The metabolic syndrome in mice overexpressing neuropeptide Y in noradrenergic neurons

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   Figure 1

   Liver histology and triglyceride accumulation of obese OE-NPY^DBH mice. (A) Representative hematoxylin and eosin stained liver sections from 4-month-old homozygous female and male OE-NPY^DBH vs wild-type mice showing ballooning degeneration and triglyceride accumulation in males (scale bar 50 µm). (B) Representative Oil red O (scale bar 100 µm) and hematoxylin and eosin (scale bar 50 µm) stained liver sections, and (C) liver triglyceride content of 7-month-old homozygous male OE-NPY^DBH vs wild-type mice (n = 9–10/group) showing hepatosteatosis. Values are expressed as means ± s.e.m. *P < 0.05 with Student’s t-test. H&E = hematoxylin and eosin staining, ORO = Oil red O staining, WT = wild-type mice, OE-NPY = OE-NPY^DBH mice.
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   Figure 2

   Hepatic fatty acid metabolism in OE-NPY^DBH mice. (A) mRNA expression of selected genes involved in fatty acid metabolism in 2-month-old heterozygous (pre-obese) (n = 5/group) and 7-month-old homozygous (obese) (n = 10/group) OE-NPY^DBH mice relative to wild-type mice. Beta actin was used as endogenous control. (B) Total palmitate oxidation in the livers of 2-month-old homozygous OE-NPY^DBH vs wild-type mice (n = 6–9/group). Values are expressed as means ± s.e.m. *P< 0.05 and ***P < 0.001 with Student’s t-test. Srebp1c = Sterol regulatory element binding transcription factor 1, Fas = fatty acid synthase, Acc = acetyl-CoA carboxylase, Ppara = peroxisome proliferator-activated receptor alpha, Acox1 = acyl-Coenzyme A oxidase 1, Cpt1 = carnitine palmitoyltransferase 1, Crat = carnitine acetyltransferase, Acsl4 = acyl-CoA synthetase long-chain family member 4, WT = wild-type mice, OE-NPY = OE-NPY^DBH mice.
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   Figure 3

   Cholesterol metabolism in OE-NPY^DBH mice. (A) Cholesterol and (B) bile acid synthesis in 6-month-old homozygous female OE-NPY^DBH vs wild-type mice measured by fecal ratio method (n = 5–10/group). (C) mRNA expression of cholesterol and bile acid synthesis enzymes in 2-month-old heterozygous (pre-obese) (n = 5/group) and 7-month-old homozygous (obese) (n = 10/group) OE-NPY^DBH mice relative to wild-type mice. Beta actin was used as endogenous control. (D) Cholesterol absorption measured by fecal ratio method and (E) mRNA expression of jejunal cholesterol influx and efflux proteins in 6-month-old homozygous female OE-NPY^DBH mice relative to wild-type mice (n = 7–9/group). Beta actin was used as endogenous control. Values are expressed as means ± s.e.m. *P < 0.05, **P < 0.01 and ***P < 0.001 with Student’s t-test. Hmgcr = 3-hydroxy-3-methylglutaryl-CoA reductase, Fdft1 = farnesyl diphosphate farnesyl transferase 1, Dhcr7 = 7-dehydrocholesterol reductase, Ldlr = LDL-receptor, Srb1 = Scavenger receptor, class B, type 1, Cyp7a1 = cytochrome P450 7a1, Npc1l1 = Niemann-Pick C1-Like 1, Acat2 = acetyl-Coenzyme A acetyltransferase 2, Abca1 = ATP-binding cassette A1, Abcg5 = ATP-binding cassette G5, Abcg8 = ATP-binding cassette G8, WT = wild-type mice, OE-NPY = OE-NPY^DBH mice.
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   Figure 4

