Gender Differences in the Impact of a High-Fat, High-Sugar Diet in Skeletal Muscles of Young Female and Male Mice

Abstract

In the context of the increasing number of obese individuals, a major problem is represented by obesity and malnutrition in children. This condition is mainly ascribable to unbalanced diets characterized by high intakes of fat and sugar. Childhood obesity and malnutrition are not only associated with concurrent pathologies but potentially compromise adult life. Considering the strict correlation among systemic metabolism, obesity, and skeletal muscle health, we wanted to study the impact of juvenile malnutrition on the adult skeletal muscle. To this aim, 3-week-old C56BL/6 female and male mice were fed for 20 weeks on a high-fat. high-sugar diet, and their muscles were subjected to a histological evaluation. MyHCs expression, glycogen content, intramyocellular lipids, mitochondrial activity, and capillary density were analyzed on serial sections to obtain the metabolic profile. Our observations indicate that a high-fat, high-sugar diet alters the metabolic profile of skeletal muscles in a sex-dependent way and induces the increase in type II fibers, mitochondrial activity, and lipid content in males, while reducing the capillary density in females. These data highlight the sex-dependent response to nutrition, calling for the development of specific strategies and for a systematic inclusion of female subjects in basic and applied research in this field.

Keywords: Western diet; cell metabolism; fiber plasticity; obesity; skeletal muscle.

Figure 1

Representative examples of serial sections from soleus muscles sections stained for MyHC I and II (A), fiber-type composition (B), and fiber CSA (C) of female and male C57BL/6 fed on control or HFHS diet. Data on graphs are reported as mean ± SD (* significantly different p < 0.05, immumo staining was performed in 4 control females, 10 HFHS females, 5 control males, and 6 HFHS males); one asterisk highlights an MyHC I fiber; two asterisks highlight an MyHC II fiber in the serial sections, Bar 100 μm.

Figure 2

Representative examples of serial sections from soleus muscles sections stained with PAS (A) and relative quantification (B) of female and male C57BL/6 fed on control or HFHS diet. Data on graph are reported as mean ± SD (PAS staining was performed in 5 control females, 11 HFHS females, 4 control males, and 6 HFHS males); Bar 100 μm, A.U., arbitrary units.

Figure 3

Representative examples of serial sections from soleus muscles sections reporting SDH activity (A), global (B), and fiber-type specific (C) quantification of female and male C57BL/6 fed on control or HFHS diet. Data on graphs are reported with mean ± SD (*** significantly different p < 0.001; **** significantly different p < 0.0001, SDH staining was performed in 5 control females, 10 HFHS females, 5 control males, and 6 HFHS males); Bar 100 μm, A.U., arbitrary units.

Figure 4

Representative examples of serial sections from soleus muscles sections stained with SB (A), global (B), and fiber-type specific (C) quantification of female and male C57BL/6 fed on control or HFHS diet. Data on graphs are reported with mean ± SD (* significantly different p < 0.05, SB staining was performed in 5 control females, 10 HFHS females, 5 control males, and 5 HFHS males); Bar 100 μm, A.U., arbitrary units.

Figure 5

Representative examples of serial sections from soleus muscles sections stained with Alkaline phosphatase to detect capillaries (A), and relative quantification of the capillary density (B) and capillaries per fiber (C) in C57BL/6 female and male mice fed on control or HFHS diet. In panel A, arrowheads point towards some capillaries. Data on graph are reported with mean ± SD; (** significantly different p < 0.01, **** significantly different p < 0.0001, capillary density and capillaries per fiber have been quantified in 4 control females, 10 HFHS females, 5 control males, and 6 HFHS males); Bar 100 μm, C.D., capillary density.