Endocrinol Metab.  2015 Dec;30(4):569-575. 10.3803/EnM.2015.30.4.569.

Omega-3 Polyunsaturated Fatty Acids May Attenuate Streptozotocin-Induced Pancreatic beta-Cell Death via Autophagy Activation in Fat1 Transgenic Mice

• Hwang WM
• Bak DH
• Kim DH
• Hong JY
• Han SY
• Park KY
• Lim K
• Lim DM
• Kang JG

• KMID: 2169667
• DOI: http://doi.org/10.3803/EnM.2015.30.4.569

Abstract

BACKGROUND
Inflammatory factors and beta-cell dysfunction due to high-fat diets aggravate chronic diseases and their complications. However, omega-3 dietary fats have anti-inflammatory effects, and the involvement of autophagy in the etiology of diabetes has been reported. Therefore, we examined the protective effects of autophagy on diabetes using fat-1 transgenic mice with omega-3 self-synthesis capability.
METHODS
Streptozotocin (STZ) administration induced beta-cell dysfunction in mice; blood glucose levels and water consumption were subsequently measured. Using hematoxylin and eosin (H&E) and Masson's trichrome staining, we quantitatively assessed STZ-induced changes in the number, mass, and fibrosis of pancreatic islets in fat-1 and control mice. We identified the microtubule-associated protein 1A/1B light chain 3-immunoreactive puncta in beta-cells and quantified p62 levels in the pancreas of fat-1 and control mice.
RESULTS
STZ-induced diabetic phenotypes, including hyperglycemia and polydipsia, were attenuated in fat-1 mice. Histological determination using H&E and Masson's trichrome staining revealed the protective effects of the fat-1 expression on cell death and the scarring of pancreatic islets after STZ injection. In the beta-cells of control mice, autophagy was abruptly activated after STZ treatment. Basal autophagy levels were elevated in fat-1 mice beta-cells, and this persisted after STZ treatment. Together with autophagosome detection, these results revealed that n-3 polyunsaturated fatty acid (PUFA) enrichment might partly prevent the STZ-related pancreatic islet damage by upregulating the basal activity of autophagy and improving autophagic flux disturbance.
CONCLUSION
Fat-1 transgenic mice with a n-3 PUFA self-synthesis capability exert protective effects against STZ-induced beta-cell death by activating autophagy in beta-cells.

Keyword

Omega 3 fatty; Beta cell; Fat-1 transgenic mice

MeSH Terms

Animals
Autophagy*
Blood Glucose
Cell Death
Chronic Disease
Cicatrix
Diet, High-Fat
Dietary Fats
Drinking
Eosine Yellowish-(YS)
Fatty Acids, Omega-3
Fatty Acids, Unsaturated*
Fibrosis
Hematoxylin
Hyperglycemia
Islets of Langerhans
Mice
Mice, Transgenic*
Pancreas
Phenotype
Polydipsia
Streptozocin
Blood Glucose
Dietary Fats
Eosine Yellowish-(YS)
Fatty Acids, Omega-3
Fatty Acids, Unsaturated
Hematoxylin
Streptozocin

Figure

• 

  Fig. 1 Schematic Illustration of the hypothesis in this experiments. STZ, streptozotocin; WT, wild-type; TG, transgenic.

• 

  Fig. 2 Genetic enrichment of n-3 fatty acid confers resistance to diabetes-related physical status. (A) Changes of blood glucose concentrations of wild-type (WT) and fat-1 mice for 18 days after streptozotocin (STZ) treatment. (B) Changes of water intakes of WT and fat-1 mice for 18 days after STZ treatment. Values are expressed as mean±SD from three independent experiments (n=20 per group). aP<0.001 vs. WT+STZ.

• 

  Fig. 3 Genetic enrichment of n-3 fatty acid preserves pancreatic islets against streptozotocin (STZ)-induced damages. (A) Representative H&E stained pancreatic tissues of wild-type (WT) and fat-1 mice after STZ treatments. Arrowheads indicates the pancreatic islets (scale bar=100 µm). (B) Quantitative bar graphs for comparison of islets which were bigger than 10,000 µm2. Values are expressed as mean percentage±SD. aP<0.001 vs. WT+STZ.

• 

  Fig. 4 Genetic enrichment of n-3 fatty acid inhibits streptozotocin (STZ)-induced fibrosis in pancreas. Representative Masson trichrome-stained pancreatic tissues of wild-type (WT) and fat-1 mice after STZ treatments. (A, B) In STZ-treated WT mice, a significant amount of fibrosis was observed. (C, D) STZ-treated fat-1 mice had fewer fibrotic lesions. Arrowheads indicates fibrotic scars (scale bar=750 µm).

• 

  Fig. 5 Basal autophagy is upregulated and streptozotocin (STZ)-induced autophagic disturbance is attenuated in pancreatic islets of fat-1 mice. (A) Representative confocal microscopic images of light chain 3 (LC3)-immunostained pancreatic islet cells of wild-type (WT) and fat-1 mice with or without STZ treatments. Indicated rectangular areas magnified for clearer visualization of LC3 puncta. Arrowheads indicates the LC3-stained autophagosomes. 4',6-Diamidino-2-phenylindole was used for nuclear stains (scale bar=20 µm). (B) Representative immunoblot for quantification of p62 expression in pancreatic tissues of WT and fat-1 mice with or without STZ treatments. Actin was used for loading control.

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