The effects of bariatric surgery on bone and nephrolithiasis

Delta weight loss unlike genetic variation associates with hyperoxaluria after malabsorptive bariatric surgery

The risk of enteric hyperoxaluria is significantly increased after malabsorptive bariatric surgery (MBS). However, its underlying determinants are only poorly characterized. In this case-control study, we aimed at identifying clinical and genetic factors to dissect their individual contributions to the development of post-surgical hyperoxaluria. We determined the prevalence of hyperoxaluria and nephrolithiasis after MBS by 24-h urine samples and clinical questionnaires at our obesity center. Both hyperoxaluric and non-hyperoxaluric patients were screened for sequence variations in known and candidate genes implicated in hyperoxaluria (AGXT, GRHPR, HOGA1, SLC26A1, SLC26A6, SLC26A7) by targeted next generation sequencing (tNGS). The cohort comprised 67 patients, 49 females (73%) and 18 males (27%). While hyperoxaluria was found in 29 patients (43%), only one patient reported postprocedural nephrolithiasis within 41 months of follow-up. Upon tNGS, we did not find a difference regarding the burden of (rare) variants between hyperoxaluric and non-hyperoxaluric patients. However, patients with hyperoxaluria showed significantly greater weight loss accompanied by markers of intestinal malabsorption compared to non-hyperoxaluric controls. While enteric hyperoxaluria is very common after MBS, genetic variation of known hyperoxaluria genes contributes little to its pathogenesis. In contrast, the degree of postsurgical weight loss and levels of malabsorption parameters may allow for predicting the risk of enteric hyperoxaluria and consecutive kidney stone formation.

Effect of preoperative metabolic profiling to reduce the risk of kidney stones after bariatric surgery in patients with a history of stone formation

BACKGROUND

Roux-en-Y gastric bypass (RYGB) is associated with an increased risk of kidney stone formation. This is not observed after sleeve gastrectomy (SG).

OBJECTIVES

Aim of this study was to assess whether preoperative metabolic profiling is helpful in selecting the most optimal bariatric procedure for patients with a kidney stone history.

SETTING

General hospital, the Netherlands.

METHODS

Patients with a kidney stone history and in the run up to bariatric surgery were screened with non-contrast abdominal computed tomography (CT), serum profiling, and 24-hour urine analysis. Those with stones on radiologic imaging and/or high preoperative urinary oxalate were advised to undergo SG instead of RYGB. Pre- and postoperative urine and serum profile differences between both groups were evaluated retrospectively.

RESULTS

Postoperatively, RYGB (N = 28, M:F = 8:20) was associated with a 23.5% reduction in urinary volume, a 85% increase in urinary oxalate excretion with a 230% increase in calcium oxalate (CaOx) supersaturation and a 62% decrease in urinary citrate. Although SG (N = 30, M:F = 12:18) was also associated with a reduction in urinary volume, it had no adverse effects on urinary oxalate and citrate excretion, nor on calcium oxalate supersaturation (CaOx-SS). Both RYGB and SG showed favorable effects on postoperative sodium, calcium, uric acid, and phosphate excretion.

CONCLUSIONS

This study indicates that preoperative metabolic profiling is important to select the optimal bariatric procedure in patients with an a priori increased risk of kidney stone development. These patients should be strongly encouraged to undergo SG instead of RYGB to prevent progressive or recurrent kidney stone disease.

Adequate vitamin D supplementation does not ameliorate bone loss following long limb-biliopancreatic diversion in morbidly obese women

OBJECTIVES

The objective of this study is to investigate the effect of adequate vitamin D supplementation on bone mineral density (BMD) following long limb-biliopancreatic diversion (LL-BPD), a malabsorptive bariatric operation.

BACKGROUND

Marked weight loss following bariatric surgery is associated with significant decrease in BMD, attributed to the weight loss and to nutritional, mineral, and vitamin D deficiencies resulting in secondary hyperparathyroidism.

METHODS

Two groups, of 35 and 37 healthy, obese (BMI, 50.4 + 6.6 and 46.5 + 4.8 g/cm²), premenopausal, normally menstruating women underwent LL-BPD. Both groups received high-calcium diets, 600 IU of vitamin D, and 1000 mg elemental calcium daily, while group B received an extra dose of vitamin D (10,000 IU/day) during the first postoperative month, followed by dose adjustment in order to maintain 25OHD concentration higher than 30 μg/L. Areal BMD (aBMD) was measured at the lumbar spine preoperatively and 1 year postoperatively.

