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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the effects of peripherally administered pyruvate and lactate on the intake of high fat (HF) and low fat (LF) diets by a strain of rat either sensitive (Osborne-Mendel, OM) or resistant (SSB/Pl) to high fat-induced obesity. Both pyruvate and lactate inhibited the intake of HF and LF diets by OM rats and these effects were blocked by selective hepatic vagotomy. In contrast, in S5B/Pl rats fed an LF diet the responses to pyruvate and lactate were attenuated and were absent in S5B/Pl rats fed the HF diet. These data suggest that OM and S5B/Pl rats differ either in their metabolism of pyruvate and lactate or in their responses to these metabolites.
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PMID:Effects of pyruvate and lactate on food intake in rat strains sensitive and resistant to dietary obesity. 870 Sep 60

This study compared the effects of exogenous pyruvate and lactate on the serum levels of pyruvate, lactate, glucose, alanine, and insulin, as well as the activity of hepatic pyruvate dehydrogenase (PDH) in strains of rat that were either sensitive [Osborne-Mendel (OM)] or resistant (S5B/Pl) to high-fat diet-induced obesity. Serum pyruvate and lactate were significantly higher and glucose lower in ad libitum-fed OM rats, but these differences disappeared after an 18-h fast. The increase in pyruvate and lactate after exogenous pyruvate administration was significantly greater in S5B/Pl rats than OM rats. There were no differences in serum alanine with strain or diet. The total PDH activity was similar across strains and diets but the proportion of PDH in its activated form (PDHa) was decreased in ad libitum-fed S5B/Pl rats. Pyruvate injection increased insulin and hepatic PDHa activity in OM rats fed both high- and low-fat diets, but these responses were greatly attenuated or absent in S5B/Pl rats. The data are consistent with the hypothesis that modulation of carbohydrate oxidation by PDH may be related to susceptibility to obesity when rats are fed a high-fat diet.
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PMID:Pyruvate and hepatic pyruvate dehydrogenase levels in rat strains sensitive and resistant to dietary obesity. 878 Feb 12

The purpose of this study was to assess the effects of voluntary wheel running on the expression of leptin mRNA in rats that are either sensitive (OM) or resistant (S5B/Pl) to diet-induced obesity. Male OM and S5B/Pl rats had ad libitum access to standard rodent diet and water. At 3-5 weeks of age, animals of both strains were randomly assigned to either an exercise or sedentary control group. The exercise groups had 24-h access to a running wheel, and they trained for 7 weeks. During weeks 1-4, animals in both OM and S5B/Pl exercise groups progressively increased their running. During weeks 5-7, S5B/Pl exercisers tended to run more than did OM (approximately 60 vs. 45 km/week), but by the end of the study both groups had an equally greater heart weight (mg/g body weight) and planteris citrate synthase activity than their sedentary controls. Oral glucose tolerance tests performed during the last week of training revealed that compared with their appropriate controls, insulin sensitivity was enhanced (P < 0.05) in OM but not in the S5B/Pl wheel-running groups. Inguinal, epididymal, and retroperitoneal fat pads weighed less in the running than in the nonrunning groups of both strains (P < 0.01). Additionally, exercised animals had an increased percentage of smaller cells (40-60 microm; P < 0.05) and a decreased percentage of larger cells (120-160 microm; P < 0.05) in the epididymal fat depot. Epididymal leptin mRNA measured by Northern blot analysis was reduced in the exercise-trained rats of both strains (P < 0.05). Furthermore, serum leptin was reduced in exercise-trained compared with the control animals of both strains. In comparison to S5B/Pl, control OM animals exhibited both a higher expression and higher circulating levels of leptin (P < 0.05). While serum leptin levels were decreased and food intake was increased in the exercise-trained animals of both strains (P < 0.05), the exact relationship between exercise, leptin, and food intake in this rat model of dietary obesity remains to be determined. Nonetheless, these results suggest that the expression and secretion of leptin can be influenced by exercise training and that these changes (i.e., reduced expression and secretion of protein) can occur independently of changes in whole-body insulin sensitivity and susceptibility to diet-induced obesity.
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PMID:Voluntary wheel running decreases adipose tissue mass and expression of leptin mRNA in Osborne-Mendel rats. 920 Jun 51

