Fat malabsorption induced by gastrointestinal lipase inhibitor leads to an increase in urinary oxalate excretion

Pharmacologic Treatment of Obesity in adults and its impact on comorbidities: 2024 Update and Position Statement of Specialists from the Brazilian Association for the Study of Obesity and Metabolic Syndrome (Abeso) and the Brazilian Society of Endocrinology and Metabolism (SBEM)

Pharmacological treatment of obesity is passing through many changes in the last decades; different agents have been approved, and newer options are leaning towards higher efficacy and a more favourable safety profile; however, medications approved for a longer time are still available and useful for many patients. This document is an 2024 Update Position Statement of Specialists from the Brazilian Association for the Study of Obesity and Metabolic Syndrome (Abeso) and the Brazilian Society of Endocrinology and Metabolism (SBEM), with the aim of reviewing all the approved medications for the management of obesity in Brazil (sibutramine, orlistat, liraglutide, semaglutide and bupropion/naltrexone fixed dose), with the addition of tirzepatide, that is approved in other countries and likely approved soon in Brazil. The review is focused on efficacy, safety profile and the impact of drugs (based on existing studies) on different comorbidities.

Changes in 24-Hour Urine Chemistry in Patients with Nephrolithiasis during Weight Loss with Glucagon-Like Peptide 1-Based Therapies

Key Points

Background

Obesity is an independent risk factor of incident and recurrent nephrolithiasis. The effect of weight loss through glucagon-like peptide 1 (GLP-1) receptor agonists and dual GLP-1/gastric inhibitory polypeptide receptor agonists (GLP-based therapies) on nephrolithiasis is not well understood. This study examined the changes in 24-hour urine chemistry assessing for stone risk during weight loss through GLP-based therapies.

Methods

This retrospective analysis identified adult stone formers followed at our academic institution's weight wellness clinic between September 2015 and August 2023 and included patients with at least two 24-hour urine collections for stone risk assessment. 24-hour urine parameters before and during weight loss in patients on GLP-based therapies were compared.

Results

Forty-four obese patients with nephrolithiasis experienced significant weight reduction (−6.6±7.3 kg, P < 0.001) over a median 1.1 years of follow-up with GLP-based therapies. During this period, there was a significant decrease in 24-hour urine oxalate (40±16 to 32±11 mg/d, P = 0.002), sulfate (21±10 to 17±9 mmol/d, P = 0005), and ammonium (35±22 to 29±15 mEq/d, P = 0.01) excretion rates. There were nonsignificant changes in urine calcium, citrate, uric acid, pH, phosphorus, sodium, potassium, magnesium, chloride, creatinine, or total volume. In addition, there was no statistical difference in urine supersaturation indices with respect to calcium oxalate, calcium phosphate, and uric acid.

Conclusions

Our results indicate that weight loss through GLP-based therapies is not associated with prolithogenic changes in 24-hour urine chemistry in patients with nephrolithiasis, unlike what happens with other weight loss modalities.

Pharmacovigilance analysis of orlistat adverse events based on the FDA adverse event reporting system (FAERS) database

Objective

Based on the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database, we analyzed the signals of potential adverse events (AEs) of orlistat in the real world to provide a reference for its safe clinical use.

Methods

The FAERS database and OpenVigil 2.1 were used to obtain data on adverse events of orlistat from the first quarter of 2004 to the first quarter of 2023, and to analyze the population in which the adverse events occurred. And the signals of their potential adverse events were mined using reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network (BCPNN) and empirical Bayesian geometric mean (EBGM).

Result

A total of 21,079 reports of adverse events with orlistat as the primary suspected drug were collected in this study. Using four disproportionate analyses, we screened 117 preferred terms (PTs) involving 18 system organ classes (SOCs). We found that the most common adverse events at SOC level for orlistat remained "gastrointestinal disorders", while "metabolism and nutrition disorders", "renal and urinary disorders", "musculoskeletal and connective tissue disorders" and "hepatobiliary disorders" also ranked high in the number of case reports. In addition, at the PT level, we identified several new signals of adverse events not mentioned in the specification, including "lipiduria", "anal haemorrhage", "rectal haemorrhage", "haematochezia", "sigmoiditis", "diverticulitis" and "muscle spasms".

Conclusion

Most of the adverse events found in this study are consistent with the results described in the drug label. At the same time, we also found some new adverse events, which require more prospective studies to verify and elucidate their relationship with orlistat.

Beneficial roles of gastrointestinal and urinary microbiomes in kidney stone prevention via their oxalate-degrading ability and beyond

Formation of calcium oxalate (CaOx) crystal, the most common composition in kidney stones, occurs following supersaturation of calcium and oxalate ions in the urine. In addition to endogenous source, another main source of calcium and oxalate ions is dietary intake. In the intestinal lumen, calcium can bind with oxalate to form precipitates to be eliminated with feces. High intake of oxalate-rich foods, inappropriate amount of daily calcium intake, defective intestinal transporters for oxalate secretion and absorption, and gastrointestinal (GI) malabsorption (i.e., from gastric bypass surgery) can enhance intestinal oxalate absorption, thereby increasing urinary oxalate level and risk of kidney stone disease (KSD). The GI microbiome rich with oxalate-degrading bacteria can reduce intestinal oxalate absorption and urinary oxalate level. In addition to the oxalate-degrading ability, the GI microbiome also affects expression of oxalate transporters and net intestinal oxalate transport, cholesterol level, and short-chain fatty acids (SCFAs) production, leading to lower KSD risk. Recent evidence also shows beneficial effects of urinary microbiome in KSD prevention. This review summarizes the current knowledge on the aforementioned aspects. Potential benefits of the GI and urinary microbiomes as probiotics for KSD prevention are emphasized. Finally, challenges and future perspectives of probiotic treatment in KSD are discussed.

Anti-obesity pharmacotherapy in adults with chronic kidney disease

Obesity is a leading risk factor for the development and progression of kidney disease and a major barrier to optimal management of patients with chronic kidney disease. While in the past anti-obesity drugs offered only modest weight loss efficacy in exchange for various safety and tolerability risks, a wave of safer, more tolerable, and more effective treatment options is transforming the management of obesity. This review evaluates current and future pharmacologic anti-obesity therapy in adults through a kidney-oriented lens. It also explores the goals of anti-obesity treatment, describes the underlying putative mechanisms of action, and raises important scientific questions that deserve further exploration in people with chronic kidney disease.

