Effects on Glucagon Secretion from Pancreatic α Cells
The first CBD metabolites to be identified were isolated from rat liver homogenate and their structures were determined as a primary alcohol derived from the oxidation at the allylic C-7 methyl group on the cyclohexene moiety (7-OH-CBD) and a secondary alcohol resulting from the oxidation of the central (C-3) methylene group of the pentyl side chain (3-OH-CBD; for numbering, see Fig. 1) in ,57a Since then, biotransformation studies in mammals, including humans, using various types of CBD administration have indicated considerable species ,58,59 All studies in vivo appear to have been restricted to the characterization of urinary CBD metabolites.Fats strongly enhance GIP secretion38,113, and GIP levels are high in obese T2DM patients114. GIP has been proposed to have a physiological role on nutrient uptake into adipose tissues, thereby linking overnutrition to obesity. An initial clue came in the early 1980s from an experiment showing that GIP, in the presence of insulin, induces fatty acid incorporation into rat epididymal fat pads115. Later, GIPR was shown to be expressed in adipose tissues116, and genetic ablation of GIPR further shows the critical role of GIP in fat accumulation26. Several drugs used in therapy are metabolically converted into active metabolites and interindividual variations in the generation and pharmacokinetics of such active species may cause variability in the response to treatment by different The use of relatively high daily doses of CBD in human clinical trials as well as in self-medicating patients is not uncommon. For example, in a 30-day CBD monotherapy study, an escalating oral dose reaching 1280mg/day was Although information is lacking, the metabolites formed from CBD are assumed to be present in the body at pharmacologically relevant concentrations.
Other important compounds present in garlic homogenate are 1 -propenyl allyl thiosulfonate, allyl methyl thiosulfonate, (E,Z)-4,5,9-trithiadodeca- l,6,11-triene 9- oxide (ajoene), and y-L-glutamyl-S-alkyl- L-cysteine. The adenosine concentration increases several-fold as the homogenate is incubated at room temperature for several hours. There have been only a few in vivo investigations with selected monooxygenated metabolites. In the standard mouse tetrade test using i. p. injection of 20mg/kg of the compounds, Fride et al. reported84 that CBD was inactive that reflects its lack of affinity to central CB1 and CB2 receptors (see Bisogno et ); 7-COOH-CBD caused slight hypothermia (1. 1C) and a minimal inhibition of intestinal motility (defecation).
, 1986 ), and damage membranes (Ghannoum, 1988 ). Over 100years have passed since the discovery of the incretin concept, which later opened up the possibility of a novel therapy in the treatment of diabetes. Inspired by Bayliss and Starlings discovery of secretin in 19021, Moore etal. hypothesized that gut extracts contain a hormone that regulates the endocrine pancreas, and showed that administration of gut extracts reduces the amount of urine sugars in patients with diabetes, presumably through stimulation of the endocrine pancreas2. In 1929, La Barre purified the glucoselowering element from gut extracts, and named it incretin (INtestine seCRETtion Insulin)3. However, incretin was forgotten for three decades until radioimmunoassay to measure insulin became available in the 1960s. Oral glucose load was shown to produce a much greater insulin response than i. v. injection of glucose4,5, which now can be attributed to incretins released from the gut after ingestion of glucose or nutrients to stimulate insulin secretion from pancreatic β cells. Secretion and metabolism of glucosedependent insulinotropic polypepide (GIP) and glucagonlike peptide (GLP)1.
6μg/mL at 4h and 8. 6μg/mL at 4h, respectively). The effects of cosolvents and excipients on pharmacokinetics, involving cytochrome P450 (CYP450) oxidases and P-glycoprotein efflux transporters, of lipophilic substances in general have been extensively ,54 Interestingly, inspection of the chemical structures of the abundant 7-COOH-CBD derivatives, which account for about the half of the metabolites identified in the above study, reveals the branched alkyl chain of (2E)-2-propylpent-2-enoic acid (Δ2(E)-valproate) embedded in the cyclohexenecarboxylic acid moiety of such acidic CBD metabolites.
