Sex-specific differences in metabolic outcomes after sleeve gastrectomy and intermittent fasting in obese middle-aged mice

Abstract

Despite the high prevalence of obesity among middle-aged subjects, it is unclear if sex differences in middle age affect the metabolic outcomes of obesity therapies. Accordingly, in this study, middle-aged obese female and male mice were randomized to one of three groups: sleeve gastrectomy (SG), sham surgery ad libitum (SH-AL), or sham surgery with weight matching to SG through intermittent fasting with calorie restriction (SH-IF). Comprehensive measures of energy and glucose homeostasis, including energy intake, body weight, energy expenditure, glucose and insulin tolerance, and interscapular brown adipose tissue (iBAT) sympathetic innervation density were obtained. At the end of 8 wk, SG and SH-IF females had better metabolic outcomes than their male counterparts. SG females had improved weight loss maintenance, preservation of fat-free mass (FFM), higher total energy expenditure (TEE), normal locomotor activity, and reduced plasma insulin and white adipose tissue (WAT) inflammatory markers. SH-IF females also had lower plasma insulin and WAT inflammatory markers, and higher TEE than SH-IF males, despite their lower FFM. In addition, SH-IF females had higher iBAT sympathetic nerve density than SG and SH-AL females, whereas there were no differences among males. Notably, SH-IF mice of both sexes had the most improved glucose tolerance, highlighting the benefits of fasting, irrespective of weight loss. Results from this study demonstrate that in middle-aged obese mice, female sex is associated with better metabolic outcomes after SG or IF with calorie restriction. Clinical studies are needed to determine if sex differences should guide the choice of obesity therapies.NEW & NOTEWORTHY SG or IF with calorie restriction produces better metabolic outcomes in females than in males. IF with calorie restriction prevents metabolic adaptation, even in the face of fat-free mass loss. IF with calorie restriction in females only, is associated with increased iBAT sympathetic innervation, which possibly mitigates reductions in energy expenditure secondary to fat-free mass loss. Lastly, IF leads to better glucose homeostasis than SG, irrespective of sex.

Keywords: brown adipose tissue; energy expenditure; glucose homeostasis; leptin; metabolic adaptation.

Graphical abstract

Figure 1.

Body weight and body composition at baseline, week 4, and week 8 after sleeve gastrectomy (SG), sham surgery ad libitum (SH-AL), and sham surgery weight-matched to SG through intermittent fasting with caloric restriction (SH-IF). A, D, G: body weight, fat mass, and fat-free mass in females. B, E, H: body weight, fat mass, and fat-free mass in males. C, F, I: body weight, fat mass, and fat-free mass in female SG mice compared with male SG mice. Please see text in results for detailed statistics. For statistical significance, *P < 0.05, **P < 0.01; ****P < 0.0001; ns for P > 0.05. n = 7–14 mice/group. Data expressed as means ± SE.

Figure 2.

A: weekly food intake in females only. B: weekly food intake in males only. C: cumulative food intake in females, males, and females versus males. D: fecal free-fatty acid content in females, males, and females versus males. Please see text in results for detailed statistics. For statistical significance, *P < 0.05, **P < 0.01; ***P < 0.001; ****P < 0.0001; ns for P > 0.05. n = 7–14 mice/group. Data expressed as means ± SE. SG, sleeve gastrectomy; SH-AL, sham surgery ad libitum; SH-IF, sham surgery weight-matched to SG through intermittent caloric restriction.

Figure 3.

A–C: oral glucose tolerance test (OGTT) at baseline, week 4, and week 8 after SG. A: OGTT in females only. B: OGTT in males only. C: OGTT in female SG mice compared with male SG mice D: insulin tolerance test (ITT) AUC at 4 wk in the female cohort, in the male cohort, and for female SG mice versus male SG mice. E: plasma insulin levels at 8 wk after SG in the female cohort, in the male cohort, and for female SG mice versus male SG mice. Please see text in results for detailed statistics. For statistical significance, *P < 0.05, **P < 0.01; ***P < 0.001; ns for P > 0.05. n = 7–14 mice/group. Data expressed as means ± SE. AUC, area under the curve; SG, sleeve gastrectomy; SH-AL, sham surgery ad libitum; SH-IF, sham surgery weight-matched to SG through intermittent fasting with caloric restriction.

