EFFECT OF INTESTINAL BYPASS ON CHOLESTEROL ABSORPTION AND BLOOD LEVELS IN THE RABBIT

Recent advances in metabolic and bariatric surgery

Obesity and its associated medical conditions continue to increase and add significant burden to patients, as well as health-care systems, worldwide. Bariatric surgery is the most effective treatment for severe obesity and its comorbidities, and resolution of diabetes is weight loss-independent in the case of some operations. Although these weight-independent effects are frequently described clinically, the mechanisms behind them are not well understood and remain an intense area of focus in the growing field of metabolic and bariatric surgery. Perceptions of the mechanisms responsible for the beneficial metabolic effects of metabolic/bariatric operations have shifted from being mostly restrictive and malabsorption over the last 10 to 15 years to being more neuro-hormonal in origin. In this review, we describe recent basic and clinical findings of the major clinical procedures (adjustable gastric banding, vertical sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion) as well as other experimental procedures (ileal interposition and bile diversion) that recapitulate many of the metabolic effects of these complex operations in a simpler fashion. As the role of bile acids and the gut microbiome on metabolism is becoming increasingly well described, their potential roles in these improvements following metabolic surgery are becoming better appreciated. Bile acid and gut microbiome changes, in light of recent developments, are discussed in the context of these surgical procedures, as well as their implications for future study.

Plant Sterols, Stanols, and Sitosterolemia

Phytosterolemia (sitosterolemia) is a rare autosomal recessive sterol storage disease caused by mutations in either of the adenosine triphosphate (ATP) binding cassette transporter genes; (ABC) G5 or ABCG8, leading to impaired elimination of plant sterols and stanols, with their increased accumulation in the blood and tissues. Thus the disease is characterized by substantially elevated serum plant sterols and stanols, with moderate to high plasma cholesterol levels, and increased risk of premature atherosclerosis. Hematologic abnormalities including macrothrombocytopenia, stomatocytosis and hemolysis are frequently observed in sitosterolemia patients. Currently, ezetimibe, a sterol absorption inhibitor, is used as the routine treatment for sitosterolemia, with reported improvement in plant sterol levels and hemolytic parameters. This review summarizes the research related to the health impact of plant sterols and stanols on sitosterolemia.

Alterações funcionais e histológicas das glândulas paratireóides após derivação jejuno-cólica: estudo comparativo em ratos

Com a finalidade de estudar as glândulas paratireóides durante a fase de redução ponderal, 48 ratos Wistar, machos, foram distribuídos em dois grupos. Os animais do Grupo1, no total de 28, foram submetidos à derivação jejuno-cólica. Os animais do Grupo2, no total de 20, foram submetidos à operação simulada. Estudaram-se, à microscopia óptica, os aspectos histológicos, e à microscopia eletrônica, os aspectos ultraestruturais. A função das glândulas paratireóides foi estudada mediante determinações séricas do Hormônio da Paratireóide - Parato-hormônio (PTH), Cálcio, Fosfato, Albumina e Proteínas Totais. Procedeu-se à avaliação da evolução ponderal e variação percentual, pesando-se os animais nos dias 7, 14, 21 e 28. A determinação sérica do PTH, Cálcio, Fosfato, Albumina e Proteínas Totais foi realizada antes dos sacrifícios e os estudados da microscopia, após os mesmos, nos 7o, 14o, 21o e 28o dias. Os valores do peso, da variação percentual e das dosagens bioquímicas e hormonais foram submetidos à análise estatística separadamente para cada grupo. Compararam-se também os Grupos 1 e 2 em relação aos valores das variáveis estudadas nos 7o, 14o, 21o e 28o dias do sacrifício. Os animais submetidos à derivação jejuno-cólica apresentaram progressiva perda ponderal demonstrada a partir do sétimo dia e os animais de controle, crescente ganho de peso a partir do 14o dia. A média dos valores das determinações séricas do PTH dos ratos submetidos à derivação jejuno-cólica foi maior do que dos animais-controle já a partir do 7o dia, embora estatisticamente significantes. Os valores séricos do fosfato só foram estatisticamente significantes no 21o dia, o da albumina no 14o, 21o e 28o dias e os das proteínas totais em todos os períodos. A média dos valores do cálcio foi menor nos animais-controle dos que nos submetidos à derivação jejuno-cólica, não sendo esse valores estatisticamente significantes. O estudo da microscopia eletrônica e óptica nos animais submetidos à derivação jejuno-cólica diferenciou dos encontrados nos animais-controle pela predominância das células principais, sendo que as células escuras predominam no 21o dia e as células claras no 28º dia.

Effect of partial ileal bypass surgery on mortality and morbidity from coronary heart disease in patients with hypercholesterolemia. Report of the Program on the Surgical Control of the Hyperlipidemias (POSCH)

BACKGROUND AND METHODS

The Program on the Surgical Control of the Hyperlipidemias (POSCH), a randomized clinical trial, was designed to test whether cholesterol lowering induced by the partial ileal bypass operation would favorably affect overall mortality or mortality due to coronary heart disease. The study population consisted of 838 patients (417 in the control group and 421 in the surgery group), both men (90.7 percent) and women, with an average age of 51 years, who had survived a first myocardial infarction. The mean follow-up period was 9.7 years.