Review article: Pharmacologic management of obesity - updates on approved medications, indications and risks

BACKGROUND

Obesity has reached epidemic proportions, with >40% of the US population affected. Although traditionally managed by lifestyle modification, and less frequently by bariatric therapies, there are significant pharmacological advancements.

AIMS

To conduct a narrative review of the neurohormonal and physiological understanding of weight gain and obesity, and the development, clinical testing, indications, expected clinical outcomes, and associated risks of current FDA-approved and upcoming anti-obesity medications (AOMs).

METHODS

We conducted a comprehensive review in PubMed for articles on pathophysiology and complications of obesity, including terms 'neurohormonal', 'obesity', 'incretin', and 'weight loss'. Next, we searched for clinical trial data of all FDA-approved AOMs, including both the generic and trade names of orlistat, phentermine/topiramate, bupropion/naltrexone, liraglutide, and semaglutide. Additional searches were conducted for tirzepatide and retatrutide - medications expecting regulatory approval. Searches included combinations of terms related to mechanism of action, indications, side effects, risks, and future directions.

RESULTS

We reviewed the pathophysiology of obesity, including specific role of incretins and glucagon. Clinical data supporting the use of various FDA-approved medications for weight loss are presented, including placebo-controlled or, when available, head-to-head trials. Beneficial metabolic effects, including impact on liver disease, adverse effects and risks of medications are discussed, including altered gastrointestinal motility and risk for periprocedural aspiration.

CONCLUSION

AOMs have established efficacy and effectiveness for weight loss even beyond 52 weeks. Further pharmacological options, such as dual and triple incretins, are probable forthcoming additions to clinical practice for combating obesity and its metabolic consequences such as metabolic dysfunction-associated steatotic liver disease.

Risks of the ketogenic diet in CKD - the con part

The ketogenic diet is a very low carbohydrate diet that has received a lot of attention for its role in the treatment of type 2 diabetes and obesity. For patients with chronic kidney disease, there is limited evidence on the risks and/or benefits of this diet. However, from the limited evidence that does exist, there are several inferences that can be drawn regarding this diet for patients with kidney disease. The ketogenic diet may not be better than comparator higher carbohydrate diets over the long term. The diet also has low adherence levels in studies lasting ≥12 months. The diet's emphasis on fat, which often comes from animal fat, increases the consumption of saturated fat, which may increase the risk of heart disease. It has the potential to worsen metabolic acidosis by increasing dietary acid load and endogenous acid production through the oxidation of fatty acids. In addition, the diet has been associated with an increased risk of kidney stones in patients using it for the treatment of refractory epilepsy. For these reasons, and for the lack of safety data on it, it is reasonable for patients with kidney disease to avoid utilizing the ketogenic diet as a first-line option given alternative dietary patterns (like the plant-dominant diet) with less theoretical risk for harm. For those adopting the ketogenic diet in kidney disease, a plant-based version of the ketogenic diet may mitigate some of the concerns with animal-based versions of the ketogenic diet.

Popular Diets and Kidney Stones

Popular diets often influence dietary patterns, which have different implications for kidney stone risk. Despite the wide variety of popular diets, some general principles can be gleaned from investigating their potential impact on nephrolithiasis. Plant-based diets, including Dietary Approaches to Stop Hypertension, Mediterranean, flexitarian, and vegetarian diets, may protect against nephrolithiasis when they consist largely of unprocessed plant foods, while carbohydrate-restricted diets (including high-protein diets and the ketogenic diet) may raise kidney stone risk. Patients should be advised to consume a diet rich in whole plants, particularly fruits and vegetables, and minimize their consumption of animal proteins. Accompanying fruits and vegetables that are higher in oxalate content with more water and some dairy intake may also be useful. (We address the oxalate content of fruits and vegetables further below). Calcium consumption is an important component of decreasing the risk of kidney stones, as higher dietary calcium from dairy or nondairy sources is independently associated with lower kidney stone risk. Patients should also be advised to be conscious of fat intake, as fat in the intestinal lumen may complex with calcium and therefore increase urinary oxalate excretion. Finally, patients should avoid consumption of processed foods, which often contain added fructose and high sodium content, two factors that increase kidney stone risk.

Untargeted and targeted metabolomics reveal bile acid profile changes in rats with ethylene glycol-induced calcium oxalate nephrolithiasis

Calcium oxalate (CaOx) nephrolithiasis is a prevalent disorder linked to metabolism. Examining metabolic alterations could potentially give an initial understanding of the origins of CaOx nephrolithiasis. This study aims to determine gut metabolic biomarkers differentiating CaOx nephrolithiasis utilizing untargeted and targeted metabolomics. CaOx nephrolithiasis model rats were built by 1% ethylene glycol administration. Histologic staining and renal function measurement revealed the presence of crystals in the lumen of the renal tubules, the renal injury and interstitial fibrosis in CaOx rats, demonstrating that the models of CaOx were established successfully. Hematoxylin & eosin (H&E) staining showed that CaOx group had inflammation and damage in the ileal tissue. Immunofluorescence and PCR results displayed that the tight junction proteins, ZO-1 and Occludin levels were decreased in the ileal tissues of the CaOx group. The untargeted metabolomic analysis revealed that 269 gut metabolites were differentially expressed between the CaOx group and the control group. Meanwhile, bile secretion, the main metabolic pathway in CaOx nephrolithiasis, was identified. Following, five significant bile acid metabolites were selected utilizing the targeted bile acid metabolomics, including Hyodeoxycholic acid (HDCA), Glycohyodeoxycholic acid (GHDCA), Nor-Deoxycholic Acid, omega-muricholic acid, and Taurolithocholic acid. Among these metabolites, HDCA and GHDCA presented the highest predictive accuracy with AUC = 1 to distinguish the CaOx group from the control group. As a result of network pharmacology, target genes of HDCA and GHDCA in CaOx nephrolithiasis were enriched in oxidative stress and apoptosis pathways. Conclusively, our study provides insight into bile acids metabolic changes related to CaOx nephrolithiasis. Although alterations in biochemical pathways indicate a complex pathology in CaOx rats, bile acid changes may serve as biomarkers of CaOx nephrolithiasis.

