Effects of manipulations of glucoregulation on feeding in the ground squirrel

Nizielski, Steven E.; Morley, John E.; Bartness, Timothy J.; Seal, Ulysses S.; Levine, Allen S.

doi:10.1016/0031-9384(86)90072-7

Cited by 9 publications

(3 citation statements)

References 42 publications

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“…Thus part of estradiol's inhibitory action on feeding in normally cycling female rats may be mediated by modulation of the activity of the glucagon satiation-signaling pathway. Glucagon has previously been reported to decrease feeding in female rats (30), rabbits (36), ground squirrels (31), and dogs (23,28). In these studies, however, estrous cycling was not monitored, the role of estradiol was not investigated, and the responses of male and female animals were not compared.…”

Section: Discussionmentioning

confidence: 99%

Estradiol increases glucagon's satiating potency in ovariectomized rats

Geary

Asarian

2001

American Journal of Physiology-Regulatory, Integrative and Comp

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Estradiol decreases meal size, food intake, and body weight in female rats. To investigate whether these effects of estradiol involve a change in the sensitivity of the signaling pathway through which pancreatic glucagon released during meals contributes to meal termination (satiation), glucagon or glucagon antibodies were infused via the hepatic portal vein in ovariectomized rats that were chronically treated with estradiol benzoate (2 microg/day sc) or vehicle alone (100 microl sesame oil). Infusions began at 1 h after dark onset, as rats were refed after 7 h of food deprivation. Glucagon (3 microg/min for 30 min) decreased feeding during the initial 45 min of food access in both groups of rats, but the inhibition was significantly greater in estradiol- than in oil-treated rats. Similarly, antagonism of endogenous glucagon by infusion of glucagon antibodies (a dose neutralizing 3 ng of glucagon in vitro during the first 3 min of refeeding) increased feeding significantly more in estradiol- than in oil-treated rats. These data indicate that an increase in the activity of the endogenous glucagon satiation-signaling pathway may be part of the mechanism for estradiol's inhibitory effect on feeding.

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Section: Discussionmentioning

confidence: 99%

Estradiol increases glucagon's satiating potency in ovariectomized rats

Geary

Asarian

2001

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Species that undergo annual cycles of fat gain and loss, including ground squirrels (Spermophilus lateralis; Ref. 13 (48), but they lack food intake responses to energy challenges such as food deprivation (1,2,15) or glucoprivation (1,14,53). Thus a likely mechanism underlying lipectomy-induced compensation in these species is decreased energy expenditure, as suggested by decreased sympathetic activity of BAT (70), and thus decreased thermogenesis.…”

Section: Discussionmentioning

confidence: 99%

Sexually dimorphic responses to fat loss after caloric restriction or surgical lipectomy

Shi

Strader²,

Woods

et al. 2007

American Journal of Physiology-Endocrinology and Metabolism

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Specifically, males tend to accumulate relatively more visceral fat, whereas females accumulate relatively more subcutaneous fat. The phenomenon of maintaining typical sex-specific fat distributions suggests sex-specific mechanisms that regulate energy balance and adiposity. We used two distinct approaches to reduce fat mass, caloric restriction (CR), and surgical fat removal (termed lipectomy) and assessed parameters involved in the regulation of energy balance. We found that male and female mice responded differentially to CR-and to lipectomy-induced fat loss. Females decreased energy expenditure during CR or after lipectomy. In contrast, males responded by eating more food during food return after CR or after lipectomy. Female CR mice conserved subcutaneous fat, whereas male CR mice lost adiposity equally in the subcutaneous and visceral depots. In addition, female mice had a reduced capability to restore visceral fat after fat loss. After CR, plasma leptin levels decreased in male but not in female mice. The failure to increase food intake after returning to ad libitum intake in females could be due to the relatively stable levels of leptin. In summary, we have found sexual dimorphisms in the response to fat loss that point to important underlying differences in the strategies by which male and female mice regulate body weight. food intake; energy expenditure; leptin; subcutaneous fat; visceral fat THE WORLDWIDE PREVALENCE OF obesity with its accompanying comorbidities, including type 2 diabetes, cardiovascular disease, and cancer (7,41,58), continues to rise and has reached epidemic proportions (22,59,81). White adipose tissue (WAT) is the principal site for lipid accumulation in the body, and decreasing WAT is an important therapeutic goal because it would reduce medical complications. This is difficult to achieve, however, because total body fat is regulated by a robust and accurate process that matches energy intake to energy expenditure over time (39). Demonstrations of this include the failure of humans to maintain weight and fat loss after dieting (24, 75) and liposuction surgeries (6) and the return to baseline fat levels after caloric restriction (CR) or partial lipectomy in rodent models.CR and lipectomy represent two ways to accomplish decreased adiposity. CR leads to a spectrum of changes, including decreased basal metabolic rate (33), increased spontaneous activity (32, 56, 65), increased lipid mobilization (26, 37), and many others that collectively lead to reduced body fat (60). In contrast, surgical removal of fat via lipectomy may result in comparably decreased body fat, but the fat loss is specific to selected fat depots depending on the removal site. Altered metabolism and behavior after lipectomy induce compensatory enlargement of nonexcised WAT pads in many species, including mice and rats (48). The fat restoration after either CR or lipectomy is consistent with the hypothesis that total body fat is highly defended and maintained.In humans, the distribution of body fat differs between ma...

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“…Plasma glucose and glycogen in the liver of arctic squirrels decline steadily during hibernating periods (William et al, 1970), indicating that glucose consumption exceed gluconeogenesis, an imbalance between catabolism and synthesis of glucose, during hibernation. However, Nizielski et al (1986) noted that glucose utilization is negligible at the time of deep torpor in ground squirrels, resulting in the increase in blood glucose level.…”

Section: Discussionmentioning

confidence: 99%