A prolactin inhibitory factor with immunocharacteristics similar to thyrotropin releasing factor (TRH) is present in rat pituitary tumors (GH3 and W5), testicular tissue and a plant material, alfalfa

A Treatment to Cure Diabetes Using Plant-Based Drug Discovery

The field of peptides and proteins has opened up new doors for plant-based medication development because of analytical breakthroughs. Enzymatic breakdown of plant-specific proteins yields bioactive peptides. These plant-based proteins and peptides, in addition to their in vitro and vivo outcomes for diabetes treatment, are discussed in this study. The secondary metabolites of vegetation can interfere with the extraction, separation, characterization, and commercialization of plant proteins through the pharmaceutical industry. Glucose-lowering diabetic peptides are a hot commodity. For a wide range of illnesses, bioactive peptides from flora can offer up new avenues for the development of cost-effective therapy options.

Plant-Derived Bioactive Peptides: A Treatment to Cure Diabetes

ABSTRACT

Recent advances in analytical techniques have opened new opportunities for plant-based drug discovery in the field of peptide and proteins. Enzymatic hydrolysis of plant parent proteins forms bioactive peptides which are explored in the treatment of various diseases. In this review, we will discuss the identified plant-based bioactive proteins and peptides and the in vitro, in vivo results for the treatment of diabetes. Extraction, isolation, characterization and commercial utilization of plant proteins is a challenge for the pharmaceutical industry as plants contain several interfering secondary metabolites. The market of peptide drugs for the treatment of diabetes is growing at a fast rate. Plant-based bioactive peptides might open up new opportunities to discover economic lead for the management of various diseases.

GRAPHIC ABSTRACT

Enzymes Involved in Processing Glutathione Conjugates

Many potentially toxic electrophiles react with glutathione to form glutathione S-conjugates in reactions catalyzed or enhanced by glutathione S-transferases. The glutathione S-conjugate is sequentially converted to the cysteinylglycine-, cysteine- and N-acetyl-cysteine S-conjugate (mercapturate). The mercapturate is generally more polar and water soluble than the parent electrophile and is readily excreted. Excretion of the mercapturate represents a detoxication mechanism. Some endogenous compounds, such as leukotrienes, prostaglandin (PG) A2, 15-deoxy-Δ^12,14-PGJ₂, and hydroxynonenal can also be metabolized to mercapturates and excreted. On occasion, however, formation of glutathione S- and cysteine S-conjugates are bioactivation events as the metabolites are mutagenic and/or cytotoxic. When the cysteine S-conjugate contains a strong electron-withdrawing group attached at the sulfur, it may be converted by cysteine S-conjugate β-lyases to pyruvate, ammonium and the original electrophile modified to contain an –SH group. If this modified electrophile is highly reactive then the enzymes of the mercapturate pathway together with the cysteine S-conjugate β-lyases constitute a bioactivation pathway. Some endogenous halogenated environmental contaminants and drugs are bioactivated by this mechanism. Recent studies suggest that coupling of enzymes of the mercapturate pathway to cysteine S-conjugate β-lyases may be more common in nature and more widespread in the metabolism of electrophilic xenobiotics than previously realized.

Effect of intratesticular administration of anti-corticotropin-releasing factor antiserum (a-CRF) on testicular function in neonatal rats

The possible physiological role of testicular corticotropin-releasing factor (CRF) in the regulation of testicular functions was studied in neonatal rats. Two microlitres of anti-CRF-antiserum (dilution: 1:10 or 1:100) was injected intratesticularly to 5 d-old rats with two testes and to hemicastrates. Five days after hemicastration and treatment of the remaining testis with the antiserum, serum testosterone concentration and basal testosterone secretion in vitro decreased significantly. Unilateral testicular injection of a-CRF in rats with two testes resulted in a significant drop in serum testosterone level with no change in basal testosterone production. Data indicate that in neonatal rats testicular CRF might be a local stimulator of steroidogenesis.

The involvement of pineal gland and melatonin in immunity and aging: II. Thyrotropin-releasing hormone and melatonin forestall involution and promote reconstitution of the thymus in anterior hypothalamic area (AHA)-lesioned mice

A stereotactic electrolytic lesion of the anterior hypothalamic area in mice produces a rapid involution of the thymus and a reduction of lymphocytes in the peripheral blood. This effect on the thymus and blood lymphoid compartment can be prevented by postoperational administration of thyrotropin-releasing hormone (TRH) or melatonin. These activities of TRH or melatonin are antagonized by the opioid receptor blocker naltrexone. They do not seem to depend on stimulation of the thyroid gland or of the endogenous opioid system but rather on a direct activity of TRH on thymic targets or binding sites on lymphocytes.

Could dietary proteins serve as cyclo(His-Pro) precursors?

Cyclic dipeptides or diketopiperazines are readily generated during in vitro hydrolysis of proteins and polypeptides. This led us to examine whether cyclo(His-Pro) (CHP), a diketopiperazine containing histidine and proline, could be formed in vivo from dietary proteins. The data presented here show that at least in rat, neither urinary nor plasma concentration of CHP is elevated by consumption of a diet rich in proteins. Several dietary supplements derived from casein and/or soy protein hydrolysates, however, contain high levels of CHP-LI. Oral intake of one such supplement led to a sharp increase in the plasma level of CHP-LI.

