Journal Article•
Regulation of lipid metabolism
About: This article is published in The Physiologist.The article was published on 1970-05-01 and is currently open access. It has received 91 citations till now. The article focuses on the topics: Lipid metabolism & Lipid droplet.
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TL;DR: While not definitively established, roles for placental lactogen and prolactin are attractive possibilities in homeorhetic regulation of maternal tissues to support pregnancy and the initiation of lactaion, respectively.
1,697 citations
TL;DR: Somatotropin is almost certainly a predominant homeorhetic influence during lactation because its exogenous administration causes specific changes in glucose metabolism (and many other functions) of various nonmammary tissues which faithfully mimic normal adaptations to early lactation.
Abstract: Increased glucose requirements of the gravid uterus during late pregnancy and even greater requirements of the lactating mammary glands necessitate major adjustments in glucose production and utilization in maternal liver, adipose tissue, skeletal muscle, and other tissues In ruminants, which at all times rely principally on hepatic gluconeogenesis for their glucose supply, hepatic glucose synthesis during late pregnancy and early lactation is increased to accommodate uterine or mammary demands even when the supply of dietary substrate is inadequate At the same time, glucose utilization by adipose tissue and muscle is reduced In pregnant animals, these responses are exaggerated by moderate undernutrition and are mediated by reduced tissue sensitivity and responsiveness to insulin, associated with decreased tissue expression of the insulin-responsive facilitative glucose transporter, GLUT4 Peripheral tissue responses to insulin remain severely attenuated during early lactation but recover as the animal progresses through mid lactation Specific homeorhetic effectors of decreased insulin-mediated glucose metabolism during late pregnancy have yet to be conclusively identified In contrast, somatotropin is almost certainly a predominant homeorhetic influence during lactation because its exogenous administration causes specific changes in glucose metabolism (and many other functions) of various nonmammary tissues which faithfully mimic normal adaptations to early lactation
500 citations
TL;DR: Targeting of dietary fatty acids toward ovarian and uterine function may enhance efficiency of reproductive management and fertility.
466 citations
TL;DR: The results indeed suggest that 1st-yr re- cruitment of largemouth bass in southern systems is governed by several functionally dependent critical events, and it is suggested that future recruitment studies should adopt a more synthetic approach.
Abstract: Four early life events (i.e., hatching, the ontogenetic diet shift to piscivory, fall lipid accumulation, and the first winter) are conceptualized as being critical to 1st-yr recruitment success of largemouth bass (Micropterus salmoides) via cause-and-effect as- sociations among them. Toward this end, we conducted a multiple life-stage investigation of largemouth bass to examine the functional dependency and significance to recruitment of these temporally separated early life events. Specifically, we quantified growth and survival of two largemouth bass year-classes in six Alabama ponds from hatching to the end of the first winter. The first winter was an important survival bottleneck with lower largemouth bass sur- vival in ponds with smaller largemouth bass (high-density ponds), relative to ponds with larger fish (low-density ponds). While cannibalism was not important, we found size- dependent first-winter mortality to be regulated directly by lipid reserves (i.e., triglycerides) accumulated during fall, and indirectly by both hatch date and the ontogenetic diet shift to piscivory during summer. Early-hatched largemouth bass attained an initial length ad- vantage, remaining large relative to late-hatched fish, despite the relatively higher growith rate of late-hatched fish during their first month of life. Enhanced size permitted early- hatched fish to become piscivorous before late-hatched fish, increasing their access to fish prey (i.e., sunfishes) during fall. This in turn elevated their fall lipid accumulation and winter survival above that of late-hatched fish. Our results indeed suggest that 1st-yr re- cruitment of largemouth bass in southern systems is governed by several functionally dependent critical events. Because each is likely vital to understanding recruitment vari- ability, we suggest that future recruitment studies should adopt a more synthetic (i.e., multiple life-stage) approach.
279 citations
TL;DR: Energy balance data for early lactation cows fed supplemental fat are not plentiful; however, slight but statistically nonsignificant increases have been observed when feeding fat.
Abstract: Improved reproductive performance and reduced incidence of metabolic disorders have been postulated to be benefits of feeding supplemental fat to dairy cows. Increased plasma nonesterified fatty acid concentrations during fat supplementation may result from incomplete tissue uptake of fatty acids after lipoprotein lipase hydrolysis of very-low-density lipoprotein triglyceride; however, evidence suggests that net adipose tissue triglyceride hydrolysis may be increased during fat supplementation. Plasma 3-OH-butyrate concentrations remain relatively constant during fat supplementation but may have a tendency to be reduced if fat is supplemented to cows having relatively high basal plasma 3-OH-butyrate concentrations. Because plasma ketone levels usually increase when nonesterified fatty acid concentrations are elevated, it is hypothesized that potential antiketogenic effects of added fat are due to a glucose sparing effect. Supplemental fat does not seem to reduce hepatic lipid infiltration near the time of calving. Potential mechanisms by which supplemental fat may improve reproductive performance include stimulation of prostaglandin F2 a synthesis and secretion and enhanced utilization of blood cholesterol for progesterone synthesis. Days postpartum until first ovulation and luteal function of dairy cattle have been related to energy balance during the first 3 wk postpartum. Energy balance data for early lactation cows fed supplemental fat are not plentiful; however, slight but statistically nonsignificant increases have been observed when feeding fat. Cows fed supplemental fat that experience improved energy balance may begin to cycle sooner because of enhanced follicular growth and development. Applied studies examining the effects of supplemental fat on reproductive performance have provided inconsistent results.
279 citations