Pancreatic exocrine insufficiency is a risk factor for kidney stones in patients with chronic pancreatitis

INTRODUCTION

Most patients with chronic pancreatitis (CP) develop pancreatic exocrine insufficiency (PEI) over the course of the disease. PEI may lead to hyperoxaluria and development of urinary oxalate stones. It has been postulated that the patients with CP may be at increased risk of kidney stone formation, but the data is scarce. We aimed to estimate incidence and risk factors for nephrolithiasis in a Swedish cohort of patients with CP.

PATIENTS AND METHODS

We performed retrospective analysis of an electronical medical database of patients diagnosed with definite CP during 2003-2020. We excluded patients <18 years of age, those with missing relevant data in medical charts, patients with probable CP (according to the M-ANNHEIM classification system) and those in whom kidney stones were diagnosed before CP diagnosis.

RESULTS

Some 632 patients with definite CP were followed over a median of 5.3 (IQR 2.4-6.9) years. There were 41 (6.5%) patients diagnosed with kidney stones, of whom 33 (80.5%) were symptomatic. Comparing to patients without kidney stones, patients with nephrolithiasis were older, with median age of 65 (IQR 51-72) years, and a male predominance (80% vs 63%). Cumulative incidence of kidney stones was 2.1%, 5.7%, 12.4% and 16.1% at 5, 10, 15, and 20 years after CP diagnosis, respectively. Multivariable cause-specific Cox regression analysis revealed PEI as independent risk factor for nephrolithiasis (adjusted HR 4.95, 95%CI 1.65-14.84; p = 0.004). Another risk factors were increase in BMI (aHR 1.16 95% CI 1.04-1.30; p = 0.001 per unit increment), and a male sex (4.51, 95% CI 1.01-20.3, p = 0.049).

CONCLUSION

PEI and increase in BMI are risk factors for kidney stone development in patients with CP. Male CP patents are particularly at increased risk of nephrolithiasis. This should be taken into consideration in general clinical approach to raise awareness among patients and medical workers.

Effect of Two Different Dietary Weight Loss Strategies on Risk Factors for Urinary Stone Formation and Cardiometabolic Risk Profile in Overweight Women

Overweight has been suggested to increase the risk of kidney stone formation. Although weight reduction might affect risk factors for urolithiasis, findings on the impact of different dietary weight loss strategies are limited. This randomized, controlled study evaluated the effect of a conventional energy-restricted modified diet with (MR group) or without meal replacement (C group) on risk factors for stone formation in overweight women without a history of urolithiasis. Of 105 participants, 78 were included into the per-protocol analysis. Anthropometric, clinical, biochemical, and 24 h urinary parameters were collected at baseline and after 12 weeks. Although both dietary interventions resulted in a significant weight reduction, relative weight loss and rate of responders were higher in the MR group. Weight loss improved cardiometabolic risk profile in both groups. Unfortunately, the benefit of decreased GPT activity in the C group was offset by a significant increase in homocysteine and a decline in GFR. While the relative supersaturation of calcium oxalate decreased significantly in both groups, a significant decline in serum uric acid concentration and relative supersaturation of uric acid was observed only in the MR group. Finally, the energy-restricted modified diet with meal replacement showed significant advantages over the energy-restricted modified diet alone.

Secondary Osteoporosis and Metabolic Bone Diseases

Fragility fracture is a worldwide problem and a main cause of disability and impaired quality of life. It is primarily caused by osteoporosis, characterized by impaired bone quantity and or quality. Proper diagnosis of osteoporosis is essential for prevention of fragility fractures. Osteoporosis can be primary in postmenopausal women because of estrogen deficiency. Secondary forms of osteoporosis are not uncommon in both men and women. Most systemic illnesses and organ dysfunction can lead to osteoporosis. The kidney plays a crucial role in maintaining physiological bone homeostasis by controlling minerals, electrolytes, acid-base, vitamin D and parathyroid function. Chronic kidney disease with its uremic milieu disturbs this balance, leading to renal osteodystrophy. Diabetes mellitus represents the most common secondary cause of osteoporosis. Thyroid and parathyroid disorders can dysregulate the osteoblast/osteoclast functions. Gastrointestinal disorders, malnutrition and malabsorption can result in mineral and vitamin D deficiencies and bone loss. Patients with chronic liver disease have a higher risk of fracture due to hepatic osteodystrophy. Proinflammatory cytokines in infectious, autoimmune, and hematological disorders can stimulate osteoclastogenesis, leading to osteoporosis. Moreover, drug-induced osteoporosis is not uncommon. In this review, we focus on causes, pathogenesis, and management of secondary osteoporosis.

Systematic Review of the Prevalence of Kidney Stones in Cystic Fibrosis

Purpose: To investigate the prevalence of urolithiasis in cystic fibrosis (CF) and to summarize the available clinical features within this unique population. Methods: Studies reporting the prevalence of urolithiasis in CF patients were identified by a systematic search of the literature from inception to July 31, 2020 on three databases: Ovid Medline, Ovid Embase, and Web of Science. Data were extracted on a predetermined standardized form by two independent authors. Results: A total of 596 publications were retrieved and screened, 15 of which met the eligibility criteria. The publications were published between 1993 and 2019 and were all observational in design. There was a total of 2982 patients with CF included in this review. The overall prevalence of stone formation in the CF population was 4.6% (137/2982). The mean age of diagnosis was 25.1 ± 9.6 and ranged from 0.25 to 47. Ultrasound was the most common imaging modality for kidney stone diagnosis. There was no apparent sex difference, with a female to male ratio of 1:1. Surgical intervention was required in 37.8% (34/90) of cases. Stone recurrence was reported in 42.9% (33/77) of stone formers. Conclusions: This review provides the most recent update for the prevalence of urolithiasis in CF patients and summarizes the available clinical data. Our findings suggest that patients with CF could be at risk for developing stones at a younger age and require interventional management strategies at higher rates compared with the general population. Given the heterogeneity of the literature for urolithiasis in CF, larger population-based studies reporting the epidemiology, clinical features, and management strategies are required to further our understanding of urolithiasis in CF.