RESULTS

When compared with the control group at five years, the surgery group had a total plasma cholesterol level 23.3 percent lower (4.71 +/- 0.91 vs. 6.14 +/- 0.89 mmol per liter [mean +/- SD]; P less than 0.0001), a low-density lipoprotein cholesterol level 37.7 percent lower (2.68 +/- 0.78 vs. 4.30 +/- 0.89 mmol per liter; P less than 0.0001), and a high-density lipoprotein cholesterol level 4.3 percent higher (1.08 +/- 0.26 vs. 1.04 +/- 0.25 mmol per liter; P = 0.02). Overall mortality and mortality due to coronary heart disease were reduced, but not significantly so (deaths overall [control vs. surgery], 62 vs. 49, P = 0.164; deaths due to coronary disease, 44 vs. 32, P = 0.113). The overall mortality in the surgery subgroup with an ejection fraction greater than or equal to 50 percent was 36 percent lower (control vs. surgery, 39 vs. 24; P = 0.021). The value for two end points combined--death due to coronary heart disease and confirmed nonfatal myocardial infarction--was 35 percent lower in the surgery group (125 vs. 82 events; P less than 0.001). During follow-up, 137 control-group and 52 surgery-group patients underwent coronary-artery bypass grafting (P less than 0.0001). A comparison of base-line coronary arteriograms with those obtained at 3, 5, 7, and 10 years consistently showed less disease progression in the surgery group (P less than 0.001). The most common side effect of partial ileal bypass was diarrhea; others included occasional kidney stones, gallstones, and intestinal obstruction.

CONCLUSIONS

Partial ileal bypass produces sustained improvement in the blood lipid patterns of patients who have had a myocardial infarction and reduces their subsequent morbidity due to coronary heart disease. The role of this procedure in the management of hypercholesterolemia remains to be determined. These results provide strong evidence supporting the beneficial effects of lipid modification in the reduction of atherosclerosis progression.

Partial ileal bypass for hypercholesterolemia. 20- to 26-year follow-up of the first 57 consecutive cases

Between 1963 and 1968, 57 patients underwent partial ileal bypass (PIB) at the University of Minnesota for primary hypercholesterolemia. Preoperative total plasma cholesterol (TC) was 363.3 +/- 136.8 mg/dL (mean +/- SD) in these patients. Baseline and follow-up TC results demonstrated highly significant (p less than or equal to 0.001) TC reduction, 34% (n = 48), 28% (n = 49), 35% (n = 26), 35% (n = 11), and 30% (n = 25) at 1, 2 to 5, 6 to 10, 11 to 15, and more than 20 years, respectively, after PIB. In 21 patients with baseline, 1-year, and more than 20-year results TC decreased 33% by 1 year and remained 29% less than baseline more than 20 years after surgery (p = NS versus 1 year). Plasma triglyceride results were available in fewer patients, and no statistically significant changes developed after PIB. Two patients (3.5%) underwent PIB reversal, one for intractable diarrhea and one for recurrent nephrolithiasis. In the 25 nonreversed, long-term survivors, no statistically significant weight change was noted. Twenty-four per cent had 0 to 2, 52% had 3 to 5, and 24% had more than 5 bowel movements per day. Subsequent cholecystectomy was required in eight patients, and nephrolithiasis developed in 10 (40%). During 20 to 26 years, most survivors developed clinically apparent atherosclerosis: angina (60%), myocardial infarction (16%), or coronary artery bypass (28%). Coronary heart disease was the predominant cause of death among nonsurvivors (80%). Overall survival rates were 95% 88%, 75%, 59%, 53%, and 41% at 1, 5, 10, 15, 20, and 25 years, respectively, after PIB. Partial ileal bypass leads to highly significant TC reduction, which is sustained, essentially unchanged, more than 20 years after operation. In comparison to available epidemiologic and clinical trial data, these results support the hypothesis that TC reduction has a beneficial effect in patients with hypercholesterolemia.

The partial ileal bypass operation in treatment of the hyperlipidemias

Partial ileal bypass is, today, the single most effective means available for lowering the plasma lipids, in particular the plasma cholesterol concentration. The cholesterol lowering effect of this procedure is universally lasting; response escape or rebound of lipid levels has not occurred. The operation is safe. In addition, the obligatory benefits of this mode of therapy make it attractive as a therapeutic alternative, especially in a young and asymptomatic population. We do not advocate this operation as the treatment of choice for all hyperlipidemic individuals. It may be the treatment of choice for certain patients with hyperlipidemia.

Ten years clinical experience with partial ileal bypass in management of the hyperlipidemias

The first partial ileal bypass operation specifically for the reduction of plasma lipids was performed by us in 1963. Since then we have operated upon and followed for more than three months 126 hyperlipidemic patients. Clinical metabolic studies, before and after the procedure, have demonstrated a 60% decrease in cholesterol absorption, a 3.8-fold increase in total fecal steroid excretion, a 5.7-fold increase in cholesterol synthesis, a 3-fold increase in cholesterol turnover, and a one-third decrease in the miscible cholesterol pool. Circulating cholesterol levels have been lowered an average 41.1% from the preoperative but postdietary baseline. An average 53% cholesterol reduction has been achieved from a pretreatment baseline using a combination of dietary and surgical management. Plasma triglycerides have been reduced in primary hypertriglyceridemic patients (type IV) an average of 52.6% from their preoperative but postdietary baseline. One patient died in the hospital and there have been 13 late deaths over the past 10 years. Four cases of postoperative bowel obstruction required reoperation. Diarrhea following partial ileal bypass is, as a rule, transistory and not a significant problem. No appreciable weight loss results from partial ileal bypass, which is an obvious distinction from the results of the far more massive jejuno-ileal bypass procedure for obesity. We have not encountered hepatotoxic, lithogenic, or nephrolithiasis complications in our partial ileal bypass patients. Sixty-nine per cent of our patients with preoperative angina pectoris have postoperative improvement or total remission of this symptom complex. Serial appraisal of followup coronary arteriographic studies offers preliminary evidence for lesion regression. It is concluded that partial ileal bypass is the most effective means for lipid reduction available today; it is obligatory in its actions, safe, and associated with minimal side effects.