Effects of peptide YY[3-36] on short-term food intake in mice are not affected by prevailing plasma ghrelin levels.

The gut-derived hormones peptide YY[3-36] (PYY[3-36]) and ghrelin are believed to influence similar hypothalamic circuits, albeit with opposing actions on energy balance. Thus, we carried out a series of studies to evaluate the interaction of these hormones on short-term food intake responses in mice. Intraperitoneal PYY[3-36] injection reduced short-term food intake by up to 50% in overnight-fasted mice and in postabsorptive animals during the early and late light cycle. This effect was not sensitive to the prevailing endogenous plasma acyl-ghrelin concentrations, which ranged from high physiological (overnight-fasted, 1252 +/- 108 pg/ml) to low levels (late light cycle, 402 +/- 33 pg/ml). PYY[3-36] administration did not reduce plasma total or acyl-ghrelin concentration in conjunction with its anorexigenic actions. Ghrelin increased short-term food intake by up to 1.8-fold in mice treated ip in the early light cycle, but was ineffective in animals treated after an overnight fast or during the late light cycle. Ghrelin did not increase food intake or GH secretion unless plasma levels were increased above high physiological fasting values. The anorexigenic effect of PYY[3-36] over a range of doses was not compromised by coinjection of ghrelin, and PYY[3-36] reduced food intake in agouti mice, which lack fully functional melanocortin signaling. These results in mice support a model in which 1) PYY[3-36] diminishes short-term food intake at least in part through mechanisms distinct from the neuropeptide Y/proopiomelanocortin neural circuits engaged by ghrelin; and 2) a reduction in circulating ghrelin is not requisite for the anorexigenic effects of PYY[3-36].

Lipoprotein subclass profiles of hyperlipidemic diabetic mice measured by nuclear magnetic resonance spectroscopy.

Dyslipidemia accelerates vascular complications of diabetes. Nuclear magnetic resonance (NMR) analysis of lipoprotein subclasses is used to evaluate a mouse model of human familial hypercholesterolemia +/- streptozotocin (STZ)-induced diabetes. A double knockout (DKO) mouse (low-density lipoprotein receptor [LDLr] -/-; apolipoprotein B [apoB] mRNA editing catalytic polypeptide-1 [Apobec1] -/-) was studied. Wild-type (WT) and DKO mice received sham or STZ injections at age 7 weeks, yielding control (WT-C, DKO-C) and diabetic (WT-D, DKO-D) groups. Fasting serum was collected when the mice were killed (age 40 weeks) for Cholestech analysis (Cholestech Corp, Hayward, CA) and NMR lipoprotein subclass profile. By Cholestech, fasting triglyceride and total cholesterol increased in DKO-C versus WT-C. Diabetes further increased total cholesterol in DKO. High-density lipoprotein cholesterol (HDL-C) was similar among all groups. NMR revealed that LDL in all groups was present in a subclass the size of large human LDL and was increased 48-fold in DKO-C versus WT-C animals, but was unaffected by diabetes. HDL was found in a subclass equivalent to large human HDL, and was similar among groups. In conclusion, NMR analysis reveals lipoprotein subclass distributions and the effects of genetic modification and diabetes in mice, but lack of particles the size of human small LDL and small HDL may limit the relevance of the present animal model to human disease.

Nephropathy in a hypercholesterolemic mouse model with streptozotocin-induced diabetes.

BACKGROUND/AIMS: The contribution of preexisting hypercholesterolemia to diabetic nephropathy remains unclear. We assessed the impact of hypercholesterolemia on diabetic nephropathy using a double knockout (DKO) mouse, null for the low-density lipoprotein receptor (LDLRNDASH;/NDASH;) and the apoB mRNA editing catalytic polypeptide 1 (APOBEC1NDASH;/NDASH;). METHODS: Wild-type (WT) and DKO mice received sham or streptozotocin injections at age 7 weeks, yielding control (WT-C, DKO-C) and diabetic (WT-D, DKO-D) groups. At sacrifice (age 40 weeks), albuminuria was determined by ELISA, and kidney sections were examined by light and electron microscopy. RESULTS: Albuminuria increased in diabetic mice (WT-D: 82.4 +/- 37.2 microg/18 h; DKO-D: 58.0 +/- 45.7 microg/18 h) versusnondiabetic controls (WT-C: 10.2 +/- 7.2 microg/18 h; DKO-C: 8.6 +/- 5.3 microg/18 h) (p LT; 0.0001), but was unaffected by hypercholesterolemia. Light microscopy of kidney sections demonstrated increased collagen levels in glomeruli in WT-D mice, but not in DKO-D mice or either control group. Electron microscopy showed a thickened glomerular basement membrane in WT-D mice only. The proximal tubular basement membrane thickness was increased in both diabetic groups versusnondiabetic controls (p LT; 0.01); in WT-D mice this was attributable to collagen accumulation, but in DKO-D mice it was mainly caused by lipid vacuoles. CONCLUSIONS: In this animal model, preexisting hypercholesterolemia did not exacerbate either glomerular lesions of diabetes (collagen accumulation, basement membrane thickening) or albuminuria, but appeared to mitigate these effects. Furthermore, the combination of hypercholesterolemia and diabetes resulted in a significant lipid accumulation in the tubular basement membrane.