Frontiers in endocrinology

A systematic review and meta-analysis was conducted to synthesize the available data from clinical trials and assess the safety issues of tirzepatide (pancreatitis and gallbladder or biliary disease) in type 2 diabetes (T2D) and obesity. A systematic search was conducted in three electronic databases, namely Embase, PubMed, and the Cochrane Library, up until March 1, 2023, to identify randomized controlled trials (RCTs) comparing tirzepatide to either placebo or active hypoglycemic drugs in individuals with T2D and obesity. Heterogeneity was assessed using the I2 value and Cochran's Q test, and a fixed effects model was employed to estimate the safety profile of tirzepatide. The safety outcomes of interest, including pancreatitis, the composite of gallbladder or biliary diseases, cholecystitis, and cholelithiasis and biliary diseases, were evaluated. (The composite of gallbladder or biliary diseases incorporated cholelithiasis, cholecystitis, other gallbladder disorders, and biliary diseases.). A total of nine trials with 9871 participants (6828 in the tirzepatide group and 3043 in the control group) that met the pre-specified criteria were included. When compared to all control groups consisting of basal insulin (glargine or degludec), selective GLP1-RA (dulaglutide or semaglutide once weekly), and placebo, an increased risk of pancreatitis was not found to be significantly associated with tirzepatide (RR 1.46, [95% CI] 0.59 to 3.61; I2 = 0.0%, p = 0.436). For gallbladder or biliary disease, the composite of gallbladder or biliary disease was significantly associated with tirzepatide compared with placebo or basal insulin (RR 1.97, [95% CI] 1.14 to 3.42; I2 = 0.0%, p = 0.558), but not with the risk of cholelithiasis, cholecystitis or biliary diseases. Based on the currently available data, tirzepatide appears to be safe regarding the risk of pancreatitis. However, the increased risk of the composite outcome of gallbladder or biliary diseases observed in RCTs warrants further attention from physicians in clinical practice. https://www.crd.york.ac.uk/PROSPERO, identifier CRD42023412400.

Mitochondrial ORF of the 12S rRNA Type-C (MOTS-c) is a mitochondrial-derived peptide composed of 16 amino acids encoded by the 12S rRNA region of the mitochondrial genome. The MOTS-c protein is transferred to the nucleus during metabolic stress and directs the expression of nuclear genes to promote cell balance. Different tissues co-expressed the protein with mitochondria, and plasma also contained the protein, but its level decreased with age. In addition, MOTS-c has been shown to improve glucose metabolism in skeletal muscle, which indicates its benefits for diseases such as diabetes, obesity, and aging. Nevertheless, MOTS-c has been used less frequently in disease treatment, and no effective method of applying MOTS-c in the clinic has been developed. Throughout this paper, we discussed the discovery and physiological function of mitochondrial-derived polypeptide MOTS-c, and the application of MOTS-c in the treatment of various diseases, such as aging, cardiovascular disease, insulin resistance, and inflammation. To provide additional ideas for future research and development, we tapped into the molecular mechanisms and therapeutic potentials of MOTS-c to improve diseases and combined the technology with synthetic biology in order to offer a new approach to its development and application.

Pathologic cardiac remodeling and dysfunction are the most common complications of type 2 diabetes. Physical exercise is important in inhibiting myocardial pathologic remodeling and restoring cardiac function in diabetes. The mitochondrial-derived peptide MOTS-c has exercise-like effects by improving insulin resistance, combatting hyperglycemia, and reducing lipid accumulation. We investigated the effects and transcriptomic profiling of MOTS-c and aerobic exercise on cardiac properties in a rat model of type 2 diabetes which was induced by feeding a high fat high sugar diet combined with an injection of a low dose of streptozotocin. Both aerobic exercise and MOTS-c treatment reduced abnormalities in cardiac structure and function. Transcriptomic function enrichment analysis revealed that MOTS-c had exercise-like effects on inflammation, myocardial apoptosis, angiogenesis and endothelial cell proliferation and migration, and showed that the NRG1-ErbB4 pathway might be an important component in both MOTS-c and exercise induced attenuation of cardiac dysfunction in diabetes. Moreover, our findings suggest that MOTS-c activates NRG1-ErbB4 signaling and mimics exercise-induced cardio-protection in diabetes.

The pathophysiological function of the G-protein coupled melatonin MT 1 and MT 2 receptors has not yet been well-clarified. Recent advancements using selective MT 1 / MT 2 receptor ligands and MT 1 /MT 2 receptor knockout mice have suggested that the activation of the MT 1 receptors are mainly implicated in the regulation of rapid eye movement (REM) sleep, whereas the MT 2 receptors selectively increase non-REM (NREM) sleep. Studies in mutant mice show that MT 1 knockout mice have an increase in NREM sleep and a decrease in REM sleep, while MT2 knockout mice a decrease in NREM sleep. The localization of MT 1 receptors is also distinct from MT2 receptors; for example, MT 2 receptors are located in the reticular thalamus (NREM area), while the MT 1 receptors in the Locus Coeruleus and lateral hypothalamus (REM areas). Altogether, these findings suggest that these two receptors not only have a very specialized function in sleep, but that they may also modulate opposing effects. These data also suggest that mixed MT 1 -MT 2 receptors ligands are not clinically recommended given their opposite roles in physiological functions, confirmed by the modest effects of melatonin or MT 1 /MT 2 non-selective agonists when used in both preclinical and clinical studies as hypnotic drugs. In sum, MT 1 and MT 2 receptors have specific roles in the modulation of sleep, and consequently, selective ligands with agonist, antagonist, or partial agonist properties could have therapeutic potential for sleep; while the MT 2 agonists or partial agonists might be indicated for NREM-related sleep and/or anxiety disorders, the MT 1 agonists or partial agonists might be so for REM-related sleep disorders. Furthermore, MT 1 but not MT 2 receptors seem involved in the regulation of the circadian rhythm. Future research will help further develop MT 1 and/or MT 2 receptors as targets for neuropsychopharmacology drug development.

The neurohormone N-acetyl-5-methoxytryptamine, better known as melatonin, is a tryptophan derivative with a wide range of biological effects that is present in many organisms. These effects are believed to rely either on the chemical properties of melatonin itself as scavenger of free radicals or on the binding of melatonin to protein targets. More than 15 proteins, including receptors (MT 1 , MT 2 , Mel1c, CAND2, ROR, VDR), enzymes (QR2, MMP-9, pepsin, PP2A, PR-10 proteins), pores (mtPTP), transporters (PEPT1/2, Glut1), and other proteins (HBS, CaM, tubulin, calreticuline), have been suggested to interact with melatonin at sub-nanomolar to millimolar melatonin concentrations. In this review we assemble for the first time the available information on proposed melatonin targets and discuss them in a comprehensive manner to evaluate the robustness of these findings in terms of methodology, physiological relevance, and independent replication.