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.

Hyperoxaluria in a Model of Mini-Gastric Bypass Surgery in Rats

BACKGROUND

Bariatric surgery is associated with hyperoxaluria hence predisposing to nephrolithiasis. The present study aimed to investigate the underlying mechanisms contributing to increased urinary oxalate in a mini-gastric bypass (MGB) surgery model in rats under different dietary conditions. The expression of intestinal oxalate transporters was also evaluated.

METHODS

Male rats underwent MGB (n = 21) or Sham procedure (n = 21) and after recovery were fed a standard or high-fat diet with or without oxalate for 8 weeks. Stool and urine were collected before surgery (baseline) and at the end of protocol (final), when intestinal fragments were harvested for expression of Slc26a3 and Slc26a6 oxalate transporters.

RESULTS

MGB groups fed with fat, irrespective of oxalate supplementation, presented steatorrhea. In MGB animals fed with fat and oxalate (Fat + Ox), final values of urinary oxalate and calcium oxalate supersaturation risk were markedly and significantly increased versus baseline or Sham animals under the same diet, as well as MGB groups under other diets. Slc26a3 was decreased in biliopancreatic limbs of MGB rats, probably reflecting a physiological adaptation to the restriction of food passage. Slc26a6 was not altered in any harvested intestinal fragment.

CONCLUSIONS

A high-fat and oxalate diet induced hyperoxaluria and elevation in calcium oxalate supersaturation risk in a MGB rat model. The presence of fat malabsorption and increased dietary oxalate absorption, but not modifications of Slc26a3 and Slc26a6 oxalate transporters, accounted for these findings, suggesting that bariatric patients may benefit from a low-fat and low-oxalate diet.

Association between chronic pancreatitis and urolithiasis: A population-based cohort study

Purpose

Chronic pancreatitis (CP) can cause fat or bile acid malabsorption due to exocrine insufficiency. Fat or bile acid malabsorption has been reported to increase the risk of urolithiasis through increased intestinal oxalate absorption. However, no studies have reported an association between CP and urolithiasis.

Methods

We identified 15,848 patients (age: ≥20 years) diagnosed as having CP between 2000 and 2010 from the National Health Insurance Research Database as the study cohort. Beneficiaries without a history of CP were randomly selected and propensity-matched with the study cohort in a 1:4 ratio according to age; sex; comorbidities of hyperlipidemia, diabetes, obesity, hypertension, chronic obstructive pulmonary disease, alcohol-related illness, stroke, and coronary artery disease; and the index date. The prevalence of inflammatory bowel disease (0.44%), hyperparathyroidism (0.10%), or end stage renal disease (1.55%) in CP patients was low, but these comorbidities were also considered in the analysis. All patients were followed until the end of 2011 or withdrawal from the National Health Insurance program to determine the incidence of urolithiasis.

Results

The cumulative incidence of urolithiasis was higher in the CP cohort than that in the non-CP cohort (log-rank test, P < 0.001) with a 1.89-fold risk of urolithiasis (95% confidence interval [CI] = 1.74–2.06). The prevalence of CP was higher in men (81.9%) and in patients younger than 49 years (63.5%; mean age: 48.5 ± 15.3 years). CP was associated with the development of urolithiasis in each age group (≤49 years: aHR = 2.00, 95% CI = 1.81–2.22; 50–64 years: aHR = 1.71, 95% CI = 1.40–2.09; ≥65 years: aHR = 1.54, 95% CI = 1.20–1.98) and each sex (women: aHR = 2.10, 95% CI = 1.67–2.66; men; aHR = 1.86, 95% CI = 1.70–2.04). Among the patients without comorbidities, the rate of urolithiasis increased from 2.93/1,000 person-years in non-CP patients to 8.28/1,000 person-years in CP patients. Among the patients with comorbidities, the rate of urolithiasis increased from 6.12/1,000 person-years in non-CP patients to 10.9/1,000 person-years in CP patients. The contribution of CP to the relative risk of urolithiasis was greater in patients without comorbidities (without comorbidities: aHR = 2.81, 95% CI = 2.30–3.44) than in those with comorbidities (aHR = 1.76, 95% CI = 1.61–1.94).

Conclusion

CP is associated with urolithiasis in this population-based cohort study. The contribution of CP to the relative risk of urolithiasis was even greater in patients with a lower risk of urolithiasis, such as those without other comorbidities. Our findings warrant a survey and education on urolithiasis for patients with CP.

Orlistat-induced oxalate nephropathy: an under-recognised cause of chronic kidney disease

Two patients developed kidney failure due to oxalate deposition in the kidney while taking orlistat. Cessation of orlistat was followed by partial recovery of kidney function. The mechanism by which orlistat causes hyperoxaluria and the management of orlistat-induced oxalate nephropathy is reviewed. We suggest that all patients taking orlistat are at risk of this condition, which may develop insidiously and is easily overlooked. Monitoring of kidney function of patients taking orlistat is warranted.

