Hexarelin, a Growth Hormone Secretagogue, Improves Lipid Metabolic Aberrations in Nonobese Insulin-Resistant Male MKR Mice

Strategy for Pre-Clinical Development of Active Targeting MicroRNA Oligonucleotide Therapeutics for Unmet Medical Needs

We present here an innovative modular and outsourced model of drug research and development for microRNA oligonucleotide therapeutics (miRNA ONTs). This model is being implemented by a biotechnology company, namely AptamiR Therapeutics, in collaboration with Centers of Excellence in Academic Institutions. Our aim is to develop safe, effective and convenient active targeting miRNA ONT agents for the metabolic pandemic of obesity and metabolic-associated fatty liver disease (MAFLD), as well as deadly ovarian cancer.

Hexarelin attenuates abdominal aortic aneurysm formation by inhibiting SMC phenotype switch and inflammasome activation

Hexarelin, a synthetic growth hormone-releasing peptide, is shown to be protective in cardiovascular diseases such as myocardial infraction and atherosclerosis. However, the functional role of hexarelin in abdominal aortic aneurysm (AAA) remains undefined. The present study determined the effect of hexarelin administration (200 μg/kg twice per day) in a mouse model of elastase-induced abdominal aortic aneurysm. Echocardiography and in situ pictures showed hexarelin decreased infrarenal aorta diameter. Histology staining showed elastin degradation was improved in hexarelin-treated group. Hexarelin rescued smooth muscle cell contractile phenotype with increased α-SMA and decreased MMP2. Furthermore, hexarelin inhibited inflammatory cell infiltration, NLRP3 inflammasome activation and IL-18 production. Particularly, hexarelin suppressed NF-κB signaling pathway which is a key initiator of inflammatory response. These results demonstrated that hexarelin attenuated AAA development by inhibiting SMC phenotype switch and NF-κB signaling mediated inflammatory response.

Time-Restricted Feeding Restored Insulin-Growth Hormone Balance and Improved Substrate and Energy Metabolism in MC4RKO Obese Mice

BACKGROUND

Dysregulation of metabolic regulatory hormones often occurs during the progress of obesity. Key regulatory hormone insulin-growth hormone (GH) balance has recently been proposed to maintain metabolism profiles. Time-restricted feeding (TRF) is an effective strategy against obesity without detailed research on pulsatile GH releasing patterns.

METHODS

TRF was performed in an over-eating melanocortin 4 receptor-knockout (MC4RKO) obese mouse model using normal food. Body weight and food intake were measured. Series of blood samples were collected for 6-h pulsatile GH profile, glucose tolerance test, and insulin tolerance test at 5, 8, and 9 weeks of TRF, respectively. Indirect calorimetric recordings were performed by the Phenomaster system at 6 weeks for 1 week, and body composition was measured by nuclear magnetic resonance spectroscopy (NMR). Substrate- and energy metabolism-related gene expressions were measured in terminal liver and subcutaneous white adipose tissues.

RESULTS

TRF increased pulsatile GH secretion in dark phase and suppressed hyperinsulinemia in MC4RKO obese mice to reach a reduced insulin/GH ratio. This was accompanied by the improvement in insulin sensitivity, metabolic flexibility, glucose tolerance, and decreased glucose fluctuation, together with appropriate modification of gene expression involved in substrate metabolism and adipose tissue browning. NMR measurement showed that TRF decreased fat mass but increased lean mass. Indirect calorimeter recording indicated that TRF decreased the respiratory exchange ratio (RER) reflecting consumption of more fatty acid in energy production in light phase and increased the oxygen consumption during activities in dark phase.

CONCLUSIONS

TRF effectively decreases hyperinsulinemia and restores pulsatile GH secretion in the overeating obese mice with significant improvement in substrate and energy metabolism and body composition without reducing total caloric intake.

