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arkie6 04-30-2001 10:42 AM

Niacin causes insulin resistance?
 
Niacin causes insulin resistance and hyperglycemia (the beginnings of Type II diabetes)? So says the published articles here that I copied from the Protein Power bulletin board:

Niacin revisited: clinical observations on an important but underutilized drug
Henkin Y; Oberman A; Hurst DC; Segrest JP
Atherosclerosis Research Unit, University of Alabama Medical Center 35294.
Am J Med, 1991 Sep, 91:3, 239-46
STUDY OBJECTIVE: To evaluate the efficacy and side effects of niacin therapy in dyslipidemicindividuals.
DESIGN: A retrospective analysis of patients' charts.
SETTING: An outpatient referral-based clinic specializing in the treatment of lipid disorders.
PATIENTS: All patients with dyslipidemia treated by niacin (n = 82) at the Atherosclerosis Detection and Prevention Clinic during 1987 to 1990, including a subgroup of 17 dyslipidemic heart transplant recipients. RESULTS: Niacin was well tolerated in 83% of the nontransplant group (n = 65) at an average dose of 2.5 +/- 0.9 g/day. Similar beneficial lipoprotein effects were found in the transplant and nontransplant patients. The high-density lipoprotein cholesterol (HDL-C) response to niacin therapy was independent of the baseline (HDL-C level. In the transplant group, 11 patients (65%) discontinued treatment, primarily because of hyperglycemia; this was especially prominent in those patients with pretreatment diabetes mellitus.Of the 15 patients using sustained-release niacin, eight cases of hepatitis were recorded, some during therapy with relatively low niacin doses. Several different sustained-release preparations were responsible for this phenomenon, suggesting that the cause was not a contaminant in the preparation. No cases of hepatitis were documented in the 67 patients using regular niacin. One case of hepatitis was recently observed in a patient who switched from one type to regular niacin to another; however, we have data to suggest that the substituted preparation was not an immediate-release niacin. A familial predisposition to hepatitis is suggested by the occurrence of this side effect in identical twin brothers and two sisters. A pharmacy survey disclosed that most pharmacists are unaware of the relationship of sustained-release niacin to hepatitis, have a negative impression of regular niacin, and do not stock this formulation. Finally, we found that in this small sample of patients, niacin used with lovastatin is a particularly effective drug combination and appears to have few side effects beyond those seen with niacin alone.
CONCLUSIONS: Our experience supports the fact that regular niacin is a useful lipid-modifying drug. When used appropriately, patients can usually tolerate adequate doses for prolonged periods and achieve meaningful results. However, this requires a certain amount of physician skill and patient motivation. The use of sustained-release preparations to overcome this problem can lead to harmful consequences and should only be done under strict medical supervision. In our opinion, the availability of sustained-release niacin as a nonprescription drug is unjustified and should be reexamined. Finally, we have observed that reduction of very-low-density lipoprotein cholesterol (VLDL-C) with niacin alone leads to an elevation in low-density lipoprotein cholesterol in many patients; this indicates to us that the mechanism whereby niacin lowers VLDL-C and total cholesterol is not solely the result of a decreased synthesis of VLDL-C.

Effect of nicotinic acid-induced insulin resistance on pancreatic B cell function in normal and streptozocin-treated baboons.
McCulloch DK; Kahn SE; Schwartz MW; Koerker DJ; Palmer JP
Department of Medicine, University of Washington, Seattle 98108.
J Clin Invest, 1991 Apr, 87:4, 1395-401
Abstract
To study the interaction between insulin secretion and insulin action in maintaining glucose homeostasis, we induced experimental insulin resistance in eight normal baboons, in six baboons treated with 40 mg/kg streptozocin (STZ-40), and in six baboons treated with 200 mg/kg streptozocin (STZ-200). Insulin resistance was induced by a 20-d continuous intravenous infusion of nicotinic acid (NA). Normal animals showed compensatory increases in several measures of insulin secretion (fasting insulin [FI], acute insulin response to arginine [AIRarg], acute insulin response to glucose [AIRgluc], and glucose potentiation slope [delta AIRarg/delta G]), with no net change in fasting plasma glucose (FPG) or glycosylated hemoglobin (HbAtc). STZ-40 animals showed compensatory increases in FI, AIRarg, and AIRgluc, but delta AIRarg/delta G failed to compensate. Although FPG remained normal in this group during NA infusion, HbA1c rose significantly. STZ-200 animals failed to show compensatory changes in both AIRgluc and delta AIRarg/delta G, with both HbA1c and FPG rising. These animals showed a paradoxical inhibition of insulin secretion in response to intravenous glucose during NA infusion, at a time when they were hyperglycemic. These data indicate that a significant degree of insulin resistance does not cause hyperglycemia in the presence of normal B cell function but, in animals with reduced B cell mass and superimposed insulin resistance, the degree of hyperglycemia is proportional to the degree of pancreatic B cell dysfunction.

Nicotinamide's effects on glucose metabolism in subjects at risk for IDDM
Greenbaum CJ; Kahn SE; Palmer JP
Department of Medicine, University of Washington, Seattle, USA.
Diabetes, 1996 Nov, 45:11, 1631-4
Abstract
Nicotinamide is being used in trials to prevent or delay the development of clinical IDDM. A related compound, niacin, has been shown to cause insulin resistance in normal subjects, resulting in increased insulin secretion. This study was designed to answer the question: Does the short-term administration of nicotinamide cause insulin resistance in subjects who have a high risk of developing IDDM? Eight islet cell antibody-positive (ICA+) relatives of IDDM patients were given nicotinamide at a dose of 2 g/day for 2 weeks. Measurements of first-phase insulin release, insulin sensitivity, glucose effectiveness, and the constant for glucose disappearance (Kg) were measured at baseline, at the end of 2 weeks of therapy, and after subjects had been off therapy for at least 2 weeks. Nicotinamide administration caused a 23.6% decrease in insulin sensitivity (P = 0.02). This decrease was associated with a fall in Kg despite increased insulin secretion. Our data suggest that the use of nicotinamide in subjects who are at risk of developing IDDM may be complicated by the drug's effects on insulin sensitivity. By inducing insulin resistance, a therapeutic effect of nicotinamide on the diabetes disease process may be missed, and the interpretation of insulin secretion measurements that are obtained during the intervention trials using nicotinamide may be complicated by the changes in insulin secretion that are caused by the increased insulin resistance. Therefore, we strongly support the recommendation that at least one subgroup of subjects enrolled in clinical trials to prevent IDDM have regular measurements of both insulin sensitivity and insulin secretion performed. This subgroup should be randomly assigned and large enough for statistical analysis to interpret properly the changes in insulin secretion that may occur.


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