Insulin resistance of hind-limb tissues <i>in vivo</i> in lactating sheep

Vernon, Richard G.; Faulkner, Anne; Hay, William W.; Calvert, D. T.; Flint, David

doi:10.1042/bj2700783

Cited by 30 publications

(24 citation statements)

References 30 publications

(30 reference statements)

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“…Contrary to previous results using sheep at a similar stage of lactation (e.g. Faulkner & Pollock, 1989;Faulkner & Martin, 1999), we found no reduction in peripheral resting insulin levels in the lactating animals, although this is in agreement with the findings of Vernon et al (1990) that lactation had no effect on pre-infusion levels of insulin in sheep. Ultimately, these differences in insulin levels found amongst the published studies in sheep comparing lactating and control animals may reflect varying levels of nutrition since this is thought to be a major factor in determining sensitivity to insulin (Metcalf & Weekes, 1990).…”

Section: Figurecontrasting

confidence: 57%

“…The difference in the pre-infusion levels of glucose between control and lactating animals may reflect a degree of insulin resistance (i.e. reduced glucose disposal) which is thought to occur in lactating sheep (Faulkner & Martin, 1999); resting glucose levels were also found to be slightly higher in lactating sheep (Vernon et al 1990). Contrary to previous results using sheep at a similar stage of lactation (e.g.…”

Section: Figurementioning

confidence: 99%

“…The dose of Mg used was similar to that previously used to treat stroke patients (Muir & Lees, 1998). We have used a sheep model in this study since, as mentioned above, Mg deprivation produced changes in glucose disposal in a manner similar to that in humans (Matsunobu et al 1990); the lactating group were included since turnover of minerals is high during lactation, and lactating sheep have been reported to show some insulin resistance, at least in skeletal muscle (Vernon et al 1990). …”

Section: Intravenous Magnesium Reduces the Rate Of Glucose Disposal Imentioning

confidence: 99%

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Intravenous Magnesium Reduces the Rate of Glucose Disposal in Lactating Sheep

Gow

Mitchell

Wait

2003

Experimental Physiology

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Magnesium deficiency is generally associated with an impaired ability to dispose of glucose. In order to test whether or not increasing the peripheral free Mg concentration ([Mg 2+ ]) would enhance glucose disposal, we have carried out glucose infusions in sheep with and without simultaneous infusion of Mg. Basal plasma glucose levels were higher in lactating sheep ('lactators') than in non-lactating sheep (controls) (P < 0.05). The glucose disposal rate (K G ) with no added Mg was greater in lactators than controls (P < 0.05). When Mg was added to the infusate, K G in lactators was reduced (P < 0.005). Infusion of Mg depressed basal insulin levels in controls and lactators (P < 0.0001 for both). The insulin response to the intravenous glucose tolerance test (IVGTT) was lower in lactators compared with controls (P < 0.0001); however, after correcting for the reduced basal insulin level when Mg was included during the IVGTT, there was no difference between the two groups. We conclude that intravenous Mg at the doses used in this study leads to a decrease in basal insulin secretion, and that increasing serum

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Section: Figurecontrasting

confidence: 57%

Section: Figurementioning

confidence: 99%

Section: Intravenous Magnesium Reduces the Rate Of Glucose Disposal Imentioning

confidence: 99%

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Intravenous Magnesium Reduces the Rate of Glucose Disposal in Lactating Sheep

Gow

Mitchell

Wait

2003

Experimental Physiology

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“…9). Second, insulin-dependent glucose uptake is impaired in early lactating ruminants (7,50), and recent evidence in other species indicates that glucose uptake is a primary determinant of AT leptin synthesis (36,38). In humans, the plasma leptin response during hypo-and euglycemic clamp experiments is more closely related to glucose infusion rates than either glucose or insulin concentration (53).…”

Section: Discussionmentioning

confidence: 96%

Effect of insulin and growth hormone on plasma leptin in periparturient dairy cows

