Plasma growth hormone secretion is impaired in  obesity-prone rats before onset of diet-induced obesity

Lauterio, Thomas J.; Barkan, Ariel L.; DeAngelo, Mark; DeMott-Friberg, Roberta; Ramirez, Ray

doi:10.1152/ajpendo.1998.275.1.e6

Cited by 24 publications

(28 citation statements)

References 31 publications

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“…28 The previous study indicated that the secretion of growth hormones has been shown to be impaired before the onset of a high-fat diet in obesity-prone rats. 31 Growth hormones might induce fast-to-slow transformation of muscle fibre type composition. 32,33 It is possible that the impairment of growth hormone secretion induced both body fat accumulation and fibre type transformation in obesity-prone rats in the study of Abou Mrad et al 28 In the present study, FFDR had higher CS and HAD activities than CR in the M. plantaris but not in the M. gastrocnemius or soleus.…”

Section: Discussionmentioning

confidence: 99%

Dietary obesity-resistance and muscle oxidative enzyme activities of the fast-twitch fibre dominant rat

Suwa

Kumagai

Higaki³

et al. 2002

Int J Obes

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OBJECTIVES:To clarify whether the muscle fibre composition and=or muscle oxidative enzyme activity are related to dietary body weight gain and abdominal fat accumulation. METHODS: Genetically fast-twitch fibre dominant rats (FFDR) and control rats (CR) were divided into low-fat (20% of energy from fat) or high-fat (60% of energy from fat) diet groups: CR with a low-fat diet (CL); CR with a high-fat diet (CH); FFDR with a low-fat diet (FL); and FFDR with a high-fat diet (FH). After 6 weeks of following such diets, the body weight gain, abdominal fat content, food intake, muscle fibre composition and oxidative enzyme activities were estimated. RESULTS: The total body weight gain in CH was from 18 to 62% higher than in the other groups (P < 0.05) and percentage abdominal fat in CH was also from 26 to 61% higher than in the other groups (P < 0.05), while the energy intake did not differ among the groups. The percentage of type IIX fibres of M. gastrocnemius in FL (33.4%) and FH (36.3%) were higher than in CL (16.8%) and CH (19.8%; P < 0.05), and the type IIA fibres of M. soleus in FL (14.1%) and FH (11.8%) were higher than in CL (2.0%) and CH (3.5%; P < 0.05). The citrate synthase (CS) activity of of M. plantaris in FL and FH were higher than CL (46 and 54%, respectively, P < 0.05). b-Hydroxyacyl CoA dehydrogenase (HAD) activity in FL and FH were higher than in CL (21 and 31%, respectively, P < 0.05) and that in FH was higher than CH (23%, P < 0.05). On the other hand, the enzyme activities of M. gastrocnemius and soleus were identical among the groups. CONCLUSION: The FFDR was more obesity-resistant than the CR after a high-fat diet. These results suggest that the muscle oxidative capacity rather than muscle fibre composition is a possible determinant of obesity.

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Section: Discussionmentioning

confidence: 99%

Dietary obesity-resistance and muscle oxidative enzyme activities of the fast-twitch fibre dominant rat

Suwa

Kumagai

Higaki³

et al. 2002

Int J Obes

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“…Assignment of rats into obesity-prone (OP, nϭ6) and obesity-resistant (OR, nϭ6) groups was performed as previously described. 24,25 In brief, construction of body-weight-gain histograms was performed at the end of the study for MHF and LF diet groups. OR rats were defined as those with weight gains equal to or less than the heaviest controls, and the OP rats, as those with greater weight gains.…”

Section: · Dmentioning

confidence: 99%

Pioglitazone Prevents Hypertension and Reduces Oxidative Stress in Diet-Induced Obesity