RESULTS

One year postoperatively, BMI decreased by approximately 19 kg/m² in both groups, while 25-OH-vitamin D levels did not change in group A (18.7 + 9.1 to 20.2 + 13.0 μg/L, (p = 0.57)) and increased in group B (15.58 ± 5.73 to 52.97 ± 15.46 μg/L, (p = < 0.001). PTH levels increased in group A (from 38.5 ± 12.2 to 51.2 ± 32.8 pg/ml) (p = 0.047) and decreased in group B (from 51.61 ± 18.7 to 45.1 ± 17.8 pg/ml) (p = 0.042). Lumbar spine aBMD decreased similarly in both groups (p = 0.311, for the comparison between groups) from 1.198 + 0.14 to 1.103 + 0.15 g/cm² in group A (p < 0.001) and from 1.157 + 0.14 to 1.076 + 0.14 g/cm² in group B (p < 0.001) and Z-score from 0.93 + 0.97 to 0.19 + 1.02, (p < 0.001) and from 1.15 + 1.29 to 0.419 + 1.28, (p < 0.001), respectively.

CONCLUSIONS

LL-BPD leads to similar and significant bone mass reduction 1 year postoperatively, irrespective of adequate vitamin D replacement and in the absence of secondary hyperparathyroidism.

Recommendations Based on Evidence by the Andalusian Group for Nutrition Reflection and Investigation (GARIN) for the Pre- and Postoperative Management of Patients Undergoing Obesity Surgery

In order to develop evidence-based recommendations and expert consensus for nutrition management of patients undergoing bariatric surgery and postoperative follow-up, we conducted a systematic literature search using PRISMA methodology plus critical appraisal following the SIGN and AGREE-II procedures. The results were discussed among all members of the GARIN group, and all members answered a Likert scale questionnaire to assess the degree of support for every recommendation. Patients undergoing bariatric surgery should be screened preoperatively for some micronutrient deficiencies and treated accordingly. A VLCD (Very Low-Calorie Diet) should be used for 4–8 weeks prior to surgery. Postoperatively, a liquid diet should be maintained for a month, followed by a semi-solid diet also for one month. Protein requirements (1–1.5 g/kg) should be estimated using adjusted weight. Systematic use of specific multivitamin supplements is encouraged. Calcium citrate and vitamin D supplements should be used at higher doses than are currently recommended. The use of proton-pump inhibitors should be individualised, and vitamin B12 and iron should be supplemented in case of deficit. All patients, especially pregnant women, teenagers, and elderly patients require a multidisciplinary approach and specialised follow-up. These recommendations and suggestions regarding nutrition management when undergoing bariatric surgery and postoperative follow-up have direct clinical applicability.

Dietary Recommendations for Bariatric Patients to Prevent Kidney Stone Formation

Bariatric surgery (BS) is one of the most common and efficient surgical procedures for sustained weight loss but is associated with long-term complications such as nutritional deficiencies, biliary lithiasis, disturbances in bone and mineral metabolism and an increased risk of nephrolithiasis, attributed to urinary metabolic changes resultant from low urinary volume, hypocitraturia and hyperoxaluria. The underlying mechanisms responsible for hyperoxaluria, the most common among all metabolic disturbances, may comprise increased intestinal oxalate absorption consequent to decreased calcium intake or increased dietary oxalate, changes in the gut microbiota, fat malabsorption and altered intestinal oxalate transport. In the current review, the authors present a mechanistic overview of changes found after BS and propose dietary recommendations to prevent the risk of urinary stone formation, focusing on the role of dietary oxalate, calcium, citrate, potassium, protein, fat, sodium, probiotics, vitamins D, C, B6 and the consumption of fluids.

Bone Metabolism in Adolescents and Adults Undergoing Roux-En-Y Gastric Bypass: a Comparative Study

OBJECTIVE

To compare the bone metabolism of adolescents and adults with obesity before undergoing a Roux-en-Y gastric bypass (RYGB) and 6 and 12 months after the surgery.