Leury¹,

Baumgard²,

Block³

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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After parturition, dairy cows suffer from an intense energy deficit caused by the onset of copious milk secretion and an inadequate increase in voluntary food intake. We previously showed that this energy deficit contributes to a decline in plasma leptin. This decline mirrors that of plasma insulin but is reciprocal to the profile of plasma growth hormone (GH), suggesting that both hormones may regulate plasma leptin in periparturient dairy cows. To study the role of insulin, hyperinsulinemic-euglycemic clamps were performed on six dairy cows in late pregnancy (LP, 31 days prepartum) and early lactation (EL, 7 days postpartum). Infusion of insulin (1 microg.kg body wt-1.h-1) caused a progressive rise in the plasma concentration of leptin that reached maximum levels at 24 h during both physiological states. At steady states, the absolute increase in plasma leptin was greater in LP than in EL cows (2.4 vs. 0.4 ng/ml). Insulin infusion increased leptin mRNA in adipose tissue during LP but not during EL. During lactation, mammary epithelial cells expressed leptin mRNA but insulin did not increase milk leptin output. In contrast, a 3-day period of GH administration had no effect on plasma leptin during LP or EL. Therefore, insulin increases plasma leptin in LP by stimulating adipose tissue synthesis but has only marginal effects in EL, when cows are in negative energy balance. Other factors, such as increased response of adipose tissue to beta-adrenergic signals, probably contribute to the reduction of plasma leptin in early lactating dairy cows.

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“…Other workers have reported reduced plasma levels of IGF-binding protein-3 and increased levels of IGF-binding protein-2, concomitant with the reduction of circulating IGF-I (Simmons et al 1994;Segoale et al 1997). Associated with lactation-induced insulin resistance in peripheral tissues (Vernon et al 1990), these endocrine changes must have at least a permissive regulatory influence in suppressing protein synthesis and enhancing proteolysis. The removal of the normal positive influence of growth hormone on plasma IGF-I and IGF-binding protein-3 is consistent with similar observations during later lactation in cows that were moderately or severely underfed (McGuire et al 1995).…”

Section: Nutritional and Endocrine Regulation Of Tissue Protein Mobilmentioning

confidence: 99%

Protein nutrition in late pregnancy, maternal protein reserves and lactation performance in dairy cows

2000

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Empirical evidence suggests that prolonged underfeeding of protein to late-pregnant dry cows can have modest negative carry-over effects on milk volume and/or protein yield during early lactation, and may also cause increased incidence of metabolic diseases associated with fatty liver. However, assessment of requirements is hampered by lack of information on relationships between dietary intake of crude protein (N × 6·25) and metabolizable protein supply during late pregnancy, and by incomplete understanding of the quantitative metabolism of amino acids in maternal and conceptus tissues. Inability of the postparturient cow to consume sufficient protein to meet mammary and extra-mammary amino acid requirements, including a significant demand for hepatic gluconeogenesis, necessitates a substantial, albeit transient, mobilization of tissue protein during the first 2 weeks of lactation. Ultimately, much of this mobilized protein appears to be derived from peripheral tissues, especially skeletal muscle and, to a lesser extent, skin, through suppression of tissue protein synthesis, and possibly increased proteolysis. In the shorter term, soon after calving, it is likely that amino acids required for hepatic glucose synthesis are diverted from high rates of synthesis of splanchnic tissue and export proteins, including serum albumin. The prevailing endocrine milieu of the periparturient cow, including major reductions in plasma levels of insulin and insulin-like growth factor-I, together with insulin resistance in peripheral tissues, must permissively facilitate, if not actively promote, net mobilization of amino acids from these tissues.

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Insulin resistance of hind-limb tissues in vivo in lactating sheep

Cited by 30 publications

References 30 publications

Intravenous Magnesium Reduces the Rate of Glucose Disposal in Lactating Sheep

Intravenous Magnesium Reduces the Rate of Glucose Disposal in Lactating Sheep

Effect of insulin and growth hormone on plasma leptin in periparturient dairy cows

Protein nutrition in late pregnancy, maternal protein reserves and lactation performance in dairy cows

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