Effect of Trypsin Treatment of Rat Adipocytes on Biological Effects and Binding of Insulin and Insulin‐Like Growth Factors

Zapf, J.; Schoenle, Eugen J.; Waldvogel, M.; Sand, I. Charles; Froesch, E. R.

doi:10.1111/j.1432-1033.1981.tb05105.x

Cited by 147 publications

(86 citation statements)

References 23 publications

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“…Calculated on a molar basis, its biological insulin-like activity is two-to threefold higher than that of normal IGF II. Since IGFs stimulate glucose metabolism in rat fat cells via the insulin receptor (28,29), big IGF II may activate the insulin receptor more efficiently than normal IGF II. However, this is not yet sufficient to explain hypoglycemia in tumor patients: in normal serum > 98% of total IGF II is bound to IGFBPs (30), and 70-80% is associated with a 1 50-kD IGFBP complex (31 ).…”

Section: Discussionmentioning

confidence: 99%

Can "big" insulin-like growth factor II in serum of tumor patients account for the development of extrapancreatic tumor hypoglycemia?

Zapf¹,

Futo²,

Peter³

et al. 1992

J. Clin. Invest.

166

171

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The pathogenesis of extrapancreatic tumor hypoglycemia has been related to the secretion of big insulin-like growth factor (IGF) II by the tumor. In 25 of 28 patients with this type of hypoglycemia we found 1.5-8-fold elevated serum levels of immunoreactive big (15-25 kD), but decreased levels of normal IGF II. After removal of the tumor, big IGF II disappeared and normal IGF II increased. Tumors contained elevated levels of IGF II, 65-80% in the big form. The insulin-like bioactivity of big IGF II and its affinity towards IGF-binding proteins (IGFBP)-2 and -3 are similar to those of normal IGF II, but two-to threefold higher on a molar basis. Big IGF II is mainly bound to the 50-kD IGFBP complex. The latter contains -10 times more of this peptide than in normal serum and displays three-to fourfold increased insulin-like bioactivity. The formation of the 150-kD IGFBP complex with "25I-recombinant human IGFBP-3 is impaired in tumor serum. This results in sequestration of IGFBP-3 and predominant association of big IGF II with IGFBP-2 and -3 in the 50-kD complex. Increased bioavailability of big IGF II in this complex due to unrestricted capillary passage and enhanced insulin bioactivity of this big IGF II pool provide a continuous increased insulin-like potential available to insulin and type 1 IGF receptors of insulin-sensitive tissues and thus may lead to sustained hypoglycemia. (J.

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Section: Discussionmentioning

confidence: 99%

Can "big" insulin-like growth factor II in serum of tumor patients account for the development of extrapancreatic tumor hypoglycemia?

Zapf¹,

Futo²,

Peter³

et al. 1992

J. Clin. Invest.

166

171

View full text Add to dashboard Cite

show abstract

“…19 Briefly, the mixture was shaken horizontally for 10 min in a shaker and centrifuged for 10 min at 2000 g. The upper aqueous phase was removed by suction, and 1 ml of copper reagent was added to the lower organic phase. The copper reagent was prepared by the method of Zapf et al 20 The mixture was shaken again for 10 min and centrifuged for 10 min at 2000 g. A 0.5 ml sample of the upper organic phase, which contained the copper salts of the extracted fatty acids, was treated with 0.05% (w=v) bathocuproin in chloroform containing 0.05% (w=v) 3-tert-butyl-4-hydroxyanisole. Colorimetric determination was performed at 480 nm.…”