During a Phase I study with healthy male subjects, potential drugdrug interactions of THC/CBD oromucosal spray (Sativex, nabiximols) in combination of CYP450 inducers and inhibitors were assessed using various dose The antibiotic rifampicin, an inducer of CYP3A4 involved in the metabolism of CBD, significantly reduced the peak plasma concentration of CBD, while the antifungal ketoconazole, a CYP3A4 inhibitor, nearly doubled the peak plasma concentration of CBD; however, the moderate CYP2C19 inhibitor omeprazole, a proton-pump inhibitor used to treat gastroesophageal reflux disease, did not significantly alter the pharmacokinetics of CBD. The presence and role of CBD metabolites in the observed drug interactions have not been reported. Antifingal activity was first established in 1936 by Schmidt and Marquardt whilst working with epidermophyte cultures (Lemar et al. , 2002 ). Many fungi are sensitive to garlic, including Candida (Yousuf, 2011 ), Torulopsis, Trichophyton, Cryptococcus (Fromtling and Bulmer, 1978), Aspergillus (Hitokoto et al. , 1980 ), Trichosporon, and Rhodotorula (Tansey and Appleton, 1975 ). Garlic extracts have been shown to decrease the oxygen uptake (Szymona, 1952 ), reduce the growth of the organism, inhibit the synthesis of lipids, proteins, and nucleic acids (Adetumbi et al.
Physiological Functions of Endogenous GIP and GLP1 in Other Organs
Activation of PKA and EPAC2 by elevated cAMP levels was also shown to inhibit activation of caspase3 and subsequent apoptosis of palmitatetreated RINm5F cells88 (Figure6). Activation of Akt/PKB, a downstream effecter of PI3K, by GLP1 was also shown to prevent apoptosis of INS1 cells in response to glucolipotoxicity or staurosporin89,90, possibly through the activation of nuclear factor kappalightchainenhancer of activated B cells (NFκB) and the upregulation of the antiapoptotic NFκB target genes bcl2 and IAP289. GLP1R activation also reduces the ER stress response, thereby promoting β cell survival in INS1 cells as well as in human islets9193. A critical difference in the antiapoptotic function of GLP1 is the requirement for PI3K, which is not required for the antiapoptotic action of GIP. While activation of Akt/PKB by GIP is mediated by EPAC282, activation of Akt/PKB by GLP1 requires CREBmediated induction of IRS2, which might also potentiate PI3K and Akt/PKB94 (Figure6).
Binding of GIP and GLP1 to their specific receptors, the GIP receptor (GIPR) and the GLP1 receptor (GLP1R) leads to activation of adenylate cyclase and subsequent elevation of intracellular cyclic adenosine monophosphate (cAMP) levels. Increased cAMP then activates protein kinase A (PKA) and exchange protein activated by cAMP2 (EPAC2)/cAMPguanine nucleotide exchange factor (GEF)II. Activation of PKA promotes closure of KATP channels and facilitates membrane depolarization. PKA also leads to inhibition of the delayed rectifying K+ (Kv) channel, a negative regulator of insulin secretion in pancreatic β cells, resulting in prolongation of action potentials. Depolarization opens the voltagegated Ca2+ channels (VDCC), allowing an increase of intracellular Ca2+ concentrations that mobilizes Ca2+ from intracellular stores through PKA and EPAC2dependent mechanisms. The increased Ca2+ concentrations eventually trigger fusion of insulincontaining granules with the plasma membrane and insulin secretion from the β cells.
Although it is not discussed in the present review, recent advances in understanding the molecular mechanisms underlying GIP and GLP1 secretion from K and L cells49 should clarify the differing results on GIP and GLP1 responses in T2DM patients in the various studies. Cannabielsoin (at 10mg/kg i. v. ) showed no CNS activity in rodents,86 and did not affect body temperature or pentobarbital-induced sleep time in ,67 In rabbits, a 5mg/kg i. v. dose of cannabielsoin reduced intraocular pressure; CBD had no effect at 10mg/kg, while THC was active at 1mg/ Racial differences in secretion and metabolism of (a) glucosedependent insulinotropic polypepide (GIP) and (b) glucagonlike peptide (GLP)1. GIP secretion in healthy Japanese subjects after ingestion of glucose or mixed meals were higher than those of healthy Caucasian subjects, whereas levels of intact GIP were similar37,4042. This suggests processing of GIP by dipeptidyl peptidase4 (DPP4) in Japanese subjects might be enhanced. Considerably low levels of intact GLP1 after ingestion of glucose or mixed meals are also consistent with enhanced DPP4 activities in Japanese subjects.
, 2013a ). Finally, an analysis of in vivo distribution of CBs in five postmortem cases indicated relatively high CBD concentrations in bile (up to 63ng/mL) and muscle (up to 32ng/g) tissues, and it was noted that the CBD content of the brain was unexpectedly high (up to 6. 7ng/g)48 (see also Fabritius et ). In these cases, however, factors influencing CB pharmacokinetics were unknown. The investigation revealed 24 occurrences of the common cold in the garlic group compared with 65 in the placebo group, resulting in fewer days of illness in the garlic group compared with the placebo group. However, claims of effectiveness of garlic on common cold appear to rely largely on poor quality evidence (Lissiman et al. , 2012 ). Many countries have used garlic extract for clinical treatments, but the untoward actions of garlic following long-term administration should be fully noted. Even though many studies on garlic and its derivatives have been performed, the exact biological mechanism of garlic extract still remains to be elucidated.
