Lactate Production from Glucose and Response to Insulin in Perifused Adipocytes from Mesenteric and Epididymal Regions of Lean and Obese Rats

Abstract

KING, JOYCE L, MARIO DIGIROLAMO. Lactate production from glucose and response to insulin in perifused adipocytes from mesenteric and epididymal regions of lean and obese rats. Obes Res. 1998;6:69-75. Lactate, an important metabolic substrate for peripheral tissues and the liver, is released in significant amounts from adipose tissue. Using a perifusion system, we measured lactate production from glucose and response to insulin in isolated mesenteric and epididymal adipocytes removed from fed or fasted male Wistar rats at two stages of growth and development: (a) lean rats (7 weeks to 9 weeks old, weighing -250 g), and (b) fatter rats (6 months to 8 months old, weighing -550 8). The results show that lactate production in perifused adipocytes is regulated by the prior nutritional state of the animals, by the adipose tissue region, and by the presence of insulin in the perifusate. In fat cells from lean rats, basal lactate production was significantly higher (Pc0.05) in mesenteric cells when compared with epididymal cells, both in the fed state (7.8 nmoY107 fat cells per minute vs. 2.9 nm0YlO' fat cells per minute) and after 2 days of fasting (13.6 nmol vs. 3.5 nmol). When the response to 1 mU/mL insulin was studied, however, the relative increase in lactate production produced by insulin was greater in the epididymal cells than in the mesenteric cells, in both the fed (194% vs. 91% over basal, respectively) and fasted (360% vs. 55% over basal, p<0.05) state. When larger epididymal adipocytes

Hepatic glucose uptake, gluconeogenesis and the regulation of glycogen synthesis

“…These data in humans are consistent with studies in overweight cafeteria-fed rats that demonstrated, after a 24 h fast, increased glycogen stores, lower glucose output and increased lactate uptake in the liver [240]. This brings us full circle to lactate as a possible important intermediate associated with the development of insulin resistance, particularly in obesity where it may well be excessively released from mesenteric adipose tissue [241][242][243][244] and provide a portal signal and substrate, accentuated after meals, for increased gluconeogenesis and glycogen synthesis.…”

Efecto de la tiramina, una amina de la dieta, sobre la liberación de glicerol y de lactato por los adipocitos en rata

“…In fact, we found that tyramine weakly but significantly increased basal lactate release. Lactate release has been reported to be positively correlated with glucose uptake and glucose utilization (9). Our results are therefore in good agreement with previous reports which showed that tyramine and benzylamine were able to stimulate glucose transport and lipogenesis in rat adipose tissues by in vitro and in vivo studies (13,24).…”

“…First, basal lactate release is, under our conditions, already elevated: 3 to 4 fold higher than that observed in studies performed on younger rats (4). It is now well established that lactate release increases in large adipocytes from adipose tissues in old or obese rats (9) and it looks likely that, in our old rats (6-to 8-month old), basal lactate release reached its maximal capacity. A similar low stimulating effect observed with insulin may confirm this hypothesis.…”

A method for the measurement of lactate, glycerol and fatty acid production from14C-glucose in primary cultures of rat epididymal adipocytes

“…The measurement of labelled CO2 52 , and up to a degree, its incorporation in cells 53 or removal from the medium 54 have been used often with success. However, the studies using perfused 55 or perifused 56 organs and incubations with pieces of tissue 57 , now seldom used, have been the main methods available for analyses of the utilization of glucose and release of 3C units by live tissues.…”