Effects of diet and time of the day on serum and CSF leptin levels in Osborne-Mendel and S5B/Pl rats. 2004

Yuri Ishihara, and Christy L White, and Haruaki Kageyama, and Asako Kageyama, and David A York, and George A Bray
Pennington Biomedical Research Center, Louisiana State University, Baton Rouge 70808, USA.

OBJECTIVE To characterize the effects of dietary fat on the diurnal variation in serum and cerebrospinal fluid (CSF) leptin levels in Osborne-Mendel (OM) and S5B/Pl rats and quantitate the dose response to lower doses of leptin administered into the third cerebral ventricle. METHODS Rats were fitted with implanted vascular ports or third ventricular cannulas and fed either laboratory chow or one of two semipurified high-fat or low-fat diets. Leptin and insulin were measured by immunoassay. RESULTS Serum leptin and insulin levels were positively correlated and had similar patterns of diurnal change. CSF leptin and insulin also had diurnal rhythms, with a peak at 7:00 am, but the diurnal oscillations of leptin and insulin were significantly lower in the S5B/Pl rats than the OM rats. Thus, the ratio of CSF to serum leptin was significantly higher in the S5B/Pl rats than in the OM rats. Dietary fat had no effect on these diurnal patterns. There was a right shift in the dose response to leptin in the OM rats compared with the S5B/P1 rats. S5B/P1 rats treated with leptin had higher signal transduction and translation (STAT-3) mRNA levels compared with pair-fed or saline injected S5B/P1 rats. Hypothalamic suppressors of cytokine signaling mRNA levels were not statistically different between the groups. CONCLUSIONS The higher CSF-to-serum leptin ratio in the S5B/P1 rats, the enhanced suppression of food intake and body weight with leptin injections, and the higher STAT-3 activity in these animals suggest that S5B/P1 rats are more sensitive to leptin than OM rats.

UI MeSH Term Description Entries
D007328 Insulin A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1). Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D008297 Male Males
D009765 Obesity A status with BODY WEIGHT that is grossly above the recommended standards, usually due to accumulation of excess FATS in the body. The standards may vary with age, sex, genetic or cultural background. In the BODY MASS INDEX, a BMI greater than 30.0 kg/m2 is considered obese, and a BMI greater than 40.0 kg/m2 is considered morbidly obese (MORBID OBESITY).
D011922 Rats, Mutant Strains Rats bearing mutant genes which are phenotypically expressed in the animals. Mutant Strains Rat,Mutant Strains Rats,Rat, Mutant Strains,Strains Rat, Mutant,Strains Rats, Mutant
D012097 Repressor Proteins Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release. Repressor Molecules,Transcriptional Silencing Factors,Proteins, Repressor,Silencing Factors, Transcriptional
D001835 Body Weight The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms. Body Weights,Weight, Body,Weights, Body
D002940 Circadian Rhythm The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs or environmental and physiological stimuli. Diurnal Rhythm,Nyctohemeral Rhythm,Twenty-Four Hour Rhythm,Nycthemeral Rhythm,Circadian Rhythms,Diurnal Rhythms,Nycthemeral Rhythms,Nyctohemeral Rhythms,Rhythm, Circadian,Rhythm, Diurnal,Rhythm, Nycthemeral,Rhythm, Nyctohemeral,Rhythm, Twenty-Four Hour,Rhythms, Circadian,Rhythms, Diurnal,Rhythms, Nycthemeral,Rhythms, Nyctohemeral,Rhythms, Twenty-Four Hour,Twenty Four Hour Rhythm,Twenty-Four Hour Rhythms
D003345 Corticosterone An adrenocortical steroid that has modest but significant activities as a mineralocorticoid and a glucocorticoid. (From Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed, p1437)
D004032 Diet Regular course of eating and drinking adopted by a person or animal. Diets
D004041 Dietary Fats Fats present in food, especially in animal products such as meat, meat products, butter, ghee. They are present in lower amounts in nuts, seeds, and avocados. Fats, Dietary,Dietary Fat,Fat, Dietary

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