A meta-analysis including 39 primary trials of the effect of 2 months administration of garlic preparations on total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides was performed (Ried et al. , 2013b ). The results suggest garlic is effective in reduction of total serum cholesterol by 176 mg/dL and low-density lipoprotein cholesterol by 9 6 mg/dL in subjects with elevated total cholesterol levels (>200 mg/dL). An 8 reduction in total serum cholesterol is of clinical relevance and is associated with a 38 reduction in risk of coronary events at 50 years of age. High-density lipoprotein cholesterol levels improved only slightly, and triglycerides were not influenced significantly. Garlic was highly tolerable in all trials and was associated with minimal side effects. The antiapoptotic function of GLP1 on pancreatic β cells was suggested by studies of the pancreas of exendin4treated db/db mice or GLP1infused diabetic VDF Zucker rats, which showed an increase in β cell mass and a decrease in apoptotic β cells85,86. Subsequently, it was shown that activation of GLP1R by exendin4 inhibits apoptosis of MIN6 cells exposed to hydrogen peroxide in a cAMP and PI3Kdependent manner, in association with upregulation of Bcl2 and BclxL, and reduced poly(ADPribose)polymerase87.
Cannabidiol (CBD), the main nonpsychoactive constituent of Cannabis sativa, has shown a wide range of therapeutically promising pharmacological effects either as a sole drug or in combination with other drugs in adjunctive therapy. However, the targets involved in the therapeutic effects of CBD appear to be elusive. Furthermore, scarce information is available on the biological activity of its human metabolites which, when formed in pharmacologically relevant concentration, might contribute to or even account for the observed therapeutic effects. The present overview summarizes our current knowledge on the pharmacokinetics and metabolic fate of CBD in humans, reviews studies on the biological activity of CBD metabolites either in vitro or in vivo, and discusses relevant drugdrug interactions. To facilitate further research in the area, the reported syntheses of CBD metabolites are also catalogued. Ancient Chinese and Indian medicine recommended garlic to aid respiration and digestion and to treat leprosy and parasitic infestation (Rivlrn, 1998 ).
Pharmacological studies with such metabolites are scarce yet suggest interesting biological activities, which are unrelated or not directly related to CB receptors. Thus, intriguing questions arise: Another important aspect of GIP and GLP1 action on β cells is the stimulation of the proliferation of β cells and/or progenitor cells. An early investigation evaluating the effects of exendin4 in rats showed that activation of GLP1R promotes proliferation and neogenesis of pancreatic β cells96. Later, proliferative effects were also shown of GIPR activation in INS1 cells97,98. It has been shown that GIP activates the RafMek1/2ERK1/2 signaling module through cAMP/PKA signaling in GIPRoverexpressing Chinese hamster ovary cells98100 (Figure6). Consistent with these observations, PKA and MEK inhibitors have been shown to prevent GIPinduced proliferation of cultured islet cells101.
PKA, together with phosphoinositide 3kinase (PI3K), also leads to inhibition of the delayed rectifying K+ (Kv) channel, which results in prolongation of action potentials68. Depolarization opens the voltagegated Ca2+ channels (VDCC), allowing an increase of intracellular Ca2+ concentrations, which then mobilizes Ca2+ from intracellular stores through PKA and EPAC2dependent mechanisms6973. The increased Ca2+ concentrations eventually trigger fusion of insulincontaining granules with the plasma membrane and increase insulin secretion from the β cells. Mobilization of Ca2+ from intracellular stores stimulates adenosine triphosphate (ATP) synthesis in mitochondria, which further enhances membrane depolarization by KATP channel closure74. Furthermore, activation of EPAC2 has recently been shown to increase the density of insulincontaining granules near the plasma membrane, facilitating insulin secretion from the β cells75.
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The same study further showed that GIP, as well as GLP1, induces transcription of cyclin D1 that is critical for G1 phase progression and Sphase entry in most cell types101. Interestingly, PI3K inhibitor also prevents GIP and GLP1dependent proliferation of cultured islet cells and INS1 cells, suggesting involvement of the PI3K pathway in the proliferation of pancreatic β cells induced not only by GLP1, but also by GIP. Delineation of the proliferative action of GLP1 further showed that it involves activation of PI3K and upregulation of PDX1 transcription through transactivation of epidermal growth factor receptor (EGFR)102,103. Although these findings could explain the involvement of EGFR transactivation and subsequent PI3K activation in the proliferative action of GLP1, whether or not the same mechanism might be involved in the proliferative action of GIP must be investigated. Importantly, the proliferative and antiapoptotic effects of GIP and GLP1 on pancreatic β cells could be achieved by pharmacological levels of incretins rather than physiological levels, because no reduction of β cell mass has been reported in animals lacking both GIPR and GLP1R25,27,29.