MATERIALS AND METHODS

Adolescents (G1) and adults (G2) with obesity assessed before (T0), six (T1), and 12 months after (T2) RYGB. Sun exposure, serum concentrations of 25(OH)D, calcium, phosphorous, magnesium, zinc, alkaline phosphatase, parathyroid hormone (PTH), and bone mineral density (BMD) were evaluated.

RESULTS

Sixty adolescents and 60 adults were assessed. At T0, there was no significant difference between the groups' serum 25(OH)D levels (G1 21.87 + 7.52 ng/mL, G2 21.73 + 7.60 ng/mL, p = 0.94) or sun exposure (G1 17 ± 2.0 min/day, G2 13.2 ± 5.2 min/day, p = 0.85). G1 had high levels of inadequacy of calcium (66.7%), phosphorous (80.0%), and zinc (18.3%) at T0 and had a significant fall in their 25(OH)D (p < 0.01) and magnesium (p < 0.01) levels from T1 to T2. G2 saw a significant lowering of their serum zinc levels from T0 to T1 and T2 (T1 p < 0.01; T2 p < 0.01). In both groups, there was a significant rise in PTH from T1 to T2 (G1 p = 0.04, G2 p = 0.02) and from T0 to T2 (G1 and G2 p < 0.01). In G2, 40.4% of individuals with osteopenia and osteoporosis presented inadequacy of 25(OH)D.

CONCLUSION

RYGB was found to worsen the inadequacy of micronutrients related to bone metabolism and was associated with secondary hyperparathyroidism and low BMD values, especially among the adolescents. The irreversible damaging effects of obesity on bone metabolism can occur in adolescence.

Effect of bisphosphonate on the prevention of bone loss in patients with gastric cancer after gastrectomy: A randomized controlled trial

BACKGROUND

Bone loss is highly prevalent after gastrectomy in gastric cancer patients. Therefore, the efficacy of medical treatment should be evaluated in patients undergoing gastrectomy.

METHODS

We conducted an unblinded, randomized controlled trial of patients who underwent gastrectomy to treat gastric cancer. The intention-to-treat participants (n = 107) were randomly assigned to receive either alendronate at a weekly dose of 70 mg and daily elemental calcium (500 mg) with cholecalciferol (1000 IU) or daily elemental calcium (500 mg) with cholecalciferol (1000 IU) only. The primary endpoint was defined by the changes in bone mineral density of four measurement sites: the lumbar spine, femur neck, total hip, and trochanter. Changes in bone turnover markers, osteocalcin and collagen I carboxyterminal telopeptide were also observed.

RESULTS

At baseline, there were no differences between the two groups in bone mineral density. In the lumbar spine and trochanter, there were no significant percentage changes compared with the baseline in the alendronate group, but a significant decrease was noted in the control group (p < 0.001 for both lumbar spine and trochanter). In the femur neck and total hip, a larger decrease was observed compared with the baseline in the control group (p < 0.001 for both femur neck and total hip). Significant percentage increases in serum osteocalcin compared with baseline were noted in the control group (p for trend <0.001), but there was no change in the alendronate group (p for trend = 0.713). Collagen I carboxyterminal telopeptide significantly declined in the alendronate group over 12 months (p for trend <0.001).

CONCLUSIONS

Prevention and treatment with bisphosphonate effectively reduces bone loss by suppressing bone resorption in gastric cancer patients undergoing gastrectomy.

Bilateral subtrochanteric femur insufficiency fractures after bariatric surgery: a case report

There have been case reports of proximal femur insufficiency fractures in patients who have previously undergone bariatric surgery. We present a follow-up case of a patient who developed bilateral complete proximal femur insufficiency fractures several years after bariatric surgery. Our patient underwent bilateral intramedullary fixation with a satisfactory postoperative outcome. We review and discuss the definition and pathogenesis of atypical femur fractures (AFFs), which may represent a larger category of insufficiency fractures not exclusive to bisphosphonate use, which includes patients with fractures after bariatric surgery.

DObesity: Relationship between vitamin D deficiency, obesity and sclerostin as a novel biomarker of bone metabolism

Aim

To study the relationship between obesity, insulin resistance, vitamin D deficiency and sclerostin as a bone biomarker.

