial node.

RATIONALE: Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) have been implicated in the generation of arrhythmias and cardiac muscle nuclear signaling. However, in the mammalian sinoatrial node (SAN), where the heart beat originates, the expression and functional activity of IP(3)Rs have not been investigated. OBJECTIVES: To determine whether SAN express IP(3)Rs and which isoforms are present. To examine the response of the SAN to IP(3)R agonists and antagonist, and the potential role played by IP(3)Rs in cardiac pacemaking. METHODS AND RESULTS: The expression and distribution of IP(3)Rs were studied by reverse-transcription polymerase chain reaction, Western blotting, and immunolabeling. Ca(2+) signaling and electric activity in intact mouse SAN were measured with Ca(2+)-sensitive fluorescent dyes. We found that although the entire SAN expressed three IP(3)R mRNA isoforms, the type II IP(3)R (IP(3)R2) was the predominant protein isoform detected by Western blot using protein extracts from the SAN, atrioventricular node, and atrial tissue. Immunohistochemistry studies also showed that IP(3)R2 was expressed in the central SAN region. Studies using isolated single pacemaker cells revealed that IP(3)R2 (but not IP(3)R1) was located with a similar distribution to the sarcoplasmic reticulum marker protein SERCA2a with some labeling adjacent to the surface membrane. The application of membrane-permeable IP(3) (IP(3)-butyryloxymethyl ester) increased Ca(2+) spark frequency and the pacemaker firing rate in single isolated pacemaker cells. In intact SAN preparations, IP(3)R agonists, endothelin-1 and IP(3)-butyryloxymethyl ester both increased intracellular Ca(2+) and the pacemaker firing rate, whereas the IP(3)R antagonist, 2-aminoethoxydiphenyl borate decreased Ca(2+) and the firing rate. Both of these effects were absent in the SAN from transgenic IP(3)R2 knockout mice. CONCLUSIONS: This study provides new evidence that functional IP(3)R2s are expressed in the mouse SAN and could serve as an additional Ca(2+)-dependent mechanism in modulating cardiac pacemaker activity as well as other Ca(2+)-dependent processes.