Garlic administration in rats suffering from hypercholesterolemia, induced by a high-cholesterol diet, significantly reduced serum cholesterol, triglyceride, and LDL, but there was no effect on serum HDL (Kamanna and Chandrasekhara, 1982 ). In in vitro experiments, garlic administration suppressed LDL oxidation and increased HDL, which may be one of the protective mechanisms of the beneficial effects of garlic in cardiovascular health (Rahman and Lowe, 2006 ). Long term application of garlic and its preparations on experimental atherosclerosis induced by a high cholesterol diet, showed 50 reduction in atheromatous lesions, particularly in the aorta (Jain, 1977 ). Most of human studies on lipid lowering effects of garlic and garlic preparations described significant decrease in serum cholesterol and triglyceride (Gardner et al. , 2001 ; Ziaei et al. , 2001 ).
Nevertheless, the proliferative effects of GIP and GLP1 on pancreatic β cells are clinically relevant for treatment of diabetes, and remain to be tested in patients with diabetes. In the case of HIV, it is thought that ajoene acts by inhibiting the integrin dependent processes (Tatarintsev et al. , 1992 ). Allyl alcohol and diallyl disulfide have also proven effective against HIV-infected cells (Shoji et al. , 1993 ). No activity has been observed with allicin or S-allyl cysteine. It appears that only allicin and allicin-derived substances are active. Taken together, the beneficial effects of garlic extract make it useful in medicine. There are insufficient clinical trials regarding the effects of garlic in preventing or treating the common cold. A single trial suggested that garlic may prevent occurrences of the common cold, but more studies are needed to validate this finding. This trial randomly assigned 146 participants to either a daily garlic supplement (with 180 mg of allicin content) or a placebo for 12 weeks. For example, GIP has been shown to have an antiapoptotic function in pancreatic β cells.
However, the molecular mechanisms underlying the impaired insulinotropic action of GIP in T2DM patients are still largely unknown. Various studies in model animals suggest downregulation of GIPR mRNA5558, accelerated degradation of GIPR59, and alternative splicing of GIPR mRNA60, all of which might contribute to the reduced GIP sensitivity of pancreatic β cells. Polymorphisms in the human GIPR gene have been shown to decrease GIP sensitivity in β cells, but no correlation has been observed between these polymorphisms and T2DM61. However, genetic variation in GIPR has been recently reported to be associated with the reduction in early phase insulin reaction and elevation in 2h glucose levels after ingestion of 75gram glucose, suggesting that defective GIPR signaling might play a critical role in the early pathophysiology of impaired glucose tolerance and T2DM62. It remains to be determined why GIP but not GLP1 signaling is selectively impaired in hyperglycemic conditions in humans.
The physiological impact of differences in PI3K requirement and other yet to be identified differences between GIP and GLP1 have recently been investigated in mice treated with GLP1R agonist, GIPR agonist or DPP4 inhibitor95. This study showed that GLP1R agonist exerts the most robust effect on the survival of β cells compared with that of GIPR agonist or DPP4 inhibitor invivo in mice95. Further investigation of the mechanisms underlying the effects of GIP and GLP1 could show potential therapeutic targets to increase β cell mass by inhibiting apoptosis. With regard to metabolic enzymes, not only CBD but also its 6α/β-OH, 6-oxo (not observed species in humans), and 10-OH metabolites effectively inactivated mouse liver microsomal CYP2C and CYP3A oxidases isolated from mice treated i. p. with 120mg/kg The key role of the resorcinol moiety of CBD (and of its metabolites) in the inhibition has been ,76 A recent patent described 7-OH- and 7-COOH-CBD as anti-inflammatory substances in the mouse and as dose-dependent inhibitors in vitro of the generations of nitric oxide and reactive oxygen species as well as the production of TNF-α.
