Bariatric Surgery Flashcards
Definition of bariatric surgery
Surgery on the GI tract for the purpose of inducing weight loss in extremely obese subjects.
Objective of bariatric surgery
Reducing caloric intake through modifications of the gastro-intestinal system
Classifications of bariatric surgery
- Restrictive procedures
- Malabsorptive procedures
- Combined procedures
Eligibility criteria for bariatric surgery
Canadian clinical practice guidelines:
* Previous unsuccessful attempts at losing weight through lifestyle modification
* Have a BMI > 40 kg/m2 or a BMI > 35kg/m2 with obesity related comorbidities (such as T2D)
* Be properly consulted on procedure
* Be emotionally and mentally prepared (psychologically able to receive procedure)
* Have proper support systems
* Be committed to life-long adherence to lifestyle changes after surgery
Pros of bariatric surgery
- Average weight loss of 65%
- Sustained weight loss
- Resolution of obesity related comorbidities
- Reduction in mortality
- Improved health outcomes and quality of life
Cons of bariatric surgery
- Cost
- Long term issues with fat malabsorption, protein-energy malnutrition, micronutrient deficiencies
- Permanent procedure (RYGB, VSG)
- Surgical Complications
- Dumping syndrome
- Hypoglycemia (may secrete too much insulin)
- excess of skin, may need corrective surgery afterwards
What are the 4 common procedures for bariatric surgery?
- vertical sleeve gastrectomy (VSG)
- Adjustable gastric banding
- Roux-en-Y gastric bypass (RYGB)
- Bilio-pancreatic diversion with duodenal switch
Describe VSG
Removing a part of the stomach creating smaller stomach (restricted procedure exclusively) so eat little and then feel full
Describe the adjustable gastric binding
Band placed around stomach and is adjustable so can change size; reversible of neccessary (restrictive procedure)
Describe RYGB
More complex; reduce size of stomach (gastrectomy) and then also reattach colon directly to stomach and reattach the other colon to get all the enzymes so bypass a certain region of GI tract (malabsorption)
Describe Bilio-pancreatic diversion with duodenal switch
Bypass duodenum but still attach to colon to get enzymes (malabsorption)
Prevalence of bariatric
metabolic outcomes of different bariatric procedures
bariatric surgery and BMI
Bariatric surgery alone results in greater reduction in BMI than multidisciplinary approaches
bariatric surgery and weight loss
Bariatric surgery induces significant and durable weight reduction
What is diabetes remission defined as?
- HbA1c <5.7%
- Fasting blood glucose <5.6mmol/L
- Without dependence of diabetic medications
How fast can T2D remission post bariatric surgery occur?
Diabetes remission results from improvements in both insulin resistance and beta-cell function. The degree of their improvement depends on the
type of surgery performed
* Restrictive procedures are thought to achieve glycemic control purely through weight loss without an entero-hormonal effect (In that case, the remission of diabetes is slow and occurs in parallel with gradual weight loss)
* Roux-en-Y gastric bypass (RYGB) elicits significant hormonal changes after surgery. Glycemic control is acute and immediate via a weight-independent mechanism → ~75% of diabetic patients go into remission within days (sometimes even 24 hours!) after RYGB surgery
Effectiveness of bariatric surgery on diabetes remission
Bariatric surgery is more effective than multidisciplinary interventions when it comes to diabetes remission
* Gastric bypass: 75%
* BPD/DS: 95%
* Sleeve gastrectomy: 80%
* Gastric banding: 47.9%
Versus NHANES III: 7.3% of T2D adults on a
lifestyle intervention reached HbA1c < 7%
(Saydah 2004)
Timeline for diabetes remission
When does ↓ insulin resistance (HOMA–IR) occur?
- Roux-en-Y, BPD/DS: 2 weeks
- Sleeve: 1 month
- Gastric banding: 6 months (due to weight loss)
What are common improvements of metabolic markers 2 yr post-surgery
- Weight loss with↓ visceral fat mass
- ↓ fat tissue accumulation & ↓ systemic inflammation
- ↑ insulin sensitivity
Huge decreases in markers such as SFD, VFD, VFD/SFD, hs-CRP, leptin, adiponectin
what other comorbidities associated with obesity might be resolved by bariatric surgery?
- Hypertension, lipid profile, CVDs
- Sleep apnea
- Gastro-oesophagal reflux disease, NAFLD
- Systemic inflammation
- Osteoarthritis
- Quality of life, psychological health
- Type 2 diabetes mellitus (14 years after surgery, >80% of the patients still maintain normal blood glucose levels)
Health agencies recommandations for bariatric surgery
Proposed theories for improved glycemic control following bariatric surgery
Bariatric surgery induces fast and durable improvement of glycemic control in T2D subjects, even before significant weight loss is achieved; Potential mechanisms include:
* Caloric restriction
* Reduction of foregut orexigenic hormones (ghrelin, other unknown factors)
* Increased secretion of incretin by the distal GI tract
* Increased circulating bile acids
Proposed hypotheses for improved glycemic control following bariatric surgery
- Hindgut hypothesis: (may secrete something that is good) Nutrients reach the distal bowel rapidly. Potential mediators include GLP1 and other appetite suppressing hormones
- Foregut Hypothesis: (exclude something that is bad somehow) Exclusion of the duodenum and proximal jejunum prevents an anti-incretin signal (which promotes insulin resistance and T2D)
Effects of bariatric surgery on various hormones
RYGB effect on GLP-1
GLP-1 is increased early after Roux-en-Y gastric bypass in humans
* basically restores secretion
How does GLP-1 mediate effects with bariatric surgery?
Gave meal after surgery and see give rise on all the effects on glucose and so argue huge contribution of GLP-1 in remission because with blocker competency abolish it.
How are bile acids effected by bariatric surgery?
BA levels are normally decreased in obesity but are re-established following gastric bypass
What are bile acids and their role?
Bile acids are steroidal molecules and they emulsify and help in digestion of dietary fat
How to bile acids act as signalling molecules?
- They act as ligands for the transcription factor Farnesoid X receptor (FXR). FXR controls liver gluconeogenesis, TG and cholesterol metabolism
- Bile acids also activate TGR5 in L-cells to stimulate GLP1 release.
Whole body effect of bile acids as a signalling molecule through FXR and TGR5
How does microbiota differ in obese individuals?
Obesity is associated with ↑ Firmicutes > bacteriodes with a decrease in microbiome diversity
* firmicutes love refined carbs and added sugar
* bacteriodes prefer fibre rich whole foods
How does bariatric surgery affect the gut microbiota?
Bariatric surgery alters the gut microbiota by ↓ firmicutes/bacteriodes ratio and ↑ diversity
* Mice colonized with stools from bariatric surgery patients displayed reduced fat deposition (so changes in microbiome may not only be consequence but also cause)
* Alterations in gut microbiome could play a role in some of the metabolic improvements
Summary of alterations with bariatric surgery
