Formation of Carbohydrates from Non-Glycerol Fraction of Lipoids in the Rat

Abstract

Although the study of the metabolic disturbance in the depancreatized dog has contributed in a large measure to our present knowledge of metabolism, there is still no universal agreement as to the exact nature of this disturbance. Two main schools of thought exist on this question. The theory which gained early acceptance in this country postulates an inability of the diabetic tissue to utilize carbohydrate. The opposing theory, more widely accepted in Europe, and gaining more credence in this country, states that the diabetic organism can utilize carbohydrate but that the essential disturbance is an overproduction of sugar from non-carbohydrate sources. A necessary corollary to this latter theory is a formation of carbohydrate from the non-glycerol fraction of lipoids.

We have previously reported that carbohydrate is utilized by the completely depancreatized dog not receiving insulin, 1 and many older and more recent reports may be drawn in support of this thesis. 2 , 3 , 4 The existing evidence for the conversion of fat to carbohydrate in the higher animal species is largely based on the D :N ratio and Respiratory Quotient, and is disputed on theoretical grounds, 5 although it is conceded that this conversion occurs in plants and probably also in insects. The present preliminary report offers direct proof, of a crucial nature, that carbohydrate can be derived from the non-glycerol fraction of lipoids in the rat.

Magne, Mayer and Plantefol 6 observed a marked depletion of the tissue carbohydrates in animals following the administration of dinitrophenol. Later, Dodds and Greville, 7 working with isolated tissues, concluded that the increased metabolism following dinitrophenol administration occurred solely at the expense of carbohydrates. It was difficult to reconcile these results with the work of Hall, Field, et al.