We have investigated the central effect of a kappa-opioid agonist and an antagonist on the macronutrient preference in two strains of rat, the Osborne Mendel (OM) and S5B/P1 rats, that have different susceptibility to obesity and differential preference for dietary fat intake. OM rats prefer diets high in fat and are sensitive to diet-induced obesity, whereas S5B/P1 prefer a low fat diet and are resistant to high-fat diet-induced obesity. Rats adapted to a two-choice high fat (HF)/low fat (LF) diet were food deprived (20 h) and then infused into the third cerebroventricle with 10 micrograms nor-binaltorphimine (nor-BNI), a selective kappa-antagonist. Nor-BNI preferentially suppressed HF intake, but not LF intake in OM rats, whereas it affected neither diet in S5B rats. Infusion of U50488, a selective kappa-agonist (33 nmol), into the third cerebroventricle in sated rats, potently stimulated the intake of HF only in the OM rats, whereas it induced a significant but moderate stimulation of intake of both HF and LF diets in the S5B/P1 rats. Total energy intake following U50488 was not significantly different between the two strains. These findings suggest that the enhanced sensitivity of the OM rats to kappa-opioid stimulation for dietary fat may contribute to their preference for dietary fat and possibly their increased susceptibility for obesity.
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PMID:Differential response to kappa-opioidergic agents in dietary fat selection between Osborne-Mendel and S5B/P1 rats. 943 46

The Differential Display technique has been used to identify differences in mRNA expression in adipose tissue after the introduction of a high fat diet to two strains of rat (OM and S5B/PI) that differ in their susceptibility to develop obesity on this diet. The insulin receptor tyrosine kinase inhibitor protein (fetuin) was shown to be differentially expressed in OM but not S5B/PI rats. This circulating protein may play a role in the development of peripheral insulin resistance associated with high fat diets.
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PMID:Differential expression of insulin receptor tyrosine kinase inhibitor (fetuin) gene in a model of diet-induced obesity. 967 49

Osborne-Mendel (OM) and S5B/Pl rats differ in their sensitivity to develop obesity when fed a high fat (HF) diet; OM rats become obese, whereas S5B/Pl rats remain thin. We have investigated the possibilities that either an impaired leptin response or resistance to leptin action underlies the sensitivity to this form of obesity in OM rats. In Experiment 1, OM and S5B/Pl rats fed a nonpurified diet were killed at d 0 or were fed either a HF (56% fat energy) or a low fat (LF, 10% fat energy) diet for 2 or 7 d. The HF diet increased serum leptin significantly by d 2 to levels that were similar in both rat strains. At 7 d, leptin levels were lower than at d 2 but remained higher than levels in the d 0 control groups. The leptin mRNA:18S RNA ratio in epididymal adipose tissue increased to higher levels in HF-fed OM rats than in S5B/Pl rats fed that diet. However, although the LF diet had no effect in S5B/Pl rats, it increased leptin mRNA levels in epididymal adipose tissue of OM rats compared with the controls fed the nonpurified diet. In Experiment 2, OM and S5B/Pl rats were fed HF or LF diets for 5 wk. At that time, their feeding response to a range of leptin doses (0, 1, 5 or 10 microgram) given intracerebroventricularly was tested after overnight food deprivation. There was a similar dose-dependent reduction in energy intake in response to leptin in both OM and S5B/Pl rats. These responses were independent of the diet. The data suggest that the susceptibility of OM rats to HF diet-induced obesity is not related to either a loss of central sensitivity to leptin or a failure to enhance leptin production acutely, although the failure to maintain chronically increased levels of serum leptin could contribute to the obesity.
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PMID:The effects of a high fat diet on leptin mRNA, serum leptin and the response to leptin are not altered in a rat strain susceptible to high fat diet-induced obesity. 977 25

We previously demonstrated that taste receptor cells (TRCs) respond to cis-polyunsaturated fatty acids (PUFAs) through an inhibition of delayed rectifying K channels (KDR), which may represent the transduction mechanism for dietary fat. To determine if there is a link between the sensitivity of fungiform TRCs to PUFAs and dietary fat preferences, we compared the PUFA-sensitivity of TRCs using patch clamp techniques from Osborne-Mendel (O-M) and S5B/Pl rats, which display dietary preferences for fat over carbohydrate and carbohydrate over fat, respectively. In isolated TRCs, the PUFAs, linoleic (C18:2), linolenic (C18:3) and arachidonic acid (C20:4) inhibit KDR in a concentration-dependent manner in both strains, while the unsaturated lauric acid (C12:0) was ineffective. KDR from TRCs of S5B/Pl rats were significantly more sensitive to inhibition by all three PUFAs (10 microM) than were TRCs from O-M rats. We are currently investigating whether this differential responsiveness is due to (i) the relative affinity of the interaction between cis-PUFAs and the delayed rectifying K channels or (ii) the relative density of delayed rectifying K channels in the two rat strains. Whatever the mechanism, these data suggest an inverse correlation between peripheral gustatory sensitivity to PUFAs and the dietary preference for fat. This finding may provide insight into the mechanism for sensing dietary fat that allows the S5B rats to reduce fat intake on a high-fat diet and avoid the obesity which results when O-M rats eat a high-fat diet.
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PMID:Dietary fat preferences are inversely correlated with peripheral gustatory fatty acid sensitivity. 992 99

