Growth hormone (GH) is an anabolic mitogen with widespread influence on cellular growth and differentiation as well as on glucose and lipid metabolism. GH binding to the growth hormone receptor (GHR) on hepatocytes prompts expression of insulin growth factor I (IGF-1) involved in nutritionally induced compensatory hyperplasia of pancreatic β-cell islets and insulin release. A prolonged hyperactivity of the IGF-1/insulin axis in the face of insulinotropic nutrition, on the other hand, can lead to collapse of the pancreatic islets and glucose intolerance. Individuals with Laron syndrome carry mutations in the GHR gene resulting in severe congenital IGF-1 deficiency and elevated GH serum levels leading to short stature as well as perturbed lipid and glucose metabolism. However, these individuals enjoy a reduced prevalence of acne, cancer and possibly diabetes. Minipigs have become important biomedical models for human conditions due to similarities in organ anatomy, physiology, and metabolism relative to humans. The purpose of this study was to generate transgenic Wuzhishan minipigs by handmade cloning with impaired systemic GHR activity and assess their growth profile and glucose metabolism. Transgenic minipigs featuring overexpression of a dominant-negative porcine GHR (GHR(dm)) presented postnatal growth retardation and proportionate dwarfism. Molecular changes included elevated GH serum levels and mild hyperglycemia. We believe that this model may prove valuable in the study of GH functions in relation to cancer, diabetes and longevity.

This study investigated the differences in meat quality during postmortem aging of yak meat from different altitudes as well as the relationship between the release of hypoxic factor HIF‐1α and meat quality. The results showed that the HIF‐1α increased with altitude but during aging process, there was an initial increase before a subsequent decrease (p < .05). Moreover, significant increases were showed in glycolytic potential, a* value, pH, HIF‐1α mRNA expression, HIF‐1α protein expression and shear force with altitude (p < .05). Additionally, the b* value, L* value, water holding power and MFI decreased significantly (p < .05). HIF‐1α was shown, by PLS‐DA method analysis, to be the main protein marker for differences in the quality during aging time of meat from three altitude groups. HIF‐1α protein expression was high correlated with glycolytic potential, pH value, meat color, tenderness and water holding capacity during postmortem aging. The results demonstrated that HIF‐1α is a novel marker protein that influences meat quality in yak from different altitudes and that HIF‐1α‐mediated glycolytic pathway was key to the meat quality during postmortem aging. Practical applications Yak meat has the advantages of high protein, low fat, good amino acid and fatty acid composition, so the nutritional value of yak meat is in line with the current best‐selling beef with less fat in domestic and foreign markets. But consumers often think that the meat tenderness of yak meat is worse than that of beef and improving the quality of yak meat was worthy of attention specifically. This study investigated the differences in meat quality during postmortem aging of yak meat at different altitudes and the relationship between hypoxic factor HIF‐1α release and meat quality.

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