Low serum sodium concentrations in patients with obesity normalizes with weight loss.

BACKGROUND & AIMS: Obesity is associated with higher extracellular fluid (ECF) compared to intracellular fluid (ICF) volume and this dysregulation is associated with hypertension and abdominal obesity, associated with metabolic syndrome. As sodium is predominantly an extracellular cation, a higher ECF/ICF ratio will lower serum sodium concentration. The aim of the study was to see whether weight loss, due to dieting and bariatric surgery, had any impact on serum sodium concentrations in patients with severe obesity. METHODS: Patients with a BMI ≥35 kg/m2 admitted for bariatric surgery at Innlandet Hospital Trust, Norway during 2012-14 were included in the study (n = 119). Clinical data and blood samples were recorded at inclusion, after mean six months of dieting, as well as six and 12 months after bariatric surgery. RESULTS: At inclusion, mean serum sodium was in the lower normal range, 138.3 (SD 2.4) mmol/L, but increased to 141.8 (SD 1.9) mmol/L after weight loss. The increase was significantly correlated to total weight loss (rho: 0.29, p = 0.007). Twelve months after surgery, serum sodium was significantly higher in patients with a normal BMI (<25 kg/m2) compared to patients with overweight. CONCLUSION: Obesity and hypertension are associated with body fluid dysregulation affecting serum sodium concentrations. As mild hyponatremia, even within the normal sodium range, is associated with increased total mortality and major cardiovascular disease events, serum sodium might be a potential risk marker in patients with obesity.

Cadmium, lead and mercury in Norwegian obese patients before and 12 months after bariatric surgery.

PURPOSE: Previous studies have suggested a role for the toxic elements lead (Pb), mercury (Hg) and cadmium (Cd) in the development of insulin resistance and hypertension. Increased blood Pb levels have been reported after bariatric surgery and weight loss. As about 80% of patients undergoing bariatric surgery are women, most of them of childbearing age, there are concerns regarding fetal exposure to toxic trace elements. We measured whole blood Hg, Pb and Cd concentrations in morbidly obese patients before and 12 months after Roux-en-Y gastric bypass (RYGB). PATIENTS AND METHODS: Forty-six patients eligible for bariatric surgery were recruited at Innlandet Hospital Trust, Norway (2012-2014). The majority were women and 54% were of reproductive age. Whole blood samples were collected prior to and 12 months after surgery. Trace element concentrations were measured using mass spectrometry (HR-ICP-MS). RESULTS: Median whole blood Pb concentrations increased by 73% during the 12 months study period while Hg and Cd decreased by 31% and 27%, respectively. We found a negative correlation between Pb levels before surgery and BMI (p = 0.02). Before surgery patients with hypertension had significantly higher median whole blood Hg levels compared to patients with normal blood pressure (p < 0.001). CONCLUSION: One year after bariatric surgery, the median whole blood Pb concentration was increased, while Hg and Cd concentrations were decreased. The majority of bariatric surgery patients are women of reproductive age and weight loss is associated with improved fertility. As even low dose Pb exposure during fetal life is associated with negative effects on the central nervous system, the observed increase in whole blood Pb after weight loss causes concern. Further studies are needed to elucidate these observations.

Improved Magnesium Levels in Morbidly Obese Diabetic and Non-diabetic Patients After Modest Weight Loss.

Serum magnesium (Mg) is reported to be reduced in individuals with obesity, hypertension, and diabetes mellitus and has been suggested as a marker for metabolic syndrome. We have studied changes in serum Mg concentrations in a group of obese patients (n = 92) with and without diabetes mellitus after weight loss induced by dieting and bariatric surgery. At inclusion, 11% (10/92) of the population had severe Mg deficiency (< 0.75 mmol/L) and median serum Mg was lower in diabetic (n = 20) compared to non-diabetic (n = 72) patients (p = 0.002). A weight loss of 10 kg after 8 weeks of lifestyle interventions was accompanied by increased serum Mg of about 5% in both diabetic and non-diabetic patients. Serum Mg remained stable thereafter in the non-diabetic patients, while it continued to increase in the diabetic patients after bariatric surgery. Six months after bariatric surgery, there was no significant difference in serum Mg concentration between the groups (p = 0.08). The optimal range of circulating Mg concentration is not known, but as even small increments in serum Mg are reported to lower the risk of cardiovascular and ischemic heart disease, our results are interesting in a public health perspective.