The effects of duodenal infusions of fats on sham feeding was measured in two strains of rats that differ in their susceptibility to fat-induced obesity. Osborne-Mendel rats are prone to developing obesity on a high-fat diet and preferentially choose fats over carbohydrates in macronutrient selection paradigms. In contrast, S 5B/PL rats are resistant to developing obesity when eating a high-fat diet, and preferentially choose carbohydrates in macronutrient selection paradigms. To test the hypothesis that differences in the satiating potency of fats in the small intestine contributed to these differences between the two strains, we measured the effects of duodenal infusions of Intralipid and sodium linoleate on sham-feeding intakes. The results were consistent with the hypothesis. Duodenal infusions of either of these fats decreased intake significantly more in S5B/PL rats than in Osborne-Mendel rats. Both rat strains sham fed similar amounts when intestinally infused with 0.15 M NaCl. These results suggest that differences in responses to intestinal satiating mechanisms may contribute to the differences in susceptibility to fat-induced obesity in these rat strains.
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PMID:Differential satiating effects of fats in the small intestine of obesity-resistant and obesity-prone rats. 1038 6

One of the transduction mechanisms for the chemoreception of fat has been proposed to involve the inhibition of delayed rectifying potassium (DRK) channels by polyunsaturated free fatty acids (PUFAs). In the present study we have compared the responsiveness of fungiform taste receptor cells (TRCs) to fatty acids in obesity-prone (Osborne-Mendel; O-M) and obesity-resistant (S5B/Pl) rat strains using patch clamp recording. TRCs from S5B/Pl rats were markedly more responsive to PUFAs than those from O-M, yet with identical inhibition constants. Moreover, addition of PUFAs to subthreshold concentrations of saccharin enhanced preference for the mixture in two-bottle preference tests compared to the saccharin alone in S5B/Pl but not O-M rats. The correlation between electrophysiological and behavioral effects of PUFAs suggested that differences in fatty acid-sensitive DRK expression may underlie the phenotypic differences between S5B/Pl and O-M rats. Consistent with this hypothesis, O-M rats exhibit a greater DRK current density and express quantitatively more DRK channels as assayed using quantitative real-time PCR. No differences were found when comparing expression of fatty acid activated two pore domain potassium channels. We propose that the ratio of fatty acid-sensitive DRK channels to fatty acid-insensitive DRK channels may be important to contributing to overall peripheral fatty acid sensitivity and in that way influence the strength of the resulting chemosensory response to fat.
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PMID:Fatty acid responses in taste cells from obesity-prone and -resistant rats. 1624 10

Stimulation of mu opioid receptors preferentially increases the intake of a high fat diet. In this paper we investigated whether there was a difference in the expression of mu opioid receptors between animals susceptible (Osborne-Mendel) or resistant (S5B/Pl) to obesity induced by eating a high fat diet. Immunohistochemical studies demonstrated that Osborne-Mendel rats eating a chow diet had an increased number of mu opioid receptors in the arcuate nucleus when compared to S5B/Pl rats. These immunohistochemical findings were supported by Real Time-PCR which demonstrated that the mRNA level of mu opioid receptors was also increased in the hypothalamus of Osborne-Mendel rats compared to S5B/Pl rats. Low doses of the mu opioid receptor agonist DAMGO [d-Ala(2)-N-Me-Phe(4)-Glycol(5)]-enkephalin administered to Osborne-Mendel rats caused a significant increase in the preference for a diet high in fat. The same doses of DAMGO switched the diet preference of S5B/Pl rats to high fat but did not significantly increase food intake. The combination of these findings suggests that the increased levels of hypothalamic mu opioid receptors in Osborne-Mendel rats may contribute to their preference for a diet high in fat and increase their susceptibility to becoming obese.
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PMID:Increased expression of mu opioid receptors in animals susceptible to diet-induced obesity. 1699 47


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