Pathology and Epidemiology of Oxalate Nephrosis in Cheetahs

To investigate cases of acute oxalate nephrosis without evidence of ethylene glycol exposure, archived data and tissues from cheetahs ( Acinonyx jubatus) from North America ( n = 297), southern Africa ( n = 257), and France ( n = 40) were evaluated. Renal and gastrointestinal tract lesions were characterized in a subset of animals with ( n = 100) and without ( n = 165) oxalate crystals at death. Crystals were confirmed as calcium oxalate by Raman spectroscopy in 45 of 47 cheetahs tested. Crystals were present in cheetahs from 3.7 months to 15.9 years old. Cheetahs younger than 1.5 years were less likely to have oxalates than older cheetahs ( P = .034), but young cheetahs with oxalates had more oxalate crystals than older cheetahs ( P < .001). Cheetahs with oxalate crystals were more likely to have renal amyloidosis, interstitial nephritis, or colitis and less likely to have glomerular loop thickening or gastritis than those without oxalates. Crystal number was positively associated with renal tubular necrosis ( P ≤ .001), regeneration ( P = .015), and casts ( P ≤ .001) but inversely associated with glomerulosclerosis, renal amyloidosis, and interstitial nephritis. Crystal number was unrelated to the presence or absence of colitis and was lower in southern African than American and European animals ( P = .01). This study found no evidence that coexisting chronic renal disease (amyloidosis, interstitial nephritis, or glomerulosclerosis), veno-occlusive disease, gastritis, or enterocolitis contributed significantly to oxalate nephrosis. Oxalate-related renal disease should be considered as a potential cause of acute renal failure, especially in young captive cheetahs. The role of location, diet, stress, and genetic predisposition in the pathogenesis of oxalate nephrosis in cheetahs warrants further study.

Obesity: Current and potential pharmacotherapeutics and targets

Obesity is a global epidemic that contributes to a number of health complications including cardiovascular disease, type 2 diabetes, cancer and neuropsychiatric disorders. Pharmacotherapeutic strategies to treat obesity are urgently needed. Research over the past two decades has increased substantially our knowledge of central and peripheral mechanisms underlying homeostatic energy balance. Homeostatic mechanisms involve multiple components including neuronal circuits, some originating in hypothalamus and brain stem, as well as peripherally-derived satiety, hunger and adiposity signals that modulate neural activity and regulate eating behavior. Dysregulation of one or more of these homeostatic components results in obesity. Coincident with obesity, reward mechanisms that regulate hedonic aspects of food intake override the homeostatic regulation of eating. In addition to functional interactions between homeostatic and reward systems in the regulation of food intake, homeostatic signals have the ability to alter vulnerability to drug abuse. Regarding the treatment of obesity, pharmacological monotherapies primarily focus on a single protein target. FDA-approved monotherapy options include phentermine (Adipex-P®), orlistat (Xenical®), lorcaserin (Belviq®) and liraglutide (Saxenda®). However, monotherapies have limited efficacy, in part due to the recruitment of alternate and counter-regulatory pathways. Consequently, a multi-target approach may provide greater benefit. Recently, two combination products have been approved by the FDA to treat obesity, including phentermine/topiramate (Qsymia®) and naltrexone/bupropion (Contrave®). The current review provides an overview of homeostatic and reward mechanisms that regulate energy balance, potential therapeutic targets for obesity and current treatment options, including some candidate therapeutics in clinical development. Finally, challenges in anti-obesity drug development are discussed.

Weight loss at a high cost: Orlistat-induced late-onset severe kidney disease

AIM

This report describes a case of kidney failure secondary to orlistat, a lipase inhibitor commonly used in the treatment of obesity.

CASE REPORT

An 80-year-old man with type 2 diabetes who was being treated with orlistat developed rapidly progressive kidney failure. Low-grade albuminuria argued against diabetic nephropathy. Renal biopsy showed tubulointerstitial nephritis associated with numerous calcium oxalate crystals. Enteric hyperoxaluria was attributed to the orlistat treatment. The latter was stopped and the patient received calcium supplements. Six months after orlistat withdrawal, oxaluria was normalized and kidney function stabilized.

CONCLUSION

Oxalate nephropathy may result from hyperoxaluria secondary to orlistat treatment. This suggests that kidney function and oxaluria be closely monitored in patients taking orlistat.

Benefit-risk assessment of orlistat in the treatment of obesity

Orlistat, an inhibitor of intestinal lipase, has been available for the treatment of obesity for nearly two decades. In conjunction with a hypocaloric diet, orlistat treatment results in a placebo-subtracted reduction in body weight of around 3 kg at 1 year, and increases the likelihood of achieving clinically significant (≥5%) weight loss by around 20%. Orlistat-induced weight loss also confers modest improvements in systolic and diastolic blood pressure, low-density lipoprotein (LDL) cholesterol, glycemic parameters, and progression to diabetes in people with impaired glucose tolerance. Overall, it has a good safety profile, and serious adverse events (including reports of severe kidney and liver injury) are rare. However, a high rate of gastrointestinal side effects limits adherence to treatment.

Does orlistat cause acute kidney injury?

Orlistat is an inhibitor of gastric and pancreatic lipase with proven efficacy in the augmentation and maintenance of weight loss. Although its use has been limited by troublesome but benign gastrointestinal side effects, it has more recently been associated with acute kidney injury (AKI). In this review, we summarize orlistat's benefits and drawbacks and discuss the body of evidence supporting its role as a cause of AKI. Although we cannot yet draw an unequivocal causal link between orlistat and AKI, there is enough evidence to include orlistat exposure in the clinical assessment of patients with AKI.

Acute oxalate nephropathy associated with orlistat: a case report with a review of the literature

Orlistat is a gastrointestinal lipase inhibitor used for weight reduction in obese individuals. Enteric hyperoxaluria caused by orlistat leads to oxalate absorption. Acute oxalate nephropathy is a rare complication of treatment with orlistat. Herein we report a patient presenting with acute renal failure which improved minimal with intravenous hydration. She was found to have oxalate crystals on renal biopsy. Patient admitted orlistat use over the counter for weight reduction on further questioning. The purpose of this case review is to increase awareness among patients since they are more focused on losing weight. This case also calls for the provider attention to educate patients regarding side effects of orlistat because of easy availability of orlistat over the counter.

Acute oxalate nephropathy associated with orlistat: a case report with a review of the literature

Orlistat is a gastrointestinal lipase inhibitor used for weight reduction in obese individuals. Enteric hyperoxaluria caused by orlistat leads to oxalate absorption. Acute oxalate nephropathy is a rare complication of treatment with orlistat. Herein we report a patient presenting with acute renal failure which improved minimal with intravenous hydration. She was found to have oxalate crystals on renal biopsy. Patient admitted orlistat use over the counter for weight reduction on further questioning. The purpose of this case review is to increase awareness among patients since they are more focused on losing weight. This case also calls for the provider attention to educate patients regarding side effects of orlistat because of easy availability of orlistat over the counter.

