Chronological age represents the single greatest risk factor for human disease. One plausible explanation for this correlation is that mechanisms that drive ageing might also promote age-related diseases. Cellular senescence, which is a permanent state of cell cycle arrest induced by cellular stress, has recently emerged as a fundamental ageing mechanism that also contributes to diseases of late life, including cancer, atherosclerosis and osteoarthritis. Therapeutic strategies that safely interfere with the detrimental effects of cellular senescence, such as the selective elimination of senescent cells (SNCs) or the disruption of the SNC secretome, are gaining significant attention, with several programmes now nearing human clinical studies.

Metabolic and vascular factors have been invoked in the pathogenesis of diabetic neuropathy but their interrelationships are poorly understood. Both aldose reductase inhibitors and vasodilators improve nerve conduction velocity, blood flow, and (Na',K+)-ATPase activity in the streptozotocin diabetic rat, implying a metabolic-vascular interaction. NADPH is an obligate cofactor for both aldose reductase and nitric oxide synthase such that activation of aldose reductase by hyperglycemia could limit nitric oxide synthesis by cofactor competition, producing vasoconstriction, ischemia, and slowing of nerve conduction. In accordance with this construct, N-nitro-L-arginine methyl ester, a competitive inhibitor of nitric oxide synthase reversed the increased nerve conduction velocity afforded by aldose reductase inhibitor treatment in the acutely diabetic rat without affecting the attendant correction of nerve sorbitol and myo-inositol. With prolonged administration, N-nitro-L-arginine methyl ester fully reproduced the nerve conduction slowing and (Na',K+)-ATPase impairment characteristic of diabetes. Thus the aldose reductase-inhibitor-sensitive component of conduction slowing and the reduced (Na+,K+)-ATPase activity in the diabetic rat may reflect in part impaired nitric oxide activity, thus comprising a dual metabolicischemic pathogenesis. (J. Clin. Invest. 1994. 94:853-859.)

The primary objective of this study was to evaluate insulin sensitivity in healthy subjects treated with olanzapine or risperidone. Subjects were randomly assigned to single-blind therapy with olanzapine (10 mg/d), risperidone (4 mg/d), or placebo for approximately 3 wk. Insulin sensitivity was assessed pre- and posttreatment using a 2-step, hyperinsulinemic, euglycemic clamp. Glucose and insulin responses were also assessed by a mixed meal tolerance test. Of the 64 subjects randomized, 22, 14, and 19 in the olanzapine, risperidone, and placebo groups, respectively, completed the study procedures. There were no significant within-group changes in the glucose disposal rate or the insulin sensitivity index for the active therapy groups. Further, the results of the mixed meal tolerance test did not demonstrate clinically significant changes in integrated glucose metabolism during treatment with these medications. In summary, this study did not demonstrate significant changes in insulin sensitivity in healthy subjects after 3 wk of treatment with olanzapine or risperidone.

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The goal of this study was to evaluate the effect of olanzapine or risperidone treatment on beta-cell function in healthy volunteers. Subjects were randomly assigned to single-blind therapy with olanzapine (10 mg/d; n = 17), risperidone (4 mg/d; n = 13), or placebo (n = 18) for 15-17 d. Insulin secretion was quantitatively assessed at baseline and the end of the study period using the hyperglycemic clamp. Weight increased significantly (P < 0.01) in the olanzapine (2.8 +/- 1.7 kg) and risperidone (3.1 +/- 2.1 kg) treatment groups. An increase ( approximately 25%) in the insulin response to hyperglycemia and a decrease ( approximately 18%) in the insulin sensitivity index were observed after treatment with olanzapine and risperidone. The change in insulin response was correlated (r = 0.5576; P = 0.019) with a change in body mass index. When the impact of weight change was accounted for by multivariate regression analyses, no significant change in insulin response or insulin sensitivity was detected after treatment with olanzapine or risperidone. We found no evidence that treatment of healthy volunteers with olanzapine or risperidone decreased the insulin secretory response to a prolonged hyperglycemic challenge. The results of this study do not support the hypothesis that olanzapine or risperidone directly impair pancreatic beta-cell function.