Recombinant betatrophin (Angptl‑8/lipasin) ameliorates streptozotocin‑induced hyperglycemia and β‑cell destruction in neonatal rats

Figures

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  Figure 1.. Betatrophin treatment decreases STZ-promoted hyperglycemia in neonatal rats. (A) Illustration of the design of the study. Trend in the variation of (B) plasma glucose and (C) body weight of each group of rats from day 1 to 7. (D) Daily weight gain (g/day) in the STZ+betatrophin and STZ rats. (E) Western blot analysis was performed on protein extracts obtained from livers of the untreated and STZ groups of neonates on days 2, 4 and 7. Graphs represent the densitometric analysis of betatrophin normalized to β-tubulin. Data are presented as means ± SEM. n=6–18. *P<0.05, **P<0.01, ***P<0.001, STZ+betatrophin rats vs. STZ rats. #P<0.05, ##P<0.01, STZ rats vs untreated rats. STZ, streptozotocin; IPGTT, glucose tolerance test.

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  Figure 2.. Betatrophin treatment reverses the depletion of plasma insulin and the mortality caused by STZ. Plasma insulin levels (µIU/ml) of (A) 4- and (B) 7-day-old neonates in the untreated (n=6, 7), Untreated+betatrophin (n=5, 6), STZ (n=4, 9) and STZ+betatrophin groups (n=7, 11). (C) The mortality rate of the STZ-induced diabetic rat neonates with (STZ+betatrophin group) and without (STZ group) betatrophin treatment was calculated at day 7 after birth. A Fisher exact test with Freeman-Halton extension was used to determine significance for mortality, P=0.00037681; significance was determined at P<0.05. (D) Changes in the survival rate. Bars represent mean ± SEM *P<0.05, **P<0.01, ***P<0.001, STZ rats vs. STZ+betatrophin rats. STZ, streptozotocin.

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  Figure 3.. Betatrophin promotes β-cell proliferation in STZ-induced diabetic neonates. Double immunofluorescence staining of insulin and Ki67 in pancreatic tissue from the (A) 4- and (C) 7-day-old rats. Scale bar, 50 µm. (B and D) Statistical analyses show the ratio of double-stained cells/β cells. On day 4 (A), Untreated rats (n=6); Untreated+betatrophin rats (n=5); STZ rats (n=4); STZ + betatrophin rats (n=7); On day 7 (C), Untreated rats (n=7); Untreated+betatrophin rats (n=6); STZ rats (n=9); STZ+betatrophin rats (n=11); Bars represent mean ± SEM. **P<0.01 STZ rats vs. STZ+betatrophin rats. STZ, streptozotocin.

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  Figure 4.. Betatrophin treatment increases PDX-1 levels and reduces the ratio of Bax/Bcl-2 in STZ-treated neonatal pancreas. Western blot analysis was performed on protein extracts obtained from pancreatic tissues from the (A) 4- and (D) 7-day-old rats. Graphs represent the densitometric analysis of (B and E) PDX-1 normalized to β-tubulin and (C and F) Bax/Bcl-2 ratio. On day 4, effects of betatrophin on (B) PDX-1 expression and (C) Bax/Bcl-2 ratio in the pancreas of each group. Untreated rats (n=6); Untreated + betatrophin rats (n=5); STZ rats (n=4); STZ+betatrophin rats (n=7). On day 7, effects of betatrophin on (E) PDX-1 expression and (F) Bax/Bcl-2 ratio in the pancreas of each group. Untreated rats (n=7); Untreated+betatrophin rats (n=6); STZ rats (n=9); STZ+betatrophin rats (n=11); Bars represent mean ± SEM. *P<0.05, **P<0.01, STZ rats vs. STZ+betatrophin rats. STZ, streptozotocin; PDX-1, pancreatic duodenal homeobox gene-1; Bcl-2, B-cell lymphoma-2.

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  Figure 5.. Early administration of betatrophin reduces blood glucose and improves glucose intolerance in STZ-treated adult rats. (A) The plasma glucose concentration was measured per week (from 1 to 10 weeks) of age across the study. (B) The IPGTT results measured at 3, 5, 7 and 9 weeks of age are shown. (C) AUC (area under the blood glucose concentration time curve) were calculated for each group. Untreated rats (n=4); STZ rats (n=6); STZ+betatrophin rats (n=5). Values are the means ± SEM. #P<0.05, ##P<0.01, ###P<0.001, Untreated rats vs. STZ rats. *P<0.05, **P<0.01 STZ rats vs. STZ+betatrophin rats. STZ, streptozotocin; IPGTT, glucose tolerance test.

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  Figure 6.. Long-term effects on blood glucose, body weight, insulin levels and β-cell mass after neonatal treatments of STZ and betatrophin. (A) Plasma glucose, (B) body weight and (C) overnight fasting plasma insulin concentration of the 10-week-old rats. and (D) β-cell area ratio and (E) immunohistochemical staining of insulin in rats at the age of 10 weeks. Untreated rats (n=4); STZ rats (n=6); STZ+betatrophin rats (n=5). Values are the means ± SEM. *P<0.05, **P<0.01, STZ rats vs. STZ+betatrophin rats. ###P<0.001, Untreated rats vs. STZ rats. STZ, streptozotocin.