Korean J Physiol Pharmacol.  2015 Jul;19(4):309-318. 10.4196/kjpp.2015.19.4.309.

Chronic Alcohol Consumption Results in Greater Damage to the Pancreas Than to the Liver in the Rats

• Lee SS
• Hong OK
• Ju A
• Kim MJ
• Kim BJ
• Kim SR
• Kim WH
• Cho NH
• Kang MI
• Kang SK
• Kim DJ
• Yoo SJ

• KMID: 2285573
• DOI: http://doi.org/10.4196/kjpp.2015.19.4.309

Abstract

Alcohol consumption increases the risk of type 2 diabetes. However, its effects on prediabetes or early diabetes have not been studied. We investigated endoplasmic reticulum (ER) stress in the pancreas and liver resulting from chronic alcohol consumption in the prediabetes and early stages of diabetes. We separated Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type-2 diabetic animal model, into two groups based on diabetic stage: prediabetes and early diabetes were defined as occurrence between the ages of 11 to 16 weeks and 17 to 22 weeks, respectively. The experimental group received an ethanol-containing liquid diet for 6 weeks. An intraperitoneal glucose tolerance test was conducted after 16 and 22 weeks for the prediabetic and early diabetes groups, respectively. There were no significant differences in body weight between the control and ethanol groups. Fasting and 120-min glucose levels were lower and higher, respectively, in the ethanol group than in the control group. In prediabetes rats, alcohol induced significant expression of ER stress markers in the pancreas; however, alcohol did not affect the liver. In early diabetes rats, alcohol significantly increased most ER stress-marker levels in both the pancreas and liver. These results indicate that chronic alcohol consumption increased the risk of diabetes in prediabetic and early diabetic OLETF rats; the pancreas was more susceptible to damage than was the liver in the early diabetic stages, and the adaptive and proapoptotic pathway of ER stress may play key roles in the development and progression of diabetes affected by chronic alcohol ingestion.

Keyword

Alcohol; Endoplasmic reticulum stress; OLETF rat

MeSH Terms

Alcohol Drinking*
Animals
Body Weight
Diet
Eating
Endoplasmic Reticulum
Endoplasmic Reticulum Stress
Ethanol
Fasting
Glucose
Glucose Tolerance Test
Liver*
Models, Animal
Pancreas*
Prediabetic State
Rats*
Rats, Inbred OLETF
Ethanol
Glucose

Figure

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  Fig. 1 Experimental design (animal groups and treatment). IP-GTT, intraperitoneal glucose tolerance test.

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  Fig. 2 Changes in blood glucose concentration during the IP-GTT. (A) IP-GTT data in 16-week-old OLETF rats (prediabetes). (B) IP-GTT data in 22-week-old OLETF rats (early diabetes). Data represent the mean±SE of three independent measurements. IP-GTT, intraperitoneal glucose tolerance test; OLETF, Otsuka Long-Evans Tokushima Fatty; Pd-O-C, prediabetes/OLETF rat/control diet; Pd-O-E, prediabetes/OLETF rat/ethanol diet; D-O-C, early diabetes/OLETF rat/control diet; D-O-E, early diabetes/OLETF rat/ethanol diet. *p<0.05 compared to control.

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  Fig. 3 ER stress of the liver in prediabetic OLETF rats. (A) Representative Western blot analysis showing ER stress of the liver in the alcohol treatment group. (B) The result of A is expressed as the mean±SE of the relative band density from three independent experiments. ER, endoplasmic reticulum; OLETF, Otsuka Long-Evans Tokushima Fatty; Pd-O-C, prediabetes/OLETF rat/control diet; Pd-O-E, prediabetes/OLETF rat/ethanol diet. *p<0.05 compared to control. Data are the mean of four independent experiments.

