Acarbose improves health and lifespan in aging HET3 mice

Abstract

To follow-up on our previous report that acarbose (ACA), a drug that blocks postprandial glucose spikes, increases mouse lifespan, we studied ACA at three doses: 400, 1,000 (the original dose), and 2,500 ppm, using genetically heterogeneous mice at three sites. Each dose led to a significant change (by log-rank test) in both sexes, with larger effects in males, consistent with the original report. There were no significant differences among the three doses. The two higher doses produced 16% or 17% increases in median longevity of males, but only 4% or 5% increases in females. Age at the 90th percentile was increased significantly (8%-11%) in males at each dose, but was significantly increased (3%) in females only at 1,000 ppm. The sex effect on longevity is not explained simply by weight or fat mass, which were reduced by ACA more in females than in males. ACA at 1,000 ppm reduced lung tumors in males, diminished liver degeneration in both sexes and glomerulosclerosis in females, reduced blood glucose responses to refeeding in males, and improved rotarod performance in aging females, but not males. Three other interventions were also tested: ursolic acid, 2-(2-hydroxyphenyl) benzothiazole (HBX), and INT-767; none of these affected lifespan at the doses tested. The acarbose results confirm and extend our original report, prompt further attention to the effects of transient periods of high blood glucose on aging and the diseases of aging, including cancer, and should motivate studies of acarbose and other glucose-control drugs in humans.

Keywords: acarbose; health measures; heterogeneous mice; lifespan.

Figure 1

Effects of ACA on lifespan and body weight. Effects of dietary ACA dose on: (a, b) lifespans; (c, d) body weights over lives of the same mice. Lifespan curves (a and b for females and males) show the entire lifespan from the data used to produce Table 1, which includes sample sizes and statistical analyses of differences in median and 90th percentile values from the control as a result of each ACA dose. Body weights (c and d for females and males) represent 115–165 mice tested at 6, 12, 18, and 24 months of age in the ACA‐fed groups. Numbers of controls were about twice as high. Using one‐way ANOVA with Sidak post hoc test, there was no effect of ACA at 6 months. At 12 and 18 months, weights were significantly different as shown by >: Males – Control, ACA_lo > ACA_hi, ACA_mid; Females – Control > ACA_lo > ACA_mid, ACA_hi. At 24 months of age, there were no significant differences between Control and treated males, while in Females – Control, ACA_Lo > ACA_hi, ACA_mid. Weights at 24 months are hard to interpret, due to unbalanced death rates at the three sites, and possible weight loss due to ill health

Figure 2

Changes with age in body composition due to dietary ACA. Effects of 1,000 ppm ACA diet starting at 8 months of age on weights and body composition from 8 to 22 months of age at UT. Giving numbers of mice at 8–22 months of age: females (32–28 controls, 32–28 ACA‐treated); males (32–14 controls, 33–30 ACA‐treated). The same groups of mice were tested at 8, 12, 16, 20, and 22 months. ACA‐treated have blue dots; controls black dots. Data are shown as mean ± SE, and weights and body fat were significantly lower, while lean mass was significantly higher in both males and females fed the ACA diet as measured by 2‐way ANOVA using GraphPad version 7.03, which accounted for the missing mice

Figure 3

Effects of ACA on fat depends on specific fat type. Effects of ACA on amount of fat relative to body weight in 12‐month‐old HET3 mice at UM. Numbers of male ACA and controls are 9 each, while 8 females received ACA and 6 were controls. In subscapular fat, ACA effects are sex‐specific: females, p = 0.71; males, p < 0.001. In mesenteric fat, ACA results in a strong reduction in both sexes: p < 0.001. In gonadal fat, ACA effects are similar in both sexes, but weak: p = 0.074. In Inguinal fat, ACA has no effect. p values, from analysis of covariance, reflect differences in the intercept term, which measures whether ACA alters fat pad weight after adjustment for body weight. HET3 mice were fed diet with 1,000 ppm ACA starting at 4 months; controls were fed the base diet. Mice were fasted for 18 hr prior to dissection. This was part of a larger study in which mice had a sham‐operation procedure at age 3 months. They were anesthetized, gonads were exteriorized through an incision and then returned to the abdominal cavity, and the wound closed

Figure 4

Microhistopathology effects of ACA. Lesions are compared in controls and mice fed the 1,000 ppm ACA diet starting at 4 months of age. Numbers of mice: ACA old – 57 F and 54 M. The Control group consisted of 41 male and 43 female animals, of which 11 males and 14 females were contemporaneous with the current ACA population, and the remainder consisted (as a preplanned strategy) of controls from earlier cohorts also evaluated at 22 months of age. About a third of the mice came from each site. The values shown are percentage of cases with the indicated lesions, and p‐values reflect differences between two proportions using an asymptotically, normally distributed z statistic, as documented in the STATA program

Figure 5

ACA effects on blood glucose after refeeding. Postprandial blood glucose is reduced in males but not in females by 6 weeks on ACA diets. Male and female UM‐HET3 mice were given one of four diets for 6 weeks starting at 4 months of age. Each point represents the mean ± SEM of 10 mice, tested at the indicated times. Green symbols indicate diets formulated with ACA at 2,500 ppm; blue 1,000 ppm; red 400 ppm; and white 0 ppm (control). Mice were fasted from 18:00 until 9:00 the next day. Blood glucose was measured at “0” min (before food was returned), and at 30, 60, 180, and 360 min after the food was returned to their cages. All measures were made in each sex in a single session, but in different sessions for each sex. Data were analyzed using RM one‐way analysis of variance (ANOVA) for male and female mice separately. In both sexes, we compared the differences between the four groups using GraphPad Prism 7.03. In females, the different diets did not affect blood glucose levels significantly (p = 0.092). In males, the different diets had significant effects on blood glucose (p = 0.002)

Figure 6

Effects of ACA on rotarod performance. Training on a rotarod was more effective in females fed ACA, but there was no benefit in males. Groups of male and female UM‐HET3 mice were fed control or acarbose‐containing diets (1,000 ppm) beginning at 8 months of age until they were 22 months of age. A group of 4‐month‐old mice fed the control diet served as the young control group. Mice were trained on a rotarod for 5 days, with a final test done on day 6, and the latency to fall was tested. Average performance is shown by treatment, day, and sex. Error bars represent standard errors of the means. Sample sizes for female mice were as follows: young control = 19, ACA‐fed = 27, and old control = 27; and for male mice: young control = 19, ACA‐fed = 29, and old control = 14. Since mice with lower weights tended to have higher rotarod times, weight was regressed onto group, and the residuals from this model used to adjust for weight in an ANCOVA comparing averages between groups (young vs. acarbose vs. untreated)