Figure 4.

A–D: TEE at 8 wk after surgery. A: FFM and FM-adjusted TEE for females only. B: FFM and FM-adjusted TEE for males only. C: FFM and FM-adjusted TEE for female SG mice compared with male SG mice. D: TEE/FFM ratio for females only, for males only, and for female SG mice compared with male SG mice. E–G: RER at 8 wk after SG. E: RER for females only. F: RER for males only. G: RER for female SG mice compared with male SG mice. H: average RER for females, males, and for female SG mice compared with male SG mice. I–K: locomotor activity. I: in females only. J: in males only. K: in female SG mice compared with male SG mice. L: total (sum) locomotor activity in females, males, and female SG mice compared with male SG mice. Please see text in results for detailed statistics. For significance, *P < 0.05, **P < 0.01; ***P < 0.001; ****P < 0.0001; ns for P > 0.05. n = 7–14 mice/group. Data expressed as means ± SE. FFM, fat-free mass; FM, fat mass; Loc activity, locomotor activity (x, y, z activity planes); RER, respiratory exchange ratio; SG, sleeve gastrectomy; SH-AL, sham surgery ad libitum; SH-IF, sham surgery weight-matched to SG through intermittent fasting with caloric restriction; TEE, total energy expenditure.

Figure 5.

A–C: plasma leptin 8 wk after sleeve gastrectomy (SG), sham surgery ad libitum (SH-AL), and sham surgery weight-matched to SG through intermittent fasting with caloric restriction (SH-IF). A: absolute plasma leptin for females only, males only, and for female SG mice compared with male SG mice. B: plasma leptin adjusted to total fat mass for females only, males only, and for female SG mice compared with male SG mice. C: leptin mRNA expression in iWAT and gWAT 8 wk after surgery. D: IL-6 mRNA expression in iWAT and gWAT at 8 wk after surgery. E: TNFα mRNA expression in iWAT and gWAT 8 wk after surgery. Please see text in results for detailed statistics. For statistical significance, *P < 0.05, **P < 0.01; ***P < 0.001; ****P < 0.0001; ns for P > 0.05. n = 7–12/group; for mRNA expression, n = 4–8 mice/group. Data expressed as means ± SE. iWAT, inguinal white adipose tissue; gWAT, gonadal white adipose tissue.

Figure 6.

PGP9.5-labeled and TH-labeled axons in iBAT of female mice 8 wk after sleeve gastrectomy (SG), sham surgery ad libitum (SH-AL), and sham surgery weight-matched to SG through intermittent fasting with caloric restriction (SH-IF). A, D, and G: in females, PGP9.5-labeled axons in green. B, E, and H: in females, TH-labeled axons in magenta; blue arrows indicate synaptic puncta. C, F, and I: in females, merging of PGP9.5-labeled and TH-labeled axons in white; white arrows indicate colocalization. J: in females, PGP9.5-labeled axons filament length analysis. K: in females, TH-labeled axons filament length analysis. L, O, and R: in males, PGP9.5-labeled axons in green. M, P, and S: in males, TH-labeled axons in magenta; blue arrows indicate synaptic puncta. N, Q, and T: in males, merging of PGP9.5-labeled and TH-labeled axons in white; white arrows indicate colocalization. U: in males, PGP9.5-labeled axons filament length analysis. V: in males, TH-labeled axons filament length analysis. Please see text in results for detailed statistics. For statistical significance *P < 0.05. n = 3–5 mice/group. Data expressed as means ± SE. iBAT, interscapular brown adipose tissue; PGP9.5, protein gene product 9.5; TH, tyrosine hydroxylase.