Quantification of the glycolytic origin of plasma glycerol: Implications for the use of the rate of appearance of plasma glycerol as an index of lipolysis in vivo

Nurjhan, Nurjahan; Kennedy, Frank P.; Consoli, Agostino; Martin, C. Dianne; Miles, John M.; Gerich, John E.

doi:10.1016/0026-0495(88)90140-0

Cited by 53 publications

(27 citation statements)

References 15 publications

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“…The same applies to splanchnic balance studies, where blood flow is equally high and arteriovenous differences similarly small. Use of high-performance liquid chromatography (HPLC), which permits precise determination of arteriovenous differences in plasma concentrations and specific activities [24,25] has helped to minimize this problem.…”

Section: Methodological Considerationsmentioning

confidence: 99%

Renal glucose production and utilization: new aspects in humans

et al. 1997

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Summary According to current textbook wisdom the liver is the exclusive site of glucose production in humans in the postabsorptive state. Although many animal and in vitro data have documented that the kidney is capable of gluconeogenesis, production of glucose by the human kidney in the postabsorptive state has generally been regarded as negligible. This traditional view is based on net balance measurements which, other than after a prolonged fast or during metabolic acidosis, showed no significant net renal glucose release. However, recent studies have refuted this view by combining isotopic and balance techniques, which have demonstrated that renal glucose production accounts for 25 % of systemic glucose production. Moreover, these studies indicate that glucose production by the human kidney is stimulated by epinephrine, inhibited by insulin and is excessive in diabetes mellitus. Since renal glucose release is largely, if not exclusively, due to gluconeogenesis, it is likely that the kidney is as important a gluconeogenic organ as the liver. The most important renal gluconeogenic precursors appear to be lactate, glutamine and glycerol. The implications of these recent findings on the understanding of the physiology and pathophysiology of human glucose metabolism are discussed. [Diabetologia (1997) 40: 749-757].

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Section: Methodological Considerationsmentioning

confidence: 99%

Renal glucose production and utilization: new aspects in humans

et al. 1997

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“…The assumptions for the use of this calculation have been described previously (10). Briefly, this calculation assumes that in elephant seals, as in humans, 1) the hydrolysis of triglycerides in adipose tissue is complete (9, 38), 2) mono-and diacylglyceride concentrations in adipocytes are low (1), and 3) glycolysis does not significantly contribute to glycerol flux (32). Furthermore, it is assumed that very low-density lipoproteins account for a negligible proportion of glycerol flux, as has been observed in rats (42), and that mesenteric lipolysis is minimal, as observed in dogs and humans in the resting state (3,5,39).…”

Section: Sample Processingmentioning

confidence: 99%

Lipolysis and glycerol gluconeogenesis in simultaneously fasting and lactating northern elephant seals

Houser¹,

Champagne²,

Crocker³

2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Adult female elephant seals (Mirounga angustirostris) combine long-term fasting with lactation and molting. Glycerol gluconeogenesis has been hypothesized as potentially meeting all of the glucose requirements of the seals during these fasts. To test this hypothesis, a primed constant infusion of [2-14 C]glycerol was administered to 10 ten adult female elephant seals at 5 and 21-22 days postpartum and to 10 additional adult females immediately after the molt. Glycerol kinetics, rates of lipolysis, and the contribution of glycerol to glucose production were determined for each period. Plasma metabolite levels as well as insulin, glucagon, and cortisol were also measured. Glycerol rate of appearance was not significantly correlated with mass (P ϭ 0.14, r 2 ϭ 0.33) but was significantly related to the percentage of glucose derived from glycerol (P Ͻ 0.01, r 2 ϭ 0.81) during late lactation. The contribution of glycerol to glucose production was Ͻ3% during each fasting period, suggesting a lower contribution to gluconeogenesis than is observed in other long-term fasting mammals. Because of a high rate of endogenous glucose production in fasting elephant seals, it is likely that glycerol gluconeogenesis still makes a substantial contribution to the substrate needs of glucose-dependent tissues. The lack of a relationship between glucoregulatory hormones and glycerol kinetics, glycerol gluconeogenesis, and metabolites supports the proposition that fasting elephant seals do not conform to the traditional insulinglucagon model of substrate metabolism. reesterification; lipid metabolism; lactogenesis; glucagon; insulin GLUCONEOGENESIS IS an important physiological process in maintaining blood glucose levels during fasting and can meet Ͼ90% of glucose needs after just 2 days of fasting (28). Both amino acids and glycerol can be metabolized to glucose when exogenous carbohydrate becomes unavailable. However, under long-term fasting conditions the loss of protein is generally minimized to stay the eventual loss of organ function that results from protein depletion. Under these conditions glycerol becomes an increasingly important gluconeogenic precursor. In the postabsorptive state, the conversion of glycerol to glucose accounts for ϳ3-4.5% of glucose production; however, after fasting for several days, the contribution of glycerol to glucose production increases to ϳ10 -22% (2, 7, 29). After weeks of fasting glycerol can contribute up to 60% of glucose production (7), although the basis for this calculation has come into question because of methodological issues related to the separation of radiolabeled glycerol from radiolabeled glucose (2). Thus, during long-duration fasts, the availability of lipid stores not only serves to provide energy via fatty acid oxidation but also contributes to meeting the energetic costs of glucose-dependent tissues.Northern elephant seals (Mirounga angustirostris) undertake prolonged fasts of 1-3 mo. Adult females undertake two fasts each year, one while lactating and another while molting. Bot...

