Sodium, Glucose and Dysregulated Glucagon Secretion: The Potential of Sodium Glucose Transporters

SGLT2 Inhibitors in Management of Severe Hypomagnesemia in Patients Without Diabetes: A Report of 4 Cases

Sodium/glucose cotransporter 2 (SGLT2) inhibitors have demonstrated a class effect in improving serum magnesium levels in patients with diabetes. Additionally, recent reports have shown their promising beneficial effects in the treatment of refractory hypomagnesemia in patients with diabetes. However, their role in treating hypomagnesemia in patients without diabetes remains unexplored. Here, we report 4 cases of severe and refractory hypomagnesemia that showed dramatic improvement after initiating SGLT2 inhibitors in patients without diabetes. Case 1 had calcineurin inhibitor-associated severe hypomagnesemia. Cases 2, 3, and 4 had refractory hypomagnesemia associated with platinum-based chemotherapy with or without gastrointestinal losses. Case 1 was able to withdraw from high-dose oral magnesium supplementation. Cases 2 and 3 achieved independence from intravenous magnesium supplementation, whereas case 4 had decreased intravenous magnesium requirements. All the cases demonstrated sustainably improved serum magnesium levels. Withdrawal of SGLT2 inhibitors in case 4 resulted in worsening serum magnesium levels and intravenous magnesium requirements. The extraglycemic benefit of this group of medications not only suggests the need for further studies to better understand the effect of SGLT2 inhibitors on magnesium homeostasis but also supports expanded use in a larger patient population.

Metabolic regulation of glucagon secretion

Since the discovery of glucagon 100 years ago, the hormone and the pancreatic islet alpha cells that produce it have remained enigmatic relative to insulin-producing beta cells. Canonically, alpha cells have been described in the context of glucagon's role in glucose metabolism in liver, with glucose as the primary nutrient signal regulating alpha cell function. However, current data reveal a more holistic model of metabolic signalling, involving glucagon-regulated metabolism of multiple nutrients by the liver and other tissues, including amino acids and lipids, providing reciprocal feedback to regulate glucagon secretion and even alpha cell mass. Here we describe how various nutrients are sensed, transported and metabolised in alpha cells, providing an integrative model for the metabolic regulation of glucagon secretion and action. Importantly, we discuss where these nutrient-sensing pathways intersect to regulate alpha cell function and highlight key areas for future research.

Dual sodium-glucose cotransporter (SGLT) 1/2 versus pure SGLT2 inhibitors: two distinct drug categories or one class with multiple faces?

INTRODUCTION

According to their selectivity for sodium-glucose cotransporters (SGLT) 1 and 2, gliflozins could be subdivided into two additional categories: pure SGLT2 inhibitors, which are highly selective for SGLT2, and dual SGLT1/2 inhibitors which, in addition to SGLT2, exhibit strong inhibitory activity for SGLT1.

AREAS COVERED

This article aims to discuss whether the pharmacological differences between the two subtypes of gliflozins could be translated into different efficacy and safety characteristics that might be important for clinical practice.

EXPERT OPINION

In large cardiovascular outcome trials, dual inhibitors have shown a unique efficacy profile in terms of reducing glycemia in patients with severe renal impairment and decreasing the risk of atherosclerotic outcomes. These features do not characterize selective SGLT2 inhibitors and could be attributed to the parallel inhibition of SGLT1. The increased risk of diarrhea and severe hypoglycemia observed only with dual inhibitors is probably related to their action in the gut and brain, respectively. However, differences in populations included in various studies should be considered when attempting to translate their findings into clinical practice; therefore, head-to-head trials are needed to shed more light on this issue and provide clear guidance to clinicians.

Sweet Taste Signaling: The Core Pathways and Regulatory Mechanisms

Sweet taste, a proxy for sugar-derived calories, is an important driver of food intake, and animals have evolved robust molecular and cellular machinery for sweet taste signaling. The overconsumption of sugar-derived calories is a major driver of obesity and other metabolic diseases. A fine-grained appreciation of the dynamic regulation of sweet taste signaling mechanisms will be required for designing novel noncaloric sweeteners with better hedonic and metabolic profiles and improved consumer acceptance. Sweet taste receptor cells express at least two signaling pathways, one mediated by a heterodimeric G-protein coupled receptor encoded by taste 1 receptor members 2 and 3 (TAS1R2 + TAS1R3) genes and another by glucose transporters and the ATP-gated potassium (K_ATP) channel. Despite these important discoveries, we do not fully understand the mechanisms regulating sweet taste signaling. We will introduce the core components of the above sweet taste signaling pathways and the rationale for having multiple pathways for detecting sweet tastants. We will then highlight the roles of key regulators of the sweet taste signaling pathways, including downstream signal transduction pathway components expressed in sweet taste receptor cells and hormones and other signaling molecules such as leptin and endocannabinoids.

Case Report: High-Calorie Glucose Infusion and Tight Glycemic Control in Ameliorating Refractory Acidosis of Empagliflozin-Induced Euglycemic Diabetic Ketoacidosis

The current widespread use of sodium-glucose co-transporter 2 (SGLT2) inhibitors has triggered an increase in reported cases of euglycemic diabetic ketoacidosis (EDKA), often characterized by a protracted metabolic acidosis that is resistant to conventional DKA treatment. We report a case of empagliflozin-induced EDKA with severe metabolic acidosis intractable to aggressive fluid resuscitation and boluses of bicarbonate infusion. Following the introduction of high-calorie glucose infusion coupled with tight glycemic control, the recalcitrant acidosis was successfully corrected. This is the first case report that adopts the above approach, representing a paradigm shift in the management of SGLT2 inhibitor-induced EDKA.