Baoping Zhao

Administration of a mutated myostatin propeptide to neonatal mice significantly enhances skeletal muscle growth.

Myostatin is a dominant inhibitor of skeletal muscle development and growth. As transgenic over‐expression of myostatin propeptide dramatically enhanced muscle mass, we hypothesized that administration of myostatin propeptide will increase muscle growth. In this study, the wild‐type form of porcine myostatin propeptide and its mutated form at the cleavage site of metalloproteinases of BMP‐1/TLD family were produced from insect cells. In vitro A204 cells reporter assays showed that both wild‐type and the mutated propeptides depressed myostatin activity. The recombinant propeptides at four‐fold myostatin concentration can effectively block myostatin function during co‐incubation with A204 cells. In particular, the mutated propeptide appeared much more effective than wild‐type propeptide over a long period during the in vitro co‐incubation. Administration of the mutated propeptide to neonatal mice at the age of 11 and 18 days was tested and showed significant increase in growth performance by 11–15% from the age of 25 to 57 days (P < 0.05). The major skeletal muscles of mice that were injected with mutated propeptide were 13.5–24.8% heavier than the control group (P < 0.05) as a result of muscle fiber hypertrophy. In conclusion, administration of the mutated myostatin propeptide during the neonatal period is an effective way for promoting muscle growth. Mol. Reprod. Dev. 77: 76–82, 2010.

Transgenic over-expression of growth differentiation factor 11 propeptide in skeleton results in transformation of the seventh cervical vertebra into a thoracic vertebra†

Growth differentiation factor 11 (GDF11) is one of the significant genes that control skeletal formation. Knockout of GDF11 function causes abnormal patterning of the anterior/posterior axial skeleton. The mRNA of GDF11 is initially translated to a precursor protein that undergoes a proteolytic cleavage to generate the C‐terminal peptide or mature GDF11, and the N‐terminal peptide named GDF11 propeptide. The propeptide can antagonize GDF11 activity in vitro. To investigate the effects of GDF11 propeptide on GDF11 function in vivo, we generated transgenic mice that over‐express the propeptide cDNA in skeletal tissue. The transgenic mice showed formation of extra ribs on the seventh cervical vertebra (C7) as a result of transformation of the C7 vertebra into a thoracic vertebra. The GDF11 propeptide transgene mRNA was detected in tail tissue in embryos and was highly expressed in tail and calvaria bones after birth. A high frequency of C7 rib formation was noticed in the transgenic mouse line with a high level of transgene expression. The anterior boundaries of Hoxa‐4 and Hoxa‐5 mRNA in situ expressions showed cranial shifts from their normal prevertebra locations in transgenic embryos. These results demonstrated significant effects of GDF11 propeptide transgene on vertebral formation, which are likely occurring through depressing GDF11 function and altered locations of Hoxa‐4 and Hoxa‐5 expression. Mol. Reprod. Dev. 77:990–997, 2010.

Enhanced muscle by myostatin propeptide increases adipose tissue adiponectin, PPAR-α, and PPAR-γ expressions

Muscle tissue utilizes a large portion of metabolic energy for its growth and maintenance. Previously, we demonstrated that transgenic over-expression of myostatin propeptide in mice fed a high-fat diet enhanced muscle mass and circulating adiponectin while the wild-type mice developed obesity and insulin resistance. To understand the effects of enhanced muscle growth on adipose tissue metabolism, we analyzed adiponectin, PPAR-alpha, and PPAR-gamma mRNA expressions in several fat tissues. Results indicated muscled transgenic mice fed a high-fat diet displayed increased epididymal adiponectin mRNA expression by 12 times over wild-type littermates. These transgenic mice fed either a high or normal fat diet also displayed significantly high levels of PPAR-alpha and PPAR-gamma expressions above their wild-type littermates in epididymal fat while their expressions in mesenteric fats were not significantly different between transgenic mice and their littermates. This study demonstrates that enhanced muscle growth has positive effects on fat metabolisms through increasing adiponectin expression and its regulations.

Decreased expression of calpain and calpastatin mRNA during development is highly correlated with muscle protein accumulation in neonatal pigs

It is well known that rapid gain of muscle mass in neonatal pigs is highly related to protein synthesis. However, the role of protein degradation in muscle gain of the neonatal period has not been well established. Calpains and their endogenous inhibitors, calpastatins, play a significant role in early-stage myofibrillar protein degradation. To investigate the role of calpain-calpastatin system in muscle protein accumulation, we studied the expressions of their mRNA in muscle tissue sampled at days 1, 4, 6, 12, 20 and 28 from a total of 36 neonatal pigs. The steady-state mRNA levels of calpains 1A, 2 and 3A, calpastatin types 1, 2 and 3, obtained by quantitative real-time PCR analysis, decreased by 2-4 folds at the age of 4 to 6 days compared to 1-day-old piglets. Then, the relatively low expression level was maintained through 28 days of age. Expressions of calpains 1A, 3A and calpastatin type 1 were significantly correlated with the measurements of muscle protein accumulations such as muscle protein content and RNA/protein ratio. Expressions of calpain 1A, calpastatin types 1 and 3 were negatively correlated with birth weight and fractional rate of growth. The levels of calpains 1A and 2 mRNA were correspondent to their protease activities. In conclusion, decreased levels of calpain and calpastatin expressions over development in neonatal pigs are associated with high protein accumulations, suggesting that dramatic muscle growth during the neonatal period may be partially controlled by down-regulated calpain-calpastatin system.

Growth performances of F1 angus plus calves grazing on pasture in Hawaii's tropical climate

Angus Plus cattle offer advantages for heat tolerance and forage utilization by introduction of Brangus and Brahman to Angus. To evaluate its adaptability in Hawaii Islands, we reported the growth performances of 213 F1 Angus Plus calve grazing on pasture. Least-square means of pre-weaning ADG ranged from 1,087 to 1,167 g in bull calves and from 1,030 to 1,048 g in heifer calves. The 205 d-adjusted weaning weight were 226 to 285 kg in bulls and 214 to 252 kg in heifers. The birth weight and hip height at birth were significantly correlated with weaning weight, 205 d-adjusted weaning weight, hip height at weaning and pre-weaning ADG (P < 0.01). Sire group significantly influenced pre-weaning growth performances through interaction with sex of calf. Bull calves from sire group of high growth were 1.0–3.8 kg heavier in birth weight than the bull calves from other sires (P < 0.001). Sire group x sex interaction was significant (P < 0.05) for calf birth weight, 205-d adjusted weaning weight and pre-weaning ADG. Sire group also played a significant role in hip height at birth (P < 0.05). Selections of the sires preferable for growth significantly improved calf pre-weaning growth performances.