GIP is secreted from K cells of the upper intestine; GLP1 is secreted from L cells of the lower intestine. Released GIP and GLP1 rapidly undergoes proteolytic processing by dipeptidyl peptidase4 (DPP4), and is thereby inactivated and excreted from the kidney. The intact incretins, GIP(142), GLP1(737), and GLP1(736)amide, have insulinotropic effects on pancreatic β cells, whereas the DPP4processed incretins, GIP(342), GLP1(937), and GLP1(936)amide, have lost their insulinotropic effects. Enhancement of glucosedependent insulin secretion by incretins in healthy volunteers was directly shown by i. v. infusion of GIP9 and GLP116; their insulinotropic effects are similar50 and additive51 in healthy humans. Critically, the effects of infused GIP at pharmacological levels are impaired in Caucasians with T2DM, although those of GLP1 are substantially preserved52,53. The insulinotropic effects of endogenous GIP are also diminished in Japanese T2DM patients48. Furthermore, the impaired insulinotropic action of GIP, but not that of GLP1, are strikingly similar in perfused islets of diabetic GotoKakizaki rats54.
These effects have been largely attributed to i) reduction of risk factors for cardiovascular diseases, ii) reduction of cancer risk, iii) antioxidant effect, iv) antimicrobial effect, and v) enhancement of detoxification foreign compound and hepatoprotection (Colín-González, 2012 ; Aviello, 2009 ). In this review, a survey on current experimental as well as clinical state of knowledge about the preventive and therapeutic effects of garlic in different diseases is given. Several studies have shown that the extract was effective against a host of protozoa including Candida albicans (Lemar et al. , 2002 ), Scedosporium prolificans (Davis et al. , 2003 ), tinea pedis (Ledezma et al. , 2000 ), Opalina ranarum, Balantidium entozoon, Entamoeba histolytica, Trypanosomes, Leishmania, Leptomonas, and Crithidia (Reuter et al. , 1966 ). Garlic has been used for centuries in various societies to combat infectious disease.
Interestingly, unnatural (+)-CBD and its 7-OH and 7-COOH derivatives potently inhibited defecation indicating peripheral activity perhaps through a CB receptor-independent mechanism; furthermore, weak antinociceptive effects for 7-OH-(+)-CBD were also ,77 As mentioned before, antinociceptive as well as anti-inflammatory effects in mice of 7-OH-CBD and 7-COOH-CBD have been described in a patent but these experiments used chemicals as noxious A recent study compared plasma and brain levels of CBD after oral or intraperitoneal (i. p. ) administrations of the drug in Cremophor at 120mg/kg to rats and Following i. p. administration, mice had a higher CBD plasma level than rats (14. 3 and 2. 6μg/mL, respectively), whereas oral dosing resulted in a similar peak plasma concentration in both species (2μg/mL). Oral administration offered six times higher brain peak CBD concentrations in rats than in mice (8. 6 vs. 1. 3μg/g). It was also noted that oral administration of CBD (120mg/kg) dissolved in the micelle-forming Solutol resulted in enhanced absorption of the drug compared to the solution based on the emulsion-forming surfactant Cremophor as evidenced by higher peak concentrations and prolonged exposures in blood (3. 2μg/mL at 6h and 2μg/mL at 2h, respectively) and brain (12.
Historically, it is believed that Louis Pasteur described the antibacterial effect of garlic in 1858 for the first time, although no reference is available. More recently, garlic has been proven to be effective against a plethora of gram-positive, gram-negative, and acid-fast bacteria. These include Salmonella, Escherichia coli (Adler and Beuchat, 2002 ), Pseudomonas, Proteus, Staphylococcus aureus (Cavallito, 1944 ), Escherichia coli, Salmonella (Johnson and Vaughn, 1969 ), Klebsiella (Jezowa and Rafinski, 1966 ), Micrococcus, Bacillus subtulis (Sharma et al. , 1977 ), Clostridium (De Witt et al. , 1979 ), Mycobacterium (Delaha and Garagusi, 1985 ), and Helicobacter (OGara et al. , 2000 ). It has been documented that garlic exerts a differential inhibition between beneficial intestinal microflora and potentially harmful enterobacteria (Ress et al. , 1993 ). The human skin permeation of CBD solutions was investigated in vitro and CBD concentrations as high as 6.
This effect involves activation of the cAMP response elementbinding (CREB) and Akt/PKB pathways (Figure6). In INS1 cells, binding of GIP to GIPR leads to the elevation of intracellular cAMP levels and activation of PKA, which then migrates into the nucleus and directly phosphorylates nuclear CREB79,80. In addition, activated PKA inhibits AMPK, which then results in dephosphorylation and nuclear import of the transducer of regulated CREB activity 2 (TORC2)79. In the nucleus, phosphorylated CREB and TORC2 form a complex in the promoter of the antiapoptotic gene bcl2, thereby promoting its gene transcription79. Binding of GIP to GIPR also results in the activation of Akt/PKB, promoting phosphorylation of the nuclear transcription factor Foxo1 in INS1 cells (Figure6)81. Phosphorylated Foxo1 is exported from the nucleus, leading to downregulation of the proapoptotic gene bax, one of the Foxo1 direct target genes, which promotes β cell apoptosis in response to glucolipotoxicity81.
