Symptomatic Hypoglycemia After Gastric Bypass: Incidence and Predictive Factors in a Cohort of 1,138 Consecutive Patients

An Imbalance of Pathophysiologic Factors in Late Postprandial Hypoglycemia Post Bariatric Surgery: A Narrative Review

With a rise in obesity and more patients opting for bariatric surgery, it becomes crucial to understand associated complications like postprandial hypoglycemia (PPH). After bariatric surgery, significant changes are seen in insulin sensitivity, beta cell function, glucagon-like peptide 1 (GLP-1) levels, the gut microbiome, and bile acid metabolism. And in a small subset of patients, exaggerated imbalances in these functional and metabolic processes lead to insulin-glucose mismatch and hypoglycemia. The main treatment for PPH involves dietary modifications. For those that do not respond, medications or surgical interventions are considered to reverse some of the imbalances. We present a few case reports of patients that safely tolerated GLP-1 agonists. However, larger randomized control trials are needed to further characterize PPH and understand its treatment.

Counter-regulatory responses to postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia vs surgical and non-surgical control individuals

AIMS/HYPOTHESIS

Post-bariatric hypoglycaemia is an increasingly recognised complication of bariatric surgery, manifesting particularly after Roux-en-Y gastric bypass. While hyperinsulinaemia is an established pathophysiological feature, the role of counter-regulation remains unclear. We aimed to assess counter-regulatory hormones and glucose fluxes during insulin-induced postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia after Roux-en-Y gastric bypass vs surgical and non-surgical control individuals.

METHODS

In this case-control study, 32 adults belonging to four groups with comparable age, sex and BMI (patients with post-bariatric hypoglycaemia, Roux-en-Y gastric bypass, sleeve gastrectomy and non-surgical control individuals) underwent a postprandial hypoglycaemic clamp in our clinical research unit to reach the glycaemic target of 2.5 mmol/l 150-170 min after ingesting 15 g of glucose. Glucose fluxes were assessed during the postprandial and hypoglycaemic period using a dual-tracer approach. The primary outcome was the incremental AUC of glucagon during hypoglycaemia. Catecholamines, cortisol, growth hormone, pancreatic polypeptide and endogenous glucose production were also analysed during hypoglycaemia.

RESULTS

The rate of glucose appearance after oral administration, as well as the rates of total glucose appearance and glucose disappearance, were higher in both Roux-en-Y gastric bypass groups vs the non-surgical control group in the early postprandial period (all p<0.05). During hypoglycaemia, glucagon exposure was significantly lower in all surgical groups vs the non-surgical control group (all p<0.01). Pancreatic polypeptide levels were significantly lower in patients with post-bariatric hypoglycaemia vs the non-surgical control group (median [IQR]: 24.7 [10.9, 38.7] pmol/l vs 238.7 [186.3, 288.9] pmol/l) (p=0.005). Other hormonal responses to hypoglycaemia and endogenous glucose production did not significantly differ between the groups.

CONCLUSIONS/INTERPRETATION

The glucagon response to insulin-induced postprandial hypoglycaemia is lower in post-bariatric surgery individuals compared with non-surgical control individuals, irrespective of the surgical modality. No significant differences were found between patients with post-bariatric hypoglycaemia and surgical control individuals, suggesting that impaired counter-regulation is not a root cause of post-bariatric hypoglycaemia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04334161.

Roux-en-Y Gastric Bypass Increases Glycemic Excursions During Pregnancy and Postpartum: A Prospective Cohort Study

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) and pregnancy markedly alter glucose metabolism, but evidence on glucose metabolism in pregnancy after RYGB is limited. Thus, the aims of the Bariatric Surgery and Consequences for Mother and Baby in Pregnancy study were to investigate interstitial glucose (IG) profiles during pregnancy, risk factors associated with hypoglycemia, and the association between fetal growth and hypoglycemia in pregnant women previously treated with RYGB, compared with control participants.

RESEARCH DESIGN AND METHODS

Twenty-three pregnant women with RYGB and 23 BMI- and parity-matched pregnant women (control group) were prospectively studied with continuous glucose monitoring in their first, second, and third trimesters, and 4 weeks postpartum. Time in range (TIR) was defined as time with an IG level of 3.5-7.8 mmol/L.