Materials and methods

Cross-section study of 75 subjects grouped into 3 groups; obese (n = 31), overweight (n = 23) and normal (n = 21) subjects. Sclerostin, fasting insulin, fasting plasma glucose and 25(OH)D were measured and anthropometric measures were taken.

Results

25(OH)D was lower in obese subjects than overweight and control groups (mean ± SD 5.27 ± 5.14 vs. 12.55 ± 6.99 vs.17.65 ± 4.07 ng/L, p < 0.001). Sclerostin was significantly lower in obese subjects versus the control (mean ± SD 1.02 ± 0.45 vs 1.58 ± 0.83 ng/mL, p = 0.014).

Conclusion

These results lead us to hypothesize that the relationship between sclerostin and Vitamin D levels has an important role in the link between obesity and bone metabolism. DObesity could be an active focus of research in the coming years.

Multiple vertebral fractures sustained 5 months after Roux-en-Y gastric bypass: a case report

INTRODUCTION

We report a case of a patient sustaining multiple simultaneous vertebral fractures 5 months after Roux-en-Y gastric bypass (RYGB) surgery. Obesity is associated with increased rates of morbidity and mortality and obesity rates globally continue to rise. Bariatric surgical procedures are successful in inducing sustained weight loss with many improved health outcomes. Potential complications include nutritional deficiencies and adverse effects on bone mineral metabolism with increased rates of fracture.

CASE STUDY

We have recently cared for a 40-year-old female who sustained multiple vertebral fractures after bending forwards, occurring only 5 months after she underwent RYGB surgery, with post-operative weight loss of 55 kg. Blood tests performed several months after the fractures occurred revealed she had biochemical secondary hyperparathyroidism with low serum vitamin D levels.

DISCUSSION

It has been previously demonstrated that RYGB surgery is associated with an increased incidence of fractures, and with reduction in bone mineral density. Patients undergoing bariatric surgery are frequently vitamin D deficient pre-operatively and show variable responses to vitamin D supplementation in the post-operative period. With particular reference to the RYGB procedure, there is evidence from several studies that bone mineral density is reduced at 12 and 24 post-operative months. To the best of our knowledge, this case may be the first time that multiple vertebral fractures have been documented so soon after weight loss surgery. It therefore highlights the growing conclusion that early consideration must be given to the maintenance of bone health in patients undergoing weight loss surgery.

Vitamin D Metabolism in Bariatric Surgery

Hypovitaminosis D is common in obese patients and persists after roux-en-Y gastric bypass and sleeve gastrectomy. Several societies recommend screening for vitamin D deficiency before bariatric surgery, and replacement doses of 3000 IU/d and up to 50,000 IU 1 to 3 times per week, in case of deficiency, with periodic monitoring. These regimens are mostly based on expert opinion. Large trials are needed to assess the vitamin D dose response, by type of bariatric surgery, and evaluate the effect on surrogate markers of skeletal outcomes. Such data are essential to derive desirable vitamin D levels in this population.

The gut microbiota and gastrointestinal surgery

Surgery involving the gastrointestinal tract continues to prove challenging because of the persistence of unpredictable complications such as anastomotic leakage and life-threatening infections. Removal of diseased intestinal segments results in substantial catabolic stress and might require complex reconstructive surgery to maintain the functional continuity of the intestinal tract. As gastrointestinal surgery necessarily involves a breach of an epithelial barrier colonized by microorganisms, preoperative intestinal antisepsis is used to reduce infection-related complications. The current approach to intestinal antisepsis varies widely across institutions and countries with little understanding of its mechanism of action, effect on the gut microbiota and overall efficacy. Many of the current approaches to intestinal antisepsis before gastrointestinal surgery run counter to emerging concepts of intestinal microbiota contributing to immune function and recovery from injury. Here, we review evidence outlining the role of gut microbiota in recovery from gastrointestinal surgery, particularly in the development of infections and anastomotic leak. To make surgery safer and further reduce complications, a molecular, genetic and functional understanding of the response of the gastrointestinal tract to alterations in its microbiota is needed. Methods can then be developed to preserve the health-promoting functions of the microbiota while at the same time suppressing their harmful effects.

