Ketogenesis evaluation in perfused liver of diabetic rats submitted to short-term insulin-induced hypoglycemia

Instant coffee extract with high chlorogenic acids content inhibits hepatic G-6-Pase in vitro, but does not reduce the glycaemia

Coffee is the main source of chlorogenic acid in the human diet, and it contains several chlorogenic acid isomers, of which the 5-caffeoylquinic acid (5-CQA) is the predominant isomer. Because there are no available data about the action of chlorogenic acids from instant coffee on hepatic glucose-6-phosphatase (G-6-Pase) activity and blood glucose levels, these effects were investigated in rats. The changes on G-6-Pase activity and liver glucose output induced by 5-CQA were also investigated. Instant coffee extract with high chlorogenic acids content (37.8%) inhibited (p < 0.05) the G-6-Pase activity of the hepatocyte microsomal fraction in a dose-dependent way (up to 53), but IV administration of this extract did not change the glycaemia (p > 0.05). Similarly, 5-CQA (1 mM) reduced (p < 0.05) the activity of microsomal G-6-Pase by about 40%, but had no effect (p > 0.05) on glucose output arising from glycogenolysis in liver perfusion. It was concluded that instant coffee extract with high content of chlorogenic acids inhibited hepatic G-6-Pase in vitro, but failed to reduce the glycaemia probably because the coffee chlorogenic acids did not reach enough levels within the hepatocytes to inhibit the G-6-Pase and reduce the liver glucose output.

Short-term but not long-term hypoglycaemia enhances plasma levels and hepatic expression of HSP72 in insulin-treated rats: an effect associated with increased IL-6 levels but not with IL-10 or TNF-α

The inducible expression of the 70-kDa heat shock proteins (HSP70) is associated with homeostatically stressful situations. Stresses involving sympathetic nervous system (SNS) activation, including α1-adrenergic agonists and physical exercise, are capable of inducing HSP70 expression and release of the HSP70 inducible form, HSP72. However, whether hypoglycaemia is capable of influencing HSP70 status under a stressful situation such as insulin-induced hypoglycaemia (IIH), which also involves SNS activation, is unsettled. Hence, we decided to investigate whether the predominant signal for HSP70 expression and delivery into the blood comes from either low glucose, high insulin, or both during short-term IIH (STIIH) and long-term IIH (LTIIH). Our data indicated that low glucose level (up to 1.56 ± 0.14 mM), but not insulin, is the triggering factor responsible for a dramatic rise in HSP72 plasma concentrations (from 0.15 ± 0.01 in fed state to 0.77 ± 0.13 ng/mL during hypoglycaemic episodes). This was observed in parallel with up to 7-fold increases in interleukin-6 (IL-6) but not interleukin-10 (IL-10) or tumour necrosis factor-α (TNF-α) at STIIH. Together, the observations may suggest that HSP72 is released under hypoglycaemic conditions as a part of the homeostatic stress response, whereas at long-term, both hypoglycaemia and insulin may influence HSP72 expression in the liver, but not in kidneys. Secreted extracellular HSP72 (eHSP72) may be purely a danger signal to all the tissues of the body for the enhancement of immune and metabolic surveillance state or actively participates in glycaemic control under stressful situations.

Oral glutamine is superior than oral glucose to promote glycemia recovery in mice submitted to insulin-induced hypoglycemia

The effect of the oral administration of blood glucose precursors on glycemia recovery and liver glucose production in fasted mice subjected to insulin-induced hypoglycemia (IIH) was investigated. IIH was obtained with increasing doses (from 0.5 to 2.0 U·kg(-1)) of intraperitoneal regular insulin where glycemia was evaluated from 0 to 300 min after insulin injection. The dose of 1.0 U·kg(-1) showed the best results, that is, a clear glycemia recovery phase without convulsions or deaths. Thus, this dose was used in all experiments. Afterwards, mice submitted to IIH received orally by gavage: saline (control group), glucose (100 mg·kg(-1)), glycerol (100 mg·kg(-1)), lactate (100 mg·kg(-1)), alanine (100 mg·kg(-1)), or glutamine (100 mg·kg(-1)). It was observed that glutamine was more effective in promoting glycemia recovery if compared with glucose, lactate, glycerol, or alanine. In agreement with these results, the best performance in terms of liver glucose production was obtained when glutamine was used as glucose precursors. These results open perspectives for clinical studies to investigate the impact of oral administration of gluconeogenic amino acids to promote glycemia recovery during hypoglycemia.

Low-carbohydrate diets: a matter of love or hate

Low-carbohydrate diets (LChD) have become very popular among the general population. These diets have been used to lose body weight and to ameliorate various abnormalities like diabetes, nonalcoholic fatty liver disease, polycystic ovary syndrome, narcolepsy, epilepsy, and others. Reports suggest that body weight reduction and glycemic control could be attained while following LChD. However, these advantages are more notably found in short periods of time consuming an LChD. Indeed, the safety and efficacy of the latter diets in the long term have not been sufficiently explored. In contrast to what has been proposed, other mentioned pathologies are not improved or are even worsened by carbohydrate restriction. Therefore, the aim of this review is to define the concept of LChD and to explain their clinical effects in the short and long term, their influence on metabolism, and the opinion of nutrition or health authorities. Finally, evincing the research gaps of LChD that are here exposed will later allow us to reach a consensus with regard to their utilization.

Paradoxical increase in liver ketogenesis during long-term insulin-induced hypoglycemia in diabetic rats

It is well established that insulin inhibits liver ketogenesis. However, during insulin-induced hypoglycemia (IIH) the release of counterregulatory hormones could overcome the insulin effect on ketogenesis. To clarify this question the ketogenic activity in livers from alloxan-diabetic rats submitted to long-term IIH was investigated. Moreover, liver glycogenolysis, gluconeogensis, ureagenesis and the production of l-lactate were measured, and its correlation with blood levels of ketone bodies (KB), l-lactate, glucose, urea and ammonia was investigated. For this purpose, overnight fasted alloxan-diabetic rats (DBT group) were compared with control non-diabetic rats (NDBT group). Long-term IIH was obtained with an intraperitoneal injection of Detemir insulin (1 U/kg), and KB, glucose, l-lactate, ammonia and urea were evaluated at 0, 2, 4, 6, 8 or 10 h after insulin injection. Because IIH was well established two hours after insulin injection this time was used for liver perfusion experiments. The administration of Detemir insulin decreased ( P < 0.05) blood KB and glucose levels, but there was an increase in the blood l-lactate levels and a rebound increase in blood KB during the glucose recovery phase of IIH. In agreement with these results, the capacity to produce KB from octanoate was increased in the livers of DBT rats. Moreover, the elevated blood l-lactate levels in DBT rats could be attributed to the higher ( P < 0.05) glycogenolysis when part of glucose from glycogenolysis enters glycolysis, producing l-lactate. In contrast, except glycerol, gluconeogenesis was negligible in the livers of DBT rats. Therefore, during long-term IIH the higher liver ketogenic capacity of DBT rats increased the risk of hyperketonemia. In addition, in spite of the fact that the insulin injection decreased blood KB, there was a risk of worsening lactic acidosis.