Optimum nutrition for kidney stone disease

We summarize the data regarding the associations of individual dietary components with kidney stones and the effects on 24-hour urinary profiles. The therapeutic recommendations for stone prevention that result from these studies are applied where possible to stones of specific composition. Idiopathic calcium oxalate stone-formers are advised to reduce ingestion of animal protein, oxalate, and sodium while maintaining intake of 800 to 1200 mg of calcium and increasing consumption of citrate and potassium. There are few data regarding dietary therapy of calcium phosphate stones. Whether the inhibitory effect of citrate sufficiently counteracts increasing urine pH to justify more intake of potassium and citrate is not clear. Reduction of sodium intake to decrease urinary calcium excretion would also be expected to decrease calcium phosphate stone recurrence. Conversely, the most important urine variable in the causation of uric acid stones is low urine pH, linked to insulin resistance as a component of obesity and the metabolic syndrome. The mainstay of therapy is weight loss and urinary alkalinization provided by a more vegetarian diet. Reduction in animal protein intake will reduce purine ingestion and uric acid excretion. For cystine stones, restriction of animal protein is associated with reduction in intake of the cystine precursor methionine as well as cystine. Reduction of urine sodium results in less urine cystine. Ingestion of vegetables high in organic anion content, such as citrate and malate, should be associated with higher urine pH and fewer stones because the amino acid cystine is soluble in more alkaline urine. Because of their infectious origin, diet has no definitive role for struvite stones except for avoiding urinary alkalinization, which may worsen their development.

Lanthanum carbonate inhibits intestinal oxalate absorption and prevents nephrocalcinosis after oxalate loading in rats

PURPOSE

Increased intestinal oxalate absorption leads to increased urinary oxalate excretion (secondary hyperoxaluria) and calcium oxalate crystal formation, contributing to nephrocalcinosis/lithiasis. Lanthanum carbonate is an intestinal phosphate binder that is orally administered to patients on dialysis to treat hyperphosphatemia. It is hypothesized that lanthanum can also bind oxalate, in addition to phosphate. We evaluated this in vitro and in vivo.

MATERIALS AND METHODS

In vitro oxalate binding was evaluated by oxalate precipitation from a solution by lanthanum. In vivo oxalate absorption kinetics and the effect of lanthanum carbonate on nephrocalcinosis development were assessed in male Sprague-Dawley® rats that received 1) 1,000 mg lanthanum carbonate and oxalate, 2) carboxymethylcellulose and oxalate or 3) carboxymethylcellulose by gavage for up to 12 hours (kinetics) or 7 days (nephrocalcinosis). Plasma and urinary oxalate concentrations were measured at several time points after gavage. The degree of nephrocalcinosis was assessed histomorphometrically on von Kossa stained sections and by measuring total calcium content in renal tissue.

RESULTS

In vitro lanthanum bound oxalate in a pH range comparable to the range of the intestine. In vivo oxalate administration in untreated animals resulted in a biphasic pattern of increased plasma oxalate levels, which was almost abolished in lanthanum treated rats. In the urine of treated rats oxaluria and calcium oxalate crystalluria were blunted. Moreover, significantly decreased nephrocalcinosis was observed compared with that in untreated rats.

CONCLUSIONS

Lanthanum carbonate is a promising agent for the future prevention/treatment of secondary hyperoxaluria.

Response to dietary oxalate after bariatric surgery

BACKGROUND AND OBJECTIVES

Bariatric surgery (BS) may be associated with increased oxalate excretion and a higher risk of nephrolithiasis. This study aimed to investigate urinary abnormalities and responses to an acute oxalate load as an indirect assessment of the intestinal absorption of oxalate in this population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Twenty-four-hour urine specimens were collected from 61 patients a median of 48 months after BS (post-BS) as well as from 30 morbidly obese (MO) participants; dietary information was obtained through 24-hour food recalls. An oral oxalate load test (OLT), consisting of 2-hour urine samples after overnight fasting and 2, 4, and 6 hours after consuming 375 mg of oxalate (spinach juice), was performed on 21 MO and 22 post-BS patients 12 months after BS. Ten post-BS patients also underwent OLT before surgery (pre-BS).

RESULTS

There was a higher percentage of low urinary volume (<1.5 L/d) in post-BS versus MO (P<0.001). Hypocitraturia and hyperoxaluria (P=0.13 and P=0.36, respectively) were more frequent in BS versus MO patients. The OLT showed intragroup (P<0.001 for all periods versus baseline) and intergroup differences (P<0.001 for post-BS versus MO; P=0.03 for post-BS versus pre-BS). The total mean increment in oxaluria after 6 hours of load, expressed as area under the curve, was higher in both post-BS versus MO and in post-BS versus pre-BS participants (P<0.001 for both).

CONCLUSIONS

The mean oxaluric response to an oxalate load is markedly elevated in post-bariatric surgery patients, suggesting that increased intestinal absorption of dietary oxalate is a predisposing mechanism for enteric hyperoxaluria.

Hyperoxaluria: a gut-kidney axis?

Hyperoxaluria leads to urinary calcium oxalate (CaOx) supersaturation, resulting in the formation and retention of CaOx crystals in renal tissue. CaOx crystals may contribute to the formation of diffuse renal calcifications (nephrocalcinosis) or stones (nephrolithiasis). When the innate renal defense mechanisms are suppressed, injury and progressive inflammation caused by these CaOx crystals, together with secondary complications such as tubular obstruction, may lead to decreased renal function and in severe cases to end-stage renal failure. For decades, research on nephrocalcinosis and nephrolithiasis mainly focused on both the physicochemistry of crystal formation and the cell biology of crystal retention. Although both have been characterized quite well, the mechanisms involved in establishing urinary supersaturation in vivo are insufficiently understood, particularly with respect to oxalate. Therefore, current therapeutic strategies often fail in their compliance or effectiveness, and CaOx stone recurrence is still common. As the etiology of hyperoxaluria is diverse, a good understanding of how oxalate is absorbed and transported throughout the body, together with a better insight in the regulatory mechanisms, is crucial in the setting of future treatment strategies of this disorder. In this review, the currently known mechanisms of oxalate handling in relevant organs will be discussed in relation to the different etiologies of hyperoxaluria. Furthermore, future directions in the treatment of hyperoxaluria will be covered.

