High glucose uptake in growing rats adapted to a low-protein, high-carbohydrate diet determines low fasting glycemia even with high hepatic gluconeogenesis

Abstract

The our objective was to investigate the adaptations induced by a low-protein, high-carbohydrate (LPHC) diet in growing rats, which by comparison with the rats fed a control (C) diet at displayed lower fasting glycemia and similar fasting insulinemia, despite impairment in insulin signaling in adipose tissues. In the insulin tolerance test the LPHC rats showed higher rates of glucose disappearance (30%) and higher tolerance to overload of glucose than C rats. The glucose uptake by the soleus muscle, evaluated in vivo by administration of 2-deoxy-[(14)C]glucose, increased by 81%. The phosphoenolpyruvate carboxykinase content and the incorporation of [1-(14)C]pyruvate into glucose was also higher in the slices of liver from the LPHC rats than in those from C rats. The LPHC rats showed increases in l-lactate as well as in other gluconeogenic precursors in the blood. These rats also had a higher hepatic production of glucose, evaluated by in situ perfusion. The data obtained indicate that the main substrates for gluconeogenesis in the LPHC rats are l-lactate and glycerol. Thus, we concluded that the fasting glycemia in the LPHC animals was maintained mainly by increases in the hepatic gluconeogenesis from glycerol and l-lactate, compensating, at least in part, for the higher glucose uptake by the tissues.

A low-protein, high-carbohydrate diet increases browning in perirenal adipose tissue but not in inguinal adipose tissue

“…Male Wistar rats weighing approximately 100 g (30 to 32 d old) were randomized into either the C group or the LPHC group. Rats in the C group were fed a diet containing 17% protein, 63% carbohydrates, and 7% lipids [25], and those in the LPHC group were fed a diet containing 6% protein, 74% carbohydrates, and 7% lipids for 15 d. The diets were isocaloric (16.3 kJ$g -1 ), with the energy difference from the reduction in dietary protein compensated for by increasing the carbohydrate content [13][14][15][16][17][18][19][20][21][22][23]25] (Table 1). The rats were individually housed in metabolic cages in an environmentally controlled room (lights on from 0600 to 1800; temperature 22 AE 1 C).…”

“…We have been steadily focusing on the effects of administering a low-protein, high-carbohydrate (LPHC) diet to rats, introduced during the early phase of life [13][14][15][16][17][18][19][20][21][22] because children in occidental societies are often fed diets with these characteristics, introduced soon after weaning [23]. Fifteen days after introducing this diet, alterations in the energy balance occur, along with increased food intake and energy gain; these changes increase the amount of body lipids [13].…”

“…Fifteen days after introducing this diet, alterations in the energy balance occur, along with increased food intake and energy gain; these changes increase the amount of body lipids [13]. Adaptation to the LPHC diet increases plasma norepinephrine, epinephrine, corticosterone, tumor necrosis factor (TNF)-a, leptin, and insulin sensitivity [14,15,18]. Additionally, the LPHC diet increases energy expenditure by increasing thermogenesis in the interscapular brown adipose tissue (iBAT), enhancing UCP1 content, and resulting in a higher response to adrenaline stimulation; this attenuates the energetic gains in these animals as they ingest 18% more calories than rats fed a control (C) diet [13].…”

“…Additionally, the LPHC diet increases energy expenditure by increasing thermogenesis in the interscapular brown adipose tissue (iBAT), enhancing UCP1 content, and resulting in a higher response to adrenaline stimulation; this attenuates the energetic gains in these animals as they ingest 18% more calories than rats fed a control (C) diet [13]. Elucidation of major changes in the hormonal profiles and specific responses from these tissues have improved the understanding of the mechanisms involved in thermogenesis in iBAT and other alterations and processes in the adipose tissues, liver, and muscles of these animals [13][14][15][16][17][18][19][20][21][22].…”

A Low‐Protein, High‐Carbohydrate Diet Stimulates Thermogenesis in the Brown Adipose Tissue of Rats via ATF‐2

“…Our laboratory has investigated the effects of a low protein, high-carbohydrate (LPHC) diet in rats [22][23][24][25][26][27][28][29] because the nutrition of children, after weaning, across the Western world is rich in carbohydrates and poor in protein content [30,31]. The administration of this diet to young rats (soon after weaning) promotes an increase in their food and calorie intake.…”