Metformin mitigates the impaired development of skeletal muscle in the offspring of obese mice

Abstract

Background: Maternal obesity is linked with offspring obesity and type 2 diabetes. Skeletal muscle (SM) insulin resistance is central to the development of diabetes. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is inhibited in SM of fetuses born to obese mothers.

Objective: The aim of this study was to evaluate the effect of maternal metformin administration on AMPK activity and reversion of adverse changes in offspring SM of obese mice.

Design: Female weanling C57BL/6J mice received either control diet (CON, 6 mice) or high-fat diet (HFD; OB, 12 mice) for 8 weeks before mating. After mating, mice continued receiving their respective CON or OB diets. In addition, 6 of those 12 mice fed with fat diet also received metformin administration (2 mg per ml in drinking water) throughout gestation and lactation (MET). After weaning at postnatal 21 days, offspring were fed a HFD to mimic a postnatal obesogenic environment until necropsy.

Results: Mothers receiving the fat diet developed obesity. OB offspring showed higher adiposity than CON and MET offspring. AMPK phosphorylation was lower in SM of OB offspring. β-Catenin and myogenic regulatory factors, MyoD and myogenin, were downregulated in OB muscle, whereas the adipogenic marker, peroxisome proliferator-activated receptor-γ, was upregulated compared with CON muscle. Metformin administration prevented these changes in OB offspring SM. OB but not MET offspring demonstrated glucose intolerance. Mitochondrial content decreased, and activities of citrate synthase and β-hydroxyacyl-CoA dehydrogenase also decreased in OB offspring SM, whereas they were recovered in MET offspring SM.

Conclusion: Maternal metformin administration improves SM development in OB offspring.

Figure 1

AMPK phosphorylation in day-1 and -15 offspring hindleg muscle, and day-60 male offspring gastrocnemius muscle of CON, OB and MET mothers. Data are expressed as mean±s.e., n=6. ^#P<0.05 versus CON; ^(#)P<0.1 versus CON; and ^*P<0.05 versus OB.

Figure 2

Contents of β-catenin, myogenic markers and PPAR-γ in day-1 and -15 offspring hindleg muscle, and day-60 male offspring gastrocnemius muscle of CON, OB and MET mothers. (a) Beta-catenin content; (b) MyoD content; (c) Myogenin content; (d) PPARgamma content. Data are expressed as mean±s.e., n=6. ^#P<0.05 versus CON; ^(#)P<0.1 versus CON; ^*P<0.05 versus OB; and ^(*)P<0.1 versus OB.

Figure 3

Hematoxylin and eosin (H&E) staining of day-1 and -15 offspring muscle of CON, OB and MET mothers. A section of dorsum of the trunk was dissected, embedded in OCT and frozen in liquid N₂. Cryofixed muscle specimens were cross-sectioned at 10-um thickness and stained with H&E, × 100 magnification. (a) CON muscle at day 1; (b) OB muscle at day 1; (c) MET muscle at day 1; (d) CON muscle at day 15; (e) OB muscle at day 15; (f) MET muscle at day 15.

Figure 4

Glucose tolerance test (GTT) on postnatal day-15 and -60 offspring of CON, OB, and MET mothers. (a) Intraperitoneal GTT in day-15 male offspring mice. The histogram represents the incremental area under the respective glucose curve. (b) Intraperitoneal GTT in postnatal day-60 male offspring mice. The histogram represents the incremental area under the glucose curve. Data are expressed as mean±s.e., n=4 for both ages. ^#P<0.05 versus CON; ^(#)P<0.10 versus CON; ^*P<0.50 versus OB; and ^(*)P<0.50 versus OB.