RESULTS

Women with RYGB were 4 years (interquartile range [IQR] 0-7) older than control participants. Pregnancies occurred 30 months (IQR 15-98) after RYGB, which induced a reduction in BMI from 45 kg/m2 (IQR 42-54) presurgery to 32 kg/m2 (IQR 27-39) prepregnancy. Women with RYGB spent decreased TIR (87.3-89.5% vs. 93.3-96.1%; P < 0.01) owing to an approximately twofold increased time above range and increased time below range (TBR) throughout pregnancy and postpartum compared with control participants. Women with increased TBR had a longer surgery-to-conception interval, lower nadir weight, and greater weight loss after RYGB. Finally, women giving birth to small-for-gestational age neonates experienced slightly increased TBR.

CONCLUSIONS

Women with RYGB were more exposed to hypoglycemia and hyperglycemia during pregnancy compared with control participants. Further research should investigate whether hypoglycemia during pregnancy in women with RYGB is associated with decreased fetal growth.

Unraveling, contributing factors to the severity of postprandial hypoglycemia after gastric bypass surgery

BACKGROUND

Despite the increasing prevalence of postbariatric hypoglycemia (PBH), a late metabolic complication of bariatric surgery, our understanding of its diverse manifestations remains incomplete.

OBJECTIVES

To contrast parameters of glucose-insulin homeostasis in 2 distinct phenotypes of PBH (mild versus moderate hypoglycemia) based on nadir plasma glucose.

SETTING

University Hospital (Bern, Switzerland).

METHODS

Twenty-five subjects with PBH following gastric bypass surgery (age, 41 ± 12 years; body mass index, 28.1 ± 6.1kg/m²) received 75g of glucose with frequent blood sampling for glucose, insulin, C-peptide, and glucagon-like peptide 1 (GLP)-1. Based on nadir plasma glucose (</≥50mg/dL), subjects were grouped into level 1 (L1) and level 2 (L2) PBH groups. Beta-cell function (BCF), GLP-1 exposure (λ), beta-cell sensitivity to GLP-1 (π), potentiation of insulin secretion by GLP-1 (PI), first-pass hepatic insulin extraction (HE), insulin sensitivity (SI), and rate of glucose appearance (Ra) were calculated using an oral model of GLP-1 action coupled with the oral minimal model.

RESULTS

Nadir glucose was 43.3 ± 6.0mg/dL (mean ± standard deviation) and 60.1 ± 9.1mg/dL in L2- and L1-PBH, respectively. Insulin exposure was significantly higher in L2 versus L1 (P = .004). Mathematical modeling revealed higher BCF in L2 versus L1 (34.3 versus 18.8 10^-9∗min^-1; P = .003). Despite an increased GLP-1 exposure in L2 compared to L1 PBH (50.7 versus 31.9pmol∗L^-1∗min∗10²; P = .021), no significant difference in PI was observed (P = .204). No significant differences were observed for HE, Ra, and SI.

CONCLUSIONS

Our results suggest that higher insulin exposure in PBH patients with lower postprandial nadir glucose values mainly relate to a higher responsiveness to glucose, rather than GLP-1.

Evaluation and Management of Patients Referred for Post-Bariatric Surgery Hypoglycemia at a Tertiary Care Center

PURPOSE

Following bariatric surgery, patients can develop non-specific symptoms self-described as hypoglycemia. However, confirming hypoglycemia can be technically challenging, and therefore, these individuals are frequently treated empirically. This study aimed to describe what diagnostic evaluation and therapeutic interventions patients referred for post-bariatric surgery hypoglycemia undergo.

METHODS

Retrospective observational cohort study of patients with a history of bariatric surgery was evaluated for post-bariatric surgery hypoglycemia in a tertiary referral center from 2008 to 2017. We collected demographic and bariatric surgery information, clinical presentation of symptoms referred to as hypoglycemia, laboratory and imaging studies performed to evaluate these symptoms, and symptom management and outcomes.

RESULTS

A total of 60/2450 (2.4%) patients who underwent bariatric surgery were evaluated in the Department of Endocrinology for hypoglycemia-related symptoms. The majority were middle-aged women without type 2 diabetes who had undergone Roux-en-Y gastric bypass. Thirty-nine patients (65%) completed a biochemical assessment for hypoglycemia episodes. Six (10%) had confirmed hypoglycemia by Whipple's triad, and four (6.7%) met the criteria for post-bariatric surgery hypoglycemia based on clinical and biochemical criteria. All patients were recommended dietary modification as the initial line of treatment, and this intervention resulted in most patients reporting at least some improvement in their symptoms. Eight patients (13%) were prescribed pharmacotherapy, and two patients required additional interventions for symptom control.

CONCLUSIONS

In our experience, evaluation for hypoglycemia-related symptoms after bariatric surgery was rare. Hypoglycemia was confirmed in the minority of patients. Even without establishing a diagnosis of hypoglycemia, dietary changes were a helpful strategy for symptom management for most patients.