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  Fig. 4 ER stress of the liver in diabetic OLETF rats. (A) Representative Western blot analysis showing ER stress of the liver in the alcohol treatment group. (B) The result of A is expressed as the mean± SE of the relative band density from three independent experiments. ER, endoplasmic reticulum; OLETF, Otsuka Long-Evans Tokushima Fatty; D-O-C, early diabetes/OLETF rat/control diet; D-O-E, early diabetes/OLETF rat/ethanol diet (Lieber-DeCarli diet). *p<0.05 compared to control. Data are the mean of four independent experiments.

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  Fig. 5 Effect of alcohol on liver tissue. (A) Liver section from an OLETF rat fed control diet from 11 to 16 weeks of age (prediabetes). (B) Liver section from an OLETF rat fed a Lieber-DeCarli ethanol diet from 11 to 16 weeks of age. (C) Liver section from an OLETF rat fed a control diet from 17 to 22 weeks of age (diabetes). (D) Liver section from an OLETF rat fed a Lieber-DeCarli ethanol diet from 17 to 22 weeks of age. OLETF, Otsuka Long-Evans Tokushima Fatty; Pd-O-C, prediabetes/OLETF rat/control diet; Pd-O-E, prediabetes/OLETF rat/ethanol diet; D-O-C, early diabetes/OLETF rat/control diet; D-O-E, early diabetes/OLETF rat/ethanol diet (×200, H&E stain).

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  Fig. 6 ER stress of the pancreas in prediabetic OLETF rats. (A) Representative Western blot analysis showing ER stress of the pancreas in the alcohol treatment group. (B) The result of A is expressed as the mean±SE of the relative band density from three independent experiments. ER, endoplasmic reticulum; OLETF, Otsuka Long-Evans Tokushima Fatty; Pd-O-C, prediabetes/OLETF rat/control diet; Pd-O-E, prediabetes/OLETF rat/ethanol diet. *p<0.05 compared to control. Data are the mean of four independent experiments.

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  Fig. 7 ER stress of the pancreas in diabetic OLETF rats. (A) Representative Western blot analysis showing ER stress of the pancreas in the alcohol treatment group. (B) The result of A is expressed as the mean±SE of the relative band density from three independent experiments. ER, endoplasmic reticulum; OLETF, Otsuka Long-Evans Tokushima Fatty; D-O-C, early diabetes/OLETF rat/control diet; D-O-E, early diabetes/OLETF rat/ethanol diet. *p<0.05 compared to control. Data are the mean of four independent experiments.

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  Fig. 8 Morphology of the pancreatic islets in OLETF rats. (A~D) H&E staining of the pancreatic islets. (A) A 16-week-old OLETF rat fed a control diet. (B) A 16-week-old OLETF rat fed an ethanol diet. (C) A 22-week-old OLETF rat fed a control diet. (D) A 22-week-old OLETF rat fed an ethanol diet. (E~H) Representative immunohistochemical staining of insulin, glucagon, and the nucleus. The insulin, glucagon, and nuclei are stained red, green, and blue, respectively. (E) A 16-week-old OLETF rat fed a control diet. (F) A 16-week-old OLETF rat fed an ethanol diet. (G) A 22-week-old OLETF rat fed a control diet. (H) A 22-week-old OLETF rat fed an ethanol diet. OLETF, Otsuka Long-Evans Tokushima Fatty; Pd-O-C, prediabetes/OLETF rat/control diet; Pd-O-E, prediabetes/OLETF rat/ethanol diet; D-O-C, early diabetes/OLETF rat/control diet; D-O-E, early diabetes/OLETF rat/ethanol diet (A~H, ×400).

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  Fig. 9 The islet area in the pancreas of OLETF rats. The size of the islets was quantified and analyzed. (A) Islet area data in 16-week-old OLETF rats (prediabetes). (B) Islet area data in 22-week-old OLETF rats (diabetes). Data represent mean±SE. Pd-O-C, prediabetic OLETF rat-control diet; Pd-O-E, prediabetic-OLETF rat-ethanol diet; D-O-C, diabetic OLETF rat-control diet; D-O-E, diabetic OLETF rat-ethanol diet. There were no statistically significant differences between the control group and ethanol group.

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