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SummaryThe objective of this article is to systematically review the changes in insulin resistance after various types of bariatric surgical procedures. A Pubmed and EMBASE search for studies measuring insulin resistance before and after bariatric surgery was done and all original research articles from 1980 to present (2011) were included. Only the currently widely performed bariatric procedures were included. A meta-analysis of change in HOMA-IR was conducted, grouping studies with similar duration of follow-up. The percentage decrease in HOMA-IR at <=2 weeks, 1 month, 3 months, 6 months, 12 months and >16-18 months was found to be (mean Ϯ standard error) -33.48 Ϯ 5.78, -46.43 Ϯ 6.99, -38.79 Ϯ 9.64, -58.62 Ϯ 7.38, -44.91 Ϯ 7.98 and -67.04 Ϯ 10.78%, respectively. RYGB (gastric bypass) and BPD (biliopancreatic diversion) produced a significant decrease in insulin resistance at 2 weeks after surgery, while LSG (sleeve gastrectomy) was strongly trending. LSG produced an earlier decrease in insulin resistance when compared to LAGB (gastric banding). RYGB, BPD and LSG produce an early decrease in insulin resistance through yet unknown mechanisms. Keywords: BPD, HOMA, insulin resistance, LAGB.Abbreviations: RYGB, Roux-en-Y gastric bypass; LAGB, laparoscopic adjustable gastric banding; BPD, biliopancreatic diversion; DS, duodenal switch; LSG, laparoscopic sleeve gastrectomy; HOMA-IR, homeostasis model of assessment of insulin resistance; HIEC, hyperinsulinemic euglycemic clamp; QUICKI, quantitative insulin-sensitivity check index; IVGTT, intravenous glucose tolerance test; FSIVGTT, frequently sampled intravenous glucose tolerance test; CIGMA, continuous infusion of glucose with model assessment; OGTT, oral glucose tolerance test; BMI, body mass index; TNFa, tumour necrosis factor alpha; GIP, glucosedependent insulinotropic polypeptide; GLP-1, glucagon-like peptide-1; IL-1, interleukin-1; IRS, insulin receptor substrate; OGIS, oral glucose insulin sensitivity. obesity reviews (2012) 13, [316][317][318][319][320][321][322][323][324][325][326][327][328]

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We have previously shown that mice lacking the TSH receptor (TSHR) exhibit osteoporosis due to enhanced osteoclast formation. The fact that this enhancement is not observed in double-null mice of TSHR and TNFalpha suggests that TNFalpha overexpression in osteoclast progenitors (macrophages) may be involved. It is unknown how TNFalpha expression is regulated in osteoclastogenesis. Here, we describe a receptor activator for nuclear factor-kappaB ligand (RANKL)-responsive sequence (CCG AGA CAG AGG TGT AGG GCC), spanning from -157 to -137 bp of the 5'-flanking region of the TNFalpha gene, which functions as a cis-acting regulatory element. We further show how RANKL treatment stimulates the high-mobility group box proteins (HMGB) HMGB1 and HMGB2 to bind the RANKL-responsive sequence and up-regulates TNFalpha transcription. Exogenous HMGB elicits the expression of cytokines, including TNFalpha, as well as osteoclast formation. Conversely, TSH inhibits the expression of HMGB and TNFalpha and the formation of osteoclasts. These results suggest that HMGB play a pivotal role in osteoclastogenesis. We also show a direct correlation between the expression of HMGB and TNFalpha and osteoclast formation in TSHR-null mice and TNFalpha-null mice. Taken together, we conclude that HMGB and TNFalpha play critical roles in the regulation of osteoclastogenesis and the remodeling of bone.

Bariatric surgery is an effective treatment option for obesity. Commonly utilized procedures are either restrictive, malabsorptive, or both. Substantial weight loss can be achieved. Postoperatively, patients experience nutritional, metabolic, and hormonal changes that have important clinical implications. The postoperative diet should be advanced carefully, according to protocol. Micronutrient deficiencies such as vitamin C, vitamin A, and zinc deficiencies are common, especially following malabsorptive procedures. Bone metabolism is greatly affected, in part due to vitamin D deficiency, decreased calcium absorption, and secondary hyperparathyroidism. Diabetes improves acutely in malabsorptive procedures and in sequence with weight loss in restrictive procedures. Polycystic ovarian syndrome improves in nearly all women with this condition who undergo bariatric surgery. Testosterone levels in men also improve after surgery. Consideration of these nutritional, metabolic, and hormonal changes allows for optimal medical management following bariatric surgery.