   Glucose metabolism in OE-NPY^DBH mice. (A) Glucose tolerance test and (B) glucose-induced hyperinsulinemia in 4-month-old homozygous OE-NPY^DBH vs wild-type mice (n = 7/group). (C) Glucose (D) and pyruvate tolerance tests of 4-month-old and 7-month-old homozygous OE-NPY^DBH vs wild-type mice (n = 6–11/group). (E) mRNA expression of selected genes involved in glucose metabolism in 2-month-old heterozygous (pre-obese) (n = 5/group) and 7-month-old homozygous (obese) (n = 10/group) OE-NPY^DBH mice relative to wild-type mice. Beta actin was used as endogenous control. (F) Representative periodic acid-Schiff stained liver slides showing glycogen accumulation into the hepatocytes in 7-month-old OE-NPY^DBH vs wild-type mice (scale bar 50 µm). Values are expressed as means ± s.e.m. *P < 0.05, **P < 0.01 and ***P < 0.001 with two-way ANOVA of repeated measures (A–D) or Student’s t-test (E). GTT = glucose tolerance test, PTT = pyruvate tolerance test, Pck1 = phosphoenolpyruvate carboxykinase 1, Pgc1a = peroxisome proliferative activated receptor, gamma, coactivator 1 alpha, Gys2 = Glycogen synthase 2, Pygl = liver glycogen phosphorylase, WT = wild-type mice, OE-NPY = OE-NPY^DBH mice.
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   Figure 5

   Type 2 diabetes model in OE-NPY^DBH mice. (A) Weight gain, (B) whole body fat mass %, (C) fasting blood glucose, (D) glucose and (E) insulin tolerance tests, (F) fasting serum insulin levels, (G) quantitated pancreatic insulin intensity, and (H) the amount and size of beta cells in homozygous OE-NPY^DBH vs wild-type mice (n = 7/group) subjected to high caloric diet from age of 13 weeks and low-dose streptozotocin from age of 16 weeks (Week 0) onwards. Values are expressed as means ± s.e.m. *P < 0.05, **P < 0.01 and ***P < 0.001 with two-way ANOVA and Bonferroni post hoc test (B) or two-way ANOVA of repeated measures (C–D). Gray dashed line = glucose 13.8 mmol L⁻¹, the limit for diabetes in mice, STZ = streptozotocin, GTT = glucose tolerance test, ITT = Insulin tolerance test, WT = wild-type mice, OE-NPY = OE-NPY^DBH mice.
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   Figure 6

   Roles of NPY and adrenergic receptors in OE-NPY^DBH mice. (A) mRNA expression of liver NPY- and adrenergic receptors in 2-month-old heterozygous (pre-obese) (n = 4–5/group) and 7-month-old homozygous (obese) (n = 6–7/group) OE-NPY^DBH mice relative to wild-type mice. Beta actin was used as endogenous control. (B) Weight gain, (C) fat mass gain, (D) cumulative food intake, (E–F) serum lipids, (G–H) liver lipids and I) liver 8-isoprostane in OE-NPY^DBH vs wild-type mice (n = 10–13/group) treated with Y1R-antagonist BIBO3044 or vehicle for 4 weeks. (J) Energy expenditure, (K) respiratory exchange ratio and (L) physical activity of wild-type mice (n = 4/group) treated with Y1R-antagonist or vehicle for 1 week. Values are expressed as means ± s.e.m. *P < 0.05, **P < 0.01 and ***P < 0.001 difference between genotypes with Student’s t-test (A, H and I) or with two-way ANOVA and Bonferroni post hoc test (B–D and F–G). #P < 0.05 and ##P < 0.01 difference between treatments within a same genotype with two-way ANOVA and Bonferroni post hoc test (E and H), or with two-way ANOVA of repeated measures (L). Adrb1 = adrenergic-beta1-receptor, Adrb2 = adrenergic-beta2-receptor, Y1r = Y1-receptor, EE = energy expenditure, RER = respiratory exchange ratio, WT = wild-type mice, OE-NPY = OE-NPY^DBH mice.

• © 2017 Society for Endocrinology