Vitamin D alteration associated with obesity and bariatric surgery

Obesity and severe obesity constitute growing serious health problems reaching epidemic proportion in most countries. Interactions and relationships between obesity and bone tissue and its metabolism are complex but are more and more studied and recognized. Obesity is associated with an altered hormonal profile including particularly bone-regulating hormones like vitamin D. Bariatric surgery procedures, thanks to their effectiveness to achieve therapeutic endpoints for comorbidities associated with obesity, have had an increasing success. However, these surgeries by producing mechanical restriction and or malabsorption syndrome lead to nutritional deficiencies including vitamin D. In this review, we aim to (1) discuss the nutritional deficiency of vitamin D in the obese, (2) to summarize the different surgical options in bariatric surgery and to present the evidence concerning these procedures and their associated profile in vitamin D post-operative insufficiency, (3) to present the different recommendations in clinical practice to prevent or treat vitamin D deficiencies or insufficiencies in patients treated by bariatric surgery and finally to introduce emerging assumptions on the relationship between vitamin D, microbiota composition and circulating bile acids. Impact statement Obesity and severe obesity constitute growing serious health problems reaching epidemic proportion in most countries with a prevalence increasing from 6.4 in 1975 to 14.9% in 2014. This present review summarizes currently available data on vitamin D deficiencies in the obese population before and after bariatric surgery. The important evidence emerging from our evaluation confirms that obese patients are at risk of multiple nutritional deficiencies, especially vitamin D deficiency, before bariatric surgery. Our survey confirms that the precise role of the gut microbiome and its associated changes on the vitamin D metabolism after the different bariatric surgery procedures has not yet been studied. Furthermore, whether differences in the microbiota may alter the therapeutic responses to vitamin D is not known.

Progress in Understanding the Genetics of Calcium-Containing Nephrolithiasis

Renal stone disease is a frequent condition, causing a huge burden on health care systems globally. Calcium-based calculi account for around 75% of renal stone disease and the incidence of these calculi is increasing, suggesting environmental and dietary factors are acting upon a preexisting genetic background. The familial nature and significant heritability of stone disease is known, and recent genetic studies have successfully identified genes that may be involved in renal stone formation. The detection of monogenic causes of renal stone disease has been made more feasible by the use of high-throughput sequencing technologies and has also facilitated the discovery of novel monogenic causes of stone disease. However, the majority of calcium stone formers remain of undetermined genotype. Genome-wide association studies and candidate gene studies implicate a series of genes involved in renal tubular handling of lithogenic substrates, such as calcium, oxalate, and phosphate, and of inhibitors of crystallization, such as citrate and magnesium. Additionally, expression profiling of renal tissues from stone formers provides a novel way to explore disease pathways. New animal models to explore these recently-identified mechanisms and therapeutic interventions are being tested, which hopefully will provide translational insights to stop the growing incidence of nephrolithiasis.

Clinical Outcomes of Metabolic Surgery: Efficacy of Glycemic Control, Weight Loss, and Remission of Diabetes

Since the 2007 Diabetes Surgery Summit in Rome, Italy, and the subsequent publishing of the world's first guidelines for the surgical treatment of type 2 diabetes (T2D), much new evidence regarding the efficacy and safety of metabolic surgery has emerged. Additional observational cohort studies support the superior effects of surgery over medical treatment with respect to glycemic control, weight loss, and even reduction in mortality and microvascular complications associated with T2D. Furthermore, new safety data suggest that the perioperative morbidity and mortality of metabolic surgery (5% and 0.3%, respectively) are now similar to that of common low-risk procedures, such as cholecystectomy and hysterectomy. The largest advance, however, has been the completion of 11 randomized controlled trials from around the globe that compare surgery with medical treatment of T2D. These studies with follow-up duration of 1-5 years involve nearly 800 patients without surgical mortality and with major complication rates of less than 5% and a reoperation rate of 8%. All but 1 of the 11 randomized controlled trials have shown the superiority of surgery over medical management at achieving remission or glycemic improvement. Surgery was also superior to medical treatment with respect to improving cardiovascular risk factors, such as weight loss and dyslipidemia, while reducing medication burden. This new efficacy and safety evidence should help guide physicians across the globe to the appropriate use of surgery as an effective treatment for patients suffering from T2D and obesity.