The Chromogranin A (CgA)-derived peptide Catestatin (CST: hCgA352-372) is highly conserved (>90% in 90% species) in mammalian species. The highest-evolved primates show 58.8% similarity with the lowest-evolved monotremes. CST was initially identified as a physiological brake in catecholamine secretion by inhibiting nicotinic-cholinergic signaling. CST also inhibits desensitization of catecholamine secretion, indicating that CST can act both as a cholinergic antagonist (short-term) and as a cholinergic agonist (long-term). The long-term effect sustains catecholamine secretion during stressful situations. CST is now established as a pleiotropic hormone: it affects the cardiovascular system by lowering blood pressure and cardiac contractility, enhancing baroreflex sensitivity, increasing heart rate variability, and promoting angiogenesis; and it increases insulin sensitivity by reducing inflammation, inhibiting hepatic glucose production, attenuating endoplasmic reticulum stress, and inducing glycogen production. The present review will highlight the important direct and indirect effects of CST, CST1-15 (aka cateslytin), D-CST1-15 (where L-amino acids were changed to D-amino acids), and human variants of CST (Gly364Ser-CST and Pro370Leu-CST) on microbial growth inhibition and their potential as therapy for antibiotic-resistant pathogenic microbes.

Type 2 diabetes (T2D) has a complex pathophysiology which makes modeling the disease difficult. We aimed to develop a novel model for simulating T2D in vitro, including hyperglycemia, hyperlipidemia, and variably elevated insulin levels targeting muscle cells. We investigated insulin resistance (IR), cellular respiration, mitochondrial morphometry and the associated function in different T2D -mimicking conditions in rodent skeletal (C2C12) and cardiac (H9C2) myotubes. Physiological controls included 5mM glucose with 20mM mannitol as osmotic controls. To mimic hyperglycemia, cells were exposed to 25mM glucose. Further treatments included insulin, palmitate, or both. After short-term (24h) or long-term (96h) exposure, we performed radioactive glucose uptake and mitochondrial function assays. Mitochondrial size and relative frequencies were assessed by morphometric analyses using electron micrographs. C2C12 and H9C2 cells treated short- or long-term with insulin and/or palmitate and HG showed IR. C2C12 myotubes exposed to T2D -mimicking conditions showed significantly decreased ATP-linked respiration and spare respiratory capacity, and less cytoplasmic area occupied by mitochondria, implying mitochondrial dysfunction. In contrast, H9C2 myotubes showed elevated ATP-linked and maximal respiration and increased cytoplasmic area occupied by mitochondria, indicating better adaptation to stress and compensatory lipid oxidation in a T2D environment. Both cell lines displayed elevated fractions of swollen/vacuolated mitochondria after T2D -mimicking treatments.Our stable and reproducible in vitro model of T2D rapidly induced IR, changes in ATP-linked respiration, shifts in energetic phenotypes, and mitochondrial morphology, which are comparable to the muscles of patients suffering from T2D. Thus, our model should allow studying disease mechanisms, potential new targets, and screen candidate therapeutic compounds.