et al. 2004

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Abstract-The objective of this study was to determine the effect of pioglitazone on blood pressure (BP) and oxidative balance in obese, hypertensive, Sprague-Dawley rats and to identify some of the molecular mechanisms involved. After 12 weeks of a moderately high-fat diet, rats diverged into obesity-prone (OP) and obesity-resistant (OR) groups (nϭ6 per group). At the end of the diet, peroxisome proliferator activated receptor-␥ (PPAR␥) mRNA expression and activity in the renal cortex and medulla of OP rats were significantly lower compared with that in OR rats. Pioglitazone treatment increased PPAR␥ expression and activity in OP rats, suggesting a possible direct ligand-related effect of pioglitazone. As opposed to the untreated OP group, which showed moderate hypertension (systolic BPϭ159Ϯ5.3 mm Hg) after 12 weeks, pioglitazone-treated rats were normotensive (systolic BPϭ123.9Ϯ2.7 mm Hg). Insulin production was reduced by 2-fold in the OP group treated with pioglitazone. Urinary isoprostanes and renal lipid peroxides were also reduced in OP rats treated with pioglitazone compared with untreated counterparts. Also, expression of p47phox and gp91phox, both increased in OP versus OR rats, was reduced in the former by pioglitazone treatment. In addition, pioglitazone treatment increased nitrate/nitrite excretion and expression of renal endothelial and neuronal nitric oxide synthase. Collectively, the results show that pioglitazone treatment prevented hypertension and renal oxidative stress both by reducing free-radical production and by increasing nitric oxide production/availability. Key Words: kidney Ⅲ oxidative stress Ⅲ free radicals Ⅲ nitric oxide Ⅲ vitamins O besity is a widespread and increasingly prevalent condition associated with a large number of comorbid diseases, one of the most important of which is obesityinduced hypertension. A pleiotropic class of molecules involved in regulation of gene expression in a variety of metabolic and cardiovascular conditions is the peroxisome proliferator-activated receptors (PPARs). PPARs are ligandactivated transcription factors that form heterodimers with the 9-cis retinoic acid receptor RXR␣. 1 PPAR␥ is one of the three PPAR isoforms and is one of the major regulators of adipogenesis. 2 In addition, PPAR␥ exerts pleiotropic effects on blood pressure, lipid metabolism, and insulin action.Recent genetic analysis showed that 2 dominant-negative mutations in PPAR␥ were associated with severe hypertension in humans. 3,4 Consistent with these findings, thiazolidinendiones, the insulin-sensitizer drugs (pioglitazone, rosiglitazone) that are also high-affinity PPAR␥ ligands, 5 have been shown to lower blood pressure (BP) in a variety of hypertensive animal models 6 -8 as well as in diabetic and nondiabetic, 9 hypertensive humans. However, the mechanism underlying the antihypertensive effects of PPAR␥ agonists is not known. PPAR␥ and RXR have been found constitutively expressed in the inner medullary collecting ducts, thick ascending limb, glomerulus, and renal medullary mic...

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“…These markers of obesity include initial weight gain during the first few days on a high-fat diet, 1,8 levels of leptin after a single high-fat meal in rats maintained on a lab chow diet, 9 meal-induced release of insulin 10 and fasting levels of triglycerides or basal growth hormone secretion in rats on chow. 11,12 While still at normal weight, the OP rats are found to exhibit a phenotype that has similarities to that seen in adult rats after they have become obese. [7][8][9][13][14][15][16] This phenotype in OP animals on a high-fat diet includes a small elevation of insulin, leptin, triglycerides and glucose, reduced sensitivity to insulin and leptin administration, and reduced capacity in muscle to metabolize fat.…”

Section: Introductionmentioning

confidence: 95%

Weight gain model in prepubertal rats: prediction and phenotyping of obesity-prone animals at normal body weight

et al. 2007

Int J Obes

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Objective: Male Sprague-Dawley rats maintained from birth on a high-fat diet were examined to determine whether a specific measure before puberty can identify and allow one to characterize prepubertal rats at normal weight with high vs low risk for adult obesity. Materials and methods: Measures from weaning (day 21) to around puberty (day 45) were taken of weight gain, absolute body weight and daily energy intake on a high-fat diet and related to the amount of body fat accumulated at maturity (80-100 days of age). Rats identified by a specific prepubertal measure as obesity-prone (OP) vs obesity-resistant (OR) were then characterized before and after puberty. Results: Prepubertal weight gain from days 30 to 35 of age was the strongest and earliest positive correlate of ultimate body fat accrual in adult rats. The highest (8-10 g/day) compared to lowest (5-7 g/day) weight-gain scores identified accurately and reproducibly distinct OP and OR subgroups at day 35 that became obese or remained lean, respectively, as adults. The OP rats with rapid prepubertal weight gain and 50% greater adiposity at maturity (day 100) exhibited the expected phenotype of already-obese rats. These included elevated levels of leptin, insulin, triglycerides and glucose, increased galanin (GAL) peptide levels in the paraventricular nucleus (PVN) and reduced neuropeptide Y (NPY) levels in the arcuate nucleus (ARC). Before puberty (day 35), the OP rats with normal fat pad weights, energy intake and endocrine profile similar to OR rats exhibited these disturbances characteristic of obese rats. They had decreased capacity for fat oxidation in muscle, increased GAL expression in PVN and reduced expression of NPY and agouti-related protein in ARC. Conclusion: Prepubertal weight gain can identify OP rats on day 35 when they have minimal body fat but exhibit specific metabolic and neurochemical disturbances expected to promote obesity and characteristics of already-obese adult rats.

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Plasma growth hormone secretion is impaired in obesity-prone rats before onset of diet-induced obesity

Cited by 24 publications

References 31 publications

Dietary obesity-resistance and muscle oxidative enzyme activities of the fast-twitch fibre dominant rat

Dietary obesity-resistance and muscle oxidative enzyme activities of the fast-twitch fibre dominant rat

Pioglitazone Prevents Hypertension and Reduces Oxidative Stress in Diet-Induced Obesity

Weight gain model in prepubertal rats: prediction and phenotyping of obesity-prone animals at normal body weight

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