HGH isoforms: cDNA expression, adipogenic activity and production in cell culture

Origin of personalized medicine in pioneering, passionate, genomic research

Personalized medicine, one of the main promises of the Human Genome Project (HGP) that began three decades ago, is now a new therapeutic paradigm. With its arrival the era of developing drugs to suit all patients, yet often having to withdraw a promising new one because a minority of patients was at risk, even though it had proved valuable for the majority was consigned to history as were trial-and-error strategies being the predominant means of tailoring therapy. But how did it originate and the earliest examples emerge? Is it true that the first personalized diagnostic test was the companion test for Herceptin®? This account of a remarkable journey from genomic and translational research to therapeutic and diagnostic innovations, describes how sequencing the human growth hormone (hGH) locus provided proof of principle for HGP-inspired personalized medicine. Sequencing this locus and the resultant biomanufacture of HGH and the development of a test capable of detecting which patients would benefit from its administration helped silence the skeptics who questioned the validity of such an approach. The associated companion diagnostic was created four years before the invention of the HercepTest® (registered as the first companion diagnostics ever developed). By cultivating genomic research with passion and pursuing its applications, we and many others contributed to the emergence of a new diagnostics industry, the discovery of better actionable gene-targets and to a revitalized pharmaceutical industry capable of developing safer and more effective therapies. In combination, these developments are beginning to fulfill the promise of the HGP, offering each patient the opportunity to adopt the right treatment at the correct dosage in an opportune manner.

Growth hormone and placental lactogen: biology, medicine and biotechnology

Molecular cloning gave us access to the gene members of the human growth hormone and placental lactogen multigene family. Genomic sequencing provided clues for the understanding of the origin, functioning and regulation of this family. It has also allowed us to develop new diagnostic approaches for deficiencies of these hormones and to make new biotechnological contributions.

Secretion of authentic 20-kDa human growth hormone (20K hGH) in Escherichia coli and properties of the purified product

Using Bacillus amyloliquefaciens neutral protease gene (npr), we have constructed a secretion system of 20-kDA human growth hormone (20K hGH) in E. coli. The secretion-signal region from npr was modified inserting a fragment coding a 2Lys-5Leu cluster. In this system we found that co-expression of glutathione reductase remarkably increased accumulation level of 20K hGH in periplasm and confirmed that secreted 20K hGH was correctly processed. The recombinant 20K hGH was highly purified and subjected to analyses of physicochemical properties and biological activities which are still unclear and controversial due to difficulty in preparing the sample with authentic structure. The secreted recombinant product had authentic disulfide linkages and showed molecular weight of 20,270.5 +/- 3.7 (theoretical value, 20,269.9). The results suggest that the recombinant 20K hGH is a full agonist on rat growth promotion and lipolysis stimulation in isolated rat adipose tissues. In particular, the lipolysis-stimulating activity of 20K hGH was distinct as compared with that of 22K hGH under physiological concentration. Cell proliferation activity via prolactin-receptor in Nb-2 lymphoma was obviously low as compared with that of 22K hGH.

Increased hepatic delta 6-desaturase activity with growth hormone expression in the MG101 transgenic mouse

Growth hormone (GH) has many metabolic effects, but its mechanism(s) of action are not fully understood. We studied the short-term effects of endogenously produced GH on liver delta 6-desaturase activity and adipose and liver lipid fraction fatty acid composition in transgenic mice. MG101 transgenic mice ages 73-114 d received zinc to activate the ovine GH transgene for 7 d. Nontransgenic littermates, used as controls, also received zinc. Liver lipids were fractionated into phospholipids (PL), cholesteryl esters, and triglycerides (TG), and retroperitoneal adipose fractionated into PL and TG for fatty acid analysis. Liver microsomes were assayed for delta 6-desaturase activity. Animals expressing the ovine growth hormone transgene had a 2.5-fold higher liver delta 6-desaturase activity than controls. Arachidonate and docosahexaenoate were significantly higher in liver PL of GH transgenic animals compared to controls, but both were decreased in adipose PL in the GH animals. We conclude that increased production of GH affects both production and organ distribution of highly unsaturated fatty acids. The changes in arachidonate in various lipid pools following transgene expression may mediate the systemic actions of GH.

Development of obesity following inactivation of a growth hormone transgene in mice

Mice with a temporally regulatable ovine metallothionein 1a--ovine growth hormone transgene (oMT1a-oGH) were utilized to study the effects of withdrawal of elevated circulating levels of growth hormone (GH) on growth and body composition. The transgene was activated from 21-42 days of age by provision of zinc sulfate in the drinking water. At 42 days, mice were allocated to either activated transgenic (remain on zinc sulfate) or inactivated transgenic (removal of zinc sulfate) groups, and to receive either ad libitum or restricted (80-90% of ad libitum) access to feed. Non-transgenic control mice were treated similarly. Body weights and intakes were recorded weekly. Mice were killed at 70 d and epididymal and subcutaneous fat pads, trimmed hind carcass and various organs were weighed. The main findings of this study are: (1) food-restricted mice possessing an activated oMT1a-oGH transgene fail to demonstrate increased growth, but exhibit significantly reduced levels of fat (P < 0.05) relative to all other genotype x feed level combinations; and (2) inactivation of the oMT1a-oGH transgene, following a period of elevated GH levels, leads to development of obesity as evidenced by two to three fold increases in epididymal and subcutaneous fat pad weights (P < 0.01) relative to both activated transgenic and non-transgenic control mice. These large increases in fat deposition also occurred when intake was restricted to 80-90% of ad libitum levels, indicating that metabolic changes independent of intake occur in these inactivated transgenic mice. It is possible that highly elevated production of GH in activated oMT1a-oGH transgenic mice leads to (1) enhanced promotion of preadipocyte differentiation, leading to increased numbers of adipocytes that, upon cessation of oGH production, are available for lipid deposition resulting in obesity, or (2) alterations in production of or responsiveness to insulin, leading to increased fat deposition upon removal of the chronic anti-lipogenic actions of GH. The oMT1a-oGH transgenic mouse line should provide a new genetic model with which to investigate the mechanisms by which growth hormone affects obesity.