Adiponectin is an adipocyte-derived hormone that plays an important role in lipid metabolism and glucose homeostasis. Objectives of this study were 1) to determine the presence and distribution of adiponectin and its receptors 1 and 2 (adipoR1 and adipoR2) in porcine tissues; 2) to characterize pig adiponectin, adipoR1, and adipoR2 mRNA levels in various fat depots from three different breeds of pigs; and 3) to study, in stromal-vascular cell culture, the effects of leptin and tumor necrosis factor-alpha (TNFalpha) on pig adiponectin, adipoR1, and adipoR2 gene expression. To this end, fat Chinese Upton Meishan (UM, n = 10), lean Ham Line (HL, n = 10), and Large White (LW, n = 10) gilts were used. We report the isolation of partial cDNA sequences of pig adipoR1 and adipoR2. Porcine-deduced AA sequences share 97 to 100% homology with human and murine sequences. Pig adipoR1 mRNA is abundant in skeletal muscle, visceral fat, and s.c. fat tissues, whereas adipoR2 mRNA is predominantly expressed in liver, heart, skeletal muscle, and visceral and s.c. fat tissues. Pig adiponectin mRNA levels in s.c. and visceral fat tissues were not associated with plasma insulin and glucose in fasting animals. Subcutaneous (r = -0.44, P < 0.05), visceral (r = -0.43, P < 0.05), and total body fat (r = -0.42, P < 0.05) weights were negatively correlated with adiponectin mRNA levels measured in visceral, but not s.c., fat. Pig adipoR1 and adipoR2 mRNA levels, in visceral fat, were less expressed in fat UM gilts than in the lean HL gilts (P < 0.05). Inverse associations were found between s.c. (r = -0.57, P < 0.01), visceral (r = -0.46, P < 0.05), and total body fat (r = -0.56, P < 0.01) weights and adipoR2 mRNA levels in visceral fat only. We were unable to find such associations for adipoR1 mRNA levels in the overall gilt population. The current study demonstrated that TNFalpha downregulates adiponectin and adipoR2, but not adi-poR1, mRNA levels in stromal-vascular cell culture. Moreover, leptin significantly decreased adiponectin mRNA levels, whereas there was no effect on adiponectin receptors. We conclude that adiponectin and adi-poR2 mRNA levels, but not adipoR1, are modulated in pig visceral fat tissues. Furthermore, our results indicate that TNFalpha interferes with adiponectin function by downregulation of adipoR2 but not of adipoR1 mRNA levels in pigs.

Hammerhead self-cleavage of dimeric, monomeric, truncated and mutated transcripts derived from both polarities of the peach latent mosaic viroid (PLMVd) were characterized. In contrast to some results previously published for a very close sequence variant (see ref. 1), these RNAs exhibit a virtually identical selfcleavage during transcription and after purification. By self-cleavage of dimeric transcripts with normal and mutated hammerhead domains and by complementation experiments, we show that the cleavage reactions involve only single hammerhead structures. This observation contrasts with the case of avocado sunblotch viroid (ASBVd), the other self-cleaving viroid, whose mechanism involves mostly double hammerhead structures, whereas single hammerhead cleavage is associated with viroid-like plant satellite RNAs. The difference in stability between the native secondary structures adopted by viroids and the autocatalytic structures, including the hammerhead motif, governs the efficiency of the self-cleavage reaction. The transition between these conformers is the limiting step in catalysis and is related exclusively to the left arm region of PLMVd secondary structure, which includes the hammerhead sequences. Most of the mutations between the variant we used and the sequence variant previously published are located in this left arm region, which may explain to a great extent the differences in their cleavage efficiency. No interactions with long-range sequences contributing to the autocatalytic tertiary structure were revealed in these experiments.