Testicular immunoregulatory factors

The present data indicate that immune cells are regulated locally in the testis by Leydig cells, Sertoli cells and resident testicular macrophages. The effects of these cells are mediated by several peptide factors, including protectin, a group of high molecular weight testicular immunosuppressive factors, and testicular interleukin-1 alpha-like factor. The testicular interleukin-1 alpha-like factor is produced by Sertoli cells and is under hypophyseal control. Its synthesis starts at puberty concomitantly with the onset of spermatogenesis and it may act as a spermatogonial growth factor. Protectin, which is under hypophyseal control, may be involved in the mechanism of prolonged transplant survival in the testicular interstitial tissue. Its levels increase at puberty. Both the testicular interleukin-1 alpha-like activity and protectin may be important in testicular pathophysiology.

Immunohistochemical localization of growth hormone-releasing hormone in human gonads

Human gonads were examined for the presence of ir growth hormone-releasing-hormone. We demonstrated the presence of immunostainable cells both in ovarian and in testicular tissue using a non-crossreactive anti-GRH antiserum and the immunoperoxidase detection technique. In ovaries from ovulating women, GRH immunoreactivity was localized in the corpora lutea; granulosa cells, theca cells and cells of primary follicles did not stain. In premenopausal ovaries, staining was detectable in scattered luteinized stromal cells. In testes from post-puberal men GRH immunoreactivity was localized in the Leydig cells; cells of the germinal epithelium did not stain. These results demonstrate the presence of GRH in human gonads and suggest that this peptide may exert regulatory function at the testicular and ovarian levels.

Plasma levels of thyrotropin-releasing-hormone in various splanchnic, renal, suprarenal, and cerebral veins

Endogenous TRH levels were determined in plasma obtained selectively via percutaneous transhepatic and femoral catheterization. TRH was measured using a very sensitive RIA method. In the pancreatic veins, internal jugular vein, left testicular vein, and other described veins, normal peripheral levels were found. An involvement of the TRH degrading enzyme (TDE) or a rapid intravasal dilution leading to normal peripheral TRH levels in the veins leaving the brain or pancreas, respectively, is discussed.

The evolutionary origins of intercellular communication and the Maginot Lines of the mind

By extending the evolutionary age of the vertebrate hormones from the vertebrates to include the metazoans, we expand their phyletic distribution about 30-fold. By tracing these molecules into the unicellular range including both eukaryotes and prokaryotes, the distribution of these molecules becomes very wide indeed. While "universal" or "ubiquitous" is probably not yet warranted, their recognition as "cosmic" molecules rather than "parochial" molecules does seem appropriate. Interestingly, the breakdown of the barriers for the hormonal molecules between the vertebrates and the rest of the metazoans, between the metazoans and the unicellular organisms, between the eukaryotes and prokaryotes, or the eubacteria and archebacteria is concordant with findings in multiple other systems. For example, hemoglobin or myoglobin is present in higher plants, Protozoa, and insects. The photosynthetic proteins of higher plants have their homologues in the photosynthetic bacteria, and the heat shock proteins of eukaryotes have their equivalents in the prokaryotes as well.

Human semen contains thyrotropin releasing hormone (TRH), a TRH-homologous peptide, and TRH-binding substances

High levels of thyrotropin releasing hormone (TRH) and TRH-homologous peptide, with the general structure pGlu=X-Pro-NH2 where X is either Histidine (His) or a neutral amino acid residue, have been identified in rat and human prostate (Pekary et al, 1980, 1981a, 1982c). Because of the secretory nature of prostatic tissue, it was considered likely that these peptides would be measurable in human semen. The mean (+/- SD) TRH immunoreactivity (TRH IR) in semen from 26 normal donors, aged 26 and 41 years, was found to be 12.2 +/- 5.2 ng/ml. TRH and TRH-homologous peptide, were undetectable in unconcentrated human serum. TRH IR levels in semen from azoospermic donors were in the normal range. The level of TRH IR in semen from vasectomized donors was significantly less (P less 0.01) than in semen from normal subjects. Evidence for at least two TRH-binding substances, which coextract and bind to added synthetic TRH, was obtained by exclusion and cation exchange chromatography. Purification of extracts of human semen by TRH affinity chromatography or gradient, reversed phase high pressure liquid chromatography (HPLC) revealed two major TRH immunoreactive peptides, one corresponding to the TRH-homologous peptide previously reported in rat and human prostate and one cochromatographing with synthetic TRH.

Neuropeptides and thermoregulation: the interactions of bombesin, neurotensin, TRH, somatostatin, naloxone and prostaglandins

In this study we have examined the interactions of bombesin (1 microgram ICV), neurotensin (1 microgram ICV), TRH (10 micrograms ICV), somatostatin (10 micrograms ICV), PGE2 (10 micrograms ICV) and naloxone (10 mg/kg SC) on thermoregulation in the rat at room temperature (20 +/- 1 degree C). Given alone, bombesin, neurotensin, somatostatin and naloxone all produced hypothermia (bombesin greater than neurotensin greater than somatostatin congruent to naloxone). PGE2 was hyperthermic, and TRH had no effect. Bombesin and PGE2 neutralized one another's effects. Neurotensin had no effect on PGE2-induced hyperthermia. Naloxone enhanced the hypothermic effect of bombesin and somatostatin enhanced the rate of onset of hypothermia after bombesin. TRH had no effect on bombesin-induced hypothermia. TRH, somatostatin and naloxone had no effect on neurotensin-induced hypothermia. TRH antagonized the hypothermia due to naloxone and somatostatin.