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Diet‐induced obesity in rats decreases insulin sensitivity and baroreflex gain
Author(s) -
Zhao Ding,
Azar Afaf S.,
Brooks Virginia L.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.785.4
Subject(s) - endocrinology , medicine , baroreflex , leptin , phenylephrine , obesity , weight gain , blood pressure , insulin , chemistry , heart rate , body weight
Baroreflex gain (BRG) is impaired in Zucker rats that are obese due to mutation of the leptin receptor. However, whether diet‐induced obesity also decreases BRG is unknown. To test this hypothesis, we measured BRG in conscious outbred SD male rats (~250 g) fed a moderately high fat diet (HFD; 33% kcal fat) for 4‐5 weeks; rats in the top tertile of weight gain were obesity prone (OP), whereas the lowest tertile were obesity resistant (OR). BRG was quantified using a 4 parameter sigmoidal fit of heart rate (HR) responses to slow ramp (3‐5 min) changes in arterial pressure (AP), induced by infusing nitroprusside and phenylephrine. To test if BRG impairment in OP rats is related to decreases in insulin sensitivity (IS), IS was also measured using the hyperinsulinemic‐euglycemic clamp method. OP rats weighed more than OR rats after 4 weeks of HFD (OP: 463±19 g, n=6; OR: 367±22 g, n=5; P<0.01). Neither AP (OP: 106±8 mmHg; OR: 95±4 mmHg) nor HR (OP: 373±27 bpm; OR: 369±3 bpm) differed significantly. BRG was reduced in OP rats (2.9±0.2 bpm/mmHg, OP; 4.0±0.3 bpm/mmHg, OR; P<0.05); however, other sigmoidal parameters were not different. Interestingly, OP rats also exhibited reduced IS (7.0±1.0 mg/kg ?min, OP; 22.6±1.9 mg/kg▸min, OR; P<0.01). In summary, BRG and IS decrease with diet‐induced obesity in rats. Because insulin enhances BRG, we speculate that the decreases in BRG and IS are functionally linked. Supported by AHA and NIH HL088552.