Acute loss of adipose tissue-derived adiponectin triggers immediate metabolic deterioration in mice

AIM/HYPOTHESIS

Adiponectin (APN), a circulating hormone secreted by mature adipocytes, has been extensively studied because it has beneficial metabolic effects. While many studies have focused on the congenital loss of APN and its effects on systemic body glucose and lipid metabolism, little is known about the effects triggered by acute loss of APN in the adult mouse. We anticipated that genetically induced acute depletion of APN in adult mice would have a more profound effect on systemic metabolic health than congenital deletion of Adipoq, the gene encoding APN, with its associated potential for adaptive responses that may mask the phenotypes.

METHODS

Mice carrying loxP-flanked regions of Adipoq were generated and bred to the Adipoq (APN) promoter-driven reverse tetracycline-controlled transactivator (rtTA) (APN-rtTA) gene and a tet-responsive Cre line (TRE-Cre) to achieve acute depletion of APN. Upon acute removal of APN in adult mice, systemic glucose and lipid homeostasis were assessed under basal and insulinopenic conditions.

RESULTS

The acute depletion of APN results in more severe systemic insulin resistance and hyperlipidaemia than in mice with congenital loss of APN. Furthermore, the acute depletion of APN in adult mice results in a much more dramatic reduction in survival rate, with 50% of inducible knockouts dying in the first 5 days under insulinopenic conditions compared with 0% of congenital Adipoq knockout mice under similar conditions.

CONCLUSIONS/INTERPRETATION

Acute systemic removal of APN results in a much more negative metabolic phenotype compared with congenital knockout of Adipoq. Specifically, our data demonstrate that acute depletion of APN is especially detrimental to lipid homeostasis, both under basal and insulinopenic conditions. This suggests that compensatory mechanisms exist in congenital knockout mice that offset some of the metabolic actions covered by APN.

Hyperglycemic, high anion-gap metabolic acidosis in patients receiving SGLT-2 inhibitors for diabetes management

Sodium-glucose cotransporter-2 inhibitors (SGLT-2i) are a class of antidiabetic medications that improve glycemic control via inhibiting the reabsorption of filtered glucose and are approved for use in type 2 diabetes (T2DM). These drugs have recently been associated with euglycemic diabetic ketoacidosis (DKA). An increasing number of cases of SGLT-2i-associated DKA have occurred in patients with T2DM. Herein, we describe five episodes of hyperglycemic DKA in four type 2 diabetes patients receiving SGLT-2i therapy. Risk for ketoacidosis in our case series was mediated predominately by reduction of insulin dose and insulinopenia. None of the patients reported a history of low carbohydrate diet or alcohol use, and all but one patient had negative glutamic acid decarboxylase antibodies. Resolution of DKA in SGLT-2i treated patients took longer than for T1DM patients with DKA based on literature data. The mechanisms by which SGLT-2i are associated with ketoacidosis are not fully understood and likely involve hyperglucagonemia and other factors. Further studies are needed to elucidate the precise mechanism.

Early diabetic neuropathy: Triggers and mechanisms

Peripheral neuropathy, and specifically distal peripheral neuropathy (DPN), is one of the most frequent and troublesome complications of diabetes mellitus. It is the major reason for morbidity and mortality among diabetic patients. It is also frequently associated with debilitating pain. Unfortunately, our knowledge of the natural history and pathogenesis of this disease remains limited. For a long time hyperglycemia was viewed as a major, if not the sole factor, responsible for all symptomatic presentations of DPN. Multiple clinical observations and animal studies supported this view. The control of blood glucose as an obligatory step of therapy to delay or reverse DPN is no longer an arguable issue. However, while supporting evidence for the glycemic hypothesis has accumulated, multiple controversies accumulated as well. It is obvious now that DPN cannot be fully understood without considering factors besides hyperglycemia. Some symptoms of DPN may develop with little, if any, correlation with the glycemic status of a patient. It is also clear that identification of these putative non-glycemic mechanisms of DPN is of utmost importance for our understanding of failures with existing treatments and for the development of new approaches for diagnosis and therapy of DPN. In this work we will review the strengths and weaknesses of the glycemic hypothesis, focusing on clinical and animal data and on the pathogenesis of early stages and triggers of DPN other than hyperglycemia.