In the medieval period, garlic was also played an important role in the treatment of different diseases. Avicenna (1988) , in his well-known book, Al Qanoon Fil Tib (The Canon of Medicine), recommended garlic as a useful compound in treatment of arthritis, toothache, chronic cough, constipation, parasitic infestation, snake and insect bites, gynecologic diseases, as well as in infectious diseases (as antibiotic). With the onset of Renaissance, special attention was paid in Europe to the health benefits of garlic. Garlic has attracted particular attention of modern medicine because of widespread belief about its effects in maintaining good health. In some Western countries, the sale of garlic preparations ranks with those of leading prescription drugs. There is appreciable epidemiologic evidence that demonstrates therapeutic and preventive roles for garlic. Several experimental and clinical investigations suggest many favorable effects of garlic and its preparations.
Taken together, these lines of evidence show the critical functions of PKA and EPAC2 pathways in the insulinotropic actions of GIP and GLP1. The first demonstration of CB biotransformation in humans appears to be the study of Christiansen and Rafaelsen56 who in 1969 reported the separation by thin layer chromatography several polar CB derivatives from the urine of 10 volunteers drinking cannabis tea; however, no attempts were made to identify the substances. Subsequently, the use of sophisticated analytical techniques, especially GC-MS and, occasionally, reliance on synthetic standards for structure confirmation allowed the unequivocal identification of CB metabolites in humans (see below). It has been suggested that the mechanism of antihypertensive activity of garlic is due to its prostaglandin-like effects, which decrease peripheral vascular resistance (Rashid and Khan, 1985 ). Aged garlic extract was superior to placebo in lowering systolic blood pressure in patients suffering from uncontrolled hypertension. A dosage of 240-960 mg of aged garlic extract containing of S-allylcysteine significantly lowered blood pressure by about 12 mmHg over 12 weeks (Ried et al.
Molecular mechanisms underlying the antiapoptotic and proliferative effects of glucosedependent insulinotropic polypepide (GIP) and glucagonlike peptide (GLP)1. Signaling cascades linking the GIP receptor (GIPR) and the GLP1 receptor (GLP1R) with antiapoptotic and proliferative effects share similarities and differences as shown. Involvement of epidermal growth factor (EGFR) and phosphoinositide 3kinase (PI3K) has been shown to be a critical difference between the GIPR and GLP1Rsignaling pathways.
77 Because GIP and GLP1 rapidly undergo proteolytic degradation catalyzed by DPP430,31, not only intact but also total (i. e. intact plus DPP4metabolized) forms of GIP and GLP1 must be measured to study their secretion and processing invivo (Figure3). However, immunoassays for GIP and GLP1 levels, especially those used to measure their intact forms in plasma, require specific antibodies and are not widely available33. Furthermore, because carboxylterminal arginine of GLP1 is susceptible to amidation, GLP1 occurs in both nonamidated GLP1(737) and amidated GLP1(736)amide, both of which show similar insulinotropic effects and metabolism in humans34. Although most of the GLP1 secreted from the gut is amidated in humans35, careful considerations are required when measuring the levels of GLP1 because some antibodies only recognize amidated GLP1. Glucuronidation of CBD at the phenolic oxygen is a major Phase II biotransformation in humans,59,62 but hydroxylated metabolites of CBD may also be substrates. Sulfation of CBD species may also occur but such conjugates remain unknown. Studies should thus use appropriate hydrolysis before Phase I metabolite Anti-proliferative activity of ajoene was demonstrated against a panel of human tumor cell lines (Li et al. , 2002 ).
Δ2(E)-Valproate is the major active metabolite of valproic acid, and unlike the parent saturated acid, its anticonvulsant properties are not compromised by hepatotoxicity and teratogenicity, and is well tolerated in Whether the 7-COOH-CBD metabolite species with a Δ2(E)-valproate-like structure are involved in the antiepileptic activity of CBD remains to be established. The antibacterial effect of different concentrations of garlic extract against human dental plaque microbiota has been shown in in vitrostudy (Houshmand et al. , 2013 ). The synergism between ciprofloxacin with garlic extract has been shown, but not between ampicillin and the garlic extracts (Zain al-abdeen et al. , 2013 ). The cloves of garlic and rhizomes of ginger, extracted with 95 ethanol, suggested to have anti-bacterial activity against multi-drug clinical pathogens and can be used for prevention of drug resistant microbial diseases. Pseudomonas aeruginosa was the most sensitive germ to the mixture (Karuppiah and Rajaram, 2013 ). Garlic also suggested as a treatment for multi-drug resistant tuberculosis (Dini et al. , 2011 ).