Mitochondrial dysfunction subsequent to increased oxidative stress and alterations in energy metabolism is considered to play a role in the development of cardiac hypertrophy and its progression to failure, although the sequence of events remains to be elucidated. This study aimed at characterizing the impact of hypertrophy development on the activity and expression of mitochondrial NADP+-isocitrate dehydrogenase (mNADP+-ICDH), a metabolic enzyme that controls redox and energy status. We expanded on our previous finding of its inactivation through posttranslational modification by the lipid peroxidation product 4-hydroxynonenal (HNE) in 7-wk-old spontaneously hypertensive rat (SHR) hearts before hypertrophy development (Benderdour et al. J Biol Chem 278: 45154-45159, 2003). In this study, we used 7-, 15-, and 30-wk-old SHR and Sprague-Dawley (SD) rats with abdominal aortic coarctation. Compared with age-matched control Wistar-Kyoto (WKY) rats, SHR hearts showed a significant 25% decrease of mNADP+-ICDH activity, which preceded in time 1) the decline in its protein and mRNA expression levels (between 10% and 35%) and 2) the increase in hypertrophy markers. The chronic and persistent loss of mNADP+-ICDH activity in SHR was associated with enhanced tissue accumulation of HNE-mNADP+-ICDH and total HNE-protein adducts at all ages and contrasted with the profile of changes in the activity of other mitochondrial enzymes involved in antioxidant or energy metabolism. Two-way ANOVA of the data also revealed a significant effect of age on most parameters measured in SHR and WKY hearts. The mNADP+-ICDH activity, protein, and mRNA expression were reduced between 25% and 35% in coarctated SD rats and were normalized by treatment of SHR or coarctated SD rats with renin-angiotensin system inhibitors, which prevented or attenuated hypertrophy. Altogether, our data show that cardiac mNADP+-ICDH activity and expression are differentially and sequentially affected in hypertrophy development and, to a lesser extent, with aging. Decreased cardiac mNADP+-ICDH activity, which is attributed at least in part to HNE adduct formation, appears to be a relevant early and persistent marker of mitochondrial oxidative stress-related alterations in hypertrophy development. Potentially, this could also contribute to the aetiology of cardiomyopathy.

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Embryonic diapause is the reversible arrest of embryo development prior to implantation under a regime of uterine control that is not well understood. Our objective was to explore uterine modifications associated with the emergence of embryonic diapause in the mink, a species in which embryonic diapause characterizes every gestation. We investigated the uterine transcriptome at reactivation using the suppressive subtractive hybridization technique. A library of 123 differentially expressed genes between uteri with blastocysts in diapause and reactivated blastocysts was generated. Among those genes, 41.5% encode for potential secreted products that are implicated in regulation of cell proliferation (14%), homeostasis (14%), protein folding (11%), electron transport chain (8%), and innate immune response (8%), therefore suggesting that these biological processes are implicated in blastocyst reactivation. Two genes, the high-mobility group nucleosome binding domain 1 ( HMGN1), a chromatin remodeling factor, and the secreted protein acidic and cystein-rich ( SPARC), which is implicated in extracellular cell-cell interactions, were submitted to more detailed analysis of expression patterns in the mink uterus at blastocyst reactivation. Expression of both HMGN1 and SPARC was increased significantly in the uterus at embryo reactivation compared with diapause, principally in the endometrial epithelium and subepithelial stroma. These results provide new insight into uterine signaling at the emergence of the blastocyst from diapause and highlight the factors HMGN1 and SPARC as potential inductors of uterine environment modifications underlying uterine signaling during emergence of the embryo from embryonic diapause.

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Tumor-associated hypoglycemia has been reported in dogs with pancreatic beta-cell tumors, hepatic tumors, and, rarely, with other neoplasms. This article describes 4 dogs with marked hypoglycemia associated with smooth muscle tumors (jejunal leiomyoma, gastric leiomyoma and leiomyosarcoma, and splenic leiomyosarcoma). Presenting clinical signs included grand mal seizures, lethargy, weakness, ataxia, and, in 1 dog, polyuria/polydipsia. The serum insulin concentration was low in 1 dog and normal in the other dog evaluated. Immunohistochemical staining for insulin was negative in the 4 tumors; the 3 tumors arising from the stomach and jejunum stained diffusely positive for glucagon. Blood glucose concentrations rapidly returned to normal after complete surgical resection of the tumors, and clinical signs associated with hypoglycemia resolved. Long-term follow-up available in 3 of the 4 dogs found no recurrence of clinical signs related to hypoglycemia at 15, 31, and 38 months after surgery, respectively.