Calcitonin in metabolic disorders

Modulators of amyloid protein aggregation and toxicity: EGCG and CLR01

Abnormal protein folding and self-assembly causes over 30 cureless human diseases for which no disease-modifying therapies are available. The common side to all these diseases is formation of aberrant toxic protein oligomers and amyloid fibrils. Both types of assemblies are drug targets, yet each presents major challenges to drug design, discovery, and development. In this review, we focus on two small molecules that inhibit formation of toxic amyloid protein assemblies — the green-tea derivative (−)-epigallocatechin-3-gallate (EGCG), which was identified through a combination of epidemiologic data and a compound library screen, and the molecular tweezer CLR01, whose inhibitory activity was discovered in our group based on rational reasoning, and subsequently confirmed experimentally. Both compounds act in a manner that is not specific to one particular protein and thus are useful against a multitude of amyloidogenic proteins, yet they act via distinct putative mechanisms. CLR01 disrupts protein aggregation through specific binding to lysine residues, whereas the mechanisms underlying the activity of EGCG are only recently beginning to unveil. We discuss current in vitro and, where available, in vivo literature related to EGCG and CLR01’s effects on amyloid β-protein, α-synuclein, transthyretin, islet amyloid polypeptide, and calcitonin. We also describe the toxicity, pharmacokinetics, and mechanism of action of each compound.

Hypercalcitoninemia in pancreatitis--evidence for immunochemical heterogeneity

Recently in our laboratory we have demonstrated increased immunoreactive calcitonin (iCT) levels in 4 patients with acute pancreatitis and hypocalcemia. The present study consists of 17 additional patients in whom serial determinations for (iCT) were performed. Furthermore, with the use of 2 different antisera directed against human calcitonin we present evidence for immunochemical heterogeneity of this hormone in acute pancreatitis.

Calcitonin: antagonism at intestinal muscarinic receptors

The action of calcitonin was studied on the motility of isolated innervated segments of rabbit and guinea-pig intestines as well as longitudinal muscle with adherent myenteric plexus dissected from the guinea-pig ileum. Calcitonin (0.25 muM) antagonized contractile responses to acetylcholine and the cholinergic response to electrical field stimulation. This hormonal effect was relatively specific since it was not observed at nicotinic receptors or adrenoceptors, nor did calcitonin act as a local anaesthetic or directly on the contractile machinery of smooth muscle. Perivascular adrenergic and intrinsic non-adrenergic inhibitory responses also were unaffected by calcitonin. However, calcitonin did have antihistaminic properties directed against H1-receptors. The concentration of calcitonin required to achieve muscarinic antagonism in our experiments is not reached at the resting level of circulating hormone.

Hypercalcitoninemia in infancy

Immunoreactive calcitonin (iCT) was measured in 19 infants with neonatal hypocalcemia. The infants had a variety of neonatal diseases and stresses. iCT levels were generally elevated to two to 20 times the adult values. Poor correlation existed between the infant age and the level of iCT or between iCT alone and the serum calcium. However, there was significant correlation between the serum calcium and the ratio of the iCT to infant age from conception, suggesting that both infant age and iCT levels in combination may be related to hypocalcemia. Also, it appears that a variety of neonatal stresses may be associated with increased sensitivity to the hypocalcemic effect of iCT, as well as increased levels of iCT.