Effects on Glucagon Secretion from Pancreatic α Cells
1mg per gram skin preparation could be achieved under certain experimental Various CBD formulations for transdermal and intranasal delivery have also been studied in rodent ,45 Although GIP was shown to increase the activity of lipoprotein lipase (LPL), an enzyme that is bound to the cell surface of adipocytes and hydrolyzes lipoproteinassociated triglycerides to produce free fatty acids available for local uptake26, the molecular mechanism by which GIP acts on adipocytes is largely unknown. It was recently shown that binding of GIP to GIPR in 3T3L1 cells and rat epididymal fat results in enhanced secretion of resistin through a pathway involving p38 MAPK and the stressactivated protein kinase/Jun aminoterminal kinase (SAPK/JNK)124. GIP activates PI3K and Akt/PKB through secreted resistin, thereby suppressing AMPK and increasing LPL activity in adipocytes124,125. Interestingly, another GIPR agonist, DAla2GIP(130), shows a potency equivalent to GIP(142) on β cell function and survival, but greatly reduced action on lipoprotein lipase activity in 3T3L1 cells126.
Further investigation on the differential effects of DAla2GIP(130) in β cell and adipocytes might shed light on the molecular mechanisms underlying GIP action in fat accumulation as well as might open up a possibility of GIPbased antidiabetic therapy that does not promote obesity. Importantly, GLP1 does not show any role in fat accumulation. While GLP1R is expressed in adipocytes127, activation of GLP1R affects none of the aforementioned signaling molecules and does not increase LPL activity in adipocytes124,125. Another important aspect of the insulinotropic effects of GIP and GLP1 is their synergy with the sulfornylurea drugs. Sulfornylureas efficiently cause mobilization of Ca2+ by closure of the KATP channels, membrane depolarization and subsequent VDCC opening, even in T2DM patients with impaired mitochondrial ATP production. As discussed earlier, GIP and GLP1 affects events downstream of the KATP channel closure, thereby enhancing the ability of sulfornylureas to promote insulin secretion (Figure5). In addition, it has recently been shown that certain sulfornylureas bind to EPAC2 and activate downstream molecules78, thereby enhancing the insulinotropic effects of GIP and GLP1.
Taken together, it is clinically important to note that sulfornylureas and incretinrelated therapies act synergistically to stimulate insulin secretion. Thus, caution is required for the combination of sulfornylureas and incretinrelated drugs that potentially cause hypoglycemia, especially among Asians in whom diabetes is characterized by reduced insulin secretory capacity and sulfornylureas would be the first choice of drugs. In both Caucasians and Japanese with type2 diabetes (T2DM), the GIP response is enhanced compared with that in healthy volunteers47,48, whereas the GLP1 response in Caucasians with T2DM is reduced compared with that in healthy controls37. The physiological cause for the enhanced GIP response in patients with T2DM is not yet clear. Furthermore, the incretin response in T2DM patients is still controversial, because Caucasian and Japanese patients with a relatively short duration of diabetes show GIP and GLP1 response similar to those of healthy controls36,42.
Downregulation of Bax and upregulation of Bcl2 is observed not only in INS1 cells, but also in islets of the Vancouver diabetic fatty (VDF) Zucker rats receiving 2week continuous infusion of GIP81. While the mechanisms underlying activation of Akt/PKB by GIP are yet unclear, it has been shown recently that activation of EPAC2, but not PI3K, Erk1/2 or PKA, is responsible for Akt/PKB activation and the antiapoptotic function of GIP82. Furthermore, activation of Akt/PKB by GIP has been shown to suppress mitochondrial translocation of Bad and BimEL and the subsequent activation of caspase3 by inhibiting p38 MAPK and JNK in INS1 cells exposed to staurosporin, a rapid activator of the mitochondriamediated apoptotic pathway83,84. Suppression of p38 MAPK and JNK has also been shown to be critical for the antiapoptotic actions of GIP in INS1 cells exposed to endoplasmic reticulum (ER) stress and genotoxic stress84.
