Insulin oedema and its clinical significance: metabolic studies in three cases

Three patients with insulin-dependent diabetes mellitus are described in whom generalized oedema and weight gain followed the administration of excessive monocomponent insulins, in two cases associated with symptomatic hypoglycaemia. Serial measurements of plasma volume and transcapillary escape rate of albumin (TERA) using 125I-labelled albumin, serum colloid osmotic pressure (COP) using a membrane colloid osmometer, packed cell volume (PCV), and serum proteins, showed that oedema was associated with an increased plasma volume and TERA, while serum albumin and total protein concentration and serum COP were reduced. A reduction in daily insulin dose abolished hypoglycaemia and resulted in weight loss, natriuresis, diuresis, a reduction in plasma volume and TERA, and an increase in serum albumin, total protein, and COP. Strict metabolic control in previously poorly controlled patients may cause insulin-induced increments in plasma volume and albumin escape rate.

Insulin-induced factors derived from lymph node cells influence anaphylactoid reaction in the rat

The effect of supernatants of isolated lymph node cells exposed to insulin has been studied on the anaphylactoid reaction induced by dextran in the rat paw. Native supernatants derived from rat lymphocytes were shown to increase dextran response only from April to October, while in the intermediate period no potentiation was obtained. The supernatants were filtered through sephadex G-25, G-50, and G-100 gels. Pro-inflammatory activity was recovered in the void volume of sephadex G-25 or G-50 columns, while it ran with bovine serum albumin marker suggesting an approximate mol. wt. of 70-kilodalton. Potentiation was detectable in adrenalectomized rats from November through April. A fraction of the eluate recovered from sephadex G-25 gels in the range of 1- to 6-kilodalton was found to suppress dextran edema. Supernatants of calf lymph node cells with insulin were fractionated on DEAE-sephadex A-50 and yielded two distinct fractions, one with pro-inflammatory and the other with anti-inflammatory effect. These results suggest that insulin affects anaphylactoid reaction via the release of some lymphocyte mediators.

Histamine release by sugar polymers in the rat

Histamine release into the peritoneal cavity of rats following intraperitoneal injections of sugar polymers such as dextran or dextrin was potentiated by insulin, even when the hormone was given simultaneously with the polymer and the blood sugar level was unchanged. Hypoglycaemia is therefore not the factor responsible for the potentiation. A direct effect of insulin on peritoneal mast cells in vivo is suggested, particularly as the potentiation by insulin occurred in diabetic rats and this was inhibited by disodium cromoglycate.

Further studies on the anti-inflammatory effect of insulin

Experiments performed on rats showed that insulin, when applied i.v. or s.c., inhibited the foot edema induced by carrageenin, thermic effect of 45.7 degrees C, compound 48/80 and 5-HT, but moderately increased the paw swelling evoked by kallikrein, a kinin-forming enzyme. The increased vascular permeability elicited by intradermal injection of histamine, 5-HT, bradykinin, PGE1, carrageenin and compound 48/80 was also suppressed. The anti-inflammatory effect was not significantly altered by propranolol and adrenalectomy on the thermal and carrageenin edema, it was variably inhibited on the skin test, and was completely abolished on the paw swelling induced by 5-HT and compound 48/80. Since insulin had little or no effect on the vascular response when given topically together with the vasoactive agents, its complex effect on the acute inflammation appears to be brought about via indirect mechanisms.