Metabolic Impact of Bariatric Surgery on Rheumatic Diseases

Obesity is associated with a number of comorbid conditions, including rheumatic diseases. However, in some cases, excess weight loss can reverse the risk for disease progression and even improve these conditions.

While bariatric surgery is considered the sole option for long-term dramatic weight loss, it is primarily indicated for people with obesity and severe associated comorbidities.¹ To understand the long-term effects of bariatric surgery — not just on weight loss, but also on other chronic conditions — it is essential to view the physiological responses in context of changes to the gastrointestinal tract morphology.

Bariatric procedures have shown positive effects on comorbid diseases like diabetes and hypertension; therefore, it is not farfetched to suggest that surgically induced weight loss may have similar effects on rheumatic disease outcomes. However, through metabolic and musculoskeletal interactions, it is important to recognize potential consequences of bariatric surgery on rheumatic comorbidities, especially in bone health.

How does bariatric surgery promote weight loss?

Obesity is a metabolic condition, and dramatic weight loss changes the way bodies utilize energy and maintain homeostasis. Even though bariatric surgery is largely restrictive, several procedures rely on malabsorptive mechanisms to increase weight loss.² In other words, bariatric surgery cuts calories as well as alters the pathways that regulate the appetite and control the distribution and the rate of energy use.

Besides reducing the mechanical load of joints, bariatric surgery also affects changes to energy metabolism by mediating bone and fat crosstalk.¹ For example, certain neuropeptides that typically regulate bone formation in an environment of high calorie intake and weight gain, repress osteoblast activity based on signals of starvation (as occurs in dramatic weight loss).³ Also, due to the reduction of ingestion of nutrients and minerals, calcium from the bone is released into the blood, further changing the composition of bone tissue.⁴

This means that while bariatric procedures can be successful at weight loss, they can have a rather deleterious effect on bone tissue. Hence, it is important to explore the effects of bariatric surgery on diseases that are not only influenced by metabolic function, but also by those diseases that further modulate the musculoskeletal system.

How are obesity and rheumatic diseases related?

Rheumatic diseases are primarily characterized by inflammation of musculoskeletal tissues, including joints, tendons, ligaments, bones, and muscles. Obesity, while chiefly a metabolic condition, has also been associated with low-grade inflammation, specifically of white adipose tissue.¹

The impact of obesity on rheumatic diseases — besides imposing an abnormally large mechanical load on structural tissues — attenuates the inflammatory mechanism by triggering increased production of proinflammatory mediators.² Obesity can induce the initiation and progression of rheumatic diseases through altered hormonal and metabolic pathways, and secondarily, by promoting inflammation.

A few studies observed improvements in rheumatic arthritis outcomes (in terms of disease severity and activity) following bariatric surgery. In these studies, the proportion of participants reporting moderate to severe disease activity dropped from 57% to 6% a year after surgery. In subsequent follow-up visits, 74% of patients achieved remission compared with 26% at baseline.¹

What are the mechanisms of bariatric surgery and how do they affect bone health?

In general, there are 3 established procedures for dramatic weight loss: laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy, and laparoscopic Roux-en-Y gastric bypass. The first procedure is purely restrictive; however, the other 2 procedures combine restrictive and malabsorptive mechanisms of action.

Sleeve gastrectomy resects a significant part of the gastric fundus where ghrelin production is dramatically reduced, which, in turn, induces the action of appetite-regulating hormones.¹ In Roux-en-Y gastric bypass, the digestive tract is rearranged, which causes changes in the production and secretion of neuroendocrine and gastrointestinal hormones (and leads to metabolic effects).

Both malabsorptive procedures are associated with a greater increase in bone turnover markers (in favor of increased bone resorption); also, losses in bone mineral density profoundly increase skeletal fragility. In fact, studies show that malabsorptive weight loss procedures were associated with increased risk for fracture, whereas there was no such association found with weight loss procedures such as gastric banding that were only restrictive in nature.¹

What are the consequences of bariatric surgery?

The primary consequence of bariatric surgery that poses a major risk to a rheumatic population is its deleterious effects on bone. As discussed, malabsorptive procedures cause hormonal adaptations and changes in body composition that result in a more fragile musculoskeletal system.

Another consequence of bariatric surgery that affects the musculoskeletal system is acute gout flare, which may be triggered by large changes in serum uric acid levels. In addition, early studies on bariatric procedures have associated various arthritic syndromes and rare joint and skin conditions with circulating immune complexes along with bacterial overgrowth and other byproducts from the resected bowel.¹

How is weight loss indicated in disease management?

Body mass index is a theoretically modifiable risk factor. While obesity is associated with worse rheumatic disease outcomes, excess weight loss has been indicated to improve the ability of an individual to respond to treatment. This was demonstrated in a study linking obesity in early rheumatoid arthritis with decreased likelihood of achieving disease control: the response rate to anti-tumor necrosis factor was much lower among obese patients than those at a normal weight.¹

Weight loss has often been indicated for the management of a number of conditions. For example, losing weight can reduce uricemia levels and the incidence of gouty arthritis. In a study of patients with lupus and obesity, 42% of patients were able to decrease the number of immunosuppressive drugs they were taking and 19.3% were able to stop glucocorticoid therapy.¹

Can bariatric surgery improve rheumatic diseases?

Labeling bariatric surgery as a “metabolic procedure” is thoroughly appropriate as these interventions can result in the improvement of metabolic parameters, including those of rheumatic conditions, eg, modifying hyperuricemia. However, if bariatric surgery is recommended, healthcare professionals should weigh its negative impact on bone health — and on a deeper level, the complications that occur when metabolic changes intersect with musculoskeletal function.

For individuals with morbid obesity and chronic comorbid conditions, excess weight loss can benefit overall health. But for rheumatoid conditions, awareness of the impact of bariatric surgery on musculoskeletal integrity is a crucial consideration. Understanding the appropriateness of the procedure (less malabsorptive and more restrictive) and aggressive supplementation with calcium and vitamin D may be valuable for improving clinical outcomes.⁴

References

1. Lespessailles E, Hammoud E, Toumi H, Ibrahim-Nasser N. Consequences of bariatric surgery on outcomes in rheumatic diseases. Arthritis Res Ther. 2019;21:83.
2. Nikiphorou E, Fragoulis GE. Inflammation, obesity, and rheumatic disease: common mechanistic links. A narrative review. Ther Adv Musculoskelet Dis. 2018;10(8):157-167.
3. Shi YC, Baldock PA. Central and peripheral mechanisms of the NPY system in the regulation of bone and adipose tissue. Bone. 2012;50(2):430-436.
4. Dimitriadis GK, Randeva MS, Miras AD. Potential hormone mechanisms of bariatric surgery. Curr Obes Rep. 2017;6(3):253-265.