Furthermore, allicin inhibits proliferation of human mammary endometrial and colon cancer cells. Growth inhibition is accompanied by an accumulation of the cells in WIG1 and G2lM phase of the cell cycle. Thus allicin is also responsible for the anti-proliferative effect of garlic derivatives. Diallyl sulfide and diallyl disulfide, inhibit arylamine N-acetyltransferase activity and 2-aminofluorene-DNA in human promyelocytic leukemia cells (Lin et al. , 2002 ). Reduction of the risk of some malignancies by consumption of selenium-enriched plants, such as garlic was suggested (Finley, 2003 ). DATS inhibited cell growth of human melanoma A375 cells and basal cell carcinoma cells by enhancement of the levels of intracellular reactive oxygen species and DNA damage and by inducing endoplasmic reticulum stress and mitochondria-mediated apoptosis (Wang et al. , 2012 ). Molecular mechanisms underlying the insulinotropic effects of glucosedependent insulinotropic polypepide (GIP) and glucagonlike peptide (GLP)1.
AC, adenylate cyclase; Akt, vakt murine thymoma viral oncogene homolog; Bad, Bcl2 antagonist of cell death; Bcl, Bcell CLL/lymphoma; BimEL, Bcl2 interacting mediator of cell death EL; BTC, betacellulin; cAMP, cyclic adenosine monophosphate; CREB, cAMP response elementbinding; cSrc, protooncogene tyrosineprotein kinase Src; EPAC2, exchange protein directly activated by cAMP2; ERK, extracellular signalregulated kinase; Foxo1, forkhead box protein O1; IRS2, insulin receptor substrate 2; JNK, cJun Nterminal kinase; MAPK, mitogenactivated protein kinase; Mek, mitogenactivated protein kinase kinase; NFκB, nuclear factor kappalightchainenhancer of activated B cells; PDX1, pancreas/duodenum homeobox protein 1; PKA, protein kinase A; PKB, protein kinase B; TORC2, transducer of regulated CREB activity 2. Garlic is a bulbous plant; grows up to 1. 2 m in height. Garlic is easy to grow and can be grown in mild climates (Figure). There are different types or subspecies of garlic, most notably hardneck garlic and softneck garlic. Allicin (allyl 2-propenethiosulfinate or diallyl thiosulfinate) is the principal bioactive compound present in the aqueous extract of garlic or raw garlic homogenate. When garlic is chopped or crushed, allinase enzyme is activated and produce allicin from alliin (present in intact garlic).
Increased Ca2+ levels also promote transcription of the proinsulin gene, thereby increasing the insulin content of the β cell. Activation of EPAC2 has been shown to increase the density of insulincontaining granules near the plasma membrane to potentiate insulin secretion from the β cell. ATP, adenosine triphosphate. Both GIP and GLP1 exert their insulinotropic effects by binding to GIP and GLP1 receptors expressed on pancreatic β cells. Incretinbound receptors increase intracellular cAMP levels63,64, thereby activating protein kinase A (PKA)65 and exchange protein activated by cAMP2 (EPAC2)/cAMPguanine nucleotide exchange factor (GEF) II66. PKA and EPAC2 are involved in a wide variety of intracellular events including altered ion channel activity, elevated cytosolic calcium levels and enhanced exocytosis of insulincontaining granules, all of which contribute to stimulation of insulin section in a glucosedependent manner (Figure5). Many studies have been carried out using inhibitors and activators that affect signal transduction or GLP1 receptor agonist exentin4, assuming that the molecular mechanisms downstream of both GIPR and GLP1R are similar. Activation of PKA results in phosphorylation of the SUR1 subunit, thereby closing the KATP channels and facilitating membrane depolarization67.
Experiments in vitro with seven recombinant human CYP450 isoforms indicated 6α-OH-, 6β-OH-, 7-OH-, and 4-OH-CBD as main monohydroxylated Specifically, CYP1A1 is involved in the formation of 6α/β-OH-, 7-OH-, and 1-OH-CBD; CYP1A2 is responsible for the formation of 6α/β-OH-CBD, as well as of 1-, 2-, 3-, and 4-OH-CBD species; CYP2C19 is involved in the formation mostly of 6α-OH-, 7-OH-, and 4-OH-CBD; CYP2D6 appears to be the main isoform responsible for the formation of 6α/β-OH-CBD as well as of 7-OH-, 4-OH-, and 5-OH-CBD; CYP3A4 efficiently catalyzes the formation of 6α/β-OH-CBD, although the 7-OH-, 2-OH-, 4-OH-, and 5-OH-CBD metabolites are also produced by this isoform; CYP3A5 is involved in the formation mainly of 6α/β-OH-CBD although the 7-OH-, 2-OH-, 3-OH-, and 4-OH-CBD metabolites are also produced. The role of CYP2A9 appears to be minor, but 6α/β-OH-, 7-OH-, 4-OH-, and 5-OH-CBD could be formed by this isoform.Source: https://www.ncbi.nlm.nih.gov