Section: Measurement Of Norepinephrine-stimulated Lipolysis In Isolatmentioning

confidence: 99%

The hormonal responses of lipoprotein lipase activity and lipolysis in adipose tissue differ depending on the stage of the estrous cycle in female rats

et al. 2002

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OBJECTIVE: This study was designed to elucidate whether there were differences in the hormonal responses of the parameters involving triacylglycerol (TG) deposition and mobilization in adipose tissue among the stages of the estrous cycle in female rats. MEASUREMENTS: Adipose tissue was obtained from the parametrial region in female rats at each stage of the estrous cycle. Lipoprotein lipase (LPL) activity in the extracts of acetone=ether powders of the tissues was measured as a parameter for TG deposition. Norepinephrine-stimulated lipolysis in isolated fat cells was measured as a parameter for TG mobilization. RESULTS: LPL activity changed periodically during the estrous cycle; the activity level was highest at diestrus, began to decrease at proestrus, reached a minimum at estrus, began to increase again at metestrus-1, and increased further at metestrus-2. At diestrus and proestrus, LPL activity was increased with an increase in plasma insulin levels, suggesting that plasma insulin was the predominant up-regulator of LPL. But at estrus, metestrus-1 and metestrus-2, LPL activity remained low even when plasma insulin levels were high, indicating that it was not up-regulated by plasma insulin. Norepinephrine-stimulated lipolysis in fat cells was high at estrus and metestrus-1 and low at diestrus. CONCLUSION: The hormonal responses of LPL activity and lipolysis in adipose tissue differed depending on the stage of the estrous cycle.

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“…This sonicated substrate suspension (100 ml) was incubated with 50 ml (10 units) of pancreatic lipase and 100 ml of various concentrations of chitin-chitosan suspension for 30 min at 37 C in a total volume of 250 ml. The amount of oleic acid produced was determined by the method of Zapf et al, 7 with a slight modi®-cation. 8 The incubation mixtures were added to 3 ml aliquots of a 1:1 (vav) mixture of chloroform and heptane containing 2% (vav) methanol and extracted by shaking the tubes horizontally for 10 min in a shaker.…”

Section: Measurement Of Pancreatic Lipase Activitymentioning

confidence: 99%

Reduction in fat storage during chitin-chitosan treatment in mice fed a high-fat diet

1999

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Japan OBJECTIVE: Chitin and chitosan are polymers containing more than 5000 acetylglucosamine and glucosamine units, respectively, and their molecular weights are over one million Daltons. The present study assessed the effects of chitin-chitosan on the activity of pancreatic lipase in vitro and on the degree of fat storage induced in mice by the oral administration of a high-fat diet for nine weeks. DESIGN: Mice were fed a high-fat diet and treated with chitin-chitosan for nine weeks. Experiments were also carried out to clarify whether or not chitin-chitosan inhibited pancreatic lipase activity in assay systems using triolein emulsi®ed with lecithin, gum arabic or Triton X-100. RESULTS: Chitin-chitosan prevented the increase of body weight, hyperlipidaemia and fatty liver induced by a high-fat diet. Chitin-chitosan inhibited hydrolysis of triolein, emulsi®ed with phosphatidylcholine, but not that of triolein emulsi®ed with gum arabic and Triton X-100. These results suggest that the site of inhibitory action of chitin-chitosan may not be the enzyme but its substrate. CONCLUSION: The anti-obesity effects of chitin-chitosan in high-fat diet-treated mice might be partly due to the inhibition of intestinal absorption of dietary fat. Consequently, chitin-chitosan might cause improvement of the fatty liver and hyperlipidaemia in mice fed a high fat diet through inhibiting intestinal absorption of dietary fat.

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Effect of Trypsin Treatment of Rat Adipocytes on Biological Effects and Binding of Insulin and Insulin‐Like Growth Factors

Cited by 147 publications

References 23 publications

Can "big" insulin-like growth factor II in serum of tumor patients account for the development of extrapancreatic tumor hypoglycemia?

Can "big" insulin-like growth factor II in serum of tumor patients account for the development of extrapancreatic tumor hypoglycemia?

The hormonal responses of lipoprotein lipase activity and lipolysis in adipose tissue differ depending on the stage of the estrous cycle in female rats

Reduction in fat storage during chitin-chitosan treatment in mice fed a high-fat diet

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