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“…For other determinations, samples were placed immediately in a 4°C ice bath, and plasma was separated within 30 min by centrifugation at 4°C. [6-3 H]glucose specific activities were determined using 4 ml of plasma in duplicate by HPLC (46) with a CV of 0.5%. Plasma [6,6-2 H2]glucose enrichments were determined by gas chromatography-mass spectroscopy (GC-MS) as previously described (14).…”

Section: Subjectsmentioning

confidence: 99%

Role of human liver, kidney, and skeletal muscle in postprandial glucose homeostasis

Meyer¹,

Dostou²,

Welle

et al. 2002

American Journal of Physiology-Endocrinology and Metabolism

231

163

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. Role of human liver, kidney, and skeletal muscle in postprandial glucose homeostasis. Am J Physiol Endocrinol Metab 282: E419-E427, 2002; 10.1152/ ajpendo.00032.2001.-Recent studies indicate a role for the kidney in postabsorptive glucose homeostasis. The present studies were undertaken to evaluate the role of the kidney in postprandial glucose homeostasis and to compare its contribution to that of liver and skeletal muscle. Accordingly, we used the double isotope technique along with forearm and renal balance measurements to assess systemic, renal, and hepatic glucose release as well as glucose uptake by kidney, skeletal muscle, and splanchnic tissues in 10 normal volunteers after ingestion of 75 g of glucose. We found that, during the 4.5-h postprandial period, 22 Ϯ 2 g (30 Ϯ 3% of the ingested glucose) were initially extracted by splanchnic tissues. Of the remaining 53 Ϯ 2 g that entered the systemic circulation, 19 Ϯ 3 g were calculated to have been taken up by skeletal muscle and 7.5 Ϯ 1.7 g by the kidney (26 Ϯ 3 and 10 Ϯ 2%, respectively, of the ingested glucose). Endogenous glucose release during the postprandial period (16 Ϯ 2 g), calculated as the difference between overall systemic glucose appearance and the appearance of ingested glucose in the systemic circulation, was suppressed 61 Ϯ 3%. Surprisingly, renal glucose release increased twofold (10.6 Ϯ 2.5 g) and accounted for ϳ60% of postprandial endogenous glucose release. Hepatic glucose release (6.7 Ϯ 2.2 g), the difference between endogenous and renal glucose release, was suppressed 82 Ϯ 6%. These results demonstrate a hitherto unappreciated contribution of the kidney to postprandial glucose homeostasis and indicate that postprandial suppression of hepatic glucose release is nearly twofold greater than had been calculated in previous studies (42 Ϯ 4%), which had assumed that there was no renal glucose release. We postulate that increases in postprandial renal glucose release may play a role in facilitating efficient liver glycogen repletion by permitting substantial suppression of hepatic glucose release.gluconeogenesis; glycogenolysis; glucose disposal CONSIDERABLE INFORMATION has recently accumulated regarding postprandial glucose homeostasis. It appears that about one-third of ingested carbohydrate is immediately taken up by splanchnic tissues (5, 22, 33-35, 37, 38, 44, 60). Of the remaining two-thirds of the ingested carbohydrate that enters the systemic circulation, some is extracted by the liver (23), but most is taken up by peripheral tissues. Limb balance measurements indicate that skeletal muscle is the predominant site for this peripheral glucose disposal, being responsible for about one-fourth of the ingested carbohydrate (5, 26, 33-35, 37, 38, 44). The fate of the remaining 40% of the ingested carbohydrate is less clear.In addition to tissue uptake of ingested carbohydrate, another important factor for postprandial glucose homeostasis is suppression of the release of glucose endogenously produced by gluconeogenesis and breakdown of ...

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Quantification of the glycolytic origin of plasma glycerol: Implications for the use of the rate of appearance of plasma glycerol as an index of lipolysis in vivo

Cited by 53 publications

References 15 publications

Renal glucose production and utilization: new aspects in humans

Renal glucose production and utilization: new aspects in humans

Lipolysis and glycerol gluconeogenesis in simultaneously fasting and lactating northern elephant seals

Role of human liver, kidney, and skeletal muscle in postprandial glucose homeostasis

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