Ghrelin receptor agonist hexarelin attenuates antinociceptive tolerance to morphine in rats

Ghrelin, a peptide hormone released from the gastric endocrine glands, shows analgesic activity apart from its various physiological effects. Nevertheless, the effects of ghrelin receptor (GHS-R) agonists on morphine analgesia and tolerance have not yet been elucidated. The purpose of this study was to evaluate the effects of the ghrelin receptor agonist hexarelin and antagonist [d-Lys3]-GHRP-6 on morphine antinociception and tolerance in rats. A total of 104 Wistar albino male adult rats (weighing approximately 220-240 g) were used in the experiments. To induce morphine tolerance, a three-day cumulative dose regimen was used in the rats. Then, randomly selected rats were evaluated for morphine tolerance on day 4. The analgesic effects of hexarelin (0.2 mg·kg-1), [d-Lys3]-GHRP-6 (10 mg·kg-1), and morphine (5 mg·kg-1) were measured at 30-min intervals (0, 30, 60, 90, and 120 min) by tail-flick and hot-plate analgesia tests. The findings suggest that hexarelin in combination with morphine attenuates analgesic tolerance to morphine. On the other hand, ghrelin receptor antagonist [d-Lys3]-GHRP-6 has no significant analgesic activity on the morphine tolerance in analgesia tests. Furthermore, co-administration of hexarelin and morphine increases the analgesic effect. In conclusion, these data indicate that administration of GHS-R agonist hexarelin with morphine enhances the antinociception and attenuates morphine tolerance.

Trabectedin and Lurbinectedin Extend Survival of Mice Bearing C26 Colon Adenocarcinoma, without Affecting Tumor Growth or Cachexia

Trabectedin (ET743) and lurbinectedin (PM01183) limit the production of inflammatory cytokines that are elevated during cancer cachexia. Mice carrying C26 colon adenocarcinoma display cachexia (i.e., premature death and body wasting with muscle, fat and cardiac tissue depletion), high levels of inflammatory cytokines and subsequent splenomegaly. We tested whether such drugs protected these mice from cachexia. Ten-week-old mice were inoculated with C26 cells and three days later randomized to receive intravenously vehicle or 0.05 mg/kg ET743 or 0.07 mg/kg PM01183, three times a week for three weeks. ET743 or PM01183 extended the lifespan of C26-mice by 30% or 85%, respectively, without affecting tumor growth or food intake. Within 13 days from C26 implant, both drugs did not protect fat, muscle and heart from cachexia. Since PM01183 extended the animal survival more than ET743, we analyzed PM01183 further. In tibialis anterior of C26-mice, but not in atrophying myotubes, PM01183 restrained the NF-κB/PAX7/myogenin axis, possibly reducing the pro-inflammatory milieu, and failed to limit the C/EBPβ/atrogin-1 axis. Inflammation-mediated splenomegaly of C26-mice was inhibited by PM01183 for as long as the treatment lasted, without reducing IL-6, M-CSF or IL-1β in plasma. ET743 and PM01183 extend the survival of C26-bearing mice unchanging tumor growth or cachexia but possibly restrain muscle-related inflammation and C26-induced splenomegaly.

Rhythmic growth hormone secretion in physiological and pathological conditions: Lessons from rodent studies

Evolutionally conserved in all mammalians, the release of GH occurs in a rhythmic pattern, characterized by several dominant surges (pulsatile GH) with tonic low inter-pulse levels (tonic GH). Such pulsatile secretion pattern is essential for many physiological actions of GH on different tissues with defined gender dimorphism. Rhythmic release of pulsatile GH is tightly controlled by hypothalamic neurons as well as peripheral metabolic factors. Changes of GH pattern occur within a range of sophisticated physiological and pathological settings and significantly contribute to growth, ageing, survival and disease predispositions. Precise analysis of GH secretion pattern is vitally important for a comprehensive understanding of the function of GH and the components that regulate GH secretion pattern.

The CD36-PPARγ Pathway in Metabolic Disorders

Uncovering the biological role of nuclear receptor peroxisome proliferator-activated receptors (PPARs) has greatly advanced our knowledge of the transcriptional control of glucose and energy metabolism. As such, pharmacological activation of PPARγ has emerged as an efficient approach for treating metabolic disorders with the current use of thiazolidinediones to improve insulin resistance in diabetic patients. The recent identification of growth hormone releasing peptides (GHRP) as potent inducers of PPARγ through activation of the scavenger receptor CD36 has defined a novel alternative to regulate essential aspects of lipid and energy metabolism. Recent advances on the emerging role of CD36 and GHRP hexarelin in regulating PPARγ downstream actions with benefits on atherosclerosis, hepatic cholesterol biosynthesis and fat mitochondrial biogenesis are summarized here. The response of PPARγ coactivator PGC-1 is also discussed in these effects. The identification of the GHRP-CD36-PPARγ pathway in controlling various tissue metabolic functions provides an interesting option for metabolic disorders.