Orlistat and calcium oxalate crystalluria: an association that needs consideration

Obesity is currently an epidemic across the globe. Obese patients unable to achieve significant weight loss with lifestyle changes alone may require drug therapy. Clinical trials have shown that orlistat administration may not only lead to weight loss but also protect against type 2 diabetes in around 37% of cases. Orlistat can induce and maintain weight loss, even in patients with comorbid conditions such as hypertension or type 2 diabetes. Recently, orlistat can induce marked weight loss in individuals with chronic kidney disease (CKD). In small numbers of individuals especially those with CKD, orlistat administration may precipitate oxalate nephropathy and renal stone disease. The focus of this article is to review current studies showing impact of orlistat on renal function and outcomes.

Effects of Lactobacillus casei and Bifidobacterium breve on urinary oxalate excretion in nephrolithiasis patients

It had been suggested that lactic acid bacteria (LAB) may degrade oxalate in the intestinal lumen, reducing urinary oxalate excretion. We aimed to evaluate the effect of a LAB mixture containing Lactobacillus casei (LC) and Bifidobacterium breve (BB) (LC + BB) upon urinary oxalate reduction in stone-forming (SF) patients without hyperoxaluria under conditions of an oxalate-rich diet. After an oxalate restriction period (7 days washout), 14 SF patients consumed an oxalate-rich diet during 4 weeks (200 mg/day) and a lyophilized LC + BB preparation was given t.i.d. after meals during the last 2 weeks. Twenty-four-hour urine samples were collected for determination of oxalate, calcium, magnesium, citrate, sodium, potassium and creatinine at baseline, after 2 weeks (DIET) and 4 weeks (DIET + LC + BB). The mean urinary oxalate excretion was significantly higher after DIET versus baseline (27 +/- 8 vs. 35 +/- 11 mg/24 h), but the mean decrease was not significant between DIET + LC + BB and DIET periods (35 +/- 11 vs. 33 +/- 10 mg/24 h). Seven out of 14 patients presented a reduction in oxaluria after LC + BB versus DIET, being the reduction higher than 25% in 4, and up to 50% in 2 of them. The latter two patients were those who had presented the greatest increase in oxaluria in response to dietary oxalate. In conclusion, this mixture of L. casei and B. breve was shown to possess a variable lowering effect upon urinary oxalate excretion that may be dependent on dietary oxalate intake.

Obesity and urolithiasis

The current obesity epidemic in the United States has deleterious effects on the health of the population. Temporally related to the increase in obesity is an increase in the prevalence of urolithiasis. Epidemiologic studies have shown that the incident stone risk increases with body mass index. Obesity can increase stone risk in multiple ways. Excess nutritional intake increases traffic of lithogenic substances such as calcium, oxalate, and uric acid. Metabolic syndrome, commonly associated with obesity, alters renal acid-base metabolism, resulting in a lower urine pH and increased risk of uric acid stone disease. The low urine pH is caused by deficient ammonia production, which appears to be related to insulin resistance. Even weight-loss programs to combat obesity can influence stone risk. Contemporary bariatric surgery has been shown to frequently cause hyperoxaluria with associated stone formation and even oxalate nephropathy. Commonly used low-carbohydrate diets increase the risk of both calcium and uric acid stones. Certainly, the many health risks of obesity, including urolithiasis, necessitate weight loss, but recognition of the potential complications of such therapies is required to prevent induction of new and equally severe medical problems. The optimal approach to weight control that minimizes stone risk needs to be determined.

Evaluation of urinary oxalate levels in patients receiving gastrointestinal lipase inhibitor

OBJECTIVE

The purpose of this study was to examine the possible effects of a gastrointestinal lipase inhibitor "Orlistat (Xenical)" on the intestinal absorption of oxalate and thereby on the urinary levels of oxalate excretion in overweight patients.

METHODS AND PROCEDURES

Long-term follow-up data of 95 cases (57 men, 38 women; M/W=1.5) were documented. Patients were randomly assigned into two groups. While the patients in group I (n=55) were treated with orlistat (Xenical) for 6 months, patients in group II (n=40) received no specific medication. Calcium, oxalate, and citrate levels were determined in a 24-h urine collection from each patient. To evaluate the significance in the groups as well as the differences between the two groups, ANOVA test was performed and the results were given as mean +/- s.d.

RESULTS

Comparative evaluation of urinary oxalate levels during 3-month follow-up clearly showed that urinary oxalate excretion significantly increased in 34/55 patients (61.8%) in the first group (P<0.05). Of these 34 patients, 30 (88.2%) continued to have increased urinary oxalate excretion during 6-month follow-up (P=0.001). However, our data did not show any significant effect of this medication on urinary citrate and calcium levels during 3- and 6-month follow-up evaluation (P=0.05).

DISCUSSION

Our results suggest that increased intestinal absorption of dietary oxalate due to this type of medication in obese patients could make a substantial contribution to urinary oxalate excretion and may increase the risk of stone formation.

Drug-induced crystal nephropathy: an update

BACKGROUND

Several medications that are insoluble in human urine are known to precipitate within the renal tubules. Intratubular precipitation of either exogenously administered medications or endogenous crystals (induced by certain drugs) can promote chronic and acute kidney injury, termed crystal nephropathy. Clinical settings that enhance the risk of drug or endogenous crystal precipitation within the kidney tubules include true or effective intravascular volume depletion, underlying kidney disease, and certain metabolic disturbances that promote changes in urinary pH favoring crystal precipitation.

OBJECTIVE

Identify and review previously described and recently recognized medications that cause crystal nephropathy.

METHOD

A literature review was performed, using PubMed, Ovid, and Google Scholar, focusing on drugs (sulfadiazine, acyclovir, indinavir, triamterene, methotrexate (MTX), orlistat, oral sodium phosphate preparation, ciprofloxacin) that cause crystal nephropathy.

