The beneficial effects of metformin on cancer prevention and therapy: a comprehensive review of recent advances

Metformin is a widely used drug in today’s prescriptions by physicians due to its specific effects in treating and curing type II diabetes. Diabetes is a common disease that may occur throughout human life, and can increase the likelihood of the occurrence of various types of cancer, such as colon, rectum, pancreas and liver cancers, compared to non-diabetic patients. Metformin inhibits mTOR activity by activating ATM (ataxia telangiectasia mutated) and LKB1 (liver kinase B1) and then adenosine monophosphate-activated kinase (AMPK), and thus prevents protein synthesis and cell growth. Metformin can activate p53 by activating AMPK and thereby ultimately stop the cell cycle. Given the potential of metformin in the treatment of cancer, it can be used in radiotherapy, chemotherapy and to improve the response to treatment in androgen derivatives (ADT), and also, according to available evidence, metformin can also be used to prevent various types of cancers. Generally, metformin can: 1) reduce the incidence of cancers, 2) reduce the mortality from cancers, 3) increase the response to treatment in cancer cells when using radiotherapy and chemotherapy, 4) optimize tumor movement and reduce the malignancy, 5) reduce the likelihood of relapse, and 6) reduce the damaging effects of ADT. Therefore, this drug can be used as a complementary therapeutic agent for cancer treatment and prevention. In this review, we have summarized the data from various experimental and clinical studies and highlight the possible potential effects of metformin on cancer therapeutic responses.

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GABA(B) receptors and opioid mechanisms involved in homotaurine-induced analgesia

1. The involvement of GABA(B) receptors and opioid mechanisms in homotaurine-induced analgesia has been investigated in current models of nociception by using a GABA(B) receptor antagonist, morphine, and naloxone. CGP 35348 (50-200 mg/kg IP), a highly selective GABA(B) antagonist, was administered prior to carrying out a dose-response curve of homotaurine (22.6-445 mg/kg IP) antinociceptive effect in the abdominal constriction (mice) and tail flick (rats) tests. 2. The tail flick test was performed in animals pretreated with morphine (0.5 mg/kg SC) and naloxone (1 mg/kg), 15 min before amino acid. Animals treated with saline 10 ml/kg (mice) or 1.25 ml/kg (rats) were included as control for the vehicle used. 3. CGP 35348 antagonized the antinociceptive effect of homotaurine in both tests. The range of doses affected by the interaction depended on the test assayed, but it was coincident for the main part of the dose-response curve. 4. A subanalgesic dose of morphine potentiated the antinociceptive effect of lower doses of homotaurine in the tail flick test. Naloxone pretreatment inhibited the antinociceptive effect of homotaurine. 5. These data imply that GABA(B) receptor subpopulations and opiate mechanisms are involved in the antinociceptive effect of homotaurine. Because functional relationships have been found between GABAergic and opiate systems in analgesic effects, an interaction of the two mechanisms may be operating in the effects described for homotaurine.

Comparison of the Effect of EMLA™ Cream and the Valsalva Maneuver on Pain Severity during Vascular Needle Insertion in Hemodialysis Patients: A Controlled, Randomized, Clinical Trial

Background

Pain due to vascular needle insertion has been reported in 40-60% of hemodialysis (HD) patients. Evidence suggests that there is typically no single method for relieving the pain of inserting vascular needles in HD patients. This study aimed to compare the effectiveness of EMLA cream and Valsalva maneuver (VM) on pain severity during vascular needle insertion in HD patients.

Methods

This randomized, controlled, clinical trial was conducted on 90 patients undergoing hemodialysis in the hemodialysis unit of Kowsar Hospital, affiliated with Semnan University of Medical Sciences, in Semnan, Iran. Patients were selected via convenience sampling and were randomly assigned to one of the three groups (EMLA, VM, and control groups). For the patients in the EMLA group, 2.5 g of EMLA cream was applied 60 minutes before the start of dialysis. For patients in the VM group, a maneuver was performed for 16-20 seconds before the needle was inserted. Patients in the control group received only routine care without any additional interventions. The pain severity in the three groups was measured using the visual analog scale (VAS) two minutes after vascular needle insertion.

Results

The results showed that the mean pain severity during cannulation was 2.06 ± 2.19 in the EMLA group, 3.2 ± 30.42 in the VM group, and 6.20 ± 1.49 in the control group, suggesting a significant difference between the groups (P < 0.001). Pairwise comparison of the mean pain severity showed that it differed significantly in the EMLA and VM groups from the control group (P < 0.001), but no significant difference was found between the EMLA and VM groups (P=0.067).

Conclusion

According to the results, EMLA cream was as effective as VM in reducing the pain severity caused by arteriovenous fistula (AVF) cannulation. Therefore, the use of EMLA cream and VM is recommended for reducing the severity of AVF cannulation pain. Trial Registration. Iranian Registry of Clinical Trials, Trial No : IRCT20120109008665N12, registered on 3 June 2020.

Role of K+ -channels in homotaurine-induced analgesia

In previous articles, antinociceptive activity for homotaurine has been demonstrated to be mediated by opioid, GABAergic and cholinergic mechanisms. GABAB-agonists affect K+-channels and it is known that K+-channels modulate specific activation of opioid receptors. In this study, we examined the involvement of K+-channels in the antinociceptive activity of homotaurine (22-445 mg/kg). Antinociceptive response was obtained after icv pretreatment with the channel specific blockers 4-aminopyridine (voltage-dependent channels), tetraethylammonium (Ca++ and voltage-dependent) and gliquidone (ATP-dependent). The nociceptive tests performed were acetic acid induced abdominal constriction (mice) and tail flick (rats) tests. Acetic acid responses to homotaurine were inhibited by tetraethylammonium (5 microg) and gliquidone (16 microg). Tail flick response to homotaurine was inhibited by tetraethylammonium (50 microg), gliquidone (40 and 80 microg) and 4-aminopyridine (25 and 250 ng). These results suggest an involvement of the three types of K+-channels in antinociception by homotaurine, depending on specific homotaurine and blocker doses. At a spinal level, they appear to be involved together with GABAB and opioid mechanisms. Peripherally, only tetraethylammonium channels would be substantially activated during homotaurine antinociceptive effect.

Flaxseed oil (Linum Usitatissimum) attenuates restraint stress-induced depressive-like behavior: Upregulation of neurotrophic factors in CA1 region of hippocampus

Objectives: In this study, we aimed to evaluate the anti-depressant effects of FS oil on the depressive-like behavior following immobility stress in mice. Methods: In this study, 32 male mice were divided into four groups: Control group; FS oil group; Model group: The immobility stress (using falcon for 20 day, 6 hours a day) + feeding with normal saline by oral gavage for another 20 days); Model+FS group: The immobility stress + feeding with 0.2 ml/kg of FS oil by oral gavage for another 20 days. At the end, all mice were evaluated with tail suspension test (TST) and sacrificed through cardiac puncture method. The brain was isolated and prepared for molecular and histopathological studies. Results: The gene expression and protein level of BGNF and GDNF were significantly increased in FS oil treated groups (P<0.05). In microscopic evaluations, the number of dead neurons significantly deceased in FS group (P<0.05). TST results showed a significant decrease in immobility time and depressive-like behaviors in FS oil treated group (P<0.05). Conclusion: FS oil feeding may be effective in treatment of depressive like disorders through its anti-oxidative and neurotrophic promoting features. Therefore, it can be used as an appropriate alternative choice in daily diet to prevent depression in clinical investigations.