Increased insulin sensitivity and responsiveness during lactation in rats

Abstract

In 12-day lactating rats blood glucose and plasma insulin were decreased by, respectively, 20 and 35% when compared with nonlactating rats, despite a 25% increase of their glucose turnover rate. Then, by using the euglycemic hyperinsulinemic clamp technique, dose-response curves for the effects of insulin on glucose production and utilization in lactating and nonlactating rats were performed. Glucose production rate was totally suppressed at 250 microU/ml of insulin in lactating rats and for plasma insulin concentrations higher than 500 microU/ml in nonlactating rats. Plasma insulin level inducing half-maximal inhibition of glucose production was decreased by 60% during lactation. The maximal effect of insulin on glucose utilization rate and glucose metabolic clearance rate was, respectively, increased 1.5- and 2.4-fold during lactation and was obtained for plasma insulin concentrations lower in lactating than in nonlactating rats (250 vs. 500 microU/ml). Insulin concentrations inducing half-maximal stimulation of glucose utilization and glucose metabolic clearance were decreased by 50% during lactation. In conclusion, this study has shown that insulin sensitivity and responsiveness of liver and peripheral tissues are improved at peak lactation in the rat.

Adiposity and fat metabolism during combined fasting and lactation in elephant seals

“…In mammals that feed throughout lactation, insulin decreases but insulin sensitivity increases (Tigas et al, 2002;Hatfield et al, 1999;Sartin et al, 1985;Debras et al, 1989;Burnol et al, 1986), which is counter to the pattern exhibited by elephant seals. In humans, obesity is linked to delayed lactogenesis and a detrimental reduction of lactation duration; with strong implications that impaired insulin sensitivity is a driving force behind these characteristics (Nommsen-Rivers, 2016).…”

Hormonal regulation of glucose clearance in lactating northern elephant seals (Mirounga angustirostris)

“…Diabetes is notable among these conditions, but insulin resistance is demonstrated in pregnancy (Bauman and Bell, 1997;Ryan, 2003), as well as during prolonged fasting in humans (Cahill et al, 1966). Although a review by Bauman and Bell (Bauman and Bell, 1997) suggests that lactating ruminants experience reduced tissue sensitivity to insulin, the data on insulin resistance during lactation in other species appear equivocal (Burnol et al, 1986;Debras et al, 1989;Hoffman et al, 2003;Sano et al, 1991;Tigas et al, 2002). Performing an insulin tolerance test would give a clearer picture of the level of insulin resistance in adult lactating elephant seals.…”

Endocrine control of metabolic adaptation during lactation

“…Insulin activation of pyruvate dehydrogenase in rat liver in vivo appears to be unaltered by lactation in the rat (Kilgour & Vernon, 1987). Indirect evidence suggests that the liver may become more sensitive to insulin during lactation (Burnol et al 19866), as may be inferred from the fact that glucose utilization and lipogenesis are increased while ketogenesis is depressed in rat liver (Table 2) despite the hypoinsulinaemia of lactation. This postulated increase in hepatic sensitivity to insulin is not associated with any change in the number or affinity of insulin receptors during lactation (Flint, 1980).…”