RESULTS/CONCLUSION

Sulfadiazine, acyclovir, indinavir, triamterene, and MTX are known to cause crystal nephropathy. Recently, several medications, including orlistat, ciprofloxacin, and oral sodium phosphate solution, along with underlying risk factors have been described as causing crystal nephropathy.

Orlistat-associated adverse effects and drug interactions: a critical review

Orlistat, an anti-obesity drug, is a potent and specific inhibitor of intestinal lipases. In light of the recent US FDA approval of the over-the-counter sale of orlistat (60 mg three times daily), clinicians need to be aware that its use may be associated with less well known, but sometimes clinically relevant, adverse effects. More specifically, the use of orlistat has been associated with several mild-to-moderate gastrointestinal adverse effects, such as oily stools, diarrhoea, abdominal pain and faecal spotting. A few cases of serious hepatic adverse effects (cholelithiasis, cholostatic hepatitis and subacute liver failure) have been reported. However, the effects of orlistat on non-alcoholic fatty liver disease are beneficial. Orlistat-induced weight loss seems to have beneficial effects on blood pressure. No effect has been observed on calcium, phosphorus, magnesium, iron, copper or zinc balance or on bone biomarkers. Interestingly, the use of orlistat has been associated with rare cases of acute kidney injury, possibly due to the increased fat malabsorption resulting from the inhibition of pancreatic and gastric lipase by orlistat, leading to the formation of soaps with calcium and resulting in increased free oxalate absorption and enteric hyperoxaluria. Orlistat has a beneficial effect on carbohydrate metabolism. No significant effect on cancer risk has been reported with orlistat.Orlistat interferes with the absorption of many drugs (such as warfarin, amiodarone, ciclosporin and thyroxine as well as fat-soluble vitamins), affecting their bioavailability and effectiveness. This review considers orlistat-related adverse effects and drug interactions. The clinical relevance and pathogenesis of these effects is also discussed.

Oxalate nephropathy with a granulomatous lesion due to excessive intake of peanuts

A 65-year-old Japanese male developed renal dysfunction, showing proteinuria and marked urinary excretion of beta2-microglobulin. He had consumed approximately 100-200 g peanuts and 750-1,000 ml beer every day for two or three months. He had previously been treated for hypertension with an angiotensin-converting enzyme inhibitor, enalapril. He then visited his primary-care doctor with mild fever, and renal dysfunction with mild diabetes mellitus were diagnosed. He was referred to our hospital, and because no diabetic retinopathy was observed by ophthalmological tests, renal biopsy examination was performed to clarify renal dysfunction. Renal biopsy specimens showed intimal thickening in the small arteries and interstitial nephritis with a granulomatous lesion, accompanied by oxalate crystals under polarized light. Glomeruli were unremarkable without any immunoglobulin deposition, and nodular lesions. Because he daily consumed a large amount of peanuts, oxalate nephropathy due to excessive intake of peanuts was strongly suspected. This case revealed that unusual food habits, including nuts, can cause oxalate nephropathy, and that close examination by renal biopsy was useful for clarifying the etiology of the unknown renal damage.

Acute oxalate nephropathy associated with orlistat, a gastrointestinal lipase inhibitor

Orlistat is an oral inhibitor of gastrointestinal lipase used for weight reduction in obese patients. Although most adverse drug effects manifest in the gastrointestinal tract, this is the first reported case of orlistat-induced acute kidney injury secondary to acute oxalate nephropathy in a white woman with underlying chronic kidney disease. Acute kidney injury was associated temporally with an increased dose of orlistat and the development of increased fat malabsorption (more frequent loose oily stools). Urine sediment showed abundant calcium oxalate crystals and increased 24-hour urine oxalate concentration. Kidney biopsy showed deposition of calcium oxalate crystals within tubular lumens, consistent with acute oxalate nephropathy. Orlistat therapy was discontinued, and oral fluid intake was increased. A second kidney biopsy performed 1 month later to evaluate the slow resolution of kidney failure did not show calcium oxalate crystals within tubules. A steady improvement in renal function subsequently was observed. Results of a repeated 24-hour urine oxalate collection performed 3 weeks later when kidney function had improved were within normal limits.

The use of orlistat in the treatment of obesity, dyslipidaemia and Type 2 diabetes

Orlistat (tetrahydrolipstatin) is an inhibitor of gastrointestinal lipases, especially pancreatic lipase. It is used as an adjunct to diet and exercise in order to achieve weight loss in obese individuals (body mass index > 30 kg/m2) or in overweight individuals (body mass index > 27 kg/m2) with other risk factors for atherosclerotic vascular disease, such as hypertension, dyslipidaemia or diabetes. Short- and long-term studies of up to 4 years duration have shown the drug to have significant benefits in weight loss, as well as in the reduction in lipids, glucose and haemoglobin A1c, and in time to onset of Type 2 diabetes compared with diet alone or placebo groups. The incremental amount of weight loss that orlistat produces is modest, but sufficient to result in improvement in obesity comorbidities such as elevated blood pressure, dyslipidaemia and hyperglycaemia compared with diet and exercise alone. Orlistat should only be prescribed for individuals who are motivated to adhere to lifestyle modifications, especially dietary fat restriction.

A new animal model of hyperoxaluria and nephrolithiasis in rats with small bowel resection

An association between small bowel resection and stone disease has been noted, which is primarily due to increased gut oxalate absorption and resulting excretion by the kidney. In order to better understand the factors affecting both oxalate absorption and renal excretion, and the resulting renal lesions, we have developed a rodent model of small bowel resection and hyperoxaluria. Using this model, we have studied the renal histology in animals with hyperoxaluria over time spans from 2 weeks to 7 months. The initial lesion appears to be crystal formation along the brush border of the proximal tubule, with eventual crystal deposition in collecting ducts and papillary interstitium, and eventual tubule obstruction, interstitial inflammation and fibrosis. Crystal formation appears to dissociate from urinary supersaturation. We hypothesize that oxalate transporters in the proximal tubule may increase local saturations, leading to crystal formation at this site initially. Further studies are required to better characterize the causes and consequences of hyperoxaluria in this animal model.